G L O S S A R Y APPENDIX I

G L O S S A R Y APPENDIX I
APPENDIX I
GLOSSARY
FOREHAND WELDING— Welding in the same direction as the torch flame points.
ACC— Air carbon arc cutting.
ARC BLOW— The tendency for an arc to wander or
whip from its normal course during arc welding.
FUSION— The melting together of metals.
ASME— American Society of Mechanical Engineers.
GMAW— Gas metal arc welding.
AWS— American Welding Society.
GTAW— Gas tungsten arc welding.
BACKFIRE— Momentary burning back of the flame
into the torch tip during welding or cutting.
IMPACT STRENGTH— The ability of a metal to
resist suddenly applied loads; measured in footpounds of force.
BACKHAND WELDING— Welding in the direction
opposite the direction the gas flame is pointing.
KERF— The narrow slit formed in metal as cutting
progresses.
BURR— The sharp edge remaining on metal after cutting.
LAYOUT— The process of measuring and marking
materials for cutting, bending, drilling, or welding.
CARBURIZING FLAME— Produced by burning an
excess of fuel gas.
MALLEABILITY— The property that enables a material to withstand permanent deformation caused
by compression.
CHAMFER— Bevel angling the metal edge where
welding is to take place.
COMPRESSION STRESSES— The stresses developed within a material when forces tend to compress or crush the material.
MAPP— A stabilized methyl acetylene-propadiene
fuel gas. A Dow Chemical Company product.
METALLOID— A nonmetal that can combine with a
metal to form an alloy.
DCRP— Direct current reverse polarity.
DCSP— Direct current straight polarity.
DISTORTION— The warping of a structure.
METALLURGY— The science and technology of
metals.
DUCTILITY— The property that enables a material to
withstand extensive permanent deformation due to
MIG— A term used to describe gas metal arc welding
(metal inert gas).
tension.
NEUTRAL FLAME— Produced when equal amounts
of oxygen and fuel gas are burned.
ELASTICITY— The ability of a material to return to
its original form after deformation.
FATIGUE—- The tendency of a material to fail after
repeated stressing at the same point.
NORMALIZING— A heat-treating operation involving the heating of an iron-base alloy above its
critical temperature range and cooling it in still air
for the purpose of removing stresses.
FATIGUE STRENGTH— The ability of a material to
resist various kinds of rapidly alternating stresses.
NONFERROUS— Metals containing no iron.
FERROUS— Denotes the family of metals in which
iron is the major ingredient.
OFW— Oxyfuel welding.
OXIDIZING FLAME— Produced by burning about
twice as much oxygen as fuel gas.
FLASHBACK— The flame burning in or beyond the
torch mixing chamber during welding or cutting.
PASS— A single progression of a welding operation
along a joint or weld deposit. The result of a pass is
a weld bead.
FLUX— A chemical used to promote fusion of metals
during the welding process.
AI-1
PLASTICITY— The ability of a material to permanently deform without breaking or rupturing.
STINGER— An electrode holder; a clamping device
for holding the electrode securely in any position.
POROSITY— The presence of gas pockets or voids in
metal.
STRESS— External or internal force applied to an objectl
QUENCHING— The process of rapid cooling from an
elevated temperature by contact with fluids or
gases.
TENSILE STRENGTH— The resistance to being
pulled apart.
TENSION STRESSES— The stresses developed
when a material is subjected to a pulling load.
QUENCHING MEDIUM— The oil, water, brine, or
other medium used for rapid cooling.
TIG— A term used to describe gas tungsten arc welding
(tungsten inert gas).
RSW— Resistance spot welding.
RW— Resistance welding.
SEIZE— To bind securely the end of a wire rope or
strand with seizing wire.
TINNING— A term applied to soldering where the
metals to be soldered together are first given a coat
of the soldering metal.
SHEARING STRESSES— The stresses developed
within a material when external forces are applied
along parallel lines in opposite directions.
WELD— To join metals by heating them to a melting
temperature and causing the molten metal to flow
together.
SMAW— Shielded metal arc welding.
WELDMENT— An assembly whose parts are joined
by welding.
SOAKING— Holding a metal at a required temperature for a specified time to obtain even temperature
throughout the section.
ULTIMATE STRENGTH— The maximum strain that
a material is capable of withstanding.
AI-2
APPENDIX II
REFERENCES USED TO DEVELOP
THE TRAMAN
Chapters
References
Althouse, Andrew D., Carl H. Turnquist, and William A.
Bowditch, Modern Welding, Goodheart-Wilcox Co.
Inc., 1970.
1-8
Bennet, A. E., and Louis J. Sky, Blueprint Reading for
Welders, 3d ed., Delmar Publishers Inc., 1983.
3
Blueprint Reading and Sketching, N A V E D T R A
10077-F1, Naval Education and Training Program
Management Support Activity, Pensacola, Fla., 1988.
3
Equipment Operator 3, NAVEDTRA 10392, Naval
Education and Training Program Management
Support Activity, Pensacola, Fla., 1990.
7
Giachino and Weeks, Welding Skills, American Technical
Publishers Inc., 1985.
1-8
Heat Treatment and Inspection of Metals, ATC Manual
52-5, Air Training Command, Scott Air Force Base,
Ill., 1963.
2
Naval Construction Force Welding Materials Handbook,
P-433, Naval Facilities Engineering Command,
Department of the Navy, Washington D. C., 1991.
3,6
The Oxy-Acetylene Handbook, 2d ed., Linde Company,
Union Carbide Corporation, 270 Park Avenue, New
York, 1960.
3-5,6
Safety and Health Requirements Manual, EM 385-1, U.S.
Army Corps of Engineers, United States Government
Printing Office, Washington, D. C., 1987.
4,5,8
Smith, David, Welding Skills and Technology, Gregg
Division, McGraw-Hill, 1984.
3-8
Welding Theory and Application, TM 9-237, Department
of the Army Technical Manual, Headquarters,
Department of the Army, Washington D.C., 1976.
1-8
AII-1
INDEX
A
Carburizing, 2-5
Acetylene, 4-3
Acetone, 4-3
Carburizing flame, 4-14
Chip test, 1-12
Air carbon-arc cutting, 7-30
Chain clamps, 5-14
Air carbon-arc gouging, 7-32
Circular magnetization, 7-33
Arc length, 7-11
Cleaning equipment, 7-4
Arc starting methods, 7-9
Color warnings, 4-25
Arc welding, 7-1
Color codes, 8-6
equipment, 7-1
Corrosion resistance of metals, 1-4 .
positions, 7-12,7-18,7-21
Cup sizes, 8-5
Current setting, 7-10
B
Cutting and beveling pipe, 4-19
Backfire and flashback, 4-23
Cutting and welding hoses, 4-8
Beveling mild steel, 4-17
Cutting cast iron, 4-16
Brazing, 6-8
Cutting mild-carbon steel, 4-14,4-21
equipment, 6-8
Cutting on containers, 4-21
filler metals, 6-8
Cutting quality, 4-22
fluxes, 6-8
Cutting rivets, 4-21
fluxing, 6-11
Cutting thin steel, 4-15
heating devices, 6-8
Cutting thick steel, 4-16
joint designs, 6-9
Cutting torches, 4-8
procedures, 6-10
Cutting torch tips, 4-9
silver, 6-12
Cutting torch tip maintenance, 4-11
surface preparation, 6-10
Cutting wire rope, 4-21
work support, 6-11
Cutting, metal electrode arc, 7-32
Braze welding, 6-12
equipment, 6-12
filler metal, 6-14
Cyaniding, 2-5
Cylinders,
4-3,4-4,4-23,4-26
D
flux, 6-14
procedures, 6-14
Butt joints, 3-5,6-4,7-13,7-18,7-21, 8-10
Dimensions, 3-25
Dimensioning, 3-28
Dimensions applied to weld symbols, 3-29
C
Drag lines, 4-22
Cable size selection guide, 7-3
Drawings, 3-21
Carbon-arc cutting, 7-30
Drawing views, 3-26
INDEX-1
E
Gas shielded-arc welding (GSAW), 8-1
Electric drive cutting torch carriage, 4-18
Gas tungsten-arc welding (~A~, 8-1
Electrical terms, 7-1
Gas welding, 5-1
Electrodes, 7-6, 8-5
GMAW, 8-14
Electrode angle, 7-12
Gouging mild steel, 4-17
Electrode holder, 7-4
Grinding wheel dresser, 1-10
Electrode selection, 7-27
Ground clamps, 7-4
Electrode sizes, 7-30
~AW welding, 8-1
Etching test, 7-41
common metals, 8-13
Expansion and contraction of metal, 3-17
preparation, 8-8
procedures, 8-9
control of, 3-18
Guided-bend test, 7-39
F
Ferrous metals, 1-4
H
Filler metals, 3-4
Heat colors for steel, 2-2
Filler rods, 5-4, 8-8
Heat treating theory, 2-1
Filler wires, 8-17
Heat treatment, 2-1
Filter lenses, 3-33
annealing, 2-2
Flame hardening methods, 2-6
hardening, 2-4
Flowmeter, 8-6
normalizing, 2-4
Fluxes, 3-5
types of, 2-2
brazing, 6-8
soldering, 6-5
welding, 3-5
Forehand welding, 5-7
I
Impact test, 7-40
Inspection, 7-37
Free bend test, 7-37
radiographic, 7-37
Fusion welding of pipe, 5-13
ultrasonic, 7-37
G
J
Gas flow rates, 8-8
Joints, 3-5
Gas metal arc welding, 8-14
butt, 3-13,8-10
common metals, 8-22
comer, 3-14
equipment, 8-19
edge, 3-15
joints, 8-19
lap, 3-15,8-11
positions, 8-20
tee, 3-14,8-11
preparation, 8-19
Joint designs for brazing, 6-9,6-10
procedures, 8-19
butt joints, 6-9
types of, 8-18
lap joints, 6-9
INDEX-2
Joint designs for brazing—Continued
scarf joints, 6-9
Joint edge preparation, 5-8
Joint preparation, 7-26
P
Pipe welding, 7-25
Preheating, 7-28
Protective equipment, 8-8,8-18
L
Q
Liquid penetrant inspection, 7-35
Line characters and uses, 3-24
Quenching media, 2-8
R
M
Magnetic test, 1-13
Magnetization, 7-33
Magnetic particle inspection, 7-33
Maintenance of oxygas welding equipment, 5-5
MAPP gas, 4-4
Radiographic inspection, 7-37
Regulators, 8-6,8-17
S
Safety, 7-4
equipment, 7-4
cutting tips, 4-12
precautions, 4-23
cylinder, 4-4
regulations, 3-43
safety, 4-4
Metal electrode arc cutting, 7-32
Metal identification, 1-9
Metal properties, 1-1
Metals, 1-4
Service ownership titles, 4-25
Shielded metal-arc welding, 7-1,7-5
Shielding gas, 8-16
Shielding gases for GMAW and GTAW, 8-6,8-7
Shovel teeth, 7-29
N
Spacers, 7-27
Nick-break test, 7-40
Soaking periods for steel, 2-3
Nitriding, 2-5
Soldering, 6-1
Nondestructive testing, 7-33
Soldering equipment, 6-1
coppers, 6-1
Nonfemous metals, 1-6
fluxes, 6-5
O
heat sources, 6-1
Oxide colors, 2-8
solder, 6-4
Oxidizing flame, 4-14
Solder, 6-4
Oxygas cutting equipment, 4-1
Soldering techniques, 6-6
Oxygas cutting operations, 4-13
Spark patterns, 1-11
Oxygas welding equipment, 4-13,5-1,5-4
Spark test, 1-9
Oxygas welding of metals, 5-8
Stages of heat treatment, 2-1
Oxygas welding techniques, 5-6
Steel, 1-5
Oxygen, 4-5
Structural steel, 1-5
Oxygen regulators, 4-6
Surface colors of metals, 1-8
INDEX-3
Symbols, 3-27
Welding-Continued
supplementary, 3-30
fluxes, 5-11
weld, 3-27
forehand, 5-7
gas tungsten arc, 8-1
T
gas shielded metal arc, 3-3
Tack welding, 7-27
gas, 5-1
Tempering steel, 2-7
gas metal-arc, 8-14
Tests, 7-37
gas metal arc welding, 8-14
etching, 7-42
machine operation and maintenance, 7-5
fillet-welded joint, 7-41
machines, 7-2,7-3
free bend, 7-39
motor generator, 7-2
guided bend, 7-39
multilayer, 5-7
impact, 7-40
pipe, 7-25
nick-break, 7-40
positions, 3-16,7-12,7-18,7-21
tensile, strength, 7-42
preparation, 5-11, 8-8
Testing, 7-37
problems and difficulties, 7-24,7-25
destructive, 7-37
procedure specification, 3-22
eddy current, 7-37
procedures, 3-20,6-14,8-9
Torch gas leaks, 5-5
processes, 3-1
Torch tips, 5-4
quality control, 7-33
rectifier, 7-3
W
rods, 5-11
Wearfacing, 6-15,7-27
shielded metal arc, 3-3
Wearfacing materials
tack, 7-27
iron-base alloys, 6-16
techniques, 5-12,7-28
procedures, 6-16
torches, 5-1
tungsten carbide, 6-16
Welds, 3-9
Weld joints, 3-5
parts of, 3-11
parts of, 3-7
Welded joint design, 3-12
types, 3-9
Weld defects, 8-21
Welding, 3-1
burn through, 8-22
allied processes, 3-2
cold lap, 8-22
alternating-current transfer, 7-2
lack of penetration, 8-22
arc, 3-1
porosity, 8-21
area requirements, 7-5
whiskers, 8-22
backhand, 5-7
Wire diameters, 8-17
braze, 6-12
Wire-feed speed, 8-18
equipment, 7-1
Wire stick out, 8-18
INDEX-4
CHAPTER 1
PROPERTIES AND USES OF METAL
An “alloy” is defined as a substance having metallic
properties that is composed of two or more elements.
The elements used as alloying substances are usually
metals or metalloids. The properties of an alloy differ
from the properties of the pure metals or metalloids that
make up the alloy and this difference is what creates the
usefulness of alloys. By combining metals and metalloids, manufacturers can develop alloys that have the
particular properties required for a given use.
In the seabees, Steelworkers are the resident
experts on the properties and uses of metal. We lay
airfields, erect towers and storage tanks, assemble
pontoon causeways, and construct buildings. We use
our expertise to repair metal items, resurface worn
machinery parts, and fabricate all types of metal
objects. To accomplish these tasks proficiently, one
must possess a sound working knowledge of various
metals and their properties. As we learn their different
properties and characteristics, we can then select the
right type of metal and use the proper method to
complete the job. Steelworkers primarily work with
iron and steel; however, we also must become familiar
with the nonferrous metals coming into use more and
more each day. As Steelworkers, we must be able to
identify various metals and to associate their
individual properties with their proper application or
use.
Table 1-1 is a list of various elements and their
symbols that compose metallic materials.
Table 1-1.—Symbols of Base Metals and Alloying Elements
The primary objective of this chapter is to present
a detailed explanation of some of the properties of
different metals and to provide instruction on using
simple tests in establishing their identity.
METAL PROPERTIES
There is no simple definition of metal; however,
any chemical element having “metallic properties” is
classed as a metal. “Metallic properties” are defined
as luster, good thermal and electrical conductivity, and
the capability of being permanently shaped or
deformed at room temperature. Chemical elements
lacking these properties are classed as nonmetals. A
few elements, known as metalloids, sometimes behave
like a metal and at other times like a nonmetal. Some
examples of metalloids are as follows: carbon,
phosphorus, silicon, and sulfur.
Although Steelworkers seldom work with pure
metals, we must be knowledgeable of their properties
because the alloys we work with are combinations of
pure metals. Some of the pure metals discussed in this
chapter are the base metals in these alloys. This is true
of iron, aluminum, and magnesium. Other metals
discussed are the alloying elements present in small
quantities but important in their effect. Among these are
chromium, molybdenum, titanium, and manganese.
1-1
Figure 1-1.—Stress applied to a materiaI.
Common types of stress are compression, tension,
shear, torsion, impact, 1-2 or a combination of these
stresses, such as fatigue. (See fig. 1-1.)
Very rarely do Steelworkers work with elements
in their pure state. We primarily work with alloys and have
to understand their characteristics. The characteristics
of elements and alloys are explained in terms of
physical, chemical, electrical, and mechanical
properties. Physical properties relate to color, density,
weight, and heat conductivity. Chemical properties
involve the behavior of the metal when placed in
contact with the atmosphere, salt water, or other
substances. Electrical properties encompass the
electrical conductivity, resistance, and magnetic
qualities of the metal. The mechanical properties
relate to load-carrying ability, wear resistance,
hardness, and elasticity.
Compression stresses develop within a material
when forces compress or crush the material. A column
that supports an overhead beam is in compression, and
the internal stresses that develop within the column are
compression.
Tension (or tensile) stresses develop when a
material is subject to a pulling load; for example, when
using a wire rope to lift a load or when using it as a
guy to anchor an antenna. “Tensile strength” is defined
as resistance to longitudinal stress or pull and can be
measured in pounds per square inch of cross section.
Shearing stresses occur within a material when
external forces are applied along parallel lines in
opposite directions. Shearing forces can separate
material by sliding part of it in one direction and the
rest in the opposite direction.
When selecting stock for a job, your main
concern is the mechanical properties of the metal.
The various properties of metals and alloys were
determined in the laboratories of manufacturers and
by various societies interested in metallurgical
development. Charts presenting the properties of a
particular metal or alloy are available in many
commercially published reference books. The
charts provide information on the melting point,
tensile strength, electrical conductivity, magnetic
properties, and other properties of a particular metal
or alloy. Simple tests can be conducted to determine
some of the properties of a metal; however, we
normally use a metal test only as an aid for
identifying apiece of stock. Some of these methods
of testing are discussed later in this chapter.
Some materials are equally strong in compression,
tension, and shear. However, many materials show
marked differences; for example, cured concrete has a
maximum strength of 2,000 psi in compression, but
only 400 psi in tension. Carbon steel has a maximum
strength of 56,000 psi in tension and compression but
a maximum shear strength of only 42,000 psi;
therefore, when dealing with maximum strength, you
should always state the type of loading.
A material that is stressed repeatedly usually fails
at a point considerably below its maximum strength in
tension, compression, or shear. For example, a thin
steel rod can be broken by hand by bending it back and
forth several times in the same place; however, if the
same force is applied in a steady motion (not bent back
and forth), the rod cannot be broken. The tendency of
a material to fail after repeated bending at the same
point is known as fatigue.
MECHANICAL PROPERTIES
Strength, hardness, toughness, elasticity, plasticity,
brittleness, and ductility and malleability are
mechanical properties used as measurements of how
metals behave under a load. These properties are
described in terms of the types of force or stress that
the metal must withstand and how these are resisted.
1-2
Table 1-2.—Mechanical Properties of Metals/Alloys
Rockwell “C” number. On nonferrous metals, that are
softer, a metal ball is used and the hardness is indicated
by a Rockwell “B” number. To get an idea of the
property of hardness, compare lead and steel. Lead can
be scratched with a pointed wooden stick but steel
cannot because it is harder than lead.
Strength
Strength is the property that enables a metal to resist
deformation under load. The ultimate strength is the
maximum strain a material can withstand. Tensile
strength is a measurement of the resistance to being
pulled apart when placed in a tension load.
A full explanation of the various methods used to
determine the hardness of a material is available in
commercial books or books located in your base library.
Fatigue strength is the ability of material to resist
various kinds of rapidly changing stresses and is expressed by the magnitude of alternating stress for a
specified number of cycles.
Toughness
Impact strength is the ability of a metal to resist
suddenly applied loads and is measured in foot-pounds
of force.
Toughness is the property that enables a material to
withstand shock and to be deformed without rupturing.
Toughness may be considered as a combination of
strength and plasticity. Table 1-2 shows the order of
some of the more common materials for toughness as
well as other properties.
Hardness
Hardness is the property of a material to resist
permanent indentation. Because there are several methods of measuring hardness, the hardness of a material is
always specified in terms of the particular test that was
used to measure this property. Rockwell, Vickers, or
Brinell are some of the methods of testing. Of these tests,
Rockwell is the one most frequently used. The basic
principle used in the Rockwell testis that a hard material
can penetrate a softer one. We then measure the amount
of penetration and compare it to a scale. For ferrous
metals, which are usually harder than nonferrous metals,
a diamond tip is used and the hardness is indicated by a
Elasticity
When a material has a load applied to it, the load
causes the material to deform. Elasticity is the ability of
a material to return to its original shape after the load is
removed. Theoretically, the elastic limit of a material is
the limit to which a material can be loaded and still
recover its original shape after the load is removed.
1-3
METAL TYPES
Plasticity
The metals that Steelworkers work with are divided
into two general classifications: ferrous and nonferrous.
Ferrous metals are those composed primarily of iron and
iron alloys. Nonferrous metals are those composed primarily of some element or elements other than iron.
Nonferrous metals or alloys sometimes contain a small
amount of iron as an alloying element or as an impurity.
Plasticity is the ability of a material to deform
permanently without breaking or rupturing. This property is the opposite of strength. By careful alloying of
metals, the combination of plasticity and strength is used
to manufacture large structural members. For example,
should a member of a bridge structure become overloaded, plasticity allows the overloaded member to flow
allowing the distribution of the load to other parts of the
bridge structure.
FERROUS METALS
Ferrous metals include all forms of iron and steel
alloys. A few examples include wrought iron, cast iron,
carbon steels, alloy steels, and tool steels. Ferrous metals are iron-base alloys with small percentages of carbon
and other elements added to achieve desirable properties. Normally, ferrous metals are magnetic and nonferrous metals are nonmagnetic.
Brittleness
Brittleness is the opposite of the property of plasticity. A brittle metal is one that breaks or shatters before
it deforms. White cast iron and glass are good examples
of brittle material. Generally, brittle metals are high in
compressive strength but low in tensile strength. As an
example, you would not choose cast iron for fabricating
support beams in a bridge.
Iron
Pure iron rarely exists outside of the laboratory. Iron
is produced by reducing iron ore to pig iron through the
use of a blast furnace. From pig iron many other types
of iron and steel are produced by the addition or deletion
of carbon and alloys. The following paragraphs discuss
the different types of iron and steel that can be made
from iron ore.
Ductility and Malleability
Ductility is the property that enables a material to
stretch, bend, or twist without cracking or breaking. This
property makes it possible for a material to be drawn out
into a thin wire. In comparison, malleability is the
property that enables a material to deform by compressive forces without developing defects. A malleable
material is one that can be stamped, hammered, forged,
pressed, or rolled into thin sheets.
PIG IRON.— Pig iron is composed of about 93%
iron, from 3% to 5% carbon, and various amounts of
other elements. Pig iron is comparatively weak and
brittle; therefore, it has a limited use and approximately
ninety percent produced is refined to produce steel.
Cast-iron pipe and some fittings and valves are manufactured from pig iron.
CORROSION RESISTANCE
Corrosion resistance, although not a mechanical
property, is important in the discussion of metals. Corrosion resistance is the property of a metal that gives it
the ability to withstand attacks from atmospheric,
chemical, or electrochemical conditions. Corrosion,
sometimes called oxidation, is illustrated by the rusting
of iron.
WROUGHT IRON.— Wrought iron is made from
pig iron with some slag mixed in during manufacture.
Almost pure iron, the presence of slag enables wrought
iron to resist corrosion and oxidation. The chemical
analyses of wrought iron and mild steel are just about
the same. The difference comes from the properties
controlled during the manufacturing process. Wrought
iron can be gas and arc welded, machined, plated, and
easily formed; however, it has a low hardness and a
low-fatigue strength.
Table 1-2 lists four mechanical properties and the
corrosion resistance of various metals or alloys. The first
metal or alloy in each column exhibits the best characteristics of that property. The last metal or alloy in each
column exhibits the least. In the column labeled “Toughness,” note that iron is not as tough as copper or nickel;
however, it is tougher than magnesium, zinc, and aluminum. In the column labeled “Ductility,” iron exhibits a
reasonable amount of ductility; however, in the columns
labeled “Malleability” and “Brittleness,” it is last.
CAST IRON.— Cast iron is any iron containing
greater than 2% carbon alloy. Cast iron has a high-compressive strength and good wear resistance; however, it
lacks ductility, malleability, and impact strength. Alloying it with nickel, chromium, molybdenum, silicon, or
vanadium improves toughness, tensile strength, and
1-4
hardness. A malleable cast iron is produced through a
prolonged annealing process.
easily as the low-carbon steels. They are used for crane
hooks, axles, shafts, setscrews, and so on.
INGOT IRON.— Ingot iron is a commercially pure
iron (99.85% iron) that is easily formed and possesses
good ductility and corrosion resistance. The chemical
analysis and properties of this iron and the lowest carbon
steel are practically the same. The lowest carbon steel,
known as dead-soft, has about 0.06% more carbon than
ingot iron. In iron the carbon content is considered an
impurity and in steel it is considered an alloying element. The primary use for ingot iron is for galvanized
and enameled sheet.
HIGH-CARBON STEEL/VERY HIGH-CARBON STEEL.— Steel in these classes respond well to
heat treatment and can be welded. When welding, special electrodes must be used along with preheating and
stress-relieving procedures to prevent cracks in the weld
areas. These steels are used for dies, cutting tools, mill
tools, railroad car wheels, chisels, knives, and so on.
LOW-ALLOY, HIGH-STRENGTH, TEMPERED STRUCTURAL STEEL.— A special lowcarbon steel, containing specific small amounts of
alloying elements, that is quenched and tempered to get
a yield strength of greater than 50,000 psi and tensile
strengths of 70,000 to 120,000 psi. Structural members
made from these high-strength steels may have smaller
cross-sectional areas than common structural steels
and still have equal or greater strength. Additionally,
these steels are normally more corrosion- and abrasionresistant. High-strength steels are covered by ASTM
specifications.
Steel
Of all the different metals and materials that we use
in our trade, steel is by far the most important. When
steel was developed, it revolutionized the American iron
industry. With it came skyscrapers, stronger and longer
bridges, and railroad tracks that did not collapse. Steel
is manufactured from pig iron by decreasing the amount
of carbon and other impurities and adding specific
amounts of alloying elements.
NOTE: This type of steel is much tougher than
low-carbon steels. Shearing machines for this type of
steel must have twice the capacity than that required for
low-carbon steels.
Do not confuse steel with the two general classes of
iron: cast iron (greater than 2% carbon) and pure iron
(less than 0.15% carbon). In steel manufacturing, controlled amounts of alloying elements are added during
the molten stage to produce the desired composition.
The composition of a steel is determined by its application and the specifications that were developed by the
following: American Society for Testing and Materials
(ASTM), the American Society of Mechanical Engineers (ASME), the Society of Automotive Engineers
(SAE), and the American Iron and Steel Institute (AISI).
STAINLESS STEEL.— This type of steel is classified by the American Iron and Steel Institute (AISI)
into two general series named the 200-300 series and
400 series. Each series includes several types of steel
with different characteristics.
The 200-300 series of stainless steel is known as
AUSTENITIC. This type of steel is very tough and
ductile in the as-welded condition; therefore, it is ideal
for welding and requires no annealing under normal
atmospheric conditions. The most well-known types of
steel in this series are the 302 and 304. They are commonly called 18-8 because they are composed of 18%
chromium and 8% nickel. The chromium nickel steels
are the most widely used and are normally nonmagnetic.
Carbon steel is a term applied to a broad range of
steel that falls between the commercially pure ingot iron
and the cast irons. This range of carbon steel may be
classified into four groups:
Low-Carbon Steel . . . . . . . . 0.05% to 0.30% carbon
Medium-Carbon Steel . . . . . . 0.30% to 0.45% carbon
The 400 series of steel is subdivided according to
their crystalline structure into two general groups. One
group is known as FERRITIC CHROMIUM and the
other group as MARTENSITIC CHROMIUM.
High-Carbon Steel . . . . . . . . 0.45% to 0.75% carbon
Very High-Carbon Steel . . . . . 0.75% to 1.70% carbon
LOW-CARBON STEEL.— Steel in this classification is tough and ductile, easily machined, formed,
and welded. It does not respond to any form of heat
treating, except case hardening.
Ferritic Chromium.— This type of steel contains
12% to 27% chromium and 0.08% to 0.20% carbon.
These alloys are the straight chromium grades of stainless steel since they contain no nickel. They are nonhardenable by heat treatment and are normally used in the
annealed or soft condition. Ferritic steels are magnetic
MEDIUM-CARBON STEEL.— These steels are
strong and hard but cannot be welded or worked as
1-5
and frequently used for decorative trim and equipment
subjected to high pressures and temperatures.
to cut after it becomes red-hot. A good grade of this steel
contains from 13% to 19% tungsten, 1% to 2% vanadium, 3% to 5% chromium, and 0.6% to 0.8% carbon.
Because this alloy is expensive to produce, its use is
largely restricted to the manufacture of drills, lathe tools,
milling cutters, and similar cutting tools.
Martensitic Chromium.— These steels are magnetic and are readily hardened by heat treatment. They
contain 12% to 18% chromium, 0.15% to 1.2% carbon,
and up to 2.5% nickel. This group is used where high
strength, corrosion resistance, and ductility are required.
Molybdenum. — This is often used as an alloying
agent for steel in combination with chromium and
nickel. The molybdenum adds toughness to the steel. It
can be used in place of tungsten to make the cheaper
grades of high-speed steel and in carbon molybdenum
high-pressure tubing.
ALLOY STEELS.— Steels that derive their properties primarily from the presence of some alloying
element other than carbon are called ALLOYS or ALLOY STEELS. Note, however, that alloy steels always
contain traces of other elements. Among the more common alloying elements are nickel, chromium, vanadium, silicon, and tungsten. One or more of these
elements may be added to the steel during the manufacturing process to produce the desired characteristics.
Alloy steels may be produced in structural sections,
sheets, plates, and bars for use in the “as-rolled” condition. Better physical properties are obtained with these
steels than are possible with hot-rolled carbon steels.
These alloys are used in structures where the strength of
material is especially important. Bridge members, railroad cars, dump bodies, dozer blades, and crane booms
are made from alloy steel. Some of the common alloy
steels are briefly described in the paragraphs below.
Manganese Steels.— The amount of manganese
used depends upon the properties desired in the finished
product. Small amounts of manganese produce strong,
free-machining steels. Larger amounts (between 2%
and 10%) produce a somewhat brittle steel, while still
larger amounts (11% to 14%) produce a steel that is
tough and very resistant to wear after proper heat treatment.
NONFERROUS METALS
Nonferrous metals contain either no iron or only
insignificant amounts used as an alloy. Some of the more
common nonferrous metals Steelworkers work with are
as follows: copper, brass, bronze, copper-nickel alloys,
lead, zinc, tin, aluminum, and Duralumin.
Nickel Steels.— These steels contain from 3.5%
nickel to 5% nickel. The nickel increases the strength
and toughness of these steels. Nickel steel containing
more than 5% nickel has an increased resistance to
corrosion and scale. Nickel steel is used in the manufacture of aircraft parts, such as propellers and airframe
support members.
NOTE: These metals are nonmagnetic.
Copper
Chromium Steels.— These steels have chromium
added to improve hardening ability, wear resistance, and
strength. These steels contain between 0.20% to 0.75%
chromium and 0.45% carbon or more. Some of these
steels are so highly resistant to wear that they are used
for the races and balls in antifriction bearings. Chromium steels are highly resistant to corrosion and to
scale.
This metal and its alloys have many desirable properties. Among the commercial metals, it is one of the
most popular. Copper is ductile, malleable, hard, tough,
strong, wear resistant, machinable, weldable, and corrosion resistant. It also has high-tensile strength, fatigue
strength, and thermal and electrical conductivity. Copper is one of the easier metals to work with but be careful
because it easily becomes work-hardened; however, this
condition can be remedied by heating it to a cherry red
and then letting it cool. This process, called annealing,
restores it to a softened condition. Annealing and softening are the only heat-treating procedures that apply
to copper. Seams in copper are joined by riveting, silver
brazing, bronze brazing, soft soldering, gas welding, or
electrical arc welding. Copper is frequently used to give
a protective coating to sheets and rods and to make ball
floats, containers, and soldering coppers.
Chrome Vanadium Steel.— This steel has the
maximum amount of strength with the least amount of
weight. Steels of this type contain from 0.15% to 0.25%
vanadium, 0.6% to 1.5% chromium, and 0.1% to 0.6%
carbon. Common uses are for crankshafts, gears, axles,
and other items that require high strength. This steel is
also used in the manufacture of high-quality hand tools,
such as wrenches and sockets.
Tungsten Steel.— This is a special alloy that has the
property of red hardness. This is the ability to continue
1-6
sinks or protect bench tops where a large amount of acid
is used. Lead-lined pipes are used in systems that carry
corrosive chemicals. Frequently, lead is used in alloyed
form to increase its low-tensile strength. Alloyed with
tin, lead produces a soft solder. When added to metal
alloys, lead improves their machinability.
True Brass
This is an alloy of copper and zinc. Additional
elements, such as aluminum, lead, tin, iron, manganese,
or phosphorus, are added to give the alloy specific
properties. Naval rolled brass (Tobin bronze) contains
about 60% copper, 39% zinc, and 0.75% tin. This brass
is highly corrosion-resistant and is practically impurity
free.
CAUTION
Brass sheets and strips are available in several
grades: soft, 1/4 hard, 1/2 hard, full hard, and spring
grades. Hardness is created by the process of cold rolling. All grades of brass can be softened by annealing at
a temperature of 550°F to 600°F then allowing it to cool
by itself without quenching. Overheating can destroy
the zinc in the alloy.
When working with lead, you must take
proper precautions because the dust, fumes, or
vapors from it are highly poisonous.
Zinc
Bronze
You often see zinc used on iron or steel in the form
of a protective coating called galvanizing. Zinc is also
used in soldering fluxes, die castings, and as an alloy in
making brass and bronze.
Bronze is a combination of 84% copper and 16% tin
and was the best metal available before steel-making
techniques were developed. Many complex bronze alloys, containing such elements as zinc, lead, iron, aluminum, silicon, and phosphorus, are now available.
Today, the name bronze is applied to any copper-based
alloy that looks like bronze. In many cases, there is no
real distinction between the composition of bronze and
that of brass.
Tin
Tin has many important uses as an alloy. It can be
alloyed with lead to produce softer solders and with
copper to produce bronze. Tin-based alloys have a high
resistance to corrosion, low-fatigue strength, and a compressive strength that accommodates light or medium
loads. Tin, like lead, has a good resistance to corrosion
and has the added advantage of not being poisonous;
however, when subjected to extremely low temperatures, it has a tendency to decompose.
Copper-Nickel Alloys
Nickel is used in these alloys to make them strong,
tough, and resistant to wear and corrosion. Because of
their high resistance to corrosion, copper nickel alloys,
containing 70% copper and 30% nickel or 90% copper
and 10% nickel, are used for saltwater piping systems.
Small storage tanks and hot-water reservoirs are construtted of a copper-nickel alloy that is available in sheet
form. Copper-nickel alloys should be joined by metalarc welding or by brazing.
Aluminum
This metal is easy to work with and has a good
appearance. Aluminum is light in weight and has a high
strength per unit weight. A disadvantage is that the
tensile strength is only one third of that of iron and one
fifth of that of annealed mild steel.
Lead
A heavy metal that weighs about 710 pounds per
cubic foot. In spite of its weight, lead is soft and malleable and is available in pig and sheet form. In sheet form,
it is rolled upon a rod so the user can unroll it and cut
off the desired amount. The surface of lead is grayish in
color; however, after scratching or scraping it, you can
see that the actual color of the metal is white. Because
it is soft, lead is used as backing material when punching
holes with a hollow punch or when forming shapes by
hammering copper sheets. Sheet lead is also used to line
Aluminum alloys usually contain at least 90% aluminum. The addition of silicon, magnesium, copper,
nickel, or manganese can raise the strength of the alloy
to that of mild steel. Aluminum, in its pure state, is soft
and has a strong affinity for gases. The use of alloying
elements is used to overcome these disadvantages; however, the alloys, unlike the pure aluminum, corrodes
unless given a protective coating. Threaded parts made
of aluminum alloy should be coated with an antiseize
compound to prevent sticking caused by corrosion.
1-7
Table 1-3.—Surface Colors of Some Common Metals
Duralumin
Monel
One of the first of the strong structural aluminum
alloys developed is called Duralumin. With the development of a variety of different wrought-aluminum
alloys, a numbering system was adopted. The digits
indicate the major alloying element and the cold-worked
or heat-treated condition of the metal. The alloy, originally called Duralumin, is now classified in the metal
working industries as 2017-T. The letter T indicates that
the metal is heat-treated.
Monel is an alloy in which nickel is the major
element. It contains from 64% to 68% nickel, about 30%
copper, and small percentages of iron, manganese, and
cobalt. Monel is harder and stronger than either nickel
or copper and has high ductility. It resembles stainless
steel in appearance and has many of its qualities. The
strength, combined with a high resistance to corrosion,
make Monel an acceptable substitute for steel in systems
where corrosion resistance is the primary concern. Nuts,
bolts, screws, and various fittings are made of Monel.
This alloy can be worked cold and can be forged and
welded. If worked in the temperature range between
1200°F and 1600°F, it becomes “hot short” or brittle.
Alclad
This is a protective covering that consists of a thin
sheet of pure aluminum rolled onto the surface of an
aluminum alloy during manufacture. Zinc chromate is
a protective covering that can be applied to an aluminum
surface as needed. Zinc chromate is also used as a primer
on steel surfaces for a protective coating.
K-Monel
This is a special type of alloy developed for greater
strength and hardness than Monel. In strength, it is
1-8
comparable to heat-treated steel. K-monel is used for
instrument parts that must resist corrosion.
Inconel
This high-nickel alloy is often used in the exhaust
systems of aircraft engines. Inconel is composed of
78.5% nickel, 14% chromium, 6.5% iron, and 1% of
other elements. It offers good resistance to corrosion and
retains its strength at high-operating temperatures.
METAL IDENTIFICATION
Figure 1-2.—Terms used in spark testing.
Many methods are used to identify a piece of metal.
Identification is necessary when selecting a metal for
use in fabrication or in determining its weldability.
Some common methods used for field identification are
surface appearance, spark test, chip test, and the use of
a magnet.
SPARK TEST
The spark test is made by holding a sample of the
material against an abrasive wheel. By visually inspecting the spark stream, an experienced metalworker can
identify the metals with considerable accuracy. This test
is fast, economical, convenient, and easily accomplished, and there is no requirement for special equipment. We can use this test for identifying metal salvaged
from scrap. Identification of scrap is particularly important when selecting material for cast iron or cast steel
heat treatment.
SURFACE APPEARANCE
Sometimes it is possible to identify metals by their
surface appearance. Table 1-3 indicates the surface colors of some of the more common metals. Referring to
the table, you can see that the outside appearance of a
metal helps to identify and classify metal. Newly fractured or freshly filed surfaces offer additional clues.
When you hold a piece of iron or steel in contact
with a high-speed abrasive wheel, small particles of the
metal are torn loose so rapidly that they become red-hot.
As these glowing bits of metal leave the wheel, they
follow a path (trajectory) called the carrier line. This
carrier line is easily followed with the eye, especial] y
when observed against a dark background.
A surface examination does not always provide
enough information for identification but should give us
enough information to place the metal into a class. The
color of the metal and the distinctive marks left from
manufacturing help in determining the identity of the
metal. Cast iron and malleable iron usually show evidence of the sand mold. Low-carbon steel often shows
forging marks, and high-carbon steel shows either forging or rolling marks. Feeling the surface may provide
another clue. Stainless steel is slightly rough in the
unfinished state, and the surfaces of wrought iron, copper, brass, bronze, nickel, and Monel are smooth. Lead
also is smooth but has a velvety appearance.
The sparks given off, or the lack of sparks, aid in the
identification of the metal. The length of the spark
stream, the color, and the form of the sparks are features
you should look for. Figure 1-2 illustrates the terms used
in referring to various basic spark forms produced in
spark testing.
Steels having the same carbon content but differing
alloying elements are difficult to identify because the
alloying elements affect the carrier lines, the bursts, or
the forms of characteristic bursts in the spark picture,
The effect of the alloying element may slow or accelerate the carbon spark or make the carrier line lighter or
darker in color. Molybdenum, for example, appears as
a detached, orange-colored spearhead on the end of the
carrier line. Nickel appears to suppress the effect of the
carbon burst; however, the nickel spark can be identified
When the surface appearance of a metal does not
give enough information to allow positive identification, other identification tests become necessary. Some
of these tests are complicated and require equipment we
do not usually have; however, other tests are fairly
simple and reliable when done by a skilled person. Three
of these tests areas follows: the spark test, the chip test,
and the magnetic tests.
1-9
by tiny blocks of brilliant white light. Silicon suppresses
the carbon burst even more than nickel. When silicon is
present, the carrier line usually ends abruptly in a white
flash of light.
l Never overload a grinder or put sideways pressure against the wheel, unless it is expressly built to
withstand such use.
l Always wear appropriate safety goggles or a face
shield while using the grinder. Ensure that the tool rest
(the device that helps the operator hold the work) is
adjusted to the minimum clearance for the wheel. Move
the work across the entire face of the wheel to eliminate
grooving and to minimize wheel dressing. Doing this
prolongs the life of the wheel.
Spark testing may be done with either a portable or
stationary grinder. In either case, the speed on the outer
rim of the wheel should not be less than 4,500 feet per
minute. The abrasive wheel should be rather coarse,
very hard, and kept clean to produce a true spark
To conduct a spark test on an abrasive wheel, hold
the piece of metal on the wheel in a position that allows
the spark stream to cross your line of vision. By trial and
error, you soon discover what pressure is needed to get
a stream of the proper length without reducing the speed
of the grinder. Excessive pressure increases the temperature of the spark stream. This, in turn, increases the
temperature of the burst and gives the appearance of a
higher carbon content than actually is present. When
making the test, watch a point about one third of the
distance from the tail end of the spark stream. Watch
only those sparks that cross your line of vision and try
to forma mental image of the individual spark. Fix this
spark image in your mind and then examine the whole
spark picture.
l Keep your fingers clear of the abrasive surface,
and do not allow rags or clothing to become entangled
in the wheel.
l Do not wear gloves while using an abrasive
wheel.
l Never hold metal with tongs while grinding.
. Never grind nonferrous metals on a wheel intended for ferrous metals because such misuse clogs the
pores of the abrasive material. This buildup of metal
may cause it to become unbalanced and fly apart.
c Grinding wheels require frequent reconditioning. Dressing is the term used to describe the process of
cleaning the periphery. This cleaning breaks away dull
abrasive grains and smooths the surface, removing all
the grooves. The wheel dresser shown in figure 1-3 is
used for dressing grinding wheels on bench and pedestal
grinders. For more information on grinding wheels, you
should consult chapter 5 of NAVEDTRA 10085-B2
(Tools and Their Uses).
While on the subject of abrasive wheels, it is a good
idea to discuss some of the safety precautions associated
with this tool.
l Never use an abrasive wheel that is cracked or
out of balance because the vibration causes the wheel to
shatter. When an abrasive wheel shatters, it can be
disastrous for personnel standing in line with the wheel.
Referring now to figure 1-4, notice that in lowcarbon steel (view A), the spark stream is about 70
inches long and the volume is moderately large. In
high-carbon steel (view B), the stream is shorter (about
55 inches) and the volume larger. The few sparklers that
may occur at any place in low-carbon steel are forked,
l Always check the wheel for secure mounting and
cracks before putting it to use. When you install a new
wheel on a grinder, be sure that it is the correct size.
Remember, as you increase the wheel radius, the peripheral speed at the rim also increases, even though the
driving motor rpm remains the same. Thus, if you should
use an oversized wheel, there is a distinct danger the
peripheral speed (and consequent centrifugal force) can
become so great that the wheel may fly apart. Use
wheels that are designed for a specific rpm. Guards are
placed on grinders as protection in case a wheel should
shatter.
. Never use a grinder when the guards have been
removed. When turning the grinder on, you should stand
to one side. This places you out of line with the wheel
in case the wheel should burst.
Figure 1-3.—Using a grinding wheel dresser.
1-10
Figure 1-4.—Spark patterns formed by common metals.
1-11
Table 1-4.—Metal Identification by Chip Test
and in high-carbon steel, they are small and repeating.
Both metals produce a spark stream white in color.
these metals must be distinguished from each other by
some other method.
Gray cast iron (view C) produces a stream of sparks
about 25 inches in length. The sparklers are small and
repeating, and their volume is rather small. Part of the
stream near the wheel is red, and the outer portion is
straw-colored.
Stainless steel (view E) produces a spark stream
about 50 inches in length, moderate volume, and with
few sparklers. The sparklers are forked. The stream next
to the wheel is straw-colored, and at the end, it is white.
The wrought-iron spark test (view F) produces a
spark stream about 65 inches in length. The stream has
a large volume with few sparklers. The sparks appear
near the end of the stream and are forked. The stream
next to the wheel is straw-colored, and the outer end of
the stream is a brighter red.
Monel and nickel (view D) form almost identical
spark streams. The sparks are small in volume and
orange in color. The sparks form wavy streaks with no
sparklers. Because of the similarity of the spark picture,
1-12
from small, broken fragments to a continuous strip. The
chip may have smooth, sharp edges; it maybe coarsegrained or fine-grained; or it may have sawlike edges.
The size of the chip is important in identifying the metal.
The ease with which the chipping can be accomplished
should also be considered. The information given in
table 1-4 can help you identify various metals by the
chip test.
One way to become proficient in spark testing ferrous metals is to gather an assortment of samples of
known metals and test them. Make all of the samples
about the same size and shape so their identities are not
revealed simply by the size or shape. Number each
sample and prepare a list of names and corresponding
numbers. Then, without looking at the number of the
sample, spark test one sample at a time, calling out its
name to someone assigned to check it against the names
and numbers on the list. Repeating this process gives
you some of the experience you need to become proficient in identifying individual samples.
MAGNETIC TEST
The use of a magnet is another method used to aid
in the general identification of metals. Remember that
ferrous metals, being iron-based alloys, normally are
magnetic, and nonferrous metals are nonmagnetic. This
test is not 100-percent accurate because some stainless
steels are nonmagnetic. In this instance, there is no
substitute for experience.
CHIP TEST
Another simple test used to identify an unknown
piece of metal is the chip test. The chip testis made by
removing a small amount of material from the test piece
with a sharp, cold chisel. The material removed varies
1-13
CHAPTER 2
BASIC HEAT TREATMENT
As Steelworkers, we are interested in the heat treatment of metals, because we have to know what effects
the heat produced by welding or cutting has on metal.
We also need to know the methods used to restore metal
to its original condition. The process of heat treating is
the method by which metals are heated and cooled in a
series of specific operations that never allow the metal
to reach the molten state. The purpose of heat treating is
to make a metal more useful by changing or restoring
its mechanical properties. Through heat treating, we can
make a metal harder, stronger, and more resistant to
impact. Also, heat treating can make a metal softer and
more ductile. The one disadvantage is that no heat-treating procedure can produce all of these characteristics in
one operation. Some properties are improved at the
expense of others; for example, hardening a metal may
make it brittle.
water vapor, and other various hydrocarbons. Fuel-fired
furnaces can provide three distinct atmospheres when
you vary the proportions of air and fuel. They are called
oxidizing, reducing, and neutral.
STAGES OF HEAT TREATMENT
Heat treating is accomplished in three major stages:
l Stage l—Heating the metal slowly to ensure a
uniform temperature
l Stage 2—Soaking (holding) the metal at a given
temperature for a given time and cooling the
metal to room temperature
l Stage 3—Cooling the metal to room temperature
HEATING STAGE
HEAT-TREATING THEORY
The primary objective in the heating stage is to
maintain uniform temperatures. If uneven heating occurs, one section of a part can expand faster than another
and result in distortion or cracking. Uniform temperatures are attained by slow heating.
The various types of heat-treating processes are
similar because they all involve the heating and cooling
of metals; they differ in the heating temperatures and the
cooling rates used and the final results. The usual methods of heat-treating ferrous metals (metals with iron) are
annealing, normalizing, hardening, and tempering.
Most nonferrous metals can be annealed, but never
tempered, normalized, or case-hardened.
The heating rate of a part depends on several factors.
One important factor is the heat conductivity of the
metal. A metal with a high-heat conductivity heats at a
faster rate than one with a low conductivity. Also, the
condition of the metal determines the rate at which it
may be heated. The heating rate for hardened tools and
parts should be slower than unstressed or untreated
metals. Finally, size and cross section figure into the
heating rate. Parts with a large cross section require
slower heating rates to allow the interior temperature to
remain close to the surface temperature that prevents
warping or cracking. Parts with uneven cross sections
experience uneven heating; however, such parts are less
apt to be cracked or excessively warped when the heating rate is kept slow.
Successful heat treatment requires close control
over all factors affecting the heating and cooling of a
metal. This control is possible only when the proper
equipment is available. The furnace must be of the
proper size and type and controlled, so the temperatures
are kept within the prescribed limits for each operation.
Even the furnace atmosphere affects the condition of the
metal being heat-treated.
The furnace atmosphere consists of the gases that
circulate throughout the heating chamber and surround
the metal, as it is being heated. In an electric furnace,
the atmosphere is either air or a controlled mixture of
gases. In a fuel-fired furnace, the atmosphere is the
mixture of gases that comes from the combination of the
air and the gases released by the fuel during combustion.
These gases contain various proportions of carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen,
SOAKING STAGE
After the metal is heated to the proper temperature,
it is held at that temperature until the desired internal
structural changes take place. This process is called
SOAKING. The length of time held at the proper
2-1
is used for metals that require a rapid cooling rate, and
oil mixtures are more suitable for metals that need a
slower rate of cooling. Generally, carbon steels are
water-hardened and alloy steels are oil-hardened. Nonferrous metals are normally quenched in water.
temperature is called the SOAKING PERIOD. The
soaking period depends on the chemical analysis of the
metal and the mass of the part. When steel parts are
uneven in cross section, the soaking period is determined by the largest section.
During the soaking stage, the temperature of the
metal is rarely brought from room temperature to the
final temperature in one operation; instead, the steel is
slowly heated to a temperature just below the point at
which the change takes place and then it is held at that
temperature until the heat is equalized throughout the
metal. We call this process PREHEATING. Following
preheat, the metal is quickly heated to the final required
temperature.
HEAT COLORS FOR STEEL
You are probably familiar with the term red-hot as
applied to steel. Actually, steel takes on several colors
and shades from the time it turns a dull red until it
reaches a white heat. These colors and the corresponding temperatures are listed in table 2-1.
During hardening, normalizing, and annealing,
steel is heated to various temperatures that produce
color changes. By observing these changes, you can
determine the temperature of the steel. As an example,
assume that you must harden a steel part at 1500°F. Heat
the part slowly and evenly while watching it closely for
any change in color. Once the steel begins to turn red,
carefully note each change in shade. Continue the even
heating until the steel is bright red; then quench the part.
When apart has an intricate design, it may have to
be preheated at more than one temperature to prevent
cracking and excessive warping. For example, assume
an intricate part needs to be heated to 1500°F for hardening. This part could be slowly heated to 600°F, soaked
at this temperature, then heated slowly to 1200°F, and
then soaked at that temperature. Following the final
preheat, the part should then be heated quickly to the
hardening temperature of 1500°F.
The success of a heat-treating operation depends
largely on your judgment and the accuracy with which
you identify each color with its corresponding temperature. From a study of table 2-1, you can see that close
observation is necessary. You must be able to tell the
difference between faint red and blood red and between
dark cherry and medium cherry. To add to the difficulty,
your conception of medium cherry may differ from that
of the person who prepared the table. For an actual
heat-treating operation, you should get a chart showing
the actual colors of steel at various temperatures.
NOTE: Nonferrous metals are seldom preheated,
because they usually do not require it, and preheating
can cause an increase in the grain size in these metals.
COOLING STAGE
After a metal has been soaked, it must be returned
to room temperature to complete the heat-treating process. To cool the metal, you can place it in direct contact
with a COOLING MEDIUM composed of a gas, liquid,
solid, or combination of these. The rate at which the
metal is cooled depends on the metal and the properties
desired. The rate of cooling depends on the medium;
therefore, the choice of a cooling medium has an important influence on the properties desired.
TYPES OF HEAT TREATMENT
Four basic types of heat treatment are used today.
They are annealing, normalizing, hardening, and tempering. The techniques used in each process and how
they relate to Steelworkers are given in the following
paragraphs.
Quenching is the procedure used for cooling metal
rapidly in oil, water, brine, or some other medium.
Because most metals are cooled rapidly during the hardening process, quenching is usually associated with
hardening; however, quenching does not always result
in an increase in hardness; for example, to anneal copper, you usually quench it in water. Other metals, such
as air-hardened steels, are cooled at a relatively slow rate
for hardening.
ANNEALING
In general, annealing is the opposite of hardening,
You anneal metals to relieve internal stresses, soften
them, make them more ductile, and refine their grain
structures. Annealing consists of heating a metal to a
specific temperature, holding it at that temperature for
a set length of time, and then cooling the metal to room
temperature. The cooling method depends on the
Some metals crack easily or warp during quenching,
and others suffer no ill effects; therefore, the quenching
medium must be chosen to fit the metal. Brine or water
2-2
Table 2-1.—Heat Colors for Steel
Table 2-2.—Approximate Soaking Periods for Hardening, Annealing, and Normalizing Steel
Ferrous Metal
metal and the properties desired. Some metals are
furnace-cooled, and others are cooled by burying them
To produce the maximum softness in steel, you heat
the metal to its proper temperature, soak it, and then let
it cool very slowly. The cooling is done by burying the
hot part in an insulating material or by shutting off the
furnace and allowing the furnace and the part to cool
together. The soaking period depends on both the mass
of the part and the type of metal. The approximate
soaking periods for annealing steel are given in tablc
2-2.
in ashes, lime, or other insulating materials.
Welding produces areas that have molten metal next
to other areas that are at room temperature. As the weld
cools, internal stresses occur along with hard spots and
brittleness. Welding can actually weaken the metal.
Annealing is just one of the methods for correcting these
problems.
2-3
Steel with an extremely low-carbon content requires the highest annealing temperature. As the carbon
content increases, the annealing temperatures decrease.
HARDENING
The hardening treatment for most steels consists of
heating the steel to a set temperature and then cooling it
rapidly by plunging it into oil, water, or brine. Most
steels require rapid cooling (quenching) for hardening
but a few can be air-cooled with the same results.
Hardening increases the hardness and strength of the
steel, but makes it less ductile. Generally, the harder the
steel, the more brittle it becomes. To remove some of
the brittleness, you should temper the steel after hardening.
Nonferrous Metal
Copper becomes hard and brittle when mechanically worked; however, it can be made soft again by
annealing. The annealing temperature for copper is between 700°F and 900°F. Copper maybe cooled rapidly
or slowly since the cooling rate has no effect on the heat
treatment. The one drawback experienced in annealing
copper is the phenomenon called “hot shortness.” At
about 900°F, copper loses its tensile strength, and if not
properly supported, it could fracture.
Many nonferrous metals can be hardened and their
strength increased by controlled heating and rapid cooling. In this case, the process is called heat treatment,
rather than hardening.
Aluminum reacts similar to copper when heat treating. It also has the characteristic of “hot shortness.” A
number of aluminum alloys exist and each requires
special heat treatment to produce their best properties.
To harden steel, you cool the metal rapidly after
thoroughly soaking it at a temperature slightly above its
upper critical point. The approximate soaking periods
for hardening steel are listed in table 2-2. The addition
of alloys to steel decreases the cooling rate required to
produce hardness. A decrease in the cooling rate is an
advantage, since it lessens the danger of cracking and
warping.
NORMALIZING
Normalizing is a type of heat treatment applicable
to ferrous metals only. It differs from annealing in that
the metal is heated to a higher temperature and then
removed from the furnace for air cooling.
Pure iron, wrought iron, and extremely low-carbon
steels have very little hardening properties and are difficult to harden by heat treatment. Cast iron has limited
capabilities for hardening. When you cool cast iron
rapidly, it forms white iron, which is hard and brittle.
And when you cool it slowly, it forms gray iron, which
is soft but brittle under impact.
The purpose of normalizing is to remove the internal
stresses induced by heat treating, welding, casting, forging, forming, or machining. Stress, if not controlled,
leads to metal failure; therefore, before hardening steel,
you should normalize it first to ensure the maximum
desired results. Usually, low-carbon steels do not require normalizing; however, if these steels are normalized, no harmful effects result. Castings are usually
annealed, rather than normalized; however, some castings require the normalizing treatment. Table 2-2 shows
the approximate soaking periods for normalizing steel.
Note that the soaking time varies with the thickness of
the metal.
In plain carbon steel, the maximum hardness obtained by heat treatment depends almost entirely on the
carbon content of the steel. As the carbon content increases, the hardening ability of the steel increases;
however, this capability of hardening with an increase
in carbon content continues only to a certain point. In
practice, 0.80 percent carbon is required for maximum
hardness. When you increase the carbon content beyond
0.80 percent, there is no increase in hardness, but there
is an increase in wear resistance. This increase in wear
resistance is due to the formation of a substance called
hard cementite.
Normalized steels are harder and stronger than annealed steels. In the normalized condition, steel is much
tougher than in any other structural condition. Parts
subjected to impact and those that require maximum
toughness with resistance to external stress are usually
normalized. In normalizing, the mass of metal has an
influence on the cooling rate and on the resulting structure. Thin pieces cool faster and are harder after normalizing than thick ones. In annealing (furnace cooling), the
hardness of the two are about the same.
When you alloy steel to increase its hardness, the
alloys make the carbon more effective in increasing
hardness and strength. Because of this, the carbon content required to produce maximum hardness is lower
than it is for plain carbon steels. Usually, alloy steels are
superior to carbon steels.
2-4
heated in a furnace. To cool the parts, you can leave the
container in the furnace to cool or remove it and let it
air cool. In both cases, the parts become annealed during
the slow cooling. The depth of the carbon penetration
depends on the length of the soaking period. With today’s methods, carburizing is almost exclusively done
by gas atmospheres.
Carbon steels are usually quenched in brine or
water, and alloy steels are generally quenched in oil.
When hardening carbon steel, remember that you must
cool the steel to below 1000°F in less than 1 second.
When you add alloys to steel, the time limit for the
temperature to drop below 1000°F increases above the
l-second limit, and a slower quenching medium can
produce the desired hardness.
CYANIDING.— This process is a type of case
hardening that is fast and efficient. Preheated steel is
dipped into a heated cyanide bath and allowed to soak.
Upon removal, it is quenched and then rinsed to remove
any residual cyanide. This process produces a thin, hard
shell that is harder than the one produced by carburizing
and can be completed in 20 to 30 minutes vice several
hours. The major drawback is that cyanide salts are a
deadly poison.
Quenching produces extremely high internal
stresses in steel, and to relieve them, you can temper the
steel just before it becomes cold. The part is removed
from the quenching bath at a temperature of about 200°F
and allowed to air-cool. The temperature range from
200°F down to room temperature is called the “cracking
range” and you do not want the steel to pass through it.
In the following paragraphs, we discuss the different methods of hardening that are commercially used.
In the Seabees, we use a rapid surface hardening compound called “Case” that can be ordered through the
Navy supply system. Information on the use of “Case”
is located in the Welding Materials Handbook, P-433.
NITRIDING.— This case-hardening method produces the hardest surface of any of the hardening processes. It differs from the other methods in that the
individual parts have been heat-treated and tempered
before nitriding. The parts are then heated in a furnace
that has an ammonia gas atmosphere. No quenching is
required so there is no worry about warping or other
types of distortion. This process is used to case harden
items, such as gears, cylinder sleeves, camshafts and
other engine parts, that need to be wear resistant and
operate in high-heat areas.
Case Hardening
Case hardening produces a hard, wear-resistant surface or case over a strong, tough core. The principal
forms of casehardening are carburizing, cyaniding, and
nitriding. Only ferrous metals are case-hardened.
Case hardening is ideal for parts that require a
wear-resistant surface and must be tough enough internally to withstand heavy loading. The steels best suited
for case hardening are the low-carbon and low-alloy
series. When high-carbon steels are case-hardened, the
hardness penetrates the core and causes brittleness. In
case hardening, you change the surface of the metal
chemically by introducing a high carbide or nitride
content. The core remains chemically unaffected. When
heat-treated, the high-carbon surface responds to hardening, and the core toughens.
Flame Hardening
Flame hardening is another procedure that is used
to harden the surface of metal parts. When you use an
oxyacetylene flame, a thin layer at the surface of the part
is rapidly heated to its critical temperature and then
immediately quenched by a combination of a water
spray and the cold base metal. This process produces a
thin, hardened surface, and at the same time, the internal
parts retain their original properties. Whether the process is manual or mechanical, a close watch must be
maintained, since the torches heat the metal rapidly and
the temperatures are usually determined visually.
CARBURIZING.— Carburizing is a case-hardening process by which carbon is added to the surface of
low-carbon steel. This results in a carburized steel that
has a high-carbon surface and a low-carbon interior.
When the carburized steel is heat-treated, the case becomes hardened and the core remains soft and tough.
Flame hardening may be either manual or automatic. Automatic equipment produces uniform results and
is more desirable. Most automatic machines have variable travel speeds and can be adapted to parts of various
sizes and shapes. The size and shape of the torch depends on the part. The torch consists of a mixing head,
straight extension tube, 90-degree extension head, an
adjustable yoke, and a water-cooled tip. Practically any
shape or size flame-hardening tip is available (fig. 2-1).
Two methods are used for carburizing steel. One
method consists of heating the steel in a furnace containing a carbon monoxide atmosphere. The other
method has the steel placed in a container packed with
charcoal or some other carbon-rich material and then
2-5
Figure 2-2.—Progressive hardening.
Figure 2-1.—Progressive hardening torch tip.
hardening produces a hard case that is highly resistant
to wear and a core that retains its original properties.
Tips are produced that can be used for hardening flats,
rounds, gears, cams, cylinders, and other regular or
irregular shapes.
Flame hardening can be divided into five general
methods: stationary, circular band progressive, straightline progressive, spiral band progressive, and circular
band spinning.
STATIONARY METHOD.— In this method the
torch and the metal part are both held stationary.
In hardening localized areas, you should heat the
metal with a standard hand-held welding torch. Adjust
the torch flame to neutral (see chapter 4) for normal
heating; however, in corners and grooves, use a slightly
oxidizing flame to keep the torch from sputtering. You
also should particularly guard against overheating in
comers and grooves. If dark streaks appear on the metal
surface, this is a sign of overheating, and you need to
increase the distance between the flame and the metal.
CIRCULAR BAND PROGRESSIVE METHOD.—
This method is used for hardening outside surfaces of
round sections. Usually, the object is rotated in front of
a stationary torch at a surface speed of from 3 to 12
inches per minute. The heating and quenching are done
progressively, as the part rotates; therefore, when the
part has completed one rotation, a hardened band encircles the part. The width of the hardened band depends
upon the width of the torch tip. To harden the full length
of a long section, you can move the torch and repeat the
process over and over until the part is completely hardened. Each pass or path of the torch should overlap the
previous one to prevent soft spots.
For the best heating results, hold the torch with the
tip of the inner cone about an eighth of an inch from the
surface and direct the flame at right angles to the metal.
Sometimes it is necessary to change this angle to obtain
better results; however, you rarely find a deviation of
more than 30 degrees. Regulate the speed of torch travel
according to the type of metal, the mass and shape of the
part, and the depth of hardness desired.
STRAIGHT-LINE PROGRESSIVE METHOD.—
With the straight-line progressive method, the torch
travels along the surface, treating a strip that is about the
same width as the torch tip. To harden wider areas, you
move the torch and repeat the process. Figure 2-2 is an
example of progressive hardening.
In addition, you must select the steel according to
the properties desired. Select carbon steel when surface
hardness is the primary factor and alloy steel when the
physical properties of the core are also factors. Plain
carbon steels should contain more than 0.35% carbon
for good results inflame hardening. For water quenching, the effective carbon range is from 0.40% to 0.70%.
Parts with a carbon content of more than 0.70% are
likely to surface crack unless the heating and quenching
rate are carefully controlled.
SPIRAL BAND PROGRESSIVE METHOD.—
For this technique a cylindrical part is mounted between
lathe centers, and a torch with an adjustable holder is
mounted on the lathe carriage. As the part rotates, the
torch moves parallel to the surface of the part. This travel
is synchronized with the parts rotary motion to produce
a continuous band of hardness. Heating and quenching
occur at the same time. The number of torches required
depends on the diameter of the part, but seldom are more
than two torches used.
The surface hardness of a flame-hardened section is
equal to a section that was hardened by furnace heating
and quenching. The decrease in hardness between the
case and the core is gradual. Since the core is not
affected by flame hardening, there is little danger of
spalling or flaking while the part is in use. Thus flame
CIRCULAR BAND SPINNING METHOD.—
The circular band spinning method provides the best
2-6
is more than 1 inch thick, increase the time by 1 hour for
each additional inch of thickness.
results for hardening cylindrical parts of small or medium diameters. The part is mounted between lathe
centers and turned at a high rate of speed pasta stationary torch. Enough torches are placed side by side to heat
the entire part. The part can be quenched by water
flowing from the torch tips or in a separate operation.
Normally, the rate of cooling from the tempering
temperature has no effect on the steel. Steel parts are
usually cooled in still air after being removed from the
tempering furnace; however, there are a few types of
steel that must be quenched from the tempering temperature to prevent brittleness. These blue brittle steels
can become brittle if heated in certain temperature
ranges and allowed to cool slowly. Some of the nickel
chromium steels are subject to this temper brittleness.
When you perform heating and quenching as separate operations, the tips are water-cooled internally, but
no water sprays onto the surface of the part.
In flame hardening, you should follow the same
safety precautions that apply to welding (see chapter 3).
In particular, guard against holding the flame too close
to the surface and overheating the metal. In judging the
temperature of the metal, remember that the flame
makes the metal appear colder than it actually is.
Steel may be tempered after being normalized, providing there is any hardness to temper. Annealed steel is
impossible to temper. Tempering relieves quenching
stresses and reduces hardness and brittleness. Actually,
the tensile strength of a hardened steel may increase as
the steel is tempered up to a temperature of about 450°F.
Above this temperature it starts to decrease. Tempering
increases softness, ductility, malleability, and impact
resistance. Again, high-speed steel is an exception to the
rule. High-speed steel increases in hardness on tempering, provided it is tempered at a high temperature (about
1550°F). Remember, all steel should be removed from
the quenching bath and tempered before it is complete] y
cold. Failure to temper correctly results in a quick failure
of the hardened part.
TEMPERING
After the hardening treatment is applied, steel is
often harder than needed and is too brittle for most
practical uses. Also, severe internal stresses are set up
during the rapid cooling from the hardening temperature. To relieve the internal stresses and reduce brittleness, you should temper the steel after it is hardened.
Tempering consists of heating the steel to a specific
temperature (below its hardening temperature), holding
it at that temperature for the required length of time, and
then cooling it, usually instill air. The resultant strength,
hardness, and ductility depend on the temperature to
which the steel is heated during the tempering process.
Permanent steel magnets are made of special alloys
and are heat-treated by hardening and tempering. Hardness and stability are the most important properties in
permanent magnets. Magnets are tempered at the minimum tempering temperature of 212°F by placing them
in boiling water for 2 to 4 hours. Because of this lowtempering temperature, magnets are very hard.
The purpose of tempering is to reduce the brittleness
imparted by hardening and to produce definite physical
properties within the steel. Tempering always follows,
never precedes, the hardening operation. Besides reducing brittleness, tempering softens the steel. That is unavoidable, and the amount of hardness that is lost
depends on the temperature that the steel is heated to
during the tempering process. That is true of all steels
except high-speed steel. Tempering increases the hardness of high-speed steel.
Case-hardened parts should not be tempered at too
high a temperature or they may loose some of their
hardness. Usually, a temperature range from 212°F to
400°F is high enough to relieve quenching stresses.
Some metals require no tempering. The design of the
part helps determine the tempering temperature.
Color tempering is based on the oxide colors that
appear on the surface of steel, as it is heated. When you
slowly heat a piece of polished hardened steel, you can
see the surface turn various colors as the temperature
changes. These colors indicate structural changes are
taking place within the metal. Once the proper color
appears, the part is rapidly quenched to prevent further
structural change. In color tempering, the surface of the
steel must be smooth and free of oil. The part may be
heated by a torch, in a furnace, over a hot plate, or by
radiation.
Tempering is always conducted at temperatures below the low-critical point of the steel. In this respect,
tempering differs from annealing, normalizing, and
hardening in which the temperatures are above the upper
critical point. When hardened steel is reheated, tempering begins at 212°F and continues as the temperature
increases toward the low-critical point. By selecting a
definite tempering temperature, you can predetermine
the resulting hardness and strength. The minimum temperature time for tempering should be 1 hour. If the part
2-7
Table 2-3.—0xide Colors for Tempering Steel
cutting edge. When you have completed the above described process, the chisel will be hardened and tempered and only needs grinding.
Cold chisels and similar tools must have hard cutting edges and softer bodies and heads. The head must
be tough enough to prevent shattering when struck with
shammer.The cutting edge must be more than twice as
hard as the head, and the zone separating the two must
be carefully blended to prevent a lineof demarcation. A
method of color tempering frequently used for chisels
and similar tools is one in which the cutting end is heated
by the residual heat of the opposite end of the same tool.
To harden and tempera cold chisel by this method, you
heat the tool to the proper hardening temperature and
then quench the cutting end only. Bob the chisel up and
down in the bath, always keeping the cutting edge below
the surface. This method air-cools the head while rapidly
quenching the cutting edge. The result is a tough head,
fully hardened cutting edge, and a properly blended
structure.
During the tempering, the oxide color at which you
quench the steel varies with the properties desired in the
part. Table 2-3 lists the different colors and their corresponding temperatures. To see the colors clearly, you
must turn the part from side to side and have good
lighting. While hand tempering produces the same result
as furnace tempering, there is a greater possibility for
error. The slower the operation is performed, the more
accurate are the results obtained.
QUENCHING MEDIA
The cooling rate of an object depends on many
things. The size, composition, and initial temperature of
the part and final properties are the deciding factors in
selecting the quenching medium. A quenching medium
must cool the metal at a rate rapid enough to produce
the desired results.
When the cutting end has cooled, remove the chisel
from the bath and quickly polish the cutting end with a
buff stick (emery). Watch the polished surface, as the
heat from the opposite end feeds back into the quenched
end. As the temperature of the hardened end increases,
oxide colors appear. These oxide colors progress from
pale yellow, to a straw color, and end in blue colors. As
soon as the correct shade of blue appears, quench the
entire chisel to prevent further softening of the cutting
edge. The metal is tempered as soon as the proper oxide
color appears and quenching merely prevents further
tempering by freezing the process. This final quench has
no effect on the body and the head of the chisel, because
their temperature will have dropped below the critical
point by the time the proper oxide color appears on the
Mass affects quenching in that as the mass increases, the time required for complete cooling also
increases. Even though parts are the same size, those
containing holes or recesses cool more rapidly than solid
objects. The composition of the metal determines the
maximum cooling rate possible without the danger of
cracking or warping. This critical cooling rate, in turn,
influences the choice of the quenching medium.
The cooling rate of any quenching medium varies
with its temperature; therefore, to get uniform results,
2-8
you must keep the temperature within prescribed limits.
The absorption of heat by the quenching medium also
depends, to a large extent, on the circulation of the
quenching medium or the movement of the part. Agitation of the liquid or the part breaks up the gas that forms
an insulating blanket between the part and the liquid.
Normally, hardening takes place when you quench
a metal. The composition of the metal usually determines the type of quench to use to produce the desired
hardness. For example, shallow-hardened low-alloy and
carbon steels require severer quenching than deep-hardened alloy steels that contain large quantities of nickel,
manganese, or other elements. Therefore, shallow-hardening steels are usually quenched in water or brine, and
the deep-hardening steels are quenched in oil. Sometimes it is necessary to use a combination quench,
starting with brine or water and finishing with oil. In
addition to producing the desired hardness, the quench
must keep cracking, warping, and soft spots to a minimum.
Figure 2-3.—Portable quench tank.
coils. Self-contained coolers are integral parts of large
quench tanks.
The volume of quenching liquid should be large
enough to absorb all the heat during a normal quenching
operation without the use of additional cooling. As more
metals are quenched, the liquid absorbs the heat and this
temperature rise causes a decrease in the cooling rate.
Since quenching liquids must be maintained within
definite temperature ranges, mechanical means are used
to keep the temperature at prescribed levels during
continuous operations.
A typical portable quench tank is shown in figure
2-3. This type can be moved as needed to various parts
of the heat-treating shop. Some tanks may have one or
more compartments. If one compartment contains oil
and the other water, the partition must be liquid-tight to
prevent mixing. Each compartment has a drain plug, a
screen in the bottom to catch scale and other foreign
matter, and a mesh basket to hold the parts. A portable
electric pump can be attached to the rim of the tank to
circulate the liquid. This mechanical agitation aids in
uniform cooling.
LIQUID QUENCHING
Water
The two methods used for liquid quenching are
called still-bath and flush quenching.
Water can be used to quench some forms of steel,
but does not produce good results with tool or other alloy
steels. Water absorbs large quantities of atmospheric
gases, and when a hot piece of metal is quenched, these
gases have a tendency to form bubbles on the surface of
the metal. These bubbles tend to collect in holes or
recesses and can cause soft spots that later lead to
cracking or warping.
Instill-bath quenching, you cool the metal in a tank
of liquid. The only movement of the liquid is that caused
by the movement of the hot metal, as it is being
quenched.
For flush quenching, the liquid is sprayed onto the
surface and into every cavity of the part at the same time
to ensure uniform cooling. Flush quenching is used for
parts having recesses or cavities that would not be
properly quenched by ordinary methods. That assures a
thorough and uniform quench and reduces the possibilities of distortion.
The water in the quench tank should be changed
daily or more often if required. The quench tank should
be large enough to hold the part being treated and should
have adequate circulation and temperature control. The
temperature of the water should not exceed 65°F.
When aluminum alloys and other nonferrous metals
require a liquid quench, you should quench them in
clean water. The volume of water in the quench tank
should be large enough to prevent a temperature rise of
more than 20°F during a single quenching operation. For
Quenching liquids must be maintained at uniform
temperatures for satisfactory results. That is particularly
true for oil. To keep the liquids at their proper temperature, they are usually circulated through water-cooled
2-9
Table 2-4.—Properties and Average Cooling Abilities of Quenching Media
can cause cracking or stress in high-carbon or low-alloy
steels that are uneven in cross section.
heavy-sectioned parts, the temperature rise may exceed
20°F, but should be kept as low as possible. For wrought
products, the temperature of the water should be about
65°F and should never exceed 100°F before the piece
enters the liquid.
Because of the corrosive action of salt on nonferrous metals, these metals are not quenched in brine.
Oil
Brine
Oil is used to quench high-speed and oil-hardened
steels and is preferred for all other steels provided that
the required hardness can be obtained. Practically any
type of quenching oil is obtainable, including the various animal oils, fish oils, vegetable oils, and mineral
oils. Oil is classed as an intermediate quench. It has a
slower cooling rate than brine or water and a faster rate
than air. The quenching oil temperature should be kept
within a range of 80°F to 150°F. The properties and
average cooling powers of various quenching oils are
given in table 2-4.
Brine is the result of dissolving common rock salt
in water. This mixture reduces the absorption of atmospheric gases that, in turn, reduces the amount of bubbles.
As a result, brine wets the metal surface and cools it
more rapidly than water. In addition to rapid and uniform cooling, the brine removes a large percentage of
any scale that may be present.
The brine solution should contain from 7% to 10%
salt by weight or three-fourths pound of salt for each
gallon of water. The correct temperature range for a
brine solution is 65°F to 100°F.
Water usually collects in the bottom of oil tanks but
is not harmful in small amounts. In large quantities it
can interfere with the quenching operations; for example, the end of a long piece may extend into the water at
Low-alloy and carbon steels can be quenched in
brine solutions; however, the rapid cooling rate of brine
2-10
the bottom of the tank and crack as a result of the more
rapid cooling.
Air quenching is used for cooling some highly
alloyed steels. When you use still air, each tool or part
should be placed on a suitable rack so the air can reach
all sections of the piece. Parts cooled with circulated air
are placed in the same manner and arranged for uniform
cooling. Compressed air is used to concentrate the cooling on specific areas of a part. The airlines must be free
of moisture to prevent cracking of the metal.
Nonferrous metals are not routinely quenched in oil
unless specifications call for oil quenching.
Caustic Soda
A solution of water and caustic soda, containing 10
percent caustic soda by weight, has a higher cooling rate
than water. Caustic soda is used only for those types of
steel that require extremely rapid cooling and is NEVER
used as a quench for nonferrous metals.
Although nonferrous metals are usually quenched
in water, pieces that are too large to fit into the quench
tank can be cooled with forced-air drafts; however, an
air quench should be used for nonferrous metal only
when the part will not be subjected to severe corrosion
conditions and the required strength and other physical
properties can be developed by a mild quench.
WARNING
CAUSTIC SODA REQUIRES SPECIAL
HANDLING BECAUSE OF ITS HARMFUL
EFFECTS ON SKIN AND CLOTHING.
Solids
The solids used for cooling steel parts include castiron chips, lime, sand, and ashes. Solids are generally
used to slow the rate of cooling; for example, a cast-iron
part can be placed in a lime box after welding to prevent
cracking and warping. All solids must be free of moisture to prevent uneven cooling.
DRY QUENCHING
This type of quenching uses materials other than
liquids. Inmost cases, this method is used only to slow
the rate of cooling to prevent warping or cracking.
2-11
CHAPTER 3
INTRODUCTION TO WELDING
most common welding process. The primary differences between the various welding processes are the
methods by which heat is generated to melt the metal.
Once you understand the theory of welding, you can
apply it to most welding processes.
In the Navy as well as private industry, welding is
widely used by metalworkers in the fabrication, maintenance, and repair of parts and structures. While there
are many methods for joining metals, welding is one of
the most convenient and rapid methods available. The
term welding refers to the process of joining metals by
heating them to their melting temperature and causing
the molten metal to flow together. These range from
simple steel brackets to nuclear reactors.
The most common types of welding are oxyfuel gas
welding (OFW), arc welding (AW), and resistance
welding (RW). As a Steelworker, your primary concern
is gas and arc welding. The primary difference between
these two processes is the method used to generate the
heat.
Welding, like any skilled trade, is broad in scope and
you cannot become a welder simply by reading a book.
You need practice and experience as well as patience;
however, much can be gained through study. For instance, by learning the correct method or procedure for
accomplishing a job from a book, you may eliminate
many mistakes that otherwise would occur through trial
and error.
GAS WELDING
One of the most popular welding methods uses a gas
flame as a source of heat. In the oxyfuel gas welding
process (fig. 3-2), heat is produced by burning a combustible gas, such as MAPP (methylacetylene-propadiene) or acetylene, mixed with oxygen. Gas welding is
widely used in maintenance and repair work because of
the ease in transporting oxygen and fuel cylinders. Once
you learn the basics of gas welding, you will find the
oxyfuel process adaptable to brazing, cutting, and heat
treating all types of metals. You will learn more about
gas welding in chapter 5.
This chapter is designed to equip you with a background of basic information applicable to welding in
general. If you take time to study this material carefully,
it will provide you with the foundation needed to become a skilled welder.
WELDING PROCESSES
ARC WELDING
Welding is not new. The earliest known form of
welding, called forge welding, dates back to the year
2000 B.C. Forge welding is a primitive process of
joining metals by heating and hammering until the metals are fused (mixed) together. Although forge welding
still exists, it is mainly limited to the blacksmith trade.
Arc welding is a process that uses an electric arc to
join the metals being welded. A distinct advantage of arc
welding over gas welding is the concentration of heat.
In gas welding the flame spreads over a large area,
sometimes causing heat distortion. The concentration of
heat, characteristic of arc welding, is an advantage because less heat spread reduces buckling and warping.
This heat concentration also increases the depth of penetration and speeds up the welding operation; therefore,
you will find that arc welding is often more practical and
economical than gas welding.
Today, there are many welding processes available.
Figure 3-1 provides a list of processes used in modern
metal fabrication and repair. This list, published by the
American Welding Society (AWS), shows the official
abbreviations for each process. For example, RSW
stands for resistance spot welding. Shielded metal arc
welding (SMAW) is an arc-welding process that fuses
(melts) metal by heating it with an electric arc created
between a covered metal electrode and the metals being
joined. Of the welding processes listed in figure 3-1,
shielded metal arc welding, called stick welding, is the
All arc-welding processes have three things in common: a heat source, filler metal, and shielding. The
source of heat in arc welding is produced by the arcing
of an electrical current between two contacts. The power
3-1
MASTER CHART OF WELDING AND ALLlED PROCESSES
Figure 3-1.—We1ding processes.
3-2
Figure 3-2.—0xyfuel gas welding (OFW).
Figure 3-3.—Shielded metal arc welding (SMAW).
source is called a welding machine or simply, a welder.
This should not be confined with the same term that is
also used to describe the person who is performing the
welding operation. The welder (welding machine) is
either electric- or motor-powered. In the Naval Construction Force (NCF), there are two main types of
arc-welding processes with which you should become
familiar. They are shielded metal arc welding and gas
shielded arc welding.
therefore the process is called shielded metal arc
welding. The main advantages of shielded metal arc
welding are that high-quality welds are made rapidly at
a low cost. You will learn more about shielded metal arc
welding in chapter 7.
Gas Shielded Arc Welding
Shielded Metal Arc Welding
(SMAW)
The primary difference between shielded metal arc
welding and gas shielded arc welding is the type of
shielding used. In gas shielded arc welding, both the arc
and the molten puddle are covered by a shield of inert
gas. The shield of inert gas prevents atmospheric contamination, thereby producing a better weld. The primary gases used for this process are helium, argon, or
carbon dioxide. In some instances, a mixture of these
gases is used. The processes used in gas shielded arc
welding are known as gas tungsten arc welding
Shielded metal arc welding (fig. 3-3) is performed
by striking an arc between a coated-metal electrode and
the base metal. Once the arc has been established, the
molten metal from the tip of the electrode flows together
with the molten metal from the edges of the base metal
to forma sound joint. This process is known as fusion.
The coating from the electrode forms a covering over
the weld deposit, shielding it from contamination;
3-3
Figure 3-5.—Gas metal arc welding (GMAW).
Figure 3-4.—Gas tungsten arc welding (GTAW).
WELDING TERMINOLOGY
To become a skilled welder, you first need to learn
the technical vocabulary ‘(language) of welding. The
sections in this chapter introduce you to some of the
basic terms of the welding language. Once you understand the language of welding, you will be prepared to
interpret and communicate welding information accurately.
(GTAW) (fig. 3-4) and gas metal arc welding (GMAW)
(fig. 3-5). You will also hear these called “TIG” and
“MIG.” Gas shielded arc welding is extremely useful
because it can be used to weld all types of ferrous and
nonferrous metals of all thicknesses.
Now that we have discussed a few of the welding
processes available, which one should you choose?
There are no hard-and-fast rules. In general, the controlling factors are the types of metal you are joining, cost
involved, nature of the products you are fabricating, and
the techniques you use to fabricate them. Because of its
flexibility and mobility, gas welding is widely used for
maintenance and repair work in the field. On the other
hand, you should probably choose gas shielded metal
arc welding to repair a critical piece of equipment made
from aluminum or stainless steel.
No matter what welding process you use, there is
some basic information you need to know. The remainder of this chapter is devoted to this type of information.
Study this information carefully because it allows you
to follow welding instructions, read welding symbols,
and weld various types of joints using the proper welding techniques.
FILLER METALS
When welding two pieces of metal together, you
often have to leave a space between the joint. The
material that you add to fill this space during the welding
process is known as the filler metal, or material. Two
types of filler metals commonly used in welding are
welding rods and welding electrodes.
The term welding rod refers to a form of filler metal
that does not conduct an electric current during the
welding process. The only purpose of a welding rod is
to supply filler metal to the joint. This type of filler metal
is often used for gas welding.
In electric-arc welding, the term electrode refers to
the component that conducts the current from the electrode holder to the metal being welded. Electrodes are
3-4
classified into two groups: consumable and nonconsumable. Consumable electrodes not only provide a path
for the current but they also supply fuller metal to the
joint. An example is the electrode used in shielded
metal-arc welding. Nonconsumable electrodes are only
used as a conductor for the electrical current, such as in
gas tungsten arc welding. The filler metal for gas tungsten arc welding is a hand fed consumable welding rod.
Additional information about filler rods and electrodes is covered in other chapters of this TRAMAN that
deal with specific welding processes.
It remains stable and does not change to a vapor
rapidly within the temperature range of the welding procedure.
It dissolves all oxides and removes them from the
joint surfaces.
It adheres to the metal surfaces while they are
being heated and does not ball up or blow away.
It does not cause a glare that makes it difficult to
see the progress of welding or brazing.
It is easy to remove after the joint is welded.
FLUXES
It is available in an easily applied form.
Before performing any welding process, you must
ensure the base metal is clean. No matter how much the
base metal is physically cleaned, it still contains impurities. These impurities, called oxides, result from oxygen combining with the metal and other contaminants
in the base metal. Unless these oxides are removed by
using a proper flux, a faulty weld may result. The term
flux refers to a material used to dissolve oxides and
release trapped gases and slag (impurities) from the base
metal; thus the flux can be thought of as a cleaning agent.
In performing this function, the flux allows the filler
metal and the base metal to be fused.
Different types of fluxes are used with different
types of metals; therefore, you should choose a flux
formulated for a specific base metal. Beyond that, you
can select a flux based on the expected soldering, brazing, or welding temperature; for example, when brazing,
you should select a flux that becomes liquid at the
correct brazing temperature. When it melts, you will
know it is time to add the filler metal. The ideal flux has
the right fluidity at the welding temperature and thus
blankets the molten metal from oxidation.
Fluxes are available in many different forms. There
are fluxes for oxyfuel gas applications, such as brazing
and soldering. These fluxes usually come in the form of
a paste, powder, or liquid. Powders can be sprinkled on
the base metal, or the fuller rod can be heated and dipped
into the powder. Liquid and paste fluxes can be applied
to the filler rod and to the base metal with a brush. For
shielded metal arc welding, the flux is on the electrode.
In this case, the flux combines with impurities in the
base metal, floating them away in the form of a heavy
slag which shields the weld from the atmosphere.
You should realize that no single flux is satisfactory
for universal use; however, there are a lot of good
general-purpose fluxes for use with common metals. In
general, a good flux has the following characteristics:
CAUTION
Nearly all fluxes give off fumes that may
be toxic. Use ONLY in well-ventilated spaces.
It is also good to remember that ALL welding
operations require adequate ventilation whether
a flux is used or not.
WELD JOINTS
The weld joint is where two or more metal parts are
joined by welding. The five basic types of weld joints
are the butt, corner, tee, lap, and edge, as shown in figure
3-6.
It is fluid and active at the melting point of the
fuller metal.
Figure 3-6.—Basic weld joints.
3-5
Figure 3-7.—Root of joint.
Figure 3-8.—The groove face, root face, and root edge of joints.
3-6
Figure 3-9.—Bevel angle, groove angle, groove radius, and root opening of joints for welding.
PARTS OF JOINTS
A butt joint is used to join two members aligned in
the same plane (fig. 3-6, view A). This joint is frequently
used in plate, sheet metal, and pipe work. A joint of this
type may be either square or grooved. Some of the
variations of this joint are discussed later in this chapter.
While there are many variations of joints, the parts
of the joint are described by standard terms. The root of
a joint is that portion of the joint where the metals are
closest to each other. As shown in figure 3-7, the root
may be a point, a line, or an area, when viewed in cross
section. A groove (fig. 3-8) is an opening or space
provided between the edges of the metal parts to be
welded. The groove face is that surface of a metal part
included in the groove, as shown in figure 3-8, view A.
A given joint may have a root face or a root edge. The
root face, also shown in view A, is the portion of the
prepared edge of a part to be joined by a groove weld
that has not been grooved. As you can see, the root face
has relatively small dimensions. The root edge is basically a root face of zero width, as shown in view B. As
you can see in views C and D of the illustration, the
groove face and the root face are the same metal surfaces
in some joints.
The specified requirements for a particular joint are
expressed in such terms as bevel angle, groove angle,
groove radius, and root opening. A brief description of
each term is shown in figure 3-9.
Corner and tee joints are used to join two members
located at right angles to each other (fig. 3-6, views B
and C). In cross section, the corner joint forms an
L-shape, and the tee joint has the shape of the letter T.
Various joint designs of both types have uses in many
types of metal structures.
A lap joint, as the name implies, is made by lapping
one piece of metal over another (fig. 3-6, view D). This
is one of the strongest types of joints available; however,
for maximum joint efficiency, you should overlap the
metals a minimum of three times the thickness of the
thinnest member you are joining. Lap joints are commonly used with torch brazing and spot welding applications.
An edge joint is used to join the edges of two or
more members lying in the same plane. Inmost cases,
one of the members is flanged, as shown in figure 3-6,
view E. While this type of joint has some applications
in platework, it is more fixquently used in sheet metal
work An edge joint should only be used for joining
metals 1/4 inch or less in thickness that are not subjected
to heavy loads.
The above paragraphs discussed only the five basic
types of joints; however, there are many possible variations. Later in this chapter, we discuss some of these
variations.
The bevel angle is the angle formed between the
prepared edge of a member and a plane perpendicular
to the surface of the member.
The groove angle is the total angle of the groove
between the parts to be joined. For example, if the edge
of each of two plates were beveled to an angle of 30
degrees, the groove angle would be 60 degrees. This is
3-7
Figure3-10.—Root penetration and joint penetration of welds.
Figure 3-11.—Weld reinforcement.
Figure 3-12.—Simple weld bead.
often referred to as the “included angle” between the
Having an adequate root opening is essential for root
parts to be joined by agroove weld.
penetration.
Root penetration and joint penetration of welds are
The groove radius is the radius used to form the
shown in figure 3-10. Root penetration refers to the
shape of a J- or U-groove weld joint. It is used only for
depth that a weld extends into the root of the joint. Root
special groove joint designs.
penetration is measured on the center line of the root
The root opening refers to the separation between
cross section. Joint penetration refers to the minimum
the parts to be joined at the root of the joint. It is
sometimes called the “root gap.”
To determine the bevel angle, groove angle, and root
depth that a groove (or a flange) weld extends from its
face into a joint, exclusive of weld reinforcement. As
you can see in the figure, the terms, root penetration and
opening for a joint, you must consider the thickness of
the weld material, the type of joint to be made, and the
joint penetration, often refer to the same dimension.
welding process to be used. As a general rule, gas
This is the case in views A, C, and E of the illustration.
welding requires a larger groove angle than manual
metal-arc welding.
The root opening is usually governed by the diameter of the filler material. This, in turn, depends on the
thickness of the base metal and the welding position.
View B, however, shows the difference between root
penetration and joint penetration. View D shows joint
penetration only. Weld reinforcement is a term used to
describe weld metal in excess of the metal necessary to
fill a joint. (See fig. 3-11.)
3-8
Figure 3-13.—Standard groove welds.
TYPES OF WELDS
There are many types of welds. Some of the common types you will work with are the bead, groove,
fillet, surfacing, tack, plug, slot, and resistance.
As a beginner, the first type of weld that you learn
to produce is called a weld bead (referred to simply as
a bead). A weld bead is a weld deposit produced by a
single pass with one of the welding processes. An example of a weld bead is shown in figure 3-12. A weld
bead may be either narrow or wide, depending on the
amount of transverse oscillation (side-to-side movement) used by the welder. When there is a great deal of
oscillation, the bead is wide; when there is little or no
oscillation, the bead is narrow. A weld bead made without much weaving motion is often referred to as a
stringer bead. On the other hand, a weld bead made
with side-to-side oscillation is called a weave bead.
Figure 3-14.—Multiple-pass layers.
Groove welds are simply welds made in the groove
between two members to be joined. The weld is adaptable to a variety of butt joints, as shown in figure 3-13.
Groove welds may be joined with one or more weld
beads, depending on the thickness of the metal. If two
or more beads are deposited in the groove, the weld is
made with multiple-pass layers, as shown in figure
3-14. As a rule, a multiple-pass layer is made with
stringer beads in manual operations. As a Steelworker,
you will use groove welds frequently in your work.
Another term you should be familiar with, when
making a multiple-pass weld, is the buildup sequence,
as shown in figure 3-15. Buildup sequence refers to the
Figure 3-15.—Weld layer sequence.
order in which the beads of a multiple-pass weld are
deposited in the joint.
NOTE: Often welding instructions specify an interpass temperature. The interpass temperature refers
to the temperature below which the previously
deposited weld metal must be before the next pass may
be started.
3-9
Figure 3-16.—Fillet welds.
Figure 3-17.—Surfacing welds.
After the effects of heat on metal are discussed, later
in the chapter, you will understand the significance of
the buildup sequence and the importance of controlling
the interpass temperature.
Across-sectional view of a fillet weld (fig. 3-16) is
triangular in shape. This weld is used to join two surfaces that are at approximately right angles to each other
in a lap, tee, or comer joint.
Surfacing is a welding process used to apply a hard,
wear-resistant layer of metal to surfaces or edges of
worn-out parts. It is one of the most economical methods
of conserving and extending the life of machines, tools,
and construction equipment. As you can see in figure
3-17, a surfacing weld is composed of one or more
stringer or weave beads. Surfacing, sometimes known
as hardfacing or wearfacing, is often used to build up
worn shafts, gears, or cutting edges. You will learn more
about this type of welding in chapter 6 of this training
manual.
A tack weld is a weld made to hold parts of an
assembly in proper alignment temporarily until the final
welds are made. Although the sizes of tack welds are not
specified, they are normally between 1/2 inch to 3/4 inch
in length, but never more than 1 inch in length. In
determining the size and number of tack welds for a
specific job, you should consider thicknesses of the
metals being joined and the complexity of the object
being assembled.
Figure 3-18.—Plug and slot welds.
hole. The hole may or may not be completely filled with
weld metal. These types of welds are often used to join
face-hardened plates from the backer soft side, to install
liner metals inside tanks, or to fill up holes in a plate.
Resistance welding is a metal fabricating process
in which the fusing temperature is generated at the joint
by the resistance to the flow of an electrical current. This
is accomplished by clamping two or more sheets of
metal between copper electrodes and then passing an
electrical current through them. When the metals are
heated to a melting temperature, forging pressure is
applied through either a manual or automatic means to
weld the pieces together. Spot and seam welding
(fig. 3-19) are two common types of resistance welding
processes.
Spot welding is probably the most commonly used
type of resistance welding. The material to be joined is
placed between two electrodes and pressure is applied.
Next, a charge of electricity is sent from one electrode
through the material to the other electrode. Spot welding
is especially useful in fabricating sheet metal parts.
Plug and slot welds (fig. 3-18) are welds made
through holes or slots in one member of a lap joint.
These welds are used to join that member to the surface
of another member that has been exposed through the
Seam welding is like spot welding except that the
spots overlap each other, making a continuous weld
3-10
Figure 3-19.—Spot and seam welds.
Figure 3-20.—Parts of a groove weld and fillet weld.
seam. In this process, the metal pieces pass between
roller type of electrodes. As the electrodes revolve, the
current is automatically turned on and off at the speed
at which the parts are set to move. Seabees do not
normally use seam welding, because this type of welding is most often used in industrial manufacturing.
PARTS OF WELDS
For you to produce welds that meet the job requirements, it is important that you become familiar with the
terms used to describe a weld. Figure 3-20 shows a
groove weld and a fillet weld. ‘he face is the exposed
3-11
Figure 3-22.—Zones in a weld.
length of the legs of the weld. The two legs are assumed
to be equal in size unless otherwise specified.
A gauge used for determining the size of a weld is
known as a welding micrometer. Figure 3-21 shows
how the welding micrometer is used to determine the
various dimensions of a weld.
Some other terms you should be familiar with are
used to describe areas or zones of welds. As we discussed earlier in the chapter, fusion is the melting together of base and/or fuller metal. The fusion zone, as
shown in figure 3-22, is the region of the base metal that
is actually melted. The depth of fusion is the distance
that fusion extends into the base metal or previous
welding pass.
Another zone of interest to the welder is the heataffected zone, as shown in figure 3-22. This zone includes that portion of the base metal that has not been
melted; however, the structural or mechanical properties
of the metal have been altered by the welding heat.
Because the mechanical properties of the base metal are
affected by the welding heat, it is important that you
learn techniques to control the heat input. One technique
often used to minimize heat input is the intermittent
weld. We discuss this and other techniques as we progress through this chapter; but, first we will discuss
some of the considerations that affect the welded joint
design.
Figure 3-21.—Using a welding micrometer.
surface of a weld on the side from which the weld was
made. The toe is the junction between the face of the
weld and the base metal. The root of a weld includes the
points at which the back of the weld intersects the base
metal surfaces. When we look at a triangular cross
section of a fillet weld, as shown in view B, the leg is
the portion of the weld from the toe to the root. The
throat is the distance from the root to a point on the face
of the weld along a line perpendicular to the face of the
weld. Theoretically, the face forms a straight line between the toes.
WELDED JOINT DESIGN
The details of a joint, which includes both the geometry and the required dimensions, are called the joint
design. Just what type of joint design is best suited for
a particular job depends on many factors. Although
welded joints are designed primarily to meet strength
and safety requirements, there are other factors that must
be considered. A few of these factors areas follows:
NOTE: The terms leg and throat apply only to fillet
welds.
In determining the size of a groove weld (fig. 3-20,
view A), such factors as the depth of the groove, root
opening, and groove angle must be taken into consideration. The size of a fillet weld (view B) refers to the
3-12
some of the variations of the welded joint designs and
the efficiency of the joints.
BUTT JOINTS
The square butt joint is used primarily for metals
that are 3/16 inch or less in thickness. The joint is
reasonably strong, but its use is not recommended when
the metals are subject to fatigue or impact loads. Preparation of the joint is simple, since it only requires matching the edges of the plates together; however, as with
any other joint, it is important that it is fitted together
correctly for the entire length of the joint. It is also
important that you allow enough root opening for the
joint. Figure 3-23 shows an example of this type of joint.
When you are welding metals greater than 3/16 inch
in thickness, it is often necessary to use a grooved butt
joint. The purpose of grooving is to give the joint the
required strength. When you are using a grooved joint,
it is important that the groove angle is sufficient to allow
the electrode into the joint; otherwise, the weld will lack
penetration and may crack. However, you also should
avoid excess beveling because this wastes both weld
metal and time. Depending on the thickness of the base
metal, the joint is either single-grooved (grooved on one
side only) or double-grooved (grooved on both sides).
As a welder, you primarily use the single-V and doubleV grooved joints.
The single-V butt joint (fig. 3-23, view B) is for
use on plates 1/4 inch through 3/4 inch in thickness.
Each member should be beveled so the included angle
for the joint is approximately 60 degrees for plate and
75 degrees for pipe. Preparation of the joint requires a
special beveling machine (or cutting torch), which
makes it more costly than a square butt joint. It also
requires more filler material than the square joint; however, the joint is stronger than the square butt joint. But,
as with the square joint, it is not recommended when
subjected to bending at the root of the weld.
Figure 3-23.—Butt joints.
Whether the load will be in tension or compression and whether bending, fatigue, or impact
stresses will be applied
How a load will be applied; that is, whether the
load will be steady, sudden, or variable
The direction of the load as applied to the joint
The cost of preparing the joint
Another consideration that must be made is the ratio
of the strength of the joint compared to the strength of
the base metal. This ratio is called joint efficiency. An
efficient joint is one that is just as strong as the base
metal.
Normally, the joint design is determined by a designer or engineer and is included in the project plans
and specifications. Even so, understanding the joint
design for a weld enables you to produce better welds.
Earlier in this chapter, we discussed the five basic
types of welded joints—butt, corner, tee, lap, and edge.
While there are many variations, every joint you weld
will be one of these basic types. Now, we will consider
The double-V butt joint (fig. 3-23, view C) is an
excellent joint for all load conditions. Its primary use is
on metals thicker than 3/4 inch but can be used on
thinner plate where strength is critical. Compared to the
single-V joint, preparation time is greater, but you use
less filler metal because of the narrower included angle.
Because of the heat produced by welding, you should
alternate weld deposits, welding first on one side and
then on the other side. This practice produces a more
symmetrical weld and minimizes warpage.
Remember, to produce good quality welds using the
groove joint, you should ensure the fit-up is consistent
for the entire length of the joint, use the correct groove
3-13
Figure 3-24.—Additiona1 types of groove welds.
angle, use the correct root opening, and use the correct
root face for the joint. When you follow these principles,
you produce better welds every time. Other standard
grooved butt joint designs include the bevel groove,
J-groove, and U-groove, as shown in figure 3-24.
CORNER JOINTS
The flush corner joint (fig. 3-25, view A) is designed primarily for welding sheet metal that is 12 gauge
or thinner. It is restricted to lighter materials, because
deep penetration is sometimes difficult and the design
can support only moderate loads.
The half-open corner joint (fig. 3-25, view B) is
used for welding materials heavier than 12 gauge. Penetration is better than in the flush corner joint, but its use
is only recommended for moderate loads.
The full-open corner joint (fig. 3-25, view C)
produces a strong joint, especially when welded on both
sides. It is useful for welding plates of all thicknesses.
TEE JOINTS
The square tee joint (fig. 3-26, view A) requires a
fillet weld that can be made on one or both sides. It can
be used for light or fairly thick materials. For maximum
strength, considerable weld metal should be placed on
each side of the vertical plate.
Figure 3-25.—Corner joints.
3-14
Figure 3-27.—Lap joints,
Figure 3-26.—T ee joints.
Figure 3-28.—Flanged edge Joints.
The single-bevel tee joint (fig. 3-26, view B) can
withstand more severe loadings than the square tee joint,
because of better distribution of stresses. It is generally
used on plates of 1/2 inch or less in thickness and where
welding can only be done from one side.
the seam. The strength of the weld depends on the size
of the fillet. Metal up to 1/2 inch in thickness and not
subject to heavy loads can be welded using this joint.
When the joint will be subjected to heavy loads, you
should use the double-fillet lap joint (fig. 3-27, view
B). When welded properly, the strength of this joint is
very close to the strength of the base metal.
The double-bevel tee joint (fig. 3-26, view C) is for
use where heavy loads are applied and the welding can
be done on both sides of the vertical plate.
LAP JOINTS
EDGE JOINTS
The single-fillet lap joint (fig. 3-27, view A) is easy
to weld, since the filler metal is simply deposited along
The flanged edge joint (fig. 3-28, view A) is suitable for plate 1/4 inch or less in thickness and can only
3-15
Figure 3-29.—Welding positions—plate.
sustain light loads. Edge preparation for this joint may
be done, as shown in either views B or C.
groove welds can be made in all of these positions.
Figure 3-29 shows the various positions used in plate
welding. The American Welding Society (AWS) identi-
WELDING POSITIONS
fies these positions by a number/letter designation; for
All welding is done in one of four positions: (1) flat,
(2) horizontal, (3) vertical, or (4) overhead. Fillet or
instance, the 1G position refers to a groove weld that is
to be made in the flat position. Here the 1 is used to
3-16
Figure 3-30.—Welding position-pipe.
indicate the flat position and the G indicates a groove
weld. For a fillet weld made in the flat position, the
number/letter designation is 1F (F for fillet). These
number/letter designations refer to test positions. These
are positions a welder would be required to use during
a welding qualification test. As a Steelworker, there is a
good possibility that someday you will be required to
certify or perform a welding qualification test; therefore,
it is important that you have a good understanding and
can apply the techniques for welding in each of the test
positions.
Test position 1G is made with the pipe in the horizontal position. In this position, the pipe is rolled so that
the welding is done in the flat position with the pipe
rotating under the arc. This position is the most advantageous of all the pipe welding positions. When you are
welding in the 2G position, the pipe is placed in the
vertical position so the welding can be done in the
horizontal position. The 5G position is similar to the 1G
position in that the axis of the pipe is horizontal. But,
when you are using the 5G position, the pipe is not
turned or rolled during the welding operation; therefore,
the welding is more difficult in this position. When you
are using the 6G position for pipe welding, the axis of
the pipe is at a 45-degree angle with the horizontal and
the pipe is not rolled. Since the pipe is not rolled,
welding has to be done in all the positions— flat, vertical, horizontal, and overhead. If you can weld pipe in
this position, you can handle all the other welding positions.
Because of gravity, the position in which you are
welding affects the flow of molten filler metal. Use the
flat position, if at all possible, because gravity draws the
molten metal downward into the joint making the welding faster and easier. Horizontal welding is a little more
difficult, because the molten metal tends to sag or flow
downhill onto the lower plate. Vertical welding is done
in a vertical line, usually from bottom to top; however,
on thin material downhill or downhand welding may
be easier. The overhead position is the most difficult
position. Because the weld metal flows downward, this
position requires considerable practice on your part to
produce good quality welds.
NOTE: There is no 3G or 4G test position in pipe
welding. Also, since most pipe welds are groove welds,
they are identified by the letter G.
We will discuss more about the techniques used for
welding in the various positions later in this training
manual, but for now, let’s talk about the effects of heat
on metal.
Although the terms flat, horizontal, vertical, and
overhead sufficiently describe the positions for plate
welding, they do not adequately describe pipe welding
positions. In pipe welding, there are four basic test
positions used (fig. 3-30). Notice that the position refers
to the position of the pipe, not the position of welding.
EXPANSION AND CONTRACTION
When apiece of metal is heated, the metal expands.
Upon cooling, the metal contracts and tries to resume
its original shape. The effects of this expansion and
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to internal stresses, distortion, and warpage. Figure 3-32
shows some of the most common difficulties that you
are likely to encounter.
When you are welding a single-V butt joint (fig.
3-32, view A), the highest temperature is at the surface
of the molten puddle. The temperature decreases as you
move toward the root of the weld and away from the
weld. Because of the high temperature of the molten
metal, this is where expansion and contraction are greatest. When the weld begins to cool, the surface of the
weld joint contracts (or shrinks) the most, thus causing
warpage or distortion. View B shows how the same
Figure 3-31.—Effects of expansion and contraction.
contraction are shown in figure 3-31. View A shows a
bar that is not restricted in any way. When the bar is
heated, it is free to expand in all directions. If the bar is
allowed to cool without restraint, it contracts to its
original dimensions.
principles apply to a tee joint. Views C and D show the
distortions caused by welding a bead on one side of a
plate and welding two plates together without proper
tack welds.
All metals, when exposed to heat buildup during
welding, expand in the direction of least resistance.
Conversely, when the metal cools, it contracts by the
same amount; therefore, if you want to prevent or reduce
the distortion of the weldment, you have to use some
method to overcome the effects of heating and cooling.
When the bar is clamped in a vise (view B) and
heated, expansion is limited to the unrestricted sides of
the bar. As the bar begins to cool, it still contracts
uniformly in all directions. As a result, the bar is now
deformed. It has become narrower and thicker, as shown
in view C.
These same expansion and contraction forces act on
the weld metal and base metal of a welded joint; however, when two pieces of metal are welded together,
expansion and contraction may not be uniform throughout all parts of the metal. This is due to the difference in
the temperature from the actual weld joint out to the
edges of the joint. This difference in temperature leads
CONTROLLING DISTORTION
You can control the distortion caused by expansion
and contraction during welding by following the simple
procedures listed below.
Figure 3-32.—Distortion caused by welding.
3-18
Figure 3-33.—Intermittent welds.
Figure 3-34.—Back-step welding.
Proper Edge Preparation and Fit-up
input. An intermittent weld (sometimes called a skip
weld) is often used instead of one continuous weld.
When you are using an intermittent weld, a short weld
is made at the beginning of the joint. Next, you skip to
the center of the seam and weld a few inches. Then, you
weld at the other end of the joint. Finally, you return to
the end of the first weld and repeat the cycle until the
weld is finished. Figure 3-33 shows the intermittent
weld.
As discussed earlier in this chapter, proper edge
preparation and fit-up are essential to good quality
welds. By making certain the edges are properly beveled
and spacing is adequate, you can restrict the effects of
distortion. Additionally, you should use tack welds,
especially on long joints. Tack welds should be spaced
at least 12 inches apart and run approximately twice as
long as the thickness of the weld.
Another technique to control the heat input is the
back-step method (fig. 3-34). When using this technique, you deposit short weld beads from right to left
along the seam.
Control the Heat Input
You should understand that the faster a weld is
made, the less heat is absorbed by the base metal. As you
gain welding experience, it will become easier for you
to weld a seam with the minimum amount of heat by
simply speeding up the welding process.
Preheat the Metal
As discussed earlier, expansion and contraction
rates are not uniform in a structure during welding due
to the differences in temperature throughout the metal.
Regardless of your experience, it is often necessary
to use a welding technique designed to control heat
3-19
Figure 3-35.—Weld passes.
To control the forces of expansion and contraction, you
preheat the entire structure before welding. After the
welding is complete, you allow the structure to cool
slowly. More about preheating and postheating is discussed later in this training manual.
Figure 3-36.—Allowing for distortion.
be considered. Later, we discuss additional techniques
that you can apply to specific welding situations.
Limit the Number of Weld Passes
You can keep distortion to a minimum by using as
few weld passes as possible. You should limit the number of weld passes to the number necessary to meet the
requirements of the job. (See fig. 3-35.)
WELDING PROCEDURES
There are many factors involved in the preparation
of any welded joint. The detailed methods and practices
used to prepare a particular weldment are called the
welding procedure. A welding procedure identifies all
the welding variables pertinent to a particular job or
project. Generally, these variables include the welding
process, type of base metal, joint design, welding position, type of shielding, preheating and postheating requirements, welding machine setting, and testing
requirements.
Use Jigs and Fixtures
Since holding the metal in a fixed position prevents
excessive movements, the use of jigs and fixtures can
help prevent distortion. A jig or fixture is simply a device
used to hold the metal rigidly in position during the
welding operation.
Allow for Distortion
A simple remedy for the distortion caused by expansion and contraction is to allow for it during fit-up. To
reduce distortion, you angle the parts to be welded
slightly in the opposite direction in which the contraction takes place. When the metal cools, contraction
forces pull the pieces back into position. Figure 3-36
shows how distortion can be overcome in both the butt
and tee joints.
Welding procedures are used to produce welds that
will meet the requirements of commonly used codes.
The American Welding Society (AWS) produces the
Structural Welding Code that is used for the design and
construction of steel structures. Another code that is
used for the construction of steam boilers and pressure
vessels is published by the American Society of Mechanical Engineers (ASME). These codes provide a
standardized guide of proven welding practices and
procedures.
There is more to being a good welder than just being
able to lay a good bead. There are many factors that must
While you are not directly responsible for developing welding procedures, you could be assigned to a
3-20
welding job that requires you to follow them. For example, when a job is assigned to a Naval Construction
Force unit, it is accompanied by a set of drawings and
specifications. When there is welding required for the
job, the specifications normally require it to be accomplished according to a specific code requirement. For
instance, if your unit is tasked to fabricate a welded steel
structure, the specifications may require that all welding
be accomplished according to AWS D1.1 (Structural
Welding Code). The unit is then responsible for ensuring
that the welders assigned to the job are qualified to
produce the welds according to this welding procedure
specification. As shown in figure 3-37, a welding procedure specification is simply a document that provides
details of the required variables for a specific welding
application.
READING DRAWINGS
To read a drawing, you must know how engineers
use lines, dimensions, and notes to communicate their
ideas on paper. In this section, we briefly discuss each
of these drawing elements. For a more thorough discussion, refer to publications, such as Blueprint Reading
and Sketching, NAVEDTRA 10077-F1, or to Engineering Aid 3, NAVEDTRA 10696.
Figure 3-38 shows many of the different types of
lines that are used in drawings. You can see that each
line has a specific meaning you must understand to
interpret a drawing correctly. Let’s discuss a few of the
most important types. A visible line (sometimes called
object line) is used to show the edges of an object that
are visible to the viewer. For example, if you look at one
of the walls of the room you are in, you can see the
outline of the walls and (depending on the wall you are
looking at) the outline of doors and windows. On a
drawing, these visible outlines or edges can be shown
using visible lines that are drawn as described in
figure 3-38.
For an NMCB, the welding procedure specification
is normally prepared by the certified welding inspector
at the local Naval Construction Training Center. Using
the Structural Welding Code, along with the project
drawings and specifications, the welding inspector develops a welding procedure specification that meets the
requirements of the job. The importance of this document is that it assures that each of the variables can be
repeated by qualified welders.
Once a welding procedure specification has been
developed and qualified, welders are then required to
perform a Welding Performance Qualification test. After the test is complete, the weld specimens are tested
according to the requirements of the Welding Procedure
Specification. You may use either destructive or nondestructive tests. One example of a destructive test is the
guided-bend test. An X-ray test is considered nondestructive. Testing is discussed in greater detail later in
this training manual.
Now look at the wall again. Assuming that the
wall is wood frame, you know that there are studs or
framing members inside the wall that you cannot see.
Also, the wall may contain other items, such as water
pipes and electrical conduit, that you also cannot see.
On a drawing, the edges of those concealed studs and
other items can be shown using hidden lines (fig.
3-38). These lines are commonly used in drawings. As
you can imagine, the more hidden lines there are, the
more difficult it becomes to decipher what is what;
however, there is another way these studs and other
items can be “seen.” Imagine that you “cut away” the
wallboard that covers the wall and replace it with a
sheet of clear plastic. That clear plastic can be thought
of as a cutting or viewing plane (fig. 3-38) through
which the previously concealed studs, piping, and
conduit are now visible. Now those items can be
drawn using visible lines, rather than hidden lines. A
view of this type is called a sectional view, and a
drawing of the view is called a section drawing.
Section drawings are commonly used to show the
internal components of a complicated object.
NOTE: When you are assigned to do a welding job,
make a thorough examination of the drawings and specifications. Look carefully at the notes on the drawings
and Section 5 (metals) of the specifications. If specific
codes are cited, inform the project supervisor so that you
can receive the training needed to perform the required
welds.
DRAWINGS
Drawings or sketches are used to convey the ideas
of an engineer to the skilled craftsman working in the
shop. As a welder, you must be able to work from a
drawing in order to fabricate metal parts exactly as the
engineer has designed them.
Many times, you will see lines drawn on the visible
surfaces of a section drawing. These lines, called section
lines, are used to show different types of materials.
3-21
Figure 3-37.—Welding procedure specification.
3-22
Figure 3-37.—Welding procedure specification-Continued.
3-23
page 3-24.
Figure 3-38.—Line characters and uses.
Some of the types of section lines you are likely to
encounter as a welder are shown in figure 3-39.
Another use of lines is to form symbols, such as
welding symbols, that are discussed later in this chapter.
Dimensions
While engineers use lines to describe the shape or
form of an object, they use dimensions to provide a
complete size description. Dimensions used on drawings are of two types: size and location. As implied by
their names, a size dimension shows the size of an
object or parts of an object and a location dimension
is used to describe the location of features. Examples
of both size and location dimensions are shown in
figure 3-40.
Figure 3-39.—Section lines for various metals.
Figure 3-40.—Elements of an orthographic drawing.
3-25
While on the subject of dimensions, it should be
noted that large objects are seldom drawn to their true
size. Instead, the engineer or draftsman reduces the size
of the object “to scale.” For example, when drawing a
40-foot tower, the drawing may be prepared using a
scale of 1/2"= 1'-0". In this case, the height of the tower,
on paper, is 20 inches. The scale used to prepare working
drawings is always noted on the drawing. It maybe a
fractional scale, such as discussed here, or a graphic
scale, such as the one shown in figure 3-40. In the Navy,
both numerical and graphic scales are usually shown on
construction drawings.
When you are using a drawing, the dimensions of
an object should never be measured (scaled) directly
from the drawing. These measurements are frequently
inaccurate, since a change in atmospheric conditions
causes drawing paper to shrink or expand. To ensure
accuracy, always use the size and location dimensions
shown on the drawing. If a needed dimension is not
shown on the drawing, you should check the graphic
scale, since it will always shrink or expand at the same
rate as the drawing paper.
Figure 3-41.—Pictorial drawing of a steel part.
Notes
Drawing notes are used for different purposes and
are either general or specific in nature. One example of
how notes are used are the two notes shown in figure
3-40 that give the inside diameters of the holes. As you
can see, these notes are used for size dimensioning. They
are specific notes in that, by using a leader line, each
note is referred to a specific hole or set of holes.
I
A general note is used to provide additional information that does not apply to any one particular part or
feature of the drawing. For example, the drawing shown
in figure 3-40 could contain a general note saying: “All
holes shall be reamed using a tolerance of ± 1/64 inch.”
Figure 3-42.—Three-view orthographic drawing of the steel part
shown in figure 3-41.
Drawing Views
Assume you are holding the object shown in figure
3-41 in your hands. When you hold the object so you are
looking directly at the top face of the object, the view
you see is the top view. A drawing of that view is called
an orthographic drawing.
Look at the drawing shown in figure 3-41. This type
of drawing is called a pictorial drawing. These drawings are frequently used to show how an object should
appear after it is manufactured. Pictorial drawings are
used as working drawings for a simple item, such as a
metal washer. For a more complex object, as shown in
figure 3-41, it becomes too difficult to provide a complete description in a pictorial drawing. In this case, it is
common practice to prepare orthographic drawings to
describe the object fully.
Obviously, an orthographic drawing of only the top
view of the object is insufficient to describe the entire
object; therefore, additional orthographic drawings of
one or more of the other faces of the object are necessary.
The number of orthographic views needed to describe
an object fully depends upon the complexity of the
object. For example, a simple metal washer can be fully
described using only one orthographic view; however,
an extremely complex object may require as many as
3-26
Handling and Care of Drawings
Special care should be exercised in the handling of
drawings. When they are not being used, keep them on
a rack or in another assigned place of storage. Drawings
are valuable, and they may be difficult or impossible to
replace if they are lost or damaged.
Now, we will discuss some special symbols. These
are symbols a welder must be able to read and to
understand how they are used to convey information.
Figure 3-43.—Standard welding symbol.
WELDING SYMBOLS
six views (top, front, left side, right side, back, and
bottom). Most objects, such as the steel part shown in
figure 3-41, can be sufficiently described using three
views: top, front, and right side. For the object shown in
figure 3-41, orthographic drawings of the top, front, and
right-side views are shown in figure 3-42.
Special symbols are used on a drawing to specify
where welds are to be located, the type of joint to be
used, as well as the size and amount of weld metal to be
deposited in the joint. These symbols have been standardized by the American Welding Society (AWS). You
will come into contact with these symbols anytime you
do a welding job from a set of blueprints. You need to
have a working knowledge of the basic weld symbols
and the standard location of all the elements of a welding
symbol.
Notice the placement of the views shown in figure
3-42. This is a standard practice that you should be
aware of when reading orthographic drawings. By this
standard practice, the top view is always placed above
the front view and the right-side view is placed to the
right of the front view. When additional views are
needed, the left side is always drawn to the left of the
front view and the bottom is drawn below the front view.
Placement of the back view is somewhat flexible; however, it is usually drawn to the left of the left-side view.
When reading and understanding the different orthographic views, you find it is sometimes helpful to prepare a pictorial sketch. You can find a discussion of
sketching in Blueprint Reading and Sketching,
NAVEDTRA 10077-F1 .
A standard welding symbol (fig. 3-43) consists of a
reference line, an arrow, and a tail. The reference line
becomes the foundation of the welding symbol. It is
used to apply weld symbols, dimensions, and other data
to the weld. The arrow simply connects the reference
line to the joint or area to be welded. The direction of
the arrow has no bearing on the significance of the
reference line. The tail of the welding symbol is used
only when necessary to include a specification, process,
or other reference information.
Weld Symbols
Think of drawings as a form of communication.
They are intended to help you understand all the necessary information you need to fabricate and assemble an
object regardless of the complexity. It is important that
The term weld symbol refers to the symbol for a
specific type of weld. As discussed earlier, fillet, groove,
surfacing, plug, and slot are all types of welds. Basic
weld symbols are shown in figure 3-44. The weld
you learn to read drawings.
Figure 3-44.—Basic weld symbols.
3-27
Figure 3-47.—Arrowhead indicates beveled plate.
symbol is only part of the information required in the
welding symbol. The term welding symbol refers to the
total symbol, which includes all information needed to
specify the weld(s) required.
Figure 3-45.—Weld symbols applied to reference line.
Figure 3-45 shows how a weld symbol is applied to
the reference line. Notice that the vertical leg of the weld
symbol is shown drawn to the left of the slanted leg.
Regardless of whether the symbol is for a fillet, bevel,
J-groove, or flare-bevel weld, the vertical leg is always
drawn to the left.
Figure 3-46 shows the significance of the positions
of the weld symbols position on the reference line. In
view A the weld symbol is on the lower side of the
reference line that is termed the arrow side. View B
shows a weld symbol on the upper side of the reference
line that is termed the other side. When weld symbols
are placed on both sides of the reference line, welds must
be made on both sides of the joint (view C).
When only one edge of a joint is to be beveled, it is
necessary to show which member is to be beveled.
When such a joint is specified, the arrow of the welding
symbol points with a definite break toward the member
to be beveled. This is shown in figure 3-47.
Figure 3-48 shows other elements that may be
added to a welding symbol. The information applied to
the reference line on a welding symbol is read from left
to right regardless of the direction of the arrow.
Dimensioning
In figure 3-48, notice there are designated locations
for the size, length, pitch (center-to-center spacing),
groove angle, and root opening of a weld. These locations are determined by the side of the reference line on
which the weld symbol is placed. Figure 3-49 shows
how dimensions are applied to symbols.
Figure 3-46.—Specifying weld locations.
3-28
Figure 3-48.—Elements of a welding symbol.
Figure 3-49.—Dimensions applied to weld symbols.
3-29
Figure 3-50.—Dimensioning of welds.
shows a tee joint with 2-inch intermittent fillet welds
that are 5 inches apart, on center. The size of a groove
weld is shown in view C. Both sides are 1/2 inch, but
note that the 60-degree groove is on the other side of the
joint and the 45-degree groove is on the arrow side.
Supplementary Symbols
In addition to basic weld symbols, a set of supplementary symbols may be added to a welding symbol.
Some of the most common supplementary symbols are
shown in figure 3-51.
Contour symbols are used with weld symbols to
show how the face of the weld is to be formed. In
addition to contour symbols, finish symbols are used to
indicate the method to use for forming the contour of the
weld.
When a finish symbol is used, it shows the method
of finish, not the degree of finish; for example, a C is
used to indicate finish by chipping, an M means machining, and a G indicates grinding. Figure 3-52 shows how
contour and finish symbols are applied to a weldng
symbol. This figure shows that the weld is to be ground
flush. Also, notice that the symbols are placed on the
same side of the reference line as the weld symbol.
Figure 3-51.—Supplementary symbols.
Figure 3-50 shows the meaning of various welding
dimension symbols. Notice that the size of a weld is
shown on the left side of the weld symbol (fig. 3-50,
view A). The length and pitch of a fillet weld are
indicated on the right side of the weld symbol. View B
3-30
Figure 3-52.—Finish and contour symbols.
Figure 3-54.—Representing multiple welds.
Figure 3-55.—Example of welding symbol in use.
Figure 3-53.—Specifying additional welding information.
fig. 3-53.) If additional information is not needed, then
the tail is omitted.
Another supplementary symbol shown in figure
3-51 is the weld-all-around symbol. When this symbol
is placed on a welding symbol, welds are to continue all
around the joint.
Welds that cannot be made in the shop are identified
as field welds. Afield weld symbol is shown in figure
3-51. This symbol is a black flag that points toward the
tail of the welding symbol.
Multiple-Weld Symbols
When you are fabricating a metal part, there are
times when more than one type of weld is needed on the
same joint; for example, a joint may require both a bevel
groove weld and a fillet weld. Two methods of illustrating these weld symbols are shown in figure 3-54. Note
that in each welding symbol, the bevel groove weld is
to be completed first, followed by the fillet weld.
Specifying Additional Information
It is sometimes necessary to specify a certain welding process, a type of electrode, or some type of reference necessary to complete a weld. In this case, a note
can be placed in the tail of the reference line. (See
Applying a Welding Symbol
Figure 3-55 shows an example of how a welding
symbol may appear on a drawing. This figure shows a
3-31
Figure 3-56.—Eye protection devices.
the vicinity of the welding and cutting operations. Eye
protection is necessary because of the hazards posed by
stray flashes, reflected glare, flying sparks, and globules
of molten metal. Devices used for eye protection include
helmets and goggles.
steel pipe column that is to be welded to a baseplate. The
symbol tells the welder that the pipe is to be beveled at
a 30-degree angle followed by a bevel groove weld all
around the joint. This is followed by a 1/2-inch fillet
weld that is also welded all around the joint. Finally,
finish the fillet weld by grinding it to a flush contour. As
the field weld symbol indicates, all welds are to be
accomplished in the field.
NOTE: In addition to providing eye protection,
helmets also provide a shield against flying metal and
ultraviolet rays for the entire face and neck. Figure 3-56
shows several types of eye protection devices in common use.
For additional information about welding symbols,
refer to Symbols for Welding and Nondestructive Testing, ANSI/AWS A2.4-86.
Flash goggles (view A) are worn under the welder’s
helmet and by persons working around the area where
welding operations are taking place. This spectacle type
of goggles has side shields and may have either an
adjustable or nonadjustable nose bridge.
SAFETY
Mishaps frequently occur in welding operations. In
many instances, they result in serious injury to the
welder or other personnel working in the immediate
area. In most cases, mishaps occur because of carelessness, lack of knowledge, and the misuse of available
equipment. Precautions that apply to specific welding
equipment are pointed out in the chapters that cover that
equipment. In this section we are particularly interested
in such topics as protective clothing, eye protection
devices, and practices applicable to the personal safety
of the operator and personnel working nearby.
Eyecup or cover type of goggles (view B) are for
use in fuel-gas welding or cutting operations. They are
contoured to fit the configuration of the face. These
goggles must be fitted with a shade of filter lens that is
suitable for the type of work being done.
NOTE: The eyecup or cover type of goggles are
NOT to be used as a substitute for an arc-welding
helmet.
For electric arc-welding and arc-cutting operations,
a helmet having a suitable filter lens is necessary. The
helmet shown in view C has an opening, called a
Proper eye protection is of the utmost importance.
This covers the welding operator and the other personnel, such as helpers, chippers, or inspectors, who are in
3-32
Table 3-1.—Recommended Filter Lenses for Various Welding Operations
window, for a flip-up filter lens 2 inches by 4 1/4 inches
in size. The helmet shown in view D has a 4 1/2-inch by
5 1/4-inch window. The larger window affords the
welder a wider view and is especially useful when the
welder is working in a confined place where head and
body movement is restricted. When welding in locations
where other welders are working, the welder should
wear flash goggles beneath his helmet to provide protection from the flashes caused by the other welders’
arcs. The flash goggles will also serve as eye protection
when chipping the slag from a previous weld deposit.
second is to eliminate the harmful infrared and ultraviolet radiations coming from the arc or flame; consequently, the filter lens shade number you select must not
vary more than two shades from the numbers recommended in table 3-1.
Rule of thumb: When selecting the proper shade of
filter lens for electric-arc welding helmets, place the lens
in the helmet and look through the lens as if you were
welding. Look at an exposed bare light bulb and see if
you can distinguish its outline. If you can, then use the
next darker shade lens. Repeat the test again. When you
no longer see the outline of the bulb, then the lens is of
the proper shade. Remember that this test should be
performed in the same lighting conditions as the welding
operation is to be performed. Welding in a shop may
require a shade lighter lens than if the same job were
being performed in bright daylight. For field operations,
this test may be performed by looking at a bright reflective object.
Helmets and welding goggles used for eye protection are made from a nonflammable insulating material.
They are fitted with a removable protective colored filter
and a clear cover lens.
NOTE: The purpose of the clear cover lens is to
protect the filter lens against pitting caused by sparks
and hot metal spatter. The clear lens must be placed on
the outside of the filter lens. The clear lens should be
replaced when it impairs vision.
WARNING
Filter lenses are furnished in a variety of shades,
which are designated by number. The lower the number,
the lighter the shade; the higher the number, the darker
the shade. Table 3-1 shows you the recommended filter
lens shade for various welding operations. The filter lens
shade number selected depends on the type of work and
somewhat on the preference of the user. Remember, a
filter lens serves two purposes. The first is to diminish
the intensity of the visible light to a point where there is
no glare and the welding area can be clearly seen. The
Never look at the welding arc without
proper eye protection. Looking at the arc with
the naked eye could lead to permanent eye
damage. If you receive flash burns, they should
be treated by medical personnel.
A variety of special welder’s clothing is used to
protect parts of the body. The clothing selected varies
3-33
with the size, location, and nature of the work to be
performed. During any welding or cutting operation,
you should always wear flameproof gauntlets. (See fig.
3-57.) For gas welding and cutting, five-finger gloves
like those shown in view A should be used. For electricarc welding, use the two-finger gloves (or mitts) shown
in view B.
Both types of gloves protect the hands from heat and
metal spatter. The two-finger gloves have an advantage
over the five-finger gloves in that they reduce the danger
of weld spatter and sparks lodging between the fingers.
They also reduce finger chafing which sometimes occurs when five-finger gloves are worn for electric-arc
welding.
Many light-gas welding and brazing jobs require no
special protective clothing other than gloves and
Figure 3-57.—Welding gloves and mitts.
Figure 3-58.—Welder’s protective clothing.
3-34
and chest. Use of the bib, in combination with the cape
and sleeves, gives added protection to the chest and
abdomen. The jacket should be worn when there is a
need for complete all-around protection to the upperpart
of the body. This is especially true when several welders
are working in close proximity to one another. Aprons
and overalls provide protection to the legs and are suited
for welding operations on the floor. Figure 3-58 shows
some of the protective clothing available to welders.
goggles. Even here, it is essential that you wear your
work clothes properly. Sparks are very likely to lodge in
rolled-up sleeves, pockets of clothing, or cuffs of trousers or overalls. Sleeves should be rolled down and the
cuffs buttoned. The shirt collar, also, should be fully
buttoned. Trousers should not be cuffed on the outside,
and pockets not protected by button-down flaps should
be eliminated from the front of overalls and aprons. All
other clothing must be free of oil and grease. Wear high
top-safety shoes; low-cut shoes are a hazard because
sparks and molten metal could lodge in them, especially
when you are sitting down.
To prevent head burns during overhead welding
operations, you should wear leather or flameproof caps
under the helmet. Earplugs also should be worn to keep
sparks or splatter from entering and burning the ears.
Where the welder is exposed to falling or sharp objects,
combination welding helmet/hard hats should be used.
For very heavy work, fire-resistant leggings or high
boots should be worn. Shoes or boots having exposed
nailheads or rivets should NOT be worn. Oilskins or
plastic clothing must NOT be worn in any welding
operation.
Medium- and heavy-gas welding, all-electric welding, and welding in the vertical or overhead welding
position require special flameproof clothing made of
leather or other suitable material. This clothing is designed to protect you against radiated heat, splashes of
hot metal, or sparks. This clothing consists of aprons,
sleeves, combination sleeves and bib, jackets, and overalls. They afford a choice of protection depending upon
the specific nature of the particular welding or cutting
job. Sleeves provide satisfactory protection for welding
operations at floor or bench level.
NOTE: If leather protective clothing is not available, then woolen clothing is preferable to cotton.
Woolen clothing is not as flammable as cotton and helps
protect the operator from the changes in temperature
caused by welding. Cotton clothing, if used, should be
chemically treated to reduce its flammability.
The cape and sleeves are particularly suited for
overhead welding, because it protects the back of the
neck, top of the shoulders, and the upperpart of the back
3-35
CHAPTER 4
GAS CUTTING
and cut bevels or other shapes that require holding the
torch at an angle.
The common methods used in cutting metal are
oxygas flame cutting, air carbon-arc cutting, and
plasma-arc cutting. The method used depends on the
type of metal to be cut and the availability of equipment.
As a Steelworker, oxygas or air carbon-arc equipment
is the most common type of equipment available for
your use. Oxygas equipment is explained in this chapter
and air carbon-arc cutting is covered in chapter 7.
Partial oxidation of the metal is a vital part of the
oxygas cutting process. Because of this, metals that do
not oxidize readily are not suitable for oxygas cutting.
Carbon steels are easily cut by the oxygas process, but
special techniques (described later in this chapter) are
required for the cutting of many other metals.
The oxygas cutting torch has many uses in steelwork. At most naval activities, the Steelworker finds the
cutting torch an excellent tool for cutting ferrous metals.
This versatile tool is used for operations, such as beveling plate, cutting and beveling pipe, piercing holes in
steel plate, and cutting wire rope.
OXYGAS CUTTING EQUIPMENT
An oxygas cutting outfit usually consists of a cylinder of acetylene or MAPP gas, a cylinder of oxygen, two
regulators, two lengths of hose with fittings, and a
cutting torch with tips (fig. 4-1). An oxygas cutting
outfit also is referred to as a cutting rig.
When using the oxygas cutting process, you heat a
spot on the metal to the kindling or ignition temperature
(between 1400°F and 1600°F for steels). The term for
this oxygas flame is the PREHEATING FLAME. Next,
you direct a jet of pure oxygen at the heated metal by
pressing a lever on the cutting torch. The oxygen causes
a chemical reaction known as OXIDATION to take place
rapidly. When oxidation occurs rapidly, it is called
COMBUSTION or BURNING. When it occurs slowly,
it is known as RUSTING.
In addition to the basic equipment mentioned above,
numerous types of auxiliary equipment are used in
oxygas cutting. An important item is the spark igniter
that is used to light the torch (fig. 4-2, view A). Another
item you use is an apparatus wrench. It is similar in
design to the one shown in figure 4-2, view B. The
apparatus wrench is sometimes called a gang wrench
because it fits all the connections on the cutting rig. Note
that the wrench shown has a raised opening in the handle
that serves as an acetylene tank key.
When you use the oxygas torch method to cut metal,
the oxidation of the metal is extremely rapid and part of
the metal actually burns. The heat, liberated by the
burning of the iron or steel, melts the iron oxide formed
by the chemical reaction and accelerates the preheating
of the object you are cutting. The molten material runs
off as slag, exposing more iron or steel to the oxygen jet.
Other common accessories include tip cleaners, cylinder trucks, clamps, and holding jigs. Personal safety
apparel, such as goggles, hand shields, gloves, leather
aprons, sleeves, and leggings, are essential and should
be worn as required for the job at hand. Information on
safety apparel is also contained in chapter 3 of this text.
In oxygas cutting, only that portion of the metal that
is in the direct path of the oxygen jet is oxidized. The
narrow slit, formed in the metal as the cutting progresses, is called the kerf. Most of the material removed
from the kerf is in the form of oxides (products of the
oxidation reaction). The remainder of the material is
molten metal that is blown or washed out of the kerf by
the force of the oxygen jet.
Oxygas cutting equipment can be stationary or portable. A portable oxygas outfit, such as the one shown in
figure 4-3, is an advantage when it is necessary to move
the equipment from one job to another.
To conduct your cutting requirements, you must be
able to set up the cutting equipment and make the
required adjustments needed to perform the cutting operation. For this reason it is important you understand
the purpose and function of the basic pieces of equipment that make up the cutting outfit. But, before discussing the equipment, let’s look at the gases most often used
in cutting: acetylene, MAPP gas, and oxygen.
The walls of the kerf formed by oxygas cutting of
ferrous metals should be fairly smooth and parallel to
each other. After developing your skills in handling the
torch, you can keep the cut within close tolerances;
guide the cut along straight, curved, or irregular lines;
4-1
Figure 4-1.—Oxygas cutting outfit.
Figure 4-2.—(A)Spark igniter; (B) apparatus wrench.
4-2
Figure 4-3.—A portable oxygas cutting and welding outfit.
ACETYLENE
Acetylene is a flammable fuel gas composed of
carbon and hydrogen having the chemical formula
C2H2.Whenburned with oxygen, acetylene produces a
hot flame, having a temperature between 5700°F and
6300°F. Acetylene is a colorless gas, having a disagreeable odor that is readily detected even when the gas is
highly diluted with air. When a portable welding outfit,
similar to the one shown in figure 4-3 is used, acetylene
is obtained directly from the cylinder. In the case of
stationary equipment, similar to the acetylene cylinder
bank shown in figure 4-4, the acetylene can be piped to
a number of individual cutting stations.
Figure 4-4.—Stationary acetylene cylinder bank.
Cylinder Design
Acetylene can be safely compressed up to 275 psi
when dissolved in acetone and stored in specially designed cylinders filled with porous material, such as
balsa wood, charcoal, finely shredded asbestos, corn
pith, portland cement, or infusorial earth. These porous
filler materials aid in the prevention of high-pressure gas
pockets forming in the cylinder.
Acetone is a liquid chemical that dissolves large
portions of acetylene under pressure without changing
the nature of the gas. Being a liquid, acetone can be
drawn from an acetylene cylinder when it is not upright.
You should not store acetylene cylinders on their side,
but if they are, you must let the cylinder stand upright
for a minimum of 2 hours before using. This allows the
acetone to settle to the bottom of the cylinder.
Hazards
Pure acetylene is self-explosive if stored in the free
state under a pressure of 29.4 pounds per square inch
(psi). A slight shock is likely to cause it to explode.
NOTE: Acetone contaminates the hoses, regulators, torch, and disrupts the flame.
WARNING
Acetylene is measured in cubic feet. The most common cylinder sizes are 130-, 290-, and 330-cubic-foot
capacity. The standard size cylinder the Navy uses holds
Acetylene becomes extremely dangerous
if used above 15 pounds pressure.
4-3
Cylinder Design
Total weight for a MAPP cylinder, which has the
same physical size as a 225-cubic-foot acetylene cylinder, is 120 pounds (70 pounds which is MAPP gas).
MAPP cylinders contain only liquid fuel. There is no
cylinder packing or acetone to impair fuel withdrawal;
therefore, the entire contents of a MAPP cylinder can be
used. For heavy-use situations, a MAPP cylinder delivers more than twice as much gas as an acetylene cylinder
for the same time period.
MAPP Characteristics
Because of its superior heat transfer characteristics,
MAPP produces a flame temperature of 5300°F when
burned with oxygen. MAPP equals, or exceeds, the
performance of acetylene for cutting, heating, and brazing.
MAPP is not sensitive to shock and is nonflammable in the absence of oxygen. There is no chance of an
explosion if a cylinder is bumped, jarred, or dropped.
You can store or transport the cylinders in any position
with no danger of forming an explosive gas pocket.
The characteristic odor, while harmless, gives warnings of fuel leaks in the equipment long before a dangerous condition can occur. MAPP gas is not restricted
to a maximum working pressure of 15 psig, as is acetylene. In jobs requiring higher pressures and gas flows,
MAPP can be used safely at the full-cylinder pressure
of 95 psig at 70°F. Because of this, MAPP is an excellent
gas for underwater work.
Figure 4-5.—Acetylene cylinder.
225 cubic feet of acetylene. Just because a cylinder has
a 225-cubic-foot capacity does not necessarily mean it
has 225 cubic feet of acetylene in it. Because it is
dissolved in acetone, you cannot judge how much acetylene is left in a cylinder by gauge pressure. The pressure
of the acetylene cylinder will remain fairly constant until
most of the gas is consumed.
An example of an acetylene cylinder is shown in
figure 4-5. These cylinders are equipped with fusible
plugs that relieve excess pressure if the cylinder is
exposed to undo heat. The standard Navy acetylene
cylinder contains 225 cubic feet of acetylene and weighs
about 250 pounds. The acetylene cylinder is yellow, and
all compressed-gas cylinders are color-coded for identification. More on the color coding of cylinders is
covered later in this chapter.
Bulk MAPP Gas
Bulk MAPP gas facilities, similar to liquid oxygen
stations, are installed at some activities where large
supplies of the gas are used. In bulk installations, MAPP
gas is delivered through a piping system directly to the
user points. Maximum pressure is controlled centrally
for efficiency and economy.
Cylinder-filling facilities are also available from
bulk installations that allow users to fill their cylinders
on site. Filling a 70-pound MAPP cylinder takes one
man about 1 minute and is essentially like pumping
water from a large tank to a smaller one.
MAPP GAS
MAPP (methylacetylene-propadiene) is an all-purpose industrial fuel having the high-flame temperature
of acetylene but has the handling characteristics of
propane. Being a liquid, MAPP is sold by the pound,
rather than by the cubic foot, as with acetylene. One
cylinder containing 70 pounds of MAPP gas can accomplish the work of more than six and one-half 225-cubicfoot acetylene cylinders; therefore, 70 pounds of MAPP
gas is equal to 1,500 cubic feet of acetylene.
MAPP Gas Safety
MAPP gas vapor is stable up to 600°F and 1,100
psig when exposed to an 825°F probe. The explosive
limits of MAPP gas are 3.4 percent to 10.8 percent in air
or 2.5 percent to 80 percent in oxygen. As shown in
4-4
Figure 4-6.—Explosive limits of MAPP and acetylene in air.
Figure 4-7.—Typical oxygen cylinder.
figure 4-6, you can see these limits are narrow in comparison with that of acetylene.
MAPP gas has a highly detectable odor. The smell
is detectable at 100 ppm, or at a concentration of 1/340th
of its lower explosive limit. Small fuel-gas systems may
leak 1 or 1 1/2 pounds of fuel or more in an 8-hour shift;
bulk systems will leak even more. Fuel-gas leaks are
often difficult to find and often go unnoticed; however,
a MAPP gas leak is easy to detect and can be repaired
before it becomes dangerous.
MAPP toxicity is rated “very slight,” but high concentrations (5,000 ppm) may have an anesthetic effect.
Local eye or skin contact with MAPP gas vapor causes
no adverse effect; however, the liquid fuel can cause
dangerous frostlike burns due to the cooling caused by
the rapid evaporation of the liquid.
The identification markings on a MAPP cylinder are
a yellow body with band “B” colored orange and the top
yellow.
corrosion of aluminum are all due to the action of
atmospheric oxygen. This action is known as oxidation.
Oxygen is obtained commercially either by the
liquid-air process or by the electrolytic process. In the
liquid-air process, the air is compressed and then
cooled to a point where the gases become liquid (approximately –375°F). The temperature is then raised to
above –321 ‘F, at which point the nitrogen in the air
becomes gas again and is removed. When the temperature of the remaining liquid is raised to –297°F, the
oxygen forms gas and is drawn off. The oxygen is
further purified and compressed into cylinders for use.
The other process by which oxygen is produced—
the electrolytic process—consists of running an electrical current through water to which an acid or an alkali
has been added. The oxygen collects at the positive
terminal and is drawn off through pipes to a container.
Oxygen is supplied for oxyacetylene welding in
seamless steel cylinders. A typical oxygen cylinder is
shown in figure 4-7. The color of a standard oxygen
cylinder used for industrial purposes is solid green.
Oxygen cylinders are made in several sizes. The size
most often used in welding and cutting is the 244-cubicfoot capacity cylinder. This cylinder is 9 inches in diameter, 51 inches high, and weighs about 145 pounds
and is charged to a pressure of 2,200 psi at 70°F.
OXYGEN
Oxygen is a colorless, tasteless, and odorless gas
and is slightly heavier than air. It is nonflammable but
supports combustion with other elements. In its free
state, oxygen is one of the more common elements. The
atmosphere is made up of about 21 parts of oxygen and
78 parts of nitrogen, the remainder being rare gases.
Rusting of ferrous metals, discoloration of copper, and
4-5
You can determine the amount of oxygen in a compressed-gas cylinder by reading the volume scale on the
high-pressure gauge attached to the regulator.
REGULATORS
You must be able to reduce the high-pressure gas in
a cylinder to a working pressure before you can use it.
This pressure reduction is done by a regulator or reducing valve. The one basic job of all regulators is to take
the high-pressure gas from the cylinder and reduce it to
a level that can be safely used. Not only do they control
the pressure but they also control the flow (volume of
gas per hour).
Regulators come in all sizes and types. Some are
designed for high-pressure oxygen cylinders (2,200
psig), while others are designed for low-pressure gases,
such as natural gas (5 psig). Some gases like nitrous
oxide or carbon dioxide freeze when their pressure is
reduced so they require electrically heated regulators.
Most regulators have two gauges: one indicates the
cylinder pressure when the valve is opened and the other
indicates the pressure of the gas coming out of the
regulator. You must open the regulator before you get a
reading on the second gauge. This is the delivery pressure of the gas, and you must set the pressure that you
need for your particular job.
Figure 4-8.—Single-stage regulators.
The pressures that you read on regulator gauges is
called gauge pressure. If you are using pounds per
square inch, it should be written as psig (this acronym
means pounds per square inch gauge). When the gauge
on a cylinder reads zero, this does not mean that the
cylinder is empty. In actuality, the cylinder is still full of
gas, but the pressure is equal to the surrounding atmospheric pressure. Remember: no gas cylinder is empty
unless it has been pumped out by a vacuum pump.
not made to withstand the high pressures that oxygen
regulators are subjected to.
In the oxygen regulator, the oxygen enters through
the high-pressure inlet connection and passes through a
glass wool falter that removes dust and dirt. Turning the
adjusting screw IN (clockwise) allows the oxygen to
pass from the high-pressure chamber to the low-pressure chamber of the regulator, through the regulator
outlet, and through the hose to the torch. Turning the
adjusting screw further clockwise increases the working
pressure; turning it counterclockwise decreases the
working pressure.
There are two types of regulators that control the
flow of gas from a cylinder. These are either single-stage
or double-stage regulators.
Single-Stage Regulators
Regulators are used on both high- and low-pressure
systems. Figure 4-8 shows two SINGLE-STAGE regulators: one for acetylene and one for oxygen. The regulator mechanism consists of a nozzle through which the
gases pass, a valve seat to close off the nozzle, a diaphragm, and balancing springs. These mechanisms are
all enclosed in a suitable housing. Fuel-gas regulators
and oxygen regulators are basically the same design.
The difference being those designed for fuel gases are
The high-pressure gauge on an oxygen regulator is
graduated from 0 to 3,000 psig and from 0 to 220 in
cubic feet. This allows readings of the gauge to determine cylinder pressure and cubic content. Gauges are
calibrated to read correctly at 70°F. The working pressure gauge may be graduated in “psig” from 0 to 150,
0 to 200, or from 0 to 400, depending upon the type of
regulator used. For example, on regulators designed for
4-6
Figure 4-9.—Double-stage regulator.
heavy cutting, the working pressure gauge is graduated
from 0 to 400.
regulator at the speed of sound. If there is any dirt
present in the connections, it will be blasted into the
precision-fitted valve seats, causing them to leak This
results in a condition that is known as creep. Creep
occurs when you shut of the regulator but not the cylinder and gas pressure is still being delivered to the
low-pressure side.
The major disadvantage of single-stage regulators
is that the working gas pressure you set will decrease as
the cylinder pressure decreases; therefore, you must
constantly monitor and reset the regulator if you require
a fixed pressure and flow rate. Keeping the gas pressure
and flow rate constant is too much to expect from a
regulator that has to reduce the pressure of a full cylinder
from 2,200 psig to 5 psig. This is where double-stage
regulators solve the problem.
Regulators are built with a minimum of two relief
devices that protect you and the equipment in the case
of regulator creep or high-pressure gas being released
into the regulator all at once. All regulator gauges have
blowout backs that release the pressure from the back
of the gauge before the gauge glass explodes. Nowadays, most manufacturers use shatterproof plastic instead of glass.
Double-Stage Regulators
The double-stage regulator is similar in principle to
the one-stage regulator. The main difference being that
the total pressure drop takes place in two stages instead
of one. In the high-pressure stage, the cylinder pressure
is reduced to an intermediate pressure that was predetermined by the manufacturer. In the low-pressure stage,
the pressure is again reduced from the intermediate
pressure to the working pressure you have chosen. A
typical double-stage regulator is shown in figure 4-9.
The regulator body is also protected by safety devices. Blowout disks or spring-loaded relief valves are
the two most common types of devices used. When a
blowout disk ruptures, it sounds like a cannon. Springloaded relief valves usually make howling or shrieking
like noises. In either case, your first action, after you
recover from your initial fright, should be to turn off the
cylinder valve. Remove the regulator and tag it for repair
or disposal.
Problems and Safety
When opening a gas cylinder, you should just
“crack” the valve a little. This should be done before
attaching the regulator and every time thereafter. By
opening the cylinder before connecting the regulator,
you blow out any dirt or other foreign material that
might be in the cylinder nozzle. Also, there is the
Regulators are precise and complicated pieces of
equipment. Carelessness can do more to ruin a regulator
than any other gas-using equipment. One can easily
damage a regulator by simply forgetting to wipe clean
the cylinder, regulator, or hose connections. When you
open a high-pressure cylinder, the gas can rush into the
4-7
possibility of a regulator exploding if the cylinder valve
is opened rapidly.
WARNING
Oil or other petroleum products must never
be used around oxygen regulators because these
products will either cause a regulator explosion
or fire.
HOSES
Figure 4-10.—Types of twin welding hose.
The hoses used to make the connections between
the torch and the regulators must be strong, nonporous,
light, and flexible enough to make torch movements
easy. They must be made to withstand internal pressures
that can reach as high as 100 psig. The rubber used in
hose manufacture is specially treated to remove the
sulfur that could cause spontaneous combustion.
All connections for welding and cutting hoses have
been standardized by the Compressed Gas Association.
Letter grades A, B, C, D, and E plus the type of gas used
correspond directly with the connections on the regulators. A, B, and C are the most common size connections.
A-size is for low-flow rates; B-size for medium-flow
rates; and C-size is for heavy-flow rates. D and E sizes
are for large cutting and heating torches.
Welding hose is available in single- and doublehose lengths. Size is determined by the inside diameter,
and the proper size to use depends on the type of work
for which it is intended. Hose used for light work has a
3/1 6 or 1/4 inch inside diameter and one or two plies of
fabric. For heavy-duty welding and cutting operations,
use a hose with an inside diameter of 5/1 6 inch and three
to five plies of fabric. Single hose is available in the
standard sizes as well as 1/2-, 3/4-, and 1-inch sizes.
These larger sizes are for heavy-duty heating and for use
on large cutting machines.
When ordering connections, you must specify the
type of gas the hose will be carrying. This is because the
connections will be threaded different y for different
types of gas. Fuel gases use left-hand threads, while
oxygen uses right-hand threads. The reason for this is to
prevent the accidental hookup of a fuel gas to a life-support oxygen
system or vice versa.
/
The basic hose connection consists of a nut and
gland. The nut has threads on the inside that match up
with the male inlet and outlet on the torch and regulator.
The gland slides inside the hose and is held in place by
a ferrule that has been crimped. The nut is loose and can
be turned by hand or a wrench to tighten the threaded
nut onto the equipment.
The most common type of cutting and welding hose
is the twin or double hose that consists of the fuel hose
and the oxygen hose joined together side by side. They
are joined together by either a special rib (fig. 4-10, view
A) or by clamps (fig. 4-10, view B). Because they are
joined together, the hoses are less likely to become
tangled and are easier to move from place.
Another important item that is often overlooked are
check valves. These inexpensive valves prevent personal injuries and save valuable equipment from flashbacks. When ordering, make sure you specify the type
of gas, connection size, and thread design. The check
valves should be installed between the torch connection
and the hose.
The length of hose you use is important. The delivery pressure at the torch varies with the length of the
hose. A 20-foot, 3/16-inch hose maybe adequate for a
job, but if the same hose was 50 feet long, the pressure
drop would result in insufficient gas flow to the torch.
Longer hoses require larger inside diameters to ensure
the correct flow of gas to the torch. When you are having
problems welding or cutting, this is one area to check
CUTTING TORCHES
The equipment and accessories for oxygas cutting
are the same as for oxygas welding except that you use
a cutting torch or a cutting attachment instead of a
welding torch. The main difference between the cutting
torch and the welding torch is that the cutting torch has
The hoses used for fuel gas and oxygen are identical
in construction, but they differ in color. The oxygen hose
cover is GREEN, and the fuel-gas hose cover is RED.
This color coding aids in the prevention of mishaps that
could lead to dangerous accidents.
4-8
Figure 4-11.—One piece oxygas cutting torch.
Figure 4-12.—Cutting attachment for combination torch.
an additional tube for high-pressure cutting oxygen.The
flow of high-pressure oxygen is controlled from a valve
on the handle of the cutting torch. In the standard cutting
torch, the valve may be in the form of a trigger assembly
like the one in figure 4-11. On most torches, the cutting
oxygen mechanism is designed so the cutting oxygen
can be turned on gradually. The gradual opening of the
cutting oxygen valve is particularly helpful in operations, such as hole piercing and rivet cutting.
unscrew the welding tip and then screw on the cutting
attachment. The high-pressure cutting oxygen is controlled by a lever on the torch handle, as shown in figure
4-12.
Cutting Torch Tips
As in welding, you must use the proper size cutting
tip if quality work is to be done. The preheat flames must
furnish just the right amount of heat, and the oxygen jet
orifice must deliver the correct amount of oxygen at just
the right pressure and velocity to produce a clean cut.
All of this must be done with a minimum consumption
of oxygen and fuel gases. Careless workers and workers
not acquainted with the correct procedures waste both
oxygen and fuel gas. This does not seem important when
you are working in a shop, but if you are deployed, it
Torch Body
Most welding torches are designed so the body of
the torch can accept either welding tips or a cutting
attachment. This type of torch is called a combination
torch. The advantage of this type of torch is the ease in
changing from the welding mode to the cutting mode.
There is no need to disconnect the hoses; you just
4-9
Figure 4-13.—Common cutting torch tips and their uses.
becomes critical due to the long lead time between
resupply.
chases its cutting and welding equipment, there is the
possibility of having two or three different types of
cutting torches in your kits. Make sure that the cutting
Each manufacturer makes many different types of
cutting tips. Although the orifice arrangements and the
tip material are much the same among the manufacturers, the part of the tip that fits into the torch head often
differs in design. Because of the way the Navy pur-
tips match the cutting attachment and ensure that the
cutting attachment matches the torch body. Figure 4-13
shows the different styles of tips, their orifice arrangements, and their uses. The tips and seats are designed to
4-10
127.376
Figure 4-14.—Four cutting-tip conditions.
produce a even flow of gas and to keep themselves as
cool as possible. The seats must produce leakproof
joints. If the joints leak, the preheat gases could mix
with the cutting oxygen or escape to the atmosphere,
resulting in poor cuts or the possibility of flashbacks.
tips is to push the cleaner straight in and out of the
orifice. Be careful not to turn or twist the cleaning
wire. Figure 4-15 shows a typical set of tip cleaners.
Occasionally the cleaning of the tips causes
enlargement and distortion of the orifices, even when
using the proper tip cleaners. If the orifices become
enlarged, you will get shorter and thicker preheating
flames; in addition, the jet of cutting oxygen will
spread, rather than leave the torch, in the form of a
long, thin stream. If the orifices become belled for a
short distance at the end, you can sometimes correct
this by rubbing the tip back and forth against emery
cloth placed on a flat surface. This action wears down
the end of the tip where the orifices have been belled,
thus bringing the orifices back to their original size.
Obviously, this procedure will not work if the damage
is great or if the belling extends more than a slight
distance into the orifice.
To make clean and economical cuts, you must
keep the tip orifices and passages clean and free of
burrs and slag. If the tips become dirty or
misshapened, they should be put aside for restoration.
Figure 4-14 shows four tips: one that is repairable,
two that need replacing, and one in good condition.
Since it is extremely important that the sealing
surfaces be clean and free of scratches or burrs, store
the tips in a container that cannot scratch the seats.
Aluminum racks, plastic racks, and wood racks or
boxes make ideal storage containers.
TIP MAINTENANCE.— In cutting operations,
the stream of cutting oxygen sometimes blows slag
and molten metal into the tip orifices which partially
clogs them. When this happens, you should clean the
orifices thoroughly before you use the tip again. A
small amount of slag or metal in an orifice will
seriously interfere with the cutting operation. You
should follow the recommendations of the torch
manufacturer as to the size of drill or tip cleaner to
use for cleaning the orifices. If you do not have a tip
cleaner or drill, you may use a piece of soft copper
wire. Do not use twist drills, nails, or welding rods for
cleaning tips because these items are likely to enlarge
and distort the orifices.
After reconditioning a tip, you may test it by lighting
the torch and observing the preheating flames. If the
Clean the orifices of the cutting torch tip in the
same manner as the single orifice of the welding torch
tip. Remember: the proper technique for cleaning the
Figure 4-15.—Tip cleaners.
4-11
MAPP GAS CUTTING TIPS.— Four basic types
of MAPP gas cutting tips are used: two are for use with
standard pressures and normal cutting speeds, and two
are for use with high pressures and high cutting speeds.
Only the standard pressure tips, types SP and FS, will
be covered here since they are the ones that Steelworkers will most likely use. SP stands for standard pressure
and FS for fine standard.
The SP tip (fig. 4-16, view A) is a one-piece standard
pressure tip. It is used for cutting by hand, especially by
welders who are accustomed to one-piece tips. SP tips
are more likely to be used in situations where MAPP gas
is replacing acetylene as the fuel gas.
The FS tip (fig. 4-16, view B) is a two-piece, fine
spline, standard pressure tip. It is used for cutting by
hand as well as by machine. Welders accustomed to
two-piece cutting tips will use them in hand cutting,
especially when MAPP gas is replacing natural gas or
propane as the fuel gas. The FS tips will produce heavier
preheating flames and faster starts than the SP tips;
however, two-piece tips will not take as much thermal
or physical abuse as one-piece tips. But in the hands of
skilled Steelworkers, they should last as long as onepiece tips.
Figure 4-16.—MAPP gas cutting tips.
flames are too short, the orifices are still partially
blocked. If the flames snap out when you close the
valves, the orifices are still distorted.
If the tip seat is dirty or scaled and does not properly
fit into the torch head, heat the tip to a dull red and
quench it in water. This will loosen the scale and dirt
enough so you can rub it off with a soft cloth.
Recommended tip sizes and gas pressures for use in
cutting different thicknesses of steel using MAPP gas as
a fuel are given in table 4-1.
Table 4-1.—Recommended MAPP Gas Tip Sizes and Oxyfuel Pressures
4-12
OXYGAS CUTTING OPERATIONS
and 5 psig. After the hose has been purged, turn the
screw back out again (counterclockwise) to shutoff the
oxygen. Do the same for the fuel-gas hose, but do it
ONLY in a well-ventilated place that is free from sparks,
flames, or other possible sources of ignition.
Before you begin a cutting operation with an oxygas
cutting torch, make a thorough inspection of the area.
Ensure that there are no combustible materials in the
area that could be ignited by the sparks or slag produced
by the cutting operation. If you are burning into a wall,
inspect the opposite side of the wall, and post a fire
watch as required.
. Connect the hoses to the torch. The RED
(fuel-gas) hose is connected to the connection gland
with the needle valve marked “FUEL.” The GREEN
(oxygen) hose is connected to the connection gland with
the needle valve marked “OXY.”
EQUIPMENT SETUP
l With the torch valves closed, turn both regulator
screws clockwise to test the hose connections for leaks.
If none are found, turn the regulator screws
counterclockwise and drain the hose by opening the
torch valves.
Setting up the oxygas equipment and preparing for
cutting must be done carefully and systematically to
avoid costly mistakes. To ensure your own safety, as
well as the safety of your coworkers and equipment,
make sure the following steps are taken before any
attempt is made to light the torch:
Q Select the correct cutting tip and install it in the
cutting torch head. Tighten the assembly by hand, and
then tighten with your gang wrench.
l Secure the cylinders so they cannot be accidently
knocked over. A good way to do this is to either put them
in a corner or next to a vertical column and then secure
them with a piece of line. After securing the cylinders,
remove the protective caps. Cylinders should never be
secured to a structural member of a building that is a
current conductor.
l Adjust the working pressures. The fuel-gas
pressure is adjusted by opening the torch needle valve
and turning the fuel-gas regulator screw clockwise.
Adjust the regulator to the working pressure needed for
the particular tip size, and then close the torch needle
valve. To adjust MAPP gas, you should set the gauge
pressure with the torch valves closed. To adjust the
oxygen working pressure, you should open the oxygen
torch needle valve and proceed in the same manner as
in adjusting the fuel-gas pressure.
l Standing to one side, crack each cylinder valve
slightly and then immediately close the valve again. This
blows any dirt or other foreign matter out of the cylinder
valve nozzle. Do not bleed fuel gas into a confined area
because it may ignite. Ensure the valves are closed and
wipe the connections with a clean cloth.
In lighting the torch and adjusting the flame, always
follow the manufacturer’s directions for the particular
model of torch being used. This is necessary because the
procedure varies somewhat with different types of
torches and, in some cases, even with different models
made by the same manufacturer.
c Connect the fuel-gas regulator to the fuel-gas
cylinder and the oxygen regulator to the oxygen
cylinder. Using a gang wrench, snug the connection nuts
sufficiently to avoid leaks.
l Back off the regulator screws to prevent damage
to the regulators and gauges and open the cylinder
valves slowly. Open the fuel-gas valve only one-half
turn and the oxygen valve all the way. Some fuel-gas
cylinders have a handwheel for opening the fuel-gas
valve while others require the use of a gang wrench or
T-handle wrench. Leave the wrench in place while the
cylinder is in use so the fuel-gas bottle can be turned off
quickly in an emergency. Read the high-pressure gauge
to check the contents in each cylinder.
In general, the procedure used for lighting a torch is
to first open the torch oxygen needle valve a small
amount and the torch fuel-gas needle valve slightly
more, depending upon the type of torch. The mixture of
oxygen and fuel gas coming from the torch tip is then
lighted by means of a spark igniter or stationary pilot
flame.
CAUTION
l Connect the RED hose to the fuel-gas regulator
and the GREEN hose to the oxygen regulator. Notice the
left-hand threads on the fuel-gas connection.
NEVER use matches to light the torch; their
length requires bringing the hand too close to
the tip. Accumulated gas may envelop the hand
and, upon igniting, result in a severe burn. Also,
never light the torch from hot metal.
l To blow out the oxygen hose, turn the regulator
screw in (clockwise) and adjust the pressure between 2
4-13
Strongly carburizing flames are not used in cutting
low-carbon steels because the additional carbon they
add causes embrittlement and hardness. These flames
are ideal for cutting cast iron because the additional
carbon poses no problems and the flame adds more heat
to the metal because of its size.
Slightly carburizing flames are ideal for cutting
steels and other ferrous metals that produce a large
amount of slag. Although a neutral flame is best for most
cutting, a slightly carburizing flame is ideal for producing a lot of heat down inside the kerf. It makes fairly
smooth cuts and reduces the amount of slag clinging to
the bottom of the cut.
NEUTRAL FLAME.— The most common preheat
flame for oxygas cutting is the neutral flame. When you
increase the oxygen, the carburizing flame becomes
neutral. The feather will disappear from the inner flame
cone and all that will be left is the dark blue inner flame
and the lighter blue outer cone. The temperature is about
5600°F.
Figure 4-17.—MAPP-gas flames.
After checking the fuel-gas adjustment, you can
adjust the oxygas flame to obtain the desired characteristics for the work at hand, by further manipulating
the oxygen and fuel-gas needle valves according to the
torch manufacturer’s direction.
The neutral flame will not oxidize or add carbon to
the metal you are cutting. In actuality, a neutral flame
acts like the inert gases that are used in TIG and MIG
welding to protect the weld from the atmosphere. When
you hold a neutral preheat flame on one spot on the metal
until it melts, the molten puddle that forms looks clear
and lies very quietly under the flame.
There are three types of gas flames commonly used
for all oxygas processes. They are carburizing, neutral,
and oxidizing. To ensure proper flame adjustment, you
should know the characteristics of each of these three
types of flame. Figure 4-17 shows how the three different flames look when using MAPP gas as the fuel.
OXIDIZING FLAME.— When you add a little
more oxygen to the preheat flame, it will quickly become shorter. The flame will start to neck down at the
base, next to the flame ports. The inner flame cone
changes from dark blue to light blue. Oxidizing flames
are much easier to look at because they are less radiant
than neutral flames. The temperature is about 6000°F.
A pure fuel-gas flame is long and bushy and has a
yellowish color. It takes the oxygen it needs for combustion from the surrounding air. The oxygen available is
not sufficient enough to burn the fuel gas completely;
therefore, the flame is smokey and consists of soot. This
flame is not suitable for use. You need to increase the
amount of oxygen by opening the oxygen needle valve
until the flame takes on a bluish white color, with a
bright inner cone surrounded by a flame envelope of a
darker hue. It is the inner cone that develops the required
operating temperature.
The oxidizing flame is rarely used for conventional
cutting because it produces excessive slag and does not
leave square-cut edges. Oxidizing flames are used in
conjunction with cutting machines that have a high-low
oxygen valve. The machine starts the cut with a oxidizing flame then automatically reverts to a neutral flame.
The oxidizing flame gives you fast starts when using
high-speed cutting machines and is ideal for piercing
holes in plate. Highly oxidizing flames are only used in
cutting metal underwater where the only source of oxygen for the torch is supplied from the surface.
CARBURIZING FLAME.— The carburizing
flame always shows distinct colors; the inner cone is
bluish white, the intermediate cone is white, the outer
envelope flame is light blue, and the feather at the tip of
the inner cone is greenish. The length of the feather can
be used as a basis for judging the degree of carburization. The highly carburizing flame is longer with yellow
or white feathers on the inner cone, while the slightly
carburizing flame has a shorter feather on the inner cone
and becomes more white. The temperature of carburizing flames is about 5400°F.
CUTTING MILD-CARBON STEEL
To cut mild-carbon steel with the oxygas cutting
torch, you should adjust the preheating flames to neutral.
4-14
Figure 4-19.—The effect of moving a cutting torch too rapidly
across the work.
Figure 4-18.—Position of torch tip for starting a cut.
Hold the torch perpendicular to the work, with the inner
cones of the preheating flames about 1/16 inch above
the end of the line to be cut (fig. 4-18). Hold the torch
in this position until the spot you are heating is a bright
red. Open the cutting oxygen valve slowly but steadily
by pressing down on the cutting valve lever.
When the cut is started correctly, a shower of sparks
will fall from the opposite side of the work, indicating
that the flame has pierced the metal. Move the cutting
torch forward along the line just fast enough for the
flame to continue to penetrate the work completely. If
you have made the cut properly, you will get a clean,
narrow cut that looks almost like it was made by a saw.
When cutting round bars or heavy sections, you can save
preheating time by raising a small burr with a chisel
where the cut is to begin. This small raised portion will
heat quickly, allowing you to start cutting immediately.
Figure 4-20.—Recommended procedure for cutting thin steel.
Notice that the two preheat flames are in line with the cut
(kerf).
Once you start the cut, you should move the torch
Slowly along the cutting mark or guide. As you move
the torch along, watch the cut so you can tell how it is
progressing. Adjust the torch as necessary. You must
move the torch at the correct speed, not too fast and not
too slow. If you go too slowly, the preheating flame
melts the top edges along the cut and could weld them
back together again. If you go too rapidly, the flame will
not penetrate completely, as shown in figure 4-19. When
this happens, sparks and slag will blow back towards
you. If you have to restart the cut, make sure there is no
slag on the opposite side.
When cutting steel 1/8 inch or less in thickness, use
the smallest cutting tip available. In addition, point the
tip in the direction the torch is traveling. By tilting the
tip, you give the preheating flames a chance to heat the
metal ahead of the oxygen jet, as shown in figure 4-20.
If you hold the tip perpendicular to the surface, you
decrease the amount of preheated metal and the adjacent
metal could cool the cut enough to prevent smooth
cutting action. Many Steelworkers actually rest the edge
of the tip on the metal during this process. If you use this
method, be careful to keep the end of the preheating
flame inner cone just above the metal.
Cutting Thin Steel
4-15
Figure 4-21.—Progress of a cut in thick steel. A. Preheat flames are 1/16 to 1/8 inch from the metal surface. Hold the torch in this spot
until the metal becomes cherry red. B. Move the torch slowly to maintain the rapid oxidation, even though the cut is only partially
through the metal. C. The cut is made through the entire thickness; the bottom of the kerf lags behind the top edge slightly.
Cutting Thick Steel
start the cut without preheating the entire edge of the
plate. In the second method, you place an iron filler rod
at the edge of a thick plate. As you apply the preheat
flames to the edge of the plate, the filler rod rapidly
reaches the cherry red temperature. At this point, turn
the cutting oxygen on and the rod will oxidize and cause
the thicker plate to start oxidizing.
Steel, that is greater than 1/8 inch thick, can be cut
by holding the torch so the tip is almost vertical to the
surface of the metal. If you are right-handed, one method
to cut steel is to start at the edge of the plate and move
from right to left. Left-handed people tend to cut left to
right. Either direction is correct and you may cut in the
direction that is most comfortable for you. Figure 4-21
shows the progress of a cut in thick steel.
CUTTING CAST IRON
It is more difficult to cut cast iron than steel because
the iron oxides in cast iron melt at a higher temperature
than the cast iron itself. Before you cut cast iron, it is
best to preheat the whole casting to prevent stress fractures. Do not heat the casting to a temperature that is too
high, as this will oxidize the surface and make cutting
After heating the edge of the steel to a dull cherry
red, open the oxygen jet all the way by pressing on the
cutting lever. As soon as the cutting action starts, move
the torch tip at a even rate. Avoid unsteady movement
of the torch to prevent irregular cuts and premature
stopping of the cutting action.
To start a cut quicker in thick plate, you should start
at the edge of the metal with the torch angled in the
opposite direction of travel. When the edge starts to cut,
bring the torch to a vertical position to complete the cut
through the total thickness of the metal. As soon as the
cut is through the metal, start moving the torch in the
direction of travel.
Two other methods for starting cuts are used. In the
first method, you nick the edge of the metal with a cold
chisel at the point where the cut is to start. The sharp
edges of the metal upset by the chisel will preheat and
oxidize rapidly under the cutting torch, allowing you to
Figure 4-22.—Torch movements for cutting cast iron.
4-16
Figure 4-24.—Using angle iron to cut bevels on steel plate.
Figure 4-23.—Typical gouging operation using a low-velocity
cutting jet for better control of depth and width.
spots, and rapidly prepare metal edges for welding.
Figure 4-23 shows a typical gouging operation.
If the gouging cut is not started properly, it is possible to cut accidently through the entire thickness of the
plate. If you cut too shallow, you can cause the operation
to stop. The travel speed of the torch along the gouge
line is important. Moving too fast creates a narrow,
shallow gouge and moving too slow creates the opposite; a deep, wide gouge.
more difficult. A preheat temperature of about 500°F is
normally satisfactory.
When cutting cast iron, adjust the preheating flame
of the torch to a carburizing flame. This prevents the
formation of oxides on the surface and provides better
preheat. The cast-iron kerf is always wider than a steel
kerf due to the presence of oxides and the torch movement. The torch movement is similar to scribing semicircles along the cutting line (fig. 4-22). As the metal
becomes molten, trigger the cutting oxygen and use its
force to jet the molten metal out of the kerf. Repeat this
action until the cut is complete.
BEVELING MILD STEEL
Frequently, you must cut bevels on plate or pipe to
form joints for welding. The flame must actually cut
through 2.8 inches of metal to make a bevel cut of 45
degrees on a 2-inch steel plate. You must take this into
consideration when selecting the tip and adjusting the
pressures. You use more pressure and less speed for a
bevel cut than for a straight cut.
Because of the difficulty in cutting cast iron with
the usual oxygas cutting torch, other methods of cutting were developed. These include the oxygen lance,
carbon-arc powder, inert-gas cutting, and plasma-arc
methods.
When bevel cutting, you adjust the tip so the preheating orifices straddle the cut. Apiece of l-inch angle
iron, with the angle up, makes an excellent guide for
beveling straight edges. To keep the angle iron in place
while cutting, you should use a heavy piece of scrap, or
tack-weld the angle to the plate being cut. Move the
torch along this guide, as shown in figure 4-24.
GOUGING MILD STEEL
Cutting curved grooves on the edge or surface of a
plate and removing faulty welds for rewelding are additional uses for the cutting torch. The gist of groove
cutting or gouging is based on the use of a large orifice,
low-velocity jet of oxygen instead of a high-velocity jet.
The low-velocity jet oxidizes the surface metal only and
gives better control for more accurate gouging. By
varying the travel speed, oxygen pressure, and the angle
between the tip and plate, you can make a variety of
gouge contours.
ELECTRIC DRIVE CUTTING
TORCH CARRIAGE
An improvement over mechanical guides is an electric motor-driven cutting torch carriage. The speed of
the motor can be varied allowing the welder to cut to
dimensions and to cut at a specific speed. A typical
motor driven carriage has four wheels: one driven by a
reduction gear, two on swivels (castor style), and one
freewheeling. The torch is mounted on the side of the
carriage and is adjusted up and down by a gear and rack
A gouging tip usually has five or six preheat orifices
that provide a more even preheat distribution. Automatic
machines can cut grooves to exact depths, remove bad
4-17
127.383
Figure 4-25.—Electric motor-driven carriage being used to cut a circle in steel plate.
equipped with an off-and-on switch, a reversing
switch, a clutch, and a speed-adjusting dial that is
calibrated in feet per minute.
Figure 4-26 shows an electric drive carriage on a
straight track being used for plate beveling. The
operator must ensure that the electric cord and gas
hoses do not become entangled on anything during the
cutting operation. The best way to check for hose,
electric cord, and torch clearance is to freewheel the
carriage the full length of the track by hand.
You will find that the torch carriage is a valuable
asset during deployment. This is especially true if
your shop is called upon to produce a number of
identical parts in quantity. Such an assignment might
involve the fabrication of a large supply of handhole
covers for runway fixtures, or another assignment
might be the production of a large quantity of thick
base plates for vertical columns. When using the torch
carriage, you should lay the track in a straight line
along a line parallel to the edge of the plate you are
going to cut. Next, you light the torch and adjust the
flame for the metal you are cutting. Move the carriage
so the torch flame preheats the edge of the plate and
then open the cutting oxygen valve and turn on the
carriage motor. The machine begins moving along the
track and continues to cut automatically until the end
of the cut is reached. When the cut is complete,
The rack is a part of the special torch. The torch also can
be tilted for bevel cuts. This machine comes with a
straight two-groove track and has a radial bar for use in
cutting circles and arcs. A motor-driven cutting torch
cutting a circle is shown in figure 4-25. The carriage is
127.384
Figure 4-26.—Electric motor-driven carriage being used
on straight track to cut a beveled edge on steel plate.
4-18
Figure 4-27.—Cutting pipe with an oxygas cutting torch.
you should do the following: promptly turn off the
cutting oxygen, turn off the current, and extinguish the
flame-in that order. The cutting speed depends upon
the thickness of the steel being cute
CUTTING AND BEVELING PIPE
Pipe cutting with a cutting torch requires a steady
hand to obtain a good bevel cut that is smooth and true.
Do not attempt to cut and bevel a heavy pipe in one
operation until you have developed considerable skill.
First, you should cut the pipe off square, and ensure all
the slag is removed from the inside of the pipe. Next,
you should bevel the pipe. This procedure produces a
cleaner and better job; it is ideal for use by an inexperienced Steelworker.
When cutting a piece of pipe, you should keep the
torch pointed toward the center line of the pipe. Start the
cut at the top and cut down one side. Then begin at the
top again and cut down the other side, finishing at the
bottom of the pipe. This procedure is shown in figure
4-27.
When you make T and Y fittings from pipe, the
cutting torch is a valuable tool. The usual procedure for
fabricating pipe fittings is to develop a pattern like the
one shown in figure 4-28, view A-1.
After you develop the pattern, wrap it around the
pipe, as shown in figure 4-28, view A-2. Be sure to leave
enough material so the ends overlap. Trace around the
pattern with soapstone or a scribe. It is a good idea to
mark the outline with a prick punch at 1/4-inch intervals.
During the cutting procedure, as the metal is heated, the
punch marks stand out and make it easier to follow the
line of cut. Place the punch marks so the cutting action
will remove them. If punch marks are left on the pipe,
they could provide notches from which cracking may
Starte
An experienced Steelworker can cut and bevel pipe
at a 45-degree angle in a single operation. A person with
little cutting experience should do the job in two steps.
Figure 4-28.—Fabricating a T.
In that case, the first step involves cutting the pipe at a
90-degree angle. In the second step, you bevel the edge
of the cut to a 45-degree angle. With the two-step
procedure, you must mark an additional line on the pipe.
This second line follows the contour of the line traced
around the pattern, but it is drawn away from the original
pattern line at a distance equal to the thickness of the
pipe wall. The first (90-degree) cut in the two-step
procedure is made along the second line. The second
(45-degree) cut is made along the original pattern line.
The primary disadvantage of the two-step procedure. is
it is time consuming and uneconomical in oxygen and
gas consumption.
The one-step method of cutting and beveling pipe
is not difficult, but it does require a steady hand and a
4-19
plate out on firebricks or other suitable material so the
flame does not damage anything when it burns through
the plate. Next, hold the torch over the hole location with
the tips of the inner cone of the preheating flames about
1/4 inch above the surface of the plate. Continue to hold
the torch in this position until a small spot has been
heated to a bright red. Then open the cutting oxygen
valve gradually, and at the same time, raise the nozzle
slightly away from the plate. As you start raising the
torch and opening the oxygen valve, rotate the torch
with a slow spiral motion. This causes the molten slag
to be blown out of the hole. The hot slag may fly around,
so BE SURE that your goggles are tightly fitted to your
face, and avoid placing your head directly above the cut.
great deal of experience to turn out a first-class job. An
example of this method for fabricating a T is shown in
figure 4-28. View A of figure 4-28 outlines the step-bystep procedures for fabricating the branch; view B
shows the steps for preparing the main section of the T;
and view C shows the assembled T, tack-welded and
ready for final welding.
Step 3 of view A shows the procedure for cutting the
miter on the branch. You should begin the cut at the end
of the pipe and work around until one half of one side is
cut. The torch is at a 45-degree angle to the surface of
the pipe along the line of cut. While the tip is at a
45-degree angle, you should move the torch steadily
forward, and at the same time, swing the butt of the torch
upward through an arc. This torch manipulation is necessary to keep the cut progressing in the proper direction
with a bevel of 45 degrees at all points on the miter. Cut
the second portion of the miter in the same reamer as
the first.
If you need a larger hole, outline the edge of the hole
with a piece of soapstone, and follow the procedure
indicated above. Begin the cut from the hole you pierced
by moving the preheating flames to the normal distance
from the plate and follow the line drawn on the plate.
Round holes are made easily by using a cutting torch
with a radius bar attachment.
The torch manipulation necessary for cutting the
run of the T is shown in Steps 3 and 4 of view B in figure
4-28. Step 3 shows the torch angle for the starting cut
and Step 4 shows the cut at the lowest point on the pipe.
Here you change the angle to get around the sharp curve
and start the cut in an upward direction. The completed
cut for the run is shown in Step 5 (fig. 4-28, view B).
CUTTING RIVETS
The cutting torch is an excellent tool for removing
rivets from structures to be disassembled. Rivet cutting
procedures are shown in figure 4-30. The basic method
is to heat the head of the rivet to cutting temperature by
using the preheating flames of the cutting torch. When
the rivet head is at the proper temperature, turn on the
oxygen and wash it off. The remaining portion of the
rivet can then be punched out with light hammer blows.
The step-by-step procedure is as follows:
Before final assembly and tack welding of any of
the parts of a fabricated fitting, you must clean the slag
from the inner pipe wall and check the fit of the joint.
The bevels must be smooth and have complete fusion
when you weld the joint.
PIERCING HOLES
1. Use the size of tip and the oxygen pressure
required for the size and type of rivet you are going to
cut.
The cutting torch is a valuable tool for piercing
holes in steel plate. Figure 4-29 shows the steps you
should use to pierce holes in steel plate. First, lay the
2. Heat a spot on the rivet head until it is bright red.
3. Move the tip to a position parallel with the
surface of the plate and turn on the cutting oxygen
slowly.
4. Cut a slot in the rivet head like the screwdriver
slot in a roundhead screw. When the cut nears the plate,
draw the nozzle back at least 1 1/2 inches from the rivet
so you do not cut through the plate.
5. When cutting the slot through to the plate, you
should swing the tip through a small arc. This slices half
of the rivet head off.
6. Swing the tip in an arc in the other direction to
slice the other half of the rivet head off.
Figure 4-29.—Piercing a hole with an oxygas cutting torch.
4-20
Figure 4-30.—Using a cutting torch to remove a rivet head,
By the time the slot has been cut, the rest of the rivet
head is at cutting temperature. Just before you get
through the slot, draw the torch tip back 1 1/2 inches to
allow the cutting oxygen to scatter slightly. This keeps
the torch from breaking through the layer of scale that
is always present between the rivet head and the plate.
It allows you to cut the head of the rivet off without
damaging the surface of the plate. If you do not draw
the tip away, you could cut through the scale and into
the plate.
rope strands from unlaying during cutting, seize the wire
rope on each side of the place where you intend to cut.
Adjust the torch to a neutral flame and make the cut
between the seizings. If the wire rope is going to go
through sheaves, then you should fuse the strand wires
together and point the end. This makes reeving the block
much easier, particularly when you are working with a
large-diameter wire rope and when reeving blocks that
are close together. To fuse and point wire rope, adjust
the torch to a neutral flame; then close the oxygen valve
until you get a carburizing flame. With proper torch
manipulation, fuse the wires together and point the wire
rope at the same time.
A low-velocity cutting tip is best for cutting buttonhead rivets and for removing countersunk rivets. A
low-velocity cutting tip has a cutting oxygen orifice with
a large diameter. Above this orifice are three preheating
orifices. Always place a low-velocity cutting tip in the
torch so the heating orifices are above the cutting orifice
when the torch is held in the rivet cutting position.
Wire rope is lubricated during fabrication and is
lubricated routinely during its service life. Ensure that
all excess lubricant is wiped off the wire rope before you
begin to cut it with the oxygas torch.
CUTTING WIRE ROPE
CUTTING ON CONTAINERS
You can use a cutting torch to cut wire rope. Wire
rope consists of many strands, and since these strands
do not form one solid piece of metal, you could experience difficulty in making the cut. To prevent the wire
Never perform cutting or welding on containers that
have held a flammable substance until they have been
cleaned thoroughly and safeguarded. Cutting, welding,
or other work involving heat or sparks on used barrels,
4-21
drums, tanks, or other containers is extremely dangerous
and could lead to property damage or loss of life.
Whenever available, use steam to remove materials
that are easily volatile. Washing the containers with a
strong solution of caustic soda or a similar chemical will
remove heavier oils.
Even after thorough cleansing, the container should
be further safeguarded by falling it with water before any
cutting, welding, or other hot work is done. In almost
every situation, it is possible to position the container so
it can be kept filled with water while cutting or other hot
work is being done. Always ensure there is a vent or
opening in the container for the release of the heated
vapor inside the container. This can be done by opening
the bung, handhole, or other fitting that is above water
level.
When it is practical to fill the container with water,
you also should use carbon dioxide or nitrogen in the
vessel for added protection. From time to time, examine
the gas content of the container to ensure the concentration of carbon dioxide or nitrogen is high enough to
prevent a flammable or explosive mixture. The air-gas
mixture inside any container can be tested with a suitable gas detector.
The carbon dioxide concentration should beat least
50 percent of the air space inside the container, and 80
percent or more when the presence of hydrogen or
carbon monoxide is detected. When using nitrogen, you
must ensure the concentration is at least 10 percent
higher than that specified for carbon dioxide.
Carbon dioxide or nitrogen is used in apparently
clean containers because there may still be traces of oil
or grease under the seams, even though the vessel was
cleaned and flushed with a caustic soda solution. The
heat from the cutting or welding operation could cause
the trapped oil or grease to release flammable vapors
that form an explosive mixture inside the container.
Figure 4-31.—Effects of correct and incorrect cutting procedures.
oxygas cut. In general, the quality of an oxygas cut is
judged by four characteristics:
A metal part that is suspiciously light maybe hollow
inside; therefore, you should vent the part by drilling a
hole in it before heating. Remember: air or any other gas
that is confined inside a hollow part will expand when
heated. The internal pressure created may be enough to
cause the part to burst. Before you do any hot work, take
every possible precaution to vent the air confined in
jacketed vessels, tanks, or containers.
1. The shape and length of the draglines
2. The smoothness of the sides
3. The sharpness of the top edges
4. The amount of slag adhering to the metal
DRAG LINES
JUDGING CUTTING QUALITY
Drag lines are line markings that show on the surface of the cut. Good drag lines are almost straight up
and down, as shown in figure 4-31, view A. Poor drag
To know how good of a cutting job you are doing,
you must understand know what constitutes a good
4-22
lines, as shown in figure 4-31, view B, are long and
irregular or curved excessively. Drag lines of this type
indicate a poor cutting procedure that could result in the
loss of the cut (fig. 4-31, views B and C). Draglines are
the best single indication of the quality of the cut made
with an oxygas torch. When the draglines are short and
almost vertical, the sides smooth, and the top edges
sharp, you can be assured that the slag conditions are
satisfactory.
BACKFIRE AND FLASHBACK
Improper operation of the oxygas torch can cause
the flame to go out with a loud snap or pop. This is called
a “backfire.” Close the torch valves, check the connections, and review your operational techniques before
relighting the torch. You may have caused the backfire
by touching the tip against the work, by overheating the
tip, or by operating the torch with incorrect gas pressures. A backfire also may be caused by a loose tip or
head or by dirt on the seat.
SIDE SMOOTHNESS
A flashback occurs when the flame burns back
inside the torch, usually with a shrill hissing or squealing
noise. You should close the torch oxygen valve that
controls the flame to stop the flashback at once. Then
you should close the gas valve and the oxygen and gas
regulators. Be sure you allow the torch to cool before
relighting it. Also, blow oxygen through the cutting tip
for a few seconds to clear out soot that may have
accumulated in the passages. Flashbacks may extend
back into the hose or regulators. Flashbacks indicate that
something is wrong, either with the torch or with the
way it is being operated. Every flashback should be
investigated to determine its cause before the torch is
relighted. A clogged orifice or incorrect oxygen and gas
pressures are often responsible. Avoid using gas pressures higher than those recommended by the manufacturer.
A satisfactory oxygas cut shows smooth sides. A
grooved, fluted, or ragged cut surface is a sign of poor
quaility.
TOP EDGE SHARPNESS
The top edges resulting from an oxygas cut should
be sharp and square (fig. 4-31, view D). Rounded top
edges, such as those shown in view E of figure 4-31, are
not satisfactory. The melting of the top edges may result
from incorrect preheating procedures or from moving
the torch too slowly.
SLAG CONDITIONS
CYLINDERS
An oxygas cut is not satisfactory when slag adheres
so tightly to the metal that it is difficult to remove.
Gas cylinders are made of high-quality steel. High-pressure gases, such as oxygen, hydrogen, nitrogen, and
compressed air, are stored in cylinders of seamless
construction. Only nonshatterable high-pressure gas
cylinders may be used by ships or activities operating
outside the continental United States. Cylinders for lowpressure gases, such as acetylene, may be welded or
brazed. Cylinders are carefully tested, either by the
factory or by a designated processing station, at pressures above the maximum permissible charging pressure.
SAFETY PRECAUTIONS
In all cutting operations, you must ensure that hot
slag does not come in contact with combustible material.
Globules of hot slag can roll along the deck for long
distances. Do not cut within 30 to 40 feet of unprotected
combustible materials. If you cannot remove the combustible materials, cover them with sheet metal or other
flameproof guards. Keep the fuel gas and oxygen cylinders far enough away from the work so hot slag does not
fall on the cylinders or hoses.
Identification of Cylinders
Color warnings provide an effective means for
marking physical hazards and for indicating the location
of safety equipment. Uniform colors are used for marking compressed-gas cylinders, pipelines carrying hazardous materials, and fire protection equipment.
Many of the safety precautions discussed in chapters 5 through 8 of this manual apply to cutting as well
as to welding. Be sure you are completely familiar with
all the appropriate safety precautions before attempting
oxygas cutting operations.
Five classes of material have been selected to represent the general hazards for dangerous materials,
4-23
Table 4-2.—Standard Colors
Figure 4-32.—Titles and color codes for compressed-gas cylinders.
4-24
while a sixth class has been reserved for fire protection
equipment. A standard color has been chosen to represent
each of these classes and is shown in table 4-2.
Since you work with fuel gas and oxygen, you must
become familiar with the colors of the cylinders in which
these gases are contained. The fuel-gas cylinder is yellow,
and the oxygen cylinder is green.
In addition to color coding, the exact identification of
the material contained in a compressed-gas cylinder must
be indicated by a written title that appears in two
locations-diametrically opposite and parallel to the
longitudinal axis of the cylinder. Cylinders, having a
background color of yellow, orange, or buff have the title
painted black Cylinders, having a background color of red,
brown, black, blue, gray, or green, have the title painted
white.
COLOR WARNINGS.— The appearance on the
body, top, or as a band(s) on compressed-gas cylinders of
the six colors specified should provide a warning of danger
from the hazard involved.
CYLINDER COLOR BANDS.— Cylinder color
bands appear upon the cylinder body and serve as color
warnings when they are yellow, brown, blue, green, or
gray. The bands also provide color combinations to
separate and distinguish cylinders for convenience in
handling, storage, and shipping. Color bands for
segregation purposes will not be specified for new
materials not presently covered by MIL-STD-101B.
DECALS.— Two decals may be applied on the
shoulder of each cylinder. They should be diametrically
opposite and at right angles to the titles. They should
indicate the name of the gas, precautions for handling, and
use. A background color corresponding to the primary
warning color of the contents should be used.
SHATTERPROOF CYLINDERS.— A shatterproof cylinder should be stenciled with the phrase “NONSHAT’’ longitudinally 90 degrees from the titles. Letters
must be black or white and approximately 1 inch in size.
SERVICE OWNERSHIP.— On cylinders owned
by or procured for the Department of Defense, the
bottom and the lower portion of the cylinder body
opposite the valve end may be used for service
ownership titles.
The six colors identified in table 4-2 are used on the
body and top of, or as a band on, a compressed-gas cylinder
to serve as a warning of the hazard involved in handling
the type of material contained in the cylinder.
Figure 4-32 shows titles and color codes for
compressed-gas cylinders most often found in a construction
C54.9
Figure 4-33.—Identifying color patterns for gas cylinders.
battalion or in a public works department where Seabee
personnel are working. Figure 4-33 shows how cylinders are
identified by the overall painted color code and
4-25
by the stenciled name of the gas. For a complete listing
of compressed-gas cylinders, refer to MIL-STD 101B,
“Color Code for Pipelines and for Compressed-Gas
Cylinders.”
spaces. Protect the cylinder valves and safety devices
from ice and snow. A safety device may not work if it is
frozen.
l Never store fuel cylinders and oxidizers within
the same space. Oxidizers must be stored at least 50 feet
from fuel cylinders. Use fire-resistant partitions
between cylinder storage areas.
NOTE: Ensure you have a manual with the latest
up-to-date changes inserted, as changes may occur in
MIL-STD 101B after this manual is published. It should
be noted that the color code of cylinders shown in figure
4-32 is military only; the commercial industry does not
necessarily comply with these color codes.
l Never mix empty cylinders with full cylinders.
Do not mix cylinders that contain different gases.
Always replace the cylinder cap and mark the cylinder
“Empty” or “MT.” Store the cylinders in a cool, dry
place ready for pickup by the supplier. Even in storage,
chain the cylinders when they are stored in the upright
position.
Handling and Storing Gas Cylinders
Each compressed-gas cylinder carries markings indicating compliance with Interstate Commerce Commission (ICC) requirements. When the cylinders are at
your work site, they become your responsibility. There
are several things you should not do when handling and
storing compressed-gas cylinders.
l Never drag a cylinder to move it. When available,
use a cylinder truck. If at all possible, leave the cylinders
on the hand truck and operate them from there;
otherwise, tilt the cylinder slightly and roll it on the
bottom edge. Always install the cylinder cap before
moving the cylinder. Never use slings or magnets to
carry cylinders. If you lift a cylinder upright by the cap,
make sure that it is screwed on tightly. If the cylinder
cap comes off, the cylinder could fall and either crush
your foot or snap the valve off. If a cylinder is dropped
and the valve breaks, it could launch itself like a rocket.
. Never fill your own cylinders. It requires special
training and special equipment.
. Never alter or fix the safety devices on a cylinder.
It is illegal and also stupid. The only personnel permitted
to work on cylinder safety devices are the cylinder
owners and suppliers.
When cylinders have been stored outside in freezing
weather, they sometimes become frozen to the ground
or to each other. This is true particularly in the antarctic
and arctic areas. To free the cylinders, you can pour
warm water (not boiling) over the frozen or icy areas.
As a last resort, you can pry them loose with a prybar.
If you use a prybar, never pry or lift under the valve cap
or valve.
l Never store cylinders near a heat source or in
direct sunlight. Heat causes the gas inside a cylinder to
expand. This could result in cylinder failure or fire.
l Never store cylinders in a closed or unventilated
space. If one of the cylinders were to leak, it could cause
an explosion or asphyxiate someone entering the space.
Store cylinders in protected, well-ventilated, and dry
4-26
CHAPTER 5
GAS WELDING
welding torch with tips (fig. 5-1). An oxygas welding
outfit also is called a welding rig.
This chapter discusses equipment and materials
used in gas welding. Information is provided on the
operation and maintenance of oxyacetylene and oxyMAPP equipment. Included are welding techniques and
safety precautions associated with gas welding.
In addition to the basic equipment mentioned, you
also use the same auxiliary equipment that was discussed in chapter 4. This equipment consists of tip
cleaners, cylinder trucks, clamps, and holding jigs.
Safety apparel, which includes goggles, hand shields,
gloves, leather aprons, sleeves and leggings, is essential
and should be worn as required. Information on safety
apparel is contained in chapter 3.
Oxyacetylene and oxy-MAPP (methylacetylenepropadiene) welding are two types of gas-welding processes. They require a gas-fueled torch to raise the
temperature of two similar pieces of metal to their fusion
point that allows them to flow together. A filler rod is
used to deposit additional metal. The gas and oxygen are
mixed to correct proportions in the torch, and you can
adjust the torch to produce various types of flames.
Oxygas welding equipment, like cutting equipment,
may be stationary or portable. A portable oxygas outfit,
as shown in figure 5-2, is an advantage when it becomes
necessary to move the equipment.
A properly made gas weld is consistent in appearance, showing a uniform deposit of weld metal. Complete fusion of the sidewalls is necessary to forma good
joint. Some of the factors you must consider when
making a gas weld are as follows: edge preparation,
spacing and alignment of the parts, temperature control
(before, during, and after the welding process), size of
the torch tip, size and type of the filler rod, flame
adjustment, and rod and torch manipulation. In some
cases, fluxes are needed to remove oxides and slag from
the molten metal and to protect the puddle from atmospheric contamination.
To perform your welding duties, you must be able
to set up the welding equipment and make the adjustments required to perform the welding operation. Thus
it is important that you understand the purpose and
function of the basic pieces of equipment that makeup
the welding outfit. The gases, cylinders, regulators,
hoses, and safety equipment are covered in chapter 4. If
you have any questions, you should review chapter 4
before continuing.
When you join sections of plate by gas welding, the
edges of the plate at the joint are uniformly melted by
the heat from the torch. When welding heavier sheets
and plates, you have to use filler metals. The edges of
the heavier plate are beveled to permit penetration to the
base of the joint. Both the filler metal and the base metal
are melted, and as they solidify, they form one continuous piece. For welding light sheet metal, filler metal is
usually not necessary. The edges of light sheet metal are
flanged at the joint so they flow together to form one
solid piece when you melt them.
WELDING TORCHES
The oxygas welding torch mixes oxygen and fuel
gas in the proper proportions and controls the amount
of the mixture burned at the welding tip. Torches have
two needle valves: one for adjusting the oxygen flow
and the other for adjusting the fuel gas flow. Other basic
parts include a handle (body), two tubes (one for oxygen
and another for fuel), a mixing head, and a tip. On some
models the tubes are silver-brazed to the head and the
rear end forgings, which are, in turn, fitted into the
handle. Welding tips are made from a special copper
alloy and are available indifferent sizes to handle a wide
range of uses and plate thicknesses.
OXYGAS WELDING EQUIPMENT
An oxygas welding outfit is basically the same as
an oxygas cutting outfit with the exception of the torch.
The welding outfit usually consists of a cylinder of
acetylene or MAPP gas, a cylinder of oxygen, two
regulators, two lengths of hose with fittings, and a
Two general types of welding torches are used:
l Low pressure
l Medium pressure
5-1
Figure 5-1.—An oxygas welding outfit.
The low-pressure torch is also known as an injector
torch. The fuel-gas pressure is 1 psi (pound per square
inch) or less. The oxygen pressure ranges between 10 to
40 pounds, depending on the size of the torch tip. A jet
of relatively high-pressure oxygen produces the suction
necessary to draw the fuel gas into the mixing head. The
welding tips may or may not have separate injectors in
the tip. Atypical mixing head for the low-pressure (or
injector) torch is shown in figure 5-3.
Medium-pressure torches are often called balancedpressure or equal-pressure torches because the fuel gas
and the oxygen pressure are kept equal. Operating pressures vary, depending on the type of tip used.
DANGER
If acetylene is used as the fuel gas, the
pressure must never be allowed to exceed 15 psi
because acetylene becomes very dangerous at
15 psi and self-explosive at 29.4 psi.
Figure 5-2.—A portable oxygas welding and cutting outfit,
5-2
Figure 5-3.—Mixing head for the low-pressure torch.
Figure 5-4.—Equal-pressure welding torch.
A typical equal-pressure welding torch, also called
a general-purpose torch, is shown in figure 5-4. The
medium-pressure torch is easier to adjust than the lowpressure torch and, since equal gas pressures are used,
you are less likely to get a flashback. (Flashbacks are
covered in chapter 4.)
Welding TIPS and MIXERS are designed in several
ways, depending on the manufacturer. Some torch designs have a separate mixing head or mixer for each tip
size. Other designs have only one mixer for several tip
sizes. Tips come in various types; some are one-piece
hard-copper tips and others are two-piece tips that
5-3
SELECTING THE WELDING
TORCH TIP SIZE
include an extension tube to make the connection between the tip and the mixing head. When used with an
extension tube, removable tips are made of hard copper,
brass, or bronze. Tip sizes are designated by numbers,
and each manufacturer has his own arrangement for
classifying them. Tip sizes differ in the diameter of the
hole.
Welding torch tip size is designated by a number
stamped on the tip. The tip size is determined by the size
of the orifice. There is no standard system of numbering
welding torch tip sizes; each manufacturer has his own
numbering system. In this manual, the tip size is given
in the number drill orifice size. Number drills consist of
a series of 80 drills, number 1 through 80. The diameter
of a number 1 drill is 0.2280 of an inch and the diameter
of a number 80 drill is 0.0135 of an inch.
FILLER RODS
The term filler rod refers to a filler metal used in gas
welding, brazing, and certain electric welding processes
in which the filler metal is not a part of the electrical
circuit. The only function of the filler rod is to supply
filler metal to the joint. Filler rod comes in wire or rod
form that is often referred to as “welding rod.”
NOTE: As the drill size number increases, the size
of the drill decreases.
Once you become familiar with the use of a specific
manufacturer’s torch and numbering system, it becomes
unnecessary to refer to orifice number drill size. The
orifice size determines the amount of fuel gas and oxygen fed to the flame; therefore, it determines the amount
of heat produced by the torch. The larger the orifice, the
greater the amount of heat generated.
As a rule, filler rods are uncoated except for a thin
film resulting from the manufacturing process. Filler
rods for welding steel are often copper-coated to protect
them from corrosion during storage. Most rods are
furnished in 36-inch lengths and a wide variety of diameters, ranging from 1/32 to 3/8 inch. Rods for welding cast iron vary from 12 to 24 inches in length and are
frequently square, rather than round. You determine the
rod diameter for a given job by the thickness of the metal
you are joining.
If the torch tip orifice is too small, not enough heat
will be available to bring the metal to its fusion temperature. If the torch tip is too large, poor welds result from
the following: the weld is made too fast, control of the
welding rod melting is difficult, and the appearance and
quality of the weld is unsatisfactory.
Except for rod diameter, you select the filler rod
based on the specifications of the metals being joined.
These specifications may be federal, military, or Navy
specifications. This means that they apply to all federal
agencies, the Military Establishment, or the Navy, respectively. Filler metals are presently covered by one or
more of these three types of specifications. Eventually,
all Navy specifications will be rewritten as military
(MIL) specifications. For that reason, some of the specifications for welding materials presented in this section
may subsequently be published as military, rather than
Navy specifications.
For practice purposes, using an equal-pressure
torch, the welding rod sizes and the tip sizes shown in
table 5-1 should give satisfactory results.
EQUIPMENT SETUP
Setting up the oxygas equipment and preparing for
welding is identical to setting up for oxygas cutting
(chapter 4) except for the selection of the torch tip.
Select the correct tip and mixing head (depending on
torch manufacturer), and connect them to the torch body.
Tighten the assembly by hand, and then adjust to the
proper angle. After the desired adjustment has been
made, tighten the tip. On some types of equipment, the
tip is tightened with a wrench, while on other types, only
hand tightening is required.
Many different types of rods are manufactured for
welding ferrous and nonferrous metals. In general,
welding shops stock only a few basic types that are
suitable for use in all welding positions. These basic
types are known as general-purpose rods.
OPERATION AND MAINTENANCE OF
OXYGAS EQUIPMENT
TORCH LIGHTING AND FLAME
ADJUSTMENT
This section discusses basic procedures involved in
setting up oxygas equipment, lighting off, adjusting the
flame, and securing the equipment. Information also is
provided on the maintenance of oxygas welding equipment.
When lighting the torch and adjusting the flame, you
should always follow the manufacturer’s directions for
the particular model of torch being used. This is necessary because the procedure varies somewhat with
5-4
Table 5-1.—Welding Rod Sizes and Tip Sizes Used to Weld Various Thicknesses of Metal
different types of torches and, in some cases, even with
different models made by the same manufacturer.
types of maintenance duties that you will be required to
perform,
After lighting the torch, you adjust the flame according to the type of metal being welded. In-depth
coverage of the different types of flames is covered in
chapter 4.
Torch Gas Leaks
At times the needle valves may fail to shut off when
hand tightened in the usual manner. When this happens,
do not use a wrench to tighten the valve stem. Instead,
open the valve and try to blow the foreign matter off the
valve seat, using the working gas pressure in the hose.
If this fails, it will be necessary to remove the stem
assembly and wipe the seat clean. Reassemble the valve
and try closing it tightly by hand several times. If these
measures fail to stop the leak, you should have the parts
replaced or the valve body reseated. These repairs
should be made only by qualified personnel.
The carburizing flame is best used for welding
high-carbon steels, for hardfacing, and for welding nonferrous alloys, such as Monel. A neutral flame is the
correct flame to use for welding most metals. When steel
is welded with this flame, the puddle of molten metal is
quiet and clear, and the metal flows without boiling,
foaming, or sparking. The welding flame should always
be adjusted to neutral before either the oxidizing or
carburizing flame mixture is set.
The oxidizing flame has a limited use and is harmful
to many metals. When applied to steel, the oxidizing
flame causes the molten metal to foam and produce
sparks. The major use of the flame is that of the slightly
oxidizing flame used to braze steel and cast iron. A
stronger oxidizing flame is used for fusion welding
brass and bronze. You determine the amount of excess
oxygen to use by watching the molten metal.
When there is leakage around the torch valve stem,
you should tighten the packing nut or repack it if necessary. For repacking, you should use only the packing
recommended by the manufacturer of the torch. DO
NOT USE ANY OIL. If the valve stem is bent or badly
worn, replace it with a new stem.
Before you use a new torch for the first time, it is a
good idea to check the packing nut on the valves to make
sure it is tight. The reason is that some manufacturers
ship torches with these nuts loose.
MAINTAINING THE EQUIPMENT
For welding equipment to operate at peak efficiency
and give useful service, you must perform the proper
maintenance and upkeep on it. Your responsibilities
involve the maintenance and care of oxygas welding
equipment. You will not be required to make major
repairs to welding equipment; but when major repairs
are needed, it is your responsibility to see that the
equipment is removed from service and turned in for
repair. This section briefs you on some of the common
Leaks in the mixing-head seat of the torch causes
oxygen and fuel-gas leaks between the inlet orifices
leading to the mixing head. This problem causes improper gas mixing and results in flashbacks. The problem can be corrected by having the seat in the torch head
reamed and by truing the mixing-head seat. Usually, you
must send the equipment to the manufacturer for these
repairs.
5-5
Figure 5-5.—Welding tip orifice cleaner.
Figure 5-7.—Reconditioning the orifice end of a torch tip.
The flame end of the tip must be clean and smooth.
The surface must beat right angles to the centerline of
the tip orifice to ensure a proper shaped flame. A 4-inch
mill file or the file in the tip cleaner can be used to
recondition the surface, as shown in figure 5-7.
Recondition the tip if it becomes rough and pitted
or the orifice is bell-mouthed. An easy method to use
involves placing apiece of emery cloth, grit side up, on
a flat surface; hold the tip perpendicular to the emery
cloth, and rub the tip back and forth just enough to true
the surface and to bring the orifice back to its original
diameter.
Figure 5-6.—A welding tip cleaner in use.
Welding Torch Tips
Regulator Leaks
Welding tips are subject to considerable abuse and
you must keep the orifice smooth and clean if the tip is
to perform satisfactorily. When cleaning a welding tip,
you must be careful and ensure you do not enlarge or
scar the orifice. Carbon deposits and slag must be removed regularly to ensure good performance.
With regulators, gas leakage between the regulator
seat and nozzle is the most common type of trouble. You
often hear this problem referred to as regulator creep.
This problem can be detected by the gradual rise in
pressure on the working-pressure gauge without moving the adjusting screw. Frequently, this trouble is
caused by worn or cracked seats. It also can be caused
by foreign matter lodged between the seat and the nozzle. It is important that you have leaking regulators
repaired at once; otherwise, injury to personnel or equipment damage could result. This is particular y dangerous with fuel-gas regulators because fuel gas at a high
pressure in a hose becomes an explosive hazard. To
ensure the safety of personnel and equipment, ensure
that regulators with such leaks are removed from service
and turned in for repair.
Avoid dropping a tip because the seat that seals the
joint may be damaged. Also, the flame end of the tip also
may receive damage if it is allowed to come in contact
with the welding work, bench, or firebricks. This damage roughens the end of the tip and causes the flame to
burn with a “fishtail.”
Special welding tip cleaners have been developed
to remove the carbon or slag from the tip orifice. The
cleaner consists of a series of broachlike wires that
correspond in diameter to the diameter of the tip orifices
(fig. 5-5). These wires are packaged in a holder, which
makes their use safe and convenient. Figure 5-6 shows
a tip cleaner in use. Some welders prefer to use a number
drill the size of the tip orifice to clean welding tip
orifices. A number drill must be used carefully so the
orifice is not enlarged, bell-mouthed, reamed out of
round, or otherwise deformed.
OXYGAS WELDING TECHNIQUES
Oxygas welding maybe done using either the forehand or the backhand method. Each of these techniques
has special advantages and you should become skillful
with both. The deciding factor that determines whether
a technique is considered forehand or backhand is the
relative position of the torch and rod during welding, not
5-6
Figure 5-8.—Forehand welding.
Figure 5-9.—Backhand welding.
the direction of welding. The best method to use depends
upon the type of joint, joint position, and the need for
heat control on the parts to be welded.
Less motion is used in the backhand method than in
the forehand method. If you use a straight welding rod,
you should rotate it so the end rolls from side to side and
melts off evenly. You might have to bend the rod when
working in confined spaces. If you do, it becomes difficult to roll a bent rod, and to compensate, you have to
move the rod and torch back and forth at a rather rapid
rate. When making a large weld, you should move the
rod so it makes complete circles in the molten puddle.
The torch is moved back and forth across the weld while
it is advanced slowly and uniformly in the direction of
the welding.
FOREHAND WELDING
Forehand welding (fig. 5-8) is often called PUDDLE or RIPPLE WELDING. In this method of welding,
the rod is kept ahead of the flame in the direction in
which the weld is being made. You point the flame in
the direction of travel and hold the tip at an angle of
about 45 degrees to the working surfaces. This flame
position preheats the edges you are welding just ahead
of the molten puddle. Move the rod in the same direction
as the tip, and by moving the torch tip and the welding
rod back and forth in opposite, semicircular paths, you
can distribute the heat evenly. As the flame passes the
welding rod, it melts a short length of the rod and adds
it to the puddle. The motion of the torch distributes the
molten metal evenly to both edges of the joint and to the
molten puddle.
The backhand method is best for welding material
more than 1/8 of an inch thick. You can use a narrower
vee at the joint than is possible in forehand welding. An
included angle of 60 degrees is a sufficient angle of
bevel to get a good joint. The backhand method requires
less welding rod or puddling as the forehand method.
By using the backhand technique on heavier material, you can increase your welding speed, better your
control of the larger puddle, and have more complete
fusion at the weld root. If you use a slightly reducing
flame with the backhand technique, a smaller amount of
base metal is melted while welding the joint. When you
are welding steel with a backhand technique and a
slightly reducing flame, the absorption of carbon by a
thin surface layer of metal reduces the melting point of
the steel. This speeds up the welding operation, This
technique is also used in surfacing with chromium-cobalt alloys.
The forehand method is used in all positions for
welding sheet and light plate up to 1/8 of an inch thick.
This method is ideal because it permits better control of
a small puddle and results in a smoother weld. The
forehand technique is not recommended for welding
heavy plate due to its lack of base metal penetration.
BACKHAND WELDING
In backhand welding (fig. 5-9), the torch tip precedes the rod in the direction of welding and the flame
points back at the molten puddle and completed weld.
The welding tip should make an angle of about 60
degrees with the plates or joint being welded. The end
of the welding rod is placed between the torch tip and
the molten puddle.
MULTILAYER WELDING is used in order to
avoid carrying too large a puddle of molten metal when
welding thick plate and pipe. Large puddles are difficult
to control. Concentrate on getting a good weld at the
bottom of the vee in the first passe Then, in the next
5-7
layers, concentrate on getting good fusion with the sides
of the vee and the previous layer. The final layer is easily
controlled to get a smooth surface. This method of
welding has an added advantage in that it refines the
previous layer as the succeeding layer is made. In effect,
it heat-treats the weld metal by allowing one layer to
cool to a black heat before it is reheated This improves
the ductility of the weld metal. If this added quality is
desired in the last layer, an additional or succeeding
layer is deposited and then machined off.
JOINT EDGE PREPARATION
Sheet metal is easily melted and does not require
special edge preparation. In welding operations
involving plate, joint edge preparation and proper spacing between edges are important factors. The thickness
of the plates determines the amount of edge preparation
required. The faces of square edges can be butted together and welded You can use this type of joint on plate
up to 3/16 of an inch thick. For plate 3/16 to 1/4 of an
inch thick, a slight root opening between the parts is
necessary to get complete penetration. Plate more than
1/4 of an inch thick requires beveled edges and a root
opening of 1/16 of an inch. For oxygas welding on plate
more than 1/4 of an inch thick, bevel the edges at an
angle of 30 degrees to 45 degrees, making the groove
included angle from 60 degrees to 90 degrees. You can
prepare the edges by flame cutting, shearing, flame
grooving, machining, chipping, or grinding. In any case,
the edge surfaces should be free of oxides, scale, dirt,
grease, or other foreign matter.
During the welding process, you should enclose the
molten puddle with the flame envelope to ensure the
molten metal does not contact the air. If the metal is
exposed to the air, it will oxidize rapidly. You also should
avoid overheating the metal.
The proper flame adjustment is required to make a
good weld Adjust the flame to a neutral or slightly
reducing (carburizing) flame. Do not use an oxidizing
flame. Manipulate the torch and rod so the tip of the
oxygas cone is about 1/16 to 1/8 of an inch from the
surface of the metal. Melt the end of the filler rod in the
puddle, not with the flame. The welding of low-carbon
steels and cast steels presents no special problems other
than the selection of the proper filler rod Low-alloy
steels usually require prewelding and postwelding heat
treatment. This heat treatment relieves the stresses developed during the welding phase and produces the
desired physical properties of the metal.
As the carbon content of a steel increases, welding
becomes more difficult. Steels whose carbon content is
within the 0.3-percent to 0.5-percent range are welded
with a slightly carburizing flame. These low-carbon
steels require postwelding heat treatment to develop
their best physical properties.
High-carbon steel and tool steel require a slightly
different technique. While protecting the parts from
drafts, slowly preheat them to about 1000°F. Complete
the weld as rapidly as possible using a carburizing flame
and no flux. Do not manipulate either rod or torch and
add the filler metal in small amounts, as it is needed. You
should use a smaller flame and lower gas pressure than
that used for low-carbon steel. This is to ensure you do
not overheat the steel. You must heat-treat high-carbon
steels and tool steels after welding to develop the physical properties required.
Plate from 3/8 to 1/2 of an inch thick can be welded
from one side only, but thicker sections should be
welded by preparing the edges on both sides. Generally,
butt joints prepared on both sides permit easier welding,
produce less distortion, and ensure better weld qualities.
The procedure for oxygas welding of WROUGHT
IRON is the same as that for low-carbon or mild steel;
however, you should keep several points in mind.
Wrought iron contains a slag that was incorporated in it
during the manufacturing stage. This slag gives the
surface of the molten puddle a greasy appearance. Do
not confuse this greasy appearance with the appearance
of actual fusion. Continue heating until the sidewalls of
the joint break down into the puddle. Best results with
wrought iron are obtained when the filler metal (usually
mild steel) and base metal are mixed in the molten
puddle with a minimum of agitation
Heavy steel plate is rarely welded with oxygas
unless other types of welding equipment are not available. The welding of heavy plate is just not cost effective
because of the amount of gas consumed and time used
to complete a weld. If at all possible, use a form of
electric arc welding because the joint can be welded
faster, cheaper, and there is less heat distortion
OXYGAS WELDING OF
FERROUS METALS
Low-carbon steel, low-alloy steel, cast steel, and
wrought iron are easily welded by the oxygas process.
A flux is not necessary with these metals because their
oxides melt at a lower temperature than the base metal.
Oxygas welding of CAST IRON is not difficult, but
does require a modification of the procedure used with
steel. For material that does not exceed 3/16 of an inch
5-8
metals as for ferrous metals in most cases. Oxygas
welding of nonferrous metals usually requires mechanical cleaning of the surfaces before welding and the use
of flux during welding. Filler metals must be suitable
for the base metal being welded A separate section on
aluminum and aluminum alloys is included as part of
this chapter since you may need more detailed instructions in welding these materials.
in thickness, you do not need to make a V-groove. Metal
that is between 3/16 of an inch and 3/8 of an inch should
have a single V-butt joint with an included angle of 60
degrees. For metal over 3/8 of an inch, use a double
V-butt joint with 60-degree included angles.
Before you begin welding, preheat the entire weldment to a temperature between 750°F and 900°F The
welding should be done with a neutral flame using the
backhand method. Use a cast-iron filler metal and the
appropriate flux. The flux is necessary, but use it sparingly as needed Add filler metal by directing the inner
cone of the flame against the rod instead of dipping the
tip of the rod into the puddle. The filler metal should be
deposited inlayers not exceeding 1/8 of an inch thick.
Upon completion of the weld, you must stress relieve
the weldment by heating it to a temperature between
1100°F and 1150°F and then cool it slowly. Oxygas
welding cast iron gives a good color match and good
machinability; however, if color match is not essential,
a cast-iron repair can be made more easily and economically by braze welding.
Copper
Pure copper can be welded using the oxygas torch.
Where high-joint strength is required you should use
DEOXIDIZED copper (copper that contains no oxygen). A neutral flame is used and flux is required when
welding copper alloys. Because of the high thermal
conductivity of copper, you should preheat the joint area
to a temperature ranging between 500°F to 800°F and
use a larger size torch tip for welding. The larger size tip
supplies more heat to the joint and thus makes it possible
to maintain the required temperature at the joint. After
welding is completed, cool the part slowly. Other than
the extra volume of heat required, the technique for
welding copper is the same as for steel.
Oxygas welding can be used with some CHROMIUM-NICKEL STEELS (STAINLESS STEELS). As
a rule, oxygas welding is used only for light sheet;
heavier pieces of these steels are usually joined by one
of the electric arc welding processes. On material 20
gauge (0.040 of an inch) or less in thickness, a flange
equal to the thickness of the metal is turned up and the
weld is made without filler metal. Before welding, you
should clean the joint surfaces of the metal with sandpaper or other abrasives and then apply a stainless steel
flux. The torch tip used for welding stainless steel is
usually one or two sizes smaller than the tip used to weld
mild steel of the same thickness. Adjust the torch so you
have a carburizing flame, as seen through your goggles,
with an excess fuel-gas feather extending about 1/16 of
an inch beyond the tip of the inner cone. Hold the torch
so the flame makes an angle of 80 degrees to the surface
of the sheet. The tip of the cone should almost, but not
quite touch the molten metal. Make the weld in one pass,
using a forehand technique. Do not puddle or retrace the
weld. A uniform speed of welding is essential. If it is
necessary to stop the welding process or reweld a section, wait until the entire weld has cooled.
Copper-Zinc Alloy (Brasses)
Copper-zinc alloys (brasses) can be welded using
the same methods as deoxidized copper; however, a
silicon-copper rod is used for welding brasses. The rods
are usually flux-coated so the use of additional flux is
not required. Preheat temperatures for these metals
range between 200°F to 300°F.
Copper-Silicon Alloy (Silicon Bronze)
Copper-silicon alloy (silicon bronze) requires a different oxygas welding technique from that used for
copper and copper-zinc. You weld this material with a
slightly oxidizing flame and use a flux having a high
boric acid content. Add filler metal of the same composition as the base metal; as the weld progresses, dip the
tip of the rod under the viscous film that covers the
puddle. Keep the puddle small so the weld solidifies
quickly. A word of caution: when welding copper-zinc,
you should safeguard against zinc poisoning by either
doing all the welding outdoors or by wearing a respirator
or by both, depending on the situation
OXYGAS WELDING OF
NONFERROUS METALS
Although brazing and braze welding are used extensively to make joints in nonferrous metals, there are
many situations in which oxygas welding is just as
suitable. The joint designs are the same for nonferrous
Copper-Nickel Alloy
Oxygas welding of copper-nickel alloys requires
surface preparation and preheating. The flux used for
5-9
thickness of the lead. The length of the flame varies from
about 1 1/2 inches to 4 inches, depending upon the gas
pressures used. When you are welding in the horizontal
and flat positions, a soft, bushy flame is most desirable.
But, when you are welding in the vertical and overhead
positions, better results are obtained with a more pointed
flame.
this welding is a thin paste and is applied by brush to all
parts of the joint and to the welding rod. Adjust the torch
to give a slightly carburizing flame; the tip of the inner
cone should just touch the base metal. Do not melt the
base metal any more than necessary to ensure good
fusion. Keep the end of the filler rod within the protective envelope of the flame, adding the filler metal without disturbing the molten pool of weld metal. If possible,
run the weld from one end of the joint to the other
without stopping. After you complete the weld, cool the
part slowly and remove the remaining traces of flux with
warm water.
For oxygas welding of lead, you should ensure that
the filler metal has the same composition as the base
metal. The molten puddle is controlled and distributed
by manipulating the torch so the flame moves in a
semicircular or V-shaped pattern. Each tiny segment of
the weld is made separately, and the torch is flicked
away at the completion of each semicircular or V-shaped
movement. Joints are made in thin layers. Filler metal
is not added during the first pass, but it is added on
subsequent passes.
Nickel and High-Nickel Alloys
Oxygas welding of nickel and high-nickel alloys is
similar to that for copper-nickel alloys. Good mechanical cleaning of the joint surfaces is essential. The joint
designs are basically the same as steel of equivalent
thickness. The included angle for V-butt welds is approximately 75 degrees. You may weld plain nickel
without a flux, but high-nickel alloys require a special
boron-free and borax-free flux. The flux is in the form
of a thin paste and should be applied with a small brush.
You should flux both sides of the seam, the top and
bottom, and the filler rod. Adjust the torch to give a very
slightly carburizing flame; the tip selected should be the
same size or one size larger than for steel of the same
thickness. The flame should be soft and the tip of the
cone kept in contact with the molten pool. Use a rod
suitable for the base metal, and always keep the rod well
within the protective envelope of the flame. After the
weld is completed, postheat the part and cool it slowly.
Then remove the flux with warm water.
When welding lead or lead alloys, you should wear
a respirator of a type approved for protection against
lead fumes.
WARNING
LEAD FUMES ARE POISONOUS.
Aluminum and Aluminum Alloys
When assigned to work with nonferrous metals, you
can expect jobs that involve the welding of aluminum
and aluminum alloys. Pure aluminum has a specific
gravity of 2.70 and a melting point of 1210°F. Pure
aluminum is soft and seldom used in its pure form
because it is not hard or strong enough for structural
purposes; however, the strength of aluminum can be
improved by the addition of other elements to form
aluminum alloys.
Lead
Oxygas welding of lead requires special tools and
special techniques. Although you do not require a flux,
you must ensure that the metal in the joint area is
scrupulously clean. You may accomplish this by shaving
the joint surfaces with a scraper and wire brushing them
to remove oxides and foreign matter. In the flat-welding
position, a square butt joint is satisfactory. In other
positions, a lap joint is used almost exclusively. When
you use a lap joint, the edges should overlap each other
from 1/2 of an inch to 2 inches, depending upon the
thickness of the lead.
Aluminum alloys are usually 90-percent pure.
When elements, such as silicon, magnesium, copper,
nickel, and manganese, are added to aluminum, an alloy
stronger than mild steel results; whereas pure aluminum
is only about one fourth as strong as steel.
A considerable number of aluminum alloys are
available. You may use some of the aluminum alloys in
sheet form to make and repair lockers, shelves, boxes,
trays, and other containers. You also may have to repair
chairs, tables, and other items of furniture that are made
of aluminum alloys.
To weld lead, use a special, lightweight, fingertip
torch, with tips ranging from 68 to 78 in drill size. Adjust
your torch to a neutral flame with the gas pressure
ranging from 1 1/2 psig to 5 psig, depending on the
Oxygas welding of aluminum alloys is usually confined to materials from 0.031 of an inch to 0.125 of an
inch in thickness. Also, thicker material can be welded
5-10
by the oxygas process if necessary; however, thinner
material is usually spot or seam welded.
MELTING CHARACTERISTICS.— Before attempting to weld aluminum alloy for the first time, you
should become familiar with how the metal reacts when
under the welding flame.
A good example of how aluminum reacts when
heated can be seen if you place a small piece of sheet
aluminum on a welding table and heat it with a neutral
flame. Hold the flame perpendicular to the surface of
the sheet and bring the tip of the inner cone almost in
contact with the metal. Observe that almost without
warning the metal suddenly melts and runs away, leaving a hole in the sheet. Now repeat the operation with
the torch held at an angle of about 30 degrees to the plane
of the surface. With a little practice, you will be able to
melt the surface metal without forming a hole. Now try
moving the flame slowly along the surface of the sheet,
melting a small puddle. Observe how quickly the puddle
solidifies when the flame is removed. Continue this
practice until you are able to control the melting. When
you have mastered this, proceed by practicing actual
welding. Start with simple flanged and notched butt
joints that do not require a welding rod. Next, you should
try using a welding rod with thin sheet and then with
castings.
Figure 5-10.—Edge preparation for gas-welding aluminum.
these joints. In all cases, the flux should be applied to
both the bottom and top sides of the sheet in the area of
the weld. After you finish welding, it is important that
you remove all traces of flux. You can do this by using
a brush and hot water. If aluminum flux is left on the
weld, it will corrode the metal.
WELDING RODS.— Two types of welding rods
available for gas welding aluminum alloys are the 1100
and 4043 rods. The 1100 rod is used when maximum
resistance to corrosion and high ductility are of primary
importance. The 1100 rod is used for welding 1100 and
3003 type aluminum alloys only. The 4043 rod is used
for greater strength and minimizes the tendency for
cracking. It also is used for all other wrought aluminum
alloys and castings.
WELDING PREPARATION.— The thickness of
the aluminum determines the method of edge preparation. On material up to 0.062 of an inch, the edges should
be formed to a 90-degree flange. The height of the flange
should be about the same height, or a little higher, as the
thickness of the material (fig. 5-10, view A). The only
requirement for the flanges is that their edges be straight
and square. If desired, material up to 0.125 of an inch
can be welded with a flange joint. No filler rod is
necessary if you flange the edges.
WELDING FLUXES.— The use of the proper flux
in welding aluminum is extremely important. Aluminum welding flux is designed to remove the aluminum
oxide by chemically combining with it. In gas welding,
the oxide forms rapidly in the molten metal. It must be
removed or a defective weld will result. To ensure
proper distribution, you should paint flux on the welding
rod and the surface to be welded.
Unbeveled butt welds can be made on thicknesses
from 0.062 of an inch to 0.188 of an inch; but in these
applications, it is necessary to notch the edges with a
saw or cold chisel in a manner similar to that shown in
view B of figure 5-10. Edge notching is recommended
in aluminum welding because it aids in getting full
penetration and prevents local distortion. All butt welds
made in material over 0.125 of an inch thick are usually
notched in some manner.
Aluminum flux is usually in powder form and is
prepared for use by mixing with water to form a paste.
The paste should be kept in an aluminum, glass, or
earthenware container because steel or copper containers tend to contaminate the mixture.
It is essential that plenty of flux be applied to the
edges of flanged joints because no filler rod is used in
5-11
In welding aluminum more than 0.188 of an inch
thick, bevel the edges and notch them, as shown in view
C of figure 5-10. The included angle of bevel maybe
from 90 to 120 degrees.
material, care must be taken to break the oxide film as
the flange melts down. This may be done by stirring the
melted flange with a puddling rod. A puddling rod is
essentially a paddle flattened and shaped from a 1/4inch stainless steel welding rod.
After you have prepared the edges of the pieces
properly, you should then clean the surfaces to be
welded. If heavy oxide is present on the metal surface,
you may have to use a stainless-steel wire brush to
remove it. Dirt, grease, or oil can be removed by wiping
the weld area with a solvent-soaked rag.
With aluminum alloys above 0.188 of an inch in
thickness, you should give the torch a more uniform
lateral motion to distribute the weld metal over the entire
width of the weld. A slight back-and-forth motion assists
the flux in its removal of oxides. Dip the filler rod in the
weld puddle with a forward motion.
Aluminum plate 1/4 of an inch thick or greater
should be preheated to a temperature ranging between
500°F to 700°F. This aids in avoiding heat stresses.
Preheating also reduces fuel and oxygen requirements
for the actual welding. It is important that the preheating
temperature does exceed 700°F. If the temperature does
go above 700°F, the alloy maybe severely weakened.
High temperatures also could cause large aluminum
parts to collapse under their own weight. Thin material
should be warmed with the torch before welding. This
slight preheat helps to prevent cracks.
The angle of the torch is directly related to the
welding speed. Instead of lifting the flame from time to
time to avoid melting holes in the metal, you will find it
advantageous to hold the torch at a flatter angle to the
work The welding speed should be increased as the
edge of the sheet is approached. The inner cone of the
flame should never be permitted to come in contact with
the molten metal, but should beheld about 1/8 of an inch
away from the metal.
WELDING TECHNIQUES.— After preparing
and fluxing the pieces for welding, you should pass the
flame, in small circles, over the starting point until the
flux melts. Keep the inner cone of the flame off the flux
to avoid burning it. If the inner cone of the flame should
burn the flux, it will be necessary to clean the joint and
apply new flux. Next, scrape the rod over the surface at
about 3- or 4-second intervals, permitting the rod to
come clear of the flame each time. If you leave the rod
in the flame too long, it melts before the parent metal
does. The scraping action indicates when you can start
welding without overheating the metal. Maintain this
cycle throughout the course of welding except for allowing the rod to remain under the flame long enough to
melt the amount of metal needed. With practice, the
movement of the rod can be easily mastered.
In the vertical position, the torch is given an up-anddown motion, rather than a rotating one. In the overhead
position, alight back-and-forth motion is used the same
as in flat welding.
Heat-treatable alloys should be held in a jig for
welding, whenever possible. This helps to eliminate the
possibility of cracking. The likelihood of cracking can
also be reduced by the use of a 4043 filler rod. This rod
has a lower melting range than the alloy being joined
which permits the base metal to solidify before the weld
puddle freezes. As the weld is the last area to solidify,
all of the contraction strains are in the weld bead, rather
than throughout the base metal. You may reduce weld
cracking by tack welding the parts while they are in the
Forehand welding is usually preferred for welding
aluminum alloys because the flame points away from
the completed weld, and this preheats the edges to be
welded that prevents too rapid melting. Hold the torch
at a low angle when you are welding thin material. For
thicknesses 0.188 of an inch and above, you should
increase the angle of the torch to a near vertical position.
Changing the angle of the torch according to the thickness of the metal minimizes the possibility of burning
through the sheet during welding.
jig and then loosening the clamps before completing the
seam.
As soon as the weld is completed and the work has
had time to cool, you should thoroughly wash the weld.
This can be done by vigorously scrubbing it with a stiff
brush while hot water runs over it until all traces of the
flux are removed. This is important, because if any flux
is left on the weld, it can corrode the metal. If hot water
is not available, you may use a diluted solution of 10
When welding aluminum alloys up to 0.188 of an
inch thick, you have little need to impart any motion to
the torch other than moving it forward. On flanged
percent sulfuric acid. The acid solution should then be
washed off with cold, fresh water after using.
5-12
Figure 5-11.—Welding operation with backhand technique.
FUSION WELDING PIPE
In oxygas welding of pipe, many tests have proved
that fusion welded pipe joints, when properly made, are
as strong as the pipe itself.
For success in oxygas welding of pipe, three essential requirements must be met: there must be a convenient source of controlled heat available to produce rapid
localized melting of the metal, the oxides present on the
surface or edges of the joints must be removed, and a
metal-to-metal union between the edges or surfaces to
be joined must be made by means of molten metal.
One method used for welding steel and wrought iron
pipe is known as FUSION WELDING. This method
involves melting the pipe metal and adding metal from
a rod of similar composition. The welding operation
performed at the top of a joint in a horizontal pipe is
shown diagrammatically in figure 5-11. This shows the
BACKHAND welding technique. The rod and flame are
moved alternately toward and away from each other, as
shown in figure 5-12. Full strength oxygas welds can be
made in any welding position.
Figure 5-12.—Flame and rod motion with backhand technique.
to keep the molten metal in the puddle from running or
falling.
The soundness and strength of welds depend on the
quality of the welding rod used. If you have any doubt
about the quality of the rods or are not sure of the type
to use, then it would be to your advantage to contact the
manufacturer or one of his distributors. If the rod is
supplied through the federal stock system, supply per-
The cohesiveness of the molten metal, the pressure
of the flame, the support of the weld metal already
deposited, and the manipulation of the rod all combine
sonnel should be able to look up the information based
on the federal stock number of the rod.
5-13
Figure 5-13.—Chain clamps quickly align pipe fittings of any description.
Thus, even in high-carbon, high-strength pipe, the weld
metal is as strong as, or stronger than the pipe material.
The Linde Company has a method of fusion welding
that is remarkably fast and produces welds of high
quality. Anyone can use this process for welding pipe if
they adhere to the following conditions:
3. BACKHAND TECHNIQUE. This technique
produces faster melting of the base metal surfaces. Also,
a smaller bevel can be used which results in a savings
of 20 to 30 percent in welding time, rods, and gases.
1. Use an excess fuel-gas flame.
2. Use a welding rod containing deoxidizing
agents.
One of the most valuable tools you can use when
welding pipe is the pipe clamp. Pipe clamps hold the
pipe in perfect alignment until tack welds are placed.
They are quick opening and you can move or attach a
clamp quickly.
3. Use the backhand welding technique.
The following is a brief explanation of the previously mentioned conditions:
1. EXCESS FUEL-GAS FLAME. The base metal
surface, as it reaches white heat, absorbs carbon from
the excess fuel-gas flame. The absorption of carbon
lowers the melting point of steel, thereby the surface
melts faster and speeds up the welding action.
Figure 5-13 shows four different types of chain
clamps that are used for pipe welding. If these clamps
are not available, you can fabricate your own by welding
two C-clamps to a piece of heavy angle iron. A piece of
3/8-inch angle iron that is 4 inches by 4 inches by 12
inches is usually suitable. When working with small-diameter pipe, you can lay it in apiece of channel iron to
obtain true alignment for butt welding. When the pipe
you are working on has a large diameter, you can use a
wide flange beam for alignment purposes.
2. SPECIAL WELDING ROD. The deoxidizing
agents in the recommended rod eliminates the
impurities and prevents excess oxidation of carbon.
Were it not for this action, considerable carbon, the most
valuable strengthening element of steel, would be lost.
5-14
CHAPTER 6
SOLDERING, BRAZING, BRAZE WELDING,
AND WEARFACING
actually a form of brazing, because the temperature used
is above 800°F.
This chapter describes the following: equipment
and materials required for soldering, the basic methods
used to make soldered joints, and the special techniques
required to solder aluminum alloys.
The information presented in chapter 5 covered the
joining of metal parts by the process of fusion welding.
In this chapter, procedures that do not require fusion are
addressed. These procedures are as follows: soldering,
brazing, braze welding, and wearfacing. These procedures allow the joining of dissimilar metals and produce
high-strength joints. Additionally, they have the important advantages of not affecting the heat treatment or
warping the original metal as much as conventional
welding.
EQUIPMENT
Soldering requires very little equipment. For most
soldering jobs, you only need a heat source, a soldering
copper or iron, solder, and flux.
SOLDERING
Sources of Heat
Soldering is a method of using a filler metal (commonly known as solder) for joining two metals without
heating them to their melting points. Soldering is valuable to the Steelworker because it is a simple and fast
means for joining sheet metal, making electrical connections, and sealing seams against leakage. Additionally,
it is used to join iron, nickel, lead, tin, copper, zinc,
aluminum, and many other alloys.
Soldering is not classified as a welding or brazing
process, because the melting temperature of solder is
below 800°F. Welding and brazing usually take place
above 800°F. The one exception is lead welding that
occurs at 621°F. Do not confuse the process of SILVER
SOLDERING with soldering, for this process is
The sources of heat used for soldering vary according to the method used and the equipment available.
Welding torches, blow-torches, forges, and furnaces are
some of the sources of heat used. Normally, these heating devices are used to heat the soldering coppers that
supply the heat to the metal surfaces and thus melt the
solder. Sometimes, the heating devices are used to heat
the metal directly. When this is done, you must be
careful to prevent heat damage to the metal and the
surrounding material.
SOLDERING COPPERS.— A soldering copper
(usually called a soldering iron) consists of a forged
copper head and an iron rod with a handle. (See fig. 6-1.)
Figure 6-1.—Soldering irons.
6-1
Figure 6-4.—Tinning a copper (solder placed on cake of sal
ammoniac).
Figure 6-2.—Soldering copper heads.
Also, coppers must be filed and retinned after overheating or for any other reason that caused the loss of their
solder coating. The procedure for filing and tinning a
copper is as follows:
1. Heat the copper to a cherry red.
2. Clamp the copper in a vise, as shown in figure
6-3.
3. File the copper with a single-cut bastard file.
Bear down on the forward stroke, and release pressure
on the return stroke. Do not rock the file. Continue filing
the tapered sides of the copper until they are bright and
smooth.
Figure 6-3.—Filing a soldering copper.
The handle, which may be wood or fiber, is either forced
or screwed onto the rod.
CAUTION
Soldering heads are available in various shapes.
Figure 6-2 shows three of the more commonly used
types. The pointed copper is for general soldering work
The stub copper is used for soldering flat seams that
need a considerable amount of heat. The bottom copper
is used for soldering seams that are hard to reach, such
as those found in pails, pans, trays, and other similar
objects.
Remember that the copper is hot! Do not
touch it with your bare hands.
4. Smooth off the point of the copper and smooth
off any sharp edges.
5. Reheat the copper until it is hot enough to melt
the solder.
Nonelectrical coppers are supplied in pairs. This is
done so one copper can be used as the other is being
heated. The size designation of coppers refers to the
weight (in pounds) of TWO copperheads; thus a reference to a pair of 4-pound coppers means that each
copper head weighs 2 pounds. Pairs of coppers are
usually supplied in 1-pound, 1 1/2-pound, 3-pound,
4-pound, and 6-pound sizes. Heavy coppers are designed for soldering heavy gauge metals, and light coppers are for thinner metals. Using the incorrect size of
copper usually results in either poorly soldered joints or
overheating.
When sal ammoniac is not available, use powdered
rosin instead. In this instance, place the powdered rosin
on top of a brick. Rub the copper back and forth to pick
up the rosin and then place the solder directly onto the
copper. (See fig. 6-5.)
Filing and Tinning Coppers.— New soldering
coppers must be tinned (coated with solder) before use.
Commercially prepared soldering salts are also used
in tinning soldering coppers. These salts are available in
6. Rub each filed side of the copper back and forth
across a cake of sal ammoniac, as shown in figure 6-4.
7. Apply solder to the copper until it is tinned. You
may rub the solder directly onto the copper, or place it
on the cake of sal ammoniac. Do not push the iron into
the cake of sal ammoniac, because this can split the cake.
6-2
Figure 6-5.—Tinning a copper (solder placed directly on copper).
Figure 6-7.—Presto-lite heating unit.
4. Reheat the copper to a bright red, and use a
flat-faced hammer to remove as many hollows as
possible.
5. File and tin the copper using the previously
described procedure.
ELECTRIC SOLDERING COPPERS.— Electric soldering coppers, or soldering irons, as they sometimes are called, are built with internal heating coils. The
soldering heads are removable and interchangeable.
Tinning is basically the same with the exception that the
tip usually does not become cherry red. Forging or
reshaping is not necessary, because the heads are easily
replaced.
Figure 6-6.—Forging a soldering copper.
powder form. Dissolve the powder in water according
to the directions and dip the soldering copper into the
solution and then apply the solder.
Forging Soldering Coppers.— Soldering coppers
may be reshaped by forging when they become blunt or
otherwise deformed. The procedure for forging a copper
is as follows:
Electric soldering irons are usually used for electrical work or other small jobs. They are especially suited
for this type of work, because they do not require
auxiliary heating and they can be manufactured as small
1. File the copper to remove all old tinning and to
smooth the surfaces.
as a pencil.
GAS TORCHES.— Gas torches can be used in
combination with soldering head attachments or as a
direct heat source. The Presto-lite heating unit is ideal
for soft soldering, because it delivers a small controllable flame. It also may be used effectively to heat
2. Heat the copper to a bright red.
3. Hold the copper on an anvil and forge it to the
required shape by striking it with a hammer. (See
fig. 6-6.) As you reshape the copper, a hollow will
appear at the point. Keep this hollow to a minimum by
striking the end of the copper. Do not shape too long a
taper or sharp point, because this causes the copper to
cool too rapidly. Turn the copper often to produce the
necessary squared-off sides and reheat the copper as
often as necessary during this part of the forging.
soldering coppers. As figure 6-7 shows, this heating unit
includes a fuel tank regulator, hose, and torch. It burns
acetylene or MAPP gas as fuel in the presence of oxygen. The torch tip (stem) is interchangeable with other
tips that come with the unit.
6-3
Soft Solder
There are many different types of solder being used
by industry. Solders are available in various forms that
include bars, wires, ingots, and powders. Wire solders
are available with or without a flux core. Because of the
many types of solder available, this chapter only covers
the solders most commonly used by Steelworkers.
TIN-LEAD SOLDER.— The largest portion of all
solders in use is solders of the tin-lead alloy group. They
have good corrosion resistance and can be used for
joining most metals. Their compatibility with soldering
processes, cleaning, and most types of flux is excellent.
In describing solders, it is the custom of industry to state
the tin content first; for example, a 40/60 solder means
to have 40% tin and 60% lead.
Figure 6-8.—Tin-lead alloy constitutional diagram.
Tin-lead alloy melting characteristics depend upon
the ratio of tin to lead. The higher the tin content, the
lower the melting temperature. Tin also increases the
wetting ability and lowers the cracking potential of the
solder.
TIN-ZINC SOLDER.— Several tin-zinc solders
have come into use for the joining of aluminum alloys.
The 91/9 and 60/40 tin-zinc solders are for higher temperature ranges (above 300°F), and the 80/20 and 70/30
tin-zinc alloys are normally used as precoating solders.
The behavior of tin-lead solder is shown by the
diagram in figure 6-8. This diagram shows that 100%
lead melts at 621°F and 100% tin melts at 450°F. Solders
that contain 19.5% to 97.5% tin remain a solid until they
exceed 360°F. The eutectic composition for tin-lead
solder is about 63% tin and 37% lead. (“Eutectic” means
the point in an alloy system that all the parts melt at the
same temperature.) A 63/37 solder becomes completely
liquid at 361°F. Other compositions do not. Instead, they
remain in the pasty stage until the temperature increases
to the melting point of the other alloy. For instance,
50/50 solder has a solid temperature of 361°F and a
liquid temperature range of 417°F. The pasty temperature range is 56°F—the difference between the solid and
the liquid.
LEAD-SILVER SOLDER.— Lead-silver solders
are useful where strength at moderately high temperatures is required. The reason lead by itself cannot be used
is that it does not normally wet steel, cast iron, or copper
and its alloys. Adding silver to lead results in alloys that
more readily wet steel and copper. Flow characteristics
for straight lead-silver solders are rather poor, and these
solders are susceptible to humidity and corrosion during
storage. The wetting and flow characteristics can be
enhanced as well as an increased resistance to corrosion
by introducing a tin content of 1%.
Lead-silver solders require higher soldering temperatures and special fluxing techniques. The use of a
zinc-chloride base flux or uncoated metals is recommended, because rosin fluxes decompose rapidly at high
temperatures.
Solders with lower tin content are less expensive
and primarily used for sheet metal products and other
high-volume solder requirements. High tin solders are
extensively used in electrical work. Solders with 60%
tin or more are called fine solders and are used in
instrument soldering where temperatures are critical.
TIN-ANTIMONY SOLDER.— Tin-antimony
solders are used for refrigeration work or for joining
copper to cast-iron joints. The most common one is the
95/5 solder.
TIN-ANTIMONY-LEAD SOLDER.— Antimony
is added to a tin-lead solder as a substitute for some of
the tin. The antimony, up to 6%, increases the strength
and mechanical properties of the solder. A word of
caution, solders having a high antimony content should
not be used on aluminum, zinc, or zinc-coated materials.
They form an intermetallic compound of zinc and antimony that causes the solder to become very brittle.
TIN-SILVER SOLDER.— Tin-silver solder (96/4)
is used for food or beverage containers that must be
cadmium and lead-free. It also can be used as a replacement for tin-antimony solder (95/5) for refrigeration
work
6-4
Table 6-1.—Fluxes Used for Soldering Some Common Metals
The most commonly used corrosive fluxes are sal
ammoniac (ammonium chloride) and zinc chloride.
These fluxes are frequently used in either solution or in
paste form. The solvent, if present, evaporates as the
work heats, leaving a layer of solid flux on the work.
When the metal reaches the soldering temperature, this
layer of flux melts, partially decomposes, and liberates
hydrochloric acid. The hydrochloric acid dissolves the
oxides from the work surfaces and the solder, making
them ready for soldering.
These solders and the procedures for their use are
also listed in the Welding Materials Handbook,
NAVFAC, P-433.
Fluxes
Scale, rust, and oxides form on most metal surfaces
when exposed to air, and heating accelerates this formation. Solder will not adhere to or wet the metal unless
these pollutants are removed. Fluxes are chemical compounds used to clean and maintain the metal surfaces
during the soldering process. They also decrease the
surface tension of the solder, making it abetter wetting
agent. Fluxes are manufactured in cake, paste, liquid, or
powder form and are classified as either noncorrosive
or corrosive. Table 6-1 shows the fluxes that are normally used for soldering common metals.
Zinc chloride (sometimes called CUT ACID or
KILLED ACID) can be made in the shop as long as
safety precautions are followed. To prepare zinc chloride, pour a small amount of muriatic acid (the commercial form of hydrochloric acid) into a glass or
acid-resistant container and then add small pieces of
zinc. As you add the zinc, the acid boils and bubbles as
a result of a chemical reaction that produces zinc chloride and hydrogen gas. Keep adding small pieces of zinc
to the mixture until the liquid no longer boils and bubbles. At this point, the reaction is complete and you then
dilute the liquid in the container with an equal amount
of water. Make only enough as required and strain it
before use. If any is leftover, store it in a tightly sealed
glass container.
NONCORROSIVE FLUXES.— Noncorrosive
fluxes are for soldering electrical connections and for
other work that must be free of any trace of corrosive
residue. Rosin is the most commonly used noncorrosive
flux. In the solid state, rosin is inactive and noncorrosive. When heated, it melts and provides some fluxing
action. Rosin is available in powder, paste, or liquid
form.
Rosin fluxes frequently leave a brown residue. This
residue is nonconductive and sometimes difficult to
remove. The removal problem can be reduced by adding
a small amount of turpentine to the rosin. Glycerine is
added to the rosin to make the flux more effective.
WARNING
When diluting the acid, you always add the
acid to the water. Adding water to acid can result
in an explosive reaction, resulting in serious
injuries.
CORROSIVE FLUXES.— Corrosive fluxes have
the most effective cleaning action, but any trace of
corrosive flux that remains on the work can cause corrosion later. For this reason, corrosive fluxes are not
used on electrical connections or other work where
corrosion would cause a serious problem.
Specific precautions must be taken when preparing
zinc chloride. Rubber gloves, a full-face visor, and an
apron are required. The fumes given off by muriatic acid
or by the mixture of muriatic acid and zinc are a health
6-5
hazard as well as an explosive. Prepare zinc chloride
under a ventilation hood, out in the open, or near openings to the outside to reduce inhalation of the fumes or
the danger of explosion. It is essential that precautions
be taken to prevent flames or sparks from coming in
contact with the liberated hydrogen.
&
,,, //
Another type of corrosive flux in use is known as
SOLDERING SALTS. Commercially prepared soldering salts are normally manufactured in a powder form
that is water soluble that allows you to mix only the
amount needed.
After a corrosive flux has been used for soldering,
you should remove as much of the flux residue as
possible from the work. Most corrosive fluxes are water
soluble; therefore, washing the work with soap and
water and then rinsing thoroughly with clear water
usually removes the corrosive residue. To lessen damage, you should ensure the work is cleaned immediately
after the soldering.
Figure 6-9.—Soldering a seam.
heat the joint with a soldering copper or a torch until the
solder melts and joins the pieces together. Remove the
source of heat and keep the parts firmly in position until
the solder has completely hardened. Cleaning any residue from the soldered area completes the job.
SOLDERING TECHNIQUES
The two soldering methods most often used
are soldering with coppers or torch soldering. The
considerations that apply to these methods of soldering
are as follows:
Seam Soldering
Seam soldering involves running a layer of solder
along the edges of a joint. Solder seam joints on the
inside whenever possible. The best method to use for
this process is soldering coppers, because they provide
better control of heat and cause less distortion.
1. Clean all surfaces of oxides, dirt, grease, and
other foreign matter.
2. Use the proper flux for the particular job. Some
work requires the use of corrosive fluxes, while other
work requires the use of noncorrosive fluxes.
Remember, the melting point of the flux must be
BELOW the melting point of the solder you are going
to use.
Clean and flux the areas to be soldered. If the seam
is not already tacked, grooved, riveted, or otherwise held
together, tack the pieces so the work stays in position.
Position the piece so the seam does not rest directly on
the support. This is necessary to prevent loss of heat to
the support. After you have firmly fastened the pieces
together, solder the seam.
3. Heat the surfaces just enough to melt the solder.
Solder does not stick to unheated surfaces; however, you
should be very careful not to overheat the solder, the
soldering coppers, or the surfaces to be joined. Heating
solder above the work temperature increases the rate of
oxidation and changes the proportions of tin and lead.
Heat the area by holding the copper against the
work. The metal must absorb enough heat from the
copper to melt the solder, or the solder will not adhere.
Hold the copper so one tapered side of the head is flat
against the seam, as shown in figure 6-9. When the
solder begins to flow freely into the seam, draw the
copper along the seam with a slow, steady motion. Add
as much solder as necessary without raising the copper
from the work. When the copper becomes cold, you
should use the other copper and reheat the first one.
Change coppers as often as necessary. Remember, the
best soldered seams are made without lifting the copper
from the work and without retracing completed work.
Allow the joint to cool and the solder to set before
4. After making a soldered joint, you should
remove as much of the corrosive flux as possible.
Sweat Soldering
Sweat soldering is used when you need to make a
joint and not have the solder exposed. You can use this
process on electrical and pipe connections. To make a
sweated joint, you should clean, flux, and tin each
adjoining surface. Hold the pieces firmly together and
6-6
Figure 6-12.—Soldering a bottom seam.
Figure 6-10.—Soldering a riveted seam.
6-12. Hold the copper in one position until the solder
starts to flow freely into the seam. Draw the copper
slowly along the seam, turning the work as you go. Add
more beads as you need them and reheat the copper as
necessary.
To heat an electric soldering copper, you merely
plug it in. Otherwise, the procedure is much the same as
that just described. Be very careful not to let an electric
soldering copper overheat. Overheating can burn out the
electrical element as well as damage the copper and
tinning,
Figure 6-11.—Making solder beads.
Soldering Aluminum Alloys
Soldering aluminum alloys is more difficult than
soldering many other metals. The difficult y arises primarily from the layer of oxide that always covers aluminum alloys. The thickness of the layer depends on the
type of alloy and the exposure conditions.
moving the joint. When you use a corrosive flux, clean
the joint by rinsing it with water and then brushing or
wiping it with a clean, damp cloth.
Riveted seams are often soldered to make them
watertight. Figure 6-10 shows the procedure for soldering a riveted seam.
Using the proper techniques, many of the aluminum
alloys can be successfully soldered. Wrought aluminum
alloys are usually easier to solder than cast aluminum
alloys. Heat-treated aluminum alloys are extremely difficult to solder, as are aluminum alloys containing more
than 1% magnesium.
Solder beads, or solder shots, are sometimes used
for soldering square, rectangular, or cylindrical bottoms.
To make the solder beads, hold the solder against a hot
copper and allow the beads to drop onto a clean surface,
as shown in figure 6-11.
The solders used for aluminum alloys are usually
tin-zinc or tin-cadmium alloys. They are generally
called ALUMINUM SOLDERS. Most of these solders
have higher melting points than the tin-lead solders used
for ordinary soldering. Corrosive and noncorrosive
fluxes are used for soldering aluminum.
To solder a bottom seam with solder beads, you
should first flux the seam before dropping one of the
cold beads of solder into the container. Place the hot
soldering copper against the seam, as shown in figure
6-7
EQUIPMENT
The first step in soldering aluminum is to clean the
surfaces and remove the layer of oxide. If a thick layer
of oxide is present, you should remove the main part of
it mechanically by filing, scraping, sanding, or wire
brushing. A thin layer of oxide can often be removed by
using a corrosive flux. Remember, remove any residual
flux from the joint after the soldering is finished.
Brazing requires three basic items. You need a
source of heat, filler metals, and flux. In the following
paragraphs these items are discussed.
Heating Devices
After cleaning and fluxing the surfaces, you should
tin the surfaces with aluminum solder. Apply flux to the
work surfaces and to the solder. You can tin the surfaces
with a soldering copper or with a torch. If you use a
torch, do not apply heat directly to the work surfaces, to
the solder, or to the flux. Instead, play the torch on a
nearby part of the work and let the heat conduct through
the metal to the work area. Do not use more heat than is
necessary to melt the solder and tin the surfaces. Work
the aluminum solder well into the surfaces. After tinning
the surfaces, the parts may be sweated together.
The source of heat depends on the type and amount
of brazing required. If you are doing production work
and the pieces are small enough, they can be put into a
furnace and brazed all at once. Individual torches can be
mounted in groups for assembly line work, or you can
use individual oxyacetylene or Mapp-oxygen torches to
braze individual items.
Filler Metals
Another procedure you can use for soldering aluminum alloys is to tin the surfaces with an aluminum solder
and then use a regular tin-lead solder to join the tinned
surfaces. This procedure can be used when the shape of
the parts prevents the use of the sweating method or
demands a large amount of solder. When using tin-lead
solder with aluminum solder, you do not have to use
flux.
Filler metals used in brazing are nonferrous metals
or alloys that have a melting temperature below the
adjoining base metal, but above 800°F. Filler metals
must have the ability to wet and bond with the base
metal, have stability, and not be excessively volatile.
The most commonly used filler metals are the silverbased alloys. Brazing filler metal is available in rod,
wire, preformed, and powder form.
After soldering is complete, you should clean the
joints with a wire brush, soap and water, or emery cloth.
Ensure that you remove all the flux from the joint since
any flux left will cause corrosion.
Brazing filler metals include the following eight
groups:
1. Silver-base alloys
2. Aluminum-silicon alloys
3. Copper
BRAZING
4. Copper-zinc (brass) alloys
Brazing is the process of joining metal by heating
the base metal to a temperature above 800°F and adding
a nonferrous filler metal that melts below the base metal.
Brazing should not be confused with braze welding,
even though these two terms are often interchanged. In
brazing, the filler metal is drawn into the joint by capillary action and in braze welding it is distributed by
tinning. Brazing is sometimes called hard soldering or
silver soldering because the filler metals are either hard
solders or silver-based alloys. Both processes require
distinct joint designs.
5. Copper-phosphorus alloys
6. Gold alloys
7. Nickel alloys
8. Magnesium alloys
Fluxes
Brazing processes require the use of a flux. Flux is
the substance added to the metal surface to stop the
formation of any oxides or similar contaminants that are
formed during the brazing process. The flux increases
both the flow of the brazing filler metal and its ability to
stick to the base metal. It forms a strong joint by bringing
the brazing filler metal into immediate contact with the
Brazing offers important advantages over other
metal-joining processes. It does not affect the heat treatment of the original metal as much as welding does, nor
does it warp the metal as much. The primary advantage
of brazing is that it allows you to join dissimilar metals.
6-8
adjoining base metals and permits the filler to penetrate
the pores of the metal.
You should carefully select the flux for each brazing
operation. Usually the manufacturer’s label specifies the
type of metal to be brazed with the flux. The following
factors must be considered when you are using a flux:
l Base metal or metals used
. Brazing filler metal used
l Source of heat used
Flux is available in powder, liquid, and paste form.
One method of applying the flux in powdered form is to
dip the heated end of a brazing rod into the container of
the powdered flux, allowing the flux to stick to the
brazing rod. Another method is to heat the base metal
slightly and sprinkle the powdered flux over the joint,
allowing the flux to partly melt and stick to the base
metal. Sometimes, it is desirable to mix powdered flux
with clean water (distilled water) to form a paste.
Figure 6-13.—Three types of common joint designs for brazing.
in thickness of the final product. For maximum strength,
the overlap should be at least three times the thickness
of the metal. A 0.001-inch to 0.003-inch clearance between the joint members provides the greatest strength
with silver-based brazing filler metals. You should take
precautions to prevent heat expansion from closing
joints that have initial close tolerances.
Flux in either the paste or liquid form can be applied
with a brush to the joint. Better results occur when the
filler metal is also given a coat.
The most common type of flux used is borax or a
mixture of borax with other chemicals. Some of the
commercial fluxes contain small amounts of phosphorus and halogen salts of either iodine, bromine, fluorine,
chlorine, or astatine. When a prepared flux is not available, a mixture of 12 parts of borax and 1 part boric acid
may be used.
Butt Joints
Butt joints are limited in size to that of the thinnest
section so maximum joint strength is impossible. Butt
joint strength can be maximized by maintaining a joint
clearance of 0.001 to 0.003 of an inch in the finished
braze. The edges of the joint must be perfectly square to
maintain a uniform clearance between all parts of the
joint. Butt joints are usually used where the double
thickness of a lap joint is undesirable. When doublemetal thickness is objectionable and you need more
strength, the scarf joint is a good choice.
WARNING
Nearly all fluxes give off fumes that may
be toxic. Use them only in WELL-VENTILATED spaces.
JOINT DESIGN
In brazing, the filler metal is distributed by capillary
action. This requires the joints to have close tolerances
and a good fit to produce a strong bond. Brazing has
three basic joint designs (fig. 6-13): lap, butt, and scarf.
These joints can be found in flat, round, tubular, or
irregular shapes.
Scarf Joints
A scarf joint provides an increased area of bond
without increasing the thickness of the joint. The area of
bond depends on the scarf angle cut for the joint. Usually, an area of bond two to three times that of a butt joint
is desirable. A scarf angle of 30 degrees gives a bond
area twice that of a 90-degree butt joint, and an angle of
19 1/2 degrees increases the bond area three times.
Lap Joints
The lap joint is one of the strongest and most frequently used joint in brazing, especially in pipe work
The primary disadvantage of the lap joint is the increase
6-9
Figure 6-14.—Joints designed to produce good brazing results.
Figure 6-15.—Some well-designed joints that have been prepared for brazing, and some poorly designed joints shown for comparison
voids in the joint or accidental movement during brazing
and cooling operations.
Figure 6-14 shows some variations of butt and lap
joints designed to produce good brazing results. A comparison of good and bad designed joints is shown in
figure 6-15.
Surface Preparation
BRAZING PROCEDURES
The surfaces of the metal must be cleaned for capillary action to take place. When necessary, chemically
clean the surface by dipping it in acid. Remove the acid
by washing the surface with warm water. For mechanical cleaning, you can use steel wool, a file, or abrasive
paper. Do not use an emery wheel or emery cloth,
The procedure for brazing is very similar to braze
and oxyacetylene welding. The metal needs to be
cleaned by either mechanical, chemical, or a combination of both methods to ensure good bonding. The two
pieces must befitted properly and supported to prevent
6-10
Figure 6-16.—Brazing a butt joint.
The best way to determine the temperature of the
joint, as you heat it, is by watching the behavior of the
flux. The flux first dries out as the moisture (water) boils
off at 212°F. Then the flux turns milky in color and starts
to bubble at about 600°F. Finally, it turns into a clear
liquid at about 1100°F. That is just short of the brazing
temperature. The clear appearance of the flux indicates
that it is time to start adding the filler metal. The heat of
the joint, not the flame, should melt the filler metal.
When the temperature and alignment are proper, the
filler metal spreads over the metal surface and into the
joint by capillary attraction. For good bonding, ensure
the filler metal penetrates the complete thickness of the
metal. Figure 6-16 shows a good position for the torch
and filler metal when brazing a butt joint.
because abrasive particles or oil might become embedded in the metal.
Work Support
Mount the work in position on firebricks or other
suitable means of support, and if necessary, clamp it.
This is important because if the joint moves during the
brazing process, the finished bond will be weak and
subject to failure.
Fluxing
The method of application varies, depending upon
the form of flux being used and the type of metal you
are brazing. Refer to the material on fluxes previously
described. It is extremely important that the flux is
suitable for your job.
Stop heating as soon as the filler metal has completely covered the surface of the joint, and let the joint
cool slowly. Do not remove the supports or clamps or
move the joint in any way until the surface is cool and
the filler metal has completely solidified.
Finally, clean the joint after it has cooled sufficiently. This can be done with hot water. Be sure to
remove all traces of the flux because it can corrode the
metal. Excess metal left on the joint can be filed smooth.
Brazing
The next step is to heat the parts to the correct
brazing temperature. Adjust the torch flame (oxygas) to
a neutral flame because this flame gives the best results
under normal conditions. A reducing flame produces an
exceptionally neat-looking joint, but strength is sacrificed. An oxidizing flame will produce a strong joint but
it has a rough-looking surface.
The above described procedure is a general one, but
it applies to the three major types of brazing: silver,
copper alloy, and aluminum. The differences being the
base metals joined and the composition of the filler
metals.
6-11
Table 6-2.—Silver Brazing Filler Metal Alloys
comparable to those made by fusion welding without
the destruction of the base metal characteristics. Braze
welding is also called bronze welding.
Silver Brazing
Often, you will be called on to do a silver brazing
job. Table 6-2 lists different types of silver brazing
alloys and their characteristics. A popular way to apply
silver brazing metal on a tubing is to use silver alloy
rings, as shown in figure 6-17. This is a practical and
economical way to add silver alloy when using a production line system. Another method of brazing by using
preplaced brazing shims is shown in figure 6-18. The
requirements of each job varies; however, through experience you can become capable of selecting the proper
procedure to produce quality brazing.
Braze welding has many advantages over fusion
welding. It allows you to join dissimilar metals, to
minimize heat distortion, and to reduce extensive preheating. Another side effect of braze welding is the
elimination of stored-up stresses that are often present
in fusion welding. This is extremely important in the
repair of large castings. The disadvantages are the loss
of strength when subjected to high temperatures and the
inability to withstand high stresses.
BRAZE WELDING
EQUIPMENT
Braze welding is a procedure used to join two
pieces of metal. It is very similar to fusion welding
with the exception that the base metal is not melted.
The filler metal is distributed onto the metal surfaces
by tinning. Braze welding often produces bonds that are
The equipment needed for braze welding is basically identical to the equipment used in brazing. Since
braze welding usually requires more heat than brazing,
an oxyacetylene or oxy-mapp torch is recommended.
6-12
Figure 6-17.—Silver-brazed joints designed to use preplaced silver alloy rings. The alloy forms almost
perfect fillets, and no further finishing is necessary.
Figure 6-18.—A machining tool bit showing how the carbide insert is brazed to the tool bit body using
preplaced brazing filler metal shims.
6-13
Table 6-3.—Copper Alloy Brazing Filler Metals
Filler Metal
BRAZE WELDING PROCEDURES
The primary elements of a braze welding rod are
copper and zinc. These elements improve ductility and
high strength. Small amounts of iron, tin, aluminum,
manganese, chromium, lead, nickel, and silicon are also
added to improve the welding characteristics of the rod.
They aid in deoxidizing the weld metal, increasing flow
action, and decreasing the chances of fuming. Table 6-3
lists some copper alloy brazing filler metals and their
use. The most commonly used are brass brazing alloy
and naval brass. The selection of the proper brazing filler
metal depends on the types of base metals.
Edge preparation is essential in braze welding. The
edges of the thick parts can be beveled by grinding,
machining, or filing. It is not necessary to bevel the thin
parts (one-fourth inch or less). The metal must be bright
and clean on the underside as well as on the top of the
joint. Cleaning with a file, steel wool, or abrasive paper
removes most foreign matter such as oil, greases, and
oxides. The use of the proper flux completes the process
and permits the tinning to occur.
After you prepare the edges, the parts need to be
aligned and held in position for the braze welding process. This can be done with clamps, tack welds, or a
combination of both. The next step is to preheat the
assembly to reduce expansion and contraction of the
metals during welding. The method you use depends
upon the size of the casting or assembly.
Flux
Proper fluxing is essential in braze welding. If the
surface of the metal is not clean, the filler metal will not
flow smoothly and evenly over the weld area. Even after
mechanical cleaning, certain oxides often remain and
interfere with the flow of the filler metal. The use of the
correct flux eliminates these oxides.
Once preheating is completed, you can start the
tinning process. Adjust the flame of the torch to a
slightly oxidizing flame and flux the joint. Through
experience, you will find that the use of more flux during
the tinning process produces stronger welds. Apply heat
to the base metal until the metal begins to turn red. Melt
some of the brazing rod onto the surface and allow it to
spread along the entire joint. You may have to add more
filler metal to complete the tinning. Figure 6-19 shows
Flux may be applied directly to the weld area, or it
can be applied by dipping the heated end of the rod into
the flux. Once the flux sticks to the rod, it then can be
transferred to the weld area. A prefluxed braze welding
rod is also available, and this eliminates the need to add
flux during welding.
6-14
Figure 6-19.—Braze welding cast iron, using the backhand method.
are put into service for the first time. There are several
different methods of wearfacing; however, in this discussion we only cover the oxygas process of wearfacing.
an example of tinning being used with the backhand
method of welding.
Temperature control is very important. If the base
metal is too hot, the filler metal bubbles or runs around
like beads of water on a hot pan. If the filler metal forms
little balls and runs off the metal, then the base metal is
too cold.
Wearfacing provides a means of maintaining sharp
cutting edges and can reduce wear between metal parts.
It is an excellent means for reducing maintenance costs
and downtime. These and other advantages of wearfacing add up to increased service life and high efficiency
of equipment.
After the base metal is tinned, you can start adding
beads of filler metal to the joint. Use a slight circular
motion with the torch and run the beads as you would
in regular fusion welding. As you progress, keep adding
flux to the weld. If the weld requires several passes, be
sure that each layer is fused into the previous one.
Wearfacing with the oxygas flame is, in many respects, similar to braze welding. The wearfacing metals
generally consist of high-carbon filler rods, such as high
chromium or a Cr-Co-W alloy, but, in some instances,
special surfacing alloys are required. In either event,
wearfacing is a process in which a layer of metal of one
composition is bonded to the surface of a metal of
another composition.
After you have completed the braze welding operation, heat the area around the joint on both sides for
several inches. This ensures an even rate of cooling.
When the joint is cold, remove any excess flux or any
other particles with a stiff wire brush or steel wool.
The process of hard-surfacing is suitable to all lowcarbon alloy and stainless steels as well as Monel and
cast iron. It is not intended for aluminum, copper, brass,
or bronze, as the melting point of these materials prohibits the use of the hard-surfacing process. It is possible
to increase the hardness of aluminum by applying a
zinc-aluminum solder to the surface. Copper, brass, and
bronze can be improved in their wear ability by the
overlay of work-hardening bronze. Carbon and alloy
tool steels can be surface-hardened, but they offer difficulties due to the frequent development of shrinkage and
strain cracks. If you do surface these materials, they
should be in an annealed, and not a hardened condition.
When necessary, heat treating and hardening can be
accomplished after the surfacing operation. Quench the
part in oil, not water.
WEARFACING
WEARFACING is the process you use to apply an
overlay of special ferrous or nonferrous alloy to the
surface of new or old parts. The purpose is to increase
their resistance to abrasion, impact, corrosion, erosion,
or to obtain other properties. Also, wearfacing also can
be used to build up undersized parts. It is often called
hard-surfacing, resurfacing, surfacing, or hardfacing.
As a Steelworker, there are times when you are
required to build up and wear-face metal parts from
various types of construction equipment. These parts
include the cutting edges of scraper or dozer blades,
sprocket gears, and shovel or clamshell teeth. You may
even wear-face new blades or shovel teeth before they
6-15
wearfacing. If in doubt as to when to use a buildup rod,
you should check with your leading petty officer.
WEARFACING MATERIALS
A surfacing operation using a copper-base alloy
filler metal produces a relatively soft surface. Workhardening bronzes are soft when applied and give
excellent resistance against frictional wear. Other types
of alloys are available that produce a surface that is
corrosion and wear resistant at high temperatures. Wearfacing materials are produced by many different manufacturers; therefore, be sure that the filler alloys you
select for a particular surfacing job meet Navy specifications.
Preheating
Most parts that require wearfacing can be preheated
with a neutral welding flame before surfacing. You
should use a neutral flame of about 800°F. Do not
preheat to a temperature higher than the critical temperature of the metal or to a temperature that can cause
the formation of scale.
Application
Two types of hard-surfacing materials in general use
in the Navy are iron-base alloys and tungsten carbide.
In general, the torch manipulations and the wearfacing procedures are similar to brazing techniques. However, higher temperatures (about 2200°F) are necessary
for wearfacing, and tips of one or two sizes larger than
normal are used.
Iron-Base Alloys
These materials contain nickel, chromium, manganese, carbon, and other hardening elements. They are
used for a number of applications requiring varying
degrees of hardness. A Steelworker frequently works
with iron-base alloys when he builds up and resurfaces
parts of construction equipment.
To begin, you heat a small area of the part with a
sweeping torch movement until the surface of the base
metal takes on a sweating or wet appearance. When the
surface of the base metal is in this condition, bring the
end of the surfacing alloy into the flame and allow it to
melt. Do not stir or puddle the alloy; let it flow. When
the surface area has been properly sweated, the alloy
flows freely over the surface of the base metal.
Tungsten Carbide
You use this for building up wear-resistant surfaces
on steel parts. Tungsten carbide is one of the hardest
substances known to man. Tungsten carbide can be
applied in the form of inserts or of composite rod. Inserts
are not melted but are welded or brazed to the base
metal, as shown in figure 6-18. The rod is applied with
the same surfacing technique as that used for oxygas
welding; a slightly carburizing flame adjustment is necessary.
Being able to recognize a sweated surface is essential for surfacing. Sweating occurs when you heat the
steel with a carburizing flame to a white heat temperature. This carburizes an extremely thin layer of the base
metal, approximately 0.001 inch thick. The carburized
layer has a lower melting point than the base metal. As
a result, it becomes a liquid, while the underlying metal
remains a solid. This liquid film provides the medium
for flowing the filler metal over the surface of the base
metal. The liquid film is similar to and serves the same
purpose as a tinned surface in soldering and braze welding.
WEARFACING PROCEDURES
Proper preparation of the metal surfaces is an important part of wearfacing operations. Make sure that
scale, rust, and foreign matter are removed from the
metal surfaces. You can clean the metal surfaces by
grinding, machining, or chipping. The edges of grooves,
corners, or recesses should be well rounded to prevent
base metal overheating and to provide a good cushion
for the wearfacing material.
When you heat steel with a carburizing flame, it first
becomes red. As heating continues, the color becomes
lighter and lighter until a bright whiteness is attained. At
this point, a thin film of liquid, carburized metal appears
on the surface. Surfacing alloy added at this time flows
over the sweated surface and absorbs the film of carburized metal. This surface condition is not difficult to
recognize, but you should make several practice passes
before you try wearfacing for the first time.
Weafacing material is applied so it forms a thin
layer over the base metal. The thickness of the deposit
is usually from one sixteenth to one eighth of an inch
and is seldom over one fourth of an inch. It is generally
deposited in a single pass. Where wear is extensive, it
may become necessary to use a buildup rod before
When you use an oxygas torch for surfacing with
chromium cobalt, the torch flame should have an excess
fuel-gas feather about three times as long as the inner
6-16
Figure 6-20.—Grader blade with hardfacing material applied to cutting edge.
grader blade is usually wearfaced by the electric arc
process. If the electric arc process is not available, you
may use the oxygas torch.
cone. Unless the excess fuel-gas flame is used, the
proper base metal surface condition cannot be developed. Without this condition, the surfacing alloy does
not spread over the surface of the part.
Welding Materials Handbook, NAVFAC P-433, is
an excellent source of information for wearfacing con-
Figure 6-20 shows a grader blade with a deposit of
hardfacing material applied along the cutting edge. A
struction equipment.
6-17
CHAPTER 7
SHIELDED METAL-ARC WELDING
AND WEARFACING
requires a number of accessories that include a combination chipping hammer and wire brush, welding table
(for shopwork), C-clamps, and protective apparel.
The shielded metal-arc welding process, referred to
as metallic-arc welding, arc welding, or stick welding,
is extensively used in welding ferrous and nonferrous
metals. It has many applications for producing a vast
assortment of metal products. Shielded metal-arc welding is found in the ship building industry and in the
construction industry for fabricating girders, beams, and
columns. Because it is easy to use and portable, shielded
metal-arc welding is universally used in the repair and
servicing of equipment, machinery, and a host of other
items.
Before we discuss the different types of welding
machines, you must first have a basic knowledge of the
electrical terms used with welding.
Electrical Terms
Many terms are associated with arc welding. The
following basic terms are especially important.
ALTERNATING CURRENT.— Alternating current is an electrical current that has alternating negative
and positive values. In the first half-cycle, the current
flows in one direction and then reverses itself for the
next half-cycle. In one complete cycle, the current
spends 50 percent of the time flowing one way and the
other 50 percent flowing the other way. The rate of
change in direction is called frequency, and it is indicated by cycles per second. In the United States, the
alternating current is set at 60 cycles per second.
MANUAL SHIELDED METAL-ARC
WELDING
Arc welding provides you the ability to join two
metals by melting them with an arc generated between
a coated-metal electrode and the base metal. The temperatures developed by the arc can reach as high as
10000°F. The arc energy is provided by a power source
that generates either direct or alternating current. The
electrodes that carry the current produce a gas that
shields the arc from the atmosphere and supplies filler
metal to develop the weld shape.
AMPERE.— Amperes, sometimes called “amps,”
refers to the amount of current that flows through a
circuit. It is measured by an “amp” meter.
ARC-WELDING EQUIPMENT
CONDUCTOR.— Conductor means any material
that allows the passage of an electrical current.
A wide variety of welding equipment is available,
and there are many differences between the makes and
models of the equipment produced by the manufacturers. However, all types of arc-welding equipment are
similar in their basic function of producing the high-amperage, low-voltage electric power required for the
welding arc. In this discussion, we are primarily concerned with the typical items of arc-welding equipment,
rather than the specific types. For specific information
about the equipment your battalion or duty station has
available, consult the manufacturer’s instruction manual. For additional operational information and safety
instruction, have your leading welding petty officer
explain the operation to you.
CURRENT.— Current is the movement or flow of
an electrical charge through a conductor.
DIRECT CURRENT.— Direct current is an electrical current that flows in one direction only.
ELECTRICAL CIRCUIT.— Electrical circuit is
the path taken by an electrical current flowing through
a conductor from one terminal of the source to the load
and returning to the other terminal of the source.
POLARITY.— Polarity is the direction of the flow
of current in a circuit. Since current flows in one direction only in a dc welder, the polarity becomes an important factor in welding operations.
The basic parts of a typical shielded metal-arc welding outfit include a welding machine, cables, electrode
holder (stinger), and electrodes. The Steelworker also
RESISTANCE.— Resistance is the opposition of
the conductor to the flow of current. Resistance causes
electrical energy to be changed into heat.
7-1
127.517
Figure 7-1.—A 300 amp ac/dc portable welding
machine.
Figure 7-2.—An ac arc-welding transformer.
1. Machines rated 150 and 200 amperes—30 volts
are for light-shielded metal-arc welding and for inertgas arc welding. They are also for general-purpose
jobs or shopwork.
VOLT.— A volt is the force required to make the
current flow in an electrical circuit. It can be
compared to pressure in a hydraulic system. Volts are
measured with a volt meter.
2. Machines rated 200,300, and 400 amperes—40
volts are for general welding purposes by machine or
manual application.
Power Source
The power source used in arc welding is called a
welding machine or a welder. Three basic types of
welding machines are presently in use: motorgenerators, transformers, and rectifiers.
3. Machines rated 600 amperes—40 volts are for
submerged-arc welding or carbon-arc cutting.
ALTERNATING-CURRENT TRANSFORMER
WELDING MACHINES.— Practically all the
alternating current (at) arc-welding machines in use
are the static-transformer type, as shown in figure 72. These types of machines are the smallest, least
expensive, and the lightest type of welders made.
Industrial applications for manual operation use
machines having 200, 300, and 400 ampere ratings.
Machines with a 150-ampere rating are used in light
industrial, garage, and job/shop welding.
The transformers are usually equipped with arcstabilizing capacitors. Current control is provided in
several
ways
by
the
welding
transformer
manufacturers. One such method is an adjustable
reactor that is set by turning a crank until the
appropriate setting is found. Another method is by
plugging the electrode cable into different sockets
located on the front of the machine.
One major advantage of ac transformers is the
freedom from arc blow, which often occurs when welding
with direct-current (dc) machines. Arc blow causes the arc
to wander while you are welding in corners on heavy
metal or using large coated electrodes.
MOTOR-GENERATOR
WELDING
MACHINES.— These types of welding machines are
powered by electrical, gasoline, or diesel motors. The
diesel and gasoline motors are ideal for use in areas
where electricity is not available. Portable gas/diesel
welding machines are part of the equipment
allowance for Naval Mobile Construction Battalions.
These machines usually have the capability of
generating alternating or direct current. On the
newer machines, when you are welding in the directcurrent mode, the polarity can be changed by turning
a switch. Some of the older machines require
reversing the cable connections. One of the
advantages of a direct-current (dc) welding generator
is that you have the choice of welding with either
straight or reverse polarity. The welding machine, as
shown in figure 7-1, consists of a heavy-duty, ac/dc
300 amp generator powered by a diesel engine. The
generator is also capable of producing 3 kilowatts of
60 cycle ac power.
Welding machines are made in six standardized
ratings for general purposes and are listed as follows:
7-2
Table 7-1.—Cable Size Selection Guide
polarity current. By flicking a switch, the welder can
select the current that best suits the job. Figure 7-3 shows
an example of a combination ac/dc rectifier.
Cables
Welding cables carry the current to and from the
workpiece. One of the cables runs from the welding
machine to the electrode holder and the other cable
connects the workpiece to the welding machine. The
cable that connects the workpiece to the welding machine is called the ground. When the machine is turned
on and the operator touches the electrode to the workpiece, the circuit is completed, current begins to flow,
and the welding process commences.
The welding cables must be flexible, durable, well
insulated, and large enough to carry the required current.
Only cable that is specifically designed for welding
should be used. A highly flexible cable must be used for
the electrode holder connection. This is necessary so the
operator can easily maneuver the electrode holder during the welding process. The ground cable need not be
so flexible because once it is connected, it does not
move.
Two factors determine the size of welding cable to
use: the amperage rating of the machine and the distance
between the work and the machine. If either amperage
or distance increases, the cable size also must increase.
(See table 7-1.) A cable that is too small for the amperage
or the distance between the machine and the work will
overheat. On the other hand, larger size cables are more
Figure 7-3.—Combination ac, dc transformer-rectifier arc welder.
RECTIFIER WELDING MACHINES.— Rectifier welders are single-phase or three-phase transformers that have selenium or silicon rectifiers added to
rectify (change) the output current from alternating to
direct current. Most of these machines have the capability of producing either ac or dc straight or reverse
7-3
difficult to handle, especially if you are working on a
structure that requires a lot of moving around. The best
size cable is one that meets the amperage demand but is
small enough to manipulate with ease.
As a rule, the cable between the machine and the
work should be as short as possible. Use one continuous
length of cable if the distance is less than 35 feet. If you
must use more than one length of cable, join the sections
with insulated lock-type cable connectors. Joints in the
cable should be at least 10 feet away from the operator.
Figure 7-4.—C-clamped ground cable.
Electrode Holder
An electrode holder, commonly called a stinger, is
a clamping device for holding the electrode securely in
any position. The welding cable attaches to the holder
through the hollow insulated handle. The design of the
electrode holder permits quick and easy electrode exchange. Two general types of electrode holders are in
use: insulated and noninsulated. The noninsulated holders are not recommended because they are subject to
accidental short circuiting if bumped against the workpiece during welding. For safety reasons, try to ensure
the use of only insulated stingers on the jobsite.
Figure 7-5.—A spring-loaded ground clamp for the ground lead.
Electrode holders are made in different sizes, and
manufacturers have their own system of designation.
Each holder is designed for use within a specified range
of electrode diameters and welding current. You require
a larger holder when welding with a machine having a
300-ampere rating than when welding with a 100-ampere machine. If the holder is too small, it will overheat.
Ground Clamps
Figure 7-6.—Bolted and tack-welded ground clamps.
The use of a good ground clamp is essential to
producing quality welds. Without proper grounding, the
circuit voltage fails to produce enough heat for proper
welding, and there is the possibility of damage to the
welding machine and cables. Three basic methods are
used to ground a welding machine. You can fasten the
ground cable to the workbench with a C-clamp (fig. 74), attach a spring-loaded clamp (fig. 7-5) directly onto
the workpiece, or bolt or tack-weld the end of the ground
cable to the welding bench (fig. 7-6). The third way
creates a permanent common ground.
part of the welder’s equipment. After initial cleaning and
a weld bead has been deposited, the slag cover must be
removed before additional beads are added. The chipping hammer was specifically designed for this task.
The chipping operation is then followed by more brushing, and this cycle is repeated until the slag has been
removed. When the slag is not removed, the result is
porosity in the weld that weakens the weld joint.
Cleaning can also be accomplished by the use of
power tools or chemical agents. If these items are used,
it is essential that all safety precautions are followed.
Cleaning Equipment
Safety Equipment
Strong welds require good preparation and procedure. The surface area of the workpiece must be free of
all foreign material, such as rust, paint, and oil. A steel
brush is an excellent cleaning tool and is an essential
Arc welding not only produces a brilliant light, but
it also emits ultraviolet and infrared rays that are very
7-4
dangerous to your eyes and skin. In chapter 3, personal
safety items, such as helmets, lenses, and gloves, were
covered. An important item that needs to be covered
here is welding screens. The welder not only has to
protect himself but he also must take precautions to
protect other people who may be working close by.
When you are welding in the field, you must install a
welding screen around your work area. It can be an
elaborate factory-manufactured screen or as simple as
one constructed on site from heavy fire-resistant canvas.
literature and check with your senior petty officer or
chief on the items that you do not understand. Machine
setup involves selecting current type, polarity, and current settings. The current selection depends on the size
and type of electrode used, position of the weld, and the
properties of the base metal.
Cable size and connections are determined by the
distance required to reach the work the size of the
machine, and the amperage needed for the weld.
Operator maintenance depends on the type of welding machine used. Transformers and rectifiers require
little maintenance compared to engine-driven welding
machines. Transformer welders require only to be kept
dry and a minimal amount of cleaning. Internal maintenance should only be done by electricians due to the
possibilities of electrical shock Engine-driven machines require daily maintenance of the motors. Inmost
places you will be required to fill out and turn in a daily
inspection form called a “hard card” before starting the
engine. This form is a list of items, such as oil level,
water level, visible leaks, and other things, that affect
the operation of the machine. Transportation departments are the ones who usually handle these forms.
WARNING
Never look at thes welding arc without
proper eye protection. Looking at the arc with
the naked eye could result in permanent eye
damage. If you receive flash burns, they should
be treated by medical personnel.
Another area often overlooked is ventilation. Welding produces a lot of smoke and fumes that can be
injurious to the welder if they are allowed to accumulate.
This is especially true if you are welding in a tank or
other inclosed area. Permanent welding booths should
be equipped with a exhaust hood and fan system for
removal of smoke and fumes.
After all of the above items have been checked, you
are now ready to start welding.
EQUIPMENT OPERATION AND
MAINTENANCE
SHIELDED-METAL ARC WELDING
Learning to arc weld requires you to possess many
skills. Among these skills are the abilities to set up,
operate, and maintain your welding equipment.
Before you start to weld, ensure that you have all
the required equipment and accessories. Listed below
are some additional welding rules that should be followed.
WELDING AREA REQUIREMENTS
Clear the welding area of all debris and clutter.
In most factory environments, the work is brought
to the welder. In the Seabees, the majority of the time
the opposite is true. You will be called to the field for
welding on buildings, earthmoving equipment, well
drilling pipe, ship to shore fuel lines, pontoon causeways, and the list goes on. To accomplish these tasks,
you have to become familiar with your equipment and
be able to maintain it in the field. It would be impossible
to give detailed maintenance information here because
of the many different types of equipment found in the
field; therefore, only the highlights will be covered.
Do not use gloves or clothing that contains oil or
grease.
Check that all wiring and cables are installed
properly.
Ensure that the machine is grounded and dry.
Follow all manufacturer’s directions on operating the welding machine.
Have on hand a protective screen to protect
others in the welding area from FLASH bums.
WELDING MACHINE OPERATION
AND MAINTENANCE
Always keep fire-fighting equipment on hand.
You should become familiar with the welding machine that you will be using. Study the manufacturer’s
Clean rust, scale, paint, or dirt from the joints
that are to be welded.
7-5
Figure 7-7.—Electrode covering and gaseous shield that protects
weld metal from the atmosphere.
ELECTRODES
In general, all electrodes are classified into five
main groups:
1. Mild steel
Figure 7-8.—Explanation of AWS classification numbers.
2. High-carbon steel
3. Special alloy steel
the molten metal from oxidation or contamination by the
surrounding atmosphere.
As molten metal is deposited in the welding process,
it attracts oxygen and nitrogen. Since the arc stream
takes place in the atmosphere, oxidation occurs while
the metal passes from the electrode to the work. When
this happens, the strength and ductility of the weld are
reduced as well as the resistance to corrosion. The
coating on the electrode prevents oxidation from taking
place. As the electrode melts, the heavy coating releases
an inert gas around the molten metal that excludes the
atmosphere from the weld (fig. 7-7).
The burning residue of the coating forms a slag over
the deposited metal that slows down the cooling rate and
produces a more ductile weld. Some coatings include
powdered iron that is converted to steel by the intense
heat of the arc as it flows into the weld deposit.
4. Cast iron
5. Nonferrous
The widest range of arc welding is done with electrodes
in the mild steel group.
Electrodes are manufactured for use in specific
positions and for many different types of metal. They
also are specially designed to use with ac or dc welding
machines. Some manufacturer’s electrodes work identically on either ac or dc, while others are best suited for
flat-position welding. Another type is made primarily
for vertical and overhead welding, and some can be used
in any position. As you can see, electrode selection
depends on many variables.
Types of Electrodes
Electrodes are classified as either bare or shielded.
The original bare electrodes were exactly as their name
implied—bare. Today, they have a light covering, but
even with this improvement they are rarely used because
of their limitations. They are difficult to weld with,
produce brittle welds, and have low strength. Just about
all welding is done with shielded electrodes.
The shielded electrode has a heavy coating of several chemicals, such as cellulose, titania sodium, lowhydrogen sodium, or iron powder. Each of the chemicals
in the coating serves a particular function in the welding
process. In general, their main purposes are to induce
easier arc starting, stabilize the arc, improve weld
appearance and penetration, reduce spatter, and protect
Electrode Identification
Electrodes are often referred to by a manufacturer’s
trade name. The American Welding Society (AWS) and
the American Society foresting and Materials (ASTM)
have set up certain requirements for electrodes to assure
some degree of uniformity in manufacturing electrodes.
Thus different manufacturer’s electrodes that are within
the classification established by the AWS and ASTM
should have the same welding characteristics. (See
fig. 7-8.)
In this classification, each type of electrode is
assigned a specific symbol, such as E-6010, E-7010, and
E-8010. The prefix E identifies the electrode for
7-6
Table 7-2.—Electrode Selection Guide
The fourth digit of the symbol represents special
characteristics of the electrode, such as weld quality,
type of current, and amount of penetration. The numbers
range from 0 through 8. Since the welding position is
dependent on the manufacturer’s characteristics of the
coating, the third and fourth numbers are often identified
together.
electric-arc welding. The first two digits in the symbol
designate the minimum allowable tensile strength in
thousands of pounds per square inch of the deposited
weld metal. For example, the 60-series electrodes have
a minimum tensile strength of 60,000 pounds per square
inch, while the 70-series electrodes have a strength of
70,000 pounds per square inch.
The third digit of the symbol indicates the joint
position for which the electrode is designed. Two numhers are used for this purpose: 1 and 2. Number 1 designates an electrode that can be used for welding in any
position. Number 2 represents an electrode restricted for
welding in the horizontal and flat positions only.
Electrode Selection
Several factors are critical when you choose an
electrode for welding. The welding position is particularly significant. Table 7-2 shows the recommended
7-7
current types and welding positions for the most common electrodes.
As a rule of thumb, you should never use an electrode that has a diameter larger than the thickness of the
metal that you are welding. Some operators prefer larger
electrodes because they permit faster travel, but this
takes a lot of expedience to produce certified welds.
Position and the type of joint are also factors in
determining the size of the electrode. For example, in a
thick-metal section with a narrow vee, a small-diameter
electrode is always used to run the frost weld or root pass.
This is done to ensure full penetration at the root of the
weld. Successive passes are then made with larger electrodes.
For vertical and overhead welding, 3/16 inch is the
largest diameter electrode that you should use regardless
of plate thickness. Larger electrodes make it too difficult
to control the deposited metal. For economy, you should
always use the largest electrode that is practical for the
work It takes about one half of the time to deposit an
equal quantity of weld metal from 1/4-inch electrodes
as it does from 3/16-inch electrodes of the same type.
The larger sizes not only allow the use of higher currents
but also require fewer stops to change electrodes.
Deposit rate and joint preparation are also important
in the selection of an electrode. Electrodes for welding
mild steel can be classified as fast freeze, fill freeze, and
fast fill. FAST-FREEZE electrodes produce a snappy,
deep penetrating arc and fast-freezing deposits. They are
commonly called reverse-polarity electrodes, even
though some can be used on ac. These electrodes have
little slag and produce flat beads. They are widely used
for all-position welding for both fabrication and repair
work
FILL-FREEZE electrodes have a moderately forceful arc and a deposit rate between those of the fast-freeze
and fast-fill electrodes. They are commonly called the
straight-polarity electrodes, even though they may be
used on ac. These electrodes have complete slag coverage and weld deposits with distinct, even ripples. They
are the general-purpose electrode for a production shop
and are also widely used for repair work They can be
used in all positions, but fast-freeze electrodes are still
preferred for vertical and overhead welding.
Among the FAST-FILL electrodes are the heavycoated, iron powder electrodes with a soft arc and fast
deposit rate. These electrodes have a heavy slag and
produce exceptionally smooth weld deposits. They are
generally used for production welding where the work
is positioned for flat welding.
Another group of electrodes are the low-hydrogen
type that were developed for welding high-sulfur and
high-carbon steel. These electrodes produce X-ray
quality deposits by reducing the absorption of hydrogen
that causes porosity and cracks under the weld bead.
Welding stainless steel requires an electrode containing chromium and nickel. All stainless steels have
low-thermal conductivity that causes electrode overheating and improper arc action when high currents are
used. In the base metal, it causes large temperature
differentials between the weld and the rest of the work,
which warps the plate. A basic rule in welding stainless
steel is to avoid high currents and high heat. Another
reason for keeping the weld cool is to avoid carbon
corrosion.
There are also many special-purpose electrodes for
surfacing and welding copper and copper alloys, aluminum, cast iron, manganese, nickel alloys, and nickelmanganese steels. The composition of these electrodes
is designed to match the base metal. The basic rule in
selecting electrodes is to pick one that is similar in
composition to the base metal.
Electrode Storage
Electrodes are expensive; therefore, the loss or deterioration through improper handling or storage can
become very costly. Always store them in a dry place at
room temperature with 50-percent maximum relative
humidity. Moisture causes the coating on electrodes to
disintegrate and fall off. Low-hydrogen rods are especially sensitive to moisture. After removing these rods
from their original packaging, you should store them in
a storage space maintained at a temperature between
250°F to 400°F. Portable or stationary drying ovens are
used to store and preserve electrodes at specified temperatures. Care should be taken when handling electrodes because bumping or dropping them can cause the
coatings to fall off, rendering the rod useless.
Polarity
Earlier in this chapter, ac and dc current was briefly
covered. With ac welding machines, polarity is not a
problem. When using dc welding machines, you can
weld with either straight polarity or reverse polarity.
Polarity is the direction of the current flow in a
circuit, as shown in figure 7-9. In straight polarity, the
electrode is negative and the workpiece positive; the
electrons flow from the electrode to the workpiece. In
reverse polarity, the electrode is positive and the workpiece negative; the electrons flow from the workpiece
to the electrode. To help you remember the difference,
think of straight polarity as a SENator and reverse
polarity as a REPresentative. Use only the first three
letters of each key word. SEN stands for Straight Electrode Negative; REP for Reverse Electrode Positive.
7-8
Figure 7-10.—Striking or brushing method of starting the arc.
opposite is true and the greatest heat is produced on the
negative side. Electrode coatings affect the heat conditions differently. One type of heavy coating may provide
the most desirable heat balance with straight polarity,
while another type of coating on the same electrode may
provide a more desirable heat balance with reverse
polarity.
Reverse polarity is used in the welding of nonferrous metals, such as aluminum, bronze, Monel, and
nickel. Reverse polarity is also used with some types of
electrodes for making vertical and overhead welds.
You can recognize the proper polarity for a given
electrode by the sharp, crackling sound of the arc. The
wrong polarity causes the arc to emit a hissing sound,
and the welding bead is difficult to control.
One disadvantage of direct-current welding is “arc
blow.” As stated earlier, arc blow causes the arc to
wander while you are welding in corners on heavy metal
or when using large-coated electrodes. Direct current
flowing through the electrode, workpiece, and ground
clamp generates a magnetic field around each of these
units. This field can cause the arc to deviate from the
intended path. The arc is usually deflected forward or
backward along the line of travel and may cause excessive spatter and incomplete fusion. It also has the tendency to pull atmospheric gases into the arc, resulting
in porosity.
Arc blow can often be corrected by one of the
following methods: by changing the position of the
ground clamp, by welding away from the ground clamp,
or by changing the position of the workpiece.
Figure 7-9.—Straight and reverse polarity in electric welding.
On some of the older machines, polarity is changed
by switching cables. On many of the newer machines,
the polarity can be changed by turning a switch on the
machine.
Polarity affects the amount of heat going into the
base metal. By changing polarity, you can direct the
amount of heat to where it is needed. When you use
straight polarity, the majority of the heat is directed
toward the workpiece. When you use reverse polarity,
the heat is concentrated on the electrode. In some welding situations, it is desirable to have more heat on the
workpiece because of its size and the need for more heat
to melt the base metal than the electrode; therefore,
when making large heavy deposits, you should use
STRAIGHT POLARITY.
On the other hand, in overhead welding it is necessary to rapidly freeze the filler metal so the force of
gravity will not cause it to fall. When you use REVERSE
POLARITY, less heat is concentrated at the workpiece.
This allows the filler metal to cool faster, giving it
greater holding power. Cast-iron arc welding is another
good example of the need to keep the workpiece cool;
reverse polarity permits the deposits from the electrode
to be applied rapidly while preventing overheating in
the base metal.
In general, straight polarity is used for all mild steel,
bare, or lightly coated electrodes. With these types of
electrodes, the majority of heat is developed at the
positive side of the current, the workpiece. However,
when heavy-coated electrodes are used, the gases given
off in the arc may alter the heat conditions so the
STARTING THE ARC
Two basic methods are used for starting the arc: the
STRIKING or BRUSHING method (fig. 7-10) and the
7-9
After you strike the arc, the end of the electrode
melts and flows into the molten crater of the base metal.
To compensate for this loss of metal, you must adjust
the length of the arc. Unless you keep moving the
electrode closer to the base metal, the length of the arc
will increase. An arc that is too long will have a humming type of sound. One that is too short makes a
popping noise. When the electrode is fed down to the
plate and along the surface at a constant rate, a bead of
metal is deposited or welded onto the surface of the base
metal. After striking the arc, hold it for a short time at
the starting point to ensure good fusion and crater deposition. Good arc welding depends upon the control of
the motion of the electrode along the surface of the base
metal.
Setting the Current
Figure 7-11.—Tapping method of starting the arc.
The amount of current used during a welding operation depends primarily upon the diameter of the electrode. As a rule, higher currents and larger diameter
electrodes are better for welding in the flat position than
the vertical or overhead position. Manufacturers of electrodes usually specify a current range for each type and
size of electrode; this information is normally found on
the face of the electrode container.
Since most recommended current settings are only
approximate, final current settings and adjustments
need to be made during the welding operation. For
example, when the recommended current range for an
electrode is 90-100 amperes, the usual practice is to set
the controls midway between the two limits, or at 95
amperes. After starting the weld, make your final adjustments by either increasing or decreasing the current.
When the current is too high, the electrode melts
faster and the molten puddle will be excessively large
and irregular. High current also leaves a groove in the
base metal along both sides of the weld. This is called
undercutting, and an example is shown in figure 7-12,
view C.
With current that is too low, there is not enough heat
to melt the base metal and the molten pool will be too
small. The result is poor fusion and a irregular shaped
deposit that piles up, as shown in figure 7-12, view B.
This piling up of molten metal is called overlap. The
molten metal from the electrode lays on the work without penetrating the base metal. Both undercutting and
overlapping result in poor welds, as shown in figure
7-13.
When the electrode, current, and polarity are correct,
a good arc produces a sharp, crackling sound. When any
of these conditions are incorrect, the arc produces a
steady, hissing sound, such as steam escaping.
TAPPING method (fig. 7-11). In either method, the arc
is started by short circuiting the welding current between
the electrode and the work surface. The surge of high
current causes the end of the electrode and a small spot
on the base metal beneath the electrode to melt instantly.
In the STRIKING or BRUSHING method, the electrode
is brought down to the work with a lateral motion similar
to striking a match. As soon as the electrode touches the
work surface, it must be raised to establish the arc
(fig. 7-10). The arc length or gap between the end of the
electrode and the work should be equal to the diameter
of the electrode. When the proper arc length is obtained,
it produces a sharp, crackling sound.
In the TAPPING method, you hold the electrode in
a vertical position to the surface of the work. The arc is
started by tapping or bouncing it on the work surface
and then raising it to a distance equal to the diameter of
the electrode (fig. 7-11). When the proper length of arc
is established, a sharp, crackling sound is heard.
When the electrode is withdrawn too slowly with
either of the starting methods described above, it will
stick or freeze to the plate or base metal. If this occurs,
you can usually free the electrode by a quick sideways
wrist motion to snap the end of the electrode from the
plate. If this method fails, immediately release the electrode from the holder or shutoff the welding machine.
Use alight blow with a chipping hammer or a chisel to
free the electrode from the base metal.
CAUTION
NEVER remove your helmet or the shield
from your eyes as long as there is any possibility
that the electrode could produce an arc.
7-10
Figure 7-12.—Comparison chart of welds.
Figure 7-14.—Setting the length of an arc.
to stick frequently to the base metal, and produces
uneven deposits with irregular ripples. The recommended length of the arc is equal to the diameter of the
bare end of the electrode, as shown in figure 7-14.
The length of the arc depends upon the type of
Figure 7-13.—Undercuts and overlaps in welding.
electrode and the type of welding being done; therefore,
Length of Arc
for smaller diameter electrodes, a shorter arc is necessary than for larger electrodes. Remember: the length of
When an arc is too long, the metal melts off the
electrode in large globules and the arc may break frequently. This produces a wide, spattered, and irregular
deposit with insufficient fusion between the base metal
and the weld (fig. 7-12, view F).
When an arc is too short, it fails to generate enough
heat to melt the base metal properly, causes the electrode
the arc should be about equal to the diameter of the bare
electrode except when welding in the vertical or overhead position. In either position, a shorter arc is desirable because it gives better control of the molten puddle
and prevents atmospherical impurities from entering the
weld.
7-11
Travel Speed
Travel speed is the rate at which the electrode travels
along a weld seam. The maximum speed of welding
depends on the skill of the operator, the position of the
weld, the type of electrode, and the required joint penetration.
Normally, when the travel speed is too fast, the
molten pool cools too quickly, locking in impurities and
causing the weld bead to be narrow with pointed ripples,
as shown in figure 7-12, view D. On the other hand, if
the travel speed is too slow, the metal deposit piles up
excessively and the weld is high and wide, as shown in
figure 7-12, view E. In most cases, the limiting factor is
the highest speed that produces a satisfactory surface
appearance of a normal weld, as shown in figure 7-12,
view A.
Figure 7-15.—Work angle.
Breaking the Arc
The most commonly used method to break the arc
is to hold the electrode stationary until the crater is filled
and then slowly withdraw the electrode. This method
reduces the possibilities of crater cracks.
Reestablishing the Arc
When it becomes necessary to reestablish the arc (as
in a long weld that requires the use of more than one
electrode), the crater must first be cleaned before striking the arc. Strike the tip of the new electrode at the
forward (cold) end of the crater and establish an arc.
Move the arc backward over the crater, and then move
forward again and continue the weld. This procedure
fills the crater and prevents porosity and slag inclusions.
Figure 7-16.—Travel angle.
Peening
Peening is a procedure that involves lightly hammering a weld as it cools. This process aids in relieving
built-up stresses and preventing surface cracking in the
joint area; however, peening should be done with care
because excess hammering can work harden and increase stresses in the weld. This condition leads to weld
embrittlement and early failure. Some welds are covered by specific codes that prohibit peening so you
should check the weld specification before peening.
Electrode Angle
The angle at which you hold the electrode greatly
affects the shape of the weld bead which is very important in fillet and deep groove welding. The electrode
angle consists of two positions: work angle and travel
angle. Work angle is the angle from the horizontal
measured at right angles to the direction of welding (fig,
7-15). Travel angle is the angle in the direction of
welding and may vary from 5 to 30 degrees, depending
on the welder’s choice and conditions (fig. 7-16).
Work angle is especially important in multiple-pass
fillet welding. Normally, a small variance of the work
angle will not affect the appearance or quality of a weld;
however, when undercuts occur in the vertical section
of a fillet weld, the angle of the arc should be lowered
and the electrode directed more toward the vertical
section.
ARC WELDING POSITIONS
The types of welds, joints, and welding positions
used in manual-shielded metal arc welding are very
similar to those used in oxygas welding. Naturally, the
techniques are somewhat different because of the equipment involved is different.
7-12
Figure 7-17.—Butt joints in the flat position.
FLAT-POSITION WELDING
can be made on just about any type of joint providing
you can rotate the section you are welding on to the
appropriate position. Techniques that are useful in making butt joints in the flat position, with and without the
use of backing strips, are described below.
Earlier reexplained that welding can be done in
any position, but it is much simpler when done in the
flat position. In this position, the work is less tiring,
welding speed is faster, the molten puddle is not as likely
to run, and better penetration can be achieved. Whenever possible, try to position the work so you can weld
in the flat position. In the flat position, the face of the
weld is approximately horizontal.
BUTT JOINTS WITHOUT BACKING
STRIPS.— A butt joint is used to join two plates having
surfaces in about the same plane. Several forms of butt
joints are shown in figure 7-17.
Plates up to 1/8 inch thick can be welded in one pass
with no special edge preparation. Plates from 1/8 to 3/16
inch in thickness also can be welded with no special
Joint Type
Butt joints are the primary type of joints used in the
flat position of welding; however, flat-position welding
edge preparation by welding on both sides of the joint.
7-13
Figure 7-18.—Butt welds with multipass beads.
Figure 7-20.—Undercutting in butt joint welds.
In making multipass welds, as shown in figure 7-18,
the second, third, and fourth layers of weld metal are
made with a weaving motion of the electrode. Clean
each layer of metal before laying additional beads. You
may use one of the weaving motions shown in figure
7-19, depending upon the type of joint and size of
electrode.
Figure 7-19.—Weave motions used in manual shielded arc
welding.
In the weaving motion, oscillate or move the electrode uniformly from side to side, with a slight hesitation
at the end of each oscillation. Incline the electrode 5 to
15 degrees in the direction of welding as in bead welding. When the weaving motion is not done properly,
undercutting could occur at the joint, as shown in figure
7-20. Excessive welding speed also can cause undercutting and poor fusion at the edges of the weld bead.
Tack welds should be used to keep the plates aligned for
welding. The electrode motion is the same as that used
in making a bead weld.
In welding 1/4-inch plate or heavier, you should
prepare the edges of the plates by beveling or by J-, U-,
or V-grooving, whichever is the most applicable. You
should use single or double bevels or grooves when the
specifications and/or the plate thickness requires it. The
first bead is deposited to seal the space between the two
plates and to weld the root of the joint. This bead or layer
of weld metal must be thoroughly cleaned to remove all
slag and dirt before the second layer of metal is deposited.
BUTT JOINTS WITH BACKING STRIPS.—
Welding 3/16-inch plate or thicker requires backing
strips to ensure complete fusion in the weld root pass
and to provide better control of the arc and the weld
metal. Prepare the edges of the plates in the same
manner as required for welding without backing strips.
7-14
Figure 7-22.—Horizonta1 groove weld.
Figure 7-21.—Use of backing strips in welding butt joints.
For plates up to 3/8 inch thick, the backing strips should
be approximately 1 inch wide and 3/16 inch thick. For
plates more than 1/2inch thick, the backing strips should
be 1 1/2 inches wide and 1/4 inch thick Tack-weld the
backing strip to the base of the joint, as shown in figure
7-21. The backing strip acts as a cushion for the root
pass. Complete the joint by welding additional layers of
metal. After you complete the joint, the backing strip
may be “washed” off or cut away with a cutting torch.
When specified, place a seal bead along the root of the
joint.
Figure 7-23.—Horizontal fillet weld,
HORIZONTAL-POSITION WELDING
You will discover that it is impossible to weld all
pieces in the flat position. Often the work must be done
in the horizontal position. The horizontal position has
two basic forms, depending upon whether it is used with
a groove weld or a fillet weld. In a groove weld, the axis
of the weld lies in a relative horizontal plane and the face
of the weld is in a vertical plane (fig. 7-22). In a fillet
weld, the welding is performed on the upper side of a
relatively horizontal surface and against an approximately vertical plane (fig. 7-23).
Bear in mind that many times it will not always be
possible to use a backing strip; therefore, the welder
must be able to run the root pass and get good penetration without the formation of icicles.
7-15
Figure 7-24.—Horizontal welding angles.
Figure 7-26.—Position of electrode and fusion area of fillet weld
on a tee joint.
As you move in and out of the crater, pause slightly
each time you return. This keeps the crater small and the
bead has less tendency to sag.
Joint Type
Horizontal-position welding can be used on most
types of joints. The most common types of joints it is
used on are tee joints, lap joints, and butt joints.
Figure 7-25.—Tack-weld to hold the tee joint elements in place.
TEE JOINTS.— When you make tee joints in the
horizontal position, the two plates are at right angles to
each other in the form of an inverted T. The edge of the
vertical plate may be tack-welded to the surface of the
horizontal plate, as shown in figure 7-25.
An inexperienced welder usually finds the horizontal position of arc welding difficult, at least until he has
developed a fair degree of skill in applying the proper
technique. The primary difficulty is that in this position
you have no “shoulder” of previously deposited weld
metal to hold the molten metal.
A fillet weld is used in making the tee joint, and a
short arc is necessary to provide good fusion at the root
and along the legs of the weld (fig. 7-26, view A). Hold
the electrode at an angle of 45 degrees to the two plate
surfaces (fig. 7-26, view B) with an incline of approximately 15 degrees in the direction of welding.
When practical, weld light plates with a fillet weld
in one pass with little or no weaving of the electrode.
Welding of heavier plates may require two or more
passes in which the second pass or layer is made with a
semicircular weaving motion, as shown in figure 7-27.
To ensure good fusion and the prevention of undercutting, you should make a slight pause at the end of each
weave or oscillation.
Electrode Movement
In horizontal welding, position the electrode so that
it points upward at a 5- to 10-degree angle in conjunction
with a 20-degree travel angle (fig. 7-24). Use a narrow
weaving motion in laying the bead. This weaving motion distributes the heat evenly, reducing the tendency
of the molten puddle to sag. You should use the shortest
arc length possible, and when the force of the arc undercuts the plate at the top of the bead, lower the electrode
holder a little to increase the upward angle.
For fillet-welded tee joints on 1/2-inch plate or
heavier, deposit stringer beads in the sequence shown in
figure 7-28.
7-16
Figure 7-30.—Tack welding a lap joint.
Figure 7-27.—Weave motion for multipass fillet weld.
Figure 7-28.—Order of making string beads for a tee joint in
heavy plate.
Figure 7-31.—Position of electrode on a lap joint.
strength to that of a joint that has a fillet weld along the
entire length of one side. Intermittent welds also have
the advantage of reduced warpage and distortion.
LAP JOINTS.— When you make a lap joint, two
overlapping plates are tack-welded in place (fig. 7-30),
and a fillet weld is deposited along the joint.
The procedure for making this fillet weld is similar
to that used for making fillet welds in tee joints. You
should hold the electrode so it forms an angle of about
30 degrees from the vertical and is inclined 15 degrees
in the direction of welding. The position of the electrode
in relation to the plates is shown in figure 7-31. The
weaving motion is the same as that used for tee joints,
except that the pause at the edge of the top plate is long
enough to ensure good fusion without undercut. Lap
joints on 1/2-inch plate or heavier are made by depositing a sequence of stringer beads, as shown in figure
7-31,
Figure 7-29.—Intermittent fillet welds.
Chain-intermittent or staggered-intermittent fillet
welds, as shown in figure 7-29, are used on long tee
joints. Fillet welds of these types are for joints where
high weld strength is not required; however, the short
welds are arranged so the finished joint is equal in
In making lap joints on plates of different thickness,
you should hold the electrode so that it forms an angle
of between 20 and 30 degrees from the vertical
7-17
(fig. 7-32). Be careful not to overheat or undercut the
thinner plate edge.
BUTT JOINTS.— Most butt joints, designed for
horizontal welding, have the beveled plate positioned on
the top. The plate that is not beveled is on the bottom
and the flat edge of this plate provides a shelf for the
molten metal so that it does not run out of the joint (fig.
7-33). Often both edges are beveled to forma 60-degree
included angle. When this type of joint is used, more
skill is required because you do not have the retaining
shelf to hold the molten puddle.
Figure 7-32.—Lap joints on plates of different thickness.
The number of passes required for a joint depends
on the diameter of the electrode and the thickness of the
metal. When multiple passes are required (fig. 7-34),
place the first bead deep in the root of the joint. The
electrode holder should be inclined about 5 degrees
downward. Clean and remove all slag before applying
each following bead. The second bead should be placed
with the electrode holder held about 10 degrees upward.
For the third pass, hold the electrode holder 10 to 15
degrees downward from the horizontal. Use a slight
weaving motion and ensure that each bead penetrates
the base metal.
VERTICAL-POSITION WELDING
A “vertical weld” is defined as a weld that is applied
to a vertical surface or one that is inclined 45 degrees or
less (fig. 7-35). Erecting structures, such as buildings,
pontoons, tanks, and pipelines, require welding in this
position. Welding on a vertical surface is much more
difficult than welding in the flat or horizontal position
due to the force of gravity. Gravity pulls the molten
metal down. To counteract this force, you should use
fast-freeze or fill-freeze electrodes.
Figure 7-33.—Horizontal butt joint.
Vertical welding is done in either an upward or
downward position. The terms used for the direction of
welding are vertical up or vertical down. Vertical down
welding is suited for welding light gauge metal because
the penetration is shallow and diminishes the possibility
of burning through the metal. Furthermore, vertical
down welding is faster which is very important in production work.
Figure 7-34.—Multiple passes.
Current Settings and Electrode Movement
In vertical arc welding, the current settings should
be less than those used for the same electrode in the flat
position. Another difference is that the current used for
welding upward on a vertical plate is slightly higher than
the current used for welding downward on the same
plate.
Figure 7-35.—Vertical weld plate positions.
7-18
Figure 7-36.—Bead welding in the vertical position.
To produce good welds, you must maintain the
proper angle between the electrode and the base metal.
In welding upward, you should hold the electrode at 90
degrees to the vertical, as shown in figure 7-36, view A.
When weaving is necessary, oscillate the electrode, as
shown in figure 7-36, view B.
In vertical down welding, incline the outer end of
the electrode downward about 15 degrees from the
horizontal while keeping the arc pointing upward toward the deposited molten metal (figure 7-36, view C).
When vertical down welding requires a weave bead, you
should oscillate the electrode, as shown in figure 7-36,
view D.
Joint Type
Vertical welding is used on most types of joints. The
types of joints you will most often use it on are tee joints,
lap joints, and butt joints.
When making fillet welds in either tee or lap joints
in the vertical position, hold the electrode at 90 degrees
to the plates or not more than 15 degrees off the horizontal for proper molten metal control. Keep the arc
short to obtain good fusion and penetration.
TEE JOINTS.— To weld tee joints in the vertical
position, start the joint at the bottom and weld upward.
7-19
Figure 7-37.—Fillet welds in the vertical position.
Move the electrode in a triangular weaving motion, as
shown in figure 7-37, view A. A slight pause in the
weave, at the points indicated, improves the sidewall
penetration and provides good fusion at the root of the
joint.
When more than one pass is necessary to make a tee
weld, you may use either of the weaving motions shown
in figure 7-37, views C and D. A slight pause at the end
of the weave will ensure fusion without undercutting the
edges of the plates.
When the weld metal overheats, you should quickly
shift the electrode away from the crater without breaking the arc, as shown in figure 7-37, view B. This permits
the molten metal to solidify without running downward.
Return the electrode immediately to the crater of the
weld in order to maintain the desired size of the weld.
LAP JOINTS.— To make welds on lap joints in the
vertical position, you should move the electrode in a
triangular weaving motion, as shown in figure 7-37,
view E. Use the same procedure, as outlined above for
the tee joint, except direct the electrode more toward the
vertical plate marked “G.” Hold the arc short, and pause
7-20
with no undercutting. Welds made on plates with a
backup strip should be done in the same manner.
E-7018 Electrode Welding Technique
The previously described vertical welding techniques generally cover all types of electrodes; however,
you should modify the procedure slightly when using
E-7018 electrodes.
When vertical down welding, you should drag the
electrode lightly using a very short arc. Refrain from
using a long arc since the weld depends on the molten
slag for shielding. Small weaves and stringer beads are
preferred to wide weave passes. Use higher amperage
with ac than with dc. Point the electrode straight into the
joint and tip it forward only a few degrees in the direction of travel.
On vertical up welding, a triangular weave motion
produces the best results. Do not use a whipping motion
or remove the electrode from the molten puddle. Point
the electrode straight into the joint and slightly upward
in order to allow the arc force to help control the puddle.
Adjust the amperage in the lower level of the recommended range.
Figure 7-38.—Butt joint welding in the vertical position.
OVERHEAD-POSITION WELDING
Overhead welding is the most difficult position in
welding. Not only do you have to contend with the force
of gravity but the majority of the time you also have to
assume an awkward stance. Nevertheless, with practice
it is possible to make welds equal to those made in the
other positions.
slightly at the surface of plate G. Try not to undercut
either of the plates or to allow the molten metal to
overlap at the edges of the weave.
Lap joints on heavier plate may require more than
one bead. If it does, clean the initial bead thoroughly and
place all subsequent beads as shown in figure 7-37, view
F. The precautions to ensure good fusion and uniform
weld deposits that was previously outlined for tee joints
also apply to lap joints.
Current Settings and Electrode Movement
To retain complete control of the molten puddle, use
a very short arc and reduce the amperage as recommended. As in the vertical position of welding, gravity
causes the molten metal to drop or sag from the plate.
When too long an arc is held, the transfer of metal from
the electrode to the base metal becomes increasingly
difficult, and the chances of large globules of molten
metal dropping from the electrode increase. When you
routinely shorten and lengthen the arc, the dropping of
molten metal can be prevented; however, you will defeat
your purpose should you carry too large a pool of molten
metal in the weld.
BUTT JOINTS.— Prepare the plates used in vertical welding identically to those prepared for welding in
the flat position. To obtain good fusion and penetration
with no undercutting, you should hold a short arc and
the motion of the arc should be carefully controlled.
Butt joints on beveled plates 1/4 inch thick can be
welded in one pass by using a triangular weave motion,
as shown in figure 7-38, view A.
Welds made on 1/2-inch plate or heavier should be
done in several passes, as shown in figure 7-38, view B.
Deposit the last pass with a semicircular weaving motion with a slight “whip-up” and pause of the electrode
at the edge of the bead. This produces a good cover pass
One of the problems encountered in overhead welding is the weight of the cable. To reduce arm and wrist
fatigue, drape the cable over your shoulder when welding in the standing position. When sitting, place the
7-21
cable over your knee. With experience, cable placement
will become second nature.
WARNING
Because of the possibility of falling molten
metal, use a protective garment that has a tight
fitting collar that buttons or zips up to the neck.
Roll down your sleeves and wear a cap and
appropriate shoes.
Type of Welds
Techniques used in making bead welds, butt joints,
and fillet welds in the overhead position are discussed
in the following paragraphs.
BEAD WELDS.— For bead welds, the work angle
of the electrode is 90 degrees to the base metal (fig. 7-39,
view A). The travel angle should be 10 to 15 degrees in
the direction of welding (fig. 7-39, view B).
Figure 7-39.—Position of electrode and weave motion in the
overhead position.
Weave beads can be made by using the motion
shown in figure 7-39, view C. A rather rapid motion is
necessary at the end of each semicircular weave to
control the molten metal deposit. Avoid excessive weaving because this can cause overheating of the weld
deposit and the formation of a large, uncontrollable
pool.
BUTT JOINTS.— Prepare the plates for overhead
butt welding in the same manner as required for the flat
position. The best results are obtained when backing
strips are used; however, you must remember that you
will not always be able to use a backing strip. When you
bevel the plates with a featheredge and do not use a
backing strip, the weld will repeatedly burn through
unless extreme care is taken by the operator.
For overhead butt welding, bead welds are preferred
over weave welds. Clean each bead and chip out the
rough areas before placing the next pass. The electrode
position and the order of deposition of the weld beads
when welding on 1/4- or 1/2-inch plate are shown in
figure 7-40, views B and C. Make the first pass with the
electrode held at 90 degrees to the plate, as shown in
figure 7-40, view A. When you use an electrode that is
too large, you can not hold a short arc in the root area.
This results in insufficient root penetration and inferior
joints.
FILLET WELDS.— In making fillet welds in
either tee or lap joints in the overhead position, maintain
a short arc and refrain from weaving of the electrode.
Figure 7-40.—Multipass butt joint in the overhead position.
7-22
Figure 7-41.—Fillet welding in the overhead position.
the arc and allow the metal to solidify. Immediately
return the electrode to the crater and continue welding.
Overhead fillet welds for either tee or lap joints on
heavy plate require several passes or beads to complete
the joint. One example of an order of bead deposition is
shown in figure 7-41, view A. The root pass is a string
bead made with no weaving motion of the electrode. Tilt
the electrode about 15 degrees in the direction of
welding, as shown in figure 7-41, view C, and with a
Hold the electrode at approximately 30 degrees to the
vertical plate and move it uniformly in the direction of
welding, as shown in figure 7-41, view B. Control the
arc motion to secure good penetration in the root of the
weld and good fusion with the sidewalls of the vertical
and horizontal plates. When the molten metal becomes
too fluid and tends to sag, whip the electrode quickly
away from the crater and ahead of the weld to lengthen
7-23
Table 7-3—Causes and Cures of Common Welding Problems
7-24
the root gap to maintain the strength requirement. In
some cases, it is advantageous to make a groove weld l
to avoid extremely large fillet welds.
slight circular motion make the second, third, and fourth
passes. This motion of the electrode permits greater
control and better distribution of the weld metal.
Remove all slag and oxides from the surface of each pass
by chipping or wire brushing before applying additional
beads to the joint.
13. Inspect your work after completion and
immediately remove and replace any defective weld.
14. Observe the size requirement for each weld and
make sure that you meet or slightly exceed the specified
size.
WELDING DIFFICULTIES
Many of the welding difficulties in metal-arc welding are the same as in oxygas welding. A few such
problems include undercut, cracked welds, poor fusion,
and incomplete penetration.
15. Make sure that the finished appearance of the
weld is smooth and that overlaps and undercuts have
been repaired.
Table 7-3 provides an illustration of the most common welding problems encountered during the arcwelding process and methods to correct them.
PIPE WELDING
Welding is the simplest and easiest way to join
sections of pipe. The need for complicated joint designs
and special threading equipment is eliminated. Welded
pipe has reduced flow restrictions compared to mechanical connections and the overall installation costs
are less. The most popular method for welding pipe is
the shielded metal-arc process; however, gas shielded
arc methods have made big inroads as a result of new
advances in welding technology.
Every welder has the responsibility of making each
weld the best one possible. You can produce quality
welds by adhering to the rules that follow.
1. Use only high-quality welding machines,
electrodes, and welding accessories.
2. Know the base material that you are working
on.
Pipe welding has become recognized as a profession in itself. Even though many of the skills are comparable to other types of welding, pipe welders develop
skills that are unique only to pipe welding. Because of
the hazardous materials that most pipelines carry, pipe
welders are required to pass specific tests before they
can be certified
3. Select the proper welding process that gives the
highest quality welds for the base material used.
4. Select the proper welding procedure that meets
the service requirement of the finished weldment.
5. Select the correct electrode for the job in
question.
In the following paragraphs, pipe welding positions,
pipe welding procedures, definitions, and related information are discussed.
6. When preheating is specified or required make
sure you meet the temperature requirements. In any
case, do not weld on material that is below 32°F without
first preheating.
PIPE WELDING POSITIONS
7. Clean the base metal of all slag, paint, grease,
oil, moisture, or any other foreign materials.
You may recall from chapter 3 of this manual that
there are four positions used in pipe welding (fig. 3-30).
They are known as the horizontal rolled position (1G),
the horizontal fixed position (5G), pipe inclined fixed
(6G), and the vertical position (2G). Remember: these
terms refer to the position of the pipe and not to the weld
8. Remove weld slag and thoroughly clean each
bead before making the next bead or pass.
9. Do not weld over cracks or porous tack welds.
Remove defective tack welds before welding.
PIPE WELDING PROCEDURES
10. Be particularly alert to obtain root fusion on the
first pass of fillet and groove welds.
Welds that you cannot make in a single pass should
be made in interlocked multiple layers, not less than one
layer for each 1/8 inch of pipe thickness. Deposit each
layer with a weaving or oscillating motion. To prevent
entrapping slag in the weld metal, you should clean each
layer thoroughly before depositing the next layer.
11. When groove weld root gaps are excessive,
build up one side of the joint before welding the pieces
together.
12. When fillet weld root gaps are excessive, be
sure you increase the size of the fillet weld to the size of
7-25
Figure 7-43.—Flange connections.
Figure 7-42.—Butt joints and socket fitting joints.
Butt joints are commonly used between pipes and
between pipes and welded fittings. They are also used
for butt welding of flanges and welding stubs. In making
a butt joint, place two pieces of pipe end to end, align
them, and then weld them. (See fig. 7-42.)
When the wall thickness of the pipe is 3/4 inch or
less, you can use either the single V or single U type of
Figure 7-44.—Flange alignment.
JOINT PREPARATION AND FIT-UP
butt joint; however, when the wall thickness is more than
3/4 inch, only the single U type should be used.
Fillet welds are used for welding slip-on and
You must carefully prepare pipe joints for welding
if you want good results. Clean the weld edges or
surfaces of all loose scale, slag, rust, paint, oil, and other
foreign matter. Ensure that the joint surfaces are smooth
and uniform. Remove the slag from flame-cut edges;
however, it is not necessary to remove the temper color.
When you prepare joints for welding, remember
that bevels must be cut accurately. Bevels can be made
by machining, grinding, or using a gas cutting torch. In
fieldwork, the welding operator usually must make the
bevel cuts with a gas torch. When you are beveling, cut
away as little metal as possible to allow for complete
fusion and penetration. Proper beveling reduces the
amount of filler metal required which, in turn, reduces
time and expense. In addition, it also means less strain
in the weld and a better job of design and welding.
threaded flanges to pipe. Depending on the flange and
type of service, fillet welds may be required on both
sides of the flange or in combination with a bevel weld
(fig. 7-43). Fillet welds are also used in welding screw
or socket couplings to pipe, using a single fillet weld
(fig. 7-42). Sometimes flanges require alignment. Figure 7-44 shows one type of flange square and its use in
vertical and horizontal alignment.
Another form of fillet weld used in pipe fitting is a
seal weld A seal weld is used primarily to obtain tightness and prevent leakage. Seal welds should not be
considered as adding strength to the joint.
7-26
yet not exceeding 3/16 inch, that ensures complete
fusion and penetration without undercutting and slag
inclusions.
Make certain the welding current is within the range
recommended by the manufacturers of the welding
machines and electrodes.
WEATHER CONDITIONS
Do not assign a welder to a job under any of the
following conditions listed below unless the welder and
the work area are properly protected:
c When the atmospheric temperature is less than
0°F
Figure 7-45.—Angle iron jig.
Align the piping before welding and maintain it in
alignment during the welding operation. The maximum
alignment tolerance is 20 percent of the pipe thickness.
To ensure proper initial alignment, you should use
clamps or jigs as holding devices. Apiece of angle iron
makes a good jig for a small-diameter pipe (fig. 7-45),
while a section of channel or I-beam is more suitable for
larger diameter pipe.
l When the surfaces are wet
l When rain or snow is falling, or moisture is
condensing on the weld surfaces
l During periods of high wind
At temperatures between 0°F and 32°F, heat the
weld area within 3 inches of the joint with a torch to a
temperature warm to the hand before beginning to weld.
TACK WELDING
When welding material solidly, you may use tack
welds to hold it in place temporarily. Tack welding is
one of the most important steps in pipe welding or any
other type of welding. The number of tack welds required depends upon the diameter of the pipe. For
1/2-inch pipe, you need two tacks; place them directly
opposite each other. As a rule, four tacks are adequate
for standard size of pipe. The size of a tack weld is
determined by the wall thickness of the pipe. Be sure
that a tack weld is not more than twice the pipe thickness
in length or two thirds of the pipe thickness in depth.
Tack welds should be the same quality as the final weld.
Ensure that the tack welds have good fusion and are
thoroughly cleaned before proceeding with the weld.
WEARFACING
The Seabee welder can greatly extend the life of
construction equipment by the use of wearfacing procedures. Wearfacing is the process of applying a layer of
special composition metal onto the surface of another
type of metal for the purpose of reducing wear. The
selection of a wearfacing alloy for application is based
on the ability of the alloy to withstand impact or abrasion. Impact refers to a blow or series of blows to a
surface that results in fracture or gradual deterioration.
Abrasion is the grinding action that results when one
surface slides, rolls, or rubs against another. Under
high-compressive loads, this action can result in gouging.
Alloys that are abrasion resistant are poor in withstanding impact. Conversely, those that withstand impact well are poor in resisting abrasion; however, there
are many alloys whose wearfacing properties fall between the two extremes. These alloys offer some protection against abrasion and withstand impact well.
SPACERS
In addition to tack welds, spacers sometimes are
required to maintain proper joint alignment. Spacers are
accurately machined pieces of metal that conform to the
dimensions of the joint design used. Spacers are sometimes referred to as chill rings or backing rings, and they
serve a number of purposes. They provide a means for
maintaining the specified root opening, provide a convenient location for tack welds, and aid in the pipe
alignment. In addition, spacers can prevent weld spatter
and the formation of slag or icicles inside the pipe.
WORKPIECE PREPARATION
Before you wear-face a workpiece, all dirt, oil, rust,
grease, and other foreign matter must be removed. If you
do not, your finished product will be porous and subject
to spalling. You also need a solid foundation; therefore,
repair all cracks and remove any metal that is fatigued
or rolled over.
ELECTRODE SELECTION
Select the electrode that is best suited for the position and type of welding to be done. For the root pass of
a multilayer weld, you need an electrode large enough,
7-27
TECHNIQUES
Where possible, position the workpiece for downhand welding. This allows you to finish the job quicker
and at less cost.
The building up and wearfacing of cast iron is not
generally recommended because cast iron tends to
crack. However, some cast-iron parts that are subject to
straight abrasion can be wearfaced successfully. You
must preheat these parts to temperatures of 1000°F to
1200°F and then allow them to cool slowly after wearfacing. Peening deposits on cast iron helps to relieve
stresses after welding.
Welding materials for building up worn parts differ
from those used in wearfacing the same parts. Before
wearfacing a badly worn part, you must first build it up
to 3/16 to 3/8 of an inch of its finished size. The buildup
material must be compatible with both the base metal
and the wearfacing overlay as well as being strong
enough to meet the structural requirements. Also, they
must have the properties that enable them to resist cold
flowing, mushing under high-compressive loads, and
plastic deformation under heavy impact. Without these
properties, the buildup materials cannot support the
wearfacing overlay. When the overlay is not properly
supported, it will span.
Many times high-alloy wearfacing materials are
deposited on the parts before they are placed in service.
The maximum allowable wear is usually no more than
two layers deep (1/4 inch) before wearfacing. Try to
deposit the wearfacing alloy in layers that are not too
thick. Thick layers creates more problems than no overlay at all. Usually you only need two layers. The frost
layer produces an admixture with the base metal; the
second forms a wear-resistant surface.
In wearfacing built-up carbon-steel parts, maintain
high interpass temperatures and use a weaving bead,
rather than a stringer bead. (See fig. 7-46.) Limit the thickness of a single pass bead to 3/16 inch. Use the same
technique for each layer and avoid severe quenching.
Deposits made with high-alloy electrodes should
check on the surface. Checking reduces residual
Figure7-46.—Wearfacing techniques.
PREHEATING
Depending on the type of metal, sometimes it is
necessary to preheat the base metal to lessen distortion,
to prevent spalling or cracking, and to avoid thermal
shock The preheating temperature depends on the carbon and alloy content of the base metal. In general, as
carbon content increases so does the preheating temperature. Improper heating can adversely affect a metal
by reducing its resistance to wear, by making it hard and
brittle, or by making it more prone to oxidation and
scaling.
To preheat properly, you must know the composition of the base metal. A magnet can be used to determine if you are working with carbon steel or austenitic
manganese steel. Carbon steel is magnetic, but be careful because work-hardened austenitic manganese steel
is also magnetic. Make sure that you check for magnetism in a nonworked part of the austenitic manganese
steel. There are other ways to tell the difference between
metals, such as cast iron and cast steel. Cast iron chips
or cracks, while cast steel shaves. Also, some metals
give off telltale sparks when struck by a chisel.
In preheating, you should raise the surface temperature of the workpiece to the desired point and then soak
it until the heat reaches its core. After wearfacing, cool
the work places slowly.
Figure 7-47.—Comparison between cross-checking and cracking.
7-28
naturally or if it is unlikely to occur, as in large parts
where heat builds up. You can bring on checking by
sponging the deposit with a wet cloth or by spraying it
with a fine mist of water. Also you can speed up checking by occasionally striking it with a hammer while it is
cooling. When a check-free deposit is required, use a
softer alloy and adjust preheating and postheating requirements.
Figure 7-48.—Wearfacing bulldozer end bits.
Bulldozer Blades
Bulldozer blades are wear-faced by placing the end
bits in the flat position and welding beads across the
outer corners and along the edges. Be sure to preheat the
high-carbon blades before wearfacing. On worn end
bits, weld new corners and then wear-face (fig. 7-48).
Shovel teeth
Figure 7-49.—Wearfacing shovel teeth.
Wear-face shovel teeth when they are new and
before being placed into service. The weld bead pattern
used in wearfacing can have a marked effect on the
service life of the teeth. Wear-face shovel teeth that work
mainly in rock with beads running the length of each
tooth (fig. 7-49). This allows the rock to ride on the hard
metal beads. Teeth that are primarily used to work in
dirt, clay, or sand should be wear-faced with beads
running across the width of each tooth, perpendicular to
the direction of the material that flows past the teeth.
(See fig. 7-49.) This allows the material to fill the spaces
between the beads and provide more protection to the
base metal. Another effective pattern is the waffle or
crosshatch (fig. 7-50). The wearfacing is laid on the top
and sides of each tooth, 2 inches from its point. Stringer
beads behind a solid deposit reduce wash (fig. 7-51).
Figure 7-50.—Waffle or crosshatching.
(locked-in) stresses. Without checking, the combination
of residual stresses and service stresses may exceed
tensile strength and cause deep cracks or spalling (fig.
7-47). Be sure to induce checking if it does not occur
Figure 7-51.—Comparison of wearfacing patterns for shovel teeth.
7-29
Table 7-4.—Table of Recommended Electrode Sizes, Current Settings, and Cutting Speeds for Carbon-Arc Cutting Different Thicknesses
of Steel Plate
More information on wearfacing applications may
be obtained from the NCF Welding Materials Handbook, NAVFAC P-433.
The carbon-arc method of cutting is successful on
cast iron because the arc temperature is high enough to
melt the oxides formed. It is especially important to
undercut the cast-iron kerf to produce an even cut.
Position the electrode so the molten metal flows away
from the gouge or cutting areas. Table 7-4 is a list of
cutting speeds, plate thicknesses, and current settings
for carbon-arc cutting.
CARBON-ARC CUTTING
Metals can be cut cleanly with a carbon electrode
arc because no foreign metals are introduced at the arc.
The cutting current should be 25 to 50 amps above the
welding current for the same thickness of metal.
Because of the high currents required, the graphite
form of carbon electrode is better. To reduce the heating
effect on the electrode, you should not let it extend more
than 6 inches beyond the holder when cutting. If the
carbon burns away too fast, shorten the length that it
extends out of the electrode holder to as little as 3 inches.
Operating a carbon electrode at extremely high temperatures causes its surface to oxidize and burn away, resulting in a rapid reduction in the electrode diameter.
The carbon electrode point should be ground so that
it is very sharp. During the actual cutting, move the
carbon electrode in a vertical elliptical movement to
undercut the metal; this aids in the removal of the molten
metal. As in oxygen cutting, a crescent motion is preferred. Figure 7-52 shows the relative positions of the
electrode and the work in the cutting of cast iron.
Carbon-arc cutting does not require special generators. Standard arc-welding generators and other items
of arc-welding station equipment are suitable for use.
Straight polarity direct current (DCSP) is always used.
Because of the high temperature and the intensity
of the arc, choose a shade of helmet lens that is darker
than the normal shade you would use for welding on the
same thickness of metal. A number 12 or 14 lens shade
is recommended for carbon-arc welding or cutting.
AIR CARBON-ARC CUTTING
Air carbon-arc cutting (ACC) is a process of cutting,
piercing, or gouging metal by heating it to a molten state
and then using compressed air to blow away the molten
Figure 7-52.—Carbon-arc cutting on cast iron.
7-30
welding. The electrode holder operates at air pressures
varying between 60 and 100 psig.
During use, bare carbon or graphite electrodes become smaller due to oxidation caused by heat buildup.
Copper coating these electrodes reduces the heat
buildup and prolong their use.
The operating procedures for air carbon-arc cutting
and gouging are basically the same. The procedures are
as follows:
l Adjust the machine to the correct current for
electrode diameter.
l Start the air compressor and adjust the regulator
to the correct air pressure. Use the lowest air
pressure possible-just enough pressure to blow
away the molten metal.
l Insert the electrode in the holder. Extend the
carbon electrode 6 inches beyond the holder.
Ensure that the electrode point is properly
Figure 7-53.—Air carbon-arc cutting.
shaped.
metal. Figure 7-53 shows the process. The equipment
consists of a special holder, as shown in figure 7-54, that
l Strike the arc; then open the air-jet valve. The
air-jet disc can swivel, and the V-groove in the
disc automatically aligns the air jets along the
electrode. The electrode is adjusted relative to the
holder.
uses carbon or graphite electrodes and compressed air
fed through jets built into the electrode holder. A push
button or a hand valve on the electrode holder controls
the air jet.
l Control the arc and the speed of travel according
to the shape and the condition of the cut desired.
The air jet blows the molten metal away and usually
leaves a surface that needs no further preparation for
Figure 7-54.—Air carbon-arc electrode holder with carbon electrode installed.
7-31
Figure 7-56.—Steel electrode being used to cut plate.
Figure 7-55.—V-groove gouged in 2-inch-thick carbon steel.
METAL ELECTRODE ARC CUTTING
. Always cut away from the operator as molten
metalworking applications, such as metal shaping and
Metal can be removed with the standard electric arc,
but for good gouging or cutting results, you should use
special metal electrodes that have been designed for this
type of work, Manufacturers have developed electrodes
with special coatings that intensify the arc stream for
rapid cutting. The covering disintegrates at a slower rate
than the metallic center. This creates a deep recess that
produces a jet action that blows the molten metal away
(fig. 7-56). The main disadvantage of these electrodes
is that the additional metal produced must be removed.
other welding preparations. For gouging, hold the elec-
These electrodes are designed for cutting stainless
trode holder so the electrode slopes back from the direc-
steel, copper, aluminum, bronze, nickel, cast iron, manganese, steel, or alloy steels.
metal sprays some distance from the cutting action. You may use this process to cut or gouge
metal in the flat, horizontal, vertical, or overhead
positions.
AIR CARBON-ARC GOUGING
Air carbon-arc gouging is useful in many various
tion of travel. The air blast is directed along the electrode
toward the arc. The depth and contour of the groove are
Atypical gouge-cutting operation is shown in figure
controlled by the electrode angle and travel speed. The
7-57. Notice that the angle between the electrode and
plate is small (5 degrees or less). This makes it easy to
remove the extra metal produced by the electrode.
width of the groove is governed by the diameter of the
electrode.
When cutting or gouging a shallow groove on the
The recommended current setting is as high as the
surface of a piece of metal, you should position the
electrode will take without becoming overheated to the
point of cracking the covering. For 1/8-inch electrodes,
the setting ranges between 125 and 300 amperes; for
5/32-inch electrodes, the setting ranges between 250 and
375 amperes; and for 3/16-inch electrodes, the setting
ranges between 300 and 450 amperes. Use a very short
arc, and when cutting takes place underwater, the coating must be waterproof.
electrode holder at a very flat angle in relation to the
work. The speed of travel and the current setting also
affect the depth of the groove. The slower the movement
and the higher the current, the deeper the groove. An
example of a V-groove cut made in a 2-inch-thick mild
steel plate by a machine guided carbon-arc air-jet is
shown in figure 7-55.
7-32
Figure 7-58.—Circular magnetization (prod method).
Figure 7-57.—Gouge-cutting operation using a solid core arccutting electrode.
WELDING QUALITY CONTROL
In the fabrication or repair of equipment, tests are
used to determine the quality and soundness of the
welds. Many different tests have been designed for
specific faults. The type of test used depends upon the
requirements of the welds and the availability of testing
equipment. In this section, nondestructive and destructive testing are briefly discussed.
NONDESTRUCTIVE TESTING
Nondestructive testing is a method of testing that
does not destroy or impair the usefulness of a welded
item. These tests disclose all of the common internal and
surface defects that can occur when improper welding
procedures are used. A large choice of testing devices is
available and most of them are easier to use than the
destructive methods, especially when working on large
and expensive items.
Figure 7-59.—Longitudinal magnetization (coil method).
It is used in metals or alloys in which you can induce
magnetism. While the test piece is magnetized, a liquid
containing finely ground iron powder is applied. As long
as the magnetic field is not disturbed, the iron particles
will form a regular pattern on the surface of the test
piece. When the magnetic field is interrupted by a crack
or some other defect in the metal, the pattern of the
suspended ground metal also is interrupted. The particles of metal cluster around the defect, making it easy
to locate.
Visual Inspection
Visual inspection is usually done automatically by
the welder as he completes his welds. This is strictly a
subjective type of inspection and usually there are no
definite or rigid limits of acceptability. The welder may
use templates for weld bead contour checks. Visual
inspections are basically a comparison of finished welds
with an accepted standard. This test is effective only
when the visual qualities of a weld are the most important.
You can magnetize the test piece by either having
an electric current pass through it, as shown in figure
7-58, or by having an electric current pass through a coil
of wire that surrounds the test piece, as shown in figure
7-59. When an electric current flows in a straight line
from one contact point to the other, magnetic lines of
Magnetic Particle Inspection
Magnetic particle inspection is most effective for
the detection of surface or near surface flaws in welds.
7-33
that induces longitudinal magnetism in the part of the
workpiece that is surrounded by the coiled cable
(fig. 7-59)0
force are in a circular direction, as shown in figure 7-58.
When the current flow is through a coil around the test
piece, as shown in figure 7-59, the magnetic lines of
force are longitudinal through the test piece.
Although you can use either of these two methods,
the prod method is probably the easier to apply. Inmost
instances, it effectively serves to detect surface defects.
With the prods, however, only a small area of the test
piece can be magnetized at any one time. This magnetized area is limited to the distance between prod contact
points and a few inches on each side of the current path.
To check the entire surface, you must test each adjacent
area by changing the location of the prod contact points.
Each area of the test piece must be inspected twice—
once with the current passing through the metal in one
direction and then with the current passing through the
metal in a direction at right angles to the direction of the
first test. One of the advantages of the prod method is
that the current can be easily passed through the metal
in any desired direction. Thus, when a given area is
suspect, magnetic fields of different directions can be
induced during the test.
When a defect is to show up as a disturbance in the
pattern of the iron particles, the direction of the magnetic
field must be at right angles to the major axis of the
defect. A magnetic field having the necessary direction
is established when the current flow is parallel to the
major axis of the defect. Since the orientation of the
defect is unknown, different current directions must be
used during the test. As shown in figure 7-58, circular
magnetism is induced in the test piece so you can inspect
the piece for lengthwise cracks, while longitudinal magnetism, as shown in figure 7-59, is induced so you can
inspect the piece for transverse cracks. In general, magnetic particle inspection is satisfactory for detecting
surface cracks and subsurface cracks that are not more
than 1/4 inch below the surface.
The type of magnetic particle inspection unit commonly used in the Navy is a portable low-voltage unit
having a maximum magnetizing output of 1,000 amperes, either alternating or direct current. It is ready to
operate when plugged into the voltage supply specified
by the manufacturer. The unit consists of a magnetizing
current source, controls, metering, three 10-foot lengths
of flexible cable, and a prod kit. The prod kit includes
an insulated prod grip fitted with an ON-OFF relay or
current control switch, a pair of heavy copper contact
prods, and two 5-foot lengths of flexible cable. Cable
fittings are designed so that either end of the cable can
be connected to the unit, to the prods, or to any other
cable. The three outlets on the front of the unit make
changing from alternating to direct current or vice versa
very easy. The outlets are labeled as follows: left is ac,
the center is COMMON, and the right is dc. One cable
will always be plugged into the COMMON outlet,
while the other cable is plugged into either the ac or dc
outlet, depending upon what type of current the test
requires. For most work, alternating current magnetization effectively locates fatigue cracks and similar defects extending through to the surface. When you
require a more sensitive inspection to detect defects
below the surface, use direct current.
The prod method is accomplished by adjusting the
unit for a current output suitable for the magnetizing and
testing of any particular kind of metal. The current
setting required depends on the distance between prod
contact points. With the prod kit that is supplied with the
unit, the space between prod contact points is 4 to 6
inches. A current setting between 300 and 400 amperes
is satisfactory when the material thickness is less than
3/4 inch. When the material thickness is over 3/4 inch,
use 400 to 600 amperes. When the prod contact points
are closer together, the same magnetic field force can be
obtained with less current. With prods constantly at the
same spacing, more current will induce a greater field
strength.
After adjusting the unit, place the prods in position.
Hold them infirm contact with the metal and turn on the
current. Then apply magnetic particles to the test area
with the duster bulb and look for any indicator patterns.
With the current still on, remove the excess particles
from the test area with a blower bulb and complete the
inspection. Do not move the prods until after the current
has been turned off. To do so could cause the current to
arc, resulting in a flash similar to that occurring in arc
welding.
You can use the unit with alternating or direct
current in either of two ways: (1) with prods attached to
the flexible cable and used as contacts for the current to
pass into and out of a portion of the test piece, setting
up circular magnetization in the area between the prods
contact points, as shown in figure 7-58; or (2) with the
flexible cable wrapped around the work to form a coil
When you use magnetic particle inspection, hairline
cracks that are otherwise invisible are readily indicated
by an unmistakable outline of the defect. Large voids
beneath the surface are easier to detect than small voids,
but any defect below the surface is more difficult to
detect than one that extends through to the surface. Since
7-34
alternating current. Set the current regulator to deliver a
current identical to that used for the inspection and turn
on the unit. Gradually decrease the current until the
ammeter indicates zero. On large pieces, it may be
necessary to demagnetize a small portion of the work at
a time.
false indications frequently occur, you must be able to
interpret the particle indications accurately.
The factors that help you interpret the test results
include the amount of magnetizing current applied, the
shape of the indication, the sharpness of the outline, the
width of the pattern, and the height or buildup of the
particles. Although these characteristics do not determine the seriousness of the fault, they do serve to
identify the kind of defect.
A check for the presence of a magnetic field may be
made by using a small compass. A deviation of the
needle from the normal position, when the compass is
held near the workpiece, is an indication that a magnetic
field is present. Also you can use an instrument called a
field indicator to check for the presence of a magnetic
field. This instrument usually comes with the magnetic
particle inspection unite
The indication of a crack is a sharp, well-defined
pattern of magnetic particles having a definite buildup.
This indication is produced by a relatively low-magnetizing current. Seams are revealed by a straight, sharp,
fine indication. The buildup of particles is relatively
weak, and the magnetizing current must be higher than
that required to detect cracks. Small porosity and
rounded indentations or similar defects are difficult to
detect for inexperienced inspectors. A high-magnetizing
current continuously applied is usually required. The
particle patterns for these defects are fuzzy in outline
and have a medium buildup.
Liquid Penetrant Inspection
Liquid penetrant methods are used to inspect metals
for surface defects that are similar to those revealed by
magnetic particle inspection. Unlike magnetic particle
inspection, which can reveal subsurface defects, liquid
penetrant inspection reveals only those defects that are
open to the surface.
The specifications governing the job determine
whether or not an indicated defect is to be chipped or
ground out and repaired by welding. Surface cracks are
always removed and repaired. Indications of subsurface
defects detected by magnetic particle inspection are
evaluated by the inspector. When the indication is positive, the standard policy is to grind or chip down to solid
metal and make the repair. Unless the inspector can
differentiate accurately between true and false indications, the use of magnetic particle inspection should be
restricted to the detection of surface defects, for which
this application is almost foolproof.
Four groups of liquid penetrants are presently in
use. Group I is a dye penetrant that is nonwater washable. Group II is a water washable dye penetrant. Group
III and Group IV are fluorescent penetrants. Carefully
follow the instructions given for each type of penetrant
since there are some differences in the procedures and
safety precautions required for the various penetrants.
Before using a liquid penetrant to inspect a weld,
remove all slag, rust, paint, and moisture from the
surface. Except where a specific finish is required, it is
not necessary to grind the weld surface as long as the
weld surface meets applicable specifications. Ensure the
weld contour blends into the base metal without undercutting. When a specific finish is required, perform the
liquid penetrant inspection before the finish is made.
This enables you to detect defects that extend beyond
the final dimensions, but you must make a final liquid
penetrant inspection after the specified finish has been
given.
After the indicated defects have been repaired, you
should reinspect the areas to ensure that the repair is
sound. The final step in magnetic particle inspection, is
to demagnetize the workpiece. This is especially important when the workpiece is made of high-carbon steel.
Demagnetization is essential when you use direct current to induce the magnetic field; however, it is not as
necessary when alternating current was used in the test.
In fact, the usual demagnetization procedure involves
placing the workpiece in an ac coil or solenoid and
slowly withdrawing it while current passes through the
coil.
Before using a liquid penetrant, clean the surface of
the material very carefully, including the areas next to
the inspection area. You can clean the surface by swabbing it with a clean, lint-free cloth saturated in a nonvolatile solvent or by dipping the entire piece into a
solvent. After the surface has been cleaned, remove all
traces of the cleaning material. It is extremely important
to remove all dirt, grease, scale, lint, salts, or other
Demagnetization can be accomplished with the
portable unit if a special demagnetizer is not available.
To demagnetize with the portable unit, form a coil of
flexible cable around the workpiece. Ensure that
the cable is plugged into the unit for the delivery of
7-35
Figure 7-60.—Liquid penetrant inspection.
The following actions take place when using dye
penetrants. First, the penetrant that is applied to the
surface of the material will seep into any passageway
open to the surface, as shown in figure 7-60, view A.
The penetrant is normally red in color, and like penetrating oil, it seeps into any crack or crevice that is open to
the surface. Next, the excess penetrant is removed from
the surface of the metal with the penetrant remover and
a lint-free absorbent material. Only the penetrant on top
of the metal surface is removed (fig. 7-60, view B),
leaving the penetrant that has seeped into the defect.
materials and to make sure that the surface is entirely
dry before using the liquid penetrant.
Maintain the temperature of the inspection piece
and the liquid penetrant in the range of 50°F to 100°F.
Do not attempt to use the liquid penetrant when this
temperature range cannot be maintained. Do not use an
open flame to increase the temperature because some of
the liquid penetrant materials are flammable.
After thoroughly cleaning and drying the surface,
coat the surface with the liquid penetrant. Spray or brush
on the penetrant or dip the entire piece into the penetrant.
To allow time for the penetrant to soak into all the cracks,
crevices, or other defects that are open to the surface,
keep the surface of the piece wet with the penetrant for
a minimum of 15 or 30 minutes, depending upon the
penetrant being used.
Finally, the white developer is applied to the surface
of the metal, as shown in figure 7-60, view C. The
developer is an absorbing material that actually draws
the penetrant from the defect. Therefore, the red penetrant indications in the white developer represent the
defective areas. The amount of red penetrant drawn
from the defective areas indicates the size and sometimes the type of defect. When you use dye penetrants,
the lighting in the test area must be bright enough to
enable you to see any indications of defects on the test
surface.
After keeping the surface wet with the penetrant for
the required length of time, remove any excess penetrant
from the surface with a clean, dry cloth, or absorbent
paper towel. Then dampen a clean, lint-free material
with penetrant remover and wipe the remaining excess
penetrant from the test surface. Next, allow the test
surface to dry by normal evaporation or wipe it dry with
a clean, lint-free absorbent material. In drying the surface, avoid contaminating it with oil, lint, dust, or other
materials that would interfere with the inspection.
The indications you see during a liquid penetrant
inspection must be carefully interpreted and evaluated.
In almost every inspection, some insignificant indications are present. Most of these are the result of the
failure to remove all the excess penetrant from the
surface. At least 10 percent of all indications must be
removed from the surface to determine whether defects
are actually present or whether the indications are the
result of excess penetrant. When a second inspection
does not reveal indications in the same locations, it is
usually safe to assume that the first indications were
false.
After the surface has dried, apply another substance,
called a developer. Allow the developer (powder or
liquid) to stay on the surface for a minimum of 7 minutes
before starting the inspection. Leave it on no longer than
30 minutes, thus allowing a total of 23 minutes to
evaluate the results.
7-36
Eddy current testing operates on the principle that
whenever a coil carrying a high-frequency alternating
current is placed next to a metal, an electrical current is
produced in the metal by induction. This induced current
is called an eddy current.
Remove all penetrant inspection materials as soon
as possible after the final inspection has been made. Use
water or solvents, as appropriate. Since some of the
liquid penetrant materials are flammable, do not use
them near open flames, and do not apply them to any
surface that is at a temperature higher than 100°F. In
addition to being flammable, many solvents are poisonous in the vapor form and highly imitating to the skin in
the liquid form.
The test piece is exposed to electromagnetic energy
by being placed in or near high-frequency ac current
coils. The differences in the weld cause changes in the
impedance of the coil, and this is indicated on electronic
instruments. When there are defects, they show up as a
change in impedance, and the size of the defect is shown
by the amount of this change.
Radiographic Inspection
Radiographic inspection is a method of inspecting
weldments by the use of rays that penetrate through the
welds. X rays or gamma rays are the two types of waves
used for this process. The rays pass through the weld
and onto a sensitized film that is in direct contact with
the back of the weld. When the film is developed, gas
pockets, slag inclusions, cracks, or poor penetration will
be visible on the film.
DESTRUCTIVE TESTING
In destructive testing, sample portions of the welded
structures are required. These samples are subjected to
loads until they actually fail. The failed pieces are then
studied and compared to known standards to determine
the quality of the weld. The most common types of
destructive testing are known as free bend, guided bend,
nick-break, impact, fillet welded joint, etching, and
tensile testing. The primary disadvantage of destructive
testing is that an actual section of a weldment must be
destroyed to evaluate the weld. This type of testing is
usually used in the certification process of the welder.
Because of the danger of these rays, only qualified
personnel are authorized to perform these tests. As
Seabees, you will rarely come in contact with these
procedures.
Ultrasonic Inspection
Ultrasonic inspection of testing uses high-frequency vibrations or waves to locate and measure defects in welds. It can be used in both ferrous and
nonferrous materials. This is an extremely sensitive
system and can locate very fine surface and subsurface
cracks as well as other types of defects. All types of
joints can be tested.
Some of the testing requires elaborate equipment
that is not available for use in the field. Three tests that
may be performed in the field without elaborate equipment are the free-bend test, the guided-bend test, and the
nick-break test.
This process uses high-frequency impulses to check
the soundness of the weld. In a good weld, the signal
travels through the weld to the other side and is then
reflected back and shown on a calibrated screen. Irregularities, such as gas pockets or slag inclusions, cause the
signal to reflect back sooner and will be displayed on
the screen as a change in depth. When you use this
system, most all types of materials can be checked for
defects. Another advantage of this system is that only
one side of the weld needs to be exposed for testing.
Free-Bend Test
The FREE-BEND TEST is designed to measure the
ductility of the weld deposit and the heat-affected area
adjacent to the weld. Also it is used to determine the
percentage of elongation of the weld metal. Ductility,
you should recall, is that property of a metal that allows
it to be drawn out or hammered thin.
The first step in preparing a welded specimen for
the free-bend test is to machine the welded reinforcement crown flush with the surface of the test plate. When
the weld area of a test plate is machined, as is the case
of the guided-bend as well as in the free-bend test,
perform the machining operation in the opposite direction that the weld was deposited.
Eddy Current Testing
Eddy current is another type of testing that uses
electromagnetic energy to detect faults in weld deposits
and is effective for both ferrous and nonferrous materials. As a Seabee, you will rarely use this type of testing
in the field.
The next step in the free-bend testis to scribe two
lines on the face of the filler deposit. Locate these lines
7-37
Figure 7-61.—Free-bend test
Figure 7-62.—Guided-bend test jig.
1/16 inch from each edge of the weld metal, as shown
in figure 7-61, view B. Measure the distance, in inches,
between the lines to the nearest 0.01 inch and let the
resulting measurement equal (x). Then bend the ends of
the test specimen until each leg forms an angle of 30
degrees to the original centerline.
With the scribed lines on the outside and the piece
placed so all the bending occurs in the weld, bend the
7-38
Requirements for a satisfactory test area minimum
elongation of 15 percent and no cracks greater than 1/16
inch on the face of the weld.
Guided-Bend Test
Figure 7-63.—Guided-bend test specimens.
test piece by using a hydraulic press or similar machine.
When the proper precautions are taken, a blacksmith’s
forging press or hammer can be used to complete the
bending operation. If a crack more than 1/16 inch develops during the test, stop the bending because the weld
has failed; otherwise, bend the specimen flat. After
completing the test, measure the distance between the
scribed lines and call that measurement (y). The percentage of elongation is then determined by the formula:
You use the GUIDED-BEND TEST to determine
the quality of weld metal at the face and root of a welded
joint. This test is made in a specially designed jig. An
example of one type of jig is shown in figure 7-62.
The test specimen is placed across the supports of
the die. A plunger, operated from above by hydraulic
pressure, forces the specimen into the die. To fulfill the
requirements of this test, you must bend the specimen
180 degrees—the capacity of the jig. No cracks should
appear on the surface greater than 1/8 inch. The facebend tests are made in this jig with the face of the weld
in tension (outside), as shown in figure 7-63. The rootbend tests are made with the root of the weld in tension
(outside), as shown in figure 7-63.
Figure 7-64 shows a machine used for making the
guided-bend test. It is used in many welding schools and
Figure 7-64.—Testing machine for making guided-bend tests.
7-39
which the test piece bends by the position of an auxiliary
hand that is carried along by the gauge pointer. The hand
remains at the point of maximum load after the pointer
returns to zero.
Nick-Break Test
The NICK-BREAK TEST is useful for determining
the internal quality of the weld metal. This test reveals
various internal defects (if present), such as slag inclusions, gas pockets, lack of fusion, and oxidized or
burned metal. To accomplish the nick-break test for
checking a butt weld, you must first flame-cut the test
specimens from a sample weld (fig. 7-65). Make a saw
cut at each edge through the center of the weld. The
depth of cut should be about 1/4 inch.
Next, place the saw-nicked specimen on two steel
supports, as shown in figure 7-65. Using a heave hammer, break the specimen by striking it in the zone where
you made the saw cuts. The weld metal exposed in the
break should be completely fused, free from slag inclusions, and contain no gas pockets greater than 1/16 inch
across their greatest dimension. There should not be
more than six pores or gas pockets per square inch of
exposed broken surface of the weld.
Figure 7-65.—Nick-break test of a butt weld.
testing laboratories for the daily testing of specimens.
Simple in construction and easy to use, it works by
hydraulic pressure and can apply a direct load up to
40,000 pounds, and even more on small specimens.
When you make the test, position the specimen in the
machine as previously indicated and start pumping the
actuator. Keep your eye on the large gauge and watch
the load increase. You will know the actual load under
Impact Test
You use the IMPACT TEST to check the ability
of a weld to absorb energy under impact without
Figure 7-66.—Test pieces for impact testing.
7-40
Figure 7-67.—Performing impact test.
fracturing. This is a dynamic test in which a test specimen is broken by a single blow, and the energy used in
breaking the piece is measured in foot-pounds. This test
compares the toughness of the weld metal with the base
metal. It is useful in finding if any of the mechanical
properties of the base metal were destroyed by the
welding process.
The two kinds of specimens used for impact testing
are known as Charpy and Izod (fig. 7-66). Both test
pieces are broken in an impact testing machine. The only
difference is in the manner that they are anchored. The
Charpy piece is supported horizontally between two
anvils and the pendulum strikes opposite the notch,
as shown in figure 7-67, view A. The Izod piece is
supported as a vertical cantilever beam and is struck on
the free end projecting over the holding vise (fig. 7-67,
view B).
Fillet-Welded Joint Test
You use the FILLET-WELDED JOINT TEST to
check the soundness of a fillet weld. Soundness refers
to the degree of freedom a weld has from defects
found by visual inspection of any exposed welding
surface. These defects include penetrations, gas
pockets, and inclusions. Prepare the test specimen,
as shown in figure 7-68. Now apply force at Point A
Figure 7-68.—Test plate for fillet weld test.
7-41
Figure 7-70.—Standard tensile test specimen.
The essential features of a tensile testing machine
are the parts that pull the test specimen and the devices
that measure the resistance of the test specimen. Another
instrument, known as an extensometer or strain gauge,
is also used to measure the strain in the test piece. Some
equipment comes with a device that records and plots
the stress-strain curve for a permanent record.
Figure 7-69.—Rupturing fillet weld test plate.
(fig. 7-69) until a break occurs in the joint. This force
may be applied by hydraulics or hammer blows.
The tensile test is classified as a destructive test
because the test specimen must be loaded or stressed
until it fails. Because of the design of the test machine,
weld samples must be machined to specific dimensions.
This explains why the test is made on a standard specimen, rather than on the part itself. It is important that the
test specimen represents the part. Not only must the
specimen be given the same heat treatment as the part
but it also must be heat-treated at the same time.
In addition to checking the fractured weld for
soundness, now is a good time to etch the weld to check
for cracks.
Etching Test
The ETCHING TEST is used to determine the
soundness of a weld and also make visible the boundary
between the base metal and the weld metal.
There are many standard types of tensile test specimens, and figure 7-70 shows one standard type of specimen commonly used. The standard test piece is an
accurately machined specimen. Overall length is not a
critical item, but the diameter and gauge length are. The
0.505-inch-diameter (0.2 square inch area) cross section
of the reduced portion provides an easy factor to manipulate arithmetically. The 2-inch gauge length is the
distance between strain-measuring points. This is the
portion of the specimen where you attach the extensometer. In addition, you can use the gauge length to
determine percent elongation.
To accomplish the test, you must cut a test piece
from the welded joint so it shows a complete transverse
section of the weld. You can make the cut by either
sawing or flame cutting. File the face of the cut and then
polish it with grade 00 abrasive cloth. Now place the test
piece in the etching solution.
The etching solutions generally used are hydrochloric acid, ammonium persulfate, iodine and potassium
iodide, or nitric acid. Each solution highlights different
defects and areas of the weld. The hydrochloric acid
dissolves slag inclusions and enlarges gas pockets,
while nitric acid is used to show the refined zone as well
as the metal zone.
The tensile test amounts to applying a smooth,
steadily increasing load (or pull) on a test specimen and
measuring the resistance of the specimen until it breaks.
Even if recording equipment is not available, the testis
not difficult to perform. During the test, you observe the
behavior of the specimen and record the extensometer
and gauge readings at regular intervals. After the specimen breaks and the fracturing load is recorded, you
measure the specimen with calipers to determine the
percent of elongation and the percent reduction in area.
In addition, you should plot a stress-strain curve. From
the data obtained, you can determine tensile strength,
Tensile Strength Test
The term TENSILE STRENGTH may be defined as
the resistance to longitudinal stress or pull and is measured in pounds per square inch of cross section. Testing
for tensile strength involves placing a weld sample in a
tensile testing machine and pulling on the test sample
until it breaks.
7-42
yield point, elastic limit, modulus of elasticity, and other
properties of the material.
l Keep welding cables dry and free of oil or grease.
Keep the cables in good condition and always take
appropriate steps to protect them from damage. When it
is necessary to run cables some distance from the machine, lay them overhead, if at all possible, using adequate support devices.
SAFETY REGULATIONS
You, as the welder, must have a thorough KNOWLEDGE of the safety precautions relating to the job. That
is not all; you should also consider it your responsibility
to observe all of the applicable safety precautions. When
welding, carelessness can cause serious injury to yourself as well as others.
Q When you are using portable machines, make
sure that the primary power cable is separate from the
welding cables so they do not become entangled. Any
portable equipment mounted on wheels should be securely blocked to prevent accidental movement during
welding operations.
Bear in mind the safety precautions for operating
welding equipment can vary considerably because of
the different types of equipment involved; therefore,
only general precautions on operating metal arc-welding equipment are presented here. For specific instructions on the operation and maintenance of your
individual equipment, consult the equipment manufacturer’s instruction manual. In regards to general precautions, know your equipment and how to operate it. Use
only approved welding equipment, and ensure that it is
maintained properly.
l When stopping work for any appreciable length
of time, be sure to de-energize the equipment. When the
equipment is not in use, you should completely disconnect it from its source of power.
. Keep the work area neat and clean. If at all
possible, make it a practice to dispose the hot electrode
stubs in a metal container.
Chapter 3 contains information on protective clothing, eye protection, and safe practices applicable to the
personal safety of the operator and other persons who
may be working nearby so that information will not be
repeated here. If necessary, go back and review the
section entitled “Safety” in chapter 3 before proceeding
to the next chapter.
l Before you start welding, ensure that the welding
machine frame is grounded, that neither terminal of the
welding generator is bonded to the frame, and that all
electrical connections are secure. The ground connection must be attached firmly to the work, not merely laid
loosely upon it.
7-43
CHAPTER 8
GAS SHIELDED-ARC WELDING
The primary goal of any welding operation is to
make a weld that has the same properties as the base
metal. The only way to produce such-a weld is to protect
the molten puddle from the atmosphere. In gas
shielded-arc welding, briefly discussed in chapter 3,
you use a gas as a covering shield around the arc to
prevent the atmosphere from contaminating the weld.
Gas shielding makes it possible to weld metals that are
otherwise impractical or difficult to weld by eliminating
atmospheric contamination from the molten puddle.
Figure 8-1 shows the basic principle of gas shielded-arc
welding.
The two general types of gas shielded-arc welding
processes are gas tungsten-arc welding (GTA) and gas
metal-arc welding (GMA). GTA is often tilled TIG
(tungsten inert gas) and GMA is referred to as MIG
(metal inert gas). The term inert refers to a gas that will
not combine chemically with other elements.
GAS TUNGSTEN-ARC
WELDING—GTAW
Gas tungsten-arc welding is basically a form of arc
welding; however, in gas tungsten-arc welding, the electrode is used only to create the arc. The electrode is not
consumed in the weld as in the shielded metal-arc
process. The gas tungsten-arc welding process generally
produces welds that are far superior to those produced
by metallic arc welding electrodes. Especially useful for
welding aluminum, it also may be used for welding
many other types of metals. The GTA process is most
effective for joining metals up to 1/8 inch thick, although
you can use it to weld thicker material.
As shown in figure 8-2, the basic GTA process
involves an intense arc between the base metal and a
Figure 8-1.—Gas shielded-arc welding principle.
Figure 8-2.—GTA welding process.
8-1
Figure 8-3.—Power supply unit specifically designed for gas tungsten-arc welding.
GTA WELDING EQUIPMENT
AND SUPPLIES
tungsten electrode. The arc, the electrode, and the weld
zone are surrounded by an inert gas (usually either
helium or argon or a mixture of the two) that displaces
The equipment and supplies required for gas tungsten-arc welding consist of an electric power unit,
shielding gas, a pressure-reducing regulator and flowmeter, an electrode holder (commonly called a torch),
nonconsumable tungsten electrodes, filler rods, a supply
of cooling water (when required), and personal protective gear.
the air and eliminates the possibility of weld contamination by the oxygen and nitrogen present in the
atmosphere. The tungsten electrode has a high melting
point that makes it virtually nonconsumable.
Specific advantages of gas tungsten-arc welding
include the following:
Welding can be done in all positions.
Electric Power Unit
The weld is usually equal to the base metal in
Most welding power sources can provide the current needed for GTA welding. The common welding
machines, whether alternating current (at) or direct
current (de), have their advantages in certain welding
applications; however, they can be cumbersome and
their hose and cable connections can create difficulties.
Because of this, specially designed machines with all
the necessary controls are available for gas tungsten-arc
welding (fig. 8-3).
composition.
Flux is not used; therefore, finished welds do not
require cleaning of corrosive residue.
Smoke or fumes are not present to obscure vision; therefore, you can easily see the welding
process.
Distortion of the base metal is minimal because
GTA power units are equipped with solenoid valves
that turn the flow of shielding gas and cooling water on
and off. They are also equipped with a hand- or footoperated remote-control switch that turns the water and
gas on and off. Some of these remote-control devices
the heat is concentrated in a small area.
No splatter is produced because metal is not
transferred across the arc.
8-2
Figure 8-5.—The ac welding cycle.
Figure 8-4.—Effects of polarity on the weld.
also turn the main welding current on and off at the same
time. This not only allows the operator to start and stop
without leaving the work but also to adjust the current
while welding.
Most of these welding machines can produce both
ac and dc current. The choice of ac or dc depends on the
welding characteristics required.
Figure 8-6.—ACHF combines the desired cleaning action of
DCRP with the good penetration of DCSP.
DIRECT CURRENT.— As you learned in chapter
7, a direct-current welding circuit maybe either straight
or reverse polarity. When the machine is set on straight
polarity, the electrons flow from the electrode to the
plate, concentrating most of the heat on the work With
reverse polarity, the flow of electrons is from the plate
to the electrode, thus causing a greater concentration of
heat at the electrode. Because of this intense heat, the
electrode tends to melt off; therefore, direct-current
reverse polarity (DCRP) requires a larger diameter electrode than direct-current straight polarity (DCSP).
action of positive-charged gas ions. When these gas ions
strike the metal, they pierce the oxide film and form a
path for the welding current to follow. This same cleaning action occurs in the reverse polarity half of an
alternating-current welding cycle.
ALTERNATING CURRENT.— AS shown in figure 8-5, ac welding is actually a combination of DCSP
and DCRP; however, the electrical characteristics of the
oxides on the metal often prevent the current from
flowing smoothly in the reverse polarity half of the
cycle. This partial or complete stoppage of current flow
(rectification) causes the arc to be unstable and sometimes go out. Ac welding machines were developed with
a high-frequency current flow unit to prevent this rectification. The high-frequency current pierces the oxide
film and forms a path for the welding current to follow.
The effects of alternating current high-frequency
(ACHF) are shown in figure 8-6. Notice that ACHF
offers both the advantages of DCRP and DCSP. ACHF
is excellent for welding aluminum.
The effects of polarity on the weld are shown in
figure 8-4. Notice that DCSP produces a narrow, deep
weld. Since the heat is concentrated on the work, the
welding process is more rapid and there is less distortion
of the base metal. Overall, straight polarity is preferred
over reverse polarity because you can achieve better
welds.
DCRP forms a wide and shallow weld and is rarely
used in the GTAW process. The exception to this is when
it is used to weld sections of aluminum or magnesium.
DCRP has excellent cleaning power that results from the
8-3
Table 8-1.—Current Selection Guide for GTA Welding of Common Metals
You can use table 8-1 as a guide for selecting the
current for welding some of the more common metals.
For more specific information, refer to the operator’s
manual for the specific machine you are using.
NOTE: To avoid torch overheating caused by clogging and flow restrictions, you must keep the water
clean.
The GTA welding torch carries the welding current
and directs the gas to the weld area. The torch must have
Torches
GTA welding torches are designed to conduct both
welding current and inert gas to the weld zone. The
torches can be either air or water cooled, depending on
the welding current. Air-cooled torches are used for
welding light-gauge materials at relatively low-current
settings. Water-cooled torches are recommended for
currents above 200 amperes. A sectional view of a GTA
water-cooled torch is shown in figure 8-7. When you are
using this type of torch, a circulating stream of water
flows around the torch to keep it from overheating.
Figure 8-7.—GTA water-cooled torch.
Figure 8-8.—GTA torch parts.
8-4
Table 8-2.—Approximate Cup Size for GTA Welding
Table 8-3.—Approximate Current Ranges for Tungsten Electrodes
The diameter of the electrode selected for GTA
welding is governed by the amount of welding current
used. Remember: DCRP requires larger electrodes than
DCSP. Recommended electrode sizes for various ranges
of welding current are shown in table 8-3. These current
ranges are broad. You should refer to the manufacturer’s
recommendations for specific current ranges and electrode sizes based on the type of material you are welding.
the proper insulation for the maximum current ranges to
ensure ‘operational safety. Current is transmitted-from
the weld-rig machine through the power cable to a collet
holding the tungsten electrode. A variety of collet sizes
are available, depending on the diameter of the electrode. Figure 8-8 shows the various parts of a typical
GTA torch.
Gas is fed to the welding zone through the torch
nozzle that consists of a ceramic cup. Nozzles also are
made of steel (chrome plated), plastic, and glass (Pyrex)
materials. These nozzles (gas cups) vary in size, depending upon the type and size of torch and the diameter of
the electrode. See table 8-2 for sizes.
Basic diameters of nonconsumable electrodes are
.040, 1/16, 3/32, and 1/8 of an inch. They are either pure
tungsten or alloyed tungsten. The alloyed electrodes are
of three types: 1% thorium alloy, 2% thorium alley, and
zirconium alloy. Pure tungsten is routinely used with ac
welding and is sufficient for most GTA welding operations. The thoriated types are normally used for DCSP
welding. These electrodes give slightly better penetration and arc-starting characteristics over a wider range
of current settings. The zirconium alloy is excellent for
ac welding and has high resistance to contamination.
The electrodes alloyed with thorium and zirconium are
primarily used for critical weldments in the aircraft and
missile industries.
Electrodes
The electrode should extend beyond the end of the
gas cup a distance equal to its diameter for butt welding
and slightly further for fillet welding. Selecting the right
size electrode for each job is important to prevent electrode damage and poor welds caused by too high or too
low a current. Excessive current causes tungsten particles to transfer to the weld, while not enough current
allows the arc to wander emetically over the end of the
electrode.
8-5
Figure 8-9.—Tungsten electrode shapes for ac
and dc welding.
127.286
Figure 8-10.—Combination regulator and
flowmeter.
Tungsten electrodes are usually color-coded at one
end. A green color indicates that the rod is pure
tungsten; yellow indicates a 1-percent thoriated tungsten
rod; red indicates a 2-percent thoriated tungsten rod; and
brown indicates that the rod is alloyed with zirconium.
To produce good quality welds with the GTA
process, you must shape the electrode properly. The
general practice is to use a pointed electrode with dc
welding and a spherical end with ac welding (fig. 8-9).
Shielding Gas
Shielding gas for GTA welding can be argon, helium, or a mixture of argon and helium. Argon is by far
the most popular. When compared to helium, argon has
greater cleaning action and provides a more stable arc.
Argon is heavier than air; therefore, it provides a blanket
over the weld that protects it from contaminants.
Helium, being lighter than air, requires a higher gas flow
than argon and is therefore more expensive to use.
However, as a shielding gas, helium - allows greater
penetration and faster welding speeds because the arc is
hotter in the helium atmosphere than in the argon
atmosphere. The opposite is true for GMA welding;
therefore, a mixture of argon and helium is sometimes
used in welding metals that require a higher heat input.
Table 8-4 lists a selection of shielding gases
recommended for various metals for both the GTA and
GMA welding processes. Notice that for most GTA
welding operations, you use pure argon.
Figure 8-11.—Cross section of flowmeter.
for GMA/GTA show the flow of shielding gas in cubic
feet per hour (cfh) or liters per minute (lpm).
Regulators used for GMA/GTA welding have a
flowmeter instead of a working pressure gauge along
with the cylinder pressure gauge. See figure 8-10.
Regulators
The primary difference between the regulators used
for oxyfuel welding and for GTA/GMA welding is that the
working pressure on the oxyfuel regulators is shown in
pounds per square inch (psi) while the regulators used
The flowmeter consists of a plastic or glass tube that
contains a loosely fitting ball. As the gas flows up the
tube, it passes around the ball and lifts it up. The more
8-6
Table 8-4.—Selection of Shielding Gases for Various GMAW and GTAW Applications
pressure. If you use higher inlet pressures, the gas flow
rate will be higher than the actual reading. The reverse
is true if the inlet pressure is lower than 50 psig; therefore, it is important to use accurately adjusted regulators.
With an accurate flowmeter, these regulators can deliver
inert gas flows up to 60 cfh. You should read the scale
by aligning the top of the ball with the cfh desired.
gas that moves up the tube, the higher the ball is lifted.
Figure 8-11 shows a cross section of the flowmeter.
The shielding gas regulator has a constant outlet
pressure to the flowmeter of about 50 psig. This is
important because the flowmeter scales are accurate
only if the gas entering them is at that approximate
8-7
Table 8-5.—Suggested Inert Gas Flow Rates for Various Metals
To obtain an accurate reading, you must mount the
meter in a vertical position. Any slant will create an
off-center gas flow and result in an inaccurate reading.
Also, because gas densities vary, you should use different flowmeters for different gases.
welding. The correct shade of lens depends on the
intensity of the arc. Chapter 3 provides a chart of recommended lens shades based on the current setting of
the machine. For normal GTA welding at current ranges
of 76 to 200 amperes, a shade No. 10 lens is satisfactory.
Eye fatigue indicates you should use a different shade
of lens or there is leakage around the protective filter
glass.
The flow of gas necessary for good GTA welding
depends primarily on the thickness of the material.
Other factors include the following: welding current,
size of nozzle, joint design, speed of welding, and a
draft-free area in the location the welding is done. This
last factor can affect gas coverage and use considerably.
Table 8-5 shows the approximate gas flow rates for
various types of metals.
In addition to the welding hood, protective clothing,
such as gloves and an apron, should be worn. Bare skin
should never be exposed to the rays of the welding arc
because painful burns may result.
GTA WELDING PREPARATION
Filler Rods
Although it can produce outstanding results, GTA
welding can be expensive. The equipment, electrodes,
and shielding gas are costly and the material you weld
is usually much more expensive than the material
welded by other welding processes. To avoid costly
mistakes, you should take the time to prepare for each
welding operation fully. Preparation is the key to producing quality weldments.
Normally you do not require filler metal when GTA
welding light-gauge materials since they tend to flow
together easily. Thick material and thin material that
needs reinforcing should be welded using a filler metal.
Special filler rods are available for GTA welding;
therefore, you should not use welding rods designed for
oxyfuel welding because they can contaminate the tungsten electrode. You should use filler rods that have the
same composition as the base metal; for example, use
mild steel rods to weld low-carbon steel and aluminum
rods for welding aluminum. Additionally, there are
many different compositions of the same metal; therefore, you should select a filler metal of the same composition as the metal you are welding.
Specific information on the different manufacturers
of GTA welding equipment is not provided in this training manual. You should read the manufacturer’s instructional pamphlets for specific information on your
machine. The following suggestions are considered
general and you can apply them to any GTA welding
operation:
Personal Protective Equipment
l Prepare the joint according to the welding procedure you are performing. Refer to chapter 3 of
this training manual for specific information
about joint preparation.
A welding hood like the one used in shielded
metal-arc welding should be used for gas tungsten-arc
8-8
Clean the metal of all oxidation, scale, oil, dirt,
or other foreign matter. Regardless of the type of
joint used, proper cleaning of the metal is essential. For best results, use a stainless steel wire
brush.
Check all electrical circuit connections to make
sure they are properly connected and all fittings
are tight.
Be sure the torch is the right type and capacity
for the current at which most of the welding will
be done. Some manufacturers offer different
torches for different ranges of welding current.
Figure 8-12.—Contaminated and good tungsten electrode.
Check the size, appearance, and position of the
tungsten electrode in the torch. Ensure that the
electrode diameter and nozzle size meet the
manufacturer’s recommendations. The tip
should be properly shaped as discussed earlier
(refer to figure 8-9). The electrode should extend
beyond the end of the gas cup a distance ranging
from 1/8 to 3/16 of an inch for butt welding and
1/4 to 3/8 of an inch for fillet welding. Check the
electrode for positioning and good electrical contact. The electrode should be clean and silvery. A
dirty tungsten electrode can usually be cleaned
satisfactorily with a fine emery cloth. If severely
contaminated, the electrode should be replaced
or the tip broken off and dressed on a grinding
wheel. A contaminated tungsten electrode and a
good tungsten electrode are shown in figure 8-12.
Figure 8-13.—Torch position for the starting swing to strike
the arc.
procedure for a particular welded joint includes many
variables. The same variables that must be considered
for other welding processes also must be considered for
gas shielded-arc welding. Some of the variables that you
must consider include the following: type of base metal,
the joint design, the welding position, the type of shielding gas, and the welding machine setting.
Check the ground cable connections to the workpiece. The connections should be periodically
checked after welding begins because they tend
to work loose. When this happens, the welding
current varies.
Set the machine for the correct welding amperage. (Follow manufacturer’s recommendations.)
Starting the Arc
Open the cylinder valve and adjust the gas flow.
Before welding, check the connections on the gas
supply for leaks with soapy water.
Before starting the arc, you should form a ball on
the end of the electrode for ac welding. To do this,
simply set the current to DCRP and strike an arc for a
moment on a piece of carbon or a piece of copper. The
ball diameter should be only slightly larger than the
original diameter of the tungsten electrode.
If using a water-cooled torch, turn on the water.
Be sure the water pressure is not higher than
recommended by the torch manufacturer.
GTA WELDING PROCEDURES
When starting the arc with an ac high-frequency
current, you do not have to bring the electrode into
contact with the workpiece. To strike the arc, you must
hold the torch in a horizontal position about 2 inches
above the work surface, as shown in figure 8-13. Then
As we discussed in chapter 3, the detailed methods
and practices used to prepare a particular weldment are
called the welding procedure. We also said that the
8-9
Figure 8-14.—Torch position at the end of the swing when the
arc strikes.
Figure 8-15.—Forming a molten puddle with a GTA torch.
rapidly swing the electrode end of the torch down to
within 1/8 of an inch of the work surface. The high-frequency arc will then jump the gap between the electrode
and the plate, establishing the arc. Figure 8-14 shows
the torch position at the time the arc strikes.
Figure 8-16.—Addition of filler metal in the flat position.
with small circular motions, as shown in figure 8-15,
form a molten puddle. After you form the molten puddle,
hold the torch at a 75-degree angle to the work surface
and move it slowly and steadily along the joint at a speed
that produces a bead of uniform width. Move the torch
slowly enough to keep the puddle bright and fluid. No
oscillating or other movement of the torch is necessary
except the steady forward movement.
If you are using a dc machine, hold the torch in the
same position, but touch the plate to start the arc. When
the arc is struck withdraw the electrode so it is about
1/8 of an inch above the plate.
To stop the arc, quickly swing the electrode back to
the horizontal position. If the machine has a foot pedal,
gradually decrease the current before stopping the arc.
When you must use a filler metal, form the molten
puddle as described previously. When the puddle becomes bright and fluid, you should move the arc to the
rear of the puddle and add the filler metal by quickly
touching the rod to the front edge of the puddle. Hold
the rod at about a 15-degree angle from the work.
Because the electrode is pointing toward the filler metal
or pushing it, it is known as the push angle. Remove the
Welded Joints
In the following paragraphs the different types of
joints and the procedures used to weld them is discussed.
BUTT JOINTS.— After you strike the arc, hold the
torch at a 90-degree angle to the workpiece surface, and
8-10
Figure 8-17.—GTA welding a tee joint.
Figure 8-18.—GTA welding a lap joint.
filler rod and bring the arc back to the front edge of the
the arc. You should practice making single-pass butt
welds until you can produce satisfactory welds.
puddle. When the puddle becomes bright and fluid
again, you should repeat the steps as described before.
Figure 8-16 shows the correct procedures for adding
LAP AND TEE JOINTS.— In chapter 3, we said
that lap and tee joints are welded using the fillet weld.
Fillet welds are slightly awkward to make using the GTA
welding process because of the gas nozzle. Once you
establish the arc, you should pay close attention to the
molten puddle. Figures 8-17 and 8-18 show the correct
torch and rod angles for the tee and lap joints.
filler metal. Continue this sequence until the weld joint
has been completed. The width and height of the weld
bead is determined by the speed of travel, by the movement of the torch, and by the amount of filler metal
added.
In welding a tee or lap joint, the puddle forms a
V-shape. The center of the V is called a notch, and the
speed at which you fill the notch governs how fast you
should move the torch. Do NOT get ahead of the notch.
If you do, the joint will have insufficient fusion and
penetration. As you weld along the joint, dip the rod in
In welding practice, it is again stressed that good
(GTA welding depends on following this definite procedure—form the molten pool and then feed filler rod
intermittently to the leading edge of the pool as you
move the torch forward. DO NOT feed the filler rod into
8-11
Figure 8-19.—GTA welding in the horizontal position.
Figure 8-21.—GTA welding vertical upward.
Figure 8-20.—GTA welding vertical downward.
Figure 8-22.—GTA welding overhead.
and out of the puddle about every 1/4 of an inch of travel.
If you add the filler rod to the molten puddle at just the
right time uniform welds result every time.
joint. Then hold the torch at a work angle of 15 degrees
and a push angle of 15 degrees. After you establish the
puddle, dip the rod into the front edge of the puddle on
the high side as you move the torch along the joint (fig.
8-19). Maintain an arc length as close as possible to the
diameter of the electrode. Correct arc length coupled
with the correct speed of travel helps prevent undercutting and permits complete penetration.
Out-of-Position Welding
Rules for quality welding in the flat position also
must be followed for out-of-position GTA welding.
Cleanliness, good joint fit-up, preheat, sufficient shielding gas, and correct welding current are important. In
addition, you should not use high welding current or
deposit large weld beads. Direct the arc so there is no
overheating at anyone area that could cause sagging or
undercutting. The adding of filler metal, bead size, and
sequence must be done correctly to ensure complete
fusion between passes.
VERTICAL WELDING.— When welding thin
material with the GTA welding process, you should weld
from the top, moving downward (fig. 8-20). This helps
you produce an adequate weld without burning through
the metal. Filler material is not normally needed for
welding downward.
On heavier materials, you should weld from the
bottom, upwards (fig. 8-21). This enables you to achieve
adequate penetration. When welding upward, you normally need to use a filler rod.
HORIZONTAL WELDING.— When welding in
the horizontal position, start the arc on the edge of the
8-12
The amperage settings for GTA welding stainless
steel are higher than for aluminum. The amperage used
for different thicknesses of stainless should be according to the recommended settings that you can find in the
manufacturer’s technical manual or the information
pamphlets provided with the equipment.
OVERHEAD WELDING.— When GTA welding
in the overhead position, you should lower the welding
current by 5 to 10 percent of what normally is used for
flat welding. This reduced welding current enables you
to maintain better control of the welding puddle.
Conversely, you need a higher flow of shielding gas.
Hold the torch and the rod as you do for flat welding
(fig. 8-22). You should try to maintain a small weld
puddle to avoid the effects of gravity. Most inexperienced welders find overhead welding awkward; therefore, try to get in as comfortable and relaxed a position
as possible when welding. This helps you to maintain
steady, even torch and filler rod manipulation.
Copper and Its Alloys
Pure copper is easily welded; however, as with any
of the other metals we have discussed, it must be thoroughly cleaned before to welding. The GTA weldability
of each copper-alloy group depends largely upon the
alloying elements. Copper-silicon and copper-nickel
alloys are weldable using the GTA process. Copperzinc, copper-tin, and copper-lead alloys are difficult or
impossible to weld by the GTA process. Plates up to 1/4
of an inch thick are generally prepared with a square
edge. The forehand welding technique with DCSP is
recommended for materials thicker than 0.050 of an
inch. On lighter material, ACHF also can be used.
GTA WELDING COMMON METALS
The actual welding technique for gas tungsten-arc
welding common metals is virtually the same; however,
each of the metals that we discuss has its own unique
welding characteristics. In this section we discuss some
of those characteristics. It is not the scope of this training
manual to provide you with an in depth study of the
welding procedures required to weld all types of metals.
This chapter is merely an introduction to gas shieldedarc welding. For more information, refer to the manufacturer’s literature for the specific welding equipment
you use or any of the references listed in this book.
Cast Iron
You can make sound welds using the GTA welding
process in three principal grades of cast iron: gray,
white, and malleable. Cast-iron parts must always be
preheated before to welding. Gray cast iron should be
preheated to a temperature ranging between 500°F to
1250°F. The required temperature depends on the size
and shape of the workpiece.
Aluminum
Steelworkers use the gas tungsten-arc welding procedure more for aluminum than for any other metal.
Aluminum is available in a variety of compositions.
Series 1000,3000, and 5000 aluminum alloys are considered nonheat-treatable and are easily weldable. The
heat-treatable alloys in the series 2000, 6000, and 7000
also can be welded; however, higher welding temperatures and speed are needed.
In either GTA or GMA welding, you should allow
the workpiece to cool slowly after welding. You can
accomplish this by covering the workpiece in a bed of
lime or ashes. This slow cooling prevents cracking and
residual stresses.
Magnesium
You can weld aluminum in all positions, but better
welds are normally produced in the flat position. You
should also use copper backup blocks whenever
possible, especially on thin material. For best results use
ACHF current and argon for shielding gas.
The welding characteristics of magnesium are comparable to those of aluminum. Both have high-heat
conductivity, a low-melting point, high-thermal expansion, and both oxidize rapidly. Both DCRP and ac provide excellent cleaning action to the weld metal. DCRP
can be used with helium gas to produce wide weld
deposits, high heat, and shallow penetration. ACHF with
helium, argon, or a mixture of the gases can be used to
join metals ranging from 0.20 to over 0.25 of an inch.
DCSP with helium produces deep penetration but no
surface cleaning.
Stainless Steel
In GTA welding of stainless steel, the welding techniques used are similar to those used with aluminum.
The major differences are in the selection of the welding
current and the type of tungsten electrode used. To get
the best results in welding stainless steel, you should use
DCSP welding current; however, ACHF can be used.
The forehand welding technique should be used.
Most satisfactory results on magnesium are obtained by using the electrode in as nearly a vertical
8-13
Figure 8-23.—GMA welding process.
Figure 8-24.—Diagram of GMA welding equipment.
position as possible. The electrode is advanced along the
line of weld, using the forehand technique.
preset controlled speed. As the wire passes through the
contact tube of the gun, it picks up the welding current.
The consumable wire electrode serves two functions: it
maintains the arc and provides filler metal to the joint.
The method of delivery of the filler metal allows
CAUTION
GMAW welding to be basically a one-handed operation
which does not require the same degree of skill as
GTAW. Figure 8-23 shows the basic principle of gas
metal-arc welding.
Always be sure there is good ventilation
when welding. The fumes from some of these
metals are highly toxic; therefore, a good ventilating system is essential.
An important factor in the GMA welding process is
the high rate at which metal can be deposited. This high
rate of metal deposition and high speed of welding
results in minimum distortion and a narrow heat-af-
GAS METAL-ARC WELDING-GMAW
The gas metal-arc welding process (GMAW), often
called MIG, has revolutionized arc welding. In this
process, a consumable electrode (in the form of wire) is
fed from a spool through the torch (welding gun) at a
fected zone. When you are deciding whether to use GTA
or GMA welding, the thickness of the material should
8-14
be a deciding factor. GMAW is often chosen for welding
thicker material.
Like GTA welding, gas metal-arc welding also uses
a shielding gas to protect the weld zone during welding.
The inert gas is fed through the gun into the weld zone
and prevents atmospheric contamination.
GMAW offers many of the advantages of GTAW.
Since there is no flux, GMA welds are clean and there
is no slag to remove. GMAW enables you to produce
sound welds in all positions quickly. Now let’s take a
look at the equipment you will use for GMA welding.
GMA WELDING EQUIPMENT
AND SUPPLIES
Gas metal-arc welding equipment basically consists
of four units: the power supply, the wire feeding mechanism, the welding gun (also referred to as the torch), and
the gas supply. Figure 8-24 shows atypical GMA welding outfit.
Welding Machine
Figure 8-25.—Constant voltage (CV) power unit.
When you use a conventional type of welding machine for GMA welding, the voltage varies depending
on the length of the arc. Whenever the nozzle-to-work
distance changes, the arc length and the voltage changes.
The only way to produce uniform welds with this type
of power source is to maintain the arc length and voltage
at a constant value. Besides producing nonuniform
welds, this inconsistent voltage can cause the wire to
burn back to the nozzle.
the nozzle-to-work distance will not change the arc
length and burn back is virtually eliminated.
In gas metal-arc welding, direct-current reverse polarity (DCRP) is recommended. You should recall from
the previous section that DCRP produces excellent
cleaning action and allows for deeper penetration.
Wire Feed Drive Motor
A constant voltage (CV) power source was developed to overcome the inconsistent voltage characteristics of a conventional welding machine, (See fig.
8-25). It can be either a dc rectifier or motor generator
that supplies current with normal limits of 200 to 250
amperes.
The wire feed drive motor is used to automatically
drive the electrode wire from the wire spool through the
gun up to the arc point. You can vary the speed of the
wire feed by adjusting the controls on the wire-feed
control panel. The wire feeder can be mounted on the
power unit or it can be separate from the welding machine.
The CV type power source has a nearly flat voltampere characteristic. This means that the machine maintains the same voltage regardless of the amount of
current used. With this type of power source, you can
change the wire-feed speed over a considerable range
without causing the wire to burn back to the nozzle.
When the wire-feed speed is set at a specific rate,
a proportionate amount of current is automatically
drawn. In other words, the current selection is based on
the wire-feed speed. When the wire is fed faster, the
current increases; when it is fed slower, the current
decreases. With this type of power supply, variations in
Welding Gun
The function of the welding gun is to carry the
electrode wire, the welding current, and the shielding
gas to the arc area. The gun has a trigger switch that
controls the wire feed and arc as well as the shielding
gas. The welding operator directs the arc and controls
the weld with the welding gun. GMA welding guns are
available in many different styles, some of which are
8-15
127.258B
Figure 8-27.—GMA welding torch with wire feed
motor and wire spool inside.
other gases for arc shielding. Argon reduces spatter by
producing a quiet arc and reducing arc voltage that
results in lower power in the arc and thus lower
penetration. The combination of lower penetration
and reduced spatter makes argon desirable when
welding sheet metal.
Pure argon is seldom used for arc shielding
except in welding such metals as aluminum, copper,
nickel, and titanium. The use of pure argon to weld
steel usually results in undercutting, poor bead
contour, and the penetration is somewhat shallow.
Figure 8-26.—GMA welding guns.
shown in figure 8-26. When using these guns, the wire
is fed to the torch by an automatic wire feeding
machine which pushes the wire through a flexible
tube to the arc point.
Figure 8-27 shows another type of GMA welding
gun that Steelworkers could use. This model incorporates the drive motor and a small spool of wire inside
the gun. This type of gun is attached directly to the
welding unit and gas supply, eliminating the need for
a separate control unit and wire drive assembly.
As with the GTA welding torch, the torch nozzle
must be kept clean at all times. Also, you should clean
the tube through which the electrode wire passes each
time the electrode reel is changed.
ARGON-OXYGEN.— Small amounts of oxygen
added to argon can produce excellent results.
Normally oxygen is added in amounts of 1, 2, or 5
percent. When oxygen is added to argon, it improves
the penetration pattern. It also improves the bead
contour and eliminates the undercut at the edge of the
weld. You use argon-oxygen mixtures in welding alloy
steels, carbon steels, and stainless steel.
HELIUM.— Helium, like argon, is an inert gas.
But there are few similarities between the two gases.
Argon is heavier than air and helium is lighter than
air. Helium has a high-voltage change as the arc
length changes. When you use helium for GMA
welding, more arc energy is lost in the arc itself and is
not transmitted to the work In the section on GTA
welding, we said that helium produces good
penetration and fast welding speeds. For GMA
welding, the opposite is true. In GMA welding, helium
produces a broader weld bead, but shallower
penetration.
Because of its high cost, helium is primarily used
for special welding tasks and for welding nonferrous
metals, such as aluminum, magnesium, and copper. It
is also used in combination with other gases.
Shielding Gas
In gas metal-arc welding, as with gas tungstenarc welding, the shielding gas can have a major effect
on the properties of the base metal. Some of the
shielding gases commonly used with the GMA process
are pure argon, argon-helium, argon-oxygen, argoncarbon dioxide, and carbon dioxide. Refer to table 8-4
for a selection of shielding gases recommended for
various metals for both the GMA and GTA welding
processes. The smoothness of operation, weld
appearance, weld quality, and welding speeds are
affected indifferent ways with each type of metal,
thickness, and gas mixture.
ARGON.— Earlier in this chapter, we said that
argon provides greater cleaning action than other gases.
Because it is heavier than air, argon blankets the weld
from contamination. Also, when you are using argon as a
shielding gas, the welding arc tends to be more stable.
For this reason, argon is often used in combination with
CARBON DIOXIDE (CO2).— Argon and helium
gases are composed of single atoms. Carbon dioxide, on
the other hand, consists of molecules. Each molecule
contains one carbon atom and two oxygen atoms. At
8-16
Table 8-6.—Recommended Wire Diameters for GMA Welding Using Welding Grade CO2 and a Wire Stick-out of 1/4 to 3/8 of an Inch
more gas cylinders (manifold) together to maintain
higher gas flow.
For most welding conditions, the gas flow rate is
approximately 35 cubic feet per hour (cfh). This flow
rate may be increased or decreased, depending upon the
particular welding application. Final adjustments usually are made on a trial-and-error basis. The proper
amount of gas shielding results in a rapidly crackling or
sizzling arc sound. Inadequate gas shielding produces a
popping arc sound and results in weld discoloration,
porosity, and spatter.
normal temperatures carbon dioxide is essentially an
inert gas; however, at high temperatures it decomposes
into carbon monoxide (CO) and oxygen (O 2). Because
the excess oxygen atoms can combine with carbon or
iron in the weld metal, wires used with this gas must
contain deoxidizing elements. A deoxidizing element
has a great affinity for the oxygen and readily combines
with it. Some of the more common deoxidizers used in
wire electrodes are manganese, silicon, and aluminum.
Carbon dioxide is used primarily for the GMA
welding of mild steel. Because of its low cost, CO2 is
often used in combination with other shielding gases for
welding different types of metals. Direct-current reverse
polarity (DCRP) is generally used with CO2. The current
setting is about 25 percent higher with CO 2 than with
other shielding gases.
Carbon dioxide produces abroad, deep penetration
pattern. It also produces good bead contour and there is
no tendency toward undercutting. The only problem
with CO2 gas is the tendency for the arc to be violent.
This can lead to spatter problems; however, for most
applications this is not a problem and the advantages of
CO2 far outweigh the disadvantages.
Filler Wires
The composition of the filler wire used for GMA
welding must match the base metal. For mild steel, you
should select mild steel wire; for aluminum, you should
select aluminum wire. Additionally, you should try to
select electrode wire that matches the composition of the
various metals you are welding. For instance, when you
are welding Type 308 aluminum, you should use an
ER-308L filler wire.
Wires are available in spools of several different
sizes. The wire varies in diameter from .020 to 1/8 of an
inch. You should select the proper diameter of wire
based on the thickness of the metal you are welding as
well as the position in which you are welding. Wires of
0.020,0.030, and 0.035 of an inch are generally used for
welding thin materials. You also can use them for welding low- and medium-carbon steels and low-alloy/highstrength steels of medium thicknesses. (See table 8-6.)
Medium thicknesses of metals are normally welded with
Regulators
You should use the same type of regulator and
flowmeter for gas metal-arc welding that you use for gas
tungsten-arc welding. The gas flow rates vary, depending on the types and thicknesses of the material and the
joint design. At times it is necessary to connect two or
8-17
wire-feed speed. This adjustment is limited to a definite
range, depending on the welding current used. (See table
8-6). The wire-feed speed is measured in inches per
minute (ipm). For a specific amperage setting, a high
wire-feed speed results in a short arc, whereas a low
speed produces a long arc. You use higher speeds for
overhead welding than with flat-position welding.
Personal Protective Equipment
0.045-inch or 1/16-inch diameter wires. For thicker
metals, larger diameter electrodes may be required.
As with any other welding process, SAFETY is
extremely important. A welding hood like the one used
in shielded metal-arc welding should be used for gas
metal-arc welding. The correct shade of lens depends on
the intensity of the arc. Chapter 3 provides a chart of
recommended lens shades based on the current setting
of the machine. Eye fatigue indicates you should use a
different shade of lens or there is leakage around the
protective filter glass.
As you learned earlier, the position of welding is a
factor that must be considered. For instance, when you
are welding in the vertical or overhead positions, you
normally use smaller diameter electrodes.
In addition to the welding hood, protective clothing,
such as gloves and an apron, should be worn. Bare skin
should never be exposed to the rays of the welding arc
because it could result in painful burns.
Figure 8-28.—Correct wire stick-out.
Special attention must be given to ensure the wire
is clean. Unsound welds result from the use of wire that
is contaminated by oil, grease, dust, or shop fumes. You
can obtain the best welding results with wire that has
just been taken out of its carton. Wire should be stored
in a hot locker or in a warm dry area, and should be kept
covered. If welding is stopped for a long period of time,
you should remove the wire and place it in its original
carton to prevent contamination.
TYPES OF GMA WELDING
When using the GMA welding process, metal is
transferred by one of three methods: spray transfer,
globular transfer, or short-circuiting transfer. The type
of metal transfer depends on the arc voltage, current
setting, electrode wire size, and shielding gas.
Spray-Arc Welding
WIRE STICK-OUT.— In gas metal-arc welding,
wire stick-out refers to the distance the wire extends
from the nozzle of the gun (fig. 8-28). The correct
amount of wire stick-out is important because it influences the welding current of the power source. Since the
power source is self-regulating, the current output is
automatically decreased when the wire stick-out increases. Conversely, when the stick-out decreases, the
power source is forced to furnish more current. Too little
stickout causes the wire to fuse to the nozzle tip, which
decreases the tip life.
Spray-arc transfer is a high-current range method
that produces a rapid disposition of weld metal. This
type of transfer is effective for welding heavy-gauge
metals because it produces deep weld penetration. The
use of argon or a mixture of argon and oxygen are
necessary for spray transfer. Argon produces a pinching
effect on the molten tip of the electrode, permitting only
small droplets to form and transfer during the welding
process. Spray transfer is useful when welding aluminum; however, it is not practical for welding light-gauge
metal.
For most GMA welding, the wire stickout should
measure from 3/8 to 3/4 of an inch. For smaller (micro)
wires, the stick-out should be between 1/4 and 3/8 of an
inch.
Globular Transfer
WIRE-FEED SPEED.— As we stated earlier, you
can adjust the wire-feed drive motor to vary the
Globular transfer occurs when the welding current
is low. Because of the low current, only a few drops are
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transferred per second, whereas many small drops are
transferred with a higher current setting. In this type of
transfer, the ball at the tip of the electrode grows in size
before it is transferred to the workpiece. This globule
tends to reconnect with the electrode and the workpiece,
causing the arc to go out periodically. This results in
poor arc stability, poor penetration, and excessive spatter.
GMA welding can actually lower material costs, since
you use less weld metal in the joint.
Equipment
The following suggestions are general and can be
applied to any GMA welding operation:
Check all hose and cable connections to make
sure they are in good condition and are properly
connected.
Globular transfer is not effective for GMA welding.
When it is used, it is generally restricted to thin materials
where low heat input is desired.
Check to see that the nozzle is clean and the
correct size for the particular wire diameter used.
Short-Circuiting Arc Transfer
Make sure that the guide tube is clean and that
the wire is properly threaded through the gun.
Short-circuiting arc transfer is also known as short
arc. Short arc was developed to eliminate distortion,
burn-through, and spatter when welding thin-gauge
metals. It can be used for welding in all positions,
especially vertical and overhead where puddle control
is more difficult. In most cases, it is used with current
levels below 200 amperes and wire of 0.045 of an inch
or less in diameter. Small wire produces weld puddles
that are small and easily manageable.
Determine the correct wire-feed speed and adjust
the feeder control accordingly. During welding,
the wire-speed rate may have to be varied to
correct for too little or too much heat input.
Make sure the shielding gas and water coolant
sources are on and adjusted properly.
Check the wire stick-out.
The shielding gas mixture for short-arc welding is
75% carbon dioxide and 25% argon. The carbon dioxide
provides for increased heat and higher speeds, while the
argon controls the spatter. Straight CO2 is now being
used for short-arc welding; however, it does not produce
the excellent bead contour that the argon mixture does.
GMA WELDING PROCEDURES
As with any other type of welding, the GMA welding procedure consists of certain variables that you must
understand and follow. Many of the variables have
already been discussed. This section applies some of
these variables to the actual welding procedure.
GMA WELDING PREPARATION
Starting the Arc
Preparation is the key to producing quality weldments with the gas metal-arc welding process. As in
GTA welding, the equipment is expensive; therefore,
you should make every effort to follow the manufacturer’s instruction manuals when preparing to use GMA
welding equipment.
Joints
For a good arc start, the electrode must make good
electrical contact with the work For the best results, you
should clean the metal of all impurities. The wire stickout must be set correctly because as the wire stick-out
increases, the arc initiation becomes increasingly difficulte
For the most part, the same joint designs recommended for other arc welding processes can be used for
gas metal-arc welding (refer to chapter 3). There are
some minor modifications that should be considered due
to the welding characteristics of the GMA process. Since
the arc in GMA welding is more penetrating and narrower than the arc for shielded metal-arc welding,
groove joints can have smaller root faces and root openings. Also, since the nozzle does not have to be placed
within the groove, less beveling of the plates is required.
When preparing to start the arc, hold the torch at an
angle between 5 and 20 degrees. Support the weight of
the welding cable and gas hose across your shoulder to
ensure free movement of the welding torch. Hold the
torch close to, but not touching, the workpiece. Lower
your helmet and squeeze the torch trigger. Squeezing the
trigger starts the flow of shielding gas and energizes the
welding circuit. The wire-feed motor does not energize
until the wire electrode comes in contact with the workpiece. Move the torch toward the work, touching the
wire electrode to the work with a sideways scratching
8-19
wire-feed dial slightly counterclockwise. This decreases
the wire-feed speed and increases the arc length. A
clockwise movement of the dial has the opposite effect.
With experience, you can recognize the sound of the
proper length of arc to use.
To break the arc, you simply release the trigger. This
breaks the welding circuit and de-energizes the wirefeed motor. Should the wire electrode stick to the work
when striking the arc or during welding, release the
trigger and clip the wire with a pair of side cutters.
Figure 8-29.—Striking the arc (GMAW).
Welding Positions
motion, as shown in figure 8-29. To prevent sticking,
you should pull the torch back quickly, about 1/2 of an
inch—the instant contact is made between the wire
electrode and the workpiece. The arc strikes as soon as
contact is made and the wire-feed motor feeds the wire
automatically as long as the trigger is held.
In gas metal-arc welding, the proper position of the
welding torch and weldment are important. The position
of the torch in relation to the plate is called the work and
travel angle. Work and travel angles are shown in figure
8-30. If the parts are equal in thickness, the work angle
should normally be on the center line of the joint;
however, if the pieces are unequal in thickness, the torch
should angle toward the thicker piece.
A properly established arc has a soft, sizzling sound.
Adjustment of the wire-feed control dial or the welding
machine itself is necessary when the arc does not sound
right. For example, a loud, crackling sound indicates
that the arc is too short and that the wire-feed speed is
too fast. You may correct this problem by moving the
The travel angle refers to the angle in which welding
takes place. This angle should be between 5 and 25
degrees. The travel angle may be either a push angle or
a drag angle, depending on the position of the torch.
Figure 8-30.—Travel and work angle for GMA welding.
8-20
For the best results, you should position the weldment in the flat position. ‘This position improves the
molten metal flow, bead contour, and gives better shielding gas protection.
After you have learned to weld in the flat position,
you should be able to use your acquired skill and knowledge to weld out of position. These positions include
horizontal, vertical-up, vertical-down, and overhead
welds. The only difference in welding out of position
from the fiat position is a 10-percent reduction in amperage.
When welding heavier thicknesses of metal with the
GMA welding process, you should use the multipass
technique (discussed in chapter 3). This is accomplished
by overlapping single small beads or making larger
beads, using the weaving technique. Various multipass
welding sequences are shown in figure 8-32. The numbers refer to the sequences in which you make the
passes.
Figure 8-31.—Pulling and pushing travel angle techniques.
When the torch is ahead of the weld, it is known as
pulling (or dragging) the weld. When the torch is behind
the weld, it is referred to as pushing the metal (fig. 8-31).
Common Weld Defects
The pulling or drag technique is for heavy-gauge
metals. Usually the drag technique produces greater
penetration than the pushing technique. Also, since the
welder can see the weld crater more easily, better quality
welds can consistently be made. The pushing technique
is normally used for light-gauge metals. Welds made
with this technique are less penetrating and wider because the welding speed is faster.
Once you get the feel of welding with GMA equipment, you will probably find that the techniques are less
difficult to master than many of the other welding processes; however, as with any other welding process,
GMA welding does have some pitfalls. To produce good
quality welds, you must learn to recognize and correct
possible welding defects. The following are a few of the
more common defects you may encounter along with
corrective actions that you can take.
Figure 8-32.—Multipass welding.
8-21
section, we discuss some of the welding methods associated with a few of the more commonly welded metals.
SURFACE POROSITY.— Surface porosity usually results from atmospheric contamination. It can be
caused by a clogged nozzle, shielding gas set too low or
too high, or welding in a windy area. To avoid surface
porosity, you should keep the nozzle clean of spatter, use
the correct gas pressure, and use a protective wind shield
when welding in a windy area.
Carbon Steels
The majority of welding by all methods is done on
carbon steels. When you are using GMA to weld carbon
steels, both the spray-arc and short-arc methods may be
applied. For spray-arc welding, a mixture of 5-percent
oxygen with argon is recommended. As we mentioned
earlier, this mixture provides a more stable arc. Also you
may use a mixture of argon and CO2 or straight CO2.
Straight CO2 is often used for high-speed production
welding; however, with CO2 the arc is not a true spray
arc. For short-arc welding, a 25-percent CO2 and 75-percent argon mixture is preferred.
CRATER POROSITY.— Crater porosity usually
results from pulling the torch and gas shield away before
the crater has solidified. To correct this problem, you
should reduce the travel speed at the end of the joint.
You also may try reducing the tip-to-work distance.
COLD LAP.— Cold laps often result when the arc
does not melt the base metal sufficiently. When cold lap
occurs, the molten puddle flows into an unwelded base
metal. Often this results when the puddle is allowed to
become too large. To correct this problem, you should
keep the arc at the leading edge of the puddle. Also,
reduce the size of the puddle by increasing the travel
speed or reducing the wire-feed speed. You also may use
a slight whip motion.
For GMA welding of thin materials (0.035 inch to
1/8 inch), no edge preparation is needed and a root
opening of 1/16 of an inch or less is recommended. For
production of adequate welds on thicker material, some
beveling is normally required. When welding plates 1/4
of an inch or greater in thickness, you should prepare a
single or double-V groove with 50- to 60-degree included angle(s).
LACK OF PENETRATION.— Lack of penetration usually results from too little heat input in the weld
zone. If the heat input is too low, increase the wire-feed
speed to get a higher amperage. Also, you may try
reducing the wire stick-out.
Aluminum
The joint design for aluminum is similar to that of
steel; however, aluminum requires a narrower joint
spacing and lower welding current setting.
BURN-THROUGH.— Burn-through (too much
penetration) is caused by having too much heat input in
the weld zone. You can correct this problem by reducing
the wire-feed speed, which, in turn lowers the welding
amperage. Also you can increase the travel speed. Burnthrough can also result from having an excessive
amount of root opening. To correct this problem, you
increase the wire stick-out and oscillate the torch
slightly.
The short-arc welding method is normally used for
out-of-position welding or when welding thin materials
because short-arc produces a cooler arc than the spray
type arc. When welding thinner material (up to 1 inch in
thickness), you should use pure argon.
The spray-arc welding method is recommended for
welding thicker materials. With spray arc, more heat is
produced to melt the wire and base metal. When you are
welding thicker material (between 1 and 2 inches) a
mixture of 90-percent argon and 10-percent helium is
recommended. The helium provides more heat input and
the argon provides good cleaning action.
WHISKERS.— Whiskers are short pieces of electrode wire sticking through the root side of the weld
joint. This is caused by pushing the wire past the leading
edge of the weld puddle. To prevent this problem, you
should cut off the ball on the end of the wire with side
cutters before pulling the trigger. Also, reduce the travel
speed and, if necessary, use a whipping motion.
Stainless Steel
DCRP with a 1- or 2-percent oxygen with argon
mixture is recommended for most stainless steel welding. In general, you weld stainless steel with the sprayarc welding method and a pushing technique. When
welding stainless steel up to 1/1 6 of an inch in thickness,
you should use a copper backup strip. For welding thin
materials in the overhead or vertical positions, the shortarc method produces better results.
GMA WELDING COMMON METALS
You can use the welding equipment and techniques
for gas metal-arc welding to join all types of metals;
however, as we discussed in the GTAWprocess, each of
the metals requires a unique welding method. In this
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