WELDING OPERATIONS, I SUBCOURSE EDITION OD1651

WELDING OPERATIONS, I SUBCOURSE EDITION OD1651
SUBCOURSE
OD1651
EDITION
8
WELDING OPERATIONS, I
WELDING OPERATIONS, I
SUBCOURSE NO. OD1651
United States Army Combined Arms support Command
Fort Lee, Virginia 23801-1809
6 Credit Hours
GENERAL
The purpose of this course is to introduce
involved in metal-arc welding operations.
the
basic
requirements
The scope of this subcourse consists of describing the classification
of electrodes and their intended uses; describing automotive welding
processes, materials and identification processes; describing the
methods of destructive and nondestructive testing of welds and
troubleshooting procedures; describing the type and techniques of joint
design; and describing the theory, principles, and procedures of
welding armor plate.
Six credit
subcourse.
Lesson 1
hours
are
awarded
for
successful
completion
of
this
ELECTRODES CLASSIFICATION AND INTENDED USES; AUTOMOTIVE
WELDING
PROCESSES,
MATERIALS,
AND
IDENTIFICATION
PROCESSES; METHODS OF DESTRUCTIVE AND NONDESTRUCTIVE
TESTING OF WELDS AND TROUBLESHOOTING PROCEDURES; TYPES
AND TECHNIQUES OF JOINT DESIGN; AND THE THEORY,
PRINCIPLES, AND PROCEDURES OF WELDING ARMOR PLATE
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WELDING OPERATIONS I - OD1651
TASK 1: Describe the processes for identifying
electrodes by classification, and intended uses; and
the automotive welding processes, materials, and
identification
processes;
and
the
types
and
techniques of joint design.
TASK
2:
Describe
the
theory,
principles,
and
procedures of welding armor plate; and methods of
destructive and nondestructive testing of welds, and
troubleshooting procedures.
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WELDING OPERATIONS I - OD1651
TABLE OF CONTENTS
Section
Page
TITLE..........................................................
i
TABLE OF CONTENTS..............................................
iii
Lesson 1:
ELECTRODES CLASSIFICATION AND
INTENDED USES, AUTOMOTIVE WELDING
PROCESSES, MATERIALS, AND
IDENTIFICATION PROCESSES; METHODS
OF DESTRUCTIVE AND NONDESTRUCTIVE
TESTING OF WELDS AND
TROUBLESHOOTING PROCEDURES; TYPES
AND TECHNIQUES OF JOINT DESIGN; AND
THE THEORY, PRINCIPLES, AND
PROCEDURES OF WELDING ARMOR
PLATE..............................................
1
Task 1: Describe the processes for
identifying electrodes by classification,
and intended uses; and the automotive
welding processes, materials, and
identification processes; and the types
and techniques of joint design............................
1
Task 2: Describe the theory, principles,
and procedures of welding armor plate; and
methods of destructive and nondestructive
testing of welds, and troubleshooting
procedures................................................
61
Practice Exercise 1............................................
103
Answers to Practice Exercise 1.................................
105
REFERENCES.....................................................
107
iii
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
LESSON 1
ELECTRODES CLASSIFICATION AND
INTENDED USES; AUTOMOTIVE WELDING PROCESSES,
MATERIALS, AND IDENTIFICATION PROCESSES;
METHODS OF DESTRUCTIVE AND NONDESTRUCTIVE
TESTING OF WELDS AND TROUBLESHOOTING PROCEDURES;
TYPES AND TECHNIQUES OF JOINT DESIGN; AND
THE THEORY, PRINCIPLES, AND PROCEDURES OF
WELDING ARMOR PLATE
TASK 1.
Describe the processes for identifying
electrodes by classification, and intended
uses; and the automotive welding
processes, materials, and identification
processes; and the types and techniques of
joint design.
CONDITIONS
Within a self-study environment and given the subcourse text, without
assistance.
STANDARDS
Within three hours
REFERENCES
No supplementary references are needed for this task.
1.
Introduction
Welding is one of the most important functions performed in both an
intermediate direct support (IDS) and intermediate general support
(IGS) maintenance company.
Experience gained during the second world
war revealed that many broken parts can be welded and put back into
service, thus often saving the expense of fabricating or purchasing a
new piece of equipment.
As a result of this experience, a service
section containing a metalworking shop with welding capabilities is now
established within these maintenance organizations.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
The first task of this lesson is designed to assist you in
learning
the
processes
for
identifying
electrodes
by
classification,
and
intended
uses;
the
automotive
welding
processes, materials, and identification processes, and the
techniques of joint design as they pertain to electric arc
welding.
2.
Identification and Uses of Electrodes
a.
General. During electric arc welding operations, when molten
metal is exposed to the atmosphere, it will absorb oxygen and
nitrogen from the air and will become brittle.
To protect it
from this damaging reaction, a slag cover over the molten or
solidifying metal must be provided.
This cover is made by
coating the electrode with a substance that will vaporize and
defuse in the arc stream to form a protective cover that will
stabilize the arc and protect the metal.
Because there are
several different types of metals used in Army equipment, it is
necessary to use the correct electrode whenever welding this
equipment.
The
following
subparagraphs
describe
the
classification of electrodes, their intended uses, and the
factors to be considered when selecting electrodes.
b.
Factors in Selecting an Electrode. The purpose of selecting
the correct type electrode is to provide arc stability,
smoothness of the weld bead, easy slag removal, and minimum
spatter that are essential to top quality welding. Factors to be
considered when selecting electrodes are:
(1) Specific metal properties required in the weld such
corrosion resistance, ductility, or high tensile strength.
as
(2) Type of base metal to be welded.
(3) Position of the weld, such as flat or vertical.
(4) The type of electrical current that is available.
(5) Electric current polarity (straight or reverse) which is
available.
(6) Dimensions of the section to be welded.
(7) The type of fit that the work permits.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
c.
Classification of Electrodes.
(1) Metal-arc electrodes may be grouped and classified as bare
electrodes, thinly coated electrodes, and shielded-arc or heavy
coated electrodes.
A classification number series, (formulated
by the American Welding Society), has been adopted by the welding
industry for the identification of electrodes. By means of this
numbering system, the following characteristics of a given
electrode can be identified:
(a) Whether the electrode has a light or heavy coating.
(b) The composition of the coating.
(c) The recommended welding position.
(d) The type of electric current (direct or alternating
current) and the polarity for which the electrode is intended.
(e) The base metal for which the electrode is recommended.
(2) The identification system for steel arc welding electrodes
is a four digit number series preceded by a letter as described
below:
(a) The symbol E indicates that the electrode is intended for
use in electrical welding.
(b) The first two (or three) digits of the number indicate the
tensile strength (the resistance of the material to forces trying
to pull it apart), in thousands of pounds per square inch, of the
deposited metal.
(c) The third (or fourth) digit indicates the position of the
weld.
The number 0 in either one of these positions indicates
the classification is not used.
The number 1 indicates the
electrode may be used for all welding positions.
The number 2
indicates that the electrode may be used only in the flat and
horizontal positions. The number 3 indicates the electrode is to
be used only in the flat welding position.
(d) The fourth (or last) digit indicates the type of coating on
the electrode, and the power supply (either alternating current
(ac) or direct
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
current (dc), straight polarity (sp), or reverse polarity (rp))
to be used with the pertinent electrode.
(e) A listing of the types of coatings, welding currents, and
polarity requirements of the fourth (or last) identifying digit
of the electrode is listed below.
(f) The number E6010 identifies an electric welding electrode
with a minimum stress relieved tensile strength of 60,000 psi
(pounds per square inch).
It can be used to weld in all
positions, preferably using direct current reverse polarity
electricity.
However, alternating current and direct current
straight polarity can also be used.
(3) The electrode identification
arc-welding is set up as follows:
system
for
stainless
steel
(a) The symbol E indicates electric welding.
(b) The first three digits indicate the American Iron and Steel
Institute type of stainless steel.
(c) The last two digits indicate the current and the welding
position in which it is used.
(d) According to this system, the number E-308-16 identifies a
stainless steel electrode type 308, for use with alternating or
reverse polarity direct current in all welding positions.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
d.
Types of Electrodes.
There are three different types of
electrodes.
They are: bare, thinly coated, and shielded-arc or
heavy-coated electrodes.
(1) Bare Electrodes.
Bare electrodes are made of wire
compositions required for specific applications and have no
coatings other than those required in wire drawing.
These wire
drawing coatings have some slight stabilizing effect on the arc,
but are otherwise of no consequence.
Bare electrodes are used
for welding manganese alloy steel, and other purposes where a
coated electrode is not required or is undesirable.
A
diagrammatic sketch of the transfer of metal across the arc of a
bare electrode is shown in figure 1, view A, on the following
page.
(2) Thinly Coated Electrodes.
(a) Thinly coated electrodes are made of a wire of a definite
composition.
A thin coating is applied on the surface of the
electrode by washing, dipping, brushing, spraying, tumbling, or
wiping to improve the stability and characteristics of the arc
stream.
They are listed under the E45 series in the electrode
identification system described in paragraph 2c, beginning on
page 3.
(b) The coating on these types of electrodes generally serves
the functions described below:
1 It dissolves or reduces impurities, such as oxides, sulfur,
and phosphorous, and thus keeps impurities out of the weld
deposit.
2 It reduces the adhesive force between the molten metal and
the end of the electrode, or changes the surface tension of the
molten metal so that the globules of metal leaving the end of the
electrode are smaller and more frequent, thus making the flow of
molten metal more uniform and continuous.
3 It increases the stability of the arc by introducing
materials readily ionized into the arc stream.
That is, the
coating fuels the arc by providing smaller particles when the
electric charge occurs.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 1.
BARE ELECTRODE MOLTEN METAL
TRANSFER AND LIGHT COATED
ELECTRODE ARC ACTION.
(c) Some of the light coatings may produce a slag, but it is
quite thin and does not act in the same manner as the shieldedarc, slag-type electrode.
The action of an arc obtained with a
light-coated electrode is shown in figure 1, view B.
(3) Shielded-arc or Heavy-coated Electrodes.
Shielded-arc or
heavy-coated electrodes are used for welding steels and cast
iron. The arc action obtained with a shield-arc or heavy-coated
electrode is shown in figure 2, view A, on the following page.
This type of electrode is made of wire with a thick coating which
has been applied by
6
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 2.
ARC ACTION AND ELECTRIC
WELDING POLARITY.
dipping, extrusion, or other suitable process.
The electrodes
are manufactured with three general types of coatings: cellulose,
mineral, and combinations of mineral and cellulose coating.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(a) The cellulose-coated types are composed of soluble cotton
or other forms of cellulose with a small amount of potassium,
sodium, or titanium and, in some cases, other minerals.
This
coating provides protection to the molten or solidifying metal by
developing a gaseous zone around the arc and a slag deposit over
the weld.
(b) The mineral coatings consist of sodium silicate, metallic
oxides, clay, and other inorganic substances or combinations
thereof.
With the mineral-coated electrode, protection to the
molten or solidifying metal is provided only by a slag deposit.
(c) The combination of a mineral and cellulose coating is
composed of various quantities of the substances previously
described for each of these coatings.
These coatings provide
various protection effects to the arc, and to the molten or
solidifying metal, depending on the type of base metal being
welded.
e.
Functions of Electrode Coatings. Some of the more important
functions of the coatings on the shielded-arc or heavy-coated arc
electrodes are described in the following subparagraphs.
(1) The coatings produce a reducing or nonoxidizing atmosphere
around the arc; thus, preventing the contamination of the metal
in the arc by oxygen and nitrogen from the air.
Without this
coating, the oxygen would readily combine with the molten metal,
remove alloying elements from the metal, and cause porosity and
oxidation of the weld. The nitrogen would cause brittleness, low
ductility and, in some cases, low strength and poor resistance to
corrosion.
(2) The coatings reduce impurities such as oxides, sulfur, and
phosphorous so that these impurities will not impair the weld
deposit.
(3) They provide substance to the arc, which tend to increase
its stability, so that the arc can be maintained without
excessive spattering.
(4) Coatings reduce the attractive force between the molten
metal and the end of the electrode, and reduce the surface
tension of the molten metal. Vaporized and melted coatings cause
the molten
8
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
metal (at the end of the electrode) to break up into fine small
particles.
(5) The coatings contain ingredients such as silicates that,
when melted, form a slag over the melted weld and base metal.
Since the slag solidifies at a relatively slow rate, it holds the
heat and allows the underlying metal to cool and solidify slowly.
This slow solidification of the metal precludes the trapping of
gases within the weld and permits solid impurities to float to
the surface.
Slow cooling also has an annealing effect on the
weld deposit.
(6) The physical characteristics of the weld deposit are
modified by incorporating alloying materials in the electrode
coating.
Also, the fluxing action of the slag will produce a
weld of a better quality and permit welding at higher speeds.
(7) The coating insulates the sides of the electrode so that
the arc, at the end of the electrode, is concentrated into a
confined area.
This facilitates welding in a deep "U" or "V"
groove.
(8) The coating produces a cup, cone, or sheath, as shown in
figure 2, view A, on page 7, at the tip of the electrode, which
acts as a shield, concentrates and directs the arc, reduces heat
losses, and increases the temperature at the end of the electrode.
f.
Polarity of Welding Current (figure 2, view B).
(1) The electrode
manufacturer should
is being used. The
or "reverse."
In
negative side of
electrode is in the
polarity recommendations established by the
be followed when a specific type of electrode
polarity recommended may be either "straight"
straight polarity, the electrode is in the
the circuit.
With reverse polarity, the
positive side of the circuit.
(2) In general, straight polarity is used for all mild-steel,
bare, or lightly coated electrodes.
With electrodes of this
type, the greater heat is developed at the workpiece being welded
which is the positive side of the current. However, when heavycoated electrodes are used, the gases given off in the arc may
alter the heat conditions so
9
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
that the opposite is true and the greater heat is produced on the
negative side.
Electrode coatings affect the heat conditions
differently, depending on their composition.
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.
(3) 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.
(4) The proper polarity for a given electrode can be recognized
when attempting a weld by the sharp, cracking sound of the arc.
The wrong polarity will cause the arc to emit a hissing sound and
the welding bead will be difficult to control.
g.
Direct Current Arc-welding Electrodes.
(1) In general, direct current (dc), shielded-arc electrodes
are designed either for reverse polarity (electrode positive) or
for
straight
polarity
(electrode
negative)
and
are
not
interchangeable.
Many, but not all, of the direct current
electrodes, both reverse and straight polarity, also can be used
with alternating current.
Direct current is preferred for many
types of bare and covered nonferrous and alloy steel electrodes.
These electrodes are used when ferrous welds are to be made in
horizontal, vertical, or overhead positions.
Recommendations
from electrode manufacturers include the type of base metal for
which given electrodes are suitable.
(2) In most cases, straight polarity electrodes (electrode
negative) will provide less penetration than the reverse polarity
electrodes (electrode positive) and, for this reason, will permit
greater welding speed.
Good penetration can be obtained with
either type under proper welding conditions and arc manipulation.
h.
Alternating Current Arc-welding Electrodes.
(1) Coated electrodes that can be used with either direct or
alternating current are available.
Alternating current is more
desirable under certain operating conditions.
Alternating
current reduces
10
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
arc blow (an unstable arc condition) that is particularly harmful
when welding in corners or restricted places and when high
currents, as required in thick sections, are used. Arc blow, in
these cases, causes blowholes and slag inclusions in the weld as
well as a lack of fusion.
(2) Alternating current is used in atomic hydrogen welding, and
in those carbon-arc processes that require the use of two carbon
electrodes, in order that a uniform rate of welding and electrode
consumption may be accomplished.
In carbon-arc processes, where
one carbon electrode is used, straight polarity with direct
current is recommended because the electrode is thus consumed at
a slower rate.
i.
Electrode Defects and their Effects.
(1) If certain elements, or their oxides, are present in
electrode coatings, they will materially effect the stability of
the arc.
If these impurities are present in considerable
quantities of light or heavy coatings, the electrodes will not be
able to compensate for defects in the wire. In bare electrodes,
because there is almost no coating on the wire, the composition
and uniformity of the wire is an important factor in the control
of arc stability.
Impurities in the wire can cause the arc to
become unstable.
(2) Aluminum or aluminum oxide, even when present in quantities
not exceeding 0.01 percent, will cause the arc to become
unstable.
Silicon, silicon dioxide, and iron sulfate also tend
to make the arc unstable.
But, iron oxide, manganese oxide,
calcium oxide, and iron sulfide tend to stabilize the arc.
(3) When phosphorous or sulfur are present in excess of 0.04
percent, they will impair the weld metal because they are
transferred from the electrode to the molten metal. Phosphorous
causes grain growth, brittleness, and "cold shortness" (brittle
when below red heat) in the weld, and these defects increase in
magnitude as the carbon content of the steel increases.
Sulfur
acts as a slag, breaks up the soundness of the weld metal, and
causes "hot shortness" (brittle when above red heat). Sulfur is
particularly harmful to bare, low-carbon steel electrodes with a
low manganese
11
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
content.
Manganese promotes the formation of sound welds.
(4) If the heat treatment given the wire core of an electrode
is not uniform, the electrode will produce welds inferior to
those produced with an electrode of the same composition which
has been properly heat treated.
(5) This completes the discussion of classifying types and uses
of electrodes.
The succeeding paragraphs describe the welding
processes, materials, and identification processes of automotive
welding.
3.
Automotive Welding Processes, Materials, and Identification
a.
Determining Weldability of Equipment.
Before repairing any
damaged materiel, it is necessary to first determine whether or
not
the
material
can
be
satisfactorily
welded.
This
determination can be made by considering the following factors:
(1) The nature and extent of the damage and the amount
straightening and fitting of the metal that will be required.
of
(2) The possibility of restoring the structure to an operable
condition without welding it.
(3) The type of metal used in the damaged part, whether it was
heat treated, and if so, what heat treatment was used.
(4) If the welding heat will distort the shape or in any manner
impair the physical properties of the part to be repaired.
(5) Determine if heat treating or other equipment or materials
will be required in order to make the repair by welding.
b.
Determining Weldable Parts.
Welding operations on Army
materiel are restricted largely to those parts whose essential
physical properties are not impaired by the welding heat.
Successful welded repairs cannot be made on machined parts that
carry a dynamic load.
This applies particularly to high alloy
steels that are heat treated for hardness or toughness, or both.
Machined parts such as gears, shafts, anti-friction bearings,
springs, connecting
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
rods, pistons, valves, and cams are considered unsuitable for
field welding. The principal reason for this is that these parts
have been previously heat treated to create desirable performance
characteristics (hardness or toughness); welding heat alters or
destroys these characteristics.
c.
Determining the Welding Method. Automotive equipment such as
trucks,
tanks,
truck-tractors,
and
other
vehicles,
are
constructed from a large variety of metals that are heat treated
under various processes.
The metals used include copper alloys
of various types, carbon and alloy steels, titanium, aluminum,
magnesium, lead, among others.
The principal joining processes
that may be used are oxyacetylene, arc welding, brazing, and
soldering.
Oxyacetylene welding is used for welding of thin
metals and brazing of cast iron parts on automotive equipment,
while soldering is used for repairing such parts as fuel tanks,
radiators, and electrical connections.
This lesson, however,
concentrates on the arc welding processes for repair of
automotive equipment.
For further information pertaining to
oxyacetylene gas welding and soldering, refer to TM 9-237.
The
following subparagraphs describe weldable automotive parts and
the methods of repair.
This listing is an extract.
A more
complete list of repairable parts can be found in Tables B-2 and
B-3 of TM 9-237.
(1) Cast Iron, Cast Steel, Carbon Steel, and Forgings.
Generally, parts composed of these metals can be repaired by the
same procedure as that used for their assembly or by brazing or
soldering if the joining equipment originally used is not
available or suitable for the purpose.
For example, cast iron
and cast steel may be repaired by gas welding, arc welding, or by
brazing.
Parts or sections made of carbon steel originally
assembled by spot, projection, or flash welding may be repaired
by gas or arc welding. This same procedure is true of forgings.
(2) Cast Iron Engine Blocks (figure 3, on the following page).
(a) General.
Engine blocks may be repaired by welding or
brazing in the field only under extreme emergency conditions and
if a replacement block is not available.
Welding or brazing of
engine blocks is limited to those areas described below:
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 3.
PREPARING ENGINE BLOCK
FOR WELDING.
1 Accessory mounts such as generator, starter, or engine
mounts.
Because of possible warpage, mount alignment must be
checked after welding.
2 Small sand pits (casting defects) detected at time of ovl
usually be too porous and must be removed and the weld repeated
until a sound first pass is obtained.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(b) Procedure.
Both the shielded metal-arc method and brazing
with oxyacetylene may be used for repair of cracks in cast iron
engine blocks.
When using the shielded metal-arc method of
repair, a welding rod with a high nickel content of at least 50
to 60 percent must be used. Cracks in a cast iron engine block
must be properly prepared prior to welding, otherwise (after
cooling), the weld deposit shrinks, which pulls the crack
together and results in the formation of internal stress.
This
stress finally relieves itself by cracking due to continued
vibration during engine operation. Subsequent paragraphs provide
the steps that should be followed to eliminate this stress and
effectively repair the crack.
1 Drill a 1/8 inch diameter hole 1/4 inch beyond each end of
the crack as shown in figure 3, view A, on the previous page.
2 Clean and groove the crack and remove the "as cast" surface
or skin by grinding or machining.
3 Preheat the casting by baking or locally heating the
casting at 1000° Fahrenheit for a few minutes to remove all
moisture.
(It is imperative that all moisture be removed,
otherwise the weld will not adhere to the base metal.)
4 Drill and tap a hole to receive a 1/4 inch bolt in the
center of the crack as shown in figure 3, view B.
Screw and
tighten a bolt slightly deeper than the thickness of the base
metal. Stake the sides of the bolt with a center punch so that
it will not back out, and cut off the bolt as shown in figure 3,
view C.
5 Weld the crack using the backstep method shown in figure 3,
view D, and peen each bead with a round nose tool.
6 The minimum preheat and interpass temperature should not be
below 400° to 500° F when using a nickel rod, and the weld should
not be allowed to cool when applying more than one pass. If all
the impregnated oil or gas is not eliminated during preheating,
the first pass will usually be too porous and must be removed and
the weld repeated until a sound first pass is obtained.
7 Allow the completed weld to cool
asbestos blanket over the welded area.
slowly
by
placing
an
15
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
Nonuniform or rapid cooling will create internal stresses.
Welded engine blocks must be leak tested before placing them back
in operation. Leak testing procedures are specified in TM 9-237.
(3) Heat Treated Parts.
(a) The functions performed by certain parts in automotive
equipment require heat treatment during their manufacture.
Welding of these parts should not be attempted unless the repair
shop is equipped with suitable heat treating equipment for
handling these parts after welding.
(b) In some cases, alloy steels, or specially treated parts,
may be repaired by using a heat affected zone that is weaker than
the original heat treated part. In general, where it is possible
to heat treat the parts after welding, they should be annealed
prior to welding them.
Filler metal of the same composition or
properties as the base metal should be used, and the parts heat
treated after welding.
(c) In cases where the part to be welded is in a heat treated
condition, a stainless steel filler rod and the transition bead
welding method may be used as described below:
1 Deposit a layer of stainless steel (25 percent chromium, 20
percent nickel, or modified 18 percent chromium, 8 percent nickel
stainless steel rod) on the surfaces of the broken edges.
2 Weld the prepared edges with mild steel or high strength
filler metal.
Use 11 to 14 percent manganese or high strength
filler metal on the stainless steel layer instead of mild steel
where hardness and toughness are required. The weld then may be
covered with a layer of hard surfacing metal.
(d) These methods are useful in the field, but should be used
under emergency conditions only.
(4) Wheel Vehicle Components.
(a) Frames. The repair of frames by welding is not authorized.
Crossmembers and horns for the frame may be straightened,
repaired, and reinforced.
A commonly used method of repairing
and strengthening a broken or weakened crossmember or horn is
performed by using reinforcing plates as
16
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
shown in figure 4. This method of repair should be followed when
reinforcement plates are welded to angles, tees, box sections, or
I-beams.
The type of reinforcement selected depends on the
location of the repair and possible interference with the
FIGURE 4.
REINFORCING FRAME MEMBERS.
17
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
operation of components.
All protrusions should be ground down
flush before reinforcing plates are applied.
Reinforcement
plates should be approximately the same thickness as the frame
section and the width sufficient to bring the weld flush with the
top and bottom sections of the channel. It should be noted that
the welded ends of the plates produce heat affected areas of
decreased strength across the back and legs of the channel.
(b) Front Axles.
Front axles are made of heat treated alloy
drop forgings.
Repairs by welding should not be made on these
axles except as a temporary measure under extreme emergency
conditions.
(c) Rear Axle Housings.
These components are made of welded
pressed steel or malleable cast iron or cast steel. The pressed
steel and cast steel housings can be arc welded.
The malleable
iron housings should be repaired by brazing; although, they can
be welded if extreme precautions are maintained. Castings should
be kept clean in the vicinity of the weld.
(d) Drive Shafts.
Drive shafts are usually made of medium
carbon steel seamless tubing and are readily weldable by either
arc or gas welding.
(e) Machined Alloy Steel Parts.
These type parts such as
crankshafts, connecting rods, gears, and axle drive shafts are
not generally repaired by welding because the heat of welding
will impair the metal qualities produced by previous heat
treatment.
(f) Radiators.
Radiators can be repaired with an oxyacetylene
welding torch containing a proper tip, common 50-50 solder, and
flux. The oxyacetylene flame should be adjusted to give a slight
carburizing mixture.
The areas around the leaks in the copper
tubes should be thoroughly cleaned, preferably with a 5 percent
solution of hydrochloric acid, and tinned before the joint is
made in order to ensure a tight joint. For leaks between copper
and cast iron, the surface of the iron should be pickled before
the repair is made. Pickling the surface of the iron is done by
applying a 5 percent hydrochloric acid solution to it at the
joint and heating it until thoroughly cleaned.
18
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(5) Combat Vehicles. Tank hulls are constructed of armor plate
for protection of the crew and to which the internal and external
mechanisms of the tank are fastened to the hull. The suspension
system consists largely of castings and forgings.
Various
castings are used throughout the powertrain.
Component parts
that do not carry the driving power load can be repaired by
welding. In general, the repair of these parts requires special
precautions such as preheating, postweld heat treatments, and the
proper welding procedure. One of the principal repairs performed
on combat vehicles is welding damage sections of armor plate.
The technique for welding armor plate will be discussed in Task
2. The following paragraphs describe the type and techniques of
joint design.
4.
Welding Joint Design
a.
General.
The properties of a welded joint depend partly on
the correct preparation of the edges being welded.
The joint
edges should be cleaned of all rust, oxides and other impurities,
and prepared to permit fusion without excessive melting.
This
preparation is governed by the form, thickness, kind of metal,
the load to be supported, and the available means for preparing
the joint.
b.
Types of Joints.
There are basically five types of joints
used to weld various forms of metal.
These types of joints are
described in the following subparagraphs.
(1) Butt Joint (figure 5 on the following page).
This type
joint is used for joining the edges of two plates or surfaces
located approximately in the same plane.
Plain square butt
joints for thin metal sections are shown in figure 5, view A.
These joints are used for butt welding light sheet metal.
Butt
joints for heavy sections with several types of edge preparation
are shown in figure 5, views B through E.
These edges can be
prepared by flame cutting, shearing, flame grooving, machining,
chipping, or grinding. Plate thicknesses of 3/8 to 1/2 inch can
be welded using the single V or single U joints as shown in
figure 5, views B and C. The edges of heavier sections should be
prepared as shown in figure 5, views D and E. In general, butt
joints prepared from both sides permit easier welding, produce
less distortion, and ensure better weld metal qualities in heavy
sections than joints prepared from one side only.
19
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 5.
BUTT JOINTS.
(2) Corner Joint (figure 6, views A through D, on the following
page).
This type joint is used to join two members located
approximately at right angles to each other in the form of an L.
The fillet weld corner joint, shown in figure 6, view A, is used
in the construction of boxes, box frames, tank containers and
similar fabrications.
The closed corner joint, shown in figure
6, view B, is used on lighter sheets when high strength is not
required at the joint.
When using oxyacetylene welding, the
overlapping edge is melted down and
20
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 6.
CORNER, EDGE, LAP, AND
TEE JOINTS.
little or no filler metal is added. In arc welding, only a very
light bead is required to make the joint. The open corner joint,
shown in figure 6, view C, is used on heavier sheets and plates;
the two edges are melted down and filler metal is added to fill
up the corner.
Corner joints on heavy plates are welded from
both sides as shown in figure 6, view D.
The joint is first
welded from the outside, then reinforced from the back side with
a seal bead.
21
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(3) Edge Joint (figure 6, views E, F, and G on the previous
page).
This type joint is used to join two or more parallel
members such as edges of sheet metal, angles, mufflers, liquid
tank containers, assembly housings, and reinforcing plates in
flanges of I beams.
Two parallel plates are joined together as
shown in figure 6, view E.
On heavy plates, sufficient filler
metal is added to fuse or melt each plate edge completely and to
reinforce the joint. Light sheets are welded as shown in figure
6, view F.
No preparation is necessary other than to clean the
edges and tack weld them in position.
The edges can then be
fused together without filler metal required.
The heavy plate
joint shown in figure 6, view G, requires that the edges be
beveled for good penetration and fusion of the side walls.
Filler metal is used in this joint.
(4) Lap Joint (figure 6, views H, I, and J).
This type of
joint is used to join two overlapping members.
A single lap
joint, where welding must be done from one side, is shown in
figure 6, view H. The double lap joint shown in figure 6, view
I, is welded on both sides and develops the full strength of the
welded members. The offset lap joint shown in figure 6, view J,
is used where two overlapping plates must be joined and welded in
the same plane. The offset lap joint is stronger than the single
lap type, but is more difficult to prepare.
(5) Tee Joint.
Tee joints are used to weld two plates or
sections whose surfaces are located approximately 90 degrees to
each other at the joint.
A plain tee joint welded from both
sides is shown in figure 6, view L. A plain tee joint, requiring
only cleaning the end of the vertical plate and the surface of
the horizontal plate, is shown in figure 7, view A, on the
following page.
The single bevel joint shown in figure 7, view
B, is used in plates and sections up to 1/2 inch thick.
The
double bevel joint shown in figure 7, view C, is used on heavy
plates that can be welded from both sides.
The single J joint
shown in figure 7, view D, is used for welding plates 1 inch
thick or heavier where welding is done from one side. The double
J joint shown in figure 7, view E, is used for welding very heavy
plates from both sides.
22
WELDING OPERATIONS I – OD1651 - LESSON 1/TASK 1
FIGURE 7.
TEE JOINT EDGE PREPARATION.
c.
Types of Welds.
The type of weld used will determine the
manner of seam, joint, or surface preparation. A listing of the
different welds used is provided in the following subparagraphs.
(1) Groove Weld (figure 8 on the following page).
These are
welds that are made in a groove between two members to be joined.
In this position, the axis of the weld lies approximately in a
horizontal plane and the face of the weld lies approximately in a
vertical plane.
(2) Surfacing Weld (figure 9 on page 25).
This type weld is
composed of one or more string or weave beads deposited on an
unbroken surface to obtain desired properties or dimensions.
23
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 8.
24
GROOVE WELDS.
WELDING OPERATIONS I – 0D1651 - LESSON 1/TASK 1
FIGURE 9.
SURFACING, PLUG AND SLOT WELDS.
(3) Plug Weld (figure 9). This is a circular weld made through
one member of a lap or tee joint joining that one member with the
other. This type weld may or may not be made through a hole in
the first member.
(4) Slot Weld (figure 9).
This weld is made in an elongated
hole in one member of a lap joint or tee joint joining that
member to the surface of the other member that is exposed through
the hole.
(5) Fillet Weld. This type weld is shown in figure 6, view L,
on page 21.
It is a triangular cross section weld joining two
surfaces at right angles to each other.
(6) Flash Weld (figure 10 on the following page). This weld is
made by the application of pressure over the entire area of
abutting surfaces after heating them is completed.
25
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 10.
SEAM, SPOT, FLASH, AND UPSET WELDS.
(7) Seam Weld (figure 10).
This weld is made either by arc
seam welding in which a continuous weld is made along fraying
surfaces by drawing the arc between the electrode and the
workpiece, or by resistance seam welding where the weld is a
series of overlapping spot welds made progressively along a joint
by rotating the circular electrodes.
26
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(8) Spot Weld (figure 10 on the previous page). This is a weld
made by either arc spot welding where a weld is made in one spot
by drawing the arc between the electrode and the workpiece, or
resistance spot welding where the size and shape of the
individually formed welds are limited by the size and contour of
the electrodes.
(9) Upset Weld (figure 10). This is a weld made simultaneously
over the entire area of abutting surfaces or progressively along
a joint while pressure is applied before heating is started and
is maintained throughout the heating period.
d.
Welding Positions (figure 11 on the following page).
All
welding can be classified according to the position of the
workpiece or the position of the joint on the plates or sections
being welded.
There are four general positions in which welds
are required to be made. These positions are designated as flat,
horizontal, vertical, and overhead.
5.
Welding Techniques
a.
General.
In metal-arc welding a number of separate factors
are responsible for the transfer of molten filler metal and
molten slag to the base metal.
Among these are the techniques
employed in the actual process of welding.
The following
subparagraphs serve to describe these techniques.
b.
Welding Current, Voltage, and Adjustments.
(1) The selections of the proper welding currents and voltages
depend on the size of the electrode, the thickness of the plate
being welded, the welding position, and the welder's skill.
Electrodes of the same size can withstand higher current and
voltage values when welding in the flat welding position than in
vertical or the overhead welding position.
In general, the
proper current and voltage settings are obtained from experience
and should fill the requirements of the particular welding
operation.
Since several factors affect current and voltage
requirements, data provided by welding apparatus and electrode
manufacturers should be used. For initial
27
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 11.
28
WELDING POSITIONS.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
settings, table 1, indicates the current to be used when welding
with bare or lightly coated electrodes.
The arc voltage will
vary from approximately 15 volts for 1/16 inch electrodes to 30
volts for 3/8 inch electrodes of either the bare or lightly
coated types.
Usually, a 3/16 inch diameter electrode is the
maximum size for vertical and overhead welding positions.
TABLE 1.
CURRENT SETTINGS FOR BARE AND
LIGHTLY COATED ELECTRODES.
(2) The mineral-coated type of shielded-arc electrode, which
produces a slag as a shield, requires a higher welding current
than the cellulose-coated type, which produces a large volume of
gas to shield the arc stream.
Table 2 on the following page
shows the current requirements for the mineral-coated and the
cellulose-coated types of electrodes.
The welding voltage will
range from 20 volts for the 3/32 inch electrode to 30 volts for
the 3/8 inch heavy-coated electrodes of either type.
(3) Shielded-arc or heavy-coated electrodes are used for most
welding operations on steel rather than the bare or lightly
coated types.
The heavy-coated electrodes allow higher welding
speeds, provide alloying elements into the weld metal by means of
the coating on the electrode, as is done with certain stainless
steel electrodes. The shielded-arc type of electrode is used for
welding nonferrous metals and certain alloy steels, particularly,
stainless steel alloys.
29
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
TABLE 2. CURRENT SETTINGS FOR MINERAL AND
CELLULOSE COATED ELECTRODES.
(4) In preparation for welding, the welding machine must be
adjusted to provide proper welding conditions for the particular
size and type of electrode being used. These adjustments include
proper polarity, as well as current and voltage settings.
The
dual-control machines make possible the separate control of
voltage and current that is delivered to the arc.
In singlecontrol units, the welding current is controlled manually while
the voltage is adjusted automatically.
(5) When proper adjustment of the welding machine is obtained,
the exposed end of the electrode should be gripped in the
electrode holder so that the entire usable length can be
deposited, without breaking the arc. In some cases, when welding
with long electrodes, the center of the electrode is bared and
gripped in the center. Carbon and graphite electrodes should be
gripped short of the full length to avoid overheating the entire
electrode.
c.
Starting the Arc (figure 12 on the following page).
(1) The following are two methods used for starting the arc:
(1) the striking or brushing method shown in figure 12, view A,
and (2) the tapping method shown in figure 12, view B. In both
methods, the arc is formed by short circuiting the welding
current between the electrode and the work surface. The surge of
high current causes both the end of the electrode and a small
spot on the base metal beneath the electrode to melt instantly.
30
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 12.
STARTING THE ARC.
(2) In the striking and brushing method, the electrode is
brought down to the work with a lateral motion similar to that of
striking a match.
As soon as the electrode touches the work
surface, the electrode is raised to establish the arc.
The arc
length or gap between the end of the electrode and the work
should be approximately equal to the diameter of the electrode.
When the proper length of the arc is obtained, a sharp crackling
sound can be heard.
(3) In the tapping method, the electrode is held in a position
vertical to the surface of the work.
31
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
The arc is established by lowering the electrode, tapping or
bouncing it on the work surface, then slowly raising it a short
distance, approximately the diameter of the electrode. When the
proper length of arc is obtained, a sharp crackling sound can be
heard.
(4) If the electrode is withdrawn too slowly, with either arc
starting method described above, it will stick or freeze to the
plate or base metal.
If this occurs, the electrode can usually
be freed by a quick sideways wrist motion to snap the end of the
electrode from the plate.
When this method fails, remove the
electrode holder from the electrode or stop the welding machine
and free the electrode with a light chisel blow.
WARNING
If the electrode becomes frozen to the base metal
during the process of starting the arc, all work to
free the electrode when the current is on should be
done with the face shield pulled down over the eyes.
(5) Some electrodes, known as contact electrodes, are normally
struck by holding them in contact with the work.
These
electrodes are used mostly by private industry rather by the Army
in the field.
(6) Two procedures, described in the following subparagraphs,
are used to break the arc.
(a) In manual welding, when the electrode is changed and the
weld is to be continued from the crater, the arc is shortened and
the electrode moved quickly sideways out of the crater. When the
arc is re-established it is started at the forward or cold end of
the crater, moved backward over the crater, then forward again to
continue the weld. The crater is also filled by this procedure.
(b) In semiautomatic welding, where filling or partial filling
of the crater is required, the electrode is held stationary for a
time sufficient to fill the crater and then is gradually
withdrawn until the arc breaks.
32
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
d.
Proper and Improper Arc Control.
(1) Maladjustments.
Table 3 provides a listing of the effects on
welding as a result of improper current, voltage, and welding speed
control.
TABLE 3.
EFFECTS OF MALADJUSTMENTS OF
WELDING CURRENT VOLTAGE AND
SPEED ON THE BEAD
CHARACTERISTICS.
33
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(2) Long Arc (figure 13).
When welding with a long arc, as
shown in figure 13, view A, the protecting arc flame, as well as
the molten globule at the end of the electrode, will whirl and
oscillate from side to side.
The fluctuating flame will permit
the molten base metal to become
FIGURE 13.
34
ARC CHARACTERISTICS,
AND DEFECTS.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
oxidized or burned before reaching the molten metal.
The
direction of the molten filler metal, as it passes through the
arc, will be difficult to control and a considerable portion of
this metal will be lost as spatter. The long arc will melt the
electrode quickly, and the metal is not always deposited at the
point desired.
In general, the long arc results in poor weld
penetration, excessive overlap, and burned and porous metal in
the weld as shown in figure 13, views B through D, on the
previous page.
(3) Short Arc.
(a) The short arc (figure 13, view E) is the correct and
desired procedure for welding.
With the short arc, the molten
metal leaving the end of the electrode passes from the atmosphere
by way of an enveloping arc flame. The short arc permits better
control of the weld metal deposited resulting in a welded bead of
better quality.
Generally, a short arc provides maximum
penetration and better physical properties in the weld and
deposits the maximum amount of metal at the point of welding.
Porosity, overlap, and weld metal spatter are kept to a minimum.
(b) A very short arc, however, is undesirable. It will produce
much spatter, will go out frequently, and make continuous welding
difficult; the results being similar to those shown in figure 13,
view B.
e.
Bead Welding (figure 14 on the following page).
(1) When the arc is struck, metal particles melt off the end of
the electrode and are deposited in the molten puddle on the
surface of the work.
As the electrode melts it becomes shorter
and causes the arc to increase in length unless the electrode is
fed down to the work as fast as the end is melted off and
deposited.
Before moving the electrode forward, the arc should
be held at the starting point for a short time to ensure good
fusion and to allow the bead to build up slightly.
When the
welding machine is adjusted for proper current and polarity, good
bead welds can be made by maintaining a short arc and welding in
a straight line at a constant speed.
35
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 14.
CORRECT ELECTRODE POSITION FOR
WELDS AND PROPER BEAD WELDS.
(2) For bead welding, the electrode should be held at or near a 90
degree angle to the base metal as shown in figure 14, view A. However,
in order to obtain a clearer view of the molten puddle, crater, and
arc, the electrode should be tilted between 5 and 15 degrees toward the
direction of travel as shown in figure 14, view B.
(3) The proper arc length cannot be accurately judged by the eye, but
can be recognized by the sound of the arc.
When bead welding with a
short arc, the typical sharp, crackling sound should be heard all the
time the electrode is in contact and being moved along the surface of
the work.
36
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(4) A properly made bead weld should leave little spatter on
the surface of the work (figure 14, view C, on the previous
page). When the arc is broken, the crater or depression in the
bead, shown in figure 14, view C, should be built up slightly.
This metal build-up should not overlap the top surface of the
weld. An overlap would indicate poor fusion at this point of the
weld. The depth of the crater at the end of the bead can also be
used as an indication of penetration into the base metal.
f.
Flat Position Welding (figure 15 on the following page).
(1) Butt Joints in the Flat Position. A butt joint is used to
join two plates having surfaces in approximately the same plane.
Several forms of joints are used to make butt welds in the flat
position. The most important of these forms are described in the
following subparagraphs.
(a) Plates 1/8 inch thick can be welded in one pass without any
special edge preparation being necessary.
Plates from 1/8 to
3/16 inch thickness can be welded with no special edge
preparation by making a bead weld on both sides of the joint.
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.
(b) When welding 1/4 inch or heavier plates, the edges of the
plates should be prepared by beveling or by "J," "U," or "V"
grooving, whichever is the most applicable.
Single or double
bevels or grooves may be used depending on the thickness of the
plate being welded.
The first bead should be deposited to seal
the space between the two plates and to weld the root of the
joint.
This bead (also referred to as a layer or weld metal)
must be thoroughly cleaned to remove all slag before the second
layer of metal is deposited. When making multipass welds (figure
16, view A, on page 39), the second, third, and fourth layers of
weld metal are deposited using any of the weaving motions of the
electrode, as shown in figure 16, view B.
Each layer of metal
must be cleaned before depositing the succeeding layers.
37
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 15.
38
FLAT POSITION WELDING.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 16.
MULTIPASS BEAD WELDS, WELDING
MOTIONS, UNDERCUTTING, AND
WELDS WITH BACKSTRIPS.
39
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(c) When using any of the weaving motions, the electrode should
be oscillated or moved uniformly from side to side with slight
hesitation at the end of each oscillation and, as in bead
welding, the electrode should be inclined 5 to 15 degrees in the
direction of welding.
If the weaving motion is not properly
performed, undercutting will occur at the joint as shown in
figure 16, view C, on the previous page. Excessive welding speed
will also cause undercutting and poor fusion at the edges of the
weave bead.
(2) Butt Joints in Flat Position with Backup Strips (figure 16,
view D).
(a) Backup or backing strips are used when welding 3/16 inch
plate or heavier to obtain complete fusion at the root of the
weld and to provide better control of the arc and the weld metal.
The edge of the plates to be welded are prepared in the same
manner as required for welding without backing strips.
The
backing strips, 1 inch wide and 3/16 inch thick for plates up to
3/8 inch thick, 1 1/2 inch side, and 1/4 inch thick for plates
over 1/8 inch thick, are tack welded to the base of the joint.
The backing strip will act as a cushion for the first bead or
layer deposited in the joint.
(b) The joint should be completed by adding additional layers
of metal using the procedures prescribed in paragraphs 5e, on
pages 35 and 36.
(c) After the joint is completed, the backup strip may be
washed off or cut away with a cutting torch and, if necessary, a
sealing bead may then be applied along the root of the joint.
(3) Plug and Slot Joints (figure 17 on the following page).
(a) Plug and slot welds, shown in figure 17, views A and B, are
used to join two overlapping plates, by depositing and filling a
hole or slot in the upper plate.
Slot welds are used in butt
straps to join face hardened armor plate edges from the back or
soft side. They are also used to fill up holes in plates and to
join two overlapping plates where it is impossible to join them
by any other method.
40
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 17.
PLUG AND SLOT JOINTS, AND
TACK WELDING TEE JOINTS.
(b) A continuous fillet weld as shown in view B is made to
obtain a good fusion between the sidewalls of the hole or slot
and the surface of the lower plate.
The procedure for this
fillet weld is the same as for lap joints, which will be
described in paragraph 5g(2) on page 45.
The hole or slot is
then filled in to provide additional strength in the weld.
(c) The plug weld procedure may be used to remove bolts or
studs that have been broken or twisted off flush with the surface
of the part. A
41
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
nut, somewhat smaller than the bolt size, should be centered on
the bolt or stud to be removed.
A heavy-coated electrode is
lowered into the nut and an arc struck on the exposed end of the
broken bolt or stud. The nut is then welded onto the broken bolt
or stud and sufficient metal is added to fill the hole..
The
broken bolt or stud can then be removed with a wrench.
g.
Horizontal Position Welding.
(1) Tee Joints (figure 17, view C, on the previous page).
In
making tee joints in the horizontal position the two plates are
located approximately 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.
(a) A fillet weld (figure 18, views A and B, on the following
page) is used in making the joint by using a short arc to provide
good fusion at the root and along the legs of the weld.
The
electrode should be held at an angle of 45 degrees to the two
plate surfaces and inclined approximately 15 degrees in the
direction of welding.
(b) Light plates can be fillet welded in one pass with little
or no weaving of the electrode.
Welding of heavier plates may
require two or more passes with the second pass or layer made
using a semicircular weaving motion as shown in figure 18, view
C.
A slight pause is made at the end of each weave to obtain
good fusion between the weld and base metal without any
undercutting.
(c) A fillet-welded tee joint on 1/2 inch or thicker plate can
be made by depositing string beads in the sequence shown in
figure 18, view D.
(d) Chain or staggered intermittent fillet weldings as shown in
figure 19, view A, on page 44 are used for long tee joints.
Fillet welds of these types are used where high weld strength is
not required; however, the short welds are so arranged that the
finished joint is equal in strength to a fillet weld along the
entire length of a joint from one side only.
Also, the warpage
and distortion of the welded parts are held to a minimum with
intermittent welds.
42
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 18.
FILLET WELDING.
43
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 19.
44
INTERMITTENT FILLET WELDS,
TACK WELDING, AND
ELECTRODE POSITION.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(2) Lap Joint (figure 19, views B and C, on the previous page).
(a) In making lap joints, two overlapping plates are tack
welded in place and a fillet weld in the horizontal position is
deposited along the joint.
(b) The procedure for making this weld is similar to that used
for making fillet welds in tee joints.
The electrode should be
held so as to form an angle approximately 30 degrees from the
vertical and tilted 15 degrees in the direction of welding. The
position of the electrode in relation to the plates is shown in
figure 19, view C. The weaving notion is the same as that used
for tee joints, except that the pause at the edge of the top
plate is sufficiently long to ensure good fusion and no under
cut.
Lap the joint by depositing a series of overlapping beads
on top of each other.
(c) In making lap joints on plates of different thicknesses as
shown in figure 20, view A, on the following page, the electrode
is held so as to form an angle of 20 to 30 degrees from the
vertical.
Care must be taken not to overheat or undercut the
thinner plate edge. Also, the arc must be controlled to wash up
the molten metal to the edge of this plate.
h.
Vertical Position Welding.
(1) Bead Welds (figure 20, views B through E).
(a) Welding on a vertical surface is more difficult than
welding in the flat position.
Because of the force of gravity,
the molten metal tends to flow downward.
(b) When metal-arc welding in the vertical position, current
settings should be less than those used for the same electrode in
the flat position.
The currents used for welding upward on a
vertical surface are slightly higher than those used for welding
downward on the same surface.
(c) The proper angle between the electrode and the base metal
is also necessary in order to deposit a good bead weld when
welding vertically.
45
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
FIGURE 20.
46
LAP JOINTS AND WELDING
VERTICALLY.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(d) When welding upward, the electrode should be held at 90
degrees to the vertical as shown in figure 20, view B, on the
previous page. When welding upward and weaving is necessary, the
electrode should be oscillated as shown in figure 20, view C.
(e) When welding downward, the outer end of the electrode
should be inclined downward about 15 degrees from the horizontal
with the arc pointing upward toward the deposited molten metal as
shown in figure 20, view D.
When welding downward, in the
vertical position, and a weave bead is required, the electrode
should be oscillated as shown in figure 20, view E.
(f) When depositing a bead weld in the horizontal direction on
a vertical plate, the electrode should be held at right angles to
the vertical as shown in figure 21, view A, on the following page
and tilted 15 degrees toward the direction of welding so as to
provide a better view of the arc and crater.
(2) Butt Joints.
(a) Butt joints on plates in the vertical position are prepared
for welding in the same way as those required for butt joints in
the flat position.
(b) In order to obtain good fusion and penetration with no
undercutting, a short arc should be held and the motion of the
arc should be carefully controlled.
(c) Butt joints on beveled plates 1/4 inch thick can be made by
using a triangular weave motion as shown in figure 21, view B.
Welds on 1/2 inch plate or heavier should be made in several
passes as shown in figure 21, view C.
The last pass should be
deposited with a semicircular weaving motion with a slight whipup and pause to the electrode at the edge of the bead.
(d) When welding butt joints in the horizontal direction on
vertical plates, a short arc is necessary at all times and the
metal is deposited in multipass beads as shown in figure 21, view
D. The first pass is made with the electrode held at 90 degrees
to the vertical plates. The second, third, and subsequent passes
are made with the
47
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
electrode held parallel to the beveled edge opposite the edge on
which the bead is being deposited.
FIGURE 21.
48
VERTICAL WELDING AND
BUTT JOINTS.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(3) Fillet Welds (figure 22).
(a) When making fillet welds in either tee or lap joints in the
vertical position, the electrode should be held at 90 degrees to the
plates or not
FIGURE 22.
VERTICAL FILLET WELDS.
49
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
more than 15 degrees above the horizontal for proper molten metal
control. The arc should be held short to obtain good fusion and
penetration.
(b) When welding tee joints in the vertical position, the joint
should be started at the bottom and welded upward and the
electrode should be moved in a triangular weaving motion as shown
in figure 22, view A, on the previous page.
A slight pause in
the weave, at the points indicated, will improve the sidewall
penetration and provide good fusion at the root of the joint.
1 If the weld metal should overheat, the electrode should
quickly shifted away from the crater without breaking the arc
shown in figure 22, view B. This will permit the molten metal
solidify without running downward.
The electrode should
returned immediately to the crater of the weld in order
maintain the desired size of the weld.
be
as
to
be
to
2 When more than one pass is necessary to make a tee weld,
either of the weaving motions shown in figure 22, views C and D,
may be used. A slight pause at the end of the weave will develop
good fusion without undercutting at the edges of the plates.
(c) To make welds on lap joints in the vertical position, the
electrode should be moved in a triangular weaving motion as shown
in figure 22, view E.
The same procedure for making the tee
joint is used except the electrode is directed toward the
vertical plate marked "G" in figure 22, view E.
The arc should
be held short, and the pause at the surface of plate "G" should
be slightly longer. Care should be taken not to undercut either
of the plates or to allow the molten metal to overlap at the
edges of the weave.
(d) Lap joints in the vertical position on heavy plate require
more than one layer of metal.
The deposited bead should be
thoroughly cleaned and subsequent beads deposited as shown in
figure 22, view F.
i. Overhead Position Welding (figure 23 on the following page).
(1) Bead Welds.
The overhead position is the most difficult
position to weld in because it
50
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
requires a very short arc which must be maintained in order to
retain complete control of the molten metal.
As in vertical
position welding, the force of gravity tends to cause the molten
metal to drop
FIGURE 23.
OVERHEAD POSITION WELDING.
51
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
down or sag on the plate. If the arc is too long, the difficulty
in transferring metal from the electrode to the base metal is
increased and large globules of molten metal will drop from the
electrode and the base metal.
This action can be prevented by
first shortening and then lengthening the arc at intervals. Care
must be taken not to carry too large a pool of molten metal in
the weld.
(a) When bead welding, the electrode should be held at an angle
of 90 degrees to the base metal as shown in figure 23, view A, on
the previous page. The electrode may be tilted approximately 15
degrees in the direction of welding as shown in figure 23, view B
to provide a better view of the arc and crater of the weld.
(b) Weave beads can be made in the overhead position by using
the motion illustrated in figure 23, view C.
A rapid motion is
necessary at the end of each semicircular weave in order to
control the molten metal deposit.
Excessive weaving should be
avoided because this will cause overheating of the weld deposit
and the formation of a large pool of metal which will be hard to
control.
(2) Butt Joints.
(a) The plates should be prepared for butt welding in the
overhead position in the same manner as that required in the flat
position, and the most satisfactory results are obtained if
backup strips are used. If the plates are beveled with a feather
edge and no backup strip is used, the weld will tend to burn
through repeatedly unless extreme care is taken by the operator.
(b) For overhead butt welding, bead rather than weave welds are
preferred.
Each bead should be cleaned and the rough areas
chipped out before the following pass is deposited.
The first
pass should be made with the electrode held at 90 degrees to the
plate as shown in figure 23, view D.
(c) The position of the electrode and the order to be followed
in depositing beads on 1/4 and 1/2 inch plates are illustrated in
figure 23, views E and F.
(d) Fairly small diameter electrodes should be used to assist
in holding a short arc and developing a good penetration at the
root of the
52
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
joint. Excessive current will create a very fluid puddle, which
will be difficult to control.
(3) Fillet Welds (figure 24).
(a) In making fillet welds in either tee or lap joints in the
overhead position, a short arc should be held and there should be
no weaving of the electrode.
The order in which the beads are
deposited is shown in figure 24, view A. The electrode should be
held approximately 30 degrees to the vertical plate and moved
uniformly in the direction of the welding as shown in figure 24,
view B.
The arc motion should be controlled to secure good
penetration to the root of the weld and good fusion with the
sidewalls of the vertical and horizontal plates.
If the molten
metal becomes too fluid and tends to sag, the electrode should be
whipped away quickly from the crater and ahead of the weld so as
to lengthen the arc and allow the metal to solidify.
The
electrode should then be returned immediately to the crater and
the welding continued.
FIGURE 24.
OVERHEAD POSITION
FILLET WELDING.
53
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(b) Fillet welds for either tee or lap joints, on heavy plate
in the overhead position, require several passes to make the
joint. The first pass is a string bead with no weaving motion of
the electrode.
The second, third, and fourth passes are made
with a slight circular motion of the electrode with its top
tilted about 15 degrees in the direction of welding as shown in
figure 24, view C, on the previous page.
This motion of the
electrode permits greater control and better distribution of the
weld metal being deposited. All slag and oxides must be removed
from the surface of each pass by chipping or wire-brushing before
applying additional beads.
6.
Electric Arc Welding of Ferrous Metals
a.
General.
All of the ferrous metals used on Army ground
equipment can be successfully electric arc welded, provided
normal care is used and the correct procedure followed.
The
following subparagraphs provide the welding techniques for four
of the most common types of ferrous metals found on this
equipment.
The description of welding techniques for other
ferrous metals may be found in TM 9-237.
b.
High-Carbon Steels.
(1) General.
High-carbon steels include those that have a
carbon content exceeding 0.45 percent.
Because of the high
carbon content and the heat treatment usually given to these
steels, their basic properties are to some degree impaired by arc
welding.
Preheating the metal between 500 to 800 Fahrenheit
before welding and stress relieving it by heating from 1200 to
1450 with slow cooling should be used to avoid hardness and
brittleness in the fusion zone.
Either mild-steel or stainless
steel electrodes can be used to weld these steels.
(2) Welding Technique.
(a) The welding heat should be adjusted to provide good fusion
at the sidewalls and root of the joint without excessive
penetration. High welding heat will cause excessive penetration
and puddling which in turn can cause large areas in the fusion
zone to become hard and brittle. Control of the welding heat and
excessive penetration can be accomplished by depositing the weld
metal in small string beads. The area of these hard zones in the
54
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
base metal can be reduced by making the weld with a series of
small string or weave beads. Fusion between the filler metal and
the sidewalls should be confined to a narrow zone.
This can be
accomplished by directing the electrode toward the previously
deposited filler metal adjacent to the side walls than toward the
side walls directly.
This procedure causes the weld metal to
wash up against the side of the joint and fuse with it without
deep or excessive penetration.
(b) When welding sheet metal up to 1/8 inch in thickness, the
plain square butt joint type of edge preparation may be used.
Heavy plates should be beveled up to 60 degrees, depending on the
thickness.
The parts should be tack welded and the root weld
made with a 1/8 to 5/32 inch electrode.
Additional passes of
filler metal should be made with a 5/32 or 3/16 electrode. Heavy
sections that have been beveled from both sides should be welded
by depositing weave beads alternately on one side and then the
other to reduce the amount of distortion in the weld structure.
(c) Small high-carbon steel parts are sometimes repaired by
building up worn surfaces.
When this is done, the piece should
be annealed or softened by heating to a red heat and cooling
slowly. Then the piece should be welded or built up with mediumcarbon or high-strength electrodes and heat treated, after
welding, to restore its original properties.
c.
Tool Steels.
(1) General.
Steels in this group have a carbon content
ranging from 0.80 to 1.5 percent. They are rarely welded by arc
welding because of the excessive hardness produced in the fusion
zone of the base metal.
If arc welding must be done, either
mild-steel or stainless-steel electrodes can be used.
(2) Welding Technique.
(a) If the parts to be welded are small, they should be
annealed or softened before welding.
The edges should then be
preheated up to 1,000, depending on the carbon content and
thickness of the plate, and the welding done with either a mildsteel or high-strength electrode.
55
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(b) High-carbon electrodes should not be used for welding tool
steels. The carbon picked up from the base metal by this filler
metal will cause the weld to become glass hard; whereas, the
mild-steel weld metal can absorb additional carbon without
becoming excessively hard. The welded part should then be heattreated to restore its original properties.
(c) When welding with stainless steel electrodes, the edges of
the plates should be preheated to prevent the formation of hard
zones in the base metal. The weld metal should be deposited in
small string beads to keep the heat input down to a minimum. In
general, the application procedure is the same as that required
for high-carbon steels described in paragraph 6b(2) beginning on
page 54.
d.
High Yield Strength, Low Alloy Structural Steels.
(1) General.
High yield strength, low alloy structural steels
are special steels that are tempered to obtain extreme toughness
and durability. The special alloys and general make-up of these
steels require special treatment to obtain satisfactory weldments.
(2) Welding Techniques.
(a) Reliable welding of high yield strength, low alloy
structural steels can be performed by using the correct
electrodes.
Hydrogen is the number one enemy of sound welds in
alloy steels.
Therefore, use only low hydrogen (MIL-E-18038 or
MIL-E22200/1) electrodes to prevent cracking. Underbead cracking
is caused by hydrogen picked up in the electrode coating,
released into the arc, and absorbed by the molten metal.
(b) Electrodes must be kept dry to eliminate absorption of
hydrogen.
If the electrodes are in an airtight container,
immediately upon opening the container, place the electrodes in a
ventilated holding oven set at 250° to 300° F. In the event that
the electrodes are not in an airtight container, put them in a
ventilated baking oven and bake for 1 to 1 1/4 hours at 800° F.
Baked electrodes should, while still warm, be placed in a holding
oven until used.
Electrodes must be kept dry to eliminate
absorption of hydrogen.
56
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(c) Electrodes are identified by classification numbers which
are always marked on the electrode containers. For low hydrogen
coatings, the last two numbers of the electrode classification
should be 15, 16, or 18.
Electrodes of 5/32 and 1/8 inch in
diameter are the most commonly used since they are more adaptable
to all types of welding of this type steel.
(3) It is important to avoid excessive heat concentration when
welding in order to allow the weld area to cool rather quickly.
For satisfactory welds, along with good welding practices, use a
straight stringer bead whenever possible. Restrict the weave to
a partial weave pattern.
Best results are obtained by a slight
circular motion of the electrode with the weave area never
exceeding two electrode diameters.
Never use a full weave
pattern.
Skip weld as practical, and peen the weld to relieve
stresses while cooling larger pieces.
Avoid toe cracks and
undercutting.
A soft steel wire pedestal can help to absorb
shrinkage forces.
Butter welding (laying a bead, then grinding
it off) in the toe area before fillet welding strengthens the
area where a toe crack may start.
e.
Cast Iron.
(1) General.
Gray cast iron has low ductility; therefore, it
will neither expand, nor stretch, to any considerable extent
before breaking or cracking.
Because of this characteristic,
preheating is necessary when cast iron is welded by the
oxyacetylene welding process. However, it can be welded with the
metal arc without preheating if the welding heat is carefully
controlled.
This can be accomplished by welding only short
lengths of the joint and allowing these sections to cool.
By
this procedure, the heat of welding is confined to a small area
and the danger of cracking the casting is eliminated.
Large
castings with complicated sections, such as motor blocks, can be
welded without dismantling or preheating.
Special electrodes
designed for this purpose are usually desirable.
(2) Welding Techniques.
(a) Cast iron can be satisfactorily welded with a coated steel
electrode, but this method should be used as an emergency measure
only. When using a steel electrode the contraction of the
57
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
steel weld metal, the carbon picked up from the cast iron by the
weld metal, and the hardness of the weld metal caused by rapid
cooling must be considered.
Steel shrinks more than cast iron
when cooled from a molten to a solid state and, when a steel
electrode is used, this uneven shrinkage will cause strains at
the joint after welding.
When a large quantity of filler metal
is applied to the joint, the cast iron may crack just back of the
line of fusion unless preventive steps are taken.
To overcome
these difficulties, the prepared joint should be welded by
depositing the weld in short string beads, 3/4 to 1/4 inch long,
made intermittently and, in some cases, by the step-back or skipwelding procedure. To avoid hard spots, the arc should be struck
in the V and not on the surface of the base metal.
Each short
length of weld metal applied to the joint should be lightly
peened, while hot, with a small ballpeen hammer and allowed to
cool before additional weld metal is applied. The peening action
forges the metal and relieves metal strain during cooling.
(b) The electrodes used should be 1/8 inch in diameter so as to
prevent generating excessive welding heat. The welding should be
done with reverse polarity.
Weaving of the electrode should be
held to a minimum.
Each metal deposit should be thoroughly
cleaned before additional metal is deposited.
(c) Cast iron electrodes are used where subsequent machining of
the welded joint is required.
Stainless steel electrodes are
used when machining of the weld is not required.
The procedure
for making welds with these electrodes is the same as that
outlined for welding with mild-steel electrodes. Stainless steel
electrodes provide excellent fusion between the filler and base
metals; however, great care must be taken not to overheat the
base metal.
Overheating the base metal will cause cracking of
the base metal alongside the weld metal.
The reason for this
cracking of the base metal is that stainless steel expands and
contracts approximately 50 percent more than mild steel in equal
changes of temperature.
7.
Electric Arc Welding of Nonferrous Metals
a.
General.
Most of the nonferrous metals used in Army ground
equipment can be successfully electric arc welded provided the
proper procedures are
58
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
adhered to.
The following subparagraphs describe the welding
techniques used only for aluminum. Aluminum and aluminum alloys
can be satisfactorily welded by metal-arc, carbon-arc, and other
arc-welding processes. The principal advantage of using the arcwelding processes is that a highly concentrated heating zone is
obtained with the arc and, for this reason, excessive expansion
and distortion of the metal is prevented. With the exception of
the welding rod used, the welding techniques used for other
nonferrous metals, namely titanium, nickel, bronze, brass,
magnesium, and monel, are the same as those used for aluminum.
b.
Welding Techniques.
(1) Because of the difficulty of controlling the arc, butt and
fillet welds are difficult to produce in plates less than 1/8
inch thick. In welding plate heavier than 1/8 inch, a plate with
a 30 bevel will have strength equal to a weld made by the
oxyacetylene process, but this weld may be porous and unsuited
for liquid- or gas-tight joints. Metal arc welding is, however,
particularly suitable for heavy material and is used on plates up
to 2 1/2 inches thick.
(2) The current and polarity settings will vary with each
manufacturer's type of electrodes, and the polarity to be used
should be determined by trial on the joints to be made.
(3) Before being welded, a broken aluminum casting should be
carefully cleaned by wire brushing with mineral spirits, paint
thinner, or dry cleaning solvent used to remove all oil, grease,
and other foreign matter.
If the casting has a heavy cross
section, the crack should be tooled out to form a "V."
(4) Either metal arc or carbon arc welding can be used for
aluminum castings, but the carbon arc is preferred because it
produces welds free of oxides and porosity. Flux-coated rods are
essential for good arc welds. All slag and flux must be removed
from the finished weld to prevent corrosion of the joint and the
entire piece should be covered with sand or asbestos to afford
slow cooling.
59
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
8.
Conclusion
This task served to describe methods for identifying electrodes
by type and intended use; the automotive welding processes,
materials, and identification processes; and the types and
techniques of joint design.
This information provides a basis
for the following task. The next task will describe the theory,
principles, and procedures of welding armor plate; and the
methods of destructive and nondestructive testing welds, and
troubleshooting procedures.
60
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
LESSON 1
ELECTRODES CLASSIFICATION AND
INTENDED USES; AUTOMOTIVE WELDING PROCESSES,
MATERIALS, AND IDENTIFICATION PROCESSES;
METHODS OF DESTRUCTIVE AND NONDESTRUCTIVE
TESTING OF WELDS AND TROUBLESHOOTING PROCEDURES;
TYPES AND TECHNIQUES OF JOINT DESIGN; AND
THE THEORY, PRINCIPLES, AND PROCEDURES OF
WELDING ARMOR PLATE
TASK 2.
Describe the theory, principles, and
procedures of welding armor plate; and
methods of destructive and nondestructive
testing of welds, and troubleshooting
procedures.
CONDITIONS
Within a self-study environment and given the subcourse text, without
assistance.
STANDARDS
Within two hours
REFERENCES
No supplementary references are needed for this task.
1.
Introduction
The previous task described the methods for classifying electrodes by
type and intended uses; the automotive welding processes, materials,
and identification processes; and the types and techniques of joint
design.
The previous information provided the basis for this task,
which describes the theory, principles, and procedures for welding
armor plate, the methods of destructive and nondestructive testing, and
troubleshooting of welds.
61
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
2.
General
a.
Armor Plate Uses.
Armor plate is used on tanks, selfpropelled guns, and other combat vehicles for the protection of
personnel and equipment from the destructive force of enemy
projectiles.
It is fabricated both in the form of castings and
rolled plates, which are heat treated to develop the desired
structural and protective properties.
The manufacture of gun
turrets and combat tank hulls includes one-piece castings and
welded assemblies of rolled plates and sections that have been
cast.
b.
Repair of Armor Plate. Welding has replaced riveting for the
repair of armor plate although, in some cases, riveting is still
used on some vehicles protected by face hardened armor.
Developing a suitable technique for welding armor plate depends
upon consideration of the following factors affecting the
weldability of armor plate:
(1) knowledge of the exact types of armor being welded;
(2) knowledge of the proper repair methods;
(3) the function of the damaged structure;
(4) proper
procedures;
selection
of
welding
materials
and
repair
(5) urgency of the repair required to accomplish the combat
mission;
(6) careful analysis of the defect in terms of the proper
joint, electrode, current, voltage, polarity, and minimum welding
stresses and warpage during repair; and
(7) knowledge
procedures.
of
safety
hazards
fire
and
safety
hazard
The theory, principles, and procedures for welding armor plate
are basically the same as those used for industrial fabrication,
but must be modified at times because of the varying types of
damage that can occur in the battlefield.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
3.
Welding Armor Plate
a.
Properties of Armor Plate.
Armor plate is hardened by
normalizing or heating it to its upper critical point and letting
it cool in still air.
The base metal quenching effect produced
next to a weld in heavy armor plate under normal welding
conditions is about halfway between the effects of air cooling
and oil quenching it.
During the welding of armor plate the
temperature of the weld metal ranges upwards of 3000° F from the
original temperature of the base metal. Therefore, a narrow zone
on each side of the deposited weld metal is heated above its
critical temperature.
This narrow zone is then quenched by the
relatively cold base metal and becomes a hard brittle zone known
as martensite. It is in this zone that cracks are most likely to
occur upon the application of a load.
For this reason, special
precautions must be taken in all welding operations to minimize
the formation of hard zones. In addition, care must be taken to
prevent rapid cooling of the armor plate after welding in order
to avoid the formation of cracks in hard zones.
b.
Types of Armor Plate.
(1) General.
There are two types of armor that are used on
combat vehicles: homogeneous, which can be cast or rolled, and
face hardened, which is rolled.
It is essential that the armor
plate be specifically identified before any welding or cutting
operations are performed. This is important because the welding
procedures for each type of armor are distinctly different and
are not interchangeable.
(2) Homogeneous Armor Plate. Homogeneous armor is heat treated
through its entire thickness to develop good shock or impact
resisting properties. This type of armor is uniform in hardness,
composition, and structure throughout and can be welded on either
side. Aluminum armor plate is in the homogeneous class. Welding
procedures for aluminum armor plate are the same as for gas
metal-arc welding, which are discussed in the inert gas welding
operation subcourse.
(3) Face Hardened Armor Plate.
Face hardened armor plate has
an extremely hard surface layer which is obtained by carburizing.
(Carburizing is the process of combining carbon with another
alloy
63
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
or impregnating a metal with carbon to strengthen it). This hard
surface extends to a depth of 1/5 to 1/4 of the outward facing
thickness of the armor on the tank or armored vehicle.
The
primary purpose of face hardened armor is to provide good
resistance against penetration from enemy projectiles. The inner
side is comparatively soft and has properties similar to those of
homogeneous armor.
As a matter of fact, the inside and outside
of face hardened armor plate has two different kinds of steel.
Face hardened steel up to 1/2 inch in thickness should be welded
from the soft side only.
c.
Identification of Armor Plate.
A very important part of
welding lies in the welder having the ability to identify metal
products to be welded.
The following paragraphs describe two
simple but accurate tests that may be made in a field shop for
identifying armor plate.
(1) File Test. This type test is performed with the use of an
ordinary file found in the mechanics and welders tool sets.
(a) Homogeneous Armor. A file will bite into homogeneous armor
on both the outside and inside of the plate.
As the file is
drawn across either surface of the armor plate, the teeth on the
file will bite into the metal, making it necessary to apply force
to draw the file across the metal.
This type test is performed
by applying the file only once or twice across the surface. The
armor protection qualities of the armor plate can be impaired by
repeated applications of the file; therefore, the number of
applications should be limited.
(b) Face Hardened Armor. In this type armor the file will bite
only into the soft side of face hardened armor plate.
When
applied across the face side (outside) of the armor plate, the
file will slip instead of biting into the metal.
But when the
file is applied to the reverse side (inside), the file will bite
as in homogeneous metal.
(2) Fracture Test.
Some metals can be quickly identified by
looking at the surface of the broken part or by studying the
chips produced with a hammer and chisel.
64
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(a) Homogeneous Armor. The metal edges of holes or cracks made
by an anti-tank projectile in homogeneous armor plate are ragged
and bent, with the metal drifted in the direction of penetration.
Cracks in homogeneous armor are usually caused by stresses in the
metal. These cracks are present at severe bulges or bends in the
damaged armor plate.
(b) Face Hardened Armor.
The metal edges of holes and cracks
in face hardened armor are relatively clean cut and sharp.
The
plates do not bulge to any great extent before cracking.
By
examining the edges of freshly broken face hardened armor, it can
be noted that the metal at the face side is brighter and of a
finer structure than the metal at the soft side.
The brighter
metal extends to a depth of approximately 1/5 to 1/4 inch in
thickness from the outside surface.
4.
Cutting Armor Plate
a.
Homogeneous Armor Plate. Either the oxygen cutting torch or
the electric arc can be used to cut homogeneous armor plate. The
oxygen cutting torch, however, is preferable. The carbon arc can
be used to cut out welds and to cut castings and plates, but the
shielded metal-arc is preferred when oxygen and acetylene are not
available.
b.
Face Hardened Armor Plate.
(1) General.
The procedure for cutting this type of armor is
essentially the same as that required for homogeneous armor.
However, every precaution should be taken to keep as much heat as
possible away from the hard face side of the plate. This is done
by cutting from the soft side of the armor plate.
Cutting from
the soft side limits the extent of heating and consequent
softening of the hard face side.
(2) Cutting with the Oxygen Torch.
(a) The general practice used for oxygen torch cutting
applied for cutting armor plate, but the tip size,
oxygen, and preheating gas temperatures should be kept
minimum,
consistent
with
good
quality
cuts,
to
overheating.
(b) Stainless steel is a nonoxidizing metal.
cutting stainless steel type welds
can be
cutting
at the
prevent
Therefore, when
65
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
with an oxygen cutting torch, it is necessary to use an
oxidizable steel rod.
The oxygen combines with metal from the
steel rod creating high temperature drops of molten steel. These
drops of molten steel wash off onto the weld and help melt the
stainless steel weld. This washing action is accomplished by an
oscillating motion of the torch tip which causes the molten weld
metal to wash away in thin layers.
When thick stainless steel
welds are cut, the steel rod should be held against the side of
the weld and fed downward slowly to generate the high temperature
required to create the molten steel into drops.
The cutting
process using a steel rod is illustrated in figure 25.
FIGURE 25.
66
CUTTING STAINLESS STEEL WELDS.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(c) Cracks or other defects on the face of stainless steel
welds can be removed by holding the cutting tip at a slight angle
away from the face of the weld as shown in figure 26.
The
reaction between the cutting oxygen and the steel rod develops
sufficient heat to melt the weld metal and is then washed away.
Afterwards, the joint surface can be rewelded.
FIGURE 26.
REMOVING SURFACE DEFECTS FROM
STAINLESS STEEL WELDS.
67
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(3) Cutting with the Electric Arc.
(a) Electric arc cutting is a procedure whereby metal is cut
using the heat of an arc maintained between the electrode and the
base metal.
Three procedures described in the following
subparagraphs are used in cutting with the electric arc.
(b) Carbon-arc cutting is a process whereby the cutting of
metals is accomplished by progressive melting with the heat of an
electric arc between a metal electrode and the base metal.
Direct
current
straight
polarity
(electrode
negative)
is
preferred.
The carbon arc is used under some conditions in
conjunction with a jet of compressed air for the removal of
defective austenitic (corrosion resistant) weld metal.
Cutting
with the carbon arc is used for cutting both ferrous and
nonferrous metal, but does not produce a cut of particularly good
appearance.
The electrodes are either carbon or graphite,
preferably with a pointed end to reduce arc wandering, and thus
produce less erratic cuts.
(c) Metal-arc cutting is a process whereby the cut is produced
by progressively melting the metal.
Direct current straight
polarity is preferred for this process.
Coated electrodes
ranging in diameter from 1/8 to 1/4 inch are used; larger
diameters are not satisfactory because of excessive spatter. The
thickness of the metal that can be cut by the metal-arc process
is limited only by the length of the electrode.
The coating on
the electrode serves as an insulator between the core of the
electrode and the side wall of the cut, resulting in less shortcircuiting against the kerf. Cuts made by the metal-arc process
are less ragged than those produced with carbon-arc, but they
must still be prepared by grinding or chiseling before rewelding
is accomplished.
(d) Oxy-arc cutting is accomplished by directing a stream of
oxygen into the molten pool of metal. The pool is kept molten by
the arc struck between the base metal and the coated tubular
cutting rod.
The rod is consumed during the cutting operation.
The tubular rod also provides an oxidizing flux and a means of
converging oxygen onto the surface being cut. The
68
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
tubular cutting electrode is made of mild steel.
Contamination
of the metal is eliminated by the extremely high heat and oxygen
emitted by this process. This high heat and oxygen also oxidize
the rod and coating thereby preventing the rod metal from fusing
with the base metal.
(e) After completing the cut with an arc cutting process, the
rough edges and slag should be removed by hammering, chipping, or
grinding prior to welding.
5.
Welding Homogeneous Armor Plate
a.
General.
Before welding damaged armor plate, the type of
armor must first be identified.
This identification can be
accomplished in the field by one of the methods described in
paragraph 2c on page 63.
Homogeneous armor plate can be
satisfactorily welded using the electric arc welding process and
18-8 stainless steel heavy coated electrodes with reverse
polarity. Armored vehicles that have been exposed to conditions
of extreme cold should not be welded until the base metal has
been preheated sufficiently to bring the temperature of the base
metal in the zone of welding up to no less than 100 F. At this
temperature, the metal will be noticeably warm to the touch. If
this preheat is not applied, cracking will occur in the deposited
weld metal.
b.
Procedure.
(1) Simple cracks as shown in figure 27, view A, on the
following page, should be flame cut into a beveled V joint as
shown in figure 27, view B, before welding. Care should be taken
to round off the corners at the toe and root of the joint. This
is necessary in order to eliminate excessive weld metal dilution.
The included angle of bevel, as shown in figure 27, view C,
should be approximately 45 degrees to provide electrode clearance
for making the root welding beads. The root opening, as shown in
figure 27, view D, should be from 3/16 to 5/16 inch, depending on
plate thickness.
(2) The weld
good quality.
cracks, oxide
excessive weld
recommended as
beads deposited at the root of the weld must be
It is essential that care be taken to prevent
and slag inclusions, incomplete penetration, or
metal dilution in this area. Some of the methods
preparatory steps for root
69
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 27.
70
WELDING CRACKS IN
HOMOGENEOUS ARMOR.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
bead welding are shown on figure 28. For narrow root openings, a
3/16 inch stainless steel electrode without coating can be tack
welded in place as shown in figure 28, view A.
Welding bead
numbers 1 through 4 are then deposited sequentially. To ensure a
sound weld, remove all slag and oxides from the joint before
depositing beads 3 and 4. If a mild steel rod or strip, as shown
in figure 28, view B, the back side of the backing rod or strip
should be chipped out after beads 1 and 2 are deposited to
minimize dilution in beads 3 and 4. The use of a stainless steel
strip as a backing for root beads in a wide root opening is shown
as view C of figure 28. An alternate
FIGURE 28.
ROOT BEAD WELD.
71
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
method, shown in figure 28, view D, on the previous page, uses a
mild steel strip. When this method is used, the backing rod or
strip should be chipped out before depositing beads 3 and 4.
Another procedure, as shown in figure 28, view E, uses a copper
backing bar. The copper bar is removed after beads 1 and 2 are
deposited. (The beads will not weld to the copper bar.) Beads 3
and 4 are deposited after removal of the copper bar. In certain
cases, where plates of homogeneous armor are cracked along their
entire cross section of the plate, another method of joint
preparation, as shown at figure 28, view F, can be used. In this
other method, root beads A and B are deposited opposite from each
other at the base of the bevel. These root beads act as backing
for beads 1 through 6, which are deposited afterwards.
(3) Weld crater and fusion zone cracking, especially in the
root beads, is a major factor involved in welding cracks in armor
that terminate within the plates.
To prevent this cracking, an
intermittent backstep and overlap procedure, as shown in figure
29, view A, on the following page, is recommended. It should be
noted that all of the welding steps necessary for bead number 1
must be completed before depositing bead number 2.
By back
stepping, the craters at the end of each previous pass are
located and filled.
All craters on subsequent passes, that do
not terminate on previous deposited metal, should be filled by a
hesitation and drawback technique.
The filling up of weld
craters avoids the formation of star cracks which are caused by
the solidification of shallow deposits of molten weld metal.
(4) Each pass in beads 1 through 4, shown in figure 29, views B
and C, is limited from 1 to 2 inches in length and should be
peened while the weld metal is still hot to help overcome the
cooling stresses.
No electrode weaving motion should be used
when the root beads are deposited.
The welding should be
performed preferably with a 5/32 inch electrode.
Peening also
tends to eliminate or minimize warpage in the section being
welded. Arc blow should be controlled by properly adjusting the
method of welding.
Some of the more common defects encountered
when welding root beads on homogeneous armor plate and the proper
remedial procedures are shown in figure 30, on page 74.
72
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 29.
WELD BEADS ON HOMOGENEOUS
ARMOR PLATE.
73
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 30.
HOMOGENEOUS ARMOR COMMON DEFECTS
AND REMEDIAL PROCEDURES.
(5) The sequence of welding beads and the procedure recommended
to completely weld the single V joint are shown in figure 31, on
the following page.
Welding should be performed with a 5/32 or
3/16 inch electrode. The electrode is directed against the side
wall of the joint, so as to form an angle of approximately 20 to
30 degrees with the vertical.
The electrode should also be
inclined 5 to 15 degrees in the direction of welding.
By this
procedure,
the
side
wall
penetration
can
be
effectively
controlled. The electrode weaving motion should not exceed 2 1/2
electrode core wire diameters.
This is important because
stainless steel has a coefficient of expansion approximately 1
1/2 times that of mild steel; if a weaving motion
74
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 31.
WELDING SINGLE V JOINTS ON
HOMOGENEOUS ARMOR PLATE.
greater than that recommended is used, longitudinal
cracks in the weld or fusion zone may develop.
shrinkage
(6) The sequence of passes used for completely filling a double
joint is shown in figure 32, views A through C, on the following
page. The depth of penetration of weld metal into the base metal
should be controlled in order to obtain good fusion without
excessive dilution of the weld.
75
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 32.
76
WELDING DOUBLE V JOINTS ON
HOMOGENEOUS ARMOR PLATE.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
Excessive dilution will cause the weld to be non-stainless,
brittle, and subject to cracking. Proper penetration will give a
long scalloped heat affected zone on each side of the weld as
shown in figure 32, view D, on the previous page.
Insufficient
penetration (surface fusion) will produce a fairly straight edged
heat affected zone on each side of the weld.
This condition is
undesirable from the standpoint of good ballistic properties.
(7) Better control can be maintained of the heat input at the
joint and of the shape of the joint, by alternately depositing
the weld metal on one side of the joint and then the other. Each
layer of metal deposited serves to stress relieve the weld metal
immediately beneath it, and to partially temper the heat affected
zone produced in the base metal by the previous welding bead.
The passes at the toe of the weld joint, as shown in figure 32,
view C, also serve to anneal the base metal and are deposited
before the intermediate passes are added to fill the weld joint.
The annealing passes at the toe of the weld joint are an
important factor in the elimination of fusion zone cracks which
might start at the surface of the weld. Through careful control
of the depth of penetration, a heat affected zone with a
scalloped effect is produced.
c.
Emergency Repairs.
Two methods of emergency repairs on
cracked armor plate that can be made by using butt straps are
shown in figure 33, views E and F, on the following page. These
straps are welded to the back of the cracked armor plate.
The
primary purpose of these butt straps is to strengthen the section
weakened by the crack.
d.
Repairing Penetrations. Complete penetrations in homogeneous
armor plate are repaired by using the procedures shown in figures
34 through 36, on pages 79 through 81.
Figure 35, view A, on
page 80, shows that considerable structural damage has been done
to the metal immediately adjacent to the shell penetration.
Shell penetration holes smaller than the thickness of the armor
plate can be repaired by the butt strap method.
To effect
repairs, all torn and irregular edges of the damaged metal should
be removed to permit good contact between the butt strap and the
base armor
77
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 33.
BUTT STRAP WELDS ON
CRACKED ARMOR PLATE.
plate as shown in figure 34, on the following page.
For holes
that are larger than the thickness of the armor plate, a plug
patch of homogeneous metal of the same thickness as the base
metal should be used as shown in figure 35, view B, on page 80.
The correct and incorrect method of preparing and welding the
plug patch is shown in figure 36, views A and B, on page 81.
Small diameter penetrations can be repaired by plug welding
without the use of a patch.
e.
Repairing Bulges. Bulges in armor that are also cracked, but
do not interfere with the operation of internal mechanisms in the
vehicle, can be repaired by welding the cracked section using the
procedure described in paragraph c above. For best results, the
bulge should be cut out and a patch inserted.
Bulges in the
armor that interfere with the operation of internal mechanisms
may be removed by grinding or chipping them away. In all
78
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
cases, the welds should be made to the full thickness of the
plate and all cracks over 1/4 inch in width should be chipped out
before rewelding.
f.
Repairs Made from One Side. Where it is not feasible to make
the welding repair from both sides of the armor, the joint must
then be made from one side as shown in figure 31 on page 75.
Note that either a butt strap or stainless steel strip can be
used as a backup for the root beads of the weld.
FIGURE 34.
EMERGENCY REPAIRS.
79
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 35.
80
DOUBLE V PLUG WELDING.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 36.
CORRECT AND INCORRECT PLUG
WELD PREPARATION.
81
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
g. Repairs with Nonwelded Butt Strap.
A technique that
permits removal of the butt strap after welding is shown in
figure 37, view A. This technique is used for applications where
a butt strap would interfere with the operation of internal
mechanisms.
It permits welding a single V joint in homogeneous
armor plate without welding the butt strap to the weld metal.
This technique
FIGURE 37.
82
WELDING WITHOUT A BUTT STRAP.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
requires increasing the angle of the electrode to 60 degrees, as
shown in figure 37, view B, on the previous page, at the middle
of the weave while simultaneously increasing the weaving speed.
As a result, the weld metal is deposited to the base metal and to
previously deposited metal instead of adhering to the butt strap.
At the end of each weave, the angle of the electrode is decreased
to 15 degrees, as shown in figure 37, view C, simultaneous with
the weaving speed, and the electrode is held momentarily adjacent
to the side wall to ensure good side wall penetration.
After
depositing the root pass, the butt strap can be removed by
breaking the tack welds which secure it to the armor plate.
A
final pass can be applied to the root of the weld after removing
the butt strap.
h.
Repairing Gouges. Occasionally, a projectile will impact on
the armor plate at an angle and only gouge it without
penetrating.
To effect repairs, the gouge should be prepared
into a double V joint, as shown in figure 38, view A, on the
following page, to allow welding from both sides. Merely filling
the gouge with weld metal, as shown in figure 38, view B, is not
satisfactory, since it does not remove any subsurface cracks that
may have been caused by the shell impact.
Also, the heat zone
produced at the base of the filled-in gouge has poor ballistic
strength.
6.
Welding Face Hardened Armor Plate
a.
General.
(1) The face side of face hardened armor is extremely hard and
brittle.
Cracks on this type armor plate can be welded
satisfactorily from the soft side. These cracks can be repaired
by using 18-8 stainless steel reverse polarity heavy coated
electrodes. Special precautions, however, must be taken to avoid
distorting and excessively heating the armor plate.
Distortion
and excessive heat place stress on the base metal causing the
plate face to crack.
(2) Satisfactory methods for welding this type of armor makes
use of the butt strap and butt welding techniques, shown in
figures 39 and 40 on pages 85 and 86. The dimensions of the butt
strap depend on the thickness of the armor.
Butt strap
dimensions for armor up to one inch thick are
83
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 38.
REPAIRING GOUGES IN HOMOGENEOUS
ARMOR PLATE.
provided in TM 9-237, if desired. The butt strap is tack welded
to the soft side of the armor through elongated slots cut into
the strap. The slots are then completely filled by plug welding
them. Do not use excessive weld reinforcement or undercutting at
the surface of the plug.
84
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 39.
BUTT STRAP WELDS FOR FACE
HARDENED ARMOR PLATE.
(3) To seal a crack in face hardened armor, as shown in figure
40, view A, on the following page, against spatter and to make it
watertight, weld a seal bead on the soft side and grind it flush
before applying the butt strap. All welding should be performed
on clean, scale free surfaces.
Previously deposited weld metal
should be thoroughly cleaned by chipping and wire brushing to
remove slag and oxides to ensure sound welds.
85
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 40.
86
SEALING CRACK IN FACE
HARDENED ARMOR.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(4) Crater cracks can be eliminated by the backstep and overlap
procedures or by using the electrode hesitation and drawback technique.
Crater cracks formed in the initial weld passes should be chipped out
before additional weld metal is applied.
Then they can be welded out
successfully by the subsequent passes.
As a precaution, string beads
should be used on the initial passes.
On subsequent passes, do not
weave the electrode more than 2 1/2 electrode core wire diameters. The
efficiency of the joint welded by this method depends upon good fusion
to the base metal and side walls of the slots in the butt strap.
(5) If straightening is necessary, use a hammer only on the soft side
of face hardened armor, on the butt strap, or on the plug welds.
Do
not hammer on the face hardened side. As a rule, force should not be
applied to straighten face hardened armor if the applied force will
produce tension on the face hardened side.
(6) When two or more butt straps are used to repair irregular cracks
or to make patch welds, the butt straps are welded together for
additional strength as shown in figure 41.
FIGURE 41.
BUTT STRAP.
87
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
b. Armor Plate Repair Methods.
(1) Corner joints can be repaired by using angle iron for butt
straps as shown in figure 42. The procedures used to effect this
type of repair are the same as those used in making plug welds
for repairing cracks in face hardened armor and described in
paragraph 6a(2) beginning on page 83.
FIGURE 42.
88
CORNER JOINT IN
ARMOR PLATE.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(2) Generally, the butt strap method is satisfactory for
repairing up to one inch or thicker of face hardened armor.
However, it is usually only used on thicknesses up to and
including 1/2 inch plate.
(3) Another accepted procedure for welding face hardened armor
above 1/2 inch in thickness is the double V joint method, as
shown in figure 43.
This method requires that the soft side of
the plate be
FIGURE 43.
V JOINT WELDING FACE
HARDENED ARMOR PLATE.
89
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
completely welded before welding on the face side. Using string
bead welds, and the backstep and overlap procedures for the root
passes, reduces the danger of cracks developing in the weld. To
keep the structure free of warpage, no weaving motion of the
welding rod should be used on this type joint.
(4) A modified procedure, known as the depressed joint method,
shown in figure 44, view A, is used for welding up to and
including 1/2 inch thick face hardened armor plate. This method
uses a 1/8 inch
FIGURE 44.
90
DEPRESSED JOINT ON FACE HARDENED
ARMOR PLATE AND SEAL BEAD WELD.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
by 1/4 inch stainless steel bar which is placed in the damaged
portion of the armor plate.
It is then bead welded in place.
The principal advantages of this joint are its simplicity, and
good structural and ballistic properties.
Care should be taken
that no welding is done on the hard face side of the armor plate.
c.
Armor Plate Welding Electrodes.
(1) The most satisfactory method for the repair of homogeneous
and face hardened armor plate is the arc welding process with
stainless steel electrodes.
(2) In the oxyacetylene welding process, a large section of
base metal must be heated to maintain a welding puddle to weld
satisfactorily. This heating destroys the heat treatment of the
base metal, causing large areas to become structurally and
ballistically weak.
In addition, this process is slow and
produces considerable warpage of the base metal.
(3) Initially, developments in armor plate welding required the
use of stainless steel electrodes containing 25 percent chromium
and 20 percent nickel.
Further developments served to produce
electrodes with a core of 18 percent chromium and 8 percent
nickel, and a coating of manganese or molybdenum, or both, which
produce excellent results.
These electrodes are known as
manganese modified 18-8, and molybdenum modified 18-8 stainless
steel electrodes.
They can be used for welding all types of
armor plate by the electric arc process without preheating or
postheating the base metal structure.
(4) Current and Polarity.
The exact current required for arc
welding with the electrodes previously discussed depend to some
extent on the joint type, electrode design, and position of
welding.
Listed below are the recommended welding current
settings listed for direct current reverse polarity, all
position, heavy coated, modified 18-8 stainless steel electrodes.
91
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
7.
Strengthening Riveted Joints in Armor Plate
a.
Buttonhead Riveted Joints. To strengthen buttonhead riveted
joints in armor plate, a seal bead weld is recommended as shown
in figure 44, view B, on page 90. To apply the bead, the arc is
struck at the top of the rivet using a stainless steel electrode.
The electrode is held above the top of the rivet long enough to
melt approximately 1/2 inch of the electrode.
The electrode is
then moved along the curved surface of the rivet down to the
armor plate and around the edge of the rivet until the rivet is
completely welded to the armor plate.
Rivet joints in
homogeneous armor plate can be seal welded on both sides. Rivet
joints in face hardened armor, however, should be seal welded
only on the soft side of the plate.
b.
Countersunk Rivet Joints.
Countersunk rivet
sealed in the same manner as buttonhead rivet joints.
joints
are
c.
Advantage of Welding Rivet Joints.
Seal bead welding rivet
joints prevents the rivet head from shearing off, and the rivet
shank from punching through the plate upon a projectile impacting
on the armor plate.
8.
Testing of Welds
a.
General. To ensure the satisfactory performance of a welded
structure, the quality of the welds must be determined by
adequate testing procedures.
The welded structure, therefore,
must be proof tested under conditions that are the same or more
severe than those found in the field.
Tests also serve to
determine the proper welding design; and forestall injury,
inconvenience, and untimely failure of materiel.
Generally,
there are two types of tests that can be performed to ensure the
satisfactory performance of the welded structure. They are, the
performance and the physical types of tests.
b.
Performance Tests.
Materiel repaired by standard welding procedures may be tested by
operating it to perform the functions for which it was designed.
For example, a weapon can be tested by firing an extra heavy
charge to determine the safety of the weld; a wheel vehicle can
be tested at high speeds over rough
92
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
terrain; and welded armor plate and other heavy structural
members can be tested by gunfire.
But, test firing of weapons
and testing of armor plate by gunfire is not feasible for
maintenance units in the field.
The succeeding paragraphs,
therefore, describe only those physical type tests that can be
conducted in intermediate direct and general support maintenance
units, in field depot maintenance operations, and in CONUS
(continental United States) depot maintenance operations.
c.
Physical Tests.
(1) General.
These types of tests are designed to check the
skill of the welder, the quality of the weld metal, and the
strength of the welded joint.
Some of these tests, such as the
free bend and nick break tests, are destructive. In these tests,
the specimen is tested until it fails in order that the desired
information can be gained.
Other physical tests, such as the
hydrostatic and magnetic particle tests, are not destructive.
Then there are simple physical tests, such as the appearance,
fracture, and grinding tests, that can be performed with tools
found in a field maintenance company shop. These simple physical
tests are described in the following subparagraph.
The
destructive and nondestructive type tests are described in the
succeeding subparagraphs.
(2) Simple Physical Tests.
(a) Appearance Test.
This is a nondestructive test.
In this
type test, a visual examination is made of the weld to check for
such defects as brittleness, cracks, craters, undercut, overlap
and slag inclusions. All these defects are unacceptable and the
joint must be reconstructed and rewelded.
(b) Fracture Test.
This is a destructive test.
To perform
this test, a cross section specimen must be cut off from the
welded metal. The specimen is then fractured to expose the weld.
The welded zone is then visually examined to check for unevenness
of the weld metal grain, cracks, craters, and inadequate
penetration of the weld into the base metal.
(c) Grinding Test.
This is a nondestructive test.
It is
particularly applicable to seal bead welds made for waterproofing
and sealing cracks in
93
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
face hardened metal.
This type weld must be ground down flush
with the base metal before welding of the strap to reinforce the
damaged area. After grinding, the weld is then visually examined
to check for proper penetration, craters, cracks, and evenness in
the weld metal grain.
(3) Destructive and Nondestructive Tests.
In the following
subparagraphs, we will describe a total of six tests, three
destructive and three nondestructive.
These six test are the
ones most likely to be performed in maintenance units in the
field and depot maintenance operations.
If more information on
other tests is desired, it is provided in TM 9-237.
(a) Destructive Tests.
1 Guided Bend Test.
a This type test serves to determine the quality of the
weld metal at the face, the root of the welded joint, and the
degree of penetration and fusion to the base metal. These tests
are made on a jig as shown in figure 45, view A, on the following
page. This jig can be fabricated to any size desired in a field
maintenance company machine shop.
b To perform this test, the test specimens must be
machined from welded plates to a thickness within the capacity of
the bending jig.
The specimen is then placed across die
supports.
The weld on the specimen must be centered on the U
portion of the die.
The plunger is then lowered onto the
specimen from above by a hydraulic jack or other device to force
the specimen into the U portion of the die.
To fulfill the
requirements of this test, the specimen must bend 180 degrees and
have no cracks greater than 1/8 inch on its surface.
c Both a face bend and a root bend test of weld, as shown
in figure 45, view B, can be performed on this jig. To perform
the face bend test, place the face of the weld facing down on the
jig. The root bend test is performed by placing the specimen on
the die with the face of the weld facing up.
94
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 45.
GUIDED BEND TEST JIG.
95
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
2 Free Bend Test.
a The free bend test has been devised to measure the
ductility of the weld metal deposited in a weld joint.
A test
specimen is machined from the welded plate with the weld located
in the center as shown in figure 46, view A, on the following
page. Each lengthwise edge of the specimen should be rounded off
to a radius not to exceed one-tenth of the thickness of the
specimen.
Any tool marks should be made lengthwise of the
specimen. And two lines, opposite each other, are scribed on the
face of the weld at a distance of 1/16 inch inward from the edges
of the weld as shown in figure 46, view B. The distance between
these two lines is measured in inches and recorded as the initial
distance X. The ends of the specimen are then bent to form two
30 degree angles at approximately one-third of the length inward
from the ends. The weld is thus centrally located to ensure that
all bending occurs in the weld.
b The bent specimen is then placed in a hydraulic or
mechanical machine as shown in figure 46, view C, and bent until
a crack greater than 1/16 inch appears on the face of the weld.
If no cracks appear on thin armor plate, continue bending until
the specimen can be bent in a vise. Heavier plate specimens are
usually tested in a hydraulic press or bending jig.
To prevent
slipping of the specimen, a groove should be machined in the
upper and lower contact plates of the bending equipment, as shown
in figure 46, view E.
c After being bent to the specifications prescribed in the
preceding subparagraph, the distance between the scribed lines is
again measured and recorded as the distance Y.
Find the
percentage of elongation by using the formula shown in figure 46.
The tested specimen must have a minimum elongation of 15 percent
with no cracks greater than 1/16 inch at the weld to pass this
test.
3 Nick Break Test.
a The nick break test has been devised to determine if the
weld metal of a welded butt joint has any internal defects, such
as slag inclusions, gas pockets, poor fusion, and/or oxidized or
burnt metal.
The specimen is obtained from a welded butt joint
either by machining or by cutting with an
96
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
FIGURE 46.
FREE BEND TEST.
97
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
oxyacetylene torch. Each end of the weld at the joint is slotted
with a hacksaw or band saw as shown in figure 47. The specimen
is then bridged across two steel blocks, and struck with a heavy
hammer until the section of the weld between the slots fractures.
The metal thus exposed should be completely fused and free from
slag inclusions. The size of any gas pocket must not be greater
than 1/16 inch at its widest point. The number of gas pockets or
pores should not exceed six per square inch.
b Another break test method is used to determine the
soundness of fillet welds.
This is known as the fillet weld
break test. This test is performed by applying force on the apex
of the V shaped specimen with a hydraulic press or by striking it
with a hammer until the fillet weld ruptures.
The surfaces of
the fracture are then examined for the same defects mentioned in
the preceding paragraph.
FIGURE 47.
98
NICK BREAK TEST.
WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(b) Nondestructive Tests.
1 Hydrostatic Test.
a This nondestructive test is used to check the quality of
welds on closed containers such as pressure vessels and liquid
tanks.
b One method of performing this test is to fill the vessel
with water and apply a pressure greater than the working pressure
of the vessel.
The outside surface of the vessel is then
observed for leaks through the welds.
To check welds in
nonpressurized tanks, they may be filled with water and observed
for seepage or leaks through the welds.
2 Magnetic Particle Test. This method of testing is used on
welds and parts made of magnetic alloy steels. It is applicable
only to ferromagnetic materials in which the deposited weld is
also ferromagnetic.
A strong magnetic field is set up in the
ferromagnetic specimen by an electric current. Any discontinuity
in the metal will set up a leakage field with local magnetic
poles of its own.
These poles then attract the magnetic
particles sprinkled on the surface of the specimen indicating a
discontinuity in the overall pattern of the magnetized specimen.
This discontinuity indicates that a defect, such as a crack,
exists on or close to the surface of the specimen.
3 Fluorescent
Penetrant
Test.
Fluorescent
penetrant
inspection is a nondestructive test whereby cracks, pores, leaks,
and other discontinuities can be located in solid materials. It
is
particularly
useful
for
locating
surface
defects
in
nonmagnetic materials such as aluminum, magnesium and austenitic
steel welds and for locating leaks in all types of welds.
This
test makes use of a water-washable and highly fluorescent
material. This material is applied to the clean, dry surface of
the specimen by brushing, spraying, or dipping.
The excess
material is removed by rinsing, wiping with clean water-soaked
cloths, or by sandblasting. A wet or dry type developer is then
applied.
Afterwards, a black light is used to reveal
discontinuities in the weld specimen.
The discontinuities will
show up as brilliant fluorescent spots on the surface of the
specimen.
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
9.
Troubleshooting Welds.
a.
Thus far, this lesson has described the processes for
identifying electrodes, the automotive welding processes, the
types and techniques of joint design, the procedures for welding
armor plate, and the methods of destructive and nondestructive
testing of welds.
This material provided the basis for the
troubleshooting of welds to be discussed in the succeeding
paragraphs. Each of the troubleshooting procedures discussed are
based on specific malfunctions detected as a result of visually
examining welds. The troubleshooting procedures discussed below,
therefore, are based on a total of five specific malfunctions
most likely to be encountered in a maintenance unit in the field.
For further information on other troubleshooting procedures refer
to TM 9-237.
b.
Procedure.
Listed below are the procedures that the welder
would follow in troubleshooting a weld upon detecting the
malfunction indicated.
(1) Poor Fusion.
Step 1. Check the diameter and the length of the electrode. The
electrode selected should be of a size that will permit its
reaching the bottom of the joint to obtain adequate penetration
and good fusion.
Step 2. Check the welding current setting.
Use sufficient
welding current to permit adequate deposit and penetration of the
weld.
Heavier plates require higher current for a given
electrode than light plates.
Step 3. Check the welding technique used.
Be sure that the
weave is wide enough to thoroughly melt the sidewalls of the
joint.
Step 4. Check the preparation of the joint. The deposited metal
should fuse with the base metal and not curl away from it or
merely stick to it.
(2) Poor Penetration.
Step 1. Check to see if the electrode is designed for the
welding position being used.
Electrodes should be used for
welding in the position for which they were designed. Be sure to
allow the proper root openings at the bottom of a weld. Use
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
a backup bar if possible. Chip or cut out the back of the joint
and deposit a bead of weld metal at this point.
Step 2. Check the size of the electrode being used.
Do not
expect excessive penetration from an electrode.
Use small
diameter electrodes in a narrow welding groove to permit reaching
the bottom of the groove.
Step 3. Check the welding current setting.
welding current to obtain proper penetration.
Use
sufficient
Step 4. Check the welding speed.
Do not weld too rapidly.
Control the welding speed to permit penetration to the bottom of
the welded joint.
(3) Undercut.
Step 1. Check the welding current setting. Use moderate welding
current and do not try to weld at too high a speed.
Step 2. Check for proper manipulation of the electrode. Do not
use too large an electrode.
If the puddle of molten metal
becomes too large, undercut may result. Excessive width of weave
will cause undercut and should not be used. A uniform weave, not
over three times the electrode diameter, will aid greatly in
preventing undercut in butt welds.
If an electrode is held too
near the vertical plate in making a horizontal fillet weld,
undercut on the vertical plate will result.
(4) Poor Weld Appearance.
Step 1. Check welding technique for proper current and electrode
manipulation technique.
Ensure the use of the proper welding
technique for the electrode used.
Do not use excessive welding
current. Use a uniform weave or rate of travel at all times.
Step 2. Check the characteristics of type electrode used.
Use
an electrode designed for the type of weld, base metal, and the
position in which the weld is to be made.
Step 3. Check the welding position for which the electrode is
designed. Do not make fillet welds
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
with downhand (flat position) electrodes unless the parts are
positioned properly.
Step 4. Check for the proper joint preparation.
joints are properly prepared.
Make sure all
(5) Warping of Thin Plates.
Step 1. Check for shrinkage of the deposited weld metal. Select
an electrode with high welding speed and moderate penetrating
properties.
Step 2. Check for excessive local heating at the joint.
Weld
rapidly to prevent excessive local heating of the plates adjacent
to the weld.
Step 3. Check for proper preparation of the weld joint.
Avoid
an excessive root opening in the joint between the parts to be
welded.
Hammer the joint edges thinner than the rest of the
plates before welding.
Hammering elongates the edges and the
weld shrinkage causes them to pull back to the original shape.
Step 4. Check the welding procedure.
Use either the special
intermittent or alternating welding sequence, or backstep or skip
welding procedure.
Step 5. Check the clamping of parts.
Properly clamp parts
adjacent to the joint. Use backup fixtures to cool parts rapidly.
10. Conclusion
This task served to describe the theory, principles, and
procedures of welding armor plate; the methods of destructive and
nondestructive testing of welds, and the troubleshooting of welds
pertaining to electric arc welding. This task completes the text
material of this lesson.
The next task consists of a practical
exercise which you are required to complete by providing the
answers to the questions.
102
WELDING OPERATIONS I - OD1651 - LESSON 1/PE 1
PRACTICAL EXERCISE
Instructions
This exercise is provided to test your progress in learning the
materials in the subcourse.
Please answer the questions that
follow.
You may check your answers from the page that follows
the questions.
1.
List two of the seven factors that must be considered in
selecting electrodes.
2.
What are the three groups into which metal-arc electrodes may
be grouped and classified?
3.
The American Welding Society has formulated a number series
for the identification of electrodes.
a.
What
signify?
does
the
letter
E
at
the
beginning
of
this
number
b.
What two digits of this number series indicate the position
of the weld and the type of electrical current required?
4.
What is one of the functions performed by the coating on
thinly-coated electrodes?
5.
What two types of electric current are used for electric arc
welding?
6.
What two methods of welding may be used to repair cracks in
cast iron engine blocks?
7.
By what commonly used method are broken or weakened vehicle
frames crossmembers repaired or strengthened?
8.
Name two of the five type welding joints used in metal-arc
welding.
9.
What is the preferred arc lengths for obtaining
control of the filler metal deposited during welding?
better
10. Of the four general positions used for welding, which is most
difficult to weld in?
103
WELDING OPERATIONS I - OD1651 - LESSON 1/PE 1
11. What are the two types of armor plate used on Army combat
vehicles?
12. What type of armor plate may be repaired from both sides?
13. What is one of the three simple tests that can be performed
in a maintenance company shop for testing welds?
14. What is one of the three nondestructive tests that is used
for testing welds?
15. What is the first step in troubleshooting a weld with poor
fusion?
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WELDING OPERATIONS I - OD1651 - LESSON 1/PE 1
LESSON 1.
PRACTICAL EXERCISE - ANSWERS
1.
a.
b.
c.
d.
e.
f.
g.
Specific properties
Type of base metal
Position of the weld
Type of current available
Current polarity available
Dimensions of the section to be welded
The type of fit permitted by the work
2.
a.
b.
c.
Bare
Thinly coated
Shielded-arc or heavy coated
3.
a.
The letter in the number series indicates that
welding rod is intended for use in metal-arc welding
The third and fourth numbers respectively
b.
4.
a.
b.
c.
the
It dissolves or reduces impurities on the weld metal
deposited
It reduces the adhesive force between the molten metal
and the end of the electrode
It increases the stability of the arc
5.
Alternating and direct current.
6.
Metal-arc welding and brazing with oxyacetylene.
7.
By the use of reinforcing plates.
8.
a.
b.
c.
d.
e.
9.
Short arc length.
Butt joint
Corner joint
Edge joint
Lap joint
Tee joint
10. The overhead position.
11. Homogeneous and face hardened armor plate.
12. Homogeneous plate.
13. a.
b.
c.
Appearance test
Fracture test
Grinding test
105
WELDING OPERATIONS I - OD1651 - LESSON 1/PE 1
14. a.
b.
c.
Guided bend test
Free bend test
Nick break test
15. Check the diameter of the electrode.
106
WELDING OPERATIONS I - OD1651 - REFERENCES
REFERENCES
107
WELDING OPERATIONS I - OD1651 - REFERENCES
REFERENCES
The following documents were
developing this subcourse:
TM 9-237
108
used
as
resource
materials
in
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