Flux Cored Arc Welding (FCAW)

Flux Cored Arc Welding (FCAW)
Flux Cored Arc Welding
Topics
1.0.0
Introduction to the Process
2.0.0
Principles of Operation
3.0.0
Equipment for Welding
4.0.0
Equipment Setup, Operation, and Shut Down
5.0.0
Shielding Gas and Electrodes
6.0.0
Welding Applications
7.0.0
Welding Metallurgy
8.0.0
Weld and Joint Design
9.0.0
Welding Procedure Variables
10.0.0
Welding Procedure Schedules
11.0.0
Preweld Preparations
12.0.0
Welding Discontinuities and Problems
13.0.0
Postweld Procedures
14.0.0
Welder Training and Qualification
15.0.0
Welding Safety
Overview
Flux cored arc welding, or FCAW, evolved from the gas metal arc welding, or GMAW
process to improve arc action, metal transfer, weld metal properties, and weld
appearance. The heat is provided by an arc between a continuously fed tubular
electrode wire and the workpiece. The major difference is that FCAW utilizes an
electrode very different from the solid electrode used in GMAW. In fact, it is closer to the
electrodes used in shielded metal arc welding, or SMAW or stick welding, except the
flux is on the inside of a flexible electrode instead of on the outside of a very stiff
electrode.
The flux-cored electrode is a fabricated electrode and, as the name implies, flux
material is deposited into its core. The flux-cored electrode begins as a flat metal strip
that is formed first into a "U" shape. Flux and alloying elements are deposited into the
"U" and then the shape is closed into a tubular configuration by a series of forming rolls.
Shielding is obtained by the flux contained within the tubular electrode wire, or by the
flux and the addition of a shielding gas.
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This chapter is designed to give you a basic understanding of the FCAW process and
equipment along with the key variables that affect the quality of welds, such as
electrode selection, polarity and amperage, arc length, travel speed, and electrode
angles. It will also cover core competencies, such as setting up welding equipment,
preparing weld materials, fitting up weld materials, welding carbon steel plates, and
repairing welds. It will also provide you with an understanding of the safety precautions
for FCAW and an awareness of the importance of safety in welding.
Always refer to the manufacturer’s manuals for specific operating and maintenance
instructions.
Objectives
When you have completed this chapter, you will be able to do the following:
1. Describe the process of flux cored arc welding.
2. Describe the principles of operation used for flux cored arc welding.
3. Describe the equipment associated with flux cored arc welding.
4. Describe the setup, operation and shut down of flux cored arc welding
equipment.
5. Identify the classification and selection of flux-cored electrodes flux-cored
electrodes used for flux cored arc welding.
6. Identify the welding applications for flux cored arc welding.
7. Describe the welding metallurgy of flux cored arc welding.
8. Identify weld and joint designs used for flux cored arc welding.
9. Describe the welding procedure variables associated with flux cored arc
welding.
10. Identify welding procedure schedules used for flux cored arc welding.
11. Describe pre-weld preparations for flux cored arc welding.
12. Identify defects and problems associated with flux cored arc welding.
13. Describe post-weld procedures for flux cored arc welding.
14. State the welder training and qualifications associated with flux cored arc
welding.
15. Describe the welding safety associated with flux cored arc welding.
Prerequisites
None
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11-2
This course map shows all of the chapters in Steelworker Basic. The suggested training
order begins at the bottom and proceeds up. Skill levels increase as you advance on
the course map.
Introduction to Reinforcing Steel
Introduction to Structural Steel
Pre-Engineered Structures:
Buildings, K-Spans, Towers and Antennas
Rigging
Wire rope
S
T
E
E
L
Fiber Line
W
Layout and Fabrication of Sheet-Metal and Fiberglass Duct
O
Welding Quality Control
R
K
Flux Cored Arc Welding-FCAW
E
Gas-Metal Arc Welding-GMAW
R
Gas-Tungsten Arc Welding-GTAW
Shielded Metal Arc Welding-SMAW
B
A
Plasma Arc Cutting Operations
S
Soldering, Brazing, Braze Welding, Wearfacing
I
Gas Welding
C
Gas Cutting
Introduction to Welding
Basic Heat Treatment
Introduction to Types and Identification of Metal
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information is for review. When you have completed your review, select
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again.
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1.0.0 INTRODUCTION to the PROCESS
Flux cored arc welding (FCAW) is an arc welding process in which the heat for welding
is produced by an arc between a continuously fed tubular electrode wire and the work.
Shielding is obtained by a flux contained within the tubular electrode wire or by the flux
and an externally supplied shielding gas (Figure 11-1).
Flux cored arc welding is similar to gas metal arc welding in many ways, but the fluxcored wires used for this process give it different characteristics. Flux cored arc welding
is widely used for welding ferrous metals and is particularly good for applications where
high deposition rates are desirable. Also, at high welding currents, the arc is smooth
and more manageable when compared to using large diameter gas metal arc welding
electrodes with carbon dioxide. With FCAW, the arc and weld pool are clearly visible to
the welder, and a slag coating is left on the surface of the weld bead, which must be
removed. Since the filler metal transfers across the arc, some spatter is created and
some smoke produced.
Figure 11-1 — FCAW self shielded and external gas shielded electrodes.
As in GMAW, FCAW depends on a gas shield to protect the weld zone from detrimental
atmospheric contamination. However, with FCAW, there are two primary ways this is
accomplished:
1. The gas is applied from an external source, in which case the electrode is
referred to as a gas shielded flux-cored electrode.
2. The gas is generated from the decomposition of gas-forming ingredients
contained in the electrode's core. In this instance, the electrode is known as a
self-shielding flux-cored electrode.
In addition to the gas shield, the flux-cored electrode produces a slag covering for
further protection of the weld metal as it cools, which must be manually removed with a
wire brush or chipping hammer.
The main advantage of the self-shielding method is that its operation is somewhat
simplified because of the absence of external shielding equipment. Although selfNAVEDTRA 14250A
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shielding electrodes have been developed for welding low-alloy and stainless steels,
they are most widely used on mild steels. The self-shielding method generally uses a
long electrical stickout (distance between the contact tube and the end of the unmelted
electrode, commonly from one to four inches). Electrical resistance is increased with the
long extension, preheating the electrode before it is fed into the arc. This preheating
enables the electrode to burn off at a faster rate and increases deposition. The
preheating also decreases the heat available for melting the base metal, resulting in a
more shallow penetration than the gas shielded process.
A major drawback of the self-shielded process is the metallurgical quality of the
deposited weld metal. In addition to gaining its shielding ability from gas-forming
ingredients in the core, the self-shielded electrode contains a high level of deoxidizing
and denitrifying alloys, primarily aluminum, in its core. Although the aluminum performs
well in neutralizing the effects of oxygen and nitrogen in the arc zone, its presence in
the weld metal will reduce ductility and impact strength at low temperatures. For this
reason, the self-shielding method is usually restricted to less critical applications.
The self-shielding electrodes are more suitable for welding in drafty locations than the
gas-shielded types. Since the molten filler metal is on the outside of the flux, the gases
formed by the decomposing flux are not totally relied upon to shield the arc from the
atmosphere. To compensate, the deoxidizing and denitrifying elements in the flux
further help to neutralize the effects of nitrogen and oxygen present in the weld zone.
The gas-shielded flux-cored electrode has a major advantage over the self-shielded
flux-cored electrode, which is, the protective envelope formed by the auxiliary gas shield
around the molten puddle. This envelope effectively excludes the atmosphere without
the need for core ingredients, such as aluminum. Because of this more thorough
shielding, the weld metallurgy is cleaner, which makes this process suitable for welding
not only mild steels, but also low-alloy steels in a wide range of strength and impact
levels.
The gas-shielded method uses a shorter electrical stickout than the self-shielded
process. (Refer to Figure 11-1 again) Extensions from 1/2" to 3/4" are common on all
diameters, and 3/4" to 1-1/2" on larger diameters. Higher welding currents are also used
with this process, enabling high deposition rates. The auxiliary shielding helps to reduce
the arc energy into a columnar pattern. The combination of high currents and the action
of the shielding gas contributes to the deep penetration inherent with this process. Both
spray and globular transfer are utilized with the gas-shielded process.
1.1.0 Methods of Application
Although flux cored arc welding may be applied semiautomatically, by machine, or
automatically, the process is usually applied semiautomatically. In semiautomatic
welding, the wire feeder feeds the electrode wire and the power source maintains the
arc length. The welder manipulates the welding gun and adjusts the welding
parameters. FCAW is also used in machine welding where, in addition to feeding the
wire and maintaining the arc length, the machinery also provides the joint travel. The
welding operator continuously monitors the welding and makes adjustments in the
welding parameters. Automatic welding is used in high production applications. In
automatic welding, the welding operator only starts the operation.
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1.2.0 Advantages and Limitations
Flux cored arc welding has many advantages for a wide variety of applications. It often
competes with shielded metal arc welding, gas metal arc welding, and submerged arc
welding (SAW) for many applications. Some of the advantages of this process are:
1. It has a high deposition rate and faster travel speeds.
2. Using small diameter electrode wires, welding can be done in all positions.
3. Some flux-cored wires do not need an external supply of shielding gas, which
simplifies the equipment.
4. The electrode wire is fed continuously so there is very little time spent on
changing electrodes.
5. Deposits a higher percentage of the filler metal when compared to shielded metal
arc welding.
6. Obtains better penetration than shielded metal arc welding.
2.0.0 PRINCIPLES of OPERATION
Flux cored arc welding uses the heat of an electric arc between a consumable, tubular
electrode and the part to be welded. Electric current passing through an ionized gas
produces an electric arc. The gas atoms and molecules are broken up and ionized by
losing electrons and leaving a positive charge. The positive gas ions then flow from the
positive pole to the negative pole and the electrons flow from the negative pole to the
positive pole. The electrons carry about 95% of the heat and the rest is carried by the
positive ions. The heat of the arc melts the electrode and the surface of the base metal.
One of two methods shields the molten weld metal, heated weld zone, and electrode.
The first method is by the decomposition of the flux core of the electrode. The second
method is by a combination of an externally supplied shielding gas and the
decomposition of the flux core of the electrode wire. The flux core has essentially the
same purpose as the coating on an electrode for shielded metal arc welding. The
molten electrode filler metal transfers across the arc and into the molten weld puddle,
and a slag forms on top of the weld bead that can be removed after welding.
The arc is struck by starting the wire feed which causes the electrode wire to touch the
workpiece and initiate the arc. Arc travel is usually not started until a weld puddle is
formed. The welding gun then moves along the weld joint manually or mechanically so
that the edges of the weld joint are joined. The weld metal then solidifies behind the arc,
completing the welding process. A large amount of flux is contained in the core of a selfshielding wire as compared to a gas-shielded wire. This is needed to provide adequate
shielding and because of this, a thicker slag coating is formed. In these wires,
deoxidizing and denitrifying elements are needed in the filler metal and flux core
because some nitrogen is introduced from the atmosphere.
2.1.0 Arc Systems
The FCAW process may be operated on both constant voltage and constant current
power sources. A welding power source can be classified by its volt-ampere
characteristics as a constant voltage (also called constant potential) or constant current
(also called variable voltage) type, although there are some machines that can produce
both characteristics. Constant voltage power sources are preferred for a majority of
FCAW applications.
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In the constant voltage arc system, the voltage delivered to the arc is maintained at a
relatively constant level that gives a flat or nearly flat volt-ampere curve, as shown in
Figure 11-2. This type of power source is widely used for the processes that require a
continuously fed wire electrode. In this system, the arc length is controlled by setting the
voltage level on the power source and the welding current is controlled by setting the
wire feed speed.
As Figure 11-2 shows, a slight change in
the arc length (voltage level) will produce a
large change in the welding current.
Most power sources have a fixed slope built
in for a certain type of flux cored arc
welding. Some constant voltage welding
machines are equipped with a slope control
used to change the slope of the voltampere curve.
Figure 11-3 shows different slopes obtained
from one power source. The slope has the
effect of limiting the amount of shortcircuiting current the power supply can
deliver. This is the current available from
the power source on the short-circuit
Figure 11-2 — Constant voltage
between the electrode wire and the work.
system volt-ampere curve.
This is not as important in FCAW as it was
in GMAW because short-circuiting metal transfer is not encountered except with alloy
cored, low flux content wires.
A slope control is not required, but may be
desirable, when welding with small
diameter, alloy cored, low flux content
electrodes at low current levels. The shortcircuit current determines the amount of
pinch force available on the electrode. The
pinch forces cause the molten electrode
droplet to separate from the solid electrode.
The flatter the slope of the volt-ampere
curve, the higher the short-circuit and the
pinch force. The steeper the slope, the
lower the short-circuit and pinch force. The
pinch force is important with these
electrodes because it affects the way the
droplet detaches from the tip of the
electrode wire. When a high short-circuit
and a flat slope cause pinch force,
excessive spatter is created. When a very
Figure 11-3 — Different slopes
low short-circuit current and pinch force are
from a constant voltage motor
caused by a steep slope, the electrode wire
generator power source.
tends to freeze in the weld puddle or pile up
on the work piece. When the proper amount of short-circuit current is used, it creates
very little spatter.
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The inductance of the power supply also has an effect on the arc stability. When the
load on the power supply changes, the current takes time to find its new level. The rate
of current change is determined by the inductance of the power supply. Increasing the
inductance will reduce the rate of current rise. The rate of the welding current rise
increases with the current that is also affected by the inductance in the circuit. Increased
arc time or inductance produces a flatter and smoother weld bead as well as a more
fluid weld puddle. Too much inductance will cause more difficult arc starting.
The constant current arc system provides a nearly constant welding current to the arc,
which gives a drooping volt-ampere characteristic, as shown in Figure 11-4. This arc
system is used with the SMAW and GTAW processes. A dial on the machine sets the
welding current and the welding voltage is
controlled by the arc length held by the
welder.
This system is necessary for manual
welding because the welder cannot hold a
constant arc length, which causes only
small variations in the welding current.
When flux cored arc welding is done with a
constant current system, a special voltagesensing wire feeder is used to maintain a
constant arc length.
For any power source, the voltage drop
across the welding arc is directly dependent
on the arc length. An increase in the arc
length results in a corresponding increase
in the arc voltage and a decrease in the arc
length results in a corresponding decrease
in the arc voltage.
Figure 11-4 — Volt-ampere curve
for a constant current arc system.
Another important relationship exists
between the welding current and the melt off-rate of the electrode. With low current, the
electrode melts off slower and the metal is deposited slower. This relationship between
welding current and wire feed speed is definite, based on the wire size, shielding gas
type and type of electrode. A faster wire feed speed will give a higher welding current.
In the constant voltage system, instead of regulating the wire to maintain a constant arc
length, the wire is fed into the arc at a fixed speed and the power source is designed to
melt off the wire at the same speed. The self-regulating characteristic of a constant
voltage power source comes about by the ability of this type of power source to adjust
its welding current in order to maintain a fixed voltage across the arc.
With the constant current arc system, the welder changes the wire feed speed as the
gun is moved toward or away from the weld puddle. Since the welding current remains
the same, the burn-off rate of the wire is unable to compensate for the variations in the
wire feed speed, which allows stubbing or burning back of the wire into the contact tip to
occur. To lessen this problem, a special voltage-sensing wire feeder is used, which
regulates the wire feed speed to maintain a constant voltage across the arc.
The constant voltage system is preferred for most applications, particularly for small
diameter wire. With smaller diameter electrodes, the voltage-sensing system is often
unable to react fast enough to feed at the required burn-off rate, resulting in a higher
instance of burnback into the contact tip of the gun.
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Figure 11-5 shows a comparison of the voltampere curves for the two arc systems. This
shows that for these particular curves, when
a normal arc length is used, the current and
voltage levels are the same for both the
constant current and constant voltage
systems. For a long arc length, there is a
slight drop in the welding current for the
constant current machine and large drop in
the current for a constant voltage machine.
For constant voltage power sources, the
volt-ampere curve shows that when the arc
length shortens slightly, a large increase in
welding current occurs. This results in an
increased burn-off rate, which brings the arc
length back to the desired level. Under this
system, changes in the wire feed speed,
caused by the welder, are compensated for
electrically by the power source.
Figure 11-5 — Volt-ampere curves.
2.2.0 Metal Transfer
Metal transfer, from consumable electrodes across an arc, has been classified into
three general modes of transfer: spray transfer, globular transfer, and short-circuiting
transfer. The metal transfer of most flux-cored electrodes resembles a fine globular
transfer. Only the alloy-cored, low flux content wires can produce a short-circuiting
metal transfer similar to GMAW.
On flux-cored electrodes, the molten
droplets build up around the periphery or
outer metal sheath of the electrode. By
contrast, the droplets on solid wires tend to
form across the entire cross section at the
end of the wire. A droplet forms on the
cored wire, is transferred, and then a
droplet is formed at another location on the
metal sheath. The core material appears to
transfer independently to the surface of the
weld puddle. Figure 11-6 shows the metal
transfer in flux=cored arc welding.
At low currents, the droplets tend to be
larger than at higher current levels. If the
welding current using a 3/32 in. (2.4 mm)
electrode wire is increased from 350 to 550
Figure 11-6 — Metal transfer in
amps, the metal transfer characteristics will
FCAW.
change. Transfer is much more frequent
and the droplets become smaller as the current is increased. At 550 amperes, some of
the metal may transfer by the spray mode, although the globular mode prevails. There
is no indication that higher currents cause a transition to a spray mode of transfer,
unless an argon-oxygen shielding gas mixture is used.
The larger droplets at the lower currents cause a certain amount of "splashing action"
when they enter the weld puddle. This action decreases with the smaller droplet size.
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This explains why there is less visible spatter. The arc appears smoother to the
operator, and the deposition efficiency is higher when a wire is used with a high current
density rather than at the low end of its current range.
Test your Knowledge (Select the Correct Response)
1.
What does the welding process leave on the surface of the weld bead that must
be removed?
A.
B.
C.
D.
2.
Dross
Splatter
Slag
Rust
What is “pinch force”?
A.
B.
C.
D.
The amount of pressure applied by the grounding clamp
The grip between the wire feed rollers
It causes the molten electrode droplet to separate from the electrode
It helps the arc transfer from the work piece to the electrode
3.0.0 EQUIPMENT for WELDING
The equipment used for FCAW is very similar to that used for GMAW. The basic arc
welding equipment consists of a power source, controls, wire feeder, welding gun, and
welding cables. A major difference between the gas-shielded electrodes and self shielded electrodes is that the gas shielded wires also require a gas shielding system.
This may also have an effect on the type of welding gun used. Fume extractors are
often used with this process. For machine and automatic welding, several items, such
as seam followers and motion devices, are added to the basic equipment. A diagram of
the equipment for semiautomatic FCAW is shown in Figure 11-7.
Figure 11-7 — Equipment for flux cored arc welding.
3.1.0 Power Sources
The power source (welding machine) provides the electric power of the proper voltage
and amperage to maintain a welding arc. Most power sources operate on 230 or 460
volt input power, but machines that operate on 200 or 575 volt input are available as
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options. Power sources may operate on either single-phase or three-phase input with a
frequency of 50 to 60 Hz.
3.1.1 Power Source Duty Cycle
Duty cycle is defined as the ratio of arc time to total time. Most power sources used for
FCAW have a duty cycle of 100%, which indicates that they can be used to weld
continuously. However, some machines have a duty cycle of 60%. For a welding
machine, a 10 minute time period is used. Thus, for a 60% duty cycle machine, the
welding load would be applied continuously for 6 minutes and would be off for 4
minutes. Most industrial type, constant current machines are rated at 60% duty cycle.
The formula for determining the duty cycle of a welding machine for a given load current
is:
% Duty Cycle =
( Rated Current ) 2
X Rated Duty Cycle
( Load Current ) 2
For example, if a welding machine is rated at a 60% duty cycle at 300 amperes, the
duty cycle of the machine when operated at 350 amperes would be.
% Duty Cycle =
(300) 2
X 60 = 44%
(350) 2
In general, these lower duty cycle machines are the constant current type, which are
used in plants where the same machines are also used for SMAW and gas tungsten arc
welding. Some of the smaller constant voltage welding machines have a 60% duty
cycle.
3.1.2 Types of Current
FCAW uses direct current, which can be connected in one of two ways: electrode
positive (reverse polarity) or electrode
negative (straight polarity). The electrically
charged particles flow between the tip of the
electrode and the work as shown in Figure
11-8.
Flux-cored electrode wires are designed to
operate on either DCEP or DCEN. The wires
designed for use with an external gas
shielding system are generally designed for
use with DCEP, while some self-shielding
flux-cored wires are used with DCEP and
others are used with DCEN. Electrode
positive current gives better penetration into
the weld joint. Electrode negative current
gives lighter penetration, and is used for
welding thinner metal or where there is poor
fit-up. The weld created by DCEN is wider
and shallower than the weld produced by
DCEP
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Figure 11-8 — Particle flow for
DCEP and DCEN.
11-12
3.1.3 Types of Power Sources
The power sources generally recommended for flux cored arc welding are direct current
constant voltage types. Both rotating (generator) and static (single- or three-phase
transformer-rectifiers) are used. Any of these types of machines are available to
produce constant current or constant voltage output, or both. The same power sources
used with GMAW are used with FCAW, but FCAW generally uses higher welding
currents, which sometimes requires a larger power source. It is important to use a
power source capable of producing the maximum current level required for an
application.
3.1.3.1 Generator and Alternator Welding Machines
Generator welding machines used for this
process can be powered by an electric
motor for shop use, or an internal
combustion engine for field applications.
Gasoline or diesel engine-driven welding
machines have either liquid or air-cooled
engines and many of them provide auxiliary
power for emergency lighting, power tools,
etc. Many of the engine-driven generators
used for FCAW in the field are combination
constant current-constant voltage types.
These types are popular for applications
where both SMAW and FCAW can be
accomplished using the same power source.
Figure 11-9 shows an engine-driven
generator machine used for flux cored arc
welding. The motor-driven generator welding
machines are gradually being replaced by
Figure 11-9 — Gas powered
transformer-rectifier welding machines.
welder/generator.
Motor-driven generators produce a very
stable arc, but they are noisier, more expensive, consume more power and require
more maintenance than transformer-rectifier machines. They can, however, function
without being sourced by an electrical power supply and, in fact, can produce the
auxiliary electricity during power outages.
An alternator welding machine is an electric generator made to produce AC power. This
power source has a rotating assembly. These machines are also called rotating or
revolving field machines.
3.1.3.2 Transformer Welding Machines
Transformer-rectifiers are the most widely used welding machines for FCAW. . Adding a
rectifier to a basic transformer circuit is a method of supplying direct current to the arc
without using a rotating generator.. A rectifier is an electrical device which changes
alternating current into direct current. These machines are more efficient electrically
than motor-generator welding machines and they provide quieter operation. There are
two basic types of transformer-rectifier welding machines: those that operate on singlephase input power and those that operate on three-phase input power.
The single-phase transformer-rectifier machines provide DC current to the arc and a
constant current volt-ampere characteristic, but are not as popular as three-phase
transformer-rectifier welding machines for FCAW. When using a constant current power
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source, a special variable speed or voltage-sensing wire feeder must be used to
maintain a uniform current level. A limitation of the single-phase system is that the
power required by the single-phase input power may create an unbalance of the power
supply lines which is objectionable to most power companies. These machines normally
have a duty cycle of 60%.
The most widely used type of power source
for this process is the three-phase
transformer-rectifier. These machines
produce DC current for the arc, and for
FCAW, most have a constant voltage voltampere characteristic. When using these
constant voltage machines, a constantspeed wire feeder is used. This type of wire
feeder maintains a constant wire feed speed
with slight changes in welding current. The
three-phase input power gives these
machines a more stable arc than singlephase input power and avoids the line
unbalance that occurs with the single-phase
machines.
Many of these machines also use solid state
controls for the welding. A 650 amp solid
Figure 11-10 — Three-phase, 650
state controlled power source is shown in
amp solid state power source.
Figure 11-10. This machine will produce the
flattest volt-ampere curve of the different constant voltage power sources. Most threephase transformer-rectifier power sources are rated at a 100% duty cycle.
3.2.0 Controls
The controls for this process are located on
the front of the welding machine, on the
welding gun, and on the wire feeder or a
control box.
The welding machine controls for a
constant voltage machine include an on-off
switch, a voltage control, and often a switch
to select the polarity of direct current. The
voltage control can be a single knob, or it
can have a tap switch for setting the voltage
range and a fine-voltage control knob.
Other controls are sometimes present, such
as a switch for selecting constant current
(CC) or constant voltage (CV) output on
Figure 11-11 — Programmable
combination machines, or a switch for a
control unit.
remote control. On constant current welding
machines, there is an on-off switch, a
current level control knob, and sometimes a knob or switch for selecting the polarity of
direct current.
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11-14
The trigger or switch on the welding gun is a remote control used by the welder in
semiautomatic welding to stop and start the welding current, wire feed, and shielding
gas flow. For semiautomatic welding, a wire feed speed control is normally part of, or
close by, the wire feeder assembly. The wire feed speed sets the welding current level
on a constant voltage machine. For machine or automatic welding, a separate control
box is often used to control the wire feed speed. A control box for semiautomatic or
automatic welding is shown in Figure 11-11. There may also be switches to turn the
control on and off on the wire feeder control box, and gradually feed the wire up and
down.
Other controls for this process are used for special applications, especially when a
programmable power source is used. An example is a timer for spot welding. Controls
that produce a digital readout are popular because it is easier for concise control.
3.3.0 Wire Feeders
The wire feed motor provides the power for driving the electrode through the cable and
gun to the work. There are several different wire feeding systems available. The
selection of the best type of system depends on the application. Most FCAW wire feed
systems are the constant speed type, which are used with constant voltage power
sources. This means the wire feed speed is set before welding. The wire feed speed
controls the amount of welding current. Variable speed or voltage-sensing wire feeders
are used with constant current power sources. With a variable speed wire feeder, a
voltage-sensing circuit maintains the desired arc length by varying the wire feed speed.
Variations in the arc length increase or decrease the wire feed speed.
A wire feeder consists of an electrical motor connected to a gear box containing drive
rolls. The gear box and wire feed motor shown in Figure 11-12 have four feed rolls in
the gear box. While many systems have only two, in a four-roll system, the lower two
rolls drive the wire.
Because of their structure, flux-cored wires can be easily flattened. The type of drive roll
used is based on the size of the tubular wire being fed. The three basic types of drive
rolls are the “U” groove, “V” knurled, and “U” cogged, as shown in Figure 11-13. “U”
groove drive rolls are only used on small diameter wires. These can be used because
small diameter tubular wires are less easily flattened. “V” knurled drive rolls are most
commonly used for wire sizes 1/16 in. (1.6 mm) and greater. These drive rolls are lightly
knurled to prevent slipping of the wire. The “U” cogged drive rolls are used for large
diameter flux-cored wires. A groove is cut into both rolls. Different gear ratios are used,
depending on the wire feed speed required. Table 11-1 shows the wire feed speeds that
can be obtained from different gear ratios.
NAVEDTRA 14250A
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Figure 11-12 — Wire feed assembly.
Figure 11-13 — Drive roll types and applications.
NAVEDTRA 14250A
11-16
Table 11-1 — Wire feed speeds obtained from different gear ratios.
Wire Feed Speed
Gear Ratio
In/min
(mm/s)
15:1
500-2000
212-846
37.5:1
60-1000
25-423
46:1
50-825
21-349
75:1
30-500
13-212
90:1
25-400
11-169
150:1
15-250
6-106
300:1
8-125
3-53
600:1
4-63
2-27
1200:1
2-30
1-13
Wire feed systems may be the pull, push, or push-pull type, depending on the method of
application and the distance between the welding gun and the coil or spool of wire. Pull
type wire feeders have the drive rolls attached to the welding gun. Most machine and
automatic welding stations use this type of
system, but pull type wire feeders are rarely
used in semiautomatic welding. Pull wire
feeders have the advantage for welding
small diameter aluminum and soft nonferrous metals with GMAW because it
reduces wire feeding problems, but, since
most flux-cored wires are steel, this is not
an advantage for FCAW.
The push type system with the drive rolls
mounted near the coil or spool of wire is the
most commonly used wire feed method for
semiautomatic welding (Figure 11-14). The
wire is pulled from the coil or spool and
then pushed into a flexible conduit and
through the gun. The relatively large
diameter wires used in FCAW are well
Figure 11-14 — Semi-automatic,
suited to this type of system. The length of
solid state control wire feeder.
the conduit can be up to about 12 feet (3.7
m). Another advantage of this push type system is that the wire feed mechanism is not
attached to the gun, which reduces the weight and makes the gun easier to handle.
Some wire feed systems contain a two-gun, two wire feeder arrangement connected to
a single control box, which is connected to a single power source. Both wire feeders
may be set up, and there is a switch on the control to automatically select which of the
two systems will be used.
NAVEDTRA 14250A
11-17
One advantage to this system is that the second wire feeder and gun can provide
backup in case of breakdown, gun maintenance, or electrode change. Another
advantage is that two different electrodes for different applications can be set up. For
example, a GMAW electrode and gun can be set up on one schedule for welding a root
pass, and a second schedule can be set up with a flux-cored wire to weld the rest of the
joint with FCAW’s faster deposition. This eliminates the need for two power sources or
the need to change the electrode wire and gun. The liner is made of flexible metal and
is available in sizes compatible with the electrode size. The liner guides the electrode
wire from the wire feeder drive rolls through the cable assembly and prevents
interruptions in the travel.
Heavy-duty welding guns are normally used because of the large size electrode wires
typically used and the corresponding high welding current levels required. Because of
the intense heat created by this process, heat shields are attached to the gun in front of
the trigger to protect the welder's hand.
Both air-cooled and water-cooled guns are used for FCAW. Air-cooled guns are cooled
primarily by the surrounding air, but when a shielding gas is used, this will have an
additional cooling effect.
A water-cooled gun is similar to an air-cooled gun, except that ducts to permit the water
to circulate around the contact tube and nozzle have been added. Water-cooled guns
permit more efficient cooling of the gun. Figure 11-15 shows a 500-ampere watercooled gun. Water-cooled guns are preferred for many applications using 500 amperes
and recommended for use with welding currents greater than 600 amperes. Welding
guns are rated at the maximum current capacity for continuous operation.
Figure 11-15 — Water-cooled gun.
Air-cooled guns are lighter and easier to manipulate. Figure 11-16 shows a 350 ampere
air-cooled welding gun.
NAVEDTRA 14250A
11-18
Figure 11-16 — Air-cooled gun.
Some self-shielded electrode
wires require a specific minimum
electrode extension to develop
proper shielding, so welding guns
for these electrodes have guide
tubes with an insulated extension
guide. This guide supports the
electrode and insures a minimum
electrode extension, as shown in
Figure 11-17.
3.3.1 Machine Welding Guns
Machine and automatic welding
guns use the same basic design
principles and features as the
semiautomatic welding guns.
These guns often have very high
current-carrying capacities and
may also be air cooled or watercooled. Large diameter wires up
to 1/8 in. (3.2 mm) are commonly
used with high amperages.
Figure 11-17 — Insulated extension guide.
Machine welding guns must be
heavy duty because of the high amperages and duty cycles required, and the welding
gun is mounted directly below the wire feeder. Figure 11-18 shows a machine welding
head for FCAW.
If a gas-shielded wire is to be used, the gas can be supplied by a nozzle that is
concentric around the electrode or by a side delivery tube, as is shown in Figure 11-18.
The side shielding permits the welding gun to be used in deep, narrow grooves and
reduces spatter buildup problems in the nozzle. Side shielding is only recommended for
welding using carbon dioxide. A concentric nozzle is preferred when using argon-carbon
dioxide and argon-oxygen mixtures, and a concentric nozzle provides better shielding
and is sometimes recommended for CO2 at high current levels when a large weld
puddle exists.
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3.4.0 Fume Extractors
Fume extractors are often used to
help reduce the smoke levels
produced by flux-cored electrodes.
This reduces air pollution and
gives better visibility. Welding guns
can be equipped with a fume
extractor that consists of an
exhaust nozzle that encircles the
gun nozzle, as shown in Figure 1119. The nozzle is connected to a
filter and an exhaust pump. The
fume extraction nozzle should be
located at a distance far enough
from the arc to draw in the rising
fumes without disturbing the
shielding gas flow.
The major advantage of this fume
extraction system is that it is
always close to the point of
welding. A portable fume exhaust
fan cannot be positioned as close
to the arc, and requires
repositioning for every change in
welding position.
Figure 11-18 — Automatic welding head.
The major disadvantage of the
fume extractor is that it makes the
gun bulkier and more difficult to
manipulate. Fume extractors are
generally not necessary in a
welding booth that is well
ventilated.
3.5.0 Shielding Gas
Equipment
The shielding gas equipment used
for gas-shielded flux-cored wires
consists of a gas supply hose, a
gas regulator, control valves, and
supply hose to the welding gun.
The shielding gases are supplied
in liquid form when they are in
Figure 11-19 — Fume extractor nozzle.
storage tanks with vaporizers or in
a gas form in high-pressure
cylinders. An exception is carbon dioxide. When put in high-pressure cylinders, it exists
in both the liquid and gas forms. The bulk storage tank system is used when there are
large numbers of welding stations using the same type of shielding gas in large
quantities. For applications where there are large numbers of welding stations but
relatively low gas usage, a manifold system is often used. This consists of several high
NAVEDTRA 14250A
11-20
pressure cylinders connected to a manifold, which then feeds a single line to the
welding stations. Individual high-pressure cylinders are used when the amount of gas
usage is low, when there are few welding
stations, or when portability is required.
The purpose of a gas flow regulator is to
reduce the pressure from the gas supply
source and maintain a constant delivery
pressure. The gas flowmeter is then used to
control the flow of gas from the regulator to
the welding gun. A valve at the flowmeter
outlet adjusts the gas flow rate. The
flowmeter is often attached to the regulator,
as shown in Figure 11-20. Regulators and
flowmeters are designated for use with
specific shielding gases and should only be
used with the gas for which they were
designed.
The hoses are normally connected to
solenoid valves on the wire feeder to turn the
gas flow on and off with the welding current.
A hose is used to connect the flowmeter to
the welding gun, and is usually part of the
welding gun assembly.
Figure 11-20 — Flowmeter and
regulator for carbon dioxide.
3.6.0 Welding Cables
The welding cables and connectors connect the power source to the welding gun and to
the work. These cables are normally made of copper or aluminum with copper being the
most common. The cable consists of hundreds of wires enclosed in an insulated casing
of natural or synthetic rubber. The cable connecting the power source to the welding
gun is called the electrode lead. In semiautomatic welding, this cable is often part of the
cable assembly, which also includes the shielding gas hose and the conduit the
electrode wire feeds through. For machine or automatic welding, the electrode lead is
normally separate.
The cable connecting the work to the power source is called the work lead. Work leads
are usually connected to the work by pincher clamps or a bolt. The size of the welding
cables used depends on the output capacity of the welding machine, the duty cycle of
the machine, and the distance between the welding machine and the work. Cable sizes
range from the smallest at American Wire Gauge (AWG) No.8 to AWG No. 4/0 with
amperage ratings of 75 amperes on up. Table 11-2 shows recommended cable sizes
for use with different welding currents and cable lengths; too small a cable may become
too hot during welding.
NAVEDTRA 14250A
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Table 11-2 — Recommended cable sizes for different welding currents and cable
lengths.
Weld
Weld
Length of Cable Circuit in Feet-Cable Size A.W.G.
Type
Current
60’
100’
150’
200’
300’
400’
Manual
100
4
4
4
2
1
1/0
(Low
150
2
2
2
1
2/0
3/0
Duty
200
2
2
1
1/0
3/0
4/0
Cycle)
250
2
2
1/0
2/0
300
1
1
2/0
3/0
350
1/0
1/0
3/0
4/0
400
1/0
1/0
3/0
450
2/0
2/0
4/0
500
2/0
2/0
4/0
Automatic
400
4/0
4/0
(High
800
4/0
4/0
Duty
1200
4/0
4/0
Cycle)
3.7.0 Other Equipment
For machine and automatic welding, several
items, such as seam followers, water
circulators, and motion devices, are added to
the basic equipment
3.7.1 Water Circulators
When a water-cooled gun is used, a water
supply must be included in the system. This
can be supplied by a water circulator or
directly from a hose connection to a water
tap. The water is carried to the welding gun
through hoses that may or may not go
through a valve in the welding machine. A
typical water circulator is shown in Figure 1121.
3.7.2 Motion Devices
Figure 11-21 — Water circulator.
Motion devices are used for machine and
automatic welding. These motion devices
can be used to move the welding head, workpiece, or gun, depending on the type and
size of work and the preference of the user.
Motor-driven carriages that run on tracks or directly on the workpiece are commonly
used. Carriages can be used for straight line, contour, vertical, or horizontal welding.
Side beam carriages are supported on the vertical face of a flat track and can be used
NAVEDTRA 14250A
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for straight line welding. Multiple electrode welding heads can be used to obtain higher
deposition rates.
Welding head manipulators may be used for longitudinal welds and, in conjunction with
a rotary weld positioner, for circumferential welds. Available in many boom sizes, they
can also be used for semiautomatic welding with mounted welding heads.
Oscillators are optional equipment used to oscillate the gun for surfacing, vertical-up
welding, and other welding operations that require a wide bead. Oscillators can either
be mechanical or electromagnetic devices.
3.7.3 Accessories
Accessory equipment for FCAW consists of items for cleaning the weld bead and
cutting the electrode wire. Because of the slag coating formed, chipping hammers and
wire brushes are usually required to remove the slag. A grinder is often used for final
cleaning and for removing spatter. A pair of wire cutters or pliers is used to cut the end
of the electrode wire between stops and starts.
4.0.0 EQUIPMENT SETUP, OPERATION, and SHUT DOWN
It is necessary for a welder to be able to set up, weld, and secure the equipment that
will be used. The following is a brief overview on what materials you will need and what
to look for when you are welding, followed by a short description on how to secure the
welding machine.
4.1.0 Protective Clothing and Tools
The FCAW process could be a dangerous process if you do not protect yourself from
the heat, radiation, and spatter. You must wear a leather coat, gloves, safety glasses,
and a welding helmet.
Normally, a number 11 or 12 filter lens is required to protect your eyes from the intense
arc created by this welding process.
You should also be equipped with a wire brush, wire cutters, pliers, and chipping
hammer.
4.2.0 Obtaining Materials
You will need to select the proper electrode according to the base metal you will be
welding. You can obtain the proper electrode type and diameter using the AWS
classifications.
You may also be using a shielding gas, depending on which electrode wire you are
using. Welding-grade carbon dioxide or a mixture of carbon dioxide and argon are
normally used.
4.3.0 Set Up Equipment
Now that you have your electrode wire, you need to know how to install it on the welding
machine.
Small diameter flux-cored electrode wires are generally spooled in the manner as solid
wires used for GMAW, and can be loaded in the same manner.
Large-diameter electrode wires are usually much stiffer. Rather than being stored on
spools, the large-diameter flux-cored electrode wires are rolled into coils. These wires
NAVEDTRA 14250A
11-23
have a surprising amount of tension and can cause serious injury if they are allowed to
unwind suddenly or uncontrollably.
When removing the wire, four equally spaced bands should be used in order to
completely secure the wire and prevent the coil from distorting in shape while handling.
Cut the wire between the coil and the wire feeder, and then loosen the hold down
brackets, to remove the secured coil.
The wire feed rollers should then be removed from the wire feeder before mounting the
new coil.
With the coil removed, advance the wire feeder until the cutoff end of the wire is
released from the drive rollers. Remove the wire with a pair of pliers.
Every time a coil or spool is used or changed, the liner should be cleaned or replaced if
damaged. To clean the liner, first remove the two set screws, then remove the gun from
the wire feeder and pull the liner from the cable. Use a compressed air supply to purge
any contaminants from the liner. Replace in the same manner.
Before adding a new coil, the contact tube and nozzle should be removed from the
welding gun and examined for evidence of excessive wear damage. Replace these
parts if necessary.
With the coil in place on the feeder, slip the end of the electrode through the wire feeder
guides. Manually advance the wire through the wire feed guides, replace the fee rolls,
then clip the bands as the wire is advanced through the system.
Some self-shielded electrode wires require a higher preheat to help decompose the flux
and provide shielding gas. The welding gun for these wires was designed to maintain as
much as 2 1/2 inches of stickout. The contact tube is recessed as much as 1 1/2 inches,
and an insert, which acts as an insulator, is placed in the nozzle to protect the
preheated wire. The length of the insert controls the amount that the contact tube is
recessed into the nozzle.
Gas-shielded wires require a gas nozzle. The electrode stickout is generally between
three-fourths and 1 1/2 inches.
Welding guns may be cooled by either air or water, depending on the application. When
welding currents over 500 amps are used, water-cooled guns are necessary.
Due to the large amounts of smoke given off by the flux-cored process, a smoke
exhaust system can be fitted to the gun, or even manufactured as part of the gun.
High current densities and production welding may require that a heat shield be
attached to the gun to protect the hand from the intense heat.
Welding gun maintenance is not complicated. Periodically, the gun should be cleaned to
remove spatter and dirt from inside the nozzle.
The flux-cored electrode wire is easily flattened during feeding. To prevent this from
happening, the feed rollers must match the size of the wire being used.
Of the types of feed rolls available, the knurled V-groove is generally used with largediameter electrodes, from one sixteenth to one eighth in diameter.
Medium diameter electrodes should be used with groove geared drive rolls. Normally,
groove gear rolls can handle either solid or tubular wire from .045-to 7/64-inch in
diameter.
NAVEDTRA 14250A
11-24
Small-diameter electrodes require a concave roller with a smooth face to prevent the
wire from flattening.
In most cases, the drive rollers are mounted in pairs, with two pair being a typical
feeding system. The electrode wire is pushed from the wire feeder to the gun.
4.4.0 Adjust Equipment
The voltage is adjusted by turning the voltage control knob to the desired range.
To adjust the gas flow rate, stand to one side as a safety measure, open the cylinder
valve of the shielding gas, and check the regulator dial to assure there is sufficient
pressure. Press the button on the wire feeder, and at the same time, adjust the
flowmeter.
If the wire feeder is not equipped with a purge button, set the wire feed control to zero,
press the gun trigger, and then set the flowmeter for the desired gas flow rate.
Select the correct current and polarity. Direct current electrode positive is usually used
for gas-shielded wires. Direct current electrode positive or negative may be used for
self-shielded wires as appropriate to the work material.
To adjust the amperage setting when using a constant voltage power source, it will be
necessary to start the arc by pressing the gun trigger, and then tune the wire feed
speed control until the current is within the desired range. Since the current will register
on the ammeter only during welding, it may be necessary to ask someone to watch the
meter while you maintain the arc.
4.5.0 Perform the Weld
Flux-cored wires are sensitive to changes in voltage; it is important that the electrode
stickout remain in the recommended range (Figure 11-22).
Allowing the stickout to increase reduces the amperage, while reducing the stickout will
cause the amperage to increase. Since penetration is greatly influenced by welding
current, you can use stickout to a limited degree to control penetration without
interrupting the arc to adjust the welding machine.
The flux core of the electrode will cover the weld with a glass-like slag, which must be
chipped and brushed from the weld before inspecting. Always wear eye protection when
performing any welding operation.
NAVEDTRA 14250A
11-25
Figure 11-22 — Different effects of voltage and current on a weld.
NAVEDTRA 14250A
11-26
4.6.0 Shut Down Equipment
Shut down the welding equipment. Close the shielding gas cylinder valve. Purge the
shielding gas cylinder lines. Some welding machines are equipped with a purge button.
On other equipment, it may be necessary to set the wire feed to zero and press the gun
trigger. Adjust the flowmeter to zero.
Turn off the power source.
Cleanup your work area
5.0.0 SHIELDING GAS and ELECTRODES
FCAW electrodes provide the filler metal to the weld puddle and shielding for the arc,
but a shielding gas is required for some electrode types. The purpose of the shielding
gas is to provide protection to the arc and molten weld puddle from the atmosphere.
The chemical composition of the electrode wire and flux core in combination with the
shielding gas will determine the weld metal composition and mechanical properties of
the weld.
5.1.0 Shielding Gas
The primary purpose of a shielding gas in FCAW, as in any gas-shielded arc welding
process, is to protect the arc and weld puddle from the contaminating effects of the
atmosphere. If allowed to be exposed to the molten weld metal, the nitrogen and
oxygen of the atmosphere can cause porosity and brittleness.
In SMAW, protection is accomplished by placing an outer coating on the electrode,
which produces a gaseous shield as the coating disintegrates in the welding arc. In
FCAW, the same effect is accomplished by decomposition of the electrode core, or by a
combination of this and surrounding the arc area with a shielding gas supplied from an
external source.
A shielding gas displaces air in the arc area. Welding is then accomplished under a
blanket of shielding gas, and since the molten weld metal is exposed only to the
shielding gas, the atmosphere does not contaminate it.
Oxygen, which makes up 21% of air, is a highly reactive element that, at high
temperatures, combines readily with other elements in metals, and specifically in steels,
to form undesirable oxides and gases. Oxygen combines with the iron in steels to form
compounds that can lead to inclusions in the weld metal and lower its mechanical
properties. On heating, free oxygen in the molten metal combines with the carbon of the
steel to form carbon monoxide. If gas is trapped in the weld metal as it cools, it collects
in pockets and causes pores in the weld deposit.
Nitrogen, which makes up 78% of air, causes the most serious problems when welding
steel. When steel is molten, it can take a relatively large amount of nitrogen into
solution. At room temperature, the solubility of nitrogen in steel is very low. Therefore, in
cooling, nitrogen precipitates or comes out of the steel as nitrites. These nitrites cause
high yield strength, tensile strength, hardness, and a pronounced decrease in the
ductility and impact resistance of the steel. The loss of ductility due to the presence of
iron nitrites often leads to cracking of the weld metal. Excessive amounts of nitrogen
can also lead to extensive porosity in the weld deposit.
Hydrogen may come from water in the atmosphere or from moisture on surfaces welded
and is harmful to welds. Hydrogen is also present in oils, paints, and some protective
coverings. Even very small amounts of hydrogen in the atmosphere can produce an
NAVEDTRA 14250A
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erratic arc. Of more importance is the effect that hydrogen has on the properties of the
weld deposit. As in the case of nitrogen, steel can hold a relatively large amount of
hydrogen when it is molten but, upon cooling, it has a low solubility for hydrogen. As the
metal starts to solidify, it rejects the hydrogen. The hydrogen entrapped in the solidifying
metal collects at small discontinuities and causes pressure stresses to occur. This
pressure can lead to minute cracks in the weld metal, which can later develop into
larger cracks. Hydrogen also causes defects known as "fish eyes" and underbead
cracks. Underbead cracking is caused by excessive hydrogen that collects in the heataffected zone.
Inert and active gases may be used for FCAW. Active gases, such as carbon dioxide,
argon-oxygen mixtures, and argon-carbon dioxide mixtures are used for almost all
applications, with carbon dioxide being the most common. Active gases are not
chemically inert and can form compounds with the metals. Since almost all flux cored
arc welding is done on ferrous metals, this is not a problem.
The choice of the proper shielding gas for a specific application is based on:
1. Type of metal to be welded
2. Arc characteristics and metal transfer
3. Availability
4. Cost of the gas
5. Mechanical property requirements
6. Penetration and weld bead shape
5.1.1 Carbon Dioxide
Carbon dioxide is manufactured from fuel
gases that are given off by the burning of
natural gas, fuel oil, or coke. It is also
obtained as a by-product of calcining
operation in limekilns, from the
manufacturing of ammonia, and from the
fermentation of alcohol. The carbon dioxide
given off by the manufacturing of ammonia
and the fermentation of alcohol is almost
100% pure. Carbon dioxide is made
available to the user in either cylinder or
bulk containers, with the cylinder being
more common. With the bulk system,
carbon dioxide is usually drawn off as a
liquid and heated to the gas state before
going to the welding gun. The bulk system is
normally only used when supplying a large
Figure 11-23 — Carbon dioxide gas
number of welding stations. In the cylinder,
cylinder.
the carbon dioxide is in both a liquid and a
vapor form, with the liquid carbon dioxide occupying approximately two thirds of the
space in the cylinder, as shown in Figure 11-23. By weight, this is approximately 90% of
the content of the cylinder. Above the liquid, it exists as a vapor gas. As carbon dioxide
is drawn from the cylinder, it is replaced with carbon dioxide that vaporizes from the
liquid in the cylinder; therefore, the overall pressure will be indicated by the pressure
gauge. When the pressure in the cylinder has dropped to 200 psi (1.4 MPa) the cylinder
NAVEDTRA 14250A
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should be replaced. A positive pressure should always be left in the cylinder in order to
prevent moisture and other contaminants from backing up into the cylinder. The normal
discharge rate of the CO2 cylinder is about 10 to 50 cubic feet per hour (4.7 to 24 liters
per minute). However, a maximum discharge rate of 25 cfh (12 L/min.) is recommended
when welding using a single cylinder. As the vapor pressure drops from cylinder
pressure to discharge pressure through the regulator, it absorbs a great deal of heat. If
flow rates are set too high, this absorption of heat can lead to freezing of the CO2
regulator and flow meter, which interrupts the shielding gas flow. When flow rates higher
than 25 cfh (12 L/min.) are required, normal practice is to manifold two CO2 cylinders in
parallel, or to place a heater between the cylinder and gas regulator, pressure regulator,
and flow meter. Figure 11-24 shows a
manifold system used for connecting several
cylinders together. Excessive flow rates can
also result in drawing liquid from the
cylinder.
Carbon dioxide is the most widely used
shielding gas for FCAW. Most active gases
cannot be used for shielding, but carbon
dioxide provides several advantages for use
in welding steel, such as deep penetration,
low cost, and it promotes a globular transfer.
The carbon dioxide shielding gas breaks
down into components, such as carbon
monoxide and oxygen. Because carbon
dioxide is an oxidizing gas, deoxidizing
elements are added to the core of the
Figure 11-24 — Manifold system for
electrode wire to remove oxygen. The
CO2.
oxides formed by the deoxidizing elements
float to the surface of the weld and become part of the slag covering. Some of the
carbon dioxide gas will break down to carbon and oxygen. If the carbon content of the
weld pool is below about .05%, carbon dioxide shielding will tend to increase the carbon
content of the weld metal. Carbon, which can reduce the corrosion resistance of some
stainless steels, is a problem for critical corrosion applications. Extra carbon can also
reduce the toughness and ductility of some low-alloy steels. If the carbon content in the
weld metal is greater than about .10%, carbon dioxide shielding will tend to reduce the
carbon content. This loss of carbon can be attributed to the formation of carbon
monoxide, which can be trapped in the weld as porosity deoxidizing elements in the flux
core, reducing the effects of carbon monoxide formation.
5.1.2 Argon-Carbon Dioxide Mixtures
Argon and carbon dioxide are sometimes mixed for use with FCAW. A high percentage
of argon gas in the mixture tends to promote a higher deposition efficiency due to
creating less spatter. This mixture also creates less oxidation and lower fumes. The
most commonly used argon-carbon dioxide mixture contains 75% argon and 25%
carbon dioxide. This gas mixture produces a fine globular metal transfer that
approaches a spray. It also reduces the amount of oxidation that occurs, compared to
pure carbon dioxide. The weld deposited in an argon-carbon dioxide shield generally
has higher tensile and yield strengths. Argon-carbon dioxide mixtures are often used for
out-of-position welding, achieving better arc characteristics and welder appeal. This
mixture also improves arc transfer on smaller diameters. Argon/CO2 is often used on
low-alloy steels and stainless steels.
NAVEDTRA 14250A
11-29
Electrodes designed for use with CO2 may cause an excessive build-up of manganese,
silicon, and other deoxidizing elements if they are used with shielding gas mixtures
containing a high percentage of argon, and this will have an effect on the mechanical
properties of the weld.
5.1.3 Argon-oxygen mixture
Argon-oxygen mixtures containing 1 or 2% oxygen are used for some applications.
Argon-oxygen mixtures tend to promote a spray transfer that reduces the amount of
spatter. A major application of these mixtures is in welding stainless steels where
carbon dioxide can cause corrosion problems.
5.2.0 Electrodes
The electrodes for FCAW consist of a metal
sheath surrounding a core of fluxing and/or
alloying compounds, as shown in Figure 1125. The core of carbon steel and low-alloy
electrodes contains primarily fluxing
compounds. Some of the low-alloy steel
electrode cores contain high amounts of
alloying compounds with a low flux content.
Most low-alloy steel electrodes require gas
shielding.
The sheath comprises approximately 75 to
90% of the weight of the electrode. Selfshielded electrodes contain more fluxing
compounds than gas shielded electrodes.
The compounds contained in the electrode
perform essentially the same functions as
the coating of a covered electrode used in
shielded metal arc welding. These functions
are:
Figure 11-25 — Cross section of a fluxcored wire.
1. To form a slag coating that floats on
the surface of the weld metal and
protects it during solidification
2. To provide deoxidizer and
scavengers which help purify and
produce solid weld metal
3. To provide arc stabilizers which
produce a smooth welding arc and
keep spatter to a minimum
4. To add alloying elements to the weld
metal which will increase the strength
and improve other properties in the
weld metal
5. To provide shielding gas, as gasshielded wires require an external
supply of shielding gas to supplement
NAVEDTRA 14250A
Figure 11-26 — Making a flux-cored
wire.
11-30
that produced by the core of the electrode
The manufacture of a flux-cored electrode is an extremely technical and precise
operation requiring specially designed machinery. Figure 11-26 shows a simplified
version of the apparatus for producing tubular type cored electrodes on continuous
production. A thin, narrow, flat, low-carbon steel strip passes through forming rolls,
which form the strip into a U-shaped cross-section. This U-shaped steel passes through
a special filling device where a measured amount of the specially formulated granular
core material is added. The flux-filled U-shaped strip then flows through special closing
rolls which form it into a tube and tightly compress the core materials. This tube is then
pulled through draw dies to reduce its diameter and further compress the core
materials. Drawing tightly seals the sheath and additionally secures the core materials
inside the tube under compression, thus avoiding discontinuities in the flux. The
electrode may or may not be baked during, or between, drawing operations. This
depends on the type of electrode and the type of elements and compounds enclosed in
the sheath.
Additional drawing operations are performed on the wire to produce various electrode
diameters. Flux-cored electrode wires are commonly available in sizes ranging from
.035- to 5/32-inch.
The finished electrode is wound into a continuous coil, spool, reel, or drum. These are
available as 10 lb., 15 lb., or 50 lb. spools, 60 lb. (27 kg) coils, 250 or 500 lb. (113-225
kg) reels, or a 600 lb. drum. Electrode wires are generally wrapped in plastic to prevent
moisture pick-up.
5.2.1 Classification
The American Welding Society (AWS) devised the classification system used for tubular
wire electrodes throughout industry in the United States. There are several different
specifications covering flux cored arc welding electrodes for steels as shown in Table
11-3.
Table 11-3 — Specifications covering flux-cored electrodes.
AWS
Specification
Metal
A5.20
Carbon Steel
A5.22
Stainless Steel
A5.29
Low-alloy Steel
NAVEDTRA 14250A
11-31
Table 11-4 — As-welded mechanical property requirements of carbon steel fluxcored electrodes (AWS A.5.20).
AWS
Shielding
Classification
E6XT-13
Gas
None
E6XT-G
Not Specified
E6XT-GS
Not Specified
E7XT-1
CO2
75-80%Ar/bal
CO2
E7XT-1M
E7XT-2
E7XT-2M
CO2
75-80%Ar/bal
CO2
E7XT-3
None
E7XT-4
None
E7XT-5
E7XT-5M
CO2
75-80%Ar/bal
CO2
E7XT-6
None
E7XT-7
None
E7XT-8
None
E7XT-9
E7XT-9M
CO2
75-80%Ar/bal
CO2
E7XT-10
None
E7XT-11
None
E7XT-12
E7XT-12M
CO2
75-80%Ar/bal
CO2
E7XT-13
None
E7XT-14
None
E7XT-G
Not Specified
E7XT-GS
Not Specified
NAVEDTRA 14250A
Tensile
Strength
ksi
(Mpa)
60(415)
60
(415)
60
(415)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70 (480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
70
(480)
Yield
Strength
% Elongation
Min in
ksi (Mpa)
48 (330)
1" (50mm)
22
48 (330)
48 (330)
22
Not
Specified
58 (400)
22
58 (400)
58 (400)
22
Not
Specified
Not
Specified
58 (400)
22
Not Specified
58 (400)
22
58 (400)
22
58 (400)
22
58 (400)
22
Not Specified
20 @ -20 (27 @ 29)
20 @ -20 (27 @ 29)
20 @ -20 (27 @ 29)
58 (400)
22
58 (400)
22
58 (400)
22
58 (400)
58 (400)
22
Not
Specified
58 (400)
20
58 (400)
22
58 (400)
22
Not
Specified
Not
Specified
58 (400)
58 (400)
58 (400)
Not
Specified
Not
Specified
22
Not
Specified
Min Impact
Strength
ft-Ibs @OF(J
@0C)
Not Specified
Not Specified
Not Specified
20 @ -20 (27 @ 18)
20 @ -20 (27 @ 18)
Not Specified
Not Specified
Not Specified
20 @ -20 (27 @ 29)
20 @ -20 (27 @ 29)
20 @ -20 (27 @ 29)
Not Specified
Not Specified
20 @ -20 (27 @ 29)
20 @ -20 (27 @ 29)
Not Specified
Not Specified
Not Specified
Not Specified
11-32
Carbon and low-alloy steels are classified on the basis of the following items:
1. Mechanical properties of the weld metal
2. Position of welding
3. Chemical composition of the weld metal
4. Type of welding current
5. Whether or not CO2 shielding gas is used
An example of a carbon-steel electrode classification is E70T-4 where:
1. The "E" indicates an electrode.
2. The second digit indicates the minimum tensile strength in units of 10,000 psi (69
Mpa). Table 11-4 shows the mechanical property requirements for carbon steel
electrodes.
3. The third digit indicates the welding position. A "0" indicates flat and horizontal
positions only, and a "1" indicates all positions.
4. The "T" stands for a tubular (flux-cored) wire classification.
5. The suffix "4" gives the performance and usability capabilities as shown in Table
11-5.
When a "G" classification is used, no specific performance requirements are indicated.
This classification is intended for electrodes not covered by another classification. The
chemical composition requirements of the deposited weld metal for carbon steel
electrodes are shown in Table 11-6.
Table 11-7 shows the mechanical properties requirements of low-alloy flux-cored
electrodes. Single-pass electrodes do not have chemical composition requirements
because checking the chemistry of undiluted weld metal does not give the true results of
normal single-pass weld chemistry.
NAVEDTRA 14250A
11-33
Table 11-5 —Performance and usability characteristics of carbon steel flux-cored
electrodes (AWS A5.20).
AWS
Welding
Shielding
Classification
EXXT-1
EXXT-2
EXXT-3
EXXT-4
EXXT-5
EXXT-6
EXXT-7
EXXT-8
EXXT-9
EXXT-10
EXXT-11
EXXT-12
EXXT-13
EXXT-14
EXXT-G
EXXT-GS
Current
DCEP
DCEP
DCEP
DCEP
DCEP
DCEP
DCEN
DCEN
DCEN
DCEN
DCEN
DCEN
DCEN
DCEN
Not Specified
Not Specified
Gas
CO2
CO2
None
None
CO2
None
None
None
None
None
None
None
CO2
None
Not Specified
Not Specified
NAVEDTRA 14250A
Single or
Multiple
Pass
Multiple
Single
Single
Multiple
Multiple
Multiple
Multiple
Multiple
Multiple
Single
Multiple
Multiple
Single
Single
Multiple
Single
11-34
Table 11-6 — Chemical composition requirements of carbon-steel flux-cored
electrodes (AWS A5.20).
AWS
Classification
E7XT-1
E7XT-1M
E7XT-5
E7XT-5M
E7XT-9
E7XT-9M
E7XT-4
E7XT-6
E7XT-7
E7XT-8
E7XT-11
EXXT-G
E7XT-12
E7XT-12M
E6XT-13
E7XT-2
E7XT-2M
EXXT-3
EXXT-10
E7XT-13
E7XT-14
EXXT-GS
UNS
Number
Chemical Composition (%max.)
C
Mn
Si
S
P
Cr
Ni
Mo
V
AI
Cu
0.18
1.75
0.90
0.03
0.03
0.20
0.50
0.30
0.08
(b)
1.75
0.60
0.03
0.03
0.20
0.50
0.30
0.08
1.8
0.35
(b)
1.75
0.90
0.03
0.03
0.20
0.50
0.30
0.08
1.8
0.35
0.15
1.75
0.90
0.03
0.03
0.20
0.50
0.30
0.08
1.8
0.35
W07601
W07605
0.35
W07609
W07604
W07606
W07607
W07608
W07611
W07612
W06613
W07602
W07603
W07610
W07613
W07614
c
Not Specified
a. Chemical compositions are based on the analysis of the deposited weld metal.
b. No requirement, but the amount of carbon shall be determined and reported.
c. Since these are single-pass welds, the analysis of the undiluted weld metal is not meaningful.
NAVEDTRA 14250A
11-35
Table 11-7 — Mechanical property requirements of low-alloy flux-cored
electrodes (AWS A5.29).
Tensile Strength
AWS
Range
Yield Strength
@0.2 Offset
Min
Percent Elongation
in 2 in (51 mm)
Classification
ksi
MPa
ksi
MPa
Min
E6XTX-X
60-80
410-550
50
340
22
E7XTX-X
70-90
490-620
58
400
20
E8XTX-X
80-100
550-690
68
470
19
E9XTX-X
90-110
620-760
78
540
17
E10XTX-X
100-120
690-830
(b)
(b)
610
560670
16
E10XTX-K9 -K9M
88
8297
E11XTX-X
110-130
760-900
98
680
15
E12XTX-X
120-140
830-970
108
750
14
18
EXXXTX-Ga
EXXTG-Xa
Properties as agreed between supplier and purchaser
EXXTG-Ga
a. Placement of a "G" in this designation indicates those properties as agreed upon between the
supplier and purchaser.
Other properties are dictated by the digit(s) or suffix replacing the X. Variations used in this
specification include the following:
(1) EXXTX-G-Alloy requirements are as agreed upon. The mechanical properties and slag
system are as indicated by the digits used.
(2) EXXTG-X-The slag system and shielding gas are as agreed upon. Mechanical properties
and alloy requirements conform to those indicated by the digits.
(3) EXXTG-G-The slag system, shielding gas, and alloy requirements are as agreed upon.
Mechanical properties conform to those indicated by the digits.
b. For this classification, E10XTX-K9, K9M, the "10" approximates the tensile strength, not a
requirement.
NAVEDTRA 14250A
11-36
The classification of low-alloy steel electrodes is similar to the classification of carbonsteel electrodes. An example of a low-alloy steel classification is ES1T1-Ni2 where:
1. The "E" indicates an electrode.
2. The second digit indicates the minimum tensile strength in units of 10,000 psi (69
Mpa). The mechanical property requirements for low-alloy steel electrodes are
shown in Table 11-8.
3. The third digit indicates the welding position capabilities of the electrode. A "0"
indicates flat and horizontal positions only, and a "1" indicates all positions.
4. The "T" stands for a tubular (flux-cored) wire classification.
5. The fifth digit describes the usability and performance characteristics of the
electrode. These digits are the same as used in carbon steel electrode
classification but only EXXT1-X, EXXT4-X, EXXT5-X and EXXTS-X are used
with low-alloy steel flux-cored electrode classifications.
6. The suffix tells the chemical composition of the deposited weld metal as shown in
Table 11-9.
The classification system for stainless steel electrodes is based on the chemical
composition of the weld metal and the type of shielding to be used during welding. An
example of a stainless steel electrode classification is E30ST-1 where:
1. The "E" indicates an electrode.
2. The digits between the "E" and the "T" indicate the chemical composition of the
weld as shown in Table 11-10.
3. The 'T' stands for a tubular (flux-cored) wire classification.
4. The suffix indicates the type of shielding to be used as shown in Table 11-11.
NAVEDTRA 14250A
11-37
Table 11-8 — Impact requirements for low-alloy flux-cored electrodes (AWS
A5.29)
Classifications
Condition
(a)
Minimum Impact Strength
PWHT
Not Required
EBXT1-A 1 ,-Ai M
PWHT
20 ft·lbf @ -20°F (27 J @ -29°C)
E7XT5-A 1, -A 1 M
PWHT
Not Required
EBXT1-B1, -B1M
PWHT
Not Required
EBXT1-B1L, -B1LM
PWHT
Not Required
EBXT1-B2, -B2M
PWHT
Not Required
EBXT5-B2, -B2M
PWHT
Not Required
EBXT1-B2H, -B2HM
PWHT
Not Required
EBXT1-B2L, -B2LM
PWHT
Not Required
EBXT5-B2L, -B2LM
PWHT
Not Required
EBXT5-B6, -B6M
PWHT
Not Required
EBXT5-B6L, -B6LM
PWHT
Not Required
EBXT5-BB, -BBM
PWHT
Not Required
EBXT5-BBL, -BBLM
PWHT
Not Required
E9XT1-B3, -B3M
PWHT
Not Required
E9XT5-B3, -B3M
PWHT
Not Required
E10XT1-B3, -B3M
PWHT
Not Required
E9XT1-B3L, -B3LM
PWHT
Not Required
E9XT1-B3H, -B3HM
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E6XT1-Ni1, -Ni1M
AW
E7XT6-Ni1
20 ft·lbf @ -20°F (27 J @ -29°C)
AW
E7XTB-Ni1
20 ft·lbf @ -20°F (27 J @ -29°C)
AW
EBXT1-Ni1, -Ni1 M
20 ft·lbf @ -20°F (27 J @ -29°C)
PWHT
E9XTS-N11, -Ni1 M
20 ft·lbf @ -60°F (27 J @ -51°C)
AW
E7XTB-Ni2
20 ft·lbf @ -20°F (27 J @ -29°C)
AW
EBXTB-Ni2
20 ft·lbf @ -20°F (27 J @ -29°C)
AW
EBXT1-Ni2, -Ni2M
20 ft·lbf @ -40F (27 J @ -40°C)
PWHT
EBXT5-Ni2(b), -Ni2M(b
20 ft·lbf @ -75°F (27 J @ -60°C)
AW
20 ft·lbf @ -40°F (27 J @ -40°C)
E9XT1-Ni2, -Ni2M
PWHT
20 ft·lbf @ -100°F (27 J @ -73°C)
EBXT5-Ni3(b), -Ni3M(b)
AW
20 ft·lbf @ 0°F (27 J @ -18°C)
EBXT11-Ni3
PWHT
20 ft·lbf @ -100°F (27 J @ -73°C)
E9XT5-Ni3(b), -Ni3M(b)
AW
20 ft·lbf @ -40°F (27 J @ -40°C)
E9XT1-D1, -D1M
PWHT
20 ft·lbf @ -60°F (27 J @ -51°C)
E9XT5-D2, -D2M
PWHT
20 ft·lbf @ -40°F (27 J @ -40°C)
E10XT5-D2, -D2M
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E9XT1-D3, -D3M
AW
20 ft·lbf @ -40°F (27 J @ -40C)
EBXTS-K1, -K1M
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E7XT7-K2
AW
20 ft·lbf @ 0°F (27 J @ -18°C)
E7XT4-K2
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E7XTB-K2
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
EBXT1-K2, -K2M
AW
20 ft·lbf @ 0°F (27 J @ -18°C)
E9XT1-K2, -K2M
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
EBXT5-K2, -K2M
AW
20 ft·lbf @ +32°F (27 J @ 0°C)
E7XT11-K2
AW
20 ft·lbf @ -60°F (27 J @ -51°C)
E9XT5-K2, -K2M
AW
20 ft·lbf @ 0°F (27 J @ -18°C)
E10XT1-K3, -K3M
AW
20 ft·lbf @ 0°F (27 J @ -18°C)
E11 XT1-K3, -K3M
AW
20 ft·lbf @ -60°F (27 J @ -51°C)
E10XT5-K3, -K3M
AW
20 ft·lbf @ -60°F (27 J @ -51°C)
E11 XT5-K3, -K3M
AW
20 ft lbf @ 0°F (27 J @ -18°C)
E 11 XT1-K4, -K4M
AW
20 ft·lbf @ -60°F (27 J @ -51°C)
E11XT5-K4, -K4M
AW
20 ft·lbf @ -60°F (27 J @ -51°C)
E12XT5-K4, -K4M
AW
Not Required
E12XT1-K5, -K5M
AW
20 ft·lbf @ -75°F (27 J @ -60°C)
E7XT5-K6, -K6M
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E6XTB-K6
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E7XTB-K6
AW
20 ft·[email protected] -60°F (27 J @ -51°C)
E10XT1-K7, -K7M
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
E9XTB-KB
AW
35 ft·lbf @ -60°F (47 J @ -51°C)
E10XT1-K9, -K9M
AW
20 ft·lbf @ -20°F (27 J @ -29°C)
EBXT1-W2, -W2M
EXXXTX-G
(c)
Not Specified
Not Specifiedc
EXXXTG-G
EXXXTG-X
a. AW= As welded
PWHT = Postweld heat treated in accordance with AWS 5.29 Specification.
b. PWHT temperatures in excess 1150°F (620°C) will decrease the impact value.
c. See Table 11-7, Note a
NAVEDTRA 14250A
11-38
Table 11-9 — Chemical composition requirements for low-alloy flux-cored
electrodes (AWS A5.29).
Chemical Composition Weight-Percenta
AWS
Classification
UNS
Number
E7XT5-A1-A1M
ESXT1-A1-A1M
Mn
W17035
W17031
0.12
1.25
P
S
Si
Ni
Carbon-Molybdenum Steel Electrodes
0.03
0.03
0.80
ESXT1-B1-B1M
ESXT1-B1L-B1LM
ESXT1-B2-B2M
ESXT5-B2-B2M
ESXT1-B2L-B2LM
ESXT5-B2L-B2LM
ESXT1-B2H-B2HM
E9XT1-B3-B3M
E9XT5-B3-B3M
E10XT1-B3-B3M
E9XT1-B3L-B3LM
E9XT1-B3H-B3HM
ESXT5-B6-B6M
ESXT5-B6L-B6LM
ESXT5-BS-BSM
ESXT5-BSL-BSLM
W51031
W51131
W52031
W52035
W52131
W52135
W52231
W53031
W53035
W53031
W53131
W53231
W50231
W50230
W50431
W50430
0.05-0.12
0.05
0.05-0.12
1.25
1.25
1.25
Chromium-Molybdenum Steel Electrodes
0.03
0.03
0.80
0.03
0.03
0.80
0.03
0.03
0.80
0.40-0.65
0.40-0.65
1.00-1.50
0.40-0.65
0.40-0.65
0.40-0.65
0.05
1.25
0.03
0.03
0.80
1.00-1.50
0.40-0.65
0.10-0.15
1.25
0.03
0.03
0.80
1.00-1.50
0.40-0.65
0.05-0.12
1.25
0.03
0.03
0.80
2.00-2.50
0.90-1.20
0.05
0.10-0.15
0.05-0.12
0.05
0.05-0.12
0.05
1.25
1.25
1.25
1.25
1.25
1.25
0.03
0.03
0.04
0.04
0.04
0.03
2.00-2.50
2.00-2.50
4.0-6.0
4.0-6.0
8.0-10.5
8.0-10.5
0.90-1.20
0.90-1.20
0.45-0.65
0.45-0.65
0.85-1.20
0.85-1.20
E7XTS-Ni1
E7XT6-Ni1
E6XT1-Ni1-Ni1M
ESXT1-Ni1-Ni1M
ESXT5-Ni1 -Ni1M
ESXT1-Ni2 -Ni2M
ESXT5-Ni2 -Ni2M
E9XT1-Ni2 -Ni2M
E7XTS-Ni2
ESXTS-Ni2
ESXT5-Ni3 -Ni3M
E9XT5-Ni3 -Ni3M
ESXT11-Ni3
W21038
W21038
W21031
W21031
W21035
W22031
W22035
W22031
W22038
W22038
W23035
W23035
W23039
0.12
1.50
0.03
0.15
0.35
0.05
0.12
1.50
0.03
0.03
0.80
0.80-1.10
0.15
0.35
0.05
0.12
1.50
0.03
0.03
0.80
1.75-2.75
0.12
1.50
0.03
0.03
0.80
1.75-2.75
0.12
0.12
0.12
1.50
1.50
1.50
E9XT1-01 -01M
E9XT5-02 -02M
E10XT5-02 -02M
E9XT1-03 -03M
W19131
W19235
W19235
W19331
0.12
0.15
1.25-2.00
1.65-2.25
0.12
1.00-1.75
ESXT5-K1, K1M
E7XT4-K2
E7XT7-K2
E71TS-K2
E7XT11-K2
ESXT1-K2 -K2M
E9XT1-K2 -K2M
ESXT5-K2 -K2M
E9XT5-K2 -K2M
E10XT1-K3 -K3M
E11XT1-K3 -K3M
E10XT5-K3 -K3M
E11XT5-K3 -K3M
E11XT1-K4 -K4M
E11XT5-K4 -K4M
E12XT5-K4 -K4M
E12XT1-K5 -K5M
E6XTS-K6
E7XTS-K6
E7XT5-K6 -K6M
E10XT1-K7 -K7M
E9XTS-KS
E10XT1-K9 -K9M
ESXT1-W2 -W2M
EXXTX-G
W21135
W21234
W21237
W2123S
W21239
W21231
W21231
W21235
W21235
W21331
W21331
W21335
W21335
W22231
W22235
W22235
W21531
W21048
W21048
W21045
W22051
W21438
W23230
W21031
0.15
0.03
0.80
0.03
0.80
0.03
1.0
0.40
0.03
1.0
0.40
0.03
1.0
0.40
0.03
1.0
0.40
Nickel-Steel Electrodes
0.03
0.80
0.80-1.10
Cr
Mo
A1b
C
V
Cu
0.40-0.65
0.50
0.50
0.50
0.50
1.8
1.8
0.03
0.03
0.80
2.75-3.75
0.03
0.03
0.80
2.75-3.75
0.03
0.03
0.80
2.75-3.75
Manganese-Molybdenum Steel Electrodes
0.03
0.03
0.80
0.03
0.03
0.80
1.8
0.25-0.65
0.25-0.55
0.80-1.40
0.03
0.03
0.80
All Other Low-Alloy Steel Electrodes
0.03
0.03
0.80
0.80-1.10
0.40-0.65
0.15
0.20-0.65
0.05
0.15
0.50-1.75
0.03
0.03
0.80
1.00-2.00
0.15
0.35
0.05
0.15
0.50-1.75
0.03
0.03
0.80
1.00-2.00
0.15
0.35
0.05
0.15
0.75-2.25
0.03
0.03
0.80
1.25-2.80
0.15
0.25-0.65
0.05
0.15
1.20-2.25
0.03
0.03
0.80
1.75-2.60
0.20-0.60
0.20-0.65
0.03
0.010-0.25
0.15
0.60-1.60
0.50-1.50
0.03
0.03
0.03
0.03
0.80
0.80
0.75-2.00
0.40-1.00
0.20-0.70
0.20
0.15-0.55
0.15
0.05
0.05
0.15
0.15
0.15
0.07
0.12
0.50-1.50
1.00-1.75
1.00-2.00
0.50-1.50
0.50-1.30
1.75c
0.03
0.03
0.03
0.15
0.03
0.03
0.03
0.03
0.03
0.15
0.03
0.03
0.80
0.80
0.40
0.80
0.35-0.80
0.80c
0.40-1.00
2.00-2.75
0.50-1.50
1.30-3.75
0.40-0.80
0.50c
0.20
0.15
0.05
0.20
0.20
0.45-0.70
0.30c
0.20
0.50
0.05
0.05
1.8
c
c
c
0.20
0.10
1.8
1.8
0.8
0.06
0.30-0.75
a. Single values are maximum unless otherwise noted.
b. For self-shielded electrodes only.
c. In order to meet the alloy requirements of the G group, the undiluted weld metal shall have the minimum of at least one of the elements listed in this table.
Shielding gas, slag system, and mechanical properties are dictated by the digit(s) replacing XIs).
NAVEDTRA 14250A
11-39
Table 11-10 — Undiluted weld metal composition requirements for stainless steel
electrodes (AWS A5.22).
Chemical Composition Weight-Percenta
AWS
UNS
Cb(Nb)
Classificationb
Numberc
C
Cr
Ni
Mo
Mn
Si
P
S
E307TX-X
W30731
013
18.0-20.5
9.0-10.5
0.5-1.5
3.30-4.75
1.0
0.04
0.03
0.5
E308TX-X
W30831
0.08
18.0-21.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E308LTX-X
W30835
0.04
18.0-21.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E308HTX-X
W30831
0.04-0.08
18.0-21.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E308MoTX-X
W30832
0.08
18.0-21.0
9.0-11.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E308LMoTX-X
W30838
0.04
18.0-21.0
9.0-12.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E309TX-X
W30931
0.10
22.0-25.0
12.0-14.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E309LCbTX-X
W30932
0.04
22.0-25.0
12.0-14.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E309LTX-X
W30935
0.04
22.0-25.0
12.0-14.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E309MoTX-X
W30939
0.12
21.0-25.0
12.0-16.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E309LMoTX-X
W30938
0.04
21.0-25.0
12.0-16.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E309LNiMoTX-X
W30936
0.04
20.5-23.5
15.0-17.0
2.5-3.5
0.5-2.5
1.0
0.04
0.03
0.5
E310TX-X
W31031
0.20
25.0-28.0
20.0-22.5
0.5
1.0-2.5
1.0
0.03
0.03
0.5
E312TX-X
W31331
0.15
28.0-32.0
8.0-10.5
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E316TX-X
W31631
0.08
17.0-20.0
11.0-14.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E316LTX-X
W31635
0.04
17.0-20.0
11.0-14.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E317LTX-X
W31735
0.04
18.0-21.0
12.0-14.0
3.0-4.0
0.5-2.5
1.0
0.04
0.03
0.5
E347TX-X
W34731
0.08
18.0-21.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
+Ta
0.70-1.00
8 x C min.
N
Cu
1.0 max.
E409TX-Xd
W40931
0.10
10.5-13.5
0.60
0.5
0.80
1.0
0.04
0.03
0.5
E410TX-X
W41031
0.12
11.0-13.5
0.60
0.5
1.2
1.0
0.04
0.03
0.5
E410NiMoTX-X
W41036
0.06
11.0-12.5
4.0-5.0
0.40-0.70
1.0
1.0
0.04
0.03
0.5
E410NiTiTX-Xd
W41038
0.04
11.0-12.0
3.6-4.5
0.5
0.70
0.50
0.03
0.03
0.5
E430TX-X
W43031
0.10
15.0-18.0
0.60
0.5
1.2
1.0
0.04
0.03
0.5
E502TX-X
W50231
0.10
4.0-6.0
0.40
0.45-0.65
1.2
1.0
0.04
0.03
0.5
E505TX-X
W50431
0.10
8.0-10.5
0.40
0.85-1.20
1.2
1.0
0.04
0.03
0.5
E307T0-3
W30733
0.13
19.5-22.0
9.0-10.5
0.5-1.5
3.30-4.75
1.0
0.04
0.03
0.5
E308T0-3
W30833
0.08
19.5-22.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E308LT0-3
W30837
0.03
19.5-22.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E308HT0-3
W30833
0.04-0.08
19.5-22.0
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E308MoT0-3
W30839
0.08
18.0-21.0
9.0-11.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E308LMoT0-3
W30838
0.03
18.0-21.0
9.0-12.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E308HMoT0-3
W30830
0.07-0.12
19.0-21.5
9.0-10.7
1.8-2.4
1.25-2.25
0.25-0.80
0.04
0.03
0.5
E309T0-3
W30933
0.10
23.0-25.5
12.0-14.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E309LT0-3
W30937
0.03
23.0-25.5
12.0-14.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E309LCbT0-3
W30934
0.03
23.0-25.5
12.0-14.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E309MoT0-3
W30939
0.12
21.0-25.0
12.0-16.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E309LMoT0-3
W30938
0.04
21.0-25.0
12.0-16.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E310T0-3
W31031
0.20
25.0-28.0
20.0-22.5
0.5
1.0-2.5
1.0
0.03
0.03
0.5
E312T0-3
W31231
0.15
28.0-32.0
8.0-10.5
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E316T0-3
W31633
0.08
18.0-20.5
11.0-14.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
0.70-1.00
E316LT0-3
W31637
0.03
18.0-20.5
11.0-14.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E316LKT0-3e
W31630
0.04
17.0-20.0
11.0-14.0
2.0-3.0
0.5-2.5
1.0
0.04
0.03
0.5
E317LT0-3
W31737
0.03
18.5-21.0
13.0-15.0
3.0-4.0
0.5-2.5
1.0
0.04
0.03
0.5
E347T0-3
W34733
0.08
19.0-21.5
9.0-11.0
0.5
0.5-2.5
1.0
0.04
0.03
0.5
E409T0-3d
W40931
0.10
10.5-13.5
0.60
0.5
0.80
1.0
0.04
0.03
0.5
E410T0-3
W41031
0.12
11.0-13.5
0.60
0.5
1.0
1.0
0.04
0.03
0.5
E410NiMoT0-3
W41036
0.06
11.0-12.5
4.0-5.0
0.40-0.70
1.0
1.0
0.04
0.03
0.5
E410NiTiT0-3d
W41038
0.04
11.0-12.0
3.6-4.5
0.5
0.70
0.50
0.03
0.03
0.5
E430T0-3
W43031
0.10
15.0-18.0
0.60
0.5
1.0
1.0
0.04
0.03
E2209T0-X
W39239
0.04
21.0-24.0
7.5-10.0
2.5-4.0
0.5-2.0
1.0
0.04
0.03
0.80-2.0
0.5
E2553T0-X
W39553
0.04
24.0-27.0
8.5-10.5
2.9-3.9
0.5-1.5
0.75
0.04
0.03
0.10-0.20
1.5-2.5
8 x C min.
1.0 max.
0.5
EXXXTX-G
Not Specified
a. Single values shown are maximum.
b. In this table, the "X" following the ''T'' refers to the position of welding (1 for all-position operation or 0 for flat or horizontal operation) and the "X" following the dash refers to the
shielding medium (-1 or -4).
c. ASTM/SAE Unified Number System for Metals and Alloys.
NAVEDTRA 14250A
11-40
d. Titanium - 10 x C min., 1.5% max.
e. This alloy is designed for cryogenic applications.
Table 11-11 — Performance and usability characteristics for stainless steel fluxcored electrodes.
AWS Classification
External Shielding Gas
Welding Polarity
EXXXT-1
CO2
DCEP
EXXXT-3
None (Self-shielded)
DCEP
EXXXT-4
75-80% Argon/remainder CO2
DCEP
EXXXT-G
Not Specified
Not Specified
5.2.2 Electrode Selection
The selection of the proper electrode for an application is based on the type of metal to
be welded and the specific chemical and mechanical properties required of the joint.
Identification of the base metal is required to select an electrode. If the type of metal is
not known, tests must be made based on visual, magnetic, chisel, flame, fracture,
spark, or chemistry tests.
The selection of the proper filler metal for a specific job application is quite involved but
may be based on the following factors.
1. Base Metal Strength Properties — This is done by choosing an electrode wire to
match the tensile or yield strength of a metal. This is usually one of the most
important criteria for selecting a filler metal to be used on low-carbon and many
low-alloy steels.
2. Base Metal Composition — The chemical composition of the metal to be welded
should be known. Closely matching the filler and base metal com positions is
important when corrosion resistance and creep resistance are needed. The filler
metals for welding stainless steels and alloy steels are usually chosen based on
matching chemical compositions.
3. Welding Position — Flux-cored electrodes are designed to be used in specific
positions. Wire diameter is the major factor limiting the position in which an
electrode can be used. All-position electrodes are available only in the smaller
sizes. Flat and horizontal-position-only electrodes may have very similar
compositions but are available in all sizes or the larger sizes that cannot be
easily used for vertical and overhead welding. Electrodes should be selected to
match the welding position.
4. Welding Current — Flux-cored electrodes are designed to operate on either
direct current electrode negative or direct current electrode positive. Electrodes
operating on DCEN generally give lighter penetration and higher deposition
rates. Electrodes operating on DCEP generally provide deeper penetration.
5. Joint Design and Fit-up — Electrodes should be chosen according to their
penetration characteristics. Gas-shielded flux-cored wires produce deeper
penetration than self-shielding wires. This can have an effect on the joint design
used.
NAVEDTRA 14250A
11-41
6. Thickness and Shape of Base Metal — Weldments may include thick sections or
complex shapes that may require maximum ductility to avoid weld cracking.
Electrodes that give the best ductility should be used for these applications.
7. Service Conditions and/or Specifications — For weldments subject to severe
conditions, such as low temperature, high temperature, or shock loading, an
electrode that matches the ductility and impact strength of the steel should be
selected.
8. Production Efficiency and Job Conditions — Large-diameter electrodes should
be used, if possible, to give higher deposition rates.
Flux-cored electrodes for carbon and low-alloy steels are each designed for specific
applications based on the composition of the flux core of the wire. Each suffix used
indicates a general grouping of electrodes that have similar flux components and
usability characteristics.
T-I electrodes are single- or multiple-pass electrodes. They operate on DCEP and
require gas shielding. They produce a flat to slightly convex weld bead with a moderate
slag coating. T-I electrodes produce a fine globular transfer and low spatter levels.
Welds produced with T-1 electrodes have good mechanical properties.
T-2 electrodes operate on DCEP and also require gas shielding. These electrodes are
similar to T-I types, but are designed to weld over rust and scale. They are for
singlepass welding only because of their high silicon and manganese contents.
T-3 electrodes are self-shielding wires using DCEP for single-pass welding operations.
These electrodes produce a fine globular transfer, and are designed for welding sheet
metal at high welding speeds.
T-4 electrodes are self-shielding wires using DCEP for single- or multiple-pass
operation. These electrodes produce a globular metal transfer and light penetration for
joints with poor fit-up. Desulfurizing elements are contained in the flux core to help
prevent weld cracking.
T-5 electrodes can be used to weld higher carbon steels, or for joining low-alloy steels
to carbon steels because of cleaner welds and lower hydrogen levels.
T-6 electrodes are self-shielded electrodes for single- or multiple-pass welding using
DCEP. A fine globular transfer and deep penetration characterize these electrodes. The
slag coating has good deep-groove removal characteristics and produces good low
temperature impact properties.
T-7 electrodes are self-shielded electrodes that operate on DCEN for single- or multiplepass welding. The larger sizes of this type of electrode are designed to produce high
deposition rates. The smaller sizes are used for all-position welding. The slag coating
desulfurizes the weld metal to a very low level that helps prevent cracking.
T-8 electrodes are self-shielding electrodes for single- or multiple- pass welding that
operate on DCEN. The slag system is designed to allow all-position welding. The slag
also desulfurizes the weld metal and produces good low temperature impact properties.
T-10 electrodes are self-shielded, single-pass electrodes that operate on DCEN. These
electrodes are used for making welds in the flat and horizontal positions at high travel
speeds.
T-11 electrodes are self-shielded electrodes that operate on DCEN for single- and
multiple-pass welding. These are general-purpose electrodes for all-position welding at
moderate travel speeds. They produce a fine globular transfer.
NAVEDTRA 14250A
11-42
T-G electrodes are for multiple-pass welding not covered by another classification.
T-GS electrodes are single-pass electrodes not covered by another classification. The
operating conditions and characteristics are not defined for the T-G and the T-GS
electrodes.
5.2.3 Conformance and Approvals
Flux cored arc welding electrodes must conform to specifications, or be approved by
code-making organizations for many FCAW applications. Some of the code-making
organizations that issue specifications or approvals are the American Welding Society
(AWS), the American Bureau of Shipping (ABS), and other state and federal highway
and military organizations.
The American Welding Society provides specifications for flux-cored wire electrodes.
Electrodes must meet specific requirements in order to conform to a particular electrode
classification.
Many code-making organizations, such as the American Society of Mechanical
Engineers (ASME) and the American Petroleum Institute (API), recognize and use the
AWS specifications.
Some of the code-making organizations, such as the American Bureau of Shipping
(ABS) and the military, must directly approve the electrodes before they can be used for
welding on a project covered by that code. These organizations send inspectors to
witness the welding and testing, as well as to approve the classification of the flux-cored
electrodes.
To conform to the AWS specifications for carbon- and low-alloy steel filler metals, the
electrodes must produce a weld deposit that meets the specific mechanical and
chemical requirements. For stainless steel filler metal, the electrodes must produce a
weld deposit with a specific chemical composition. The requirements will vary
depending on the class of the electrodes.
Test your Knowledge (Select the Correct Response)
3.
For what wire size is the knurled V-groove drive rolls most commonly used?
A.
B.
C.
D.
4.
1/32 and smaller
1/16 and smaller
1/32 and larger
1/16 and larger
(True or False) Electrodes are designed to be used in specific positions.
A.
B.
True
False
6.0.0 WELDING APPLICATIONS
Flux cored arc welding has gained popularity for a wide variety of applications. FCAW
has replaced SMAW for some applications. One of the major advantages of the process
is the high deposition rates obtained when compared to the manual arc welding
processes. FCAW deposition rates are also generally higher than those obtained from
gas metal arc welding. Because FCAW is a semiautomatic process, higher productivity
can be obtained compared to SMAW. This process also lends itself easily to machine
NAVEDTRA 14250A
11-43
and automatic welding. Because of the versatility of FCAW, it has obtained wide
application in shop fabrication, maintenance, and field erection work.
Each of the two variations of FCAW has their advantages, but the areas of application
of the two variations often overlap. The method of welding used depends on the joint
design, fit-up, availability of electrodes, and mechanical property requirements of the
welded joints.
The self-shielding electrode wire variation can often be used for applications that can be
done by SMAW. This is especially true when welding in locations where compressed
gas cylinders are difficult to handle.
Gas-shielded flux-cored wires are used for many applications that compete with GMAW.
There are many different applications possible but the most common ones are
discussed below.
6.1.0 Industries
FCAW is the welding process of choice in a number of civilian industries because it is
versatile, has high deposition rates, and is user friendly.
6.1.1 Structures
One of the most important applications of FCAW is in the structural fabrication industry.
This industry uses a wide variety of low-carbon and low-alloy steels in many different
thicknesses. Welding is done in the shop and in the field, and FCAW is readily
adaptable to both types of wires. The major advantages of this process in the structural
industry are the high deposition rates, high production rates, deep penetrating
characteristics, and the adaptability of the process for field erection welding. Because a
large percentage of the welds made in
structural work are fillets, FCAW is widely
used for making large single-pass fillet
welds. Many of these welds would require
multiple passes using GMAW and SMAW.
Gas-shielded flux-cored wires have replaced
SMAW and GMAW for many shop
applications. FCAW is widely used for
welding the thicker structural members
where the higher deposition rates provide
more advantage. Figure 11-27 shows
welding a bridge girder using a gas-shielded
flux-cored wire in the flat position. Out-ofposition welding is done using the smaller
diameter wires.
For field welding, the self-shielding fluxcored wires are commonly used. These fluxFigure 11-27 — Flux cored arc
cored wires are preferred over the gaswelding of structures.
shielded types because a supply of shielding
gas is not required, which makes the equipment more portable.
Another advantage of the self-shielding electrodes for field construction is that they can
be used in windier conditions. This is because the decomposition of the flux core that
provides the shielding is less sensitive to wind than an external gas shielding supply.
NAVEDTRA 14250A
11-44
Figure 11-28 shows FCAW being used.
Note the welder’s hand shield in place to
protect from the higher heat created by the
FCAW process.
Another application of self-shielding
electrodes is for welding galvanized steel
roof decking. Single-pass electrodes using
DCEN are preferred for most applications
because of the lighter penetration produced,
which reduces the chances of burning
through the decking.
6.1.2 Ships
FCAW is used in the shipbuilding industry
because of the wide variety of low-carbon
and low-alloy steels and metal thicknesses
being welded. Because this process can be
used in the vertical and overhead positions,
it is used in places where submerged arc
welding (SAW) cannot be used. The
process is also useful for vertical welding on
metal thicknesses too thin for electroslag
welding to be economical. Most FCAW is
done semiautomatically but some automatic
welding applications are used. Figure 11-29
shows an automatic welding system welding
a cargo hoist control unit.
Figure 11-28 — Self-shielded flux
cored welding.
6.1.3 Industrial Piping
FCAW is used to some extent in the
industrial piping industry. This process is
used for welding pipe in both the shop and
the field for steam generating plants,
refineries, distilleries, and chemical
processing plants. FCAW competes with
submerged arc welding, SMAW, and
GMAW.
Figure 11-29 — Automatic
welding system.
This process may be used to deposit all
passes or it may be used to deposit the fill and cover passes over a root pass welded by
another process. Flat roll welding (I G position) is often used for both semiautomatic and
automatic welding applications. This allows higher welding currents with larger diameter
wires and requires fewer weld passes. Roll welding is often used, especially on largediameter piping. Copper backing strips are sometimes used to allow higher current
levels and insure full penetration to the root of the joint. When welding fixed position
pipe, smaller diameter electrodes are used. These electrodes operate at lower current
levels and require more passes. In these positions, the root pass is often welded using
GMAW and sometimes GTAW. In horizontal fixed (5 G position) welding, the root pass
by FCAW is done using a downhill technique. The remaining passes are then welded
using an uphill technique.
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FCAW is used for welding both carbon-steel and alloy-steel pipe. A major application of
the process is for welding chromium-molybdenum steel pipe. This is the major type of
alloy steel used for pipe. Flux-cored electrodes are preferred over the solid wire when
matching chemical compositions. This is because porosity is hard to avoid. In addition,
with the solid wire electrodes the operating characteristics of solid wires are not as
good, which makes them more difficult to use. Most of the electrodes used for FCAW
pipe are gas-shielded because of the better penetration and the generally better
mechanical properties produced.
6.1.4 Railroads
FCAW is used extensively in the railroad industry. Other processes, such as SMAW,
GMAW and SAW, are also widely used, so
the choice of the welding process is based
on the weld size, joint accessibility, joint
length and welding position. The longest
welds on the heavier metal thicknesses in
the flat position are generally welded using
SAW. FCAW is usually used on the heavier
metal thicknesses where SAW is not
practical. Examples would be for joints in
other positions, shorter joints, and where
accessibility is more limited. FCAW is
preferred over SMAW and GMAW for many
uses because of the higher deposition rates
obtained. Many different components on the
engines and the rail cars are commonly
welded. Figure 11-30 shows FCAW of a
seam on a rail car.
6.1.5 Automotive Products
FCAW has gained popularity for use in the
automobile and truck manufacturing
industries. This process is used because of
the high production rates that can be
obtained. Both the self-shielding and the
gas-shielded electrode wires have been
used. The gas-shielded wires are generally
used when deeper penetration is required.
FCAW is also popular because it can be
easily automated. Components such as
frames, truck wheels, trailers, and axle
housings are common applications. FCAW
is more popular for trucks because of the
larger thicknesses of metal generally used.
An example of FCAW is shown in Figure 1131 where a truck trailer chassis is being
welded. This part had previously been a
casting that was made into a weldment.
Because of the relatively thick plate being
welded, FCAW is more economical on this
application than GMAW. Another advantage
NAVEDTRA 14250A
Figure 11-30 — FCAW of a
railroad car.
Figure 11-31 — FCAW of a truck
frame.
11-46
of this application is that the depth of some bevels has been reduced and some bevels
have been eliminated because of the deep penetrating characteristics of the process.
The use of FCAW has increased over GMAW for many frame welding applications
because joint fit-up is less important, better appearing weld beads can be produced,
and FCAW has better welder appeal. Many flux-cored electrodes have been developed
for welding over some rust and scale, which reduces the metal preparation time.
A special application of FCAW is for welding catalytic converters. These are made of
type 409 stainless steel that is welded with an equivalent filler metal using gas shielding.
6.1.6 Heavy Equipment
The heavy equipment manufacturing industry includes mining, agricultural, and earth
moving equipment, as well as other items such as forklift trucks and armored vehicles.
FCAW is popular in these industries because of the high deposition rates obtained.
Fillet welds are often encountered in these industries, and large single-pass fillet welds
can often be welded by FCAW, which eliminates interpass cleaning time and increases
productivity.
The mining equipment manufacturing industry also is a major user of FCAW for welding
a wide variety of low-carbon and low-alloy steels.
6.1.7 Maintenance and Repair
The FCAW process is very useful for maintenance and surfacing operations.
Maintenance operations range from repairing and modifying plant and building facilities
to repairing pipe, production equipment, and castings. Surfacing and salvaging
operations include the repair of mismachined parts, foundry defects, accommodating
engineering changes, rebuilding worn parts (especially shafting and rollers), and
overlaying parts with special materials. Reclamation includes the disassembly and
rewelding of defective items manufactured in the factory and in the field. It has been
used for maintaining and repairing items too expensive to repair with oxyacetylene
welding and other arc welding processes. Self-shielding flux-cored electrodes are
popular for field repairs and maintenance because the equipment is more portable.
A metal overlay can be used to extend the usable life of new parts that lack some of the
wear-resistant qualities required for certain applications. Overlays are used mostly to
replace metal that has been worn away by abrasion, corrosion, and impacts. An overlay
provides toughness and resistance to corrosion, abrasion, and wear at the exact
location on the part where it is needed most. The primary reason for weld overlaying
parts is to prepare them for certain applications and to extend their service life. FCAW is
widely used because of its characteristic high deposition rate and good weld bead
appearance.
6.2.0 Flux Cored Arc Spot Welding
Flux cored arc spot welding (FCASW) is a variation of the process where a fusion weld
is made through one sheet into an adjacent sheet of a lap joint while the welding gun is
held stationary. The equipment used for arc spot welding is the same as for normal
welding, except that it requires a timer and a special gun nozzle. FCASW is used on
low-carbon and low-alloy steels and is generally preferred for welding thicker sheet
metal and thin plate sections. This is because of the greater penetrating capability of the
process as compared to gas tungsten (GTASW) or gas metal arc spot welding
(GMASW). The FCASW process also provides a wider penetration spot weld at the
interface between the plates to be joined. This produces a larger diameter spot weld
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with greater strength. FCASW is identical to GMASW except that a flux-cored electrode
wire is used. Carbon dioxide shielding is generally used but argon-CO2 mixtures are
sometimes used to reduce the amount of penetration. When welding thinner metals, a
backup bar is used under the sheet metal.
The advantages of FCASW over resistance spot welding are:
1. Access is only required from the top of the joint.
2. Spot welding can be done in all positions more easily.
3. The gun is light and portable and can be taken to the weldment.
4. Weld joint fit-up is not as critical.
5. Faster production rates can be obtained, particularly on thicker metal.
The main disadvantage of arc spot welding is the consistency of weld size and strength
is not as good.
Either the gas-shielded or self-shielding fluxcored electrodes may be used. The weld is
made by depressing the trigger that starts
the shielding gas, if used, and, after a
preflow interval, starts the arc and the wire
feed. The arc melts through the top sheet of
the lap joint and fuses into the bottom sheet.
When the preset weld time is finished, the
arc and wire feed are stopped, followed by
the gas flow, if used. FCASW is shown in
Figure 11-32. This process is used for
making welds in metal ranging from 16
gauge (1.5 mm) to 1/4-in. (6.4 mm) in
thickness. Metals of the same or different
thicknesses can be made. If dissimilar
thicknesses are being welded, the thinner
member should always be placed on top.
Figure 11-32 — FCASW.
The length of the spot weld cycle affects the
penetration and the amount of reinforcement
on the surface of the weld bead. FCASW generally produces larger, stronger weld
nuggets on the same metal thicknesses as compared to GMASW. The rest of the
welding variables affect the weld in the same way as normal weld.
7.0.0 WELDING METALLURGY
Welding metallurgy concerns the chemical, physical, and atomic properties and
structures of metals, and the principles by which metals are combined to form alloys.
7.1.0 Properties of the Weld
The properties of a weld include the chemical composition, mechanical strength,
ductility, toughness, and the microstructure. These items will relate to the weldability of
the metal. The weldability of a metal is the quality obtained and the ease of welding for
the intended service conditions. The types of materials used affect the chemical,
physical, and mechanical properties of the weld. The mechanical properties and
microstructure are determined by the heat input as well as the chemical composition
and physical properties of the weld.
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7.2.0 Chemical Properties
The chemical composition of the base and filler metal has a great influence on the
weldability of a metal, and this property has an influence on the preheating and
postheating used, as well as the welding parameters.
For welding stainless steels, the chemical composition of the weld is often the most
important property. The chemical composition of the weld must match the composition
of the base metal when corrosion resistance, thermal and electrical conductivity, and
appearance are major considerations. The chemical composition can also affect the
high and low temperature strength, as well as the microstructure and mechanical
properties of the weld. Preheating reduces the cooling rate of the weld after welding to
prevent cracking. The amount of preheat needed depends on the type of metal being
welded, the metal thickness, and the amount of joint restraint.
Steels with higher carbon contents need higher preheat than steels with lower carbon
equivalents. Table 11-12 shows typical preheat values for different metals welded by
FCAW.
Another major factor that determines the amount of preheat needed is the thickness of
the base metal. Thicker base metals usually need higher preheat temperatures than
thinner base metals. Thick metal draws the heat away from the welding zone more
quickly because there is a large mass of metal to absorb the heat. This would cause a
quicker cooling of the weld if the same preheat temperature was used, as on thinner
base metals.
The third major factor for determining the amount of preheat needed is the amount of
joint restraint. Joint restraint is the resistance of a joint configuration to moving or
relieving the stresses due to welding during the heating and cooling of the weld zone.
Where there is high resistance to moving or high joint restraint, large amounts of
internal stresses build up. Higher preheat temperatures are needed as the amount of
joint restraint increases. Slower cooling rates reduce the amount of internal stresses
that are building up as the weld cools.
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Table 11-12 —Preheats for various metals.
Type of Steel
Preheat
Low-Carbon Steel
Room Temperature or up to 200°F (93°C)
Medium-Carbon Steel
400-500°F (205-260°C)
High-Carbon Steel
500-600°F (260-315°C)
Low-alloy Nickel Steel
-Less than ¼’ (6.4 mm) thick
Room Temperature
-More than ¼’ (6.4 mm) thick
500°F (260°C)
Low-alloy Nickel-Chrome Steel
-Carbon content below .20%
200-300°F (93-150°C)
-Carbon content .20% to .35%
600-800°F (315-425°C)
-Carbon content above .35%
900-1100°F (480-595°C)
Low-alloy Manganese Steel
400-600°F (205-315°C)
Low-alloy Chrome Steel
Up to 750°F (400°C)
Low-alloy Molybdenum Steel
Carbon content below .150%
Room Temperature
Carbon content above .15%
400-650°F (205-345°C)
Low-alloy High Tensile Steel
150-300°F (66-150°C)
Austenitic Stainless Steel
Room Temperature
Ferritic Stainless Steel
300-350°F (150-260°C)
Martensitic Stainless Steel
Note:
400-600°F (205-315°C)
The actual preheat needed may depend on several other factors, such as the thickness of the base
metal, the amount of joint restraint, and whether or not low-hydrogen types of electrodes are used. This
chart is intended as general information; the specifications of the job should be checked for the specific
preheat temperature used.
7.3.0 Mechanical Properties
The mechanical properties that are most important in the weld are the tensile strength,
yield strength, elongation, reduction of area, and impact strength. The first two are
measures of the strength of the material, the next two are a measure of the ductility, and
the last is a measure of the impact toughness. These properties are often important in
FCAW steels designed to give maximum strength, ductility, and toughness.
FCAW can produce good properties in the weld- and heat-affected zone. The slag
coating in FCAW slows the cooling rate of the weld metal, which reduces the tendency
to become brittle.
FCAW produces a higher heat input, which will also tend to produce a slower cooling
rate. A disadvantage of the higher heat input is that distortion is more of a problem than
with GMAW. The mechanical properties of the weld will vary, depending on whether a
self-shielded or gas-shielded flux-cored wire is used. Some self-shielded electrodes
contain high amounts of deoxidizers, which may produce weld metal with relatively low
impact toughness. Most of the gas-shielded flux-cored wires produce welds that have
better impact toughness.
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The yield strength, ultimate tensile strength,
elongation, and reduction of area are all
measured from a .505 in. (12.8 mm)
diameter machined tensile testing bar. The
metal is tested by pulling it in a tensile
testing machine. Figure 11-33 shows a
tensile bar before and after testing. The
yield strength of the metal is the stress at
which the material is pulled beyond the point
where it will return to its original length. The
ultimate tensile strength is the maximum
stress or load that can be carried by the
metal without breaking. This is also
measured in psi (MPa). Elongation is a
measure of ductility that is also measured
on the tensile bar. Two points are marked
on the bar 2 in. (51 mm) apart before
testing. After testing, the distance between
the two points is measured again and the
percent of change in the distance between
them, or percent of elongation, is measured.
Figure 11-33 — Tensile strength
testing bars.
Reduction of area is another method of measuring ductility. The original diameter of the
testing bar is .20 sq in (128 sq mm). During the testing, the diameter of the bar reduces
as it elongates. When the bar finally breaks, the diameter of the bar at the breaking
point is measured, which is then used to
determine the area. The percent reduction of
this cross-sectional area is called the
reduction of area.
Impact tests are used to measure the
toughness of a metal. The toughness of a
metal is the ability of a metal to absorb
mechanical energy by deforming before
breaking. The Charpy V-notch test is the
most commonly used method of making
impact toughness tests. Figure 11-34 shows
some typical Charpy V-notch test bars. Bars
with V-notches are put in a machine where
they are struck by a hammer attached to the
end of a pendulum. The energy that it takes
to break these bars is known as the impact
strength and it is measured in foot-pounds
(joules, also called newton-meters).
NAVEDTRA 14250A
Figure 11-34 — Charpy V-notch
bars.
11-51
7.4.0 Microstructure
Figure 11-35 shows a cross section of a
weld bead showing the weld metal zone,
the heat-affected zone, and the base metal
zone- the three basic microstructural areas
within a weldment. The weld metal zone is
where the metal was molten during welding.
The heat-affected zone is the area where
the heat from welding has an effect on the
microstructure of the base metal. The base
metal zone is the area that was not affected
by the welding. The extent of change of the
microstructure is dependent on four factors:
1. Maximum temperature exposure
2. Temperature exposure time
3. The chemical composition of the
base metal
Figure 11-35 — Cross section of
weld bead showing in the three
areas.
4. The cooling rate of the weld
The weld metal zone, which is the area heated above about 2800°F (1540°C) and
melted, generally has the coarsest grain structure of the three areas. Generally, a fairly
fine grain size is produced on cooling in most metals. Large grain size is undesirable
because it gives poor weld toughness and cracking resistance. The filler metal starts to
solidify at the edges of the weld puddle. The grains that form at the edge are called
dendrites and they grow toward the center
of the weld into the area that is still molten
(Figure 11-36).
These dendrites give the weld metal its
characteristic columnar grain structure. The
grains that form in the weld zone are similar
to the grains that form in castings.
Deoxidizers and scavengers are often
added to filler metal to help refine the grain
size in the weld. The greater the heat input
to the weld and the longer that it is held at
high temperature, the larger the grain size.
A faster cooling rate will produce a smaller
grain size than a slower cooling rate.
Preheating will give larger grain sizes, but is
often necessary to prevent the formation of
a hard, brittle microstructure.
Figure 11-36 — Solidification
The heat-affected zone is an area of change
pattern of the weld.
in the microstructure of the base metal. The
area that is closest to the weld metal usually
undergoes grain growth. Other parts of the heat-affected zone will go through grain
refinement. Other areas may be annealed and considerably softened. Because of the
changes due to the heat input and cooling rate, areas of the heat-affected zone can
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become embrittled and become the source of cracking. A large heat input during
welding will cause a larger heat-affected zone. This is often not desirable, so the
welding parameters used can help influence the size of the heat-affected zone.
7.5.0 Metals Weldable
FCAW is commonly used to weld most steels and stainless steels. This process also
welds some nickel alloys. Most nonferrous metals are not welded by this process
because of the high heat input and because suitable electrode wires have not been
developed.
7.5.1 Steels
FCAW is widely used for welding steels. In general, steel is classified according to the
carbon content, such as low-carbon, mild, medium-carbon, and high-carbon steels. In
addition, steel is also classified according to the alloys used. For the purpose of
discussion in this chapter, the different steels will be grouped according to their welding
characteristics.
When welding steel, the carbon and other alloy content influences the hardness and
hardenability of the weld metal, which in turn influences the amount of preheat needed.
The two terms, hardness and hardenability, are not the same. The maximum hardness
of a steel is primarily a function of the amount of carbon in the steel. Hardenability is a
measure of how easily a martensite structure is formed when the steel is quenched.
Martensite is the phase or metallurgical structure in steel where the maximum hardness
of the steel can be obtained. Steels with low hardenability must have very high cooling
rates after welding to form martensite, where steels with high hardenability will form
martensite even when they are slow cooled. The hardenability wiII determine to what
extent a steel will harden during welding. The carbon equivalent formula is one of the
best methods of determining the weldability of steels. This value is determined by the
amounts of the alloying elements used. There are several different formulas used. One
of the most popular is as follows:
Carbon Equivalent = %C +
%Cr % Mn % Mo % Ni %Cu
+
+
+
+
10
6
10
20
40
Steels with lower carbon equivalents generally are more readily weldable and require
fewer precautions, such as the use of preheat and postheat. Steels with higher carbon
equivalents are generally more difficult to weld. When welding some of the steels, it is
more important to match the mechanical properties than the chemical composition of
the filler metal to the base metal. Often, filler metal with a lower carbon content than the
base metal is used because the weld metal absorbs carbon from the base metal. This is
done to minimize the tendency for weld cracking.
7.5.1.1 Low-carbon and Mild Steels
Low-carbon and mild steels are those that have low carbon contents and are the most
readily weldable. This group of steels is the most widely used in industrial fabrication.
This group also includes the high strength structural steels.
Low-carbon steels have carbon contents up to .14%. Mild steel has carbon contents
ranging from .15 to .29%. For many applications, preheating is not required except on
thick sections, highly restrained joints, or where codes require preheating. Other
precautions, such as interpass temperature control and postheating, are sometimes
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used. With thicker sections and highly restrained joints, preheating, interpass
temperature control, and postheating are usually required to prevent cracking. When
welding these steels, electrodes of the E70-T class are used with carbon dioxide. Selfshielding wires are also widely used. The filler metal should be chosen so that it
matches the tensile strength of the base metal. When welding rimmed steels, which
have silicon contents less than .05%, filler metal with sufficient amounts of deoxidizers
must be chosen to prevent porosity. This precaution is not necessary for welding steels
containing more than .05% silicon.
The high-strength structural steels are steels whose yield strength falls between 45,000
psi (310 MPa) and 70,000 psi (485 MPa) and their carbon content is generally below
.25%. These steels have relatively small amounts of alloying elements. Some common
examples of these steels are the ASTM designations of A242, A441, A572, A588, A553,
and A537.
Some low-carbon and mild steel electrodes are designed for welding over some rust
and mill scale. The flux core helps to reduce the bad effects of rust and mill scale but
some reduction in weld quality may occur. These FCAW electrodes are preferred for
many applications because cleaning of the base metal is less important. For
applications where the maximum mechanical properties are not as important as higher
deposition rates and travel speeds, high welding currents can be used.
7.5.1.2 Low-alloy Steels
The low-alloy steels discussed here will be those steels that are low-carbon and have
alloy additions less than 5%. This includes the quenched and tempered steels, heattreated low-alloy steels, and the low-nickel-alloy steels. Elements such as nickel,
chromium, manganese, and molybdenum are the main alloying elements used. These
steels have a higher hardenability than mild steels and that is the principal complication
in welding. Low-alloy steels have good weldability but are not as good as the mild
steels. This higher hardenability permits martensite to form at lower cooling rates. As
the alloy content and the carbon content increases, the hardenability also increases.
In general, the weldability of the steel decreases as the hardenability increases. One of
the best methods for determining the weldability of a low-alloy steel is the use of the
carbon equivalent formula. Steels that have carbon equivalents below about .40%
usually do not require the use of preheating and postheating in the welding procedure
and generally have the best weldability. Steels with carbon equivalents higher than
.40% require more precautions for welding. Generally, the higher the carbon equivalent,
the more difficult the steel is to weld.
The selection of electrodes for welding steels is usually based on the strength and
mechanical properties desired of the weld, rather than matching chemical compositions.
Low-alloy steels are often welded using the gas-shielded EXXT-1 and EXXT-5
electrodes. These wires produce good, low temperature toughness and are preferred
for most applications. EXXT-4 and EXXT-8 self-shielded wires often contain nickel for
good strength and aluminum as a deoxidizer to help give good mechanical properties.
In other cases, such as for welding low nickel steels, the electrode wires are chosen to
match the chemical composition of the base metal.
The quenched and tempered heat-treated steels have yield strengths ranging from
50,000 psi (345 MPa) to very high yield strengths and have carbon contents ranging up
to .25%. Some common examples of these types of steel are the ASTM designations
A533 Grade B, A514, A517, A543, and A553. The .25% carbon limit is used to provide
fairly good weldability. These steels provide high tensile and yield strength along with
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good ductility, notch toughness, corrosion resistance, fatigue strength, and weldability.
The presence of hydrogen is always bad in steel, but it is even more critical in these
types of steels compared to mild steels. Preheat is generally not used on thinner
sections, but it is used on thicker or highly restrained sections. Postweld heat treatment
is usually not used because the flux cored arc welds made in these have a good
toughness. The steels are generally used in the welded or stress-relieved conditions.
The nickel alloy steels included in these low-alloy steel groups are those with less than
5% nickel contents. The 2-1/4% and 3-1/2% nickel steels are usually welded with
electrodes that have the same general chemical compositions as the base metal.
Preheating is required with highly restrained joints. Most self-shielding wires for lowalloy steels have been developed for welding the low nickel steels.
7.5.1.3 Heat Treatable Steels
The heat treatable steels are the medium- and high-carbon steels and medium-carbon
steels that have been alloyed. This group includes quenched and tempered steels after
welding, normalized or annealed steels, and medium- and high-carbon steels. These
steels are more difficult to weld than other types of steels already mentioned in this
chapter. The most important factor for selecting the type of electrode to be used is
matching the chemical compositions of the base metal and the filler metal.
Medium-carbon steels are those that have carbon contents ranging from .30% to .59%
and high-carbon steels have carbon contents ranging from .60% to about 1.0%. When
medium- and high-carbon steels are welded, precautions should be included in the
welding procedure because of the hardness that can occur in the weld joint. As the
carbon content increases up to .60%, the hardness of the fully hardened structure (or
martensite) increases to a maximum value. When the carbon content is above .60%,
the hardness of the fully hardened structure does not increase, so these steels can be
welded using about the same welding procedures as the medium-carbon steels.
Martensite, which is the phase that steel is in at its fullest hardness, is harder and more
brittle in a high-carbon steel than it is in low-carbon steel. A high-carbon, martensitic
structure can have a tendency to crack in the weld metal and heat-affected zone during
cooling.
Welding procedures that lower the hardness of the heat-affected zone and the weld
metal reduce the cracking tendency. This can be done by using a procedure that
requires a lower carbon content in the filler metal, and by slowing the cooling rate. The
procedure includes preheating, interpass temperature control, and postheating.
The procedures used for welding medium-carbon steels can be simpler than the one
just mentioned, but that depends on the specific applications. Medium-carbon steels
can be welded with the E70T-E90T classifications. High-carbon steels should be welded
with the E80T-E120T, using the electrode of the proper tensile strength to match the
tensile strength of the base metal. Generally, very high-carbon steels are not used in
welded production work. These steels are usually only welded in repair work. Mild steel
electrodes may also be used, but the deposited weld metal absorbs carbon from the
base metal and thus loses a considerable amount of ductility. Stainless steel electrodes
of the austenitic type are sometimes used, but the fusion zone may still be hard and
brittle. A preheat and/or postheat will help reduce the brittle structure.
The quenched and tempered steels, after welding, have carbon contents ranging from
about .25% to .45%, which distinguishes them from the steels that are quenched and
tempered before welding. These steels also have small additions of alloying elements.
Some common examples of these steels are the AISI designations 4130, 4140, and
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4340. Because of the higher carbon contents, the steels in this group can be heat
treated to extremely high levels of strength and hardness. Some of these steels have
enough alloy content to give them high hardenability. Because of this combination of
carbon and alloy content, the steels must be preheated before welding. The weldability
of these steels is also influenced by the purity of the steels. High amounts of sulfur and
phosphorous in the steel increase the sensitivity to cracking and reduce the ductility.
FCAW is often used for welding these steels. Filler metal of the same chemical
composition as the base metal is required to obtain the maximum strength. The
composition of the weld metal is usually similar to that of the base metal.
7.5.1.4 Chromium-Molybdenum Steels
The low chromium-molybdenum steels in this section are those with alloy contents of
about 6% or less. These steels are in the low-carbon range, generally up to .15%, and
are readily weldable. The chromium- and molybdenum-alloying elements provide these
steels with good oxidation resistance and high temperature strength. The chromium is
mainly responsible for the high oxidation resistance and the molybdenum is mainly
responsible for the high temperature strength.
The higher chrome-moly steels contain about 6-10% chromium and .5-1% molybdenum.
These steels are limited to a maximum carbon content of about .10% to limit the
hardness because these steels are very sensitive to air hardening. For welding these
steels, preheating, interpass temperature control, slow cooling, and postweld heat
treatment are required to make a weld with good mechanical properties. These steels
generally do not require preheating except when welding thick sections or highly
restrained joints. Postheating is usually not required on chromium molybdenum steels
that contain less than 2-1/4% Cr and 1% Mo.
FCAW is one of the most common methods of welding the chromium-molybdenum
steels. The steels with less than 6% chromium are welded with a carbon dioxide or
argon-carbon dioxide mixture. For the steels with 6% chromium or more, argon with
small additions of carbon dioxide is often used. The filler metal is chosen to match the
chemical composition of the base metal as closely as possible to give good corrosion
resistance.
7.5.1.5 Free Machining Steels
Free machining steels are steels that have additions of sulfur, phosphorous, selenium,
or lead in them to make these steels easier to machine. Except for the high sulfur, lead,
selenium, or phosphorous, these steels have chemical compositions similar to mild, lowalloy, and stainless steels. The addition of these elements makes these steels difficult to
weld. The reason for this is that the elements- lead, phosphorous, selenium and sulfurhave melting points that are much lower than the melting point of the steel. As the weld
solidifies, these elements retain liquid much longer than the steel so that they coat the
grain boundaries, which cause hot cracking in the weld. Hot cracking is cracking that
occurs before the weld has had a chance to cool. Because of this hot cracking problem,
free machining steels cannot be welded easily. High manganese filler metal and low
base metal dilution will help give the best results possible.
7.5.1.6 Stainless Steels
FCAW can weld most types of stainless steels. The types that are very difficult to weld
are types such as 303,416,416 Se, 430 F, and 430 FSe, which have high sulfur and
selenium contents, and Type 440, which has a high carbon content. The element that
distinguishes stainless steels from the other types of steel is the chromium. Steels that
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have chromium contents greater than 11 % are considered stainless steels. The high
chromium content gives them very good corrosion and oxidation resistance. The three
major groups of stainless steels that are welded are the austenitic, martensitic, and
ferritic types.
The austenitic types of stainless steels are generally the easiest to weld. In addition to
the high chromium content of about 16-26%, these types have high nickel contents
ranging from 6-22%. These steels are designated by the AISI as the 300 series. The
200 series, which has high manganese contents to replace some of the nickel, is also
austenitic. Nickel and manganese are strong austenite formers and maintain an
austenitic structure at all temperatures. This structure gives these steels good
toughness and ductility but also makes them non-hardenable. A major problem when
welding these types of steels is carbide precipitation or sensitization, which only occurs
in the austenitic structure. This occurs when the temperature of the steel is between
approximately 1000°-1600° F (540°-870° C) and can greatly reduce the resistance to
corrosion. There are several methods for preventing this problem:
1. A fast cooling rate after welding through this temperature range. This is a major
reason why preheating is usually not used and why these steels require a
relatively low maximum interpass temperature on multiple-pass welds.
2. The use of extra low-carbon base and filler metal (.03% C max.). Examples are
304L and 316L.
3. The use of a stabilized base and filler metal alloy containing columbium,
tantalum, or titanium. Examples are 347 and 321.
4. The use of a solution heat treatment to resolve the carbides after welding.
Martensitic stainless steels are not as easy to weld as the austenitic stainless steels.
These stainless steels have approximately 11-18% chromium, (the major alloying
element), and are designated by the AISI as the 400 series. Some examples are
403,410, 420, and 440. These types of stainless steels are heat treatable because they
generally contain higher carbon contents and a martensitic structure. Stainless steels
with higher carbon contents are more susceptible to cracking and some, such as Type
440, have carbon contents so high that they are often considered unweldable. A
stainless steel with a carbon content greater than .10% will often need preheating.
Preheating is usually done in the range of from 400-600° F (205-315° C) to avoid
cracking. For steels containing carbon contents greater than .20%, a postweld heat
treatment, such as annealing, is often required to improve the toughness of the weld
produced.
Ferritic stainless steels are also more difficult to weld than austenitic stainless steels
because they produce welds having lower toughness than the base metal. These
stainless steels form a ferritic grain structure and are also designated by the AISI as the
400 series. Some examples are Types 405, 430, 442, and 446. These types are
generally less corrosion resistant than austenitic stainless steel. To avoid a brittle
structure in the weld, preheating and postheating are often required. Typical preheat
temperatures range from 300-500° F (150-260° C). Annealing is often used after heat
treatment welding to increase the toughness of the weld.
The FCAW process can produce stainless steel weld deposits with a quality similar to
those produced by GMAW. Lower current levels may be desirable for welding stainless
steel compared to welding mild steel because of the higher thermal expansion, lower
thermal conductivity, and lower melting point of stainless steel. The lower thermal
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conductivity and higher thermal expansion cause more distortion and warpage for a
given heat input.
Carbon dioxide, argon-carbon dioxide, and argon-oxygen mixtures are used. Carbon
dioxide causes a loss of silicon and manganese and an increase in carbon in the lowcarbon stainless steels. The use of carbon dioxide or EXXT-1 electrodes is restricted for
welding many of the stainless steels, especially austenitic grades, because the
corrosion resistance may be reduced due to carbon added to the weld by gas. When
good corrosion resistance is required, argon-carbon dioxide or argon-oxygen mixtures
are used. The argon-oxygen mixtures containing 1 or 2% oxygen are used to improve
the arc stability and weld puddle wetting, as well as to eliminate carbon pickup from the
shielding gas. When the self-shielding EXXXT-3 electrodes are used, there is greater
pickup of nitrogen from the atmosphere into the weld metal. Nitrogen is an austenite
stabilizer and when the weld absorbs excessive nitrogen, there is a greater chance for
micro-cracking to occur. The welding position and arc length have a large influence on
this problem. An excessive arc length will usually cause excessive nitrogen pickup in
the weld. For this reason, procedures for out-of-position welding with self-shielding
wires should be carefully controlled to produce a sound weld deposit.
The filler metal used for welding stainless steel is generally chosen to match the
chemical composition of the base metal. In the 200-series austenitic stainless steels,
300-series austenitic filler metal is usually used due to a lack of availability of 200-series
filler metal. This weld joint will generally be weaker than the surrounding base metal.
300-series filler metal is used on 300-series base metal. The Type 410 and 420
electrodes are the only martensitic stainless steel types recognized by the AWS. This
limitation is often the reason why austenitic stainless steel filler metal is used for welding
martensitic stainless steel. Austenitic filler metal provides a weld with lower strength but
higher toughness and eliminates the need for preheating and postheating. For welding
ferritic stainless steels, both ferritic and austenitic filler metal may be used. Ferritic filler
metal is used when higher strength and an annealing postheat are required. Austenitic
filler metal is used when higher ductility is required. Table 11-13 shows filler metal
selection for stainless steels.
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Table 11-13 — Filler metal selection for welding stainless steel.
AISI
No.
C%
Mn%
Si%
201
202
301
302
3028
304
304L
305
308
309
309S
310
310S
314
316
316L
317
321
330
347
348
403
410
414
420
431
501
502
405
430
442
446
0.15 max
0.15 max
0.15 max
0.15 max
0.15 max
0.08 max
0.03 max
0.12 max
0.08 max
0.20 max
0.08 max
0.25 max
0.08 max
0.25 max
0.08 max
0.03 max
0.08 max
0.08 max
0.35 max
0.08 max
0.08 max
0.15 max
0.15 max
0.15 max
Over 0.15
0.20 max
Over 0.10
0.10 max
0.08 max
0.12 max
0.20 max
0.20 max
5.5-7.5
7.5-10.0
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.50
1.00
1.00
1.00
1.00
2.00-3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.50
1.50
1.50-3.00
1.00
1.00
1.00
1.00
2.50
1.00
1.00
0.50
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
Cr%
16.00-18.00
17.00-19.00
16.00-18.00
17.00-19.00
17.00-19.00
18.00-20.00
18.00-20.00
17.00-19.00
19.00-21.00
22.00-24.00
22.00-24.00
24.00-26.00
24.00-26.00
23.00-26.00
16.00-18.00
16.00-18.00
18.00-20.00
17.00-19.00
13.00-17.00
17.00-19.00
18.00-19.00
11.50-13.00
11.50-13.50
11.50-13.50
12.00-14.00
15.00-17.00
4.00-6.00
4.00-6.00
11.50-14.50
14.00-18.00
18.00-23.00
23.00-27.00
Ni%
3.50-5.50
4.00-6.00
6.00-8.00
8.00-10.00
8.00-10.00
8.00-12.00
8.00-12.00
10.00-13.00
10.00-12.00
12.00-15.00
12.00-15.00
19.00-22.00
19.00-22.0
19.00-22.00
10.00-14.00
10.00-14.00
11.00-15.00
9.00-12.00
33.00-37.00
9.00-13.00
9.00-13.00
—
—
1.25-2.50
—
1.25-2.50
—
—
—
—
—
—
Other Elements
N 0.25 max
N 0.25 max
—
—
—
—
—
—
—
—
—
—
—
—
Mo 2.00-3.00
Mo 2.00-3.00
Mo 3.00-4.00
Ti 5 x C min
—
Cb + Ta 10 x C min
Cb + Ta 10 C min. Ta 0.10
—
—
—
—
—
Mo 0.40-0.65
Mo 0.40-0.65
AI 0.10-0.30
—
—
N 0 .25 max
Filler Metal
Selection
308
308
308
308
308
308
308L
308, 310
308
309
309
310
310
310, 312
316
316L
317
347
330
347
347, 348
410, 309, 310
410, 309, 310
410, 309, 310
410, 420
430, 309, 310
502
502
410, 309, 310
430, 309, 310
309, 310
309, 310
Test your Knowledge (Select the Correct Response)
5.
What primary property determines the maximum hardness of steel?
A.
B.
C.
D.
6.
The amount of heat used to make the steel
The amount of carbon in the steel
The amount of alloy in the steel
The thickness of the steel
What type of stainless steel is generally the easiest to weld?
A.
B.
C.
D.
Annealed
Ferritic
Modular
Austenitic
8.0.0 WELD and JOINT DESIGN
Like other welding processes, the weld joint designs used in FCAW are determined by
the design of the weldment, metallurgical considerations, and codes or specifications.
Another factor to consider is the method of FCAW to be used. A properly selected joint
design should allow the highest quality weld to be made at the lowest possible cost. A
weld joint consists of a specific weld being made in a specific joint. A joint is defined as
the junction of members which are to be, or have been, joined. Figure 11-37 shows the
five basic joint classifications.
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11-59
Figure 11-37 — Types of joints.
Each of the different types of joints can be joined by many different types of welds.
Figure 11-38 shows the most common types of welds made.
Figure 11-38 — Types of welds.
The type of weld made is governed by the joint configuration. Each of the different types
of welds has its own specific advantages. The nomenclature used for the various parts
of groove and fillet welds is given in Figure 11-39. There are several factors that
influence the joint design to be used:
1. Process Method
2. Strength Required
3. Welding Position
4. Joint Accessibility
5. Metal Thickness
6. Type of Metal
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11-60
Figure 11-39 — Weld nomenclature.
The edge and joint preparation are important because they affect both the quality and
cost of welding. The cost items to be considered are the amount of filler metal required,
the method of joint preparation, the amount of labor required, and the quality level
required. Joints that are more difficult to weld will often have more repair work
necessary than those that are easier to weld. This can lead to significant increases in
cost, since repair welding sometimes requires more time and expense than the original
weld. All of the five basic joint types are applicable to FCAW, although the butt and Tjoints are the most widely used. Lap joints have the advantage of not requiring much
preparation other than squaring off the edges and making sure the members are in
close contact. Edge joints are widely used on thin metal. Corner joints generally use
similar edge preparations to those used on T-joints.
Many of the joint designs used for FCAW are similar to those used in GMAW or SMAW.
FCAW has some characteristics that may affect the joint design. The joint should be
designed so the welder has good access to the joint and is properly able to manipulate
the electrode. Joints must be located so an adequate distance between the joint and
nozzle of the welding gun is created. The proper distance will vary depending on the
type of flux-cored electrode being used.
8.1.0 Process Method
The joint design as well as the welding procedure will vary, depending on whether the
welding is done using gas-shielded or self-shielded electrodes. Both methods of FCAW
achieve deeper penetration than SMAW. This permits the use of narrower grooves with
NAVEDTRA 14250A
11-61
smaller groove angles, larger root faces, and narrower root openings. Differences also
exist between the two FCAW methods because of the deeper penetration that is
produced by the gas-shielded electrode wires. Figure 11-40 shows a comparison of a
flat position, V-groove weld on a backing strip for each of the two methods.
Figure 11-40 — Comparison between gas-shielded and self-shielded wire joint
designs for the flat position.
The joint design for the self-shielding wire requires a larger root opening to allow better
access to the root of the joint. The joint design for the gas-shielded wire does not need
such a wide root opening because complete penetration is easier to obtain. This weld
would be less expensive to make using the gas-shielded electrode because less filler
metal is required. This difference in joint design usually only applies when a backing
strip is used. For joints not requiring a backing strip, gas-shielded and self-shielded
wires use the same joint designs.
8.2.0 Type of Metal
The FCAW process is used to weld steel, some stainless steels, and some nickels. The
influence of the type of metal on the joint design is based primarily on the physical
properties of the metal to be welded and whether or not the metal has an oxide coating.
For example, stainless steels have a lower thermal conductivity than carbon steels. This
causes the heat from welding to remain in the weld zone longer, which enables slightly
greater thicknesses of stainless steels to be welded using a square groove joint design.
Stainless steels also have an oxide coating that tends to reduce the depth of fusion of
the weld. Consequently, stainless steels normally use larger groove angles and root
openings than carbon steels. This allows the welder to direct the arc on the base metal
surfaces to obtain complete fusion.
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11-62
8.3.0 Strength
The strength required of a weld joint is a major factor governing weld joint design. Weld
joints may be either full or partial penetration, depending on the strength required of the
joint. Full or complete penetrating welds are those that have weld metal through the full
cross section of the joint. Partial penetrating welds are those where weld metal only
extends partially through the joint thickness. Welds that are subject to cyclic, impact, or
dynamic loading require complete
penetration. This is even more important for
applications that require low temperature
service. Partial penetration welds may be
adequate for joints where loading is static
only. This type of joint is easier to prepare
and requires less filler metal than full
penetration joints. Fillet welds of the same
leg size made by this process are stronger
than those made by SMAW. This is because
of the deeper penetration obtained from
FCAW, as shown in Figure 11-41. For some
applications, the size of the weld can be
reduced which decreases the amount of
filler metal required. This can reduce the
total cost also.
The root opening and root face used will
Figure 11-41 — Comparison
affect the amount of penetration obtained. A
between the penetrating
root opening is used to allow good access to
characteristics of SMAW and
the root of the joint and is usually used in full
penetrating weld joints. A root opening is
FCAW.
usually not used in partial penetration weld
joints because access to the root is not
necessary and parts are easier to fit together without a root opening. The size of the
root face is also affected. A larger root face is used more for partial penetration welds
than for complete penetration welds because less penetration is required. Because of
the deep penetrating characteristics of the FCAW process, larger root faces are used
compared to SMAW and GMAW, which use short circuiting metal transfer. This is to
prevent burning through the back of the joint being welded, which can be a problem in
FCAW because of the high welding currents used. When compared to SMAW, smaller
groove angles are used because the flux-cored wire is smaller than a covered electrode
and operates with a higher current density. Because of the smaller electrode, access to
the root of the joint is better.
8.4.0 Position
FCAW may be used in all welding positions based on the size and type of electrode
wire used. A diagram of the welding position capabilities is shown in Figure 11-42.
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11-63
Figure 11-42 — Welding test positions.
Welding positions are classified by a set of numbers and letters. The four basic welding
positions are designated by the numbers 1 for flat, 2 for horizontal, 3 for vertical, and 4
for overhead. A G designation indicates a groove weld and an F designation indicates a
fillet weld. The 5G and 6G positions are used in pipe welding. The large diameter wires,
which are over 1/16 in. (1.6 mm) in diameter,
are limited to the flat and horizontal positions
only because the weld puddle becomes too
large to control. The smaller diameter
electrodes, which are 1/16 in. (1.6 mm) and
less, can generally be used easily in all
positions.
The joint configuration will vary depending
on the position of welding. One example of
this is wider groove angles needed for
vertical position welding. This is done to
provide enough room to manipulate the
electrode wire in the joint. Weaving of the
electrode is usually required in vertical
position welding to prevent excessive
reinforcement or dropping the weld metal out
of the puddle. Joint designs for overhead
welding are generally the same as for flat
position welding. Joints that are welded in
NAVEDTRA 14250A
Figure 11-43 — V-groove joint in
the horizontal position.
11-64
the horizontal position often have an unsymmetrical joint configuration. This usually
consists of a groove angle that has a horizontal lower groove face, as shown in Figure
11-43. The upper groove face is raised accordingly to provide a groove angle large
enough to provide good access. The horizontal lower groove face is used as a shelf to
support the molten weld metal. This joint configuration is less expensive to prepare
because the bevel is only made in one plate.
8.5.0 Thickness
The thickness of the base metal has a large influence on the joint preparation required
to produce the best quality weld joint. FCAW is used to weld thicknesses down to 18
gauge (1.2 mm), but the process is also suitable for welding thick metal. Because of
this, wide varieties of joint designs are used. The most common groove preparations
used on butt joints are the square-, V-, J-, U- bevel-, and combination-grooves. The
square-, J-, bevel-, and combination-groove preparations are also used on tee joints.
The different preparations are used on different thicknesses to make it possible to get
complete or adequate penetration.
Square-groove welds are used on the thinnest metal thicknesses. The square-groove
joint design is the easiest to prepare and requires the least filler metal. Thicknesses up
to 3/8-in. (9.5 mm) thick can be welded with full penetration from both sides. This is
thicker than the square-groove joints that can be welded with full penetration by SMAW
or GTAW because of the hotter arc and deeper penetration produced by this process.
Root openings are used to allow complete penetration through the joint. Many squaregroove welds are made in one pass. A backing strip may be used so the root can be
opened enough to provide better accessibility and insure adequate penetration.
V-grooves for butt joints and bevel-grooves for tee joints are commonly used for thicker
metal up to about 3/4-in. (19.1 mm). These joints are more difficult to prepare and
require more filler metal than square-groove welds. The included angle for a V-groove is
usually up to 75° with smaller groove angles, such as 45° or 60°, being more commonly
used. The smaller groove angles become even more economical as the thickness of the
metal increases. The wider groove angles are used to provide better accessibility to the
root of the joint. Because of the deeper penetrating characteristics of this process,
single V-groove or single bevel-groove welds are often welded with little or no root
opening. Larger root faces and smaller groove angles are often used compared to those
used for SMAW and GTAW. This helps to minimize the amount of distortion and reduce
the amount of filler metal required. For complete penetration welds, root faces usually
are close to 1/8-in. (3.2 mm).
U- and J-grooves are generally used on thicknesses greater than 5/8-in. (14.3 mm).
These joint preparations are the most difficult and expensive to prepare but the radius at
the root of the joint allows better access to the root of the joint. Another advantage is
that smaller groove angles may be used compared to those used in V-grooves. On
thicker metal, this reduces the amount of filler metal required, and on very thick metals,
the savings become very substantial.
8.6.0 Accessibility
The accessibility of the weld joint is another important factor in determining the weld
joint design. Welds can be made from one or both sides of the weld joint. Single V-, J-,
U-, bevel-, and combination grooves are used when accessibility is from one side only
and on thinner metal. Double V-, J-, U-, bevel-, and combination grooves are used on
thicker metal where the joint can be welded from both sides. Double-groove welds have
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11-65
three major advantages over single-groove welds where accessibility is only from one
side. The first is that distortion is more easily controlled through alternate weld bead
sequencing. Weld beads are alternated from one side to the other to keep the distortion
from building up in the one direction. The weld roots are nearer the center of the plate.
A second advantage is that less filler metal is required to fill a double groove joint than a
single-groove joint. This tends to make double-groove welds more economical on metal
1-in. (25 mm) thick or greater.
The third advantage is that complete penetration can be more easily insured. The root
of the first pass on the plate can be gouged or chipped out before the root pass on the
second side is welded, to make sure there is complete fusion at the root. The
disadvantages of joints welded from both sides are that more joint preparation is
required and gouging or chipping is usually required to remove the root of the first pass.
The amount of savings in the filler metal needed for a double-groove weld may more
than compensate for the extra joint preparation costs; both of these add to the labor
time required. Welding on both sides of a square-groove weld joint provides fuller
penetration in thicker metal than metal welded from one side only. This would also save
joint preparation time.
8.6.1 Backing Strips
When backing strips are used, joints are accessible from one side only. Backing strips
allow better access to the root of the joint and support the molten weld metal. These
strips are available in two forms, which are fusible or nonfusible. Fusible backing strips
are made of the metal being welded and remain part of the weldment after welding.
These may be cut or machined off. Nonfusible backing strips are made of copper,
carbon, flux, or ceramic backing in tape or composite form. These forms of backing do
not become part of the weld. Backing strips on square-groove joints make a full
penetration weld from one side easier. For this application, using a backing strip is more
expensive because of the cost of a backing strip and the larger amount of filler metal
required. However, on V-groove joints, the backing strip allows wider root openings and
removes the need for a root face, which reduces the groove preparation costs. Another
advantage is that because the root may be opened up, the groove angle may be
reduced, which will reduce the amount of filler metal required in thicker metal. These
effects are shown in Figure 11-44, where single V-groove joints are shown with and
without a backing strip.
As discussed earlier in this chapter, the use of a backing strip will have an effect on the
joint designs used for gas-shielded and self-shielded electrodes. The deeper
penetrating characteristics of the gas-shielded electrode allow the joint designs to be
adjusted to take advantage of this.
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11-66
Figure 11-44 — Single V-groove joints with and without backing strip in the
same thickness metal.
8.7.0 Weld Joint Designs
The details of a joint, which include both the geometry and the required dimensions, are
called the joint design. Just what type of joint design is best suited for a particular job
depends on many factors. Although welded joints are designed primarily to meet
strength and safety requirements, there are other factors that must be considered. A
few of these factors are as follows:
1. Whether the load will be in tension or compression and whether bending, fatigue,
or impact stresses will be applied
2. How a load will be applied; that is, whether the load will be steady, sudden, or
variable
3. The direction of the load as applied to the joint
4. The cost of preparing the joint
Another consideration that must be made is the ratio of the strength of the joint
compared to the strength of the base metal. This ratio is called joint efficiency. An
efficient joint is one that is just as strong as the base metal.
Normally, the joint design is determined by a designer or engineer and is included in the
project plans and specifications. Even so, understanding the joint design for a weld
enables you to produce better welds.
Earlier in this chapter, we discussed the five basic types of welded joints—butt, corner,
tee, lap, and edge.
Just keep in mind that there are many different variations of the basic joint welds. If you
want more information refer to Chapter 3, Introduction to Welding. The weld joint
designs shown in Figures 11-45 through 11-56 are those typically used for FCAW. All of
the partial penetration weld joint designs covered may be welded using either the selfNAVEDTRA 14250A
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shielded or gas-shielded electrode wires. The joint dimensions will vary for full
penetration welds using backing strips, depending on which method of FCAW is being
used. The joint designs that should be used only by the gas-shielded method are
indicated on these joints. All other full penetration welds may be made by either of the
two methods.
Ranges are given on many of the joint dimensions to account for varying fit-up and
types of electrode wires. The thickness ranges given are those typically recommended
for use with the joint designs. Minimum effective throat thicknesses are commonly used
for partial penetration welds. Recommended minimum effective throat sizes are given in
Table 11-14.
Table 11-14 — Effective throat thickness for partial joint
penetration groove welds.
Base Metal Thickness of
Thicker Part Joined
Inch
(mm)
Minimum Effective
Throat
Inch
(mm)
To 1/4
(6.5)
Inclusive
1/8
(3)
Over1/4 to 1/2
(6.4 to 12.7)
Inclusive
3/16
(5)
Over1/2 to 3/4
(12.7 to 19.0)
Inclusive
1/4
(6)
Over3/4 to 1 1/2
(19.0 to 38.1)
Inclusive
5/16
(8)
Over1 1/2 to 2 1/4
(38.1 to 57.1)
Inclusive
3/8
(10)
Over2 1/4 to 6
(57.1 to 152)
1/2
(13)
Over 6
(152)
5/8
(16)
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Figure 11-45 — Welding symbols.
11-69
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Figure 11-46 — Welding symbols (cont.).
11-70
Figure 11-47 — Application of arrow and other side convention.
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Figure 11-48 — Applications of break in arrow of welding symbol.
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Figure 11-49 — Combinations of weld symbols.
11-73
Figure 11-50 — Combinations of weld symbols (cont.).
Figure 11-51 — Specification of location and extent of fillet welds.
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Figure 11-52 — Specification of location and extent of fillet welds (cont.).
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11-75
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Figure 11-53 — Specification of extent of welding.
11-76
Figure 11-54 — Specification of extent of welding (cont.).
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11-77
Figure 11-55 — Specification of extent of welding (cont.).
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Figure
NAVEDTRA 14250A
11-56 — Applications of melt-through symbol.
11-79
8.8.0 Arc Welding Positions
The types of welds, joints, and welding positions used in FCAW are very similar to those
used in GMAW, with the exception of overhead welding. Manual overhead welding is
rarely used in FCAW because the filler metal is so fluid due to the powdered core.
8.8.1 Flat-Position Welding
Welding can be done in any position, but it is much simpler when done in the flat
position. In this position, the work is less tiring, welding speed is faster, the molten
puddle is not as likely to run, and better penetration can be achieved. Whenever
possible, try to position the work so you can weld in the flat position. In the flat position,
the face of the weld is approximately horizontal.
Butt joints are the primary type of joints used in the flat position of welding; however,
flat-position welding can be made on just about any type of joint, providing you can
rotate the section you are welding on to the appropriate position. Techniques that are
useful in making butt joints in the flat position, with and without the use of backing strips,
are described below.
Butt joints without backing strips — A butt joint is used to join two plates having surfaces
in about the same plane. Several forms of butt joints are shown in Figure 11-57.
Plates up to 1/8-inch thick can be welded in one pass with no special edge preparation.
Plates from 1/8- to 3/16 -inch thick also can be welded with no special edge preparation
by welding 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.
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Figure 11-57 — Butt joints in the flat position.
In welding 1/4-inch plate or heavier, you should prepare the edges of the plates by
beveling or by J-, U-, or V-grooving, whichever is the most applicable. You should use
single or double bevels or grooves when the specifications and/or the plate thickness
require it. The first bead is deposited to seal the space between the two plates and to
weld the root of the joint. This bead or layer of weld metal must be thoroughly cleaned
to remove all slag and dirt before the second layer of metal is deposited.
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In making multi pass welds, as shown in Figure 11-58, the second, third, and fourth
layers of weld metal are made with a weaving motion of the electrode. Clean each layer
of metal before laying additional beads. You may use one of the weaving motions
shown in Figure 11-59, depending upon the type of joint and size of electrode.
Figure 11-58 — Butt welds with multipass beads.
In the weaving motion, oscillate
or move the electrode uniformly
from side to side, with a slight
hesitation at the end of each
oscillation. Incline the electrode 5
to 15 degrees in the direction of
welding as in bead welding.
When the weaving motion is not
done properly, undercutting could
occur at the joint, as shown in
Figure 11-60. Excessive welding
speed also can cause
undercutting and poor fusion at
the edges of the weld bead.
Butt joints with backing strips —
Welding 3/16-inch plate or thicker
requires backing strips to ensure
complete fusion in the weld root
pass and to provide better control
of the arc and the weld metal.
Prepare the edges of the plates
Figure 11-59 — Weave motions used in
in the same manner as required
FCAW.
for welding without backing
strips. For plates up to 3/8-inch thick, the backing strips should be approximately 1-inch
wide and 3/16-inch thick. For plates more than 1/2-inch thick, the backing strips should
be 1 1/2 inches wide and 1/4-inch thick. Tack-weld the backing strip to the base of the
joint, as shown in Figure 11-61. The backing strip acts as a cushion for the root pass.
Complete the joint by welding additional layers of metal. After you complete the joint,
the backing strip may be “washed” off or cut away with a cutting torch. When specified,
place a seal bead along the root of the joint.
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Bear in mind that many times it will not always be possible to use a backing strip;
therefore, the welder must be able to run the root pass and get good penetration without
the formation of icicles.
Figure 11-60 — Undercutting in
butt joint welds.
8.8.2 Horizontal-Position Welding
Figure 11-61 — Use of back strips in welding
butt joints.
You will discover that it is impossible to weld all pieces in the flat position. Often the
work must be done in the horizontal position. The horizontal position has two basic
forms, depending upon whether it is used with a groove weld or a fillet weld. In a groove
weld, the axis of the weld lies in a relative horizontal plane and the face of the weld is in
a vertical plane (Figure 11-62). In a fillet weld, the welding is performed on the upper
side of a relatively horizontal surface and against an approximately vertical plane
(Figure 11-63).
Figure 11-62 — Horizontal groove
weld.
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Figure 11-63 — Horizontal fillet
11-83
weld.
Inexperienced welders usually find the horizontal position of arc welding difficult, at least
until they have developed a fair degree of skill in applying the proper technique. The
primary difficulty is that in this position, you have no “shoulder” of previously deposited
weld metal to hold the molten metal.
8.8.2.1 Electrode Movement
In horizontal welding, position the electrode
so that it points upward at a 5- to 10-degree
angle in conjunction with a 20-degree travel
angle (Figure 11-64). Use a narrow weaving
motion in laying the bead. This weaving
motion distributes the heat evenly, reducing
the tendency of the molten puddle to sag.
You should use the shortest arc length
possible, and when the force of the arc
undercuts the plate at the top of the bead,
lower the electrode holder a little to increase
the upward angle.
As you move in and out of the crater, pause
slightly each time you return. This keeps the
crater small and the bead has fewer
tendencies to sag.
Figure 11-64 — Horizontal
welding angles.
8.8.2.2 Joint Type
Horizontal-position welding can be used on most types of joints. The most common
types of joints it is used on are tee joints, lap joints, and butt joints.
Tee joints — When you make tee joints in the horizontal position, the two plates are at
right angles to each other in the form of an inverted T. The edge of the vertical plate
may be tack-welded to the surface of the horizontal plate, as shown in Figure 11-65.
Figure 11-65 — Tack-weld to hold
the tee joint elements in place.
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Figure 11-66 — Position of
electrode on a fillet weld.
11-84
A fillet weld is used in making the tee joint, and a short arc is necessary to provide good
fusion at the root and along the legs of the weld (Figure 11-66, View A). Hold the
electrode at an angle of 45 degrees to the two plate surfaces (Figure 11-66, View B)
with an incline of approximately 15 degrees
in the direction of welding.
When practical, weld light plates with a fillet
weld in one pass with little or no weaving of
the electrode. Welding of heavier plates
may require two or more passes in which
the second pass or layer is made with a
semicircular weaving motion, as shown in
Figure 11-67. To ensure good fusion and
the prevention of undercutting, you should
make a slight pause at the end of each
weave or oscillation.
For fillet-welded tee joints on 1/2-inch plate
or heavier, deposit stringer beads in the
sequence shown in Figure 11-68.
Chain-intermittent or staggered-intermittent
Figure 11-67 — Weave motion for
fillet welds, as shown in Figure 11-69, are
multipass fillet weld.
used on long tee joints. Fillet welds of these
types are for joints where high weld
strength is not required; however, the short welds are arranged so the finished joint is
equal in strength to that of a joint that has a fillet weld along the entire length of one
side. Intermittent welds also have the advantage of reduced warpage and distortion.
Figure 11-68 — Order of string
beads for tee joint on heavy
plate.
Figure 11-69 — Intermittent fillet
welds.
Lap joints — When you make a lap joint, two overlapping plates are tack-welded in
place (Figure 11-70), and a fillet weld is deposited along the joint.
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The procedure for making this fillet weld is similar to that used for making fillet welds in
tee joints. You should hold the electrode so it forms an angle of about 30 degrees from
the vertical and is inclined 15 degrees in the direction of welding. The position of the
Figure 11-70 — Tack welding a
lap joint.
Figure 11-71 — Position of
electrode on a lap joint.
electrode in relation to the plates is shown in Figure 11-71. The weaving motion is the
same as that used for tee joints, except that the pause at the edge of the top plate is
long enough to ensure good fusion without undercut. Lap joints on 1/2-inch plate or
heavier are made by depositing a sequence of stringer beads, as shown in Figure 1171.
In making lap joints on plates of different thickness, you should hold the electrode so
that it forms an angle of between 20 and 30 degrees from the vertical (Figure 11-72). Be
careful not to overheat or undercut the thinner plate edge.
Figure 11-72 — Lap joints on
plates of different thickness.
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Figure 11-73 — Horizontal butt
joint.
11-86
Butt joints— Most butt joints designed for horizontal welding have the beveled plate
positioned on the top. The plate that is not beveled is on the bottom and the flat edge of
this plate provides a shelf for the molten
metal so that it does not run out of the joint
(Figure 11-73). Often, both edges are beveled
to form a 60-degree included angle. When
this type of joint is used, more skill is required
because you do not have the retaining shelf
to hold the molten puddle.
The number of passes required for a joint
depends on the diameter of the electrode and
the thickness of the metal. When multiple
passes are required (Figure 11-74), place the
first bead deep in the root of the joint. The
electrode holder should be inclined about 5
degrees downward. Clean and remove all
slag before applying each following bead.
The second bead should be placed with the
electrode holder held about 10 degrees
upward. For the third pass, hold the electrode
Figure 11-74 — Multiple passes.
holder 10 to 15 degrees downward from the
horizontal. Use a slight weaving motion and
ensure that each bead penetrates the base metal.
8.8.3 Vertical-Position Welding
A “vertical weld” is defined as a weld that is
applied to a vertical surface or one that is
inclined 45 degrees or less (Figure 11-75).
Erecting structures, such as buildings,
pontoons, tanks, and pipelines, require
welding in this position. Welding on a vertical
surface is much more difficult than welding in
the flat or horizontal position due to the force
of gravity. Gravity pulls the molten metal
down. To counteract this force, you should
use fast-freeze or fill-freeze electrodes.
Vertical welding is done in either an upward
or downward position. The terms used for the
direction of welding are vertical up or vertical
down. Vertical down welding is suited for
welding light gauge metal because the
penetration is shallow and diminishes the
possibility of burning through the metal.
Furthermore, vertical down welding is faster,
which is very important in production work.
Figure 11-75 — Vertical weld
plate positions.
8.8.3.1 Current Settings and Electrode Movement
In vertical arc welding, the current settings should be less than those used for the same
electrode in the flat position. Another difference is that the current used for welding
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upward on a vertical plate is slightly higher than the current used for welding downward
on the same plate.
To produce good welds, you must maintain the proper angle between the electrode and
the base metal. In welding upward, you should hold the electrode at 90 degrees to the
vertical, as shown in Figure 11-76, View A. When weaving is necessary, oscillate the
electrode, as shown in Figure 11-76, View B. In vertical down welding, incline the outer
end of the electrode downward about 15 degrees from the horizontal while keeping the
arc pointing upward toward the deposited molten metal (Figure 11-76, View C). When
vertical down welding requires a weave bead, you should oscillate the electrode, as
shown in Figure 11-76, View D.
Figure 11-76 — Bead welding in vertical position.
8.8.3.2 Joint Type
Vertical welding is used on most types of joints. The types of joints you will most often
use it on are tee joints, lap joints, and butt joints.
Hold the electrode at 90 degrees to the plates or not more than 15 degrees off the
horizontal for proper molten metal control when making fillet welds in either tee or lap
joints in the vertical position. Keep the arc short to obtain good fusion and penetration.
Tee joints — To weld tee joints in the vertical position, start the joint at the bottom and
weld upward. Move the electrode in a triangular weaving motion, as shown in Figure 1177, View A. A slight pause in the weave at the points indicated improves the sidewall
penetration and provides good fusion at the root of the joint.
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When the weld metal overheats, you should quickly shift the electrode away from the
crater without breaking the arc, as shown in Figure 11-77, View B. This permits the
molten metal to solidify without running downward. Return the electrode immediately to
the crater of the weld in order to maintain the desired size of the weld.
When more than one pass is necessary to make a tee weld, you may use either of the
weaving motions shown in Figure 11-77, Views C and D. A slight pause at the end of
the weave will ensure fusion without undercutting the edges of the plates.
Lap joints — To make welds on lap joints in the vertical position, you should move the
electrode in a triangular weaving motion, as shown in Figure 11-77, View E. Use the
same procedure as outlined above for the tee joint, except direct the electrode more
toward the vertical plate marked “G.” Hold the arc short and pause slightly at the surface
of plate G. Try not to undercut either of the plates or to allow the molten metal to overlap
at the edges of the weave.
Figure 11-77 — Fillet welds in the vertical position.
Lap joints on heavier plate may require more than one bead. If it does, clean the initial
bead thoroughly and place all subsequent beads, as shown in Figure 11-77, View F.
The precautions to ensure good fusion and uniform weld deposits that were previously
outlined for tee joints also apply to lap joints.
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Butt joints — Prepare the plates used in
vertical welding identically to those prepared
for welding in the flat position. To obtain
good fusion and penetration with no
undercutting, you should hold a short arc
and the motion of the arc should be carefully
controlled.
Butt joints on beveled plates 1/4-inch thick
can be welded in one pass by using a
triangular weave motion, as shown in Figure
11-78, View A.
Welds made on 1/2-inch plate or heavier
should be done in several passes, as shown
in Figure 11-78, View B. Deposit the last
pass with a semicircular weaving motion and
a slight “whip-up” and pause of the electrode
at the edge of the bead. This produces a
good cover pass with no undercutting.
Welds made on plates with a backup strip
should be done in the same manner.
Figure 11-78 — Butt joint welding
in the vertical position.
8.8.4 Overhead-Position Welding
Overhead welding is the most difficult position in welding. Not only do you have to
contend with the force of gravity, but the majority of the time you also have to assume
an awkward stance. Nevertheless, with practice it is possible to make welds equal to
those made in the other positions.
8.8.4.1 Current Settings and Electrode Movement
To retain complete control of the molten puddle, use a very short arc and reduce the
amperage as recommended. As in the vertical position of welding, gravity causes the
molten metal to drop or sag from the plate. When too long an arc is held, the transfer of
metal from the electrode to the base metal becomes increasingly difficult and the
chances of large globules of molten metal dropping from the electrode increase. When
you routinely shorten and lengthen the arc, the dropping of molten metal can be
prevented; however, you will defeat your purpose should you carry too large a pool of
molten metal in the weld.
One of the problems encountered in overhead welding is the weight of the cable. To
reduce arm and wrist fatigue, drape the cable over your shoulder when welding in the
standing position. When sitting, place the cable over your knee. With experience, cable
placement will become second nature.
WARNING
Because of the possibility of falling molten metal, use a protective garment that has
a tight fitting collar that buttons or zips up to the neck. Roll down your sleeves and
wear a cap and appropriate shoes.
NAVEDTRA 14250A
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8.8.4.2 Type of Welds
Techniques used in making bead
welds, butt joints, and fillet welds
in the overhead position are
discussed in the following
paragraphs.
Bead welds — For bead welds,
the work angle of the electrode is
90 degrees to the base metal
(Figure 11-79, View A). The travel
angle should be 10 to 15 degrees
in the direction of welding (Figure
11-79, View B).
Weave beads can be made by
using the motion shown in Figure
11-79, View C. A rather rapid
motion is necessary at the end of
each semicircular weave to
control the molten metal deposit.
Avoid excessive weaving
because this can cause
overheating of the weld deposit
and the formation of a large,
uncontrollable pool.
Figure 11-79 — Position of electrode and
weave motion in the overhead position.
Butt Joint — Prepare the plates for overhead butt welding in the same manner as
required for the flat position. The best results are obtained when backing strips are
used; however, you must remember that you will not always be able to use a backing
strip. When you bevel the plates with a featheredge and do not use a backing strip, the
weld will repeatedly burn through
unless extreme care is taken by
the operator.
For overhead butt welding, bead
welds are preferred over weave
welds. Clean each bead and chip
out the rough areas before
placing the next pass. The
electrode position and the order
of deposition of the weld beads
when welding on 1/4- or 1/2-inch
plate are shown in Figure 11-80,
views B and C. Make the first
pass with the electrode held at
90 degrees to the plate, as
shown in Figure 11-80, View A.
When you use an electrode that
is too large, you cannot hold a
short arc in the root area. This
results in insufficient root
penetration and inferior joints.
NAVEDTRA 14250A
Figure 11-80 — Multipass butt joint in the
overhead position.
11-91
Fillet welds — In making fillet welds in either tee or lap joints in the overhead position,
maintain a short arc and refrain from weaving of the electrode. Hold the electrode at
approximately 30 degrees to the vertical plate and move it uniformly in the direction of
welding, as shown in Figure 11-80, View B. Control the arc motion to secure good
penetration in the root of the weld and good fusion with the sidewalls of the vertical and
horizontal plates. When the molten metal becomes too fluid and tends to sag, whip the
electrode quickly away from the crater and ahead of the weld to lengthen the arc and
allow the metal to solidify. Immediately return the electrode to the crater and continue
welding.
Overhead fillet welds for either tee or lap joints on heavy plate require several passes or
beads to complete the joint. One example of an order of bead deposition is shown in
Figure 11-81, View A. The root pass is a string bead made with no weaving motion of
the electrode. Tilt the electrode about 15 degrees in the direction of welding, as shown
in Figure 11-81, View C, and with a slight circular motion make the second, third, and
fourth pass. This motion of the electrode permits greater control and better distribution
of the weld metal. Remove all slag and oxides from the surface of each pass by
chipping or wire brushing before applying additional beads to the joint.
Figure 11-81 – Fillet welding in the overhead position.
8.8.5 Pipe welding
Welding is the simplest and easiest way to join sections of pipe. The need for
complicated joint designs and special threading equipment is eliminated. Welded pipe
has less flow restriction compared to mechanical connections and the overall installation
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costs are less. The most popular method for welding pipe is the shielded metal arc
process; however, gas shielded arc methods (TIG, MIG & FCAW) have made big
inroads as a result of new advances in welding technology.
Pipe welding has become recognized as a profession in itself. Even though many of the
skills are comparable to other types of welding, pipe welders develop skills that are
unique only to pipe welding. Because of the hazardous materials that most pipelines
carry, pipe welders are required to pass specific tests before they can be certified.
In the following paragraphs, pipe
welding positions, pipe welding
procedures, definitions, and
related information are discussed.
8.8.5.1 Pipe welding positions
You may recall that there are four
positions used in pipe welding.
They are known as the horizontal
rolled position (1G), the horizontal
fixed position (5G), pipe inclined
fixed (6G), and the vertical
position (2G). Remember: these
terms refer to the position of the
pipe and not to the weld.
8.8.5.2 Pipe welding procedures
Welds that you cannot make in a
single pass should be made in
interlocked, multiple layers, not
less than one layer for each 1/8inch of pipe thickness. Deposit
each layer with a weaving or
oscillating motion. To prevent
entrapping slag in the weld metal,
you should clean each layer
thoroughly before depositing the
next layer.
Figure 11-82 — Butt joints and socket fitting
joints.
Butt joints are commonly used
between pipes and between pipes
and welded fittings. They are also
used for butt welding of flanges
and welding stubs. In making a
butt joint, place two pieces of pipe
end to end, align them, and then
weld them. (See Figure 11-82).
When the wall thickness of the
pipe is 3/4-inch or less, you can
use either the single V or single U
type of butt joint; however, when
the wall thickness is more than
NAVEDTRA 14250A
Figure 11-83 — Flange connections.
11-93
3/4-inch, only the single U type should be used.
Fillet welds are used for welding slip-on and threaded flanges to pipe. Depending on the
flange and type of service, fillet welds may be required on both sides of the flange or in
combination with a bevel weld (Figure 11-83). Single-fillet welds are also used in
welding screw or socket couplings to pipe
(Figure 11-83). Sometimes flanges require
alignment. Figure 11-84 shows one type of
flange square and its use in vertical and
horizontal alignment.
Another form of fillet weld used in pipe fitting
is a seal weld. A seal weld is used primarily
to obtain tightness and prevent leakage.
Seal welds should not be considered as
adding strength to the joint.
8.8.5.3 Joint preparation and fit-up
You must carefully prepare pipe joints for
welding if you want good results. Clean the
weld edges or surfaces of all loose scale,
slag, rust, paint, oil, and other foreign
matter. Ensure that the joint surfaces are
Figure 11-84 — Flange alignment.
smooth and uniform. Remove the slag from
flame-cut edges; however, it is not necessary to remove the temper color.
When you prepare joints for welding, remember that bevels must be cut accurately.
Bevels can be made by machining, grinding, or using a gas cutting torch. In fieldwork,
the welding operator usually must make the bevel cuts with a gas torch. When you are
beveling, cut away as little metal as possible
to allow for complete fusion and penetration.
Proper beveling reduces the amount of filler
metal required, which in turn reduces time
and expense. In addition, it also means less
strain in the weld and a better job of design
and welding.
Align the piping before welding and maintain
it in alignment during the welding operation.
The maximum alignment tolerance is 20
percent of the pipe thickness. To ensure
proper initial alignment, you should use
clamps or jigs as holding devices. A piece of
angle iron makes a good jig for a smalldiameter pipe (Figure 11-85), while a section
of channel or I-beam is more suitable for
larger diameter pipe.
8.8.6 Tack welding
Figure 11-85 — Angle iron jig.
When welding material solidly, you may use tack welds to hold it in place temporarily.
Tack welding is one of the most important steps in pipe welding or any other type of
welding. The number of tack welds required depends upon the diameter of the pipe. For
1/2-inch pipe, you need two tacks. Place them directly opposite each other. As a rule,
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four tacks are adequate for standard size of pipe. The size of a tack weld is determined
by the wall thickness of the pipe. Be sure that a tack weld is not more than twice the
pipe thickness in length or two-thirds of the pipe thickness in depth. Tack welds should
be the same quality as the final weld. Ensure that the tack welds have good fusion and
are thoroughly cleaned before proceeding with the weld.
8.8.7 Spacers
In addition to tack welds, spacers sometimes are required to maintain proper joint
alignment. Spacers are accurately machined pieces of metal that conform to the
dimensions of the joint design used. Spacers are sometimes referred to as chill rings or
backing rings, and they serve a number of purposes. For example, they provide a
means for maintaining the specified root opening, provide a convenient location for tack
welds, and aid in the pipe alignment. In addition, spacers can prevent weld spatter and
the formation of slag or icicles inside the pipe.
8.8.8 Electrode selection
Select the electrode that is best suited for the position and type of welding to be done.
For the root pass of a multilayer weld, you need an electrode large enough, yet not
exceeding 3/16-inch, that ensures complete fusion and penetration without undercutting
and slag inclusions.
Make certain the welding current is within the range recommended by the
manufacturers of the welding machines and electrodes.
8.8.9 Weather conditions
Do not assign a welder to a job under any of the following conditions listed below unless
the welder and the work area are properly protected:
When the atmospheric temperature is less than 0°F
When the surfaces are wet
When rain or snow is falling, or moisture is condensing on the weld surfaces
During periods of high wind, unless using self-shielded electrodes
At temperatures between 0°F and 32°F, within 3 inches of the joint, heat the weld area
with a torch to a temperature warm to the hand before beginning to weld.
Test your Knowledge (Select the Correct Response)
7.
How many basic types of weld joints are there?
A.
B.
C.
D.
8.
4
5
6
8
Which type of weld is used for welding slip-on and threaded flanges to pipe?
A.
B.
C.
D.
Fillet
Bead
Butt
Tee
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11-95
9.0.0 WELDING PROCEDURE VARIABLES
The welding procedure variables are those that control the welding process and the
quality of the welds that are produced. When all of the variables are in proper balance,
the result will be a smooth running arc and a quality weld deposit. You need to
understand the effect of each variable on the different properties or characteristics of
the weld to increase the probability of producing the required weld properties. You
should recognize that some welding variables are more easily applied as controls of a
welding process. There are three major types of welding variables used for welding.
These are the fixed or preselected, primary adjustable, and the secondary adjustable
variables.
The preselected or fixed variables are those that can only be changed in large steps or
intervals and are therefore unfavorable as controls. For the FCAW process, these
variables are set according to the type of material being welded, the thickness of the
material, welding position, deposition rate required, and mechanical properties required.
These variables cannot be changed once the welding starts.
The primary adjustable variables are the major variables used to control the welding
process once the fixed variables have been selected. The primary variables control the
formation of the weld bead by affecting the bead width, bead height, penetration, arc
stability, and weld soundness. The primary welding variables are welding current, arc
voltage, and travel speed. These can be easily adjusted and measured so they can be
used effectively to control the welding
process. Specific values can be assigned to
the primary adjustable variables and these
values can be accurately reset time after
time.
The secondary adjustable variables can also
be changed continuously over a wide range
of values. However, they are sometimes
difficult to measure accurately. It is not easy
to use them as controls since, for the most
part, they cannot be assigned exact values.
This is especially true in semiautomatic
welding operations. Although difficult to
measure, these variables should be
controlled within the range for proper
operation. Secondary adjustable variables
are such things as electrode extension or
stickout, work and travel angles.
Figure 11-86 — Bead height,
bead width, and penetration.
The different variables affect the
characteristics of the weld, such as the penetration of the weld, bead height, bead
width, and the deposition rate. The penetration of the weld is defined as the greatest
depth below the surface of the base metal that the weld metal reaches. The bead height
or reinforcement is the height of the weld metal above the surface of the base metal.
The deposition rate is the weight of the metal that is deposited per unit of time. The
definitions of bead height, bead width, and penetration are shown in Figure 11-86.
The welding variables are discussed with particular attention to the three major
characteristics of penetration, deposition rate, and bead shape. Table 11-15 is a chart
showing the effects of welding variables on the three major characteristics.
NAVEDTRA 14250A
11-96
Table 11-15 — Recommended welding variable adjustment for FCAW.
Change
Required
Welding
Variable
Deeper
Penetration
Shallower
Penetration
Larger
Bead
Smaller
Bead
Bead
Height
Higher
and
Narrower
Bead
Bead
Flatter
Width
Wider
Bead
Faster
Deposition Rate
Slower
Disposition Rate
Arc
Voltage
Welding
Current
(See footnote)
Travel
Speed
Nozzle
Angle
3
Trailing
Max. 25°
3
Leading
1
Increase
1
Decrease
Stickout or
Tip to Work
Distance
Wire
Size
Gas
Type
2
Decrease
5 (a)
Smaller
4
CO2
2
Increase
5 (a)
Larger
4 (C)
Ar+CO2
1
Increase
2
Decrease
3 (a)
Increase
1
Decrease
2
Increase
3 (a)
Decrease
1
Decrease
2
Trailing
3
Increase
1
Increase
2
90° or
Leading
3
Decrease
1
Increase
2 (a)
Increase
3 (b)
Smaller
1
2 (a)
3 (b)
Decrease
Decrease
Larger
Footnote: Same adjustment is required for wire feed speed.
Key 1-first choice, 2-second choice, 3-third choice, 4-fourth choice, 5-fifth choice.
a. When these variables are changed, the wire feed speed must be adjusted so the welding current remains constant.
b. See deposition rate section of welding variables section.
c. This change is especially helpful on materials 20 gauge and smaller in thickness.
9.1.0 Fixed Variables
Fixed variables include electrode size and type, welding current type, and polarity.
9.1.1 Electrode Type
The type of electrode wire will have an effect on the welding characteristics of this
process. The flux cores of the electrodes contain different components that affect bead
shape, penetration, deposition rate, and the operating characteristics. Because of this, a
wide variety of operating characteristics exist, which are similar to those found with the
various covered electrodes used in SMAW. Some self-shielded flux-cored electrodes
have been developed to operate on DCEN. These electrodes produce relatively light
penetration, and are used for many sheet metal welding and weld surfacing operations.
Self-shielded electrodes that operate on DCEP produce deeper penetration. Gasshielded electrode wires operate on DCEP and provide the deepest penetration due to
the gas shielding addition to the flux core.
NAVEDTRA 14250A
11-97
Many FCAW electrodes are
designed to produce a stable arc
and high deposition rates at the
higher current levels. Figures 1187 and 11-88 show some
deposition rate comparisons
between several types of fluxcored electrodes.
9.1.2 Electrode Size
Each electrode wire diameter of a
given type has a usable welding
current range. Larger diameter
electrode wires use higher
welding currents to produce
higher deposition rates and
deeper penetration. The rate at
which the electrode melts is
based on the welding current
density and the components in
the flux. If two electrode wires of
Figure 11-87 — Deposition rate vs. current
the same type, but different
for externally shielded FCAW electrode wire.
diameters, are operated at the
same current level, the smaller
electrode will give a higher
deposition rate because the
current density is higher. Figures
11-87 and 11-88 also show the
deposition rates produced by
different electrode diameters. The
amount of penetration is also
based on the current density. A
smaller electrode will produce
deeper penetration than a larger
electrode at the same current
setting, but the weld bead will be
wider when using the larger
electrode wire. The choice of the
optimum electrode size to be
used is based on the thickness of
the metal to be welded, the
amount of penetration required,
the position of welding, the
deposition rate desired, the bead
profile desired, and the cost of
Figure 11-88 — Deposition rate vs. current
the electrode wires. A smaller
for self-shielded FCAW electrode wire.
diameter electrode is more costly
on a weight basis, although for out-of-position welding, the smaller diameter electrodes
are the only ones that can be used. For each application, an optimum electrode size
can be used to produce minimum welding costs.
NAVEDTRA 14250A
11-98
9.2.0 Primary Variables
Primary variables include welding current, travel speed, and welding voltage.
9.2.1 Welding Current
The amount of welding current has the greatest effect on the deposition rate, weld bead
size and shape, and the weld penetration. Welding current is proportional to the wire
feed speed for a given electrode type, shielding gas type and pressure, and amount of
electrode extension. In a constant voltage system, the welding current is controlled by
the knob on the wire feeder control, which sets the wire feed speed. The welding current
increases with the wire feed speed.
As shown in Figures 11-87 and 11-88, the deposition rate of the process increases as
the welding current increases. The lower part of the curve is flatter than the upper part
because at higher current levels, the melting rate of the electrode increases at a faster
rate as the current increases. This can be attributed to resistance heating of the
electrode extension beyond the contact tube. When all of the other variables are held
constant, increasing the welding current will increase the electrode deposition rate,
increase penetration, and increase the size of the weld bead. Figure 11-89 shows the
effect of welding current.
Figure 11-89 — Effect of welding current on bead formation.
NAVEDTRA 14250A
11-99
An excessive welding current
level will create a large, deeppenetrating weld bead that
causes excessive convexity and
can burn through the bottom of
the joint. Insufficient welding
current produces large globular
transfer and excessive spatter
in addition to poor penetration
and excessive piling up of the
weld metal. With self-shielding
electrodes, insufficient current
can cause porosity and pickup
too much nitrogen from the
atmosphere. The nitrogen
causes a harder weld that has
poorer ductility. Figures 11-90,
11-91, and 11-92 show the
effects of welding current on the
penetration, bead height, and
bead width.
Figure 11-90 — Effect of travel speed, arc
volts, and welding current on penetration.
Figure 11-91 — Effect of travel speed, arc
volts, and welding current on bead height.
NAVEDTRA 14250A
11-100
Figure 11-92 — Effect of travel speed, arc
volts, and welding current on bead width.
9.2.2 Welding Voltage (Arc Length)
The welding voltage is determined by the distance between the tip of the electrode and
the work. In a constant voltage system, a voltage control knob on the front of the power
source adjusts the welding voltage. The power source maintains a given voltage that
maintains a certain arc length. In a constant current system, the voltage-sensing wire
feeder controls the voltage. The voltage-sensing wire feeder regulates the wire feed
speed to maintain the arc length that produces the preselected arc voltage. For a given
welding current, a certain voltage will provide the smoothest welding arc. The arc
voltage required for an application is dependent on the electrode size, type of shielding
gas, position of welding, type of joint, and base metal thickness. When the other welding
variables are held constant and the welding voltage is increased, the weld bead
becomes wider and flatter. The effect of varying the arc voltage on a gas-shielded
electrode is shown in Figure 11-93. The penetration will increase up to an optimum
voltage level and then begin to decrease, as shown in Figure 11-90. A higher voltage is
often used to bridge a gap because of the decreased penetration obtained. An
excessive voltage or arc length will result in excessive amounts of spatter and
irregularly shaped weld beads. When using self-shielded electrodes, an excessive arc
length can also cause nitrogen pickup, which causes porosity in low-carbon steel weld
metal. With the self-shielded stainless steel electrodes, nitrogen absorption can cause
cracking. With all types of electrodes, undercutting can also be produced. A decrease in
the arc length results in a narrower weld bead with a greater convexity and deeper
penetration. An arc voltage that is too low will cause a narrow convex weld bead with
excessive spatter and reduced penetration. Figures 11-91 and 11-92 show the effects of
the welding voltage on bead height and bead width.
NAVEDTRA 14250A
11-101
Figure 11-93 — Effects of arc voltage on the weld bead.
9.2.3 Travel Speed
The travel speed influences the weld penetration and the shape of the weld deposit. In
semiautomatic welding, this is controlled by the welder and will vary somewhat,
depending on the welder. In machine and automatic welding, as shown in Figure 11-90,
the penetration is at a maximum with a certain travel speed. Increasing or decreasing
the travel speed from this point will reduce the amount of penetration. When the travel
speed is decreased, the amount of filler metal deposited per unit of length increases,
which creates a large, shallow weld puddle. Weld metal tends to get slightly ahead of
the arc, which reduces the penetration and produces a wide weld bead. Reducing the
travel speed will increase the bead height, as is shown in Figure 11-91, and the bead
width, as shown in Figure 11-92. Travel speeds that are too slow can result in
overheating the weld metal because of the excessive heat input, which creates a very
large heat affected zone. It can also cause excessive piling up of the weld metal, which
has a rough appearance and may trap slag. As the travel speed is increased, the heat
input into the base metal is reduced, which decreases the melting of the base metal,
limits penetration, and the bead height and the bead width are also reduced. An
excessive travel speed will result in an irregular, ropy weld bead that may have
undercutting along the edges. Figure 11-94 shows the effects of travel speed on the
shape of the weld bead.
NAVEDTRA 14250A
11-102
Figure 11-94 — Effects of travel speed on the weld bead.
The effects of the primary welding variables are summarized in Figure 11-95 for gasshielded flux-cored electrodes and in Figure 11-96 for self-shielded flux-cored
electrodes.
Figure 11-95 — Externally shielded flux cored arc good and bad welds.
NAVEDTRA 14250A
11-103
Figure 11-96 — Self-shielded flux cored arc good and bad welds.
9.3.0 Secondary Variables
Secondary variables include work and travel
angles of the electrode.
9.3.1 Electrode Extension
The electrode extension, sometimes referred
to as the stickout, is the distance between
the tip of the contact tube and the tip of the
electrode as shown in Figure 11-97.
The length of electrode that extends beyond
the contact tube is resistance heated in
proportion to its length. The amount of
resistance heating that occurs affects the
electrode deposition rate and the amount of
penetration, as well as weld quality and arc
stability, by varying the welding current.
Increasing the electrode extension reduces
the welding current, as shown in Figure 1198.
NAVEDTRA 14250A
Figure 11-97 — Electrode
extension or stickout.
11-104
In semiautomatic welding, the electrode
extension can be varied by the welder to
compensate for joint variation without
interrupting the welding operation. Electrode
extension provides a good control during
welding to change the amount of penetration
obtained. In FCAW, the electrode extension
is a variable that must be held in balance
with the shielding conditions and the related
welding variables. As the electrode
extension is increased, the amount of
preheating of the wire is increased. For gasshielded flux-cored electrodes, an electrode
extension ranging from ¾- to 1-1/2-in. (1938 mm) is normally recommended.
Because the shielding comes from the core
of self-shielded electrodes alone, a longer
Figure 11-98 — Effect of
electrode extension is generally
electrode
extension on welding
recommended to take advantage of the
current.
extra preheating effect needed to activate
the shielding components in the electrode
core. Welding guns for self-shielded electrodes often have nozzles where the contact
tube is set inside far enough to ensure a minimum electrode extension. Electrode
extensions ranging from ¾- to 3-1/2-in. (19-89 mm) are commonly used. This will vary
depending on the type of electrode wire so the manufacturer's data should be consulted
for each electrode. An electrode extension
that is too long will produce an unstable arc
and cause excessive spatter. A short
extension will cause an excessive arc length
at a particular voltage setting. With gasshielded electrodes, excessive spatter may
result, which can build up in the nozzle and
restrict the shielding gas flow. Poor shielding
gas coverage can result in porosity and
surface oxidation of the weld bead.
The amount of electrode extension also has
an effect on the deposition rate. Increasing
the electrode extension will increase the
preheating effect on the electrode and
therefore increase the deposition rate.
Figure 11-99 shows this for a gas-shielded
flux-cored electrode.
NAVEDTRA 14250A
Figure 11-99 — Effect of
electrode extension on
deposition rate.
11-105
9.3.2 Electrode Angles
The angle at which the welding electrode is held with respect to the weld joint is called
the electrode angles. These angles have an effect on the shape of the weld bead and
the amount of penetration. The electrode angles are called the travel and work angles
and are shown in Figure 11-100.
Figure 11-100 — Travel angle and work angle.
The travel angle is the angle between the joint and electrode in the longitudinal plane. A
push angle exists when the electrode points in the direction of travel. A drag angle
exists when the electrode points in the direction opposite of travel. The work angle is the
angle between the electrode and the plane perpendicular to travel.
The angle at which the electrode is held during welding determines the direction in
which the arc force acts on the weld pool. The electrode angles are used to shape the
weld bead and to prevent the slag from running ahead of the weld pool and becoming
trapped in the weld. When making flat position fillet and groove welds, gravity tends to
make the molten slag run ahead of the weld pool. To compensate for this, a drag angle
is used, which forces the slag back. The proper travel angle depends on the method of
FCAW being used, the thickness of the base metal, and the position of welding. Using
gas-shielded electrodes, maximum weld penetration is obtained with a 10° drag angle.
Drag angles ranging from about 2° to 15° are normally recommended, but a drag angle
greater than 25° should not be used. Drag angles greater than this do not provide good
control of penetration. As the drag angle is decreased, the bead height decreases and
the width increases.
NAVEDTRA 14250A
11-106
This effect continues into the push angle up
to a point where the bead will start to
narrow down again. Push angles are
generally not recommended because of the
greater chances of slag entrapment
occurring. For self-shielded electrodes, the
drag angles used are similar to those used
in SMAW. Flat and horizontal position
welding is done using drag angles ranging
from 20° to 45°. Larger angles may be used
for thin sections. As the thickness of the
metal increases, smaller angles are used to
increase the penetration. For vertical
position, uphill welding, a push angle of 5°
to 10° is recommended. When making fillet
welds in the horizontal position, the weld
metal tends to flow in both the horizontal
and vertical directions. To compensate for
Figure 11-101 — Positioning the
the vertical flow, a work angle of 40° to 50°
electrode for fillet welds.
from the upper plate is used. The electrode
should be centered about one diameter of
the electrode below the center of the weld, as shown in Figure 11-101. This will prevent
an unequal legged fillet weld from being formed.
10.0.0 WELDING PROCEDURE SCHEDULES
The welding procedure schedules in this chapter give typical welding conditions that can
be used to obtain high quality welds under normal welding conditions. FCAW uses a
wide variety of operating conditions for welding mainly steels, some stainless steels,
and some nickels. The procedure schedules presented in this chapter are in no way a
complete guide to the procedures that can be used for FCAW and are not the only
conditions that may be used to obtain a specific weld. Other conditions could be used
because of factors such as weld appearance, welder skill, method of application, and
the specific application that may require variations from the schedules. For example,
automatic FCAW normally requires higher amperage settings and faster travel speeds
than semiautomatic welding. The type of electrode wire has a significant effect on the
conditions. This is because the type of electrode wire indicates whether a shielding is
required, the recommended electrical polarity, the recommended amount of electrode
extension, and other factors. As the particular requirements of the application become
known, the settings may be adjusted to obtain the optimum welding conditions.
Qualifying tests or finals should be made under the actual conditions before applying
the information in the tables to actual production welding.
When changing or adjusting the variables for welding, the effect of the variables on
each other must be considered. One variable cannot usually be drastically changed
without adjusting or changing the other variables in order to obtain a stable arc and
good overall welding conditions.
The following schedules are based on welding plain carbon steels using various types
of electrode wires in appropriate positions. Generally, electrode wires over 1/16–in. (1.6
mm) diameter are limited to the flat and horizontal positions. The welding schedules
include the semiautomatic and automatic methods of application, using self-shielded
and CO2-shielded electrode wires. The tables use the base metal thickness or fillet size,
NAVEDTRA 14250A
11-107
number of weld passes,
electrode diameter, welding
current, welding voltage, wire
feed speed, gas flow rate (if
used), and travel speed as
variables. Each table contains
the type of shielding gas (if
used), type of joint, and the
position of welding being used.
All of the schedules are based
on using DCEP. Both the
welding current and wire feed
speed values are given because,
even through the welding current
is set by the wire feed speed, it
is sometimes more convenient to
directly establish the welding
current without exactly knowing
the wire feed speed. Figures 11102 and 11-103 show wire feed
speeds and their corresponding
welding currents for several
sizes of tubular electrode wire.
Figure 11-102 — Wire feed speed vs.
welding current for externally-shielded
tubular wires.
Many of the charts include
welding conditions for both
groove and fillet welds given on
the same chart. Generally, fillet
welds will use the higher current
levels for the ranges given and
groove welds will use the lower
end of the current range.
Figure 11-103 — Wire feed speed vs.
welding current for self-shielded tubular
wires.
NAVEDTRA 14250A
11-108
Table 11-16 — Flux cored arc welding of plain and low-alloy steels using
external shielding.
Thickness
of Base
Electrode
Wire Feed
Gas Flow
Travel
Speed
Rate
Speed
3
Metal
No. of
Diameter
Welding
Welding
In/min
Ft /hr
in/min
in (mm)
Passes
In (mm)
Voltage
Current
(mm/s)
(L/mm)
(mm/s)
1/8 (3.2)
1
3/32 (.24)
24-26
300
100 (42)
35-45 (17-21)
44 (19)
3/16 (4.8)
1
3/32 (2.4)
24-26
350
120(51)
35-45 (17-21)
42 (18)
3/16 (4.8)
1
1/8 (3.2)
24-26
450
90 (38)
35-45 (17-21)
47 (20)
1/4 (6.4)
1
3/32 (2.4)
24-26
400
155 (66)
35-45 (17-21)
24 (10)
1/4 (6.4)
1
3/32 (2.4)
25-27
500
105 (44)
35-45 (17-21)
30 (13)
5/16 (7.9)
1
3/32 (2.4)
28-30
500
205 (87)
35-45 (17-21)
22 (9)
5/16 (7.9)
1
1/8 (3.2)
28-30
500
105 (44)
35-45 (17-21)
22 (9)
3/8 (9.5)
1
3/32 (2.4)
28-30
500
205 (87)
35-45 (17-21)
15 (6)
3/8 (9.5)
1
1/8 (3.2)
29-31
575
130 (55)
35-45 (17-21)
20 (8)
1/2 (12.7)
1
3/32 (2.4)
29-31
525
220 (93)
35-45 (17-21)
11 (5)
1/2 (12.7)
1
1/8 (3.2)
30-32
625
150 (63)
35-45 (17-21)
14 (6)
5/8 (15.9)
3
3/32 (2.4)
29-31
475
190 (80)
35-45 (17-21)
12 (5)
5/8 (15.9)
3
1/8 (3.2)
28-30
500
105 (44)
35-45 (17-21)
14 (6)
3/4 (19.1)
3
3/32 (2.4)
29-31
500
205 (87)
35-45 (17-21)
13 (5)
3/4 (19.1)
3
1/8 (3.2)
29-31
500
105 (44)
35-45 (17-21)
13 (5)
NAVEDTRA 14250A
11-109
Table 11-17 — Welding procedure schedules for flux cored arc welding carbon
and low-alloy steel using external shielding.
Thickness
of Base
Electrode
Wire Feed
Gas Flow
Travel
Speed
Rate
Speed
3
Metal
No. of
Diameter
Welding
Welding
In/min
Ft /hr
in/min
in (mm)
Passes
In (mm)
Voltage
Current
(mm/s)
(L/mm)
(mm/s)
1/8 (3.2)
1
3/32 (.24)
24-26
350
120(51)
35-45 (17-21)
60 (25)
3/16 (4.8)
1
3/32 (2.4)
24-26
400
155 (55)
35-45 (17-21)
36 (15)
3/16 (4.8)
1
1/8 (3.2)
24-26
425
75 (32)
35-45 (17-21)
38 (16)
1/4 (6.4)
1
3/32 (2.4)
24-26
400
155 (66)
35-45 (17-21)
24 (10)
1/4 (6.4)
1
3/32 (2.4)
25-27
450
90 (38)
35-45 (17-21)
26 (11)
5/16 (7.9)
1
3/32 (2.4)
25-27
440
175 (74)
35-45 (17-21)
20 (8)
5/16 (7.9)
1
1/8 (3.2)
26-28
460
93 (39)
35-45 (17-21)
20 (8)
3/8 (9.5)
1
3/32 (2.4)
26-28
475
190 (80)
35-45 (17-21)
15 (6)
3/8 (9.5)
1
1/8 (3.2)
28-30
500
105 (44)
35-45 (17-21)
16 (7)
1/2 (12.7)
3
3/32 (2.4)
24-26
400
155 (66)
35-45 (17-21)
18 (8)
1/2 (12.7)
3
1/8 (3.2)
25-27
450
90 (38)
35-45 (17-21)
20 (8)
5/8 (15.9)
3
3/32 (2.4)
26-28
450
180 (90)
35-45 (17-21)
14 (6)
5/8 (15.9)
3
1/8 (3.2)
27-29
450
90 (38)
35-45 (17-21)
14 (6)
3/4 (19.1)
6
3/32 (2.4)
28-30
400
155 (66)
35-45 (17-21)
20 (8)
3/4 (19.1)
6
1/8 (3.2)
28-30
470
96 (41)
35-45 (17-21)
22 (9)
NAVEDTRA 14250A
11-110
Table 11-18 — Flux cored arc welding of plain and low-alloy steels using
external shielding.
Metal
Electrode
Wire Feed
Gas Flow
Travel
Speed
Rate
Speed
Thickness
No. of
Diameter
Welding
Welding
in/min
ft3/hr
in/min
in (mm)
Passes
in (mm)
Voltage
Current
(mm/s)
(L/mm)
(mm/s)
1/8 (3.2)
1
3/32 (2.4)
24-26
325-350
120 (51)
35-45 (17-21)
56 (24)
3/16 (4.8)
1
3/32 (2.4)
24-26
350-375
130 (55)
35-45 (17-21)
48 (20)
1/4 (6.4)
1
3/32 (2.4)
25-27
375-400
137 (58)
35-45 (17-21)
41 (17)
3/8 (9.5)
2
1/8 (3.2)
26-28
450-500
107 (45)
35-45 (17-21)
24 (10)
1/2 (12.7)
2
1/8 (3.2)
28-30
475-525
120 (51)
35-45 (17-21)
14 (6)
5/8 (15.9)
2
1/8 (3.2)
30-32
575-600
155 (66)
35-45 (17-21)
14-16 (6)
3/4 (19.1)
3
1/8 (3.2)
30-32
575-600
155 (66)
35-45 (17-21)
15-20 (6-8)
7/8 (22.2)
3
1/8 (3.2)
30-32
575-600
155 (66)
35-45 (17-21)
13-18 (5-8)
1 (25.4)
4
1/8 (3.2)
31-32
575-600
155 (66)
35-45 (17-21)
12-20 (5-8)
NAVEDTRA 14250A
11-111
Table 11-19 — Flux cored arc welding of plain and low-alloy steels using
external shielding.
Metal
Electrode
Thickness
No. of
Diameter
Welding
Wire Feed
Gas Flow
Travel
Speed
Rate
Speed
Welding
in/min
3
ft /hr
in (mm)
Passes
in (mm)
Voltage
Current
(mm/s)
(L/mm)
1/8 (3.2)
1
3/32 (2.4)
16-18
225-250
65 (27)
35-45 (17-21)
3/16 (4.8)
1
1/4 (6.4)
1
3/8 (9.5)
1
1/2 (12.7)
1
5/8 (15.9)
3
3/4 (19.1)
3
3/32 (2.4)
3/32 (2.4)
1/8 (3.2))
3/32 (2.4)
1/8 (3.2)
3/32 (2.4)
1/8 (3.2)
3/32 (2.4)
1/8 (3.2)
3/32 (2.4)
1/8 (3.2)
17-19
26-28
27-29
27-29
29-31
27-29
29-31
27-29
29-31
27-29
29-31
275-300
350-375
375-400
400-425
500-525
425-450
525-550
400-425
475-500
400-425
475-500
90 (38)
240 (102)
125 (53)
270 (114)
185 (78)
290 (123)
190 (80)
270 (114)
170 (72)
270 (114)
170 (72)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
NAVEDTRA 14250A
in/min
(mm/s)
55 (23)
36 (15)
22 (9)
14 (6)
17 (7)
14 (6)
14 (6)
13 (5)
14-20 (6-8)
13-18 (5-8)
14-20 (6-8)
13-18 (5-8)
11-112
Table 11-20 — Flux cored arc welding of plain and low-alloy steels using selfshielding electrode wires.
Thickness
of Base
metal
in (mm)
11 ga. (3.2)
3/16 (4.8)
1/4 (6.4)
3/8 (9.5)
1/2 (12.7)
5/8 (15.9)
3/4 (19.1)
7/8 (22.2)
1 (25.4)
NAVEDTRA 14250A
No. of
Passes
1
1
1
2
2
3
3
3
4
Electrode
Diameter Welding
in (mm)
Voltage
3/32 (2.4)
25
3/32 (2.4)
26
3/32 (2.4)
26
1/8 (3.2)
28
1/8 (3.2)
29
1/8 (3.2)
28-30
1/8 (3.2)
28-30
1/8 (3.2)
28-31
1/8 (3.2)
28-31
Welding
Current
200-225
250-275
350-375
400-425
425-450
400-425
425-450
475-500
425-450
Wire
Feed
Speed
in/min
(mm/s)
80 (34)
95 (40)
130 (55)
95 (40)
107 (45)
95 (40)
107 (45)
120 (51)
107 (45)
Travel
Speed
in/min
(mm/s)
16 (7)
12 (5)
10 (4)
12-14 (5-6)
14 (6)
12-16 (5-7)
12-16 (5-7)
12-16 (5-7)
12-16 (5-7)
11-113
Table 11-21 — Flux cored arc welding of plain and low-alloy steels using selfshielding electrode wires.
Thickness
Of Base
Metal
No. of
in (mm)
Passes
1/8 (3.2)
1
3/16 (4.8)
1
1/4 (6.4)
1
3/8 (9.5)
2
1/2 (12.7)
2
5/8 (15.9)
3
3/4 (19.1)
3
7/8 (22.2)
3
1 (25.4)
4
NAVEDTRA 14250A
Electrode
Diameter
in (mm)
3/32 (2.4)
3/32 (2.4)
1/8 (3.2)
1/8 (3.2)
1/8 (3.2)
1/8 (3.2)
1/8 (3.2)
1/8 (3.2)
1/8 (3.2)
Welding
Voltage
19
20
28
28-30
27-29
29-31
28-30
29-31
29-31
Welding
Current
200-225
250-275
375-400
400-425
425-450
400-425
425-450
475-500
425-450
Wire Feed
Speed
in/min
(mm/s)
60 (25)
80 (34)
110 (47)
135 (57)
150 (63)
130 (55)
150 (63)
170 (72)
150 (63)
Travel
Speed
in/min
(mm/s)
12 (5)
9 (4)
14 (6)
13-16 (5-7)
14-16 (6-7)
13-18 (5-8)
13-16 (5-7)
13-18 (5-8)
13-16 (5-7)
11-114
Table 11-22 — Flux cored arc welding of plain and low-alloy steels using small
diameter externally-shielded electrode wires.
Fillet
Weld
Size or
Metal
Thickness No. of
in (mm)
Passes
1/8 (3.2)
1
3/16 (4.8)
1
1/4 (6.4)
1
3/8 (9.5)
2
1/2 (12.7)
2
3/4 (19.1)
3
NAVEDTRA 14250A
Electrode
Diameter
in (mm)
.045 (1.1)
.045 (1.1)
.045 (1.1)
.045 (1.1)
.045 (1.1)
.045 (1.1)
Welding Welding
Voltage Current
22-24
150
22-24
200
23-25
220
24-25
220
24-26
220
24-26
220
Wire Feed
Speed
in/min
(mm/s)
200 (85)
270 (114)
320 (135)
320 (135)
320 (135)
320 (135)
Gas Flow
Rate
ft3/hr
(L/mm)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
35-45 (17-21)
Travel
Speed
in/min
(mm/s)
30 (13)
24-30 (10-13)
15-18 (6-8)
8-10 (3-4)
8-10 (3-4)
8-10 (3-4)
11-115
11.0.0 PREWELD PREPARATIONS
Several operations may be required before making a weld. These operations include
preparing the weld joint, setting up or fixturing the weldment, possible maintenance of
welding gun and cable assembly, setting the variables, and in some cases preheating.
The amount of preweld preparation depends upon the size of the weld, the material to
be welded, the ease of fit-up, the quality requirements, the governing code or
specification, and the welder.
11.1.0 Preparing the Weld Joint
There are different ways of preparing the edges of the joint for welding. The methods
most often used for edge preparation are oxygen fuel gas cutting, plasma arc cutting, air
carbon arc gouging, shearing, machining, grinding, and chipping. When they can be
used, the thermal cutting methods, oxyfuel gas, plasma arc cutting, and air carbon arc
cutting are generally faster than the mechanical cutting methods, with the exception of
shearing. Oxygen fuel gas cutting is used on carbon and low-alloy steels. Plasma arc
cutting is used on carbon, low-alloy, and stainless steels and is best for applications
where high production rates are required. Air carbon arc cutting is used for preparing
joints in most steels, including stainless steels. This process should not be used on
stainless steels for critical corrosion applications because of the carbon deposited,
unless the cut surfaces are cleaned by grinding and brushing. The surfaces cut by these
thermal methods sometimes have to be ground lightly to remove scale or
contamination. Common types of prepared weld joints are the square-, V-, U-, J-,
bevel-, and combination grooves. The more complex types of bevels require a longer
joint preparation time, which makes the joint preparation more expensive.
Since FCAW is used on all metal thicknesses, all of the different joint preparations are
widely used. Joints for fillet or square-groove welds are prepared simply by squaring the
edges of the members to be welded if the as-received edge is not suitable.
Next to the square edge preparation, the V-groove and single-bevel grooves are the
types most easily prepared by oxygen fuel cutting, plasma arc cutting, chipping, or
machining. These methods leave a smooth surface if properly done. The edges of Uand J-grooves can be done by using special tips and techniques with oxy-fuel cutting or
by machining. Machining produces the uniform groove. Carbon arc cutting is used
extensively for preparing U-grooves in steels and for removing part of root passes so
that the joint can be welded from both sides. Chipping is sometimes done on the back
side of the weld, when full penetration is required and a thermal cutting method is not
being used.
Weld backings are commonly used in FCAW to provide support for the weld metal and
to control the heat input. Copper, steel, stainless steel, and backing tape are the most
common types of weld backing. Copper is a widely used method of weld backing
because it does not fuse to thin metals. It also provides a fast cooling rate because of
the high heat conductivity of copper, which makes this the best method of controlling the
heat input. Steel backing is used when welding steels. These are fusible and remain
part of the weldment unless they are cut off. Often, these are removed by oxy-fuel, aircarbon arc cutting, or grinding. Stainless steels are good backing materials for welding
stainless steels. Backing tape is popular because it can be molded to any joint
configuration, such as the inside of a pipe.
NAVEDTRA 14250A
11-116
11.2.0 Cleaning the Work Metal
The welds made by FCAW are susceptible to contamination during the welding process.
The surface of the base metal should be free of grease, oil, paint, plating, dirt, oxides, or
any other foreign material. This is especially critical when welding stainless steel. FCAW
is less sensitive to contaminants than GMAW because of the scavengers and
deoxidizers present in the flux core. Some flux-cored electrodes are made specifically
for welding over rust and scale. This is done to make preweld cleaning less expensive.
Very dirty workpieces are usually cleaned by using solvent cleaners followed by vapor
degreasing. Simple degreasing is often used for cleaning carbon and low-alloy steels
that have oxide free surfaces. Acid pickling is generally used for cleaning scale and rust,
and can be removed mechanically by grinding and abrasive blasting.
The type of cleaning operation will vary, depending on the type of metal. Carbon and
low-alloy steels may be cleaned chemically in a hydrochloric acid solution. Nickel alloys
and stainless steels may be cleaned by pickling, which removes iron, sand blast
residue, and other contaminants. Welding should never be done near chlorinated
solvents because the arc can create phosgene gas, which is toxic. Chemical cleaning
can be done by pickling.
Just before welding, several other tasks should be performed. One is to grind or file the
edges of the joint smooth so that there are no burrs present. Burrs can cause physical
pain as well as create a place to trap contaminants in a weld joint. Grinding is often
used on plain carbon and low-alloy steels to remove burrs and rust or mill scale from the
area in and around the joint. The surfaces of the joint and surrounding area should be
wire brushed. Mild steel brushes are used for cleaning plain carbon and low-alloy steel.
Stainless steel wire brushes are used for cleaning stainless steel. The joint surfaces and
surface of the previous weld bead should also be cleaned off between passes of a
multiple-pass weld. Stainless steel brushes should be used on these metals to avoid
contamination due to rust or carbon from the mild steel wire brushes. Welding should be
done soon after cleaning, especially on metals that form surface oxides, such as
stainless steel. Wire brushing does not completely remove the oxide but it reduces the
thickness and makes them easier to weld. Gloves should be worn while cleaning
stainless steels to prevent oil or dirt from the fingers or from getting on the joint
surfaces, which can also cause contamination.
11.3.0 Fixturing and Positioning
Fixturing can affect the shape, size, and uniformity of a weld bead. Fixtures are devices
that are used to hold the parts to be welded in proper relation to each other. The
alignment is called fit-up. When fixturing is not used, it usually indicates that the
resulting weld distortion can be tolerated or corrected by straightening operations. The
three major functions of fixtures are:
1. Locate and maintain parts in their position relative to the assembly.
2. Increase the welding efficiency of the weld.
3. Control distortion in the weldment.
When a welding fixture is used, the components of a weldment can be assembled and
securely held in place while the weldment is positioned and welded. The use of those
devices is dependent on the specific application. These devices are more often used
when large numbers of the same part are produced. When a fixture is used, the
production time for the weldments can be greatly reduced. They are also good for
applications where close tolerances must be held. Positioners are used to move the
NAVEDTRA 14250A
11-117
workpiece into a position so welding can be done more conveniently, which improves
the appearance and the quality of the weld bead.
Positioning is sometimes needed simply to make the weld joint more accessible. The
main objective of positioning is to put the joint in the flat or other more favorable
position. Positioners are particularly important in FCAW because they allow the use of
larger diameter flux-cored electrode wires when the weld joint can be rotated into the
flat or horizontal fillet. The larger diameter electrodes produce higher deposition rates,
are less expensive, and generally reduce the overall welding costs. Flat position welding
usually increases the quality of the weld because it makes the welding easier.
11.4.0 Preheating
The use of preheat is sometimes needed, depending on the type of metal being welded,
the base metal thickness, and the amount of joint restraint. For a refresher, refer again
to topic 7.0.0 and Table 11-12. The specific amount of preheat needed for a given
application is often obtained from the welding procedure.
The preheat temperature of the base metal is often carefully controlled. Several good
methods of doing this are furnace heating, electric induction coils, and electric
resistance heating blankets. On thin metals, hot air blasts or radiant lamps may be
used. With these methods, temperature indicators are connected to parts being
preheated. Another method of preheating is using torches, which give more localized
heating than the previously mentioned methods. However, when using torches for
preheating, it is important to avoid localized overheating and deposits of incomplete
combustion products from collecting on the surface of the parts to be welded. Colored
chalks and pellets are often used to measure the preheat temperature. Chalks and
pellets melt at a specific, predetermined temperature. Another method of measuring the
temperature is by using a hand-held temperature indicator. These indicators can give
meter readings, digital readings, or recorder readings, depending on the type of
temperature indicator.
Test your Knowledge (Select the Correct Response)
9.
Which of the following is NOT a major type of welding variable?
A.
B.
C.
D.
10.
Fixed
Primary adjustable
Secondary adjustable
Secondary fixed
Fixtures and jigs are devices that are used to hold the parts to be welded in
proper relation to each other. What is this alignment called?
A.
B.
C.
D.
Fixed-up
Jigged-up
Fit-up
Butted-up
12.0.0 WELDING DEFECTS and PROBLEMS
Flux cored arc welding, like other welding processes, has welding procedure problems
that may develop, which can cause defects in the weld. Some defects are caused by
problems with the materials. Other welding problems may not be foreseeable and may
require immediate corrective action.
NAVEDTRA 14250A
11-118
12.1.0 Discontinuities Caused by Welding Technique
A poor welding technique and improper choice of welding parameters can cause weld
defects. Defects that can occur when using the FCAW process are slag inclusions,
wagon tracks, porosity, wormhole porosity, undercutting, lack of fusion, overlapping,
burn through, arc strikes, craters, and excessive weld spatter. Many of these welding
technique problems weaken the weld and can cause cracking. A poor welding
technique and improper choice of welding parameters are major causes of weld defects.
Some defects are caused by the use of improper base metal, filler metal, or shielding
gas. The base metal and filler metal should also be cleaned to avoid creation of a
discontinuity. Other problems that can occur and reduce the quality of the weld are arc
blow, loss of shielding, defective electrical contact between the contact tube and the
electrode, and wire feed stoppages.
12.1.1 Slag Inclusions
FCAW produces a slag covering over the weld. Slag inclusions (Figure 11-104) occur
when slag particles are trapped inside the weld metal, which produces a weaker weld.
Slag inclusions can be caused by:
1. Slag left on the previous weld pass
2. An erratic travel speed
3. Improper electrode angles that let
the slag get ahead of the arc
4. A weaving motion that is too wide
5. A travel speed that is too slow which
lets the weld puddle get ahead of the
arc
Figure 11-104 — Slag inclusions.
6. an Amperage setting too low
This defect can be prevented by:
1. Cleaning the slag off of the previous weld bead, especially along the toes of the
weld
2. Using a uniform travel speed
3. Increasing the drag angle to prevent the slag from getting ahead of the arc
4. Using a tighter weaving motion
5. Increasing the travel speed so that the arc is at the front of the weld puddle
6. Increasing the amperage setting
12.1.2 Wagon Tracks
Wagon tracks (Figure 11-105) are linear
slag inclusions that run the longitudinal axis
of the weld. They result from allowing the
slag to run ahead of the weld puddle and by
slag left on the previous weld pass.
This is especially common when slag forms
in undercuts on the previous pass. This
discontinuity occurs along the toe line of the
previous weld bead and can be corrected
NAVEDTRA 14250A
Figure 11-105 — Wagon tracks.
11-119
by correcting the electrode travel angles, increasing the travel speed, or by doing a
better slag cleaning.
12.1.3 Porosity
Porosity (Figure 11-106) is gas pockets in
the weld metal that may be scattered in
small clusters or along the entire length of
the weld. Porosity weakens the weld in
approximately the same way that slag
inclusions do. Porosity may be internal, on
the surface of the weld bead, or both.
Porosity may be caused by:
Figure 11-106 — Porosity.
1. Inadequate shielding gas flow rate
for gas-shielded electrodes
2. Wind drafts that deflect the shielding gas coverage
3. Contaminated or wet shielding gas
4. Excessive welding current
5. Excessive welding voltage
6. Excessive electrode extension
7. An excessive travel speed, which causes freezing of the weld puddle before
gases can escape
8. Rust, grease, oil, moisture, or dirt on the surface of the base metal or electrode
9. Impurities in the base metal, such as sulfur and phosphorous in steel
Porosity can be prevented by:
1. Increasing the shielding gas flow rate
2. Setting up wind shields
3. Replacing the cylinder of shielding gas
4. Lowering the welding current (reducing the wire feed speed)
5. Decreasing the voltage
6. Decreasing the electrode extension
7. Reducing the travel speed
8. Cleaning the surface of the base metal or electrode
9. Changing to a different base metal
with a different composition
12.1.4 Wormhole Porosity (Piping
Porosity)
Wormhole porosity (Figure 11-107) is the
name given to elongated gas pockets and
is usually caused by sulfur or moisture
trapped in the weld joint
The best methods of preventing this are to
clean the surfaces of the joint and preheat
NAVEDTRA 14250A
Figure 11-107 — Wormhole
porosity.
11-120
to remove moisture. If sulfur in the steel is the problem, a more weldable grade of steel
should be selected.
12.1.5 Undercutting
Undercutting (Figure 11-108) is a groove melted in the base metal next to the toe or root
of a weld that is not filled by the weld metal. Undercutting causes a weaker joint and it
can cause cracking. This defect is caused
by:
1. Excessive welding current
2. Arc voltage too high
3. Excessive travel speed, which does
not allow enough filler metal to be
added
4. Erratic feeding of the electrode wire
5. Excessive weaving speed
Figure 11-108 — Undercutting.
6. Incorrect electrode angles, especially on vertical and horizontal welds
On vertical and horizontal welds, undercutting can also be caused by too large an
electrode size and incorrect electrode angles. This defect can be prevented by:
1. Reducing the weld current
2. Reducing the welding voltage
3. Using a travel speed slow enough so that the weld metal can completely fill all of
the melted out areas of the base metal
4. Cleaning the nozzle inside the contact tube, or removing the jammed electrode
wire
5. Pausing at each side of the weld bead when a weaving technique is used
6. Correcting the electrode angles being used
12.1.6 Lack of Fusion
Lack of fusion (Figure 11-109) occurs when the weld metal is not fused to the base
metal. This can occur between the weld
metal and the base metal or between
passes in a multiple-pass weld. This is less
of a problem with FCAW than with SMAW
and short-circuiting transfer GMAW because
of the deeper penetration obtained. More
care should be taken when using a weaving
technique because there is a greater
chance of creating this discontinuity.
Figure 11-109 — Lack of fusion.
Incomplete fusion between passes in a
multiple-pass weld often is the result of
welding over a previous weld bead that has excessive convexity. If an excessively
convex weld bead is created, the surface should be ground off enough so that complete
fusion can be made in the next pass. Causes of this defect can be:
1. Excessive travel speed
NAVEDTRA 14250A
11-121
2. Electrode size too large
3. Welding current too low
4. Poor joint preparation
5. Letting the weld metal get ahead of the arc
Lack of fusion can usually be prevented by:
1. Reducing the travel speed
2. Using a smaller diameter electrode
3. Increasing the welding current
4. Better joint preparation
5. Using a proper electrode angle
12.1.7 Overlapping
Overlapping (Figure 11-110) is the
protrusion of the weld metal over the edge
or toe of the weld bead. This defect can
cause an area of lack of fusion and create a
notch that can lead to crack initiation. If
overlapping is allowed to occur, grinding off
the excess weld metal after welding can be
done. Overlapping is often produced by:
Figure 11-110 — Overlapping.
1. A travel speed that is too slow, which
permits the weld puddle to get ahead of the electrode
2. An arc welding current that is too low
3. An incorrect electrode angle that allows the force of the arc to push the molten
weld metal over unfused sections of the base metal
Overlapping can be prevented by or corrected by:
1. A higher travel speed
2. Using a higher welding current
3. Using the correct electrode angle
12.1.8 Melt-Through
Melt-through (Figure 11-111) occurs when
the arc burns through the bottom of the
weld. It is usually caused by the heat input
being too high. This can be caused by:
1. Excessive welding current
2. Too slow of a travel speed
NAVEDTRA 14250A
Figure 11-111 — Melt-through.
11-122
3. Too wide of a root gap
This can be prevented by:
1. Reducing the welding current
2. Increasing the travel speed
3. Reducing the size of the root gap
12.1.9 Excessive Weld Spatter
FCAW may produce a small amount of spatter but excessive weld spatter creates a
poor weld appearance, wastes electrodes, causes difficult slag removal, and can lead to
incomplete fusion in multipass welds. Excessive spatter can also block the flow of
shielding gas from the nozzle that causes porosity. The amount of spatter produced by
FCAW will vary, depending on the type of metal transfer, type of electrode, and the type
of shielding gas used. (Electrode wires that produce a large droplet size globular metal
transfer will produce more spatter than those that produce a fine globular transfer. Selfshielded electrodes tend to produce higher spatter levels than gas-shielding types.)
The shielding gas provides slightly better arc stability. A gas-shielded electrode that is
used with carbon dioxide shielding will produce higher spatter levels than the same
electrode used with argon-carbon dioxide or argon-oxygen mixtures. This is due to the
coarser droplet size promoted by the carbon dioxide shielding. Excessive weld spatter
may also result from operating the electrode wire outside the operating ranges of
amperage, voltage, and electrode extension for which the manufacturer designed the
electrode. Methods of reducing the amount of spatter would be to reduce the welding
current, welding voltage, or electrode extension. When gas-shielded wires are being
used, changing the shielding gas from carbon dioxide to an argon-carbon dioxide
mixture will further reduce spatter levels. If spatter is caused, it can be removed by
grinding or chipping.
12.1.10 Arc Strikes
Many codes prohibit striking the arc on the surface of the workpiece. Striking the arc on
the base metal outside the weld joint can produce a hard spot on the base metal
surface. Failures can then occur due to the notch effect. The arc strikes might create a
small notch on the surface of the metal that can act as an initiating point for cracks.
12.1.11 Craters
Weld craters (Figure 11-112) are depressions on the weld surface at the point where
the arc was broken. These craters are caused by the solidification of the metal after the
arc has been broken. The weld crater often
cracks and can serve as an origin for linear
cracking back into the weld metal or into the
base metal. These craters can usually be
removed by chipping or grinding and the
depression can be filled in with a small
deposit of filler metal. The best way of
preventing weld craters is to reverse the
travel of the electrode a little way back into
Figure 11-112 — Weld crater.
the weld bead from the end of the weld
bead before breaking the arc. Another
NAVEDTRA 14250A
11-123
method is to stop the travel long enough to fill the crater before breaking the arc.
12.2.0 Cracking
An improper welding procedure, welder technique, or materials may cause cracking. All
types of cracking can be classified as either hot cracking or cold cracking, and these
cracks can be oriented transversely or longitudinally to the weld. Transverse cracks are
perpendicular to the axis of the weld, where longitudinal cracks are parallel to the axis of
the weld. Transverse cracks are often the result of longitudinal shrinkage strains acting
on excessively hard and brittle weld metal. Longitudinal cracks are often caused by high
joint restraint and high cooling rates. Hot cracking is a defect that occurs at higher
temperatures and generally happens just after the weld metal starts to solidify. This type
of cracking is often caused by excessive sulfur, phosphorous, and lead contents in the
base metal. It can also occur because of an improper method of breaking the arc or in a
root pass when the cross-sectional area of the weld bead is small compared to the
mass of the base metal. Hot cracking often occurs in deep penetrating welds and it can
continue through successive layers if it is not repaired. Hot cracking may be prevented
or minimized by:
1. Preheating
2. Using uncontaminated shielding gas, base metals, and filler metals
3. Increasing the cross-sectional area of the weld bead
4. Changing the contour of the weld bead
5. Using base metal with very low sulfur, phosphorous, and lead contents
6. Using filler metals that are high in manganese when welding steel
Crater cracks are shallow hot cracks that are caused by improperly breaking the arc.
Several types are shown in Figure 11-113.
Figure 11-113 — Crater cracks.
Crater cracks may be prevented the same way that craters are prevented: by reversing
the travel of the electrode a little way back into the weld from the end of the weld or
stopping the travel before breaking the arc.
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Cold cracking occurs after the weld metal solidification is complete. Cold cracking may
occur several days after welding and is generally caused by hydrogen embrittlement,
excessive joint restraint, and rapid cooling. Preheating, the use of a dry, high purity
shielding gas, and a proper cleaning procedure can help reduce this problem. Cold
cracking is often less of a problem with FCAW than GMAW because of the higher heat
input of FCAW, which provides more of a
preheating effect. The preheating helps to
reduce slightly the problems with cold
cracking due to excessive cooling rates.
Centerline cracks are cold cracks that often
occur in single-pass, concave fillet welds. A
centerline crack is a longitudinal crack that
runs down the center of the weld, as shown
in Figure 11-114.
Figure 11-114 — Centerline crack.
This problem may be caused by:
1. Too small of a weld bead for the thickness of the base metal
2. Poor fit-up
3. High joint restraint
4. Extension of a crater crack
The chief methods of preventing centerline
cracks are:
1. Increasing the bead size
2. Decreasing the gap width
3. Positioning the joint slightly uphill
4. Preventing weld craters
Figure 11-115 — Underbead
cracks.
Base metal and underbead cracks are cold
cracks that form in the heat-affected zone of the base metal. Underbead cracks occur
underneath the weld bead, as shown in Figure 11-115.
Base metal cracks are those cracks that originate in the heat-affected zone of the weld.
These types of cracking are caused by excessive joint restraint, hydrogen, and a brittle
microstructure. Rapid cooling causes a brittle microstructure or excessive heat input.
Underbead and base metal cracking can be reduced or eliminated by using preheat.
12.3.0 Other Problems
A number of other welding problems may occur, such as those caused by magnetic
fields, improper moisture, or indirect electrode arc.
12.3.1 Arc Blow
The electric current that flows through the electrode, workpiece, and work cable sets up
magnetic fields in a circular path perpendicular to the direction of the current. When the
magnetic fields around the arc are unbalanced, it tends to bend away from the greatest
concentration of the magnetic field. This deflection of the arc is called arc blow.
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Deflection is usually in the direction of travel or opposite to it, but it sometimes occurs to
the side. Arc blow can result in an irregular weld bead and incomplete fusion.
Direct current is susceptible to arc blow, especially when welding is being done in
corners and near the end of joints. Arc blow occurs with direct current because the
induced magnetic field is in one direction. Arc blow is shown in Figure 11-116.
Figure 11-116 — Arc blow.
Arc blow is often encountered when welding magnetized metal or near a magnetized
fixture. This problem also occurs when welding complex structures and on massive
structures with high currents and poor fit-up. Forward arc blow is encountered when
welding away from the ground connection or at the beginning of a weld joint. Backward
arc blow occurs toward the grounding connection, into a corner, or toward the end of a
weld joint. Several methods can be used to correct the arc blow problem:
1. Welding toward an existing weld or tack weld
2. Reducing the welding current and the arc voltage
3. Placing the work connection as far as possible from the weld, at the end of the
weld, or at the start of the weld, and weld toward the heavy tack weld
4. Change position of fixture or demagnetize base metal or fixture
12.3.2 Inadequate Shielding
Many discontinuities that occur in FCAW are caused by inadequate shielding of the arc.
Inadequate shielding can cause oxidation of the weld puddle and porosity in the weld
bead. This will usually appear as surface porosity. This problem can easily be detected
because the arc will change color, the weld bead will be discolored, and the arc will
become unstable and difficult to control.
The most common causes of this problem when using gas-shielded flux-cored arc wires
are:
1. Blockage of gas flow in the torch or hoses, or freezing of the regulator with
carbon dioxide
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2. A leak in the gas system
3. Weld spatter blocking the nozzle of the welding gun
4. A very high travel speed
5. Improper flow rate
6. Winds or drafts
7. Too much distance between nozzle and work
The most common causes of inadequate shielding for self-shielded electrodes are:
1. Electrode extension that is too short and does not allow proper activation of
shielding gas core components
2. A very high travel speed
3. Winds or drafts- self-shielding electrodes can withstand higher winds and drafts
than gas-shielded electrodes; popular for use in field conditions where wind is a
problem
In general, inadequate shielding is more of a problem with gas-shielding electrodes.
There are several ways that this problem can be corrected or prevented. The torch and
hoses should be checked before welding to make sure that the shielding gas can flow
freely and is not leaking. The nozzle and contact tube should be cleaned of spatter
regularly. A very high travel speed may leave the weld puddle or part of it exposed to
the atmosphere. This may be corrected, in some cases by inclining the gun in the
direction of travel, using a nozzle that directs shielding gas back over the heated area,
or by increasing the gas flow rate. The best method is to slow the travel speed.
Increasing the gas flow rate will increase the expense of the welding. An improper flow
rate may occasionally be a problem. For example, when using carbon dioxide shielding
in the overhead position, highest gas flow rates may have to be used to provide
adequate shielding. Carbon dioxide is heavier than air and will tend to fall away from the
weld area. An excessive gas flow rate can cause excessive turbulence in the weld
puddle. When winds or air drafts are present, several corrective steps may be taken.
One method is to switch from a gas-shielded electrode to a self-shielded electrode.
Setting up screens around the operation is another method of solving this problem.
Increasing the gas flow rate is helpful when using gas-shielded electrodes, or increasing
the electrode extension when using self-shielded electrodes. An excessive distance
between the end of the nozzle and the molten weld puddle will also create a problem in
providing adequate shielding, which can be corrected by shortening this distance.
12.3.3 Clogged or Dirty Contact Tube
The power delivered to the arc in FCAW depends on a transfer of current from the tip of
the contact tube to the electrode by means of a sliding contact tube. A clogged, dirty, or
worn contact tube can cause changes for power transferred to the electrode, which can
have an effect on the arc characteristics. It can also cause an irregular weld bead and
possible incomplete fusion because of the power fluctuations. A clogged contact tube
can stop the feed of the electrode wire, which stops the welding arc. A contact tube can
become dirty or clogged by spatter from the arc, by rust, scale, drawing compounds left
from the manufacture of the wire on the surface of the electrode, or by metal chips
created by tight wire feed rolls. These problems can best be prevented by making sure
that the electrode wire is clean and the wire feed rolls are tight enough to feed the wire
without creating chips. A wire wipe made of cloth is often attached to the wire feeder to
clean the electrode wire as it is fed.
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12.3.4 Wire Feed Stoppages
Wire feed stoppages are generally less of a problem with FCAW than with GMAW
because of the larger diameter electrode wires used in FCAW. However, this can still be
a problem. Wire feed stoppages cause the arc to be extinguished and can create an
irregular weld bead because of the stops and starts. Wire stoppages can also cause a
loss of welding time because many of the problems take a long time to correct when
wire becomes wrapped around the wire feed rolls, wadded up in bird nests in the wire
feeder, or broken. Wire feed stoppages can be caused by:
1. A clogged contact tube
2. A clogged circuit in the welding gun assembly
3. Sharp bends or kinks in the wire feed conduit
4. Excessive pressure on the wire feed roll, which can cause breakage of the wire
5. Inadequate pressure on the wire feed rolls
6. Attempting to feed the wire over excessively long distances
7. A spool of wire clamped too tightly to the wire reel support
Wire feed stoppages, in many cases, must be corrected by taking the disassembling the
gun and cutting and removing the wire, or by cutting and removing the wire from the
wire feeder. Both result in time lost to locate the problem and feed the new length of
wire through the assembly to the gun. Wire stoppages can be prevented by:
1. Cleaning the contact tube
2. Cleaning the conduit, which is usually done with compressed air
3. Straightening or replacing the wire feed conduit
4. Reducing the pressure on the wire feed rolls to prevent breakage
5. Increasing the pressure on the wire feed rolls to provide adequate driving force
6. Using a shorter distance from the wire feeder to the gun or from the wire feeder
to the electrode wire source
7. Reducing clamping pressure on the wire spool
13.0.0 POSTWELD PROCEDURE
Several operations may be required after welding, such as cleaning, inspection of the
welds, and postheating. These items may or may not be part of the procedure, the
operations performed will depend on the governing code or specification, type of metal,
and the quality of the weld deposit.
13.1.0 Cleaning
FCAW produces a moderate slag covering that must be removed after welding. Slag
removal is also required between passes of a multipass weld to prevent slag inclusions
and incomplete fusion.
Slag removal is generally done using a chipping hammer. A certain amount of spatter is
created in FCAW, which can make slag removal slightly more difficult. If an excessive
amount of spatter is created, slag removal may become very difficult. After the slag has
been removed, wire brushing or buffing can be done to remove the loose slag particles
and to remove discoloration around the bead. Mild steel brushes can be used on most
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steels but stainless steel brushes should be used on stainless steel to prevent
contamination. Spatter can be removed by grinding or wire brushing. FCAW usually
produces a smooth weld surface. If a different weld profile is needed, grinding can be
used, although grinding of weld profiles should be avoided due to the expense.
13.2.0 Inspection and Testing
Inspection and testing of the weld is done after cleaning to determine the quality of the
weld joint. There are many different methods of inspection and testing which will not be
covered in detail in this course. The uses of these methods wiII often depend on the
code or specification that covered the welding. Testing of a weldment may be done
nondestructively or destructively.
Nondestructive testing is used to locate defects in the weld and base metal. There are
many different nondestructive testing methods. Some of the most widely used methods
are visual, magnetic particle, liquid penetrant, ultrasonic, and radiographic. Visual,
magnetic particle and liquid penetrant inspection are used to locate surface defects,
while ultrasonic and radiographic inspections are used to locate internal defects.
Destructive testing is used to determine the mechanical properties of the weld, such as
the strength, ductility, and toughness. Destructive testing is also done by several
methods, depending on the mechanical properties being tested. Some of the most
common types of destructive testing are tensile bar tests, impact tests, and bend tests.
13.3.0 Repairing of Welds
Repairing the weld is usually needed when defects are found during inspection. When a
defect is found, it can be gouged, ground, chipped, or machined out, depending on the
type of material being welded. For steels, grinding and air carbon arc gouging are
commonly used. When maximum corrosion resistance is required, air carbon arc
gouging is used on stainless steels only when grinding or wire brushing of the groove
face to remove carbon deposits is done. For stainless steels, chipping is a common
method for removing defects. Air carbon arc gouging is preferred for many applications
because it is usually the quickest method. Grinding is popular for removing surface
defects and shallow-lying defects. Once the defects have been removed, the low areas
created by the grinding and gouging can be rewelded using FCAW or some other
welding process. The welds are then reinspected to make sure that the defects have
been properly repaired.
13.4.0 Postheating
Postheating is the heat treatment applied to the weld or weldment after welding.
Postheating is often required after the weld has been completed, depending on the type
of metal being welded, the specific application, and the governing code or
specifications. Many of the low-carbon and low-alloy steels are rarely postheated.
Various types of postheating are used to obtain specific properties. Some of the most
commonly used postheats are annealing, stress relieving, normalizing, and quenching
and tempering. Stress relieving is the most widely used heat treatment after welding.
Postheating is accomplished by most of the same methods that are used for preheating,
such as furnaces, induction coils, and electric resistance heating blankets. One method
used for stress relieving that does not involve the reheating of the weldments is called
vibratory stress relief. This method vibrates the weldment during or after welding to
relieve the residual stresses during or after solidification.
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Annealing is a process involving heating and cooling that is usually applied to induce
softening. This process is widely used on steels that become very hard and brittle
because of welding. There are several different kinds and when used on ferrous metals,
it is called full annealing. Full annealing is the heating up of a material to cause
recrystallization of the grain structure, which causes softening. This softening process is
done by heating a ferrous metal to a temperature above the transformation range and
slowly cooling to a temperature below this range. This process is usually done in a
furnace to provide a controlled cooling rate.
Normalizing is a heat treatment that is applied only to ferrous metals. Normalizing
occurs when the metal is heated to a temperature above the transformation range and
is cooled in still air to a temperature below this range. The main difference between
normalizing and annealing is that a normalized weldment is cooled in still air that
produces a quicker cooling rate and an annealed weldment is slowly cooled in a
furnace. A normalizing heat treatment will refine the metal grain size and give a tougher
weld, while an annealing heat treatment will result in a softer weld.
Stress relieving is the uniform heating of a weldment to a high enough temperature,
below the critical range, to relieve most of the residual stresses due to welding. This
operation is performed on many steels after welding to relieve the residual stresses due
to welding. This also reduces warpage during machining that may occur with a high
residual stress buildup. On parts and metals that are likely to crack due to the internal
stress created by welding, the parts should be put into stress relief immediately after
welding, without being allowed to cool to room temperature. The terms normalizing and
annealing are misnomers for this heat treatment.
Quenching and tempering is another postweld heat treatment commonly used. The
metal is heated up and then quenched to form a hard and brittle metallurgical structure.
The weldment is then tempered by reheating to a particular temperature, dependent on
the degree of ductility, strength, toughness, and hardness desired. Tempering reduces
the hardness of the part as it increases the strength, toughness, and ductility of the
weld.
Test your Knowledge (Select the Correct Response)
10.
What causes slag inclusions?
A.
B.
C.
D.
11.
Steady travel speed
A weaving motion that is too narrow
Slag left on the previous weld pass
Using an electrode that is too small
Which of the following is a nondestructive test?
A.
B.
C.
D.
Etching
Liquid penetrant
Tensile strength
Free-bend
14.0.0 WELDER TRAINING and QUALIFICATION
To become a fully certified welder, you must know the requirements for training and
qualifications. While these requirements may differ somewhat from organization to
organization, and you may need to demonstrate your skills to qualify for a particular
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project and specific welding task, the basic guidelines are the same for achieving the
training and qualifications.
14.1.0 Welder Training
FCAW requires a certain degree of skill to produce good quality welds. In
semiautomatic welding, the welder has to manipulate the welding gun and control the
speed of travel. Less skill is required to operate this process when compared to the
manual welding processes because the machine controls the arc length and feeds the
electrode wire. Welders skilled in manual welding processes and GMAW generally have
less difficulty learning FCAW. This process uses similar equipment and welding
techniques to those used in GMAW. At higher current levels, when using larger
diameter wires, FCAW has a smoother arc and is easier to handle than larger diameter
solid wires with a carbon dioxide shielding. Because of the deep penetrating
characteristics of the process, lack of fusion and incomplete penetration are easier to
avoid and compensate for than GMAW using short-circuiting transfer.
The exact content of a training program will vary, depending on the specific application
of the process. A training program should have enough flexibility so that it can be
adapted to changing needs and applications. Because of this, the emphasis may be
placed on certain areas of training based on the complexity of the parts to be welded,
type of metal, and governing code or specification. A welding course that covers all
position welding requires more training time than one that simply covers flat position
welding only. A welding course for pipe requires more training time than one for welding
plate. The major purpose of the training program is to give the welder the skill and
knowledge to be able to do the best job possible. A training program may be broken up
into several areas, depending on the training requirements of the student.
14.1.1 Basic Flux Cored Arc Welding
The basic FCAW training program is used to teach the students the basic skills
necessary to weld plate. This course provides training on how to make quality fillet and
groove welds. The course also gives the students the knowledge of how to set up the
equipment, clean the base metal, basic operating principles, and the difficulties that are
commonly encountered. The training also covers the different welding techniques used
for gas-shielded and self-shielded electrodes. Also covered are the techniques for
welding out-of-position using small diameter electrodes. The training obtained by the
student should give the skill to perform a job welding plate. This course should also
provide the background skill and knowledge required to take an advanced course for a
specific application, such as for welding pipe. The following is an outline for a course
approximately 35 hours long:
Topic
1. Flux Cored Arc Welding Introduction
2. Safety and Health of Welders
3. Stringer Bead, Flat Position and Adjustment of the Welding Equipment for GasShielded Electrodes
4. Fillet Weld, Lap Joint, Flat Position with a Gas-Shielded Electrode
5. Fillet Weld, Lap Joint, Horizontal Position with a Gas-Shielded Electrode
6. Equipment Set-up, Operation, and Adjustment
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7. Stringer Bead, Flat Position and Adjustment of the Welding Equipment for SelfShielded Electrodes
8. Fillet Weld, Lap Joint, Flat Position with a Self-Shielded Electrode
9. Fillet Weld, Lap Joint, and Horizontal Position with a Self-Shielded Electrode
10. Joint Preparation and Weld Quality
11. Single-V-Groove Weld, and Butt Joint, Flat Position with a Gas-Shielded
Electrode
12. Single-Bevel-Groove Weld, Butt Joint, Horizontal Position with a Gas-Shielded
Electrode
13. Single-Bevel-Groove Weld, Butt Joint, Horizontal Position, Cut and Etch Test
14. Fillet Weld, Tee Joint, Vertical Position - Uphill Travel with an All-Position GasShielded Electrode.
15. Single-V-Groove Weld, Butt Joint, Vertical Position - Uphill Travel with an AllPosition Gas-Shielded Electrode
16. Single-V-Groove Weld, Butt Joint, Vertical Position - Uphill Travel, Guided Bend
Test
17. Fillet Weld, Tee Joint, Overhead Position with an All-Position Gas-Shielded
Electrode
14.2.0 Welder Qualification
Before a welder can begin work on any job covered by a welding code or specification,
he or she must become certified under the code that applies. Many different codes are
in use today, and it is exceedingly important that the specific code is referred to when
taking qualification tests. In general, the following type of work is covered by codes:
pressure vessels and pressure piping, highway and railway bridges, public buildings,
tanks and containers that will hold flammable or explosive materials, cross country
pipeline, aircraft, ordnance material, ships and boats, and nuclear power plants.
Several of the specifications include consideration of the FCAW process. These are:
1. ASME Boiler and Pressure Vessel Code, Section IX, Welding and Brazing
Qualifications
2. AWS 01.1, Structural Welding Code
3. AWS 05.2, Standard for Welded Steel Elevated Tanks, Standpipes, and
Reservoirs for Water Storage
4. AWS 010.9, Standard for Qualification of Welding Procedures and Welders for
Piping
5. AWS 014.1, Specification for Welding Industrial and Mill Cranes
6. AWS 014.2, Specification for Metal Cutting Machine Tool Weldments
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7. AWS 014.3, Specification for Welding Earthmoving and Construction Equipment
8. API 1104 Standard for Welding Pipelines and Related Facilities
9. Marine Engineering Regulations and Material Specifications (CG 115)
These specifications do not provide qualifications of the FCAW process for all
applications and service requirements. For applications where AWS or other
specifications are not available or do not apply and general criteria for qualification is
desired, AWS B2.1, Standard for Welding Procedure and Performance Qualification, is
often used. Qualification is obtained differently under the various codes. Qualification
under one code will not necessarily qualify a welder to weld under a different code. In
most cases, qualification for one employer will not allow the welder to work for another
employer. If the welder uses a different process or the welding procedure is altered
drastically, requalification is required. In most cases, if the welder is continually;
employed, welding requalification is not required, providing the work performed meets
the quality requirements.
Responsible manufacturers or contractors may give qualifications tests. On pressure
vessel work, the welding procedure must also be qualified and this will be done before
the welders are qualified. Under other codes, this is not necessary. To become
qualified, the welder must make specified welds using the required process, base metal,
base metal thickness, electrode type, position, and joint design. For example, in the
AWS Structural Welding Code (D1.1), certain joint designs are considered prequalified
for FCAW. Test specimens must be made according to standardized sizes and under
the observation of a qualified person. For most government specifications, a
government inspector must witness the making of weld specimens. Specimens must be
properly identified and prepared for testing. The most common test is a guided bend
test. In some cases, radiographic examinations, fracture tests, or other tests are used.
Satisfactory completion of test specimens, provided that they meet acceptability
standards, will qualify the welder for specific types of welding. Again, the welding that
will be allowed depends on the particular code. In general, the code indicates the range
of thicknesses that may be welded, the positions that may be used, and the alloys that
may be welded.
Qualification of welders is a highly technical subject and cannot be covered fully here.
You should obtain and study the actual code prior to taking any tests.
15.0.0 WELDING SAFETY
Safety is an important consideration when welding. Every welding shop should have a
safety program and take adequate safety precautions to help protect welders. The
welders should also be made aware of safety precautions and procedures. Employees
who fail to follow adequate safety precautions can cause physical injury to themselves
and others, and damage property. Any of these conditions can result in physical
discomfort and loss of property, time, and money. Welding is a safe occupation when
safety rules and common sense are followed. A set of safety rules is presented in the
American National Standard Z49.1, "Safety in Welding and Cutting," published by the
American Welding Society, which should be followed.
There are several types of hazards associated with FCAW. These hazards do not
necessarily result in serious injuries. They can also be of a minor nature, which can
cause discomforts that irritate and reduce the efficiency of the welders. These hazards
are:
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1. Electrical shock
2. Arc radiation
3. Air contamination
4. Compressed Gases
5. Fire and explosion
6. Weld cleaning and other hazards
15.1.0 Electrical Shock
There are several precautions that should be taken to prevent an electrical shock
hazard. The first item that should be done before welding is to make sure the arc
welding equipment is installed properly, grounded, and in good working condition. The
electrical equipment should be maintained and installed in accordance with the National
Electrical Code and any state and local codes that apply. Power supplies should be
connected to an adequate electrical ground, such as an approved building ground, cold
water pipe, or ground rod. Power supplies are connected to ground through the cable
that connects the power supply to the electrical system ground. Cables with frayed or
cracked insulation and faulty or badly worn connections can cause electrical short
circuits and shocks. If it is necessary to splice lengths of welding cable together, the
electrical connections should be tight and insulated. The proper size welding cables
should also be used because constantly overloading a welding cable that is too small
can destroy the insulation and create bare spots in the insulation. This occurs because
excessive heat builds up in the cable and destroys the insulation. An improperly
insulated welding cable is both an electrical shock hazard and a fire hazard.
The welding area should be dry and free of any standing water, which could cause
electrical shock. When it is necessary to weld in a damp or wet area, the welder should
wear rubber boots and stand on a dry, insulated platform.
15.2.0 Arc Radiation
The welding arc of FCAW emits large amounts of invisible ultraviolet and infrared rays.
Skin exposed to the arc, even for a short time, can suffer serious ultraviolet and infrared
burns, which are essentially the same as sunburn, but the burn caused by welding can
take place in a much shorter time and can be very painful. Because of this, the welder
should always wear protective clothing suitable for the welding to be done. These
clothes should be fairly heavy and not easily burned. Leather is often used to make
jackets, capes and bibs, or other similar arrangements to shield the arms, shoulders,
chest, and stomach from the arc radiation and arc spatter. Leather is also used to make
gloves and gauntlets for the welder.
The eyes must also be protected from the radiation emitted by the welding arc. Arc-burn
can result if the eyes are not protected. Arc-burn of the eye is similar to sunburn of the
skin and it is extremely painful for about 24 to 48 hours. Usually, arc-burn does not
permanently injure the eyes, but it can cause intense pain as though several grains of
sand were in your eyes. There are several commercial solutions available to soothe the
skin and eyes during the period of suffering.
Infrared arc rays can cause fatigue of the retina of the eye. The effects of infrared rays
are not nearly as noticeable or immediate as the effects of ultraviolet rays. Infrared rays
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are probably more dangerous in that their effects can be longer lasting and result in
impaired vision.
The flux-cored welding arc is a relatively high energy arc that is much brighter than
lower current welding arcs. Even though more smoke is given off from the arc area, it
does not shield arc rays effectively.
The best protection for the eyes and face is provided by a headshield that has a window
set in it with a filter lens in the window. Headshields are generally made of fiberglass or
a pressed fiber material that is lightweight. The filter lens is made of a dark glass
capable of absorbing infrared rays, ultraviolet rays, and most visible light coming from
the arc. The type of lens used varies for different welders but it should be dark enough
so the arc can be viewed without discomfort, yet not so dark the welder cannot see what
he or she is doing. Table 11-23 shows the different lenses commonly recommended for
use in shielded metal arc welding. The higher the lens numbers, the darker the lens. A
clear, replaceable glass should be put on the outside of the welding lens to protect it
from spatter and breakage.
Table 11-23— Recommended Filter Lens Shades Used in Shielded Metal Arc
Welding (ANSI/AWS Z49.1)
Welding Current
Range-Amperes
Lens Shade Number
75-200
10 to 11
200-400
12 to 13
Above 400
14
15.3.0 Air Contamination
One of the main problems with FCAW is that it gives off more smoke and fumes than
processes such as GTAW, GMAW, and SAW. It even tends to produce higher smoke
and fume levels than SMAW. A hazard warning for fume is placed on the electrode wire
box.
The welding area should be adequately ventilated because fumes and gases, such as
ozone, carbon monoxide, and carbon
dioxide, are hazardous for the welder to
breathe. When welding is done in confined
areas, an external air supply is required.
This is furnished by the use of a respirator
on a special helmet. A second person
should stand just outside the confined area
to lend assistance to the welder, if
necessary. Another method is to use an
exhaust system to remove welding fumes.
Special fume extractor nozzles attached to
the welding gun are popular for use with
FCAW to reduce the smoke levels
produced. These nozzles are connected to
a filter and an exhaust pump, which greatly
Figure 11-117 — FCAW with fume
reduce the smoke level as shown in Figure
extractor nozzle.
11-117.
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The shielding gas may displace the air that the welder needs for breathing. Because of
this, welding should not be done in an enclosed area or hole, which can cause
suffocation without the use of a respirator. Welding should never be done near
degreasing and cleaning operations. The fumes from chlorinated solvents used for
cleaning form a very toxic gas, called phosgene, when exposed to an arc. A mechanical
exhaust system should be used when welding metals with lead, cadmium, and zinc
coatings. AWS/ANSI Z49.1 should be consulted for ventilation requirements.
15.4.0 Compressed Gases
The shielding gas used for FCAW is compressed and stored in cylinders. One
advantage of self-shielded flux-cored wire is that compressed gas cylinders are not
required, so this is primarily a safety consideration when gas-shielded electrodes are
used. Improper handling of compressed gas cylinders can create a safety hazard. When
in use, gas cylinders should be secured to a wall or other structural support. The valve
of the cylinder should be opened slowly and the welder should stand away from the face
of the regulator when doing this. The welding arc should never be struck on a
compressed gas cylinder. When not in use, gas cylinders should be stored with their
caps on. Caps should also be on when they are moved. If the valve would get knocked
off, the cylinder acts like a missile because of the escaping gas and can cause injury
and damage. When compressed gas cylinders are empty, the valve should be closed
and they should be marked as empty. This is done by marking the letters, "MT" or
"EMPTY" on the cylinder.
15.5.0 Fires and Explosions
Fires and explosions are hazards that can exist in a welding area if the proper
precautions are not taken. The FCAW process produces sparks and spatters which can
start a fire or explosion in the welding area if not kept free of flammable, volatile, or
explosive materials. Welding should never be done near degreasing and other, similar
operations. Welders should wear leather clothing for protection from burns because
leather is fireproof. Fires can also be started by an electrical short or by overheated,
worn cables. In case of a fire started by a flammable liquid or an electrical fire, a CO2 or
dry chemical type of fire extinguisher is used. Fire extinguishers should be kept at
handy spots around the shop and welders should make a mental note of where they are
located.
Other precautions that have to do with explosions are also important. A welder should
not weld on containers that have held combustibles unless it is absolutely certain there
are no fumes or residue left. Welding should not be done on sealed containers without
providing vents and taking special precautions. The welding arc should never be struck
on a compressed gas cylinder. When the electrode holder is set down or not in use, it
should never be allowed to touch a compressed gas cylinder.
15.6.0 Weld Cleaning and Other Hazards
Hazards can also be encountered during the weld cleaning process. Precautions must
be taken to protect the skin and eyes from hot slag particles. FCAW produces a
moderate slag covering which much be removed. The welding helmet, gloves, and
heavy clothing protect the skin from slag chipping and grinding of the weld metal. Safety
glasses should also be worn underneath the welding helmet to protect the eyes from
particles that could get inside the welding helmet. Screens should be set up if there are
other people in the area to protect them from arc burn.
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15.7.0 Summary of Safety Precautions
1. Make sure your arc welding equipment is properly installed, grounded, and in
good working condition.
2. Always wear protective clothing suitable for the welding to be done.
3. Always wear proper eye protection when welding, grinding, or cutting.
4. Keep your work area clean and free of hazards. Make sure no flammable,
volatile, or explosive materials are in or near the work area.
5. Handle all compressed gas cylinders with extreme care. Keep caps on when not
in use.
6. When compressed gas cylinders are empty, close the valve, and mark the
cylinder “EMPTY”.
7. Do not weld in a confined space without special precautions.
8. Do not weld on containers that have held combustibles without taking special
precaution.
9. Do not weld on sealed containers or compartments without providing vents and
taking special precautions.
10. Use mechanical exhaust at the point of welding when welding lead, cadmium,
chromium, manganese, brass, bronze, zinc, or galvanized steel.
11. When it is necessary to weld in a damp or wet area, wear rubber boots and stand
on a dry, insulated platform.
12. Shield others from the light rays produced by your welding arc.
13. Do not weld near degreasing operations.
14. When the welding gun is in use, do not hang it on a compressed gas cylinder.
Summary
This chapter has introduced you to the FCAW process, from the types of power
sources, controls, and electrodes to the types of training and qualifications needed. It
also described the industries that use the FCAW process and its applications. Welding
metallurgy, weld and joint design, and welding procedure variables were also
discussed. The chapter finished up with a description of weld defects and how to
identify them, then covered welder training and the common safety precautions
applicable to all welding processes. As always, use the manufacturer’s operator
manuals for the specific setup and safety procedures of the welder you will be using.
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Review Questions (Select the Correct Response)
1.
What type of current is used in flux cored arc welding?
A.
B.
C.
D.
2.
What is the main advantage of self shielding flux cored electrodes?
A.
B.
C.
D.
3.
Horizontal position only
Flat position only
Horizontal and flat positions
Vertical and overhead
What is the largest diameter electrode that can be used for vertical and overhead
welding?
A.
B.
C.
D.
6.
E118T-1
E802T-2
E801T-2
E7018-1
A welding electrode that has an AWS classification of E700T should be used for
a metal-arc welding job in what position(s)?
A.
B.
C.
D.
5.
Formation of slag
Prevention of oxidation
Simplified process
All of the above
An electrode that has a minimum tensile strength of 80,000 psi for use in all
positions for low alloy has what designation?
A.
B.
C.
D.
4.
Constant
Indirect
Unmodulated low frequency
Modulated high frequency
1/16-inch
1/8-inch
3/16-inch
5/32-inch
Which of the following properties is the basic rule for selecting an electrode for a
job?
A.
B.
C.
D.
Great tensile strength
Composition similar to the base metal
The melting temperature
The least expensive
NAVEDTRA 14250A
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7.
When the electrode is positive and the workpiece is negative, the electrons flow
from the workpiece to the electrode. What polarity is being used?
A.
B.
C.
D.
8.
Which one of the following steps do you take to correct arc blow?
A.
B.
C.
D.
9.
15° to 20°
20° to 45°
45° to 60°
60° to 90°
When using gas shielded electrodes, what angle is used for maximum
penetration?
A.
B.
C.
D.
12.
It is withdrawn slowly from the crater after the arc has lengthened.
It is held stationary until the crater is filled, then withdrawn slowly.
It is held stationary until the equipment is secured.
It is lowered into the crater until contact is made, then quickly withdrawn.
What drag angle is used for flat and horizontal position welding using self
shielded electrodes?
A.
B.
C.
D.
11.
Change the polarity of the work piece.
Weld toward the edge of the workpiece from the ground clamp.
Reduce the weld current.
All of the above
Of the following practices, which one is correct for breaking an arc with an
electrode?
A.
B.
C.
D.
10.
Straight
Negative
Positive
Reverse
5°
10°
15°
20°
For which of the following reasons do you use relatively small electrodes for
overhead butt welding?
A.
B.
C.
D.
A long arc is needed to penetrate to the root of the joint.
A short arc is needed to develop penetration at the root of the joint.
Reduced current flow through the small electrode is needed to create a
fluid puddle.
Accelerated current flow is needed to control the fluid puddle.
NAVEDTRA 14250A
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13.
Which of the following mistakes can cause undercutting in welds?
A.
B.
C.
D.
14.
Which of the following mistakes can cause excessive spatter in welds?
A.
B.
C.
D.
15.
Current too low
Current too high
Rigid joints
Faulty postheating
When pipe has _____ wall thickness, only the single U-type of butt joint should
be used.
A.
B.
C.
D.
19.
Current too low
Current too high
Welding speed too slow
Rigid joints
Which of the following mistakes can cause brittle welds?
A.
B.
C.
D.
18.
Improper welding technique
Improper welder technique
Improper material
All of the above
Which of the following mistakes can cause poor penetration?
A.
B.
C.
D.
17.
Arc too short
Arc too long
Current too low
Rigid joints
Which of the following mistakes can cause cracked welds?
A.
B.
C.
D.
16.
Current too high
Current too low
Faulty preheating
Joints too rigid
1/4-inch or less
1/2-inch or less
1/2-inch or more
3/4-inch or more
You do NOT need to do which of the following procedures when preparing a joint
for welding?
A.
B.
C.
D.
Clean the edges of surfaces to be welded
Adjust the joint surfaces so they are smooth and uniform
Remove slag from flame-cut edges
Remove temper color
NAVEDTRA 14250A
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20.
What maximum nominal diameter of electrode should you NOT exceed when
making the root pass of a multilayer weld on pipe?
A.
B.
C.
D.
21.
The root of a fillet weld is where the _____.
A.
B.
C.
D.
22.
length of the weld
distance from the root of the joint to the toe
groove face adjacent to the root joint
exposed surface of the weld
The throat of a fillet is the shortest distance from the _____.
A.
B.
C.
D.
26.
junction between the face of the weld and the base metal
rippled surface of the weld
root of the weld to the face
edge of the weld that intersects the base metal
The leg of the weld is the _____.
A.
B.
C.
D.
25.
exposed surface of the weld
edge of the weld that intersects the base metal
groove face adjacent to the root joint
separation between the members to be joined
The toe of a fillet weld is the _____.
A.
B.
C.
D.
24.
edge of the weld intersects the base metal
back of the weld intersects the base metal surfaces
face of the weld and the base metal meet
face and the toe meet
The face of a fillet weld is the _____.
A.
B.
C.
D.
23.
3/32-inch
1/8-inch
3/16-inch
1/4-inch
face to the toe
root of the weld to the face
root to the toe
toe to the leg
Welding machine installations should be _____.
A.
B.
C.
D.
installed according to electrical codes
plugged into the nearest receptacle
connected to mobile generators only
simple with no grounding
NAVEDTRA 14250A
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27.
Welding machine frames should be _____.
A.
B.
C.
D.
28.
The welding arc gives off ultra-violet rays, which can cause eye injury. Injury can
be prevented by _____.
A.
B.
C.
D.
29.
Immediately
After drawing back the electrode
After the weld puddle is formed
Before the formation of slag
When welding over a previously deposited bead, _____.
A.
B.
C.
D.
33.
are hazardous
can be ignored
are used as shielding gases
are inert gases
After striking an arc, when should the travel angle start?
A.
B.
C.
D.
32.
do not damage skin
can cause skin damage similar to sunburn.
are a good source of vitamin C
are harmful if inhaled
Vaporized metals, such as zinc, cadmium, lead, and beryllium _____.
A.
B.
C.
D.
31.
wearing the proper lens shade in the helmet
using eye drops
closing your eyes
turning your head away from the arc
Ultra-violet rays from the arc _____.
A.
B.
C.
D.
30.
grounded electrically
not grounded electrically
rigid and heavy
insulated from ground
hold a long arc to melt the slag on the previous bead
use a weaving motion for deep penetration
tap the weld bead and electrode several times
clean the previous bead thoroughly before depositing the next weld
At the completion of the weld, the crater should _____.
A.
B.
C.
D.
overlap the workpiece
be filled to the height of the bead
remain unfilled
be twice the size it originally was
NAVEDTRA 14250A
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34.
Horizontal position fillet welding is done from the_____.
A.
B.
C.
D.
35.
In the flat position welding, the face of the weld is approximately _____.
A.
B.
C.
D.
36.
Complete range
Middle range
Upper range
Lower range
Tack welds should be _____.
A.
B.
C.
D.
40.
Amperage
Voltage
Electrode angle
Electrode diameter
When reading current ranges in a welding schedule, fillet welds use the _____.
A.
B.
C.
D.
39.
10-20°
20-30°
30-40°
45-90°
What determines the direction the arc force applies to the weld pool?
A.
B.
C.
D.
38.
perpendicular
at a right angle
horizontal
vertical
At what angle should you hold the electrode when making lap joints with metal of
differing thickness?
A.
B.
C.
D.
37.
upper side of the joint
lower side of the joint
perpendicular to the weld
opposite side of the face of the joint
cleaned before the full weld is made
half the length of the weld joint
welded over without cleaning
only on opposite corners
(True or False) You are responsible for performing all checks and procedure
steps before, during, and after welding.
A.
B.
True
False
NAVEDTRA 14250A
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41.
How do you clean the slag form a weld bead?
A.
B.
C.
D.
42.
(True or False) You must be certified under the code that applies to the type of
welding you will be doing.
A.
B.
43.
True
False
A destructive test is _____.
A.
B.
C.
D.
45.
True
False
(True or False) A sound weld can be made over dirt, paint, and grease if the
correct electrode is used.
A.
B.
44.
Hammer
High Pressure air
Mechanical disc
Chemicals
a good way to test workmanship
used to test a break fixture
a type of nondestructive testing
only used for small jobs
It is necessary to know the position in which welding is to be done _____.
A.
B.
C.
D.
only when selecting iron powder electrodes
when making any electrode selection
when selecting electrodes that end in EXXT only
to select the proper welding machine to use
NAVEDTRA 14250A
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Trade Terms Introduced in this Chapter
Alloying
An alloy is a compound of one or more metals or other
elements. For example, brass is the alloy of copper and
zinc.
Austenitic
Consisting mainly of austenite, which is a nonmagnetic
solid solution of ferric carbide, or carbon in iron used in
making corrosion-resistant steel.
Ferritic
Consisting of the pure iron constituent of ferrous metals,
as distinguished from the iron carbides.
Ferrous
An adjective used to indicate the presence of iron. The
word is derived from the Latin word ferrum ("iron").
Ferrous metals include steel and pig iron (with a carbon
content of a few percent) and alloys of iron with other
metals (such as stainless steel).
Nonferrous
The term used to indicate metals other than iron and
alloys that do not contain an appreciable amount of iron.
NAVEDTRA 14250A
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Additional Resources and References
This chapter is intended to present thorough resources for task training. The following
reference works are suggested for further study. This is optional material for continued
education rather than for task training.
Principles of Shielded Metal Arc Welding, Miller Electric Manufacturing Company,
Appleton, WI.
Safety in Welding, Cutting, and Allied Processes, ANSI/ASC Z49.1:2005 An American
National Standard, American Welding Society, Miami FL, 2005.
Shielded Metal Arc Welding, Hobart Institute of Welding Technology , Troy Ohio,1998.
Welding and Allied Processes, S9086-CH-STM-010/CH-074R4, Commander, Naval
Sea Systems Command, Washington Navy Yard, Washington D.C.,1999.
Welding Theory and Application, TC 9-237, Department of the Army Technical Manual,
Headquarters, Department of the Army, Washington D.C., 1993.
Welding Theory and Application, TM 9-237, Department of the Army Technical Manual,
Headquarters, Department of the Army, Washington D.C., 1976.
NAVEDTRA 14250A
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NAVEDTRA 14250A
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