ESAB MIG Welding Handbook

7/30/2019 ESAB MIG Welding Handbook

1/138

Introduction

In Gas Metal Arc Welding (GMAW), also known as Metal Inert Gas (MIG) welding, an electric arc is

established between the workpiece and a consumable bare wire electrode. The arc continuously melts the

wire as it is fed to the weld puddle. The weld metal is shielded from the atmosphere by a flow of an inert

gas, or gas mixture. Figure 1-1 shows this process and a portion of the welding torch.

The mig welding process operates on D.C. (direct current) usually with the wire electrode positive. This is

known as reversepolarity. Straightpolarity, is seldom used because of poor transfer of molten metal from

the wire electrode to the workpiece. Welding currents of from 50 amperes up to more than 600 amperes are

commonly used at welding voltages of 15V to 32V. A stable, self correcting arc is obtained by using theconstant potential (voltage) power system and a constant wire feed speed.

Continuing developments have made the mig process applicable to the welding of all commercially

important metals such as steel, aluminum, stainless steel, copper and several others. Materials above .030

in. (.76 mm) thick can be welded in all positions, including flat, vertical and overhead.

It is simple to choose the equipment, wire electrode, shielding gas, and welding conditions capable of

producing high-quality welds at a low cost.

Basic Mig Welding Process

1

Variations-Metal

Transfer

Introduction

Equipment

Description

Short ArcWeldingPower

Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


2/138

2

ADVANTAGES

The mig welding process provides many advantages in manual and automatic metal joining for both low and

high production applications. Its combined advantages when compared to covered (stick) electrode,

submerged arc, and tig are:

1) Welding can be done in all positions.

2) No slag removal required.

3) High weld metal deposition rate.

4) Overall times for weld completion about 1/2 that of covered electrode.

5) High welding speeds. Less distortion of the workpiece.

6) High weld quality.

7) Large gaps filled or bridged easily, making certain kinds of repair welding more efficient.

8) No stub loss as with covered electrode.

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


3/138

3

Process Variations-Metal Transfer

The basic mig process includes three distinctive process techniques: short circuiting metal transfer, globular

transfer, and spray arc. These techniques describe the manner in which metal is transferred from the wire to

the weld pool. In short circuiting metal transfer, also known as Short Arc, Dip Transfer, and Microwire,

metal transfer occurs when an electrical short circuit is established. This occurs as the molten metal at the

end of the wire touches the molten weld pool. In spray arc welding, small molten drops of metal are

detached from the tip of the wire and projected by electromagnetic forces towards the weld pool. Globular

transfer occurs when the drops of metal are quite large and move toward the weld pool under the influence

of gravity. Factors that determine the manner of metal transfer are the welding current, wire size, arc length

(voltage), power supply characteristics, and shielding gas.

Figure 1-1 Types of Metal Transfer

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


4/138

4

Short Circuit (Short Arc) Welding

Short arc welding uses small wire in the range of .030 in. (.76 mm) to .045 in. (1.1 mm) diameter andoperates at low arc lengths (low voltages) and welding currents. A small, fast-freezing weld puddle is

obtained. This welding technique is particularly useful for joining thin materials in any position, thick

materials in the vertical and overhead position, and for filling large gaps. Short arc welding should also be

used where minimum distortion of the workpiece is a requirement.

Metal is transferred from the wire to the weld pool only when contact between the two is made, or at each

short circuit. The wire short circuits to the workpiece 20 to 200 times per second.

Figure 1-2 - Current-Voltage vs. Time Typical Short Arc Cycle

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


5/138

5

Figure 1- 2 illustrates one complete short arc cycle. As the wire touches the weld pool (A), current begins to

rise to a short circuit current. When this high current is reached, the metal is transferred. The arc is thenreignited. Because the wire is being fed faster than the arc can melt it, the arc will eventually be

extinguished by another short (I). The cycle begins again. There is no metal transferred during the arcing

period; only at the short circuits.

To insure good arc stability, relatively low welding currents must be employed when using the short arc

technique. Table 1-1 illustrates the optimum current range for short circuiting metal transfer with several wire

sizes. These ranges can be broadened, depending upon the shielding gas selected.

Table 1-1 Optimum Short Arc Current Range for Various Steel Wires

WIRE ELECTRODE DIAM. WELDING CURRENT (AMPS)

IN. mm MINIMUM MAXIMUM

.76 50 150

.035 .89 75 175

.045 1.1 100 225

.030

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


6/138

6

Globular Transfer

As the welding current and voltage are increased above the maximum recommended for short arc welding,metal transfer will begin to take on a different appearance. This welding technique is commonly known as

globular transfer, with metal transferring through the arc. Usually, the drops of molten metal have a greater

diameter than the wire itself. This mode of metal transfer can be erratic, with spatter and occasional short

circuiting being common.

Table 1-2 Minimum Current for Spray Arc Welding

WIRE

ELECTRODE

DIAMETER

MINIMUM

WIRE ELECTRODE SHIELDING SPRAY ARC

TYPE IN. mm GAS CURRENT (AMP)

MILD STEEL .030 .76 98% ARGON-2% OXY 150

MILD STEEL .035 .89 98% ARGON-2% OXY 165

MILD STEEL .045 1.1 98% ARGON-2% OXY 220



STAINLESS STEEL .035 .89 99% ARGON-1% OXY 170

STAINLESS STEEL .045 1.1 99% ARGON-1% OXY 225

STAINLESS STEEL .062 1.6 99% ARGON-1% OXY 285

ALUMI NUM .030 .76 ARGON 95

ALUMIN UM .046 1.19 ARGON 135

ALUMINUM .062 1.6 ARGON 180

DEOXI DIZED COPPER .035 .89 ARGON 180

DEOXIDIZED COPPER .045 1.1 ARGON 210

DEOXIDIZED COPPER .062 1.6 ARGON 310

SILICON BRONZE .035 .89 ARGON 165

SILICON BRONZE .045 1.1 ARGON 205

SILICON BRONZ E .062 1.6 ARGON 270

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


7/138

7

Continued on next page...

Spray Arc Welding

By raising the welding current and voltage still further, the metal transfer will become a true spray arc. The

minimum welding current at which this occurs is called the transition current. Table 1-2 shows typical values

of transition current for various filler metals and shielding gases. As seen in this table, the transition current

depends on the metal wire diameter and shielding gas. However, if the shielding gas for welding carbon

steel contains more than about 15% CO2there is no transition from globular transfer to spray transfer.

Figure 1-3 shows the typical fine arc column and pointed wire of the spray arc. The molten drops from the

wire are very small, affording good arc stability. Short circuiting is rare. Little spatter is associated with this

welding technique.Spray arc welding can produce high deposition rates of weld metal. This welding technique is generally used

for joining materials 3/32 in. (2.4mm) and greater in thickness. Except when welding aluminum or copper,

the spray arc process is generally restricted to welding in the flat position only because of the large weld

puddle. However, mild steel can be welded out of position with this technique when small weld puddles are

used; generally with a .035 in. (.89mm) or .045 in. (1.1mm) diameter wires.

Figure 1-3

Spray Arc Welding Technique

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


8/138

8

A variation of this spray arc technique is known as pulsed spray welding. In pulsed spray arc welding, the

current is varied between a high and low value. The low level of current is below the transition current whilethe high level is well into the spray arc region. Metal is only transferred to the work during the period of high

current. Usually one droplet is transferred during each high current pulse. Figure 1-4 depicts the welding

current pattern used in pulsed spray arc welding. In the United States, only 60 or 120 pulses per second are

used. Because the peak current is in the spray arc region, arc stability is similar to that of conventional spray

arc welding. The period of low current maintains the arc and serves to reduce the average current. Thus, the

pulse spray technique will produce a spray arc at lower average current levels than are required for

conventional spray arc welding. The lower average current makes it possible to weld thinner gauge

materials with spray type transfer using larger sized wire electrodes than otherwise possible. Pulsed spray

arc welding can also be used for out-of-position welding of heavier sections.

Figure 1-4 - Pulsed Spray Arc Welding Technique

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


9/138

9

Cored Wire Welding

The flux-cored electrode is a continuous, tubular electrode wire, with a sheath of low carbon, mild steel and

core containing deoxidizers, slag formers and arc stabilizers in powder form. Both strip and core materials

are carefully monitored to conform with rigorous specifications. Automatic controls during production pro-

vide a uniform, high quality product. Flux-cored wires are specifically designed to weld mild steel using

either CO2gas or Argon-Co2gas mixtures.

Flux-cored arc welding offers many inherent advantages over stick electrode welding. Higher deposition

rates (typically double) and increased duty cycles (no electrode changing) mean savings in labor costs. The

deeper penetration achieved with cored wire also permits less joint preparation, yet provides quality weldsfree from lack of fusion and slag entrapment. Also flux-cored wire welding is easy to learn.

Variations-Metal

Transfer

Introduction

Equipment

Description


Supply

ShieldingGases

GlobularTransfer

Spray ArcWelding

Cored WireWelding

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


10/138

1

Equipment-Manual and Mechanized

Mig welding equipment can be used either manually or automatically. Figures 2-1 and 2-3 show equipment

for both.

Manual Welding

A manual welding station is simple to install. Because arc travel is performed by the welder, only three major

elements are necessary:

1) Welding torch and accessories

2) Welding control and wire feed motor

3) Power source

1 POWER CABLE (NEGATIVE)

2 WATER FROM TORCH - POWER CABLE

3 SHIELDING GAS

4 TORCH SWITCH

5 WATER TO TORCH6 WIRE CONDUIT

7 SHIELDING GAS FROM CYLINDER

8 COOLING WATER OUT

9 COOLING WATER IN

10 115 VAC IN - WELDING CONTACTOR CONTROL

11 POWER CABLE (POSITIVF)

12 TO PRIMARY POWER 230/460/575 V

Figure 2-1 Manual Welding Installation

Variations-Metal

Transfer

Manual

Equipment

Mechanized

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


11/138

2

WELDING TORCHES AND ACCESSORIES

The welding torch guides the wire and shielding gas into the weld zone. It also brings welding power to the

wire. Different types of welding torches have been designed to provide maximum welding utility for different

types of applications. They range from heavy duty torches for high current work to lightweight torches for low

current and out-of-position welding. In both types, water or air cooling and curved or straight front ends are

available.

Figure 2-2 shows a cross-sectional view of a typical air cooled, curved front end torch with these necessary

accessories:

a. contact tube (or tip)

b. shielding gas cup or nozzle

c. wire conduit and liner

d. one-piece composite cable

Figure 2-2 - Typical Mig Welding Torch

Variations-Metal

Transfer

Manual

Equipment

Mechanized

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


12/138


13/138

4

POWER SOURCE

Almost all mig welding is done with reverse polarity. The positive (+) lead is connected to the torch while the

negative () lead is connected to the workpiece. Since wire feed speed and, hence, current, is regulated by

the welding control, the basic adjustment made through the power source is arc length. Arc length is set by

adjusting the power source voltage. Power source may also have one or two additional adjustments for use

with other welding applications.

Most power sources require either 230V or 460V AC input power. Except for the power cable, the only other

connection to the power source is a multi-connector cable from the control, so as to have the power in

sequence with other control functions. Power sources will be discussed further in the next section.

SEQUENCE OF OPERATION

As an example, consider the operation of the welding installation pictured in Figure 2-1:

1) Main line power to power source turned on.

2) Set power source switch to READY to turn on powersource cooling fan motor and control circuit.

3) Turn the welding control switch to ON to energize the control.4) Close torch switch to cause shielding gas and cooling water to flow. Weld power goes to torch and

wire feed begins at set speed. The feeding wire electrode touches the workpiece. Welding begins.

5) Release torch switch No. 4 above reversed.

Most welding installations operate in a similar manner. However, the design and construction of the

equipment will differ. It is for this reason that the equipment instruction booklet should be consulted.

Complete troubleshooting data is generally supplied with all equipment.

Variations-Metal

Transfer

Manual

Equipment

Mechanized

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


14/138

5

Mechanized Welding Station

A mechanized station is used when the work can more easily be brought to the welding station or where a

great deal of repetitive welding justifies special fixtures. Arc travel is automatic and controlled by the fixture

travel speed. Weld speed is usually increased and weld quality improved.

As shown in Fig. 2-3, the welding equipment in a mechanized fixture is much the same as in a manual

station except:

1) The welding torch is usually mounted directly under the wire feed motor, eliminating the need for a

wire conduit.

2) The welding control is mounted away from the wire feed motor. Remote control boxes can be used.

3) In addition, other equipment is used to provide automatic fixture travel. Examples of this equipment

are side-beam carriages and turning fixtures.

The welding control also coordinates carriage travel with the weld start and stop.

Variations-Metal

Transfer

Manual

Equipment

Mechanized

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


15/138

6

Figure 2-3 - Automatic (Mechanized) Welding Installation

1 POWER CABLE (NEGATIVE)

2 POWER CABLE (POSITIVE)

3 WELDING VOLTAGE & CURRENT DETECTION

4 115 VAC IN

5 TO PRIMARY POWER 230/460/575 V

6 COOLING WATER IN

7 SHIELDING GAS IN

8 TO CARRIAGE DRIVE MOTOR

9 115 VAC IN TRAVEL START/STOP

10 WIRE FEED MOTOR

11 SHIELDING GAS IN

12 COOLING WATER IN

13 COOLING WATER OUT

Variations-Metal

Transfer

Manual

Equipment

Mechanized

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables


16/138

1

The Power Source

Direct current, constant potential(voltage) power sources are used for most mig welding. This contrasts withtig and stick electrode welding which use constantcurrent power sources. A mig power source provides arelatively constant voltage to the arc during welding. This voltage determines the arc length. When there is a

sudden change in wire-feed speed, or a momentary change in arc length, the power source abruptly

increases or decreases the current (and thereby the wire burnoff rate) depending on the arc length change.

The burnoff rate of wire changes automatically to restore the original arc length. As a result, permanent

changes in arc length are made by adjusting the output voltage of the power source. The wire-feed speed,

which the operator selects prior to welding, determines the arc current (see Fig. 3-1). It can be changed over

a considerable range before the arc length changes enough to cause stubbing to the workpiece or burningback to the guide tube.

Power Source Variables

The self-correcting arc length feature of the constant voltage welding system is very important in producing

stable welding conditions. Specific electrical characteristics are needed to control the arc heat, spatter, etc.

These include voltage, slope, and inductance.

Figure 3-1 - Affect of Wire Feed Speed

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Slope

Inductance


17/138

2

VOLTAGE

Arc voltage is the voltage between the end of the wire and the workpiece. Because of voltage drops

encountered in the welding system, the arc voltage cannot be directly read on the power source voltmeter.

Welding voltage (arc length) has an important effect on the type of process variation or metal transfer

desired. Short arc welding requires relatively low voltages while spray arc requires higher voltages. It should

be noted, too, as welding current and wire burnoff are increased, the welding voltage must also be

increased somewhat to maintain stability. Figure 3-2 shows a relationship of arc voltage to welding current

for the most common shielding gases employed for mig welding carbon steel. The arc voltage is increased

with increasing current to provide the best operation.

Figure 3-2 - Arc Voltage-Welding Current Relationship

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Slope

Inductance


18/138

3

SLOPE

Figure 3-3 illustrates the volt-ampere characteristics for a mig power source. The slant from horizontal of the

curve is referred to as the slope of the power source. Slope refers to the reduction in output voltage with

increasing current. Thus, a constant voltage power source with slope does not really provide constant

voltage for reasons to be considered.

As an example of slope, suppose the open circuit voltage is set at 25V and the welding condition is 19V

and 200 amps as shown in Figure 8-3. The voltage decreases from 25 to 19 in 200 amps; the slope is 3V/

100 amps.

The slope of the power source by itself, as specified by the manufacturer and measured at its output

terminals, is not the total slope of the arc system. Anything which adds resistance to the welding system

adds slope and increases the voltage drop at a given welding current. Power cables, connections, loose

terminals, dirty contacts, etc., all add to the slope. Therefore, in a welding system, slope should be

measured at the arc.


Figure 3-3 Slope Calculation of a

Welding System

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Slope

Inductance


19/138

4

Slope in a mig system is used during short arc welding to limit the short circuit current so that spatter is

reduced when short circuits between the wire electrode and workpiece are cleared. The greater the slope,

the lower the short circuit currents and within limits, the lower the spatter.

The amount of short circuit current must be high enough (but not too high) to detach the molten drops from

the wire. When little or no slope is present in the welding circuit, the short circuit current rises to a very high

level, and a violent, but miniature, reaction takes place. THIS CAUSES SPATTER.

When a short circuit current is limited to excessively low values by use of too much slope, the wire electrode

can carry the full current and the short circuit will not clear itself. In that case, the wire either piles up on the

workpiece or may stub to the puddle occasionally and flash off. This is schematically shown in Figure 3-4.

Figure 3-4 - Effect of Too Much Slope

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Slope

Inductance


20/138

5

When the short circuit current is at the correct value, the parting of the molten drop from the wire is smooth,

with very little spatter. Typical short circuit currents required for metal transfer and the best arc stability

appear on Table 3-1.

Table 3-1 Typical Circuit Currents Reguired for Metal Transfer

WIRE ELECTRODE

WIRE ELECTRODE DIAMETER SHORT CIRCUIT

TYPE IN. mm CURRENT

MILD STEEL .030 .76 300

MILD STEEL .035 .89 320

MILD STEEL .045 1.1 370

MILD STEEL .052 1.3 395

MILD STEEL .062 1.6 430

ALUMINUM .030 .76 175

ALUMINUM .035 .89 195

ALUMINUM .045 1.1 225

ALUMINUM .062 1.6 290

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Slope

Inductance


21/138

6

INDUCTANCE

Power sources do not respond instantly to load changes. The current takes a finite time to attain a new

level. Inductance in the circuit is responsible for this time lag. The effect of inductance can be illustrated by

analyzing the curve appearing in Figure 3-5. Curve A shows a typical current-time curve with inductance pre-

sent as the current rises from zero to a final value. Curve B shows the path which the current would have

taken if there were no inductance in the circuit. The maximum amount of current attainable during a short is

determined by the slope of the power source. Inductance controls the rate of rise of short circuit current. The

rate can be slowed so that the short may clear with minimum spatter. The inductance also stores energy. It

supplies this energy to the arc after the short has cleared and causes a longer arc.

In short arc welding, an increase in inductance increases the arc on time. This, in turn, makes the puddle

more fluid, resulting in a flatter, smoother weld bead. The opposite is true when the inductance is

decreased. Figure 3-6 shows the influence of inductance on the appearance of short-arc welds made both

with an argon-oxygen gas mixture and with a helium-argon-carbon dioxide mixture. Weld No. 1, made with amixture of 98% argon and 2% oxygen shielding gas and no added inductance, is rolled or peaked as seen in

the top cross-section. Midway along the sample, inductance of about 500 micro-henries was added. Freeze

lines are not as prominent, and the bead remains convex.


Figure 3-5 - Change in Current Rise Due to Inductance

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Slope

Inductance


22/138

7

Weld No. 2, made with the He-Ar-Co2 mixture is also convex. Spatter on the plate is considerable. When

inductance is introduced midway through the sample, the reduction in spatter is dramatic; the bead

becomes flat and the cross-section on the bottom right shows penetration of the weld bead into the

workpiece has increased.

In spray arc welding, the addition of some inductance to the power source will produce a better arc start. Too

much inductance will result in erratic starting.

When conditions of both correct shorting current and correct rate of current rise exist, spatter is minimal.

The power source adjustments required for minimum spatter conditions vary with the electrode material and

size. As a general rule, both the amount of short circuit current and the amount of inductance needed for

ideal operation are increased as the electrode diameter is increased.

Figure 3-6 - Effect of Inductance on

Weld Appearance

Variations-Metal

Transfer

Description

Equipment

Voltage

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Slope

Inductance


23/138

1

Shielding Gases

Introduction

Air in the weld zone is displaced by a shielding gas in order to prevent contamination of the molten weld

puddle. This contamination is caused mainly by nitrogen, oxygen and water vapor present in the

atmosphere.

As an example, nitrogen in solidified steel reduces the ductility and impact strength of the weld and can

cause cracking. In large amounts, nitrogen can also cause weld porosity.

Excess oxygen in steel combines with carbon to form carbon monoxide (CO). This gas can be trapped in themetal, causing porosity. In addition, excess oxygen can combine with other elements in steel and form com-

pounds that produce inclusions in the weld metal.

When hydrogen, present in water vapor and oil, combines with either iron or aluminum, porosity will result

and underbead weld metal cracking may occur.

To avoid these problems associated with contamination of the weld puddle, three main gases are used for

shielding. These are argon, helium and carbon dioxide. In addition, small amounts of oxygen, nitrogen and

hydrogen have proven beneficial for some applications. Of these gases, only argon and helium are inert

gases. Compensation for the oxidizing tendencies of other gases is made by special wire electrodeformulations.

Argon, helium and carbon dioxide can be used alone, in combinations or mixed with others to provide defect

free welds in a variety of weld applications and weld processes.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


24/138

2

Properties of Gases

The basic properties of shielding gases that affect the performance of the welding process include:

1) Thermal properties at elevated temperatures.

2) Chemical reaction of the gas with the various elements in the base plate and welding wire.

3) Effect of each gas on the mode of metal transfer.

The thermal conductivity of the gas at arc temperatures influences the arc voltage as well as the thermal

energy delivered to the weld. As thermal conductivity increases, greater welding voltage is necessary to

sustain the arc. For example, the thermal conductivity of helium and CO2

is much higher than that of argon;

because of this, they deliver more heat to the weld. Therefore, helium and CO2 require more welding voltage

and power to maintain a stable arc.

The compatibility of each gas with the wire and base metal determines the suitability of the various gas

combinations. Carbon dioxide and most oxygen bearing shielding gases should not be used for welding

aluminum, as aluminum oxide will form. However, CO2and 02are useful at times and even essential when

GMAW welding steels. They promote arc stability and good fusion between the weld puddle and base

material. Oxygen is a great deal more oxidizing tham CO 2. Consequently, oxygen additions to argon are

generally less than 12 percent by volume whereas 100 percent CO, can be used for GMAW mild steels.

Steel wires must contain strong deoxidizing elements to supress porosity when used with oxidizing gases,particularly mixtures with high percentages of CO2or 02 and especially 100 percent CO2.

Shielding gases also determine the mode of metal transfer and the depth to which the workpiece is melted

(depth of penetration). Tables(4-1 and 4-2) summarize recommended shielding gases for various materialsand metal transfer types. Spray transfer is not obtained when the gas is rich in CO2. For example, mixtures

containing more than about 20 percent CO2 do not exhibit true spray transfer. Rather, mixtures up to 30

percent CO2 can have a spray-like shape to the arc at high current level but are unable to maintain the arc

stability of lower CO2 mixtures. Spatter levels will also tend to increase when mixtures are rich in CO 2.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


25/138

3

Figure 4-1 - Effect of Oxygen Additions to Argon

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


26/138

4

Argon

Argon is an inert gas which is used both singularly and in combination with other gases to achieve desired

arc characteristics for the welding of both ferrous and non-ferrous metals. Almost all welding processes can

use argon or mixtures of argon to achieve good weldability, mechanical properties, arc characteristics and

productivity. Argon is used singularly on non-ferrous materials such as aluminum, nickel based alloys,

copper alloys, and reactive metals which include zirconium, titanium, and tantalum. Argon provides excellent

spray arc welding stability, penetration and bead shape on these materials. Some short circuiting arc

welding of thin materials is also practiced. When using ferrous materials, argon is usually mixed with other

gases such as oxygen, helium, hydrogen, carbon dioxide and/or nitrogen.

The low ionization potential of argon creates an excellent current path and superior arc stability. Argon

produces a constricted arc column at a high current density which causes the arc energy to be concentrated

in a small area. The result is a deep penetration profile having a distinct finger like shape.

Carbon Dioxide

Pure carbon dioxide is not an inert gas, because the heat of the arc breaks down the CO2into carbon

monoxide and free oxygen. This oxygen will combine with elements transferring across the arc to form

oxides which are released from the weld puddle in the form of slag and scale. Although CO 2 is an active gas

and produces an oxidizing effect, sound welds can be consistently and easily achieved which are free of

porosity and defects.

Carbon dioxide is widely used for the welding of steel. Its popularity is due to the common availability and

quality weld performance as well as its low cost and simple installation. It should be mentioned that low cost

per unit of gas does not automatically translate to lower cost per foot of weld and is greatly dependent on

the welding application. Factors such as lower deposition efficiency for CO2 caused by spatter loss,

influence the final weld cost.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


27/138

5

Carbon dioxide will not spray transfer; therefore, the arc performance is restricted to short circuiting and

globular transfer. The advantage of CO2 is fast welding speeds and deep penetration. The major drawbacks

of CO, are a harsh globular transfer and high weld spatter levels. The weld surface resulting from pure CO2

shielding is usually heavily oxidized. A welding wire having higher amounts of deoxidizing elements is

sometimes needed to compensate for the reactive nature of the gas. Overall, good mechanical properties

can be achieved with CO2. Argon is often mixed with CO2 to off-set pure CO2 performance characteristics. If

impact properties have to be maximized, a CO2 +argon mixture is recommended.

Helium

Helium is an inert gas which is used on weld applications requiring higher heat input for improved bead

wetting, deeper penetration and higher travel speed. In GMAW it does not produce as stable an arc as

argon. Compared to argon, helium has a higher thermal conductivity and voltage gradient and yields a


Figure 4-2 Comparison of Ar-5% O2 and CO2 Shielding Gas

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


28/138

6

broader and more shallow penetration pattern. Aluminum welding with pure helium does not give the

cleaning action that pure argon experiences but is beneficial and sometimes recommended for welding thick

aluminum. The helium arc column is wider than argon which reduces current density. The higher voltagegradient causes increased heat inputs over argon thus promoting higher puddle fluidity and subsequent

bead wetting. This is an advantage when welding aluminum, magnesium and copper alloys.

Helium is often mixed with various percentages of argon to take advantage of the good characteristics of

both gases. The argon improves arc stability and cleaning action, in the case of aluminum and magnesiurn,

while the helium improves wetting and weld metal coalescence.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


29/138

7

Binary (2) Shielding Gas Mixtures

Argon-Oxygen

The addition of srnall amounts of 02 to argon greatly stabilizes the weld arc, increases the filler metal droplet

rate, lowers the spray arc transition current, and improves wetting and bead shape. The weld puddle is more

fluid and stays molten longer allowing the metal to flow out towards the toe of the weld. This reduces

undercutting and helps flatten the weld bead. Occasionally, small oxygen additions are used on non- ferrous

applications. For example, its been reported by NASA that .1% oxygen has been useful for arc stabilization

when welding very clean aluminum plate.

Argon-1%O2 This mixture is primarily used for spray transfer on stainless steels. One percent oxygen isusually sufficient to stabilize the arc, improve the droplet rate, provide coalescence and improve

appearance.

Argon-2%O2 This mixture is used for spray arc welding on carbon steels, low alloy steels and stainless

steels. It provides additional wetting action over the 1% 02 mixture. Mechanical properties and corrosion

resistance of welds made in the 1 and 2% 02additions are equivalent.

Argon-5%O2 This mixture provides a more fluid but controllable weld pool. It is the most commonly usedargon-oxygen mixture for general carbon steel welding. The additional oxygen also permits higher travel

speeds.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


30/138


31/138

9

action as identical amounts of 02. From 5 to10% CO2 the arc column becomes very stiff and defined. The

strong arc forces that develop give these mixtures more tolerance to mill scale and a very controllable

puddle.

Argon-11-20%CO2 This mixture range has been used for various narrow gap, out-of-position sheet metal

and high speed GMAW applications. Most applications are on carbon and low alloy steels. By mixing the

CO2 within this range, maximum productivity on thin gauge materials can be achieved. This is done by

minimizing burnthrough potential while at the same time maximizing deposition rates and travel speeds. The

lower CO2 percentages also improve deposition efficiency by lowering spatter loss.

Argon-21-25% CO2 (C-25) This range is universally known as the gas used for GMAW with short circuiting

transfer on mild steel. It was originally formulated to maximize the short circuit frequency on .030 and .035-

in. diameter solid wires but through the years has become the defacto- standard for most diameter solid wirewelding and commonly used with flux cored wires.

This mixture also operates well in high current applications on heavy materials and can achieve good arc

stability, puddle control and bead appearance as well as high productivity. See Figure 4-3.

Argon-50% CO2 This mixture is used where high heat input and deep penetration are needed.

Recommended material thicknesses are above 1/8 in. and welds can be made out-of-position. This mixture

is very popular for pipe welding using the short circuiting transfer. Good wetting and bead shape without

excessive puddle fluidity are the main advantages for the pipe welding application. Welding on thin gauge

materials has more tendency to burnthrough which can limit the overall versatility of this gas. When weldingat high current levels, the metal transfer is more like welding in pure CO 2 than previous mixtures but some

reduction in spatter loss can be realized due to the argon addition. See Figure 4-3.

Argon-75% CO2 A 75% CO2 mixture is sometimes used on heavy wall pipe and is the optimum in good

side-wall fusion and deep penetration. The argon constituent aids in arc stabilization and reduced spatter.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures


32/138

10


Argon-Hel ium

Regardless of the percentage, argon-helium mixtures are used for non-ferrous materials such as aluminum,

copper, nickel alloys and reactive metals. These gases used in various combinations increase the voltage

and heat of GTAW and GMAW arcs while maintaining the favorable characteristics of argon. Generally, the

heavier the material the higher the percentage of helium. Small percentages of helium, as low as 10%, will

affect the arc and the mechanical properties of the weld. As helium percentages increase, the arc voltage,

spatter and penetration will increase while minimizing porosity. A pure helium gas will broaden the

penetration and bead but depth of penetration could suffer. However arc stability also increases. The argon

percentage must be at least 20% when mixed with helium to produce and maintain a stable spray arc. See

Figure 4-4.

Figure 4-3 Effect of CO, Additions to Argon

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

V i ti


33/138

11

Argon-25% He (HE-25) This little used mixture is sometimes recommended for welding aluminum wherean increase in penetration is sought and bead appearance is of primary importance.

Argon-75% He (HE-75) This commonly used mixture is widely employed for mechanized welding ofaluminum greater than one inch thick in the flat position. HE-75 also increases the heat input and reduces

porosity of welds in 1/4 and 1/2 in. thick conductivity copper.

Argon-90% He (HE-90) This mixture is used for welding copper over1/2 in. thick and aluminum over 3-in.thick. It has an increased heat input which improves weld coalescence and provides good X-ray quality. It isalso used for short circuiting transfer with high nickel filler metals.

Figure 4-4 Effect of Helium Additions to Argon

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations


34/138

12

Argon-Nitrogen

Small amounts of nitrogen have been added to Ar-1% 02to achieve a completely austenitic microstructure inwelds made with type 347 stainless steel filler metal. Nitrogen concentrations in the range of 1.5 to 3% have

been used. Quantities above 10% produced considerable fuming but welds are sound. Additions greater

than2% N2produced porosity in single pass GMAW welds made in mild steel; additions less than 1/2%

caused porosity in multipass GMAW welds in carbon steel. A few attempts have been made to utilize N 2 rich

argon mixtures for GMAW welding of copper and its alloys, but spatter percentage is high.

Argon-Chlorine

Chlorine is sometimes bubbled through molten aluminum to remove hydrogen from ingots or castings. Since

this degassing operation is successful it follows that chlorine might remove hydrogen from aluminum weld

metal. Some claims were made that Ar-C12 mixtures eliminated porosity in GMAW but fabricators have not

been able to achieve consistent results. Moreover, since chlorine gas forms chloric acid in the respiratory

system, such mixtures can be disagreeable or noxious to operators and those in the vicinity of welding.

Consequently, Ar-C12 mixtures are not popular or recommended except in special cases where adequate

safety and control is implemented.

Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations-


35/138

13

Ternary (3) Shield ing Gas Mixtures

Argon-Oxygen-Carbon Diox ide

Mixtures containing these three components have been termed universal mixtures due to their ability to

operate using short circuiting, globular, spray, pulse and high density type transfer characteristics. Several

triple-mixes are available and their application will depend on the desired metal transfer mechanism and

optimization of the arc characteristics.

Argon-5-10% CO2- 1-3%02 This ternary mixture range has gained popularity in the U.S. over the last

several years. The chief advantage is its versatility to weld carbon steel, low alloy steel and stainless steel of

all thicknesses utilizing whatever metal transfer type applicable. Stainless steel welding should be limited tospray arc only due to the stiffness of the puddle at low current levels. Carbon pick-up on stainless steel

should also be considered in some instances. On carbon and low alloy steels, this mixtures produces good

welding characteristics and mechanical properties. On thin gauge materials, the 02constituent assists the

arc stability at very low current levels (30 to 60 amps) permitting the arc to be kept short and controllable.

This helps minimize burnthrough and distortion by lowering the total heat input into the weld zone.

Argon - 10-20% CO2 - 5%02 This mixtureis not common in the U.S. but has found applications in Europe.

The mix produces a hot short circuiting transfer and fluid puddle characteristics. Spray arc transfer is good

and seems to have some benefit when welding with triple deoxidized wires since a sluggish puddle is

characteristic of these wires.

Argon-Carbon Dioxide-Hydrogen

Small additions of hydrogen (1-2%) have been shown to improve bead wetting and arc stability when Pulse

Mig welding stainless steel. The CO2is also kept low (1-3%) to minimize carbon pick-up and maintain good

arc stability. This mixture is not recommended on low alloy steels in the excessive weld metal hydrogen

levels could develop causing weld cracking and poor mechanical properties.


Variations-Metal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations-


36/138

14

Argon-Hel ium-Carbon Diox ide

Helium and CO2 addition to argon increase the heat input to the weld and improve arc stability. Betterwetting and bead profile is achieved. When welding on carbon and low alloy steels, helium additions are

used to increase the heat input and improve the puddle fluidity in much the same way that oxygen is used

except that helium is inert and oxidation of the weld metal and alloy loss are not a problem. When welding

low alloy material, mechanical properties can be achieved and maintained more easily.

Argon - 10-30% He - 5-15% CO2 Mixtures in this range have been developed and marketed for pulse

spray arc welding of both carbon and low alloy steel. Best performance is on heavy section, out-of-position

applications where welding is desired at maximum deposition rates. Good mechnical properties and puddle

control are characteristic of this mixture. Pulse spray arc welding with low average currents is acceptable but

mixtures with low CO, and/or 0, percentages will improve arc stability.

60-70% He - 20-35% Ar - 4-5% CO2 This mixture is used for short circuiting transfer welding of high

strength steels, especially for out-of- position applications. The CO2content is kept low to insure good weld

metal toughness. The helium provides the heat necessary for puddle fluidity. High helium contents are not

necessary, as the weld puddle may become too fluid for easy control.

90% He - 7.5% Ar - 2.5% CO2 This mixture is widely used for short arc welding of stainless steel in all

positions. The CO2 content is kept low to minimize carbon pickup and assure good corrosion resistance,

especially in multipass welds. The CO2 +argon addition provides good arc stability and penetration. The

high helium content provides heat input to overcome the sluggish nature of the stainless steel weld puddle.

Argon-Hel ium-Oxygen

J ust as a helium addition to argon increases the arc energy when welding non-ferrous materials, so does a

helium addition to argon-oxygen affect the arc with the GMAW process on ferrous materials. Ar-He-O2mixtures have been used occasionally for spray arc welding and surfacing low alloy and stainless steels to

improve puddle fluidity and bead shape and reduce porosity.

VariationsMetal

Transfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations-


37/138

15

Quaternary (4) Shielding Gas Mixtures

Argon-Heli um - Co2- O2

Commonly known as a quad mix, this combination is most popular for high deposition GMAW using the

high density metal transfer type arc characteristic. This mixture will give good mechanical properties and

operability throughout a wide range of deposition rates. Its major application is welding low alloy high tensile

base materials but has been used on mild steel for high productivity welding. Weld economics are an

important consideration in using this gas for mild steel welding, in that other less expensive mixtures are

available for high deposition welding.

Regardless of the type of welding that need to be done, there is a shielding gas that will best suit therequirements.Tables 4-1 and 4-2 summarize which shielding gas is best suited for welding a variety of

materials using both the short arc and spray arc process.

MetalTransfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations-


38/138

16

Table 4-1 Mig Shielding Gas Selection Chart-Short Arc Welding

ARGON-

ARGON ARGON- HELIUM

HELIUM CO2 C02

METAL ARGON HELIUM MIXTURES MIXTURES MIXTURES AR-O2-CO2 CO2

ALUMINUM

(HE-75)

CARBON (1)

STEEL (C-25) OR STARGON

(C-50) OR

(C-8) (4)

(C-15)

HIGH STARGON

STRENGTH (A-415) UP TO

STEELS OVER 14 GA. 14 GA.

COPPER (HE-75)

STAINLESS

STEELS (C-25) (1) (A-1025) STARGON

NICKEL

ALLOY (90% HE- (A-1025)

10% AR)

OR

(HE-75)

REACTIVE (HE-75)

METALS

(1) WIRE DESIGNED FOR CO2 REQD.

MetalTransfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations-M t l


39/138

17

Table 4-2 Mig Shielding Gas Selection Chart-Spray Arc & Pulse Spray Arc Welding

ARGON-

HELIUM Ar Ar

ARGON- GAS He (2) CO (3)

METAL ARGON HELIUM OXYGEN AR-CO2 MIXTURES CO2 AR-02-CO2 H2 CO2ALUMINUM (90%HE-10%

AR) OR

(HE-75)

CARBON

STEELS (O2-2) (C-15) STARGON

(O2

-5) (C-8) OR LINDE 5-22

(C-25) (1)

Pulse

Blend

C-5

LOW ALLOY

STEELS (O2-2) (C-8) A415 STARGON

OVER 3/32

LINDE 5-22

COPPER &

SILICON (90% HE-10%

BRONZE AR) OR

(HE-75)

STAINLESS (O2-1) H21

STEELS (O2-2) CO2-2

NICKEL

ALLOYS (HE-75)

REACTIVE

METALS

(1) SINGLE PASS WELDS (2) HIGHER QUALITY ON HEAVY MILL SCALE PLATE WHEN USED WITH L-TEC 83 AND 87 HP

WIRES. (3) USED WITH FLUX CORED WIRE AND FOR HIGH SPEED SOLID WIRE WELDING. (4) THIN MATERIAL

MetalTransfer

Introduction

Equipment

Gas

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Binary

Ternary

Properties

Mixtures

Mixtures

QuaternaryMixtures

Variations-Metal


40/138

1

Wire Electrodes

One of the most important factors to consider in mig welding is the correct filler wire selection. This wire, in

combination with the shielding gas will produce the deposit chemistry that determines the resulting physical

and mechanical properties of the weld. Basically, there are five major factors that influence the choice of

filler wire for mig welding.

1. Base plate chemical composition

2. Base plate mechanical properties

3. Shielding gas employed

4. Type of service or applicable specification requirements

5. Type of weld joint design.

However, long experience in the welding industry has generated American Welding Society Standards to

greatly simplify the selection. Wires have been developed and manufactured that consistently produce the

best results with specific plate materials. Although there is no industry-wide specification, most wires con-

form to an AWS standard.

MetalTransfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials

Non FerrousMaterials

Variations-Metal


41/138

2

Ferrous Materials

Before turning to the specific wires for the mig welding of ferrous materials, there are basic similarities thatevery ferrous wire shares in the alloying elements added to iron. For mig welding carbon steels, the primary

function of the alloying additions is to control the deoxidation of the weld puddle and to help determine the

weld mechanical properties. Deoxidation is the combination of an element with oxygen from the weld puddle

resulting in a slag or glass formation on the surface. Removing oxygen from the puddle eliminates it as a

cause of weld metal porosity.

Silicon (Si) Silicon is the most commonly employed deoxidizing element in wires used for mig welding.Generally, wires contain 0.40% to 1.00% Si, depending on their intended use. In this percentage range,

silicon exhibits very good deoxidizing ability. Increasing amounts of Si will increase the strength of the weldwith only a small decrease in the ductility and toughness. However, above 1-1.2% Si, the weld metal may

become crack sensitive.

Manganese (Mn) Manganese is also a commonly used deoxidizer and strengthener. Manganese

constitutes 1.00% to 2.00% of mild steel wires. Increasing amounts of Mn increases the weld metal strength

to a greater degree from Si. Manganese will also reduce the hot crack sensitivity of the weld metal.

Aluminum (Al), Titanium (Ti) and Zircon ium (Zr ) These elements are very strong deoxidizers. Very

small additions of these elements are sometimes made, usually not more than 0.20% combined. In this

range, some increase in strength is also achieved.Carbon (C) Carbon influences the structural and mechanical properties more profoundly than any otherelement. For the purpose of mig welding steels, the carbon content of wires is usually held between 0.05%

to 0.12%. This level is sufficient to provide necessary weld metal strength without appreciably affecting

ductility, toughness, and porosity. Increasing carbon content in both wire and plate has an effect on porosity,

particularly when welding with CO2 shielding gas. When the carbon content of the wire electrode and/or the

workpiece exceeds 0.12% the weld metal will lose carbon in the form of CO. This can cause porosity, but

additional deoxidizers help to overcome this.


MetalTransfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal


42/138

3

Others Nickel, chromium and molybdenum are often added to improve mechanical and/or corrosion

resistance properties. In small amounts, they can be used in carbon steel wires to improve the strength and

toughness of the deposit. They are used in larger amounts in stainless steel wires. Generally, when weldingis done in Argon with 1% to 3% oxygen or with mixtures of argon containing low CO2 content, the weld metal

chemical composition will not vary greatly from the analysis of the wire electrode. However, when CO 2 is

used for shielding, reductions in Si, Mn and other deoxidizing elements can be expected. Ni, Cr, Mo and

carbon contents will remain quite constant. Wires with very low carbon contents (.04-.06 percent) will

produce, with CO2,a weld metal with a higher carbon content.

CARBON STEEL ELECTRODES

Table 5-1* lists the chemical requirements and designations for all mild steel wires covered under the

American Welding Society Specification A5.18. The minimum as-welded mechanical properties of welds

conforming to each classification appear in Table 5-2*. Although mechanical properties and service

requirements do influence the wire selection in some cases, a more general consideration will be found

most useful for the majority of applications and weld joint designs. As either the welding current, weld

puddle size, amount of rust, mill scale and oil found on the base plate surface, or the O 2and CO2 content of

the shielding gas increases, the Mn and Si content of the wire electrode should also increase to provide the

highest quality weld. The following is a description of the characteristics and intended use of the most

common wire electrodes of each classification appearing in Table 5-2.

ER70S-2 (Spoolarc 65) This wire is heavily deoxidized and is designed for producing sound welds in all

grades of carbon steel: killed, semi-killed and rimmed. Because of the added deoxidants (Al, Zr and Ti) in

addition to Mn and Si, it is suited for welding carbon steels having a rusty surface. Ar-O2, Ar-CO2 and CO2shielding gases can be used. In general, an extremely viscous weld puddle will be produced, making it well

suited for short-arc welding out of position. To improve the wetting, 02or CO2content should be kept

relatively high.


MetalTransfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal


43/138

4

ER70S-3 (Spoolarc 29S and Spoolarc 82) Wire electrodes of this classification are one of the most

widely used for a variety of applications. E70S-3 wires can be used with either CO 2, Ar-O2or Ar-CO2 to

produce sound welds in killed and semi-killed steels. Rimmed steels should be welded with only Ar-O, or Ar-CO2to produce medium quality welds. The use of high welding current and CO2shielding gas may result in

low strength. Either single pass welding of gage material or multipass welds can be made with this wire

electrode. The tensile strength for a single pass weld in low and medium carbon steel gage material will

exceed the base metal and ductility will be adequate. In a multipass weld, the tensile strength will range

between 65,000 and 85,000 psi depending on the base metal dilution and shielding gas. The weld puddle is

more fluid than ER70S-2, producing better wetting characteristics and a flatter bead. This wire has its

application on automobiles, farm implements and home appliances.

ER70S-4 (Spoolarc 85) Wire electrodes of this classification contain a still higher level of manganese andsilicon than E70S-3. This improves the soundness on semi-killed or rimmed steels and increases the weldmetal strength. It performs well with Ar-O2, Ar-CO2and CO2 shielding gases using either the spray arc or

short arc technique. Structural steels such as A7, A36, common ship steels, piping and boiler and pressure

vessel steels, and A515 Grade 55 to 70 are usually welded with this wire. Weld beads are generally flatter

and wider than those made with ER70S-2 and ER70S-3, using identical shielding gases and welding

conditions.

ER70S-5 E70S-5 wires, in addition to silicon and manganese, also contain aluminum as a deoxidizer.Because of the high Al content, they can be used for welding killed, semi-killed and rimmed steel with CO 2

shielding gas and high welding currents. Ar-O2and Ar-CO2 may also be used; however, short-circuiting typetransfer should be avoided because of the excessive puddle viscosity. Base materials containing rusty

surfaces can also be welded with this wire, with a slight sacrifice in weld quality. Welding is restricted to the

flat position only.


Transfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal


44/138

5

ER70S-6(Spoolarc 86) Wires of this class contain the highest silicon and high manganese contents asdeoxidizers. As with the E70S-S, they will yield good weld quality when welding most carbon steels with CO 2

shielding and high welding currents. They are also used with Ar-O2 mixtures containing 5% or more 02 forhigh-speed welding. Because this wire contains no aluminum, the short-arc technique using CO2 or Ar-CO2

shielding gases can now be implemented. The weld puddle is quite fluid, similar in appearance to those

made with ER70S-4.

ER70S-7 (Spoolarc 87HP) This is a multipurpose, high performance wire designed for use where superiorweld quality and optimum appearance are desired. With higher manganese/silicon ratios than ER70S-3 and

ER70S-6 wires, 87HP provides superior edge wetting and bead shape over a wide range of welding

parameters with a variety of shielding gases. A higher level of deoxidizers produces cleaner welds with few

or no inclusions. The favorable ratio of manganese to silicon assures that impurities are floated to the weld

surface and not trapped within the weld. The extra deoxidizing capability of this wire helps to minimize the

occurrence of porosity defects when welding over mill scale or light rust.

ER8OS-D2 (Spoolarc 83) These wires contain silicon and manganese as deoxidants, as well asmolybdenum for increased strength. They can be used for all position welding with Ar-CO2 and CO2

shielding gases as well as Ar-O2for the flat position. Maximum mechanical properties are obtained with

Ar-O2 and Ar-CO2 mixtures. Welding can also be done over slightly rusty surfaces with some sacrifice of quality,

similar to that produced with ER70S-2. This wire can be used for welding low alloy steels such as AISI 4130.

High-yield strength steels such as T-1, NaXtra and SSS-100 are also commonly welded with this wire where

the ultimate in mechanical properties is not necessary.

Transfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal

T f


45/138

6

STAINLESS STEEL ELECTRODES

In choosing the appropriate wire for welding a stainless steel, there are generally fewer factors to consideras:

1) Shielding gases are usually limited toAr-1% 02 for spray arc and A-1025 for short arc. All wires canbe used with either gas.

2) Wires are for the most part chosen to match the chemistry of the base material.

3) Deoxidizer levels are not of great importance. Table 5-3* lists the chemical requirements and

designations for all stain less steel wires covered by theAmericanWelding Society SpecificationA5.9.

Unlike carbon and steel wires, there are no mechanical property require ments for the resulting weld

metal. Some of the most commonly used wire classifications and their intended uses are as follows:

ER308L (Arcaloy 308/308L) Wires of these types can be used for welding 304 stainless steel. The

chromium and nickel contents are identical. The lower carbon content reduces any possibility of carbide

precipitation and the intergranular corrosion that can occur. Carbon content is less than 0.04%.

ER308LSi (Arcaloy 308Si/308LSi) Similar chemistry and type of materials weldable as ER308L.However, a higher silicon level improves the wetting characteristics of the weld metal, particularly when Ar-

1% 02 shielding gas is used. If the dilution of the base plate is extensive, high silicon content can cause

greater crack sensitivity than a low silicon content. This results from the weld being fully austenitic or a low

ferrite.

ER309L (Arcaloy 309/309L) Used to weld type 309 and 309 stainless steel. These can been used to weld

type 304 stainless steel where severe corrosion conditions will be encountered and for joining mild steel to

type 304 stainless.

ER316L (Arcaloy 316/316L) Used to weld type 316 stainless steel. The addition of molybdenum makes

this wire electrode applicable for high service where creep resistance is desired. Carbon content is less than

0.04%.

*Table 5-3 appears in t he back of t he book.


Transfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal

Transfer


46/138

7

ER316LHSi (Arcaloy 316Si/316LSi) This wire, due to its lower carbon content, will be less susceptible to

intergranular corrosion caused by carbide precipitation when used in place of ER316L. Again, the higher sili-

con level (Si type) will improve the wetting, but may increase crack sensitivity if dilution of the base material

is extensive.

ER347 (Arcaloy 347) This wire is much less subject to intergranular corrosion from carbide precipitation,

as tantalum and/or columbium are added to act as stabilizers. It is used for welding base materials with

similar chemistry and where high temperature strength is required.

Transfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal

Transfer


47/138

8

Non-Ferrous Materials

ALUMINUM & ALUMINUM ALLOYS

The principal elements used to produce aluminum alloy wire electrodes are magnesium, manganese, zinc,

silicon and copper. The primary reason for adding these elements is to increase the strength of pure

aluminum. However, corrosion resistance and weldability are also major considerations. Each wire contains

additions of several alloying elements to improve the weld properties, and is designed to weld a given type

of aluminum. The most popular wires are the magnesium-containing 5356 and the silicon-containing 4043.

The manner in which elements are combined to form the various wire electrodes used for mig welding of

aluminum appear in Table 5-4*. This table lists the chemical requirements and designations for all aluminumwires covered by the American Welding Society Specification A5.10. There are no mechanical property

requirements for the weld metal.

The choice of aluminum electrodes is influenced by the same considerations previously listed. Again,

experience of the welding industry has made selection straightforward. Table 5-5* lists the wire electrodes

suitable for welding various base plate materials. Wire-workpiece combinations not appearing in this table

will usually yield inferior welds.

Transfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

Weld

Defects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal

Transfer


48/138

9

COPPER & COPPER ALLOYS

The majority of copper wires also contain alloying elements. Although these elements generally decreasethe conductivity of pure copper, they are necessary to increase strength, deoxidize the weld metal and

match the base material chemistry.

Tables 5-6 and 5-7, located in back of book present the various copper- base wire electrodes and the

required transverse tensile strengths of the weld metal. P rimarily, selection of the proper wire depends on

the base plate chemistry; however, this is not always possible. Again, the choice is not dependent on

shielding gas, as only argon and helium are recommended. The intended uses of the various wire

electrodes are as follows:

ERCu (All-State Deox-Copper) Because of the low alloy content, ERCu wires are restricted to thewelding of pure copper. Deoxidized and oxygen-free copper can be soundly welded with good strength.

However, electrolytic tough pitch copper shouldnot be welded with an ERCu electrode if quality is required.ERCuSi-A (All-State Silicon Bronze) This wire is primarily used to join copper-silicon alloys, as the

chemistry match is adequate. In addition, it can be used to weld copper-zinc alloys. Because of the high

silicon level and the resulting deoxidation of the puddle, electrolytic tough pitch copper can be adequately

welded. In this case, soundness and mechanical properties will be superior to welds made with ERCu

electrodes. ERCuSi wires also perform similarly to mild steel wires with respect to arc stability and weld

puddle fluidity. Because of this, the welding of carbon steel plate and galvanized steel plate can be

successfully accomplished.

ERCuSn-A (All-State Phosphorus Bronze) Wire electrodes of this classification are primarily used for

welding phosphor bronzes, but can be used to weld cast iron and mild steel. Again, because of the

deoxidizing ability of the phosphorus, they can be used on electrolytic tough pitch. However, ERCuSnA

wires do not yield a fluid weld puddle so preheating may be necessary. Copper-zinc alloys can also be

welded.

*Tables 5-4 and 5-5 appear in the back of this book.

Transfer

Equipment

PowerSupply

ShieldingGases

WireElectrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials



49/138

Variations-Metal

Transfer


50/138

11

E71T-1M/T-9M (Dual Shield 7100 Ult ra) ALL POSITION This wire was formulated with a fast freezing

slag that will support the molten weld puddle out of position. At low (140-200 amps) they exhibit good gap

bridging characteristics necessary to weld poor fitup. At high amps (200-250 amps) they exhibit deep rootpenetration and can achieve higher out of position deposition rates than stick. This wire produces low fume

generation.

E81T1-Ni2 (Dual Shield 8000 Ni2) HIGH TOUGHNESS ALL POSITION These wires contain 2-3%

nickel. They operate essentially the same as the E71T-1 all position wires they are derived from. The 2-3%

nickel addition yields CVN toughness of 40-60 ft.-lbs. at 30-50 ft.-lbs. depending on shielding gas and

cooling rates. Most of these wires will also maintain 70 ksi min. UTS after stress relief, making them useful

in the vessel fabrication industry. This wire also meets AWS D.1.1 E8018-C1 chemical requirements for

welding A242 and A588 weathering steels.

Equipment

PowerSupply

ShieldingGases

Wire

Electrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Ferrous

Introduction

Materials


Variations-Metal

Transfer


51/138

1

Precautions and Safe Practices

FUMES and GASES can harm your health.

Keep your head out of the fumes. Do not breathe fumes and gases caused by the arc. Use enoughventilation. The type and the amount of fumes and gases depend on the equipment and supplies

used. Air samples can be used to find out what respiratory protection is needed.

Provide enough ventilation wherever welding and cutting are performed. Proper ventilation will protect the

operator from the evolving noxious fumes and gases. The degree and type of ventilation will depend on the

specific welding and cutting operation. It varies with the size of work area; on the number of operators; and

on the types of materials to be welded or cut. Potentially hazardous materials may exist in certain fluxes,

coatings, and filler metals. They can be released into the atmosphere during welding and cutting. In somecases, general natural-draft ventilation may be adequate. Other operations may require forced-draft

ventilation, local exhaust hoods or booths, or personal filter respirators or air supplied masks. Welding inside

tanks, boilers, or other confined spaces require special procedures, such as the use of an air supplied hood

or hose mask.

Check the welding atmosphere and ventilation system if workers develop unusual symptoms or complaints.

Measurements may be needed to determine whether adequate ventilation is being provided. A qualified

person, such as an industrial hygienist, should survey the welding operations and environment. Follow their

recommendations for improving the ventilation of the work area.

Do not weld on dirty plate or plate contaminated with unknown material. The fumes and gases which are

formed could be hazardous to your health. Remove all paint and galvanized coatings before welding. All

fumes and gases should be considered as potentially hazardous.

More complete information on health protection and ventilation recommendations for general welding and

cutting can be found in the American National Standard Z49.1, Safety in Welding and Cutting.

Equipment

PowerSupply

ShieldingGases

Wire

Electrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Electric Shock

Arc Rays &

Filters to Use

Spatter

Fumes andGases

Variations-Metal

Transfer


52/138

2

ELECTRIC SHOCK can kill you.

Do not touch live electrical parts.

Electric shock can be avoided. Follow the recommended practices listed below. Faulty installation, improper

grounding, and incorrect operation and maintenance of electrical equipment are always sources of danger.

1. Ground all electrical equipment and the workpiece. Prevent accidental electrical shocks. Connectpower source, control cabinets, and workpiece to an approved electrical ground. The work lead is not a

ground lead. It is used to complete the welding circuit. A separate connection is required to ground the work

(illustrated on p. 5); or the work lead terminal on the power source may be connected to ground. Do not

mistake the work lead for a ground connection.

2. Use the correct cable size. Sustained overloading will cause cable failure and result in possible

electrical shock or fire hazard. Work cable should be the same rating as the torch cable.

3. Make sure all electrical connections are tight, clean, and dry. Poor electrical connections can heat up,and even melt. They can also cause bad welds and produce dangerous arcs and sparks. Do not allow

water, grease, or dirt to accumulate on plugs, sockets, or electrical units.

4. Keep dry . Moisture and water can conduct electricity. To prevent shock, it is advisable to keep work

areas, equipment, and clothing dry at all times. Fix water leaks immediately. Make sure that you are well

insulated. Wear dry gloves, rubber-soled shoes, or stand on a dry board or platform.5. Keep cables and connectors in good cond ition. Improper or worn electrical connections can cause

short circuits and can increase the chance of an electrical shock. Do not use worn, damaged, or bare

cables.

6. Avoid open-circuit vol tage. Open-circuit voltage can cause electric shock. When several welders are

working with arcs of different polarities, or when using multiple alternating-current machines, the open-circuit

voltages can be additive. The added voltages increase the severity of the shock hazard.


Equipment

PowerSupply

ShieldingGases

Wire

Electrodes

Safety

WeldingTechniques

WeldingConditions

Economics

WeldDefects

Mig SpotWelding

Tables

Electric Shock

Arc Rays &

Filters to Use

Spatter

Fumes andGases

Variations-Metal

Transfer


53/138

3

7. Wear insulated gloves when adjusting equipment. Power should be shut off and insulated gloves

should be worn when making any equipment adjustment to assure shock protection.

8. Follow recognized safety standards. Follow the recommendations in American National StandardZ49.1, Safety in Welding and Cutting, available from the American Welding Society, P. O. Box 351040,

Miami, FL 33135, and also the National Electrical Code, NFPA No. 70, which is available from the National

Fire Protection Association, Batterymarch Park, Quincy, MA 02269.

ARC RAYS and SPATTER can in jure eyes and burn skin.

Wear cor rect eye, ear, and body protection.

Electric arc radiation can burn eyes and skin the same way as strong sunlight. Electric arcs emit bothultraviolet and infrared rays. Operators, and particularly those people susceptible to sun- burn, may receive

eye and skin burns after brief exposure to arc rays. Reddening of the skin by ultraviolet rays becomes

apparent seven or eight hours later. Long exposures may cause a severe skin burn. Eyes may be severly

burned by both ultraviolet and infrared rays. Hot welding spatter can cause painful skin burns and perma-

nent eye damage.

To be sure you are fully protected from arc radiation and spatter, follow these precautions:

1. Cover all skin surfaces and wear safety glasses for protection from arc burns and burns from

sparks or spatter.Keep sleeves rolled down. Wear gloves and a helmet. Use correct lens shade to prevent

eye injury. Choose the correct shade from the table below. Observers should also use proper protection.

See Filter Recommendations on page 5.

2. Protect against arc flashes, mechanical injury, or other mishaps. Wear spectacles or goggles with

No. 2 shade filter lens and side shields inside the welding helmet or hand shield. Helpers and observers

should wear similar protection.

Continued

ESAB MIG Welding Handbook

Documents