MIG

Question 1

MAG is short for ____.

Answer 1

metal active gas welding

Question 2

Which of the following tasks is done by a machine?

Answer 2

Maintaining the arc in semiautomatic welding processes.

Question 3

Which of the following tasks are done by the welder?

Answer 3

Providing the joint guidance in machine welding processes.

Question 4

The shielding gas used on carbon steel is ____.

Answer 4

carbon dioxide, or a mixture of carbon dioxide and argon

Question 5

Which of the following is true of axial spray metal transfer?

Answer 5

There are hundreds of drops per second crossing from the wire to the base metal.

Question 6

In axial spray metal transfer, the shielding gas is usually a mixture of ____.

Answer 6

95% to 98% argon and 2% to 5% oxygen

Question 7

Which of the following is true of axial spray transfers using high current settings?

Answer 7

High current settings may cause the weld to be difficult to control in out-of-position welds.

Question 8

Which of the following is true of globular transfer?

Answer 8

It is used in combination with pulsed-spray transfer.

Question 9

Globular transfer occurs at a rate of ____ drops per second.

Answer 9

a few

Question 10

In the pulsed-arc metal transfer current cycle, ____ refers to how the electric current in a transformer takes a few milliseconds to build up the magnetic field to full strength once the coil is energized.

Answer 10

ramp up

Question 11

In the pulsed-arc metal transfer current cycle, ____ refers to the surging electrical current passing through the transformer like a wave on water.

Answer 11

overshoot

Question 12

In the pulsed-arc metal transfer current cycle, ____ is the peak current that flows across the arc during the high current pulse.

Answer 12

high pulse current

Question 13

In the pulsed-arc metal transfer current cycle, ____ is a function of the time it takes the magnetic field in the transformer to collapse once the coil is de-energized.

Answer 13

ramp down

Question 14

With the addition of ____ to the argon gas, the transfer becomes progressively more ____.

Answer 14

helium, globular

Question 15

As much as ____ can be added to the argon to increase the power in the arc without affecting the desirable qualities of the spray mode.

Answer 15

80% helium

Question 16

GMAW power supplies are ____ type machines.

Answer 16

constant-voltage constant-potential

Question 17

Which of the following is true of backhand welding?

Answer 17

It has good bead visibility and makes welds with deeper joint penetration.

Question 18

Which of the following is true of perpendicular welding technique?

Answer 18

It has a good balance between penetration and reinforcement and is used on automated welding.

Question 19

The purpose of the ____ is to provide a steady and reliable supply of wire to the weld.

Answer 19

electrode feed unit

Question 20

GMA welding machines have ____ duty cycle.

Answer 20

100 percent

Question 21

Which of the following is true of pull-type feed systems?

Answer 21

The gun is heavier and more difficult to use.

Question 22

An advantage of the ____ feed system is that the bulky system of gears is eliminated.

Answer 22

linear

Question 23

____ is a series of ridges cut into the groove.

Answer 23

Knurling

Question 24

In the ____ feed system, the electrode must have enough strength to be pushed through the conduit without kinking.

Answer 24

push-type

Question 25

Which of the following is true of GMA spot welding?

Answer 25

The burning back of the thin material allows the thicker metal to be melted.

Question 26

MIG, MAG, and wire welding are other names for ____________________.

Answer 26

gas metal arc welding
GMAW
gas metal arc welding (GMAW)

Question 27

GMAW is relatively free from spatter because it uses a mode of metal transfer called ____________________ metal transfer.

Answer 27

axial spray

Question 28

The axial spray metal transfer process requires a current level above a critical amount, called the ____________________ current.

Answer 28

transition

Question 29

____________________ transfer can be used on thin materials and at a very low current range.

Answer 29

Globular

Question 30

____________________ systems interlock the power supply and wire feeder.

Answer 30

Synergic

Question 31

The ____________________ rate, measured in inches per minute or pounds per hour, is the rate at which the arc consumes the wire.

Answer 31

wire melting

Question 32

The ____________________ rate is the measure of the weld metal deposited.

Answer 32

deposition

Question 33

The relationships between current and voltage with different combinations of arc length or wire-feed speeds are called ____________________ characteristics.

Answer 33

volt-ampere

volt ampere

Question 34

The rate of voltage decrease as the amperage increases within the working range is known as ____________________.

Answer 34

slope

Question 35

The ____________________ is the distance from the contact tube to the arc measured along the wire.

Answer 35

electrode extension

stickout

Question 36

Explain the axial spray metal transfer process.

Answer 36

his process is identified by the pointing of the wire tip from which very small drops are projected axially across the arc gap to the molten weld pool. There are hundreds of drops per second crossing from the wire to the base metal. These drops are propelled by arc forces at high velocity in the direction the wire is pointing. This projection of drops enables welding in the vertical and overhead positions without losing control of transfer. Some axial spray transfers using high current settings can produce a large molten weld pool that is very fluid, and the weld may be difficult to control in out-of-position welds. Because the drops are very small and directed at the molten weld pool, the process is spatter free.

This spray transfer process requires three conditions: argon shielding (or argon-rich shielding gas mixtures), DCEP polarity, and a current level above a critical amount called the transition current.

Question 37

Explain why the power supply is critical in the short-circuiting transfer process.

Answer 37

The power supply is most critical. It must have a constant potential output and sufficient inductance to slow the time rate of current increase during the short-circuit interval. Too little inductance causes spatter due to high current surges. Too much inductance causes the system to become sluggish. The short-circuiting rate decreases enough to make the process difficult to use. Also, the power supply must sustain an arc long enough to premelt the electrode tip in anticipation of the transfer at recontact with the weld pool.

Question 38

Explain why the use of GMA welding can help reduce waste of filler metals.

Answer 38

GMA welding’s 98% deposition rate of filler metal into the weld makes it one of the most efficient welding processes. Filler metal carries a high cost when it does not get deposited into the weld because of spatter or electrode stubs and becomes wasted material. Using GMA welding will reduce waste.

Question 39

Explain how to measure the wire-feed ipm.

Answer 39

To accurately measure wire-feed ipm, snip off the wire at the contact tube. Squeeze the trigger for 6 seconds; release and snip off the wire electrode. Measure the number of inches of wire that was fed out in the 6 seconds. Now using basic shop math, multiply its total length in inches by 10. The result is how many inches of wire were fed per minute

Question 40

Explain how the GMAW molten weld pool is affected by the travel speed.

Answer 40

Because the location of the arc inside the molten weld pool is important, the welding travel speed cannot exceed the ability of the arc to melt the base metal. Too high a travel speed can result in overrunning of the weld pool and an uncontrollable arc. Fusion between the base metal and filler metal can completely stop if the travel rate is too fast. If the travel rate is too slow and the weld pool size increases excessively, it can also restrict fusion to the base plate.

Question 41

In the beginning, the GMAW process was used to

Answer 41

weld aluminum using argon gas for shielding.

Question 42

The heat produced during axial spray welding using large diameter wire or high current may

Answer 42

be intense enough to shatter the filter lens in a welding helmet.

Question 43

Pulsed-arc welding systems were developed in the

Answer 43

1960s.

Question 44

The thin copper coating on a steel wire electrode either burns off or is diluted into the weld pool with

Answer 44

no significant effect to the weld bead.

Question 45

GMA spot welding is an excellent process for

Answer 45

auto body repair.