MIG Flashcards
MAG is short for ____.
metal active gas welding
Which of the following tasks is done by a machine?
Maintaining the arc in semiautomatic welding processes.
Which of the following tasks are done by the welder?
Providing the joint guidance in machine welding processes.
The shielding gas used on carbon steel is ____.
carbon dioxide, or a mixture of carbon dioxide and argon
Which of the following is true of axial spray metal transfer?
There are hundreds of drops per second crossing from the wire to the base metal.
In axial spray metal transfer, the shielding gas is usually a mixture of ____.
95% to 98% argon and 2% to 5% oxygen
Which of the following is true of axial spray transfers using high current settings?
High current settings may cause the weld to be difficult to control in out-of-position welds.
Which of the following is true of globular transfer?
It is used in combination with pulsed-spray transfer.
Globular transfer occurs at a rate of ____ drops per second.
a few
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.
ramp up
In the pulsed-arc metal transfer current cycle, ____ refers to the surging electrical current passing through the transformer like a wave on water.
overshoot
In the pulsed-arc metal transfer current cycle, ____ is the peak current that flows across the arc during the high current pulse.
high pulse current
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.
ramp down
With the addition of ____ to the argon gas, the transfer becomes progressively more ____.
helium, globular
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.
80% helium
GMAW power supplies are ____ type machines.
constant-voltage constant-potential
Which of the following is true of backhand welding?
It has good bead visibility and makes welds with deeper joint penetration.
Which of the following is true of perpendicular welding technique?
It has a good balance between penetration and reinforcement and is used on automated welding.
The purpose of the ____ is to provide a steady and reliable supply of wire to the weld.
electrode feed unit
GMA welding machines have ____ duty cycle.
100 percent
Which of the following is true of pull-type feed systems?
The gun is heavier and more difficult to use.
An advantage of the ____ feed system is that the bulky system of gears is eliminated.
linear
____ is a series of ridges cut into the groove.
Knurling
In the ____ feed system, the electrode must have enough strength to be pushed through the conduit without kinking.
push-type
Which of the following is true of GMA spot welding?
The burning back of the thin material allows the thicker metal to be melted.
MIG, MAG, and wire welding are other names for ____________________.
gas metal arc welding
GMAW
gas metal arc welding (GMAW)
GMAW is relatively free from spatter because it uses a mode of metal transfer called ____________________ metal transfer.
axial spray
The axial spray metal transfer process requires a current level above a critical amount, called the ____________________ current.
transition
____________________ transfer can be used on thin materials and at a very low current range.
Globular
____________________ systems interlock the power supply and wire feeder.
Synergic
The ____________________ rate, measured in inches per minute or pounds per hour, is the rate at which the arc consumes the wire.
wire melting
The ____________________ rate is the measure of the weld metal deposited.
deposition
The relationships between current and voltage with different combinations of arc length or wire-feed speeds are called ____________________ characteristics.
volt-ampere
volt ampere
The rate of voltage decrease as the amperage increases within the working range is known as ____________________.
slope
The ____________________ is the distance from the contact tube to the arc measured along the wire.
electrode extension
stickout
Explain the axial spray metal transfer process.
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.
Explain why the power supply is critical in the short-circuiting transfer process.
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.
Explain why the use of GMA welding can help reduce waste of filler metals.
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.
Explain how to measure the wire-feed ipm.
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
Explain how the GMAW molten weld pool is affected by the travel speed.
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.
In the beginning, the GMAW process was used to
weld aluminum using argon gas for shielding.
The heat produced during axial spray welding using large diameter wire or high current may
be intense enough to shatter the filter lens in a welding helmet.
Pulsed-arc welding systems were developed in the
1960s.
The thin copper coating on a steel wire electrode either burns off or is diluted into the weld pool with
no significant effect to the weld bead.
GMA spot welding is an excellent process for
auto body repair.
