GMAW Fundamentals: Part 1 of 2 (WDTM3)

The learner will examine the fundamentals of GMAW.

Author - Craig Schmidt

Question 1: What does the abbreviation GMAW stand for?

Answer 1: Great Metal Arc Working

Answer 2: Gas Material Arc Welding

Answer 3: Gas Metal Arc Welding

Correct Answer: Gas Metal Arc Welding

Feedback: Gas metal arc welding is a welding process that uses an arc between a continuous filler metal electrode and the weld pool.

Question 2: What is another abbreviation for GMAW ?

Answer 1: MIG

Answer 2: WAMG

Answer 3: MEG

Correct Answer: MIG

Feedback: MIG stands for Metal Inert Gas.

Question 3: The three basic metal transfer modes in GMAW are short circuiting, globular transfer, and spray transfer. What would a fourth one be?

Answer 1: Under arc

Answer 2: Hot spray

Answer 3: Pulse spray

Answer 4: Under arc or hot spray

Correct Answer: Pulse spray

Feedback: Pulse spray is much like a spray transfer but it has two levels of current: one constant lower background current and a second pulsing current that goes above the “transition current” to spray. Pulse spray also requires a special pulsing power source.

Question 4: What material thickness is recommended for short circuit transfer?

Answer 1: 2 inch

Answer 2: Thin

Answer 3: Thick

Answer 4: Any thickness

Correct Answer: Thin

Feedback: Because of the low voltages and currents (amps) used, thin material is best suited for short circuit transfer.

Question 5: How many short circuits occur per second while welding in short circuit transfer?

Question Image

Answer 1: 5-15

Answer 2: 600-800

Answer 3: Two

Answer 4: 20-250

Correct Answer: 20-250

Feedback: "Short circuit" is defined as an arc-on/arc-off weld cycle.

Question 6: Buried arc is an offshoot of short circuit. What makes buried arc different from short circuit?

Answer 1: The name

Answer 2: The wire and gas used

Answer 3: Excessive wire feed speeds (WFS)

Answer 4: The machine being used

Correct Answer: Excessive wire feed speeds (WFS)

Feedback: Buried arc creates short circuits below the surface of the material.

Question 7: Globular transfer is the least preferred transfer method.

Answer 1: True

Answer 2: False

Correct Answer: True

Feedback: Globular transfer is the least preferred transfer method because of the large amounts of spatter created and the possibilities of weld discontinuities.

Question 8: Spray transfer requires an argon gas content of at least what percentage?

Answer 1: 75%

Answer 2: 50%

Answer 3: 90%

Answer 4: 80%

Correct Answer: 80%

Question 9: How many times does the electrode contact the material when welding in spray transfer?

Question Image

Answer 1: 20-200

Answer 2: 50-100

Answer 3: One

Answer 4: 10

Correct Answer: One

Feedback: Spray transfer is defined as an open arc (always on). Droplets form and detach across the arc at a rate of hundreds per second and therefore only contact the material once at the arc start.

Question 10: Spray transfer requires high voltages and high WFS. What positions and thickness of material is spray transfer best suited for?

Answer 1: All positions and all thicknesses

Answer 2: Overhead and vertical positions using thin materials

Answer 3: Flat and horizontal positions using thicker materials

Correct Answer: Flat and horizontal positions using thicker materials

Feedback: Because of surface tension and gravity, spray transfer is not suited for overhead or vertical positions. And because of the high voltages and WFS, thin materials are not recommended.

Question 11: Increasing wire feed speed will increase all except what?

Answer 1: Depth and width of penetration

Answer 2: Deposition rate

Answer 3: Quality

Answer 4: Weld bead size

Correct Answer: Quality

Feedback: Welding amperage (current) varies with the wire feed speed setting if no other variables are changed. Increasing the current will increase the heat on the wire, producing greater penetration.

Question 12: What happens when voltage is increased?

Answer 1: The fusion zone increases

Answer 2: The weld profile flattens

Answer 3: The fusion zone increases and the weld zone flattens

Answer 4: It makes no difference

Correct Answer: The fusion zone increases and the weld zone flattens

Feedback: Welding voltage is directly related to the arc length. Increasing the voltage will heat the base material more, producing a wider, flatter bead profile.

Question 13: What happens when voltage is decreased?

Answer 1: A narrow weld bead with a high crown is produced

Answer 2: The weld profile flattens

Answer 3: The fusion zone decreases

Answer 4: It makes no difference

Correct Answer: A narrow weld bead with a high crown is produced

Question 14: What two settings dictate the mode of transfer you are in?

Answer 1: There is only one setting: wire feed speed

Answer 2: There is only one setting: voltage

Answer 3: Power switch and time

Answer 4: Wire feed speed and voltage

Correct Answer: Wire feed speed and voltage

Question 15: What material can NOT be welded with GMAW?

Answer 1: Copper

Answer 2: Aluminum

Answer 3: Stainless steel

Answer 4: Titanium

Answer 5: Carbon steel

Answer 6: Low alloy steel

Answer 7: Cardboard

Correct Answer: Cardboard

Feedback: Carbon steel, high-strength low-alloy steel, stainless steel, aluminum, copper, titanium, and nickel alloys can be welded with GMAW by choosing the appropriate combination of shielding gases, electrodes, and welding variables.

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