AWS Gas Metal Arc Welding (GMAW/MIG) 5

Question 1

In pulsed GMAW (GMAW-P), what is the primary advantage over conventional spray transfer?

Accepted Answer

Allows spray-like transfer at lower average heat input, enabling out-of-position welding

Answer

GMAW-P alternates between peak and background current to achieve spray transfer droplet detachment at a lower average heat input, making out-of-position welding on thinner materials feasible.

Question 2

When qualifying a GMAW procedure per AWS D1.1, changing from ER70S-3 to ER70S-6 wire with the same diameter typically:

Accepted Answer

Is a non-essential variable and does not require re-qualification

Answer

Under AWS D1.1, changing between filler metals of the same F-number and A-number classification is a non-essential variable that does not require re-qualification of the WPS.

Question 3

A GMAW gun's liner becomes kinked or contaminated. What is the most likely symptom during welding?

Accepted Answer

Erratic wire feeding causing arc instability and burn-back

Answer

A damaged or contaminated liner creates friction that causes intermittent wire feeding, leading to arc instability, burn-back, and inconsistent bead quality.

Question 4

What is 'burn-back' in GMAW and what typically causes it?

Accepted Answer

The wire fusing to the contact tip when wire feed speed is too low relative to voltage

Answer

Burn-back occurs when wire feed speed is insufficient relative to the arc voltage, causing the arc to climb up the wire and fuse it to the contact tip.

Question 5

Which shielding gas mixture is generally preferred for GMAW on austenitic stainless steel to minimize carbon pickup and maintain corrosion resistance?

Accepted Answer

98% Ar / 2% O2 or 98% Ar / 2% CO2

Answer

A tri-mix or binary argon gas with only 1–2% CO2 or O2 provides arc stability while minimizing carbon introduction that could sensitize the stainless steel HAZ.

AWS Practice Test

AWS Practice Test

AWS Gas Metal Arc Welding (GMAW/MIG) 5