AWS Troubleshooting & Diagnostics 3 — Questions and Answers
Question 1: Porosity is found throughout a GMAW weld on galvanized steel. What is the primary cause?
- Incorrect polarity
- Zinc vapor from the coating contaminating the weld pool (Correct answer)
- Travel speed too slow
- Contact tip too far from the work
Correct answer: Zinc vapor from the coating contaminating the weld pool
Galvanized steel releases zinc vapors during welding that become trapped in the solidifying weld pool, causing porosity.
Question 2: A welder experiences arc blow when using SMAW with DC current. Which is the most effective remedy?
- Switch to AC current (Correct answer)
- Increase electrode diameter
- Reduce shielding gas flow
- Increase amperage
Correct answer: Switch to AC current
Arc blow is caused by magnetic fields associated with DC current; switching to AC eliminates the directional magnetic force that causes arc deflection.
Question 3: Crater cracks appear at the end of a weld pass. What is the most effective prevention technique?
- Increase travel speed at the end of the pass
- Use a run-off tab or backfill the crater before extinguishing the arc (Correct answer)
- Reduce preheat at the end of the joint
- Switch to a smaller electrode
Correct answer: Use a run-off tab or backfill the crater before extinguishing the arc
Using a run-off tab or backfilling the crater ensures the shrinkage void is filled before the weld metal solidifies, preventing crater cracks.
Question 4: During SMAW in the vertical-up position, the welder notices the weld metal sagging. What adjustment should be made?
- Increase amperage
- Use a larger diameter electrode
- Reduce amperage and use a weaving technique (Correct answer)
- Increase travel speed and voltage
Correct answer: Reduce amperage and use a weaving technique
Reducing amperage lowers heat input so the weld pool is less fluid, and a weaving technique allows the metal to partially solidify before depositing more.
Question 5: A weld joint shows incomplete joint penetration (IJP) on a butt weld. Which factor is least likely to be the cause?
- Root opening too narrow
- Amperage too low
- Travel speed too fast
- Shielding gas mixture containing argon (Correct answer)
Correct answer: Shielding gas mixture containing argon
Argon-containing shielding gas is used routinely in GMAW and is not a cause of incomplete joint penetration; root gap, amperage, and travel speed all directly affect penetration.
Question 6: Weld cracks appear in the heat-affected zone (HAZ) of a high-carbon steel weld shortly after welding. This is most likely:
- Hot cracking
- Hydrogen-induced cracking (cold cracking) (Correct answer)
- Crater cracking
- Solidification cracking
Correct answer: Hydrogen-induced cracking (cold cracking)
Hydrogen-induced cracking occurs in the HAZ of high-carbon or high-hardenability steels, typically within hours or days after welding.
Question 7: A GTAW weld on stainless steel shows a grey, scaly discoloration that extends well beyond the weld bead. This indicates:
- Correct shielding gas coverage
- Inadequate back-purging or trailing shielding (Correct answer)
- Excessive filler metal addition
- Correct heat input
Correct answer: Inadequate back-purging or trailing shielding
Grey or black oxidation on stainless steel indicates that the weld and HAZ were exposed to oxygen, pointing to inadequate shielding on the root or trailing side.
AWS Troubleshooting & Diagnostics 3
Porosity is found throughout a GMAW weld on galvanized steel.
What is the primary cause?