AWS Weld Discontinuities & Defects 5 — Questions and Answers
Question 1: A weld cross-section shows weld metal that has rolled over the base metal surface without fusing to it. This discontinuity is called:
- Undercut
- Overlap (Correct answer)
- Cold lap
- Convexity
Correct answer: Overlap
Overlap (also called cold lap) occurs when weld metal flows over the base metal surface and solidifies without achieving fusion, creating a notch-like condition.
Question 2: Which type of porosity is characterized by a single large void elongated along the weld axis?
- Cluster porosity
- Wormhole (piping) porosity (Correct answer)
- Scattered porosity
- Surface porosity
Correct answer: Wormhole (piping) porosity
Wormhole or piping porosity consists of elongated tubular voids that form parallel to the weld axis due to gas escaping during solidification.
Question 3: During multi-pass welding, which action is MOST important to prevent inter-pass slag inclusions?
- Increasing amperage on each subsequent pass
- Thoroughly removing slag between passes (Correct answer)
- Reducing preheat temperature
- Using a larger diameter electrode for fill passes
Correct answer: Thoroughly removing slag between passes
Thorough slag removal between passes prevents slag from being trapped under subsequent weld beads, which would create slag inclusions.
Question 4: Incomplete joint penetration (IJP) in a groove weld is MOST commonly caused by:
- Excessive preheat
- Insufficient groove angle or root opening (Correct answer)
- Too high a travel speed combined with excessive current
- Moisture in the shielding gas
Correct answer: Insufficient groove angle or root opening
Insufficient groove angle or inadequate root opening prevents the arc from reaching the root of the joint, resulting in incomplete joint penetration.
Question 5: Which of the following BEST describes a 'cold crack' in welding?
- A crack that forms above 1000°F during solidification
- A crack that forms at or near room temperature after the weld has cooled (Correct answer)
- A crack caused by excessive heat input during welding
- A crack that only occurs in aluminum alloys
Correct answer: A crack that forms at or near room temperature after the weld has cooled
Cold cracks (hydrogen-induced cracks) form at or near room temperature after the weld cools, driven by hydrogen, residual stress, and a susceptible microstructure.
Question 6: A radiograph shows a dark, rounded indication with a fuzzy outline at the center of a weld bead. This is MOST likely:
- Tungsten inclusion
- Gas porosity (Correct answer)
- Slag inclusion
- Incomplete fusion
Correct answer: Gas porosity
Gas porosity appears as rounded, dark indications with relatively smooth edges on a radiograph because the spherical void absorbs less radiation than surrounding metal.
Question 7: Which discontinuity is UNIQUE to gas tungsten arc welding (GTAW) and not found in other arc welding processes?
- Porosity
- Tungsten inclusion (Correct answer)
- Undercut
- Overlap
Correct answer: Tungsten inclusion
Tungsten inclusions are unique to GTAW because the non-consumable tungsten electrode can contaminate the weld pool if it contacts the molten metal or is improperly sized.
AWS Weld Discontinuities & Defects 5
A weld cross-section shows weld metal that has rolled over the base metal surface without fusing to it.
This discontinuity is called: