AWS Weld Discontinuities & Defects 1 — Questions and Answers
Question 1: Which weld discontinuity is described as a groove melted into the base metal along the toe of the weld?
- Overlap
- Undercut (Correct answer)
- Underfill
- Incomplete fusion
Correct answer: Undercut
Undercut is a groove or channel melted into the base metal at the weld toe or weld root that is left unfilled by weld metal.
Question 2: What is the primary cause of porosity in a completed weld?
- Excessive preheat temperature
- Entrapped gas in the solidifying weld pool (Correct answer)
- Too slow a travel speed
- High interpass temperature
Correct answer: Entrapped gas in the solidifying weld pool
Porosity is caused by gas that becomes entrapped in the solidifying weld pool before it can escape, forming voids or pockets.
Question 3: The term 'incomplete fusion' refers to which weld discontinuity?
- Weld metal that overflows onto the base metal surface
- A lack of bond between weld metal and base metal or between weld passes (Correct answer)
- Insufficient depth of weld penetration
- A surface crack along the centerline of the weld
Correct answer: A lack of bond between weld metal and base metal or between weld passes
Incomplete fusion (also called lack of fusion) occurs when the weld metal fails to fuse properly with the base metal or with adjacent weld passes.
Question 4: Overlap in a weld is best described as:
- Weld metal protruding beyond the weld toe onto the base metal without fusion (Correct answer)
- Excessive weld reinforcement above the base metal surface
- An undercut groove at the edge of the weld
- Weld metal that bridges over slag inclusions
Correct answer: Weld metal protruding beyond the weld toe onto the base metal without fusion
Overlap is a condition where weld metal flows over the base metal surface beyond the weld toe but does not fuse with it, creating a mechanical notch.
Question 5: Crater cracks most commonly form at which location?
- Along the heat-affected zone (HAZ)
- At the start of a weld bead
- In the depression at the end of a weld bead where the arc was extinguished (Correct answer)
- At the weld root on the back side of the joint
Correct answer: In the depression at the end of a weld bead where the arc was extinguished
Crater cracks form in the crater (depression) left at the end of a weld bead when the arc is extinguished, because the small pool cools rapidly under high restraint.
Question 6: A longitudinal crack in a weld is oriented in which direction?
- Perpendicular to the weld axis
- Parallel to the weld axis (Correct answer)
- At a 45-degree angle to the weld surface
- Parallel to the plate surface in the HAZ only
Correct answer: Parallel to the weld axis
A longitudinal crack runs parallel to the weld axis (along the length of the weld) and can occur in the weld metal or heat-affected zone.
Question 7: Underfill is a weld discontinuity that occurs when:
- The weld pool is too hot and burns through the base metal
- The weld face or root surface is below the adjacent base metal surface (Correct answer)
- Slag is trapped between weld passes
- The weld metal overlaps the base metal without fusing
Correct answer: The weld face or root surface is below the adjacent base metal surface
Underfill occurs when the deposited weld metal is insufficient to fill the groove or joint, leaving the weld face or root surface below the plane of the base metal.
AWS Weld Discontinuities & Defects 1
Which weld discontinuity is described as a groove melted into the base metal along the toe of the weld?