AWS Certified Welding Inspector — FundamentalsWelding MetallurgyEasy
A welding inspector is performing a visual inspection on a newly fabricated carbon steel pipe. The inspector notices that the weld bead has a convex profile and appears to have spilled over the edges of the joint without properly fusing to the base metal. What type of weld discontinuity is this?
- AIncomplete Fusion
- BOverlap
- CUndercut
- DUnderfill
Show answer & explanationAnswer & explanation
Correct answer: B. Overlap
Overlap is a weld discontinuity characterized by the weld metal extending beyond the toe or root of the weld, over the surface of the base metal, without being fused to it. The description of a convex profile and spilling over the edges without proper fusion perfectly matches the definition of overlap.
Why the other options are wrong
- A. Incomplete fusion is a lack of coalescence between the weld metal and the base metal or between adjacent weld beads within the weld.
- C. Undercut is a groove melted into the base metal adjacent to the toe or root of a weld, left unfilled by weld metal.
- D. Underfill is a depression on the face or root surface of the weld, below the level of the adjacent base metal.
Overlap (Weld Discontinuity)
A weld discontinuity where the weld metal extends beyond the toe or root of the weld, over the surface of the base metal, without being fused to it.
- Appearance: convex weld bead that 'rolls over' the edges.
- Occurs at the weld toe or root.
- Indicates lack of fusion in the overlapping area.
- Often caused by low travel speed, incorrect electrode angle, or low heat input.
Memory trick: Overlap is when the weld metal 'laps over' without sticking.