How can you identify an undercut in a weld?

An undercut in a weld is identified by the presence of a groove or crater at the edge of the weld bead. This defect occurs when the base metal is melted away along the edges of the weld, leaving a depression or notch that can compromise the integrity of the weld joint. The undercut can lead to stress concentration in that area, ultimately affecting the overall strength and durability of the weld.

Recognizing an undercut is crucial for ensuring the quality of the weld, as it may not be visually appealing and can be a potential point for crack initiation under stress. Understanding this defect helps welders to adjust their techniques or settings accordingly to prevent it in future welds.