What does the term 'undercut' describe in welding?

Undercut refers specifically to a type of weld defect characterized by a groove or notch that forms at the edge of a weld joint. This defect occurs when there is inadequate filler material in the weld pool, leading to the melting of the base metal adjacent to the weld but not being filled adequately with the weld metal. The presence of an undercut can significantly weaken the joint by reducing the effective cross-sectional area, thereby making the weld susceptible to cracks and premature failure under stress.

Identifying undercut is important because it impacts the overall strength and integrity of the weldment. Weld inspectors often look for undercuts during quality control checks, as it serves as an indicator of the quality of the welding practices used. Correcting undercuts typically involves increasing the amount of filler material or adjusting the welding parameters to ensure better fusion between the base metal and the weld itself. Understanding this defect is critical for welders and inspectors alike to maintain high standards in welding practices.