What is the term for a depression at the edge of a weld where the base metal has melted?

The term that describes a depression at the edge of a weld, where the base metal has melted, is undercut. This occurs when excessive heat from the welding process causes the edges of the weld to melt away, creating a groove or depression. This defect can negatively impact the structural integrity of the joint by reducing its cross-sectional area and potentially leading to stress concentrations, which can cause failure under load.

Understanding undercut is essential in radiographic testing since it is important to identify such defects on welds to ensure overall weld quality and safety in the component. Recognizing undercut during inspection allows for corrective actions to be taken, ultimately ensuring the weld meets necessary standards and specifications. It's crucial in weld quality control and contributes to the reliability of welded structures in various applications.