AWS Welding Inspection and Testing Certification Practice Test

Undercut in a weld typically refers to a groove or channel that forms at the edge of the weld bead and can compromise the integrity of the weld joint. This defect is often caused by a number of factors related to the welding technique used.

A high travel speed can lead to undercut because it does not allow sufficient heat input into the base metal. When the welder moves too quickly, the heat does not have enough time to penetrate adequately, resulting in inadequate melting of the parent material at the edge of the weld. This insufficient melting leads to a lack of fusion at the edges, creating a concave groove or undercut.

In contrast, other factors such as slow travel speed or improper filler materials tend to create different types of weld defects, such as excessive heat input or poor bead shape, rather than specifically leading to undercut. High heat input can also create problems but in ways that might not directly create undercut but instead might lead to other defects like burn-through or distortion.

By understanding these causes, welders can adjust their techniques to avoid undercut and ensure stronger, more reliable welds.