Which of the following defects is unlikely to be found by visual inspection?

• A. Linear misalignment
• B. Undercut
• C. Overlap
• D. Linear slag inclusion

Answer: (D)

Linear slag inclusion is unlikely to be detected through visual inspection due to its typically internal nature within the weld bead. This defect occurs when slag, which is a byproduct of the welding process, becomes trapped within the weld metal rather than being cleaned away. Since linear slag inclusions do not necessarily alter the surface profile of the weld significantly, they may not be visible to the naked eye.

In contrast, defects such as linear misalignment, undercut, and overlap generally manifest on the surface of the weld. For instance, linear misalignment can be observed directly as a deviation from the intended alignment in the welded joint. Undercut presents as a groove or recess along the edge of the weld, and overlap appears as a metal layer that has not fused properly, both of which can be assessed visually. Therefore, these defects can typically be identified during visual inspections, making them distinguishable from linear slag inclusions.