What can cause undercut in a weld?

Undercut in a weld refers to the groove or notch that can occur along the edges of the weld bead, which can significantly weaken the joint if not addressed. The selection of the wrong electrode angle directly influences the weld bead's formation and can lead to improper fusion and inadequate fill of the joint. When the electrode angle is not optimized—whether it’s too steep or too flat—the molten metal may not adequately penetrate or cover the base metal, resulting in a gap that manifests as undercut.

While other factors like welding speed, improper cooling, and excessive heat input can also affect weld quality, they primarily contribute to different defects rather than specifically causing undercut. For instance, an incorrect welding speed can lead to a range of problems such as incomplete penetration but does not necessarily create undercut. Similarly, improper cooling may cause issues like cracks or warping but doesn't directly result in undercut. Excessive heat input can lead to a myriad of defects, including distortion and loss of properties, but the direct relationship to undercut is primarily associated with how the electrode angle governs the weld profile. Thus, the electrode angle plays a crucial role in achieving a strong and defect-free weld, making it essential to maintain the correct angle for proper weld integrity.