What can cause undercut in a weld?

Undercut in a weld occurs when there is a groove or ditch at the weld toe or along the edges of the weld bead, which can significantly weaken the joint. The selection of an improper electrode angle is crucial because it affects the heat concentration and the direction of the molten filler metal. When the angle is incorrect, it may lead to insufficient melting of the base material or improper fusion, causing an unintentional cavity at the edges of the weld. This can prevent the weld metal from properly bonding with the base materials, resulting in undercut.

Other factors like the wrong time setting can affect the weld quality but do not specifically contribute to undercut as directly as the angle of the electrode. Incorrect filler material affects the mechanical properties and compatibility of the weld but does not lead to undercut specifically. Inadequate cleaning can lead to contamination issues and poor bonding but is also not the primary cause of undercut itself.