What could cause undercut during welding?

When considering the causes of undercut during welding, having the current setting too high is indeed a significant factor. When the welding current is set too high, it leads to excessive heat input. This increased heat can cause the molten metal to erode the edges of the weld pool, leading to undercutting along the base metal. The undercut occurs because the base metal melts away more than desired, creating a groove or notch along the edges of the weld bead, where no filler metal has been deposited.

While electrode size, angle, and the cleanliness of the base metal can also impact weld quality, they do not directly produce undercut in the same way that excessive heat from a high current setting does. Adjusting the current appropriately is crucial to ensure proper penetration and fusion without eroding the base material excessively.