Excessively high current leads to which of the following effects?

• A. Melt through; excessively long HAZ; Undercut; Increased distortion
• B. Only improved penetration
• C. No effect
• D. Only increased bead width

Answer: (A)

Excessive current injects a lot of heat into the weld zone, so heat input becomes too high. That extra heat pushes the weld pool to be deeper and wider, which can cause the base metal to melt through in thin sections and create an excessively long heat-affected zone where the surrounding metal undergoes microstructural changes. The excessive heat also erodes the weld toe, producing an undercut, a groove along the edge of the weld. As the metal heats and then cools, it warps and distorts because of uneven expansion and contraction and the buildup of residual stresses. So, you get melt-through, an overly large HAZ, undercut, and more distortion—all tied to too much current. Higher current can improve penetration in some cases, but when it’s excessive, these defects dominate, which is why this option is the best description.