Undercut is commonly caused by which condition during welding?

Undercut is commonly caused by which condition during welding?

• A. Low current and slow travel speed
• B. Inadequate shielding gas coverage
• C. Excess filler metal addition
• D. High current or improper technique causing groove at the base metal edge

Answer: (D)

Undercut happens when the weld consumes and melts away the edge of the base metal at the weld toe, leaving a groove that the weld metal doesn’t fill. This is typically caused by too much heat input—often from too high current—or improper technique, which melts the base metal edge more than the filler metal can fill in. The arc is too aggressive or directed in a way that eats back the edge, so a groove forms along the edge rather than a smooth, filled weld. Other factors don’t fit this pattern: inadequate shielding gas mainly leads to porosity or contamination, not a groove at the edge; too little heat (low current, slow travel) reduces penetration and fusion rather than carving out the edge; adding excess filler metal generally causes buildup or excess weld metal rather than a groove along the base metal edge.

Undercut happens when the weld consumes and melts away the edge of the base metal at the weld toe, leaving a groove that the weld metal doesn’t fill. This is typically caused by too much heat input—often from too high current—or improper technique, which melts the base metal edge more than the filler metal can fill in. The arc is too aggressive or directed in a way that eats back the edge, so a groove forms along the edge rather than a smooth, filled weld.

Other factors don’t fit this pattern: inadequate shielding gas mainly leads to porosity or contamination, not a groove at the edge; too little heat (low current, slow travel) reduces penetration and fusion rather than carving out the edge; adding excess filler metal generally causes buildup or excess weld metal rather than a groove along the base metal edge.