What is meaning of Under Cut in Welding?

1. UNDER CUT –

 “A defect that appears as a groove formed in the BM adjacent to the toe of a weld along the edge of the weld & left unfilled by the weld metal”.

• Generally located parallel to the junction of weld metal & base metal at the toe or root of the weld
• Reduces the cross-sectional thickness of the base metal
• Acts as stress raiser in fatigue loading

Cause and prevention of undercut:

Cause – 

• High welding current & arc voltage
• Too large electrode dia
• Incorrect electrode angle
• Longer arc length

 Prevention:

• Use prescribed welding current for electrode size.
• Adjust electrode angle to fill undercut area.
• Correct travel speed, arc length, etc.