Inadequate joint fit-up commonly leads to which defect?

• A. Excess reinforcement
• B. Improved electrical conductivity
• C. Lack of fusion
• D. Faster welding speed

Answer: (C)

When joint fit-up isn’t tight, the molten weld metal can’t properly bridge the gap to the base metals. That means the weld doesn’t fully fuse to the base material in the joint region, creating unjoined areas known as lack of fusion. This defect weakens the weld because a portion of the joint remains unfused rather than being bonded across the entire thickness. Excess reinforcement would come from depositing too much weld metal, not from poor fit-up, and improved electrical conductivity or faster welding speed aren’t defects caused by any fit-up issue.