Which statement best describes the filler pass in terms of fusion and penetration?

• A. Complete fusion with little penetration
• B. High penetration with fusion
• C. No fusion
• D. Excessive penetration

Answer: (A)

The filler pass is meant to add material and fill the joint while relying on the root already established. It should fuse with the base metal and the previous weld beads to create a sound weld, but its depth into the joint isn’t the goal—the root pass provides the penetration. So a filler pass should exhibit complete fusion with the base metal but only little penetration, which is exactly what the statement describes. High penetration would be a result of too much heat or a root-pass effect, no fusion would mean a weak or incomplete weld, and excessive penetration isn’t characteristic of a filler pass.