What is crater fill and how is it achieved in GMAW?

• A. Stopping immediately at the crater
• B. Continuing the bead into the crater or weaving slightly in
• C. Filling with separate cold filler wire after the weld
• D. Grinding the crater after weld

Answer: (B)

In GMAW, crater fill means finishing the weld so the end of the bead is fully filled with molten metal, not left as an open indentation. The best way to do this is to extend the bead into the crater or weave slightly as you end the weld so the last portion of metal flows into and fills the crater. This creates a smooth, continuous fusion with the rest of the bead and reduces the risk of cracking as the metal cools.

Stopping right at the crater leaves an unfilled recess that can crack as it cools, and grinding the crater only reshapes the surface without adding metal. Filling with separate cold filler wire after the weld isn’t how crater fill is typically done in GMAW and can introduce alignment and metallurgical issues. So continuing the bead into the crater or weaving a bit into it best accomplishes crater fill.