Which technique helps prevent crater cracking at the end of a weld bead in GMAW?

• A. Reducing shielding gas flow to end the arc earlier
• B. Gradually slowing and filling the crater, or performing a small restart or tie-in before finishing the bead
• C. Stopping abruptly at the end
• D. Increasing travel speed to finish quickly

Answer: (B)

Ending a weld bead in GMAW is prone to crater cracking because the last portion of the pool can cool and contract too quickly, creating a weak, stressed termination. The best way to prevent this is to manage heat and fill the crater as you finish: gradually slow the travel as you approach the end and fill the crater, or perform a small restart or tie-in before finishing the bead. This keeps the weld pool continuous and allows the last section to fuse smoothly with the rest of the bead, reducing residual stresses and preventing a crack from starting as the metal solidifies.

Why this works: a controlled crater fill or tie-in ensures the final solidification occurs with proper heat input and fusion, avoiding a sharp, uncontrolled termination that can act as a crack initiation site. It also helps maintain consistent bead shape and strength at the end.

Reducing shielding gas flow to end the arc early would expose the weld area to contamination and porosity rather than addressing crater cracking. Stopping abruptly creates a sharp crater and high stress concentration. Increasing travel speed finishes the bead quickly but lowers heat input and can leave an underfilled, vulnerable termination.