49 Crater Cracks
Crater cracks are star-shaped, hot cracks that extend from the center of the crater of the weld to the edge of the weld. Crater cracks are caused by failing to back-fill the crater before terminating the arc at the end of a weld.
Crater cracks are most often found in materials with high coefficients of expansion such as aluminum and austenitic stainless steels. Crater cracks may be the starting point for throat cracks, particularly when the crater formed is not filled to the full cross section of the weld.
Crater cracks are most commonly detected by visual examination (VT), as they are clearly visible to the naked eye as star-shaped fissures in the small crater formed at the termination of a weld pass.
Crater Crack Prevention
Crater cracks are prevented by properly terminating the weld. Methods used to prevent cracks include:
- Back-stepping the arc into previously solidified material before breaking it
- Filling craters to a slightly convex shape prior to breaking the arc
- Using a run-off tab
A run-off tab is a piece of metal of the same composition and thickness as the base metal that is tacked to the metal to allow the weld to be completed. The run-off tab is later removed by cutting it off.
