When is crater cracking most likely to occur?

Crater cracking is most likely to occur during the welding process, particularly in the heat-affected zone of the weld. This phenomenon is associated with the changes in material properties due to the intense heat generated while welding.

As the weld pool solidifies, it may do so in an uneven manner, leading to stress concentrations in the microstructure of the material. These stresses can exceed the tensile strength of the material, especially in areas where impurities or changes in crystal structure exist. The rapid cooling and solidification process can create a non-uniform distribution of temperature and mechanical properties, which increases the likelihood of cracks forming at the end of the weld bead or in craters left behind after the welding process.

While other stages such as preheating or cooling could potentially lead to issues, crater cracking is specifically associated with the weld itself, making the welding phase the most critical time for its occurrence. Inspection, which occurs after welding, generally aims at identifying any already existing defects rather than being a stage where new defects, like crater cracks, develop.