Thermally induced reheat crack
A crack that forms during a post-weld heat treatment in high-strength steels when the material cools too fast and grain coarsening occurs.
Physicochemical mechanism of action
Post-weld heat treatment (e.g., tempering) aims to increase the strength and hardness of steels by holding the material at a high temperature and then cooling it slowly. However, if the material cools too quickly, uneven stress distribution occurs in the material. These stresses can lead to cracks, especially if the material has a coarse grain.
Metallurgical relevance & risks in welding
A thermally induced reheat crack can occur during post-weld heat treatment or during cooling after welding. This results in a fine, glass-hard crack in the material that is difficult to detect and repair. The crack can impair the mechanical strength and reliability of the components.
Workshop practice & instructions
To avoid thermally induced reheat cracks, a controlled cooling process should be followed after welding and heat treatment. This means the material must be cooled slowly and uniformly to minimize stress distribution. The exact cooling rate depends on the steel used and the desired material properties. It is important to follow the manufacturer's instructions and, if necessary, use special heat treatment equipment.