Cold Crack
Cold cracks are cracks that form only during cooling below room temperature. Causes are dissolved hydrogen, hard microstructures, and residual stresses. They lead to wear and fracture.
Physical-chemical mechanism
Cold cracks occur due to the diffusion of dissolved hydrogen into the metal during welding. During cooling, hydrogen gas forms, stressing the material structure and causing cracks.
Metallurgical relevance & risks in welding
Cold cracks can lead to wear and fracture, especially in hard microstructures like martensite. They are particularly dangerous if not detected and treated, as they can significantly shorten the service life of components.
Workshop practice & action instructions
To avoid cold cracks, it is important to carefully select the welding process and materials. For hard steels, hydrogen diffusion can be reduced by treating the metal in a cold water bath before welding or by using a suitable protective agent. After welding, sufficient cooling is required to minimize hydrogen gas formation.