Cracks are one of the most dangerous defects in the performance of the structure of the rust joint, and any form of crack is prohibited in the cracks.

Cracking is a crack in the joint of materials caused by the combined effect of the joint force of the substrate and other brittle factors, forming a gap in the new territories interface. 

According to the production conditions of the crack, it can be divided into thermal crack, cold crack, reheat thermal crack, layered tear and stress corrosion crack. Following we introduce the most common crack form - thermal crack.