crack defect

Cracks are a common welding defect in threaded steel pipes, posing a significant impact on pipeline safety. They not only accelerate the corrosion rate of steel pipes but also carry the risk of crack propagation, thereby creating substantial safety hazards. The conditions under which steel pipe cracks occur vary and can be classified into hot cracks and cold cracks. Hot cracks form during the welding process due to the aggregation of certain substances, ultimately resulting from weld shrinkage. The diffusion direction of hot cracks primarily leads to the formation of transverse cracks. On the other hand, cold cracks are transformations that occur when the weld cools down to the martensitic temperature after welding. Cold cracks are mainly influenced by factors such as stress, hardened structures, and diffusible hydrogen, which can lead to the formation of both transverse and longitudinal cracks.