28.9. Crack defects?

Cracks are a common welding defect in rebar steel pipes, significantly affecting the safety of pipelines. They not only accelerate the corrosion rate of the steel pipes but also pose a risk of crack propagation, resulting in serious safety hazards. The conditions under which steel pipe cracks develop vary and can be divided into hot cracks and cold cracks. Hot cracks occur during the welding process when certain substances accumulate, ultimately leading to cracks due to the shrinkage of the weld. The propagation direction of hot cracks primarily results in transverse cracks. Cold cracks occur when the temperature drops to martensite temperature after welding. Cold cracks are mainly influenced by stress and factors such as hardened structures and diffused hydrogen, potentially leading to both transverse and longitudinal cracks.