Cold crack in steel pipe welding

　　Cold crack reasons: the person to be subjected to welding when a large tensile force can be easily torn in the process of cooling the welding material hardenability; welding cooling rate was too late to escape the residual hydrogen in the weld, a hydrogen atom bonded to a hydrogen molecules to a gaseous state into the fine pores of the metal and cause a lot of pressure, so that the local cold-formed metal cracks a lot of pressure; welding stress and tensile stress analysis with a focus on hydrogen embrittlement and hardening occur simultaneously easy to form when cold cracking.

　　Prevention measures: preheat and slow cooling after welding, heat-affected zone austenite decomposition can be a sufficient temperature range, to avoid hardened tissue, while reducing the role of stress in welding; timely hypothermia after welding annealing, dehydroepiandrosterone treatment, eliminate stress generated during welding, and to the diffusion of hydrogen in a timely manner to the outside to go; selection of low hydrogen type electrode and an alkaline flux or austenitic stainless steel welding wire, etc., consumables required drying and strict clean-up groove; protecting and strengthening welding welded at the surface cleaning, to avoid intrusion of hydrogen; choose reasonable welding specifications, using reasonable assembly and welding sequence.

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