What are the causes of welding cracks in stainless steel pipes

1. Welding cracks in stainless steel pipes is caused by overheating.

Hot cracks are cracks that occur during the high-temperature stage of the welding cooling process and mainly exist in the weld metal. A small number also occur near the joint, and they are classified as crystallization (solidification) cracks, liquefaction cracks, and multilayer cracks. Among them, crystallization cracks are a common type of crack, mainly occurring in the welding of carbon steel with a high content of impurity elements.

2. Welding cracks in stainless steel pipes is caused by reheating.

During the stress relief process of thick plate welded structures, when there is stress concentration of varying degrees in the coarse-grained region of the heat-affected zone, the additional deformation caused by stress relaxation exceeds the creep plasticity of that area, thus producing reheating cracks. The production temperature is usually 550℃~650℃; cracks in 36L stainless steel pipes are usually located in the coarse-grained region of the heat-affected zone. The crack morphology is along the grain boundaries.

3. Welding cracks in stainless steel pipes are caused by cold cracks.

When the welded joint cools to a lower temperature (the unit for steel is m), cracks that occur due to the temperature being lower than the required level are called cold cracks. Cold cracks can appear immediately after welding or after a period of time. This type of crack, also called delayed cracking, is a common form of cold cracking and is quite dangerous.

4. Welding cracks in stainless steel pipes are caused by stress corrosion cracking.

Some welded structures experience delayed cracking. Under the combined action of corrosive media and stress, it can occur at any temperature; cracks typically appear in the weld and heat-affected zone. The crack morphology is intergranular or transgranular.

5. Welding cracks in stainless steel pipes is caused by delamination.

This is mainly due to the presence of layered inclusions in the steel plate (along the rolling direction). Stress perpendicular to the rolling direction exists at the weld, leading to "step-like" layered cracking in the heat-affected zone or slightly further away. The formation temperature is usually below 400℃; the crack is usually located near the heat-affected zone. The crack morphology is transgranular or intergranular.