Why does 304 stainless steel pipe crack

The reasons for the cracking of stainless steel pipes may be as follows:

1. Material quality issues: The quality of the 304 stainless steel pipe is poor or the material does not meet the standards, which may lead to insufficient strength of the pipe, resulting in cracking during use. Non-metallic inclusions in the structure of 304 stainless steel will destroy the integrity of the passivation film on the metal surface and reduce the corrosion resistance of stainless steel. Therefore, the level of non-metallic inclusions should be strictly controlled below level 1.5.

2. Processing technology issues: During the processing of 304 stainless steel pipes, if the processing technology is improper or the processing equipment is inappropriate, cracks may appear on the surface of the pipe, leading to cracking. The Cr content in the 304 stainless steel base material and weld metal is relatively low. Cr deficiency reduces the density of the chromium passivation film on the stainless steel surface. Therefore, the quality requirements for steel pipes and welding materials should be improved, and the ingredients entering the factory should be strictly tested to ensure that the metal composition of the weld is not weaker than the base metal. During the welding process, the welding parameters should be strictly controlled, and the welding heat input should be as small as possible to prevent sensitization, which will cause Cr to precipitate along the grain boundaries to form Cr23C6, and to avoid intergranular corrosion of stainless steel.

3. Use environment issues: During use, if the 304 stainless steel pipe is affected by environmental factors such as excessive temperature, pressure, or corrosion, it may cause the pipe to crack. In a marine atmospheric environment, the chloride ion content in the air is high, and there is a suitable temperature and humidity that accelerates corrosion, which causes the oxide film on the surface of stainless steel to be easily destroyed, causing electrochemical corrosion on the surface of stainless steel, and corrosion micro-cracks in the residual stress Accelerates expansion under the action of, causing stress corrosion cracking. Therefore, the on-site air environment should be strictly controlled and the salt spray environment should be isolated (such as painting or adding a protective layer) to prevent the damaging effects of chloride ions. The damage to 304 stainless steel pipe is stress corrosion cracking. Stainless steel has poor thermal conductivity. The steel pipe produces residual stress due to high temperature after welding. The corrosion micro-cracks generated after the stainless steel pipe is corroded will accelerate its expansion rate under the action of residual stress, forming stress corrosion cracking.