Causes of cracking of stainless steel flange

　　First of all, the chemical composition of the cracked stainless steel flange was analyzed. The analysis results showed that the chemical composition of the stainless steel flange and welding data met the requirements of relevant specifications. The Brinell hardness of the stainless steel flange surface and the sealing surface is respectively conducted, and the Brinell hardness value meets the requirements. On the premise that the chemical composition of the data is qualified, the pipeline device meets the technical requirements, the hardness test is qualified, and the operation standard of the pressure test, the stainless steel flange cracks during the pressure test. It is clarified that the defects are related to the internal structure of the stainless steel flange or other unknown elements.

　　The appearance of the leakage stainless steel flange was cut off from the pipeline. The macroscopic inspection of the stainless steel flange showed that there were cracks on the inner and outer surfaces of the stainless steel flange, and rust stains were found on the inner and outer surfaces of the stainless steel flange bolt holes.

　　A number of non-metallic inclusions were found on the stainless steel flange sealing surface and other positions. Some non-metallic inclusions were scattered on the surface of the stainless steel flange sealing surface to form small pits, and the edge of the pits had tiny cracks visible to the naked eye. On site macro inspection shall be carried out for other austenitic stainless steel flanges of the same batch.

　　It is found that there are different levels of defects in many stainless steel flanges, and obvious cracks are found on the surface of some stainless steel flanges. The macro inspection results further indicate that the leakage of stainless steel flange is related to the flange itself. The profile crack morphology is the real reason of stainless steel flange leakage.