Physical and chemical analysis of cracking causes of Haokun stainless steel flange
Firstly, the chemical composition of the cracked stainless steel flange was analyzed
The analysis results show that the chemical composition of thestainless steel flange and welding material meet the requirements of relevant standards. The Brinell hardness test was carried out on the outer surface of the stainless steel flange neck and the sealing surface respectively, and the Brinell hardness test value met the requirements of jb4728-2000 standard.
On the premise that the chemical composition of the material is qualified, the hardness test is qualified, the pipeline installation meets the technical requirements and the operation specifications of the pressure test, the pipeline stainless steel flange cracks during the pressure test, indicating that the defects are related to the internal organization structure of the stainless steel flange or other unknown factors.
2 crack property analysis of stainless steel flange
2.1 surface crack morphology
Cut the leaking stainless steel flange from the pipeline and conduct a comprehensive macro inspection. Stainless steel flange is found that there are cracks on the inner surface of the stainless steel flange, 3mm long and 0.5mm wide, and rust stains have been generated near the cracks; Many cracks are also found on the inner surface of stainless steel flange bolt holes; A number of non-metallic inclusions were found on the stainless steel flange sealing surface and other positions. Individual non-metallic inclusions fell off and formed small pits on the flange sealing surface. The pits were 2.0mm in size and 0.8mm in size. There were small cracks visible to the naked eye at the edge of the pits.
Through on-site macro inspection of other austenitic stainless steel flanges of the same manufacturer and batch, it is found that many flanges have different degrees of defects, and there are obvious cracks visible to the naked eye on the outer surface of some flanges. The macro inspection results further show that the stainless steel flange leakage is related to the factors of the stainless steel flange.
