Research on Deformation-Induced Martensite of the Austenite Stainless Steel Bellows Based on Magnetism Testing Method

Stainless steel bellows expansion joint is an important part of city gas pipelines. In recent years, accidents occur frequently due to stress corrosion. The research on failure mechanism for bellows has high practical significance. According to magnetic variety of the deformation-induced martensite, the martensite phase content was tested by using the MP30E-S measurement instrument, for the bellows made of the SUS304 and SUS316L materials separately formed by machine-bulge method and SUS304 materials formed by hydraulic pressure method which there is or not a solution treatment respectively. The results showed that, there are great relations between the martensite phase content and materials, deformation rate, and heat treatment. The martensite phase content of SUS316L is less than SUS304, the more martensite phase content because the more deformation rate, there are less and even martensite phase after solution treatment.