Stainless steel butterfly valve rust phenomenon occurs during use. After metallographic analysis, dyeing test face, heat treatment test face, SEM and other test analysis, the key factor to find out the material corrosion is that the carbides along the grain boundary in the material form a chromium-depleted zone, resulting in corrosion of the stainless steel butterfly valve. Stainless steel butterfly valve rust solution 1 test method Shanghai Hongfeng Valve Reference: Sampling for chemical composition analysis (to determine compliance with the standards), metallographic examination, heat treatment process test and SEM analysis. 2 test results and analysis 2.1 Chemical composition Chemical composition analysis results and standard components. 2.2 Metallographic analysis From the rust phenomenon of the butterfly valve cut the metallographic sample, after grinding polishing, corrosion with aqueous ferric chloride, Neophot-32 metallographic microscope was observed and analyzed, the microstructure of austenitic Body with another precipitate composition. In theory, the normal austenitic stainless steel after heat treatment should be uniform austenite. Another precipitate appears in the organization what is tissue, there are two judgments: one is σ phase, the other is carbide. The conditions for the formation of sigma phase and carbides are different, but all have one common feature that is the sensitivity of austenitic stainless steel to intergranular corrosion.
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