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What are the factors that cause corrosion of stainless steel valves?

Stainless steel two-way pressure butterfly valve made of CF8M is corroded in the process of use. After normal heat treatment, the structure of austenitic stainless steel should be austenitic at room temperature, which has good corrosion resistance. In order to analyze the cause of butterfly valve corrosion, sample on it for analysis. Meili De two-way pressure butterfly valve valve

1. Test method

Chemical composition analysis (to determine whether it meets the standard requirements), metallographic microstructure inspection, heat treatment process test and SEM analysis were carried out.

2. Test results and analysis

2.1. Chemical composition

Chemical composition analysis results and standard composition.

2.2. Metallographic analysis

The metallographic samples were cut from the corroded butterfly valve. After grinding and polishing, the samples were etched with ferric chloride solution, and observed and analyzed on the Neophot-32 metallographic mirror. The metallographic structure consisted of austenite and another precipitate. Theoretically, austenitic stainless steel should be homogeneous after normal heat treatment. There are two kinds of judgment as to what the other precipitates in the structure are: one is σ phase, the other is carbide. Although the conditions for the formation of σ phase and carbide are different, they all share one common characteristic, that is, the sensitivity of austenitic stainless steel to intergranular corrosion.