Abstract: Based on simulating corrosion environments of centrifugal compressor for natural gas pipe line ， the stress corrosion cracking (SCC) of FV520B steel was studied by slow strain rate testing (SSRT) method， and the effecting law and action mechanism of concentration of H₂S and CO₂， temperature and pressure on the SCC were discussed. The results show that H₂S plays a major role on the corrosion， the stress corrosion sensitivity index (I_S) increases with the increase of concentration of H₂S， while the stress in certain range has little effect. We researched the corrosion behavior of FV520B steel by analyzing the micro fracture morphology， calculated the I_S in different environment parameters. Finally， the mathematical model of the environment parameters and the I_S of FV520B was established with the regression analysis method. The model shows that the influence of H₂S concentration and temperature on the I_S is significant， and four parameters have interaction on the I_S.

Key words: centrifugal compressor, FV520B, stress corrosion, H₂S, CO₂, regression analysis