Thermodynamic Simulation Calculation Analysis of Precipitation Phases in Hydropower Steel with Varying Vanadium Content Using JMatPro Software

In order to investigate the influence of vanadium（V） content on the precipitation phase and microstructure of hydropower steel, the thermodynamic simulation was carried out by JMatPro. Three kinds of hydropower steel with different V contents（0%, 0.05% and 0.09%） were studied, and their equilibrium phase diagrams were compared and analyzed in the same temperature range. The results indicate that all test steels contain the base phases of austenite and ferrite, while the primary precipitate phases include four types:M₂₃C₆ phase, M₆C phase, M₂（C, N） phase, and M（C, N） phase. The tempered microstruc-ture primarily consists of tempered sorbite along with some carbides. As V content increases, the precipitation of the M₂₃C₆ phase and M₂（C, N） phase decrease, whereas the precipitation of the M₆C phase and M（C,N） phase increase. This phenomenon confirms the influence of vanadium on phase transformation within the alloy and suggests that vanadium's binding ability with carbon is significantly stronger than that with other elements. Consequently, vanadium preferentially binds with carbon in the precipitates, forming various types of carbides. These newly formed carbides not only significantly affect the quantity and distribution of precipitated phases but also promote the refinement of ferrite grains. Furthermore, the interaction of V with other alloying elements notably alter the quantity and precipitation temperature of the precipitated phases, thereby optimizing the microstructure of hydroelectric steel. In conclusion, the increase of V content plays a critical role in enhancing the microstructure and properties of hydropower steel.