Theoretical Calculation of Carbonitrides in Medium-carbon V-Ti-N Microalloyed Steel

The equilibrium solubility of TiN and V(CxN1-x),and the compositional coefficient of V(CxN1-x) in austenite of steel 35Mn2V for oil well tubes were calculated.The effects of C,V and N contents fluctuating on austenite composition were also investigated.The kinds and precipitation sequence of the different carbonitrides in the manufacture process of N80 grade hot-rolling 35Mn2V seamless tubes were analyzed based on the hypothesis,of which TiN and V(CxN1-x) show mutual solubility due to the similarity of their crystal structure.The results have shown that the initial precipitated temperature of V(CxN1-x) is about 955 ℃.The amount of V(CxN1-x) increases noticeably in range of 900-750 ℃.The x in V(CxN1-x) is more than 0.5 when the temperature lower than 900 ℃.The fluctuating of carbon,nitrogen and vanadium has visible effect on the precipitation of vanadium.