Abstract: Based on Thermo-Calc thermodynamic calculations, optical microscopy, transmission electron microscopy, and austenite grain growth model calculations, the effects of different V contents (0.13%, 0.23% and 0.34%), austenitizing temperature and time on austenite grain growth in Cr-Mo-V high speed railway brake disc test steel were studied. The deviation between the Beck model of grain growth and actual grain growth was analyzed under different V contents. The results show that when the austenitizing time is 1 h and the austenitizing temperature is 950 ℃, the V content has no obvious effect on the austenite grain growth. Nevertheless, above 950 ℃, the austenite grain size decreases with the increase of V content. The austenite grain sizes of the tested steel grow gradually with the increase of austenitizing temperature. When the austenitizing temperature is below 1000 ℃, the grain size increases slowly with the austenitizing temperature increasing, while when the austenitizing temperature is above 1000 ℃, the austenite grains grows rapidly. At the same austenitizing temperature, the austenite grains grow slowly with the increase of austenitizing time. Based on combination of the measured austenite grain size data and the theory of austenite growth kinetics, the kinetic model of grain growth of 0.34%V steel is calculated to be D=111 974.$1 t^{0.095} \exp \left(-\frac{96319.4}{R T}\right)$. The predicted data of the model has a small deviation from the experimental data, and a good model fitting.

Key words: Cr-Mo-V steel, grain growth, austenitization, mathematical model