Abstract: Austenite grain growth behavior during the isothermal heating processes at different heating temperatures(950-1200 ℃) holding for 30 min of vanadium containing steel HRB400E and the effect of vanadium precipitates on the austenite grain growth was studied by using high-temperature laser scanning confocal microscope and transmission electron microscope(TEM). The results show that the effect of heating temperature on the austenite grain growth in the tested steel is significantly greater than that of the holding time, and the isothermal growth rate of austenite grains increases significantly when the heating temperature exceeds 1100 ℃. The TEM observation shows that the growth behavior of austenite grains in the steel is influenced by V(C, N) particles in the matrix. When the heating temperature is 950 ℃, there is a large amount of undissolved V(C, N) particles in the steel, which can effectively pin the austenite grain boundaries and slow the grain growth. When the heating temperature rises to 1100 ℃, the fine V(C, N) particles dissolve and coarsen with the prolongation of the holding time, the pinning effect decreases, at this time the austenite grains grow rapidly. A kinetic model for the isothermal growth of austenite grains in the tested steel is established based on the measured austenite grain size and combined with the Sellers model and Anelli model, and it is found that the calculated values of the model are in good agreement with the measured values.

Key words: seismic steel HRB400E, austenite grain growth, kinetic model, V(C,N) precipitate