Numerical Simulation Of Austenite Grain Of B1500HS Steel Based On Monte Carlo Method And Its Experimental Study

With the vapid development of the automobile industry in recent years,ultrahigh strength steel plates (UHSS) have been extensively applied to the practical production of automobile parts due to their properties such as safety, environmental protection and energy conservation. However, the cold forming performance of the ultrahigh strength steel plates is so poor that the conventional cold forming process does not work for it, the hot stamping technique was rising in response to such situation due to its excellent advantages. Since proposed by Plannja, the hot stamping has been extensively applied in automobile industry.The forming performance and the microstructure, which determinate the parts properties of the ultrahigh strength steel, of the steel plates are dependent on the heat treatment conditions in the hot stamping process.The research of the transformation regularity of the microstructure of the UHSS, therefore, could have make some senses for the process optimization of the hot stamping.With the Baosteel steel plates B1500HS as the research object, the austenite grains under heating and heat preservation and thermal deformation were studied by quenching experiments, metallographical technique and simulation of microstructure. The law of the grain change,such as the quantitative relationship among the grain size, heating temperature and the time of heat preservation, in UHSS at 900?1000? was obtained by experiment. The growth model of new grains was established combining with the grain growth model of Sellers and Anelli, the dynamics equation of grain growth was obtained from the experimental data.Based on the Monte Carlo Potts model, the simulation of the grain growth and recrystallization process of the UHSS was performed by ameliorating the conventional model and parameters and editing program.By introducing the model Turnbull linear rate equation and the time parameters, the relationship between the time of simulation and experiment was established. In the process of grain growth, through the analysis of the simulation results and the calculation of grain size, the grain growth coefficient was calculated as 0.5074, which very close to the theoretical value 0.5, and the grain shape was consistent with the grain growth regularity.By analyzing simulation results and calculating recrystallization volume fraction, the static recrystallization process of metal was presented.The simulation of dynamics recrystallization in hot deformation process of metal showed the phenomenon of dynamic recrystallization under different deformation and deformation rate. Based on the analysis of the simulation results and the calculation of the average grain size, the simulation results were found in good agreement with the experimental results, which proved that the model can simulate recrystallization process effectively.