Simulation Study On Heat Transfer And Microstructure Of Continuous Casting Process For Heavy Rail Steel

Heavy rail steel is an important material for railway transportation and the foundation of railway transportation.The rapid development of high-speed railway requires heavy rail steel continuous casting bloom to have good surface and internal quality.According to the actual production of U71Mn heavy rail steel bloom continuous casting produced by a steelworks,this paper uses the finite element simulation software ProCAST as the main tool,using the numerical simulation technology to study the solidification heat transfer,microstructure of solidification process and secondary cooling process optimization of continuous casting of heavy rail steel,and a reasonable process program is put forward,which can increase the equiaxial crystal ratio of bloom and improve the product quality.In this study,the finite element method is used to establish the solidification and heat transfer model of bloom continuous casting and the solidification structure coupling model based on cellular automata-finite element method(CAFE)to simulate the solidification process of bloom casting.By comparing the simulation results with the field actual data,the relative error between the simulated temperature and the actual temperature is within 1.5%,and the simulation results of solidification structure are in good agreement with the actual structure,which verifies the accuracy of the mathematical model.Based on the simulation results of temperature field,the solidification law of heavy rail steel bloom continuous casting is simulated.The results show that under the existing process,the surface temperature recovery rate of the bloom in the first stage of secondary cooling is too high and the cooling process needs to be optimized.At the same time,based on this,the effects of casting speed,superheat and water ratio on the solidification heat transfer of the bloom are analyzed,the results show that the effect of drawing speed on solidification process is greater than that of superheat and water ratio.The CAFE model is used to study the influence of continuous casting process parameters on solidification structure of blooms.The results show that the influence of superheat is relatively large.With the decrease of superheat,the number of grains increases continuously and the central equiaxial crystal ratio increases significantly.With the increase of casting speed or the appropriate decrease of secondary cooling strength,the central equiaxial crystal ratio increases to some extent.The influence of superheat is more significant than that of drawing speed and secondary cooling water ratio.In view of the existing problems in the secondary cooling process of U71Mn steel bloom continuous casting,the existing process is optimized.After optimization,the surface temperature of the bloom becomes more reasonable,which improves the cooling process effectively and saves the cooling water of the bloom.After optimization,when the casting speed is 0.70m/min and 0.75m/min respectively,the equiaxial crystal ratio before optimization is 33.5%and 37.2%,and after optimization the equiaxial crystal ratio is 38.2%and 41.5%respectively,the equiaxial crystal ratio of the bloom is obviously improved,which has achieved remarkable results.