Study On Solidification Structure And Carbon Element Segregation Of High-speed Wheel Steel

In recent years,the speed and load of China's railway transportation have been increasing,and the performance demand of high-speed wheel steel is increasing.It can improve the mechanical properties and machining properties of the steel by reducing the segregation of carbon in high-speed wheel steel and improving the solidification structure.This paper mainly studies the trend of carbon element segregation and cooling solidification structure.Pro CAST software is used to simulate the solidification process of high-speed wheel steel,Of secondary cooling water and heat are two different parameters in the experiment,to study the change tendency of the casting organization.The effects of heat treatment temperature and time on the segregation of tissue and carbon elements were studied by heat treatment experiments.There are several conclusions as follow:(1)The Pro CAST software is used to simulate the solidification process for high-speed wheel steel,CAFE model is adopted to calculate the cast structure at the macro level.Microstructure change of microbillet was expressed by KGT model.The microstructure of the parameters of the Fitting Parameters is determined.(2)When the superheat is 20?.The simulation results show that the low superheat can increase the equiaxed crystal area,and the quality of the billet is improved.The cooling water content of the Secondary cooling zone can be increased to move the position of CET to the edge of the billet,reduce the columnar crystal area and increase the cooling water amount in the appropriate range.(3)The long time thermal insulation treatment can reduce the concentration area of carbon element in the center part of the billet,and the effect of excessive heat preservation time on homogenization is no longer obvious.In the proper range,increasing the insulation temperature can make the carbon element homogenization more obviously,the excessive heat preservation temperature will cause the melting region in the inner part of the billet,affecting the quality of the billet.(4)Calculation,the diffusion coefficient of high-speed wheel steel is D0=8.5×10-5 mm2/s,The heat preservation effect after 15 h is no longer obvious.,the largest macro trend of carbon segregation index dropped,longer holding time at this time to reduce the carbon segregation effect is not obvious.The higher the heat preservation temperature,reduce the carbon segregation effect is better,but because of the influence of the solid phase line and decarburization,should not exceed 1300?.(5)Diffusion annealing treatment can make the dendrite arm and interdendritic boundaries gradually disappeared,reduce segregation phenomenon,within a certain range of heat preservation temperature,improve the heat preservation temperature and increasing the holding time can effective reduce the dendritic segregation phenomenon.The micro carbon segregation experiment testing shows that 1200? when the best time of heat preservation for 10 hours,segregation ratio variation is 15.6%.Insulation case,5 hours of 1250?,there is 13.9% segregation ratio variation.