Simulation And Experiment Studies On Electroslag Remelting Process Of GCr15 Bearing Steel For High-speed Railway

High-speed rail bearing steel should have excellent quality and performance.Electroslag remelting is a secondary refining method,which can effectively improve the solidification microstructure performance of bearing steel.In the electroslag remelting process,the original microstructural characteristics of the bearing steel are likely to be inherited to the final product,resulting in changes in the quality and performance of the high-speed rail bearing and service safety issues.This paper takes GCr15 bearing steel for high-speed rail as the research object,and simulates the characteristics of solidification and heat transfer of electroslag remelting,the change of molten pool shape and the characteristics of solidification microstructure,and analyzes the influence of different process parameters.The accuracy of the simulation results was verified by the macrostructure observation test,and the relationship between the quality performance of GCr15 bearing steel and the solidification structure was deeply studied.The main research contents and conclusions of this paper are as follows:The solidification heat transfer model of electroslag remelting of GCr15 bearing steel is established by Pro CAST software,the distribution characteristics of the temperature field of the electroslag ingot and the liquid fraction of the molten pool are obtained,and the influence laws of different processes are analyzed.The simulation results illustrate the cooling intensity increases,the temperature decreases and the liquid fraction decreases.And the higher the slag pool temperature,the higher the electroslag ingot temperature,and the greater the liquid fraction.As the remelting speed increases,the temperature of the steel ingot decreases,and the liquid fraction of the molten metal pool at the same height of the ingot increases.This paper uses the CAFE module of to build a microstructure model based on the solidification heat transfer model,The characteristics of the solidification microstructure,the distribution of crystal regions and the ratio of the molten pool depth to the radius of the ingot h/R under different ingot heights are obtained,and the effect of process parameters is deeply researched.The simulation results illustrate the cooling intensity increase,the h/R decreases,the columnar crystals increase and the grain size becomes larger.The temperature of the slag pool increases,the h/R increases,the size of the solidification microstructure increases,and the equiaxed crystal ratio decreases.The greater the remelting speed,the greater the h/R,and the larger the grain size.So as to better the solidification microstructure performance of bearing steel electroslag ingots and enhance the service life of high-speed rail bearings,the cooling strength and slag pool temperature should be reduced under the premise of ensuring the depth of the molten pool,and low remelting speed should be adopted.In this paper,the electroslag remelting production test of GCr15 bearing steel was carried out and the macrostructure of the steel ingot was observed.In order to further explore the relationship between solidification microstructure and quality performance,the electroslag steel ingots were tested for high magnification microstructure observation,chemical composition segregation detection and hardness detection.The test results show that the content of carbon and chromium in the common region of the surface layer fine crystal region and the columnar crystal region is less,and the content of carbon and chromium is more in the region where the columnar crystal transforms to the central equiaxed crystal.There is evenly distributed pearlite in the central equiaxed crystal region,acicular ferrite appears in the columnar crystal region,the fine grained region of the surface layer is organized into fine sized pearlite.The average hardness at the bottom of the electroslag ingot is slightly greater than the average hardness at the top,and the hardness distribution at the bottom is more uniform.The hardness in the central equiaxed crystal region is higher,the hardness in the columnar crystal region is obviously smaller,and the hardness of the fine crystal region on the surface layer gradually increases.The research of this paper enriches the basic theory of the control technology of electroslag remelting of GCr15 bearing steel,and it has engineering guiding significance for improving the solidification microstructure performance of bearing steel and promoting the service reliability and quality of high-speed rail bearings.