Research On The Key Technology Of Metallurgical Process Of Bearing Steel For High-speed Rail

Severe standard has been established for high-speed rail due to the high quality and high safety of bearing.In this paper,GCr15 bearing steel for high-speed rail is studied.The smelting process is BOF?LF?RH?CC.The key difficulties and emphases of quality control of bearing steel for high-speed railway are studied.It has formed the key technology integration of the smelting process of bearing steel for high-speed rail,which has great significance to improve the production level of bearing steel for high-speed rail in China.This study carried out relevant research by laboratory research,thermal simulation experiment,numerical simulation,and industrial experiment.The whole smelting process of bearing steel in the converter is studied and analyzed.To improve the purity of liquid steel,a“C-P-T”collaborative control process model is established and used in the smelting production of bearing steel.The results show that the phosphorus content in tapping terminal can be controlled under 0.01%,the carbon content in tapping terminal should be controlled at about 0.30%,the average dissolved oxygen content in tapping terminal is 0.0114%,the tapping terminal temperature of liquid steel is controlled between 1620?to1630?.The furnace proportion of carbon,phosphorus,and temperature hitting the target at the same time reaches 76.67%,and the purity of liquid steel is greatly improved.The control process of ultralow oxygen in refining is studied.It reveals the transport law of oxygen between slag and metal in the refining process of bearing steel.Based on the combination of laboratory research and industrial production verification,a highly effective deoxidizer which can be suspended in the slag-metal interface is developed.The production practice shows that the?(Fe O+Mn O)content in the top slag can be controlled stably at about 0.48%,and the total oxygen(T.[O])content in steel can be controlled between 5.5×10^-6 to 8.5×10^-6.Ultralow oxygen control technology can effectively reduce the oxidation of slag,block the secondary oxidation of air to liquid steel,stabilize the T.[O]content of steel.This is beneficial to reduce the flocculation phenomenon in the subsequent casting process.It can improve the number of continuous casting furnace and the product quality of bearing steel.The solidification law of bearing steel bloom and the cause of macro-segregation are studied and analyzed.Aiming at the 370mm×480mm section bloom,the collaborative control technology of multi-stage electromagnetic stirring and soft reduction is put forward to eliminate or improve the macro-segregation of the bloom.It is verified that the total reduction quantity reaches 15mm and the distribution ratio is3.5mm-4mm-4mm-3.5mm.The central carbon segregation of bearing steel bloom is controlled between 1.01 to 1.04,and the macro-segregation is greatly improved.After the implementation of key technology improvement,the quality of GCr15bearing steel is improved.The T.[O]content in steel shall not exceed 6×10^-6.The non-metallic inclusion,decarburization layer,and non-uniformity of carbide in steel all meet the requirements of super high quality of national standard.The center porosity of the initial casting billet is less than 0.5 grade,and the center segregation is less than 1.0grade.There is no shrinkage,cavity,cracks,and bubbles in the billet.This paper makes a detailed and in-depth study on the key technology of the smelting process of bearing steel for high-speed rail.The effective quality control of bearing steel is realized.The product quality meets the requirements of high-speed rail bearing with the speed of 250km/h and above listed in relevant literature.