The Industry Practice Of Bearing Steel Production With RH Refining Process

Bearing steel is the core products of Beiman Special Steel Co.,Ltd.,which is mainly used for machinery and motor manufacturing,etc.The original main process of bearing steel is 90t top-bottom combined blowing converter?90t LF refining furnace?90t double position VD furnace?four-machine four-flow square billet continuous casting machine.Clearance of ladle.Due to the height restrictions of the converter and LF platform,a series of problems are induced due to the factors that the ladle height limitation,the molten steel is not tapped completely in converter,and the continuous casting steel water is not supplied sufficiently which severely limits the production capacity.Most importantly,the poor degassing effects,more inclusions and lower levels on cleanliness control for the VD vacuum refining furnace lead to the limitation of the high-end production of the bearing steel.In response to the above problems,the company built a new RH vacuum refining furnace to make the realization of the capacity release and product quality improvement.Firstly,the RH refining process was designed and developed for the common GCr15 bearing steel,and the small batch production test was carried out.The experimental results show that RH refining has the advantages of short production cycle,low gas content,and low inclusion content compared with VD refining process.However,at the same time,there are some problems such as large temperature loss,less number of continuous casting tanks and unstable production process.In view of the above problems,there are systematically optimized for the converter smelting process,LF refining process,RH process and continuous casting process,and the key technology of bearing steel was produced by integrating LD-LF-RH-CC process.The production practice results show that the composition of the high-end bearing steel represented by SKF3S is stable,the H content and N content are controlled stably below 1.5 ppm and 35 ppm,respectively.The cleanliness of molten steel is significantly improved.The DS inclusions obove first grade are less than 12%.The number of continuous casting furnaces can be stably controlled above 8 furnaces,which promotes the improvement of production efficiency,and the output of 250mm × 280mm blanks increases by 11.8 tons/hour.