Optimization Of Metallurgical Production Process For Continuous Casting Bearing Steel In Beiman Special Steel

In order to reduce the oxygen content of bearing steel and improve quality and competitiveness,the change of gases in each step of the entire production process were comprehensively analyzed by sampling and testing analysis.The effects of different kinds of slag,vacuum process and method and continuous casting process on the oxygen content were analyzed under the present production conditions based on the theoretical analysis and experimental study.The improvements of converter/electric furnace,LF,VD/RH and continuous casting process were explored to reduce the oxygen content of steel.Optimization of the ultra pure bearing steel production process and thereof new technologies were actively carried out.The results are as follows:(1)Nitrogen content significantly increases by 11-13 ppm during the LF refining process with the increasing nitrogen rate 14-20%.RH possesses a certain denitrification capacity,where the amount of denitrification is 45 ppm and the denitrification rate is about 50%.Total oxygen content in the end of the LF refining is controlled to about 20-28 ppm.Oxygen content of the molten steel after RH vacuum treatment is reduced averagely to 13 ppm,with a significant deoxidization effect of 65%deoxidation rate.(2)From the comparison results of the composite slags,the production of low titanium composite slag nearly reduces the oxygen content of the bearing steel,but has a significant effect on reducing the Ti content of the bearing steel.With optimizing the refining slag system by adjusting the high alkalinity slag,slag sulfur capacity increases by 30%and the oxygen content decreases by 3 ppm.According to the amount and the composition of slags,the most suitable refining time is about 70 minutes or less,and the product of the oxygen content gets relatively lower.(3)Actual deoxidation rate of VD is very low(about 10.9%).In the oxygen content indicators,average oxygen content of bearing steel after RH treatment is about 7.5 ppm,0.3 ppm lower than that after VD treatment,while degassing effect is better than that of VD.By using a one-time feeding aluminum process,a suitable range of Al is between 0.010 to 0.026%;purged argon into tundish before pouring opening,T-tundish,the tundish capped,optimization nozzle insertion depth and other operations can effectively prevent reoxidation.(4)Through the optimization of key control points in the converter,LF,RH and continuous casting process,Ti content of the products was 16 ppm.Average oxygen content is 6.7 ppm.(5)During the production process of converter/electric furnace?RH?LF?billet continuous casting,RH removes oxygen obviously with the removal rate 73%and the oxygen content decrease by 37 ppm.However,oxygen content increases with LF temperaturing to be double finally after LF.The end oxygen content is higher,which provides technical support to explore high purity bearing steel production technology.