Research On New Technology Of Inclusion Control And Refining For Bearing Steel

As an important special steel product,the metallurgical quality of bearing steel has a direct impact on the stability of mechanical equipment.In actual production,improving the quality of bearing steel is mainly controlled by three aspects: chemical composition,cleanliness(inclusions in steel)and uniformity of structure.The composition,morphology,content,size and size distribution of inclusions are important factors affecting the fatigue life of steel.As a major steel producer in the world,China still has a distance from the advanced foreign countries in quality of bearing steel.It is mainly manifested in the cleanliness and fatigue life of bearing steel,such as oxygen content controlling and inclusion controlling in steel.Based on this,a new technology for controlling inclusion in bearing steel is put forward in this paper.The following research has been carried out:(1)The quality evaluation of a domestic plant bearing steel is carried out.The analysis shows that the quality level of bearing steel produced by this factory is high,but the control of the number and size of inclusions is low.The number of large inclusions is much higher than that of foreign bearing steel.Adopting the internationally widely used range method,the maximum inclusion size is predicted to be 55.92 ?m,which is 3.3 times higher than that in Shanyang of Japan.(2)The morphology and energy spectrum of bearing steel GCr15 were analyzed by SEM.The main compositions and morphological characteristics of inclusions of class A,B,D and Ds were analyzed.(3)The main features of the inclusions in the pre LF,mid LF,late LF and RH refining stages of the refining process were analyzed by scanning electron microscopy and metallographic method.The inclusions were analyzed by energy spectrum.The composition of the inclusions at each stage was determined.The source,formation mechanism and evolution mechanism were studied by tracer test.(4)The new refining process is used to pruduce the 40 Cr steel in industry.The results show that the new technology can control the T.O in the steel in 8.0ppm,reduce the nitrogen content notification by 23.2% and the content of Ti content in steel by 43.48%.It also can reduce the number of large inclusions by 84.3% and the amount of refining aluminum consumption.Besides it can save the refining cost.(5)The bearing steel GCr15 is tested by new technology in factory.The results show that the new process reduces the amount of T.O to 4.82 ppm and the number of inclusions greatly reduced.The number of oxide is reduced by 56.77%.Refining cost per ton steel is reduced by 17.55 yuan.(6)The desulphurization and detitanium ability of bearing steel refining process is investigated through industrial tests.The results show that the desulfurization capacity of the new process is equal to that of the original process.The control of titanium content is greatly improved.The average content of titanium is 13 ppm with a decrease of 40.91%.