Effect of Nb microalloy elements on the structure and properties of carburized bearing steel
In order to study the method of controlling the growth of austenite grains of carburized bearing steel,the simulated carburization method was adopted,and 930℃was insulated for 1 h,3 h and 6 h respectively,and compared the size of austenite grains with niobium and without niobium at different insulation times.The re-sults show that when the carburization temperature is 930℃,the addition of 0.026%niobium can effectively in-hibit the tendency of austenite grains of 20Cr steel,and the suitable carburization time is 1 h and 3 h.With the ex-tension of the insulation time,the grain size of austenite gradually increases,and the obvious mixed crystal appears at 6 h.The addition of niobium can obtain the smaller tissue of ferrites.In 930℃carburization treatment,Nb,Ti in austenite are precipitate in the form of NbC and TiN.Under the same carburization conditions,the addition of ni-obium can improve the microhardness of 20Cr sample under different carburization times,and reach the maximum hardness difference of 53 HV at 6 h.
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