Nb微合金元素对渗碳轴承钢组织和性能的影响

Effect of Nb microalloy elements on the structure and properties of carburized bearing steel

为了研究控制渗碳轴承钢奥氏体晶粒长大的方法,采用模拟渗碳法晶粒度检验方式,930℃分别保温1 h、3 h和6 h,对比研究含铌与不含铌的20Cr钢在不同保温时间下的奥氏体晶粒尺寸。结果表明,渗碳温度为930℃时,添加0.026%的铌能有效抑制20Cr钢奥氏体晶粒长大的倾向,适宜渗碳时间为1 h和3 h,随着保温时间的延长,奥氏体晶粒尺寸逐渐增大,6 h出现明显混晶。加入铌元素可以得到铁素体更为细小的组织,在930℃渗碳处理时,奥氏体晶界析出物主要为NbC和少量的TiN。相同渗碳条件下,添加铌能提高不同渗碳时间下,20Cr试样的显微硬度,在6 h时达到最大硬度差53 HV。

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 results show that when the carburization temperature is 930℃,the addition of 0.026%niobium can effectively inhibit the tendency of austenite grains of 20Cr steel,and the suitable carburization time is 1 h and 3 h.With the extension 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 niobium can improve the microhardness of 20Cr sample under different carburization times,and reach the maximum hardness difference of 53 HV at 6 h.