铌微合金化对高铁车轴钢淬透性的影响

Effect of niobium addition on hardenability of high-speed railway axle steel

为了研究铌对DZ2高铁车轴钢淬透性的影响规律和机理,通过末端淬透性试验和物理化学相分析等方法,研究了铌质量分数分别为0、0.026%和0.039%的DZ2钢的微观组织、析出相和淬透性。结果表明,距淬火端20mm以内,铌微合金化车轴钢硬度均高于对比钢,不同铌含量试验钢的淬透性曲线拐点位置均在距淬火端25~30mm处,总体来看,3种试验钢淬透性相当;随着铌质量分数的增加,奥氏体晶粒尺寸越小,降低了钢的淬透性;铌微合金化抑制了M3C相的析出,增加了奥氏体中碳、锰、铬固溶量,从而提高了钢的淬透性,弥补了晶粒细化造成的淬透性下降,综合作用下淬透性基本保持不变。

In order to study the effect and mechanism of Nb addition on hardenability of DZ2 high-speed railway axle steel,the microstructure,precipitated phase and hardenability of DZ2 high-speed railway axle steel with different mass percent of Nb(0,0.026%and 0.039%)were investigated by way of Jominy test and physicochemical phase analysis.The results show that hardness of Nb microalloyed steels are higher than that of DZ2 steel within 20 mm from the quenched end and for those test steels with different content of Nb,inflection points of hardenability curves are all located in a distance range of 25-30 mm from quenched end,which mean test steels have equivalent hardenability.The austenite grain size decreases with the increase of Nb content,thus reducing hardenability.Meanwhile,the precipitation of M3C phase is inhibited with Nb addition,which increase the dissolved content of C,Mn and Cr in austenite,thus improving hardenability and making up for the decrease of hardenability caused by grain refinement.Therefor,hardenability is hardly changed after Nb microalloyed under the comprehensive action.