含稀土轧辊用高速钢淬回火过程微观组织转变

Microstructural characterization of a high speed steel containing rare earths for rolls under quenching and tempering condition

利用金相(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)及能损谱(EELS)等手段,研究了含稀土轧辊用高速钢在1100℃淬火和550℃两次回火热处理过程的微观组织变化特征,重点探讨了碳化物行为。结果表明,淬火加热过程中热稳定性较高的MC和M6C型一次共晶碳化物难以溶解,亚稳态的M2C型一次共晶碳化物则发生分解反应得到MC和M6C两种碳化物,分解形成的M6C较MC量多且尺寸较大,小颗粒MC包含在M6C之中;淬火基体组织由马氏体和残留奥氏体组成,淬火马氏体既有板条马氏体也有孪晶型马氏体。经两次回火后,残留奥氏体得以有效消除,大量细小富V的MC型二次碳化物弥散析出产生二次硬化现象。

Microstructural characterization of a high speed steel containing rare earth for rolls during quenching and tempering was investigated by means of optical microscopy（OM）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD） and electron energy loss spectroscopy（EELS）.The results show that it is difficult of stable MC and M6C eutectic carbides to dissolve in the process of quench heating,while the M2C eutectic carbides decompose to MC and M6C.The more M6C carbides with larger size are formed by the decomposition of M2C carbides compared with that of the smaller MC carbides embedded in the M6C carbides.The matrix of the quenched steel consists of lath martensite with a little twinned martensite and retained austenite.A number of fine vanadium-rich secondary carbides precipitate dispersedly and the retained austenite is eliminated effectively after twice tempering.