W6Mo5Cr4V2高速钢复合轧辊包覆层组织特征研究

Study on the Microstructure Features of Cladding Layer for W6Mo5Cr4V2 High-Speed Steel Composites Roll

采用电渣重熔水冷结晶器快速冷却W6Mo5Cr4V2高速钢熔体与电磁感应预热35CrMo锻钢芯棒相结合的方法制备复合轧辊包覆层,并研究了包覆层一侧的显微组织特征。运用光学显微镜、扫描电镜、电子探针和X射线衍射仪观察和分析了靠近结晶器、包覆层中间区域和靠近复合界面三个典型不同位置处包覆层显微组织特征。结果表明:初始态下包覆层显微组织主要由珠光体以及呈连续、粗大和网状分布的晶界碳化物体组成。包覆层内各个区域的冷却速度不同使得组织形貌出现了明显的差异:外层靠近结晶器组织晶粒细小,晶界碳化物网的连续性和完整性较差;中间区域网状碳化物的连续性和完整性最强,且晶界碳化物增多、增大,晶粒粗大;靠近复合界面内层组织与外层相似,但其组织形貌介于外层和中间区域之间。

This paper investigates the as-annealed microstructure characteristics of cladding layer for a high speed steel composites roll, which was produced by the combination of the W6Mo5Cr4V2 high-speed steel melt as cladding layer with a 35CrMo low-alloy forged steel rod as roll core using electromagnetic induction preheating and rapidly cooling in a water cooling electro-slag remelting crystallizer. The microstructure of the high speed steel cladding layer was observed by optical microscopy, scanning electron microscopy, electronic probe and X-ray diffraction in three typical regions, i.e., near crystallizer, middle layer and close to composite interface. The results show that the as-annealed microstructure of the W6Mo5Cr4V2 cladding layer is composed of pearlite matrix and carbides distributing at grain boundary to form a continuous, coarse and network. The microstructure morphologies within the high-speed cladding layer exhibit significant differences because of different cooling rate from near surface of the crystallizer to the composite interface. The matrix grains were finer near the crystallizer and then gradually coarser toward the middle layers. The continuity and integrity of the network carbides are poorer near water crystallizer and then gradually get to be strongest when approaching middle areas. The microstructure morphologies close to the composite interface are similar to that near surface of the crystallizer and between the outer and middle layers.