添加铬合金化和复合变质处理对白口铸铁组织性能的影响

Effect of chromium alloying and complex modification on structures and properties of white cast iron

在熔炼过程中通过对熔体进行复合变质处理,制备普通白口铸铁和含铬白口铸铁试样及其在相同铸造条件下的变质试样;对试样进行金相显微组织观察、碳化物定量分析和宏观硬度测量,研究添加铬合金化和复合变质处理对普通白口铸铁碳化物类型、形态、分布和性能的影响。研究结果表明,铸铁铬含量较低时,碳化物类型为(Fe,Cr)3C或(Fe,Cr)3C+(Cr,Fe)7C3,呈粗大网状结构;经复合变质处理后,碳化物变得孤立、分散,网状结构被消除;随着铬含量增加,碳化物全部转变为(Cr,Fe)7C3,共晶团中碳化物呈菊花状分布,并在共晶团心部附近出现近似六方形的块状(Cr,Fe)7C3碳化物;经复合变质处理后,共晶碳化物变的细小分散、分布均匀,菊花状形态消失,但六方形(Cr,Fe)7C3碳化物仍然存在;白口铸铁经复合变质处理后,其洛氏(HRC)硬度比变质前有明显提高。

Normal white cast iron and chromium alloying white cast iron were prepared using a melt-casting process, and their corresponding modified samples were cast after their melt were treated by a complex modification technique. By means of metallographic observation, carbide quantitative analysis and hardness measurement, effects of chromium alloying and complex modification on shape, distribution of carbides in white cast iron and properties were investigated. The results show that white cast iron has a network structure of （Fe, Cr）3C or （Fe, Cr）3C＋（Cr, Fe）7C3 carbides when chromium content is low. By complexly modifying, the carbides become isolated and decentralized. With the increase of chromium content, all the carbides can change into （Cr, Fe）7C3 and exhibit chrysanthemum morphosis in a eutectic colony, with hexagon shape carbides appearing. Meanwhile the uniform distributed carbides without chrysanthemum morphosis can be obtained, but the hexagon shape carbides still exist. The Rockwell （HRC） hardness of the white cast iron is obviously increased by complexly modifying compared with the corresponding cast iron without modification.