重熔时间对半固态过共晶高铬铸铁初生相的影响

Effect of Remelting Time on Initial Phase in Semisolid Microstructure of Hypereutectic High Chromium Cast Iron

为考察触变重熔时间对初生碳化物形貌的影响,对Cr17过共晶高铬铸铁半固态坯料在1 270 ℃进行了部分重熔,重熔时间分别为5、15、25和30 min,并借助Leica图像分析仪分别定量描述了碳化物形状因子及粒度因子的变化规律.研究表明:碳化物形貌的演化过程包括3个阶段,即熔断阶段、球化和细化阶段及合并长大阶段;碳化物演化过程是溶质原子扩散和相界面张力共同作用的结果,且分别在触变重熔初期和中后期占主导地位;在1 270 ℃部分重熔15 min,可获得理想的重熔组织.

To investigate the effect of thixo-remelting time on the morphologies of initial carbides, semi-solid billets of Crl7 hypereutectic high chromium cast iron were partially remelted at 1270°C for four distinct periods (5 min, 15 min, 25 min, and 30 min, respectively), and the shape factor and grain factor of carbide grains were characterized quantitatively via a Leica image analyzer. The results indicate that firstly the evolution process of grain morphology during partial remelting undergoes grains melting, spheroidization and refining, and grains growth; secondly, the solute diffusion and interface tension play a predominant role respectively at the primary stage and the middle-final stage in the process of microstructure evolution; finally, the perfect remelting microstructure could be expected to obtain at 1270°C for 15 min in this investigation.