高镍合金铸铁的组织与性能研究

Study on Microstructure and Properties of High Ni Cast Iron

采用高频感应加热设备熔配含Ni量为20%-60%的高镍合金铸铁样品,研究了Ni含量对铸铁基体组织、石墨形态及合金硬度的影响。结果表明,在高Ni合金铸铁中,随着Ni含量的增大,一方面,合金的石墨化能力显著增强,可以获得无渗碳体相的凝固组织,石墨形态由粗大片状依次向细小片状→点状→粗化点状转变;另一方面,合金结晶温度区间变窄,成分过冷倾向减小,奥氏体枝晶分枝能力减弱,形成了形态不甚发达的粗大枝晶乃至等轴晶组织,在Ni余量为20%及以上时高镍合金铸铁的硬度呈现出单调减小的趋势。

The high nickel cast iron alloys with 20%～60% Ni were prepared by using high frequency induction heating equipment.Effects of Ni content on matrix structure,graphite morphology and hardness of cast iron were systematically investigated.The results show that with the increase of Ni content,on the one hand,the ability of graphitization is enhanced significantly so that the solidification microstructure without cementite phase can be obtained in the high nickel cast iron alloys and the graphite morphology transforms from coarse flake to fine flake to dot and then to coarse dot graphite;on the other hand,the temperature range of crystallization become narrow.The tendency of constitutional undercooling decreases,and the branching ability of austenite dendrite declines resulting in the formation of coarse dendrites even equiaxed grain.Meanwhile,the hardness of high nickel cast iron alloys decreases monotonically.