稀土对Ni9铸钢低温机械性能及断口形貌的影响

着重研究了稀土对Ｎｉ９铸钢常温、低温机械性能和宏观、微观断口形貌的影响；考察了添加稀土钢和未添加稀土钢晶界裂纹倾向程度的大小．分析、讨论了低温机械性能、晶界裂纹倾向、断口形貌、夹杂物含量之间的关系．结果表明：添加稀土后．Ｎｉ９铸钢的晶界裂纹倾向明显降低，钢的常温、低温拉伸性能显著提高，并降低了钢的沿晶断裂倾向，但钢的低温冲击韧性并未得到改善．这与钢中晶界裂纹的倾向和夹杂物的含量有关．

Influence of rare earth on mechanical properties at cryogenic temperatures and fracture morphology of Ni9 cast steel

In the paper, the influence of rare earth on mechanical properties at room and cryogenic temperatures and fracture macromorphology and micromorphology of Ni9 cast steel are emphatically researched. The tendency of intergranular crack formation of cast steels both with and without rare earth addition is also researched. In addition, the correlation between mechanical properties at cryogenic temperature, the tendency of intergranular crack formation, fracture morphology and amount of inclusions is also analyzed and discussed. The results show that in the case of rare earth addition in Ni9 cast steel, the tendency of intergranular crack formation is remarkablely decreased; the tensile properties at room temperature and cryogenic temperature are significantly improved; the tendency of fracture along grain boundary is reduced. However, the impact toughness has not been improved and this may be related to the tendency of intergranular crack formation and inclusion amount.