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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．
The effects of rare earth on the mechanical properties at room temperature and low temperature of Ni9 cast steel as well as the macroscopic and microscopic fracture appearances were studied emphatically. The magnitude of the propensity to crack in the grain boundaries of rare earth-added steel and non-added rare earth steel was investigated. The relationship between low temperature mechanical properties, grain boundary crack tendency, fracture morphology and inclusion content was analyzed and discussed. The results show that: after adding rare earth. Ni9 cast steel grain boundary cracking tendency significantly reduced at room temperature, low temperature tensile properties of steel significantly increased, and reduce the tendency of steel intergranular fracture, but the low temperature impact toughness of steel has not been improved. This is related to the tendency of grain boundaries in steel and inclusions.