系统研究了不同含量的硅对Mn Si Cr B系贝氏体铸钢强韧性的影响。结果表明 ,Si量在铸钢中为 1 6%～ 2 4%时 ,脆性的渗碳体被韧性的残留奥氏体代替 ,得到无碳化物贝氏体 ,其组织特征为含碳过饱和的板条贝氏体铁素体和分布在其中的薄膜状富碳残留奥氏体。在其硬度基本保持不变的情况下 ,冲击韧度显著提高 ,由 5～ 6J/cm2 提高到 8～ 1 2J/cm2 (U型缺口 )和由1 2～ 1 3J/cm2 提高到 2 0～ 30J/cm2 (无缺口 )。但是 ,Si增加铸钢的枝晶偏析和块状残留奥氏体 ,当钢中硅量达到 2 4% ,铸钢硬度明显下降。 The effects of different contents of silicon on the toughness of Mn Si Cr B series bainitic cast steel were studied systematically. The results show that when the amount of Si is 16% ~ 24% in the cast steel, the brittle cementite is replaced by ductile retained austenite and the carbide-free bainite is obtained. The microstructure is characterized by supersaturated carbon Lath bainitic ferrite and film-like carbon-rich retained austenite distributed therein. The impact toughness increased significantly from 5 ~ 6J / cm2 to 8 ~ 12J / cm2 (U-notch) and from 12 ~ 13J / cm2 to 20 ~ 30J / cm2 (no notch). However, Si increases the dendritic segregation and retained austenite in the cast steel. When the amount of silicon in the steel reaches 24%, the hardness of the cast steel obviously decreases.