A2冷作模具钢中心孔洞缺陷分析

Defect analysis of central cavity for A2 cold work die steel

采用金相显微镜、扫描电镜及能谱仪探讨了A2冷作模具钢中心孔洞缺陷的形成原因。结果表明:试验钢具有严重的液析碳化物偏析,心部的液析碳化物尺寸及数量较边部大,具有明显的块状聚集;孔洞型缺陷主要分布在钢锭心部,其内表面平滑,缺陷的形成与A2钢中Cr7C3型液析碳化物的回熔有关。此外,心部大尺寸的液析碳化物经锻造破碎后产生的间隙,由于成分偏析而大量偏聚于液析碳化物边缘的小颗粒碳化物,非金属夹杂物及片状石墨均能促使A2钢中心形成孔洞型缺陷。

The cause of central cavity defect in cold work die steel A2 was discussed with OM,SEM and EDS. The results showed that the test steel has serious segregation of primary carbides,and the size and quantity of primary carbides in the center of the ingot are bigger than that on the edge. These carbides are in block aggregation. Cavity defects are mainly located in the heart of ingot,while the inner surface of cavity defect is smooth. The formation of defects in A2 steel is pertaining to the remelting of Cr7C3 primary carbides. In addition,the gap caused by the fractured large size primary carbides in the center of ingot,small carbides segregated outside of the primary carbides,nonmetallic inclusions and flake graphite could also induce the central cavity defects of A2 steel.