采用光学显微镜、扫描电镜、硬度计和能谱仪等对国产3Cr2NiMnMo钢大型模块的显微组织、硬度及元素分布进行了研究,对增加高温扩散退火前后的模块进行了对比.结果表明:未增加高温扩散退火前,该大型模块中存在粗大针状异常组织,主要为中高碳下贝氏体和粒状贝氏体,其显微硬度明显高于正常基体组织,还存在着铬、碳、钼等元素的偏析;增加了高温扩散处理后,改善了元素的偏析,消除了异常组织,使模块的组织及硬度均匀性得到显著提高,达到国外产品水平.

The microstructure,hardness and element distribution of domestic large-size die block of the 3Cr2NiMnMo steel were studied by means of optical microscope,SEM,hardness tester and energy spectrometer.The die blocks before and after high temperature diffusion annealing were compared.The results show that there exist abnormal coarse acicular microstructure in the large-size die block before high temperature diffusion annealing,which was mainly C-rich lower bainite and granular bainite,whose hardness was much higher than the matrix.Element segregation of Cr,C,Mo was observed also.The process of high temperature diffusion annealing could improve the element segregation and eliminate the abnormal microstructure.The microstructure and hardness uniformity of the die block were improved significantly,that could reach the export product standard.