对预硬型大截面718塑料模具钢不同位置试样进行热处理，再经机械抛光和手动抛光后测试其表面粗糙度，研究了显微组织对表面抛光性能的影响。结果表明：原始组织为不均匀粒状贝氏体试样在热处理后，组织和硬度分布均匀性最差，导致抛光后的表面粗糙度最大，抛光性能最差；原始组织为均匀粒状贝氏体试样在热处理后，组织均匀性最好，硬度较大且分布均匀，抛光后的表面粗糙度最小，且经工程抛光（应用在工程上的专业手动抛光）后表面未出现橘皮纹或麻点等缺陷，表面粗糙度极限可达0.019 μm，表面质量满足高端塑料模具钢的使用要求；原始组织为回火马氏体试样热处理后的组织中均匀分布的碳化物使其表面抛光性能略优于原始组织为下贝氏体试样的。

Samples at different positions of prehardened large section 718 plastic mold steel were heat treated, and then mechanically polished and manually polished. The surface roughness was tested. The effect of microstructure on the surface polishing performance was studied. The results show that after heat treatment, the sample with the original microstructure of non-uniform granular bainite had the worst uniformity of microstructure and hardness distribution, leading to the largest surface roughness and the worst polishing performance after polishing. The sample with the original microstructure of uniform granular bainite after heat treatment had the best uniformity of microstructure, and the hardness was relatively large and distributed uniformly; therefore the surface roughness after polishing was the smallest. Moreover, no orange lines or pitting defects appeared on the surface after engineering polishing (professional manual polishing for engineering applications), and the limit of surface roughness reached 0.019 μm; the surface quality met the application requirements of high-end plastic mold steel. The uniform distribution of carbides in the sample with the original microstructure of tempered martensite after heat treatment made the surface polishing performance slightly better than that of the lower bainite sample.