根据光学金相、扫描电镜、x射线衍射、电子探针等分析,发现渗硼共晶化组织有两类共晶:(γ+Fe_2B)及[γ+Fe_3(C、B)]。渗硼共晶化处理后,工业纯铁及低碳钢生成(γ+Fe_2B)共晶,组织是鱼骨状;商碳钢生成[γ+Fe_3(C、B)]共晶,其中包有少量Fe_2B,组织呈菊花状;中碳钢是鱼骨状与菊花状两种共晶的混合。本文还探讨了渗硼共晶层形成机理。 According to the analysis of optical metallography, scanning electron microscopy, X-ray diffraction and electron probe, there are two types of eutectic phases: (γ + Fe_2B) and [γ + Fe_3 (C, B)]. After the boronizing eutectics treatment, industrial pure iron and low carbon steel produce (γ + Fe_2B) eutectic and the structure is fishbone; commercial carbon steel produces [γ + Fe_3 (C, B) A small amount of Fe_2B, the organization was daisy-like; medium-carbon steel is fishbone and chrysanthemum-like two kinds of eutectic mixture. This paper also explores the formation mechanism of boronizing eutectic layer.