Abstract: The thickness of the shell of the 300 mm × 340 mm continuous casting billet of 8620 series gear steel （/% 0.18 - 0.24C， 0.18 - 0.32Si， 0.65 - 1.0Mn， 0.45 - 0.55Cr， 0.50 - 0.80Ni， 0.15 - 0.25Mo， ≤ 0.025P， ≤0.020S） at the place of each tension leveler （point crack method） ， is calculated by using the point crack pressed on the solidifying front of the casting blank by tension leveler， and then the solid phase ratio of the center of the bloom is calculated by substituting the calibration model with the data， to design the pressure reduction . The total 4 tension levelers of 5 th，6 th，7 th and 8 th are used to press down， with pressure reduction 2 mm、3 mm、5 mm、4 mm respectively， and total pressure reduction is 14 mm.After experiment ， the carbon-sulfur analysis is carried out by drilling holes in the bloom and rolled material samples.The results show that， comparing to the cast billet without light pressure， the ratio of carbon segregation index 0.97-1.03 of gear steel 8620 CC bloom increases from original 83.5% to 94.2% ， and the ratio of carbon segregation index of rolled steel increases from original 91.5% to 98.8% ，in situ analysis density of macro structure test piece increase from 0.899 9 to 0.976 9， porocity decreases from 0.100 3 to 0.017 8， and the composition segregation and density of casting billet improve.

Key words: 8620 Series Gear Steel, Soft Reduction, Piont Crack Method, Macro-Segreation

摘要： 通过使用拉矫机在铸坯凝固前沿压出的点状裂纹推算出8620系齿轮钢（/%：0.18～0.24C，0.18～0.32Si，0.65～1.0Mn，0.45～0.55Cr，0.50～0.80Ni，0.15～0.25Mo，≤0.025P，≤0.020S）300 mm × 340 mm连铸坯经过每一台拉矫机处铸坯的坯壳厚度（点状裂纹法），以此数据代入并校准铸坯凝固模型，计算出铸坯中心固相率，并设计压下量参数，采用第5、6、7、8共4台拉矫机进行压下，压下量分别为2、3、5、4 mm，总压下量共14 mm，试验后，在铸坯和轧材试样上钻孔进行碳硫分析。结果显示，和未经轻压下的铸坯相比，8620系齿轮钢铸坯碳偏析指数0.97～1.03的比例由原工艺的83.5%提升至94.2%，轧材碳偏析指数0.97～1.03的比例由原工艺的91.5%提升至98.8%，低倍试样原位分析致密度由0.899 9提升至0.976 9，疏松度由0.100 3降低至0.017 8，铸坯成分偏析和致密度有所改善。

关键词: 8620系齿轮钢, 轻压下, 点状裂纹法, 宏观偏析