Abstract:  For improving the level of GCr15 bearing steel CC billet chemical homogenization and defects such as inner crack and shrinkage cavity， the soft reduction process was optimized by the physical calculation of shell thickness growth ratio， steel grade thermal property test， desin casting process under large pressure and combined soft reduction test， monitor the surface temperature of the casting process and the working condition of the tension leveler. The results show that the reasonable starting position R of continuous casting SR is 42%～45%， in order to obtain better macrostructure quality， the starting position of three CC billet sizes 200 mm×200 mm， 240 mm×240 mm， 300 mm×340 mm is 1～3 m behind the original process； Taking 200 mm×200 mm GCr15 billet as an example， increasing the amount of casting reduction from 1.25 mm/m to 2.5 mm / m， which can reduce the cracks of billet， significantly improve the Y-Z longitudinal of casting billet macrostructure composition and homogenization， and the central carbon segregation index of the rolling material generally reaches 0.97～1.03， realizing the goal of not producing obvious cracks under soft reduction， and modifying the central segregation and V-segregation defects.

Key words: GCr15 Bearing Steel, Macrostructure of CC Billet, Soft Reduction, Chemical Homogenization, Solidification and Heat Transfer, Strain

摘要： 为提高GCr15轴承钢连铸坯均质化水平，改善内部裂纹、缩孔等缺陷，通过实物计算坯壳厚度生长比例、钢种热属性测试，设计浇注过程大压下和联合轻压下试验，监控浇注过程铸坯表面温度和拉矫机工作状态等方法，优化轻压下工艺。结果表明，连铸轻压下合理的起始位置R为42%～45%，为获得更优低倍质量，200 mm×200 mm、240 mm×240 mm、300 mm×340 mm三种规格连铸轻压下起始位置较原工艺后置1～3 m；以200 mm×200 mm GCr15为例，增加铸坯压下量，由1.25 mm/m提高到2.5 mm/m，可减轻铸坯轻压下裂纹，显著改善铸坯Y-Z纵向低倍成分和组织均匀性，轧材中心碳偏指数普遍达到0.97～1.03，实现了既不产生明显轻压下裂纹、又能改善中心偏析和V型偏析缺陷的目标。

关键词: GCr15轴承钢, 铸坯低倍, 轻压下, 均质化, 凝固传热, 应变