Abstract: With using the macro examination method for macro structure of casting bloom and the analysis technology for metal original position statistic distribution the effect of mold electromagnetic stirring current (200-450 A, 3 Hz) on equiaxed crystal zone rate, density fraction and carbon segregation of Φ650 mm heavy round casting bloom of 0.35C steel produced at steelworks has been studied. Test results show that with stirring frequency 3 Hz as current increases from 200 A to 450 A, the equiaxed crystal zone rate increases from 24.2% to 56. 8% while the density fraction of each zone in casting bloom increases gradually and the density fraction at center zone of casting bloom increases obviously i. e. from 0.8649 increasing to 0.9376, and with increasing stirring current the carbon segregation of easting bloom occurs the trend to lighten. Comprehensively considering each factor, as mold electromagnetic stirring current is 450A with frequency 3 Hz the equiaxed crystal zone rate in bloom is largest and the internal quality of bloom is best.

Key words: Φ650 mm Heavy Round Bloom, Mold Electromagnetic Stirring, Equiaxed Crystal Zone Rate, Density Fraction, Carbon Segregation

摘要： 通过铸坯低倍组织宏观检验方法和金属原位统计分布分析技术,以钢厂生产的35钢（0.35%C）为例,研究了结晶器电磁搅拌电流（200~450 A,3 Hz）对Φ650 mm大断面连铸圆坯等轴晶率、致密度和碳偏析度的影响。结果表明,搅拌频率3 Hz时,结晶器电磁搅拌电流由200 A增加至450 A时,等轴晶率由24.2%提高至56.8%,同时铸坯各区域致密度呈现逐渐增大的趋势,其中铸坯中心区域致密度增加明显,由0.864增至0.9376;随着搅拌电流的增加,铸坯碳偏析度呈现逐渐减轻的趋势。综合考虑各因素,当结晶器电磁搅拌电流为450 A,频率为3 Hz,铸坯等轴晶比例最大,铸坯内部质量最好。

关键词: Φ650 mm大断面圆坯, 结晶器电磁搅拌, 等轴晶率, 致密度, 碳偏析