Abstract: The effect of single roll soft reduction (0〜14 mm) and reduction position ( 1^# ~ 7^#) on inacrostructure and central carbon segregation of 240 mm x 240 mm casting bloom of low carbon steel 20CrMnTiH has been tested and studied. Results show that as from roll No. 3 reduction and maximum soft reduction 9 mm, the ratio of the without shrinkage cavity increases by 12.3% and the ratio of center porosity 1.0 rating and center carbon segregation do not improve obviously ；as from roll No. 2 reduction with maximum soft reduction 1 1 mm, the ratios of center porosity 1.0 rating and the without shrinkage cavity decrease, and the ratio of center carbon segregation increases by 14. 2% ； as from roll No. 1 reduction and the maximum soft reduction 14 mm, the ratios of center porosity 1.0 rating and without shrinkage cavity are up to 100% , and the ratio of center carbon segregation is 71.4% . By comprehensive analysis it is obtained that with casting speed 0.85 m/min, mold stirring 300 A and 5 Hz, the central carbon segregation and macrostructure of steel 20CrMnTiH 240 mm x 240 mm casting billet are better by single roll soft reduction 14 mm.

摘要： 试验研究了单辊轻压下量（0～14 mm）和压下位置（1^#～7^#）对低碳钢20CrMnTiH 240 mm×240 mm铸坯低倍组织和中心碳偏析的影响。结果表明,从3^#拉矫辊开始压下,最大压下量9 mm,低倍无缩孔比例上升12.3%,中心疏松1.0级比例和中心碳偏析无明显改善;从2^#拉矫辊开始压下,最大压下量1 1 mm,中心疏松1.0级比例和无缩孔比例下降,中心碳偏析合格率提升14.2%;从1^#拉矫辊开始压下,最大压下量14 mm,中心疏松1.0级和无中心缩孔比例均为100%,中心碳偏析合格率达到71.4%。综合分析得出,20CrMnTiH 240 mm×240mm铸坯在拉速0.85 m/min、结晶器搅拌300 A、5 Hz、单辊轻压下量14 mm时,铸坯中心碳偏析和低倍组织最佳。