轻压下对20CrMnTiH钢240mm×240mm铸坯中心碳偏析和低倍组织的影响

Effect of Soft Reduction on Cenral Carbon Segregation and Macrostructure of 240 mm × 240 mm Casting Bloom of Steel 20CrMnTiH

试验研究了单辊轻压下量(0-14mm)和压下位置(1^#-7^#)对低碳钢20CrMnTiH240mm×240mm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9mm,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11mm,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14mm,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,20CrMnTiH240mm×240mm铸坯在拉速0.85m/min、结晶器搅拌300A、5Hz、单辊轻压下量14mm时,铸坯中心碳偏析和低倍组织最佳。

The effect of single roll soft reduction(0~14 mm) and reduction position(1~#~7~#) on macrostructure and central carbon segregation of 240 mm ×240 mm c asting bloom of low carbon ste el 20 CrMnTiH 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 reducation with maximum soft reduction 11 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 reducation 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 speed0.85 in/min,mold stirring 300 A and 5 Hz,the central carbon segregation and macrostructure of steel 20 CrMnTiH240 mm ×240 mm casting billet are better by single roll soft reduction 14 mm.