Hi-B钢连铸坯凝固组织及偏析的研究

Study on solidification structure and segregation of continuous casting slab of Hi-B steel

通过工业试验,借助低倍检验、化学分析和原位分析等手段,对不同过热度和二冷比水量条件下Hi-B钢铸坯的宏观凝固组织和元素偏析进行分析检测,探究钢水过热度和二冷强度对铸坯凝固组织和元素分布的影响规律。结果表明,提高二冷强度,可使柱状晶率增加,降低过热度,可保留一定数量的等轴晶区。但过热度和二冷强度对铸坯中心等轴晶晶粒尺寸影响较小,铸坯中心等轴晶尺寸为3.0~3.4 mm。随着柱状晶率增加,碳的偏析逐渐改善,硫偏析先加剧后减轻。在过热度20℃、比水量1.38 L/kg的铸坯中,内弧侧粗大晶粒可达9.8 mm,高溶质浓度的钢液在枝晶间隙流动,造成严重的碳、硫偏析。

Through industrial test,macro-solidification structure and elements segregation of Hi-B steel slab under different superheat and secondary cooling water ratio were analyzed.With the help of macroscopic examination,chemical components analysis and original position statistic distribution analysis(OPA),the influence of superheat and intensity of secondary cooling on solidification macrostructure and element distribution in slab were explored.The results show that increasing the secondary cooling intensity can increase the columnar crystal ratio,and reducing the superheat can retain a certain equiaxed crystal area.However,superheat and intensity of secondary cooling have little effect on the central equiaxed grain size of the slab,and the central equiaxed grain size is 3.0-3.4 mm.With the increase of columnar crystal ratio,the carbon segregation gradually improved,and the sulfur segregation first increased and then decreased.In the slab under superheat of 20℃and specific water volume of 1.38 L/kg,the coarse grains size in the inner arc side can reach 9.8 mm.The molten steel with high solute concentration flows in the dendrite gap,resulting in serious carbon and sulfur segregation.