水口注流模式与电磁搅拌对大方坯铸态组织及宏观偏析分布特征有重要影响，进而影响轧材的致密性与均质性。以中碳结构钢大方坯及其热轧棒材为研究对象，通过对铸坯和轧材进行低倍侵蚀和成分分析，揭示了连铸控流模式对大方坯凝固组织与宏观偏析分布特征的影响及其铸轧遗传性。研究表明：常规直通水口浇注模式下，结晶器电磁搅拌(Mold electromagnetic stirring, M-EMS)电流由0A增加到800A，铸坯等轴晶率由6.06%仅可增加到11.71%，难以有效避免大方坯常见的中心缩孔缺陷与突出的中心线偏析。采用新型五孔水口浇注模式，即使不开启M-EMS，铸坯中心等轴晶率仍可达23.1%，大方坯中心缩孔级别可降至1.0级以下，满足后续热轧大棒材探伤要求。同时发现，五孔水口浇注模式下，大方坯铸态组织中往往会出现较为明显的柱状晶到等轴晶转变(Columnar to equiaxed transition, CET)区，铸坯断面碳偏析指数呈M型分布，表现为断面1/4位置CET区域碳偏析指数最高。大棒材轧制基本改变不了铸坯断面宏观偏析的分布形态，且可能导致中心线偏析指数增加。指出，基于连铸控流模式的作用规律和铸-轧遗传性特征，以及特殊钢长材热加工对中心致密度和偏析分布与程度的要求，实际生产中应从连铸工艺源头通过合理的控流模式来获得相应的铸态组织与宏观偏析分布形态。
Nozzle injection modes, together with electromagnetic stirring, play a key role on the as-cast macrostructure and the distribution of macro-segregation in bloom continuous castings, and then reach to the soundness and compositional homogeneity of the final as-rolled products. Based on the production process of a middle carbon steel bloom casting and its heavy section bars, various flow control modes have been adopted in casting production to study their effect on the semi-product solidification structure, carbon distribution across the bloom section and the following rolled bars. By the conventional nozzle with a single straight port, it shows that the equiaxed crystal ratio in the casting can only increase from 6.06% to 11.71% while M-EMS intensity changes from 0A to 800A, in which there still exists the obvious shrinkage cavity and macro-segregation along the centerline. While the novel five ports nozzle has been adopted, the equiaxed crystal ratio can reach to 23.1% even with M-EMS power off，and the center cavity index drop down to grade 1.0 or below, which meet the requirement of micro-void flaw detection for the bar products. Additionally, it is observed that the carbon segregation across the bloom cross section looks like a M-shaped curve with maximum carbon segregation index in the CET zone instead of the popular center region. For the heavy section bars rolled from the bloom casting, similar carbon distribution pattern as cast is observed after the hot working but with even higher centerline segregation index. Accordingly, it is pointed that, for the consideration of any special following hot working quality requirement, the macrostructure and both the pattern and intensity of macro-segregation should be regulated from very beginning casting with a reasonable flow control mode as mentioned in the study.