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宏观偏析水平是衡量矩形坯铸坯质量的重要指标,宏观偏析分为中心偏析和中间偏析。从本钢矩形坯的生产实践出发,针对轻压下、电磁搅拌、二次冷却等工艺进行了大量对比试验。对试验铸坯进行了取样分析,通过检验计算不同工艺的碳偏析指数,总结出了轻压下、电磁搅拌等因素对于铸坯宏观偏析的影响规律:对于中心偏析来说,轻压下对于改善铸坯的中心偏析具有明显的作用,但与总压下量的大小没有显著线性对应关系;铸坯二次冷却越强,中心偏析越大;一定范围内,结晶器电搅电流的增加有助于改善铸坯中心偏析。对于中间偏析来说,轻压下对铸坯的中间偏析改善效果不明显;降低结晶器电磁搅拌电流,可以缩小铸坯中间碳偏析指数范围,改善铸坯的中间偏析。经工艺调整后,本钢矩形坯的中心偏析及中间偏析得到很大改善,轴承钢等高碳钢的中心碳偏析指数能够达到1.10以下,中低碳钢的中间碳偏析指数范围缩窄到0.95~1.05。
Macro-segregation level is an important indicator to measure the quality of rectangular billet. Macro-segregation is divided into center segregation and middle segregation. Starting from the production practice of the rectangular billet of Benxi Iron and Steel Co., Ltd., a large number of comparative tests have been carried out for the processes of soft reduction, electromagnetic stirring and secondary cooling. The sample slab was sampled and analyzed, and the carbon segregation index of different processes was calculated through inspection. The influence of light pressure, electromagnetic stirring and other factors on macro segregation of slab was summarized. For center segregation, The center segregation of slab has obvious effect, but there is no significant linear relationship with the total reduction. The secondary cooling of the slab is stronger and the center segregation is bigger. Within a certain range, the increase of mold electrocution current helps To improve the slab center segregation. For the middle segregation, the effect of mild segregation on the middle segregation of the slab is not obvious. Reducing the electromagnetic stirring current of the mold can reduce the middle segregation index range of the slab and improve the middle segregation of the slab. After the process adjustment, the central segregation and intermediate segregation of the billet of Benxi Iron & Steel Company have been greatly improved. The center carbon segregation index of high carbon steel such as bearing steel can reach below 1.10 while the middle carbon segregation index of medium and low carbon steel narrows to 0.95 ~ 1.05.