连铸方坯中心线凝固行为波动现象及变化规律  

Fluctuation phenomenon and variation regulation of solidification behavior in centerline of continuous casting billets

作　　者：郭东伟 侯自兵[1,2] 郭坤辉 张福利 曾子航 文光华[1,2] GUO Dong-wei;HOU Zi-bing;GUO Kun-hui;ZHANG Fu-li;ZENG Zi-hang;WEN Guang-hua(College of Materials Science and Engineering,Chongqing University,Chongqing 400044,China;Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学材料科学与工程学院,重庆400044 [2]重庆大学钒钛冶金及新材料重庆市重点实验室,重庆400044

出　　处：《钢铁》2023年第1期78-90,共13页Iron and Steel

基　　金：国家自然科学基金资助项目(52274318)。

摘　　要：连铸坯中心线区域钢液的凝固行为与中心偏析缺陷的形成及控制密切相关。基于中碳钢连铸方坯纵断面的实际凝固组织,以中心偏析点内部二次枝晶间距计算局部冷却速率,揭示了铸坯中心线局部冷却速率的波动特征。结合连铸三维凝固模型,研究了铸坯中心线固相率波动引起局部冷却速率波动并最终影响铸坯中心组织和性能的均匀性的机理;对不同工况铸坯中心线固相率和局部冷却速率波动的周期性进行了分析对比,提出了连铸坯凝固终点位置的周期性波动机理并得到了不同拉速下凝固终点波动距离的判断方程,对于所选连铸方坯,凝固终点波动距离为25.0~27.5 mm;在此基础之上,研究了拉速对中心线固相率波动程度的影响规律,并分析了凝固终点波动距离变化对末端电磁搅拌(final electromagnetic stirring,F-EMS)和轻压下(mechanical soft reduction,MSR)作用均匀性的影响。结果表明,拉速由1.8 m/min提高至2.4 m/min后,虽然液相穴长度增加可能增加整体偏析程度,但铸坯中心线固相率波动程度降低了20%,这有利于减轻中心线偏析沿拉坯方向的波动性,提高铸坯中心质量的均匀性。并且,虽然凝固终点波动距离随着拉速提高而逐渐增大,但其对F-EMS和MSR作用均匀性的影响却由于液相穴长度的增加而逐渐减小。可以为F-EMS和MSR的应用以及连铸方坯中心质量的精细化控制提供理论和方法参考。Nowadays,the development of the steel industry needs to improve the quality uniformity and stability of the continuous casting billets.The centerline segregation formed in the continuous casting process represents the nonuniformity of solute elements and quality of the billets,which is closely related to the solidification process of solute-enriched liquid in the centerline of the billets.At the same time,the final electromagnetic stirring(F-EMS)and mechanical soft reduction(MSR)are widely used in the actual continuous casting process to improve the inner quality uniformity of the billets.However,the fluctuation of the solidification end point will affect the effect uniformity of the F-EMS and MSR.Thus,it′s essential to investigate the solidification behavior and fluctuation characteristics in the centerline and explore the fluctuation of the solidification end point for improving the quality uniformity of the billets.It′s found that the fluctuation of solid fraction in the centerline will cause the fluctuation of the local cooling rate,and ultimately affect the quality uniformity of the billets.Subsequently,this work has analyzed the fluctuation periods of solid fraction and local cooling rate in the centerline of the billets and proposed the periodic fluctuation mechanism of the solidification end point in the continuous casting process.At the same time,the judgment equation of fluctuation distance of solidification end point under different casting speeds was obtained.On this basis,the effect of casting speed on the fluctuation of solid fraction in the centerline was discussed,and the influence of fluctuation distance of solidification end point on the effect uniformity of the F-EMS and MSR was also analyzed.The results show that the increase in casting speed can reduce the fluctuation degree of solid fraction and improve the inner quality uniformity of the billets.On the other hand,although the fluctuation distance of the solidification end point increases with the increase of the casting speed,its influe

关 键 词：连铸 偏析 中心线固相率波动 凝固终点波动 拉速 

分 类 号：TF777[冶金工程—钢铁冶金]