喂钢带碳浓度对连铸大圆坯宏观偏析的影响

doi:10.12068/j.issn.1005-3026.2024.04.006

摘要/Abstract

摘要：

结晶器喂钢带工艺是提高大截面连铸坯中心质量的有效方法之一.本文发展了液相-柱状晶-等轴晶三相体积平均凝固模型，探究了喂入钢带的碳浓度对连铸大圆坯凝固组织结构及宏观偏析分布的影响规律.结果表明：喂入钢带的碳浓度会极大地影响等轴晶与柱状晶的生长，碳浓度过低或过高均会降低喂钢带对等轴晶体积分数提高的效果.通过调控钢带溶质浓度可以直接影响铸坯内溶质浓度及分布，喂入1.0倍钢液碳浓度（ $r C$ =1.0）的钢带对连铸坯宏观偏析的改善效果最佳，其中铸坯径向碳极差和宏观偏析指数极值差分别为0.165 7%和38.36%.

关键词: 连铸大圆坯, 喂钢带, 钢带碳浓度, 宏观偏析, 体积平均凝固模型

Abstract:

Feeding a cold steel strip into continuous casting （CC） mold is an effective method to improve the center quality of large round bloom. A liquid‐columnar‐equiaxed solidification three‐phase volume averaged solidification model was developed to explore the effect of feeding strip carbon content on solidification structure and macrosegregation distribution of large CC round bloom in this paper. The results show that the carbon content of feeding steel strip has a significant effect on the growth of equiaxed crystals and columnar crystals. Under the condition of both low and high strip carbon contents， the effect of feeding steel strip on increasing equiaxed grain volume fraction will be reduced. The solute concentration and distribution in the casting bloom can be directly affected by regulating the solute concentration of steel strip. The steel strip with 1.0 times the carbon content of casting steel （ $r C$ =1.0） has the best improvement effect on the large CC round bloom， with the radial extreme difference of carbon content and macrosegregation index of the bloom being 0.165 7% and 38.36%， respectively.

Key words: large continuous casting round bloom, feeding steel strip, strip carbon content, macrosegregation, volume averaged solidification model

中图分类号:

TF 777

姚毓超, 刘中秋, 荣文杰, 李宝宽. 喂钢带碳浓度对连铸大圆坯宏观偏析的影响[J]. 东北大学学报（自然科学版）, 2024, 45(4): 499-506.

Yu-chao YAO, Zhong-qiu LIU, Wen-jie RONG, Bao-kuan LI. Effect of Feeding Steel Strip Carbon Content on Macrosegregation Distribution in Large Continuous Casting Round Bloom[J]. Journal of Northeastern University(Natural Science), 2024, 45(4): 499-506.

图/表 12

图1 连铸大圆坯物理模型及边界条件（修改自文献[18]）

Fig.1 Physical model and boundary conditions of large continuous casting round bloom （modified based on ref. [18]）

表1 连铸大圆坯材料的热物理性质参数及过程参数

Table 1 Thermophysical properties and process parameters of large continuous casting round bloom

参数	数值	参数	数值
纯铁熔点/K	1 805.15	液相黏度/（kg·m^-1·s^-1）	4.2×10^-3
比热容/（J·kg^-1·K^-1）	500	一次枝晶间距/m	5×10^-4
热导率/（W·m^-1·K^-1）	34	最大形核密度/m^-3	5×10⁸
凝固潜热/（J·kg^-1）	271 000	液相扩散系数/（m²·s^-1）	2×10^-8
热膨胀系数/K^-1	1.07×10^-4	固相扩散系数/（m²·s^-1）	1×10^-9
溶质膨胀系数/%^-1	1.46×10^-2	浇注温度/K	1 795
钢液碳浓度/%	0.432	拉速/（m·s^-1）	3.3×10^-3
密度/（kg·m^-3）	6 990	大圆坯直径/m	0.70
固液相密度差/（kg·m^-3）	150	喂入钢棒直径/m	0.10
液相线斜率/（K·%^-1）	-80.45	钢棒温度/K	500
溶质平衡分配系数	0.36

图2 铸坯表面温度的工业数据和模拟结果

Fig.2 Industrial data and simulation results of bloom surface temperature

图3 流线分布及液相体积分数的等值线（φl=0.1,0.5和0.9）（a）—不喂带；（b）—rC=0.5；（c）—rC=1.0；（d）—rC=1.5.

Fig.3 Stream line distribution overlapped with isolines of liquid fraction （φl=0.1,0.5 and 0.9）

图4 温度分布图及液相体积分数的等值线（φl=0.1,0.5和0.9）（a）—不喂带；（b）—rC=0.5；（c）—rC=1.0；（d）—rC=1.5.

Fig.4 Temperature distribution overlapped with isolines of liquid fraction（φl=0.1,0.5 and 0.9）

图5 rC=1.0工况下相分布图及液相体积分数的等值线（φl=0.1,0.5和0.9）（a）—液相；（b）—等轴晶相；（c）—柱状晶相.

Fig.5 Phases distribution overlapped with isolines of liquid fraction at rC=1.0 （φl=0.1,0.5 and 0.9）

图6 沿中心线的等轴晶相分布

Fig.6 Equiaxed phase distribution along the centerline

图7 弯月面下20 m处的等轴晶相分布

Fig.7 Equiaxed phase distribution at 20 m under the meniscus

图8 宏观偏析指数分布图及液相体积分数的等值线（φl=0.1，0.5和0.9）（a）—不喂带；（b）—rC=0.5；（c）—rC=1.0；（d）—rC=1.5.

Fig.8 Macrosegregation index distribution overlapped with isolines of liquid fraction （φl=0.1，0.5 and 0.9）

图9 沿中心线的宏观偏析指数分布

Fig.9 Macrosegregation index distribution along the centerline

图10 弯月面下20 m处的宏观偏析指数分布

Fig.10 Macrosegregation index distribution at 20 m from the meniscus

表2 不同喂带条件下对应连铸大圆坯碳浓度及碳极差

Table 2 Carbon concentration and maximum carbon difference of large CC round bloom under different feeding steel strip conditions

参数	数值
喂带条件	不喂带	r_C=0.5	r_C=1.0	r_C=1.5
最大碳浓度/%	0.538 7	0.476 6	0.474 6	0.475 4
最小碳浓度/%	0.210 3	0.257 6	0.308 9	0.296 9
碳极差/%	0.328 4	0.219 0	0.165 7	0.178 5

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