Effect of Feeding Steel Strip Carbon Content on Macrosegregation Distribution in Large Continuous Casting Round Bloom

doi:10.12068/j.issn.1005-3026.2024.04.006

Abstract

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

CLC Number:

TF 777

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.

Figures/Tables 12

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

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

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

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

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

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

Fig.6 Equiaxed phase distribution along the centerline

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

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

Fig.9 Macrosegregation index distribution along the centerline

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

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

References 19

1	刘中秋，李宝宽，肖丽俊，等.连铸结晶器内高温熔体多相流模型化研究进展［J］.金属学报，2022，58（10）：1236-1252.
	Liu Zhong‐qiu， Li Bao‐kuan， Xiao Li‐jun，et al.Modeling progress of high‐temperature melt multiphase flow in continuous casting mold［J］.Acta Metallurgica Sinica，2022，58（10）：1236-1252.
2	Liu Z Q， Niu R， Wu Y D，et al.Physical and numerical simulation of mixed columnar‐equiaxed solidification during cold strip feeding in continuous casting［J］.International Journal of Heat and Mass Transfer，2021，173：121237.
3	王卓，李宝宽，刘中秋，等.垂直连铸凝固过程的数值模拟研究［J］.东北大学学报（自然科学版），2020，41（9）：1257-1261.
	Wang Zhuo， Li Bao‐kuan， Liu Zhong‐qiu，et al.Numerical simulation of solidification process during vertical continuous casting［J］.Journal of Northeastern University （Natural Science），2020，41（9）：1257-1261.
4	Yao Y C， Liu M， Liu Z Q，et al.Review on effect of applied internal cooling source and vibration on metal solidification process［J］.Journal of Iron and Steel Research International，2023，30（6）：1059-1072.
5	Flemings M C.Our understanding of macrosegregation：past and present［J］.ISIJ International，2000，40（9）：833-841.
6	Lesoult G.Macrosegregation in steel strands and ingots：characterisation，formation and consequences［J］.Materials Science and Engineering：A，2005，413/414：19-29.
7	Suzuki M， Kimura K， Kawami A，et al.Improvement in center segregation of high carbon steel continuous casting blooms［J］.Revue De Métallurgie，1992，89（1）：83-92.
8	Habu Y， Itoyama S， Emi T，et al.Improving cast structure and centerline segregation of continuously cast slabs by adding steel strip into mold［J］.Tetsu-to-Hagane，1981，67（9）：1498-1507.
9	Zhao S， Zhang L.Effect of steel strip‐feeding process on solidification structure［J］.Advanced Materials Research，2014，941/942/943/944：1744-1747.
10	Zhao S， Wei D L， Xu J H，et al.Influence of steel strip‐feeding process on density and segregation of casting ingot［J］.Materials Science Forum，2016，872：45-49.
11	牛冉.连铸喂钢带工艺相变体系热质传递研究［D］.沈阳：东北大学，2020.
	Niu Ran.Heat and solute transport in phase change system in steel strip feeding into continuous casting mold process［D］.Shenyang：Northeastern University，2020.
12	Ludwig A， Wu M H.Modeling of globular equiaxed solidification with a two‐phase approach［J］.Metallurgical and Materials Transactions A，2002，33（12）：3673-3683.
13	Wu M H， Ludwig A， Bührig‐Polaczek A，et al.Influence of convection and grain movement on globular equiaxed solidification［J］.International Journal of Heat and Mass Transfer，2003，46（15）：2819-2832.
14	Wu M H， Ludwig A.Modeling equiaxed solidification with melt convection and grain sedimentation. I：model description［J］.Acta Materialia，2009，57（19）：5621-5631.
15	Wu M H， Ludwig A.Modeling equiaxed solidification with melt convection and grain sedimentation.II：model verification［J］.Acta Materialia，2009，57（19）：5632-5644.
16	Niu R， Li B K， Liu Z Q，et al.Experimental investigation of solidification in the cast mold with a consumable cooler introduced inside［J］.Metals，2019，9（1）：55.
17	Ramani A， Beckermann C.Dendrite tip growth velocities of settling NH₄Cl equiaxed crystals［J］.Scripta Materialia，1997，36（6）：633-638.
18	Yao Y C， Liu Z Q， Li B K，et al.Effect of steel strip feeding on the columnar‐equiaxed solidification in a large continuous casting round bloom［J］.Journal of Materials Research and Technology，2022，20：1770-1785.
19	Zheng Y J， Wu M H， Kharicha A，et al.Simulation of macrosegregation in a large vertical continuous casting of steel［J］.IOP Conference Series：Materials Science and Engineering，2016，143（1）：012032.