Investigation on thermal shrinkage deformation of the continuously cast slab
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摘要: 连铸过程铸坯已凝固坯壳因冷却降温发生热收缩变形，该变形是制定连铸机基础收缩辊缝的重要依据。以板坯连铸过程为对象，建立了三维热-力耦合有限元模型，揭示了板坯连铸过程已凝固坯壳沿厚度方向热收缩变形规律。结果表明，浇铸过程中坯壳热收缩变形不断增大，在凝固终点位置热收缩出现短时加速增大趋势，铸机末端位置坯壳宽向中心位置热收缩约8 mm；板坯宽向不同位置热收缩变形存在较明显差异，由宽向中心至铸坯角部方向，已凝固坯壳厚度方向热收缩变形呈先减小后增大趋势。随着拉速增加，相同铸流位置热收缩变形减小，拉速增加0.1 m/min，铸机末端位置的坯壳宽向中心与宽向1/8位置热收缩减小约1.2 mm。研究结果为优化铸机基础收缩辊缝，改善因不合理基础辊缝导致的铸坯内部质量问题提供了数据支撑。Abstract: In the continuous casting process, thermal shrinkage deformation of the solidified shell occurs due to the temperature decrease during the cooling process, and this thermal shrinkage deformation is the important basis for designing basic shrinkage gap of the continuous casting machine. In the present work, a 3D thermal-mechanical coupling model was developed, and the thermal shrinkage deformation of the continuous casting slab was investigated. The results indicate that the thermal shrinkage deformation continuously increased during the continuous casting process and a rapidly increasing trend was observed at the solidification end of the strand. The total shrinkage of the wide surface center was ～8 mm at the exit of the continuous casting machine. The difference of the thermal shrinkage deformation along the slab width direction was obvious, and the shrinkage deformation showed a decreasing trend first and then an increasing trend from the slab surface center to its corner. The thermal shrinkage at the same strand position decreased with increasing the casting speed, and the total thermal shrinkage of the wide surface center and 1/8 width decreased ～1.2 mm with increasing the casting speed by 0.1 m/min. The present work provided data support for optimizing the basic shrinkage gap of the continuous casting machine and thus alleviating the internal quality of the continuous casting steel.
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Key words:
- continuously cast /
- slab /
- 3D thermal-mechanical coupling /
- finite element /
- thermal shrinkage
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图 1 宽厚板坯热收缩三维热/力耦合有限元模型
Figure 1. 3D thermal-mechenical coupled model for thermal shrinkage of the wide-thick slab
图 2 不同温度钢的线性膨胀系数及瞬时线性膨胀系数
Figure 2. The theoretically calculated thermal linear expansion coefficient and transient thermal linear expansion coefficient
图 4 二冷5区至8区范围内实测宽向水流密度
Figure 4. The measured water flux distribution along the slab width direction in Zone 5～8
图 5 温度计算值与实测值对比
Figure 5. Comparison between the measured and the predicted temperatures
图 6 二冷8区末铸坯横断面两相区形貌及不同特征点位置
Figure 6. Profile of the unsolidified region at the end of zone 8 and the distribution of the typical points
图 8 (a)铸坯热收缩沿宽向分布与(b)横断面温度场云图
Figure 8. (a) Thermal shrinkage distribution along the slab width direction and (b) the corresponding temperature field of the slab transverse section at the end of zone 8 and the caster
图 9 不同拉速下铸坯各特征点热收缩规律
Figure 9. Thermal shrinkage variation with different casting speeds at the typical points
表 1 冷却分区参数
Table 1. Parameters of the cooling zones
冷却分区 起始铸流位置/m 结束铸流位置/m 结晶器 0 0.80 二冷1区 0.80 1.04 二冷2区 1.04 1.60 二冷3区 1.60 2.71 二冷4区 2.71 4.26 二冷5区 4.26 6.18 二冷6区 6.18 10.02 二冷7区 10.02 13.86 二冷8区 13.86 20.49 二冷9区 20.49 30.33 
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表 2 模拟参数
Table 2. Simulation paraeters
Q345主要成分(w/ %) 液相线温度/℃ 固相线温度/℃ 板坯厚度/mm 板坯宽度/mm 过热度/oC 拉速/(m.min−1) C Si Mn P S 0.17 0.31 1.5 0.014 0.011 1517.7 1467.5 280 1600,1800,2000 30 0.7,0.8,0.9
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