Investigation on the bulging deformation of continuously cast wide-thick slab with numerical calculation method
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摘要: 连铸过程中铸坯已凝固，坯壳在钢水静压力作用下发生鼓肚变形，影响浇铸过程顺行与铸坯质量。以宽厚板连铸坯为对象，采用数值计算方法定量研究了其在连铸过程三个典型铸流位置L1 (弯曲位置)、L2 (弧形段中间位置)、L3 (矫直位置)的鼓肚变形规律。由L1至L3，坯壳鼓肚变形及其导致的凝固前沿拉伸应变均不断增加。凝固前沿厚度方向拉伸应变εxx、拉坯方向拉伸应变εyy与宽度方向拉伸应变εzz呈集中分布趋势，三者分别加剧三角区裂纹、中间裂纹及角部裂纹风险。随着拉速由0.7 m/min增大至0.9 m/min，宽面坯壳鼓肚变形与εxx、εzz先增加后减小，而窄面坯壳鼓肚变形与εyy持续增大。Abstract: In continuous casting process, bulging deformation of the solidified shell occurs due to the ferrostatic pressure, which influences the smooth production and the internal quality of the continuously cast steel. In the present work, the continuously casting wide-thick slab was taken as the research object, and its bulging deformation at three typical strand positions L1(bending region), L2(middle of the bow region) and L3(straightening region) was quantitatively investigated with numerical calculation method. Bulging deformation of the solidified shell and the tensile strain distribution on the solidification front continuously increase from L1 to L3. The tensile strain along the slab thickness direction(εxx), along the casting direction(εyy) and along the slab width direction(εzz) present a characteristic of concentrated distribution and increase the risk of inducing triple-point cracks, midway cracks and internal corner cracks, respectively. With the casting speed increased from 0.7 m/min to 0.9 m/min, bulging deformation of the wide surface of the solidified shell and εxx, εzz firstly increase and then decrease, but the bulging deformation of the narrow surface of the solidified shell and εyy continuously increase.
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Key words:
- continuously cast /
- wide-thick slab /
- bulging /
- internal cracks /
- numerical calculation
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图 3 拉速0.8 m/min时L1~L3位置坯壳沿厚度向鼓肚变形(δx, mm)与宽度方向鼓肚变形(δz, mm)分布
Figure 3. Distributions of bulging deflection (mm) in thickness direction (δx) and width direction (δz) at L1~L3 with casting speed of 0.8 m/min
图 4 三个典型铸流位置坯壳宽面及窄面的鼓肚变形规律
Figure 4. Bulging deflection of the (a) wide surface and (b) narrow surface at three strand positions
图 5 三个位置处坯壳凝固前沿轴向应变集中分布趋势及板坯内裂纹示意
Figure 5. (a) Distribution of the normal strains in axes directions on the solidification front at three strand positions, and (b) schematic of the internal cracks that often occur in a continuously cast slab
图 6 坯壳凝固前沿应变提取位置示意图及提取的集中拉伸应变在三个铸流位置的变化趋势
Figure 6. (a) Schematic of the positions where the tensile strain concentrated on the solidification front was extracted, and (b) the variation of the corresponding concentrated tensile strains at three strand positions
图 7 L2位置拉速对坯壳宽面与窄面鼓肚变形及应变影响趋势
Figure 7. Effect of casting speed on the bulging deflection of (a) wide surface, (b) narrow surface and (c) normal strains at L2
表 1 冷却分区参数
Table 1. Parameters of the cooling zones in caster
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 Q345E主要化学成分
Table 2. The main chemical compositions of the Q345E %
C Si Mn P S 0.17 0.31 1.5 0.014 0.011
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表 3 坯壳最大鼓肚变形量公式计算值与模型计算值对比
Table 3. Comparison of the maximum bulging deflection calculated by the FE model and the formulas
位置 辊径/mm 坯壳厚度/mm 钢水静压力/MPa 最大坯壳鼓肚变形量计算值/mm 公式(4) 公式(5) 公式(6) 有限元模型 1 200 46 0.313 0.05 0.01 0.72 0.02 2 280 80 0.791 0.10 0.03 0.68 0.12 3 360 110 1.065 0.15 0.04 0.56 0.44
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