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<p>Mechanical reduction (MR), as a low-cost and flexible technology for internal quality improvement of continuously cast steel, is widely applied at the crater end of stand with the roller gap adjustment, and thus, the roller shape has a great effect on the internal improvement of continuously cast wide-thick. In the present study, a three-phase solidification model incorporating both solidification and thermal shrinkage is developed to investigate the effect of mechanical reduction with flat roller (FMR) and convex roller (CMR) on the macrosegregation and solidification structure in continuously cast wide-thick. The results reveal the fundamental influence of shrinkage behavior on macrosegregation in continuously cast wide-slab. Namely, solidification shrinkage at the crater end primarily induces center negative segregation, whereas thermal shrinkage plays the dominant factor to drive center positive segregation. For reduction modes, FMR demonstrates a limited capacity to alter equiaxed crystal distribution but it can effectively inhibit the solute-rich molten steel suction induced by the shrinkage at the crater end. When the reduction amount reaches 20 mm, the center segregation ratio is reduced to roughly 1.08. With further increase of reduction amount, the center segregation ratio changes a little. For the CMR, the wide-slab shows a significant depression at the loose side, and also the central equiaxed zone in the wide-slab is deformed, indicating that the reduction amount is highly impinging into the liquid core. When the reduction amount reaches 20 mm, the center segregation ratio reduces to 1.07, but the edge segregation in the wide-slab is still as high as to 1.11, because the solute-rich molten steel in liquid core is squeezed toward the slab edges. Consequently, a novel hybrid mechanical reduction method with FMR and CMR is proposed to improve the solidification structure and macrosegregation, namely, applying FMR during the earlier stage (<i>f</i><sub><i>s</i></sub>&lt;0.5) and switching to CMR in the later stage (<i>f</i><sub><i>s</i></sub>&gt;0.5). When this hybrid reduction is applied within the solidification fraction range of 0.3&lt;<i>f</i><sub><i>s</i></sub>&lt;0.9 with a reduction amount of 20 mm, the center macrosegregation ratio of the wide-thick slab can be reduced to 1.06, while edge segregation is improved to 1.09.</p>

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Numerical Investigation on Improvement of Solidification Structure and Macrosegregation in Wide-Thick Slab with Different Mechanical Reduction Roller Shapes via Three-Phase Solidification Model

  • 期刊论文

  • 发表日期：

    2026年5月26日

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  • Kangkang Li,
  • Sen Luo,
  • Weiling Wang,
  • Miaoyong Zhu

摘要

Mechanical reduction (MR), as a low-cost and flexible technology for internal quality improvement of continuously cast steel, is widely applied at the crater end of stand with the roller gap adjustment, and thus, the roller shape has a great effect on the internal improvement of continuously cast wide-thick. In the present study, a three-phase solidification model incorporating both solidification and thermal shrinkage is developed to investigate the effect of mechanical reduction with flat roller (FMR) and convex roller (CMR) on the macrosegregation and solidification structure in continuously cast wide-thick. The results reveal the fundamental influence of shrinkage behavior on macrosegregation in continuously cast wide-slab. Namely, solidification shrinkage at the crater end primarily induces center negative segregation, whereas thermal shrinkage plays the dominant factor to drive center positive segregation. For reduction modes, FMR demonstrates a limited capacity to alter equiaxed crystal distribution but it can effectively inhibit the solute-rich molten steel suction induced by the shrinkage at the crater end. When the reduction amount reaches 20 mm, the center segregation ratio is reduced to roughly 1.08. With further increase of reduction amount, the center segregation ratio changes a little. For the CMR, the wide-slab shows a significant depression at the loose side, and also the central equiaxed zone in the wide-slab is deformed, indicating that the reduction amount is highly impinging into the liquid core. When the reduction amount reaches 20 mm, the center segregation ratio reduces to 1.07, but the edge segregation in the wide-slab is still as high as to 1.11, because the solute-rich molten steel in liquid core is squeezed toward the slab edges. Consequently, a novel hybrid mechanical reduction method with FMR and CMR is proposed to improve the solidification structure and macrosegregation, namely, applying FMR during the earlier stage (fs<0.5) and switching to CMR in the later stage (fs>0.5). When this hybrid reduction is applied within the solidification fraction range of 0.3<fs<0.9 with a reduction amount of 20 mm, the center macrosegregation ratio of the wide-thick slab can be reduced to 1.06, while edge segregation is improved to 1.09.