The distribution of surface macro-inclusions is an important parameter that can directly influence the surface quality of IF steel sheets. In the present work, macro-inclusions > 100 μ m within a 20-mm zone from the slab surface across the whole slab width were characterized by step machining methods, and the total analyzed area was 3,300,000 mm 2 . Three kinds of macro-inclusions were detected: bubbles (including single and aggregated), alumina associated with bubbles and refractory-related alumina. The three-dimensional distribution of surface macro-inclusions across the whole slab width was reconstructed, which showed macro-inclusions along the thickness direction almost concentrated 8 to 20 mm from the slab surface, corresponding to the center of the upper roll zone and stagnant zone below the submerged entry nozzle bottom according to the full-scale water mold model simulation. An inclusion stability model was established that indicated that increasing the flow velocity sharply decreased the stability degree at the solidification front because of the washing effect. The calculated results by this model agree with the fact that macro-inclusions were mainly concentrated in the slab center because of the low flow velocity at this location. The present work indicates that increasing the flow velocity at the solidification front as well as eliminating the stagnant zone is a potential way to improve the surface quality of IF steel slabs.

中文翻译：

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IF钢板表层大尺寸夹杂物的三维分布

表面宏观夹杂物的分布是直接影响IF钢板表面质量的重要参数。在目前的工作中，在整个板坯宽度上距板坯表面 20 毫米区域内大于 100 微米的宏观夹杂物通过阶梯加工方法进行表征，总分析面积为 3,300,000 毫米 2 。检测到三种宏观夹杂物：气泡（包括单个和聚集体）、气泡伴生氧化铝和耐火氧化铝。重建了整个板坯宽度的表面宏观夹杂物的三维分布，显示沿厚度方向的宏观夹杂物几乎集中在距板坯表面8-20mm处，根据全尺寸水模模型模拟，对应于浸入式喷嘴底部下方的上辊区和停滞区的中心。建立的夹杂物稳定性模型表明，由于洗涤作用，提高流速会显着降低凝固前沿的稳定度。该模型的计算结果与宏观夹杂物主要集中在板坯中心的事实一致，因为该位置的流速较低。目前的工作表明，提高凝固前沿的流速以及消除停滞区是改善 IF 钢坯表面质量的潜在途径。建立的夹杂物稳定性模型表明，由于洗涤作用，提高流速会显着降低凝固前沿的稳定度。该模型的计算结果与宏观夹杂物主要集中在板坯中心的事实一致，因为该位置的流速较低。目前的工作表明，增加凝固前沿的流速以及消除停滞区是改善 IF 钢坯表面质量的潜在途径。建立的夹杂物稳定性模型表明，由于洗涤作用，提高流速会显着降低凝固前沿的稳定度。该模型的计算结果与宏观夹杂物主要集中在板坯中心的事实一致，因为该位置的流速较低。目前的工作表明，增加凝固前沿的流速以及消除停滞区是改善 IF 钢坯表面质量的潜在途径。