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低碳铝镇静钢铸坯皮下有明显的钩状坯壳,钩状坯壳很容易捕获夹杂物和气泡,使得簇群状氧化铝夹杂和气泡+氧化铝在铸坯的近表层聚集。对低碳铝镇静钢铸坯的宽面、窄面以及角部综合取样,研究分析了铸坯不同位置处钩状坯壳的特征与变化规律。结果显示,在铸坯宽面,中心处钩状坯壳较深;在铸坯窄面,越靠近角部,钩状坯壳越深;在铸坯角部,钩状坯壳呈现三维形貌。此外,提出了钩状坯壳对夹杂物和气泡的捕获机理,认为连铸过程中的Marangoni力对夹杂物和气泡的捕获起着至关重要的作用。此机理很好地解释了钩状坯壳更易捕获大尺寸夹杂物和气泡的原因;根据该机理,提出了减小钩状坯壳捕获大尺寸夹杂物的相关措施。
Low-carbon aluminum killed steel castings have obvious hook-shaped shell under the skin, hooked shell is easy to capture inclusions and bubbles, making the cluster-shaped alumina inclusions and bubbles + alumina in the slab near the surface aggregation. The wide surface, narrow surface and corner of low carbon aluminum killed steel slab were comprehensively sampled. The characteristics and variation of hooked shell at different positions of slab were studied and analyzed. The results show that in the wide slab, the center of the hook-shaped shell deep; in the narrow slab, the closer to the corner, the deeper the hook-shaped shell; in the corner of the slab, hook-shaped shell presents three-dimensional morphology . In addition, the catching mechanism of inclusions and bubbles in the hook-shaped shell is proposed. It is considered that the Marangoni force in the continuous casting process plays a crucial role in capturing inclusions and bubbles. This mechanism well explains the reason why the hooked shell is more apt to trap large inclusions and bubbles. Based on this mechanism, some measures to reduce the size of the hooked shell to trap large inclusions are proposed.