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Wenjie Tong, Sen Luo, Xiaohua Wang, Chunxin Wei, Weiling Wang, and Miaoyong Zhu, Hook formation and control mechanisms in continuously cast slabs of ultra–low carbon steel, Int. J. Miner. Metall. Mater., (2025). https://doi.org/10.1007/s12613-025-3112-z
Wenjie Tong, Sen Luo, Xiaohua Wang, Chunxin Wei, Weiling Wang, and Miaoyong Zhu, Hook formation and control mechanisms in continuously cast slabs of ultra–low carbon steel, Int. J. Miner. Metall. Mater., (2025). https://doi.org/10.1007/s12613-025-3112-z
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超低碳钢连铸板坯凝固钩形成与控制机制

摘要: 本研究聚焦于超低碳钢连铸板坯中凝固钩(hook)的形成机制及其控制方法。通过显微分析与数值模拟相结合的方法,系统揭示了凝固钩的形成过程及其分布特征。弯月面区域的“冻结–溢流”行为是造成凝固钩形成的主要原因:实验所测得得振痕间距的理论值与实测值相差约2%,主要由不同程度的钢液溢流引起,影响了振痕的形态及其最深点位置,该结果也进一步证实了弯月面区域的冻结与溢流确实是由结晶器的周期性振动所引起。通过二维与三维切片揭示了凝固钩分布的空间特征,并表明瞬时的流动与传热是造成凝固钩形成过程“随机性”和“倾向性”的关键原因。随机性表现在凝固钩偏转角度的变化,倾向性则体现在钩深度与钢液过热度之间的负相关关系。在凝固钩的成因及其轮廓特征的基础上,提出了调控凝固钩深度的“正弦定则”。通过两组不同过热度的工业实验验证表明,在控制液位波动范围一定的条件下,随着过热度升高,钩长与钩深均明显减小,该控制方法的有效性。

 

Hook formation and control mechanisms in continuously cast slabs of ultra–low carbon steel

Abstract: The hook formation mechanism in continuously cast slabs of ultra-low carbon steel was analyzed in detail through numerical calculations and experimental observations using optical microscopy, and its distribution characteristics were determined. Numerical simulations confirmed that the freezing–overflow mechanism is the primary cause of hook formation. They also revealed that the freezing event occurs unpredictably, while the overflow event takes place during the positive strip time. The average pitch of oscillation marks (OMs) on the slab surface was 8.693 mm, while the theoretical pitch was 8.889 mm, with a difference of approximately 2%. This discrepancy primarily results from varying degrees of overflow, which affects the morphology of the OMs and the positions of their deepest points. Notably, this result further confirmed that the freezing and overflow in the meniscus were indeed caused by the periodic oscillation of the mold. Higher superheat hindered hook formation, leading to a negative correlation between the hook depth distribution around the slab and the temperature distribution within the mold. Therefore, the depth of the corner hook was greater than that of other positions, which was caused by the intensified cooling effect of the corner. Moreover, key factors influencing hook development were analyzed, providing insights into transient fluid flow and heat transfer characteristics within the mold. Transient fluid flow and heat transfer contributed to the randomness and tendency of hook formation. This randomness was reflected in the varying angles of the hooks, whereas the tendency was evident in the negative correlation between superheat and hook length. Based on the randomness and tendency of hook formation and its profile characteristics, a new method for controlling hook depth based on “sine law” is proposed.

 

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