李源源, 张炯明, 崔衡, 尹延斌, 邓深, 杨剑洪. IF钢连铸开浇工艺对头坯洁净度影响的研究[J]. 工程科学学报, 2023, 45(6): 899-906. DOI: 10.13374/j.issn2095-9389.2022.04.15.001
引用本文: 李源源, 张炯明, 崔衡, 尹延斌, 邓深, 杨剑洪. IF钢连铸开浇工艺对头坯洁净度影响的研究[J]. 工程科学学报, 2023, 45(6): 899-906. DOI: 10.13374/j.issn2095-9389.2022.04.15.001
LI Yuan-yuan, ZHANG Jiong-ming, CUI Heng, YIN Yan-bin, DENG Shen, YANG Jian-hong. Effect of casting speed rising on the cleanliness of IF steel slab during the initial casting stage[J]. Chinese Journal of Engineering, 2023, 45(6): 899-906. DOI: 10.13374/j.issn2095-9389.2022.04.15.001
Citation: LI Yuan-yuan, ZHANG Jiong-ming, CUI Heng, YIN Yan-bin, DENG Shen, YANG Jian-hong. Effect of casting speed rising on the cleanliness of IF steel slab during the initial casting stage[J]. Chinese Journal of Engineering, 2023, 45(6): 899-906. DOI: 10.13374/j.issn2095-9389.2022.04.15.001

IF钢连铸开浇工艺对头坯洁净度影响的研究

Effect of casting speed rising on the cleanliness of IF steel slab during the initial casting stage

  • 摘要: IF钢连铸开浇过程头坯洁净度水平较低,目前各企业一般将开浇坯作判废或降级处理,这导致了产品质量不稳定,成材率低等问题。为研究IF钢非稳态开浇阶段连铸坯的洁净度水平及优化措施,采用现场取样、检测分析及数值模拟计算相结合的方法,分析了IF钢开浇阶段不同拉速变化曲线条件下连铸坯沿拉坯方向的洁净度变化规律。通过实验检测发现沿拉坯方向头坯TO、N及显微夹杂物含量呈现明显下降趋势,距离头坯头部6 m处 TO含量为13×10−6,接近正常坯水平,距离头坯头部7 m处 N含量约为19×10−6,接近正常坯水平,开浇工艺对于连铸坯TO、N及显微夹杂物含量影响不大。匀速、前快后慢和前慢后快三种拉速工艺条件下,大型夹杂物在距离头坯头部2 m处的质量分数约为0.2 mg∙kg−1,但之后均存在不同程度的大型夹杂物数量波动现象,而前快后慢工艺影响范围最小,在5.5 m后均达到正常水平。通过数值计算同样发现,前快后慢的提拉速工艺条件下产生的头坯洁净度更快地接近正常坯洁净度水平(约开浇430 s后,对应拉坯5 m)。基于本文研究,提出了一种优化的IF钢连铸开浇过程提拉速的工艺方法。

     

    Abstract: During the initial casting stage of the IF steel, the cleanliness of the first slab deteriorates. Steel plants treat the initial casting slabs as waste or demoting products. Moreover, the cleanliness deterioration of initial casting slabs leads to unstable quality and low product yield. In the present study, to investigate the cleanliness of continuous casting slabs and the optimization measures during the initial casting stage of the IF steel, the cleanliness of the initial casting slabs is evaluated by field sampling and experimental analysis. Moreover, the effect of the casting speed rising method on the cleanliness of the IF steel slab during the initial casting stage is investigated. Additionally, numerical simulations are conducted to reveal the level of fluctuations of the molten steel in the mold during the initial casting stage. The results show that the variations in TO, N, and the content of microinclusions in the slab decrease obviously along the casting direction. The contents of TO and N in the slab reach the normal slab level of 6 m (approximately 13×10−6) and 7 m (approximately 19×10−6) away from the dummy bar head, respectively. Nevertheless, the effects of the casting speed rising method on the contents of TO, N, and microinclusions in the initial casting slabs are inapparent during the open casting process. For the three conditions of open casting (different casting speed rising methods), the contents of the macroinclusions in the slab reach the normal slab level of around 2 m (approximately 2 mg/10 kg) away from the dummy bar head, respectively. Subsequently, the fluctuation of the macroinclusion content can be determined. Furthermore, under the condition of “quick-slow” casting speed rising, the fluctuation can be quickly alleviated, and the macroinclusion content normalizes. Numerical simulations reveal that the variations in the fluctuation level of the molten steel at different positions (near the nozzle, a quarter of the width, and near the narrow face) in the mold during the initial casting stage of the three casting speed rising modes are similar. First, the fluctuation level is extremely intense. Then, the fluctuation level gradually weakens for some time. Finally, the fluctuation level of the molten steel at different positions in the mold stabilizes. Additionally, the numerical simulation results reveal that the slab cleanliness can quickly normalize (430 s after initial casting and about 5 m away from the dummy bar head) under the “quick-slow” casting speed rising mode during the initial casting stage.

     

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