Development and Application of Capping Delayed Running Out Process for Large Round Bloom Continuous Casting
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摘要: 对比分析了ø380~ø800 mm大圆坯连铸尾坯的凝固组织、低倍质量与正常坯的差异;发现尾坯存在等轴晶比例低、白亮带比例高、中心缩孔和疏松级别高等问题。基于收尾坯工艺,理论分析了其产生原因,并提出了一种延迟封顶收尾坯工艺来改善尾坯质量。工业试验结果表明:延迟封顶收尾坯工艺通过在钢液面加入发热剂并按顺序关闭各段二冷水,延迟了封顶的时间,有效增加了熔池的补缩效果;在切尾长度减小0.5 m时尾坯低倍不合格比例由6.25%降低到1.96%,钢水收得率平均提高0.55%。Abstract: The difference of solidification structure and macro quality between trail bloom and normal bloom has been comparatively analyzed for ø380~ø800 mm large round bloom. Some defects such as low ratio of equiaxed crystal zone,high ratio of white band,serious central porosity,cavity and crack are observed in the trail bloom.The causes have been theoretically analyzed based on running out process,and a capping delayed running out process has been put forward to improve the trail bloom quality.Industrial test result shows that the capping delayed running out process can delay the strand capping by adding some heating agent on the top surface and switching off the spraying water in order,which leads to more sufficient contraction compensation.Thus,unqualified ratio of trail bloom decreases from 6.25% to 1.96% when tail cropping length is reduced by 0.5 m,and the liquid steel yield is improved by 0.55%.
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Key words:
- continuous casting /
- large round bloom /
- running out process /
- inner defect /
- heating agent /
- capping
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