凝固压下对大方坯中心致密性的影响

Effect of solidification reduction process on center compactness of continuous casting bloom

为了改善大方坯的中心致密性,研究了连铸凝固压下对铸坯中心缩孔的影响。采用热-弹-塑性模型计算了凝固压下时大方坯中心缩孔的变形规律。结果表明,在铸坯完全凝固后压下可有效提高中心致密性,其效果比相同变形量下的均热轧制提高了22.5%。随着压下量的增大,缩孔尺寸明显减小,但由于凝固压下变形量有限,大尺寸缩孔难以完全消除。为进一步消除缩孔,建议凝固末端轻压下速率提高到0.02 mm/s,或增大凝固后压下量。SA-213 T12大方坯采用凝固压下技术后大部分中心缩孔已被焊合,残留缩孔的最大尺寸由8减小到2 mm,同时缩孔数量降低了50%。

In order to improve the center compactness of continuous casting bloom,the effect of post solidification reduction process on the center shrinkage cavity existing in the bloom was studied. The deformation behavior of shrinkage cavity during solidification reduction was analyzed using thermo-elastic-plastic model. The results revealed that the center compactness of bloom can be effectively improved when reduction technology was applied after complete solidification,and the effect is 22.5% higher than hot rolling under the same deformation. With the increase of reduction amount,the size of the center shrinkage cavity is significantly reduced. However,it is difficult to completely eliminate the large size shrinkage cavity due to the limited reduction amount of post solidification reduction. To further eliminate the shrinkage cavity,it is advisable to increase the soft reduction rate to 0.02 mm/s at the end of solidification to reduce the initial size of shrinkage cavities,or increase the post solidification reduction amount. Post solidification reduction technology was applied to the production of continuous casting bloom SA-213T12. Experiment result shows that most of the center shrinkage cavities have been welded. The size of the remaining shrinkage cavities is reduced from 8 mm to 2 mm,and the number is reduced by 50%.