凝固末端电磁搅拌和轻压下复合技术对大方坯高碳钢偏析和中心缩孔的影响

基于ANSYS软件建立了310mm×360mm断面大方坯连铸过程二维凝固传热数学模型,并采用窄面射钉试验及铸坯表面测温试验对模型的准确性进行了验证.通过模型研究了过热度、拉速和二冷比水量对铸坯中心固相率以及凝固坯壳分布的影响,并结合高碳耐磨球钢BU的高温拉伸试验结果,确定了最佳的拉速以及最优轻压下压下区间要求.通过工业试验对理论模型进行了验证,并分析研究了拉速对采用凝固末端电磁搅拌(F-EMS)以及凝固末端17mm大压下量的轻压下技术生产310mm×360mm断面大方坯高碳耐磨球钢BU铸坯的偏析和中心缩孔的影响.结果表明:采用凝固末端电磁搅拌和轻压下复合技术,通过调整拉速优先满足轻压下压下区间要求,可显著降低中心偏析、V型偏析及中心缩孔,但如果仅达到凝固末端电磁搅拌位置要求时,则铸坯中心质量不会得到明显改善.拉速为0.52m·min-1且轻压下压下区间铸坯中心固相率为0.30~0.75时,偏析和中心缩孔有很大程度的改善,不合理的压下量分配会引起铸坯出现内裂纹以及中心负偏析.

Effect of combining F-EMS and MSR on the segregation and shrinkage cavity in continuously cast high-carbon steel blooms

This study established a two-dimensional mathematical model of solidification and heat transfer for a bloom with a 310mm×360mm cross-section using ANSYS software, which was verified by nail-shooting experiments in the narrow side of the bloom and surface temperature testing.The effect of the casting process parameters, such as superheat, casting speed, and secondary cooling intensity, on the solid fraction in the strand centerline and the solidified shell was investigated.Moreover, the optimum casting speed and the optimum solid fraction in the core of the partially solidified strand throughthe soft reduction zone were determined by the model considering the hot ductility of the high-carbon wear-resistant ball steel BU.Plant trials of BU with different casting speeds were performed to validate the theoretical model and analyze the effect of the casting speed on the segregation and shrinkage cavity of BU on a 310mm×360mm bloom caster equipped with final electromagnetic stirring (F-EMS) combined with mechanical soft reduction (reduction amount with 17mm).The results show that the inner defects (e.g., center segregation, V-segregation, and shrinkage cavity) significantly improve when the casting speed is adjusted to meet the required soft reduction zone as a matter of priority;otherwise, the casting speed is only adjusted to preferentially satisfy the required F-EMS stirring region.The inner quality does not show any obvious improvement.Except for the internal cracks and the negative center segregation caused by the improper distribution of the reduction amount, the inner defects (e.g., macro segregation and shrinkage cavity) significantly improve with a casting speed of 0.52m·min-1 and a solid fraction in the strand centerline ranging from 0.30 and 0.75 in the soft reduction zone.