连铸絮流产生原因及措施解析

Analysis of generated cause and counter measure of flocculating flow

通过对连铸过程絮流产生原因分析，结合工业试验结果，探讨了转炉操作制度、挡渣出钢、钢包扒渣、钢包顶渣改质、底吹氩搅拌、水口设计、脱氧工艺及喂线改性夹杂等解决连铸絮流关键控制要点。研究表明，控制超低碳钢转炉出钢碳质量分数0．04％～0．06％，控制下渣量3～5kg／t，顶渣改质添加3～5kg／t活性石灰，酸溶铝控制中下限，优化浸入式水口结构设计，增大水口内径及侧流孔，中包烘烤1200℃以上等措施均可改善絮流。si＋Al脱氧工艺与全A1脱氧工艺相比虽未能缓解絮流，但可改变夹杂物形态，可满足薄材钢种对夹杂物的要求。

Based on analyzing the reasons of flocculation during casting, combined with industrial test results, some key measures to deal with flocculation during casting were established, such as optimizing operation system of converter, tapping with skimming, skimming in ladle, modifing the top slag in ladle, stiring by blowing Ar from the bottom of ladle, nozzle design, deoxidization process, modifing inclusion in molten steel by feeding cored wire etc. The results showed that, controlling the tapping carbon mass fraction at the range of 0. 04 ~if0 - 0.06 ~if0 for ultra-low carbon steel, slag quantity at the range of 3 - 5 kg/t, adding 3 - 5 kg/t active lime for modifying the top slag in ladle, acid aluminium content at lower limit, optimizing design of submerged nozzle structure, increasing the nozzle diameter and side flow hole diameter, the temperature of firing tundish above 1 200 ℃ etc, the flocculation could be alleviated. Comparison with aluminum deoxidization, Si ＋ Al deoxidization process had failed to ease floceulation, but the shape of inclusion was changed, the requirement of thin sheet steel for inclusion also could be satisfied.