冷轧薄板线状缺陷的工艺控制

针对某钢厂结晶器液面翻腾导致卷渣严重与中间包过热度控制缺乏依据为背景,对结晶器内流态和过热度对表面质量影响开展研究。文献调研与大量线状缺陷电镜分析发现,导致线状缺陷的夹杂物主要是氧化铝和保护渣,且引起线状缺陷的大尺寸夹杂物主要分布在铸坯表层5mm内。减少吹氩量与增大浸入深度可提高双股流比例,基于水模型和工业试验,提出控制临界吹气量得到双股流。应用该结果后,消除了结晶器液面翻腾现象,提高中间包过热度可减少钩状坯壳深度与铸坯表层夹杂物数量。综合考虑钢水洁净度提出冷轧薄板钢过热度控制在25~40℃。基于以上措施,该厂炼钢缺陷导致降级率由1.1%降至0.6%。

Process control for sliver defects in cold rolled steel sheets

Based on the severe mold entrapment due to the mold splashing and the lack of the basis of the tundish superheat control, the effects of the flow pattern in the mold and the superheat on the surface quality were investigated. It can be concluded that the alumina and mold powder primarily accounted for the slivers defect in this mill and the location of these inclusions were trapped in the first 5 mm of the solidified shell in the upper part of the mold based on the literature review and numerous SEM analysis of steel sheets. Decreasing the gas flow rates and increasing the SEN depth can promote the double roll flow (DRF). Therefore, based on the water model and the industrial experiment, the critical gas flow rates were put forward to control the DRF and the mold splashing was eliminated after applying the results in the real casters. Furthermore, increasing the superheat in tundish can retard the solidification front and decrease the hook depth, thus improve the surface quality of slabs. The tundish superheat in the casting practice was set to 25 to 40 ℃taking into the consideration of steel cleanliness. The degradation ratio decreased from 1.1% to 0.6% after applying these countermeasures.