高品质冷轧薄板钢中非金属夹杂物控制技术

Non-Metallic Inclusion Control Technology for High Quality Cold Rolled Steel Sheets

能够造成冷轧薄板表面缺陷的钢中夹杂物主要是簇群状Al2O3、"Ar气泡+Al2O3"和结晶器保护渣卷入形成的大型夹杂物。在正常稳定连铸条件下,目前已能够做到对结晶器保护渣卷渣形成夹杂物加以有效控制。在各类非稳浇铸铸坯中,浇次开浇头坯的品质降低最严重,浇次尾坯中保护渣卷渣形成的夹杂物数量明显多于正常坯,炉-炉间交接坯和快换浸入式水口期间浇铸铸坯中,来源于保护渣卷入形成的夹杂物数量也多于正常坯试样。首钢京唐公司生产冷轧薄板钢类,在1.0-2.0m/min拉速范围,大型夹杂物随拉速增加呈减少趋势,对此应加以关注。研究发现,尺寸100μm以上的有害夹杂物主要存在于铸坯2mm表层内,生产"无表面缺陷"要求的汽车外板,应该采用铸坯表面清理。

The non-metallic inclusions which can create surface defects of the cold rolled sheets mainly are the large sized Al2O3 clusters, ＂Ar＋Al2O3 ＂ typed inclusions and the entrapped mold powder particles. Nowadays, under normal and stable casting conditions, the inclusions formed due to the mold powder entrapment can be well controlled. Among various types of unsteady cast slabs, the quality of the first slab of the cast is deteriorated most severely. In the bottom slab of the cast, inclusions from the mold powder entrapment are much more than the normal cast slabs. Also, the inclusions from mold powders are more in the slabs cast during heat/heat ladle exchange and during SEN quick change than the normal cast slabs. It is noted that, in Shougang Jingtang Iron and Steel Co. , Ltd. , the number density of the large inclusions decreases with increasing the casting speed when the casting speed is 1.0-2.0 m/min. The harmful inclusions larger than 100 μm were found mostly in 0-2 nun sub-surface layers of the slabs. To produce surface defects free sheets for automotives, slab surface conditioning treatment should be adopted.