304不锈钢冷轧板线鳞缺陷改进实践

针对304不锈钢冷轧板表面发生的线鳞缺陷,采用扫描电子显微镜对缺陷表面及横截面形貌和成分进行分析,并对影响线鳞缺陷的因素进行了探讨。结果表明,304不锈钢线鳞缺陷主要由CaO-SiO2-Al2O3-MgO系夹杂物引起的。通过在AOD还原阶段使用低铝硅铁或适量降低AOD出钢渣碱度,降低了304不锈钢铸坯中夹杂物熔点,对于改善夹杂物的塑性变形能力有利。此外,加快连铸交接炉换包节奏,提高最小中包液位达85%以上,稳定中间包流场;同时增加大包余钢量至5~6 t,避免大包下渣,从源头限制夹杂物,提高钢液洁净度。以上改进措施实施后,304不锈钢冷轧板线鳞缺陷降级率能稳定控制在0.2%以内。

Improvement practice of line scale defect of 304 stainless steel cold rolled plate

In view of the line scale defect on the surface of 304 stainless steel cold rolled sheet in a factory, the morphology and composition of the defect surface and cross section were analyzed by scanning electron microscopy, and the factors affecting the line scale defect were discussed. The results show that the linear scale defects of 304 stainless steel are mainly caused by CaO-SiO2-Al2O3-MgO system inclusions.The melting point of inclusions in 304 stainless steel slab is reduced by using low aluminium ferrosilicon or reducing the basicity of AOD tapping slag in AOD reduction stage, which is beneficial to improving the plastic deformation ability of inclusions.In addition, the tundish changing rhythm is accelerated, the minimum tundish tonnage proportion increases to more than 85 %,and the tundish flow field is stabilized.At the same time, the amount of remaining molten steel in large ladle should be increased to 5-6 t, so as to avoid large ladle slag entering tundish, limit inclusions from the source and improve the purity of molten steel.After the implementation of the above improvement measures, the degradation rate of line scale defect of 304 stainless steel cold rolled sheet can be stably controlled within 0.2 %.