Abstract: SEM, EDS and metallographic microscope were been used to study flakes peel-like defects on the surface of cold-rolled strip steel combined with mathematical simulation. The analytical results show that the flakes peeling was induced by non-metallic inclusions and scales. Inclusions could be derived from steel de-oxidation or slag entrapment, and scales, initiating cracks inside billet, which could be exposed to the surface on cold-rolling process, were caused by de-carbonization because of improper heating mode or time. Numerical simulation shows that after pouring within the first 6 s, temperature dropped to 124.9℃/s and solidified shrinkage rate to 0.07 mm/s, that makes corner cracks. Crack index of solidified front increased up to 0.75 at the end of solidification, with formation of porosity and shrinkage cavity. Crack index was over 1 near the surface from the edge to 41 mm thickness, where middle cracks formed. Temperature rally in the secondary cooling zone II resulted in extension of middle cracks along columnar grain boundary.

Key words: cold-rolled strip steel, flake peeling, metallography, mathematical simulation, temperature rally

摘要： 结合SEM及EDS、金相分析、数值模拟方法研究了冷轧Q195L钢带冷轧过程中出现的鱼鳞状掉皮现象. 试样检测表明，非金属夹杂物和氧化铁共同作用导致这种缺陷，前者来源于钢水夹杂驱除不净或保护渣卷渣，后者根源在于连铸坯内部裂纹发生脱碳氧化，最终在冷轧中暴露于表面. 数值模拟表明，铸坯角部裂纹发生在结晶器内，钢水开始浇注的前6 s内铸坯角部降温速率为124.9℃/s，凝固收缩速率达0.07 mm/s. 凝固前裂纹指数呈增长趋势，在凝固末端达0.75，伴随疏松与缩孔形成中心裂纹；凝固坯壳内从近表面到距离边部41 mm处裂纹指数均出现过大于1的情况，中间裂纹形成于此，铸坯二冷II段内回温会导致中间裂纹沿弱化的柱状晶晶界扩展.

关键词: 冷轧钢带, 鱼鳞状掉皮, 金相, 数值模拟, 回温