高强IF钢冷轧边部条带缺陷机理分析与控制

通过光学显微镜、扫描电镜、能谱分析以及酸洗模拟等方法，研究了高强IF钢HC250IF表面条带缺陷的产生原因、结构特点和控制措施。结果表明，氧化铁皮沿带钢宽度方向的不均匀分布以及拉矫破碎效果不充分导致了带钢边部比中部更容易发生过酸洗。在磷元素表面富集和晶界偏聚作用下，基体晶界处优先发生选择性侵蚀，侵蚀裂纹沿晶界从表面向内部扩展，形成具有厚度差的多孔区和粗糙区结构。冷轧过程中，缺陷部位变形撕裂，产生了大量表面微裂纹，增大了局部粗糙度差异，进而在带钢边部形成条带缺陷。以优化匹配热轧和酸洗工艺参数、改善热轧带钢表面状态为基础，通过控制酸洗进程、提高酸洗质量均匀性等措施，能够有效减少这类缺陷的发生。

Mechanism analysis and control of cold rolled edge strip defects of high strength IF steel

The causes of black strip defects on the surface of HC250IF and its structural features and control measures during different processes were analyzed by optical microscope, scanning electron microscope, energy spectrum analysis and pickling simulation test. The results show that the fields near strip edge have been over pickled owing to the uneven distribution of oxide scale and insufficient scale breaking effects of tension straightening mill in the width direction of strip. Under the existing of surface enrichment and grain boundary segregation for phosphorus, HCl solution erodes the matrix grain boundary preferentially after removing the surface oxide scale. The erosion process develops along the grain boundaries and forms erosion channels, which extend from the strip surface to the inside, resulting in structure characteristic of staggered distribution of porous area and rough area with certain thickness difference. After cold rolling, the metal in the porous area deforms intensively, and a large number of micro-cracks are formed along the rolling direction. The present of cracks strengthens the roughness difference of surface locally, and leads to the strip defect with color difference near the edge area of cold rolled strip. On the basis for optimizing matching of hot rolling and pickling process parameters and improving the surface state of hot rolling strip steel before pickling, the occurrence of such defects can be effectively reduced by controlling the pickling process and improving the quality uniformity of pickling.