晶粒特征在汽车板表面缺陷分析中的应用

以普冷及热镀锌汽车板表面的擦伤、麻点、涂装针孔、冲压桔皮、冲压条纹及斑迹等多种缺陷为研究对象，使用扫描电镜和光学显微镜重点观察了缺陷位置的晶粒，发现了细晶粒、粗晶粒、未再结晶晶粒和晶粒变形4种晶粒特征。研究发现，可以利用缺陷位置的晶粒特征对缺陷发生的位置做出进一步的判断，以缩小工艺排查的范围。针对连续退火本机组产生的麻点或擦伤缺陷，可根据局部晶粒变形推测缺陷发生在其冷却段；根据局部粗晶粒可推测缺陷发生在加热段后期至均热段结束之间；根据局部细晶粒推测缺陷发生在加热段、清洗段或源自轧硬板来料缺陷。

Application of grain characteristic in analysis of surface defects on automotive steel sheets

A variety of surface defects on continuous annealed or galvanized automotive steel sheets such as scratches, dents, coating pinhole, stamping orange peel, stamping streak and streaky mark were studied. The crystalline grains located in defects were observed by scanning electron microscope(SEM) and optical microscope(OM), and four types of grain characteristics were found including fine grains, coarse grains, non-recrystallized grains, and deformed grains. The results indicated that the grain characteristics at the defect position could be utilized to further determine the defect origination and reduce the scope of inspection. For the scratches or dents originated from the continuous annealing line, the local deformed grains indicated that the defect may originate in the cooling section. The local coarse grains suggested a strain-induced secondary recrystallization occurred in the ends of heating section or in the beginning of soaking section. The local fine grains meant that the defect probably occurred in the heating section, cleaning section or it might be brought by the as received cold rolled steel sheet.