热镀锌表面亮点缺陷分析及控制

Analysis and control for bright spot defect on surface of hot dip galvanized sheet

应用扫描电镜及能谱仪对镀锌板表面亮点缺陷微观形貌及化学成分进行分析。结果发现共有4类亮点缺陷,并且产生原因各不相同。第I类是钢基和铁-锌合金层之间Fe2Al5抑制层完整性、均质性受到破坏,影响带钢局部锌液浸润性;第II类是在镀后塔顶辊、光整机工作辊或个别转向辊上粘附有异物,对带钢表面刮蹭;第III类是因为带钢表面粘附有渣粒、氧化膜、金属间化合物等物质;第IV类是因为未清洁生产而导致环境污染物粘附在带钢表面。针对四类亮点缺陷产生的原因,提出了提高锌液浸润性、定时清理辊面、控制锌渣数量和清洁生产等具体控制措施。

With scanning electron microscope and energy spectrometer,the micro morphology and chemical composition of bright spot defect on hot dip galvanize sheet was analyzed. It is found that there are four types of bright spot defects and the root causes are various. For type I,the cause of the spot is that the integrity and homogeneity of Fe_2Al_5 inhibition layer between steel-base and iron-zinc alloy layer is damaged,which deteriorated locally strip wettability to liquid zinc; for type II,it comes from foreign matter adhering on the top roller,working roller of skin pass mill or some deflector rollers,which scratched the galvanized coatings; for type III,the zinc particles,oxide or intermetallic compound sticking on the sheet surface is the main reason of the formation of the spot; for type IV,the cause is due to the environmental pollutants adhered to the surface of sheet. For each type of bright spot defects,controlling measures such as improving strip wettability to liquid zinc,cleaning roller surface regularly,controlling quantity of zinc particles and cleaner production are presented.