热镀锌板隐形锌渣缺陷的典型特征及控制措施

采用扫描电子显微镜和能谱仪研究了热镀锌板中5种隐形锌渣缺陷的微观形貌和微区化学成分,并提出了相应的控制措施。结果表明:热镀锌板中的隐形锌渣缺陷主要包括富铝-锌类、富铁-铝类、富铁-锌类、残铁类、ZnO类等5种;富铝-锌类锌渣缺陷呈灰白相间的疏松状;富铁-铝类锌渣缺陷呈灰白色的针状或片状,分布较分散;富铁-锌类锌渣与锌层混杂,或以颗粒状嵌入锌层中;残铁类锌渣缺陷呈黑色或深灰色线状或片状,分布较集中;ZnO类锌渣缺陷主要由嵌入锌层的ZnO形成,呈连续片状,分布较分散;在采用高铝控制工艺、设备优化和调节、露点控制和定期清理锌灰等方法后,热镀锌板的整体平均返修率由40%降低至6.88%,其表面质量得到明显提高。

Typical Characteristics and Control Measures of Invisible Zinc Dross Defect in Hot Dip Galvanized Sheet

The micromorphology and micro-area chemical composition of five invisible zinc dross defects in hot dip galvanized sheet were studied by scanning electron microscope and energy spectrometer,and corresponding control measures were proposed.The results show that the invisible zinc dross defects in the hot dip galvanized sheet includedrich Al-Zn type,rich Fe-Al type,rich Fe-Zn type,residual Fe type and ZnO type.Rich Al-Zn zinc dross defect was loose shaped with color of grey and white;rich Fe-Al zinc dross defect was needle shaped or platy shaped with the color of off-white and distributed dispersively;rich Fe-Zn zinc dross defect was mixed with zinc coating or embedded in the zinc coating in the form of granules;residual Fe zinc dross defect was linear or flaky with color of black or dark grey,and the distribution was centralized;ZnO zinc dross defect was formed by ZnO embedded in zinc coating with continuous platy shape and distributed dispersively.After taking measures of high-aluminium control technology,equipment optimization and adjustment,dew point controlling and termly cleaning zinc ash,the overall average repair rate of the hot dip galvanized sheet was reduced from 40% to 6.88%,and the surface quality was improved obviously.