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对焊接钢管热浸镀锌表面凸起缺陷成因及相应改进措施进行了研究。结果表明,镀层表面凸起缺陷与镀层基体呈解离态,有明显的界限,凸起处镀层组织疏松,表面与内部存在缩孔,与基体连接处亦有许多气孔状缺陷。凸起处与正常镀层表面处的化学成分都为Fe和Zn。由于助镀剂酸性提高和锌液成分不均在锌液中形成Fe-Zn合金渣,粘附在钢管镀层表面形成凸起缺陷。通过严格控制助镀剂的浓度、p H值和保证锌液成分均匀可避免缺陷的产生。
The cause of forming defect of hot-dip galvanized surface of welded steel pipe and corresponding improvement measures were studied. The results show that there is a clear boundary between the protuberances on the surface of the coating and the substrate. There are obvious demarcations between the protuberances on the surface and the substrate. The chemical composition at the convex and normal coating surfaces is both Fe and Zn. Due to the improvement of acidity of the flux and the uneven composition of the zinc liquid, Fe-Zn alloy slag is formed in the zinc liquid and sticks to the surface of the steel pipe coating to form bulge defects. By strictly controlling the concentration of the flux, the p H value and the uniformity of the zinc solution can prevent the occurrence of defects.