热镀锌底渣在合金化过程中的转变研究

Study on the transformation of bottom dross during the galvannealing process

研究了锌锅中的底渣以及合金化镀层钢板、纯锌镀层钢板、不同程度模拟合金化镀层钢板表面的底渣缺陷的微观特征,揭示了底渣在合金化过程中的转变行为。研究发现,锌锅中的底渣尺寸较大,且聚集成块,当被带到带钢表面并经过镀锌平整后,镀层表面形成小黑点缺陷。镀层经过合金化之后,底渣与周围纯锌相发生迅速的锌铁扩散,形成爆发组织,导致缺陷位置的镀层进一步增厚、凸起,平整后在镀层表面表现为小亮点缺陷,在基板表面留下较深的凹坑。GI镀层中的底渣缺陷与纯锌相的形貌及Fe、Al含量明显不同,但GA镀层中的底渣与周围锌铁合金相融为一体,可通过Al含量的差异进行区分。

The microscopic features of the bottom dross in the zinc pot and typical bottom dross defects on the galvannealed,galvanized and laboratory galvannealed coating with different soaking time were studied and the transformation behavior of the bottom dross during the galvannealing process was revealed.It is found that the size of the bottom dross in the zinc pot is large enough to cause small black spot defects on the galvanized coating when it is brought onto the strip and being temper rolled.During the galvannealing process,the rapid diffusion between the bottom dross and the surrounding pure zinc phase forms outburst structure,resulting in further thickening of the coating at the defect location.After being temper rolled,it appears as shiny spot on the galvannealed coating and causes a deeper dent on the substrate.The bottom dross in the galvanized coating shows different morphology and Fe,Al content from the pure zinc phase.However,the bottom dross in the galvannealed coating is integrated with the surrounding zinc-iron alloy and can be identified by the difference in Al content.