7075铝合金排材黑线缺陷原因分析

Cause Analysis on Black Line Defect of 7075 Aluminum Alloy Strip

文章结合生产实践,通过运用金相分析、扫描电镜能谱测试等分析测试方法,分析了7075铝合金排材出现氧化后表面黑线的形态、分布特点,对比了黑线区域和正常区域组织的晶粒以及第二相形状、分布、大小等情况,同时分析和讨论了偏析、挤压死区对氧化后表面黑线的影响。结果表明,粗大而连续分布的第二相组织是导致7075铝合金排材氧化出现黑线的主要原因,通过改善铸锭的铸造工艺、增大铸锭的车皮量以及优化模具设计,可以消除并最大限度的预防7075铝合金排材氧化后出现表面黑线。

Combined with the production practice, this paper analysis the morphology and distribution characteristics of the black line on the surface of 7075 aluminum alloy after oxidation by means of metallographic analysis, scanning electron microscope (SEM) and energy spectrum test, compared the microstructure of the black line area and the normal area and the shape, distribution and size of the second phase, etc. The effects of segregation and extrusion dead zone on the black line on the oxidized surface are also analyzed and discussed. The results show that the thick and continuous distribution of the second phase structure is the main reason for the black line in the oxidation of 7075 aluminum alloy, and the balck line on the surface of 7075 aluminum alloy strip can be eliminated and prevented to the maximum extent by improving the casting process of ingot, increasing the amount of the car skin and optimizing the mold design.