Study on the behavior of impurities in zone melting of aluminum

In this study, the migration and distribution behaviors of Cu, Si, Fe, and Ti impurities in the process of preparing high-purity Al by zone melting under an argon atmosphere were investigated. The width of the molten zone during the experiment was determined as 40 mm, based on simulation calculation results. The influences of the travel speed of the molten area and number of zone melting times on the migration and distribution of the Cu, Si, Fe, and Ti impurities in the Al were experimentally demonstrated. The contents of the impurities Cu, Si, Fe, and Ti in the middle of the sample (i.e., 140 mm from the head end) were 0.9057, 0.8116, 0.1202, and 0.4237 ppm, respectively, when the travel speed of the molten area was 1.0 mm/min and with 15 times of zone melting. The contents of all the above impurities were reduced to the requirements of Chinese national standard and 99.9995% (i.e., 5N5) high-purity Al was obtained from 4 N Al by the zone melting method under the above optimal experimental conditions. The experimental results show that the effect of the number of zone melting times on the removal of the Cu, Si, and Fe impurities is more evident, and that these impurities are easier to separate than Ti. Therefore, high-purity Al with lower Cu, Si, and Fe contents can be obtained by optimizing the travel speed of the molten area and number of zone melting times.