Effects of Electroslag Refining on Removal of Iron Impurity and Alumina Inclusions from Aluminum

Abstract

Effects of electroslag refining on removal of iron impurity and alumina inclusions from aluminum were studied on a laboratory-scale apparatus. The electroslag refining experiments were carried out using KCl-NaCl-Na3AlF6 slag. In the experiments, the electrodes of 40 mm diameter and 80 cm length were fed into the molten slag to obtain ingots of 70 mm diameter and 20–25 cm length under a voltage of 10–12 V, a current of 600–700 A and a descending speed of 26–106 mm•min−1. In the experiment, the 10wt%Na2B4O7 was added to the slag for the removal of iron. The purification efficiency of electroslag refining for aluminum increases with the decrement of the melt rate. The iron content can decrease from 0.42% to 0.20wt%(more than a 50% reduction in iron content) after electroslag refining under the melt rate of 180 g•min−1, and the removal efficiency of electroslag refining for alumina inclusions can exceed 97% under the melt rate of 108 g•min−1.