Electrode reactions in dc electroslag remelting of steel rod

The non-metallic inclusion content increased significantly when a steel rod of Fe-Ni was remelted by dc electroslag remelting. The silicon content increased slightly. The manganese and sulphur contents did not change. The total aluminium content in the ingot was max. 0.7%, while that in the electrode was only 10 ppm. The aluminium cations Al3+ in the slag are reduced to metallic aluminium at the slag/electrode interface, while O-2(-) anions are oxidised to dissolved (O) under bar in the metal pool. This Al and (O) under bar subsequently recombine to form alumina inclusions in the metal pool. The inclusion content was dependent on the alumina content in the slag. When a rod of plain carbon steel was remelted, however, the increase in nonmetallic inclusion content was as little as one-tenth of that for the remelted Fe-Ni rod. The non-metallic inclusion content was independent of the polarity of the electrode.