Transfer of rare earth to alloy and inclusion during slag-metal reaction

Rare earth metal transfer from slag to alloy and inclusion was investigated by slag-metal reaction method. Rare earth oxide (CeO2) employed in the refining slags was used a sample case. The results show that direct application of rare earth oxide in the slag is an alternative to traditional way which uses pure rare earth metal or rare-earth ferrous alloy to add rare earth in an alloy. Slag-metal reaction method proves to be an effective way to improve the rare earth transfer from slags to alloys with high content of Al. The content of Ce in the alloy increased with the increasing CeO2/Al2O3 mass ratio of the slag. As the Ce concentration of molten alloy increased from 0 to 105 ppm, the Al2O3 type inclusion was changed into cerium oxide, cerium sulfide and cerium oxy-sulfide inclusions. In addition, the morphology of inclusions was transformed from irregular to near spherical. Finally, the mechanism was discussed by thermodynamic analysis.