Recycling of Rare Earth Magnet Waste by Removing Rare Earth Oxide with Molten Fluoride

Recycling of rare earth magnet scrap is required for improving resource conservation. Removal of rare earth oxide from off-specification magnet alloy scrap was investigated by remelting the scrap together with fluoride flux, LiF–50 mol% NdF3 and LiF–25 mol% NdF3–25 mol% DyF3, at 1503 K for the development of novel recycling process. As a result, separation of magnet alloy from fluoride flux after remelting was fine, and neither suspension of alloy in the flux nor suspension of flux in the alloy was observed. Oxygen concentration of alloy decreased from 5000 to 160 mass-ppm by charging flux of 1.5 times of equivalent amount for complete dissolution of oxide. Substitution of neodymium in the alloy and dysprosium in the flux was observed. The investigated process should be utilized for mildly contaminated waste such as a used (end-of-life) magnet because of simple process, energy saving and unlimited location.