In order to develop a new recycling process for neodymium permanent magnet generated in town, equilibrium relations between B
2O
3 slag, RE
xO
y-B
2O
3 slag (RE = rare earths), and molten Fe-C alloy were experimentally investigated. When neodymium magnet was melted together with B
2O
3 and Fe-C alloy in graphite crucible, the sample was separated to 3 liquid phases of B
2O
3 slag, RE
xO
y-B
2O
3 slag and molten Fe-C alloy. The concentration of RE in RE
xO
y-B
2O
3 slag was increased with the decrease of the melting temperature, while that in B
2O
3 slag was increased with the decrease of the melting temperature. Cr, P, Ni, Co, and Cu were enriched in molten Fe-C alloy. Si and Al were enriched in B
2O
3 slag and RE
xO
y-B
2O
3 slag. Utilizing such phenomena, a novel recycling process consisting of melting treatment with B
2O
3 and hydrometallurgical treatment using oxalic acid was proposed. The recovery rate of RE with the proposed process was over 99 %.
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