Neodymium-based rare earth permanent magnet and process for producing same
View Patent ↗Provided is a neodymium-based rare earth permanent magnet having a purity of 99.9 wt % or higher excluding gas components and component elements. The present invention can remarkably improve the magnetic properties in a neodymium-based rare earth permanent magnet by highly purifying the magnetic materials. Furthermore, the present invention aims to provide a high-performance neodymium-based rare earth permanent magnet with improved heat resistance and corrosion resistance, which are inherent drawbacks of magnetic materials.
1. A method of producing a neodymium-based rare earth permanent magnet, comprising the steps of:
refining a neodymium raw material and an elemental, uncompounded boron raw material by molten salt electrolysis to achieve a purity of 99.99 wt % or higher,
refining an iron raw material by aqueous electrolysis to achieve a purity of 99.99 wt % or higher,
subsequently vacuum melting a compound obtained by combining the refined neodymium, the refined iron, and the refined boron to obtain an ingot,
pulverizing the ingot to produce a powder,
molding the powder by pressing,
sintering and subjecting the obtained molding to heat treatment to produce a sintered compact, and
subjecting the sintered compact to surface treatment to produce a neodymium-based rare earth permanent magnet consisting of Nd, Fe, B, impurities, and gas components and having a purity, excluding gas components, Nd, Fe and B, of 99.99 wt % or higher such that the impurities are limited to 100 wtppm or less in total, and
wherein a content of Al as one of said impurities is 34 wtppm or less.
2. The method of producing a neodymium-based rare earth permanent magnet according to claim 1 , wherein the neodymium raw material is refined by molten salt electrolysis to achieve a purity of 99.999% or higher, and the iron raw material is refined by aqueous electrolysis to achieve a purity of 99.999% or higher.
3. The method of producing a neodymium-based rare earth permanent magnet according to claim 2 , wherein metal plating is performed after the surface treatment.
4. The method of producing a neodymium-based rare earth permanent magnet according to claim 1 , wherein metal plating is performed after the surface treatment.
5. The method of producing a neodymium-based rare earth permanent magnet according to claim 1 , wherein said content of Al is 21 wtppm or less.
6. The method of producing a neodymium-based rare earth permanent magnet according to claim 5 , wherein said content of Al is 2 to 21 wtppm.
7. The method of producing a neodymium-based rare earth permanent magnet according to claim 6 , wherein the purity of the neodymium-based rare earth permanent magnet, excluding gas components, Nd, Fe and B, is 99.999 wt % or higher such that the impurities are limited to 10 wtppm or less in total.
8. The method of producing a neodymium-based rare earth permanent magnet according to claim 1 , wherein the neodymium-based rare earth permanent magnet has a maximum energy product (BH)max, which is a product of residual magnetic flux density (B) and coercive force (H), of 47 or more.
9. The method of producing a neodymium-based rare earth permanent magnet according to claim 1 , wherein the neodymium-based rare earth permanent magnet has a heatproof temperature, below which demagnetization does not occur, of 210° C. or higher.
10. A method of producing a neodymium-based rare earth permanent magnet, comprising the steps of:
refining a neodymium raw material and an elemental, uncompounded boron raw material by molten salt electrolysis to achieve a purity of 99.99 wt % or higher;
refining an iron raw material by aqueous electrolysis to achieve a purity of 99.99 wt % or higher;
refining a dysprosium raw material by vacuum distillation to achieve a purity of 99.99 wt % or higher;
subsequently vacuum melting a compound obtained by combining the refined neodymium, the refined iron, the refined boron, and refined dysprosium to obtain an ingot;
pulverizing the ingot to produce a powder;
molding the powder by pressing;
sintering and subjecting the obtained molding to heat treatment to produce a sintered compact; and
subjecting the sintered compact to surface treatment to produce a neodymium-based rare earth permanent magnet consisting of Nd, Dy, Fe, B, impurities, and gas components and having a purity, excluding gas components, Nd, Dy, Fe and B, of 99.99 wt % or higher such that the impurities are limited to 100 wtppm or less in total, and
wherein a content of Al as one of said impurities is 34 wtppm or less.
11. The method of producing a neodymium-based rare earth permanent magnet according to claim 10 , wherein the neodymium raw material is refined by molten salt electrolysis to achieve a purity of 99.999% or higher, and the iron raw material is refined by aqueous electrolysis to achieve a purity of 99.999% or higher.
12. The method of producing a neodymium-based rare earth permanent magnet according to claim 10 , further comprising the step of metal plating the sintered compact after the surface treatment.
13. The method of producing a neodymium-based rare earth permanent magnet according to claim 10 , wherein the purity of the neodymium-based rare earth permanent magnet, excluding gas components, Nd, Dy, Fe and B, is 99.999 wt % or higher such that the impurities are limited to 10 wtppm or less in total.
14. The method of producing a neodymium-based rare earth permanent magnet according to claim 10 , wherein the neodymium-based rare earth permanent magnet has a maximum energy product (BH)max, which is a product of residual magnetic flux density (B) and coercive force (H), of 47 or more.
15. The method of producing a neodymium-based rare earth permanent magnet according to claim 10 , wherein the neodymium-based rare earth permanent magnet has a heatproof temperature, below which demagnetization does not occur, of 210° C. or higher.
16. The method of producing a neodymium-based rare earth permanent magnet according to claim 10 , wherein said content of Al is 1 to 34 wtppm.