Neodymium-based rare earth permanent magnet and process for producing same

Patent metadata

Field	Value
Publication number	US-9972428-B2
Application number	US-201214380416-A
Country	US
Kind code	B2
Filing date	Aug 31, 2012
Priority date	Feb 23, 2012
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

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.

First claim

The invention claimed is:

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.

Assignees

• Shindo Yuichiro
• Jx Nippon Mining & Metals Corp

Inventors

• Shindo Yuichiro

Classifications

• H01F41/0266 Primary

  Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11) · CPC title

• H01F1/0577

  sintered · CPC title

• H01F1/0536 Primary

  sintered · CPC title

• C22C33/04

  by melting · CPC title

• C22C38/005

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title