Manufacturing Nd—Fe—B magnets using hot pressing with reduced dysprosium or terbium

Patent metadata

Field	Value
Publication number	US-10186374-B2
Application number	US-201414193113-A
Country	US
Kind code	B2
Filing date	Feb 28, 2014
Priority date	Mar 15, 2013
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

A method of making a magnetic material for a permanent magnet using hot-pressing or die-upset methods, or both, by combining two powders and optimizing grain boundary diffusion of Dy or Tb. The method can include making magnetic material for a permanent magnet using hot pressing using a core powder containing Nd, Fe and B and a surface powder containing Dy or Tb in metallic alloy form, combining the materials, forming a solid material in a shaped mold under a magnetic field in vacuum, heating the solid material, hot pressing it to form a magnetic material in a die, heat treating it if necessary, and then cooling it.

First claim

What is claimed is:

1. A method of making a magnetic material for a permanent magnet using hot pressing comprising:
providing:
a first material in the form of a core powder containing Nd, Fe and B;
a second material in the form of a surface powder containing Dy, Tb, or both in metallic alloy form;

combining and mechanically milling the first material with the second material such that the first material is substantially coated with a layer of the second material, wherein the combined materials are milled with sufficient energy to result in mechanical alloying between the first material and the second material;
forming the coated first material in a shaped mold under a first magnetic field in a vacuum or under an inert atmosphere;
heating the formed coated first material from a first range of about 5° C. to about 35° C. to a second range of about 500° C. to about 850° C.;
hot pressing the formed coated first material under a second magnetic field in a die to achieve a deformation of not more than ten percent; and
cooling the pressed coated first material in the vacuum or under an inert atmosphere for from about 1 to about 5 hours.

2. The method of claim 1 wherein each of the first magnetic field and the second magnetic field is from about 1 to about 2.5 Tesla (T).

3. The method of claim 1 wherein heating the coated first material comprises heating the coated first material and maintaining a temperature within the second range of from about 500° C. to about 850° C. for from about 0.5 to about 2 hours.

4. The method of claim 1 wherein the vacuum comprises from about 10 to about 2 torr.

5. The method of claim 1 wherein the inert atmosphere comprises Ar or N2.

6. The method of claim 1 wherein the hot pressing comprises from about 30 to about 90 Megapascals (MPa).

7. The method of claim 1 wherein the hot pressing comprises from about 50 to about 80 Megapascals (MPa).

8. The method of claim 1 wherein the second material comprises from about 5 to about 80 wt % dysprosium.

9. The method of claim 1 wherein the second material powder is flake-shaped.

10. The method of claim 9 , further comprising removing by screening the flake-shaped powder that did not coat, prior to the forming the coated first material.

11. The method of claim 1 wherein the cooling comprises cooling to from about 5° C. to about 35° C.

12. The method of claim 1 further comprising an aging heat treatment after the hot pressing and prior to the cooling, the aging heat treatment comprising heating at from about 500° C. to about 1000° C. for from about 0.5 to about 8 hours in a vacuum at about 10 to about 2 torr or under an inert atmosphere containing Ar or N2.

13. The method of claim 1 wherein after combining the first material with the second material, the thickness of the layer of the second material is about 1 to about 100 micrometers.

14. The method of claim 1 wherein after combining the first material with the second material, the thickness of the layer of the second material is about 10 to about 50 micrometers.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Wang Yucong

Classifications

• H01F41/0266 Primary

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

• H01F7/02

  Permanent magnets {[PM]} · CPC title

• H01F1/0577

  sintered · CPC title