R-T-B sintered magnet and preparation method thereof

Patent metadata

Field	Value
Publication number	US-11705257-B2
Application number	US-202117244880-A
Country	US
Kind code	B2
Filing date	Apr 29, 2021
Priority date	Apr 30, 2020
Publication date	Jul 18, 2023
Grant date	Jul 18, 2023

Abstract

The present invention relates to an R-T-B sintered magnet and a preparation method thereof. The sintered magnet includes a grain boundary region T1, a shell layer region T2 and an R2Fe14B grain region T3; at 10 μm to 60 μm from a surface of the sintered magnet toward a center thereof, an area ratio of the shell layer region T2 to the R2Fe14B grain region T3 is 0.1 to 0.3, and a thickness of the shell layer region T2 is 0.5 μm to 1.2 μm; and an average coating percent of the shell layer region T2 on the R2Fe14B grain region T3 is 80% or more. In the present invention, by optimizing a preparation process and a microstructure of a traditional rare earth permanent magnet, diffusion efficiency of heavy rare earth in the magnet is improved, such that coercivity of the magnet is greatly improved, and manufacturing cost is reduced.

First claim

What is claimed is:

1. A R-T-B sintered magnet, comprising a grain boundary region T 1 , a shell layer region T 2 and an R 2 Fe 14 B grain region T 3 , and the shell layer region T 2 is located at the junction of the grain boundary area T 1 and the R 2 Fe 14 B grain area T 3 , which covers the R 2 Fe 14 B grain area T 3 and has a predetermined thickness; wherein
R contains light rare earth LRE and heavy rare earth HRE, and a content proportion of the HRE is 0.05 wt. % to 1.5 wt. %; and
T contains Al and M, and a proportion of Al is 0.22 wt. % to 0.35 wt. %; and M is at least one of Ga, Cu and Zn, and a mass ratio of M/Al is 2 to 3; and
at 10 μm to 60 μm from a surface of the sintered magnet toward a center thereof, an area ratio of the shell layer region T 2 to the R 2 Fe 14 B grain region T 3 is 0.1 to 0.3, and a thickness of the shell layer region T 2 is 0.5 μm to 1.2 μm; and an average coating percent of the shell layer region T 2 on the R 2 Fe 14 B grain region T 3 is 80% or more; and
a mass ratio of (HRE+M+Al)/(LRE+T) in the shell layer region T 2 is 0.02 to 0.4;
a mass ratio of HRE/(LRE+T) in the shell layer region T 2 is greater than a mass ratio of HRE/(LRE+T) in the R 2 Fe 14 B grain region T 3 ; and
a mass ratio of Al/(LRE+T) in the shell layer region T 2 is greater than a mass ratio of Al/(LRE+T) in the R 2 Fe 14 B grain region T 3 .

2. The R-T-B sintered magnet according to claim 1 , wherein
the HRE contains Tb and Dy, a content proportion of R is 29 wt. % to 33 wt. %; and
a content proportion of B is 0.82 wt. % to 0.95 wt. %.

3. A preparation method of the sintered magnet according to claim 2 , comprising:
preparing a sintered blank;
depositing an alloy film layer on a surface of the sintered blank; and
acquiring the sintered magnet by performing heat treatment on the sintered blank deposited with the alloy film layer.

4. The R-T-B sintered magnet according to claim 1 , wherein
in the sintered magnet, R is at least one rare earth element, and T is one or more non-rare earth metals containing Fe and/or FeCo.

5. A preparation method of the sintered magnet according to claim 4 , comprising:
preparing a sintered blank;
depositing an alloy film layer on a surface of the sintered blank; and
acquiring the sintered magnet by performing heat treatment on the sintered blank deposited with the alloy film layer.

6. A preparation method of the sintered magnet according to claim 1 , comprising:
preparing a sintered blank;
depositing an alloy film layer on a surface of the sintered blank; and
acquiring the sintered magnet by performing heat treatment on the sintered blank deposited with the alloy film layer.

7. The preparation method according to claim 6 , wherein said preparing the sintered blank comprises:
acquiring an alloy by smelting a raw material, and preparing a flake with a thickness of 0.25 μm to 0.35 μm for a sintered body by using the alloy, the raw materials comprising 24.6 wt % of Nd, 5.8 wt % of Pr, 1.1 wt % of Co, 0.15 wt % of Al, 0.10 wt % of Cu, 0.15 wt % of Zr, 0.83 wt % of B and the balance of Fe;
crushing the flake into alloy powder;
acquiring a green body by shaping the alloy powder in a magnetic field; and
acquiring the sintered blank by sintering and tempering the green body.

8. The preparation method according to claim 7 , wherein said crushing the flake into the alloy powder comprises: performing hydrogen absorption on the flake at room temperature, then performing dehydrogenation at 620° C. for 1.5 hours, and finally acquiring fine powder of 3.5 μm to 4.5 μm by grinding the resulted flake in a nitrogen atmosphere.

9. The preparation method according to claim 6 , wherein said depositing the alloy film layer on the surface of the sintered blank comprises:
removing an oxide scale on the surface of the sintered blank, and drying the sintered blank; and
placing a diffusion source comprising components of heavy rare earth HRE, Al and M on the surface of the sintered blank, wherein M is at least one of Ga, Cu and Zn, and a mass ratio of M/Al is 2 to 3.

10. The preparation method according to claim 9 , wherein the diffusion source in use is in a state of: a molten alloy liquid of a diffusion source alloy, a quenched strip of the diffusion source alloy, a sheet of the diffusion source alloy, powder of the diffusion source alloy, diffusion source alloy slurry acquired by mixing the alloy powder of the diffusion source alloy with a solvent, or a film layer acquired by physical vapor deposition.

11. The preparation method according to claim 6 , wherein said acquiring the sintered magnet by performing the heat treatment on the sintered blank deposited with the alloy film layer comprises: performing diffusion treatment at 650° C. to 1000° C. for 1 h to 24 h, and tempering at 400° C. to 700° C. for 0.5 h to 10 h, wherein the heat treatment is performed under protection of vacuum or an inert gas.

Assignees

• Grirem Advanced Mat Co Ltd
• Rare Earth Functional Mat Xiong An Innovation Center Co Ltd
• Grirem Rongcheng Co Ltd
• Rare Earth Functional Mat Xiongan Innovation Center Co Ltd
• Griceon Rongcheng Co Ltd

Inventors

• Luo Yang
• Yu Dunbo
• Zhu Wei
• Bai Xinyuan
• Lin Xiao
• Zhu Shengjie
• Wang Zilong
• Peng Haijun

Classifications

• H01F1/22 Primary

  pressed, sintered, or bound together · CPC title

• C22C38/005 Primary

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

• C22C38/06

  containing aluminium · CPC title

• C22C38/10

  containing cobalt · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title