US 12,293,868 B2
NdFeB permanent magnet with high coercivity and high resistivity and method for preparing the same
Changjiang Yan, Zhejiang (CN); Nijian Qian, Zhejiang (CN); and Zhiguo Wu, Zhejiang (CN)
Filed by NINGBO KETIAN MAGNET CO., LTD., Zhejiang (CN)
Filed on Dec. 7, 2021, as Appl. No. 17/544,745.
Claims priority of application No. 202110385184.8 (CN), filed on Apr. 9, 2021.
Prior Publication US 2022/0328244 A1, Oct. 13, 2022
Int. Cl. H01F 41/26 (2006.01); H01F 1/057 (2006.01); H01F 41/02 (2006.01)
CPC H01F 41/026 (2013.01) [H01F 1/0576 (2013.01); H01F 41/0293 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A method for preparing an NdFeB permanent magnet, wherein coercivity of the NdFeB permanent magnet is not lower than 27.4 kOe, and resistivity of the NdFeB permanent magnet is not lower than 2523 μΩ·cm; the method comprising the steps of:
Step S1, preparing a flaky NdFeB magnet blank;
Step S2, treating the NdFeB magnet blank by using surface cleaning process, so as to obtain a clean NdFeB magnet blank;
Step S3, coating a layer of slurry on a surface of the clean NdFeB magnet blank to obtain a coated NdFeB magnet blank, wherein the slurry comprises heavy rare earth powder, compound powder and organic solvent, the compound powder comprises carbide powder and/or oxide powder;
Step S4, stacking a plurality of sheets of coated NdFeB magnet blanks on top of each other to obtain a stack of NdFeB magnet blanks; and
Step S5, performing three-stage thermal diffusion treatment on the stack of NdFeB magnet blanks to obtain the NdFeB permanent magnet with the coercivity and the resistivity, wherein the three-stage thermal diffusion treatment comprises: during the first stage of heat treatment, the blank is exposed to a high temperature of 1000° C.-1100° C. for 4 hours to 6 hours; during the second stage of heat treatment, the blank is exposed to a high temperature of 850° C.-950° C. for 4 hours to 10 hours; and during the third stage of heat treatment, the blank is exposed to a high temperature of 450° C.-550° C. for 2 hours to 6 hours.