US 11,657,960 B2
Sintered body, sintered permanent magnet and preparation methods thereof
Suo Bai, Baotou (CN); Shujie Wu, Baotou (CN); Yi Dong, Baotou (CN); Zhimin Wu, Baotou (CN); Shuai Zhang, Baotou (CN); Bo Yuan, Baotou (CN); Yi Yuan, Baotou (CN); Ya Chen, Baotou (CN); and Wenjie Yuan, Baotou (CN)
Assigned to Baotou Tianhe Magnetics Technology Co., Ltd.
Filed by Baotou Tianhe Magnetics Technology Co., Ltd., Baotou (CN)
Filed on Mar. 17, 2020, as Appl. No. 16/821,180.
Claims priority of application No. 201910759260.X (CN), filed on Aug. 16, 2019.
Prior Publication US 2021/0050150 A1, Feb. 18, 2021
Int. Cl. H01F 41/02 (2006.01); H01F 1/057 (2006.01)
CPC H01F 41/0293 (2013.01) [H01F 1/0577 (2013.01)] 1 Claim
 
1. A method for preparing the sintered permanent magnet, comprising the following steps:
(1) providing raw materials according to a composition of a sintered body;
wherein the sintered body comprises Nd2Fe14B crystal phase as a primary phase and a rare earth rich phase as a grain boundary phase and has the composition expressed by a composition formula (PrNd)15.2B5.7Ga0.2Cu0.2Al1.2Zr0.12Co1.8Febalance with an atomic ratio of Pr to Nd of 25. 44:74.56, wherein in the sintered body, an atomic percentage of oxygen α is 0.69%, an atomic percentage of nitrogen β is 0.30% and an atomic percentage of carbon γ is 0.41%;
(2) smelting the raw materials to obtain a master alloy sheet with a thickness of 0.278 mm;
(3) crushing the master alloy sheet into magnetic particles, grounding the magnetic particles into magnetic powder with a D50 of 3.8 μm and D90/D10 of 3.8;
(4) pressing the magnetic powder in an alignment magnetic field with a magnetic field intensity of 2.0 T into a compact with a density of 4 g/cm3, and then isostatically pressing the compact to obtain a green body;
(5) heat treating the green body under conditions of a vacuum degree of 4.0×10−3 Pa and a temperature of 1050° C. for 5 h, and then heat treating under conditions of a vacuum degree of 4.0×10−1 Pa and a temperature of 900° C. for 3 h, and finally heat treating under conditions of a vacuum degree of 4.0×10−1 Pa and a temperature of 500° C. for 5 h to obtain a product; cutting the product into a sintered body with a thickness of 4 mm;
(6) using a vacuum magnetron sputtering coating method to uniformly plate a Tb metal film onto a surface of the sintered body to obtain a coated sintered body; wherein a amount of Tb is 0.6 wt %, based on the weight of the sintered body;
(7) heat treating the coated sintered body under conditions of a vacuum degree of 1.5×10−2 Pa and a temperature of 925° C. for 7 h, and then heat treating under conditions of a vacuum degree of 1.5×10−2 Pa and a temperature of 495° C. for 5 h to obtain a sintered permanent magnet with a coercive force of 27.67 kOe.