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.
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