Preparation method of high-magnetic-energy-product and high-coercivity sintered neodymium iron boron magnet

Abstract

The invention discloses a preparation method of a high-magnetic-energy-product and high-coercivity sintered neodymium iron boron magnet; the preparation method comprises the following steps of preparing materials according to the design ingredients, performing smelting on the ingredients, carrying out rapid hardening and casting, and obtaining a rapid hardened cast sheet; performing hydrogen crushing, a disproportionation reaction and airflow grinding and powder making on the neodymium-iron-boron cast sheet to obtain neodymium-iron-boron fine powder of 0.5-10[mu]m; adopting a thermal resistance evaporation deposition method to enable Dy/Tb particles and Pr/Nd particle element particles to be deposited on neodymium-iron-boron fine powder in a step-by-step manner or synchronously; and performing magnetic field orientation compression molding, cold isostatic pressing, vacuum sintering and heat treatment on the neodymium-iron-boron fine powder coated with Dy/Tb particles and Pr/Nd particles to finally obtain the high-magnetic-energy-product and high-coercivity sintered neodymium iron boron magnet. By coating the surface of the neodymium-iron-boron magnetic powder with the Pr/Nd and Dy/Tb thin layer, the volume ratio of the ferromagnetic phase is effectively increased, the rare-earth-rich phase distribution of the grain boundary is improved, the utilization rate of heavy rare earthelements is increased, and the magnetic energy product and the coercive force of the magnet are remarkably improved.

Description

technical field [0001] The invention relates to a preparation technology of a rare earth permanent magnet material, in particular to a preparation method of a sintered NdFeB magnet with high magnetic energy product and high coercive force. Background technique [0002] NdFeB permanent magnet materials are the most concerned rare earth application industry in my country's rare earth industry. With the development of science and technology and technological progress, the demand for high-performance NdFeB permanent magnet materials is becoming more and more extensive. In order to improve the remanence, coercive force and high temperature usability of NdFeB, the commonly used method is to add a small amount of heavy rare earth elements (such as Dy, Tb, etc.) or optimize the process to refine the magnet grains. [0003] At present, the methods to reduce the usage of heavy rare earth mainly include double alloy process and grain boundary diffusion heavy rare earth element process....

AI Technical Summary

Problems solved by technology

The grain boundary diffusion heavy rare earth element process is to form a heavy rare earth element covering layer on the surface of NdFeB by smearing, spraying, dipping and coating, and diffuse the heavy rare earth element into the interior of the magnet through high temperature grain boundary diffusion to improve the coercive force of the magnet. , to achieve the purpose of using a small amount of heavy rare earth; but this process is limited to the production of thinner magnets (thickness generally not exceeding 5mm), and the coercive force is not significantly improved when preparing (sintered) large magnets

[0004] At present, the method of refining magnet grains is mainly to add trace amounts of W, Mo, V, Ti, Ta, Zr, Nb, Co, Cr and other elements through the smelting process to inhibit the growth of magnet grains, but these elements in the magnet Inhomogeneous distribution such as segregation will occur in the medium, and the inhibitory effect on grain growth is limited. If the addition amount is too high, it will have a serious impact on the performance of the magnet.

[0005] The prior art uses physical vapor deposition, such as magnetron sputtering, electron beam evaporation, vacuum induction evaporation, and coating NdFeB powder to prepare (sintered) NdFeB magnets, but the disadvantage of magnetron sputtering method is the utilization of materials The efficiency is less than 50%; the electron beam evaporation equipment is expensive, and the requirements for vacuum and evaporation temperature are high; although the material utilization rate of vacuum induction evaporation is close to 99%, the disadvantage is that high vacuum is required, and the evaporation rate is low due to low temperature

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