A high resistivity sintered r-fe-b permanent magnet and preparation method thereof

Abstract

The invention belongs to the technical field of preparation of rare earth permanent magnet materials, in particular to a high resistivity sintered R-Fe-B permanent magnet and a preparation method thereof. Carbon nitride is a corrosion-resistant two-dimensional inert material that can be efficiently prepared by low-temperature heat treatment of its precursors. In the present invention, the magnetic powder wrapped by the precursor is pressed, and in the heat treatment process, the low temperature zone of the sintering process is strictly controlled and the heating rate of the multi-stage variable temperature heating process is controlled. The thin layer can completely encapsulate the entire magnetic powder grain and densify the sintered magnet. The existence of a carbon nitride layer with a controllable thickness can improve the resistivity of the magnet, while suppressing the growth of the main phase grains and the exchange coupling between grains; reducing the eddy current loss and minimizing the loss of magnetic properties. The process of the invention is simple, the raw materials are cheap and easy to obtain, and the invention is green and environmentally friendly.

Description

technical field [0001] The invention belongs to the technical field of preparation of rare earth permanent magnet materials, in particular to a sintered R-Fe-B permanent magnet with high resistivity and a preparation method thereof. Background technique [0002] Sintered R-Fe-B permanent magnets are widely used in emerging green industries such as wind power generation, artificial intelligence, and new energy vehicles due to their excellent magnetic properties. However, in the working state of high speed or multi-maximum torque, due to its high alternating frequency, the eddy current loss of the magnet increases, which causes the temperature rise of the magnet, resulting in a significant decrease in the performance of the magnet, thus limiting the application range of the magnet. Improving the eddy current loss of permanent magnets by increasing the product resistivity is the most direct and effective method. Therefore, how to increase the resistance of the magnet and reduc...

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Problems solved by technology

For example, in Chinese patents CN106653271B and CN104851544A, inorganic non-metallic powders or sheets such as silicon with high resistivity are doped in the material to increase the resistivity of the material, and a magnet with high Curie temperature and good temperature stability is obtained, but the preparation During the process, the complete coating of the magnetic powder by the insulating material cannot be achieved, resulting in poor uniformity of the magnet performance

In Chinese patent CN101740193A, high-resistance magnets are prepared by mixing NdFeB magnetic powder with titanate coupling agent and bisphenol A epoxy resin. This method not only has the defect of incomplete coating, but also has organic doping at high temperature. The risk of material falling off, high process requirements and other deficiencies

However, in this patent, the process required to realize the contact of each NdFeB powder with ammonia gas and uniform reaction to form a nitride layer is complicated to operate and difficult to industrialize, and it is difficult to ensure that all NdFeB powders are wrapped.

[0007] In addition, none of the coatings added in the above studies can achieve a controllable preparation of the thickness of the coating layer. Different thicknesses of the coating layer will cause a decrease in the density of the magnet, resulting in different degrees of reduction in magnetic properties.

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