Method for improving the coercivity of sintered neodymium iron boroncomposite magnets

Abstract

The invention discloses a method for improving the coercivity of sintered neodymium iron boron composite magnets, and belongs to the field of preparation of rare earth permanent magnetic materials. The methodoptimizes the composition of the Nd-Fe-B alloy and the Dy-Fe-B alloy, appropriately reduces the content of Nd in the Nd-Fe-B alloy, andincreases the content of Dy content in the Dy-Fe-B alloy.Since the content of the Nd elementin the Nd-Fe-B alloy is small, the diffusion degree of the Nd element decreases in the sintering process, so the Dy in the Dy-Fe-B alloy is less likely to be replaced by the Nd element, the anisotropy field of Dy-Fe-B phase high magnetic crystalis maintained, and the coercivity of magnet with small addition amount of Dy-Fe-B alloy powder can be improved significantly. The method can also reduce the amount of rare earth and Dy elements, and reduce the cost of raw materials while improving the magnetic performance.

Description

Technical field: [0001] The invention relates to a method for improving the coercivity of a sintered neodymium iron boron composite magnet, and belongs to the field of rare earth permanent magnet material preparation. Background technique: [0002] The rare earth permanent magnet Nd-Fe-B Nd-Fe-B has a high magnetic energy product and is widely used in the fields of transportation, energy, computer, communication, machinery, medical treatment, home appliances, and national defense technology. It has promoted the development of related industries and is a must for modern science and technology. The production and consumption of the missing key materials have become one of the important indicators for measuring the comprehensive national strength and the level of national economic development. At present, my country has become the world's largest production base of rare earth NdFeB permanent magnets and an important application market for NdFeB permanent magnets. [0003] Although th...

AI Technical Summary

Problems solved by technology

In the annealing process, the Dy alloy powder is added to the surface of the magnet by coating or other methods, and the Dy element will diffuse from the surface of the magnet to the interior; but the diffusion of the Dy element from the surface to the interior of the magnet is not uniform by this method, and the coercive force of the magnet increases. The extent is limited, and due to the limitation of diffusion depth, this method is only suitable for the production of small-sized magnets, not suitable for mass production of sintered NdFeB magnets

[0005] Chinese patent CN103219117A (application publication number) adopts the double alloy method to mix Nd-Fe-B and Dy-Fe-B alloys, because the Dy-Fe-B phase has an ultra-high magnetocrystalline anisotropy field, the coercivity of the magnet The force can be improved in theory; but in fact, the Nd element will diffuse into the Dy-Fe-B phase to replace Dy during high-temperature sintering, which will significantly reduce the magnetocrystalline anisotropy field of the Dy-Fe-B phase, and the coercivity of the magnet The degree of strength increase is not very significant

Chinese patent CN103794322A (Application Publication No.) mixes a field-dominant alloy with high magnetocrystalline anisotropy and a field-dominant alloy with low magnetocrystalline anisotropy to prepare a magnet, but this patent does not have a clear method to control the diffusion of elements between the two alloys. In order to improve the coercive force of the magnet, it is necessary to mix and add a certain amount of intergranular additive phase, which will increase the amount of heavy rare earth Dy element, reduce the remanence of the magnet, and is not conducive to reducing the production cost of the magnet