Method for preparing neodymium iron boron magnetic powder for sintered magnet

Abstract

The invention provides a method for preparing neodymium iron boron magnetic powder for a sintered magnet, and belongs to the field of magnetic materials. The method includes the followingprocesses that neodymium iron boron powder particles are prepared by adopting a gas atomization method, crystalline grains inside the powder particles grow to 1-3 microns by vacuum heat treatment, the intergranular fracture of the powder particles occurs after hydrogen decomposing, and single crystal particles with a particle size of 1 to 3 microns are finally obtained after dehydrogenation. The method has theadvantages that the neodymium-rich phase of the neodymium iron boron particles prepared by the gas atomization method is evenly distributed at the boundary ofNd2Fe14B main phase crystalline grains, and the neodymium-rich phase uniformly covers the surface of the Nd2Fe14B main phase crystalline grains in the form of a thin layer by means of hydrogen absorption intergranular fracture, so that the neodymium-rich phase in the finally prepared sinteredneodymium iron boronmagnetuniformly covers the periphery of the Nd2Fe14B main phase crystalline grains in the form of a thin layer, demagnetizationexchange coupling is greatly enhanced, neodymium iron boroncrystalline grains prepared by the method are fine and uniform, and the magnetic properties of the obtained neodymium iron boron magnet, particularly the coercive force, are high after orientation molding, sintering and tempering treatment areconducted on the neodymium iron boron magnetic powder prepared by the method.

Description

technical field [0001] The invention relates to a preparation method of NdFeB magnetic powder for sintered magnets, belonging to the field of magnetic materials. Background technique [0002] As the "third generation" permanent magnet material, sintered NdFeB magnet is currently the permanent magnet material with the highest magnetic energy product, and is widely used in many fields such as automobiles, electronics, wind power generation, medical equipment, and national defense industry. High-end applications require sintered NdFeB magnets to have both high remanence Br and high coercive force Hci. [0003] It is well known that since Dy2Fe14B and Tb2Fe14B have high magnetocrystalline anisotropy field HA, a common method to improve the coercive force and temperature stability of Nd-Fe-B permanent magnets is to add Dy or Tb to the base alloy and other heavy rare earth elements, but this will bring about a decline in remanence. Sintered NdFeB grain boundary diffusion of rare...

AI Technical Summary

Problems solved by technology

[0005] The traditional method of preparing NdFeB magnetic powder for sintered magnets is to prepare quick-setting cast flakes first, and then obtain magnetic powder through hydrogen breaking and jet milling. There is a relatively uniform neodymium-rich phase distribution in the direction, but there is no vertical direction. Therefore, after subsequent hydrogen breaking and jet milling, the surface of the magnetic powder particles cannot be completely covered by the neodymium-rich phase, thus limiting the neodymium-rich phase in the magnet after sintering and tempering. Uniform distribution of phase along the grains of the main phase