Sintered NdFeB magnet on the magnetic powder has strict requirements, powder size, dimensions directly affect the physical properties of sintered NdFeB magnets. In order to get a good orientation of the magnet, the magnetic powder has the following requirements:
First, the powder particle size (3-4 microns) and narrower size distribution, which called for 3-4 micron 80% -90% particles do not have less than 1 micron and greater than 7 microns, so as to ensure that all of the powder particles are single crystals;
Second, the powder particles were spherical or nearly spherical;
Third, the powder particles less crystal defects as possible;
Fourth, the powder particles and gas surface adsorption of impurities less as possible, especially the oxygen content should be less than 0.0015, the milling process should be in high purity inert gas or under vacuum conditions to prevent the NdFeB magnet powder and contact with oxygen or moist air.