Sintered magnets are currently the largest commercial magnets. The process basically follows the powder metallurgy method for preparing samarium-cobalt magnets. The procedures are: melting and sintering - alloy ingot crushing - grinding - orientation forming under magnetic field - sintering - tempering and aging - magnetization detection and so on. First, Fe and B are smelted into Fe-B alloy, and then in a vacuum reaction furnace according to certain requirements, they are melted into a ternary alloy under Ar gas, and cast into a water-cooled copper mold. Then, milling is carried out, usually by methods such as ball milling and jet milling, as well as reduction diffusion milling, HDDR milling, and rapid quenching technology plus ball milling or jet milling. The permanent magnetic properties of sintered NdFeB magnets depend on the intrinsic magnetic properties and microstructure. Intrinsic magnetism is mainly determined by the chemical composition of the material and is structurally insensitive. Intrinsic magnetism determines the theoretical limit of the macroscopic magnetic properties of materials. In order to obtain high-performance NdFeB magnets, the saturation magnetic polarization of the magnetic phase in NdFeB magnets must first be increased, which can be achieved by the following measures:

(1) Ensure the purity of raw materials to reduce performance degradation caused by impurity elements;

(2) Increase the content of the magnetic phase in the NdFeB magnet, which can make the composition of the magnet after production close to the composition of the magnetic phase under the premise of ensuring the coercive force through a suitable composition ratio;

(3) To improve the orientation degree of the magnetic phase, mainly through the production process to ensure that the particles in the magnet are all single crystal particles or close to single crystal particles, and have a good particle size distribution. Under the premise of a certain purity of raw materials, the production process determines the performance of the magnet.