Classification of NdFeB

Due to different manufacturing methods and usage requirements, NdFeB permanent magnets can be divided into three categories:

(1) Bonded NdFeB: NdFeB bonded magnets are obtained by quenching microcrystalline powder. Each powder contains multiple Nd-Fe-B microcrystalline grains. The powders are then mixed and bonded with polymers or other binders and then pressed, extruded or rolled to form a plastic permanent magnet. Therefore, the usual NdFeB bonded magnets are non-dense isotropic magnets.

The magnetic properties of the usual NdFeB bonded magnets are much lower than those of the NdFeB sintered magnets, but the NdFeB bonded magnets have many irreplaceable advantages over the NdFeB sintered magnets: high processing accuracy, high yield rate, high precision, excellent magnetic properties, good corrosion resistance, and good temperature stability; in addition, the Nd-Fe-B bonded magnets are also easy to magnetize in any direction, and can be easily made into multi-pole or even multi-pole integral magnets.

(2) Sintered NdFeB: Sintered NdFeB permanent magnets are made by powder metallurgy. The main processes are: alloying (melting) → coarse crushing → fine crushing → grinding into 3-5.0µm fine powder → magnetic field orientation pressing → vacuum sintering and tempering → inspection → processing → finished product.

Sintered NdFeB permanent magnets have high coercivity and good mechanical properties. They can be cut into different shapes and drilled, but they are prone to rust, so different surface coatings must be applied according to different requirements. They are also very hard and brittle, highly resistant to demagnetization, and not suitable for high operating temperatures.

(3) Injection molded NdFeB (Zhusu NdFeB): They have extremely high precision and are easy to make into thin-walled rings or thin magnets with complex anisotropic shapes.