How much do you know about NdFeB magnets?

Permanent magnet materials mainly include AlNiCo (AlNiCo) system metal permanent magnet, the first generation SmCo5 permanent magnet (called 1:5 samarium cobalt alloy), the second generation Sm2Co17 (called 2:17 samarium cobalt alloy) permanent magnet, the third generation rare earth permanent magnet alloy NdFeB (called NdFeB alloy). With the development of science and technology, the performance of NdFeB permanent magnet material has been improved and the application field has been expanded. The sintered NdFeB with high magnetic energy product (50 MGA ≈ 400kJ/m3), high coercivity (28EH, 32EH) and high operating temperature (240C) has been produced industrially. The main raw materials of NdFeB permanent magnets are rare earth metal Nd (Nd) 32%, metal element Fe (Fe) 64% and non-metal element B (B) 1% (a small amount of dysprosium (Dy), terbium (Tb), cobalt (Co), niobium (Nb), gallium (Ga), aluminum (Al), copper (Cu) and other elements). NdFeB ternary system permanent magnet material is based on Nd2Fe14B compound, and its composition should be similar to the compound Nd2Fe14B molecular formula. However, the magnetic properties of the magnets are very low or even non-magnetic when the ratio of Nd2Fe14B is completely distributed. Only when the content of neodymium and boron in the actual magnet is more than the content of neodymium and boron in Nd2Fe14B compound, it can get better permanent magnetic property.

Sintering: Ingredients (formula) → smelting → powder making → pressing (forming orientation) → sintering and aging → magnetic property inspection → mechanical processing → surface coating treatment (electroplating) → finished product inspection
Bonding: raw material → particle size adjustment → mixing with binder → molding (compression, extrusion, injection) → firing treatment (compression) → reprocessing → inspection of finished product

There are three main parameters: remanence Br (Residual Induction), unit Gauss, after the magnetic field is removed from the saturation state, the remaining magnetic flux density, representing the external magnetic field strength of the magnet; coercive force Hc (Coercive Force), unit Oersteds, is to put the magnet in a reverse applied magnetic field, when the applied magnetic field increases to a certain strength, the magnetic flux density of the magnet will be higher. When the applied magnetic field increases to a certain strength, the magnetism of the magnet will disappear, the ability to resist the applied magnetic field is called Coercive Force, which represents the measure of demagnetization resistance; Magnetic energy product BHmax, unit Gauss-Oersteds, is the magnetic field energy generated per unit volume of material, which is a physical quantity of how much energy the magnet can store.

At present, the main application areas are: permanent magnet motor, generator, MRI, magnetic separator, audio speaker, magnetic levitation system, magnetic transmission, magnetic lifting, instrumentation, liquid magnetization, magnetic therapy equipment, etc. It has become an indispensable material for automobile manufacturing, general machinery, petrochemical industry, electronic information industry and cutting-edge technology.

NdFeB is the strongest permanent magnet material in the world, its magnetic energy product is ten times higher than the widely used ferrite, and about twice as high as the first and second generation of rare earth magnets (SmCo permanent magnet), which is known as the “king of permanent magnet”. By replacing other permanent magnet materials, the volume and weight of the device can be reduced exponentially. Due to the abundant resources of neodymium, compared with samarium-cobalt permanent magnets, the expensive cobalt is replaced by iron, which makes the product more cost effective.