Permanent magnetic materials are also called hard magnetic materials. It is characterized by high anisotropy field, high coercivity, large hysteresis loop area, and large magnetization field required for magnetization to saturation. After removing the external magnetic field, it can still maintain strong magnetism for a long time. The material of permanent magnet has ferrite, rubber magnet, injection magnet, samarium cobalt, neodymium iron boron magnets, and alnico.
Ferrite is a non-metallic magnetic material. Ferrite compound can also be called magnetic ceramics. When we take apart the traditional radio, the speaker magnet inside is made of ferrite.
2. Rubber magnet
Rubber magnets are one of the ferrite magnet series. It is a soft, elastic and twistable magnet made of bonded ferrite magnetic powder and synthetic rubber compounded by extrusion molding, calendering molding, injection molding and other processes. Therefore, it can be processed into strips, rolls, sheets, blocks, rings and various complex shapes.
3. Injection magnet
Injection magnets are a kind of magnets that are firstly mixed and pelletized by polymer resin and magnetic powder through an extruder, and finally injection molded. Its toughness is good. It can not only be machined, but also can be directly injected into various complex parts.
4. Samarium cobalt
Samarium cobalt magnets are mainly composed of samarium and cobalt. Since these two materials are expensive, samarium cobalt magnets are also the most expensive among several types of magnets. The energy product of samarium cobalt magnets can currently reach 30MGOe, or even higher. In addition, samarium cobalt magnets have high coercivity and high temperature resistance. It can be used at high temperature of 350 ℃. Therefore, it cannot be replaced in many applications.
5. Neodymium iron boron
Neodymium magnet material is a magnet product that is widely used and developed rapidly. NdFeB has only been widely used since its invention for more than 20 years. The price is not very high because of its high magnetic properties and easy processing, so its application field is expanding rapidly.
6. Aluminum nickel cobalt
AlNiCo magnets have two processes: casting and sintering. The magnetic energy product of AlNiCo can reach 9MGOe. In addition, its biggest feature is high temperature resistance, and its working temperature can be as high as 550 degrees Celsius. However, AlNiCo is very easy to demagnetize under a reverse magnetic field. If you push the same poles of two AlNiCo (two N or two S) together, the magnetic field of one of the magnets will be returned or reversed. Therefore, it is not suitable for working in a reverse magnetic field (such as a motor).