Permanent magnets fall into two categories:
The most important of these are alloy magnets including neodymium magnets (Nd2Fe14B), cobalt magnets (SmCo) and aluminum-nickel-cobalt magnets.
Another major category is ferrite permanent magnets.
1. Ndfeb magnet: It is the highest commercial performance magnet found at present, known as the magnetic king. It has extremely high magnetic energy, its maximum magnetic energy product (BHmax) is more than 10 times higher than ferrite. Its mechanical ability is also quite good. The maximum operating temperature can reach 200℃. And hard texture, stable performance, high cost performance, so widely used. However, because of its strong chemical activity, it must be surface treated. (e.g. zinc, nickel, electrophoresis, passivation, etc.)
2. Ferrite magnet: The main raw materials are ferrite, ferrite, ferrite. Made of ceramic technology, hard and fragile. Ferrite magnet has good temperature resistance, low price and moderate performance, and has become the most widely used permanent magnet.
3. Al-nickel-cobalt magnet: It is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. Castings can be machined into different sizes and shapes, with good machining performance. The casting Al-Ni cobalt magnet has the lowest reversible temperature coefficient, and the operating temperature can reach more than 600℃. Aluminum-cobalt magnets are widely used in various fields such as instrumentation.
4. Samarium cobalt (SmCo) can be divided into SmCo5 and Sm2Co17 according to different components. Its development is limited to some extent by the high price of raw materials. As a rare earth permanent magnet, cobalt (SmCo) not only has a high magnetic energy product (14-28 Mgoe), but also has good coercivity and temperature characteristics. Compared with neodymium magnet, it has better performance in high temperature environment.
