Neodymium magnets: NdFeB is the most commercialized magnet found at present. It is known as the king of magnet. It has very high magnetic properties, and its maximum magnetic energy product (BHmax) is more than 10 times that of Ferrite. So it is commonly known as: strong magnet, magnetic steel and so on. Its performance of own mechanical processing is also quite good. And its working temperature can be up to 200 degrees centigrade. Moreover, it has a hard texture, stable performance and good cost performance, so its application is extremely extensive. But because of its strong chemical activity, it must carry out surface treatment.
NdFeB permanent magnet is made of intermetallic compound Nd2Fe14B. Compared with the
permanent magnetic materials of Al-Ni-Co system and ferrite permanent magnetic material, NdFeB has a high magnetic energy product and coercive force, which can absorb 640 times the weight of its own weight. Nd-Fe-B permanent magnetic materials are widely used in modern industry and electronic technology because of its high energy density. It makes miniaturization, lightening and thinning of instruments, electroacoustic motors, magnetic separators and magnetization devices possible. The advantages of NdFeB are high cost performance, good mechanical characteristics and it is easy to machining. Its deficiency lies in the low temperature point of Curie, poor temperature characteristic and it is easy to be pulverized and corroded. It must be improved by adjusting its chemical composition and using the surface treatment method to meet the requirements of practical application.
The manufacturing process of NdFeB is made by powder metallurgy. The raw materials, such as neodymium, dysprosium, iron, cobalt, niobium, praseodymium, aluminum, copper and borate, contain a certain proportion. All of these raw materials should be smelted into alloy ingot by medium frequency induction melting furnace, and then they should be crushed into 3~5μm powder and pressed in the magnetic field. The formed green body is sintered densely in a vacuum sintering furnace and tempered and aged, thus we can obtain the permanent magnet blank with certain magnetic properties. After grinding, drilling and slicing, the finished product of Nd-Fe-B is obtained by surface treatment.
