How to distinguish bonded NdFeB from sintered NdFeB?

Neodymium magnet can be called neodymium iron boron magnet, which is the general name of powerful magnet. Its chemical formula is Nd2Fe14B, which is a kind of artificial permanent magnet. The shape of NdFeB magnets can be processed into different shapes according to specific requirements, such as round, square, perforated, magnetic tile, magnetic rod, convex or trapezoidal, etc.

How to distinguish bonded NdFeB from sintered NdFeB? In fact, both magnets belong to NdFeB. These two kinds of magnets are distinguished according to their different production processes. Bonded NdFeB magnets are actually molded by injection molding, while sintered NdFeB magnets are molded by high temperature heating after being evacuated.

Bonded NdFeB magnets, because they are molded by injection molding, contain adhesives, of which the density is generally only 80% of the theoretical value. The sintered NdFeB magnet is heated at high temperature through a complex process, so the magnetic attenuation of bonded NdFeB is about 30% relative to sintered NdFeB.

Sintered Nd-Fe-B magnets are anisotropic magnets produced by powder sintering. In general, only the blank can be produced by sintering, and then the magnet with various shapes can be produced by machining (such as wire cutting, slicing, grinding, etc.). Sintered Nd-Fe-B is a kind of hard and brittle material which is difficult to process. It has large loss, high cost, poor dimensional accuracy and poor corrosion resistance. The surface needs electroplating treatment. But the advantage is that the performance is high, and it has achieved more than 50m.

All in all, the magnetic properties of bonded NdFeB magnets are only about 5% of that of sintered NdFeB magnets. At present, the energy product of sintered NdFeB magnets can reach more than 50m, while that of bonded magnets is generally less than 10m, and the best one is only 12m. The performance of the magnetic powder used in the bonded magnet is generally 15m, which is only 10.5m at most. Therefore, sintered NdFeB is widely used than bonded NdFeB.