How to distinguish bonded NdFeB and sintered NdFeB magnet?
Neodymium magnet can be called NdFeB magnet. It is a general term for strong magnet. Its chemical formula is Nd2Fe14B. It is a kind of artificial permanent magnet. So far, it has the strongest magnetic force. NdFeB magnets have N35-N52 material grades, which can be processed into different shapes according to specific requirements, such as circular, square, perforated, magnetic tile, magnetic rod, convex or trapezoidal.
How to distinguish bonded NdFeB and sintered NdFeB?
In fact, both magnets belong to NdFeB. The two types of magnets are distinguished according to their different production processes. Bonded Nd-Fe-B magnets are actually formed by injection moulding, while sintered Nd-Fe-B magnets are formed by evacuation and heating at high temperature.
The bonded Nd-Fe-B magnet is formed by injection moulding, so it contains adhesives. The density of the adhesives is generally only 80% of the theoretical density. The sintered Nd-Fe-B magnets are heated at high temperatures through complex processes. Therefore, the magnetism of bonded Nd-Fe-B magnets decreases by about 30% compared with sintered Nd-Fe-B magnets.
Black epoxy is usually plated on the surface of bonded NdFeB
Sintered NdFeB magnets are anisotropic magnets produced by powder sintering. Generally, only the blank can be produced by sintering, and then machined (such as wire cutting, slicing, grinding, etc.) to become magnets of various shapes. Sintered NdFeB is a kind of hard and brittle material which is difficult to process. It has high loss, high cost, poor dimensional accuracy, poor corrosion resistance and needs electroplating treatment. But the advantage is that the performance is high, and it has achieved more than 50M at present.
Sintered Nd-Fe-B surfaces are usually galvanized and nickel-copper-nickel plated.
In conclusion, the magnetism of bonded Nd-Fe-B magnets is only about 5% of that of sintered magnets. At present, the energy product of sintered NdFeB magnets can reach more than 50M, while bonded magnets are generally below 10M, and the best is only 12M. The properties of bonded magnets are generally 15M, and only 10.5M after bonded magnets are made. Therefore, sintered Nd-Fe-B is generally more widely used than bonded Nd-Fe-B.