The rare-earth permanent magnet alloys used for bonding magnets are submicron grain alloy powders, which allow one to easily break the alloy powders to the desired size distribution required for filling and formation, and then mix or mix with adhesives. According to the difference of physical or chemical properties of adhesives and forming methods, different mixing and mixing processes are needed.
Compression forming magnet
The proportion of magnetic powder is 96%~98% (mass fraction), the adhesive adopts thermosetting resin (usually epoxy) plus curing agent, dissolve the resin and curing agent with organic solvent and mix evenly, and then add the magnetic powder into the solution and stir fully, so that the magnetic powder is evenly dispersed and standing in the solution, so that the adhesive in the solution forms a coating film on the surface of the magnetic powder. Then the organic solvent is volatilized by heating or natural drying, and then the dried and bonded magnetic powder is broken to the required particle size, which can be shaped for the next process. In order to improve the filling, orientation and compacting properties of magnetic particles and improve the mechanical strength of magnets, it is sometimes necessary to conduct coupling treatment of magnetic particles before mixing, or add lubricant after mixing crushing.
Injection or extrusion forming magnet
The use of thermoplastic resin, to a large extent extend the use of plastic particle mixing technology, and the biggest difference with the plastic industry is its high solid filling ratio, general plastic modification of glass fiber, carbon fiber or other inorganic filler volume ratio is 40%~50%, and bonding rare earth permanent magnet in order to obtain high performance, this proportion may be as high as 80%, So the mechanical structure of the equipment to do a great adjustment, need to increase the length to diameter ratio, in order to make the grain fully plasticized, mixed and exercise, but also for serious mechanical wear to take the surface hardening treatment of mixing parts. Considering the oxidation of magnetic powder and resin deterioration caused by high temperature mixing and subsequent forming process, as well as the injection/extrusion processing of granule with high filling ratio, appropriate selection should be made in the combination of resin and various additives and mixing process.
