5. The production process of the key processes introduced
⑤ sintering, tempering
The formed powder compact has lower relative density, larger porosity and lower bonding strength between particles. Such powder compacting bodies do not have the microstructure of high-performance magnetic magnets. In order to further increase the density, improve the powder's direct contact properties, increase the strength and make the magnet have the microstructure characteristics of high permanent magnet properties, it is necessary to heat the green compact to the temperature at which the powder collective phase melts, and to perform the heat treatment for a period of time Known as sintering. The sintering process makes a series of physical and chemical changes in the compact, which is one of the key technologies in the manufacture of sintered magnets and has an important effect on the performance of permanent magnets.
NdFeB permanent magnet alloy sintering and fast cooling (sintered state) lower magnetic properties, the need for tempering heat treatment, the processing temperature is generally slightly lower than the sintering temperature. Tempering can significantly improve the magnetic properties of NdFeB alloys, especially coercivity. Sintered permanent magnet magnetic properties of the process factors are very sensitive, the same composition of the alloy due to sintering and heat treatment process, its magnetic properties can be several times, several times, even hundreds of times change. Therefore, to master the sintering, heat treatment process on the magnetic properties of the law is very important. Sintering, tempering process equipment used is a vacuum sintering furnace, as shown below.
Vacuum sintering furnace
Machining is the process of changing a blank into a finished product. By machining can change the shape of the rough, the size of the surface quality. All kinds of permanent magnets due to the different materials, leading to their processing performance vary greatly. Among them, AlNiCo has the best machinability and therefore the highest machining accuracy possible. For samarium cobalt, neodymium iron boron and ferrite, these types of magnets larger brittle, so the processing performance is relatively worse, the machining can only rely on grinding or EDM or mechanical chip processing, but often lead to Magnet spalling, cracking or fracture, resulting in reduced yield of 10 to 20%. Grinding which mainly include coarse grinding (vigorously grinding, double-sided grinding) and fine grinding (shaped grinding, molding grinding). Subsequent processes are slicing (internal circle cutting, wire cutting, shingles), fine grinding, shelling holes and turning holes. The picture below shows the picture of machining equipment.
Article from NdFeB Industry Network