The third process of magnet production process: air flow mill

NdFeB magnet jet mill powder technology in the magnetic material powder process has been popularized, promoted for many years, with the NdFeB sling and hydrogen crushing process mature, new energy-saving and more efficient jet mill gradually developed and utilized.

The jet mill used by NdFeB magnets is a circulating tubular jet mill, which is composed of a jet mill, a cyclone separator, a dust collector and an induced draft fan.

After the compressed air is filtered and dried, it is sprayed into the crushing chamber at high speed through the Laval nozzle. At the intersection of multiple high-pressure airflows, the materials are repeatedly collided, rubbed and sheared to be crushed. The crushed materials move to the classification area with the rising airflow under the action of the suction force of the fan, and the coarse and fine materials are separated under the action of the strong centrifugal force generated by the high-speed rotating classification turbine, the fine particles that meet the particle size requirements enter the cyclone separator and dust collector through the classification wheel, and the coarse particles drop to the crushing zone to continue crushing.

Combined with the characteristics of rare earth magnetic materials that are easy to oxidize and require fine particle size, the whole process uses nitrogen as the power gas flow, and the return gas is compressed by the compressor to form a closed loop with a pipeline.

At present, most NdFeB production enterprises adopt the technology of throwing belt piece and hydrogen crushing, and the throwing belt piece after hydrogen crushing becomes very loose, and the gas flow grinding is carried out directly after hydrogen crushing. Not only improve the discharge speed and can be more fine grinding NdFeB magnetic powder, can reach.2.8~3.5 microns, so that the magnet grain reaches less than 10 microns, the grain size can improve the coercive force of the magnet, while improving the corrosion resistance of the magnet. At present, many enterprises in the first line have been able to develop high-power air flow mill equipment with higher efficiency suitable for special grinding and hydrogen crushing. The powder output per hour may reach 150~200kg or even higher. This kind of air flow mill adopts high-power frequency conversion screw compressor and accurate automatic nitrogen supplement technology, which makes the equipment operation more reliable and stable and saves the production cost as much as possible.

Source: magnet manufacturers Youlian Magnetic Industrywww.youliancy.com