The second process of magnet production process: hydrogen crushing

After the rare earth raw material of the magnet is melted and cooled in the melting furnace to form a sling sheet, it enters the hydrogen crushing section, which is the rough crushing and medium grinding of rare earth alloys, and the feed size.100 -- 0.1MM, powder size: 10-1000UM. The powder particle size of NdFeB permanent magnet should be 3-5UM, which should be finely ground by air flow mill. Hydrogenation fragmentation (HD) method is hydrogen absorption lattice expansion and dehydrogenation reduction to refine the particle size, and hydrogen absorption or dehydrogenation is a reversible chemical reaction process, physical and chemical reaction has its chemical composition and magnetic change.

NdFeB crystal hydrogen absorption, the generated hydride lattice expansion, and generate heat, chemical process; The internal stress of expansion makes NdFeB crystal crack into loose body as a physical phenomenon, both of which are carried out at the same time. Heating and dehydrogenation treatment, most of the main phase hydride back to the originalNd2Fe14B powders, some of the remaining Nd-rich phase hydrides require advanced treatment. In the hydrogen absorption process of NdFeB, the first hydrogen absorption is the Nd-rich phase exposed on the surface, followed by the reaction of the main phase Nd2Fe14B with H2, the formation of the main phase hydride is accompanied by an exothermic reaction, and the total heat can raise the temperature of the reactant to 300 degrees. The lattice constant becomes larger and the thermal expansion process produces powder burst, and the HD powder of NdFeB has undergone qualitative change.

Dehydrogenation makesThe Nd2Fe14Bhy becomes Nd2Fe14B, I .e. the hydride decomposes. Effects of temperature and pressure, 650. C, Nd-rich phase change soft melting, continue to heat up the HDDE reaction, now the best dehydrogenation temperature is 500. C, under this condition, the hydrogen of the main phase hydride is released, and the neodymium rich phase hydride NdH3 is 500. After C, part of the hydrogen is removed and becomes NdH2, 1040. C can completely discharge hydrogen from the main phase Nd2Fe14B

Source: magnet manufacturers Youlian Magnetic Industrywww.youliancy.com