MANUFACTURING METHOD FOR MAGNETIC POWDER FOR FORMING SINTERED BODY OF RARE-EARTH MAGNET PRECURSOR

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Provided is a manufacturing method for a magnetic powder that forms a sintered body of a rare-earth magnet precursor, whereby fine magnetic powder not including coarse particles in the structure thereof can be accurately and efficiently sorted and magnetic powder having a structure comprising crystal grains of the optimal nanosize can be manufactured. In the manufacturing method for a magnetic powder (p) that forms a sintered body (S) that is a precursor of a rare-earth magnet, the sintered body (S), which comprises nano-crystalline Nd-Fe-B main phase crystal grains and a grain-boundary phase, is subjected to hot plastic working to impart anisotropy to the sintered body (S), and an alloy for improving coercivity is diffused therein. Molten metal is discharged to a cooling roller (R) to produce a rapidly-quenched ribbon (B). The rapidly-quenched ribbon (B) is pulverized to fall within the particle size range 50μm-1000μm, and magnetic powder within the mass range 0.0003mg-0.3mg is produced. The magnetic powder within said mass range is tested for adhesion to a magnet having a surface magnetic flux density of at most 2mT. The magnetic powder (p) that does not adhere is sorted as the magnetic powder for forming the sintered body (S).