PROCESS FOR PRODUCING RARE EARTH PERMANENT MAGNET MATERIAL

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PROBLEM TO BE SOLVED : To provide a process for producing the material of a rare earth permanent magnet as an R-Fe-B based anisotropic sintered magnet where magnetic characteristics impaired by grinding are recovered. SOLUTION : An anisotropic sintered magnet body represented by composition formula R1x(Fe1-yCoy)100-x-z-aBzMa (R1 is one kind or more than one kinds selected from rare earth elements including Sc and Y, M is one kind or more than one kinds selected from Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta and W, and x, y, z and a are atomic ratios in percent satisfying following relations; 10≤x≤15, 0≤y≤0.4, 3≤z≤15, 0≤a≤11) is ground to have a specific surface area of 6 mm-1 or above. Subsequently, under such a state as containing one kind or more than one kinds selected from an oxide of R2, a fluoride of R3, and an acid fluoride of R4 (R2, R3 and R4 are one kind or more than one kinds selected from rare earth elements including Sc and Y) with powder having an average particle size of 100 μm or less existing on the surface of a processed magnet, disproportionation reaction is caused in an R12Fe14B type compound of main phase by heat treatment in an atmosphere containing hydrogen gas for the magnet and powder, and recombination reaction on that compound is caused by further heat treatment thus making the crystal grain of that compound phase as fine as 1 μm or less, and absorbing one kind or more than one kinds of R2, R3 and R4 contained in the powder to the magnet. COPYRIGHT : (C)2008, JPO&INPIT