METHOD FOR PREPARING R-T-B PERMANENT MAGNET

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A method for preparing an R-T-B permanent magnet. Main steps of the preparation method are : (1) performing melting and casting on a raw material to obtain a strip; (2) performing hydrogen explosion processing on the strip, to obtain intermediate grinding powder; (3) performing jet milling on the intermediate grinding powder to produce powder; (4) performing press forming in a sealed vertical compressor; (5) performing pre-sintering in vacuum or in an inert gas atmosphere; (6) performing machine processing on a pre-sintered compact into a desired shape; (7) coating processing : scattering heavy rare earth compound powder into an organic solvent to form a slurry, immersing the pre-sintered compact in the slurry, and then placing the processed pre-sintered compact in a bin; and (8) performing secondary sintering at 820°C to 950°C and simultaneously performing primary diffusion on heavy rare earth elements, after cooling, performing secondary diffusion of the heavy rare earth elements within a temperature range of 450°C to 620°C, and performing cooling to obtain an R-T-B permanent magnet. For the permanent magnet prepared according to the preparation method, remanence and coercivity are significantly improved, and rectangularity is clearly improved.