METHOD FOR PRODUCING RARE EARTH PERMANENT MAGNET

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The present invention provides a method of producing a rare earth permanent magnet that can exert an improved coercive force and thermal characteristics by effectively diffusing heavy rare earth elements along the grain boundaries of a sintered magnet. The method of producing a rare earth permanent magnet according to one embodiment of the present invention includes the steps of : preparing an NdFeB sintered magnet; coating a surface of the NdFeB sintered magnet with a grain boundary diffusion material including R hydrate or R fluoride, and RaMb or M, to form a grain boundary diffusion coating layer; and diffusing the grain boundary diffusion material into a grain boundary of the NdFeB sintered magnet by heat treatment, wherein M is a metal having a melting point higher than a heat treatment temperature during the diffusion, R is a rare earth element, and a and b respectively represent atomic percentages which satisfy the following expressions (1) and (2) : 0.1 (AA) Manufacture of NdFeB sintered magnet(BB) Manufacture of cobalt alloy molten metal(CC) Manufacture of cobalt alloy ingot(DD) Prepare intergranular diffusion material by pulverizing cobalt alloy ingot(EE) Formation of grain boundary diffusion coating layer on NdFeB sintered magnet surface(FF) Manufacture rare earth permanent magnet by diffusing grain boundary diffusion materialCOPYRIGHT KIPO 2018