R-T-M-B-BASED SINTERED MAGNET AND PRODUCTION METHOD THEREFOR

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PROBLEM TO BE SOLVED : To solve such a problem in the production of a R-T-M-B-based sintered magnet that an alloy produced by strip casting generates ultrafine powder, containing a lot of rare earth-rich phases, easily in a pulverization step, and the fine powder containing a lot of these rare earth-rich phases brings about degradation of the magnet characteristics, because it is easily-oxidizable. SOLUTION : Each step of hydrogen treatment, milling, and molding is performed under an inert gas or nitrogen gas atmosphere. In the milling step, oxygen is not added, and fine powder containing a lot of rare-earth is not removed. R is at least one kind of rare-earth element selected from Sc and Y, T is at least one element selected from Fe and Co, M is at least one element selected from a group of Ti, Ni, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Cu, Ga, Mo, W and Ta, B is boron, the weight composition ratio of each element is 29%≤R≤35%, 62%≤T≤70%, 0.1%≤M≤1.8%, 0.9%≤B≤1.2%, and the oxygen containing weight is 0.07% or less. COPYRIGHT : (C)2015, JPO&INPIT