| 简介 |
PROBLEM TO BE SOLVED : To provide a method for producing a rare earth permanent magnet where an R-T-B based rare earth permanent magnet in which variation in coercive force is suppressed, and which has satisfactory magnetic properties can be stably produced. SOLUTION : Raw material alloy pieces in the same lot formed from the same molten metal are sampled by a prescribed number N of pieces. Then, the ratio between the average crystal grain diameter D1 in one face side in the sampled respective raw material alloy pieces and the average crystal grain diameter D2 in the other face side, D1/D2 is calculated. In the sampled number N of pieces of raw material alloy pieces, the number n of pieces of the raw material alloy pieces in which the ratio D1/D2 satisfies a predetermined standard value or above is calculated, and the abundance ratio of the raw material alloy pieces in which the ratio D1/D2 satisfies the predetermined standard value or above, i.e., including coarse grains, n/N is obtained. Then, only the group of the raw material alloy pieces in the lot in which the abundance ratio n/N satisfies the fixed value or below is fed to a pulverization stage, thus an R-T-B based permanent magnet having high coercive force is produced. COPYRIGHT : (C)2008, JPO&INPIT |
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