R-FeCo-B R-FeCo-B SINTERED MAGNET AND MAKING METHOD

摘要

According to the present invention, an R-(Fe,Co)-B based sintered magnet essentially comprising: 12 to 17 atomic percent of R including Nd and Pr, 0.1 to 3 atomic percent of M_1 (typically, Si), 0.05 to 0.5 atomic percent of M_2 (typically Ti), B, and the remainder of Fe, and containing R_2(Fe, Co)_14B as a main phase has the coercivity of at least 10 kOe. The magnet has a M_2 borate phase in a triple-grain boundary junction part and the main phase has a core/shell structure coated with a grain boundary phase. The grain boundary phase comprises: an amorphous and/or nano-crystalline R-(Fe,Co)-M_1 phase including 25 to 35 atomic percent of R including Pr; 2 to 8 atomic percent of M_1 (typically Si); 8 atomic percent as the maximum of Co; and the remainder of Fe. The amount covering the main phase by R-(Fe,Co)-M_1&prime is at least 50% and a grain boundary phase between grains has a width of at least 50 nm.