R- (Fe, Co) -B system sintered magnet and its manufacturing method

摘要

PROBLEM TO BE SOLVED: To provide a novel R-(Fe,Co)-B based sintered magnet which has a high coercive force at a room temperature and a high temperature, and a method for manufacturing the magnet.SOLUTION: An R-(Fe,Co)-B based sintered magnet comprises 12-17% of R (R essentially includes Nd and Pr), 0.1-3% of M(Si), 0.05-0.5% of M(Ti), and B. The magnet includes a R(Fe,Co)B intermetallic compound as a main phase, and has a coercive force of 10 kOe or more. The magnet has a core-shell structure, in which the main phase is covered with: an amorphous and/or microcrystalline R'-(Fe,Co)-M' phase comprising a Mboride phase and no RFeBcompound phase at a triple point of grain boundaries, and 25-35% of R'(Pr), 2-8% of M'(Si), 8% or less of Co, and the balance consisting of Fe; or a grain boundary phase including the phase and an amorphous or microcrystalline R'-M" phase (Si), where R' accounts for 50% or more. The coverage of the R'-(Fe,Co)-M' phase covering the main phase is 50% or more. The width of the grain boundary phase located between two particles of the main phase is 50 nm or more on average.SELECTED DRAWING: None