Process for manufacturing a permanent magnet.

摘要

A process for manufacturing a rare eath-iron-boron alloy permanent magnet by, after sintering, keeping the sintered alloy at temperatures of 750 - 1000°C for 0.2 - 5 hours, slowly cooling it at a cooling rate of 0.3 - 5 °C/min. to temperatures between room temperature and 600°C; annealing it at temperatures of 550 - 700°C for 0.2 - 3 hours, and rapidly cooling it at a cooling rate of 20 - 400 °C/min. The permanent magnet consists essentially of a matrix, a B-rich phase and a Nd-rich phase. In grain boundaries of the matrix phases covered by bcc phases, thin, fine plates of the bcc phases projecting into the matrix phases are once increased by the first heat treatment and slow cooling and then eliminated by the annealing.