PROCESS FOR PRODUCING RFeB-BASED SINTERED MAGNET

摘要

This process for producing an RFeB-based sintered magnet comprises: a step S1 in which an RFeB-based alloy billet having a rare-earth-element R content of 26.5-29.5 wt% is subjected to an HDDR treatment in which the billet is heated in a hydrogen atmosphere having a temperature of 700-1,000ºC and thereafter the atmosphere is made vacuum while keeping the temperature at 750-900ºC, thereby producing an HDDR-treated raw alloy billet consisting of a polycrystalline object made up of crystal grains having an average grain diameter of 1 µm or smaller in terms of equivalent circular diameter determined from an electron microscope image; a step S2 in which the HDDR-treated raw alloy billet is heated to a temperature of 700-950ºC while keeping the billet in contact with a contact object comprising a second alloy having a higher rare-earth-element R content than the RFeB-based alloy, thereby producing a raw alloy billet having a high rare-earth content; a step S3 in which the raw alloy billet having a high rare-earth content is pulverized to an average particle diameter of 1 µm or smaller, thereby producing a raw alloy powder; an orientation step S4 in which the raw alloy powder is put into a mold and a magnetic field is applied to the raw alloy powder without performing compression molding; and a sintering step S5 in which the raw alloy powder which has undergone the orientation step is heated to a temperature of 850-1,050ºC.