The present invention provides a method for producing a rare earth sintered magnet and a molding device therefor that can stably mold molded bodies with less variation in unit weight. The method includes: 1) preparing a slurry including an alloy powder and a dispersion medium, the alloy powder containing a rare earth element; 2) disposing an upper punch and a lower punch in respective through holes provided in a die, thereby preparing a plurality of cavities; 3) applying a magnetic field in each of the cavities by an electromagnet in a direction substantially parallel to a direction in which at least one of the upper punch and the lower punch is movable, and then supplying the slurry into the plurality of cavities; 4) producing a molded body of the alloy powder in each of the cavities by press molding in the magnetic field; and 5) sintering the molded body.

A mold comprising a die, an upper punch, and a lower punch, the pressure surface of one or both of the upper and lower punches being shaped non-planar, a cavity being defined between the die and the lower punch, is combined with a feeder including a shooter provided with a main sieve at its lower end port, the main sieve having a sifting surface of substantially the same non-planar shape as the pressure surface. A rare earth sintered magnet is prepared by feeding an alloy powder into the cavity through the shooter and sieve while applying weak vibration to the shooter, applying a uniaxial pressure to the alloy powder fill in the cavity under a magnetic field to form a precursor, and heat treating the precursor.

The present invention provides a method for producing a rare earth sintered magnet and a molding device therefor that can stably mold molded bodies with less variation in unit weight. The method includes: 1) preparing a slurry that includes an alloy powder containing a rare earth element, and a dispersion medium; 2) disposing an upper punch and a lower punch in respective through holes provided in a die, thereby preparing a plurality of cavities; 3) applying a magnetic field in each of the cavities by an electromagnet in a direction substantially parallel to a direction in which at least one of the upper punch and the lower punch is movable, and then supplying the slurry into the plurality of cavities; 4) producing a molded body of the alloy powder in each of the cavities by press molding in the magnetic field; and 5) sintering the molded body.

The present invention provides a method for producing a long and large-sized rare earth sintered magnet having a large size in a magnetic field application direction in which a single magnet body in each portion has uniform and high magnetic characteristics. Disclosed is a method for producing a rare earth sintered magnet, including particular steps of: 1) preparing a slurry; 2) preparing a cavity that is enclosed with a mold, an upper punch and a lower punch; 3) applying a magnetic field of 1.5 T or more in the cavity, and supplying the slurry at a flow rate of 20 to 600 cm.sup.3/second, to fill the cavity with the slurry; 4) producing a molded body of the alloy powder by press molding in the magnetic field; and 5) sintering the molded body.

A rare earth sintered magnet is prepared from a corresponding alloy powder, using a mold comprising a die, an upper punch, and a lower punch which is divided into a plurality of punch segments which are independently movable within the die. The method comprises the steps of filling the mold cavity with the alloy powder when one or more selected punch segments are moved to a higher position than the remaining punch segments; moving the selected punch segments down to the position where the selected and remaining punch segments assume the normal shape of the lower punch during the compression step; compressing the alloy powder between the upper and lower punches under a magnetic field while the normal shape of the lower punch is maintained, for thereby molding a compact; and heat treating the compact.