Shin-etsu Chemical Co., Ltd.

Mitsuo Kitagawa

Takehisa Minowa

Koji Sato

Kazuaki Sakaki

Koji Sati

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.

Method and apparatus for preparing rare earth sintered magnet

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 and vertical reciprocation 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.

A radially anisotropic magnet is prepared by furnishing a cylindrical magnet-compacting mold comprising a die, a core, and top and bottom punches, packing a magnet powder in the mold cavity, applying a magnetic field across the magnet powder, and forcing the top and bottom punches to compress the magnet powder for compacting the magnet powder by a horizontal magnetic field vertical compacting process. The top punch is divided into segments so that the magnet powder may be partially compressed; in the step of compacting the magnet powder packed in the mold cavity by a horizontal magnetic field vertical compacting process, the magnet powder is partially compressed by the segments of the top punch cooperating with the bottom punch for thereby consolidating the partially compressed zones of magnet powder to a density from 1.1 times the packing density to less than the compact ultimate density; and thereafter, the entire magnet powder in the cavity is compressed under a pressure equal to or greater than that of partial compression by the entire top and bottom punches for finally compacting the magnet powder.

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Echizen, Japan

Mitsuo Kitagawa