Radial orientation rare earth-cobalt magnet rings

Details Radial orientation rare earth-cobalt magnet rings Radial orientation rare earth-cobalt magnet rings

1985-08-05

1986-12-16

Lechert, Jr., Stephen J.

Presses

Plural presses

Concurrently actuated

29609, 29DIG95, 100917, 148103, 264DIG58, 428928, B30B 1514

Patent

active

046288090

ABSTRACT:
Apparatus and method for forming radial orientation rare earth-transition metal magnets in continuous arc rings by hot isostatic pressing. A method includes the steps of compacting rare earth-transition metal powders having a particle size up to 40 microns into radially oriented rings in a mold provided with a radially aligning field, stacking a plurality of compacted radially oriented rings within an annular cavity within a sealed, evacuated canister to form a cylinder of a predetermined height, subjecting the canister to temperatures in the range of 900.degree. to 1150.degree. C. under a gas pressure of 15 kpsi to densify the compacts, and cooling the canister and the compacts to room temperature. An apparatus for performing the above-described method, includes a mold for forming green compacts having a central iron core or mandrel, as outer housing forming an annular space between it and the iron mandrel, plungers for compacting into a ring rare earth-transition metal powder within the annular space, and means for forming a radially oriented magnetic field. The magnetic field forming means includes a pair of electromagnetic coils with bucking fields disposed on opposite axial ends of the annular space. Ferromagnetic paths guide the flux through the inner and outer walls of the mold and through the powder to form a radial field for powder alignment. A canister is used for forming magnets from the green compacts and the canister is typically composed of a soft iron that will collapse around the magnets and transmit compressive forces to the green compacts for densification thereof. The canister includes an annular space for stacking green compacts bounded by inner and outer walls and an evacuation tube. A central mandrel may be provided if a ring magnet having a predetermined inner diameter is desired.

REFERENCES:
patent: 4104787 (1978-08-01), Jandeska et al.
patent: 4144060 (1979-03-01), Jandeska et al.
patent: 4533407 (1985-08-01), Das et al.

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