Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1991-06-27
1993-11-30
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148104, 419 12, 419 13, 419 14, 419 29, 419 35, 419 38, H01F 102
Patent
active
052661288
ABSTRACT:
This invention relates to a process for producing a rare earth-containing powder comprising crushing a rare earth-containing alloy in water, drying the crushed alloy material at a temperature below the phase transformation temperature of the material, and treating the crushed alloy material with a passivating gas at a temperature from the ambient temperature to a temperature below the phase transformation temperature of the material. Rare earth-containing alloys suitable for use in producing magnets utilizing the powder metallurgy technique, such as Nd-Fe-B and Sm-Co alloys, can be used. The passivating gas can be nitrogen, carbon dioxide or a combination of nitrogen and carbon dioxide. If nitrogen is used as the passivating gas, the resultant powder has a nitrogen surface concentration of from about 0.4 to about 26.8 atomic percent. Moreover, if carbon dioxide is used as the passivating gas, the resultant powder has a carbon surface concentration of from about 0.02 to about 15 atomic percent.
The present invention further relates to the production of a permanent magnet comprising the above steps for producing the rare earth-containing powder, and then compacting the powder, sintering the compacted material at a temperature of from about 900.degree. C. to about 1200.degree. C., and heat treating the sintered material at a temperature of from about 200.degree. C. to about 1050.degree. C.
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Sheehan John P.
SPS Technologies, Inc.
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