Metal treatment – Stock – Magnetic
Patent
1991-06-27
1993-01-19
Sheehan, John P.
Metal treatment
Stock
Magnetic
428403, 428570, H01F 1053
Patent
active
051804450
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.
REFERENCES:
patent: 4849035 (1989-07-01), Stadelmaier et al.
patent: 4952239 (1990-08-01), Tokunaga et al.
Dee James D.
Nerenberg Aaron
Sheehan John P.
SPS Technologies, Inc.
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