Metal treatment – Stock – Magnetic
Patent
1990-06-08
1992-06-16
Sheehan, John P.
Metal treatment
Stock
Magnetic
148101, 148104, 148105, 428403, 428547, 419 12, 419 13, 419 14, 419 29, 419 30, 419 34, 419 35, 419 38, 419 44, 419 55, 427127, 427215, 4272554, 427399, 75236, 75238, 75242, 75244, H01F 1053
Patent
active
051222035
ABSTRACT:
This invention relates to a process for producing a rare earth-containing material capable of being formed into a permanent magnet comprising crushing a rare earth-containing alloy and treating the alloy with a passivating gas at a temperature below the phase transformation temperature of the alloy. This invention further relates to a process for producing a rare earth-containing powder comprising crushing a rare earth-containing alloy in a passivating gas at a temperature from ambient temperature to a temperature below the phase transformation temperature of the material. This invention also 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. Additionally, this invention relates to a process for producing a rare earth-containing powder compact comprising crushing a rare earth-containing alloy in water, compacting the crushed alloy material, drying the compacted alloy material at a temperature below the phase transformation temperature of the material, and treating the compacted alloy material with a passivating gas at a temperature from 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 or compact 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 or compact 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, and then 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. An improved permanent magnet in accordance with the present invention can have a nitrogen surface concentration of from about 0.4 to about 26.8 atomic percent if nitrogen is used as a passivating gas. The improved permanent magnet can also have a carbon surface concentration of from about 0.02 to about 15 atomic percent if carbon dioxide is used as a passivating gas.
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Dee James D.
Nerenberg Aaron
Sheehan John P.
SPS Technologies, Inc.
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