Stock material or miscellaneous articles – All metal or with adjacent metals – Having metal particles
Patent
1991-07-18
1993-07-13
Sheehan, John P.
Stock material or miscellaneous articles
All metal or with adjacent metals
Having metal particles
148105, 148302, 427127, B22F 300
Patent
active
052272478
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.
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.
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Kim et al., "Effect of Oxygen, Carbon and Nitrogen Contents on the Corrosion Resistance of Nd-Fe-B Magnets".
Coey et al., "Improved Magnetic Properties by Treatment of Iron Based Roare Earth Intermetallic Compounds in Ammonia", 1990.
Dee James D.
Sheehan John P.
SPS Technologies, Inc.
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