US3904448A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for preparing magnetic alloy powder by surface nitriding
Assignee: Victor Company of Japan Ltd
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Filing: 1974-01-03
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Granted: 1975-09-09
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Expires: 1994-01-03
Abstract
Abstract In the course of the reduction of metal salts powder such as a ternary oxalate of Fe, Co and Ni by heating in a reducing atmosphere, a nitrogen-containing compound gas such as NH3 is introduced into the reaction system atmosphere in order to form a layer of metal nitride on the surface of the powder. The nitride layer protects the resulting alloy powder against air-oxidation and deterioration in the magnetic properties.
Inventors
- 👤 Noboru Takahashi
- 👤 Koji Chiba
- 👤 Mutsuaki Nakamura
- 👤 Sadao Ozaki
- 👤 Hiromasa Isono
- 👤 Tunehide Naruse
- 👤 Toshikazu Mishihara
- 👤 Iwao Fukushima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 18:28
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70615; B; B22; B22F; B22F1/00; B22F1/14; B22F1/145; C; C23; C23C; C23C8/00; C23C8/06; C23C8/08; C23C8/24; C23C8/26; B22F2201/00; B22F2201/01; B22F2201/016; B22F2201/02
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
128 words
A PROCESS FOR PREPARING A MAGNETIC ALLOY POWDER ESSENTIALLY CONSISTING OF IRON AND AT LEAST ONE OF COBALT AND NICKEL, THE PROCESS COMPRISING THE STEPS OF. A. HEATING A CRYSTALINE POWDER MATERIAL COMPRISING REDUCIBLE SALTS OF IRON AND SAID COBALT AND/OR NICKEL, SAID REDUCIBLE SALTS BEING SELECTED FROM THE GROUP CONSISTING OF OXALATES AND FORMATES, IN A REDUCING ATMOSPHERE AT A TEMPERATURE OF ABOUT 300*C FOR A PERIOD OF 2 TO 6 HOURS TO INCOMPLETELY REDUCE SAID SALTS TO THE CORRESPONDING METALS, A. CONTINUING HEATING THE INCOMPLETELY REDUCED POWDER MATERIAL IN A GAS STREAM CONTAINING A NITROGEN-CONTAING COMPOUND GAS AT A TEMPERATURE OF 250* TO 400*C FOR A PERIOD OF 15 TO 60 MINUTES TO NITRIFY THE SURFACE REGION OF SAID POWDER POWDER MATERIAL C. COMPLETING THE REDUCTION.
Claim 2
Dependent Claim
128 words
A PROCESS FOR PREPARING A MAGNETIC ALLOY POWDER ESSENTIALLY CONSISTING OF IRON AND AT LEAST ONE OF COBALT AND NICKEL, THE PROCESS COMPRISING THE STEPS OF. A. HEATING A CRYSTALINE POWDER MATERIAL COMPRISING REDUCIBLE SALTS OF IRON AND SAID COBALT AND/OR NICKEL, SAID REDUCIBLE SALTS BEING SELECTED FROM THE GROUP CONSISTING OF OXALATES AND FORMATES, IN A REDUCING ATMOSPHERE AT A TEMPERATURE OF ABOUT 300*C FOR A PERIOD OF 2 TO 6 HOURS TO INCOMPLETELY REDUCE SAID SALTS TO THE CORRESPONDING METALS, A. CONTINUING HEATING THE INCOMPLETELY REDUCED POWDER MATERIAL IN A GAS STREAM CONTAINING A NITROGEN-CONTAING COMPOUND GAS AT A TEMPERATURE OF 250* TO 400*C FOR A PERIOD OF 15 TO 60 MINUTES TO NITRIFY THE SURFACE REGION OF SAID POWDER POWDER MATERIAL C. COMPLETING THE REDUCTION.
Claim 3
Dependent Claim
18 words
The method as claimed in claim 1, wherein said nitrogen-containing compound gas is gaseOus ammonia or hydrazine vapors.
Claim 4
Dependent Claim
17 words
The process as claimed in claim 1, in which said reducing atmosphere essentially consists of hydrogen gas.
Claim 5
Dependent Claim
13 words
The process as claimed in claim 2 wherein said nitrogen-containing compound is ammonia.
Claim 6
Dependent Claim
13 words
The process as claimed in claim 2, wherein said nitrogen-containing compound is hydrazine.
Claim 7
Dependent Claim
15 words
A process as claimed in claim 3, in which said gas stream includes hydrogen gas.
Claim 8
Dependent Claim
26 words
A method as claimed in claim 6, in which the amount of said nitrogen-containing compound gas is at least 10% by volume of said reducing gas.
Claim 9
Dependent Claim
26 words
A process as claimed in claim 6, in which the amount of said ammonia gas is from 20 to 80% by volume of said hydrogen gas.
Claim 10
Dependent Claim
34 words
A process as claimed in claim 1, wherein said crystalline powder material is a ternary oxalate of substantially 50 mole % of iron, 48 mole % of cobalt and 2 mole % of nickel.
Claim 11
Dependent Claim
38 words
A process as claimed in claim 1, wherein said crystalline powder material is a quaternary oxalate of substantially 48 Mole % of iron, 46 % of cobalt, 2 mole % of nickel and 4 mole % of aluminum.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-08 | 1979-03-10 | 1979-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-08 | 1983-03-10 | 1983-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-08 | 1987-03-10 | 1987-09-09 | $7700.00 | Window Closed / Lapsed |