US4106931A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Methods for sintering powder metallurgy parts
Assignee: Airco Inc
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Filing: 1977-05-18
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Granted: 1978-08-15
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Expires: 1997-05-18
Abstract
Abstract Steel powder metallurgy parts having approximately 0.2 to 10% carbon in the form of graphite and approximately 1% lubricant are sintered in the hot zone of a furnace under temperatures of approximately 2050° F for periods of up to approximately 1.0 hour under an atmosphere comprised of at least 90% nitrogen, up to 9.75% hydrogen and carbon monoxide with a maximum 5% carbon monoxide, 0.25-2.0% methane or equivalent hydrocarbon and a dewpoint of the mixed atmosphere of less than -60° F.
Inventors
- 👤 Harbhajan S. Nayar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:43
CPC Classifications
B; B22; B22F; B22F3/00; B22F3/10; B22F3/1003; B22F3/1007; B22F2201/00; B22F2201/01; B22F2201/02; B22F2201/04
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
109 words
A process for sintering carbon steel powder metallurgy parts having a density of less than 90% theoretical maximum density and 0.3 to 1.3% carbon in the form of graphite in the hot zone of a sintering furnace comprising the steps of heating said hot zone to a temperature of at least 2000° F, passing said parts through said hot zone while supplying to said hot zone an atmosphere comprised of the following constituents by volume: at least 90% nitrogen, up to 9.75% hydrogen and carbon monoxide with said carbon monoxide comprising 5% or less of said atmosphere, 0.25-2.0% gaseous hydrocarbon and having a dewpoint of -60° F or less.
Claim 2
Dependent Claim
109 words
A process for sintering carbon steel powder metallurgy parts having a density of less than 90% theoretical maximum density and 0.3 to 1.3% carbon in the form of graphite in the hot zone of a sintering furnace comprising the steps of heating said hot zone to a temperature of at least 2000° F, passing said parts through said hot zone while supplying to said hot zone an atmosphere comprised of the following constituents by volume: at least 90% nitrogen, up to 9.75% hydrogen and carbon monoxide with said carbon monoxide comprising 5% or less of said atmosphere, 0.25-2.0% gaseous hydrocarbon and having a dewpoint of -60° F or less.
Claim 3
Dependent Claim
32 words
The process as defined in claim 1 wherein said step of supplying said atmosphere comprises premixing the constituents thereof and introducing said premixed constituents through a single inlet to said hot zone.
Claim 4
Dependent Claim
39 words
The process as defined in claim 1 wherein said step of passing said parts comprises translating said parts at a rate such that the dwell time of said parts in the hot zone is approximately 0.5 hours or less.
Claim 5
Dependent Claim
31 words
The process as defined in claim 1 wherein the step of supplying said atmosphere comprises introducing an atmosphere essentially consisting of approximately 99% nitrogen and 1.0% methane into said hot zone.
Claim 6
Dependent Claim
32 words
The process as defined in claim 1 wherein the step of supplying said atmosphere comprises introducing an atmosphere essentially consisting of approximately 5.0% hydrogen, 1.0% methane, balance nitrogen into said hot zone.
Claim 7
Dependent Claim
32 words
The process as defined in claim 1 wherein the step of supplying said atmosphere comprises introducing an atmosphere essentially consisting of approximately 5% hydrogen, 1% methane, 4% carbon monoxide and balance nitrogen.
Claim 8
Dependent Claim
33 words
The process as defined in claim 1 wherein the step of supplying said atmosphere comprises introducing an atmosphere essentially consisting of approximately 1.0% methane, 4.0% carbon monoxide, balance nitrogen into said hot zone.
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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) | 1981-08-14 | 1982-02-13 | 1982-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-08-14 | 1986-02-13 | 1986-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-08-14 | 1990-02-13 | 1990-08-15 | $7700.00 | Window Closed / Lapsed |