US3779747A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for heating and sintering ferrous powder metal compacts
Assignee: Gleason Works
•
Filing: 1972-09-05
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Granted: 1973-12-18
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Expires: 1992-09-05
Abstract
Abstract An induction field is utilized for rapidly raising the temperature of a ferrous powder metal compact to a sintering temperature where the compact is deoxidized and its particles coalesced into a homogenous mass. In order to overcome a characteristic incubation period which delays initial increase in temperature of such a compact in an induction field, the outer surfaces of the compact are preheated for a relatively short time by known heating means to raise its surface temperature to about 400* F prior to subjecting the compact to a magnetic induction field. After the preheating step, heating in the induction field is used to raise the temperature of the entire compact to a level above 1,800* F, and this temperature is maintained for a sufficient period of time to deoxidize and sinter the compact. After the heating and sintering treatments, the compact is cooled to a temperature of about 1,500*-1,900* F for a final forming operation which establishes a useful, full, dense, finished shape.
Inventors
- 👤 R Conta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 04:32
CPC Classifications
B; B22; B22F; B22F3/00; B22F3/10; B22F3/1017; B22F2998/00; B22F2998/10
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
31 words
The process of claim 1 wherein said preheating step is carried out at a temperature level which raises the temperature of the material of the compact to at least 400* F.
Claim 2
Dependent Claim
48 words
The process of claim 1 wherein said preheating step is carried out in a radiant heating zone at a temperature level in a range of about 1,200* F to 2,000* F for a time period of about 30 seconds, or more depending upon the size of the compact.
Claim 3
Dependent Claim
26 words
The process of claim 1 wherein said step of subjecting said compact to an induction field raises the temperature of the compact to over 1,800* F.
Claim 4
Dependent Claim
25 words
The process of claim 4 wherein said induction field raises the temperature of said compact to about 2,350* F but to less than 2,500* F.
Claim 5
Dependent Claim
27 words
The process of claim 4 wherein said step of maintaining the temperature of the compact at said sintering level is carried out in a radiant heating zone.
Claim 6
Dependent Claim
26 words
The process of claim 1 wherein said cooling step reduces the temperature of the compact to a temperature of 1,500*-1,900* F just prior to being formed.
Claim 7
Dependent Claim
44 words
The process of claim 1 wherein said cooling step reduces the temperature of at least portions of said compact to a level below the temperature required for forming, and including a subsequent step of reheating the entire compact to the temperature desired for forming.
Claim 8
Dependent Claim
98 words
The process of claim 1 wherein each compact is subjected to said heating and sintering treatments in a continuous process which subjects the compact to preheating of its surfaces to about 400* F, followed by rapid induction heating of the entire compact to about 2,300* to 2,400* F, followed by continued heating and sintering at about 2,300* F to 2,400* F, followed by an adjusting of the temperature of the entire compact to about 1,850* F, after which the compact is formed while hot and before there is a reoxidation of the material of which it is composed.
Claim 9
Dependent Claim
19 words
The process of claim 1 wherein said steps of heating and sintering are carried out in a reducing atmosphere.
Claim 10
Dependent Claim
86 words
A process for increasing the rate at which ferrous metal powder compacts can be efficiently heated in an induction field, comprising the steps of preheating the powder metal compact sufficiently to raise the temperature level of the material in its outer surfaces to at least 300*F but less than the sintering temperature for the material, and thereafter subjecting the compact to an induction field which rapidly raises the temperature level of the material of the compact to a level at which the compact can be sintered.
Claim 11
Dependent Claim
31 words
The process of claim 11 wherein said preheating step is carried out at a temperature level which raises the temperature of the material of the compact to at least 400* F.
Claim 12
Dependent Claim
48 words
The process of claim 11 wherein said preheating step is carried out in a heating zone at a temperature level in a range of about 1,500* F to 2,000* F and for a time period of about 30 seconds, or more, depending upon the size of the compact.
Claim 13
Dependent Claim
30 words
The process of claim 11 wherein the temperature level of the material of said compact is raised to a temperature between 2, 050* and 2,400* F in said induction field.
Claim 14
Dependent Claim
23 words
The process of claim 14 wherein induction heating is carried out in a field having a current frequency of at least 1 KHz.
Claim 15
Dependent Claim
44 words
The process of claim 14 and including a step of maintaining the temperature of said compact at a level higher than 1,800* F for a sufficient period of time to sinter the compact after said step of subjecting the compact to an induction field.
Claim 16
Dependent Claim
42 words
The process of claim 14 wherein the temperature level of the material of said compact is raised to about 2,350* F in said induction field and thereafter maintained at about 2,350* F for a sufficient period of time to sinter the compact.
Claim 17
Dependent Claim
31 words
The process of claim 17 and including a step of adjusting the temperature of said compact, after it has been sintered, to condition the compact for a lower temperature forming operation.
Claim 18
Dependent Claim
23 words
The process of claim 11 wherein said compact is allowed to cool after said preheating step and before being subjected to induction heating.
Claim 19
Dependent Claim
35 words
The process of claim 11 wherein said compact is subjected to induction heating immediately after said preheating step in a continuous process which subjects the compact to sintering temperatures before a final hot forming operation.
Claim 20
Dependent Claim
35 words
The process of claim 11 wherein said preheating step is carried out in a sufficiently short time span to raise the temperature of only the outer surface of said compact to at least 200* F.
References Cited (Backward Citations)
US3331686A
Cited
US3708645A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-17 | 1977-06-18 | 1977-12-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-17 | 1981-06-18 | 1981-12-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-17 | 1985-06-18 | 1985-12-18 | $7700.00 | Window Closed / Lapsed |