Patent US3894892A successfully refreshed from Google Patents.
US3894892A
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Process for heating and sintering ferrous powder metal compacts with radio frequency magnetic field
Assignee: Gleason Works
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Filing: 1973-10-15
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Granted: 1975-07-15
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Expires: 1993-10-15
Abstract
Abstract A relatively high frequency (in the radio frequency range) magnetic field is used for reducing electrical resistivity of ferrous powder metal compacts prior to subjecting the compacts to a relatively lower frequency magnetic field which rapidly raises the temperature level of the material of each compact to a sintering temperature.
Inventors
- 👤 Robert L Conta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:24
CPC Classifications
B; B30; B30B; B30B15/00; B30B15/34; B22; B22F; B22F3/00; B22F3/10; B22F3/1017; B22F3/105; B22F5/00; B22F5/08; B22F2202/00; B22F2202/05; B22F2998/00; B22F2998/10
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
129 words
A PROCESS FOR HEATING AND SINTERING FERROUS POWDER METAL COMPACTS, COMPRISING THE STEPS OF PRETREATING A POWDER METAL COMPACT IN A MAGNETIC FIELD HAVING A RELATIVELY HIGH FREQUENCY SELECTED FROM A RADIO FREQUENCY MAGNETIC FIELD AT ABOUT 50 KHZ OR ABOVE TO INDUCE CURRENT IN THE COMPACT TO A DEPTH DISTANCE OF ABOUT ONE-FOURTH OF THE MAXIMUM THICKNESS OF THE COMPACT, CONTINUING SAID PRETREATING FOR A SUFFICIENT TIME TO EFFECT A SUBSTANTIAL DECREASE IN ELECTRICAL RESISTIVITY OF SAID COMPACT WITHOUT SIGNIFICANT SINTERING OF THE COMPACT, AND THEREAFTER SUBJECTING THE COMPACT TO A MAGNETIC FIELD HAVING A RELATIVELY LOW FREQUENCY OF ABOUT 10 KHZ OR LESS WHICH PROVIDES FOR AN EFFICIENT HEATING OF SAID COMPACT TO A SINTERING TEMPERATURE LEVEL IN ACCORDANCE WITH THE CHANGED ELECTRICAL RESISTIVITY OF THE COMPACT.
Claim 2
Dependent Claim
129 words
A PROCESS FOR HEATING AND SINTERING FERROUS POWDER METAL COMPACTS, COMPRISING THE STEPS OF PRETREATING A POWDER METAL COMPACT IN A MAGNETIC FIELD HAVING A RELATIVELY HIGH FREQUENCY SELECTED FROM A RADIO FREQUENCY MAGNETIC FIELD AT ABOUT 50 KHZ OR ABOVE TO INDUCE CURRENT IN THE COMPACT TO A DEPTH DISTANCE OF ABOUT ONE-FOURTH OF THE MAXIMUM THICKNESS OF THE COMPACT, CONTINUING SAID PRETREATING FOR A SUFFICIENT TIME TO EFFECT A SUBSTANTIAL DECREASE IN ELECTRICAL RESISTIVITY OF SAID COMPACT WITHOUT SIGNIFICANT SINTERING OF THE COMPACT, AND THEREAFTER SUBJECTING THE COMPACT TO A MAGNETIC FIELD HAVING A RELATIVELY LOW FREQUENCY OF ABOUT 10 KHZ OR LESS WHICH PROVIDES FOR AN EFFICIENT HEATING OF SAID COMPACT TO A SINTERING TEMPERATURE LEVEL IN ACCORDANCE WITH THE CHANGED ELECTRICAL RESISTIVITY OF THE COMPACT.
Claim 3
Dependent Claim
29 words
The process of claim 1 wherein said pretreating step is carried out for a time duration of less than 20 seconds for a compact which weighs about 900 grams.
Claim 4
Dependent Claim
25 words
The process of claim 1 wherein said pretreating step comprises an application of a radio frequency magnetic field to only surface areas of said compact.
Claim 5
Dependent Claim
45 words
The process of claim 3 wherein said application of a radio frequency magnetic field to surface areas of the compact is carried out with a sufficient energy input to result in a low temperature preheating of sections of the compact adjacent to said surface areas.
Claim 6
Dependent Claim
34 words
The process of claim 4 wherein said sections adjacent to said surface areas are preheated to a temperature of at least 150*C but less than the sintering temperature for the material of said compact.
Claim 7
Dependent Claim
50 words
The process of claim 1 wherein said pretreating step comprises an application of a radio frequency magnetic field to selected areas of a compact so as to provide for a differential response time for separate areas of the compact when the compact is placed in a lower frequency induction field.
Claim 8
Dependent Claim
27 words
The process of claim 1 wherein the duration of said pretreating step is determined by a change in an electrical parameter of the radio frequency heating circuit.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-07-14 | 1979-01-13 | 1979-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-14 | 1983-01-13 | 1983-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-14 | 1987-01-13 | 1987-07-15 | $7700.00 | Window Closed / Lapsed |