US4872926A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for heat treating metals or metal alloys in a thermal plasma
Assignee: American Air Liquide Inc
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Filing: 1987-12-30
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Granted: 1989-10-10
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Expires: 2007-12-30
Abstract
Abstract Workpieces of metal are treated with a high temperature, ambient pressure argon arc plasma system to facilitate surface and through hardening. The argon flame is directed against the outer surface of the rotating workpiece. The surface temperature is monitored by a non contact I.R. temperature sensor and controlled by varying the inert gas flowrate through the plasma generator and/or varying the electrical power input to the plasma generator.
Inventors
- 👤 Frederick Giacobbe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:59
CPC Classifications
C; C21; C21D; C21D1/00; C21D1/34; C21D1/06; C21D1/09
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
177 words
A method for localized heat treating of a workpiece of metal to a predetermined depth in a plasma flame generated by plasma generating means, comprising the steps of: directing inert gas through the plasma generating means; igniting the inert gas in the plasma generating means to produce a plasma flame having a temperature exceeding 10,000° C.; moving the workpiece into the plasma flame path; rotating the workpiece at a speed fast enough so that significant cooling does not occur between the position where said workpiece is heated in said plasma flame and the position in which the surface temperature of the workpiece is monitored; monitoring the surface temperature of said workpiece by noncontact surface temperature measurement means; varying the inert gas flow rate through the plasma generating means, in response to the monitored surface temperature, to thereby control the temperature of the plasma flame and thus the workpiece surface temperature in order to maintain a predetermined heating rate and to rapidly reach the desired soaking temperature for the workpiece; extinguishing the plasma flame; and quenching the workpiece.
Claim 2
Independent Claim
177 words
A method for localized heat treating of a workpiece of metal to a predetermined depth in a plasma flame generated by plasma generating means, comprising the steps of: directing inert gas through the plasma generating means; igniting the inert gas in the plasma generating means to produce a plasma flame having a temperature exceeding 10,000° C.; moving the workpiece into the plasma flame path; rotating the workpiece at a speed fast enough so that significant cooling does not occur between the position where said workpiece is heated in said plasma flame and the position in which the surface temperature of the workpiece is monitored; monitoring the surface temperature of said workpiece by noncontact surface temperature measurement means; varying the inert gas flow rate through the plasma generating means, in response to the monitored surface temperature, to thereby control the temperature of the plasma flame and thus the workpiece surface temperature in order to maintain a predetermined heating rate and to rapidly reach the desired soaking temperature for the workpiece; extinguishing the plasma flame; and quenching the workpiece.
Claim 3
Dependent Claim
17 words
A method according to claim 1, wherein said non contact surface temperature measurement means are I.R. means.
Claim 4
Dependent Claim
20 words
A method according to claim 1, wherein the desired soaking temperature is maintained between about 600° C. and 1000° C.
Claim 5
Dependent Claim
18 words
A method according to claim 1, further comprising a step of translating the workpiece along the rotational axis.
Claim 6
Dependent Claim
37 words
A method according to claim 4, wherein it further comprises a step of varying the speed of translation of the workpiece according to its geometry in order to treat about the same depth all over the workpiece.
Claim 7
Dependent Claim
39 words
A method according to claim 1 or 5, wherein it further comprises a step of varying the speed of rotation of the workpiece according to its geometry in order to treat about the same depth all over the workpiece.
Claim 8
Dependent Claim
35 words
A method according to claim 1, further comprising a step of simultaneously heat-treating different zones of the same workpiece with a plurality of plasma generating means, each being associated with non contact surface temperature means.
Claim 9
Dependent Claim
21 words
A method according to claim 7, wherein each of the different zones is treated at a different temperature from the others.
Claim 10
Dependent Claim
21 words
A method according to claim 7, wherein each of the different zones is treated at a different thickness from the others.
Claim 11
Dependent Claim
25 words
A method according to claim 15, wherein the gas is hydrogen, helium, neon, argon, krypton, zenon, radon, nitrogen, oxygen, carbon dioxide or a mixture thereof.
Claim 12
Dependent Claim
18 words
A method according to claim 1, wherein said quenching is made immediately after the flame has been extinguished.
Claim 13
Dependent Claim
23 words
A method according to claim 1, wherein said quenching step is made by spraying a cooling fluid onto the surface of the workpiece.
Claim 14
Dependent Claim
17 words
A method according to claim 12, wherein said quenching is made while the workpiece is still rotating.
Claim 15
Dependent Claim
22 words
A method according to claim 12, wherein said quenching is made by spraying a liquefied gas onto the surface of said workpiece.
References Cited (Backward Citations)
CA665105A
Cited
US2491134A
Cited
GB767381A
Cited
GB887506A
Cited
GB940018A
Cited
US3615924A
Cited
US3660630A
Cited
US4181845A
Cited
US4312685A
Cited
US4420346A
Cited
JPH01270328A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-09 | 1993-04-10 | 1993-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-09 | 1997-04-10 | 1997-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-09 | 2001-04-10 | 2001-10-10 | $7700.00 | Window Closed / Lapsed |