US4035203A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for the heat-treatment of steel and for the control of said treatment
Assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Filing: 1974-12-19
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Granted: 1977-07-12
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Expires: 1994-12-19
Abstract
Abstract The invention relates to a method of and an installation for the heat treatment of steels, such as heating before hardening, annealing, carburization and carbo-nitridation, carried out in a furnace in the presence of a protection or carbon-enrichment atmosphere which flows continuously through the furnace, the atmosphere being obtained by the mixture, before its introduction into the furnace, of a carrier gas including nitrogen and possibly hydrogen, and an active gas constituted by a hydrocarbon, the mixture containing at least 0.2% by volume of hydrocarbon. The active gas may be constituted by ethylene, ethane or acetylene and the treatment is carried out at a temperature between 700° and 1050° C. The installation includes a device for analyzing the atmosphere at the furnace outlet, this analyzer actuating a regulating valve for the inlet flow of active gas through a servo-mechanism, in dependence on the proportion of carbon in the treated steel.
Inventors
- 👤 Mathurin L'Hermite
- 👤 Raymond Le Bossenec
- 👤 Pierre Godart
- 👤 Francois Pierrard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:38
CPC Classifications
C; C21; C21D; C21D1/00; C21D1/74; C21D1/76; C23; C23C; C23C8/00; C23C8/06; C23C8/28; C23C8/30; C23C8/32
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
204 words
A method of heat treatment of steel comprising the steps of mixing a nitrogen-containing carrier gas, ammonia and an active gas including a hydrocarbon selected from the group consisting of the compounds C 2 H 4 , C 2 H 2 , C 2 H 6 , C 3 H 8 and CH 4 , the mixture containing 0.1 to 30% by volume of ammonia, less than 30% by volume of hydrogen and between 0.2 to 30% by volume of hydrocarbon, continuously introducing the thus formed mixture into a furnace containing the steel to be heat-treated, to provide an atmosphere consisting substantially entirely of said mixture around the steel, heating the steel and the surrounding atmosphere to a temperature within the range of from 650° C. to 950° C., continuously withdrawing the atmosphere from said furnace, measuring the residual content of hydrocarbon in the atmosphere withdrawn from said furnace, comparing the thus measured residual hydrocarbon content with a predetermined hydrocarbon content level to thereby ascertain the hardness of the steel, and regulating the flow rate of hydrocarbon in the atmosphere introduced into the furnace as a function of said comparison to provide a residual hydrocarbon content corresponding to the desired hardness of the steel.
Claim 2
Independent Claim
204 words
A method of heat treatment of steel comprising the steps of mixing a nitrogen-containing carrier gas, ammonia and an active gas including a hydrocarbon selected from the group consisting of the compounds C 2 H 4 , C 2 H 2 , C 2 H 6 , C 3 H 8 and CH 4 , the mixture containing 0.1 to 30% by volume of ammonia, less than 30% by volume of hydrogen and between 0.2 to 30% by volume of hydrocarbon, continuously introducing the thus formed mixture into a furnace containing the steel to be heat-treated, to provide an atmosphere consisting substantially entirely of said mixture around the steel, heating the steel and the surrounding atmosphere to a temperature within the range of from 650° C. to 950° C., continuously withdrawing the atmosphere from said furnace, measuring the residual content of hydrocarbon in the atmosphere withdrawn from said furnace, comparing the thus measured residual hydrocarbon content with a predetermined hydrocarbon content level to thereby ascertain the hardness of the steel, and regulating the flow rate of hydrocarbon in the atmosphere introduced into the furnace as a function of said comparison to provide a residual hydrocarbon content corresponding to the desired hardness of the steel.
Claim 3
Dependent Claim
22 words
A method as claimed in claim 1, in which the steel is heated to a temperature of between 800° and 900° C.
Claim 4
Dependent Claim
52 words
A method as claimed in claim 2, in which, for an XC 10 steel, said controlled atmosphere is constituted by a mixture containing the following compounds in the specified proportions by volume: N 2 . . . 97% c 2 h 6 . . . 1% nh 3 . . . 2%.
Claim 5
Dependent Claim
50 words
a method as claimed in claim 2, in which, for a 20 CD 2 steel, said controlled atmosphere is constituted by the compounds in the specified following proportions by volume: N 2 . . . 95.0% c 2 h 4 . . . 1.7% nh 3 . . . 3.3%.
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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) | 1980-07-11 | 1981-01-10 | 1981-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-11 | 1985-01-10 | 1985-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-11 | 1989-01-10 | 1989-07-12 | $7700.00 | Window Closed / Lapsed |