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US4191600A
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US
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Method of continuously heat-treating steel sheet or strip
Assignee: Centre de Recherches Metallurgiques CRM ASBL
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Filing: 1978-05-02
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Granted: 1980-03-04
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Expires: 1998-05-02
Abstract
Abstract Cold-rolled steel sheet or strip (e.g. containing max. 0.15% C., max. 0.60% Mn, max. 0.020% Si, and 0.001-0.050% B) is heated to a temperature higher than its recrystallization temperature and then cooled by immersion in an aqueous bath at above 75° C. The cooling by immersion consists of two successive stages, in the first of which cooling occurs at a rate of 25°-180° C./s to 200°-425° C., the product of the cooling rate v in ° C./s times the sheet or strip thickness e in mm being greater than 25, and in the second of which v is 90°-500° C./s and v times e is at least 35. Optionally a further annealing or overageing step comprises holding at 275°-525° C. for 30-250 s.
Inventors
- 👤 Philippe A. Paulus
- 👤 Marios Economopoulos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:50
CPC Classifications
C; C21; C21D; C21D9/00; C21D9/46; C21D9/48; C21D1/00; C21D1/26
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
158 words
In a method of continuously heat treating cold-rolled steel strip or sheets, in which the strip or sheet is heated to a temperature higher than its recrystallisation temperature and subsequently cooled in two steps, the first taking place by immersion in an aqueous bath, the temperature of which is between 80° C. and 150° C., cooling taking place at a speed between 25° C./sec and 180° C./sec., the product of this speed times the thickness of the strip or sheet being higher than 25, the improvement wherein the first step ends when the temperature of the strip or sheet is between 200° C. and 425° C., and the second step also takes place in an aqueous bath, at a cooling speed between 90° C./sec and 500° C./sec to a temperature between 80° C. and 150° C., the product of the thickness of the strip or sheet times the cooling speed of the second step being higher than 75.
Claim 2
Dependent Claim
158 words
In a method of continuously heat treating cold-rolled steel strip or sheets, in which the strip or sheet is heated to a temperature higher than its recrystallisation temperature and subsequently cooled in two steps, the first taking place by immersion in an aqueous bath, the temperature of which is between 80° C. and 150° C., cooling taking place at a speed between 25° C./sec and 180° C./sec., the product of this speed times the thickness of the strip or sheet being higher than 25, the improvement wherein the first step ends when the temperature of the strip or sheet is between 200° C. and 425° C., and the second step also takes place in an aqueous bath, at a cooling speed between 90° C./sec and 500° C./sec to a temperature between 80° C. and 150° C., the product of the thickness of the strip or sheet times the cooling speed of the second step being higher than 75.
Claim 3
Dependent Claim
39 words
The method of claim 1, in which the ratio of the product of rate times thickness in the second stage and the product of rate times thickness in the first stage is in the range from 1.5 to 5.
Claim 4
Dependent Claim
18 words
The method of claim 2, in which the said ratio is in the range from 2 to 4.
Claim 5
Dependent Claim
46 words
The method of claim 1, further comprising the step of: (c) annealing or overageing the sheet or strip by heating the sheet or strip to a temperature of 275° to 525° C. and holding it at that temperature for a time of 30 to 250 seconds.
Claim 6
Dependent Claim
15 words
The method of claim 4, in which the said temperature is 380° to 490° C.
Claim 7
Dependent Claim
15 words
The method of claim 4, in which the said time is 40 to 180 seconds.
Claim 8
Dependent Claim
28 words
The method of claim 4, in which the said time, t, in seconds, is related to the said temperature, T, in degrees centigrade, by the following equation: t=(94,500/T)-180.
Claim 9
Dependent Claim
29 words
The method of claim 4, including, after holding the sheet or strip at the said temperature for the said time, slowly cooling it to a temperature below 400° C.
Claim 10
Dependent Claim
17 words
The method of claim 8, in which the slow cooling is to a temperature below 350° C.
Claim 11
Dependent Claim
49 words
The method of claim 4, in which step (c) comprises heating the sheet or strip to a first temperature of 400° to 500° C., holding it at the first temperature, rapidly cooling it to a second temperature of 300° to 400° C., and holding it at the second temperature.
Claim 12
Dependent Claim
29 words
The method of claim 10, in which the rapid cooling step comprises quenching the sheet or strip in an aqueous bath at a temperature of at least 60° C.
Claim 13
Dependent Claim
15 words
The method of claim 11, in which the bath temperature is at least 80° C.
Claim 14
Dependent Claim
32 words
The method of claim 10, in which the holding time at the first temperature is at least 10 seconds and the holding time at the second temperature is at least 15 seconds.
Claim 15
Dependent Claim
17 words
The method of claim 13, in which the said holding times are each at least 20 seconds.
Claim 16
Dependent Claim
20 words
The method of claim 1, in which the steel contains max. 0.15% C, max. 0.60% Mn, and max. 0.020% Si.
Claim 17
Dependent Claim
13 words
The method of claim 15, in which the carbon content is max. 0.10%.
Claim 18
Dependent Claim
13 words
The method of claim 15, in which the manganese content is max. 0.50%.
Claim 19
Dependent Claim
15 words
The method of claim 15, in which the steel additionally contains 0.001 to 0.050% B.
Claim 20
Dependent Claim
47 words
The method of claim 18, in which the steel additionally contains nitrogen in an amount such that the boron and nitrogen contents satisfy the following equation: B=K.N where B is percentage of boron N is percentage of nitrogen K is a coefficient ranging from 1 to 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) | 1983-03-04 | 1983-09-03 | 1984-03-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-03-04 | 1987-09-03 | 1988-03-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-03-04 | 1991-09-03 | 1992-03-04 | $7700.00 | Window Closed / Lapsed |