US4325751A
Expired / Lapsed
US
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Method for producing a steel strip composed of a dual-phase steel
Assignee: SSAB AB
•
Filing: 1980-05-12
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Granted: 1982-04-20
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Expires: 2000-05-12
Abstract
Abstract A steel strip displaying high strength and formability properties is fabricated by coiling a steel strip which has been previously processed through a hot-strip mill from an initial steel having a very low amount of alloying compounds and having a temperature of between 750° and 900° C., the coiled steel strip being maintained at a temperature of between 800° and 650° C. for a period of at least one minute, and thereafter cooled to a temperature of below 450° C., the cooling being accomplished at a rate exceeding 10° C./second.
Inventors
- 👤 Erik A. A. Josefsson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:34
CPC Classifications
C; C21; C21D; C21D8/00; C21D8/02; C21D8/0221; C21D8/0226; C21D2211/00; C21D2211/005; C21D2211/008; C21D8/0247; C21D8/0263
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
163 words
A method of forming a steel strip which displays high strength and formability properties, the steel in said steel strip comprising a dual-phase steel containing mostly fine-grained ferrite with grains of martensite dispersed therein, which method comprises (a) processing an initial steel which comprises 0.05-0.20% carbon, 0.50-2.0% silicon, 0.50-1.5% manganese, 0-1.5% chromium, 0-0.15% vanadium, 0-0.15% molybdenum, 0-0.04% titanium, 0-0.02% niobium, balance of iron and normal impurities through a hot-strip mill so as to form a hot steel strip, (b) cooling the hot steel strip of step (a) to a temperature of between 800° and 650° C., (c) coiling the steel strip of step (b), (d) maintaining the temperature of the coiled steel strip of step (c) within the range of 800° and 650° C. for a time period of more than one minute, (e) uncoiling the steel strip of step (d), and (f) cooling the steel strip from step (e) to a temperature of below 450° C. at a rate exceeding 10° C./second.
Claim 2
Independent Claim
163 words
A method of forming a steel strip which displays high strength and formability properties, the steel in said steel strip comprising a dual-phase steel containing mostly fine-grained ferrite with grains of martensite dispersed therein, which method comprises (a) processing an initial steel which comprises 0.05-0.20% carbon, 0.50-2.0% silicon, 0.50-1.5% manganese, 0-1.5% chromium, 0-0.15% vanadium, 0-0.15% molybdenum, 0-0.04% titanium, 0-0.02% niobium, balance of iron and normal impurities through a hot-strip mill so as to form a hot steel strip, (b) cooling the hot steel strip of step (a) to a temperature of between 800° and 650° C., (c) coiling the steel strip of step (b), (d) maintaining the temperature of the coiled steel strip of step (c) within the range of 800° and 650° C. for a time period of more than one minute, (e) uncoiling the steel strip of step (d), and (f) cooling the steel strip from step (e) to a temperature of below 450° C. at a rate exceeding 10° C./second.
Claim 3
Dependent Claim
25 words
A method according to claim 1 wherein the hot steel strip is cooled in step (b) to a temperature of between 750° and 650° C.
Claim 4
Dependent Claim
29 words
A method according to claim 1 wherein the steel strip coming out of the hot-strip mill in step (a) has a temperature of between 750° C. and 900° C.
Claim 5
Dependent Claim
52 words
A method according to claim 1 wherein the temperature of the steel strip in step (b) is maintained at a temperature of between 800° and 650° C. for a time period sufficient to cause at least 80% of the ferrite in the steel which would normally form during slow cooling to precipitate.
Claim 6
Dependent Claim
43 words
A method according to claim 1 wherein the cooling in step (f) is accomplished at a sufficient rate that at most 5% of the amount of austenite remaining in the steel of the coiled steel strip after step (e) is transformed into pearlite.
Claim 7
Dependent Claim
43 words
A method according to claim 1 wherein the cooling in step (b) is accomplished while the steel strip passes through a first cooling device, and wherein the cooling in step (f) is accomplished while the steel strip passes through a second cooling device.
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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) | 1985-04-19 | 1985-10-19 | 1986-04-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-04-19 | 1989-10-19 | 1990-04-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-04-19 | 1993-10-19 | 1994-04-20 | $7700.00 | Window Closed / Lapsed |