US4159218A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for producing a dual-phase ferrite-martensite steel strip
Assignee: National Steel Corp
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Filing: 1978-08-07
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Granted: 1979-06-26
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Expires: 1998-08-07
Abstract
Abstract A dual-phase steel strip is produced by heating a hot rolled steel strip to a temperature within the intercritical temperature range, annealing the heated strip for a period of from 15 seconds to 5 minutes, and controlling the average cooling rate to about 3.6F. DEG -45F. DEG /sec. (2C. DEG -25C. DEG /sec.) down to the martensite formation temperature of about 850 DEG F.+/-100 DEG F. (454 DEG C.+/-56 DEG C.). The hot rolled strip will have a chemical composition of 0.08 to 0.12% C, 1.25 to 1.8% Mn, 0.5 to 0.7% Si, and 0.1 to 0.7% Cr, the balance being substantially Fe.
Inventors
- 👤 David A. Chatfield
- 👤 Robert R. Goodhart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:08
CPC Classifications
C; C21; C21D; C21D1/00; C21D1/18; C21D1/185; C21D8/00; C21D8/02; C21D8/0247; C21D8/0263; C21D2211/00; C21D2211/005; C21D2211/008; C21D8/0221; C21D8/0226
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
118 words
A method for producing a dual-phase steel strip having high strength and formability which comprises providing a hot rolled steel strip containing from 0.08 to 0.12% carbon, 1.25 to 1.8% manganese, 0.5 to 0.7% silicon and 0.1 to 0.7% chromium, the balance being substantially iron, heating said steel strip to a temperature within the intercritical temperature range between the A 1 transformation point and the A 3 transformation point, annealing said strip in said temperature range for a period of from 15 seconds to 5 minutes, and cooling said annealed strip with an average cooling rate of about 3.6° F.-45° F./sec. (2° C.-25° C./sec.) down to a martensite formation temperature of about 850° F.±100° F. (454° C.±56° C.).
Claim 2
Independent Claim
118 words
A method for producing a dual-phase steel strip having high strength and formability which comprises providing a hot rolled steel strip containing from 0.08 to 0.12% carbon, 1.25 to 1.8% manganese, 0.5 to 0.7% silicon and 0.1 to 0.7% chromium, the balance being substantially iron, heating said steel strip to a temperature within the intercritical temperature range between the A 1 transformation point and the A 3 transformation point, annealing said strip in said temperature range for a period of from 15 seconds to 5 minutes, and cooling said annealed strip with an average cooling rate of about 3.6° F.-45° F./sec. (2° C.-25° C./sec.) down to a martensite formation temperature of about 850° F.±100° F. (454° C.±56° C.).
Claim 3
Dependent Claim
14 words
A method according to claim 1 wherein said steel contains 0.2 to 0.4% chromium.
Claim 4
Dependent Claim
22 words
A method according to claim 1 wherein the annealing is performed within the temperature range of 1337° F.-1616° F. (725° C.-880° C.).
Claim 5
Dependent Claim
22 words
A method according to claim 3 wherein the annealing is conducted within a temperature range of 1400° F.-1499° F. (760° C.-815° C.).
Claim 6
Independent Claim
109 words
A method for producing a dual-phase ferrite-martensite steel strip having high strength and formability comprising hot rolling a steel containing from 0.08 to 0.12% carbon, 1.25 to 1.8% manganese, 0.5 to 0.7% silicon and 0.1 to 0.7% chromium, the balance being substantially iron, heating said hot rolled steel to a temperature within the intercritical range of 1337° F.-1616° F. (725° C.-880° C.), annealing the steel in said temperature range for a period from 15 seconds to 5 minutes, and cooling the steel with an average cooling rate of about 3.6° F.-45° F./sec. (2° C.-25° C./sec.), down to a martensite formation temperature of about 850° F.±100° F. (454° C.±56° C.).
Claim 7
Independent Claim
109 words
A method for producing a dual-phase ferrite-martensite steel strip having high strength and formability comprising hot rolling a steel containing from 0.08 to 0.12% carbon, 1.25 to 1.8% manganese, 0.5 to 0.7% silicon and 0.1 to 0.7% chromium, the balance being substantially iron, heating said hot rolled steel to a temperature within the intercritical range of 1337° F.-1616° F. (725° C.-880° C.), annealing the steel in said temperature range for a period from 15 seconds to 5 minutes, and cooling the steel with an average cooling rate of about 3.6° F.-45° F./sec. (2° C.-25° C./sec.), down to a martensite formation temperature of about 850° F.±100° F. (454° C.±56° C.).
Claim 8
Dependent Claim
14 words
A method according to claim 5 wherein said steel contains 0.2 to 0.4% chromium.
Claim 9
Dependent Claim
32 words
A method according to claim 5 wherein the hot rolling is conducted with a finishing temperature of about 1650° F. (900° C.) and a coiling temperature of about 1094° F. (590° C.).
Claim 10
Dependent Claim
19 words
A method according to claim 5 wherein the intercritical temperature range employed is 1400° F.-1499° F. (760° C.-815° C.).
Claim 11
Dependent Claim
17 words
A method according to claim 5 wherein the resulting dual-phase steel contains about 10-25% by weight martensite.
Claim 12
Dependent Claim
17 words
A dual-phase steel strip having high strength and formability produced according to the method of claim 1.
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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) | 1982-06-25 | 1982-12-25 | 1983-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-06-25 | 1986-12-25 | 1987-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-06-25 | 1990-12-25 | 1991-06-26 | $7700.00 | Window Closed / Lapsed |