US4067756A
Expired / Lapsed
US
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High strength, high ductility low carbon steel
Assignee: United States Department of Energy
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Filing: 1976-11-02
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Granted: 1978-01-10
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Expires: 1996-11-02
Abstract
Abstract A high strength, high ductility low carbon steel consisting essentially of iron, 0.05-0.15 wt% carbon, and 1-3 wt% silicon. Minor amounts of other constituents may be present. The steel is characterized by a duplex ferrite-martensite microstructure in a fibrous morphology. The microstructure is developed by heat treatment consisting of initial austenitizing treatment followed by annealing in the (α + γ) range with intermediate quenching.
Inventors
- 👤 Jayoung Koo
- 👤 Gareth Thomas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 02:57
CPC Classifications
C; C21; C21D; C21D1/00; C21D1/18; C21D1/185
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
139 words
A method for producing a high strength, high ductility steel characterized by a duplex ferrite-martensite microstructure in a fibrous morphology which comprises: heating a steel composition consisting essentially of iron, from about 0.05 to about 0.15 wt% carbon and from about 1 to about 3 wt% silicon at a temperature, T 1 , above the critical temperature at which austenite forms for a period of time to substantially completely austenitize the steel; quenching the resulting austenitic composition to substantially completely transform the austenite to martensite; heating the resulting martensitic composition at a temperature, T 2 , in the (α+γ) range for a period of time sufficient to transform the martensite to a mixture of ferrite and austenite; and quenching the resulting ferritic-austenitic composition to transform the austenite to martensite; thereby developing said duplex ferrite-martensite microstructure in a fibrous morphology.
Claim 2
Independent Claim
139 words
A method for producing a high strength, high ductility steel characterized by a duplex ferrite-martensite microstructure in a fibrous morphology which comprises: heating a steel composition consisting essentially of iron, from about 0.05 to about 0.15 wt% carbon and from about 1 to about 3 wt% silicon at a temperature, T 1 , above the critical temperature at which austenite forms for a period of time to substantially completely austenitize the steel; quenching the resulting austenitic composition to substantially completely transform the austenite to martensite; heating the resulting martensitic composition at a temperature, T 2 , in the (α+γ) range for a period of time sufficient to transform the martensite to a mixture of ferrite and austenite; and quenching the resulting ferritic-austenitic composition to transform the austenite to martensite; thereby developing said duplex ferrite-martensite microstructure in a fibrous morphology.
Claim 3
Dependent Claim
36 words
A method according to claim 1 wherein T 1 is in the range from about 1050° C to about 1170° C and T 2 is in the range from about 800° C to about 1000° C.
Claim 4
Dependent Claim
18 words
A method according to claim 1 wherein the silicon content of the steel composition is about 2 wt%.
Claim 5
Dependent Claim
43 words
A method according to claim 1 wherein the martensitic composition is heated in the (α+γ) range under conditions to provide a mixture of ferrite and austenite such that the subsequent quenching step results in a microstructure containing 20 - 50 volume percent martensite.
Claim 6
Dependent Claim
38 words
A high strength, high ductility steel composition consisting essentially of iron, from about 0.05 to about 0.15 wt% carbon, and from about 1 to 3 wt% silicon and characterized by a duplex ferrite-martensite microstructure in a fibrous morphology.
Claim 7
Dependent Claim
38 words
A high strength, high ductility steel composition consisting essentially of iron, from about 0.05 to about 0.15 wt% carbon, and from about 1 to 3 wt% silicon and characterized by a duplex ferrite-martensite microstructure in a fibrous morphology.
Claim 8
Dependent Claim
16 words
A composition according to claim 5 wherein said microstructure contains 20 - 50 volume percent martensite.
Claim 9
Dependent Claim
103 words
A composition according to claim 5 wherein said microstructure is developed by a heat treatment process comprising: heating said composition at a temperature, T 1 , above the critical temperature at which austenite forms for a period of time sufficient to substantially completely austenitize the steel; quenching the resulting austenitic composition to substantially completely transform the austenite to martensite; heating the resulting martensitic composition at a temperature, T 2 , in the (α+γ) range for a period of time sufficient to transform the martensite to a mixture of ferrite and austenite; and quenching the resulting ferritic-austenitic composition to transform the austenite to martensite.
Claim 10
Dependent Claim
36 words
A composition according to claim 7 wherein T 1 is in the range from about 1050° C to about 1170° C and T 2 is in the range from about 800° C to about 1000° C.
Claim 11
Dependent Claim
35 words
A high strength, high ductility steel composition consisting essentially of iron, from about 0.05 to about 0.15 wt% carbon, and about 2 wt% silicon and characterized by a duplex ferrite-martensite microstructure in a fibrous morphology.
Claim 12
Dependent Claim
35 words
A high strength, high ductility steel composition consisting essentially of iron, from about 0.05 to about 0.15 wt% carbon, and about 2 wt% silicon and characterized by a duplex ferrite-martensite microstructure in a fibrous morphology.
Claim 13
Dependent Claim
16 words
A composition according to claim 9 wherein said microstructure contains 20 - 50 volume percent martensite.
Claim 14
Dependent Claim
103 words
A composition according to claim 9 wherein said microstructure is developed by a heat treatment process comprising: heating said composition at a temperature, T 1 , above the critical temperature at which austenite forms for a period of time sufficient to substantially completely austenitize the steel; quenching the resulting austenitic composition to substantially completely transform the austenite to martensite; heating the resulting martensitic composition at a temperature, T 2 , in the (α+γ) range for a period of time sufficient to transform the martensite to a mixture of ferrite and austenite; and quenching the resulting ferritic-austenitic composition to transform the austenite to martensite.
Claim 15
Dependent Claim
36 words
A composition according to claim 11 wherein T 1 is in the range from about 1050° C to about 1170° C and T 2 is in the range from about 800° C to about 1000° C.
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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) | 1981-01-09 | 1981-07-11 | 1982-01-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-09 | 1985-07-11 | 1986-01-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-09 | 1989-07-11 | 1990-01-10 | $7700.00 | Window Closed / Lapsed |