High strength, high ductility low carbon steel
AssigneeThe United States of America as represented by the United States Department of Energy
InventorsJayoung Koo, Gareth Thomas
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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 (.alpha. + .gamma.) range with intermediate quenching.
Claims12
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.sub.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.sub.2, in the (.alpha.+.gamma.) 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.
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.
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.
Dependencies are inferred from the claim text.