United States Steel Corporation

David Paul Hoydick

Eduardo Augusto Silva

Matthew Michael McCosby

The present invention provides steel sheet products having controlled compositions that are subjected to two-step annealing processes to produce sheet products having desirable microstructures and favorable mechanical properties such as high strength and ultra-high formability. Steels processed in accordance with the present invention exhibit combined ultimate tensile strength and total elongation (UTS·TE) properties of greater than 25,000 MPa %. Steels with these properties fall into the category of Generation 3 advanced high strength steels, and are highly desired by various industries including automobile manufacturers.

Annealing processes for making high strength steel products

The present invention provides steel sheet products having controlled compositions that are subjected to two-step annealing processes to produce sheet products having desirable microstructures and favorable mechanical properties such as high strength and ultra-high formability. The steel sheet products may be cold rolled or hot rolled. Steels processed in accordance with the present invention exhibit favorable combined ultimate tensile strength and total elongation (UTS•TE) properties, and may fall into the category of Generation 3 advanced high strength steels, desirable in various industries including automobile manufacturers.

High strength annealed steel products and annealing processes for making the same

Methods of producing high strength continuously cast hot rolled steel sheet products are disclosed. The methods include continuously casting a steel slab and then hot rolling with finish rolling on a hot strip mill, quenching on the hot strip mill to form a predominantly matrensitic microstructure, and performing a thermal cycling step including soaking at an intercritical temperature followed by holding at a lower temperature. The resultant hot rolled steel sheet products have a microstructure comprising ferrite and retained austenite. Steels processed in accordance with the present invention exhibit favorable combined ultimate tensile strength and total elongation (UTS&#xb7;TE) properties, and may fall into the category of Generation 3 advanced high strength steels, desirable in various industries including automobile manufacturers.

Methods of producing continuously cast hot rolled high strength steel sheet products

The present invention provides steel sheet products having controlled compositions that are subjected to two-step annealing processes to produce sheet products having desirable microstructures and favorable mechanical properties such as high strength and ultra-high formability. Steels processed in accordance with the present invention exhibit combined ultimate tensile strength and total elongation (UTS&#xb7;TE) properties of greater than 25,000 MPa-%. Steels with these properties fall into the category of Generation 3 advanced high strength steels, and are highly desired by various industries including automobile manufacturers.

High strength annealed steel products

High strength steel products and annealing processes for making the same

Dual phase steel sheet is made using a time/temperature cycle including a soak at about A+45&#xb0; F. to A+135&#xb0; F. and a hold at 850-940F, where the steel has the composition in weight percent, carbon: 0.02-0.20; aluminum: 0.010-0.150; titanium: 0.01 max; silicon: 0.5 max; phosphorous: 0.060 max; sulfur: 0.030 max; manganese: 0.8-2.40; chromium: 0.03-1.50; molybdenum: 0.03-1.50; with the provisos that the amounts of manganese, chromium and molybdenum have the relationship: (Mn+6Cr+10 Mo)=at least 3.5%. The sheet is preferably in the form of a strip suitable for coating in a continuous galvanizing or galvannealing line, and the product is predominantly ferrite and martensite. The strip may be galvanized or galvannealed at a temperature within thirty degrees F. of the temperature of the bath.

Dual phase steel strip suitable for galvanizing

Dual phase steel sheet is made using a time/temperature cycle including a soak at about 1340-1425F and a hold at 850-920F, where the steel has the composition in weight percent, carbon: 0.02-0.20; aluminum: 0.010-0.150; titanium: 0.01 max; silicon: 0.5 max; phosphorous: 0.060 max; sulfur: 0.030 max; manganese: 1.5-2.40; chromium: 0.03-1.50; molybdenum: 0.03-1.50; with the provisos that the amounts of manganese, chromium and molybdenum have the relationship: Mn&plus;6Cr&plus;10Mo)&equals;at least 3.5%. The sheet is preferably in the form of a strip treated in a continuous galvanizing or galvannealing line, and the product is predominantly ferrite and martensite.

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Pittsburgh, PA, United States of America

David Paul Hoydick