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AssigneeUnited States Steel Corporation
InventorsDavid Paul Hoydick, Eduardo Augusto Silva, Matthew Michael McCosby
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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.
A high strength rolled steel sheet product comprising from 0.12 to 0.5 weight percent C, from 1 to 3 weight percent Mn, from 0.8 to 3 weight percent of a combination of Si and Al, balance Fe wherein the steel sheet product has been subjected to a two-step annealing process, comprises ferrite, substantially equiaxed retained austenite grains having an average aspect ratio of less than 2.0:1, and less than 15 volume percent of fresh, untempered martensite, is substantially free of tempered martensite, and has a combination of ultimate tensile strength and total elongation UTS•TE of greater than 25,000 MPa % and a hole expansion ratio of at least 30 percent.
Dependencies are inferred from the claim text.