Patent ID: 8366844
Filing Date: 2013-02-05
Classification: C22C,Y10T

Abstract:
1. A method of making a hot rolled dual phase steel sheet, comprising: (I) hot rolling a steel slab into a hot band at a hot rolling termination temperature in a range between about (A (II) cooling the hot band after completion of hot rolling at a mean rate of at least about 5° C./s (about 9° F./s) to a coiling temperature not higher than about 750° C. (about 1382° F.); and (III) coiling the hot band to form a coil at a temperature more than the martensite formation temperature obtaining a steel sheet comprising (a) a dual phase microstructure comprising a martensite phase of 11-28% by volume and a ferrite phase, (b) said composition, and (c) properties comprising a tensile strength of at least about 590 megapascals and a hole expansion ratio more than about 70%.