Patent ID: 9157138
Filing Date: 2015-10-13
Classification: B32B,C21D,C22C,C23C,Y10T

Abstract:
1. A complex metallographic structured cold rolled steel comprising: (a) a composition comprising the following elements by weight: carbon in a range from greater than 0.05% to about 0.2%, manganese in a range from about 0.2% to about 3.5%, phosphorous less than or equal to about 0.1%, sulfur less than or equal to about 0.03%, silicon less than or equal to about 1.2%, aluminum in a range from about 0.01% to about 0.10%, nitrogen less than or equal to about 0.02%, copper less than or equal to about 0.8%, vanadium less than or equal to about 0.12%, one chosen from molybdenum, chromium, nickel, and a combination thereof, in a range between about 0.05% and about 3.5%, and one chosen from titanium, niobium and a combination thereof, in a range between about 0.005% and about 0.8%, wherein, if present, titanium (Ti) is present with nitrogen (N) and sulfur (S) satisfying a relationship Ti* greater than or equal to about 0.01% and less than or equal to about 0.6%, where Ti* equals (Ti-(24/7)N-(3/2)S), and the balance of the composition comprising iron and incidental ingredients; (b) a multi-phase microstructure having in combination ferrite, martensite between about 3% and about 65% by volume, and at least one microstructure selected from the group consisting of bainite and retained austenite, and having fine precipitates selected from the group of TiC, NbC, TiN, NbN, (Ti.Nb)C, (Ti.Nb)N and (Ti.Nb)(C.N) particles having at least 50% smaller than 20 nm in size, and (c) physical properties comprising tensile strength greater than about 780 megapascals and at least one of the following properties of elongation greater than about 10%, yield ratio greater than about 70%, and hole expansion ratio greater than about 50%.