Abstract: Provided is a steel sheet having: ferrite and pearlite composing 80% or more, in area fraction, of the microstructure; yield strength of 60 ksi or more; elongation of at least 23%; an n-value of at least 0.14; incidental impurities; and, in weight percent: C: 0.03˜0.10 Si: 0˜0.6 Mn: 0.5˜1.5 Cu: 0˜1.0 Ni: 0˜1.0 Nb: 0˜0.06 Ti: 0˜0.1 Mo: 0˜0.5% Cr: 0˜1.0 Al: 0˜0.06 N: 0.0001˜0.006 Ca: 0˜0.006 P: 0˜0.02 S: 0˜0.005.
Abstract: A flat rolled, high strength, formable steel product has a yield strength of at least about 100 ksi. The product has sufficient formability such that it can withstand a longitudinal or transverse 180° bend of less than 1.0 times its thickness and is preferably comprised of a high strength, low alloy steel composition containing a vanadium-nitride microalloy. The steel product is preferably produced by cold rolling a first steel product having a yield strength of at least about 70 ksi and a n-value from about 0.1 to about 0.16. Cold rolling of the first steel product reduces its thickness and increases its yield strength to at least 100 ksi.
Abstract: A process and apparatus are disclosed for manufacturing high strength low alloy (HSLA) flat rolled steel products having high yield strength and formability. A preferred process comprises the formation of an as-cast product; reducing the thickness of the as cast product in a roughing mill; holding the temperature of the rough-reduced product at a temperature sufficient to permit substantially complete recrystallization of austenite grains in the rough-reduced product; followed by a final reduction step in a hot rolling strip mill. In this process, there is little or no precipitation of microalloy until after the material passes through the strip mill and therefore the material being rolled is relatively soft compared to known processes. Therefore, less power is required to roll the material to its final dimensions, with a corresponding improvement in dimensional control.