ArcelorMittal S.A.
Cold rolled and heat treated steel sheet and a method of manufacturing thereof

Abstract:

A cold rolled and heat treated steel sheet having a composition with the following elements, expressed in percentage by weight 0.10%.ltoreq.Carbon.ltoreq.0.5%, 1%.ltoreq.Manganese.ltoreq.3.4%, 0.5%.ltoreq.Silicon.ltoreq.2.5%, 0.03%.ltoreq.Aluminum.ltoreq.1.5%, Sulfur.ltoreq.0.003%, 0.002%.ltoreq.Phosphorus.ltoreq.0.02%, Nitrogen.ltoreq.0.01% and can contain one or more of the following optional elements 0.05%.ltoreq.Chromium.ltoreq.1%, 0.001%.ltoreq.Molybdenum.ltoreq.0.5%, 0.001%.ltoreq.Niobium.ltoreq.0.1%, 0.001%.ltoreq.Titanium.ltoreq.0.1%, 0.01%.ltoreq.Copper.ltoreq.2%, 0.01%.ltoreq.Nickel.ltoreq.3%, 0.0001%.ltoreq.Calcium.ltoreq.0.005%, Vanadium.ltoreq.0.1%, Boron.ltoreq.0.003%, Ceriums.ltoreq.0.1%, Magnesiums.ltoreq.0.010%, Zirconiums.ltoreq.0.010% the remainder composition being composed of iron and the unavoidable impurities caused by processing, and a microstructure of the said rolled steel sheet having by area fraction, 10 to 30% Residual Austenite, 5 to 50% Annealed Bainite, 10 to 40% of Bainite, 1% to 20% Quenched Martensite, and less than 30% Tempered Martensite where the combined presence of Bainite and Residual Austenite shall be 30% or more.