ArcelorMittal S.A.
COLD ROLLED AND COATED STEEL SHEET AND A METHOD OF MANUFACTURING THEREOF

Abstract:

A cold rolled and heat treated steel sheet having a composition having the following elements: 0.13%.ltoreq.Carbon.ltoreq.0.18%, 1.1%.ltoreq.Manganese.ltoreq.1.8%, 0.5%.ltoreq.Silicon.ltoreq.0.9%, 0.6%.ltoreq.Aluminum.ltoreq.1%, 0.002%.ltoreq.Phosphorus.ltoreq.0.02%, 0%.ltoreq.Sulfur.ltoreq.0.003%, 0%.ltoreq.Nitrogen.ltoreq.0.007% 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%, 0%.ltoreq.Vanadium.ltoreq.0.1%, 0%.ltoreq.Boron.ltoreq.0.003%, 0%.ltoreq.Cerium.ltoreq.0.1%, 0%.ltoreq.Magnesium.ltoreq.0.010%, 0%.ltoreq.Zirconium.ltoreq.0.010%, the remainder composition being iron and unavoidable impurities caused by processing, the microstructure of the steel sheet being in area fraction, 60 to 75% Ferrite, 20 to 30% Bainite, 10 to 15% Residual Austenite, and 0% to 5% Martensite, wherein the cumulated amounts of Residual Austenite and Ferrite is between 70% and 80%.