ArcelorMittal S.A.
COLD ROLLED AND HEAT-TREATED STEEL SHEET AND METHOD OF MANUFACTURING THE SAME

Abstract:

A cold rolled and heat-treated steel sheet having a composition including, by weight percent: C 0.3-0.4%, Mn 2.0-2.6%, Si: 0.8-1.6%, Al 0.01-0.6%, Mo 0.15-0.5%, Cr 0.3-1.0%, Nb.ltoreq.0.06%, Ti.ltoreq.0.06%, Ni.ltoreq.0.8%, S.ltoreq.0.010%, P.ltoreq.0.020% and N.ltoreq.0.008%, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, and having a microstructure consisting of, in surface fraction: between 15% and 30% of retained austenite, said retained austenite having a carbon content of at least 0.7%, between 70% and 85% of tempered martensite, at most 5% of fresh martensite and at most 5% of bainite. It also deals with a manufacturing method thereof.