ArcelorMittal S.A.
Steel sheet having high tensile strength and ductility

Abstract:

A hot-rolled steel sheet having a tensile strength greater than 800 MPa and an elongation at break greater than 10% is provided. A composition of the steel includes, the contents being expressed by weight: 0.050%.ltoreq.C.ltoreq.0.090%, 1%.ltoreq.Mn.ltoreq.2%, 0.015%.ltoreq.Al.ltoreq.0.050%, 0.1%.ltoreq.Si.ltoreq.0.3%, 0.10%.ltoreq.Mo.ltoreq.0.40%, S.ltoreq.0.010%, P.ltoreq.0.025%, 0.003%.ltoreq.N.ltoreq.0.009%, 0.12%.ltoreq.V.ltoreq.0.22%, Ti.ltoreq.0.005%, Nb.ltoreq.0.020% and optionally, Cr.ltoreq.0.45%. A balance of the composition includes iron and inevitable impurities resulting from the smelting. A microstructure of the sheet or part includes, as a surface fraction, at least 80% upper bainite, and a remainder includes lower bainite, martensite and residual austenite. A sum of the martensite and residual austenite, as a surface fraction, is less than 5%.