ArcelorMittal S.A.
Hot rolled steel sheet and associated manufacturing method

Abstract:

The present invention provides a hot rolled steel sheet with yield stress greater than 680 MPa and less than or equal to 840 MPa a tensile strength between 780 MPa and 950 MPa, elongation at failure greater than 10% and hole-expansion ratio (Ac) greater than or equal to 45%. The chemical composition includes, with the contents expressed by weight: 0.05%.ltoreq.Mo.ltoreq.0.35%, 0.15<C.ltoreq.0.6% when 0.05%.ltoreq.Mo.ltoreq.0.11%, or 0.10%.ltoreq.Cr.ltoreq.0.6% when 0.11%<Mo.ltoreq.0.35%. The microstructure includes at least 70% granular bainite, less than 20% ferrite, with the remainder, if any, including lower bainite, martensite and residual austenite. The sum of the martensite and residual austenite contents is less than 5%.