Abstract: A method for the fabrication of a hot rolled steel includes providing a liquid metal comprising a certain chemical composition; carrying out a vacuum or SiCa treatment, the chemical composition including, expressed by weight 0.0005%?Ca?0.005%, if a SiCA treatment is carried out; dissolving quantities of Ti and N in the liquid metal so as to satisfy (% [Ti])×(% [N])<6.10?4%2; casting the steel to obtain a cast semi-finished product; rolling the cast semi-finished product with an end-of-rolling temperature between 880° C. and 930° C., a reduction rate of the penultimate pass being less than 0.25, and a start-of-rolling temperature of the penultimate pass being less than 960° C. to obtain a hot-rolled product, then cooling the hot rolled product at a rate between 20 and 150° C./s to obtain a hot rolled steel sheet; and coiling the hot rolled product to obtain a hot rolled steel sheet.

Abstract: A method for the fabrication of a hot rolled steel includes providing a liquid metal comprising a certain chemical composition; carrying out a vacuum or SiCa treatment, the chemical composition including, expressed by weight 0.0005%?Ca?0.005%, if a SiCA treatment is carried out; dissolving quantities of Ti and N in the liquid metal so as to satisfy (% [Ti])×(% [N])<6.10?4%2; casting the steel to obtain a cast semi-finished product; rolling the cast semi-finished product with an end-of-rolling temperature between 880° C. and 930° C., a reduction rate of the penultimate pass being less than 0.25, and a start-of-rolling temperature of the penultimate pass being less than 960° C. to obtain a hot-rolled product, then cooling the hot rolled product at a rate between 20 and 150° C./s to obtain a hot rolled steel sheet; and coiling the hot rolled product to obtain a hot rolled steel sheet.

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%?Mo?0.35%, 0.15<C?0.6% when 0.05%?Mo?0.11%, or 0.10%?Cr?0.6% when 0.11%<Mo?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%.

Abstract: The present invention provides a hot rolled steel sheet. The hot rolled steel sheet has a yield stress greater than 680 MPa and less than or equal to 840 MPa, at least in a direction transverse to a rolling direction, 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: 0.04%?C?0.08% 1.2%?Mn?1.9% 0.1%?Si?0.3% 0.07%?Ti?0.125% 0.05%?Mo?0.35% 0.15%<Cr?0.6% when 0.05%?Mo?0.11%, or 0.10%?Cr?0.6% when 0.11%<Mo?0.35% Nb?0.045% 0.005%?Al?0.1% 0.002%?N?0.01% S?0.004% P?0.020% and optionally 0.001%?V?0.2%. The remainder includes iron and unavoidable impurities resulting from processing. The microstructure includes granular bainite, the area percentage of which is greater than 70%, and ferrite, the area percentage of which is less than 20%, with the remainder, if any, including lower bainite, martensite and residual austenite.