Arcelormittal

Arcelormittal France

Christine Colin

Sebastien Allain

Thierry Iung

Audrey Couturier

Sébastien Allain

The invention relates to a hot-rolled steel sheet having a tensile strength of greater than 1200 MPa, an R/Rratio of less than 0.75 and an elongation at break of greater than 10%, the composition of which contains, the contents being expressed by weight: 0.10%&#x2264;C&#x2264;0.25%; 1%&#x2264;Mn&#x2264;3%; Al&#x2265;0.015%; Si&#x2264;1.985%; Mo&#x2264;0.30%; Cr&#x2264;1.5%; S&#x2264;0.015%; P&#x2264;0.1%; Co&#x2264;1.5%; B&#x2264;0.005%; it being understood that 1%&#x2264;Si+Al&#x2264;2%; Cr+(3&#xd7;Mo)&#x2265;0.3%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting, the microstructure of the steel consisting of at least 75% bainite, residual austenite in an amount equal to or greater than 5% and martensite in an amount equal to or greater than 2%.

Process for manufacturing steel sheet

The invention relates to a hot-rolled steel sheet having a tensile strength of greater than 1200 MPa, an R/Rratio of less than 0.75 and an elongation at break of greater than 10%, the composition of which contains, the contents being expressed by weight: 0.10%&#x2266;C&#x2266;0.25%; 1%&#x2266;Mn&#x2266;3%; Al&#x2267;0.015%; Si&#x2266;1.985%; Mo&#x2266;0.30%; Cr&#x2266;1.5%; S&#x2266;0.015%; P&#x2266;0.1%; Co&#x2266;1.5%; B&#x2266;0.005%; it being understood that 1%&#x2266;Si+Al&#x2266;2%; Cr+(3&#xd7;Mo)&#x2267;0.3%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting, the microstructure of the steel consisting of at least 75% bainite, residual austenite in an amount equal to or greater than 5% and martensite in an amount equal to or greater than 2%.

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Maizieres-les-Metz, France

Christine Colin