Arcelormittal

Arcelormittal France

Thierry Iung

Sebastien Allain

Audrey Couturier

Christine Colin

Jean-Christophe Hell

Marie-Christine Theyssier

Gerard Petitgand

Nicolas Charbonnier

Blandine Remy

Colin Scott

Sébastien Allain

A method for manufacturing a recovered steel sheet having an austenitic matrix presenting at least one mechanical property (M) equal or above a target value Mis provided. The method includes a calibrating process involving heat treatments on at least 2 samples of the steel, corresponding to Pareq values P, submitting said samples to X-ray diffraction so as to obtain spectrums including a main peak whose width at mid height FWHM is being measured, measuring a mechanical property (M) of said samples, measuring a recovery or recrystallization state of each sample, drawing a curve of M as a function of FWMH in a domain where the samples are recovered from 0 to 100%, but not recrystallized. The method further includes calculating a FWHMcorresponding to a target mechanical property M, determining a pareq value Pof the heat treatment to perform to reach Mand selecting a time tand a temperature T°corresponding to the Pvalue. The method further includes feeding a recrystallized steel sheet having a M, cold-rolling the recrystallized steel sheet in order to obtain a steel sheet having a Mand annealing the cold rolled steel sheet at a temperature T°during a time t.

Method for producing a TWIP steel sheet having an austenitic microstructure

A method for the manufacture of a cold rolled, recovered TWIP steel sheet coated with a metallic coating is provided including the following steps: (A) the feeding of a slab having the following composition: 0.1&#x3c;C&#x3c;1.2%, 13.0&#x2264;Mn&#x3c;25.0%, S&#x2264;0.030%, P&#x2264;0.080%, N&#x2264;0.1%, Si&#x2264;3.0%, and on a purely optional basis, one or more elements such as Nb&#x2264;0.5%, B&#x2264;0.005%, Cr&#x2264;1.0%, Mo&#x2264;0.40%, Ni&#x2264;1.0%, Cu&#x2264;5.0%, Ti&#x2264;0.5%, V&#x2264;2.5%, Al&#x2264;4.0%, 0.06&#x2264;Sn&#x2264;0.2%, the remainder of the composition making up of iron and inevitable impurities resulting from elaboration; (B) Reheating such slab and hot rolling it; (C) A coiling step; (D) A first cold-rolling; (E) A recrystallization annealing; (F) A second cold-rolling; and (G) A recovery heat treatment performed by hot-dip coating.

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%.

Process for manufacturing steel sheet having very high strength, ductility and toughness characteristics, and sheet thus produced

Growing community of inventors

Jarny, France

Thierry Iung