Arcelormittal

Nicolas Charbonnier

Jean-Christophe Hell

Marie-Christine Theyssier

Thierry Iung

Sebastien Allain

Gerard Petitgand

Blandine Remy

Gérard Petitgand

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 TWIP steel is provided including: (A) feeding of a slab comprising by weight: 0.5&#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%, 0.051%&#x2264;Al&#x2264;4.0%, 0.1&#x2264;V&#x2264;2.5%, and on a purely optional basis, one or more of 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%, 0.06&#x2264;Sn&#x2264;0.2%, the remainder of the composition being made of iron and inevitable impurities resulting from the elaboration, (B) reheating the slab and hot rolling the slab to provide a hot rolled slab, (C) coiling the hot rolled slab to provide a coiled slab, (D) first cold-rolling the coiled slab to provide a first cold rolled slab, (E) recrystallization annealing the first cold rolled slab such that an annealed steel sheet having an UTSis obtained and (F) second cold-rolling the annealed steel sheet with a reduction rate CR % that satisfies the following equation A: 1216.472&#x2212;0.98795*UTS&#x2264;(&#x2212;0.0008*UTS+1.0124)*CR %+(0.0371*UTS&#x2212;29.583)*CR %.

Method for the manufacture of TWIP steel sheet having an austenitic matrix

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Metz, France

Nicolas Charbonnier