METHOD FOR PRODUCING A TWIP STEEL SHEET HAVING AN AUSTENITIC MICROSTRUCTURE

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 Mtarget is provided. The method includes a calibrating process involving heat 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 FWHMtarget corresponding to a target mechanical property Mtarget, determining a pareq value Ptarget of the heat treatment to perform to reach Mtarget and selecting a time ttarget and a temperature T°target corresponding to the Ptarget value. The method further includes feeding a recrystallized steel sheet having a Mrecrystallization, cold-rolling the recrystallized steel sheet in order to obtain a steel sheet having a Mcold-roll and annealing the cold rolled steel sheet at a temperature T°target during a time ttarget.