Abstract: A hot rolled and heat-treated steel sheet, made of a steel having a composition including, by weight percent: C: 0.03-0.18%, Mn: 6.0-11.0%, Mo: 0.05-0.5%, B: 0.0005-0.005%, S?0.010%, P?0.020%, N?0.008%, and including optionally one or more of the following elements, in weight percentage: Al<3%, Si?1.20%, Ti?0.050%, Nb=0.050%, Cr?0.5%, V?0.2%, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, the steel sheet having a microstructure including, in surface fraction, from 10% to 60% of retained austenite, from 40% to 90% of ferrite, less than 5% of martensite, carbides below 0.8%, and an inhomogeneous repartition of manganese, characterized by a manganese distribution with a slope above or equal to ?40.

Abstract: A press hardened coated steel part with high resistance to delayed fracture, the coating containing (Fex—Aly) intermetallic compounds resulting from the diffusion of iron into an aluminum or an aluminum-based alloy, or an aluminum alloy of a precoating, wherein the chemical composition of the steel includes, in weight: 0.16%?C?0.42%, 0.1%?Mn?3%, 0.07%?Si?1.60%, 0.002%?Al?0.070%, 0.02%?Cr?1.0%, 0.0005?B?0.005%, 0.002%?Mg?0.007%, 0.002%?Ti?0.11%, 0.0008%?O?0.005%, wherein (Ti)×(O)2×107?2, 0.001%?N?0.007%, 0.001%?S?0.005%, 0.001%?P?0.025% and optionally one or more elements selected from the list of: 0.005%?Ni?0.23%, 0.005%?Nb?0.060%, the remainder being Fe and unavoidable impurities, and wherein the microstructure includes at least 95% martensite.

Abstract: A cold rolled and annealed steel sheet, made of a steel having a composition including, by weight percent C: 0.03-0.18% Mn: 6.0-11.0% Al: 0.2-3% Mo: 0.05-0.5% B: 0.0005-0.005% S?0.010% P?0.020% N?0.008% and including optionally one or more of the following elements, in weight percentage: Si?1.20% Ti?0.050% Nb?0.050% Cr?0.5% V?0.2% the remainder of the composition being iron and unavoidable impurities resulting from the smelting, the steel sheet having a microstructure including, in surface fraction, from 30% to 55% of retained austenite, from 45% to 70% of ferrite, less than 5% of fresh martensite a carbon [C]A and manganese [Mn]A content in austenite, expressed in weight percent, satisfying [C]A*[Mn]A/((0.1+C %2)*(Mn %+2))?1.10 and an inhomogeneous repartition of manganese characterized by a manganese distribution with a slope above or equal to ?30.

Abstract: A press hardened coated steel part with high resistance to delayed fracture, the coating containing (Fex—Aly) intermetallic compounds resulting from the diffusion of iron into an aluminum or an aluminum-based alloy, or an aluminum alloy of a precoating, wherein the chemical composition of the steel includes, in weight: 0.16%?C?0.42%, 0.1%?Mn?3%, 0.07%?Si?1.60%, 0.002%?Al?0.070%, 0.02%?Cr?1.0%, 0.0005?B?0.005%, 0.002%?Mg?0.007%, 0.002%?Ti?0.11%, 0.0008%?O?0.005%, wherein (Ti)×(O)2×107?2, 0.001%?N?0.007%, 0.001%?S?0.005%, 0.001%?P?0.025% and optionally one or more elements selected from the list of: 0.005%?Ni?0.23%, 0.005%?Nb?0.060%, the remainder being Fe and unavoidable impurities, and wherein the microstructure includes at least 95% martensite.

Abstract: A TWIP steel sheet is provided having an austenitic matrix including by weight: 0.1?C?1.2%, 13.0?Mn<25.0%, 0.1?Si?3.0%, 0.1?Cu?5.0%, S?0.030%, P?0.080%, N?0.1%, 0.1?Al?4.0% and 0.1?V?2.50% in such way that:—when the amount of Al<2.0%, the weight ratio Al/V is between 0.2 and 8 or—when the amount of Al?2.0%, the amount of V>0.25%, and on a purely optional basis, one or more of Nb?0.5%, B?0.005%, Cr?1.0%, Mo?0.40%, Ni?1.0%, Ti?0.5%, and/or 0.06?Sn?0.2%, the remainder of the composition being made of iron and inevitable impurities resulting from elaboration.

Abstract: 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.