STEEL SHEET WITH HIGH MECHANICAL STRENGTH, DUCTILITY AND FORMABILITY PROPERTIES, PRODUCTION METHOD AND USE OF SUCH SHEETS

The invention relates to the production of a cold-rolled steel sheet with a strength of more than 1000 MPa, a uniform elongation of more than 12% and a V-pliability of more than 90°, the composition of which comprises the following with the amounts expressed by weight: 0.15% = C < 0.25%, 1.8% = M...

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Bibliographische Detailangaben
Hauptverfasser:	HENNION, ARNAUD, MAHIEU, JAN, MASTRORILLO, THIERRY, CROUVIZIER, MICKAEL DENIS, ALLAIN, SEBASTIEN
Format:	Patent
Sprache:	eng ; fre
Schlagworte:	ALLOYS CHEMISTRY FERROUS OR NON-FERROUS ALLOYS GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS LAYERED PRODUCTS LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT ORNON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS METALLURGY METALLURGY OF IRON MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS PERFORMING OPERATIONS TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION TECHNICAL SUBJECTS COVERED BY FORMER USPC TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS TRANSPORTING TREATMENT OF ALLOYS OR NON-FERROUS METALS
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Beschreibung
Zusammenfassung:	The invention relates to the production of a cold-rolled steel sheet with a strength of more than 1000 MPa, a uniform elongation of more than 12% and a V-pliability of more than 90°, the composition of which comprises the following with the amounts expressed by weight: 0.15% = C < 0.25%, 1.8% = Mn = 3.0%, 1.2% = Si = 2%, 0% < Al = 0.10%, 0% = Cr = 0.50%, 0% = Cu = 1%, 0% = Ni = 1%, 0% = S - 0.005%, 0% = P < 0.020%, Nb = 0.015%, Ti = 0.020%, V = 0.015%, Co = 1%, N = 0.008%, B = 0.001%, with the understanding that Mn+Ni+Cu = 3%, the rest of the composition consisting of iron and inevitable impurities resulting from the production method. By area, the microstructure consists of between 5 and 20% of polygonal ferrite, between 10 and 15% of residual austenite, and between 5 and 15% of martensite, the remainder consisting of laths of bainite comprising carbides between said laths, such that the number N of inter-lath carbides larger than 0.1 micrometres in size per unit area is 50,000 mm-2 or less. L'invention concerne la fabrication d'une tôle d'acier laminée à froid de résistance supérieure à 1000 MPa, d'allongement réparti supérieur à 12%, et de pliabilité en V supérieure à 90°, dont la composition comprend, les teneurs étant exprimées en poids : 0.15%= C < 0,25%, 1,8%= Mn= 3,0%, 1,2%= Si= 2%, 0% < Al= 0,10%, 0%= Cr= 0,50%, 0 %= Cu= 1%, 0 %= Ni= 1 %, 0%= S -.0,005%, 0 %= P < 0,020%, Nb=0,015%, Ti=0,020%. V=0,015%, Co=1%, N=0,008%. B=0,001% étant entendu que Mn+Ni+Cu= 3%, le reste de la composition étant constitué de fer et d'impuretés inévitables résultant de l'élaboration. La microstructure est constituée, en proportions surfaciques, de 5 à 20 % de ferrite polygonale, de 10 à 15% d'austénite résiduelle, de 5 à 15 % de martensite, le solde étant constitué de bainite sous forme de lattes et comprenant entre lesdites lattes des carbures tels que le nombre N des carbures ïnter-lattes de taille supérieure à 0,1 micromètre par unité de surface est inférieur ou égal à 50000 / mm2.