STEEL SHEET HAVING VERY HIGH MECHANICAL PROPERTIES OF STRENGTH AND DUCTILITY, MANUFACTURING METHOD AND USE OF SUCH SHEETS

The invention relates to the manufacture of a cold-rolled steel sheet having a strength of more than 900 MPa, an elastic limit of more than 700 MPa and distributed elongation of more than 12 %, the composition of which includes, the contents being expressed as weight percentages: 0.26 % ≤ C ≤ 0.45 %...

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Bibliographische Detailangaben
Hauptverfasser:	ALLAIN, SÉBASTIEN, YVES, PIERRE, HELL, JEANRISTOPHE, FRANÇOIS
Format:	Patent
Sprache:	eng ; fre
Schlagworte:	ALLOYS CHEMICAL SURFACE TREATMENT CHEMISTRY COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING MATERIAL WITH METALLIC MATERIAL COATING METALLIC MATERIAL DIFFUSION TREATMENT OF METALLIC MATERIAL FERROUS OR NON-FERROUS ALLOYS GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS METALLURGY METALLURGY OF IRON MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION TREATMENT OF ALLOYS OR NON-FERROUS METALS
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Beschreibung
Zusammenfassung:	The invention relates to the manufacture of a cold-rolled steel sheet having a strength of more than 900 MPa, an elastic limit of more than 700 MPa and distributed elongation of more than 12 %, the composition of which includes, the contents being expressed as weight percentages: 0.26 % ≤ C ≤ 0.45 %, 1.0 % ≤ Mn ≤ 3.0 %, 1.0 % ≤ Si ≤ 3.0 %, Al ≤ 0.10 %, 0 % ≤ Cr ≤ 1.5 %, S ≤ 0.005 %, P ≤ 0.020 %, Nb ≤ 0.1 %, Ti ≤ 0.020 %, V ≤ 0.015 %, N ≤ 0.01 %, the remainder of the composition being iron and inevitable impurities as a result of the production process. The microstructure, given in surface proportions, comprises 13 % to 25 % residual austenite and 13 % to 30 % MA islands, the remainder consisting of bainite and possibly ferrite. L'invention concerne la fabrication d'une tôle d'acier laminée à froid de résistance supérieure à 900 MPa, de limite élastique supérieure à 700 MPa et d'allongement réparti supérieur à 12%, dont la composition comprend, les teneurs étant exprimées en poids : 0,26% ≤ C ≤ 0,45%, 1,0% ≤ Mn ≤ 3,0%, 1,0% ≤ Si ≤ 3,0%, Al ≤ 0.10% %, 0% ≤ Cr ≤ 1,5 %, S ≤0,005%, P ≤ 0,020%, Nb≤0,1 %, Ti≤0,020%, V≤0,015%, N≤0,01 %, 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 13 à 25 % d'austénite résiduelle, de 13 à 30% d'îlots MA, le solde étant constitué de bainite et éventuellement de ferrite.