GALVANIZED HIGH-STRENGTH STEEL SHEET HAVING LOW YIELD RATIO AND METHOD OF PRODUCING THE SAME

Disclosed is a galvanized steel sheet which has a tensile strength of not less than 80 kgf/mm2 and a yield ratio of not more than 60%, and which is applicable to members of an automobile body, particularly those requiring strength. By appropriately controlling the amounts of C within the range of 0....

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Bibliographische Detailangaben
Hauptverfasser:	SAKATA, KEI, MASUI, SUSUMU, TOGASHI, FUSAO
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:	Disclosed is a galvanized steel sheet which has a tensile strength of not less than 80 kgf/mm2 and a yield ratio of not more than 60%, and which is applicable to members of an automobile body, particularly those requiring strength. By appropriately controlling the amounts of C within the range of 0.08-0.20 wt%, Mn within the range of 1.5-3.5 wt%, Al within the range of 0.01-0.1 wt%, P 0.01 wt% or less, S 0.01 wt% or less, and one or both of Ti and Nb within the range of 0.01-0.1 wt%, the structure of the steel sheet is formed into a dual-phase structure having a second phase structure. The steel sheet is recrystallization-annealed, galvanized while it is maintained at a temperature range near 500.degree.C, and then is cooled. By controlling the rate of cooling the steel sheet, the second phase structure generated is prevented from hardening more than necessary. The galvanized high-strength steel sheet has a low yield ratio and excellent stretch-flanging properties.