HIGH STRENGTH STEEL SHEET EXCELLENT IN MOLDABILITY AND MANUFACTURING METHOD OF THE SAME

• Main Authors: OKUDA KANEHARU, TAKAGI SHUSAKU
• Format: Patent
• Language: English
• Published: 17.03.2014
• Subjects: 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

PROBLEM TO BE SOLVED: To provide a high strength cold rolling steel sheet excellent in moldability.SOLUTION: A steel material having a composition containing, by mass%, C:0.14 to 0.30%, Si:0.1 to 2.0%, Mn:2.0 to 3.5%, and Al:0.01 to 1.5%, satisfying Si+Al:0.5% or more, and containing one or two kinds selected from Ti:0.01 to 0.20% and Nb:0.01 to 0.20% is heated to 1100 to 1300°C, applied to hot rolling at a finish rolling finishing temperature of 800 to 950°C, then cooled to 750°C with a cooling velocity of 5 to 200°C/s on average, rolled at 350 to 650°C, further heated to a temperature range of Ac3 transformation point or higher with 1 o 50°C/s at 300 to 600°C and 0.1°C/s or more and less than 10°C/s at 600°C to a firing temperature, maintained for 10 to 500 s, cooled with the cooling velocity with which ferrite transformation starts at the temperature range of over 700°C, and applied to a firing treatment of maintaining it in the temperature range of 350 to 500°C for 30 s or longer.