HIGH-STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

• Main Authors: KIDO Akimasa, TADANI Tetsushi, KIZU Taro
• Format: Patent
• Language: English; French; German
• Published: 16.09.2020
• Subjects: ALLOYS; APPARATUS THEREFOR; 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; ELECTROFORMING; ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; 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; MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVINGMATERIAL; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; PERFORMING OPERATIONS; PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTIONOF COATINGS; PUNCHING METAL; ROLLING OF METAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; TRANSPORTING; TREATMENT OF ALLOYS OR NON-FERROUS METALS

[Object] Provided is a high-strength steel sheet having excellent bendability and a method for manufacturing the steel sheet. [Solution] A high-strength steel sheet has a chemical composition containing, by mass%, C: 0.04% to 0.20%, Si: 0.6% to 1.5%, Mn: 1.0% to 3.0%, P: 0.10% or less, S: 0.030% or less, Al: 0.10% or less, N: 0.010% or less, one, two, or all of Ti, Nb, and V in an amount of 0.01% to 1.0% each, and the balance being Fe and inevitable impurities, a microstructure including, in terms of area ratio, 50% or more of ferrite, in which an average grain diameter at a position located 50 µm from a surface of the steel sheet in a thickness direction is 3000 × [tensile strength TS (MPa)] -0.85 µm or less, a C content in precipitates having a grain diameter of less than 20 nm formed in steel is 0.010 mass% or more, and a amount of precipitated Fe (an amount of Fe precipitated in a form of cementite) is 0.03 mass% to 1.0 mass%, and an arithmetic average roughness Ra of 3.0 µm or less.