HOT-PRESSED MEMBER, COLD-ROLLED STEEL SHEET FOR HOT-PRESSED MEMBER, AND METHODS RESPECTIVELY FOR PRODUCING THESE PRODUCTS

Objects are to provide a hot-pressed member and a method for producing the hot-pressed member, the hot-pressed member having a tensile strength of 1780 MPa or greater and improved delayed fracture resistance, and to provide a cold-rolled steel sheet for a hot-pressed member and a method for producin...

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Bibliographische Detailangaben
Hauptverfasser:	TAKASHIMA Katsutoshi, TANAKA Minoru, ARAKAWA Shingo, TSUZUMI Kenji, SAKURAI Michitaka
Format:	Patent
Sprache:	eng ; fre ; ger
Schlagworte:	ALLOYS CHEMISTRY FERROUS OR NON-FERROUS ALLOYS GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS METALLURGY METALLURGY OF IRON MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS TREATMENT OF ALLOYS OR NON-FERROUS METALS
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Beschreibung
Zusammenfassung:	Objects are to provide a hot-pressed member and a method for producing the hot-pressed member, the hot-pressed member having a tensile strength of 1780 MPa or greater and improved delayed fracture resistance, and to provide a cold-rolled steel sheet for a hot-pressed member and a method for producing the cold-rolled steel sheet.A hot-pressed member has a predetermined chemical composition. In the hot-pressed member, a steel sheet has a microstructure in which a prior austenite average grain diameter is 8 µm or less, and martensite is present in a volume fraction of 95% or greater in a region within 30 µm of a surface; a Ni diffusion region having a thickness of 0.5 µm or greater exists in a surface layer; a standard deviation of Vickers hardness values is 35 or less; Mndif (mass%) in a sheet thickness direction ≤ 0.20, where Mndif (mass%) is a degree of Mn segregation; and a tensile strength is 1780 MPa or greater.