STEEL SHEET

Provided are a steel sheet having a predetermined chemical composition and having the following steel structure, and a method of manufacturing the steel sheet.(1) In area ratio %, ferrite: 0 to 5%, martensite: 90 to 100%, a ratio of tempered martensite to total martensite: 80 to 100%, and retained a...

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Bibliographische Detailangaben
Hauptverfasser:	OBUCHI, Tatsuya, HAYASHI, Kunio, YOKOYAMA, Takafumi, SHIOKAWA, Kazuki
Format:	Patent
Sprache:	eng
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:	Provided are a steel sheet having a predetermined chemical composition and having the following steel structure, and a method of manufacturing the steel sheet.(1) In area ratio %, ferrite: 0 to 5%, martensite: 90 to 100%, a ratio of tempered martensite to total martensite: 80 to 100%, and retained austenite: 0.5 to 6.0% are contained.(2) The number density of inclusions satisfying the maximum diameter≥3 μm is 40 inclusions/mm2 or less.(3) When the number density of the inclusions satisfying the maximum diameter≥3 μm in each section is calculated, the number density in the section where the number density of inclusions is in the top 10% is 80 inclusions/mm2 or less.(4) Formula (A) is satisfied.Vγ′/Vγ≥0.1 (A)Vγ: Initial retained austenite, Vγ′: Retained austenite after deep cooling at −196° C.(5) The tensile strength is 1470 MPa or more.