HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Provided is a high-strength hot rolled steel sheet that has excellent stretch flange formability, bendability, and low-temperature toughness while maintaining high strength of a tensile strength TS of 1180 MPa or more, and a method for manufacturing the high-strength hot rolled steel sheet.The high-...

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Hauptverfasser: YOKOTA Takeshi, KAIHO Sumio, MORIYASU Noriaki, YAMAZAKI Kazuhiko
Format: Patent
Sprache:eng ; fre ; ger
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Zusammenfassung:Provided is a high-strength hot rolled steel sheet that has excellent stretch flange formability, bendability, and low-temperature toughness while maintaining high strength of a tensile strength TS of 1180 MPa or more, and a method for manufacturing the high-strength hot rolled steel sheet.The high-strength hot rolled steel sheet includes a specific chemical composition, and a steel structure in which a lower bainite phase and/or a tempered martensite phase at 90% or more in terms of a total area fraction is contained as a dominant phase, an average grain size of the dominant phase is 10.0 µm or less, and an amount of Fe in Fe-based precipitates is 0.70% or less in mass%, in which an arithmetic average roughness (Ra) of a surface is 2.50 µm or less, and a tensile strength TS is 1180 MPa or more.