Cold-rolled steel sheet

冷延鋼板

Abstract

PROBLEM TO BE SOLVED: To attain a high tensile cold-rolled steel plate excellent in ductility, work-hardenability, and stretch flange formability.SOLUTION: The cold-rolled steel sheet contains, by mass%, >0.020 and <0.30% C, >0.10% and ≤3.00% Si, and >1.00 and ≤3.50% Mn, and optionally further contains an appropriate amount of one or more elements of Ti, Nb, V, Cr, Mo, B, Ca, Mg, REM and Bi, and has a metallic structure in which a main phase is a low-temperature transformation-produced phase and a second phase includes retained austenite and polygonal ferrite, wherein the retained austenite counts for >4.0% and <25.0% by a volume fraction, and has an average diameter of <0.80 μm, and a number density of the retained austenite particles having a particle size of ≥1.2 μm among the retained austenite is ≤3.0×10pieces/μm, and the polygonal ferrite counts for >2.0% and <27.0% by a volume fraction, and has an average particle size of <5.0 μm.
【課題】延性、加工硬化性、伸びフランジ性に優れた高張力冷延鋼板の実現。 【解決手段】質量%で、C:0.020%超0.30%未満、Si:0.10%超3.00%以下、Mn:1.00%超3.50%以下、場合によりさらに適量のTi、Nb、V、Cr、Mo、B、Ca、Mg、REMおよびBiの1種又は2種以上を含有し、主相が低温変態生成相で第二相に残留オーステナイトおよびポリゴナルフェライトを含む金属組織を備え、前記残留オーステナイトは体積率が4.0%超25.0%未満、平均粒径0.80μm未満であり、前記残留オーステナイトの内、粒径1.2μm以上の残留オーステナイト粒の数密度が3.0×10 −2 個/μm 2 以下、前記ポリゴナルフェライトは体積率が2.0%超27.0%未満、平均粒径5.0μm未満である。 【選択図】図3

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Patent Citations (3)

    Publication numberPublication dateAssigneeTitle
    JP-2005336526-ADecember 08, 2005Kobe Steel Ltd, Shinshu Tlo:Kk, 株式会社信州Tlo, 株式会社神戸製鋼所High strength steel sheet having excellent workability and its production method
    JP-2006336074-ADecember 14, 2006Kobe Steel Ltd, 株式会社神戸製鋼所High strength and high ductility steel sheet having excellent chemical convertibility
    JP-2007182625-AJuly 19, 2007Kobe Steel Ltd, 株式会社神戸製鋼所耐パウダリング性に優れた高強度合金化溶融亜鉛めっき鋼板およびその製造方法

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