HIGH-YIELD-RATIO HIGH STRENGTH STEEL SHEET AND METHOD FOR PRODUCING THE SAME

• Main Authors: JIN TAKAYOSHI, KOBAYASHI TAKASHI, KAWASAKI YOSHIYASU, ITO KATSUTOSHI, TAKAHASHI NORITAKA
• Format: Patent
• Language: English; Japanese
• Published: 24.01.2019
• Subjects: 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

To provide a high-yield-ratio high strength steel sheet having more than 0.70 of a yield ratio and 590 MPa or more of a tensile strength, and having excellent moldability and chemical conversion treatability.SOLUTION: A high-yield-ratio high strength steel sheet contains, in mass%, C: more than 0.050% to 0.200% or less, Si: 0.01% or more to less than 0.50%, Mn: more than 1.80% to less than 2.60%, P: 0.100% or less, S: 0.0200% or less, Al: 2.000% or less, N: 0.0100% or less, and Ti: 0.005% or more to 0.100% or less and/or Nb: 0.005% or more and 0.100% or less with the balance being Fe and inevitable impurities, wherein, in area ratios, ferrite is 40.0-90.0%, martensite is 5.0-30.0%, and perlite is 2.0-30.0%, with Mn content in steel/Mn content in ferrite≥1.10, Mn content in martensite/Mn content in steel≥1.80, wherein a measure of Mn content is mass%.SELECTED DRAWING: None 【課題】０．７０超の降伏比および５９０ＭＰａ以上の引張強さを有し、成形性および化成処理性に優れる高降伏比型高強度鋼板を提供する。【解決手段】質量％で、Ｃ：０．０５０％超０．２００％以下、Ｓｉ：０．０１％以上０．５０％未満、Ｍｎ：１．８０％超２．６０％未満、Ｐ：０．１００％以下、Ｓ：０．０２００％以下、Ａｌ：２．０００％以下、Ｎ：０．０１００％以下、ならびに、Ｔｉ：０．００５％以上０．１００％以下および／またはＮｂ：０．００５％以上０．１００％以下を含有し、残部がＦｅおよび不可避的不純物からなり、面積率でフェライトが４０．０〜９０．０％、マルテンサイトが５．０〜３０．０％、パーライトが２．０〜３０．０％であり、鋼中のＭｎ量／フェライト中のＭｎ量≧１．１０、マルテンサイト中のＭｎ量／鋼中のＭｎ量≧１．８０、Ｍｎ量の単位は質量％である。【選択図】なし