STEEL, STEEL PIPE FOR OIL WELL, AND METHOD FOR PRODUCING STEEL

• Main Authors: SOMA ATSUSHI, KAMIYA YUKI, ARAI YUJI, YOSHIDA SHINJI
• Format: Patent
• Language: English; Japanese
• Published: 11.07.2019
• 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 steel having a yield strength of more than 1069-1172 MPa, excellent low-temperature toughness, and excellent SSC resistance and a steel pipe for oil well.SOLUTION: A steel according to the present disclosure has a chemical composition containing, in mass%, C: 0.15 to 0.50%, Si: 0.05-1.00%, Mn: 0.05-1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005-0.100%, Cr: 0.20-1.50%, Mo: 0.25-1.50%, Ti: 0.002-0.050%, B: 0.0001-0.0050%, N: 0.0100% or less, and O: 0.0100% or less, with the balance being Fe and impurities. The steel according to the present disclosure further contains solid solution C of 0.010-0.060 mass%, wherein, the old austenite grain size number is 8.0 or more, and the yield strength is more than 1069-1172 MPa and the yield ratio is 85% or more.SELECTED DRAWING: Figure 1 【課題】降伏強度１０６９超〜１１７２ＭＰａと、優れた低温靭性と、優れた耐ＳＳＣ性とを有する、鋼材及び油井用鋼管を提供する。【解決手段】本開示による鋼材は、質量％で、Ｃ：０．１５〜０．５０％、Ｓｉ：０．０５〜１．００％、Ｍｎ：０．０５〜１．００％、Ｐ：０．０２５％以下、Ｓ：０．０１００％以下、Ａｌ：０．００５〜０．１００％、Ｃｒ：０．２０〜１．５０％、Ｍｏ：０．２５〜１．５０％、Ｔｉ：０．００２〜０．０５０％、Ｂ：０．０００１〜０．００５０％、Ｎ：０．０１００％以下、及び、Ｏ：０．０１００％以下を含有し、残部がＦｅ及び不純物からなる化学組成を有する。本開示による鋼材はさらに、固溶Ｃを０．０１０〜０．０６０質量％含有する。旧オーステナイト結晶粒の結晶粒度番号は８．０以上である。降伏強度は１０６９超〜１１７２ＭＰａであり、降伏比は８５％以上である。【選択図】図１