SEAMLESS STEEL PIPE

• Main Authors: SOMA ATSUSHI, KAMIYA YUKI
• Format: Patent
• Language: English; Japanese
• Published: 11.10.2021
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; METALLURGY; TREATMENT OF ALLOYS OR NON-FERROUS METALS

To provide a seamless steel pipe that has 758 MPa or more of yield strength and excellent SSC resistance, and in which a surface flaw is difficult to be formed on a processed surface even if processed surface is formed on a pipe end part.SOLUTION: A seamless steel pipe has a chemical composition containing C:0.15 to 0.45%, Si:0.05 to 1.00%, Mn:0.05 to 1.50%, P:0.030% or less, S:0.0050% or less, Cr:0.30 to 1.50%, Mo:0.25 to 2.00%, Ti:0.002 to 0.030%, Al:0.005 to 0.100%, N:0.0100% or less, and O:0.0050% or less in mass%, and has yield strength of 758 MPa or more. In the case where a wall thickness is D, macro-streak-flaws are 2.0 pcs./100 cm2 or less at 0.3D depth position from an external surface of the seamless steel pipe.SELECTED DRAWING: None 【課題】７５８ＭＰａ以上の降伏強度と優れた耐ＳＳＣ性とを有し、管端部に加工表面を形成しても、加工表面に表面疵が形成されにくい、継目無鋼管を提供する。【解決手段】本開示による継目無鋼管は、化学組成が、質量％で、Ｃ：０．１５〜０．４５％、Ｓｉ：０．０５〜１．００％、Ｍｎ：０．０５〜１．５０％、Ｐ：０．０３０％以下、Ｓ：０．００５０％以下、Ｃｒ：０．３０〜１．５０％、Ｍｏ：０．２５〜２．００％、Ｔｉ：０．００２〜０．０３０％、Ａｌ：０．００５〜０．１００％、Ｎ：０．０１００％以下、及び、Ｏ：０．００５０％以下を含有し、降伏強度が７５８ＭＰａ以上である。肉厚をＤとした場合、継目無鋼管の外表面から０．３Ｄ深さ位置において、地きずが２．０個／１００ｃｍ2以下である。【選択図】なし