Abstract: A high-strength stainless steel seamless pipe for oil country tubular goods has a composition that contains, in mass %, C: 0.012 to 0.05%, Si: 0.05 to 0.50%, Mn: 0.04 to 1.80%, P: 0.030% or less, S: 0.005% or less, Cr: 11.0 to 14.0%, Ni: 0.5 to 6.5%, Mo: 0.5 to 3.0%, Al: 0.005 to 0.10%, V: 0.005 to 0.20%, Co: 0.01 to 0.3%, N: 0.002 to 0.15%, O: 0.010% or less, and Ti: 0.001 to 0.20%, and in which Cr, Ni, Mo, Cu, C, Si, Mn, N, and Ti satisfy predetermined relations, and the balance is Fe and incidental impurities, the high-strength stainless steel seamless pipe having a steel microstructure with 6 to 20% retained austenite in terms of a volume percentage, a yield strength of 758 MPa or more, and an absorption energy vE?60 at ?60° C. of 70 J or more.

Abstract: The invention provides a martensitic stainless steel seamless pipe for oil country tubular goods having high strength, and excellent sulfide stress corrosion cracking resistance and a method for manufacturing the same. The martensitic stainless steel seamless pipe for oil country tubular goods has a yield stress of 655 to 758 MPa, and has a composition containing, in mass %, C: 0.10% or less, Si: 0.5% or less, Mn: 0.05 to 2.0%, P: 0.030% or less, S: 0.005% or less, Ni: 4.0 to 8.0%, Cu: 0.02% or more and less than 1.0%, Cr: 10.0 to 14.0%, Mo: 1.0 to 3.5%, V: 0.003 to 0.2%, Co: 0.02% or more and less than 1.0%, Al: 0.1% or less, N: 0.1% or less, Ti: 0.50% or less, and the balance Fe and incidental impurities, wherein C, Mn, Cr, Cu, Co, Ni, Mo, W, Nb, N, and Ti satisfy the predetermined relations.

Abstract: A stainless steel seamless pipe has a component composition containing, in terms of mass%, C: 0.06% or less, Si: 1.0% or less, Mn: 0.01% or more and 0.90% or less, P: 0.05% or less, S: 0.005% or less, Cr: 15.70% or more and 18.00% or less, Mo: 1.60% or more and 3.80% or less, Cu: 1.10% or more and 4.00% or less, Ni: 3.0% or more and 6.0% or less, AI: 0.10% or less, N: 0.10% or less, O: 0.010% or less, V: 0.120% or more and 1.000% or less, C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfying a predetermined formula, and a remainder consisting of Fe and unavoidable impurities, and has a microstructure including 30% or more of a martensitic phase, 60% or less of a ferritic phase, and 40% or less of a retained austenitic phase, and a yield strength is 758 MPa or higher.

Abstract: A martensitic stainless steel seamless pipe for oil country tubular goods having a yield stress of 758 MPa or more, and excellent sulfide stress corrosion cracking resistance, and a method for manufacturing the same. The martensitic stainless steel seamless pipe has a composition that contains, by mass %, C: 0.010% or more, Si: 0.5% or less, Mn: 0.05 to 0.50%, P: 0.030% or less, S: 0.005% or less, Ni: 4.6 to 8.0%, Cr: 10.0 to 14.0%, Mo: 1.0 to 2.7%, Al: 0.1% or less, V: 0.005 to 0.2%, N: 0.1% or less, Ti: 0.255 to 0.500%, Cu: 0.01 to 1.0%, Co: 0.01 to 1.0%, and the balance being Fe and incidental impurities. C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti satisfy a predetermined relationship.

Abstract: An alloy pipe and a method for producing the same are disclosed. The alloy pipe of the present invention contains, as a component composition, in terms of % by mass, Cr: 11.5-35.0%, Ni: 23.0-60.0%, and Mo: 0.5-17.0%, has an austenitic phase as a microstructure, has a Mo concentration (% by mass) in a grain boundary of the austenitic phase that is 4.0 times or less than a Mo concentration (% by mass) within grains of the austenitic phase, and has a tensile yield strength in a pipe axial direction of 689 MPa or more and a ratio (compressive yield strength in a pipe axial direction)/(tensile yield strength in a pipe axial direction) of 0.85 to 1.15.

Abstract: A duplex stainless steel having excellent carbon dioxide corrosion resistance, excellent sulfide stress corrosion cracking resistance, and excellent sulfide stress cracking resistance. The duplex stainless steel comprises, by mass %, C: 0.03% or less, Si: 1.0% or less, Mn: 0.10 to 1.5%, P: 0.030% or less, S: 0.005% or less, Cr: 20.0 to 30.0%, Ni: 5.0 to 10.0%, Mo: 2.0 to 5.0%, Cu: 2.0 to 6.0%, N: less than 0.07%, at least one selected from Al: 0.05 to 1.0%, Ti: 0.02 to 1.0%, and Nb: 0.02 to 1.0%, and the balance being Fe and unavoidable impurities, and has a structure that is 20 to 70% austenite phase, and 30 to 80% ferrite phase in terms of a volume fraction.

Abstract: A dual-phase stainless steel or dual-phase stainless steel seamless pipe has a certain composition, the dual-phase stainless steel or dual-phase stainless steel seamless pipe having a microstructure containing 20 to 70% austenitic phase and 30 to 80% ferritic phase by volume, the dual-phase stainless steel or dual-phase stainless steel seamless pipe having a yield strength, YS, of 448 MPa or more, and containing oxide inclusions of which oxide inclusions having an average particle diameter of 1 ?m or more have a number density of 15/mm2 or less, and at most 50 mass % of the oxide inclusions having an average particle diameter of 1 ?m or more are oxide inclusions containing aluminum.

Abstract: Provided herein is a stainless steel seamless pipe having a composition that contains, in mass %, C: 0.06% or less, Si: 1.0% or less, Mn: 0.01% or more and 1.0% or less, P: 0.05% or less, S: 0.005% or less, Cr: 15.2% or more and 18.5% or less, Mo: 1.5% or more and 4.3% or less, Cu: 1.1% or more and 3.5% or less, Ni: 3.0% or more and 6.5% or less, Al: 0.10% or less, N: 0.10% or less, O: 0.010% or less, and Sn: 0.001% or more and 1.000% or less, and in which C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy the predetermined formula, and the balance is Fe and incidental impurities, the stainless steel seamless pipe having a microstructure containing 30% or more martensitic phase, 65% or less ferrite phase, and 40% or less retained austenite phase by volume.

Abstract: A high-strength stainless steel seamless pipe for oil country tubular goods has a composition that comprises, in mass%, C : 0.002 to 0.05%, Si: 0.05 to 0.50%, Mn: 0.04 to 1.80%, P: 0.030% or less, S: 0.002% or less, Cr: more than 14.0% and 17.0% or less, Ni: 4.0 to 8.0%, Mo: 1.5 to 3.0%, Al: 0.005 to 0.10%, V : 0.005 to 0.20%, Co: 0.01 to 1.0%, N : 0.002 to 0.15%, and O: 0.006% or less, and that satisfies the predetermined formulae, and in which the balance is Fe and incidental impurities, the high-strength stainless steel seamless pipe having a microstructure containing prior austenite having an average grain size of 40 µm or less, the high-strength stainless steel seamless pipe having a yield strength of 758 MPa or more.

Abstract: Provided herein is a stainless steel seamless pipe for oil country tubular goods. A method for manufacturing such a stainless steel seamless pipe is also provided. The stainless steel seamless pipe has: a composition that contains, in mass %, C: 0.10% or less, Si: 0.5% or less, Mn: 0.05 to 0.50%, P: 0.030% or less, S: 0.005% or less, O: 0.0040% or less, Ni: 3.0 to 8.0%, Cr: 10.0 to 14.0%, Mo: 0.5 to 2.8%, Al: 0.1% or less, V: 0.005 to 0.2%, N: 0.10% or less, Cu: 0.01 to 1.0%, Co: 0.01 to 1.0%, and Ca: 0.0005 to 0.0030%, and in which the balance is Fe and incidental impurities; a microstructure containing at most 20 non-metallic inclusions having a predetermined composition ratio of CaO and Al2O3 and a major axis of 5 ?m or more per 100 mm2; and a yield stress of 655 MPa or more.

Abstract: A stainless steel pipe of a predetermined composition is provided that has an axial tensile yield strength of 689 MPa or more, an axial compressive yield strength/axial tensile yield strength ratio of 0.85 to 1.15, and a microstructure that is 20 to 80% ferrite phase by volume with the remainder containing an austenite phase, the stainless steel pipe having pipe end portions at least one of which has a fastening portion for an external thread or an internal thread, and having a curvature radius of 0.2 mm or more for a corner R formed by a bottom surface of a thread root and a pressure-side flank surface of the thread, measured in an axial plane section of the fastening portion.

Abstract: A stainless steel pipe of a predetermined composition is provided that comprises N, Ti, Al, V, and Nb so as to satisfy the predetermined formula, the stainless steel pipe having an axial tensile yield strength of 757 MPa or more, an axial compressive yield strength/axial tensile yield strength ratio of 0.85 to 1.15, and a microstructure that is 20 to 80% ferrite phase by volume with the remainder containing an austenite phase, the stainless steel pipe having pipe end portions at least one of which has a fastening portion for an external thread or an internal thread, and having a curvature radius of 0.2 mm or more for a corner R formed by a bottom surface of a thread root and a pressure-side flank surface of the thread, measured in an axial plane section of the fastening portion.

Abstract: A stainless steel seamless pipe is provided that is a stainless steel comprising, in mass %, Cr: 11.5 to 35.0%, and Mo: 0.5 to 6.0%, and including ferrite and austenite, the stainless steel seamless pipe having a ferrite grain boundary and/or a ferrite-austenite grain boundary with a Mo concentration (mass %) that is at most 4.0 times the intragranular Mo concentration (mass %) of ferrite, or an austenite grain boundary with a Mo concentration (mass %) that is at most 4.0 times the intragranular Mo concentration (mass %) of austenite, the stainless steel seamless pipe having an axial tensile yield strength of 689 MPa or more, and an axial compressive yield strength/axial tensile yield strength ratio of 0.85 to 1.15.

Abstract: The seamless pipe in which a thin-walled portion in a pipe circumferential direction is formed in a pipe axial direction, in which a line segment formed by connecting one end and the other end of the thin-walled portion along a pipe surface with a shortest distance in a formation direction of the thin-walled portion is inclined at an angle ? of 5.0° or more with respect to the pipe axial direction. It is preferable that one end and the other end of the thin-walled portion are set from a region in a pipe selected with a shorter length between a length of 1.0 m in the pipe axial direction and 90% of a length in the pipe axial direction where the thin-walled portion turns once in the pipe circumferential direction.

Abstract: Provided herein is a high-strength seamless steel pipe, and a method for manufacturing same. A high-strength seamless steel pipe of the present invention has a yield strength of 758 MPa or more, and a KILIMIT value of 23.0 MPa?m or more as an evaluation index of sulfide stress corrosion cracking resistance.

Abstract: Provided herein is a stainless steel seamless pipe having a composition that contains, in mass %, C: 0.06% or less, Si: 1.0% or less, Mn: 0.01% or more and 1.0% or less, P: 0.05% or less, S: 0.005% or less, Cr: 15.2% or more and 18.5% or less, Mo: 1.5% or more and 4.3% or less, Cu: 1.1% or more and 3.5% or less, Ni: 3.0% or more and 6.5% or less, Al: 0.10% or less, N: 0.10% or less, O: 0.010% or less, and Sb: 0.001% or more and 1.000% or less, and in which C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy the predetermined formula, and the balance is Fe and incidental impurities, the stainless steel seamless pipe having a microstructure containing 30% or more martensitic phase, 65% or less ferrite phase, and 40% or less retained austenite phase by volume.

Abstract: To provide a high-strength seamless stainless steel pipe for oil well that has high strength, is excellent in hot workability, has excellent carbon dioxide gas corrosion resistance, and is excellent in SSC resistance under a low temperature environment. A high-strength seamless stainless steel pipe for oil well having a composition containing the particular components, the balance being Fe and unavoidable impurities, and satisfying certain expressions, having a number density of an inclusion having a major axis of 5 ?m or more and 0.5<Ti/(Ti+Al+Mg+Ca)<1.0 of 0.5 per mm2 or more and 3 per mm2 or less, and having a yield strength of 655 MPa or more, wherein in 0.5<Ti/(Ti+Al+Mg+Ca)<1.0, Ti, Al, Mg, and Ca represent the contents (% by mass) of the elements in the inclusion, and an element that is not contained is designated as 0.

Abstract: Provided herein is a dual-phase stainless steel having excellent carbon dioxide corrosion resistance, excellent sulfide stress corrosion cracking resistance, and excellent sulfide stress cracking resistance. The dual-phase stainless steel contains, in mass %, C: 0.03% or less, Si: 1.0% or less, Mn: 0.10 to 1.5%, P: 0.030% or less, S: 0.005% or less, Cr: 20.0 to 30.0%, Ni: 5.0 to 10.0%, Mo: 2.0 to 5.0%, Cu: 2.0 to 6.0%, N: less than 0.07%, and the balance Fe and unavoidable impurities, and has a structure that is 20 to 70% austenite phase, and 30 to 80% ferrite phase in terms of a volume fraction.

Abstract: Provided herein is a high-strength seamless steel pipe, and a method for manufacturing same. A high-strength seamless steel pipe of the present invention has a steel microstructure with a prior austenite grain size of 11.0 or more in terms of a grain size number in compliance with ASTM E112, and has a yield strength of 862 MPa or more and 965 MPa or less.

Abstract: A seamless steel pipe of the present invention is a seamless steel pipe having a composition that includes, in mass %, C: 0.02 to 0.12%, Si: 0.010 to 1.00%, Mn: 0.10 to 2.00%, P: 0.050% or less, S: 0.004% or less, Al: 0.010 to 0.100%, Cu: 0.03 to 0.80%, Ni: 0.02 to 0.50%, Cr: 0.55 to 1.00%, Sb: 0.005 to 0.20%, and the balance Fe and incidental impurities, and satisfying the following formula (1), 1.7×Cu*+11×Cr*+3.8×Sb*?13.5 ??(1), where Cu*, Cr*, and Sb* represent average concentrations of Cu, Cr, and Sb, respectively, in mass %, as measured in a region 0.5 to 2.0 mm away from an outer surface of the steel pipe, the seamless steel pipe having a yield strength of 230 MPa or more, and a tensile strength of 380 MPa or more.