Jfe Steel Corporation

Kenichiro Eguchi

Yasuhide Ishiguro

Masao Yuga

Yuichi Kamo

Mitsuo Kimura

Takeshi Suzuki

Hiroki Ota

Yusuke Yoshimura

Yukio Miyata

Kazuki Fujimura

Haruo Nakamichi

Hideo Sato

Katsumi Yamada

Yuji Tanaka

Mitsuhiro Okatsu

Masahito Tanaka

Tetsu Nakahashi

Hiroshi Yokogawa

Tadao Katagiri

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.

High-strength stainless steel seamless pipe for oil country tubular goods and method for manufacturing same

The invention is intended to provide a duplex stainless steel and a method for manufacturing same. A duplex stainless steel pipe is also provided. A duplex stainless steel of the present invention has a specific composition, and has a microstructure containing an austenitic phase and a ferrite phase. The duplex stainless steel satisfies the following contents for C, Si, Mn, Cr, Mo, Ni, N, Cu, and W in the formula (1) below, and has a yield strength YS of 655 MPa or more, and an absorption energy vEof 40 J or more as measured by a Charpy impact test at a test temperature of −10° C.0.55[% C]−0.056[% Si]+0.018[% Mn]−0.020[% Cr]−0.087[% Mo]+0.16[% Ni]+0.28[% N]−0.506[% Cu]−0.035[% W]+[% Cu*F]≤0.94  (1)

Duplex stainless steel and method for manufacturing same, and duplex stainless steel pipe

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.

Duplex stainless steel and method for producing same

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.

Dual-phase stainless steel, and method of production thereof

A high strength stainless steel seamless pipe for oil country tubular goods which is excellent in hot workability, has a high strength, suppresses scattering in the strength, and has excellent carbon dioxide corrosion resistance. The steel pipe has a yield strength of 655 MPa or more, and a chemical composition comprising, by mass %, C: 0.005 to 0.05%, Si: 0.05 to 0.50%, Mn: 0.20 to 1.80%, P: 0.030% or less, S: 0.005% or less, Cr: 12.0 to 17.0%, Ni: 4.0 to 7.0%, Mo: 0.5 to 3.0%, Al: 0.005 to 0.10%, V: 0.005 to 0.20%, Co: 0.01 to 1.0%, N: 0.005 to 0.15%, and O: 0.010% or less with the balance being Fe and inevitable impurities. Cr, Ni, Mo, Cu, and C satisfy a specified expression, and Cr, Mo, Si, C, Mn, Ni, Cu, and N satisfy another specified expression.

High strength stainless steel seamless pipe for oil country tubular goods

Provided herein is a high-strength stainless steel seamless pipe for oil country tubular goods. The high-strength stainless steel seamless pipe having a yield strength of 862 MPa or more contains, in mass %, C:0.05% or less, Si: 0.5% or less, Mn: 0.15 to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 14.5 to 17.5%, Ni: 3.0 to 6.0%, Mo: 2.7 to 5.0%, Cu: 0.3 to 4.0%, W: 0.1 to 2.5%, V: 0.02 to 0.20%, Al: 0.10% or less, N: 0.15% or less, B: 0.0005 to 0.0100%, and the balance Fe and unavoidable impurities, and in which the composition satisfies specific formulas. The stainless steel pipe has more than 45% martensite phase, 10 to 45% ferrite phase, and 30% or less retained austenite phase. The ferrite grains have a maximum crystal grain size of 500 &#x3bc;m or less.

High-strength stainless steel seamless pipe for oil country tubular goods, and method for producing same

The invention is intended to provide a high-strength stainless steel seamless pipe for oil country tubular goods having high strength with a yield strength of 862 MPa (125 ksi) or more, excellent low-temperature toughness, and excellent corrosion resistance. The invention is also intended to provide a method for manufacturing such a high-strength stainless steel seamless pipe. The high-strength stainless steel seamless pipe has a microstructure that is at least 45% tempered martensite phase, 20 to 40% ferrite phase, and more than 10% and 25% or less retained austenite phase by volume. The high-strength stainless steel seamless pipe has a yield strength of 862 MPa or more, and a maximum crystal grain diameter of 500 &#x3bc;m or less for ferrite crystal grains when crystal grains with a crystal orientation difference of within 15&#xb0; are defined as the same crystal grains.

High-strength stainless steel seamless pipe for oil country tubular goods, and method for manufacturing same

Provided herein is a high strength seamless stainless steel pipe. A method for producing such a high strength seamless stainless steel pipe is also provided. The high strength seamless stainless steel pipe has a certain composition. The high strength seamless stainless steel pipe has a structure that includes a tempered martensite phase as a primary phase, and 20 to 40% ferrite phase, and at most 25% residual austenite phase in terms of a volume fraction, and in which C, Cr, Ni, Mo, Nb, N, W, and Cu in the residual austenite phase satisfy a predetermined formula.

High strength seamless stainless steel pipe and method for producing same

Provided is a high-strength seamless stainless steel pipe for oil country tubular goods which possesses a high strength, excellent low-temperature toughness and excellent corrosion resistance even when the steel pipe has a large wall thickness. The high-strength seamless stainless steel pipe has the composition which contains, by mass %, C: 0.05% or less, Si: 1.0% or less, Mn: 0.1 to 0.5%, P: 0.05% or less, S: less than 0.005%, Cr: more than 15.0% to 19.0% or less, Mo: more than 2.0% to 3.0% or less, Cu: 0.3 to 3.5%, Ni: 3.0% or more and less than 5.0%, W: 0.1 to 3.0%, Nb: 0.07 to 0.5%, V: 0.01 to 0.5%, Al: 0.001 to 0.1%, N: 0.010 to 0.100%, O: 0.01% or less, and Fe and unavoidable impurities as a balance. Nb, Ta, C, N and Cu satisfy a specified formula. The steel pipe has a microstructure which is formed of 45% or more of a tempered martensite phase, 20 to 40% of a ferrite phase, and more than 10% and 25% or less of a residual austenite phase in terms of volume ratio.

High-strength seamless stainless steel pipe for oil country tubular goods and method of manufacturing high-strength seamless stainless steel pipe

Provided herein is a high-strength seamless stainless steel pipe. The high-strength seamless stainless steel pipe contains, in mass %, C: 0.05% or less, Si: 0.5% or less, Mn: 0.15 to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 14.5 to 17.5%, Ni: 3.0 to 6.0%, Mo: 2.7 to 5.0%, Cu: 0.3 to 4.0%, W: 0.1 to 2.5%, V: 0.02 to 0.20%, Al: 0.10% or less, N: 0.15% or less, and the balance being Fe and unavoidable impurities. C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy a specific formula. Cu, Mo, W, Cr, and Ni satisfy another specific formula. The high-strength seamless stainless steel pipe has more than 45% martensite phase, 10 to 45% ferrite phase, and 30% or less retained austenite phase. The total amount of precipitated Cr, precipitated Mo, and precipitated W is 0.75 mass % or less.

High-strength seamless stainless steel pipe for oil country tubular goods, and method for producing the same

A low alloy high strength thick-walled seamless steel pipe for oil country tubular goods is provided having a wall thickness of 40 mm or more and a yield strength of 758 MPa or more, the steel pipe including a composition containing, in terms of mass %, C: 0.25 to 0.31%, Si: 0.01 to 0.35%, Mn: 0.55 to 0.70%, P: 0.010% or less, S: 0.001% or less, O: 0.0015% or less, Al: 0.015 to 0.040%, Cu: 0.02 to 0.09%, Cr: 0.8 to 1.5%, Mo: 0.9 to 1.6%, V: 0.04 to 0.10%, Nb: 0.005 to 0.05%, B: 0.0015 to 0.0030%, Ti: 0.005 to 0.020%, and N: 0.005% or less, and having Ti/N of 3.0 to 4.0, with the balance being Fe and inevitable impurities, wherein a cumulative frequency rate at a measurement point at which a Mo segregation degree by a predetermined expression is 1.5 or more is 1% or less.

Low alloy high strength thick-walled seamless steel pipe for oil country tubular goods

A high-strength seamless stainless steel pipe has a composition including, by mass %, 0.05% or less C, 1.0% or less Si, 0.1 to 0.5% Mn, 0.05% or less P, 0.005% or less S, more than 16.0% to 18.0% or less Cr, more than 2.0% to 3.0% or less Mo, 0.5 to 3.5% Cu, 3.0% or more and less than 5.0% Ni, 0.01 to 3.0% W, 0.01 to 0.5% Nb, 0.001 to 0.3% Ti, 0.001 to 0.1% Al, less than 0.07% N, 0.01% or less O, and Fe and unavoidable impurities as a balance, wherein the steel pipe has a microstructure including a tempered martensite phase forming a main phase, 20 to 40% of a ferrite phase in terms of volume ratio, and 25% or less of a residual austenite phase in terms of volume ratio, an average grain size of the ferrite phase is 40 &#x3bc;m or less, and a sum of amounts of Ti and Nb precipitated as precipitates having a grain size of 2 &#x3bc;m or less is 0.06 mass % or more, whereby the steel pipe has high strength where yield strength YS is 758 MPa or more and high toughness where an absorbing energy value vEin a Charpy impact test at a test temperature of &#x2212;10&#xb0; C. is 40 J or more.

High-strength seamless stainless steel pipe and method of manufacturing high-strength seamless stainless steel pipe

A steel pipe is formed by performing pipe making of a raw material having a composition containing C: 0.05% or less, Si: 0.50% or less, Mn: 0.20% to 1.80%, P: 0.030% or less, S: 0.005% or less, Cr: 14.0% to 18.0%, Ni: 5.0% to 8.0%, Mo: 1.5% to 3.5%, Cu: 0.5% to 3.5%, Al: 0.10% or less, Nb: more than 0.20% and 0.50% or less, V: 0.20% or less, N: 0.15% or less, and O: 0.010% or less, on a percent by mass basis, wherein Cr+0.65Ni+0.6Mo+0.55Cu&#x2212;20C&#x2265;18.5 and Cr+Mo+0.3Si&#x2212;43.3C&#x2212;0.4Mn&#x2212;Ni&#x2212;0.3Cu&#x2212;9N&#x2264;11 are satisfied and subjecting the resulting steel pipe to a quenching treatment to heat to a temperature higher than or equal to the Atransformation temperature and, subsequently, cool to a temperature of 100&#xb0; C. or lower at a cooling rate higher than or equal to the air cooling rate and a tempering treatment to temper at a temperature lower than or equal to the Atransformation temperature.

Stainless steel seamless pipe for oil well use and method for manufacturing the same

A method of manufacturing a high-strength stainless steel pipe includes forming a steel pipe having a predetermined size, the steel having a composition comprising by mass % 0.005 to 0.05% C, 0.05 to 1.0% Si, 0.2 to 1.8% Mn, 0.03% or less P, 0.005% or less S, 14 to 20% Cr, 1.5 to 10% Ni, 1 to 5% Mo, 0.5% or less V, 0.15% or less N, 0.01% or less O, 0.002 to 0.1% Al, and Fe and unavoidable impurities as a balance; applying a quenching treatment two times or more to the steel pipe where the steel pipe is quenched by reheating to a temperature of 750&#xb0; C. or above and cooling to a temperature of 100&#xb0; C. or below at a cooling rate equal to or higher than an air-cooling rate; and applying a tempering treatment where the steel pipe is tempered at a temperature of 700&#xb0; C. or below.

High-strength stainless steel pipe

A high-strength stainless steel seamless tube or pipe has excellent corrosion resistance, where excellent carbon dioxide gas corrosion resistance in high-temperature environments containing COand Clat high temperatures up to 200&#xb0; C. and excellent sulfide stress cracking resistance and excellent sulfide stress corrosion cracking resistance at corrosive environments further containing HS are ensured based on a composition of C: 0.05% or less, Si: 0.5% or less, Mn: 0.15% to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 15.5% to 17.5%, Ni: 3.0% to 6.0%, Mo: 1.5% to 5.0%, Cu: 4.0% or less, W: 0.1% to 2.5%, and N: 0.15% or less such that &#x2212;5.9&#xd7;(7.82+27C-0.91Si+0.21Mn&#x2212;0.9Cr+Ni-1.1Mo+0.2Cu+11N)&#x2265;13.0 is satisfied.

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Tokyo, Japan

Kenichiro Eguchi