Jfe Steel Corporation

Kawasaki Steel Corporation

Exxonmobil Upstream Research Company

Kabushiki Kaisha Kobe Seiko Sho

Mitsuhiro Okatsu

Masao Yuga

Hiroki Ota

Yasuhide Ishiguro

Fumimaru Kawabata

Keniti Amano

Kazuki Fujimura

Noritsugu Itakura

Yoichi Ito

Seiji Nabeshima

Tohru Hayashi

Shigeru Endo

Junji Shimamura

Tomoya Koseki

Hiroyuki Takai

Toshiharu Hirama

Kenji Oi

Yasumasa Takemura

Nobuyuki Ishikawa

Narasimha-Rao Venkata Bangaru

Jayoung Koo

Hyun-Woo Jin

Kenichiro Eguchi

Douglas Paul Fairchild

Adnan Ozekcin

Raghavan Ayer

Norichika Aramaki

Nobuo Shikanai

Haruo Nakamichi

Shigeki Nishiyama

Masahito Tanaka

Naoya Hayakawa

Keito Ishizaki

Moriyasu Nagae

Shinichi Kakihara

Danny Lee Beeson

Makoto Ota

Shuichi Sakaguchi

Tatsuo Koide

James B LeBleu, Jr

Douglas S Hoyt

Yoshiyuki Sugano

Masayuki Fukami

Kaoru Nagatani

Keiji Ueda

Danny L Beeson

Narasimha V Bangaru

Kimihito Shirasaki

Kimihiro Nishimura

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.

High-strength seamless steel pipe and method for manufacturing same

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 Kvalue of 23.0 MPa√m or more as an evaluation index of sulfide stress corrosion cracking resistance.

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),

Seamless steel pipe having desirable sulfuric acid dew-point corrosion resistance, and method for manufacturing same

A seamless steel pipe of the present invention is a seamless steel pipe having a composition including, in mass %, C: 0.01 to 0.12%, Si: 0.01 to 0.8%, Mn: 0.10 to 2.00%, P: 0.050% or less, S: 0.040% or less, Al: 0.010 to 0.100%, Cu: 0.03 to 0.80%, Ni: 0.01 to 0.50%, Mo: 0.01 to 0.20%, Sb: 0.002 to 0.50%, Cr: 0.004% or less, W: 0.002% or less, and the balance Fe and incidental impurities, and a structure including a ferrite phase having an area percentage of 50 to 65%, a pearlite phase having an area percentage of 2% or less, and one or both of a bainite phase and a martensitic phase representing the remainder, the seamless steel pipe having a yield strength of 230 MPa or more, and a tensile strength of 380 MPa or more.

Provided herein is a low-alloy high-strength seamless steel pipe. The steel pipe of the present invention has a composition that contains, in mass %, C: 0.20 to 0.50%, Si: 0.01 to 0.35%, Mn: 0.45 to 1.5%, P: 0.020% or less, S: 0.002% or less, 0: 0.003% or less, Al: 0.01 to 0.08%, Cu: 0.02 to 0.09%, Cr: 0.35 to 1.1%, Mo: 0.05 to 0.35%, B: 0.0010 to 0.0030%, Ca: 0.0010 to 0.0030%, Mg: 0.001% or less, and N: 0.005% or less, and in which the balance is Fe and incidental impurities. The steel pipe has a microstructure in which the number of oxide-base nonmetallic inclusions satisfying the composition ratios represented by predefined formulae is 20 or less per 100 mm, and in which the number of oxide-base nonmetallic inclusions satisfying the composition ratios represented by other predefined formulae is 50 or less per 100 mm.

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

Provided herein is a low-alloy high-strength seamless steel pipe. The steel pipe of the present invention has a composition that contains, in mass %, C: 0.25 to 0.50%, Si: 0.01 to 0.40%, Mn: 0.3 to 1.5%, P: 0.010% or less, S: 0.001% or less, O: 0.0015% or less, Al: 0.015 to 0.080%, Cu: 0.02 to 0.09%, Cr: 0.5 to 0.8%, Mo: 0.5 to 1.3%, Nb: 0.005 to 0.05%, B: 0.0005 to 0.0040%, Ca: 0.0010 to 0.0020%, Mg: 0.001% or less, and N: 0.005% or less, and in which the balance is Fe and incidental impurities. The steel pipe has a microstructure in which the number of oxide-base nonmetallic inclusions satisfying the composition ratios represented by predefined formulae is 10 or less per 100 mm, and in which the number of oxide-base nonmetallic inclusions satisfying the composition ratios represented by other predefined formulae is 30 or less per 100 mm.

Provided herein is a low-alloy high-strength seamless steel pipe. The steel pipe of the present invention has a composition that contains, in mass %, C: 0.25 to 0.50%, Si: 0.01 to 0.40%, Mn: 0.45 to 0.90%, P: 0.010% or less, S: 0.001% or less, O: 0.0015% or less, Al: 0.015 to 0.080%, Cu: 0.02 to 0.09%, Cr: 0.9 to 1.5%, Mo: 1.4 to 2.0%, Nb: 0.005 to 0.05%, B: 0.0005 to 0.0040%, Ca: 0.0010 to 0.0020%, Mg: 0.001% or less, and N: 0.005% or less, and in which the balance is Fe and incidental impurities. The steel pipe has a microstructure in which the number of oxide-base nonmetallic inclusions satisfying the composition ratios represented by predefined formulae is 5 or less per 100 mm, and in which the number of oxide-base nonmetallic inclusions satisfying the composition ratios represented by other predefined formulae is 20 or less per 100 mm.

Provided herein is a high-strength seamless steel pipe containing a particular chemical composition. The volume fraction of tempered martensite is 90% or more in terms of a volume fraction. The number of nitride inclusions with a particle diameter of 4 &#x3bc;m or more is 50 or less per 100 mm, the number of nitride inclusions with a particle diameter of less than 4 &#x3bc;m is 500 or less per 100 mm, the number of oxide inclusions with a particle diameter of 4 &#x3bc;m or more is 40 or less per 100 mm, and the number of oxide inclusions with a particle diameter of less than 4 &#x3bc;m is 400 or less per 100 mmin a cross section perpendicular to a rolling direction.

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

The high-strength seamless steel pipe has a volume fraction of tempered martensite of 95% or more, and a prior austenite size number of 8.5 or more, and contains nitride inclusions having a size of 4 &#x3bc;m or more and whose number is 100 or less per 100 mm, nitride inclusions having a size of less than 4 &#x3bc;m and whose number is 700 or less per 100 mm, oxide inclusions having a size of 4 &#x3bc;m or more and whose number is 60 or less per 100 mm, and oxide inclusions having a size of less than 4 &#x3bc;m and whose number is 500 or less per 100 mm, in a cross section perpendicular to a rolling direction.

High-strength seamless steel pipe for oil country tubular goods, and production method for high-strength seamless steel pipe for oil country tubular goods

The steel pipe of the present invention is a low alloy high strength seamless steel pipe for oil country tubular goods including a composition containing, in terms of mass %, C: 0.23 to 0.27%, Si: 0.01 to 0.35%, Mn: 0.45 to 0.70%, P: 0.010% or less, S: 0.001% or less, O: 0.0015% or less, Al: 0.015 to 0.080%, Cu: 0.02 to 0.09%, Cr: 0.8 to 1.5%, Mo: 0.5 to 1.0%, Nb: 0.02 to 0.05%, B: 0.0015 to 0.0030%, Ti: 0.005 to 0.020%, and N: 0.005% or less, and having a ratio of the Ti content to the N content (Ti/N) of 3.0 to 4.0, with the balance being Fe and inevitable impurities, the steel pipe having a ratio of a stress at a strain of 0.7% to a stress at a strain of 0.4% in a stress-strain curve of 1.02 or less and a yield strength of 655 MPa or more.

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

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 seamless steel pipe having a specific chemical composition. A ratio of Ti to N is in a range of 2.0 to 5.0. The steel pipe has a microstructure including tempered martensite having a volume ratio of 95% or more, and prior austenite grains having a grain size number of 8.5 or more. In a cross-section perpendicular to a rolling direction of the steel pipe a number of nitride-based inclusions having a particle size of 4 &#x3bc;m or more is 100 or less per 100 mm, a number of nitride-based inclusions having a particle size of less than 4 &#x3bc;m is 1000 or less per 100 mm, a number of oxide-based inclusions having a particle size of 4 &#x3bc;m or more is 40 or less per 100 mm, and a number of oxide-based inclusions having a particle size of less than 4 &#x3bc;m is 400 or less per 100 mm.

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

A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: 0.3% to 0.9%, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.01% to less than 0.05%, Nb: 0.001% to less than 0.01%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 &#x3bc;m or more is 100 or less per 100 mm, the number of nitride-based inclusions having a grain size of less than 4 &#x3bc;m is 1000 or less per 100 mm, the number of oxide-based inclusions having a grain size of 4 &#x3bc;m or more is 40 or less per 100 mm, and the number of oxide-based inclusions having a grain size of less than 4 &#x3bc;m is 400 or less per 100 mm.

A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: more than 0.6% to 1.5% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.05% to 0.3%, Nb: 0.001% to 0.020%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 m or more is 100 or less per 100 mm, the number of nitride-based inclusions having a grain size of less than 4 &#x3bc;m is 1000 or less per 100 mm, the number of oxide-based inclusions having a grain size of 4 &#x3bc;m or more is 40 or less per 100 mm, and the number of oxide-based inclusions having a grain size of less than 4 &#x3bc;m is 400 or less per 100 mm, and methods of producing the same.

Provided is a high-strength seamless steel pipe having the composition which contains, by mass %, 0.20 to 0.50% C, 0.05 to 0.40% Si, 0.3 to 0.9% Mn, 0.015% or less P, 0.005% or less S, 0.005 to 0.1% Al, 0.008% or less N, more than 0.6% and 1.7% or less Cr, more than 1.0% and 3.0% or less Mo, 0.01 to 0.30% V, 0.001% or more and less than 0.01% Nb, 0.0003 to 0.0030% B, and 0.0030% or less O (oxygen). The high-strength seamless steel pipe has the microstructure where a volume fraction of a tempered martensitic phase is 95% or more, and prior austenitic grains have a grain size number of 8.5 or more, and a segregation degree index Ps which is defined by a formula Ps=8.1 (X+X+X)+1.2Xis set to less than 65.

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Tokyo, Japan

Mitsuhiro Okatsu