Jfe Steel Corporation

Kansai Paint Company, Ltd.

Haruo Nakamichi

Takashi Ueno

Yoshitsugu Suzuki

Takashi Kawano

Nobuyuki Ishikawa

Daisuke Mizuno

Yoichiro Yamanaka

Kenichiro Eguchi

Kyono Yasuda

Masanari Tomozawa

Kaoru Sato

Katsumi Yamada

Yuji Tanaka

Mitsuo Kimura

Masaaki Yamashita

Masao Yuga

Yasuhide Ishiguro

Akira Matsuzaki

Mitsuhiro Okatsu

Takahiro Kubota

Naoto Yoshimi

Reijiro Nishida

Shoichi Tanaka

Hisato Noro

Masahiro Murata

Hiroyasu Matsuki

Yoshikazu Morohoshi

Shingo Amaki

Okai Kazuhisa

It is provided a surface-treated steel sheet that can be produced without using hexavalent chromium and has excellent sulfide staining resistance and coating secondary adhesion. It is a surface-treated steel sheet having: a Sn plating layer; a metallic Cr layer disposed on the Sn plating layer; and a Cr oxide layer disposed on the metallic Cr layer, on at least one surface of a steel sheet, and the surface-treated steel sheet has a water contact angle of 50° or less and a total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface to Cr of 5% or less.

Surface-treated steel sheet and method of producing the same

It is provided a surface-treated steel sheet that can be produced without using hexavalent chromium and has excellent film wet adhesion and coating secondary adhesion as well as high film corrosion resistance and coating corrosion resistance. It is a surface-treated steel sheet having: a steel sheet; a metallic Cr layer disposed on at least one surface of the steel sheet; and a Cr oxide layer disposed on the metallic Cr layer, and the surface-treated steel sheet has a water contact angle of 50° or less and a total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface to Cr of 5% or less.

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 steel material for highly deformable line pipes that has superior strain aging resistance, superior HIC resistance, and a metallographic structure including ferrite, bainite, and martensite-austenite constituent. The area fraction of the martensite-austenite constituent is 0.5 to 5.0%, and the difference in hardness between the ferrite and the bainite is 60 or more in terms of Vickers hardness. Additionally, the steel material has a uniform elongation of 9% or more and a yield ratio of 90% or less both before a strain aging treatment at a temperature of 300&#xb0; C. or lower and after the strain aging treatment.

Steel material for highly deformable line pipes having superior strain aging resistance and superior HIC resistance, method for manufacturing same, and welded steel pipe

A steel material for highly deformable line pipes that has superior strain aging resistance, superior HIC resistance, and a metallographic structure composed mainly of ferrite and bainite. The total area fraction of the ferrite and the bainite is 90% or more, and the difference in hardness between the ferrite and the bainite is 70 or more in terms of Vickers hardness. Additionally, the steel material has a uniform elongation of 9% or more and a yield ratio of 90% or less both before a strain aging treatment at a temperature of 300&#xb0; C. or lower and after the strain aging treatment.

A seamless steel tube contains 0.15% to 0.50% C, 0.1% to 1.0% Si, 0.3% to 1.0% Mn, 0.015% or less P, 0.005% or less S, 0.01% to 0.1% Al, 0.01% or less N, 0.1% to 1.7% Cr, 0.4% to 1.1% Mo, 0.01% to 0.12% V, 0.01% to 0.08% Nb, and 0.0005% to 0.003% B or further contains 0.03% to 1.0% Cu on a mass basis and has a microstructure which has a composition containing 0.40% or more solute Mo and a tempered martensite phase that is a main phase and which contains prior-austenite grains with a grain size number of 8.5 or more and 0.06% by mass or more of a dispersed MC-type precipitate with substantially a particulate shape.

High-strength seamless steel tube, having excellent resistance to sulfide stress cracking, for oil wells and method for manufacturing the same

The invention is to provide a surface-treated steel sheet of good white rust resistance with no chromium in its surface treatment film, and it has realized a surface-treated steel sheet of higher-level corrosion resistance by forming a reaction layer of plating metal with a barrier layer effective for anticorrosion not in a two-layered film but in a single-layered film. The surface-treated steel sheet is fabricated by applying a surface-treating composition that contains:

Surface-treated steel sheets of good white rust resistance, and method for producing them

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Tokyo, Japan

Haruo Nakamichi