Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Nhk Spring Co., Ltd.

Tetsuo Ishitsuka

Akira Tange

Ken Takahashi

Hiroyuki Ogawa

Koichi Nose

Osamu Yoshida

Akihiro Miyasaka

Hitoshi Asahi

Yasuhiro Shinohara

Shinya Sakamoto

Takaaki Fukushi

Hiroyuki Mimura

Kiyoshi Kurimoto

Shunichi Kobayashi

Toshiyuki Ogata

Takashi Tsusue

Hideto Kawano

Kozo Denpo

Shuji Iwamoto

Motofumi Koyuba

Yutaka Wakabayashi

Mizuo Sakakibara

Satoshi Araki

Koichi Takeda

Michihisa Ito

Takahiro Ichiyama

Naoki Takasugi

Bunshi Kato

Junichi Okamoto

Kenzo Tashima

Masamichi Iwamura

Teruhisa Takamoto

Kazuhiro Inoue

An as-rolled type K55 electric resistance welded oil well pipe includes, in terms of % by mass, 0.30 to 0.50% of C, 0.05 to 0.40% of Si, 0.50 to 1.20% of Mn, 0 to 0.030% of P, 0 to 0.020% of S, 0.002 to 0.080% of Al, 0 to 0.0080% of N, 0 to 0.30% of Cu, 0 to 0.30% of Ni, 0 to 0.30% of Cr, 0 to 0.10% of Mo, 0 to 0.10% of V, 0 to 0.050% of Nb, 0 to 0.030% of Ti, 0 to 0.0100% of Ca, and the balance being Fe and impurities. In the pipe, a metallographic structure at a position of &#xbc; of a pipe thickness in an L cross-section at a base metal 90&#xb0; position is a ferrite-pearlite structure in which prior &#x3b3;-grains are flattened, includes grain boundary ferrite and intragranular ferrite, and has a rate of a total area of the grain boundary ferrite and the intragranular ferrite, of 10 to 30%.

As-rolled type K55 electric resistance welded oil well pipe and hot-rolled steel sheet

Electric resistance welded steel pipe securing the high strength and high toughness demanded from oil well pipe in recent years. The metal structure in a region having a width of 0.5 mm in both the thickness directions from a reference point, when using a point defined as a point &#xbc; of the thickness in the thickness direction from the surface in the base material part of the steel as the reference point, consists of polygonal ferrite: 10 area % or less and a balance: bainitic ferrite. The thickness is 15 mm or more.

High strength electric resistance welded steel pipe and method for producing high strength electric resistance welded steel pipe

The invention provides a steel pipe excellent in deformation characteristics, most notably a steel pipe for expandable-pipe oil well and a low-yield-ratio line pipe, and a method of producing the same without conducting water cooling requiring large-scale heat treatment equipment, namely a method of producing a steel pipe excellent in deformation characteristics whose microstructure is a two-phase structure including a martensite-austenite constituent at an area fraction of 2 to 10% and a soft phase, which method comprises: heating at Ac+10&#xb0; C. to Ac+60&#xb0; C. and thereafter cooling a precursor steel pipe which contains, in mass %, C: 0.04 to 0.10% and Mn: 1.00 to 2.50%, is limited to Si: 0.80% or less, P: 0.03% or less, S: 0.01% or less, Al: 0.10% or less and N: 0.01% or less, further contains one or more of Ni: 1.00% or less, Mo: 0.60% or less, Cr: 1.00% or less and Cu: 1.00% or less, where content of Mn and content of one or more of Cr, Ni, Mo and Cu satisfy Mn+Cr+Ni+2Mo+Cu&#x2267;2.00, and a balance of iron and unavoidable impurities.

Steel pipe excellent in deformation characteristics and method of producing the same

Alloy having high corrosion resistance in environment of high

Alloy and multilayer steel tube having corrosion resistance in fuel

An alloy exhibiting corrosion resistance in a combustion environment where V, Na, S and Cl are present comprises, in weight percent, not more than 0.05% C, 0.02-0.5% Si, 0.02-0.5% Mn, 15-35% Cr, 0.5-4% Mo, 10-40% Co, 5-15% Fe, 0.5-5% W, 0.0003-0.005% Ca and the remainder of Ni at a content of not less than 4% and unavoidable impurities, provided that Cr (%)+0.5Ni (%)+3Mo (%).gtoreq.30 (%) and Ni (%)+0.5Co (%).gtoreq.Cr (%)+Mo (%)+W (%). A composite steel tube exhibiting corrosion resistance in a combustion environment where V, Na, S and Cl are present comprises an inner tube constituted of Cr-containing boiler tube and an outer tube constituted of the alloy.

Alloy and composite steel tube with corrosion resistance in combustion

An alloy exhibiting corrosion resistance in a combustion environment where V, Na, S and Cl are present comprises, in weight percent, not more than 0.05% C, 0.02-0.5% Si, 0.02-0.5% Mn, 15-35% Cr, 0.5-4% Mo, more than 40% but not more than 60% Co, 5-15% Fe, 0.5-5% W, 0.0003-0.005% Ca and the remainder of Ni at a content of not less than 4% and unavoidable impurities, provided that Cr (%)+0.5Ni (%)+3Mo (%).gtoreq.30 (%). A composite steel tube exhibiting corrosion resistance in a combustion environment where V, Na, S and Cl are present comprises an inner tube constituted of Cr-containing boiler tube and an outer tube constituted of the alloy.

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Tokyo, Japan

Tetsuo Ishitsuka