Jfe Steel Corporation

Shinsuke Ide

Atsushi Matsumoto

Takatoshi Okabe

Shin Ishikawa

Takeshi Suzuki

Akihide Matsumoto

Noriko Makiishi

Tomohiro Ishii

Takumi Ujiro

Yuji Hashimoto

Masayasu Nagoshi

Yasushi Kato

Kunio Fukuda

Osamu Furukimi

Hiroki Ota

Atsushi Miyazaki

Sota Goto

Naoki Nishiyama

Yukio Miyata

Kenji Takao

Hiroyuki Shirosawa

Atsutaka Honda

Ryo Nakazawa

An electric resistance welded steel pipe having excellent formability and torsional fatigue resistance and a method for manufacturing the same. The electric resistance welded steel pipe includes a seam region and a base metal region, the seam region having a range of ±10 degrees in a pipe circumferential direction with respect to an electric resistance welded seam formed in a pipe longitudinal direction, the base metal region being a region other than the seam region. The electric resistance welded steel pipe has an r-value in the pipe longitudinal direction of 1.0 or greater, H (mm) and W (mm) satisfy a specified formula, and Ts(mm) and Tb(mm) satisfy a specified formula.

Electric resistance welded steel pipe, method for manufacturing the same, and automotive structural member

Provided are a hot-rolled steel sheet for an electric resistance welded steel pipe and a method for manufacturing the same, an electric resistance welded steel pipe and a method for manufacturing the same, a line pipe, and a building structure. The hot-rolled steel sheet has a chemical composition containing, by mass %, C: 0.030% or more and 0.20% or less, Si: 0.02% or more and 1.0% or less, Mn: 0.40% or more and 3.0% or less, P: 0.050% or less, S: 0.020% or less, N: 0.0070% or more and 0.10% or less, and Al: 0.005% or more and 0.080% or less, the balance being Fe and incidental impurities, in which N dissolved in steel is contained in an amount of 0.0010% or more and 0.090% or less, and letting a sheet thickness be t, a steel microstructure at a ½t position has an average grain size of 20.0 μm or less.

Hot-rolled steel sheet for electric resistance welded steel pipe and method for manufacturing the same, electric resistance welded steel pipe and method for manufacturing the same, line pipe, and building structure

A metal pipe having an outer diameter of 150 mm to 3,000 mm and a wall thickness of 2 mm to 50 mm, and a method for manufacturing the same. The method includes a pipe-end-portion expansion step of expanding pipe end portions that are located at both ends of a mother pipe and an internal pressure application step that is performed after the pipe-end-portion expansion step and in which the mother pipe is expanded by applying an internal pressure, p, to the entire interior of the mother pipe until the internal pressure, p (MPa), that corresponds to changes in an axial compression amount s (mm), the axial compression amount, s, representing an amount of compression in a pipe axial direction against pipe extreme ends which are the both ends of the mother pipe, becomes a preset maximum internal pressure pmax (MPa), and p and s satisfy a specified formula.

Metal pipe and method for manufacturing metal pipe

Provided is a clad welded pipe or tube that has improved pipe or tube mechanical properties by reducing the width of a weld without its function as a clad pipe or tube being impaired. A clad welded pipe or tube comprises: a first layer made of base metal; and a second layer placed on one surface of the first layer, and made of first cladding metal that is a material different from the base metal, wherein a pipe or tube circumferential length L1 of weld metal at a pipe or tube inner surface and a pipe or tube circumferential length L2 of the weld metal at a pipe or tube outer surface in a weld are each 0.0010 mm or more and 1.0 mm or less, and the base metal is not exposed at a first cladding metal-side surface of the clad welded pipe or tube in the weld.

Clad welded pipe or tube and method of producing same

Provided is an electric resistance welded clad steel pipe or tube in which a region where solidification microstructure is formed, i.e. a region in a weld particularly having significant influence on properties, is reduced without impairing its function as a clad pipe or tube. An electric resistance welded clad steel pipe or tube comprises: a first layer made of carbon steel or low-alloy steel as base metal; and a second layer placed on one surface of the first layer, and made of stainless steel or a nickel-containing alloy as cladding metal, wherein the base metal is not exposed at a cladding metal-side surface of the electric resistance welded clad steel pipe or tube in a weld, and no solidification microstructure is contained in each of circular sections of 0.1 mm in radius respectively centered at specific three positions in a plane perpendicular to a pipe or tube longitudinal direction.

Electric resistance welded clad steel pipe or tube and method of producing same

An electric-resistance-welded stainless clad steel pipe or tube that is excellent in both the fracture property of the weld and the corrosion resistance of the pipe or tube inner surface as electric resistance welded without additional welding treatment such as weld overlaying after electric resistance welding is provided. An electric-resistance-welded stainless clad steel pipe or tube comprises: an outer layer of carbon steel or low-alloy steel; and an inner layer of austenitic stainless steel having a predetermined chemical composition, wherein a flatness value h/D in a 90&#xb0; flattening test in accordance with JIS G 3445 is less than 0.3, and a pipe or tube inner surface has no crack in a sulfuric acid-copper sulfate corrosion test in accordance with ASTM A262-10, Practice E, where h is a flattening crack height (mm), and D is a pipe or tube outer diameter (mm).

Electric-resistance-welded stainless clad steel pipe or tube

Method of producing electric-resistance-welded stainless clad steel pipe or tube

Provided is a method for producing a circumferential weld joint. With this method, when low-carbon martensitic stainless steel pipes used for pipelines for transportation of petroleum and natural gas are subjected to circumferential welding, the circumferential welding can be performed efficiently using a low-cost welding material having a composition similar to the composition of the low-carbon martensitic stainless steel pipes. Pipe ends of low-carbon martensitic stainless steel pipes containing prescribed components are butted against each other and subjected to multi-pass arc welding using a welding material containing prescribed components. In the first pass in the multi-pass arc welding, CMT welding is performed in which the welding material is moved back and forth against a molten pool to generate an arc intermittently. In the second and subsequent passes, one selected from GMA welding, GTA welding, and the CMT welding is performed.

Method for producing circumferential weld joint for low-carbon martensitic stainless steel pipes

A stainless steel having a low surface contact resistance for fuel cell separators is provided. The stainless steel has a Cr content of 16 to 40 mass % or more. The stainless steel includes a region having a fine textured structure on its surface, and the area percentage of the region is 50% or more, preferably 80% or more. The region having a fine textured structure is a region which has a structure having depressed portions and raised portions at an average interval between depressed portions or raised portions of 20 nm or more and 150 nm or less when observed with a scanning electron microscope.

Stainless steel for fuel cell separators

A stainless steel for use in a fuel cell separator is produced by subjecting stainless steel containing 16 mass % or more of Cr to electrolytic treatment and thereafter to immersion treatment in a solution containing fluorine. The electrolytic treatment is carried out by anodic electrolyzation or by a combination of anodic electrolyzation and cathodic electrolyzation, and an anodic electrolytic quantity Qa and a cathodic electrolytic quantity Qc preferably satisfy Qa&#x2267;Qc. The solution containing fluorine preferably has a temperature of 40&#xb0; C. or higher, and hydrofluoric acid concentration [HF] (mass %) and nitric acid concentration [HNO] (mass %) satisfying [HF]&#x2267;0.8&#xd7;[HNO].

Method for producing stainless steel for fuel cell separator, stainless steel for fuel cell separator, fuel cell separator, and fuel cell

A stainless steel for a fuel cell having good corrosion resistance throughout a wide potential range and a method for producing the same are provided. In particular, a coating having an intensity ratio [(OO/OH)/(Cr/Fe)] of 1.0 or more determined by X-ray photoelectron spectroscopy analysis is formed by performing an anodic electrolyzation treatment on a surface of a stainless steel in an electrolyte solution, the stainless steel containing 16% by mass or more of Cr and preferably having a composition that includes, in terms of percent by mass, C: 0.03% or less, Si: 1.0% or less, Mn: 1.0% or less, S: 0.01% or less, P: 0.05% or less, Al: 0.20% or less, N: 0.03% or less, Cr: 20 to 40%, at least one selected from Nb, Ti, and Zr, in total: 1.0% or less, and the balance being Fe and unavoidable impurities.

Stainless steel for fuel cell having good corrosion resistance and method for producing the same

A stainless steel having good conductivity and ductility for use in a fuel cell separator is provided. In particular, the stainless steel has a composition of, in terms of % by mass, C: 0.01% or less, Si: 1.0% or less, Mn: 1.0% or less, S: 0.01% or less, P: 0.05% or less, Al: 0.20% or less, N: 0.02% or less, Cr: 20 to 40%, Mo: 4.0% or less, and at least one selected from Nb, Ti, and Zr: 0.05 to 0.60% in total, the balance being Fe and unavoidable impurities. At least one precipitate having an equivalent circle diameter of 0.1 &#x3bc;m or more is present per 100 &#x3bc;m, a ratio of a thickness t (&#x3bc;m) to a maximum diameter Dmax (&#x3bc;m) of the precipitates satisfies formula (1) below20&#x2266;max&#x2003;&#x2003;(1)and the thickness is 200 &#x3bc;m or less.

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Tokyo, Japan

Shinsuke Ide