Jfe Steel Corporation

Tatsuo Koide

Tomohiro Inoue

Takatoshi Okabe

Mitsuhiro Okatsu

Kazuhito Kenmochi

Hiroyasu Yokoyama

Hiroyuki Takai

Yuji Sugimoto

Hiroyuki Shirosawa

Tetsuro Sawaki

Yasumasa Takemura

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.

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

Manufacturing equipment of electric resistance welding pipes having excellent characterization of welded seams, includes an apparatus that supplies a strip, an apparatus that reforms a shape, an apparatus that performs roll forming, an induction heater, and a contacting apparatus of strip edges by pressing, and having a finpass forming apparatus incorporating a fin having at least two stages of tapering in a middle portion of the roll forming, wherein tapering of the strip immediately before electric resistance welding is conducted such that an angle from a surface of a strip edge toward a vertical direction is in a range of 25 degrees to 50 degrees, and length of a perpendicular angle from a starting position to an end position of the tapering at one side is 20% to 45% of strip thickness, and by shaping the tapering with a fin, having at least two stages of tapering, incorporated in a finpass forming end stand.

Manufacturing equipment for electric resistance welding pipes having excellent characterization for welded seam

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Tokyo, Japan

Tatsuo Koide