Jfe Steel Corporation

Nkk Corporation

Yasuhiro Matsuki

Tomohiro Inoue

Chikara Kami

Satoru Ando

Toyofumi Watanabe

Masaki Abe

Hiroshi Nakata

Masaya Morita

Yukimitsu Shiohara

Yoshitsugu Iijima

Takahiko Ogura

Satoru Udagawa

Hiroshi Shigeta

Yoshimitsu Fukui

Kei Mikami

Akimasa Kido

A low-yield ratio high-strength electric resistance welded steel pipe has a yield ratio of 80% or less and a TS of 655 MPa or more. A steel material has a composition containing 0.38% to 0.45% C, 0.1% to 0.3% Si, 1.0% to 1.8% Mn, 0.03% or less P, 0.03% or less S, 0.01% to 0.07% sol. Al, and 0.01% or less N on a mass basis.

Low-yield ratio high-strength electric resistance welded steel pipe, steel strip for electric resistance welded steel pipes, and methods of manufacturing them

Provided is a metal strip for a pipe with which the weight of a pipe can be reduced while maintaining the strength of a joint portion that tends to be structurally the weakest. A metal strip L is formed by rolling. The thickness of each of a head end portionand a tail end portion, which are longitudinal end portions, is greater than the thickness of an intermediate portion excluding the longitudinal end portions. The metal strips are connected to each other in series by welding, and a pipe is made by performing a pipe-forming operation.

Metal strip

A surface treated steel sheet comprises: a steel sheet containing C, Si, Mn, P, S, Ni, Ti, Cu and B; a diffused alloy layer containing Fe, Ni, and P; and a zinc coating layer formed on the diffused alloy layer. A method for producing a surface treated steel sheet comprises the steps of: preparing a steel sheet; coating the steel sheet with a Ni-P coating layer; heat-treating the steel sheet coated with the Ni-P coating layer; and forming a zinc coating layer on the diffused alloy layer.

Surface treated steel sheet

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Kawasaki, Japan

Yasuhiro Matsuki