Jfe Steel Corporation

Nobuyuki Kageyama

Yoshimasa Funakawa

Takeshi Yokota

Akio Kobayashi

Chikara Kami

Kazuhiro Seto

Toru Hoshi

Hiroshi Nakata

Tetsuo Shimizu

Koji Iwata

Tetsuo Yamamoto

A hot-pressed steel sheet member has a composition containing, by mass, C: 0.09% to 0.38%, Si: 0.05% to 2.0%, Mn: 0.5% to 3.0%, P: 0.05% or less, S: 0.05% or less, Al: 0.005% to 0.1%, N: 0.01% or less, Sb: 0.002% to 0.03%, and the balance being Fe and inevitable impurities, and having a tensile strength TS of 980 to 2,130 MPa.

Hot-pressed steel sheet member, steel sheet for hot-press, and method for manufacturing hot-pressed steel sheet member

A hot-rolled steel strip having superior low temperature toughness and weldability, which is suitably used as a starting material for high strength electric resistance welding pipe, is provided at a low cost without constructing new production facilities and increasing cost. The hot-rolled steel strip is low carbon steel containing at least one of about 0.5.% or less of Cu, about 0.5% or less of Ni, and about 0.5% or less of Mo, wherein Pcm represented by the following equation (1) is 0.17 or less:=(% C)+(% Si)/30+((% Mn)+(% Cu))/20+(% Ni)/60+(% Mo)/7+(% V)/10&#x2003;&#x2003;Equation (1),(where (% M) indicates the content of element M on a mass percent basis), and the balance includes Fe and incidental impurities. In addition, in the entire microstructure, the ratio of bainitic ferrite, which is a primary phase, is controlled to be about 95 percent by volume or more.

Hot-rolled steel strip for high strength electric resistance welding pipe and manufacturing method thereof

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Chiba, Japan

Nobuyuki Kageyama