Jfe Steel Corporation

Takeshi Murai

Yuji Miki

Hiroshi Matsuda

Koichi Taniguchi

Yoshihiko Ono

Nobuyuki Nakamura

Minoru Takashima

Yukihiro Shingaki

Tadashi Nakanishi

Hiroyuki Ohno

Shimpei Yoshioka

Norichika Aramaki

Yuma Honda

Toshiyuki Ito

Toru Inoue

Tomoharu Ishida

Kohei Furumai

Yukio Usui

Haruka Nakamura

Kengo Matsuda

A high-strength steel sheet of the present invention has a specific chemical composition. Furthermore, in the steel sheet, a degree of Mn segregation in a specific region is 1.5 or less; a maximum P concentration in a specific region is 0.08 mass % or less; in a specific region, at least one specific MnS particle group is present, the number of specific MnS particle groups is 2.0 or fewer per 1 mm, and the number of specific oxide-based inclusions is 8 or fewer per 1 mm; of all oxide-based inclusions, oxide-based inclusions having a specific composition are present in a number ratio of 80% or greater; the microstructure includes, in terms of a volume fraction, 30 to 95% martensite, 5 to 70% ferrite phase, less than 30% (and 0% or greater) bainite, and less than 2.0% (and 0% or greater) austenite phase; and a tensile strength is 980 MPa or greater.

High-strength steel sheet and method for producing same

A method of producing a steel material includes a step of adding Ca to molten steel with an amount of Ca adjusted within a range satisfying the formula (1) below: where Ca is the amount [kg] of Ca added, y is an yield [%] of Ca, [S] is a concentration [% by mass] of S in the steel before addition of Ca, [AlO] is an amount [% by mass] of AlOin the steel before addition of Ca, and W is a weight [kg] of the molten steel.

Method of producing steel material

In a method for continuously casting an extremely low carbon steel using a continuous casting machine, by adjusting the chemical components of extremely low carbon steel within a specified range by taking into account an interface tension gradient in a concentration boundary layer on a front surface of a solidified shell, and also by optimizing intensities of the DC magnetic fields applied to the upper magnetic poles and the lower magnetic poles respectively corresponding to a slab width of a slab to be casted and a casting speed, it is possible to acquire the slab having high quality not only with the small number of defects caused by the entrainment of bubbles, non-metallic inclusion and a mold flux into the molten steel.

Continuous casting method for steel and method for manufacturing steel sheet

The present invention provides a grain-oriented electrical steel sheet produced by a method for promoting secondary recrystallization without an inhibitor, the grain-oriented electrical steel sheet including 2.0% or more and 4.5% or less of Si and 0.01% or more and 0.5% or less of Mn on a mass % basis, wherein the number of oxide particles having a diameter of 1 to 3 &#x3bc;m among that (oxide particles) of containing Ca and/or Mg is 400 or less per unit area (1 cm) in a transverse cross-section perpendicular to a rolling direction. Therefore, the grain-oriented electrical steel sheet has excellent stable magnetic properties throughout the length of a coil.

Grain-oriented electrical steel sheet and process for producing the same

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Kurashiki, Japan

Takeshi Murai