Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)

Voestalpine Stahl Gmbh

Shinshu Tlo Co., Ltd.

Fumio Yuse

Junichiro Kinugasa

Yoichi Mukai

Kouji Kasuya

Toshio Murakami

Kenji Saito

Muneaki Ikeda

Koichi Sugimoto

Shushi Ikeda

Mikako Takeda

Hideo Hata

Takenori Nakayama

Michiharu Nakaya

Hiroshi Akamizu

Yukihiro Utsumi

Andreas Pichler

Michitaka Tsunezawa

Shinji Kozuma

Shigenobu Namba

Atsuhiro Shiraki

Kosuke Shibata

Akira Ibano

Takahiro Ozawa

Toshiaki Kan

Sandra Traint

Toshiya Nakata

Yoshihiro Miyake

Provided is an ultra-high-strength steel sheet having a component composition that includes specific amounts of each of C, Mn, and Al and a remainder of iron and unavoidable impurities, and in which the amounts of each of P, S, and N among the unavoidable impurities are limited to a specific amount. The ultra-high-strength steel sheet includes 2 area% or more of a region having a structure that includes 90% or more of martensite and 0.5% or more of residual austentite by area ratio relative to the entire structure, the local Mn concentration in said region being at least 1.1 times that of the Mn content of the entire steel sheet. The ultra-high-strength steel sheet has a tensile strength of 1470 MPa or more.

Ultra-high-strength steel sheet having excellent delayed fracture resistance at cut end thereof

Disclosed is a high strength steel sheet having excellent hydrogen embrittlement resistance. The steel sheet has a tensile strength of 1180 MPa or more, and satisfies the following conditions: with respect to an entire metallographic structure thereof, bainite, bainitic ferrite and tempered martensite account for 85 area % or more in total; retained austenite accounts for 1 area % or more; and fresh martensite accounts for 5 area % or less (including 0 area %).

High strength steel sheet having excellent hydrogen embrittlement resistance

Disclosed is a high-strength cold-rolled steel sheet having improved stretch-flange formability and excellent hydrogen embrittlement resistance. In addition to Fe, C, Si, Mn, P, S, N, and Al, the steel sheet contains V or at least one element of Nb, Ti and Zr. The contents of the at least one element of Nb, Ti and Zr, if present, satisfy the expression of [% C]&#x2212;[% Nb]/92.9&#xd7;12&#x2212;[% Ti]/47.9&#xd7;12&#x2212;[% Zr]/91.2&#xd7;12&#x3e;0.03. The steel sheet has an area ratio of tempered martensite of 50% or more with ferrite as the remainder. The number of precipitates having a circle-equivalent diameter of 1 to 10 nm is 20 particles or more per 1 &#x3bc;mof the tempered martensite. The number of precipitates containing V or the at least one element of Nb, Ti and Zr and having a circle-equivalent diameter of 20 nm or more is 10 particles or less per 1 &#x3bc;mof the tempered martensite.

Cold-rolled steel sheet

A galvannealed steel sheet obtained by subjecting a base steel sheet to hot-dip galvanization and then alloying the galvanization layer, the base steel sheet being obtained by hot rolling a specified steel. A method for producing the galvannealed steel sheet.

Galvannealed steel sheet and production method thereof

The present invention is the thin steel sheet containing C, Si, Mn, P, S, Al, Mo, Ti, B, and N wherein a value Z calculated by the equation described below is 2.0-6.0, an area ratio against all the structure is 1% or above for retained austenite and 80% or above for total of bainitic ferrite and martensite, a mean axis ratio of the retained austenite crystal grain is 5 or above, and tensile strength is 980 MPa or above whereValue Z=9&#xd7;[C]+[Mn]+3&#xd7;[Mo]+490&#xd7;[B]+7&#xd7;[Mo]/{100&#xd7;([B]+0.001),andthe thin steel sheet has 980 MPa or above tensile strength and enhanced hydrogen embrittlement resistance properties.

High-strength thin steel sheet

The invention relates to an ultrahigh-strength thin steel sheet excellent in the hydrogen embrittlement resistance, the steel sheet including, by weight %, 0.10 to 0.60% of C, 1.0 to 3.0% of Si, 1.0 to 3.5% of Mn, 0.15% or less of P, 0.02% or less of S, 1.5% or less of Al, 0.003 to 2.0% of Cr, and a balance including iron and inevitable impurities; in which grains of residual austenite have an average axis ratio (major axis/minor axis) of 5 or more, the grains of the residual austenite have an average minor axis length of 1 &#x3bc;m or less, and the grains of the residual austenite have a nearest-neighbor distance between the grains of 1 &#x3bc;m or less.

Ultrahigh-strength thin steel sheet

The present invention provides a high strength steel used for spring steel that has excellent hydrogen embrittlement resistance. The high strength steel which spring steel having excellent hydrogen embrittlement resistance comprises 0.20 to 0.60% of C, 1.0 to 3.0% of Si, 1.0 to 3.5% of Mn, higher than 0% and not higher than 1.5% of Al, 0.15% or less P, 0.02% or less S, and balance of iron and inevitable impurities and the structure includes:

High strength spring steel having excellent hydrogen embrittlement resistance

A steel suitable for a fabric with or without painting and has good corrosion resistance with reproducibility, even if the steel is composed mainly of ordinary carbon steel or low alloy steel, wherein the surface of the steel is coated with rust comprising one or more selected from Ti, Nb, Ta, Zr, V and Hf in the total amount of 0.01 wt % or more. In the steel, the fraction of &agr;-FeOOH and an amorphous rust is 35 wt % or more, and the fraction of &bgr;-FeOOH is 20 wt % or less.

Steel material excellent in corrosion resistance and fabric using the same

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Kobe, Japan

Fumio Yuse