Nippon Steel Corporation

Dai Nippon Printing Co., Ltd.

Sony Corporation

Bridgestone Corporation

Nippon Steel Sumitomo Metal Corporation

D.t. Circuit Technology Co., Ltd.

Hitachi, Ltd.

Yokogawa Electric Corporation

Hitachi Vlsi Engineering Corp.

Yokogawa Hokushin Electric Corp.

Yuji Yamaguchi

Satoshi Uchida

Hiroyuki Kawata

Takafumi Yokoyama

Masahiro Nakata

Kunio Hayashi

Natsuko Sugiura

Naoki Maruyama

Kohichi Sano

Kohei Ueda

Osamu Shimada

Yoshitaka Fukuoka

Takeshi Yasui

Hiroyuki Hirai

Ryosuke Komami

Riki Okamoto

Toyomitsu Nakamura

Makoto Uno

Taihei Kaneto

Hayato Arai

Ryoichi Nishiyama

Hiroshi Yagi

Atsushi Morishita

Akinobu Murasato

Kenji Sasaoka

Kenichi Matsumura

Tooru Serizawa

Kazuhiro Shinozaki

Kazuki Shiokawa

Tatsuya Nakada

Satoshi Shibazaki

Yuichi Nakahira

Tatsuro Imamura

Eisaku Sakurada

Masahiro Fuda

Hironori Sato

Akinobu Minami

Jin Satoh

Kazuo Taniguchi

Chishiro Tanabe

Takao Asaka

Mitsuharu Ohki

Tomoo Mitsunaga

Hiromichi Suzuki

Hiroyuki Ozawa

Tetsugo Inada

Kazumasa Ito

Takamasa Suzuki

Osamu Saito

Masahiko Yamamoto

Masao Kurosaki

Hideto Iwaoka

Takuya Kuwayama

Genki Abukawa

Kei Ito

Hiromasa Shoji

Tomohisa Nishikawa

Makoto Tsuruta

Tetsuhito Tsukagoshi

Masaharu Yoshimori

Hidetoshi Nagano

Naoki Inoue

Takayuki Okinaga

Hiroyuki Teratani

Shohei Yabu

Takashi Emata

Masahiro Igarashi

Osamu Horiuchi

Masatoshi Imai

Naosuke Asari

Masayuki Miyabayashi

Ryohei Iida

Kazunori Katoh

Takayuki Kitazawa

Yugo Zuigyo

Yoshinori Imai

Tadanari Inoue

Marina Mori

Takuma Kawanaka

Yasuhiro Nakashima

Toshiharu Noda

Sumito Arakawa

Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined chemical composition, and contains ferrite: 50% or less, retained austenite: 30% or less, tempered martensite: 5% or more, fresh martensite: 10% or less, and pearlite and cementite in total: 5% or less, remaining structures consist of bainite, and a number ratio of tempered martensite with a Mn concentration profile satisfying [Mn]/[Mn]>1.2 and [Mn]/[Mn]<2.0 ([Mn] is the Mn content in the base steel sheet, [Mn]is the average Mn concentration in the tempered martensite, and [Mn]is the Mn concentration at the interfaces of different phases of the tempered martensite and ferrite phase and bainite phase) is 0.2 or more with respect to the total number of tempered martensite, and a method for producing the same.

Hot dip galvanized steel sheet and method for producing same

Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined composition and contains ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, remaining structures consist of bainite, when defining a region having a hardness of 90% or less of the hardness at a position of ¼ thickness to the base steel sheet side from an interface of the base steel sheet and a hot dip galvanized layer as a 'soft layer', there is a soft layer having a thickness of 10 μm or more at the base steel sheet side from the interface, the soft layer contains tempered martensite, and an increase rate in a thickness direction of an area % of tempered martensite from the interface to the inside of the base steel sheet inside the soft layer is 5.0%/μm or less, and a method for producing the same.

A hot-rolled steel sheet includes, as chemical composition, C, Si, Mn, and sol.Al. In the hot-rolled steel sheet, an average of pole densities in crystal orientation group consisting of {110}<110> to {110}<001> in surface region is 0.5 to 3.0, a standard deviation of the pole densities in the crystal orientation group is 0.2 to 2.0, and the tensile strength is 780 to 1370 MPa.

Hot-rolled steel sheet

A hot dip galvanized steel sheet includes a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition, and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, when there are remaining structures, the remaining structures consist of bainite, a concentration of B atoms at prior austenite grain boundaries is 2.0 atm % or more, and an average effective crystal grain size is 7.0 μm or less, and a method for producing the same.

A zinc-plated steel sheet includes a steel sheet having a predetermined chemical composition and a zinc-plated layer. In the steel sheet, steel microstructures in a range of ⅛ thickness to ⅜ thickness, having the center at ¼ thickness from a steel sheet surface, include, by vol %, ferrite: 0% to 10%, bainite: 0% to 30%, tempered martensite: 50% or more, fresh martensite: 0% to 10%, retained austenite: more than 10% and 30% or less, and pearlite: 0% to 5%. In the zinc-plated steel sheet, the amount of hydrogen emitted when the steel sheet is heated to 200° C. from room temperature after removal of the zinc-plated layer is 0.40 ppm or less per mass of the steel sheet, the tensile strength is 1470 MPa or more, and no cracking occurs in a U-shape bending test where a stress equivalent to 1000 MPa is applied for 24 hours.

Zinc-plated steel sheet and manufacturing method thereof

Provided are a hot dip galvanized steel sheet comprising a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 6% to 30%, bainite: 5% or more, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, a number density of tempered martensite with a circle equivalent diameter of 5.0 &#x3bc;m or more is 20/1000 &#x3bc;mor less, and an area ratio of fresh martensite with a circle equivalent diameter of 2.0 &#x3bc;m or more after imparting 5% plastic strain is 10% or less, and a method for producing the same.

A zinc-plated steel sheet of an aspect of the present invention includes a steel sheet having a predetermined chemical composition and a zinc-plated layer. In the steel sheet, steel microstructures in a range of &#x215b; thickness to &#x215c; thickness, having the center at &#xbc; thickness from a steel sheet surface, include, by vol %, ferrite: 0% to 10%, bainite: 0% to 20%, tempered martensite: 70% or more, fresh martensite: 0% to 10%, retained austenite: 0% to 10%, and pearlite: 0% to 5%. In the zinc-plated steel sheet, the amount of hydrogen emitted when the steel sheet is heated to 200&#xb0; C. from a room temperature after removal of the zinc-plated layer is 0.40 ppm or less per mass of the steel sheet, the tensile strength is 1470 MPa or more, and no cracking occurs in a U-shape bending test where a stress equivalent to 1000 MPa is applied for 24 hours.

A steel sheet has a specific chemical composition and has a structure represented by, by area ratio, ferrite: 5 to 60%, and bainite: 40 to 95%. When a region that is surrounded by a grain boundary having a misorientation of 15&#xb0; or more and has a circle-equivalent diameter of 0.3 &#x3bc;m or more is defined as a crystal grain, the proportion of crystal grains each having an intragranular misorientation of 5 to 14&#xb0; to all crystal grains is 20 to 100% by area ratio. A precipitate density of Ti(C,N) and Nb(C,N) each having a circle-equivalent diameter of 10 nm or less is 10precipitates/mmor more. A ratio (Hvs/Hvc) of a hardness at 20 &#x3bc;m in depth from a surface (Hvs) to a hardness of the center of a sheet thickness (Hvc) is 0.85 or more.

Steel sheet and plated steel sheet

A steel sheet wherein a steel structure of an inside of the steel sheet contains, by volume fraction, soft ferrite: 0% to 30%, retained austenite: 3% to 40%, fresh martensite: 0% to 30%, a sum of pearlite and cementite: 0% to 10%, and a remainder including hard ferrite. In the steel sheet, in a &#x215b; to &#x215c; thickness range, a proportion of retained austenite having an aspect ratio of 2.0 or more is 50% or more, and a soft layer having a thickness of 1 to 100 &#x3bc;m from a surface in a sheet thickness direction is present. When an emission intensity at a wavelength indicating Si is analyzed in the sheet thickness direction from the surface by a radio-frequency glow discharge analysis method, a peak of the emission intensity appears in a range of more than 0.2 &#x3bc;m and 5.0 &#x3bc;m or less from the surface.

Steel sheet and manufacturing method of therefor

In a thickness range of which center is a &#xbc; thickness from the surface of a base steel sheet, a volume fraction of a ferrite phase is 0% to less than 50%, a volume fraction of the total of a hard structure composed of one or more of a bainite structure, a bainitic ferrite phase, a fresh martensite phase, and a tempered martensite phase is 50% or more, a volume fraction of a retained austenite phase is 0-8%, and a volume fraction of the total of a pearlite phase and a coarse cementite phase is 0-8%, at an interface between a plating layer and the base steel sheet, a Fe&#x2014;Al alloy layer is provided, the Fe&#x2014;Al alloy layer having an average thickness of 0.1-2.0 &#x3bc;m and a difference between a maximum thickness and a minimum thickness in the width direction of the steel sheet being within 0.5 &#x3bc;m.

Hot-dip galvanized steel sheet

A steel sheet has a chemical composition with a steel structure containing, by volume fraction, soft ferrite: 0-30%, retained austenite: 3-40%, fresh martensite: 0-30%, pearlite and cementite: 0-10%, and a remainder including hard ferrite. In the steel sheet, a number proportion of retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, and a soft layer having a thickness of 1-100 &#x3bc;m is present. In the soft layer, a volume fraction of ferrite grains having an aspect ratio of less than 3.0 is 50% or more, and a volume fraction of retained austenite is 50% or more of the volume fraction of the retained austenite of the inside of the steel sheet. A peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 &#x3bc;m to 5 &#x3bc;m or less from the surface.

Steel sheet and manufacturing method therefor

A high-strength hot-dip galvanized steel sheet contains predetermined amounts of C, Si, Mn, P, S, N, O, sol. Al, Ti, and B, 0.1 to 1.5 mass % of Cr+2&#xd7;Mo, and a balance in a form of Fe and inevitable impurities. A steel structure includes, in area %, ferrite: 1 to 50%, martensite: 20 to 70%, residual austenite: 0 to 5%, pearlite: 0 to 5%, MA and cementite having 0.2 &#x3bc;m or more grain size: 0 to 5% in total, and a balance in a form of bainite. A number density of MA or cementite having 0.2 &#x3bc;m or more grain size and isolated in ferrite or bainite grains is 100 pcs/1000 &#x3bc;mor less, and an average hardness of martensite is in a range from 330 to 500 Hv.

High strength hot-dip galvanized steel sheet and production method therefor

A cold-rolled steel sheet is provided that has a tensile strength of 980 MPa or more, and has a prescribed chemical composition. The microstructure is composed of, in area %, ferrite: 1 to 29%, retained austenite: 5 to 20%, martensite: less than 10%, pearlite: less than 5%, and the balance: bainite and/or tempered martensite. The total sum of the lengths of phase boundaries where ferrite comes in contact with martensite or retained austenite having a circle-equivalent radius of 1 &#x3bc;m or more is 100 &#x3bc;m or less per 1000 &#x3bc;m. The cold-rolled steel sheet is excellent in workability and low-temperature toughness, and in particular is excellent in low-temperature toughness after introduction of plastic strain.

Cold-rolled steel sheet and hot-dip galvanized cold-rolled steel sheet

A hot-dip galvanized steel sheet including: a hot-dip galvanizing layer on at least one side of a base steel sheet. The hot-dip galvanizing layer has a Fe content of more than 0% to 3.0% and an Al content of more than 0% to 1.0%. The hot-dip galvanized steel sheet includes a Fe&#x2014;Al alloy layer provided on an interface between the hot-dip galvanizing layer and the base steel sheet and a fine-grain layer provided in the base steel sheet and directly in contact with the Fe&#x2014;Al alloy layer. The Fe&#x2014;Al alloy layer has a thickness of 0.1-2.0 &#x3bc;m. The fine-grain layer has an average thickness of 0.1-5.0 &#x3bc;m, includes a ferrite phase with an average grain diameter of 0.1-3.0 &#x3bc;m, and contains oxides of one or more out of Si and Mn, a maximum diameter of the oxides being 0.01-0.4 &#x3bc;m.

A steel sheet has a specific chemical composition and has a structure represented by, by area ratio, ferrite: 30 to 95%, and bainite: 5 to 70%. When a region that is surrounded by a grain boundary having a misorientation of 15&#xb0; or more and has a circle-equivalent diameter of 0.3 &#x3bc;m or more is defined as a crystal grain, the proportion of crystal grains each having an intragranular misorientation of 5 to 14&#xb0; to all crystal grains is 20 to 100% by area ratio. An average aspect ratio of ellipses equivalent to the crystal grains is 5 or less. An average distribution density of the total of Ti-based carbides and Nb-based carbides each having a grain size of 20 nm or more on ferrite grain boundaries is 10 carbides/&#x3bc;m or less.

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Tokyo, Japan

Yuji Yamaguchi