Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Other

Renesas Technology Corp.

Denso Corporation

Hiroyuki Kawata

Naoki Maruyama

Yuji Yamaguchi

Takeshi Yasui

Takafumi Yokoyama

Kohichi Sano

Masafumi Azuma

Akihiro Uenishi

Kohei Ueda

Kengo Takeda

Takuya Kuwayama

Koichi Sato

Yasuhiro Ito

Satoshi Uchida

Kunio Hayashi

Riki Okamoto

Eisaku Sakurada

Yuri Toda

Katsuya Nakano

Kaoru Hiramatsu

Noriyuki Suzuki

Koutarou Hayashi

Yasunobu Miyazaki

Fuminori Watanabe

Masahiro Kubo

Kenichiro Otsuka

Natsuko Sugiura

Masahiro Saito

Masahiro Nakata

Nobuhiro Fujita

Naoki Yoshinaga

Shigeru Yonemura

Daisuke Maeda

Jun Maki

Takamasa Suzuki

Kaoru Kawasaki

Koji Shibata

Tohru Okada

Yuya Suzuki

Akinobu Murasato

Akinobu Minami

Chisato Wakabayashi

Hiroyuki Ban

Toyomitsu Nakamura

Ryosuke Komami

Jun Haga

Mahito Sawada

Hiroshi Tobimatsu

Hayato Arai

Hideki Hamatani

Masaharu Kameda

Kazuki Shiokawa

Yuichi Nakahira

Seiji Furusako

Hiroaki Kubota

Hatsuhiko Oikawa

Chisato Yoshinaga

Koyu Asai

Kouji Oda

Genki Abukawa

Masanori Yasuyama

Takayuki Nozaki

Yasuharu Sakuma

Takashi Tsuboi

Hajime Hasegawa

Mai Nagano

Yasuyoshi Toda

Genichi Shigesato

Yuuki Kamiura

Takayuki Kitazawa

Kouji Shibata

Hitoshi Nikaido

Keitaro Matsuda

Sho Matsui

Satoshi Hironaka

Yoshinori Imai

Tsuyoshi Oki

Yasuhiro Nakashima

A galvanized steel sheet comprising a steel sheet containing C: 0.05 to 0.30%, Si: 0.01 to 3.00%, Mn: 0.80 to 3.00%, and Al: 0.010 to 2.000% and having a thickness of 0.10 to 0.95 mm, and a galvanized layer on the steel sheet, wherein a tensile strength is 550 to 1500 MPa, and, when defining a thickness of an internal oxide layer per surface of the steel sheet as 'A' (μm), a thickness of a decarburized layer per surface of the steel sheet as “B” (μm), and a thickness of the steel sheet as “t” (μm), A/B: 0.01 to 0.50 and B/t: 0.001 to 0.200.

Galvanized steel sheet

A steel sheet has a predetermined chemical composition, in which a metallographic structure in a surface layer region ranging from a surface to a position of 20 μm from the surface in a sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 0.01% to 5.0%, a metallographic structure in an internal region ranging from a position of more than 20 μm from the surface in the sheet thickness direction to a ¼thickness position from the surface in the sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 2.0% to 10.0%, the volume fraction of the secondary phase in the surface layer region is less than the volume fraction of the secondary phase in the internal region, and in the surface layer region, an average grain size of the secondary phase is 0.01 μm to 4.0 μm, and a texture in which an Xas the ratio of the intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.60 or more and less than 2.00 is included.

Steel sheet and method for manufacturing same

A steel sheet includes a predetermined composition, in which a microstructure at a ¼ thickness position from a surface in a sheet thickness direction includes, by vol %, ferrite: 80% or more, martensite: 2% or less, and residual austenite: 2% or less, a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and in the microstructure of the steel sheet stretched by 10% at the ¼ thickness position from the surface in the sheet thickness direction, a number density of voids having a maximum diameter of 1.0 μm or more is 1.0×10pieces/mor less.

Steel sheet and method of manufacturing the same

A high-strength steel sheet excellent in formability, toughness and weldability has a chemical composition including: by mass %, C: 0.05 to 0.30%, Si: 2.50% or less, Mn: 0.50 to 3.50%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance consisting of Fe and inevitable impurities. The high-strength steel sheet has a microstructure in a region from ⅛ t (t: sheet thickness) to ⅜ t (t: sheet thickness) from a steel sheet surface, the microstructure including: by volume %, acicular ferrite (): 20% or more, and martensite (): 10% or more, polygonal ferrite: 20% or less, residual austenite: 2.0% or less, and the martensite satisfies a formula (A),

High-strength steel plate having excellent formability, toughness and weldability, and production method of same

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

This steel sheet has a predetermined chemical composition, a microstructure contains, in terms of a volume fraction, ferrite: 10% to 75%, martensite: 20% to 90%, retained austenite: 0% to 5%, bainite and bainitic ferrite in total: 0% to 50%, and pearlite: 0% to 5%, a proportion of unrecrystallized ferrite in the ferrite is 0% to 25%, cementite that is contained in the martensite satisfies a predetermined relational expression, a density of transition carbide included in the martensite is 1.0×10pieces/mor more, a density of coarse inclusion having an equivalent circle diameter of 10 μm or more is 0.50 pieces/mmor less, in a surface parallel to the surface at a position ¼ of the sheet thickness deep from the surface in the sheet thickness direction, a ratio of a maximum value Hvof Vickers hardness to a minimum value Hvof the Vickers hardness is 1.40 or less, and an average value of minimum distances between peaks of the Vickers hardness in a distribution map of the Vickers hardness is 1.00 mm or less.

Steel sheet and production method for same

A steel sheet of the present invention is a steel sheet having a predetermined chemical composition and containing at least ferrite, residual austenite, and/or martensite in a microstructure, and furthermore, is a steel sheet in which, in a plane parallel to a rolled surface, an average distance between centers of high Mn regions adjacent to each other is 1.00 mm or less, a density Dof the high Mn regions at a sheet width center portion and a density Dof the high Mn regions at a ¼ position from a sheet width end portion satisfy a relationship of 0.77≤D/D≤1.30, a ratio of an average hardness of the high Mn regions to an average hardness of the low Mn regions is 1.1 to 2.0, and a difference between an average of a top 5% and an average of a bottom 5% of Mn contents in the low Mn regions is 0.3% or more.

Steel sheet and method for producing same

A steel sheet includes, as a chemical composition, by mass %: C: 0.0015% to 0.0400%; Mn: 0.20% to 1.50%; P: 0.010% to 0.100%; Cr: 0.001% to 0.500%; Si: 0.200% or less; S: 0.020% or less; sol. Al: 0.200% or less; N: 0.0150% or less; Mo: 0% to 0.500%; B: 0% to 0.0100%; Nb: 0% to 0.200%; Ti: 0% to 0.200%; Ni: 0% to 0.200%; Cu: 0% to 0.100%; and a remainder including iron and impurities, in which a metallographic structure in a surface layer region includes ferrite having a volume fraction of 90% or more, and in the surface layer region, an average grain size of the ferrite is 1.0 μm to 15.0 μm, and a texture in which an Xas a ratio of an intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.30 or more and less than 3.50 is included.

This steel sheet has a predetermined chemical composition, in which the area ratio of plate martensite is 10% or more, the average grain size of prior austenite grains is 2.0 μm to 10.0 μm, the maximum diameter thereof is 20.0 μm or less, the amount of solid solution C in martensite is 0.20 mass % or less, the average carbide size is 0.25 μm or less, the crystal orientation difference between plate martensite and another martensite adjacent thereto in the same prior austenite grain is 10.0° or less, and the P concentration at grain boundaries of the prior austenite grains is 4.0 at % or less.

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.

Provided are: a steel sheet having a high strength and excellent hydrogen embrittlement resistance; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which a standard deviation σ of Mn concentration satisfies σ≥0.15 Mn(wherein, Mnrepresents an average Mn concentration) and a region with a Mn concentration of higher than (Mn+1.3σ) has a circle-equivalent diameter of less than 10.0 μm. The method of producing the steel sheet includes: the hot rolling step that includes finish rolling a slab having a prescribed chemical composition under prescribed conditions; the step of coiling the thus obtained hot-rolled steel sheet at a coiling temperature of 450 to 700° C.; and the step of cold rolling the hot-rolled steel sheet and subsequently annealing this steel sheet at 800 to 900° C.

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 steel sheet including a steel micro-structure containing, in volume fraction,

A high-strength steel sheet includes a chemical composition including: by mass %, C: 0.080 to 0.500%, Si: 2.50% or less, Mn: 0.50 to 5.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance: Fe and inevitable impurities. The high-strength steel sheet satisfying a predetermined formula has a microstructure in a region from ⅛t to ⅜t from a steel sheet surface. The microstructure includes: by volume %, 20% or more of acicular ferrite, 20% or more of an island-shaped hard structure including residual austenite, 2% to 25% of residual austenite, and 20% or less of aggregated ferrite.

High-strength steel sheet having excellent moldability and impact resistance, and method for manufacturing high-strength steel sheet having excellent moldability and impact resistance

A steel sheet includes a predetermined composition satisfying Expression (1), in which the microstructure at the ¼ thickness position from the surface in the sheet thickness direction includes, by vol %, ferrite: 95% or more and a remainder of the microstructure: 5% or less, has a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and a half width w and an X-ray wavelength λ at a peak of (200) plane of the ferrite satisfy Expression (2).0.80≤{(Ti/48−N/14)+Nb/93}/(C/12)≤5.00  (1)×λ≥0.20  (2)

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Tokyo, Japan

Hiroyuki Kawata