Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Mitsubishi Jidosha Kogyo Kabushiki Kaisha

Takeshi Toyoda

Tetsuya Hirashima

Riki Okamoto

Eisaku Sakurada

Tatsuo Yokoi

Daisuke Ito

Daisuke Maeda

Masafumi Azuma

Kenichiro Otsuka

Hiroshi Shuto

Genki Abukawa

Kohei Nakada

Takeshi Yamamoto

Hiroshi Sakai

Takehiro Takahashi

Jun Takahashi

Takeshi Imai

Natsuko Sugiura

Takeshi Kawachi

Hidetoshi Shindo

Shohei Yabu

Yuuki Kanzawa

Toshifumi Mizui

Ryo Tabata

Kazuki Matsuda

Yukiko Kobayashi

Hitoshi Nikaido

Daiki Kamada

Ryohta Niiya

Mayuko Kikuzuki

Yui Yamashita

A high-strength hot-rolled steel sheet: having a predetermined chemical composition; having a mean dislocation density of from 1×10to 1×10m, and containing at least bainitic ferrite, in which a total area ratio of the bainitic ferrite and ferrite is 70% or more and less than 90%, and in which a total area ratio of martensite and retained austenite is 5% or more and 30% or less, in which, in ferrite crystal grains and in bainitic ferrite crystal grains, a mean number density of TiC precipitates is from 1×10to 5×10[precipitates/cm], in which an amount of Ti present as a TiC precipitate precipitated in a matrix not on dislocations is 30 mass % or more of a total amount of Ti in the steel sheet, and in which a tensile strength is 850 MPa or more.

High-strength hot-rolled steel sheet

A vehicle travel control device calculates torques required for a motor in a first regenerative control mode and a second regenerative control mode based on an accelerator opening degree and a vehicle speed, selects torque required for the motor suitable for the first regenerative control mode or the second regenerative control mode from among the calculated torques required for the motor, and limits a change rate of the torque required for the motor when the selected torque required for the motor changes beyond a predetermined change rate by switching from the first regenerative control mode to the second regenerative control mode.

Vehicle travel control device

A high-strength steel sheet includes a predetermined chemical composition, a microstructure contains, by volume percentage, 95% or more of tempered martensite and bainite in total, and a remainder consists of ferrite and pearlite, the microstructure contains 5.0×10pieces/mm or more of, per unit volume, precipitate having an equivalent circle diameter of 5.0 nm or less and containing Ti, Hvs/Hvc which is a ratio of an average hardness Hvs at a position of a depth of 20 μm from a surface to an average hardness Hvc at a position of 0.20 to 0.50 mm from the surface is 0.85 or more, a tensile strength is 980 MPa or more, and a product of the tensile strength and elongation is 12,000 MPa×% or more.

High-strength steel sheet and method for manufacturing same

To provide a hot-rolled steel sheet comprising by mass %: C: 0.12% or more and 0.25% or less, Si: 0.01% or more and 2.0% or less, Mn: 0.5% or more and 3.0% or less, Al: 0.001% or more and 0.10% or less, and B: 0.0005% or more and 0.0050% or less, and comprising one or both of: Nb: 0.001% or more and 0.020% or less, and Ti: 0.001% or more and 0.20% or less, wherein a metal structure at a position of ¼ thickness from a surface contains more than 90%, in area ratio, of tempered martensite, carbides in the tempered martensite have an average grain size of 10 nm or less, prior austenite grains have an average grain size of less than 40 μm, the prior austenite grains have an aspect ratio of 3.5 or less, and an X-ray random intensity ratio of {112}<110> orientation at a position of ½ thickness from a surface is 4.0 or less, and a method for manufacturing the same.

Hot-rolled steel sheet and method for manufacturing same

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a ¼ position of a sheet thickness in a sheet thickness direction from a surface, a primary phase is bainite, a secondary phase is martensite or a martensite-austenite mixed phase, an average grain size of the secondary phase is 1.5 μm or less, an average grain size of particles having grain diameters that are largest 10% or less out of all particles in the secondary phase is 2.5 μm or less, a pole density in a (110)<112> orientation is 3.0 or less, and, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110)<1-11> orientation is 3.0 or less.

Hot-rolled steel sheet

Hot-rolled steel sheet having a chemical composition including, in mass %, C: 0.02 to 0.20%, Si: 0.01 to 1.50%, Mn: 0.10 to 3.00%, P: 0.10% or less, S: 0.010% or less, Al: 0.005 to 0.100%, Ti: 0.02 to 0.20%, N: 0.001 to 0.010%, Cu: 0 to 0.50%, Ni: 0 to 0.50%, Cr: 0 to 1.00%, Mo: 0 to 0.40%, Nb: 0 to 0.060%, V: 0 to 1.00%, B: 0 to 0.0100%, Ca: 0 to 0.0050%, O: 0.0100% or less, and the balance: Fe and impurities; in which: a steel micro-structure includes, in area %, ferrite: 60 to 80%, and a total of ferrite and bainite: 90% or more; an average of the crystal grain size of ferrite and bainite is 7.0 μm or less, a standard deviation of the crystal grain size is 2.0 μm or less; and a standard deviation of a diameter of Ti carbo-nitrides is 10 nm or less.

Hot-rolled steel sheet and weld joint, and methods for producing same

As a burring processed member able to suppress the formation of fatigue cracks in a burring part, one having a structure satisfying the following relations (1) to (3) is disclosed: 3≤Ra≤100 . . . (1), 3.0<h . . . (2), 24+r−[TS/(40+0.28×Ra)]<h . . . (3), where, 'Ra' is an arithmetic mean roughness (μm) of the burring end face, “h” is a height (mm) from the first surface to the burring end face, “r” is a radius of curvature (mm) of the curved wall part, and “TS” is the tensile strength (MPa) of the sheet-shaped part.

Burring processed member

A high-strength steel sheet includes a predetermined chemical composition, a microstructure contains, by volume percentage, 80% or more of tempered martensite, and a remainder consists of ferrite and bainite, the microstructure contains 5.0×10pieces/mmor more of, per unit volume, precipitate containing Ti and having an equivalent circle diameter of 5.0 nm or less, Hvs/Hvc which is a ratio of an average hardness Hvs at a position of a depth of 20 μm from a surface to an average hardness Hvc at a position of 0.20 to 0.50 mm from the surface is 0.85 or more, and the tensile strength is 1,180 MPa or more.

Provided is a hot rolled steel sheet having a tensile strength of 780 MPa or more, a sheet thickness of 1.2 to 4.0 mm, and a sheet width of 750 mm or more, and satisfying −15≤(λ+λ)/2−λ≤15 (where λand λrespectively indicate hole expansion ratios (%) at ⅛ positions of the sheet width from one end of the hot rolled steel sheet in a sheet width direction perpendicular to a rolling direction and the other end at an opposite side, and λindicates a hole expansion ratio (%) of a sheet width center part).

Hot rolled steel sheet

Provided is a hot rolled steel sheet comprising a predetermined composition wherein the hot rolled steel sheet comprises ferrite with an average orientation difference in the same grain of 0.5 to 5.0&#xb0; in 30 to 70 vol %, the ferrite and martensite in a total of 90 vol % or more, and a balance microstructure of 10 vol % or less, has an average grain size of the ferrite of 0.5 to 5.0 &#x3bc;m, and has an average grain size of the martensite and the balance microstructure of 1.0 to 10 &#x3bc;m. Provided is a method for producing a hot rolled steel sheet comprising rolling where two or more consecutive passes of rolling including a final pass are performed under conditions of a rolling temperature: A point or more and less than Aepoint, a strain rate: 1.0 to 50/sec, and a time between passes: within 10 seconds and where a total strain amount of all passes satisfying the conditions is 1.4 to 4.0, cooling by a 20&#xb0; C./sec or more average cooling rate, and coiling the steel sheet at room temperature or more and less than 300&#xb0; C.

Hot rolled steel sheet and method for producing same

In a hot-rolled steel sheet having a predetermined chemical composition and having a metallographic structure including 90 vol % or greater of martensite and 0 vol % to 10 vol % of a residual structure, the residual structure includes one or both of bainite and ferrite, the average prior austenite grain size in an L-section parallel to a rolling direction and an average prior austenite grain size in a C-section parallel to a direction orthogonal to the rolling direction are 1.0 &#x3bc;m to 10.0 &#x3bc;m the aspect ratio associated with the prior austenite grain size is 1.8 or less, the average grain size of the residual structure in the L-section and the average grain size of the residual structure in the C-section are 5.0 &#x3bc;m or less, and the aspect ratio associated with the average grain size of the residual structure is 2.0 or less.

Hot-rolled steel sheet and production method therefor

Provided is a hot rolled steel sheet comprising a predetermined composition wherein the hot rolled steel sheet comprises first ferrite with an average orientation difference in the same grain of 0.5 to 5.0&#xb0; in 30 to 70 vol %, at least one type of structures among bainite and second ferrite with an average orientation difference of 0 to less than 0.5&#xb0; and the first ferrite in a total of 95 vol % or more, a balance microstructure of 5 vol % or less, has an average grain size of the first ferrite of 0.5 to 5.0 &#x3bc;m, and has an average grain size of the other structures of 1.0 to 10 &#x3bc;m. Provided is a method for producing a hot rolled steel sheet comprising rolling where two or more consecutive passes of rolling including a final pass are performed under conditions of a rolling temperature: A point or more and less than Aepoint etc., and where a total strain amount of all passes satisfying the conditions is 1.4 to 4.0, cooling by a 20 to 50&#xb0; C./sec average cooling rate, and coiling the steel sheet at 300&#xb0; C. to 600&#xb0; C.

The hot-rolled steel sheet includes, in % by mass, 0.10% or more and 0.50% or less of C; 0.10% or more and 3.0% or less of Si; 0.5% or more and 3.0% or less of Mn; 0.10% or less of P; 0.010% or less of S; 1.00% or less of Al; 0.010% or less of N; 0% or more and 0.20% or less of Ti; 0% or more and 0.100% or less of Nb; 0% or more and 0.0060% or less of Ca; 0% or more and 0.50% or less of Mo; and 0% or more and 1.00% or less of Cr; with the balance comprising Fe and impurities, and an average grain size of prior austenite in a structure is 0.1 &#x3bc;m or larger and 3.0 &#x3bc;m or smaller, and a sheet crown quantity corresponding to a thickness difference between a width center portion and a portion away, by 10 mm, from a width edge portion in the widthwise direction toward the width center portion is 80 &#x3bc;m or smaller.

A hot rolled steel sheet according to an aspect of the present invention has a predetermined chemical composition, and a metallographic structure in which martensite is the major structure, wherein an average length of grains in an L direction parallel to a rolling direction is 0.2 &#x3bc;m or more and 5.0 &#x3bc;m or less, an average length of grains in a C direction parallel to a transverse direction is 0.1 &#x3bc;m or more and 5.0 &#x3bc;m or less, the ratio of the average length in the C direction to the average length in the L direction is 0.2 or more and 5.0 or less, and the tensile strength is 1180 MPa or more.

Hot rolled steel sheet and method for manufacturing same

A hot rolled steel sheet is provided, which is excellent in collision characteristics, excellent in anisotropy of toughness, and high in strength. The hot rolled steel sheet is characterized by containing, by mass %, C: 0.10% to 0.50%, Si: 0.10% to 3.00%, Mn: 0.5% to 3.0%, P: 0.100% or less, S: 0.010% or less, Al: 1.00% or less, N: 0.010% or less and a balance of Fe and impurities, wherein a metal structure at position of &#xbc; thickness from surface in L-cross-section of the steel sheet comprises prior austenite grains of average value of aspect ratios of 2.0 or less, average grain size of 0.1 &#x3bc;m to 3.0 &#x3bc;m, and coefficient of variation of a standard deviation of grain size distribution/average grain size of 0.40 or more, and a texture with X-ray diffraction intensity ratio of {001}&#x3c;110&#x3e;orientation for random samples of 2.0 or more, and the steel sheet has tensile strength of 1180 MPa or more.

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Tokyo, Japan

Takeshi Toyoda