Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Arcelor France

Arcelormittal France

Nippon Steel & Sumitomo Metal Corporatin

Arcelormittal

Usinor

Takuya Kuwayama

Naoki Maruyama

Akinobu Minami

Noriyuki Suzuki

Hiroyuki Kawata

Akihiro Uenishi

Shigeru Yonemura

Akinobu Murasato

Takeshi Yasui

Kaoru Hiramatsu

Toshiyuki Niwa

Hiroyuki Ban

Yukihisa Kuriyama

Takashi Ariga

Mitsuharu Yamagata

Shin Toyokawa

Masafumi Azuma

Yuji Yamaguchi

Takamasa Suzuki

Natsuko Sugiura

Yasunobu Miyazaki

Takafumi Yokoyama

Kazuhiko Honda

Masahiko Yoshino

Atsushi Seto

Yasuaki Naito

Yusuke Tsunemi

Tatsuya Obuchi

Patrick Duroux

Provided are a steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 1 to 50%, ratio of nonrecrystallized ferrite in the ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 10%, total of pearlite and cementite: 0 to 5%, and balance: bainite, and, when analyzing the surface by an EPMA, an area ratio of regions with an Al/Siratio of 0.2 or less is 50% or less, and a tensile strength is 980 MPa or more, and a method for producing the same.

Steel sheet and method for producing same

There is provided a surface shape defect generating region estimating method for estimating a generating region of a surface shape defect of a deformation-processed product obtained by performing deformation processing with respect to a workpiece, the method including: a first stress distribution obtaining process of obtaining first stress distribution &#x3c3;; a second stress distribution obtaining process of obtaining a second stress distribution &#x3c3;; a comparative stress distribution obtaining process of obtaining comparative stress distribution &#x3c3;; a division comparative stress distribution obtaining process of obtaining division comparative stress distribution &#x3c3;; and a surface shape defect generating region estimating process of estimating whether or not each of the divided regions Dis a generating region of the surface shape defect.

Surface shape defect generating region estimating method, surface shape defect source region estimating method, surface shape defect generating region estimating device, surface shape defect source region estimating device, program, and recording medium

A laser welded joint has weld metal provided between a plurality of steel sheets. A chemical composition of the weld metal has predetermined components, and average hardness of the weld metal is 350 to 540 in Vickers hardness. In the weld metal, distribution density of porosities having a diameter of 2 &#x3bc;m to 50 &#x3bc;m is equal to or less than 5.0 pieces/mm. In the weld metal, distribution density of oxide inclusions having a diameter of 3 &#x3bc;m or more is 0.1 to 8.0 pieces/mm.

Laser welded joint, vehicle component, manufacturing method of laser welded joint, and manufacturing method of vehicle component

Disclosed is a press forming method press forming a workpiece between a die and a punch, while pushing the punch into the die by means of a relative motion of the die and the punch, the method includes: producing an intermediate molding (B) having ridges () formed in predetermined parts of the workpiece, and then press forming the intermediate molding (B) into a final shape, to thereby substantially thicken and work-harden the predetermined parts of the workpiece.

Press forming method and vehicle component

The present invention provides a high-strength steel sheet excellent in shape fixability. The high-strength steel sheet contains C, Si, Mn, P, S, Al, N, and O with predetermined contents, in which a retained austenite phase of 5 to 20% in volume fraction is contained, an amount of solid-solution C contained in the retained austenite phase is 0.80 to 1.00% in mass %, Wis 1.10 times or more W, Wis 1.10 times or more W, and when a frequency distribution is measured with respect to a sum of a ratio between Wand Wand a ratio between Wand W, a mode value of the frequency distribution is 1.95 to 2.05, and a kurtosis is 2.00 or more.

High-strength steel sheet and high-strength galvanized steel sheet excellent in shape fixability, and manufacturing method thereof

A bending fracture limit stress is calculated for each of (bend radius at sheet thickness center of a metal sheet)/(initial sheet thickness of the metal sheet); a fracture limit curve and a fracture limit stress are calculated from work hardening characteristics; a fracture limit curve corresponding to (the metal sheet bend radius at sheet thickness center)/(the initial sheet thickness of the metal sheet) is calculated; a corresponding fracture limit stress is calculated from stress of the element subject to determination and the fracture limit curve; a risk ratio that is a ratio between the stress of the element subject to determination and the fracture limit stress is computed; and performing fracture determination for the element subject to determination based on the risk ratio.

Metal sheet bending fracture determination method and recording medium

There is provided a high-strength hot-dip galvanized steel sheet and the like excellent in mechanical cutting property, which are capable of obtaining high ductility while ensuring high strength with maximum tensile strength of 900 MPa or more. The high-strength hot-dip galvanized steel sheet has a sheet thickness of 0.6 to 5.0 mm and has a plating layer on a surface of a steel sheet with component compositions being set in appropriate ranges, in which the steel sheet structure contains a 40 to 90% ferrite phase and a 3% or more retained austenite phase by volume fraction. In the retained austenite phase, a solid solution carbon amount is 0.70 to 1.00%, an average grain diameter is 2.0 &#x3bc;m or less, an average distance between grains is 0.1 to 5.0 &#x3bc;m, a thickness of a decarburized layer in a steel sheet surface layer portion is 0.01 to 10.0 &#x3bc;m, an average grain diameter of oxides contained in the steel, sheet surface layer portion is 30 to 120 nm and an average density thereof is 1.0&#xd7;10oxides/mor more, and moreover, a work hardening coefficient (n value) during a 3 to 7% plastic deformation is 0.080 or more on average.

High-strength hot-dip galvanized steel sheet and high-strength alloyed hot-dip galvanized steel sheet excellent in mechanical cutting property, and manufacturing method thereof

A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of &#x215b; thickness to &#x215c; thickness centered around &#xbc; thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 &#x3bc;m or less, a maximum effective crystal grain diameter is 20 &#x3bc;m or less, and a decarburized layer with a thickness of 0.01 &#x3bc;m to 10.0 &#x3bc;m is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0&#xd7;10to 1.0&#xd7;10oxides/m, and an average grain diameter of the oxides is 500 nm or less.

High-strength hot-dip galvanized steel sheet excellent in impact resistance property and manufacturing method thereof, and high-strength alloyed hot-dip galvanized steel sheet and manufacturing method thereof

High strength steel sheet which secures tensile maximum strength 900 MPa or more high strength while having excellent shapeability, which high strength steel sheet which is excellent in shapeability characterized by having a predetermined composition of ingredients, by the steel sheet structure including a ferrite phase and martensite phase, by the ratio of Cu particles incoherent with the bcc iron being 15% or more with respect to the Cu particles as a whole, by a density of Cu particles in the ferrite phase being 1.0&#xd7;10/mor more, and by an average particle size of Cu particles in the ferrite phase being 2.0 nm or more.

High strength steel sheet and high strength galvanized steel sheet excellent in shapeability and methods of production of same

The present invention provides a high-strength galvanized steel sheet with maximum tensile strength of 900 MPa or more. The high-strength galvanized steel sheet has an alloyed galvanized layer formed on a surface of a base steel sheet containing predetermined amounts of C, Si, Mn, P, S, Al, N, O with a balance being constituted of iron and inevitable impurities, in which in a structure of the base steel sheet, retained austenite is limited to 8% or less in volume fraction, kurtosis K* of the hardness distribution between 2% hardness and 98% hardness is &#x2212;0.30 or less, a ratio between Vickers hardness of surface layer of the base steel sheet and Vickers hardness of &#xbc; thickness of the base steel sheet is 0.35 to 0.70, and a content of iron in the alloyed galvanized layer is 8 to 12% in mass %.

High-strength galvanized steel sheet excellent in bendability and manufacturing method thereof

A vehicle frame member structure has a closed cross-sectional structure including a pair of first wall portions, and a pair of second wall portions connected to the pair of the first wall portions, in which first beads are provided on the pair of first wall portions along a circumferential direction of the closed cross-sectional structure, a second bead is provided on either of the pair of second wall portions along the closed cross-sectional circumferential direction on a line extending from the first bead in the circumferential direction, the first and second beads are connected in two corner portions between the first wall portions and the second wall portion, a recessed embossed portion is provided in a connection portion of the first and second beads in at least one of the corner portions, and the sheet thickness of the embossed portion is larger than that of the first or second wall portion.

Vehicle frame member structure with excellent impact resistance performance

Steel contains each of C, Si, Mn, P, S, Al, N, O, at a range from &#x215b; thickness centered around a &#xbc; sheet thickness from a surface to &#x215c; thickness centered around the &#xbc; sheet thickness from the surface at a base steel sheet, a structure of the base steel sheet contains, in volume fraction, 3% or more of a retained austenite phase, 50% or less of a ferrite phase, and 40% or more of a hard phase, average dislocation density is 5&#xd7;10/mor more, solid-solution C amount contained in the retained austenite phase is in mass % 0.70 to 1.00%, X-ray random intensity ratio of FCC iron in an texture of the retained austenite phase is 3.0 or less, ratio between a grain diameter relative to a rolling direction and a grain diameter relative to a sheet width direction of the retained austenite phase is 0.75 to 1.33.

High-strength hot-dip galvanized steel sheet, high-strength alloyed hot-dip galvanized steel sheet excellent in bake hardenability, and manufacturing method thereof

A hot-dip galvanizing layer or an alloyed hot dip galvanizing layer is formed on the surface of a base steel sheet in which in volume fraction, 40 to 90% of a ferrite phase and 5% or less of a retained austenite phase are contained, and a ratio of non-recrystallized ferrite to the entire ferrite phase is 50% or less in volume fraction, and further a grain diameter ratio being a value of, of crystal grains in the ferrite phase, an average grain diameter in the rolling direction divided by an average grain diameter in the sheet width direction is 0.75 to 1.33, a length ratio being a value of, of hard structures dispersed in island shapes, an average length in the rolling direction divided by an average length in the sheet width direction is 0.75 to 1.33, and an average aspect ratio of inclusions is 5.0 or less.

High-strength hot-dip galvanized steel sheet having excellent delayed fracture resistance and manufacturing method thereof

Exemplary embodiments of a press-forming device, press-forming method, computer program/software arrangement and storage medium can be provided. The exemplary press-forming device can include a material characteristic input configured to input material characteristics. A state variable detector can be configured to measure a state variable comprising a metal mold distortion amount. A processing condition computer arrangement can be configured to determine from a first moment to a second moment at least one particular processing condition. Further, a processing condition controller can be configured to control the at least one processing condition from processing conditions.

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Tokyo, Japan

Takuya Kuwayama