Jfe Steel Corporation

H-one Co., Ltd.

Yasushi Kitani

Asato Hara

Seiji Okabe

Yoshihiko Ono

Shigehiro Takajo

Takeshi Fujita

Shinjiro Kaneko

Rinsei Ikeda

Noriaki Kohsaka

Yasuaki Okita

Yoshikiyo Tamai

Koichi Yasuda

Muneo Matsushita

Hiroyuki Sumi

Kenji Oi

Hiroyuki Akimoto

Junya Tobata

Yoichiro Matsui

Hiroyuki Takebe

Tadachika Chiba

Shohei Iwata

Tokihiko Kataoka

Syoma Murakami

A thin steel sheet has a specific chemical composition. The thin steel sheet has a microstructure in which ferrite is present in an area fraction of 4% or less (including 0%), as-quenched martensite is present in an area fraction of 10% or less (including 0%), retained austenite is present in an amount of 7% or more and 20% or less, and upper bainite, lower bainite, and tempered martensite are present in a total area fraction of more than 71% and less than 93%; and BCC iron that has a misorientation of 1° or less and surrounds retained austenite having an equivalent circular diameter of 1 μm or less is present in an area fraction of 4% or more and 50% or less, and BCC iron that has a misorientation of more than 1° is present in an area fraction of 25% or more and 85% or less.

Thin steel sheet and method for manufacturing same

The steel sheet has a steel microstructure containing ferrite: 6% to 90% by area, a microstructure composed of one or more of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 10% to 94% by area in total, and retained γ: 3% to 20% by volume, a ratio (S/S)×100(%) of an area ratio Sof an upper bainite with a width in the range of 0.8 to 7 μm, a length in the range of 2 to 15 μm, and an aspect ratio of 2.2 or more in contact with retained γwith a grain width in the range of 0.17 to 0.80 μm and an aspect ratio in the range of 4 to 25 to an area ratio Sof the microstructure composed of one or more of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ ranges from 2.0% to 15%.

Steel sheet and method for producing the same

A double-sided friction stir welding method, methods for producing a cold-rolled steel strip and a coated steel strip, a double-sided friction stir welding apparatus, and facilities for producing a cold-rolled steel strip and a coated steel strip. The double-sided friction stir welding method includes pressing two rotating tools, which are disposed on a first surface and a second surface of a butt portion or overlap portion of the steel strips, against the butt portion or overlap portion of steel strips and moving the rotating tools in the welding direction while rotating the rotating tools in opposite directions to each other, so that an unwelded portion of the steel strips is softened by frictional heat generated between the rotating tools and the unwelded portion of the steel strips, and the softened portion is stirred with the rotating tools to generate plastic flow so as to weld the steel strips together.

Double-sided friction stir welding method, methods for producing cold-rolled steel strip and coated steel strip, double-sided friction stir welding apparatus, and facilities for producing cold-rolled steel strip and coated steel strip

A weld inspection apparatus that detects a weld defect in a welded portion of metal plates and includes a liquid application head disposed over one side surface of the metal plates and capable of moving in a welding direction of the metal plates, and an air jet head disposed over another side surface of the metal plates and capable of moving in the welding direction of the metal plates. The liquid application head includes a liquid application nozzle that projects toward the one side surface of the metal plates and applies liquid for sealing the welded portion. The air jet head includes an air jet nozzle that projects toward the another side surface of the metal plates and discharges air toward the welded portion to which the liquid has been applied.

Weld inspection apparatus

The present invention includes a laser-welded lap joint including a weld zone formed by laser lap welding in a lapped portion including a plurality of lapped steel sheets. The weld zone includes a main weld zone that penetrates the steel sheets in the lapped portion and a final weld zone formed at one end of the main weld zone and having a crater, and the weld zone satisfies formulas (1) to (4):&#x2265;15.0;&#x2003;&#x2003;(1)10.0&#x2265;2&#x2265;2;&#x2003;&#x2003;(2)1&#x2265;2;&#x2003;&#x2003;(3)&#x2003;&#x2003;(4).

Laser-welded lap joint, method for producing laser-welded lap joint, and automobile frame component

A laser-welded lap joint includes a weld zone formed by joining a plurality of steel sheets one over another together by laser welding. The weld zone has a J shape and includes a main weld zone having a linear weld line shape and a weld terminal end zone having an arcuate or circular weld line shape. The length Lof the main weld zone is &#x2154; or more and &#x2158; or less of the full length L of the weld zone represented by formula (1). The radius R of the weld terminal end zone satisfies formula (2). The angle &#x3b8; of the weld terminal end zone satisfies formula (3). The total size of a gap between the plurality of steel sheets in a lapped portion is 0% or more and 15% or less of the total thickness of the plurality of steel sheets.

This device scans a high-energy beam in a direction traversing a feed path of a grain-oriented electrical steel sheet having subjected to final annealing so as to irradiate a surface of the steel sheet being passed through with the high-energy beam to thereby perform magnetic domain refinement, the device including an irradiation mechanism for scanning the high-energy beam in a direction orthogonal to the feed direction of the steel sheet, in which the irradiation mechanism has a function of having the scanning direction of the high-energy beam oriented diagonally, relative to the orthogonal direction, toward the feed direction at an angle determined based on a sheet passing speed of the steel sheet on the feed path.

Device to improve iron loss properties of grain-oriented electrical steel sheet

A laser lap-welded joint being formed from stacked steel sheets and including a plurality of welded portions each having a substantially C-shaped surface, each of the welded portions being formed of a first linear portion and second linear portions having a surface having a semicircular shape. The radius R of the semicircular shape and the sheet thickness t of one of the steel sheets having a larger sheet thickness satisfy 0&#x3c;R&#x2264;1.5 t. The pitch &#x3bb; between the adjacent welded portions and a weld length l satisfy 0.4&#x2264;l/&#x3bb;&#x3c;0.7. The space X between an end of a contact portion where the steel sheets are in contact with each other and each of the welded portions satisfy 2 t&#x2264;X&#x2264;4 t. The sheet thickness t and the width W of each of the welded portions satisfy 0.3&#x2264;W/t&#x2264;1.0.

Laser lap-welded joint, method of manufacturing the same, and automobile framework component

An automobile frame component includes a closed section constituted by welding a flange portion to a panel part, wherein when a welding position coordinate is represented in a coordinate system in which an end of a contact position between the flange portion and the panel part is assumed as 0, and a flange outer end side of the flange portion is assumed as negative (&#x2212;) whereas a vertical wall side is assumed as positive (+), and when a radius of a circular arc-like portion connecting a vertical wall portion and the flange portion in the substantially hat-like shape is denoted as R (mm), and a weldable gap amount is denoted as a (mm), a welding position X represented by the following formula is continuously welded using a one-side welding method:+&#x221a;(2)&#x2265;&#x3e;1.5 where&#x2265;2.

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Tokyo, Japan

Yasushi Kitani