公开(公告)号：US20230347440A1

公开(公告)日：2023-11-02

申请号：US18011567

申请日：2021-06-22

Applicant: JFE STEEL CORPORATION

Inventor： Daiki YAMAGISHI ,  Katsutoshi TAKASHIMA ,  Hiroshi MATSUDA

IPC: C22C38/38 ,  C22C38/26 ,  C22C38/14 ,  C22C38/60 ,  C22C38/02 ,  C22C38/12 ,  B23K11/14 ,  C22C38/28 ,  C22C38/16 ,  C22C38/10 ,  C22C38/06 ,  C22C38/04 ,  C22C38/00

CPC classification number: B23K11/14 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/105 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/26 ,  C22C38/28 ,  C22C38/38 ,  C22C38/60

Abstract: A projection welded joint is formed by joining a steel sheet having a tensile strength of 980 MPa or higher and a nut by performing projection welding. In a hardness distribution from the steel sheet to the nut through a weld metal zone, and a hardened region exists on each of the steel sheet side and the nut side. A hardness of each hardened region is higher than that of the base metal on the corresponding side, and each hardened region extends continuously for a distance of 500 µm or more. The maximum hardness NHmax on the nut side is higher than the maximum hardness SHmax on the steel sheet side. A region where the maximum hardness SHmax on the steel sheet side exists is formed of a martensite microstructure having a prior austenite grain size of 20 µm or less.

公开(公告)号：US20200370140A1

公开(公告)日：2020-11-26

申请号：US16620615

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takashi KOBAYASHI ,  Yoshimasa FUNAKAWA ,  Seiji NAKAJIMA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/16 ,  C22C38/10 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18 ,  C23C30/00 ,  B21D22/02

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing as high as TS: 1780 MPa or more, and excellent indentation peeling strength at projection welds by properly adjusting its chemical composition and its microstructure such that a prior austenite average grain size is 7 μm or less within a range of 50 μm or less in a thickness direction from a surface of the member, a volume fraction of martensite is 90% or more, and an average intergrain distance of Nb and Ti carbonitrides having a grain size of less than 0.10 μm within a depth range of 20 μm to 100 μm in the thickness direction from the surface of the member is 5 μm or less.

公开(公告)号：US20250065438A1

公开(公告)日：2025-02-27

申请号：US18683248

申请日：2022-07-21

Applicant: JFE STEEL CORPORATION ,  KAWASAKI JUKOGYO KABUSHIKI KAISHA

Inventor： Daiki YAMAGISHI ,  Katsutoshi TAKASHIMA ,  Hiroshi MATSUDA ,  Ryoji OHASHI ,  Yoshitaka MURAMATSU ,  Takuya FUKUDA

IPC: B23K20/12 ,  B23K103/04 ,  B32B7/05 ,  B32B15/01

Abstract: Provided is a friction stir spot welded joint having high cross tensile strength even in the case where a steel sheet having a soft surface layer is used as a material to be welded. An annular groove is formed on an upper surface of an upper sheet out of overlapping steel sheets, and a shape and hardness of a welded portion are appropriately controlled simultaneously.

公开(公告)号：US20240351133A1

公开(公告)日：2024-10-24

申请号：US18683510

申请日：2022-07-21

Applicant: JFE STEEL CORPORATION ,  KAWASAKI JUKOGYO KABUSHIKI KAISHA

Inventor： Daiki YAMAGISHI ,  Katsutoshi TAKASHIMA ,  Hiroshi MATSUDA ,  Ryoji OHASHI ,  Yoshitaka MURAMATSU ,  Takuya FUKUDA

IPC: B23K20/12 ,  B23K101/18 ,  B23K101/34 ,  B23K103/04

CPC classification number: B23K20/12 ,  B23K2101/18 ,  B23K2101/34 ,  B23K2103/04

Abstract: Provided is a friction stir spot welded joint having high joint strength even in the case where a high strength steel sheet, particularly a steel sheet with a tensile strength (TS) of 980 MPa or more, is used as a material to be welded. An annular groove is formed on an upper surface of an upper sheet out of overlapping steel sheets, and a shape, microstructure, and hardness of a welded portion are appropriately controlled simultaneously.

公开(公告)号：US20230407484A1

公开(公告)日：2023-12-21

申请号：US18251242

申请日：2021-11-05

Applicant: JFE STEEL CORPORATION

Inventor： Shunsuke YAMAMOTO ,  Katsutoshi TAKASHIMA ,  Yusuke OKUMURA ,  Tomomi KANAZAWA ,  Katsuya HOSHINO ,  Takashi KAWANO ,  Takako YAMASHITA ,  Hiroshi MATSUDA ,  Yoichi MAKIMIZU

IPC: C23C28/02 ,  C23C2/28 ,  C23C2/06 ,  C22C38/02 ,  C25D3/20 ,  C23C2/02 ,  C22C38/06 ,  C22C38/04 ,  C21D8/02

CPC classification number: C23C28/021 ,  C23C2/28 ,  C23C2/06 ,  C22C38/02 ,  C25D3/20 ,  C23C2/022 ,  C22C38/06 ,  C22C38/04 ,  C21D8/0236

Abstract: Disclosed is a galvannealed steel sheet including: a Si-containing cold-rolled steel sheet containing Si in an amount of 0.1 mass % or more and 3.0 mass % or less; an Fe-based electroplating layer formed on at least one surface of the Si-containing cold-rolled steel sheet; and a galvannealed layer formed on the Fe-based electroplating layer, in which in an intensity profile measured by glow discharge optical emission spectrometry, ISi,Fe/ISi,bulk is 0.30 or more, and an average value of C concentration in a region ranging from 10 μm to 20 μm in the thickness direction from the interface between the galvannealed layer and the Fe-based electroplating layer towards the Fe-based electroplating layer is 0.10 mass % or less.

公开(公告)号：US20220056552A1

公开(公告)日：2022-02-24

申请号：US17432349

申请日：2019-11-21

Applicant: JFE STEEL CORPORATION

Inventor： Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Katsutoshi TAKASHIMA ,  Takayuki FUTATSUKA ,  Kentaro SATO

IPC: C21D9/48 ,  C21D8/02 ,  C21D6/00 ,  B32B15/01 ,  C23C2/40 ,  C22C38/38 ,  C22C38/28 ,  C22C38/26 ,  C22C38/60 ,  C22C38/16 ,  C22C38/12 ,  C22C38/08 ,  C22C38/10 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: A hot-pressed member having excellent bending collapsibility, a method for manufacturing the same, and a method for manufacturing a steel sheet for the hot-pressed member. The hot-pressed member includes a steel sheet as a base material, the steel sheet having a specified chemical composition. The hot-pressed member has a microstructure in which a martensite microstructure is present in a volume fraction of 70% or greater, and a number density of inclusions having a longest diameter of 25 μm or greater is 0.02/mm2 or less. The hot-pressed member has a tensile strength of 1.8 GPa or greater.

公开(公告)号：US20210324492A1

公开(公告)日：2021-10-21

申请号：US17285304

申请日：2019-10-16

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Katsutoshi TAKASHIMA ,  Junya TOBATA ,  Yoichiro MATSUI

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/60 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/08 ,  B32B15/01

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 6 to 90% in terms of an area fraction, and a constituent formed of at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 10 to 94% in terms of an area fraction, and retained γ: 3 to 15% in terms of a volume fraction. A total area fraction of SC-enriched is 0.1 to 5%, a total area fraction of SγBlock of at least one of (i) fresh martensite having a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains having a specified equivalent circular grain diameter and aspect ratio is 5% or less, and prior γ in a surface layer has a grain diameter of 2 to 12 μm.

公开(公告)号：US20200172991A1

公开(公告)日：2020-06-04

申请号：US16616602

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takashi KOBAYASHI ,  Yoshimasa FUNAKAWA ,  Seiji NAKAJIMA

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/16 ,  C22C38/08 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18 ,  C23C2/12 ,  C23C2/06 ,  C23C2/40 ,  B32B15/01 ,  C25D3/54 ,  C25D3/22 ,  C25D3/56 ,  B21D22/20 ,  B21K29/00

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing, excellent delayed fracture resistance, and high tensile shear stress after resistance spot welding by properly adjusting its chemical composition and its microstructure such that at least 20 Nb-based precipitates having a grain size of less than 0.10 μm are present on average per 100 μm2 of a cross section parallel to a thickness direction of the member, a prior austenite average grain size is 8 μm or less, an average aspect ratio of prior austenite grains is 2.5 or less, and a volume fraction of martensite is 90% or more, and such that a standard deviation of Vickers hardness measured every 200 μm on a surface of the member is 40 or less.

公开(公告)号：US20240181555A1

公开(公告)日：2024-06-06

申请号：US18285571

申请日：2022-03-07

Applicant: JFE STEEL CORPORATION

Inventor： Nao KAWABE ,  Chikaumi SAWANISHI ,  Katsutoshi TAKASHIMA ,  Koichi TANIGUCHI ,  Hiroshi MATSUDA ,  Daiki YAMAGISHI

IPC: B23K11/11 ,  B23K11/16 ,  B23K101/34 ,  B23K103/04

CPC classification number: B23K11/115 ,  B23K11/166 ,  B23K2101/34 ,  B23K2103/04

Abstract: A resistance spot welding method for joining two or more steel sheets including at least one zinc-coated steel sheet. The method includes a first current applying step and a second current applying step. The first current applying step involves forming a nugget having a nugget diameter of 3√t or more and 4.5√t or less by setting a current value I1 (kA) and a weld time, where t is a thickness of the thinnest steel sheet among the overlapping steel sheets. The second current applying step involves growing the nugget by repeating a cooling step for maintaining a zero-current state for 10 ms or more and less than 160 ms and a current applying step for applying a current for 20 ms or more and less than 200 ms at a current value I2 (kA) greater than or equal to the current value I1 (kA).

公开(公告)号：US20240009962A1

公开(公告)日：2024-01-11

申请号：US18251244

申请日：2021-11-05

Applicant: JFE STEEL CORPORATION

Inventor： Shunsuke YAMAMOTO ,  Yusuke OKUMURA ,  Katsutoshi TAKASHIMA ,  Mai AOYAMA ,  Tomomi KANAZAWA ,  Katsuya HOSHINO ,  Yoichi MAKIMIZU ,  Takashi KAWANO ,  Takako YAMASHITA ,  Hiroshi MATSUDA

IPC: B32B15/01 ,  C22C38/02 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/00 ,  C21D9/46 ,  C22C33/04 ,  C21D8/02 ,  C21D6/00 ,  C22C38/32 ,  C22C38/28 ,  C22C38/38 ,  C25D3/20 ,  C25D5/50 ,  C23F17/00 ,  C23C2/02 ,  C23C2/28 ,  C23C2/06

CPC classification number: B32B15/011 ,  C22C38/02 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/002 ,  C22C38/001 ,  C21D9/46 ,  C22C33/04 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0278 ,  C21D6/001 ,  C21D6/005 ,  C21D6/008 ,  C22C38/32 ,  C22C38/28 ,  C22C38/38 ,  C21D6/002 ,  C25D3/20 ,  C25D5/50 ,  B32B15/01 ,  C23F17/00 ,  C23C2/02 ,  C23C2/28 ,  C23C2/06

Abstract: To provide an Fe-based electroplated steel sheet that not only has excellent chemical convertibility or excellent coating appearance when subjected to hot-dip galvanizing, but also has excellent resistance to cracking in resistance welding. Disclosed is an Fe-based plated steel sheet including: a cold-rolled steel sheet having a chemical composition containing Si in an amount of 0.1 mass % or more and 3.0 mass % or less; and an Fe-based electroplating layer formed on one or both surfaces of the cold-rolled steel sheet with a coating weight per surface of 1.0 g/m2 or more, in which a thickness of an internal oxidation layer is 2.00 μm or less, and an average value of C concentration in a range of 10 μm to 20 μm in a thickness direction from the surface of the Fe-based electroplating layer is 0.10 mass % or less.