公开(公告)号：US11136644B2

公开(公告)日：2021-10-05

申请号：US16325299

申请日：2017-08-29

Applicant: JFE STEEL CORPORATION

Inventor： Yoshie Obata ,  Katsutoshi Takashima ,  Takashi Kobayashi ,  Hiroshi Matsuda

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C23F17/00 ,  B32B15/01 ,  C23C2/06 ,  C22C38/60 ,  C21D8/04 ,  C22C38/18 ,  C23C2/28 ,  C23C2/40 ,  C21D1/18 ,  C21D1/25 ,  C22C18/04 ,  C25D3/22

Abstract: A high-strength cold rolled steel sheet having a specified chemical composition and a method for producing the same. The steel sheet having a microstructure including, in terms of volume fraction, 35% or less of ferrite, 1% or more and 10% or less of retained austenite, 2% or more and 12% or less of as-quenched martensite, and a total of 25% to 70% of bainite and tempered martensite. The microstructure has an average crystal grain diameter of the ferrite: 5.0 μm or less, an average crystal grain diameter of the retained austenite: 2.0 μm or less, an average crystal grain diameter of the as-quenched martensite: 3.0 μm or less, an average crystal grain diameter of the bainite and the tempered martensite phase: 4.0 μm or less, and an average intergrain distance of the as-quenched martensite of 1.0 μm or more.

公开(公告)号：US20210207234A1

公开(公告)日：2021-07-08

申请号：US16092323

申请日：2017-03-22

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Yoshimasa Funakawa ,  Takashi Kobayashi

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: A high-strength steel sheet having a chemical composition containing, by mass %, C: 0.15% to 0.25%, Si: 1.00% to 2.20%, Mn: 2.00% to 3.50%, P: 0.05% or less, S: 0.005% or less, Al: 0.01% to 0.50%, N: 0.010% or less, B: 0.0003% to 0.0050%, one, two, or more selected from Ti: 0.005% to 0.05%, Cu: 0.003% to 0.50%, Ni: 0.003% to 0.50%, Sn: 0.003% to 0.50%, Co: 0.003% to 0.05%, and Mo: 0.003% to 0.50%, and the balance being Fe and inevitable impurities and a microstructure including, in terms of volume fraction, 15% or less (including 0%) of ferrite, 2% to 15% of retained austenite, 10% or less (including 0%) of martensite, and the balance being bainite and tempered martensite, in which the average number of cementite grains having a grain diameter of 0.04 μm or more existing in the bainite and tempered martensite grains is 10 or more.

公开(公告)号：US10940556B2

公开(公告)日：2021-03-09

申请号：US16323570

申请日：2017-08-21

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Hiroshi Matsuda ,  Rinsei Ikeda ,  Yoshiyasu Kawasaki

IPC: B32B15/00 ,  B23K11/16 ,  C21D6/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/16 ,  C22C38/26 ,  C22C38/28 ,  C22C38/38 ,  C22C38/14 ,  B23K11/20 ,  C22C38/04 ,  B23K11/11 ,  C22C38/12 ,  B32B15/01 ,  B23K11/00 ,  F16B5/08 ,  B23K103/04 ,  B23K103/18 ,  B23K101/18 ,  B23K101/34 ,  B23K101/00

Abstract: Provided is an automotive member, or particularly, a steel sheet having a tensile strength exceeding 900 MPa. The automotive member has a resistance weld for fixing two or more steel sheets containing a predetermined composition, in which a maximum hardness (HVBM) in a heat-affected zone of the resistance weld is at least 1.1 times hardness (HVW) of a nugget in the resistance weld formed in a softest steel sheet of a sheet set during resistance welding, and furthermore, an average grain size of a steel sheet structure of the heat-affected zone within 2 mm in a direction at a right angle to a sheet thickness from an end part of the nugget of the high-strength steel sheet is 3 μm or less, and a minimum hardness (HVmin) in the heat-affected zone is at least 90% of hardness (HVα) of the high-strength steel sheet before the resistance welding.

公开(公告)号：US10900096B2

公开(公告)日：2021-01-26

申请号：US16087931

申请日：2017-03-21

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Chikaumi Sawanishi ,  Yoshimasa Funakawa

IPC: C22C38/02 ,  C21D8/02 ,  C21D9/46 ,  C22C38/14 ,  C22C38/38 ,  C22C38/16 ,  C22C38/00 ,  C22C38/08 ,  C22C38/50 ,  C22C38/48 ,  C21D1/74 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C23C2/02 ,  C23C2/06 ,  C23C2/40

Abstract: Provided herein is a steel sheet of a specific composition that has a micro structure containing, by volume, 75 to 95% of ferrite, 3 to 15% of martensite, 0.5 to 10% of perlite, 10% or less of unrecrystallized ferrite, and 21.5% or less of a low-temperature occurring phase representing the remainder, and in which the ferrite has an average crystal grain diameter of 6 μm or less, and the martensite has an average crystal grain diameter of 3 μm or less, and an average aspect ratio of 4.0 or less, and in which a Nb base precipitate having an average grain diameter of 0.10 μm or less is contained. The steel sheet has a tensile strength of 590 MPa or more.

公开(公告)号：US20200165708A1

公开(公告)日：2020-05-28

申请号：US16076098

申请日：2017-01-30

Applicant: JFE Steel Corporation

Inventor： Hiroshi Hasegawa ,  Yoshimasa Funakawa ,  Hiromi Yoshitomi ,  Katsutoshi Takashima

IPC: C22C38/04 ,  C22C38/14 ,  C21D8/02 ,  C23C18/54 ,  C23C2/40 ,  C22C38/08 ,  C22C38/02 ,  C22C38/06 ,  C22C38/00 ,  C22C38/12 ,  C23C2/02 ,  C22C38/32 ,  C21D9/46 ,  C22C38/16 ,  C22C38/60

Abstract: A high-strength galvanized steel sheet includes a steel sheet and a particular galvanized layer. The steel sheet has a particular composition and a steel microstructure. The steel microstructure contains ferrite and carbide-free bainite constituting 25% or less (including 0%) by area fraction in total, tempered martensite and carbide-containing bainite constituting 70% to 97% by area fraction in total, martensite and retained austenite constituting 3% to 20% by area fraction in total, and retained austenite constituting 1% to 5% by area fraction. The ferrite, the carbide-free bainite, the martensite, and the retained austenite constitute 3% to 30% by area fraction in total. The retained austenite has a C content of 0.10% to 0.50%. The carbide-containing bainite and the tempered martensite have an average grain size of 5 to 20 μm.

公开(公告)号：US10329636B2

公开(公告)日：2019-06-25

申请号：US15301097

申请日：2015-03-17

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Kohei Hasegawa

IPC: C21D9/46 ,  C21D1/25 ,  C21D8/02 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/34 ,  C22C38/38 ,  C22C38/58 ,  C22C38/00 ,  C21D8/04 ,  B22D11/00 ,  C22C38/08 ,  C22C38/12 ,  C22C38/16 ,  C22C38/28 ,  C22C38/32

Abstract: A high-strength cold-rolled steel sheet having good ductility, hole expandability, and delayed fracture resistance and being excellent in material homogeneity. The steel sheet has a chemical composition containing, in mass %, C: 0.15 to 0.25%, Si: 1.2 to 2.2%, Mn: 1.7 to 2.5%, P: 0.05% or less, S: 0.005% or less, Al: 0.01 to 0.10%, N: 0.006% or less, Ti: 0.003 to 0.030%, B: 0.0002 to 0.0050%, and Fe and inevitable impurities. The steel sheet has a microstructure that includes ferrite having an average crystal grain diameter of 4 μm or less at a volume fraction of 5 to 20%, retained austenite at a volume fraction of 5% or less, including 0%, and tempered martensite at a volume fraction of 80 to 95%. Additionally, the mean free path of the ferrite is 3.0 to 7.5 μm.

公开(公告)号：US20190085427A1

公开(公告)日：2019-03-21

申请号：US16086426

申请日：2017-03-21

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Yoshimasa Funakawa

IPC: C21D9/46 ,  C23C2/28 ,  C23C2/40 ,  B32B15/01 ,  C22C38/58 ,  C22C38/50 ,  C22C38/32 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/20 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/06

Abstract: Provided herein is a plated steel sheet having a yield ratio, strength (tensile strength), elongation, hole expansibility, and CTS. A method for producing the plated steel sheet is also provided, among others. A steel sheet of a specific composition is provided that has a micro structure containing 70 to 90% of ferrite, 5 to 20% of martensite, 5% or less of retained austenite, 10% or less of bainite, and 5% or less of perlite by volume. The ferrite has an average crystal grain diameter of 20 μm or less. The martensite has an average crystal grain diameter of 5 μm or less. The retained austenite has an average crystal grain diameter of 5 μm or less. The bainite has an average crystal grain diameter of 7 μm or less. The steel sheet has a tensile strength of 590 MPa or more.

公开(公告)号：US20190078173A1

公开(公告)日：2019-03-14

申请号：US16087931

申请日：2017-03-21

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Chikaumi Sawanishi ,  Yoshimasa Funakawa

IPC: C21D8/02 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/12 ,  C22C38/00 ,  C23C2/06 ,  C23C2/02 ,  C23C2/40

Abstract: Provided herein is a steel sheet of a specific composition that has a micro structure containing, by volume, 75 to 95% of ferrite, 3 to 15% of martensite, 0.5 to 10% of perlite, 10% or less of unrecrystallized ferrite, and 21.5% or less of a low-temperature occurring phase representing the remainder, and in which the ferrite has an average crystal grain diameter of 6 μm or less, and the martensite has an average crystal grain diameter of 3 μm or less, and an average aspect ratio of 4.0 or less, and in which a Nb base precipitate having an average grain diameter of 0.10 μm or less is contained. The steel sheet has a tensile strength of 590 MPa or more.

公开(公告)号：US20190001429A1

公开(公告)日：2019-01-03

申请号：US16062407

申请日：2016-12-13

Applicant: JFE STEEL CORPORATION

Inventor： Chikaumi Sawanishi ,  Koichi Taniguchi ,  Katsutoshi Takashima ,  Hiroshi Matsuda ,  Rinsei Ikeda

IPC: B23K11/11 ,  B23K11/16

Abstract: Provided is a resistance spot welding method that inhibits, in accordance with the degree of axis misalignment between electrodes, the occurrence of cracking in a weld regardless of the steel grade. In resistance spot welding methods according to the present invention, H (ms) is an electrode force retaining time after completion of current passage, D (mm) is an amount of axis misalignment between the electrodes, t (mm) is a total sum of sheet thicknesses of a plurality of overlapping steel sheets, T (MPa) is a tensile strength of a steel sheet having a highest tensile strength among the plurality of steel sheets, F (N) is an electrode force, and d (mm) is a tip diameter of one electrode of the pair of electrodes that has a smaller tip diameter. The electrode force retaining time H is specified to be a predetermined value or greater.

公开(公告)号：US10156005B2

公开(公告)日：2018-12-18

申请号：US14911088

申请日：2014-07-18

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Yoshihiko Ono ,  Kohei Hasegawa

IPC: C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/12 ,  C21D9/46 ,  C21D8/02 ,  C22C38/38 ,  C22C38/00 ,  C22C38/08 ,  C22C38/16 ,  C22C38/28 ,  C22C38/32 ,  C21D1/84 ,  C21D6/00 ,  C21D8/04 ,  C21D1/25

Abstract: A steel sheet includes a microstructure containing a volume fraction of 20% to 55% of ferrite having an average grain size of 7 μm or less, a volume fraction of 5% to 15% of retained austenite, a volume fraction of 0.5% to 7% of martensite having an average grain size of 4 μm or less, and a structure composed of bainite and/or tempered martensite and having an average grain size of 6 μm or less, and a difference in nano-hardness between ferrite and the structure composed of bainite and/or tempered martensite being 3.5 GPa or less and a difference in nano-hardness between the structure composed of bainite and/or tempered martensite and martensite being 2.5 GPa or less.