公开(公告)号：US12065711B2

公开(公告)日：2024-08-20

申请号：US17262884

申请日：2019-06-10

Applicant: JFE Steel Corporation

Inventor： Kazuhiko Yamazaki ,  Takeshi Yokota ,  Sumio Kaiho ,  Noriaki Moriyasu

IPC: C22C38/00 ,  C21D6/00 ,  C21D8/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/16 ,  C22C38/22 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38

CPC classification number: C21D9/46 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/005 ,  C21D8/0226 ,  C21D8/0263 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/16 ,  C22C38/22 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C21D2211/002 ,  C21D2211/008

Abstract: A high-strength hot rolled steel sheet and a method for manufacturing the high-strength hot rolled steel sheet are disclosed. The high-strength hot rolled steel sheet includes a specific chemical composition, and a steel structure in which a lower bainite phase and/or a tempered martensite phase at 90% or more in terms of a total area fraction is contained as a dominant phase, an average grain size of the dominant phase is 10.0 μm or less, and an amount of Fe in Fe-based precipitates is 0.70% or less in mass %, in which an arithmetic average roughness (Ra) of a surface is 2.50 μm or less, and a tensile strength TS is 1180 MPa or more.

公开(公告)号：US10711333B2

公开(公告)日：2020-07-14

申请号：US15516698

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu Kawasaki ,  Hiroshi Matsuda ,  Takeshi Yokota ,  Takako Yamashita ,  Kazuhiro Seto

IPC: C21D9/46 ,  C22C38/14 ,  C23C2/12 ,  C22C38/60 ,  C23C2/02 ,  C22C38/00 ,  C23C2/06 ,  C23C2/28 ,  B32B15/01 ,  B32B15/18 ,  B32B15/20 ,  C21D1/26 ,  C21D6/00 ,  C21D8/02 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C23C2/40 ,  C23F17/00 ,  C25D3/22

Abstract: Disclosed is a steel sheet having a predetermined chemical composition and a steel microstructure that contains, in area ratio, 15% or more and 55% or less of polygonal ferrite and 15% or more and 30% or less of martensite, and that contains, in volume fraction, 12% or more of retained austenite, in which the polygonal ferrite, the martensite, and the retained austenite have a mean grain size of 4 μm or less, 2 μm or less, and 2 μm or less, respectively, and each have a mean grain aspect ratio of 2.0 or less, and in which a value obtained by dividing an Mn content in the retained austenite in mass % by an Mn content in the polygonal ferrite in mass % equals 2.0 or more.

公开(公告)号：US10662495B2

公开(公告)日：2020-05-26

申请号：US15326116

申请日：2015-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu Kawasaki ,  Hiroshi Matsuda ,  Kazunori Tahara ,  Takeshi Yokota ,  Kaneharu Okuda ,  Kazuhiro Seto

IPC: C21D9/46 ,  C22C38/00 ,  C22C38/04 ,  C22C38/60 ,  B32B15/01 ,  C21D1/60 ,  C21D8/02 ,  C22C38/02 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/38 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00

Abstract: Disclosed is a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more and excellent in ductility, fatigue properties, stretch flangeability, surface characteristics, and sheet passage ability that can be obtained by providing a predetermined chemical composition and a steel microstructure that contains, by area, 20-50% of ferrite, 5-25% of bainitic ferrite, 1-10% of martensite, and 5-15% of tempered martensite, and that contains, by volume, 10% or more of retained austenite, in which the retained austenite has a mean grain size of 2 μm or less, a mean Mn content in the retained austenite in mass % is at least 1.2 times the Mn content in the steel sheet in mass %, the retained austenite has a mean free path of 1.2 μm or less, and the tempered martensite has a mean free path of 1.2 μm or less.

公开(公告)号：US10392677B2

公开(公告)日：2019-08-27

申请号：US15521515

申请日：2015-10-05

Applicant: JFE STEEL CORPORATION

Inventor： Koichi Nakagawa ,  Takeshi Yokota ,  Kazuhiro Seto

IPC: C21D9/46 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C21D1/18 ,  C22C38/00 ,  C22C38/06 ,  C22C38/60 ,  C21D6/00 ,  C21D8/02 ,  C21D8/04 ,  C23C2/40 ,  C22C38/02 ,  C22C38/04 ,  C22C38/08 ,  C22C38/38 ,  B21D22/02 ,  B32B15/01 ,  C21D1/673 ,  C22C18/00 ,  C22C38/12 ,  C22C38/14 ,  C21D9/48

Abstract: A high-strength hot-pressed part having a specified chemical composition, a microstructure including, in terms of volume fraction, 80% or more of a martensite phase, in a range of 3.0% to 20.0% of a retained austenite phase, a tensile strength TS of 1500 MPa or more, and a uniform elongation uEl of 6.0% or more. A method for manufacturing the high-strength hot-pressed part, the method comprising performing a heating process and a hot press forming process on a raw material steel sheet in order to obtain a hot-pressed part having a specified shape.

公开(公告)号：US10260133B2

公开(公告)日：2019-04-16

申请号：US14779783

申请日：2014-03-26

Applicant: JFE STEEL CORPORATION

Inventor： Hidetaka Kawabe ,  Takeshi Yokota ,  Reiko Sugihara ,  Kazunori Tahara

IPC: C22C38/06 ,  C21D9/46 ,  C22C38/00 ,  C21D8/02 ,  C23C2/06 ,  C23C2/02 ,  C23C2/40 ,  C25D5/36 ,  C25D7/06 ,  C21D6/00 ,  C22C38/02 ,  C22C38/04 ,  C25D3/22 ,  C25D7/00 ,  C22C38/22

Abstract: There is provided a high-strength steel sheet having a tensile strength (TS) of 900 MPa or more and excellent elongation, stretch flangeability, and bendability in a component system in which an expensive alloy element is not intentionally added. A high-strength steel sheet includes a composition including, on a mass % basis, C: 0.15 to 0.40%, Si: 1.0 to 2.0%, Mn: 1.5 to 2.5%, P: 0.020% or less, S: 0.0040% or less, Al: 0.01 to 0.1%, N: 0.01% or less, and Ca: 0.0020% or less, with the balance including Fe and incidental impurities. The high-strength steel sheet has a microstructure including 40% to 70% of a ferrite phase and a bainite phase in total, 20% to 50% of a martensite phase, and 10% to 30% of a retained austenite phase in terms of an area fraction relative to the entire microstructure.

公开(公告)号：US12195819B2

公开(公告)日：2025-01-14

申请号：US17632566

申请日：2020-07-16

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Takeshi Yokota

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C23C2/02 ,  C23C2/28 ,  C23G1/08

Abstract: The high-strength thin steel sheet has a chemical composition containing C, Si, Mn, P, S, Al, and N, with the balance being Fe and inevitable impurities, and a complex structure containing ferrite, tempered martensite, and bainite, where a volume fraction of a total of tempered martensite and bainite containing five or more carbides with a particle size of 0.1 μm or more and 1.0 μm or less in a grain with respect to a total of the tempered martensite and the bainite is 85% or more, and C mass % and Mn mass % in a region of 20 μm or less in a thickness direction from a surface of the steel sheet are each 20% or less with respect to C mass % and Mn mass % in a region of 100 μm or more and 200 μm or less from the surface of the steel sheet.

公开(公告)号：US11939642B2

公开(公告)日：2024-03-26

申请号：US17283840

申请日：2019-08-20

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu Minami ,  Yuji Tanaka ,  Junya Tobata ,  Takeshi Yokota

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23G1/00 ,  C25D3/22 ,  C25D3/44

CPC classification number: C21D9/46 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C23C2/02 ,  C23C2/0224 ,  C23C2/024 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23G1/00 ,  C25D3/22 ,  C25D3/44 ,  C21D2211/001 ,  C21D2211/008

Abstract: A high-strength steel sheet having a tensile strength of 1,180 MPa or more, and specified chemical composition. The steel sheet includes a steel structure in which an area fraction of martensite having a carbon concentration of more than 0.7×[% C] and less than 1.5×[% C] is 55% or more, an area fraction of tempered martensite having a carbon concentration of 0.7×[% C] or less is 5% or more and 40% or less, a ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite is 0.05 or more and 0.40 or less, and the martensite and the tempered martensite each have an average grain size of 5.3 μm or less, where [% C] represents the content, by mass %, of compositional element C in steel.

公开(公告)号：US11434542B2

公开(公告)日：2022-09-06

申请号：US16964627

申请日：2019-01-22

Applicant: JFE Steel Corporation

Inventor： Yuka Miyamoto ,  Takashi Kobayashi ,  Yasuhiro Sakurai ,  Takeshi Yokota

IPC: C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/60 ,  C21D8/02 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54

Abstract: A high-carbon hot-rolled steel sheet has a composition containing, on a percent by mass basis, C: 0.10% or more and less than 0.20%, Si: 0.5% or less, Mn: 0.25% to 0.65%, P: 0.03% or less, S: 0.010% or less, sol. Al: 0.10% or less, N: 0.0065% or less, Cr: 0.05% to 0.50%, and B: 0.0005% to 0.005%, the balance being Fe and incidental impurities, the high-carbon hot-rolled steel sheet having a microstructure containing ferrite and cementite, in which the percentage of the number of cementite grains having an equivalent circular diameter of 0.1 μm or less is 12% or less based on the total number of cementite grains, the amount of Cr dissolved in the steel sheet is 0.03% to 0.50%, and the high-carbon hot-rolled steel sheet has a hardness of 73 or less in terms of HRB and a total elongation of 37% or more.

公开(公告)号：US10472697B2

公开(公告)日：2019-11-12

申请号：US15547659

申请日：2016-01-27

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu Minami ,  Shinjiro Kaneko ,  Takeshi Yokota ,  Kazuhiro Seto

IPC: C21D9/46 ,  C22C38/02 ,  C22C38/60 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/04 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28

Abstract: A steel sheet has a microstructure that contains ferrite in an area ratio of 20% or more, martensite in an area ratio of 5% or more, and tempered martensite in an area ratio of 5% or more. The ferrite has a mean grain size of 20.0 μm or less. An inverse intensity ratio of γ-fiber to α-fiber in the ferrite is 1.00 or more and an inverse intensity ratio of γ-fiber to α-fiber in the martensite and the tempered martensite is 1.00 or more.

公开(公告)号：US10266906B2

公开(公告)日：2019-04-23

申请号：US14779772

申请日：2014-03-26

Applicant: JFE STEEL CORPORATION

Inventor： Hidetaka Kawabe ,  Takeshi Yokota

IPC: C21D8/02 ,  C23C2/06 ,  C23C2/40 ,  C21D9/46 ,  C22C38/00 ,  C22C38/06 ,  B32B15/01 ,  C22C38/02 ,  C22C38/04 ,  C23C2/02 ,  C23C2/28 ,  C21D6/00 ,  C23F17/00

Abstract: A high-strength galvanized steel sheet has a chemical composition containing, by mass %, C: 0.16% or more and 0.24% or less, Si: 0.8% or more and 1.8% or less, Mn: 1.0% or more and 3.0% or less, P: 0.020% or less, S: 0.0040% or less, Al: 0.01% or more and 0.1% or less, N: 0.01% or less, Ca: 0.0001% or more and 0.0020% or less, and the balance including Fe and incidental impurities, and a microstructure, in which the total area ratio of a ferrite phase and a bainite phase with respect to the whole microstructure is 30% or more and 70% or less, in which the area ratio of a tempered martensite phase with respect to the whole microstructure is 20% or more and 40% or less, in which the area ratio of a retained austenite phase with respect to the whole microstructure is 10% or more and 20% or less, and in which the area ratio of a martensite phase with respect to the whole microstructure is 2% or more and 20% or less.