公开(公告)号：US11293074B2

公开(公告)日：2022-04-05

申请号：US16617133

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Chikaumi Sawanishi ,  Takashi Kobayashi ,  Yoshimasa Funakawa

IPC: C21D9/46 ,  B21D22/02 ,  B32B15/01 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/10 ,  C22C38/16 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38

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, excellent resistance to resistance welding cracking, and excellent delayed fracture resistance after resistance welding by having a specific chemical composition, and a microstructure such that a prior austenite average grain size is 7 μm or less, a volume fraction of martensite is 90% or more, and at least 5 Nb-based precipitates having a grain size of less than 0.08 μm are present on average per 100 μm2 of a cross section parallel to a thickness direction of the member within a range of 100 μm in the thickness direction from a surface of the member, and such that a Ni diffusion region having a thickness of 0.5 μm or more is present in a surface layer of the member.

公开(公告)号：US20150000801A1

公开(公告)日：2015-01-01

申请号：US14370121

申请日：2012-12-25

Applicant: JFE STEEL CORPORATION

Inventor： Yuka Miyamoto ,  Takashi Kobayashi ,  Nobuyuki Nakamura ,  Yoshimasa Funakawa

IPC: C21D9/46 ,  C22C38/60 ,  C22C38/32 ,  C22C38/00 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C21D8/02 ,  C22C38/22

CPC classification number: C21D9/46 ,  B21B3/00 ,  B22D11/1206 ,  B22D11/1213 ,  C21D1/26 ,  C21D6/00 ,  C21D8/0226 ,  C21D8/0263 ,  C21D2211/003 ,  C21D2211/004 ,  C21D2211/005 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/22 ,  C22C38/32 ,  C22C38/60 ,  Y02P10/212

Abstract: A high-carbon hot rolled steel sheet with excellent hardenability and small in-plane anisotropy, and a method for manufacturing the steel sheet are provided. The steel sheet has a chemical composition including, by mass %, C: 0.20 to 0.48%, Si: not more than 0.1%, Mn: not more than 0.5%, P: not more than 0.03%, S: not more than 0.01%, sol. Al: not more than 0.10%, N: not more than 0.005% and B: 0.0005 to 0.0050%, the balance including Fe and inevitable impurities. The steel sheet includes a microstructure containing ferrite and cementite. The cementite has an average grain size of not more than 1.0 μm. The steel sheet has an in-plane anisotropy of r value, Δr, of not more than 0.1 in absolute value.

Abstract translation: 提供了具有优异的淬透性和小的面内各向异性的高碳热轧钢板，以及钢板的制造方法。 该钢板具有以质量％计含有C：0.20〜0.48％，Si：0.1％以下，Mn：0.5％以下，P：0.03％以下，S：0.01以下的化学成分 ％，sol。 Al：不大于0.10％，N：不大于0.005％，B：0.0005至0.0050％，余量包括Fe和不可避免的杂质。 钢板包括含有铁素体和渗碳体的微结构。 渗碳体的平均粒径不大于1.0μm。 该钢板的r值的面内各向异性＆Dgr; r绝对值不大于0.1。

公开(公告)号：US11408058B2

公开(公告)日：2022-08-09

申请号：US16485197

申请日：2018-02-09

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu Minami ,  Takashi Kobayashi ,  Shinjiro Kaneko ,  Yuji Tanaka

IPC: C22C38/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/60 ,  C23C2/06 ,  C21D8/02 ,  C21D8/04 ,  C21D9/46

Abstract: There is provided a high-strength steel sheet and a method for producing the same. The steel sheet has a specified chemical composition and a microstructure including, in terms of area percentage, 20.0% or more and 60.0% or less ferrite, 40.0% or more and 80.0% or less of a hard phase composed of bainitic ferrite, tempered martensite, fresh martensite, and retained austenite, 35.0% or more and 55.0% or less bainitic ferrite with respect to the entire hard phase, 20.0% or more and 40.0% or less tempered martensite with respect to the entire hard phase, 3.0% or more and 15.0% or less fresh martensite with respect to the entire hard phase, and 5.0% or more and 20.0% or less retained austenite with respect to the entire hard phase.

公开(公告)号：US11408044B2

公开(公告)日：2022-08-09

申请号：US16485083

申请日：2018-02-09

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu Minami ,  Fusae Shiimori ,  Shinjiro Kaneko ,  Takashi Kobayashi ,  Yuji Tanaka

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C21D1/26 ,  C22C38/24 ,  C22C38/60 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: There is provided a high-strength steel sheet and a method for producing the same. The high-strength steel sheet has a specified chemical composition and a steel microstructure including, by area fraction, 75.0% or more tempered martensite, 1.0% or more and 20.0% or less fresh martensite, and 5.0% or more and 20.0% or less retained austenite. A hardness ratio of the fresh martensite to the tempered martensite is 1.5 or more and 3.0 or less, the ratio of the maximum KAM value in the tempered martensite in the vicinity of the heterophase interface between the tempered martensite and the fresh martensite to the average KAM value in the tempered martensite is 1.5 or more and 30.0 or less, and the average of ratios of grain sizes of prior austenite grains in the rolling direction to those in the thickness direction is 2.0 or less.

公开(公告)号：US11193180B2

公开(公告)日：2021-12-07

申请号：US16092323

申请日：2017-03-22

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Yoshimasa Funakawa ,  Takashi Kobayashi

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

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：US11136643B2

公开(公告)日：2021-10-05

申请号：US16320864

申请日：2017-08-10

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Koichi Taniguchi ,  Takashi Kobayashi ,  Hiroshi Matsuda ,  Rinsei Ikeda

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/38 ,  C22C38/12 ,  C22C38/08 ,  C22C38/22 ,  C22C38/00 ,  C22C38/26 ,  C22C38/24 ,  C22C38/28 ,  C22C38/14 ,  C22C38/32 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C21D6/00 ,  C21D1/30 ,  C22C38/20 ,  C22C38/58

Abstract: A high-strength steel sheet having a specified chemical composition and a method for producing the same. The steel sheet including a multi-phase structure including, by volume fraction, ferrite of 35% to 65%, residual austenite of 7% or less (including 0%), martensite of 20% to 60%, bainite of 20% or less (including 0%), the ferrite having an average crystal grain size of 8 μm or less and an average aspect ratio of 3.5 or less, the martensite having an average crystal grain size of 3 μm or less, and the bainite having an average crystal grain size of 3 μm or less when contained. A standard deviation of Vickers hardness of the steel sheet being 30 or less when measured at 200 μm intervals from a position of 100 μm from a surface to a central portion in a thickness direction of the sheet.

公开(公告)号：US11085101B2

公开(公告)日：2021-08-10

申请号：US16618887

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Takashi Kobayashi ,  Yoshimasa Funakawa ,  Seiji Nakajima

IPC: B32B15/01 ,  C21D9/46 ,  B21D22/02 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/16 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C23C2/06 ,  C23C2/12 ,  C23C2/40

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 delayed fracture resistance after projection welding by properly adjusting its chemical composition and its microstructure such that at least 5 Ti-based precipitates having a grain size of 0.10 μm or less are present on average per 100 μm2 of a cross section parallel to a thickness direction of the member within a range of 100 μm in a thickness direction from a surface of the member, a volume fraction of martensite is 95% to 100% within a depth range of 20 μm to 100 μm in the thickness direction from the surface of the member, and at least 10 cementite grains having a grain size of less than 0.20 μm are present on average in a prior austenite grain.

公开(公告)号：US20200232074A1

公开(公告)日：2020-07-23

申请号：US16486908

申请日：2018-02-13

Applicant: JFE Steel Corporation

Inventor： Yuka Miyamoto ,  Yasuhiro Sakurai ,  Takashi Kobayashi ,  Shunsuke Toyoda

IPC: C22C38/18 ,  C22C38/02 ,  C22C38/04 ,  C22C38/00 ,  C21D8/02 ,  C21D9/46

Abstract: Provided are a high-carbon hot-rolled steel sheet with excellent formability and hardenability and a method for manufacturing the same.The high-carbon hot-rolled steel sheet has a composition containing, on a mass basis, C: 0.10% to 0.33%, Si: 0.15% to 0.35%, Mn: 0.5% to 0.9%, P: 0.03% or less, S: 0.010% or less, sol. Al: 0.10% or less, N: 0.0065% or less, and Cr: 0.90% to 1.5%, the remainder being Fe and inevitable impurities, has a microstructure containing ferrite and cementite, a cementite density being 0.25 grains/μm2 or less, and has a hardness of 110 HV to 160 HV and a total elongation of 40% or more.

公开(公告)号：US11447841B2

公开(公告)日：2022-09-20

申请号：US16349443

申请日：2017-11-15

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu Kawasaki ,  Takako Yamashita ,  Masayasu Ueno ,  Yuki Toji ,  Takashi Kobayashi ,  Yoshimasa Funakawa

IPC: C21D8/02 ,  C23C2/12 ,  C23C2/40 ,  C22C38/00 ,  C22C38/06 ,  C22C38/02 ,  C22C38/14 ,  C22C38/60 ,  C22C38/38 ,  C22C38/12 ,  C22C38/16 ,  C22C38/08 ,  C21D9/46 ,  C23C2/02 ,  C22C38/04 ,  C21D6/00 ,  C23C2/06

Abstract: To provide a high-strength steel sheet with excellent ductility and hole expansion formability, a yield ratio of less than 68%, and a tensile strength of 590 MPa or more, by having a predetermined chemical composition and a microstructure where ferrite is 35% or more and 80% or less and martensite is 5% or more and 25% or less in area ratio, retained austenite is 8% or more in volume fraction, the average grain size of ferrite, martensite and retained austenite is 6.0 μm or less, 3.0 μm or less and 3.0 μm or less respectively, the average aspect ratio of crystal grain of ferrite, martensite and retained austenite is each more than 2.0 and 15.0 or less, and the value obtained by dividing the Mn content (mass %) in retained austenite by the Mn content (mass %) in ferrite is 2.0 or more.

公开(公告)号：US11359267B2

公开(公告)日：2022-06-14

申请号：US16486908

申请日：2018-02-13

Applicant: JFE Steel Corporation

Inventor： Yuka Miyamoto ,  Yasuhiro Sakurai ,  Takashi Kobayashi ,  Shunsuke Toyoda

IPC: C22C38/18 ,  C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04

Abstract: Provided are a high-carbon hot-rolled steel sheet with excellent formability and hardenability and a method for manufacturing the same.
The high-carbon hot-rolled steel sheet has a composition containing, on a mass basis, C: 0.10% to 0.33%, Si: 0.15% to 0.35%, Mn: 0.5% to 0.9%, P: 0.03% or less, S: 0.010% or less, sol. Al: 0.10% or less, N: 0.0065% or less, and Cr: 0.90% to 1.5%, the remainder being Fe and inevitable impurities, has a microstructure containing ferrite and cementite, a cementite density being 0.25 grains/μm2 or less, and has a hardness of 110 HV to 160 HV and a total elongation of 40% or more.