公开(公告)号：US11447840B2

公开(公告)日：2022-09-20

申请号：US16349422

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 ,  C22C38/60 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/14 ,  C21D9/46 ,  C23C2/40 ,  C23C2/06 ,  C23C2/12 ,  C22C38/12 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/08 ,  C23C2/02 ,  C21D6/00 ,  C22C38/04 ,  C23C2/28

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 980 MPa or more, by having a predetermined chemical composition and a microstructure where ferrite is 15% or more and 55% or less and martensite is 15% or more and 30% or less in area ratio, retained austenite is 12% or more in volume fraction, the average grain size of ferrite, martensite and retained austenite is 4.0 μm or less, 2.0 μm or less and 2.0 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：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：US11420247B2

公开(公告)日：2022-08-23

申请号：US16618243

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

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

IPC: B32B15/00 ,  B21D22/02 ,  B32B15/01 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/24 ,  C22C38/26 ,  C22C38/32 ,  C22C38/42 ,  C22C38/44 ,  C22C38/50 ,  C23C30/00

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing of 1780 MPa or more, excellent delayed fracture resistance, and high cross tensile strength after resistance spot welding by properly adjusting its chemical composition and its microstructure such that a prior austenite average grain size is 8 μm or less, a volume fraction of martensite is 90% or more, and at least 10 cementite grains having a grain size of 0.05 μm or more are present on average per 200 μm2 of a cross section parallel to a thickness direction of the member, and such that at least 10 Ti-based precipitates having a grain size of less than 0.10 μm are present on average per 100 μm2 of the cross section parallel to the thickness direction of the member in a range of 100 μm in the thickness direction from a surface of the member.

公开(公告)号：US11377709B2

公开(公告)日：2022-07-05

申请号：US16616602

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

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

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

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：US11236406B2

公开(公告)日：2022-02-01

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

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：US11111558B2

公开(公告)日：2021-09-07

申请号：US16619814

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

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

IPC: B32B15/01 ,  C21D9/48 ,  C21D6/00 ,  C21D8/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/60 ,  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 resistance to resistance welding cracking by properly adjusting its chemical composition and its microstructure such that a prior austenite average grain size is 7.5 μm or less, a volume fraction of martensite is 95% or more, and at least 10 Nb-based and Ti-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 within a range of 100 μm or less in the thickness direction from the surface of the member, and such that a B concentration in prior austenite grain boundaries is at least 3.0 times a B concentration at a position 5 nm away from the grain boundaries.

公开(公告)号：US10077491B2

公开(公告)日：2018-09-18

申请号：US14370314

申请日：2012-12-26

Applicant: JFE STEEL CORPORATION

Inventor： Nobuyuki Nakamura ,  Takashi Kobayashi ,  Yoshimasa Funakawa

IPC: C22C38/60 ,  C21D9/46 ,  C22C38/00 ,  C22C38/06 ,  C21D8/02 ,  C22C38/02 ,  C22C38/04 ,  C22C38/18 ,  C21D1/26 ,  C22C38/08 ,  C22C38/12 ,  C22C38/16 ,  C22C38/32 ,  C22C38/54 ,  C21D1/32

CPC classification number: C22C38/60 ,  C21D1/26 ,  C21D1/32 ,  C21D8/0226 ,  C21D8/0263 ,  C21D9/46 ,  C21D2211/003 ,  C21D2211/005 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/16 ,  C22C38/18 ,  C22C38/32 ,  C22C38/54 ,  Y02P10/212

Abstract: A high carbon hot rolled steel sheet and a method for manufacturing the same are provided, wherein excellent cold workability and excellent hardenability are obtained stably. The high carbon hot rolled steel sheet has a composition containing C: 0.20% to 0.48%, Si: 0.1% or less, Mn: 0.5% or less, P: 0.03% or less, S: 0.01% or less, sol. Al: more than 0.10% and 1.0% or less, N: 0.005% or less, B: 0.0005% to 0.0050%, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, and a microstructure composed of ferrite and cementite, wherein the average grain size of the above-described ferrite is 10 to 20 μm and the spheroidization ratio of the above-described cementite is 90% or more.

公开(公告)号：US20210310095A1

公开(公告)日：2021-10-07

申请号：US17295950

申请日：2019-11-18

Applicant: JFE Steel Corporation

Inventor： Junya Tobata ,  Hidekazu Minami ,  Takashi Kobayashi

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/26 ,  C22C38/16 ,  C22C38/24 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/14 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18 ,  B32B15/01

Abstract: There is provided a high-strength steel sheet in which content amounts of a specific steel composition are limited and manufacturing conditions are optimized and that has a steel structure that contains ferrite and a harder phase and in which ferrite accounts for 30% to 70% in terms of area ratio, the harder phase contains bainitic ferrite, tempered martensite, martensite (including 0%), and retained austenite (including 0%), the maximum grain diameter of ferrite dmax is 2.5 μm or less, and the area ratio of ferrite AF and the average grain diameter of ferrite dF satisfy AF [%]/dF [μm]≤15.

公开(公告)号：US10400299B2

公开(公告)日：2019-09-03

申请号：US14903911

申请日：2014-07-08

Applicant: JFE STEEL CORPORATION

Inventor： Yuka Miyamoto ,  Takashi Kobayashi ,  Chikara Kami

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/60 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/18 ,  C21D6/00 ,  C22C38/32 ,  C21D1/32

Abstract: There is provided a high-carbon hot-rolled steel sheet and method for producing the same. The steel sheet has excellent hardenability consistently, even when annealed in a nitrogen atmosphere, and excellent workability. The steel sheet has a hardness in the range of 65 or less in terms of HRB and a total elongation El of 40% or more before a quenching treatment is performed.

公开(公告)号：US20140332122A1

公开(公告)日：2014-11-13

申请号：US14370319

申请日：2012-12-26

Applicant: JFE STEEL CORPORATION

Inventor： Nobuyuki Nakamura ,  Takashi Kobayashi ,  Yoshimasa Funakawa

IPC: C22C38/54 ,  C22C38/32 ,  C22C38/28 ,  C22C38/24 ,  C22C38/00 ,  C22C38/20 ,  C22C38/04 ,  C22C38/06 ,  C22C38/02 ,  C21D8/02 ,  C22C38/22

CPC classification number: C22C38/54 ,  C21D8/0221 ,  C21D8/0226 ,  C21D8/0263 ,  C21D9/46 ,  C21D2211/003 ,  C21D2211/005 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/28 ,  C22C38/32 ,  Y02P10/212

Abstract: A high carbon hot rolled steel sheet having a chemical composition containing by mass %, C: 0.20% to 0.48%, Si: 0.1% or less, Mn: 0.5% or less, P: 0.03% or less, S: 0.01% or less, Al: 0.1% to 0.6%, Cr: 0.05% to 0.5%, B: 0.0005% to 0.0050%, Ca: 0.0010% to 0.0050%, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, where the average amount of N in a surface layer portion from the surface to the position at a depth of 0.1 mm in thickness direction is 0.1% or more and the average amount of N in the central portion in thickness is 0.01% or less, and a microstructure composed of ferrite and carbides, wherein the average grain size of the ferrite is 10 to 20 and the spheroidization ratio of the carbides is 90% or more.

Abstract translation: 化学组成为C：0.20％〜0.48％，Si：0.1％以下，Mn：0.5％以下，P：0.03％以下，S：0.01％以下的高碳热轧钢板， 以质量％计，Al：0.1〜0.6％，Cr：0.05〜0.5％，B：0.0005〜0.0050％，Ca：0.0010〜0.0050％，余量由Fe和杂质构成 其中，从表面到层厚0.1mm的深度位置的表面层的平均含量为0.1％以上，中央部的平均N的平均量为0.01％以下， 以及由铁素体和碳化物组成的微观结构，其中铁素体的平均粒径为10〜20，碳化物的球化率为90％以上。