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：US20200040420A1

公开(公告)日：2020-02-06

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：US20190284656A1

公开(公告)日：2019-09-19

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 ,  C23C2/02 ,  C22C38/12 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/08

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：US20190271051A1

公开(公告)日：2019-09-05

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 ,  C23C2/02 ,  C22C38/00 ,  C22C38/06 ,  C22C38/02 ,  C22C38/14 ,  C22C38/60 ,  C22C38/38 ,  C22C38/12 ,  C22C38/16 ,  C22C38/08 ,  C21D9/46

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：US20170121787A1

公开(公告)日：2017-05-04

申请号：US15129520

申请日：2015-03-26

Applicant: JFE STEEL CORPORATION

Inventor： Yuka MIYAMOTO ,  Takashi KOBAYASHI ,  Kaneharu OKUDA

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

CPC classification number: C21D9/46 ,  C21D8/0226 ,  C21D8/0263 ,  C21D2211/003 ,  C21D2211/005 ,  C21D2211/009 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/18 ,  C22C38/32 ,  C22C38/60

Abstract: A high-carbon hot-rolled steel sheet having a chemical composition containing, by mass %, C: 0.20% or more and 0.40% or less, Si: 0.10% or less, Mn: 0.50% or less, P: 0.03% or less, S: 0.010% or less, sol.A1: 0.10% or less, N: 0.0050% or less, B: 0.0005% or more and 0.0050% or less, and at least one of Sb, Sn, Bi, Ge, Te, and Se in an amount of 0.002% or more and 0.030% or less in total. The steel sheet has a microstructure including ferrite and cementite, in which the density of cementite in the ferrite grains is 0.08 pieces/m2 or less. Additionally, the steel sheet has a hardness of 73 or less in terms of HRB and a total elongation of 39% or more.

公开(公告)号：US20160145709A1

公开(公告)日：2016-05-26

申请号：US14903842

申请日：2014-07-08

Applicant: JFE STEEL CORPORATION

Inventor： Yuka MIYAMOTO ,  Takashi KOBAYASHI ,  Chikara KAMI ,  Hayato SAITO ,  Kaneharu OKUDA

IPC: C21D9/46 ,  C22C38/06 ,  C22C38/04 ,  C21D1/26 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C22C38/60 ,  C22C38/02

CPC classification number: C21D9/46 ,  C21D1/26 ,  C21D1/32 ,  C21D1/74 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0247 ,  C21D8/0263 ,  C21D2211/003 ,  C21D2211/005 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/60

Abstract: There is provided is 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 formability. The steel sheet has a hardness in the range of 83 HRB or less and a total elongation of 30% or more before being subjected to a quenching treatment.

Abstract translation: 提供一种高碳热轧钢板及其制造方法。 即使在氮气氛中退火，钢板也具有优异的淬透性，成型性优异。 在进行淬火处理之前，钢板的硬度为83HRC以下，总伸长率为30％以上。

公开(公告)号：US20200283862A1

公开(公告)日：2020-09-10

申请号：US16766703

申请日：2018-10-29

Applicant: JFE STEEL CORPORATION

Inventor： Seigo TSUCHIHASHI ,  Hidekazu MINAMI ,  Takashi KOBAYASHI

IPC: C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/20 ,  C22C38/60 ,  C22C38/32 ,  C21D9/46

Abstract: Provided is a high-strength steel sheet having a tensile strength (TS) of 750 MPa or more and excellent in ductility and stretch flangeability, in which the steel sheet has a predetermined chemical composition and a microstructure containing, in area ratio, ferrite: 50% to 90%, quenched martensite: 1% to 8%, tempered martensite: 3% to 40%, and retained austenite: 6% to 15%, the quenched martensite has an average grain size of 2.5 μm or less, the quenched martensite has an average circularity index of 0.50 or more, the circularity index being defined as 4 πM/D2, where D is a perimeter of the quenched martensite and M is an area of the quenched martensite, and the steel sheet has a ratio of an area ratio of the quenched martensite fM to a total area ratio of the quenched martensite and the tempered martensite fM+TM, fM/fM+TM, of 50% or less.

公开(公告)号：US20190161822A1

公开(公告)日：2019-05-30

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

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：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：US20190276907A1

公开(公告)日：2019-09-12

申请号：US16090883

申请日：2017-03-08

Applicant: JFE STEEL CORPORATION

Inventor： Takako YAMASHITA ,  Yoshiyasu KAWASAKI ,  Takashi KOBAYASHI ,  Masayasu UENO ,  Yasunobu NAGATAKI

IPC: C21D8/02 ,  C22C38/00 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C22C38/08 ,  C22C38/28 ,  C22C38/38 ,  C22C38/16 ,  C21D9/46 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40

Abstract: A steel sheet having TS of 590 MPa or more and YR of 68% or more is obtained by providing a predetermined chemical composition and a predetermined steel microstructure, where an average aspect ratio of crystal grains of each phase (polygonal ferrite, martensite, and retained austenite) is 2.0 or more and 15.0 or less, wherein the polygonal ferrite has an average grain size of 6 μm or less, the martensite has an average grain size of 3 μm or less, the retained austenite has an average grain size of 3 μm or less, and a value obtained by dividing a Mn content in the retained austenite in mass % by a Mn content in the polygonal ferrite in mass % equals 2.0 or more.