Patents by Inventor Takeshi Yokota

Takeshi Yokota has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 11492446
    Abstract: An object of the present invention is to reduce or eliminate a defect (e.g., a void) by achieving (i) a semipreg and a prepreg each of which allows a reduction in residual volatile component and (ii) methods for producing the semipreg and the prepreg, respectively, and consequently to achieve (iii) a fiber-reinforced composite material which has high heat resistance and superior mechanical strength and a (iv) a method for producing the fiber-reinforced composite material. The present invention attains the above object by providing, for example, a semipreg containing: powders of an imide oligomer; and reinforcement fibers, the imide oligomer being represented by a specific general formula (1).
    Type: Grant
    Filed: March 22, 2018
    Date of Patent: November 8, 2022
    Assignees: KANEKA CORPORATION, JAPAN AEROSPACE EXPLORATION AGENCY
    Inventors: Yoshio Furukawa, Takefumi Furuta, Takeshi Chiba, Rikio Yokota, Yuichi Ishida
  • Publication number: 20220307019
    Abstract: A double-stranded nucleic acid complex is a double-stranded nucleic acid complex including a first nucleic acid strand and a second nucleic acid strand bonded to each other, the second nucleic acid strand including a complementary region having a base sequence complementary to the first nucleic acid strand; the first nucleic acid strand including natural nucleosides and non-natural nucleosides; some of the nucleosides in at least one nucleic acid strand selected from the group consisting of the first nucleic acid strand and the second nucleic acid strand being bonded together by bonds including asymmetric phosphorus atoms; and absolute configurations of the asymmetric phosphorus atoms being regulated.
    Type: Application
    Filed: March 25, 2020
    Publication date: September 29, 2022
    Applicants: National University Corporation Tokyo Medical and Dental University, Wave Life Sciences Ltd
    Inventors: Takanori YOKOTA, Takeshi WADA, Mamoru SHIMIZU
  • Patent number: 11434542
    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 ?m 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.
    Type: Grant
    Filed: January 22, 2019
    Date of Patent: September 6, 2022
    Assignee: JFE Steel Corporation
    Inventors: Yuka Miyamoto, Takashi Kobayashi, Yasuhiro Sakurai, Takeshi Yokota
  • Publication number: 20220275471
    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 ?m or more and 1.0 ?m 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 ?m 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 ?m or more and 200 ?m or less from the surface of the steel sheet.
    Type: Application
    Filed: July 16, 2020
    Publication date: September 1, 2022
    Applicant: JFE STEEL CORPORATION
    Inventors: Katsutoshi TAKASHIMA, Takeshi YOKOTA
  • Publication number: 20220251676
    Abstract: Provided are a high-strength hot-dip galvanized steel sheet that has a tensile strength of 1180 MPa or more and excellent ductility, stretch flangeability, bendability and LME resistance and can manufacture parts with high dimensional accuracy, and its manufacturing method. The high-strength steel sheet with a tensile strength of 1180 MPa or more has a chemical composition containing C, Si, Mn, P, S, Al and N, with [% Si], [% Mn], [% P], [% Mo] and [% Cr] satisfying a predetermined relationship and the balance being Fe and inevitable impurities, and a steel microstructure including ferrite, tempered martensite and bainite, and retained austenite, where the diffusible hydrogen amount in the steel sheet is 0.60 mass ppm or less, a thickness of softened surface layer is 5 ?m or more and 150 ?m or less, and a frequency of coincidence boundary in the steel sheet surface layer after a high-temperature tensile test is 0.45 or less.
    Type: Application
    Filed: June 19, 2020
    Publication date: August 11, 2022
    Applicant: JFE STEEL CORPORATION
    Inventors: Hidekazu MINAMI, Takeshi YOKOTA, Yoshiyasu KAWASAKI, Shotaro TERASHIMA
  • Patent number: 11401594
    Abstract: Provided are a hot-rolled steel sheet for coiled tubing and a method for manufacturing the steel sheet. The steel sheet has a yield strength of 480 MPa or more, a tensile strength of 600 MPa or more, a yield-strength difference (?YS) of 100 MPa or more, where the yield-strength difference is defined as a difference in yield strength between before and after a prestrain-heat treatment performed for simulation of a tube-making process and a stress-relief annealing heat treatment which are currently implemented, and a yield strength of 620 MPa or more after the prestrain-heat treatment.
    Type: Grant
    Filed: January 16, 2019
    Date of Patent: August 2, 2022
    Assignee: JFE Steel Corporation
    Inventors: Hideyuki Kimura, Shuji Kawamura, Ichiro Sugimoto, Makoto Asai, Takeshi Yokota
  • Patent number: 11390931
    Abstract: A hot-rolled steel plate has a predetermined chemical composition and a microstructure. In the microstructure, in a plate thickness 1/2 position, an area fraction of martensite is less than 3%, an area fraction of bainitic ferrite is 95% or greater, the bainitic ferrite has an average grain diameter of 6.0 ?m or less, an amount of Nb precipitated as Nb carbonitride is 0.025 mass % or greater, and an amount of Nb precipitated as Nb carbonitride having a grain diameter of 20 nm or greater constitutes 50% or greater of a total mass of the Nb precipitated as Nb carbonitride. The hot-rolled steel plate has a tensile strength of 640 MPa or greater, a yield ratio of 85% or less, a Charpy impact absorbed energy at ?40° C. of 300 J or greater, and a percent ductile fracture (SA value) of 85% or greater as determined by a DWTT test at ?40° C.
    Type: Grant
    Filed: December 11, 2018
    Date of Patent: July 19, 2022
    Assignee: JFE Steel Corporation
    Inventors: Hideyuki Kimura, Takeshi Yokota, Satoshi Tsutsumi
  • Publication number: 20220195552
    Abstract: A high-strength steel sheet comprises: a chemical composition containing C, Si, Mn, P, S, Al, N, Mo, Cr, Ca, and Sb with a balance consisting of Fe and inevitable impurities, wherein [% Si], [% Mn], [% P], [% Mo], and [% Cr] satisfy a predetermined relationship; a steel microstructure that contains ferrite, hard phase, and retained austenite and in which a carbon concentration in the retained austenite is 0.55% or more and 1.10% or less, an amount of diffusible hydrogen in the steel sheet is 0.80 mass ppm or less, a surface layer softening thickness is 5 ?m or more and 150 ?m or less, and a corresponding grain boundary frequency in a surface layer of the steel sheet after a high-temperature tensile test is 0.45 or less; and a tensile strength of 980 MPa or more.
    Type: Application
    Filed: February 21, 2020
    Publication date: June 23, 2022
    Applicant: JFE STEEL CORPORATION
    Inventors: Hidekazu MINAMI, Yuji TANAKA, Takeshi YOKOTA
  • Patent number: 11365460
    Abstract: A high-carbon cold rolled steel sheet having a specified chemical composition, and a method for manufacturing the same. The method includes forming a hot rolled steel sheet, performing cooling at an average cooling rate of 30° C./s or more and 70° C./s or less through a temperature range of a finish rolling end temperature to 660° C., coiling a hot rolled steel sheet at a temperature of 500° C. or more and 660° C. or less, and, optionally, pickling the coiled hot rolled steel sheet, and then performing a first box-annealing of holding at an annealing temperature in a temperature range of 650 to 720° C., then performing cold rolling at a rolling reduction ratio of 20 to 50%, and then performing a second box-annealing of holding at an annealing temperature in a temperature range of 650 to 720° C.
    Type: Grant
    Filed: February 20, 2019
    Date of Patent: June 21, 2022
    Assignee: JFE STEEL CORPORATION
    Inventors: Yuka Miyamoto, Yoichiro Matsui, Shogo Sato, Takeshi Yokota
  • Publication number: 20220154301
    Abstract: A steel sheet and a member excellent in cold workability, hardenability, and post-quenching surface layer hardness, and methods for manufacturing the steel sheet and the member. The steel sheet has a specified chemical composition and a microstructure containing ferrite and carbides, a ratio of the volume of ferrite and carbides to the volume of the entire microstructure is 90% or more, a ratio of the volume of proeutectoid ferrite to the volume of the entire microstructure is 20% or more and 80% or less, a Mn concentration in the carbides is 0.10 mass % or more and 0.50 mass % or less, and a ratio of the number of carbides with particle diameters of 1 ?m or more to the total number of carbides is 30% or more and 60% or less.
    Type: Application
    Filed: February 28, 2020
    Publication date: May 19, 2022
    Applicant: JFE STEEL CORPORATION
    Inventors: Yoichiro MATSUI, Yuka MIYAMOTO, Takeshi YOKOTA
  • Publication number: 20220064752
    Abstract: A high-strength cold rolled steel sheet has a specific composition and a steel structure that is, by volume %, 10%-70% ferrite, 1%-10% retained austenite, 10%-60% bainite, and 2%-50% martensite, the average crystal grain size of the ferrite being no more than 6.0 ?m, the average crystal grain size of the retained austenite being no more than 4.0 ?m, the average crystal grain size of the bainite being no more than 6.0 ?m, and the average crystal grain size of the martensite being no more than 4.0 ?m. The concentration ratio of the average concentration of Si to a depth of 10 ?m from the surface of the high-strength cold-rolled steel sheet to the average concentration of Si throughout the high-strength cold-rolled steel sheet is, by mass ratio, greater than 1.00 but less than 1.30.
    Type: Application
    Filed: December 23, 2019
    Publication date: March 3, 2022
    Applicant: JFE Steel Corporation
    Inventors: Yoshie Obata, Katsutoshi Takashima, Takeshi Yokota
  • Publication number: 20210381075
    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 ?m or less, where [% C] represents the content, by mass %, of compositional element C in steel.
    Type: Application
    Filed: August 20, 2019
    Publication date: December 9, 2021
    Applicant: JFE STEEL CORPORATION
    Inventors: Hidekazu MINAMI, Yuji TANAKA, Junya TOBATA, Takeshi YOKOTA
  • Patent number: 11085100
    Abstract: A high strength steel sheet having a high Young's modulus, the steel sheet having a chemical composition including, by mass %, C: 0.060% or more and 0.150% or less, Si: 0.50% or more and 2.20% or less, Mn: 1.00% or more and 3.00% or less, and one or both of Ti: 0.001% or more and 0.200% or less and Nb: 0.001% or more and 0.200% or less, in which the contents of C, N, S, Ti, and Nb satisfy the equation 500?C*?1300. The steel sheet has a microstructure including ferrite in an amount of 20% or more and martensite in an amount of 5% or more, in terms of area ratio, such that the average grain size of the ferrite is 20.0 ?m or less and the inverse intensity ratio of ?-fiber for ?-fiber is 1.00 or more in the ferrite and the martensite.
    Type: Grant
    Filed: June 26, 2019
    Date of Patent: August 10, 2021
    Assignee: JFE STEEL CORPORATION
    Inventors: Hidekazu Minami, Takeshi Yokota, Kazuhiro Seto
  • Patent number: 11035019
    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 ?m or less. An inverse intensity ratio of ?-fiber to ?-fiber in the ferrite is 1.00 or more and an inverse intensity ratio of ?-fiber to ?-fiber in the martensite and the tempered martensite is 1.00 or more.
    Type: Grant
    Filed: January 27, 2016
    Date of Patent: June 15, 2021
    Assignee: JFE STEEL CORPORATION
    Inventors: Hidekazu Minami, Shinjiro Kaneko, Takeshi Yokota, Kazuhiro Seto
  • Publication number: 20210140007
    Abstract: Provided is a high-strength hot rolled steel sheet that has excellent stretch flange formability, bendability, and low-temperature toughness while maintaining high strength of a tensile strength TS of 1180 MPa or more, and a method for manufacturing the high-strength hot rolled steel sheet. 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 ?m 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 ?m or less, and a tensile strength TS is 1180 MPa or more.
    Type: Application
    Filed: June 10, 2019
    Publication date: May 13, 2021
    Applicant: JFE Steel Corporation
    Inventors: Kazuhiko Yamazaki, Takeshi Yokota, Sumio Kaiho, Noriaki Moriyasu
  • Patent number: 10954578
    Abstract: Disclosed is a steel sheet having a predetermined chemical composition and a steel microstructure that contains, in area ratio, 35% or more and 80% or less of polygonal ferrite and 5% or more and 25% or less of martensite, and that contains, in volume fraction, 8% or more of retained austenite, in which the polygonal ferrite, the martensite, and the retained austenite have a mean grain size of 6 ?m or less, 3 ?m or less, and 3 ?m 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.
    Type: Grant
    Filed: October 29, 2015
    Date of Patent: March 23, 2021
    Assignee: JFE STEEL CORPORATION
    Inventors: Yoshiyasu Kawasaki, Hiroshi Matsuda, Takeshi Yokota, Takako Yamashita, Kazuhiro Seto
  • Patent number: 10934600
    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 ?m or less. An inverse intensity ratio of ?-fiber to ?-fiber in the ferrite is 1.00 or more and an inverse intensity ratio of ?-fiber to ?-fiber in the martensite and the tempered martensite is 1.00 or more.
    Type: Grant
    Filed: January 27, 2016
    Date of Patent: March 2, 2021
    Assignee: JFE STEEL CORPORATION
    Inventors: Hidekazu Minami, Shinjiro Kaneko, Takeshi Yokota, Kazuhiro Seto
  • Publication number: 20210054487
    Abstract: Provided are a hot-rolled steel sheet for coiled tubing and a method for manufacturing the steel sheet. The steel sheet has a yield strength of 480 MPa or more, a tensile strength of 600 MPa or more, a yield-strength difference (AYS) of 100 MPa or more, where the yield-strength difference is defined as a difference in yield strength between before and after a prestrain-heat treatment performed for simulation of a tube-making process and a stress-relief annealing heat treatment which are currently implemented, and a yield strength of 620 MPa or more after the prestrain-heat treatment.
    Type: Application
    Filed: January 16, 2019
    Publication date: February 25, 2021
    Applicant: JFE Steel Corporation
    Inventors: Hideyuki Kimura, Shuji Kawamura, Ichiro Sugimoto, Makoto Asai, Takeshi Yokota
  • Publication number: 20210054477
    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 ?m 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.
    Type: Application
    Filed: January 22, 2019
    Publication date: February 25, 2021
    Applicant: JFE Steel Corporation
    Inventors: Yuka Miyamoto, Takashi Kobayashi, Yasuhiro Sakurai, Takeshi Yokota
  • Publication number: 20200392600
    Abstract: A high-carbon cold rolled steel sheet having a specified chemical composition, and a method for manufacturing the same. The method includes forming a hot rolled steel sheet, performing cooling at an average cooling rate of 30° C./s or more and 70° C./s or less through a temperature range of a finish rolling end temperature to 660° C., coiling a hot rolled steel sheet at a temperature of 500° C. or more and 660° C. or less, and, optionally, pickling the coiled hot rolled steel sheet, and then performing a first box-annealing of holding at an annealing temperature in a temperature range of 650 to 720° C., then performing cold rolling at a rolling reduction ratio of 20 to 50%, and then performing a second box-annealing of holding at an annealing temperature in a temperature range of 650 to 720° C.
    Type: Application
    Filed: February 20, 2019
    Publication date: December 17, 2020
    Applicant: JFE STEEL CORPORATION
    Inventors: Yuka MIYAMOTO, Yoichiro MATSUI, Shogo SATO, Takeshi YOKOTA