Patents by Inventor Yoshiyasu Kawasaki

Yoshiyasu Kawasaki 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).

  • Publication number: 20220364196
    Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, tempered martensite: 3.0% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 ?m or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.
    Type: Application
    Filed: October 8, 2020
    Publication date: November 17, 2022
    Applicant: JFE Steel Corporation
    Inventors: Kazuki Endoh, Yoshiyasu Kawasaki, Yuki Toji
  • Patent number: 11447840
    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 ?m or less, 2.0 ?m or less and 2.0 ?m 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.
    Type: Grant
    Filed: November 15, 2017
    Date of Patent: September 20, 2022
    Assignee: JFE STEEL CORPORATION
    Inventors: Yoshiyasu Kawasaki, Takako Yamashita, Masayasu Ueno, Yuki Toji, Takashi Kobayashi, Yoshimasa Funakawa
  • Patent number: 11447841
    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 ?m or less, 3.0 ?m or less and 3.0 ?m 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.
    Type: Grant
    Filed: November 15, 2017
    Date of Patent: September 20, 2022
    Assignee: JFE STEEL CORPORATION
    Inventors: Yoshiyasu Kawasaki, Takako Yamashita, Masayasu Ueno, Yuki Toji, Takashi Kobayashi, Yoshimasa Funakawa
  • Publication number: 20220267876
    Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, martensite: 5% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 ?m or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.
    Type: Application
    Filed: October 8, 2020
    Publication date: August 25, 2022
    Applicant: JFE Steel Corporation
    Inventors: Kazuki Endoh, Yoshiyasu Kawasaki, Yuki Toji
  • 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: 11384407
    Abstract: Provided are a high-strength galvannealed steel sheet, and a manufacturing method therefor. The manufacturing method is for a high-strength galvannealed steel sheet which includes a zinc coated layer with a coating weight of 20 to 120 g/m2 per side on a surface of a steel sheet having a chemical composition containing, in mass %, C: 0.03 to 0.35%, Si: 0.01 to 1.00%, Mn: 3.6 to 8.0%, Al: 0.001 to 1.00%, P: 0.100% or less, and S: 0.010% or less, with the balance being Fe and inevitable impurities. The method includes: setting a cold rolling reduction ratio to 20% or more and 35% or less when cold rolling is performed on the steel sheet, and setting a maximum steel sheet temperature to be reached in an annealing furnace to 600° C. or higher and 700° C. or lower when annealing is further performed on the steel sheet.
    Type: Grant
    Filed: June 5, 2017
    Date of Patent: July 12, 2022
    Assignee: JFE STEEL CORPORATION
    Inventors: Satoshi Maeda, Yoichi Makimizu, Yoshitsugu Suzuki, Yoshiyasu Kawasaki
  • Publication number: 20220186334
    Abstract: An object is to provide a high strength steel sheet having a TS (tensile strength) of 980 MPa or more and excellent formability and a method for manufacturing the steel sheet. A high strength steel sheet which is excellent in terms of formability, which is manufactured under optimized manufacturing conditions, and which has a predetermined chemical composition and a steel microstructure including, in terms of area fraction, 35% or more and 80% or less of ferrite, 5% or more and 35% or less of as-quenched martensite, 0.1% or more and less than 3.0% of tempered martensite, and 8% or more of retained austenite, in which the average grain size of the ferrite is 6 ?m or less, in which the average grain size of the retained austenite is 3 ?m or less, in which a value calculated by dividing the average Mn content in the retained austenite by the average Mn content in the ferrite is 1.
    Type: Application
    Filed: December 10, 2019
    Publication date: June 16, 2022
    Applicant: JFE STEEL CORPORATION
    Inventors: Kazuki ENDOH, Yoshiyasu KAWASAKI, Yuki TOJI, Yoshimasa FUNAKAWA, Mai AOYAMA
  • Publication number: 20220017986
    Abstract: A method for producing a high-strength hot-dip galvannealed steel sheet, in which a high-strength steel sheet is used as a base material, includes a rolling step (x) of rolling a hot-dip galvannealed steel sheet with a coating layer having an Fe concentration of 8% to 17% by mass, and a heat treatment step (y) of heating the coated steel sheet which has been subjected to the rolling step (x) under the conditions satisfying the following formulae (1) and (2): (273+T)×(20+2×log10(t))?8000??(1) 40?T?160??(2) where T: heating temperature (° C.) of the coated steel sheet, and t: holding time (hr) at the heating temperature T.
    Type: Application
    Filed: October 1, 2021
    Publication date: January 20, 2022
    Applicant: JFE Steel Corporation
    Inventors: Satoshi Maeda, Yoshiyasu Kawasaki, Yusuke Fushiwaki, Mai Aoyama
  • Publication number: 20220018747
    Abstract: A collision performance evaluation test with few variations in test results with high accuracy in which a complicated phenomenon that actually occurs can be reproduced in a simple manner by considering the history of deformation in both the press forming and a collision. A collision performance evaluation test method for a metal sheet material for an automobile body is characterized in that a press working apparatus first forms a flat test specimen made of a metal sheet material to be tested into a V shape by primary bending, a bending test apparatus then deforms, by secondary bending, the test specimen formed by the primary bending in a direction intersecting with the primary bending direction, and a bending load and a bending stroke for the test specimen during the secondary bending deformation are recorded and evaluated.
    Type: Application
    Filed: December 16, 2019
    Publication date: January 20, 2022
    Applicant: JFE STEEL CORPORATION
    Inventors: Kentaro SATO, Takayuki FUTATSUKA, Tomohiro SAKAIDANI, Shinsuke KOMINE, Yoshiyasu KAWASAKI
  • Patent number: 11136641
    Abstract: High-strength galvannealed steel sheet including any of a) an oxide containing Fe and Mn, b) an oxide containing Fe and Mn and an Fe oxide, c) an oxide containing Fe and Mn and a Mn oxide, d) an oxide containing Fe and Mn, an Fe oxide, and a Mn oxide, and e) an Fe oxide and a Mn oxide is present in a zinc coated layer. The total amount of oxide is 0.01 to 0.100 g/m2; the ratio by mass % of Mn to Fe, e.g., Mn/Fe, contained in the oxide is 0.10 to 10.00; an oxide of at least one selected from Fe and Mn is present in an amount of 60% or more; and an oxide of at least one selected from Fe and Mn is present in a surface layer portion of a steel sheet in an amount of 0.040 g/m2 or less (not including zero).
    Type: Grant
    Filed: December 8, 2016
    Date of Patent: October 5, 2021
    Assignee: JFE STEEL CORPORATION
    Inventors: Satoshi Maeda, Yoichi Makimizu, Yoshitsugu Suzuki, Katsumi Yamada, Yoshiyasu Kawasaki
  • Patent number: 11098392
    Abstract: A hot rolled steel sheet having a chemical composition containing, by mass %, C: 0.04% or more and 0.20% or less, Si: 0.7% or more and 2.3% or less, Mn: 0.8% or more and 2.8% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.1% or less, N: 0.008% or less, and the balance being Fe and inevitable impurities. The microstructure of the hot rolled steel sheet includes ferrite and pearlites, in which the area ratio of the ferrite is 75% or more and less than 95%, the mean grain size of the ferrite is 5 ?m or more and 25 ?m or less, the area ratio of pearlite is 5% or more and less than 25%, the mean grain size of pearlite is 2.0 ?m or more, and the mean free path of pearlite is 5 ?m or more.
    Type: Grant
    Filed: November 28, 2018
    Date of Patent: August 24, 2021
    Assignee: JFE Steel Corporation
    Inventors: Yoshiyasu Kawasaki, Shinjiro Kaneko, Yasunobu Nagataki
  • Publication number: 20210115541
    Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80%, martensite being 5% to 35%, and tempered martensite being 0% to 5% in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 ?m or less; and the retained austenite being 3 ?m or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.
    Type: Application
    Filed: March 20, 2019
    Publication date: April 22, 2021
    Applicant: JFE STEEL CORPORATION
    Inventors: Kazuki ENDO, Yoshiyasu KAWASAKI, Yuki TOJI, Yoshimasa FUNAKAWA, Mai AOYAMA
  • Publication number: 20210108282
    Abstract: A high-strength steel includes a steel structure with: in area fraction, 60.0% to less than 90.0% of ferrite, 0% to less than 5.0% of unrecrystallized ferrite, 2.0% to 25.0% of martensite, 0% to 5.0% of carbide, and 0% to 3.0% of bainite; in volume fraction, more than 7.0% of retained austenite; in a cross-sectional view of 100 ?m×100 ?m, a value obtained by dividing number of retained austenite that are not adjacent to retained austenite whose crystal orientations are different by a total number of retained austenite being less than 0.80, an average crystal grain size of the ferrite being 6.0 ?m or less, an average crystal grain size of the retained austenite being 3.0 ?m or less, and a value obtained by dividing, by mass %, an average content of Mn in the retained austenite by an average content of Mn in steel being 1.50 or more.
    Type: Application
    Filed: March 20, 2019
    Publication date: April 15, 2021
    Applicant: JFE STEEL CORPORATION
    Inventors: Yoshiyasu KAWASAKI, Kazuki ENDO, Yuki TOJI, Yoshimasa FUNAKAWA, Satoshi MAEDA, Mai AOYAMA
  • 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: 10940556
    Abstract: Provided is an automotive member, or particularly, a steel sheet having a tensile strength exceeding 900 MPa. The automotive member has a resistance weld for fixing two or more steel sheets containing a predetermined composition, in which a maximum hardness (HVBM) in a heat-affected zone of the resistance weld is at least 1.1 times hardness (HVW) of a nugget in the resistance weld formed in a softest steel sheet of a sheet set during resistance welding, and furthermore, an average grain size of a steel sheet structure of the heat-affected zone within 2 mm in a direction at a right angle to a sheet thickness from an end part of the nugget of the high-strength steel sheet is 3 ?m or less, and a minimum hardness (HVmin) in the heat-affected zone is at least 90% of hardness (HV?) of the high-strength steel sheet before the resistance welding.
    Type: Grant
    Filed: August 21, 2017
    Date of Patent: March 9, 2021
    Assignee: JFE Steel Corporation
    Inventors: Katsutoshi Takashima, Hiroshi Matsuda, Rinsei Ikeda, Yoshiyasu Kawasaki
  • Publication number: 20210010100
    Abstract: A method for producing a high-strength hot-dip galvannealed steel sheet, in which a high-strength steel sheet is used as a base material, includes a rolling step (x) of rolling a hot-dip galvannealed steel sheet with a coating layer having an Fe concentration of 8% to 17% by mass, and a heat treatment step (y) of heating the coated steel sheet which has been subjected to the rolling step (x) under the conditions satisfying the following formulae (1) and (2): (273+T)×(20+2×log10(t))?8000 ??(1) 40?T?160 ??(2) where T: heating temperature (° C.) of the coated steel sheet, and t: holding time (hr) at the heating temperature T.
    Type: Application
    Filed: March 26, 2019
    Publication date: January 14, 2021
    Applicant: JFE Steel Corporation
    Inventors: Satoshi Maeda, Yoshiyasu Kawasaki, Yusuke Fushiwaki, Mai Aoyama
  • Publication number: 20210010101
    Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80% and tempered martensite being greater than 5% and 20% or less in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 ?m or less; and the retained austenite being 3 ?m or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.
    Type: Application
    Filed: March 20, 2019
    Publication date: January 14, 2021
    Applicant: JFE STEEL CORPORATION
    Inventors: Kazuki ENDO, Yoshiyasu KAWASAKI, Yuki TOJI, Yoshimasa FUNAKAWA, Mai AOYAMA
  • Patent number: 10858717
    Abstract: A high strength steel sheet having excellent surface quality and formability with a tensile strength of 980 MPa or more and a TS-El balance of 30000 MPa % or more is provided. A high strength steel sheet comprises: a chemical composition containing C: 0.08% to 0.30%, Si: 2.0% or less, Mn: more than 3.0% and 10.0% or less, P: 0.05% or less, S: 0.01% or less, Al: 1.5% or less, Ti: 0.010% to 0.300%, and N: 0.0020% to 0.0100% in a range satisfying 1.1?(Ti+Mn1/2/400)/(0.01+5N)?6.0; and a microstructure including a retained austenite phase and a ferrite phase, wherein a ratio ?Mn/?Mn of an average Mn concentration (?Mn) of the retained austenite phase to an average Mn concentration (?Mn) of the ferrite phase is 1.5 or more.
    Type: Grant
    Filed: August 10, 2016
    Date of Patent: December 8, 2020
    Assignee: JFE STEEL CORPORATION
    Inventors: Kenji Tsuzumi, Yoshiyasu Kawasaki, Yuji Miki
  • Patent number: 10837074
    Abstract: A method for manufacturing a high strength galvanized steel sheet and a high strength galvanized steel sheet are provided. A base steel sheet having a chemical composition comprising C: 0.03% to 0.35%, Si: 0.01% to 0.50%, Mn: 3.6% to 8.0%, Al: 0.001% to 1.000%, P?0.10%, S?0.010%, and the balance comprising Fe and incidental impurities, on a percent by mass basis, is subjected to annealing and galvanization treatment, wherein the maximum steel sheet temperature in an annealing furnace is 600° C. or higher and 700° C. or lower, the steel sheet transit time in a temperature region of the maximum steel sheet temperature of 600° C. or higher and 700° C. or lower is specified to be 30 seconds or more and 10 minutes or less, and the dew point in an atmosphere is specified to be ?45° C. or lower.
    Type: Grant
    Filed: March 7, 2013
    Date of Patent: November 17, 2020
    Assignee: JFE STEEL CORPORATION
    Inventors: Yusuke Fushiwaki, Yoshiyasu Kawasaki, Yasunobu Nagataki
  • Publication number: 20200308664
    Abstract: Provided are a high-strength galvannealed steel sheet, and a manufacturing method therefor. The manufacturing method is for a high-strength galvannealed steel sheet which includes a zinc coated layer with a coating weight of 20 to 120 g/m2 per side on a surface of a steel sheet having a chemical composition containing, in mass %, C: 0.03 to 0.35%, Si: 0.01 to 1.00%, Mn: 3.6 to 8.0%, Al: 0.001 to 1.00%, P: 0.100% or less, and S: 0.010% or less, with the balance being Fe and inevitable impurities. The method includes: setting a cold rolling reduction ratio to 20% or more and 35% or less when cold rolling is performed on the steel sheet, and setting a maximum steel sheet temperature to be reached in an annealing furnace to 600° C. or higher and 700° C. or lower when annealing is further performed on the steel sheet.
    Type: Application
    Filed: June 5, 2017
    Publication date: October 1, 2020
    Applicant: JFE Steel Corporation
    Inventors: Satoshi Maeda, Yoichi Makimizu, Yoshitsugu Suzuki, Yoshiyasu Kawasaki