Patents by Inventor Yoichi Makimizu

Yoichi Makimizu 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: 20190242000
    Abstract: Provided is a method for manufacturing a high-strength galvanized steel sheet. Heating in a first half of oxidizing treatment is performed at a temperature of 400° C. to 750° C. in an atmosphere having a particular O2 concentration and a particular H2O concentration, and heating in a second half of the oxidizing treatment is performed at a temperature of 600° C. to 850° C. in an atmosphere having a particular O2 concentration and a particular H2O concentration. Subsequently, heating in a heating zone for reduction annealing is performed to a temperature of 650° C. to 900° C. at a particular heating rate in an atmosphere having a particular H2 concentration and a particular H2O concentration with the balance being N2 and inevitable impurities, and soaking in a soaking zone for the reduction annealing is performed in an atmosphere having a particular H2 concentration and a particular H2O concentration with the balance being N2 and inevitable impurities.
    Type: Application
    Filed: September 14, 2017
    Publication date: August 8, 2019
    Applicant: JFE Steel Corporation
    Inventors: Yoichi Makimizu, Gentaro Takeda, Hiroshi Hasegawa, Yoshimasa Himei, Yoshikazu Suzuki
  • Patent number: 10370737
    Abstract: A high-strength galvanized steel sheet and method for producing the same. The high-strength galvanized steel sheet including a specified chemical composition and a microstructure comprising, in terms of area fraction, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 15% or less, and other phases: 10% or less (including 0%), the other phases comprising a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%), the tempered martensite phase having an average grain size of 8 ?m or less, the ferrite phase having an average grain size of 5 ?m or less, and the retained austenite phase having a C content less than 0.7% by mass.
    Type: Grant
    Filed: November 24, 2015
    Date of Patent: August 6, 2019
    Assignee: JFE STEEL CORPORATION
    Inventors: Hiroshi Hasegawa, Hideyuki Kimura, Yoshimasa Funakawa, Yoichi Makimizu, Yoshitsugu Suzuki
  • Patent number: 10227672
    Abstract: A high-strength hot-dip galvanized steel sheet having a surface coated with a hot-dip galvanized coating, the steel sheet having a chemical composition comprising C: more than 0.10% and less than 0.18%, Si: 0.01 to 1.00%, Mn: 1.5 to 4.0%, P: 0.100% or less, S: 0.020% or less, Al: 0.010 to 0.500%, Cr: 0.010 to 2.000%, Nb: 0.005 to 0.100%, Ti: 0.005 to 0.100%, B: more than 0.0005% and 0.0030% or less, and Fe and incidental impurities, and a method for producing the same. The steel sheet has a microstructure including ferrite having an area fraction in the range of 0 to 10%, martensite having an area fraction in the range of 15 to 60%, tempered martensite having an area fraction in the range of 20 to 50%, and bainitic ferrite having an area fraction in the range of 20 to 50%.
    Type: Grant
    Filed: December 1, 2014
    Date of Patent: March 12, 2019
    Assignee: JFE STEEL CORPORATION
    Inventors: Hiroshi Hasegawa, Shinjiro Kaneko, Yoichi Makimizu, Yoshitsugu Suzuki
  • Publication number: 20190040511
    Abstract: A high-strength galvanized steel sheet having improved post-work impact resistance, a method for producing the high-strength galvanized steel sheet, and a high-strength member produced using the steel sheet. The high-strength galvanized steel sheet includes a steel sheet having a microstructure including ferrite and carbide-free bainite, martensite and carbide-containing bainite, and retained austenite, the total area fraction of ferrite and carbide-free bainite being 0% to 55%, the total area fraction of martensite and carbide-containing bainite being 45% to 100%, and the area fraction of retained austenite being 0% to 5%. Additionally, a galvanizing layer is disposed on the steel sheet. The density of gaps that cut across the entire thickness of the galvanizing layer in a cross section of the galvanizing layer, which is taken in the thickness direction so as to be perpendicular to the rolling direction, is 10 gaps/mm or more.
    Type: Application
    Filed: January 26, 2017
    Publication date: February 7, 2019
    Applicant: JFE STEEL CORPORATION
    Inventors: Hiroshi HASEGAWA, Yoshimasa FUNAKAWA, Hiromi YOSHITOMI, Yoichi MAKIMIZU, Yoshitsugu SUZUKI, Gentaro TAKEDA, Yoshikazu SUZUKI, Yoshimasa HIMEI
  • Publication number: 20190003006
    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: Application
    Filed: December 8, 2016
    Publication date: January 3, 2019
    Applicant: JFE Steel Corporation
    Inventors: Satoshi Maeda, Yoichi Makimizu, Yoshitsugu Suzuki, Katsumi Yamada, Yoshiyasu Kawasaki
  • Patent number: 10138530
    Abstract: A method for producing high-strength galvannealed steel sheets having excellent workability and fatigue resistance. The method comprises subjecting a steel sheet to an oxidation treatment, the oxidation treatment including heating the steel sheet in an upstream stage at a temperature in the range of 400° C. to 750° C. in an atmosphere having an O2 concentration of not less than 1000 ppm by volume and a H2O concentration of not less than 1000 ppm by volume and a downstream stage at a temperature in the range of 600° C. to 850° C. in an atmosphere having an O2 concentration of less than 1000 ppm by volume and a H2O concentration of not less than 1000 ppm by volume. The method further comprises subjecting the steel sheet to reducing annealing, hot-dip galvanizing treatment and alloying treatment.
    Type: Grant
    Filed: December 11, 2014
    Date of Patent: November 27, 2018
    Assignee: JFE STEEL CORPORATION
    Inventors: Yoichi Makimizu, Yoshitsugu Suzuki, Mai Aoyama, Hiroshi Hasegawa, Gentaro Takeda
  • Patent number: 10087500
    Abstract: There is provided a method for manufacturing a high-strength galvannealed steel sheet having excellent coating adhesiveness and corrosion resistance whose base material is a high-strength steel sheet containing Si and Mn. The method includes performing an oxidation treatment on a steel sheet including Si and Mn in a first zone having an atmosphere of an oxygen concentration in the range of more than 0 vol % and less than 1 vol %, thereafter performing an oxidation treatment in a second zone having an atmosphere of an oxygen concentration in the range of 1 vol % or more, thereafter performing reduction annealing and galvanizing, and further performing an alloying treatment by heating the galvanized steel sheet.
    Type: Grant
    Filed: May 19, 2014
    Date of Patent: October 2, 2018
    Assignee: JFE STEEL CORPORATION
    Inventors: Yoichi Makimizu, Yoshitsugu Suzuki, Yasunobu Nagataki
  • Publication number: 20180237896
    Abstract: A method includes: annealing a steel strip by conveying the steel strip through a heating zone, a soaking zone, and a cooling zone in this order inside an annealing furnace; and applying a hot-dip galvanized coating onto the steel strip discharged from the cooling zone. Reducing gas or non-oxidizing gas supplied into the soaking zone includes humidified gas and dry gas. While a width and a sheet passing speed of the steel strip passing through the soaking zone are constant, a variation of pressure in the annealing furnace is suppressed by adjusting a flow rate of the dry gas, and a variation range of an amount of moisture supplied into the soaking zone by the humidified gas is limited to 20% or less.
    Type: Application
    Filed: August 5, 2016
    Publication date: August 23, 2018
    Applicant: JFE STEEL CORPORATION
    Inventors: Gentaro TAKEDA, Hideyuki TAKAHASHI, Yoichi MAKIMIZU, Yoshikazu SUZUKI, Yoshimasa HIMEI
  • Publication number: 20180051356
    Abstract: A method of producing a galvannealed steel sheet whereby favorable coating appearance can be obtained with high coating adhesion even in the case of galvannealing a steel strip whose Si content is 0.2 mass % or more, and a decrease in tensile strength can be prevented by lowering the alloying temperature. Mixed gas of humidified gas and dry gas, and dry gas are supplied to a soaking zone in an annealing furnace. The mixed gas is timely supplied from a position of lower half of the soaking zone. The dry gas is timely supplied from near an upper hearth roll in the soaking zone, and furnace gas is timely discharged from a gas discharge port located higher than the upper hearth roll, to control a dew point in at least an uppermost part of the soaking zone to ?20° C. or more and 0° C. or less.
    Type: Application
    Filed: December 18, 2015
    Publication date: February 22, 2018
    Applicant: JFE STEEL CORPORATION
    Inventors: Gentaro TAKEDA, Masaru MIYAKE, Yoichi MAKIMIZU, Yoshitsugu SUZUKI
  • Publication number: 20180030564
    Abstract: A high-strength galvanized steel sheet and method for producing the same. The high-strength galvanized steel sheet including a specified chemical composition and a microstructure comprising, in terms of area fraction, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 15% or less, and other phases: 10% or less (including 0%), the other phases comprising a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%), the tempered martensite phase having an average grain size of 8 ?m or less, the ferrite phase having an average grain size of 5 ?m or less, and the retained austenite phase having a C content less than 0.7% by mass.
    Type: Application
    Filed: November 24, 2015
    Publication date: February 1, 2018
    Applicant: JFE STEEL CORPORATION
    Inventors: Hiroshi HASEGAWA, Hideyuki KIMURA, Yoshimasa FUNAKAWA, Yoichi MAKIMIZU, Yoshitsugu SUZUKI
  • Publication number: 20180002800
    Abstract: A high-strength galvanized steel sheet that includes a chemical composition containing, by mass %, C: 0.15% or more and 0.25% or less, Si: 0.50% or more and 2.5% or less, Mn: 2.3% or more and 4.0% or less, P: 0.100% or less, S: 0.02% or less, Al: 0.01% or more and 2.5% or less, and Fe and inevitable impurities. The steel sheet having a microstructure containing, by an area percentage basis, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 20% or less, and other phases: 10% or less (including 0%), the other phases containing a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%).
    Type: Application
    Filed: November 24, 2015
    Publication date: January 4, 2018
    Applicant: JFE STEEL CORPORATION
    Inventors: Hiroshi HASEGAWA, Hideyuki KIMURA, Yoshimasa FUNAKAWA, Yoichi MAKIMIZU, Yoshitsugu SUZUKI
  • Patent number: 9828663
    Abstract: Provided is a galvannealed steel sheet with excellent anti-powdering property when press forming is performed, without controlling the contents of chemical elements in steel which are effective for strengthening a steel sheet, such as Si and P, to be low in order to achieve required material properties and without increasing cost due to, for example, processes being complicated. A galvannealed steel sheet with excellent anti-powdering property has a coated layer taking in grains of a base steel sheet such that the grains constitute 2.0% or more and 15.0% or less of the coated layer in terms of cross section area ratio.
    Type: Grant
    Filed: June 18, 2013
    Date of Patent: November 28, 2017
    Assignee: JFE Steel Corporation
    Inventors: Yoichi Makimizu, Yoshitsugu Suzuki, Hideki Nagano, Yasunobu Nagataki
  • Publication number: 20170253943
    Abstract: A method for producing high-strength galvanized steel sheets having excellent coating adhesion, workability and appearance. The method comprises hot rolling a slab comprising, by mass %, C: 0.05 to 0.30%, Si: 0.1 to 2.0% and Mn: 1.0 to 4.0%, then coiling the steel sheet into a coil at a specific temperature TC, and pickling the steel sheet, cold rolling the hot-rolled steel sheet resulting from the hot rolling, annealing the cold-rolled steel sheet resulting from the cold rolling under specific conditions, and galvanizing the annealed sheet resulting from the annealing in a galvanizing bath containing 0.12 to 0.22 mass % Al.
    Type: Application
    Filed: August 20, 2015
    Publication date: September 7, 2017
    Applicant: JFE STEEL CORPORATION
    Inventors: Yoichi MAKIMIZU, Yoshitsugu SUZUKI, Hideyuki TAKAHASHI, Gentaro TAKEDA, Koichiro FUJITA
  • Patent number: 9677163
    Abstract: A high strength galvanized steel sheet excellent in coating adhesiveness is made from a base material that is a high strength steel sheet containing Si, Mn, and Cr. A method includes performing an oxidation treatment on steel containing Si, Mn, and Cr in an oxidation furnace under the condition that a selected exit temperature T, reduction annealing and a galvanizing treatment, or optionally, further an alloying treatment under conditions that heating is performed at a temperature of 460° C. or higher and 600° C. or lower for an alloying treatment time of 10 seconds or more and 60 seconds or less.
    Type: Grant
    Filed: June 6, 2012
    Date of Patent: June 13, 2017
    Assignee: JFE Steel Corporation
    Inventors: Yoichi Makimizu, Yoshitsugu Suzuki, Hideki Nagano, Shinjiro Kaneko
  • Publication number: 20170130296
    Abstract: A method of producing a galvannealed steel sheet includes: annealing a steel strip by conveying the steel strip through a heating zone including a direct fired furnace, a soaking zone, and a cooling zone in this order in an annealing furnace; hot-dip galvanizing the steel strip discharged from the cooling zone; and heat-alloying a galvanized coating formed on the steel strip. Mixed gas of humidified gas and dry gas is supplied into the soaking zone from at least one gas supply port located in a region of lower ½ of the soaking zone in a height direction so that a dew point measured in a region of upper ? of the soaking zone in the height direction and a dew point measured in a region of lower ? of the soaking zone in the height direction are both ?20° C. or more and 0° C. or less.
    Type: Application
    Filed: June 5, 2015
    Publication date: May 11, 2017
    Applicant: JFE STEEL CORPORATION
    Inventors: Gentaro TAKEDA, Masaru MIYAKE, Yoichi MAKIMIZU, Yoshitsugu SUZUKI, Yoshikazu SUZUKI
  • Publication number: 20170037488
    Abstract: A high-strength hot-dip galvanized steel sheet having a surface coated with a hot-dip galvanized coating, the steel sheet having a chemical composition comprising C: more than 0.10% and less than 0.18%, Si: 0.01 to 1.00%, Mn: 1.5 to 4.0%, P: 0.100% or less, S: 0.020% or less, Al: 0.010 to 0.500%, Cr: 0.010 to 2.000%, Nb: 0.005 to 0.100%, Ti: 0.005 to 0.100%, B: more than 0.0005% and 0.0030% or less, and Fe and incidental impurities, and a method for producing the same. The steel sheet has a microstructure including ferrite having an area fraction in the range of 0 to 10%, martensite having an area fraction in the range of 15 to 60%, tempered martensite having an area fraction in the range of 20 to 50%, and bainitic ferrite having an area fraction in the range of 20 to 50%.
    Type: Application
    Filed: December 1, 2014
    Publication date: February 9, 2017
    Applicant: JFE STEEL CORPORATION
    Inventors: Hiroshi HASEGAWA, Shinjiro KANEKO, Yoichi MAKIMIZU, Yoshitsugu SUZUKI
  • Publication number: 20160363372
    Abstract: Provided are a method for controlling a dew point in a reducing furnace and a reducing furnace in which, even in the case of galvanizing Si-added steel, coating adhesion can be secured, alloying treatment can be performed without increasing the alloying temperature excessively, and it is possible to obtain a hot-dip galvanized steel sheet having an excellent coating appearance. When a steel sheet is subjected to annealing and hot-dip galvanizing treatment using continuous hot-dip galvanizing equipment including at least a radiant tube-type reducing furnace, a mixed gas of a dry gas and a humidified gas by a humidifying device having a water vapor permeable membrane is used as a gas to be supplied into the reducing furnace. The mixed gas is supplied into the reducing furnace, thereby controlling the dew point in the reducing furnace.
    Type: Application
    Filed: February 18, 2015
    Publication date: December 15, 2016
    Applicant: JFE STEEL CORPORATION
    Inventors: Gentaro Takeda, Hideyuki Takahashi, Masaru Miyake, Yoichi Makimizu, Yoshitsugu Suzuki
  • Publication number: 20160319385
    Abstract: Provided are a high-strength galvanized steel sheet which can preferably be used as a material for automobile parts and a method for manufacturing the steel sheet. The steel sheet has a C content of 0.15% or less, in which an area ratio of ferrite is 10% or less, an area ratio of bainitic ferrite is 2% or more and 30% or less, an area ratio of martensite is 60% or more and 98% or less, an area ratio of retained austenite is less than 2%, an average grain diameter of martensite adjacent to bainite is 15 ?m or less, a proportion of massive martensite adjacent only to bainite to the whole metallographic structure is 10% or less, and a value (?Hv) calculated by subtracting the Vickers hardness at a position located at 20 ?m from the surface of the steel sheet from the Vickers hardness at a position located at 100 ?m from the surface of the steel sheet is 30 or more.
    Type: Application
    Filed: December 16, 2014
    Publication date: November 3, 2016
    Applicant: JFE STEEL CORPORATION
    Inventors: Hiroshi Hasegawa, Shinjiro Kaneko, Yoichi Makimizu, Yoshitsugu Suzuki
  • Publication number: 20160312329
    Abstract: Provided are a high-strength steel sheet, which is suitable as a material of automotive parts, and a method for producing the high-strength steel sheet. In the high-strength steel sheet, the C content is 0.15% or less, the area ratio of ferrite is 8% to 45%, the area ratio of martensite is 55% to 85%, the proportion of martensite grains adjacent to only ferrite grains in the entire microstructure is 15% or less, the average crystal grain sizes of ferrite and martensite are each 10 ?m or less, and the area ratio of ferrite grains having a size of 10 ?m or more to all the ferrite grains included in a portion of the steel sheet which extends from 20 to 100 ?m below the surface thereof is less than 5%.
    Type: Application
    Filed: November 27, 2014
    Publication date: October 27, 2016
    Applicant: JFE STEEL CORPORATION
    Inventors: Hiroshi Hasegawa, Shinjiro Kaneko, Yoichi Makimizu, Yoshitsugu Suzuki
  • Publication number: 20160304982
    Abstract: A method for producing high-strength galvannealed steel sheets having excellent workability and fatigue resistance. The method comprises subjecting a steel sheet to an oxidation treatment, the oxidation treatment including heating the steel sheet in an upstream stage at a temperature in the range of 400° C. to 750° C. in an atmosphere having an O2 concentration of not less than 1000 ppm by volume and a H2O concentration of not less than 1000 ppm by volume and a downstream stage at a temperature in the range of 600° C. to 850° C. in an atmosphere having an O2 concentration of less than 1000 ppm by volume and a H2O concentration of not less than 1000 ppm by volume. The method further comprises subjecting the steel sheet to reducing annealing, hot-dip galvanizing treatment and alloying treatment.
    Type: Application
    Filed: December 11, 2014
    Publication date: October 20, 2016
    Applicant: JFE STEEL CORPORATION
    Inventors: Yoichi MAKIMIZU, Yoshitsugu SUZUKI, Mai AOYAMA, Hiroshi HASEGAWA, Gentaro TAKEDA