Patents by Inventor Yusuke HIRATSUKA

Yusuke HIRATSUKA 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: 11332817
    Abstract: A machine component includes a core made up of a steel for machine structural use, and a medium carbon-containing layer and a high carbon-containing layer formed of the steel for machine structural use, the medium carbon-containing layer covering the core, the high carbon-containing layer covering the medium carbon-containing layer and having a carbon concentration of 0.8-1.5%. The high carbon-containing layer is made up of a martensitic structure having carbides dispersed therein and a residual austenitic structure, wherein spheroidized carbides with an aspect ratio of 1.5 or less constitute 90% or more of a total number of the carbides, and the number of spheroidized carbides on prior austenite grain boundaries is 40% or less of the total number of the carbides.
    Type: Grant
    Filed: May 10, 2019
    Date of Patent: May 17, 2022
    Assignee: KOMATSU LTD.
    Inventors: Kensuke Sato, Koji Yamamoto, Yusuke Hiratsuka, Kazuya Hashimoto
  • Patent number: 11326220
    Abstract: A method for producing a machine component excellent in pitting resistance characteristics and toughness includes a carburizing step, performed on a steel material containing 0.13-0.30% C and 0.90-2.00% Cr in mass % and at least one of Si, Mn, Ni, Mo, Nb, V, Ti, B, Al, and N, balance Fe and unavoidable impurities; heating the material to 850-1030° C. to attain carbon concentration in a surface of 0.8-1.5%; cooling the material at an average rate of 5° C./sec or lower from a temperature higher than the Acm point of a surface layer to a cooling end temperature that is at least 50° C. lower than the A1 point to cause the surface layer to have a pearlite or bainite structure with dispersion; spheroidizing annealing at a temperature not higher than the Acm point at the surface layer; heating the material to not higher than the Acm point at the surface layer; and performing tempering.
    Type: Grant
    Filed: May 10, 2019
    Date of Patent: May 10, 2022
    Assignee: KOMATSU LTD.
    Inventors: Kensuke Sato, Koji Yamamoto, Yusuke Hiratsuka, Kazuya Hashimoto
  • Patent number: 11203803
    Abstract: A steel with high hardness and excellent toughness contains, in mass %, 0.55-1.10% C, 0.10-2.00% Si, 0.10-2.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-2.50% Cr, and 0.010-0.10% Al, with the balance consisting of Fe and unavoidable impurities. The structure of the steel after quenching is a dual phase structure of martensitic structure and spheroidized carbide. Spheroidized cementite particles with an aspect ratio of 1.5 or less constitute at least 90% of all cementite particles. The proportion of the number of spheroidized cementite particles on the prior austenite grain boundaries to a total number of cementite particles is 20% or less.
    Type: Grant
    Filed: September 16, 2016
    Date of Patent: December 21, 2021
    Assignees: OSAKA UNIVERSITY, KOMATSU LTD.
    Inventors: Yoritoshi Minamino, Takemori Takayama, Koji Yamamoto, Yusuke Hiratsuka
  • Patent number: 11162162
    Abstract: A steel with high hardness and excellent toughness contains, in mass %, 0.40-1.00% C, 0.10-2.00% Si, 0.10-1.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-3.20% Cr, 0.010-0.10% Al, and 0.15-0.50% V, and further contains at least one or two of 2.50% or less Ni and 1.00% or less Mo, with an amount of (C+V) being 0.60% or more in mass %, with the balance consisting of Fe and unavoidable impurities. The steel has a microstructure which is a martensitic structure with finely dispersed Fe-based ? carbides, with its prior austenite grain size being 20 ?m or less.
    Type: Grant
    Filed: August 8, 2018
    Date of Patent: November 2, 2021
    Assignees: OSAKA UNIVERSITY, KOMATSU LTD.
    Inventors: Yoritoshi Minamino, Koji Hagihara, Koji Yamamoto, Shohei Ikurumi, Yusuke Hiratsuka, Takeshi Fujimatsu, Toshiyuki Sugimoto
  • Publication number: 20210032737
    Abstract: A machine component includes a core made up of a steel for machine structural use, and a medium carbon-containing layer and a high carbon-containing layer formed of the steel for machine structural use, the medium carbon-containing layer covering the core, the high carbon-containing layer covering the medium carbon-containing layer and having a carbon concentration of 0.8-1.5%. The high carbon-containing layer is made up of a martensitic structure having carbides dispersed therein and a residual austenitic structure, wherein spheroidized carbides with an aspect ratio of 1.5 or less constitute 90% or more of a total number of the carbides, and the number of spheroidized carbides on prior austenite grain boundaries is 40% or less of the total number of the carbides.
    Type: Application
    Filed: May 10, 2019
    Publication date: February 4, 2021
    Applicant: KOMATSU LTD.
    Inventors: Kensuke SATO, Koji YAMAMOTO, Yusuke HIRATSUKA, Kazuya HASHIMOTO
  • Publication number: 20210032716
    Abstract: A method for producing a machine component excellent in pitting resistance characteristics and toughness includes a carburizing step, performed on a steel material containing 0.13-0.30% C and 0.90-2.00% Cr in mass % and at least one of Si, Mn, Ni, Mo, Nb, V, Ti, B, Al, and N, balance Fe and unavoidable impurities; heating the material to 850-1030° C. to attain carbon concentration in a surface of 0.8-1.5%; cooling the material at an average rate of 5° C./sec or lower from a temperature higher than the Acm point of a surface layer to a cooling end temperature that is at least 50° C. lower than the A1 point to cause the surface layer to have a pearlite or bainite structure with dispersion; spheroidizing annealing at a temperature not higher than the Acm point at the surface layer; heating the material to not higher than the Acm point at the surface layer; and performing tempering.
    Type: Application
    Filed: May 10, 2019
    Publication date: February 4, 2021
    Applicant: KOMATSU LTD.
    Inventors: Kensuke SATO, Koji YAMAMOTO, Yusuke HIRATSUKA, Kazuya HASHIMOTO
  • Publication number: 20200165710
    Abstract: A steel with high hardness and excellent toughness contains, in mass %, 0.55-1.10% C, 0.10-2.00% Si, 0.10-2.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-2.50% Cr, and 0.010-0.10% Al, with the balance consisting of Fe and unavoidable impurities. The structure of the steel after quenching is a dual phase structure of martensitic structure and spheroidized carbide. Spheroidized cementite particles with an aspect ratio of 1.5 or less constitute at least 90% of all cementite particles. The proportion of the number of spheroidized cementite particles on the prior austenite grain boundaries to a total number of cementite particles is 20% or less.
    Type: Application
    Filed: September 16, 2016
    Publication date: May 28, 2020
    Applicants: OSAKA UNIVERSITY, KOMATSU LTD.
    Inventors: Yoritoshi MINAMINO, Takemori TAKAYAMA, Koji YAMAMOTO, Yusuke HIRATSUKA
  • Publication number: 20200080180
    Abstract: A steel with high hardness and excellent toughness contains, in mass %, 0.40-1.00% C, 0.10-2.00% Si, 0.10-1.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-3.20% Cr, 0.010-0.10% Al, and 0.15-0.50% V, and further contains at least one or two of 2.50% or less Ni and 1.00% or less Mo, with an amount of (C+V) being 0.60% or more in mass %, with the balance consisting of Fe and unavoidable impurities. The steel has a microstructure which is a martensitic structure with finely dispersed Fe-based ? carbides, with its prior austenite grain size being 20 ?m or less.
    Type: Application
    Filed: August 8, 2018
    Publication date: March 12, 2020
    Applicants: OSAKA UNIVERSITY, KOMATSU LTD.
    Inventors: Yoritoshi MINAMINO, Koji HAGIHARA, Koji YAMAMOTO, Shohei IKURUMI, Yusuke HIRATSUKA, Takeshi FUJIMATSU, Toshiyuki SUGIMOTO