Patents by Inventor Kunikazu Tomita

Kunikazu Tomita 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: 11174543
    Abstract: A case hardening steel suitable as raw material for producing a mechanical structural part having high rotating bending fatigue strength and pitting fatigue strength at relatively low cost and a method of producing the case hardening steel are provided. A case hardening steel comprises a chemical composition containing, in mass %, C, Si, Mn, P, S, Cr, Mo, Al, N, and O in a predetermined relationship, with a balance being Fe and inevitable impurities, wherein ?I?80 (where I denotes an area (?m2) of an oxide-based inclusion located in a fish eye central portion at a fracture surface after subjecting the case hardening steel to carburizing-quenching and tempering and then performing a rotating bending fatigue test).
    Type: Grant
    Filed: May 31, 2017
    Date of Patent: November 16, 2021
    Assignee: JFE STEEL CORPORATION
    Inventors: Keisuke Ando, Takashi Iwamoto, Kunikazu Tomita, Kazukuni Hase, Kimihiro Nishimura
  • Publication number: 20210102283
    Abstract: A component comprising a core part and a surface layer is provided. The core part contains C: 0.01%? and <0.20%, Si: ?1.0%, Mn: 1.5%? and ?3.0%, P: 0.02% or less, S: ?0.06%, Cr: 0.30%? and ?3.0%, Mo: 0.005% ? and ?0.40%, V: 0.02% ? and ?0.5%, Nb: 0.003% ? and ?0.20%, Al: 0.010%? and ?2.0%, Ti: 0.005%< and <0.025%, N: <0.0200%, Sb: 0.0005% ? and ?0.02%, and the balance consisting of Fe and incidental impurities; and a steel microstructure that contains bainite phase in an area ratio of more than 50%. The surface layer has high nitrogen and carbon contents relative to the chemical composition of the core part.
    Type: Application
    Filed: December 1, 2020
    Publication date: April 8, 2021
    Applicant: JFE STEEL CORPORATION
    Inventors: Masayuki KASAI, Takashi IWAMOTO, Kunikazu TOMITA
  • Publication number: 20190352762
    Abstract: A case hardening steel suitable as raw material for producing a mechanical structural part having high rotating bending fatigue strength and pitting fatigue strength at relatively low cost and a method of producing the case hardening steel are provided. A case hardening steel comprises a chemical composition containing, in mass %, C, Si, Mn, P, S, Cr, Mo, Al, N, and O in a predetermined relationship, with a balance being Fe and inevitable impurities, wherein ?I?80 (where I denotes an area (?m2) of an oxide-based inclusion located in a fish eye central portion at a fracture surface after subjecting the case hardening steel to carburizing-quenching and tempering and then performing a rotating bending fatigue test).
    Type: Application
    Filed: May 31, 2017
    Publication date: November 21, 2019
    Applicants: JFE STEEL CORPORATION, JFE STEEL CORPORATION
    Inventors: Keisuke ANDO, Takashi IWAMOTO, Kunikazu TOMITA, Kazukuni HASE, Kimihiro NISHIMURA
  • Patent number: 10125416
    Abstract: The present invention provides a steel for nitrocarburizing having excellent mechanical workability before nitrocarburizing, and showing excellent fatigue properties after nitrocarburizing, which is suitable for applying in mechanical structural components for automobiles etc. prepared by adjusting the composition so that it contains in mass %, C: 0.01% or more and less than 0.10%, Si: 1.0% or less, Mn: 0.5% to 3.0%, P: 0.02% or less, S: 0.06% or less, Cr: 0.3% to 3.0%, Mo: 0.005% to 0.4%, V: 0.02% to 0.5%, Nb: 0.003% to 0.15%, Al: 0.005% to 0.2%, and Sb: 0.0005% to 0.02%, and the balance including Fe and incidental impurities, and setting the area ratio of bainite phase to the whole microstructure to more than 50%.
    Type: Grant
    Filed: July 22, 2013
    Date of Patent: November 13, 2018
    Assignees: JFE STEEL CORPORATION, JFE BARS AND SHAPES
    Inventors: Yasuhiro Omori, Kiyoshi Uwai, Shinji Mitao, Takashi Iwamoto, Keisuke Ando, Kunikazu Tomita
  • Publication number: 20180105919
    Abstract: The steel for nitrocarburizing has a chemical composition that contains C: 0.01% or more and less than 0.20%, Si: 1.0% or less, Mn: 1.5% or more and 3.0% or less, P: 0.02% or less, S: 0.06% or less, Cr: 0.30% or more and 3.0% or less, Mo: 0.005% or more and 0.40% or less, V: 0.02% or more and 0.5% or less, Nb: 0.003% or more and 0.20% or less, Al: 0.010% or more and 2.0% or less, Ti: more than 0.005% and less than 0.025%, N: 0.0200% or less, Sb: 0.0005% or more and 0.02% or less, and the balance consisting of Fe and incidental impurities; and a steel microstructure that contains bainite phase in an area ratio of more than 50%.
    Type: Application
    Filed: March 24, 2016
    Publication date: April 19, 2018
    Applicant: JFE STEEL CORPORATION
    Inventors: Masayuki KASAI, Takashi IWAMOTO, Kunikazu TOMITA
  • Publication number: 20180030563
    Abstract: A case hardening steel having excellent fatigue resistance is provided at relatively low production cost. A case hardening steel has a chemical composition containing C: 0.10% to 0.30%, Si: 0.10% to 1.20%, Mn: 0.30% to 1.50%, S: 0.010% to 0.030%, Cr: 0.10% to 1.00%, B: 0.0005% to 0.0050%, Sb: 0.005% to 0.020%, and N: 0.0150% or less in a predetermined range, and further containing Al: 0.010%?Al?0.120% in the case where B?(10.8/14)N ?0.0003%, and 27/14[(N?(14/10.8)B+0.030]?Al?0.120% in the case where B?(10.8/14)N<0.0003%.
    Type: Application
    Filed: January 25, 2016
    Publication date: February 1, 2018
    Applicant: JFE STEEL CORPORATION
    Inventors: Keisuke ANDO, Kazuaki FUKUOKA, Kunikazu TOMITA
  • Publication number: 20170130288
    Abstract: A steel has a predetermined chemical composition with a balance being Fe and incidental impurities, wherein a sum of Cu content and Ni content is 0.15 mass % or more, and a crystal grain size after forming into a stabilizer shape and quenching is in a range of 7.5 to 10.5 in prior austenite crystal grain size number. Thus, a highly durable stabilizer steel that has a tensile strength of 1200 MPa or more and excellent normal-temperature and low-temperature toughness and is used in an environmentally friendly manufacturing process at lower cost can be realized.
    Type: Application
    Filed: March 23, 2015
    Publication date: May 11, 2017
    Applicants: JFE Bars & Shapes Corporation, NHK SPRING CO., LTD.
    Inventors: Kazuaki FUKUOKA, Kunikazu TOMITA, Akira TANGE, Kiyoshi KURIMOTO, Yurika GOTO
  • Publication number: 20170021691
    Abstract: A steel, having a high corrosion resistance and low-temperature toughness, for a vehicle suspension spring part, the steel includes 0.21 to 0.35% by mass of C, more than 0.6% by mass but 1.5% by mass or less of Si, 1 to 3% by mass of Mn, 0.3 to 0.8% by mass of Cr, 0.005 to 0.080% by mass of sol. Al, 0.005 to 0.060% by mass of Ti, 0.005 to 0.060% by mass of Nb, not more than 150 ppm of N, not more than 0.035% by mass of P, not more than 0.035% by mass of S, 0.01 to 1.00% by mass of Cu, and 0.01 to 1.00% by mass of Ni, the balance being Fe and unavoidable impurities, with Ti+Nb?0.07% by mass, wherein crystal grains of the steel after hardening have a prior austenite grain size number of 7.5 to 10.5, and the steel having a tensile strength of not less than 1,300 MPa.
    Type: Application
    Filed: September 26, 2016
    Publication date: January 26, 2017
    Applicants: NHK SPRING CO., LTD., JFE BARS & SHAPES CORPORATION
    Inventors: Akira TANGE, Kiyoshi KURIMOTO, Yurika GOTO, Katsuhiko KIKUCHI, Kunikazu TOMITA, Kazuaki FUKUOKA, Kazuaki HATTORI
  • Publication number: 20150159261
    Abstract: The present invention provides a steel for nitrocarburizing having excellent mechanical workability before nitrocarburizing, and showing excellent fatigue properties after nitrocarburizing, which is suitable for applying in mechanical structural components for automobiles etc. prepared by adjusting the composition so that it contains in mass %, C: 0.01% or more and less than 0.10%, Si: 1.0% or less, Mn: 0.5% to 3.0%, P: 0.02% or less, S: 0.06% or less, Cr: 0.3% to 3.0%, Mo: 0.005% to 0.4%, V: 0.02% to 0.5%, Nb: 0.003% to 0.15%, Al: 0.005% to 0.2%, and Sb: 0.0005% to 0.02%, and the balance including Fe and incidental impurities, and setting the area ratio of bainite phase to the whole microstructure to more than 50%.
    Type: Application
    Filed: July 22, 2013
    Publication date: June 11, 2015
    Inventors: Yasuhiro Omori, Kiyoshi Uwai, Shinji Mitao, Takashi Iwamoto, Keisuke Ando, Kunikazu Tomita
  • Publication number: 20150020926
    Abstract: According to the present invention, it is possible to obtain steel for nitrocarburizing having a predetermined chemical composition, a bainite area ratio exceeding 50% and excellent machinability by cutting before nitrocarburizing, and having strength and toughness equivalent to conventional steel, such as SCr420 carburized steel material, and excellent fatigue properties after nitrocarburizing.
    Type: Application
    Filed: February 15, 2013
    Publication date: January 22, 2015
    Inventors: Takashi Iwamoto, Keisuke Ando, Kunikazu Tomita, Yasuhiro Omori, Kiyoshi Uwai, Shinji Mitao
  • Patent number: 8691141
    Abstract: A low carbon resulfurized free cutting steel consisting of 0.04 to 0.15% of C, more than 0.10% and 0.70% or less of Si, 0.85 to 1.50% of Mn, 0.040 to 0.120% of P, 0.250% or more and less than 0.400% of S, less than 0.005% of Al, more than 0.0020% and 0.0120% or less of O, and more than 0.0070% and 0.0150% or less of N, all by mass percentage, and the balance of Fe and inevitable impurities, and satisfying a formula (1) and a formula (2), as follows: 0.15%?Si %+2×P %?(5×Al %+10×O %+3×N %)?0.75%??(1), and ([Mn %]5)/15<S %<([Mn %]5)/2??(2).
    Type: Grant
    Filed: December 9, 2009
    Date of Patent: April 8, 2014
    Assignee: JFE Bars and Shapes Corporation
    Inventors: Toshiyuki Murakami, Kunikazu Tomita, Tetsuo Shiraga
  • Publication number: 20140060709
    Abstract: Steel, excellent in corrosion resistance and low-temperature toughness, for a vehicle suspension spring part, includes 0.15 to 0.35% by mass of C, more than 0.6% by mass but 1.5% by mass or less of Si, 1 to 3% by mass of Mn, 0.3 to 0.8% by mass of Cr, 0.005 to 0.080% by mass of sol. Al, 0.005 to 0.060% by mass of Ti, 0.005 to 0.060% by mass of Nb, not more than 150 ppm of N, not more than 0.035% by mass of P, not more than 0.035% by mass of S, 0.01 to 1.00% by mass of Cu, and 0.01 to 1.00% by mass of Ni, the balance consisting of Fe and unavoidable impurities, with Ti+Nb?0.07% by mass. The steel has a tensile strength of not less than 1,300 MPa.
    Type: Application
    Filed: November 11, 2013
    Publication date: March 6, 2014
    Applicants: JFE BARS & SHAPES CORPORATION, NHK SPRING CO., LTD.
    Inventors: Akira TANGE, Kiyoshi KURIMOTO, Yurika GOTO, Katsuhiko KIKUCHI, Kunikazu TOMITA, Kazuaki FUKUOKA, Kazuaki HATTORI
  • Patent number: 8206521
    Abstract: According to one embodiment, a high-strength stabilizer steel for vehicles having excellent corrosion resistance and low-temperature toughness, containing 0.07 to 0.20% C, more than 0.6% and 1.5% or less Si, 1 to 3% Mn, 0.1 to 1.0% Cr, 0.005 to 0.080% sAl, 0.005 to 0.060% Ti, 0.005 to 0.060% Nb, 0.070% or less Ti+Nb, 150 ppm or less N, 0.035% or less P, 0.035% or less S, 0.01 to 1.00% Cu, 0.01 to 1.00% Ni, the remainder being Fe, and unavoidable impurities, wherein a structure before molding a stabilizer is any one of a bainite, a martensite, and a mixed structure of bainite/martensite and an original austenitic crystal grain size number after a heat treatment of the stabilizer is Gh 9 or more.
    Type: Grant
    Filed: August 11, 2011
    Date of Patent: June 26, 2012
    Assignees: NHK Spring Co., Ltd., JFE Bars & Shapes Corporation
    Inventors: Katsuhiko Kikuchi, Kunikazu Tomita, Yutaka Tamai, Kazuaki Hattori, Kanji Inoue, Akira Tange, Norihiko Mori, Yurika Goto, Kiyoshi Kurimoto
  • Patent number: 8118953
    Abstract: A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 ?m, prior austenite has a grain diameter of 30 ?m or less, and the ratio by volume of the residual austenite is less than 25%.
    Type: Grant
    Filed: January 27, 2010
    Date of Patent: February 21, 2012
    Assignees: JFE Steel Corporation, JTEKT Corporation
    Inventors: Takashi Iwamoto, Kunikazu Tomita, Hideto Kimura, Takaaki Toyooka, Hisato Nishisaka, Masao Goto, Hisashi Harada
  • Publication number: 20110290382
    Abstract: According to one embodiment, a high-strength stabilizer steel for vehicles having excellent corrosion resistance and low-temperature toughness, containing 0.07 to 0.20% C, more than 0.6% and 1.5% or less Si, 1 to 3% Mn, 0.1 to 1.0% Cr, 0.005 to 0.080% sAl, 0.005 to 0.060% Ti, 0.005 to 0.060% Nb, 0.070% or less Ti+Nb, 150 ppm or less N, 0.035% or less P, 0.035% or less S, 0.01 to 1.00% Cu, 0.01 to 1.00% Ni, the remainder being Fe, and unavoidable impurities, wherein a structure before molding a stabilizer is any one of a bainite, a martensite, and a mixed structure of bainite/martensite and an original austenitic crystal grain size number after a heat treatment of the stabilizer is Gh 9 or more.
    Type: Application
    Filed: August 11, 2011
    Publication date: December 1, 2011
    Applicants: JFE BARS & SHAPES CORPORATION, NHK SPRING CO., LTD.
    Inventors: Katsuhiko KIKUCHI, Kunikazu Tomita, Yutaka Tamai, Kazuaki Hattori, Kanji Inoue, Akira Tange, Norihiko Mori, Yurika Goto, Kiyoshi Kurimoto
  • Publication number: 20110243786
    Abstract: A low carbon resulfurized free cutting steel consisting of 0.04 to 0.15% of C, more than 0.10% and 0.70% or less of Si, 0.85 to 1.50% of Mn, 0.040 to 0.120% of P, 0.250% or more and less than 0.400% of S, less than 0.005% of Al, more than 0.0020% and 0.0120% or less of O, and more than 0.0070% and 0.0150% or less of N, all by mass percentage, and the balance of Fe and inevitable impurities, and satisfying a formula (1) and a formula (2), as follows: 0.15%?Si %+2×P %?(5×Al %+10×O %+3×N %)?0.75%??(1), and ([Mn %]5)/15<S %<([Mn %]5)/2??(2).
    Type: Application
    Filed: December 9, 2009
    Publication date: October 6, 2011
    Inventors: Toshiyuki Murakami, Kunikazu Tomita, Tetsuo Shiraga
  • Publication number: 20100139819
    Abstract: A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 ?m, prior austenite has a grain diameter of 30 ?m or less, and the ratio by volume of the residual austenite is less than 25%.
    Type: Application
    Filed: January 27, 2010
    Publication date: June 10, 2010
    Applicants: JFE STEEL CORPORATION, JTEKT CORPORATION
    Inventors: Takashi Iwamoto, Kunikazu Tomita, Hideto Kimura, Takaaki Toyooka, Hisato Nishisaka, Masao Goto, Hisashi Harada
  • Publication number: 20070199632
    Abstract: A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 ?m, prior austenite has a grain diameter of 30 ?m or less, and the ratio by volume of the residual austenite is less than 25%.
    Type: Application
    Filed: February 15, 2007
    Publication date: August 30, 2007
    Applicants: JFE Steel Corporation,a corporation of Japan, JTEKT Corporation, a corporation of Japan
    Inventors: Takashi Iwamoto, Kunikazu Tomita, Hideto Kimura, Takaaki Toyooka, Hisato Nishisaka, Masao Goto, Hisashi Harada
  • Publication number: 20040074573
    Abstract: The present invention relates to a high strength hot rolled steel sheet containing 0.15% or less C, 0.02 to 0.35% Ti, and 0.05 to 0.7% Mo by weight percentage and consisting essentially of a matrix of ferrite structure single phase and fine precipitates with a grain size of smaller than 10 nm dispersed in the matrix, for example, a high strength hot rolled steel sheet which consists essentially of 0.06% or less C, 0.5% or less Si, 0.5 to 2.0% Mn, 0.06% or less P, 0.005% or less S, 0.1% or less Al, 0.006% or less N, 0.02 to 0.10% Ti, 0.05 to 0.6% Mo by weight percentage, and the balance being Fe, wherein fine precipitates with a grain size of smaller than 10 nm are dispersed in a matrix of ferrite structure single phase at a number per unit volume of 5×104/&mgr;m3 or higher. This steel sheet, which has tensile strength of not lower than 550 MPa, high elongation and excellent stretch flangeability, is suitable for intricately shaped automotive chassis parts such as a suspension arm.
    Type: Application
    Filed: October 14, 2003
    Publication date: April 22, 2004
    Applicant: NKK CORPORATION
    Inventors: Yoshimasa Funakawa, Tsuyoshi Shiozaki, Kunikazu Tomita, Takanobu Saito, Hiroshi Nakata, Kaoru Sato, Minoru Suwa, Tetsuo Yamamoto, Yasuhiro Murao, Eiji Maeda
  • Patent number: 6666932
    Abstract: The present invention relates to a high strength hot rolled steel sheet containing 0.15% or less C, 0.02 to 0.35% Ti, and 0.05 to 0.7% Mo by weight percentage and consisting essentially of a matrix of ferrite structure single phase and fine precipitates with a grain size of smaller than 10 nm dispersed in the matrix, for example, a high strength hot rolled steel sheet which consists essentially of 0.06% or less C, 0.5% or less Si, 0.5 to 2.0% Mn, 0.06% or less P, 0.005% or less S, 0.1% or less Al, 0.006% or less N, 0.02 to 0.10% Ti, 0.05 to 0.6% Mo by weight percentage, and the balance being Fe, wherein fine precipitates with a grain size of smaller than 10 nm are dispersed in a matrix of ferrite structure single phase at a number per unit volume of 5×104/&mgr;m3 or higher. This steel sheet, which has tensile strength of not lower than 550 MPa, high elongation and excellent stretch flangeability, is suitable for intricately shaped automotive chassis parts such as a suspension arm.
    Type: Grant
    Filed: March 28, 2002
    Date of Patent: December 23, 2003
    Assignee: NKK Corporation
    Inventors: Yoshimasa Funakawa, Tsuyoshi Shiozaki, Kunikazu Tomita, Takanobu Saito, Hiroshi Nakata, Kaoru Sato, Minoru Suwa, Tetsuo Yamamoto, Yasuhiro Murao, Eiji Maeda