Patents by Inventor Michiharu Nakaya

Michiharu Nakaya 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: 20230357874
    Abstract: A high-strength cold-rolled steel sheet according to one aspect of the present invention contains, in % by mass: C: 0.070 to 0.140%; Si: 0.80 to 1.80%; and Mn: 1.80 to 2.80%, with the balance being iron and unavoidable impurities; in area ratio in a structure observed with a scanning electron microscope, bainite, tempered martensite, and hard phases composed of at least one of cementite and MA made up of quenched martensite and retained austenite combined together account for 85% or more in total, the hard phase that has a breadth of 0.4 ?m or less and a length of 1.2 ?m or more accounts for 0.5% or more, the hard phase that has a breadth of 1.2 ?m or more accounts for 5.0% or less, and structures other than the bainite, the tempered martensite, and the hard phase account for 15% or less; and in volume ratio measured by X-ray diffractometry, retained austenite accounts for 3.0% or more and 7.0% or less.
    Type: Application
    Filed: September 22, 2021
    Publication date: November 9, 2023
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Shinjiro KANETADA, Michiharu NAKAYA
  • Patent number: 11408047
    Abstract: In one aspect of the present invention, a hot-dip galvannealed steel sheet includes a steel sheet and a hot-dip galvannealed layer on the surface of the steel sheet. The steel sheet has a predetermined composition and has an average oxygen concentration of 0.10 mass % or less in the region of 1 ?m from the interface between the steel sheet and the hot-dip galvannealed layer toward the steel sheet. The metal microstructure of the steel sheet at a position of t/4 where t represents the sheet thickness of the hot-dip galvannealed steel sheet includes 50 to 85 area % of martensite, 15 to 50 area % of bainite, and 5 area % or less of ferrite.
    Type: Grant
    Filed: March 12, 2019
    Date of Patent: August 9, 2022
    Assignee: Kobe Steel, Ltd.
    Inventors: Tetsuji Hoshika, Muneaki Ikeda, Michiharu Nakaya
  • Patent number: 11319622
    Abstract: A high-strength steel sheet satisfies a predetermined chemical composition in which a content of martensite is 93% by volume or more, contents of ferrite, pearlite, and bainite are 2% by volume or less in total, and a content of retained austenite is 7% by volume or less, based on an entire metal structure, a number of laths in martensite measured by a cutting method in a total length of 300 ?m in an image of the metal structure observed under a scanning electron microscope is 240 or more, and a tensile strength of the high-strength steel sheet is 1470 MPa or more.
    Type: Grant
    Filed: March 11, 2019
    Date of Patent: May 3, 2022
    Assignee: Kobe Steel, Ltd.
    Inventors: Michitaka Tsunezawa, Michiharu Nakaya, Haruka Araki
  • Publication number: 20210115542
    Abstract: A high-strength steel sheet satisfies a predetermined chemical composition in which a content of martensite is 93% by volume or more, contents of ferrite, pearlite, and bainite are 2% by volume or less in total, and a content of retained austenite is 7% by volume or less, based on an entire metal structure, a number of laths in martensite measured by a cutting method in a total length of 300 ?m in an image of the metal structure observed under a scanning electron microscope is 240 or more, and a tensile strength of the high-strength steel sheet is 1470 MPa or more.
    Type: Application
    Filed: March 11, 2019
    Publication date: April 22, 2021
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Michitaka TSUNEZAWA, Michiharu NAKAYA, Haruka ARAKI
  • Publication number: 20210017621
    Abstract: In one aspect of the present invention, a hot-dip galvannealed steel sheet includes a steel sheet and a hot-dip galvannealed layer on the surface of the steel sheet. The steel sheet has a predetermined composition and has an average oxygen concentration of 0.10 mass % or less in the region of 1 ?m from the interface between the steel sheet and the hot-dip galvannealed layer toward the steel sheet. The metal microstructure of the steel sheet at a position of t/4 where t represents the sheet thickness of the hot-dip galvannealed steel sheet includes 50 to 85 area % of martensite, 15 to 50 area % of bainite, and 5 area % or less of ferrite.
    Type: Application
    Filed: March 12, 2019
    Publication date: January 21, 2021
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Tetsuji HOSHIKA, Muneaki IKEDA, Michiharu NAKAYA
  • Patent number: 10604829
    Abstract: Disclosed herein is a high-strength plated steel sheet having a plated layer on the surface of a base steel sheet and containing predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet; and a hard layer consisting of a structure which is mainly composed of martensite and bainite and in which the average grain size of prior austenite is 20 ?m or less. The average depth D of the soft layer is 20 ?m or greater, and the average depth d of an internal oxide layer is 4 ?m or greater and smaller than D.
    Type: Grant
    Filed: January 5, 2016
    Date of Patent: March 31, 2020
    Assignee: Kobe Steel, Ltd.
    Inventors: Muneaki Ikeda, Michiharu Nakaya
  • Patent number: 10570473
    Abstract: Provided is a high-strength cold-rolled steel sheet having excellent ductility and stretch-flangeability as well as weldability in a range in which a tensile strength is 980 MPa or higher and a 0.2% yield strength is less than 700 MPa (preferably 500 MPa or higher). In the high-strength cold-rolled steel sheet of the present invention, the chemical composition is adjusted as appropriate, and the area ratio of below-mentioned metal structures at a position of ¼ sheet thickness in the steel sheet satisfies following requirements: tempered martensite: 10 area % to less than 30 area %, bainite: more than 70 area %, total of tempered martensite and bainite: 90 area % or more, ferrite: 0 area % to 5 area %, and retained austenite: 0 area % to 4 area %. The high-strength cold-rolled steel sheet has excellent ductility, stretch-flangeability, and weldability, and has a tensile strength of 980 MPa or higher and a 0.2% yield strength of less than 700 MPa.
    Type: Grant
    Filed: March 19, 2015
    Date of Patent: February 25, 2020
    Assignee: Kobe Steel, Ltd.
    Inventors: Michitaka Tsunezawa, Michiharu Nakaya
  • Patent number: 10501830
    Abstract: Provided is a high-strength cold-rolled steel sheet having excellent ductility and stretch-flangeability as well as weldability in a range in which a tensile strength is 980 MPa or higher and a 0.2% yield strength is 700 MPa or higher. In the high-strength cold-rolled steel sheet of the present invention, the chemical composition is adjusted as appropriate, and the area ratio of below-mentioned metal structures at a position of ¼ sheet thickness in the steel sheet satisfies following requirements: tempered martensite: 30 area % or more, bainite: 15 area % to 70 area %, total of tempered martensite and bainite: 90 area % or more, ferrite: 0 area % to 5 area %, and retained austenite: 0 area % to 4 area %. The high-strength cold-rolled steel sheet has excellent ductility, stretch-flangeability, and weldability, and has a tensile strength of 980 MPa or higher and a 0.2% yield strength of 700 MPa or higher.
    Type: Grant
    Filed: March 19, 2015
    Date of Patent: December 10, 2019
    Assignee: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Michitaka Tsunezawa, Michiharu Nakaya
  • Patent number: 10202664
    Abstract: The present invention relates to high strength cold rolled steel sheet suitable for applications in automobiles, construction materials and the like, specifically high strength steel excellent in formability. In particular, the invention relates to cold rolled steel sheets having a tensile strength of at least 980 MPa and a method for producing such steel sheet.
    Type: Grant
    Filed: April 2, 2013
    Date of Patent: February 12, 2019
    Assignees: VOESTALPINE STAHL GMBH, KOBE STEEL, LTD
    Inventors: Daniel Krizan, Stefan Paul, Andreas Pichler, Michiharu Nakaya
  • Publication number: 20180363092
    Abstract: Disclosed herein is a high-strength galvannealed steel sheet having a galvannealed layer on a surface of a base steel sheet and containing predetermined steel components. The steel sheet sequentially has, from the interface of the base steel sheet and the galvannealed layer, towards the base steel sheet: an internal oxide layer and containing at least one oxide selected from the group consisting of Si and Mn; a soft layer including the internal oxide layer, and satisfying a predetermined Vickers hardness; and a hard layer made up of a structure mainly composed of martensite. The average depth D of the soft layer is 20 ?m or greater, and the average depth d of the internal oxide layer is 4 ?m or greater and smaller than D. A coefficient of variation of KAM of the base steel sheet at the portion t/4 is 0.66 or less.
    Type: Application
    Filed: August 22, 2018
    Publication date: December 20, 2018
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Muneaki IKEDA, Michiharu NAKAYA
  • Patent number: 10106874
    Abstract: The present invention relates to high strength cold rolled steel sheet suitable for applications in automobiles, construction materials and the like, specifically high strength steel sheet excellent in formability. In particular, the invention relates to cold rolled steel sheets having a tensile strength of at least 980 MPa and a method for producing such steel sheet.
    Type: Grant
    Filed: April 2, 2013
    Date of Patent: October 23, 2018
    Assignees: VOESTALPINE STAHL GMBH, KOBE STEEL LTD
    Inventors: Stefan Paul, Daniel Krizan, Andreas Pichler, Michiharu Nakaya
  • Patent number: 10023934
    Abstract: The present disclosure relates to a high-strength hot-dip galvannealed steel sheet excellent in bake hardenability and bendability and having a component composition containing, in mass %, C: from 0.05 to 0.30%, Si: from 0.5 to 3.0%, Mn: from 0.2 to 3.0%, P: from 0 to 0.10%, S: from 0 to 0.010%, N: form 0 to 0.010%, and Al: from 0.001 to 0.10%, with the remainder being iron and unavoidable impurities. The steel sheet has a steel structure containing, in terms of area percentage, martensite: form 50 to 85% and ferrite: 0% or more and less than 5%, with the remainder being bainite. The steel sheet has a dislocation density of 5.0×1015 m?2 or more, a solute carbon amount of 0.08 mass % or more and a tensile strength of 1180 MPa or more.
    Type: Grant
    Filed: March 4, 2015
    Date of Patent: July 17, 2018
    Assignee: Kobe Steel, Ltd.
    Inventors: Kosuke Shibata, Toshio Murakami, Muneaki Ikeda, Michiharu Nakaya
  • Publication number: 20180171442
    Abstract: Provided is a high-strength cold-rolled steel sheet having excellent ductility and stretch-flangeability as well as weldability in a range in which a tensile strength is 980 MPa or higher and a 0.2% yield strength is 700 MPa or higher. In the high-strength cold-rolled steel sheet of the present invention, the chemical composition is adjusted as appropriate, and the area ratio of below-mentioned metal structures at a position of ¼ sheet thickness in the steel sheet satisfies following requirements: tempered martensite: 30 area % or more, bainite: 15 area % to 70 area %, total of tempered martensite and bainite: 90 area % or more, ferrite: 0 area % to 5 area %, and retained austenite: 0 area % to 4 area %. The high-strength cold-rolled steel sheet has excellent ductility, stretch-flangeability, and weldability, and has a tensile strength of 980 MPa or higher and a 0.2% yield strength of 700 MPa or higher.
    Type: Application
    Filed: March 19, 2015
    Publication date: June 21, 2018
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Michitaka TSUNEZAWA, Michiharu NAKAYA
  • Publication number: 20180010207
    Abstract: Disclosed herein is a high-strength plated steel sheet containing an internal oxidized layer, a soft layer including the internal oxidized layer, and a hard layer including a structure having metallic structure containing a low-temperature-transformation produced phase in a proportion of 70% or more by area of the whole of the metallic structure, in which polygonal ferrite is in a proportion of 0% or more by area, and 10% or less by area of the same, and retained austenite is in a proportion of 5% or more by volume of the same. The high-strength plated steel sheet satisfies the average depth D of the soft layer is 20 ?m or more, the average depth d of the internal oxidized layer is 4 ?m or more and less than D, and a tensile strength of 980 MPa or more.
    Type: Application
    Filed: January 5, 2016
    Publication date: January 11, 2018
    Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.)
    Inventors: Yuichi FUTAMURA, Muneaki IKEDA, Michiharu NAKAYA
  • Publication number: 20180010226
    Abstract: The high-strength plated steel sheet of the present invention has a plated layer on the surface of a base steel sheet and contains predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet: and a hard layer containing martensite, bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 ?m or greater, and the average depth d of an internal oxide layer is 4 ?m or greater and smaller than D.
    Type: Application
    Filed: January 5, 2016
    Publication date: January 11, 2018
    Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.
    Inventors: Muneaki IKEDA, Yuichi FUTAMURA, Michiharu NAKAYA
  • Publication number: 20180010227
    Abstract: Disclosed herein is a high-strength plated steel sheet having a plated layer on the surface of a base steel sheet and containing predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet; and a hard layer consisting of a structure which is mainly composed of martensite and bainite and in which the average grain size of prior austenite is 20 ?m or less. The average depth D of the soft layer is 20 ?m or greater, and the average depth d of an internal oxide layer is 4 ?m or greater and smaller than D.
    Type: Application
    Filed: January 5, 2016
    Publication date: January 11, 2018
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Muneaki IKEDA, Michiharu NAKAYA
  • Publication number: 20180002799
    Abstract: A high-strength plated steel sheet sequentially includes an internal oxidized layer, a soft layer containing the internal oxidized layer, and a hard layer including a structure having metallic structure which contains a low-temperature-transformation produced phase in a proportion of 20 to 85% by area of the whole of the metallic structure, polygonal ferrite in a proportion more than 10% by area, and 70% or less by area of the whole of the metallic structure, and-retained austenite in a proportion of 5% or more by volume of the whole of the metallic structure. The high-strength plated steel sheet satisfies the average depth D of the soft layer being 20 ?m or more, the average depth d of the internal oxidized layer being 4 ?m or more and less than D, and a tensile strength being 980 MPa or more.
    Type: Application
    Filed: January 5, 2016
    Publication date: January 4, 2018
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Yuichi FUTAMURA, Muneaki IKEDA, Michiharu NAKAYA
  • Publication number: 20170369965
    Abstract: A high-strength plated steel sheet has a plated layer on the surface of a base steel sheet and contains predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet; and a hard layer containing martensite and bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 ?m or greater, and the average depth d of an internal oxide layer is 4 ?m or greater and smaller than D.
    Type: Application
    Filed: January 5, 2016
    Publication date: December 28, 2017
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Muneaki IKEDA, Yuichi FUTAMURA, Michiharu NAKAYA
  • Publication number: 20170183751
    Abstract: Provided is a high-strength cold-rolled steel sheet having excellent ductility and stretch-flangeability as well as weldability in a range in which a tensile strength is 980 MPa or higher and a 0.2% yield strength is less than 700 MPa (preferably 500 MPa or higher). In the high-strength cold-rolled steel sheet of the present invention, the chemical composition is adjusted as appropriate, and the area ratio of below-mentioned metal structures at a position of ¼ sheet thickness in the steel sheet satisfies following requirements: tempered martensite: 10 area % to less than 30 area %, bainite: more than 70 area %, total of tempered martensite and bainite: 90 area % or more, ferrite: 0 area % to 5 area %, and retained austenite: 0 area % to 4 area %. The high-strength cold-rolled steel sheet has excellent ductility, stretch-flangeability, and weldability, and has a tensile strength of 980 MPa or higher and a 0.2% yield strength of less than 700 MPa.
    Type: Application
    Filed: March 19, 2015
    Publication date: June 29, 2017
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Michitaka TSUNEZAWA, Michiharu NAKAYA
  • Patent number: 9631266
    Abstract: Provided is a method that enables manufacture, with good productivity, of a high-strength cold-rolled steel with improved elongation (EL), stretch-flangeability (?), bendability (R), and balance of these properties (TS×EL×?/1000), outstanding composite workability as evaluated by Erichsen test, and a tensile strength of at least 980 MPa. A steel material satisfying a prescribed constituent composition is held and soaked for at least fifty seconds at a temperature at or above the Ac3 point, after which the steel material is cooled at an average cooling rate of at least 15° C./sec to a discretionary temperature (T) that satisfies expression (1) below, held for 5-180 seconds in a temperature range that satisfies expression (1) below, then heated to a temperature region that satisfies expression (2) below, held for at least 50 seconds in this temperature region, and then cooled. 300° C.?T1(° C.)<400° C.??(1) 400° C.?T2(° C.)<540° C.
    Type: Grant
    Filed: February 28, 2013
    Date of Patent: April 25, 2017
    Assignee: Kobe Steel, Ltd.
    Inventors: Yuichi Futamura, Michiharu Nakaya