Patents by Inventor Akinobu Minami

Akinobu Minami 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: 10351937
    Abstract: The present invention provides a high-strength steel sheet excellent in impact resistance. The high-strength steel sheet contains predetermined contents of C, Si, Mn, P, S, Al, Ti, N, and O, with the balance being iron and inevitable impurities, and has a steel sheet structure in which, in a ? thickness to ? thickness region across ¼ of a sheet thickness, 1 to 8% retained austenite is contained in volume fraction, an average aspect ratio of the retained austenite is 2.0 or less, an amount of solid-solution Mn in the retained austenite is 1.1 times an average amount of Mn or more, and TiN grains having a 0.5 ?m average grain diameter or less are contained, and a density of AlN grains with a 1 ?m grain diameter or more is 1.0 pieces/mm2 or less, wherein a maximum tensile strength is 900 MPa or more.
    Type: Grant
    Filed: July 27, 2012
    Date of Patent: July 16, 2019
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Hajime Hasegawa, Chisato Wakabayashi, Tsuyoshi Oki
  • Patent number: 9988700
    Abstract: The present invention provides a high-strength steel sheet excellent in shape fixability. The high-strength steel sheet contains C, Si, Mn, P, S, Al, N, and O with predetermined contents, in which a retained austenite phase of 5 to 20% in volume fraction is contained, an amount of solid-solution C contained in the retained austenite phase is 0.80 to 1.00% in mass %, WSi? is 1.10 times or more WSi*, WMn? is 1.10 times or more WMn*, and when a frequency distribution is measured with respect to a sum of a ratio between WSi and WSi* and a ratio between WAl and WAl*, a mode value of the frequency distribution is 1.95 to 2.05, and a kurtosis is 2.00 or more.
    Type: Grant
    Filed: July 27, 2012
    Date of Patent: June 5, 2018
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Akinobu Minami, Hiroyuki Kawata, Akinobu Murasato, Yuji Yamaguchi, Natsuko Sugiura, Takuya Kuwayama, Naoki Maruyama, Takamasa Suzuki
  • Patent number: 9896751
    Abstract: High strength steel sheet and high strength galvanized steel sheet which are excellent in shapeability which secure a tensile maximum strength 900 MPa or more high strength while obtaining excellent ductility and stretch flangeability, which sheets have predetermined compositions of ingredients, have steel sheet structures which contain volume fraction 1 to 20% of residual austenite phases, and which have martensite transformation points of the residual austenite phases of ?60° C. or less.
    Type: Grant
    Filed: July 27, 2012
    Date of Patent: February 20, 2018
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Yuji Yamaguchi, Natsuko Sugiura
  • Patent number: 9708679
    Abstract: There is provided a high-strength hot-dip galvanized steel sheet and the like excellent in mechanical cutting property, which are capable of obtaining high ductility while ensuring high strength with maximum tensile strength of 900 MPa or more. The high-strength hot-dip galvanized steel sheet has a sheet thickness of 0.6 to 5.0 mm and has a plating layer on a surface of a steel sheet with component compositions being set in appropriate ranges, in which the steel sheet structure contains a 40 to 90% ferrite phase and a 3% or more retained austenite phase by volume fraction. In the retained austenite phase, a solid solution carbon amount is 0.70 to 1.00%, an average grain diameter is 2.0 ?m or less, an average distance between grains is 0.1 to 5.0 ?m, a thickness of a decarburized layer in a steel sheet surface layer portion is 0.01 to 10.0 ?m, an average grain diameter of oxides contained in the steel, sheet surface layer portion is 30 to 120 nm and an average density thereof is 1.
    Type: Grant
    Filed: September 28, 2012
    Date of Patent: July 18, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Patent number: 9702035
    Abstract: A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of ? thickness to ? thickness centered around ¼ thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 ?m or less, a maximum effective crystal grain diameter is 20 ?m or less, and a decarburized layer with a thickness of 0.01 ?m to 10.0 ?m is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×1012 to 1.0×1016 oxides/m2, and an average grain diameter of the oxides is 500 nm or less.
    Type: Grant
    Filed: December 3, 2014
    Date of Patent: July 11, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Patent number: 9694561
    Abstract: High strength steel sheet which secures tensile maximum strength 900 MPa or more high strength while having excellent shapeability, which high strength steel sheet which is excellent in shapeability characterized by having a predetermined composition of ingredients, by the steel sheet structure including a ferrite phase and martensite phase, by the ratio of Cu particles incoherent with the bcc iron being 15% or more with respect to the Cu particles as a whole, by a density of Cu particles in the ferrite phase being 1.0×1018/m3 or more, and by an average particle size of Cu particles in the ferrite phase being 2.0 nm or more.
    Type: Grant
    Filed: July 27, 2012
    Date of Patent: July 4, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Masafumi Azuma, Takuya Kuwayama, Shigeru Yonemura
  • Patent number: 9551057
    Abstract: Provided are: a galvannealed steel sheet, improved in the adhesiveness of a plated layer with a base steel sheet, as a galvannealed steel sheet, prepared by using a high-strength steel sheet as a base material; and a method for producing the galvannealed steel sheet. A galvannealed layer is formed on the base steel sheet including a high-strength steel having a predetermined composition. The average amount of Fe in the galvannealed layer is 8.0 to 12.0%. The absolute value of a difference (?Fe) between the amount of Fe in the vicinity of an interface with the base steel sheet and the amount of Fe in the vicinity of the external surface of the plated layer in the plated layer is 0.0 to 3.0%.
    Type: Grant
    Filed: July 27, 2012
    Date of Patent: January 24, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui
  • Patent number: 9234268
    Abstract: The present invention provides a high-strength galvanized steel sheet with maximum tensile strength of 900 MPa or more. The high-strength galvanized steel sheet has an alloyed galvanized layer formed on a surface of a base steel sheet containing predetermined amounts of C, Si, Mn, P, S, Al, N, O with a balance being constituted of iron and inevitable impurities, in which in a structure of the base steel sheet, retained austenite is limited to 8% or less in volume fraction, kurtosis K* of the hardness distribution between 2% hardness and 98% hardness is ?0.30 or less, a ratio between Vickers hardness of surface layer of the base steel sheet and Vickers hardness of ¼ thickness of the base steel sheet is 0.35 to 0.70, and a content of iron in the alloyed galvanized layer is 8 to 12% in mass %.
    Type: Grant
    Filed: July 27, 2012
    Date of Patent: January 12, 2016
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Shigeru Yonemura
  • Patent number: 9162422
    Abstract: Steel contains each of C, Si, Mn, P, S, Al, N, O, at a range from ? thickness centered around a ¼ sheet thickness from a surface to ? thickness centered around the ¼ sheet thickness from the surface at a base steel sheet, a structure of the base steel sheet contains, in volume fraction, 3% or more of a retained austenite phase, 50% or less of a ferrite phase, and 40% or more of a hard phase, average dislocation density is 5×1013/m2 or more, solid-solution C amount contained in the retained austenite phase is in mass % 0.70 to 1.00%, X-ray random intensity ratio of FCC iron in an texture of the retained austenite phase is 3.0 or less, ratio between a grain diameter relative to a rolling direction and a grain diameter relative to a sheet width direction of the retained austenite phase is 0.75 to 1.33.
    Type: Grant
    Filed: September 28, 2012
    Date of Patent: October 20, 2015
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Patent number: 8993120
    Abstract: A hot-dip galvanizing layer or an alloyed hot dip galvanizing layer is formed on the surface of a base steel sheet in which in volume fraction, 40 to 90% of a ferrite phase and 5% or less of a retained austenite phase are contained, and a ratio of non-recrystallized ferrite to the entire ferrite phase is 50% or less in volume fraction, and further a grain diameter ratio being a value of, of crystal grains in the ferrite phase, an average grain diameter in the rolling direction divided by an average grain diameter in the sheet width direction is 0.75 to 1.33, a length ratio being a value of, of hard structures dispersed in island shapes, an average length in the rolling direction divided by an average length in the sheet width direction is 0.75 to 1.33, and an average aspect ratio of inclusions is 5.0 or less.
    Type: Grant
    Filed: September 28, 2012
    Date of Patent: March 31, 2015
    Assignee: Nippon Steel & Sumitomo Metal Corporation
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Publication number: 20150083278
    Abstract: A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of ? thickness to ? thickness centered around ¼ thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 ?m or less, a maximum effective crystal grain diameter is 20 ?m or less, and a decarburized layer with a thickness of 0.01 ?m to 10.0 ?m is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×1012 to 1.0×1016 oxides/m2, and an average grain diameter of the oxides is 500 nm or less.
    Type: Application
    Filed: December 3, 2014
    Publication date: March 26, 2015
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki KAWATA, Naoki MARUYAMA, Akinobu MURASATO, Akinobu MINAMI, Takeshi YASUI, Takuya KUWAYAMA, Hiroyuki BAN, Kaoru HIRAMATSU
  • Patent number: 8932729
    Abstract: A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of ? thickness to ? thickness centered around ¼ thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 ?m or less, a maximum effective crystal grain diameter is 20 ?m or less, and a decarburized layer with a thickness of 0.01 ?m to 10.0 ?m is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×1012 to 1.0×1016 oxides/m2, and an average grain diameter of the oxides is 500 nm or less.
    Type: Grant
    Filed: September 28, 2012
    Date of Patent: January 13, 2015
    Assignee: Nippon Steel & Sumitomo Metal Corporation
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Publication number: 20140287263
    Abstract: There is provided a high-strength hot-dip galvanized steel sheet and the like excellent in mechanical cutting property, which are capable of obtaining high ductility while ensuring high strength with maximum tensile strength of 900 MPa or more. The high-strength hot-dip galvanized steel sheet has a sheet thickness of 0.6 to 5.0 mm and has a plating layer on a surface of a steel sheet with component compositions being set in appropriate ranges, in which the steel sheet structure contains a 40 to 90% ferrite phase and a 3% or more retained austenite phase by volume fraction. In the retained austenite phase, a solid solution carbon amount is 0.70 to 1.00%, an average grain diameter is 2.0 ?m or less, an average distance between grains is 0.1 to 5.0 ?m, a thickness of a decarburized layer in a steel sheet surface layer portion is 0.01 to 10.0 ?m, an average grain diameter of oxides contained in the steel, sheet surface layer portion is 30 to 120 nm and an average density thereof is 1.
    Type: Application
    Filed: September 28, 2012
    Publication date: September 25, 2014
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Publication number: 20140242414
    Abstract: The present invention provides a high-strength steel sheet excellent in shape fixability. The high-strength steel sheet contains C, Si, Mn, P, S, Al, N, and O with predetermined contents, in which a retained austenite phase of 5 to 20% in volume fraction is contained, an amount of solid-solution C contained in the retained austenite phase is 0.80 to 1.00% in mass %, WSi? is 1.10 times or more WSi*, WMn? is 1.10 times or more WMn*, and when a frequency distribution is measured with respect to a sum of a ratio between WSi and WSi* and a ratio between WAl and WAl*, a mode value of the frequency distribution is 1.95 to 2.05, and a kurtosis is 2.00 or more.
    Type: Application
    Filed: July 27, 2012
    Publication date: August 28, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Akinobu Minami, Hiroyuki Kawata, Akinobu Murasato, Yuji Yamaguchi, Natsuko Sugiura, Takuya Kuwayama, Naoki Maruyama, Takamasa Suzuki
  • Publication number: 20140234660
    Abstract: Steel contains each of C, Si, Mn, P, S, Al, N, O, at a range from ? thickness centered around a ¼ sheet thickness from a surface to ? thickness centered around the ¼ sheet thickness from the surface at a base steel sheet, a structure of the base steel sheet contains, in volume fraction, 3% or more of a retained austenite phase, 50% or less of a ferrite phase, and 40% or more of a hard phase, average dislocation density is 5×1013/m2 or more, solid-solution C amount contained in the retained austenite phase is in mass % 0.70 to 1.00%, X-ray random intensity ratio of FCC iron in an texture of the retained austenite phase is 3.0 or less, ratio between a grain diameter relative to a rolling direction and a grain diameter relative to a sheet width direction of the retained austenite phase is 0.75 to 1.33.
    Type: Application
    Filed: September 28, 2012
    Publication date: August 21, 2014
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Publication number: 20140234659
    Abstract: A hot-dip galvanizing layer or an alloyed hot dip galvanizing layer is formed on the surface of a base steel sheet in which in volume fraction, 40 to 90% of a ferrite phase and 5% or less of a retained austenite phase are contained, and a ratio of non-recrystallized ferrite to the entire ferrite phase is 50% or less in volume fraction, and further a grain diameter ratio being a value of, of crystal grains in the ferrite phase, an average grain diameter in the rolling direction divided by an average grain diameter in the sheet width direction is 0.75 to 1.33, a length ratio being a value of, of hard structures dispersed in island shapes, an average length in the rolling direction divided by an average length in the sheet width direction is 0.75 to 1.33, and an average aspect ratio of inclusions is 5.0 or less.
    Type: Application
    Filed: September 28, 2012
    Publication date: August 21, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Publication number: 20140227555
    Abstract: A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of ? thickness to ? thickness centered around ¼ thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 ?m or less, a maximum effective crystal grain diameter is 20 ?m or less, and a decarburized layer with a thickness of 0.01 ?m to 10.0 ?m is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×1012 to 1.0×1016 oxides/m2, and an average grain diameter of the oxides is 500 nm or less.
    Type: Application
    Filed: September 28, 2012
    Publication date: August 14, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Hiroyuki Ban, Kaoru Hiramatsu
  • Publication number: 20140212684
    Abstract: The present invention provides a high-strength galvanized steel sheet with maximum tensile strength of 900 MPa or more. The high-strength galvanized steel sheet has an alloyed galvanized layer formed on a surface of a base steel sheet containing predetermined amounts of C, Si, Mn, P, S, Al, N, O with a balance being constituted of iron and inevitable impurities, in which in a structure of the base steel sheet, retained austenite is limited to 8% or less in volume fraction, kurtosis K* of the hardness distribution between 2% hardness and 98% hardness is ?0.30 or less, a ratio between Vickers hardness of surface layer of the base steel sheet and Vickers hardness of ¼ thickness of the base steel sheet is 0.35 to 0.70, and a content of iron in the alloyed galvanized layer is 8 to 12% in mass %.
    Type: Application
    Filed: July 27, 2012
    Publication date: July 31, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui, Takuya Kuwayama, Shigeru Yonemura
  • Publication number: 20140205855
    Abstract: [Summary] The present invention provides a high-strength steel sheet excellent in impact resistance. The high-strength steel sheet contains predetermined contents of C, Si, Mn, P, S, Al, Ti, N, and O, with the balance being iron and inevitable impurities, and has a steel sheet structure in which, in a ? thickness to ? thickness region across ¼ of a sheet thickness, 1 to 8% retained austenite is contained in volume fraction, an average aspect ratio of the retained austenite is 2.0 or less, an amount of solid-solution Mn in the retained austenite is 1.1 times an average amount of Mn or more, and TiN grains having a 0.5 ?m average grain diameter or less are contained, and a density of AlN grains with a 1 ?m grain diameter or more is 1.0 pieces/mm2 or less, wherein a maximum tensile strength is 900 MPa or more.
    Type: Application
    Filed: July 27, 2012
    Publication date: July 24, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Hajime Hasegawa, Chisato Wakabayashi, Tsuyoshi Oki
  • Publication number: 20140193665
    Abstract: Provided are: a galvannealed steel sheet, reliably and sufficiently improved in the adhesiveness of a plated layer with a base steel sheet, as a galvannealed steel sheet, prepared by using a high-strength steel sheet as a base material; and a method for producing the galvannealed steel sheet. The galvannealed steel sheet wherein a galvannealed layer is formed on a base steel sheet including a high-strength steel having predetermined component composition; the average amount of Fe in the galvannealed layer is in a range of 8.0 to 12.0%; and the absolute value ?Fe of a difference between the amount of Fe in the vicinity of an interface with the base steel sheet (the amount of Fe in the vicinity of an internal side) and the amount of Fe in the vicinity of the external surface of the plated layer (the amount of Fe in the vicinity of an external side) in the plated layer is in a range of 0.0 to 3.0%.
    Type: Application
    Filed: July 27, 2012
    Publication date: July 10, 2014
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Takeshi Yasui