Patents by Inventor Hiroyuki Kawata

Hiroyuki Kawata 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: 11447848
    Abstract: A steel sheet wherein a steel structure of an inside of the steel sheet contains, by volume fraction, soft ferrite: 0% to 30%, retained austenite: 3% to 40%, fresh martensite: 0% to 30%, a sum of pearlite and cementite: 0% to 10%, and a remainder including hard ferrite. In the steel sheet, in a ? to ? thickness range, a proportion of retained austenite having an aspect ratio of 2.0 or more is 50% or more, and a soft layer having a thickness of 1 to 100 ?m from a surface in a sheet thickness direction is present. When an emission intensity at a wavelength indicating Si is analyzed in the sheet thickness direction from the surface by a radio-frequency glow discharge analysis method, a peak of the emission intensity appears in a range of more than 0.2 ?m and 5.0 ?m or less from the surface.
    Type: Grant
    Filed: March 30, 2018
    Date of Patent: September 20, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Takafumi Yokoyama, Kohichi Sano, Riki Okamoto, Hiroyuki Kawata, Eisaku Sakurada, Yuji Yamaguchi, Kazuki Shiokawa, Yuichi Nakahira, Kohei Ueda, Masahiro Nakata, Satoshi Uchida
  • Publication number: 20220282351
    Abstract: Provided are: a steel sheet having a high strength and excellent hydrogen embrittlement resistance; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which a standard deviation ? of Mn concentration satisfies ??0.15 Mnave (wherein, Mnave represents an average Mn concentration) and a region with a Mn concentration of higher than (Mnave+1.3?) has a circle-equivalent diameter of less than 10.0 ?m. The method of producing the steel sheet includes: the hot rolling step that includes finish rolling a slab having a prescribed chemical composition under prescribed conditions; the step of coiling the thus obtained hot-rolled steel sheet at a coiling temperature of 450 to 700° C.; and the step of cold rolling the hot-rolled steel sheet and subsequently annealing this steel sheet at 800 to 900° C.
    Type: Application
    Filed: March 12, 2020
    Publication date: September 8, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Kengo TAKEDA, Hiroyuki KAWATA, Takafumi YOKOYAMA, Katsuya NAKANO
  • Publication number: 20220267874
    Abstract: A steel sheet having a tensile strength of 1100 MPa or more and excellent in crash resistance, having a micro-structure containing tempered martensite: 95 vol. % or more, wherein in a cross section parallel to a sheet-thickness direction of the steel sheet, when a sheet thickness is denoted by t, in a 300-?m-square region centered about a t/2 point, a standard deviation of Vickers hardnesses that are measured under a load of 9.8 N at 30 points is 30 or less, wherein when a 100-?m-square region centered about a t/2 point is divided into 10×10, 100 subregions, and at a center of each of the subregions, a nano hardness is measured under a maximum load of 1 mN, out of the subregions, the number of subregions each of which makes a difference in nano hardness of 3 GPa or more from any one of eight surrounding subregions is 10 or less.
    Type: Application
    Filed: June 26, 2020
    Publication date: August 25, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Katsuya NAKANO, Kengo TAKEDA, Hiroyuki KAWATA, Akihiro UENISHI, Yuya SUZUKI
  • Patent number: 11377710
    Abstract: A steel sheet has a chemical composition with a steel structure containing, by volume fraction, soft ferrite: 0-30%, retained austenite: 3-40%, fresh martensite: 0-30%, pearlite and cementite: 0-10%, and a remainder including hard ferrite. In the steel sheet, a number proportion of retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, and a soft layer having a thickness of 1-100 ?m is present. In the soft layer, a volume fraction of ferrite grains having an aspect ratio of less than 3.0 is 50% or more, and a volume fraction of retained austenite is 50% or more of the volume fraction of the retained austenite of the inside of the steel sheet. A peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 ?m to 5 ?m or less from the surface.
    Type: Grant
    Filed: March 30, 2018
    Date of Patent: July 5, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Takafumi Yokoyama, Kohichi Sano, Riki Okamoto, Hiroyuki Kawata, Eisaku Sakurada, Yuji Yamaguchi, Kazuki Shiokawa, Yuichi Nakahira, Kohei Ueda, Masahiro Nakata, Satoshi Uchida
  • Publication number: 20220195556
    Abstract: A steel sheet including a steel micro-structure containing, in volume fraction, tempered martensite: 85% or more, retained austenite: 5% or more to less than 15%, and ferrite, pearlite, bainite, and as-quenched martensite being less than 10% in total, when contents of Mn and C in the retained austenite are denoted by MnA and CA, and when contents of Mn and C in a matrix are denoted by MnM and CM, respectively, following Formulas (1) to (3) are satisfied, and the number of carbides having an equivalent circle radius of 0.1 ?m or more is 100 or less in a region measuring 20000 ?m2, and the steel sheet has a tensile strength of 1100 MPa or more. The steel sheet is excellent in crash resistance and formability. MnA/MnM?1.2??(1) CA/CM?5.0??(2) CA?1.
    Type: Application
    Filed: June 26, 2020
    Publication date: June 23, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Katsuya NAKANO, Kengo TAKEDA, Hiroyuki KAWATA, Akihiro UENISHI
  • Publication number: 20220186337
    Abstract: This steel sheet has a predetermined chemical composition, in which the area ratio of plate martensite is 10% or more, the average grain size of prior austenite grains is 2.0 ?m to 10.0 ?m, the maximum diameter thereof is 20.0 ?m or less, the amount of solid solution C in martensite is 0.20 mass % or less, the average carbide size is 0.25 ?m or less, the crystal orientation difference between plate martensite and another martensite adjacent thereto in the same prior austenite grain is 10.0° or less, and the P concentration at grain boundaries of the prior austenite grains is 4.0 at % or less.
    Type: Application
    Filed: April 8, 2020
    Publication date: June 16, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Kohichi SANO, Hiroyuki KAWATA, Kengo TAKEDA
  • Publication number: 20220154302
    Abstract: This steel sheet has a predetermined chemical composition, a microstructure contains, in terms of a volume fraction, ferrite: 10% to 75%, martensite: 20% to 90%, retained austenite: 0% to 5%, bainite and bainitic ferrite in total: 0% to 50%, and pearlite: 0% to 5%, a proportion of unrecrystallized ferrite in the ferrite is 0% to 25%, cementite that is contained in the martensite satisfies a predetermined relational expression, a density of transition carbide included in the martensite is 1.0×1013 pieces/m3 or more, a density of coarse inclusion having an equivalent circle diameter of 10 ?m or more is 0.50 pieces/mm2 or less, in a surface parallel to the surface at a position ¼ of the sheet thickness deep from the surface in the sheet thickness direction, a ratio of a maximum value Hvmax of Vickers hardness to a minimum value Hvmin of the Vickers hardness is 1.40 or less, and an average value of minimum distances between peaks of the Vickers hardness in a distribution map of the Vickers hardness is 1.
    Type: Application
    Filed: March 5, 2020
    Publication date: May 19, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventor: Hiroyuki KAWATA
  • Publication number: 20220145417
    Abstract: Provided are: a steel sheet having a high strength and excellent stretch formability; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which the integration degree of the (111)<112> orientation of ferrite is 3.0 or higher, and the integration degree of the (252)<2-11> orientation of martensite and tempered martensite is 5.0 or lower. The method of producing the steel sheet includes: the step of continuously casting a molten steel having the prescribed chemical composition, and performing 5 to 40% rolling reduction at a temperature of 800° C. to lower than 1,200° C. in a period after the continuous casting until cooling to room temperature; the hot rolling step of performing hot rolling with a finishing temperature of 650 to 950° C.; the step of coiling the resulting hot-rolled steel sheet at a coiling temperature of 400 to 700° C.; the step of retaining the hot-rolled steel sheet at (coiling start temperature+20° C. to 100° C.
    Type: Application
    Filed: March 12, 2020
    Publication date: May 12, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Kengo TAKEDA, Hitoshi NIKAIDO, Hiroyuki KAWATA, Takafumi YOKOYAMA
  • Patent number: 11326234
    Abstract: A cold-rolled steel sheet is provided that has a tensile strength of 980 MPa or more, and has a prescribed chemical composition. The microstructure is composed of, in area %, ferrite: 1 to 29%, retained austenite: 5 to 20%, martensite: less than 10%, pearlite: less than 5%, and the balance: bainite and/or tempered martensite. The total sum of the lengths of phase boundaries where ferrite comes in contact with martensite or retained austenite having a circle-equivalent radius of 1 ?m or more is 100 ?m or less per 1000 ?m2. The cold-rolled steel sheet is excellent in workability and low-temperature toughness, and in particular is excellent in low-temperature toughness after introduction of plastic strain.
    Type: Grant
    Filed: March 31, 2017
    Date of Patent: May 10, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Takafumi Yokoyama, Riki Okamoto, Yuji Yamaguchi, Kazuki Shiokawa, Yuichi Nakahira, Hiroyuki Kawata
  • Publication number: 20220127691
    Abstract: A high-strength steel sheet includes a chemical composition including: by mass %, C: 0.080 to 0.500%, Si: 2.50% or less, Mn: 0.50 to 5.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance: Fe and inevitable impurities. The high-strength steel sheet satisfying a predetermined formula has a microstructure in a region from ?t to ?t from a steel sheet surface. The microstructure includes: by volume %, 20% or more of acicular ferrite, 20% or more of an island-shaped hard structure including residual austenite, 2% to 25% of residual austenite, and 20% or less of aggregated ferrite.
    Type: Application
    Filed: December 11, 2018
    Publication date: April 28, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Hiroyuki KAWATA, Eisaku SAKURADA, Kohichi SANO, Takafumi YOKOYAMA
  • Publication number: 20220127709
    Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined chemical composition, and contains ferrite: 50% or less, retained austenite: 30% or less, tempered martensite: 5% or more, fresh martensite: 10% or less, and pearlite and cementite in total: 5% or less, remaining structures consist of bainite, and a number ratio of tempered martensite with a Mn concentration profile satisfying [Mn]b/[Mn]a>1.2 and [Mn]a/[Mn]<2.0 ([Mn] is the Mn content in the base steel sheet, [Mn]a is the average Mn concentration in the tempered martensite, and [Mn]b is the Mn concentration at the interfaces of different phases of the tempered martensite and ferrite phase and bainite phase) is 0.2 or more with respect to the total number of tempered martensite, and a method for producing the same.
    Type: Application
    Filed: February 6, 2020
    Publication date: April 28, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Takafumi YOKOYAMA, Hiroyuki KAWATA, Kunio HAYASHI, Yuji YAMAGUCHI, Satoshi UCHIDA
  • Publication number: 20220119909
    Abstract: A steel sheet of the present invention is a steel sheet having a predetermined chemical composition and containing at least ferrite, residual austenite, and/or martensite in a microstructure, and furthermore, is a steel sheet in which, in a plane parallel to a rolled surface, an average distance between centers of high Mn regions adjacent to each other is 1.00 mm or less, a density DA of the high Mn regions at a sheet width center portion and a density DB of the high Mn regions at a ¼ position from a sheet width end portion satisfy a relationship of 0.77?DA/DB?1.30, a ratio of an average hardness of the high Mn regions to an average hardness of the low Mn regions is 1.1 to 2.0, and a difference between an average of a top 5% and an average of a bottom 5% of Mn contents in the low Mn regions is 0.3% or more.
    Type: Application
    Filed: April 8, 2020
    Publication date: April 21, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Kohichi SANO, Hiroyuki KAWATA
  • Publication number: 20220119908
    Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition, and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, when there are remaining structures, the remaining structures consist of bainite, a concentration of B atoms at prior austenite grain boundaries is 2.0 atm % or more, and an average effective crystal grain size is 7.0 ?m or less, and a method for producing the same.
    Type: Application
    Filed: February 6, 2020
    Publication date: April 21, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Takafumi YOKOYAMA, Hiroyuki KAWATA, Kunio HAYASHI, Yuji YAMAGUCHI, Satoshi UCHIDA
  • Publication number: 20220112569
    Abstract: A steel sheet includes, as a chemical composition, by mass %: C: 0.0015% to 0.0400%; Mn: 0.20% to 1.50%; P: 0.010% to 0.100%; Cr: 0.001% to 0.500%; Si: 0.200% or less; S: 0.020% or less; sol. Al: 0.200% or less; N: 0.0150% or less; Mo: 0% to 0.500%; B: 0% to 0.0100%; Nb: 0% to 0.200%; Ti: 0% to 0.200%; Ni: 0% to 0.200%; Cu: 0% to 0.100%; and a remainder including iron and impurities, in which a metallographic structure in a surface layer region includes ferrite having a volume fraction of 90% or more, and in the surface layer region, an average grain size of the ferrite is 1.0 ?m to 15.0 ?m, and a texture in which an XODF{001}/{111}, S as a ratio of an intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.30 or more and less than 3.50 is included.
    Type: Application
    Filed: January 7, 2020
    Publication date: April 14, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Masahiro KUBO, Hiroyuki KAWATA, Kenichiro OTSUKA, Masafumi AZUMA
  • Publication number: 20220090248
    Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined composition and contains ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, remaining structures consist of bainite, when defining a region having a hardness of 90% or less of the hardness at a position of ¼ thickness to the base steel sheet side from an interface of the base steel sheet and a hot dip galvanized layer as a “soft layer”, there is a soft layer having a thickness of 10 ?m or more at the base steel sheet side from the interface, the soft layer contains tempered martensite, and an increase rate in a thickness direction of an area % of tempered martensite from the interface to the inside of the base steel sheet inside the soft layer is 5.0%/pm or less, and a method for producing the same.
    Type: Application
    Filed: February 6, 2020
    Publication date: March 24, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Takafumi YOKOYAMA, Hiroyuki KAWATA, Kunio HAYASHI, Yuji YAMAGUCHI, Satoshi UCHIDA
  • Patent number: 11274356
    Abstract: A steel sheet having a chemical composition of the base metal including, in mass %, C: 0.17 to 0.40%, Si: 0.10 to 2.50%, Mn: 1.00 to 10.00%, P: 0.001 to 0.03%, S: 0.0001 to 0.02%, Al: 0.001 to 2.50%, N: 0.0001 to 0.010%, O: 0.0001 to 0.010%, Ti: 0 to 0.10%, Nb: 0 to 0.10%, V: 0 to 0.10%, B: 0 to 0.010%, Cr: 0 to 2.00%, Ni: 0 to 2.00%, Cu: 0 to 2.00%, Mo: 0 to 2.00%, Ca: 0 to 0.50%, Mg: 0 to 0.50%, REM: 0 to 0.50%, the balance: Fe and impurities, wherein the steel sheet has an internal oxidized layer in which at least one part of a crystal grain boundary is covered by oxides, and in which a grain boundary coverage ratio of oxides is 60% or more in a region from the surface of the base metal to a depth of 5.0 ?m.
    Type: Grant
    Filed: December 15, 2017
    Date of Patent: March 15, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Kengo Takeda, Kunio Hayashi, Akihiro Uenishi, Hiroyuki Kawata, Chisato Yoshinaga, Yasunobu Miyazaki, Toyomitsu Nakamura
  • Publication number: 20220074015
    Abstract: A steel sheet has a predetermined chemical composition, in which a metallographic structure in a surface layer region ranging from a surface to a position of 20 ?m from the surface in a sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 1.0% to 15.0%, the metallographic structure in an internal region ranging from a position of more than 20 ?m from the surface in the sheet thickness direction to a ¼ thickness position from the surface in the sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 5.0% to 25.0%, the volume fraction of the secondary phase in the surface layer region is less than the volume fraction of the secondary phase in the internal region, and in the surface layer region, the average grain size of the secondary phase is 0.5 ?m to 4.0 ?m, and a texture in which an XODF{001}/{111} as the ratio of the intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.70 to 2.
    Type: Application
    Filed: January 7, 2020
    Publication date: March 10, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Masahiro KUBO, Hiroyuki KAWATA, Masahiro SAITO, Kenichiro OTSUKA, Masafumi AZUMA
  • Publication number: 20220064771
    Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 6% to 30%, bainite: 5% or more, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, a number density of tempered martensite with a circle equivalent diameter of 5.0 ?m or more is 20/1000 ?m2 or less, and an area ratio of fresh martensite with a circle equivalent diameter of 2.0 ?m or more after imparting 5% plastic strain is 10% or less, and a method for producing the same.
    Type: Application
    Filed: February 6, 2020
    Publication date: March 3, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Takafumi YOKOYAMA, Hiroyuki KAWATA, Kunio HAYASHI, Yuji YAMAGUCHI, Satoshi UCHIDA
  • Publication number: 20220063245
    Abstract: High strength steel sheet improved in formability, bending load, and bendability is provided. The high strength steel sheet has a center part of sheet thickness and a surface soft part formed at one side or two sides of the center part of sheet thickness, has metal structures of the center part of sheet thickness comprised of, by area ratio, tempered martensite: 85% or more, one or more of ferrite, bainite, pearlite, and retained austenite: total of less than 15%, and as-quenched martensite: less than 5%, has metal structures of the surface soft part comprised of, by area ratio, ferrite: 65% or more, pearlite: 5% or more and less than 20%, one or more of tempered martensite, bainite, and retained austenite: total of less than 10%, and as-quenched martensite: less than 5%, has average distances of pearlite at the surface soft part of 3 ?m or more, and has Vickers hardness (Hc) of the center part of sheet thickness and Vickers hardness (Hs) of the surface soft part satisfying 0.50?Hs/Hc?0.75.
    Type: Application
    Filed: March 16, 2020
    Publication date: March 3, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Katsuya NAKANO, Kengo TAKEDA, Hiroyuki KAWATA
  • Patent number: 11225701
    Abstract: A hot dip galvanized steel sheet and hot dip galvannealed steel sheet improved in uniform ductility and local ductility, yield strength and tensile strength, and low temperature impact property, characterized by having a predetermined chemical composition, having a metal structure containing, by volume %, retained austenite: over 5.0% and tempered martensite: over 5.0%, having retained austenite containing C: 0.85 mass % or more, and having a ratio [C]?gb/[P]?gb of an amount of segregation of C (number of atoms/nm2): [C]?gb to an amount of segregation of P (number of atoms/nm2): [P]?gb at prior austenite grain boundaries of 4.0 or more.
    Type: Grant
    Filed: March 30, 2018
    Date of Patent: January 18, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Jun Haga, Kohichi Sano, Koutarou Hayashi, Kunio Hayashi, Masaharu Kameda, Akihiro Uenishi, Hiroyuki Kawata