Patents by Inventor Kunio Hayashi

Kunio Hayashi 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: 20220259692
    Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which a microstructure contains, by area %, bainite: 80.0% or more, ferrite: 10.0% or less, and a remainder in the microstructure: 10.0% or less, a total density of a length L7 of a grain boundary having a crystal orientation difference of 7° and a length L68 of a grain boundary having a crystal orientation difference of 68° about a <110> direction in the bainite is 0.35 to 0.60 ?m/?m2, and a tensile strength is 780 MPa or more.
    Type: Application
    Filed: October 12, 2020
    Publication date: August 18, 2022
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Shohei YABU, Kunio HAYASHI, Koutarou HAYASHI, Kazumasa TSUTSUI
  • Patent number: 11408046
    Abstract: High strength steel sheet having a tensile strength of 800 MPa or more comprising a middle part in sheet thickness and a soft surface layer arranged at one side or both sides of the middle part in sheet thickness, wherein each soft surface layer has a thickness of more than 10 ?M and 30% or less of the sheet thickness, the soft surface layer has an average Vickers hardness of more than 0.60 time and 0.90 time or less the average Vickers hardness of the sheet thickness 1/2 position, and the soft surface layer has a nano-hardness standard deviation of 0.8 or less is provided.
    Type: Grant
    Filed: February 20, 2018
    Date of Patent: August 9, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Yuya Suzuki, Katsuya Nakano, Genki Abukawa, Kunio Hayashi
  • Patent number: 11332803
    Abstract: A high-strength hot-dip galvanized steel sheet contains predetermined amounts of C, Si, Mn, P, S, N, O, sol. Al, Ti, and B, 0.1 to 1.5 mass % of Cr+2×Mo, and a balance in a form of Fe and inevitable impurities. A steel structure includes, in area %, ferrite: 1 to 50%, martensite: 20 to 70%, residual austenite: 0 to 5%, pearlite: 0 to 5%, MA and cementite having 0.2 ?m or more grain size: 0 to 5% in total, and a balance in a form of bainite. A number density of MA or cementite having 0.2 ?m or more grain size and isolated in ferrite or bainite grains is 100 pcs/1000 ?m2 or less, and an average hardness of martensite is in a range from 330 to 500 Hv.
    Type: Grant
    Filed: March 22, 2018
    Date of Patent: May 17, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Takafumi Yokoyama, Yuji Yamaguchi, Masahiro Nakata, Kunio Hayashi, Satoshi Uchida, Takuma Kawanaka
  • 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: 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: 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: 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
  • Patent number: 11261505
    Abstract: High strength steel sheet having a tensile strength of 800 MPa or more comprising a middle part in sheet thickness and a soft surface layer arranged at one side or both sides of the middle part in sheet thickness, wherein each soft surface layer has a thickness of more than 10 ?m and 30% or less of the sheet thickness, the soft surface layer has an average Vickers hardness of 0.60 time or less the average Vickers hardness of the sheet thickness ½ position, and the soft surface layer has a nano-hardness standard deviation of 0.8 or less is provided.
    Type: Grant
    Filed: February 20, 2018
    Date of Patent: March 1, 2022
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Katsuya Nakano, Yuya Suzuki, Genki Abukawa, Kunio Hayashi
  • 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
  • Patent number: 11208705
    Abstract: A high-strength cold-rolled steel sheet which is a steel sheet having a tensile strength of 980 MPa or more has a predetermined chemical component composition, a metallographic microstructure of the steel sheet contains, by area ratio, ferrite and granular bainite: 10% or more and 50% or less in total, one or both of upper bainite and lower bainite: 10% or more and 50% or less in total, tempered martensite: more than 0% and 30% or less, retained austenite: 5% or more, and one or more of pearlite, cementite, and martensite: 0% to 10% in total, and an area ratio of the ferrite with respect to a total area ratio of the ferrite and the granular bainite is 25% or less.
    Type: Grant
    Filed: November 15, 2017
    Date of Patent: December 28, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Yuri Toda, Kunio Hayashi, Katsuya Nakano, Eisaku Sakurada, Akihiro Uenishi, Kengo Takeda
  • Publication number: 20210230712
    Abstract: A zinc-plated steel sheet of an aspect of the present invention includes a steel sheet having a predetermined chemical composition and a zinc-plated layer. In the steel sheet, steel microstructures in a range of ? thickness to ? thickness, having the center at ¼ thickness from a steel sheet surface, include, by vol %, ferrite: 0% to 10%, bainite: 0% to 20%, tempered martensite: 70% or more, fresh martensite: 0% to 10%, retained austenite: 0% to 10%, and pearlite: 0% to 5%. In the zinc-plated steel sheet, the amount of hydrogen emitted when the steel sheet is heated to 200° C. from a room temperature after removal of the zinc-plated layer is 0.40 ppm or less per mass of the steel sheet, the tensile strength is 1470 MPa or more, and no cracking occurs in a U-shape bending test where a stress equivalent to 1000 MPa is applied for 24 hours.
    Type: Application
    Filed: April 26, 2019
    Publication date: July 29, 2021
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Takafumi YOKOYAMA, Kunio HAYASHI, Masahiro NAKATA, Yuji YAMAGUCHI, Satoshi UCHIDA
  • Patent number: 11028469
    Abstract: A hot press-formed part according to an aspect of the present invention contains a predetermined chemical composition; in which a microstructure in a thickness ¼ portion includes, by unit vol %, tempered martensite: 20% to 90%, bainite: 5% to 75%, and residual austenite: 5% to 25%, and ferrite is limited to 10% or less; and a pole density of an orientation {211}<011> in the thickness ¼ portion is 3.0 or higher.
    Type: Grant
    Filed: August 16, 2016
    Date of Patent: June 8, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Mutsumi Sakakibara, Natsuko Sugiura, Kunio Hayashi, Kaoru Kawasaki
  • Patent number: 11027522
    Abstract: A steel sheet for hot stamping includes a steel structure represented by an area fraction of bainite, fresh martensite and tempered martensite: 80% or more in total, and a product of a number density (pieces/?m2) of carbides and a proportion of carbides precipitated into prior austenite grains in carbides: 0.50 or more.
    Type: Grant
    Filed: January 17, 2017
    Date of Patent: June 8, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Genki Abukawa, Kunio Hayashi, Kazuo Hikida, Kaoru Kawasaki
  • Publication number: 20210155999
    Abstract: A zinc-plated steel sheet of an aspect of the present invention includes a steel sheet having a predetermined chemical composition and a zinc-plated layer. In the steel sheet, steel microstructures in a range of ? thickness to ? thickness, having the center at ¼ thickness from a steel sheet surface, include, by vol %, ferrite: 0% to 10%, bainite: 0% to 30%, tempered martensite: 50% or more, fresh martensite: 0% to 10%, retained austenite: more than 10% and 30% or less, and pearlite: 0% to 5%. In the zinc-plated steel sheet, the amount of hydrogen emitted when the steel sheet is heated to 200° C. from room temperature after removal of the zinc-plated layer is 0.40 ppm or less per mass of the steel sheet, the tensile strength is 1470 MPa or more, and no cracking occurs in a U-shape bending test where a stress equivalent to 1000 MPa is applied for 24 hours.
    Type: Application
    Filed: April 26, 2019
    Publication date: May 27, 2021
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Takafumi YOKOYAMA, Kunio HAYASHI, Masahiro NAKATA, Yuji YAMAGUCHI, Satoshi UCHIDA
  • Patent number: 11007598
    Abstract: The present invention provides a spot welding method for a member to be welded constituted of a plurality of steel sheets that are overlapped with each other at at least a welding zone, in which at least an overlapped face of at least one of the plurality of steel sheets at the welding zone is coated with zinc plating, a total sheet thickness t (mm) of the plurality of steel sheets is 1.35 mm or more, a squeeze time St (seconds) from the time when welding electrodes are brought into contact with the member to be welded to the time when electric current flow for welding starts satisfies “0.020?St”, and a hold time Ht( seconds) after welding from the time when electric current flow for welding between the welding electrodes ends to the time when the welding electrodes and the member to be welded are brought out of contact satisfies “0.015t2+0.020?Ht”.
    Type: Grant
    Filed: September 2, 2016
    Date of Patent: May 18, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Chisato Yoshinaga, Yasunobu Miyazaki, Kunio Hayashi, Hiroyuki Kawata, Masanori Yasuyama
  • Publication number: 20210040588
    Abstract: A steel sheet has a predetermined chemical composition and a metal structure represented by, in area fraction, polygonal ferrite: 40% or less, martensite: 20% or less, bainitic ferrite: 50% to 95%, and retained austenite: 5% to 50%. In area fraction, 80% or more of the bainitic ferrite is composed of bainitic ferrite grains that have an aspect ratio of 0.1 to 1.0 and have a dislocation density of 8×102 (cm/cm3) or less in a region surrounded by a grain boundary with a misorientation angle of 15° or more. In area fraction, 80% or more of the retained austenite is composed of retained austenite grains that have an aspect ratio of 0.1 to 1.0, have a major axis length of 1.0 ?m to 28.0 ?m, and have a minor axis length of 0.1 ?m to 2.8 ?m.
    Type: Application
    Filed: March 30, 2018
    Publication date: February 11, 2021
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Yuri TODA, Eisaku SAKURADA, Kunio HAYASHI, Akihiro UENISHI
  • Patent number: 10907235
    Abstract: A steel sheet according to an aspect of the present invention has a chemical composition within a predetermined range; in which a metallographic structure at a thickness ¼ portion includes, by unit area %, ferrite: 10% or more and less than 50%, granular bainite: 5% or more and less than 50%, and martensite: 20% or more and less than 60%; in the metallographic structure at the thickness ¼ portion, a total of upper bainite, lower bainite, residual austenite, and pearlite is 0% or more and less than 15% by unit area %; at the thickness ¼ portion, a product of an area ratio Vm of the martensite and an average hardness Hv of the martensite is 12,000 to 34,000; and a tensile strength is 980 MPa or higher.
    Type: Grant
    Filed: September 13, 2016
    Date of Patent: February 2, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Yuri Toda, Kunio Hayashi, Katsuya Nakano, Hiroyuki Kawata, Akihiro Uenishi
  • Publication number: 20210017622
    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: Application
    Filed: March 30, 2018
    Publication date: January 21, 2021
    Applicant: NIPPON STEEL CORPORATION
    Inventors: Jun HAGA, Kohichi SANO, Koutarou HAYASHI, Kunio HAYASHI, Masaharu KAMEDA, Akihiro UENISHI, Hiroyuki KAWATA
  • Patent number: 10895002
    Abstract: A steel sheet includes a predetermined chemical composition and a metal structure represented by, in area fraction, ferrite: 30% to 50%, granular bainite: 5% to 20%, martensite: 30% to 55%, bainite: less than 35%, and retained austenite and pearlite: 10% or less in total. Preferably, of the steel sheet, a tensile strength is 1180 MPa or more, elongation is 10% or more, and a hole expansion value is 20% or more. Further preferably, a VDA bending angle in the case where a thickness is set to t (mm) is “7.69t2?38.4t+109” or more.
    Type: Grant
    Filed: January 30, 2017
    Date of Patent: January 19, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Katsuya Nakano, Kunio Hayashi, Yuri Toda, Eisaku Sakurada, Akihiro Uenishi