Patents by Inventor Tatsuya Nakagaito
Tatsuya Nakagaito 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).
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Publication number: 20250003021Abstract: A steel sheet having high strength, excellent ductility, high YR, and excellent bendability is provided. The steel sheet includes a defined chemical composition, the steel microstructure includes: area ratio of ferrite: 5% or more and 65% or less, area ratio of martensite: 10% or more and 60% or less, area ratio of bainite: 10% or more and 60% or less, and area ratio of retained austenite: 5% or more. The relationship in the following Formula (1) is satisfied. Average solute C concentration of the retained austenite [C]? is 0.5 mass % or more, and standard deviation of C concentration distribution in the retained austenite is 0.250 mass % or less. [ Mn ] ? ? / [ Mn ] ? 1.Type: ApplicationFiled: October 14, 2022Publication date: January 2, 2025Applicant: JFE STEEL CORPORATIONInventors: Katsuya HATA, Shotaro TERASHIMA, Tatsuya NAKAGAITO, Seisuke TSUDA
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Patent number: 12157923Abstract: A high-strength hot-dip galvanized steel sheet includes a hot-dip galvanized layer on a surface of the steel sheet and has a specific component composition and a steel microstructure containing, on an area percentage basis, 90% to 100% of martensite and carbide-containing bainite in total and 0% to 10% of retained austenite, and containing prior austenite grains having an aspect ratio of 2.0 or less, in a region extending from 300 ?m to 400 ?m from the surface layer, in which the ratio of the average amount of C at 5 ?m from the surface layer to the average amount of C at 70 ?m from the surface layer is 0.2 to 0.8, and the ratio of the standard deviation of the amount of C to the average amount of C in a region extending from 300 ?m to 400 ?m from the surface layer is 0.40 or less.Type: GrantFiled: August 23, 2019Date of Patent: December 3, 2024Assignee: JFE Steel CorporationInventors: Hiroshi Hasegawa, Hidekazu Minami, Tatsuya Nakagaito
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Patent number: 12139771Abstract: A high-strength steel sheet that has a predetermined component composition, that has a steel microstructure in which an area percentage of ferrite ranges from 5% to 50% in a thickness cross-section in a rolling direction, a total area percentage of fresh martensite and retained ? ranges from 2% to 30%, each of the fresh martensite and the retained ? has an average grain size of 5 ?m or less, and a ratio of the fresh martensite and the retained ? adjacent only to ferrite with respect to the fresh martensite and the retained ? from a surface to 200 ?m in the thickness direction is 30% or less in total area percentage, and that has a yield strength of 550 MPa or more.Type: GrantFiled: October 18, 2019Date of Patent: November 12, 2024Assignee: JFE Steel CorporationInventors: Lingling Yang, Tatsuya Nakagaito, Yuki Takeda
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Patent number: 12116649Abstract: The high-strength hot-dip galvanized steel sheet has a specific chemical composition and the following steel microstructure. In a region extending from 300 to 400 ?m from a surface layer of the steel sheet in a thickness direction of the steel sheet, the total area fraction of martensite and bainite containing carbides is 60 to 100%, and the average grain size of prior austenite is 15 ?m or less. In the region extending from 300 to 400 ?m from the surface layer of the steel sheet in the thickness direction of the steel sheet, the ratio of the height of a peak of P in an Auger electron spectrum at a position 5 nm or more from a prior-austenite grain boundary to the height of a peak of P in an Auger electron spectrum at the prior-austenite grain boundary is 0.20 or more.Type: GrantFiled: August 23, 2019Date of Patent: October 15, 2024Assignee: JFE Steel CorporationInventors: Hiroshi Hasegawa, Tatsuya Nakagaito, Yuki Takeda
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Publication number: 20240318287Abstract: A galvanized steel sheet combining high strength with excellent formability, specifically, excellent ductility, hole expansion formability, local ductility, strain hardenability, and dimensional accuracy when forming a member. The base steel sheet has a defined chemical composition and a steel microstructure as follows: ferrite area ratio: 35.0% or more and 95.0% or less, bainitic ferrite area ratio: 1.0% or more and 40.0% or less, tempered martensite area ratio: 50.0% or less (including 0%), retained austenite area ratio: 1.5% or more, fresh martensite area ratio: 20.0% or less (including 0 %), SBF+STM+2×SMA: 10.0% or more and less than 65.0%, SBF+STM: 3.0 % or more and 60.0% or less, SMA1/SMA: 0.40 or less, IDR [% C?]: 0.16% or more, and tensile strength: 590 MPa or more and less than 980 MPa.Type: ApplicationFiled: March 18, 2022Publication date: September 26, 2024Applicant: JFE STEEL CORPORATIONInventors: Sho HIGUCHI, Yoshiyasu KAWASAKI, Tatsuya NAKAGAITO, Takako YAMASHITA, Tomomi KANAZAWA, Shunsuke YAMAMOTO
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Patent number: 12098439Abstract: A steel sheet having a tensile strength (TS) of 1180 MPa or more, high LME resistance, and good weld fatigue properties. The steel sheet has a specific chemical composition and a specific steel microstructure. Crystal grains containing an oxide of Si and/or Mn in a region within 4.9 ?m in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 ?m, the lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy a specified formula.Type: GrantFiled: March 25, 2021Date of Patent: September 24, 2024Assignee: JFE STEEL CORPORATIONInventors: Lingling Yang, Yoshiyasu Kawasaki, Tatsuya Nakagaito, Shotaro Terashima, Shunsuke Yamamoto, Katsuya Hoshino, Yuki Takeda
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Patent number: 12091723Abstract: A galvanized steel sheet includes: a steel sheet having a chemical composition satisfying an equivalent carbon content Ceq of 0.35% or more and less than 0.60%, and a specified steel microstructure; and a galvanized layer on a surface of the steel sheet. The retained austenite has a solute C content of 0.6% or more by mass, and retained austenite grains with an aspect ratio of less than 2.0 constitute 50% or more of all retained austenite grains. In 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction, an L cross section in a 0 to 50 ?m region from a surface of the steel sheet on a compression side has a number density of voids of 1000/mm2 or less, and the galvanized steel sheet has a tensile strength of 590 MPa or more.Type: GrantFiled: June 30, 2021Date of Patent: September 17, 2024Assignee: JFE STEEL CORPORATIONInventors: Shinsuke Komine, Tatsuya Nakagaito, Kentaro Sato, Tomohiro Sakaidani
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Publication number: 20240229201Abstract: A steel sheet including a chemical composition satisfying an equivalent carbon content of 0.35% or more and less than 0.60% and a steel microstructure with an area fraction of ferrite: 40% to 85%, tempered martensite and bainite: 10% to 55% in total, retained austenite: 3% to 15%, and ferrite, tempered martensite, bainite, and retained austenite: 93% or more in total. A 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction causes a change of 0.50 or more in (a grain size in a thickness direction)/(a grain size in a direction perpendicular to the thickness) of the tempered martensite in an L cross section in a 0- to 50-?m region from a surface of the steel sheet on a compression side, and the steel sheet has a tensile strength of 590 MPa or more.Type: ApplicationFiled: June 30, 2021Publication date: July 11, 2024Applicant: JFE STEEL CORPORATIONInventors: Shinsuke KOMINE, Tatsuya NAKAGAITO, Kentaro SATO, Tomohiro SAKAIDANI
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Publication number: 20240158884Abstract: A clad steel plate having tensile strength (TS) of 780 MPa or more, excellent ductility, bendability, collision resistance, and LME resistance. The clad steel plate having a base metal and a cladding metal on front and back surfaces of the base metal, and the chemical composition and microstructure of the base metal and the cladding metal being appropriately controlled so that the average Vickers hardness (HVL) of the cladding metal is 260 or less, the average Vickers hardness (HVL) of the cladding metal divided by the average Vickers hardness (HVB) of the base metal is 0.80 or less, the boundary roughness between the base metal and the cladding metal is 50 ?m or less at the maximum height Ry, and the number of voids at the boundary between the base metal and the cladding metal is controlled to 20 or fewer per 10 mm length of the boundary.Type: ApplicationFiled: February 28, 2022Publication date: May 16, 2024Applicant: JFE STEEL CORPORATIONInventors: Yoshiyasu KAWASAKI, Yuki TOJI, Tatsuya NAKAGAITO, Shinya YAMAGUCHI, Masayasu UENO, Katsutoshi TAKASHIMA, Tomohiro ONO
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Publication number: 20240150882Abstract: To provide a galvanized steel sheet having high strength, specifically, a tensile strength of 1,150 MPa or more, and excellent resistance spot weldability, a base steel sheet has a defined chemical composition, an amount of diffusible hydrogen in the base steel sheet is 0.20 mass ppm or less, and surface roughness Ra of the galvanized steel sheet is 0.6 ?m or less.Type: ApplicationFiled: February 25, 2022Publication date: May 9, 2024Applicant: JFE STEEL CORPORATIONInventors: Satoshi MAEDA, Hiromi YOSHITOMI, Masaki KOBA, Nao KAWABE, Tatsuya NAKAGAITO, Katsuya HOSHINO, Hiroshi MATSUDA
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Publication number: 20240150876Abstract: A clad steel plate having tensile strength (TS) of 780 MPa or more, excellent bendability, collision resistance, and LME resistance. The clad steel plate having a base metal and a cladding metal on front and back surfaces of the base metal, and the chemical composition and microstructure of the base metal and the cladding metal being appropriately controlled so that the average Vickers hardness (HVL) of the cladding metal is 260 or less, the average Vickers hardness (HVL) of the cladding metal divided by the average Vickers hardness (HVB) of the base metal is 0.80 or less, the boundary roughness between the base metal and the cladding metal is 50 ?m or less at the maximum height Ry, and the number of voids at the boundary between the base metal and the cladding metal is controlled to 20 or fewer per 10 mm length of the boundary.Type: ApplicationFiled: February 28, 2022Publication date: May 9, 2024Applicant: JFE STEEL CORPORATIONInventors: Yoshiyasu KAWASAKI, Yuki TOJI, Tatsuya NAKAGAITO, Shinya YAMAGUCHI, Masayasu UENO, Katsutoshi TAKASHIMA, Tomohiro ONO
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Patent number: 11976341Abstract: A steel sheet including a chemical composition satisfying an equivalent carbon content of 0.60% or more and less than 0.85%, and a steel microstructure with an area fraction of ferrite: less than 40%, tempered martensite and bainite: 40% or more in total, retained austenite: 3% to 15%, and ferrite, tempered martensite, bainite, and retained austenite: 93% or more in total. A 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction causes a change of 0.40 or more in (a grain size in a thickness direction)/(a grain size in a direction perpendicular to the thickness) of the tempered martensite in an L cross section in a 0- to 50-?m region from a surface of the steel sheet on a compression side. The steel sheet has a tensile strength of 980 MPa or more.Type: GrantFiled: June 30, 2021Date of Patent: May 7, 2024Assignee: JFE STEEL CORPORATIONInventors: Shinsuke Komine, Tatsuya Nakagaito, Kentaro Sato, Tomohiro Sakaidani
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Publication number: 20240124964Abstract: Provided is a galvanized steel sheet having a TS of 980 MPa or more, high YS, excellent ductility, strain hardenability, and hole expansion formability. A base steel sheet has a defined chemical composition and a steel microstructure as follows: area ratio of ferrite: 65.0% or less (including 0%), area ratio of bainitic ferrite: 5.0% or more and 40.0% or less, area ratio of tempered martensite: 0.5% or more and 80.0% or less, area ratio of retained austenite: 3.0% or more, area ratio of fresh martensite: 20.0% or less (including 0%), SBF+STM+2×SMA: 65.0% or more, SMA1/SMA: 0.80 or less, and SMA2/SMA: 0.20 or more.Type: ApplicationFiled: March 18, 2022Publication date: April 18, 2024Applicant: JFE STEEL CORPORATIONInventors: Sho HIGUCHI, Yoshiyasu KAWASAKI, Tatsuya NAKAGAITO, Tomomi KANAZAWA, Shunsuke YAMAMOTO
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Publication number: 20240035105Abstract: Provided is a hot-dip galvanized steel sheet having both high strength and good workability, as well as excellent coating quality. The chemical composition of the base steel sheet is set within a specified range, the steel microstructure of the base steel sheet is a complex structure of ferrite, martensite and bainite, oxygen is present as oxides in the surface layer of the base steel sheet in an amount of 0.05 g/m2 or more and 0.50 g/m2 or less per surface, and the hot-dip galvanized layer contains Fe in an amount of 0.40 mass % or more.Type: ApplicationFiled: December 15, 2021Publication date: February 1, 2024Applicant: JFE STEEL CORPORATIONInventors: Takuya HIRASHIMA, Tatsuya NAKAGAITO, Masaki KOBA, Yoichi MAKIMIZU, Katsuya HATA, Shotaro TERASHIMA
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Publication number: 20240026481Abstract: Provided is a steel sheet having excellent workability while ensuring excellent strength. The steel sheet comprises: a predetermined chemical composition; and a steel microstructure that contains ferrite: 45% to 90%, martensite: 5% to 30%, bainite: 1% to 25%, and retained austenite: 3% or more and in which [Mn]M/[Mn] is 1.00 to 1.15 and [Mn]M/[Mn]F is 1.00 to 1.30, wherein TS×El is 16000 MPa·% or more.Type: ApplicationFiled: December 15, 2021Publication date: January 25, 2024Applicant: JFE STEEL CORPORATIONInventors: Takuya HIRASHIMA, Tatsuya NAKAGAITO, Masaki KOBA, Kyoko NAITO, Seisuke TSUDA, Katsuya HATA, Shotaro TERASHIMA
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Publication number: 20230349019Abstract: A steel sheet according to the present invention has a specific chemical composition and a steel microstructure including, in terms of area fraction, ferrite: 60% or more and 85% or less, bainite: 3% or more and 15% or less, retained austenite: 3% or more and 15% or less, fresh martensite: 3% or more and 15% or less, and the remainder: 5% or less. Cementite particles are present in the retained austenite, a ratio of an area fraction of the cementite particles in the retained austenite to an area fraction of the retained austenite is 5% or more and 25% or less, and the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa.Type: ApplicationFiled: February 24, 2021Publication date: November 2, 2023Applicant: JFE Steel CorporationInventors: Yusuke Wada, Tatsuya Nakagaito, Shotaro Terashima, Lingling Yang, Takeshi Yokota, Shunsuke Yamamoto, Yuki Takeda
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Publication number: 20230349020Abstract: A steel sheet according to the present invention has a specific chemical composition and a steel microstructure including, in terms of area fraction, ferrite: 40% or more and 70% or less, a total of bainite and tempered martensite: 5% or more and 30% or less, retained austenite: 4% or more and 18% or less, fresh martensite: 8% or more and 35% or less, and the remainder: 5% or less. Cementite particles are present in the retained austenite, a ratio of an area fraction of the cementite particles in the retained austenite to an area fraction of the retained austenite is 5% or more and 25% or less, and the steel sheet has a tensile strength of 780 MPa or more and less than 980 MPa.Type: ApplicationFiled: February 24, 2021Publication date: November 2, 2023Applicant: JFE Steel CorporationInventors: Yusuke Wada, Tatsuya Nakagaito, Shotaro Terashima, Lingling Yang, Takeshi Yokota
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Patent number: 11795531Abstract: A high-strength galvanized steel sheet of the present invention includes a steel sheet having a specific chemical composition, and a steel structure containing, in terms of area ratio, 4% or more and 20% or less of retained austenite, 30% or less (including 0%) of ferrite, 40% or more of martensite, and 10% or more and 50% or less of bainite; and a galvanized layer provided on the steel sheet, in which an amount of diffusible hydrogen in the steel is less than 0.20 mass ppm, a tensile strength is 1100 MPa or more, a relationship between a tensile strength TS (MPa), an elongation El (%), and a sheet thickness t (mm) satisfies a (1) formula below, and a yield ratio YR is 67% or more. TS×(El+3?2.Type: GrantFiled: March 29, 2019Date of Patent: October 24, 2023Assignee: JFE Steel CorporationInventors: Hiromi Yoshitomi, Yoshihiko Ono, Tatsuya Nakagaito
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Publication number: 20230287553Abstract: A galvanized steel sheet including a steel sheet having a chemical composition with an equivalent carbon content Ceq of 0.60% or more and less than 0.85%, and a specified steel microstructure; and a galvanized layer on a surface of the steel sheet. The retained austenite has a solute C content of 0.6% or more by mass, and retained austenite grains with an aspect ratio of less than 2.0 constitute 50% or more of all retained austenite grains. In 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction, an L cross section in a 0- to 50-µm region from a surface of the steel sheet on a compression side has a number density of voids of 1500 /mm2 or less, and the galvanized steel sheet has a tensile strength of 980 MPa or more.Type: ApplicationFiled: June 30, 2021Publication date: September 14, 2023Applicant: JFE STEEL CORPORATIONInventors: Shinsuke KOMINE, Tatsuya NAKAGAITO, Kentaro SATO, Tomohiro SAKAIDANI
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Publication number: 20230243014Abstract: A galvanized steel sheet includes: a steel sheet having a chemical composition satisfying an equivalent carbon content Ceq of 0.35% or more and less than 0.60%, and a specified steel microstructure; and a galvanized layer on a surface of the steel sheet. The retained austenite has a solute C content of 0.6% or more by mass, and retained austenite grains with an aspect ratio of less than 2.0 constitute 50% or more of all retained austenite grains. In 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction, an L cross section in a 0 to 50 ?m region from a surface of the steel sheet on a compression side has a number density of voids of 1000/mm2 or less, and the galvanized steel sheet has a tensile strength of 590 MPa or more.Type: ApplicationFiled: June 30, 2021Publication date: August 3, 2023Applicant: JFE STEEL CORPORATIONInventors: Shinsuke KOMINE, Tatsuya NAKAGAITO, Kentaro SATO, Tomohiro SAKAIDANI