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: 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: 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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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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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
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Publication number: 20230220510Abstract: 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: ApplicationFiled: June 30, 2021Publication date: July 13, 2023Applicant: JFE STEEL CORPORATIONInventors: Shinsuke KOMINE, Tatsuya NAKAGAITO, Kentaro SATO, Tomohiro SAKAIDANI
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Publication number: 20230160032Abstract: A steel sheet having a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, 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: ApplicationFiled: March 25, 2021Publication date: May 25, 2023Applicant: JFE STEEL CORPORATIONInventors: Lingling YANG, Yoshiyasu KAWASAKI, Hidekazu MINAMI, Tatsuya NAKAGAITO, Shotaro TERASHIMA, Shunsuke YAMAMOTO, Katsuya HOSHINO, Yuki TAKEDA
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Publication number: 20230151451Abstract: A steel sheet with a tensile strength (TS) of 1180 MPa or more, a member, and a method for producing them. In a region of the steel sheet within 4.9 ?m in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 ?m or more. 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 the following formula (1): LSi+LMn?(TSi+TMn)/4??(1).Type: ApplicationFiled: March 25, 2021Publication date: May 18, 2023Applicant: JFE STEEL CORPORATIONInventors: Yoshiyasu KAWASAKI, Lingling YANG, Shotaro TERASHIMA, Tatsuya NAKAGAITO, Shunsuke YAMAMOTO, Katsuya HOSHINO, Yuki TAKEDA
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Patent number: 11643701Abstract: The high-strength hot-dip galvanized steel sheet, which includes a hot-dip galvanized coating layer on a surface of the steel sheet, has a component composition containing, in mass %, C: 0.07% to 0.20%, Si: 0.1% to 2.0%, Mn: 2.0% to 3.5%, P: 0.05% or less, S: 0.05% or less, and sol. Al: 0.005% to 0.1%, with the balance being Fe and incidental impurities; and has a steel microstructure containing, in area fraction, 60% or less of ferrite, 40% or more of tempered martensite, and 10% or less of fresh martensite and having a void number density of 1,500/mm2 or less in a bent portion in the VDA bending test.Type: GrantFiled: October 18, 2019Date of Patent: May 9, 2023Assignee: JFE STEEL CORPORATIONInventors: Shinsuke Komine, Tatsuya Nakagaito, Kentaro Sato, Tomohiro Sakaidani
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Publication number: 20230127243Abstract: 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: ApplicationFiled: March 25, 2021Publication date: April 27, 2023Applicant: JFE STEEL CORPORATIONInventors: Lingling YANG, Yoshiyasu KAWASAKI, Tatsuya NAKAGAITO, Shotaro TERASHIMA, Shunsuke YAMAMOTO, Katsuya HOSHINO, Yuki TAKEDA
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Publication number: 20230129828Abstract: A steel sheet with a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, a member, and a method for producing them. In a region of the steel sheet within 4.9 ?m in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 ?m or more. The lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m 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 the following formula (1): LSi+LMn?(TSi+TMn)/4??(1).Type: ApplicationFiled: March 25, 2021Publication date: April 27, 2023Applicant: JFE STEEL CORPORATIONInventors: Yoshiyasu KAWASAKI, Lingling YANG, Shotaro TERASHIMA, Hidekazu MINAMI, Tatsuya NAKAGAITO, Shunsuke YAMAMOTO, Katsuya HOSHINO, Yuki TAKEDA
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Publication number: 20230072557Abstract: A steel sheet according to the present invention has a specific chemical composition and a steel microstructure including, in terms of area fraction, ferrite: 20% or more and 60% or less, a total of bainite and tempered martensite: 25% or more and 60% or less, retained austenite: 7% or more and 20% or less, fresh martensite: 8% or more and 40% 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 980 MPa or more.Type: ApplicationFiled: February 24, 2021Publication date: March 9, 2023Applicant: JFE Steel CorporationInventors: Yusuke Wada, Tatsuya Nakagaito, Shotaro Terashima, Lingling Yang, Takeshi Yokota
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Patent number: 11560614Abstract: A high-strength galvanized steel sheet includes a steel sheet having a chemical composition containing a predetermined component element, a mass ratio of a content of Si to a content of Mn in the steel (Si/Mn) being 0.1 or more and less than 0.2, and the balance: Fe and incidental impurities, and a steel structure in which an average grain size of inclusions containing at least one of Al, Si, Mg, and Ca and existing in an area extending from a surface to a position of ? of a sheet thickness is 50 ?m or less, and an average nearest distance between ones of the inclusions is 20 ?m or more; and a galvanized layer provided on a surface of the steel sheet, in which an amount of diffusible hydrogen contained in the steel is less than 0.25 mass ppm, and a tensile strength is 1100 MPa or more.Type: GrantFiled: March 29, 2019Date of Patent: January 24, 2023Assignee: JFE Steel CorporationInventors: Hiromi Yoshitomi, Masaki Koba, Tatsuya Nakagaito, Yoshitsugu Suzuki