Patents by Inventor Michitaka Sakurai
Michitaka Sakurai 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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Patent number: 11850821Abstract: A hot-pressed member has a predetermined chemical composition. In the hot-pressed member, a steel sheet has a microstructure in which a prior austenite average grain diameter is 8 ?m or less, and martensite is present in a volume fraction of 95% or greater in a region within 30 ?m of a surface; a Ni diffusion region having a thickness of 0.5 ?m or greater exists in a surface layer; a standard deviation of Vickers hardness values is 35 or less; Mndif (mass %) in a sheet thickness direction ?0.20, where Mndif (mass %) is a degree of Mn segregation; and a tensile strength is 1780 MPa or greater.Type: GrantFiled: December 26, 2019Date of Patent: December 26, 2023Assignee: JFE STEEL CORPORATIONInventors: Katsutoshi Takashima, Minoru Tanaka, Kenji Tsuzumi, Shingo Arakawa, Michitaka Sakurai
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Publication number: 20230082367Abstract: To obtain a high-strength hot-dip galvanized steel sheet having excellent surface appearance even in the case where a steel strip containing Mn at a predetermined ratio or more to Si is subjected to hot-dip galvanizing treatment, a method of producing a hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus comprises: subjecting a steel strip to annealing, by conveying it in an annealing furnace; and subjecting the steel strip discharged from a cooling zone to hot-dip galvanizing using a hot-dip galvanizing line, to obtain a hot-dip galvanized steel sheet. The steel strip has a chemical composition containing, in mass %, Mn: 1.7% or more and 3.5% or less and Si: 0.2% or more and 1.05% or less and satisfying [Si]/[Mn]?0.30. The chemical composition, a dew point of an atmosphere in the soaking zone, and a delivery temperature of the heating zone satisfy Formula (1).Type: ApplicationFiled: November 19, 2020Publication date: March 16, 2023Applicant: JFE STEEL CORPORATIONInventors: Shunsuke YAMAMOTO, Shotaro TERASHIMA, Yuki TAKEDA, Michitaka SAKURAI, Katsuya HOSHINO, Yoshiyasu KAWASAKI
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Publication number: 20220186339Abstract: Provided is a hot-pressed member that combines both high strength of 1850 MPa or more in TS and excellent delayed fracture resistance. A hot-pressed member comprises: a predetermined chemical composition; a microstructure in which a prior austenite average grain size is 8 ?m or less, a volume fraction of martensite is 95% or more, and a volume fraction of granular carbide of 0.1 ?m or more in grain size is 0.10% to 4.0%; a Ni diffusion region of 2.0 ?m or more in a depth direction in a surface layer; and a tensile strength of 1850 MPa or more.Type: ApplicationFiled: January 17, 2020Publication date: June 16, 2022Applicant: JFE STEEL CORPORATIONInventors: Katsutoshi TAKASHIMA, Minoru TANAKA, Yoshie OBATA, Michitaka SAKURAI
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Publication number: 20220118741Abstract: A hot-pressed member has a predetermined chemical composition. In the hot-pressed member, a steel sheet has a microstructure in which a prior austenite average grain diameter is 8 ?m or less, and martensite is present in a volume fraction of 95% or greater in a region within 30 ?m of a surface; a Ni diffusion region having a thickness of 0.5 ?m or greater exists in a surface layer; a standard deviation of Vickers hardness values is 35 or less; Mndif (mass %) in a sheet thickness direction ?0.20, where Mndif (mass %) is a degree of Mn segregation; and a tensile strength is 1780 MPa or greater.Type: ApplicationFiled: December 26, 2019Publication date: April 21, 2022Applicant: JFE Steel CorporationInventors: Katsutoshi Takashima, Minoru Tanaka, Kenji Tsuzumi, Shingo Arakawa, Michitaka Sakurai
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Patent number: 11186889Abstract: A high-strength steel sheet contains, in mass %, C: 0.07 to 0.14%, Si: 0.65 to 1.65%, Mn: 1.8 to 2.6%, P: 0.05% or less, S: 0.005% or less, Al: 0.08% or less, N: 0.0060% or less, Ti: 0.005 to 0.030%, B: 0.0002 to 0.0030%, and either or both of Cr: 0.01 to 0.40% and Mo: 0.01 to 0.50% and satisfies the expression (1); where: an average grain size of a ferrite phase is 1.5 ?m or less; an area ratio of the ferrite phase is 2% or more and 15% or less; an area ratio of a tempered martensite phase is 75% or more and 96% or less; and a total length per unit area of an interface between an untempered martensite phase and the ferrite phase and an interface between the untempered martensite phase and the tempered martensite phase is 6.3×108 ?m/m2 to 5.0×1011 ?m/m2.Type: GrantFiled: August 10, 2017Date of Patent: November 30, 2021Assignee: JFE Steel CorporationInventors: Noriaki Kohsaka, Michitaka Sakurai, Yoshikazu Suzuki, Yoshimasa Himei
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Publication number: 20200347473Abstract: A high-strength steel sheet contains, in mass %, C: 0.07 to 0.14%, Si: 0.65 to 1.65%, Mn: 1.8 to 2.6%, P: 0.05% or less, S: 0.005% or less, Al: 0.08% or less, N: 0.0060% or less, Ti: 0.005 to 0.030%, B: 0.0002 to 0.0030%, and either or both of Cr: 0.01 to 0.40% and Mo: 0.01 to 0.50% and satisfies the expression (1); where: an average grain size of a ferrite phase is 1.5 ?m or less; an area ratio of the ferrite phase is 2% or more and 15% or less; an area ratio of a tempered martensite phase is 75% or more and 96% or less; and a total length per unit area of an interface between an untempered martensite phase and the ferrite phase and an interface between the untempered martensite phase and the tempered martensite phase is 6.3×108 ?m/m2 to 5.0×1011 ?m/m2.Type: ApplicationFiled: August 10, 2017Publication date: November 5, 2020Inventors: Noriaki Kohsaka, Michitaka Sakurai, Yoshikazu Suzuki, Yoshimasa Himei
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Patent number: 10590505Abstract: A high-strength steel sheet having a composition containing C: 0.09% to 0.17%, Si: 0.6% to 1.7%, Mn: 3.5% or less, P: 0.03% or less, S: 0.005% or less, Al: 0.08% or less, N: 0.006% or less, Ti: 0.05% or less, and B: 0.0002% to 0.0030% on a mass basis, the remainder being Fe and inevitable impurities. The steel sheet also has a microstructure containing less than 20% (including 0%) of a ferrite phase, 75% or more (including 100%) of a tempered martensite phase, 10% or less (including 0%) of an untempered martensite phase, and less than 5% (including 0%) of a retained austenite phase in terms of area fraction. The tempered martensite phase has a Vickers hardness of 280 to 340 and a tensile strength of 950 MPa to 1,120 MPa.Type: GrantFiled: January 14, 2016Date of Patent: March 17, 2020Assignee: JFE STEEL CORPORATIONInventors: Noriaki Kohsaka, Yoshimasa Funakawa, Michitaka Sakurai, Yoshikazu Suzuki
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Publication number: 20180237880Abstract: A high-strength steel sheet having a composition containing C: 0.09% to 0.17%, Si: 0.6% to 1.7%, Mn: 3.5% or less, P: 0.03% or less, S: 0.005% or less, Al: 0.08% or less, N: 0.006% or less, Ti: 0.05% or less, and B: 0.0002% to 0.0030% on a mass basis, the remainder being Fe and inevitable impurities. The steel sheet also has a microstructure containing less than 20% (including 0%) of a ferrite phase, 75% or more (including 100%) of a tempered martensite phase, 10% or less (including 0%) of an untempered martensite phase, and less than 5% (including 0%) of a retained austenite phase in terms of area fraction. The tempered martensite phase has a Vickers hardness of 280 to 340 and a tensile strength of 950 MPa to 1,120 MPa.Type: ApplicationFiled: January 14, 2016Publication date: August 23, 2018Applicant: JFE STEEL CORPORATIONInventors: Noriaki KOHSAKA, Yoshimasa FUNAKAWA, Michitaka SAKURAI, Yoshikazu SUZUKI
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Patent number: 9816153Abstract: A high strength steel sheet is formed of steel having the composition containing by mass % over 0.015% and less than 0.100% C, less than 0.50% Si, over 1.0% and less than 2.0% Mn, 0.05% or less P, 0.03% or less S, 0.01% or more and 0.3% or less sol. Al, 0.005% or less N, less than 0.35% Cr, 0.0010% or more and 0.0050% or less B, less than 0.15% Mo, less than 0.030% Ti, and iron and unavoidable impurities as a balance, wherein the steel satisfies 2.1?[Mneq]?3.1, the microstructure of the steel includes a ferrite and a second phase, a volume fraction of the second phase is set to 2.0 to 12.0%, a total ratio of a volume fraction of martensite and a volume fraction of retained ? to the volume fraction of second phase is 60% or more, and the number of carbides which are present within ferrite particles, have an aspect ratio of 3.0 or less and have a diameter of 0.25 to 0.90 ?m is set to 10000 pieces/mm2 or less.Type: GrantFiled: September 28, 2011Date of Patent: November 14, 2017Assignee: JFE Steel CorporationInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Yusuke Fushiwaki, Michitaka Sakurai
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Patent number: 9534269Abstract: A method of manufacturing a high strength cold rolled steel sheet includes hot-rolling and cold-rolling a steel slab annealing the steel sheet at an annealing temperature of 750° C. to 830° C.; subjecting the steel sheet to first cooling at an average cooling rate of 3° C./sec to 40° C./sec in a temperature range from the annealing temperature to 480° C.; subjecting the steel sheet to second cooling at an average cooling rate of 8° C./sec to 80° C./sec in a temperature range from 480° C. to Tc (° C.) given by formula (6): Tc=435?40×[% Mn]?30×[% Cr]?30×[% V]??(6) wherein [% A] is the content (% by mass) of alloying element A; and subjecting the steel sheet to third cooling at an average cooling rate of 0.3° C./sec to 30° C./sec in a temperature range from Tc (° C.) to 200° C.Type: GrantFiled: October 21, 2013Date of Patent: January 3, 2017Assignee: JFE Steel CorporationInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Shoichiro Taira, Michitaka Sakurai, Yusuke Fushiwaki
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Patent number: 9255318Abstract: A high-strength galvanized steel sheet has a low YP, good stretch flangeability, and excellent corrosion resistance and contains, on a percent by mass basis, more than 0.015% to less than 0.10% of C, 0.5% or less of Si, 1.0% to 1.9% of Mn, 0.015% to 0.050% of P, 0.03% or less of S, 0.01% to 0.5% of sol. Al, 0.005% or less of N, less than 0.40% of Cr, 0.005% or less of B, less than 0.15% of Mo, 0.4% or less of V, and less than 0.020% of Ti, in which 2.2?[Mneq]?3.1 and [% Mn]+3.3[% Mo]?1.9, and [% Mn]+3.3[% Mo])/(1.3[% Cr]+8[% P]+150B*)<3.5 are satisfied.Type: GrantFiled: June 25, 2010Date of Patent: February 9, 2016Assignee: JFE Steel CorporationInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Shoichiro Taira, Michitaka Sakurai, Yusuke Fushiwaki
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Patent number: 9039847Abstract: A multiphase steel sheet has a steel composition containing, in percent by mass, more than 0.015% to less than 0.100% of carbon, less than 0.40% of silicon, 1.0% to 1.9% of manganese, more than 0.015% to 0.05% of phosphorus, 0.03% or less of sulfur, 0.01% to 0.3% of soluble aluminum, 0.005% or less of nitrogen, less than 0.30% of chromium, 0.0050% or less of boron, less than 0.15% of molybdenum, 0.4% or less of vanadium, 0.02% or less of titanium, wherein [Mneq] is 2.0 to 2.8, the balance being iron and incidental impurities.Type: GrantFiled: July 27, 2010Date of Patent: May 26, 2015Assignee: JFE Steel CorporationInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Shoichiro Taira, Michitaka Sakurai, Yusuke Fushiwaki
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Publication number: 20150047751Abstract: A high strength steel sheet is formed of steel having the composition containing by mass % over 0.015% and less than 0.100% C, less than 0.50% Si, over 1.0% and less than 2.0% Mn, 0.05% or less P, 0.03% or less S, 0.01% or more and 0.3% or less sol. Al, 0.005% or less N, less than 0.35% Cr, 0.0010% or more and 0.0050% or less B, less than 0.15% Mo, less than 0.030% Ti, and iron and unavoidable impurities as a balance, wherein the steel satisfies 2.1?[Mneq]?3.1, the microstructure of the steel includes a ferrite and a second phase, a volume fraction of the second phase is set to 2.0 to 12.0%, a total ratio of a volume fraction of martensite and a volume fraction of retained ? to the volume fraction of second phase is 60% or more, and the number of carbides which are present within ferrite particles, have an aspect ratio of 3.0 or less and have a diameter of 0.25 to 0.90 ?m is set to 10000 pieces/mm2 or less.Type: ApplicationFiled: September 28, 2011Publication date: February 19, 2015Applicant: JFE Steel CorporationInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Yusuke Fushiwaki, Michitaka Sakurai
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Publication number: 20140102596Abstract: A method of manufacturing a high strength cold rolled steel sheet includes hot-rolling and cold-rolling a steel slab annealing the steel sheet at an annealing temperature of 750° C. to 830° C.; subjecting the steel sheet to first cooling at an average cooling rate of 3° C./sec to 40° C./sec in a temperature range from the annealing temperature to 480° C.; subjecting the steel sheet to second cooling at an average cooling rate of 8° C./sec to 80° C./sec in a temperature range from 480° C. to Tc (° C.) given by formula (6): Tc=435?40×[% Mn]?30×[% Cr]?30×[% V](6) wherein [% A] is the content (% by mass) of alloying element A; and subjecting the steel sheet to third cooling at an average cooling rate of 0.3° C./sec to 30° C./sec in a temperature range from Tc (° C.) to 200° C.Type: ApplicationFiled: October 21, 2013Publication date: April 17, 2014Applicant: JFE Steel CorporationInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Shoichiro Taira, Michitaka Sakurai, Yusuke Fushiwaki
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Patent number: 8389128Abstract: A high tensile-strength galvanized steel sheet includes C: at least 0.05% but less than 0.12%, Si: at least 0.01% but less than 0.35%, Mn: 2.0% to 3.5%, P: 0.001% to 0.020%, S: 0.0001% to 0.0030%, Al: 0.005% to 0.1%, N: 0.0001% to 0.0060%, Cr: more than 0.5% but not more than 2.0%, Mo: 0.01% to 0.50%, Ti: 0.010% to 0.080%, Nb: 0.010% to 0.080%, and B: 0.0001% to 0.0030%, the remainder being Fe and unavoidable impurities, wherein the high tensile-strength galvanized steel sheet has a microstructure that contains 20% to 70% by volume ferrite having an average grain size of 5 ?m or less. The high tensile-strength galvanized steel sheet has a tensile strength of at least 980 MPa, and excellent formability and weldability.Type: GrantFiled: April 7, 2008Date of Patent: March 5, 2013Assignee: JFE Steel CorporationInventors: Shusaku Takagi, Hidetaka Kawabe, Kohei Hasegawa, Toshihiko Ooi, Yasuaki Okita, Michitaka Sakurai
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Publication number: 20120180909Abstract: A multiphase steel sheet has a steel composition containing, in percent by mass, more than 0.015% to less than 0.100% of carbon, less than 0.40% of silicon, 1.0% to 1.9% of manganese, more than 0.015% to 0.05% of phosphorus, 0.03% or less of sulfur, 0.01% to 0.3% of soluble aluminum, 0.005% or less of nitrogen, less than 0.30% of chromium, 0.0050% or less of boron, less than 0.15% of molybdenum, 0.4% or less of vanadium, 0.02% or less of titanium, wherein [Mneq] is 2.0 to 2.8, the balance being iron and incidental impurities.Type: ApplicationFiled: July 27, 2010Publication date: July 19, 2012Applicant: JFE STEEL CORPORATIONInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Shoichiro Taira, Michitaka Sakurai, Yusuke Fushiwaki
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Publication number: 20120118439Abstract: A high-strength galvanized steel sheet has a low YP, good stretch flangeability, and excellent corrosion resistance and contains, on a percent by mass basis, more than 0.015% to less than 0.10% of C, 0.5% or less of Si, 1.0% to 1.9% of Mn, 0.015% to 0.050% of P, 0.03% or less of S, 0.01% to 0.5% of sol. Al, 0.005% or less of N, less than 0.40% of Cr, 0.005% or less of B, less than 0.15% of Mo, 0.4% or less of V, and less than 0.020% of Ti, in which 2.2?[Mneq]?3.1 and [% Mn]+3.3[% Mo]?1.9, and [% Mn]+3.3 [% Mo])/(1.3[% Cr]+8[% P]+150B*)<3.5 are satisfied.Type: ApplicationFiled: June 25, 2010Publication date: May 17, 2012Applicant: JFE STEEL CORPORATIONInventors: Yoshihiko Ono, Kenji Takahashi, Kaneharu Okuda, Shoichiro Taira, Michitaka Sakurai, Yusuke Fushiwaki
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Publication number: 20100326572Abstract: A method produces a high-strength cold-rolled steel sheet includes hot-rolling and cold-rolling steel having a composition which contains, by % by mass, over 0.01% to less than 0.08% of C, 0.2% or less of Si, 0.8% to less than 1.7% of Mn, 0.03% or less of P, 0.02% or less of S, 0.3% or less of sol. Al, 0.01% or less of N, and over 0.4% to 2% of Cr, and which satisfies 1.9<[Mneq]<3 and 0.34?[% Cr]/[% Mn], the balance being composed of iron and inevitable impurities; heating at an average heating rate of less than 3° C./sec in a temperature range of 680° C. to 740° C.; annealing at an annealing temperature of over 740° C. to less than 820° C.; cooling at an average cooling rate of 2 to 30° C./sec in a temperature range of the annealing temperature to 650° C.; cooling at an average cooling rate of 10° C./sec or more in the temperature range of 650° C. to Tc° C.Type: ApplicationFiled: July 10, 2008Publication date: December 30, 2010Applicant: JFE STEEL CORPORATIONInventors: Yoshihiko Ono, Hideyuki Kimura, Kaneharu Okuda, Takeshi Fujita, Michitaka Sakurai
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Publication number: 20100330392Abstract: A high-strength galvanized steel sheet has a steel composition which contains, by % by mass, 0.01 to 0.12% of C, 0.2% or less of Si, less than 2% of Mn, 0.04% or less of P, 0.02% or less of S, 0.3% or less of sol. Al, 0.01% or less of N, and over 0.3% to 2% of Cr, and which satisfies 2.1?[Mneq]?3 and 0.24?[% Cr]/[% Mn], the balance being composed of iron and inevitable impurities, and has a steel microstructures containing ferrite and a second phase.Type: ApplicationFiled: July 10, 2008Publication date: December 30, 2010Applicant: JFE STEEL CORPORATIONInventors: Yoshihiko Ono, Hideyuki Kimura, Kaneharu Okuda, Takeshi Fujita, Michitaka Sakurai
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Publication number: 20100132849Abstract: A high tensile-strength galvanized steel sheet includes C: at least 0.05% but less than 0.12%, Si: at least 0.01% but less than 0.35%, Mn: 2.0% to 3.5%, P: 0.001% to 0.020%, S: 0.0001% to 0.0030%, Al: 0.005% to 0.1%, N: 0.0001% to 0.0060%, Cr: more than 0.5% but not more than 2.0%, Mo: 0.01% to 0.50%, Ti: 0.010% to 0.080%, Nb: 0.010% to 0.080%, and B: 0.0001% to 0.0030%, the remainder being Fe and unavoidable impurities, wherein the high tensile-strength galvanized steel sheet has a microstructure that contains 20% to 70% by volume ferrite having an average grain size of 5 ?m or less. The high tensile-strength galvanized steel sheet has a tensile strength of at least 980 MPa, and excellent formability and weldability.Type: ApplicationFiled: April 7, 2008Publication date: June 3, 2010Applicant: JFE STEEL CORPORATIONInventors: Shusaku Takagi, Hidetaka Kawabe, Kohei Hasegawa, Toshihiko Ooi, Yasuaki Okita, Michitaka Sakurai