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).
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Patent number: 10718044Abstract: A hot-dip galvanized steel sheet includes: a predetermined chemical composition; and a steel structure represented by: in terms of area ratio, polygonal ferrite: 10% or less; upper bainite: 20% or less; retained austenite: 5% or less; and martensite: 70% or more, in which: martensite having Fe carbides at a number density of 1×106/mm2 or more is contained by 50% or more, in terms of area ratio, with respect to the entire amount of martensite; and the steel structure has an average effective crystal grain diameter of 5.0 ?m or less.Type: GrantFiled: July 15, 2016Date of Patent: July 21, 2020Assignee: NIPPON STEEL CORPORATIONInventors: Takafumi Yokoyama, Kunio Hayashi, Masafumi Azuma, Eisaku Sakurada, Hiroyuki Kawata, Genki Abukawa
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Patent number: 10704132Abstract: A high-strength hot-dip galvanized steel sheet excellent in impact resistance and worked portion corrosion resistance including a hot-dip galvanized plating layer on a steel sheet base material whose tensile strength is 590 MPa or more, wherein the plating layer includes projecting alloy layers being in contact with the steel sheet base material, a number density of the projecting alloy layers is 4 pieces/mm or more, wherein the steel sheet base material includes: a miniaturized layer being directly in contact with the interface between the steel sheet base material and the plating layer; a decarburized layer being in contact with the miniaturized layer; and an inner layer other than the miniaturized layer and the decarburized layer, and one or more kinds of oxides of Si and Mn are contained in layers of the miniaturized layer, the decarburized layer, and the projecting alloy layers.Type: GrantFiled: February 25, 2016Date of Patent: July 7, 2020Assignee: NIPPON STEEL CORPORATIONInventors: Takeshi Yasui, Hiroyuki Kawata, Yuji Yamaguchi, Ryosuke Komami, Satoshi Uchida, Akinobu Murasato
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Patent number: 10544474Abstract: A high-strength cold-rolled steel sheet includes, as a component composition, by mass %: C: 0.075% to 0.300%; Si: 0.30% to 2.50%; Mn: 1.30% to 3.50%; P: 0.001% to 0.050%; S: 0.0001% to 0.0100%; Al: 0.001% to 1.500%; and N: 0.0001% to 0.0100%, in which a surface microstructure contains residual austenite of 3% to 10% and ferrite of 90% or less by volume fraction, an inner microstructure at a depth of t/4 from the surface assuming that a sheet thickness is t contains residual austenite of 3% to 20% by volume fraction, a ratio Hvs/Hvb between a surface hardness Hvs of the steel sheet surface and a hardness Hvb at a depth of ¼ of the thickness is more than 0.75 to 0.90, and a maximum tensile strength is 700 MPa or more.Type: GrantFiled: February 4, 2013Date of Patent: January 28, 2020Assignee: NIPPON STEEL CORPORATIONInventors: Masafumi Azuma, Takayuki Nozaki, Chisato Wakabayashi, Koichi Sato, Hiroyuki Kawata, Nobuhiro Fujita
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Publication number: 20200024709Abstract: 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: ApplicationFiled: March 31, 2017Publication date: January 23, 2020Applicant: NIPPON STEEL CORPORATIONInventors: Takafumi YOKOYAMA, Riki OKAMOTO, Yuji YAMAGUCHI, Kazuki SHIOKAWA, Yuichi NAKAHIRA, Hiroyuki KAWATA
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Patent number: 10507629Abstract: A hot-dip galvanized steel sheet wherein the hot-dip galvanized steel sheet comprises a base steel sheet and a hot-dip galvanized layer, a ferrite phase is, by volume fraction, 40% or more and 97% or less in a range of ? thickness to ? thickness centered at a position of ¼ thickness from the surface of the base steel sheet, a hard structure is 3% or more in total, wherein the hot-dip galvanized steel sheet has the hot-dip galvanized layer in which Fe is 5.0% or less and Al is 1.0% or less, and columnar grains formed of a ? phase is 20% or more in an entire interface between the plated layer and the base steel sheet on the surface of the base steel sheet in which a ratio of a volume fraction of the hard structure in a surface layer range of 20 ?m depth in a steel sheet direction from an interface between the hot-dip galvanized layer and the base steel sheet is 0.10 times or more to 0.Type: GrantFiled: November 5, 2015Date of Patent: December 17, 2019Assignee: NIPPON STEEL CORPORATIONInventors: Hiroyuki Kawata, Takeshi Yasui, Kohei Ueda, Naoki Maruyama, Yuji Yamaguchi, Satoshi Uchida, Ryosuke Komami, Hayato Arai, Yasuhiro Nakashima, Toyomitsu Nakamura
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Patent number: 10501832Abstract: A base material (13) included in a plated steel sheet (1) includes a structure, at a ¼ sheet thickness position, represented by, in volume fraction: tempered martensite: 3.0% or more; ferrite: 4.0% or more; and retained austenite: 5.0% or more. An average hardness of the tempered martensite in the base material (13) is 5 GPa to 10 GPa, and a part or all of the tempered martensite and the retained austenite in the base material form an M-A. A volume fraction of ferrite in a decarburized ferrite layer (12) included in the plated steel sheet (1) is 120% or more of the volume fraction of the ferrite in the base material (13) at the ¼ sheet thickness position, an average grain diameter of the ferrite in the decarburized ferrite layer (12) is 20 ?m or less, a thickness of the decarburized ferrite layer (12) is 5 ?m to 200 ?m, a volume fraction of tempered martensite in the decarburized ferrite layer (12) is 1.0 volume% or more, a number density of the tempered martensite in the decarburized ferrite layer (12) is 0.Type: GrantFiled: April 22, 2016Date of Patent: December 10, 2019Assignee: NIPPON STEEL CORPORATIONInventors: Koutarou Hayashi, Akihiro Uenishi, Masaharu Kameda, Jun Haga, Kunio Hayashi, Kohichi Sano, Hiroyuki Kawata
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Publication number: 20190226046Abstract: 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: ApplicationFiled: September 13, 2016Publication date: July 25, 2019Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Yuri TODA, Kunio HAYASHI, Katsuya NAKANO, Hiroyuki KAWATA, Akihiro UENISHI
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Publication number: 20190218652Abstract: In a metal coated steel sheet, a chemical composition contains, in mass %, at least C: 0.03% to 0.70%, Si: 0.25% to 2.50%, Mn: 1.00% to 5.00%, P: 0.100% or less, S: 0.010% or less, sol. Al: 0.001% to 2.500, N: 0.020% or less, and a balance composed of iron and impurities, a metal structure contains greater than 5.0 vol % of retained austenite and greater than 5.0 vol % of tempered martensite, and satisfies a C content in the retained austenite being 0.85 mass % or more.Type: ApplicationFiled: October 19, 2016Publication date: July 18, 2019Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Jun HAGA, Kohichi SANO, Koutarou HAYASHI, Kunio HAYASHI, Masaharu KAMEDA, Akihiro UENISHI, Hiroyuki KAWATA
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Patent number: 10350701Abstract: A spot welding method able to simply prevent liquid metal embrittlement cracks in spot welding of plated steel sheets, comprising, before spot welding, removing the plating at least in a zone including the inside of a circle centered at a scheduled location where the center of the nugget is formed and having an outer circumference of the inside of the outer edge of a weld affected zone or a zone at the mated surfaces of the steel sheets to be welded at the inside of a circle sharing a center of a scheduled location becoming the center of the nugget formed at the mated surfaces of the steel sheets and having an outer circumference of the inside of the outer edge of a weld affected zone.Type: GrantFiled: March 30, 2016Date of Patent: July 16, 2019Assignee: NIPPON STEEL CORPORATIONInventors: Yasunobu Miyazaki, Fuminori Watanabe, Chisato Wakabayashi, Kunio Hayashi, Hiroyuki Kawata, Seiji Furusako, Sho Matsui
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Patent number: 10351937Abstract: The present invention provides a high-strength steel sheet excellent in impact resistance. The high-strength steel sheet contains predetermined contents of C, Si, Mn, P, S, Al, Ti, N, and O, with the balance being iron and inevitable impurities, and has a steel sheet structure in which, in a ? thickness to ? thickness region across ¼ of a sheet thickness, 1 to 8% retained austenite is contained in volume fraction, an average aspect ratio of the retained austenite is 2.0 or less, an amount of solid-solution Mn in the retained austenite is 1.1 times an average amount of Mn or more, and TiN grains having a 0.5 ?m average grain diameter or less are contained, and a density of AlN grains with a 1 ?m grain diameter or more is 1.0 pieces/mm2 or less, wherein a maximum tensile strength is 900 MPa or more.Type: GrantFiled: July 27, 2012Date of Patent: July 16, 2019Assignee: NIPPON STEEL CORPORATIONInventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Hajime Hasegawa, Chisato Wakabayashi, Tsuyoshi Oki
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Publication number: 20190169729Abstract: A hot-dip galvanized steel sheet includes: a predetermined chemical composition; and a steel structure represented by: in terms of area ratio, polygonal ferrite: 10% or less; upper bainite: 20% or less; retained austenite: 5% or less; and martensite: 70% or more, in which: martensite having Fe carbides at a number density of 1×106/mm2 or more is contained by 50% or more, in terms of area ratio, with respect to the entire amount of martensite; and the steel structure has an average effective crystal grain diameter of 5.0 ?m or less.Type: ApplicationFiled: July 15, 2016Publication date: June 6, 2019Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takafumi YOKOYAMA, Kunio HAYASHI, Masafumi AZUMA, Eisaku SAKURADA, Hiroyuki KAWATA, Genki ABUKAWA
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Publication number: 20190030637Abstract: By obtaining a spot-welded joint being a spot-welded joint formed by overlapping a plurality of pieces of steel plates (1A, 1B) and performing spot welding on the steel plates, including a high-strength steel plate whose tensile strength is 750 (MPa) to 2500 (MPa), being at least one piece of steel plate out of the plurality of pieces of steel plates, in which a carbon equivalent Ceq of the high-strength steel plate is 0.20 mass % to 0.55 mass %, and ten or more of iron-based carbides in each of which a length of a longest portion is 0.1 (?m) or more exist in a square region 103 within a heat-affected zone 4 of a cross section that passes through a center of a welding mark, and is cut along a plate thickness direction of the steel plates (1A, 1B), a cross tensile strength of the spot-welded joint to be formed is improved.Type: ApplicationFiled: September 28, 2018Publication date: January 31, 2019Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Chisato WAKABAYASHI, Fuminori WATANABE, Seiji FURUSAKO, Yasunobu MIYAZAKI, Hiroyuki KAWATA, Tohru OKADA, Hideki HAMATANI
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Publication number: 20190024208Abstract: The present method for manufacturing a high strength steel sheet having a tensile strength of 780 MPa or higher includes continuous annealing by heating a steel sheet having a predetermined chemical composition to 750° C. to 900° C. and holding the steel sheet in the temperature range for 0 seconds to 300 seconds, in which, during heating and holding, a hydrogen concentration in a furnace atmosphere is less than 10 volume %, when a temperature of the steel sheet is 700° C. or lower, a furnace body average value is higher than ?3.01 and lower than ?0.07, when the temperature is higher than 700° C. and 800° C. or lower, the value is higher than ?1.36 and lower than ?0.07, when the temperature is higher than 800° C., the value is higher than ?3.01 and ?0.53 or lower, and a dew point is lower than ?10° C.Type: ApplicationFiled: February 25, 2016Publication date: January 24, 2019Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takayuki KITAZAWA, Kohei UEDA, Hiroyuki KAWATA, Kaoru HIRAMATSU
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Publication number: 20190003009Abstract: A high-strength steel sheet includes: a specific chemical composition; and a microstructure represented by, in a ? thickness to ? thickness range with ¼ thickness of a sheet thickness from a surface being a center, in volume fraction, ferrite: 85% or less, bainite: 3% or more and 95% or less, tempered martensite: 1% or more and 80% or less, retained austenite: 1% or more and 25% or less, pearlite and coarse cementite: 5% or less in total, and fresh martensite: 5% or less, in which the solid-solution carbon content in the retained austenite is 0.70 to 1.30 mass %, and to all grain boundaries of retained austenite grains having an aspect ratio of 2.50 or less and a circle-equivalent diameter of 0.80 ?m or more, the proportion of interfaces with the tempered martensite or the fresh martensite is 75% or less.Type: ApplicationFiled: March 23, 2017Publication date: January 3, 2019Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Hiroyuki KAWATA, Yuji YAMAGUCHI, Takayuki KITAZAWA, Satoshi UCHIDA, Kohei UEDA, Naoki MARUYAMA
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Publication number: 20180312954Abstract: A high-strength hot-dip galvanized steel sheet including a hot-dip galvanized plating layer on a steel sheet base material whose tensile strength is 590 MPa or more, wherein the plating layer includes projecting alloy layers being in contact with the steel sheet base material, a number density of the projecting alloy layers is 4 pieces/mm or more per unit length of an interface between the steel sheet base material and the plating layer when seen from a sectional direction, and a maximum diameter of the projecting alloy layers at the interface is 100 ?m or less, wherein the steel sheet base material includes: a miniaturized layer being directly in contact with the interface between the steel sheet base material and the plating layer; a decarburized layer being in contact with the miniaturized layer and existing on an inward side of the steel sheet base material; and an inner layer other than the miniaturized layer and the decarburized layer, and one kind or two kinds or more of oxides of Si and Mn are containType: ApplicationFiled: February 25, 2016Publication date: November 1, 2018Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takeshi YASUI, Hiroyuki KAWATA, Yuji YAMAGUCHI, Ryosuke KOMAMI, Satoshi UCHIDA, Akinobu MURASATO
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Patent number: 10113223Abstract: A hot-dip galvanized steel sheet having a base steel sheet and a hot-dip galvanized layer, a ferrite phase is, by volume fraction, 50% or less in a range of ? thickness to ? thickness centered at a position of ¼ thickness from the surface of the base steel sheet, a hard structure is 50% or more, wherein the hot-dip galvanized steel sheet has the hot-dip galvanized layer in which Fe is 5.0% or less and Al is 1.0% or less, and columnar grains formed of a ? phase is 20% or more in an entire interface between the plated layer and the base steel sheet. On the surface of the base steel sheet, a volume fraction of a residual austenite is 3% or less.Type: GrantFiled: November 5, 2015Date of Patent: October 30, 2018Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Hiroyuki Kawata, Takeshi Yasui, Kohei Ueda, Naoki Maruyama, Yuji Yamaguchi, Satoshi Uchida, Ryosuke Komami, Hayato Arai, Toyomitsu Nakamura
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Publication number: 20180298462Abstract: A steel sheet for galvannealed steel contains, by mass %, C: 0.25 to 0.70%, Si: 0.25 to 2.50%, Mn: 1.00 to 5.00%, Al: 0.005 to 3.50%, P: 0.15% or less, S: 0.03% or less, N £ 0.02%, O £ 0.01%, and optionally one or more selected from Ti, Nb, V, Cr, Mo, Cu, Ni, B, Ca, REM, Mg, W, Zr, Sb, Sn, As, Te, Y, Hf and Co, a balance being Fe and impurities. The microstructure consists of, by vol. %, retained g: 10.0 to 60.0%, high-temperature tempered martensite3 5.0%, low-temperature tempered martensite3 5.0%, fresh martensite £ 10.0%, a: 0 to 15.0%, P: 0 to 10.0%, a balance being bainite. Total volume ratio of tempered martensite and bainite is 30.0% or more, tensile strength is 1470 MPa or more, tensile strength×uniform elongation is 13000 MPa % or more, and tensile strength×local elongation is 5000 MPa % or more.Type: ApplicationFiled: June 10, 2016Publication date: October 18, 2018Inventors: Kohichi SANO, Jun HAGA, Koutarou HAYASHI, Hiroyuki KAWATA, Riki OKAMOTO, Akihiro UENISHI
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Publication number: 20180274069Abstract: A steel sheet has a predetermined chemical composition, and a surface exhibits an absorption peak at which a reflectance is not less than 50% nor more than 85% in a range of wave numbers of 1200 cm?1 to 1300 cm?1 by a Fourier transform-infrared spectroscopy analysis by a reflection absorption spectrometry method, and does not exhibit an absorption peak in a range of wave numbers of 1000 cm?1 to 1100 cm?1, or exhibits an absorption peak at which a reflectance is 85% or more in the range of wave numbers of 1000 cm?1 to 1100 cm?1, wherein Ni of 3 mg/m2 to 100 mg/m2 adheres to the surface.Type: ApplicationFiled: September 25, 2015Publication date: September 27, 2018Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Kohei UEDA, Hiroyuki KAWATA, Takayuki KITAZAWA, Takeshi YASUI, Hiroyuki BAN
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Publication number: 20180243853Abstract: 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: ApplicationFiled: September 2, 2016Publication date: August 30, 2018Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Chisato YOSHINAGA, Yasunobu MIYAZAKI, Kunio HAYASHI, Hiroyuki KAWATA, Masanori YASUYAMA
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Publication number: 20180237881Abstract: A steel sheet includes: a predetermined chemical composition; and a steel structure containing, in are a fraction, 2% or more of ferrite and bainite, in which an average dislocation density in the ferrite and an average dislocation density in the bainite are both h3×1012 m/m3 to 1×1014 m/m3, and an average grain diameter of the ferrite and the bainite is 5 ?m or less.Type: ApplicationFiled: August 21, 2015Publication date: August 23, 2018Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Riki OKAMOTO, Hiroyuki KAWATA, Masafumi AZUMA, Akihiro UENISHI, Naoki MARUYAMA