Patents by Inventor Michiharu Nakaya
Michiharu Nakaya 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: 20170088914Abstract: Disclosed herein is a high-strength galvannealed steel sheet having a galvannealed layer on a surface of a base steel sheet and containing predetermined steel components. The steel sheet sequentially has, from the interface of the base steel sheet and the galvannealed layer, towards the base steel sheet: an internal oxide layer and containing at least one oxide selected from the group consisting of Si and Mn; a soft layer including the internal oxide layer, and satisfying a predetermined Vickers hardness; and a hard layer made up of a structure mainly composed of martensite. The average depth D of the soft layer is 20 ?m or greater, and the average depth d of the internal oxide layer is 4 ?m or greater and smaller than D. A coefficient of variation of KAM of the base steel sheet at the portion t/4 is 0.66 or less.Type: ApplicationFiled: March 17, 2015Publication date: March 30, 2017Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)Inventors: Muneaki IKEDA, Michiharu NAKAYA
-
Patent number: 9605335Abstract: Disclosed is a hot-dip galvanized steel sheet for stamping, which has excellent cold workability, has such satisfactory surface quality as to be free from unplating and other defects even in the absence of dedicated facilities, and ensures a strength of 1370 MPa or more after quenching even when cooled at a low rate. Also disclosed is a method effective for the produce of the hot-dip galvanized steel sheet for stamping. The hot-dip galvanized steel sheet for stamping comprises a base steel sheet and a hot-dip galvanized layer on a surface of the base steel sheet, in which the base steel sheet has a predetermined chemical composition and has a microstructure comprising equiaxed ferrite having an average aspect ratio of 4.0 or less and cementite and/or pearlite having an average major axis of grains of 20 ?m or less.Type: GrantFiled: March 28, 2013Date of Patent: March 28, 2017Assignees: Kobe Steel, Ltd., VOESTALPINE STAHL GmbHInventors: Michiharu Nakaya, Tatsuya Asai, Andreas Pichler, Thomas Kurz
-
Publication number: 20170009315Abstract: The present disclosure relates to a high-strength hot-dip galvannealed steel sheet excellent in bake hardenability and bendability and having a component composition containing, in mass %, C: from 0.05 to 030%, Si: from 0.5 to 3.0%, Mn: from 0.2 to 3.0%, P: from 0 to 0.10%, S: from 0 to 0.010%, N: form 0 to 0.010%, and Al: from 0.001 to 0.10%, with the remainder being iron and unavoidable impurities. The steel sheet has a steel structure containing, in terms of area percentage, martensite: form 50 to 85% and ferrite: 0% or more and less than 5%, with the remainder being bainite. The steel sheet has a dislocation density of 5.0×1015 m?2 or more, a solute carbon amount of 0.08 mass % or more and a tensile strength of 1180 MPa or more.Type: ApplicationFiled: March 4, 2015Publication date: January 12, 2017Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.)Inventors: Kosuke SHIBATA, Toshio MURAKAMI, Muneaki IKEDA, Michiharu NAKAYA
-
Publication number: 20160355920Abstract: Provided are: a high-strength steel sheet which is improved in both elongation and local formability and thus exhibits excellent workability; and a manufacturing method thereof. The high-strength steel sheet contains C, Si, Mn, Al, P and S with the remainder including iron and unavoidable impurities, and has a metal structure which includes polygonal ferrite, bainite, tempered martensite, and retained austenite. In the metal structure, (1) the bainite has a composite microstructure including both a high-temperature-formed bainite having an average distance between adjacent regions of retained austenite and/or carbide of 1 ?m or more and a low-temperature-formed bainite having an average distance between adjacent regions of retained austenite and/or carbide of less than 1 ?m each identified upon observation with a scanning electron microscope; and (2) the retained austenite is present in a volume percentage of 5% or more of the entire metal structure as determined by a saturation magnetization measurement.Type: ApplicationFiled: August 18, 2016Publication date: December 8, 2016Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.)Inventors: Yuichi FUTAMURA, Michiharu NAKAYA, Takayuki KIMURA
-
Patent number: 9464337Abstract: Disclosed is a high strength steel sheet having excellent hydrogen embrittlement resistance. The steel sheet has a tensile strength of 1180 MPa or more, and satisfies the following conditions: with respect to an entire metallographic structure thereof, bainite, bainitic ferrite and tempered martensite account for 85 area % or more in total; retained austenite accounts for 1 area % or more; and fresh martensite accounts for 5 area % or less (including 0 area %).Type: GrantFiled: May 28, 2010Date of Patent: October 11, 2016Assignees: KABUSHIKI KAISHA KOBE SEIKO SHO, VOESTALPINE STAHL GMBHInventors: Yoichi Mukai, Kouji Kasuya, Michiharu Nakaya, Michitaka Tsunezawa, Fumio Yuse, Junichiro Kinugasa, Sandra Traint, Andreas Pichler
-
Publication number: 20150167133Abstract: The present invention relates to high strength cold rolled steel sheet suitable for applications in automobiles, construction materials and the like, specifically high strength steel sheet excellent in formability. In particular, the invention relates to cold rolled steel sheets having a tensile strength of at least 980 MPa and a method for producing such steel sheet.Type: ApplicationFiled: April 2, 2013Publication date: June 18, 2015Inventors: Stefan Paul, Daniel Krizan, Andreas Pichler, Michiharu Nakaya
-
Publication number: 20150101712Abstract: Provided is a method that enables manufacture, with good productivity, of a high-strength cold-rolled steel with improved elongation (EL), stretch-flangeability (?), bendability (R), and balance of these properties (TS×EL×?/1000), outstanding composite workability as evaluated by Erichsen test, and a tensile strength of at least 980 MPa. A steel material satisfying a prescribed constituent composition is held and soaked for at least fifty seconds at a temperature at or above the Ac3 point, after which the steel material is cooled at an average cooling rate of at least 15° C./sec to a discretionary temperature (T) that satisfies expression (1) below, held for 5-180 seconds in a temperature range that satisfies expression (1) below, then heated to a temperature region that satisfies expression (2) below, held for at least 50 seconds in this temperature region, and then cooled. 300° C.?T1 (° C.)<400° C. ??(1) 400° C.?T2 (° C.)<540° C.Type: ApplicationFiled: February 28, 2013Publication date: April 16, 2015Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.)Inventors: Yuichi Futamura, Michiharu Nakaya
-
Publication number: 20150044502Abstract: Disclosed is a hot-dip galvanized steel sheet for stamping, which has excellent cold workability, has such satisfactory surface quality as to be free from unplating and other defects even in the absence of dedicated facilities, and ensures a strength of 1370 MPa or more after quenching even when cooled at a low rate. Also disclosed is a method effective for the produce of the hot-dip galvanized steel sheet for stamping. The hot-dip galvanized steel sheet for stamping comprises a base steel sheet and a hot-dip galvanized layer on a surface of the base steel sheet, in which the base steel sheet has a predetermined chemical composition and has a microstructure comprising equiaxed ferrite having an average aspect ratio of 4.0 or less and cementite and/or pearlite having an average major axis of grains of 20 ?m or less.Type: ApplicationFiled: March 28, 2013Publication date: February 12, 2015Applicants: KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.), VOESTALPINE STAHL GMBHInventors: Michiharu Nakaya, Tatsuya Asai, Andreas Pichler, Thomas Kurz
-
Publication number: 20150034218Abstract: The present invention relates to high strength cold rolled steel sheet suitable for applications in automobiles, construction materials and the like, specifically high strength steel excellent in formability. In particular, the invention relates to cold rolled steel sheets having a tensile strength of at least 980 MPa and a method for producing such steel sheet.Type: ApplicationFiled: April 2, 2013Publication date: February 5, 2015Inventors: Daniel Krizan, Stefan Paul, Andreas Pichler, Michiharu Nakaya
-
Publication number: 20140044988Abstract: Provided are: a high-strength steel sheet which is improved in both elongation and local formability and thus exhibits excellent workability; and a manufacturing method thereof. The high-strength steel sheet contains C, Si, Mn, Al, P and S with the remainder including iron and unavoidable impurities, and has a metal structure which includes polygonal ferrite, bainite, tempered martensite, and retained austenite. In the metal structure, (1) the bainite has a composite microstructure including both a high-temperature-formed bainite having an average distance between adjacent regions of retained austenite and/or carbide of 1 ?m or more and a low-temperature-formed bainite having an average distance between adjacent regions of retained austenite and/or carbide of less than 1 ?m each identified upon observation with a scanning electron microscope; and (2) the retained austenite is present in a volume percentage of 5% or more of the entire metal structure as determined by a saturation magnetization measurement.Type: ApplicationFiled: March 21, 2012Publication date: February 13, 2014Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd.)Inventors: Yuichi Futamura, Michiharu Nakaya, Takayuki Kimura
-
Patent number: 8257513Abstract: The present invention provides a high strength steel sheet with 780 MPa class tensile strength excellent in bending workability and fatigue strength. The high strength steel sheet is (1) a steel sheet whose steel composition contains: C: 0.05-0.20%; Si: 0.6-2.0%; Mn: 1.6-3.0%; P: 0.05% or below; S: 0.01% or below; Al: 0.1% or below; and N: 0.01% or below, the balance comprising iron and inevitable impurities, in which (2) a microstructure comprises a polygonal ferrite structure and a structure formed by low-temperature transformation, in which, when a sheet plane located at a depth of 0.1 mm from a surface of the steel sheet is in the observation under a scanning electron microscope with respect to twenty sights in total in different positions in the sheet-width direction, the maximum value of the areal proportion of the polygonal ferrite (Fmax) and the minimum value of the areal proportion of the ferrite (Fmin) in a 50 ?m×50 ?m area in each sight satisfy Fmax?80%, Fmin?10%, and Fmax?Fmin?40%.Type: GrantFiled: May 28, 2008Date of Patent: September 4, 2012Assignee: Kobe Steel, Ltd.Inventors: Michiharu Nakaya, Tetsuji Hoshika
-
Patent number: 8197617Abstract: The present invention provides a high-strength steel sheet which has a 980 MPa class tensile strength as well as has excellent elongation, stretch flangeability and weldability, and also has excellent anti-delayed fraction property. The high-strength steel sheet comprises steel satisfying: C: 0.12 to 0.25%, Si: 1.0 to 3.0%, Mn: 1.5 to 3.0%, P: 0.15% or less, S: 0.02% or less, Al: 0.4% or less, and comprising the remnant made from iron and unavoidable impurities, wherein a ratio of the contents of Si and C (Si/C) is within the range from 7 to 14 in terms of a mass ratio, and a microstructure in a longitudinal section comprises, by an occupancy ratio based on the entire structure, 1) bainitic ferrite: 50% or more, 2) lath-type residual austenite: 3% or more, and 3) block-type residual austenite: 1% or more to ½×occupancy ratio of lath-type residual austenite, and 4) average size of block-type second phase is 10 ?m or less.Type: GrantFiled: June 4, 2007Date of Patent: June 12, 2012Assignee: Kobe Steel, Ltd.Inventors: Michiharu Nakaya, Yoichi Mukai, Koichi Sugimoto
-
Publication number: 20120132327Abstract: Disclosed is a high strength steel sheet having excellent hydrogen embrittlement resistance. The steel sheet has a tensile strength of 1180 MPa or more, and satisfies the following conditions: with respect to an entire metallographic structure thereof, bainite, bainitic ferrite and tempered martensite account for 85 area % or more in total; retained austenite accounts for 1 area % or more; and fresh martensite accounts for 5 area % or less (including 0 area %).Type: ApplicationFiled: May 28, 2010Publication date: May 31, 2012Applicants: VOESTALPINE STAHL GMBH, Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)Inventors: Yoichi Mukai, Kouji Kasuya, Michiharu Nakaya, Michitaka Tsunezawa, Fumio Yuse, Junichiro Kinugasa, Sandra Traint, Andreas Pichler
-
Publication number: 20100221138Abstract: The present invention provides a high-strength composite steel sheet which has a tensile strength of 980 MPa class as well as excellent and excellent anti-delayed fraction property, and also has excellent spot-weldability. The high-strength composite steel sheet comprises a steel satisfying: C: 0.10 to 0.25% (% by mass in case of a chemical component, the same shall apply hereinafter), Si: 1.0 to 3.0%, Mn: 1.5 to 3.0%, P: 0.15% or less, S: 0.02% or less, Al: 0.4% or less, and comprising the remnant made from iron and unavoidable impurities; the contents of Si, Al, Mn and Cr satisfy the relationship of “(Si+Al)/Mn or (Si+Al)/(Mn+Cr)=0.74 to 1.26”; and microstructure is specified.Type: ApplicationFiled: June 4, 2007Publication date: September 2, 2010Applicants: Kabushiki Kaisha Kobe Seiko Sho, Shinshu TLO Co., Ltd.Inventors: Michiharu Nakaya, Yoichi Mukai, Koichi Sugimoto
-
Publication number: 20100183472Abstract: The present invention provides a high strength steel sheet with 780 MPa class tensile strength excellent in bending workability and fatigue strength. The high strength steel sheet is (1) a steel sheet whose steel composition contains: C: 0.05-0.20%; Si: 0.6-2.0%; Mn: 1.6-3.0%; P: 0.05% or below; S: 0.01% or below; Al: 0.1% or below; and N: 0.01% or below, the balance comprising iron and inevitable impurities, in which (2) a microstructure comprises a polygonal ferrite structure and a structure formed by low-temperature transformation, in which, when a sheet plane located at a depth of 0.1 mm from a surface of the steel sheet is in the observation under a scanning electron microscope with respect to twenty sights in total in different positions in the sheet-width direction, the maximum value of the areal proportion of the polygonal ferrite (Fmax) and the minimum value of the areal proportion of the ferrite (Fmin) in a 50 ?m×50 ?m area in each sight satisfy Fmax?80%, Fmin?10%, and Fmax?Fmin?40%.Type: ApplicationFiled: May 28, 2008Publication date: July 22, 2010Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd.)Inventors: Michiharu Nakaya, Tetsuji Hoshika
-
Publication number: 20100172786Abstract: The present invention provides a high-strength steel sheet which has a 980 MPa class tensile strength as well as has excellent elongation, stretch flangeability and weldability, and also has excellent anti-delayed fraction property. The high-strength steel sheet comprises steel satisfying: C: 0.12 to 0.25%, Si: 1.0 to 3.0%, Mn: 1.5 to 3.0%, P: 0.15% or less, S: 0.02% or less, Al: 0.4% or less, and comprising the remnant made from iron and unavoidable impurities, wherein a ratio of the contents of Si and C (Si/C) is within the range from 7 to 14 in terms of a mass ratio, and a microstructure in a longitudinal section comprises, by an occupancy ratio based on the entire structure, 1) bainitic ferrite: 50% or more, 2) lath-type residual austenite: 3% or more, and 3) block-type residual austenite: 1% or more to ½×occupancy ratio of lath-type residual austenite, and 4) average size of block-type second phase is 10 ?m or less.Type: ApplicationFiled: June 4, 2007Publication date: July 8, 2010Applicants: KABUSHIKI KAISHA KOBE SEIKO SHO, SHINSHU TLO CO., LTD.Inventors: Michiharu Nakaya, Yoichi Mukai, Koichi Sugimoto
-
Patent number: 6280538Abstract: A hot rolled high strength steel sheet having a satisfactory strength-elongation balance and an stretch frangibility and with excellent formability comprising a steel, which contains: C :0.05 ˜ 0.15% Si :0.5 ˜ 2.0% Mn :0.5 ˜ 2.0% P :0.05% or less S :0.010% or less Al :0.005 ˜ less than 0.10%, and the balance of Fe and inevitable impurities, and in which the metal structure mainly comprises three phases of ferrite, retained austenite and bainite, the amount of the ferrite [V(F)] is 60˜95 area %, the amount of the retained austenite [V(&ggr;)] is 3˜15 vol %, the amount of the bainite [V(B)] in the area ratio is 1.5 times or more of the amount of the retained austenite [V(&ggr;)], and the average hardness of the bainite is 240-400 Hv.Type: GrantFiled: November 12, 1999Date of Patent: August 28, 2001Assignee: Kabushiki Kaisha Kobe Seiko ShoInventors: Tetsuo Soshiroda, Yoichi Mukai, Michiharu Nakaya