Patents by Inventor Masafumi Azuma

Masafumi Azuma 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: 20140377582
    Abstract: 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: Application
    Filed: February 4, 2013
    Publication date: December 25, 2014
    Inventors: Masafumi Azuma, Takayuki Nozaki, Chisato Wakabayashi, Koichi Sato, Hiroyuki Kawata, Nobuhiro Fujita
  • Publication number: 20140342183
    Abstract: Provided is a high-strength hot-dip galvanized steel sheet having excellent plating adhesion, formability, and hole expandability with an ultimate tensile strength of 980 MPa or more, the hot-dip galvanized steel sheet comprising a hot-dip galvanized layer formed on a surface of a base steel sheet. The base steel sheet contains, by mass %, C: 0.05% to 0.4%; Si: 0.01% to 3.0%; Mn: 0.1% to 3.0%; Al: 0.01 to 2.0%; in which Si+Al>0.5%, P: limited to 0.04% or less; S: limited to 0.05% or less; N: limited to 0.01% or less; and a balance including Fe and inevitable impurities, a microstructure of the base steel sheet contains 40% or more by total volume fraction of martensite and bainite, 8% or more by volume fraction of residual austenite, and a balance of the microstructure being ferrite or ferrite and 10% or less by volume fraction of pearlite.
    Type: Application
    Filed: September 28, 2012
    Publication date: November 20, 2014
    Inventors: Chisato Wakabayashi, Masafumi Azuma, Nobuhiro Fujita, Kohichi Sano
  • Publication number: 20140242415
    Abstract: Provided is a high-strength hot-dip galvanized steel sheet having small material anisotropy and excellent formability with an ultimate tensile strength of 980 MPa or more. The hot-dip galvanized steel sheet includes a hot-dip galvanized layer formed on a surface of a base steel plate. The base steel plate contains, by mass %, C: 0.1 to less than 0.40%, Si: 0.5 to 3.0%, Mn: 1.5 to 3.0%, O: limited to 0.006% or less, P: limited to 0.04% or less, S: limited to 0.01% or less, Al: limited to 2.0% or less, N: limited to 0.01% or less, and a balance including Fe and inevitable impurities. A microstructure of the base steel sheet contains ferrite of 40% or more, residual austenite of 8 to less than 60%, by volume fraction, and a balance being bainite or martensite. In a sheet thickness range of ? to ? from the surface of the base steel sheet, a pole density of specific crystal orientation is within a predetermined range.
    Type: Application
    Filed: September 28, 2012
    Publication date: August 28, 2014
    Inventors: Masafumi Azuma, Chisato Wakabayashi, Takayuki Nozaki, Nobuhiro Fujita, Manabu Takahashi
  • Publication number: 20140234658
    Abstract: A galvanized steel sheet includes a steel sheet and a plating layer on the surface of the steel sheet, in which the steel sheet includes, as a steel chemical composition, by mass %, C: 0.05 to 0.40%, Si: 0.5 to 3.0% and Mn: 1.5 to 3.0%, a microstructure of the steel sheet includes ferrite, bainite, by volume fraction, 30% or more of a tempered martensite, and 8% or more of an austenite, and tensile strength of the steel sheet is 980 MPa or more, and the plating layer includes an oxide including at least one chemical element selected from Si, Mn and Al, and when seen at a cross section including the steel sheet and the plating layer in a plate thickness direction, a projection area fraction of the oxide is 10% or more.
    Type: Application
    Filed: September 28, 2012
    Publication date: August 21, 2014
    Inventors: Takayuki Nozaki, Manabu Takahashi, Nobuhiro Fujita, Masafumi Azuma, Chisato Wakabayashi
  • Publication number: 20140234657
    Abstract: A hot-dip galvanized steel sheet includes: a steel sheet; and a plated layer on a surface of the steel sheet, a microstructure contains, by volume fraction, equal to or more than 20% and equal to or less than 99% in total of one or two of martensite and bainite, a residual structure contains one or two of ferrite, residual austenite of less than 8% by volume fraction, and pearlite of equal to or less than 10% by volume fraction, tensile strength is equal to or greater than 980 MPa, the plated layer is a hot-dip galvanized layer which contains oxides including one or two or more of Si, Mn, and Al, contains equal to or less than 15 mass % of Fe, and a remainder including Zn, Al, and unavoidable impurities, and when a cross section including the steel sheet and the hot-dip galvanized layer is seen in a sheet thickness direction, a projected area ratio is equal to or more than 10% and equal to or less than 90%.
    Type: Application
    Filed: September 28, 2012
    Publication date: August 21, 2014
    Inventors: Masafumi Azuma, Chisato Wakabayashi, Takayuki Nozaki, Manabu Takahashi, Nobuhiro Fujita
  • Publication number: 20140178712
    Abstract: Hot rolled steel sheet which has a maximum tensile strength of 600 MPa or more and has an excellent low temperature impact energy absorption and HAZ softening resistance and a method of production of the same are provided, that is, sheet which contains, by mass %, C: 0.04 to 0.09%, Si: 0.4% or less, Mn: 1.2 to 2.0%, P: 0.1% or less, S: 0.02% or less, Al: 1.0% or less, Nb: 0.02 to 0.09%, Ti: 0.02 to 0.07%, and N: 0.005% or less, where 2.0?Mn+8[% Ti]+12[% Nb]?2.6, has a balance of Fe and unavoidable impurities, has an area percentage of pearlite of 5% or less, has a total area percentage of martensite and retained austenite of 0.5% or less, has a balance of a metal structure of ferrite and/or bainite, has an average grain size of ferrite and bainite of 10 ?m or less, has an average particle size of alloy carbonitrides with incoherent interfaces which contain Ti and Nb of 20 nm or less, and has a yield ratio of 0.85 or more.
    Type: Application
    Filed: August 8, 2012
    Publication date: June 26, 2014
    Inventors: Naoki Maruyama, Naoki Yoshinaga, Masafumi Azuma, Yasuharu Sakuma, Atsushi Itami
  • Publication number: 20140170440
    Abstract: High strength steel sheet which secures tensile maximum strength 900 MPa or more high strength while having excellent shapeability, which high strength steel sheet which is excellent in shapeability characterized by having a predetermined composition of ingredients, by the steel sheet structure including a ferrite phase and martensite phase, by the ratio of Cu particles incoherent with the bcc iron being 15% or more with respect to the Cu particles as a whole, by a density of Cu particles in the ferrite phase being 1.0×1018/m3 or more, and by an average particle size of Cu particles in the ferrite phase being 2.0 nm or more.
    Type: Application
    Filed: July 27, 2012
    Publication date: June 19, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Akinobu Minami, Masafumi Azuma, Takuya Kuwayama, Shigeru Yonemura
  • Patent number: 8657970
    Abstract: This hot-rolled steel sheet contains, in terms of mass %, C: 0.015% or more to less than 0.040%; Si: less than 0.05%; Mn: 0.9% or more to 1.8% or less; P: less than 0.02%; S: less than 0.01%; Al: less than 0.1%; N: less than 0.006%; and Ti: 0.05% or more to less than 0.11%, with the remainder being Fe and inevitable impurities, wherein Ti/C is in a range of 2.5 or more to less than 3.5, Nb, Zr, V, Cr, Mo, B and W are not included, a microstructure includes a mixed microstructure of polygonal ferrite and quasi-polygonal ferrite in a proportion of greater than 96%, a maximum tensile strength is 520 MPa or more and less than 720 MPa, an aging index AI is more than 15 MPa, a product of a hole expansion ratio (?) % and a total elongation (El) % is 2350 or more, and a fatigue limit is 200 MPa or more.
    Type: Grant
    Filed: November 12, 2008
    Date of Patent: February 25, 2014
    Assignee: Nippon Steel & Sumitomo Metal Corporation
    Inventors: Naoki Yoshinaga, Masafumi Azuma, Yasuharu Sakuma, Naoki Maruyama
  • Patent number: 8460481
    Abstract: The invention is directed to providing, for application in automobiles, construction materials, household appliances and the like, high-strength sheets excellent in formability properties such as hole expansibility and ductility, and also in fatigue resistance, characterized in comprising, in specified contents expressed in mass %, C, Si, Mn, P, S, Al, N and O and a balance of iron and unavoidable impurities, and having a steel sheet structure composed mainly of ferrite and hard structures, a crystal orientation difference between some ferrite adjacent to hard structures and the hard structures of less than 9°, and a maximum tensile strength of 540 MPa or greater.
    Type: Grant
    Filed: April 9, 2009
    Date of Patent: June 11, 2013
    Assignee: Nippon Steel & Sumitomo Metal Corporation
    Inventors: Masafumi Azuma, Noriyuki Suzuki, Naoki Maruyama, Naoki Yoshinaga, Akinobu Murasato
  • Publication number: 20120222781
    Abstract: High strength steel plate with an ultimate tensile strength of 900 MPa or more which is excellent in hydrogen embrittlement resistance characterized in that, in the structure of the steel plate, (a) by volume fraction, ferrite is present in 10 to 50%, bainitic ferrite and/or bainite in 10 to 60%, and tempered martensite in 10 to 50%, and (b) iron-based carbides which contain Si or Si and Al in 0.1% or more are present in 4×108 (particles/mm3) or more.
    Type: Application
    Filed: November 30, 2010
    Publication date: September 6, 2012
    Inventors: Masafumi Azuma, Noriyuki Suzuki, Naoki Maruyama, Akinobu Murasato, Yasuharu Sakuma, Hiroyuki Kawata, Chisato Wakabayashi
  • Patent number: 8216397
    Abstract: The present invention provides: a high-strength high-ductility hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having high fatigue resistance and corrosion resistance; a high-strength hot-dip galvanized steel sheet excellent in ductility, which improves non-plating defects and plating adhesion after severe deformation, and a method of producing the same; a high-strength and high-ductility hot-dip galvanized steel sheet having high fatigue resistance and corrosion resistance; a high-strength hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having superior appearance and workability, which suppresses the generation of non-plating defects, and a method of producing the same; and a high-strength hot-dip galvannealed steel sheet and a high-strength hot-dip galvanized steel sheet, which suppress non-plating defects and surface defects and have both corrosion resistance, in particular corrosion resistance in an environment containing chlorine ion, and high ductility, and a meth
    Type: Grant
    Filed: June 10, 2009
    Date of Patent: July 10, 2012
    Assignee: Nippon Steel Corporation
    Inventors: Nobuhiro Fujita, Masafumi Azuma, Manabu Takahashi, Yasuhide Morimoto, Masao Kurosaki, Akihiro Miyasaka
  • Publication number: 20120152411
    Abstract: Provided is a galvanized steel sheet having a tensile strength of 770 MPa or more including a steel sheet portion, and a plated layer formed on the surface of the steel sheet portion, in which the plated layer is a galvanized plated layer or an galvannealed plated layer, the steel sheet portion has a soft layer that directly adjoins the interface with the plated layer and an inside layer that is other than the soft layer, the thickness D of soft layer is 0.001% to 5% of thickness t of the steel sheet portion, and, when the hardness of the soft layer measured by nano-indentation method is indicated by H1, and the representative hardness of the steel sheet portion measured by the nano-indentation method is indicated by Ha in cross section that goes along the thickness direction of the steel sheet portion, H1 is 5% to 75% of Ha.
    Type: Application
    Filed: August 31, 2010
    Publication date: June 21, 2012
    Inventors: Yasuhide Morimoto, Nobuhiro Fujita, Akihiro Miyasaka, Masafumi Azuma, Noriyuki Suzuki, Toshiki Nonaka
  • Publication number: 20120141829
    Abstract: Provided is a spot welded joint (10) which includes at least one thin steel plate with a tensile strength of 750 MPa to 1850 MPa and a carbon equivalent Ceq of equal to or more than 0.22 mass % to 0.55 mass % and in which a nugget (3) is formed in an interface of the thin steel plates (1A, 1B). In a nugget outer layer zone, a microstructure consists of a dendrite structure in which an average value of arm intervals is equal to or less than 12 ?m, an average grain diameter of carbides contained in the microstructure is 5 nm to 100 nm, and a number density of carbides is equal to or more than 2×106/mm2.
    Type: Application
    Filed: August 30, 2010
    Publication date: June 7, 2012
    Inventors: Hatsuhiko Oikawa, Hideki Hamatani, Masafumi Azuma, Noriyuki Suzuki, Fuminori Watanabe, Naoki Maruyama, Hiroyuki Kawata
  • Patent number: 8163108
    Abstract: This cold-rolled steel sheet includes, in terms of mass %, C: not less than 0.05% and not more than 0.095%, Cr: not less than 0.15% and not more than 2.0%, B: not less than 0.0003% and not more than 0.01%, Si: not less than 0.3% and not more than 2.0%, Mn: not less than 1.7% and not more than 2.6%, Ti: not less than 0.005% and not more than 0.14%, P: not more than 0.03%, S: not more than 0.01%, Al: not more than 0.1%, N: less than 0.005%, O: not less than 0.0005% and not more than 0.005%, and contains as the remainder, iron and unavoidable impurities, wherein the microstructure of the steel sheet includes mainly polygonal ferrite having a crystal grain size of not more than 4 ?m, and hard microstructures of bainite and martensite, the block size of the martensite is not more than 0.9 ?m, the Cr content within the martensite is 1.1 to 1.5 times the Cr content within the polygonal ferrite, and the tensile strength is at least 880 MPa.
    Type: Grant
    Filed: March 26, 2009
    Date of Patent: April 24, 2012
    Assignee: Nippon Steel Corporation
    Inventors: Masafumi Azuma, Naoki Yoshinaga, Naoki Maruyama, Noriyuki Suzuki, Yasuharu Sakuma
  • Patent number: 8070889
    Abstract: The invention is directed to providing, for application in automobiles, construction materials, household appliances and the like, high-strength sheets excellent in formability properties such as hole expansibility and ductility, and also in fatigue resistance, characterized in comprising, in specified contents expressed in mass %, C, Si, Mn, P, S, Al, N and O and a balance of iron and unavoidable impurities, and having a steel sheet structure composed mainly of ferrite and hard structures, a crystal orientation difference between some ferrite adjacent to hard structures and the hard structures of less than 9°, and a maximum tensile strength of 540 MPa or greater.
    Type: Grant
    Filed: April 9, 2009
    Date of Patent: December 6, 2011
    Assignee: Nippon Steel Corporation
    Inventors: Masafumi Azuma, Noriyuki Suzuki, Naoki Maruyama, Naoki Yoshinaga, Akinobu Murasato
  • Publication number: 20110024004
    Abstract: The invention is directed to providing, for application in automobiles, construction materials, household appliances and the like, high-strength sheets excellent in formability properties such as hole expansibility and ductility, and also in fatigue resistance, characterized in comprising, in specified contents expressed in mass %, C, Si, Mn, P, S, Al, N and O and a balance of iron and unavoidable impurities, and having a steel sheet structure composed mainly of ferrite and hard structures, a crystal orientation difference between some ferrite adjacent to hard structures and the hard structures of less than 9°, and a maximum tensile strength of 540 MPa or greater.
    Type: Application
    Filed: April 9, 2009
    Publication date: February 3, 2011
    Inventors: Masafumi Azuma, Noriyuki Suzuki, Naoki Maruyama, Naoki Yoshinaga, Akinobu Murasato
  • Publication number: 20110017360
    Abstract: This hot-rolled steel sheet contains, in terms of mass%, C: 0.015% or more to less than 0.040%; Si: less than 0.05%; Mn: 0.9% or more to 1.8% or less; P: less than 0.02%; S: less than 0.01%; Al: less than 0.1%; N: less than 0.006%; and Ti: 0.05% or more to less than 0.11%, with the remainder being Fe and inevitable impurities, wherein Ti/C is in a range of 2.5 or more to less than 3.5, Nb, Zr, V, Cr, Mo, B and W are not included, a microstructure includes a mixed microstructure of polygonal ferrite and quasi-polygonal ferrite in a proportion of greater than 96%, a maximum tensile strength is 520 MPa or more and less than 720 MPa, an aging index AI is more than 15 MPa, a product of a hole expansion ratio (A) % and a total elongation (El) % is 2350 or more, and a fatigue limit is 200 MPa or more.
    Type: Application
    Filed: November 12, 2008
    Publication date: January 27, 2011
    Inventors: Naoki Yoshinaga, Masafumi Azuma, Yasuharu Sakuma, Naoki Maruyama
  • Publication number: 20110008647
    Abstract: This cold-rolled steel sheet includes, in terms of mass %, C: not less than 0.05% and not more than 0.095%, Cr: not less than 0.15% and not more than 2.0%, B: not less than 0.0003% and not more than 0.01%, Si: not less than 0.3% and not more than 2.0%, Mn: not less than 1.7% and not more than 2.6%, Ti: not less than 0.005% and not more than 0.14%, P: not more than 0.03%, S: not more than 0.01%, Al: not more than 0.1%, N: less than 0.005%, O: not less than 0.0005% and not more than 0.005%, and contains as the remainder, iron and unavoidable impurities, wherein the microstructure of the steel sheet includes mainly polygonal ferrite having a crystal grain size of not more than 4 ?m, and hard microstructures of bainite and martensite, the block size of the martensite is not more than 0.9 ?m, the Cr content within the martensite is 1.1 to 1.5 times the Cr content within the polygonal ferrite, and the tensile strength is at least 880 MPa.
    Type: Application
    Filed: March 26, 2009
    Publication date: January 13, 2011
    Inventors: Masafumi Azuma, Naoki Yoshinaga, Naoki Maruyama, Noriyuki Suzuki, Yasuharu Sakuma
  • Patent number: 7824509
    Abstract: The present invention provides: a high-strength high-ductility hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having high fatigue resistance and corrosion resistance; a high-strength hot-dip galvanized steel sheet excellent in ductility, which improves non-plating defects and plating adhesion after severe deformation, and a method of producing the same; a high-strength and high-ductility hot-dip galvanized steel sheet having high fatigue resistance and corrosion resistance; a high-strength hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having superior appearance and workability, which suppresses the generation of non-plating defects, and a method of producing the same; and a high-strength hot-dip galvannealed steel sheet and a high-strength hot-dip galvanized steel sheet, which suppress non-plating defects and surface defects and have both corrosion resistance, in particular corrosion resistance in an environment containing chlorine ion, and high ductility, and a meth
    Type: Grant
    Filed: August 16, 2007
    Date of Patent: November 2, 2010
    Assignee: Nippon Steel Corporation
    Inventors: Nobuhiro Fujita, Masafumi Azuma, Manabu Takahashi, Yasuhide Morimoto, Masao Kurosaki, Akihiro Miyasaka
  • Publication number: 20090272467
    Abstract: The present invention provides: a high-strength high-ductility hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having high fatigue resistance and corrosion resistance; a high-strength hot-dip galvanized steel sheet excellent in ductility, which improves non-plating defects and plating adhesion after severe deformation, and a method of producing the same; a high-strength and high-ductility hot-dip galvanized steel sheet having high fatigue resistance and corrosion resistance; a high-strength hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having superior appearance and workability, which suppresses the generation of non-plating defects, and a method of producing the same; and a high-strength hot-dip galvannealed steel sheet and a high-strength hot-dip galvanized steel sheet, which suppress non-plating defects and surface defects and have both corrosion resistance, in particular corrosion resistance in an environment containing chlorine ion, and high ductility, and a meth
    Type: Application
    Filed: June 10, 2009
    Publication date: November 5, 2009
    Applicant: Nippon Steel Corporation
    Inventors: Nobuhiro Fujita, Masafumi Azuma, Manabu Takahashi, Yasuhide Morimoto, Masao Kurosaki, Akihiro Miyasaka