With Working Patents (Class 148/602)
  • Patent number: 10934609
    Abstract: [Object] To provide a steel sheet for carburizing that demonstrates improved extreme deformability prior to carburizing, and a method for manufacturing the same. [Solution] A steel sheet consisting of, in mass %, C: more than or equal to 0.02%, and less than 0.30%, Si: more than or equal to 0.005%, and less than 0.5%, Mn: more than or equal to 0.01%, and less than 3.0%, P: less than or equal to 0.1%, S: less than or equal to 0.1%, sol. Al: more than or equal to 0.0002%, and less than or equal to 3.0%, N: less than or equal to 0.2%, and the balance: Fe and impurities, in which average value of X-ray random intensity ratio, assignable to an orientation group of ferrite crystal grain ranging from {100}<011> to {223}<110>, is 7.0 or smaller, average equivalent circle diameter of carbide is 5.0 ?m or smaller, percentage of number of carbides with an aspect ratio of 2.
    Type: Grant
    Filed: August 30, 2018
    Date of Patent: March 2, 2021
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Yuri Toda, Kazuo Hikida, Motonori Hashimoto
  • Patent number: 10900097
    Abstract: Provided is a high-strength hot-dip galvanized steel sheet having good surface quality and spot weldability. The high-strength hot-dip galvanized steel sheet includes a base steel sheet and a zinc plating layer formed on the base steel sheet. The base steel sheet includes carbon (C): 0.1% to 0.3%, silicon (Si): 0.5% to 2.5%, manganese (Mn): 2.0% to 8.0%, soluble aluminum (sol.Al): 0.001% to 0.5%, phosphorus (P): 0.04% or less (excluding 0%), sulfur (S): 0.015% or less, nitrogen (N): 0.02% or less, chromium (Cr): 0.01% to 0.7%, titanium (Ti): (48/14)*[N] % to 0.1%, and a balance of iron (Fe) and inevitable impurities. The base steel sheet has a microstructure comprising ferrite in an area fraction of 5% to 30%, austenite in an area fraction of 5% to 20%, bainite and martensite in an area fraction of 50% to 80%, and precipitates in an area fraction of 2% or less.
    Type: Grant
    Filed: December 13, 2016
    Date of Patent: January 26, 2021
    Assignee: POSCO
    Inventors: Myung-Soo Kim, Ki-Cheol Kang, Il-Jeong Park
  • Patent number: 10801085
    Abstract: A high-strength steel sheet having high yield ratio, excellent stretch flange formability, and resistance to secondary working embrittlement. The steel sheet has a composition containing C: 0.02% to less than 0.10%, Si: less than 0.3%, Mn: less than 1.0%, P: 0.10% or less, S: 0.020% or less, Al: 0.01% to 0.10%, N: 0.010% or less, and Nb: 0.003% to less than 0.070% on a mass basis, the remainder being Fe and inevitable impurities. A steel microstructure of the steel sheet contains ferrite: 90% or more and a total of pearlite, martensite, retained austenite, and cementite: 0% to 10% on an area fraction basis, in which the average grain size of the ferrite is 15.0 ?m or less, and in which the average aspect ratio of the ferrite is 1.2 or more; and a tensile strength of 500 MPa or less.
    Type: Grant
    Filed: May 26, 2016
    Date of Patent: October 13, 2020
    Assignee: JFE STEEL CORPORATION
    Inventors: Yuma Honda, Yoshimasa Funakawa, Kozo Harada
  • Patent number: 10752972
    Abstract: A hot-rolled steel sheet includes a predetermined chemical composition, and a structure which includes, by area ratio, a ferrite in a range of 5% to 60% and a bainite in a range of 30% to 95%, in which in the structure, in a case where a boundary having an orientation difference of equal to or greater than 15° is defined as a grain boundary, and an area which is surrounded by the grain boundary and has an equivalent circle diameter of equal to or greater than 0.3 ?m is defined as a grain, the ratio of the grains having an intragranular orientation difference in a range of 5° to 14° is, by area ratio, in a range of 20% to 100%.
    Type: Grant
    Filed: February 22, 2016
    Date of Patent: August 25, 2020
    Assignee: NIPPON STEEL CORPORATION
    Inventors: Natsuko Sugiura, Mitsuru Yoshida, Hiroshi Shuto, Tatsuo Yokoi, Masayuki Wakita
  • Patent number: 10570479
    Abstract: An elongated steel element having a non-round cross-section and being in a work-hardened state, said elongated steel element having as steel composition: a carbon content ranging from 0.20 weight percent to 1.00 weight percent, a silicon content ranging from 0.05 weight percent to 2.0 weight percent, a manganese content ranging from 0.40 weight percent to 1.0 weight percent, a chromium content ranging from 0.0 weight percent to 1.0 weight percent, a sulfur and phosphor content being individually limited to 0.025 weight percent, contents of nickel, vanadium, aluminium, molybdenum or cobalt all being individually limited to 0.5 weight percent, the remainder being iron and unavoidable impurities, said steel having martensitic structure that comprises martensitic grains, wherein a fraction of at least 10 volume percent of martensitic grains is oriented.
    Type: Grant
    Filed: January 28, 2016
    Date of Patent: February 25, 2020
    Assignee: NV BEKAERT SA
    Inventors: Christophe Mesplont, Geert Tempelaere, Wim Van Haver, Maarten De Clercq
  • Patent number: 10472696
    Abstract: A method for producing a hardened sheet steel, in particular a sheet steel that is coated with a metallic anti-corrosion layer; the sheet steel is first heated to an austenitization temperature and the austenite transformation is completed and then the sheet steel is pre-cooled to a temperature that lies above the transformation temperature of the austenite to other phases and is then transferred to a press-hardening die and in the press-hardening die, is shaped and, for hardening purposes, is quenched; for pre-cooling purposes, the blank is blasted in at least some areas or zones with dry ice, dry snow, or a gas flow containing dry ice particles.
    Type: Grant
    Filed: September 9, 2015
    Date of Patent: November 12, 2019
    Assignee: voestalpine Stahl GmbH
    Inventors: Christoph Wagner, Siegfried Kolnberger
  • Patent number: 10323293
    Abstract: A high-carbon hot rolled steel sheet with excellent hardenability and small in-plane anisotropy, and a method for manufacturing the steel sheet are provided. The steel sheet has a chemical composition including, by mass %, C: 0.20 to 0.48%, Si: not more than 0.1%, Mn: not more than 0.5%, P: not more than 0.03%, S: not more than 0.01%, sol. Al: not more than 0.10%, N: not more than 0.005% and B: 0.0005 to 0.0050%, the balance including Fe and inevitable impurities. The steel sheet includes a microstructure containing ferrite and cementite. The cementite has an average grain size of not more than 1.0 ?m. The steel sheet has an in-plane anisotropy of r value, ?r, of not more than 0.1 in absolute value.
    Type: Grant
    Filed: December 25, 2012
    Date of Patent: June 18, 2019
    Assignee: JFE Steel Corporation
    Inventors: Yuka Miyamoto, Takashi Kobayashi, Nobuyuki Nakamura, Yoshimasa Funakawa
  • Patent number: 10138536
    Abstract: A high-strength hot-rolled steel sheet including a chemical composition containing, in percent by mass, 0.05% to 0.12% of C, 0.05% to 1.0% of Si, 0.5% to 1.8% of Mn, 0.04% or less of P, 0.0030% or less of S, 0.005% to 0.07% of Al, 0.006% or less of N, 0.05% to 0.15% of Ti, and the balance being Fe and incidental impurities, in which, in a region in the range of ? to ? of the sheet thickness, the content of Ti*, which is Ti existing as precipitates, is 0.3×[Ti] to 0.6×[Ti], where [Ti] is the Ti content, and the steel sheet has a microstructure in which the area fraction of the bainite phase in the entire structure is more than 95%.
    Type: Grant
    Filed: December 26, 2012
    Date of Patent: November 27, 2018
    Assignee: JFE Steel Corporation
    Inventors: Katsumi Nakajima, Hayato Saito, Yoshimasa Funakawa
  • Patent number: 10053757
    Abstract: A process for producing hot-rolled steel strip with a tensile strength of between 760 and 940 MPa and a steel produced therewith, suitable for producing parts by working such as press forming, bending or stretch flanging.
    Type: Grant
    Filed: July 15, 2013
    Date of Patent: August 21, 2018
    Assignee: TATA STEEL IJMUIDEN BV
    Inventors: David Neal Hanlon, Theo Arnold Kop, Stefanus Matheus Cornelis Van Bohemen
  • Patent number: 9976205
    Abstract: The invention relates to a steel and to a flat steel product produced therefrom that have optimized mechanical properties and at the same time can be produced at low cost, without having to rely for this on expensive alloying elements that are subject to great fluctuations with regard to their procurement costs. The steel and the flat steel product have for this purpose the following composition according to the invention (in % by weight): C: 0.11-0.16%; Si: 0.1-0.3%; Mn: 1.4-1.9%; Al: 0.02-0.1%; Cr: 0.45-0.85%; Ti: 0.025-0.06%; B: 0.0008-0.002%, the remainder Fe and impurities that are unavoidable for production-related reasons, which include contents of phosphorus, sulfur, nitrogen or molybdenum as long as the following respectively apply for their contents: P: ?0.02%, S: ?0.003%, N: ?0.008%, Mo: ?0.1%. Similarly, the invention relates to a method for producing a flat steel product that consists of a steel according to the invention.
    Type: Grant
    Filed: June 5, 2013
    Date of Patent: May 22, 2018
    Assignee: ThyssenKrupp Steel Europe AG
    Inventors: Ekatherina Bocharova, Sigrun Ebest, Dorothea Mattissen, Roland Sebald
  • Patent number: 9920408
    Abstract: Disclosed are a hot stamping part with enhanced toughness and a method for manufacturing the same, in which the hot stamping part has a tensile strength (TS) of 700-1,200 MPa after hot stamping while guaranteeing elongation (EL) of 12% or more by adjusting alloy components and controlling process conditions.
    Type: Grant
    Filed: May 15, 2013
    Date of Patent: March 20, 2018
    Assignee: HYUNDAI STEEL COMPANY
    Inventors: Seung-Man Nam, Seung-Ha Lee
  • Patent number: 9752217
    Abstract: In a hot-rolled steel sheet, an average pole density of an orientation group {100}<011> to {223}<110>, which is represented by an arithmetic mean of pole densities of orientations {100}<011>, {116}<110>, {114}<110>, {112}<110>, and {223}<110> is 1.0 to 4.0 and a pole density of a crystal orientation {332}<113> is 1.0 to 4.8, in a thickness center portion which is a thickness range of ? to ? from the surface of the steel sheet; an average grain size in the thickness center portion is less than or equal to 10 ?m and a grain size of cementite precipitating in a grain boundary of the steel sheet is less than or equal to 2 ?m; and an average grain size of precipitates containing TiC in grains is less than or equal to 3 nm and a number density per unit volume is greater than or equal to 1×1016 grains/cm3.
    Type: Grant
    Filed: April 13, 2012
    Date of Patent: September 5, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Tatsuo Yokoi, Hiroshi Shuto, Riki Okamoto, Nobuhiro Fujita, Kazuaki Nakano, Takeshi Yamamoto
  • Patent number: 9738960
    Abstract: The high strength steel sheet has a chemical composition including 0.08% to 0.20% of C, 0.3% or less of Si, 0.1% to 3.0% of Mn, 0.10% or less of P, 0.030% or less of S, 0.10% or less of Al, 0.010% or less of N, 0.20% to 0.80% of V, and the remainder composed of Fe and incidental impurities on a percent by mass basis, and a microstructure which includes 95% or more of ferrite phase on an area percentage basis, in which fine precipitates are dispersed having a distribution in such a way that the number density of precipitates having a particle size of less than 10 nm is 1.0×105/?m3 or more and the standard deviation of natural logarithm values of precipitate particle sizes with respect to precipitates having a particle size of less than 10 nm is 1.5 or less.
    Type: Grant
    Filed: April 18, 2013
    Date of Patent: August 22, 2017
    Assignee: JFE Steel Corporation
    Inventors: Taro Kizu, Yoshimasa Funakawa, Hidekazu Ookubo, Tokunori Kanemura, Masato Shigemi, Shoji Kasai, Shinji Yamazaki, Yusuke Yasufuku
  • Patent number: 9670569
    Abstract: This is a cold-rolled steel sheet includes, by mass %, C: 0.02% to 0.4%, Si: 0.001% to 2.5%, Mn: 0.001% to 4.0%, and Al: 0.001% to 2.0%. The sum of the Si content and the Al content is 1.0% to 4.5%. An average pole density of an orientation group from {100}<011> to {223}<110> is 1.0 to 6.5, and a pole density of a crystal orientation {332}<113> is 1.0 to 5.0. A microstructure includes, by an area ratio %, 5% to 80% of ferrite, 5% to 80% of bainite, and 2% to 30% of retained austenite. In the microstructure, by an area ratio %, martensite is limited to 20% or less, pearlite is limited to 10% or less, and tempered martensite is limited to 60% or less.
    Type: Grant
    Filed: March 28, 2012
    Date of Patent: June 6, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Takayuki Nozaki, Manabu Takahashi, Nobuhiro Fujita, Hiroshi Yoshida, Shinichiro Watanabe, Takeshi Yamamoto
  • Patent number: 9650690
    Abstract: A high-strength steel sheet includes: 0.03 to 0.20% of C, 0.08 to 1.5% of Si, 0.5 to 3.0% of Mn, 0.05% or less of P, 0.0005% or more of S, 0.008 to 0.20% of acid-soluble Ti, 0.0005 to 0.01% of N, more than 0.01% of acid-soluble Al, and 0.001 to 0.04% of one or both of Ce and La in terms of mass %; and the balance including Fe and inevitable impurities. The ratio of (Ce+La)/acid-soluble Al is equal to or more than 0.1 and the ratio of (Ce+La)/S is in the range of 0.4 to 50 in a mass base, and the density of the number of inclusions, having a circle equivalent diameter of 2 ?m or less, which are present in the steel sheet is equal to or more than 15/mm2.
    Type: Grant
    Filed: June 15, 2009
    Date of Patent: May 16, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Kenichi Yamamoto, Katsuhiro Sasai, Hideaki Yamamura, Hiroshi Harada, Kaoru Kawasaki
  • Patent number: 9228244
    Abstract: A high strength hot dipped galvanized steel sheet is provided. By controlling the amount of addition of Ti instead of the addition of Nb or B, it is possible to obtain an effect of retarding recrystallization and grain growth even if annealing by a continuous annealing process in a temperature range of the general annealing temperature of 720° C. to a temperature of the lower of 800° C. or Ac3 temperature. By controlling the rolling and heat treatment conditions, it is possible to control the ferrite phase rate, grain size of the low temperature transformed phases, ratio of average values of the nano hardnesses of the ferrite phase and low temperature transformed phases, and fluctuations of hardnesses of the low temperature transformed phases in a composite structure steel of ferrite and low temperature transformed phases and obtain a high strength hot dipped galvanized steel sheet.
    Type: Grant
    Filed: March 31, 2011
    Date of Patent: January 5, 2016
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Kengo Takeda, Kazuhisa Kusumi, Haruhiko Eguchi, Jun Hirowatari, Shintarou Fujii
  • Patent number: 9139885
    Abstract: This high-strength steel sheet includes by mass percentage: 0.05 to 0.4% of C; 0.1 to 2.5% of Si; 1.0 to 3.5% of Mn; 0.001 to 0.03% of P; 0.0001 to 0.01% of S; 0.001 to 2.5% of Al; 0.0001 to 0.01% of N; 0.0001 to 0.008% of O; and a remainder composed of iron and inevitable impurities, wherein a steel sheet structure contains by volume fraction 10 to 50% of a ferrite phase, 10 to 50% of a tempered martensite phase, and a remaining hard phase, wherein a 98% hardness is 1.5 or more times as high as a 2% hardness in a range from ? to ? of a thickness of the steel sheet, wherein a kurtosis K* of the hardness distribution between the 2% hardness and the 98% hardness is ?1.2 to ?0.4, and wherein an average crystal grain size in the steel sheet structure is 10 ?m or less.
    Type: Grant
    Filed: September 16, 2011
    Date of Patent: September 22, 2015
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Hiroyuki Kawata, Naoki Maruyama, Akinobu Murasato, Naoki Yoshinaga, Chisato Wakabayashi, Noriyuki Suzuki
  • Patent number: 9011615
    Abstract: Provided are a bake hardening steel having a crystalline grain size of ASTM No. 9 or more and a method for preparing the bake hardening steel by controlling the winding, rolling and cooling conditions. The bake hardening steel includes: C:0.0016˜0.0025%, Si:0.02% or less, P:0.01˜0.05%, S:0.01% or less, sol.Al:0.08˜0.12%, N:0.0025% or less, Ti:0.003% or less, Nb:0.003˜0.011%, Mo:0.01˜0.1%, B:0.0005˜0.0015% or less, balance Fe and other inevitable impurities, wherein % is weight %, and Mn and P satisfy the relation of ?30(° C.)?803P?24.4Mn?58.
    Type: Grant
    Filed: June 9, 2009
    Date of Patent: April 21, 2015
    Assignee: POSCO
    Inventors: Seong-Ho Han, Il-Ryoung Sohn, Shin-Hwan Kang, Min-Ki Seun
  • Publication number: 20150101717
    Abstract: A slab has a steel composition including 0.020% to 0.065% of C, 0.1% or less of Si, 0.40% to less than 0.80% of Mn, 0.030% or less of P, 0.005% or less of S, 0.08% to 0.16% of Ti, 0.005% to 0.1% of Al, 0.005% or less of N, and the balance being Fe and incidental impurities, in which Ti*(=Ti?(48/14)×N) satisfies [Ti*?0.08] and [0.300?C/Ti*?0.375], is subjected to hot rolling to obtain a hot-rolled steel sheet in which the steel microstructure includes, in terms of area fraction, 95% or more of a ferrite phase; the average ferrite grain size is 10 ?m or less; the average grain size of Ti carbides precipitated in steel is 10 nm or less; and Ti in the amount of 80% or more of Ti* is precipitated as Ti carbides.
    Type: Application
    Filed: April 26, 2012
    Publication date: April 16, 2015
    Applicant: JFE STEEL CORPORATION
    Inventors: Noriaki Kosaka, Kazuhiro Seto, Hidetaka Kawabe
  • Patent number: 8999085
    Abstract: A high-ductility, high-strength and high Mn steel strip used for steel strips of automobiles requiring superior formability and high strength, a plated steel strip produced by using the same, and a manufacturing method thereof are disclosed. The high Mn steel strip comprises, by weight %, 0.2˜1.5% of C, 10˜25% of Mn, 0.01˜3.0% of Al, 0.005˜2.0% of Si, 0.03% or less of P, 0.03% or less of S, 0.040% or less of N, and the balance of Fe and other unavoidable impurities. The high-ductility, high-strength and high Mn steel strip, and the plated steel strip produced by using the same have superior surface properties and plating characteristics.
    Type: Grant
    Filed: December 22, 2006
    Date of Patent: April 7, 2015
    Assignee: Posco
    Inventors: Seong-Ju Kim, Kwang-Geun Chin, Hyun-Gyu Hwang, Sung-Kyu Kim, Il-Ryoung Sohn, Young-Kook Lee, Oh-Yeon Lee
  • Publication number: 20150090376
    Abstract: A high carbon hot rolled steel sheet and a method for manufacturing the same are provided, wherein excellent cold workability and excellent hardenability are obtained stably. The high carbon hot rolled steel sheet has a composition containing C: 0.20% to 0.48%, Si: 0.1% or less, Mn: 0.5% or less, P: 0.03% or less, S: 0.01% or less, sol. Al: more than 0.10% and 1.0% or less, N: 0.005% or less, B: 0.0005% to 0.0050%, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, and a microstructure composed of ferrite and cementite, wherein the average grain size of the above-described ferrite is 10 to 20 ?m and the spheroidization ratio of the above-described cementite is 90% or more.
    Type: Application
    Filed: December 26, 2012
    Publication date: April 2, 2015
    Applicant: JFE STEEL CORPORATION
    Inventors: Nobuyuki Nakamura, Takashi Kobayashi, Yoshimasa Funakawa
  • Publication number: 20150056468
    Abstract: The high strength steel sheet has a chemical composition including 0.08% to 0.20% of C, 0.3% or less of Si, 0.1% to 3.0% of Mn, 0.10% or less of P, 0.030% or less of S, 0.10% or less of Al, 0.010% or less of N, 0.20% to 0.80% of V, and the remainder composed of Fe and incidental impurities on a percent by mass basis, and a microstructure which includes 95% or more of ferrite phase on an area percentage basis, in which fine precipitates are dispersed having a distribution in such a way that the number density of precipitates having a particle size of less than 10 nm is 1.0×105/?m3 or more and the standard deviation of natural logarithm values of precipitate particle sizes with respect to precipitates having a particle size of less than 10 nm is 1.5 or less.
    Type: Application
    Filed: April 18, 2013
    Publication date: February 26, 2015
    Inventors: Taro Kizu, Yoshimasa Funakawa, Hidekazu Ookubo, Tokunori Kanemura, Masato Shigemi, Shoji Kasai, Shinji Yamazaki, Yusuke Yasufuku
  • Publication number: 20150030880
    Abstract: The present invention provides a high-strength hot-rolled steel sheet having both excellent strength and excellent workability (particularly, bending workability), and a method of producing the same. The steel sheet of the present invention has a certain composition as well as microstructures such that an area ratio of ferrite phase is 95% or more, an average grain size of the ferrite phase is 8 ?m or less, and carbides in grains of the ferrite phase have an average particle size of less than 10 nm. The steel sheet of the present invention also has a tensile strength of 980 MPa or more.
    Type: Application
    Filed: January 21, 2013
    Publication date: January 29, 2015
    Applicant: JEF STEEL CORPORATION
    Inventors: Noriaki Kosaka, Yoshimasa Funakawa, Masato Shigemi, Hidekazu Ookubo, Tokunori Kanemura
  • Publication number: 20150020933
    Abstract: Provided is a heat-resistant cold rolled ferritic stainless steel sheet containing, in terms of mass %, 0.02% or less of C, 0.1% to 1.0% of Si, greater than 0.6% to 1.5% of Mn, 0.01% to 0.05% of P, 0.0001% to 0.0100% of S, 13.0% to 20.0% of Cr, 0.1% to 3.0% of Mo, 0.005% to 0.20% of Ti, 0.3% to 1.0% of Nb, 0.0002% to 0.0050% of B, 0.005% to 0.50% of Al, and 0.02% or less of N, with the balance being Fe and inevitable impurities, in which {111}-oriented grains are present at an area ratio of 20% or greater in a region from a surface layer to t/4 (t is a sheet thickness), {111}-oriented grains are present at an area ratio of 40% or greater in a region from t/4 to t/2, and {011}-oriented grains are present at an area ratio of 15% or less in the entire region in a thickness direction.
    Type: Application
    Filed: March 26, 2013
    Publication date: January 22, 2015
    Applicant: Nippon Steel & Sumikin Stainless Steel Corporation
    Inventors: Junichi Hamada, Yuji Koyama, Yoshiharu Inoue, Tadashi Komori, Fumio Fudanoki, Toshio Tanoue, Naoto Ono
  • Publication number: 20150000801
    Abstract: A high-carbon hot rolled steel sheet with excellent hardenability and small in-plane anisotropy, and a method for manufacturing the steel sheet are provided. The steel sheet has a chemical composition including, by mass %, C: 0.20 to 0.48%, Si: not more than 0.1%, Mn: not more than 0.5%, P: not more than 0.03%, S: not more than 0.01%, sol. Al: not more than 0.10%, N: not more than 0.005% and B: 0.0005 to 0.0050%, the balance including Fe and inevitable impurities. The steel sheet includes a microstructure containing ferrite and cementite. The cementite has an average grain size of not more than 1.0 ?m. The steel sheet has an in-plane anisotropy of r value, ?r, of not more than 0.1 in absolute value.
    Type: Application
    Filed: December 25, 2012
    Publication date: January 1, 2015
    Applicant: JFE STEEL CORPORATION
    Inventors: Yuka Miyamoto, Takashi Kobayashi, Nobuyuki Nakamura, Yoshimasa Funakawa
  • Publication number: 20140360634
    Abstract: A hot rolled steel sheet having a chemical composition containing, by mass %, C: 0.04% or more and 0.20% or less, Si: 0.7% or more and 2.3% or less, Mn: 0.8% or more and 2.8% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.1% or less, N: 0.008% or less, and the balance being Fe and inevitable impurities. The microstructure of the hot rolled steel sheet includes ferrite and pearlites, in which the area ratio of the ferrite is 75% or more and less than 95%, the mean grain size of the ferrite is 5 ?m or more and 25 ?m or less, the area ratio of pearlite is 5% or more and less than 25%, the mean grain size of pearlite is 2.0 ?m or more, and the mean free path of pearlite is 5 ?m or more.
    Type: Application
    Filed: August 9, 2012
    Publication date: December 11, 2014
    Applicant: JFE Steel Corporation
    Inventors: Yoshiyasu Kawasaki, Shinjiro Kaneko, Yasunobu Nagataki
  • Publication number: 20140363696
    Abstract: A high-strength hot rolled steel sheets with excellent stretch flangeability has small variations in mechanical properties in individual coils. Variations in strength from place to place in a coil are decreased by minimally reducing the Si and Mn contents to suppress the occurrence of problems such as segregation. Further, the microstructure of the steel sheets is configured such that a ferrite phase represents an area ratio of not less than 95%, the ferrite crystal grains have an average grain size of not less than 1 ?m, and the ferrite crystal grains contain TiC with an average particle size of not more than 7 nm dispersed in the crystal grains.
    Type: Application
    Filed: December 14, 2012
    Publication date: December 11, 2014
    Inventors: Yoshimasa Funakawa, Tetsuo Yamamoto, Hiroshi Uchomae, Hiroshi Nakano, Taro Kizu
  • Publication number: 20140352852
    Abstract: The steel sheet has a chemical composition containing, by mass %, C: 0.04-0.08%, Si: 0.50% or less, Mn: 0.8-2.2%, P: 0.02% or less, S: 0.006% or less, Al: 0.1% or less, N: 0.008% or less, and Cr: 0.05-0.8%, and further Nb: 0.01-0.08%, V: 0.001-0.12%, and Ti: 0.005-0.04% in adjusted amounts, with the balance including Fe and incidental impurities. The steel sheet has a surface layer having a microstructure containing bainite as a main phase, martensite as a second phase in a volume fraction of 0.5-4%, and at lease one of ferrite phase, pearlite, and cementite as a third phase in a total volume fraction of 10% or less.
    Type: Application
    Filed: December 21, 2012
    Publication date: December 4, 2014
    Inventors: Hiroshi Nakata, Tomoaki Shibata, Chikara Kami
  • Publication number: 20140338801
    Abstract: A high-strength hot-rolled steel sheet including a chemical composition containing, in percent by mass, 0.05% to 0.12% of C, 0.05% to 1.0% of Si, 0.5% to 1.8% of Mn, 0.04% or less of P, 0.0030% or less of S, 0.005% to 0.07% of Al, 0.006% or less of N, 0.05% to 0.15% of Ti, and the balance being Fe and incidental impurities, in which, in a region in the range of ? to ? of the sheet thickness, the content of Ti*, which is Ti existing as precipitates, is 0.3×[Ti] to 0.6×[Ti], where [Ti] is the Ti content, and the steel sheet has a microstructure in which the area fraction of the bainite phase in the entire structure is more than 95%.
    Type: Application
    Filed: December 26, 2012
    Publication date: November 20, 2014
    Applicant: JFE STEEL CORPORATION
    Inventors: Katsumi Nakajima, Hayato Saito, Yoshimasa Funakawa
  • Patent number: 8888933
    Abstract: This high-strength steel sheet includes: in terms of percent by mass, 0.03 to 0.10% of C; 0.01 to 1.5% of Si; 1.0 to 2.5% of Mn; 0.1% or less of P; 0.02% or less of S; 0.01 to 1.2% of Al; 0.06 to 0.15% of Ti; and 0.01% or less of N; and contains as the balance, iron and inevitable impurities, wherein a tensile strength is in a range of 590 MPa or more, and a ratio between the tensile strength and a yield strength is in a range of 0.80 or more, a microstructure includes bainite at an area ratio of 40% or more and the balance being either one or both of ferrite and martensite, a density of Ti(C,N) precipitates having sizes of 10 nm or smaller is in a range of 1010 precipitates/mm3 or more, and a ratio (Hvs/Hvc) of a hardness (Hvs) at a depth of 20 ?m from a surface to a hardness (Hvc) at a center of a sheet thickness is in a range of 0.85 or more.
    Type: Grant
    Filed: May 26, 2010
    Date of Patent: November 18, 2014
    Assignee: Nippon Steel & Sumitomo Metal Corporation
    Inventors: Kunio Hayashi, Toshimasa Tomokiyo, Nobuhiro Fujita, Naoki Matsutani, Koichi Goto
  • Publication number: 20140332122
    Abstract: A high carbon hot rolled steel sheet having a chemical composition containing by mass %, C: 0.20% to 0.48%, Si: 0.1% or less, Mn: 0.5% or less, P: 0.03% or less, S: 0.01% or less, Al: 0.1% to 0.6%, Cr: 0.05% to 0.5%, B: 0.0005% to 0.0050%, Ca: 0.0010% to 0.0050%, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, where the average amount of N in a surface layer portion from the surface to the position at a depth of 0.1 mm in thickness direction is 0.1% or more and the average amount of N in the central portion in thickness is 0.01% or less, and a microstructure composed of ferrite and carbides, wherein the average grain size of the ferrite is 10 to 20 and the spheroidization ratio of the carbides is 90% or more.
    Type: Application
    Filed: December 26, 2012
    Publication date: November 13, 2014
    Applicant: JFE STEEL CORPORATION
    Inventors: Nobuyuki Nakamura, Takashi Kobayashi, Yoshimasa Funakawa
  • Patent number: 8876987
    Abstract: A high strength pressed member has excellent ductility and stretch flangeability and tensile strength of 780-1400 MPa, with a predetermined steel composition and steel microstructure relative to the entire microstructure of steel sheet, where area ratio of martensite 5-70%, area ratio of retained austenite 5-40%, area ratio of bainitic ferrite in upper bainite 5% or more, and total thereof is 40% or more, 25% or more of martensite is tempered martensite, polygonal ferrite area ratio is above 10% and below 50% to the entire microstructure of steel sheet, and average grain size is 8 ?m or less, average diameter of a group of polygonal ferrite grains is 15 ?m or less, the group of polygonal ferrite grains represented by a group of ferrite grains of adjacent polygonal ferrite grains, and average carbon content in retained austenite is 0.70 mass % or more and tensile strength is 780 MPa or more.
    Type: Grant
    Filed: October 2, 2012
    Date of Patent: November 4, 2014
    Assignee: JFE Steel Corporation
    Inventors: Hiroshi Matsuda, Yoshimasa Funakawa, Kaneharu Okuda, Kazuhiro Seto
  • Publication number: 20140305550
    Abstract: A high strength hot rolled steel sheet has a matrix that has a ferrite phase with an area ratio of 95% or more with respect to an overall structure; and a structure where a fine carbide is dispersedly precipitated, the fine carbide containing Ti and V having an average particle size of less than 10 nm in the matrix, the fine carbide has a volume fraction of 0.0050 or more with respect to the overall structure, a proportion of a number of carbides with a particle size of 30 nm or more containing Ti is less than 10% with respect to a total number of carbides, the high strength hot rolled steel sheet has a tensile strength of 980 MPa or more.
    Type: Application
    Filed: November 6, 2012
    Publication date: October 16, 2014
    Inventors: Tamako Ariga, Yoshimasa Funakawa, Yasunobu Uchida
  • Publication number: 20140299237
    Abstract: The invention relates to a method for manufacturing a high-strength structural steel and to a high-strength structural steel product. The method comprises a providing step for providing a steel slab, a heating step (1) for heating said steel slab to 950 to 1300 C, a temperature equalizing step (2) for equalizing the temperature of the steel slab, a hot rolling step including a hot rolling stage of type I (5) for hot rolling the steel slab in the no-recrystallization temperature range below the recrystallization stop temperature (RST) but above the ferrite formation temperature A3, a quenching step (6) for quenching said hot-rolled steel at cooling rate of at least 20 C/s to a quenching-stop temperature (QT) between Ms and Mf temperatures, a partitioning treatment step (7, 9) for partitioning said hot-rolled steel in order to transfer carbon from martensite to austenite, and a cooling step (8) for cooling said hot-rolled steel to room temperature.
    Type: Application
    Filed: July 2, 2012
    Publication date: October 9, 2014
    Applicant: RAUTARUUKKI OYJ
    Inventors: Mahesh Chandra Somani, David Arthur Porter, Leo Pentti Karjalainen, Tero Tapio Rasmus, Ari Mikael Hirvi
  • Publication number: 20140299238
    Abstract: A hot rolled steel sheet has a chemical composition including, by mass %, C: 0.060% to 0.120%; Si: 0.10% to 0.70%; Mn: 1.00% to 1.80%; P: 0.10% or less; S: 0.010% or less; Al: 0.01% to 0.10%; N: 0.010% or less; Nb: 0.010% to 0.100%, wherein Nb is contained so that content of solute Nb is 5% or more relative to the total Nb content; the balance being Fe and incidental impurities. The hot rolled steel sheet has a microstructure containing ferrite of not more than 15 ?m in average crystal grain diameter by a volume fraction of not less than 75%, the balance being low-temperature-induced phases. The hot rolled steel sheet can be suitably utilized for manufacturing a cold rolled steel sheet or hot-dip galvanized steel sheet having a tensile strength of 590 MPa or more, excellent in material homogeneity and capable of giving excellent cold rolling property.
    Type: Application
    Filed: September 27, 2012
    Publication date: October 9, 2014
    Applicant: JEF Steel Corporation
    Inventors: Katsutoshi Takashima, Yuki Toji, Kohei Hasegawa, Shinya Yamaguchi
  • Publication number: 20140295210
    Abstract: A hot rolled steel sheet includes a composition including: C: 0.03% to less than 0.07%; Si: 0.3% or less; Mn: 0.5% to 2.0%; P: 0.025% or less; S: 0.005% or less; N: 0.0060% or less; Al: 0.1% or less; Ti: 0.07% to 0.11%; and V: 0.08% to less than 0.15% on a mass percent basis, such that Ti and V contents satisfy: 0.18?Ti+V?0.24 (where Ti and V are contents of the elements (by mass %)), the balance including Fe and inevitable impurities, a matrix having a ferrite phase with an area ratio of 95% or more; and a structure where fine carbide is dispersedly precipitated in the matrix, the fine carbide containing Ti and V has an average particle size of less than 10 nm, and a volume fraction of the fine carbide is 0.0020 or more, wherein the steel sheet has a tensile strength of 780 MPa or more.
    Type: Application
    Filed: November 6, 2012
    Publication date: October 2, 2014
    Inventors: Tamako Ariga, Yoshimasa Funakawa, Noriaki Moriyasu
  • Publication number: 20140290807
    Abstract: A low yield ratio and high-strength hot rolled steel sheet having a composition containing, on a mass percent basis, 0.03% to 0.10% C, 0.10% to 0.50% Si, 1.4% to 2.2% Mn, 0.005 % to 0.10% Al, 0.02% to 0.10% Nb, 0.001% to 0.030% Ti, 0.05% to 0.50% Mo, 0.05% to 0.50% Cr, and 0.01% to 0.50% Ni, in which Moeq preferably satisfies the range of 1.4% to 2.2%; and a microstructure including a main phase that contains bainitic ferrite having an average grain size of 10 ?m or less and a secondary phase that contains massive martensite having an aspect ratio of less than 5.0 in an area ratio of 1.4% to 15%.
    Type: Application
    Filed: June 13, 2012
    Publication date: October 2, 2014
    Applicant: JFE Steel Corporation
    Inventors: Sota Goto, Hiroshi Nakata, Chikara Kami, Toshifumi Abe, Takato Tamai
  • Publication number: 20140261915
    Abstract: A process for producing high strength steel is provided. The process includes providing a steel slab having a chemical composition in weight percent within a range of 0.025-0.07 C, 1.20-1.70 Mn, 0.050-0.085 Nb, 0.022 max Ti, 0.065 max N, 0.0040 max S, 0.10-0.45 Si, 0.070 max P, with the balance being Fe and incidental impurities. The steel slab is soaked within a temperature range of 1150-1230° C., hot rolled using a roughing treatment in order to produce a transfer bar and further hot rolled using a finishing treatment in order to produce hot rolled strip. The hot rolled strip is cooled using a cooling rate between 10-100° C./second (sec) and coiled within a temperature range of 580-400° C. Finally, the coiled hot rolled strip has a yield strength of at least 80 ksi and a DWTT transition temperature equal or less than ?20° C.
    Type: Application
    Filed: March 14, 2014
    Publication date: September 18, 2014
    Applicant: AM/NS CALVERT LLC
    Inventors: Bertram Wilhelm Ehrhardt, Chris John Paul Samuel, Ranbir Singh Jamwal, Gerald McGloin, Stanley Wayne Bevans, Markus Wilhelm Forsch, Rudolf Schonenberg
  • Publication number: 20140261914
    Abstract: A process for manufacturing hot rolled high strength dual phase steels. In some instances, hot rolled strip is continuously cooled to less than 100° C. prior to coiling using a cooling rate between 40-70° C./second. In other instances, hot rolled strip is cooled to less than 100° C. prior to coiling using a step cooling treatment. In yet other instances, hot rolled strip is continuously cooled to less than 100° C. prior to coiling using a cooling rate between 70-100° C./second. For hot rolled strip subjected to a cooling rate between 40-70° C./second, or subjected to the step cooling treatment, hot rolled steel sheet with a tensile strength greater than 590 MPa is produced. For hot rolled strip subjected to a cooling rate between 70-100° C./second, hot rolled steel sheet with a tensile strength greater than 690 MPa is produced. Also, the hot rolled steel sheet has a ferrite plus martensite microstructure free of pearlite and bainite.
    Type: Application
    Filed: January 31, 2014
    Publication date: September 18, 2014
    Applicant: THYSSENKRUPP STEEL USA, LLC
    Inventors: Ranbir Singh Jamwal, Bertram Wilhelm Ehrhardt, Stanley Wayne Bevans, Bernd Trilling, Harald Van Bracht
  • Publication number: 20140251513
    Abstract: A high-strength hot rolled steel sheet with excellent bendability and low-temperature toughness includes a chemical composition including, in mass %, C: 0.08 to 0.25%, Si: 0.01 to 1.0%, Mn: 0.8 to 2.1%, P: not more than 0.025%, S: not more than 0.005% and Al: 0.005 to 0.10%, the balance including Fe and inevitable impurities, and a microstructure having a bainite phase and/or a tempered martensite phase as a main phase, the average grain diameter of prior austenite grains being not more than 20 ?m as measured with respect to a cross section parallel to a rolling direction and not more than 15 ?m as measured with respect to a cross section perpendicular to the rolling direction.
    Type: Application
    Filed: October 31, 2012
    Publication date: September 11, 2014
    Inventors: Chikara Kami, Kazuhiko Yamazaki
  • Publication number: 20140238555
    Abstract: A high strength hot rolled steel sheet having a tensile strength of 780 MPa or more is produced by specifying the composition to contain C: more than 0.035% and 0.07% or less, Si: 0.3% or less, Mn: more than 0.35% and 0.7% or less, P: 0.03% or less, S: 0.03% or less, Al: 0.1% or less, N: 0.01% or less, Ti: 0.135% or more and 0.235% or less, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, in such a way that C, S, N, and Ti satisfy ((Ti?(48/14)N?(48/32)S)/48)/(C/12)<1.0 (C, S, N, and Ti: content of the respective elements (percent by mass)) and specifying the microstructure in such a way that a matrix includes more than 95% of ferritic phase on an area fraction basis and fine Ti carbides having an average grain size of less than 10 nm are precipitated in the grains of the above-described ferritic phase.
    Type: Application
    Filed: November 1, 2012
    Publication date: August 28, 2014
    Inventors: Yoshimasa Funakawa, Tamako Ariga, Tetsuo Yamamoto, Hiroshi Uchomae, Hiroshi Owada
  • Publication number: 20140242416
    Abstract: A high strength pressed member has excellent ductility and stretch flangeability and tensile strength of 780-1400 MPa, with a predetermined steel composition and steel microstructure relative to the entire microstructure of steel sheet, where area ratio of martensite 5-70%, area ratio of retained austenite 5-40%, area ratio of bainitic ferrite in upper bainite 5% or more, and total thereof is 40% or more, 25% or more of martensite is tempered martensite, polygonal ferrite area ratio is above 10% and below 50% to the entire microstructure of steel sheet, and average grain size is 8 ?m or less, average diameter of a group of polygonal ferrite grains is 15 ?m or less, the group of polygonal ferrite grains represented by a group of ferrite grains of adjacent polygonal ferrite grains, and average carbon content in retained austenite is 0.70 mass % or more and tensile strength is 780 MPa or more.
    Type: Application
    Filed: October 2, 2012
    Publication date: August 28, 2014
    Inventors: Hiroshi Matsuda, Yoshimasa Funakawa, Kaneharu Okuda, Kazuhiro Seto
  • Publication number: 20140242414
    Abstract: The present invention provides a high-strength steel sheet excellent in shape fixability. The high-strength steel sheet contains C, Si, Mn, P, S, Al, N, and O with predetermined contents, in which a retained austenite phase of 5 to 20% in volume fraction is contained, an amount of solid-solution C contained in the retained austenite phase is 0.80 to 1.00% in mass %, WSi? is 1.10 times or more WSi*, WMn? is 1.10 times or more WMn*, and when a frequency distribution is measured with respect to a sum of a ratio between WSi and WSi* and a ratio between WAl and WAl*, a mode value of the frequency distribution is 1.95 to 2.05, and a kurtosis is 2.00 or more.
    Type: Application
    Filed: July 27, 2012
    Publication date: August 28, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Akinobu Minami, Hiroyuki Kawata, Akinobu Murasato, Yuji Yamaguchi, Natsuko Sugiura, Takuya Kuwayama, Naoki Maruyama, Takamasa Suzuki
  • Publication number: 20140216614
    Abstract: The present invention focuses on Sn and has as its problem to not only improve the corrosion resistance and rust resistance of Cr-containing ferritic stainless steel but also improve the ridging resistance. The present invention derives the relationship between Ap, which shows the ?-phase rate at 1100° C. due to a predetermined ingredient, and Sn in ferritic stainless steel which becomes a dual phase structure of ?+? in the hot rolling temperature region, applies and adds Sn, and hot rolls the steel to give a total rolling rate of 15% or more in 1100° C. or higher hot rolling to thereby obtain ferritic stainless steel sheet which has good ridging resistance, which also has excellent corrosion resistance and rust resistance, and which can be applied to general durable consumer goods: 0.060?Sn?0.634?0.
    Type: Application
    Filed: June 18, 2012
    Publication date: August 7, 2014
    Inventors: Masaharu Hatano, Eiichiro Ishimaru, Akihiko Takahashi, Ken Kimura, Shinichi Teraoka
  • Publication number: 20140212660
    Abstract: Disclosed is a medium carbon steel sheet for cold working that has a hardness of 500 HV to 900 HV when subjected to high-frequency quenching in which a temperature is raised at an average heating rate of 100° C./second, the temperature is held at 1,000° C. for 10 seconds, and a quick cooling to a room temperature is carried out at an average cooling rate of 200° C./second. The medium carbon steel sheet includes, by mass %, C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.03% or less, S: 0.0075% or less, Al: 0.005 to 0.10%, N: 0.001 to 0.01%, and Cr: 0.001 to 0.10%, the balance composed of Fe and inevitable impurities. An average diameter d of a carbide is 0.6 ?m or less, a spheroidizing ratio p of the carbide is equal to or more than 70% and less than 90%, and the average diameter d (?m) of the carbide and the spheroidizing ratio p % of the carbide satisfy d?0.04×p?2.6.
    Type: Application
    Filed: September 22, 2011
    Publication date: July 31, 2014
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Kengo Takeda, Masayuki Abe, Yasushi Tsukano, Takashi Aramaki, Shinichi Yamaguchi
  • Patent number: 8784577
    Abstract: A high-tensile-strength hot-rolled steel sheet is provided having a composition which contains 0.02 to 0.08% C, 0.01 to 0.10% Nb, 0.001 to 0.05% Ti and Fe and unavoidable impurities as a balance, wherein the steel sheet contains C, Ti and Nb in such a manner that (Ti+(Nb/2))/C<4 is satisfied, and the steel sheet has a structure where a primary phase of the structure at a position 1 mm away from a surface in a sheet thickness direction is one selected from a group consisting of a ferrite phase, tempered martensite and a mixture structure of a ferrite phase and tempered martensite, a primary phase of the structure at a sheet thickness center position is formed of a ferrite phase, and a difference ?V between a structural fraction (volume %) of a secondary phase at the position 1 mm away from the surface in the sheet thickness direction and a structural fraction (volume %) of a secondary phase at the sheet thickness center position is 2% or less.
    Type: Grant
    Filed: January 29, 2010
    Date of Patent: July 22, 2014
    Assignee: JFE Steel Corporation
    Inventors: Chikara Kami, Hiroshi Nakata, Kinya Nakagawa
  • Patent number: 8778097
    Abstract: A low specific gravity and high strength steel sheet includes C of 0.2% to 0.8%, Mn of 2% to 10%, P of 0.02% or less, S of 0.015% or less, Al of 3% to 15%, and N of 0.01% or less. A ratio of Mn/Al is 0.4 to 1.0. Retained austenite in a structure is included in the range of 1% or more. The steel sheet further includes one or two or more elements selected from the group consisting of Si of 0.1% to 2.0%, Cr of 0.1% to 0.3%, Mo of 0.05% to 0.5%, Ni of 0.1% to 2.0%, Cu of 0.1% to 1.0%, B of 0.0005% to 0.003%, Ti of 0.01% to 0.2%, Zr of 0.005% to 0.2%, Nb of 0.005% to 0.2%, W of 0.1% to 1.0%, Sb of 0.005% to 0.2%, and Ca of 0.001% to 0.2%.
    Type: Grant
    Filed: October 29, 2008
    Date of Patent: July 15, 2014
    Assignee: Posco
    Inventors: Kwang Geun Chin, Jai Hyun Kwak
  • Publication number: 20140190597
    Abstract: The present invention provides a hot coil for line pipe use which can reduce deviation in ordinary temperature strength and improve low temperature toughness despite the numerous restrictions in production conditions due to the coiling step and provides a method of production of the same, specifically makes the steel plate stop for a predetermined time between rolling passes in the recrystallization temperature range and performs cooling by two stages after hot rolling so as to thereby make the steel structure at the center part of plate thickness and effective crystal grain size of 3 to 10 ?m, make the total of the area ratios of bainite and acicular ferrite 60 to 99%, and make the absolute value of A-B 0 to 30% when the totals of the area ratios of bainite and acicular ferrite at any two portions are designated as respectively A and B.
    Type: Application
    Filed: September 27, 2012
    Publication date: July 10, 2014
    Inventors: Takuya Hara, Takeshi Kinoshita, Kazuaki Tanaka
  • 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