Yokohama, Japan
Yokohama, Japan

JFE Holdings, Inc. is a corporation headquartered in Tokyo, Japan. It was formed in 2002 by the merger of NKK and Kawasaki Steel Corporation . At the time, NKK Corporation was Japan's second largest steelmaker and Kawasaki Steel was the third largest steelmaker.Both companies were major military vessel manufacturers during World War II.JFE's main business is steel production. It also engages in engineering, ship building, real-estate redevelopment, and LSi business. The company also operates several overseas subsidiaries, including California Steel in the United States, Fujian Sino-Japan Metal in China, and Minas da Serra Geral in Brazil. Other than steel, they are also known for products such as the bicycle tree.JFE Holdings is the fifth largest Steel maker in the world with revenue in excess of US$30 billion. JFE Holdings has several subsidiaries including JFE Engineering, JFE Steel and JFE Shoji.NKK and Siderca S.A. of Argentina established a seamless pipe joint venture by spinning off the seamless pipe division of NKK's Keihin Works in 2000. In November 2009, JFE agreed to partner with JSW Steel, India's third-largest steel producer, to construct a joint steel plant in West Bengal.Its shipbuilding unit, Universal Shipbuilding was created in 2002 when NKK Corporation a predecessor of JFE, merged its shipbuilding unit with that of Hitachi Zosen. In 2012, JFE merged its ship building unit, Universal Shipbuilding Corporation, with Marine United Inc. of IHI after discussion started in April 2008 to form Japan Marine United Corporation It would be Japan’s largest shipbuilder. Wikipedia.


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A galvanized steel sheet has formability and crashworthiness, consists of 0.03% to 0.13% C, 1.0% to 2.0% Si, 2.4% to 3.5% Mn, 0.001% to 0.05% P, 0.0001% to 0.01% S, 0.001% to 0.1% Al, 0.0005% to 0.01% N, and 0.0003% to 0.01% B on a mass basis; and optionally contains at least one selected from the following A-C: A: at least one selected from the group consisting of 0.0005% to 0.1% Ti and 0.0005% to 0.05% Nb on a mass basis; B: at least one selected from the group consisting of 0.01% to 1.0% Mo, 0.01% to 2.0% Ni, and 0.01% to 2.0% Cu on a mass basis; and C: 0.001% to 0.005% Ca on a mass basis; the remainder being Fe and unavoidable impurities, and a microstructure containing a tempered martensitic phase and a bainitic phase such that the sum of an area fraction of the tempered martensitic phase and an area fraction of the bainitic phase is 30% or more, the area fraction of the tempered martensitic phase is 30% or more in the absence of the bainitic phase, wherein a distance of closest approach of the tempered martensitic phase is 10 m or less and contents of C, Mn, and B satisfy (1): (% Mn)+1000(% B)35(% C)(1).


Patent
Jfe Holdings | Date: 2017-04-26

Provided is a cold-rolled ferritic stainless steel sheet excellent in terms of surface appearance quality before and after a forming process and having sufficient formability. The chemical composition contains, by mass%, C: 0.01% or more and 0.05% or less, Si: 0.02% or more and 0.75% or less, Mn: 0.1% or more and 1.0% or less, P: 0.04% or less, S: 0.01% or less, Al: 0.001% or more and 0.10% or less, N: 0.01% or more and 0.06% or less, Cr: 16.0% or more and 18.0% or less, and the balance being Fe and inevitable impurities. The metallographic structure includes a ferrite phase, in which the average grain diameter of a ferrite phase is 10 m or less, in which the proportion of ferrite grains having a grain diameter of 10 m or more and less than 40 m to the whole metallographic structure is 60% or more in terms of area ratio, and in which the proportion of ferrite grains having a grain diameter of less than 5 m to the whole metallographic structure is less than 20% in terms of area ratio.


The invention provides a method for producing high-strength galvanized steel sheets having excellent coating adhesion, workability and appearance. The method for producing high-strength galvanized steel sheets includes a hot rolling step of hot rolling a slab including, in mass%, C: 0.05 to 0.30%, Si: 0.1 to 2.0% and Mn: 1.0 to 4.0%, thereafter coiling the steel sheet into a coil at a specific temperature T_(C), and pickling the steel sheet, a cold rolling step of cold rolling the hot-rolled steel sheet resulting from the hot rolling step, an annealing step of annealing the cold-rolled steel sheet resulting from the cold rolling step under specific conditions, and a galvanizing step of galvanizing the annealed sheet resulting from the annealing step in a galvanizing bath containing 0.12 to 0.22 mass% Al.


An ultrasonic flaw detection apparatus 1 includes: a ultrasonic flaw detection sensor head 11 installed downstream from a seam detection unit 13; a seam position calculation unit 14a that calculates a seam position and a bead cutting position of an electric resistance welded pipe P by using a thermal image of a welded seam portion captured by the seam detection unit 13; a bead cutting band detection unit 15 that is installed immediately before or immediately after the ultrasonic flaw detection sensor head 11 and that detects a bead cutting band of the electric resistance welded pipe P; a bead cutting position calculation unit 14c that calculates, based on the bead cutting band detected by the bead cutting band detection unit 15, a bead cutting position of the electric resistance welded pipe P; and a tracking movement amount calculation unit 14d that calculates a tracking movement amount of the ultrasonic flaw detection sensor head 11 by using the seam position and bead cutting position calculated by the seam position calculation unit 14a and the bead cutting position calculated by the bead cutting position calculation unit 14c.


A molten steel fluidity estimation method estimates fluidity of molten steel in a casting mold of a continuous casting machine in such a manner that a CPU 113 calculates, at positions where thermocouples 41 are arranged in the casting mold of the continuous casting machine, an error between temperature distribution of the molten steel that is measured by using the thermocouples 41 and temperature distribution of the molten steel that is calculated by using a physical model; applies an external force in the vicinity of a discharge opening of a nozzle that discharges the molten steel into the casting mold; and calculates the fluidity of the molten steel in a state in which the external force adjusted to compensate the error is applied.


Patent
Jfe Holdings | Date: 2017-05-17

Provided is a method of producing a galvannealed steel sheet, the production method being capable of achieving a favorable plated appearance and of suppressing reductions in tensile strength. This method of producing a galvannealed steel sheet has: a step wherein a steel strip is transported through the inside of an annealing furnace, in order through a heating zone that includes a direct-firing-type furnace, a soaking zone, and a cooling zone, and the steel strip is annealed; a step wherein, after being discharged from the cooling zone, the steel strip is hot-dip galvanized; and a step wherein the zinc-plating applied to the steel strip is heated and alloyed. The production method is characterized in that a mixed gas that includes a humidified gas and a dry gas is supplied to the inside of the soaking zone from at least one gas supply port that is provided to the height-direction lower half of the soaking zone, and in that the dew point measured in the height-direction upper fifth of the soaking zone and the dew point measured in the height-direction lower fifth are both -20-0 C.


Patent
Jfe Holdings | Date: 2017-05-24

A pipe expander that can manufacture a steel pipe at low cost is provided. The pipe expander includes a cone that is fitted around the tip of a draw bar connected to a cylinder and has an outer periphery of which the size changes gradually in the axial direction thereof, and a pipe expansion head outer surface member disposed on the outer periphery of the cone. The cone pulled by the cylinder in the axial direction radially expands the pipe expansion head outer surface member by wedge action of the cone and the pipe expansion head outer surface member, to expand a steel pipe placed on the outer periphery of the pipe expansion head outer surface member. The cone has a detachable liner on a contact surface thereof with the pipe expansion head outer surface member.


When the resistance to sulfide stress corrosion cracking is evaluated by applying a constant load stress (MPa) to a round bar tensile test specimen immersed in a test solution and checking whether failure occurs before a particular time passes, the round bar tensile test specimen including a parallel section, a shoulder section, and a grip section is used. In the round bar tensile test specimen, the shoulder section is formed by a curve having two or more radii of curvature, a radius of curvature R1 (mm) of a portion adjacent to the parallel section is 15 mm or more and satisfies (0.22 - 119) R1 100, a length X1 (mm) of a portion of the curve having the radius of curvature R1 in a longitudinal direction of the test specimen satisfies X1 {(r/8) (R1 - r^(2)/4)} (r: radius (mm) of the round bar tensile test specimen in the parallel section), and the radius of curvature R1 is larger than other radii of curvature. Thus, even when the steel is a high-strength steel having a yield strength of 758 MPa or higher, the occurrence of the failure in the shoulder section is suppressed, and the resistance to sulfide stress corrosion cracking can be properly evaluated.


Provided is a method for manufacturing a galvanized steel sheet whose surface appearance quality and mechanical properties have small annealing-temperature dependency by using steel containing C, Si, Mn and so forth, which are necessary to increase strength to a TS of 1180 MPa or more. A method for manufacturing a high-strength galvanized steel sheet includes performing hot rolling, cold rolling, first annealing, pickling, and second annealing on a steel slab having a specified chemical composition. The first annealing is performed under specified conditions in order to obtain a steel sheet having a steel microstructure including ferrite in an amount of 10% or more and 60% or less in terms of area ratio, and martensite, bainite, and retained austenite in a total amount of 40% or more and 90% or less in terms of area ratio. The second annealing includes heating to an annealing temperature of 750C or higher and 850C or lower, holding at the annealing temperature for 10 seconds or more and 500 seconds or less, cooling at an average cooling rate of 1C/s or more and 15C/s or less, performing a galvanizing treatment, and cooling to a temperature of 150C or lower at an average cooling rate of 5C/s or more and 100C/s or less in order to obtain a steel sheet having a steel microstructure including, in terms of area ratio, 10% or more and 60% or less of ferrite and, in terms of area ratio, 40% or more and 90% or less of martensite.


The invention provides a method for producing a cold-rolled steel strip with a yield ratio Re/Rm of at least 0.7, the cold-rolled steel product consisting of a steel comprising iron, unavoidable production impurities and (in wt. % ) C: 0.05 - 0.20%, Si: 0.25 - 1.00%, Mn: 1.0 - 3.0%, Al : 0.02 - 1.5%, Cr: 0.1 - 1.5%, N: less than 0.02%, P: less than 0.03%, S: less than 0.05% and optionally one or more elements from the group Ti, Mo, Nb, V, B subject to Ti: being up to 0.15%, Mo: less than 2%, Nb: less than 0.1%, V: less than 0.12%, and B: 0.0005 - 0.003%. According to the invention the cold-rolled flat steel product provided undergoes additional heat treatment, during which it is annealed for an annealing time of 4.5 - 24 hours at an annealing temperature of up to 150 - 400C. It has surprisingly transpired that as a result of such long-time annealing carried out at comparatively low temperatures a dramatic increase in the yield strength Re and an improvement in the hole expansion occurs. The invention also provides a cold rolled flat steel product consisting of the steel mentioned before and having a structure comprising at least two phases, which (in vol.-%) contains at least 10% tempered martensite, less than 10 % bainite, less than 10 % residual austenite and as the remainder ferrite, the steel having a yield ratio Re/Rm of at least 0.7, a tensile strength R of more than 750 MPa and a hole expansion LA of at least 18%.

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