Abstract: Provided is a chromium-containing steel sheet for a current collector of a nonaqueous electrolyte secondary battery. The chromium-containing steel sheet for a current collector of a nonaqueous electrolyte secondary battery has a chemical composition containing Cr in an amount of 10% by mass or more. A parameter Sa defined in ISO 25178 is from 0.15 ?m to 0.50 ?m inclusive, and a parameter Ssk defined in ISO 25178 is more than 0.
Abstract: A molten iron refining method that prevents a cold iron source from remaining unmelted even under the condition of a high ratio of the cold iron source. An auxiliary material is added, and an oxidizing gas is supplied, to cold iron source and molten pig iron that are contained or fed in converter-type vessel, and molten iron is subjected to refining process. Prior to refining process, a pre-charged cold iron source that is charged all at once into the converter-type vessel before the molten pig iron is charged into the converter-type vessel is charged in an amount not larger than 0.15 times the sum of an amount of the pre-charged cold iron source and a charge amount of the molten pig iron, or is not charged. A furnace-top-added cold iron source that is added from a furnace top of the converter-type vessel is fed into converter-type vessel during refining process.
December 17, 2021
February 22, 2024
JFE STEEL CORPORATION
Futoshi OGASAWARA, Yudai HATTORI, Rei YOKOMORI, Ryo KAWABATA
Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in the test welding, 0.2?Vtp/Vtm?1.5 is satisfied where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding and Vtp is an average value of a voltage between the electrodes in subsequent current passage in the test welding, and in each of main current passage and subsequent current passage in the actual welding, a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are stored in a corresponding one of the main current passage and the subsequent current passage in the test welding are set as a target, and adaptive control welding is performed to control a current passage amount according to the target.
Abstract: To prevent fracture of a box under a tensile load without increasing the outer diameter of the box. The presently disclosed threaded joint for pipes includes a pin provided with a male thread portion at one end of a first pipe, and a box provided with a female thread portion at one end of a second pipe, where each of a plurality of thread grooves of the female thread portion has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a corner portion on a load flank side of a first thread groove includes a first arc portion that has a first curvature radius, and a second arc portion that has a second curvature radius, and a ratio of the second curvature radius to the first curvature radius is 3 or more.
Abstract: A submerged arc welded joint in a high-Mn content steel material that can be formed with reduced occurrence of hot cracking during the welding process and has high strength and excellent cryogenic impact toughness. In the welded joint, the high-Mn content steel material has a chemical composition including, by mass %, C: 0.10 to 0.80%, Si: 0.05 to 1.00%, Mn: 18.0 to 30.0%, P: 0.030% or less, S: 0.0070% or less, Al: 0.010 to 0.070%, Cr: 2.5 to 7.0%, N: 0.0050 to 0.0500%, and O: 0.0050% or less, the balance being Fe and incidental impurities, and a weld metal has a chemical composition including C: 0.10 to 0.80%, Si: 0.05 to 1.00%, Mn: 15.0 to 30.0%, P: 0.030% or less, S: 0.030% or less, Al: 0.100% or less, Cr: 6.0 to 14.0%, and N: 0.100% or less, the balance being Fe and incidental impurities.
Abstract: Provided is a method of manufacturing a grain-oriented electrical steel sheet, with which a grain-oriented electrical steel sheet with low iron loss and little variation in iron loss can be stably manufactured by a tandem mill. The method includes subjecting a steel material to hot rolling to obtain a hot-rolled sheet, subjecting the hot-rolled sheet to cold rolling once or twice or more with intermediate annealing performed therebetween to obtain a cold-rolled sheet with a final sheet thickness, and then subjecting the cold-rolled sheet to decarburization annealing and then to secondary recrystallization annealing, wherein final cold rolling is performed by a tandem mill, and in the final cold rolling, the hot-rolled sheet is heated to a temperature range of 70° C. or higher and 200° C. or lower, then cooled to 60° C. or lower, and then introduced into a first pass of the tandem mill.
Abstract: Provided is a grain-oriented electrical steel sheet that can benefit from the iron loss improving effect by groove formation while effectively suppressing a decrease in magnetic flux density. A grain-oriented electrical steel sheet comprises predetermined linear grooves, wherein in each linear groove, a proportion of predetermined flat portions to an entire length of the linear groove is 30% or more and 90% or less, the number of flat portions each of which is continuous for a predetermined length is 10 or more per 100 cm2 surface area, and a ratio of ten-point average roughness Rzjis to average depth D is 0.1 or more and 1 or less.
Abstract: Provided are a steel sheet and a member, having high strength and high delayed fracture resistance, and methods for manufacturing the steel sheet and the member. The steel sheet has a specific chemical composition and a microstructure in which the area fraction of martensite is 95% to 100%, with the balance being one or more of bainite, ferrite, and retained austenite. In the steel sheet, prior-austenite grains have an average grain size of 18 ?m or less, 90 mass % or more of the total content of Nb and Ti contained is present as a carbonitride having an equivalent circular diameter of 100 nm or more, and a Nb carbonitride and a Ti carbonitride, having an equivalent circular diameter of 1.0 ?m or more, are present at a rate of 800 pieces/mm2 or less in total. The steel sheet has a tensile strength of 1310 MPa or more.
Abstract: A high strength steel sheet has a yield-point elongation of 1% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. A ratio of retained austenite grains adjoining a retained austenite grain having a different crystal orientation to total retained austenite grains is 0.60 or greater, the ferrite has an average grain size of 5.0 ?m or less, and the retained austenite has an average grain size of 2.0 ?m or less. A value obtained by dividing a volume fraction V?a by a volume fraction V?b is 0.40 or greater, where the volume fraction V?a is a volume fraction of retained austenite in a fractured portion of a tensile test specimen after a warm tensile test at 150° C., and the volume fraction V?b is a volume fraction of retained austenite before the warm tensile test at 150° C.
Abstract: A high strength steel sheet has a yield-point elongation of 1.0% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. The ferrite has an average grain size of 5.0 ?m or less, the retained austenite has an average grain size of 2.0 ?m or less, a value obtained by dividing a Mn content of the retained austenite by a Mn content of steel is 1.50 or greater, 15% or more of all retained austenite grains in the retained austenite have an aspect ratio of 3.0 or greater, and 15% or more of all the retained austenite grains in the retained austenite have an aspect ratio of less than 2.0.
Abstract: A method for charging raw materials into a blast furnace is as follows. The blast furnace includes a bell-less charging device that includes a plurality of main hoppers and an auxiliary hopper. The auxiliary hopper has a smaller capacity than the main hoppers. The method includes discharging ore charged in at least one of the plurality of main hoppers, and then sequentially charging the ore from a furnace wall side toward a furnace center side by using a rotating chute. The discharging of low-reactivity ore charged in the auxiliary hopper is started simultaneously with a start of charging of the ore or at a point in time after the start of the charging; and then, the low-reactivity ore is charged together with the ore from the rotating chute. The charging of the low-reactivity ore is stopped at least before a point in time at which charging of 56 mass % of the ore is completed.
October 25, 2023
February 15, 2024
JFE Steel Corporation
Kazuhira Ichikawa, Yasushi Ogasawara, Takeshi Sato
Abstract: A metal structure evaluator for rolled steel sheets includes: a magnetic property measuring unit configured to measure a magnetic property of an evaluation target point in at least two or more different magnetization directions by performing, in the at least two or more different magnetization directions, processing of: applying a magnetic field on a surface of a rolled steel sheet in one direction; and measuring a magnetic property of the evaluation target point on the surface of the rolled steel sheet; and a determination unit configured to determine a metal structure of the evaluation target point based on the magnetic property measured by the magnetic property measuring unit.
Abstract: A high-strength steel sheet according to the present invention includes a specific chemical composition, and a steel structure in which a total area fraction of martensite and bainite in a position of ¼ of a sheet thickness is 95% or more and 100% or less, the balance in a case where the total area fraction is not 100% contains retained austenite, and an area fraction of ferrite in a region extending up to 10 ?m in a sheet thickness direction from a surface is 10% or more and 40% or less, in which a tensile strength is 1320 MPa or more, and a Vickers hardness in a position of 15 ?m in the sheet thickness direction from the surface satisfies a specified formula.
Abstract: A continuous casting method of steel of continuously casting a slab by using a vertical liquid bending type continuous casting machine. The method includes, while performing continuous casting by using an in-mold electromagnetic stirring device, applying an alternating-current moving magnetic field that moves in a width direction of a mold to molten steel inside the mold, inducing a swirling flow in the molten steel, and stirring the molten steel. A travel speed of the alternating-current moving magnetic field calculated by a specified formula is in a range of 0.20 to 1.50 m/s.
Abstract: A shape change prediction method of a press formed part predicts a shape change in which an end side in a longitudinal direction is twisted due to stress relaxation with a lapse of time after springback at a moment of die release from a tool of press forming with respect to the press formed part having a U-shaped cross-sectional shape including a top portion and side wall portions, and includes: acquiring a shape and a residual stress of the press formed part immediately after the springback by a springback analysis of the press formed part; setting a value of stress relaxed and reduced compared to the residual stress immediately after the springback for at least one of the side wall portions; and acquiring a shape with which moment of force is balanced for the press formed part in which the value of the relaxed and reduced stress is set.
Abstract: A method of evaluating central segregation in steel with excellent correlation with HIC susceptibility is provided. A method of evaluating central segregation in steel includes: taking a sample from a steel, the sample having a cross section including a central segregation area; measuring an area ratio of an inclusion containing a segregation metal element in a region to be measured including the central segregation area in the cross section; and evaluating central segregation in the steel based on the area ratio measured.
Abstract: To further enhance the evaluation accuracy of a delayed fracture. Focusing on the fact that a calculated stress value serving as the reference for the occurrence of the delayed fracture changes depending on analysis conditions of a forming analysis, a value obtained by changing a stress value serving as the reference for the occurrence of the delayed fracture according to the analysis conditions for analyzing an intended formed article (article for practical use) is used as the reference for evaluating the delayed fracture. For example, analysis conditions of a forming analysis in an evaluation test of the delayed fracture are matched with analysis conditions of a forming analysis of an article for practical use represented by an actual automobile component.
Abstract: An annealing separator, by being applied to a steel sheet, enables retention of a good shape of a coil after annealing obtained by winding the steel sheet with the annealing separator applied thereto into a coil which is then annealed at a high temperature exceeding 1000° C. A powder used as the annealing separator: contains magnesium oxide as a main component and B: 0.020 mass % or more and 0.200 mass % or less, SO3: 0.030 mass % or more and 2.000 mass % or less, and P2O3: 0.050 mass % or more and 1.000 mass % or less; and contains 0.2 mass % or more and 5.0 mass % or less of particles having a particle size of more than 45 ?m and 75 ?m or less. The particles having this particle size contain (boron) B: 0.002 mass % or more and less than 0.020 mass %, SO3: less than 0.030 mass %, and P2O3: less than 0.050 mass %.
Abstract: Disclosed is a duplex stainless clad steel plate in which a duplex stainless steel plate as a cladding metal is bonded or joined to one or both surfaces of a base steel plate, in which the base steel plate comprises a predetermined chemical composition such that Nb/N is 3.0 or more and Ceq is 0.35 to 0.45, and the duplex stainless steel plate comprises: a predetermined chemical composition such that PI is 34.0 to 43.0; and a microstructure containing a ferrite phase in an area fraction of 35% to 65%, and in the microstructure, an amount of precipitated Cr is 2.00% or less and an amount of precipitated Mo is 0.50% or less.
Abstract: A control method for a continuous casting machine, includes: estimating, by on-line real-time system, a flow state of molten steel in a mold by using an operation condition of a continuous casting machine and temperature data on the molten steel in the mold; calculating, by on-line real-time system, a molten steel flow index based on the estimated flow state of the molten steel, the molten steel flow index being a factor of mixing of an impurity into a casting inside the mold; and controlling the operation condition of the continuous casting machine such that the calculated molten steel flow index is within an appropriate range.