Abstract: A steel material excellent in rolling fatigue property, the steel material including, in mass %: C: 0.10% to 1.50%, Si: 0.01% to 0.80%, Mn: 0.10% to 1.50%, Cr: 0.02% to 2.50%, Al: 0.002% to less than 0.010%, Ce+La+Nd: 0.0001% to 0.0025%, Mg: 0.0005% to 0.0050%, O: 0.0001% to 0.0020%, Ti: 0.000% to less than 0.005%, N: 0.0180% or less, P: 0.030% or less, S: 0.005% or less, Ca: 0.0000% to 0.0010%, V: 0.00 to 0.40%, Mo: 0.00 to 0.60%, Cu: 0.00 to 0.50%, Nb: 0.000 to less than 0.050%, Ni: 0.00 to 2.50%, Pb: 0.00 to 0.10%, Bi: 0.00 to 0.10%, B: 0.0000 to 0.0050%, and the balance being Fe and an impurity, wherein a fatigue-initiating inclusion detected by an ultrasonic fatigue test contains one or more of Ce, La, and Nd, and Mg, Al, and O, and a composition ratio in the fatigue-initiating inclusion satisfies Formula (1).
September 13, 2018
July 9, 2020
NIPPON STEEL CORPORATION
Koji WATARI, Tatsuya IWASAKI, Junya YAMAMOTO
Abstract: An electrical steel sheet has an insulation coating on a steel sheet surface. The insulation coating includes: a binder consisting of 100 parts by mass of a metal phosphate and 1 to 50 parts by mass of an organic resin having an average particle size of 0.05 to 0.50 ?m; and a carboxylic acid-containing compound with a carbon number of 2 to 50 in an amount of 0.1 to 10.0 parts by mass based on 100 parts by mass of solids content of the binder. The organic resin is at least one selected from the group consisting of acrylic resins, epoxy resins, and polyester resins. The insulation coating of this electrical steel sheet shows good edge corrosion resistance after blanking.
Abstract: A high-strength hot-dip galvanized steel sheet excellent in impact resistance and worked portion corrosion resistance including a hot-dip galvanized plating layer on a steel sheet base material whose tensile strength is 590 MPa or more, wherein the plating layer includes projecting alloy layers being in contact with the steel sheet base material, a number density of the projecting alloy layers is 4 pieces/mm or more, wherein the steel sheet base material includes: a miniaturized layer being directly in contact with the interface between the steel sheet base material and the plating layer; a decarburized layer being in contact with the miniaturized layer; and an inner layer other than the miniaturized layer and the decarburized layer, and one or more kinds of oxides of Si and Mn are contained in layers of the miniaturized layer, the decarburized layer, and the projecting alloy layers.
Abstract: A predetermined composition is had, when a C content is represented by (C %), in a case of (C %) being not less than 0.35% nor more than 0.65%, a volume fraction of pearlite is 64×(C %)+52% or more, and in a case of (C %) being greater than 0.65% and 0.85% or less, the volume fraction of pearlite is not less than 94% nor more than 100%, and a structure of the other portion is composed of one or two of proeutectoid ferrite and bainite. Further, in a region to a depth of 1.0 mm from a surface, a volume fraction of pearlite block having an aspect ratio of 2.0 or more is not less than 70% nor more than 95%, and a volume fraction of pearlite having an angle between an axial direction and a lamellar direction on a cross section parallel to the axial direction of 40° or less is 60% or more with respect to all pearlite.
Abstract: A continuous hot-dip plating machine includes: a sink roll provided in a plating bath and configured to upwardly change a transfer direction of the steel strip; a first support roll provided in the plating bath and located above the sink roll, the first support roll being in contact with a first surface of the steel strip in contact with the sink roll; and a second support roll provided in the plating bath and located above the first support roll, the second support roll being in contact with a second surface of the steel strip opposite the first surface. A diameter of the first support roll, a diameter of the second support roll, and a vertical distance between a rotation axis of the first support roll and a rotation axis of the second support roll satisfy specific conditions.
Abstract: A method of manufacturing a flaring-processed metal pipe from a hollow shell including a plurality of portions having different deformation resistances in a circumferential direction is provided, the method includes: among the plurality of portions, specifying a portion having a relatively small deformation resistance as a low deformation resistance section, and a portion having a relatively large deformation resistance as a high deformation resistance section; and press-fitting a pipe expansion punch into the hollow shell such that a thickness reduction rate of the low deformation resistance section is smaller than a thickness reduction rate of the high deformation resistance section.
Abstract: A grain-oriented electrical steel sheet includes: a base steel sheet; an intermediate layer arranged in contact with the base steel sheet; and an insulation coating arranged in contact with the intermediate layer to be an outermost surface, in which a Cr content of the insulation coating is 0.1 at % or more on average, and when viewing a cross section whose cutting direction is parallel to a thickness direction, the insulation coating has a compound layer containing a crystalline phosphide in an area in contact with the intermediate layer.
Abstract: A method for producing H-shaped steel, the method includes: a rough rolling step; an intermediate rolling step; and a finish rolling step, wherein: a rolling mill that performs the rough rolling step is engraved with a plurality of calibers configured to shape a material to be rolled; the plurality of calibers include: one or a plurality of split calibers formed with projections configured to create splits vertically with respect to a width direction of the material to be rolled to form divided parts at end parts of the material to be rolled; and a plurality of bending calibers formed with projections configured to come into contact with the splits and sequentially bend the divided parts formed by the split caliber; and the projections formed in a final split caliber of the split calibers are each composed a tip part in a tapered shape having a predetermined tip angle, and a base part located at a base of the tip part and having a tapered shape with a gentle inclination as compared with the tip part.
Abstract: The disclosed heat generating apparatus includes: a rotary shaft, a heat generator, a plurality of permanent magnets, a magnet holder, and a heat recovery system. The rotary shaft is rotatably supported by a non-rotative body. The heat generator is fixed to the body. The magnets are arrayed to face the heat generator with a gap such that magnetic pole arrangements of adjacent ones of the magnets are opposite to each other. The magnet holder holds the magnets and is fixed to the rotary shaft. The heat recovery system collects heat generated in the heat generator. A non-magnetic partition wall is provided in the gap between the heat generator and the magnets.
Abstract: A laser welded joint has weld metal provided between a plurality of steel sheets. A chemical composition of the weld metal has predetermined components, and average hardness of the weld metal is 350 to 540 in Vickers hardness. In the weld metal, distribution density of porosities having a diameter of 2 ?m to 50 ?m is equal to or less than 5.0 pieces/mm2. In the weld metal, distribution density of oxide inclusions having a diameter of 3 ?m or more is 0.1 to 8.0 pieces/mm2.
Abstract: A steel sheet for a fuel tank according to the present invention includes: a Zn—Ni alloy plated layer placed on one surface or each of both surfaces of a base metal; and a chromate-free chemical conversion coating film which is placed over the Zn—Ni alloy plated layer. The Zn—Ni alloy plated layer has a crack starting from an interface with the chromate-free chemical conversion coating film and reaching an interface with the steel sheet, the chromate-free chemical conversion coating film consists of an organosilicon compound consisting of a condensation polymer of a silane coupling agent, a phosphoric acid compound and/or a phosphonic acid compound, a vanadium compound, and a titanium compound and/or a zirconium compound, and a concentration of a total of amounts in terms of metal, per surface, of the phosphoric acid compound and/or the phosphonic acid compound+the vanadium compound+the titanium compound and/or the zirconium compound, is 5 mass % to 20 mass %.
Abstract: A method for manufacturing a press-formed product includes: a first step of preparing a long material having a bending portion; and a second step of decreasing curvature of the bending portion while restricting both ends of the long material in a longitudinal direction.
Abstract: A press-formed product is shaped by press-working from a tailored blank made up of a plurality of metal sheets butt-welded together. The press-formed product includes a flange section, and an arc-shaped area which is an area of the flange section which is formed by stretch flange deformation, and in which an inner peripheral edge is open. A weld line of the tailored blank intersects with the inner peripheral edge and an outer peripheral edge of the arc-shaped area. An angle ? formed by the weld line and a maximum principal strain direction of the stretch flange deformation is 17 to 84°.
Abstract: The amount of absorbed energy at the time of load input is improved with high mass efficiency. A hollow member includes: a hollow metal member having a bending induction portion in a portion in a longitudinal direction; and a resin material which is made of a resin having a Young's modulus of 20 MPa or more and is disposed in the bending induction portion in close contact with the metal member.
Abstract: Provided is a hot rolled steel sheet comprising a predetermined composition wherein the hot rolled steel sheet comprises a dual structure of, by area fraction, a structural fraction of a martensite phase of 10 to 40% and a structural fraction of a ferrite phase of 60% or more, has an average grain size of ferrite grains of 5.0 ?m or less, and has a coverage rate of martensite grains by ferrite grains of more than 60%. Also provided is a method for producing a hot rolled steel sheet comprising rolling a steel sheet wherein the respective rolling loads of the final three rolling stands are 80% or more of an immediately previous rolling stand and an average value of these rolling temperatures is 800 to 950° C., and forcibly cooling, then coiling the steel sheet wherein the forcibly cooling includes cooling started within 1.5 seconds after the rolling ends and cooling the steel sheet by a 30° C./second or more average cooling rate down to 600 to 750° C.
Abstract: A method for manufacturing a hat-shaped cross-section component includes a gripping process, a bending and stretching process, and a bend back process. In the gripping process, a pair of vertical walls of an elongated preliminarily formed component are disposed outside of a punch, and a top plate is gripped using the punch and a pad. In the bending and stretching process, die moves toward the punch side relative to the preliminarily formed component, and the die bends and stretches the vertical walls toward the opposite side to the top plate at one side in the length direction of the preliminarily formed component. In the bend back process, a holder moves toward the pad side relative to the preliminarily formed component, and the holder bends back the vertical walls toward the top plate side at another side in the length direction of the preliminarily formed component.
Abstract: A steel sheet for a fuel tank includes: a Zn—Ni alloy plated layer which is placed on one surface or each of both surfaces of a base metal and formed on at least one surface; and an inorganic chromate-free chemical conversion coating film which is placed over the Zn—Ni alloy plated layer. The Zn—Ni alloy plated layer has a crack starting from an interface between the Zn—Ni alloy plated layer and the inorganic chromate-free chemical conversion coating film and reaching an interface between the Zn—Ni alloy plated layer and the steel sheet, and a water contact angle on a surface of the inorganic chromate-free chemical conversion coating film is more than or equal to 50 degrees.
Abstract: A hot-rolled steel sheet includes a chemical composition represented by, in mass %, C: 0.010% to 0.100%, Si: 0.30% or less, Cr: 0.05% to 1.00%, Nb: 0.003% to 0.050%, Ti: 0.003% to 0.200% and others, wherein a proportion of grains having an intragranular misorientation of 5° to 14° in all grains is 20% or more by area ratio, the grain being defined as an area which is surrounded by a boundary having a misorientation of 15° or more and has a circle-equivalent diameter of 0.3 ?m or more.
Abstract: This welded structure member includes a base metal member including a first surface and a second surface; a joined metal member including an abutting surface of which an end surface abuts onto the first surface; a weld bead which is formed on the first surface; and a weld overlay section which is formed on the second surface of the base metal member, in which the weld bead includes a weld bead end section in a position which is separated to the front of the abutting end section.