JFE Steel Patente

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To collect a deposit under a belt of a belt conveyor provided with a mobile machine and move the deposit to the outside of rails. A cleaning device for cleaning up a deposit accumulated under the belt of the belt conveyor, the cleaning device including a collecting unit mounted on the mobile machine that travels on the rails provided along the conveying direction of the belt conveyor, which collects the deposit under the belt and moves the deposit to the outside of the rails.

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To provide a structural member with a tensile strength of 980 MPa or more and 1.8 GPa or less and good axial crushing characteristics. A structural member including a steel sheet having a base steel sheet, wherein the structural member has a cross-sectional shape that includes a top sheet portion extending in a width direction, and two vertical wall portions extending from both ends in a width direction of the top sheet portion in a direction different from a direction of extension of the top sheet portion, the base steel sheet of the top sheet portion has, in a surface layer, a surface soft layer with a Vickers hardness that is 84% or less of a Vickers hardness at a quarter thickness, the surface soft layer has a thickness satisfying the following formula (1), and the structural member has a tensile strength of 980 MPa or more and 1.8 GPa or less, 20 ≤ X ≤ 0.1 × t − 3800 × Sb − 1900 × Sn wherein X denotes the thickness of the surface soft layer (µm), t denotes a thickness of the base steel sheet (µm), and [Sb] and [Sn] denote an Sb content and a Sn content (% by mass) of the base steel sheet, respectively.

To provide a technique for a steel sheet having a TS of 780 MPa or more and less than 1180 MPa, a high YS, and high press formability in the inner portion of the steel sheet and at an end portion of the steel sheet.In the steel sheet, a base steel sheet has a predetermined chemical composition and has a surface soft layer having a Vickers hardness of 84% or less with respect to that at the quarter thickness from the surface of the base steel sheet and satisfying the following formula (1),the surface soft layer has a microstructure in a specific range, the base steel sheet has a microstructure in a specific range at the quarter thickness, and the steel sheet has a tensile strength of 780 MPa or more and less than 1180 MPa.20≤X≤120−3800×Sb−1900×SnIn the formula (1), X denotes the thickness of the surface soft layer (µm), and [Sb] and [Sn] denote an Sb content and a Sn content of steel (% by mass), respectively.

To provide a steel sheet having a TS of 1180 MPa or more and less than 1470 MPa, high YS, high ductility, high press formability in the inner portion of the steel sheet and at the end portion of the steel sheet, and high crack propagation resistance. The steel sheet has a base steel sheet having a predetermined chemical composition and has a surface soft layer having a Vickers hardness of 84% or less relative to that at the quarter thickness from the surface of the base steel sheet and satisfying the following formula (1), wherein the surface soft layer has a microstructure in a specific range, the base steel sheet has a microstructure in a specific range at the quarter thickness, the length of a crack that propagates from a bending ridge line end portion in a ridge line direction is 200 µm or less in a 90-degree V-bending test with a bending radius of 0.5 mm, El is 6.0% or more in a notch tensile test after a heat treatment at 170°C for 20 minutes, and El is 5.0% or more in a notch tensile test after a nominal tensile strain of 2% is introduced and after a heat treatment at 170°C for 20 minutes is performed. 20 ≤ X ≤ 120 − 3800 × Sb − 1900 × Sn <img class="EMIRef" id="05b76f3d-cb48-4209-86f8-c31468675743-ia01" />

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A method of predicting a breakout of the present invention includes: a step of receiving input of a dimension of a cast strand to be pulled out from a mold included in a continuous casting machine; a step of detecting temperatures of the mold with a plurality of thermometers buried in the mold; a step of executing interpolation processing in accordance with a dimension of the cast strand on detected temperatures detected by the plurality of thermometers; a step of calculating temperature change amounts by comparison with temperatures before a first period; a step of acquiring a standard deviation of temperature change amounts of the thermometers in a second period; a step of standardizing temperature changes by dividing the temperature change amounts by the standard deviation; a step of calculating a component in a direction orthogonal to an influence coefficient vector obtained by principal component analysis, as a deviation degree from a normal operation time when no breakout occurs, based on a temperature change amount calculated by executing the interpolation processing; and a step of predicting the breakout based on the deviation degree.

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A method of calculating the rolling load distribution of a rolling mill 10, the method comprising: calculating the contact arc length of at least one of the elastic recovery region and the elastic reduction region based on Hooke's law under the plane-strain condition of a rolled material 1, the force balance within the roll bite of the rolling mill 10, and the rolling-direction stress distribution approximated by a function dependent on the position coordinate in the rolling direction of the rolling mill 10; and calculating the rolling load distribution of at least one of the elastic recovery region and the elastic reduction region based on the contact arc length.

Provided is a butt welding method capable of, even if weld metal is soft as in the case of a welded portion formed when a high-Ni austenitic or low-carbon ferritic filler wire is used, strengthening the weld metal and preventing fracture at the welded portion during sheet passage through a continuous processing line. Upon butting a trailing end of a preceding steel sheet and a leading end of a succeeding steel sheet at an entry side of the processing line and pressing a solidified welded portion at a butted portion, an excess weld metal height h [mm] of the welded portion satisfies h > 0, and a reduction ratio during the pressing is controlled to satisfy 0 ≤ H<w> - H<1> < 100, where H<w> is hardness of the welded portion after the pressing and H<1> is base metal hardness of a lower-hardness steel sheet among the butted steel sheets.

Provided is a butt welding method capable of, even if weld metal is soft as in the case of a welded portion formed when a high-Ni austenitic or low-carbon ferritic filler wire is used, increasing the strength of the weld metal and preventing fracture at the welded portion during sheet passage through a processing line. Upon butting a trailing end of a preceding steel sheet and a leading end of a succeeding steel sheet at an entry side of the processing line and pressing a solidified welded portion at a butted portion, a pressing force during the pressing is controlled to satisfy 0 ≤ H_w - H₁ < 100, where H_w is hardness of the welded portion after the pressing and H₁ is base metal hardness of a steel sheet having lower hardness among the butted steel sheets.

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