JFE Steel Patente

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

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" />

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 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.

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

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.

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.

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Provided is an electric furnace equipment/system that prevents overheating of molten metal by converting heat transfer between the molten metal and slag from thermal conduction to forced convection, thereby improving productivity without requiring oversized equipment. The electric furnace equipment/system is configured to accommodate molten metal, slag, a metal raw material, and an auxiliary raw material in stacked layers, and to discharge the molten metal and slag. The electric furnace equipment/system comprises: an arc furnace having a bottom portion, a furnace wall, and a furnace cover; and an electromagnetic stirrer disposed at a predetermined position at the bottom portion or on the side wall of the arc furnace to enable stirring of the molten metal within the arc furnace.

Provided is a method for operating an electric furnace that achieves high productivity and involves little wear of a refractory material when producing molten metal by melting a metal raw material in the electric furnace. Specifically, provided is a method for operating an electric furnace operated by accommodating molten metal, molten slag, a metal raw material, and an auxiliary raw material in this order in stacked layers within the electric furnace, and continuously discharging the molten metal and the molten slag, characterized in that the electric furnace includes a bottom portion, a furnace wall, a furnace cover, and stirring means for molten metal, input power per unit surface area of molten metal is set to 300 kW/m<2> or greater, and a stirring power density of the stirring means for the molten metal is set in a range of 5 to 100 W/t.

To provide a method for melting a metal raw material that can perform a process of melting a large amount of metal raw material by appropriately setting the conditions for performing a process of melting a metal raw material composed partially or entirely of reduced iron, using a submerged arc furnace (SAF), and by passing a stable current. Specifically, provided is a method for melting a metal raw material using an electric furnace comprising accommodating molten iron, molten slag, a metal raw material, and an auxiliary raw material in stacked layers in the electric furnace, and discharging the molten iron and the molten slag, in which the resistivity within the electric furnace is set within a range of 0.01 to 0.02 (Ω·m) when a current is supplied to the molten metal to heat the molten metal through an arc or via the molten slag and the metal raw material.

There are provided a method capable of evaluating delayed fracture in a sheared end surface with higher accuracy and a method for manufacturing a press-formed article using the method. A method for evaluating delayed fracture for evaluating the delayed fracture characteristics of a sheared end surface of a metal sheet including: testing whether the delayed fracture occurs with respect to application of forming strain and load stress to the sheared end surface of the metal sheet; for each of two or more evaluation positions along the sheet thickness direction of the sheared end surface, determining evaluation information on whether the delayed fracture occurs with respect to the forming strain and the load stress at the evaluation position based on the test; and determining, from the determined evaluation information, evaluation criteria for the delayed fracture evaluation with the evaluation position, the forming strain, and the load stress as variables.

There is provided a method for producing a Cu-Sn-containing steel which, even in hot working using a heating furnace with a low heating capacity, can prevent surface cracking of a Cu-Sn-containing steel and avoid troubles in the heating furnace, thus enabling stable production of the steel. The method for producing a Cu-Sn-containing steel includes: a hot heating step of attaching a first flux, which includes at least one of B<2>O<3>, P<2>O<5>, K<2>O, PbO, Na<2>O-FeO, Na<2>O-SiO<2>, Na<2>O-TiO<2>, and Li<2>O-SiO<2> as a component, and has a liquid fraction of 10 mass % or more at 1000°C, to a surface of a Cu-Sn-containing slab such that the mass of the first flux per unit area of the surface of the slab falls within the range of not less than 50 g/m<2> and not more than 5000 g/m<2>, and then attaching a second flux, which has a liquid fraction of 0 mass % at 1400°C or lower, to the surface of the Cu-Sn-containing slab such that the mass of the second flux per unit area of the surface of the slab falls within the range of not less than 50 g/m<2> and not more than 5000 g/m<2>, and heating the Cu-Sn-containing slab at a temperature of not less than 1000°C and not more than 1400°C; and a hot working step of hot-working the Cu-Sn-containing slab.

A method for predicting delayed fracture in a press formed part according to the present invention includes: calculating a stress distribution and a strain distribution in a press formed part (S1); calculating a stress gradient in a direction of crack propagation due to delayed fracture at a delayed fracture portion-of-concern in the press formed part (S3); setting a hydrogen concentration distribution corresponding to the strain distribution in the press formed part (S5); performing hydrogen diffusion analysis on the press formed part based on the stress distribution and the hydrogen concentration distribution to calculate a hydrogen concentration distribution after hydrogen diffusion (S7); and predicting whether delayed fracture will occur at the delayed fracture portion-of-concern based on delayed fracture determination conditions based on stress, strain, and hydrogen concentration at the stress gradient, and stress, strain, and hydrogen concentration at the delayed fracture portion-of-concern (S9).

Proposed is a method for producing a reduced iron briquette that can improve both the apparent density and strength thereof when briquetting reduced iron through hot briquetting. The method for producing a reduced iron briquette of the present invention is a method for producing a reduced iron briquette including performing hot briquetting on a reduced iron aggregate including pellet-shaped reduced iron containing an iron component, using briquetting rolls, and thus briquetting the reduced iron aggregate, the method also including performing hot briquetting on the reduced iron aggregate by changing a rotation speed of the briquetting rolls and/or a gap between the briquetting rolls in accordance with a T.Fe content of the pellet-shaped reduced iron. As a preferred embodiment, the rotation speed of the briquetting rolls is changed to be slower and/or the gap between the briquetting rolls is changed to be narrower as the proportion of gangue components is higher.

Proposed is a method for producing a reduced iron briquette that can improve both the apparent density and strength thereof when briquetting reduced iron through hot briquetting. The method for producing a reduced iron briquette of the present invention includes, in performing hot briquetting on a reduced iron aggregate composed of pellet-shaped reduced iron containing an iron component, a step of controlling a particle size distribution of the reduced iron aggregate, and a step of performing hot briquetting on the reduced iron aggregate with the controlled particle size distribution. An apparatus for producing a reduced iron briquette of the present invention includes a reduced iron production facility that produces pellet-shaped reduced iron containing an iron component to form a reduced iron aggregate, a crushing facility that crushes the reduced iron aggregate, a classification facility that screens the crushed reduced iron aggregate, using a sieve having a plurality of sieve meshes, a mixing facility that mixes the reduced iron aggregate having a plurality of particle size levels, separated by the screening, to prevent uneven distribution of the particle sizes within a mold for hot briquetting, and a reheating facility that heats the mixed reduced iron aggregate to a briquetting temperature required for the hot briquetting.

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …

An energy operation support device in a steel mill includes: an optimization unit configured to optimize operation of an energy utility in a facility in the steel mill; and an upper-limit relaxation unit configured to set an operational upper limit, which is an upper limit in operation, with respect to a facility upper limit, which is an upper limit in output of facility capacity of the facility, in which the upper-limit relaxation unit is configured to set the operational upper limit at a target time or in a target calculation period by determining a predetermined ratio with respect to the facility upper limit, and a total energy operation cost of the steel mill and an adjustment variable of an energy utility with a difference between the facility upper limit and the operational upper limit as an upper limit are included as an objective function of optimization calculation in the optimization unit.

Zusammenfassung wird geladen …

Zusammenfassung wird geladen …