Abstract: This manufacturing method for a slab is a method for manufacturing a slab by a continuous casting equipment including a twin-drum type continuous casting apparatus, a cooling apparatus, an in-line mill, and a coiling apparatus. The method includes calculating a friction coefficient from measured values of a rolling load and a forward slip when the slab is rolled, by use of a rolling analysis model, and controlling a lubrication condition during rolling of the slab so that the friction coefficient falls within a predetermined range, wherein, when the friction coefficient is calculated from the measured values of the rolling load and the forward slip by use of an Orowan theory and a deformation resistance model formula based on a Shida's approximate formula as the rolling analysis model, the predetermined range is 0.15 or more and 0.25 or less.

Abstract: Provided is a nozzle header which sprays pressurized water to a high-temperature object, capable of inhibiting a member provided to spray nozzles from being deformed or damaged by heat at the time of operation, caused by radiation heat from the high-temperature object. The nozzle header for spraying water to a targeted object includes a header which supplies pressurized water, one or more of spray nozzles which spray the pressurized water supplied from the header, and a heat removal structure attached so as to be in contact with at least one of the spray nozzles, wherein the heat removal structure includes a coolant passage through which a cooling medium for cooling the heat removal structure itself and the spray nozzles passes.

Abstract: Provided is a nozzle header which sprays pressurized water to a high-temperature object, capable of inhibiting a member provided to spray nozzles from being deformed or damaged by heat at the time of operation, caused by radiation heat from the high-temperature object. The nozzle header for spraying water to a targeted object includes a header which supplies pressurized water, one or more of spray nozzles which spray the pressurized water supplied from the header, and a heat removal structure attached so as to be in contact with at least one of the spray nozzles, wherein the heat removal structure includes a coolant passage through which a cooling medium for cooling the heat removal structure itself and the spray nozzles passes.

Abstract: In order to provide a manufacturing device and a manufacturing method for a hot-rolled steel strip, which are capable of obtaining the desired quality of material by rapid uniform cooling immediately after rolling, and improving yield by early sheet tension and sheet shape measurements, a manufacturing device for a hot-rolled steel strip is provided with a finishing rolling mill line (11), a first cooling unit (13) installed just behind the exit side of the finishing rolling mill line, and a pinch roll (14) which is installed on the exit side of the first cooling unit and in contact with both the upper and lower surfaces of a strip (S), at least a wiping roll (15) located on the upper side of the strip (S) is disposed between the first cooling unit and the pinch roll, and a tension/shape measuring unit (16) for measuring the tension and shape of the strip (S); is installed between the wiping roll and the pinch roll.

Abstract: A method for manufacturing a hot-rolled sheet attains grain refinement of the steel sheet whose grain size is extremely fine. In particular, a ferrite grain size of less than average 2 ?m is obtained, which is not laminar but has ferrite grains with equiaxed morphology and exhibits high formability in forming. The method comprises the steps of rolling and cooling, wherein the rolling reductions, cooling steps, and temperature are closely regulated. A hot rolled sheet made from the method of manufacturing has a controlled ferrite grain in different regions of sheet thickness.

Abstract: A method for manufacturing a hot-rolled sheet attains grain refinement of the steel sheet whose grain size is extremely fine. In particular, a ferrite grain size of less than average 2 ?m is obtained, which is not laminar but has ferrite grains with equiaxed morphology and exhibits high formability in forming. The method comprises the steps of rolling and cooling, wherein the rolling reductions, cooling steps, and temperature are closely regulated. A hot rolled sheet made from the method of manufacturing has a controlled ferrite grain in different regions of sheet thickness.

Abstract: In order to provide a manufacturing device and a manufacturing method for a hot-rolled steel strip, which are capable of obtaining the desired quality of material by rapid uniform cooling immediately after rolling, and improving yield by early sheet tension and sheet shape measurements, a manufacturing device for a hot-rolled steel strip is provided with a finishing rolling mill line (11), a first cooling unit (13) installed just behind the exit side of the finishing rolling mill line, and a pinch roll (14) which is installed on the exit side of the first cooling unit and in contact with both the upper and lower surfaces of a strip (S), at least a wiping roll (15) located on the upper side of the strip (S) is disposed between the first cooling unit and the pinch roll, and a tension/shape measuring unit (16) for measuring the tension and shape of the strip (S); is installed between the wiping roll and the pinch roll.

Abstract: The present invention provides a cooling apparatus of a hot-rolled steel sheet capable of manufacturing a hot-rolled steel sheet having ultra fine crystal grains. In the cooling apparatus, when defining as L1, a length in a transporting direction of a steel sheet, of a zone from a rolling reduction point in a final stand to an exit side of a housing post; defining as L2, a length in the transporting direction of the steel sheet, of an area where high-pressure water is continuously sprayed over the steel sheet, within the zone; and defining a ratio of L2/L1 as X, an average value Ps [kPa], in the transporting direction of the steel sheet, of an impact pressure of the high-pressure water on a surface of the steel sheet in the area of the length L2 satisfies Ps?2.5X(?1/0.6) on the above upper surface and lower surface of the steel sheet.

Abstract: A method for manufacturing a hot-rolled sheet is provided, wherein the method attains grain refinement of the steel sheet containing C, Si, and Mn, wherein the grain size thereof is set to particularly below average of 2 ?m, which has ferrite grain with equiaxed morphology, which has high formability in forming, and the ferrite grain-size deviation in the thickness direction is uniformed down to the level not higher than a predetermined amount whereby uniform formability in forming is high. The method includes a first rolling for rolling the sheet such that the total rolling reduction is 80% or more or the average grain size is 30 ?m or less in a form of single phase of austenite, a second rolling of a single-pass, a third rolling being conducted thereafter, and a following cooling.

Abstract: The present invention provides a cooling apparatus of a hot-rolled steel sheet capable of manufacturing a hot-rolled steel sheet having ultra fine crystal grains. In the cooling apparatus, when defining as L1, a length in a transporting direction of a steel sheet, of a zone from a rolling reduction point in a final stand to an exit side of a housing post; defining as L2, a length in the transporting direction of the steel sheet, of an area where high-pressure water is continuously sprayed over the steel sheet, within the zone; and defining a ratio of L2/L1 as X, an average value Ps [kPa], in the transporting direction of the steel sheet, of an impact pressure of the high-pressure water on a surface of the steel sheet in the area of the length L2 satisfies Ps?2.5X(?1/0.6) on the above upper surface and lower surface of the steel sheet.

Abstract: The present invention provides a method for manufacturing the hot-rolled sheet, which includes: a step A including a first rolling in which a steel sheet containing 0.04-0.20% C, 0.01-2.0% Si, 0.5-3.0% Mn by mass, and the reminder being Fe and inevitable impurities, is rolled by successive multi-pass rolling at a total rolling reduction of 80% or more while keeping the steel sheet at temperatures not lower than the para-equilibrium transformation temperature Ae3; a step B including a second rolling in which a single-pass rolling is carried out at a rolling reduction of 30-55% when an entry side temperature is not lower than the para-equilibrium transformation temperature Ae3; a step C including a third rolling in which a single-pass rolling is carried out at a rolling reduction of 35-70% when an entry side temperature is set within a predetermined range; and a step D in which within 0.2 seconds after the third rolling, the rolled sheet is cooled at a cooling rate of 600 degree C.