Method for winding hot-rolled steel sheet, winding device for hot-rolled steel sheet, and method for manufacturing hot-rolled steel sheet

Abstract

To provide a taking-up method for a hot rolled steel sheet, etc., capable of accurately presenting a spring-back reduction effect in an outermost peripheral part of a coil by accurately determining a cooling time, with which a temperature difference between an outer peripheral surface and an inner peripheral surface of an outermost peripheral plate of the coil becomes maximum, from an outer diameter, a plate thickness, etc., of the coil for each coil when determining the cooling time.SOLUTION: A spray control step (step S2) in a taking-up method for a hot rolled steel sheet includes a cooling time calculation step (step S23) of calculating a cooling time τ, with which a temperature difference between an outer peripheral surface and an inner peripheral surface of an outermost peripheral plate of a coil C for an arc length Lc of a cooling range in the coil C becomes maximum, on the basis of an installation position of the coil C, an outer diameter D of the coil C, a plate thickness t of the coil C, positions of nozzles 4a and 4b, a direction α of the nozzles 4a and 4b, an injection angle β of cooling water from the nozzles 4a and 4b, a cooling width Wc in the coil C by the cooling water from the nozzles 4a and 4b, a flow quantity Q of the cooling water from the nozzles 4a and 4b, and a surface temperature T0 of the coil C before cooling when taking up the coil.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for winding a hot-rolled steel plate, a hot-rolled steel plate winding device, and a method for manufacturing a hot-rolled steel plate, for stably producing a hot-rolled steel plate, particularly a high-strength thick-walled hot-rolled steel plate used as a material for steel pipe piles and square columns. [Background technology]

[0002] In recent years, there has been an increasing demand for steel pipe piles, which are primarily used as foundation piles for port buildings and other structures, and square columns, which are used as building pillars. These steel pipe piles and square columns require high strength and high toughness. For this reason, they are manufactured using high-strength, thick-walled hot-rolled steel plate. These high-strength, thick-walled hot-rolled steel plates have a thickness of approximately 12 to 30 mm and a width of approximately 1100 to 2200 mm.

[0003] After passing through the hot rolling line, the hot-rolled steel sheet is wound by a winding device (down coiler). In this case, in the case of a high-strength, thick-walled material, the elastic deformation (springback) of the outermost periphery of the hot-rolled steel sheet wound into a coil (hereinafter, the hot-rolled steel sheet wound into a coil) becomes large. Because the elastic deformation force of the outermost periphery of the coil is greater than the coil's own weight in the winding device, the coil C is lifted by the elastic deformation force of the outermost periphery C1 of the coil C (the coil C is lifted from the cradle rolls 107a and 107b supporting the coil C), as shown in FIG. 15 . This may cause contact between the coil C and the mandrel 102, which has been reduced in diameter, and the coil C may not be able to be released from the mandrel 102. Furthermore, contact between the coil C and the mandrel 102 may also result in damage to the mandrel 102. Furthermore, after the hot-rolled steel sheet is wound, the outermost periphery C1 of the coil C experiences a large elastic deformation force, which may cause the restraining band (not shown) that restrains the outer periphery of the coil C to tear during transportation, potentially causing the coil C to fly off. Steel pipe pile and column materials require strength and toughness, so samples must be collected for material testing. To collect these samples, the hot-rolled steel sheet is cooled after being wound into a coil and then gas-cut by hand. However, the moment the restraining band that restrains the coil C is removed, the elastic deformation force of the outermost periphery C1 of the coil C causes the hot-rolled steel sheet to jump up, creating a very dangerous situation. Therefore, suppressing the elastic deformation of the outermost periphery C1 of the coil C is essential for the production of hot-rolled steel sheets.

[0004] As a method for suppressing elastic deformation of the outermost periphery of a coil, a coiling method for a hot-rolled steel sheet as disclosed in Patent Document 1 has been proposed. The method of winding a hot-rolled steel sheet disclosed in Patent Document 1 involves winding the hot-rolled steel sheet from its leading end to its tail end into a coil, and then spraying cooling water onto the outer periphery of the coil while planetary wrapper rolls are pressed against the coil. After the outer periphery of the coil is cooled for a predetermined cooling time, the cooling is stopped and the coil is retained in the winding device for a predetermined retention time, after which the wrapper rolls are released and the coil is removed from the winding device.

[0005] Furthermore, as a method for suppressing elastic deformation of the outermost periphery of a coil, for example, a method for winding a high-strength thick hot-rolled steel sheet as shown in Patent Document 2 has been proposed. The coiling method for high-strength thick hot-rolled steel sheet shown in Patent Document 2 involves winding the high-strength thick hot-rolled steel sheet from its leading end to its tail end around a mandrel in the form of a coil, and then spraying cooling water onto the outer periphery of the coil while a plurality of wrapper rolls are pressed against the coil, thereby rapidly cooling the outer periphery of the coil to a predetermined temperature, and then unwinding the coil from the winding device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-24793 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-162594 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, in the coiling method of hot-rolled steel sheet shown in Patent Document 1, it is said that the effect of reducing springback is achieved when the cooling time of the outer peripheral plate of the coil is approximately equal to the time when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost peripheral plate of the coil becomes maximum. In the coiling method of hot-rolled steel sheet shown in Patent Document 1, coil winding experiments and the like were conducted to determine the cooling time at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of the coil becomes maximum, and the cooling time was set to 5 seconds or more for materials that meet API standard X65 or higher and have a product thickness of 19 mm or higher.

[0008] However, when determining the cooling time that will maximize the temperature difference between the outer and inner surfaces of the outermost coil plate, for materials that meet API standards of X65 or higher and have a product thickness of 19 mm or more, it is not enough to simply set it at 5 seconds or more; it must be accurately determined for each coil based on the outer diameter and plate thickness of the coil, the position and direction of the nozzle that sprays the cooling water, the flow rate of the cooling water, etc. Furthermore, in the coiling method for high-strength thick hot-rolled steel sheet shown in Patent Document 2, cooling water is sprayed onto the outer periphery of the coil to rapidly cool it down to a predetermined temperature. However, there is no mention whatsoever of setting the cooling time of the outer periphery sheet of the coil to the time that maximizes the temperature difference between the outer periphery surface and the inner periphery surface of the outermost sheet of the coil in order to exert the effect of reducing springback.

[0009] Therefore, the present invention has been made to solve the conventional problems, and its object is to provide a coiling method for a hot-rolled steel sheet, a coiling device for a hot-rolled steel sheet, and a manufacturing method for a hot-rolled steel sheet, which, when determining the cooling time that maximizes the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of a coil, can be accurately determined for each coil based on the outer diameter and sheet thickness of the coil, the position and orientation of the nozzle that sprays the cooling water, the flow rate of the cooling water, etc., and can accurately demonstrate the effect of reducing springback in the outermost part of the coil. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, one aspect of the present invention provides a method for winding a hot-rolled steel sheet, which comprises winding a hot-rolled steel sheet from its leading end to its trailing end into a coil shape on a mandrel of a winding device, and then rotating the mandrel while pressing a plurality of wrapper rolls arranged in a planetary pattern against the coil, spraying cooling water from a nozzle onto the outer peripheral plate of the coil, thereby cooling the outer peripheral portion of the coil for a predetermined cooling time, wherein the predetermined cooling time for the outer peripheral portion of the coil is set equal to the time when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost peripheral plate of the coil becomes maximum. The method includes a spray control step of controlling the rotation of the mandrel and the spray of cooling water from the nozzles so that cooling water is sprayed from the nozzles onto the peripheral plate, and the spray control step includes a cooling time calculation step of calculating the cooling time at which the temperature difference between the outer surface and the inner surface of the outermost plate of the coil over the arc length of the cooling range of the coil becomes maximum, based on the installation position of the coil, the outer diameter of the coil, the plate thickness of the coil, the position of the nozzle, the orientation of the nozzle, the spray angle of the cooling water from the nozzle, the cooling width of the coil by the cooling water from the nozzle, the flow rate of the cooling water from the nozzle, and the surface temperature of the coil before cooling when winding the coil.

[0011] Furthermore, a coiling device for a hot-rolled steel sheet according to another aspect of the present invention is a coiling device for a hot-rolled steel sheet, which winds up the hot-rolled steel sheet from the leading end to the trailing end into a coil shape around a mandrel, and then rotates the mandrel while pressing a plurality of wrapper rolls arranged in a planetary pattern against the coil against the coil, and sprays cooling water from a nozzle onto the outer peripheral plate of the coil to cool the outer peripheral portion of the coil for a predetermined cooling time, and in this coiling device for a hot-rolled steel sheet, the predetermined cooling time for the outer peripheral portion of the coil is set to be equal to the time when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost peripheral plate of the coil becomes maximum, The method includes a spray control unit that controls the rotation of the mandrel and the spray of cooling water from the nozzle so that cooling water is sprayed from the nozzle onto the mandrel, and the spray control unit includes a cooling time calculation unit that calculates the cooling time at which the temperature difference between the outer surface and inner surface of the outermost plate of the coil over the arc length of the cooling range of the coil will be maximized, based on the installation position of the coil, the outer diameter of the coil, the plate thickness of the coil, the position of the nozzle, the orientation of the nozzle, the spray angle of the cooling water from the nozzle, the cooling width of the coil by the cooling water from the nozzle, the flow rate of the cooling water from the nozzle, and the surface temperature of the coil before cooling when winding the coil.

[0012] Furthermore, a method for producing a hot-rolled steel sheet according to another aspect of the present invention is summarized as including a winding step of winding the hot-rolled steel sheet into a coil shape by a winding device using the above-mentioned method for winding the hot-rolled steel sheet. [Effects of the Invention]

[0013] According to the coiling method for hot-rolled steel sheet, the coiling device for hot-rolled steel sheet, and the manufacturing method for hot-rolled steel sheet of the present invention, when determining the cooling time that maximizes the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of the coil, it is possible to accurately determine the cooling time for each coil based on the outer diameter and thickness of the coil, the position and orientation of the nozzle that sprays cooling water, the flow rate of cooling water, etc., and to provide a coiling method for hot-rolled steel sheet, the coiling device for hot-rolled steel sheet, and the manufacturing method for hot-rolled steel sheet that can accurately demonstrate the effect of reducing springback in the outermost portion of the coil. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a coiling device for a hot-rolled steel sheet according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a spray control unit in the winding device shown in FIG. [Figure 3] FIG. 3 is a schematic configuration diagram of a cooling time calculation unit in the spray control unit shown in FIG. 2. [Figure 4] 2 is a flowchart showing the flow of processing in a winding control device in the winding device shown in FIG. [Figure 5] 5 is a flowchart showing details of the process flow in step S2 (spray control step) in the flowchart showing the process flow in the take-up control device shown in FIG. [Figure 6] 6 is a flowchart showing details of the processing flow in step S23 (cooling time calculation step) in the flowchart showing the processing flow in step S2 (spray control step) shown in FIG. 5. [Figure 7] 1 shows the control contents by the winding control device, where (a) is wrapper roll control, (b) is spray control, (c) is air cooling control, and (d) is tail end stop control. [Figure 8] 10A and 10B are diagrams for explaining the plastic bending moment of the outermost plate of the coil. [Figure 9] FIG. 10 is a diagram for explaining a coil's own weight moment. [Figure 10] FIG. 10 is a diagram for explaining calculation of the arc length of the cooling range in the coil. [Figure 11] This is a graph showing the relationship between the temperature difference between the outer surface and the inner surface of the outermost plate of the coil and the cooling time for each plate thickness (t=12, 15 mm). [Figure 12] This graph shows the relationship between the time it takes to reach the maximum temperature difference between the outermost surface and the inner surface of the outermost plate of the coil and the plate thickness of the coil for each heat transfer coefficient (h = 6000, 10000, 20000 kcal (m2.hr·°C)-1). [Figure 13]1 is a graph showing the relationship between the time until the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil reaches a maximum and the heat transfer coefficient for each plate thickness (t=10, 15, 20, 25.4 mm). [Figure 14] 10 is a diagram for explaining the process of the ejection nozzle pattern selection unit and step S25 (ejection nozzle pattern selection step). FIG. [Figure 15] 10 is a diagram illustrating how the coil is lifted due to springback at the outermost periphery of the coil when the coil is removed from the mandrel. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the materials, shapes, structures, arrangements, etc. of the components. In addition, the drawings are schematic, and therefore it should be noted that the relationship between thickness and planar dimensions, ratios, etc. may differ from the actual relationship, and the drawings may also contain parts where the relationship and ratio of dimensions differ from each other.

[0016] FIG. 1 shows a schematic configuration of a coiling device for a hot-rolled steel sheet according to one embodiment of the present invention. A coiling device 1 for a hot-rolled steel sheet shown in FIG. 1 is provided in a hot rolling line (not shown), and is equipment for coiling a hot-rolled steel sheet after it has been hot-rolled. The hot-rolled steel sheet winding device 1 winds up the hot-rolled steel sheet S from its leading end to its trailing end in the form of a coil (the hot-rolled steel sheet S wound up in the form of a coil will be referred to as a coil C hereinafter).

[0017] The hot-rolled steel plate S is a high-strength, thick hot-rolled steel plate with a thickness of about 12 to 30 mm and a width of about 1100 to 2200 mm. Steel pipe piles and square columns are manufactured from this high-strength, thick hot-rolled steel plate. As described above, when the hot-rolled steel sheet S is a high-strength, thick material, the springback of the outermost portion C1 of the coil C (see FIG. 15) is greater than the weight of the coil C. As a result, as shown in FIG. 15, the springback of the outermost portion C1 of the coil C causes the coil C to lift (the coil C is lifted from the cradle rolls 107a and 107b supporting the coil C). This causes the coil C to come into contact with the reduced-diameter mandrel 102, which may prevent the coil C from being released from the mandrel 102. Furthermore, the contact between the coil C and the mandrel 102 may damage the mandrel 102. Furthermore, because the springback of the outermost portion C1 of the coil C is large after the hot-rolled steel sheet S is wound, there is a risk that the restraining band (not shown) that restrains the outer periphery of the coil C may tear during transport, causing the coil C to fly off at that moment.

[0018] For this reason, it is important to reduce springback at the outermost portion C1 of the coil C. In this embodiment, the winding device 1 winds the hot-rolled steel sheet S into a coil shape around the mandrel 2, and then rotates the mandrel 2 while pressing multiple (four in this embodiment) wrapper rolls 3a to 3d arranged in a planetary pattern against the coil C against the coil C. While rotating the mandrel 2, cooling water is sprayed from nozzles 4a and 4b onto the outer peripheral plate of the coil C, thereby cooling the outer peripheral portion of the coil C for a predetermined cooling time. This reduces springback at the outermost portion C1 of the coil C. This is achieved by cooling the outer peripheral plate of the coil C to create a temperature difference in the thickness direction and increase the plastic deformation region. Subsequently, the outer side of the coil C reheats and thermally expands due to heat conduction from the inside of the coil C. This thermal expansion of the outer peripheral portion generates a force that deforms the inside of the coil C, thereby reducing springback.

[0019] The predetermined cooling time for the outer periphery of coil C by nozzles 4a and 4b is set equal to the time when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of coil C is maximized. The reason for this is that the effects of the plastic deformation and thermal expansion described above are greatest when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of coil C is maximized, thereby maximizing the springback reduction effect. The plastic deformation range described above is determined by the maximum temperature difference when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of coil C is maximized, so the springback reduction effect remains unchanged even with long cooling times, and the cooling time when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of coil C is maximized is sufficient.

[0020] In order to achieve cooling of the outer periphery of the coil C by such nozzles 4a, 4b, in this embodiment, the winding device 1 is equipped with a winding control device 10 that controls the winding of the hot-rolled steel sheet S by the mandrel 2, as shown in Figure 1, and has a wrapper roll control unit 11, a spray control unit 12, an air cooling control unit 13, and a tail end stop control unit 14.

[0021] The winding control device 10 is a computer system with a processing function, and executes various dedicated computer programs pre-stored in the hardware, thereby enabling the functions of the wrapper roll control unit 11, the spray control unit 12, the air cooling control unit 13, and the tail end stop control unit 14 (steps S1 to S4, described later, see FIG. 4) to be realized on the software.

[0022] When the tail end Sa of the hot-rolled steel sheet S passes through the pinch rolls 5a and 5b, the wrapper roll control unit 11 of the winding control device 10 controls the movement of the multiple wrapper rolls 3a to 3d so as to press the multiple wrapper rolls 3a to 3d against the coil C, as shown in Figure 7(a). A signal indicating that the tail end Sa of the hot-rolled steel sheet S has passed through the pinch rolls 5a and 5b is detected by a tail end detection sensor (not shown) provided on the wrapper rolls 3a to 3d, and when the wrapper roll control unit 11 receives the signal from the tail end detection sensor, it controls the movement of the multiple wrapper rolls 3a to 3d so as to press the multiple wrapper rolls 3a to 3d against the coil C.

[0023] The wrapper roll control unit 11 is connected to a host computer 15. The host computer 15 stores information such as the installation position of the coil C (coil center position CP(x0, y0) in FIG. 10), the outer diameter of the coil C (D in FIG. 10), the thickness of the coil C (hot-rolled steel sheet S) (t in FIG. 8), the width of the coil C (hot-rolled steel sheet S) (not shown), and the unit weight P of the coil C (hot-rolled steel sheet S). W , yield stress σ of coil C (hot-rolled steel sheet S) y The host computer 15 also stores information about the coil C, such as the positions of the nozzles 4a and 4b (N in FIG. 10). i (x i ,y i )), the orientation of the nozzles 4a, 4b (the tilt angle α from the horizontal state in FIG. 10), the spray angle of the cooling water from the nozzles 4a, 4b (the angle β that defines the spray width of the cooling water in FIG. 10), the cooling width Wc in the coil C by the cooling water from the nozzles 4a, 4b, and the flow rate Q of the cooling water from the nozzles 4a, 4b are stored.

[0024] In addition, after the wrapper roll control unit 11 controls the multiple wrapper rolls 3a to 3d to be pressed against the coil C, the spray control unit 12 controls the rotation of the mandrel 2 and the spraying of cooling water from the nozzles 4a and 4b so that cooling water is sprayed from the nozzles 4a and 4b onto the outer peripheral plate of the coil C while rotating the mandrel 2, as shown in Figure 7(b). The spray control unit 12 is also connected to the host computer 15. Here, the detailed configuration of the spray control unit 12 will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the spray control unit 12 in the winding device 1 shown in Fig. 1.

[0025] As shown in Figure 2, the spray control unit 12 includes a material information acquisition unit 12a, a cooling necessity determination unit 12b, a cooling time calculation unit 12c, a coil total cooling time calculation unit 12d, an injection nozzle pattern selection unit 12e, and a drive control unit 12f. The material information acquisition unit 12a acquires information about the coil C, such as the outer diameter D of the coil C, the thickness t of the coil C, the width of the coil C, and the unit weight P of the coil C. W , yield stress σ of coil C (hot-rolled steel sheet S) y In addition, information on the Young's modulus E of coil C (hot-rolled steel sheet S), the radius of curvature ρ of the outermost sheet in coil C, and the second moment of area I of the outermost sheet in coil C is obtained from the host computer 15.

[0026] Furthermore, the cooling necessity determining unit 12b determines whether or not it is necessary to spray cooling water onto the outer periphery of the coil C to cool it, based on the information about the coil C acquired from the material information acquiring unit 12a. The cooling necessity determining unit 12b determines whether the plastic bending moment M of the outermost plate of the coil C is equal to the coil weight moment (=P W The coil extraction feasibility judgment is based on whether the plastic bending moment M of the outermost plate of coil C is less than the band securing moment (= σ·bt·w·g·D·N) using the band securing feasibility judgment formula given by the following (2).

[0027] When the following equation (1) is satisfied, the aforementioned plastic bending moment M is smaller than the coil's own weight moment, and the coil C does not lift off the cradle rolls 7a and 7b, preventing the coil C from coming into contact with the mandrel 2 when being removed from the mandrel 2. Furthermore, when the following formula (2) is established, the aforementioned plastic bending moment M is smaller than the band fastening moment, and there is no risk of the restraining band restraining the outer periphery of the coil C being torn off.

[0028]

number

[0029] M<σ bt w g D N (2) In the above equation (1), λ e is the elastic deformation rate and is expressed by the following equation (3). λ e =2δ / t=2·ρ·σ y / E·t ···(3) In equation (1), E is the Young's modulus E of coil C (hot-rolled steel sheet S), I is the second moment of area of ​​the outermost sheet in coil C, ρ is the radius of curvature of the outermost sheet in coil C, and in equation (3), ρ is the radius of curvature of the outermost sheet in coil C, σ y is the yield stress of the coil C (hot-rolled steel sheet S), E is the Young's modulus of the coil C (hot-rolled steel sheet S), and t is the thickness of the coil C (hot-rolled steel sheet S). The cooling necessity determination unit 12b acquires this information from the material information acquisition unit 12a.

[0030] In addition, in the above equation (1), P W is the unit weight of the coil C, and this information is acquired by the cooling necessity determination unit 12b from the material information acquisition unit 12a. In addition, in equation (1), L is the distance between the centers 7a1 and 7b1 of the cradle rolls 7a and 7b that support the coil C, as shown in Figure 9, and this information is acquired by the cooling necessity determination unit 12b from the host computer 15.

[0031] In addition, in the above-mentioned formula (2), σ is the band yield strength of the restraint band that restrains the outer periphery of coil C, bt is the plate thickness of the restraint band, w is the plate width of the restraint band, g is the gravitational acceleration, and N is the number of restraint bands, and this information is acquired by the cooling necessity determination unit 12b from the host computer 15. In addition, in the above-mentioned formula (2), D is the outer diameter of coil C, and this information is acquired by the cooling necessity determination unit 12b from the material information acquisition unit 12a.

[0032] If the plastic bending moment M of the outermost plate of coil C does not satisfy at least one of equations (1) and (2), it is determined that it is necessary to spray cooling water onto the outer periphery of coil C to cool it, and if the plastic bending moment M satisfies both equations (1) and (2), it is determined that it is not necessary to spray cooling water onto the outer periphery of coil C to cool it.

[0033] In addition, when the cooling necessity determination unit 12b determines that it is necessary to inject cooling water onto the outer periphery of the coil C to cool it, the cooling time calculation unit 12c determines whether it is necessary to inject cooling water onto the outer periphery of the coil C based on the installation position of the coil (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the thickness t of the coil C (hot-rolled steel sheet S), the positions of the nozzles 4a and 4b (N in FIG. 10), i (x i ,y i )), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that determines the spray width of the cooling water in FIG. 10), the cooling width Wc of the coil C by the cooling water from the nozzles 4a and 4b, the flow rate Q of the cooling water from the nozzles 4a and 4b, and the surface temperature T0 of the coil C before cooling when winding the coil are used to calculate the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of the coil C over the arc length Lc of the cooling range of the coil C becomes maximum.

[0034] Here, the cooling time calculation unit 12c will be described in detail. Fig. 3 shows a schematic configuration of the cooling time calculation unit 12c. As shown in FIG. 3, the cooling time calculation unit 12c includes a cooling range arc length calculation unit 12ca, a flow density calculation unit 12cb, a heat transfer coefficient calculation unit 12cd, and a maximum temperature difference cooling time calculation unit 12ce. The cooling range arc length calculation unit 12ca calculates the coil installation position (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the positions of the nozzles 4a and 4b (N in FIG. 10), and the i (x i ,y i )), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), and the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that defines the spray width of the cooling water in FIG. 10).

[0035] In FIG. 10, the arc length Lc of the cooling range in the coil C is determined by the nozzles 4a and 4b (position N) which are inclined by α. i (x i ,y i )) at a spray angle β, and the length on the outer periphery of the coil from the end point P2 of the cooling water W where the cooling water W comes into contact with the outer plate of the coil C to the end point P1 of the cooling water W. The positions of the end points P1 and P2 of the cooling water W are the positions of the nozzles 4a and 4b (N in FIG. 10). i (x i ,y i )), the direction of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that determines the spray width of the cooling water in FIG. 10), the installation position of the coil (the coil center position CP(x0, y0) in FIG. 10), and the outer diameter D of the coil C.

[0036] The length of this cooling water W on the outer periphery of the coil from end point P2 to end point P1 is expressed as D / 2 × (θ1 - θ2), where θ1 is the rotation angle from a predetermined point P0 on the outer periphery of the coil C to end point P1, and θ2 is the rotation angle from the predetermined point P0 on the outer periphery of the coil C to end point P2, and D is the outer diameter of the coil C. Therefore, the arc length Lc of the cooling range in the coil C can be calculated using the following equation (4). Lc=D / 2×(θ1-θ2) (4) Here, Lc is the arc length (mm) of the cooling range in coil C, D is the outer diameter (mm) of coil C, and θ1 and θ2 are the rotation angles (rad).

[0037] The coil installation position (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the positions of the nozzles 4a and 4b (N in FIG. 10) i (x i ,y i )), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), and the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that defines the spray width of the cooling water in FIG. 10) are acquired by the cooling range arc length calculation unit 12ca from the host computer 15.

[0038] Furthermore, the flow density calculation unit 12cb calculates the flow density w based on the arc length Lc of the cooling range calculated by the cooling range arc length calculation unit 12ca, the cooling width Wc in the coil C by the cooling water from the nozzles 4a and 4b, and the flow rate Q of the cooling water from the nozzles 4a and 4b. The flow density w of the cooling water is calculated by the following equation (5). w=Q / (Ac×10 -6 )=Q / (Lc×Wc×10 -6 ) ···(5)

[0039] where w is the flow density of the cooling water (L / (min m 2 ), Q is the flow rate of cooling water from the nozzles 4a and 4b (L / min), and Ac is the specific cooling area (mm 2 ), Lc is the arc length (mm) of the cooling range in coil C, and Wc is the cooling width (mm) of coil C by the cooling water from nozzles 4a and 4b (the width cooled by the cooling water in the width direction of C). The flow density calculation unit 12cb acquires information on the cooling width Wc and the flow rate Q of the cooling water from the host computer 15.

[0040] Further, the heat transfer coefficient calculation unit 12cd calculates the heat transfer coefficient h based on the flow density w calculated by the flow density calculation unit 12cb and the surface temperature T0 of the coil C before cooling during coiling. The heat transfer coefficient h is calculated using the following equation (6): h=494.3w 0.595 x10 -0.00179T0 ···(6) where h is the heat transfer coefficient (kcal(m 2 .hr·℃) -1 ), w is the flow density of the cooling water (L / (min m 2 ), T0 is the surface temperature of coil C before cooling during coil winding (°C).

[0041] The surface temperature T0 of the coil C before cooling during coil winding is measured by a thermometer 6 installed on the exit side of the pinch rolls 5a and 5b, as shown in Fig. 1. Information on the measured surface temperature T0 of the coil C before cooling during coil winding is then sent from the thermometer 6 to the heat transfer coefficient calculation unit 12cd. The surface temperature T0 of the coil C before cooling during coil winding can be measured by the thermometer 6, or a target surface temperature T0 can be determined in advance and stored in the host computer 15, and the heat transfer coefficient calculation unit 12cd can acquire information on the target surface temperature T0 from the host computer 15.

[0042] In addition, the maximum temperature difference cooling time calculation unit 12ce calculates the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of coil C over the arc length Lc of the cooling range is maximized based on the heat transfer coefficient h calculated by the heat transfer coefficient calculation unit 12cd and the plate thickness t of coil C. Here, Fig. 11 shows the relationship between the temperature difference between the outer and inner peripheral surfaces of the outermost plate of coil C and the cooling time for each plate thickness (t = 15, 25 mm). Also, Fig. 12 shows the relationship between the time until the temperature difference between the outer and inner peripheral surfaces of the outermost plate of the coil reaches the maximum and the plate thickness of the coil, as a function of the heat transfer coefficient (h = 6000, 10000, 20000 kcal(m 2 .hr·℃) -1 Furthermore, Fig. 13 shows the relationship between the time it takes to reach the maximum temperature difference between the outer surface and the inner surface of the outermost plate of the coil and the heat transfer coefficient for each plate thickness (t = 10, 15, 20, 25.4 mm).

[0043] As shown in Figure 11, the temperature difference between the outer and inner surfaces of the outermost plate of coil C increases as the cooling time increases, and after reaching a maximum, the temperature difference gradually decreases. In Figure 11, when the plate thickness t of coil C is 12 mm, the cooling time until the aforementioned temperature difference reaches a maximum is 1.5 seconds, and when the plate thickness t of coil C is 25 mm, the cooling time until the aforementioned temperature difference reaches a maximum is 5.5 seconds. In the graph of Figure 11, when the heat transfer coefficient is 20,000 kcal (m 2 .hr·℃) -1 The data shown is for the time.

[0044] The time until the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of coil C reaches a maximum (maximum temperature difference) increases as the plate thickness t of coil C increases, as shown in Figures 11 and 12. Also, the time until the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of coil C reaches a maximum (maximum temperature difference) decreases as the heat transfer coefficient h increases, as shown in Figure 13. In the graph of Figure 12, when the heat transfer coefficient is 6000 kcal (m 2 .hr·℃) -1 , 10,000kcal(m 2 .hr·℃) -1 , 20,000kcal(m 2 .hr·℃) -1 13 shows data when the thickness t of the coil C is 10 mm, 15 mm, 20 mm, and 25.4 mm.

[0045] The time until the temperature difference between the outer surface and the inner surface of the outermost plate of coil C reaches its maximum (maximum temperature difference), derived from the graphs shown in Figures 12 and 13, is expressed by the following equation (7), which is proportional to the power of the plate thickness t and inversely proportional to the power of the heat transfer coefficient h. Therefore, the maximum temperature difference cooling time calculation unit 12ce calculates the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C over the arc length Lc of the cooling range becomes maximum based on the following equation (7).

[0046]

number

[0047] where τ is the cooling time (sec) at which the temperature difference between the outer and inner surfaces of the outermost sheet of coil C over the arc length Lc of the cooling range becomes maximum, t is the thickness (mm) of coil C (hot-rolled steel sheet S), and h is the heat transfer coefficient (kcal (m 2 .hr·℃) -1 The information on the thickness t of the coil C (hot-rolled steel sheet S) is acquired by the maximum temperature difference cooling time calculation unit 12ce from the host computer 15.

[0048] Next, the total coil cooling time calculation unit 12d of the spray control unit 12 shown in FIG. 2 calculates the total coil cooling time T when cooling water is sprayed from the nozzles 4a and 4b to cool the outer periphery of the coil C for one revolution based on the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C over the arc length Lc of the cooling range calculated by the cooling time calculation unit 12c, the arc length Lc of the cooling range, and the outer diameter D of the coil C. total The information on the outer diameter D of the coil C is acquired by the coil total cooling time calculation unit 12d from the host computer 15. The rotation speed ω of the mandrel 2 can be calculated by the following equation (8).

[0049]

number

[0050] Here, ω is the rotation speed (rpm) of the mandrel 2, Lc is the arc length (mm) of the cooling range in coil C, τ is the cooling time (sec) at which the temperature difference between the outer surface and inner surface of the outermost plate of coil C over the arc length Lc of the cooling range becomes maximum, and D is the outer diameter (mm) of coil C. The total cooling time T of the coil when cooling the outer periphery of the coil C by injecting cooling water from the nozzles 4a and 4b is total can be calculated using the following equation (9): T total =1 / ω (9)

[0051] where T totalis the total coil cooling time (min) when cooling water is sprayed from the nozzles 4a and 4b to cool the outer periphery of the coil C for one revolution, and ω is the rotation speed (rpm) of the mandrel 2. Here, since multiple nozzles (two nozzles, nozzle 4a and nozzle 4b in this embodiment) are installed along the outer periphery of coil C, assuming that cooling water is sprayed from each of the multiple nozzles 4a, 4b onto the outer periphery of coil C, the processing is performed for each of the multiple nozzles 4a, 4b in the cooling time calculation unit 12c and the total coil cooling time calculation unit 12d described above.

[0052] Then, in the coil total cooling time calculation unit 12d, for each of the plurality of nozzles 4a, 4b, the rotation speed ω of the mandrel 2 and the coil total cooling time T when cooling the outer periphery of the coil C for one revolution are calculated. total and calculate. In addition, the spray nozzle pattern selection unit 12e of the spray control unit 12 shown in Figure 2 selects the spray nozzle from which to spray the cooling water (only nozzle 4a, only nozzle 4b, or both nozzle 4a and nozzle 4b), the rotation speed ω of the mandrel 2 (ω2, ω1, or the faster of ω2 and ω1), and the rotation angle of the mandrel 2 (360°, 360°, or θ1), as shown in Figure 14.

[0053] The ejection nozzle pattern selection unit 12e will now be described in detail. The injection nozzle pattern selection unit 12e selects the total coil cooling time T total Compare the shortest time among the above with the time in case B below. And the total coil cooling time in case A below is T total If the shortest time among the plurality of nozzles 4a and 4b is shorter than the time in case B below, the jet nozzle pattern selection unit 12e selects one of the plurality of nozzles 4a and 4b as the jet nozzle for jetting cooling water, the jet nozzle pattern selection unit 12e selecting the nozzle that is the shortest among the plurality of nozzles 4a and 4b for jetting cooling water, the jet nozzle pattern selection unit 12e selecting the nozzle that is the shortest among the plurality of nozzles 4 totalThe injection nozzle pattern selection unit 12e selects the nozzle with the shortest length (only nozzle 4a or only nozzle 4b). Furthermore, the injection nozzle pattern selection unit 12e selects the rotation speed (ω2 or ω1) of the mandrel 2 for the selected nozzle (only nozzle 4a or only nozzle 4b) as the rotation speed ω of the mandrel 2. Furthermore, the injection nozzle pattern selection unit 12e selects the rotation angle of the mandrel for one revolution of the coil C (360° or 360°) for the selected nozzle (only nozzle 4a or only nozzle 4b).

[0054] On the other hand, the time in case B below is the total coil cooling time T total If the cooling time is shorter than the shortest time among the above, the injection nozzle pattern selection unit 12e selects all of the multiple nozzles 4a, 4b as injection nozzles for injecting cooling water. Furthermore, the injection nozzle pattern selection unit 12e selects, as the rotation speed of the mandrel 2, the rotation speed ω2 of the mandrel 2 for any one nozzle 4a and the rotation speed ω1 of the mandrel 2 for the adjacent nozzle 4b, whichever is faster (ω2 or ω1). Furthermore, the injection nozzle pattern selection unit 12e selects, as the rotation angle of the mandrel 2, the rotation angle (θ1) from point a in the cooling range on the outer periphery of the coil C by any one nozzle 4a to point b in the cooling range on the outer periphery of the coil C by the adjacent nozzle 4b.

[0055] A: The total coil cooling time T calculated by the total coil cooling time calculation unit 12d when cooling the outer periphery of the coil C for each of the plurality of nozzles 4a and 4b for one revolution. total B: Imagine one of the nozzles 4a, 4b with the largest rotation angle θ1 from point a in the cooling range on the outer periphery of the coil C by one of the nozzles 4a to point b in the cooling range on the outer periphery of the coil C by the adjacent nozzle 4b that is adjacent to that nozzle 4a in the rotation direction of the mandrel 2. Then, the time when the mandrel is rotated by the rotation angle θ1 from point a in the cooling range by one of the nozzles 4a to point b in the cooling range by the adjacent nozzle 4b at the rotation speed (ω2 or ω1) of the mandrel 2 that is faster between the rotation speed ω1 of the mandrel 2 for one of the nozzles 4a and the rotation speed ω2 of the mandrel 2 for the adjacent nozzle 4b

[0056] In addition, when only one nozzle is installed, specifically, for example, when only nozzle 4a is installed on the outer periphery of coil C, processing is performed in cooling time calculation unit 12c and total coil cooling time calculation unit 12d for nozzle 4a, assuming that cooling water is sprayed from nozzle 4a onto the outer periphery of coil C. Then, in the coil total cooling time calculation unit 12d, the rotation speed ω2 of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C for one revolution are calculated for the nozzle 4a. total and calculate. Then, the jet nozzle pattern selection unit 12e selects the nozzle 4a as the jet nozzle for jetting cooling water, the rotation speed ω2 of the mandrel 2, and the rotation angle of the mandrel 2 as 360°.

[0057] 2 controls the rotation of the mandrel 2 and the spray from the spray nozzle based on the spray nozzle (only nozzle 4a, only nozzle 4b, or both nozzles 4a and 4b) that sprays cooling water, the rotation speed ω of the mandrel 2 (ω2, ω1, or ω2 and ω1, whichever is faster), and the rotation angle (360°, 360°, or θ1) of the mandrel 2 selected by the spray nozzle pattern selection unit 12e. A control signal from the drive control unit 12f is sent to a drive device for the mandrel 2 and an injector of the spray nozzle (not shown), and these drive device for the mandrel 2 and the injector of the spray nozzle control the rotation of the mandrel 2 and the spray from the spray nozzle (the flow rate is Q as described above) based on the control signal from the drive control unit 12f.

[0058] In addition, the control signal from the drive control unit 12f is also sent to the drive devices of the wrapper rolls 3a to 3d, and the drive devices of the wrapper rolls 3a to 3d control the rotation of the wrapper rolls 3a to 3d to synchronize with the rotation of the mandrel 2 based on the control signal from the drive control unit 12f. The time for spraying cooling water from the nozzles 4a and 4b by the spray control unit 12 is the total coil cooling time T total This is the shortest time when compared with the time in case B.

[0059] 7(c), after the spray control unit 12 has finished controlling the spraying of cooling water from the nozzles 4a and 4b, the air-cooling control unit 13 of the winding control device 10 shown in FIG. 1 rotates the mandrel 2 and the wrapper rolls 3a to 3d for a preset time to air-cool the coil C. The air-cooling control unit 13 is also connected to the host computer 15. After the air-cooling control of the coil C by the air-cooling control unit 13 has finished, the tail end stop control unit 14 of the winding control device 10 controls the rotation of the mandrel 2 and the wrapper rolls 3a to 3d so as to stop the tail end Sa of the coil C at the designated tail end position P, as shown in Figure 7(d). Then, the tail end stop control unit 14 controls the wrapper rolls 3a to 3d to be released after the cradle rolls 7a, 7b support the underside of the coil C. The tail end stop control unit 14 is also connected to the host computer 15.

[0060] Thereafter, when the coil C is to be removed from the mandrel 2, the mandrel 2 contracts in diameter as shown in FIG. 7(d), and the coil C can be removed from the mandrel 2. Here, according to the hot-rolled steel sheet winding device 1 according to this embodiment, the spray control unit 12 determines the coil installation position (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the thickness t of the coil C (hot-rolled steel sheet S), the positions of the nozzles 4a and 4b (N in FIG. 10), i (x i ,y i )), the orientation of the nozzles 4a, 4b (the tilt angle α from the horizontal state in FIG. 10), the spray angle of the cooling water from the nozzles 4a, 4b (the angle β that defines the spray width of the cooling water in FIG. 10), the cooling width Wc of the coil C by the cooling water from the nozzles 4a, 4b, the flow rate Q of the cooling water from the nozzles 4a, 4b, and the surface temperature T0 of the coil C before cooling when winding the coil, the cooling time calculation unit 12c calculates the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of the coil C over the arc length Lc of the cooling range in the coil C becomes maximum.

[0061] Therefore, when determining the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C becomes maximum, the outer diameter D of the coil C, the plate thickness t, and the positions N of the nozzles 4a and 4b for injecting the cooling water are determined. i (x i ,y i ), direction α, cooling water flow rate Q, etc., can be accurately determined for each coil C, thereby providing a hot-rolled steel sheet winding device 1 that can accurately reduce springback at the outermost periphery of the coil C. Because the effect of reducing springback in the outermost portion of the coil C can be achieved with high precision, when the coil C is removed from the mandrel 2, the springback of the outermost portion C1 of the coil C causes the coil C to lift up, which can prevent the coil C from coming into contact with the reduced diameter mandrel 102. Furthermore, since the springback of the outermost portion C1 of the coil C is reduced after the hot-rolled steel sheet S is wound, it is possible to avoid the risk of tearing off the restraining band that restrains the outer periphery of the coil C during transport.

[0062] Furthermore, according to the hot-rolled steel sheet winding device 1 of this embodiment, the cooling time calculation unit 12c calculates the cooling time by calculating the coil installation position CP(x0, y0), the outer diameter D of the coil C, the sheet thickness t of the coil C, the positions N of the nozzles 4a and 4b, i (x i ,y i 10), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), and the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that defines the spray width of the cooling water in FIG. 10). The cooling time calculation unit 12c also includes a flow density calculation unit 12cb that calculates a flow density w based on the arc length Lc of the cooling range calculated by the cooling range arc length calculation unit 12ca, the cooling width Wc of the coil C due to the cooling water from the nozzles 4a and 4b, and the flow rate Q of the cooling water from the nozzles 4a and 4b. The cooling time calculation unit 12c also includes a heat transfer coefficient calculation unit 12cd that calculates a heat transfer coefficient h based on the flow density w calculated by the flow density calculation unit 12cb and the surface temperature T0 of the coil C before cooling during coil winding. Furthermore, the cooling time calculation unit 12c is equipped with a maximum temperature difference cooling time calculation unit 12ce that calculates the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of the coil C over the arc length Lc of the cooling range becomes maximum based on the heat transfer coefficient h calculated by the heat transfer coefficient calculation unit 12cd and the plate thickness t of the coil C. This allows the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C becomes maximum to be determined with higher accuracy.

[0063] Furthermore, according to the hot-rolled steel sheet winding device 1 of this embodiment, the spray control unit 12 calculates the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of the coil C over the arc length Lc of the cooling range is maximized, based on the arc length Lc of the cooling range and the outer diameter D of the coil C, and calculates the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling water is sprayed from the nozzles 4 a and 4 b to cool the outer peripheral portion of the coil C over one revolution. total The coil total cooling time calculation unit 12d calculates the total coil cooling time. As a result, the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C by spraying cooling water from the nozzles 4a and 4b are total It is possible to calculate with high accuracy.

[0064] Furthermore, according to the hot-rolled steel sheet winding device 1 of this embodiment, a plurality of nozzles 4a, 4b are installed along the outer periphery of the coil C. Then, assuming that cooling water is sprayed from each of the plurality of nozzles 4a, 4b onto the outer periphery of the coil, the cooling time calculation unit 12c and the total coil cooling time calculation unit 12d perform processing for each of the plurality of nozzles 4a, 4b, and the total coil cooling time calculation unit 12d calculates, for each of the plurality of nozzles 4a, 4b, the rotation speed ω of the mandrel 2 and the total coil cooling time T when the outer periphery of the coil C is cooled for one revolution. total and calculate. As a result, for each of the plurality of nozzles 4a and 4b, the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C for one revolution by injecting cooling water from the nozzles 4a and 4b are total It is possible to calculate with high accuracy.

[0065] Furthermore, according to the hot-rolled steel sheet winding device 1 of this embodiment, the spray control unit 12 is equipped with a spray nozzle pattern selection unit 12e that selects the spray nozzle (only nozzle 4a, only nozzle 4b, or both nozzle 4a and nozzle 4b) from which to spray cooling water when spraying cooling water, the rotation speed ω of the mandrel 2 (ω2, ω1, or the faster of ω2 and ω1), and the rotation angle of the mandrel 2 (360°, 360°, or θ1).

[0066] The injection nozzle pattern selection unit 12e then selects the total coil cooling time T total The shortest time among these is compared with the time in case B described above. And the total coil cooling time in case A mentioned above is T total If the shortest time among the plurality of nozzles 4a and 4b is shorter than the time in the case of B, the jet nozzle pattern selection unit 12e selects the nozzle that is the shortest among the plurality of nozzles 4a and 4b for jetting the cooling water, ... pattern selection unit 12e selects the nozzle that is the shortest among the plurality of nozzles 4a and 4b for total The injection nozzle pattern selection unit 12e selects the nozzle with the shortest length (only nozzle 4a or only nozzle 4b). Furthermore, the injection nozzle pattern selection unit 12e selects the rotation speed (ω2 or ω1) of the mandrel 2 for the selected nozzle (only nozzle 4a or only nozzle 4b) as the rotation speed ω of the mandrel 2. Furthermore, the injection nozzle pattern selection unit 12e selects the rotation angle (360° or 360°) of the mandrel 2 for one revolution of the coil C for the selected nozzle (only nozzle 4a or only nozzle 4b) as the rotation angle of the mandrel 2.

[0067] On the other hand, the time in case B is the total coil cooling time T total If the cooling time is shorter than the shortest time among the above, the injection nozzle pattern selection unit 12e selects all of the multiple nozzles 4a, 4b as injection nozzles for injecting cooling water. Furthermore, the injection nozzle pattern selection unit 12e selects, as the rotation speed of the mandrel 2, the rotation speed ω2 of the mandrel 2 for any one nozzle 4a and the rotation speed ω1 of the mandrel 2 for the adjacent nozzle 4b, whichever is faster (ω2 or ω1). Furthermore, the injection nozzle pattern selection unit 12e selects, as the rotation angle of the mandrel 2, the rotation angle (θ1) from point a in the cooling range on the outer periphery of the coil C by any one nozzle 4a to point b in the cooling range on the outer periphery of the coil C by the adjacent nozzle 4b.

[0068] As a result, when multiple nozzles 4a, 4b are installed, the nozzle that sprays the cooling water (only nozzle 4a, only nozzle 4b, or both nozzles 4a and 4b), the rotation speed ω of the mandrel 2 (ω2, ω1, or the faster of ω2 and ω1), and the rotation angle of the mandrel 2 (360°, 360°, or θ1) can be selected to shorten the cooling time, thereby shortening the cooling time of the coil.

[0069] Next, the processing flow in the winding control device 10 will be described with reference to Figs. 4 to 6. Fig. 4 is a flowchart showing the processing flow in the winding control device 10. Fig. 5 is a flowchart showing details of the processing flow in step S2 (spray control step) in the flowchart showing the processing flow in the winding control device shown in Fig. 4. Fig. 6 is a flowchart showing details of the processing flow in step S23 (cooling time calculation step) in the flowchart showing the processing flow in step S2 (spray control step) shown in Fig. 5.

[0070] First, in step S1, when the tail end portion Sa of the hot-rolled steel sheet S passes through the pinch rolls 5a, 5b, the wrapper roll control unit 11 of the winding control device 10 controls the movement of the multiple wrapper rolls 3a to 3d so as to press the wrapper rolls 3a to 3d against the coil C, as shown in Figure 7(a) (wrapper roll control step). Next, in step S2, after the multiple wrapper rolls 3a to 3d are pressed against the coil C in step S1 (wrapper roll control step), the spray control unit 12 of the winding control device 10 controls the rotation of the mandrel 2 and the spraying of cooling water from the nozzles 4a, 4b so that cooling water is sprayed from the nozzles 4a, 4b onto the outer plate of the coil C while rotating the mandrel 2, as shown in Figure 7(b) (spray control step).

[0071] Details of this step S2 (spray control step) will be described with reference to FIG. First, in step S21, the material information acquisition unit 12a of the spray control unit 12 acquires information about the coil C, such as the outer diameter D of the coil C, the thickness t of the coil C, the width of the coil C, and the unit weight P of the coil C. W , yield stress σ of coil C (hot-rolled steel sheet S) y In addition, information on the Young's modulus E of coil C (hot-rolled steel sheet S), the radius of curvature ρ of the outermost sheet in coil C, and the second moment of area I of the outermost sheet in coil C is obtained from the host computer 15 (material information acquisition step).

[0072] Next, in step S22, the cooling necessity determining unit 12b determines whether or not it is necessary to spray cooling water onto the outer periphery of the coil C to cool it, based on the information about the coil C acquired in step S21 (cooling necessity determining step). The cooling necessity determining unit 12b determines whether the plastic bending moment M of the outermost plate of the coil C is equal to the coil weight moment (=P W The coil extraction feasibility judgment is based on whether the plastic bending moment M of the outermost plate of coil C is less than the band securing moment (= σ·bt·w·g·D·N) using the band securing feasibility judgment formula (2) described above.

[0073] If the plastic bending moment M of the outermost plate of the coil C does not satisfy at least one of the formulas (1) and (2), it is determined that it is necessary to spray cooling water onto the outer periphery of the coil C for cooling, and the process proceeds to step S23. On the other hand, if the plastic bending moment M satisfies both the formulas (1) and (2), it is determined that it is not necessary to spray cooling water onto the outer periphery of the coil C for cooling, and the process in step S2 (spray control step) ends.

[0074] Next, in step S23, the cooling time calculation unit 12c calculates the installation position of the coil (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the thickness t of the coil C (hot-rolled steel sheet S), the positions of the nozzles 4a and 4b (N in FIG. 10), i (x i,y i )), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that determines the spray width of the cooling water in FIG. 10), the cooling width Wc of the coil C by the cooling water from the nozzles 4a and 4b, the flow rate Q of the cooling water from the nozzles 4a and 4b, and the surface temperature T0 of the coil C before cooling when winding the coil, a cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of the coil C over the arc length Lc of the cooling range in the coil C becomes maximum is calculated (cooling time calculation step).

[0075] The details of the processing flow in step S23 will be described with reference to FIG. First, in step S231, the cooling range arc length calculation unit 12ca of the cooling time calculation unit 12c calculates the coil installation position (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the positions of the nozzles 4a and 4b (N in FIG. 10), i (x i ,y i )), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), and the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that defines the spray width of the cooling water in FIG. 10), the arc length Lc of the cooling range in the coil C is calculated in the above-mentioned (4) (cooling range arc length calculation step).

[0076] Next, in step S232, the flow density calculation unit 12cb calculates the flow density w using the aforementioned equation (5) based on the arc length Lc of the cooling range calculated in step S231, the cooling width Wc in the coil C by the cooling water from the nozzles 4a and 4b, and the flow rate Q of the cooling water from the nozzles 4a and 4b (flow density calculation step). Next, in step S233, the heat transfer coefficient calculation unit 12cd calculates the heat transfer coefficient h using the aforementioned equation (6) based on the flow rate density w calculated in step S232 and the surface temperature T0 of the coil C before cooling during coil winding (heat transfer coefficient calculation step).

[0077] Next, in step S234, the maximum temperature difference cooling time calculation unit 12ce calculates the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of coil C over the arc length Lc of the cooling range is maximized using the aforementioned equation (7) based on the heat transfer coefficient h calculated by the heat transfer coefficient calculation unit 12cd and the plate thickness t of coil C (maximum temperature difference cooling time calculation step). This completes the process in step S23. When the processing in step S23 is completed, the process proceeds to step S24.

[0078] In step S24, the total coil cooling time calculation unit 12d of the spray control unit 12 calculates the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C over the arc length Lc of the cooling range is maximized, based on the arc length Lc of the cooling range and the outer diameter D of the coil C, and calculates the total coil cooling time T when cooling water is sprayed from the nozzles 4a and 4b to cool the outer peripheral portion of the coil C over one revolution. total is calculated (total coil cooling time calculation step).

[0079] The rotation speed ω of the mandrel 2 can be calculated by the above-mentioned equation (8). In addition, the total coil cooling time T when cooling the outer periphery of the coil C by injecting cooling water from the nozzles 4a and 4b is total can be calculated using the above-mentioned formula (9). Here, since multiple nozzles (two nozzles, nozzle 4a and nozzle 4b in this embodiment) are installed along the outer periphery of coil C, the aforementioned steps S23 and S24 are performed for each of the multiple nozzles 4a and 4b, assuming that cooling water is sprayed from each of the multiple nozzles 4a and 4b onto the outer periphery of coil C.

[0080] Then, in step S24, the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C for one revolution are calculated for each of the plurality of nozzles 4a and 4b. total and calculate. Next, in step S25, the spray nozzle pattern selection unit 12e of the spray control unit 12 selects the spray nozzle from which to spray the cooling water (only nozzle 4a, only nozzle 4b, or both nozzle 4a and nozzle 4b), the rotation speed ω of the mandrel 2 (ω2, ω1, or the faster of ω2 and ω1), and the rotation angle of the mandrel 2 (360°, 360°, or θ1) (spray nozzle pattern selection step).

[0081] In step S25, the injection nozzle pattern selection unit 12e first selects the total coil cooling time T total The shortest time among these is compared with the time in case B described above. And the total coil cooling time in case A mentioned above is T total If the shortest time among the plurality of nozzles 4a and 4b is shorter than the time in the case of B described above, the jet nozzle pattern selection unit 12e selects the nozzle that is the shortest among the plurality of nozzles 4a and 4b for jetting the cooling water, the nozzle that is the shortest among the plurality of nozzles 4a and 4b for jetting the cooling water, the nozzle pattern selection unit 12e selects ... total The injection nozzle pattern selection unit 12e selects the nozzle with the shortest length (only nozzle 4a or only nozzle 4b). Furthermore, the injection nozzle pattern selection unit 12e selects the rotation speed (ω2 or ω1) of the mandrel 2 for the selected nozzle (only nozzle 4a or only nozzle 4b) as the rotation speed ω of the mandrel 2. Furthermore, the injection nozzle pattern selection unit 12e selects the rotation angle of the mandrel for one revolution of the coil C (360° or 360°) for the selected nozzle (only nozzle 4a or only nozzle 4b).

[0082] On the other hand, the time in case B is the total coil cooling time T totalIf the cooling time is shorter than the shortest time among the above, the injection nozzle pattern selection unit 12e selects all of the multiple nozzles 4a, 4b as injection nozzles for injecting cooling water. Furthermore, the injection nozzle pattern selection unit 12e selects, as the rotation speed of the mandrel 2, the rotation speed ω2 of the mandrel 2 for any one nozzle 4a and the rotation speed ω1 of the mandrel 2 for the adjacent nozzle 4b, whichever is faster (ω2 or ω1). Furthermore, the injection nozzle pattern selection unit 12e selects, as the rotation angle of the mandrel 2, the rotation angle (θ1) from point a in the cooling range on the outer periphery of the coil C by any one nozzle 4a to point b in the cooling range on the outer periphery of the coil C by the adjacent nozzle 4b.

[0083] In addition, when only one nozzle is installed, specifically, for example, when only the nozzle 4a is installed on the outer periphery of the coil C, steps S23 and S24 are performed for the nozzle 4a, assuming that cooling water is sprayed from the nozzle 4a onto the outer periphery of the coil C. Then, in step S24, the total coil cooling time calculation unit 12d calculates, for the nozzle 4a, the rotation speed ω2 of the mandrel 2 and the total coil cooling time T when cooling one revolution of the outer periphery of the coil C. total Then, in step S25, the jet nozzle pattern selection unit 12e selects the nozzle 4a as the jet nozzle for jetting cooling water, the rotation speed ω2 of the mandrel 2, and the rotation angle of the mandrel 2 as 360°.

[0084] Next, in step S26, the drive control unit 12f of the spray control unit 12 controls the rotation of the mandrel 2 and the spray of the spray nozzle (drive control step) based on the spray nozzle (only nozzle 4a, only nozzle 4b, or both nozzle 4a and nozzle 4b) that sprays the cooling water selected in step S25 (spray nozzle pattern selection step), the rotation speed ω of the mandrel 2 (ω2, ω1, or ω2 and ω1, whichever is faster), and the rotation angle of the mandrel 2 (360°, 360°, or θ1).

[0085] The control signal from the drive control unit 12f is sent to the drive device of the mandrel 2 and the injection device of the injection nozzle (not shown), and these drive device of the mandrel 2 and the injection device of the injection nozzle control the rotation of the mandrel 2 and the injection of the injection nozzle (the flow rate is Q as mentioned above) based on the control signal from the drive control unit 12f. In addition, the control signal from the drive control unit 12f is also sent to the drive devices of the wrapper rolls 3a to 3d, and the drive devices of the wrapper rolls 3a to 3d control the rotation of the wrapper rolls 3a to 3d to synchronize with the rotation of the mandrel 2 based on the control signal from the drive control unit 12f.

[0086] The time for spraying cooling water from the nozzles 4a and 4b by the spray control unit 12 is the total coil cooling time T total This is the shortest time when compared with the time in case B. This completes the process in step S2, and the process proceeds to the next step S3. In step S3, after the processing in step S2 is completed, the air-cooling control unit 13 of the winding control device 10 rotates the mandrel 2 and wrapper rolls 3a to 3d for a preset time as shown in Figure 7(c) to air-cool the coil C (air-cooling control step).

[0087] Finally, in step S4, after the processing in step S3 is completed, the tail end stop control unit 14 of the winding control device 10 controls the rotation of the mandrel 2 and the wrapper rolls 3a to 3d so as to stop the tail end portion Sa of the coil C at the designated tail end position P, as shown in Figure 7(d) (tail end stop control step). Then, in step S24, the tail end stop control unit 14 controls the cradle rolls 7a and 7b to support the lower side of the coil C, and then releases the wrapper rolls 3a to 3d. Thereafter, when the coil C is to be removed from the mandrel 2, the mandrel 2 contracts in diameter as shown in FIG. 7(d), and the coil C can be removed from the mandrel 2.

[0088] As described above, according to the method for winding a hot-rolled steel sheet according to this embodiment, the spray control step (step S2) is carried out based on the coil installation position (coil center position CP(x0, y0) in FIG. 10), the outer diameter D of the coil C, the thickness t of the coil C (hot-rolled steel sheet S), the positions of the nozzles 4a and 4b (N in FIG. 10), i (x i ,y i )), the orientation of the nozzles 4a, 4b (the tilt angle α from the horizontal state in FIG. 10), the spray angle of the cooling water from the nozzles 4a, 4b (the angle β that defines the spray width of the cooling water in FIG. 10), the cooling width Wc of the coil C by the cooling water from the nozzles 4a, 4b, the flow rate Q of the cooling water from the nozzles 4a, 4b, and the surface temperature T0 of the coil C before cooling when winding the coil, the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of the coil C over the arc length Lc of the cooling range in the coil C becomes maximum.

[0089] Therefore, when determining the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C becomes maximum, the outer diameter D of the coil C, the plate thickness t, and the positions N of the nozzles 4a and 4b for injecting the cooling water are determined. i (x i ,y i ), direction α, cooling water flow rate Q, etc., can be accurately determined for each coil C, thereby providing a coiling method for hot-rolled steel sheet that can accurately reduce springback at the outermost periphery of the coil C. Because the effect of reducing springback in the outermost portion of the coil C can be achieved with high precision, when the coil C is removed from the mandrel 2, the springback of the outermost portion C1 of the coil C causes the coil C to lift up, which can prevent the coil C from coming into contact with the reduced diameter mandrel 102. Furthermore, since the springback of the outermost portion C1 of the coil C is reduced after the hot-rolled steel sheet S is wound, it is possible to avoid the risk of tearing off the restraining band that restrains the outer periphery of the coil C during transport.

[0090] According to the coiling method for a hot-rolled steel sheet according to this embodiment, the cooling time calculation step (step S23) is carried out based on the coil installation position CP (x0, y0), the outer diameter D of the coil C, the sheet thickness t of the coil C, the positions N of the nozzles 4a and 4b, i (x i ,y i 10), the orientation of the nozzles 4a and 4b (the tilt angle α from the horizontal state in FIG. 10), and the spray angle of the cooling water from the nozzles 4a and 4b (the angle β that defines the spray width of the cooling water in FIG. 10). The cooling time calculation step (step S23) also includes a flow density calculation step (step S232) that calculates a flow density w based on the arc length Lc of the cooling range calculated in the cooling range arc length calculation step (step S231), the cooling width Wc of the coil C due to the cooling water from the nozzles 4a and 4b, and the flow rate Q of the cooling water from the nozzles 4a and 4b. The cooling time calculation step (step S23) also includes a heat transfer coefficient calculation step (step S233) that calculates a heat transfer coefficient h based on the flow density w calculated in the flow density calculation step (step S232) and the surface temperature T0 of the coil C before cooling during coil winding. Furthermore, the cooling time calculation step (step S23) includes a maximum temperature difference cooling time calculation step (step S234) that calculates the cooling time τ at which the temperature difference between the outer surface and the inner surface of the outermost plate of coil C over the arc length Lc of the cooling range is maximized based on the heat transfer coefficient h calculated in the heat transfer coefficient calculation step (step S233) and the plate thickness t of coil C. This allows the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil C becomes maximum to be determined with higher accuracy.

[0091] Furthermore, according to the coiling method of the hot-rolled steel sheet according to this embodiment, the spray control step (step S2) calculates the cooling time τ at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of the coil C over the arc length Lc of the cooling range becomes maximum, based on the arc length Lc of the cooling range and the outer diameter D of the coil C, and the rotation speed ω of the mandrel 2, and the total coil cooling time T when cooling water is sprayed from the nozzles 4a and 4b to cool the outer peripheral portion of the coil C over one revolution. total The method includes a coil total cooling time calculation step (step S24) for calculating the total coil cooling time. As a result, the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C by spraying cooling water from the nozzles 4a and 4b are total It is possible to calculate with high accuracy.

[0092] Furthermore, according to the coiling method for a hot-rolled steel sheet according to this embodiment, a plurality of nozzles 4a, 4b are installed along the outer periphery of the coil C. Then, assuming that cooling water is sprayed from each of the plurality of nozzles 4a, 4b onto the outer periphery of the coil, a cooling time calculation step (step S23) and a total coil cooling time calculation step (step S24) are performed for each of the plurality of nozzles 4a, 4b, and in the total coil cooling time calculation step (step S24), the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C for one revolution are calculated for each of the plurality of nozzles 4a, 4b. total and calculate. As a result, for each of the plurality of nozzles 4a and 4b, the rotation speed ω of the mandrel 2 and the total coil cooling time T when cooling the outer periphery of the coil C for one revolution by injecting cooling water from the nozzles 4a and 4b are total It is possible to calculate with high accuracy.

[0093] Furthermore, according to the method for winding hot-rolled steel sheet of this embodiment, the spray control step (step S2) includes a spray nozzle pattern selection step (step S25) for selecting the spray nozzle (only nozzle 4a, only nozzle 4b, or both nozzle 4a and nozzle 4b) for spraying cooling water, the rotation speed ω of the mandrel 2 (ω2, ω1, or ω2 and ω1, whichever is faster), and the rotation angle of the mandrel 2 (360°, 360°, or θ1).

[0094] Then, in the injection nozzle pattern selection step (step S25), the injection nozzle pattern selection unit 12e selects the total coil cooling time T total The shortest time among these is compared with the time in case B described above. And the total coil cooling time in case A mentioned above is T total If the shortest time among the plurality of nozzles 4a and 4b is shorter than the time in the case of B, the jet nozzle pattern selection unit 12e selects the nozzle that is the shortest among the plurality of nozzles 4a and 4b for jetting the cooling water, ... pattern selection unit 12e selects the nozzle that is the shortest among the plurality of nozzles 4a and 4b for total The shortest nozzle (only nozzle 4a or only nozzle 4b) is selected, and the rotation speed ω of the mandrel 2 (ω2 or ω1) for the selected nozzle (only nozzle 4a or only nozzle 4b) is selected as the rotation speed ω of the mandrel 2, and the rotation angle of the mandrel 2 for one revolution of the coil C (360° or 360°) for the selected nozzle (only nozzle 4a or only nozzle 4b) is selected as the rotation angle of the mandrel 2.

[0095] On the other hand, the time in case B is the total coil cooling time T totalIf the time is shorter than the shortest time among the above, the injection nozzle pattern selection unit 12e selects all of the multiple nozzles 4a, 4b as the injection nozzles for injecting cooling water, and selects, as the rotation speed of the mandrel 2, the rotation speed (ω2 or ω1) of the mandrel 2 that is faster between the rotation speed ω2 of the mandrel 2 for any one of the nozzles 4a and the rotation speed ω1 of the mandrel 2 for the adjacent nozzle 4b, and selects, as the rotation angle of the mandrel 2, the rotation angle (θ1) from point a in the cooling range on the outer periphery of the coil C by any one of the nozzles 4a to point b in the cooling range on the outer periphery of the coil C by the adjacent nozzle 4b.

[0096] As a result, when multiple nozzles 4a, 4b are installed, the nozzle that sprays the cooling water (only nozzle 4a, only nozzle 4b, or both nozzles 4a and 4b), the rotation speed ω of the mandrel 2 (ω2, ω1, or the faster of ω2 and ω1), and the rotation angle of the mandrel 2 (360°, 360°, or θ1) can be selected to shorten the cooling time, thereby shortening the cooling time of the coil.

[0097] Using this method for winding a hot-rolled steel sheet, a hot-rolled steel sheet can be manufactured by providing a winding step in which the hot-rolled steel sheet S is wound into a coil by a winding device 1. That is, by using the method for winding a hot-rolled steel sheet and the winding device for a hot-rolled steel sheet according to the present invention, the effect of reducing springback in the outermost portion C1 of the coil C can be achieved with high precision, and a manufacturing method can be provided that can solve the problems of impaired manufacturability and equipment damage caused by increased springback in the outermost portion C1 of the coil C even during the manufacturing of the hot-rolled steel sheet S.

[0098] Although the embodiment of the present invention has been described above, the present invention is not limited to this and various modifications and improvements can be made. For example, the number of nozzles 4a and 4b is not limited to two, but may be one, or three or more. Furthermore, the air-cooling control by the air-cooling control unit 13 does not necessarily have to be performed. [Explanation of symbols]

[0099] 1. Hot-rolled steel sheet winding equipment 2 mandrels 3a, 3b, 3c, 3d Wrapper Roll 4a, 4b nozzle 5a, 5b Pinch roll 6 thermometer 7a, 7b Cradle Roll 10 Winding control device 11 Wrapper roll control section 12 Spray control unit 13 Air cooling control section 14 Tail end stop control unit 15 Upper computer C coil S hot rolled steel plate Sa caudal end

Claims

1. A method for winding a hot-rolled steel sheet, in which the hot-rolled steel sheet is wound into a coil from its leading end to its trailing end on a mandrel of a winding device, and then a plurality of wrapper rolls arranged in a planetary pattern relative to the coil are pressed against the coil while the mandrel is rotated, and cooling water is sprayed from a nozzle onto the outer plate of the coil, thereby cooling the outer periphery of the coil for a predetermined cooling time, wherein the predetermined cooling time for the outer periphery of the coil is set equal to the time when the temperature difference between the outer surface and the inner surface of the outermost plate of the coil becomes maximum. a spray control step of controlling the rotation of the mandrel and the spraying of cooling water from the nozzles so that cooling water is sprayed from the nozzles onto the outer peripheral plate of the coil while rotating the mandrel; the spray control step includes a cooling time calculation step of calculating a cooling time at which a temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil over an arc length of a cooling range in the coil becomes maximum, based on the installation position of the coil, the outer diameter of the coil, the plate thickness of the coil, the position of the nozzle, the orientation of the nozzle, the spray angle of the cooling water from the nozzle, the cooling width in the coil by the cooling water from the nozzle, the flow rate of the cooling water from the nozzle, and the surface temperature of the coil before cooling when winding the coil, the cooling time calculation step includes: a cooling range arc length calculation step of calculating an arc length of a cooling range in the coil based on an installation position of the coil, an outer diameter of the coil, a position of the nozzle, an orientation of the nozzle, and an angle of spray of cooling water from the nozzle; a flow rate density calculation step of calculating a flow rate density based on the arc length of the cooling range calculated in the cooling range arc length calculation step, a cooling width in the coil by the cooling water from the nozzle, and a flow rate of the cooling water from the nozzle; a heat transfer coefficient calculation step of calculating a heat transfer coefficient based on the flow rate density calculated in the flow rate density calculation step and a surface temperature of the coil before cooling at the time of coiling; and a maximum temperature difference cooling time calculation step of calculating a cooling time at which a temperature difference between an outer peripheral surface and an inner peripheral surface of an outermost sheet of the coil corresponding to the arc length of the cooling range is maximum based on the heat transfer coefficient calculated in the heat transfer coefficient calculation step and a thickness of the coil.

2. 2. The coiling method for a hot-rolled steel sheet according to claim 1, wherein the spray control step includes a total coil cooling time calculation step of calculating a rotational speed of the mandrel and a total coil cooling time when cooling water is sprayed from the nozzles to cool one revolution of the outer periphery of the coil, based on the cooling time calculated in the cooling time calculation step at which a temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of the coil over the arc length of the cooling range becomes maximum, the arc length of the cooling range, and the outer diameter of the coil.

3. A plurality of the nozzles are installed along the outer periphery of the coil, 3. The coiling method for a hot-rolled steel sheet according to claim 2, characterized in that the cooling time calculation step and the total coil cooling time calculation step are performed for each of the plurality of nozzles, assuming that cooling water is sprayed from each of the plurality of nozzles onto the outer periphery of the coil, and in the total coil cooling time calculation step, the rotation speed of the mandrel and the total coil cooling time required to cool the outer periphery of the coil for one revolution are calculated for each of the plurality of nozzles.

4. the spray control step includes a spray nozzle pattern selection step of selecting a spray nozzle for spraying cooling water, a rotation speed of the mandrel, and a rotation angle of the mandrel when spraying cooling water; In the injection nozzle pattern selection step, the shortest time among the total coil cooling times in the case of A below is compared with the time in the case of B below, and if the shortest time among the total coil cooling times in the case of A below is shorter than the time in the case of B below, a nozzle having the shortest total coil cooling time is selected from among the plurality of nozzles as an injection nozzle for injecting cooling water, and the mandrel rotation speed for the selected nozzle is selected as the mandrel rotation speed.

4. The coiling method for a hot-rolled steel sheet according to claim 3, characterized in that, as the mandrel rotation angle, a mandrel rotation angle for one circumference of the coil for the selected nozzle is selected, and if the time in case B below is shorter than the shortest of the total coil cooling times in case A below, all of the plurality of nozzles are selected as injection nozzles for injecting cooling water, and as the mandrel rotation speed, the mandrel rotation speed for any one of the nozzles below and the mandrel rotation speed for an adjacent nozzle below, whichever is faster, is selected, and as the mandrel rotation angle, a rotation angle from a point within the cooling range on the outer periphery of the coil by any one of the nozzles below to a point within the cooling range on the outer periphery of the coil by the adjacent nozzle below is selected. A: The total coil cooling time calculated in the total coil cooling time calculation step when cooling one revolution of the outer periphery of the coil for each of the plurality of nozzles. B: Assuming one of the multiple nozzles and the adjacent nozzle that have the largest rotation angle from a point in the cooling range on the coil outer periphery by one of the nozzles to a point in the cooling range on the coil outer periphery by an adjacent nozzle that is adjacent to that nozzle in the mandrel rotation direction, the time required to rotate the mandrel through the rotation angle from a point in the cooling range by one of the nozzles to a point in the cooling range by the adjacent nozzle at the mandrel rotation speed for the one of the nozzles and the mandrel rotation speed for the adjacent nozzle, whichever is faster.

5. A winding device for hot-rolled steel sheet, in which a hot-rolled steel sheet is wound into a coil from its leading end to its trailing end on a mandrel, and then cooling water is sprayed from a nozzle onto the outer peripheral plate of the coil while rotating the mandrel with a plurality of wrapper rolls arranged in a planetary pattern relative to the coil pressed against the coil, thereby cooling the outer peripheral portion of the coil for a predetermined cooling time, wherein the predetermined cooling time for the outer peripheral portion of the coil is set equal to the time when the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost peripheral plate of the coil is maximum. a spray control unit that controls the rotation of the mandrel and the spraying of cooling water from the nozzle so that cooling water is sprayed from the nozzle onto the outer peripheral plate of the coil while rotating the mandrel; the spray control unit includes a cooling time calculation unit that calculates the cooling time at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost plate of the coil over the arc length of the cooling range in the coil becomes maximum, based on the installation position of the coil, the outer diameter of the coil, the plate thickness of the coil, the position of the nozzle, the orientation of the nozzle, the spray angle of the cooling water from the nozzle, the cooling width in the coil by the cooling water from the nozzle, the flow rate of the cooling water from the nozzle, and the surface temperature of the coil before cooling when winding the coil; a flow rate density calculation unit that calculates a flow rate density based on the arc length of the cooling range calculated by the cooling range arc length calculation unit, a cooling width of the coil by the cooling water from the nozzle, and a flow rate of the cooling water from the nozzle; a heat transfer coefficient calculation unit that calculates a heat transfer coefficient based on the flow rate density calculated by the flow rate density calculation unit and a surface temperature of the coil before cooling during coiling; and a maximum temperature difference cooling time calculation unit that calculates a cooling time at which a temperature difference between an outer peripheral surface and an inner peripheral surface of an outermost sheet of the coil corresponding to the arc length of the cooling range is maximum based on the heat transfer coefficient calculated by the heat transfer coefficient calculation unit and a thickness of the coil.

6. 6. The hot-rolled steel sheet coiling device according to claim 5, wherein the spray control unit includes a coil total cooling time calculation unit that calculates the rotation speed of the mandrel and the total coil cooling time when cooling water is sprayed from the nozzles to cool the outer peripheral portion of the coil for one revolution, based on the cooling time calculated by the cooling time calculation unit at which the temperature difference between the outer peripheral surface and the inner peripheral surface of the outermost sheet of the coil for the arc length of the cooling range is maximized, the arc length of the cooling range, and the outer diameter of the coil.

7. A plurality of the nozzles are installed along the outer periphery of the coil, 7. The hot-rolled steel sheet coiling device according to claim 6, characterized in that, assuming that cooling water is sprayed from each of the plurality of nozzles onto the outer periphery of the coil, processing is performed in the cooling time calculation unit and the total coil cooling time calculation unit for each of the plurality of nozzles, and the total coil cooling time calculation unit calculates, for each of the plurality of nozzles, the rotation speed of the mandrel and the total coil cooling time required to cool the outer periphery of the coil for one revolution.

8. the spray control unit includes a spray nozzle pattern selection unit that selects a spray nozzle for spraying cooling water, a rotation speed of the mandrel, and a rotation angle of the mandrel when spraying cooling water, The injection nozzle pattern selection unit compares the shortest time among the total coil cooling times in case A below with the time in case B below, and if the shortest time among the total coil cooling times in case A below is shorter than the time in case B below, selects, as the injection nozzle for injecting cooling water, the nozzle having the shortest total coil cooling time from the plurality of nozzles, and selects, as the mandrel rotation speed, the mandrel rotation speed for the selected nozzle, and selects, as the mandrel rotation angle, the mandrel rotation angle for one circumference of the coil for the selected nozzle; if the time in case B below is shorter than the shortest time among the total coil cooling times in case A below, selects all of the plurality of nozzles as injection nozzles for injecting cooling water, and selects, as the mandrel rotation speed, the mandrel rotation speed for any one of the nozzles below and the mandrel rotation speed for an adjacent nozzle below, whichever is faster, and selects, as the mandrel rotation speed, the mandrel rotation speed for the 8. The coiling device for hot-rolled steel strip according to claim 7, characterized in that the rotation angle is selected to a point within the cooling range on the outer periphery. A: The total coil cooling time calculated in the total coil cooling time calculation step when cooling one revolution of the outer periphery of the coil for each of the plurality of nozzles. B: Assuming one of the multiple nozzles and the adjacent nozzle that have the largest rotation angle from a point in the cooling range on the coil outer periphery by one of the nozzles to a point in the cooling range on the coil outer periphery by an adjacent nozzle that is adjacent to that nozzle in the mandrel rotation direction, the time required to rotate the mandrel through the rotation angle from a point in the cooling range by one of the nozzles to a point in the cooling range by the adjacent nozzle at the mandrel rotation speed for the one of the nozzles and the mandrel rotation speed for the adjacent nozzle, whichever is faster.

9. A method for manufacturing a hot-rolled steel sheet, comprising a winding step of winding the hot-rolled steel sheet into a coil shape by a winding device using the method for winding a hot-rolled steel sheet according to any one of claims 1 to 4.

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