Metal strip shape control method, manufacturing method, shape control device, and manufacturing facility

Abstract

To provide a method and a device for controlling the shape of a metallic strip by which the occurrence of defective shape in cold rolling is suppressed even when the material in the width direction of the metallic strip to be subjected to cold rolling is uneven.SOLUTION: A method for controlling the shape of a metal strip according to the present invention is a method for controlling the shape of a metal strip using rolling equipment including a heating device that heats an end portion in a width direction of a metal strip that is continuously conveyed, a rolling mill that rolls the metal strip heated by the heating device, and a shape measurement device that measures the shape of the metal strip rolled by the rolling mill, the method including: a leading end shape specifying step of specifying a shape of a leading end portion of the metal strip rolled by the rolling mill using the shape measurement device; a heating condition setting step of setting a heating condition for the end portion in the width direction of the metal strip by the heating device in accordance with the specified shape of the leading end portion of the metal strip; and a rolling control step of rolling the metal strip heated at the end portion in the width direction by the rolling mill under the set heating condition.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a shape control method for a metal strip, a manufacturing method, a shape control device, and a manufacturing facility. [Background technology]

[0002] In recent years, environmental regulations have led to an increasing need for lighter automobiles, and this has led to an increased demand for high-strength steel sheets. Generally, automotive steel sheets, including high-strength steel sheets, are produced through continuous casting, hot rolling, and cold rolling, followed by an annealing line or a hot-dip galvanizing line that combines the functions of annealing and galvanizing.

[0003] In the hot rolling of high-strength steel sheets, the steel sheets are typically rolled to a predetermined dimension by a finishing mill on a hot rolling line, wound into a coil at a temperature of, for example, 700°C or less, and then cooled in the air while still in the coiled state. In this case, the cooling rate differs between the inner and outer peripheral parts of the coil and between the widthwise ends and the widthwise center of the coil, which can result in the steel sheets being cooled to room temperature having uneven properties in the width and longitudinal directions.

[0004] For example, in a high-strength steel sheet containing approximately 0.5 to 3.5% Mn for the purpose of increasing strength, an upper bainite structure is formed in the widthwise center of the hot-rolled steel sheet (hot-rolled steel sheet), and a lower bainite structure or martensite structure is formed in the widthwise edges, resulting in a difference in the metal structure in the width direction. As a result, the hot-rolled steel sheet may have a harder structure in the widthwise edges than in the widthwise center.

[0005] When a hot-rolled steel sheet having such non-uniform properties is sent to a cold rolling line after undergoing a pickling process, it is likely to have a defective shape during cold rolling. That is, because the deformation resistance of the hot-rolled steel sheet varies in the width direction, the rolling strain imparted by cold rolling is distributed in the width direction, and the shape (flatness) of the steel sheet at the exit of the cold rolling mill deteriorates.

[0006] As a result, in a continuous annealing line that controls the material properties of a steel sheet after cold rolling, poor sheet passing may occur due to poor flatness of the steel sheet. Specifically, the meandering of the steel sheet in the continuous annealing furnace may cause the steel sheet to come into contact with equipment inside the furnace, resulting in scratches and other defects in the steel sheet product. Furthermore, if the line speed of the continuous annealing line is slowed down to prevent the steel sheet from suddenly meandering, the productivity of the steel sheet product will decrease.

[0007] Against this background, Patent Document 1 proposes a solution to the problem that, when a hot-rolled steel sheet containing a relatively large amount of martensite structure at the width direction edges is cold-rolled, cracks are likely to occur at the width direction edges due to low ductility at the width direction edges. Specifically, the method described in Patent Document 1 suppresses cracks at the width direction edges by heating both width direction edges of the hot-rolled steel sheet to a predetermined temperature to soften the structure at the width direction edges of the hot-rolled steel sheet, and then carrying out a pickling process and a cold rolling process.

[0008] Furthermore, Patent Document 2 proposes a method for suppressing fracture of a hot-rolled steel sheet when cold-rolling the hot-rolled steel sheet, whose deformation resistance varies in the longitudinal and width directions. Specifically, the method described in Patent Document 2 measures the width-direction deformation resistance distribution by measuring the width-direction material distribution of the hot-rolled steel sheet on the upstream side of a cold tandem rolling mill, calculates the width-direction temperature distribution for making the measured deformation resistance distribution uniform, and heats the width-direction end portions of the hot-rolled steel sheet to be charged into the first stand so as to achieve the calculated width-direction temperature distribution.

[0009] Furthermore, Patent Document 3 proposes a method for suppressing the occurrence of brittle fracture when cold rolling a silicon steel sheet with a high Si content. Specifically, the method described in Patent Document 3 involves heating the silicon steel sheet using a transverse full-width heating device so that the temperature of the widthwise ends of the silicon steel sheet is higher than the temperature of the widthwise center of the silicon steel sheet at the entry side of a cold rolling mill. Patent Document 3 also describes that the temperatures of the widthwise center and widthwise ends of the silicon steel sheet are calculated according to the Si content. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2019-141888 [Patent Document 2] Patent Publication No. 2021-30239 [Patent Document 3] Japanese Patent Publication No. 2022-170841 [Non-patent literature]

[0011] [Non-Patent Document 1] Noriyuki Tsuchida, Stephanus Haruyo, Takahisa Onuki, Akira Tomoda, "Stress-Strain Curve of Steel Materials", Tetsu-to-Hagané, Vol. 100 (2014), No. 10, pp. 1191-1206 Summary of the Invention [Problem to be solved by the invention]

[0012] The method described in Patent Document 1 involves softening the widthwise edges of a hot-rolled steel sheet by heat treatment before cold rolling. However, the non-uniformity in the material properties of the coil in the widthwise direction after hot rolling is not easily eliminated by a short-term heat treatment. Furthermore, the heat treatment conditions (heating temperature and heating time) for uniforming the deformation resistance of the hot-rolled steel sheet in the widthwise direction vary depending not only on the chemical composition of the hot-rolled steel sheet but also on the manufacturing conditions of the hot-rolled steel sheet in the hot-rolling line. For this reason, a distribution of deformation resistance in the widthwise direction remains in the steel sheet subjected to cold rolling. As a result, the method described in Patent Document 1 makes it difficult to suppress shape defects in the steel sheet during cold rolling.

[0013] The method described in Patent Document 2 calculates the distribution of deformation stress in the width direction of a hot-rolled steel sheet by measuring the grain size, which is a material property index correlated with deformation stress. However, while the deformation stress can be calculated relatively accurately when the structure of the hot-rolled steel sheet is a structure such as a ferrite single-layer structure in which the correlation between deformation stress and grain size is strong, the correlation between deformation stress and grain size is not necessarily strong for high-strength steel sheets used for automotive steel sheets, etc. For this reason, the method described in Patent Document 2 makes it difficult to accurately estimate the distribution of deformation stress in the width direction of the hot-rolled steel sheet. Therefore, even if the width-direction end portions of the steel sheet charged into the first stand are heated based on the estimated deformation stress distribution, it is difficult to suppress shape defects after cold rolling.

[0014] The method described in Patent Document 3 is considered effective in that it provides a temperature distribution in the width direction according to the amounts of the elements contained in the silicon steel sheet, thereby enabling heating according to the distribution of deformation resistance in the width direction of the silicon steel sheet. Here, in the case of silicon steel sheets, a certain degree of correlation between the Si content and deformation resistance has been observed. However, in the case of high-strength steel sheets used for automotive steel sheets, etc., various alloy elements are contained, and the microstructure changes in complex ways depending on the combination of these elements. Therefore, it is difficult to accurately estimate the distribution of deformation resistance in the width direction of the steel sheet based solely on the steel sheet's composition. Therefore, even if the method described in Patent Document 3 estimates the distribution of deformation resistance using the steel sheet's composition and sets the heating conditions in the width direction of the steel sheet based on the estimated results, it is difficult to suppress shape defects after cold rolling.

[0015] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method and apparatus for controlling the shape of a metal strip, which are capable of suppressing the occurrence of shape defects in cold rolling even when the material of the metal strip to be cold rolled is non-uniform in the width direction. Another object of the present invention is to provide a method and equipment for manufacturing a metal strip, which are capable of manufacturing a metal strip controlled to a predetermined shape by cold rolling. [Means for solving the problem]

[0016] The method for controlling the shape of a metal strip according to the present invention is a method for controlling the shape of a metal strip using rolling equipment including a heating device that heats the widthwise ends of a metal strip that is continuously transported, a rolling mill that rolls the metal strip heated by the heating device, and a shape measuring device that measures the shape of the metal strip rolled by the rolling mill, and includes the following steps: a leading edge shape specifying step that specifies the shape of the leading edge of the metal strip rolled by the rolling mill using the shape measuring device; a heating condition setting step that sets heating conditions for the widthwise ends of the metal strip by the heating device in accordance with the specified shape of the leading edge of the metal strip; and a rolling control step that rolls the metal strip, the widthwise ends of which have been heated under the set heating conditions, by the rolling mill.

[0017] The rolling control step may include a step of performing feedback control to set a shape control actuator of the rolling mill in accordance with the shape of the metal strip, the width direction end portions of which have been heated under the set heating conditions, after being rolled by the rolling mill.

[0018] The rolling control step preferably maintains the heating conditions of the heating device set in the heating condition setting step while the metal strip, the width direction end portions of which have been heated under the set heating conditions, is being rolled by the rolling mill.

[0019] In the heating condition setting step, it is preferable to set at least one of the heating temperature and heating range of the widthwise end of the metal strip as the heating conditions in accordance with the shape of the tip of the metal strip identified using the shape measuring device.

[0020] A method for producing a metal strip according to the present invention includes a step of producing a metal strip using the method for controlling the shape of a metal strip according to the present invention.

[0021] The metal strip shape control device of the present invention is a metal strip shape control device used in rolling equipment that includes a heating device that heats the widthwise ends of a continuously transported metal strip, a rolling mill that rolls the metal strip heated by the heating device, and a shape measuring device that measures the shape of the metal strip rolled by the rolling mill, and includes a tip shape specifying unit that specifies the shape of the tip end of the metal strip rolled by the rolling mill, and a heating condition setting unit that sets the heating conditions of the heating device in accordance with the shape of the tip end of the metal strip specified by the tip shape specifying unit.

[0022] The rolling mill may further include a feedback control setting unit that sets a shape control actuator of the rolling mill in accordance with the shape of the metal strip measured by the shape measuring device.

[0023] The metal strip manufacturing equipment of the present invention comprises a heating device that heats the widthwise end portion of a continuously transported metal strip, a rolling mill that rolls the metal strip heated by the heating device, a shape measuring device that measures the shape of the metal strip rolled by the rolling mill, and a shape control device that controls the shape of the metal strip rolled by the rolling mill, wherein the shape control device comprises a tip shape specifying unit that specifies the shape of the tip end of the metal strip rolled by the rolling mill based on the shape of the metal strip measured by the shape measuring device, and a heating condition setting unit that sets the heating conditions of the heating device in accordance with the shape of the tip end of the metal strip specified by the tip shape specifying unit.

[0024] The shape control device may include a feedback control setting unit that sets a shape control actuator of the rolling mill in accordance with the shape of the metal strip measured by the shape measuring device.

[0025] The rolling mill is preferably a cold tandem rolling mill, the heating device is disposed on the inlet side of the cold tandem rolling mill, and the shape measuring device is disposed on the outlet side of the cold tandem rolling mill. [Effects of the Invention]

[0026] According to the metal strip shape control method and shape control device of the present invention, it is possible to suppress the occurrence of shape defects in cold rolling even if the material of the metal strip to be cold rolled is non-uniform in the width direction. Also, according to the metal strip manufacturing method and manufacturing equipment of the present invention, it is possible to manufacture a metal strip that is controlled to a predetermined shape by cold rolling. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a metal strip shape control system that is applied to a metal strip manufacturing facility according to the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of the rolling equipment shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing an example of the configuration of the heating device shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing an example of the configuration of a rolling stand. [Figure 5] FIG. 5 is a flowchart showing the flow of a method for controlling the shape of a metal strip according to one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of the hardness distribution in the width direction of a high-strength steel plate. [Figure 7] FIG. 7 is a diagram showing an example of steepness in the width direction of a high-strength steel sheet after cold rolling. [Figure 8] FIG. 8 is a diagram showing the relationship between Vickers hardness and temperature. [Figure 9] FIG. 9 is a flowchart showing the flow of a modified example of the method for controlling the shape of a metal strip shown in FIG. [Figure 10] FIG. 10 is a diagram showing the steepness in the width direction of the metal strip in the example. [Figure 11] FIG. 11 is a diagram showing the steepness in the width direction of the metal strip in the comparative example. [Figure 12] FIG. 12 is a diagram showing the edge wave steepness and the intermediate elongation steepness in the invention examples and the comparative examples. [Figure 13] FIG. 13 is a diagram showing the steepness in the longitudinal direction of the metal strip in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, a metal strip shape control method, a manufacturing method, a shape control device, and a manufacturing facility according to an embodiment of the present invention will be described with reference to the drawings.

[0029] [Metal Strip Shape Control System] First, with reference to FIGS. 1 and 2, the configuration of a metal strip shape control system applied to a metal strip manufacturing facility according to the present invention will be described.

[0030] 1 is a block diagram showing an example of the configuration of a metal strip shape control system 1 that is applied to a metal strip manufacturing facility according to the present invention. As shown in FIG. 1, the metal strip shape control system 1 includes a rolling facility 10 and a shape control device 20.

[0031] The rolling equipment 10 is equipped with a rolling control controller (PLC) 11 for controlling each device that constitutes the rolling equipment 10, a control computer (process computer) 12 that gives control commands to the rolling control controller 11, and a host computer 13 that gives manufacturing instructions to the rolling equipment 10.

[0032] Various controls such as the thickness of the metal strip, which is the material to be rolled in the rolling equipment 10, are performed by the control computer 12, which sets control target values ​​for each device that constitutes the rolling equipment 10, based on the host computer 13 or production instructions from the host computer 13. The rolling control controller 11 operates each device that constitutes the rolling equipment 10 in accordance with the set control target values. The rolling control controller 11 also has the function of collecting information obtained by various sensors (tracking sensors, thickness gauges, tension meters, etc.) installed in the rolling equipment 10 at a predetermined sampling period and outputting the information to the control computer 12.

[0033] The rolling equipment 10 is equipped with a heating device 14 that heats the widthwise ends (edge ​​portions) of the metal strip. The heating device 14 is arranged upstream of the rolling mill that constitutes the rolling equipment 10 in the transport direction of the metal strip. The heating device 14 heats both widthwise ends of the metal strip before the metal strip is rolled, thereby reducing the deformation resistance of the widthwise ends of the metal strip. This promotes elongation of the widthwise ends of the metal strip during cold rolling by the rolling mill, for metal strips whose widthwise ends have greater deformation resistance than the widthwise center portion, and controls the shape of the metal strip. The device configuration of the heating device 14 will be described later.

[0034] The rolling equipment 10 is equipped with a shape measuring device 15 that measures the shape of the metal strip rolled by the rolling mill. The shape measuring device 15 is a device that measures the widthwise shape of the metal strip rolled by the rolling mill. An example of the shape measuring device 15 is a contact-type shape measuring device using divided rolls, but the shape measuring device 15 is not limited to this. The shape measuring device 15 may be any device that can measure the widthwise tension distribution of the metal strip at the delivery side of the rolling mill in real time, and may be a non-contact shape measuring device such as a vibration-type, magnetic permeability-type, or deflection-type.

[0035] The shape control device 20 includes a control unit 21, an acquisition unit 22, a storage unit 23, and an output unit 24. The shape control device 20 acquires metal strip identification information that specifies the dimensions, steel type, product specifications, etc. of the metal strip from the control computer 12. The shape control device 20 is capable of communicating with the control computer 12 via a network, and may acquire the metal strip identification information via another operation data server. Furthermore, the shape control device 20 outputs control command values ​​calculated by calculations within the shape control device 20 and information regarding the timing of control execution to the rolling control controller 11 or the control computer 12. The rolling control controller 11 or the control computer 12, which has acquired the control commands from the shape control device 20, controls the operation of each device of the rolling equipment 10 in accordance with the control commands from the shape control device 20.

[0036] The shape control device 20 may be realized by, for example, a computer. The computer may include, for example, a memory or a hard disk drive (storage device), a CPU (Central Processing Unit), etc. The program may be stored in the hard disk drive, and may be read from the hard disk drive to the memory when executed by the CPU. Data during processing is stored in memory, and if necessary, stored in the hard disk drive. The storage unit 23 may be realized by, for example, a storage device. The functions of the control unit 21, the acquisition unit 22, and the output unit 24 may be realized by, for example, the CPU reading and executing the program.

[0037] The control unit 21 includes a dynamic setup unit 25 and a feedback control setting unit 26. The control unit 21 may be configured to include at least one processor, such as a CPU or a GPU (Graphics Processing Unit). The dynamic setup unit 25 and the feedback control setting unit 26 may each be configured as separate processors. The dynamic setup unit 25 and the feedback control setting unit 26 may also be configured as a single processor. The processor constituting the control unit 21 may realize the functions of the shape control device 20 by reading and executing a program stored in the storage unit 23.

[0038] The dynamic setup unit 25 is equipped with a tip end shape specifying unit 27 and a heating condition setting unit 28. The tip end shape specifying unit 27 specifies the shape of the tip end of the metal strip rolled by the rolling mill. The tip end of the metal strip is in a range of 10 to 100 m from the tip end of the metal strip in the longitudinal direction. The tip end shape specifying unit 27 specifies shape data measured in a range of 10 to 100 m from the tip end of the metal strip from the shape data of the metal strip acquired via the acquisition unit 22. The tip end shape specifying unit 27 may specify the tip end of the metal strip based on tracking information of the tip end of the metal strip (the joining point with the preceding material) generated by the rolling control controller 11 or the control computer 12, and specify the shape data of the tip end.

[0039] The heating condition setting unit 28 sets the heating conditions for the heating device 14 according to the shape of the leading end of the metal strip identified by the leading end shape specifying unit 27. As a result, the leading end of the metal strip is rolled under the operating conditions preset by the control computer 12, and then the heating conditions for the heating device 14 are set according to the shape of the leading end of the metal strip identified by the leading end shape specifying unit 27. Then, rolling of the metal strip continues under the heating conditions of the width direction end portion set. The heating condition setting unit 28 executes dynamic setup control to set the heating conditions for the heating device 14 based on actual data of the leading end rolled under the preset operating conditions. By executing dynamic setup control by the heating condition setting unit 28, even if the metal strip has a width direction deformation resistance distribution before being charged into the rolling mill, the shape of the metal strip after the heating conditions for the heating device 14 are set can be controlled to a predetermined shape (e.g., a flat shape).

[0040] That is, before the metal strip passes through the rolling mill, the operating conditions for the metal strip are set by preset control executed by the control computer 12, and when the leading end of the metal strip passes through the shape measuring device 15, the heating condition setting unit 28 performs dynamic setup control to set the heating conditions for the heater 14. Therefore, the leading end of the metal strip is rolled under the operating conditions set by preset control, and the region excluding the leading end of the metal strip is rolled by applying the heating conditions for the heater 14 set by dynamic setup control in addition to the operating conditions set by preset control.

[0041] The heating conditions of the heating device 14 may be included in the operating conditions set by the preset control by the control computer 12. Conventional techniques such as those described in Patent Documents 2 and 3 can be applied to the preset control of the leading end of the metal strip. This makes it possible to reduce shape defects at the leading end of the metal strip to some extent, and to further flatten the shape of the metal strip in the region other than the leading end of the metal strip by dynamic setup control. In this case, the setting of the heating conditions of the heating device 14 by the heating condition setting unit 28 means resetting the heating conditions set by the preset control.

[0042] The feedback control setting unit 26 sets the setting values ​​of the shape control actuators of the rolling mill in accordance with the shape of the metal strip measured by the shape measuring device 15. The control unit 21 preferably causes the feedback control setting unit 26 to execute processing after the dynamic setup unit 25 sets the heating conditions of the heating device 14 for the metal strip. Even if a shape defect remains in the metal strip rolled under the heating conditions of the heating device 14 set by the dynamic setup unit 25, the feedback control setting unit 26 flattens the defect through so-called shape feedback control. That is, when the shape of the metal strip measured by the shape measuring device 15 differs from the target shape, the feedback control setting unit 26 changes the setting values ​​of the shape control actuators of the rolling mill. This makes it possible to suppress shape defects caused by setting errors in the heating conditions of the heating device 14 through dynamic setup control and shape defects caused by fluctuations over time in the thermal crown of the rolling rolls of the rolling mill.

[0043] However, the feedback control setting unit 26 does not necessarily have to have a function of calculating the setting values ​​of the shape control actuators of the rolling mill. For example, if the rolling equipment 10 is equipped with a shape feedback control system that sets the shape control actuators of the rolling mill in accordance with the shape of the metal strip measured by the shape measuring device 15, the feedback control setting unit 26 may simply transmit a control command to start shape feedback control to the rolling controller 11. When the feedback control setting unit 26 transmits a control command to start shape feedback control to the rolling controller 11, the shape feedback control provided in the rolling equipment 10 is executed. In this case, it is preferable that the feedback control setting unit 26 transmits a control command to the rolling controller 11 to stop the shape feedback control until the dynamic setup unit 25 has completed setting the heating conditions for the heating device 14. This is to prevent disturbances from occurring to the shape of the metal strip due to the execution of shape feedback control when the dynamic setup unit 25 sets the heating conditions for the heating device 14.

[0044] The control unit 21, having the dynamic setup unit 25 and the feedback control setting unit 26, exhibits the following effects. That is, even if the metal strip has a widthwise deformation resistance distribution, the dynamic setup unit 25 heats the widthwise end portion of the metal strip on the rolling mill inlet side in accordance with the shape performance data at the leading end of the metal strip, thereby making it possible to flatten the shape of the metal strip after rolling. Furthermore, the feedback control setting unit 26 sets the shape control actuators of the rolling mill based on the shape performance data during rolling of the metal strip, making it possible to flatten the shape of the metal strip after rolling even if there is an error in setting the heating conditions of the heating device 14, fluctuations in the deformation resistance of the metal strip in the longitudinal direction, and changes over time in the thermal crown of the rolling rolls of the rolling mill.

[0045] In particular, when the deformation resistance of the widthwise ends of the metal strip is large, it is often difficult to flatten the shape after rolling simply by setting the shape control actuators of the rolling mill, so it is effective to reduce the deformation resistance by heating the widthwise ends of the metal strip with the heating device 14. However, because the heating device 14 is located upstream of the rolling mill, even if the heating conditions of the heating device 14 are changed, there is a long dead time until the shape is controlled by the rolling mill. In contrast, shape feedback control has the advantage that, although it may be difficult to sufficiently flatten the shape after rolling when the deformation resistance distribution in the widthwise direction of the metal strip is large, the distance between the rolling mill and the shape measuring device 15 is relatively short, and therefore the dead time for the operation of the shape control actuators is short.

[0046] For example, in the rolling facility 10 shown in FIG. 2, the time it takes for the metal strip S to travel from the rolling stand 2E (final stand 2E) equipped with a shape control actuator to the shape measuring device 15 is 0.1 to 3.0 seconds, whereas the time it takes for the metal strip S to travel from the heating device 14 to the shape measuring device 15 is 3.0 to 25.0 seconds. Furthermore, when changing the setting value of the shape control actuator of the rolling mill, the hydraulic device completes the setting change in about 2 seconds, whereas changing the heating temperature of the heating device 14 requires about 5 to 10 seconds. For this reason, the shape of the metal strip can be further flattened by performing dynamic setup control in response to the deformation resistance distribution in the width direction of the metal strip and by performing shape feedback control in response to disturbances in the longitudinal direction of the metal strip and over time.

[0047] From this perspective, the control unit 21 preferably issues a control command to the control computer 12 or the rolling control controller 11 to maintain the line speed of the rolling mill at a low speed of, for example, 50 to 150 m / min, from the time the leading end of the metal strip passes through the rolling mill until the dynamic setup unit 25 has completed setting the heating conditions for the heating device 14. Thereafter, when the feedback control setting unit 26 executes shape feedback control, the line speed of the rolling mill is preferably increased to a steady speed (for example, 600 to 1800 m / min). This makes it possible to shorten the region in which the shape of the metal strip is difficult to control due to the dead time required to set the heating conditions for the heating device 14.

[0048] After the dynamic setup unit 25 has completed setting the heating conditions for the heating device 14, the control unit 21 preferably transmits a control signal to the heating device 14 to maintain the heating conditions for the heating device 14 set by the dynamic setup unit 25 while the feedback control setting unit 26 is executing the shape feedback control. If the heating conditions for the heating device 14 are changed after the shape feedback control has started, this may cause a disturbance to the shape feedback control, which may result in the shape of the metal strip not being stabilized, and this is to suppress the occurrence of such a disturbance.

[0049] Returning to FIG. 1 , the acquisition unit 22 is equipped with a communication interface that acquires measurement values ​​(shape data) of the shape of the metal strip measured by the shape measuring device 15. The acquisition unit 22 acquires the shape data of the metal strip measured by the shape measuring device 15 via a network. The acquisition unit 22 may be configured to acquire the shape data of the metal strip measured by the shape measuring device 15 from the rolling control controller 11 or the control computer 12. The acquisition unit 22 acquires identification information of the metal strip from the rolling control controller 11 or the control computer 12.

[0050] The storage unit 23 is configured by, for example, an information recording medium such as an updatable flash memory, a hard disk, or a memory card. The storage unit 23 stores, for example, programs or data for implementing the functions of the control unit 21. The storage unit 23 may store, as a database or program, information on the heating conditions of the heating device 14 that are set in accordance with shape data of the metal strip.

[0051] The output unit 24 outputs the heating conditions of the heating device 14 set by the control unit 21 to the rolling equipment 10. The output unit 24 may output control commands related to shape feedback control set by the feedback control setting unit 26 of the control unit 21 to the rolling equipment 10. The output unit 24 may be connected to a display device and configured to display on the display device the heating conditions of the heating device 14 set by the control unit 21 and the status of the control commands related to shape feedback control. The display device may be configured to include a liquid crystal display, an organic EL panel, or the like. The display device may also be configured by the display of a terminal device such as a smartphone or a tablet. By displaying the control information set by the control unit 21 on the display device, the operator in charge of operating the rolling equipment 10 can understand the control status of the shape control being performed on the metal strip.

[0052] [Rolling equipment] Next, the configuration of the rolling equipment 10 will be described in detail with reference to FIGS.

[0053] Fig. 2 is a schematic diagram showing an example of the configuration of the rolling equipment 10 shown in Fig. 1. As shown in Fig. 2, the rolling equipment 10 includes a rolling mill 2, a rolling control controller 11, a control computer 12, a host computer 13, a heating device 14, and a shape measuring device 15. The rolling equipment 10 also includes, as devices installed on the inlet side of the rolling mill 2, a payoff reel 3, a joining device 4, loopers 5A and 5B, a pickling tank 6, and a rinsing tank 7. The rolling equipment 10 also includes, as devices installed on the outlet side of the rolling mill 2, a cutting machine 8 and a tension reel 9.

[0054] The shape control device 20 is capable of transmitting and receiving control signals and operation data between the rolling mill 2, the heating device 14, and the shape measuring device 15 via a rolling control controller 11 and a control computer 12. The equipment including the rolling equipment 10 and the shape control device 20 is called the manufacturing equipment.

[0055] The rolling equipment 10 is equipment that performs cold rolling on hot-rolled steel sheets (hot-rolled steel strips) mainly produced by a hot rolling line. In other words, the metal strip S mainly refers to steel strips. The thickness of the metal strip S supplied to the rolling equipment 10 is, for example, 1.2 to 4.0 mm. The thickness of the metal strip S produced by the rolling equipment 10 is, for example, 0.20 to 2.6 mm. The width of the metal strip S is, for example, 700 to 1800 mm. The length of the metal strip S is, for example, 600 to 4000 m. The rolling equipment 10 is suitable for producing high-strength steel sheets as the metal strip S, with a tensile strength of 780 to 1470 MPa. Because a distribution of deformation resistance is likely to occur in the width direction of a hot-rolled steel sheet, the hot-rolled steel sheet is suitable for shape control by the metal strip shape control method according to the present invention.

[0056] The payoff reel 3 is a device that pays off the metal strip S. The rolling facility 10 may be equipped with a plurality of payoff reels 3. In this case, each of the plurality of payoff reels pays off a different metal strip S.

[0057] The joining device 4 is a device that joins the tail end of the metal strip (leading material) that has been previously discharged from the pay-off reel 3 with the front end of the metal strip (following material) that has been subsequently discharged from the pay-off reel 3 to form a joined metal strip. A flash butt welder or a laser welder is preferably used as the joining device 4. The joint between the leading material and the following material made by the joining device 4 is called a joining point.

[0058] The loopers 5A and 5B are devices for temporarily storing the metal strip S. The looper 5A, which is located between the payoff reel 3 and the pickling tank 6, stores the metal strip S so that the pickling process can continue in the pickling tank 6 and the rinsing tank 7 until the metal strips are joined together by the joining device 4 (until joining is completed). On the other hand, the looper 5B, which is located between the rinsing tank 7 and the rolling mill 2, stores the metal strip S so that the speed of the pickling process in the pickling tank 6 can be kept constant even if the line speed fluctuates while the rolling mill 2 is rolling the metal strip S.

[0059] The pickling tank 6 is a device that removes oxides (scale) formed on the surface of the metal strip S in the hot rolling line. A pickling solution is stored in the pickling tank 6, and the scale on the surface of the metal strip S is removed by immersing the metal strip S in the pickling solution.

[0060] The rinsing tank 7 is a device for washing and removing the pickling solution adhering to the surface of the metal strip S in the pickling tank 6. The pickling tank 6 and the rinsing tank 7 may be integrated into one unit. Also, a device such as a dryer for drying the metal strip S may be provided.

[0061] The heating device 14 is disposed on the upstream side (entrance side) of the rolling mill 2 and heats the widthwise end portions of the metal strip S after surface scale removal before cold rolling the metal strip S. The heating device 14 is preferably disposed at a position 5 to 50 m upstream of the rolling stand 2A (first stand 2A) of the rolling mill 2 in the conveying direction of the metal strip S. This allows the widthwise end portions of the metal strip S to be cold rolled while being heated. The heating device 14 is installed to heat the widthwise end portions (both edge portions) on both the left and right sides of the conveying direction of the metal strip S. If the distance between the heating device 14 and the first stand 2A is less than 5 m, interference may occur with ancillary equipment such as guides installed in the first stand 2A. Furthermore, if the distance between the heating device 14 and the first stand 2A exceeds 50 m, the temperature of the widthwise end portions of the metal strip S heated by the heating device 14 decreases, reducing the effect of elongating the widthwise end portions of the metal strip S in the first stand 2A.

[0062] Fig. 3 is a schematic diagram showing a configuration example of the heating device 14. The heating device 14 shown in Fig. 3 heats (induction heats) both edge portions of the metal strip S by an induction heating method. As shown in Fig. 3, the heating device 14 includes a pair of C-shaped inductors 31a and 31b that sandwich the widthwise edge portions Sa and Sb of the metal strip S from both sides in the thickness direction of the metal strip S (e.g., in the upper and lower directions) without contacting each other.

[0063] A heating coil 34a is provided on the legs 32a and 33a of the inductor 31a. When an edge portion Sa of the metal strip S passes through the gap between the legs 32a and 33a of the inductor 31a, the heating coil 34a applies a magnetic flux in the thickness direction to the edge portion Sa, thereby inductively heating the edge portion Sa. Meanwhile, a heating coil 34b is provided on the legs 32b and 33b of the inductor 31b. When an edge portion Sb of the metal strip S passes through the gap between the legs 32b and 33b of the inductor 31b, the heating coil 34b applies a magnetic flux in the thickness direction to the edge portion Sb, thereby inductively heating the edge portion Sb.

[0064] The heating device 14 also includes a matching board 37, a high-frequency power supply 38, and a heating control unit 39. The high-frequency power supply 38 is connected to the heating coils 34a and 34b via the matching board 37. The heating control unit 39 is also connected to the high-frequency power supply 38. The heating control unit 39 instructs the high-frequency power supply 38 to output high-frequency current to be passed through the heating coils 34a and 34b according to the heating conditions set by the heating condition setting unit 28 of the shape control device 20. The high-frequency power supply 38 passes high-frequency current through the heating coils 34a and 34b via the matching board 37 based on the output instruction from the heating control unit 39, thereby generating magnetic flux (high-frequency magnetic flux) in the thickness direction of the heating coils 34a and 34b. This high-frequency magnetic flux generates an induced current in the edge portions Sa and Sb of the metal strip S, and the induced current generates Joule heat in the edge portions Sa and Sb. The edge portions Sa and Sb are induction-heated by the generated Joule heat, and as a result, the widthwise ends of the metal strip S are heated. In this case, the greater the output of the high-frequency current flowing through the heating coils 34a, 34b, the higher the temperature of the width direction end portions of the metal strip S. Note that the heating device 14 may perform preset control to set heating conditions for the metal strip S based on the thickness, conveying speed, and steel type of the metal strip S before the leading end of the metal strip S reaches the rolling mill 2.

[0065] The heating device 14 includes carriages 35a and 35b that move the inductors 31a and 31b in the width direction of the metal strip S, respectively, and position control units 36a and 36b that control the positions of the inductors 31a and 31b. The inductor 31a is placed on the carriage 35a, and the inductor 31b is placed on the carriage 35b. The carriages 35a and 35b move in the width direction of the metal strip S, thereby moving the inductors 31a and 31b in the width direction of the metal strip S. A heating control unit 39 is connected to the position control units 36a and 36b. The heating control unit 39 sets the target positions of the inductors 31a, 31b in the width direction of the metal strip S (more specifically, the target positions of the heating coils 34a, 34b) based on the heating conditions set by the heating condition setting unit 28 of the shape control device 20, and the position control units 36a, 36b drive and control the carriages 35a, 35b, which in turn control the positions of the inductors 31a, 31b. This makes it possible to control the heating ranges La, Lb of the width direction ends of the metal strip S (the distances from the width direction ends of the metal strip S over which the temperature of the metal strip S is raised).

[0066] Returning to FIG. 2, the rolling mill 2 is a device that cold rolls the metal strip S to a target thickness. The rolling mill 2 is a cold tandem rolling mill in which five rolling stands 2A, 2B, 2C, 2D, and 2E are arranged in series in this order from the upstream side in the conveying direction of the metal strip S. However, the rolling mill 2 is not limited to a cold tandem rolling mill having five rolling stands, and the rolling mill 2 is not limited to a cold tandem rolling mill, but may be a single rolling stand in which the thickness of the metal strip S is set to a target value.

[0067] 4(a) and 4(b) are schematic diagrams showing the detailed configuration of one rolling stand of the rolling mill 2. As shown in FIGS. 4(a) and 4(b), the rolling mill 2 is a four-high rolling mill. The rolling mill 2 is equipped with a pair of work rolls 41a, 41b arranged vertically across the pass line PL. The work rolls 41a, 41b are supported by backup rolls 42a, 42b, respectively. One end of each of the work rolls 41a, 41b is connected to a driving motor via a coupling or a reducer. The driving motor rotates the work rolls 41a, 41b. The work rolls 41a, 41b are held in bearing boxes (work roll chocks) 47a, 47b provided at both ends of the work rolls 41a, 41b.

[0068] The backup rolls 42a (42b) are supported by bearing housings (backup roll chocks) 43a1, 43b1 (43a2, 43b2) arranged at the axial ends. The rolling load applied to the metal strip S is transmitted to the housings 44a, 44b via the backup roll chocks 43a1, 43b1 (43a2, 43b2). Load cells 45a, 45b, which are load detectors, are arranged between the housings 44a, 44b and the backup roll chocks 43a2, 43b2, making it possible to measure the rolling load applied to the metal strip S.

[0069] Electric or hydraulic screw down devices 46a, 46b are arranged on the work side (WS) and drive side (DS) of the rolling mill 2. The screw down devices 46a, 46b adjust the gap (also called the roll gap or roll opening) between the work rolls 41a and 41b by vertically displacing the backup roll chocks 43a1, 43b1, respectively.

[0070] The rolling mill 2 is equipped with a shape control actuator for controlling the shape (flatness) of the metal strip S. The shape control actuator is a device that changes the distribution of the roll gap in the width direction of the metal strip S. The shape control actuator is, for example, a work roll bender. The work roll bender applies a bending force to the work rolls 41 a, 41 b by applying force between the upper work roll chock 47 a and the lower work roll chock 47 b, thereby causing the work rolls 41 a, 41 b to bend. This adjusts the distribution of the roll gap in the width direction of the metal strip S. The work roll bender is equipped with a hydraulic device (not shown) for applying force between the work roll chocks 47 a, 47 b. However, the shape control actuator of the rolling mill 2 is not limited to a work roll bender. Shape control actuators suitable for each type of rolling mill, such as a one-sided taper work roll shift mill, a CVC (Continual Variable Control) mill, or a pair cross mill, can be used as the rolling mill 2. Furthermore, the rolling mill 2 is not limited to a four-high rolling mill, but may be a six-high rolling mill. In this case, the shape control actuator may be a system that shifts intermediate rolls arranged between the work rolls and backup rolls in the axial direction.

[0071] Returning to Fig. 2, the shape measuring device 15 is a device for measuring the shape of the metal strip S rolled by the rolling mill 2 in the width direction.

[0072] The cutter 8 is a device that cuts the rolled metal strip S. The cutter 8 separates the joined preceding material and succeeding material at the entry side of the rolling equipment 10.

[0073] The tension reel 9 is a device that winds up the metal strip S cut by the cutting machine 8. The type of tension reel 9 is not limited, and it may be, for example, a carousel tension reel. The rolling equipment 10 may also be equipped with multiple tension reels 9. In this case, the multiple tension reels 9 continuously wind up multiple metal strips S.

[0074] Although not shown, the rolling equipment 10 is further equipped with sensors such as a thickness gauge for measuring the thickness of the metal strip S rolled by the rolling mill 2 and a tension meter for measuring the tension applied to the metal strip S.

[0075] [Method for controlling the shape of a metal strip] Next, a method for controlling the shape of a metal strip according to one embodiment of the present invention will be described with reference to FIG.

[0076] Fig. 5 is a flowchart showing the flow of a method for controlling the shape of a metal strip according to one embodiment of the present invention. As shown in Fig. 5, the method for controlling the shape of a metal strip according to one embodiment of the present invention includes a leading edge shape specifying step S1 in which the shape of the leading edge of the metal strip S rolled by the rolling mill 2 is specified using the shape measuring device 15, a heating condition setting step S2 in which heating conditions for the width direction ends of the metal strip S by the heating device 14 are set in accordance with the shape of the leading edge of the metal strip S specified in the leading edge shape specifying step S1, and a rolling control step S3 in which the metal strip S whose width direction ends have been heated under the heating conditions set in the heating condition setting step S2 is rolled by the rolling mill 2.

[0077] In the rolling control of the metal strip S by the rolling equipment 10, before the joint formed by joining the tail end of the preceding material and the front end of the succeeding material, the metal strip S, reaches the first stand 2A of the rolling mill 2, the control computer 12 executes a preset calculation to calculate the operating conditions for the metal strip S. Then, in accordance with the tracking information of the joint, the rolling control controller 11 operates each device constituting the rolling equipment 10 to set the operating conditions for the metal strip S. The operating conditions in this case include the roll gap of each rolling stand of the rolling mill 2, the work roll peripheral speed, the shape control actuator, and various control target values ​​for the thickness, shape, etc. of the metal strip S.

[0078] As described above, the method for controlling the shape of a metal strip in this embodiment is started after the control computer 12 executes preset calculations for the metal strip S and the rolling control controller 11 sets operating conditions corresponding to the metal strip S.

[0079] In the tip shape specifying step S1, the tip shape specifying unit 27 specifies shape data of the tip portion of the metal strip S from the shape data of the metal strip S measured by the shape measuring device 15. The shape data of the tip portion of the metal strip S represents the shape of the metal strip S corresponding to the operating conditions set by the preset calculation. In other words, the shape data of the tip portion of the metal strip S is data that reflects the deformation resistance distribution in the width direction of the metal strip S and the influence of thermal crown on the rolling rolls of the rolling mill 2.

[0080] In the tip end shape specifying step S1, the tip end shape specifying unit 27 preferably specifies the shape data of the tip end of the metal strip S using actual data of the shape measured in a range of 10 to 100 m from the tip of the metal strip S. The range less than 10 m from the tip of the metal strip S corresponds to the outermost periphery of the hot-rolled coil, and the shape may be disturbed due to handling of the metal strip S, etc. Therefore, in the tip end shape specifying step S1, it is preferable not to use shape data measured in a range less than 10 m from the tip of the metal strip S as the shape data of the tip end of the metal strip S. On the other hand, if actual data of the shape measured at a position more than 100 m from the tip of the metal strip S is used as the shape data of the tip end of the metal strip S, the timing for starting control by the dynamic setup unit 25 will be delayed, which may result in a decrease in product yield due to poor shape.

[0081] The shape data at the leading end of the metal strip S may be actual data of the shape measured at any position in the longitudinal direction of the metal strip S, as long as it is within a range of 10 to 100 m from the leading end of the metal strip S. Alternatively, an average value may be calculated from actual data of multiple shapes measured within a range of 10 to 100 m from the leading end, and this may be used as the shape data at the leading end of the metal strip S.

[0082] The shape data of the leading end of the metal strip S identified in the leading end shape identifying step S1 may be an index representing the unevenness of the elongation of the metal strip S in the width direction, such as the steepness, differential elongation rate, I-unit, etc.

[0083] In the heating condition setting step S2, the heating condition setting unit 28 sets the heating conditions for the width direction ends of the metal strip S by the heating device 14 in accordance with the shape of the front end of the metal strip S. Since the heating condition setting step S2 is performed after the front end of the metal strip S has been rolled, new heating conditions are set for the region excluding the front end after the heating conditions for the width direction ends of the metal strip S by the heating device 14 have been set.

[0084] The heating device 14 heats both widthwise ends of the metal strip S before the metal strip S is rolled, thereby reducing the deformation resistance of both widthwise ends of the metal strip S. Therefore, when the heating device 14 is not used (the output of the heating device 14 is zero) to roll the leading end of the metal strip S, if the leading end of the metal strip S has a center-stretched shape (also called a belly-stretched shape), the output of the heating device 14 can be increased to stretch both widthwise ends of the metal strip S, and the metal strip S after rolling can be controlled to have a flat shape. However, if the leading end of the metal strip S has an edge-wave shape (also called an edge-stretched shape), using the heating device 14 will worsen the edge-wave shape, so the heating conditions are set in the heating condition setting step S2 so as not to increase the output of the heating device 14.

[0085] On the other hand, when the output of the heating device 14 is set in advance by preset calculation and rolling is performed on the leading end of the metal strip S under conditions in which the width direction end of the metal strip S is heated, the heating conditions of the heating device 14 can be set as follows. That is, when the leading end of the metal strip S has a central elongation shape, the output value of the heating device 14 is set to a value higher than the output value set by preset calculation. This makes it possible to reduce the central elongation of the metal strip S. On the other hand, when the leading end of the metal strip S has a selvedge wave shape, the output value of the heating device 14 is set to a value lower than the output value set by preset calculation. This makes it possible to reduce the selvedge wave of the metal strip S.

[0086] In the heating condition setting step S2, it is preferable to set at least one of the heating temperature and heating range of the widthwise end of the metal strip S as heating conditions for the heating device 14, depending on the shape of the leading end of the metal strip S identified using the shape measuring device 15. The heating temperature set as a heating condition for the heating device 14 refers to the maximum temperature in the width direction of the metal strip S. The heating temperature of the metal strip S can be adjusted by setting the high-frequency current output from the high-frequency power supply 38 of the heating device 14. By setting the heating temperature of the metal strip S higher, the deformation resistance of the widthwise end of the metal strip S can be further reduced. On the other hand, the heating range set as a heating condition for the heating device 14 refers to the range over which heating is performed by the heating device 14 from the widthwise end of the metal strip S toward the widthwise center. The heating range of the metal strip S can be set by changing the target positions of the inductors 31a and 31b using the position control units 36a and 36b of the heating device 14. In the example of the heating device 14 shown in Fig. 3, the heating range corresponds to the lengths La and Lb of the horizontal overlap between the heating coils 34a and 34b and the widthwise ends of the metal strip S. By increasing the heating ranges La and Lb of the metal strip S, it is possible to reduce the deformation resistance over a wider range from the widthwise ends of the metal strip S toward the widthwise center.

[0087] Once the heating condition setting step S2 is completed as described above, the rolling control step S3 is performed in which the metal strip S, the width direction end portions of which have been heated under the heating conditions in the heating device 14 set in the heating condition setting step S2, is rolled by the rolling mill 2. Since the heating conditions in the heating device 14 are set in accordance with the deformation resistance distribution in the width direction of the metal strip S in the heating condition setting step S2, the metal strip S rolled by the rolling mill 2 can have a good shape even if the setting values ​​of the shape control actuators set by the preset calculation are not appropriate.

[0088] [Heating conditions] Next, the heating conditions of the heating device 14 set in the heating condition setting step S2 will be described with reference to FIGS.

[0089] A method for controlling the shape of a metal strip according to one embodiment of the present invention is highly effective when the metal strip S fed to the rolling equipment 10 has a deformation resistance distribution in the width direction. An example of a metal strip S having a deformation resistance distribution in the width direction is a high-strength steel plate having a tensile strength of 780 MPa or more. The method is also suitable for cold rolling of a high-strength steel plate having a chemical composition containing 0.10-0.15 wt% C, 0.50-1.50 wt% Si, and 1.50-3.50 wt% Mn, with optional additions, as well as Fe and unavoidable impurities. This method is particularly suitable for use when the deformation resistance at the width-direction ends of the metal strip S fed to the rolling equipment 10 is 0-200 MPa greater than the deformation resistance at the width-direction center.

[0090] FIG. 6 shows an example of a high-strength steel sheet having a hardness distribution in the width direction. The high-strength steel sheet shown in FIG. 6 is a hot-rolled steel sheet having a thickness of 2.6 mm and a width of 906 mm. The chemical composition includes 0.13 wt% C, 1.50 wt% Si, and 2.10 wt% Mn. The hardness distribution shown in FIG. 6 was measured on a high-strength steel sheet that was air-cooled in a coil after being coiled at a coiling temperature of 570 to 620°C on a hot rolling line. The horizontal axis of FIG. 6 indicates the distance from one end of the steel sheet in the width direction, and the vertical axis indicates the Vickers hardness (HV) measured on the cross section of the steel sheet. The hardness distribution shown in FIG. 6 shows that the hardness at the end in the width direction is higher than that at the center in the width direction, resulting in a hardness difference of about 10 to 50 Hv between the center and the end in the width direction. From the conversion between Vickers hardness and deformation resistance, it can be estimated that a hardness difference of 50 Hv corresponds to a deformation resistance difference of approximately 150 MPa. In this case, the yield stress at the center of the high-strength steel plate in the width direction is 615 MPa, so the yield stress at the ends in the width direction is approximately 750 MPa. However, if there is a difference in yield stress of approximately 150 MPa in the width direction of the metal strip S, it is often difficult to flatten the shape after rolling using the shape control actuators of a conventional rolling mill. The conversion from Vickers hardness to yield stress can be estimated, for example, using the conversion formula described in Non-Patent Document 1.

[0091] FIG. 7 shows an example of the shape of a high-strength steel sheet after cold rolling, measured using a shape measuring device 15. The horizontal axis of FIG. 7 indicates the widthwise position of the high-strength steel sheet, and the vertical axis indicates the relative value of the steepness in the widthwise direction. From FIG. 7, it can be seen that the shape of the high-strength steel sheet after rolling is a centrally elongated shape. In other words, the steepness at the widthwise central portion of the high-strength steel sheet is a maximum of 1.4%, which exceeds the general steepness tolerance of 1.0%. In this way, when a steel sheet having a higher yield stress at the widthwise ends compared to the widthwise central portion is rolled, a large centrally elongated shape is formed.

[0092] That is, by rolling the leading end portion of a metal strip S having the hardness distribution shown in FIG. 6 using a rolling mill 2, the shape of the leading end portion of the metal strip S as shown in FIG. 7 is measured. That is, shape data of the metal strip S shown in FIG. 7 is identified in a leading end shape identifying step S1. In the metal sheet shape control method of this embodiment, a heating condition setting step S2 is executed in which heating conditions for the heating device 14 are set based on the shape data identified in this manner. In the heating condition setting step S2, heating conditions for the heating device 14 are set to control the central elongation shape shown in FIG. 7 to a flat shape.

[0093] Figure 8 shows the relationship between Vickers hardness and temperature measured on the high-strength steel plate at elevated temperatures. Figure 8 shows that increasing the temperature of the high-strength steel plate reduces the Vickers hardness. Furthermore, by increasing the temperature of the widthwise edge of the high-strength steel plate to approximately 400°C, the hardness difference of 50 Hv can be eliminated. Furthermore, Figure 8 shows that the effect of increasing the temperature of the high-strength steel plate on reducing the Vickers hardness is evident in the range from room temperature to 200°C, and that the effect of reducing the hardness weakens even when the temperature is increased above 200°C. The Vickers hardness at high temperatures can be measured in accordance with JIS Z 2252-1991, "High-Temperature Vickers Hardness Test Method."

[0094] For the above reasons, in the heating condition setting step S2, the heating temperature of the metal strip S should be set in the range of room temperature to 400°C. In particular, in the case of high-strength steel plates, if the temperature is raised to a temperature exceeding 400°C, a thick oxide layer will be formed on the surface, which may deteriorate the surface quality after rolling, so the upper limit of the heating temperature should be set to 400°C. Furthermore, it is more preferable to set the heating temperature of the metal strip S in the range of room temperature to 200°C. This is because if the temperature of the metal strip S is raised to a temperature exceeding 200°C, the softening effect will not be significant and the energy consumption of the heating device 14 will increase.

[0095] In the heating condition setting step S2, for example, the steepness or difference in elongation of the leading end of the metal strip S may be divided into multiple categories (approximately 2 to 5 levels), and the heating temperature of the widthwise ends of the metal strip S by the heating device 14 may be set according to the category of the steepness or difference in elongation of the leading end of the metal strip S. That is, when the shape of the leading end of the metal strip S is a centrally elongated shape, it is advisable to set the heating conditions of the heating device 14 so that the heating temperature increases as the steepness or difference in elongation increases. By increasing the temperature of the widthwise ends of the metal strip S as the shape defect of the centrally elongated shape increases, the elongation of the widthwise ends of the metal strip S in the rolling mill 2 can be promoted, and the shape after rolling can be flattened.

[0096] In the heating condition setting step S2, actual data on the deformation resistance distribution in the width direction of the metal strip S and actual data on the shape of the metal strip S after being rolled by the rolling mill 2 are accumulated, and a statistical method such as machine learning using the accumulated database can be applied. For example, a deformation resistance estimation model can be generated in which the shape data of the metal strip S after being rolled is used as input data and the deformation resistance distribution in the width direction of the metal strip S is used as output data. Then, actual data obtained by previously measuring the relationship between the temperature and deformation resistance of the metal strip S can be used to calculate the heating temperature and heating range for reducing the distribution of deformation resistance estimated by the deformation resistance estimation model. In this case, the generated deformation resistance estimation model can be stored in the memory unit 23 of the shape control device 20, and the heating condition setting unit 28 of the control unit 21 can set the heating conditions of the heating device 14 by referring to the deformation resistance estimation model.

[0097] On the other hand, by applying the metal strip shape control method of this embodiment to the rolling equipment 10 and operating it for, for example, about one to two months, a database can be generated that accumulates historical data on the shape of the front end of the metal strip S identified in the front end shape identification step S1, historical data on the heating conditions of the heating device 14 set in the heating condition setting step S2, and historical data on the shape of the metal strip S rolled in the rolling control step S3. This allows a statistical method such as machine learning using the accumulated database to generate a heating condition estimation model, in which the shape data of the metal strip S after rolling is used as input data and the heating conditions of the heating device 14 for flattening the shape after rolling are used as output data. Then, by replacing the conventional heating condition setting step S2 with the heating condition estimation model generated in this way, more accurate shape control can be achieved. In this case, the generated heating condition estimation model may be stored in the memory unit 23 of the shape control device 20, and the heating condition setting unit 28 of the control unit 21 may set the heating conditions of the heating device 14 by referring to the heating condition estimation model. Furthermore, by updating the heating condition estimation model using operational results over a certain period of time, the heating condition estimation model can be made more accurate.

[0098] [Modification] Next, a modified example of the method for controlling the shape of a metal strip shown in FIG. 5 will be described with reference to FIG.

[0099] Fig. 9 is a flowchart showing the flow of a modified example of the method for controlling the shape of a metal strip shown in Fig. 5. As shown in Fig. 9, this modified example includes a leading edge shape specifying step S1 in which the shape of the leading edge of the metal strip S rolled by the rolling mill 2 is specified using the shape measuring device 15, a heating condition setting step S2 in which heating conditions for the width direction ends of the metal strip S by the heating device 14 are set in accordance with the shape of the leading edge of the metal strip S specified in the leading edge shape specifying step S1, and a rolling control step S4 in which feedback control is performed to set the shape control actuators of the rolling mill 2 in accordance with the shape of the metal strip S after being rolled by the rolling mill 2 when the metal strip S whose width direction ends have been heated under the heating conditions set in the heating condition setting step S2 is rolled by the rolling mill 2. Here, the leading edge shape specifying step S1 and the heating condition setting step S2 have been described above.

[0100] The rolling control step S4 differs from the rolling control step S3 shown in FIG. 5 in that shape feedback control using the shape measuring device 15 is performed. In this case, as with the above, the heating condition setting step S2 can suppress shape defects after rolling due to the distribution of deformation resistance in the width direction for each metal strip S. However, if longitudinal fluctuations in deformation resistance due to material variations in the metal strip S in the longitudinal direction or changes in the thermal crown of the rolling rolls over time occur while the metal strip S is being rolled by the rolling mill 2, the shape of the metal strip S in the longitudinal direction may fluctuate. In contrast, the rolling control step S4 performs shape feedback control using the shape measuring device 15, thereby suppressing the effects of these longitudinal fluctuations and fluctuations over time and thereby suppressing fluctuations in the shape of the metal strip S in the longitudinal direction. Furthermore, shape feedback control using the shape measuring device 15 has less dead time than changing the heating conditions of the heating device 14 upstream of the rolling mill 2. Therefore, the shape of the metal strip S after rolling can be controlled with good responsiveness.

[0101] In the rolling control step S4, the shape feedback control using the rolling equipment 10 shown in Fig. 2 is preferably performed by setting the shape control actuator of the final stand 2E of the rolling mill 2 in accordance with the actual shape of the metal strip S measured by the shape measuring device 15. This is because the shape of the metal strip S on the downstream side of the rolling mill 2 can be directly controlled. Furthermore, fluctuations in the product shape of the metal strip S produced by the rolling equipment 10 in the longitudinal direction can be suppressed, and a metal strip S with excellent shape uniformity in the longitudinal direction can be produced.

[0102] In the rolling control step S4, while the metal strip S, the width direction end portions of which have been heated under the heating conditions set in the heating condition setting step S2, is being rolled by the rolling mill 2, it is preferable to maintain the heating conditions of the heating device 14 set in the heating condition setting step S2 to roll the metal strip S. This is because if the heating conditions of the heating device 14 are changed after the shape feedback control has been started, this may cause a disturbance to the shape feedback control, preventing the shape of the metal strip S from stabilizing.

[0103] [Metal strip manufacturing equipment] As described above, the metal strip shape control system 1 can be configured as a metal strip manufacturing facility including a heating device 14 that heats the width direction ends of a continuously transported metal strip S, a rolling mill 2 that is disposed downstream of the heating device 14 in the transport direction of the metal strip S, a shape measuring device 15 that is disposed downstream of the rolling mill 2 in the transport direction of the metal strip S, and a shape control device 20 that controls the shape of the metal strip S rolled by the rolling mill 2. In this case, the shape control device 20 includes a tip shape specifying unit 27 that specifies the shape of the tip end of the metal strip S rolled by the rolling mill 2, and a heating condition setting unit 28 that sets the heating conditions of the heating device 14 in accordance with the shape of the tip end of the metal strip S specified by the tip shape specifying unit 27. Furthermore, in the metal strip shape control system 1, it is preferable that the shape control device 20 includes a feedback control setting unit 26 that sets the shape control actuator of the rolling mill 2 in accordance with the shape of the metal strip S measured by the shape measuring device 15.

[0104] Furthermore, in the above-described metal strip shape control system 1, it is preferable that the rolling mill 2 is a cold tandem rolling mill composed of two or more rolling stands, and that the heating device 14 is arranged upstream of the first stand of the cold tandem rolling mill, and that the shape measuring device 15 is arranged downstream of the final stand of the cold tandem rolling mill, as a metal strip manufacturing facility. By arranging the heating device 14 upstream of the first stand of the cold tandem rolling mill, the metal strip S, whose width direction end portions have been heated by the heating device 14, is rolled by multiple rolling stands, so that the shape of the metal strip S downstream of the cold tandem rolling mill can be flattened even if the metal strip S charged into the cold tandem rolling mill has a large deformation resistance distribution in the width direction. Furthermore, by arranging the shape measuring device 15 downstream of the final stand of the cold tandem rolling mill, the product shape of the metal strip S manufactured by the metal strip manufacturing facility can be flattened, and a decrease in yield due to shape defects can be suppressed.

[0105] In the metal strip shape control system 1, the rolling equipment 10 is not limited to the configuration shown in FIG. 2. The rolling equipment 10 may include, in this order, a heating device 14 for heating the width direction ends of the continuously transported metal strip S, a rolling mill 2 for rolling the metal strip S, and a shape measuring device 15 for measuring the shape of the metal strip S rolled by the rolling mill 2. Therefore, the shape measuring device 15 may be disposed between the rolling stands of the rolling mill. For example, the shape measuring device 15 may be disposed between the first stand 2A and the rolling stand 2B (second stand 2B) of the rolling mill 2. In this case, the rolling equipment 10 includes the heating device 14, the first stand 2A, and the shape measuring device 15 for measuring the shape of the metal strip S rolled by the first stand 2A. As a result, the rolling equipment 10 can control the shape of the metal strip S rolled by the first stand 2A to a predetermined shape, thereby suppressing the occurrence of operational problems (such as drawing) caused by poor shape when rolling the metal strip S from the second stand 2B located downstream of the first stand 2A to the final stand 2E. Furthermore, the rolling equipment 10 does not necessarily have to be provided with the pickling tank 6 and the rinsing tank 7. In other words, the rolling equipment 10 does not necessarily have to be a combined line of pickling and tandem rolling machines, but may be a continuous cold rolling line. [Example]

[0106] Example 1 As an embodiment of the present invention, an example will be described in which a high-strength steel plate is produced as a metal strip using a cold tandem rolling mill having the configuration shown in Fig. 2 as rolling equipment 10. As shown in Fig. 2, rolling mill 2 is a cold tandem rolling mill having five rolling stands, each of which is a four-high rolling mill. The diameters of the work rolls used in rolling mill 2 (rolling stands 2A, 2B, 2C, 2D, and 2E) are 450 to 550 mm, the diameters of the backup rolls are 1350 to 1500 mm, and the barrel lengths of the work rolls and backup rolls are both 2000 mm.

[0107] In the examples, the high-strength steel sheet fed to the rolling equipment 10 was a hot-rolled steel sheet having a tensile strength of 780 MPa and a chemical composition (mass%) of 0.13% C, 1.50% Si, and 2.10% Mn, and was produced under conditions where the coiling temperature in hot rolling was 570 to 620°C. The hot-rolled steel sheet had a thickness of 2.6 mm and a width of 906 mm. The metal strip S rolled by the rolling mill 2 had a thickness of 1.2 mm and a length of 1220 m.

[0108] The rolling equipment 10 is equipped with a heating device 14 located 8 m upstream of the first stand 2A in the conveying direction of the metal strip S. The heating device 14 is an induction heating type heating device capable of heating the widthwise end of the metal strip S up to a maximum of 400°C. Here, the heating device 14 was set to heat a range of 50 mm from the widthwise end of the metal strip S. A contact-type shape meter using divided rolls was used as the shape measuring device 15. The shape measuring device 15 calculated the distribution of the differential elongation in the width direction of the metal strip S based on the output of the shape meter, and calculated the steepness from the calculated differential elongation, which was used as the shape data. To convert the differential elongation to steepness, the position with the smallest differential elongation in the width direction of the metal strip S was used as a reference, and the steepness λ (%) was calculated from the differential elongation Δε at other widthwise positions using the following mathematical formula (1):

[0109]

number

[0110] In the example, the method for controlling the shape of a metal strip was carried out by the steps (S1 to S3) shown in the flowchart of FIG. 5. Specifically, the method includes a leading edge shape specifying step S1 in which the shape of the leading edge of the metal strip S rolled by the rolling mill 2 is specified using the shape measuring device 15, a heating condition setting step S2 in which heating conditions for the width direction ends of the metal strip S by the heating device 14 are set in accordance with the shape of the leading edge of the metal strip S specified in the leading edge shape specifying step S1, and a rolling control step S3 in which the metal strip S whose width direction ends have been heated under the heating conditions set in the heating condition setting step S2 is rolled by the rolling mill 2. In this case, the leading edge of the metal strip S was defined as a range of 10 to 50 m from the leading edge, and the average value of the steepness in the range of 10 to 50 m from the leading edge of the metal strip S was used as shape data for the leading edge of the metal strip S. In addition, in the preset calculation of the metal strip S, a condition was set in which the metal strip S was not heated by the heating device 14. In other words, the leading edge of the metal strip S was not heated by the heating device 14.

[0111] In the embodiment, in the heating condition setting step S2, the heating conditions of the heating device 14 were set according to the steepness of the leading edge of the metal strip S identified in the leading edge shape identifying step S1. That is, when the steepness of the leading edge of the metal strip S is a central elongation shape of 1.4% or more, the heating conditions were set so that the heating temperature of the width direction ends of the metal strip S by the heating device 14 would be 150°C, and when the steepness of the leading edge of the metal strip S is a central elongation shape of 1.0% or more but less than 1.4%, the heating conditions were set so that the heating temperature of the width direction ends of the metal strip S by the heating device 14 would be 100°C. When the steepness of the leading edge of the metal strip S is other than the above, the heating conditions by the heating device 14 were not changed, that is, the width direction ends of the metal strip S were not heated.

[0112] Next, in the rolling control step S3, the metal strip S, for which the heating conditions of the heating device 14 were set in the heating condition setting step S2, was rolled while maintaining the settings of the shape control actuators of the rolling mill 2 at the settings at the time of the preset calculation. During this process, shape data for the portion of the metal strip S excluding the leading end was acquired by the shape measuring device 15. The shape data for the portion of the metal strip S excluding the leading end was acquired as the average value and standard deviation of the steepness in the longitudinal direction. In the example, the above-described shape control method was applied to five metal strips to produce the metal strips S. As a result, the average steepness in the example was 0.7%, and the standard deviation, which represents the variation among the metal strips S, was 0.2%. Figure 10 shows the steepness of the metal strip S measured by the shape measuring device 15 in the example. It can be seen from Figure 10 that the steepness of the metal strip S was controlled within the range of 1.0%, which is the upper limit of the product tolerance.

[0113] On the other hand, as a conventional example, a high-strength steel sheet having high hardness at its widthwise ends was used, as in the example. Shape feedback control using the shape measuring device 15 provided in the rolling equipment 10 was performed on five metal strips S without heating using the heating device 14. That is, the shape of the high-strength steel sheet having high hardness at its widthwise ends was controlled by the shape control actuators of the rolling mill 2. As a result, the average steepness of the longitudinal center of the metal strip S, i.e., the steady portion of the metal strip S, in the conventional example was 1.4%, and the standard deviation representing the variation for each metal strip S was 0.5%. FIG. 7 shows the steepness of the metal strip S measured by the shape measuring device 15 in the conventional example. It can be seen from FIG. 7 that the steepness of the metal strip S exceeded 1.0%, exceeding the allowable steepness range. As such, it can be seen that for high-strength steel sheets having high hardness at their widthwise ends, it may be difficult to achieve flatness of the high-strength steel sheet using the rolling mill 2 with shape control using only the shape control actuators of the rolling mill 2.

[0114] Furthermore, as a comparative example of the present invention, the hardness distribution in the width direction was measured in advance, and the heating conditions of the heating device 14 were set by preset calculation so as to offset the hardness distribution. That is, the heating conditions for the metal strip S were set based on the hardness distribution in the width direction of the metal strip S, and the metal strip S heated under the preset heating conditions from the leading end to the trailing end of the metal strip S was rolled by the rolling mill 2. As a result, the average steepness of the longitudinal center portion of the metal strip S, i.e., the steady portion of the metal strip S, in the comparative example was 1.2%, and the standard deviation representing the variation for each metal strip S was 0.3%. Figure 11 shows the steepness of the metal strip measured by the shape measuring device 15 in the comparative example. It can be seen from Figure 11 that the steepness of the metal strip exceeded 1.0%, resulting in an edge wave shape that exceeds the allowable steepness range. In this way, it was confirmed that the preset calculation, which sets the heating conditions of the heating device 14 for the metal strip in advance, cannot flatten the shape of the steady part of the metal strip S after rolling due to setting errors in the heating conditions, changes in the deformation resistance in the longitudinal direction of the metal strip S, changes over time in the thermal crown of the rolling rolls of the rolling mill 2, etc.

[0115] Example 2 As in Example 1, an example will be described in which a high-strength steel plate was produced as a metal strip using a cold tandem rolling mill having the configuration shown in Fig. 2 as the rolling equipment 10. The heating device 14 and shape measuring device 15 used in this example were the same as those in Example 1.

[0116] In this example, the method for controlling the shape of a metal strip was carried out by the steps (S1, S2, S4) shown in the flowchart of Fig. 9. Specifically, the method includes a leading edge shape specifying step S1 in which the shape of the leading edge of the metal strip S rolled by the rolling mill 2 is specified using the shape measuring device 15, a heating condition setting step S2 in which heating conditions for the width direction ends of the metal strip S by the heating device 14 are set in accordance with the shape of the leading edge of the metal strip S specified in the leading edge shape specifying step S1, and a rolling control step S4 in which feedback control is performed to set the shape control actuators of the rolling mill 2 in accordance with the shape of the metal strip S after being rolled by the rolling mill 2 when the metal strip S whose width direction ends have been heated under the heating conditions set in the heating condition setting step S2 is rolled by the rolling mill 2.

[0117] In the tip shape specifying step S1, the range of 10 to 50 m from the tip of the metal strip S was defined as the tip, and the average value of the steepness in that range was used as shape data for the tip of the metal strip S. In addition, in the preset calculation of the metal strip S, the heating conditions for the metal strip S by the heating device 14 were set for the succeeding material to be the same as the heating conditions for the preceding material connected via the joining point.

[0118] In the heating condition setting step S2, a heating condition estimation model generated in advance was used to set the heating conditions for the width direction end portions of the metal strip S by the heating device 14. Specifically, a database was generated in advance from past operational records of the rolling equipment 10 using the heating device 14, in which historical data on the shape of the front end portion of the metal strip S, historical data on the heating conditions of the heating device 14, and historical data on the shape of the metal strip S rolled by the rolling equipment 10 were associated with each other. Next, operational data in which the edge wave steepness was 0.5% or less and the intermediate elongation steepness was 0.5% or less was extracted as the historical data on the shape of the front end portion of the metal strip S. Machine learning was then performed using the extracted operational data to generate a heating condition estimation model in which the shape data of the metal strip S after rolling was used as input data and the heating conditions of the heating device 14 were used as output data. In other words, a heating condition estimation model was generated that outputs the heating conditions of the heating device 14 for flattening the shape after rolling by the rolling equipment 10. The generated heating condition estimation model is then stored in the memory unit 23 of the shape control device 20, and the heating condition setting unit 28 of the control unit 21 is configured to set the heating conditions of the heating device 14 by referring to the heating condition estimation model.

[0119] In the rolling control step S4, feedback control was performed by changing the setting value of the work roll bender, which is a shape control actuator in the final stand 2E of the rolling mill 2, in accordance with the actual shape of the metal strip S measured by the shape measuring device 15. Specifically, the shape data of the metal strip S measured by the shape measuring device 15 was approximated by a quadratic function, and the direction of operation of the work roll bender (increase bender or decrease bender) was set in accordance with the coefficient of the approximated quadratic function, and the amount of operation was also set.

[0120] In this example, a high-strength steel sheet having a tensile strength of 980 MPa and a chemical composition (mass%) of 0.12% C, 1.4% Si, and 1.9% Mn was cold-rolled using the rolling equipment 10. The hot-rolled steel sheet fed to the rolling equipment 10 had a thickness of 2.0 mm and a width of 1250 mm, and the thickness after rolling was 1.0 mm. The rolling of the metal strip S using the rolling equipment 10 was performed under the conditions of a rolling mill outlet speed of 150 m / min when the joining point passed through the rolling mill 2 and 600 m / min in the steady state.

[0121] As Example 2 of this embodiment, the high-strength steel sheet was continuously rolled into 10 coils, and shape data for the entire length of the metal strip S was obtained using the shape measuring device 15 to identify the maximum steepness (edge ​​wave steepness, center elongation steepness) in the longitudinal direction of each coil. Figure 12(a) shows the maximum value of edge wave steepness within the coil in Example 2, and Figure 12(b) shows the maximum value of center elongation steepness within the coil. As shown in Figures 12(a) and (b), in Example 2, even when 10 coils were continuously rolled using the rolling equipment 10, the maximum steepness within the coil was 1.0% or less for both the edge wave shape and the center elongation shape.

[0122] On the other hand, in Comparative Example 2, dynamic setup was not performed on the leading edge of the metal strip S by the dynamic setup unit 25, and feedback control was performed to set the heating conditions for the width direction ends of the metal strip S by the heater 14 in accordance with the actual shape of the metal strip S measured by the shape measuring device 15. That is, in Comparative Example 2, feedback control was performed to set the output of the heater 14 as needed in accordance with the shape of the metal strip S after being rolled by the rolling mill 2. In this case, the shape control actuator in the final stand 2E of the rolling mill 2 maintained the setting value set by preset control during rolling of the metal strip S. Figures 12(a) and (b) show the maximum steepness values ​​in Comparative Example 2 when 10 coils of high-strength steel plate were continuously rolled, as in Example 2. As shown in Figures 12(a) and (b), in Comparative Example 2, the maximum selvage wave steepness values ​​for the fourth to eighth coils exceeded 1.0%, and good shapes were not obtained in some cases.

[0123] In Comparative Example 2, when rolling consecutive coils, the widthwise ends of the metal strip S were heated by the heating device 14, which gradually increased the thermal expansion of the portion of the work rolls of the rolling mill 2 that corresponded to the heated area of ​​the metal strip S. As a result, when the metal strip S was rolled by the rolling mill 2, the roll gap at the widthwise ends of the metal strip S narrowed, which is thought to have caused the ear waves of the metal strip S to become larger in the fourth and subsequent coils. At this time, the shape measuring device 15 also detected the ear waves generated in the metal strip S and changed the settings of the heating device 14. However, even if the output of the heating device 14 located on the inlet side of the rolling mill 2 was changed, the dead time until the metal strip S reached the shape measuring device 15 from the heating device 14 was long, about 3.7 to 14.8 seconds. This is thought to have caused the ear waves to become excessively large in some parts of the coil.

[0124] Furthermore, even if the output of the heating device 14 arranged on the inlet side of the rolling mill 2 was changed, it took a relatively long time for the thermal expansion formed in the work roll to be alleviated, and therefore it is believed that the large selvedge waves continued up to the eighth coil. In contrast, in Example 2 of the invention, even if the thermal expansion of the part of the work roll of the rolling mill 2 corresponding to the heated area of ​​the metal strip S gradually increased, the shape control actuator of the rolling mill 2 was able to suppress the selvedge waves from becoming large. In particular, it is believed that the dead time of the feedback control by the work roll bender of the rolling mill 2 was approximately 0.2 to 0.8 seconds, which prevented the selvedge waves from becoming large in part of the longitudinal direction of the metal strip S.

[0125] Furthermore, in Comparative Example 3, dynamic setup of the leading edge of the metal strip S by the dynamic setup unit 25 was not performed, and feedback control was performed to change the heating conditions of the widthwise ends of the metal strip S by the heater 14 and the setting value of the work roll bender, which is a shape control actuator in the final stand 2E of the rolling mill 2, in accordance with the actual shape of the metal strip S measured by the shape measuring device 15. That is, in Comparative Example 3, feedback control was performed using both the output of the heater 14 and the shape control actuator of the rolling mill 2 as feedback control in accordance with the shape of the metal strip S after being rolled by the rolling mill 2. Figures 12(a) and (b) show the maximum steepness values ​​in Comparative Example 3 when 10 coils of high-strength steel plate were continuously rolled, as in Example 2. As shown in Figures 12(a) and (b), in Comparative Example 3, the maximum edge wave steepness values ​​sometimes exceeded 1.0% for the seventh and eighth coils, and the maximum intermediate elongation steepness values ​​sometimes exceeded 1.0% for the eighth and ninth coils.

[0126] Furthermore, in Comparative Example 3, feedback control is configured to operate both the heating conditions of the heating device 14 and the work roll bender of the rolling mill 2 according to the actual shape of the metal strip S, and interference between these controls can cause the shape of the metal strip S to become unstable in the longitudinal direction, resulting in an increase in the maximum value of the steepness. Figure 13 shows an example in which the steepness is plotted against the longitudinal position of the metal strip S (longitudinal position) using the position of the steady part of the seventh coil as a reference. Note that in Figure 13, the edge wave steepness is shown as a positive (+) value, and the center buckling steepness is shown as a negative (-) value. Figure 13 shows how edge waves and center buckling are alternately formed in the longitudinal direction of the metal strip S.

[0127] For example, when central elongation occurs in the metal strip S, feedback control is performed to reduce the bender force of the work roll bender, increase the rolling force at the widthwise ends of the metal strip S, and increase the output of the heater 14 to raise the temperature at the widthwise ends of the metal strip S. However, because the dead time of the heater 14 is longer than the dead time of the work roll bender, the metal strip S reaches the rolling mill 2 with its widthwise ends more heated after the shape of the metal strip S has been flattened by the work roll bender. Then, when the metal strip S is rolled by the rolling mill 2, the deformation resistance of the widthwise ends is reduced, so the widthwise ends of the metal strip S are further pressed down, which is thought to cause ear waves in the metal strip S. Then, once ear waves occur, feedback control is used to increase the bender force of the work roll bender and reduce the output of the heater 14 to suppress the temperature rise at the widthwise ends of the metal strip S. In this case, too, central elongation is thought to occur again in the metal strip S because the metal strip S reaches the rolling mill 2 with its widthwise ends not yet sufficiently heated after the work roll bender is set to flatten the shape of the metal strip S.

[0128] In other words, when feedback control is configured to operate both the heating conditions of the heating device 14 and the work roll bender of the rolling mill 2 in accordance with the actual shape of the metal strip S, as in Comparative Example 3, the shape of the metal strip S fluctuates in the longitudinal direction due to differences in the dead time of the shape control actuator and the heating device 14. As a result, the maximum value of the steepness increases in part of the metal strip S. In contrast, in Invention Example 2, the heating device 14 performs dynamic setup for the front end of the metal strip S, and feedback control is performed using the shape control actuator of the rolling mill 2. It is believed that this enabled the suppression of interference caused by the operation of the heating conditions of the heating device 14 and the work roll bender of the rolling mill 2, as in Comparative Example 3.

[0129] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention. [Explanation of symbols]

[0130] 1 Metal strip shape control system 2. Rolling mill 2A, 2B, 2C, 2D, 2E Rolling Stands 3 Payoff Reel 4 Joining equipment 5A, 5B Looper 6 Pickling tank 7 Rinse tank 8 cutting machine 9 Tension Reel 10 Rolling equipment 11 Rolling control controller 12 Control computer 13 Upper computer 14 Heating device 15 Shape measuring device 20 Shape control device 21 Control section 22 Acquisition Department 23 Memory section 24 Output section 25 Dynamic Setup Section 26 Feedback control setting section 27 Tip shape identification part 28 Heating condition setting section 31a, 31b Inductor 32a,32b,33a,33b Legs 34a, 34b Heating coil 35a, 35b cart 36a, 36b Position control section 37 Matching board 38 High frequency power supply 39 Heating Control Unit 41a, 41b Work rolls 42a, 42b Backup roll 43a1, 43b1, 43a2, 43b2 Bearing box (backup roll chock) 44a, 44b Housing 45a, 45b Load cell 46a, 46b Screw-down device 47a, 47b Bearing box (work roll chock) PL Pass Line S Metal Strip

Claims

1. A method for controlling the shape of a metal strip using rolling equipment including a heating device that heats widthwise ends of a continuously transported metal strip, a rolling mill that rolls the metal strip heated by the heating device, and a shape measuring device that measures the shape of the metal strip rolled by the rolling mill, comprising: a leading end shape specifying step of specifying the shape of the leading end of the metal strip rolled by the rolling mill using the shape measuring device; a heating condition setting step of setting heating conditions for the width direction end portion of the metal strip by the heating device in accordance with the identified shape of the leading end portion of the metal strip; a rolling control step of rolling the metal strip, the width direction end portions of which have been heated under set heating conditions, by the rolling mill; A method for controlling the shape of a metal strip, comprising:

2. 2. The method for controlling the shape of a metal strip according to claim 1, wherein the rolling control step includes a step of performing feedback control to set a shape control actuator of the rolling mill in accordance with the shape of the metal strip, the width direction ends of which have been heated under the set heating conditions, after being rolled by the rolling mill.

3. 2. The method for controlling the shape of a metal strip according to claim 1, wherein the rolling control step maintains the heating conditions of the heating device set in the heating condition setting step while the metal strip, the width direction end portions of which have been heated under the set heating conditions, is rolled by the rolling mill.

4. 2. The metal strip shape control method according to claim 1, wherein the heating condition setting step sets at least one of the heating temperature and heating range of the widthwise end of the metal strip as the heating condition in accordance with the shape of the leading end of the metal strip identified using the shape measuring device.

5. A method for manufacturing a metal strip, comprising the step of manufacturing a metal strip using the method for controlling the shape of a metal strip according to any one of claims 1 to 4.

6. A metal strip shape control device for use in rolling equipment, the device comprising: a heating device for heating width direction ends of a continuously transported metal strip; a rolling mill for rolling the metal strip heated by the heating device; and a shape measuring device for measuring the shape of the metal strip rolled by the rolling mill, a tip shape specifying unit that specifies the shape of the tip of the metal strip rolled by the rolling mill; a heating condition setting unit that sets heating conditions of the heating device in accordance with the shape of the leading end of the metal strip identified by the leading end shape identifying unit; A shape control device for a metal strip comprising:

7. The metal strip shape control device according to claim 6, further comprising a feedback control setting unit that sets a shape control actuator of the rolling mill in accordance with the shape of the metal strip measured by the shape measuring device.

8. a heating device for heating the width direction end portion of the continuously transported metal strip; a rolling mill that rolls the metal strip heated by the heating device; a shape measuring device for measuring the shape of the metal strip rolled by the rolling mill; a shape control device for controlling the shape of the metal strip rolled by the rolling mill, The shape control device includes: a leading end shape specifying unit that specifies the shape of the leading end of the metal strip rolled by the rolling mill based on the shape of the metal strip measured by the shape measuring device; a heating condition setting unit that sets heating conditions of the heating device in accordance with the shape of the tip end of the metal strip identified by the tip end shape identifying unit; A metal strip manufacturing facility comprising:

9. 9. The metal strip manufacturing facility according to claim 8, wherein the shape control device comprises a feedback control setting unit that sets a shape control actuator of the rolling mill in accordance with the shape of the metal strip measured by the shape measuring device.

10. 10. The metal strip manufacturing facility according to claim 8 or 9, wherein the rolling mill is a cold tandem rolling mill, the heating device is arranged on the inlet side of the cold tandem rolling mill, and the shape measuring device is arranged on the outlet side of the cold tandem rolling mill.

Images