Method for determining whether a steel plate can be threaded through a straightening machine, straightening method, manufacturing method, and method for generating a model for determining whether a steel plate can be threaded through a straightening machine

Abstract

To provide a determination method of propriety of plate passage to a correction machine of a steel plate which can determine the propriety of plate passage to the correction machine of the steel plate according to a warpage shape of a tip of the steel plate.SOLUTION: A determination method of propriety of plate passage to a correction machine of a steel plate according to the present invention is performed on a steel plate manufacturing facility that includes: the correction machine having at least a pair of rolls; a conveyance device which charges the steel plate into the correction machine; and a warpage shape measurement device which measures a warpage shape of a tip of the steel plate. The method comprises: a warpage shape measurement step of measuring, by using the warpage shape measurement device, a warpage height and a warpage curvature of the tip of the steel plate before the steel plate is charged into the correction machine; and a plate passage propriety determination step of determining propriety of plate passage to the correction machine of the steel plate on the basis of the warpage height and warpage curvature of the tip of the steel plate measured in the warpage shape measurement step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for determining whether a steel plate can be passed through a straightening machine, a straightening method, a manufacturing method, and a method for generating a model for determining whether a steel plate can be passed through a straightening machine. [Background technology]

[0002] In the manufacturing process of steel plate, if the steel plate is cooled after hot rolling, the occurrence of cooling unevenness in the steel plate may cause deterioration of the flatness of the steel plate product, occurrence of camber due to residual stress, variation in mechanical properties, etc., so it is preferable to perform cooling as uniformly as possible. Therefore, the flatness of the steel plate may be corrected before cooling the steel plate after hot rolling. For example, when the steel plate after hot rolling is accelerated cooled in the manufacturing process of thick steel plate, the flatness of the steel plate may be corrected by a straightener such as a roller leveler before accelerated cooling in order to suppress the occurrence of cooling unevenness. In addition, when a relatively thick material such as a line pipe material is manufactured in the manufacturing process of hot rolled steel plate, if the steel plate (sheet bar) after rough rolling has a warp, the passing of the plate in the finish rolling becomes unstable, so the flatness of the steel plate after rough rolling may be corrected before finish rolling. However, the steel plate after hot rolling often has a warp at the tip due to the temperature difference in the thickness direction. If there is a large warp at the tip of the steel plate, a problem may occur in which the steel plate does not bite into the straightener. Furthermore, if the front end of a steel sheet has an uneven planar shape such as a fishtail shape or a tongue shape, the steel sheet may collide with the straightening roll when passing through the straightening machine, causing bending at the front end of the steel sheet and resulting in a threading failure. If such a problem occurs in the steel sheet being caught in the straightening machine or a threading failure occurs, the efficiency of the subsequent cooling process and finish rolling process is hindered, resulting in a large opportunity loss.

[0003] In contrast, in the past, when it was determined by visual inspection that the warpage at the tip of a steel sheet was large before the steel sheet was passed through the straightener, the steel sheet was stopped from passing through the straightener, the steel sheet was once reversed to a hot rolling mill, the warpage was straightened by the hot rolling mill, and the steel sheet was passed through the straightener again. In addition, there was also a case where a knockdown roll arranged on the entry side of the straightener was used to give bending deformation to the tip of the steel sheet before passing the steel sheet through the straightener. However, if an additional process is added before the steel sheet is passed through the straightener, the temperature of the steel sheet decreases during that time, and the cooling start temperature in accelerated cooling cannot be secured, which causes poor material quality of the steel sheet product. Therefore, Patent Document 1 discloses a method of arranging a steel sheet guide on the entry side of the straightener. It is said that this allows the steel sheet to be stably bitten into the straightener even if the tip of the steel sheet is warped. In addition, Patent Document 2 discloses an apparatus that has two guide guides divided along the conveying direction of the steel sheet at the entry side of the straightener, and the position of the downstream guide guide is synchronized with the elevation of the straightening roll of the straightener. This is said to enable the steel plate to be stably bitten into the straightener even when the warp or thickness of the leading end of the steel plate varies. Patent Document 3 also discloses a method in which the roll indentation of the straightener is maintained smaller than a desired roll indentation when the leading end of the steel plate is bitten into the straightener, and then the roll indentation is increased to the desired roll indentation. This is said to reduce the resistance acting on the steel plate when it is bitten into the straightener, and to prevent the steel plate from becoming stuck. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5007697 [Patent Document 2] Patent No. 5531772 [Patent Document 3] JP 2003-117606 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 is for enabling the steel plate to be bitten into the straightener even when warpage occurs at the tip of the steel plate, and if the warpage at the tip of the steel plate becomes excessive, the occurrence of sheet threading failure cannot be suppressed. In addition, although Patent Document 1 describes a suitable condition for the installation angle of the steel plate guide, it is difficult to completely prevent sheet threading failure at the tip of the steel plate. The method described in Patent Document 2 is similar, and although a suitable range of the installation angle of the guide to prevent sheet threading failure is described, the amount of warpage of the steel plate that can be threaded is not disclosed. In addition, it is not possible to determine in advance whether the steel plate can be threaded through the straightener when there is warpage at the tip of the steel plate. On the other hand, Patent Document 3 describes that the roll push amount of the straightener that allows the tip of the steel plate to be bitten is set from experiments and operation record data using the equipment specifications of the straightener and the dimensions of the steel plate as parameters. However, since the initial roll push amount is set regardless of the amount of warpage at the tip of the steel plate, it is difficult to completely prevent sheet threading failure at the tip of the steel plate. In addition, the amount of warping of steel plates that can be threaded is not disclosed, and if there is warping at the leading edge of a steel plate, it is not possible to determine in advance whether the steel plate can be threaded through a straightening machine.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for determining whether a steel plate can be passed through a straightening machine, which is capable of determining whether the steel plate can be passed through the straightening machine depending on the warpage shape at the leading end of the steel plate. Another object of the present invention is to provide a method for straightening a steel plate, which is capable of suppressing the occurrence of defects in passing the steel plate through the straightening machine. Still another object of the present invention is to provide a method for manufacturing a steel plate, which is capable of manufacturing a steel plate having excellent uniformity in material properties. Another object of the present invention is to provide a method for generating a model for determining whether a steel plate can be passed through a straightening machine, which is capable of generating a model for determining whether the steel plate can be passed through a straightening machine depending on the warpage shape at the leading end of the steel plate. [Means for solving the problem]

[0007] A method for determining whether a steel plate can be passed through a straightening machine according to a first aspect of the present invention is a method for determining whether a steel plate can be passed through a straightening machine in a steel plate manufacturing facility including a straightening machine having at least one pair of rolls, a conveying device for loading the steel plate into the straightening machine, and a warp shape measuring device for measuring the warp shape of a leading end of the steel plate, the method including a warp shape measuring step of measuring a warp height and a warp curvature of the leading end of the steel plate using the warp shape measuring device before the steel plate is loaded into the straightening machine, and a passing feasibility determination step of determining whether the steel plate can be passed through the straightening machine based on the warp height and the warp curvature of the leading end of the steel plate measured in the warp shape measuring step.

[0008] The step of determining whether or not the steel plate can be passed through the straightening machine may include a step of determining whether or not the steel plate can be passed through the straightening machine based on one or more operational parameters selected from the warp height and warp curvature of the tip of the steel plate measured in the warp shape measuring step, as well as the thickness, width, length, and weight of the steel plate, and the charging speed of the steel plate into the straightening machine by the conveying device.

[0009] The steel plate manufacturing equipment may be equipped with a planar shape measuring device that measures the planar shape of the tip of the steel plate, and the step of determining whether or not the steel plate can be passed through the straightening machine may further include a step of determining whether or not the steel plate can be passed through the straightening machine using the planar shape of the tip of the steel plate measured using the planar shape measuring device before the steel plate is loaded into the straightening machine.

[0010] A method for determining whether a steel plate can be passed through a straightening machine, according to a second aspect of the present invention, is a method for determining whether a steel plate can be passed through a straightening machine in a manufacturing facility including a straightening machine having at least one pair of rolls, a conveying device for loading the steel plate into the straightening machine, and a warp shape measuring device for measuring the warp shape of the leading end of the steel plate, and includes a step of determining whether the steel plate can be passed through the straightening machine using a passing ability determination model learned by machine learning, the passing ability determination model including, as input data, the warp height and warp curvature of the leading end of the steel plate measured by the warp shape measuring device before the steel plate is loaded into the straightening machine, and output data including information on whether the steel plate can be passed through the straightening machine.

[0011] The method for straightening a steel plate according to the present invention includes a step of determining whether or not the steel plate can be passed through a straightening machine before the steel plate is loaded into the straightening machine using the method for determining whether or not the steel plate can be passed through a straightening machine according to the present invention, and if it is determined that the steel plate cannot be passed through, resetting the operating conditions of the steel plate manufacturing equipment.

[0012] The method for manufacturing a steel plate according to the present invention includes a step of manufacturing a steel plate using the method for straightening a steel plate according to the present invention.

[0013] The method for generating a model for determining whether a steel plate can be passed through a straightening machine according to the present invention is a method for generating a model for determining whether a steel plate can be passed through a straightening machine, which is used to determine whether a steel plate can be passed through a straightening machine in a steel plate manufacturing facility including a straightening machine having at least one pair of rolls, a conveying device for loading the steel plate into the straightening machine, and a warp shape measuring device for measuring the warp shape of a leading end of the steel plate, and includes the steps of acquiring a plurality of learning data including, as input actual data, the warp height and warp curvature of the leading end of the steel plate measured by the warp shape measuring device before being loaded into the straightening machine, and output actual data being information on whether the steel plate can be passed through the straightening machine corresponding to the input actual data, and generating the model for determining whether a steel plate can be passed through a straightening machine by machine learning using the acquired plurality of learning data. Effect of the Invention

[0014] According to the method for determining whether a steel plate can be passed through a straightening machine of the present invention, it is possible to determine whether the steel plate can be passed through the straightening machine depending on the warpage shape at the leading end of the steel plate. Moreover, according to the method for straightening a steel plate of the present invention, it is possible to suppress the occurrence of defects in passing a steel plate through the straightening machine. Moreover, according to the method for manufacturing a steel plate of the present invention, it is possible to manufacture a steel plate having excellent uniformity in material properties. Moreover, according to the method for generating a model for determining whether a steel plate can be passed through a straightening machine of the present invention, it is possible to generate a model for determining whether a steel plate can be passed through a straightening machine depending on the warpage shape at the leading end of the steel plate. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a steel sheet manufacturing facility according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a configuration example of the warp shape measuring device shown in FIG. [Diagram 3] FIG. 3 is a diagram for explaining the function of the warp shape analysis unit shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing another configuration example of the warp shape measuring device shown in FIG. [Diagram 5] FIG. 5 is a diagram for explaining the function of the planar shape analysis unit. [Figure 6] FIG. 6 is a diagram for explaining a sheet threading defect at the leading end of a steel sheet. [Figure 7] FIG. 7 is a diagram showing an example of the results of investigating the conditions under which failure to pass a steel plate through a straightening machine occurs. [Figure 8] FIG. 8 is a diagram showing an example of the results of investigating the influence of the charging speed of the steel plate by the conveying device and the plate length of the steel plate on the failure of the steel plate to pass through the straightener. [Figure 9] FIG. 9 is a diagram for explaining a method for generating a model for determining whether or not a strip can be threaded using machine learning. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a neural network. [Figure 11] FIG. 11 is a diagram showing the erroneous determination rates in the embodiment and the conventional example. [Figure 12] FIG. 12 is a diagram showing the rate of occurrence of material defects in the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, with reference to the drawings, a method for determining whether a steel plate can be passed through a straightening machine, a straightening method, a manufacturing method, and a method for generating a model for determining whether a steel plate can be passed through a straightening machine, which are one embodiment of the present invention, will be described in detail.

[0017] [Steel plate manufacturing equipment] First, the configuration of a steel sheet manufacturing facility to which the present invention is applied will be described with reference to Figs. 1 to 5.

[0018] FIG. 1 is a schematic diagram showing the configuration of a steel plate manufacturing facility according to an embodiment of the present invention. As shown in FIG. 1, the steel plate manufacturing facility according to an embodiment of the present invention includes a straightener 1 having at least one pair of rolls arranged in the vertical direction, a conveying device 2 for feeding a steel plate S into the straightener 1, and a warpage shape measuring device 3 for measuring the warpage shape of the front end of the steel plate S. The steel plate manufacturing facility of this embodiment also includes a planar shape measuring device 4 for measuring the planar shape of the front end of the steel plate S. However, the planar shape measuring device 4 may not be provided. The steel plate manufacturing facility of this embodiment also includes a control computer 5 for setting and controlling the operating conditions of the steel plate manufacturing facility. The steel plate manufacturing facility of this embodiment is arranged as a part of a hot rolling line, and the steel plate S that has been reverse-rolled by one or two rolling mills arranged upstream of the steel plate manufacturing facility is transported to the steel plate manufacturing facility. A cooling facility for cooling the steel plate S may be arranged downstream of the steel plate manufacturing facility. By subjecting the steel plate S that has been hot-rolled by a rolling mill to accelerated cooling using cooling equipment, a thick steel plate with excellent material properties can be manufactured.

[0019] The steel sheet S to be straightened in the straightener 1 has, for example, a thickness of 6 to 30 mm, a width of 2000 to 4500 mm, a length of 10 to 50 m, and a weight of 8 to 25 tons. The temperature of the steel sheet S to be charged into the straightener 1 is not limited, but in the case of a straightener arranged in a hot rolling line, it is about 650 to 950°C. The straightener 1 has at least one pair of rolls arranged in the vertical direction (thickness direction of the steel sheet S) and has a function of straightening the shape of the steel sheet S. The straightener 1 is, for example, a roller leveler. The roller leveler flattens the shape of the steel sheet S by repeatedly bending and unbending deformation to the steel sheet S using a plurality of straightening rolls arranged in a staggered pattern in the vertical direction. For example, 4 to 6 straightening rolls are arranged on the upper side and 4 to 6 straightening rolls are arranged on the lower side. In a typical roller leveler, the upper straightening roll is held by an upper frame, and the lower straightening roll is held by a lower frame. Then, by fixing the position of the lower frame and tilting the upper frame, bending deformations of different curvatures are sequentially given to the steel sheet S in the conveying direction of the steel sheet S. In this case, in the example shown in FIG. 1, the pushing amount of the straightening roll 6_1 located at the most upstream side among the upper straightening rolls performing the tilting reduction and the pushing amount of the straightening roll 6_i (i=4 to 6) located at the most downstream side are set in advance according to the material and dimensions of the steel sheet S. However, the pushing method of the straightening rolls may be a method in which the pushing amount of each straightening roll can be arbitrarily set instead of the tilting pushing method. In addition, the straightening machine 1 may be equipped with a pair of rolls arranged opposite to each other in the vertical direction. This is similar to a so-called rolling mill, in which the steel sheet S is pressed by a pair of rolls arranged opposite to each other in the vertical direction to straighten the shape of the steel sheet S. In this embodiment, a steel sheet guide 7 is arranged on the inlet side of the straightening machine 1. This is because the steel sheet guide 7 can reduce sheet passing defects when the leading end of the steel sheet S is charged into the straightening machine 1.

[0020] The conveying device 2 conveys the steel sheet S from the upstream side of the straightener 1 and operates to load the leading end of the steel sheet S into the straightener 1. The conveying device 2 may be a conveying table of a steel sheet manufacturing facility. In that case, the conveying table may be divided into a plurality of zones and controlled individually. In this embodiment, the conveying table of the zone that is upstream of the straightener 1 and closest to the straightener 1 is referred to as the conveying device 2. The charging speed of the steel sheet S into the straightener 1 by the conveying device 2 is set by the control computer 5. The control computer 5 sets the pressing amount of the straightening roll of the straightener 1 and the rotation speed of the straightening roll. The charging speed of the steel sheet S by the conveying device 2 is often set to about 0.5 to 0.8VL with respect to the rotation speed VL of the straightening roll. This is because the charging speed of the steel sheet S by the conveying device 2 is set to be smaller than the rotation speed VL of the straightening roll to reduce the impact force when the steel sheet S is bitten into the straightener 1 and suppress damage to the facility.

[0021] The warpage shape measuring device 3 measures the warpage shape of the front end of the steel sheet S. The front end of the steel sheet S refers to the part on the front end side in the conveying direction of the steel sheet S. The front end of the steel sheet S refers to, for example, a range of 1 to 3 m from the front end of the steel sheet S. When the front end of the steel sheet S is loaded into the straightening machine 1, slippage or the like occurs between the front end of the steel sheet S and the straightening roll, which often results in a sheet passing failure. The warpage shape measuring device 3 may be any measuring device that can quantitatively determine the amount of warpage at the front end of the steel sheet S. For example, the warpage shape measuring device 3 may use an image processing method that extracts the contour shape of the steel sheet S from an image of the front end of the steel sheet S and determines the amount of warpage at the front end of the steel sheet S by image processing. The warpage shape measuring device 3 may also use a distance measuring method that installs a distance meter at a position a predetermined distance above or below the steel sheet S and determines the amount of warpage at the front end of the steel sheet S from information on the height distribution in the longitudinal direction of the steel sheet S.

[0022] As shown in FIG. 2, the warpage shape measuring device 3 using the image processing method includes an imaging section (area camera) 3a that captures an image of the tip of the steel sheet S, and a warpage shape analyzing section 3b that identifies the warpage shape of the steel sheet S from the image data captured by the imaging section 3a. The area camera used as the imaging section 3a may be of a color type or a black and white type. Any imaging element such as a CCD or a CMOS may be used as the imaging element. The imaging section 3a may be an area camera of an infrared type that selectively converts a specific wavelength signal among light wavelengths into an image. The imaging section 3a may be appropriately selected from those having an effective pixel count of 640×480 pixels to those having an effective pixel count of about 4872×3248 pixels according to the resolution required to identify the warpage shape of the tip of the steel sheet S by image processing, the distance between the imaging section 3a and the tip of the steel sheet S, and the like. In this embodiment, the imaging range (field of view) V1 of the steel sheet S by the imaging section 3a is preferably set so that the tip of the steel sheet S (within a range of 1 to 3 m from the tip) fits into one image. The imaging unit 3a is preferably disposed at a position slightly above the conveying device 2 from the lateral side in the conveying direction of the steel sheet S so as to photograph the leading edge of the steel sheet S at an angle downward. However, the leading edge of the steel sheet S may be photographed in a generally horizontal direction from approximately the same height as the conveying device 2 toward the side of the steel sheet S. This is because it is easy to distinguish the outline of one end face of the steel sheet S.

[0023] The warpage shape analysis unit 3b identifies the warpage shape of the steel sheet S from the image data of the leading end of the steel sheet S captured by the imaging unit 3a. FIG. 3 is a diagram for explaining the function of the warpage shape analysis unit 3b. The warpage shape analysis unit 3b detects the contour of the width direction end of the steel sheet S by image processing within the range of the image data of the leading end of the steel sheet S (edge ​​detection). Then, the warpage shape analysis unit 3b calculates the warpage height and warpage curvature of the leading end of the steel sheet S as the warpage shape from the contour of the width direction end of the steel sheet S. Specifically, as shown in FIG. 3, the warpage shape analysis unit 3b calculates the difference between the height H of the steel sheet S at the reference position and the height of the leading end as the warpage height, with a position at a distance L preset from the leading end of the steel sheet S as the reference position. In addition, the warpage shape analysis unit 3b calculates an approximation circle TL that approximates the coordinates on the approximation curve connecting the reference position and the leading end of the steel sheet S by an approximation method such as the least squares method, and calculates the reciprocal of the radius as the warpage curvature. It is advisable to convert the height and curvature on the image data into the actual height and curvature according to the imaging magnification of the image data. The warp height and the warp curvature may be calculated so that the direction can be distinguished by assuming that the warp of the steel sheet S is an upward warp and a downward warp as a positive value and a negative value, respectively. On the other hand, when the warp shape of the front end of the steel sheet S is specified using the distance measurement method, as shown in FIG. 4, the warp shape analysis unit 3b acquires height information of the front end of the steel sheet S from the reference position using a distance meter 3c arranged at a reference position a predetermined distance away from the top of the steel sheet S, and specifies the warp shape of the steel sheet S from the height information of the front end of the steel sheet S. As a method for acquiring the height information of the distance meter 3c, a method based on a known technology such as laser light or microwaves can be used. In addition, the warp shape analysis unit 3b acquires information on the conveying speed of the steel sheet S using a speed meter 3d. As a result, the distance from the front end of the steel sheet S is associated with the height information of the front end of the steel sheet S, and the warp height and warp curvature of the front end of the steel sheet S can be calculated as the warp shape in the same manner as described above.

[0024] The planar shape measuring device 4 measures the planar shape of the tip of the steel sheet S before the steel sheet S is loaded into the straightening machine 1. As the planar shape measuring device 4, a measuring device capable of quantitatively identifying the planar shape of the tip of the steel sheet S is used. For example, the planar shape measuring device 4 may use an image processing method in which the contour shape of the steel sheet S is extracted based on an image of the tip of the steel sheet S captured from the top, and the planar shape of the tip of the steel sheet S is identified by image processing. The planar shape measuring device 4 includes an imaging unit (area camera) 4a (see FIG. 1) that images the top surface of the tip of the steel sheet S from above in the conveying direction of the steel sheet S, and a planar shape analyzing unit 4b (see FIG. 5) that identifies the planar shape of the steel sheet S from the image data acquired by the imaging unit 4a. The area camera used as the imaging unit 4a may be the same as that used in the warpage shape measuring device 3. The planar shape analyzing unit 4b identifies the planar shape of the steel sheet S from the image data of the top surface of the tip of the steel sheet S captured by the imaging unit 4a. Fig. 5 is a diagram for explaining the function of the planar shape analysis unit 4b. As shown in Fig. 5, the planar shape analysis unit 4b detects the contour of the steel sheet S by image processing within a range V2 of image data of the top surface of the leading end of the steel sheet S. Then, the planar shape analysis unit 4b acquires the longitudinal distance (leading end crop length) between the most protruding position and the most recessed position in the width direction of the steel sheet S as a measurement value of the planar shape. In this case, the leading end crop length may be defined as positive when the most protruding position in the width direction of the steel sheet S is on the end side of the steel sheet S in the width direction, and negative when the most protruding position in the width direction of the steel sheet S is on the central side of the width direction.

[0025] [Improper threading of the tip of the steel plate] Next, threading defects at the leading end of a steel plate will be described with reference to Figs.

[0026] The passage (biting) of the steel sheet S into the straightening machine 1 refers to the process in which the leading edge of the steel sheet S reaches the straightening machine 1 and passes through the positions of all the straightening rolls. In other words, it includes not only the case in which the leading edge of the steel sheet S collides with the steel sheet guide 7 or the housing of the straightening machine 1 before passing between the straightening rolls arranged in the vertical direction and the steel sheet S does not pass through the straightening rolls, but also the case in which the leading edge of the steel sheet S passes between some of the straightening rolls, but slip occurs between the steel sheet S and the straightening rolls, and the steel sheet S stops without being transported. Figures 6(a) to (c) are schematic diagrams showing the process in which the steel sheet S is charged into the straightening machine 1 equipped with the steel sheet guide 7. As shown in Figure 6(a), if the leading edge of the steel sheet S has a large upward camber when being charged into the straightening machine 1, the leading edge of the steel sheet S comes into contact with the steel sheet guide 7. At this time, since the steel sheet S is given an inertial force (kinetic energy) by the conveying device 2, when the inertial force of the steel sheet S is larger than the reaction force that the steel sheet S receives from the steel sheet guide 7, the leading end of the steel sheet S is guided by the steel sheet guide 7 and guided between the upper and lower straightening rolls as shown in FIG. 6(b). Then, as shown in FIG. 6(c), when the leading end of the steel sheet S passes between the upper and lower straightening rolls, if the energy of the driving force for rotating the straightening rolls is sufficient for the bending work given to the steel sheet S, the steel sheet S advances in the conveying direction in the straightening machine 1, and the leading end of the steel sheet S passes through the positions of all the straightening rolls. On the other hand, when the inertial force of the steel sheet S is smaller than the reaction force that the steel sheet S receives from the steel sheet guide 7 or the energy of the driving force for rotating the straightening rolls is insufficient, the advance of the steel sheet S stops in the straightening machine 1, resulting in a sheet passing failure.

[0027] The present inventors have investigated the conditions under which such a failure to pass the steel sheet S through the straightener 1 occurs, and have obtained the following findings. First, it has been found that a steel sheet with a large warpage height at its front end and a large plate thickness is prone to failure to pass through the straightener 1. This is believed to be because, when the front end of the steel sheet S collides with the steel sheet guide 7 and the front end of the steel sheet S is bent to pass through the straightening roll, a large amount of kinetic energy due to the inertial force of the steel sheet S is consumed when the front end of the steel sheet S collides with the steel sheet guide 7. FIG. 7 shows an example of the results of investigating the conditions under which a failure to pass the steel sheet S through the straightener 1 occurs. FIG. 7 shows the conditions under which a failure to pass through the straightener 1 occurs, which were obtained under the operating conditions of a steel sheet S having a thickness of 25 to 30 mm, a sheet length of 30 to 32 m, and a charging speed (biting speed) of the steel sheet S into the straightener 1 by the conveying device 2 of 50 m / min. From FIG. 7, it can be seen that even if the warpage height at the front end of the steel sheet S is the same, when the warpage curvature at the front end of the steel sheet S is small, no threading failure occurs, and when the warpage curvature is large, threading failure occurs. On the other hand, FIG. 8 shows an example in which the influence of the charging speed of the steel sheet S by the conveying device 2 and the plate length of the steel sheet S on the threading failure of the steel sheet S into the straightener 1 was investigated for steel sheets S having the same warpage height and warpage curvature. In this case, the plate thickness of the steel sheet S is 25 to 30 mm, and the front end warpage height is 100 to 120 mm. From FIG. 8, it can be seen that the greater the charging speed of the steel sheet S into the straightener 1 by the conveying device 2 and the plate length of the steel sheet S, the more improved the threading property of the steel sheet S into the straightener 1. It is considered that this is because the inertial force (kinetic energy) increases when the steel sheet S is charged into the straightener 1, thereby suppressing the biting failure of the steel sheet S into the straightener 1. Furthermore, the inventors have found that the planar shape of the tip of the steel sheet S also affects the occurrence of threading defects of the steel sheet S through the straightener 1. As shown in FIG. 5, when the tip of the steel sheet S has an uneven shape, the part (tip crop) that locally protrudes forward when biting is likely to break. The longer the length (tip crop length) of this tip crop part is and the narrower the width is, the more likely the steel sheet S is to break and the more likely threading defects of the steel sheet S are to occur. For example, when a steel sheet having a thickness of 30 mm and a tip warp height of 100 mm was investigated with respect to the tip crop length and the occurrence of threading defects, it was possible to thread a steel sheet S with a tip crop length of 50 mm, but a threading defect occurred for a steel sheet S with a tip crop length of 200 mm.Incidentally, the temperature of the steel sheet S when the steel sheet S is loaded into the straightening machine 1 and the yield stress of the steel sheet S at that temperature may affect the bite ability into the straightening machine 1. This is because there is a correlation between the temperature and yield stress of the steel sheet S and the resistance force when the leading end of the steel sheet S passes through the steel sheet guide 7.

[0028] [Table for determining whether or not strip can be threaded] Next, a description will be given of a plate threading feasibility determination table used in the method of determining whether a steel plate can be threaded through a straightening machine according to this embodiment.

[0029] In the method of judging whether or not a steel sheet S can be passed through a straightening machine according to the present embodiment, in order to judge whether or not the steel sheet S can be passed through the straightening machine 1 based on the warpage height and warpage curvature of the leading end of the steel sheet S, a passing possibility judgment table is generated in advance based on past operation performance data and the like. Specifically, using the past operation performance, for each category of performance data on the warpage height and warpage curvature of the leading end of the steel sheet S, performance data on whether or not the steel sheet S could be bitten into the steel sheet manufacturing equipment is collected, and a passing possibility judgment table is generated. The warpage height of the leading end of the steel sheet can be divided into 4 to 10 categories. For example, the warpage height can be divided into categories every 20 to 50 mm. Meanwhile, the warpage curvature of the leading end of the steel sheet can be divided into 4 to 10 categories. For example, the warpage curvature can be divided into categories every 0.0001 to 0.0002 / mm. For the record data on whether or not a steel plate can be threaded through the steel plate manufacturing equipment corresponding to each category, the probability of whether or not the steel plate can be threaded may be calculated, and information on whether or not the steel plate can be threaded (information for determining whether or not the steel plate can be threaded) may be determined based on a preset probability threshold. However, it is preferable to determine that "threading is not possible (biting failure)" if there is a record of even one threading failure occurring through the straightener 1 among steel plates belonging to the same category, and to determine that "threading is possible (good biting)" if no threading failure occurs for any steel plate. This is because if a threading failure occurs for a steel plate S in a steel plate manufacturing equipment, it can cause damage to the steel plate manufacturing equipment or a long-term shutdown of the equipment, which has a large impact on the operation, and therefore it is preferable to reduce the risk of threading failure as much as possible.

[0030] It is preferable to collect data on the performance of the steel sheet S in the steel sheet manufacturing equipment, not only in terms of the warp height and warp curvature of the front end of the steel sheet S, but also in terms of classifications subdivided by other parameters. For example, in addition to the warp height and warp curvature of the front end of the steel sheet S, it is preferable to classify the steel sheet S using one or more operation parameters selected from the thickness, width, length, and weight of the steel sheet S, and the charging speed of the steel sheet S into the straightening machine 1 by the conveying device 2. This is because these operation parameters affect the mass or conveying speed of the steel sheet S when the steel sheet S is charged into the straightening machine 1, and the biteability of the steel sheet S into the straightening machine 1 changes due to the inertial force (kinetic energy) of the steel sheet S. On the other hand, when the steel sheet manufacturing equipment is equipped with a planar shape measuring device 4 that measures the planar shape of the front end of the steel sheet S, the planar shape of the front end of the steel sheet S before the steel sheet S is charged into the straightening machine 1, which is measured by the planar shape measuring device 4, may be added to the above classification. This is because the planar shape of the front end of the steel sheet S affects the biteability of the steel sheet S into the straightening machine.

[0031] Table 1 shows a table of whether or not a steel plate S can be threaded through a steel plate manufacturing facility, which is generated by collecting data on whether or not a steel plate S can be threaded through the steel plate manufacturing facility, based on past operational results. The table is classified into categories of the warpage height at the tip of the steel plate, the curvature at the tip, the crop length (tip crop length) which is the planar shape of the tip, the plate length of the steel plate, and the loading speed (conveying speed) of the steel plate S into the straightening machine 1 by the conveying device 2. The "◯" indicating whether or not a steel plate can be threaded indicates "biting possible (good biting)" and "×" indicates "not possible to thread (poor threading)". A category in which a threading failure has occurred even once is labeled with information indicating that the steel plate is poor to thread. The data of whether or not a steel plate can be threaded is marked with "×" if a threading failure has occurred even once within the same category. The table of whether or not a steel plate can be threaded does not need to be generated only from past operational results data. For example, a table of whether or not a steel plate can be threaded may be generated using a numerical analysis method such as the finite element method for the operational conditions corresponding to each category.

[0032] [Table 1]

[0033] [Method for determining whether a steel plate can be threaded through a straightening machine] Next, a method for determining whether or not a steel plate can be passed through a straightening machine according to this embodiment will be described.

[0034] The threading possibility determination table is stored in a storage device or the like inside the control computer 5. During operation, as shown in FIG. 1, a warpage shape measuring step is performed in which the warpage height and warpage curvature of the front end of the steel sheet S are measured using the warpage shape measuring device 3 before the steel sheet S is loaded into the straightener 1. The warpage shape measuring step can be performed by, for example, the warpage shape measuring device 3 equipped with the imaging unit 3a and the warpage shape analyzing unit 3b as described above. The warpage height and warpage curvature of the front end of the steel sheet S specified in the warpage shape measuring step are sent from the warpage shape measuring device 3 to the control computer 5. The control computer 5 determines whether the steel sheet S can be threaded in the steel sheet manufacturing facility by referring to information on whether the steel sheet S can be threaded in the corresponding section of the threading possibility determination table based on the measured values ​​of the warpage height and warpage curvature of the front end of the steel sheet S acquired from the warpage shape measuring device 3 (threading possibility determination step).

[0035] When one or more operation parameters selected from the thickness, width, length, and weight of the steel plate S, and the charging speed of the steel plate S to the straightener 1 by the conveying device 2 are included as categories in the threading feasibility determination table, these operation parameters are information generated inside the control computer 5 as operation conditions of the steel plate manufacturing equipment, so that the operation parameters for the steel plate S can be acquired. On the other hand, when a planar shape measuring device 4 for measuring the planar shape of the leading end of the steel plate S is provided and the planar shape of the leading end of the steel plate S is included as a category in the threading feasibility determination table, data on the planar shape of the leading end of the steel plate S specified by the planar shape measuring device 4 is sent to the control computer 5. As a result, it is possible to determine whether the steel plate S can be threaded in the steel plate manufacturing equipment by referring to the threading feasibility determination table inside the control computer 5.

[0036] Using the above-mentioned method for determining whether the steel sheet S can be passed through the steel sheet manufacturing equipment, whether the steel sheet S can be passed through the steel sheet manufacturing equipment is determined before the steel sheet S is charged into the straightening machine 1, and if it is determined that the steel sheet S can be passed through (no passing defects), the steel sheet S can be straightened by the straightening machine 1 under the operating conditions previously set by the control computer 5 for the steel sheet manufacturing equipment. On the other hand, if it is determined that the steel sheet S cannot be passed through (there is a passing defect) before the steel sheet S is charged into the straightening machine 1, the operating conditions of the steel sheet manufacturing equipment are reset (resetting step). For example, the operating conditions of the conveying device 2 are reset so as to increase the charging speed of the steel sheet S into the straightening machine 1, which is previously set by the control computer 5. In addition, as described in Patent Document 3, the operating conditions may be reset so as to reduce the amount of pressing of the straightening roll when the front end of the steel sheet S is charged into the straightening machine 1. Such a steel plate straightening method is preferably applied to a hot leveler (hot straightener) arranged between a rolling mill and a cooling device (accelerated cooling device) in a thick plate production line. Since the steel plate S is straightened to a flat shape in the steel plate production equipment, the occurrence of uneven cooling of the steel plate S in the cooling device can be suppressed. In addition, when the steel plate S is loaded into the straightener 1, a decrease in temperature of the steel plate S caused by an increase in the processing time of the steel plate S due to poor plate threading can be suppressed, and an appropriate cooling start temperature can be secured in the cooling equipment, so that the desired material properties can be secured.

[0037] [Model for determining whether strip can be threaded] Next, a model for determining whether or not a strip can be threaded, which is one embodiment of the present invention, will be described with reference to Figs.

[0038] Instead of the above-mentioned threading possibility judgment table, a threading possibility judgment model generated by machine learning may be used to judge whether the steel sheet S can be threaded. Specifically, the threading possibility judgment model learned by machine learning may be used to judge whether the steel sheet S can be threaded through the straightening machine 1, in which the input data includes the warp height and warp curvature of the front end of the steel sheet S measured by the warp shape measuring device 3 before the steel sheet S is charged into the straightening machine 1, and the output data includes information on whether the steel sheet S can be threaded through the straightening machine 1. In addition, the input data preferably includes one or more operation parameters selected from the thickness, width, length, and weight of the steel sheet S, and the charging speed of the steel sheet S into the straightening machine 1 by the conveying device 2. Furthermore, it is preferable to judge whether the steel sheet S can be threaded through the straightening machine 1 using the planar shape of the front end of the steel sheet S measured by the planar shape measuring device 4 before the steel sheet S is charged into the straightening machine 1 as the input data. This is because these input data are correlated with the threading ability of the steel sheet S in the straightening machine 1, as described above.

[0039] The strip threading feasibility determination model can be generated by machine learning using past operation performance data. Fig. 9 is a diagram for explaining a method for generating a strip threading feasibility determination model using machine learning. As shown in Fig. 9, the strip threading feasibility determination model generation unit 11 of this embodiment includes a database unit 11a and a machine learning unit 11b.

[0040] The database unit 11a accumulates the actual data of the warp height and warp curvature of the front end of the steel sheet S measured by the warp shape measuring device 3, and the actual data of the information on whether the steel sheet S can be threaded in the steel sheet manufacturing equipment. The database unit 11a may accumulate the actual data of the operation parameters such as the thickness and width of the steel sheet S, and the actual data of the planar shape (tip crop length) of the front end of the steel sheet S measured by the planar shape measuring device 4, as necessary. In this case, it is preferable to appropriately acquire information stored in the control computer 5 for controlling the operation of the steel sheet manufacturing equipment as the input actual data of the threading possibility judgment model. In addition, a data acquisition unit 12 may be provided to collect the input actual data, and the actual data may be temporarily stored in the data acquisition unit 12, and a data set in which multiple types of actual data are associated may be generated and then accumulated in the database unit 11a. 500 or more data sets are accumulated in the database unit 11a. Preferably, 2000 or more, more preferably 10000 or more. The data accumulated in the database unit 11a may be screened as necessary. This is because measurement errors may occur in the measurement of the warp height and warp curvature by the warp shape measuring device 3, and the accuracy of the judgment model for judging whether or not a strip can be threaded is improved by accumulating highly reliable data. On the other hand, the number of data sets accumulated in the database unit 11a may be set to a certain number as an upper limit, and the data sets accumulated in the database unit 11a may be updated as appropriate within the upper limit.

[0041] The machine learning unit 11b uses the data set accumulated in the database unit 11a to generate a threading suitability judgment model M that predicts the threading suitability information of the steel sheet by machine learning using multiple learning data. The learning data is the actual data of the warp height and warp curvature of the leading end of the steel sheet S as input actual data, and the actual data of the threading suitability information of the steel sheet S as output actual data. The machine learning model for generating the threading suitability judgment model M may be any machine learning model as long as it can obtain sufficient judgment accuracy of the threading suitability information of the steel sheet S for practical use. For example, a commonly used neural network (including deep learning and convolutional neural network, etc.), decision tree learning, random forest, support vector regression, etc. may be used. An ensemble model combining multiple models may also be used. A classification model such as k-nearest neighbor method or logistic regression may also be used. For example, the threading suitability judgment model M can be generated by machine learning using a general neural network as shown in FIG. 10. In addition, the symbols L1, L2, and L3 in FIG. 10 respectively indicate an input layer, an intermediate layer, and an output layer. In particular, when deep learning is used, it is possible to freely select other operational parameters that are correlated with the threading suitability information of steel plate S as inputs without having to consider the problem of multicollinearity, thereby improving the estimation accuracy of the threading suitability judgment of steel plate S. For example, a neural network with two intermediate layers, each with three nodes, and using a sigmoid function as the activation function can be used. It is preferable to use a softmax function in the output layer to output the threading suitability information of steel plate S as a binary classification result.

[0042] The machine learning unit 11b may improve the estimation accuracy of the threading suitability information of the steel sheet S by dividing the data set accumulated in the database unit 11a into training data and test data and performing learning. For example, the machine learning unit 11b may use the training data to learn the weight coefficients of the neural network, and generate the threading suitability judgment model M while appropriately changing the structure of the neural network (the number of intermediate layers and the number of nodes) so that the accuracy rate of the threading suitability information of the steel sheet S in the test data is high. The weight coefficients can be updated using an error propagation method. The threading suitability judgment model M may be updated to a new model by re-learning, for example, every six months or every year. This is because the more data stored in the database unit 11a, the more accurate the prediction of the threading suitability information of the steel sheet S can be. By updating the threading suitability judgment model M based on the latest data, a threading suitability judgment model M that reflects changes in the manufacturing conditions of the steel sheet S to be charged into the steel sheet manufacturing facility can be generated. EXAMPLES

[0043] As an embodiment of the present invention, an example in which the steel plate manufacturing equipment shown in FIG. 1 is arranged as a roller leveler downstream of a reverse rolling mill arranged in a thick plate rolling line will be described. In this embodiment, a warp shape measuring device 3 and a planar shape measuring device 4 are arranged upstream of the roller leveler. These devices take images of the steel plate tip with a CCD camera, and calculate the warp height, warp curvature, and planar shape (tip crop length) of the steel plate tip by image processing. In addition, as operation data of the steel plate manufacturing equipment, the plate thickness, plate length, steel plate temperature when being charged into the straightener 1, and charging speed of the steel plate S were obtained. Then, a plate threading possibility judgment table was generated using operation performance data for about half a year. The plate threading possibility judgment table is divided into 10 categories for each of the seven parameters of the warp height, warp curvature, tip crop length, plate thickness, plate length, steel plate temperature, and charging speed of the steel plate S at the tip, and the category in which a plate threading defect occurred in the past operation is marked as "x", and the category in which a plate threading defect did not occur is marked as "o". The plate threading possibility judgment table was stored in the storage unit of the control computer 5, and the control computer 5 was provided with a plate threading possibility judgment unit inside. Meanwhile, a plate threading possibility judgment model M was generated by machine learning using the neural network shown in FIG. 10, using two intermediate layers and a softmax function in the output layer. As input record data when generating the plate threading possibility judgment model M, seven parameters were used, namely, the warp height at the tip of the steel plate, the warp curvature, the tip crop length, the plate thickness, the plate length, the steel plate temperature, and the charging speed, as in the classification of the plate threading possibility judgment table. In addition, the output record data was set to "plate threading possibility (x)" for a classification in which a plate threading defect occurred in past operations, and "no plate threading defect (o)" for a classification in which a plate threading defect did not occur. The generated plate threading possibility judgment model M was also stored in the storage unit of the control computer 5, and the control computer 5 was provided with a plate threading possibility judgment unit inside.

[0044] Thereafter, during operation, before the steel sheet S was loaded into the straightening machine 1, it was determined whether the steel sheet S could be threaded in the steel sheet manufacturing equipment. However, regardless of the result of the determination as to whether the steel sheet S could be threaded, the operating conditions of the steel sheet manufacturing equipment were not reset, and the steel sheet S was straightened by the straightening machine 1 with the initial settings. In Example 1, the rate of cases in which the steel sheet S was judged to be threadable (no threading defects) using a previously generated threading possibility determination table, but in fact a threading defect occurred in the steel sheet S on the straightening machine 1, was taken as the erroneous determination rate. In Example 2, the erroneous determination rate was also evaluated for the results of the threading possibility determination using the threading possibility determination model M. On the other hand, as a conventional example, the rate of cases in which an operator in charge of the operation of the steel sheet manufacturing equipment visually confirmed the warping state of the steel sheet tip, and the operator judged that the steel sheet S could be threaded, but in fact a threading defect occurred, was evaluated. FIG. 11 shows the results of evaluating the erroneous determination rate for 20,000 steel sheets with a thickness of 20 to 40 mm. 11, it is understood that the erroneous determination rate is lower in Example 1 than in the conventional example. Moreover, it is understood that the erroneous determination rate is further lowered in Example 2.

[0045] Next, the threading feasibility determination model M created in Example 2 was used online to determine whether the steel sheet S can be threaded in a threading feasibility determination step before the steel sheet S was loaded into the straightening machine 1. Then, when it was determined that there was no threading defect (◯), straightening was performed by the straightening machine 1 under the operation conditions previously set by the control computer 5. On the other hand, when it was determined that there was a threading defect (×), the operation conditions of the straightening machine 1 included an increase in the charging speed of the steel sheet S into the straightening machine 1 from the initial setting value, and operation was performed. As a result, as shown in FIG. 12, when the operation conditions of the steel sheet manufacturing equipment were reset (Example), the occurrence rate of material defects (defects in which the mechanical properties of the steel sheet are outside the target range) was lower than when they were not reset (Comparative Example).

[0046] Although the embodiments of the present invention have been described above, the present invention is not limited by the descriptions and drawings that form part of the disclosure of the present invention according to the present embodiments. In other words, other embodiments, examples, and operation techniques, etc., made by those skilled in the art based on the present embodiments are all included in the scope of the present invention. [Explanation of symbols]

[0047] 1 straightening machine 2. Conveyor device 3. Warpage shape measuring device 3a, 4a Imaging unit (area camera) 3b Warp shape analysis section 3c rangefinder 3d speedometer 4 Planar shape measuring device 4b Planar shape analysis section 5 Control computer 11. Strip threading suitability judgment model generation unit 11a Database Section 11b Machine Learning Department 12 Data Acquisition Section M Strip threading judgement model S steel plate

Claims

1. A method for determining whether a steel plate can be passed through a straightener in a steel plate manufacturing facility including a straightener having at least one pair of rolls, a conveying device for feeding a steel plate into the straightener, and a warpage shape measuring device for measuring a warpage shape of a leading end of the steel plate, comprising: a warpage shape measuring step of measuring a warpage height and a warpage curvature of a tip end portion of the steel plate using the warpage shape measuring device before the steel plate is loaded into a straightening machine; a plate threading possibility determination step of determining whether the steel plate can be threaded through the straightener based on the warp height and the warp curvature of the tip portion of the steel plate measured in the warp shape measurement step; Including, The method for determining whether a steel plate can be passed through a straightening machine includes a step of determining whether the steel plate can be passed through the straightening machine based on operational parameters that affect the mass or transport speed of the steel plate when the steel plate is loaded into the straightening machine, selected from the warp height and warp curvature of the tip of the steel plate measured in the warp shape measurement step, as well as the thickness, width, length, and weight of the steel plate, and the loading speed of the steel plate into the straightening machine by the transport device.

2. The steel plate manufacturing facility includes a planar shape measuring device that measures a planar shape of a tip end of the steel plate, 2. The method for determining whether a steel plate can be passed through a straightening machine as described in claim 1, wherein the step of determining whether the steel plate can be passed through the straightening machine further includes a step of determining whether the steel plate can be passed through the straightening machine using the planar shape of the leading end of the steel plate measured using the planar shape measuring device before the steel plate is loaded into the straightening machine.

3. A method for determining whether a steel plate can be passed through the straightener in a manufacturing facility including a straightener having at least one pair of rolls, a conveying device for feeding a steel plate into the straightener, and a warpage shape measuring device for measuring a warpage shape of a leading end of the steel plate, comprising: a step of judging whether the steel plate can be threaded through the straightening machine by using a threading possibility judgment model learned by machine learning, the model including, as input data, a warpage height and a warpage curvature of a front end portion of the steel plate measured by the warpage shape measuring device before the steel plate is loaded into the straightening machine, and output data, information on whether the steel plate can be threaded through the straightening machine; The input data includes, in addition to the warp height and warp curvature at the tip of the steel plate, one or more operational parameters that affect the mass or transport speed of the steel plate when the steel plate is loaded into the straightening machine, selected from the plate thickness, plate width, plate length, and weight of the steel plate, and the loading speed of the steel plate into the straightening machine by the transport device.

4. 4. A method for straightening a steel plate, comprising: using the method for determining whether a steel plate can be passed through a straightening machine according to claim 1 or 3, determining whether the steel plate can be passed through the straightening machine before the steel plate is loaded into the straightening machine; and, if it is determined that the steel plate cannot be passed through, resetting operating conditions of the steel plate manufacturing equipment.

5. A method for manufacturing a steel plate, comprising the step of manufacturing a steel plate using the method for straightening a steel plate according to claim 4.

6. A method for generating a judgment model for determining whether a steel plate can be passed through a straightener in a steel plate manufacturing facility including a straightener having at least one pair of rolls, a conveying device for loading a steel plate into the straightener, and a warpage shape measuring device for measuring a warpage shape of a leading end of the steel plate, the method comprising: a step of acquiring a plurality of learning data, the learning data including, as input record data, a warpage height and a warpage curvature of a front end portion of a steel plate measured by the warpage shape measuring device before the steel plate is loaded into the straightening machine, and output record data including information on whether the steel plate can be threaded through the straightening machine corresponding to the input record data, and generating the threading possibility judgment model by machine learning using the acquired plurality of learning data; The input actual data includes, in addition to the warp height and warp curvature at the tip of the steel plate, one or more operational parameters that affect the mass or transport speed of the steel plate when the steel plate is loaded into the straightening machine, selected from the thickness, width, length, and weight of the steel plate, and the loading speed of the steel plate into the straightening machine by the transport device.

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