Method for measuring shape of plate-shaped object, method for rolling plate-shaped object, method for manufacturing plate-shaped object, device for measuring shape of plate-shaped object, and facility for manufacturing plate-

Abstract

To provide a shape measuring method of a plate-like object, a rolling method of the plate-like object, a manufacturing method of the plate-like object, a shape measuring device of the plate-like object, and a manufacturing facility of the plate-like object capable of easily measuring a shape of the whole width of the plate-like object during hot rolling or immediately after the hot rolling by using a simple device.SOLUTION: In the shape measurement method for a plate-shaped object, the inclination angle is estimated from the luminance distribution of the heat radiation light emitted from the surface of the plate-shaped object based on the relationship between the inclination angle of the surface of the plate-shaped object obtained from the image of the side surface of the plate-shaped object and the luminance distribution obtained from the image of the heat radiation light emitted from the surface of the plate-shaped object including the side surface, which are obtained in advance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the shape of a plate-like object, a method for rolling a plate-like object, a method for manufacturing a plate-like object, an apparatus for measuring the shape of a plate-like object, and a manufacturing facility for a plate-like object. [Background technology]

[0002] Heavy plates such as steel plates are manufactured by hot rolling steel materials such as slabs. During the hot rolling process, the steel plate can buckle and lose its planar shape due to factors such as deflection of the rolling mill when a rolling load is applied, changes in plate crown (thickness deviation in the steel plate width direction) caused by work roll bending pressure, and impacts when the leading and trailing edges of the steel plate collide with the table rolls during transportation.

[0003] As a means for eliminating distortions generated after rolling, straightening treatments such as a hot / cold leveller straightener or a press straightener are often carried out. Furthermore, for example, Patent Documents 1 and 2 disclose techniques for optically measuring the shape of a steel plate and reflecting the results in straightening treatments such as pressing.

[0004] Furthermore, Patent Documents 3 to 6 disclose techniques for measuring or predicting the strain state of a steel sheet during rolling and feeding back the results to control the strain shape of the steel sheet during rolling or the steel sheet to be rolled next. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-237546 [Patent Document 2] Patent Publication No. 2021-18160 [Patent Document 3] Japanese Patent Application Publication No. 6-15321 [Patent Document 4] Japanese Patent Application Publication No. 10-5868 [Patent Document 5] Japanese Patent Application Laid-Open No. 2003-334604 [Patent Document 6] Japanese Patent Application Laid-Open No. 2016-65863 Summary of the Invention [Problem to be solved by the invention]

[0006] In the techniques disclosed in Patent Documents 1 and 2, the steel sheet is straightened in a cold state, which limits the straightening capacity and takes time. Therefore, it is desirable to eliminate distortion as much as possible in hot straightening during or after rolling, and to simplify or eliminate the cold straightening process.

[0007] When hot leveling is performed during or after rolling, the distortion shape of the steel plate is easily affected by the wear state of the work rolls and thermal expansion. Therefore, it is necessary to measure the distortion shape of the steel plate after rolling and adjust the rolling conditions for the next pass or later, or to measure the distortion shape of the steel plate during rolling and adjust the rolling conditions for the next pass or later.

[0008] Patent Documents 3 and 4 disclose methods for adjusting the rolling conditions for subsequent steel sheets based on the results of measuring the distortion shape of steel sheets cooled after rolling. However, for example, Patent Document 3 targets only edge elongation due to temperature deviation in the width direction, and does not target web elongation (center elongation). Furthermore, Patent Document 4 targets water-cooled controlled steel sheets, but in actual operation, there are a certain proportion of steel sheets in which temperature control is performed by air cooling only, or in which controlled cooling is not performed, and it is not possible to control the distortion state of these steel sheets.

[0009] Patent Documents 5 and 6 disclose methods for measuring the distortion or warpage of a steel sheet in a high-temperature state, regardless of the cooling conditions of the steel sheet, and feeding the results back to the rolling conditions. However, the methods disclosed in Patent Documents 5 and 6 each have problems, such as being unable to measure the shape at the width center, and although they can measure the shape across the entire width, they require a large-scale optical device, which is costly.

[0010] The present invention has been made in consideration of the above, and aims to provide a method for measuring the shape of a plate-like object, a method for rolling a plate-like object, a method for manufacturing a plate-like object, an apparatus for measuring the shape of a plate-like object, and equipment for manufacturing a plate-like object, which can easily measure the shape of the entire width of a plate-like object during hot rolling or immediately after hot rolling using a simple device. [Means for solving the problem]

[0011] (1) A method for measuring the shape of a plate-like object according to the present invention includes: based on a relationship between a previously determined inclination angle of the surface of the plate-like object obtained from an image of the side surface of the plate-like object and a luminance distribution obtained from an image of thermal radiation light emitted from the surface of the plate-like object including the side surface, The tilt angle is estimated from the luminance distribution of thermal radiation light emitted from the surface of the plate-like object.

[0012] (2) The method for measuring the shape of a plate-like object according to the present invention is the method for measuring the shape of a plate-like object described in (1) above, in which the optical axis of an imager that captures the thermal radiation light emitted from the surface of the plate-like object is set at an angle of less than 70° with respect to the normal direction of the surface of the plate-like object.

[0013] (3) A method for rolling a plate-like object according to the present invention includes the steps of measuring the shape of the plate-like object by the method for measuring the shape of the plate-like object described in (1) or (2) above; setting rolling conditions for the next pass of the plate-like object or for the plate-like object to be rolled next based on the measured shape of the plate-like object; Includes.

[0014] (4) The method for rolling a plate-like object according to the present invention is the method for rolling a plate-like object described in (3) above, wherein the rolling conditions are one or more of the total number of passes, the reduction amount, the rolling load, the rotational speeds of the upper and lower work rolls, the bending pressure of the upper and lower work rolls, and the shift amount of the upper and lower work rolls.

[0015] (5) A method for producing a plate-like object according to the present invention includes the method for rolling a plate-like object described in (3) or (4) above.

[0016] (6) The shape measuring device for a plate-like object according to the present invention is an imager that captures an image of thermal radiation light emitted from the surface of the plate-like object; a database storing information relating to a relationship between a previously determined tilt angle of the surface of a plate-like object obtained from an image of the side surface of the plate-like object and a luminance distribution obtained from an image of thermal radiation light emitted from the surface of the plate-like object including the side surface; an image processing device that estimates the inclination angle from the luminance distribution of the surface of the plate-like object captured by the image capture device, based on information relating to the relationship between the inclination angle of the surface of the plate-like object and the luminance distribution of the surface of the plate-like object; Equipped with.

[0017] (7) The shape measuring device for a plate-like object according to the present invention is the shape measuring device for a plate-like object described in (6) above, wherein the optical axis of the imaging device is set at an angle of less than 70° with respect to the normal direction of the surface of the plate-like object.

[0018] (8) A manufacturing facility for a plate-like object according to the present invention includes the shape measuring device for a plate-like object according to (6) or (7) above. [Effects of the Invention]

[0019] According to the method for measuring the shape of a plate-like object, the method for rolling a plate-like object, the method for manufacturing a plate-like object, the device for measuring the shape of a plate-like object, and the manufacturing equipment for a plate-like object of the present invention, the shape of the entire width of a plate-like object during or immediately after hot rolling can be easily measured using simple equipment without introducing large-scale equipment. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an apparatus for measuring the shape of a plate-like object according to an embodiment of the present invention. [Figure 2]FIG. 2 is a schematic diagram showing an example of the light-receiving angle and measurement range of an image pickup device of an apparatus for measuring the shape of a plate-like object according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing an example of the light-receiving angles and measurement ranges of two image sensors of an apparatus for measuring the shape of a plate-like object according to an embodiment of the present invention. [Figure 4] Figure 4 is an example of an apparatus configuration when creating tilt angle / brightness distribution information, and is a schematic diagram showing an example of the field of view of an imager and an example of measurement points for the brightness of thermal radiation light emitted from the surface of a steel plate. [Figure 5] Figure 5 is an example of an apparatus configuration when creating tilt angle / brightness distribution information, and is a schematic diagram showing an example of the field of view of an imager and an example of measurement points for the brightness of thermal radiation light emitted from the side surface of a steel plate. [Figure 6] FIG. 6 is a flowchart illustrating a procedure for creating tilt angle / luminance distribution information. [Figure 7] FIG. 7 is a graph showing an example in which the brightness value of point A in FIG. 4 is acquired for each of a plurality of images captured by the imaging device and plotted against the distance in the longitudinal direction of the steel plate. [Figure 8] FIG. 8 is a diagram showing an example of an image of the side surface of a steel plate captured by an imaging device. [Figure 9] FIG. 9 is a diagram showing an example of an image (binarized image) obtained by performing binarization processing on the image of FIG. [Figure 10] FIG. 10 is a diagram showing an example of coordinates of the contour of the surface (upper surface) of the steel plate, obtained by performing labeling processing on the image of FIG. [Figure 11] FIG. 11 is a schematic diagram for explaining how to determine the inclination angle θ of the steel sheet surface. [Figure 12] FIG. 12 is a graph showing an example in which the tilt angle θ of the steel plate surface at the same point as point A in FIG. 4 is obtained for each of multiple images captured by an imaging device and plotted against the distance in the longitudinal direction of the steel plate. [Figure 13] FIG. 13 shows FIGS. 7 and 12 on the same graph. [Figure 14]FIG. 14 is a graph showing the correlation between the brightness value obtained in FIG. 13 and the inclination angle θ of the steel sheet surface. DETAILED DESCRIPTION OF THE INVENTION

[0021] A method for measuring the shape of a plate-like object, a rolling method for a plate-like object, a manufacturing method for a plate-like object, a shape measuring device for a plate-like object, and a manufacturing facility for a plate-like object according to embodiments of the present invention will be described with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by a person skilled in the art, or those that are substantially identical.

[0022] (shape measuring device) The configuration of an apparatus for measuring the shape of a plate-like object according to an embodiment will be described with reference to FIGS.

[0023] The shape measuring device according to the embodiment is a device for measuring the shape (shape distortion) of a plate-like object. Specifically, the shape measuring device measures the tilt angle (amount of shape distortion) of the surface of the plate-like object. The following description will be given assuming that the shape measuring device is used to measure the shape of a high-temperature plate-like object during hot rolling or immediately after hot rolling. The following description will be given assuming that the plate-like object to be measured is a steel plate. Note that the plate-like object may be a strip-shaped steel strip in addition to a steel plate.

[0024] As shown in FIG. 1, the shape measuring device according to the embodiment includes an imaging device 1, an image processing device 2, a database 3, a process computer 4, and a rolling mill 5.

[0025] The imaging device 1 captures an image of thermal radiation light emitted from the surface of the steel sheet S during or immediately after hot rolling (hereinafter referred to as "steel sheet surface"), that is, the imaging device 1 captures an image of the luminance distribution of the steel sheet surface.

[0026] As the imager 1, it is preferable to use an industrial camera or the like that is sensitive to the infrared region of wavelengths of 800 nm or more, has high resolution, and allows for flexible control of the exposure time and frame rate, rather than a digital camera or the like that is commercially available to the general public. Furthermore, it is preferable to install the imager 1 in a position as close as possible to the conveyance direction of the steel sheet S. Furthermore, it is preferable to set the optical axis of the imager 1 at an angle of 70° or more with respect to the normal direction of the steel sheet surface. Details of the installation angle of the imager 1 will be described later (see Figures 2 and 3).

[0027] The image processing device 2 is realized by, for example, a general-purpose computer such as a workstation or a personal computer, or a server located on the cloud. The image processing device 2 acquires from the imager 1 an image of thermal radiation light of the steel plate surface captured by the imager 1. The image processing device 2 also acquires from the database 3 information relating to the relationship, which has been calculated in advance, between the tilt angle of the steel plate surface obtained from the image of the side surface of the steel plate S and the luminance distribution obtained from the image of thermal radiation light emitted from the steel plate surface including the side surface.

[0028] Then, the image processing device 2 estimates the inclination angle of the steel plate surface from the brightness distribution of the thermal radiation light on the steel plate surface contained in the image acquired from the imaging device 1, based on the relationship between the inclination angle of the steel plate surface and the brightness distribution on the steel plate surface.

[0029] Information relating to the relationship between the tilt angle of the steel sheet surface and the luminance distribution of the steel sheet surface (hereinafter referred to as "tilt angle / luminance distribution information") is stored in the database 3. A method for creating the tilt angle / luminance distribution information will be described later in detail.

[0030] The process computer 4 feeds back the inclination angle of the steel sheet surface estimated by the image processing device 2 to the rolling control of the rolling mill 5. That is, the process computer 4 sets the rolling conditions for the next pass of the steel sheet S and thereafter, or the rolling conditions for the steel sheet S to be rolled next, based on the inclination angle of the steel sheet surface estimated by the image processing device 2. The rolling mill 5 rolls the steel sheet S based on the information (rolling conditions) fed back from the process computer 4.

[0031] (Installation angle of imager 1) The relationship between the tilt angle of the steel plate surface and the luminance distribution on the steel plate surface is derived from the relationship between the acceptance angle φ of the image sensor 1 and the luminance (radiance) of the thermal radiation light on the steel plate surface. It has been experimentally and theoretically proven that there is a linear relationship between the acceptance angle φ and the luminance of the thermal radiation light on the steel plate surface within a limited range. While this result is expected to vary depending on the physical properties of the object being measured and the measurement conditions, it is an undeniable fact that the luminance becomes more constant as the acceptance angle φ of the image sensor 1 approaches the normal direction of the object being measured. The acceptance angle φ is the angle of the optical axis of the image sensor 1 relative to the normal direction of the steel plate surface. As an example, Figure 2 shows a case where the steel plate is horizontal, i.e., the steel plate surface is the steel plate reference plane. In this invention, the reference plane of the steel plate S is also simply referred to as the steel plate reference plane. This is the reference plane along which the steel plate is placed or transported on a conveying line, the so-called pass line, and is usually a horizontal plane.

[0032] For this reason, in order to ensure that the light-receiving angle φ is a condition for accurately calculating the brightness, it is preferable to set the optical axis of the imager 1 at 70° or more with respect to the normal to the steel sheet S at the measurement position. On the other hand, if the light-receiving angle φ is set to 70° or more with respect to the reference surface of the steel sheet S, the measurement range of the imager 1 will be limited.

[0033] The measurement range refers to the measurable angle, among the angles formed by the steel plate reference surface and the optical axis of the imager 1 with respect to the set light-receiving angle φ, that satisfies the condition for the angular range measurable by the imager 1. The minimum measurable angle is 0°, that is, the state in which the tangent to the measurement point on the steel plate surface and the optical axis of the imager 1 are parallel. The maximum measurable angle is the angle θ formed by the tangent to the measurement point on the steel plate surface and the optical axis of the imager 1, which satisfies a linear relationship with the brightness of the thermal radiation light on the steel plate surface, and is also expressed as θmax. For example, the case in which θmax = 20°, i.e., the measurable angle is 0 to 20°, will be explained below.

[0034] In this case, as shown in Fig. 2, if the light-receiving angle φ is set to 80°, it is only possible to measure shape distortion in a state where there is no shape distortion (=0°), that is, shape distortion in the range of -10 to 10° relative to the steel sheet reference surface. In actual cases, the shape distortion of the steel sheet S may be 10° or more relative to the steel sheet reference surface, in which case the shape distortion cannot be measured. Therefore, the shape measuring device according to this embodiment solves this problem by the following (1) or (2).

[0035] (1) Addition of imaging equipment Simply put, to measure large-angle shape distortion, it is necessary to change the acceptance angle φ of the image sensor 1. However, since large and small shape distortions may coexist even within the same steel sheet S, for example, if the amount of shape distortion of the steel sheet S being measured is large, adjustments such as increasing the acceptance angle φ of the image sensor 1 during measurement to match this should not be made. Therefore, this problem can be solved by adding another image sensor 6 with a different acceptance angle φ from that of the image sensor 1, as shown in Figure 3, for example.

[0036] For example, by using imager 1, which has a light-receiving angle of 80°, and imager 6, which has a light-receiving angle of 60°, it becomes possible to measure shape distortion in the range of 10 to 30° with respect to the steel plate reference surface. Imager 6 is a camera with the same specifications as imager 1, and has a measurement range of 0 to 20°. The light-receiving angle φ of imager 6 is set to a shallower angle than the light-receiving angle φ of imager 1, i.e., less than 70°.

[0037] In this method, if the tilt angle (amount of shape distortion) of the steel sheet surface is large, the angle becomes negative, making measurement difficult. However, because the shape distortion of steel sheet S can be approximated as a sine wave, if the positive side shape distortion can be measured, it is possible to estimate the negative side shape distortion to some extent.

[0038] (2) Adding brightness extraction points Instead of increasing the number of image sensors as in (1) above, it is also possible to artificially change the measurement range by, for example, adding a point (brightness extraction point) from which brightness is extracted within an image captured by a single image sensor 1. That is, the measurement range is artificially changed by changing the measurement position on the steel plate S within the angle of view of the image sensor 1. In this case, it is necessary to adjust the exposure time of the image sensor 1 in order to extract brightness from two points at different positions within the same image.

[0039] It should be noted that for (1) and (2) above, the optical conditions change in order to change the measurement range, so the same "tilt angle / luminance distribution information" stored in database 3 cannot be reused. In this case, by determining the "tilt angle / luminance distribution information" according to the light-receiving angle φ, it is possible to address the above (1) and (2).

[0040] (How to create tilt angle / brightness distribution information) To create the tilt angle / brightness distribution information, it is necessary to know the relationship between the tilt angle of the steel plate surface and the brightness distribution. The brightness distribution of the steel plate surface can be obtained from the image captured by imager 1. The tilt angle of the steel plate surface must be obtained using a cold flatness meter or another imager that captures the side of the steel plate S from directly beside it.

[0041] The relationship between the tilt angle of the steel plate surface and the luminance distribution is highly dependent on optical conditions such as the distance between the imager 1 and the steel plate S and the light-receiving angle φ of the imager 1. Images captured of the thermal radiation light from the steel plate S show all or part of the steel plate S, but when calculating the tilt angle from the luminance distribution using the above-mentioned "tilt angle / luminance distribution information," it is necessary to adjust the conversion formula appropriately for each optical condition at each point on the steel plate surface. In addition, the optical conditions are fixed by determining a single point in the image from which luminance is extracted, and the luminance, which changes as the steel plate S is transported, is extracted for each image.

[0042] There is no need to explain the method for determining the brightness distribution from an image, but it is necessary to set the exposure time appropriately so that the pixel information does not exceed the upper or lower limit of what can be expressed (to prevent whiteout and blackout). Because the amount of thermal radiation light from the steel sheet S is highly dependent on the temperature of the steel sheet S, the exposure time needs to be adjusted each time depending on the temperature of the object to be imaged, but the exposure time can be set appropriately by receiving temperature information of the steel sheet S in advance from the process computer 4, for example.

[0043] 4 and 5 show an example of an apparatus configuration when creating tilt angle / brightness distribution information. When creating tilt angle / brightness distribution information, for example, another imager 7 is used in addition to imager 1. These imagers 1 and 7 are both connected to an image processing device 2. Note that FIG. 4 is a view of the steel sheet S as seen from the upstream side of the conveying line, and FIG. 5 is a view of the imager 7 as seen from behind.

[0044] As described above, the imager 1 captures an image of thermal radiation light emitted from the surface of the steel sheet during hot rolling or immediately after hot rolling.

[0045] The imager 7 captures an image of the side surface (edge ​​portion) of the steel sheet S during transportation in synchronization with the imager 1 capturing an image of the thermal radiation light of the steel sheet S. As shown in Fig. 5, the imager 7 is installed at an angle that is perpendicular and horizontal to the side surface of the steel sheet S. In other words, the imager 7 is placed almost directly to the side of the steel sheet S during transportation.

[0046] Imager 7 captures an image of the side (edge) of the steel plate S during transport at the same time that imager 1 captures an image of the thermal radiation light of the steel plate S. As shown in FIG. 5, imager 7 is installed at an angle that is perpendicular and horizontal to the side of the steel plate S. In other words, imager 7 is placed almost directly to the side of the steel plate S during transport. Furthermore, imager 7 captures images in synchronization with imager 1. The synchronization of images only requires that the images be captured at substantially the same time. "Substantially the same time" means that slight deviations that occur due to differences in the operating characteristics of imager 1 and imager 7 are allowed.

[0047] The field of view of the imager 7 is set to a field of view that includes the measurement point (point A) on the side surface of the steel sheet S, as shown in Fig. 5, for example. In other words, the field of view of the imager 7 is set to always include the measurement point (point A) on the side surface of the steel sheet S that is included in the field of view of the imager 1. In this way, by including the same measurement point in the field of view of the imager 7 and the field of view of the imager 1, it becomes possible to associate the respective images captured at the same timing.

[0048] The image processing device 2 acquires the luminance values ​​of thermal radiation light at a plurality of measurement points (e.g., points A, B, and C in FIG. 4) on the surface of the steel plate S from the image captured by the image capture device 1. Next, the image processing device 2 acquires the inclination angle θ of the surface of the steel plate S at a measurement point (e.g., point A) on the side of the steel plate S among the plurality of measurement points (e.g., points A, B, and C) from the image captured by the image capture device 7.

[0049] Next, the image processing device 2 uses the brightness values ​​acquired as described above and the tilt angle θ acquired as described above to calculate a calibration curve (correction coefficients) that converts brightness values ​​into tilt angle θ. Then, the image processing device 2 converts brightness values ​​at other measurement points (for example, point B and point C) into tilt angle θ.

[0050] 6 shows an example of the flow of a method for creating tilt angle / brightness distribution information. Note that the tilt angle / brightness distribution information may be created in advance before measuring the tilt angle of the steel sheet surface using the shape measuring device according to this embodiment.

[0051] The method of creating the tilt angle / luminance distribution information includes a luminance value acquisition step (steps S1 to S3), an angle acquisition step (steps S4 to S7), and a correction step (steps S8 and S9), as shown in Fig. 6. The luminance value acquisition step and the angle acquisition step may be performed in parallel. Alternatively, the angle acquisition step may be performed first, followed by the luminance value acquisition step.

[0052] <Brightness value acquisition step> In this step, first, the surface of the steel sheet S being transported is imaged at a predetermined frame rate by the imager 1, thereby capturing images corresponding to changes in the distance in the longitudinal direction of the steel sheet S (step S1). The acquired images are stored and accumulated in a predetermined memory area (not shown). The frame rate (the time interval between images) when capturing images by the imager 1 is preferably determined taking into consideration, for example, the pitch of the expected shape distortion of the steel sheet S and the transport speed of the steel sheet S. Furthermore, the frame rate is preferably set so as to include at least the darkest and brightest parts for one shape distortion.

[0053] The section of the steel sheet surface imaged in step S1 may be the entire length of the steel sheet S, or may be limited to a specific section on the steel sheet surface. The images captured in step S1 are stored in, for example, a storage area of ​​the image processing device 2.

[0054] Next, the image processing device 2 sets a plurality of measurement points, including a measurement point (point A) on the side surface of the steel plate S, in the image acquired in step S1 (step S2). In step S2, a plurality of measurement points are set, such as points A, B, and C shown in FIG. 4. Also, in step S2, a measurement point is always set at the same location as the measurement point (point A) corresponding to the side surface of the steel plate S imaged by the imager 7 in step S4, which will be described later. This is because, in the correction steps (steps S8 and S9), which will be described later, the brightness value acquired at point A is used to perform correction processing on the other points B and C.

[0055] Point A, which is always set as a measurement point in step S2, may be a fixed coordinate, for example, as long as the side surface of the steel sheet S always passes through the same point in the width direction of the steel sheet S. Furthermore, if the side surface of the steel sheet S varies in the width direction, the coordinates of the side surface of the steel sheet S may be detected and point A may be determined based on those coordinates. Furthermore, it is preferable to set multiple other measurement points in the width direction, such as points B and C shown in Figure 4, by adjusting the distance between point A and the steel sheet S in the longitudinal direction. In other words, it is preferable to set the multiple measurement points set in step S2 so that they are aligned in the width direction of the steel sheet S. Note that the number of measurement points is not limited to three, points A, B, and C, and four or more points may be set.

[0056] Next, the image processing device 2 acquires a brightness value for each measurement point for each image captured by the image capture device 1, and creates a graph showing the change in brightness value (brightness distribution) with respect to the distance of the steel plate S based on the frame rate of the image capture device 1 and the conveying speed of the steel plate S (step S3). The graph created in step S3 for point A on the steel plate S (see FIG. 4) is shown in FIG. 7.

[0057] In Fig. 7, the vertical axis represents the brightness value, and the horizontal axis represents the distance in the longitudinal direction of the steel sheet S. The graph in Fig. 7 was created from images of the steel sheet S being transported at approximately 3.6 m / sec, captured at a frame rate of 20 Hz. Therefore, brightness values ​​were acquired at 180 mm intervals in the transport direction of the steel sheet S.

[0058] Furthermore, Figure 7 confirms that the brightness value changes like a wave in response to changes in the longitudinal distance of the steel plate S. This brightness change is thought to indicate the distortion shape of the steel plate S, but since it is extremely difficult to quantify the shape distortion using only this value, it is compared with the true value. Therefore, as will be described later, we investigated a method for determining a correction coefficient for converting the brightness value into the inclination angle θ of the steel plate surface by obtaining the true value of the inclination angle θ of the steel plate surface at point A based on the image captured by the imager 7.

[0059] <Angle acquisition step> In this step, first, the side of the steel sheet S being transported is imaged by the imager 7 at a predetermined frame rate, thereby capturing images corresponding to changes in the longitudinal distance of the steel sheet S (step S4). The captured images are stored and accumulated in a predetermined storage area (not shown). The frame rate and image capturing timing when capturing images by the imager 7 are synchronized with those of the imager 1. This makes it possible to capture images corresponding to the same longitudinal distance of the steel sheet S.

[0060] The section of the side surface of the steel sheet S imaged in step S4 may be the entire length of the steel sheet S, or may be limited to a specific section of the side surface of the steel sheet S. The images captured in step S4 are stored, for example, in a memory area of ​​the image processing device 2. An example of an image acquired in step S4 is shown in FIG. 8. In FIG. 8, the side surface of the steel sheet S can be seen, but because the steel sheet S is distorted downward, the brightness of the thermal radiation light emitted from the surface of the steel sheet is also captured. Note that in FIG. 8, the conveying rolls are visible below the steel sheet S.

[0061] Next, the image processing device 2 binarizes the image acquired in step S4 (step S5). In step S5, focusing on the fact that the surface of the steel sheet is imaged brighter than the side surface, a threshold value is determined from the brightness value of the side surface of the steel sheet S, and binarization is performed. In step S5, the image (binarized image) obtained by binarizing the image of FIG. 8 is shown in FIG. 9. In the binarized image shown in FIG. 9, it can be seen that the portion corresponding to the steel sheet surface has been removed and the upper contour of the side surface of the steel sheet S has been clearly extracted, compared to the image of FIG. 7 before binarization processing. This binarization processing in step S5 is performed on all images captured in step S4.

[0062] Next, the image processing device 2 performs a labeling process on the binarized image created in step S5 to extract the contour shape of the steel plate surface (step S6). The contour shape of the steel plate surface (top surface of the steel plate S) extracted in step S6 from the binarized image of Fig. 9 is shown in Fig. 10. In Fig. 10, the vertical axis represents height, and the horizontal axis represents the distance in the longitudinal direction of the steel plate S. This contour shape extraction process in step S6 is performed on all images captured in step S4.

[0063] Next, the image processing device 2 calculates the angle θ (hereinafter referred to as the "inclination angle") between the tangent at point A and the horizontal plane in the contour shape of the steel plate surface, and creates a graph showing the change in the inclination angle θ with respect to the distance of the steel plate S (step S7).

[0064] The inclination angle θ of the steel plate surface is the angle between the horizontal plane and a tangent corresponding to the inclination of the steel plate surface at the same point as point A imaged by the imager 1, as shown in Fig. 11. Also, as shown in Fig. 11, the inclination angle θ of the steel plate surface is always the angle on the tail end side of the steel plate S, with point A as the reference, when viewed perpendicularly to the conveyance direction of the steel plate S. In this case, the inclination angle θ of the steel plate surface takes a positive value when it is inclined above the horizontal plane, and takes a negative value when it is inclined below the horizontal plane.

[0065] The image processing device 2 creates a graph in which the vertical axis represents the inclination angle θ of the steel sheet surface at point A and the horizontal axis represents the longitudinal distance of the steel sheet S, based on the order in which the images are captured, the frame rate of the image capture device 7, and the conveying speed of the steel sheet S. An example of the graph created in step S7 is shown in Fig. 12.

[0066] Since the imaging timing of the imaging device 7 is the same as that of the imaging device 1, the horizontal axis of Fig. 12 is the same as the horizontal axis of Fig. 7. In Fig. 12, the positive and negative expressions for the tilt angle θ of the steel plate S are expressed as positive on the side where the steel plate S is raised toward the imaging device 1 and negative on the side where it is laid back.

[0067] 7 and 12 are plotted on a two-axis graph in Fig. 13. As shown in Fig. 13, it can be seen that the brightness value obtained by imager 1 and the tilt angle θ of the steel plate surface obtained by imager 7 follow the same trend over time. Therefore, when the relationship between the brightness value and the tilt angle θ was plotted as a correlation diagram, Fig. 14 was obtained.

[0068] The correlation coefficient between the brightness value obtained at point A in Figure 14 and the inclination angle θ of the steel plate surface is 0.9, indicating a strong positive correlation. Therefore, in the subsequent correction step, the brightness value of the measurement point obtained by the imager 1 is corrected as the inclination angle θ of the steel plate surface.

[0069] <Correction step> In the correction step, the image processing device 2 first creates a calibration curve for converting the brightness value to the tilt angle θ from the relationship between the brightness value at point A obtained in Figure 14 and the tilt angle θ, using, for example, the least squares method (step S8).

[0070] In step S8, when creating the calibration curve, the reliability of the calibration curve can be taken into consideration by, for example, calculating a correlation coefficient and setting a threshold value. If the value falls below the specified threshold value, the data may be regarded as unreliable, or by outputting the data externally, it is possible to detect that there is a defect in the acquisition of the brightness value at point A, the tilt angle θ of the steel sheet surface, or both.

[0071] Next, the image processing device 2 converts the brightness values ​​into tilt angle θ by applying the calibration curve as a correction coefficient to measurement points other than point A (for example, points B and C) (step S9). This corrects the graph for measurement points other than point A created in step S3 and makes it possible to convert it into a graph of the tilt angle θ of the steel sheet surface versus the longitudinal distance of the steel sheet S, as shown in Fig. 12. As a result, it becomes possible to quantify the shape distortion of the steel sheet S based on the relationship between the longitudinal distance of the steel sheet S and the tilt angle θ of the steel sheet surface.

[0072] In the method for measuring the shape of a plate-like object according to the embodiment, the inclination angle of the steel plate S is estimated from the brightness distribution of the thermal radiation light emitted from the surface of the steel plate S based on the inclination angle / brightness distribution information obtained in advance, as described above.

[0073] (Plate-shaped object manufacturing equipment) The shape measuring device for plate-like objects according to the embodiment can also be applied to a manufacturing facility for plate-like objects. In this case, the manufacturing facility for plate-like objects is configured to include the shape measuring device for plate-like objects. In the manufacturing facility for plate-like objects according to the embodiment, the shape measuring device can quantify the actual amount of shape distortion from the luminance value of the thermal radiation light of the plate-like object with a low-cost and simple configuration. Therefore, the plate-like object can be manufactured by efficiently performing correction using a leveler, press, or the like on the plate-like object according to the actual amount of shape distortion.

[0074] (Method for rolling plate-shaped objects) The method for measuring the shape of a plate-like object according to the embodiment can also be applied to a method for rolling a plate-like object. In this case, the method for rolling a plate-like object includes the steps of measuring the shape of the plate-like object using the method for measuring the shape of the plate-like object, and setting (changing) rolling conditions for the next pass of the plate-like object or for the plate-like object to be rolled next, based on the measured shape of the plate-like object.

[0075] The rolling conditions include, for example, one or more of the total number of passes, the reduction, the rolling load, the rotational speeds of the upper and lower work rolls, the bending pressure of the upper and lower work rolls, and the shift amount of the upper and lower work rolls. Furthermore, in the method for rolling a plate-like object, the conditions for controlled cooling by water cooling, such as the flow rate, and the reduction amount of the hot leveler, may be changed based on the results of measuring the shape after rolling. The conditions for controlled cooling, such as the flow rate, and the reduction amount of the hot leveler, may be changed.

[0076] In the rolling method for a plate-like object according to the embodiment, the shape measurement method can reflect and quantify the actual amount of shape distortion from the brightness value of the thermal radiation light of the plate-like object, so that the rolling conditions for the plate-like object can be optimally set with a low-cost and simple configuration.

[0077] (Method of manufacturing a plate-shaped object) The rolling method for a plate-like object according to the embodiment can also be applied to a method for manufacturing a plate-like object. In this case, the method for manufacturing a plate-like object includes a rolling method for a plate-like object. In the method for manufacturing a plate-like object according to the embodiment, the shape measurement method can quantify the actual amount of shape distortion from the luminance value of the thermal radiation light of the plate-like object, reflecting the actual amount of shape distortion. Therefore, the plate-like object can be manufactured by efficiently performing correction using a leveler, a press, or the like on the plate-like object according to the actual amount of shape distortion.

[0078] According to the above-described embodiments of the method for measuring the shape of a plate-like object, the method for rolling a plate-like object, the method for manufacturing a plate-like object, the device for measuring the shape of a plate-like object, and the manufacturing equipment for a plate-like object, the shape of the entire width of a plate-like object during or immediately after hot rolling can be easily measured using a simple device without introducing large-scale equipment.

[0079] The method for measuring the shape of a plate-like object, the method for rolling a plate-like object, the method for manufacturing a plate-like object, the shape measuring device for a plate-like object, and the manufacturing equipment for a plate-like object according to the present invention have been specifically described above using the preferred embodiment and examples for carrying out the invention, but the scope of the present invention is not limited to these descriptions and should be broadly interpreted based on the claims. Furthermore, it goes without saying that various changes and modifications based on these descriptions are also included in the scope of the present invention. [Explanation of symbols]

[0080] 1,6,7 Imager 2. Image processing device 3 Database 4 Process Computer 5. Rolling Mill S steel plate

Claims

1. based on a relationship between a previously determined inclination angle of the surface of the plate-like object obtained from an image of the side surface of the plate-like object and a luminance distribution obtained from an image of thermal radiation light emitted from the surface of the plate-like object including the side surface, A method for measuring the shape of a plate-like object, which estimates the tilt angle from the brightness distribution of thermal radiation light emitted from the surface of the plate-like object.

2. A method for measuring the shape of a plate-like object as described in claim 1, wherein the optical axis of an imager that captures the thermal radiation light emitted from the surface of the plate-like object is set at an angle of less than 70° with respect to the normal direction of the surface of the plate-like object.

3. a step of measuring the shape of the plate-like object by the method for measuring the shape of the plate-like object according to claim 1 or 2; setting rolling conditions for the next pass of the plate-like object or for the plate-like object to be rolled next based on the measured shape of the plate-like object; A method for rolling a plate-like object, comprising:

4. 4. The method for rolling a plate-like object according to claim 3, wherein the rolling conditions are one or more of the total number of passes, the reduction amount, the rolling load, the rotational speeds of the upper and lower work rolls, the bender pressure of the upper and lower work rolls, and the shift amount of the upper and lower work rolls.

5. A method for manufacturing a plate-like object, comprising the method for rolling a plate-like object according to claim 3 or 4.

6. an imager that captures an image of thermal radiation light emitted from the surface of the plate-like object; a database storing information relating to a relationship between a previously determined tilt angle of the surface of a plate-like object obtained from an image of the side surface of the plate-like object and a luminance distribution obtained from an image of thermal radiation light emitted from the surface of the plate-like object including the side surface; an image processing device that estimates the inclination angle from the luminance distribution of the surface of the plate-like object captured by the image capture device, based on information relating to the relationship between the inclination angle of the surface of the plate-like object and the luminance distribution of the surface of the plate-like object; A shape measuring device for a plate-like object comprising:

7. 7. The apparatus for measuring the shape of a plate-like object according to claim 6, wherein the optical axis of the image pickup device is set at an angle of less than 70 degrees with respect to the normal direction of the surface of the plate-like object.

8. A manufacturing facility for plate-like objects, comprising the apparatus for measuring the shape of a plate-like object according to claim 6 or 7.

Images