Method for measuring strain, apparatus for measuring strain, and method for manufacturing steel plates

Abstract

To provide a distortion measurement method capable of precisely measuring the distortion amount even at the plate ends of a steel plate, and a distortion amount measuring device.SOLUTION: The distortion measurement method includes the following steps: a surface shape data acquisition step in which 3D surface shape data of a steel plate measured by a shape measuring device is acquired; a surface shape profile acquisition step in which, defining the predetermined position in the longitudinal or transverse direction of the steel plate as x, a curve (y=f(x)) with a surface shape profile whose height is y at a predetermined position x is acquired from the 3D surface shape data; and a distortion amount measurement step in which the distortion amount of the multiple at the predetermined position x is calculated by using the formula (1), and the maximum distortion amount among the multiple distortion amounts obtained is determined as the distortion amount δ(x) at the predetermined position x. LP is the longitudinal length of the steel plate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the amount of distortion in a steel sheet, a device for measuring the amount of distortion in a steel sheet, and a method for manufacturing a steel sheet using the said distortion measurement method. [Background technology]

[0002] In steel plate manufacturing, a device called a leveler, which consists of multiple rolls arranged vertically, is generally used to transport the steel plate between these rolls, correcting shape defects such as warping and rippling that occur during manufacturing. However, since the bending moment required to correct the shape is proportional to the cube of the plate thickness, the leveler cannot completely correct the shape of thick steel plates with a thickness of 40 mm or more. Therefore, if shape defects occur in thick steel plates, the steel plate is removed from the production line and the shape defects are corrected offline using a press machine.

[0003] In the process of straightening the shape of thick steel plates using a press, the amount of strain at various points on the surface of the steel plate is measured, and the position and force of the press's pressure ram are determined based on this amount of strain. Traditionally, the amount of strain was measured by an operator placing a stretcher (square) of a predetermined length on the surface of the steel plate and observing the size of the gap between the stretcher and the surface of the steel plate. However, this method had the problem of placing a heavy burden on the operator and hindering productivity improvements, as the operator had to manually check the amount of strain at numerous points on the surface of the steel plate.

[0004] To address these challenges, Patent Document 1 discloses a method for evaluating the strain of a steel plate, which involves acquiring three-dimensional surface shape data of a steel plate using a steel plate shape measuring device such as a 3D scanner, and then calculating the amount of strain at each position on the surface of the steel plate using this three-dimensional surface shape data. According to Patent Document 1, a stretcher is virtually applied to the obtained surface shape, and the gap between the stretcher and the surface shape is calculated. Furthermore, by calculating multiple gaps by changing the length of the stretcher, and using the largest of these gaps as the amount of strain in the steel plate, the amount of strain in the steel plate can be calculated with high accuracy. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-151222 [Patent Document 2] Japanese Patent Publication No. 2010-155272 [Overview of the project] [Problems that the invention aims to solve]

[0006] Figure 1 is a graph showing the method for calculating the strain amount δ(x1,L) at position x1 using the method disclosed in Patent Document 1. In Patent Document 1, as shown in Figure 1, the strain amount δ(x1,L) at position x1 is calculated by the following equation (2) when the surface shape profile is a curve y=f(x) and the unit length is L.

[0007]

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[0008] In calculating the strain amount δ using the above equation (2), the strain amount δ at the edge of the plate cannot be calculated unless the unit length L is shortened, but the measurement of strain amount δ near the edge of the plate is not disclosed in Patent Document 1. The strain amount δ near the edge of the plate is measured by shortening the unit length L as described above, but x1 is 0 or L P In this case, considering that the strain amount δ must be 0, if x1 is less than L / 2, it is possible to reduce the unit length L to 2 × x1, as shown in equation (3) below.

[0009]

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[0010] Using equation (3) above, when x1 is 0, the strain δ is 0. PEven when the value is greater than -L / 2, the strain amount δ can be defined using a similar approach. However, generally, the strain amount δ decreases as the unit length L decreases. Therefore, there is a risk that the strain amount δ calculated using equation (3) above will be underestimated as it approaches the edge of the plate. Our investigation has revealed that a problem with the strain amount calculated in this way is that there is often a large discrepancy between the actual strain amount and the calculated strain amount.

[0011] This invention has been made in view of the above problems, and its objective is to provide a strain measurement method and strain measurement device that can measure the amount of strain with high accuracy even at the edges of steel plates. Another objective of this invention is to provide a method for manufacturing steel plates that can produce steel plates with corrected strain. [Means for solving the problem]

[0012] The means to solve the above problems are as follows: [1] A strain measurement method comprising: a data acquisition step of acquiring three-dimensional surface shape data of a steel plate measured by a shape measuring device; a profile acquisition step of acquiring a curve (y=f(x)) which is a surface shape profile from the three-dimensional surface shape data, where x is a predetermined position in the longitudinal or width direction of the steel plate and y is the height at the predetermined position x; and a strain calculation step of changing k in a range greater than 0 and less than or equal to 1, determining multiple strain amounts at the predetermined position x using the following equation (1), and defining the maximum strain amount among the multiple strain amounts as the strain amount δ(x) at the predetermined position x.

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[0013] By using the strain amount measuring method and the strain amount measuring device according to the present invention, the strain amount δ of the steel plate can be measured with high accuracy even at the plate end. Thus, if the strain amount δ can be measured with high accuracy, the strain amount δ can be detected and the steel plate can be corrected, so that a steel plate with a stably corrected strain amount can be manufactured. [Brief Description of the Drawings]

[0014] [Figure 1] FIG. 1 is a graph showing a method for calculating the strain amount δ(x1, L) at position x1 by the method disclosed in Patent Document 1. [Figure 2] FIG. 2 is a schematic diagram of a shape correction system for a steel plate including a strain amount measuring device according to the present embodiment. [Figure 3] FIG. 3 is a schematic diagram showing a configuration example of the strain amount measuring device. [Figure 4]Figure 4 is a graph (comparative example) showing the results of measuring the strain amount δ using the above equation (3). [Figure 5] Figure 5 is a graph (example of invention) showing the results of measuring the strain amount δ with the strain amount measuring device 24 according to this embodiment. [Figure 6] Figure 6 is a graph showing the amount of strain δ at a position of 1.25 m (z=1.25 m) in the width direction of the plate in Figures 4(a) and 5(a). [Figure 7] Figure 7 is a graph showing the amount of strain δ at a position of 1.25 m (z=1.25 m) in the width direction of the plate in Figures 4(b) and 5(b). [Figure 8] Figure 8 is a graph showing the amount of strain δ at the longitudinal position of 4.0m (x=4.0m) in Figures 4(c) and 5(c). [Figure 9] Figure 9 is a graph showing the amount of strain δ at the longitudinal position of 4.0m (x=4.0m) in Figures 4(d) and 5(d). [Figure 10] Figure 10 is a graph showing the measurement results of the longitudinal strain δ in another steel plate. [Modes for carrying out the invention]

[0015] The present invention will be specifically described below through embodiments of the present invention. However, the following embodiments are merely preferred examples of the present invention, and the present invention is not limited in any way by these embodiments.

[0016] First, with reference to Figure 2, the steel plate shape correction system 100 including the strain amount measuring device 24 according to this embodiment will be described. Figure 2 is a schematic diagram of the steel plate shape correction system 100 including the strain amount measuring device 24 according to this embodiment.

[0017] The steel plate shape correction system 100 is used to correct the shape of a steel plate S offline. The steel plate shape correction system 100 includes a press machine 10, a shape measuring device 22, and a strain amount measuring device 24. The press machine 10 includes a pressure ram 12, an entry bed 14, an exit bed 16, and tracking devices 18 and 20. The entry bed 14 and the exit bed 16 have a number of rollers for transporting the steel plate S, and the transport state of the steel plate S is controlled by controlling the rotation state of the rollers. The tracking devices 18 and 20 are provided on the entry bed 14. The tracking devices 18 and 20 detect the position of the steel plate S, for example, from the rotation state of the rollers. Alternatively, the tracking devices 18 and 20 may detect the position of the steel plate S by measuring its position with a laser distance meter.

[0018] The press machine 10 applies pressure to the steel plate S from above with a pressure ram 12, primarily by applying a bending moment to the steel plate S to correct its shape. The shape of the steel plate S is measured by a shape measuring device 22, which will be described later. Conditions for correcting the shape of the steel plate S include, for example, the reduction position of the pressure ram 12, the pressure applied by the pressure ram 12, the position and spacing of the shims, and the position of the steel plate S. The steel plate shape correction by the press machine 10 is performed, for example, by placing two shims under the steel plate S and applying pressure to the portion of the steel plate S between the shims with the pressure ram 12. The bending moment from the pressure ram 12 occurs only in the portion of the steel plate S between the shims. The conditions for correcting the shape of the steel plate are determined by taking into account the amount of deformation of the steel plate S due to this bending moment and the amount of springback, which is the amount of return when the pressure is released.

[0019] The shape measuring device 22 is installed, for example, to the side of the entry bed 14. The shape measuring device 22 includes a laser distance meter that detects the distance to a detection point using laser light, and a computer that measures the shape of the steel plate S from the distance data detected by the laser distance meter. The laser distance meter determines the surface shape of the steel plate S by measuring the distance to each detection point on the steel plate S. The laser distance meter is preferably a 3D scanner having a laser light irradiation device and a laser light receiving device.

[0020] The shape measuring device 22 measures the surface shape of the steel plate S being transported on the entry bed 14 and acquires three-dimensional surface shape data of the steel plate S. The specific method for measuring the three-dimensional surface shape data can be the method described in Patent Document 2. That is, a laser beam is scanned in the longitudinal and width directions of the steel plate S, and for example, the position of the steel plate surface is extracted as point cloud data in an XYZ space where the longitudinal direction is the X axis, the height direction is the Y axis, and the plate width direction is the Z axis. A regression surface is then obtained from this point cloud data and used as the three-dimensional surface shape data.

[0021] The strain measurement device 24 is also installed, for example, to the side of the entry bed 14. The strain measurement device 24 acquires three-dimensional surface shape data of the steel plate S measured by the shape measurement device 22, and obtains a curve (y=f(x)) which is a surface shape profile from the three-dimensional surface shape data. The surface shape profile is a curve (y=f(x)) where x is a predetermined position in the longitudinal or width direction of the steel plate S, and y is the height at that predetermined position x. The strain measurement device 24 measures the strain amount δ of the steel plate S using the acquired surface shape profile.

[0022] Next, the strain measurement device 24 will be described. Figure 3 is a schematic diagram showing an example of the configuration of the strain measurement device 24. The strain measurement device 24 is, for example, a general-purpose computer such as a workstation or personal computer. The strain measurement device 24 has a control unit 26, an input unit 28, an output unit 30, and a storage unit 32.

[0023] The control unit 26 is, for example, a CPU, and by executing various programs stored in the storage unit 32, the control unit 26 functions as a data acquisition unit 34, a profile acquisition unit 36, and a strain amount calculation unit 38. The input unit 28 is, for example, a keyboard, a touch panel integrated with a display, etc. The output unit 30 is, for example, an LCD, a CRT display. The storage unit 32 is, for example, an information recording medium such as an updatable flash memory, a built-in or data communication terminal-connected hard disk, or a memory card, and its reading and writing device. The storage unit 32 pre-stores programs, formulas, and data used to acquire a surface shape profile from 3D surface shape data, and programs, formulas, and data used to calculate the strain amount δ of the steel plate S from the surface shape profile. The formulas and data may be input by the operator through the input unit 28.

[0024] Next, the processes performed by the data acquisition unit 34, the profile acquisition unit 36, and the strain amount calculation unit 38 will be described. The data acquisition unit 34 performs a data acquisition step to acquire three-dimensional surface shape data of the steel plate S from the shape measuring device 22. The data acquisition unit 34 outputs the acquired three-dimensional surface shape data to the profile acquisition unit 36.

[0025] When the profile acquisition unit 36 ​​acquires three-dimensional surface shape data (curved surface), it executes a profile acquisition step to acquire a surface shape profile (y=f(x)) where y is the height at a predetermined position x in the longitudinal or width direction of the steel plate S. When the profile acquisition unit 36 ​​acquires three-dimensional surface shape data, it calculates the XY cross section at the center of the plate width for the three-dimensional surface shape data in XYZ space. This XY cross section becomes the surface shape profile where y is the height at a predetermined position x in the longitudinal direction. Similarly, the profile acquisition unit 36 ​​calculates the YZ cross section in the longitudinal direction of the steel plate S for the three-dimensional surface shape data in XYZ space. This YZ cross section becomes the surface shape profile where y is the height at a predetermined position z in the width direction. The profile acquisition unit 36 ​​outputs the longitudinal surface shape profile to the strain amount calculation unit 38. In the following explanation, we will describe a method for calculating the strain amount δ at a predetermined position x using a surface shape profile where y is the height at that position x in the longitudinal direction of the steel plate S. However, the strain amount δ at a predetermined position in the width direction of the steel plate S can also be calculated using a similar method.

[0026] The strain calculation unit 38, upon obtaining the surface shape profile (y=f(x)), executes a strain calculation step to measure the strain δ of the steel plate S. The strain calculation unit 38 changes k within the range of greater than 0 and less than or equal to 1, and calculates multiple strain values ​​δ(x,kL) at a predetermined position x with a predetermined unit length L using the surface shape profile (y=f(x)) and equation (1) below. The unit length L is, for example, between 1m and 4m.

[0027]

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[0028] The strain amount calculation unit 38 sets the maximum strain amount among the calculated multiple strain amounts δ as the strain amount at the predetermined position x. For example, when k is changed to 10 levels of 0.1, 0.2, 0.3, ···, 0.9, 1.0, the strain amount calculation unit 38 calculates 10 strain amounts σ(x,kL) at the predetermined position x. The strain amount calculation unit 38 sets the largest strain amount δ among the 10 strain amounts δ(x,kL) as the strain amount δ(x) at the predetermined position x. The strain amount calculation unit 38 calculates the strain amount δ(x) at all predetermined positions x in the longitudinal direction of the steel plate S. In this way, the strain amount calculation unit 38 measures the strain amount δ in the longitudinal direction of the steel plate S.

[0029] As shown in the above formula (1), when the predetermined position x is 0≦x<kL / 2 and L P -kL / 2≦x<L P and the plate end portion of the steel plate S, and when the predetermined position x is kL / 2≦x<L P -kL / 2, the strain amount calculation unit 38 separates the plate center portion of the steel plate S and calculates the strain amount δ. Thereby, the strain amount calculation unit 38 can measure the strain amount δ at the plate end portion of the steel plate S with higher accuracy than before.

[0030] The strain amount calculation unit 38 may cause the output unit 30 to display the measured strain amount δ of the steel plate S. In this case, the strain amount calculation unit 38 may cause the output unit 30 to display the strain amount δ of the steel plate S in a graph with the horizontal axis being the predetermined position x and the vertical axis being the strain amount δ, for example.

[0031] As described above, in the strain amount measuring device 24 according to the present embodiment, when the predetermined position x is 0≦x<kL / 2 and L P -kL / 2≦x<L P and the plate end portion of the steel plate S, and when the predetermined position x is kL / 2≦x<L PBy separating the central part of the steel plate S, which is -kL / 2, from the edge and calculating the strain amount δ, the strain amount δ at the edge of the steel plate S can be measured with higher accuracy than before. If the strain amount δ of the steel plate S at the edge can be measured with high accuracy in this way, the strain amount δ can be corrected by press straightening with press conditions corresponding to the strain amount δ, and steel plates with less strain can be manufactured. Furthermore, even if a strain amount outside the standard occurs at the edge of the plate, the strain amount δ can be detected, and by press straightening with press conditions that bring the strain amount δ within the standard value range, the yield reduction due to the manufacture of steel plates with outside the standard strain amount can be suppressed. Note that the standard value for strain is an example of a predetermined range for strain. [Examples]

[0032] Next, an example of measuring the strain amount δ of a steel plate using the strain amount measuring device 24 according to this embodiment will be described. Figure 4 is a graph (comparative example) showing the results of measuring the strain amount δ of a steel plate using the above equation (3). Figure 5 is a graph (inventive example) showing the results of measuring the strain amount δ of the same steel plate using the strain amount measuring device 24 according to this embodiment. In both Figures 4 and 5, (a) shows the strain amount δ in the longitudinal direction when the unit length L is 1 m, and (b) shows the strain amount δ in the longitudinal direction when the unit length L is 2 m. Also, (c) shows the strain amount δ in the width direction when the unit length L is 1 m, and (d) shows the strain amount δ in the width direction when the unit length L is 2 m.

[0033] In Figures 4 and 5, the areas shown in black indicate a large strain δ (±2mm to ±3mm), while the areas shown in white indicate a small strain δ (0 to ±1mm). Although there was no significant difference in the longitudinal strain δ between the inventive example and the comparative example, a clear difference in the widthwise strain δ was observed in the areas near the plate edges (z=0.2, z=2.2).

[0034] Figure 6 is a graph showing the amount of strain δ at a position of 1.25 m (z=1.25 m) in the plate width direction in Figures 4(a) and 5(a). In the longitudinal direction, where the unit length L is 1 m, no difference in magnitude was observed between the amount of strain δ measured in Figure 4(a), which is a comparative example, and Figure 5(a), which is the inventive example.

[0035] Figure 7 is a graph showing the amount of strain δ at a plate width position of 1.25m (z=1.25m) in Figures 4(b) and 5(b). For the amount of strain δ in the longitudinal direction with a unit length L of 2m, a difference in strain δ was observed between the comparative example and the inventive example at the plate end furthest from 0. The circles in Figure 7 indicate the results of manual measurement of strain δ using a 2m stretcher. As shown in Figure 7, the amount of strain δ in the inventive example and the amount of strain δ measured manually were in close agreement. From these results, it was confirmed that the amount of strain δ at the plate end in the longitudinal direction of the steel plate can be measured with high accuracy using the strain measuring device 24 according to this embodiment.

[0036] Figure 8 is a graph showing the strain amount δ at a longitudinal position of 4.0m (x=4.0m) in Figures 4(c) and 5(c). For the strain amount δ in the width direction, where the unit length L is 1m, a difference in strain amount δ was observed between the comparative example and the inventive example in the region excluding the vicinity of the center in the width direction. The circles in Figure 8 indicate the results of manual measurement of strain amount δ using a 1m stretcher. As shown in Figure 8, the strain amount δ of the inventive example and the strain amount δ measured manually were in close agreement. From these results, it was confirmed that the strain amount δ of a steel plate can be measured with high accuracy using the strain amount measuring device 24 according to this embodiment.

[0037] Figure 9 is a graph showing the strain δ at the longitudinal position 4.0m (x=4.0m) in Figures 4(d) and 5(d). For the strain δ in the width direction with a unit length L of 2m, near the center in the width direction (L / 2≦z <L P In the region excluding -L / 2), a difference in strain amount δ was observed between the comparative example and the inventive example. The circles in Figure 9 indicate the results of manual measurement of strain amount δ using a 2m stretcher. As shown in Figure 9, the strain amount δ of the inventive example and the strain amount δ measured manually were in almost agreement. From these results, it was confirmed that the strain amount δ of the steel plate can be measured with high accuracy by using the strain amount measuring device 24 according to this embodiment.

[0038] Figure 10 is a graph showing the measurement results of the longitudinal strain δ in another steel plate. In Figure 10, the unit length L was set to 2m, and the longitudinal strain δ was measured at the center in the width direction. In this measurement of strain δ, a difference in strain δ was confirmed between the comparative example and the inventive example at the plate end on the side close to 0 and the plate end on the side far from 0. The circles in Figure 10 indicate the result of manually measuring the strain δ using a 2m stretcher. As shown in Figure 10, the strain δ of the inventive example and the strain δ measured manually were in almost agreement. From these results, it was confirmed that the strain measuring device 24 according to this embodiment can measure the strain δ at the plate end in the longitudinal direction of the steel plate with high accuracy.

[0039] Furthermore, in Figure 10, if the strain amount δ of the steel plate is measured, and the strain amount δ is 2 mm or more, it is considered substandard and is pressed straightened in the press machine 10. As shown in Figure 10, in the measurement of strain amount δ using the comparative example, the strain amount δ is measured to be less than 2 mm, so it is decided not to press straighten it in the press machine 10. As a result, in reality, steel plates with a strain of 2 mm or more that are substandard are passed on to the downstream process. On the other hand, the strain amount measuring device 24 according to this embodiment can detect a strain of 2 mm or more present at the edge of the plate, and can press straighten it with press conditions corresponding to the strain amount δ, so that steel plates with a stable amount of strain corrected to within the standard can be manufactured. [Explanation of Symbols]

[0040] 10 Press machine 12 Pressurized Ram 14 beds 16 Outer bed 18 Tracking device 20 Tracking device 22 Shape measuring device 24 Strain measurement device 26 Control Unit 28 Input section 30 Output section 32 Storage Unit 34 Data Acquisition Unit 36 Profile Acquisition Unit 38 Distortion amount calculation section 100 Steel Plate Shape Correction System S steel plate

Claims

1. A data acquisition step to acquire three-dimensional surface shape data of a steel plate measured by a shape measuring device, A profile acquisition step to obtain a curve (y = f(x)) which is a surface shape profile from the three-dimensional surface shape data, where x is a predetermined position in the longitudinal or width direction of the steel plate and y is the height at the predetermined position x, A strain calculation step in which k is changed within the range of greater than 0 and less than or equal to 1, multiple strain amounts at the predetermined position x are determined using the following equation (1), and the maximum strain amount among the multiple strain amounts is set as the strain amount δ(x) at the predetermined position x, A method for measuring strain amount, comprising the characteristics of a strain measurement method. [Math 1] In equation (1) above, k is a value greater than 0 and less than or equal to 1, L Ｐ is the longitudinal length (m) of the steel plate or the width (m) of the steel plate, and L is the unit length (m).

2. A data acquisition unit that acquires three-dimensional surface shape data of a steel plate measured by a shape measuring device, A profile acquisition unit acquires a curve (y = f(x)) which is a surface shape profile from the three-dimensional surface shape data, where x is a predetermined position in the longitudinal or width direction of the steel plate and y is the height at the predetermined position x. A strain calculation unit that changes k within the range of greater than 0 and less than or equal to 1, calculates multiple strain amounts at the predetermined position x using the following formula (1), and sets the maximum strain amount among the multiple strain amounts as the strain amount δ(x) at the predetermined position x. A strain measurement device having the following features. [Math 2] In equation (1) above, k is a value greater than 0 and less than or equal to 1, L Ｐ is the longitudinal length (m) of the steel plate or the width (m) of the steel plate, and L is the unit length (m).

3. The amount of distortion of the steel plate is measured using the distortion measurement method described in claim 1. A method for manufacturing a steel plate, comprising using a press machine to press-correct the distortion of the steel plate so that the measured amount of distortion falls within a predetermined range.

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