A device for detecting the position of seams and cut sections of welded steel pipes, manufacturing equipment for welded steel pipes, a method for detecting the position of seams and cut sections of welded steel pipes, a method for manufacturing welded steel pipes, and a method for controlling the quality of welded steel pipes.

Abstract

To provide a device for detecting the position of seams and cut portions of welded steel pipes, a manufacturing facility for welded steel pipes, a method for detecting the position of seams and cut portions of welded steel pipes, a method for manufacturing welded steel pipes, and a method for quality control of welded steel pipes, which can accurately detect the position of the cut portion formed by cutting the weld bead formed by the welding process before heat treatment of the seam portion formed by welding the ends of steel plates joined by welding in the manufacturing of welded steel pipes. [Solution] The position detection device 13 for the seam and cut portion of a welded steel pipe W comprises an imaging unit 131 that captures an image of thermal radiation light from the outer surface of the welded steel pipe, and a calculation unit 132 that calculates the position of the seam and the cut portion. The imaging unit is capable of capturing wavelengths longer than the wavelength of visible light and shorter than the wavelength of far-infrared light, and the calculation unit comprises a first calculation unit that calculates a brightness profile and a second calculation unit that calculates the position of the seam and the cut portion.

Description

Technical Field

[0001] The present invention relates to a position detection device for a seam portion and a cutting portion of a welded steel pipe, a manufacturing facility for a welded steel pipe, a position detection method for a seam portion and a cutting portion of a welded steel pipe, a manufacturing method for a welded steel pipe, and a quality control method for a welded steel pipe.

Background Art

[0002] In a production line of a welded steel pipe (for example, an electric welded pipe) in a steel process, a plate-shaped steel plate is bent into a tubular shape by a forming roll, and both ends of the steel plate are abutted at the upper part for welding. A joint portion formed by both ends of the steel plate joined by welding serves as a seam of the steel pipe and is called a seam portion. On the other hand, a region affected by the heat affected zone during welding including the seam portion is called a welded portion. After welding as described above, the weld bead formed on the welded portion is cut and removed. Subsequently, in order to improve the material properties of the welded portion, a heat treatment (also called annealing) for reheating the welded portion is performed to manufacture a welded steel pipe.

[0003] The heat treatment for reheating the welded portion is often carried out multiple times by induction heating. It is important to accurately align and heat only the seam portion without affecting the base material by one or more annealer heaters. However, in reality, it is difficult to identify the seam portion from the appearance. Therefore, usually, it is assumed that the cutting portion, which is the portion where the weld bead formed on the seam portion is cut, is at the same position as the seam portion, and an operator checks whether the position of the cutting portion coincides with the heating portion heated by the annealer heater, that is, the position of the annealer heater, and conducts the operation.

[0004] For example, Patent Document 1 discloses a technique for detecting the difference in material between a seam portion and a material portion using an electromagnetic method such as an eddy current sensor or a leakage magnetic flux sensor, and calculating the seam portion. Further, Patent Document 2 discloses a technique for calculating the seam portion by detecting the cutting portion using an image method on the assumption that the center of the cutting portion and the seam portion are at the same position.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Application Publication No. 56-033542 [Patent Document 2] Japanese Patent Application Publication No. 10-170228 [Overview of the project] [Problems that the invention aims to solve]

[0006] The technology proposed in Patent Document 1, in detail, senses the phenomenon in which differences in permeability and electrical conductivity caused by differences in microstructure such as crystal grain size appear as differences in magnetic flux distribution. However, it has the problem of being easily affected by surface shape inhomogeneities such as scratches on the tube surface.

[0007] Furthermore, the technology proposed in Patent Document 1 has the problem that the sensor part is sensitive to heat. In electromagnetic methods, the closer the sensor is to the object being measured, the better the sensitivity. Therefore, in electromagnetic methods, measurements are generally taken by setting the distance from the sensor to the object being measured to, for example, 1 mm, or at most a few mm. However, since the temperature of the seam part of the object being measured is at least 400°C or higher, it is difficult to bring the sensor close to it.

[0008] Therefore, by adopting an imaging method using a camera that can be positioned tens of centimeters to several meters away from the sensor to the object to be measured, as proposed in Patent Document 2, for example, the thermal effects of the sensor can be ignored. However, the technology proposed in Patent Document 2 has the following problems.

[0009] In the technology proposed in Patent Document 2, it is assumed that a seam exists at the center of the cut portion, and the center position of the cut portion is calculated to identify the seam. However, since welded steel pipes twist in the circumferential direction with the longitudinal axis as the axis during manufacturing, even if the cut is aimed at the weld bead (excess weld) formed in the seam portion, the seam portion is not always at the center of the cut portion. Furthermore, while the cut portion is relatively easy to identify from the outside by visual inspection, the seam portion is difficult to identify from its appearance.

[0010] The present invention has been made in view of the above, and aims to provide a device for detecting the position of seams and cut portions of welded steel pipes, a manufacturing facility for welded steel pipes, a method for detecting the position of seams and cut portions of welded steel pipes, a method for manufacturing welded steel pipes, and a method for quality control of welded steel pipes, which can accurately detect the position of a cut portion formed by cutting the weld bead formed by the welding process before heat treatment of the seam portion formed by welding the ends of steel plates joined by welding in the manufacturing of welded steel pipes. [Means for solving the problem]

[0011] (1) The position detection device for the seam and cut portion of a welded steel pipe according to the present invention is a position detection device that detects the position of the seam portion including the welded end of the welded steel pipe and the position of the cut portion of a welded steel pipe having a cut portion where the weld bead formed after the end of the steel plate is welded, An imaging unit captures an image of the thermal radiation light from the outer surface of the welded steel pipe so that the cutting portion is within its field of view, A calculation unit that calculates the position of the seam and the position of the cutting portion from the captured image, Equipped with, The imaging unit is capable of imaging wavelengths longer than visible light wavelengths and shorter than far-infrared wavelengths. The aforementioned arithmetic unit, A first calculation unit calculates a brightness profile in the width direction of the welded steel pipe from the image captured by the imaging unit, A second calculation unit calculates the position of the seam and the position of the cutting portion from the calculated brightness profile, It is equipped with.

[0012] (2) The position detection device for the seam and cut portion of a welded steel pipe according to the present invention is the position detection device for the seam and cut portion of a welded steel pipe described in (1) above, The second calculation unit calculates the position of the seam portion from the position of the maximum value having the highest luminance value in the luminance profile, and calculates the position of the cutting portion from the positions of the sub-peak values ​​on both sides of the maximum value.

[0013] (3) The manufacturing equipment for welded steel pipes according to the present invention is A welding machine for welding the butt joints of cylindrical steel plates, A cutting machine for cutting the weld bead after welding, A position detection device for the seam and cut portion of a welded steel pipe as described in (1) or (2) above, An annealer heating element that heats the seam after cutting, A control device that controls the position of the annealer heater based on the relative position of the seam portion with respect to the cutting portion detected by the position detection device, It is equipped with.

[0014] (4) A method for detecting the position of a seam portion and a cut portion of a welded steel pipe according to the present invention is a method for detecting the position of a seam portion including the welded end of a welded steel pipe and the position of the cut portion of a welded steel pipe having a cut portion where the weld bead formed after the end of the steel plate is welded, The imaging step involves capturing an image of thermal radiation light from the outer surface of the welded steel pipe using an imaging unit capable of capturing wavelengths longer than visible light and shorter than far-infrared wavelengths, such that the cutting portion is within the field of view. A first calculation step involves calculating a brightness profile in the width direction of the welded steel pipe from the image captured in the above imaging step, A second calculation step involves calculating the position of the seam and the position of the cutting portion from the calculated brightness profile, It includes

[0015] (5) The method for manufacturing a welded steel pipe according to the present invention includes a welding step of welding the butted portion of a steel plate formed into a cylindrical shape, a cutting step of cutting the weld bead after welding, a position detection step of detecting the position of the seam portion and the position of the cutting portion by the position detection method of the seam portion and the cutting portion of the welded steel pipe described in (4) above, a heating step of heating the seam portion after cutting while controlling the position of the annealing heater based on the position of the seam portion relative to the cutting portion detected by the position detection step, It includes

[0016] (6) The quality control method of the welded steel pipe according to the present invention manages the quality of the welded steel pipe based on the deviation amount between the position of the seam portion with respect to the position of the cutting portion detected before the heat treatment by the position detection method of the seam portion and the cutting portion of the welded steel pipe described in (4) above and the actual heating position with respect to the cutting portion detected after the heat treatment.

Advantages of the Invention

[0017] According to the present invention, in the manufacture of a welded steel pipe, before heat-treating the seam portion composed of the ends of the steel plates joined by welding, the position of the cutting portion formed by cutting the weld bead formed by the welding process of welding the ends and the position of the seam portion can be accurately detected.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a diagram showing an example of an image of the cutting portion of a welded steel pipe taken by a far-infrared camera before the heat treatment. [Figure 2] FIG. 2 is a diagram showing the luminance profile in the width direction of the welded steel pipe calculated from the image of FIG. 1. [Figure 3]Figure 3 shows the brightness profile in the width direction of a welded steel pipe, calculated from images of the cut portion of the welded steel pipe captured with a near-infrared camera before heat treatment. [Figure 4] Figure 4 shows a schematic configuration of a welded steel pipe manufacturing facility according to an embodiment of the present invention. [Figure 5] Figure 5 shows a schematic configuration of a position detection device for the seam and cut portions of a welded steel pipe according to an embodiment of the present invention. [Figure 6] Figure 6 is a flowchart showing the flow of a method for detecting the position of the seam and cut portion of a welded steel pipe according to an embodiment of the present invention. [Figure 7] Figure 7 shows an example of an image of thermal radiation light from the outer surface of a welded steel pipe captured in the imaging step, in a method for detecting the position of the seam and cut portion of a welded steel pipe according to an embodiment of the present invention. [Figure 8] Figure 8 shows an example of a brightness profile in the width direction of a welded steel pipe calculated in the first calculation step in a method for detecting the position of the seam and cut portion of a welded steel pipe according to an embodiment of the present invention. [Figure 9] Figure 9 is a schematic diagram illustrating a method for taking the difference between adjacent brightness values ​​in the second calculation step of a method for detecting the position of seam and cut portions of a welded steel pipe according to an embodiment of the present invention. [Modes for carrying out the invention]

[0019] The position detection device for the seam and cut portion of a welded steel pipe, the manufacturing equipment for a welded steel pipe, the position detection method for the seam and cut portion of a welded steel pipe, the manufacturing method for a welded steel pipe, and the quality control method for a welded steel pipe according to the present invention will be described with reference to the drawings. In the following description, the joint portion of a steel pipe formed by welding the ends of steel plates will be referred to as the "seam portion," and the portion where the weld bead formed in the seam portion has been cut will be referred to as the "cut portion."

[0020] [Technical significance of simultaneously detecting the cut area and the seam area] In the manufacturing line for welded steel pipes, a heat treatment is performed on the seam area using an annealer heater to ensure the material properties of the welded joint. Ideally, the seam area should be identified before the heat treatment, and the heating area of ​​the annealer heater should be aligned with that seam area.

[0021] Alternatively, after heat treatment, it would be possible to detect the seam and the heated portion and use feedback control to ensure that the seam and the heated portion coincide. However, immediately after heat treatment, it is not possible to detect the position of the seam from the outer surface of the welded steel pipe. Furthermore, after heat treatment, for example, the surface temperature of the welded steel pipe exceeds 700°C, making it impossible to use sensors that detect the interior using electromagnetic or ultrasonic methods.

[0022] For example, heating the entire cutting area ensures that the seam is also heated, but this requires an annealer heater capable of heating the entire cutting area, thus increasing equipment costs. Typically, the area that can be heated by an annealer heater is not sufficiently wide relative to the cutting area, and the operator controls the annealer heater.

[0023] Furthermore, welded steel pipes often twist circumferentially around their longitudinal axis during transport. As a result, even if the absolute position of the seam can be detected after cutting, the absolute position of the seam may change due to circumferential twisting over long transport distances. On the other hand, if the relative position of the seam to the position of the cut area can be determined, the position of the seam can be calculated in reverse from the position of the cut area, even if the absolute position of the seam changes due to twisting during transport.

[0024] As described above, the position of the seam shifts due to twisting and vibration during transport, making it uncertain whether the seam will be in the same position during the heating stage. Therefore, in this invention, the position of the seam is determined along with the position of the cutting section. This makes it possible to indirectly determine the amount of displacement between the position of the seam, which was the original target, and the position of the heating section.

[0025] Furthermore, in controlling the annealer heater and conducting various inspections after heat treatment, it is essential to be able to determine the location of the cut area, as this can be used for inspections including visual inspection and camera photography (especially inspections using optical methods). Thus, the reason why the cut area is so important in welded steel pipes is that it is easy to measure before and after heat treatment, and can be easily confirmed visually. The cut area has a higher gloss than the surrounding base material, making it easy to identify its location from its appearance. For this reason, in this embodiment, the positions of both the seam and the cut area are detected.

[0026] Based on the above, if the position of the seam can be detected in advance along with the cut area before heat treatment, the position information of the seam can be effectively utilized in post-heat treatment processes. Alternatively, if the position of the seam can be detected in advance using the cut area as a reference, the position information of the seam can also be effectively utilized in post-heat treatment processes.

[0027] [Considerations leading to the invention] The seam is the area where the ends of the steel plates are welded together, and is therefore expected to be the hottest part on the outer surface of the welded steel pipe after groove welding. By measuring the temperature of the outer surface of the welded steel pipe, the area with the highest temperature and maximum value can be estimated to be the seam.

[0028] Typically, when measuring the temperature of high-temperature objects non-contactually, it is common to use a temperature measurement camera that uses far-infrared wavelengths (hereinafter referred to as "far-infrared camera"). The reason for using far-infrared wavelengths is that, according to Planck's law, for example, under certain conditions, sensitivity increases as the wavelength lengthens, allowing measurement even at low temperatures. Here, far-infrared wavelengths refer to wavelengths in the range of 4.0 to 1000.0 μm.

[0029] Figure 1 shows an example of an image of the cut area of ​​a welded steel pipe, captured with a far-infrared camera after the cutting process to remove the weld bead and before the heat treatment with the annealer heater. Figure 2 shows the brightness profile in the width direction (radial direction) of the welded steel pipe calculated from the image in Figure 1. The wavelength range of the far-infrared camera used for imaging was 8.0 to 13.0 μm. The welded steel pipe used as a sample had an outer diameter of 318 mm, a plate thickness of 12.7 mm, and a transport speed of 24 mpm. In Figure 2, the horizontal axis represents the position in the width direction of the welded steel pipe, and the vertical axis represents the brightness value.

[0030] Looking at the brightness profile in Figure 2, we can see that the waveform does not have a maximum value at the seam, but rather is an unstable waveform with a distorted peak top. From these measurement results, it is clear that even when measuring temperature using a far-infrared camera, which is commonly used for temperature measurement, it is extremely difficult to measure the seam after cutting the weld bead.

[0031] Therefore, the inventors conducted a detailed investigation to see if there were any other methods. Based on their past studies and experience, the inventors estimated that the temperature of the seam area is approximately 400-500°C in the process after the cutting process to remove the weld bead and before the heat treatment with the annealer heater. Therefore, visible light wavelengths are not sensitive enough, making it difficult to capture the temperature as brightness. So, instead of a far-infrared camera, the inventors tried photographing the seam area using a temperature measurement camera that uses near-infrared wavelengths (hereinafter referred to as a "near-infrared camera").

[0032] Figure 3 shows the brightness profile in the width direction of a welded steel pipe, calculated from images of the cut area of ​​the welded steel pipe taken with a near-infrared camera before the heat treatment in which the seam area is reheated with an annealer heater after cutting the weld bead. The wavelength range of the near-infrared camera used for imaging was 0.9 to 1.8 μm. The welded steel pipe used as a sample had an outer diameter of 318 mm, a plate thickness of 6.9 mm, and a transport speed of 24 mpm. In Figure 3, the horizontal axis represents the position in the width direction of the welded steel pipe, and the vertical axis represents the brightness value.

[0033] As shown in Figure 3, the brightness profile calculated from the image captured by the near-infrared camera has a clear maximum value α, and the location of this maximum value α can be estimated to be the location of the seam. In other words, it has been newly discovered that seam detection is possible by using the image captured by the near-infrared camera.

[0034] Furthermore, a detailed examination of the luminance profile shown in Figure 3 revealed that there are discontinuities at two separate locations on either side of the maximum value α (corresponding to the width direction of the welded steel pipe), and that sub-peak values ​​β1 and β2, which are lower than the maximum value α, appear. These two discontinuous sub-peak values ​​β1 and β2 are thought to indicate the positions of the ends of the cut sections. In other words, it has been newly discovered that the position of the cut section, in addition to the position of the seam, can be detected from the luminance profile shown in Figure 3.

[0035] One reason why such a luminance profile was successfully obtained is that near-infrared wavelengths are shorter than far-infrared wavelengths, making them less susceptible to the surface shape of the object being photographed. Another reason is that near-infrared wavelengths are longer than visible light and therefore more sensitive. Visible light refers to electromagnetic waves in the wavelength range of, for example, 360 to 800 nm.

[0036] From the above, it has been newly discovered that, in order to detect the position of the seam and cut areas of a welded steel pipe after the cutting process that removes the weld bead and before the heat treatment with an annealer heater, it is appropriate to use wavelengths that are longer than visible light wavelengths and shorter than far-infrared wavelengths, and in particular, it is most appropriate to use near-infrared wavelengths.

[0037] [Position detection device] Figure 4 shows a schematic configuration of a welded steel pipe manufacturing facility, including a position detection device for the seam and cut portions of the welded steel pipe according to the embodiment.

[0038] In the manufacturing line for welded steel pipes (e.g., electric resistance welded pipes) W described in this embodiment, plate-shaped steel sheets are bent into a tubular shape using forming rolls, and the ends of the steel sheets are butted together at the top and welded using a welding machine 11. The joint formed by the welding at both ends of the steel sheets is called the seam because it forms the joint of the steel pipe. On the other hand, the area that has been affected by the heat-affected zone during welding, including the seam, is called the welded area. After welding as described above, the weld bead formed in the welded area is cut and removed using a cutting machine 12. Subsequently, in order to improve the material properties of the welded area, a heat treatment is performed to reheat the welded area, thereby manufacturing the welded steel pipe W.

[0039] The heat treatment to reheat the welded area is often performed multiple times using induction heating, and it is important to accurately position and heat only the seam area with one or more annealer heating elements 14 without affecting the base material. However, in reality, it is difficult to identify the seam area from the outside. Therefore, it is usually assumed that the cut area, which is the part where the weld bead formed in the seam area has been cut, is in the same position as the seam area, and the operator (worker) checks whether the position of the cut area matches the heated area heated by the annealer heating element 14, i.e., the position of the annealer heating element 14, before proceeding with the operation.

[0040] The cut portion has a higher gloss than the surrounding base material, making it easy to identify its position from its appearance. The position detection device 13 for the seam and cut portion of the welded steel pipe W detects the position of the seam portion including the welded end of the welded steel pipe W and the position of the cut portion, for a welded steel pipe W having a cut portion where the weld bead formed after the end of the steel plate is welded is cut off.

[0041] The position detection device 13 according to the present invention is installed in front of the annealer heating element 14 that performs heat treatment, and detects the position of the seam and cut portion before the heat treatment. In other words, the position detection device 13 according to the present invention is installed after the cutting machine 12 that cuts the weld bead. The position detection device 13 is also connected to a control device 15 that controls the annealer heating element 14, and the position information of the seam and cut portion calculated by the position detection device 13 is transmitted to this control device 15. The position detection device 13 is also connected to a display unit 16, which is implemented by, for example, a liquid crystal display (LCD), an organic light-emitting diode (OLED), or the like.

[0042] Figure 5 shows a schematic configuration of the position detection device 13. The position detection device 13 comprises an imaging unit 131 and a calculation unit 132.

[0043] The imaging unit 131 is equipped with a channel capable of imaging wavelengths longer than visible light wavelengths and shorter than far-infrared wavelengths, and uses this channel to image the thermal radiation light from the outer surface of the welded steel pipe W. The image captured by the imaging unit 131 is transmitted to the calculation unit 132, which then detects the positions of the seam and the cut areas.

[0044] As the imaging unit 131, for example, a temperature measurement camera (near-infrared camera) equipped with a channel capable of imaging near-infrared wavelengths (wavelength range: 0.8 to 2.5 μm) can be used. Alternatively, as the imaging unit 131, a temperature measurement camera (mid-infrared camera) equipped with a channel capable of imaging mid-infrared wavelengths (wavelength range: 2.5 to 4.0 μm), which is less affected by the surface shape of the welded steel pipe W than a far-infrared camera, can also be used. Among these, it is more preferable to use a near-infrared camera equipped with a channel capable of imaging in the wavelength range of 0.9 to 1.8 μm as the imaging unit 131.

[0045] As shown in Figure 5, the imaging unit 131 is positioned so that the cut portion of the welded steel pipe W is within its field of view. Furthermore, with respect to the welded portion of the welded steel pipe W, the imaging unit 131 is positioned such that, if the longitudinal direction of the welded steel pipe W is defined as the α-axis and the height direction and perpendicular direction to the longitudinal direction is defined as the β-axis, the optical axis of the imaging unit 131 is rotated by an angle θ toward the β-axis from the α-axis.

[0046] Furthermore, with the α-axis set to 0°, the angle θ of the imaging unit 131 relative to the welded steel pipe W is preferably between 25° and 90°, and most preferably 90° (directly downward) or an angle close to it. By setting the angle θ of the imaging unit 131 relative to the welded steel pipe W as described above, the brightness of the thermal radiation light can be measured stably.

[0047] The calculation unit 132 calculates the position of the seam and the cut portion of the welded steel pipe W from the image captured by the imaging unit 131. The calculation unit 132 is implemented by a general-purpose computer such as a workstation or personal computer. Specifically, the calculation unit 132 comprises a processor and memory (storage unit). The processor consists of a CPU (Central Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field-Programmable Gate Array), etc. The memory is a main memory and consists of RAM (Random Access Memory), ROM (Read Only Memory), etc. The memory provided in the calculation unit 132 stores an image processing program and a program execution environment that calculate the positions of the seam and cut portion from the image signal transmitted from the imaging unit 131.

[0048] Furthermore, the calculation unit 132 includes a communication unit that receives image signals from the imaging unit 131 and outputs calculated position information of the seam and cutting areas to the control device 15 and the display unit 16. The calculation unit 132 also includes a first calculation unit and a second calculation unit. These are realized through cooperation with the CPU and programs stored in memory.

[0049] The first calculation unit calculates a brightness profile in the width direction of the welded steel pipe W from the image captured by the imaging unit 131. The second calculation unit then calculates the positions of the seam and the cut areas from the calculated brightness profile. In this process, the second calculation unit calculates the position of the seam from the position of the maximum value with the highest brightness value in the brightness profile, and calculates the positions of the cut areas from the positions of the sub-peak values ​​on both sides of the maximum value.

[0050] [Location detection method] The position detection method according to the present invention is performed in a step prior to the heat treatment in which the seam portion is heated by the annealer heating element 14, and the positions of the seam portion and the cut portion are detected before the heat treatment is performed. In other words, the position detection method according to the present invention is performed in a step after the cutting treatment in which the weld bead formed during welding is cut by the cutting machine 12.

[0051] Figure 6 is a flowchart illustrating the flow of the method for detecting the position of the seam and cut portion of a welded steel pipe according to the embodiment. The method for detecting the position of the seam and cut portion of a welded steel pipe according to the embodiment includes an imaging step (step S1), a first calculation step (step S2), and a second calculation step (step S3).

[0052] First, the imaging unit 131 captures an image of the thermal radiation light emitted from the outer surface of the welded steel pipe W (step S1). At that time, the imaging unit 131 is positioned so that the cut portion of the welded steel pipe W is within the field of view of the imaging unit 131.

[0053] Figure 7 shows an example of an image captured in the imaging step. The image captured by the imaging unit 131 is transmitted to the processing unit 132. The image transmitted from the imaging unit 131 is then acquired by the processing unit 132.

[0054] Next, the first calculation unit of the calculation unit 132 calculates a brightness profile from the acquired image for the region where the position of the seam and the position of the cut portion of the welded steel pipe W are detected (step S2). An example of a brightness profile obtained from Figure 7 is shown in Figure 8. In the brightness profile, the width direction of the welded steel pipe W is taken as the horizontal axis and the brightness value is taken as the vertical axis for a predetermined position in the longitudinal direction. Also, the symbols X to Y in Figure 7 and the symbols X to Y in Figure 8 are the same.

[0055] Next, the second calculation unit of the calculation unit 132 calculates the positions of the seam and the cut sections from the obtained luminance profile (step S3). In step S3, the position of the seam is calculated as the position of the maximum value (peak value) with the highest luminance on the luminance profile in the width direction. Also in step S3, the positions of the two sub-peak values ​​β1 and β2 on either side of the maximum value with the highest luminance on the luminance profile in the width direction are calculated as the positions of the ends of the cut sections. Since the cut section is the part where excess bead material that existed near the seam has been cut away, it is estimated that the luminance profile of the outer surface of the welded steel pipe W changes abruptly at the ends of the cut sections, resulting in sub-peak values.

[0056] [Details of the second calculation step] The details of the second calculation step (step S3) in Figure 6 will be explained below.

[0057] First, the second calculation unit detects the maximum value on the luminance profile. There are various algorithms for detecting the maximum value through numerical processing. For example, one method can be used to calculate an approximation curve from the obtained data and perform differential and two-step differential processing, or to divide the data into predetermined narrow intervals, assume that the interval is a straight line, and define the point where the slope changes from positive to negative as the point where the slope is closest to zero as the maximum value.

[0058] Furthermore, if it is possible to detect the maximum value, unknown techniques may also be used. In this embodiment, as an example, a method of detecting the maximum value by taking the difference between adjacent luminance values ​​will be described. Note that depending on the imaging environment, noise may be introduced into the luminance profile, so corrections such as averaging or median processing may be performed on the luminance profile before calculating the maximum value.

[0059] Figure 9 is a schematic diagram illustrating the method of taking the difference between adjacent luminance values. In Figure 9, f(x) is the profile obtained by taking the difference between all luminance values ​​on the luminance profile and the luminance value to the left of the adjacent value. Here, x represents the position in the width direction of the welded steel pipe W. If the value of f(x) is positive, the original luminance profile represents monotonically increasing luminance; if it is negative, it represents monotonically decreasing luminance.

[0060] Next, the profile obtained by shifting this f(x) one pixel to the left is f(x+1). Therefore, if we define it as shown in equation (1) below, the position where g(x) is negative is the maximum value of the original luminance profile.

[0061]

number

[0062] Furthermore, if defined as shown in equation (2) below, h(x) is positive at the location of the local maximum and negative at the location of the local minimum.

[0063]

number

[0064] Based on these factors, f(x) is determined from the original luminance profile, and g(x) and h(x) are determined from f(x). The position x where g(x) is negative and h(x) is positive can be identified as the maximum value on the original luminance profile. The second calculation unit then obtains the luminance at the identified maximum value position.

[0065] Next, the second calculation unit obtains pairs of widthwise position and luminance value for three maximum values ​​on the luminance profile. The second calculation unit then determines the position of the maximum value α, which has the highest luminance value and therefore the highest temperature, as the location of the seam. The second calculation unit also determines the positions of the remaining two subpeak values ​​β1 and β2, which have lower luminance values ​​and therefore lower temperatures than maximum value α, as the positions of the edges of the cut section. Through these steps, the second calculation unit calculates the positions of the seam section and the cut section.

[0066] [How to utilize the position of the cutting area] The position of the cutting area detected by the position detection device 13 can be used, for example, as follows. (1) The coordinates of the two points at the end of the cutting section are used directly as the position of the cutting section. (2) The midpoint of the end of the cutting section is taken as the center position of the cutting section, and the center position of the cutting section is used as the position of the cutting section. (3) The width of the end of the cut portion (distance between the coordinates of two points) is defined as the cut portion, and the percentage by which the seam portion is offset to the left or right in the width direction relative to the cut portion is determined.

[0067] [How to utilize the location of the seam] The position of the seam detected by the position detection device 13 can be used, for example, as follows. (1) Use the position of the seam as the absolute position. (2) The position of the seam is used as the relative position to the position of the cutting part.

[0068] In (2) above, for example, the center position calculated by taking the average of the coordinates of two points at the end of the cutting section is used as the position of the cutting section, and the difference between the position of the cutting section and the position of the seam section is used as the position of the seam section. This reduces the amount of information that needs to be managed, and the position of the seam section can be easily calculated based on the position of the cutting section, which is easy to detect in subsequent processes.

[0069] According to the position detection device and method for the seam and cut portion of a welded steel pipe as described above, in the manufacturing of a welded steel pipe W, it is possible to accurately detect the position of the cut portion formed by cutting the weld bead formed by the welding process that welds the end, and the position of the seam portion, after cutting the seam portion, which is composed of the end of a steel plate joined by welding, and before heat treatment.

[0070] Furthermore, according to the position detection device and method for the seam and cut portions of a welded steel pipe as embodied in this embodiment, the positions of the cut portions and seams can be accurately detected using the image of the welded steel pipe W captured by the imaging unit 131, without using a separate light source or the like.

[0071] Furthermore, according to the position detection device and method for the seam and cut portion of a welded steel pipe as described in the embodiment, the positions of the seam and cut portion of the welded steel pipe W can be detected simultaneously. In addition, by utilizing the detected position of the cut portion, it becomes possible to heat the seam portion, which could not be directly heated in the past. This makes it possible to manufacture a higher quality welded steel pipe W.

[0072] Furthermore, the position detection device and method for the seam and cut portion of a welded steel pipe according to the embodiment can also be used for welded steel pipes W that are subject to strict regulations, which require setting the penetration width into the inner surface based on the seam portion. Strict regulations refer to defining the balance of how many mm of heat penetration width there is on the left and right sides of the seam portion when the welded steel pipe W is cut into sections.

[0073] [Manufacturing equipment and methods for welded steel pipes] The manufacturing equipment 1 for welded steel pipes W includes, for example, a welding machine 11, a cutting machine 12 located downstream of the welding machine 11, one or more annealing heating elements 14 located downstream of the cutting machine 12, a control device 15, a display unit 16, and the position detection device 13 described above.

[0074] Here, the position detection device 13 is positioned behind the cutting machine 12 and in front of the annealer heater 14. Since it is preferable that the temperature of the seam and the cutting area does not decrease, it is preferable that the position detection device 13 be close to the cutting machine 12. In the manufacture of welded steel pipes, a welding step is performed to weld the butt joint of the cylindrically formed steel plate, and after the welding step, a cutting step is performed to cut the weld bead after welding. After the cutting step, a position detection step is performed to detect the position of the seam and the cutting area of ​​the welded steel pipe using the position detection method described above. After the position detection step, a heating step is performed to heat the seam after cutting while controlling the position of the annealer heater based on the relative position of the seam with respect to the cutting area detected by the position detection step.

[0075] The welding machine 11 welds the butt joint of a cylindrical steel plate. The cutting machine 12 cuts the weld bead of the welded steel pipe W formed after welding by the welding machine 11. The annealer heater 14 heats the seam after cutting by the cutting machine 12. The control device 15 can control the position of the annealer heater 14 based on the positions of the cutting portion and the seam portion detected by the position detection device 13. In particular, the annealer heater 14 can also heat the seam portion after cutting while controlling the position of the annealer heater 14 based on the relative position of the seam portion to the cutting portion detected by the position detection device 13.

[0076] [Quality control methods for welded steel pipes] The quality control method for the welded steel pipe W involves managing the quality of the welded steel pipe W based on the amount of deviation between the position of the seam relative to the cut portion detected by the position detection device 13 before heat treatment with the annealer heating element 14, and the actual heating position of the cut portion by the annealer heating element 14, detected by the operator's visual inspection or a camera after heat treatment.

[0077] In the quality control method, for example, if the aforementioned deviation amount exceeds a predetermined threshold, an inspection process is carried out to check whether the quality (e.g., toughness) of the welded steel pipe W meets predetermined required specifications. Based on the results of the inspection process, it is decided whether to reuse the welded steel pipe W as a lower grade product or to discard it as a defective product. In this way, by classifying the welded steel pipe W based on the amount of deviation between the seam position relative to the cutting position and the actual heating position by the annealer heating element 14 relative to the cutting position, it is possible to provide welded steel pipe W of superior quality.

[0078] The present invention has been described in detail above with reference to embodiments and examples of the device for detecting the position of seams and cut portions of welded steel pipes, the manufacturing equipment for welded steel pipes, the method for detecting the position of seams and cut portions of welded steel pipes, the method for manufacturing welded steel pipes, and the method for controlling the quality of welded steel pipes. However, the spirit of the present invention is not limited to these descriptions and must be interpreted broadly based on the claims. It goes without saying that various modifications and alterations based on these descriptions are also included in the spirit of the present invention. [Explanation of symbols]

[0079] 1 Manufacturing equipment 11 Welding machine 12 Cutting machine 13 Position detection device 131 Imaging Unit 132 Arithmetic section 14 Anila heating element 15 Control device 16 Display section W Welded Steel Pipe

Claims

1. A position detection device for a welded steel pipe having a cut portion where the weld bead formed after the end of the steel plate is welded is cut off, which detects the position of the seam portion including the welded end of the welded steel pipe and the position of the cut portion, An imaging unit captures an image of the thermal radiation light from the outer surface of the welded steel pipe so that the cutting portion is within its field of view, A calculation unit that calculates the position of the seam and the position of the cutting portion from the captured image, Equipped with, The imaging unit is capable of imaging wavelengths longer than visible light wavelengths and shorter than far-infrared wavelengths. The aforementioned arithmetic unit, A first calculation unit calculates a brightness profile in the width direction of the welded steel pipe from the image captured by the imaging unit, A second calculation unit calculates the position of the seam and the position of the cutting portion from the calculated brightness profile, A position detection device for the seam and cut portion of a welded steel pipe.

2. The second calculation unit calculates the position of the seam portion from the position of the maximum value having the highest brightness value in the brightness profile, and calculates the position of the cutting portion from the positions of the sub-peak values ​​on both sides of the maximum value. A device for detecting the position of the seam portion and the cut portion of a welded steel pipe according to claim 1.

3. A welding machine for welding the butt joints of cylindrical steel plates, A cutting machine for cutting the weld bead after welding, A position detection device for the seam portion and cut portion of a welded steel pipe according to claim 1 or claim 2, An annealer heating element that heats the seam after cutting, A control device that controls the position of the annealer heater based on the relative position of the seam portion with respect to the cutting portion detected by the position detection device, Manufacturing equipment for welded steel pipes.

4. A position detection method for a welded steel pipe having a cut portion where the weld bead formed after the end of the steel plate is welded is cut off, wherein the position of the seam portion including the welded end of the welded steel pipe and the position of the cut portion are detected. The imaging step involves capturing an image of thermal radiation light from the outer surface of the welded steel pipe using an imaging unit capable of capturing wavelengths longer than visible light and shorter than far-infrared wavelengths, such that the cutting portion is within the field of view. A first calculation step involves calculating a brightness profile in the width direction of the welded steel pipe from the image captured in the above imaging step, A second calculation step involves calculating the position of the seam and the position of the cutting portion from the calculated brightness profile, A method for detecting the position of the seam and cut portion of a welded steel pipe, including the cut portion.

5. A welding step in which the butt joints of tubularly formed steel plates are welded, A cutting step to remove the weld bead after welding, A position detection step for detecting the position of the seam portion and the position of the cut portion of a welded steel pipe, according to the position detection method for the seam portion and the cut portion of a welded steel pipe described in claim 4, A heating step in which the seam portion after cutting is heated while controlling the position of the annealer heater based on the relative position of the seam portion with respect to the cutting portion detected by the position detection step, A method for manufacturing welded steel pipes, including the pipes mentioned above.

6. A method for controlling the quality of a welded steel pipe, which controls the quality of the welded steel pipe based on the amount of deviation between the position of the seam portion relative to the position of the cut portion detected before heat treatment by the method for detecting the position of the seam portion and the cut portion of the welded steel pipe described in claim 4, and the actual heating position relative to the cut portion detected after heat treatment.

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