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 a light source 131, an imaging unit 132, and a calculation unit 133. The imaging unit comprises a first channel and a second channel capable of imaging wavelengths longer than the wavelength of visible light and shorter than the wavelength of far infrared light. The calculation unit comprises a first calculation unit, a second calculation unit that calculates the position of the seam from a first brightness profile, and a third calculation unit that calculates the position of 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 method for detecting the positions of the seam portion and the cutting portion of a welded steel pipe, a method for manufacturing a welded steel pipe, and a quality control method for a welded steel pipe.

Background Art

[0002] In a production line of welded steel pipes (for example, electric welded pipes) in the steel process, a plate-shaped steel sheet is bent into a tubular shape by forming rolls, and both ends of the steel sheet are butted at the top and welded. The joint portion formed by both ends of the steel sheet joined by welding serves as a seam of the steel pipe and is called a seam portion. On the other hand, the 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, and it is important to accurately align and heat only the seam portion without affecting the base material by one or more annealing 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 annealing heater, that is, the position of the annealing 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 electromagnetic methods such as an eddy current sensor and a leakage magnetic flux sensor, and calculating the seam portion. Patent Document 2 also discloses a technique for calculating the seam portion by assuming that the center of the cutting portion and the seam portion are at the same position and detecting the cutting portion using an image method.

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 Initiative] [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, A light source that irradiates the seam portion and the cut portion with light in the first wavelength range, An imaging unit having multiple channels, which captures images of thermal radiation light from the outer surface of the welded steel pipe and light in the first wavelength range, such that the cutting portion irradiated with light in the first wavelength range is within the 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 A first channel capable of imaging wavelengths longer than visible light wavelengths and shorter than far-infrared wavelengths, A second channel capable of imaging reflected light from the cutting section of the light in the first wavelength range, Equipped with, The aforementioned arithmetic unit, A first calculation unit calculates a first brightness profile of the welded steel pipe in the radial direction from a first image captured by the first channel of the imaging unit, A second calculation unit calculates the position of the seam portion from the calculated first luminance profile, A third calculation unit calculates the position of the cutting portion from the second image captured by the second channel of the imaging unit, 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 first luminance profile calculated by the first calculation unit.

[0013] (3) 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) or (2) above, The third calculation unit calculates the position of the cutting portion as the position where the brightness value of the second image exceeds a predetermined threshold.

[0014] (4) 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 any one of the above items (1) to (3), The light source and the imaging unit are arranged to satisfy the specular reflection condition.

[0015] (5) 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, The position detection device for the seam part and the cutting part of the welded steel pipe according to any one of the above (1) to (4), An annealer heater for heating the seam part after cutting, A control device that controls the position of the annealer heater based on the position of the seam part relative to the cutting part detected by the position detection device, Comprising.

[0016] (6) The position detection method for the seam part and the cutting part of the welded steel pipe according to the present invention is for a welded steel pipe having a cutting part where a weld bead formed after welding the ends of a steel plate is cut, and is a position detection method for detecting the position of the seam part including the welded ends of the welded steel pipe and the position of the cutting part, An irradiation step of irradiating the seam part and the cutting part with light in a first wavelength range by a light source, An imaging step of imaging an image of the thermal radiation light from the outer surface of the welded steel pipe and the light in the first wavelength range so that the cutting part irradiated with the light in the first wavelength range enters the field of view by an imaging unit including a first channel capable of imaging a wavelength longer than the wavelength of visible light and shorter than the far-infrared wavelength and a second channel capable of imaging the reflected light of the light in the first wavelength range reflected by the cutting part, A first calculation step of calculating a first luminance profile with respect to the radial direction of the welded steel pipe from a first image captured by the first channel of the imaging unit, A second calculation step of calculating the position of the seam part from the calculated first luminance profile, A third calculation step of calculating the position of the cutting part from a second image captured by the second channel of the imaging unit, Including.

[0017] (7) The manufacturing method of the welded steel pipe according to the present invention, A welding step of welding the butted part of the steel plate formed in a cylindrical shape, A cutting step of cutting the weld bead after welding, A position detection step in which the position of the seam portion and the position of the cut portion are detected by the position detection method of the seam portion and the cut portion of the welded steel pipe described in (6) above, 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, Includes.

[0018] (8) The quality control method for welded steel pipes according to the present invention controls the quality of the welded steel pipes 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 (6) above, and the actual heating position relative to the cut portion detected after heat treatment. [Effects of the Invention]

[0019] According to the present invention, in the manufacture of welded steel pipes, the position of the cut portion formed by cutting the weld bead formed by the welding process to weld the end, before heat-treating the seam portion which is composed of the ends of steel plates joined by welding, can be accurately detected. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 shows an example of an image of a cut section of a welded steel pipe, captured with a far-infrared camera before heat treatment. [Figure 2] Figure 2 shows the luminance profile in the width direction of the welded steel pipe calculated from the image in Figure 1. [Figure 3] Figure 3 shows the brightness profile in the width direction of the 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 (first 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 (first brightness profile) in the width direction of a welded steel pipe calculated from a first image in a method for detecting the position of seam and cut portions 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. [Figure 10] Figure 10 shows an example of an image (second image) of light in the first wavelength range 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 11] Figure 11 shows an example of a luminance profile (second luminance profile) in the width direction of a welded steel pipe calculated from a second image 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. [Modes for carrying out the invention]

[0021] The following description will explain, with reference to the drawings, an embodiment of the present invention that describes a device for detecting the position of the seam and cut portion of a welded steel pipe, a manufacturing facility for a welded steel pipe, a method for detecting the position of the seam and cut portion of a welded steel pipe, a method for manufacturing a welded steel pipe, and a method for controlling the quality of a welded steel pipe. 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."

[0022] [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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] [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 identified as the seam.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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").

[0034] Figure 3 shows the luminance 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 after the cutting process to remove the weld bead and before the heat treatment to reheat the seam area with an annealer heater. 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 luminance value.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] [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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Figure 5 shows a schematic configuration of the position detection device 13. The position detection device 13 comprises a light source 131, an imaging unit 132, and a calculation unit 133.

[0044] The light source 131 irradiates the seam and cut portions of the welded steel pipe W with light in the first wavelength range. "Light in the first wavelength range" refers to light with wavelengths that do not interfere with the thermal radiation emitted from the outer surface of the welded steel pipe W. Specifically, for example, the aforementioned visible light can be used. However, if the wavelength of the light emitted by the light source 131 is close to the wavelength of the thermal radiation (red wavelength), it may interfere with the thermal radiation, potentially leading to misdetection of the difference between the cut portion and the seam portion. In that case, one or more blue and green light sources can be selected as the light source 131. In this embodiment, a blue light source with a peak wavelength of 470 nm, whose wavelength does not interfere with near-infrared and red wavelengths, was used as the light source 131.

[0045] Since the cut portion of the welded steel pipe W has a higher specular surface compared to the base material, when light is irradiated from the light source 131 under specular reflection conditions and the reflected light is imaged, the cut portion appears to shine, resulting in a higher apparent brightness. When using this phenomenon to detect the cut portion, the light source 131 and the imaging unit 132 (described later) can be positioned relative to each other in a manner that satisfies the specular reflection conditions for imaging.

[0046] Furthermore, since the welded steel pipe W twists during manufacturing (transportation), the position of the cutting section also moves in the width direction during manufacturing. Therefore, in order to be able to image the cutting section under specular reflection conditions even if the position of the cutting section moves, it is preferable that the shape of the light source 131 be elongated in the width direction of the welded steel pipe W. Accordingly, in this embodiment, a linear light source with a width direction length of approximately 1 m was used as the light source 131. Note that since the degree of twisting of the welded steel pipe W is expected to differ from one factory production line to another, or from one measurement location to another, a light source 131 of an appropriate length should be used according to the production line.

[0047] The imaging unit 132 captures images of the thermal radiation light from the outer surface of the welded steel pipe W and the light in the first wavelength range reflected by the welded steel pipe W, so that the cutting area irradiated with light in the first wavelength range is within its field of view.

[0048] As shown in Figure 5, the imaging unit 132 is positioned such that, with respect to the position of the welded part of the welded steel pipe W, the optical axis is located at a position rotated by an angle θ toward the β axis, where the longitudinal direction of the welded steel pipe W is the α axis and the height direction and perpendicular to the longitudinal direction is the β axis. Furthermore, in order to satisfy the specular reflection condition with respect to the light source 131, the angle between the optical axis of the light source 131 and the α axis is θ', and the angles θ and θ' are made equal.

[0049] Furthermore, with the α-axis set to 0°, the angle θ of the imaging unit 132 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 132 relative to the welded steel pipe W as described above, the brightness of the thermal radiation light can be measured stably.

[0050] The imaging unit 132 uses a temperature measurement camera having multiple channels, consisting of a first channel and a second channel. The first channel is a channel capable of imaging wavelengths longer than the wavelength of visible light and shorter than the wavelength of far infrared light.

[0051] The first channel is a channel capable of receiving and imaging thermal radiation light, and is, for example, a channel capable of imaging near-infrared wavelengths (wavelength range: 0.8 to 2.5 μm). Alternatively, as the first channel, 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 channel capable of imaging in the wavelength range of 0.9 to 1.8 μm as the first channel of the imaging unit 132. The imaging unit 132 uses this first channel to image the thermal radiation light from the outer surface of the welded steel pipe W. The image captured by the imaging unit 132 (first image) is transmitted to the calculation unit 133, which then performs position detection of the seam.

[0052] The second channel is capable of receiving and imaging reflected light from the cutting area where light in the first wavelength range is reflected. The light in the first wavelength range is light of the same wavelength as the light emitted by the aforementioned light source 131, for example, light emitted from a blue light source with a peak wavelength of 470 nm. The imaging unit 132 uses this second channel to image the light in the first wavelength range reflected from the cutting area of ​​the welded steel pipe W. The image captured by the imaging unit 132 (second image) is transmitted to the calculation unit 133, which then performs position detection of the cutting area. Since the imaging unit 132 has two channels as described above, it is possible to image the welded steel pipe W without any positional shift in both channels.

[0053] The calculation unit 133 calculates the position of the seam and the cut portion of the welded steel pipe W from the image captured by the imaging unit 132. The calculation unit 133 is implemented by a general-purpose computer such as a workstation or personal computer. Specifically, the calculation unit 133 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 133 stores an image processing program and program execution environment that calculate the positions of the seam and cut portion from the image signal transmitted from the imaging unit 132.

[0054] Furthermore, the calculation unit 133 includes a communication unit that receives image signals from the imaging unit 132 and outputs calculated position information of the seam and cutting areas to the control device 15 and the display unit 16. The calculation unit 133 also includes a first calculation unit, a second calculation unit, and a third calculation unit. These are realized through cooperation with the CPU and programs stored in memory.

[0055] The first calculation unit calculates a first luminance profile of the welded steel pipe W in the radial direction from the first image captured by the first channel of the imaging unit 132. The second calculation unit then calculates the position of the seam of the welded steel pipe W from the first luminance profile calculated by the first calculation unit. In this process, the second calculation unit calculates the position of the seam from the position of the maximum value, which has the highest luminance value, in the first luminance profile calculated by the first calculation unit.

[0056] The third calculation unit calculates a second brightness profile from the second image captured by the second channel of the imaging unit 132 for the region where the position of the cut portion of the welded steel pipe W is detected. The third calculation unit also calculates the position of the cut portion of the welded steel pipe W from the calculated second brightness profile. In this process, the third calculation unit calculates the position of the cut portion as the position where the brightness value of the second image exceeds a predetermined threshold.

[0057] [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.

[0058] Figure 6 is a flowchart showing 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 irradiation step (step S1), an imaging step (step S2), a first calculation step (step S3), a second calculation step (step S4), and a third calculation step (step S5).

[0059] First, the light source 131 irradiates the vicinity of the cut portion of the welded steel pipe W with light in the first wavelength range (step S1). Next, the imaging unit 132 captures an image of the thermal radiation light emitted from the outer surface of the welded steel pipe W using the first channel (first image), and captures an image of the light in the first wavelength range reflected from the cut portion of the welded steel pipe W using the second channel (second image) (step S2). At this time, the imaging unit 132 is positioned so that the cut portion of the welded steel pipe W is within the field of view of the imaging unit 132.

[0060] Next, the calculation unit 133 calculates the position of the seam portion of the welded steel pipe W from the first image. An example of the first image captured in the imaging step is shown in Figure 7. The first image captured by the imaging unit 132 is transmitted to the calculation unit 133. The first image transmitted from the imaging unit 132 is then acquired by the calculation unit 133.

[0061] Next, the first calculation unit of the calculation unit 133 calculates a first brightness profile from the acquired first image for the region where the position of the seam of the welded steel pipe W is detected (step S3). An example of the first brightness profile obtained from Figure 7 is shown in Figure 8. In the first 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.

[0062] Next, the second calculation unit of the calculation unit 133 calculates the position of the seam from the obtained first luminance profile (step S4). In step S4, 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.

[0063] [Details of the second calculation step] The details of the second calculation step (step S4) in Figure 6 will be explained below.

[0064] First, the second calculation unit detects the maximum value on the first 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.

[0065] 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 added to the first luminance profile, so corrections such as averaging or median processing may be performed on the first luminance profile before calculating the maximum value.

[0066] 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 first luminance profile and the luminance value to the left of the adjacent value. Here, x indicates the position in the width direction of the welded steel pipe W. If the value of f(x) is positive, the original first luminance profile represents monotonically increasing luminance; if it is negative, it represents monotonically decreasing luminance.

[0067] 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.

[0068]

number

[0069] 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.

[0070]

number

[0071] Based on these factors, f(x) is determined from the original first 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 first luminance profile. The second calculation unit then obtains the luminance at the identified maximum value position.

[0072] Next, the second calculation unit obtains the widthwise position and the corresponding luminance value for multiple maximum values ​​on the first luminance profile. The second calculation unit then determines that the position of the maximum value α with the highest luminance value, i.e., the highest temperature, is the position of the seam.

[0073] Next, the calculation unit 133 calculates the position of the cut portion of the welded steel pipe W from the second image. An example of the second image captured in the imaging step is shown in Figure 10. The second image captured by the imaging unit 132 is transmitted to the calculation unit 133. The second image transmitted from the imaging unit 132 is then acquired by the calculation unit 133.

[0074] Next, the third calculation unit of the calculation unit 133 calculates a second luminance profile from the acquired second image for the region where the position of the cut portion of the welded steel pipe W is detected (step S5). The second luminance profile calculated here is at the same position as the first luminance profile calculated by the first calculation unit. An example of the second luminance profile obtained from Figure 10 is shown in Figure 11. In the second luminance profile, the width direction of the welded steel pipe W is taken as the horizontal axis and the luminance value is taken as the vertical axis for a predetermined position in the longitudinal direction. Also, the symbols V~W in Figure 10 and the symbols V~W in Figure 11 are the same.

[0075] Next, the third calculation unit of the calculation unit 133 calculates the position of the cutting area from the obtained second luminance profile (step S5). In step S5, the second luminance profile is obtained from the second image, and the position in the obtained second luminance profile where the luminance value exceeds a predetermined threshold is calculated as the cutting area. Specifically, the position in the width direction where the predetermined threshold is exceeded is calculated as the end of the cutting area.

[0076] Because the cut area has a higher specular surface compared to the base material, it appears reflective and has a higher apparent brightness when imaged under specular reflection conditions. Therefore, the system searches for a position where the brightness value exceeds a predetermined threshold, moving from the left to the right of the second brightness profile, and the position where the threshold is first exceeded is calculated as the left edge of the cut area. Subsequently, the system searches for a position where the brightness value exceeds a predetermined threshold, moving from the right to the left of the second brightness profile, and the position where the threshold is first exceeded is calculated as the left edge of the cut area.

[0077] [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.

[0078] [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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] [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.

[0084] 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.

[0085] 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.

[0086] [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.

[0087] 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.

[0088] 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]

[0089] 1 Manufacturing equipment 11 Welding machine 12 Cutting machine 13 Position detection device 131 Light source 132 Imaging Unit 133 Arithmetic section 14 Anila heating element 15 Control device 16 Display 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, A light source that irradiates the seam portion and the cut portion with light in the first wavelength range, An imaging unit having multiple channels, which captures images of thermal radiation light from the outer surface of the welded steel pipe and light in the first wavelength range, such that the cutting portion irradiated with light in the first wavelength range is within the 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 A first channel capable of imaging wavelengths longer than visible light wavelengths and shorter than far-infrared wavelengths, A second channel capable of imaging reflected light from the cutting section of the light in the first wavelength range, Equipped with, The aforementioned arithmetic unit, A first calculation unit calculates a first brightness profile of the welded steel pipe in the radial direction from a first image captured by the first channel of the imaging unit, A second calculation unit calculates the position of the seam portion from the calculated first luminance profile, A third calculation unit calculates the position of the cutting portion from the second image captured by the second channel of the imaging unit, A position detection device for the seam and cut portion of a welded steel pipe.

2. The position detection device for seam portions and cut portions of a welded steel pipe according to claim 1, wherein the second calculation unit calculates the position of the seam portion from the position of the maximum value having the greatest brightness value in the first brightness profile calculated by the first calculation unit.

3. The position detection device for seam and cut portions of a welded steel pipe according to claim 1, wherein the third calculation unit calculates the position of the cut portion as the position where the brightness value of the second image exceeds a predetermined threshold.

4. The position detection device for the seam portion and cut portion of a welded steel pipe according to claim 1, wherein the light source and the imaging unit are arranged to satisfy specular reflection conditions.

5. 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 any one of claims 1 to 4, 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.

6. 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. An irradiation step in which light in the first wavelength range is irradiated onto the seam portion and the cutting portion with a light source, An imaging step involves capturing an image of the thermal radiation light from the outer surface of the welded steel pipe and the light in the first wavelength range, using an imaging unit that includes a first channel capable of imaging wavelengths longer than the wavelength of visible light and shorter than the wavelength of far infrared light, and a second channel capable of imaging reflected light from the cutting portion where the light in the first wavelength range is reflected, so that the cutting portion irradiated with light in the first wavelength range is in the field of view. A first calculation step involves calculating a first brightness profile in the radial direction of the welded steel pipe from a first image captured by the first channel of the imaging unit, A second calculation step involves calculating the position of the seam portion from the calculated first luminance profile, A third calculation step involves calculating the position of the cutting portion from the second image captured by the second channel of the imaging unit, A method for detecting the position of the seam and cut portion of a welded steel pipe, including the cut portion.

7. 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 of detecting the position of the seam portion and the position of the cut portion by the position detection method of the seam portion and the cut portion of a welded steel pipe according to claim 6, 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 pipe itself.

8. 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 6, and the actual heating position relative to the cut portion detected after heat treatment.

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