Method and apparatus for manufacturing electrically welded pipe, and monitoring device

Abstract

A method for manufacturing an electrically welded pipe (20) includes a forming step in which a metal sheet (10) is formed into a tubular shape while being conveyed, a welding step in which both end portions (11L, 11R) of the metal sheet (10) are butted and welded to make the metal sheet (10) into the electrically welded pipe (20), a cutting step in which a weld bead (22) is cut, and a heat treatment step in which a heat treatment is performed on a welded portion (21). In the method, a convergence point (12) of the both end portions (11L, 11R) is detected as a position of a welding surface (211) in the welding step, and a first offset amount of the convergence point (12) in a circumferential direction with respect to a reference position (R) is detected. In addition, a second offset amount is calculated by multiplying a coefficient (C) by the first offset amount, and a relative relationship between a position of a cutting portion (23) in the circumferential direction and a position of the welding surface (211) in the circumferential direction is obtained based on the second offset amount. Then, whether or not the electrically welded pipe (20) is manufactured with good quality is determined based on the relative relationship.

Description

Technical Field

[0001] This disclosure relates to a method and apparatus for manufacturing electric welded pipes. Furthermore, this disclosure relates to a monitoring device, and more specifically, to a monitoring device used in the manufacturing of electric welded pipes. Background Technology

[0002] Resistance welded pipes, also known as electric welded pipes, are manufactured through forming, welding, cutting, and heat treatment processes. In the forming process, a metal sheet unwound from a coil is formed into an open tubular shape. In the welding process, the two ends of the open tubular metal sheet are welded together to form the electric welded pipe. In the welding process, the two ends of the metal sheet are heated and melted, and then upsetting is performed, thus forming weld beads on the inner and outer surfaces of the electric welded pipe. In the cutting process, the weld beads are cut using a cutting device, forming cutting marks on the surface of the electric welded pipe. In the heat treatment process, the welded portion of the electric welded pipe is subjected to heat treatments such as normalizing, annealing, or quenching using a heat treatment device.

[0003] Traditionally, in heat treatment processes, the cutting marks (cutting areas) of the weld bead are considered as the weld joint, and the heating element of the heat treatment apparatus follows the cutting area to perform heat treatment along the weld joint. The cutting area of ​​the weld bead is approximately flat and has a metallic luster immediately after cutting, thus allowing for inspection using optical methods.

[0004] In contrast, Patent Document 1 discloses a technique for detecting the true weld seam in an electric welded pipe. In Patent Document 1, a two-dimensional thermal image of the weld seam before heat treatment is obtained by capturing images of the weld seam after cutting and before heat treatment using a thermal imaging camera. Based on this two-dimensional thermal image, the position of the weld seam before heat treatment and the position of the cut portion of the weld before heat treatment are calculated. Alternatively, Patent Document 1 also captures images of the weld seam after heat treatment using a thermal imaging camera, obtaining a two-dimensional thermal image of the weld seam after heat treatment. Based on this two-dimensional thermal image, the position of the cut portion of the weld after heat treatment and the position of the heating element (induction element) after heat treatment are calculated. Based on the positions of the cut portions of the weld before and after heat treatment, an offset relative to the position of the weld seam before heat treatment is detected, and the position of the true weld seam after heat treatment is calculated. Then, based on the position of the heating element after heat treatment and the position of the true weld seam, the offset between the position of the heating element and the position of the weld seam is calculated. Based on this offset, the heating element moves circumferentially in the electric welded pipe to approximate the position of the true weld seam. Patent Document 1 describes the following: Since the position of the heating element can be corrected by using the offset of the cutting part of the weld bead before and after heat treatment and the offset of the weld joint before and after heat treatment, the accuracy of the heating element following the weld joint is improved compared with the prior art, which has errors caused by the center of the cutting part not necessarily being the center of the weld line.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-30173 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In Patent Document 1, a thermal imaging camera is used to photograph the weld joint of an electric welded pipe. However, in the actual manufacturing of electric welded pipes, heat diffusion occurs at and around the weld joint, making it difficult to obtain a clear thermal image of the weld joint. Therefore, it is difficult to accurately detect the true weld joint, i.e., the position of the weld surface in the circumferential direction of the electric welded pipe, using thermal imaging.

[0010] The subject of this disclosure is to accurately detect the position of the welded surface in the circumferential direction of the welded pipe during the heat treatment of the welded portion of the welded pipe.

[0011] Solution for solving the problem

[0012] The method for manufacturing an electric welded pipe disclosed herein includes: a forming step in which a metal sheet is formed into a tubular shape while being conveyed, with both ends of the metal sheet facing each other; a welding step in which the two ends are butt-jointed and welded to form an electric welded pipe; a cutting step in which weld beads formed on the surface of the electric welded pipe in the welding step are cut; and a heat treatment step in which the welded portion of the electric welded pipe formed in the welding step is heat-treated after the cutting step. In this manufacturing method, the convergence point where the two ends approach and converge downstream in the conveying direction of the metal sheet is taken as the position of the welded surface of the electric welded pipe in the welding step, and a first offset of the convergence point in the circumferential direction of the electric welded pipe relative to a predetermined reference position is detected. In addition, a second offset is calculated by multiplying the first offset by a predetermined coefficient corresponding to the torsion of the electric welded pipe, and the relative relationship between the circumferential position of the cut portion formed by cutting the weld beads in the cutting step and the circumferential position of the welded surface is obtained based on the second offset. Then, the manufacturing qualification of the welded pipe is determined based on this relative relationship.

[0013] Another method for manufacturing an electric welded pipe disclosed herein includes: a forming step in which a metal sheet is formed into a tubular shape while being conveyed, with both ends of the metal sheet facing each other; a welding step in which the two ends are butt-jointed and welded to form an electric welded pipe; a cutting step in which weld beads formed on the surface of the electric welded pipe in the welding step are cut; and a heat treatment step in which the welded portion of the electric welded pipe formed in the welding step is heat-treated after the cutting step. In this manufacturing method, the convergence point where the two ends approach and converge downstream in the conveying direction of the metal sheet is taken as the position of the welded surface of the electric welded pipe in the welding step, and a first offset of the convergence point in the circumferential direction of the electric welded pipe relative to a predetermined reference position is detected. In addition, a second offset is calculated by multiplying the first offset by a predetermined coefficient corresponding to the torsion of the electric welded pipe, and the relative relationship between the circumferential position of the cut portion formed by cutting the weld beads in the cutting step and the circumferential position of the welded surface is obtained based on the second offset. In the heat treatment process, based on this relative relationship, the heating element included in the heat treatment apparatus used to perform heat treatment on the welded part is moved so that the welded surface is positioned at the circumferential center of the heat treatment area of ​​the heating element.

[0014] Invention Effects

[0015] According to this disclosure, during the heat treatment of the welded portion of the welded pipe, the position of the welded surface in the circumferential direction of the welded pipe can be detected with good accuracy. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the structure of the manufacturing apparatus for the electric welded pipe involved in each embodiment.

[0017] Figure 2 It is observed along the conveying direction of the welded pipe. Figure 1 A diagram of the heat treatment apparatus included in the manufacturing apparatus shown.

[0018] Figure 3 yes Figure 1 The side view of the manufacturing apparatus shown is a diagram representing a part of the manufacturing apparatus.

[0019] Figure 4 yes Figure 1 The top view of the manufacturing apparatus shown is a diagram showing a part of the manufacturing apparatus.

[0020] Figure 5 This is an example Figure 1 A diagram showing the hardware structure of the monitoring device included in the manufacturing apparatus.

[0021] Figure 6 This is a flowchart illustrating the processing of the monitoring device according to the first embodiment.

[0022] Figure 7A This is a schematic diagram illustrating the processing of the monitoring device according to the first embodiment.

[0023] Figure 7B This is a schematic diagram illustrating the processing of the monitoring device according to the first embodiment.

[0024] Figure 7C This is a schematic diagram illustrating the processing of the monitoring device according to the first embodiment.

[0025] Figure 7D This is a schematic diagram illustrating the processing of the monitoring device involved in the first embodiment.

[0026] Figure 7E This is a schematic diagram illustrating the processing of the monitoring device according to the first embodiment.

[0027] Figure 8 This is a flowchart illustrating the processing of the monitoring device according to the second embodiment.

[0028] Figure 9 This is a schematic diagram illustrating the processing of the monitoring device involved in the second embodiment.

[0029] Figure 10 This is a schematic diagram illustrating the processing of the monitoring device involved in the second embodiment.

[0030] Figure 11 This is a schematic diagram illustrating the processing of the monitoring device involved in the second embodiment.

[0031] Figure 12 It is a diagram showing a partial cross-section of the welded pipe.

[0032] Figure 13 This is a diagram used to illustrate the verification content based on the present inventors.

[0033] Figure 14A This is a diagram used to illustrate the verification content based on the present inventors.

[0034] Figure 14B This is a diagram used to illustrate the verification content based on the present inventors. Detailed Implementation

[0035] In the manufacturing of welded pipes, the weld beads formed on the inner and outer surfaces of the welded pipe are cut off during the cutting process, and the welded portion of the welded pipe is heat-treated during the heat treatment process. As mentioned above, conventionally, in the heat treatment process, the cutting marks (cutting portions) of the weld beads are regarded as the weld joint portion, and for example, the heating element of the heat treatment apparatus that performs normalizing, annealing, or quenching follows the cutting portion of the weld beads.

[0036] However, during the manufacturing of welded pipes, twisting (rolling) sometimes occurs within the pipe due to various reasons, such as the occurrence of camber (bending) in the base material coil, uneven edge strength of the coil, or uneven thickness. On the other hand, during the cutting process, the position of the cutting device (cutting blade) in the circumferential direction of the welded pipe is fixed. Therefore, when twisting occurs in the welded pipe, such as... Figure 12 As shown, a positional offset occurs between the center of the cut portion of the weld bead and the welding surface in the circumferential direction of the welded pipe.

[0037] In the heat treatment process following the cutting process, the heating element of the heat treatment apparatus is mechanically limited to the outer surface of the welded pipe. Therefore, heat treatment of the welded portion of the welded pipe is achieved through heat conduction from the outer surface to the inner surface. At this time, the heat transferred within the welded pipe diffuses, thus the area where the heating element performs the heat treatment (the heat treatment area) becomes... Figure 12 As shown by the dashed line, the welded pipe narrows circumferentially from the outer surface to the inner surface. Therefore, if the position of the weld surface is offset circumferentially from the center of the weld bead's cutting portion, especially on the inner surface of the welded pipe, it may be impossible to heat-treat the weld surface or the heat-affected zone around it at a sufficient temperature.

[0038] To address this issue, heat treatment of the welded portion at a higher temperature was considered. However, in this case, the temperature on the outer surface of the welded tube near the heating element could rise beyond a necessary level, potentially causing grain growth. Therefore, during the heat treatment process, it is required to heat the welded surface and the heat-affected zone as a whole at an appropriate temperature, for example, slightly above point Ac3.

[0039] In the welding process, the inventors monitored the offset of the convergence point at both ends of the metal plate in the circumferential direction of the welded pipe, using the pipeline center as a reference. The pipeline center refers to the imaginary line through which the central axis of the welded pipe passes when the welded pipe, formed from the metal plate, is transported in the welded pipe manufacturing apparatus without oscillating up, down, left, or right. The position of the convergence point at both ends of the metal plate corresponds to the position of the welding surface of the welded pipe in the welding process. Furthermore, the inventors discovered that by multiplying this offset by a certain coefficient, the offset of the welding surface at the weld bead cutting position, using the pipeline center as a reference, in the circumferential direction of the welded pipe can be obtained. The verification performed by the inventors will be described in detail below.

[0040] The inventors cut samples from the welded pipe immediately after cutting the weld bead, etched the cross-section of each sample, and measured the circumferential offset of the weld surface relative to the center of the pipe. For example... Figure 13As shown, there is a positive correlation between the circumferential offset of the weld surface relative to the pipeline center monitored during the welding process and the circumferential offset of the weld surface relative to the pipeline center measured immediately after cutting the weld bead. The inventors verified this by aligning the center of the cutting device with the pipeline center in the circumferential direction of the welded pipe. Therefore, it can also be said that… Figure 13 It is shown that there is a positive correlation between the circumferential offset of the weld surface relative to the center of the pipeline and the circumferential offset of the weld surface relative to the center of the cut portion of the weld bead.

[0041] Furthermore, the inventors cut a sample from the welded pipe just before cutting the weld bead, confirming the existence of a weld surface directly below the apex of the weld bead. Then, using a single roll of material, they obtained the circumferential offset of the weld surface relative to the pipe center and the circumferential offset of the weld bead apex relative to the pipe center, both monitored during the welding process. Figure 14A and Figure 14B As shown, the offset of the weld surface and the offset of the weld bead apex exhibit the same behavior throughout the entire length of the coil. Near the end of the coil, since there is no more coil upstream in the conveying direction, the offset of the weld surface increases during the welding process, but the offset of the weld bead apex still exhibits the same behavior. Therefore, it can be seen that there is a good correlation between the circumferential offset of the weld surface relative to the pipeline center monitored during the welding process and the circumferential offset of the weld surface relative to the pipeline center measured just before the weld bead is cut.

[0042] Based on the above verification results, it is known that by detecting the positional offset of the specified reference position and the welding surface in the circumferential direction of the welded pipe during the welding process, and multiplying this positional offset by a specified coefficient representing the torsion of the welded pipe since the welding process, the positional offset of the welding surface in the circumferential direction relative to the reference position after the cutting process can be calculated. In the cutting process, a cutting portion forming the weld bead at a fixed position in the circumferential direction of the welded pipe is formed. The circumferential position of the cutting portion can be determined. Therefore, after the cutting process, as long as the positional offset of the welding surface in the circumferential direction relative to the reference position can be calculated, the relative relationship between the circumferential position of the cutting portion of the weld bead and the circumferential position of the welding surface can be obtained. Based on these insights, the inventors have completed the method for manufacturing the welded pipe according to the embodiments.

[0043] The method for manufacturing an electric welded pipe according to the embodiment includes: a forming step, in which a metal sheet is formed into a tube shape while being conveyed, with both ends of the metal sheet facing each other; a welding step, in which the two ends are butt-jointed and welded to form an electric welded pipe; a cutting step, in which weld beads formed on the surface of the electric welded pipe in the welding step are cut; and a heat treatment step, in which the welded portion of the electric welded pipe formed in the welding step is heat-treated after the cutting step. In this manufacturing method, the convergence point where the two ends approach and converge downstream in the conveying direction of the metal sheet is taken as the position of the welding surface of the electric welded pipe in the welding step, and a first offset of the convergence point in the circumferential direction of the electric welded pipe relative to a predetermined reference position is detected. In addition, a second offset is calculated by multiplying the first offset by a predetermined coefficient corresponding to the torsion of the electric welded pipe, and the relative relationship between the circumferential position of the cut portion formed by cutting the weld beads in the cutting step and the circumferential position of the welding surface is obtained based on the second offset. Then, the manufacturing qualification of the electric welded pipe is determined based on this relative relationship (first component).

[0044] Another embodiment of the method for manufacturing an electric welded pipe includes: a forming step in which a metal sheet is formed into a tube with its two ends facing each other while being conveyed; a welding step in which the two ends are joined and welded to form an electric welded pipe; a cutting step in which weld beads formed on the surface of the electric welded pipe in the welding step are cut; and a heat treatment step in which the welded portion of the electric welded pipe formed in the welding step is heat treated after the cutting step. In this manufacturing method, the convergence point where the two ends approach and converge downstream in the conveying direction of the metal sheet is taken as the position of the welded surface of the electric welded pipe in the welding step, and a first offset of the convergence point in the circumferential direction of the electric welded pipe relative to a predetermined reference position is detected. In addition, a second offset is calculated by multiplying the first offset by a predetermined coefficient corresponding to the torsion of the electric welded pipe, and the relative relationship between the circumferential position of the cut portion formed by cutting the weld beads in the cutting step and the circumferential position of the welded surface is obtained based on the second offset. In the heat treatment process, based on this relative relationship, the heating element included in the heat treatment apparatus used to perform heat treatment on the welded part is moved so that the welded surface is positioned in the circumferential center of the heat treatment area of ​​the heating element (second configuration).

[0045] In the manufacturing method of the welded pipe involved in the first and second configurations, the positional offset of the convergence points at both ends of the metal plate relative to a predetermined reference position in the circumferential direction of the welded pipe is measured as a first offset. A second offset can be calculated by multiplying the first offset by a coefficient corresponding to the torsion amount of the welded pipe. The second offset corresponds to the positional offset of the weld surface in the circumferential direction relative to the aforementioned reference position after the cutting process. If the second offset can be calculated, the relative relationship between the circumferential position of the weld bead's cutting portion and the circumferential position of the weld surface can be obtained as described above. Therefore, the position of the weld surface after the cutting process can be accurately detected; more specifically, the position of the weld surface in the circumferential direction relative to the weld bead's cutting portion can be accurately detected.

[0046] Furthermore, in the first and second configurations, it is sufficient to detect the first offset of the convergence points at both ends of the metal plate in the circumferential direction of the welded pipe during the welding process; the second offset can be derived from the first offset through calculation. Since the convergence points at both ends of the metal plate are geometric features, the first offset can be detected using optical methods. Therefore, it is not necessary to use a thermal imaging camera as in Patent Document 1, and there is no reduction in detection accuracy caused by unclear thermal images.

[0047] Therefore, according to the manufacturing method of the welded pipe involved in the first and second configurations, during the heat treatment of the welded part of the welded pipe, the position of the welded surface in the circumferential direction of the welded pipe can be detected with good accuracy.

[0048] When the weld surface deviates significantly from the cut portion of the weld bead in the circumferential direction of the welded pipe, the weld portion, specifically the weld surface and heat-affected zone, of the welded pipe tends to deviate from the heat treatment area of ​​the heating element when the heating element of the heat treatment apparatus follows the cut portion of the weld bead. In this case, it is difficult to perform sufficient heat treatment on the weld surface and heat-affected zone of the welded pipe as a whole. In contrast, in the first configuration, the manufacturing quality of the welded pipe is determined based on the circumferential position of the weld surface, not the cut portion of the weld bead. More specifically, the quality related to heat treatment can be determined based on the relative relationship between the circumferential position of the cut portion of the weld bead and the circumferential position of the weld surface. Therefore, the manufacturing quality of the welded pipe can be determined with high accuracy, and the outflow of welded pipes with insufficient heat treatment of the weld portion can be prevented.

[0049] In the second configuration, the heating element of the heat treatment apparatus is moved according to the relative relationship between the circumferential position of the weld bead's cutting portion and the circumferential position of the weld surface, so that the weld surface is positioned at the circumferential center of the heat treatment zone. That is, during the heat treatment process, the heating element follows the weld surface of the welded pipe. In this case, even if the weld surface is offset circumferentially relative to the weld bead's cutting portion, the weld surface and heat-affected zone of the welded pipe easily fall within the heat treatment zone of the heating element. Therefore, good heat treatment can be performed on the weld surface and heat-affected zone as a whole.

[0050] In the manufacturing method of the welded pipe involved in the first or second configuration, the welded pipe can have a thickness of 5.0 mm or more (third configuration).

[0051] The thicker the wall of the welded pipe, the narrower the heat treatment area of ​​the heating element of the heat treatment apparatus is in the circumferential direction on the inner surface side of the welded pipe. Therefore, when the welding surface is offset in the circumferential direction relative to the cutting portion of the weld bead, the thicker the wall of the welded pipe, the more easily the weld portion (weld surface and heat-affected zone) is offset from the heat treatment area of ​​the heating element on the inner surface side of the welded pipe. However, in the manufacturing method of the welded pipe according to the above embodiment, the relative relationship between the circumferential position of the cutting portion of the weld bead and the circumferential position of the welding surface can be determined based on the second offset amount. Therefore, as in the third configuration, even when the welded pipe has a thickness of 5.0 mm or more, it is possible to accurately determine whether the manufacturing of the welded pipe is qualified, or to enable the heating element to follow the welding surface and perform good heat treatment on the welding surface and the heat-affected zone as a whole.

[0052] The monitoring device involved in the embodiment is used in the manufacture of welded pipe. The manufacture of the welded pipe includes: a forming process in which a metal sheet is formed into a tube with its two ends facing each other while being conveyed; a welding process in which the two ends are joined and welded to form a welded pipe; a cutting process in which the weld beads formed on the surface of the welded pipe in the welding process are cut; and a heat treatment process in which the welded portion of the welded pipe formed in the welding process is heat-treated after the cutting process. The monitoring device is configured to perform the following processing: capturing images by an imaging device to acquire image data containing a convergence point, which is a point where both ends approach and converge downstream in the direction of conveying the metal plate; based on the image data, using the convergence point as the position of the welding surface of the welded pipe in the welding process, detecting a first offset of the convergence point in the circumferential direction of the welded pipe relative to a predetermined reference position; multiplying the first offset by a predetermined coefficient corresponding to the torsion of the welded pipe to calculate a second offset; obtaining, based on the second offset, the relative relationship between the circumferential position of the cutting portion formed by cutting the weld bead in the cutting process and the circumferential position of the welding surface; and determining whether the manufacture of the welded pipe is qualified based on this relative relationship (fourth configuration).

[0053] The apparatus for manufacturing an electric welded pipe according to the embodiment includes a welding device, a cutting device, a heat treatment device, and a monitoring device. The welding device is configured to butt-weld the two ends of a metal sheet that is being conveyed and formed into a tubular shape, thereby forming an electric welded pipe. The cutting device is disposed downstream of the welding device in the conveying direction of the metal sheet. The cutting device is configured to cut the weld bead formed on the surface of the electric welded pipe. The heat treatment device is disposed downstream of the cutting device in the conveying direction. The heat treatment device includes a heating element for performing heat treatment on the welded portion of the electric welded pipe. The monitoring device is configured to control the movement of the heating element. The monitoring device is configured to perform the following processing: capturing images by an imaging device to acquire image data containing a convergence point, which is a point where both ends approach and converge downstream in the direction of transport; based on the image data, taking the convergence point as the position of the welding surface of the welding pipe in the welding device, detecting a first offset of the convergence point in the circumferential direction of the welding pipe relative to a predetermined reference position; multiplying the first offset by a predetermined coefficient corresponding to the torsion of the welding pipe to calculate a second offset; obtaining, based on the second offset, the relative relationship between the circumferential position of the cutting portion formed by cutting the weld bead using a cutting device and the circumferential position of the welding surface; and, based on this relative relationship, moving the heating element so that the welding surface is positioned at the circumferential center of the heat treatment area of ​​the heating element (fifth configuration).

[0054] The following is a reference to the appendix. Figure 1The embodiments of this disclosure will be described below. In these figures, the same or equivalent components are labeled with the same reference numerals, and the same descriptions are not repeated.

[0055] <First Embodiment>

[0056] Figure 1 This is a schematic diagram showing the structure of the welding pipe manufacturing apparatus 100. (Refer to...) Figure 1 The manufacturing apparatus 100 conveys the strip-shaped metal plate 10 along its length while manufacturing the welded pipe 20 from the metal plate 10.

[0057] The metal plate 10 used as the base material is typically a steel plate (steel strip). However, the metal plate 10 can also be a metal plate other than steel, such as an aluminum alloy plate. Although not particularly limited, the manufactured welded pipe 20 can, for example, have a thickness (wall thickness) of 5.0 mm or more. The welded pipe 20 can also be a so-called thick-walled pipe. That is, the welded pipe 20 can also have a thickness of 10.0 mm or more. The welded pipe 20 can have a thickness of 12.7 mm or more, or a thickness of 15.0 mm or more. The welded pipe 20 can have a thickness of 20.0 mm or less.

[0058] like Figure 1 As shown, the manufacturing apparatus 100 includes a forming apparatus 30, a welding apparatus 40, a cutting apparatus 50, and a heat treatment apparatus 60. The forming apparatus 30, the welding apparatus 40, the cutting apparatus 50, and the heat treatment apparatus 60 are arranged sequentially from upstream to downstream in the conveying direction of the metal plate 10.

[0059] A sheet of metal 10, unwound from a coil, is continuously fed into the forming apparatus 30. The two ends 11L and 11R of the sheet of metal 10 in the width direction can be trimmed, for example, by a milling machine (not shown) before being fed into the forming apparatus 30. The forming apparatus 30 includes, for example, a roughing roller group 31, a finishing roller group 32, and a seam guide 33. The roughing roller group 31, the finishing roller group 32, and the seam guide 33 are arranged sequentially from upstream to downstream in the conveying direction of the sheet of metal 10.

[0060] The forming device 30 forms the conveyed metal sheet 10 into a tubular shape (open tubular shape). The rough forming roller group 31 performs bending processing on the two ends 11L and 11R of the metal sheet 10. Through the rough forming roller group 31, the two ends 11L and 11R of the metal sheet 10 are bent... Figure 1 The metal plate 10 is bent upwards on the paper surface, forming an arc shape. The precision forming roller group 32 performs precision forming on the metal plate 10, giving it a substantially circular cross-section. The seam guide 33 is positioned between the two ends 11L and 11R of the generally tubular metal plate 10, adjusting the spacing between the opposing ends 11L and 11R.

[0061] The welding device 40 welds the two ends 11L and 11R of the metal plate 10. More specifically, the welding device 40 is configured to butt and weld the two ends 11L and 11R of the metal plate 10, which is being conveyed and formed into a tubular shape, so that the metal plate 10 becomes an electric welded pipe 20. The welding device 40 includes a heating device 41 and an extrusion roller 42.

[0062] The heating device 41 is configured to heat and melt both ends 11L and 11R of the metal plate 10. Typically, the heating device 41 is a resistance heating device. The heating device 41 can also be a high-frequency heating device. In this case, the heating device 41 supplies a high-frequency current to the metal plate 10, using Joule heating to melt both ends 11L and 11R of the metal plate 10. The heating device 41 can use electrodes such as working coils or contact heads to inductively or directly supply a high-frequency current to the tubular metal plate 10.

[0063] The extrusion roller 42 is positioned downstream of the heating device 41 in the conveying direction of the metal plate 10. The extrusion roller 42 is configured to apply pressure to the metal plate 10 so that its two ends 11L and 11R press against each other.

[0064] The cutting device 50 is disposed downstream of the welding device 40 in the conveying direction of the metal plate 10 (welded pipe 20). The cutting device 50 is configured to cut the weld bead formed on the surface of the welded pipe 20. The cutting device 50 is disposed on both the outer surface side and the inner surface side of the welded pipe 20.

[0065] The manufacturing apparatus 100 includes at least one heat treatment apparatus 60. This heat treatment apparatus 60 is disposed downstream of the welding apparatus 40 in the conveying direction of the metal sheet 10. In this embodiment, the manufacturing apparatus 100 includes multiple heat treatment apparatuses 60. These heat treatment apparatuses 60 are arranged along the conveying direction of the metal sheet 10.

[0066] Figure 2 This is a view of a heat treatment apparatus 60 viewed along the transport direction of the welded pipe 20. The heat treatment apparatus 60 is, for example, positioned above the welded pipe 20. The heat treatment apparatus 60 includes a heating element 61 and a drive mechanism 62. The heating element 61 is typically an induction coil (heating coil). The heating element 61 performs heat treatment on the weld portion 21 of the welded pipe 20. The weld portion 21 is the portion including the weld surface 211 and the heat-affected zone surrounding the weld surface 211. The drive mechanism 62 is configured to move the heating element 61 within the heat treatment apparatus 60. Known heat treatment apparatuses can be used as the heat treatment apparatus 60. The heat treatment apparatus 60 is a device for performing normalizing, annealing, or quenching, etc., on the weld portion 21.

[0067] Although the illustration is omitted, a shaping device (sizing machine) can also be arranged downstream of the heat treatment apparatus 60 in the conveying direction of the welded pipe 20. The shaping device can adjust the shape of the welded pipe 20.

[0068] [Manufacturing method of electric welded pipe]

[0069] Next, the manufacturing method of the welded pipe 20 using the manufacturing apparatus 100 will be described. The manufacturing method of the welded pipe 20 according to this embodiment includes a forming process, a welding process, a cutting process, and a heat treatment process.

[0070] (Forming process)

[0071] return Figure 1 In the forming process, the metal sheet 10 is fed while being formed into a tubular shape with its two ends 11L and 11R facing each other. More specifically, after being unwound from the coil, the metal sheet 10 is continuously fed to the forming device 30 and formed into a tubular shape by the forming device 30. The metal sheet 10 is thus formed into an open tubular shape with its two ends 11L and 11R facing each other in the circumferential direction by the forming device 30.

[0072] (Welding process)

[0073] In the welding process, the two ends 11L and 11R of the metal plate 10 are butt-jointed and welded to form an electric welded pipe 20. More specifically, the tubular metal plate 10 formed in the forming process is continuously fed to the welding device 40. The metal plate 10 is first fed to the heating device 41, and the two ends 11L and 11R are heated by the heating device 41. As a result, the two ends 11L and 11R of the metal plate 10 melt. The metal plate 10 is fed to the extrusion roller 42 while the two ends 11L and 11R are molten. The two ends 11L and 11R of the metal plate 10 approach and contact as it moves downstream in the conveying direction. The extrusion roller 42 presses the metal plate 10, whose two ends 11L and 11R are in contact, from the outer surface side. As a result, the two ends 11L and 11R of the metal plate 10 are pressed against each other.

[0074] After passing through the extrusion rollers 42, the two ends 11L and 11R of the metal plate 10 solidify and join under natural cooling as it is conveyed downstream. The joining of the two ends 11L and 11R makes the metal plate 10 into an electric welded pipe 20.

[0075] (Cutting process)

[0076] In the welding process, weld beads are formed on the surface of the welded pipe 20. Molten metal is extruded from both ends 11L and 11R of the metal plate 10 by the extrusion rollers 42, thereby forming weld beads on the outer and inner surfaces of the welded pipe 20, respectively. In the cutting process, the weld beads formed on the surface of the welded pipe 20 are cut off. Specifically, each weld bead on the outer and inner surfaces of the welded pipe 20 is cut off by the cutting device 50.

[0077] (Heat treatment process)

[0078] The heat treatment process is performed after the cutting process. In the heat treatment process, the weld portion 21 of the electric welded pipe 20 formed in the welding process is treated. Figure 2 Heat treatment is performed. In this embodiment, when the welded pipe 20 passes through the heat treatment apparatus 60, the heating element 61 of each heat treatment apparatus 60 is used to perform heat treatment. Figure 2 The welded part 21 of the electric welded pipe 20 is subjected to heat treatment such as normalizing, annealing or quenching.

[0079] [Structure and processing of monitoring devices]

[0080] Figure 3 This is a side view of the manufacturing apparatus 100 as viewed from the side with respect to the conveying direction of the metal plate 10 and the welded pipe 20. Figure 4 This is a top view (top view) of the manufacturing apparatus 100 as viewed from above relative to the conveying direction. Figure 3 and Figure 4 The image shows, with an enlarged view, the welding device 40, the cutting device 50, and the heat treatment device 60 within the manufacturing apparatus 100. (Example) Figure 3 and Figure 4 As shown, the manufacturing apparatus 100 according to this embodiment also includes a monitoring device 70. Hereinafter, the structure and operation of the monitoring device 70 will be described in detail.

[0081] Reference Figure 3 and Figure 4 The monitoring device 70 and the imaging device 81 are communicatively connected. The monitoring device 70 is connected to the imaging device 81, for example, via a network. The imaging device 81 is positioned to capture images of the convergence point 12 at both ends 11L and 11R of the metal plate 10. The convergence point 12 is the point where the two ends 11L and 11R of the metal plate 10 approach and converge as it travels downstream in the direction of transport during the welding process. The imaging device 81 is, for example, located near the extrusion roller 42 of the welding device 40.

[0082] The imaging device 81 captures a self-illuminating pattern (radiating pattern) of the V-shaped region containing the convergence point 12 at both ends 11L and 11R of the metal plate 10. While not particularly limited, the imaging device 81 may be, for example, a 3CCD type color camera capable of having 1920 × 512 pixels. The imaging device 81 captures the region containing the convergence point 12, for example, under the conditions of a shooting field of view of 50 mm × 190 mm, a resolution of 100 μm / pixel, a shooting frame rate of 500 fps, and an exposure time of 1 / 10000 sec. The imaging device 81 can continuously capture images of the transported metal plate 10 or intermittently at predetermined time intervals.

[0083] The monitoring device 70 can also be communicatively connected to other camera devices 82. For example, the monitoring device 70 can be connected to the camera device 82 via a network. Figure 3 In this example, the imaging device 82 is located near the heat treatment device 60. The imaging device 82 can also be the same 3CCD type color camera as the imaging device 81.

[0084] The monitoring device 70 processes the data from the images captured by the imaging devices 81 and 82. The monitoring device 70 is, for example, a computer. Figure 5 This is a diagram illustrating the hardware structure of the monitoring device 70. (Example) Figure 5 As shown, the monitoring device 70 may include a central processing unit (CPU) 71, a main storage device 72, an auxiliary storage device 73, an input device 74, and an output device 75.

[0085] CPU 71 executes various programs loaded from auxiliary storage device 73 to main storage device 72, performing information processing. Main storage device 72, for example, is RAM, used as a working area to temporarily store various programs executed by CPU 71, information used by CPU 71, and the results of CPU 71's operations. Auxiliary storage device 73, for example, is HDD, ROM, etc. The function (processing) of monitoring device 70 is implemented, for example, by loading control programs stored in auxiliary storage device 73 to main storage device 72 and having CPU 71 execute the control programs. Input device 74 is a device for allowing the operator to perform input operations, including, for example, a mouse, a touch panel, a keyboard, etc. Output device 75 is a device for outputting the processing results of CPU 71, etc. Output device 75 may include a display.

[0086] Figure 6 This is a flowchart illustrating the processing of the monitoring device 70. Figures 7A-7E This is a schematic diagram illustrating the processing of the monitoring device 70. The following also refers to... Figure 6 and Figures 7A-7E The manufacturing method of the electric welded pipe 20 and the processing of the monitoring device 70 involved in this embodiment will be described in detail.

[0087] like Figure 6 As shown, the manufacturing method of the electric welded pipe 20 according to this embodiment includes steps S1 to S4. Steps S1 to S4 are controlled by the CPU 71 of the monitoring device 70. Figure 5 )implement.

[0088] In step S1, processing is performed to acquire image data captured by the imaging device 81. The image data includes the convergence points 12 of the two ends 11L and 11R of the metal plate 10. The image data is input from the imaging device 81 to the monitoring device 70, for example, via a network.

[0089] Following step S1, step S2 is performed. In step S2, based on the image data, a process for detecting a first offset is executed. The first offset is the positional offset of the convergence point 12 of the two ends 11L and 11R of the metal plate 10 relative to a predetermined reference position in the circumferential direction of the welded pipe 20. The first offset can be detected, for example, as follows.

[0090] In step S2, the positions of the convergence points 12 at both ends 11L and 11R of the metal plate 10 are derived from the image data captured by the imaging device 81. Figure 7A This is a schematic diagram illustrating an example of image data 90 captured by the imaging device 81. (See reference...) Figure 7A For example, by setting the conveying direction of the metal plate 10 as the x-direction and the direction perpendicular to the conveying direction (circumferential direction) as the y-direction, the xy coordinates of the convergence point 12 in the image data 90 can be derived. After performing necessary processing such as red component extraction, binarization, and marking on the image data 90, the monitoring device 70 can detect the front end of the V-shaped convergence region 91 (convergence region) at both ends 11L and 11R of the metal plate 10 as the convergence point 12. The position of the front end of the convergence region 91 can be derived, for example, by the method described in International Publication No. 2011 / 118560 or International Publication No. 2013 / 157422.

[0091] In this embodiment, the y-coordinate of the front end of the V-shaped convergence region 91 is used as the position of the convergence point 12 in the circumferential direction. The monitoring device 70 can obtain the position of the convergence point 12 for two or more consecutive image data in time and use their average value as the position of the convergence point 12, or it can derive the position of the convergence point 12 from a single image data.

[0092] In step S2, the difference in the circumferential (y-direction) distance between the convergence point 12 of the two ends 11L and 11R of the metal plate 10 and the specified reference position R is further derived. Figure 7AIn the example, the reference position R is the position of the pipeline center on the circumference of the welded pipe 20. However, the reference position R does not necessarily have to be set at the pipeline center. The reference position R can be any fixed position on the circumference of the welded pipe 20 that can serve as a reference.

[0093] The reference position R can be, for example, a fixed y-coordinate pre-stored in the monitoring device 70, or it can be determined by detecting a reference piece pre-set in the manufacturing apparatus 100. When a reference piece is provided in the manufacturing apparatus 100, the imaging device 81 can capture images of the reference piece along with the convergence points 12 of the two ends 11L and 11R of the metal plate 10. The monitoring device 70 can determine the y-coordinate of the reference piece based on the image data captured by the imaging device 81 and set it as the circumferential reference position R of the welded pipe 20.

[0094] The monitoring device 70 can calculate the first offset by obtaining the difference between the circumferential position of the convergence point 12 at both ends 11L and 11R of the metal plate 10 and the reference position R. The first offset is a value indicating the degree to which the convergence point 12 has shifted relative to the reference position R in the circumferential (y-direction) of the welded pipe 20. The monitoring device 70 can determine which side of the circumferential direction the convergence point 12 has shifted relative to the reference position R based on the sign of the difference between the circumferential position of the convergence point 12 at both ends 11L and 11R of the metal plate 10 and the reference position R.

[0095] Following step S2, step S3 is performed. In step S3, the first offset calculated in step S2 is multiplied by a predetermined coefficient C to calculate the second offset. (Refer to the following...) Figures 7B-7E The coefficient C and the second offset are explained.

[0096] exist Figure 7B The cross-section of the welded pipe 20 (metal plate 10) at the location of the welding device 40 is partially shown. (Refer to...) Figure 7B In the metal plate 10, the convergence point 12 formed during the welding process is at both ends 11L and 11R ( Figure 7A The point of convergence 12 corresponds to the position of the welding surface (abutment surface) 211 of the welded pipe 20 in the welding process. That is, the first offset of the convergence point 12 in the circumferential direction of the welded pipe 20 relative to the reference position R is the position offset of the welding surface 211 in the circumferential direction relative to the reference position R in the welding process.

[0097] exist Figure 7C The cross-section of the welded pipe 20 is partially shown at a position immediately in front of the cutting device 50. Figure 7D The cross-section of the welded pipe 20 is partially shown at a position immediately behind the cutting device 50. Figure 7EThe cross-section of the welded pipe 20 at the location between the cutting device 50 and the heat treatment device 60 is shown in partial view. (Refer to...) Figure 7B and Figures 7C-7E For example, the welding surface 211 may sometimes move along the circumference of the welding pipe 20 at a position downstream of the welding device 40 relative to the welding process time due to the torsion generated in the welding pipe 20.

[0098] The amount of torsion of the welded pipe 20 after the welding process corresponds to the coefficient C used in step S3. The coefficient C can be obtained in advance, for example, by conducting a preliminary test under the same conditions as the manufacturing conditions of the welded pipe 20. That is, the coefficient C is a value determined in advance during the preliminary test. In the preliminary test, the positions (coordinates) of the convergence points 12 at both ends 11L and 11R of the metal plate 10 are acquired using the monitoring device 70, and a sample of the welded pipe 20 is acquired at a measurement position downstream of the welding process to measure the position of the welding surface 211 in the circumferential direction of the welded pipe 20. The measurement position is set to a position where the relative positional relationship between the cutting area (processing area) of the cutting device 50 and the welding surface 211 in the circumferential direction can be confirmed. Specifically, a sample of the welded pipe 20 can be acquired at a position immediately in front of or immediately behind the cutting device 50 as the measurement position. Alternatively, the measurement position can be set at the location between the cutting device 50 and the heat treatment device 60, or, in the case of multiple heat treatment devices 60, at a position after the cutting device 50 and before the upstream (first) heat treatment device 60, and a sample of the welded pipe 20 can be obtained. The amount of torsion of the welded pipe 20 corresponding to the coefficient C refers to the amount of torsion generated in the welded pipe 20 between the welding position and the cutting position or the heat treatment position, and more specifically, the amount of torsion generated in the welded pipe 20 between the convergence point 12 and the measurement position of the weld surface 211 in the preliminary test.

[0099] like Figure 7C As shown, when a sample of the welded pipe 20 is obtained at a position immediately in front of (entry side) of the cutting device 50, weld beads 22 exist on the inner and outer surfaces of the welded pipe 20 before the cutting process performed using the cutting device 50. In the cross-section of the welded pipe 20, the welding surface 211 is located directly below the apex of the weld bead 22. By observing the cross-section of the welded pipe 20, the positional offset of the welding surface 211 relative to the reference position R in the circumferential direction can be confirmed. Since the cutting device 50 is fixedly arranged in the circumferential direction of the welded pipe 20, the cutting area of ​​the cutting device 50 is fixed in the circumferential direction of the welded pipe 20 relative to the reference position R. When the reference position R is the center of the pipeline as in this embodiment, the position of the center of the cutting area of ​​the cutting device 50 in the circumferential direction of the welded pipe 20 coincides with the reference position R. The position immediately in front of the cutting device 50 refers, for example, to a position 200 mm or less upstream of the cutting device 50.

[0100] like Figure 7D As shown, when a sample of the welded pipe 20 is obtained immediately behind (on the exit side) of the cutting device 50, since the cutting process is performed using the cutting device 50, a weld bead 22 ( Figure 7C The cutting portion (cutting mark) 23 of the welded pipe 20. By observing the cross-section of the welded pipe 20, the positional offset of the welded surface 211 relative to the reference position R in the circumferential direction can be confirmed. In the circumferential direction of the welded pipe 20, the center of the cutting portion 23 is aligned with the center of the pipeline. When the reference position R is the center of the pipeline as in this embodiment, the center of the cutting portion 23 in the circumferential direction of the welded pipe 20 is aligned with the reference position R. If it is immediately behind the cutting device 50, the center of the cutting portion 23 in the circumferential direction of the welded pipe 20 is aligned with the center of the cutting area of ​​the cutting device 50. The position immediately behind the cutting device 50 refers, for example, to a position 200 mm or less downstream of the cutting device 50.

[0101] like Figure 7E As shown, when a sample of the welded pipe 20 is obtained at a position between the cutting device 50 and the heat treatment device 60, if it is compared with the position immediately in front of or immediately behind the cutting device 50 ( Figure 7C and Figure 7D Sometimes, due to torsion occurring downstream of the cutting device 50 in the welding pipe 20, the welding surface 211 and the cutting portion 23 may move circumferentially along the welding pipe 20. However, even in this case, by observing the cross-section of the welding pipe 20, the positional offset of the welding surface 211 relative to the reference position R in the circumferential direction can be confirmed. In addition, the positional offset of the center of the cutting portion 23 relative to the reference position R in the circumferential direction can also be measured.

[0102] Through preliminary testing, for weld surface 211, the correlation between the circumferential offset (first offset) of weld surface 211 relative to reference position R at the moment of the welding process and the circumferential offset (second offset) of weld surface 211 relative to reference position R at the measured position after the welding process (downstream side) can be obtained in advance. The first offset and the second offset have the following characteristics: Figure 13 The positive correlation (proportional relationship) is shown. Therefore, in the manufacturing method according to this embodiment, the first offset is detected in step S2, and the second offset is calculated by multiplying the first offset by a coefficient C, which is a proportional constant, in the subsequent step S3.

[0103] In step S3, the relative relationship between the circumferential position of the cutting portion 23 of the weld bead 22 formed in the cutting process and the circumferential position of the welding surface 211 is detected based on the second offset.

[0104] As in this embodiment, when the reference position R is the pipeline center, at the time of the cutting process, the position of the center of the cutting portion 23 in the circumferential direction of the welded pipe 20 coincides with the reference position R. Therefore, when the coefficient C corresponds to the amount of torsion of the welded pipe 20 from the welding process to the cutting process, the second offset itself becomes the position offset of the welding surface 211 in the circumferential direction relative to the center of the cutting portion 23. On the other hand, even when the reference position R is the pipeline center, at a time after the cutting process, the position of the center of the cutting portion 23 may sometimes shift in the circumferential direction of the welded pipe 20 relative to the reference position R. Therefore, when the coefficient C corresponds to the amount of torsion of the welded pipe 20 from the welding process to after the cutting process and before the heat treatment process, the sum or difference between the second offset and the position offset of the center of the cutting portion 23 in the circumferential direction relative to the reference position R becomes the position offset of the welding surface 211 in the circumferential direction relative to the center of the cutting portion 23.

[0105] When the reference position R is not the center of the pipeline, the position of the circumferential center of the cutting portion 23 at the moment of the cutting operation is inconsistent with the reference position R. In this case, regardless of whether the coefficient C corresponds to the amount of torsion of the welded pipe 20 from the welding operation to the cutting operation, or to the amount of torsion of the welded pipe 20 from the welding operation to after the cutting operation and before the heat treatment operation, the sum or difference of the second offset and the position offset of the center of the cutting portion 23 in the circumferential direction relative to the reference position R becomes the position offset of the welding surface 211 in the circumferential direction relative to the center of the cutting portion 23.

[0106] The case where coefficient C corresponds to the amount of torsion of the welded pipe 20 from the welding process to the cutting process refers to the case where coefficient C is obtained at the moment of the cutting process, that is, immediately before or immediately after the cutting device 50. The case where coefficient C corresponds to the amount of torsion of the welded pipe 20 from the welding process to the moment after the cutting process and before the heat treatment process refers to the case where coefficient C is obtained after the cutting process, that is, between the cutting device 50 and the heat treatment device 60.

[0107] Following step S3, step S4 is performed. In step S3, as described above, the relative relationship between the circumferential position of the cutting portion 23 of the weld bead 22 formed in the cutting process and the circumferential position of the welding surface 211 is obtained. More specifically, in step S3, the positional offset of the welding surface 211 relative to the center of the cutting portion 23 in the circumferential direction is determined. In step S4, a process is performed to determine whether the manufacturing of the welded pipe 20 is qualified based on the relative relationship obtained in step S3.

[0108] For example, if the positional offset of the weld surface 211 relative to the center of the cutting portion 23 in the circumferential direction is large, even if, as in the past, an optical method such as using the imaging device 82 is employed to detect the cutting portion 23 before the heat treatment process and the heating element 61 is made to follow the cutting portion 23, the weld surface 211 is more likely to deviate from the range where the heat treatment is performed by the heating element 61. Therefore, it is also possible that if the absolute value of the positional offset of the weld surface 211 relative to the center of the cutting portion 23 in the circumferential direction exceeds a predetermined threshold, the monitoring device 70 will determine that the welded pipe 20 is a manufacturing defect. On the other hand, if the absolute value is below the predetermined threshold, the monitoring device 70 can determine that the welded pipe 20 is a manufacturing defect.

[0109] The threshold used in step S4 can be obtained in advance, for example, by performing a preliminary test under the same conditions as the manufacturing conditions of the welded pipe 20. For example, the extent (circumferential) of the heat treatment performed on the inner surface of the welded pipe 20 can be actually measured, and a threshold for judging whether the manufacturing is qualified, specifically whether the heat treatment is qualified, can be set based on this.

[0110] The processes in steps S1 to S4 can also be performed in real time during the manufacturing of the welded pipe 20. Alternatively, data from the manufacturing process of the welded pipe 20 can be accumulated, for example, after all the strip (coil) metal sheets 10 have been manufactured into welded pipes 20, the processes in steps S1 to S4 can be performed.

[0111] [Effect]

[0112] In this embodiment, during the manufacturing of the welded pipe 20, the first offset is defined as the positional offset of the convergence point 12 of the two ends 11L and 11R of the metal plate 10 relative to a predetermined reference position R in the circumferential direction of the welded pipe 20. Furthermore, a second offset can be calculated by multiplying the first offset by a predetermined coefficient C corresponding to the torsion amount of the welded pipe 20. Based on this second offset, the relative relationship between the circumferential position of the welded surface 211 after the cutting process and the circumferential position of the cutting portion 23 can be obtained. Therefore, during the heat treatment of the weld portion 21 of the welded pipe 20, the position of the welded surface 211 in the circumferential direction of the welded pipe 20 can be detected with high accuracy.

[0113] For example, due to the twisting of the welded pipe 20, the welding surface 211 may sometimes shift in position relative to the center of the cutting portion 23 of the weld bead 22 in the circumferential direction immediately in front of the heat treatment apparatus 60. Therefore, even if the position of the cutting portion 23 is detected and heat treatment is performed along the cutting portion 23, it is difficult to determine whether the heat-affected portion of the welding surface 211 and its surrounding area has been properly heat-treated, making it difficult to accurately determine whether the welded pipe 20 is manufactured to a satisfactory standard. In contrast, in this embodiment, the manufacturing quality of the welded pipe 20 is determined based on the position of the welding surface 211, not the position of the cutting portion 23. More specifically, the manufacturing quality of the welded pipe 20 is determined based on the relative relationship between the circumferential position of the welding surface 211 at the time of or after the cutting process and the circumferential position of the cutting portion 23. Therefore, the manufacturing quality of the welded pipe 20 can be determined with higher accuracy. As a result, the outflow of welded pipes 20 with insufficient heat treatment of the welding portion 21 can be prevented.

[0114] In this embodiment, the welded tube 20 has a thickness of 5.0 mm or more, for example. The welded tube 20 may have a thickness of 10.0 mm or more. The welded tube 20 may have a thickness of 12.7 mm or more, or a thickness of 15.0 mm or more. In this embodiment, even if the difference between the heat treatment areas of the heating element 61 on the outer and inner surface sides of the welded tube 20 increases corresponding to its thickness, the manufacturing quality of the welded tube 20 can be accurately determined by using a second offset related to the position of the welding surface 211.

[0115] <Second Implementation>

[0116] Figure 8 This is a flowchart illustrating the processing of the monitoring device 70 according to this embodiment. In this embodiment, the basic structure of the manufacturing apparatus 100 for the electric welding pipe 20 is the same as that in the first embodiment. Figures 1-5 However, the manufacturing method of the electric welding pipe 20 is slightly different from that of the first embodiment. More specifically, in this embodiment, the processing performed by the monitoring device 70 is different from that of the first embodiment.

[0117] Reference Figure 8 The manufacturing method in this embodiment includes the same steps S1 to S3 as in the first embodiment. However, the manufacturing method in this embodiment includes step S5 instead of step S4 in the first embodiment. Steps S1 to S3 and S5 are controlled by the CPU 71 of the monitoring device 70. Figure 5 The processes of steps S1 to S3 and S5 can also be performed in real time during the manufacturing of the welded pipe 20.

[0118] Similar to the first embodiment, the monitoring device 70 acquires, via steps S1 to S3, the relative relationship between the circumferential position of the weld surface 211 after the cutting process and before the heat treatment process and the circumferential position of the cutting portion 23 of the weld bead 22. Figures 7B-7E ). Reference Figure 9 and Figure 10 In step S5, a process is performed to move the heating element 61 included in the heat treatment apparatus 60 according to the relative relationship. The monitoring device 70 is configured to control the movement of the heating element 61 within the heat treatment apparatus 60. When the manufacturing apparatus 100 includes multiple heat treatment apparatuses 60, the monitoring device 70 may also be configured to control the movement of the heating element 61 for each heat treatment apparatus 60 independently of the other heat treatment apparatuses 60.

[0119] More specifically, such as Figure 9 As shown, in step S5, the imaging device 82 captures an image of the cut portion 23 formed during the cutting process, and detects the cut portion 23 based on the obtained image data. The imaging device 82 captures the cut portion 23 before heat treatment. The monitoring device 70 detects the position (coordinates) of the center of the cut portion 23 in the circumferential direction of the welded pipe 20 based on the image data acquired from the imaging device 82. The method of detecting the cut portion 23 using the optical method of the imaging device 82 is the same as conventional, so the description is omitted. The monitoring device 70 can detect the position of the cut portion 23 in the circumferential direction of the welded pipe 20 using a known optical method. For example, the monitoring device 70 can detect the positional offset of the center of the cut portion 23 in the circumferential direction relative to the reference position R.

[0120] Through the processing in steps S1 to S3, the relative position of the welding surface 211 in the circumferential direction with respect to the cutting part 23 is obtained. Therefore, if the circumferential position of the cutting part 23 is detected, the circumferential position of the welding surface 211 before the heat treatment process can be derived. That is, if the positional offset of the center of the cutting part 23 in the circumferential direction relative to the reference position R detected in step S5 and the positional offset of the center of the cutting part 23 and the welding surface 211 in the circumferential direction obtained in steps S1 to S3 are taken into account, the positional offset of the welding surface 211 in the circumferential direction relative to the reference position R can be obtained before the heat treatment process.

[0121] like Figure 10As shown, the monitoring device 70 moves the heating element 61 according to the circumferential position of the welding surface 211 before the heat treatment process, so that the welding surface 211 is positioned at the circumferential center of the heat treatment area of ​​the heating element 61. More specifically, the monitoring device 70 sends a signal to the drive mechanism 62 of the heat treatment device 60, thereby moving the heating element 61. The heating element 61 can move circumferentially or in the width direction (left-right direction) of the welding tube 20. When the manufacturing apparatus 100 includes multiple heat treatment devices 60, the monitoring device 70 moves the heating element 61 according to the circumferential position of the welding surface 211 before the heat treatment process, at least for the upstream heat treatment device 60, so that the welding surface 211 is positioned at the circumferential center of the heat treatment area of ​​the heating element 61. For other heat treatment devices 60, the monitoring device 70 can also move the heating element 61 in the same way as for the upstream heat treatment device 60.

[0122] However, for the heat treatment unit 60 other than the upstream one, it is also possible to utilize... Figure 11 The marking device 63 and detection device 64 shown are used to implement movement control of the heating element 61. The marking device 63 is disposed near the cutting device 50. The marking device 63 can be disposed at a position substantially aligned with the cutting device 50 in the conveying direction, or it can be disposed immediately in front of or immediately behind the cutting device 50. The marking device 63 marks at a predetermined position on the outer surface of the welded pipe 20. The marking device 63 can also mark at a predetermined angle (e.g., 90°) around the center of the pipe and separated from the upper end of the welded pipe 20 when viewed along the conveying direction.

[0123] The detection device 64 is provided corresponding to the heat treatment device 60 among the plurality of heat treatment devices 60, excluding the upstream heat treatment device 60. Figure 11 In this example, a detection device 64 is provided corresponding to the second heat treatment device 60 from the upstream side among the multiple heat treatment devices 60. The detection device 64 is disposed on the inlet side (upstream side) of the heat treatment device 60. The detection device 64 is capable of capturing an image including the markings applied to the outer surface of the welded pipe 20. The marking device 63 and the detection device 64 may, for example, have the same structure as the marking device and detection device described in Japanese Patent Application Publication No. 2019-217507.

[0124] Based on the image data captured by the detection device 64, the circumferential position of the mark in the welded pipe 20 can be determined. The circumferential position of the mark is fixed at the moment the marking device 63 performs the marking, i.e., during the cutting process. Furthermore, through steps S1 to S3 and S5, the circumferential offset of the weld surface 211 relative to the reference position R before the heat treatment process is determined. Therefore, the circumferential offset of the weld surface 211 relative to the reference position R at the moment the marking is detected by the detection device 64 can be derived. Therefore, based on the circumferential offset of the weld surface 211 relative to the reference position R obtained using the mark, the monitoring device 70 can move the heating element 61, excluding the upstream heat treatment device 60, to position the weld surface 211 at the circumferential center of the heat treatment area of ​​the heating element 61.

[0125] The detection device 64 can be provided corresponding to all heat treatment devices 60 except the upstream one, but it is not necessary to provide it corresponding to all heat treatment devices 60. When the detection device 64 is provided only in a portion of the heat treatment devices 60, for heat treatment devices 60 without the detection device 64, a linear approximation of the positional offset of the weld surface 211 relative to the reference position R in the circumferential direction, obtained from other heat treatment devices 60, can be performed to determine the positional offset of the weld surface 211 relative to the reference position R in the circumferential direction. In this case, the monitoring device 70, for each heat treatment device 60, can move the heating element 61 according to the positional offset of the weld surface 211 relative to the reference position R in the circumferential direction, so that the weld surface 211 is positioned at the center of the circumferential direction of the heat treatment area of ​​the heating element 61.

[0126] In this embodiment, similar to the first embodiment, the position of the welding surface 211 in the circumferential direction of the welded portion 21 of the welded pipe 20 can be detected with high accuracy during heat treatment. Furthermore, in this embodiment, based on the relative relationship between the circumferential position of the welding surface 211 after the cutting process and the circumferential position of the cutting portion 23 of the weld bead 22, the heating element 61 is moved so that the welding surface 211 is positioned at the circumferential center of the heat treatment area of ​​the heating element 61 in the heat treatment apparatus 60. That is, during the heat treatment process, the heating element 61 does not follow the cutting portion 23 but follows the welding surface 211. For example, it is possible to track the moment when the convergence point 12 detected during the welding process reaches the heat treatment apparatus 60, and then make the heating element 61 follow the welding surface 211. In this case, even if the welding surface 211 is offset relative to the cutting portion 23 in the circumferential direction, the welding surface 211 of the welded pipe 20 and its surrounding heat-affected portion easily fall into the heat treatment area of ​​the heating element 61. Therefore, it is possible to perform good heat treatment on the weld portion 21, including the weld surface 211 and the heat-affected zone. As a result, the toughness of the weld portion 21 can be improved, and high-quality welded pipe 20 can be manufactured.

[0127] In this embodiment, similar to the first embodiment, the welding tube 20 can, for example, have a thickness of 5.0 mm or more. The welding tube 20 can have a thickness of 10.0 mm or more. The welding tube 20 can have a thickness of 12.7 mm or more, or a thickness of 15.0 mm or more. In this embodiment, even when the difference in heat treatment areas of the heating element 61 on the outer and inner surface sides of the welding tube 20 increases corresponding to the thickness of the welding tube 20, good heat treatment can still be performed on the weld portion 21 as a whole because the heating element 61 follows the welding surface 211.

[0128] The above describes the implementation methods involved in this disclosure. However, this disclosure is not limited to the above implementation methods. Various changes can be made as long as they do not depart from its spirit.

[0129] Explanation of reference numerals in the attached figures

[0130] 100. Manufacturing apparatus; 10. Metal plate; 11L, 11R. End; 12. Convergence point; 20. Electric welded pipe; 21. Welding part; 211. Welding surface; 22. Weld bead; 23. Cutting part; 40. Welding device; 50. Cutting device; 60. Heat treatment device; 61. Heating element; 70. Monitoring device; 81, 82. Imaging device; 90. Image data.

Claims

1. A method for manufacturing an electric welded pipe, wherein, The manufacturing method includes: In the forming process, a metal sheet is fed while being formed into a tubular shape with its two ends facing each other. The welding process involves butt-jointing and welding the two ends together to make the metal plate a welded pipe. A cutting process, in which the weld bead formed on the surface of the welded pipe in the welding process is cut; and A heat treatment process is performed on the welded portion of the electric welded pipe formed in the welding process, after the cutting process. The convergence point where the two ends approach and converge downstream in the direction of conveying the metal plate is taken as the position of the welding surface of the welded pipe in the welding process. The first offset of the convergence point in the circumferential direction of the welded pipe relative to a specified reference position is detected. A second offset is calculated by multiplying the first offset by a predetermined coefficient corresponding to the torsion of the welded pipe. Based on the second offset, the relative relationship between the circumferential position of the cut portion formed by cutting the weld bead in the cutting process and the circumferential position of the weld surface is obtained. The manufacturing qualification of the electric welding pipe is determined based on the aforementioned relative relationship.

2. A method for manufacturing an electric welded pipe, wherein, The manufacturing method includes: In the forming process, a metal sheet is fed while being formed into a tubular shape with its two ends facing each other. The welding process involves butt-jointing and welding the two ends together to make the metal plate a welded pipe. A cutting process, in which the weld bead formed on the surface of the welded pipe in the welding process is cut; and A heat treatment process is performed on the welded portion of the electric welded pipe formed in the welding process, after the cutting process. The convergence point where the two ends approach and converge downstream in the direction of conveying the metal plate is taken as the position of the welding surface of the welded pipe in the welding process. The first offset of the convergence point in the circumferential direction of the welded pipe relative to a specified reference position is detected. A second offset is calculated by multiplying the first offset by a predetermined coefficient corresponding to the torsion of the welded pipe. Based on the second offset, the relative relationship between the circumferential position of the cut portion formed by cutting the weld bead in the cutting process and the circumferential position of the weld surface is obtained. In the heat treatment process, according to the relative relationship, the heating element included in the heat treatment apparatus used to perform heat treatment on the welded part is moved so that the welded surface is positioned at the circumferential center of the heat treatment area of ​​the heating element.

3. The manufacturing method according to claim 1 or 2, wherein, The welded pipe has a thickness of 5.0 mm or more.

4. A monitoring device used in the manufacture of an electric welded pipe, wherein the manufacture of the electric welded pipe includes: a forming process in which a metal sheet is fed and formed into a tubular shape with its two ends facing each other; a welding process in which the two ends are butt-jointed and welded to form the metal sheet into an electric welded pipe; a cutting process in which weld beads formed on the surface of the electric welded pipe in the welding process are cut; and a heat treatment process in which the welded portion of the electric welded pipe formed in the welding process is heat-treated after the cutting process, wherein... The monitoring device is configured to perform the following processes: The imaging device captures image data containing convergence points, which are the points where the two ends approach and converge as they move downstream toward the conveying direction of the metal plate. Based on the image data, the convergence point is used as the position of the welding surface of the welded pipe in the welding process, and the first offset of the convergence point relative to the specified reference position in the circumferential direction of the welded pipe is detected. The first offset is multiplied by a predetermined coefficient corresponding to the torsion of the welded pipe to calculate the second offset. Based on the second offset, the relative relationship between the circumferential position of the cutting part formed by cutting the weld bead in the cutting process and the circumferential position of the welding surface is obtained. as well as The manufacturing qualification of the electric welding pipe is determined based on the aforementioned relative relationship.

5. An apparatus for manufacturing electric welded pipes, wherein, The manufacturing apparatus includes: A welding apparatus configured to butt-weld the two ends of a metal plate, which is being conveyed and formed into a tubular shape, to form a welded pipe from the metal plate; and A cutting device is disposed downstream of the welding device in the conveying direction of the metal plate and is configured to cut the weld bead formed on the surface of the electric welding pipe. A heat treatment apparatus, disposed downstream of the cutting apparatus in the conveying direction, includes a heating element for performing heat treatment on the welded portion of the electric welded pipe; and A monitoring device configured to control the movement of the heating element. The monitoring device is configured to perform the following processes: The imaging device captures image data containing the convergence point, which is the point where the two ends approach and converge as they move downstream in the conveying direction. Based on the image data, the convergence point is used as the position of the welding surface of the electric welding pipe in the welding device, and the first offset of the convergence point relative to the specified reference position in the circumferential direction of the electric welding pipe is detected. The first offset is multiplied by a predetermined coefficient corresponding to the torsion of the welded pipe to calculate the second offset. Based on the second offset, the relative relationship between the circumferential position of the cutting part formed by cutting the weld bead with the cutting device and the circumferential position of the weld surface is obtained. as well as According to the relative relationship, the heating element is moved so that the welding surface is positioned at the circumferential center of the heat treatment area of ​​the heating element.

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