Welding management device, welding management method, manufacturing method, and welding management system for electric resistance welded steel pipe

Abstract

The invention provides a technology capable of suppressing welding defects. A welding management device (100) for an electric-resistance-welded steel pipe is provided with: a pre-electric-resistance-welding edge temperature detection unit (122) that, before electric resistance welding, detects an outer surface temperature (T0), an inner surface temperature (Ti), and a thickness center temperature (Tc) of an edge section on the basis of temperature distribution information in the thickness direction of the edge section on at least one side of an open pipe; an edge temperature difference calculation unit (125) that calculates a temperature difference ([Delta] T) between the outer surface temperature (T0) and the inner surface temperature (Ti); a V-convergence point extraction unit (133) that extracts two straight lines converging along the edge sections on the basis of image information of a region including both edge sections of the open pipe and the welding point, and extracts a V-convergence point, which is the intersection of the two straight lines; a V-convergence angle calculation unit (134) that calculates a V-convergence angle (theta); a narrow gap length calculation unit (135) that calculates the distance from the V convergence point to the welding point as a narrow gap length L; and a welding state determination unit (141) that determines whether or not the resistance welding condition is good on the basis of the information on [delta] T, Tc, [theta], and L.

Description

Technical Field

[0001] The present invention relates to a welding management device for electric resistance welded steel pipes, a welding management method for electric resistance welded steel pipes, a manufacturing method for electric resistance welded steel pipes, and a welding management system for electric resistance welded steel pipes, which can suppress welding defects by performing image analysis on the edge of an open pipe before electric resistance welding of the electric resistance welded steel pipe. Background Art

[0002] The electric resistance welded steel pipe is manufactured by continuously bending a steel plate or strip in the circumferential direction using roll forming, butting both ends to form an open pipe in the shape of a hollow tube with a circular cross section, and then continuously resistance welding both edges of the butted open pipe.

[0003] During resistance welding, the two edges are heated to a temperature above the melting point by direct current passing through a conductive nozzle or by induction current passing through an induction coil, and then the joints of the two edges are immediately butted (upsetting) by a welding roller (squeeze roller). At this time, the oxides (gray spots, penetrators) generated during the melting and heating process of the steel plate or strip are caused to flow out to the inner and outer surfaces of the pipe by upsetting, and are discharged to the unnecessary part called the pile (weld bead), thereby suppressing the occurrence of welding defects. After resistance welding, the pile is removed from the pipe by cutting tools or the like.

[0004] In order to suppress welding defects, it is important to suppress the generation of gray spots and the aggregation of gray spots until welding. To this end, it is necessary to adjust the welding conditions so that the time from the above-mentioned melting and heating process to the start of joining of the two edge parts does not become too long. In addition, it is also important to discharge the gray spots to the weld bead without stagnation during the upsetting process. To this end, it is necessary to reduce the deviation of the temperature distribution in the wall thickness direction of the edge part until the start of joining, and suppress the poor discharge of gray spots caused by the solidification of the molten edge part during upsetting.

[0005] As a method for solving the above problems, various technologies have been disclosed to suppress welding defects in the manufacture of electric resistance welded steel pipes. For example, a welding management system for the welding process has been proposed that images the resistance welding phenomenon and measures the temperature of the edge portion during the melting heating process.

[0006] Patent document 1 proposes the following welding temperature measurement method: the coordinates of the corner positions of the outer surface and the inner surface of the two edges of the open pipe before butt joint are detected based on the captured image, and the temperature distribution of the corners of the outer surface and the inner surface of the two edges is calculated, the detected coordinates are compared with the calculated temperature distribution, and the temperature of the edge at the detected coordinates is obtained, thereby controlling the heating conditions of the two edges.

[0007] Patent document 2 proposes the following monitoring device for resistance welding operation: an image of resistance welding is obtained, an image of an area including a V-convergence portion where two edges of an open pipe before butt-jointing converge in a V shape is obtained, in the image, at the butt joint of the two edges and at any one of the convergence points geometrically formed by the two edges, the temperature of the area where the molten portion inside the wall thickness begins to discharge to the surface is transformed by brightness level, and it is determined whether the temperature is above a threshold value.

[0008] Patent document 3 proposes the following operational monitoring device: obtaining an image of resistance welding, obtaining an image of an area including a V-convergence portion where two edges of an open pipe before butt-jointing converge in a V shape, measuring a distance L between a first V-convergence point where the two edges geometrically intersect and a second V-convergence point, i.e., a butt joint point of the two edge portions of the metal plate, and a V-convergence angle θ at the first V-convergence point, and determining whether the distance L and the V-convergence angle θ are within a predetermined allowable range.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 11-33621

[0012] Patent Document 2: Japanese Patent No. 5549963

[0013] Patent Document 3: Japanese Patent No. 5079929 Summary of the invention

[0014] Problems to be solved by the invention

[0015] In Patent Document 1, since the temperature of the corners (corners) of the inner and outer surfaces of the joining end faces is measured, the influence of the overlapping state of the two end faces before butting can be monitored. On the other hand, since the temperature information of the center portion of the wall thickness which is the most difficult to heat in the high-frequency heating of the resistance welding cannot be obtained, there is a problem that sufficient weld characteristics cannot be obtained due to insufficient heating of the center portion of the wall thickness.

[0016] In Patent Document 2, a lower limit value is set relative to the temperature of the outer surface or the inner surface at the butt joint of the two edges and at any one of the convergence points geometrically formed by the two edges to determine whether the welding conditions are good or bad. However, as in Patent Document 1, since the temperature information of the central part of the wall thickness cannot be obtained, there is a problem that sufficient weld characteristics cannot be obtained.

[0017] Patent Document 3 uses numerical data obtained by analyzing an image captured from the outer surface side of a resistance-welded pipe to determine whether welding conditions are good or bad. However, actual resistance welding is not only an I-shaped butt joint in which the end faces of both edges are parallel to each other, but also a V-shaped or inverted V-shaped butt joint due to the change in curvature distribution near the end portions caused by edge shaping of both edges before welding. In such a case, the appearance of the resistance weld changes between the outer surface side of the pipe and the inner surface side of the pipe, and the butt joint state of both edge portions cannot be determined in the image of the outer surface side of the pipe, resulting in a problem that sufficient weld characteristics cannot be obtained.

[0018] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a welding management device for electric resistance welded steel pipe, a welding management method for electric resistance welded steel pipe, a manufacturing method for electric resistance welded steel pipe, and a welding management system for electric resistance welded steel pipe that can suppress welding defects.

[0019] Means for solving problems

[0020] To achieve the above object, the present inventors focused on managing temperature information in the wall thickness direction of both edge end surfaces during resistance welding, particularly the temperature difference between the center of the pipe thickness and the outer and inner surfaces of the pipe.

[0021] In resistance welding, attention is paid to the relationship between the angle (V-convergence angle θ) formed geometrically by two straight lines converging along the two edge portions, and the distance between the welding point where the two edges are joined and welding starts when the intersection of the two straight lines is set as the V-convergence point, that is, the narrow gap length L. Furthermore, the inventors of the present invention have conducted in-depth research on the influence of the V-convergence angle θ and the narrow gap length L on the morphology of oxides (gray spots) remaining in the welded portion after upset forging by a squeeze roll and the characteristics of the welded portion. As a result, the following was clarified.

[0022] Here, regarding the resistance welding process, Figure 3 and Figure 4 An example of resistance welding from heating to welding will be described below.

[0023] In the past, resistance welding was performed by heating using high-frequency current based on direct current heating or induction heating. At this time, due to the heating phenomenon unique to high-frequency heating, the skin effect appears in the initial stage of heating. Therefore, the temperature of the outer surface and inner surface of the edge becomes higher than that of the center of the wall thickness. The heat transfer to the center of the wall thickness occurs through the heat conduction of the edge.

[0024] Next, as the heating process progresses, the distance between the end faces becomes closer, so the proximity effect appears and the temperature rise rate of the center of the wall thickness increases. Then, while the extreme surface layer of the entire pipe thickness of the edge portion is heated to the melting point, the resistance welding is completed at the butt joint through upsetting by the squeeze roll. At this time, the molten metal of the edge portion is discharged to the outside of the pipe together with the gray spots distributed on the surface to form a weld bead 203.

[0025] As described above, in resistance welding, the temperature of the center portion of the wall thickness is heated later than the inner surface and the outer surface of the edge portion, so the temperature is relatively easy to become low. If the center portion of the wall thickness of the edge portion is not heated sufficiently, there is a problem that a sufficient amount of weld metal cannot be obtained to discharge the gray spots generated in the center portion of the wall thickness to the weld bead 203 during the heating process.

[0026] To address this problem, the proximity effect in the center of the wall thickness needs to be discovered early in the heating process. To this end, measures such as adjusting the V-convergence angle and shortening the distance between the working coil and the extrusion roll need to be taken.

[0027] In addition, during the heating process, the temperature deviation of the inner and outer surfaces of the edge portion changes according to the butt state of the two edges to be joined. That is, in resistance welding, it is ideal that the butt of the two edges when the cylindrical cross section of the pipe is viewed from the front (front in the pipe axis direction) is not tilted, and the two edge surfaces are joined from the front face to face in an I-shaped butt, in which the temperature deviation of the inner and outer surfaces of the two edge portions is almost non-existent, and in the upset forging by the squeeze roll, the dust is discharged to the outside of the inner and outer surfaces of the pipe without stagnation.

[0028] On the other hand, when the butt joint of the two edges is inclined, the proximity effect will not be uniformly generated on the joint surface of the edge, and the heating will be biased toward the portion where the distance between the two edges is short. For example, if the butt joint of the two edges is V-shaped when the cross section of the cylinder is viewed from the front, the temperature of the inner surface side of the edge will rise significantly, and if it is an inverted V-shaped butt joint, the temperature of the outer surface side of the edge will rise significantly, and the heating will become insufficient in the portion where the distance between the two edges becomes longer. As a result, in the upset forging of the squeeze roll, the discharge of gray spots on the side where the heating is insufficient is hindered, which becomes a cause of deterioration of the quality of the weld.

[0029] Therefore, in resistance welding, it is important to establish welding conditions that can suppress heating delays in the center of the wall thickness and temperature deviations between the inner and outer surfaces of the edge in order to ensure weld quality in the heating process before upsetting with squeeze rolls.

[0030] The present invention is based on the above findings, and the gist of the present invention is as follows.

[0031] [1] A welding management device for an electric resistance welded steel pipe, the electric resistance welded steel pipe being manufactured by bending a steel plate or a steel strip in the circumferential direction, butting both edge portions to form an open pipe, and then performing resistance welding on both edge portions of the butted open pipe by upsetting, wherein the welding management device for the electric resistance welded steel pipe comprises:

[0032] The edge temperature detection unit before resistance welding detects the outer surface temperature T of the edge portion based on the information of the temperature distribution in the wall thickness direction of the edge portion of at least one side of the open pipe before resistance welding. o , inner surface temperature T i And the wall thickness center temperature Tc;

[0033] The edge temperature difference calculation unit calculates the outer surface temperature T o With the inner surface temperature T i The temperature difference ΔT;

[0034] A V-convergence point extraction unit extracts two straight lines converging along the edge portions based on image information of a region including the two edge portions of the open pipe and a welding point where the two edge portions of the open pipe are joined and welding begins, and extracts a V-convergence point which is an intersection of the two straight lines;

[0035] A V convergence angle calculation unit calculates a V convergence angle θ formed by the two straight lines;

[0036] a narrow gap length calculation unit that calculates a distance from the V-convergence point to the welding point as a narrow gap length L; and

[0037] The welding state determination unit determines whether the resistance welding condition is good or not based on information of the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc, the V convergence angle θ, and the narrow gap length L.

[0038] [2] The welding management device for electric resistance welded steel pipe according to [1], wherein:

[0039] The welding state determination unit determines that the resistance welding condition is good when the narrow gap length L is equal to or less than an upper limit value preset based on a ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc and a value of the V-convergence angle θ.

[0040] [3] The welding management device for electric resistance welded steel pipe according to [1] or [2], wherein:

[0041] The welding state determination unit determines whether the resistance welding condition is good or not based on whether a ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc is within a range preset based on a value of the V-convergence angle θ and a value of L.

[0042] [4] A welding management method for an electric resistance welded steel pipe, wherein the electric resistance welded steel pipe is manufactured by bending a steel plate or a steel strip in a circumferential direction, butting two edge portions to form an open pipe, and then performing resistance welding on the two edge portions of the butted open pipe, wherein the welding management method for the electric resistance welded steel pipe comprises:

[0043] The edge temperature detection step before resistance welding is to detect the outer surface temperature T of the edge portion based on the temperature distribution information of at least one side of the edge portion of the open pipe before resistance welding. 0 , inner surface temperature T i And the wall thickness center temperature Tc;

[0044] The edge temperature difference calculation step calculates the outer surface temperature T o With the inner surface temperature T i The temperature difference ΔT;

[0045] A V-convergence point extraction step of extracting two straight lines converging along the edge portions based on image information of a region including both edge portions of the open pipe and a welding point where both edge portions of the open pipe are joined and welding begins, and extracting a V-convergence point which is an intersection of the two straight lines;

[0046] a V convergence angle calculation step, calculating a V convergence angle θ formed by the two straight lines;

[0047] a narrow gap length calculation step of calculating the distance from the V-convergence point to the welding point as the narrow gap length L; and

[0048] The welding state determination step determines whether the resistance welding condition is good or not based on information of the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc, the V convergence angle θ, and the narrow gap length L.

[0049] [5] A method for manufacturing an electric resistance welded steel pipe, wherein the electric resistance welded steel pipe is manufactured by bending a steel plate or a steel strip in the circumferential direction, butting two edge portions to form an open pipe, and then performing resistance welding on the two edge portions of the butted open pipe by upsetting, wherein the welding management method of the electric resistance welded steel pipe comprises:

[0050] When performing the electric resistance welding, welding management is performed using the welding management method for electric resistance welded steel pipe described in [4].

[0051] [6] A welding management system for electric resistance welded steel pipes, comprising:

[0052] A welding management device for an electric resistance welded steel pipe as described in any one of [1] to [3];

[0053] an edge temperature information acquisition device for acquiring information on the temperature distribution of an edge portion of at least one side of the open pipe before resistance welding; and

[0054] The welding portion photographing device photographs the two edge portions of the open pipe and the welding point formed by the convergence of the two edge portions before resistance welding.

[0055] Effects of the Invention

[0056] According to the present invention, welding defects can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is an explanatory diagram for explaining a welding management device for implementing the present invention and a welding management system including the welding management device.

[0058] Figure 2 This is a flowchart showing the processing procedure of the welding management device according to the present embodiment.

[0059] Figure 3 This is an explanatory diagram of each part of the weld image of resistance welding.

[0060] Figure 4 This is a diagram for explaining the formation of a weld bead by edge heating and upsetting in resistance welding.

[0061] Figure 5 This is a graph showing the results of resistance welding quality (flatness height test results) corresponding to the ratio of the temperature difference between the inner and outer surfaces of the pipe at the edge of the resistance welding and the temperature at the center of the wall thickness (ΔT / Tc) and the value of the narrow gap length L.

[0062] Figure 6 This is a conceptual diagram for explaining the quality of resistance welding corresponding to the narrow gap length L and the value of ΔT / Tc at each of the V-convergence angles θ1 to θ3.

[0063] Figure 7 This is a graph for explaining the permissible range of resistance welding in Examples. DETAILED DESCRIPTION

[0064] Hereinafter, a welding management device and a welding management system as an embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the embodiment. In addition, in the description of the accompanying drawings, the same parts are marked with the same reference numerals.

[0065] First, refer to Figure 1 , a process flow, a welding management system, and a schematic configuration of a welding management device included in the system, which are objects of the present embodiment, are described. Figure 1It is a diagram for explaining a welding management device showing an example of a mode for implementing the present invention and a welding management system including the welding management device.

[0066] After the steel sheet (or steel strip) is continuously formed into a cylindrical shape by roll forming, it is formed into an open tube 1 while advancing in the direction of the arrow (welding direction) in the figure, while passing through the finishing roller 2 to ensure the stability of the cylindrical shape and centering the butt position of the two edge portions. Thereafter, high-frequency current is supplied to the two edge portions of the open tube 1 from the high-frequency oscillation device 3 via a pair of conductive nozzles 31a and 31b, and the two edge portions are heated to melt. Instead of the conductive nozzle, an induction heating working coil may be used.

[0067] Next, the open pipe 1 passes through a welding seat 40 surrounded by a roll group consisting of squeeze rolls 41a, 41b and upper rolls 42a, 42b, while both edge portions are pressed together and welding (resistance welding) is performed while molten steel is discharged to the outside (outer and inner peripheral surfaces of the tubular steel plate).

[0068] In the resistance welding, the two edges of the open pipe 1 approach each other on the upstream side (opposite to the welding direction) of the squeeze rollers 41a and 41b, and the position where the joining starts is the welding point. The position of the welding point moves forward and backward in the welding direction according to the relationship between the welding speed and the input power of the resistance welding.

[0069] In addition, when the input power is large, a state occurs where the geometric intersection point (V convergence point (intersection point of two straight lines converging along the two edges)) of the straight lines formed by the two edges of the open pipe 1 does not coincide with the welding point. This is a phenomenon caused by the fact that the molten part formed on the edge surface of the edge is discharged to the outside at a higher speed than the speed at which the two edges of the open pipe 1 approach each other on the upstream side of the squeeze rolls 41a and 41b due to the electromagnetic force generated by the current flowing through the two edges.

[0070] The welding management system 10 comprises: an edge temperature information acquisition device 11 for acquiring information on the temperature distribution of at least one edge of an open pipe before electric seam welding; a weld portion photographing device 12 for photographing both edge portions of the open pipe and a weld point formed by the convergence of the two edge portions before electric seam welding; and a welding management device 100. Hereinafter, the edge temperature information acquisition device 11, the weld portion photographing device 12, and the welding management device 100 will be described in sequence.

[0071] The edge temperature information acquisition device 11 includes, for example, a thermometer such as a thermal imager that can measure temperature distribution based on a two-dimensional image. In addition, the edge temperature information acquisition device 11 includes a camera that captures an image of the edge portion in order to acquire edge temperature distribution.

[0072] The edge temperature information acquisition device 11 is set and adjusted in position in such a way that the camera can capture the entire thickness of a specified area of ​​the edge portion of the open tube 1 located between the conductive nozzles 31a, 31b and the welding seat 40 in the wall thickness direction. The camera of the edge temperature information acquisition device 11 captures at least the surface that is heated from the outer surface of the tube to the inner surface of the tube in one of the relative edge portions. At this time, as the above-mentioned thermometer, radiation thermometers, two-color thermometers, etc. can be cited, but any thermometer that can obtain temperature distribution will suffice. In addition, the edge temperature information acquisition device 11 also has an adjuster such as a zoom lens and an exposure adjuster for adjusting the optical system. The above-mentioned adjuster preferably has a shooting field of view of 100mm×40mm, and ensures a resolution of 500μm / pixel or higher. The resolution is more preferably 100μm / pixel or higher.

[0073] In this case, the number of pixels of the video camera is preferably not less than 1920 × 1080. If the resolution is lower than 500 μm / pixel, the detection accuracy of the edge temperature may deteriorate.

[0074] The welding portion imaging device 12 includes, for example, a camera, which is set in a manner capable of imaging the downstream side of the welding seat 40 with respect to the welding direction, and uses the camera to image the situation where both edge portions (welding portions) of the split pipe 1 are heated, melted, and crimped. The position of the welding portion imaging device 12 is adjusted so that the image captured by the welding portion imaging device 12 includes the joining point (V convergence point) described later and the roller centers of the squeezing rollers 41a and 41b. At this time, the camera may be any one of a color image capturing camera and a monochrome image capturing camera.

[0075] In addition, the welding portion photographing device 12 also includes a zoom lens, an exposure adjuster and other adjusters for adjusting the optical system. The above-mentioned adjuster preferably has a photographing field of view of 100mm×40mm, and as a resolution, ensures a resolution of 100μm / pixel or higher. The resolution is more preferably 50μm / pixel or higher. At this time, the number of pixels of the camera is preferably 1920×1080 or more. If the resolution is a resolution lower than 100μm / pixel, there is a situation where the detection accuracy of the V convergence point and the welding point deteriorates. In addition, sometimes welding is performed at a welding speed of resistance welding exceeding 100m / min. In order to shoot any shooting point more than once within the area of ​​100mm of the photographing field of view, it is preferred to set the frame rate to 20fps (frames per second) or more. When the frame rate is less than 20fps, an area where image analysis cannot be performed in the welded portion of the resistance welded pipe is generated, and welding defects may be missed.

[0076] The welding management device 100 is a welding management device for manufacturing a resistance welded steel pipe by bending a steel plate or a steel strip in the circumferential direction to butt the two edges to form an open pipe, and then performing resistance welding on the two edges of the butted open pipe, wherein the device comprises: a pre-resistance welding edge temperature detection unit 122, which detects the outer surface temperature T of the edge portion based on the information of the temperature distribution in the wall thickness direction of at least one side of the edge portion of the open pipe before resistance welding. o , inner surface temperature T i and the wall thickness center temperature Tc; the edge temperature difference calculation unit 125 calculates the outer surface temperature T o and the inner surface temperature T i a V convergence point extraction unit 133, which extracts two straight lines converging along the edge portions based on image information of an area including two edge portions of an open pipe and a welding point where the two edge portions of the open pipe are joined and welding begins, and extracts the intersection of the two straight lines, namely, the V convergence point; a V convergence angle calculation unit 134, which calculates a V convergence angle θ formed by the two straight lines; a narrow gap length calculation unit 135, which calculates the distance from the V convergence point to the welding point as the narrow gap length L; and a welding state determination unit 141, which determines whether the resistance welding condition is good based on information on the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc, the V convergence angle θ, and the narrow gap length L.

[0077] Furthermore, the welding management device 100 may include an output unit 142 that outputs the determination result of the welding state determination unit 141 .

[0078] The welding management device 100 may include, for example, an edge temperature distribution data input unit 111 and a weld portion imaging data input unit 112 as the input unit 110. The welding management device 100 acquires edge temperature distribution information acquired by the edge temperature information acquisition device 11 through an input operation of the edge temperature distribution data input unit 111. In addition, the welding management device 100 acquires image information of the weld portion captured by the weld portion imaging device 12 through an input operation of the weld portion imaging data input unit 112.

[0079] The welding management device 100 is composed of a general-purpose computer such as a workstation or a personal computer, and has a calculation processing function based on a CPU, an image processing function based on a GPU, and various memory functions such as a ROM and a RAM as an example of a storage unit 143 described later. In addition, the welding management device 100 also has a recording medium such as a hard disk connected via a data communication terminal, a display device for graphics, an output unit such as an alarm device, etc.

[0080] In the welding management device 100, the outer surface temperature T of the edge portion is calculated in the edge temperature distribution processing unit 121 using a memory storing a processing program and a CPU executing the processing program.o and the inner surface temperature T i The difference ΔT is calculated, and the wall thickness center temperature Tc is detected. In addition, in the welding management device 100, the welding image processing unit 131 also calculates the V convergence angle θ and the narrow gap length L. Based on the information of ΔT, Tc, θ, and L, the welding state determination unit 141 determines whether the resistance welding condition is good.

[0081] The structure and function of the welding management device 100 will be described in more detail.

[0082] The edge temperature distribution processing unit 121 includes a pre-resistance welding edge temperature detection unit 122 and an edge temperature difference calculation unit 125 .

[0083] First, in the resistance welding pre-edge temperature detection unit 122, the temperature distribution in the wall thickness direction from the pipe outer surface to the pipe inner surface of at least one edge portion heated by the high-frequency current is detected.

[0084] The resistance welding front edge temperature detection unit 122 may include a spatial coordinate calculation unit 123 (a spatial coordinate calculation unit 123 of a temperature detection range) and a wall thickness direction temperature distribution detection unit 124 (a designated position wall thickness direction temperature distribution detection unit 124 ).

[0085] The spatial coordinate calculation unit 123 calculates coordinates in the three-dimensional space based on pixel information including temperature distribution information at an edge portion of a predetermined region for obtaining temperature distribution information.

[0086] Although not particularly limited, the spatial coordinate calculation unit 123 can calculate the spatial coordinates based on the image data that can be displayed as two-dimensional coordinates. The spatial coordinate calculation unit 123 can set the X coordinate and the Y coordinate for the image itself in the two-dimensional image data, and further set the Z coordinate in the depth direction of the image, and process the image data as three-dimensional data.

[0087] In addition, the wall thickness direction temperature distribution detection unit (specified position wall thickness direction temperature distribution detection unit) 124 detects the temperature distribution at a predetermined position in the pipe length direction. The wall thickness direction temperature distribution detection unit 124 detects at least the outer surface temperature T o , inner surface temperature T i In addition, the wall thickness direction temperature distribution detection unit 124 also detects the wall thickness center temperature Tc.

[0088] In the edge temperature difference calculation unit 125, the outer surface temperature T o and the inner surface temperature T i The temperature difference ΔT.

[0089] The welding management device 100 performs a series of processes as described above in the edge temperature distribution processing unit 121 .

[0090] The welding image processing unit 131 includes a pipe edge image detection unit 132 , a V convergence point extraction unit 133 , a V convergence angle calculation unit 134 , and a narrow gap length calculation unit 135 .

[0091] In parallel with the above-described processing in the edge temperature distribution processing unit 121, first, in the pipe edge image detection unit 132, both ends of the edge portion heated to red heat around the V convergence point are detected based on information on the welding image.

[0092] In the V-convergence point extraction unit 133, based on the image information of the region including the two edges of the open pipe and the welding point where the two edges of the open pipe are joined and welding starts, two straight lines converging along the edge portions are generated, and the intersection of the two straight lines, i.e., the V-convergence point, is extracted. The above-mentioned image information is image information obtained by the welding portion imaging device 12.

[0093] The V convergence angle θ formed by the two straight lines is calculated by the V convergence angle calculation unit 134 .

[0094] In the narrow gap length calculation unit 135 , the distance from the V convergence point to the welding point is calculated as the narrow gap length L.

[0095] The welding management device 100 performs the above-described series of processes in the welding image processing unit 131 .

[0096] Then, in the welding management device 100 , welding management processing is performed by welding state determination unit 141 based on the temperature difference ΔT, V convergence angle θ, and narrow gap length L, and output of determination result by output unit 142 .

[0097] Here, refer to Figure 2 The welding management processing procedure of the welding management device 100 is described with reference to the flowchart of FIG. Figure 2 1 is a flowchart showing the processing steps of the welding management device of this embodiment. Figure 2 In the flowchart of, for example, when the operator inputs an instruction to start the welding management process to the edge temperature distribution data input unit 111, the process proceeds to step S1. Steps S1 to S5 are also recorded as edge temperature distribution processing steps. In addition, when the operator inputs an instruction to start the welding management process to the welding portion imaging data input unit 112, the process proceeds to step S6. Steps S6 to S9 are also recorded as welding portion image processing steps. The process from step S1 (edge ​​temperature distribution processing step) and the process from step S6 (welding portion image processing step) may be performed simultaneously and in parallel.

[0098] In the processing of step S1, for at least one of the two edge portions of the open pipe 1 heated by high-frequency heating, the edge temperature distribution processing unit 121 obtains information on the two-dimensional temperature distribution of the entire thickness of the edge portion from the edge temperature information acquisition device 11 at a predetermined longitudinal position before welding.

[0099] The edge temperature distribution processing unit 121 detects two-dimensional temperature distribution information on the joining surface of the edge portion from among the temperature distribution information including the captured image information, that is, two-dimensional temperature distribution information in the tube length direction and the wall thickness direction.

[0100] Thus, the process of step S1 is completed, and the welding management process proceeds to the process of step S2.

[0101] In the processing of step S2, the spatial coordinate calculation unit 123 (the spatial coordinate calculation unit 123 of the temperature detection range) included in the resistance welding front edge temperature detection unit 122 detects a plurality of coordinate standard points based on the information of the two-dimensional temperature distribution acquired (photographed) in the processing of step S1 or the image information photographed by the camera (CCD camera) attached to the edge temperature information acquisition device 11, and performs spatial coordinate transformation from pixels to length units.

[0102] The coordinate standard point mentioned here is preferably a mark whose coordinate position or the distance between each standard point is pre-defined, but it is not limited to this. The distance between the standard points of any two points is detected by the spatial coordinate calculation unit 123, and the actual spatial distance of the distance between the standard points is input, thereby performing spatial coordinate transformation in the image information of the temperature distribution information. In the spatial coordinate calculation unit 123, the origin of the two-dimensional coordinate is set at an arbitrary position in the image information of the temperature distribution information. In addition, in the spatial coordinate calculation unit 123, the calculation formula required for the coordinate transformation from the pixel to the unit of length can also be derived in advance. Thus, the processing of step S2 is completed, and the welding management processing enters the processing of step S3.

[0103] In the processing of step S3, the wall thickness direction temperature distribution detection unit (specified position wall thickness direction temperature distribution detection unit) 124 included in the resistance welding front edge temperature detection unit 122 detects the wall thickness direction temperature distribution of the edge portion at any position in the length direction of the pipe together with the coordinate value based on the information of the temperature distribution after the above-mentioned spatial coordinate transformation processing.

[0104] There is no particular limitation on any position in the length direction of the tube, but it is preferably any position from a position moved 3 mm in the opposite direction of the welding direction relative to the center of the rollers of the extrusion rollers 41a and 41b to the middle position between the center of the rollers of the extrusion rollers 41a and 41b and the conductive nozzle 31 or the working coil (not shown).

[0105] The temperature distribution detection unit 124 in the wall thickness direction detects the temperature distribution within a range of ±0.5 mm in the longitudinal direction relative to a designated pipe longitudinal position. The temperature distribution detection unit 124 in the wall thickness direction detects the entire thickness of the edge portion.

[0106] The corners of the outer surface and the inner surface corresponding to the edge portion tend to be heated more easily than the flat portions other than the corners due to the skin effect peculiar to high-frequency heating.

[0107] Therefore, the temperature distribution in the wall thickness direction becomes a temperature distribution with the corner positions of the outer surface and the inner surface of the edge as the vertex (peak). According to this feature, as a judgment of the entire thickness area, the distance between the peaks detected at the outer surface and the inner surface of the edge is judged as the wall thickness of the pipe based on the temperature distribution in the wall thickness direction. Then, if the error between the judged wall thickness of the pipe (pipe wall thickness judgment value) and the preset wall thickness of the pipe (actual wall thickness) is within ±3%, it is judged that the temperature distribution measurement result has obtained sufficient accuracy.

[0108] If the error is not within the range of ±3%, the field of view of the edge temperature distribution information acquisition device 11 is adjusted, and the processing of steps S1 to S3 is repeated until the error is within the range of ±3%. Thus, the processing of step S3 is completed, and the welding management process enters the processing of step S4.

[0109] In the process of step S4, the resistance welding front edge temperature detection unit 122 detects the outer surface temperature T of the edge portion based on the information of the temperature distribution of at least one edge portion of the open pipe. 0 and inner surface temperature T i .

[0110] Specifically, the edge temperature detection unit 122 (wall thickness direction temperature distribution detection unit 124) before resistance welding uses the information of the temperature distribution in the wall thickness direction detected above to detect the temperature at the peak center position (peak position) of the temperature information at the outer surface of the pipe and the inner surface of the pipe at the edge as the outer surface temperature T o , inner surface temperature T i .

[0111] The resistance welding front edge temperature detector 122 (thickness direction temperature distribution detector 124) detects the temperature at the center between the peaks of the temperatures at the outer and inner surfaces of the pipe edge as the thickness center temperature Tc.

[0112] Thus, the process of step S4 is completed, and the welding management process proceeds to the process of step S5.

[0113] In the process of step S5, the edge temperature difference calculation unit 125 calculates the outer surface temperature T o and the inner surface temperature T i Here, the edge temperature difference calculation unit 125 can calculate the temperature difference ΔT from the inner surface temperature T i Subtract the external surface temperature T o The calculation of is performed, and the difference is stored in the storage unit 143 with a positive or negative sign added thereto. Thus, the process of step S5 is completed, and the welding management process proceeds to the process of step S10.

[0114] In the processing of step S6 performed in parallel with the above-mentioned steps S1 to S5, the pipe edge image detection unit 132 of the welding image processing unit 131 detects the edge portion heated to red heat by high-frequency heating based on the image information captured by the welding portion imaging device 12. Here, the edge detection method uses the differential method, but is not limited to this. Figure 3 and Figure 4 Provide explanation.

[0115] Figure 3 This is an explanatory diagram of each part of the weld image of resistance welding. Figure 4 This is a diagram for explaining the formation of a weld bead by edge heating and upsetting in resistance welding.

[0116] First, the pipe edge image detection unit 132 uses the captured image to obtain the edge detection image 20 of the welded portion based on the change in brightness around the heating unit 201. In addition, the image pixel number is converted into a length unit at the same time. Here, an XY two-axis coordinate system with the lower left end of the edge detection image 20 as the origin is used, and the length is processed into millimeters, but it is not limited to this. In the conversion process from the number of pixels to the length unit, a standard sample such as a gauge is photographed in advance in the same field of view, thereby detecting the number of pixels per 100 mm, and performing the conversion process from the number of pixels to the length. Through the above, the process of step S6 is completed, and the welding management process enters the process of step S7.

[0117] In the processing of step S7, the V-convergence point extraction unit 133 generates two straight lines converging along the edge portion based on information from the edge detection image of the weld portion (an image of an area including the two edge portions of the open pipe and the weld point where the two edge portions of the open pipe are joined and welding begins), and extracts the intersection of the two straight lines, i.e., the V-convergence point.

[0118] Specifically, for example, first, the V convergence point extraction unit 133 performs image processing in the vertical direction (direction perpendicular to the welding direction (tube circumferential direction)) from the opening 202 in the state where the two edge portions are not joined to each other in the edge detection image 20 of the above-mentioned welded portion, and sets the position where the edge is first detected as a point on each edge portion. The V convergence point extraction unit 133 performs the same processing at several points (for example, 3 to 10 points) in the entire length of the opening 202 in the longitudinal direction. Then, the V convergence point extraction unit 133 generates straight lines La and Lb that approximate the two edge end faces of the open pipe based on the plurality of points detected on each edge portion by the least square method. Here, the opening 202 is a region sandwiched by the heating portions 201 at the two edges, and before detecting the points on each edge portion, the position included in the opening 202 is manually specified in advance, but it is not limited to this.

[0119] The V convergence point extraction unit 133 extracts the intersection of the straight lines La and Lb as the V convergence point 204 .

[0120] Thus, the process of step S7 is completed, and the welding management process proceeds to the process of step S8.

[0121] In the process of step S8, the V convergence angle calculation unit 134 calculates and extracts the V convergence angle θ using the straight lines La and Lb calculated by detecting the two edges of the open pipe as described above. The V convergence angle θ in the edge detection image of the weld portion is the angle formed by the two straight lines La and Lb, and is set to be an acute angle on the opening 202 side.

[0122] The V convergence point 204 in the edge detection image of the weld is the intersection of the two straight lines La and Lb. The V convergence angle calculation unit 134 can calculate the detected V convergence angle θ using a geometric formula. In addition, the V convergence point extraction unit 133 can calculate the V convergence point 204 using a geometric formula, and convert it into numerical values ​​and coordinate data. Thus, the processing of step S8 is completed, and the welding management processing enters the processing of step S9.

[0123] In the process of step S9, the narrow gap length calculation unit 135 calculates and extracts the point where the V convergence point 204 and the two edge end surfaces 202a and 202b of the open pipe are actually physically joined (hereinafter referred to as the welding point 205 (refer to Figure 3 )) is the narrow gap length L. Here, the narrow gap length calculation unit 135 first detects the position of the welding point 205.

[0124] The narrow gap length calculation unit 135 determines whether there is an opening 202 on the downstream side (welding direction side) of the position of the V convergence point 204. At this time, the narrow gap length calculation unit 135 determines that there is an opening 202 when pixels having a brightness smaller than a predetermined threshold value on the downstream side of the V convergence point 204 continuously exist in the welding direction. The determination of the presence or absence of the opening 202 is repeatedly performed in the edge detection image 20 during a certain period of time, and the narrow gap length calculation unit 135 regards the most downstream position determined to have an opening 202 as a welding point 205, and detects it as the coordinate data of the welding point 205. The time required for the determination is preferably more than one cycle of the squeeze roller (SQ roller).

[0125] It should be noted that the vertical deviation between the position of the V-convergence point 204 and the position of the welding point 205 may be caused by the distortion (circumferential rotation of the pipe) generated during the manufacture of the electric resistance welded steel pipe, but can be adjusted by position correction as needed. However, in the above-mentioned detection of the position of the welding point 205, even if the vertical deviation occurs, it is within the range that does not affect the detection result.

[0126] The narrow gap length calculation unit 135 calculates a value obtained by subtracting the position coordinate of the horizontal component in the coordinate data of the V convergence point 204 from the position coordinate of the horizontal component in the coordinate data of the welding point as the narrow gap length L. Here, when it is determined that there is no opening 202 on the downstream side (welding direction side) of the position of the V convergence point 204, the narrow gap length calculation unit 135 calculates the narrow gap length L by setting it to 0. Thus, the processing of step S9 is completed, and the welding management processing enters the processing of step S10.

[0127] In the process of step S10, after the processes of steps S5 and S9 are completed, the welding state determination unit 141 determines the outer surface temperature T of the pipe edge surface at the above-mentioned designated position based on the outer surface temperature T of the pipe edge surface at the above-mentioned designated position. 0 and inner surface temperature T i The quality of the resistance welding conditions is determined based on the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc, the V convergence angle θ, and the narrow gap length L.

[0128] Regarding this good / bad judgment, the welding state judgment unit 141 may judge that the resistance welding condition is good when the narrow gap length L is equal to or less than an upper limit value preset based on the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc and the value of the V convergence angle θ.

[0129] The welding state determination unit may determine whether the resistance welding condition is good or not based on whether a ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc is within a range preset based on a value of the V convergence angle θ and a value of L.

[0130] As a specific example of a method for determining whether the resistance welding conditions are good or not, an offline evaluation test of the welded portion is performed using steel pipes obtained under various welding conditions. In addition, the characteristics of the obtained welded portion, the temperature Tc of the center of the wall thickness at a specified position, the outer surface temperature Tc of the pipe edge surface at a specified position, and the o and the inner surface temperature T i More specifically, the outer surface temperature Tc of the central portion of the wall thickness at the above-specified position and the outer surface temperature Tc of the pipe edge surface at the above-specified position are pre-set. o and inner surface temperature T i The upper and lower limits of the allowable range of the ratio ΔT / Tc of the temperature difference ΔT.

[0131] ΔT / Tc can take positive or negative values. When the absolute value of ΔT / Tc is large, that is, when ΔT is too large or Tc is too small, the discharge of dust specks to the outside of the pipe is easily hindered. Therefore, if ΔT / Tc is within the upper and lower limits of the positive and negative allowable range, it means that the welding condition does not hinder the discharge of dust specks.

[0132] In setting the above-mentioned allowable range, the above-mentioned narrow gap length L and the above-mentioned V convergence angle θ are treated as parameters. Off-line weld evaluation tests include flatness test, ultrasonic flaw detection test for detecting oxides in weld (based on JIS G0583 "Automatic eddy current flaw detection method for steel pipe"), Charpy impact test for cutting out test pieces from weld (based on JIS Z2242 "Charpy impact test method for metallic materials"), etc. The test method is selected according to the desired characteristics.

[0133] Below, on one side Figure 5 and Figure 6 An example of a method for setting the upper and lower limits of the allowable range of the ratio ΔT / Tc of the temperature difference ΔT between the outer surface and the inner surface of the wall thickness center Tc at the above-mentioned specified position and the pipe edge surface at the above-mentioned specified position is shown and described, but the invention is not limited to this.

[0134] First, under various welding conditions, the measurement position of the temperature difference ΔT between the outer surface and the inner surface of the wall thickness center Tc at the above-mentioned designated position and the pipe edge surface at the above-mentioned designated position is arbitrary, but it is preferably greater than the squeezing rollers 41a and 41b (refer to Figure 1 ) The edge temperature information acquisition device 11 measures the temperature at a position close to the forming machine side, that is, the upstream side (the side opposite to the welding direction). The edge temperature information acquisition device 11 measures the temperature at a position where the difference between the temperature of the wall thickness center portion Tc and the melting point of the raw material of the pipe becomes less than a predetermined value.

[0135] For example, the temperature is measured at a position where the difference between the temperature of the wall thickness center portion Tc and the melting point of the material of the pipe (the melting point (° C.) −Tc (° C.)) is 300° C. or less.

[0136] When Tc of the wall thickness center portion is lower than the melting point by more than 300°C, that is, when the melting point (°C) - Tc (°C) of the material of the tube exceeds 300°C, the heating process of the two edges until welding becomes unclear, and it is difficult to confirm the relationship between the narrow gap length L and the temperature distribution of the two edge end surfaces.

[0137] In the above-mentioned temperature measurement, the melting point (° C.)-Tc (° C.) of the raw material of the tube is preferably 200° C. or lower, and more preferably 100° C. or lower.

[0138] Next, the resistance welding is performed while the input power of welding is changed while the arbitrary V convergence angle θ is kept constant. At this time, based on the information obtained from the edge temperature information acquisition device 11 and the weld portion imaging device 12, the welding management device 100 measures the wall thickness center Tc at the designated position and the outer surface temperature Tc of the pipe edge surface at the designated position according to the end surface temperature distribution of the pipe edge. o and the inner surface temperature T i The temperature difference ΔT and the narrow gap length L are calculated and their average values ​​are calculated. The average value is calculated based on 100 image data.

[0139] Five samples of 100 mm in length were randomly selected from the electric resistance welded pipes obtained by the above-mentioned electric resistance welding, and the flatness test described in JIS G3478: 2015 was performed. The flatness H / D was calculated using the outer diameter D of the pipe and the distance H between the flat plates when cracks began to form at the welded portion in the flatness test, and the maximum value of the flatness H / D was used. The welding conditions that satisfied the desired flatness H / D were extracted from the maximum value of the flatness H / D.

[0140] Figure 5 This is a graph showing the results of resistance welding quality (flatness height test results) corresponding to the ratio of the temperature difference between the inner and outer surfaces of the pipe at the edge of the resistance weld to the temperature at the center of the wall thickness (ΔT / Tc) and the value of the narrow gap length L.

[0141] exist Figure 5In the example shown, the flatness H / D (maximum value of the flatness H / D) of the weld is 0.5 or less and marked as 0, while the flatness H / D is greater than 0.5 and marked as ×. The welding state determination unit 141 determines the boundary of the pass / fail determination and sets the upper and lower limits of the temperature ratio ΔT / Tc at the arbitrary narrow gap length L. Regarding the boundary of the pass / fail quality of the weld, there are methods of setting a boundary curve using the narrow gap length L as a function and recording it in the storage unit 143, and methods of presetting the upper and lower limits of the temperature ratio ΔT / Tc for an arbitrary narrow gap length L and recording it in the storage unit 143, but the present invention is not limited thereto.

[0142] The welding state determination unit 141 changes the V convergence angle θ for the setting of the upper and lower limits of the temperature ratio ΔT / Tc at any narrow gap length L as described above, and determines the same pass / fail determination boundary.

[0143] Furthermore, the welding state determination unit 141 can also set an upper limit value for the narrow gap length L based on ΔT / Tc, change the V convergence angle θ, and determine the pass / fail determination boundary.

[0144] The V-convergence angle θ can be adjusted by changing the fin width of the fin roll of the final fin pass stand disposed closest to the welding machine in the fin pass stand group located upstream of the squeeze roll, but is not limited thereto.

[0145] As described above, the upper and lower limits of the temperature ratio ΔT / Tc at the narrow gap length L are obtained according to each V-convergence angle θ.

[0146] Figure 6 This is a conceptual diagram for explaining the quality of resistance welding corresponding to the narrow gap length L and the value of ΔT / Tc at each V convergence angle θ1 to θ3. Figure 6 , a conceptual diagram showing the relationship between the narrow gap length L and the temperature ratio ΔT / Tc and the respective allowable ranges (flat height acceptable ranges) arranged vertically is shown.

[0147] The permissible range (flat height acceptable range) of the temperature ratio ΔT / Tc at an arbitrary narrow gap length L obtained from the condition of an arbitrary V-convergence angle θ2 is calculated by interpolation calculation.

[0148] As a specific example of this calculation method, for example, first, let the variable be the angle θ, and the pass judgment area R (L, ΔT / Tc) be a function of θ. The pass judgment area R2 of the angle θ2 assumed from the known areas R1 and R3 is calculated using a linear function of θ.

[0149] Reference Figure 6To explain, when the acceptance determination regions R1 and R3 of θ1 and θ3 are known, for example, lower limits |ΔT / Tc|1 and |ΔT / Tc|3 of ΔT / Tc with respect to the same narrow gap length L in each region are obtained.

[0150] Next, draw a straight line connecting these two points (θ1, L, |ΔT / Tc|1) and (θ3, L, |ΔT / Tc|3). Therefore, |ΔT / Tc| can be expressed as a linear function of θ, so at any angle θ2, the lower limit of the narrow gap length L, |ΔT / Tc|2, is obtained. Repeat this operation to derive the entire qualified area.

[0151] Using these boundary conditions, the welding state determination unit 141 determines that the resistance welding condition is good when the temperature ratio ΔT / Tc at the narrow gap length L under any welding condition is within the acceptable range of the welded portion according to the V convergence angle θ, and determines that the resistance welding condition is inappropriate when it is not satisfied. In addition, the welding state determination unit 141 may determine that the resistance welding condition is good when the narrow gap length L is less than an upper limit value preset according to the values ​​of ΔT / Tc and the V convergence angle θ, and determine that the resistance welding condition is inappropriate when it is not satisfied.

[0152] The result obtained by this process may be recorded in the storage unit 143. Thus, the process of step S10 is completed, and the welding management process proceeds to the process of step S11.

[0153] In the process of step S11, the output unit 142 outputs the good / bad judgment of the welding condition obtained in step S10 to the outside. The output to the outside requires the operator to recognize the judgment result, so it is preferably output to a graphic device, an alarm device, etc. provided in the welding management device 100. Thus, the process of step S11 is completed, and a series of welding management processes are ended.

[0154] As mentioned above, the welding management device for electric resistance welded steel pipe has been described as an embodiment of the present invention.

[0155] The present invention also provides a welding management method used in the welding management device, a method for manufacturing an electric resistance welded steel pipe including the welding management method, and a welding management system including the welding management device.

[0156] The method for manufacturing an electric resistance welded steel pipe is a method for manufacturing an electric resistance welded steel pipe by continuously bending a steel plate or a steel strip in a circumferential direction, butting both edge portions to form an open pipe, and then continuously performing upsetting resistance welding on both edge portions of the butted open pipe, wherein during the electric resistance welding, welding management is performed by the processing (welding management method) performed by the aforementioned welding system.

[0157] As described above, according to the present invention, welding defects can be suppressed by accurately measuring the heat distribution of the end surface during resistance welding and the narrow gap length, and also taking the amount of molten steel discharged after welding into consideration.

[0158] More specifically, by reducing the temperature distribution in the wall thickness direction during resistance welding, the accuracy of heat input adjustment is improved, and welding defects can be suppressed.

[0159] In addition, regarding the above-mentioned embodiments of the present invention, these embodiments are only examples for implementing the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, and other embodiments, examples, and application technologies completed by those skilled in the art are all included in the scope of the present invention as long as they do not deviate from the scope of the present invention.

[0160] Example

[0161] For each electric resistance welded pipe having a pipe thickness of 4 mm and an outer diameter of φ100 mm, first, in order to derive the permissible range of welding conditions, the upper and lower limits of the temperature ratio ΔT / Tc at the narrow gap length L were derived. Here, the position for measuring the temperature Tc at the center of the edge wall thickness and the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the above-mentioned designated position was set at a position 5 mm away from the upstream side (opposite to the welding direction) directly below the axis of the squeeze roll of the welding seat, the edge bending forming during forming was adjusted, and the welding speed was set to 40 m / min for resistance welding.

[0162] At this time, the fin width of the finishing roller of the final stand of the finishing stand was changed, and the V-convergence angle θ was changed to 3 to 5 degrees in 0.5 degree pitches.

[0163] Then, the upper and lower limits of the temperature ratio ΔT / Tc for an arbitrary narrow gap length L under each V convergence angle θ are derived. Here, ΔT is the inner surface temperature T of the tube edge at the measurement position. i Subtract the external surface temperature T o The value obtained.

[0164] In each resistance welding, a two-color thermometer camera was used, the frame rate was set to 20fps, the number of pixels in the tube length direction was set to 1920 pixels, the number of pixels in the tube wall thickness direction was set to 1080 pixels, and the field of view in the tube length direction was set to 50mm, to obtain a two-dimensional image of the temperature distribution before welding. In addition, a CCD camera was used in each resistance welding, the frame rate was set to 20fps, the number of pixels in the tube length direction was set to 1920 pixels, and the field of view in the tube length direction was set to 60mm, to obtain images before and after the weld during welding. Based on these obtained images, the temperature Tc of the center of the wall thickness at the specified position of each frame and the outer surface temperature Tc of the tube edge surface at the specified position were calculated. o and the inner surface temperature T iThe temperature difference ΔT, the narrow gap length L, and the V convergence angle θ are calculated. 100 data of these calculated data are averaged to obtain the operation data under each welding condition.

[0165] In addition, the steel pipe obtained by resistance welding was cut into a length of 100 mm, and a flatness test of the welded portion was performed based on JIS G3478: 2015 to measure the flatness H / D. The maximum value of the flatness H / D obtained in this way was measured 5 times as the quality data of the welded portion under each welding condition. The above-mentioned operation data and the quality data of the welded portion were reflected on a map showing the relationship between the narrow gap length L and the temperature ratio ΔT / Tc, and the condition where the maximum flatness H / D value of 0.5 or less was obtained under each welding condition was regarded as acceptable, and the condition where the maximum flatness H / D value of 0.5 or less was obtained was regarded as unacceptable, and the limit of acceptable / unacceptable judgment was set.

[0166] In this embodiment, for the upper and lower limits of the temperature ratio ΔT / Tc at the narrow gap length L that cannot be measured in advance, the upper and lower limits of the temperature ratio ΔT / Tc at the narrow gap length L that are clear before and after are used. The upper and lower limits of the temperature ratio ΔT / Tc at the narrow gap length L that cannot be measured are obtained by interpolation calculation using a linear function formula using the clear narrow gap length L as a function.

[0167] Similarly, in this embodiment, for the upper and lower limits of the temperature ratio ΔT / Tc under the condition of the V convergence angle θ that cannot be measured in advance, the upper and lower limits of the temperature ratio ΔT / Tc under a certain narrow gap length L that is clear before and after are used. The upper and lower limits of the temperature ratio ΔT / Tc under the condition of the V convergence angle θ that cannot be measured in advance are obtained by interpolation calculation using a linear function formula using the above-mentioned V convergence angle θ as a function.

[0168] Based on the above, the permissible range of welding conditions is derived.

[0169] Next, when manufacturing an electric resistance welded pipe having a pipe thickness of 4 mm and an outer diameter of φ100 mm, electric resistance welding was performed with a V-convergence angle θ set to 3° and a welding speed set to 40 m / min.

[0170] Here, the measurement conditions for measuring the temperature Tc of the center of the edge wall thickness and the temperature difference ΔT between the outer surface and the inner surface of the tube edge surface at the above-mentioned specified position, the narrow gap length L and the method of the above-mentioned V convergence angle θ are the same as the conditions for deriving the above-mentioned common range. Figure 7The following table shows an example of the permissible range of welding conditions derived in advance under the above conditions. In addition, the obtained steel pipe was cut into 100 mm lengths, and a flatness test of the welded portion was performed in accordance with JIS G3478: 2015 to measure the flatness. The flatness test was performed 10 times, and the condition where the flatness H / D was 0.5 or less in 9 or more times in each case was considered acceptable.

[0171] Table 1 shows the pass determination results of the narrow gap length L, the temperature ratio ΔT / Tc, and the flatness ratio of the steel pipe for the passed invention examples and the failed comparative examples.

[0172] In Inventive Example 1, the input power of resistance welding was adjusted so as to satisfy the relationship between the narrow gap length L and the temperature ratio ΔT / Tc within the allowable range while keeping the forming conditions constant.

[0173] In Inventive Example 2, the edge curvature during forming is adjusted so as to satisfy the relationship between the narrow gap length L and the temperature ratio ΔT / Tc within the allowable range while the input power is constant.

[0174] On the other hand, in Comparative Examples 1 and 2, welding management during resistance welding was not performed, welding power was adjusted, and the state of discharged molten steel was only confirmed visually.

[0175] In Example 3 of the invention, the input power of resistance welding was adjusted so as to satisfy the relationship between the narrow gap length L and the temperature ratio ΔT / Tc within the allowable range while keeping the forming conditions constant. In contrast, in Comparative Example 3, the distance between the working coil and the squeeze roller was extended according to the conditions of Example 3 of the invention, and no welding management was performed during resistance welding. The temperature difference T between the inner and outer surfaces of the edge portion was adjusted. i -T o The input power was adjusted in the same manner as in Invention Example 3.

[0176] In Example 4 of the invention, the input power of resistance welding was adjusted so as to satisfy the relationship between the narrow gap length L and the temperature ratio ΔT / Tc within the allowable range while the forming conditions were constant. In contrast, in Comparative Example 4, the edge curvature was increased according to the conditions of Example 4 of the invention, and welding management during resistance welding was not performed, so that the temperature Tc of the center of the wall thickness of the edge portion was the same as that of Example 4 of the invention.

[0177] 100 samples of 100 mm in length cut from the obtained electric resistance welded steel pipe were subjected to a flatness test of the welded portion in accordance with JIS G3478: 2015 to measure the flatness. In the pass judgment of the flatness, the case where the ratio of the number of steel pipes satisfying a flatness of 0.5 or less was 90% or more was considered pass. It can be seen that the steel pipe flatness in Inventive Example 1, Inventive Example 2, Inventive Example 3, and Inventive Example 4 satisfied the pass value, whereas it was lower than the pass value in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4.

[0178]

[0179] Possibility of industrial application

[0180] As described above, by using the welding management device described in the present invention, it is possible to provide an electric resistance welded steel pipe having an electric resistance welded portion having excellent quality.

[0181] Description of Reference Numerals

[0182] 1 Open tube

[0183] 2 Finishing Rollers

[0184] 3 High frequency oscillation device

[0185] 31, 31a, 31b contact nozzle

[0186] 40 welding seat

[0187] 41a, 41b squeeze roller

[0188] 42a, 42b upper roller

[0189] 10Welding Management System

[0190] 11Edge temperature information acquisition device

[0191] 12Welding section camera

[0192] 100 welding management device

[0193] 110 Input unit

[0194] 111 Edge temperature distribution data input unit

[0195] 112 Welding department shooting data input department

[0196] 121 Edge temperature distribution processing unit

[0197] 122 Resistance welding front edge temperature detection unit

[0198] 123 Space Coordinate Calculation Unit

[0199] 124 Temperature distribution detection unit in the wall thickness direction

[0200] 125 Edge temperature difference calculation unit

[0201] 131 Welding Image Processing Department

[0202] 132 Tube edge image detection unit

[0203] 133 V Convergence Point Extraction Unit

[0204] 134 V Convergence angle calculation unit

[0205] 135 Narrow Gap Length Calculation Unit

[0206] 141 Welding status determination unit

[0207] 142 Output unit

[0208] 143 Storage

[0209] 20 Edge detection image of welding part image

[0210] 201 Heating unit

[0211] 202 opening

[0212] 202a, 202b The two edge end surfaces of the open tube

[0213] La, Lb straight line

[0214] θ V Convergence Angle

[0215] 203 welds

[0216] 204 V Convergence Point (Joint Point)

[0217] 205 welding points

[0218] L Narrow gap length.

Claims

1. A welding management device for an electric resistance welded steel pipe, the electric resistance welded steel pipe being manufactured by bending a steel plate or a steel strip in the circumferential direction, butting both edges to form an open pipe, and then performing resistance welding to upsetting both edges of the butted open pipe, wherein: The welding management device of the electric resistance welded steel pipe comprises: The edge temperature detection unit before resistance welding detects the outer surface temperature T of the edge portion based on the information of the temperature distribution in the wall thickness direction of the edge portion of at least one side of the open pipe before resistance welding. o , inner surface temperature T i And the wall thickness center temperature Tc; The edge temperature difference calculation unit calculates the outer surface temperature T o With the inner surface temperature T i The temperature difference ΔT; A V-convergence point extraction unit extracts two straight lines converging along the edge portions based on image information of a region including the two edge portions of the open pipe and a welding point where the two edge portions of the open pipe are joined and welding begins, and extracts a V-convergence point which is an intersection of the two straight lines; A V convergence angle calculation unit calculates a V convergence angle θ formed by the two straight lines; a narrow gap length calculation unit that calculates a distance from the V-convergence point to the welding point as a narrow gap length L; and The welding state determination unit determines whether the resistance welding condition is good or not based on information of the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc, the V convergence angle θ, and the narrow gap length L.

2. The welding management device for electric resistance welded steel pipe according to claim 1, wherein: The welding state determination unit determines that the resistance welding condition is good when the narrow gap length L is equal to or less than an upper limit value preset based on a ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc and a value of the V-convergence angle θ.

3. The welding management device for electric resistance welded steel pipe according to claim 1 or 2, wherein: The welding state determination unit determines whether the resistance welding condition is good or not based on whether a ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc is within a range preset based on a value of the V-convergence angle θ and a value of L.

4. A welding management method for an electric resistance welded steel pipe, the electric resistance welded steel pipe being manufactured by bending a steel plate or a steel strip in the circumferential direction, butting both edges to form an open pipe, and then performing resistance welding to upsetting both edges of the butted open pipe, wherein: The welding management methods for electric resistance welded steel pipes include: The edge temperature detection step before resistance welding is to detect the outer surface temperature T0 and the inner surface temperature T0 of the edge portion based on the temperature distribution information of at least one side of the edge portion of the open pipe before resistance welding. i And the wall thickness center temperature Tc; The edge temperature difference calculation step calculates the outer surface temperature T o With the inner surface temperature T i The temperature difference ΔT; A V-convergence point extraction step of extracting two straight lines converging along the edge portions based on image information of a region including both edge portions of the open pipe and a welding point where both edge portions of the open pipe are joined and welding begins, and extracting a V-convergence point which is an intersection of the two straight lines; a V convergence angle calculation step, calculating a V convergence angle θ formed by the two straight lines; a narrow gap length calculation step of calculating the distance from the V-convergence point to the welding point as the narrow gap length L; and The welding state determination step determines whether the resistance welding condition is good or not based on information of the ratio ΔT / Tc of the temperature difference ΔT to the wall thickness center temperature Tc, the V convergence angle θ, and the narrow gap length L.

5. A method for manufacturing an electric resistance welded steel pipe, the electric resistance welded steel pipe being manufactured by bending a steel plate or a steel strip in the circumferential direction, butting both edges to form an open pipe, and then performing resistance welding to upsetting both edges of the butted open pipe, wherein: The welding management method of the electric resistance welded steel pipe includes: When the electric resistance welding is performed, welding management is performed by the welding management method for electric resistance welded steel pipe according to claim 4.

6. A welding management system for electric resistance welded steel pipes, wherein: have: The welding management device for electric resistance welded steel pipe according to any one of claims 1 to 3; an edge temperature information acquisition device for acquiring information on the temperature distribution of an edge portion of at least one side of the open pipe before resistance welding; and The welding portion photographing device photographs the two edge portions of the open pipe and the welding point formed by the convergence of the two edge portions before resistance welding.

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