Technical field
[0001]
　The present invention relates to a welding monitoring device and a welding method for monitoring electric resistance welded steel pipe.
BACKGROUND
[0002]
　ERW pipe is manufactured through the following steps. That is, first while conveying along a strip-shaped metal plate in a longitudinal direction, formed into continuous cylindrical shape rolls. Then, by a pair of squeeze rolls from the lateral side to the cylindrical metal plate which is molded while applying upsetting, and performs heat input control in the circumferential direction of the side edges of the metal plate which converge in a V-shape while, welded by butting by heating and melting the both side edges by high-frequency resistance welding or induction heating welding. Welding process of this seam welded steel pipe, because an important step that directly affect the quality of the electric resistance welded steel pipe, various studies have been made conventionally.
[0003]
　For example, Patent Document 1, the heat input to provide during welding, forms the welds are "first type", "second type", can change the "transition zone", or "second" seed "shown and are (see Figure 8). Then, in Patent Document 1, a "V convergence point is abutting points abutment of the steel sheet (V1), the welding slits generated between the molten steel discharge starts welding point from inside the steel plate (W) and arc detection area extracting means for extracting a narrow region as arc detection region including adopts the electric resistance welding operation management apparatus comprising a arc detecting means "for detecting the arc generated by the arc detection region.
　According to this configuration, the arc than the V-convergence point is regularly generated in the downstream side (hereinafter, referred to as steady arc) is it possible to determine the frequency of occurrence of.
[0004]
　Moreover, in this electric resistance welding operation management device, an arc occurrence frequency measuring means for measuring the frequency of "the arc, the welding phenomenon based on whether the frequency of occurrence of the arc is greater than or equal to the prescribed value is determined welding with a determination means "is adopted configuration.
　According to this configuration, based on the occurrence frequency of the steady arc, to grasp the form of steady arc downstream than the V-convergence point, it is assumed to perform appropriate heat input control with.
CITATION
Patent Document
[0005]
Patent Document 1: Japanese Patent 2016-78056 JP
[0006]
　According to the technique described in Patent Document 1, it can be a welding state in the downstream and appropriate than V-convergence point, there is a demand further improvement from the viewpoint of improving the quality of welds.
　For example, high-frequency electric resistance welding utilizes a proximity effect and skin effect of the steel edge in the welded portion, to concentrate the current to the welding surface is efficient welding technology, when performing a high-frequency electric resistance welding, since a large current to the steel edge, a strong electromagnetic field is formed around the steel edge. Therefore electromagnetic field becomes maximum at the welding point (V point), easily plunge the welding point to be magnetic body around.
[0007]
　Materials ERW steel pipe is often a steel sheet remains scale formed during hot rolling is attached, the scale is peeled off from the surface layer in the molding process and the fin pass rolls. In particular one that can form a fresh surface by cutting the weld surface in the fin pass roll, which may cause scale or iron powder. Also can cause iron powder as well pickling materials scale in the surface layer is hardly deposited. Thus phenomena such as exfoliated scale or shaved scale powder and iron powder are written engage the weld as foreign matter may occur. In this case, the size of the foreign matter is relatively large, and residual leave weld surface of the solid does not melt until the upset, there is a possibility that the defect without being discharged. Although such frequency of defects is not high, to lower the toughness of the weld, since the crack caused at the time of processing, regardless of the size of the foreign object size, it is highly desirable to detect during pipe-making.
[0008]
　However, in the technique disclosed in Patent Document 1 calculates the frequency of occurrence of steady arc in the downstream side of the welding point (V point), because it is intended to know the heat input state of the welded defects of foreign object by biting measures have not been taken for the occurrence.
Summary of the Invention
Problems that the Invention is to Solve
[0009]
　The present invention was made in view of the above circumstances, in the welding process of a seam welded steel pipe, it is detected in real time even relatively mild biting defects due dive foreign matter such as scale powder and iron powder, and an object thereof is to provide a welding monitoring device and a welding monitoring method.
Means for Solving the Problems
[0010]
　The present inventors have found that in order to meet the above problems, firstly, were analyzed target defect. 1A and 1B, the electric resistance welded steel pipe, installed so that the weld of the defect generation site is 90 ° position from the vertical direction, and a result of the flat test that reduction in the vertical direction, Figure 1A It shows a photograph of cracked fracture, showing the secondary electron image Figure 1B is taken with SEM. As shown in FIG. 1A, a defect of interest is the center position of the crack, there is a feature that the width of several mm or less elongated black streaks extending in the thickness direction exists. In secondary electron image as shown in FIG. 1B, the boundary between the peripheral portion black stripe portion is actualized, dimples fracture occurring characteristically in the periphery at the low heat input has been confirmed. From the above flat test results, such as to remove heat the peripheral portion, the low temperature of the foreign matter than weld surface during welding is presumed defect occurs by I bite.
[0011]
　Further, in FIGS. 2A and 2B, shows a SEM analysis of the black stripe portion. The site 3 in FIG. 2A is an enlarged view of black streaks part a result of the component analysis by SEM, one peak of iron and oxygen as shown in FIG. 2B is remarkable, since except both elements were approximately the noise level, component of black stripe portion is found to be iron oxide. Analysis of the plurality of locations, small clumps of such iron oxide black streak portion are scattered, it had become totally high concentrations. Accordingly, the defect is either I bite iron oxide (scale), or iron powder was determined to be due to oxidized by weld surface Nde bite.
[0012]
　About what these defects occur through what kind of biting process, it was not clear until now. Therefore, we artificially experiments for generating defects during welding using a scale or iron powder. In this case, the welded portion in a camera mounted in the weld upward periodically photographed, were aligned per the cracks (i.e. defect generation site) by flat test. As a result, foreign matter is likely to be written engage been transported from the left welding point upstream adhered to the welding surface, and further welding faces (edges together) when biting foreign materials between the adjacent two edges shorted arcing (hereinafter, referred to as non-stationary arcing) is found to occur. Accordingly, the present inventors have found that the unsteady arcing, utilizes a characteristic that occurs at the welding point or even from well upstream and this invented an image processing method for automatic detection.
[0013]
　That is, the present invention provides following aspects.
(1) One aspect of the present invention, an electric resistance welded steel pipe by molding into a cylindrical shape while conveying a strip-shaped metal plate, is heated and melted by abutting one another while further converging the side edges of the metal plate in a V-shape when manufacturing a a welding monitoring apparatus for monitoring a welding condition of V-shaped converging region that converges in the V-shaped of the metal plate, capturing an image of the area including the V-shaped converging region in time series an image capturing unit; based on captured the image to the time-series extracting welding points, and an image processing means for detecting the presence and position of the non-stationary arcing on the upstream side of the welding point or the weld point; a provided.
(2) In the embodiment described in the above (1), it may be configured as follows: the image by the image capturing means is photographed be RGB image; said image processing means, a red image from the RGB image and extracting at least one of the blue image, for the red image is subjected to reversal binarization and labeling process of the red image, for the blue image, detects a high brightness portion in the blue image to.
(3) In the embodiment described in the above (1) or (2), the imaging unit may be a more cameras 200 frames per second.
[0014]
(4) Further, another aspect of the present invention, by shaping the cylindrical while conveying a strip-shaped metal plate, heating and melting against each other while still converging both side edges of the metal plate in a V-shape when manufacturing the electric resistance welded steel pipe, a welding monitoring method for monitoring a welding condition of V-shaped converging region that converges in the V-shaped of the metal plate, time-series images of a region including the V-shaped converging region a photographing step of photographing the; a detecting step of the time series based on the captured the image to extract the welding point, detects the presence and position of the non-stationary arcing on the upstream side of the welding point or the weld point; having.
(5) In the embodiment described in (4) may be as follows: an RGB image is used as the image; In the detection step, and extracting at least one of the red image and blue image from said RGB image, for the red image is subjected to reversal binarization and labeling process of the red image, for the blue image to detect the high luminance portion in the blue image.
(6) In the embodiment described in (4) or (5), the shooting process, may be captured at 200 frames or more of frame rate per second.
[0015]
(7) in the manner according to any one of the above (4) to (6), the electric resistance welded steel pipe may further comprise a marking step of marking the position of the non-stationary arcing in the longitudinal direction .
(8) When according to the above (7), it may further have a problem whether the particular step of performing ultrasonic testing on site marked with the marking.
In the manner according to any one of (9) above (4) to (6), the electric resistance welded steel pipe may further comprise a tracking step that tracks the position of the non-stationary arcing in the longitudinal direction .
[0016]
　As the camera used in the image capturing means and said photographing step, when a monochrome camera, it is possible to use any color camera, to employ aspects of the (2) and (5) above, the color it is preferable to use a color camera and the degradation of the self-emission and non-stationary arcing from molten steel can be identified with high contrast.
Effect of the invention
[0017]
　According to the welding monitoring device and a welding monitoring method according to the above aspect of the present invention, a defect of foreign matter on the weld surface is generated Nde bite, can be detected, including relatively minor ones. Then, the detection information, or track in a manufacturing process of a seam welded steel pipe, or may be marked on the steel pipe itself immediately after defect detection. In this case, precisely removing the defective portion from the product, it is possible to ship only normal site without biting defective as a product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
[FIG. 1A] is a photograph showing a photograph of the target defect.
It is a photograph showing the secondary electron image of FIG. 1B] target defect.
A diagram showing an example of performing a qualitative analysis by SEM against [FIG 2A] target defect is a photograph of the SEM reflected electron image.
A diagram showing an example of performing a qualitative analysis by SEM against [FIG 2B] target defect is a graph showing the results of component analysis by SEM the site 3 of FIG 2A.
[Figure 3] was applied welding monitoring device and a welding monitoring method according to an embodiment of the present invention, is a perspective view showing an ERW welding apparatus.
Is a flowchart of an image processing algorithm to detect defects caused by [4] the welding monitoring device and the welding monitoring method.
[Figure 5] is a photograph showing an image of an image processing step of detecting a defect occurs, (a) is the captured image, (b) welding point detection, (c) the blue component detection, (d) a high intensity detection of the site, showing the.
6 is a photograph of the state of the welded portion during defect.
[7] divided by defect position and the flat test is a view showing one example of butt and site generated, it shows the appearance photograph and Jitsukizu site (a) was confirmed after the flat test, (b ) indicates the alignment per the site and image unsteady arcing occurs.
[Figure 8] A diagram illustrating an example of a conventional welding monitoring method, in the welding points, "first type", "second type", the welding of the "transition zone", and "second" seed " it is a diagram showing a phenomenon.
DESCRIPTION OF THE INVENTION
[0019]
　An embodiment of a welding monitoring apparatus and a welding method for monitoring electric sewing steel pipe of the present invention will be described below with reference to the drawings.
　3, was applied the welding monitoring device and the welding monitoring method, it shows a perspective view of an electric resistance welded steel pipe welding device. The electric resistance welded steel pipe welding device, formed into a cylindrical shape while being conveyed along a strip-shaped metal plate 1 in the longitudinal direction and both side edges of the metal plate 1 (edge) 1a, V-shaped in plan view and 1b it is an apparatus for manufacturing the electric resistance welded steel pipe by heating and melting against each other while converged to. Incidentally, reference numeral 3 shown in FIG. 3 is a V-convergence point of both side edges 1a converged in a V-shape, 1b is heated and melted abut each other. In FIG. 3, a metal plate (steel plate) 1 is so travels along its longitudinal direction towards from the front side to the depth of the page surface, when relative to the V-convergence point 3, it front side is the upstream side, verso side is the downstream side.
　Welding monitoring device of the present embodiment, when manufacturing the electric resistance welded steel pipe, to monitor the welding state of the V-shaped converging region that converges in a V-shaped metal plate 1.
[0020]
　Reference numeral 4a in Fig. 3, 4b are in the circumferential direction of the side edges 1a metal plate 1 toward V convergence point 3, a pair of contact tip arranged to contact in the vicinity of 1b. Further, reference numeral 5 in FIG. 3 is a impedance arranged in the central part of the metal plate 1 which is formed into a cylindrical shape, reference numeral 6 is a high-frequency power source connected to the respective contact tips 4a, 4b. Contact tip 4a, high-frequency current supplied from 4b, the metal plate 1 in the circumferential direction of the side edges 1a, flows as indicated by an arrow along the extending direction 1b, the and the high-frequency resistance of the metal plate 1 opposite side edges 1a, 1b is heated to melting. By this high-frequency current, similarly to the conventional heat input control is performed. Heating molten metal plates 1 of both side edges 1a, 1b are upset is added by the pair of squeeze rolls 2,2 in the vicinity of the V convergence point 3, are electric resistance welding. The contact tip 4a, instead of the high-frequency resistance welding using 4b, heated using an induction coil, welding of the induction heating method can be adopted.
[0021]
　Thus heat melted metal plate 1 opposite side edges 1a, the 1b, by adding upset by squeeze rolls 2,2, oxide on the surface of the metal plate 1 is discharged is extruded from the welding surface, good welding quality is obtained. However, as described above, foreign matter weld surface is lowered, the strength of the bite-free and weld surface, possibly cracking increases when the internal pressure is taken to processing or when steel pipes of the steel pipe.
　Welding monitoring device of the present embodiment is provided to monitor the biting defects including those mild that could not be monitored in conventional real-time, the image photographing means 7, and an image processing unit 8. According to the welding monitoring device, than welds or welds detects unsteady arcing occurring upstream (contaminated arcing), thereby enabling specifying the defect site in the electric resistance welded steel pipe with. The non-stationary arcing is different from the above-mentioned stationary arcing in the following points. That is, while the resulting downstream than the stationary arcing weld (V-shaped convergence point 3), non-stationary arcing at the upstream side of the weld (V-shaped convergence point 3) and welds (V-shaped convergence point 3) Occur. Also, steady arcing is equal to a pair of edges (edges) As a result the material of the welding site occurs as the metal plate 1 base material to occur between each other in forming the electric resistance welded steel pipe. In contrast, since in the case of non-stationary arcing is caused by foreign matter such as iron oxide (scale) and iron powder, the material of the welding portion is different from the mother material of the metal plate 1.
[0022]
　Imaging means 7, both side edges 1a of the metal plate 1, 1b is intended to photograph a surface image of the area including the V-shaped converging region that converges in a V shape, for example, a CCD camera is used. Imaging apparatus, so that a range including an upstream side of the weld (V-shaped convergence point 3) and welds (V-shaped convergence point 3) can be photographed from above the upper weld (V-shaped convergence point 3) It is located in. Such By adopting the above arrangement, for example, even when applied to a small diameter line, and a reasonably be installed without interfering with other equipment (such as nitrogen purge nozzle or a cooling water pipe).
　Metal plate 1 is the opposite side edges 1a, because 1b is heated and melted centrally, opposite side edges 1a, emits 1b and radiant light from the vicinity thereof. Imaging means 7, of the radiant light, captures an image of the surface of the metal plate 1 comprising a red light.
[0023]
　The image processing algorithms to automatically detected using an image capturing unit 7 and the image processing unit 8 shown in FIG. Also shows an example of an image processed in the FIG. 5 (a) ~ (d) .
　RGB image photographed in step S1 of FIG. 4 (a see FIG. 5 (a)) to extract at least one of the red and blue components (exemplifies a case of extracting both in Figure 4).
　In the red component extraction shown in step S2, flanked by inverted binarized to determine the weld point in the red image (step S3) and labeling process (step S4) and alms, steel edges (opposite side edges 1a, 1b) and the most downstream point of the wedge-shaped region to the welding point (in step S5. see FIG. 5 (b) too).
　On the other hand, in the blue component extraction shown in step S6, 2 binarized for blue image and (in step S7. FIG 5 (c) see also) subjected to the labeling processing (step S8), and detects the high-brightness region (in step S9. FIG 5 (d) see also). In this image obtained by photographing a radiation pattern of the molten steel, but lower levels of the blue component, if the non-stationary arcing is present can be detected as a high luminance. Here, the high brightness, refers to more than one, for example, 200 levels of 255 gradations. The high brightness portion by labeling processing (step S8), and derives the position information. Here, the labeling processing, to one of the lumps in the binary image (blob) with the same label number to extract certain blob, the position of the blob in the image (the maximum point and minimum point of the X-coordinate, Y-coordinate the maximum point and minimum point) and a width, a length, showing a process of extracting an area like. Even if a plurality of non-stationary arcing sites exist can be derived for each of the position information.
　Thus the position of the resulting weld point and a high luminance region in the comparison in step S10, if the position of the high luminance region is not the downstream side of the welding point (step S10: YES), as non-stationary arcing site generated a determination is defect (step S11), and returns to step S1. Meanwhile, if the downstream side of a position welding point of the high luminance region (step S10: NO), determines that the normal (step S12), the followed process returns to step S1.
　Thus, at all times, it has become possible defect determination. Here, has been treated to extract the blue component image in order to detect the unsteady arcing region with high contrast, non-stationary arcing site also saturates (255 levels of 255 gradations) in red component image with a high probability Therefore, it is also detectable only in the red component.
[0024]
　With camera over 200 frames per second. Before photographing, since there is no leak in the detection of non-stationary arcing site has been found experimentally, in the photographing step S1, it is used 200 frames per second or more cameras preferable.
　Examples of the present invention are described below.
Example
[0025]
　In actual production line was measured weld point position while a continuous shooting and image processing of the weld. Pipe was welded monitored is the actual pipe φ100mm × 4mmt, in the camera using the image pickup, 200 frames / sec, and setting an exposure time 1/10000 seconds.
　An example of a welding monitoring, shown in FIG. The image at the time of defect occurrence shown in FIG. 6, when the pair of welding faces (edges together) are close, between the weld surface is shorted to the foreign substance has conductivity such as scale and iron powder, unsteady arcing It has caused. In the place where the foreign matter is not attached, at the time of closest proximity is also not unsteady arcing occurs, it has also confirmed that not occur defects.
[0026]
　Shows an example of butt-jointing the this phenomenon and the defect occurs (a) and (b) of FIG.
　In (a) of FIG. 7 shows the Jitsukizu site cracking occurred after flat test, the appearance photograph corresponding to each of these Jitsukizu sites. 0.24m from steel head, 1.93 M, be cracked in three places of 2.51m occurs seen. Incidentally, "notch" in 1.17m position indicates the site containing the pre-edge notches as a marker for tracking. This marker is used as a reference position for a particular position in the longitudinal direction of the actual tube.
　(B) in FIG. 7, of the photographed image, and the image of the site welds or the non-stationary arcing upstream from it is generated, there is shown the combined per the corresponding sites. Although not shown, the is confirmed image is also markers, each occurrence site it can be seen that correspond very well with flat cracking sites. Since the images other than the corresponding sites is normal without any unsteady arcing or other abnormality, the defects was demonstrated to be associated with non-stationary arcing.
[0027]
　The gist of the welding monitoring device and a welding monitoring method according to the embodiment described above are summarized below.
(1) Welding monitoring device of the present embodiment is formed into a cylindrical shape while being conveyed along a strip-shaped metal plate 1 in the longitudinal direction, further convergence of the metal plate 1 opposite side edges 1a, and 1b in a V-shape when manufacturing the electric resistance welded steel pipe by heating and melting against each other while, to monitor the welding state of the V-shaped converging region that converges in the V-shaped of the metal plate 1. Then, the welding monitoring device, said V-shaped images of a region including the converging region and the image capturing unit 7 for capturing in time series; welding point extracted based on the image taken in the time series, the welding point or an image processing unit 8 for detecting the presence and position of the non-stationary arcing on the upstream side of the welding point; comprises.
[0028]
(2) by welding monitoring device according to (1), is constructed as follows: the image by the image capturing unit 7 is photographed be RGB image; the image processing unit 8, the RGB image extracting at least one of the red image and the blue image from, for the red image is subjected to reversal binarization and labeling process of the red image, for the blue image, a high luminance in the blue image to detect the site.
(3) In the embodiment described in the above (1) or (2), wherein the image capturing means is a more cameras 200 frames per second.
[0029]
(4) In addition, the welding monitoring method in this embodiment is formed into a cylindrical shape while being conveyed along a strip-shaped metal plate 1 in the longitudinal direction, further the metal plate 1 of opposite side edges 1a, 1b of the V-shaped when manufacturing the electric resistance welded steel pipe by heating and melting against each other while converging on, to monitor the welding state of the V-shaped converging region that converges in the V-shaped of the metal plate 1. The weld monitoring method, the image of the area including the V-shaped converging space imaging process and to shoot in chronological; welding point extracted based on the image taken in the time series, the welding points or the welded having; a detection step of detecting the presence and position of the non-stationary arcing at the upstream side of the point.
[0030]
(5) by welding monitoring method according to (4), do the following: an RGB image is used as the image; In the detection step, and extracting at least one of the red image and the blue image from said RGB image, for the red image is subjected to reversal binarization and labeling process of the red image, for the blue image to detect the high luminance portion in the blue image.
(6) above (4) or (5) Keep welding monitoring method according to the shooting process, imaging at 200 frames or more of frame rate per second.
[0031]
　Furthermore, the following (7) and (8), or can be performed step described in (9) below.
(7) (4) to keep welding monitoring method according to any one of (6), further comprising a marking step of marking the position of the non-stationary arcing of the electric resistance welded steel pipe, in the longitudinal direction.
(8) above (7) Keep welding monitoring method according to, further comprising a defect whether specific step of performing ultrasonic testing on site marked with the marking.
(9) in the manner according to any one of the above (4) to (6), further having the seam welded steel pipe, a tracking step of tracking the position of the non-stationary arcing in the longitudinal direction.
[0032]
　According to the welding monitoring device and a welding monitoring method described above, to extract the weld point, a non-stationary arcing occurrence or non-occurrence of the upstream side of the welding point near or welding point by automatically determining the biting defects in real time It can be easily detected. By marking the steel pipe in the vicinity of the squeeze roll 2 just after or unsteady arcing detection Product tracking based on the non-stationary arcing occurrence or non-occurrence information easily in the purification process with an explicit location of defects sites It can be removed. Therefore, it can be shipped only a normal region including no defect as a product.
Industrial Applicability
[0033]
　According to the present invention, in the welding process of a seam welded steel pipe, it is detected in real time even relatively mild biting defects due dive foreign matter such as scale powder and iron powder, it is possible to provide a welding monitoring device and a welding monitoring method .
DESCRIPTION OF SYMBOLS
[0034]
　1: metal plate
　1a, 1b: both sides of the metal plate edge
　2: squeeze roll
　3: welding points
　4a, 4b: contact tip
　5: impedance
　6: high-frequency power source
　7: image capturing means
　8: image processing means

The scope of the claims
[Requested item 1]
　When formed into a cylindrical shape while conveying a strip-shaped metal plate, which further produce ERW pipe by heating melted against each other while both side edges are converged in a V-shape of the metal plate, the metal plate a welding monitoring apparatus for monitoring a welding condition of V-shaped converging region that converges in the V-shape,
　the image capturing means and for capturing the image of the area including the V-shaped converging region in time series;
　taken the time series ; has been the welding point extracted based on the image, and an image processing means for detecting the presence and position of the non-stationary arcing on the upstream side of the welding point or the weld point
welding monitoring device, characterized in that it comprises a.
[Requested item 2]
　Be the image RGB image by the image capturing means captures;
　said image processing means,
　　said extracted from the RGB image at least one of the red image and the blue image,
　　with respect to the the red image, the inversion of the red image subjected to binarization and labeling processing,
　　wherein for a blue image, detects a high brightness portion in the blue image;
welding monitoring device as claimed in claim 1, characterized in that.
[Requested item 3]
　It said image capturing means is a more cameras 200 frames per second
welding monitoring device as claimed in claim 1 or 2, characterized in that.
[Requested item 4]
　When formed into a cylindrical shape while conveying a strip-shaped metal plate, which further produce ERW pipe by heating melted against each other while both side edges are converged in a V-shape of the metal plate, the metal plate a welding monitoring method for monitoring a welding condition of V-shaped converging region that converges in the V-shape,
　shot process and taking an image of the area including the V-shaped converging region in time series;
　is taken the time series ; the image weld points extracted on the basis of a detection step of detecting the presence and position of the non-stationary arcing on the upstream side of the welding point or the weld point was
welded monitoring method characterized by having a.
[Requested item 5]
　The RGB image is used as the image;
　in the detection step,
　　the extracted from the RGB image at least one of the red image and the blue image,
　　with respect to the the red image is subjected to reversal binarization and labeling process of the red image ,
　　wherein for the blue image, detects a high brightness portion in the blue image;
welding monitoring method according to claim 4, characterized in that.
[Requested item 6]
　The shooting process, imaging at 200 frames or more of frame rate per second
welding monitoring method according to claim 4 or 5, characterized in that.
[Requested item 7]
　Wherein the electric resistance welded steel pipe, further comprising a marking step of marking the position of the non-stationary arcing in the longitudinal direction
Welding monitoring method according to any one of claims 4-6, characterized in that.
[Requested item 8]
　Further comprising a failure whether specific step of performing ultrasonic testing on site marked with the marking
welding monitoring method according to claim 7, characterized in that.
[Requested item 9]
　Wherein the electric resistance welded steel pipe, further comprising a tracking process for tracking the position of the non-stationary arcing in the longitudinal direction
Welding monitoring method according to any one of claims 4-6, characterized in that.