JP2018020356A - Weldment monitoring method in electroseamed steel pipe welding process and weldment monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform diagnosis for a first kind area capable of fusion welding.SOLUTION: A weldment monitoring method in an electroseamed steel pipe welding process in which a blet-like metal plate is continuously formed into a cylindrical shape by a roll group while being transported, an upset is applied to the cylindrical metal plate from a lateral side thereof by a pair of squeeze rolls, and both ends of the metal plate in a circumferential direction, which converge in a V-shaped form, are heat-molten and abutted to each other while being heat input-controlled, whereby a steel pipe is manufactured. According to this weldment monitoring method, an image of an area including a weld zone, in which the metal plates converge in a V-shaped form and abut, is photographed, the photographed image is taken in, image processing for capturing an absolute position of a weld point and an arc occurring on a downstream side with respect to the weld point is executed based on the images which are photographed in a time sequence, existence or absence of any arc is discriminated, and further, existence or absence of any abnormality is discriminated in such a manner that a predetermined proper range of the weld point and a position of the weld point are compared.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a monitoring method and a monitoring device for detecting a welding state of an electric resistance welded pipe in real time.

  Conventionally, an electric resistance steel pipe, which is a steel pipe formed using high frequency resistance welding (high frequency electric resistance welding), is known. Moreover, it is known that the electric resistance welding phenomenon of an electric resistance welded steel pipe will exhibit welding phenomena, such as cold welding, 1st type, 2nd type, and excessive heat input, as input electric power (heat input) becomes high. Among these, the second type phenomenon was thought to provide stable weld quality under a wide range of heat input conditions.

  However, it was found that the second type was subdivided into three phenomena by quality observation focusing on welding defects and detailed observation of welding phenomena. These were defined as “second type in a narrow sense”, “transition region”, and “second type” from the lowest heat input. The second type in a narrow sense is a phenomenon in which the steel material edge to be welded converges linearly at the welding point, and is characterized by arc generation in the vicinity downstream of the welding point. The second type is a phenomenon involving a two-stage convergence in which the actual abutting point is located downstream of the convergence point of the steel material edge. There is a transition region in the heat input condition sandwiched between these two phenomenon regions, and linear convergence and initial two-stage convergence appear irregularly, so there is a high possibility that welding defects will increase.

  So far, it has been found that two-stage convergence in the 2 ′ type = full-thickness melting, and a method of controlling to appropriate welding conditions by measuring the length of the welding slit (see Patent Document 1 and Patent Document 2) Melting proof by automatically detecting two-stage convergent type 2 welding phenomenon, technology to control heat input and technology to monitor the upper limit of heat input by measuring the distance between the welding point position and squeeze roll center (patent) Document 3 etc.) has been developed, and a system for controlling the heat input state in which the second type phenomenon appears is being constructed and introduced.

  In this way, welding diagnosis has been conducted for the area above the type 2 phenomenon, but spatter that starts to occur in the type 2 area, such as mechanical and structural pipes, is the cause of defects. There is a variety that becomes a problem. Since spatter tends to increase as the input power during welding, that is, heat input, increases as shown in FIG. 8, in order to realize so-called spatterless welding that does not generate spatter, welding is performed in a region where heat input is as small as possible. There is a need to. On the other hand, depending on the welding conditions such as the V convergence angle, the pipe making speed, and the amount of upset by the squeeze roll, a cold welding or non-welding region also occurs in a region where the heat input is small. Therefore, it is necessary to accurately grasp the “first type region that can be melt-welded” for new varieties that operate on the low heat input side.

Japanese Patent No. 5014837 International Publication No. 2011/118560 Japanese Patent No. 5510615

  By the way, among the first type, the “first type region that can be melt welded” is sandwiched between the second type region on the higher heat input side and the first type region where cold welding or unwelding occurs on the lower heat input side. It is. Therefore, in order to perform welding with the lowest possible heat input while avoiding cold welding or the like, it is required to control the first type region to a very narrow region called “first type region capable of being melt welded”.

  As an index of this control, it is known that, for example, in the second type region, a minute slit (a narrow gap between the steel material edges) is generated on the downstream side of the welding point. However, since it is a very narrow slit, it is difficult to identify its presence. Furthermore, since it was considered that there is no change in the welding phenomenon in the cold welding region to the second type region (such as the welding point position and the V convergence angle), means for determining the lower limit of the “first type region where fusion welding is possible” is provided. It was difficult to find. That is, until now, since there is no index for determining the upper and lower limits of the “first type region that can be melt welded”, it has been difficult to determine the welding state.

  However, as a result of repeated research, it was found that the absolute position of the welding point slightly changes when the weld is photographed with high resolution when the heat input is changed. Further, it was found that arcing occurs in the slit in the second type. As a result, it is possible to diagnose the “first type region capable of fusion welding” in which cold welding and spatter do not occur by capturing the welding point position. In addition, heat input is the electric power (voltage x current) applied to the welded portion, and is a numerical value representing an increase / decrease in% relative to the reference value used for operation.

  The present invention has been made with such circumstances, and an object of the present invention is to make it possible to diagnose that it is a first type region capable of being melt welded.

  The present invention made to solve the above problems employs the following means. First, the first means continuously forms a cylindrical shape by a roll group while transporting a belt-shaped metal plate, and adds upset by a pair of squeeze rolls from the side to the cylindrical metal plate. Monitoring method for welding process of ERW steel pipe for manufacturing steel pipe by heating and melting by high-frequency resistance or induction heating welding while controlling heat input to circumferential ends of metal plate converging in V shape An image of a region including a welded portion where the metal plate converges and collides in a V shape, the captured image is captured, and the absolute position of the welding point is determined based on the captured image. Image processing for capturing an arc generated downstream from the welding point is performed, and the presence / absence of an abnormality is determined using a comparison result between the presence / absence of the arc and a previously determined welding point appropriate range and the position of the welding point. ERW steel pipe A welding method of monitoring the welding process.

  In the first means, when a region including a welded portion where the metal plate converges and collides in a V shape is photographed and processed, and a welding point and an arc are captured, the metal plate being formed into a cylindrical shape from the photographed image Set the area to detect the edge, detect the part with large luminance change as the edge, perform straight line approximation of these parts, calculate two approximate lines, and detect the intersection of these approximate lines as the welding point It is preferable that a rectangle having a width in a predetermined range with respect to the circumferential direction is set as the arc detection region on the downstream side from the welding point.

  In addition, whether or not cold welding has occurred is determined by determining whether or not the welding point is upstream of the most downstream limit position of the preset welding point after the intersection of the approximate lines is a welding point. Is preferred.

  Further, the second means is to continuously form a cylindrical shape by a group of rolls while transporting the belt-shaped metal plate, and add upset by a pair of squeeze rolls from the side to the cylindrical metal plate. Welding monitoring device for welding process of ERW steel pipe that manufactures steel pipe by heating and melting by high frequency resistance or induction heating welding while controlling heat input to both ends in the circumferential direction of metal plate converging in V shape An image photographing means for photographing an image of an area including a welded portion where the metal plate converges and collides with a V-shape, and an image photographed by the image photographing means is captured and the photographed image is taken. Based on the image processing means for capturing the position of the welding point and the arc generated downstream from the welding point, the presence / absence of the arc, and the presence / absence of abnormality using a comparison result of the appropriate range of the welding point and the position of the welding point Determine Wherein the determining means is provided that is a welding monitoring device of the welding process the seam welded steel pipe.

  In a second means, a metal being formed into a cylindrical shape from a photographed image as a means for photographing and processing an area including a welded portion where the metal plate converges and collides in a V shape and captures a welding point and an arc. Set the area to detect the edge of the plate, detect the part with large luminance change as the edge, perform straight line approximation of these parts, calculate two approximate lines, and detect the intersection of these approximate lines as the welding point And it is preferable to set it as the structure which has a means to set the rectangle of the width | variety of the predetermined range with respect to the circumferential direction as an arc detection area | region downstream from the said welding point.

  Further, as means for determining whether or not cold welding has occurred, there is means for determining whether or not the welding point is located upstream of the most downstream limit position of a preset welding point after the intersection of the approximate lines is a welding point. A configuration is preferable.

  When the first means and the second means are used, it is possible to diagnose that it is a first type region that can be melt welded.

It is the bird's-eye view which showed the state which is monitoring the high frequency electric-welding welding part. It is the figure which showed the positional relationship of an imaging | photography process means and a welding part. It is the picked-up image on four types of heat input conditions in the 1st type | mold area | region vicinity in which melt welding is possible. It is the figure which showed the relationship between the shift | offset | difference from the heat input used as a reference | standard, and the measured value of the distance from the center of a squeeze roll to a welding point. It is the figure which showed the algorithm of the image processing in embodiment. It is a figure showing the relationship between the image | photographed image, an approximate line, a welding point, an arc detection area | region, etc. FIG. It is a figure showing the result of the quality check by the determination result of the Example in each heat input condition, and a flat test. It is a figure showing the relationship between the amount of spatter generation, and the appropriate heat input.

  Hereinafter, embodiments of the invention will be described. 1 and 2 show a state in which a high-frequency electro-welded weld is being monitored. FIG. 1 is a bird's eye view and FIG. 2 is a side view. FIG. 1 and FIG. 2 show that the image photographing means 12 photographs from above the ERW weld. In order to perform high-frequency electric seam welding, prior to welding, the belt-shaped metal plate 22 is continuously formed into a substantially cylindrical shape by a roll group (not shown) while being conveyed. While applying an upset to the substantially cylindrical metal plate 22 by a pair of squeeze rolls 23 from the side, performing heat input control to both ends in the circumferential direction of the metal plate 22 converging in a V shape. Then, the steel pipe is manufactured by heating and melting by high-frequency contact resistance welding or high-frequency induction resistance welding. This method of manufacturing a steel pipe is a general method for manufacturing a steel pipe using electric resistance welding.

  The welding monitoring apparatus 1 according to the present embodiment used in the steel pipe manufacturing method using the electric resistance welding has an image of a region including the welded portion 42 where the metal plate 22 converges and collides with a V shape. An image photographing means 12 for photographing is provided. An image processing unit 14 is provided that captures an image captured by the image capturing unit 12 and captures the position of the welding point and an arc generated downstream from the welding point based on the image captured in time series. Further, a discriminating means 16 is provided for discriminating whether or not there is an abnormality by comparing the presence / absence of an arc with the welding point appropriate range determined in advance and the position of the welding point. If such a welding monitoring apparatus 1 is used, it can be diagnosed that it is a first type region where fusion welding is possible.

  This is because the belt-shaped metal plate 22 is continuously formed into a cylindrical shape by a group of rolls, and an upset is applied to the cylindrical metal plate 22 by a pair of squeeze rolls 23 from the side. In the welding monitoring method of the welding process of the ERW steel pipe which manufactures a steel pipe by heat-melting it by high-frequency resistance or induction heating welding while performing heat input control to both ends in the circumferential direction of the metal plate 22 converged in a letter shape The image of the region including the weld 42 where the metal plate 22 converges and collides with the V shape is captured, the captured image is captured, and the absolute value of the welding point is determined based on the image captured in time series. Image processing is performed to capture the arc generated downstream of the position and the welding point, and the presence / absence of an abnormality is determined based on the result of comparison between the presence / absence of the arc and the predetermined welding point appropriate range and the position of the welding point. This is because it is.

  As understood from the matters shown in FIGS. 1 and 2, the image photographing means 12 is disposed above the welded portion 42 in which the metal plate 22 converges in a V shape, and the welded portion 42 is disposed. Shooting the area that includes it.

  In the present embodiment, an impeder 32 is disposed inside a metal plate 22 bent into a cylindrical shape, and a work coil 34 is disposed around the steel plate. This is high frequency induction resistance welding in which high frequency power is supplied from the high frequency power source 36 to the work coil 34. The form of the electric resistance welding is not limited to such a form, and high-frequency contact resistance welding such as a form in which high-frequency power is supplied to the contact tip brought into contact with the metal plate 22 bent into a cylindrical shape. It is also possible.

  Next, a specific description will be given while showing an image photographed by the image photographing means 12. FIG. 3 is a representative example of an image taken at a resolution of 0.03 μm and a frame rate of 40 fps from above the welded portion 42 when the heat input is swung from −10% to + 4%, which is the reference heat input used in the operation. As the reference heat input, it is possible to use the heat input corresponding to the average or the center of the region where normal quality can be obtained by examining the welding quality by changing the heat input before the start of pipe making. This standard heat input is determined in advance before pipe making using already stored data, or it is welded with several stages of heat input before pipe making of the product, and is welded by cross-sectional inspection, flattening test, etc. Just check the quality. In the example shown in FIG. 3, the heat input corresponding to the center of the region is used. From this image example, it was observed that the position of the welding point moved, although it was only about 7.4 mm, due to a change in proper heat input of -10% to + 4%. FIG. 4 shows data obtained by further collecting data on heat input and the position of the welding point. FIG. 4 is a graph plotting the distance (welding point position) from the center of the squeeze roll 23 to the welding point under each heat input condition. The squeeze roll 23 also shows an image outside the left end of the image of FIG. From the items shown in FIG. 4, it can be seen that the position of the welding point can be used as an indicator of whether or not the heat input is appropriate. More specifically, by determining an appropriate range of the welding point in advance, comparing the range with the position of the welding point can be understood as an index of whether or not the heat input is appropriate.

  When the cross section of the welded portion 42 was examined and compared with the presence or absence of a weld line (bond), it was confirmed that the bond disappeared at a reference heat input of −2% or less, and the lower limit heat input that can be normally welded is −2. It was found to be over%. In general, it is known that when the bond disappears, the strength of the welded portion 42 is remarkably lowered, and the presence of the bond (white line) shown in the photograph example on the right side of FIG. It is connected. On the other hand, with respect to the upper limit, it was confirmed that an arc having a correlation with the occurrence of spatter occurred when the reference heat input exceeded + 4%. The arc is a phenomenon in which a high-luminance light emission appears on the downstream side of the welding point as shown in the image example of + 4% in FIG. 3, and it is considered that spatter is generated along with the arc. From the above, it can be seen that it is preferable to control the reference heat input to more than −2% to less than + 4%.

  FIG. 4 also plots the position of the welding point when the pipe making speed is changed, but the distance from the center of the squeeze roll 23 increases as the heat input increases regardless of the pipe making speed (upstream). To move to the side) became clear. Based on this, an arc having a correlation with the occurrence of spatter is detected in the determination of the high heat input upper limit, and a threshold value is set at the absolute position of the welding point at the low heat input lower limit, which is the first type condition that enables fusion welding. An image processing method and a determination method that can be determined have been constructed.

  The image processing and control method will be described below using the flow shown in FIG. First, an image is taken (S001). An area for detecting the edges of both steel materials is set from the photographed image, and a portion where the brightness changes rapidly is detected as an edge (a + mark in FIG. 6). In the flow shown in FIG. 5, a red component is extracted from an image photographed using a color camera (S002). At this time, it is preferable to use the red component having the highest radiance from the steel material for the processing, but the same processing can be performed with the green or blue component as long as the image can be captured at a sufficient luminance level. In addition, when a monochrome camera is used, it is not necessary to extract color components.

  A straight line approximation of the points obtained by such extraction is performed, and two approximate straight lines are calculated (S003). When photographing using a color camera, an approximate straight line is obtained by extracting the red component from the photographed image and then performing the same processing. By this step, two straight lines as shown in FIG. 6 are obtained.

  Next, the intersection of these approximate lines is detected as a welding point (S004). In addition, by measuring the image resolution and the relative position between the center of the squeeze roll 23 and the image in advance in the cold, the coordinates (pixel unit) in the image can be reprinted to the actual position.

  The bisector of the angle between the two approximate straight lines is calculated (S005). Next, an arc detection area is set (S006). This area is, for example, a rectangle with a width of ± 3 mm in the tube circumferential direction (up and down direction of the image) to the left end of the image on the downstream side from the welding point, and detects whether or not a substantially saturated region exists. Since the arc has remarkably higher luminance than the radiation of molten steel, it can be determined whether or not there is a portion having a threshold value of 200 levels or more in the arc detection region, for example, from 0 to 255 in the luminance level of the image. Based on such a reference, binarization processing is performed in the arc detection area (S007).

  At this time, primary discrimination can be made by setting the minimum area of the area detected as an arc and the upper limit of the aspect (vertical / horizontal) ratio so as not to detect noise (S008). At this time, if the upper limit is not reached, it can be determined that there is no arc (S014). Further, after the primary discrimination, the frequency of detecting the arc per second is measured (S009), so that the discrimination of 1 type / 2 types can be made (S010, S015).

  These threshold values are determined, for example, by measuring the arc occurrence frequency at the boundary between 1 type and 2 types and evaluating the welding quality by a flat test after welding (checking whether cracks due to defects occur). be able to. In the example shown in FIG. 5, when it is determined that the two-type welding phenomenon has occurred, it is output that the heat input is abnormal (S011).

  On the other hand, whether or not cold welding has occurred can be determined based on whether or not the position of the welding point calculated in the above step (S004) is upstream from a preset most downstream limit position (S012). In the example shown in FIG. 5, if the position of the welding point exceeds the most downstream limit position, it is determined as a first type phenomenon that can be melt welded (S013). Conversely, if the position of the welding point does not exceed the most downstream limit position, it is determined that cold welding has occurred (S016). In the case of the example shown in FIG. 5, if it is determined that the cold welding has occurred, it is output that the heat input is abnormal (S017).

  The most downstream limit position is obtained by changing the heat input for each product type and collecting data as shown in FIG. 4 in advance. The cross-section of the welded portion 42, that is, the heat input lower limit at which the weld line disappears and the image at that time Set the upper welding point position. In the example of FIG. 4, the distance of 21.8 mm from the center of the squeeze roll 23 when the reference heat input is −2% is the most downstream limit position.

  In the present embodiment, the metal plate 22 is formed into a cylindrical shape from a photographed image as a means for capturing and processing an area including the weld portion 42 where the metal plate 22 converges and collides in a V shape and captures a welding point and an arc. An area for detecting an edge of a certain metal plate 22 is set, a part with a large luminance change is detected as an edge, a straight line approximation of these parts is performed, two approximate straight lines are calculated, and an intersection of these approximate lines is welded. Since it has means for detecting a point and setting a rectangle having a predetermined width in the circumferential direction as an arc detection region downstream from the welding point, it is possible to appropriately capture the welding point and the arc.

  This is because the metal plate 22 is formed into a cylindrical shape from a photographed image when the region including the welded portion 42 where the metal plate 22 converges and collides with the V shape is photographed and processed to capture the welding point and the arc. Set 22 areas to detect edges, detect areas with large brightness changes as edges, perform straight line approximation of these areas, calculate two approximate lines, and detect the intersection of these approximate lines as welding points This is because a rectangle having a width in a predetermined range with respect to the circumferential direction can be set as the arc detection region downstream from the welding point.

  Further, as means for determining whether or not cold welding has occurred, there is means for determining whether or not the welding point is located upstream of the most downstream limit position of a preset welding point after the intersection of the approximate lines is a welding point. Therefore, the presence or absence of occurrence of cold welding can be determined appropriately.

  The determination as to whether or not cold welding has occurred can be determined by determining whether or not the welding point is upstream from the most downstream limit position of the preset welding point after the intersection of the approximate lines is set as the welding point. Because.

  As described above, according to the present invention, heat input can be controlled in the first type region that can be melt welded, which is a narrow region, and welding without spatter generation and cold welding can be realized. Moreover, based on this determination result, the site | part welded out of the suitable heat input range can be specified, and advanced quality control is realizable by combining with marking and tracking. More specifically, by marking (ink method) immediately after welding or sending the defective position to the process controller while measuring the length from the top of the coil, the defective portion can be identified and removed in the refining process. Advanced quality control can be realized.

  Next, examples will be described. A photographic optical system was installed in the actual production line, and the welding state was judged while continuously performing photographing and image processing. The target pipe was a real tube of φ100 mm × 5 mmt, the camera used for imaging was 40 frames / second, and the exposure time was 1/10000 seconds. A flat test was conducted from the top after pipe making, and the position where the crack occurred was measured. The heat input was changed, a flat test was performed after welding, and the determination result was compared with the quality (FIG. 7). As a result, it was found that the two agreed very well, and the effect of the present invention was proved. In addition, since the state which is not made into the state which the arc has generate | occur | produced was repeated in appropriate heat input + 4%, both images are shown in FIG.

  The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be applied without departing from the spirit of the present invention. For example, some steps can be omitted or replaced with other steps. In addition, the order of each step can be changed within a possible range.

DESCRIPTION OF SYMBOLS 1 Welding monitoring apparatus 12 Image photographing means 14 Image processing means 16 Discriminating means 22 Metal plate 23 Squeeze roll 42 Welded part

Claims (6)

Metal that is continuously formed into a cylindrical shape by a group of rolls while transporting a belt-shaped metal plate, and is converged into a V shape while being upset by a pair of squeeze rolls from the side of the cylindrical metal plate. A welding monitoring method of a welding process of an ERW steel pipe that manufactures a steel pipe by heat-melting by high-frequency resistance or induction heating welding while performing heat input control to both ends in the circumferential direction of the plate,
Taking an image of the region including the weld where the metal plate converges and collides into a V shape,
The captured image is captured, and based on the captured image, an absolute image of the welding point and an image process for capturing an arc generated downstream from the welding point are performed.
Using the comparison result of the presence or absence of the arc, the welding point appropriate range determined in advance and the position of the welding point,
A welding monitoring method for a welding process of an electric resistance welded pipe characterized by determining the presence or absence of abnormality. When capturing and processing a region including a welded portion where the metal plate converges and collides with a V shape, and captures a welding point and an arc,
Set an area to detect the edge of the metal plate that is being formed into a cylindrical shape from the photographed image, detect areas with large luminance changes as edges, perform linear approximation of these areas, and calculate two approximate lines , Detecting the intersection of these approximate lines as a welding point,
2. The welding monitoring method in the welding process for an ERW steel pipe according to claim 1, wherein a rectangle having a width in a predetermined range with respect to the circumferential direction is set as an arc detection area downstream of the welding point.   The determination as to whether or not cold welding has occurred is made by determining whether or not the intersection point of the approximate line is a welding point, and then whether or not the welding point is upstream of a preset downstream limit position of the welding point. Item 3. A welding monitoring method for a welding process of an ERW steel pipe according to Item 2. Metal that is continuously formed into a cylindrical shape by a group of rolls while transporting a belt-shaped metal plate, and is converged into a V shape while being upset by a pair of squeeze rolls from the side of the cylindrical metal plate. A welding monitoring device for the welding process of an ERW steel pipe for producing a steel pipe by heating and melting by high-frequency resistance or induction heating welding while performing heat input control to both ends in the circumferential direction of the plate,
Image photographing means for photographing an image of a region including a welded portion where the metal plate converges and collides in a V shape;
Image processing means for capturing an image captured by the image capturing means and capturing an arc generated downstream of the position of the welding point and the welding point based on the captured image;
A welding process for an ERW steel pipe, characterized by comprising: a discriminating means for discriminating the presence or absence of an abnormality by using a comparison result between the presence / absence of the arc and a predetermined welding point appropriate range and the position of the welding point. Welding monitoring equipment. As a means for capturing and processing a region including a welded portion where the metal plate converges and collides with a V shape, and captures a welding point and an arc,
Set an area to detect the edge of the metal plate that is being formed into a cylindrical shape from the photographed image, detect areas with large luminance changes as edges, perform linear approximation of these areas, and calculate two approximate lines , Detecting the intersection of these approximate lines as a welding point,
The welding monitoring of the welding process of the ERW steel pipe according to claim 4, further comprising means for setting a rectangle having a predetermined width in the circumferential direction as an arc detection area downstream from the welding point. apparatus.   As a means for determining whether or not cold welding has occurred, it has means for determining whether or not the welding point is upstream of the most downstream limit position of a preset welding point after the intersection of the approximate lines is a welding point. The welding monitoring apparatus for a welding process of an ERW steel pipe according to claim 5,