Device for detecting surface defects and straightness of large-diameter welded pipe

Abstract

The invention provides a large-diameter welded pipe surface defect and straightness detection device which comprises a support, first cameras, second cameras and an image processing system, a through hole penetrating through a welded pipe is formed in the support, a plurality of sets of first cameras are evenly distributed on one side of the support in the circumferential direction, the camera shooting ends of the first cameras face the center of the through hole, and the camera shooting ends of the second cameras face the center of the through hole. At least three sets of second cameras are arranged on the support in the moving direction of the welded pipe at equal intervals, the first cameras and the second cameras are electrically connected with the image processing system, and the image processing system is used for processing data collected by the first cameras and the second cameras, recognizing the surface defects of the welded pipe and calculating the straightness of the welded pipe. The detection device has the advantages that the problem that an existing device cannot detect the surface defects and the straightness of the welded pipe at the same time is solved, synchronous detection of the surface defects and the straightness of the welded pipe can be completed in a short time, and the detection efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the field of large-diameter welded pipe production and testing equipment, and in particular to a large-diameter welded pipe surface defect and straightness detection device. Background Art

[0002] In modern manufacturing, large-diameter welded pipes are increasingly used, especially in the oil, gas, chemical, and electric power industries. These fields have extremely high quality requirements for welded pipes, especially in terms of pressure resistance, corrosion resistance, and structural stability. Therefore, ensuring the surface quality of welded pipes and the accuracy of their straightness has become a key link in the production process.

[0003] During the production process, especially during the welding stage, various surface defects are prone to occur in welded pipes. These defects not only affect the appearance of the welded pipe, but may also cause its mechanical properties to deteriorate and increase safety hazards during use. Common surface defects include pores, inclusions, incomplete welds, cracks, rust, etc. The appearance of these defects is often closely related to multiple factors such as the quality of raw materials, welding process parameters, welding environment, and post-processing process.

[0004] In addition to surface defects, the straightness of welded pipes is also an important quality indicator. Straightness refers to the degree of bending of the welded pipe in the length direction, which affects the docking accuracy and structural stability of the welded pipe during installation and use. Unqualified straightness of welded pipes may lead to reduced fluid transportation efficiency in the pipeline system and may even cause safety hazards such as leakage. Therefore, the straightness detection of welded pipes cannot be ignored.

[0005] Although existing detection technologies have made some progress in the detection of surface defects and straightness of welded pipes, there are still many shortcomings. Traditional detection methods usually rely on manual visual inspection or simple measuring instruments, and have problems such as low detection efficiency and poor accuracy. In addition, existing equipment often cannot detect surface defects and straightness of welded pipes at the same time. This is because most traditional detection methods focus on one aspect and lack comprehensive functions. Although some equipment is capable of visual detection or laser ranging of surface defects, due to technical limitations, they cannot effectively integrate these two detection tasks at the same time. This results in the inability to obtain comprehensive quality information in real time during the production process of welded pipes, increasing the risk of subsequent inspection and rework. Therefore, there is an urgent need for a new type of equipment that can simultaneously meet the detection needs of surface defects and straightness of welded pipes. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to simultaneously meet the detection requirements of surface defects and straightness of welded pipes.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A large-diameter welded pipe surface defect and straightness detection device comprises a bracket, a first camera, a second camera, and an image processing system. The bracket is provided with a through hole through which the welded pipe passes. A plurality of first cameras are evenly distributed circumferentially on one side of the bracket. The camera ends of the first cameras are all arranged toward the center of the through hole. At least three second cameras are evenly spaced on the bracket along the moving direction of the welded pipe. The first camera and the second camera are electrically connected to the image processing system. The welded pipe passes through the first camera and the second camera in sequence, and complete circular screw hole data and multiple equally spaced arc profile data of the welded pipe at the same time are obtained respectively. The image processing system is used to process the data collected by the first camera and the second camera, identify the surface defects of the welded pipe, and calculate the straightness of the welded pipe.

[0009] The image processing system calculates the straightness of the welded pipe as follows:

[0010] The process of confirming the weld point: fit an ellipse according to the complete circle contour data, take three adjacent contour points of the ellipse, calculate the distance from the middle contour point to the line connecting the other two contour points, traverse all contour points to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point;

[0011] The process of eliminating the error caused by the natural rotation of the welded pipe: according to the angular positions θ1 and θ2 of the weld points of the complete circle at two different times t1 and t2, the rotation angle θ=θ1-θ2 is obtained; the contour of the complete circle at time t1 is rotated by an angle θ so that the welds of the complete circles at time t1 and time t2 are at the same angular position, and then the complete circle at time t1 and the arc at time t2 are searched for the nearest neighbor, and the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the nearest neighbor point cloud found, and the calculated transformation matrix is ​​applied to the complete circle at time t1 to obtain a complete circle to replace the arc at time t2; finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe when it moves forward;

[0012] Process of eliminating the jitter error of the welded pipe: Assume that the complete circle contour data obtained based on the steps of eliminating the error caused by the natural rotation of the welded pipe at two different times t1 and t2 are: complete circle contours c1, c2, c3 at time t1, complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welded pipe, c3 and c5 are also at the same position of the welded pipe, and the transformation matrices between the corresponding circle contours are calculated to be m_24 and m_35, and the transformation matrices m_24 and m_35 are weighted averaged to obtain a new matrix m_combined, which is then applied to c6 to obtain c_final, which is closer to the state of c6 at time t1. Finally, the operation is repeated for all the replaced complete circles to obtain a contour set c_finals;

[0013] The process of straightness calculation: According to the contour set c_finals, the straightness of the welded pipe at any position of 360° is calculated.

[0014] Furthermore, the specific calculation process of the weld point confirmation step is as follows: first, an ellipse fitting operation is performed on each complete circle contour in the XOZ plane to obtain the center coordinates o(x o ,z o ), further through the formula Find each contour point p(x i ,z i ) on the circle; then, take the contour point p and two points p with an interval of n to the left and right of point p l ,p r , where n is equal to 1 / 2 of the number of contour points occupied by the weld, find the distance from point p to p l and p r Connection L pl,pr The distance dist; where L pl,pr The general formula of the straight line equation is: Ax+Bz+C=0, each point p(x i ,z i ) to the straight line L pl,pr The distance is: Finally, all contour points are traversed to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point.

[0015] The detection device solves the problem that existing equipment cannot simultaneously detect surface defects and straightness of welded pipes. It can complete the simultaneous detection of surface defects and straightness of welded pipes in a short time, greatly improving the detection efficiency. Compared with traditional manual detection and step-by-step detection, the overall detection time is greatly shortened.

[0016] Furthermore, in the step of eliminating the error caused by the natural rotation of the welded pipe, the optimal transformation matrix formula for solving the source point cloud to the target point cloud is: Where R is the rotation matrix, p′ i is the target point cloud, p i is the source point cloud and N is the number of points.

[0017] Furthermore, the calculation process of the straightness calculation step is as follows: all contours are obtained by scanning in the XOZ plane, and the end point connection method is used to calculate, taking a1 and a N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line L are calculated, the maximum distance is taken as the straightness of the angle, and the position of the point with the maximum distance is recorded.

[0018] Furthermore, the bracket includes a first bracket, a second bracket, a connecting shaft and a fixed frame, the first bracket and the second bracket are connected by multiple connecting shafts, the through hole coaxially penetrates the first bracket and the second bracket, a fixed frame is fixed between the first bracket and the second bracket along the movement direction of the welding pipe, multiple groups of second cameras are fixed on the fixed frame, and the first camera is set on the first bracket.

[0019] Furthermore, a profile frame is fixed on both the first bracket and the second bracket.

[0020] Furthermore, the first camera is arranged on the first bracket via a fixing seat.

[0021] Furthermore, the fixing seat is a retractable fixing seat, so that the first camera can be retracted along the movement direction of the welding pipe.

[0022] Furthermore, the first bracket is provided with a mounting hole for mounting the fixing seat.

[0023] The advantages of the present invention are:

[0024] The detection device solves the problem that existing equipment cannot simultaneously detect surface defects and straightness of welded pipes. It can complete the simultaneous detection of surface defects and straightness of welded pipes in a short time, greatly improving the detection efficiency. Compared with traditional manual detection and step-by-step detection, the overall detection time is greatly shortened.

[0025] Automatic calculation by the image processing system can effectively reduce the impact of human factors on the detection results and improve the accuracy of detection; automatic identification and marking of defect types can avoid missed detection and false detection that may be caused by manual inspection, ensuring the reliability of welded pipe quality.

[0026] In addition, the detection device also has real-time online detection capabilities, which can promptly detect any abnormal conditions in the production process and quickly provide feedback to production management personnel, thereby reducing the influx of unqualified products, reducing rework and scrap rates, and further saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of a local structure of an embodiment of the present invention;

[0029] Figure 3 This is a front view of a first bracket according to an embodiment of the present invention;

[0030] Figure 4 A flowchart of a method for calculating the straightness of a welded pipe according to an embodiment of the present invention;

[0031] Figure 5Schematic diagram of the process of eliminating the natural rotation of the welded pipe in an embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of eliminating the vibration of the welding pipe in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] See also Figures 1 to 3 This embodiment describes a large-diameter welded pipe surface defect and straightness detection device, including a bracket 1, a first camera 2, a second camera 3, and an image processing system (not shown in the figure).

[0035] The bracket 1 includes a first bracket 11, a second bracket 12, a connecting shaft 13, a fixing frame 14 and a profile frame 15. The first bracket 11 and the second bracket 12 are connected by a plurality of connecting shafts 13. The first bracket and the second bracket are provided with through holes 101 through which the welding pipe 4 can pass. The fixing frame 14 is fixed between the first bracket 11 and the second bracket 12 along the moving direction of the welding pipe 4. The profile frame 15 is fixed to the first bracket 11 and the second bracket 12 in a circumferential direction. In the implementation, the first bracket 11 and the second bracket 12 are both aluminum alloy plates.

[0036] A plurality of groups of first cameras 2 are evenly distributed circumferentially on one side of the first bracket 11, and the camera ends of the first cameras 2 are all arranged toward the center of the through hole 101, so that the first cameras 2 can capture minute defects on the surface of the welded pipe 4. It should be noted that the number of the first cameras 2 is determined according to the aperture of the welded pipe 4. The larger the aperture, the more the number of the first cameras 2. In this embodiment, the number of the first cameras 2 is 12 groups.

[0037] Specifically, the first bracket 11 is provided with mounting holes 111 corresponding to the number and positions of the first cameras 2. Each group of first cameras 2 is set on the mounting hole 111 through a fixing seat 5. The fixing seat 5 is a retractable fixing seat, so that the first camera 2 can be retracted along the movement direction of the welding pipe 4. In this embodiment, the fixing seat 5 is set as a retractable fixing seat, which can ensure that the camera ends of each group of first cameras 2 are on the same plane, and the positions of the first cameras 2 are calibrated; through the setting of the mounting hole 111, not only the telescopic movement of the first camera 2 on the fixing seat 5 is convenient, but also the weight reduction effect is achieved.

[0038] A plurality of groups of second cameras 3 are fixed on the fixing frame 14 at equal intervals along the moving direction of the welding pipe 4 , so that the second cameras 3 can monitor the straightness of the welding pipe 4 in real time.

[0039] The first camera 2 and the second camera 3 are both electrically connected to the image processing system, and the image processing system is used to process the images captured by the first camera 2 and the second camera 3, identify the surface defects of the welded pipe, and calculate the straightness of the welded pipe.

[0040] The working principle of this embodiment is as follows: the welded pipe 4 on the production line is set with a through hole 101 and moves along its length direction. During the movement, it passes through the first camera 2 and the second camera 3 in turn. The first camera 2 scans the surface of the welded pipe 4 in real time to capture the subtle defects on the surface of the welded pipe 4. The acquired three-dimensional point cloud data is transmitted to the image processing system for analysis. The defects on the surface of the welded pipe 4 are automatically identified and classified through the image processing algorithm. At the same time, the second camera 3 also acquires the geometric shape of the surface of the welded pipe 4 in real time. The first camera 2 and the second camera 3 respectively obtain the complete circular screw hole data and multiple equally spaced arc contour data of the welded pipe 4 at the same time, and the straightness data of the welded pipe 4 is calculated through the image processing system to determine whether the quality of the welded pipe 4 meets the requirements.

[0041] In this embodiment, the detection device solves the problem that the existing equipment cannot simultaneously detect the surface defects and straightness of the welded pipe. It can complete the simultaneous detection of the surface defects and straightness of the welded pipe in a short time, greatly improving the detection efficiency. Compared with traditional manual detection and step-by-step detection, the overall detection time is greatly shortened.

[0042] Automatic calculation by the image processing system can effectively reduce the impact of human factors on the detection results and improve the accuracy of detection; automatic identification and marking of defect types can avoid missed detection and false detection that may be caused by manual inspection, ensuring the reliability of welded pipe quality.

[0043] In addition, the detection device also has real-time online detection capabilities, which can promptly detect any abnormal conditions in the production process and quickly provide feedback to production management personnel, thereby reducing the influx of unqualified products, reducing rework and scrap rates, and further saving production costs.

[0044] The specific process of calculating the straightness of the welded pipe by the image processing system is as follows:

[0045] Step 1: Weld point confirmation step. The welded pipe is made of a rectangular steel plate rolled into a tube, and the joint is welded solidly. The weld is obvious and higher than the surface of the welded pipe. This step locates the angle position of the weld on the welded pipe based on the complete circle contour data. Specifically, since the cross section of the welded pipe cannot meet the perfect circle standard, firstly, an ellipse fitting operation is performed on each complete circle contour in the XOZ plane to obtain the center coordinates o(x o ,zo ), further through the formula Find each contour point p(x i ,z i ) on the circle. Then, take the contour point p and two points p with a distance n to the left and right of point p. l ,p r , where n is equal to 1 / 2 of the number of contour points occupied by the weld, find the distance from point p to p l and p r Connection L pl,pr The distance dist. Among them, L pl,pr The general formula of the straight line equation is: Ax+Bz+C=0, each point p(x i ,z i ) to the straight line L pl,pr The distance is: Since the weld point is higher than the surface of the welded pipe, all contour points are traversed to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point.

[0046] Step 2: Eliminate the error caused by the natural rotation of the welded pipe. Based on the location of the weld in step 1, eliminate the error caused by the natural rotation of the steel pipe when it moves forward.

[0047] Step 2.1: Figure 4 As shown in the figure, the steel pipe rotates irregularly clockwise or counterclockwise when it moves forward ( Figure 5 According to step 1, the angular positions θ1 and θ2 of the complete circular weld points at two different times t1 and t2 can be obtained, and then the rotation angle θ=θ1-θ2 can be obtained.

[0048] Step 2.2: According to the value of θ obtained in step 2.1, rotate the contour of the complete circle at time t1 by an angle of θ so that the welds of the complete circles at time t1 and time t2 are at the same angle. Then, perform a nearest neighbor search on the complete circle at time t1 and the arc at time t2. Based on the nearest neighbor point cloud found, minimize the error in the formula to solve the optimal transformation matrix from the source point cloud to the target point cloud. The formula is: Where R is the rotation matrix, p′ i is the target point cloud, p i is the source point cloud, N is the number of points, and the calculated transformation matrix is ​​applied to the complete circle at time t1 to obtain a complete circle to replace the arc at time t2. The complete circle at time t2 is used to complete the arc at time t3, and so on. Finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the steel pipe when it moves forward.

[0049] Step 3: Eliminate the jitter error of the welded pipe. According to step 2, all the complete circle profile data after eliminating the rotation error are obtained, and the error effect caused by the jitter of the steel pipe when it moves forward is further eliminated.

[0050] Step 3.1: From step 2.2, we can see that the original steel pipe arc data is replaced with complete circle data, such as Figure 6 As shown, assuming that there are complete circular contours c1, c2, c3 at time t1, and complete circular contours c4, c5, c6 at time t2, since c2 and c4 are the original contour data obtained at the same position of the welded pipe, there is only a relative change in the spatial position. Similarly, c3 and c5 are also a corresponding set of circular contours (in this embodiment, at least 3 arcs are required to eliminate jitter, and only equal spacing can ensure the correspondence between c2 and c4, c3 and c5). The transformation matrix between the corresponding circular contours is calculated using the least squares method as m_24, m_35.

[0051] Step 3.2: Perform weighted averaging on the transformation matrices m_24 and m_35 with the weight set to 0.5 to obtain a new matrix m_combined, which is then applied to c6 to obtain c_final, which is closer to the state of c6 at time t1. Finally, repeat this operation for all replaced complete circles to obtain a contour set c_finals, thereby eliminating the jitter error caused by the steel pipe moving forward.

[0052] Step 4: Straightness calculation step. According to the contour set c_finals obtained in step 3.2, the straightness of any position of the whole tube 360° is calculated. It is known that all contours are obtained by scanning in the XOZ plane. The present invention uses the end point connection method for calculation. For example, to calculate the straightness in the 90° direction, the point a in all contours with an x ​​coordinate of 0 and a z coordinate greater than 0 can be specified. i (i=1,2,...,N), take a1 and a N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line L are calculated, the maximum distance is taken as the straightness of the angle, and the position of the point with the maximum distance is recorded. Similarly, the straightness of any position of the entire tube 360° can be calculated.

[0053] Based on the original data of the complete circular contour and three equally spaced arc contours in the forward direction, this embodiment uses a self-developed algorithm to locate the weld position and eliminates the influence of the natural rotation and jitter of the steel pipe when it is conveyed on the roller table on the measurement of straightness, and can accurately realize the dynamic measurement of the straightness of large-diameter welded pipes at any position of 360°; this embodiment solves the shortcomings of manual visual and manual wire drawing methods for measuring straightness, saves a lot of manpower, material and financial resources, and improves the efficiency and accuracy of the measurement results.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A large-diameter welded pipe surface defect and straightness detection device, characterized in that: It comprises a bracket, a first camera, a second camera, and an image processing system. The bracket is provided with a through hole through which the welding pipe passes. A plurality of groups of first cameras are evenly distributed in the circumferential direction on one side of the bracket. The camera ends of the first cameras are all arranged toward the center of the through hole. At least three groups of second cameras are evenly spaced along the moving direction of the welding pipe on the bracket. The first camera and the second camera are electrically connected to the image processing system. The welding pipe passes through the first camera and the second camera in sequence, and the complete circular screw hole data and a plurality of evenly spaced circular arc profile data of the welding pipe at the same time are obtained respectively. The image processing system is used to process the data collected by the first camera and the second camera, identify the surface defects of the welding pipe, and calculate the straightness of the welding pipe. The image processing system calculates the straightness of the welded pipe as follows: The process of confirming the weld point: fit an ellipse according to the complete circle contour data, take three adjacent contour points of the ellipse, calculate the distance from the middle contour point to the line connecting the other two contour points, traverse all contour points to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point; The process of eliminating the error caused by the natural rotation of the welded pipe: according to the angular positions θ1 and θ2 of the weld points of the complete circle at two different times t1 and t2, the rotation angle θ=θ1-θ2 is obtained; the contour of the complete circle at time t1 is rotated by an angle θ so that the welds of the complete circles at time t1 and time t2 are at the same angular position, and then the complete circle at time t1 and the arc at time t2 are searched for the nearest neighbor, and the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the nearest neighbor point cloud found, and the calculated transformation matrix is ​​applied to the complete circle at time t1 to obtain a complete circle to replace the arc at time t2; finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe when it moves forward; Process of eliminating the jitter error of the welded pipe: Assume that the complete circle contour data obtained based on the steps of eliminating the error caused by the natural rotation of the welded pipe at two different times t1 and t2 are: complete circle contours c1, c2, c3 at time t1, complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welded pipe, c3 and c5 are also at the same position of the welded pipe, and the transformation matrices between the corresponding circle contours are calculated to be m_24 and m_35, and the transformation matrices m_24 and m_35 are weighted averaged to obtain a new matrix m_combined, which is then applied to c6 to obtain c_final, which is closer to the state of c6 at time t1. Finally, the operation is repeated for all the replaced complete circles to obtain a contour set c_finals; The process of straightness calculation: According to the contour set c_finals, the straightness of the welded pipe at any position of 360° is calculated.

2. A large diameter welded pipe surface defect and straightness detection device according to claim 1, characterized in that: The specific calculation process of the weld point confirmation step is as follows: first, an ellipse fitting operation is performed on each complete circle contour in the XOZ plane to obtain the center coordinates o(x o ,z o ), further through the formula Find each The angle value of the contour point p (xi, zi) on the circle; then, take the contour point p and two points pl, pr with an interval of n on the left and right of point p, where n is equal to 1 / 2 of the number of contour points occupied by the weld, and calculate the distance dist from point p to the line Lpl, pr connecting pl and pr; where the general formula of the straight line equation of Lpl, pr is: Ax+Bz+C=0, and the distance from each point p (xi, zi) to the straight line Lpl, pr is: Finally, all contour points are traversed to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point.

3. A large diameter welded pipe surface defect and straightness detection device according to claim 1, characterized in that: In the step of eliminating the error caused by the natural rotation of the welded pipe, the optimal transformation matrix from the source point cloud to the target point cloud is solved. The formula is: Where R is the rotation matrix, p i is the target point cloud, p i is the source point cloud and N is the number of points.

4. A large diameter welded pipe surface defect and straightness detection device according to any one of claims 1 to 3, characterized in that: The calculation process of the straightness calculation step is as follows: it is known that all contours are obtained by scanning in the XOZ plane, and the end point connection method is used for calculation. The line connecting points a1 and aN is taken as the baseline L, and then the distance from all remaining contour points to the baseline L is calculated. The maximum distance is taken as the straightness of the angle, and the position of the point with the maximum distance is recorded.

5. A large diameter welded pipe surface defect and straightness detection device according to claim 1, characterized in that; The bracket includes a first bracket, a second bracket, a connecting shaft and a fixing frame. The first bracket and the second bracket are connected by multiple connecting shafts. The through hole coaxially penetrates the first bracket and the second bracket. A fixing frame is fixed between the first bracket and the second bracket along the movement direction of the welding pipe. Multiple groups of second cameras are fixed on the fixing frame, and the first camera is set on the first bracket.

6. A large diameter welded pipe surface defect and straightness detection device according to claim 5, characterized in that; A profile frame is fixed on both the first bracket and the second bracket.

7. A large diameter welded pipe surface defect and straightness detection device according to claim 5, characterized in that; The first camera is arranged on the first bracket via a fixing seat.

8. A large diameter welded pipe surface defect and straightness detection device according to claim 7, characterized in that; The fixing seat is a retractable fixing seat, so that the first camera can be retracted along the moving direction of the welding pipe.

9. A large diameter welded pipe surface defect and straightness detection device according to claim 8, characterized in that; The first bracket is provided with a mounting hole for mounting the fixing seat.

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