A method for supporting force-adaptive full-position welding of large-diameter pipelines

Abstract

The application discloses a kind of support stress adaptive large-diameter pipeline all-position welding methods, comprising: first, the three-dimensional profile data of the joint area of the pipeline to be welded is collected, the geometric feature parameters of the weld groove are extracted, the symmetric welding trajectory of two crawling welding robots is generated and the initial parameters are set;The pipeline is clamped in the first support tool and the second movable support tool respectively, the support stress uniformity parameters are calculated by collecting multi-point support pressure data, and the clamping is adjusted to meet the requirements;Extract the two end surface profiles, control the three-dimensional adjustment of the second movable support tool to achieve precise docking;Finally, two crawling welding robots are symmetrically arranged and synchronously welded along the trajectory.The present application solves the problems of insufficient precision in pre-welding groove measurement, lack of quantitative evaluation in clamping and supporting, low precision in assembly, and poor synchronization in double-robot welding, which leads to large welding deformation and unstable quality in existing large-diameter pipeline welding.

Description

Technical Field

[0001] This invention relates to the field of pipe welding. More specifically, this invention relates to an all-position welding method for large-diameter pipes with adaptive support stress. Background Technology

[0002] Large-diameter pipelines are widely used in pumped-storage power station water transmission systems, urban water supply trunk lines, and other engineering fields. The quality of their on-site welding directly affects the safe and stable operation of the project. Currently, during the welding construction of large-diameter pipelines, bevel measurement is mostly done manually with calipers or using simple two-dimensional scanning methods. This only obtains a limited number of basic parameters such as bevel width and depth, and cannot fully reflect the actual shape characteristics of the bevel. Due to unavoidable processing errors and surface unevenness during pipeline beveling, the welding trajectory generated based on incomplete parameters deviates from the actual bevel shape. This causes the welding torch to deviate from the weld centerline during welding, easily resulting in defects such as incomplete penetration and slag inclusions, increasing the welding rework rate. Summary of the Invention

[0003] To achieve these objectives and other advantages according to the present invention, a method for all-position welding of large-diameter pipes with adaptive support force is provided, comprising the following steps: S1. Collect three-dimensional contour data of the joint area of ​​the two large-diameter pipes to be welded, extract the geometric feature parameters of the weld groove based on the three-dimensional contour data, generate the symmetrical welding trajectory of the two crawling welding robots according to the geometric feature parameters, and set the initial welding process parameters. S2. Clamp the two large-diameter pipes onto the first support fixture and the second movable support fixture respectively. Collect multi-point support pressure data of the first support fixture and the second movable support fixture. Calculate the support force uniformity parameter based on the multi-point support pressure data. If the support force uniformity parameter is less than a preset threshold, proceed to step S3. Otherwise, adjust the clamping position of the large-diameter pipes until the support force uniformity parameter is less than the preset threshold. S3. Extract the reference end face contour of the large-diameter pipe on the first support fixture, extract the end face contour of the large-diameter pipe to be docked on the second movable support fixture, and control the second movable support fixture to perform three-dimensional position adjustment so that the matching degree between the end face contour to be docked and the reference end face contour reaches the maximum value, the geometric center coincides, and the end faces of the two pipes are completely abutted. S4. Two crawling welding robots are symmetrically arranged on both sides of the pipe weld, and the two crawling welding robots are controlled to perform welding synchronously along the corresponding symmetrical welding trajectory.

[0004] Preferably, in step S1, the geometric characteristic parameters of the weld groove include groove width, groove depth, and groove curvature.

[0005] Preferably, multiple pressure sensors are arranged on the pipe support contact surfaces of both the first support fixture and the second movable support fixture, and the multiple pressure sensors are evenly distributed along the circumference and axial direction of the pipe. The specific process of calculating the support force uniformity parameter based on the multi-point support pressure data is as follows: obtain the support pressure value of each pressure sensor, calculate the difference between each support pressure value and the historical support pressure value at the same position to obtain multiple pressure difference values, calculate the difference between the maximum and minimum values ​​of all pressure difference values ​​to obtain the difference value, calculate the average value of all pressure difference values ​​to obtain the difference mean value, and perform a weighted summation of the difference value and the difference mean value to obtain the support force uniformity parameter.

[0006] Preferably, in step S4, the two crawling welding robots are arranged symmetrically along the circumference of the weld, maintain the same welding speed and welding direction during the welding process, and the arc starting point and arc ending point are staggered.

[0007] Preferably, in step S1, the specific process of acquiring the three-dimensional contour data of the joint area of ​​the two large-diameter pipes to be welded is as follows: a line laser contour sensor is used to scan the joint area of ​​the two large-diameter pipes from multiple angles to obtain three-dimensional point cloud data. The three-dimensional point cloud data is then denoised and registered to obtain a three-dimensional pipe model. Based on the region growing algorithm, the target weld area is segmented from the three-dimensional pipe model, and the geometric feature parameters of the target weld area are extracted.

[0008] Preferably, the welding process adopts a layered welding process, first using manual welding rods to perform the root pass welding on the front side of the weld, and then controlling two crawling welding robots to perform the filler weld and the cover weld.

[0009] Preferably, in step S4, the highest point of the pipe cross-section is taken as the 0° reference, and the weld circumference is divided into three welding areas in a clockwise direction: the flat welding area is 0-30° and 330-360°, the vertical welding area is 30-120° and 240-330°, and the overhead welding area is 120-240°. Using the welding process parameters of the flat welding zone as the reference parameters, the welding current, welding voltage, and welding speed of the vertical welding zone are 90-95% of the reference parameters, and the welding current, welding voltage, and welding speed of the overhead welding zone are 80-85% of the reference parameters. Two crawling welding robots collect the molten pool temperature and corresponding support pressure values ​​of their respective welding areas in real time, and calculate the temperature difference between the two molten pools and the difference in support pressure. Based on the temperature difference between the molten pools and the difference in support pressure, the welding parameters of the two robots are dynamically adjusted so that the temperature difference between the two molten pools does not exceed 50°C, the difference in support pressure does not exceed a preset pressure threshold, and the welding speed of the two robots remains consistent.

[0010] Preferably, after each layer of welding is completed, the multi-point support pressure data of the two large-diameter pipes are collected again, and the change in support force between layers is calculated. When the change in support force between layers exceeds the preset change threshold, the welding sequence of the next layer is adjusted, and the weld on the side with smaller support force is welded first, followed by the weld on the side with larger support force.

[0011] This invention offers at least the following advantages: Based on a three-dimensional assembly method using end-face contour matching, it solves the problem of traditional center alignment failing to accommodate end-face machining errors, significantly reducing misalignment and ensuring the mechanical properties of the welded joint. Multi-point pressure detection of the support fixture enables quantitative assessment of clamping stability, eliminating potential problems such as pipe tilting and localized suspension, and preventing deformation caused by uneven support stress and welding thermal stress. Symmetrical synchronous welding by dual robots ensures that welding thermal stress is symmetrically distributed and cancels out on both sides of the pipe. Combined with all-position zonal process parameter adaptation and dynamic adjustment of molten pool temperature and support pressure, dynamic balance of heat input on both sides is achieved, guaranteeing consistent welding quality across all positions.

[0012] Other advantages, objectives and features of the present invention will be apparent in part from the following description, and in part from the understanding of those skilled in the art through study and practice of the invention. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the steps of the all-position welding method for large-diameter pipes with adaptive support force in this invention. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0015] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious modifications will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0016] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0017] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0018] like Figure 1 As shown, the present invention provides a method for all-position welding of large-diameter pipes with adaptive support force, comprising the following steps: S1. Collect three-dimensional contour data of the joint area of ​​the two large-diameter pipes to be welded, extract the geometric feature parameters of the weld groove based on the three-dimensional contour data, generate the symmetrical welding trajectory of the two crawling welding robots according to the geometric feature parameters, and set the initial welding process parameters. S2. Clamp the two large-diameter pipes onto the first support fixture and the second movable support fixture respectively. Collect multi-point support pressure data of the first support fixture and the second movable support fixture. Calculate the support force uniformity parameter based on the multi-point support pressure data. If the support force uniformity parameter is less than a preset threshold, proceed to step S3. Otherwise, adjust the clamping position of the large-diameter pipes until the support force uniformity parameter is less than the preset threshold. S3. Extract the reference end face contour of the large-diameter pipe on the first support fixture, extract the end face contour of the large-diameter pipe to be docked on the second movable support fixture, and control the second movable support fixture to perform three-dimensional position adjustment so that the matching degree between the end face contour to be docked and the reference end face contour reaches the maximum value, the geometric center coincides, and the end faces of the two pipes are completely abutted. S4. Two crawling welding robots are symmetrically arranged on both sides of the pipe weld, and the two crawling welding robots are controlled to perform welding synchronously along the corresponding symmetrical welding trajectory.

[0019] In the specific implementation of the above technical solution, step S1 is first executed, using a line laser profile sensor to scan the joint area of ​​the two large-diameter pipes to be welded from multiple angles, covering 180° of the pipe joint circumference, to acquire three-dimensional profile data of the joint area. The acquired three-dimensional profile data is transmitted to the control system, which extracts the geometric feature parameters of the weld bevel. Next, step S2 is executed, using a gantry crane to hoist the first large-diameter pipe onto the first support fixture, and the second large-diameter pipe onto the second movable support fixture. The first support fixture is a fixed roller support structure, and the second movable support fixture is a roller support structure with radial, vertical, and axial adjustment mechanisms. The control system collects multi-point support pressure data from all support points in real time and calculates the support stress uniformity parameters based on the collected data. When the calculated support force uniformity parameter is less than a preset threshold, step S3 is executed; when the support force uniformity parameter is greater than or equal to the preset threshold, the control system issues an adjustment command, adjusting the height and angle of the rollers of the support fixture via an electric push rod to change the clamping position of the pipe until the support force uniformity parameter is less than the preset threshold. Then, step S3 is executed, where the control system extracts the reference end face profile of the large-diameter pipe on the first support fixture and extracts the end face profile of the large-diameter pipe to be docked on the second movable support fixture. The second movable support fixture is controlled to move radially along the pipe, and the matching degree between the end face profile to be docked and the reference end face profile is calculated in real time. When the matching degree reaches its maximum value, the radial position of the second movable support fixture is locked. Then, the vertical height of the second movable support fixture is adjusted so that the geometric center of the end face profile to be docked coincides with the geometric center of the reference end face profile, and the vertical position is locked. Finally, the second movable support fixture is controlled to move slowly along the pipe axis until the end faces of the two large-diameter pipes are completely abutted, and the axial position is locked. Finally, in step S4, the first and second crawling welding robots are symmetrically arranged 180° around the circumference on both sides of the pipe weld. The two robots are fixed to the outer wall of the pipe using a magnetic adsorption device, ensuring the welding torch tip is aligned with the weld centerline and the angle between the welding torch and the pipe surface is maintained at 45°. The control system simultaneously sends welding commands to both robots, controlling them to weld synchronously along their respective symmetrical welding trajectories, maintaining the same welding direction and speed throughout the process.

[0020] The present invention also provides another technical solution, wherein, in step S1, the geometric characteristic parameters of the weld groove include groove width, groove depth and groove curvature.

[0021] Among these parameters, groove width refers to the vertical distance between the two edges of the weld groove, and is a key parameter determining the amount of filler metal. Groove depth refers to the vertical distance from the groove surface to the root of the groove, directly affecting the required weld penetration. Groove curvature refers to the degree of curvature of the groove surface, reflecting the shape characteristics of the groove. For non-standard grooves and grooves with large machining errors, the curvature parameter can accurately describe their shape changes. These three parameters comprehensively reflect the geometric characteristics of the weld groove and are the basis for generating accurate welding trajectories and setting reasonable welding process parameters.

[0022] The present invention also provides another technical solution, wherein multiple pressure sensors are arranged on the pipe support contact surfaces of the first support fixture and the second movable support fixture, and the multiple pressure sensors are evenly distributed along the circumference and axial direction of the pipe; the specific process of calculating the support force uniformity parameter based on the multi-point support pressure data is as follows: obtain the support pressure value of each pressure sensor, calculate the difference between each support pressure value and the historical support pressure value at the same position to obtain multiple pressure difference values, calculate the difference between the maximum and minimum values ​​of all pressure difference values ​​to obtain the difference value, calculate the average value of all pressure difference values ​​to obtain the difference mean value, and perform a weighted summation of the difference value and the difference mean value to obtain the support force uniformity parameter.

[0023] In the specific implementation of the above technical solution, two pressure sensors are arranged on the surface of each support roller of the first support fixture and the second movable support fixture. Multiple pressure sensors are evenly distributed along the circumference and axial direction of the pipeline, forming a multi-point pressure detection matrix. In step S2, the control system collects the support pressure value of each pressure sensor in real time, calculates the difference between each support pressure value and the historical support pressure value at the same position, and obtains multiple pressure difference values. Then, the maximum and minimum values ​​are found from all pressure difference values, and the difference between the two is calculated to obtain the difference value. Next, the arithmetic mean of all pressure difference values ​​is calculated to obtain the average difference value. Finally, according to the preset weighting coefficient, the difference value and the average difference value are weighted and summed to obtain the support force uniformity parameter. When the support force uniformity parameter is greater than or equal to a preset threshold, it indicates that the pipeline clamping is unstable, with tilting or local suspension. The control system adjusts the height of the corresponding support roller through an electric push rod to change the clamping position of the pipeline until the support force uniformity parameter is less than the preset threshold. This invention utilizes multiple pressure sensors evenly distributed on the pipe support contact surface of the support fixture. By employing a weighted summation method of difference values ​​and mean difference values ​​to calculate the uniformity of support stress, the stability of pipe clamping can be accurately quantified, allowing for early detection of issues such as pipe tilting and localized suspension. This method effectively avoids welding deformation and stress concentration caused by unstable clamping, improves the mechanical properties of the welded joint, and reduces the amount of adjustment work required during subsequent welding processes.

[0024] The present invention also provides another technical solution, wherein, in step S4, the two crawling welding robots are arranged symmetrically along the circumference of the weld, maintain the same welding speed and welding direction during the welding process, and the arc starting point and arc ending point are staggered.

[0025] In the specific implementation of the above technical solution, in step S4, the first crawling welding robot is positioned at 0° of the weld circumference, and the second crawling welding robot is positioned at 180° of the weld circumference, with the two robots symmetrically arranged along the weld circumference. The control system simultaneously sends an arc-starting command to both robots, and the two robots start simultaneously from their respective arc-starting points, welding synchronously along the same welding direction, maintaining the same welding speed during the welding process. The arc-ending point of the first crawling welding robot is set at 170° of the weld circumference, and the arc-ending point of the second crawling welding robot is set at 350° of the weld circumference. The arc-starting and arc-ending points of the two robots are staggered by a distance of not less than 30mm. During the welding process, the control system monitors the walking speed and welding position of the two robots in real time to ensure that the two robots always remain synchronized, avoiding welding stress concentration caused by speed deviation. This invention, by symmetrically arranging two crawling welding robots along the circumference of the weld seam and staggering the arc initiation and termination points, enables the welding thermal stress to be symmetrically distributed and mutually canceled on both sides of the pipe, effectively reducing welding deformation. Simultaneously, the staggered arc initiation and termination points prevent welding defects from concentrating in the same location, improving the continuity and mechanical properties of the weld joint and reducing the welding rework rate.

[0026] The present invention also provides another technical solution, wherein the specific process of acquiring the three-dimensional contour data of the joint area of ​​the two large-diameter pipes to be welded in step S1 is as follows: the joint area of ​​the two large-diameter pipes is scanned from multiple angles using a line laser contour sensor to obtain three-dimensional point cloud data, the three-dimensional point cloud data is denoised and registered to obtain a three-dimensional pipe model, the target weld area is segmented from the three-dimensional pipe model, and the geometric feature parameters of the target weld area are extracted.

[0027] In the specific implementation of the above technical solution, in step S1, a line laser profile sensor is used to scan the joint area of ​​two large-diameter pipes from multiple angles. During the scanning process, the line laser profile sensor moves along the pipe axis and rotates around the pipe circumference to acquire three-dimensional point cloud data of the joint area. The acquired three-dimensional point cloud data is then denoised to remove noise points and outliers, improving data accuracy. Next, the denoised point cloud data is registered, stitching together the point cloud data obtained from different angle scans into a complete three-dimensional pipe model. Based on a region growing algorithm, the target weld area is segmented from the three-dimensional pipe model. Using the edge points of the weld bevel as seed points, points with similar geometric features to the seed points are merged into the weld area, ultimately obtaining the complete target weld area. Geometric feature parameters of the weld bevel are extracted from the segmented target weld area to generate the welding trajectory and set the initial welding process parameters.

[0028] The present invention also provides another technical solution, wherein the welding process adopts a layered welding process, firstly using manual welding rods to perform the root welding on the front side of the weld, and then controlling two crawling welding robots to perform the filling welding and the cover welding.

[0029] In practice, the welding process employs a layered welding technique. First, a welder uses manual welding rods to perform the root pass welding on the front side of the weld. A low current and short arc are used during this process to ensure complete penetration at the weld root and prevent defects such as incomplete penetration or slag inclusions. After the root pass welding is completed, the weld is visually inspected, and surface slag and spatter are removed. Then, the first and second crawling welding robots are controlled to synchronously perform filler welding along a symmetrical welding trajectory. Filler welding is performed in multiple layers and passes. After each layer is completed, surface slag is removed, and the weld surface quality is checked. Only after confirming there are no defects is the next layer welded. After filler welding is completed, the two crawling welding robots are controlled to perform the cap weld welding. During cap weld welding, welding parameters are adjusted to ensure a smooth weld surface, uniform width, and weld reinforcement that meets design requirements.

[0030] This invention combines the advantages of manual welding and robotic welding by employing a layered welding process that uses manual welding rods for the root pass and a crawling welding robot for the filler and cover pass. Manual welding ensures the welding quality at the weld root and avoids defects such as incomplete penetration; robotic welding ensures the welding efficiency and quality of the filler and cover passes, while reducing the labor intensity of welders.

[0031] The present invention also provides another technical solution, wherein, in step S4, taking the highest point of the pipe cross-section as the 0° reference, the weld circumference is divided into three welding areas in a clockwise direction: the flat welding area is 0-30° and 330-360°, the vertical welding area is 30-120° and 240-330°, and the overhead welding area is 120-240°; the welding process parameters of the flat welding area are taken as the reference parameters, the welding current, welding voltage, and welding speed of the vertical welding area are 90-95% of the reference parameters, and the welding current, welding voltage, and welding speed of the overhead welding area are 80-85% of the reference parameters; two crawling welding robots collect the molten pool temperature and the corresponding support pressure value of their respective welding areas in real time, and calculate the temperature difference between the two molten pools and the difference in support pressure; the welding parameters of the two robots are dynamically adjusted according to the temperature difference between the molten pools and the difference in support pressure, so that the temperature difference between the two molten pools does not exceed 50°C, the difference in support pressure does not exceed a preset pressure threshold, and the welding speed of the two robots remains consistent.

[0032] In the specific implementation of this scheme, in step S4, the highest point of the pipe cross-section is taken as the 0° reference, and the weld circumference is divided into three welding areas in a clockwise direction: the flat welding area (0-30° and 330-360°), the vertical welding area (30-120° and 240-330°), and the overhead welding area (120-240°). The welding process parameters of the flat welding area are used as the reference parameters, and corresponding process parameter ratios are set according to the operational difficulty of different welding areas. The welding current, welding voltage, and welding speed of the vertical welding area are 90-95% of the reference parameters, and the welding current, welding voltage, and welding speed of the overhead welding area are 80-85% of the reference parameters. Two crawling welding robots collect the molten pool temperature of their respective welding areas in real time using their onboard infrared thermal imaging sensors, and simultaneously collect the support pressure values ​​at corresponding positions using pressure sensors on the support fixture. The control system calculates the temperature difference between the molten pools on both sides and the difference in support pressure, and dynamically adjusts the welding parameters of the two robots based on these differences. When the temperature difference in the molten pool exceeds 50°C, appropriately increase the welding current of the robot on the lower temperature side and decrease the welding current of the robot on the higher temperature side. When the difference in support pressure exceeds the preset pressure threshold, appropriately adjust the welding voltage of the corresponding robot. During the adjustment process, always maintain the same welding speed for both robots.

[0033] This invention divides the weld circumference into different welding zones and sets corresponding process parameter ratios, enabling it to adapt to different requirements of all-position welding and ensuring welding quality in each zone. Simultaneously, based on a dynamic adjustment method utilizing the difference in molten pool temperature and support pressure, it can compensate in real time for the impact of pipeline stress changes and molten pool temperature fluctuations on welding quality, maintaining a balance in welding heat input on both sides, further reducing welding deformation, and improving the quality stability of the weld joint.

[0034] The present invention also provides another technical solution, wherein after each layer of welding is completed, the multi-point support pressure data of the two large-diameter pipes are re-collected, and the change in support force between layers is calculated; when the change in support force between layers exceeds the preset change threshold, the sequence of welding passes for the next layer is adjusted, and the weld on the side with smaller support force is welded first, followed by the weld on the side with larger support force.

[0035] Among them, the change in interlayer support force refers to the absolute value of the difference between the support pressure value after each layer of welding is completed and the support pressure value at the corresponding position before the previous layer is welded, reflecting the degree of change in pipeline support force during the welding process; the weld on the side with smaller support force refers to the weld segment in the continuous area where the corresponding support pressure value is lower than the average pressure value of all support points; the weld on the side with larger support force refers to the weld segment in the continuous area where the corresponding support pressure value is higher than the average pressure value of all support points.

[0036] In the specific implementation of this scheme, after each layer of welding is completed, the control system re-collects the real-time support pressure data of all pressure sensors on the first and second movable support fixtures, and calculates the interlayer support force change of each pressure sensor. When the interlayer support force change of any pressure sensor exceeds a preset change threshold, it indicates that the support force of the pipeline has changed significantly during the welding process, posing a risk of welding deformation. At this time, the control system calculates the arithmetic mean of the real-time support pressure values ​​of all pressure sensors as a reference value. The weld segments corresponding to continuous areas with pressure values ​​lower than the reference value are identified as the welds on the side with lower support force, and the weld segments corresponding to continuous areas with pressure values ​​higher than the reference value are identified as the welds on the side with higher support force. The welding sequence for the next layer is adjusted, first welding the welds on the side with lower support force, using the shrinkage stress generated by welding to slightly deform the pipeline to that side, offsetting the sagging tendency of the side with higher support force due to its own weight. After the welds on the side with lower support force are completed, the welds on the side with higher support force are then welded. This invention detects changes in the interlayer support force and adjusts the welding sequence based on the detection results. It can actively control the direction and magnitude of welding deformation, effectively avoid defects such as warping and misalignment in the pipeline, adapt to the dynamic changes in the pipeline support force during welding, and improve the stability of the welding process.

[0037] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for all-position welding of large-diameter pipes with adaptive support force, characterized in that, Includes the following steps: S1. Collect three-dimensional contour data of the joint area of ​​the two large-diameter pipes to be welded, extract the geometric feature parameters of the weld groove based on the three-dimensional contour data, generate the symmetrical welding trajectory of the two crawling welding robots according to the geometric feature parameters, and set the initial welding process parameters. S2. Clamp the two large-diameter pipes onto the first support fixture and the second movable support fixture respectively. Collect multi-point support pressure data of the first support fixture and the second movable support fixture. Calculate the support force uniformity parameter based on the multi-point support pressure data. If the support force uniformity parameter is less than a preset threshold, proceed to step S3. Otherwise, adjust the clamping position of the large-diameter pipes until the support force uniformity parameter is less than the preset threshold. S3. Extract the reference end face contour of the large-diameter pipe on the first support fixture, extract the end face contour of the large-diameter pipe to be docked on the second movable support fixture, and control the second movable support fixture to perform three-dimensional position adjustment so that the matching degree between the end face contour to be docked and the reference end face contour reaches the maximum value, the geometric center coincides, and the end faces of the two pipes are completely abutted. S4. Two crawling welding robots are symmetrically arranged on both sides of the pipe weld, and the two crawling welding robots are controlled to perform welding synchronously along the corresponding symmetrical welding trajectory.

2. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, In step S1, the geometric characteristic parameters of the weld groove include groove width, groove depth, and groove curvature.

3. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, Multiple pressure sensors are arranged on the pipe support contact surfaces of both the first support fixture and the second movable support fixture. The multiple pressure sensors are evenly distributed along the circumference and axial direction of the pipe. The specific process of calculating the support force uniformity parameter based on the multi-point support pressure data is as follows: obtain the support pressure value of each pressure sensor, calculate the difference between each support pressure value and the historical support pressure value at the same position to obtain multiple pressure difference values, calculate the difference between the maximum and minimum values ​​of all pressure difference values ​​to obtain the difference value, calculate the average value of all pressure difference values ​​to obtain the difference mean value, and perform a weighted summation of the difference value and the difference mean value to obtain the support force uniformity parameter.

4. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, In step S4, the two crawling welding robots are arranged symmetrically along the circumference of the weld seam, maintaining the same welding speed and welding direction during the welding process, and the arc starting point and arc ending point are staggered.

5. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, In step S1, the specific process of acquiring the three-dimensional contour data of the joint area of ​​the two large-diameter pipes to be welded is as follows: a line laser contour sensor is used to scan the joint area of ​​the two large-diameter pipes from multiple angles to obtain three-dimensional point cloud data. The three-dimensional point cloud data is then denoised and registered to obtain a three-dimensional pipe model. The target weld area is segmented from the three-dimensional pipe model, and the geometric feature parameters of the target weld area are extracted.

6. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, The welding process adopts a layered welding process. First, manual welding rods are used to perform the root welding on the front side of the weld. Then, two crawling welding robots are controlled to perform the filling welding and the cover welding.

7. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, In step S4, taking the highest point of the pipe cross-section as the 0° reference, the weld circumference is divided into three welding areas in a clockwise direction: the flat welding area is 0-30° and 330-360°, the vertical welding area is 30-120° and 240-330°, and the overhead welding area is 120-240°. Using the welding process parameters of the flat welding zone as the reference parameters, the welding current, welding voltage, and welding speed of the vertical welding zone are 90-95% of the reference parameters, and the welding current, welding voltage, and welding speed of the overhead welding zone are 80-85% of the reference parameters. Two crawling welding robots collect the molten pool temperature and corresponding support pressure values ​​of their respective welding areas in real time, and calculate the temperature difference between the two molten pools and the difference in support pressure. Based on the temperature difference between the molten pools and the difference in support pressure, the welding parameters of the two robots are dynamically adjusted so that the temperature difference between the two molten pools does not exceed 50°C, the difference in support pressure does not exceed a preset pressure threshold, and the welding speed of the two robots remains consistent.

8. The method for all-position welding of large-diameter pipes with adaptive support force according to claim 1, characterized in that, After each layer of welding is completed, the multi-point support pressure data of the two large-diameter pipes are collected again to calculate the change in support force between layers. When the change in support force between layers exceeds the preset change threshold, the welding sequence of the next layer is adjusted. The weld on the side with less support force is welded first, and then the weld on the side with greater support force is welded.

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