Sheet type welding method and system for large transformer oil tank

Abstract

The invention provides a sheet type welding method and system for a large transformer oil tank, and the method comprises the steps: applying preset initial deformation to each sheet tank wall of the transformer oil tank, installing a detachable external rigid constraint frame at the edge of each sheet tank wall, and adopting a welding robot to carry out welding on the sheet tank wall according to a preset welding planning path and a preset heat input control strategy, executing welding between the functional accessories of the transformer oil tank and the tank wall; after welding is completed, obtaining three-dimensional point cloud data of the welded tank wall, comparing the three-dimensional point cloud data with the digital theoretical model to identify a deformation area, and correcting the deformation area to obtain the corrected transformer oil tank wall; the corrected transformer oil tank wall is integrally assembled, the geometrical shape and dimensional tolerance of the transformer oil tank body are controlled through the active adjusting mechanism arranged in the transformer oil tank body, the labor intensity and the working time cost are reduced, and the overall manufacturing precision of the oil tank, the product reliability and the production benefits are improved.

Description

Technical Field

[0001] This invention relates to the field of transformer welding technology, and specifically to a method and system for sheet welding of large transformer oil tanks. Background Technology

[0002] As a core structural component of a transformer, the large transformer tank's primary function is to house the transformer body and insulating oil, and to provide sealing, protection, and mechanical support. Therefore, the welding quality of the tank directly determines the transformer's sealing performance, mechanical strength, and long-term operational safety and reliability.

[0003] Currently, welding remains the primary connection method in the manufacturing of large transformer tanks. Traditional welding processes typically employ either integral assembly followed by welding or partial piecewise welding. However, due to the large size, relatively thin plates, and numerous and complexly distributed welds of transformer tanks, these traditional processes exhibit a series of technical shortcomings in practical applications. On one hand, large plates such as the tank walls are subjected to uneven heat input during welding, easily leading to unpredictable and uncontrollable angular deformation, wave deformation, and torsional deformation. Existing technologies mainly rely on manual experience to install temporary supporting steel sections to attempt to suppress deformation. However, this method lacks scientific prediction and proactive intervention regarding the coupling relationship between welding thermal stress and structural stiffness, resulting in highly unstable deformation prevention effects. Consequently, the flatness of the tank walls often deviates significantly after welding, necessitating subsequent arduous and technically challenging flame straightening work. On the other hand, transformer tanks are large in size and weight, making rotation during welding difficult and posing safety risks. Furthermore, they require large rotating equipment and dedicated workstations, resulting in numerous welds being placed in non-ideal positions such as overhead or vertical welding. This hinders the application of automated equipment like welding robots due to poor accessibility and inconsistent process stability. Therefore, most companies still heavily rely on manual labor, which is not only labor-intensive and inefficient, but also leads to significant fluctuations in welding quality across different products and even different parts of the same product, making consistency difficult to guarantee. Moreover, in existing technologies, welding, tooling, tank assembly, and quality inspection are often treated as independent processes, lacking systematic process design and collaborative control.

[0004] In summary, existing welding technologies for large transformer tanks have significant shortcomings in terms of production efficiency, quality control, automation level, and process synergy. Therefore, there is an urgent need in this field for an innovative welding process and system that can systematically solve the above problems and achieve high-quality, high-efficiency, and automated production.

[0005] Therefore, existing technologies still need further development. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a sheet welding method and system for large transformer tanks to solve the problems existing in the prior art.

[0007] To achieve the above-mentioned technical objectives, according to a first aspect of the present invention, the present invention provides a method for sheet welding of a large transformer tank, comprising: S100. Apply a preset initial deformation to each section of the transformer tank wall and install a detachable external rigid constraint frame at the edge of each section of the tank wall. Use a welding robot to perform welding between the functional accessories of the transformer tank and the tank wall according to the preset welding planning path and preset heat input control strategy. S200. After welding is completed, the three-dimensional point cloud data of the welded tank wall is obtained and compared with the digital theoretical model to identify the deformation area. The deformation area is then corrected to obtain the corrected transformer tank wall. S300. Assemble the corrected transformer tank wall as a whole, and use the active adjustment mechanism set inside the transformer tank to control the geometric shape and dimensional tolerance of the transformer tank body.

[0008] Specifically, the method of applying a preset initial deformation to each section of the transformer tank wall and installing a detachable external rigid constraint frame at the edge of each section of the tank wall includes: Support pads are installed below the box wall to create a pre-camber in the middle area of ​​the box wall relative to the circumferential edge of the box wall, thereby forming an initial deformation. The detachable external rigid constraint frame is a frame made of standard structural steel connected by a quick-locking mechanism, and the frame is installed on the edge of the box wall.

[0009] Specifically, the preset welding planning path is a unidirectional intermittent skip welding sequence, wherein a single weld segment in the welding sequence is limited to a predetermined length, and the welding positions of any two adjacent weld segments are spatially isolated from each other.

[0010] Specifically, the preset thermal input control strategy includes: Based on the combination of the plate thickness of the box wall and the functional accessories, a corresponding set of welding current, voltage, and welding speed parameters is matched.

[0011] Specifically, S200 includes: S210. Acquire three-dimensional point cloud data of the box wall surface and compare it with the digital theoretical model to identify and locate the deformation area; S220. An external heating device is used to perform programmed local heating on the back side of the weld corresponding to the deformation area to generate reverse deformation. Then, the edge of the box wall is mechanically straightened to correct the straightness of the box wall.

[0012] Specifically, the active adjustment mechanism includes multiple sets of lead screw pushing points set in the internal space of the box. By adjusting the extension amount of each lead screw pushing point, the verticality of the box wall and the shape of the box opening are corrected.

[0013] According to a second aspect of the present invention, a large transformer tank sheet welding system is provided, comprising: Welding workstation: includes a welding platform and a detachable rigid constraint frame. The welding platform is used to apply a preset initial deformation to the box wall. The detachable rigid constraint frame is installed on the edge of the box wall to provide external rigid constraint during the welding process. Welding robot: Used to perform welding between functional accessories and the box wall according to a preset welding planning path and preset heat input control strategy; 3D Detection and Shaping Module: Includes a 3D scanning unit and a correction execution unit. The 3D scanning unit is used to acquire the 3D point cloud data of the welded tank wall. The correction execution unit is used to compare the 3D point cloud data of the welded tank wall with the digital theoretical model to identify the deformed area, correct the deformed area, and obtain the corrected transformer tank wall. Assembly module: includes an active adjustment mechanism installed inside the box body, which is used to adjust the geometry and dimensional tolerances of the box body during the assembly of the box walls; Control module: Communicatively connected to the welding robot and the 3D detection and shaping module, used to store preset welding path planning data, heat input control parameters, and 3D point cloud data and digital theoretical model after welding.

[0014] Specifically, the detachable external rigid constraint frame is composed of six standardized steel units connected by a hydraulically or electrically driven quick-locking device.

[0015] Specifically, the correction execution unit is a multi-joint robot, and the end effector of the multi-joint robot is equipped with a heat source generator; The control module generates heating control commands and sends them to the multi-joint robot based on the comparison results between the three-dimensional point cloud data obtained by the three-dimensional scanning unit and the digital theoretical model.

[0016] Specifically, the welding path planning data stored in the control module includes a sequence of skip welding paths for different combinations of box walls and functional accessories; The heat input control parameters include a set of welding current, voltage, and speed parameters that match the skip welding path sequence.

[0017] Beneficial effects: This invention effectively suppresses angular and wave deformations caused by welding thermal stress by pre-welding functional accessories in sections before tank wall assembly and employing an active anti-deformation strategy that combines preset initial deformation with external rigid constraints. This achieves micro-shaping or even no-shaping after welding, improving quality consistency, reducing labor intensity and time costs, shortening welding time, and ensuring uniform and stable weld quality. This lays the foundation for large-scale automated production. By combining adaptive correction based on three-dimensional measurement with precision assembly based on fixed benchmarks, a closed-loop control of measurement-feedback-correction is formed, systematically improving the overall manufacturing precision of the tank and significantly enhancing product reliability and production efficiency. Attached Figure Description

[0018] Figure 1 This is a flowchart of a sheet welding method for a large transformer oil tank provided in a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the system composition of the sheet welding system for a large transformer oil tank provided in a specific embodiment of the present invention; Figure 3 This is a schematic diagram of the welding sequence during segmented pre-welding provided in a specific embodiment of the present invention; Figure 4 This is a schematic diagram of the low-pressure sidewall and endwall assembly provided in a specific embodiment of the present invention; Figure 5 This is a schematic diagram of the assembly of the high-voltage sidewall and endwall provided in a specific embodiment of the present invention; Figure 6 This is a schematic diagram of the assembled transformer tank provided in a specific embodiment of the present invention; The reference numerals in the above figures are as follows: 1. Low-pressure sidewall; 2. End wall; 3. Lead screw jacking point; 4. High-pressure sidewall; 5. Reinforcing iron; 6. Section steel. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Other similar embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort should all fall within the scope of protection of this application. Furthermore, directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings; therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0020] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments.

[0021] Example 1 Please see Figure 1 This embodiment provides a plate welding method for a large transformer tank, including: applying a preset initial deformation to each plate of the transformer tank wall, installing a detachable external rigid constraint frame at the edge of each plate wall, using a welding robot to perform welding between the functional accessories of the transformer tank and the tank wall according to a preset welding planning path and a preset heat input control strategy; after welding, acquiring three-dimensional point cloud data of the welded tank wall and comparing it with a digital theoretical model to identify the deformation area, correcting the deformation area to obtain a corrected transformer tank wall; assembling the corrected transformer tank wall as a whole, and using an active adjustment mechanism set inside the transformer tank body to control the geometric shape and dimensional tolerances of the transformer tank body.

[0022] Understandably, the above technical solution effectively suppresses angular and wave deformations caused by welding thermal stress by pre-welding functional accessories in sections before tank wall assembly and adopting an active anti-deformation strategy that combines preset initial deformation with external rigid constraints. This achieves micro-shaping or even no-shaping after welding, improves quality consistency, reduces labor intensity and time costs, shortens welding time, and ensures uniform and stable weld quality. This lays the foundation for large-scale automated production. Combined with adaptive correction based on three-dimensional measurement and precision assembly based on fixed benchmarks, a closed-loop control of measurement-feedback-correction is formed, which systematically improves the overall manufacturing precision of the tank and greatly enhances product reliability and production efficiency.

[0023] See Figure 1 The implementation steps of the sheet welding method for the large transformer oil tank in this embodiment are as follows: S100. Apply a preset initial deformation to each section of the transformer tank wall and install a detachable external rigid constraint frame at the edge of each section of the tank wall. Use a welding robot to perform welding between the functional accessories of the transformer tank and the tank wall according to the preset welding planning path and preset heat input control strategy. Furthermore, before assembling the tank walls into a complete tank body, pre-welding is performed in sections. Functional accessories such as reinforcing iron 5, lifting shafts, and manhole flanges are independently welded to the corresponding tank walls of the transformer tank. The method of applying a preset initial deformation to each tank wall section of the transformer tank and installing detachable external rigid constraints at the edges of each tank wall section includes: Support pads are installed below the box wall to create a pre-camber in the middle area of ​​the box wall relative to the circumferential edge of the box wall, thereby forming an initial deformation. The detachable external rigid constraint frame is a frame made of standard structural steel 6 connected by a quick-locking mechanism, and the frame is installed on the edge of the box wall.

[0024] It should be noted that before welding, a coordinated anti-deformation control is applied to the box wall. First, the box wall to be welded is placed on a horizontal welding platform, and support blocks are used to support it below the longitudinal centerline of the box wall, so that the central area has a pre-camber of about 5-15mm relative to the circumferential edge of the box wall, forming a slightly convex curved surface. This technical solution utilizes the torque generated by the self-weight of the box wall to pre-compensate for the angular deformation caused by thermal stress during welding, and achieves active intervention from the deformation mechanism. Then, a modular frame structure made of 18a~22a channel steel or I-beams of the same specification is quickly clamped and fixed around the edge of the box wall using a hydraulic quick-locking mechanism. This frame forms a strong external rigid constraint, which works in conjunction with the device that applies the pre-deformation to form a dual anti-deformation mechanism of active and passive. At the same time, a reinforcing iron 5 with a thickness of not less than 20mm and a length and width not less than the outer dimensions of the reinforcing iron of the hanging shaft is also tack-fixed on the back of the location of the hanging shaft. These steel sections 6 and steel plate reinforcing iron 5 are removed after the main welds of the box wall, box cover, and box edge are completed. The above technical solution effectively suppresses structural deformation caused by welding heat input, and keeps the flatness of the box wall within 3 / 1000. Through the above synergistic anti-deformation measures, the generation of welding deformation is curbed from the source, and post-weld micro-shaping or even no post-weld shaping is achieved. The workload of flame straightening, which is as high as 70% in traditional processes, is reduced to a minimum, and manufacturing precision and production efficiency are further improved.

[0025] Specifically, the aforementioned preset welding planning path is a unidirectional, intermittent, skip-type welding sequence, wherein each weld segment in the welding sequence is limited to a predetermined length, and the welding positions of any two adjacent weld segments are spatially isolated from each other. The preset heat input control strategy matches the corresponding set of welding current, voltage, and welding speed parameters based on the combination of the plate thickness of the enclosure wall and the functional accessories.

[0026] It should be noted that when welding the reinforcing iron 5 in sections, attention must be paid to the welding sequence and direction. Random welding will lead to distortion and deformation of the box wall. Therefore, the welding sequence should employ a skip welding method in the same direction. Figure 3As shown, the box wall should be laid flat before welding, preferably on a platform. A slightly higher middle section is permissible, allowing the weight of the box wall and reinforcing iron 5 to partially overcome angular deformation during welding, thus preventing post-weld reshaping. "Same direction" means that the welding direction of all single-segment welds remains consistent, avoiding stress complexity caused by alternating directions. Furthermore, any two adjacent weld segments should not be spatially adjacent, with sufficient unwelded area in between as a thermal buffer. Preferably, the predetermined length is typically limited to between 150mm and 350mm. For box walls welded on a platform, after the reinforcing iron 5 is welded, some components on the box wall, such as manhole flanges, base plates, and pipe fittings, can be spot-welded. Since flat fillet welding is performed on the ground, this not only ensures welding quality but also significantly improves production efficiency.

[0027] Specifically, the welding heat input Q mentioned above can be calculated using the following formula: Q =η (U I) / v; Where η represents thermal efficiency, U represents arc voltage, I represents welding current, and v represents welding speed. Heat input directly determines the magnitude of welding deformation. Different plate thickness combinations (such as welding 20mm thick reinforcing iron 5 to a 10mm box wall) have different optimal requirements for welding current, voltage, and speed. Therefore, in some specific embodiments, the thickness of the transformer tank wall and the thickness of the filling functional accessories (such as reinforcing iron 5) being welded are first identified to form a specific plate thickness combination code. For example, the 10-20 combination represents a 10mm tank wall welded with a 20mm functional accessory. A welding parameter database verified through extensive process testing can be stored in the control module. This database is indexed by plate thickness combinations, and each combination is associated with one or more sets of optimized welding parameters. Each set contains recommended values ​​or ranges for welding current I, arc voltage U, and welding speed v. For example, for the 10-20 combination, the database may select I=260-280A, U=28-30V, and v=25-30A. The welding robot moves to the designated position according to the planned path at a speed of cm / min. Instead of using fixed parameters for welding, it automatically calls the parameter set corresponding to the plate thickness combination of the weld at that position to perform welding. This ensures that the most suitable energy can be used to weld accessories of different thicknesses on the box wall (such as thinner pipe joints and thicker hanging shafts), avoiding overheating of thin plate areas or insufficient penetration of thick plate areas.

[0028] Understandably, a six-axis welding robot can be used to execute an automated welding program based on welding path planning and heat input control strategies. Employing a unidirectional, intermittent, skip-type welding sequence, the length of a single weld segment can be specified to be ≤300mm, and the welding positions of adjacent welds can maintain a spatial spacing of ≥500mm. This path planning strategy effectively disperses the welding heat input, avoids localized thermal stress concentration, and thus prevents torsional deformation. For different plate thickness combinations of the box wall and reinforcing iron 5, dynamically matched welding current, voltage, and travel speed parameter packages are preset for the welding robot, ensuring precise control of welding energy, guaranteeing the uniformity and consistency of weld quality, and significantly shortening welding time, laying the foundation for large-scale, high-quality automated production.

[0029] Furthermore, after all welds have cooled, place the tank wall with the inner side facing up, flatten the tank wall, and begin flame heating. The heated area is the back of the weld. After cooling, measure the flatness of the tank wall. Generally, the flatness of the non-magnetically shielded position should not exceed 6 / 1000, and the flatness of the tank wall in the magnetically shielded position should not exceed 3 / 1000. After the tank wall is shaped and qualified, spot weld a channel steel to the upper edge. Use the rigidity of the channel steel and reinforcing iron 5 to straighten the upper edge of the tank wall. The straightness should be <3mm. This facilitates the correct installation of the tank wall and the tank cover. After the tank wall and tank cover are welded together, the various parts need to be assembled together. This process is called the assembly of the oil tank.

[0030] S200. After welding is completed, the three-dimensional point cloud data of the welded tank wall is acquired and compared with the digital theoretical model to identify the deformation area. The deformation area is then corrected to obtain the corrected transformer tank wall.

[0031] Specifically, S200 includes: S210. Acquire three-dimensional point cloud data of the box wall surface and compare it with the digital theoretical model to identify and locate the deformation area; S220. An external heating device is used to perform programmed local heating on the back side of the weld corresponding to the deformation area to generate reverse deformation. Then, the edge of the box wall is mechanically straightened to correct the straightness of the box wall.

[0032] In some specific embodiments, a high-precision non-contact 3D laser scanner (such as a scanning device based on laser triangulation or structured light principles) can be used. This device can be used independently or fixed above the measurement station or carried by a robotic arm. It can acquire dense 3D point cloud data containing 3D coordinates (X, Y, Z) on the surface of the box wall in a short time. Then, the naturally cooled box wall (inside up) is transported to the measurement station and placed horizontally. The scanner is started to automatically scan the entire surface of the box wall. The scanning software automatically stitches together the data from multiple perspectives to generate a complete digital model that describes the actual shape of the box wall. The aforementioned digital theoretical model represents the precise geometry, dimensions, and theoretical plane of the box wall under ideal, deformation-free conditions. Dedicated detection software (such as PolyWorks or Geomagic Control) can be used to best fit and align the actual point cloud data obtained from scanning with the digital theoretical model. After alignment, the software calculates the normal distance (deviation value) from each point in the point cloud to the surface of the theoretical model (or the theoretical reference plane). Based on a preset tolerance threshold (e.g., a flatness requirement of ≤3 / 1000, i.e., 3mm / m, for magnetically shielded areas), the software performs color cloud rendering and numerical analysis on the overall deviation.

[0033] Preferably, the criteria for identifying a deformed area are that a series of measurement points have deviation values ​​in the same direction (both positive or all negative) and exceed the tolerance threshold. For example, an area is displayed in red (representing a depression exceeding +3mm) or blue (representing a bulge exceeding -3mm). The software can output the center coordinates, area, maximum deformation, and contour of the area, thereby completing the process from detecting deformation to locating it.

[0034] The principle of correcting the deformed area is to utilize the thermal expansion and contraction and thermoplasticity of metallic materials. The back of the weld corresponding to the concave deformation area is locally heated, causing the material in that area to expand due to heat. However, due to the constraint of the surrounding cold material, it undergoes compressive plastic deformation. After cooling, the area contracts, thereby pulling the originally concave area upward to rebound, achieving the effect of correcting the reverse deformation.

[0035] Preferably, the aforementioned external heating device is typically a robot-held flame heating gun. Its heat output can be precisely controlled by gas flow and robot movement speed. More controllable methods such as medium-frequency induction heating can also be used. The control module automatically generates the heating path, movement speed, and heating temperature based on the identified deformation area information, including location, size, and depth. The program controls the heating time through the distance between the flame and the plate, the movement speed, and the heating duration. For example, for a longitudinal weld seam causing a depression in the box wall, the robot will perform a uniform linear scan heating along its back side. The heating temperature is typically controlled between 600℃ and 750℃ (when the steel appears dark red to orange-red) to avoid material phase transformation or overheating. After heating, the box wall needs to cool naturally, and a rapid scan can be performed again to verify the correction effect. Iterative compensation heating can be performed if necessary.

[0036] Furthermore, the edges of the box wall are mechanically straightened to correct its straightness. Specifically, the edges of the box wall may be bent or not straight after welding and heat treatment, directly affecting the sealing assembly with the box cover. This step involves cold straightening by applying a controllable mechanical reaction force, which can be achieved by installing an auxiliary straightening steel profile 6. This steel profile 6 is temporarily fixed to the edge of the box wall to be straightened by intermittent spot welding. The steel profile 6 integrates multiple evenly distributed spiral push rods (positive and negative screws) or hydraulic push rods as a linear adjustment mechanism. During the straightening process, the operator uses a wrench or the control system to adjust the extension of each push rod synchronously or sequentially based on the measured edge straightness deviation. For example, for an edge with a concave middle section, the push rod in the middle is adjusted to push outwards, while the push rods on both sides are appropriately retracted to form a reverse bending moment, straightening the edge. After straightening, a ruler or string line can be used to check to ensure that the straightness error over the entire length of the edge is less than 2mm. Once the requirement is met, the auxiliary steel profile 6 can be removed before subsequent processes.

[0037] Based on the above technical solution, the combination of thermal correction for in-plane deformation and mechanical correction for edge line deformation constitutes a complete post-weld shaping solution, laying a solid foundation for subsequent precision assembly.

[0038] S300. Assemble the corrected transformer tank wall as a whole, and use the active adjustment mechanism set inside the transformer tank to control the geometric shape and dimensional tolerance of the transformer tank body.

[0039] See Figures 4-6 In this embodiment, the active adjustment mechanism includes multiple sets of lead screw pushing points 3 disposed in the internal space of the box. By adjusting the extension amount of each lead screw pushing point 3, the verticality of the box wall and the shape of the box opening are corrected.

[0040] In some specific embodiments, on an assembly platform with reference markings, the pre-welded and shaped tank walls are assembled as a whole. Multiple sets of independent and controllable positive and negative screw jacking points 3, i.e. active adjustment mechanisms, are fixed inside the tank. The movable ends of the screw jacking points 3 are pressed against the inner surface of the tank wall that needs to be adjusted. By coordinating the extension of each screw jacking point 3, the verticality of the tank wall (≤3mm) and the macroscopic shape of the tank opening are controlled, thereby improving the overall manufacturing precision of the oil tank.

[0041] Preferably, the aforementioned lead screw pushing points 3 are typically arranged in pairs or groups, for example, such as... Figure 5 As shown, a pair of lead screw jacking points 3 are set at the upper, middle, and lower positions of a certain end wall 2, respectively, to control the displacement of the upper, middle, and lower parts of the wall. Precision measuring equipment such as a laser tracker or a large three-dimensional measuring ruler can be used to measure the box after it is fixed. The degree of inclination of each end wall 2 surface relative to the horizontal reference plane is measured, i.e., the verticality of the end wall 2. The long side dimension, wide side dimension, and two diagonal dimensions of the upper opening (box edge side) and lower opening are measured, i.e., the shape of the box opening. Ideally, the box opening should be rectangular with equal diagonals. The overall squareness of the box is also measured, and evaluated by comparing the parallelism of the two relative wall panels. Then, the measurement data is input into the control module or analyzed by engineers and compared with the design tolerances. For comparison, the verticality of end wall 2 can be set to ≤3mm, and the difference in diagonal of the upper opening to ≤5mm. Based on the deviation, the required adjustment direction (pull out or retract) and adjustment amount (e.g., screwing in 1.5 turns corresponds to a displacement of about 3mm) for each jacking point can be calculated. For example, if the top of a certain end wall 2 is found to be tilted inward by 2mm, the two jacking points on the upper part of the wall need to be adjusted outward by about 2mm simultaneously. At the same time, the middle jacking point may need to be finely adjusted to keep the wall panel smooth. If the upper opening is found to be a parallelogram, that is, the diagonals are not equal, the screw jacking points 3 at the diagonal positions need to be adjusted in pairs to correct the shape of the box opening to a rectangle. This avoids the inefficient work of repeated hoisting and hammering correction and further shortens the assembly and adjustment time.

[0042] In a preferred embodiment, before performing the segmented pre-welding step, standard welding bevels and special positioning fixtures that match functional accessories such as high-pressure riser seats and oil tank bases are prepared according to preset unified interface specifications. This ensures the consistency of interface dimensions, solves the assembly interference problem caused by cumulative errors, realizes the standardization and modularization of key components, and significantly improves the interchangeability and assembly efficiency of the product.

[0043] See Figures 3-6 In this embodiment, the steps for assembling the corrected transformer tank wall as a whole are as follows: Step 1: Baseline Placement and Initial Positioning (1) Hoist the low-pressure sidewall 1, which has been corrected, to the assembly platform, placing it with its outer side (the side with the reinforcing iron 5) facing down, as shown. Figure 4 As shown, adjust the position so that the longitudinal center line coincides with the longitudinal baseline on the platform, and the end contour of the box wall is aligned with the transverse positioning line on the platform. (2) According to the design drawings, accurately draw the installation position lines of the two end walls 2 (i.e. the outer surface lines of the end walls 2) on the inner surface of the low-pressure side wall 1. Step 2: Installation and initial verticality adjustment of end wall 2 (introduction of active adjustment mechanism) (1) Use a crane to lift the first end wall 2, align its lower end with the position line marked on the low-pressure side wall 1, and make preliminary alignment using the side of the box as the height reference; (2) At the T-joint area between end wall 2 and low-pressure side wall 1, at the upper, middle, and lower key positions inside the housing, install (temporarily weld) positive and negative screw jacking points 3 respectively, such as Figure 4 As shown, for example, a screw can be fixed at each point on the inner side of the upper and lower reinforcing iron 5. By coordinating the extension of the push points 3 of these screws (such as rotating the screw), the angle of the end wall 2 relative to the low-pressure side wall 1 can be precisely controlled. The operator can make a preliminary judgment by observing the gap or using a right angle ruler, and adjust the screw to make the end wall 2 and the low-pressure side wall 1 basically perpendicular. (3) Make several positioning welds at the external butt joint to initially fix the end wall 2 and the low-pressure side wall 1, but keep the internal screw in a tight state to maintain the posture. Step 3: Box flipping and high-pressure sidewall 4 introduction (1) See Figure 4 Using the lower edge of the low-pressure sidewall 1 as the axis, a crane is used to rotate the assembly that has been connected to the low-pressure sidewall 1 and the two end walls 2 by 90 degrees, so that the box wall stands up and forms a "U" shaped structure. (2) such as Figure 5 As shown, the outer contour lines of the two end walls 2 are drawn on the high-voltage side wall 4; (3) Hoist the high-pressure side wall 4 so that it aligns with the two already positioned end walls 2. Similarly, install positive and negative screw jacking points 3 at the joints between the high-pressure side wall 4 and the end walls 2 inside the enclosure. (4) By adjusting these new sets of lead screws, the high-pressure side wall 4 is made perpendicular to the two end walls 2, and external positioning welding is performed. At this time, the box is closed on all four sides, forming a preliminary rectangular frame, such as Figure 6 As shown, multiple sets of independently adjustable lead screw jacking points 3 are arranged inside; Step 4: Active precision adjustment based on digital measurement (1) Verticality measurement and correction: Use a plumb line with a steel ruler or a total station to measure the verticality of both end walls 2 and record the measurement data, such as the top of the left end wall 2 tilting inward by 2.5mm. If the verticality exceeds the tolerance, for example, if it is required to be ≤3mm, then instead of relying on hammering, it is corrected by adjusting the multiple sets of lead screw pushing points 3 inside the box that act on the end wall 2. For example, for the above-mentioned tilt, the lead screw on the upper part of the inner side of the end wall 2 needs to be adjusted to push out, and the lower lead screw needs to be appropriately retracted to form a corrective bending moment. After adjustment, the measurement is immediately repeated until the verticality meets the standard.

[0044] (2) Measurement and correction of the top opening size and shape: Using a laser rangefinder and a large diagonal ruler, accurately measure the long side, wide side and two diagonal lengths of the top opening of the box. The difference between the diagonals can be used to determine the rectangularity, and the length and width can be used to determine the overall size. The design requires that the middle of the top opening should be slightly convex. (3) Based on the measurement results, adjust the shape of the top opening of the box by coordinating the adjustment of multiple sets of lead screw jacking points 3 acting on the four box walls. For example, if the diagonals are not equal, it indicates that the box is twisted, and the lead screws at the diagonal positions need to be adjusted in pairs. If an outward convex arc shape is required, the lead screw acting on the middle of the high and low pressure side wall 1 needs to be pushed out appropriately until the length, width, diagonal dimensions and arc shape of the top opening meet the requirements of the drawing.

[0045] Step 5: Lid Installation and Final Overall Verification (1) Spot weld temporary reinforcing beams (such as 22a I-beams) onto the box cover to prevent deformation; (2) Use a crane to lift the box cover to the top of the box body, ensuring that its center line coincides with the center line of the box body and that the sag around the perimeter is uniform. Adjust the position of the box cover so that it fits tightly against the top of the box wall and then fix it in place. (3) Use a crane to lift the entire box and measure the length, width and diagonal dimensions of the bottom opening using the same method. Since welding and hoisting may cause slight deformation, the remaining screw push point 3 inside the box can be used again for fine adjustment to ensure that the bottom opening is a regular rectangle and the dimensions are negative tolerance, so as to facilitate subsequent assembly with the box edge. (4) After confirming all dimensions, perform continuous welding on all internal and external main welds. After welding, remove all temporary screw jacking point 3 bases inside and grind them.

[0046] The above-mentioned overall assembly implementation plan eliminates differences in human experience and ensures that the geometric accuracy of each product's enclosure reaches a uniform high standard, providing a fundamental guarantee for the sealing and insulation reliability of subsequent assembly.

[0047] It should be noted that this embodiment provides a method for welding large transformer tank panels. By pre-welding functional accessories in sections before assembling the tank wall, and by adopting an active anti-deformation strategy that combines preset initial deformation with external rigid constraints, the angular deformation and wave deformation caused by welding thermal stress are effectively suppressed from the source. This achieves micro-shaping or even no-shaping after welding, improves quality consistency, reduces labor intensity and time costs, shortens welding time, and ensures uniform and stable weld quality. This lays the foundation for large-scale automated production. Combined with adaptive correction based on three-dimensional measurement and precision assembly based on fixed benchmarks, a closed-loop control of measurement-feedback-correction is formed, which systematically improves the overall manufacturing precision of the tank and significantly enhances product reliability and production efficiency.

[0048] Example 2 Please see Figure 2 This embodiment provides a large transformer tank sheet welding system for implementing the above method, such as... Figure 2 As shown, it includes: Welding workstation: includes a welding platform and a detachable rigid constraint frame. The welding platform is used to apply a preset initial deformation to the box wall. The detachable rigid constraint frame is installed on the edge of the box wall to provide external rigid constraint during the welding process. Welding robot: Used to perform welding between functional accessories and the box wall according to a preset welding planning path and preset heat input control strategy; 3D Detection and Shaping Module: Includes a 3D scanning unit and a correction execution unit. The 3D scanning unit is used to acquire the 3D point cloud data of the welded tank wall. The correction execution unit is used to compare the 3D point cloud data of the welded tank wall with the digital theoretical model to identify the deformed area, correct the deformed area, and obtain the corrected transformer tank wall. Assembly module: includes an active adjustment mechanism installed inside the box body, which is used to adjust the geometry and dimensional tolerances of the box body during the assembly of the box walls; Control module: Communicatively connected to the welding robot and the 3D detection and shaping module, used to store preset welding path planning data, heat input control parameters, and 3D point cloud data and digital theoretical model after welding.

[0049] In this embodiment, the detachable external rigid constraint frame is composed of six standardized steel units connected by a hydraulically or electrically driven quick-locking device. The calibration execution unit is a multi-joint robot, and the end effector of the multi-joint robot is equipped with a heat source generator. Furthermore, the control module generates heating control commands and sends them to the multi-joint robot based on the comparison results between the three-dimensional point cloud data obtained by the three-dimensional scanning unit and the digital theoretical model.

[0050] Preferably, the welding path planning data stored in the control module includes a sequence of skip welding paths for different combinations of box walls and functional accessories; the heat input control parameters include a set of welding current, voltage and speed parameters that match the skip welding path sequence.

[0051] It is understandable that the working principle of the large transformer tank sheet welding system in this embodiment is as follows: (1) After the system starts, the control module loads the model information of the oil tank to be produced and retrieves the corresponding complete set of process data packages from its built-in digital process database. The data package includes: the jump welding path sequence for each tank wall and different functional accessory plate thickness combination, the welding current, voltage and speed parameter set that are precisely matched with it, the preset initial deformation (pre-camber), and the digital theoretical model of the tank wall and the tank body. (2) The box wall is lifted by a crane to the platform of the welding workstation. According to the instructions, the system is assisted by the operator to place pads at specific positions below the box wall and apply the preset initial deformation to make it present the required micro-convex curved surface. (3) Subsequently, the operator or auxiliary equipment installs the detachable rigid constraint frame (made of standard steel 6 connected by a quick locking device) on the edge of the box wall and locks it to form a stable external rigid support. (4) The welding robot automatically performs intermittent jump welding in the same direction according to the welding path planning and heat input control parameters issued by the control module for specific accessories on the box wall, and accurately completes the welding of all functional accessories. During the welding process, the rigid constraint frame effectively suppresses instantaneous deformation. (5) After welding and cooling, the box wall is transferred to the inspection station. The three-dimensional inspection and shaping module is started, and its three-dimensional scanning unit (such as a laser scanner) performs a full-area scan of the box wall to obtain high-density three-dimensional point cloud data. (6) The data is transmitted to the control module in real time. The control module automatically compares and analyzes the data with the corresponding digital theoretical model to generate a three-dimensional deviation chromatogram, accurately identify and locate the deformation area that exceeds the tolerance (such as local depression or protrusion). (7) Based on the analysis results, the control module automatically plans the optimal correction scheme and generates heating control instructions, which are sent to the correction execution unit. This unit is usually a multi-joint robot with a heat source generator (such as a flame heating gun) on its end effector. The robot performs programmed local heating on the back of the weld corresponding to the deformation area according to a predetermined path, inducing reverse deformation. For edge straightness deviation, the system can prompt or drive the mechanical straightening mechanism to compensate. After correction, a quick rescan can be performed to verify the effect. (8) All the box walls that have been calibrated are sent to the assembly module. On the precision assembly platform with permanent reference lines, the operators hoist the side walls and end walls 2 in sequence for preliminary fixation. (9) During the assembly process, the active adjustment mechanism (multiple sets of lead screw jacking points 3) pre-installed inside the box is used to measure the key geometric parameters such as the verticality, opening size and diagonal of the box in real time by measuring instruments (such as total station), and the data is fed back to the control system or judged manually. (10) Based on the measurement deviation, coordinate the extension of each lead screw push point 3 to digitally and quantitatively correct the verticality of the box wall and the shape of the box opening until all dimensional tolerances meet the strict requirements, and finally complete the installation of the box cover and the welding of all continuous welds.

[0052] It should be noted that this embodiment provides a large transformer tank panel welding system, including a welding workstation, a welding robot, a 3D inspection and shaping module, an assembly module, and a control module. This system enables post-weld micro-shaping and even post-weld non-shaping, improving quality consistency, reducing labor intensity and time costs, shortening welding time, and ensuring uniform and stable weld quality. This lays the foundation for large-scale automated production. Combining adaptive correction based on 3D measurement with precision assembly based on fixed benchmarks, a closed-loop control system of measurement-feedback-correction is formed, systematically improving the overall manufacturing precision of the tank and significantly enhancing product reliability and production efficiency.

[0053] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0054] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0055] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for sheet welding of a large transformer oil tank, characterized in that, include: S100. Apply a preset initial deformation to each section of the transformer tank wall and install a detachable external rigid constraint frame at the edge of each section of the tank wall. Use a welding robot to perform welding between the functional accessories of the transformer tank and the tank wall according to the preset welding planning path and preset heat input control strategy. S200. After welding is completed, the three-dimensional point cloud data of the welded tank wall is obtained and compared with the digital theoretical model to identify the deformation area. The deformation area is then corrected to obtain the corrected transformer tank wall. S300. Assemble the corrected transformer tank wall as a whole, and use the active adjustment mechanism set inside the transformer tank to control the geometric shape and dimensional tolerance of the transformer tank body.

2. The sheet welding method for large transformer oil tanks according to claim 1, characterized in that, The method of applying a preset initial deformation to each section of the transformer tank wall and installing a detachable external rigid constraint frame at the edge of each section of the tank wall includes: Support pads are installed below the box wall to create a pre-camber in the middle area of ​​the box wall relative to the circumferential edge of the box wall, thereby forming an initial deformation. The detachable external rigid constraint frame is a frame made of standard structural steel (6) connected by a quick locking mechanism, and the frame is installed on the edge of the box wall.

3. The sheet welding method for large transformer oil tanks according to claim 1, characterized in that, The preset welding planning path is a unidirectional intermittent skip welding sequence, wherein a single weld segment in the welding sequence is limited to a predetermined length, and the welding positions of any two adjacent weld segments are spatially isolated from each other.

4. The sheet welding method for large transformer oil tanks according to claim 1, characterized in that, The preset thermal input control strategy includes: Based on the combination of the plate thickness of the box wall and the functional accessories, a corresponding set of welding current, voltage, and welding speed parameters is matched.

5. The sheet welding method for large transformer oil tanks according to claim 1, characterized in that, S200 specifically includes: S210. Acquire three-dimensional point cloud data of the box wall surface and compare it with the digital theoretical model to identify and locate the deformation area; S220. An external heating device is used to perform programmed local heating on the back side of the weld corresponding to the deformation area to generate reverse deformation. Then, the edge of the box wall is mechanically straightened to correct the straightness of the box wall.

6. The sheet welding method for large transformer oil tanks according to claim 1, characterized in that, The active adjustment mechanism includes multiple sets of lead screw pushing points (3) set in the internal space of the box. By adjusting the extension amount of each lead screw pushing point (3), the verticality of the box wall and the shape of the box opening are corrected.

7. A large transformer tank sheet welding system, characterized in that, include: Welding workstation: includes a welding platform and a detachable rigid constraint frame. The welding platform is used to apply a preset initial deformation to the box wall. The detachable rigid constraint frame is installed on the edge of the box wall to provide external rigid constraint during the welding process. Welding robot: Used to perform welding between functional accessories and the box wall according to a preset welding planning path and preset heat input control strategy; 3D Detection and Shaping Module: Includes a 3D scanning unit and a correction execution unit. The 3D scanning unit is used to acquire the 3D point cloud data of the welded tank wall. The correction execution unit is used to compare the 3D point cloud data of the welded tank wall with the digital theoretical model to identify the deformed area, correct the deformed area, and obtain the corrected transformer tank wall. Assembly module: includes an active adjustment mechanism installed inside the box body, which is used to adjust the geometry and dimensional tolerances of the box body during the assembly of the box walls; Control module: Communicatively connected to the welding robot and the 3D detection and shaping module, used to store preset welding path planning data, heat input control parameters, and 3D point cloud data and digital theoretical model after welding.

8. The large transformer tank sheet welding system according to claim 7, characterized in that, The detachable external rigid constraint frame is composed of standardized steel units connected by a hydraulically or electrically driven quick-locking device.

9. The large transformer tank sheet welding system according to claim 7, characterized in that, The correction execution unit is a multi-joint robot, and the end effector of the multi-joint robot is equipped with a heat source generator; The control module generates heating control commands and sends them to the multi-joint robot based on the comparison results between the three-dimensional point cloud data obtained by the three-dimensional scanning unit and the digital theoretical model.

10. The large transformer tank sheet welding system according to claim 7, characterized in that, The welding path planning data stored in the control module includes a sequence of skip welding paths for different combinations of box walls and functional accessories; The heat input control parameters include a set of welding current, voltage, and speed parameters that match the skip welding path sequence.

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