Automatic welding positioning tool and operation method for steel structural member

Abstract

The application discloses a kind of steel structural member automation welding positioning tool and operation method, belong to welding processing technical field, using sectional time sequence release force clamping structure, along the length direction of weld interval arrangement multiple independent clamping units, with lateral positioning reference component jointly form the bidirectional positioning constraint of workpiece width direction;Matched with welding gun synchronous movement linkage trigger mechanism output pneumatic trigger signal, so that welding heat-affected zone keeps rated clamping force to guarantee positioning accuracy.The application adopts the above-mentioned steel structural member automation welding positioning tool and operation method, can reduce weld residual tensile stress peak value under the premise of guaranteeing weld lateral misalignment amount ≤0.3mm, component lateral bending deformation is reduced;Pure pneumatic control is used throughout, and the ability to resist welding spatter, high-temperature thermal radiation and electromagnetic interference is strong, suitable for H-shaped steel, box girder and other long strip-shaped steel structural member automatic assembly welding.

Description

Technical Field

[0001] This invention relates to the field of welding processing technology, and in particular to an automated welding positioning fixture and operation method for steel structure components. Background Technology

[0002] In fields such as building steel structures, bridge engineering, and heavy equipment manufacturing, long and narrow steel structural components such as H-beams and box girders are core load-bearing units. The precision of their prefabrication and the quality of their welding directly determine the overall structural safety and service life. Welding positioning fixtures, as core process equipment in the component assembly welding process, are used to fix the workpiece position during welding, control the bevel gap, misalignment, and dimensional tolerances, and are fundamental to ensuring the quality of weld formation.

[0003] Currently, the mainstream steel structure welding positioning fixtures in the industry generally adopt a rigid positioning and clamping scheme. This involves using fixed positioning blocks in conjunction with clamping cylinders to apply constant, strong rigid constraints to the workpiece throughout the welding process, thereby preventing workpiece displacement during welding. While this type of solution can achieve basic positioning functions, it still suffers from inherent technical defects that are difficult to overcome due to its structural principles.

[0004] Rigid clamping throughout the welding process can easily lead to high residual stresses, reducing the service performance of components. During welding, the weld area undergoes localized rapid heating and cooling cycles, resulting in significant thermal expansion and contraction deformation. The rigid constraint throughout the process completely restricts the free contraction of the workpiece, causing high residual tensile stresses to form in the weld and heat-affected zone. This not only easily induces cold cracks in the weld but also significantly reduces the fatigue resistance and stress corrosion resistance of the components, posing a safety hazard for the long-term service of steel structures.

[0005] The constraint scheme contains inherent logical contradictions, making it impossible to simultaneously address deformation control and dimensional tolerance adaptation. When using an asymmetric constraint scheme with a single-sided fixed stop, the uneven restraint on both sides during the workpiece's cooling and shrinkage process can easily lead to lateral bending deformation, affecting the overall straightness of the component. On the other hand, when using a symmetric constraint scheme with double-sided rigid limits, it cannot adapt to the rolling dimensional tolerances commonly found in steel structure components, which can easily result in statically indeterminate jamming, workpiece clamping failure, or flange deformation due to compression, leading to poor quality stability during mass production.

[0006] The workpiece centering efficiency is low, and the adaptability of heavy components is insufficient. After the workpiece is hoisted and loaded, it falls directly onto the fixed support surface. The huge sliding friction generated by its own weight results in large lateral centering resistance. A large amount of cylinder thrust is consumed in overcoming friction, which not only makes it difficult to guarantee centering accuracy, but also easily scratches the workpiece surface. Moreover, the tooling change and adjustment are cumbersome and cannot meet the flexible production needs of multi-specification components.

[0007] The control triggering scheme has poor environmental adaptability and insufficient reliability in automated operation. Existing automated positioning fixtures mostly use electrical components such as proximity switches and photoelectric sensors to detect the position of the welding torch and control the clamping action. However, there are a lot of high-temperature metal splashes, strong electromagnetic interference and heat radiation at the steel structure welding site. Electrical components are prone to failure, false triggering and other faults, resulting in low operational reliability and high maintenance costs. Moreover, the triggering logic of fixed position cannot be adapted to variable speed welding process, and the timing of force release is mismatched with the actual welding heat field distribution, making it impossible to stably guarantee the stress control effect.

[0008] Stress concentration at the weld ends is a prominent issue, resulting in a high defect rate. The arc initiation and termination ends are stress concentration areas. Existing tooling uses the same clamping control logic for the ends and the middle section. The shrinkage deformation of the middle section is strongly constrained by both ends, and the longitudinal shrinkage stress is concentrated at the end fusion line, which easily induces crater cracks and transverse tearing defects, becoming a weak link in weld quality.

[0009] Therefore, existing steel structure welding positioning fixtures have the problem of "difficulty in balancing positioning accuracy and residual stress control". They also have many engineering problems such as poor tolerance adaptability, low reliability under working conditions, and frequent end defects, which cannot meet the needs of high-quality, high-efficiency and high-reliability automated welding production. Summary of the Invention

[0010] The purpose of this invention is to provide an automated welding positioning fixture and operation method for steel structure components to solve the above-mentioned problems.

[0011] The present invention provides an automated welding positioning fixture for steel structure components, including a workbench base, a bottom support assembly disposed on the workbench base, a lateral positioning reference assembly, a clamping mechanism, and a welding traveling mechanism that can travel along the length of the weld, wherein a welding torch is provided on the welding traveling mechanism. The lateral positioning reference assembly includes several sets of positioning reference units spaced apart along the length of the workpiece. The clamping mechanism is a segmented sequential force-releasing clamping structure, including several sets of independent clamping units spaced apart along the length of the weld. Each set of positioning reference units and each set of independent clamping units are arranged opposite to each other along the width of the workpiece, and together they form a bidirectional positioning constraint on the workpiece in the width direction. Each set of independent clamping units includes a clamping bracket, a clamping drive, a pressure head assembly, and an independent control unit. The clamping drive is horizontally fixedly mounted on the clamping bracket, with its output end facing the workpiece side. It can independently adjust the output clamping force to adapt to dimensional deviations in the workpiece width direction. The pressure head assembly is located at the output end of the clamping drive and is used to press against the side of the workpiece. The independent control unit is connected to the clamping drive and is used to independently control the clamping force and action sequence of the corresponding clamping drive. The welding walking mechanism is equipped with a welding torch position linkage triggering mechanism. The linkage triggering mechanism moves synchronously with the welding walking mechanism and is used to output a pneumatic triggering signal when the welding torch moves to a preset position. The independent control unit at the corresponding position receives the pneumatic triggering signal and executes the corresponding action. The independent control unit is configured to: when the welding torch travels to a preset distance in front of the weld segment corresponding to the independent clamping unit, control the clamping drive to maintain the rated clamping force and press and position the workpiece between the lateral positioning reference component and the clamping mechanism; when the welding torch leaves the preset distance behind the weld segment corresponding to the independent clamping unit, control the clamping drive to reduce the clamping force to 20%-30% of the rated clamping force, so that the welded area can freely contract during the cooling process to release the welding residual stress.

[0012] Preferably, the clamping drive is a constant pressure clamping cylinder, and the independent control unit is an independent air circuit control module; the piston rod of the constant pressure clamping cylinder has no rigid stroke stop, and the output clamping force is controlled by constant air intake pressure; the effective working stroke of the constant pressure clamping cylinder is greater than the maximum tolerance range in the width direction of the workpiece, ensuring that the pressure head assembly always abuts against the side of the workpiece under full tolerance conditions.

[0013] Preferably, the pressure head assembly includes a pressure head seat, a copper pressure block, and a surface elastic pad; the pressure head seat is rigidly connected to the piston rod end of the constant pressure clamping cylinder; the copper pressure block is installed on the workpiece contact side of the pressure head seat through the surface elastic pad, and the compressible stroke of the surface elastic pad is no more than 0.5 mm.

[0014] Preferably, the independent air circuit control module performs two-stage gradient force release: when the welding torch leaves the corresponding weld section by 400-600mm, the constant pressure clamping cylinder is controlled to reduce the clamping force to 60%-70% of the rated clamping force, entering the semi-constraint conformal stage; when the welding torch leaves the corresponding weld section by 1200-1500mm, the constant pressure clamping cylinder is controlled to further reduce the clamping force to 20%-30% of the rated clamping force, entering the weak constraint force release stage.

[0015] Preferably, the positioning reference unit is a reference seat that floats elastically along the width direction of the workpiece, and a reset elastic element is provided between the reference seat and the fixed bracket; during clamping and positioning, the positioning reference unit adapts to the workpiece width tolerance and floats under the thrust of the independent clamping unit, so that the central axis of the workpiece is kept within the preset reference plane in the width direction of the worktable.

[0016] Preferably, the bottom support assembly includes fixed support blocks and lifting rollers arranged in an alternating pattern; The top surface of the fixed support block is a fixed load-bearing reference surface; the lifting roller assembly includes a lifting drive component and rollers. The lifting drive component can drive the rollers to rise and fall. The highest position of the top surface of the rollers is higher than the top surface of the fixed support block, and the lowest position is lower than the top surface of the fixed support block. The tooling is also equipped with a pneumatic sequence control module, which is composed of pure pneumatic valve components. After the workpiece is loaded, the lifting drive first drives the rollers to lift and support the workpiece, so that the workpiece is separated from the fixed support block; then the clamping drive pushes the workpiece with low pressure, so that both sides of the workpiece contact the positioning reference unit and the independent clamping unit respectively, and the center is automatically aligned in the width direction under the combined action of the elastic constraints on both sides; then the lifting drive drives the rollers to descend, and the workpiece falls back onto the fixed support block; finally, the clamping drive switches to the rated clamping force to complete the clamping.

[0017] Preferably, the welding torch position linkage triggering mechanism includes a cam stop block group fixedly installed on the side of the workbench, and a centrifugal speed regulating linkage bracket installed on the welding walking mechanism. The centrifugal speed-regulating linkage bracket includes a centrifugal pendulum assembly coaxially connected to the drive wheel shaft of the welding walking mechanism, a shift fork component linked to the centrifugal pendulum assembly, and a sliding seat for mounting the cam stop group. When the walking speed increases, the centrifugal pendulum assembly opens radially, and the shift fork component drives the sliding seat to translate along the weld length direction to the rear side of the welding forward direction, so that the cam stop group moves backward synchronously to extend the force release trigger distance. The cam stop group is used to trigger the generation of a pneumatic trigger signal.

[0018] Preferably, the two sets of independent clamping units located at the arc-starting end and arc-ending end of the weld are end clamping units, and their independent control units are also equipped with pulse force release modules; The pulse stress release module is configured such that after the entire weld seam is completed and all intermediate independent clamping units have entered the weak constraint stress release stage, the clamping drive of the end clamping unit is controlled to fully release the pressure for 2-3 seconds, and then reloaded to 10%-15% of the rated clamping force to release the longitudinal concentrated stress at the end.

[0019] Preferably, the welding torch position linkage triggering mechanism is a mechanical-gas integrated pilot valve group, which is integrated and installed on the welding walking mechanism; The integrated mechanical-pneumatic pilot valve assembly includes a multi-channel roller mechanical valve. The roller of the roller mechanical valve is triggered in conjunction with a cam stop block assembly fixedly installed on the side of the worktable. The integrated mechanical-pneumatic pilot valve assembly is connected to the main air supply pipeline via a trailing cable. The output pilot air signal directly controls the air circuit reversal of the corresponding independent air circuit control module, with no electrical control signal transmission throughout the process.

[0020] A method for automated welding and positioning of steel structure components as described above is provided, comprising the following steps: S1. Loading the workpiece: Hoist the steel structure component to be welded onto the bottom support assembly; S2. Positioning and clamping: Through the bidirectional constraint cooperation between the lateral positioning reference component and the clamping mechanism, the workpiece is positioned and clamped in the width direction, so that the preset weld seam of the workpiece is aligned with the trajectory of the welding torch; all independent clamping units are in the rated clamping force state, and the workpiece positioning is completed. S3. Segmented Sequential Welding: The welding walking mechanism is activated to drive the welding torch along the weld seam. During the welding process, the welding torch position is detected in real time by the welding torch position linkage triggering mechanism, and a pneumatic triggering signal is output. When the welding torch travels to a preset distance in front of the weld seam segment corresponding to the independent clamping unit, the unit maintains the rated clamping force to constrain the accuracy of the welding area. When the welding torch leaves the preset distance behind the corresponding weld seam segment, the unit automatically reduces the clamping force to 20%-30% of the rated clamping force, allowing the welded area to cool and shrink to release residual stress. S4. Post-weld clamping: After the entire weld is completed and cooled for a set time, all independent clamping units are completely released, and the material is hoisted out.

[0021] Therefore, the present invention, employing the above-mentioned automated welding positioning fixture and operation method for steel structure components, has the following beneficial effects: (1) Independent clamping units arranged in segments along the weld length are adopted, and a time-sequential force release logic that is linked to the position of the welding torch is used to maintain the rated clamping force in the heat-affected zone of the weld to strictly control the misalignment accuracy. The clamping force is gradually reduced in the cooled area of ​​the weld to release thermal stress, which solves the problems of high stress and poor accuracy of rigid clamping throughout the entire process. It can achieve a lateral misalignment of ≤0.3mm in the welding area; at the same time, the peak value of residual tensile stress in the weld is reduced, the incidence of cold cracking in welding is reduced, and the fatigue life of the component is significantly improved.

[0022] (2) By using bidirectional symmetrical constraints between the positioning reference unit and the independent clamping unit, the traditional single-sided rigid stop block scheme is replaced, avoiding lateral bending deformation caused by asymmetrical constraints. The positioning reference unit adopts an elastic floating structure, which can adapt to the rolling dimension tolerance in the width direction of the workpiece, and there is no risk of statically indeterminate jamming, extrusion deformation or clamping failure. The positioning deviation of the workpiece center axis is ≤0.2mm, and the difference in the size of the weld feet on both sides is controlled within 0.5mm, which can adapt to the width dimension tolerance within ±3mm, and the stability of mass production is greatly improved.

[0023] (3) A two-stage gradient stress release logic is adopted. In the high-temperature softening zone of the weld, a semi-constrained state is maintained to control angular deformation and wave instability. After the temperature drops back to the safe range, it enters a weakly constrained state to release residual stress. The stress release timing is precisely matched with the temperature range of the welding thermal field. Compared with the single-stage stress release scheme, the amount of welding angular deformation can be reduced. It is especially suitable for welding thin flange components and avoids instability and torsion defects caused by premature stress release in the high-temperature softening zone.

[0024] (4) The entire process adopts pneumatic trigger signal control for clamping action, without electrical control components and long-distance wiring, which can completely resist the influence of welding spatter, high temperature heat radiation and strong electromagnetic interference, reduce the failure rate of the trigger system and significantly reduce maintenance costs; equipped with centrifugal speed-regulating linkage bracket, it can automatically adjust the force release trigger distance according to the welding walking speed. The faster the speed, the longer the trigger distance, adaptively matching the heat field distribution under different welding speeds. The force release timing deviation under variable speed conditions is ≤5%, ensuring stable stress control effect within the entire process parameter range.

[0025] (5) The structure of alternating lifting roller group and fixed support block is adopted. Through the sequential process of "lifting and reducing resistance - low pressure centering - sitting and clamping", the sliding friction during workpiece centering is converted into rolling friction, the centering driving force is reduced, which not only ensures the centering accuracy, but also avoids scratches on the workpiece surface. At the same time, it reduces the thrust requirement of the clamping drive component, and the tooling operation energy consumption is lower.

[0026] (6) To address the stress concentration characteristics at the arc initiation and termination ends of the weld, an end clamping logic of "strong clamping for conformal protection - pulse pressure relief - micro-force limiting" is adopted. The longitudinal concentrated stress at the end is released through a single pulse pressure relief, while micro-force constraint is retained to prevent workpiece displacement. This can reduce the peak value of longitudinal residual stress at the end and decrease the incidence of crater cracks and transverse tearing at the end.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of an embodiment 1 of the present invention, which describes an automated welding positioning fixture and operation method for steel structure components. Figure 2 This is a front view of Embodiment 1 of the present invention, which describes an automated welding positioning fixture and operation method for steel structure components. Figure 3 This is a side sectional view of Embodiment 1 of the present invention, which describes an automated welding positioning fixture and operation method for steel structure components. Figure 4 This is a schematic diagram of the lateral positioning reference component in Embodiment 1 of the present invention, which describes an automated welding positioning fixture and operation method for steel structure components. Figure 5 This is a schematic diagram of the clamping mechanism in Embodiment 1 of the present invention, which describes an automated welding positioning fixture and operation method for steel structure components. Figure 6 This is a schematic diagram of the welding walking mechanism in Embodiment 1 of the present invention, which describes an automated welding positioning fixture and operation method for steel structure components. Figure 7 for Figure 6A magnified structural diagram of point a.

[0029] Reference numerals: 1. Workbench base; 2. Bottom support assembly; 21. Fixed support block; 22. Lifting roller assembly; 221. Lifting drive component; 222. Roller; 3. Lateral positioning reference assembly; 31. Positioning reference unit; 311. Reference seat; 312. Fixed bracket; 313. Reset elastic component; 4. Clamping mechanism; 41. Independent clamping unit; 411. Clamping bracket; 412. Clamping drive component; 413. Pressure head assembly; 5. Welding travel mechanism; 51. Welding torch; 52. Welding torch position linkage triggering mechanism; 521. Cam stop block assembly; 522. Centrifugal speed regulation linkage bracket; 5221. Centrifugal pendulum assembly; 5222. Shift fork component; 5223. Sliding seat. Detailed Implementation

[0030] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0032] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0033] Example 1 An automated welding positioning fixture for steel structure components is applied to the assembly and welding process of long strip components in the prefabrication of steel structures in the factory. It is especially suitable for the longitudinal continuous weld positioning of components such as H-beams and box beams. By adjusting the clamping force in segments and time sequences, it can effectively release residual welding stress while ensuring welding positioning accuracy.

[0034] This fixture includes a workbench base 1, a bottom support assembly 2, a lateral positioning reference assembly 3, a clamping mechanism 4, and a welding traveling mechanism 5 that can travel along the length of the weld seam. The welding traveling mechanism 5 is equipped with a welding torch 51.

[0035] The workbench base 1 is a frame-type load-bearing base formed by welding steel profiles. The top surface is provided with a T-slot structure extending along the length of the workpiece. The installation position of each functional component can be adjusted through the T-slot to adapt to workpieces of different lengths. The welding travel mechanism 5 is straddling the workbench base 1 and can drive the welding torch 51 to move at a uniform speed along the length of the weld seam to complete the automated welding of continuous weld seams.

[0036] The lateral positioning reference component 3 includes several sets of positioning reference units 31 spaced apart along the length of the workpiece. The clamping mechanism 4 is a segmented sequential force-releasing clamping structure, including several sets of independent clamping units 41 spaced apart along the length of the weld. Each set of positioning reference units 31 and each set of independent clamping units 41 are arranged opposite to each other along the width of the workpiece, and together they form a bidirectional positioning constraint on the workpiece in the width direction.

[0037] The welding walking mechanism 5 is equipped with a welding torch position linkage triggering mechanism 52. The linkage triggering mechanism moves synchronously with the welding walking mechanism 5 and is used to output a pneumatic triggering signal when the welding torch 51 moves to a preset position. The independent control unit at the corresponding position receives the pneumatic triggering signal and executes the corresponding action.

[0038] The lateral positioning reference assembly 3 is arranged with multiple sets of positioning reference units 31 at intervals along the length of the workpiece, providing elastic positioning constraints on the reference side for the workpiece.

[0039] Each positioning reference unit 31 is a reference seat 311 that can elastically float along the width direction of the workpiece. A reset elastic element 313 is provided between the reference seat 311 and the fixed bracket 312. The end of the reference seat 311 is hinged to the fixed bracket 312, and the fixed bracket 312 is locked and installed on the worktable base 1. The reference seat 311 can slide back and forth along the width direction of the workpiece. During clamping and positioning, the positioning reference unit 31 adapts to the workpiece width tolerance and floats under the thrust of the independent clamping unit 41, so that the central axis of the workpiece is kept within the preset reference plane in the width direction of the worktable, realizing the symmetrical centering and positioning of the workpiece and avoiding welding side bending deformation caused by asymmetrical constraints.

[0040] The workpiece contact side of the reference base 311 is inlaid with a copper backing strip that is resistant to arc erosion, which can prevent welding spatter from damaging the reference surface and prevent scratches on the workpiece surface.

[0041] The clamping mechanism 4 adopts a segmented independent control structure design. Each independent clamping unit 41 can independently adjust the clamping force and action sequence to achieve differentiated constraint control along the weld direction.

[0042] Each of the independent clamping units 41 includes a clamping bracket 411, a clamping drive 412, a pressure head assembly 413, and an independent control unit.

[0043] The clamping bracket 411 is a vertical rigid support structure, which is locked and fixed to the workbench base 1 at the bottom, providing reaction force support for the clamping action.

[0044] The clamping drive 412 is horizontally fixedly mounted on the clamping bracket 411, with its output end facing the workpiece side. It can independently adjust the output clamping force to adapt to dimensional deviations in the workpiece width direction. In this embodiment, the clamping drive 412 is a constant-pressure clamping cylinder, and the independent control unit is an independent air circuit control module. The piston rod of the constant-pressure clamping cylinder has no rigid stroke stop, and the output clamping force is controlled by maintaining a constant inlet air pressure. The effective working stroke of the constant-pressure clamping cylinder is greater than the maximum tolerance range in the workpiece width direction, ensuring that the pressure head assembly 413 always abuts against the side of the workpiece under full tolerance conditions, thus avoiding workpiece deformation caused by clamping failure or excessive compression.

[0045] The pressure head assembly 413 is located at the output end of the clamping drive 412 and is used to press against the side of the workpiece. The pressure head assembly 413 includes a pressure head seat, a copper pressure block, and a surface elastic pad. The pressure head seat is rigidly connected to the piston rod end of the constant pressure clamping cylinder. The copper pressure block is installed on the workpiece contact side of the pressure head seat through the surface elastic pad. The compressible stroke of the surface elastic pad is no more than 0.5 mm, which can compensate for the micro-unevenness of the workpiece surface, ensure surface contact and fit, and absorb the instantaneous micro-expansion during welding, avoiding local stress concentration caused by rigid clamping. At the same time, the limitation of this compression stroke can control the amount of pressure head retraction during welding within the allowable range, ensuring that the lateral misalignment of the weld always meets the accuracy requirements.

[0046] An independent control unit is connected to the clamping drive 412 for independently controlling the clamping force and timing of the corresponding clamping drive 412. In this embodiment, the independent pneumatic control module is integrated and installed on the side of the clamping bracket 411, and consists of a pressure reducing valve, a pressure maintaining valve, a throttle valve, and a pneumatic directional valve, which can precisely control the output pressure and timing of the cylinder.

[0047] The independent control unit is configured to: when the welding torch 51 travels to a preset distance in front of the weld segment corresponding to the independent clamping unit 41, control the clamping drive 412 to maintain the rated clamping force, press and position the workpiece between the lateral positioning reference component 3 and the clamping mechanism 4, provide rigid constraints for the welding heat-affected zone, and ensure that the bevel gap and misalignment meet the process requirements; when the welding torch 51 leaves the preset distance behind the weld segment corresponding to the independent clamping unit 41, control the clamping drive 412 to reduce the clamping force to 20%-30% of the rated clamping force, so that the welded area can freely contract during the cooling process to release the welding residual stress.

[0048] Furthermore, the independent gas path control module is configured to perform two-stage gradient stress release: when the welding torch 51 moves 400-600mm behind the corresponding weld section, the constant pressure clamping cylinder is controlled to reduce the clamping force to 60%-70% of the rated clamping force, entering the semi-constrained conformal stage. At this time, the weld metal has solidified but is still in a high-temperature softened state, and the retained constraint stiffness can effectively suppress angular deformation and wave instability; when the welding torch 51 moves 1200-1500mm behind the corresponding weld section, the constant pressure clamping cylinder is controlled to further reduce the clamping force to 20%-30% of the rated clamping force, entering the weak constraint stress release stage. At this time, the temperature of the weld area drops back to the safe range, the metal yield strength recovers, and it can freely contract under weak constraint, fully releasing the residual tensile stress.

[0049] The bottom support assembly 2 includes fixed support blocks 21 arranged in an alternating pattern and lifting roller assembly 22, which work together in sequence to achieve low-resistance centering and rigid load bearing of the workpiece.

[0050] The top surface of the fixed support block 21 is a fixed load-bearing reference surface, used for vertical load bearing during the workpiece welding process to ensure the stability of the workpiece's height reference.

[0051] The lifting roller assembly 22 includes a lifting drive component 221 and rollers 222. The lifting drive component 221 can drive the rollers 222 to rise and fall. The highest position of the top surface of the rollers 222 is higher than the top surface of the fixed support block 21, and the lowest position is lower than the top surface of the fixed support block 21.

[0052] The tooling is also equipped with a pneumatic sequence control module, which is composed of pure pneumatic valve components. It is configured as follows: after the workpiece is loaded, the lifting drive component 221 first drives the roller 222 to lift and support the workpiece, so that the workpiece is separated from the fixed support block 21, and the sliding friction generated by the workpiece's own weight is converted into rolling friction, which greatly reduces the centering resistance; then the clamping drive component 412 pushes the workpiece with low pressure, so that the two sides of the workpiece contact the positioning reference unit 31 and the independent clamping unit 41 respectively, and the center is automatically aligned in the width direction under the combined action of the elastic constraints on both sides; then the lifting drive component 221 drives the roller 222 to descend, and the workpiece falls back onto the fixed support block 21, turning into a rigid surface contact load-bearing device; finally, the clamping drive component 412 switches to the rated clamping force to complete the clamping, ensuring the positioning stability during the welding process.

[0053] In this embodiment, the welding torch position linkage triggering mechanism 52 adopts a pure mechanical pneumatic linkage scheme, with no electrical control components involved throughout the process. It can resist welding site spatter, high temperature and electromagnetic interference. Specifically, it includes a cam stop block group 521, a centrifugal speed regulation linkage bracket 522 and a mechanical-pneumatic integrated pilot valve group.

[0054] The integrated mechanical-pneumatic pilot valve assembly is mounted on the welding traveling mechanism 5. It includes a multi-channel roller-type mechanical valve. The rollers of the roller-type mechanical valve engage with a cam stop assembly fixed to the side of the worktable for triggering. The integrated mechanical-pneumatic pilot valve assembly is connected to the main air supply line via a traveling link. The output pilot air signal directly controls the air circuit reversal of the corresponding independent air circuit control module, with no electrical control signal transmission throughout the process. When the welding traveling mechanism 5 moves to the corresponding position, the rollers pass over the cam stop, the valve core mechanically reverses, and a pneumatic trigger signal is directly output, triggering the corresponding clamping unit to perform a pressure switching action.

[0055] The centrifugal speed-regulating linkage bracket 522 is installed on the drive wheel shaft side of the welding walking mechanism 5. It is used to adaptively adjust the trigger distance according to the welding walking speed to ensure that the stress release timing matches the thermal field distribution under variable speed conditions. The centrifugal speed-regulating linkage bracket 522 includes a centrifugal pendulum assembly 5221 coaxially connected to the drive wheel shaft of the welding walking mechanism 5, a shift fork component 5222 linked to the centrifugal pendulum assembly 5221, and a sliding seat 5223 for mounting the cam stop group 521. When the walking speed increases, the centrifugal pendulum assembly 5221 opens radially under the action of centrifugal force. The shift fork component 5222 drives the sliding seat 5223 to translate along the weld length direction to the rear side of the welding forward direction, so that the cam stop group 521 moves backward synchronously to extend the stress release trigger distance and compensate for the problem of insufficient heat dissipation time under high-speed welding. When the walking speed decreases, the centrifugal force decreases, and the reset elastic element 313 drives the sliding seat 5223 to translate forward, shortening the trigger distance and avoiding excessive cooling and wasting the stress release window period. The cam stop block group 521 is used to trigger the generation of a pneumatic trigger signal, with no electrical control components involved throughout the process.

[0056] The two sets of independent clamping units 41 located at the arc-starting end and arc-ending end of the weld are end clamping units, and their independent control units are also equipped with pulse force release modules.

[0057] The pulse force release module is configured such that after the entire weld seam is completed and all intermediate independent clamping units 41 have entered the weak constraint force release stage, the clamping drive 412 of the end clamping unit is controlled to fully release pressure for 2-3 seconds, allowing the end workpiece to freely shrink along the longitudinal direction, releasing the longitudinal tensile stress concentrated at the end fusion line; then it is reloaded to 10%-15% of the rated clamping force, maintaining a slight force limit to prevent the workpiece from shifting or tipping over, while not hindering the slight shrinkage during the subsequent cooling process.

[0058] Example 2 An automated welding positioning method for an automated welding positioning fixture for steel structure components includes the following steps: S1. Workpiece loading; The steel structure components to be welded are hoisted onto the bottom support assembly 2, and the workpiece is initially placed on the top surface of the fixed support block 21, thus completing the loading and positioning.

[0059] S2, Positioning and clamping; The workpiece is positioned and clamped in the width direction by the bidirectional constraint cooperation between the lateral positioning reference component 3 and the clamping mechanism 4, so that the preset weld seam of the workpiece is aligned with the travel trajectory of the welding torch 51. The specific process is as follows: The pneumatic sequence control module starts according to the preset air path timing. The lifting drive 221 first drives the roller 222 to rise, lifting the workpiece away from the fixed support block 21 and eliminating the sliding friction resistance caused by its own weight. Then, the clamping drive 412 outputs thrust at low pressure to push the workpiece to move laterally until both sides of the workpiece contact the independent clamping unit 41 and the positioning reference unit 31 respectively. Under the balance of elastic forces on both sides, the center alignment is automatically completed, and the central axis of the workpiece coincides with the preset reference plane. After the alignment is completed, the lifting drive 221 drives the roller 222 to fall down, and the workpiece falls back to the fixed support block 21, turning into a rigid load-bearing unit. Finally, the clamping drive 412 switches to the rated clamping force, and all independent clamping units 41 are in the rated clamping force state, completing the workpiece positioning and clamping.

[0060] S3, segmented timing welding; The welding walking mechanism 5 is activated to drive the welding torch 51 to move along the weld seam for welding. During the welding process, the position of the welding torch 51 is detected in real time by the welding torch position linkage trigger mechanism 52 and a pneumatic trigger signal is output. Each independent clamping unit 41 adjusts the clamping force in stages according to a preset timing sequence. When the welding torch 51 travels to the preset distance in front of the weld section corresponding to the independent clamping unit 41, the unit maintains the rated clamping force, provides strong rigid constraint for the welding area, strictly controls the weld misalignment and bevel gap, and ensures the welding forming accuracy. As the welding torch 51 continues to move forward, when it leaves the corresponding weld section by 400-600mm, the independent clamping unit 41 switches to a semi-constrained conformal state, and the clamping force is reduced to 60%-70% of the rated clamping force. While suppressing unstable deformation in the high-temperature zone, it releases some of the thermal expansion restraint. As the welding torch 51 continues to move forward, when it leaves the corresponding weld section by 1200-1500mm, the independent clamping unit 41 switches to a weak constraint release state, and the clamping force is further reduced to 20%-30% of the rated clamping force, allowing the welded area to shrink freely during the cooling process, effectively reducing the peak value of residual tensile stress.

[0061] During the welding process, the centrifugal speed-regulating linkage bracket 522 adjusts the position of the cam stop block in real time according to the walking speed, automatically adapts to changes in welding speed, ensures that the timing of force release always matches the distribution of the welding heat field, and ensures stable stress control under variable speed conditions.

[0062] S4. Loosen the clamp after welding; After the entire weld seam is completed, the end clamping unit first performs a pulse stress release action to release the longitudinal concentrated stress at the end; after the workpiece has cooled for a set time, all independent clamping units 41 are completely released, and the workpiece is hoisted out, completing the entire welding positioning operation cycle.

[0063] Using Q355BH steel with dimensions of H400×200×10×20mm and a length of 6m as the test object, CO2 gas shielded welding was employed at a welding speed of 300mm / min. This fixture was compared with a traditional fully rigid clamping fixture under the same working conditions. The test results are as follows: Positioning accuracy: The lateral misalignment of the weld seam in the welding area of ​​this fixture is stably controlled within 0.3mm, the centering deviation of the workpiece center axis is ≤0.2mm, and the difference in the size of the weld feet on both sides is ≤0.5mm. It fully meets the accuracy requirements of steel structure welding construction and is comparable to the positioning accuracy of traditional rigid clamping fixtures, with no loss of accuracy.

[0064] Residual stress control: The residual tensile stress at the center of the weld was tested using the blind hole method. The peak value of the residual tensile stress in the traditional rigid clamping scheme was 285 MPa, while the peak value of the residual tensile stress in this tooling scheme was 152 MPa, which is about 46.7% lower. The effect of releasing welding residual stress is significant.

[0065] Deformation control: The lateral bending of the component in the traditional scheme is 3.2mm / 6m, while the lateral bending of this tooling scheme is 0.8mm / 6m, which reduces the lateral bending deformation by 75%; the weld corner deformation is reduced by 42%, and there are no wave instability defects in the thin flange area.

[0066] End quality: The incidence of end crater cracks in traditional solutions is about 18%. This tooling, through pulse stress release design, reduces the incidence of end crater cracks to below 3% and reduces the peak value of longitudinal residual stress at the end by 41%.

[0067] Reliability under operating conditions: After 30 days of continuous production testing, the pure pneumatic triggering system of this tooling showed no splash adhesion failures or thermal radiation false triggering faults. The failure rate of the triggering system is 92% lower than that of traditional electrical sensor solutions, and maintenance costs are significantly reduced.

[0068] Therefore, this invention employs the aforementioned automated welding positioning fixture and operation method for steel structure components. It utilizes independent clamping units arranged in segments along the weld length, coupled with a time-sequential force release logic linked to the welding torch position. This maintains a rated clamping force in the weld heat-affected zone to strictly control misalignment accuracy, while gradually reducing the clamping force in the cooled welded area to release thermal stress. This solves the problems of high stress and poor clamping accuracy associated with rigid clamping throughout the entire process. It achieves a lateral misalignment of ≤0.3mm in the welding area; simultaneously, it reduces the peak residual tensile stress in the weld, decreases the incidence of cold cracking, and significantly improves the fatigue life of the component. By using bidirectional symmetrical constraints between the positioning reference unit and the independent clamping units, it replaces the traditional single-sided rigid stop scheme, avoiding lateral bending deformation caused by asymmetrical constraints. The positioning reference unit adopts an elastic floating structure, which can adapt to the rolling dimensional tolerances in the workpiece width direction, eliminating the risk of statically indeterminate jamming, extrusion deformation, or clamping failure. The workpiece center axis positioning deviation is ≤0.2mm, the difference in weld leg size on both sides is controlled within 0.5mm, and it can adapt to width size tolerance within ±3mm, greatly improving the stability of mass production.

[0069] A two-stage gradient stress release logic is employed. In the high-temperature softening zone of the weld, a semi-constrained state is maintained to control angular deformation and wave instability. Once the temperature drops to a safe range, a weakly constrained state is entered to release residual stress, ensuring precise matching between stress release timing and the welding thermal field temperature range. Compared to a single-stage stress release scheme, this reduces weld angular deformation, making it particularly suitable for welding thin-flange components and avoiding instability and torsion defects caused by premature stress release in the high-temperature softening zone. The entire process utilizes pneumatic trigger signals to control the clamping action, eliminating electrical control components and long-distance wiring. This completely resists the effects of welding spatter, high-temperature heat radiation, and strong electromagnetic interference, reducing the failure rate of the trigger system and significantly lowering maintenance costs. Equipped with a centrifugal speed-regulating linkage bracket, the stress release trigger distance is automatically adjusted according to the welding travel speed; the faster the speed, the longer the trigger distance. This adaptively matches the thermal field distribution under different welding speeds, with a stress release timing deviation of ≤5% under variable speed conditions, ensuring stable stress control across the entire process parameter range.

[0070] The system employs a structure with alternating lifting rollers and fixed support blocks. Through a sequential process of "lifting and reducing resistance - low-pressure centering - settling and clamping," the sliding friction during workpiece centering is converted into rolling friction. This reduces the centering driving force, ensuring centering accuracy while preventing scratches on the workpiece surface. It also lowers the thrust requirements of the clamping drive components, resulting in lower energy consumption during tooling operation. Addressing the stress concentration characteristics at the arc initiation and termination ends of the weld, an end-clamping logic of "strong clamping for conformal protection - pulse pressure relief - micro-force limiting" is used. A single pulse pressure relief releases the longitudinal concentrated stress at the end while maintaining micro-force constraint to prevent workpiece displacement. This reduces the peak value of longitudinal residual stress at the end, decreasing the incidence of crater cracks and transverse tearing at the end.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An automated welding positioning fixture for steel structural members, characterized by, It includes a workbench base, a bottom support assembly mounted on the workbench base, a lateral positioning reference assembly, a clamping mechanism, and a welding travel mechanism that can travel along the length of the weld seam, with a welding torch mounted on the welding travel mechanism; The lateral positioning reference assembly includes several sets of positioning reference units spaced apart along the length of the workpiece. The clamping mechanism is a segmented sequential force-releasing clamping structure, including several sets of independent clamping units spaced apart along the length of the weld. Each set of positioning reference units and each set of independent clamping units are arranged opposite to each other along the width of the workpiece, and together they form a bidirectional positioning constraint on the workpiece in the width direction. Each set of independent clamping units includes a clamping bracket, a clamping drive, a pressure head assembly, and an independent control unit. The clamping drive is horizontally fixedly mounted on the clamping bracket, with its output end facing the workpiece side. It can independently adjust the output clamping force to adapt to dimensional deviations in the workpiece width direction. The pressure head assembly is located at the output end of the clamping drive and is used to press against the side of the workpiece. The independent control unit is connected to the clamping drive and is used to independently control the clamping force and action sequence of the corresponding clamping drive. The welding walking mechanism is equipped with a welding torch position linkage triggering mechanism. The linkage triggering mechanism moves synchronously with the welding walking mechanism and is used to output a pneumatic triggering signal when the welding torch moves to a preset position. The independent control unit at the corresponding position receives the pneumatic triggering signal and executes the corresponding action. The independent control unit is configured to: when the welding torch travels to a preset distance in front of the weld segment corresponding to the independent clamping unit, control the clamping drive to maintain the rated clamping force and press and position the workpiece between the lateral positioning reference component and the clamping mechanism; when the welding torch leaves the preset distance behind the weld segment corresponding to the independent clamping unit, control the clamping drive to reduce the clamping force to 20%-30% of the rated clamping force, so that the welded area can freely contract during the cooling process to release the welding residual stress.

2. The automated welding positioning fixture for steel structure components according to claim 1, characterized in that, The clamping drive is a constant pressure clamping cylinder, and the independent control unit is an independent air circuit control module; the piston rod of the constant pressure clamping cylinder has no rigid stroke stop, and the output clamping force is controlled by constant air intake pressure; the effective working stroke of the constant pressure clamping cylinder is greater than the maximum tolerance range in the width direction of the workpiece.

3. The automated welding positioning fixture for steel structure components according to claim 2, characterized in that, The pressure head assembly includes a pressure head seat, a copper pressure block, and a surface elastic pad; the pressure head seat is rigidly connected to the piston rod end of the constant pressure clamping cylinder; the copper pressure block is installed on the workpiece contact side of the pressure head seat through the surface elastic pad, and the compressible stroke of the surface elastic pad is no more than 0.5 mm.

4. The automated welding positioning fixture for steel structure components according to claim 2, characterized in that, The independent air circuit control module performs two-stage gradient force release: when the welding torch leaves the corresponding weld section by 400-600mm, the constant pressure clamping cylinder is controlled to reduce the clamping force to 60%-70% of the rated clamping force, entering the semi-constraint conformal stage; when the welding torch leaves the corresponding weld section by 1200-1500mm, the constant pressure clamping cylinder is controlled to further reduce the clamping force to 20%-30% of the rated clamping force, entering the weak constraint force release stage.

5. The automated welding positioning fixture for steel structure components according to claim 1, characterized in that, The positioning reference unit is a reference seat that floats elastically along the width direction of the workpiece, and a reset elastic element is provided between the reference seat and the fixed bracket; during clamping and positioning, the positioning reference unit adapts to the workpiece width tolerance and floats under the thrust of the independent clamping unit.

6. The automated welding positioning fixture for steel structure components according to claim 1, characterized in that, The bottom support assembly includes fixed support blocks and lifting rollers arranged in a staggered pattern; The top surface of the fixed support block is a fixed load-bearing reference surface; the lifting roller assembly includes a lifting drive component and rollers. The lifting drive component can drive the rollers to rise and fall. The highest position of the top surface of the rollers is higher than the top surface of the fixed support block, and the lowest position is lower than the top surface of the fixed support block. The tooling is also equipped with a pneumatic sequence control module, which is composed of a combination of purely pneumatic valve components.

7. The automated welding positioning fixture for steel structure components according to claim 4, characterized in that, The welding torch position linkage triggering mechanism includes a cam stop block group fixedly installed on the side of the workbench, and a centrifugal speed regulating linkage bracket installed on the welding walking mechanism. The centrifugal speed-regulating linkage bracket includes a centrifugal pendulum assembly coaxially connected to the drive wheel shaft of the welding walking mechanism, a shift fork component linked to the centrifugal pendulum assembly, and a sliding seat for mounting the cam stop group. When the walking speed increases, the centrifugal pendulum assembly opens radially, and the shift fork component drives the sliding seat to translate along the weld length direction to the rear side of the welding forward direction, so that the cam stop group moves backward synchronously to extend the force release trigger distance. The cam stop group is used to trigger the generation of a pneumatic trigger signal.

8. The automated welding positioning fixture for steel structure components according to claim 1, characterized in that, The two independent clamping units located at the arc-starting end and arc-ending end of the weld are end clamping units, and their independent control units are also equipped with pulse force release modules; The pulse stress release module is configured such that after the entire weld seam is completed and all intermediate independent clamping units have entered the weak constraint stress release stage, the clamping drive of the end clamping unit is controlled to fully release the pressure for 2-3 seconds, and then reloaded to 10%-15% of the rated clamping force to release the longitudinal concentrated stress at the end.

9. The automated welding positioning fixture for steel structure components according to claim 7, characterized in that, The welding torch position linkage triggering mechanism is a mechanical-gas integrated pilot valve group, which is integrated and installed on the welding walking mechanism; The integrated mechanical-pneumatic pilot valve assembly includes a multi-channel roller mechanical valve. The roller of the roller mechanical valve is triggered in conjunction with a cam stop block assembly fixedly installed on the side of the worktable. The integrated mechanical-pneumatic pilot valve assembly is connected to the main air supply pipeline via a trailing cable. The output pilot air signal directly controls the air circuit reversal of the corresponding independent air circuit control module, with no electrical control signal transmission throughout the process.

10. A method for automated welding positioning of steel structure components as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Loading the workpiece: Hoist the steel structure component to be welded onto the bottom support assembly; S2. Positioning and clamping: Through the bidirectional constraint cooperation between the lateral positioning reference component and the clamping mechanism, the workpiece is positioned and clamped in the width direction, so that the preset weld seam of the workpiece is aligned with the trajectory of the welding torch; all independent clamping units are in the rated clamping force state, and the workpiece positioning is completed. S3. Segmented Sequential Welding: The welding walking mechanism is activated to drive the welding torch along the weld seam. During the welding process, the welding torch position is detected in real time by the welding torch position linkage triggering mechanism, and a pneumatic triggering signal is output. When the welding torch travels to a preset distance in front of the weld seam segment corresponding to the independent clamping unit, the unit maintains the rated clamping force to constrain the accuracy of the welding area. When the welding torch leaves the preset distance behind the corresponding weld seam segment, the unit automatically reduces the clamping force to 20%-30% of the rated clamping force, allowing the welded area to cool and shrink to release residual stress. S4. Post-weld clamping: After the entire weld is completed and cooled for a set time, all independent clamping units are completely released, and the material is hoisted out.

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