Square and rectangular tube welding device and welding method

Abstract

The invention relates to the technical field of square and rectangular pipe welding, and discloses a square and rectangular pipe welding device and method.The welding device comprises a deformation liquid bag, two sets of square pipes and reinforcing parts are flexibly wrapped and positioned when the deformation liquid bag is filled with heat conduction liquid, and the heat conduction liquid continuously circulates in the deformation liquid bag through a liquid inlet pipe and a liquid outlet pipe; the circulating heat-conducting liquid also adjusts the temperatures of the two groups of square tubes and the reinforcing members in real time, so that the final welding effect is prevented from being influenced by abnormal temperatures of the square tubes and the reinforcing members; the welding method comprises steps S1 to S5. The flexible positioning function of the square pipe and the temperature adjusting function before and after welding are achieved at the same time through the deformation liquid bag, expansion and internal liquid circulation are conducted in the deformation liquid bag through liquid, and the temperature near a target welding seam can be adjusted through liquid circulation in the deformation liquid bag while flexible positioning is conducted; therefore, the temperature difference near the welding position is prevented from influencing the final welding result.

Description

Technical Field

[0001] The present invention relates to the technical field of square and rectangular pipe welding, and particularly relates to a square and rectangular pipe welding device and a welding method. Background Art

[0002] A square and rectangular pipe is a structure formed by welding square pipes into a rectangle, as Figure 6 shown. The prior art discloses an auxiliary device for welding rectangular metal pipes, with the application number CN202022481913.3, which includes a first positioning mechanism and a second positioning mechanism. A locking shaft is provided between the first positioning mechanism and the second positioning mechanism; locking nuts are provided at both ends of the locking shaft; the second positioning mechanism includes a first blocking mechanism and a second blocking mechanism arranged vertically. A docking block is provided between the front ends of the first blocking mechanism and the second blocking mechanism, and the locking shaft passes through the docking block; the locking nuts are installed on the outer side surface of the docking block; a first locking member is provided between one end of the first blocking mechanism and one end of the docking block, and a second locking member is provided between one end of the second blocking mechanism and the other end of the docking block; the first blocking mechanism includes a blocking plate. This application enables the ends of adjacent two metal pipes to be docked through a locking groove, thereby facilitating the welding machine to weld the metal pipes and playing an auxiliary role in welding. However, the prior art, especially this solution, still has the following problems:

[0003] When welding square and rectangular pipes, especially for some square and rectangular pipe structures with relatively high dimensional requirements and welding finished product effects, some relatively precise welding processes are required. During the welding process, temperature is a particularly important factor. Before and after the welding of the material, the temperature gradient will cause certain welding quality defects, and the temperature of the material itself will affect its actual welding effect. On the contrary, if the temperature of the material before and after welding is within a suitable and precise range, a relatively good welding effect can be obtained. For this reason, we need to propose a square and rectangular pipe welding device and a welding method. Summary of the Invention

[0004] The purpose of the present invention is to provide a technical solution to simultaneously achieve the flexible positioning function of the square pipe and the temperature adjustment function before and after welding through a deformation liquid sac, so as to solve the problems in the prior art mentioned in the above background art.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A square and rectangular pipe welding device, the square and rectangular pipe includes a reinforcement member and four groups of square pipes, including:

[0007] A base and a support member. Two sets of support seats with adjustable spacing are installed on the base through the support member. A support fixture and a positioning fixture for clamping four square tubes are installed on the support seats. Rigid shells are provided at the four corners of the square and rectangular tubes on the support seats. A deformation liquid bag is arranged inside the rigid shell, and the deformation liquid bag wraps around the outside of two square tubes and a reinforcement member.

[0008] A diversion tube is arranged outside the deformation liquid bag. The diversion tube is connected to the deformation liquid bag through multiple connecting tubes. An inlet pipe and an outlet pipe are arranged on the diversion tube. When the deformation liquid bag is filled with heat-conducting liquid, it flexibly wraps and positions the two square tubes and the reinforcement member. The inlet pipe and the outlet pipe enable the heat-conducting liquid to continuously circulate inside the deformation liquid bag, and the circulating heat-conducting liquid also adjusts the temperature of the two square tubes and the reinforcement member in real time, preventing the abnormal temperature of the square tubes and the reinforcement member from affecting the final welding effect.

[0009] Preferably, the deformation liquid bag is set as a temperature-resistant liquid bag structure. A metal wire-like interlayer is arranged inside the cavity of the deformation liquid bag, and the heat-conducting liquid is set as an oil-like heat-conducting liquid.

[0010] Preferably, the deformation liquid bag includes a mutually connected outer bag member, an inner bag member, and a bottom bag member. The outer bag member is supported outside the included angle of the two square tubes, the inner bag member is supported inside the included angle of the two square tubes, and the bottom bag member is supported at the bottom of the two square tubes.

[0011] Preferably, a heat-conducting member is arranged on the bottom bag member of the deformation liquid bag. When the square tube is placed on the deformation liquid bag, the heat-conducting member is attached to the square tube to obtain a better heat conduction effect.

[0012] Preferably, a relief groove is arranged on the rigid shell and the deformation liquid bag. The relief groove is used to make way for fitting structures such as the reinforcement member and the locking member, so that the deformation liquid bag can better fit the square and rectangular tubes.

[0013] Preferably, the square and rectangular tubes to be welded include a reinforcement member, a handle member, and four square tubes. The four square tubes are butt-jointed end to end. First, the two square tubes are welded and connected through the target weld at the top to form a rigid connection, which is convenient for subsequent welding operations. The reinforcement member needs to be welded between the two square tubes.

[0014] Preferably, both the support fixture and the positioning fixture are set to be movable and adjustable on the support seat, and the support fixture and the positioning fixture are driven by a linear telescopic member.

[0015] Preferably, the support fixture and the positioning fixture are installed on the support seat through a support, and the rigid shell is installed on the support seat through the support of the support fixture.

[0016] Preferably, the support fixture includes a first support fixture and a second support fixture, and the positioning fixture includes a first positioning fixture and a second positioning fixture. The first support fixture is used to clamp the middle section of each group of square tubes, and the second positioning fixture is used to press and align the ends of each group of square tubes. Under the combined clamping of the first support fixture and the second positioning fixture, the four groups of square tubes form the basic square structure of the square rectangular tube.

[0017] The present invention also provides a welding method for a square rectangular tube welding device, including the following steps:

[0018] Step S1, workpiece pre-positioning and fixture adjustment; Step S2, flexible positioning of the deformation liquid sac; Step S3, dynamic temperature control; Step S4, multi-pass welding implementation; Step S5, post-treatment and quality inspection.

[0019] Technical effects and advantages of the present invention: The square rectangular tube welding device and welding method proposed by the present invention have the following advantages compared with the prior art:

[0020] The present invention simultaneously realizes the flexible positioning function of the square tube and the temperature adjustment function before and after welding through the deformation liquid sac. The deformation liquid sac is arranged inside the rigid shell, and the inside of the deformation liquid sac expands through liquid and the internal liquid circulates. The two groups of square tubes of the square rectangular tube are first positioned by multiple fixtures, and then flexibly positioned by the deformation liquid sac on the rigid shell. At the same time of flexible positioning, the temperature near the target weld can be adjusted through the liquid circulation inside the deformation liquid sac, so as to prevent the temperature difference near the welding position from affecting the final welding result. Description of the drawings

[0021] Figure 1 It is a three-dimensional structure schematic diagram of the square rectangular tube welding device of the present invention;

[0022] Figure 2 For the present invention Figure 1 The enlarged structure schematic diagram of part A in;

[0023] Figure 3 It is a top view plane structure schematic diagram of the square rectangular tube welding device of the present invention;

[0024] Figure 4 For the present invention Figure 3 The enlarged structure schematic diagram of part B in;

[0025] Figure 5 It is a partial structure schematic diagram of the rigid shell, the deformation liquid sac and the square rectangular tube of the present invention;

[0026] Figure 6 It is a structure schematic diagram of the square rectangular tube in the present invention;

[0027] Figure 7 For the present invention Figure 6Schematic diagram of the enlarged structure at position C;

[0028] Figure 8 This is a schematic diagram of the specific structure of the rigid outer shell and the deformable liquid sac of the present invention.

[0029] In the figure:

[0030] 11. Support base; 12. Support member; 13. First support fixture; 14. First positioning fixture; 15. Second positioning fixture; 16. Second support fixture; 21. Rigid outer shell; 22. Deformable liquid sac; 23. Diversion pipe; 24. Liquid inlet pipe; 25. Liquid outlet pipe; 26. Connecting pipe; 27. Relief groove; 28. Outer sac member; 29. Inner sac member; 210. Bottom sac member; 211. Cavity; 212. Heat conducting member; 31. Square pipe; 32. Reinforcement member; 33. Handle member; 34. Connecting member; 35. Locking member; 36. Target weld. Detailed implementation manners

[0031] Now, the subject matter described herein will be discussed with reference to exemplary embodiments. It should be understood that discussing these embodiments is only to enable those skilled in the art to better understand and thus implement the subject matter described herein. Without departing from the scope of protection of the content of this specification, changes can be made to the functions and arrangements of the elements discussed. Each example can omit, substitute, or add various processes or components as needed. Additionally, the features described in some examples can also be combined in other examples.

[0032] The invention provides, as Figures 1 to 8 shown, a square and rectangular pipe welding device. The square and rectangular pipe includes a reinforcement member 32 and four groups of square pipes 31, and it includes:

[0033] A base and a support member 12. On the base, two groups of support seats 11 with adjustable spacing are installed through the support member 12. On the support seats 11, support fixtures and positioning fixtures for clamping the four groups of square pipes 31 are installed. At the four corners of the square and rectangular pipe on the support seats 11, there are rigid outer shells 21. Inside the rigid outer shells 21, there are deformable liquid sacs 22. The deformable liquid sacs 22 are wrapped around the outside of the two groups of square pipes 31 and the reinforcement member 32;

[0034] Outside the deformable liquid sacs 22, there are diversion pipes 23. The diversion pipes 23 are connected to the deformable liquid sacs 22 through multiple groups of connecting pipes 26. On the diversion pipes 23, there are liquid inlet pipes 24 and liquid outlet pipes 25. When the deformable liquid sacs 22 are filled with heat-conducting liquid, they flexibly wrap and position the two groups of square pipes 31 and the reinforcement member 32. The liquid inlet pipes 24 and the liquid outlet pipes 25 enable the heat-conducting liquid to continuously circulate inside the deformable liquid sacs 22. The circulating heat-conducting liquid also adjusts the temperature of the two groups of square pipes 31 and the reinforcement member 32 in real time, preventing abnormal temperatures of the square pipes 31 and the reinforcement member 32 from affecting the final welding effect.

[0035] Working principle: The deformable liquid bladder 22 simultaneously realizes the flexible positioning function for the square tube 31 and the temperature adjustment function before and after welding. The deformable liquid bladder 22 is arranged inside the rigid housing 21. The inside of the deformable liquid bladder 22 expands through the liquid and the internal liquid circulates. The two groups of square tubes 31 of the square and rectangular tube are first positioned by a plurality of jigs, and then flexibly positioned by the deformable liquid bladder 22 on the rigid housing 21. At the same time of flexible positioning, the temperature near the target weld 36 can be adjusted through the liquid circulation inside the deformable liquid bladder 22, so as to prevent the temperature difference near the welding position from affecting the final welding result.

[0036] The temperature abnormality mentioned above refers to that the temperature of the square and rectangular tube material itself is too high or too low during welding. Specifically, the defect of too low temperature: the fluidity of the molten pool decreases, and the depth-width ratio of the weld decreases; the defect of too high temperature: the grains in the heat-affected zone of the base metal are coarsened, resulting in a decrease in the tensile strength of the weld, and non-uniform thermal expansion occurs between the reinforcement 32 and the square tube 31, and the misalignment amount increases; it should be noted that the temperature abnormality here refers to the temperature of the square and rectangular tube before and after welding, not the welding temperature. The optimal temperature range of the square and rectangular tube before and after welding is 180°C - 250°C. When the temperature of the square and rectangular tube before and after welding is not within this range, it is interpreted as temperature abnormality.

[0037] In order to ensure that the deformable liquid bladder 22 and the internal heat-conducting liquid can keep the temperature of the square and rectangular tube in a suitable range, the deformable liquid bladder 22 is set as a temperature-resistant liquid bladder structure. A metal wire-like sandwich layer is arranged inside the cavity 211 of the deformable liquid bladder 22. The heat-conducting liquid is set as an oil-like heat-conducting liquid. For better heat-conducting effect, iron powder can be appropriately incorporated into the heat-conducting liquid.

[0038] As Figure 7 and Figure 8 shown, the deformable liquid bladder 22 includes an outer bladder member 28, an inner bladder member 29 and a bottom bladder member 210 that are interconnected. The outer bladder member 28 is supported on the outside of the included angle between the two groups of square tubes 31, the inner bladder member 29 is supported on the inside of the included angle between the two groups of square tubes 31, and the bottom bladder member 210 is supported on the bottom of the two groups of square tubes 31.

[0039] As Figure 8 shown, a heat-conducting member 212 is arranged on the bottom bladder member 210 of the deformable liquid bladder 22. When the square tube 31 is placed on the deformable liquid bladder 22, the heat-conducting member 212 is attached to the square tube 31 to obtain a better heat conduction effect. Specifically, the heat-conducting member 212 is set as a metal member.

[0040] As Figures 6 to 7 shown, the square and rectangular tube to be welded includes a reinforcement 32, a handle member 33 and four groups of square tubes 31. The four groups of square tubes 31 are butt-jointed end to end. The specific butt-joint method is as Figure 7As shown, the two sets of square tubes 31 are first welded and connected through the target weld 36 at the top, so as to form a rigid connection and facilitate subsequent welding operations. The reinforcement 32 needs to be welded between the two sets of square tubes 31, and this welding device is for the welding operation of the top target weld 36 and the welding operation between the reinforcement 32 and the square tube 31.

[0041] As Figure 6 shown, further, the square and rectangular tube also includes specific fittings such as a handle 33, a connecting piece 34 and a locking piece 35, etc., and multiple sets of jigs are correspondingly arranged for these fittings.

[0042] As Figure 2 and Figure 3 shown, specifically, both the support jig and the positioning jig are set to be movable and adjustable on the support base 11. The support jig includes a support jig one 13 and a support jig two 16, and the positioning jig includes a positioning jig one 14 and a positioning jig two 15. The support jig one 13 is used to clamp the middle section of each group of square tubes 31, and the positioning jig two 15 is used to abut and align the ends of each group of square tubes 31. Under the combined clamping of the support jig one 13 and the positioning jig two 15, the four groups of square tubes 31 form the basic square structure of the square and rectangular tube.

[0043] The support jig and the positioning jig are driven by a linear telescopic member. The support jig and the positioning jig are installed on the support base 11 through a support. The rigid outer shell 21 can be installed on the support base 11 through a specific support, or can be installed on the support base 11 through the support of the support jig (not shown in the figure).

[0044] As Figures 2 to 6 shown, the positioning jig one 14 is for the handle 33, the positioning jig one 14 abuts the handle 33 from one side, and the positioning jig two 15 is for the connecting piece 34, the positioning jig two 15 abuts the connecting piece 34 from the other side. The welding operations of these fittings such as the handle 33 and the connecting piece 34 are before the welding operation of the square tube 31, and this welding device is not for the welding operations of these structures.

[0045] As Figure 7 and Figure 8 shown, the rigid outer shell 21 and the deformation liquid sac 22 are provided with a relief groove 27, and the relief groove 27 is used to make way for fitting structures such as the reinforcement 32 and the locking piece 35, so that the deformation liquid sac 22 can better fit the square and rectangular tube. Specifically, there are several relief grooves 27 with different sizes, respectively making way for the reinforcement 32 and the locking piece 35.

[0046] Embodiment 2: On the basis of Embodiment 1, the present application also provides a welding method for a square and rectangular tube welding device, including the following steps:

[0047] Step S1, workpiece pre-positioning and fixture adjustment: adjust the spacing between the support seats 11: adjust the spacing between the two groups of support seats 11 through the linear slide rail of the support member 12 according to the length of the square tube; install the basic fixture: use the support fixture 13 to clamp the middle section of the four groups of square tubes 31; use the positioning fixture 2 15 to press against the end of the square tube 31 to ensure the flatness of the end surface; fix the handle 33 through the positioning fixture 14 to apply lateral positioning force;

[0048] Step S2, flexible positioning of the deformable liquid sac 22: positioning the liquid sac by filling it with liquid, injecting heat transfer oil into the deformable liquid sac 22 through the liquid inlet pipe 24; controlling the filling pressure to make the outer sac 28, the inner sac 29, and the bottom sac 210 respectively fit the angle of the square tube 31; using the metal wire interlayer to enhance the deformation constraint; adapting the yielding structure: confirming the alignment deviation between the yielding groove 27 and the reinforcing member 32 and the locking member 35; adjusting the heat transfer member 212 of the bottom sac 210 to ensure contact with the bottom surface of the square tube 31;

[0049] Step S3, dynamic temperature control: pre-welding temperature balance, start the heat transfer liquid circulation system; generate turbulence through the spiral guide plate of the guide tube 23; use an infrared thermometer to monitor the surface temperature of the square tube 31, and adjust the liquid inlet temperature to stabilize the workpiece within a certain range;

[0050] Step S4, multiple welding is performed: top weld welding, using TIG welding process, the first weld is performed along the target weld 36, while keeping the temperature fluctuation inside the liquid capsule within a certain range; welding heat is conducted out through the guide tube 23; reinforcement member 32 welding: adjusting the welding gun angle, performing fillet weld welding between the reinforcement member 32 and the square tube 31; using the heat conducting member 212 of the bottom capsule member 210 to enhance heat dissipation;

[0051] Step S5, post-processing and quality inspection: gradient cooling, maintain liquid circulation after welding is completed, and cool down at a stable rate; enhance the residual stress release effect by adding iron powder to the heat-conducting liquid; deformation monitoring, pressure relief and emptying the deformation liquid bag 22, use a laser scanner to detect the straightness of the square tube 31, and check the weld integrity in the area of ​​the make way groove 27.

[0052] In summary, the present solution also has the following comprehensive effects: a two-stage positioning mechanism, rigid fixture pre-positioning, a basic square frame is formed by the support fixture 13 (mid-section clamping) and the positioning fixture 15 (end abutting and aligning) to ensure the geometric accuracy of the four groups of square tubes 31; flexible positioning of the deformation liquid bag 22, inflating after filling with liquid, after injecting the heat-conducting liquid into the deformation liquid bag 22 (outer bag part 28, inner bag part 29, bottom bag part 210), adaptively wrapping the included angle of the square tube 31 and the reinforcement member 32 through liquid pressure; metal wire-like sandwich constraint, the wire mesh in the cavity 211 limits the excessive deformation of the liquid bag to achieve radial positioning accuracy; dynamic temperature control, preheating before welding, inputting heat-conducting oil through the liquid inlet pipe 24, circulating and heating the square tube 31 to the initial temperature range; heat dissipation after welding, enabling a low-temperature medium in the high-temperature area, forming a turbulent flow through the spiral guide vanes of the diversion pipe 23 to improve the heat exchange efficiency, and the metal heat-conducting member 212 of the bottom bag part 210 directly contacts the bottom surface of the square tube 31 to strengthen local heat dissipation; structural adaptability design, the matching of the relief groove 27, the rigid housing 21 and the relief groove 27 on the deformation liquid bag 22 precisely avoid the reinforcement member 32 and the locking member 35 to ensure the fitting of the liquid bag and the square tube 31; improvement of positioning accuracy and stability, the rigid fixture (support fixture 13 / positioning fixture 15) and the flexible liquid bag (deformation liquid bag 22) act synergistically, and the comprehensive positioning error is small; the metal wire-like sandwich restrains the creep of the liquid bag to ensure the positioning stability during the welding process; optimization of welding quality, temperature uniformity control, controlling the temperature difference in the welding area within a certain range through the circulation of the heat-conducting liquid, and reducing the width of the heat-affected zone; improvement of the weld strength, avoiding grain coarsening caused by abnormal temperature, and enhancing the tensile strength of the weld; structural compatibility and efficiency, the design of the relief groove 27 supports the welding of multi-specification fittings (reinforcement member 32 and locking member 35), and the changeover time is shortened; the liquid bag partition structure (outer bag, inner bag, bottom bag) is adapted to the special-shaped cross-section; enhancement of reliability, heat-resistant liquid bag material, wide temperature tolerance range, and long cycle life; the metal heat-conducting member 212 and the iron powder-doped liquid act synergistically, and the heat dissipation efficiency is improved compared with pure liquid.

[0053] The embodiments of the present invention have been described above, but the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms, all of which fall within the protection scope of the present invention.

Claims

1. A square tube welding device, the square tube comprising a reinforcing member (32) and four groups of square tubes (31), characterized in that: include: A base and a support member (12), wherein two groups of support seats (11) with adjustable spacing are installed on the base via the support member (12), a support fixture and a positioning fixture for clamping four groups of square tubes (31) are installed on the support seat (11), a rigid shell (21) is arranged at the four corners of the square tube on the support seat (11), a deformable liquid capsule (22) is arranged inside the rigid shell (21), and the deformable liquid capsule (22) is wrapped around the outside of the two groups of square tubes (31) and the reinforcement member (32); A flow guide tube (23) is arranged outside the deformable liquid capsule (22). The flow guide tube (23) is connected to the deformable liquid capsule (22) through a plurality of connecting tubes (26). A liquid inlet tube (24) and a liquid outlet tube (25) are arranged on the flow guide tube (23). When the deformable liquid capsule (22) is filled with heat-conducting liquid, the two groups of square tubes (31) and the reinforcement (32) are flexibly wrapped and positioned. The liquid inlet tube (24) and the liquid outlet tube (25) allow the heat-conducting liquid to circulate continuously inside the deformable liquid capsule (22). The circulating heat-conducting liquid also adjusts the temperature of the two groups of square tubes (31) and the reinforcement (32) in real time, thereby preventing the abnormal temperature of the square tubes (31) and the reinforcement (32) from affecting the final welding effect.

2. A square tube welding device according to claim 1, characterized in that: The deformable liquid capsule (22) is configured as a temperature-resistant liquid capsule structure, a metal wire-shaped interlayer is provided inside the cavity (211) of the deformable liquid capsule (22), and the heat-conducting liquid is configured as an oil-like heat-conducting liquid.

3. A square tube welding device according to claim 2, characterized in that: The deformable liquid capsule (22) comprises an outer capsule member (28), an inner capsule member (29) and a bottom capsule member (210) which are interconnected, the outer capsule member (28) being supported on the outside of an angle between two groups of square tubes (31), the inner capsule member (29) being supported on the inside of an angle between two groups of square tubes (31), and the bottom capsule member (210) being supported on the bottom of the two groups of square tubes (31).

4. A square tube welding device according to claim 3, characterized in that: A heat conducting member (212) is provided on the bottom bladder member (210) of the deformable liquid bladder (22); when the square tube (31) is placed on the deformable liquid bladder (22), the heat conducting member (212) fits the square tube (31) to obtain a better heat conduction effect.

5. A square tube welding device according to claim 4, characterized in that: The rigid shell (21) and the deformable liquid capsule (22) are provided with a clearance groove (27), and the clearance groove (27) is used to make way for accessory structures such as a reinforcement piece (32) and a locking piece (35), so that the deformable liquid capsule (22) can better fit the square tube.

6. A square tube welding device according to claim 1, characterized in that: The square tube to be welded comprises a reinforcing member (32), a handle member (33) and four groups of square tubes (31). The four groups of square tubes (31) are butt-jointed end to end. Two groups of square tubes (31) are first welded together through a target weld (36) at the top to form a rigid connection, thereby facilitating subsequent welding operations. The reinforcing member (32) needs to be welded between the two groups of square tubes (31).

7. A square tube welding device according to claim 6, characterized in that: The supporting fixture and the positioning fixture are both arranged to be movable and adjustable on the supporting seat (11), and the supporting fixture and the positioning fixture are driven by a linear telescopic member.

8. A square tube welding device according to claim 7, characterized in that: The supporting fixture and the positioning fixture are mounted on the supporting seat (11) via a support, and the rigid shell (21) is mounted on the supporting seat (11) via a support of the supporting fixture.

9. A square tube welding device according to claim 8, characterized in that: The supporting fixture comprises a supporting fixture 1 (13) and a supporting fixture 2 (16), and the positioning fixture comprises a positioning fixture 1 (14) and a positioning fixture 2 (15). The supporting fixture 1 (13) is used to clamp the middle section of each group of square tubes (31), and the positioning fixture 2 (15) is used to press and align the ends of each group of square tubes (31). Under the cooperative clamping of the supporting fixture 1 (13) and the positioning fixture 2 (15), the four groups of square tubes (31) form a basic square structure of square tubes.

10. A welding method for a square tube welding device according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: step S1, pre-positioning of workpiece and adjustment of fixture; step S2, flexible positioning of deformation liquid bag; step S3, dynamic temperature control; step S4, implementation of multi-pass welding; step S5, post-processing and quality inspection.

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