Water-cooling welding method for inner wall of ultrathin-wall pipe and inner-cooling supporting device

Abstract

The invention discloses an ultra-thin wall pipe inner wall water-cooling welding method and an inner-cooling supporting device, a moving component is provided, the moving component comprises a first pipe fitting and the inner-cooling supporting device inserted into the first pipe fitting, and the inner-cooling supporting device is provided with a supporting cooling pipe and a cooling section with a cooling liquid containing cavity; and providing a fixing component which comprises a second pipe fitting which is rotationally connected through a bracket and is sleeved on the ejector pin supporting main body. The movable component is driven to move towards the fixed component, the inner-cooling supporting device is partially inserted into the second pipe fitting, the end faces of the first pipe fitting and the second pipe fitting are in butt joint, the ejector pin and the tail end of the inner-cooling supporting device are connected and matched to achieve horizontal and coaxial positioning, and the outer wall and the inner wall of the pipe fitting form a radial annular microgap. The butt joint is welded from the outside, and during welding, a cooling medium flows in the cooling liquid containing cavity to indirectly cool a welding area. And after welding is completed, connection between the ejector pin and the inner-cooling supporting device is removed, and the moving component is moved out. A non-contact microgap indirect water cooling and precise local support collaborative technology is adopted, a welding area is efficiently cooled, and an inner cooling supporting device is conveniently taken out.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to an inner wall water cooling welding method and an inner cooling support device for ultra-thin wall pipe. BACKGROUND

[0002] Thin-walled and ultra-thin-walled metal pipes (generally referring to pipes with a wall thickness of ≤0.3 mm) have irreplaceable roles in aerospace engine fuel pipes, medical devices (such as interventional catheters), precise instrument flow paths, and semiconductor manufacturing equipment due to their lightweight and compact structure. The connection of such pipes is usually achieved by high-energy beam welding methods such as tungsten inert gas welding (TIG welding) or argon arc welding to realize high-quality sealed connection.

[0003] However, due to the extremely thin wall of the pipe, welding faces extremely severe technical challenges: first, the problem of inner wall collapse forming a convex rib. Under the action of the high-temperature arc of argon arc welding, the base metal at the joint is instantaneously melted to form a molten pool. For an ultra-thin-walled pipe with a wall thickness of about 0.2 mm, its structural rigidity and heat capacity are extremely small, and the molten metal is extremely prone to flowing into the pipe cavity, collapsing under the action of surface tension, arc pressure, and gravity, and forming a ring-shaped rib that protrudes inward after cooling and solidification. The convex rib significantly reduces the effective flow cross-sectional area of the pipe, increases the fluid pressure loss, and becomes a source of vortex generation and a stress concentration point, severely reducing the fluid performance and structural fatigue life of the component.

[0004] Second, the contradiction between weld metallurgical quality control and thermal management. To solve the problem of excessive heat input, the skilled person in the art has attempted to use forced cooling measures. One direct way is to introduce cooling water or cooling gas into the pipe to be welded. However, this method causes the weld pool and heat-affected zone to be cooled sharply, with a cooling rate much higher than the material's inherent critical cooling rate. For materials such as steel, this promotes the transformation of austenite to hard and brittle martensite, causing the hardness of the weld and heat-affected zone to increase sharply, the plasticity and toughness to decrease significantly, and cold cracks to be extremely prone to occur, seriously threatening the safety of the structure. In other words, direct liquid cooling controls deformation at the expense of the core mechanical properties of the weld.

[0005] Third, the reliability and effectiveness of the inner support tooling. Another approach is to insert a water-cooled mandrel or support pipe into the pipe to achieve the dual purpose of support and cooling. However, this solution presents a dilemma: if the mandrel and the pipe wall fit too tightly (with a small or zero gap), the workpiece will expand when heated during welding, causing a thermal expansion and contraction effect with the mandrel, resulting in the mandrel being firmly stuck inside the workpiece after cooling, making it impossible to remove and causing double scrap of the product and tooling. If the fit gap is intentionally increased to avoid being stuck, the support effect is weakened and cannot effectively resist pipe wall collapse, and the convex rib problem still exists; at the same time, the large gap leads to reduced heat conduction efficiency and poor cooling effect.

[0006] In summary, the prior art cannot balance the three mutually restrictive goals of preventing geometric deformation, ensuring metallurgical quality and realizing the feasibility of the tooling when butt welding ultra-thin-walled pipes. Therefore, there is an urgent need in the art for an innovative welding process and a special device that can systematically solve this series of related technical problems. SUMMARY

[0007] The primary purpose of the present application is to overcome the shortcomings of the prior art and provide an inner wall water cooling welding method for ultra-thin-walled pipes, which can effectively prevent the generation of welded inner ribs, while avoiding the deterioration of the weld metallographic structure due to rapid cooling and ensuring the smooth removal of the inner cooling tooling.

[0008] Another purpose of the present application is to provide an inner cooling support device that implements the above method, which is compact in structure, high in cooling efficiency, reliable in support and easy to operate.

[0009] In order to achieve the above purpose, the present application discloses an inner wall water cooling welding method for ultra-thin-walled pipes, comprising the following steps: providing a moving member, the moving member comprising a first pipe and an inner cooling support device inserted into the first pipe, the inner cooling support device comprising a support cooling pipe and a cooling section, the cooling section being provided with a cooling liquid containing cavity inside; providing a fixed member, the fixed member comprising a second pipe connected to a support body of a thimble through a bracket; driving the moving member to move towards the fixed member, so that the cooling section and part of the support cooling pipe of the inner cooling support device are inserted into the second pipe, and the end faces of the first pipe and the second pipe are butt jointed; wherein, after the moving member and the fixed member are butt jointed, the horizontal and coaxial positioning of the inner cooling support device is realized through the connection and cooperation of the thimble and the end of the inner cooling support device; wherein, the outer wall of the support cooling pipe and the cooling section and the inner wall of the first pipe and the second pipe form a radial annular micro gap; the butt joint of the first pipe and the second pipe is welded from the outside, and during the welding process, the cooling medium flows in the cooling liquid containing cavity to indirectly cool the welding area; after the welding is completed, the connection between the thimble and the inner cooling support device is released, and the moving member is removed from the welded pipe.

[0010] By adopting the above scheme, the non-contact micro gap indirect water cooling and precise local support are combined. During the welding process, the cooling medium continuously flows in the cooling liquid containing cavity, and through the heat conduction of the pipe wall, the welding area is indirectly cooled efficiently. After the welding is completed, the inner cooling support device can be easily pulled out from the pipe as a whole by using the thermal expansion space provided by the annular micro gap.

[0011] Furthermore, the connection and cooperation between the ejector pin and the end of the internal cooling support device is specifically as follows: the ejector pin includes a forward-extending insert, the end of the internal cooling support device is provided with a fitting, and the fitting has a fixing hole in the center; by rotating the ejector pin and the internal cooling support device relative to each other, the insert and the fixing hole form a detachable fixed connection.

[0012] By adopting the above scheme, it is ensured that the internal cooling support device remains horizontal and concentric with the ejector pin during the welding process, thereby ensuring high-precision coaxial alignment between the first and second pipe fittings and greatly improving the consistency of welding quality.

[0013] Furthermore, the outer surface of the insert is provided with an external thread, and the fixing hole is a matching internal thread hole, and a fixed connection is achieved by thread engagement.

[0014] By adopting the above solution, the threaded connection becomes more secure.

[0015] Furthermore, the insert has a tapered structure, and the fixing hole is a matching tapered hole, achieving a fixed connection through an interference fit of the tapered surface.

[0016] By adopting the above solution, the interference fit connection is convenient and disassembly is faster, and the conical insert effectively provides a stable support effect.

[0017] Furthermore, the size of the annular microgap ranges from 0.15 mm to 0.25 mm.

[0018] By adopting the above scheme, this size range, verified through extensive experiments, is the golden range that simultaneously meets three major functional requirements: Support function: The 0.2mm gap provides an extremely limited deformation space for a 0.2mm thick wall, effectively constraining the pipe wall radially, acting like a tight-fitting garment to resist the surface tension of the molten pool and prevent excessive inward collapse to form ribs. Anti-jamming function: It reserves sufficient space for the radial expansion of the fitting under heat, avoiding jamming problems caused by interference fits after cooling, ensuring reliable removal of the tooling. Thermal management function: This micro-gap is usually filled with protective gas, forming an ideal heat conduction interface. This ensures that heat from the cooling section is rapidly removed while avoiding direct contact between the welding area and the liquid, thus controlling the cooling rate within a reasonable range and protecting the metallographic structure of the weld.

[0019] Furthermore, the cross-sectional shape of the coolant receiving cavity is a fan-shaped ring with a central angle greater than or equal to 270 degrees.

[0020] By adopting the above scheme, the following beneficial effects are achieved: Maximizing the heat exchange area: Compared with traditional circular or small-angle fan-shaped cavities, this design makes the outer wall, i.e., the part closest to the pipe wall to be welded, more uniform in thickness, and significantly increases the heat exchange area, enabling more efficient and uniform absorption and dissipation of welding heat. Balancing structural strength and lightweighting: While ensuring sufficient structural strength to resist welding deformation, material in the central area is removed, achieving a lightweight device and reducing unnecessary heat capacity. Providing a channel for external clamps: The fan-shaped cavity naturally forms a space in the center, facilitating the installation of perforations for external support rods or pins to pass through, achieving internal clamping and fixation of the pipe fitting to be welded.

[0021] An internal cooling support device is used to realize a water-cooled welding method for the inner wall of ultra-thin-walled pipes, comprising: a supporting cooling pipe; a cooling section disposed at one end of the supporting cooling pipe, having a coolant reservoir inside, and a perforation in the center of the cooling section; and a liquid cooling pipe comprising an inlet pipe and an outlet pipe, wherein the liquid cooling pipe is connected to the coolant reservoir.

[0022] By adopting the above scheme, the supporting cold pipe is responsible for delivering the cooling section to the designated position and providing the main structural support. The coolant reservoir inside the cooling section is the key part for heat exchange. The liquid cooling pipe is set inside the supporting cold pipe or arranged along its outer wall. One end of the pipe is connected to the coolant reservoir, and the other end is used to connect to the external cooling source, forming a circulation path for the cooling medium and effectively achieving welding cooling.

[0023] Furthermore, it also includes an assembly, which is located at the end of the supporting cold pipe away from the cooling section. The assembly has a fixing hole in the center for detachably fixing to the insert of the external ejector pin. The fixing hole is an internal threaded hole or a round hole.

[0024] By adopting the above solution, the internal cooling support device can be kept horizontal as a whole, preventing downward tilting due to gravity caused by the lack of support at one end, and avoiding non-coaxial welding issues. This improves the yield rate.

[0025] Furthermore, it also includes a side plate, which is fixed to the end of the supporting cold pipe and located on the rear side of the assembly, and its outer diameter is larger than that of the supporting cold pipe.

[0026] By adopting the above solution, the following beneficial effects are achieved: Axial positioning and over-insertion prevention: When inserting the device into the pipe fitting, the side plate can serve as an axial positioning reference, preventing excessive insertion. Anti-dislodgement function: When pulling out the device after welding, the side plate provides a reliable clamping point and prevents the clamp from slipping off the pipe end, greatly facilitating operation. Enhanced system rigidity: The side plate enhances the rigidity of the entire device end, making it more stable during clamping and operation.

[0027] Furthermore, it also includes a gasket disposed between the assembly and the cooling section.

[0028] The advantages of adopting the above solution are as follows: Modular design: This allows core components such as supporting cold pipes and cooling sections to be manufactured separately, reducing the processing difficulty and cost of individual parts, and facilitating material selection and subsequent maintenance and replacement. Adjustment and sealing: Gaskets can be used to fine-tune the axial position of the cooling section, ensuring precise alignment of the weld seam, and also serve as an auxiliary seal. Stress dispersion: The structure of the gaskets helps to disperse the stress generated during welding and operation, improving the overall reliability of the device.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Through the core concept of micro-gap indirect water cooling, it creatively and ingeniously solves the three contradictory problems that have long plagued the industry: preventing rib protrusion, preserving metallographic structure, and preventing jamming. 2. The resulting weld has a beautiful internal and external appearance, no internal ridges, and good flow characteristics; the weld metal has a normal weld solidification structure, excellent mechanical properties, especially toughness and plasticity, and no risk of hardening and embrittlement. 3. The device can be easily removed without the risk of jamming, which improves production efficiency and product qualification rate, and is suitable for mass production; 4. The fan-shaped cooling chamber, side plates with anti-detachment function, and modular assembly design enable the device to have multiple advantages such as high-efficiency cooling, reliable support, convenient operation and easy manufacturing; 5. This technical solution can be widely applied to butt welding of ultra-thin-walled tubes made of various metal materials, such as stainless steel, alloy steel, titanium alloy, and copper, and has broad application prospects. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a three-dimensional structural diagram of the internal cooling support device according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the side structure of the internal cooling support device according to an embodiment of the present invention.

[0033] Figure 3 for Figure 2 Cross-sectional view at point AA.

[0034] Figure 4This is an exploded structural diagram of the internal cooling support device according to an embodiment of the present invention.

[0035] Figure 5 This is a schematic diagram of the thin-walled tube welding system according to an embodiment of the present invention.

[0036] Explanation of key figure labels: 1. Side plate; 2. Supporting cooling pipe; 3. Assembly; 31. Fixing hole; 4. Gasket; 5. Cooling section; 51. Coolant reservoir; 52. Perforation; 6. Liquid cooling pipe; 61. Liquid cooling inlet pipe; 62. Liquid cooling outlet pipe; 7. First fitting; 8. Second fitting; 9. Motor; 10. Annular micro-gap; 11. Ejector pin; 111. Support body; 112. Insert; 113. External thread; 14. Bracket; 15. Shaft; 16. Rotary wheel. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In this invention, the terms upper, lower, left, right, front, back, top, bottom, inner, outer, middle, vertical, horizontal, transverse, longitudinal, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0039] Furthermore, in addition to indicating location or positional relationships, some of the aforementioned terms may also have other meanings, such as indicating a dependency or connection relationship in certain circumstances. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0040] Furthermore, the terms installation, setting, having, connecting, and linking should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0041] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "multiple" means two or more.

[0042] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings.

[0043] Example 1: Reference Figures 1-4 This embodiment provides a fully functional internal cooling support device, which, from right to left, includes a side plate 1, a supporting cooling pipe 2, an assembly 3, a gasket 4, and a cooling section 5. All components are preferably made of thermally conductive copper or chromium-zirconium copper and are integrally connected by vacuum brazing or electron beam welding to ensure structural strength and sealing. Of course, in other embodiments, the materials and connection methods of the components can be changed to achieve similar effects.

[0044] In this embodiment 1, the side plate 1 is disc-shaped, and its outer diameter is significantly larger than the outer diameter of the supporting cooling pipe 2. For example, when the outer diameter of the supporting cooling pipe 2 is Φ3.0mm, the outer diameter of the side plate 1 can be Φ5.0mm. Its function is to limit the insertion depth and to allow the clamp to hold the plate during withdrawal, preventing slippage. "Significantly larger" should be understood as a degree that prevents the clamp from easily slipping out.

[0045] In this embodiment 1, the supporting cold pipe 2 is a thin-walled, slender pipe, the length of which is determined according to the depth of the pipe to be welded. Its outer diameter is precisely machined according to the inner diameter of the pipe to be welded, ensuring that a 0.2mm annular micro-gap 10 is formed between the two.

[0046] In this embodiment 1, the assembly 3 is welded to the supporting cold pipe 2, and the cooling section 5 is a stepped shaft-shaped component with its small end inserted into the supporting cold pipe 2. A gasket 4 is placed between the assembly 3 and the cooling section 5 to abut against both. In other embodiments, the assembly 3 can also be a stepped shaft-shaped component, with its large end welded to the supporting cold pipe 2 and its small end used to install the cooling section 5. The gasket 4 is fitted onto the small end of the assembly 3 to fine-tune the axial installation position of the cooling section 5 and to assist in sealing.

[0047] In this embodiment 1, the cooling section 5 is the core of the device. Its external outline is consistent with that of the supporting cooling pipe 2. An internal coolant receiving cavity 51 is machined, such as... Figure 3As shown, the cross-section of the cavity is a fan-shaped ring with a central angle of approximately 300 degrees. Its outer wall is tightly attached to the outer shell of the cooling section 5, thus separating it from the pipe wall to be welded by only a thin wall layer, maximizing the heat exchange area. A perforation 52 is provided in the center of the cooling section 5. The liquid cooling pipe 6 consists of parallel liquid cooling inlet pipes 61 and liquid cooling outlet pipes 62, which enter from one side of the side plate 1, pass through the interior of the supporting cooling pipe 2, and finally communicate with the coolant receiving cavity 51.

[0048] The welding method is as follows: Preparation: Place the first fitting 7 onto the external support; in this embodiment 1, the external support is the ejector pin 11. Place the second fitting 8 onto the supporting cold pipe 2 of this internal cooling support device. Connect the device to the external cooling circulation system.

[0049] Assembly alignment: The moving device and / or ejector pin 11 bring the end faces of the first tube 7 and the second tube 8 into tight contact, with the joint precisely centered on the cooling section 5. At this point, the end of the ejector pin 11 passes through the perforation 52 of the cooling section 5 and is fixed to the center of the assembly 3. A uniform 0.2mm annular micro-gap 10 is formed between the entire device and the inner walls of the two tubes.

[0050] Welding: Initiate coolant circulation. Perform argon arc welding on the butt joint from the outside using welding torch 12. The high temperature generated during welding is efficiently carried away by the internal cooling section 5 through the micro-gap 10, preventing excessive melting of the pipe wall.

[0051] Removal: After welding is complete, stop welding and allow cooling. Once the temperature has dropped slightly, the entire internal cooling support device can be easily pulled axially out of the welded pipe. Because the 0.2mm micro-gap allows space for thermal expansion, the device will not get stuck.

[0052] The chain of beneficial effects of this embodiment: The fan-shaped cavity 51 helps to increase the heat exchange area, thereby improving cooling efficiency, effectively controlling heat input, and thus reducing the amount of molten metal at the source and suppressing the formation of ridges.

[0053] The 0.2mm annular micro-gap 10 provides limited support to prevent collapse, while also reserving space to prevent jamming, achieving the beneficial effects of high yield and easy removal.

[0054] Side plate 1 provides reliable clamping points, which facilitates operation and prevents workplace injuries and product damage.

[0055] Modular design, namely component 3 and gasket 4, can reduce processing difficulty, facilitate maintenance, reduce costs, and improve economy.

[0056] Example 2: This embodiment is a simplification based on embodiment 1, omitting side plate 1.

[0057] In this device, one end of the supporting cooling tube 2 serves directly as the clamping end. To facilitate clamping, this end can be knurled or machined into a flat surface. External clamps, such as precision chucks, directly clamp the outer wall of the supporting cooling tube 2 for operation.

[0058] Its advantages include a simpler structure and further reduced manufacturing costs. It is suitable for applications where cost is extremely sensitive and the operating space allows for precision clamps to directly hold and support the cold pipe.

[0059] Example 3: This embodiment provides a more streamlined, integrated structure based on implementation 1 or 2.

[0060] The device is directly welded together from the supporting cooling pipe 2 and the cooling section 5, omitting the assembly 3 and gasket 4. The coolant receiving cavity 51 inside the cooling section 5 can be directly formed by precision machining or powder metallurgy. The liquid cooling pipe 6 is also integrated inside. In this embodiment 3, the end of the ejector pin 11 can be directly fixed and abutted against the through hole 52 of the cooling section 5.

[0061] Its advantages include an extremely compact structure, a minimal number of parts, and theoretically superior connection strength and sealing. It is suitable for miniaturized, mass-produced products. The disadvantages are that individual parts are complex to manufacture, and if a part is damaged, the entire product must be replaced.

[0062] Example 4: See Figure 5 As shown, this embodiment 4 describes a welding system and a final product using any of the above-described devices.

[0063] The welding system includes a welding torch (not shown), a power supply (not shown), a cooling circulation unit (not shown), an external support 11, and the internal cooling support device described in this invention.

[0064] The first pipe fitting 7 and the second pipe fitting 8, welded using this system, have smooth and flat weld seams with rounded transitions and no internal ribs. Metallographic analysis shows that the weld structure is a normal austenite plus a small amount of ferrite (for stainless steel) weld solidification structure, with no hardened martensite present.

[0065] The comparative results do not employ the method of this invention. Conventional argon arc welding was used, without internal support and water cooling, or with internal support having excessively large gaps. The experimental results showed that obvious internal bulges 13 formed inside the weld, severely affecting the pipe's diameter and fluid performance.

[0066] Example 5: See Figure 5As shown, an embodiment provides a thin-walled tube welding assembly. The assembly includes a first tube 7 to be welded, a second tube 8, and an internal cooling support device according to any one of claims 1-6 inserted therein. The first tube 7 and the second tube 8 have a wall thickness of 0.2 mm and an inner diameter of Φ3.2 mm. The outer diameter of the supporting cold pipe 2 and the cooling section 5 of the internal cooling support device are both Φ3.0 mm. When the device is inserted into the tube, a uniformly sized annular micro-gap 10 with a width of 0.2 mm is naturally formed between the outer wall of the device and the inner wall of the tube. This micro-gap 10 persists throughout the entire area to be welded (especially around the cooling section 5).

[0067] The cooling section 5 is precisely located below the joint between the first pipe 7 and the second pipe 8. The external support 11 can pass through the perforation 52 in the center of the cooling section 5 and press against the end of the first pipe 7 from the inside to ensure precise connection between the two pipes.

[0068] The beneficial effect of this component is that it creates an optimal physical environment before welding begins. A 0.2mm annular micro-gap 10 is pre-built into the system, ensuring the necessary support and anti-jamming functions during welding. This component clearly defines the product's state before welding, providing a clear basis for quality control.

[0069] Example 6: See Figure 5 As shown, this embodiment demonstrates a complete automated welding system, which includes a moving component and a fixed component. The moving component consists of a first pipe fitting 7 and an internal cooling support device pre-inserted inside it. The moving component is mounted on a linear module (not shown) and is driven by a stepper motor 10 for precise axial feed. The fixed component includes a bracket 14, with a pin 11 rotatably connected to the bracket 14 via a shaft 15. A roller 16 is mounted on the right end of the pin 11, and a support body 111 is mounted on the left end for fitting and supporting the end of a second pipe fitting 8. An insert 112 extends forward from the support body 111. The root of the insert 112 is cylindrical, and the end is machined with an external thread 113. An assembly 3 is fixed to the end of the internal cooling support device. An internal threaded hole, i.e., a fixing hole 31, is machined in the center of the assembly 3 to match the external thread 113.

[0070] The welding process is as follows: Initialization: The moving component is in the initial position on the right end. The second tube 8 is fitted onto the support body 111 of the ejector pin 11.

[0071] Feeding and docking: Stepper motor 10 drives the moving component to move to the left, so that the supporting cold pipe 2 and the cooling section 5 are gradually inserted into the second pipe 8 until the end face of the first pipe 7 contacts the end face of the second pipe 8.

[0072] Coaxial Locking: The operator (or via motor 10) slowly rotates the wheel 16, causing the ejector pin 11 to rotate. The external thread 113 of the insert 112 at the front end of the ejector pin 11 begins to screw into the internal threaded hole of the fitting 3. As it screws in, the internal cooling support device is gently tightened and automatically adjusts to a horizontal state coaxial with the ejector pin 11, using its connection point with the ejector pin 11 as a reference. Since the ejector pin 11 itself is precisely fixed by the bracket 14, perfect coaxial alignment of the first fitting 7 and the second fitting 8 is ensured.

[0073] Welding: Start the coolant circulation and welding torch 12 to begin welding. Throughout the welding process, the position of the internal cooling support device is firmly locked, ensuring the stability of the 0.2mm annular micro-gap.

[0074] Exit: After welding is completed, rotate wheel 16 in the opposite direction to separate ejector pin 11 from internal cooling support device. Stepper motor 10 drives moving component to the right, removing internal cooling support device from the welded pipe fitting.

[0075] Example 7: The difference between this embodiment and embodiment 6 lies in the connection method. The insert 112 at the front end of the ejector pin 11 is designed as a conical structure. Correspondingly, the fixing hole 31 of the end fitting 3 of the internal cooling support device is also machined into a matching circular hole. During docking, no rotation is required; the feed amount of the moving component is precisely controlled by the stepper motor 10 to press the conical insert into the circular hole. Utilizing the self-centering property of the conical surface, precise coaxial positioning and fixation of the internal cooling support device and the ejector pin 11 are achieved. During withdrawal, the conical surface can be separated simply by pulling back the moving component with a certain force.

[0076] The beneficial effects of this embodiment are as follows: Automation and high precision: Through motor 10 drive and precision mechanical connection (thread or tapered surface), automatic centering and welding of pipe fittings are achieved, ensuring product consistency and high quality, and making it suitable for mass production.

[0077] Easy to operate: It transforms complex coaxiality adjustment into simple rotary or linear feed actions, reducing the skill requirements for operators.

[0078] Enhanced system rigidity: The internal cooling support device is integrated with the ejector pin during welding, forming a stable internal support frame that effectively suppresses any minor vibrations or displacements during the welding process, further improving welding quality.

[0079] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A method of water-cooled welding of the inner wall of an ultrathin-walled pipe, characterized in that, The method comprises the following steps: a moving component is provided, which comprises a first pipe (7) and an internal cooling support device inserted into the first pipe (7), the internal cooling support device comprises a support cooling pipe (2) and a cooling section (5), and the cooling section (5) is internally provided with a cooling liquid containing cavity (51); a fixed component is provided, which comprises a second pipe (8) rotationally connected by a support (14), and the second pipe (8) is sleeved on a support body (111) of a thimble (11); the moving component is driven to move towards the fixed component, so that the cooling section (5) and part of the support cooling pipe (2) of the internal cooling support device are inserted into the second pipe (8), and the end faces of the first pipe (7) and the second pipe (8) are abutted; wherein, after the moving component and the fixed component are abutted, the horizontal and coaxial positioning of the internal cooling support device is realized through the connection and cooperation between the thimble (11) and the end of the internal cooling support device; wherein, the outer wall of the support cooling pipe (2) and the cooling section (5) and the inner wall of the first pipe (7) and the second pipe (8) form a radial annular micro gap (10); the abutted joint of the first pipe (7) and the second pipe (8) is welded from the outside, and during the welding process, the cooling medium flows in the cooling liquid containing cavity (51) to indirectly cool the welding area; after the welding is completed, the connection between the thimble (11) and the internal cooling support device is released, and the moving component is removed from the pipe formed by welding.

2. The method of water-cooled welding of the inner wall of an ultrathin- walled pipe according to claim 1, characterized in that, The connection and cooperation between the thimble (11) and the end of the internal cooling support device are as follows: the thimble (11) comprises an insertion piece (112) extending forward, the end of the internal cooling support device is provided with an assembly piece (3), and the assembly piece (3) is centrally provided with a fixing hole (31); the insertion piece (112) and the fixing hole (31) are detachably fixedly connected by relatively rotating the thimble (11) and the internal cooling support device.

3. The method of water-cooled welding of the inner wall of an ultrathin- walled pipe according to claim 2, characterized in that, The outer surface of the insertion piece (112) is provided with external threads, the fixing hole (31) is an internal thread hole matched with the external threads, and the fixed connection is realized by screwing.

4. The method of water-cooled welding of the inner wall of an ultrathin- walled pipe according to claim 2, characterized in that, The insertion piece (112) is a conical structure, the fixing hole (31) is a conical hole matched with the conical structure, and the fixed connection is realized by conical interference fit.

5. The method of water-cooled welding of the inner wall of an ultrathin- walled pipe according to claim 1, characterized in that, The size range of the annular micro gap (10) is 0.15mm to 0.25mm.

6. The method of water-cooled welding of the inner wall of an ultrathin- walled pipe according to claim 1, characterized in that, The cross-sectional shape of the cooling liquid containing cavity (51) is a fan ring type with a central angle greater than or equal to 270 degrees.

7. An internal cooling support device for use in the method of internal water cooling of the inner wall of an ultrathin-walled pipe according to any one of claims 1 to 7, characterized in that, The method comprises: a support cooling pipe (2); a cooling section (5) provided at one end of the support cooling pipe (2), which is internally provided with a cooling liquid containing cavity (51), and the central part of the cooling section (5) is provided with a perforation (52); a liquid cooling pipe (6) comprising an inlet pipe and an outlet pipe, which is in communication with the cooling liquid containing cavity (51).

8. The internal cooling support device of claim 7, wherein, Further comprising an assembling part (3) arranged at one end of the support cold pipe (2) away from the cooling section (5), a fixing hole (31) is arranged in the center of the assembling part (3) for detachable fixed connection with the insert (112) of the external thimble (11), the fixing hole (31) is an internal thread hole or a round hole.

9. The internal cooling support device of claim 8, wherein, Further comprising a side plate (1) fixed at the end of the support cold pipe (2) and located at the rear side of the assembling part (3), the outer diameter of the side plate (1) is greater than the outer diameter of the support cold pipe (2).

10. The internal cooling support device of claim 9, wherein, Further comprising a gasket (4) arranged between the assembling part (3) and the cooling section (5).

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