An ultra-long pipe vacuum laser welding device and welding method

Abstract

The present application relates to the technical field of laser welding, and particularly relates to a vacuum laser welding device and method for super-long pipe fittings, which comprises a vacuum welding cavity, a bellows, a distal end sealing assembly and a laser welding system; the side wall of the vacuum welding cavity is provided with an opening for the pipe fitting to pass through, one end of the bellows is sealingly connected with the opening, and the other end is sealingly connected with the distal end sealing assembly, and a vacuum passage for the pipe fitting to pass through and having an axial extension amount is formed in the bellows; the sealing member of the distal end sealing assembly seals the outer wall of the pipe fitting and allows axial displacement thereof; the first clamping member and the second clamping member are respectively arranged in the cavity and the distal end sealing assembly to clamp the two ends of the pipe fitting; the present application covers only the welding area with the vacuum cavity, and the super-long pipe fitting does not need to be accommodated as a whole, thereby solving the problems of limited size of the existing vacuum chamber, difficulty in welding of the super-long pipe fitting and poor positioning precision of single-end clamping, and reducing the equipment cost and time consumption for vacuumizing.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, specifically to a vacuum laser welding device and welding method for ultra-long pipes. Background Technology

[0002] Molybdenum and its alloys possess high melting points, high strength, and good thermal and electrical conductivity, making them commonly used in nuclear energy, shipbuilding, aerospace, and other fields to manufacture critical components such as cooling pipes. However, molybdenum has a high ductile-brittle transition temperature, poor weldability, and the molybdenum matrix is ​​mostly produced by powder metallurgy, which makes it more prone to retaining impurities and gases compared to smelting metallurgy. Furthermore, molybdenum reacts with oxygen at high temperatures to form molybdenum oxide, which can cause cracking and brittle fracture of welded joints, posing a failure risk in critical applications.

[0003] To obtain low-defect molybdenum pipe joints, the industry has successively adopted methods such as brazing, diffusion welding, electron beam welding, and laser welding to join molybdenum and its alloys. Among these, vacuum laser welding stands out due to its ultra-high energy density (10⁻⁶ ppm). 6 ~10 7 With W / cm² and a vacuum environment, welds with small heat-affected zones, low heat input, high aspect ratio, and no oxidation, porosity, or cracks can be achieved, resulting in minimal deformation. This process is considered one of the more reliable methods for precision connection of molybdenum tubes.

[0004] However, most existing vacuum laser welding equipment uses a large-volume, integrated vacuum chamber, which requires the entire workpiece to be enclosed within the chamber. When the length of the pipe to be welded reaches 2m to 4m, the effective internal length of a standard vacuum chamber is insufficient to accommodate workpieces of such size, making direct welding difficult. Customizing an ultra-large volume vacuum chamber would significantly increase the cost of chamber manufacturing, and the vacuuming time would often exceed 30 minutes, resulting in low operational efficiency. Large chambers are also prone to deformation under negative pressure, making subsequent maintenance difficult. Furthermore, clamping and positioning ultra-long workpieces in a confined, large space is also quite challenging. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, the present invention provides a vacuum laser welding device and welding method for ultra-long pipes, which realizes vacuum laser welding of ultra-long pipes of 2m to 4m without significantly increasing the volume of the vacuum chamber.

[0006] This invention is achieved through the following technical solution:

[0007] A vacuum laser welding device for ultra-long pipe fittings includes: a vacuum welding chamber, a bellows, a remote sealing assembly, and a laser welding system;

[0008] The vacuum welding chamber is provided with a laser incident window and a vacuum interface, and the side wall of the vacuum welding chamber is provided with an opening for the pipe fitting to pass through;

[0009] One end of the bellows is sealed to the opening, and the other end of the bellows is sealed to the distal sealing assembly. A vacuum channel for the pipe fitting to pass through is formed inside the bellows, and the bellows has an axial expansion and contraction amount.

[0010] The distal sealing assembly is provided with a sealing element that seals the outer wall of the pipe passing through the distal sealing assembly and allows the pipe to move axially.

[0011] The vacuum welding cavity is provided with a first clamping member, and the distal sealing assembly is provided with a second clamping member. The first clamping member and the second clamping member respectively clamp the two ends of the pipe.

[0012] The laser welding system emits light towards the welding area inside the vacuum welding chamber.

[0013] Optionally, the distal sealing assembly further includes a clamping member, the sealing member being a combined sealing member, the clamping member being disposed on the outside of the distal sealing assembly and pressing the combined sealing member axially, so that the combined sealing member grips the outer wall of the pipe.

[0014] Optionally, the corrugated pipe is a metal corrugated pipe, and the first clamping member and the second clamping member are both four-jaw chucks. The two four-jaw chucks are arranged axially along the pipe to clamp the two ends of the pipe coaxially.

[0015] Optionally, it also includes a support base located below the distal sealing assembly, the support base supporting the distal sealing assembly, the bellows and fittings, and maintaining the coaxiality of the distal sealing assembly with the vacuum welding cavity.

[0016] Optionally, a vacuum flange is fixedly provided at the opening, the bellows is sealed to the opening via the vacuum flange, and the vacuum flange is welded to the vacuum welding cavity.

[0017] Optionally, it also includes a plug and a stress relief ring, wherein the plug is fitted to one end of the pipe fitting that extends into the vacuum welding cavity and is held by the first clamping member, and the stress relief ring is disposed at the weld joint between the pipe fitting and the plug.

[0018] Optionally, it also includes an external follower support rail (16) and a slider (7). The external follower support rail (16) is arranged parallel to the bellows (5). The slider (7) is slidably engaged with the external follower support rail (16). The distal sealing assembly (6) is mounted on the slider (7) and can slide along the external follower support rail (16) via the slider (7) as the pipe (13) undergoes axial thermal expansion.

[0019] A vacuum laser welding method for ultra-long tubular fittings, based on the ultra-long tubular fitting vacuum laser welding apparatus described above, the method comprising the following steps:

[0020] One end of the pipe fitting is inserted into the vacuum welding chamber and clamped by the first clamping element;

[0021] After the other end of the pipe is passed through the corrugated pipe and the distal sealing assembly in sequence, it is clamped by the second clamping member, and the distal sealing assembly seals the outer wall of the pipe.

[0022] The vacuum welding cavity and the vacuum channel inside the bellows are evacuated to a preset vacuum level.

[0023] The laser welding system is activated so that the focused laser beam acts on the welding area of ​​the tube inside the vacuum welding chamber, and the tube rotates around its own axis to perform circumferential weld welding.

[0024] After welding, the pipe fitting is cooled in a vacuum environment, then restored to normal pressure and removed.

[0025] Optionally, the vacuuming process includes: first, using a mechanical pump to roughly pump the vacuum channel, and then using a molecular pump to finely pump it to a vacuum level of no more than 1×10⁻³Pa, and then maintaining the pressure after reaching the preset vacuum level.

[0026] Optionally, a preheating step is further included before welding the circumferential weld, wherein the laser power of the preheating step is 0.3kW to 3kW and the welding speed is 0.5m / min to 2m / min;

[0027] The laser power for welding the circumferential weld is 0.5kW to 6kW, and the welding speed is 0.5m / min to 2m / min.

[0028] Optionally, before inserting the pipe fitting into the vacuum welding chamber, a plug and a stress relief ring are first assembled on the end of the pipe fitting to be welded and then tack welded.

[0029] After welding, the pipe fitting is allowed to cool in a vacuum environment for 5 to 10 minutes.

[0030] This invention utilizes a vacuum welding cavity, a bellows, and a remote sealing structure to enable ultra-long pipe fittings to complete circumferential welds in a high-vacuum environment without the need to place the entire pipe fitting inside the vacuum cavity. Compared with existing technologies, the vacuum welding cavity only needs to cover the welding area of ​​the pipe fitting, without accommodating the entire pipe fitting. This reduces the processing cost of the cavity and the time required for vacuuming, and avoids the deformation problem of large-volume cavities under negative pressure. Attached Figure Description

[0031] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0032] Figure 1 This is a schematic diagram of the structure of the vacuum laser welding device for ultra-long pipes according to the present invention.

[0033] Figure 2 This is a schematic diagram of the plug structure according to the present invention;

[0034] Figure 3 This is a schematic diagram of the stress relief ring according to the present invention;

[0035] Figure 4 This is a schematic diagram of the assembly structure of the welding specimen provided in an embodiment of the present invention.

[0036] Reference numerals: 1-Vacuum welding cavity; 2-Laser incident window; 3-Vacuum interface; 4-Opening; 5-Bellower; 6-Remote sealing assembly; 7-Linear guide rail slider; 8-First clamping component; 9-Second clamping component; 10-Support base; 11-Vacuum flange; 12-Laser head; 13-Pipe fitting; 14-Plug; 15-Stress relief ring; 16-External follow-up support guide rail. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0039] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] In this article, the extra-long pipe fitting 13 refers to a pipe fitting 13 whose axial length exceeds the effective length of the vacuum welding cavity 1. Its length is usually 2m to 4m, for example, it can be 2m, 3m, or 4m; the material of the pipe fitting 13 can be molybdenum or molybdenum alloy.

[0042] This embodiment provides a vacuum laser welding device for an ultra-long pipe fitting 13. The device has a coaxial layout extending on one side, and its core operating unit is a vacuum welding chamber 1 that only covers the welding area, without needing to accommodate the ultra-long pipe fitting 13 as a whole. Figure 1 As shown, the device includes a vacuum welding chamber 1, a bellows 5, a remote sealing assembly 6, and a laser welding system.

[0043] The vacuum welding chamber 1 provides a sealed, high-vacuum space for welding operations. It employs a rigid, thick-walled 316L stainless steel sealing structure to prevent oxidation of the pipe fitting 13 during high-temperature welding. The vacuum welding chamber 1 is equipped with a laser incident window 2 and a vacuum interface 3. The laser incident window 2, located at the top of the vacuum welding chamber 1, is made of high-transparency quartz glass and is airtightly installed to the chamber body via a sealing ring, allowing the laser beam to penetrate without loss while maintaining vacuum stability within the chamber.

[0044] Vacuum interface 3 is located at the bottom of vacuum welding cavity 1 and serves as a connection port for the vacuum unit. It is directly connected to the vacuum unit through a vacuum pipeline to achieve rapid vacuuming and vacuum maintenance of the cavity.

[0045] The side wall of the vacuum welding chamber 1 has an opening 4 for the pipe fitting 13 to pass through. The pipe fitting 13 extends into the interior of the chamber through the opening 4, so that its welding area is located in the high vacuum space provided by the chamber. One end of the bellows 5 is sealed to the opening 4, and the other end is sealed to the distal sealing assembly 6. The interior of the bellows 5 forms a vacuum channel for the pipe fitting 13 to pass through, and this vacuum channel communicates with the internal space of the vacuum welding chamber 1.

[0046] The bellows 5 has an axial expansion and contraction amount, so that when the fitting 13 is heated and elongates axially during the welding process, the bellows 5 can expand and contract accordingly, absorbing the thermal deformation of the fitting 13 without damaging the vacuum seal.

[0047] The distal sealing assembly 6 serves as the sealing terminal at the distal end of the vacuum channel. It is equipped with a sealing element that seals the outer wall of the pipe 13 passing through the distal sealing assembly 6 and allows the pipe 13 to move axially. While maintaining the airtightness of the vacuum channel, the distal sealing assembly 6 does not restrict the slight axial movement of the pipe 13 during welding.

[0048] The vacuum welding chamber 1 is equipped with a first clamping member 8, and the distal sealing assembly 6 is equipped with a second clamping member 9. The first clamping member 8 faces the welding area and is used to clamp one end of the pipe fitting 13 that extends into the chamber; the second clamping member 9 is used to clamp the end of the pipe fitting 13 that protrudes from the distal sealing assembly 6. The first clamping member 8 and the second clamping member 9 clamp the two ends of the pipe fitting 13 respectively, forming a simultaneous clamping at both ends, so that the pipe fitting 13 remains stable throughout the welding process and avoids the shaking and misalignment caused by single-end cantilever clamping.

[0049] The laser welding system emits light towards the welding area inside the vacuum welding chamber 1. The emitted laser beam enters the chamber through the laser incident window 2 and is focused on the circumferential weld of the pipe fitting 13 to achieve deep penetration welding. The energy output of the laser welding system is adapted to the high melting point characteristics of molybdenum material, resulting in a small heat-affected zone, which helps to reduce welding stress and suppress weld cracks and porosity.

[0050] The laser welding system is the energy input unit of the device. It is adapted to the high melting point welding characteristics of molybdenum and can achieve stable deep penetration welding of circumferential welds. The core components include the laser head 12 and the laser generator. The laser head 12 is installed at the top of the vacuum chamber and can be adjusted up and down. The light outlet is directly facing the circumferential weld position in the chamber. It is equipped with a focusing lens inside, which can accurately focus the laser beam to the welding joint, ensuring uniform weld penetration and regular weld formation. The laser generator uses a fiber laser with an output power range of 500~6000W. It has stable energy output and a small welding heat-affected zone, which can effectively reduce the welding stress of molybdenum tubes and avoid defects such as cracks and porosity in the weld, perfectly matching the high-precision welding requirements of ultra-long molybdenum tubes.

[0051] In this embodiment, the vacuum welding chamber 1 only covers the welding area. Combined with the through-type vacuum channel formed by the corrugated pipe 5, the ultra-long pipe 13 does not need to be placed into the vacuum chamber as a whole. Only the welding joint needs to be placed in the chamber to achieve high vacuum welding. The first clamping member 8 and the second clamping member 9 at both ends enable the synchronous coaxial clamping of both ends of the pipe 13, and finally achieve low-cost, high-precision vacuum laser welding of ultra-long pipes 13 from 2m to 4m.

[0052] Example 2

[0053] Based on Example 1, this embodiment further explains the remote sealing, clamping, support, connection, and workpiece matching structure of the device.

[0054] The distal sealing assembly 6 also includes a clamping member, whose sealing element is a combined sealing element. The clamping member is located on the outside of the distal sealing assembly 6 and clamps the combined sealing element axially, causing the combined sealing element to grip the outer wall of the pipe fitting 13, thereby achieving a dynamic seal on the outer wall of the pipe fitting 13. In this embodiment, the clamping member can be a clamping bolt, and the degree of compaction of the combined sealing element can be adjusted by turning the clamping bolt, allowing slight axial movement of the pipe fitting 13 while ensuring a seal.

[0055] The bellows 5 is a metal bellows 5. In a specific example, the metal bellows 5 is a large-diameter 316L stainless steel bellows 5, with an inner diameter 20~50mm larger than the outer diameter of the molybdenum tube, an axial length of 2~3m, and an axial expansion and contraction of ≥15mm and radial flexibility, which can adapt to the thermal expansion and deformation during the welding of the molybdenum tube, without damaging the vacuum seal.

[0056] Both the first clamping member 8 and the second clamping member 9 are four-jaw chucks. The two four-jaw chucks are aligned along the axial direction of the pipe fitting 13, so that the two ends of the pipe fitting 13 are coaxially clamped. With the help of the four-jaw chucks at both ends, the coaxiality of the pipe fitting 13 can be detected and calibrated at multiple points along the axial direction of the pipe fitting 13, so as to avoid weld misalignment and uneven penetration during welding.

[0057] In this embodiment, both the first clamping member 8 and the second clamping member 9 are rotatable four-jaw chucks. At least one four-jaw chuck is connected to a rotary drive mechanism, which drives it to rotate around the axis of the pipe fitting 13. Since the pipe fitting 13 and the plug 14 have been connected as a whole welding specimen by tack welding before welding, when the rotary drive mechanism drives one of the four-jaw chucks to rotate, it can drive the entire welding specimen to rotate around the axis of the pipe fitting 13. The other four-jaw chuck rotates synchronously and also serves as a rotation support. The synchronous rotation of the two four-jaw chucks can prevent the pipe fitting 13 from being twisted during rotation. The pipe fitting 13 passes through the opening 4, the vacuum flange 11, and the inner cavity of the bellows 5 with clearance fit. The bellows 5 does not rotate with the pipe fitting 13, and the pipe fitting 13 rotates freely in the inner cavity of the bellows 5.

[0058] Accordingly, the combined seal of the distal sealing assembly 6 is a dynamic seal. While being pressed and held tightly against the outer wall of the pipe fitting 13 by the clamping member, it allows the pipe fitting 13 to move axially and rotate around its own axis. Thus, throughout the entire process of rotating the pipe fitting 13 to perform circumferential weld welding, the combined seal maintains a seal on the outer wall of the pipe fitting 13, thus maintaining the airtightness of the vacuum channel.

[0059] like Figure 1 As shown, the device also includes a support base 10, an external follow-up support rail 16, and a slider 7. The support base 10 is located below the distal sealing assembly 6, supports the distal sealing assembly 6, the bellows 5, and the fitting 13, limits the radial offset of the distal sealing assembly 6, maintains its coaxiality with the vacuum welding cavity 1, and prevents the bellows 5 from bending due to its own weight or workpiece load.

[0060] An external follower support rail 16 is mounted parallel to the bellows 5 on an external rigid bracket on one side of the vacuum welding chamber 1. A slider 7 slides in conjunction with the external follower support rail 16, and the distal sealing assembly 6 is mounted on the slider 7. The external follower support rail 16 supports the weight of the distal sealing assembly 6, the bellows 5, and the pipe fitting 13 via the slider 7, limiting the radial offset of the distal sealing assembly 6, overcoming the deflection caused by the weight of the extra-long pipe fitting 13, maintaining the coaxiality of the distal sealing assembly 6 and the vacuum welding chamber 1, and preventing the bellows 5 from bending due to its own weight or workpiece load.

[0061] During welding, the pipe fitting 13 undergoes axial elongation due to heat. This axial elongation is converted by the second clamping member 9 into the sliding motion of the distal sealing assembly 6 along with the slider 7 along the external follower support rail 16. Consequently, the bellows 5 undergoes slight elastic expansion and contraction. In this way, the axial thermal deformation of the pipe fitting 13 is absorbed by the follower sliding motion of the external follower support rail 16 and the elastic expansion and contraction of the bellows 5, which maintains the airtightness of the vacuum channel and releases the axial thermal stress of the pipe fitting 13, preventing buckling deformation or weld tearing of the pipe fitting 13 under the constraint of both ends.

[0062] In a specific example, the distal sealing assembly 6 includes a removable sealing blind plate. The distal end of the bellows 5 is sealed by the sealing blind plate. The second clamping member 9 is located inside the sealing blind plate and slides along the external follow-up support rail 16 together with the slider 7. By adjusting the position of the slider 7 along the external follow-up support rail 16, the sealing blind plate is made to fit the distal end of the bellows 5 and the bellows 5 is in an appropriate extension and contraction state. This can adapt to different pipe fittings 13 with lengths from 2m to 4m, while reducing the excess volume of the vacuum channel and shortening the vacuuming time.

[0063] As a specific implementation, the first clamping member 8 is an active rotating clamping member and is connected to the rotary drive mechanism for transmission. It serves as the power source for the rotation of the pipe fitting 13 and the welding positioning reference. For example, an active rotating centering chuck or a four-jaw chuck can be used. The second clamping member 9 is a driven clamping member. It rotates with the pipe fitting 13 and also serves as a rotary support. The second clamping member 9 can be a driven chuck or can be replaced by a center 19. The center 19 passively holds the end of the pipe fitting 13 to adapt to different forms of the end of the pipe fitting 13.

[0064] A vacuum flange 11 is fixed at the opening 4 of the vacuum welding chamber 1. The bellows 5 is sealed to the opening 4 via the vacuum flange 11, and the vacuum flange 11 is welded to the vacuum welding chamber 1. In a specific example, the vacuum flange 11 can be a standard KF50~KF100 vacuum flange 11, made of 316L stainless steel, with a precision polished sealing surface. It is quickly and securely assembled with the metal bellows 5 using a standard clamp and a fluororubber gasket. The weld seam is sealed to prevent vacuum leakage at the flange connection.

[0065] like Figures 2 to 4 As shown, the device also includes a plug 14 and a stress-relief ring 15. The plug 14 is fitted to the end of the pipe fitting 13 that extends into the vacuum welding chamber 1 and is held by the first clamping member 8, used to seal the end of the pipe fitting 13 and ensure the positioning accuracy of the weld joint. The stress-relief ring 15 is located at the weld joint between the pipe fitting 13 and the plug 14, used to alleviate stress concentration in the weld fusion zone and reduce the risk of cold cracking. In a specific example, the stress-relief ring 15 can be a titanium ring.

[0066] Example 3

[0067] This embodiment provides a vacuum laser welding method for ultra-long pipe fittings 13, which is implemented based on the vacuum laser welding apparatus for ultra-long pipe fittings 13 in Embodiments 1 and 2, and includes the following steps:

[0068] First, clamp the components.

[0069] One end of the pipe fitting 13 is inserted into the vacuum welding chamber 1 and clamped and fixed by the first clamping member 8 inside the chamber; the other end of the pipe fitting 13 is passed through the corrugated pipe 5 and the distal sealing assembly 6 located at the far end of the corrugated pipe 5 in sequence along the axial direction, extending to the outside of the vacuum welding chamber 1, and then clamped and fixed by the second clamping member 9 on the distal sealing assembly 6, and the distal sealing assembly 6 seals the outer wall of the pipe fitting 13.

[0070] During the clamping process, the coaxiality is checked and calibrated at multiple points along the axis of the molybdenum tube using a dial indicator to ensure that the coaxiality error is ≤0.05mm, thus avoiding problems such as weld offset and uneven penetration during welding.

[0071] Then a vacuum is drawn.

[0072] The vacuum channel inside the vacuum welding chamber 1 and the bellows 5 is evacuated to the preset vacuum level. First, a mechanical pump is used to perform a rough evacuation of the vacuum channel, quickly expelling most of the air from the vacuum welding chamber 1 and the vacuum channel. After the vacuum level has initially stabilized, a molecular pump is used for a fine evacuation, gradually reducing the vacuum level to no more than 1 × 10⁻³ Pa. Once the preset vacuum level is reached, the evacuation valve is closed, and the pressure is maintained while monitoring changes in the vacuum level in real time. If a drop in vacuum or unstable pressure occurs, the operation is stopped, and any leaks are investigated. After repair, the vacuum is re-evacuated and the pressure is maintained until the process requirements are met.

[0073] Welding is performed after vacuuming is completed.

[0074] Start the laser welding system so that the focused laser beam acts on the welding area of ​​the tube 13 inside the vacuum welding cavity 1 through the laser incident window 2.

[0075] During welding, the laser head 12 remains in a fixed position, and the first clamping member 8 and the second clamping member 9 are rotated synchronously by the rotary drive mechanism, thereby driving the pipe 13 clamped at both ends together with the plug 14 to rotate at a constant speed around its own axis; for each rotation of the pipe 13, the laser beam completes a deep penetration weld along its circumferential weld.

[0076] During this process, the combined seal of the distal sealing assembly 6 continues to maintain a seal as the pipe 13 rotates, while the bellows 5 expands and contracts axially as the pipe 13 expands due to heat, and the two together maintain the airtightness of the vacuum channel.

[0077] The first clamping member 8 actively drives the pipe 13 to rotate, and the second clamping member 9 rotates accordingly. When the pipe 13 elongates axially due to heat, the distal sealing assembly 6, together with the second clamping member 9, slides along the external follow-up support rail 16 with the slider 7. The bellows 5 then elastically expands and contracts, releasing the axial thermal deformation and thermal stress of the pipe 13 to the external follow-up support rail 16, thus preventing the pipe 13 from buckling or cracking of the weld under the constraint of both ends.

[0078] The vacuum level of the vacuum welding chamber 1 is monitored in real time during the welding process to prevent air from entering the chamber and causing oxidation in the welding area.

[0079] Welding complete.

[0080] Maintain a vacuum environment inside the vacuum welding chamber 1 to allow the pipe 13 to cool under vacuum conditions, avoiding rapid cooling that could cause thermal stress and lead to weld cracking or workpiece deformation. After cooling, slowly restore the pressure to normal. Once the pressure stabilizes, release the first clamp 8 and the second clamp 9, and smoothly remove the pipe 13 to complete the welding.

[0081] Example 4

[0082] This embodiment, based on Embodiment 3, further explains the vacuuming, welding parameters, and pre-welding preparations.

[0083] During machining, the dimensional accuracy of each component is strictly controlled to ensure the proper fit between the plug 14 and the inner wall of the molybdenum tube, and between the titanium ring and the weld joint. During cleaning, a neutral cleaning agent is used to remove oxide scale, oil, and machining impurities from the surfaces of each component. After cleaning, the components are wiped dry with anhydrous ethanol to prevent residual stains from affecting welding quality. After the workpiece is machined and cleaned, a trial assembly is performed. The plug 14, titanium ring, and molybdenum tube are assembled according to design requirements. The fit clearances and dimensional deviations of each component are checked to ensure they meet design standards, and the machined test piece is deemed suitable for subsequent welding. After successful trial assembly, the assembled welding test piece is placed on a laser spot welding machine for tack welding. The tack welds are evenly distributed circumferentially to ensure the test piece does not shift or misalign during subsequent welding.

[0084] A preheating step is included before circumferential welding. The energy input for preheating is slightly lower than that for the actual welding, with a laser power of 0.3kW to 3kW (e.g., 0.3kW, 1.5kW, 3kW) and a welding speed of 0.5m / min to 2m / min (e.g., 0.5m / min, 1m / min, 2m / min). Preheating not only increases the temperature in the welding area and reduces welding stress, but also acts as a reinforcement of the tack weld, further ensuring the stability of the workpiece positioning.

[0085] After preheating, set the formal welding parameters according to the size and material properties of the workpiece. The laser power for circumferential weld welding is 0.5kW to 6kW, for example, 0.5kW, 3kW, and 6kW; the welding speed is 0.5m / min to 2m / min, for example, 0.5m / min, 1m / min, and 2m / min.

[0086] Before inserting the pipe fitting 13 into the vacuum welding chamber 1, a plug 14 and a stress relief ring 15 are first assembled on the end of the pipe fitting 13 to be welded, and tack welding is performed on a laser spot welding machine. The tack welds are evenly distributed along the circumferential direction to ensure that the specimen does not shift or misalign during subsequent welding. After welding, the pipe fitting 13 is allowed to cool in a vacuum environment for 5 to 10 minutes, for example, 5 minutes, 8 minutes, or 10 minutes.

[0087] It should be noted that the specific values ​​given in the above embodiments are examples within the corresponding value range. Those skilled in the art can select appropriate values ​​within the range based on the material, wall thickness and size of the pipe fitting 13.

[0088] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0089] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0090] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A vacuum laser welding device for ultra-long tubular fittings, characterized in that, include: It includes a vacuum welding chamber (1), a bellows (5), a remote sealing assembly (6), and a laser welding system; The vacuum welding cavity (1) is provided with a laser incident window (2) and a vacuum interface (3), and the side wall of the vacuum welding cavity (1) is provided with an opening (4) for the pipe fitting (13) to pass through. One end of the bellows (5) is sealed to the opening (4), and the other end of the bellows (5) is sealed to the distal sealing assembly (6). A vacuum channel for the pipe fitting (13) to pass through is formed inside the bellows (5), and the bellows (5) has an axial expansion and contraction amount. The distal sealing assembly (6) is provided with a seal that seals the outer wall of the pipe (13) passing through the distal sealing assembly (6) and allows the pipe (13) to move axially. The vacuum welding cavity (1) is provided with a first clamping member (8), and the remote sealing assembly (6) is provided with a second clamping member (9). The first clamping member (8) and the second clamping member (9) respectively clamp the two ends of the pipe fitting (13). The laser welding system emits light towards the welding area inside the vacuum welding cavity (1).

2. The vacuum laser welding device for ultra-long tubular fittings according to claim 1, characterized in that, The distal sealing assembly (6) further includes a clamping member. The sealing member is a combined sealing member. The clamping member is located on the outside of the distal sealing assembly (6) and clamps the combined sealing member axially, so that the combined sealing member grips the outer wall of the pipe (13).

3. The vacuum laser welding device for ultra-long tubular fittings according to claim 1, characterized in that, The corrugated pipe (5) is a metal corrugated pipe (5). The first clamping member (8) and the second clamping member (9) are both four-jaw chucks. The two four-jaw chucks are arranged axially along the pipe (13) so that the two ends of the pipe (13) are coaxially clamped. The first clamping member (8) is an active rotary clamping member, and the second clamping member (9) is a driven clamping member.

4. The vacuum laser welding device for ultra-long tubular fittings according to claim 1, characterized in that, It also includes a support base (10) located below the distal sealing assembly (6), the support base (10) supporting the distal sealing assembly (6), the bellows (5) and the fitting (13), and maintaining the coaxiality of the distal sealing assembly (6) and the vacuum welding cavity (1).

5. The vacuum laser welding device for ultra-long tubular fittings according to claim 1, characterized in that, A vacuum flange (11) is fixed at the opening (4), and the bellows (5) is sealed to the opening (4) via the vacuum flange (11). The vacuum flange (11) is welded to the vacuum welding cavity (1).

6. The vacuum laser welding apparatus for ultra-long tubular fittings according to claim 1, characterized in that, It also includes a plug (14) and a stress relief ring (15). The plug (14) is assembled at one end of the pipe (13) that extends into the vacuum welding cavity (1) and is held by the first clamping member (8). The stress relief ring (15) is located at the weld joint between the pipe (13) and the plug (14).

7. The vacuum laser welding apparatus for ultra-long tubular components according to claim 1, characterized in that, It also includes an external follower support rail (16) and a slider (7). The external follower support rail (16) is set parallel to the bellows (5). The slider (7) is slidably engaged with the external follower support rail (16). The distal sealing assembly (6) is mounted on the slider (7) and can slide along the external follower support rail (16) via the slider (7) as the pipe (13) undergoes axial thermal expansion.

8. A vacuum laser welding method for ultra-long tubular fittings, characterized in that, The method, based on the vacuum laser welding apparatus for ultra-long tubular fittings (13) as described in any one of claims 1 to 7, comprises the following steps: One end of the pipe fitting (13) is inserted into the vacuum welding cavity (1) and clamped by the first clamping member (8); After the other end of the pipe fitting (13) is passed through the corrugated pipe (5) and the distal sealing assembly (6) in sequence, it is clamped by the second clamping member (9) and the distal sealing assembly (6) seals the outer wall of the pipe fitting (13); The vacuum channels inside the vacuum welding cavity (1) and the bellows (5) are evacuated to a preset vacuum level; Start the laser welding system so that the focused laser beam acts on the welding area of ​​the pipe (13) inside the vacuum welding cavity (1), and the pipe (13) rotates around its own axis to perform circumferential weld welding; After welding, the fitting (13) is cooled in a vacuum environment, then restored to normal pressure and the fitting (13) is removed.

9. The vacuum laser welding method for ultra-long tubular components according to claim 8, characterized in that, The vacuuming process includes: first, using a mechanical pump to roughly pump the vacuum channel, then using a molecular pump to finely pump it to a vacuum level of no more than 1×10⁻³Pa, and finally maintaining the pressure after reaching the preset vacuum level.

10. The vacuum laser welding method for ultra-long tubular fittings according to claim 8, characterized in that, Before inserting the pipe fitting (13) into the vacuum welding cavity (1), a plug (14) and a stress relief ring (15) are first assembled on the end of the pipe fitting (13) to be welded and then tack welded. After the welding is completed, the pipe fitting (13) is cooled in a vacuum environment for 5 to 10 minutes.

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