A welding fixture and method for a tail structure of a nuclear fusion high-temperature superconducting magnet coil

Abstract

A welding fixture and method for a fusion high-temperature superconducting magnet coil tail structure are disclosed, belonging to the field of manufacturing fusion high-temperature armored superconducting coils. The water-cooled fixture of the welding fixture includes a base and a top cover that cooperate with each other. Both have water flow channels, and there are two adjustable limiting blocks between them. The opposite sides of the two limiting blocks form working surfaces that match the mechanical legs of the tail structure and the shape of the superconducting magnet coil. These two working surfaces, together with the base and the top cover, form a limiting space with openings at both ends. A welding process hole penetrating the limiting space is provided in the middle of the base and the top cover. This invention optimizes the welding fixture to make the tail welding profile controllable, with significant temperature control, avoiding failure of superconducting materials at high temperatures. Furthermore, the combination of the fixture and welding method effectively reduces the deformation of the workpiece surface profile caused by welding, and the formed weld meets the technical requirements both macroscopically and microscopically.

Description

Technical Field

[0001] This invention relates to the field of manufacturing high-temperature armored superconducting coils for nuclear fusion, specifically to a welding fixture and method for the tail structure of a high-temperature superconducting magnet coil for nuclear fusion. Background Technology

[0002] The development of fusion energy is extremely difficult, and superconducting tokamak is currently one of the most promising approaches to achieving fusion energy. Large magnet coils are currently manufactured using armored superconductors.

[0003] As a core component of a fusion device, the high-intensity magnetic field generated by the superconducting coil during operation can stably confine the plasma, ensuring the continuous fusion reaction. Therefore, the quality of the superconducting coil's construction determines whether the nuclear fusion device can operate stably.

[0004] Core superconducting coils, such as those with a central solenoid coil, bear significant circumferential loads at their lead-out ends. These loads can easily damage the insulation to ground at the lead-out root. Therefore, a tail structure is being considered to reliably transfer the circumferential load from the lead-out end to the penultimate turn of the coil. In this structure, the weld between the tail structure and the superconducting coil must be a full-penetration weld, and the weld must withstand a circumferential tensile load of over 48 tons at 77K. Furthermore, the surface temperature of the superconducting cable inside the conductor must not exceed 150°C during the welding process. Summary of the Invention

[0005] To meet the stringent requirements for welding the Tail structure to the superconducting coil, this invention provides a welding fixture and method for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil. By fixing the two mechanical leg components of the Tail structure to the magnet coil using the fixture of this invention and employing a reasonable TIG method, the welding and forming of the high-temperature superconducting magnet coil Tail structure is achieved. Moreover, the superconducting performance of the superconductor is not adversely affected after forming, and the formed weld meets the technical requirements, with minimal deformation of the workpiece after welding.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a welding fixture for a nuclear fusion high-temperature superconducting magnet coil Tail structure. The welding fixture includes at least one water-cooled clamp, which includes a base and a top cover that cooperate with each other. Water flow channels are provided in both the base and the top cover. There are two adjustable limiting blocks between the base and the top cover. The opposite sides of the two limiting blocks respectively form working surfaces that match the mechanical legs of the Tail structure and the shape of the superconducting magnet coil. The two working surfaces and the base and the top cover form a limiting space with openings at both ends. A welding process hole penetrating the limiting space is provided in the middle of the base and the top cover.

[0007] As another optimized solution for the welding fixture of the above-mentioned nuclear fusion high-temperature superconducting magnet coil Tail structure, the water flow channel is U-shaped and distributed around the welding process hole, with its two ends extending out of the base or top cover to form a water flow interface for connection with the external water-cooled circulation unit.

[0008] As another optimized solution for the welding fixture of the above-mentioned nuclear fusion high-temperature superconducting magnet coil Tail structure, the upper surface of the base is provided with a positioning stop that matches the upper cover.

[0009] As another optimized solution for the welding fixture of the above-mentioned nuclear fusion high-temperature superconducting magnet coil Tail structure, the base and the top cover are fixed by a number of fasteners.

[0010] As another optimized solution for the welding fixture of the above-mentioned nuclear fusion high-temperature superconducting magnet coil Tail structure, the fastener passes through the position adjustment hole on the limiting block. The position adjustment hole has an adjustment margin perpendicular to the line connecting the opening of the limiting space, and the position of the limiting block is adjusted by multiple horizontal set screws set on the sides of the two limiting blocks.

[0011] A method for welding the Tail structure of a high-temperature superconducting magnet coil in nuclear fusion includes the following steps: 1) Pull the lead wire of the superconducting magnet coil upward along the direction perpendicular to the winding surface of the superconducting magnet coil to provide working space for welding the Tail structure to the superconducting magnet coil; 2) Install the first mechanical leg of the Tail structure between the lead-out end and the penultimate turn conductor, and compare the outer contour of the Tail structure to ensure that it does not exceed the outer contour of the superconducting magnet coil, and the welding trajectory formed at the splice of the first mechanical leg and the lead-out end is the same as the forming direction of the superconducting magnet coil. 3) A bevel is machined on the surface of the first mechanical leg that contacts the lead wire to form a welding bevel at the joint. The angle of the welding bevel is 28-32° and the length of the blunt edge is 0.4-0.6mm. 4) Fix the first mechanical leg to the wire outlet using spot welding, then install the water-cooled fixture of the above welding tooling, and adjust the position of the limit block so that the installation profile of the first mechanical leg and the wire outlet meets the minimum profile deviation state. 5) Continuously introduce deionized water into the water flow channel of the water-cooled fixture as circulating water; 6) Clean the welding bevel, and then use TIG welding to weld the first mechanical leg and the lead wire into one piece. During welding, intermittent welding operation is used. Before each welding, the weld temperature is checked and welding is carried out only after it is below 50°C. Welding time is also ensured to be no more than 5 seconds. 7) Return the lead wire to its original position, then use the connector to connect the second mechanical leg to the first mechanical leg. After that, splice the second mechanical leg with the second-to-last turn conductor, and compare the outer contour of the entire Tail structure to ensure that it does not exceed the outer contour of the superconducting magnet coil. 8) Following steps 3) to 6), weld the second mechanical leg and the penultimate turn conductor into a single structure, thereby completing the welding of the superconducting magnet coil and the Tail structure.

[0012] As an optimized solution for the above-mentioned welding method of the Tail structure of the nuclear fusion high-temperature superconducting magnet coil, in step 4), the welding current is 85-95A and the arc voltage is 8-15V when spot welding is used for fixing.

[0013] As another optimized solution for the above-mentioned welding method of the Tail structure of the nuclear fusion high-temperature superconducting magnet coil, argon gas is used as the arc protection gas in both the spot welding in step 4) and the TIG welding in step 6), and its flow rate is 8-15L / min.

[0014] As another optimized scheme of the above-mentioned welding method for the Tail structure of the nuclear fusion high-temperature superconducting magnet coil, the specific operation of interrupting the welding in step 6) is to mark the four ends of the two welds between the first mechanical leg and the lead wire as A, B, C and D in a clockwise or counterclockwise direction, and then weld them alternately from the ends of the two welds to the middle in the order of ACDB or ACBD.

[0015] As another optimized solution for the above-mentioned welding method of the Tail structure of the nuclear fusion high-temperature superconducting magnet coil, in step 6), during TIG welding, the filler weld is first used to fill the weld seam, and then the capping weld is used. During the filler weld, the welding current is 90-100A and the arc voltage is 8-15V; during the capping weld, the welding current is 80-90A and the arc voltage is 8-15V.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention achieves forced convection heat transfer in the heat-affected zone of welding by setting water flow channels distributed around the welding process holes in the base and the top cover, and continuously introducing deionized water as a circulating cooling medium during the welding process. This water cooling method can quickly remove the heat generated by welding, effectively control the conduction of welding heat input to the inside of the superconducting coil, and ensure that the surface temperature of the superconducting cable is always below the safety threshold of 150°C during the welding process. This fundamentally avoids the decrease in critical current density and degradation of superconducting performance of high-temperature superconducting materials due to thermal cycling. 2) This invention constructs a limiting space that precisely matches the shape of the workpiece by setting two adjustable limiting blocks between the base and the top cover, and machining working surfaces on the limiting blocks that match the shape of the Tail structure mechanical legs and superconducting magnet coils. This contour-following limiting structure, combined with the position adjustment function of the limiting blocks (achieved through strip holes and horizontal set screws), enables the tooling to adaptively adjust according to the dimensional deviations of different Tail structures, adjusting the installation contour of the mechanical legs and wire outlet to the minimum deviation state, ensuring welding assembly accuracy, and effectively controlling the contour deformation of the workpiece after welding. 3) By limiting the welding bevel angle to 28-32° and the blunt edge length to 0.4-0.6mm, the present invention minimizes the amount of filler metal and welding heat input while ensuring that the welding torch can enter the bottom of the bevel to achieve full penetration. This combination of bevel parameters enables the weld to obtain sufficient penetration and connection strength while effectively controlling the range and maximum temperature of the welding heat-affected zone, thus meeting the stringent mechanical performance requirements of the full penetration structure to bear a circumferential tensile load of more than 48 tons in a 77K environment. 4) This invention employs an intermittent welding operation method, and before each welding operation, the weld temperature is detected and the next welding is carried out only after it is below 50°C. The welding time of each welding operation does not exceed 5 seconds. The welding process is decomposed into multiple tiny heat input pulses. This welding strategy of "small quantity, multiple times, and sufficient cooling", combined with the forced cooling of the water-cooled fixture, ensures that the temperature of the welding heat-affected zone is always under control. This avoids the risk of heat accumulation and superconducting cable temperature exceeding the standard caused by continuous welding, and at the same time effectively reduces welding residual stress and workpiece deformation. 5) This invention marks the four ends of the two welds as A, B, C, and D in a clockwise or counterclockwise order, and then welds them in an alternating sequence from the ends to the middle using ACDB or ACBD. This achieves the alternating and dispersed input of welding heat between the two welds. This staggered welding method avoids the continuous accumulation of heat on the same weld and allows the shrinkage deformation of the two welds to mutually restrict and compensate each other, effectively controlling the contour deformation of the Tail structure after welding and ensuring that the weld does not exceed the dimensional requirements of the outer contour of the superconducting magnet coil after the weld is formed. 6) This invention employs a layered welding strategy of "filling weld first, then capping weld," combined with differentiated current parameter designs for the filling and capping welds. This ensures sufficient penetration and filler metal at the weld root, while the capping weld uses a slightly lower current to guarantee the weld surface's forming quality and aesthetics. This layered welding method not only guarantees the internal quality of the fully penetrated structure but also achieves good surface forming, ensuring that both the macroscopic and microscopic quality of the weld meets the technical requirements. 7) This invention optimizes the water-cooled fixture in the welding tooling, making the welded contour of the Tail controllable and the temperature control effect significant, avoiding failure of superconducting materials at high temperatures. Furthermore, the combination of the welding tooling and welding method of this invention effectively reduces the deformation of the workpiece surface contour caused by welding. The formed weld can meet the technical requirements both macroscopically and microscopically, ensuring the precision forming of high-temperature superconducting coil Tails under superconducting performance conditions. The weld has excellent mechanical properties at extremely low temperatures. Moreover, the welding tooling structure is lightweight, quick to install, and easy to use, making it suitable for the manufacturing of various types of nuclear fusion high-temperature superconducting coil Tails and possessing broad application prospects. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the superconducting coil lead-out end and the Tail structure; Figure 2 A schematic diagram showing the connection between the Tail structure, the lead-out terminal, and the penultimate turn of the conductor; Figure 3 This is a schematic diagram of the welding fixture of the present invention in use; Figure 4 This is a schematic diagram of the external structure of the welding fixture of the present invention; Figure 5 This is a schematic diagram of the internal structure of the welding fixture of the present invention; Figure 6 A schematic diagram showing the welding of the Tail structure to the lead-out end and the penultimate turn of the conductor; Figure 7 for Figure 6 A schematic diagram of the AA section; Figure 8 This is a diagram showing the actual temperature control effect during the welding process in the experimental example; Reference numerals: 100, superconducting magnet coil; 110, lead end; 120, penultimate turn conductor; 200, tail structure; 210, first mechanical leg; 220, connector; 230, second mechanical leg; 240, welding bevel; 300, water-cooling fixture; 310, top cover; 320, limiting block; 330, horizontal set screw; 340, water flow channel; 350, water flow interface; 360, base; 370, welding process hole; 380, fastener; 390, position adjustment hole. Detailed Implementation

[0018] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," "horizontal," and "vertical," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or order.

[0020] It should be noted that the parts not described in the following embodiments of the present invention, such as the specific model and operation mode of the TIG welding equipment, the specific selection and configuration of the water-cooled circulating unit, and the purity requirements of the argon protective gas, are all considered to be prior art known or should be known by those skilled in the art. The present invention does not make specific limitations in this regard, and those skilled in the art can make reasonable selections based on actual production conditions and equipment configuration.

[0021] Furthermore, the "Tail structure" described in this invention refers to a transition connection structure used to transfer the circumferential load at the lead-out end of a superconducting magnet coil to the penultimate turn of the coil conductor. It includes a first mechanical leg 210, a second mechanical leg 230, and a connector 220 (e.g., connecting the first mechanical leg 210 and the second mechanical leg 230) that connects the two mechanical legs. Figure 2 and Figure 6 (As shown). The "lead end" 110 refers to the conductor end led out from the winding of the superconducting magnet coil 100 (e.g., ...). Figure 1 As shown), it is used for connection to an external circuit. The "second to last turn conductor" 120 refers to the second to last turn conductor in the superconducting magnet coil 100 adjacent to the output end 110.

[0022] Example 1

[0023] A welding fixture for a nuclear fusion high-temperature superconducting magnet coil Tail structure, the welding fixture including at least one water-cooled fixture 300 (e.g. Figure 3 As shown, a water-cooled clamp 300 is installed at each of the two mechanical leg positions of the Tail structure 200. That is, the two water-cooled clamps 300 correspond to the welding positions of the first mechanical leg 210 and the wire outlet 110, and the welding positions of the second mechanical leg 230 and the penultimate turn conductor 120, respectively.

[0024] like Figure 4As shown, each water-cooled fixture 300 includes a base 360 ​​and a top cover 310 that cooperate with each other. The top cover 310 has a U-shaped cross-section (i.e., an inverted U-shaped or gate-shaped cross-section), with the opening of the U-shape facing downwards, and is used to span over the workpiece being welded. The base 360 ​​is a rectangular plate with a flat upper surface, used to support the workpiece being welded from below. The top cover 310 and the base 360 ​​are fastened together to form a limiting space for accommodating the Tail structure 200 and the superconducting magnet coil 100.

[0025] Water flow channels 340 are provided inside both the base 360 ​​and the top cover 310, such as Figure 5 As shown, the water flow channel 340 is U-shaped, extending along a U-shaped path inside the base 360 ​​or the top cover 310, and its entire structure surrounds the welding process hole 370 to maximize coverage of the welding heat-affected zone. Both ends of the water flow channel 340 extend beyond the outer surface of the base 360 ​​or the top cover 310, forming water flow interfaces 350 for connection to an external water-cooled circulation unit. The water flow interfaces 350 can be standard threaded connectors or quick-connect couplings for easy connection and disassembly to external water-cooling pipelines. In use, the external water-cooled circulation unit pumps deionized water (as the cooling medium) into the water flow channel 340 through one water flow interface 350. The water flows along the U-shaped channel through the entire welding heat-affected zone, then flows out from the other water flow interface 350 and returns to the water-cooled circulation unit, forming a closed forced convection cooling loop.

[0026] There are two adjustable limiting blocks 320 between the base 360 ​​and the top cover 310, such as... Figure 3 and Figure 5 As shown, two limiting blocks 320 are respectively disposed on the left and right sides of the limiting space (i.e., on both sides perpendicular to the weld length direction). The inner surfaces of the two limiting blocks 320 respectively form working surfaces that match the shapes of the mechanical legs (first mechanical leg 210 or second mechanical leg 230) of the Tail structure 200 and the superconducting magnet coil 100 (lead 110 or penultimate turn conductor 120). Specifically, the inner surface of one limiting block 320 fits into the shape of the mechanical leg of the Tail structure 200, and the inner surface of the other limiting block 320 fits into the shape of the lead 110 or penultimate turn conductor 120 of the superconducting magnet coil 100. These two working surfaces, together with the upper surface of the base 360 ​​and the lower surface of the cover 310, form a limiting space with openings at both ends. This limiting space extends along the weld length direction (i.e., the welding trajectory direction) and is used to accommodate and position the workpiece to be welded.

[0027] The base 360 ​​and the top cover 310 are provided with a welding process hole 370 that penetrates the limiting space (e.g., Figure 3 and Figure 4(As shown). The welding process hole 370 is a rectangular or strip-shaped through hole penetrating the base 360 ​​and the top cover 310, and its position corresponds to directly above and below the welding bevel 240 to be welded. During TIG welding, the welding torch extends from above through the welding process hole 370 on the top cover 310 into the limiting space to weld the welding bevel 240; at the same time, the shielding gas (such as argon) on the back side of the weld can be delivered from below through the welding process hole 370 on the base 360 ​​to the back side of the weld, achieving double-sided gas protection and ensuring good forming quality on both sides of the weld.

[0028] The upper surface of the base 360 ​​is provided with a positioning stop (not shown in the figure) that mates with the upper cover 310. This positioning stop is a raised step or groove structure on the edge of the upper surface of the base 360, matching the shape of the lower edge of the upper cover 310. During assembly, the lower edge of the upper cover 310 engages with the positioning stop of the base 360, achieving rapid positioning and precise alignment between the upper cover 310 and the base 360, ensuring the vertical alignment accuracy of the welding process holes 370.

[0029] The base 360 ​​and the top cover 310 are fixedly connected by a number of fasteners 380. The fasteners 380 are generally fastening bolts (i.e., connecting bolts), which pass through corresponding bolt holes on the base 360 ​​and the top cover 310, and are then locked in place with nuts. The fasteners 380 are arranged in two rows, each row corresponding to the position of one of the two limiting blocks 320. Each row of fasteners 380 is arranged along the length of the weld seam, positioned above or to the side of the corresponding limiting block 320.

[0030] The fastener 380 passes through the position adjustment hole 390 on the limiting block 320. The position adjustment hole 390 is generally a slotted hole (oblong hole) with an adjustment margin perpendicular to the line connecting the openings of the limiting space along its long axis. That is, the length direction of the slotted hole is perpendicular to the length direction of the weld (i.e., perpendicular to the line connecting the working surfaces of the two limiting blocks 320), allowing the limiting block 320 to be finely adjusted in a direction perpendicular to the weld. The width of the position adjustment hole 390 is matched to the screw diameter of the fastener 380 (clearance fit), while the length provides sufficient adjustment stroke (generally 5-10 mm).

[0031] The positions of the two limiting blocks 320 are precisely adjusted by multiple horizontal set screws 330 located on the sides of the limiting blocks 320 (e.g., Figure 4 and Figure 5(As shown). After the horizontal set screw 330 passes through the threaded hole on the side wall of the upper cover 310 or the base 360, its end contacts the side of the limiting block 320. By rotating the horizontal set screw 330, the limiting block 320 can be pushed to move in a direction perpendicular to the weld, thereby adjusting the distance between the working surfaces of the two limiting blocks 320 so that the limiting space is precisely matched with the actual size of the workpiece to be welded. The number of fasteners 380 in each row is not less than two, preferably three to four, and they are on the same straight line, which is perpendicular to the direction of the horizontal set screw 330 (i.e., arranged along the length of the weld). The number of horizontal set screws 330 is the same as the number of fasteners 380 in a row, and their positions are also one-to-one, that is, a horizontal set screw 330 is provided at the position of each fastener 380 to precisely control the local displacement of the limiting block 320 at that position.

[0032] In this embodiment, the specific method of using the water-cooled fixture 300 is as follows: First, place the workpiece to be welded (first mechanical leg 210 and lead-out head 110, or second mechanical leg 230 and penultimate turn conductor 120) on the upper surface of the base 360 ​​according to the assembly requirements, so that it is located within the limiting space between the two limiting blocks 320. Then, place the two limiting blocks 320 on both sides of the workpiece, so that the working surface of the limiting blocks 320 fits against the outer surface of the workpiece. Next, fasten the upper cover 310 onto the base 360, so that the positioning stop of the upper cover 310 mates with the positioning stop of the base 360. Pass the fasteners 380 (fastening bolts) sequentially through the position adjustment holes 390 on the upper cover 310, the limit block 320, and the corresponding through holes on the base 360, and screw on the nuts but do not tighten them yet, so that the limit block 320 has a certain amount of room for movement; Then, by rotating the horizontal set screw 330 on the side of the limiting block 320, the limiting block 320 is pushed inward or outward, so that the working surfaces of the two limiting blocks 320 are in close contact with the outer surfaces of the mechanical leg and the lead-out end (or the penultimate turn of the conductor), respectively. During the adjustment process, a feeler gauge or profilometer can be used to check the positional accuracy of the workpiece until the installation profile of the workpiece meets the minimum profile deviation. After the adjustment is completed, tighten the nuts of all fasteners 380 to lock the limiting block 320, the upper cover 310 and the base 360 ​​into a whole; Finally, connect the inlet and outlet pipes of the external water-cooled circulation unit to the two water flow interfaces 350 of the water-cooled fixture 300, start the water-cooled circulation unit, and make the deionized water continuously circulate in the water flow channel 340 to prepare for subsequent welding operations.

[0033] Example 2

[0034] like Figures 1 to 7As shown, a welding method for a high-temperature superconducting magnet coil tail structure in nuclear fusion is described. This method uses the welding fixture described in Example 1 and includes the following complete steps: Step 1: Pulling out the cable end and preparing the working space like Figure 1 As shown, the lead end 110 of the superconducting magnet coil 100 is pulled upwards along a direction perpendicular to the winding surface of the superconducting magnet coil 100. Specifically, the superconducting magnet coil 100 has a planar helical winding structure (i.e., each turn of the conductor is wound sequentially in the same plane), and its winding surface is horizontal. The lead end 110, originally located on the outer coil and extending horizontally, is pulled vertically upwards (i.e., pulled up vertically), making it stand upright from the coil plane, thereby forming an open working space between the lead end 110 and the penultimate turn of conductor 120, facilitating the installation of the Tail structure 200 and subsequent welding operations; Step 2: Installation and contour comparison of the first mechanical leg 210 like Figure 2 As shown, the first mechanical leg 210 of the Tail structure 200 is installed between the lead-out head 110 and the penultimate turn conductor 120. The first mechanical leg 210 is the part of the Tail structure 200 that connects to the lead-out head 110. It is shaped like a long strip of metal, with one end extending into the space between the lead-out head 110 and the penultimate turn conductor 120 and fitting tightly against both. The other end is connected to the second mechanical leg 230 via a connector 220. During installation, the first mechanical leg 210 is placed in the gap between the lead-out end 110 and the penultimate turn conductor 120, so that the lead-out end 110 is spliced ​​to the side of the first mechanical leg 210. After splicing, the outer contour of the Tail structure 200 is compared to ensure that its overall contour does not exceed the outer contour of the superconducting magnet coil 100 (i.e., the outermost edge of the coil). This contour requirement is to ensure that after the Tail structure 200 is installed, the entire coil assembly can still be installed into the subsequent assembly space (such as a cryogenic Dewar or magnet frame).

[0035] Simultaneously, ensure that the welding trajectory formed at the joint between the first mechanical leg 210 and the lead-out end 110 is the same as the forming direction of the superconducting magnet coil 100. The "forming direction" refers to the direction of conductor extension during the winding process of the superconducting coil, specifically the direction in which the lead-out end of the penultimate turn 120 points. This directional requirement is to ensure that the direction of force on the weld under tensile load is consistent with the conductor direction, preventing the weld from being subjected to unfavorable shear or bending loads.

[0036] Step 3: Processing the welding bevel A bevel is machined on the surface of the first mechanical leg 210 that contacts the lead wire 110, thereby forming a V-shaped welding bevel 240 at the joint between the two (e.g., Figure 7(As shown). Specifically, the upper surface of the mating end of the first mechanical leg 210 is machined (e.g., milled or ground) to form an inwardly inclined bevel. When the two are joined, the two bevels face each other, forming a V-shaped bevel; it should be noted that the surface of the lead wire 110 does not need to be machined.

[0037] The angle of the weld bevel 240 is 28-32°, preferably 30°. This angle range is narrower than the traditional 45° or 60° bevels, and is considered a narrow bevel design. The advantage of a narrow bevel is that it reduces the amount of weld metal filler and welding heat input, which helps control the temperature rise of the superconducting cable.

[0038] The blunt edge length of the welding groove 240 is 0.4-0.6 mm, preferably 0.5 mm. The blunt edge length refers to the distance from the bottom tip of the welding groove 240 (i.e., the deepest point of the V-shaped groove) to the inner wall of the first mechanical leg 210 (i.e., the side wall closest to the conductor), which is the remaining thickness of the side wall of the first mechanical leg 210. The presence of the blunt edge ensures that the bottom of the groove will not completely melt through during welding, and also provides a reference for the positioning of the welding torch, ensuring the realization of a full-penetration weld structure.

[0039] Step 4: Spot welding for fixation and installation of water-cooled fixture 300 The first mechanical leg 210 is fixed to the lead wire 110 using spot welding. The purpose of spot welding is to temporarily fix the two workpieces at several points before formal welding, preventing relative displacement during subsequent clamping and welding. During spot welding, the welding current is 85-95A, and the arc voltage is 8-15V. It should be noted that the welding current can be any value between 85-95A, such as 85A, 88A, 90A, 92A, or 95A, with 90A being preferred; the arc voltage can be any value between 8-15V, such as 8V, 10V, 12V, or 15V, with 10V being preferred. The spot welding uses the TIG welding method, with argon as the arc shielding gas, and a flow rate of 8-15L / min. Any value between 8-15L / min can be used, such as 8L / min, 10L / min, 12L / min, or 15L / min, with 12L / min being preferred. Spot welding points are usually selected near the ends and midpoint of the weld. The length of each spot weld is 3-5mm, preferably 4mm.

[0040] After spot welding is completed, the water-cooled clamp 300 of the welding fixture described in Example 1 is installed. Specifically, the water-cooled clamp 300 is straddling the joint between the first mechanical leg 210 and the wire outlet 110, as shown below. Figure 3As shown, the welding bevel 240 is positioned directly below the welding process hole 370 of the water-cooled fixture 300. The positions of the two limiting blocks 320 are adjusted so that the working surfaces of the limiting blocks 320 are in close contact with the outer surfaces of the first mechanical leg 210 and the wire outlet 110, respectively. By fine-tuning the horizontal set screw 330, the mounting profiles of the first mechanical leg 210 and the wire outlet 110 are made to meet the minimum profile deviation (meaning the mating surfaces of the two are aligned as much as possible, and the misalignment is controlled within a minimum range), and then the fasteners 380 are tightened.

[0041] Step 5: Introduce circulating cooling water Deionized water is continuously supplied as a circulating cooling medium into the water flow channel 340 of the water-cooled fixture 300. The external water-cooling circulation unit is started, allowing the deionized water to circulate within the water flow channel 340 at a certain flow rate (typically 2-5 L / min). Deionized water has excellent thermal conductivity and electrical insulation properties, effectively removing the heat generated during welding without posing any electrical safety hazards to the superconducting coil. Throughout the subsequent welding process, the water-cooling circulation must continue uninterrupted.

[0042] Step 6: TIG welding of the first mechanical leg 210 and the lead wire 110 Clean the weld bevel 240 by wiping the surface with organic solvents such as acetone or alcohol to remove contaminants such as oil, oxides, and dust, ensuring a good bond between the weld metal and the base metal.

[0043] The first mechanical leg 210 and the lead wire 110 are welded together using TIG welding (tungsten inert gas welding, DC positive polarity, using tungsten electrodes). During welding, argon is used as the arc shielding gas, with a flow rate of 8-15 L / min. Any value between 8 and 15 L / min can be selected, such as 8 L / min, 10 L / min, 12 L / min, or 15 L / min, with 12 L / min being preferred.

[0044] Welding is divided into two stages: filler welding and cover welding. During filler welding, the welding current is 90-100A, and any value between 90-100A can be selected, such as 90A, 93A, 95A, 98A, or 100A, with 95A being preferred; the arc voltage is 8-15V, and any value between 8-15V can be selected, such as 8V, 10V, 12V, or 15V, with 10V being preferred. The purpose of filler welding is to penetrate the root of the weld bevel 240 and fill most of the bevel space, forming the main load-bearing section of the weld.

[0045] During cover welding, the welding current is 80-90A, and any value between 80-90A can be selected, such as 80A, 82A, 85A, 88A, or 90A, with 85A being preferred. The arc voltage is 8-15V, and any value between 8-15V can be selected, such as 8V, 10V, 12V, or 15V, with 10V being preferred. The cover welding uses a current slightly lower than that used for filler welding to ensure the quality of the weld surface and obtain a smooth and flat weld bead surface.

[0046] Intermittent welding (i.e., segmented welding) should be used during welding. Before each weld, the weld temperature should be checked and welding should only proceed if it is below 50°C. Each weld should be completed within 5 seconds, and ideally within 4 seconds. The weld temperature can be checked using a contact thermocouple or an infrared thermometer, with the measurement point located on the base material surface 2-3 mm from the edge of the weld bevel.

[0047] The specific operation method for intermittent welding is as follows: Mark the four endpoints of the two welds between the first mechanical leg 210 and the cable outlet 110 as A, B, C, and D in a clockwise or counterclockwise order (that is, the two ends of the first weld are A and B, and the two ends of the second weld are C and D, where A and D are located on one end of the workpiece, and B and C are located on the other end of the workpiece, and AC and BD are diagonally opposite). Then weld intermittently from the endpoints of the two welds toward the middle in the order of ACDB or ACBD.

[0048] Taking the ACDB sequence as an example: First, weld a section at point A (approximately 3-5mm in length). Then move to point C and weld a section of the corresponding length. Next, move to point D and weld a section, then move to point B and weld a section. Then return to the end of the already welded section at point A and continue welding, repeating this process from the endpoints towards the middle of the weld. This "diagonally alternating, end-to-middle" welding sequence allows heat to be alternately input between different welds and different endpoints, avoiding the continuous accumulation of heat at the same location.

[0049] During each weld, the welding torch should be moved 3-5 mm (i.e., the arc length of one weld) along the weld direction, preferably 4 mm, and the welding time should be controlled within 3-4 seconds. After each weld is completed, immediately remove the welding torch and wait at least 5-10 seconds (or longer) until the weld temperature drops below 50°C before proceeding with the next weld. Throughout the entire welding process, continuously monitor the weld temperature to ensure it remains under control.

[0050] Step 7: Return the cable head 110 to its original position and install it with the second mechanical leg 230. After the first mechanical leg 210 is welded to the lead wire 110, the lead wire 110 is returned to its original position (i.e., from a vertical position to a horizontally extended position). The second mechanical leg 230 is then connected to the first mechanical leg 210 using a connector 220 (typically a bolted metal plate or a pin-connected joint). The second mechanical leg 230 is then spliced ​​to the penultimate turn conductor 120, with the end of the second mechanical leg 230 aligning with the end of the penultimate turn conductor 120. After splicing, the outer contour of the entire Tail structure 200 is compared to ensure that its overall contour does not exceed the outer contour of the superconducting magnet coil 100.

[0051] Step 8: Welding the second mechanical leg to the penultimate turn of the conductor. Following the same method as steps 3) to 6), the second mechanical leg 230 is welded to the penultimate turn conductor 120 into a single structure. Specifically, this includes: machining a bevel and a blunt edge on the surface of the second mechanical leg 230 that contacts the penultimate turn conductor 120 to form a welding bevel (bevel angle 28-32°, blunt edge length 0.4-0.6mm); fixing it using spot welding; and installing the water-cooling fixture 300 (e.g., Figure 3 (As shown on the right); introduce circulating deionized water; after cleaning the bevel, use the TIG welding method for intermittent welding (filling weld 90-100A, cover weld 80-90A, temperature <50℃ before each welding, single welding time <5S, use ACDB or ACBD alternating sequence welding).

[0052] After the second mechanical leg 230 is welded to the penultimate turn conductor 120, the connection between the entire Tail structure 200 and the superconducting magnet coil 100 is completed. The circumferential load of the lead-out end 110 is reliably transmitted to the penultimate turn conductor 120 through the first mechanical leg 210, the connector 220 and the second mechanical leg 230.

[0053] To verify the welding fixture and method of the present invention, the following experiments were conducted: The screw-type central solenoid coil tail structure of the tokamak device was welded using the apparatus of Example 1. The joint surfaces of each tail, each mechanical leg, and the superconducting coil were welded together as follows: Figure 7 The beveling process is shown. The water-cooled fixture 300 is installed, and the limiting block 320, base 360, and top cover 310 are adjusted until the installation profile of Tail and superconducting coil meets the minimum profile deviation state. Welding is performed according to the welding process method of Example 2.

[0054] Using the welding forming method and preferred parameters in Example 2, the temperature values ​​collected by thermocouples arranged near the molten pool are statistically visualized and transformed, as shown below. Figure 8As shown, the highest welding temperature during the process was 152.8℃, which is far below the failure temperature of 200℃ for high-temperature superconducting cables. Figure 8 In the figure, 1#-6# represent the thermocouple numbers respectively. After welding, the contour of the workpiece surface before and after welding was measured using a laser tracker. The measurement results showed that the maximum deformation of the workpiece surface contour caused by welding was only 0.9mm.

[0055] The above description is merely a preferred embodiment of the present invention and is not restrictive. The accompanying drawings also show only one embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A welding fixture for a nuclear fusion high-temperature superconducting magnet coil Tail structure, the welding fixture comprising at least one water-cooled clamp (300), the water-cooled clamp (300) comprising a base (360) and a top cover (310) that cooperate with each other, wherein water flow channels (340) are provided in both the base (360) and the top cover (310), characterized in that: There are two adjustable limiting blocks (320) between the base (360) and the top cover (310). The opposite sides of the two limiting blocks (320) form working surfaces that match the shape of the mechanical leg of the Tail structure (200) and the superconducting magnet coil (100). The two working surfaces together with the base (360) and the top cover (310) form a limiting space with openings at both ends. A welding process hole (370) penetrating the limiting space is provided in the middle of the base (360) and the top cover (310).

2. The welding fixture for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 1, characterized in that: The water flow channel (340) is U-shaped and distributed around the welding process hole (370). Its two ends extend out of the base (360) or the top cover (310) to form a water flow interface (350) that connects to the interface of the external water-cooled circulation unit.

3. The welding fixture for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 1, characterized in that: The upper surface of the base (360) is provided with a positioning stop that cooperates with the upper cover (310).

4. The welding fixture for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 1, characterized in that: The base (360) and the top cover (310) are secured by a number of fasteners (380).

5. The welding fixture for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 4, characterized in that: The fastener (380) passes through the position adjustment hole (390) on the limiting block (320), the position adjustment hole (390) has an adjustment margin perpendicular to the line connecting the opening of the limiting space, and the position of the limiting block (320) is adjusted by a plurality of horizontal set screws (330) provided on the sides of the two limiting blocks (320).

6. A method for welding the tail structure of a nuclear fusion high-temperature superconducting magnet coil, characterized in that, Includes the following steps: 1) Pull the lead end (110) of the superconducting magnet coil (100) upward along the direction perpendicular to the winding surface of the superconducting magnet coil (100) so that the Tail structure (200) and the superconducting magnet coil (100) have working space for welding; 2) Install the first mechanical leg (210) of the Tail structure (200) between the lead-out end (110) and the penultimate turn conductor (120), and compare the outer contour of the Tail structure (200) so that it does not exceed the outer contour of the superconducting magnet coil (100), and the welding trajectory formed at the splice of the first mechanical leg (210) and the lead-out end (110) is the same as the forming direction of the superconducting magnet coil (100); 3) A bevel is machined on the surface of the first mechanical leg (210) that contacts the wire head (110) so that a welding bevel (240) is formed at the joint between the two. The angle of the welding bevel (240) is 28-32° and the length of the blunt edge is 0.4-0.6mm. 4) Fix the first mechanical leg (210) to the wire outlet (110) using spot welding, then install the water-cooled fixture (300) of the welding tool described in any one of claims 1-5, and adjust the position of the limiting block (320) so that the installation profile of the first mechanical leg (210) and the wire outlet (110) meets the minimum profile deviation state. 5) Deionized water is continuously introduced into the water flow channel (340) of the water-cooled fixture (300) as circulating water; 6) Clean the welding bevel (240), and then use TIG welding to weld the first mechanical leg (210) and the wire head (110) together. During welding, intermittent welding operation is used. Each time welding is performed, the weld temperature is checked first. Welding is carried out only after the temperature drops below 50°C, and the welding time is ensured to be no more than 5 seconds. 7) Return the lead wire (110) to its original position, and then use the connector (220) to connect the second mechanical leg (230) to the first mechanical leg (210). Then, splice the second mechanical leg (230) with the penultimate turn conductor (120) together, and compare the outer contour of the entire Tail structure (200) to ensure that it does not exceed the outer contour of the superconducting magnet coil (100). 8) Following steps 3)-6), the second mechanical leg (230) and the penultimate turn conductor (120) are welded together to form a single structure, thereby completing the welding of the superconducting magnet coil (100) and the Tail structure (200).

7. The welding method for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 6, characterized in that: In step 4), when spot welding is used for fixing, the welding current is 85-95A and the arc voltage is 8-15V.

8. The welding method for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 6, characterized in that: In both step 4) spot welding and step 6) TIG welding, argon gas is used as the arc shielding gas, and its flow rate is 8-15 L / min.

9. The welding method for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 6, characterized in that: The specific operation of interrupting the welding in step 6) is to mark the four ends of the two welds between the first mechanical leg (210) and the wire head (110) as A, B, C and D in a clockwise or counterclockwise direction, and then weld them alternately from the ends of the two welds to the middle in the order of ACDB or ACBD.

10. The welding method for the Tail structure of a nuclear fusion high-temperature superconducting magnet coil according to claim 6, characterized in that: In step 6), during TIG welding, the filler weld is first used to fill the weld seam, and then the cover weld is used. The welding current for filler weld is 90-100A and the arc voltage is 8-15V; the welding current for cover weld is 80-90A and the arc voltage is 8-15V.

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