A precision forming device and method for welding a superconducting magnet coil case for nuclear fusion

Abstract

The application provides a welding precision forming device and method for a superconducting magnet coil box for nuclear fusion, relates to the technical field of manufacturing of armored superconducting coils for nuclear fusion, and comprises a coil wet package winding layer, a coil box, a backing plate, a shape-retaining plate, a welding fixture tool, the coil wet package winding layer is composed of glass silk belts soaked with normal-temperature solidified epoxy resin; a single-side V-shaped groove is adopted for the welding position of the coil box, and a stepped surface is adopted to limit the welding depth; the backing plate is arranged between the coil box and the shape-retaining plate; the profile of the shape-retaining plate is consistent with the standard outer shape surface of the coil box; the welding fixture tool is used for restraining the coil box during the welding process; and the welding deformation is reduced by controlling the welding temperature. For different types of superconducting magnets, the application only needs to change the adaptive welding fixture tool to effectively ensure the welding precision forming of the coil boxes of various types. The application has the advantages of light structure, quick installation, simple use, and is suitable for on-line welding of various types of coil boxes of nuclear fusion superconducting magnets, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of manufacturing technology for armored superconducting coils for nuclear fusion, specifically to a precision forming device and method for welding superconducting magnet coil boxes for nuclear fusion. Background Technology

[0002] In nuclear fusion devices, superconducting magnet coils (such as toroidal field coils) operating under high current and strong magnetic field conditions experience enormous electromagnetic forces. These coils must be encapsulated in high-strength coil boxes with a C-shaped cross-section, and the entire coil is sealed using a coil box cover. The overall deformation during welding is minimal. However, for superconducting magnet coils operating at lower currents and in weaker magnetic fields (such as correction field coils), the coil's inherent strength is sufficient to resist the electromagnetic forces during operation. Only the coil box needs to be welded to the coil terminal area (the area where liquid helium inlet / outlet pipes and the lead-out end are concentrated) to fix the terminal box structure. This type of coil box consists of two L-shaped high-strength stainless steel structural components. The localized high temperatures during welding cause thermal expansion of the material. Upon cooling, uneven contraction generates residual stress, which can easily cause deformation of the box. This deformation not only makes subsequent assembly difficult but also leads to uneven gaps between the coil box and the internal coil windings, preventing the uniform transmission of electromagnetic forces, potentially causing localized stress concentrations, and even degrading magnet performance.

[0003] To address the aforementioned issues, existing technologies (such as CN121054347B) propose a modular, weld-free coil box structure. This approach designs the coil box as multiple independent components (inner ring, outer ring, and sidewalls), assembling them using detachable methods such as bolts. Adjustable connecting components (such as wedge blocks or insulating shrink-fitters) are introduced between the outer ring wall and the box body, allowing for slight radial movement between the two. While this solution effectively avoids welding deformation and simplifies disassembly and maintenance, its core idea is to avoid welding altogether, instead relying on complex mechanical connections and buffer structures to accommodate manufacturing tolerances and operational loads.

[0004] However, given the stringent requirements for load transmission continuity and structural integrity during superconducting magnet operation, a welded monolithic coil box remains the preferred and irreplaceable solution. Therefore, how to overcome the severe deformation caused by heat input during welding for nuclear fusion superconducting magnet coil boxes, while retaining the advantages of a monolithic welded structure, and ensuring that the coil box's profile meets strict tolerance requirements (e.g., deformation less than 1 mm), thereby guaranteeing uniform gaps and sufficient contact between the coil box and the internal windings and avoiding the impact of localized stress concentration on magnet performance, has become a pressing challenge in this field. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a precision forming device and method for welding superconducting magnet coil boxes for nuclear fusion, including a coil wet winding layer, a coil box, a backing plate, a forming plate, a welding fixture, and a welding process. The coil wet-wrap layer is composed of glass fiber tape impregnated with room-temperature curing epoxy resin. It serves as an elastic transition layer between the coil box and the coil winding, effectively filling uneven gaps caused by manufacturing errors. The coil box welding position employs a "single-sided V-shaped" bevel, with a stepped surface limiting the welding depth to ensure the quality of the coil box outline and weld formation after clamping. The backing plate is a 2mm thick metal sheet placed between the coil box and the conformal plate. The metal sheet material is the same as the coil box material to prevent the conformal plate from contaminating the coil box. The conformal plate outline matches the standard outer surface of the coil box and is a high-strength metal component, ensuring accurate clamping and positioning of the coil box and preventing welding deformation. The welding fixture is used to constrain the coil box during welding, controlling welding deformation and ensuring that the coil box outline meets tolerance requirements after welding. The welding process can control the welding temperature and reduce welding deformation. For different types of superconducting magnets, this invention only requires changing the appropriate welding fixture to effectively ensure the precise welding formation of various types of coil boxes. This invention features a lightweight structure, quick installation, and simple use. It is suitable for welding and manufacturing various types of nuclear fusion superconducting magnet coil boxes and has broad application prospects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A precision forming device for welding superconducting magnet coil boxes for nuclear fusion includes a backing plate, a molded plate, and a welding fixture. The superconducting magnet coil box for nuclear fusion is composed of a first coil box and a second coil box that cooperate with each other, and the two have a welding bevel at the contact position. The backing plate is arranged between the coil box and the molded plate and fits tightly with them. The outline of the molded plate is consistent with the standard outer surface of the coil box, and the backing plate limits the position of the coil box. The welding fixture is used to clamp the molded plate to constrain the coil box.

[0008] This invention also provides a method for precision forming of welding superconducting magnet coil boxes for nuclear fusion, using the aforementioned precision forming device for welding superconducting magnet coil boxes for nuclear fusion, comprising: assembling and installing a first coil box and a second coil box with pre-processed weld bevels; attaching pads and installing conformal plates on the four outer surfaces of the coil boxes respectively; clamping the conformal plates using welding fixtures to position and clamp the coil boxes; and performing welding while meeting the minimum profile deviation.

[0009] This invention successfully solves the precision forming problem of integrally welded coil boxes through a comprehensive technical solution integrating wet winding layers, conformal plates, specialized fixtures and tooling, and controlled welding processes. Its main beneficial effects include:

[0010] 1. This invention uses a conformal plate and special fixtures to precisely position and strongly constrain the coil box, and combines intermittent welding and temperature control to minimize thermal deformation during welding, ensuring that the contour deformation of the coil box after welding is less than 1mm.

[0011] 2. The high-precision integral housing formed by this invention can fit evenly with the internal coil windings, eliminating the problem of uneven gaps. This ensures that the huge radial electromagnetic force during operation can be evenly and effectively borne and transmitted by the coil housing, improving the stability and safety of the magnet's operation.

[0012] 3. While retaining the advantages of the overall welded structure, this invention, through modular fixture design, can be adapted to various types of superconducting magnet coil boxes. It features a lightweight structure, quick installation, and simple operation, and has broad engineering application prospects. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a precision forming device for welding superconducting magnet coil boxes for nuclear fusion, provided by the present invention.

[0014] Figure 2a This is a cross-sectional view of the superconducting magnet coil box involved in the present invention.

[0015] Figure 2b for Figure 2a A magnified view of E in the middle.

[0016] Figure 3 This is a schematic diagram of the welding fixture tooling of the present invention.

[0017] Figure 4 This is a schematic diagram illustrating the actual temperature control effect during the welding process.

[0018] Figure 5 The results show the contour measurement of the upper surface of the coil box before welding.

[0019] Figure 6 The results show the contour measurement of the upper surface of the coil box after welding.

[0020] Figure 7 The measurement results show the outer contour of the coil box before welding.

[0021] Figure 8 The measurement results show the outer contour of the coil box after welding.

[0022] Figure 9 The results show the contour measurement of the bottom surface of the coil box before welding.

[0023] Figure 10 The measurement results show the contour of the bottom surface of the coil box after welding.

[0024] Figure 11 The measurement results show the inner surface contour of the coil box before welding.

[0025] Figure 12 The measurement results show the inner surface contour of the coil box after welding.

[0026] The reference numerals in the attached drawings are as follows: 100 – wet winding layer of the coil; 200 – coil box; 210 – first coil box; 220 – second coil box; 300 – pad; 400 – molded plate; 500 – welding fixture; 510 – pressure plate; 520 – frame; 530 – clamping screw; 600 – coil winding. Detailed Implementation

[0027] 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 merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] like Figure 1 , Figure 2a , Figure 2b , Figure 3 As shown, this invention provides a precision forming device for welding superconducting magnet coil boxes for nuclear fusion, comprising a coil wet winding layer 100, a coil box 200, a pad 300, a forming plate 400, and a welding fixture 500. The coil wet winding layer 100 is located in the area between the coil box 200 and the coil winding 600, and is solidified on the outer surface of the coil winding 600 and the inner surface of the coil box 200.

[0029] Preferably, the coil wet wrapping layer 100 is composed of glass ribbon and room temperature curing resin, and the compression rate of the coil wet wrapping layer 100 after the coil box 200 is installed is 25%.

[0030] Preferably, the glass ribbon used in the coil wet wrapping layer 100 has a thickness of 0.15mm to 0.25mm. The glass ribbon is impregnated with room temperature curing resin and wrapped in a semi-overlapping manner at the contact point between the coil box 200 and the coil winding 600 until the required thickness is achieved.

[0031] Preferably, the coil box 200 is composed of a first coil box 210 and a second coil box 220 with welding bevels, wherein the welding bevels are located at the contact position when the first coil box 210 and the second coil box 220 are installed together.

[0032] Preferred, such as Figure 2a , Figure 2bAs shown, at the welding point of the first coil box 210 and the second coil box 220, one end of the first coil box 210 and the second coil box 220 is opened with a single-sided V-shaped bevel with a bevel angle of 40° to 50° and a blunt edge of 1mm; the other end of the first coil box 210 and the second coil box 220 is machined with a stepped surface with a step depth of 0.5 to 1.5mm, and the two fit together.

[0033] Preferably, the pad 300 is located between the coil box 200 and the molded plate 400, and is in close contact with both.

[0034] Preferably, the pad 300 and the coil box 200 should be made of the same material, with a thickness of 2mm, and their outlines should be consistent with the contact surface of the coil box 200.

[0035] Preferably, the conformal plate 400 limits the coil box 200 by means of the pad 300.

[0036] Preferably, the yield strength of the conformal material 400 must be greater than the yield strength of the coil box 200, its thickness should be twice the thickness of the coil box 200, and its outline should be consistent with the contact surface of the coil box 200.

[0037] Preferably, the welding fixture 500 includes a pressure plate 510, a frame 520, and clamping screws 530. The frame 520 has threaded holes on its four sides. The clamping screws 530 are installed on the frame 520 through the threaded holes. By rotating all the clamping screws 530, the pressure plate 510 on all four sides can be pressed onto the molded plate 400. By adjusting the clamping screws 530, the profile of the molded plate 400, the pad 300, and the coil box 200 can be finely adjusted.

[0038] Preferably, the welding fixture 500 with multiple sets of matching coil windings 600 cross sections is evenly distributed on the mounting surface of the coil box 200 according to the contour curve of the coil box 200, which can realize the reliable clamping and limiting of the coil box 200.

[0039] This invention also provides a method for precision forming of a superconducting magnet coil box for nuclear fusion, comprising: performing wet winding of the coil at the location where the coil box 200 is installed on the coil winding 600; assembling and installing the coil box 200 with pre-processed bevels when the wet winding surface is semi-dry; attaching pads 300 to the four sides of the coil box 200 and installing form-fitting plates 400; using a welding fixture 500 to clamp the form-fitting plates 400 to position and clamp the coil box 200; and welding according to the welding process method when the installation profile meets the minimum profile deviation.

[0040] Preferably, the welding process includes stipulations on welding parameters, welding sequence, and temperature control requirements. All welding is performed using the TIG (141) welding method, with an arc shielding gas flow rate of 8L / min to 15L / min. During tack welding, the welding current is 95A to 115A and the arc voltage is 8V to 15V; during fill welding, the welding current is 100A to 130A and the arc voltage is 8V to 15V; and during cap welding, the welding current is 90A to 120A and the arc voltage is 8V to 15V.

[0041] Preferably, the welding sequence should be intermittent, proceeding from both sides towards the center of the coil box 200, and repeated multiple times until the filling welding is completed.

[0042] Preferably, the welding time for a single pass does not exceed 10 seconds. Before each welding operation, the interpass temperature (the temperature of the workpiece between two welding operations) must be monitored. If the interpass temperature is below 100°C, the next welding operation is performed, and so on.

[0043] In summary, the superconducting magnet coil box for nuclear fusion typically consists of a first coil box 210 and a second coil box 220 that cooperate with each other. This invention innovatively provides a welding bevel at the contact point between the two, with one end having a cooperating single-sided V-shaped bevel at an angle of 40°–50° and a blunt edge of 1mm; the other end has a cooperating stepped surface with a depth of 0.5–1.5mm. The coil wet winding layer 100 is located between the coil box 200 and the coil winding 600, and is composed of glass fiber tape impregnated with room-temperature curing epoxy resin. The glass fiber tape is 0.15mm–0.25mm thick and is wrapped in a semi-overlapping manner at the contact point between the coil box 200 and the coil winding until the required thickness is achieved. After installation, the compression ratio of the coil wet winding layer 100 is 25%, serving as an elastic transition layer that effectively fills gaps caused by manufacturing errors. A backing plate 300 is positioned between the coil box 200 and the conformal plate 400. It is made of the same material as the coil box 200, with a thickness of 2mm, and its outline matches the contact surface of the superconducting magnet coil box used in nuclear fusion, preventing the conformal plate 400 from contaminating the coil box 200. The conformal plate 400's outline matches the standard outer surface of the superconducting magnet coil box used in nuclear fusion. Its material yield strength is greater than that of the coil box 200, and its thickness is twice that of the coil box plate. The backing plate 300 limits the coil box 200, ensuring accurate clamping and positioning and preventing welding deformation. The frame 520 of the welding fixture 500 has threaded holes on all four sides. Clamping screws 530 pass through these threaded holes to press the pressure plate 510 onto the conformal plate 400. Adjusting the clamping screws 530 allows for fine-tuning of the contours of the conformal plate 400, backing plate 300, and coil box 200, achieving reliable clamping and positioning of the coil box 200. Through the above-mentioned specific structural design, the present invention can effectively control the thermal deformation during the welding process of the superconducting magnet coil box for nuclear fusion, ensuring that the contour deformation of the coil box after welding is less than 1mm, thereby ensuring that the gap between the coil box 200 and the internal coil winding is uniform, and improving the stability and safety of the magnet operation.

[0044] In a preferred embodiment, the "tile-shaped" correction field coil of the tokamak device is welded into a local coil box. A wet winding layer 100 is applied at the location where the local coil box 200 is installed on the coil winding. When the wet winding layer is semi-dry, it is then... Figure 2a The diagram illustrates the assembly and installation of a partially beveled coil box 200. The four sides of the coil box 200 are respectively fitted with backing plates 300 and molded plates 400. Multiple sets of welding fixtures 500 are used for positioning and clamping. Welding is performed according to the welding process method once the installation profile meets the minimum profile deviation. Using the method of this invention, the temperature values ​​collected by thermocouples arranged on the inner wall of the bevel of the partially beveled coil box 200, near the molten pool area, are statistically visualized and transformed, such as... Figure 4The welding temperature curves collected by thermocouples #1 to #8 show that the highest welding temperature during the process was 151℃, which meets the strict temperature control requirements (below 200℃) for the superconducting coil welding process; in comparison... Figure 5 The results of the contour measurement of the upper surface of the coil box before welding and Figure 6 The contour measurement results of the upper surface of the coil box after welding show that the maximum welding deformation on the upper surface is 0.38mm; compared with... Figure 7 Measurement results of the outer surface contour of the coil box before welding and Figure 8 The contour measurement results of the outer surface of the coil box after welding show that the maximum welding deformation on the outer surface is 0.39mm; compared with... Figure 9 Measurement results of the bottom surface profile of the coil box before welding and Figure 10 The contour measurement results of the bottom surface of the coil box after welding showed that the maximum welding deformation of the bottom surface was 0.91 mm; compared with... Figure 11 Measurement results of the inner surface profile of the coil box before welding and Figure 12 The contour measurement results of the inner side of the coil box after welding show that the maximum welding deformation on the inner side is 0.1 mm. The results are summarized in Table 1. The above welding test results show that the present invention has a precise control effect.

[0045] Table 1. Statistical table of coil box profile deformation results before and after welding

[0046]

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A precision forming device for welding superconducting magnet coil boxes for nuclear fusion, characterized in that, The device includes a backing plate, a conformal plate, and a welding fixture. The superconducting magnet coil box for nuclear fusion is composed of a first coil box and a second coil box that cooperate with each other, and the two have a welding bevel at the contact position. The backing plate is arranged between the coil box and the conformal plate and fits tightly against them. The outline of the conformal plate is consistent with the standard outer surface of the coil box, and the backing plate limits the position of the coil box. The welding fixture is used to clamp the conformal plate to constrain the coil box.

2. The precision forming device for welding superconducting magnet coil boxes for nuclear fusion according to claim 1, characterized in that, The first coil box and the second coil box have a matching single-sided V-shaped bevel at one end and a matching stepped surface at the other end.

3. The precision forming device for welding superconducting magnet coil boxes for nuclear fusion according to claim 1, characterized in that, The pad is made of the same material as the coil box, and its thickness is 2mm.

4. The precision forming device for welding superconducting magnet coil boxes for nuclear fusion according to claim 1, characterized in that, The yield strength of the conforming plate is greater than that of the coil box, and its thickness is twice that of the coil box plate.

5. The precision forming device for welding superconducting magnet coil boxes for nuclear fusion according to claim 1, characterized in that, The welding fixture includes a frame, a pressure plate, and clamping screws; the frame has threaded holes on all four sides, and the clamping screws pass through the threaded holes to press the pressure plate onto the molded plate.

6. The precision forming device for welding superconducting magnet coil boxes for nuclear fusion according to claim 1, characterized in that, It also includes a wet wrapping layer for the coil located between the coil box and the coil winding.

7. A method for precision forming of a superconducting magnet coil box for nuclear fusion, comprising the precision forming apparatus for welding a superconducting magnet coil box for nuclear fusion as described in any one of claims 1-6, characterized in that, include: Assemble and install the first and second coil boxes with pre-machined welded bevels; attach pads and form-fitting plates to the four outer surfaces of the coil boxes respectively; The conforming plate is clamped using a welding fixture to position and clamp the coil box; welding is then performed while ensuring that the minimum profile deviation is met.

8. The method for precision welding and forming of a superconducting magnet coil box for nuclear fusion according to claim 7, characterized in that, Welding is performed intermittently in a counter-clockwise and diagonal sequence, gradually moving from both sides of the coil box toward the center, repeating this process multiple times until welding is complete.

9. A method for precision welding and forming of a superconducting magnet coil box for nuclear fusion according to claim 7, characterized in that, Each welding session should not exceed 10 seconds, and the interpass temperature should be monitored before each welding session. The next welding session should only be performed when the interpass temperature is below 100°C.

10. A method for precision welding and forming of a superconducting magnet coil box for nuclear fusion according to claim 7, characterized in that, Before assembling and installing the coil box, a wet wrapping layer is first formed on the coil winding, and the installation is carried out when it is in a semi-dry state.

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