Method for manufacturing a traveling wave tube composite tube shell

Abstract

The application provides a preparation method of a traveling wave tube composite tube shell and relates to the field of electric vacuum device manufacturing. The preparation method comprises the following steps: S1, sleeving a pure iron magnetic screen plate on a Monel positioning column; S2, sequentially stacking a nickel foil, a Monel connecting ring plate, a nickel foil and a plurality of composite plates on the surface of the pure iron magnetic screen plate along the axis of the Monel positioning column, wherein each composite plate comprises a pure iron pole shoe plate, a nickel foil, a Monel tee plate and a nickel foil which are sequentially stacked; S3, stacking another pure iron magnetic screen plate on the nickel foil stacked on the surface of the Monel connecting ring plate, and tightly fixing the Monel positioning column on the pure iron magnetic screen plate by using a Monel nut, so as to form a composite structure; S4, welding the composite structure; S5, linear cutting the welded composite structure to form a plurality of rod-shaped structures; and S6, post-processing the plurality of rod-shaped structures to obtain a plurality of traveling wave tube composite tube shells.

Description

Technical Field

[0001] This application relates to the field of vacuum electronic device manufacturing, specifically to a method for preparing a traveling wave tube composite shell. Background Technology

[0002] Traveling wave tubes (TWTs) are key vacuum tube devices in microwave amplifiers, widely used in radar, communications, and electronic warfare. TWTs amplify microwave signals through the interaction between an electron beam emitted from an electron gun and a slow-wave structure. This slow-wave interaction structure mainly comprises a high-frequency component and a power transfer window structure, with the tube shell being the most important carrier in the high-frequency component. The straightness, length consistency, and gap consistency of the tube shell directly affect the electron beam flow, thus influencing the microwave signal amplification. Furthermore, the welding quality at the welds between different tube shell components plays a crucial role in maintaining the vacuum inside the tube.

[0003] The most significant drawback of current technology:

[0004] 1. Difficulty in controlling precision: The straightness of the tube shell can only reach 0.04mm~0.05mm, and the length fluctuates by ±0.2mm, which basically cannot meet the requirements for high-frequency composite tube shells;

[0005] 2. Poor consistency: The manufacturing process uses high-temperature welding with solder, and the pure iron pole shoes need to be electroplated with nickel. The thickness of the nickel layer fluctuates greatly, resulting in a gap of about 0.03mm to 0.05mm between the pole shoes. When assembling the magnets later, the magnets need to be ground and adapted again, which affects the consistency of the magnets and reduces the assembly efficiency.

[0006] 3. Potential vacuum quality issues: Each component, including the pole shoe and connecting ring used in the composite tube shell welding, requires complex machining and surface treatment. Differences in the surface condition of the components lead to inconsistent weld quality. Some welds contain holes, which can easily trap machining debris or cleaning fluid, ultimately affecting the vacuum and cleanliness inside the traveling wave tube. Furthermore, current assembly technology can only produce one tube shell per assembly, resulting in poor quality and low production efficiency of the traveling wave tube shells. Summary of the Invention

[0007] This application provides a method for preparing a traveling wave tube composite shell, which can solve the problems of low preparation efficiency and poor quality of existing composite shells.

[0008] This application provides a method for preparing a traveling wave tube composite shell, comprising: step S1, placing a layer of pure ferromagnetic shielding plate onto a Monel positioning post; step S2, along the axial direction of the Monel positioning post, sequentially stacking nickel foil, a Monel connecting ring plate, nickel foil, and a multilayer composite plate on the surface of the pure ferromagnetic shielding plate, wherein each layer of composite plate includes sequentially stacked pure ferro pole shoe plates, nickel foil, a Monel tee plate, and nickel foil; step S3, stacking another layer of pure ferromagnetic shielding plate on the nickel foil stacked on the surface of the multilayer composite plate, and using Monel nuts to tighten and fix the Monel positioning post on the other layer of pure ferromagnetic shielding plate to form a composite structure; step S4, welding the composite structure using a pressure diffusion welding process; step S5, wire cutting the welded composite structure to form multiple rod-shaped structures; and step S6, post-processing the multiple rod-shaped structures to obtain multiple traveling wave tube composite shells.

[0009] According to an embodiment of this application, the method further includes, before step S1: performing double-sided grinding on the pure iron pole shoe plate, the pure iron magnetic shield plate, the Monel connecting ring plate, and the Monel tee plate, so that the thickness tolerance of the pure iron pole shoe plate, the pure iron magnetic shield plate, the Monel connecting ring plate, and the Monel tee plate is ±0.003mm, the parallelism is ≤0.01mm, and the surface roughness is ≤0.8μm.

[0010] According to an embodiment of this application, the method further includes performing the following operations in sequence after double-sided grinding: degreasing the pure iron pole shoe plate, pure iron magnetic shield plate, Monel connecting ring plate, Monel tee plate, nickel foil, Monel positioning post, and Monel nut respectively; placing the pure iron pole shoe plate, pure iron magnetic shield plate, Monel connecting ring plate, and Monel tee plate in a vacuum furnace for annealing and reduction treatment respectively; and performing plasma cleaning on the pure iron pole shoe plate, pure iron magnetic shield plate, Monel connecting ring plate, and Monel tee plate respectively.

[0011] According to an embodiment of this application, step S4 includes: step S41, heating the composite structure at a first preset heating rate and pressurizing the composite structure; step S42, when the temperature of the composite structure reaches a first preset temperature and the pressure value of the composite structure is a first preset pressure, heating the composite structure at a second preset heating rate and pressurizing the composite structure; step S43, when the temperature of the composite structure reaches a second preset temperature and the pressure value of the composite structure is a second preset pressure, heating the composite structure at a third preset heating rate and pressurizing the composite structure; step S44, when the temperature of the composite structure reaches a third preset temperature and the pressure value of the composite structure is a third preset pressure, maintaining the composite structure at the third preset temperature and the third preset pressure for a preset time.

[0012] According to an embodiment of this application, step S4 further includes, after step S44: step S45, cooling the composite structure at a first preset cooling rate and depressurizing the composite structure; step S46, when the temperature of the composite structure drops to a second preset temperature and the pressure value of the composite structure is a second preset pressure, cooling the composite structure at a second preset cooling rate and depressurizing the composite structure; step S47, when the temperature of the composite structure drops to a first preset temperature and the pressure value of the composite structure is a first preset pressure, cooling the composite structure at a third preset cooling rate and depressurizing the composite structure, so that the temperature of the composite structure is a preset temperature and the pressure value of the composite structure is a preset pressure.

[0013] According to an embodiment of this application, in step S41, the first preset heating rate is 13℃ / min; in step S42, the first preset temperature is 600℃, the first preset pressure is 2MPa±0.5MPa, and the second preset heating rate is 10℃ / min; in step S43, the second preset temperature is 800℃, the second preset pressure is 3MPa±0.5MPa, and the third preset heating rate is 8℃ / min; in step S44, the third preset temperature is 1100℃±10℃, and the third preset pressure is 9MPa±0.5MPa; in step S45, the first preset cooling rate is 8℃ / min; in step S46, the second preset cooling rate is 10℃ / min; and in step S47, the third preset cooling rate is 13℃ / min.

[0014] According to an embodiment of this application, step S5 includes: uniformly distributing multiple scattered points on a circumference with the centroid of the welded composite structure as the center, and cutting a rod-shaped structure on a circumference with each scattered point as the center, thereby obtaining multiple rod-shaped structures corresponding to multiple scattered points.

[0015] According to an embodiment of this application, in step S6, the post-processing includes: for each rod-shaped structure, grinding the outer wall of the rod-shaped structure using a centerless grinder until the straightness of the outer wall is ≤0.01mm and the outer diameter tolerance is ±0.003mm; for each rod-shaped structure, dividing the rod-shaped structure into multiple sections along its axial direction; and turning each section inward along the outer wall of the rod-shaped structure to reduce the diameter of each section to a third preset diameter.

[0016] According to an embodiment of this application, in step S6, the number of traveling wave tube composite shells is 20 to 30.

[0017] According to an embodiment of this application, the method further includes, after step S6: electroplating nickel onto the outer surface of the multiple traveling wave tube composite shells.

[0018] Compared with the prior art, the method for preparing the traveling wave tube composite shell provided in this application has at least the following advantages:

[0019] (1) The size of the vacuum gap in the composite tube shell was reduced, which improved the production quality;

[0020] (2) Multiple traveling wave tube composite shells can be produced at one time, which improves production efficiency. Attached Figure Description

[0021] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0022] Figure 1 A flowchart illustrating the fabrication process of a traveling wave tube composite shell according to an embodiment of this application is shown.

[0023] Figure 2 This schematic diagram illustrates a structure during pressure diffusion welding of a composite structure according to an embodiment of this application.

[0024] Figure 3 A schematic top view of a composite structure according to an embodiment of this application is shown;

[0025] Figure 4 A flowchart illustrating the heating and pressurization stage of pressure diffusion welding according to an embodiment of this application is shown schematically.

[0026] Figure 5 A flowchart illustrating the cooling and decompression stage of pressure diffusion welding according to an embodiment of this application is shown schematically.

[0027] Figure 6 A schematic top view of a composite structure being wire-cut according to an embodiment of this application is shown;

[0028] Figure 7 A schematic diagram of a rod-shaped structure according to an embodiment of this application is shown.

[0029] Figure 8 A schematic diagram of the structure of a traveling wave tube composite shell according to an embodiment of this application is shown.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1-Pure iron pole shoe plate; 2-Pure iron magnetic shield plate; 3-Monel connecting ring plate; 4-Monel tee plate; 5-Nickel foil; 6-Monel positioning post; 7-Monel nut; 8-Rod-shaped structure; D1-Circle with a diameter of the first preset diameter; T1-First section; T2-Second section. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0035] Understandably, the composite shell of a traveling wave tube is made by assembling pure iron plates and Monel plates, and then processing them again.

[0036] The existing traveling wave tube composite shell is prepared by first processing the required pure iron plate and Monel plate, and then assembling them to obtain a composite shell. This process involves a large vacuum gap, which makes it easy to be contaminated. In addition, only one composite shell can be produced at a time, resulting in low production efficiency.

[0037] In view of this, this application provides a method for preparing a traveling wave tube composite shell, which improves the production quality and efficiency of the composite shell.

[0038] Figure 1 A flowchart illustrating a method for fabricating a traveling wave tube composite shell according to an embodiment of this application is shown.

[0039] like Figure 1 As shown, the fabrication method of the traveling wave tube composite shell in this embodiment includes the following steps S1 to S6:

[0040] Step S1: Place a layer of pure iron magnetic shielding plate 2 onto the Monel positioning post 6;

[0041] Step S2: Along the axis of the Monel positioning post 6, nickel foil 5, Monel connecting ring plate 3, nickel foil 5, and multi-layer composite plate are stacked sequentially on the surface of the pure iron magnetic shield plate 2. Each layer of composite plate includes pure iron pole shoe plate 1, nickel foil 5, Monel three-way plate 4, and nickel foil 5 stacked sequentially.

[0042] Step S3: On the nickel foil 5 stacked on the surface of the multilayer composite plate, another layer of pure iron magnetic shielding plate 2 is stacked. On the other layer of pure iron magnetic shielding plate 2, the Monel positioning post 6 is tightened and fixed using the Monel nut 7 to form a composite structure.

[0043] Step S4: The composite structure is welded using a pressure diffusion welding process;

[0044] Step S5: The welded composite structure is wire-cut to form multiple rod-shaped structures;

[0045] Step S6: Post-process the multiple rod-shaped structures to obtain multiple traveling wave tube composite shells.

[0046] For example, in step S1, refer to Figure 2 The above components are placed on the Monel positioning post 6 in the following order: pure iron magnetic shield plate 2, nickel foil 5, Monel connecting ring plate 3, nickel foil 5, pure iron pole shoe plate 1, nickel foil 5, Monel three-way plate 4, nickel foil 5, and multi-layer composite plate (each layer of composite plate includes pure iron pole shoe plate 1, nickel foil 5, and Monel three-way plate 4). Each layer is placed tightly to minimize the existence of vacuum gaps.

[0047] For example, the thickness of nickel foil 5 can be 0.02 mm. Nickel foil 5 can serve as an intermediate diffusion layer, tightly connecting adjacent plates during subsequent welding, without occupying too much space, minimizing vacuum gaps, and ensuring that the composite structure is not excessively contaminated by dust during welding.

[0048] In addition, the top view of the obtained composite structure is referenced. Figure 3 The composite structure can be approximated as a cylinder or other three-dimensional shapes.

[0049] The method for preparing the traveling wave tube composite shell according to the embodiments of this application tightly connects multiple layers of pure iron pole shoe plates, pure iron magnetic shield plates, Monel connecting ring plates, and Monel tee plates together to form a composite structure. The composite structure is then welded using a pressure diffusion welding process, making the composite structure a whole and greatly reducing the existence of vacuum gaps. Wire cutting is then performed on the welded composite structure to obtain multiple traveling wave tube composite shells at once, avoiding the problems of poor manufacturing quality and low manufacturing efficiency of the traveling wave tube composite shells.

[0050] In some embodiments, the method further includes prior to step S1:

[0051] The pure iron pole shoe plate 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, and Monel tee plate 4 are all subjected to double-sided grinding to ensure that the thickness tolerance of the pure iron pole shoe plate 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, and Monel tee plate 4 is ±0.003mm, the parallelism is ≤0.01mm, and the surface roughness is ≤0.8μm.

[0052] Before double-sided grinding, the pure iron pole shoe plate 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, and Monel tee plate 4 may be untreated metal plates with only rectangular or circular shapes and a large number of uneven surfaces. Step S0 is required to perform double-sided grinding on these metal plates to meet the predetermined processing requirements.

[0053] For example, the initial thickness of a pure iron pole shoe plate 1 is 3.05mm~3.15mm, and the initial thickness of a Monel connecting ring plate 3 is 2.04mm~2.12mm. Due to the rolling process, the surfaces of the two plates have a small oxide layer remaining, and the surface roughness is about 1.6μm. There are slight warpings that are difficult to detect with the naked eye (poor parallelism).

[0054] After double-sided grinding, the upper and lower surfaces of the pure iron pole piece 1 and the Monel connecting ring plate 3 were ground. Following grinding, the ground pure iron pole piece 1 and Monel connecting ring plate 3 were removed from the grinding machine. Five points were randomly selected on the pure iron pole piece 1 for measurement. The measured thickness at these five points was between 3.000 mm and 3.002 mm, meeting the thickness tolerance requirement of ±0.003 mm. The height difference between the two sides of the pure iron pole piece 1 was measured using a dial indicator, with a maximum difference of only 0.008 mm, satisfying the parallelism requirement of ≤0.01 mm. The surface had a uniform matte finish, and the surface roughness measured by a roughness tester was 0.6 μm, meeting the surface roughness requirement of ≤0.8 μm. Simultaneously, the thickness of the Monel connecting ring plate 3 was measured to be consistently between 2.000 mm and 2.003 mm, with a maximum parallelism value of 0.009 mm and a surface roughness value of 0.5 μm, also meeting the standards.

[0055] The polished pure iron pole shoe plate 1 and Monel connecting ring plate 3 can be used in subsequent processing, resulting in a very small cumulative thickness error in the manufactured traveling wave tube composite shell, and the total length fluctuation of the traveling wave tube is controlled within ±0.05mm. At the same time, the surface roughness of 0.6μm allows the pure iron plate and Monel plate to fit better when stacked later, providing a good foundation for eliminating weld voids.

[0056] In some embodiments, the method further includes performing the following operations sequentially after double-sided polishing:

[0057] The pure iron pole shoe plate 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, Monel tee plate 4, nickel foil 5, Monel positioning post 6, and Monel nut 7 are degreased respectively.

[0058] The pure iron pole shoe plate 1, the pure iron magnetic shield plate 2, the Monel connecting ring plate 3, and the Monel three-way plate 4 were placed in a vacuum furnace for annealing and reduction treatment, respectively.

[0059] Plasma cleaning was performed on the pure iron pole shoe plate 1, the pure iron magnetic shield plate 2, the Monel connecting ring plate 3, and the Monel tee plate 4, respectively.

[0060] For example, during the preceding double-sided grinding process and the handling and cutting of the plates, the surfaces of pure iron plates and Monel plates will inevitably be contaminated with mechanical lubricating oil, cutting fluid, rust-preventive oil, as well as organic substances such as sweat and grease from the operators' hands, requiring treatment of the pure iron plates and Monel plates.

[0061] For example, by using ultrasonic cleaning or special chemical solvent cleaning, organic contaminants on the surface of metal plates (pure iron pole shoe plate 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, Monel tee plate 4), nickel foil 5, and assembly accessories (Monel positioning post 6, nut 7) can be thoroughly removed, thereby preventing the carbonization and contamination of grease under subsequent high-temperature treatment.

[0062] Furthermore, a very thin oxide film easily forms on metal surfaces in air. Therefore, the metal plate needs to be placed in a vacuum furnace for annealing and reduction (the vacuum level in the vacuum furnace is ≤10). -3 Pa, temperature 830℃±10℃, maintained at this temperature for 10min±1min). On the one hand, high temperature can eliminate residual stress inside the plate during processing, preventing warping and deformation during subsequent processing; on the other hand, under the extreme vacuum high temperature environment, trace oxides on the metal surface will decompose or be reduced by the base metal, making the plate structure more stable and clean.

[0063] Even after degreasing and annealing reduction, the seemingly clean metal surface may still contain trace amounts of gas adsorption layers or micro-dust at the microscopic level. Therefore, the pure iron pole piece 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, and Monel tee plate 4 need to be placed in an argon atmosphere (the vacuum level inside the reaction chamber of the plasma cleaning equipment is 70Pa~90Pa). The radio frequency power of the plasma cleaning equipment is 300W~500W to generate argon plasma to flush the metal plates, thereby thoroughly removing any trace impurities that may remain on the outermost layer of the metal plate surface.

[0064] refer to Figure 4 In some embodiments, step S4 includes:

[0065] Step S41: Heat the composite structure according to the first preset heating rate and pressurize the composite structure.

[0066] Step S42: When the temperature of the composite structure rises to the first preset temperature and the pressure value of the composite structure is the first preset pressure, the composite structure is heated according to the second preset heating rate and the composite structure is pressurized.

[0067] Step S43: When the temperature of the composite structure rises to the second preset temperature and the pressure value of the composite structure is the second preset pressure, the composite structure is heated according to the third preset heating rate and the composite structure is pressurized.

[0068] Step S44: When the temperature of the composite structure rises to the third preset temperature and the pressure value of the composite structure is the third preset pressure, the composite structure is maintained at the third preset temperature and the third preset pressure for a preset time.

[0069] In step S41, the first preset heating rate is 13℃ / min;

[0070] In step S42, the first preset temperature is 600℃, the first preset pressure is 2MPa±0.5MPa, and the second preset heating rate is 10℃ / min;

[0071] In step S43, the second preset temperature is 800℃, the second preset pressure is 3MPa±0.5MPa, and the third preset heating rate is 8℃ / min;

[0072] In step S44, the third preset temperature is 1100℃±10℃, and the third preset pressure is 9MPa±0.5MPa;

[0073] For example, before step S41, the temperature of the composite structure is the same as the ambient temperature. When compression welding begins, the composite structure is heated at a rate of 13°C / min in the first stage, while a pressure of 2MPa ± 0.5MPa is applied simultaneously. When the temperature of the composite structure reaches 600°C and the pressure stabilizes at 2MPa ± 0.5MPa, the composite structure is heated at a rate of 10°C / min in the second stage, and the pressure is increased to 3MPa ± 0.5MPa. When the temperature of the composite structure reaches 600°C... When the temperature reaches 800℃ and the pressure reaches 3MPa±0.5MPa, the composite structure is heated in the third stage at a heating rate of 8℃ / min, and the pressure is significantly increased to 9MPa±0.5MPa. When the composite structure finally reaches 1100℃±10℃ and the pressure reaches 9MPa±0.5MPa, the heating is stopped, and the temperature of the composite structure is maintained at 1100℃±10℃ and the pressure at 9MPa±0.5MPa for 2 hours to allow sufficient solid-state diffusion of metal atoms in each layer.

[0074] Because the coefficients of thermal expansion of pure iron and Monel alloy may differ, directly heating the composite structure to 1100℃ and applying a high pressure of 9MPa would result in severe warping of the sheet metal due to the superposition of enormous thermal and mechanical stresses, completely destroying the extremely high parallelism achieved in the pretreatment. Therefore, this embodiment employs a three-step heating process (room temperature → 600℃ → 800℃ → 1100℃). At the lower temperature, a small pressure (2MPa ± 0.5MPa) is applied to allow the sheet metal to initially adhere and release processing stress. At an intermediate temperature, the pressure is increased (3MPa ± 0.5MPa) to induce plastic deformation in the nickel foil interlayer, filling the gaps between the sheets. At the highest temperature, the maximum pressure (9MPa ± 0.5MPa) is applied, where atomic activity is highest, the interface is void, and the high pressure maximizes the welding of the pure iron, nickel, and Monel materials, forming a high-strength, non-porous composite structure.

[0075] refer to Figure 5 In some embodiments, step S4 further includes a step following step S44:

[0076] Step S45: Cool the composite structure according to the first preset cooling rate and depressurize the composite structure.

[0077] Step S46: When the temperature of the composite structure drops to the second preset temperature and the pressure value of the composite structure is the second preset pressure, the composite structure is cooled down according to the second preset cooling rate and the pressure of the composite structure is reduced.

[0078] Step S47: When the temperature of the composite structure drops to the first preset temperature and the pressure of the composite structure is the first preset pressure, the composite structure is cooled down according to the third preset cooling rate and the pressure of the composite structure is reduced so that the temperature of the composite structure is the preset temperature and the pressure of the composite structure is the preset pressure.

[0079] In step S45, the first preset cooling rate is 8℃ / min;

[0080] In step S46, the second preset cooling rate is 10℃ / min;

[0081] In step S47, the third preset cooling rate is 13℃ / min.

[0082] For example, after the heat preservation is completed, the composite structure is cooled down at a rate of 8℃ / min, and the pressure of the composite structure is reduced simultaneously. When the temperature of the composite structure drops to 800℃ and the pressure value is reduced to 3MPa±0.5MPa, the cooling continues at a rate of 10℃ / min. When the temperature of the composite structure drops to 600℃ and the pressure value is reduced to 2MPa±0.5MPa, the rapid cooling is carried out at a rate of 13℃ / min until the plate returns to the same temperature as the environment or other preset temperatures, and the pressure value returns to the pressure before welding or other preset pressures.

[0083] For example, existing technologies often employ natural cooling within the furnace, resulting in an uncontrollable cooling rate. This easily leads to significant residual thermal stress at the weld seams, causing bending deformation of the composite structure after cooling and compromising the straightness of the subsequently produced tubing. In contrast, this embodiment employs a stepped cooling and pressure reduction method, with temperature and pressure nodes perfectly symmetrical mirror images of the heating stages. This allows for extremely uniform and segmented release of internal thermal shrinkage stress during the cooling process from 1100°C to room temperature. This ensures that the cooled composite structure maintains a high degree of flatness, thereby guaranteeing the quality of the subsequently produced composite tubing.

[0084] refer to Figure 6 and Figure 7 In some embodiments, step S5 includes:

[0085] Multiple scattered points are evenly distributed on the circumference of the first preset diameter with the centroid of the welded composite structure as the center. A rod-shaped structure is cut out on the circumference of the second preset diameter with each scattered point as the center, resulting in multiple rod-shaped structures corresponding to multiple scattered points.

[0086] Taking the welded composite structure as an example, which is a cylinder, you can refer to... Figure 6 , Figure 6 This is a top view of the welded composite structure. The outermost large circle is the outline of the composite structure. The second circle from the outside in is the circle with the centroid of the welded composite structure as the center and the first preset diameter. That is, the scattered points are evenly distributed along the circumference of the circle D1 with the diameter of the first preset diameter.

[0087] Using the centroid of the composite structure as the center, N scattered points (N=20~30, corresponding to 20~30 composite tubes produced from one composite structure) are evenly distributed on the circumference below the first preset diameter. Using each scattered point as the center, on the circumference below the second preset diameter (i.e., Figure 3 On the second layer of the circumference (from the outside to the inside), multiple small circles are distributed. Multiple rod-shaped structures are cut along the axial direction (from the top to the bottom of the composite structure) using wire cutting. These can then be processed into multiple traveling wave tube composite shells.

[0088] In addition, the rod-shaped structure obtained by wire cutting achieved the preset cutting accuracy, which includes: the straightness of the rod-shaped structure ≤ 0.02 mm and the outer diameter tolerance of ± 0.005 mm.

[0089] This embodiment can obtain multiple rod-shaped structures by fabricating a composite structure once, thereby obtaining multiple traveling wave tube composite shells after subsequent processing. Compared with the traditional method of processing and welding all the components of a composite shell in sequence to obtain a composite shell, this greatly improves the manufacturing efficiency of traveling wave tube composite shells.

[0090] Reference for cut rod-shaped structure Figure 7 As can be seen, the rod-shaped structure is formed by the stacking of pure iron pole shoe plate 1, pure iron magnetic shield plate 2, Monel connecting ring plate 3, and Monel three-way plate 4 in the early stage, and has a certain composite layered structure.

[0091] refer to Figure 8 In some embodiments, in step S6, the post-processing includes: for each rod structure, grinding the outer wall of the rod structure using a centerless grinder until the straightness of the outer wall is ≤0.01mm and the outer diameter tolerance is ±0.003mm;

[0092] For each rod-shaped structure, multiple segments are divided along the axial direction of the rod-shaped structure;

[0093] Each section is machined inward along the outer wall of the rod-shaped structure to reduce the diameter of each section to the third preset diameter.

[0094] The surface of the rod-shaped structure cut by wire EDM may have burrs and unevenness, requiring centerless grinding to improve the accuracy of the outer wall. The centerless grinding process uses a grinding wheel, guide wheel, and support plate to uniformly grind the outer wall of the rod-shaped structure, eliminating surface defects and correcting dimensions.

[0095] For example, the outer wall of the rod structure is ground uniformly along the axial direction (i.e., from the top to the bottom) so that the rod structure after grinding must meet the following requirements: straightness ≤ 0.01mm (to eliminate the slight bending of wire cutting and ensure that the rod structure is straight) and outer diameter tolerance ± 0.003mm.

[0096] Next, the ground rod-shaped structure needs to meet the design of the composite tube shell in order to obtain a traveling wave tube composite tube shell that meets the actual needs. The total length tolerance of multiple traveling wave tube composite tube shells is ±0.05mm.

[0097] For example, in the turning process of a rod-shaped structure, the precise feed of the lathe tool post cuts inward from the outer wall of each section. Figure 8In the process, each segment has a corresponding third preset diameter. The first segment T1 and the second segment T2 are pure iron pole shoe segments. Due to the presence of nickel foil between the plates during the previous preparation process, there may be gaps between the first segment T1 and the second segment T2. The length tolerance of the gap is ±0.01mm. The gap is a groove structure with a parallelism of ≤0.01mm, thus ensuring that the fabricated traveling wave tube composite shell meets the design requirements.

[0098] Assuming a rod-shaped structure with an outer diameter of 10mm, it needs to be machined into a composite tube containing 10 sets of pure iron pole shoes:

[0099] First, the outer wall of the rod-shaped structure is ground along its axial direction. The outer diameter of the ground rod-shaped structure is 10.000mm ± 0.003mm (e.g., 10.002mm or 9.998mm), and the straightness is ≤ 0.01mm (no bending). Then, the rod-shaped structure is divided into 20 sections along its axial direction (e.g., 10 pure iron pole piece sections + 10 Monel connecting ring sections). After turning, the diameter of each pure iron pole piece section can be the same as the outer diameter of the tube shell (corresponding to the size of the pure iron pole piece), and the diameter of each Monel connecting ring section is 4.999mm (corresponding to the size of the Monel connecting ring). After turning, the traveling wave tube composite tube shell is obtained. The gap length between adjacent pure iron pole piece sections is 2.22mm ± 0.01mm, and the total length of the entire composite tube shell is 100.00mm (when the preset requirement for the length of the composite tube shell is 100.01mm, the composite tube shell meets the total length tolerance of ±0.05mm).

[0100] Through the above operations, centerless grinding solves the burr and bending problems of wire EDM, improving the straightness and dimensional accuracy of the rod-shaped structure. Segmentation prevents axial misalignment of parts, and turning precisely controls the diameter of each segment, meeting the high-precision requirements of a straightness ≤0.03mm, length fluctuation within ±0.05mm, and gap length tolerance of ±0.01mm for the traveling wave tube composite shell. The overall process directly processes the welded composite structure into a conforming traveling wave tube composite shell, avoiding the error accumulation of traditional single-piece machining and improving the quality of the traveling wave tube composite shell.

[0101] In some embodiments, in step S6, the number of traveling wave tube composite shells is 20 to 30.

[0102] By performing a single wire cut on a composite structure, a rod-shaped structure can be obtained for subsequent processing to create a traveling wave tube composite shell. Similarly, multiple wire cuts can produce multiple rod-shaped structures from a single composite structure, thereby manufacturing multiple traveling wave tube composite shells. This significantly reduces the complex and inefficient process of assembling individual connecting rings, pole shoes, and magnetic screens into a single shell, which previously required multiple cycles, greatly improving the production efficiency of traveling wave tube composite shells.

[0103] In some embodiments, the method further includes a step after S5:

[0104] Nickel was electroplated onto the outer surface of a composite shell of multiple traveling wave tubes.

[0105] By electroplating nickel on the outer layer of multiple traveling wave tube composite shells in this embodiment, a dense nickel protective layer can be formed on its surface, which effectively isolates air and prevents oxidation of the outer pure iron, Monel and other metals, thereby maintaining the surface performance and dimensional stability of the composite shell.

[0106] In summary, the method for preparing the traveling wave tube composite shell provided in this application involves stacking a pure iron pole shoe plate 1, a pure iron magnetic shield plate 2, a Monel connecting ring plate 3, a Monel tee plate 4, and a nickel foil 5 together to obtain a complete composite structure. The composite structure is then pressure-diffusion welded to minimize the vacuum gap and effectively avoid contamination during processing. Multiple rod-shaped structures are then obtained by wire cutting the composite structure, and these rod-shaped structures are further processed into a traveling wave tube composite shell that meets actual requirements, greatly improving the production quality and efficiency of the traveling wave tube composite shell.

[0107] In the description of this application, it should be understood that the terms "axial," "upper," "lower," "front," "rear," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this application 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 this application. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted when they may cause confusion in understanding this application. Furthermore, the shape, size, and positional relationship of each component in the drawings do not reflect the actual size, scale, and actual positional relationship.

[0108] Similarly, to simplify this application and aid in understanding one or more of the various disclosed aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together into a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0109] 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, the word "a" or "an" preceding an element does not exclude the presence of multiple such elements.

[0110] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a traveling wave tube composite shell, characterized in that, include: Step S1: Place a layer of pure iron magnetic shielding plate (2) onto the Monel positioning post (6); Step S2, along the axial direction of the Monel positioning post (6), nickel foil (5), Monel connecting ring plate (3), nickel foil (5), and multi-layer composite plate are stacked sequentially on the surface of the pure iron magnetic shield plate (2), wherein each layer of composite plate includes pure iron pole shoe plate (1), nickel foil (5), Monel tee plate (4), and nickel foil (5) stacked sequentially. Step S3: On the nickel foil (5) stacked on the surface of the multilayer composite plate, another layer of pure ferromagnetic shield plate (2) is stacked, and the Monel positioning post (6) is tightened and fixed on the other layer of pure ferromagnetic shield plate (2) using Monel nuts (7) to form a composite structure; Step S4: The composite structure is welded using a pressure diffusion welding process; Step S5: The welded composite structure is wire-cut to form multiple rod-shaped structures; Step S6: Post-process the multiple rod-shaped structures to obtain multiple traveling wave tube composite shells.

2. The method for preparing the traveling wave tube composite shell according to claim 1, characterized in that, The method also includes the following prior to step S1: The pure iron pole shoe plate (1), the pure iron magnetic shield plate (2), the Monel connecting ring plate (3), and the Monel tee plate (4) are respectively subjected to double-sided grinding to make the thickness tolerance of the pure iron pole shoe plate (1), the pure iron magnetic shield plate (2), the Monel connecting ring plate (3), and the Monel tee plate (4) ±0.003mm, the parallelism ≤0.01mm, and the surface roughness ≤0.8μm.

3. The method for preparing the traveling wave tube composite shell according to claim 2, characterized in that, The method further includes performing the following operations sequentially after the double-sided polishing process: The pure iron pole shoe plate (1), the pure iron magnetic shield plate (2), the Monel connecting ring plate (3), the Monel tee plate (4), the nickel foil (5), the Monel positioning post (6), and the Monel nut (7) are degreased respectively; The pure iron pole shoe plate (1), the pure iron magnetic shield plate (2), the Monel connecting ring plate (3) and the Monel three-way plate (4) were respectively placed in a vacuum furnace for annealing and reduction treatment; Plasma cleaning was performed on the pure iron pole shoe plate (1), the pure iron magnetic shield plate (2), the Monel connecting ring plate (3), and the Monel three-way plate (4), respectively.

4. The method for preparing the traveling wave tube composite shell according to claim 1, characterized in that, Step S4 includes: Step S41: Heat the composite structure according to the first preset heating rate and pressurize the composite structure. Step S42: When the temperature of the composite structure rises to the first preset temperature and the pressure value of the composite structure is the first preset pressure, the composite structure is heated according to the second preset heating rate and the composite structure is pressurized. Step S43: When the temperature of the composite structure rises to the second preset temperature and the pressure value of the composite structure is the second preset pressure, the composite structure is heated and pressurized according to the third preset heating rate. Step S44: When the temperature of the composite structure rises to a third preset temperature and the pressure value of the composite structure is a third preset pressure, the composite structure is maintained at the third preset temperature and the third preset pressure for a preset time.

5. The method for preparing the traveling wave tube composite shell according to claim 4, characterized in that, Step S4 also includes the following after step S44: Step S45: Cool the composite structure according to the first preset cooling rate and depressurize the composite structure; Step S46: When the temperature of the composite structure drops to the second preset temperature and the pressure of the composite structure is the second preset pressure, the composite structure is cooled down according to the second preset cooling rate, and the pressure of the composite structure is reduced. Step S47: When the temperature of the composite structure drops to the first preset temperature and the pressure of the composite structure is the first preset pressure, the composite structure is cooled down according to the third preset cooling rate and the pressure of the composite structure is reduced so that the temperature of the composite structure is the preset temperature and the pressure of the composite structure is the preset pressure.

6. The method for preparing the traveling wave tube composite shell according to claim 5, characterized in that, In step S41, the first preset heating rate is 13°C / min; In step S42, the first preset temperature is 600℃, the first preset pressure is 2MPa±0.5MPa, and the second preset heating rate is 10℃ / min. In step S43, the second preset temperature is 800℃, the second preset pressure is 3MPa±0.5MPa, and the third preset heating rate is 8℃ / min; In step S44, the third preset temperature is 1100℃±10℃, and the third preset pressure is 9MPa±0.5MPa. In step S45, the first preset cooling rate is 8°C / min; In step S46, the second preset cooling rate is 10℃ / min; In step S47, the third preset cooling rate is 13℃ / min.

7. The method for preparing the traveling wave tube composite shell according to claim 1, characterized in that, Step S5 includes: Multiple scattered points are evenly distributed on the circumference of a circle with the centroid of the welded composite structure as the center and the diameter of the circle as the first preset diameter. A rod-shaped structure is cut out on the circumference of a circle with the scattered point as the center and the diameter of the circle as the second preset diameter, so as to obtain multiple rod-shaped structures corresponding to the multiple scattered points.

8. The method for preparing the traveling wave tube composite shell according to claim 1, characterized in that, In step S6, the post-processing includes: For each of the rod-shaped structures, the outer wall of the rod-shaped structure is ground using a centerless grinding method until the straightness of the outer wall is ≤0.01mm and the outer diameter tolerance is ±0.003mm; For each of the rod-shaped structures, multiple segments are divided along the axial direction of the rod-shaped structure; Each segment is machined inward along the outer wall of the rod-shaped structure to reduce the diameter of each segment to a third preset diameter.

9. The method for preparing the traveling wave tube composite shell according to claim 1, characterized in that, In step S6, the number of traveling wave tube composite shells is 20 to 30.

10. The method for preparing the traveling wave tube composite shell according to claim 1, characterized in that, The method further includes the following after step S6: Nickel is electroplated onto the outer surface of the multiple traveling wave tube composite shells.

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