A Vacuum High-Frequency Induction Brazing Connection Method for Flexible Satellite Pipelines

Abstract

This invention discloses a vacuum high-frequency induction brazing connection method for flexible satellite pipelines, comprising: designing a welding joint structure, the welding joint structure including a pipe joint and two straight pipe sections; removing the oxide film and cleaning the pipe joint and the two straight pipe sections; inserting the cleaned ends of the two straight pipe sections into the bottom of the inner holes on both sides of the pipe joint, leaving a weld seam; pre-placing brazing filler metal on the outside of the weld seam; welding the weld seam according to vacuum high-frequency induction brazing parameters; inspecting the welding quality of the weld seam according to welding standards; if the inspection passes, the welding is completed; otherwise, the weld seam is repaired. This method solves the problem of high-reliability sealing connection of flexible pipelines in satellite vector adjustment mechanisms.

Description

Technical Field

[0001] This invention belongs to the field of welding technology and relates to a vacuum high-frequency induction brazing connection method for satellite flexible pipelines. Background Technology

[0002] Electric propulsion technology is an important development direction in the current development of satellite propulsion systems. It has outstanding advantages such as high specific impulse and long service life, and can be widely used in many fields such as communication satellite platforms, gravity field measurement satellites and deep space exploration.

[0003] Flexible tubing is a key component of the vector control mechanism in electric propulsion systems. It possesses a wide range of flexible deformation capabilities with low deformation torque, giving it a unique advantage that is currently unmatched by domestic satellite propulsion system tubing. The flexible tubing assembly consists of parts such as a ball joint, a straight pipe, and an outer nut. Both the straight pipe and the ball joint are made of 1Cr18Ni9Ti stainless steel and are connected using tungsten inert gas (TIG) welding. Due to the straight pipe's outer diameter of Φ1.7mm and inner diameter of only Φ0.7mm, the maximum length of the TIG-welded straight pipe is limited to approximately 3600mm, constrained by the welding shielding gas pressure. However, the straight pipe length in new commercial satellite flexible tubing assemblies is approximately 8000mm, making direct TIG welding impossible. To achieve the desired product performance, the straight pipe exceeding the limit can be divided into two or more sections. First, the ball joint is connected to one section of the straight pipe using TIG welding, and then other welding methods are used to connect the multiple sections together.

[0004] For the welding of pipeline structures, scholars at home and abroad have carried out certain research work. The connection method is mainly high-frequency induction brazing. For example, Ma Long et al. [1] used BCu35NiMnCoSi brazing filler metal to connect the Φ8mm diameter stainless steel conduit and the bend under Ar gas protection and conducted microstructure analysis on the porosity defects at the brazing corner; Wang Yuzhou [2] also used the high-frequency induction brazing method to connect the stainless steel pipeline of Hall thruster and studied the interface structure and mechanical properties of the joint. The brazing filler metal used was AgCu eutectic brazing filler metal and the protective gas was inert gas; Jia Zhihua et al. [3] used HlCuNi30-2-0.2 brazing filler metal to study the argon gas protection induction brazing process of stainless steel conduit and analyzed the microstructure of the joint; German invention patent: Method for producing a heat exchanger, in particular a sorption heattransducer (patent number: DE102013222258) discloses a process method for connecting heat exchanger pipelines by low-temperature soft brazing.

[0005] The aforementioned study primarily employed inert gas-protected high-frequency induction brazing to connect 1Cr18Ni9Ti stainless steel pipes. This method utilizes localized heating, ensuring that the overall performance of the pipe, particularly the tungsten inert gas (TIG) weld joint between the straight pipe and the ball joint, remains unaffected. It also prevents deformation of the outer nut, making it suitable for connecting multiple straight pipe sections. However, compared to welding under a vacuum atmosphere, inert gas-protected weld joints still carry a certain risk of oxidation, which can adversely affect the joint's sealing and load-bearing capacity. Furthermore, the brazing filler metals used in the study included soft filler metals, AgCu filler metals, and Cu-based filler metals, resulting in relatively low operating temperatures for the joints. Therefore, the process described in the study cannot meet the requirements for high reliability and long-life flexible deformation during satellite flexible pipeline operation in orbit.

[0006] However, no reports have been found in relevant domestic and international literature and patents regarding the use of high-temperature brazing filler metal in a vacuum environment to achieve high-frequency induction brazing of stainless steel pipes. Summary of the Invention

[0007] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a vacuum high-frequency induction brazing connection method for satellite flexible pipelines, thereby solving the problem of high-reliability sealing connection of flexible pipelines in satellite vector adjustment mechanisms.

[0008] The technical solution of this invention is:

[0009] This invention discloses a vacuum high-frequency induction brazing connection method for satellite flexible pipelines, comprising:

[0010] Design a welded joint structure, which includes a pipe joint and two straight pipe sections;

[0011] The oxide film on the pipe joint and the two straight pipe sections was removed and cleaned.

[0012] Insert the cleaned ends of the two straight pipes into the bottom of the inner holes on both sides of the pipe joint, leaving a weld seam.

[0013] A brazing filler metal is pre-placed on the outside of the weld.

[0014] The weld seam was welded according to the vacuum high-frequency induction brazing parameters; the vacuum high-frequency induction brazing parameters were: vacuum degree of 1×10⁻⁶. -2 ~1×10 -5 Pa, welding current is 300-600A;

[0015] The welding quality of the weld is inspected according to welding standards;

[0016] If the inspection passes, the welding is completed; otherwise, the weld is repaired.

[0017] Furthermore, in the above connection method, the welded joint structure includes a pipe joint and two straight pipe sections; the pipe joint has inner holes at both ends, with the depth of the inner hole at one end being greater than 5mm; the inner holes at both ends respectively mate with the two straight pipe sections, with a mating clearance of 0.02-0.06mm on both sides for a length of 2-4mm at the hole opening, and a mating clearance of no more than 0.01mm on both sides for a length of 1.5-3mm at the hole bottom.

[0018] Furthermore, in the above connection method, the specific method for removing the oxide film and cleaning the pipe joint and the two straight pipe sections is as follows:

[0019] Use sandpaper of at least 800# to polish the surface of the pipe joint and the two straight pipe sections to remove the oxide film;

[0020] Measure the outer diameter of the straight pipe after grinding and the inner diameter of the pipe joint to ensure that the fitting clearance of the joint after grinding still meets the assembly and welding requirements. If the fitting clearance is too large after grinding, process a new pipe joint according to the actual measured value of the diameter of the straight pipe to be welded after grinding, and ensure that the inner diameter of the newly processed pipe joint meets the fitting clearance requirements.

[0021] After grinding, use anhydrous ethanol or acetone to ultrasonically clean the straight pipes and pipe joints to be welded; the cleaning time should not be less than 15 minutes, and then dry or air dry naturally.

[0022] After cleaning, assembly and welding should be completed as soon as possible. If welding cannot be performed immediately, the workpieces to be welded should be placed in a drying cabinet for storage, and the storage time should not exceed 24 hours. If the storage time is too long, grinding and cleaning should be carried out again before welding.

[0023] Furthermore, in the above connection method, the pre-placement of brazing filler metal outside the weld seam specifically involves attaching a brazing filler metal ring to the straight pipe at the weld seam.

[0024] Furthermore, in the above connection method, the difference between the inner and outer diameters of the brazing ring is 0.4 to 1.5 mm, the inner diameter of the brazing ring is 1.7 to 2 mm, the outer diameter is 2.5 to 4.7 mm, and the width of the brazing ring is 1 to 2.5 mm.

[0025] Furthermore, in the above connection method, the solder is a BNi-based high-temperature Ni-based solder.

[0026] Furthermore, in the above connection method, the specific method for welding the weld seam according to the vacuum high-frequency induction brazing parameters is as follows:

[0027] Set the vacuum high-frequency induction brazing parameters and perform the welding;

[0028] After the brazing filler metal melts, it is observed that the temperature is maintained for a period of time T1. After the temperature is maintained for a period of time T1, the current is turned off and the furnace is cooled. After the cooling time T2, the gas is released, the furnace is opened, and the workpiece is removed.

[0029] If any defects are found in the workpiece, such as incomplete penetration or incomplete filling, the vacuum high-frequency induction brazing parameters are adjusted and repair welding is performed.

[0030] Furthermore, in the above connection method, the heat preservation time T1 is 15-300s; T2 is greater than 30min.

[0031] Furthermore, in the above connection method, the number of welding repairs does not exceed 2.

[0032] The advantages of this invention compared to the prior art are:

[0033] (1) Compared with high-frequency induction brazing protected by inert gases such as argon, vacuum high-frequency induction brazing of the present invention can more effectively avoid oxidation at the weld, ensure better wetting and spreading of the brazing filler metal and form a higher quality metallurgical bond, and obtain a more reliable welded joint.

[0034] (2) The high-temperature Ni-based brazing filler metal of the present invention has a high operating temperature and does not introduce alloying elements that are not present in the base material itself, making the welded joint more adaptable to the harsh aerospace service environment and reducing the risk of joint failure under complex working conditions such as alternating hot and cold.

[0035] (3) This invention uses dedicated vacuum high-frequency induction brazing process parameters, resulting in good surface formation of the flexible pipe joint, high internal quality of the weld, high mechanical properties, and high sealing performance (the weld leakage rate is less than 1×10⁻⁶ at 1MPa pressure for 5 minutes). - 4 (Pa·L / s), high reliability. Attached Figure Description

[0036] Figure 1 This is a process flow diagram of a vacuum high-frequency induction brazing connection method for a satellite flexible pipeline according to the present invention;

[0037] Figure 2 This is a schematic diagram of a single flexible pipeline structure;

[0038] Figure 3 This is a schematic diagram of the pipe fitting structure dimensions;

[0039] Figure 4 This is a schematic diagram of the welding structure of the parts to be welded;

[0040] Figure 5 This is a schematic diagram showing the amount of solder used at the preset positions;

[0041] Figure 6 This is a weld appearance morphology diagram in the specific implementation method (Example 1);

[0042] Figure 7 This is a microstructure diagram of the weld seam in the specific implementation method (Example 2). Detailed Implementation

[0043] The working principle and process of the present invention will be further explained and described below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, this embodiment provides a vacuum high-frequency induction brazing connection method for satellite flexible pipelines, the steps of which include:

[0045] Design a welded joint structure, which includes a pipe fitting and two straight pipe sections;

[0046] Remove oxide film and clean the pipe joints and two straight pipe sections;

[0047] Insert the cleaned ends of the two straight pipes into the bottom of the inner holes on both sides of the pipe joint, leaving a weld seam.

[0048] Pre-place brazing filler metal on the outside of the weld;

[0049] Weld the seam according to the vacuum high-frequency induction brazing parameters;

[0050] The welding quality of the weld is inspected according to welding standards;

[0051] If the inspection passes, the welding is completed; otherwise, the weld is repaired.

[0052] The detailed steps are as follows:

[0053] Step 1, Welded Joint Structural Requirements: (Illustrated) Figure 2 The pipe fitting connects two straight pipe sections. The fitting material is the same as the straight pipe material: 1Cr18Ni9Ti stainless steel. An inner hole is machined on each side of the fitting. The inner hole is approximately a stepped hole, with a depth of 5mm on each side. The diameter of the inner hole within a 3mm length of the hole opening is [missing information]. That is, the clearance between the straight pipe and the two sides is 0.02~0.06mm, and the inner diameter within 2mm of the bottom of the hole is... That is, the clearance should not exceed 0.01mm on both sides. The end of the straight pipe may be chamfered appropriately, and the bottom of the inner hole of the pipe fitting should not have an excessively large radius to ensure that the straight pipe can be inserted into the bottom of the inner hole of the pipe fitting.

[0054] Step 2: Oxide Film Removal and Cleaning Before Welding: When an oxide film is present on the straight pipe and pipe joint to be welded, use sandpaper of at least 800# to remove the oxide film. After grinding, measure the outer diameter of the straight pipe and the inner diameter of the pipe joint at the welding location to ensure that the fitting clearance of the joint still meets the assembly and welding requirements. If the fitting clearance is too large after grinding, record the measured value of the straight pipe diameter after grinding, and then process a new pipe joint according to the measured value, ensuring that the inner diameter of the newly processed pipe joint meets the fitting clearance requirements. After grinding, use anhydrous ethanol or acetone to ultrasonically clean the straight pipe and pipe joint to be welded for at least 15 minutes, then dry or air dry. Do not touch the workpiece with bare hands after cleaning. Assembly and welding should be completed as soon as possible after cleaning. If welding cannot be performed immediately, the workpiece to be welded should be placed in a drying cabinet for storage, and the storage time should not exceed 24 hours. If the storage time is too long, grinding and cleaning must be repeated before welding.

[0055] Step 3, Pre-welding assembly and pre-positioning of brazing filler metal:

[0056] Insert the cleaned ends of the two straight pipes into the inner holes on both sides of the pipe fitting. Since the clearance at the bottom of the inner hole is small, ensure the straight pipe is inserted to a depth of 5mm. Then press... Figure 4 This diagram illustrates the pre-placement of brazing filler metal on the outside of the weld. The brazing filler metal used is a BNi-based high-temperature Ni-based filler metal (GB / T 10859 grades: BNi63~BNi95, etc., AWS American Welding Society grades BNi-1~BNi-13, etc.). Due to the small weld size and low filler metal usage, the amount of pre-placed filler metal is indicated by volume instead of weight. Figure 5 The diagram illustrates a simplified version of the pre-placed brazing filler metal, consisting of a brazing filler metal ring fitted around the outside of a straight pipe. The difference between the inner and outer diameters of the ring is approximately 0.4–1.5 mm, meaning the inner diameter of the ring is Φ1.7 mm and the outer diameter is approximately Φ2.5–4.7 mm. The width of the ring should be 1–2.5 mm. If powdered brazing filler metal is used, it should be mixed into a paste before application. If molten block brazing filler metal is used, it should be machined into a ring that meets the dimensional requirements before use. If brazing filler metal foil or wire is used, it should be shaped to ensure it meets the dimensional requirements before use. Care should be taken to ensure that the pre-placed brazing filler metal adheres tightly to the workpiece and weld seam to prevent the melted filler metal from failing to fill the weld seam. For magnetic induction coils of different shapes, such as O-shaped coils, pre-assembly and pre-placement of solder should be completed inside the coil before soldering. If a C-shaped coil is used, assembly and pre-placement of solder can be completed first, and then the joint to be soldered can be transferred to the inside of the coil. Ensure that the joint to be soldered is centered within the coil. If necessary, a positioning fixture made of non-magnetic ceramic or other materials can be used to fix the joint within the coil. The remaining part of the conduit should be coiled into a circle with a diameter of not less than Φ300mm and then fixed to avoid scratching or bending deformation of the ball joint and straight pipes in non-soldering areas.

[0057] Step 4: Perform welding according to the vacuum high-frequency induction brazing parameters:

[0058] Vacuum degree is 1×10 -2 ~1×10 -5 The welding current is 300–600 A. After observing the melting of the brazing filler metal, begin holding the workpiece at this temperature for 15–300 seconds. Then, turn off the current and allow the furnace to cool. The workpiece can only be removed after a cooling time of at least 30 minutes, after which the furnace can be vented and the workpiece taken out. This prevents severe oxidation from contact with the atmosphere when the joint temperature is high. If defects such as incomplete penetration or incomplete filling are found after welding, the process parameters can be adjusted appropriately for repair welding. The number of repair welds should not exceed two to avoid deterioration of the brazing seam structure and affecting the joint performance.

[0059] The invention will now be further described with reference to the accompanying drawings.

[0060] Example 1

[0061] This embodiment provides a vacuum high-frequency induction brazing connection method for satellite flexible pipelines, mainly including steps such as weld joint structure design, pre-weld oxide film removal and cleaning, pre-weld assembly and pre-placement of brazing filler metal, vacuum high-frequency induction brazing, and post-weld quality inspection. The weld joint structure design, pre-weld assembly and pre-placement of brazing filler metal, and vacuum high-frequency induction brazing parameters are the key aspects of this invention, involving critical processes in the development of satellite flexible pipelines. Other processes are conventional.

[0062] The implementation steps are as follows:

[0063] 1. Design of welded joint structure

[0064] according to Figure 3 As shown, a pipe fitting is used to connect two straight pipe sections. The inner hole of the pipe fitting is divided into two sections. The material of the pipe fitting is 1Cr18Ni9Ti. It is required that an inner hole be machined at each end of the pipe fitting. The inner hole is approximately a stepped hole. The clearance between the inner hole at the opening and the straight pipe is 0.02mm to 0.06mm on both sides. The clearance between the inner hole at the bottom and the straight pipe is no more than 0.01mm on both sides.

[0065] 2. Oxide film removal and cleaning before welding

[0066] (1) Remove oxide film before welding: Use 800# or higher sandpaper to grind and remove the oxide film at the welding location. After grinding, the joint assembly gap should still meet the fitting requirements. Mechanically grind to remove the oxide scale at the welding location of the straight pipe and the section of the inner hole of the pipe joint near the orifice. Take care to avoid excessive grinding, which may affect the assembly gap.

[0067] (2) Pre-welding cleaning: Use anhydrous ethanol or acetone for ultrasonic cleaning. The cleaning time should not be less than 15 minutes. After cleaning, dry the workpiece by hand or air dry it naturally. Do not touch the workpiece with bare hands. After cleaning, assemble and weld immediately or transfer it to a drying cabinet for storage. The storage time should not exceed 24 hours.

[0068] 3. Pre-welding assembly and pre-fabrication of brazing filler metal

[0069] Inside the coil, two straight tubes are inserted and assembled with a pipe fitting. High-temperature Ni-based brazing filler metal is pre-placed at the weld joint to ensure close contact between the filler metal and the workpiece to be welded. The remaining part of the tubing is coiled and fixed to prevent scratches or bending deformation of the ball head and straight tubes in non-welding areas.

[0070] (1) Pre-welding assembly: Insert the two straight pipes to be welded into the inner holes on both sides of the pipe joint, and confirm that the straight pipes are inserted to the bottom of the hole, with an insertion depth of 5mm.

[0071] (2) Pre-placed brazing filler metal: according to Figure 5 The diagram illustrates a brazing ring fitted onto the outside of a straight pipe. The brazing ring has an inner diameter of Φ1.7mm, an outer diameter of Φ2.5~Φ4.7mm, and a width of 1~2.5mm. The brazing ring should fit snugly against the workpiece and the weld.

[0072] 4. Vacuum high-frequency induction brazing

[0073] Reasonably control the amount of brazing filler metal to ensure sufficient filler metal to fill the weld gap, while avoiding excessive filler metal that could result in an excessively large weld bevel, affecting the subsequent shaping and on-orbit flexible deformation function of the flexible pipeline. Reasonably control the high-frequency current and welding time to ensure that the brazing filler metal completely melts and fills the weld gap to form a good metallurgical bond, obtaining a highly reliable sealing joint, while avoiding excessively violent reactions that could cause erosion defects.

[0074] (1) Vacuuming: The vacuum level is 1×10 -2 ~1×10 -5 Pa.

[0075] (2) Welding: Turn on the heating current, which is 300-600A. When the brazing filler melts, start holding the heat for 15-300 seconds. After holding the heat, turn off the heating current and cool down the furnace.

[0076] (3) Removal of workpieces: After cooling for no less than 30 minutes, the gas can be released and the furnace door opened to remove the workpieces.

[0077] (4) Repair welding: If there are defects such as incomplete penetration or incomplete filling on the outside of the brazing seam, repair welding can be performed. The number of repair welding should not exceed 2.

[0078] 5. Weld quality inspection

[0079] (1) External quality: Inspect the appearance of the weld with the naked eye or a 10x microscope to ensure that the brazing angle is uniform, continuous and smooth, without incomplete penetration, incomplete filling and external crack defects.

[0080] (2) Brazing rate: Select product joints by batch or use test pieces with the same structure as the actual joints to cut and grind metallographic test pieces, and inspect them with an optical microscope to ensure that the brazing rate of the weld within the 3mm insertion depth of the straight pipe is not less than 85%.

[0081] (3) Pressure Leakage Rate: Detected using a vacuum helium mass spectrometer, with a pressure hold of 1 MPa for 5 minutes, the weld leakage rate is less than 1 × 10⁻⁶. -4 Pa·L / s

[0082] like Figure 6 As shown, the inner diameters of the two sections of the pipe fitting's inner hole are respectively... and The assembly gaps are 0.02–0.04 mm and no more than 0.01 mm, respectively. Second, after removing the oxide film before welding, the weld is ultrasonically cleaned with anhydrous ethanol for 20 minutes, then air-dried and immediately assembled for welding. Third, the brazing filler metal used is BNi82CrSiBFe powder brazing filler metal with a particle size of 200 mesh. The filler metal is mixed into a paste, coated on the outside of the weld, and shaped into a ring. The inner diameter of the brazing filler metal ring is Φ1.7 mm, the outer diameter is approximately Φ2.5–Φ2.7 mm, and the width is approximately 2–2.2 mm. Fourth, the vacuum degree is 5 × 10⁻³ Pa, the welding current is 450 A, the holding time is 100 s, and the post-weld furnace cooling time is 45 min.

[0083] Example 2

[0084] like Figure 7 As shown, the difference between this embodiment and embodiment 1 is that the solder used in step 3 is BNi-2 foil solder with a thickness of 0.02 mm, while the rest is the same as in embodiment 1.

[0085] Example 3

[0086] The difference between this embodiment and Embodiment 1 is that the welding assembly gap in step one is 0.04-0.06 mm and no more than 0.01 mm, respectively, while the rest is the same as in Embodiment 1.

[0087] Example 4

[0088] The difference between this embodiment and embodiments 1, 2 or 3 is that: in step 3, the brazing filler metal used is BNi-5 powder brazing filler metal with a particle size of 200 mesh; in step 4, the welding current is 520A and the holding time is 110s, and the rest is the same as in embodiment 1.

[0089] The above embodiments are merely explanations of the present invention and should not be construed as limiting the present invention. Therefore, any implementation methods similar to the present invention or implementation methods used in other similar structures but with similar concepts to the present invention are within the protection scope of the present invention.

[0090] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0091] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A vacuum high-frequency induction brazing method for satellite flexible pipelines, characterized in that, include: Design a welded joint structure, which includes a pipe joint and two straight pipe sections; The straight pipe has an outer diameter of Φ1.7mm, an inner diameter of Φ0.7mm, and a length of 8000mm; both the pipe fittings and the straight pipe are made of 1Cr18Ni9Ti. Remove oxide film and clean the pipe joints and two straight pipe sections; Insert the cleaned ends of the two straight pipes into the bottom of the inner holes at both ends of the pipe joint, leaving a weld seam. Pre-place brazing filler metal on the outside of the weld; The weld seam was welded according to the vacuum high-frequency induction brazing parameters; the vacuum high-frequency induction brazing parameters were: vacuum degree of 1×10⁻⁶. -2 ~1×10 -5 Pa, welding current is 300~600A; The welding quality of the weld is inspected according to welding standards; If the inspection passes, the welding is completed; otherwise, the weld is repaired. The welded joint structure has a single-end inner hole depth greater than 5mm; the inner holes at both ends respectively mate with two straight pipe sections, with a 2-4mm length of inner hole fitting clearance of 0.02-0.06mm on both sides at the hole opening and a 1.5-3mm length of inner hole fitting clearance of no more than 0.01mm on both sides at the hole bottom; The solder is a BNi-based high-temperature Ni-based solder; The specific method for welding the weld seam according to the vacuum high-frequency induction brazing parameters is as follows: Set the vacuum high-frequency induction brazing parameters and perform the welding; After the brazing filler metal melts, it is observed that the temperature is maintained. After the temperature is maintained, the current is turned off and the furnace is cooled. After cooling, the gas is released and the furnace is opened to remove the workpiece. If any defects such as incomplete penetration or incomplete filling are found in the inspected workpiece, the vacuum high-frequency induction brazing parameters are adjusted and repair welding is performed. The heat preservation time is 15~300s; the cooling time is greater than 30min.

2. The vacuum high-frequency induction brazing connection method for a satellite flexible pipeline according to claim 1, characterized in that: The specific method for removing the oxide film and cleaning the pipe joint and the two straight pipe sections is as follows: Use sandpaper of at least 800# to polish the surface of the pipe joint and the two straight pipe sections to remove the oxide film; Measure the outer diameter of the straight pipe after grinding and the inner diameter of the pipe joint to ensure that the fitting clearance of the joint after grinding still meets the assembly and welding requirements. If the fitting clearance is too large after grinding, process a new pipe joint according to the actual measured value of the diameter of the straight pipe to be welded after grinding, and ensure that the inner diameter of the newly processed pipe joint meets the fitting clearance requirements. After grinding, use anhydrous ethanol or acetone to ultrasonically clean the straight pipes and pipe joints to be welded; the cleaning time should not be less than 15 minutes, and then dry or air dry naturally. After cleaning, complete the assembly and welding. If welding cannot be performed immediately, the workpieces to be welded should be placed in a drying cabinet and stored for no more than 24 hours. If the storage time exceeds 24 hours, grinding and cleaning must be performed again before welding.

3. The vacuum high-frequency induction brazing connection method for a satellite flexible pipeline according to claim 1, characterized in that: The aforementioned pre-placement of brazing filler metal outside the weld seam specifically involves attaching a brazing filler metal ring to the straight pipe at the weld seam.

4. The vacuum high-frequency induction brazing connection method for a satellite flexible pipeline according to claim 3, characterized in that: The difference between the inner and outer diameters of the brazing ring is 0.4~1.5mm, the inner diameter of the brazing ring is 1.7~2mm, the outer diameter is 2.5~4.7mm, and the width of the brazing ring is 1~2.5mm.

5. The vacuum high-frequency induction brazing connection method for a satellite flexible pipeline according to claim 1, characterized in that: The number of welding repairs should not exceed 2.

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