Pressure-resistant dissimilar conduit welding method

Abstract

The application provides a pressure-resistant dissimilar conduit welding method, which comprises the following steps: designing a welding structure of a first conduit and a second conduit, wherein the first conduit and the second conduit are made of different materials; performing finish machining and assembly on first conduit and second conduit blanks according to the designed welding structure; pre-assembling the first conduit, the second conduit and filler metal into an assembly; and welding the assembly to obtain a welded piece. The welding method can reduce the weight of the existing pipeline system.

Description

Technical Field

[0001] This invention relates to the field of dissimilar material welding, and specifically to a method for welding pressure-resistant dissimilar conduits. Background Technology

[0002] The pressurization and delivery piping system of a launch vehicle contains a large number of dissimilar conduits. These conduits are typically connected by flanges and then secured with fasteners. The weight of the connecting flanges and the entire ring of fasteners is considerable, increasing the overall weight of the piping system.

[0003] To meet the requirements for weight reduction in pipeline systems and ensure the airtightness of pipelines, it is particularly important to design a pressure-resistant dissimilar conduit welding method. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for welding pressure-resistant dissimilar conduits.

[0005] This invention provides a method for welding dissimilar pressure-resistant conduits, comprising: providing a first conduit, a second conduit, and brazing filler metal; designing a welding structure for the first and second conduits, wherein the first and second conduits are made of different materials; precision machining and fitting the first and second conduit blanks according to the designed welding structure; pre-assembling the first and second conduits and brazing filler metal into an assembly; and welding the assembly to obtain a welded part. The design of the welding structure for the first and second conduits includes: designing the ends of the first and second conduits to be fitted as tapered surfaces; calculating the taper of the end of the first conduit to be fitted based on relevant parameters of the first and second conduits.

[0006]

[0007] In the formula, T is the temperature during the solder melting stage, α is the coefficient of linear expansion of the first conduit at the brazing temperature, β is the coefficient of linear expansion of the second conduit at the brazing temperature, R is the radius of the end face of the second conduit to be welded at room temperature, ΔL is the gap between the first and second conduits at the brazing temperature, and Δh is the sliding height of the second conduit; the step of precision machining and fitting the first and second conduits according to the designed welding structure includes: machining the circumferential inner wall of the end to be fitted of the first conduit and the circumferential outer wall of the end to be fitted of the second conduit into mutually compatible conical surfaces according to the calculation results.

[0008] According to one embodiment of the present invention, after processing the circumferential inner wall of the first conduit to be sleeved end and the circumferential outer wall of the second conduit to be sleeved end into mutually compatible conical surfaces based on the calculation results, the process includes: processing a brazing groove on the end face of the first conduit to be sleeved end for placing brazing filler metal.

[0009] According to one embodiment of the present invention, before the first conduit, the second conduit, and the brazing filler metal are pre-assembled into a component, the process includes: pre-treating the first conduit, the second conduit blanks, and the brazing filler metal.

[0010] According to one embodiment of the present invention, the pretreatment of the first conduit, the second conduit blank and the brazing filler metal includes: chemical cleaning of the brazing filler metal, the first conduit and the second conduit.

[0011] According to one embodiment of the present invention, the pretreatment of the first conduit, the second conduit blank and the brazing filler metal includes: silver plating the circumferential outer side of the end of the second conduit to be welded.

[0012] According to one embodiment of the present invention, the first conduit is an aluminum tube, the second conduit is a stainless steel tube, and the brazing filler metal is an aluminum-silicon eutectic brazing filler metal; the pre-assembly of the first conduit, the second conduit, and the brazing filler metal into an assembly includes: dissolving flux in anhydrous ethanol to prepare a thick solution; uniformly applying the thick solution to the circumferential sidewalls of the ends of the first and second conduits to be connected, and drying the first and second conduits; connecting the first and second conduits together; and winding the brazing filler metal around the circumferential outer sidewall of the end of the second conduit to be connected, close to the first conduit, to form an assembly.

[0013] According to one embodiment of the present invention, welding the assembly to obtain a welded part includes: assembling the assembly into a furnace and brazing it in the furnace; assembling the assembly into the furnace includes: moving the assembly into the brazing furnace with the second guide tube on top and the first guide tube on the bottom, and keeping it horizontal and without tilting; placing a welding pressure block on the upper end of the second guide tube, and applying downward pressure to the second guide tube during the brazing process to control the gap between the first and second guide tubes; brazing it in the furnace includes: setting the temperature and heating time in the brazing program; starting the program to perform welding; and stopping the heating program after the assembly reaches the holding time.

[0014] According to one embodiment of the present invention, the process further includes finishing the welded parts and inspecting the weld seams after they are removed from the furnace.

[0015] According to one embodiment of the present invention, the weld inspection includes performing a helium mass spectrometry leak rate test on the welded component.

[0016] According to one embodiment of the present invention, the process of finishing and fitting the first and second conduit blanks according to the designed welding structure includes: setting a wall thickness allowance for the ends of the first and second conduits to be fitted during the processing.

[0017] According to the pressure-resistant dissimilar conduit welding method of the present invention, the ends of the first and second conduits to be joined are designed as conical surfaces based on the relevant parameters of the first and second conduits, and then assembled and welded. This not only reduces the weight of existing pipeline systems but also effectively controls the welding gap, ensuring the sealing, pressure resistance, and welding quality between the conduits. This welding method meets the need for weight reduction in pipeline systems and solves the problem of welding pressure-resistant dissimilar conduits.

[0018] It should be understood that the above general description and the following specific embodiments are merely exemplary and illustrative, and do not limit the scope of the invention. Attached Figure Description

[0019] The accompanying drawings, which are part of the specification of this invention, illustrate exemplary embodiments of the invention. The drawings, together with the description in the specification, serve to illustrate the principles of the invention.

[0020] Figure 1 This is a flowchart of a pressure-resistant dissimilar conduit welding method according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the assembly structure of a heterogeneous catheter assembly according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of a heterogeneous conduit assembly according to an embodiment of the present invention at the brazing temperature;

[0023] Figure 4 This is a schematic diagram of the structure of a heterogeneous catheter assembly after welding according to an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1-First guide tube; 2-Second guide tube; 3-Fining filler metal. Detailed Implementation

[0026] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and to exemplify the principles of the present invention, and are not configured to limit the present invention. In addition, the structural components in the drawings are not necessarily drawn to scale. For example, the dimensions of some structural components or regions in the drawings may be enlarged for other structural components or regions to aid in the understanding of the embodiments of the present invention.

[0027] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of the embodiments of the present invention. In the description of the present invention, it should be noted that, unless otherwise stated, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0028] Furthermore, the terms "comprising," "including," "having," or any other variations thereof are intended to cover non-exclusive inclusion, such that a structure or component that includes a list of elements includes not only those elements but also other structural elements that are not expressly listed or inherent to the structure or component. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the article or apparatus that includes the element.

[0029] Spatial relation terms such as "below," "under," "under," "low," "above," "on," and "high" are used for descriptive convenience to explain the positioning of one element relative to a second element, indicating that these terms are intended to cover different orientations of the device, in addition to those different from those shown in the figure. Furthermore, phrases such as "one element on / below another element" can indicate that two elements are in direct contact, or that there are other elements between the two elements. In addition, terms such as "first" and "second" are also used to describe individual elements, areas, parts, etc., without specifically indicating order or sequence, and should not be considered restrictive. Similar terms are used throughout the description to represent similar elements.

[0030] In the following description of the present invention, the terms "rocket," "launch vehicle," "spacecraft," "space launch vehicle," or "missile" may be used in certain scenarios for ease of description, and their connotations are not limited to the specific terms used. Generally, the launch vehicles and rockets of the present invention include space launch vehicles used to carry satellites, spacecraft, or other probes, as well as various missiles, rockets, and other weapons used to carry military payloads, and similar products capable of delivering payloads into the air. Those skilled in the art, when interpreting the above specific terms, should not limit the launch vehicle to only one of the launch vehicles or missiles based on the specific terms used in the description, thereby narrowing the scope of protection of the present invention.

[0031] It will be apparent to those skilled in the art that the present invention can be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention.

[0032] Figure 1 This is a flowchart of a pressure-resistant dissimilar conduit welding method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the assembly structure of a heterogeneous catheter assembly according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a heterogeneous conduit assembly according to an embodiment of the present invention at the brazing temperature; Figure 4 This is a schematic diagram of the structure of a heterogeneous catheter assembly after welding according to an embodiment of the present invention.

[0033] like Figure 1 As shown, this invention provides a method for welding dissimilar pressure-resistant conduits, comprising: providing a first conduit 1, a second conduit 2, and brazing filler metal 3; designing a welding structure for the first conduit 1 and the second conduit 2, wherein the first conduit 1 and the second conduit 2 are made of different materials; precision machining and fitting the blanks of the first conduit 1 and the second conduit 2 according to the designed welding structure; pre-assembling the first conduit 1, the second conduit 2, and the brazing filler metal 3 into an assembly; and welding the assembly to obtain a welded part. Designing the welding structure of the first conduit 1 and the second conduit 2 includes: designing the ends of the first conduit 1 and the second conduit 2 to be fitted as conical surfaces; calculating the taper of the end of the first conduit 1 to be fitted according to the relevant parameters of the first conduit 1 and the second conduit 2.

[0034]

[0035] In the formula, T is the temperature of the solder 3 during the melting stage, α is the linear expansion coefficient of the first conduit 1 at the brazing temperature, β is the linear expansion coefficient of the second conduit 2 at the brazing temperature, R is the radius of the end face of the second conduit 2 to be welded at room temperature, ΔL is the gap between the first conduit 1 and the second conduit 2 at the brazing temperature, and Δh is the sliding height of the second conduit 2.

[0036] According to the designed welding structure, the first conduit 1 and the second conduit 2 are precision machined and fitted together, including: according to the calculation results, the circumferential inner wall of the end to be fitted of the first conduit 1 and the circumferential outer wall of the end to be fitted of the second conduit 2 are machined into mutually compatible conical surfaces.

[0037] In this embodiment, by designing the ends of the first conduit 1 and the second conduit 2 to be fitted as conical surfaces, the conical surfaces of the first conduit 1 and the second conduit 2 are fitted together, which ensures the coaxiality of the fit between the first conduit 1 and the second conduit 2, effectively controls the welding gap, and facilitates the uniform filling of the entire welding interface by the molten filler metal 3 during the welding process. This welding method calculates the appropriate fitting taper required for conduits of different diameters based on the relevant parameters of the first conduit 1 and the second conduit 2, and then performs assembly welding.

[0038] Using the welding method of this embodiment, at least some of the connecting flanges and fasteners in the original pipeline system can be eliminated, effectively reducing the weight of the existing pipeline system. This provides an effective means to reduce the weight of the future rocket pipeline system itself and increase the launch payload of the launch vehicle. In addition, this welding method can effectively control the welding gap, ensuring the sealing, pressure resistance, and welding quality between the conduits.

[0039] According to one embodiment of the present invention, after processing the circumferential inner wall of the end to be sleeved of the first conduit 1 and the circumferential outer wall of the end to be sleeved of the second conduit 2 into mutually compatible conical surfaces based on the calculation results, the process includes: processing a brazing groove on the end face of the end to be sleeved of the first conduit 1 for placing brazing filler metal 3.

[0040] In this embodiment, the solder groove can be adapted to the shape of the solder 3, such as the width of the solder groove being the same as the diameter of the solder 3.

[0041] According to one embodiment of the present invention, before pre-assembling the first conduit 1, the second conduit 2 and the brazing filler metal 3 into an assembly, the process includes: pre-treating the blanks of the first conduit 1 and the second conduit 2 and the brazing filler metal 3.

[0042] According to one embodiment of the present invention, the pretreatment of the blanks of the first conduit 1 and the second conduit 2 and the brazing filler metal 3 includes: chemical cleaning of the brazing filler metal 3, the first conduit 1 and the second conduit 2.

[0043] In this embodiment, the brazing filler metal 3, the first conduit 1, and the second conduit 2 can be chemically cleaned simultaneously to remove surface oil, oxide film, etc.

[0044] According to one embodiment of the present invention, the pretreatment of the blanks of the first conduit 1 and the second conduit 2 and the brazing filler metal 3 includes: silver plating on the circumferential outer side of the end of the second conduit 2 to be welded.

[0045] In this embodiment, silver plating is applied to the surface of the second conduit 2 to improve the wettability of the brazing filler metal 3 on the surface of the second conduit 2 and to prevent water absorption during service, which could lead to corrosion damage to the weld.

[0046] According to one embodiment of the present invention, the first conduit 1 is an aluminum tube, the second conduit 2 is a stainless steel tube, and the brazing filler metal 3 is an aluminum-silicon eutectic brazing filler metal 3. Pre-assembling the first conduit 1, the second conduit 2, and the brazing filler metal 3 into an assembly includes: dissolving flux in anhydrous ethanol to prepare a thick solution; uniformly applying the thick solution to the circumferential sidewalls of the ends of the first conduit 1 and the second conduit 2 to be connected, and drying the first conduit 1 and the second conduit 2; and connecting the first conduit 1 and the second conduit 2 by winding the brazing filler metal 3 around the circumferential outer sidewall of the end of the second conduit 2 to be connected, close to the first conduit 1, to form an assembly.

[0047] In this embodiment, T is the temperature during the melting and filling stage of the brazing filler metal 3 (i.e., the brazing temperature), α is the coefficient of linear expansion of aluminum at the brazing temperature, β is the coefficient of linear expansion of stainless steel at the brazing temperature, R is the radius of the lower end face of the stainless steel (i.e., the end face to be welded) at room temperature, ΔL is the gap between the aluminum tube and the stainless steel tube at the brazing temperature (preferably 0.15 mm), and Δh is the sliding height of the second guide tube 2 (preferably 10 mm). The outer circumferential side of the end of the stainless steel tube to be welded is machined into a conical surface, and the vertical length of the conical surface can be 30-35 mm. According to the calculation results, the inner circumferential side of the end of the aluminum tube to be sleeved is machined into a conical surface, and the stainless steel tube is used as the fitting reference to ensure that the coaxiality of the stainless steel tube and the aluminum tube after sleeved does not exceed 0.05 mm. The brazing filler metal can be φ1.5 mm aluminum welding wire. According to the outer diameter of the stainless steel tube, the pre-treated brazing filler metal can be cut, wherein the length of the brazing filler metal is not less than the circumference of the end of the stainless steel tube to be welded. For example, fluoride flux can be dissolved in anhydrous ethanol to prepare a thick solution with a mass fraction of 60%-70%. For example, non-corrosive fluoride fluxes can be used to obtain dense and reliable sealing welds, enhance the pressure resistance of the conduit, and better meet the technical specifications of the pipeline system.

[0048] In this embodiment, the first conduit 1 can be an aluminum tube or an aluminum alloy tube. Some stainless steel tubes in the piping system can be replaced with aluminum tubes or aluminum alloy tubes to further reduce the weight of the piping system. Based on a conduit with an inner diameter of approximately φ50, compared to traditional solutions, the steel-aluminum welding technology provided in this embodiment can reduce the weight of the piping system by approximately 35% to 45%. For conduits with an inner diameter greater than φ50, the weight reduction effect is even more significant.

[0049] Furthermore, both the brazing filler metal 3 and the aluminum tube are chemically cleaned simultaneously to remove surface oil and oxide film. Then, the surface of the stainless steel tube (when the conduit is made of stainless steel) is silver-plated, with a silver layer thickness of approximately 20-30 μm. The silver plating layer can prevent the Al-Fe direct contact reaction from forming a brittle structure and improve the wettability of the brazing filler metal 3 on the surface of the stainless steel tube.

[0050] Specifically, the main problem to be solved in steel-aluminum welding is preventing the formation of brittle Al-Fe metal compounds at the steel-aluminum weld interface. Research by scholars both domestically and internationally has involved processes such as brazing, laser welding, and friction stir welding, with joint types primarily being lap welds or fillet welds. However, the aforementioned welding methods differ in the applicable connection structures and connection strengths, and are not suitable for welding pressure-resistant, sealed conduits (especially steel-aluminum conduits) in pressurized delivery systems.

[0051] According to one embodiment of the present invention, the brazing filler metal 3 can be wound around the circumferential outer wall of the end of the second conduit 2 (stainless steel tube) to be sleeved, keeping the stainless steel tube inside and the aluminum tube outside, and the brazing filler metal 3 is placed in the brazing filler metal groove of the end face of the aluminum tube to be welded.

[0052] According to one embodiment of the present invention, welding an assembly to obtain a welded part includes: assembling the assembly into a furnace and brazing it in the furnace. Assembling the assembly into the furnace includes: moving the assembly into the brazing furnace with the second conduit 2 above and the first conduit 1 below, maintaining a horizontal position without tilting; placing a welding pressure block on the upper end of the second conduit 2 and applying downward pressure to the second conduit 2 during brazing to control the gap between the first conduit 1 and the second conduit 2. Brazing in the furnace includes: setting the temperature and heating time in the brazing program; starting the program for welding; and stopping the heating program after the assembly reaches the holding time.

[0053] In this embodiment, a welding block of appropriate weight can be selected according to the outer diameter of the stainless steel pipe for auxiliary welding.

[0054] Furthermore, after closing the furnace door, the procedure for brazing two conduits (taking aluminum tube and stainless steel tube as examples) in the furnace can be set according to the table below.

[0055] Serial Number Starting temperature / ℃ End temperature / ℃ Time / min 1 room temperature 400 80～90 2 400 400 80～90 3 400 550 10～20 4 550 550 60～70 5 550 590 5～10 6 590 600 10～20

[0056] Start the welding program. After the welding program enters the 6th stage, the holding time can be adjusted according to the assembly size and real-time temperature. After the holding time is reached, stop the heating program and allow the assembly to cool to room temperature with the furnace.

[0057] According to one embodiment of the present invention, a thermocouple is brought into contact with the outer wall of the fitting area of ​​the assembly to monitor the temperature of the assembly in real time during the brazing process.

[0058] According to one embodiment of the present invention, after welding the assembly to obtain the welded part, the process further includes finishing the welded part and inspecting the weld after it is taken out of the furnace.

[0059] Furthermore, the finishing and weld inspection of the welded parts after the furnace is removed may include: removing the welded parts or assemblies and checking whether the weld legs of the conduits (such as the weld legs of steel and aluminum conduits) are fully filled and whether the appearance of the inner and outer walls is good; performing ultrasonic testing on the brazed seams of the conduits; and performing finishing on the inner and outer walls of the brazed assemblies according to the final wall thickness of the welded parts, while removing the residual flux floating on the surface.

[0060] According to one embodiment of the present invention, weld inspection includes performing a helium mass spectrometry leak rate test on the welded component.

[0061] In this embodiment, the helium mass spectrometry leak rate test of the welded component can be performed after the inner and outer walls of the brazed component have been machined. After the helium mass spectrometry leak rate test of the welded component, the pressure resistance test of the conduit can be performed.

[0062] According to one embodiment of the present invention, the blanks of the first conduit 1 and the second conduit 2 are precision machined and fitted according to the designed welding structure, including: setting a allowance for the wall thickness of the ends of the first conduit 1 and the second conduit 2 to be fitted during the machining process.

[0063] In this embodiment, during the process of finishing the outer circumferential wall of the end to be fitted of the second conduit 2 into a tapered surface, the wall thickness can be 2-3 mm more than the required final value to allow for finishing. Similarly, during the process of finishing the inner circumferential wall of the end to be fitted of the first conduit 1 into a tapered surface, the conduit thickness can be 3 mm more than the required final value to allow for finishing.

[0064] Taking the brazing of DN50 and DN70 dissimilar steel-aluminum conduits in a furnace using the welding method provided by this invention as an example, the weld legs of the conduits were fully and uniformly filled after welding. Ultrasonic testing of the weld seams of the finished conduits showed that the brazing rate of the DN50 steel-aluminum conduit was over 95%, and the brazing rate of the DN70 steel-aluminum conduit was over 90%. Helium mass spectrometry leak rate testing of the finished conduits showed that the leak rates of both the DN50 and DN70 steel-aluminum conduits were less than 1.0 × 10⁻⁶. -7 Pa·m 3 / s (The design target for leakage rate of steel and aluminum conduits is no more than 1.0×10 -5 Pa·m 3 / s, improving the leakage rate by two orders of magnitude. Therefore, this brazing method can be used in systems with even higher leakage rate requirements. For example, in a 10-cycle alternating damp heat environment test on a DN70 steel-aluminum conduit, the helium mass spectrometry leakage rate of its joint remained less than 1×10⁻⁶. -7 Pa·m 3 The structure exhibits excellent corrosion resistance. Pressure strength tests were conducted on the precision-machined conduits. The burst pressure of the DN50 steel-aluminum conduit reached 7 MPa, and the burst pressure of the DN70 steel-aluminum conduit reached 5 MPa (the design specification for the room temperature burst pressure of steel-aluminum conduits is no less than 2.5 MPa), far exceeding the design requirements. This welding method yields welded components with a large safety margin. For example, a room temperature shear test on the DN70 steel-aluminum conduit showed an ultimate breaking load of 110 kN, more than twice the ultimate breaking load of the pipe body. A liquid nitrogen temperature (-196℃) shear test on the DN70 steel-aluminum conduit showed an ultimate breaking load of 150 kN, indicating that this structure is not only suitable for room temperature fuel rockets but can also be widely applied to cryogenic fuel rockets.

[0065] The above embodiments of the present invention can be combined with each other and have corresponding technical effects.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for welding dissimilar pressure-resistant conduits, characterized in that, include: Provides a first conduit, a second conduit, and brazing filler metal; Design a welding structure for the first and second conduits, wherein the first and second conduits are made of different materials; According to the designed welding structure, the blanks of the first and second conduits are precision machined and fitted onto the vehicle. The first conduit, the second conduit, and the brazing filler metal are pre-assembled into a modular assembly. The assembled components are welded to obtain a welded part; The design of the welding structure for the first and second conduits includes: designing the ends of the first and second conduits to be fitted as tapered surfaces; calculating the taper of the end of the first conduit to be fitted based on the relevant parameters of the first and second conduits. In the formula, T is the temperature during the solder melting stage, α is the coefficient of linear expansion of the first conduit at the brazing temperature, β is the coefficient of linear expansion of the second conduit at the brazing temperature, R is the outer radius of the end face of the second conduit to be welded at room temperature, ΔL is the gap between the first and second conduits at the brazing temperature, and Δh is the sliding height of the second conduit. The process of precision machining and fitting the first and second conduit blanks according to the designed welding structure includes: machining the circumferential inner wall of the first conduit to be fitted and the circumferential outer wall of the second conduit to be fitted into mutually compatible conical surfaces according to the calculation results.

2. The welding method according to claim 1, characterized in that, After processing the circumferential inner wall of the first conduit to be sleeved end and the circumferential outer wall of the second conduit to be sleeved end into mutually compatible conical surfaces according to the calculation results, the process includes: processing a brazing groove on the end face of the first conduit to be sleeved end for placing brazing filler metal.

3. The welding method according to claim 1, characterized in that, Before pre-assembling the first conduit, the second conduit, and the brazing filler metal into a complete assembly, the process includes: pre-treating the blanks of the first conduit, the second conduit, and the brazing filler metal.

4. The welding method according to claim 3, characterized in that, The pretreatment of the first conduit, the second conduit blank, and the brazing filler metal includes: chemical cleaning of the brazing filler metal, the first conduit, and the second conduit.

5. The welding method according to claim 3, characterized in that, The pretreatment of the first conduit, the second conduit blank, and the brazing filler metal includes: silver plating the circumferential outer side of the second conduit end to be welded.

6. The welding method according to claim 1, characterized in that, The first conduit is an aluminum tube, the second conduit is a stainless steel tube, and the brazing filler metal is an aluminum-silicon eutectic brazing filler metal; The pre-assembly of the first conduit, the second conduit, and the brazing filler metal into a component includes: dissolving the brazing flux in anhydrous ethanol to prepare a thick solution; The thick solution is evenly applied to the circumferential sidewalls of the first and second conduits to be connected, and the first and second conduits are then dried. The first and second conduits are connected and assembled. The brazing filler metal is wound around the circumferential outer wall of the end of the second conduit to be sleeved, and brought close to the first conduit to form an assembly.

7. The welding method according to claim 1, characterized in that, The welding of the assembly to obtain a welded part includes: assembling the assembly into a furnace and brazing it in the furnace. The process of assembling the assembly into the furnace includes: Move the assembly into the brazing furnace with the second conduit on top and the first conduit on the bottom, keeping it horizontal and without tilting. A welding pressure block is placed on the upper end of the second conduit, and downward pressure is applied to the second conduit during the brazing process to control the gap between the first and second conduits. The brazing in the furnace includes: Set the temperature and heating time in the brazing process; Start the welding process; Stop the heating process after the assembly reaches the required heat retention time.

8. The welding method according to claim 1, characterized in that, It also includes finishing the welded parts and inspecting the welds after they come out of the furnace.

9. The welding method according to claim 8, characterized in that, The weld inspection includes performing helium mass spectrometry leak rate testing on the welded parts.

10. The welding method according to any one of claims 1-9, characterized in that, The process of precision machining and fitting the first and second conduit blanks according to the designed welding structure includes: setting a wall thickness allowance for the ends of the first and second conduits to be fitted during the machining process.

Images