Manufacturing method of piping components and piping components

Abstract

This invention discloses a method for manufacturing a pipeline assembly and the pipeline assembly manufactured by this method, belonging to the field of pipeline manufacturing technology. The method includes: S1, tangentially attaching a second pipe fitting close to a first pipe fitting, using a first solder to construct positioning weld points, locking the relative positions of the first and second pipe fittings and determining the assembly spacing, forming a wedge-shaped gap; S2, filling the wedge-shaped gap with a second solder with a lower melting point to form a thermally conductive filling layer; S3, welding the connectors fitted onto both ends of the first pipe fitting. During this process, the welding heat causes the positioning weld points to remain in a solid state to lock the assembly spacing and prevent pipe fitting detachment; while the thermally conductive filling layer remelts upon heating and relies on capillary force at the root of the wedge-shaped gap to prevent loss, releasing assembly thermal stress after cooling and solidification. This invention utilizes the difference in melting points and the remelting mechanism of the two solders to solve the problems of pipe fitting detachment and cracking caused by rigid restraint, while ensuring sufficient thermally conductive contact area and improving the temperature measurement accuracy of the sensor.

Description

Technical Field

[0001] This invention relates to the field of pipeline component manufacturing technology, and more specifically to a method for manufacturing pipeline components using composite and compatible solder for assembling pipe fittings, and a pipeline component made by the method. Background Technology

[0002] In the manufacturing process of air conditioning, refrigeration, and chemical heat exchange systems, it is often necessary to assemble and connect pipes with different functions. A typical application scenario involves attaching a straight pipe (the second fitting) used to install a temperature sensor tangentially to the main fitting (the first fitting) that transports the fluid. The first fitting is usually a U-shaped pipe.

[0003] The core function of this component is to enable a sensor installed in the second pipe to accurately and quickly sense temperature changes in the fluid inside the first pipe through heat conduction between the walls of the first and second pipes. Therefore, the thermally conductive contact area between the first and second pipes is a key indicator determining product performance.

[0004] Existing manufacturing processes typically use brazing to initially connect the first and second pipe fittings. However, in actual production processes, to facilitate rapid docking with other piping systems at the customer end or on the assembly line, it is usually necessary to pre-apply welding material to both ends of the first pipe fitting. The current common practice is to pre-fit and deposit annular weld metal as a connector onto the ends of the first pipe fitting. This process requires applying sufficient heat to the ends of the first pipe fitting to soften or slightly melt the weld ring.

[0005] Because metals have excellent thermal conductivity, when welding the connectors at both ends of the first pipe fitting, a large amount of heat will rapidly conduct along the pipe wall of the first pipe fitting towards the middle and accumulate at the connection area between the first and second pipe fittings. Under the existing technology, this will lead to three core contradictions:

[0006] 1. If the first and second fittings are connected using only conventional single-melting-point brazing filler metal, the heat conducted during welding at the end of the first fitting can easily cause the brazing filler metal layer connecting the first and second fittings to remelt and fail. Without external, complex tooling for clamping, the second fitting is highly susceptible to displacement, slippage, or even complete detachment from the first fitting due to gravity or slight vibrations during operation, resulting in product scrap.

[0007] 2. Even if the second fitting is not completely detached, secondary remelting often causes the liquid solder to leak (drip) due to loss of binding. Since the straight tube and the U-shaped tube are only in tangential contact geometrically, once the solder filling the gap between the first and second fittings leaks out, the amount of solder between the first and second fittings will decrease. This will increase the contact thermal resistance between the first and second fittings, making it impossible for the sensor in the second fitting to accurately and timely obtain the fluid temperature in the first fitting, resulting in temperature measurement lag or data deviation.

[0008] 3. Conversely, to prevent detachment, if a high-melting-point solder is used to perform a full-contact, rigid weld between the first and second pipe fittings, while solving the positional fixation problem, it introduces serious stress hazards. Due to the geometric difference between the curved structure of the first pipe fitting and the straight structure of the second pipe fitting, the fully rigid connection restricts the release of deformation at high temperatures, resulting in the accumulation of significant residual thermal stress at the connection point. This easily induces microcracks at the weld toe, causing long-term leakage hazards.

[0009] Therefore, there is an urgent need for a manufacturing method that can reliably lock the relative positions of the first and second pipe components in subsequent high-temperature processes, effectively release the assembly thermal stress between the first and second pipe components, and ensure that there is sufficient thermally conductive contact area between the first and second pipe components to ensure temperature measurement accuracy. Summary of the Invention

[0010] To address the aforementioned deficiencies in the existing technology, the present invention aims to provide a method for manufacturing a piping assembly and the piping assembly itself. This manufacturing method addresses the challenge of preventing the second pipe from detaching during the welding process at the end of the first pipe fitting, while simultaneously eliminating assembly thermal stress at the connection between the first and second pipe fittings and preventing solder loss between them. This ensures a sufficiently large thermally conductive contact area between the first and second pipe fittings, thereby guaranteeing the structural reliability of the piping assembly and the accuracy of the sensor temperature measurement.

[0011] To achieve the above objectives, the present invention provides a method for manufacturing a pipeline assembly, the pipeline assembly comprising a first pipe fitting having an arc-shaped section, a second pipe fitting having a straight section, and two connectors respectively fitted onto both ends of the first pipe fitting, the manufacturing method comprising the following steps:

[0012] S1. The straight section is tangentially close to the arc section, and a positioning weld is constructed in the tangential adjacent area between the two using the first solder; the positioning weld locks the relative position of the first pipe fitting and the second pipe fitting and determines the assembly distance between the two; at this time, a wedge-shaped gap is formed on both sides of the positioning weld due to the geometric separation of the arc section and the straight section.

[0013] S2. The wedge-shaped gap is filled with the second solder to form a thermally conductive filling layer; the solidus temperature of the first solder is higher than the liquidus temperature of the second solder.

[0014] S3. Weld the connectors fitted at both ends of the first pipe fitting. During this process, the welding heat at both ends of the first pipe fitting converges towards the middle along the first pipe fitting, causing the peak temperature of the positioning weld point to be between the liquidus temperature of the second solder and the solidus temperature of the first solder. At this time, the positioning weld point remains solid to lock the assembly distance between the first pipe fitting and the second pipe fitting unchanged.

[0015] The thermally conductive filler layer is heated and remelted into a liquid state, and relies on the capillary force at the root of the wedge-shaped gap to prevent it from being lost. After cooling and solidification, it releases the assembly thermal stress between the first and second pipe fittings.

[0016] Preferably, step S2, which involves filling the wedge-shaped gap with the second solder, is specifically performed as a pre-brazing process. In this process, the second solder is melted and wetted into the wedge-shaped gap by local heating, and the heating temperature of the pre-brazing is controlled to be lower than the solidus temperature of the first solder.

[0017] Preferably, in step S3, the welding position of the connector and the positioning weld point are spaced apart along the extension direction of the first pipe to form a heat conduction path with a predetermined length; the heat conduction path is used to attenuate the conduction of welding heat of the connector by utilizing the thermal resistance of the pipe wall of the first pipe, so that the temperature when the welding heat is conducted to the positioning weld point is reduced to below the solidus temperature of the first solder.

[0018] Preferably, in step S2, the filling volume of the second solder is 85% to 115% of the effective accommodating volume of the wedge gap, wherein the effective accommodating volume of the wedge gap refers to the volume enclosed by the region in the wedge gap where the normal distance between the pipe walls of the first pipe and the pipe walls of the second pipe is less than the critical capillary height of the second solder.

[0019] This volume range ensures that during the remelting process in step S3, the liquid thermally conductive filler layer can fully wet the wall of the wedge gap and be completely confined within the capillary action range of the wedge gap.

[0020] Preferably, during the cooling and solidification process in step S3, the free surface of the thermally conductive filling layer exposed to the outside forms a concave curved surface under the action of surface tension; the concave curved surface smoothly transitions to connect the outer walls of the first pipe and the second pipe, so as to eliminate stress concentration points at the junction of the thermally conductive filling layer with the pipe walls of the first pipe and the second pipe.

[0021] Preferably, the first pipe fitting is a U-shaped pipe, and the arc-shaped segment is located at the top of the bend of the U-shaped pipe; the second pipe fitting is a straight pipe, and the axis of the straight segment is located in the plane containing the central axis of the U-shaped pipe; in step S1, the positioning weld point is located on the axis of symmetry of the U-shaped pipe.

[0022] The present invention also provides a pipeline assembly manufactured by any of the above manufacturing methods, comprising a first pipe fitting, a second pipe fitting, and two connectors fixed to both ends of the first pipe fitting;

[0023] The first pipe fitting and the second pipe fitting are connected by a composite welding structure, the composite welding structure comprising:

[0024] The locating weld point located at the center of the tangential proximity zone retains the microstructure characteristics of the initial weld; and

[0025] The thermally conductive filler layer adjacent to the locating solder joint and filling the wedge-shaped gap has a metallographic structure with the crystallization characteristics of secondary remelting;

[0026] The melting point of the positioning solder joint is higher than that of the thermally conductive filler layer.

[0027] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0028] 1. This invention utilizes the melting point difference between the first and second solders to construct a high-temperature resistant positioning weld. During the welding of the connectors at both ends of the first pipe fitting in step S3, even if heat accumulation causes the temperature of the connection area between the first and second pipe fittings to rise, the positioning weld, with its high solidus temperature design, maintains a rigid solid state. This positioning weld firmly locks the relative position and assembly spacing of the first and second pipe fittings. This completely solves the problem in the prior art where the second pipe fitting slips off without external tooling assistance due to the complete melting of the solder, ensuring the geometric accuracy of the pipeline assembly.

[0029] 2. To address the problem in existing technologies where solder loss leads to increased thermal resistance between the first and second fittings, this invention utilizes a wedge-shaped gap as a carrier. By precisely controlling the filling volume of the second solder, it ensures that the thermally conductive filler layer can fully wet and fill the wedge-shaped areas on both sides of the positioning solder joint after remelting. This expands the connection between the first and second fittings into a wide surface contact. This thermally conductive filler layer constitutes a low-thermal-resistance, high-efficiency heat transfer channel, enabling rapid and accurate transfer of the fluid temperature within the first fitting to the sensor within the second fitting, significantly improving the accuracy and response speed of temperature detection data.

[0030] 3. In the high-temperature environment of step S3, the low-melting-point thermally conductive filler layer undergoes in-situ remelting and transforms into a liquid state. Since liquid substances cannot transmit shear stress, the first and second pipe components are essentially in a flexible, floating connection state, positioned only by locating welds, during the stage of most severe thermal expansion and deformation. The first and second pipe components can freely undergo slight thermal expansion and contraction, avoiding rigid contact. With subsequent cooling, the thermally conductive filler layer resolidifies under stress-free conditions. This mechanism of remelting and releasing stress followed by solidification minimizes residual thermal stress at the connection between the first and second pipe components, effectively preventing weld cracking and extending the component's service life.

[0031] 4. This invention strictly defines the filling volume of the second solder as 85% to 115% of the effective accommodating volume of the wedge gap, and defines the effective area of ​​the wedge gap based on the critical capillary height. This precise volume matching relationship, combined with the locking effect of the positioning solder points on the assembly distance between the first and second pipe fittings, ensures that during the remelting process in step S3, the liquid thermally conductive filling layer can be completely confined within the capillary action range of the wedge gap. This effectively prevents the liquid solder from overflowing or dripping due to excessive filling of the second solder exceeding the capillary force constraint limit of the wedge gap, thereby ensuring the stability of the aforementioned thermally conductive area.

[0032] 5. During the remelting and secondary cooling and solidification process of the thermally conductive filler layer, its exposed free surface naturally forms a concave curved surface under the action of surface tension. This concave curved surface achieves a smooth transition from the thermally conductive filler layer to the pipe walls of the first and second pipe fittings, effectively eliminating geometric abrupt changes at the junction of the thermally conductive filler layer and the pipe walls of the first and second pipe fittings, thereby eliminating stress concentration points and further improving the structural strength of the component. Attached Figure Description

[0033] Figure 1 This is a schematic diagram showing the relative positions of the first and second pipe fittings before assembly in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure after the positioning solder joint is constructed in step S1 in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure after the thermally conductive filling layer is formed by filling the wedge-shaped gap in step S2 in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the overall structure after the welding of the connector is completed in step S3 of this embodiment of the invention.

[0037] Explanation of reference numerals in the attached drawings: 10, first pipe fitting; 11, arc-shaped segment; 20, second pipe fitting; 21, straight segment; 30, connector; 40, tangential adjacent area; 41, locating weld point; 50, wedge-shaped gap; 51, thermally conductive filler layer. Detailed Implementation

[0038] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] like Figures 1 to 4 As shown, this embodiment provides a method for manufacturing a piping assembly. This piping assembly is mainly used in piping units of air conditioning, heat pump, or chemical heat exchange systems.

[0040] In this embodiment, the first pipe fitting 10 is specifically selected as a U-shaped copper pipe for conveying refrigerant fluid, having an arc-shaped section 11 at the bottom. The second pipe fitting 20 is specifically selected as a straight sensor mounting pipe for accommodating a temperature sensing element, having a straight section 21. The connector 30 is specifically selected as an annular solder (e.g., a pre-placed solder ring) for subsequent pipe connection. The two connectors 30 are respectively sleeved on both ends of the first pipe fitting 10.

[0041] The manufacturing method of this embodiment includes the following steps:

[0042] Step S1: Construct a rigid positioning structure

[0043] like Figure 1 and Figure 2 As shown, the operator tangentially brings the straight section 21 of the second pipe fitting 20 close to the arcuate section 11 of the first pipe fitting 10. To ensure spatial compactness of the assembly, the axis of the straight section 21 lies in the plane containing the central axis of the U-shaped tube. At this time, a tangential proximity zone 40 is formed in the area where the first pipe fitting 10 and the second pipe fitting 20 are geometrically closest.

[0044] Within this tangential adjacent zone 40, the operator constructs a positioning solder joint 41 using a first solder. In this embodiment, the first solder is specifically selected from bronze solders with a high solidus temperature (e.g., silicon bronze or tin bronze solder, with a solidus temperature of approximately 1000°C). To ensure the balance of the support, the positioning solder joint 41 is located on the axis of symmetry of the first pipe fitting 10.

[0045] The positioning weld point 41 plays two key roles: First, it locks the relative positions of the first pipe fitting 10 and the second pipe fitting 20, preventing misalignment; second, it acts as a precision spacer to determine the assembly spacing between the first pipe fitting 10 and the second pipe fitting 20. At this time, due to the geometric separation characteristics of the arc-shaped segment 11 and the straight segment 21, a gradually widening wedge-shaped gap 50 naturally forms on both sides of the positioning weld point 41.

[0046] Step S2: Constructing a thermally conductive filler layer

[0047] like Figure 3 As shown, the operator uses the second solder to fill the wedge-shaped gap 50 to form a thermally conductive filling layer 51. To achieve subsequent temperature difference control, in this embodiment, the solidus temperature of the first solder is higher than the liquidus temperature of the second solder. Specifically, the second solder is a copper-phosphorus solder with a low liquidus temperature (e.g., copper-phosphorus brazing filler metal, with a liquidus temperature of approximately 700℃-800℃), maintaining a temperature difference of more than 200℃ between the solidus temperature of the first solder and the liquidus temperature of the second solder.

[0048] The step of "filling the wedge-shaped gap 50 with the second solder" is specifically performed as a preliminary brazing process. In this process, the operator melts the second solder using localized flame heating or induction heating, and then wets and fills the wedge-shaped gap 50. During this process, the operator strictly controls the heating temperature of the preliminary brazing to be lower than the solidus temperature of the first solder. The technical effect of this temperature control measure is to ensure that the previously established positioning solder joints 41 do not remelt or soften during the formation of the thermally conductive filling layer 51, thereby maintaining the geometric integrity of the wedge-shaped gap 50 and avoiding gap collapse leading to filling failure.

[0049] To prevent solder loss in subsequent processes, this embodiment strictly controls the filling volume of the second solder to be between 85% and 115% of the effective accommodating volume of the wedge gap 50. The effective accommodating volume of the wedge gap 50 does not refer to the entire infinitely extending wedge-shaped space, but rather to the volume enclosed by the region within the wedge gap 50 where the normal distance between the walls of the first tube 10 and the second tube 20 is less than the critical capillary height of the second solder. For example, for a liquid silver-based solder wetting system on a copper surface, its critical capillary height against gravity is approximately 0.3 mm; therefore, only the volume of the portion of the wedge gap 50 with a width less than 0.3 mm is calculated as the effective accommodating volume. The technical effect of controlling this volume range is that if the filling volume of the second solder is less than 85% of the effective accommodating volume of the wedge gap 50, insufficient wetting area may result; if the filling volume of the second solder is greater than 115% of the effective accommodating volume of the wedge gap 50, the capillary constraint limit of the wedge gap 50 may be exceeded. This volume range ensures that during the remelting process in step S3, the liquid thermally conductive filler layer 51 can fully wet the wall of the wedge gap 50 and be completely confined within the capillary action range of the wedge gap 50, thereby preventing the liquid solder from overflowing and leaking.

[0050] Step S3: Welding of connectors and stress relief

[0051] like Figure 4 As shown, the operator welds the connectors 30 fitted at both ends of the first pipe fitting 10, that is, by heating to melt and fix the pre-placed annular solder to the pipe opening. In this embodiment, the welding process specifically adopts flame heating (such as oxy-propane flame) or high-frequency induction heating, and the heating temperature is controlled between 800°C and 900°C to ensure that the connectors 30 are fully melted and bonded to the first pipe fitting 10. During this process, the welding heat at both ends of the first pipe fitting 10 will converge along the pipe wall of the first pipe fitting 10 to the connection area between the first pipe fitting 10 and the second pipe fitting 20 in the middle.

[0052] To protect the intermediate connection structure, this embodiment utilizes the principle of structural thermal resistance. The welding positions of the connector 30 and the positioning weld points 41 are spaced apart along the extension direction of the first pipe 10, thereby forming a heat conduction path of predetermined length. This method utilizes the thermal resistance of the pipe wall of the first pipe 10 along the heat conduction path to attenuate the conduction of welding heat from the connector 30, causing the temperature to naturally decrease when the welding heat is conducted to the positioning weld point 41.

[0053] Specifically, in this embodiment, the axial distance from the welding point of the connector 30 to the positioning welding point 41 along the first pipe fitting 10 is controlled between 30mm and 80mm (e.g., 50mm). The technical basis for setting this length parameter is that if the distance is less than 30mm, due to the extremely high thermal conductivity of the copper pipe, the heat attenuation is insufficient, which may cause the temperature at the positioning welding point 41 to exceed the solidus temperature of the first solder (i.e., exceeding 1000℃), causing positioning failure; if the distance is greater than 80mm, although the heat insulation effect is better, it will cause the overall size of the first pipe fitting 10 to be too large, which does not meet the requirements of compact design, and the excessively long path may cause the heat conducted to the middle to be insufficient to remelt the second solder (i.e., below 700℃). Therefore, selecting the specific range of 30mm to 80mm can accurately control the heat transferred to the positioning welding point 41 within the ideal range of remelting the second solder (>700℃) but not enough to melt the first solder (<1000℃).

[0054] Within this specific temperature range, the present invention achieves the following combined technical effects:

[0055] 1. The centrally located locating weld 41 remains solid to lock the assembly gap between the first pipe fitting 10 and the second pipe fitting 20 in place. The locating weld 41 effectively prevents the second pipe fitting 20 from slipping or shifting due to heat without external clamping.

[0056] 2. The thermally conductive filler layer 51 located around the positioning weld point 41 is heated and remelted into a liquid state, and is prevented from being lost by the capillary force at the root of the wedge-shaped gap 50. The thermally conductive filler layer 51 in the liquid state cuts off the rigid shear force transmission path between the first pipe fitting 10 and the second pipe fitting 20, so that the first pipe fitting 10 and the second pipe fitting 20 are in a flexible floating connection state during the stage of most intense thermal expansion.

[0057] 3. After cooling and solidification, the re-solidified thermally conductive filler layer 51 releases the assembly thermal stress between the first pipe fitting 10 and the second pipe fitting 20. Specifically, during the cooling and solidification process in step S3, the free surface of the thermally conductive filler layer 51 exposed to the outside forms a concave curved surface under the action of surface tension. The concave curved surface smoothly transitions between the outer walls of the first pipe fitting 10 and the second pipe fitting 20. This geometry eliminates stress concentration points at the junction of the thermally conductive filler layer 51 with the pipe walls of the first pipe fitting 10 and the second pipe fitting 20, significantly improving the fatigue resistance of the assembly.

[0058] The pipeline assembly manufactured by the above method includes a first pipe fitting 10, a second pipe fitting 20, and two connectors 30 fixed to both ends of the first pipe fitting 10. The first pipe fitting 10 and the second pipe fitting 20 are connected by a composite welding structure.

[0059] The composite welded structure exhibits the following characteristics under a metallographic microscope: the positioning weld 41, located at the center of the tangential proximity region 40, retains the characteristics of the initial weld (i.e., it has not undergone a secondary melting and crystallization process); and the thermally conductive filler layer 51, adjacent to the positioning weld 41 and filling the wedge-shaped gap 50, has the characteristics of crystallization after secondary remelting (e.g., coarser grains or exhibiting a specific cooling dendrite orientation). Simultaneously, physical testing indicates that the melting point of the positioning weld 41 is higher than that of the thermally conductive filler layer 51.

[0060] This specification and accompanying drawings are merely illustrative examples of this application and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Therefore, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method of manufacturing a pipe assembly comprising a first pipe member (10) having an arc-shaped section (11), a second pipe member (20) having a straight section (21), and two connecting members (30) respectively sleeved on both end portions of the first pipe member (10), characterized in that, The method comprises the following steps: S1, tangentially attaching a straight section (21) to an arc section (11), and using a first solder to build a positioning weld (41) in the tangential adjacent area (40) of the two sections; the positioning weld (41) locks the relative position of the first pipe fitting (10) and the second pipe fitting (20) and determines the assembly spacing therebetween; At this time, the two sides of the positioning weld (41) form a wedge-shaped gap (50) due to the geometric separation of the arc section (11) and the straight section (21); S2, using a second solder to fill the wedge-shaped gap (50) to form a heat-conducting filling layer (51); the solidus temperature of the first solder is higher than the liquidus temperature of the second solder; S3, welding the connecting piece (30) sleeved on the two end portions of the first pipe fitting (10); in this process, the welding heat at the two ends of the first pipe fitting (10) converges to the middle along the first pipe fitting (10), so that the peak temperature of the positioning weld (41) is between the liquidus temperature of the second solder and the solidus temperature of the first solder; at this time, the positioning weld (41) remains solid to lock the assembly spacing between the first pipe fitting (10) and the second pipe fitting (20) unchanged; The heat-conducting filling layer (51) is remelted into a liquid state and prevented from flowing out by the capillary force at the root of the wedge-shaped gap (50), and releases the assembly thermal stress between the first pipe fitting (10) and the second pipe fitting (20) after cooling and solidification.

2. The manufacturing method according to claim 1, characterized by, The step S2 of filling the wedge-shaped gap (50) with the second solder is specifically implemented as a one-time pre-soldering process; in this process, the second solder is melted and wet-filled in the wedge-shaped gap (50) by local heating, and the heating temperature of the pre-soldering is controlled to be lower than the solidus temperature of the first solder.

3. The production method according to claim 1, characterized by In step S3, the welding position of the connecting piece (30) and the positioning weld (41) are arranged at intervals along the extension direction of the first pipe fitting (10) to form a heat-conducting path with a predetermined length; the heat resistance of the pipe wall of the first pipe fitting (10) on the heat-conducting path is used to attenuate the conduction of the welding heat of the connecting piece (30), so that the temperature of the welding heat conducted to the positioning weld (41) is reduced to below the solidus temperature of the first solder.

4. The production method according to claim 1, characterized by In step S2, the filling volume of the second solder is 85% to 115% of the effective containing volume of the wedge-shaped gap (50), and the effective containing volume of the wedge-shaped gap (50) refers to the volume surrounded by the region where the normal distance between the pipe wall of the first pipe fitting (10) and the pipe wall of the second pipe fitting (20) in the wedge-shaped gap (50) is less than the critical capillary height of the second solder; This volume range ensures that the liquid heat-conducting filling layer (51) can fully wet the wall surface of the wedge-shaped gap (50) and be completely limited within the capillary range of the wedge-shaped gap (50) during the remelting process in step S3.

5. The production method according to claim 1, characterized by During the cooling solidification process in step S3, the free surface of the heat-conducting filler layer (51) exposed to the outside forms a concave surface under the action of surface tension; the concave surface smoothly connects the outer walls of the first pipe fitting (10) and the second pipe fitting (20) to eliminate stress concentration points at the junctions of the heat-conducting filler layer (51) and the pipe walls of the first pipe fitting (10) and the second pipe fitting (20).

6. The production method according to claim 1, characterized by The first pipe fitting (10) is a U-shaped pipe, and the arc-shaped section (11) is located at the curved top of the U-shaped pipe; the second pipe fitting (20) is a straight pipe, and the axis of the straight section (21) is located in the plane of the central axis of the U-shaped pipe; in step S1, the positioning weld point (41) is located on the symmetry axis of the U-shaped pipe.

7. A pipe assembly made by the method of any one of claims 1 to 6, characterized in that The first pipe fitting (10), the second pipe fitting (20), and two connecting pieces (30) fixed to the two ends of the first pipe fitting (10) are included. The first pipe fitting (10) and the second pipe fitting (20) are connected through a composite welding structure, and the composite welding structure includes: a positioning weld point (41) located at the center of the tangential adjacent area (40), whose metallographic structure retains the initial welding characteristics; and a heat-conducting filler layer (51) adjacent to the positioning weld point (41) and filled in the wedge-shaped gap (50), whose metallographic structure has the crystallization characteristics after secondary remelting; wherein the melting point of the positioning weld point (41) is higher than the melting point of the heat-conducting filler layer (51).

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