Welding methods and structures for confined space pipes in fusion devices

Abstract

This invention discloses a welding method and structure for confined space pipes in fusion devices, belonging to the technical field of fusion device technology. The method includes: pre-assembling a first component and a second component, simultaneously positioning a first cooling pipe and a second cooling pipe in their designed positions; cutting along a first marking line on the unobstructed portion of the first cooling pipe to obtain a notched first cooling pipe and a pipe segment; assembling the notched first component and the second component, simultaneously aligning and spot-welding the notched first cooling pipe and the second cooling pipe; inserting a welding torch into the notch of the first cooling pipe to perform inner welds on the notched first cooling pipe and the second cooling pipe; placing the pipe segment in the notch and spot-welding; and performing outer welds on the pipe segment and the second cooling pipe, and the pipe segment and the notched first cooling pipe, using the welding torch externally. This invention enables welding of confined space cooling pipes without altering the original structure, while ensuring a high weld quality rate, thus improving production quality and efficiency.

Description

Technical Field

[0001] This invention relates to the field of nuclear fusion device technology, and in particular to a welding method and welding structure for pipes in confined spaces of a fusion device. Background Technology

[0002] The vacuum chamber of a compact tokamak fusion device operates under extreme conditions of ultra-high heat load, strong neutron irradiation, extreme vacuum, and strong electromagnetic shock. The cooling circuit of the internal components of the vacuum chamber is the core thermal management system that ensures the safe and stable operation of the device and extends the service life of the components. The "heat exchange core" of this cooling circuit is the cooling tube. The manufacturing requirements for the cooling tube are far higher than those for conventional industrial cooling components. It must simultaneously meet stringent requirements such as high temperature resistance, radiation resistance, high thermal conductivity, reliable sealing, and erosion resistance. The main cooling pipe is made of 316L steel and has a specification of φ48×3mm. It is mainly connected by welding. Due to the complex structure of the internal components of the vacuum chamber and the extremely high requirements for manufacturing process, the compact fusion energy experimental device has a relatively small size and limited space for manufacturing and installation of some components. In particular, the cooling pipe changes with the shape of the complex components. At the connection between two components, the distance between the cooling pipe and each installation reference surface is too close, less than 4mm. This makes it impossible to weld the inner part of the cooling pipe connection joint or extremely difficult to weld, and the welding is prone to defects. This is because the inner part of the weld joint is located on the side of the cooling pipe that is blocked by the component. There is a narrow space between the blocked side of the cooling pipe and the component, and there is not enough space for welding operation.

[0003] Stainless steel is the standard material for cooling pipes, and welding is typically used for connection. However, the complex and compact structure of the internal components of the vacuum chamber limits the welding space, and it's also impossible to reserve welding positions on each component when connecting two cooling pipes. Therefore, brazing or rerouting the cooling pipes is currently the primary methods used. While brazing is simple to operate and requires less welding space, the joint strength is low, defects are prone to occur, and it's difficult to guarantee safe use over a long period.

[0004] While raising or increasing the length can create welding space, it can also alter the flow path, lengthen the flow channel, and affect the cooling effect. Furthermore, it can affect the adjacent mounting reference surface, causing interference with the installation of other components of the compact fusion energy device at the mounting reference surface. This can lead to a chain reaction that requires corresponding modifications to other devices, resulting in a significant impact. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide a method for welding confined space pipes in fusion devices, which can weld cooling pipes in confined spaces without altering the original structure, while ensuring the weld quality rate and improving production quality and efficiency.

[0006] A method for welding confined space pipes in a fusion device according to a first aspect of the present invention includes the following steps:

[0007] S1: Pre-assemble the first component with the first cooling pipe and the second component with the second cooling pipe, while placing the first cooling pipe and the second cooling pipe to be welded in the designed position, and observe the situation where the first cooling pipe and the second cooling pipe are blocked by the first component and the second component.

[0008] S2: Draw a first marking line for cutting notches on the unblocked part of the first cooling pipe, and draw a second marking line at the positions corresponding to the two ends of the first marking line at the pipe opening of the second cooling pipe.

[0009] S3: Cut along the first marking line on the first cooling pipe to obtain a notched first cooling pipe and a pipe plate;

[0010] S4: Assemble the first component and the second component, and at the same time, align the notched first cooling pipe and the second cooling pipe and ensure that the two ends of the notch opening are aligned with the second marking line. Then, spot weld between the notched first cooling pipe and the second cooling pipe.

[0011] S5: Insert the welding torch into the first cooling pipe through the notch, weld the first cooling pipe and the second cooling pipe through the notch, and form an inner weld.

[0012] S6: Place the tube segment in the notch, and perform spot welding between the tube segment and the second cooling tube and between the tube segment and the first cooling tube in the notch;

[0013] S7: The welding torch is used to weld the tube segment to the second cooling tube and the tube segment to the notched first cooling tube outside the first cooling tube, forming an outer weld.

[0014] The welding method for confined space pipes in fusion devices according to the first aspect of the present invention can weld cooling pipes in confined spaces without changing the original structure, while ensuring the qualification rate of welds and improving production quality and efficiency.

[0015] In some embodiments, in step S3, all corner transitions are rounded during the cutting process.

[0016] In some embodiments, the method further includes the following step: after step S3 and before step S4, machining a bevel at the corresponding welding position in the second cooling pipe, the notched first cooling pipe, and the pipe segment.

[0017] In some embodiments, the bevel at the welding position between the second cooling pipe and the notched first cooling pipe is an inner V-shaped bevel facing the internal space of the second cooling pipe and the notched first cooling pipe, and the bevel at the welding position between the pipe segment and the second cooling pipe and the welding position between the pipe segment and the notched first cooling pipe are outer V-shaped bevels facing the external space.

[0018] In some embodiments, the angle of the bevel is 35° to 40°.

[0019] In some embodiments, after the beveling is completed, the beveling is subjected to PT testing. After the beveling passes the test, step S4 is then performed.

[0020] In some embodiments, step S5 employs argon arc welding, specifically including the following sub-steps:

[0021] S51: An argon chamber is provided on the outside of the welding position between the first cooling pipe and the second cooling pipe with the notch, so that the argon chamber is in close contact with the outer surface of the first cooling pipe and the second cooling pipe with the notch, and argon gas is filled into the argon chamber;

[0022] S52: Welding is performed from bottom to top at the position to be welded between the first cooling pipe and the second cooling pipe at the notch.

[0023] In some embodiments, the method further includes the following steps: performing VT, PT, and RT tests on the inner weld after step S5 and before step S6.

[0024] In some embodiments, the method further includes the following steps: after the VT, PT and RT tests of the inner weld are qualified, a transition slope is opened at both ends of the inner weld, and the transition slope is smoothly transitioned at the intersection with the segment.

[0025] In some embodiments, the angle of the transition slope is 45° to 50°.

[0026] In some embodiments, step S7 specifically employs argon arc welding, and includes the following sub-steps:

[0027] S71: Argon gas is filled into the internal space formed by the first cooling pipe with the notch, the tube segment and the second cooling pipe;

[0028] S72: Welding is performed from bottom to top at the position to be welded between the tube segment and the second cooling pipe, and welding is performed from bottom to top at the position to be welded between the tube segment and the notched first cooling pipe.

[0029] In some embodiments, the welding of the inner weld and the welding of the outer weld are both performed by first welding the root pass weld and then welding the cover pass weld.

[0030] In some embodiments, when performing the root pass weld, the current is 40~60A and the voltage is 10~13V; when performing the cover pass weld, the current is 50~60A and the voltage is 10~13V, and the interpass temperature is controlled below 60°C.

[0031] In some embodiments, the method further includes performing VT, PT, and RT tests on the outer weld after step S7.

[0032] This invention also proposes a welding structure for confined pipes in a fusion device.

[0033] The welding structure of the confined space pipe of the fusion device in the second aspect of the present invention is obtained by the welding method of the confined space pipe of the fusion device in the first aspect of the present invention.

[0034] Since the welding structure of the confined space pipe of the fusion device in the second aspect embodiment of the present invention is obtained by using the welding method of the confined space pipe of the fusion device in the first aspect embodiment of the present invention, the welding structure of the confined space pipe of the fusion device in the second aspect embodiment of the present invention has the same technical effect as the welding method of the confined space pipe of the fusion device in the first aspect embodiment of the present invention, and will not be described again here.

[0035] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the welding of the inner weld seam in the narrow space pipe welding method of the fusion device according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the welding of the outer weld seam in the narrow space pipe welding method of the fusion device according to an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the bevel in an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the welding direction of the inner and outer welds in an embodiment of the present invention.

[0040] Figure Labels

[0041] The fusion device features a confined space pipe welding structure 1000; a first component 100; a first cooling pipe 10; a notch 101; a notch-first cooling pipe 102; a pipe segment 103; a first component mounting reference surface 104; a second component 200; a second cooling pipe 20; an inner weld 300; an outer weld 400; a bevel 500; an argon chamber 600; a transition slope 700; an inner weld welding direction M; and an outer weld welding direction N. Detailed Implementation

[0042] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] The following is combined Figures 1 to 4 This invention describes a welding method and structure for a confined space pipe in a fusion device, according to an embodiment of the present invention.

[0044] like Figures 1 to 4 As shown, the welding method for confined space pipes in a fusion device according to a first aspect embodiment of the present invention includes the following steps:

[0045] S1: Pre-assemble the first component 100 integrating the first cooling pipe 10 and the second component 200 integrating the second cooling pipe 20, while positioning the first cooling pipe 10 and the second cooling pipe 20 to be welded in their designed positions, and observe the situation where the first cooling pipe 10 and the second cooling pipe 20 are obstructed by the first component 100 and the second component 200. It is understood that the first component 100 integrating the first cooling pipe 10 and the second component 200 integrating the second cooling pipe 20 do not change the original structural design and will not affect the original mounting reference surface (such as...). Figure 1 The first component 100's first component mounting reference surface 104 is affected; after the first component 100 and the second component 200 are pre-assembled, when the first cooling pipe 10 and the second cooling pipe 20 on them are in their original design positions, the side of the first cooling pipe 10 and the second cooling pipe 20 that is blocked by the first component 100 and the second component 200 is considered as the blocked side. The blocked side of the first cooling pipe 10 and the second cooling pipe 20 (that is, the inner part, see...) Figure 1A narrow space exists between the back side and bottom side of the first cooling pipe 10 and the second cooling pipe 20 and the first component 100 and the second component 200. This makes it impossible or difficult to weld the inner parts of the first cooling pipe 10 and the second cooling pipe 20 within the narrow space, resulting in welding quality defects. Therefore, it is necessary to observe whether the first cooling pipe 10 and the second cooling pipe 20 are obstructed by the first component 100 and the second component 200, and whether they are not obstructed, in order to better proceed to the next step.

[0046] It should be noted that when the first cooling pipe 10 is integrated into the first component 100 and the second cooling pipe 20 is integrated into the second component 200, each of their initial pipe lengths has a machining allowance. On the one hand, this avoids the possibility that manufacturing errors of the first cooling pipe 10 and the second cooling pipe 20 may cause their respective pipe lengths to be shorter than the length required for butt welding, thus preventing them from being butt welded. On the other hand, it facilitates the appropriate selection of the butt welding position (a certain position in the pipe length direction) of the first cooling pipe 10 and the second cooling pipe 20 in the subsequent process. After selection, the excess part of the first cooling pipe 10 or / and the second cooling pipe 20 is then cut off.

[0047] S2: Draw a first marking line (not shown in the figure) on the unobstructed portion of the first cooling pipe 10 for cutting the notch 101. Draw a second marking line (not shown in the figure) at the positions corresponding to the ends of the first marking line at the opening of the second cooling pipe 20. It is understood that the unobstructed portions of the first cooling pipe 10 and the second cooling pipe 20 are typically the outer parts, see [reference]. Figure 1 On one side of the front and one side of the top of the first cooling pipe 10 and the second cooling pipe 20, the outer space of the unobstructed portion of the first cooling pipe 10 and the second cooling pipe 20 is large, which can meet the welding operation space requirements for welding the outer portion of the first cooling pipe 10 and the second cooling pipe 20. A first marking line for cutting a notch 101 is drawn on the unobstructed portion of the first cooling pipe 10 to facilitate the subsequent cutting of the notch 101 so that the welding torch can enter the internal space of the first cooling pipe 10 through the notch 101 to weld the inner portion of the weld. In addition, a second marking line is drawn at the positions corresponding to the two ends of the first marking line at the pipe opening of the second cooling pipe 20. The purpose is twofold: first, to facilitate accurate alignment before subsequent welding; and second, to facilitate the machining of the inner and outer weld bevels on the inner and outer pipe opening sections between the two second marking lines of the second cooling pipe 20, respectively.

[0048] It should be noted that, Figure 1The first cooling pipe 10 shown in the diagram is located to the right of the second cooling pipe 20. After observing the unobstructed outer parts of the first cooling pipe 10 and the second cooling pipe 20, the first marking line is drawn on the first cooling pipe 10. This is because in most cases, when welding the inner weld 300 with a hand-held welding torch, it is more convenient to hold the welding torch with the right hand. Of course, it is not excluded that when the first cooling pipe 10 is located to the left of the second cooling pipe 20, it is more convenient to hold the welding torch with the left hand.

[0049] S3: Cut along the first marking line on the first cooling pipe 10 to obtain the notched first cooling pipe 102 and the pipe segment 103. Since the notched first cooling pipe 102 has a notch 101 corresponding to the pipe segment 103, the welding torch can be inserted into the notch 101 to weld the inner part of the notched first cooling pipe and the second cooling pipe at the welding position, which is convenient for welding operation.

[0050] S4: Assemble the first component 100 and the second component 200. Simultaneously, align the notched first cooling pipe 102 and the second cooling pipe 20, ensuring that both ends of the notch 101 are aligned with the second marking line to guarantee the accuracy of the joint position before welding and prevent misalignment. Then, perform spot welding between the notched first cooling pipe 102 and the second cooling pipe 20 to prevent relative displacement between them.

[0051] S5: Insert the welding torch into the first cooling pipe 10 through the notch 101 (reference) Figure 1 Welding is performed on the notched first cooling pipe 102 and the second cooling pipe 20 to form an inner weld 300. It can be understood that the welding between the notched first cooling pipe 102 and the second cooling pipe 20 is the welding between the pipe openings of the notched first cooling pipe 102 and the second cooling pipe 20. The welding torch enters the internal space of the first cooling pipe 10 through the notch 101 to weld the inner part. The welding operation space is relatively small compared to the aforementioned space, which is conducive to ensuring the welding quality and welding efficiency of the inner weld 300.

[0052] S6: Place the tube 103 in the notch 101 to fill the notch 101. Spot weld between the tube 103 and the second cooling tube 20 and between the tube 103 and the notch first cooling tube 102. This will fix the tube 103 in place and prevent it from shifting.

[0053] S7: The welding torch is used to weld the segment 103 to the second cooling pipe 20 and the segment 103 to the notched first cooling pipe 102 outside the first cooling pipe 10, forming an outer weld 400. It can be understood that there are two outer welds 400: one between the segment 103 and the second cooling pipe 20, and the other between the segment 103 and the notched first cooling pipe 102, i.e., at the original first marking line position of the first cooling pipe 10. When welding the outer weld 400, the welding operation is performed in the external space of the outer part of the first cooling pipe 10. This external space is not obstructed, making the welding operation convenient and helping to ensure the welding quality and efficiency of the outer weld 400.

[0054] In summary, the welding method for confined space pipes in fusion devices according to the first aspect of the present invention can weld cooling pipes in confined spaces without changing the original structure, while ensuring the weld qualification rate and improving production quality and efficiency.

[0055] In some embodiments, in step S3, all corner transitions are smoothly rounded during the cutting process. This prevents stress concentration or defects in subsequent welding at the corner transitions.

[0056] In some embodiments, the method further includes the following step: after step S3 and before step S4, machining a bevel 500 at the corresponding welding positions in the second cooling pipe 20, the notched first cooling pipe 102, and the segment 103. The bevel 500 is as follows: Figure 3 As shown, the 500 bevel is to ensure weld penetration by increasing the welding contact area and avoiding incomplete fusion defects.

[0057] In some embodiments, the bevel 500 at the welding position between the second cooling pipe 20 and the notched first cooling pipe 102 is an inner V-shaped bevel facing the internal space of the second cooling pipe 20 and the notched first cooling pipe 102. The bevel 500 at the welding position between the pipe segment 103 and the second cooling pipe 20, and the bevel 500 at the welding position between the pipe segment 103 and the notched first cooling pipe 102, are outer V-shaped bevels facing the external space. The purpose of the inner V-shaped bevel is to allow the welding torch to approach the bevel 500 from inside the pipe after being inserted through the notch 101, which helps to ensure welding quality. The purpose of the outer V-shaped bevel 500 is to allow the welding torch to perform welding from outside the pipe, which also helps to ensure welding quality. In summary, the bevel direction is designed according to the welding position to adapt to different welding spaces and ensure welding quality.

[0058] In some embodiments, the bevel angle 500 is 35° to 40°. The bevel angle 500 determines the amount of deposited metal and welding efficiency. 35° to 40° is an empirically optimized angle for argon arc welding of 316L stainless steel. An angle that is too small (e.g., <35°) is prone to incomplete fusion; an angle that is too large (e.g., >40°) poses a risk of deformation.

[0059] In some embodiments, after the groove 500 is machined, the groove 500 is subjected to PT inspection. After the groove 500 passes the inspection, step S4 is carried out. PT inspection is penetrant inspection, which can check whether there are open defects such as cracks, pores, and slag inclusions on the surface of the groove, ensure the welding quality, and avoid repair.

[0060] In some embodiments, in step S5, argon arc welding is adopted, which specifically includes the following sub-steps:

[0061] S51: An argon chamber 600 is arranged outside the welding position between the notch first cooling pipe 102 and the second cooling pipe 20, so that the argon chamber 600 is closely attached to the outer surfaces of the notch first cooling pipe 102 and the second cooling pipe 20, and argon is filled into the argon chamber 600. After filling argon, a local protective gas cavity is formed to prevent the inner weld 300 from being oxidized during the inner part welding and ensure the welding quality of the inner weld 300.

[0062] S52: The weld is welded from bottom to top at the welding position between the notch first cooling pipe 102 and the second cooling pipe 20 (see the arrow M in Figure 4 ). If the weld is welded from top to bottom at the welding position between the notch first cooling pipe 102 and the second cooling pipe 20, the welding melt will flow downward due to the action of gravity, and the welding quality cannot be guaranteed. Therefore, welding the weld from bottom to top at the welding position between the notch first cooling pipe 102 and the second cooling pipe 20 is beneficial to ensuring the welding quality.

[0063] In some embodiments, the following steps are further included: after step S5 and before step S6, VT, PT, and RT inspections are carried out on the inner weld 300. VT inspection is visual inspection to check the appearance of the weld; PT inspection is penetrant inspection to check surface open defects; RT inspection is radiographic inspection to check internal volume defects (such as lack of fusion, slag inclusion) of the weld. It should be noted that when the VT inspection is unqualified, further PT inspection is not required, and when the PT inspection is unqualified, RT inspection is not required. Therefore, when VT, PT, and RT are inspected step by step in sequence, it is beneficial to improve the inspection efficiency of the inner welding 300. If the inner weld 300 is found to be unqualified, repair is carried out. Finally, the qualification of the inner weld 300 needs to be ensured.

[0064] In some embodiments, the following steps are further included: after the VT, PT, and RT inspections of the inner weld 300 are qualified, transition slopes 700 are opened at both ends of the inner weld 300, and at the same time, the transition slopes 700 are smoothly transitioned at the intersection positions with the segment 103. In this way, the welding effect at the intersection position of the segment 103, the notch first cooling pipe 102, and the second cooling pipe 20 can be ensured and stress concentration can be avoided.

[0065] In some embodiments, the angle of the transition slope 700 is 45° to 50°. The inner weld 300 and the outer weld 400 intersect at the transition slope 700. The smooth transition of 45° to 50° can ensure the welding effect at the junction of the tube segment 103, the notched first cooling tube 102 and the second cooling tube 20 and avoid stress concentration.

[0066] In some embodiments, step S7 specifically employs argon arc welding, and includes the following sub-steps:

[0067] S71: Argon gas is filled into the internal space formed by the first cooling pipe 102, the pipe segment 103, and the second cooling pipe 20. This prevents oxidation of the outer weld 400 during welding of the outer part and ensures the welding quality of the outer weld 400.

[0068] S72: Weld the seam from bottom to top at the welding position between the tube segment 103 and the second cooling tube 20 (see...). Figure 4 (See arrow N in the diagram). Welding is performed from bottom to top at the welding position between segment 103 and the notched first cooling pipe 102. If welding is performed from top to bottom at the welding position between segment 103 and the second cooling pipe 20, and from top to bottom at the welding position between segment 103 and the notched first cooling pipe 102, the molten welding material will flow downwards due to gravity, which cannot guarantee the welding quality. Therefore, welding from bottom to top at the welding position between segment 103 and the second cooling pipe 20, and from bottom to top at the welding position between segment 103 and the notched first cooling pipe 102, is beneficial to ensuring the welding quality.

[0069] In some embodiments, the welding of the inner weld 300 and the outer weld 400 are both performed by first welding the root pass and then welding the cover pass. The root pass welding controls the fusion quality, while the cover pass welding ensures the appearance and dimensions, and guarantees good microstructure and mechanical properties of the weld.

[0070] It should be noted that the number of weld layers for the inner weld 300 and the outer weld 400 needs to be determined based on the pipe wall thickness.

[0071] In some embodiments, when performing the root pass welding, the current is 40 - 60 A and the voltage is 10 - 13 V; when performing the cap pass welding, the current is 50 - 60 A and the voltage is 10 - 13 V, and the interpass temperature is controlled within 60°C. It can be understood that the root pass welding adopts a small heat input. If the input heat is too large, it is easy to cause the weld to penetrate and the welding quality is poor. Therefore, on the one hand, the small heat input ensures good microstructure and mechanical properties of the root pass weld, and on the other hand, it does not cause heat accumulation and affect the subsequent cap pass welding. When performing the cap pass welding, with a current of 50 - 60 A and a voltage of 10 - 13 V, it is beneficial to improve the welding efficiency, and at the same time, it can ensure the weld quality. Controlling the interpass temperature within 60°C is beneficial to controlling the welding deformation.

[0072] In some embodiments, it further includes: after step S7, performing VT, PT, and RT inspections on the outer weld 400. It should be noted that when the VT inspection is unqualified, there is no need to further perform the PT inspection. When the PT inspection is unqualified, there is no need to perform the RT inspection. Therefore, when performing the VT, PT, and RT inspections step by step in sequence, it is beneficial to improve the inspection efficiency of the outer welding 400. If the outer weld 400 is detected to be unqualified, it is repaired. Finally, it is necessary to ensure the qualification of the outer weld 400.

[0073] The present invention also proposes a welding structure 1000 for pipes in a narrow space of a fusion device.

[0074] A welding structure 1000 for pipes in a narrow space of a fusion device according to an embodiment of the second aspect of the present invention is obtained by using the welding method for pipes in a narrow space of a fusion device according to an embodiment of the first aspect of the present invention.

[0075] Since the welding structure 1000 for pipes in a narrow space of a fusion device according to an embodiment of the second aspect of the present invention is obtained by using the welding method for pipes in a narrow space of a fusion device according to an embodiment of the first aspect of the present invention, therefore, the welding structure 1000 for pipes in a narrow space of a fusion device according to an embodiment of the second aspect of the present invention has basically the same technical effects as the welding method for pipes in a narrow space of a fusion device according to an embodiment of the first aspect of the present invention, and will not be elaborated here.

[0076] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations of the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for welding a pipe in a narrow space of a fusion device, characterized by, Includes the following steps: S1: Pre-assemble the first component with the first cooling pipe and the second component with the second cooling pipe, while placing the first cooling pipe and the second cooling pipe to be welded in the designed position, and observe the situation where the first cooling pipe and the second cooling pipe are blocked by the first component and the second component. S2: Draw a first marking line for cutting notches on the unblocked part of the first cooling pipe, and draw a second marking line at the positions corresponding to the two ends of the first marking line at the pipe opening of the second cooling pipe. S3: Cut along the first marking line on the first cooling pipe to obtain a notched first cooling pipe and a pipe plate; S4: Assemble the first component and the second component, and at the same time, align the notched first cooling pipe and the second cooling pipe and ensure that the two ends of the notch opening are aligned with the second marking line. Then, spot weld between the notched first cooling pipe and the second cooling pipe. S5: Insert the welding torch into the first cooling pipe through the notch, weld the first cooling pipe and the second cooling pipe through the notch, and form an inner weld. S6: Place the tube segment in the notch, and perform spot welding between the tube segment and the second cooling tube and between the tube segment and the first cooling tube in the notch; S7: The welding torch is used to weld the tube segment to the second cooling tube and the tube segment to the notched first cooling tube outside the first cooling tube, forming an outer weld.

2. The fusion device narrow-space pipe welding method according to claim 1, characterized by, In step S3, during the cutting process, all corner transitions are smoothly rounded.

3. The welding method for confined space pipes in a fusion device according to claim 1, characterized in that, It also includes the following steps: after step S3 and before step S4, bevels are machined at the corresponding welding positions in the second cooling pipe, the notched first cooling pipe, and the pipe segment.

4. The welding method for confined space pipes in a fusion device according to claim 3, characterized in that, The bevel at the welding position between the second cooling pipe and the notched first cooling pipe is an inner V-shaped bevel facing the internal space of the second cooling pipe and the notched first cooling pipe. The bevel at the welding position between the pipe segment and the second cooling pipe, and the bevel at the welding position between the pipe segment and the notched first cooling pipe, are outer V-shaped bevels facing the external space.

5. The welding method for confined space pipes in a fusion device according to claim 4, characterized in that, The angle of the bevel is 35°~40°.

6. The welding method for confined space pipes in a fusion device according to claim 3, characterized in that, After the beveling process is completed, the beveling is subjected to PT testing. After the beveling passes the test, step S4 is then performed.

7. The welding method for confined space pipes in a fusion device according to claim 1, characterized in that, Step S5 employs argon arc welding, specifically including the following sub-steps: S51: An argon chamber is provided on the outside of the welding position between the first cooling pipe and the second cooling pipe with the notch, so that the argon chamber is in close contact with the outer surface of the first cooling pipe and the second cooling pipe with the notch, and argon gas is filled into the argon chamber; S52: Welding is performed from bottom to top at the position to be welded between the first cooling pipe and the second cooling pipe at the notch.

8. The welding method for confined space pipes in a fusion device according to claim 1, characterized in that, It also includes the following steps: after step S5 and before step S6, VT, PT and RT tests are performed on the inner weld.

9. The welding method for confined space pipes in a fusion device according to claim 8, characterized in that, The procedure also includes the following steps: after the VT, PT and RT tests of the inner weld are qualified, a transition slope is opened at both ends of the inner weld, and the transition slope is smoothly transitioned at the intersection with the segment.

10. The welding method for confined space pipes in a fusion device according to claim 9, characterized in that, The angle of the transition slope is 45°~50°.

11. The welding method for confined space pipes in a fusion device according to claim 1, characterized in that, Step S7 specifically employs argon arc welding, and includes the following sub-steps: S71: Argon gas is filled into the internal space formed by the first cooling pipe with the notch, the tube segment and the second cooling pipe; S72: Welding is performed from bottom to top at the position to be welded between the tube segment and the second cooling pipe, and welding is performed from bottom to top at the position to be welded between the tube segment and the notched first cooling pipe.

12. The welding method for confined space pipes in a fusion device according to claim 1, characterized in that, Both the inner and outer welds are welded by first performing the root pass weld and then the cover pass weld.

13. The welding method for confined space pipes in a fusion device according to claim 12, characterized in that, When performing the root pass weld, the current is 40~60A and the voltage is 10~13V; when performing the cover pass weld, the current is 50~60A and the voltage is 10~13V, and the interpass temperature is controlled below 60℃.

14. The welding method for confined space pipes in a fusion device according to claim 1, characterized in that, Also includes: After step S7, VT, PT and RT tests are performed on the outer weld.

15. A welded pipe structure for a confined space in a fusion device, characterized in that, It is obtained by welding pipes in a confined space of a fusion device according to any one of claims 1 to 14.

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