A welding method for butt joint of nickel-copper tube

Abstract

The application provides a welding method for butt joint of nickel-copper pipes, using a filler wire manual tungsten argon arc welding process, and the welding method comprises the following steps: chamfering butt joint edges of the first and second nickel-copper pipes, the chamfering bevel faces outward, and the inclination angle is 30°; cleaning the butt joint edges of the first and second nickel-copper pipes; adjusting the butt joint seam width of the first and second nickel-copper pipes to be within a preset standard width range, forming a V-shaped circumferential groove with a single-side inclination angle of 30°, and performing a positioning welding; setting the inner argon flushing flow of the nickel-copper pipe to be within a preset argon flushing flow range, setting the protective argon flow of a welding gun to be within a preset protective gas flow range; and sequentially performing one backing welding, three filling weldings and one cap welding at the circumferential groove according to a preset welding voltage, a preset welding current, a preset welding speed and a preset welding path. The technical scheme effectively reduces the deformation amount in the welding process of the butt joint seam of the nickel-copper pipe, reduces the rework rate, improves the welding quality, and improves the production efficiency.

Description

Technical Field

[0001] This application relates to the technical field of nickel-copper pipe welding, and more specifically, to a welding method for butt welding of nickel-copper pipes. Background Technology

[0002] Nickel-copper alloy pipes (B10), also known as nickel-copper pipes, are widely used in seawater cooling systems. Due to the special properties of nickel-copper pipes, they cannot be bent using a pipe bending machine. Instead, shaped elbows are typically used at bends, and the resulting circumferential joint is then welded. For longer nickel-copper pipe systems, multiple sections of pipe are required for jointing, followed by welding the resulting circumferential joint.

[0003] Because copper-iron-nickel alloys have a large coefficient of linear expansion, they are highly susceptible to deformation under welding thermal cycles. Furthermore, using elbows in splicing increases the number of welds (butt joints) exponentially, leading to increased shrinkage and further exacerbating deformation. Therefore, ensuring that the pipe's dimensions meet manufacturing and assembly process requirements is a key challenge in welding nickel-copper pipes.

[0004] Meanwhile, current nickel-copper pipe butt welding is prone to problems such as incomplete fusion, incomplete penetration, slag inclusion, and weld beads. At the same time, the weld surface is prone to defects such as porosity, arc-end cracks, and reduced precision. Moreover, the pass rate of radiographic testing is only about 40%, resulting in a lot of rework. After rework, most of the pipes are deformed and cannot be installed or used, which wastes a lot of materials and labor. Summary of the Invention

[0005] The purpose of this application is to provide a welding method for butt welding of nickel-copper pipes, which can effectively reduce the deformation during the welding process of nickel-copper pipe butt joints, reduce the rework rate, improve the welding quality, and relatively improve production efficiency and shorten the construction cycle.

[0006] This application provides a welding method for butt welding of nickel-copper tubes, using a filler wire manual tungsten inert gas welding process. The welding method includes the following steps:

[0007] S1. Chamfer the joint edges of the first nickel-copper tube and the second nickel-copper tube, with the chamfered surface facing outwards and the angle being 30°.

[0008] S2. Clean the mating edges of the first and second nickel-copper tubes;

[0009] S3. Adjust the width of the butt joint between the first nickel-copper tube and the second nickel-copper tube to the preset standard width range to form a V-shaped circumferential bevel with a single-sided inclination angle of 30°, and fix it with tack welding;

[0010] S4. Set the argon flow rate inside the nickel-copper tube to the preset argon flow rate range, and set the shielding gas argon flow rate of the welding torch to the preset shielding gas flow rate range.

[0011] S5. According to the preset welding voltage, preset welding current, preset welding speed and preset welding path, perform one root pass, three fill passes and one cover pass at the circumferential bevel. The root pass forms a root pass layer. The three fill passes include the first fill pass, the second fill pass and the third fill pass, which form the first fill pass layer, the second fill pass layer and the third fill pass layer respectively. The cover pass forms a cover pass layer. The root pass layer is located at the innermost circle of the circumferential bevel. The first, second and third fill passes completely cover the root pass layer. The cover pass completely covers the first, second and third fill passes.

[0012] In one feasible embodiment, the first filler layer contacts the chamfered surface of the first nickel-copper tube, the second filler layer contacts the chamfered surface of the second nickel-copper tube, and the third filler layer is located between the first and second filler layers, with at least partial areas on both sides of the third filler layer respectively covering the first and second filler layers.

[0013] In one feasible embodiment, the overall weld structure formed by the base weld layer, the first filler weld layer, the second filler weld layer, the third filler weld layer, and the cover weld layer is symmetrical about the center plane of the joint between the first nickel-copper tube and the second nickel-copper tube; the center plane is parallel to the end face of the joint between the first nickel-copper tube and the second nickel-copper tube and is located in the middle of the joint.

[0014] In one feasible approach, four positions—3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock—are marked clockwise along the circumference of the bevel. The pre-defined welding path for one root pass, three fill passes, and one cap pass is the same. The pre-defined welding path includes:

[0015] The first sub-path is welded counterclockwise from the six o'clock position to the three o'clock position;

[0016] The second sub-path is welded clockwise from the six o'clock position to the nine o'clock position;

[0017] The third sub-path is welded counterclockwise from the three o'clock position to the twelve o'clock position;

[0018] The fourth sub-path is welded clockwise from the nine o'clock position to the twelve o'clock position.

[0019] In one feasible scheme, the second sub-path has at least a predetermined length covering the first sub-path at the six o'clock position; the third sub-path has at least a predetermined length covering the first sub-path at the three o'clock position; the fourth sub-path has at least a predetermined length covering the second sub-path at the nine o'clock position; and the fourth sub-path has at least a predetermined length covering the third sub-path at the twelve o'clock position.

[0020] In one feasible embodiment, during the welding of the first, second, third, and fourth sub-paths of the root pass, the preset welding current ranges from A1 to A2. During the welding of the first, second, third, and fourth sub-paths of the three fill pass, the preset welding current ranges from B1 to B2. During the welding of the first, second, third, and fourth sub-paths of the cover pass, the preset welding current ranges from C1 to C2. Where A2 ≤ B1, B2 ≤ C2, and B1 < C1.

[0021] In one feasible embodiment, during the welding of the first, second, third, and fourth sub-paths of the first filler weld, the preset welding current ranges from B11 to B21. During the welding of the first, second, third, and fourth sub-paths of the first filler weld, the preset welding current ranges from B12 to B22. During the welding of the first, second, third, and fourth sub-paths of the first filler weld, the preset welding current ranges from B13 to B23. Where A2 ≤ B11, B21 ≤ B12, B22 ≤ B13, B23 ≤ C2, and B13 ≤ C1.

[0022] In one feasible scheme, A2 < B11, B21 < B12, B22 < B13, B13 = C1, and B23 = C2.

[0023] In one feasible embodiment, step S3, prior to tack welding, further includes adjusting the concentricity of the first nickel-copper tube and the second nickel-copper tube to ≤1mm.

[0024] In one feasible approach, in step S3, the preset standard width range is 2mm-5mm; during welding, the interpass temperature is controlled below 100℃.

[0025] Compared with the prior art, the beneficial effects of this application are as follows:

[0026] Using the welding method of this application to weld nickel-copper pipes can control the shrinkage rate and effectively reduce the deformation during the welding process. Even if the nickel-copper pipe pipeline has many bends and joints, the deformation of the nickel-copper pipe can still meet the manufacturing standards after using the welding method of this application, reducing deformation problems and facilitating subsequent assembly.

[0027] Meanwhile, the welding method of this application for welding nickel-copper tubes also basically solves the problems that are easy to occur during welding, such as porosity, slag inclusion, lack of fusion, incomplete penetration, weld beads, arc-end cracks, and reduced precision. This is because the reasonable welding process parameters and methods of this method ensure that the deformation of the weld is controlled within the process requirements. Moreover, the radiographic pass rate in multiple experiments has reached more than 98%, which solves the problem of radiographic pass rate affected by various uncertain factors. This reduces rework, reduces material waste, improves production efficiency, saves costs, meets schedule requirements, and shortens the construction cycle. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating a welding method for butt welding of nickel-copper tubes according to an embodiment of this application;

[0030] Figure 2 This is a schematic diagram illustrating the connection of two nickel-copper tubes according to an embodiment of this application;

[0031] Figure 3 This is a cross-sectional view of the axial circumferential bevel at the butt joint of two nickel-copper tubes according to an embodiment of this application;

[0032] Figure 4 This is a schematic diagram of the weld layer within the bevel at the butt joint of two nickel-copper tubes according to an embodiment of this application;

[0033] Figure 5 This is a schematic diagram of the welding path along the axis at the butt joint of two nickel-copper tubes according to an embodiment of this application.

[0034] In the diagram: 11, First nickel-copper tube; 12, Second nickel-copper tube; 13, Circumferential bevel; 101, Root pass; 201, First filler pass; 202, Second filler pass; 203, Third filler pass; 301, Cap pass; 401, First sub-path; 402, Second sub-path; 403, Third sub-path; 404, Fourth sub-path. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0037] like Figure 1 As shown, this application provides a welding method for butt welding of nickel-copper pipes, using a filler wire manual tungsten inert gas welding process, for butt welding of nickel-copper pipes. Figure 2 The nickel-copper pipes shown are welded to the joint. The welding method includes the following steps:

[0038] S1. Chamfer the mating edges of the first nickel-copper tube 11 and the second nickel-copper tube 12, with the chamfered surface facing outwards at an angle of 30°; wherein, the first nickel-copper tube 11 and the second nickel-copper tube 12 can both be straight tubes, or both can be bent tubes, or as shown in the figure. Figure 2 The section shown is a straight pipe, and the section shown is a bent pipe;

[0039] S2. Clean the mating edges of the first nickel-copper tube 11 and the second nickel-copper tube 12; generally, acetone is used for wiping. After cleaning, care should be taken to prevent secondary contamination.

[0040] S3. Adjust the width m of the butt joint between the first nickel-copper tube 11 and the second nickel-copper tube 12 to a preset standard width range of 2-5mm, preferably 2.5mm-4mm, to form a joint as shown in the figure. Figure 3 The V-shaped circumferential bevel 13 with a single-sided inclination angle of 30° shown can further adjust the concentricity of the first nickel-copper tube 11 and the second nickel-copper tube 12 to meet the requirement of ≤1mm, preferably ≤0.3mm, before tack welding is performed for fixation.

[0041] S4. Set the argon flow rate inside the nickel-copper tube to the preset argon flow rate range, and set the shielding gas argon flow rate of the welding torch to the preset shielding gas flow rate range.

[0042] S5. Following the preset welding voltage, preset welding current, preset welding speed, and preset welding path, perform one root pass, three fill passes, and one cap pass at the circumferential bevel 13; where, ifFigure 4 As shown, the root pass weld forms a root pass weld layer 101; the three fill passes weld a first fill pass weld, a second fill pass weld and a third fill pass weld, which respectively form a first fill pass weld layer 201, a second fill pass weld layer 202 and a third fill pass weld layer 203; the cap pass weld forms a cap pass weld layer 301; the root pass weld layer 101 is located at the innermost circle of the circumferential bevel 13, the first, second and third fill pass weld layers completely cover the root pass weld layer 101, and the cap pass weld layer 301 completely covers the first, second and third fill pass weld layers.

[0043] In this embodiment, as Figure 4 As shown, the first filler solder layer 201 is in contact with the chamfered surface of the first nickel-copper tube 11, the second filler solder layer 202 is in contact with the chamfered surface of the second nickel-copper tube, and the third filler solder layer 203 is located between the first filler solder layer 201 and the second filler solder layer 202, and at least some areas on both sides of the third filler solder layer 203 cover the first filler solder layer 201 and the second filler solder layer 202 respectively.

[0044] In this embodiment, as Figure 4 As shown, the overall weld structure formed by the base weld layer 101, the first filler weld layer 201, the second filler weld layer 202, the third filler weld layer 203, and the cover weld layer 204 is symmetrical about the center plane of the butt joint of the first nickel-copper tube 11 and the second nickel-copper tube 12. The center plane is parallel to the end face of the butt joint of the first nickel-copper tube 11 and the second nickel-copper tube 12 and is located in the middle of the butt joint. This symmetrical welding method can effectively reduce welding deformation.

[0045] In this embodiment, as Figure 5 As shown, four positions—3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock—are marked clockwise along the circumference of the bevel 13. The preset welding paths for one root pass, three filler passes, and one cover pass are the same. The preset welding paths include a first sub-path 401, a second sub-path 402, a third sub-path 403, and a fourth sub-path 404. The first sub-path 401 welds counterclockwise from the 6 o'clock position to the 3 o'clock position; the second sub-path 402 welds clockwise from the 6 o'clock position to the 9 o'clock position; the third sub-path 403 welds counterclockwise from the 3 o'clock position to the 12 o'clock position; and the fourth sub-path 404 welds clockwise from the 9 o'clock position to the 12 o'clock position.

[0046] Preferably, in this embodiment, such as Figure 5As shown, the second sub-path 402 has at least a predetermined length covering the first sub-path 401 at the six o'clock position; the third sub-path 403 has at least a predetermined length covering the first sub-path 401 at the three o'clock position; the fourth sub-path 404 has at least a predetermined length covering the second sub-path 402 at the nine o'clock position; and the fourth sub-path 404 has at least a predetermined length covering the third sub-path 403 at the twelve o'clock position.

[0047] Preferably, in this embodiment, during the welding process of the first sub-path 401, second sub-path 402, third sub-path 403, and fourth sub-path 404 for the root pass welding, the preset welding current range is A1-A2. During the welding process of the first sub-path 401, second sub-path 402, third sub-path 403, and fourth sub-path 404 for the three fill pass welding, the preset welding current range is B1-B2. During the welding process of the first sub-path 401, second sub-path 402, third sub-path 403, and fourth sub-path 404 for the cover pass welding, the preset welding current range is C1-C2. Wherein, A2≤B1, B2≤C2, and B1<C1.

[0048] Furthermore, in this embodiment, during the welding process of the first sub-path 401, the second sub-path 402, and the third sub-path 403 of the first filler weld, the preset welding current range is B11-B21. During the welding process of the first sub-path 401, the second sub-path 402, and the third sub-path 403 of the first filler weld, the preset welding current range is B12-B22. During the welding process of the first sub-path 401, the second sub-path 402, and the third sub-path 403 of the first filler weld, the preset welding current range is B13-B23. Wherein, A2≤B11, B21≤B12, B22≤B13, B23≤C2, and B13≤C1.

[0049] Preferably, in this embodiment, A2 < B11, B21 < B12, B22 < B13, B13 = C1, and B23 = C2. By setting welding currents with stepped differences for different weld layers, interlayer temperature control can be achieved, welding deformation can be reduced, and better welding quality can be obtained.

[0050] In this embodiment, during the root pass, three fill passes, and one cap pass, the preset welding voltage is preferably ≤30V, C2 is generally ≤160A, and the preset welding speed is 3-15cm / min, with a preferred welding speed of 7-10cm / min. The low-current multi-pass welding method of this application reduces welding heat input and controls interpass temperature, thereby effectively reducing welding deformation. The interpass temperature is controlled below 100℃, generally maintained between 35℃ and 45℃, and ideally between 38℃ and 42℃.

[0051] Using the welding method of this application to weld nickel-copper pipes can effectively reduce the amount of deformation during the welding process. Even if there are many bends and joints in the nickel-copper pipe pipeline, the deformation of the nickel-copper pipe can still meet the manufacturing standards after using the welding method of this application, reducing deformation problems and facilitating subsequent assembly.

[0052] Meanwhile, the welding method of this application for welding nickel-copper tubes also basically solves the problems that are easy to occur during welding, such as porosity, slag inclusion, lack of fusion, incomplete penetration, weld beads, arc-end cracks, and reduced precision. This is because the reasonable welding process parameters and methods of this method ensure that the deformation of the weld is controlled within the process requirements. Moreover, the radiographic pass rate in multiple experiments has reached more than 98%, which solves the problem of radiographic pass rate affected by various uncertain factors. This reduces rework, reduces material waste, improves production efficiency, saves costs, meets schedule requirements, and shortens the construction cycle.

[0053] Furthermore, this application utilizes the aforementioned welding method for butt welding of nickel-copper tubes to perform actual welding of nickel-copper tubes, such as... Figure 2 As shown, in this embodiment, straight nickel-copper tubes (first nickel-copper tube 11) with a diameter of φ170 and a wall thickness of 10mm and bent nickel-copper tubes (second nickel-copper tube 12) are spliced ​​together, as detailed below.

[0054] First, the manual tungsten inert gas (TIG) welding process with filler wire was determined, using a tungsten needle diameter of 2.4 mm and a nickel-copper welding wire diameter of 2 mm. A specialized beveling device was used to chamfer the butt joint edges of the first nickel-copper tube 11 and the second nickel-copper tube 12, with the chamfered surface facing outwards at an angle of 30°. Further, the surface area within a 30 mm or greater radius around the butt joint edges of the first nickel-copper tube 11 and the second nickel-copper tube 12 was polished and cleaned (using acetone; care should be taken to prevent secondary contamination after cleaning).

[0055] Furthermore, such as Figure 3 As shown, the butt joint gap between the first nickel-copper tube 11 and the second nickel-copper tube 12 is adjusted to a preset standard width range of 2.5mm-4mm, which can be 2.5mm, 2.6mm, 3mm, 3.2mm, 3.5mm, 4mm, etc. Then, a V-shaped circumferential bevel 13 with a single-sided inclination angle of 30° is formed at the butt joint of the first nickel-copper tube 11 and the second nickel-copper tube 12. Preferably, the concentricity of the first nickel-copper tube 11 and the second nickel-copper tube 12 should be ≤0.3mm. After inspection and confirmation, the tubes are fixed with embedded iron positioning welds.

[0056] Furthermore, argon gas is purged into the first nickel-copper tube 11 and the second nickel-copper tube 12, and the argon flow rate in the nickel-copper tubes is set to a preset argon flow rate range of 15-20 L / min. At the same time, it is also necessary to ensure that the grounding is reliable to avoid arcing of the nickel-copper tubes (the nickel-copper tubes must not be grounded by welding).

[0057] Furthermore, the flow rate of the shielding gas argon during welding is adjusted to 12-15 L / min, and the welding current is adjusted to 80-120 A, the welding voltage to 13-16 V, while maintaining the welding speed between 7-10 cm / min. Preferably, the interpass temperature is controlled below 100°C during welding.

[0058] Mark the four positions—3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock—clockwise along the circumference of bevel 13. Then, perform one root pass, three filler passes, and one cap pass in sequence.

[0059] Specifically, such as Figure 4 and 5 As shown, the root pass is first performed on the innermost side of the circumferential bevel 13. The root pass includes the following steps:

[0060] (1) Weld along the first sub-path 401, from the six o'clock position to the three o'clock position in a counterclockwise direction, wherein the welding current is maintained at 75-80A and the welding voltage is maintained at 13-16V.

[0061] (2) Weld along the second sub-path 402, from the six o'clock position to the nine o'clock position clockwise, with the welding current maintained at 75-80A and the welding voltage maintained at 13-16V.

[0062] (3) Weld along the third sub-path 403, from the three o'clock position to the twelve o'clock position in a counterclockwise direction, wherein the welding current is maintained at 75-80A and the welding voltage is maintained at 13-16V.

[0063] (4) Weld along the fourth sub-path 404, from the nine o'clock position to the twelve o'clock position clockwise, with the welding current maintained at 75-80A and the welding voltage maintained at 13-16V.

[0064] After all the steps of the root pass are completed, it forms as follows: Figure 4 The shown is the base solder layer 101.

[0065] Furthermore, such as Figure 4 and 5 As shown, after the root pass is completed, a first fill pass is performed on the upper side near the root pass 101 and on the inclined surface near the first nickel-copper tube 11. The first fill pass includes the following steps:

[0066] (1) Weld along the first sub-path 401, from the six o'clock position to the three o'clock position in a counterclockwise direction, wherein the welding current is maintained at 85-90A and the welding voltage is maintained at 13-16V.

[0067] (2) Weld along the second sub-path 402, from the six o'clock position to the nine o'clock position clockwise, with the welding current maintained at 85-90A and the welding voltage maintained at 13-16V.

[0068] (3) Weld along the third sub-path 403, from the three o'clock position to the twelve o'clock position in a counterclockwise direction, wherein the welding current is maintained at 85-90A and the welding voltage is maintained at 13-16V.

[0069] (4) Weld along the fourth sub-path 404, from the nine o'clock position to the twelve o'clock position clockwise, with the welding current maintained at 85-90A and the welding voltage maintained at 13-16V.

[0070] After all the steps of the first filler weld are completed, it forms as follows: Figure 4 The first filler layer 201 is shown.

[0071] Furthermore, such as Figure 4 and 5 As shown, after the first filler weld is completed, a second filler weld is performed on the upper side near the root pass 101 and on the bevel near the second nickel-copper tube 12. The second filler weld includes the following steps:

[0072] (1) Weld along the first sub-path 401, from the six o'clock position to the three o'clock position in a counterclockwise direction, wherein the welding current is maintained at 90-95A and the welding voltage is maintained at 13-16V.

[0073] (2) Weld along the second sub-path 402, from the six o'clock position to the nine o'clock position clockwise, with the welding current maintained at 90-95A and the welding voltage maintained at 13-16V.

[0074] (3) Weld along the third sub-path 403, from the three o'clock position to the twelve o'clock position in a counterclockwise direction, wherein the welding current is maintained at 90-95A and the welding voltage is maintained at 13-16V.

[0075] (4) Weld along the fourth sub-path 404, from the nine o'clock position to the twelve o'clock position clockwise, with the welding current maintained at 90-95A and the welding voltage maintained at 13-16V.

[0076] After all the steps of the second filler weld are completed, it forms as follows: Figure 4 The second filler layer 202 is shown.

[0077] Furthermore, such as Figure 4 and 5 As shown, after the second filler solder is completed, a third filler solder is performed on the upper side between the first filler solder layer 201 and the second filler solder layer 202. The third filler solder includes the following steps:

[0078] (1) Weld along the first sub-path 401, from the six o'clock position to the three o'clock position in a counterclockwise direction, wherein the welding current is maintained at 110-120A and the welding voltage is maintained at 13-16V.

[0079] (2) Weld along the second sub-path 402, from the six o'clock position to the nine o'clock position clockwise, wherein the welding current is maintained at 110-120A and the welding voltage is maintained at 13-16V.

[0080] (3) Weld along the third sub-path 403, from the three o'clock position to the twelve o'clock position in a counterclockwise direction, wherein the welding current is maintained at 110-120A and the welding voltage is maintained at 13-16V.

[0081] (4) Weld along the fourth sub-path 404, from the nine o'clock position to the twelve o'clock position clockwise, with the welding current maintained at 110-120A and the welding voltage maintained at 13-16V.

[0082] After all the steps of the third filler weld are completed, it forms as follows: Figure 4 The third filler layer 203 is shown.

[0083] Furthermore, such as Figure 4 and 5 As shown, after the third filler weld is completed, a capping weld is performed on the upper side of the first filler weld layer 201, the second filler weld layer 202, and the third filler weld layer 203. The capping weld includes the following steps:

[0084] (1) Weld along the first sub-path 401, from the six o'clock position to the three o'clock position in a counterclockwise direction, wherein the welding current is maintained at 110-120A and the welding voltage is maintained at 13-16V.

[0085] (2) Weld along the second sub-path 402, from the six o'clock position to the nine o'clock position clockwise, wherein the welding current is maintained at 110-120A and the welding voltage is maintained at 13-16V.

[0086] (3) Weld along the third sub-path 403, from the three o'clock position to the twelve o'clock position in a counterclockwise direction, wherein the welding current is maintained at 110-120A and the welding voltage is maintained at 13-16V.

[0087] (4) Weld along the fourth sub-path 404, from the nine o'clock position to the twelve o'clock position clockwise, with the welding current maintained at 110-120A and the welding voltage maintained at 13-16V.

[0088] After all the steps of the cover weld are completed, it forms as follows: Figure 4 The cover weld layer 301 is shown.

[0089] In order to verify whether the welding quality meets the requirements, this application conducts 100% radiographic testing on the weld of the first nickel-copper pipe 11 and the second nickel-copper pipe 12 in accordance with relevant testing requirements 24 hours after the welding is completed. After the radiographic testing is completed, a pipe strength test and an internal high pressure test (pressure of 4.5 MPa) are carried out.

[0090] Inspection revealed that the completed welds were well-formed, with consistent width throughout, and X-ray flaw detection results met the requirements of relevant standards. Furthermore, the strength and pressure tests were passed, and no defects such as lack of fusion, porosity, slag inclusions, weld beads, or cracks were found in the welds.

[0091] Furthermore, the inventors also used the method of this embodiment to weld nickel-copper tubes of different diameters and wall thicknesses, and statistically analyzed the average shrinkage dimensions of the welded nickel-copper tubes of different diameters and wall thicknesses. See the table below:

[0092] Table 1. Statistics on welding deformation of nickel-copper pipes of different diameters

[0093] Specification (diameter x wall thickness) (mm) Butt joint width (mm) Sampling amount Average shrinkage size (mm) φ45 x 3 2.5 15 1.0 φ55 x 3 2.5 10 1.2 φ75 x 4 2.8 12 1.5 φ90 x 5 3.0 18 1.7 φ110 x 10 3.0 16 1.7 φ135 x 10 3.5 15 1.8 φ170 x 10 4.0 20 1.8

[0094] Statistical analysis revealed that when nickel-copper pipes of different diameters and wall thicknesses are welded using the aforementioned welding method, the overall shrinkage dimensions can meet the requirements.

[0095] In summary, the welding method for butt welding of nickel-copper pipes proposed in this application overcomes the shortcomings of existing technologies, solves the problem of severe deformation during welding of nickel-copper pipes, ensures the welding quality of nickel-copper pipes, improves the pass rate of X-ray flaw detection of welds, thereby reducing the rework rate, thus improving production efficiency, reducing production costs, meeting schedule requirements, and shortening the construction cycle.

[0096] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A welding method for butt welding of nickel-copper pipes, characterized in that, The manual tungsten inert gas (TIG) welding process using filler wire includes the following steps: S1. Chamfer the joint edges of the first nickel-copper tube and the second nickel-copper tube, with the chamfered surface facing outwards and the angle being 30°. S2. Clean the mating edges of the first and second nickel-copper tubes; S3. Adjust the width of the butt joint between the first nickel-copper tube and the second nickel-copper tube to the preset standard width range to form a V-shaped circumferential bevel with a single-sided inclination angle of 30°, and fix it with tack welding; S4. Set the argon flow rate inside the nickel-copper tube to the preset argon flow rate range, and set the shielding gas argon flow rate of the welding torch to the preset shielding gas flow rate range. S5. According to the preset welding voltage, preset welding current, preset welding speed, and preset welding path, perform one root pass, three fill passes, and one cover pass at the circumferential bevel. The root pass forms a root pass layer. The three fill passes include a first fill pass, a second fill pass, and a third fill pass, which respectively form a first fill pass layer, a second fill pass layer, and a third fill pass layer. The cover pass forms a cover pass layer. The root pass layer is located at the innermost circle of the circumferential bevel. The first, second, and third fill passes completely cover the root pass layer, and the cover pass layer completely covers the first, second, and third fill passes layer. The first filler solder layer contacts the chamfered surface of the first nickel-copper tube, the second filler solder layer contacts the chamfered surface of the second nickel-copper tube, and the third filler solder layer is located between the first filler solder layer and the second filler solder layer, and at least some areas on both sides of the third filler solder layer respectively cover the first filler solder layer and the second filler solder layer. Among them, the welding currents for the root pass, fill pass, and cover pass are set with different levels; The four positions of 3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock are marked clockwise along the circumference of the bevel. The preset welding paths for the root pass, the three fill passes, and the one cap pass are the same. The preset welding paths include: The first sub-path is welded counterclockwise from the six o'clock position to the three o'clock position; The second sub-path is welded clockwise from the six o'clock position to the nine o'clock position; The third sub-path is welded counterclockwise from the three o'clock position to the twelve o'clock position; The fourth sub-path is welded clockwise from the nine o'clock position to the twelve o'clock position; The preset welding current for the root pass is in the range of 75-80A; The preset welding current range for the first filler weld is 85-90A, the preset welding current range for the second filler weld is 90-95A, and the preset welding current range for the third filler weld is 110-120A. The preset welding current range for the cover weld is 110-120A.

2. The welding method for butt welding of nickel-copper tubes according to claim 1, characterized in that, The overall weld structure formed by the base weld layer, the first filler weld layer, the second filler weld layer, the third filler weld layer, and the cover weld layer is symmetrical about the center plane of the joint between the first nickel-copper tube and the second nickel-copper tube; the center plane is parallel to the end face of the joint between the first nickel-copper tube and the second nickel-copper tube and is located in the middle of the joint.

3. The welding method for butt welding of nickel-copper tubes according to claim 1, characterized in that, The second sub-path has at least a predetermined length that overlaps the first sub-path at the six o'clock position; The third sub-path has at least a predetermined length covering the first sub-path at the three o'clock position; The fourth sub-path has at least a predetermined length covering the second sub-path at the nine o'clock position; The fourth sub-path has at least a predetermined length covering the third sub-path at the 12 o'clock position.

4. The welding method for butt welding of nickel-copper tubes according to any one of claims 1-3, characterized in that, In step S3, before the positioning welding is performed, the concentricity of the first nickel-copper tube and the second nickel-copper tube is adjusted to meet the requirement of ≤1mm.

5. The welding method for butt welding of nickel-copper tubes according to any one of claims 1-3, characterized in that, In step S3, the preset standard width range is 2mm-5mm; during welding, the interpass temperature is controlled below 100℃.

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