An electron beam weld defect repair method

Abstract

The application discloses an electron beam weld defect repairing method. The method comprises the following steps: determining the arc receiving position of the workpiece weld for electron beam welding, so as to avoid the position with large pressure or stress and facilitate subsequent processing; removing the defect by machining trapezoidal grooves from the front and back sides of the weld; performing repair welding by adopting the MIG welding method with the aid of helium protection; comprehensively using X-ray, ultrasonic and penetration detection to perform nondestructive detection on the repair welding position after repair welding; and finally verifying the bearing capacity by air tightness and pressure test. The application solves the contradiction between the groove size and the welding operability during the repair of the electron beam weld of the large-thickness aluminum alloy by the process combination of optimizing the arc receiving position design, machining small-size grooves from the front and back sides, helium protection MIG repair welding and comprehensive detection, ensures the complete removal of the defect, maximally reduces the repair welding heat affected zone and guarantees the performance of the welded joint.

Description

Technical Field

[0001] This invention relates to the field of welding repair technology, and more specifically, to a method for repairing defects in electron beam welds. Background Technology

[0002] Vacuum electron beam welding, as a high-energy-density welding method, features a large weld depth-to-width ratio, narrow heat-affected zone, minimal welding deformation, and excellent joint performance. It is widely used in high-end manufacturing fields such as aerospace, shipbuilding, and nuclear industry. Particularly in the welding of aluminum alloy structural components, vacuum electron beam welding effectively avoids common defects such as porosity and oxidation, resulting in high-quality weld joints.

[0003] With the increasing technical requirements of components such as underwater unmanned vehicles (UUVs), the welding thickness of their main structural parts has gradually increased from the traditional 10mm to 30-50mm. In actual production, important welds involving pressure or load bearing are often welded using vacuum electron beam welding to ensure that the weld joint performance meets the usage requirements. However, in production practice, it has been found that when using vacuum electron beam welding to weld thick aluminum alloy welds, obvious welding defects often appear at the arc termination point, mainly manifested as penetrating incomplete fusion, accompanied by a certain degree of cracking. This is because the energy input is suddenly interrupted at the end of electron beam welding, the molten pool solidifies rapidly, and the heat accumulation at the arc termination point is relatively large, which easily leads to defects such as shrinkage cavities, cracks, and incomplete fusion.

[0004] To address the aforementioned defects, the traditional repair method involves using milling to create a trapezoidal bevel for welding at the defective area, followed by manual welding using MIG welding (Metal Inert Gas Welding) with a large penetration depth. However, this welding method presents several technical challenges: Firstly, if the bevel is too large, it expands the area of ​​the manually welded joint, increasing the heat input to the joint and its surrounding area, thus enlarging the heat-affected zone and significantly impacting joint performance. This is particularly problematic for heat-treated aluminum alloys like 6061-T6, where excessive heat input can damage the strengthening phase, leading to a significant decrease in joint strength. Secondly, if the bevel is too small, the welding space becomes cramped, making it difficult for the welding torch to reach the bottom of the bevel. This can easily result in new welding defects such as incomplete penetration and lack of fusion, which also affect the density and joint performance of the welded joint, ultimately impacting the workpiece's load-bearing capacity and reliability.

[0005] Therefore, how to ensure the complete removal of defects, minimize the heat-affected zone of the repair weld, guarantee the performance of the welded joint, and ensure the feasibility of the repair weld operation during the repair process of electron beam welds in thick aluminum alloys has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a method for repairing defects in electron beam welds to address the problems of large heat-affected zones and low performance of welded joints in existing technologies.

[0007] To achieve the above objectives, the present invention provides a method for repairing defects in electron beam welds. The method includes: S1, determining the arc termination position of the workpiece weld during electron beam welding; S2, processing a bevel for the arc termination position containing the defect from both sides of the weld, wherein the bevel shape is: a rectangular cross-section parallel to the weld surface and a trapezoidal cross-section perpendicular to the weld surface; S3, determining and processing the bevel depth according to the defect removal depth requirement; S4, performing a repair weld on the processed bevel using MIG welding supplemented with helium protection; S5, after the repair weld is completed, performing non-destructive testing on the repaired area using X-ray inspection, ultrasonic testing, and penetrant testing; S6, conducting airtightness and pressure tests on the inspected workpiece to verify its final load-bearing capacity.

[0008] Optionally, the method for determining the arc termination position is as follows: based on the structural characteristics of the workpiece, the arc termination position is set in the non-critical load-bearing section of the weld, and this position should be able to be approached from both the front and back sides.

[0009] Optionally, the process of repairing the weld bevel at the defective arc-end position from both sides of the weld includes: processing an upper trapezoidal bevel at the defective arc-end position from the front side of the weld; processing a lower trapezoidal bevel at the defective arc-end position from the back side of the weld; the upper trapezoidal bevel and the lower trapezoidal bevel are connected in the weld thickness direction to form a double trapezoidal combined bevel that runs through the weld.

[0010] Optionally, the bevel angle on one side of the upper trapezoidal bevel and the lower trapezoidal bevel is 15°-30°; the bottom width of the upper trapezoidal bevel and the lower trapezoidal bevel is determined to be 5-10mm based on the accessibility of the MIG welding torch.

[0011] Optionally, the method for determining the defect removal depth is as follows: the depth range of the defect is pre-determined by X-ray detection or ultrasonic detection, and the processing depth is increased by a margin of 1-3 mm compared with the maximum value of the depth range determined by detection.

[0012] Optionally, the welding current of the MIG welding is 180-260A, the welding voltage of the MIG welding is 22-28V, the welding speed of the MIG welding is 200-400mm / min, and the flow rate of the helium gas is 15-25L / min.

[0013] Optionally, the repair welding of the processed bevel includes: repairing the processed bevel using a multi-layer, multi-pass welding process; wherein the interpass temperature is controlled below 60°C, and visual inspection and cleaning are performed after each layer is welded.

[0014] Optionally, the non-destructive testing of the weld repair area using X-ray inspection, ultrasonic inspection, and penetrant testing includes: performing non-destructive testing of the weld repair area in sequence using penetrant testing, X-ray inspection, and ultrasonic inspection.

[0015] Optionally, the thickness of the weld is in the range of 30-50mm, and the base material of the weld is aluminum alloy.

[0016] Optionally, the aluminum alloy material is 6061-T6 heat-treated strengthened aluminum alloy.

[0017] The beneficial effects of this invention are: This invention provides a method for repairing defects in electron beam welds. By pre-determining the arc termination position during the workpiece design phase to avoid areas subject to significant pressure or stress, this method fundamentally reduces the impact of arc termination defects on the overall performance of the workpiece. It also facilitates subsequent repair operations and inspection, embodying the technical principle of "prevention first, combined with treatment." The method employs a trapezoidal bevel machining process from both sides of the weld, forming a double trapezoidal combined bevel. This ensures complete defect removal while keeping the size of the bevel on each side within a small range, providing ample operational space for MIG repair welding and resolving the contradiction between bevel size and welding operability in traditional repair methods. This invention utilizes a MIG welding process supplemented with helium protection. Helium, with its high ionization potential and thermal conductivity, increases weld penetration and improves welding efficiency. Simultaneously, it provides excellent protection, effectively preventing oxidation during aluminum alloy welding and ensuring the quality of the repaired weld joint. The weld repair area is inspected by combining three non-destructive testing methods: X-ray, ultrasonic, and penetrant testing. Penetrant testing can detect surface opening defects, X-ray testing can detect volumetric defects, and ultrasonic testing can detect area defects. The three methods complement each other to ensure the effective detection of various defects. Attached Figure Description

[0018] Figure 1 This is a flowchart of an electron beam weld defect repair method provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] This embodiment uses the repair of a longitudinal seam electron beam welding defect in the pressure-resistant shell of a certain type of UUV workpiece as an example to describe in detail the method for repairing defects in thick electron beam welds according to the present invention. The thickness of the weld is in the range of 30-50 mm, and the base material of the weld is aluminum alloy. The aluminum alloy is 6061-T6 heat-treated strengthened aluminum alloy. In a specific embodiment, the pressure-resistant shell material is 6061-T6 aluminum alloy with a wall thickness of 40 mm. The longitudinal seam is welded using vacuum electron beam welding. X-ray inspection after welding revealed a penetrating, unfused defect of approximately 30 mm in length at the weld termination, accompanied by microcracks. The workpiece is designed to withstand a pressure of 3 MPa, requiring the weld joint strength to be no less than 85% of the base material strength, and it must pass a hydrostatic test at twice the design pressure. To address this technical problem, the repair method of the present invention is used.

[0021] Figure 1 This is a flowchart of an electron beam weld defect repair method provided in an embodiment of the present invention, such as... Figure 1 As shown, the method includes: S1. Determine the arc termination position for electron beam welding of the workpiece weld; In an optional implementation, the arc termination position is selected at a location that facilitates subsequent beveling, welding repair, and inspection, while avoiding areas of the workpiece that are under pressure or stress. The method for determining the arc termination position is as follows: based on the structural characteristics of the workpiece, the arc termination position is set in the non-critical load-bearing section of the weld, and this position should be accessible from both sides.

[0022] First, the defect was precisely located. X-ray imaging was used to photograph the entire length of the longitudinal weld, marking the specific location and approximate extent of the defect on the film. To further determine the depth and direction of the defect and the crack propagation, ultrasonic imaging was used to perform A-scan and C-scan imaging on the defect area. The results showed that the defect was located at the weld termination point, penetrating from the weld surface to the back side, with a depth of approximately 38 mm (nearly the full thickness), and a longitudinal crack approximately 15 mm long was present in the center of the defect. Based on the inspection results, the repair area was determined to be a rectangular area with a length of 50 mm and a width of 20 mm, with the defect center as the reference point.

[0023] Based on the structural characteristics of the workpiece, the longitudinal seam is located in the middle of the pressure shell and is a major load-bearing weld, but the arc termination position is located at the end of the longitudinal seam, where the stress is relatively small.

[0024] Although the workpiece has been welded and a defect has been created, the arc termination point is located at the end of the longitudinal seam, approximately 100mm from the circumferential seam at the end of the shell, within a non-critical section of the longitudinal seam. This arc termination point is not the most critical section of the workpiece under pressure and can be considered a rework area.

[0025] In an optional implementation, prior to S2, the method of repair welding using MIG welding supplemented with helium protection is further included: determining a repair welding method. For the repair welding of 40mm thick aluminum alloy, a MIG welding method supplemented with helium shielding is considered. MIG welding is characterized by its flexibility and adaptability, making it suitable for manual repair welding. Helium, as a shielding gas, has a higher ionization potential and thermal conductivity compared to traditional argon, enabling greater penetration and higher welding speeds under the same welding parameters, making it particularly suitable for welding medium-thick aluminum alloy plates. This embodiment uses a Fonnius TPS4000 digital MIG welding torch equipped with a pusher-type wire feed mechanism. The welding wire used is ER5087 (AlMg4.5MnZr), 1.2mm in diameter, and pure helium (purity ≥99.99%) is used as the shielding gas.

[0026] S2. The defective arc-end position is repaired by welding a bevel from both sides of the weld. The bevel shape is as follows: the cross-section parallel to the weld surface is rectangular, and the cross-section perpendicular to the weld surface is trapezoidal. In an optional embodiment, the process of repairing the weld bevel at the defective arc-end position from both sides of the weld includes: A trapezoidal bevel is formed on the arc-end position containing defects from one side of the weld face. A lower trapezoidal bevel is formed on the arc-end position containing defects from the back side of the weld; the upper and lower trapezoidal bevels are connected in the weld thickness direction to form a double trapezoidal combination bevel that runs through the weld.

[0027] In an optional implementation, the bevel angle of the upper trapezoidal bevel and the lower trapezoidal bevel on one side is 15°-30°. The bottom width of the upper and lower trapezoidal bevels is determined to be 5-10 mm based on the accessibility of the MIG welding torch.

[0028] The bevel design is one of the key technical aspects of this invention. Traditional repair bevels typically use a large bevel on one side to facilitate welding torch operation, but this greatly increases the welding volume and heat input. This invention uses a method of machining small-sized bevels on both sides, which ensures the accessibility of the welding torch while minimizing the bevel volume.

[0029] The bevel designed in this embodiment is a double trapezoidal combined bevel, with the specific parameters as follows: Upper trapezoidal bevel (front): bevel depth 20mm, bevel bottom width 8mm, bevel angle on one side 20°, bevel length 50mm; Lower trapezoidal bevel (back side): bevel depth 20mm, bevel bottom width 8mm, bevel angle on one side 20°, bevel length 50mm; The joint of the upper and lower trapezoidal bevels in the thickness direction is located slightly above the center of the weld, forming a continuous and through-welding channel.

[0030] The advantages of this bevel design are: ① The bevel depth on one side is relatively small (only 20mm), which facilitates the deep operation of the welding torch and ensures good root fusion; ② The bottom width of the bevel is 8mm, which is neither too wide to increase the filling volume nor too narrow to make it difficult for the welding torch to reach; ③ The total filling volume of the double trapezoidal combined bevel is much smaller than that of the traditional single-sided large open bevel, and the heat input is reduced accordingly; ④ The bevel angle of 20° is conducive to aligning the end of the welding wire with the root of the bevel and ensuring sidewall fusion.

[0031] S3. Determine and process the bevel depth according to the defect removal depth requirements; In one optional implementation, the method for determining the defect removal depth is as follows: the depth range of the defect is pre-determined by X-ray detection or ultrasonic detection, and the processing depth is increased by a margin of 1-3 mm compared to the maximum value of the depth range determined by the detection.

[0032] Based on the preliminary ultrasonic testing results, the deepest point of the defect was 38mm, close to the full thickness. To ensure complete removal of the defect, the machining depth was determined to be 40mm (full thickness removal), which is an additional 2mm allowance based on the deepest point of the defect determined by the testing. This design takes into account both testing and machining errors, ensuring complete removal of the crack tip and preventing the crack from propagating again after rework.

[0033] Beveling was performed using a CNC gantry milling machine. First, the product was fixed on the milling machine table, and the weld position was aligned. Using a 10mm diameter carbide end mill, roughing and finishing of the upper trapezoidal bevel were performed from the front side. Strict control was maintained over the bevel dimensional accuracy during machining: the bottom width tolerance was controlled within ±0.5mm, the bevel angle tolerance within ±2°, and the bevel length tolerance within ±1mm. After the front beveling was completed, the product was rotated 180°, realigned, and the lower trapezoidal bevel on the back side was machined. During machining, compressed air was used to blow away aluminum chips to prevent scratches on the bevel surface. After machining, the bevel and surrounding area were cleaned with acetone to remove oil and aluminum chips, and the bevel surface was inspected with a magnifying glass for any residual cracks. Inspection revealed a smooth bevel surface with no visible defects.

[0034] S4. Use MIG welding with helium protection to repair the bevel. In one optional embodiment, the welding current of the MIG welding is 180-260A, the welding voltage of the MIG welding is 22-28V, the welding speed of the MIG welding is 200-400mm / min, and the flow rate of the helium gas is 15-25L / min.

[0035] In an optional implementation, the step of repairing the processed bevel by welding includes: The processed bevel is repaired using a multi-layer, multi-pass welding process; the interpass temperature is controlled below 60℃, and visual inspection and cleaning are carried out after each layer is welded.

[0036] Specifically, the welding repair process is described in detail below: (1) Preparation before repair welding Welding wire preparation: Pull out about 2m of ER5087 welding wire from the wire spool, wipe it clean with acetone to remove surface oil and oxide film, and then rewind it back onto the wire spool; Welding torch preparation: Select a water-cooled MIG welding torch with a rated current of 400A and install a 16mm diameter gas guide nozzle to ensure helium protection. Preheating of workpiece: Due to the fast thermal conductivity of aluminum alloy and the large thickness in this embodiment, in order to reduce the tendency of welding cracks, flame heating is used to locally preheat the welding area to 80-100°C. The preheating temperature is monitored by an infrared thermometer. Preset welding parameters: Based on empirical formulas and process test results, the preset welding parameters are: welding current 220A, welding voltage 24V, welding speed 300mm / min, helium flow rate 20L / min, and wire feed speed 8.5m / min.

[0037] (2) Root pass welding The root pass is crucial for the quality of the repair weld, requiring good root fusion without incomplete penetration or fusion defects. This embodiment uses a bottom-up welding sequence, starting with the back side. The welding torch is inserted deep into the back bevel, with the welding wire tip aligned with the center of the bevel root. A left-hand welding method is used, maintaining a torch angle of 10°-15°, and the arc is slightly oscillated at the bevel root to ensure good fusion of both side walls. The root pass length is 50mm. During welding, the molten pool is closely observed, and the arc is kept burning stably. After the root pass is completed, the oxide film on the weld surface is cleaned with a stainless steel wire brush, and then the weld surface is inspected with a magnifying glass for surface defects such as cracks and porosity. Inspection revealed that the root pass is well-formed and free of surface defects.

[0038] (3) Filler welding After the root pass is completed, the fill pass is performed. The fill pass uses a multi-layer, multi-pass welding process, consisting of 5 fill passes (2 on the back and 3 on the front), as detailed below: First filler layer (back side): Welding parameters are basically the same as for the root pass, with the welding current slightly increased to 230A and the welding speed slightly reduced to 280mm / min. The welding torch should be oscillated more widely to ensure good fusion with the bevel sidewall. After welding, clean with a wire brush and control the interpass temperature below 50℃.

[0039] Second layer filler (back side): At this point, the back bevel is basically filled. Welding parameters are adjusted to: current 240A, voltage 25V, welding speed 260mm / min, helium flow rate 22L / min. Post-weld cleaning and interpass temperature monitoring are performed.

[0040] Third filler layer (front side): Flip the product over and start filling from the front side. The welding parameters for the first filler layer on the front side are the same as those for the first filler layer on the back side. Make sure the arc is aligned with the bottom of the bevel to ensure fusion with the weld bead on the back side.

[0041] Fourth layer filler (front): Welding parameters are the same as the second layer on the back, with appropriate increase in the oscillation amplitude of the welding torch to ensure fusion with the bevel sidewall on the front.

[0042] Fifth layer filler (front side): Fill to about 2mm from the surface to prepare for cover welding.

[0043] Throughout the entire filler welding process, the following points must be strictly controlled: Interpass temperature: After each layer of welding, wait for the workpiece to cool to below 60℃ before welding the next layer to avoid heat input accumulation that could lead to an excessively wide heat-affected zone; Weld cleaning: After each layer of welding, use a stainless steel wire brush to clean the oxide film on the weld surface, and clean with acetone if necessary; Interpass overlap: When welding multiple passes, the subsequent pass overlaps the previous pass by about 1 / 3 of the pass width to ensure a smooth surface. Process inspection: Visual inspection is carried out after each layer is welded, and any problems are dealt with in a timely manner.

[0044] (4) Cover welding The cover weld is the final step in the repair welding process. It requires a visually appealing weld surface, slightly raised above the base metal surface, free from surface defects such as undercut and weld beads. In this embodiment, the cover weld parameters are: current 220A, voltage 24V, welding speed 300mm / min, and helium flow rate 20L / min. A slightly faster welding speed is used to avoid surface overheating. After welding, the weld surface exhibits a uniform fish-scale pattern, slightly raised about 1.5mm above the base metal, with a smooth transition to the base metal.

[0045] S5. After the repair welding is completed, non-destructive testing of the repaired area is carried out using X-ray inspection, ultrasonic inspection and penetrant testing. In an optional implementation, the non-destructive testing of the weld repair area using X-ray inspection, ultrasonic inspection, and penetrant testing includes: The weld repair area was subjected to non-destructive testing in sequence using penetrant testing, X-ray testing, and ultrasonic testing.

[0046] After the welding repair is completed, the repaired area is first subjected to local heat treatment to restore the mechanical properties of the 6061-T6 aluminum alloy. A tracked ceramic heater is used to enclose the repaired area, and the heat treatment temperature is set at 160℃ for 4 hours, followed by furnace cooling to room temperature. During the heat treatment process, thermocouples are used to monitor the temperature in real time to ensure temperature uniformity is within ±5℃.

[0047] Secondly, comprehensive non-destructive testing was conducted on the weld repair area.

[0048] (1) Penetration testing First, a penetrant testing method is performed to check for open defects on the weld repair surface. A solvent-removable dye penetrant testing method is used, and the testing steps are as follows: Pre-cleaning: Clean the weld repair area and the surrounding 25mm area with acetone to remove oil, moisture, etc. Penetration: Spray red penetrant, penetration time 15 minutes (ambient temperature 20℃); Removal: Use a cleaning agent to remove excess penetrant from the surface, being careful to avoid over-cleaning which could wash out the penetrant from the defects; Development: Spray white developer, development time 10 minutes; Observation: Under sufficient light, the imaging shows no red display in the repaired area, indicating that there are no surface opening defects.

[0049] (2) X-ray detection After passing the penetrant testing, X-ray inspection was performed to check for volumetric defects such as porosity, slag inclusions, and lack of fusion within the weld repair area. An XXQ-2505 X-ray flaw detector was used, with the following parameters: tube voltage 180kV, tube current 5mA, exposure time 2 minutes, and focal length 600mm. AGFA D7 industrial film was used and manually developed. Film observation showed that the weld repair area was dense, free of porosity, slag inclusions, and lack of fusion, and exhibited good fusion with the base material.

[0050] (3) Ultrasonic testing After passing X-ray inspection, ultrasonic testing is performed, focusing on checking for area-type defects such as cracks and lack of fusion in the weld repair area. A CTS-9009 digital ultrasonic flaw detector is used, equipped with a 5MHz, Φ10mm straight probe and a 5MHz, 8×9mm angle probe. The testing method is as follows: Straight probe inspection: Scans the weld surface to detect internal defects in the repair area, with no reduction in back wave or defect wave indication; Angle probe inspection: Scan the base material from both sides of the weld to detect the fusion line and heat-affected zone. No defects exceeding Φ2mm equivalent are detected.

[0051] The comprehensive non-destructive testing results show that the quality of the repair weld meets the Class B requirements of GB / T 22087-2008 "Guideline for Classification of Defect Quality of Arc Welded Joints of Aluminum and Aluminum Alloys".

[0052] S6. Perform airtightness and pressure tests on the inspected workpiece to verify its final load-bearing capacity.

[0053] Specifically, an airtightness test was first conducted to check for penetrating defects in the weld repair area. The product was sealed at both ends, filled with compressed air at 0.5 MPa, and then immersed in a water tank for 5 minutes. The weld repair area was then observed for any air bubbles escaping. The test results showed no air bubbles escaped, indicating good airtightness.

[0054] After passing the airtightness test, a pressure test is conducted to simulate the actual operating conditions of the product. Fill the product with water, purge the air, and connect the pressure pump. Pressurize according to the following steps: ① Slowly increase the pressure to the design pressure of 3.0MPa, hold the pressure for 10 minutes, and check for leaks; ② Continue pressurizing to 1.5 times the design pressure, 4.5 MPa, hold the pressure for 10 minutes, and check for leaks and abnormal deformation; ③ Continue pressurizing to twice the design pressure of 6.0 MPa, hold the pressure for 10 minutes, and check for leaks and ruptures.

[0055] Throughout the pressure testing process, the pressure gauge reading remained stable, there was no leakage in the welded area, and the product showed no abnormal deformation. After depressurization, the welded area underwent penetrant testing and ultrasonic testing again, and the results were consistent with those before the pressure testing, with no new defects.

[0056] The final verification results show that the products treated with the rework process of this invention fully meet the required pressure resistance and the repaired weld joints are reliable.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for repairing defects in electron beam welds, characterized in that, include: S1. Determine the arc termination position for electron beam welding of the workpiece weld; S2. The defective arc-end position is repaired by welding a bevel from both sides of the weld. The bevel shape is as follows: the cross-section parallel to the weld surface is rectangular, and the cross-section perpendicular to the weld surface is trapezoidal. S3. Determine and process the bevel depth according to the defect removal depth requirements; S4. Use MIG welding with helium protection to repair the bevel. S5. After the repair welding is completed, non-destructive testing of the repaired area is carried out using X-ray inspection, ultrasonic inspection and penetrant testing. S6. Perform airtightness and pressure tests on the inspected workpiece to verify its final load-bearing capacity.

2. The method according to claim 1, characterized in that: The method for determining the arc termination position is as follows: based on the structural characteristics of the workpiece, the arc termination position is set in the non-critical load-bearing section of the weld, and this position should be able to be approached from both the front and back sides.

3. The method according to claim 1, characterized in that, The process of repairing the weld bevel at the defective arc-end position from both sides of the weld includes: A trapezoidal bevel is formed on the arc-end position containing defects from one side of the weld face. A lower trapezoidal bevel is formed on the arc-end position containing defects from the back side of the weld; the upper and lower trapezoidal bevels are connected in the weld thickness direction to form a double trapezoidal combination bevel that runs through the weld.

4. The method according to claim 3, characterized in that: The bevel angles on one side of the upper trapezoidal bevel and the lower trapezoidal bevel are 15°-30°; The bottom width of the upper and lower trapezoidal bevels is determined to be 5-10 mm based on the accessibility of the MIG welding torch.

5. The method according to claim 1, characterized in that: The method for determining the defect removal depth is as follows: the depth range of the defect is determined in advance by X-ray detection or ultrasonic detection, and the processing depth is increased by a margin of 1-3 mm compared with the maximum value of the depth range determined by detection.

6. The method according to claim 1, characterized in that: The welding current of the MIG welding is 180-260A, the welding voltage of the MIG welding is 22-28V, the welding speed of the MIG welding is 200-400mm / min, and the flow rate of the helium gas is 15-25L / min.

7. The method according to claim 1, characterized in that, The process of repairing the bevel by welding includes: The processed bevel is repaired using a multi-layer, multi-pass welding process; the interpass temperature is controlled below 60℃, and visual inspection and cleaning are carried out after each layer is welded.

8. The method according to claim 1, characterized in that, The application of X-ray inspection, ultrasonic inspection, and penetrant testing for non-destructive testing of the weld repair area includes: The weld repair area was subjected to non-destructive testing in sequence using penetrant testing, X-ray testing, and ultrasonic testing.

9. The method according to claim 1, characterized in that, The thickness of the weld is 30-50mm, and the base material of the weld is aluminum alloy.

10. The method according to claim 9, characterized in that, The aluminum alloy material is 6061-T6 heat-treated and strengthened aluminum alloy.

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