A method for controlling deformation during argon arc welding repair of thin-walled casing assemblies

Abstract

This invention provides a method for controlling deformation during argon arc welding repair of thin-walled casing assemblies. The steps are as follows: microstructure and performance evaluation to verify whether the repair process and heat treatment process meet material quality requirements; pre-weld optical three-dimensional scanning; fluorescence detection of the weld seam and surrounding area of ​​the casing assembly; cleaning the linear display area of ​​the casing assembly until no display is visible; clamping a special anti-deformation welding fixture; turning on cooling water and shielding gas; argon arc welding repair; after repair welding, non-destructive testing of the weld seam; local stress-relieving annealing; disassembling the anti-deformation fixture and performing post-weld optical three-dimensional scanning; double-aging heat treatment of the parts; grinding the repaired weld seam to a smooth transition. This invention reduces welding deformation in the repair area, improves the dimensional accuracy of the casing assembly, effectively prevents performance degradation caused by oxidation during the welding process, ensures that the welding quality of the repair area meets forging standards, and extends the service life of the casing assembly.

Description

Technical Field

[0001] This invention relates to the technical field of aircraft engine maintenance, and more specifically, to a method for controlling deformation during argon arc welding repair of a certain type of aircraft engine casing assembly. Background Technology

[0002] The casing assembly is a multi-welded ring component made of high-temperature alloy GH4169 with a wall thickness of 2-4 mm. It consists of an outer ring, an inner ring, and eight load-bearing support rings, with the inner and outer rings welded together via these support rings. However, due to the large number of welds in the casing assembly structure and its operation in environments with high temperature, high pressure, rotational vibration, or strong corrosion, long cracks easily develop at the welds between the load-bearing support rings and the inner and outer rings, leading to its failure. To extend its service life, conventional repair methods include argon arc welding. However, the long number of cracks during repair makes it prone to oxidation and generates significant welding stress, resulting in large weld deformation after repair and failing to meet assembly accuracy and performance requirements. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a tooling system for preventing deformation during argon arc welding of a certain type of aero-engine casing assembly and a method for ensuring the quality of parts repair. The specific technical solution is as follows:

[0004] A method for controlling deformation during argon arc welding repair of thin-walled casing assemblies includes the following steps:

[0005] S1: Use welding test pieces with the same material and performance to evaluate the argon arc welding process of GH4169 welding wire, and verify whether the repair process and heat treatment process meet the material quality requirements.

[0006] S2: Use an optical 3D scanner to record the pre-welding dimensions of the casing assembly;

[0007] S3: Perform fluorescence detection on the weld area between the inner and outer rings of the casing assembly and the load-bearing support ring;

[0008] S4: After grinding and cleaning the linear display area of ​​the casing assembly, perform fluorescence detection on the ground area again. If any defects are found that have not been cleaned, multiple grinding, cleaning and fluorescence detections are required until there is no display.

[0009] S5: Special tooling for clamping and welding to prevent deformation;

[0010] S6: Turn on the cooling water and protective gas;

[0011] S7: Use the same process parameters as the process qualification to perform argon arc welding on the area to be repaired;

[0012] S8: After the repair welding is completed, visual inspection, fluorescence inspection and radiographic inspection are carried out on the repaired area to ensure that the welding quality meets the standard requirements;

[0013] S9: Perform local stress-relieving annealing on the weld repair area. The heat treatment specification is 500℃±10℃ / holding for 2 hours, followed by air cooling.

[0014] S10: Disassembly anti-deformation special tooling;

[0015] S11: Perform optical 3D scanning on the re-welded casing assembly to compare the dimensional deviations of the weld and surrounding area before and after the re-welding.

[0016] S12: Dual aging heat treatment of casing assembly;

[0017] S13: The fitter grinds the welded area to ensure a smooth transition between the weld and the base material.

[0018] Preferably, in step S3, the location and extent of the weld crack in the casing assembly are determined by fluorescence detection and marked to obtain the area to be repaired by welding.

[0019] Preferably, the anti-deformation fixture for argon arc welding of the casing assembly in step S5 consists of the following components: threaded hole in the upper cover plate, upper cover plate, threaded hole in the upper cover plate, upper support ring, inner and outer ring support devices, threaded hole in the base, base, inner support ring, and back gas protection device. All components are connected and secured with hexagonal head screws. The casing assembly is connected to the base and upper cover plate using its existing threaded holes. The base is machined with slots according to the dimensions of the casing assembly for easy assembly and positioning. There are eight inner and outer ring support devices in total, consisting of an outer support block, an L-shaped positioning block, an upper pressure plate, a T-shaped auxiliary pressure block, and a T-shaped inner support block. The L-shaped positioning block is connected to the base with screws. Threaded holes are machined on the sides of the L-shaped positioning block and the inner support ring. Screws ensure a tight fit between the casing assembly and the outer support block and the T-shaped inner support block. The T-shaped inner support block and the outer support block near the load-bearing ring to be welded are made of copper and equipped with water-cooling channels, providing both anti-deformation and cooling of the weld repair area. Tightening the upper pressure plate screws can compress the T-shaped auxiliary pressure block, reducing deformation of the upper and lower surfaces of the casing assembly. The back gas protection device consists of a baffle, a fastening rod, and a back gas protection copper block. The baffle and the back gas protection copper block are connected by the fastening rod and nuts. The back gas protection copper block is designed to conform to the shape of the load-bearing support ring of the casing assembly. Several small holes of a certain size and at a certain distance are drilled on the back of the area to be repaired using electric spark drilling. This allows argon gas to be introduced to protect the repaired area and reduce oxidation, while also serving as a support to reduce deformation in and around the repaired area.

[0020] Preferably, the argon arc welding repair process parameters in step S7 are: tungsten electrode diameter 1.6 mm, nozzle diameter 8 mm, current 20A~30A, argon flow rate for welding torch protection 12L / min~18L / min, and argon flow rate for back protection 3L / min~5L / min. During repair welding, one layer is deposited on the outer wall of the inner ring or outer ring, and another layer is deposited on the inner wall, and the repair welding is completed by repeating the process.

[0021] Preferably, in step S7, while performing argon arc welding for repair, sufficient argon gas protection is required in the repair area to ensure the quality of the repair welding and reduce heat input. Therefore, the anti-deformation tooling is equipped with back gas protection (front welding gun argon gas protection) and a water cooling device.

[0022] Preferably, in step S8, if the weld after repair is silvery-white and has a margin of 0.4–0.8 mm relative to the surrounding non-repaired area, the weld appearance inspection is qualified. Then, fluorescence detection and radiographic testing are performed respectively. If the repaired weld has cracks or porosity defects, the grinding and cleaning steps S7 and S8 are repeated, and the repaired weld is re-welded until there are no porosity or crack defects.

[0023] Preferably, in step S9, stress-relief annealing is performed by using a local heat treatment device to heat the weld repair area under the clamping of the tooling, so as to reduce stress and thus reduce the deformation of the part after the tooling is disassembled.

[0024] Preferably, the conditions for the double aging heat treatment in step S12 are: holding at 720℃±10℃ for 8 hours in a vacuum furnace, then furnace cooling to 620℃±10℃ for 8 hours at a cooling rate of 50℃ / h, and then rapid cooling with argon gas to ≤100℃ before exiting the furnace.

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

[0026] 1. The thin-walled casing argon arc welding repair method provided by the present invention can effectively control the deformation of the repair welding area, and the joint strength meets the forging standard, so that the repaired casing assembly meets the requirements of engine assembly, use and service life.

[0027] 2. The anti-deformation tooling for argon arc welding of casing components proposed in this invention can be reused for similar parts, has a wide range of applications, can ensure the quality of one-time repair welding, reduces the cost of batch repair, and is easy to promote and apply. Attached Figure Description

[0028] Figure 1 This is a structural diagram of the anti-deformation tooling for the argon arc welding of the casing assembly.

[0029] Figure 2 This is a structural diagram of the inner and outer ring support device.

[0030] Figure 3 This is a structural diagram of the T-shaped inner support water-cooled copper block in the repair welding area.

[0031] Figure 4 This is a structural diagram of the water-cooled copper block supporting the weld repair area.

[0032] Figure 5 This is a partial sectional view of the front of an anti-deformation tooling with a back gas protection device.

[0033] Figure 6This is a partial sectional view of the side of an anti-deformation tooling with a back gas protection device.

[0034] Figure 7 This is a structural diagram of the copper block for back gas protection. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. The specific process steps are as follows:

[0036] S1: Select GH4169 as the base material with the same material and performance as the casing assembly, and use GH4169 welding wire to verify the feasibility of the process (welding and heat treatment). The comprehensive performance of the weld overlay in different heat treatment states is evaluated through metallographic observation, microhardness testing, and tensile property testing. Tensile specimens are prepared using a butt joint bevel, and metallographic and microhardness measurements are also taken from the weld overlay area of ​​the butt joint bevel to obtain the bonding strength between the weld overlay and the base material.

[0037] The optimal parameters for argon arc welding were: 1.6 mm tungsten electrode diameter, 8 mm nozzle diameter, 20 A–30 A current, 12 L / min–18 L / min shielding argon gas flow rate, and 3 L / min–5 L / min back shielding argon gas flow rate. The resulting butt joint weld overlay exhibited good surface formation and a metallic luster. The hardness of the 400℃ and 500℃ annealed specimens was lower than that of the weld overlay state, while the hardness of the double-aged specimens was comparable to that of the base material. After tensile testing, the tensile strength and yield strength were essentially the same as those of the original base material, meeting the forging standards.

[0038] S2: Use an optical 3D scanner to record the pre-welding dimensions of the casing assembly;

[0039] S3: Perform fluorescence testing on each housing assembly according to HB / Z 61 "Penetration Testing" and mark the linear display area;

[0040] S4: Grind and clean the linear display area of ​​the casing assembly under fluorescent light. After complete cleaning, perform fluorescent detection on the ground area again. If any defects are found that have not been cleaned, multiple grinding, cleaning and fluorescent detections are required until there is no display.

[0041] S5: Place the casing assembly into the welding anti-deformation fixture ( Figure 1 On the base, all threaded holes must be concentric with the threaded holes on the base. Then, use screws to secure the lower surface of the casing to the base. After tightening, place the inner and outer ring support devices and tighten the screws to ensure a tight assembly between the casing assembly and the inner and outer ring support devices. Next, clamp the back gas protection device to the area to be welded and connect the water cooling and argon gas lines. Finally, place the top cover plate on top of the casing assembly and tighten all screws.

[0042] S6: Check the cooling water pipeline and argon gas pipeline. If there is no leak, turn on the cooling water and protective gas.

[0043] S7: Use the following argon arc welding parameters: tungsten electrode diameter 1.6mm, nozzle diameter 8mm, current 20A~30A, argon flow rate for welding torch protection 12L / min~18L / min, argon flow rate for back protection 3L / min~5L / min, to perform argon arc welding repair on the area to be repaired of the casing assembly.

[0044] S8: After the repair welding is completed, the repaired area shall be subjected to visual inspection, fluorescence inspection, and radiographic inspection in sequence. Visual inspection shall be performed by visual inspection, requiring that the repaired area be free of defects and have a margin of 0.4–0.8 mm relative to the surrounding non-repaired area. Fluorescence inspection shall be performed on the external quality of the repaired area of ​​the casing assembly according to HB / Z61 "Penetration Testing". The requirements are: the repaired area shall not have inclusions, cracks, porosity, or lack of fusion, and the heat-affected zone shall not have cracks. X-ray inspection shall be performed on the internal quality of the repaired area of ​​the casing assembly according to HB / Z 20160 "X-ray Radiographic Inspection". The requirements are: there shall be no cracks inside the repaired area and its heat-affected zone; the repaired area shall not have lack of fusion, flaky or sharp-angled inclusions, or sharp-angled or round pores with a diameter greater than 0.2 mm, and the repaired area shall not have sharp-angled or round pores with a diameter greater than 0.2 mm. If the repaired area fails the inspection, the grinding and cleaning steps, and steps S7 and S8 shall be repeated for re-welding until the standard requirements are met. The total number of repairs shall not exceed 3.

[0045] S9: After the argon arc welding repair is completed, the local casing assembly after the repair welding is stress-relief annealed using a ceramic heating tape. The thermocouple end needs to be placed between the part and the heating tape, and the heating tape and local parts are wrapped with asbestos for heat preservation. The heat treatment specification is 500℃±10℃ / heat preservation for 2 hours, followed by air cooling.

[0046] S10: Special tooling for disassembling and preventing deformation;

[0047] S11: Perform optical 3D scanning on the casing assembly after welding and compare it with the model before welding. Ensure that the results of each dispersed test point in the welding area are higher than 0.4mm to facilitate grinding and repair. The actual dimensions of other non-welding positions are measured. The results show that the deformation near the welding area is ≤0.2mm and the deformation far from the welding area is ≤0.06mm.

[0048] S12: The casing assembly is placed in a horizontal vacuum furnace for heat treatment. The heat treatment regime is: 720℃±10℃ / holding for 8 hours, then furnace cooled to 620℃±10℃ / holding for 8 hours at a cooling rate of 50℃ / h, and then rapidly cooled to ≤100℃ by argon before being taken out of the furnace.

[0049] S13: The repaired welding area was ground by fitter to ensure a smooth transition between the weld and the base material. After repair, it meets assembly requirements and has been installed and put into use.

[0050] The anti-deformation fixture for argon arc welding of the casing assembly consists of the following components: threaded hole 1 on the upper cover, upper cover 2, threaded hole 3 on the upper cover, upper support ring 4, inner and outer ring support devices 5, threaded hole 7 on the base, base 8, inner support ring 9, and back gas protection device 10. All components are connected and secured with hexagonal head screws. The casing assembly 6 is connected to the base 8 and upper cover 2 using the existing threaded holes. The base 8 has a slot machined according to the dimensions of the casing assembly 6 for easy assembly and positioning. There are a total of 8 inner and outer ring support devices 5, consisting of an outer support block 11, an L-shaped positioning block 12, an upper pressure plate 13, a T-shaped auxiliary pressure block 14, and a T-shaped inner support block 15. The L-shaped positioning block is connected to the base 8 with screws. The sides of the L-shaped positioning block 12 and the inner support ring 9 are machined with threaded holes. The screws ensure a tight fit between the casing assembly and the outer support block 11 and the T-shaped inner support block. The T-shaped inner support block and the outer support block near the load-bearing ring to be welded are made of copper and equipped with water cooling channels, serving the dual purpose of preventing deformation and cooling the welding area. Tightening the screws on the upper pressure plate 13 can press the T-shaped auxiliary pressure block, reducing deformation of the upper and lower surfaces of the casing assembly. The back gas protection device 10 consists of a baffle 16, a fastening rod 17, and a back gas protection copper block 18. The baffle and the back gas protection copper block are connected by the fastening rod and the nut. The back gas protection copper block is designed according to the shape of the load-bearing support ring of the casing assembly. Several small holes are drilled at a certain distance and size on the back of the area to be repaired by electric spark. This can both allow argon gas to be introduced to protect and reduce oxidation in the repaired area, and also serve as a support to reduce deformation in the repaired area and its surroundings.

[0051] Compared with existing technologies, the casing assembly repaired using the technical solution of this invention exhibits no defects such as porosity or cracks in the welded area. The microhardness of the joint is comparable to that of the forging base material, and the tensile properties meet the requirements for forgings. Overall, it demonstrates superior mechanical properties, better deformation control, and dimensional compliance with assembly requirements. Furthermore, the specialized anti-deformation tooling is applicable to similar parts, and the argon arc welding process is simple, reducing the repair cost for batch casings. It is now in use.

[0052] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Any equivalent substitutions or improvements made using the content of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling deformation during argon arc welding repair of thin-walled casing assemblies, characterized in that, Includes the following steps: S1: Use welding test pieces with the same material and performance to evaluate the argon arc welding process of GH4169 welding wire, and verify whether the repair process and heat treatment process meet the material quality requirements. S2: Use an optical 3D scanner to record the pre-welding dimensions of the casing assembly; S3: Perform fluorescence detection on the weld area between the inner and outer rings of the casing assembly and the load-bearing support ring; S4: After grinding and cleaning the linear display area of ​​the casing assembly, perform fluorescence detection on the ground area again. If any defects are found that have not been cleaned, multiple grinding, cleaning and fluorescence detections are required until there is no display. S5: A fixture for clamping the casing assembly after argon arc welding to prevent deformation. Its components are as follows: threaded hole 1 on the upper cover, threaded hole 2 on the upper cover, upper cover, upper support ring, inner and outer ring support devices, threaded hole on the base, base, inner support ring, and back gas protection device. All components are connected and secured with hexagonal head screws. The casing assembly is connected to the base and upper cover using its existing threaded holes. The base has slots machined according to the dimensions of the casing assembly for easy assembly and positioning. There are a total of 8 inner and outer ring support devices, consisting of an outer support block, an L-shaped positioning block, and... The casing assembly consists of an upper pressure plate, a T-shaped auxiliary pressure block, and a T-shaped inner support block. An L-shaped positioning block is connected to the base with screws. The L-shaped positioning block and the inner support ring have threaded holes machined on their sides. The screws ensure a tight fit between the casing assembly and the outer support block and the T-shaped inner support block. The T-shaped inner support block and the outer support block near the load-bearing ring to be welded are made of copper and equipped with water cooling channels, serving the dual purpose of preventing deformation and cooling the welding area. Tightening the screws on the upper pressure plate can press the T-shaped auxiliary pressure block, reducing deformation of the upper and lower surfaces of the casing assembly. The back gas protection device consists of a baffle, a fastening rod, and a back gas protection copper block. The baffle and the back gas protection copper block are connected by the fastening rod and nuts. The back gas protection copper block is designed according to the shape of the load-bearing support ring of the casing assembly. Several small holes are drilled at a certain distance and size on the back of the area to be repaired by electric spark. This can both allow argon gas to be introduced to reduce oxidation in the repaired area and serve as a support to reduce deformation in the repaired area and the surrounding area. S6: Turn on the cooling water and protective gas; S7: Use the same process parameters as the process qualification to perform argon arc welding on the area to be repaired; S8: After the repair welding is completed, visual inspection, fluorescence inspection and radiographic inspection are carried out on the repaired area to ensure that the welding quality meets the standard requirements; S9: Perform local stress-relieving annealing on the weld repair area. The heat treatment specification is 500℃±10℃ / holding for 2 hours, followed by air cooling. S10: Disassembly anti-deformation special tooling; S11: Perform optical 3D scanning on the re-welded casing assembly to compare the dimensional deviations of the weld and surrounding area before and after the re-welding. S12: Dual aging heat treatment of casing assembly; S13: The fitter grinds the welded area to ensure a smooth transition between the weld and the base material.

2. The method for controlling deformation repair of thin-walled casing assemblies by argon arc welding according to claim 1, characterized in that: In step S3, the location and extent of the weld crack in the casing assembly are determined by fluorescence detection and marked to obtain the area to be repaired by welding.

3. The method for controlling deformation during argon arc welding repair of a thin-walled casing assembly according to claim 1, characterized in that: The argon arc welding repair process parameters in step S7 are as follows: tungsten electrode diameter 1.6mm, nozzle diameter 8mm, current 20A~30A, argon flow rate for welding torch protection 12 L / min~18L / min, and argon flow rate for back protection 3 L / min~5 L / min. During repair welding, one layer is deposited on the outer wall of the inner ring or outer ring, and another layer is deposited on the inner wall, and the repair welding is completed by repeating the cycle. While repairing with argon arc welding, in order to ensure the quality of repair welding and reduce heat input, the repair welding area needs sufficient argon protection. Therefore, the anti-deformation tooling is equipped with back gas protection (front welding torch argon protection) and a water cooling device.

4. The method for controlling deformation during argon arc welding repair of a thin-walled casing assembly according to claim 1, characterized in that: If the weld after repair is silvery-white and has a margin of 0.4 to 0.8 mm relative to the surrounding non-repair area in step S8, the weld appearance inspection is qualified. Then, fluorescence detection and radiographic detection are performed respectively. If the repaired weld has cracks or porosity defects, the grinding and cleaning steps S7 and S8 are repeated to repair the weld again until there are no porosity or crack defects.

5. The method for controlling deformation during argon arc welding repair of a thin-walled casing assembly according to claim 1, characterized in that: In step S9, stress-relief annealing involves using a local heat treatment device to heat the weld repair area while the tooling is clamped, in order to reduce stress and thus reduce the deformation of the parts after the tooling is disassembled.

6. The method for controlling deformation during argon arc welding repair of a thin-walled casing assembly according to claim 1, characterized in that: The conditions for the double aging heat treatment in step S12 are as follows: hold at 720℃±10℃ in a vacuum furnace for 8 hours, then cool to 620℃±10℃ at a cooling rate of 50℃ / h and hold for 8 hours, and then rapidly cool to ≤100℃ with argon before exiting the furnace.

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