A method for repairing cracks in the guide ring of the inner sleeve of the engine casing

Abstract

The present invention provides a method for repairing cracks in a guide ring on an engine casing inner sleeve, comprising the following steps: S1, removing the guide ring to be repaired from the casing inner sleeve; S2, welding a replacement guide ring to the casing inner sleeve at the location where the guide ring to be repaired was removed via vacuum brazing. The advantage of this method is that it comprehensively considers repair cost and repair quality. The damaged guide ring, which is inexpensive and easily replaceable, is removed in its entirety and a new guide ring is welded. This method not only reduces repair cost and difficulty, but most importantly, ensures that the quality of the repaired casing inner sleeve meets the requirements of the drawings. The repair cost accounts for only 3% of the total cost of the casing inner sleeve, avoiding the need for complete scrapping of the casing inner sleeve and saving a significant amount of money.

Description

Technical Field

[0001] The invention belongs to the field of engine parts repair, and in particular relates to a method for repairing cracks in a guide ring of an inner sleeve of an engine casing. Background Art

[0002] The combustion chamber of an aircraft engine houses the casing inner liner. As a critical component, it provides the combustion chamber for the engine and reaches high temperatures during normal operation, reaching as high as 1400K. The casing inner liner not only supports the combustion chamber but also provides cooling air. Due to the alternating flow of hot and cold air, the guide ring on the casing inner liner can develop stress cracks of varying degrees over time. Therefore, after a lifespan, the casing inner liner needs to be returned to the factory for repair. Due to the casing inner liner's complex structure and the fact that the cracked guide ring is a thin-walled sheet metal weldment, simply welding the cracked guide ring using conventional argon arc welding would not only cause severe deformation but also create localized stress concentrations in the weld area, potentially leading to further stress cracking during operation. Given the long manufacturing time and high product value of casing inner liner components, replacing them with new ones would increase engine costs. Therefore, a simple and reliable guide ring repair method is urgently needed to meet the needs of casing inner liner repair. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for repairing cracks in an engine casing inner sleeve guide ring, which can simply and reliably replace the cracked casing inner sleeve guide ring and extend the service life of the aircraft engine casing inner sleeve.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for repairing cracks in a guide ring of an inner sleeve of an engine casing comprises the following steps:

[0006] S1, remove the guide ring to be repaired on the inner sleeve of the casing;

[0007] S2, remove the guide ring to be repaired on the inner sleeve of the casing and weld a replacement guide ring by vacuum brazing.

[0008] Preferably, S1 specifically includes:

[0009] (1) Cut off the hanging part of the guide ring to be repaired inside the casing;

[0010] (2) After the overhanging portion is cut, the remaining portion of the guide ring to be repaired welded to the inner sleeve of the casing is removed by lathing;

[0011] (3) Grinding the welded area exposed after the residual portion of the inner casing is removed;

[0012] (4) The inner sleeve of the casing is ultrasonically cleaned, and the welding area after grinding is locally cleaned with acetone.

[0013] Furthermore, in step (1), a grinding wheel is used to cut off the suspended portion of the guide ring to be repaired on the inner sleeve of the casing.

[0014] Furthermore, in step (2), an alloy cutting knife is used to turn off the remaining portion of the guide ring to be repaired that is welded to the inner sleeve of the casing.

[0015] Furthermore, in step (3), a belt grinding machine is used to grind the welding area exposed after the residual part of the inner sleeve of the casing is removed.

[0016] Preferably, S2 specifically includes:

[0017] 1) Position and weld a replacement guide ring on the inner sleeve of the casing at the same position as the guide ring to be repaired;

[0018] 2) Apply brazing filler metal to the weld between the inner casing and the replacement guide ring, apply red flow blocker to the outer area of the weld, and apply white flow blocker to the crack stop of the replacement guide ring;

[0019] 3) Vacuum brazing replaces the guide ring;

[0020] 4) The inner sleeve of the casing with the replacement guide ring welded thereon is subjected to vacuum heat treatment.

[0021] Furthermore, in step 1), during positioning welding, the fitting gap between the replacement guide ring and the wall surface of the inner sleeve of the casing is not greater than 0.1 mm.

[0022] Furthermore, in step 3), vacuum brazing is performed using the following parameters:

[0023] Cold vacuum degree: <4×10 -2 Pa;

[0024] Working vacuum degree: <4×10 -2 Pa;

[0025] Heating rate: (320-380)℃ / h→(350±10)℃, keep warm for (10-15)min; (690-730)℃ / h→(950±10)℃, keep warm for (15-25)min; (390-510)℃ / h→(1030±10)℃;

[0026] Brazing: (1030±10)℃, keep warm for (10~15)min.

[0027] Furthermore, in step 4), vacuum heat treatment is performed using the following parameters:

[0028] Heating: The inner casing of the casing is heated to 843±10℃;

[0029] Heat preservation: 843±10℃, 1h+6min;

[0030] Cooling: Cool the inner casing to 718±10℃ at a cooling rate of (3~6)℃ / min;

[0031] Insulation: 718±10℃, 8h+15min;

[0032] Cooling: vacuum cool the inner sleeve of the casing to 621±10℃ at a cooling rate of (1~2)℃ / min;

[0033] Insulation: 621±10℃, 8h+15min.

[0034] Preferably, after S2, a flow test is performed on the inner sleeve of the casing, and the flow is adjusted when the flow test shows that the flow is unqualified.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The advantage of this method is that it comprehensively considers the repair cost and repair quality. The damaged guide ring, which is cheap and easy to replace, is cut off as a whole and a new guide ring is re-welded. Not only is the repair cost very low and the repair difficulty not high, but most importantly, it can ensure that the quality of the repaired casing inner sleeve meets the requirements of the drawings. The repair cost only accounts for 3% of the overall cost of the casing inner sleeve, avoiding the overall scrapping of the casing inner sleeve and saving a lot of money.

[0037] Furthermore, since the gap between the guide ring of the overhauled casing inner sleeve and the new casing inner sleeve becomes larger after assembly, the brazing process easily causes the brazing filler metal of the brazing seam to remelt. Therefore, compared with the processing of the new casing inner sleeve, the present invention changes the brazing parameters, which can ensure the brazing quality of the overhauled casing inner sleeve and avoid the remelting of the brazing filler metal of the parts brazing seam. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of cutting guide ring;

[0039] Figure 2 Schematic diagram of the location of the welding area of the car;

[0040] Figure 3 Schematic diagram of guide ring welding;

[0041] Figure 4 Schematic diagram of the flow inhibitor injection position. DETAILED DESCRIPTION

[0042] In order to further understand the present invention, the present invention is described below in conjunction with embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0043] The method for repairing cracks in the guide ring of the inner sleeve of the engine casing of the present invention comprises the following steps:

[0044] (1) Grinding the guide ring to be repaired: Use a D100 diamond grinding wheel to cut the suspended part of the guide ring to be repaired from the outer wall of the inner sleeve of the receiver ( Figure 1 ).

[0045] (2) Turn the remaining guide ring to be repaired: Use the mounting edge of the large end of the inner casing to locate the guide ring to be repaired, and align the outer wall of the inner casing near the welding area of the guide ring to be repaired within 0.05. Use a 6mm wide alloy cutting tool to turn the remaining part of the guide ring to be repaired except for the welded part on the outer wall of the inner casing. Figure 2 ).

[0046] (3) Grinding the welding area: Use a belt grinding machine to grind the welding area of the guide ring to be repaired. Figure 2 ).

[0047] (4) Cleaning: Place the inner sleeve of the receiver in an ultrasonic cleaning tank for overall cleaning. After cleaning, use absorbent cotton dipped in acetone to thoroughly clean the welding area.

[0048] (5) Assembly and argon arc welding positioning:

[0049] Marking: Use a height gauge to mark out the axial welding position dimension A of the replacement guide ring, and use argon arc welding to position the replacement guide ring on the outer wall of the inner sleeve of the casing.

[0050] Positioning welding: 54 positioning welding points are required in the circumference. It is allowed to increase the positioning welding points locally. The total number of increased positioning welding points shall not exceed 5 points. The areas within 1-3MM from the weld edge on both sides of the crack stop hole are not allowed to be welded. Figure 3 After assembly, ensure that the gap between the replacement guide ring and the inner casing wall is no greater than 0.1mm. The replacement guide ring refers to a new guide ring.

[0051] (6) Coating of solder and flow inhibitor:

[0052] Prepare solder: prepare HBNi82CrSiB paste solder with appropriate consistency.

[0053] Apply solder: Apply a circle of HBNi82CrSiB paste solder to each replacement guide ring weld position.

[0054] Clean up excess solder: scrape off excess solder after it dries. There should be no solder in non-welding areas.

[0055] Applying flow blocker: Apply a circle of red flow blocker (brand: NICROBRAZ, standard: CSS156) in the area 1mm away from the brazing seam. The coating width should be more than 15mm. Apply white flow blocker ( Figure 4 ).

[0056] (7) Vacuum brazing guide ring: Place the inner sleeve of the casing with the large end facing upward on the graphite platform, put it into the material basket and then put it into the furnace. All test pieces (two pieces for each inner sleeve of the casing) are put into the furnace at the same time. Use the following parameters for vacuum brazing:

[0057] Cold vacuum degree: <4×10 -2 Pa;

[0058] Working vacuum degree: <4×10 -2 Pa;

[0059] Heating rate: (320-380)℃ / h→(350±10)℃, keep warm for (10-15)min; (690-730)℃ / h→(950±10)℃, keep warm for (15-25)min; (390-510)℃ / h→(1030±10)℃;

[0060] Brazing: (1030±10)℃, keep warm for (10~15)min;

[0061] Cooling: Vacuum cooling to below 900℃, backfill with argon, and gas fan cooling to below 100℃.

[0062] Taking out of the furnace: balance the furnace pressure, open the furnace door, and take out the inner sleeve of the casing.

[0063] Cleaning: After the inner cover of the casing cools to room temperature, clean the flow-blocking agent on the surface of the inner cover of the casing.

[0064] (8) Vacuum aging: Place the inner sleeve of the casing with the guide ring re-welded into a vacuum heat treatment furnace and perform vacuum heat treatment according to the following parameters:

[0065] Heating: Raise the furnace temperature to 800℃ at 10℃ / min, keep it warm until the temperature of the inner shell reaches 800℃, and at 800℃, the partial pressure is reduced to 6.65~10.64Pa (5~8×10 -2 Raise the furnace temperature to 843°C at 6°C / min and maintain the temperature until the temperature of the casing reaches 843±10°C;

[0066] Heat preservation: 843±10℃, 1h+6min;

[0067] Cooling: Cool the inner casing to 718±10℃ at a cooling rate of (3~6)℃ / min;

[0068] Insulation: 718±10℃, 8h+15min;

[0069] Cooling: vacuum cool the inner sleeve of the casing to 621±10℃ at a cooling rate of (1~2)℃ / min;

[0070] Heat preservation: 621±10, 8h+15min;

[0071] Cooling: Fill with (0.8~1.0) bar argon gas, turn on the fan, and cool the inner sleeve of the casing to below 80℃;

[0072] Taking out of the furnace: backfill with argon, open the furnace door, and wear clean gloves to take out the inner sleeve of the receiver.

[0073] (9) Flow test: Considering that replacement of the guide ring will affect the flow rate of the inner sleeve of the casing, it is necessary to re-perform the flow test according to relevant requirements.

[0074] (10) Flow regulation: When the flow rate is not up to standard, the flow rate needs to be adjusted according to the special technical documents.

[0075] (11) Cleaning: Clean the outer surface of the inner sleeve and the impurities in the inner cavity of the receiver.

[0076] The vacuum brazing parameters of the guide ring of the overhauled casing inner sleeve of the present invention are different from those of the new casing inner sleeve. The reasons are analyzed as follows.

[0077] 1. After the overhauled casing inner sleeve guide ring is assembled, the gap becomes larger than that of the new casing inner sleeve. In order to reduce the flow of brazing material in the guide ring brazing seam, the brazing material is allowed to fill the complete guide ring brazing gap as much as possible during brazing. The brazing temperature and holding time of the parts are reduced when brazing the guide ring in the overhauled casing inner sleeve.

[0078] 2. When overhauling the vacuum brazing guide ring of the inner sleeve of the casing, it is necessary not only to ensure the quality of the brazing seam of the part, but also to avoid the remelting of the brazing filler metal of other brazing seams of the part. This is because when the brazing gap of the brazing seam is too large during the furnace entry process, the expansion path of the demelting elements in the brazing filler metal is increased, resulting in insufficient diffusion of the demelting elements during the brazing process, thereby forming a eutectic brazing seam structure in places where the brazing seam gap is larger. The remelting temperature of the brazing seam that produces the eutectic phase brazing seam structure is basically the same as the melting point of the brazing filler metal. Improper parameter setting will cause the remelting of the part brazing filler metal.

[0079] In summary, in order to ensure the brazing quality of the overhauled casing inner sleeve and avoid the remelting of the brazing filler metal of the parts brazing seam as much as possible, and at the same time match the vacuum brazing parameters of the new casing inner sleeve processing, the heating rate is adjusted from (620~680)℃ / h→(950±10)℃ and keeping warm for (30~40)min during the processing of the new casing inner sleeve to (690~730)℃ / h→(950±10)℃ and keeping warm for (15~25)min. At the same time, the brazing temperature is adjusted from (1045±10)℃ and keeping warm for (20~25)min during the processing of the new casing inner sleeve to (1030±10)℃ and keeping warm for (10~15)min.

[0080] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for repairing cracks in the guide ring of an engine casing, characterized in that: The steps include: S1, remove the guide ring to be repaired on the inner sleeve of the casing; S2, where the guide ring to be repaired is removed on the inner sleeve of the casing, a replacement guide ring is welded by vacuum brazing; S2 specifically includes: 1) Place a replacement guide ring on the inner sleeve of the casing at the same position as the removed guide ring to be repaired, and weld it; 2) Apply brazing filler metal to the weld between the inner casing and the replacement guide ring, apply red flow blocker to the outer area of the weld, and apply white flow blocker to the crack stop of the replacement guide ring; 3) Vacuum brazing to replace the guide ring; 4) Vacuum heat treatment of the inner casing of the casing with the replacement guide ring welded to it; In step 3), vacuum brazing is performed using the following parameters: Cold vacuum degree: <4×10 -2 Pa; Working vacuum degree: <4×10 -2 Pa; Heating rate: (320-380)℃ / h→(350±10)℃, keep warm for (10-15)min; (690-730)℃ / h→(950±10)℃, keep warm for (15-25)min; (390-510)℃ / h→(1030±10)℃; Brazing: (1030±10)℃, keep warm for (10~15)min.

2. The method for repairing cracks in the guide ring of the inner sleeve of the engine casing according to claim 1, characterized in that: S1 specifically includes: (1) Cut off the hanging part of the guide ring to be repaired inside the casing; (2) After the overhanging part is cut, the remaining part of the guide ring to be repaired that is welded to the inner sleeve of the casing is removed by lathing; (3) Grinding the welding area exposed after the residual part of the inner cover of the casing is removed; (4) Ultrasonic cleaning is performed on the inner sleeve of the casing, and acetone is used to locally clean the welding area after grinding.

3. The method for repairing cracks in the guide ring of the engine casing according to claim 2, characterized in that: In step (1), a grinding wheel is used to cut off the suspended portion of the guide ring to be repaired on the inner sleeve of the casing.

4. The method for repairing cracks in the guide ring of the inner sleeve of the engine casing according to claim 2, characterized in that: In step (2), an alloy cutting knife is used to turn off the remaining portion of the guide ring to be repaired that is welded to the inner sleeve of the casing.

5. The method for repairing cracks in the guide ring of the inner sleeve of the engine casing according to claim 2, characterized in that: In step (3), a belt grinding machine is used to grind the welding area exposed after the residual part of the inner sleeve of the casing is removed.

6. The method for repairing cracks in the guide ring of the engine casing according to claim 1, characterized in that: In step 1), during positioning welding, the fitting gap between the replacement guide ring and the wall surface of the inner sleeve of the casing should not exceed 0.1 mm.

7. The method for repairing cracks in the guide ring of the inner sleeve of the engine casing according to claim 1, characterized in that: In step 4), vacuum heat treatment is performed using the following parameters: Heating: The inner casing of the casing is heated to 843±10℃; Heat preservation: 843±10℃, 1h+6min; Cooling: Cool the inner casing to 718±10℃ at a cooling rate of (3~6)℃ / min; Insulation: 718±10℃, 8h+15min; Cooling: vacuum cool the inner sleeve of the casing to 621±10℃ at a cooling rate of (1~2)℃ / min; Insulation: 621±10℃, 8h+15min.

8. The method for repairing cracks in the guide ring of the inner sleeve of the engine casing according to claim 1, characterized in that: After S2, the flow rate test is performed on the inner sleeve of the casing. If the flow rate test shows that the flow rate is unqualified, the flow rate is adjusted.

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