linear friction welding method for blades and bladed disks

Abstract

This invention discloses a linear friction welding method for blades and impeller disks, applicable to connecting the first ends of multiple blades uniformly arranged on the outer periphery of an impeller disk to the impeller disk in a single operation. The method includes the following steps: inserting the impeller disk into the receiving cavity of a first fixture; uniquely clamping each blade into a second fixture, ensuring the first end of the blade protrudes from one end of the corresponding second fixture; radially engaging all the second fixtures into radially arranged limiting channels uniformly arranged around the receiving cavity on the first fixture; applying a first force radially towards the impeller disk to all the second fixtures to maintain constant contact between the first ends of all blades and the impeller disk; applying an axial reciprocating vibration to the impeller disk, and after the vibration ends, applying a larger second force to all the second fixtures and maintaining this force for a period of time. This single clamping operation achieves welding of the impeller disk and all blades in one operation, preventing blade deformation.

Description

Technical Field

[0001] This invention relates to the manufacture of aircraft blades, and particularly to a method for linear friction welding of blades and bladed disks. Background Technology

[0002] Integral impellers for aero engines represent the latest structural and aerodynamic layout in the design of new aero engines, embodying the development direction of fourth- and fifth-generation high thrust-to-weight ratio aero engines. They offer advantages such as weight reduction, structural simplification, and increased efficiency. Compared to integral impellers machined from solid blanks using five-axis CNC milling or electrochemical machining tools, welded impellers feature individually machined blades that are then welded to the impeller disk to achieve overall impeller integrity. This not only significantly reduces material and machining costs but also effectively shortens the machining cycle.

[0003] Linear friction welding technology, applied to the welding of blades and bladed disks, effectively ensures that the performance of the weld area is no less than that of the main body area. Current technologies use fixtures that can only hold one blade at a time for processing. After welding one blade, the bladed disk must cool down before the next blade can be welded; otherwise, inconsistent welding temperatures of subsequent blades can occur, causing errors and affecting the overall blade performance. Therefore, the existing linear friction welding method has low processing efficiency.

[0004] Furthermore, in the process of linear friction welding, in order to ensure effective welding of the blades, the blades need to withstand a large clamping force, which is generally on the order of millions of Newtons. The blades themselves are thin plate structures with complex curved surfaces. Using conventional tooling fixtures during the welding process is very likely to cause irreversible deformation of the blades, which will seriously affect the overall performance of the blades. Summary of the Invention

[0005] To address at least one problem of the prior art, the present invention provides a linear friction welding method for blades and bladed disks.

[0006] A linear friction welding method for blades and bladed disks, suitable for connecting the first ends of multiple blades evenly arranged on the outer periphery of a bladed disk to the bladed disk in one step, includes the following steps:

[0007] The leaf disc is inserted into the receiving cavity of the first fixture;

[0008] Each blade is uniquely clamped into a second fixture, with the first end of the blade protruding from the corresponding end of the second fixture.

[0009] All the second fixtures are respectively inserted radially into the limiting channels that are set on the first fixture, evenly arranged around the accommodating cavity, and formed radially;

[0010] A first force is applied radially toward the bladed disk to each of the second fixtures to keep the first ends of all blades in constant contact with the bladed disk.

[0011] An axial reciprocating vibration is applied to the impeller, and after the vibration ends, a larger second force is applied to all the second fixtures and held for a period of time.

[0012] In some embodiments, the first fixture includes an inner ring and an outer ring;

[0013] The outer ring is concentrically set around the inner ring and connected to the inner ring;

[0014] The inner ring is provided with a first slot, and the outer ring is provided with a second slot that is radially opposite to the first slot. The first slot and the second slot define the limiting channel.

[0015] The second fixture and the first slot are interference-fitted in the width direction.

[0016] In some implementations, the first force is greater than the maximum static friction between the outer surface of the second fixture and the limiting channel.

[0017] In some embodiments, the end of the second fixture closest to the first end has a protrusion, which is located on the upper and lower sides of the second fixture when the second fixture is engaged in the limiting channel.

[0018] In some embodiments, the second fixture includes a first clamping block and a second clamping block opposite to and connected to the first clamping block;

[0019] The first clamping block and the second clamping block define an inner cavity that is adapted to the shape of the blade for clamping the blade;

[0020] The inner wall has a pressure-resistant rubber layer.

[0021] In some embodiments, the inner surface shape of the first clamping block and the inner surface shape of the second clamping block are adapted to the two curved surfaces of the blade, respectively.

[0022] In some embodiments, the first clamping block and the second clamping block clamp the blade from the left and right sides of the blade. The first clamping block has a first protrusion on the upper and lower sides of the end near the first end, and the second clamping block has a second protrusion on the upper and lower sides of the end near the first end.

[0023] In some embodiments, the first end is located inside the inner ring, and the first protrusion and the second protrusion are located outside the inner ring.

[0024] In some implementations, the first clamping block is bolted to the second clamping block through the hole.

[0025] The beneficial effects of this invention are: the bladed disk and all blades can be welded together in one clamping, which greatly improves the manufacturing efficiency of the overall bladed disk; the blades are clamped in the second fixture, and can remain undeformed when a huge second force is applied for upsetting. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the fixture state of a method according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the first fixture structure of a method according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the second fixture structure of a method according to an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the force analysis of the blade during the implementation of a method according to an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of the assembly of the second fixture and blades according to an embodiment of the present invention.

[0031] Symbol explanation:

[0032] 1. Blade; 2. Blade disc; 3. First end; 4. First fixture; 5. Second fixture; 6. Receiving cavity; 7. Inner ring; 8. Outer ring; 9. First slot; 10. Second slot; 11. Spoke; 12. First clamping block; 13. Second clamping block; 14. First protrusion; 15. Second protrusion; 16. Clamping surface; 17. Pressure-resistant rubber layer Detailed Implementation

[0033] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0034] In existing methods of welding blades to bladed disks using linear friction welding, pressure is applied to keep the blade tip in constant contact with the outer wall of the bladed disk, and the two are then subjected to linear reciprocating frictional motion to generate frictional heat. As the temperature of the friction interface rises, the friction surface enters a viscoplastic state. When the temperature and deformation of the friction welding zone reach a certain level, the blade tip is aligned with the part of the bladed disk to be welded, and a larger upsetting force is applied. The metal in the welding zone is then welded together through interdiffusion and recrystallization.

[0035] Existing linear friction welding methods, which weld blades to a disk while keeping the disk fixed, allow the blades to vibrate axially relative to the disk. This method uses a fixture that can only hold one blade at a time, meaning many blades must be welded to the disk one by one. After welding one blade, the disk must cool down before welding the next blade; otherwise, inconsistent welding temperatures can occur, causing errors and affecting the overall impeller performance. To avoid adverse effects on impeller performance, the disk temperature must be cooled down after welding the previous blade before welding the next one, resulting in low processing efficiency for existing linear friction welding methods.

[0036] Furthermore, in the process of linear friction welding, in order to ensure effective welding of the blades, the blades need to withstand a large clamping force, which is generally on the order of millions of Newtons. The blades themselves are thin plate structures with complex curved surfaces. If the tooling fixtures used in conventional linear friction welding are used during the welding process, it is very likely that the blades will undergo irreversible deformation, which will seriously affect the overall performance of the blades.

[0037] In view of this, in order to solve one or more problems existing in the prior art, the present invention provides a linear friction welding method for blade 1 and bladed disk 2, which is suitable for welding multiple blades 1 evenly arranged on the outer periphery of bladed disk 2 to bladed disk 2 in one go.

[0038] The impeller described in this invention can be an impeller used in aircraft engines, steam turbines, water pumps, centrifugal compressors, etc. In terms of material, the impeller disk can be made of titanium alloy, high-temperature alloy, intermetallic compound, nickel alloy, aluminum alloy, or various types of steel, etc., and the blades can be made of titanium alloy, high-temperature alloy, intermetallic compound, nickel alloy, aluminum alloy, or various types of steel, etc.

[0039] Structurally, the impeller comprises a circular bladed disk 2 and a plurality of blades 1 evenly distributed around the bladed disk 2 and extending radially along the bladed disk 2. Please refer to... Figure 5 One end of blade 1 is the first end 3, which needs to be welded to the side wall of impeller 2. Impeller 2 connects many blades 1 together, and when the impeller rotates, the blades 1 rotate around the center of impeller 2.

[0040] Blade 1 is an irregularly shaped thin plate, which can be formed by deformation or casting. For blades formed by casting, they can also be equiaxed crystal blades, directionally solidified columnar crystal blades, single crystal blades, or intermetallic compound blades, etc.

[0041] The present invention does not limit the number of blades 1. Since the present invention is a one-time welding, the high efficiency advantage of the method described in the present invention will be more prominent for impellers with more blades.

[0042] According to one embodiment of the present invention, the method includes the following steps:

[0043] Insert the bladed disc 2 into the receiving cavity 6 of the first fixture 4;

[0044] Each blade 1 is uniquely clamped into the second fixture 5, and the first end 3 of the blade 1 is kept protruding from the corresponding end of the second fixture 5.

[0045] All the second fixtures 5, each holding a blade 1, are respectively inserted radially into the limiting channels formed radially around the accommodating cavity 6, which are provided on the first fixture 4.

[0046] A first force is applied to all second fixtures 5 in the radial direction toward the bladed disk 2 to keep the first end 3 of all blades 1 in constant contact with the bladed disk 2.

[0047] An axial reciprocating vibration is applied to the bladed disk 2, and after the vibration ends, a second force greater than the first force is applied to all the second fixtures 5 and held for a period of time.

[0048] To implement this method, a first fixture 4 and a second fixture 5, the same number as the blades 1, are required. The first fixture 4 is mounted on a welding machine, for example. Before welding, the blades 1, the bladed disk 2, the first fixture 4, and the second fixture 5 must be assembled. According to an embodiment of the invention, please refer to... Figure 1 and Figure 4 The first fixture 4 has a circular receiving cavity 6 in the middle, into which the impeller 2 is coaxially mounted. The receiving cavity 6 extends through the first fixture 4 in its axial direction, allowing the welding machine mechanism to apply high-frequency axial vibration to the impeller 1 through the receiving cavity 6. Each second fixture 5 holds only one blade 1, and the blade 1 and the second fixture 5 are evenly distributed around the impeller 2 and secured to the first fixture 4.

[0049] Due to the action of the first force, the first end 3 of blade 1 exerts a certain pressure on the side wall of bladed disk 2, and the two are always kept in contact. When bladed disk 2 vibrates at high frequency, a large amount of frictional heat is generated at the contact point, and the surface metal gradually reaches a viscoplastic state, deforms and is extruded. After the linear frictional motion stops, the first end 3 of blade 1 is aligned with the part to be welded on bladed disk 2, and a second force with greater force is applied for upsetting, causing the metal in the welding area to be welded together through mutual diffusion and recrystallization.

[0050] The method of the present invention pre-arranges all blades 1 around the bladed disk 1 according to the designed position. During the welding process, the blades 1 are kept stationary while the bladed disk 1 reciprocates along the axial direction at a high frequency. This causes the first end 3 of each blade 1 to generate heat and viscoplastic deformation at the contact surface with the bladed disk 1. Finally, radial upsetting forces are applied to the second fixture 5 at the same time. That is, the bladed disk 2 and all blades 1 can be linearly friction welded in one clamping, which greatly improves the manufacturing efficiency of the overall bladed disk 2.

[0051] Furthermore, because the second fixture 5, which holds the blade 1, is engaged in the limiting channel, the blade 1 is restricted in the circumferential direction by the limiting channel and is less prone to displacement, thus ensuring the welding accuracy of the blade 1 in the circumferential direction of the impeller 2. The impeller with evenly distributed blades 1 has better mechanical stability and a longer service life.

[0052] According to one embodiment of the present invention, please refer to Figure 2 The first fixture 4 includes an inner ring 7 and an outer ring 8. The outer ring 8 is concentrically disposed around the inner ring 7 and connected to it. The inner ring 7 has a first groove 9, and the outer ring 8 has a second groove 10 radially opposite to the first groove 9. The first groove 9 and the second groove 10 define a limiting channel radially. The inner ring 7 is circular. The first groove 9 is evenly formed circumferentially on and penetrates the sidewall of the inner ring 7. The length direction of the first groove 9 is consistent with the axial direction of the inner ring 7, and the width direction is consistent with the circumferential direction of the inner ring 7. The outer ring 8 is circular. The second groove 10 is evenly formed circumferentially on and penetrates the sidewall of the outer ring 8. The length direction of the second groove 10 is consistent with the axial direction of the outer ring 8, and the width direction is consistent with the circumferential direction of the outer ring 8.

[0053] The first fixture 4 adopts an inner ring 7 and an outer ring 8 as its main body structure, which can reduce the weight of the first fixture 4. In addition, the limiting channel is defined by the first slot 9 and the second slot 10, so that the surface of the second fixture 5 and the limiting channel have a small contact area, which reduces the frictional resistance brought by the first fixture 4 when the second fixture 5 is inserted into the limiting channel radially.

[0054] The blade 1 is inserted into the second fixture 5, and the two are then locked into the limiting channel as a whole. Specifically, in some embodiments, the second fixture 5 is locked into the first slot 9 and the second slot 10. More specifically, the second fixture 5 and the first slot 9 are interference-fitted in the width direction, and the second fixture 5 and the second slot 10 are also interference-fitted in the width direction. Further, the width of the portion of the second fixture 5 that is locked into the first slot 9 is slightly larger than the width of the first slot 9, so that the second fixture 5 holding the blade 1 is interference-fitted with the first slot 9 in the width direction. The width of the portion of the second fixture 5 that is locked into the second slot 10 is slightly larger than the width of the second slot 10, so that it is interference-fitted with the second slot 10 in the width direction.

[0055] The interference fit between the second fixture 5 and the first slot 9, and between the second fixture 5 and the second slot 10, should not be too large. The width of the part of the second fixture 5 that engages with the first slot 9 should be only slightly larger than the width of the first slot 9, and the width of the part of the second fixture 5 that engages with the second slot 10 should be only slightly larger than the width of the second slot 10, so as to maintain the circumferential positioning accuracy of the second fixture 5. The width of the second fixture 5 should not be too large compared to the width of the first slot 9 and the width of the second slot 10, otherwise it will increase the radial movement resistance of the second fixture 5, that is, loading and unloading the second fixture 5 will become very difficult, and this resistance will lead to pressure loss transmitted to the impeller 2 when the first force is applied to the second fixture 5 during the friction stage and the second force is applied to the second fixture during the upsetting stage. Furthermore, if the width of the second fixture 5 is too large, it will compress the walls of the first slot 9 and the second slot 10, causing their deformation to exceed the elastic deformation. That is, the walls of the first slot 9 and the second slot 10 will undergo plastic deformation, which, combined with the friction and wear between the second fixture 5 and the slot walls, will be detrimental to the service life of the first fixture 4.

[0056] Alternatively, please refer to Figure 2 The inner ring 7 and the outer ring 8 are connected by spokes 11. Spokes 11 extend radially, with one end connected to the outer side of the inner ring 7 and the other end connected to the inner side of the outer ring 8. The connection can be made by bolts or by welding.

[0057] In some embodiments, the first force is greater than the maximum static friction force between the second fixture 5 and the limiting channel. The second fixture 5 is engaged in the limiting channel to maintain the welding positioning accuracy of the blade 1 in the circumferential direction. During the high-frequency friction process, the viscoplastic portion of the welded part between the blade 1 and the impeller 2 is extruded. Since the first force is greater than the maximum static friction force between the second fixture 5 and the limiting channel, the first force can slightly push the second fixture 5 towards the impeller 2, so that the first end 3 of the blade 1 always applies a certain pressure to the impeller 2, so that a large amount of frictional heat is generated at the friction part.

[0058] According to one embodiment of the present invention, please refer to Figure 3 The second fixture 5 includes a first clamping block 12 and a second clamping block 13 opposite to and connected to the first clamping block 12. The surfaces of the first clamping block 12 and the second clamping block 13 opposite to each other are clamping surfaces. An inner cavity adapted to the shape of the blade 1 for clamping the blade 1 is defined between the two clamping surfaces. The wall of the inner cavity has a pressure-resistant rubber layer 17.

[0059] Furthermore, the clamping surface shapes of the first clamping block 12 and the second clamping block 13 are respectively adapted to the curved surfaces on both sides of the blade 1. When the clamping surface of one of the first clamping block 12 and the second clamping block 13 is convex, the clamping surface of the other is concave. The blade 1 of the impeller is irregularly twisted in space, and it is not parallel to the axis of the impeller. When the second fixture 5 is engaged in the limiting channel, one of the first clamping block 12 and the second clamping block 13 is located on the left side of the blade 1, and the other is located on the right side of the blade 1, that is, the first clamping block 12 and the second clamping block 13 clamp the blade 1 from the left and right sides respectively.

[0060] Optionally, the first clamping block 12 and the second clamping block 13 each include a metal portion, wherein the inner surface shape of the metal portion of the first clamping block 12 is adapted to the surface shape of one side of the blade 1, and the inner surface shape of the metal portion of the second clamping block 13 is adapted to the surface shape of the other side of the blade 1. The metal portions can be formed by casting.

[0061] Please refer to Figure 4 The inner surfaces of the metal portions of the two clamping blocks are respectively provided with uniformly thick pressure-resistant rubber layers 17. For example, the pressure-resistant rubber layers 17 are bonded to the inner surfaces of the metal portions by a strong adhesive. The material of the pressure-resistant rubber layers 17 is rubber capable of withstanding high pressure, such as, but not limited to, nitrile rubber, hydronitrile rubber, EPDM rubber, or fluororubber. The surfaces of the two pressure-resistant rubber layers 17 are the clamping surfaces 16 of the first clamping block 12 and the second clamping block 13, respectively, forming the walls of the inner cavity of the second fixture 5. Preferably, anti-slip textures are pressed onto the surface of the molded rubber to increase its surface friction coefficient.

[0062] The stress on blade 1 during the welding process is verified as follows: Please refer to... Figure 4 The maximum force F0 experienced by blade 1 during welding is set to 1000 kN. To maintain balance of blade 1 in the pressure direction during welding, the static friction forces f1 and f2 between blade 1 and the pressure-resistant rubber must both be greater than 500 kN, and the static friction coefficient between the rubber and blade 1 must be no less than 0.8. Therefore, the pressures F1 and F2 applied to both ends of the clamp must be greater than 500 kN / 0.8 = 625 kN. If the area of ​​the bottom surface of blade 1 is 0.05 m²... 2 Therefore, the pressure on the surface of blade 1 is 625 kN / 0.05 m. 2 =12.5MPa, this pressure will hardly cause blade 1 to deform.

[0063] Optionally, the first clamping block 12 is bolted to the second clamping block 13 through the hole.

[0064] The second fixture 5 has a protrusion at its end near the first end. When the second fixture 5 is engaged in the limiting channel, the protrusion is located on the upper and lower sides of the second fixture 5. In some embodiments, the protrusion includes a first protrusion 14 and a second protrusion 15. Please refer to... Figure 3 The first clamping block 12 has first protrusions 14 on its upper and lower sides near the bladed disk 2, and the second clamping block 13 has second protrusions 15 on its upper and lower sides near the bladed disk 2. When the second fixture 5, which holds the blade 1, is assembled into the first slot 9 and the second slot 10, one of the first protrusions 14 and the second protrusion 15 is located above the other in the axial direction. The first protrusions 14 and 15 on the upper side are aligned with each other, and the first protrusions 14 and 15 on the lower side are aligned with each other. The first force and the second force are applied to the first protrusions 14 and 15, which serve as the bearing area for the external force, preventing the outer surface of the clamping block from bearing friction and effectively protecting the outer surface of the clamping block. In addition, the blade 2 is not completely locked in the second fixture 5 and may deflect slightly during welding and upsetting. Setting the protrusions close to the first end minimizes the distance between the force-bearing point and the force-applying point, further preventing blade deflection.

[0065] The first slot 9 and the second slot 10 have a certain length in the axial direction, so that the second fixture 5 can be inserted into the first slot 9 and the second slot 10. The second fixture 5, which holds the blade 1, passes radially through the second slot 10 of the outer ring and the first slot 9 of the inner ring in sequence, so that the first end enters the inner side of the inner ring and contacts the blade disk 2, while the first protrusion 14 and the second protrusion 15 remain on the outer side of the inner ring 7. Using an external device, such as a hydraulic device, radial force, namely the first force and the second force, can be applied to the protrusions.

[0066] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A linear friction welding method for blades and bladed disks, applicable to connecting the first ends of multiple blades uniformly arranged on the outer periphery of the bladed disk to the bladed disk in a single operation, characterized in that... Includes the following steps: The leaf disc is inserted into the receiving cavity of the first fixture; Each blade is uniquely clamped into a second fixture, with the first end of the blade protruding from the corresponding end of the second fixture. All the second fixtures are respectively inserted radially into the limiting channels formed radially around the accommodating cavity, which are provided on the first fixture; A first force is applied radially toward the bladed disk to each of the second fixtures to keep the first ends of all blades in constant contact with the bladed disk. An axial reciprocating vibration is applied to the bladed disk, and after the vibration ends, a larger second force is applied to all the second fixtures and held for a period of time; The first fixture includes an inner ring and an outer ring; The outer ring is concentrically arranged around the inner ring and connected to the inner ring; The inner ring is provided with a first slot, and the outer ring is provided with a second slot that is radially opposite to the first slot. The first slot and the second slot define the limiting channel. The second fixture and the first slot are interference-fitted in the width direction; The second fixture includes a first clamping block and a second clamping block opposite to and connected to the first clamping block; The first clamping block and the second clamping block define an inner cavity adapted to the shape of the blade for clamping the blade; The wall of the inner cavity has a pressure-resistant rubber layer; The inner surface shape of the first clamping block and the inner surface shape of the second clamping block are respectively adapted to the two curved surfaces of the blade; The first force is greater than the maximum static friction force between the outer surface of the second fixture and the limiting channel.

2. The linear friction welding method for blades and bladed disks according to claim 1, characterized in that, The second fixture has a protrusion at the end near the first end. When the second fixture is engaged in the limiting channel, the protrusion is located on the upper and lower sides of the second fixture.

3. The linear friction welding method for blades and bladed disks according to claim 1, characterized in that, The first clamping block and the second clamping block clamp the blade from the left and right sides of the blade. The first clamping block has a first protrusion on the upper and lower sides of the end near the first end, and the second clamping block has a second protrusion on the upper and lower sides of the end near the first end.

4. The linear friction welding method for blades and bladed disks according to claim 3, characterized in that, The first end is located inside the inner ring, and the first protrusion and the second protrusion are located outside the inner ring.

5. The linear friction welding method for blades and bladed disks according to claim 1, characterized in that, The first clamping block is bolted to the through hole of the second clamping block.

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