FR2996154A1 - Assembling two coaxial annular pieces to form a casing of a turbomachine of an aircraft, comprises a unit for radial displacement of a friction welding head compared to worpieces, and a unit for rotating workpieces relative to welding head - Google Patents

Abstract

The tool comprises: units for supporting and positioning workpieces (1a, 1b) so that the units are present in contact with an annular zone to be welded; a friction welding head that is movable in rotation around an axis perpendicular to an axis (A) of the workpieces and comprises a body and a mixing pin; a unit for radial displacement of the welding head compared to the worpieces so as to penetrate the mixing pin on the annular zone or to withdraw the mixing pin from the zone; and a unit for rotating the workpieces relative to the welding head so as to move the mixing pin along the weld zone. The tool comprises: units for supporting and positioning workpieces (1a, 1b) so that the units are present in contact with an annular zone to be welded; a friction welding head that is movable in rotation around an axis perpendicular to an axis (A) of the workpieces and comprises a body and a mixing pin projecting relative to the welding head; a unit for radial displacement of the welding head compared to the worpieces to be assembled so as to penetrate the mixing pin on the annular zone to be welded or to withdraw the mixing pin from the zone to be welded; and a unit for rotating the workpieces relative to the welding head so as to move the mixing pin along the annular weld zone. The mixing pin is movably rotated compared to the body between a retracted position in which it is placed in the body and a deployed position in which it is covered out of the body. The supporting and positioning units comprise a first flange comprising a unit for centering one of the workpieces and a second flange comprising a unit for centering the other workpiece. The two flanges are mounted on a rotatable shaft so as to rotate the flanges and the workpieces relative to the welding head. The tool further comprises: a pressure member intended to bear on one of the workpieces to be assembled at or near the weld zone; a spacer for forcing the two flanges one towards the other so as to ensure the contact of the workpieces on the weld zone; and a brake (32) ready to slow down the rotation of the workpieces and to take support on an element of one of the workpieces. The pressure member is a turning roller resting against each of the workpieces to be assembled on the weld zone. Independent claims are included for: (1) a method for assembling two coaxial annular pieces to form a casing of a turbomachine by friction welding; and (2) a method for repairing a casing of a turbomachine.

Description

The present invention relates to a tool for assembling two coaxial annular parts, intended to form a turbomachine casing, and a corresponding assembly method. The invention relates in particular to the field of Friction Stir Welding (FSW). Such a welding method, known in particular from EP 0 752 926, involves the use of a rotating mobile welding head, comprising a body and a kneading pin protruding from the body. This method consists of rotating the welding head and the kneading pin at a controlled speed and to penetrate the pin at an interface zone between two parts to be assembled. The friction thus generated causes, by heating, a softening of the material of the parts that enters the pasty phase. The corresponding edges of the pieces are then deformed plastically and the pasty material of these parts is mixed. The body generally forms with the pin a shoulder that prevents the brewed metal from moving away from the welding zone. The welding head is also moved along the area to be welded so as to form a weld bead by cooling and crystallization of the pasty material thus mixed. This pasty welding of the material is preferred for applications where it is important to maintain the original characteristics of the assembled parts. Indeed, because the material is in a pasty and non-liquid state (there is no fusion during such a welding process), the mechanical properties of said parts are slightly degraded. For example, there is a decrease of about 30% in elongation and yield strength for an aluminum alloy, which is relatively small compared to other welding processes.

Such a method makes it possible in particular to assemble parts of aluminum alloys known to be difficult to weld or very sensitive to cracking, to weld large thicknesses in a single pass and with a minimum of deformation of the parts, to obtain a microstructure to fine grains in the weld zone and minimize thermomechanical stresses and deformations during welding. It is then generally not necessary to perform a heat treatment and / or subsequent machining. For comparison, the two-piece TIG (Tungsten Inert Gas) welding generates a 50% reduction in mechanical characteristics after subsequent machining and heat treatment. Similarly, the assembly of two pieces by electron beam welding generates a reduction of about 40% in mechanical characteristics after subsequent machining and heat treatment. Friction stir welding is used for assembling flat parts in the form of metal sheets or plates. Existing tools allowing the implementation of such a welding process are not suitable for assembling annular parts. Aircraft housings are expensive annular parts requiring many machining. In order to reduce the weight of the turbomachines, aluminum alloys have been chosen for the production of certain casings. In this case, when disassembling or reassembling these housings during maintenance operations, it may happen that flanges of the housings are damaged. There is currently no technological solution for repairing these casings, which requires replacing them with new casings, which is very expensive. The invention aims in particular to provide a simple, effective and economical solution to this problem.

For this purpose, it proposes a tool for assembly by friction welding of two coaxial annular parts intended to form a turbomachine casing, comprising: - means for supporting and positioning each of the parts to be assembled so that they are in contact at the level of an annular weld zone (local clearance being however acceptable), - a friction welding head, rotatable about an axis substantially perpendicular to the axis of said parts, comprising a body and a kneading peg projecting from the body, means for moving the welding head radially relative to the parts to be assembled making it possible to penetrate the kneading peg at the area to be welded or to remove said peg. for mixing the said zone to be welded, means for rotating the parts to be assembled with respect to the welding head, so as to move the kneading pin along the zone to be welded annular. In this way, it is possible to repair a damaged casing by machining away a damaged annular portion (for example having a damaged flange) and replacing it with a replacement annular portion which is secured to the remainder of the casing by friction welding. kneading using the aforementioned tooling. According to one characteristic of the invention, the tooling comprises at least one pressing member intended to bear on at least one of said parts to be assembled, close to or at the level of the zone to be welded.

The pressing member ensures the proper positioning of the edges of the parts to be assembled at the area to be welded. This pressure member can also catch a slight deformation of the parts before assembly. The pressure member may be a roller, for example a rotating roller 30, bearing on each of the two parts to be assembled at the area to be welded.

According to another characteristic of the invention, the kneading pin is movable in translation relative to the body between a retracted position in which it is housed in the body and an extended position in which it projects out of the body.

Preferably, the support and positioning means comprise a first flange comprising centering means of one of the parts to be assembled and a second flange comprising centering means of the other part to be assembled, the two flanges being mounted on a shaft movable in rotation to rotate said flanges and said parts to be assembled relative to the welding head. The centering means may be formed for example by an annular groove in which is engaged the corresponding end of the part concerned, or by an annular element (sectored or not) projecting from the flange, around which is mounted the end corresponding part of the relevant part. The tool may also include at least one spacer to constrain the two flanges towards each other so as to ensure the contact of the two parts to be assembled at the area to be welded.

In addition, the tool may include a brake capable of braking the rotation of said parts to be assembled. The brake makes it possible to better control the speed of rotation of the parts relative to the welding head. In particular, the brake may be able to bear on an element of one of the parts to be assembled, for example on a flange of said part. The invention also relates to a method of assembling two coaxial annular parts, intended to form a turbomachine casing after assembly, by friction welding using a tool of the aforementioned type, comprising the steps of: - positioning the two parts to be assembled so that they come into contact at an annular weld zone, - rotate the welding head and move it radially so that the kneading pin enters the parts to assemble, at the level of the zone to be welded, and causes a heating by friction of said zone to be welded and a mixture of the material thus heated in order to form a weld by cooling said heated zone, - to drive in rotation the two parts to join around their axis, so as to form a weld bead on at least a portion of the annular weld zone, - remove the knurling pin from the zone welded. Finally, the invention relates to a method for repairing a turbomachine casing, consisting in eliminating by machining a deteriorated annular portion 15 of the casing and fixing a replacement annular element to the remainder of the casing by friction welding, in accordance with the aforementioned method. It will be noted that the invention can also be applied to the production of new casings, formed by assembling at least two annular pieces. The invention will be better understood and other details, characteristics and advantages of the invention will become apparent on reading the following description given by way of nonlimiting example with reference to the accompanying drawings, in which: FIG. half-view in section of a turbomachine casing, - Figure 2 is a perspective view of a tool according to the invention, - Figure 3 is a detailed view of part of the tooling of the machine. FIG. 2, showing in particular the brake, FIG. 4 is a sectional view, along axis B, of part of the welding head, FIG. 5 is a detail view illustrating in particular the position of the rollers. the pressure and the welding head with respect to the zone to be welded, - Figure 6 is a sectional view, along the axis A, of a portion of the tool according to the invention, - Figures 7 to 9 are diagrammatic views showing different steps of the friction stir assembly process; FIG. diagram showing the variation of different parameters of the tool over time, during the assembly of the two parts. An aluminum alloy turbomachine casing 1 is shown in FIG. 1. This casing 1 is a part of revolution comprising an upstream flange 2, extending radially outwardly from an upstream end of the casing 1, and a flange downstream 3 extending radially outwardly from a downstream end of the housing 1. The other structural elements of the housing 1 will not be detailed here and are well known to those skilled in the art. During maintenance operations in particular, the upstream flange 2 of the casing 1 may be damaged during a disassembly and / or reassembly of the casing 1. The invention proposes to repair such a damaged casing by eliminating it by machining. the part referenced la and having the upstream flange 2, and replacing this machined part by a substitution part which is fixed to the rest lb of the housing 1 by friction stir welding.

The invention also applies to the production of new casings by assembling two annular parts by friction stir welding. In a general manner, the following will be referred to in the following as the upstream part of the casing 1 (in the case of a new casing) or the substitution part (in the case of a casing to be repaired) per first piece la and the downstream part (in the case of a new casing) or the rest of the casing 1 after machining (in the case of a casing to be repaired) per second piece lb. Such an assembly is performed using a tool 4 shown in Figures 2 to 6.

This tool 4 comprises a flat base 5 on which is fixed a gantry having two feet 6, 7 each comprising a bearing 8 serving to support an end 9 of a rotating shaft 10. An end of the shaft 10 is coupled in rotation to a geared motor 11. The upper ends of the feet 6, 7 are connected by cross members 12 thus forming a pylon or support. A first flange 13 is mounted on the shaft 10 and rotatably coupled thereto via a key 14. The first flange 13 is located near the foot 6. Annular centering means 15 extending along the axis A are fixed to the first flange 13. These may be sectored or not. The upstream end of the first piece is mounted around these centering means 15. A second flange 16 is mounted on the shaft 10 and rotatably coupled thereto via a key 17. The second flange 16 is located near the foot 7 and has an annular groove 18 in which is engaged the downstream end of the second part 1b. The flanges 13, 16 and / or the parts 1a, 1b may also include indexing elements to ensure the correct angular positioning of one part relative to the other. Spacers 19 extending along the axis A are mounted between the flanges 13, 16 and allow them to be brought closer to one another so as to constrain the downstream end of the first piece to bear on the end. upstream of the second piece 1 b. More particularly, each spacer 19 comprises two threaded ends 20, passing through holes formed in the corresponding flanges 13, 16. Nuts 21 screwed onto the threaded ends 20 allow the flanges 13, 16 to be brought closer together and to progressively constrain the two parts 1a. , lb resting on each other. The annular support zone 22 is the zone to be welded. To weld this zone 22, the tooling comprises a welding head 23 extending along an axis B perpendicular to the axis A. The welding head 5 extends opposite the zone to be welded 22, between the sleepers 12. As best seen in Figure 4, the welding head 23 comprises a hollow body 24 in which a central rod 25 is mounted displaceable in translation. The end of this rod 25 comprises a pin 26 10 of smaller diameter, forming a kneading pin 26 projecting from the body 24. A member 27 for guiding the pin 26 is fixed to the end of the body 24, between the latter and the pin 26. The rod 25 is movable along the axis B relative to the body 24, between an extended position in which the pin 26 projects out of the body 24 and the guide member 27, and a retracted position wherein the pin 26 does not protrude from the body 24 and the guide member 27. The body 24 or the guide member 27 (which form the same assembly) form a shoulder 35 with the pin 26. The 4 further comprises means for moving the welding head 23 along the axis B, means for moving the rod 20 and the mixing pin 26 relative to the body 24, and rotating drive means. of the body 24 and the rod 25. The tooling further comprises two pressure rollers 28, mounted on s upports 29, themselves mounted on the crosspieces 12. Each roller 28 is pivotally mounted about an axis 30 and its position relative to the support 29 can be adjusted by means of appropriate adjustment means 31, so as to adjust the pressure. Each roller 28 is intended to support the two parts 1a, 1b at the level of the zone to be welded 22 in order to correctly position the corresponding ends of the parts 1a, 1b during the welding of this zone. 22. As indicated above, these rollers 28 can make it possible to make up for any deformation of the corresponding ends of the parts 1a, 1b, for example due to the prior machining of the damaged part of the casing 1. The tooling 4 also comprises a brake 32 mounted on the crosspieces 12 and having a friction pad 33 for rubbing on a surface of the downstream flange 3 of the second piece 1b. The force applied by the friction pad 33 may be adjusted using a wheel or an adjustment screw 34. The use of a brake 32 makes it possible to better control the speed of rotation of the parts 1a, lb when welding. We will now describe the method of assembling parts 1a, 1b by friction-stirring, with reference to FIGS. 7 to 10. FIG. 10 is a diagram representing several curves, in which - - curve C1 represents the evolution in the time of the relative displacement of the shaft 10 and the parts 1a, 1b to be assembled with respect to the welding head 23, the curve C2 represents the evolution over time of the speed of rotation of the welding head 23, and in particular the kneading pin 26, the curve C3 represents the evolution over time of the force exerted by the welding head 23, and in particular by the shoulder 35, on the parts 1a, 1b to be assembled, the curve C4 represents the evolution over time of the position of the welding head 23 along the axis B, the curve C5 represents the evolution over time of the position of the kneading pin 26 relative to the body 24; 23. After assembly of parts 1a, 1b between With flanges 13, 16 and tightening nuts 21, the welding head 23 is rotated, for example at a speed of the order of 1000 revolutions per minute (FIG. 7).

Meanwhile, it is moved along the axis B until the kneading pin 26 (which in the deployed position) enters the material parts 1 a, 1 b, at the region to be welded 22, and that the shoulder 35 bears on the outer surfaces of the corresponding ends of the parts 1a, 1b (Figure 8). At this moment, a force is applied by the welding head 23, so that the shoulder 35 rests on the aforementioned surfaces. It will be recalled that the pressure rollers 28 also exert their effect by applying a force on these surfaces, on either side of the welding head 23. The penetration of the kneading pin 26 into the material at the level of the zone to be welded 22 and its controlled rotation within the material causes, by frictional heating, a softening of the material parts 1 a, lb which enters the pasty phase. The corresponding ends of the parts 1a, 1b are then deformed plastically and the pasty material of these parts 1a, 1b is mixed. The shoulder 35 prevents the stirred metal from moving away from the welding zone 22.

The geared motor 11 then rotates the shaft 10, the flanges 13, 16 and the parts 1a, 1b, so that the welding head 23 moves progressively over the entire circumference of the zone to be welded 22 and on an additional recovery area. Thus, a continuous weld bead 36 (FIG. 9) is formed by cooling in ambient air and crystallization of the mixed pasty material. During this step, the speed of rotation of the parts 1a, 1b is controlled by means of the brake 32. The tangential advance speed of the welding head 23 with respect to the parts 1a, 1b is, for example, order of 60 cm / min. At the end of the stroke, the pin 26 is moved relative to the body 24 in its retracted position, the shoulder 35 continuing to maintain the material at the welded zone 22 during the withdrawal of the pin 26 (FIG. 9 ). After completion of the weld bead 36, the welding head 23 is moved away from the weld zone 22, the rotation of the welding head 23 is stopped, as is the rotation of the shaft 10 and the parts 1 a, 1 b. It remains only to remove the casing 1 and repaired the tool 4.

As indicated above, such a friction-stir welding is particularly advantageous in the case of the repair or the production of an aluminum or aluminum alloy casing, since it does not cause a significant reduction in the mechanical characteristics. assembled parts 1a, 1b at the welded zone 22. In addition, the assembled parts 1a, 1b do not require heat treatment or subsequent machining. Finally, such an assembly respects the thickness of the assembled parts 1a, 1b at the welded zone 22, the circularity and the internal and external diameters of said parts 1a, 1b (no deformation during the welding), as well as the concentricity of the welded zone 22 with respect to the other annular parts of the housing 1.

Claims (10)

REVENDICATIONS1. Tooling (4) for assembling by friction welding two coaxial annular parts (1a, 1b) intended to form a turbomachine casing (1), comprising: - support and positioning means (5, 6, 7) , 13, 15, 16, 18, 19) of each of the parts to be assembled (1a, 1b) so that they are in contact at the level of an annular welding zone (22), a head of friction welding (23), movable in rotation about an axis (B) substantially perpendicular to the axis (A) of said parts (la, 1b), comprising a body (24, 27) and a kneading pin (26). ) projecting from the body (24, 27), means for radially displacing the welding head (23) with respect to the parts to be assembled (la, I b) making it possible to penetrate the kneading pin (26) at the level of the zone to be welded (22) or to remove said kneading pin (26) from said zone to be welded (22), - means for rotating the parts to be assembled (1a, 1b) with respect to the head of oudage (23), so as to move the kneading pin (26) along the annular weld zone (22). 2. Tooling according to claim 1, characterized in that it comprises at least one pressing member (28), intended to bear on at least one of said parts to be assembled (1a, 1b), near or at the level of the area to be welded (22). 3. Tooling according to claim 2, characterized in that the pressing member is a roller (28), for example a rotating roller bearing on each of the two parts to be assembled (la, I b) at the level of the zone to solder (22). 4. Tooling according to one of claims 1 to 3, characterized in that the kneading pin (26) is movable in translation relative to the body (24, 27) between a retracted position in which it is housed in the body ( 24, 27) and an extended position in which it projects out of the body (24, 27). 5. Tooling according to one of claims 1 to 4, characterized in that the support and positioning means comprise a first flange (13) having centering means (15) of one (1a) parts to assemble (1a, 1b) and a second flange (16) comprising centering means (18) of the other part to be assembled (1b), the two flanges (13, 16) being mounted on a movable shaft (10) in rotation so as to rotate said flanges (13, 16) and said parts to be assembled (1a, 1b) with respect to the welding head (23). 6. Tooling according to claim 5, characterized in that it comprises at least one spacer (19) for constraining the two flanges (13, 16) towards one another so as to ensure the contact of the two parts to assemble (1a, 1b) at the area to be welded (22). 7. Tooling according to one of claims 1 to 6, characterized in that it comprises a brake (32) capable of braking the rotation of said parts to be assembled (1a, 1b). 8. Tooling according to claim 7, characterized in that the brake (32) is adapted to bear on an element of one of the parts to be assembled (1a, 1b), for example on a flange (3) of said part (1b). 9. A method of assembling two coaxial annular pieces (1a, 1b), intended to form a turbomachine casing (1) after assembly, by friction welding using a tool (4) according to one of the Claims 1 to 8, comprising the steps of: - positioning the two parts to be assembled (1a, 1b) so that they come into contact at the level of an annular welding zone (22); rotating the welding head (23) and moving it radially so that the kneading pin (26) penetrates the parts to be joined (1a, 1b) at the region to be welded (22) and causes a frictional heating of said welding zone (22) and a mixture of the material thus heated to form a weld (36) by cooling said heated zone, - rotating the two parts to be assembled (1a, 1b) around their axis (A), so as to form a weld bead (36) on at least a part of the zone annular weld (22), - remove the kneading pin (26) from the weld zone (22). 10. A method of repairing a turbomachine casing (1) consisting in eliminating by machining a deteriorated annular portion of the casing (1) and fixing a replacement annular element (1a) to the remainder (1b) of the casing (1). by friction welding according to the method according to claim 9.