BE1031533B1 - ORBITAL FRICTION WELDING PROCESS OF A BLADED DISC OF A TURBOMACHINE COMPRESSOR - Google Patents

Abstract

The invention relates to a method for friction welding blades (12) to a disc (2). A first half of the blades (12.1) is first welded to the disc (2). Extra thicknesses (15, 23) inherent in the friction welding method and/or provided on the blades (12.1) and/or on the disc (2) are at least partially removed by machining. Then a second half of the blades is welded to the disc (2).

Description

Description

ORBITAL FRICTION WELDING PROCESS OF A BLADED DISC

TURBOMACHINE COMPRESSOR

Domain

The invention relates to a method of welding blades to a disk or drum, to form a bladed disk ("blisk") or a bladed drum ("blum") for a turbomachine.

Prior art

Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft but also to those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products, whose

Integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and the lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, essential complements to technological progress, aeronautical biofuels.

To this end, the invention is the result of technological research aimed at significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft.

In this context, the invention relates to a friction welding method for producing a turbomachine compressor rotor.

Friction welding is a welding process in which the heat required for welding is provided by moving one or both of the parts to be joined, thereby rubbing them against each other under axial pressure.

Patent document EP 2 535 516 A1 shows an example of tooling enabling orbital friction welding. Friction is said to be orbital when the relative movement of the parts to be assembled is a circular translation, generally governed by an eccentric, as opposed to linear friction in which the relative movement is rectilinear.

In a friction welding process, a sacrificial volume of material is provided on the two parts to be joined. This sacrificial volume is caused to be kneaded (plastic shear) and extruded out of the contact interface between the two parts, thus forming a burr, called a "flash", which will then be eliminated, for example by machining.

A tool (gripper) grabs the blade and drives its movement to perform the welding. To handle the blades, they can be equipped with massive extra thicknesses, called platforms, which prevent the tool from deforming the blades during welding.

A platform that is too thin presents risks of deformation of the blades and therefore dimensional defects on the finished part (rotor, disk, drum).

Conversely, a platform that is too massive limits the "density" of blades that can be welded on a given support, for reasons of accessibility of the welding tooling. This limit hinders freedom of design, or imposes a manufacturing process other than orbital welding for rotors with many blades.

Summary of the invention

Technical problem

The invention therefore aims to propose a manufacturing method which makes it possible to assemble the blades by friction welding while retaining great design flexibility, in terms of blade density, and without deteriorating the dimensional quality of the finished part.

Technical solution

The invention relates to a method for manufacturing a turbomachine compressor bladed disk, the method comprising: manufacturing a disk with an annular row of stubs; manufacturing as many blades as stubs, the blades comprising a platform for handling them during the subsequent welding operation; friction welding a first half of the blades to a first half of the stubs, the first half of the stubs consisting of every other stub in the circumferential direction; at least partially removing, by machining, the respective platforms of the blades of the first half of the blades; welding the second half of the blades to the second half of the stubs; at least partially removing, by machining, the respective platforms of the blades of the second half of the blades.

Thus, machining, potentially in rough form, the platforms of the first half of the blades, allows, even when the rotor functionally requires very close blades, the accessibility of the tooling for welding operations. This increases the number of weldable blades on the annular row of stubs.

At the same time, this makes it possible to make the tooling more massive and more rigid, and therefore to reduce deformations (of the tooling or the blade) during welding. This results in better dimensional control of the operation. As a consequence,

* BE2023/5303 more rigid tooling allows the platform to be moved away from the surface to be welded on the blade and/or the stubs to be enlarged, since the deflection of the stub and the deflection of the blade root will be less with more rigid tooling.

Preferably, the bladed disc is a so-called “bi-material” disc comprising two different titanium alloys, more preferably, the blades are obtained from a Ta6v alloy, and the disc from one of the following alloys: Ti17, Ti575, Ti1023.

According to an advantageous embodiment of the invention, the method comprises, before welding the second half of the blades, a step of at least partial removal, by machining, of each burr resulting from the welding of the first half of the blades. Depending on the sacrificial volume envisaged, the burr, or "flash", which forms during welding may be large and it may be useful to remove it, at least in part, to ensure the accessibility of the tooling for welding the second half of the blades.

According to an advantageous embodiment of the invention, the method comprises two heat treatment steps following the welding of each half of the blades and preceding the respective machining operations. This heat treatment makes it possible to relax the internal stresses, it is carried out before the rough machining of the platforms and therefore before the removal by (adaptive) machining.

According to an advantageous embodiment of the invention, the disk has a reinforcement surrounding each stub and the method comprises a step of at least partial removal, by machining, of each reinforcement of a stub on which a blade has been welded, before welding the second half of the blades.

This allows for an imposing reinforcement to be provided which stiffens the stump and which allows good dimensional quality of the finished product.

According to an advantageous embodiment of the invention, the step of at least partial removal, by machining, of the respective platforms of the blades of the first half of the blades is a roughing step removing only the material necessary for the accessibility of the welding tool of the second half of the blades. By "removing only" it is meant that the material removed makes it possible to guarantee the accessibility of the tooling, in particular with a tolerance margin of a few millimeters. The objective of the intermediate machining step is not to get as close as possible to the nominal dimensions of the finished part but rather to offer the greatest flexibility to the design of the rotor.

According to an advantageous embodiment of the invention, the method comprises a finishing machining step after at least partial removal, by machining, of the respective platforms of the blades of the second half of the blades. This step makes it possible to complete the removal of material from the platforms, burrs and any reinforcements.

According to an advantageous embodiment of the invention, the method comprises a dimensional control step following the welding of the first half of the blades and preceding the welding of the second half of the blades. This control makes it possible to guarantee the dimensional quality of the part at an intermediate moment in the manufacturing, opening the possibility of rejecting or correcting defects before all the blades are welded to the disk. Other control steps can follow the welding phase of the second half of the blades.

According to an advantageous embodiment of the invention, the friction welding steps are orbital friction welding steps. This technique involves a complex movement of the blades and makes it all the more advantageous to free up space for the accessibility of the welding tooling.

The invention also relates to a crown intended for the manufacture of a bladed disk for a turbomachine compressor, the crown comprising a disk with an annular row of stubs, and blades friction-welded to a first half of the stubs, the first half consisting of every other stub in the circumferential direction, a second half of the stubs being free of blades. This crown constitutes an intermediate part of the manufacturing method described above.

Assembly for manufacturing a turbomachine compressor bladed disk, the assembly comprising a disk with an annular row of stubs and as many blades as there are stubs, the stubs being separated from each other circumferentially by an inter-stub distance, each blade having a substantially parallelepiped platform whose width, added to a tool for holding the blade during welding, is at most equal to the inter-stub distance. Such platforms make it possible to limit the deflections of the tool and the blade during welding and make it possible to guarantee the dimensional quality of the finished part.

Thus, the various aspects of the invention allow the design and manufacture of a rotor with a high circumferential density of blades, where the blades are friction welded, without deteriorating the structural and dimensional quality of the rotor.

Description of the drawings

Figure 1 partially shows the disc and a head-to-tail blade before assembly;

Figure 2 shows part of the disc after welding the first half of the blades;

Figure 3 illustrates the disc after a first machining step;

Figure 4 shows the disc after welding and machining of the second half of the blades;

Figure 5 describes the method according to the invention.

Description of an embodiment

In the present application, the term "bladed disk" designates a single-piece assembly comprising a generally axisymmetric disk or hub and an annular row of blades arranged at the periphery of the disk. To facilitate the reading of the present application, the description focuses on a bladed "disk" but the invention may also relate to a bladed "drum", comprising several rows of blades.

The bladed disc is intended to be used at any compression stage (including the fan) or turbine of a turbomachine. Preferably, the disc can be arranged at an intermediate position of the compressor.

Figure 1 shows a disc 2 and a blade 12 intended to be assembled by welding.

Disk 2 is partially represented. A cylindrical coordinate system (A, R, T) can be used to materialize the axial A, radial R and

/ BE2023/5303 tangential T. The axial direction A is along an axis of symmetry of the disc. In operation, the axis A is an axis of rotation of the bladed disc.

On a radially outer part of the disc is arranged a surface 3.

This is raised relative to an outer surface 4 of the disk 2, thus forming a stump M. The surface 4 is intended to constitute a surface for guiding an air flow. The surface 3 may be substantially located in a plane perpendicular to a radius of the disk 2.

Surface 3 is delimited by a contour P which can take the form of a blade profile, with a generally convex side, a generally concave side, and two connecting radii.

The stump M may optionally be surrounded by a reinforcement 5 which forms a shoulder or a staircase relative to the stump M. The reinforcement 5 is lower radially than the stump M. The reinforcement 5 may also be wider tangentially, and/or longer axially than the stump M. The reinforcement guarantees in particular the transverse stiffness of the stump.

A sacrificial volume of material, denoted V2 and highlighted by a dotted line 9, is intended to be extruded during friction. Any reinforcement does not rise radially to this volume. This ensures that even at the end of the welding operation, the blade does not come into contact with the reinforcement 5.

A blade 12 intended to be assembled to the disk 2 is illustrated on the right in FIG. 1, in a position with the head down to highlight the fact that the blade 12 has a surface 13 delimited by the same contour P as the surface 3.

For the welding operation, the surfaces 3 and 13 are brought into contact with each other. The blade 12 is set in motion while undergoing a force (in the direction R) which keeps the blade in contact with the disk. The movement of the blade 12 is a circular translation movement (orbital friction), that is to say that each point of the blade 12 has the same circular trajectory in a plane parallel to the surface 3. To be exact, the trajectory is helical but with a pitch which corresponds to the speed of consumption of the sacrificial material and which is therefore very small in comparison with the speed in the plane of the circular movement. In a variant, the movement can be linear, each point of the blade describing a straight line segment in a back-and-forth movement. The straight line segment can be substantially parallel to the axis A (= longitudinal linear friction) or to the axis T (= transverse linear friction).

A sacrificial volume of material on the blade side, denoted V12, is destined to be 5 extruded during friction. The dotted line 19 materializes the limit of V12.

The blade comprises a platform 15 at a distance d from the surface 13. This platform 15 can be parallelepipedal, of width L, and allows the blade 12 to be gripped by the tool impelling its movement. The platform 15 also makes it possible to mechanically reinforce the blade 12 to limit the deflection of the sacrificial volume V12 during friction. The distance d is sufficient to ensure that the platform 15 does not come into contact with the disk 2 during the welding operation. Depending on the materials present, the distance d can be chosen such that the volume V12 can be approximately four times greater than the volume V2. Such a ratio between the volume V12 and V2 is particularly valid when the blade is made of titanium alloy Ta6v and the stump of the disk is made of titanium alloy Ti17. Another material pair will bring a different ratio (generally less than 4).

Figure 2 shows a cross-sectional view perpendicular to the axis A of a crown 18, i.e., an intermediate product of the manufacturing process (detailed in Figure 5). Half of the blades 12 have been welded onto the crown 18. This first half of blades 12.1 occupies a first half of stubs, denoted M1, which are regularly spaced around the disk.

Figure 2 shows that the welding of each blade 12.1 causes the collapse of the sacrificial volumes V2, V12 which form a burr 23 or “flash”.

It should be noted that the stumps M1, M2 preferably include a reinforcement or extra thickness at the foot of the stump (similar to reinforcement 5 illustrated in figure 1) not shown here to simplify the reading of the figures.

Figure 2 illustrates in dotted lines the tooling 30 which holds the blade 12.1 during welding, via the platform 15. A radial force (vertical in Figure 2) is applied during the friction movement and the lateral positioning (and the inclination) of the blade are controlled thanks to the shape of the platform 15.

The spacing of the stumps M can be materialized by an inter-stump distance D, for example a curvilinear distance measured at the level of the surface 4.

The invention provides for welding only one blade out of two and then partially eliminating the platform 15 by removing material. This allows a design of the rotor with closely spaced blades (D becomes smaller) without stress on the tooling 30, and therefore without weakening the rigidity of the tool (which would reduce the dimensional quality of the finished part and/or the structural quality of the weld).

The width L of the platform can therefore be significant and can exceed a third of D. In Figure 2, which is a sectional view perpendicular to the axis A, the width L’ is annotated (which is a little larger than L given the orientation of the blade around the axis R).

Figure 3 shows crown 18 of Figure 2 after machining and before welding of the second half of the blades.

Depending on the distance available between two of these blades 12.1 (= 2xD), and the dimensions of the platform 15 and the possible reinforcement 5, the intermediate machining may require the removal of more or less material.

Machining can be done mainly by milling. If the surface condition or dimensional precision of this step are secondary, the important thing is to guarantee the accessibility of the tool 30 (with a tolerance margin) for welding the remaining blades.

Figure 4 shows the bladed disc 20, i.e. the crown 18 on which the second half of the blades 12.2 has been welded. The excess thicknesses (burrs, platforms and possible reinforcements) have been machined.

Figure 5 shows the sequence of steps of the method of the invention. The optional steps are illustrated in dotted lines.

The process begins with the manufacture 100 of the disc 2. The disc 2 can be obtained by forging, then machining. The disc 2 can be in the rough state when the blades are welded and it is not excluded that operations are carried out on the disc after the blades are welded.

In parallel, a step 110 illustrates the manufacture of the blades 12.

Step 120 involves welding half of the blades to the disk. The platforms 150 are then machined. The second half of the blades is welded at step 180 and the platforms of this second half of the blades are machined at step 210.

Other optional steps may be added to the method, including one or more of the following steps: a dimensional or structural inspection 130 of the crown 18 (for example FPI inspection, “fluorescent penetrant inspection”), a heat treatment 140, machining at least part 160 of the burrs 23, at least partial machining 170 of the reinforcements 5, inspection 190 of the bladed disk 20, its heat treatment 200, at least partial machining 220 of the burrs of the second half of the welds, at least partial machining 230 of the reinforcements 5 of the second stumps, and finishing machining 240.

The manufacturing step of the blades 110 is illustrated in parallel with the other steps.

Indeed, it is not necessary for all the blades 12 to have been manufactured before the welding step 120 begins: one blade at a time is welded to the disk and given the duration of the steps 120 to 170, it is possible to imagine carrying out the manufacture of the blades 12 at least partly in parallel with some of the steps 120 to 170.

The machining steps 150, 160 and 170 can be carried out in the same machining phase, that is to say without the crown 18 being removed from the machining table. The same can be true of steps 210 to 240.

Claims (10)

Claims 1. A method of manufacturing a bladed disk (20) for a turbomachine compressor, the method comprising: - manufacturing (100) a disk (2) with an annular row of stubs (M); - manufacturing (110) as many blades (12) as there are stubs, the blades (12) comprising a platform (15) intended for their handling during the subsequent welding operation (120, 170); - friction welding (120) a first half of the blades (12.1) to a first half of the stubs (M1), the first half of the stubs (M1) consisting of every other stub in the circumferential direction (T); - at least partial removal (150), by machining, of the respective platforms (15) of the blades (12) of the first half of the blades (12.1); - welding (180) the second half of the blades (12.2) to the second half of the stubs (M2); - removing (210) at least partially, by machining, the respective platforms (15) of the blades (12) of the second half of blades (12.2). 2. Method according to claim 1, characterized in that it comprises, before the welding (180) of the second half of blades (12.2), a step (160) of at least partial removal, by machining, of each burr (23) resulting from the welding of the first half of blades (12.1). 3. Method according to claim 1 or 2, characterized in that it comprises two heat treatment steps (140, 200) following the welding (120, 180) of each half of the blades and preceding the respective machining operations (150, 210). 4. Method according to one of claims 1 to 3, characterized in that the disk (2) has a reinforcement (5) surrounding each stub (M) and the method comprises a step (170) of at least partial removal, by machining, of each reinforcement (5) of a stub (M1) on which a blade has been welded, before the welding (180) of the second half of blades. 5. Method according to one of claims 1 to 4, characterized in that the step (150, 210) of at least partial removal, by machining, of the respective platforms (15) of the blades (12) of the first half of the blades is a roughing step removing only the material necessary for the accessibility of the welding tool (30) of the second half of the blades. 6. Method according to one of claims 1 to 5, characterized in that it comprises a step (240) of finishing machining after the at least partial removal (210), by machining, of the respective platforms of the blades (12) of the second half of blades. 7. Method according to one of claims 1 to 6, characterized in that it comprises a dimensional control step (130) following the welding (120) of the first half of the blades and preceding the welding (180) of the second half of the blades. 8. Method according to one of claims 1 to 7, characterized in that the friction welding steps (120, 180) are orbital friction welding steps. 9. Crown (18) intended for the manufacture of a bladed disk (20) for a turbomachine compressor, the crown (18) comprising a disk (2) with an annular row of stubs (M), and blades (12.1) friction welded to a first half of stubs (M1), the first half consisting of every other stub in the circumferential direction (T), a second half of stubs (M2) being free of blades. 10. Assembly (2, 12) for manufacturing a bladed disk (20) for a turbomachine compressor, the assembly comprising a disk (2) with an annular row of stubs (M) and as many blades (12) as there are stubs (M), the stubs being separated from each other circumferentially by an inter-stub distance (D), each blade having a substantially parallelepipedal platform (15) whose width (L) added to a tool for holding the blade during welding, is at most equal to the inter-stub distance (D).