Method for manufacturing a turbine compressor blade by pressing

Abstract

The invention relates to a method for manufacturing a turbine compressor blade, comprising the following steps: - mounting a primary pin (26) in a primary bore (20) of a core and a secondary pin made of a titanium-based alloy in a secondary bore of the core, the primary pin comprising a material other than the titanium-based alloy, the primary bore forming at least one polygon, - forming a stack (2) consisting of an upper skin (4), the core (14) and a lower skin (6), - pressing the stack; - removing the primary pin (26) from the primary bore (20); - removing the secondary pin from the secondary bore; and - extracting the core (14) from the stack.

Description

TECHNICAL FIELD

[0001] The present invention relates to the manufacture of a turbine blade, in particular a turbine compressor blade, by pressing. BACKGROUND

[0002] A manufacturing technique of so-called "leading edge on core" is known. This manufacturing technique is known, for example, from the document WO-2011 / 114073. This manufacturing technique consists in manufacturing a turbine compressor blade, for example for an aircraft turbojet engine. Such a blade generally comprises an upper wing surface, a lower wing surface, a leading edge and a trailing edge.

[0003] In this method, the upper skin, the core and the lower skin are stacked. The core is thus located between the two skins and will serve to define the internal volume of the blade at the leading edge of the blade. The stack is then subjected to hot isostatic pressing (CIC). During this operation, the two skins closely follow the shape of the core so that the core imparts the final shape to the two skins. The core is now enclosed between the two skins and must then be removed from the stack. This operation is a so-called "core-out" operation. The core will then be reused to manufacture new blades.

[0004] Before the pressing operation, pins are inserted into the holes made in the core. The pins are chosen and installed as follows.

[0005] One of the pins is made of a titanium-based alloy. In the remainder of the application, this pin will be referred to as the "titanium pin". This pin is used to create a point of affinity between the core and the titanium and to enable homogeneity of removal. This pin is welded to the lower skin and to the upper skin by diffusion welding. The dimensions of this pin are designed to be too long to leave a visual mark after pressing. During the CIC, under the effect of the pressure, this pin deforms and is pressed into the core.

[0006] The other four pins are made of a different material than the previous pin, for example a nickel-based material. These pins are aligned approximately parallel to the longitudinal edges of the stack. These pins enable the closure of the corresponding holes which are used to clamp the stack during the machining of the titanium after pressing. The dimensions of these pins are also designed to leave a visual mark after pressing the titanium skin around the core. These pins resist the pressure during the CIC and do not deform. The hole that receives the titanium pin is positioned at a distance from the line defined by the four pins. This line extends between the titanium pin and the longitudinal edge.

[0007] Thus, after pressing and before removing the core, the pins must be removed. The core-out operation can thus be divided into two phases. The first phase, the so-called pin-out phase, consists in freeing the holes located on the core. These holes will subsequently make it possible to form a reference system and to clamp the assembly. The second phase constitutes the strict core-out, which makes it possible to separate the shroud and the core.

[0008] In order to extract the four pins described above, a first machining operation is performed, comprising clearing the titanium facing the pins to free the path for removing the pins, then knocking out the pins to extract them from the core. To do this, a first operation of setting the stack (precise mounting of the assembly on the support) is performed.

[0009] The difficulty then lies in the extraction of the titanium pins. Remembering that the titanium pins are pressed into the core, the only option is to remove the pins by machining. But this operation must not in any case compromise the integrity of the core. To do this, it is necessary to accurately position the pins. And drilling the titanium pins without risk of affecting the core requires perpendicularity between the main surface of the stack and the centerline of the hole.

[0010] Thus, for this, a new setting must be performed which must be very strict. This second setting is performed by fixing the stack on the support via the four holes now freed. However, these holes are roughly aligned with each other and also very far from the center of gravity of the core. Thus, it is difficult to attach the stack to the support of the stack precisely and firmly. Moreover, since the four pins are roughly aligned, the four pins cannot straighten the stack firmly and precisely with respect to the main surface of the core which is used as a reference surface during the machining of the titanium pins.

[0011] It can thus be seen that this method creates two technical defects:

[0012] - the method requires two meticulous setting operations to perform the pin-out by machining, and

[0013] - the method cannot eliminate the risk of affecting the core during the machining of the titanium pins and thus having to discard the core. SUMMARY

[0014] To do this, a method for manufacturing a turbine blade is provided, comprising the following steps:

[0015] - mounting primary pins in primary holes of the core and secondary pins made of titanium-based alloy in secondary holes of the core, the primary pins comprising a material other than titanium-based alloy, the primary holes forming at least one polygon,

[0016] - forming a stack consisting of an upper skin, a core and a lower skin,

[0017] - pressing the stack,

[0018] - removing the primary pins from the primary holes,

[0019] - removing the secondary pins from the secondary holes, and

[0020] - extracting the core from the stack.

[0021] The method is particularly used to define the internal volume of the blade at the leading edge of the blade.

[0022] Defining the polygon by the primary holes makes it possible to define a more precise and stable reference frame on the surface of the core, making it possible to attach the stack on the support once these holes are released from the pins of the holes. The invention thus makes it possible to increase the bearing surface, which aims to make the fixing of the core on the tool more solid. This reference frame also makes it possible to straighten the surface on which the titanium pins are borne to machine them. This solution thus makes it possible to achieve a dimensional robustness that was not possible previously.

[0023] Furthermore, it is now sufficient to have a single setting operation to remove the primary pins. Once the parts are installed on the tool provided to extract the core, the extraction of the titanium pins can be carried out. Because this makes it possible to go from two settings to a single setting, the invention makes it possible to reduce the cycle time.

[0024] The invention does not require any major modification to the elements used in the method of the prior art (core, support and tool). These elements are conserved and simply and quickly adapted to the new solution.

[0025] The term "titanium-based alloy" should be understood to mean an alloy in which titanium forms at least 50% of the weight of the alloy.

[0026] In an embodiment, at least one of the primary pins and the secondary pins comprises a shank having a longitudinal axis and a head projecting from the shank in a direction radial to the axis.

[0027] This pin thus has a flange, which can be described as a "shouldered pin". Thus, during machining, the purpose of the pin is not only to release the hole area, but also to release the circular surface at the periphery of the hole. This releases a portion of the bearing surface of the core, which is the reference surface of the coring operation. The assembly is thus pressed against the core and not against the skin. This release of the flat circular surface coaxial with the hole makes it possible to define an even more precise and stable reference frame on the surface of the core, making it possible to attach the stack on the support once these holes are released from the pins of the holes. In other words, thanks to the geometry of the shouldered pin, the hole and the circular surface at the periphery of the hole are released. This released hole makes it possible to find the bearing surface of the core, which is the reference surface of the coring operation. When using a headless pin, the assembly is not pressed against the core but against the titanium skin, which is less precise.

[0028] Advantageously, the method comprises, after the step of pressing the stack, the following steps in this order:

[0029] - fixing the stack relative to the support,

[0030] - performing the main step while the stack is fixed on the support,

[0031] - fixing the stack on the tool by means of the attachment members, the attachment members passing through the main holes, and

[0032] - performing the steps of removing the secondary pins and extracting the core while the stack is fixed.

[0033] In an embodiment, the secondary holes extend within the polygon.

[0034] This produces a particularly good stability of the attachment of the stack to the tool, as close as possible to the main holes of the titanium pins.

[0035] It can be specified that the stack comprises straight longitudinal edges, the secondary holes extending in the same plane as a first one of the main holes, perpendicular to the longitudinal edges, the secondary holes extending between the first one of the main holes and the edges.

[0036] It can be specified that the secondary holes are separated from the first one of the main holes by a distance of at least 10 mm.

[0037] It is particularly preferred that the two holes are not too close to each other, so that the two skins properly adapt to the shape of the core around the pins in question.

[0038] It can also be specified that the method comprises at least one of the following characteristics:

[0039] - the number of main pins is odd,

[0040] - the number of main pins is at least two, and

[0041] - the step of pressing the stack is performed by hot isostatic pressing.

[0042] In particular, it can be seen here that the method of the invention is not limited to this pressing.

[0043] According to the invention, a stack can also be provided, comprising:

[0044] - an upper skin,

[0045] - a core,

[0046] - a lower skin,

[0047] - main pins comprising a material other than a titanium-based alloy and housed in the main holes of the core forming at least one polygon, and

[0048] - a secondary pin made of a titanium-based alloy and housed in a secondary hole of the core.

[0049] This can concern the stack before the pressing operation, or the stack after this operation.

[0050] Advantageously, at least one of the primary pin and the secondary pin comprises a shank having a longitudinal axis and a head projecting in a direction radial to the axis. BRIEF DESCRIPTION OF DRAWINGS

[0051] Embodiments of the application will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

[0052] - Figure 1 is an exploded perspective view showing three layers of a stack in the method implementing the method of the application;

[0053] - Figures 2 to 4 is Figure 1 three views of the core of the stack of

[0054] - Figure 5 is a perspective view showing a plurality of stacks after pressing in the case of this implementation method;

[0055] - Figure 6 and Figure 7 are views showing steps of this implementation method of the method;

[0056] - Figure 8 is a view of a tool used in the case of this implementation method,

[0057] - Figure 9 and Figure 10 show a stack attached to this tool, and

[0058] - Figure 11 show axial views of one of the pins before and after crimping. DETAILED DESCRIPTION

[0059] We will therefore describe a method implementing the method of the application, which concerns the manufacture of a turbomachine compressor blade, for example a turbomachine compressor blade of an aircraft turbojet engine. In Figure 1 The blade 2, shown in the form of a stack in

[0060] In a first step, only the core is considered.

[0061] The core 14 is made of a material sold by the company United Technologies Corp under the trade name "Waspaloy", for example.

[0062] As shown in a view of the core alone Figure 2 The core comprises primary holes 20, the number of which is odd, five in this example. Four of these primary holes are aligned substantially parallel to the straight longitudinal lower edge 22 of the core, and are located at a short distance from this edge.

[0063] The fifth primary hole 20 extends in the middle region of one of the main faces of the core, at or near the center of gravity of the core. If one considers the geometrical projection of each of the primary holes 20 on the longitudinal edge 22, these holes are uniformly spaced along this edge. The two holes located at the ends of the row are positioned close to the respective end of this edge.

[0064] Remembering that this fifth primary hole extends at a distance from the line defined by the other four primary holes, these five holes 20 together define a plurality of polygons formed by triangles. Thus Figure 3 A triangle 15 formed by three primary holes 20 located in the middle region of the core is shown.

[0065] The core 14 also comprises secondary holes 24, separate from the previous holes. The secondary holes are located within the triangle 15, between the line defined by the four aligned primary holes on the one hand and the fifth primary hole on the other hand.

[0066] The secondary holes 24 extend in the same plane P as the fifth primary hole 20, perpendicular to the longitudinal edge 22, the secondary holes 24 extending between the fifth primary hole 20 and the edge 22. This plane P is visible in the cross-section of Figure 4 . This plane is perpendicular to the plane of the figure. The secondary holes 24 are separated from the primary holes by a distance d of at least 10 mm, as shown in Figure 2

[0067] The primary holes 20 and the secondary holes 24 each pass through the core 14.

[0068] ​Five shouldered main pins 26 are mounted in the corresponding main holes 20. These pins are made of a material other than the titanium-based alloy. These pins are for example made of a nickel-based material, or of the aforementioned material sold under the trade name Waspaloy, or of a material sold under the trade name Inco manufactured by the company Special Metals Corporation. These pins 26 are used to close the corresponding holes 20 of the core, which are then used to clamp the stack during the machining after pressing. The length of the pins 26 with respect to the holes 20 of the core is overlength, for example overlength by 0.5 mm, to leave a visual mark after pressing the titanium overclad around the core.

[0069] Furthermore, as Figure 11 shown, the main pins 26 have a shoulder to cover the peripheral bearing surface on the upper skin side 4 at the centerline of the hole 20 on the core, as shown in the right-hand part of Figure 11 More precisely, each shouldered main pin 26 comprises a shank 40, here cylindrical, having a longitudinal axis, and a head 42 projecting from the shank in a direction radial to the axis. The head 42 thus forms a flange.

[0070] Secondary pins 28 made of a titanium-based alloy, for example the alloy TA6V, are also mounted in the secondary holes 24 of the stack. This pin also has a shoulder. This makes it possible to create a point d'affinité between the core 14 and the pin and to carry out l'homogénéité du retrait. The pin is welded to the core by diffusion welding. The size of the pin is designed to be overlength, for example overlength by 0.5 mm, with respect to the length of the hole of the core, to leave a visual mark after pressing.

[0071] Next, the upper skin 4, the core 14 and the lower skin 6 are stacked. The core 14 is between the two skins 4 and 6 and will serve to define the internal volume of the blade at the leading edge 8 of the blade.

[0072] The holes are formed only in the core 14, so that the pins are enclosed in the lower and upper skins. The first step of the method is thus to mount the pins, the second step is to stack the skins and the core, and the third step is to press.

[0073] Next, the stack is pressed, here by carrying out a hot isostatic pressing (CIC). During this operation, the two skins closely follow the shape of the core 14, so that the core gives the two skins their final shape. During the CIC, under the effect of the pressure, the secondary pins 28 deform and become pressed into the core. The same applies to the main pins 26.

[0074] In Figure 5The image shows a stack formed by pressing. It can be seen that before and after pressing, there is a stack 2, which includes:

[0075] - Upper wing skin 4

[0076] -Core 14,

[0077] - Lower wing skin 6

[0078] - Main pin 26, the main pin comprises materials other than titanium-based alloy and is housed in the main hole 20 forming a polygon 15 in the core, and

[0079] - Secondary pin 28, which is made of titanium-based alloy and is housed in secondary hole 24 in the core.

[0080] Pins, especially those in the core, must be removed during the pin removal step after pressing and before the core is removed.

[0081] Therefore, after the operation of setting the stack 2 on the support (not shown), the stack 2 is fixed relative to the support.

[0082] Then, remove the master pin 26 from the master hole 20. For this purpose, as in... Figure 6 and Figure 11 The diagram shows the first operation of machining the side supporting the head of the pin in the stack. During this step, the titanium facing the pin 26 of the skin is removed to release a path for the pin to move out in the volume contained between the surface 19 of the core 14 supporting the head 42 and the apex of the head. In this case, the head is removed.

[0083] Next, as in Figure 6 and Figure 7 As shown, pin 26 is knocked out to remove the pin from the core and stack.

[0084] Next, release the stack 2 from the support, and this time secure the stack to the tool 32 via the attachment member 34 (specifically, as shown in the image). Figure 8 As shown, the attachment member passes through the corresponding main hole 20 and the corresponding hole of the tool's clamp 36 to rigidly attach the stack 2 to the clamp 36. Therefore, the main hole 20 allows for the formation of a reference system and an area for clamping the stack. Thus, the area of ​​surface 19 initially located below the head 42 also serves as a reference system.

[0085] When the stacked components are thus secured, the secondary pin 28 of the secondary hole 24 is removed by machining. For this purpose, the fixture includes... Figures 8 to 10 An additional hole 38 is visible, which coincides with the secondary hole 28 of the stack. This additional hole allows a tool for machining the secondary pin to be introduced via a fixture.

[0086] Because the pins can be positioned accurately, this removal can be performed without difficulty and without compromising the integrity of the core. The stable attachment of the stack 2 to the jig 36 ensures the perpendicularity of the main surface 17 visible in the figure, between the main surface 17 and the centre line of the hole, and thus also the drilling of the titanium pins without risk of affecting the core. This same attachment enables the stack to be straightened firmly and accurately with respect to the main surface 17, which serves as a reference surface during the removal of the pins. Figure 6

[0087] Once the secondary hole has been released, the core 14 can be removed from the stack and a de-coring in the strict sense can be performed, which enables the separation of the cap and the core.

[0088] The problem that arises is whether the choice of the position of the junction between the titanium cap and the core during pressing has an impact on the geometry of the leading edge. It has been found that this is not the case.

[0089] Although the application is implemented here with an additional secondary pin compared with the prior art, the cost of this pin is negligible with respect to the manufacturing cost of the part.

[0090] Of course, many modifications can be made to the application without departing from the scope of the application. The number of primary holes and pins, and the number of secondary holes and pins, and the arrangement of all these components can be modified.​

Claims

1. A method for manufacturing a turbine blade, the method comprising the steps of: - installing a primary pin (26) in a primary bore (20) of a core and a secondary pin (28) made of a titanium-based alloy in a secondary bore (24) of the core, the primary pin comprising a material other than a titanium-based alloy, the plurality of primary bores forming at least one polygon (15), - forming a stack (2) consisting of an upper skin (4), the core (14) and a lower skin (6), - pressing the stack, - removing the primary pin (26) from the primary bore (20), - removing the secondary pin (28) from the secondary bore (24), and - extracting the core (14) from the stack, wherein the length of the primary pin (26) is greater than the length of the primary bore (20) and the length of the secondary pin (28) is greater than the length of the secondary bore (24).

2. The method of claim 1, wherein, At least one of the primary pin (26) and the secondary pin (28) comprises a shank (40) having a longitudinal axis and a head (42) protruding from the shank in a direction radial to the axis.

3. The method of claim 1, wherein, The method comprises, after the step of pressing the stack, the steps in the following order: - fixing the stack relative to a support, - performing the step of removing the primary pin (26) while the stack is fixed on the support, - fixing the stack on a tool (32) by an attachment member (34) passing through the primary bore (20), and - performing the steps of removing the secondary pin (28) and extracting the core while the stack is fixed.

4. The method of claim 1, wherein, The secondary bore (24) extends within the polygon (15).

5. The method of claim 1, wherein, The stack comprises a straight longitudinal edge (22), the secondary bore (24) extends in the same plane as a first one of the primary bores (20) perpendicular to the longitudinal edge, the secondary bore (24) extending between the first one of the primary bores (20) and the longitudinal edge (22).

6. The method of claim 5, wherein, The secondary holes (24) are separated from the first of the primary holes (20) by a distance (d) of at least 10 mm d ​ 7. The method of claim 1, wherein, The number of primary pins (26) is odd.

8. The method of claim 1, wherein, The number of primary pins (26) is at least two.

9. The method of claim 1, wherein, The step of pressing the stack (2) is performed by hot isostatic pressing.

10. A stack (2) comprising: - an upper skin (4), - a core (14), - a lower skin (6), - a primary pin (26) comprising a material other than a titanium-based alloy and housed in a plurality of primary bores (20) of the core forming at least one polygon (15), and - a secondary pin (28) made of a titanium-based alloy and housed in a secondary bore (24) of the core, wherein the length of the primary pin (26) is greater than the length of the primary bore (20) and the length of the secondary pin (28) is greater than the length of the secondary bore (24).

11. The stack of claim 10, wherein, At least one of the primary pin (26) and the secondary pin (28) comprises a shank (40) having a longitudinal axis and a head (42) protruding in a direction radial to the axis.

Images