Method for producing a plurality of turbine engine blades

Abstract

The invention relates to a method (100) for producing a plurality of blades (10) of height (Ha), which comprises: providing a mould (30) comprising an internal cavity bounded by an internal side face (34) of the mould which is axisymmetric about a longitudinal axis (X), the side face (34) extending along the longitudinal axis (X) at a height (Hf) which is greater than or equal to the height (Ha), the side face (34) defining a plurality of sections (34i) perpendicular to the longitudinal axis (X) of radius (Rfs), for each section (34i), the ratio of the height (Hf) of the side face (34) to the radius (Rfs) of the section (34i) being less than or equal to 2.0; rotating the mould about the longitudinal axis at a rotational speed of between 200 rpm-1 and 800 rpm-1; and pouring a material into the internal cavity to centrifugally form a tubular part (20) along the longitudinal axis (X).

Description

Description Title: METHOD FOR MANUFACTURING A PLURALITY OF TURBOMACHINE BLADES technical field

[0001] This description relates to a method for manufacturing a plurality of turbomachine blades. Previous technique

[0002] To manufacture turbomachine blades, it is known to first produce a tubular part 20 (also called a "barrel") and then machine from it either blanks of turbomachine blades 10 or the complete turbomachine blades 10. As shown in Figure 1a, the tubular part 20 extends along a first axis A1 between a first end and a second end and has a thickness in the radial direction. The blades 10 can thus be machined from the thickness of the tubular part 20 by being arranged circumferentially, one after the other, around the first axis A1. Thus, as shown in Figure 1b, each blade 10 extends substantially parallel to the first axis A1.

[0003] Ideally, as shown in Figure 2, the radially internal face 24 of the tubular part 20 has, in a cross-sectional plane including the first axis A1, a straight profile 25 aligned with the first axis A1. However, the tubular part 20 is generally obtained by vertical centrifugal casting, which gives a parabolic profile to the internal face 24 of the tubular part 20. Thus, the tubular part 20 has a thickness ei that is greater at the first end than the thickness e2 at the second end. The tubular part 20 therefore includes a non-functional portion 22, or excess material, at the first end that does not contribute to the production of the blades. The non-functional portion 22 is therefore removed during the manufacturing of the blades 10, which reduces the efficiency of the manufacturing process. Summary

[0004] A manufacturing process for a plurality of turbomachine blades of a certain height is proposed, the process comprising: - to provide a mold comprising an internal cavity, the internal cavity being delimited by an internal lateral face of the mold which is axisymmetric about a longitudinal axis, the lateral face extending along the longitudinal axis to a height which is greater than or equal to the height of each blade, the lateral face defining a plurality of sections perpendicular to the longitudinal axis, each section of the lateral face having a radius, the lateral face of the mold being such that, for each section, the ratio between the height of the lateral face and the radius of the section is less than or equal to 2.0; - Position the mold so that its longitudinal axis is aligned with the gravitational field, - rotate the mold around the longitudinal axis at a rotation speed of between 200 rpm1 and 800 rpm 1 , - to pour a material into the internal cavity of the mold so as to form by centrifugation a tubular part extending along the longitudinal axis.

[0005] The resulting tubular part extends longitudinally from a lower end to an upper end, with a height that coincides with the height of the mold's lateral face. Furthermore, the tubular part has an external face that coincides with the mold's lateral face. This external face is axisymmetric about the longitudinal axis. The tubular part defines a plurality of sections perpendicular to the longitudinal axis. Each section of the tubular part is associated with a corresponding section of the mold's lateral face, which is located at the same longitudinal position. Each section of the tubular part has an external radius that coincides with the radius of the corresponding section of the mold's lateral face.

[0006] Furthermore, the resulting tubular part has an internal face that is substantially frustoconical around the longitudinal axis. In other words, the profile of the internal face of the tubular part in a cross-sectional plane including the longitudinal axis is essentially a straight line segment forming an angle with the longitudinal axis. Such a profile of the internal face of the tubular part makes it possible to reduce, or even eliminate, the amount of material forming a non-functional portion of the tubular part. The process therefore reduces the initial amount of material required to produce the multiple blades. In other words, the process improves the efficiency of manufacturing the multiple turbomachine blades.

[0007] The term "functional" used in reference to parts of a tubular component indicates whether the component thus qualified allows for the production of one or more blades. Thus, a functional part of the tubular component is a part that contains the blades with a limited material allowance (such allowance is on the order of a millimeter, preferably less than 10 mm, and even more preferably less than 5 mm). The functional part of the tubular component may have a profile in a cutting plane including the longitudinal axis that is parallelogram-shaped, with one side coinciding with the external face of the tubular component. In a particular configuration, the functional part of the tubular component has a rectangular profile in a cutting plane including the longitudinal axis. Conversely, the non-functional part is a The portion that does not participate in the production of the blades. Consequently, the amount of material forming this non-functional portion is lost during the blade manufacturing process. The non-functional portion may be located radially within the functional portion.

[0008] The side face of the mold can be such that, for each section, the ratio between the height of the side face and the radius of the section is between 0.5 and 1.5, preferably between 0.75 and 1.25, preferably also equal to 1.0.

[0009] The height of the side face of the mold can be between 150 mm and 2000 mm.

[0010] Each section of the mold's side face extends in a plane perpendicular to the longitudinal axis. Each section has a circular shape centered on the longitudinal axis.

[0011] The radius of each section of the mold's side face can be defined as the distance from the side face to the longitudinal axis in the plane perpendicular to the corresponding longitudinal axis of the section. The side face may comprise at least two sections with different radii. The radius of each section of the side face can be determined based on the section's longitudinal position on the side face, for example, according to a linear law. Alternatively, the radius of each section of the side face may be identical.

[0012] The radius of each section of the side face of the mold can be between 150 mm and 1500 mm.

[0013] Each section of the tubular part extends in a plane perpendicular to the longitudinal axis.

[0014] The external face of the tubular part may have, in each section of the tubular part, a circular shape centered on the longitudinal axis.

[0015] The external radius of each section of the tubular part can be defined as the distance from the outer face of the tubular part to the longitudinal axis in the plane perpendicular to the corresponding longitudinal axis of the section. The tubular part may comprise at least two sections with different external radii. The external radius of each section of the tubular part can be determined based on the longitudinal position of the section on the tubular part, for example, according to a linear law. Alternatively, the external radius of each section of the tubular part may be identical.

[0016] The inner face of the tubular part may have, in each section of the tubular part, a circular shape centered on the longitudinal axis.

[0017] Each cross-section of the tubular part can have an internal radius. The internal radius of each cross-section of the tubular part can be defined as the distance from the inner face of the tubular part to the longitudinal axis in the plane perpendicular to the corresponding longitudinal axis of the cross-section. The internal radius of each cross-section of the tubular part can be determined based on the longitudinal position of the cross-section on the tubular part, for example, according to a linear law.

[0018] The inner face of the tubular part [may have a frustoconical shape with a semi-angle at the apex defined by y=g / (w 2 (Reo-et))] where g is the acceleration due to gravity; co is the rotational speed of the mold around the longitudinal axis; Reo is the external radius of the tubular part's cross-section located at the lower end of the tubular part; and is a theoretical thickness that satisfies (et / (Reo-et)) <O,7.

[0019] The mold may include at least one tubular wall extending along the longitudinal axis. The tubular wall may include the lateral face. The tubular wall of the mold may extend along the longitudinal axis between a lower end and an upper end.

[0020] The resulting tubular part can have multiple sections perpendicular to the longitudinal axis. The process further includes determining the amount of material to be poured into the mold so that each section of the tubular part has a thickness greater than or equal to a theoretical thickness satisfying (et / (Reo - et))^0.7, where Reo is the external radius of the section of the tubular part located at a lower end of the tubular part. This ensures that the tubular part has sufficient thickness to manufacture a turbomachine blade regardless of the longitudinal position considered on the tubular part. In other words, it represents the minimum theoretical thickness for manufacturing a turbomachine blade regardless of the longitudinal position considered on the tubular part.

[0021] The thickness of each section of the tubular part can be considered in a radial direction with respect to the longitudinal axis. The thickness of each section of the tubular part can be defined as the difference between the external radius and the internal radius of the section.

[0022] The tubular part may comprise at least two sections with different thicknesses. Alternatively, the thickness of each section of the tubular part may be identical.

[0023] In particular, the thickness of the section of the tubular part which is located at the upper end of the tubular part may be greater than or equal to a theoretical thickness which satisfies (and / (Reo-and)) <O,7 où Reo est le rayon externe de la section de la pièce tubulaire qui est située au niveau d’une extrémité inférieure de la pièce tubulaire.

[0024] The functional portion of the tubular part can have, for each cross-section of the tubular part, a thickness considered in a radial direction with respect to the longitudinal axis. The thickness of the functional portion can be greater than or equal to the theoretical thickness for each cross-section of the tubular part.

[0025] The internal cavity of the mold can be delimited by an internal lower face of the mold and an internal upper face of the mold, the lower face and the upper face being respectively connected to a lower end and an upper end of the lateral face, the lower face and the upper face preferably each being perpendicular to the longitudinal axis.

[0026] The lower face and / or the upper face of the mold can each be axisymmetric around the longitudinal axis.

[0027] The mold may include a lower wall and an upper wall, each extending transversely to the longitudinal axis. The upper and lower walls may be connected to a lower and upper end, respectively, of the tubular wall of the mold. The lower and upper walls may include the inner lower face and the inner upper face, respectively. The upper wall may include an opening for pouring material into the internal cavity. The lower wall may be without an opening.

[0028] The lateral face of the mold can be generally cylindrical in revolution around the longitudinal axis. The rotational speed of the mold around the longitudinal axis can be between 600 rpm and 1000 rpm. 1 and 800 rpm 1. Such a process makes it possible to obtain a tubular part whose mass of the non-functional part is less than or equal to 5% compared to the mass of the functional part of the tubular part.

[0029] The lateral face of the mold can be generally frustoconical in revolution around the longitudinal axis, with a cross-section that decreases in the direction of the gravitational field when the mold is positioned with the longitudinal axis aligned with the gravitational field. The rotational speed of the mold around the longitudinal axis can be between 200 rpm and 1000 rpm. 1 and 400 rpm 1 , preferably between 300 rpm 1 and 400 rpm 1 This process makes it possible to obtain a tubular part in which the mass of the non-functional portion is less than or equal to 5% of the mass of the functional portion. Furthermore, this process advantageously offers a low mold rotation speed, which allows for reducing the power required to drive the mold in rotation around the longitudinal axis and therefore the energy consumption of the process. Also, this helps to avoid certain problems inherent in high rotational speeds such as vibrations, imbalances, or the limit of the mold's rotational speed.

[0030] The lateral face of the mold has a frustoconical shape with a semi-angle at the apex defined by p=g / (where 2 (Reo-e t )) where g is the acceleration due to gravity; co is the rotational speed of the mold around the longitudinal axis; Reo is the external radius of a section of the tubular part that is perpendicular to the longitudinal axis and is located at a lower end of the tubular part; and is a theoretical thickness that satisfies (et / (Reo-et)) <O,7.

[0031] The half-angle at the apex of the mold's lateral face is thus equal to the half-angle at the apex of the inner face of the tubular part. The thickness of each section of the tubular part is therefore identical, regardless of the section's longitudinal position. This allows for a further reduction, or even elimination, of the amount of material forming a non-functional portion of the tubular part.

[0032] The lateral face of the mold may include at least one annular relief formed around the longitudinal axis. Such an annular relief allows for the partial pre-forming of the turbomachine blades within the annular part.

[0033] The annular relief can be an annular groove formed in the lateral face of the mold. The annular relief can protrude radially from the lateral face of the mold.

[0034] The material poured into the mold can be a metallic alloy, preferably titanium aluminide (TiAl), and even more preferably a y-TiAl alloy. Titanium aluminide advantageously exhibits good mechanical strength at high temperatures and a low density.

[0035] The material poured into the mold can be a y-TiAl type alloy, and the process may further include heating the material to a temperature between 1550 °C and 1700 °C before pouring it into the mold. The material poured into the mold may be molten.

[0036] The process may further include machining the tubular part to produce the plurality of turbomachine blades. Brief description of the drawings

[0037] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:

[0038] Figure 1 schematically represents in perspective different stages of a known process for manufacturing a plurality of blades;

[0039] Figure 2 schematically represents in cross-section a tubular part used in the process of Figure 1;

[0040] Figure 3 is a functional diagram of a process for manufacturing turbomachine blades according to the present description;

[0041] Figure 4 schematically represents in perspective a mold used in the process of figure 3 according to a first embodiment;

[0042] Figure 5 schematically represents in cross-section the mold of figure 4 in the cutting plane IV-IV;

[0043] Figure 6 schematically represents in cross-section the mold of figure 4 in the cutting plane VV;

[0044] Figure 7 schematically represents in perspective a mold used in the process of figure 3 according to a second embodiment;

[0045] Figure 8 schematically represents in cross-section the mold of figure 7 in the cutting plane VII-VII;

[0046] Figure 9 schematically represents a variant of the mold according to the first embodiment of figure 4;

[0047] Figure 10 schematically represents a variant of the mold according to the second embodiment of Figure 7. Description of the implementation methods

[0048] Reference is now made to Figure 3. Figure 3 is a functional diagram of a process 100 for manufacturing a plurality of turbomachine blades 10. Each blade 10 is designed to extend between a foot and a tip (or heel) to have a height Ha.

[0049] The manufacturing process 100 includes a first step 110. The first step 110 includes the provision of a mold 30. Reference is made initially to figures 4 to 6 which represent a first embodiment of the mold 30.

[0050] The mold 30 comprises, firstly, a tubular wall 31 extending along a longitudinal axis X. In the following, orientation qualifiers, such as "longitudinal," "radial," or "circumferential," are defined with reference to the longitudinal axis X. The tubular wall 31 of the mold 30 extends along the longitudinal axis X between a lower end and an upper end. The mold 30 also comprises a lower wall 33 and an upper wall 32 extending transversely to the longitudinal axis X. The upper wall 32 and the lower wall 33 are respectively connected to the upper end and the lower end of the tubular wall 31 of the mold 30. The upper wall 32 and the lower wall 33 extend radially inwards from the tubular wall 31. In the example shown, the upper wall 32 and the lower wall 33 each extend perpendicularly to the longitudinal axis X.

[0051] The mold 30 also includes an internal cavity. The internal cavity is delimited by an internal lateral face 34 of the mold 30. The lateral face 34 is formed by the tubular wall 31. In other words, the lateral face 34 is an internal face of the tubular wall 31 of the mold 30. The lateral face 34 is particularly visible in Figures 5 and 6. The internal lateral face 34 of the mold 30 is axisymmetric about a longitudinal axis X. The lateral face 34 extends along the longitudinal axis X to a height Hf that is greater than the height Ha of each blade 10. The height Hf of the lateral face 34 of the mold 30 is between 150 mm and 2000 mm.

[0052] The lateral face 34 defines a plurality of sections 34i perpendicular to the longitudinal axis X. Figure 6 shows one of the sections 34i of the lateral face 34. Each section 34i of the lateral face 34 of the mold 30 extends in a plane perpendicular to the longitudinal axis X. Each section 34i therefore has a circular shape centered on the longitudinal axis X. Each section 34i of the lateral face 34 has a radius Rf s The RF radius s The radius of each section 34i of the lateral face 34 of the mold 30 is defined as the distance separating the lateral face 34 from the longitudinal axis X in the plane perpendicular to the corresponding longitudinal axis X of section 34i. The radius Rf s of each section 34i of the lateral face 34 of the mold 30 is between 150 mm and 1500 mm.

[0053] Remarkably, according to the first embodiment, the lateral face 34 of the mold 30 is generally cylindrical in revolution about the longitudinal axis X. In other words, the radius Rf s of each section 34i of the lateral face 34 is identical.

[0054] The lateral face 34 of the mold 30 is such that, for each section 34i, the ratio between the height Hf of the lateral face 34 and the radius Rf s of section 34i is less than or equal to 2.0. The lateral face 34 of the mold 30 can be such that, for each section 34i, the ratio between the height Hf of the lateral face 34 and the radius Rf s of section 34i is between 0.5 and 1.5, preferably between 0.75 and 1.25, preferably also equal to 1.0.

[0055] The internal cavity of the mold 30 is further delimited by an internal lower face 36 of the mold 30 and an internal upper face 35 of the mold 30. The lower face 36 and the upper face 35 are formed respectively by the lower wall 33 and the upper wall 32. In other words, the lower face 36 and the upper face 35 are each an inner face respectively of the lower wall 33 and the upper wall 32. The lower face 36 and the upper face 35 are respectively connected to a lower end and an upper end of the lateral face 34. In the illustrated example, the lower face 36 and the upper face 35 are preferably each perpendicular to the longitudinal axis X. Thus, the lower face 36 and the upper face 35 of the mold 30 are here axisymmetric about the longitudinal axis X.

[0056] The manufacturing process 100 includes a second step 120. The second step 120 includes the positioning of the mold 30 so that the longitudinal axis X is aligned with the gravitational field g. The mold 30 is therefore positioned with the longitudinal axis X extending vertically.

[0057] The manufacturing process 100 includes a third step 130. The third step 130 includes driving the mold 30 in rotation around the longitudinal axis X with a rotational speed œ between 200 rpm 1 and 800 rpm 1 .

[0058] The manufacturing process 100 includes a fourth step 140. The fourth step 140 includes pouring a material into the internal cavity of the mold 30 so as to form by centrifugation a tubular part 20 extending along the longitudinal axis X. The tubular part 20 obtained is also visible in figures 5 and 6.

[0059] The tubular part 20 extends longitudinally between a lower end and an upper end with a height Hp which coincides with the height Hf of the lateral face 34 of the mold 30. Furthermore, the tubular part 20 has an external face 23 which coincides with the lateral face 34 of the mold 30. The external face 23 of the tubular part 20 is axisymmetric about the longitudinal axis X.

[0060] The tubular part 20 defines a plurality of sections 20i perpendicular to the longitudinal axis X. Each section 20i of the tubular part 20 extends in a plane perpendicular to the longitudinal axis X. Each section 20i of the tubular part 20 is associated with a corresponding section 34i of the lateral face 34 of the mold 30, which is located at the same longitudinal position. The external face 23 of the tubular part 20 therefore has, in each section 20i of the tubular part 20, a circular shape centered on the longitudinal axis X. In other words, each section 20i of the tubular part 20 has an external radius Rep s which coincides with the radius Rf s of the corresponding section 34i of the lateral face 34 of the mold 30. The external radius Rep sThe radius of each section 20i of the tubular part 20 is defined as the distance separating the external face 23 of the tubular part 20 from the longitudinal axis X in the plane perpendicular to the corresponding longitudinal axis X of the section 20i. According to the first embodiment, the external radius Rep s of each section 20i of the tubular part 20 is identical.

[0061] Moreover, due to the rotational speed œ of the mold 30 around the longitudinal axis X and the predetermined ratio between the height Hf of the lateral face 34 and the radius Rf s In each section 34i, the tubular part 20 has an internal face 24 that is substantially frustoconical about the longitudinal axis X. The internal face 24 of the tubular part 20 therefore has, in each section 20i of the tubular part 20, a circular shape centered on the longitudinal axis X. Each section 20i of the tubular part 20 has an internal radius Rip sThe internal Rip radius s of each section 20i of the tubular part 20 can be defined as the distance separating the inner face 24 of the tubular part 20 from the longitudinal axis X in the plane perpendicular to the corresponding longitudinal axis X of the section 20i.

[0062] The inner face 24 of the tubular part 20 has a frustoconical shape with a half-angle at the apex defined by y=g / (w 2 (Reo-et)) where g is the acceleration due to gravity; co is the rotational speed of the mold 30 around the longitudinal axis X; Reo is the external radius of the section 20i of the tubular part 20 located at the lower end of the tubular part 20; and is a theoretical thickness which satisfies (et / (Reo- et))^0.7.

[0063] In other words, as can be seen in Figure 5, the profile of the inner face 24 of the tubular part 20 in a cutting plane including the longitudinal axis X is a straight line segment forming an angle equal to half the angle y with the longitudinal axis X.

[0064] The Rip internal radius s For each section, 20i evolves linearly along the longitudinal axis X, according to the Rip relation s (z)=Rip s (0)+tan(y)*z where Rips(z) is the internal radius of a given section 20i; Rips(0) is the internal radius of section 20i of tubular part 20 located at the lower end of tubular part 20; z the height of section 20i given on tubular part 20.

[0065] The Rip internal radius s For each section 20i, it can evolve linearly along the longitudinal axis X, according to the Rip relation. s (z)=Rip s (0)+y*z.

[0066] A term "functional" used in reference to parts of the tubular component 20 indicates whether the part thus qualified allows for the production of one or more blades 10. Thus, the tubular component 20 includes a functional part 21 which contains the blades 10 with a limited excess material (such excess material is on the order of a millimeter, preferably less than 10 mm, and even more preferably less than 5 mm). The functional part 21 of the tubular component 20 has a profile in a cutting plane including the longitudinal axis X, which has the shape of a rectangle, one side of which coincides with the external face 23 of the tubular part 20. The tubular part 20 includes a non-functional part 22 which does not participate in the making of the blades 10. The non-functional part 22 is located radially inside the functional part 21.

[0067] Such a profile of the inner face 24 of the tubular part 20 makes it possible to reduce, or even eliminate, the amount of material forming a non-functional part 22 of the tubular part 20. The process 100 therefore makes it possible to reduce the initial amount of material required to obtain the plurality of blades 10. In other words, the process 100 improves the efficiency of the manufacture of the plurality of turbomachine blades 10.

[0068] The fourth step 140 further includes determining the quantity of material to be poured into the mold 30 so that each section 20i of the tubular part 20 has a thickness e s which is greater than or equal to a theoretical thickness and which satisfies (et / (Re0-et))^0.7. This ensures that the tubular part 20 has sufficient thickness to manufacture a turbomachine blade 10 regardless of the longitudinal position considered on the tubular part 20. Preferably, the thickness e sThe thickness of each section 20i of the tubular part 20 is approximately equal to the theoretical thickness. The thickness e s of each section 20i of the tubular part 20 is considered in a radial direction with respect to the longitudinal axis X. The thickness e s of each section 20i of the tubular part 20 is defined as the difference between the external radius Rep s and the inner radius Rip s of section 20i. According to the first embodiment, the thickness e s of each section 20i of the tubular part 20 is different in thickness e s of each other section 20i.

[0069] In particular, the thickness eh of the section 20i which is located at the upper end of the tubular part 20 is equal to the theoretical thickness and which satisfies (et / (Reo- et))^0.7 where Reo is the external radius of the section 20i of the tubular part 20 which is located at a lower end of the tubular part 20.

[0070] Furthermore, the functional part 21 of the tubular part 20 has, for each section 20i of the tubular part 20, a thickness considered in a radial direction with respect to the longitudinal axis X. The thickness of the functional part 21 is here equal to the theoretical thickness and for each section 20i of the tubular part 20.

[0071] Advantageously, the rotation speed of the mold 30 around the longitudinal axis X is between 600 rpm 1 and 800 rpm 1It is thus possible to obtain a tubular part 20 whose mass of the non-functional part 22 is less than or equal to 5% with respect to the mass of the functional part 21 of the tubular part 20.

[0072] The material cast in mold 30 is a y-TiAL type metal alloy. Such a material advantageously exhibits good mechanical resistance at high temperature and low density.

[0073] The fourth step 140 also includes heating the material to a temperature between 1550 °C and 1700 °C to be poured into the mold 30. The material poured into the mold 30 is thus molten, which facilitates pouring.

[0074] The process 100 includes a fifth step 150. This fifth step 150 comprises the production of a plurality of turbomachine blades 10 in the tubular part 20, specifically in the functional portion 21 of the tubular part 20. To accomplish this, the tubular part 20 may be machined. The machining may first include the removal (if necessary) of the non-functional portion 22. The machining may then include the production of blades 10 in the functional portion 21.

[0075] Figures 7 and 8 represent the mold 30 used in the process 100 as described above according to a second embodiment. The mold 30 according to the second embodiment differs from the mold 30 according to the first embodiment in that the lateral face 34 of the mold 30 is generally frustoconical in revolution about the longitudinal axis X with a cross-section that decreases in the direction of the gravitational field when the mold 30 is positioned with the longitudinal axis X aligned with the gravitational field.

[0076] Thus the Rf radius s the radius of each section 34i of the lateral face 34 is different from the radius Rf s of each other section 34i of the lateral face 34. In particular, the radius Rf s for each section 34i of the lateral face 34 decreases linearly along the longitudinal axis X in the direction of the gravitational field.

[0077] Here too, the external face 23 of the tubular part 20 coincides with the lateral face 34 of the mold 30. The external face 23 of the tubular part is therefore generally frustoconical in revolution about the longitudinal axis X, with a cross-section that decreases in the direction of the gravitational field when the mold 30 is positioned with the longitudinal axis X aligned with the gravitational field. Therefore, the external radius Rep s of each section 20i of the tubular part 20 is different from the external radius Rep s of each other section 20i of the tubular part 20. In particular, the external radius Rep s for each section 20i of the tubular part 20 decreases linearly along the longitudinal axis X in the direction of the gravitational field.

[0078] Advantageously, the rotation speed of the mold 30 according to the second embodiment around the longitudinal axis X is here between 200 rpm 1 and 400 rpm 1, preferably between 300 rpm 1 and 400 rpm 1 . Such a process 100 makes it possible to obtain a tubular part 20 whose mass of the non-functional part 22 is less than or equal to 5% compared to the mass of the functional part 21. In addition, such a process 100 advantageously presents a low rotation speed of the mold 30, which makes it possible to reduce the power required to drive the mold 30 in rotation around the longitudinal axis X and therefore the energy consumption of the process 100.

[0079] Furthermore, the lateral face 34 of the mold 30 has a frustoconical shape with a semi-angle at the apex defined by p=g / (where 2 (Reo-e t )) where g is the acceleration due to gravity; co is the rotational speed of the mold 30 around the longitudinal axis X; Reo is the external radius of section 20i located at the lower end of tubular part 20; and and is a theoretical thickness that satisfies (et / (Reo-et)) <O,7.

[0080] The half-angle P at the apex of the lateral face 34 of the mold 30 is thus equal to the half-angle y at the apex of the internal face 24 of the tubular part 20. The thickness e s The thickness of each section 20i of the tubular part 20 is thus identical, regardless of the longitudinal position of the section on the tubular part 20. The tubular part therefore has a constant radial thickness Hf over its entire height. In this case, this makes it possible to eliminate the non-functional part 22 of the tubular part 20. In other words, using the mold according to the second embodiment makes it possible to obtain a tubular part 20 without a non-functional part 22. In this instance, for each section, the thickness e sof the tubular part 20 is equal to the thickness of the functional part 21, i.e. in the present case to the theoretical thickness and.

[0081] Also remarkably, the functional part 21 of the tubular part 20 has, in the second embodiment, a profile in a cutting plane including the longitudinal axis X which has a parallelogram shape, one of whose sides coincides with the external face 23 of the tubular part 20.

[0082] The tubular wall 31 of the mold also has an external face 37. The external face 37 of the tubular wall 31 advantageously has a frustoconical shape. In particular, according to the example shown, the external face 37 of the tubular wall 31 has a frustoconical shape in which half the apex angle is equal to half the apex angle P of the lateral face 34. This ensures constant heat extraction along the height of the mold.

[0083] Figures 9 and 10 each represent a variant, respectively, of mold 30 according to the first embodiment and mold 30 according to the second embodiment. In each of these variants, the lateral face 34 of mold 30 comprises a first relief and a second relief, each formed annularly around the longitudinal axis X. Such Annular reliefs allow for the partial preforming of the turbomachine blades 10 within the annular part. The first annular relief 38 and the second relief are each an annular groove formed in the lateral face 34 of the mold 30. The first annular relief 38 is located near the lower end of the lateral face 34. The second annular relief 37 is located near the upper outer edge of the lateral face 34. The first annular relief 38 is intended to preform the root of each blade 10, and the second annular relief 37 is intended to preform the tip of each blade 10.

Claims

Demands

1. A method (100) for manufacturing a plurality of turbine blades (10) of height (Ha), the method comprising: - to provide a mold (30) comprising an internal cavity, the internal cavity being delimited by an internal lateral face (34) of the mold which is axisymmetric about a longitudinal axis (X), the lateral face (34) extending along the longitudinal axis (X) to a height (Hf) which is greater than or equal to the height (Ha) of each blade (10), the lateral face (34) defining a plurality of sections (34i) perpendicular to the longitudinal axis (X), each section (34i) of the lateral face (34) having a radius (Rf s ), the lateral face (34) of the mold (30) being such that, for each section (34i), the ratio between the height (Hf) of the lateral face (34) and the radius (Rf s ) of section (34i) is less than or equal to 2.0; - position the mold (30) so that the longitudinal axis (X) is aligned with the gravitational field (g), - rotate the mold (30) around the longitudinal axis (X) with a rotation speed (OÜ) between 200 rpm 1 and 800 rpm 1 , - pouring a material into the internal cavity of the mold (30) so as to form by centrifugation a tubular part (20) extending along the longitudinal axis (X).

2. A method (100) according to the preceding claim, wherein the resulting tubular part (20) has a plurality of sections (20i) perpendicular to the longitudinal axis (X), the method further comprising determining the quantity of material to be poured into the mold (30) so that each section (20i) of the tubular part (20) has a thickness (e s) which is greater than or equal to a theoretical thickness (and) which satisfies (and / (Reo-and)) <O,7 où Reo est le rayon externe de la section de la pièce tubulaire (20) qui est située au niveau d’une extrémité inférieure de la pièce tubulaire (20).

3. A method according to any one of the preceding claims, wherein the internal cavity of the mold (30) is delimited by an internal lower face (36) of the mold (30) and an internal upper face (35) of the mold, the lower face (36) and the upper face (35) being respectively connected to a lower end and an upper end of the lateral face (34), the lower face (36) and the upper face (35) preferably each being perpendicular to the longitudinal axis (X).

4. A method (100) according to any one of the preceding claims, wherein the lateral face (34) of the mold (30) is generally cylindrical of revolution about the longitudinal axis (X), and wherein the rotational speed (œ) of the mold (30) about the longitudinal axis (X) is between 600 rpm 1 and 800 rpm 1 .

5. A method (100) according to any one of claims 1 to 3, wherein the lateral face (34) of the mold (30) is globally frustoconical in revolution about the longitudinal axis (X) with a cross-section that decreases in the direction of the gravitational field (g) when the mold (30) is positioned with the longitudinal axis (X) aligned with the gravitational field (g), and wherein the rotational speed (œ) of the mold (30) about the longitudinal axis (X) is between 200 rpm 1 and 400 rpm 1 .

6. A method (100) according to the preceding claim, wherein the lateral face (34) of the mold (30) has a frustoconical shape with a half-angle (P) at the apex defined by p=g / (w 2 (Reo-et)) where g is the acceleration due to gravity; co is the rotational speed of the mold around the longitudinal axis; Reo is the external radius of a section of the tubular part that is perpendicular to the longitudinal axis and is located at a lower end of the tubular part; and is a theoretical thickness that satisfies (et / (Reo-et)) <o,7.

7. Method (100) according to any one of the preceding claims, wherein the lateral face (34) of the mold (30) comprises at least one relief (37; 38) formed annularly around the longitudinal axis (X).

8. A method (100) according to any one of the preceding claims, wherein the material cast in the mold (30) is a metal alloy, preferably a titanium aluminide (TiAl), more preferably a y-TiAl type alloy.

9. A method (100) according to any one of the preceding claims, wherein the material cast in the mold (30) is a y-TiAl type alloy, the method further comprising heating the material to a temperature between 1550 °C and 1700 °C for casting in the mold (30).

10. Method (100) according to any one of the preceding claims, the method further comprising machining the tubular part (20) to produce the plurality of turbomachine blades (10).

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