Core for metal casting an aeronautical part

Abstract

A core for the foundry of an aeronautical part such as a turbine blade, the core being intended to be disposed in an inner housing defined by a mold, the core comprising a body intended to form the internal shape of the turbine blade, an impact portion, disposed on at least a portion of the periphery of the body so as to break a fluid jet when filling the inner housing with the fluid, the impact portion comprising a top and at least one deflection wall converging towards the top.

Claims

1. A core for the foundry of an aeronautical part such as a turbine blade, the core being intended to be disposed in an inner housing defined by a mold, the core comprising: a body intended to form the internal shape of the aeronautical part, wherein the body has a longest dimension extending along a longitudinal axis, an impact portion, intended to form a sacrificial portion that will be cut, disposed on at least a portion of the periphery of the body so as to break a fluid jet when filling the inner housing with the fluid, the impact portion comprising a base, a top and at least one deflection wall converging from the base to the top, the impact portion being positioned at a longitudinal end of the core along the longitudinal axis, wherein an outermost surface in the longitudinal axis of the impact portion is rounded and the slope of the at least one deflection wall in at least one plane normal to the base and passing through the top has several values, wherein the impact portion faces a fluid inlet of the inner housing; and wherein an entirety of a portion of the core forming the aeronautical part is not in direct contact with the mold.

2. The core according to claim 1, wherein the impact portion extends continuously from the body.

3. The core according to claim 1, wherein the slope of the at least one deflection wall is lower in the vicinity of the top than the slope in the vicinity of a base of the impact portion.

4. The core according to claim 3, wherein the impact portion and the body are connected at least by a plurality of shanks.

5. The core according to claim 1, wherein the impact portion has a height comprised between 100% and 1,000% of the width of the core.

6. The core according to claim 5, wherein the impact portion and the body are connected at least by a plurality of shanks.

7. The core according to claim 1, wherein the body and the impact portion are formed integrally.

8. The core according to claim 1, wherein the impact portion and the body are connected at least by a plurality of shanks.

9. The core according to claim 1, wherein the impact portion has a height of between 100% and 1,000% of the width of the core, and the impact portion and the body are connected at least by a plurality of shanks.

10. The core according to claim 1, wherein the core is disposed in the inner housing defined by the mold, wherein the body forms the internal shape of the aeronautical part, and wherein, according to all the planes normal to the base and passing through the top, the slope of the deflection wall has several values, decreasing as they approach the top, wherein the tangent to the deflection wall in the vicinity of the base is vertical, and wherein, in the vicinity of the top, the tangent to the deflection wall is horizontal.

11. The core according to claim 1, wherein the body forms the internal shape of the aeronautical part.

12. A foundry device for a turbine blade, comprising: a mold defining an inner housing, the inner housing comprising a fluid inlet; a core according to claim 1, disposed inside the inner housing.

13. A method for producing the core according to claim 1 the method for producing the core comprising the following steps: designing a core pattern comprising the provision of the body of the core, whose geometry corresponds to the internal shape of the aeronautical part, and the generation of an impact portion, and manufacturing the core based on the pattern.

14. The method according to claim 13, wherein the step of generating the impact portion comprises an extrusion sub-step consisting of forming a prism from the body, the prism extending from the base, and a sub-step of cutting the prism.

15. The method according to claim 14, wherein, the step of generating the impact portion further comprises a sub-step of radiating the sharp edges after the sub-step of cutting the prism.

16. The method according to claim 13, wherein the step of generating the impact portion is carried out by Computer-Aided Design software.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The object of the present disclosure and its advantages will be better understood upon reading the following detailed description of embodiments of the invention given by way of non-limiting examples. This description refers to the appended drawings, in which:

(2) FIG. 1 represents a device for molding a turbine blade comprising a core of the prior art;

(3) FIG. 2 represents a device for molding a turbine blade comprising the core according to the present disclosure;

(4) FIG. 3 represents a core according to the present disclosure;

(5) FIG. 4 represents a close-up view of the impact portion;

(6) FIGS. 5A and 5B represent different embodiments of the impact portion;

(7) FIG. 6 represents an embodiment of the connection between the body and the impact portion;

(8) FIGS. 7A and 7B represent other embodiments of the connection between the body and the impact portion;

(9) FIGS. 8A to 8C represent steps of producing the impact portion of the core.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIG. 2 represents a molding device 1, suitable for the turbine blade foundry in this example. The molding device 1 comprises a mold, here a molding shell 3, defining an inner housing 5. Indeed, the exemplary embodiments represented in the figures relate more particularly to the casting of metal in a shell mold. The molding device 1 further comprises a core 7 disposed inside the inner housing 5.

(11) Core 7 has an elongated shape and extends along a main direction DP. The inner housing 5 and therefore the molding shell 3, also have an elongated shape and extend along the same main direction DP. Thus, the inner housing 5 comprises a first end area 5A and a second end area 5B.

(12) The inner housing 5 comprises a fluid inlet 9, allowing the casting of fluid in the molding device 1 so as to mold a turbine blade. The fluid inlet 9 opens onto the first end area 5A, substantially in the main direction DP.

(13) For example, the core 7 is composed of a refractory material relative to the cast or injected fluid. For example, the core 7 is made of ceramic or metal with a high melting point that is to say with a melting point above 1,500° C.

(14) The core 7, represented in more detail in FIG. 3, comprises a body 13, at least part of which is intended to form the internal shape of the turbine blade, in other words its inner cavities, that is to say the at least part of the body 13 constitutes the useful portion of the core 7. The body 13 has an elongated shape and extends along the main direction DP. The body 13 comprises a first end portion 13A, intended to form the tip of the turbine blade, and a second end portion 13B, intended to form the cavity of the turbine blade root. The first and second end portions form two blocks connected by a plurality of arms 13C. The arms 13C are intended to form the ventilation cavities of the blade.

(15) The core 7 further comprises an impact portion 15, disposed on one side of the body 13. More specifically, the impact portion 15 is disposed as a continuation of the first end portion 13A of the body 13 along the main direction DP. In this example, the first end portion 13A of the body 13 is intended to form the tip of the turbine blade. Thus, the impact portion 15 is disposed facing the fluid inlet 9 so as to break a fluid jet upon casting the fluid in the molding device 1.

(16) The impact portion 15 comprises a base 21, a top 17 and a deflection wall 19 converging from the base 21 to the top 17, the deflection wall 19 extending as a continuation of the wall of the body 13. In this example, as can be seen in FIG. 2, the top 17 is not disposed facing the fluid inlet 9. The fluid jet is therefore here broken by a lateral part of the impact portion 15.

(17) In the present example, as can be seen in FIG. 2, the fluid jet arrives from the bottom of the molding device 1, that is to say the fluid jet arrives substantially in the opposite direction of the direction of gravity. In other words, the casting is carried out at the source. The first end area 5A is therefore disposed at the bottom of the inner housing 5 along the direction of gravity. However, in other exemplary embodiments, the fluid inlet 9 could be disposed at the top of the inner housing 5, that is to say the fluid jet is directed in the direction of gravity. In this case, the impact portion is disposed at the top of the molding device, facing the fluid inlet.

(18) FIG. 2 also represents a baffle 10 which opens onto the first end area 5A. The baffle 10 serves as a grain selector, making it possible to direct the solidification of the final aeronautical part, which is monocrystalline or columnar. In the case of a source metal casting, the baffle can also serve as a metal supply system, that is to say the casting also takes place via the baffle 10.

(19) The top 17 has a rounded shape, in the exemplary embodiment represented, visible in FIGS. 3 and 4 for example. The height between the base 21 and the top 17 of the impact portion 15 along the main direction DP is approximately of 17 mm. The greatest width of the impact portion 15, at the top 17 is, for example, of about 6 mm.

(20) According to all the planes normal to the base 21 and passing through the top 17, the slope of the deflection wall 19 has several values, decreasing as they approach the top 17. The impact portion 15 therefore has a substantially domed shape. The tangent to the deflection wall 19 in the vicinity of the base 21 is generally collinear with the main direction DP that is to say, in the represented example, generally vertical. While moving towards the top 17, the tangent to the deflection wall 19 tilts relative to the main direction. In the vicinity of the top 17, the tangent to the deflection wall 19 is generally perpendicular to the main direction DP, that is to say, in the represented example, generally horizontal.

(21) FIG. 3 shows the useful portion of the core 1, between the dotted lines. It can be seen that the impact portion is located out of the useful portion of the core 7. It can also be seen that part of the second end portion 13B is located out of the useful portion of the core 7. Indeed, this part is engaged in elements for receiving the molding shell so as to hold the core 7 in position upon casting the fluid. These parts of the core 7 disposed out of the useful area allow simplifying the removal of the core from the final turbine blade. Indeed, when the material is solidified to form the turbine blade, there is more room for cutting the metal while also cutting part of the core 7. As a portion of the core 7 is cut, it is easier, after the chemical knock-out of the core 7, to remove dust from the molded turbine blade.

(22) The core 7 comprises two dimensioning housings 23. One of the dimensioning housings 23 is arranged in the impact portion 15. The other of the dimensioning housings 23 is disposed in the second end portion 13B of the body 13. The dimensioning housings 23 allow checking the correct sizing of the core 7 during its manufacture. The dimensioning housings 23 are disposed out of the useful area.

(23) As represented in FIG. 3, the core comprises shanks 24, for example made of alumina, further making it possible to create dust removal holes for the turbine blade. The first end portion 13A of the core 13 comprises holes 25 opening out onto the shanks 24 and thus giving access to the shanks 24 from the first end portion 13A.

(24) The impact portion 15 and/or the first end portion 13A of the body 13 may be solid, as represented in FIG. 5A. However, the stresses on the core 7 during cooling of the material can be significant. The core could therefore break and the material could experience recrystallization defects.

(25) Thus, it is also possible to provide that the impact portion 115 and/or the first end portion 113A of the body 113 is/are hollow, as represented in FIG. 5B. Thus, upon cooling of the material, a portion of the deflection wall 119 close to the base 121 and/or the wall of the first end portion 113A of the body 113 may shatter and thus relieve the stresses in the solidifying material. The impact portion 115 and/or the first end portion 113A of the hollow body 113 may be produced by an additive process, for example by using inserts, removed during the firing of the core 7.

(26) The body 13 and the impact portion 15 can be formed integrally, in one piece, for example injected or produced by additive manufacturing together. The impact portion 215 can also be added onto the core 7 and fixed by any means, for example by welding, gluing, co-sintering or fitting. For example, as represented in FIG. 6, the first end portion 213A of the body 213 is hollow and forms a fixing space 229. The first end portion 213A of the core 213 comprises pads 231 extending along the main direction DP. The pads 231 each comprise a central cavity, also extending along the main direction DP. The impact portion 215 comprises rods 235 fixed to the base 21 and extending along the main direction DP. The rods 235 are configured to be inserted into the cavities of the pads 231. An adhesive point 239 is disposed at the bottom of each cavity and allows retaining the impact portion 215 on the body 213. This configuration allows trapping the glue such that it does not contaminate the material. In order to avoid stresses on the walls of the fixing space 229 due to an expansion of air in the fixing space 229 during the casting of fluid in the molding device, it is possible to put the fixing space 29 under vacuum.

(27) Alternatively, as represented in FIG. 7A, instead of being fixed by an adhesive point, the impact portion 315 and the body can be fixed by a plurality of the shanks 324. In this exemplary embodiment, the shanks 324 extend through each of the pads 331 and rods 335. In this example, the rods 335 are still inserted into the cavities of the pads 331.

(28) On the other hand, in a variant of this example represented in FIG. 7B, the pads 431 and the rods 435 do not cooperate and are connected only through the shanks 424. The roughness of the shanks 424 then ensures holding the impact portion 415 on the body 413.

(29) The core 7 is made from a pattern which is then used for the actual manufacture of the core 7. The pattern is generally digital and produced by Computer-Aided Design (CAD). The design of this pattern will now be described with reference to FIGS. 8A, 8B and 8C.

(30) First, a prism is extruded from a core body pattern, which is provided. This prism is represented in FIG. 8A. The prism is extruded as a continuation of the wall of the core body pattern. Then, the prism is cut along a curve. The cut prism is represented in FIG. 8B.

(31) Then, the cut prism is radiated. The edges are radiated so as to obtain a dome shape, as represented in FIG. 8C, and thus form the impact portion pattern 15.

(32) Then, when the pattern of the core, and therefore of its impact portion is designed, the step of manufacturing the core is carried out. The core is generally manufactured by injection from a mold. The body and the core can also be manufactured in two parts, from their respective pattern, and injected separately using molds.

(33) Although the present invention has been described with reference to specific exemplary embodiments, modifications can be made to these examples without departing from the general scope of the invention as defined by the claims. Particularly, individual characteristics of the different illustrated/mentioned embodiments can be combined in additional embodiments. Consequently, the description and the drawings should be considered in an illustrative rather than a restrictive sense.