FR2962482A1 - Massive piece i.e. metallic stiffening piece, forming method for e.g. composite fan blade of turbojet engine in helicopter, involves isostatically hot-pressing fibrous structure to cause agglomeration of strands to obtain massive piece - Google Patents

Abstract

The method involves forming a three-dimensional fibrous structure (300) by weaving metal strands (301) formed of a set of metal bits twisted with each other around a longitudinal axis of each metal strand, where diameter of each bit is smaller than 0.1 mm. The fibrous structure is isostatically hot-pressed to cause agglomeration of the metal strands of the fibrous structure to obtain a massive piece, where the strands are made from titanium or different materials. An independent claim is also included for a fibrous structure formed by weaving of metal strands.

Description

PROCESS FOR PRODUCING A MASSIVE PIECE

The present invention relates to a method for producing a solid piece, such as for example a metal reinforcement of turbomachine blade. More particularly, the invention relates to a method for producing a turbomachine blade leading edge metal reinforcement. The field of the invention is that of turbomachines and more particularly that of the fan blades, made of composite or metallic material, of a turbomachine and whose leading edge comprises a metallic structural reinforcement. However, the invention is also applicable to the production of a metal reinforcement intended to reinforce a leading edge or a blade trailing edge of any type of turbomachine, whether terrestrial or aeronautical, and in particular a helicopter turbine engine or an airplane turbojet engine but also propellers such as propellers of double blowers contrarotative unducted ("open rotor" in English). The invention is also applicable to the realization of all massive pieces of complex geometric shape.

It is recalled that the leading edge corresponds to the front part of an airfoil which faces the airflow and which divides the airflow into an intrados airflow and a flow of air. extrados air. The trailing edge corresponds to the posterior part of an aerodynamic profile where the intrados and extrados flows meet.

The turbomachine blades, and in particular the fan blades, undergo significant mechanical stress, particularly related to the speed of rotation, and must meet strict conditions of weight and bulk. As a result, blades made of composite materials are used which are lighter and have better heat resistance.

It is known to equip the fan blades of a turbomachine, made of composite materials, with a metallic structural reinforcement extending over the entire height of the blade and beyond their leading edge as mentioned in EP1908919. Such a reinforcement makes it possible to protect the composite blading during an impact of a foreign body on the blower, such as, for example, a bird, hail or pebbles. In particular, the metallic structural reinforcement protects the leading edge of the composite blade by avoiding risks of delamination, fiber breakage or damage by fiber / matrix decohesion.

In a conventional manner, a turbomachine blade has an aerodynamic surface extending, in a first direction, between a leading edge and a trailing edge and, in a second direction substantially perpendicular to the first direction, between a foot and a dawn summit. The metallic structural reinforcement follows the shape of the leading edge of the aerodynamic surface of the blade and extends in the first direction beyond the leading edge of the aerodynamic surface of the blade to match the profile of the blade. the intrados and the upper surface of the dawn and in the second direction between the foot and the top of the dawn. In known manner, the metal structural reinforcement is a titanium metal part made entirely by milling from a block of material. However, the metal reinforcement of a blade leading edge is a complex piece to achieve, requiring many rework operations and complex tools involving significant realization costs. It is known to produce massive parts, including turbomachine blade metal reinforcements from a three-dimensional metal fiber structure made by weaving metal son and a hot isostatic pressing process in a tool causing the agglomeration of the metal son of the metal fibrous structure so as to obtain a massive piece; this process is described in the patent application FR0858098. Conventionally, the weaving of the fibrous structure is carried out by weaving by means of a plurality of warp threads and metal weft threads whose thread diameter is of the order of a few tenths of a millimeter, typically between 0.05mm and 0.3mm. The weaving of the fibrous structure becomes complex and difficult, or even difficult to achieve, since it is desired to produce a thicker metal fibrous structure, that is to say with larger diameter metal wires, typically of diameter. greater than 0.4 mm. Indeed, it becomes significantly more difficult to obtain a sufficient deformation of the warp and weft son to achieve the weaving with son, especially titanium, diameter greater than 0.4 mm. One solution to reduce the rigidity of the son is to perform a heat treatment of the son so as to lower their rigidity. However, this heat treatment under oxygen is not applicable on titanium son because it leads to oxidation of titanium son which degrades the quality of the part made by hot isostatic pressing. To remedy this drawback, one solution consists in carrying out a heat treatment under vacuum, that is to say in the absence of oxygen. This solution makes it possible to overcome the problems of oxidation of titanium but on the other hand causes difficulties of implementation and handling because all operations must be carried out under vacuum. Finally, the use of small diameter threads (ie less than 0.4 mm) requires the production of numerous fibrous (thin) structures by weaving, then superimposing them on each other in a tool so as to obtain a sufficient thickness for producing the part by hot compaction. The larger the workpiece, the greater the number of fibrous structures required for producing the workpiece, which consequently increases the number of operations and consequently the cost of producing such a workpiece.

In this context, the invention aims to solve the problems mentioned above, by proposing a production method for producing massive pieces of complex shape several millimeters thick quickly and simply, while simplifying the range of manufacturing and reducing the costs of producing such a piece.

To this end, the invention proposes a method for producing a solid piece comprising successively: a step of weaving a three-dimensional fibrous structure by weaving, said weaving being made from metal strands formed by a plurality of metal strands; twisted together around the longitudinal axis of the strand; a step of hot isostatic pressing of said fibrous structure causing the agglomeration of the metal strands of said fibrous structure so as to obtain a massive piece. Wire strand means a set of metal strands twisted together to form a wire rope. By massive piece is meant a one-piece piece having no hollow part and no attached part. Thanks to the invention, it is possible to produce a massive piece of complex shape, such as a turbomachine blade reinforcement which is a twisted and arched piece, simply and quickly from a weaving of a fibrous structure forming a preform of the metal reinforcement and a method of pressing or hot isostatic pressing (HIP) to obtain a compact piece without porosity by the combination of plastic deformation, creep and diffusion welding. With the method according to the invention, the fibrous structure is a flexible structure, easily deformable manually. The fibrous structure can also be plastically deformed manually, for example by folding, which allows to manually shape cold (i.e at room temperature) the fibrous structure when it is put into place in the tooling. The manual cold deformation of the fibrous structure makes it possible to dispense with a thermal deformation which is a source of oxygen oxidation of the titanium strands as well as of any complexity in the handling and handling of the titanium part during a thermal deformation under empty. The weaving of the fibrous structure by means of flexible strands also makes it possible to overcome the problems of significant springback due to the stiffness of the titanium-based yarns with a diameter greater than 0.4 mm.

Thus, the deformation of the flexible fibrous structure is achieved without the use of a folder, without the need to use a cold forging and / or hot with the tool so as to impose a particular angle to the fibrous structure. This production method makes it possible to generate the manufacture of complex parts by producing preforms woven into metal strands with cost reduction, in particular by reducing the number of operations required to produce such a part. The massive part production method according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination: said weaving step is made from metal strands formed by a plurality of strands metal whose diameter of each strand is less than 0.1 mm; said weaving step is made from metal strands with a diameter equal to or greater than 0.5 mm; said weaving step is made from metal strands with a diameter equal to or greater than 1 mm; said weaving step is made from metal strands formed by a plurality of titanium metal strands or by a plurality of metal strands of different materials; said weaving step is made from metal strands formed by a plurality of metal strands of different diameters; prior to said hot isostatic pressing step, said method comprises a step of shaping said fibrous structure, said shaping being carried out manually; said shaping of said fibrous structure is carried out during the setting up of said fibrous structure in a tool; prior to said hot isostatic pressing step, said method comprises a step of cleaning said fibrous structure; said solid piece is a metal reinforcement of the leading edge or trailing edge of a turbomachine fan blade.

The invention also relates to a fibrous structure formed by weaving metal strands formed by a plurality of metal strands twisted together about the longitudinal axis of the strand. Other characteristics and advantages of the invention will emerge more clearly from the description which is given below, by way of indication and in no way limiting, with reference to the appended figures, in which: FIG. 1 is a side view of a blade comprising a metal structural reinforcement of the leading edge obtained by means of the embodiment method according to the invention; - Figure 2 is a partial sectional view of Figure 1 along a cutting plane AA; FIG. 3 is a block diagram showing the main steps for producing a turbomachine blade leading edge metallic structural reinforcement of the embodiment method according to the invention; FIG. 4 illustrates a partial sectional view of the turbomachine blade leading edge metal reinforcement during the first step of the process illustrated in FIG. 3; FIG. 5 illustrates a partial sectional view of the turbomachine blade leading edge metal reinforcement during the second step of the process illustrated in FIG. 3; FIG. 6 illustrates a partial view of the turbomachine blade leading edge metal reinforcement during the third step of the process illustrated in FIG. 3. In all the figures, the common elements bear the same reference numerals unless otherwise specified. . FIG. 1 is a side view of a blade comprising a metallic leading edge structural reinforcement obtained by means of the embodiment method according to the invention. The blade 10 illustrated is for example a mobile blade of a fan of a turbomachine (not shown). The blade 10 has an aerodynamic surface 12 extending in a first axial direction 14 between a leading edge 16 and a trailing edge 18 and in a second radial direction 20 substantially perpendicular to the first direction 14 between a foot 22 and a summit 24.

The aerodynamic surface 12 forms the extrados face 13 and intrados 11 of the blade 10, only the extrados face 13 of the blade 10 is shown in Figure 1. The intrados 11 and the extrados 13 form the lateral faces of the blade. blade 10 which connects the leading edge 16 to the trailing edge 18 of the blade 10. In this embodiment, the blade 10 is a composite blade typically obtained by draping or shaping a woven fibrous texture. . By way of example, the composite material used may be composed of an assembly of woven carbon fibers and a resinous matrix, the assembly being formed by molding using an RTM-type resin injection process ( for "Resin Transfer Molding"). The blade 10 has a metal structural reinforcement 30 bonded at its leading edge 16 and which extends both in the first direction 14 beyond the leading edge 16 of the aerodynamic surface 12 of the blade. dawn 10 and in the second direction 20 between the foot 22 and the apex 24 of the dawn. As represented in FIG. 2, the structural reinforcement 30 matches the shape of the leading edge 16 of the aerodynamic surface 12 of the blade 10 that it extends to form a leading edge 31, said leading edge of the reinforcement . Conventionally, the structural reinforcement 30 is a one-piece piece comprising a substantially V-shaped section having a base 39 forming the leading edge 31 and extended by two lateral flanks 35 and 37 respectively fitting the intrados 11 and extrados 13 of the aerodynamic surface 12 of the dawn. Flanks 35, 37 have a tapered or thinned profile towards the trailing edge of the blade.

The base 39 has a rounded internal profile 33 adapted to conform to the rounded shape of the leading edge 16 of the blade 10. The structural reinforcement 30 is metallic and preferably based on titanium. This material has indeed a high energy absorption capacity due to shocks. The reinforcement is glued on the blade 10 by means of adhesive known to those skilled in the art, such as a cyanoacrylic or epoxy glue. This type of metal structural reinforcement 30 used for the turbomachine composite blade reinforcement is more particularly described in the patent application E P 1908919.

The method according to the invention makes it possible to produce in particular a structural reinforcement as illustrated in FIG. 2, FIG. 2 illustrating the reinforcement 30 in its final state. FIG. 3 represents a block diagram illustrating the main steps of an embodiment method 200 according to the invention for producing a blade blade leading edge structural reinforcement 10 as illustrated in FIGS. 1 and 2; The first step 210 of the production method 200 is a weaving step of a three-dimensional fibrous structure 300 by weaving metal strands 301, 302, illustrated in FIG. 4. The weaving step 210 makes it possible to produce one or more structures (s) fibrous (s) metal (s) 300 in three dimensions to achieve the final piece. As such, the fibrous structure 300 is formed by a plurality of woven strands 301, 302 acting as "warp yarn" and "weft yarn". The diameter of the metal strands 301, 302 may vary according to the needs of the user, and the material thickness necessary for the production of the part. The determination of the diameter of the strand is carried out according to a compromise between flexibility of the fibrous structure and material thickness necessary in the tooling. The diameter of the strands 301, 302 and the nature of the strands constituents may also vary especially between the strands capable of forming the warp son 301 and the strands capable of forming the weft son 302.

The metal strands 301, 302 are formed from a plurality of wire strands twisted, braided or helically wound about the longitudinal axis of the strand. Advantageously, each metal strand forming the strand has a diameter less than 0.1 mm. The principle of making the metal strands is advantageously the principle of making braided metal cables from twisted metal strands. By way of example, the metal strand 301, 302 comprises between 20 and 30 coiled strands. The use of metal strands 301, 302 formed by a plurality of coiled metal strands thus makes it possible to obtain a flexible and deformable strand manually cold (i.e., for example at room temperature). By making metal strands with a diameter greater than 0.5 mm, and even a few millimeters, the metal strands 301, 302 remain flexible enough to allow their manipulation, their manual deformation, and the weaving of a fibrous structure 300 without difficulty. The weaving patterns of the fibrous structure 300 are conventionally weaving patterns used, for example, in the field of weaving composite fibers such as, for example, the weaving patterns described in the patent application EP1526285. The metal strands used for producing the strands 301, 302 are mainly strands based on titanium. However, it is possible to incorporate in the weaving strands based on silicon carbide and titanium (SiC-Ti), boron-coated strands (SiC-Bore) or silicon carbide (SiC-SiC) . The second step 220 of the production method 200, illustrated in FIG. 5, is a step of shaping the fibrous structure 300 in a tool 400. Advantageously, the shaping of the fibrous structure 300 is carried out manually during its set up in tooling 400.

Tooling 400 comprises a cavity (die) 410 and a counterprint (punch) 420 corresponding to the final shape of the part to be produced. The fibrous structure 300 made in the previous step is a flexible structure, easily deformable manually. The fibrous structure 300 is also plastically deformable manually, for example by folding, which allows to manually shape the fibrous structure 300 when it is put into place in the tooling. The third step 230 of the production method is a Hot Isostatic Pressing (HIP) step of the fibrous structure in the tooling, illustrated in FIG. 6. Hot isostatic pressing is a method of widely used and known to reduce the porosity of metals and affect the density of many metals, such as ceramics. The isostatic pressing process also makes it possible to improve the mechanical properties and the exploitability of the materials. Isostatic pressing is carried out at high temperature (conventionally between 400 ° C. and 1400 ° C., and of the order of 1000 ° C. for titanium) and at isostatic pressure.

Thus, the application of the heat combined with the internal pressure eliminates the voids of the fibrous structure 300, as well as the microporosities by means of a combination of plastic deformation, creep, and diffusion welding to form a part 430. In the case of making a turbine engine blade metal reinforcement, the solid piece 430, resulting from the isostatic pressing step, comprises the profiles, internal and external, of the metal reinforcement 30. The solid piece 430 is then demolded from the tool 400. The isostatic pressing step is performed under vacuum, advantageously under secondary vacuum is in a welded tool in which the secondary vacuum is made or in autoclave bag; the choice of the process depends on the number of pieces to be produced. The secondary vacuum makes it possible to avoid the presence of oxygen in the tooling and at the level of the fibrous structure, during the titanium isostatic pressing step. The tooling is made of a mechanical alloy called superalloy or high performance alloy. The isostatic pressing step may previously include a step 235 of cleaning, degreasing and / or chemical etching of the flexible fibrous structure so as to remove residual impurities of the fibrous structure. Advantageously, the impurity cleaning step is carried out by dipping the fibrous assembly in a bath of cleaning agent or chemical agent. In association with these main production steps, the method according to the invention may also comprise a finishing step and machining of the massive piece obtained at the output of the tool so as to obtain the reinforcement 30. This step of recovery comprises: - a recovery step of the profile of the base 39 of the reinforcement 30 so as to refine it and in particular the aerodynamic profile of the leading edge 31; a step of recovery of the flanks 35, 37; this step consisting in particular of trimming the flanks 35, 37 and the thinning of the intrados and extrados flanks; - A finishing step to obtain the required surface condition. In association with these main production steps, the method according to the invention may also comprise non-destructive testing steps of the reinforcement 30 making it possible to ensure the geometrical and metallurgical conformity of the assembly obtained. By way of example, non-destructive inspections may be carried out by an X-ray method. The present invention has been mainly described with the use of titanium-based metal strands for the production of strands; however, the production method is also applicable with any type of metal strands. The method according to the invention makes it possible to simply produce parts with complex geometries and thicknesses varying substantially between 0.1 and 70 mm. Thus, the method according to the invention makes it possible to produce massive pieces as well as thin pieces. The invention has been particularly described for producing a metal reinforcement of a composite turbomachine blade; however, the invention is also applicable for producing a metal reinforcement of a turbomachine metal blade. The invention has been particularly described for producing a metal reinforcement of a turbomachine blade leading edge; however, the invention is also applicable to the production of a metal reinforcement of a trailing edge of a turbomachine blade or to the production of a metallic helical reinforcement composite or metal. The other advantages of the invention are in particular the following: reduction of implementation costs; - reduction of the production time; - simplification of the manufacturing range. 10 15 25

Claims (11)

REVENDICATIONS1. A method of producing (200) a solid piece (430) having successively: a step (210) of weaving a fibrous structure (300) three-dimensional by weaving, said weaving being made from metal strands (301, 302 ) formed by a plurality of metal strands twisted together about the longitudinal axis of the strand; a step (230) of hot isostatic pressing of said fibrous structure (300) causing agglomeration of the metal strands of said fibrous structure (300) so as to obtain a solid piece (430). 2. Production method (200) according to claim 1 characterized in that said step (210) of weaving is carried out from metal strands (301, 302) formed by a plurality of metal strands, the diameter of each strand is less at 0.1 mm. 3. Production method (200) according to one of claims 1 to 2 characterized in that said step (210) of weaving is carried out from metal strands (301, 302) of diameter equal to or greater than 0.5 mm . 4. Production method (200) according to one of claims 1 to 2 characterized in that said step (210) of weaving is carried out from metal strands (301, 302) of diameter equal to or greater than 1 mm. 5. Production method (200) according to one of claims 1 to 4 characterized in that said step (210) of weaving is carried out from metal strands (301, 302) formed by a plurality of metal strands of titanium or by a plurality of metal strands of different materials. 6. Production method (200) according to one of claims 1 to 5 characterized in that said step (210) of weaving is carried out from metal strands (301, 302) formed by a plurality of metal strands of different diameters . 7. Production method (200) according to one of claims 1 to 6 characterized in that prior to said step (230) of hot isostatic pressing, said method comprises a step (230) for shaping said fibrous structure (300), said shaping being performed manually. 8. Production method (200) according to claim 7 characterized in that said shaping of said fibrous structure (300) is performed during the establishment of said fibrous structure (300) in a tool (400). 9. A method of producing (200) a metal reinforcement (30) turbomachine blade according to one of claims 1 to 8 characterized in that prior to said step (230) of hot isostatic pressing, said method ( 200) comprises a step of cleaning (225) said fibrous structure (300). 5 10. Production method (200) according to one of claims 1 to 9 characterized in that said solid part (430) is a metal reinforcement (30) leading edge or trailing edge of turbine engine fan blade or propeller. 11. Fibrous structure (300) characterized in that it is formed by weaving metal strands (301, 302) formed by a plurality of metal strands twisted together about the longitudinal axis of the strand. 10