EP0700738B1 - Method of producing a hollow turbine blade - Google Patents

Abstract

The method esp. for a ducted fan turbine rotor, involves simulating the assembly of the blade's components by computer aided design, forging and machining the primary components, depositing diffusion barriers in a predetermined sequence, assembling the primary components by diffusion welding under isostatic pressure, and inflating the blade with gas pressure to achieve super-plastic moulding, followed by final machining. The forging process is carried out in a hot matrix at a temperature of 0.7 to 0.8 of the melting point of the material involved, with the pressing tools heated to 80 per cent of the workpiece temperature. The blade is made from a titanium alloy, e.g. TA6V, with a workpiece matrix temperature of between 880 and 950 deg.C and a tool temperature of 600 - 850 deg.C, designed to produce a microstructure with a grain size of under 10 mcm.

Description

The present invention relates to a manufacturing process of a hollow turbomachine blade according to claim 1.

The benefits of using large blades rope for turbomachinery appeared especially in the case of the fan rotor blades of turbojet engines double flow. These blades must meet conditions severe use and in particular have sufficient mechanical characteristics associated with anti-vibration and impact resistance properties of foreign bodies. The objective of sufficient speeds at the end dawn has also led to the search for a reduction in masses. This goal is notably achieved by the use hollow blades.

EP-A-0.500.458 describes a process for manufacturing a blade hollow for a turbomachine, in particular a rotor blade of large rope blower. The primary parts used in this manufacturing include two outer sheets and at least one central plate. The method described comprises a hot forming operation by bending and twisting the parts, a welding-diffusion operation in areas localized and a gas pressure inflation operation inducing a superplastic forming bringing the surfaces outside of dawn with the desired profile. Tools suitable, in particular shape dies, are used for carrying out these operations.

The object of the invention is to provide the numerous methods known for making hollow blades, illustrated in particular by the example cited above, improvements notably aiming to obtain blades having improved mechanical characteristics and optimized in the conditions of use, guaranteeing repetitive quality while facilitating the conditions for manufacturing at the lowest cost.

These aims are achieved by a method of manufacturing a turbomachine hollow blade, in particular a fan rotor blade long cord according to claim 1.

In the case of a titanium alloy, of the TA6V type, the size of grain obtained is less than 10 µm, for a temperature forging the part between 880 ° C and 950 ° C and a tool temperature between 600 ° C and 850 ° C.

Advantageously, the bending / twisting of the blades placed after the welding-diffusion operation allows a more great ease of application of diffusion barriers on a preset pattern on a flat piece.

Advantageously, the production of a fan blade at very high compression ratio, assumes very strong camber of the pale base and an accentuated twist and not continued. This requires a specific operation lengthening of the fibers preceding the twisting operation.

Advantageously, the twisting operation in this case can be integrated into the inflation operation under pressure gas and superplastic forming.

Advantageously, the cambering / twisting operation of the blades can be placed after the forging operation in the case of exploratory development requiring low parts series, or after the parts machining operation primary in the case of simple aerodynamic forms.

Advantageously, the cambering / twisting operation is carried out on a press, in an isothermal manner. In the case of titanium alloy type TA6V, this temperature will be between 700 and 940 ° C.

This operation requires blocking the ends in order to guarantee effective fiber elongation in the areas chosen, this without tearing. The length of the fiber central remains unchanged and the fiber elongation rate varies according to their distance to this central fiber.

• la figure 1 représente une vue schématique de la première étape de simulation de la mise à plat d'une aube creuse dans le procédé de fabrication conforme à l'invention ;
• la figure 2 représente une vue en perspective d'une pièce brute de départ dans le procédé de fabrication d'une aube creuse conforme à l'invention ;
• la figure 3 représente la pièce de la figure 2 à un premier stade de mise en forme ;
• la figure 4 représente la pièce des figures 2 et 3 au stade suivant de mise en forme ;
• la figure 5 représente selon une vue en perspective un exemple de pièce obtenue à l'issue des étapes de forgeage et usinage du procédé de fabrication d'une aube creuse selon l'invention ;
• la figure 6 représente selon une vue en coupe par un plan passant par l'axe longitudinal de la pièce suivant la ligne VI VI de la figure 5 la pièce obtenue à ce stade de fabrication selon la figure 5 ;
• la figure 7 représente un graphique reproduisant un cycle d'évolution des températures de pièce lors du forgeage par matricage sous presse des pièces primaires constitutives de l'aube ;
• la figure 8 représente une vue en perspective d'une pièce primaire constitutive de l'aube creuse obtenue par le procédé conforme à l'invention après la réalisation de l'étape de préparation par dépôt de barrières anti-diffusion ;
• les figures 9 et 10 représentent une vue en perspective des pièces primaires de l'aube creuse lors de l'étape d'assemblage suivi du soudage-diffusion du procédé conforme à l'invention ;
• les figures 11 et 12 représentent schématiquement les résultats d'une simulation numérique d'une opération de mise à longueur des fibres à effectuer sur les pièces constitutives de l'aube creuse assemblée obtenue par le procédé conforme à l'invention ;
• la figure 13 représente une vue en perspective de l'aube obtenue par ledit procédé après une opération de mise en forme conduisant à un allongement des fibres ;
• la figure 14 représente une vue schématique en perspective d'un exemple d'outil de presse utilisé pour obtenir la pièce de la figure 13 ;
• la figure 15 représente une vue en bout de l'aube de la figure 13 montrant le résultat de l'opération de cambrage du pied d'aube ;
• la figure 16 représente une vue schématique de la réalisation de l'opération de vrillage de l'aube des figures 13 et 15 ;
• la figure 17 représente selon une vue en coupe par un plan passant par l'axe longitudinal de pièce suivant une ligne XVII-XVII de la figure 16 la réalisation de l'opération de vrillage de la figure 16 ;
• la figure 18 représente selon une vue schématique en perspective une variante de réalisation de l'opération de vrillage de l'aube des figures 13 et 15 ;
• la figure 19 représente une vue en perspective de l'aube obtenue après l'opération de vrillage dudit procédé ;
• la figure 20 représente selon une vue schématique en perspective un exemple d'une partie de l'outillage utilisé lors de l'étape de formage superplastique de l'aube de la figure 19 ;
• la figure 21 représente selon une vue schématique en coupe par un plan transversal un exemple de profil d'aube avant gonflage et en tiretés, après gonflage.

Other characteristics and advantages of the invention will be better understood on reading the description which follows of embodiments of the invention, with reference to the appended drawings in which:

• FIG. 1 represents a schematic view of the first step of simulating the flattening of a hollow blade in the manufacturing process according to the invention;
• FIG. 2 represents a perspective view of a raw starting part in the method of manufacturing a hollow blade according to the invention;
• Figure 3 shows the part of Figure 2 at a first stage of shaping;
• Figure 4 shows the part of Figures 2 and 3 in the next stage of shaping;
• FIG. 5 represents a perspective view of an example of a part obtained at the end of the forging and machining steps of the method of manufacturing a hollow blade according to the invention;
• Figure 6 shows in a sectional view through a plane passing through the longitudinal axis of the part along the line VI VI of Figure 5 the part obtained at this stage of manufacture according to Figure 5;
• FIG. 7 represents a graph reproducing a cycle of evolution of the part temperatures during the forging by stamping in press of the primary parts constituting the blade;
• FIG. 8 represents a perspective view of a primary part constituting the hollow vane obtained by the method according to the invention after the completion of the preparation step by depositing anti-diffusion barriers;
• Figures 9 and 10 show a perspective view of the primary parts of the hollow blade during the assembly step followed by the diffusion welding of the process according to the invention;
• FIGS. 11 and 12 schematically represent the results of a numerical simulation of an operation of lengthening the fibers to be carried out on the constituent parts of the assembled hollow vane obtained by the method according to the invention;
• FIG. 13 represents a perspective view of the blade obtained by said method after a shaping operation leading to an elongation of the fibers;
• Figure 14 shows a schematic perspective view of an example of a press tool used to obtain the part of Figure 13;
• Figure 15 shows an end view of the blade of Figure 13 showing the result of the cambering operation of the blade root;
• FIG. 16 represents a schematic view of carrying out the twisting operation of the blade of FIGS. 13 and 15;
• Figure 17 shows in a sectional view through a plane passing through the longitudinal axis of the part along a line XVII-XVII of Figure 16 the execution of the twisting operation of Figure 16;
• Figure 18 shows in a schematic perspective view an alternative embodiment of the twisting operation of the blade of Figures 13 and 15;
• FIG. 19 represents a perspective view of the blade obtained after the twisting operation of said method;
• Figure 20 shows in a schematic perspective view an example of part of the tool used during the superplastic forming step of the blade of Figure 19;
• FIG. 21 shows in a schematic sectional view through a transverse plane an example of a blade profile before inflation and in dashed lines, after inflation.

The first step (a) of the process for manufacturing a hollow turbomachine fan blade according to the invention comprises a so-called flattening operation, from the definition of the finished part.
The flattening operation consists of deflation followed by defreezing / descaling.
As shown in Figure 1, the principles of construction and control of a fan blade are based on the use of defining sections distributed along the motor axis. Each section is worked so that all of the other constituent parts of the blade such as 11, 12 are pressed against the underside skin 13 unchanged. The thickness of the upper skin 11 is adjusted as a function of its subsequent elongation during the forming operation.
At this stage, a digital simulation of the inflation is carried out confirming the intermediate result.

As shown in Figure 1, the final geometry twisted is transformed into the flat one. The defreezing / descaling is a delicate operation for which the manufacturing process according to the invention provides a remarkable, automated method, respecting the conservation of the volume by the distribution of matter in function of the strain rate related to the position of each section.

At this stage, a new numerical simulation of the twist confirming the final result.

Advantageously, it is possible to carry out the updating. flat in a single operation, without the deflation step.

The second step (b) consists in forging the parts on press constitutive primaries of dawn such as 11, 12, 13 visible in Figure 9, by stamping. According to the techniques known in the past, this type of part is made from of rolled sheets because it is considered that the dimension and the size does not allow to ensure by forging a blank sufficiently precise and fine.

According to the invention and as it is known per se in the precision forging process, the starting blank consists, as shown in Figure 2, of a bar 3, of a titanium alloy for example TA6V, of dimension adequate (diameter between 80 and 120mm) to achieve the draft of the primary parts. As shown in the Figure 3 one or more upsetting operations allow placement of the material in high volume areas type 4 foot or blade tip. At this point, the bars are heated to a temperature between 880 ° C and 950 ° C, while the tool is heated to a temperature between 200 and 250 ° C.

One of the difficulties and therefore a remarkable stage in process according to the invention resides in the ability to produce forged blanks 5 as shown in the figure 5 of dimension and especially thickness capable of producing economically long-rope blades. The inventors have developed a method of forging blanks allowing to guarantee blanks on a high power press precise and calibrated.

Indeed the realization of fan blades of large rope turbojet requires large blanks cut. For example, a 270KN class turbojet engine thrust requires 500 mm wide blades about. This width is further increased by possible on widths up to approx. 50 mm on each edge to perform assembly, maintenance, etc ... of the product.

In order to obtain a sufficiently fine product and in order to limit raw material and machining costs, while limiting the forging pressure, the inventors have developed a process comprising a judicious combination of a form trapezoidal 6 of the blank 5 as shown in the Figure 4, lubrication and heating of tools. In particular, the forging operation on a press or forging making it possible to obtain the parts such as 5 of FIG. 4 is done by heating the room to a temperature between 880 ° C and 950 ° C and the tooling at a temperature between 700 ° C and 900 ° C.

It is then possible to produce a product with a report fineness defined by the thickness / width ratio of the blade of the order of 0.02. Figure 7 shows a graph temperature evolution at each stamping. The curve a corresponds to the temperatures of the contact surfaces of matrix, curve b the internal temperature of the tool and curve c the temperature of the tool holder. We observe that thanks to a perfectly mastered mastering cycle, the cycle temperature varies between 720 ° C and 840 ° C.

The structure of the start bars 3 is rough by compared to conventional specifications applied to bars smaller dimensions (diameter 50 mm) used for the Forging of conventional turbojet blades: forging and matrixing make it possible to refine the structure in a way significant since the grain size is reduced by 10 µm on average at 7 µm. This operation thus saves 30 MPa on average on the fatigue strength of the final product and this despite the thermal cycles of welding-diffusion and inflation following the forging operation.

In the example shown in Figures 5 and 6, the precision forging makes it possible to make the surface 8 left external finished forging: the final surface condition being obtained by selective polishing, with numerical control, performed on a 5-axis polishing machine.

The finish of the internal surface 9 of the primary parts is produced by machining by any machining process known per se, these machining operations constituting step (C) of the process in accordance with the invention.

• nettoyage parfait des surfaces, internes particulièrement ;
• application d'un produit anti-diffusant sur au moins deux des faces internes avec des motifs prédéfinis 10, par exemple par un procédé de sérigraphie classique, comme schématisé sur la figure 8 ;
• cuisson du produit anti-diffusant entre 250°C et 280°C pour dégrader tout ou partie du liant ;
  puis de l'étape suivante (e) du procédé :
• assemblage des pièces primaires 11, 12, 13 afin d'obtenir l'ensemble 14 en utilisant au moins deux pions de centrage 15, 16, comme représenté sur les figures 9 et 10 ;
• soudage TIG ou par faisceau d'électrons de la périphérie puis éventuellement de deux tubes 17, 18 de mise au vide ;
• tirage du vide dans une enceinte à vide et fermeture des tubes 17, 18 dans le cas de leur utilisation ;
• soudure-diffusion à une température de 875°C à 940°C, et sous une pression de 30 à 40 x 10⁵ MPa pendant 1 H mini.

The operations of preparing the sandwich until a welded-diffused assembly is obtained call on already known methods comprising the operations of the following step (d) of the method:

• perfect cleaning of surfaces, particularly internal;
• application of an anti-diffusing product on at least two of the internal faces with predefined patterns 10, for example by a conventional screen printing process, as shown diagrammatically in FIG. 8;
• cooking of the anti-diffusing product between 250 ° C and 280 ° C to degrade all or part of the binder;
  then the next step (e) of the process:
• assembly of the primary parts 11, 12, 13 in order to obtain the assembly 14 using at least two centering pins 15, 16, as shown in FIGS. 9 and 10;
• TIG or electron beam welding of the periphery then optionally of two vacuum tubes 17, 18;
• vacuum drawing in a vacuum enclosure and closing of the tubes 17, 18 in the case of their use;
• welding-diffusion at a temperature of 875 ° C to 940 ° C, and under a pressure of 30 to 40 x 10 ⁵ MPa for 1 H min.

The following stages (f) of inflation under gas pressure and superplastic forming and (g) final machining are then carried out under production conditions known per se, parameters, including temperature and pressures applied being determined according to the material of the rooms. Furthermore and depending on the application of the process according to the invention, in particular for obtaining fan blades, a shaping of the parts by camber / twist is required. In this case the bending / twisting is a delicate operation which requires a a number of precautions to avoid the occurrence undulations due to the lengthening of the different parts of the part during this operation.

Beforehand we carry out a geometric operation on a CAD / CAM system so as to keep on both sides of the neutral fiber, the lengths of the fibers according to their position relative to the axis 20 of the part 19, as shown in Figures 11 and 12.

At this stage, a digital simulation of the twist is carried out confirming the final result.
The operation consists of isothermal shaping of the primary part or of the welded assembly, in a press at a temperature between 700 and 940 ° C. allowing, with a tool 21, to obtain the elongations of the different fibers of the Exhibit 19.

This operation is carried out at controlled pressure between two metal or ceramic tools at the same temperature as the part is 700 ° C to 940 ° C. The geometric definition of tool 21 produced in CAD / CAM integrates the shape of the part massive foot 22 and laterally the progressive elongations fibers in particular by one or more waves 23, 24, 25, 26 whose amplitude varies with the rate of elongation necessary, as shown diagrammatically in Figures 13 and 14.

These elongations will generate compression stresses longitudinal generally located on the axis 20 of the part.

These will be contained by a fixed asset each end, foot 22 and blade tip 27.

This operation can include the arching of the foot 22. The addition of extra thicknesses 28, 29, 30 judiciously placed provides support from the first contact workpiece / tool, as shown in figure 15.

For the twisting operation and as shown schematically on the Figures 16 and 17, the welded assembly 31 is maintained at each end by two jaws 32, 33 at least one of which is movable in rotation.

The twisting operation is carried out in an oven or heating chamber, at a creep temperature included between 880 ° C and 920 ° C depending on the alloy of the assembly welded.

34.35 weights impose a twist on the part perfectly controlled by limit stops.

Advantageously, another method is to provide the rotational movement of at least one jaw by a system mechanical acting on the lever arm 37, this is then made by two fingers fixed on the movable part of a press to which a local heating chamber is added 38. Added local footprints 36 provide the accentuated aerodynamic shape of the trailing edge.

In these two cases, one of the jaws can be equipped with a helical coupling in order to apply a tensile stress during twisting, allowing avoid the appearance of a ripple phenomenon, so remarkable, in accordance with the invention.

Advantageously, it is possible to carry out the rotational movement of at least one of the jaws by a motor electric or hydraulic, thermally protected in the area of work.

The twisted vane 39 thus obtained and as shown in Figure 19 is held by these pins 40, 41 during closing the super plastic forming mold 44. These are guided vertically by notches 42, 43, as shown in Figure 20.

The super plastic forming operation is carried out between 850 and 940 ° C under a pressure of 20 to 40x10 ⁵ MPa of argon.

Advantageously, it is possible to form the blade 31 at from the geometry obtained after elongation of the fibers in the same operation as the inflation. The decrease in number of heaters promotes the conservation of high mechanical properties obtained by forging constituent parts of dawn.

Claims (15)

1. Method of manufacturing a hollow turbine-machine blade, particularly a wide-chord fan rotor blade, including the following stages:

   (a) on the basis of the definition of a blade to be obtained, design using Computer-Assisted Design and Manufacturing/CADCAM means, and carrying out a digital simulation of the flattening of the components constituting the blade;

   (b) forging of the primary components on a press by die stamping;

   (c) machining of the primary components;

   (d) deposition of diffusion barriers according to a predefined pattern;

   (e) assembly of the primary components followed by diffusion welding at isostatic pressure;

   (f) inflation under gas pressure and superplastic forming;

   (g) final machining, in which, at stage (b), the die stamping operation is carried out in a hot die, at a temperature lying in a bracket between 0.7 and 0.8 Tf, Tf being the material melting temperature, the temperature of the tooling being taken to 80% of the component temperature, the component blank used exhibits a specific trapezoidal shape so as to obtain a final product with fineness equivalent to 0.02 times the width of the blade and a working of the metal making it possible to guarantee a grain size appropriate for ensuring, at stage (e), good diffusion welding conditions and the mechanical characteristics sought for the finished blade including good fatigue resistance, the method including an additional stage of cambering and twisting causing an elongation of the fibres of the material of the components allowing the neutral fibre to be set to final length on either side of the axis (20) of the component when the thickness of the components, associated with the degree of deformation, is less than the buckling limit.
2. Method of manufacturing a hollow blade according to Claim 1, in which stage (a) includes a digital simulation of deflation, by applying the other components (11, 12) constituting the blade onto the unchanged under-surface skin (13).
3. Method of manufacturing a hollow blade according to Claim 2, in which the digital simulation is followed by untwisting/de-cambering so as to obtain a flat product (2).
4. Method of manufacturing a hollow blade according to Claim 1, in which stage (a) includes a digital simulation of complete flattening (2) in a single operation, on the basis of the final twisted geometry of the blade (1).
5. Method of manufacturing a hollow blade according to any one of Claims 1 to 4, in which the said blade is made of titanium alloy, of the TA6V type, the temperature of die stamping of the components lies between 880°C and 950°C, the tooling temperature lies between 600°C and 850 °C, and the die stamping operation makes it possible to obtain a component metallurgical microstructure with a grain size of less than 10 µm.
6. Method of manufacturing a hollow blade according to any one of Claims 1 to 5, in which the additional cambering and twisting stage (e1) is placed after the diffusion welding operation.
7. Method of manufacturing a hollow blade according to any one of Claims 1 to 5, in which an operation of elongating the fibres is carried out after the diffusion welding stage (e) and at stage (f), the twisting operation being incorporated into the operation of inflation under gas pressure and superplastic forming.
8. Method of manufacturing a hollow blade according to any one of Claims 1 to 5, in which the additional cambering and twisting stage is placed after the stage (b) of forging of the primary components.
9. Method of manufacturing a hollow blade according to any one of Claims 1 to 5, in which an additional cambering and twisting stage is placed after the stage (c) of machining of the primary components.
10. Method of manufacturing a hollow blade according to any one of Claims 1 to 6, in which the cambering and twisting operation is carried out on a press, isothermally.
11. Method of manufacturing a hollow blade according to Claim 10, in which the said blade is made of titanium alloy, of the TA6V type, and the isothermal forging temperature lies between 700°C and 940°C during the cambering and twisting operation.
12. Method of manufacturing a hollow blade according to one of Claims 10 and 11, in which, during the cambering and twisting operation, at least one of the two ends of the component is held fast so as to guarantee effective elongation of the fibres in the chosen regions, the degree of elongation of the fibres varying depending on their distance from an axial fibre of the component the length of which remains unchanged.
13. Method of manufacturing a hollow blade according to Claim 12, in which, during the twisting operation, local tooling imprint moulds (36) reposition the previously elongated fibres so as to obtain an accentuated aerodynamic shape in a chosen region.
14. Method of manufacturing a hollow blade according to one of Claims 12 and 13, in which, during the twisting operation, the system for holding at least one of the component ends fast includes a device making it possible to exert a rotation and a traction on the component along the component axis.
15. Method of manufacturing a hollow blade according to Claim 1, in which an additional stage (b1), including an operation of shaping on a press, is carried out after stage (b).

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