EP1814681A1

EP1814681A1 - Method for producing a lost pattern and a core introduced into the pattern

Info

Publication number: EP1814681A1
Application number: EP05801327A
Authority: EP
Inventors: Uwe Paul; Ursula Pickert
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2004-11-24
Filing date: 2005-11-04
Publication date: 2007-08-08
Also published as: EP1661640A1; US20080202718A1; WO2006056524A1

Abstract

The invention relates to a method for the production of a pattern for precision casting representation of a turbine component comprising at least one cavity, whereby the prepared pattern comprises at least one core and an outer contour pattern (1), at least partly enclosing the core and at least partly defining the outer contour of the turbine component. The core is made from a hardening core material (11), which hardens during the course of the method and the outer contour pattern (1) is made from a combustible or fusible material. The outer contour model (1) is first produced with at least one cavity (8a-8e) corresponding to the at least one cavity of the turbine component and subsequently, in order to form the at least one core, the hardening core material (11) is introduced into the at least one cavity (8a-8e) and hardened.

Description

description

METHOD FOR MANUFACTURING A LOST MODEL AND THEREIN

BEEN RAISED

CORE

The present invention relates to a method for producing a model for the investment casting of a component having a cavity as well as to a method for producing a casting mold for a component having at least one cavity, in which a model for the casting technique of the component is used

Of particular importance in the manufacture of hollow castings

Components such as e.g. Turbine components is creating the cavity. For example, turbine blades for gas turbines have an airfoil that has a leading edge and a trailing edge. The inflow and outflow edges are connected to one another via a suction-side and a pressure-side wall. Between the suction side and the pressure side wall, at least one cavity is arranged, which extends through a large part of the airfoil and serves for supplying a cooling fluid, for example air or steam, with which the airfoil is cooled during operation of the turbine. The cooling effect depends on the design of the cavity and its exact positioning within the airfoil. Comparatively small deviations in the positioning of the cavity can lead to a significant deviation in the cooling effect.

The shape and position of the cavity within the airfoil therefore presents a challenge to the construction of turbine blades. Not infrequently, a number of design changes are needed to optimize the location and shape of the cavity relative to the outer contour of the turbine bucket until the final design is established , In the development process, turbine blades with different designs are manufactured and tested before the final design is established.

The production of, for example, hollow castings

Turbine blades for gas turbines takes place by means of a ceramic investment casting technique. In this, a core for defining the cavity is molded or cast from a ceramic material. Subsequently, this core is inserted into a mold for spraying or casting a wax model, and the wax is injected or poured into the mold. After cooling of the wax, the finished wax model together with the ceramic core forms a model for the investment casting of the turbine blade, which in the further course of the process for producing a

Ceramic mold for casting the turbine blade is used. To make the ceramic mold, a ceramic shell is placed around the wax model. After the ceramic shell has hardened, the wax of the wax model is melted out, leaving a mold for casting the hollow

Turbine blade remains. This form comprises on the one hand the ceramic shell and on the other hand the ceramic core. Such a method is disclosed, for example, in US 5,465,780.

Since corrections of the core design in the final stage of product development must be made by means of tests in spite of numerical aids for simulating flow and cooling properties, the method described is relatively expensive in product development, since new designs for each design are available for the core and the wax model must be made.

It has therefore been proposed in DE 101 29 975 A1 to equip the casting or injection molds for casting the core with interchangeable inserts so as to be able to change the core design without a completely new casting or injection molding must be made for the core. But even this approach allows only local corrections, but not a global correction of the core design. In addition, in the method described in DE 101 29 975 Al, corrections to the design of the outer contour of the turbine blade are not possible without producing new tools such as new casting molds.

The manufacture of tools for the production of ceramic cores and wax models is still complex and costly. For example, during production process development for hollow cast turbine blades, much of the development time and development cost is spent on tooling. In addition, the tools for series production can be released only after the design of the hollow cast turbine component is released. Otherwise, design changes could lead to significant delays and high costs.

It is therefore an object of the present invention to provide an improved method for producing a model for the casting technique of a turbine component having at least one cavity and an improved method for producing a casting mold for a turbine component having at least one cavity.

This object is achieved by a method for producing a model for the casting technique of a cavity having at least one component according to claim 1 or by a method for producing a mold or an injection mold for a cavity having at least one component according to claim 10. In the method according to the invention for producing a model for the casting technique of a component having at least one cavity, the finished model comprises at least one core and an outer contour model at least partially surrounding and at least partially defining the outer contour of the component. The core is made of a hardenable core material, which is cured in the course of the process. The production of the outer contour model is made of a burn-out or fusible material. In the method according to the invention, the outer contour model is first produced with at least one cavity corresponding to the at least one cavity of the component. Subsequently, for the production of the at least one core, the curable material is filled into the at least one cavity and cured.

In the method according to the invention, therefore, the outer contour model simultaneously serves as a casting or injection mold for the core, so that no separate casting or injection mold for the core needs to be present. This can be for the

Process development up to the prototype production on the expensive production of its own casting or injection mold for the core are omitted.

As outer contour model, a resin model can be used. To prepare the resin model, a rapid prototype process, in particular a stereo lithography process, can be used. In a stereo lithography process, a resin is used which hardens upon irradiation with a laser. To produce the outer contour model, the previously flowable resin is hardened layer by layer by means of the laser until the outer contour model is completed in its desired contour. In this case, the laser curing can in particular be computer-controlled, so that designs that are already simulated in the computer can be converted relatively quickly into a model for the precision engineering of the component. When filling and / or curing the curable material, the outer contour model of a stabilizing sheath, a so-called setter be surrounded. The stabilizing sheath can also be produced by means of a rapid prototype process, for example by being produced from resin by means of a stereo lithography process. In particular, it is advantageous if the sheath contains a mechanically stabilizing material, for example a metal powder. Finally, it is also possible to produce the casing completely from metal powder, suitable rapid prototype processes, for example rapid laser sintering, for solidifying the metal powder being used.

The stabilizing sheath keeps the outer contour model in shape when filling the curable material, so that caused by the resulting pressure on the outer contour model, no design deviations of the core.

In particular, a material which is flowable before curing and which is poured or injected into the at least one cavity of the outer contour model is suitable as core material. Because of their high temperature resistance come as a core material in particular ceramic-based materials in question.

The method according to the invention for producing a model for the precision machining of a component having at least one cavity is compared with the prior art methods in which production tools, in particular casting or injection molds, have to be produced for the process development and the qualification of turbine components, variable and cheaper. In particular, when rapid prototype processes such as stereolithography processes or rapid laser sintering processes are used for producing the outer contour model and / or the stabilizing sheath, the method according to the invention also leads more quickly to a model for the precision engineering of the component than the methods according to the prior art.

For the process development up to the prototype production can be dispensed with the expensive actual production tools in the inventive method, which the

Enabling process start-up at a much earlier stage, significantly reducing development time, and greatly reducing the risk of making corrections to production tools due to design changes. Accordingly, the total tool cost can be reduced.

Finally, the method of the present invention allows much earlier market introduction of new designs as well as a faster response to service-related design changes.

In a method according to the invention for producing a casting mold or an injection mold for a component having at least one cavity, the method according to the invention for producing a model for the casting technique of the component is used.

Further features, properties and advantages of the present invention will become apparent from the following description of an embodiment with reference to the accompanying figures.

Figure 1 shows the schematic representation of an outer contour model for use in the invention

Method in a sectioned perspective view. FIG. 2 shows the outer contour model from FIG. 1 during the filling of a hardenable material in openings of the outer contour model.

FIG. 3 shows by way of example a gas turbine in a longitudinal partial section.

Figure 4 shows a perspective view of a rotor blade or vane of a turbomachine.

FIG. 5 shows a combustion chamber of a gas turbine.

FIG. 1 shows in a somewhat simplified representation a model 1 of a turbine blade as an exemplary example of a component with a cavity in a perspective, sectional view. The model 1 has an outer surface 3, which reproduces the outer contour of a turbine blade. The outer contour is divided into a pressure-side contour 4 and a suction-side contour 5. The edges at which the pressure-side contour 4 and the suction-side contour 5 merge into one another form the leading edge (edge 6) or the trailing edge (edge 7) of the later turbine blade ).

The model 1 is not solid, but it has cavities, in the present embodiment, five cavities 8a to 8e, which represent the later cooling air ducts of the turbine blade. The inner surfaces 9a to 9e of the model 1 delimiting the cavities 8a to 8e correspondingly represent the inner contour of the later turbine blade. In the area of the edge 7, the fifth cavity 8e has an opening 10 extending parallel to the edge, which represents an outlet opening for exiting cooling fluid in the later turbine blade. As explained above, the model 1 already represents both the outer contour and the inner contour of the later turbine blade. The model is made of synthetic resin that melts or burns under the influence of temperature and is used in the production of a model for the investment casting of the turbine blade to be produced.

The synthetic resin model described above represents in the model for the investment casting of the turbine blade only a model for the outer contour of the turbine blade and is therefore hereinafter referred to as outer contour model 1. The representation of the inner contour of the cavities of the turbine blade, however, takes place on the basis of a so-called core whose outer surfaces represent the inner contour of the cavities of the turbine blade. The outer contour model 1 and the cores to be described together form the model for the investment casting of the turbine blade.

The production of the outer contour model 1 takes place in

Embodiment by means of a stereo lithography process. In this process, a photoreactive liquid resin in a container is locally irradiated with laser radiation of a suitable wavelength. The irradiation leads to hardening of the resin at the irradiated point. By suitable guidance of the laser beam, the curing of the resin can be controlled so that arbitrarily shaped structures of cured synthetic resin can be realized. Stereo lithography methods are known from the prior art and therefore should not be further explained here.

By means of the stereo lithography process, the outer contour model 1 is produced from a liquid synthetic resin by targeted local hardening. The laser is controlled by a computer, so that the Production of the outer contour model 1 can be made on the basis of a pure computer model.

After the outer contour model 1 has been produced, the cores defining the cavities of the later turbine blade are produced. For this purpose, a flowable ceramic material, the so-called core mass 11, is filled into the cavities 8a to 8e of the outer contour model 1. The filling can, as shown in Figure 2, be realized for example by pouring. However, other filling methods are also possible. For example, the core mass 11 can also be brushed or injected into the cavities.

In order to prevent deformation of the outer contour model 1 during the filling of the core mass 11 due to the resulting pressure, the outer contour model 1 is surrounded before filling the ceramic core material 11 with a stabilizing sheath 12, 13. This stabilizing jacket 12, 13 is formed in two parts. A part 12 of the stabilizing jacket has an inverse surface to the pressure-side contour 4 of the outer contour model 1, while the other part 13 of the outer contour model 1 has an inverse contour to the suction side 5 of the outer contour model 1. The outer contour 4, 5 inverse surfaces of the stabilizing

Sheaths are framed by abutment surfaces at which the two parts 12, 13 abut each other when they surround the outer contour model 1 stabilizing. Accordingly, the abutment surfaces are then in the region 15, 16 of the edges 6, 7 of the outer contour model. 1

In the area 16 of the edge 7 of the outer contour model 1, for example, there is also a widening 17 of the abutment surfaces, so that they do not abut each other in the immediate vicinity of the edge 7. The flared portion 17 forms, together with the cavity 8e, the shape for that core, which later defines the inner contour of the corresponding cavity of the turbine blade.

The manufacture of the stabilizing jacket 12, 13 takes place in the present embodiment as the

Production of the outer contour model 1 by means of a stereo lithography method. It is advantageous if the resin or synthetic resin composition brought to harden in the stereo lithographic process contains a stabilizing component, for example a metal powder. A stabilizing jacket 12, 13 once made can be reused as long as no design changes are made to the outer contour of the turbine blade. The stabilizing sheath can also consist entirely of metal in a modification of the embodiment described. In this case, for example, it can be produced from metal powder by means of rapid laser sintering.

After all the cavities 8a to 8e of the outer contour model 1 are filled with the ceramic core mass 11, a

Curing the mass. After the mass has cured, the stabilizing jacket 12, 13 is removed so that the outer contour model 1 remains with ceramic cores located in its cavities. The outer contour model 1 then forms, together with the ceramic cores, a model for the investment casting of the turbine blade.

The model for the investment casting of the turbine blade thus produced can then be used for producing a casting mold for the turbine blade. For this purpose, the model is surrounded by a ceramic mass, which is then cured. In this case, the ceramic compound connects at selected locations with the ceramic cores located in the outer contour model 1. After the outer contour model 1 surrounding ceramic material is completely cured, there is a melting or burning out of the outer contour model 1 forming resin. Back one remains Casting mold for casting the turbine blade. Due to the destruction of the outer contour model 1 during burnout or melting the outer contour model 1 is also called lost model. In the casting mold, the outer contours of the ceramic cores define the inner contours of the later ones

Turbine blade and the inner contour of the ceramic mold, the later outer contour of the turbine blade.

Due to the direct implementation of a computer model in an outer contour model 1, which also serves as a mold for the ceramic cores, can be dispensed with the costly and costly production of tools such as molds for the production of ceramic cores and wax models. It is thus possible a much faster implementation of a computer model in a model suitable for the investment casting of the turbine blade. As a result, costs for the production of a casting mold for a turbine blade as well as the time required for this can be reduced.

For a better understanding of the invention, a description of a typical gas turbine, a typical turbine blade and a typical combustor follows with reference to FIGS. 3 to 5.

FIG. 3 shows by way of example a gas turbine 100 in a longitudinal partial section. The gas turbine 100 has inside a rotatably mounted about a rotation axis 102 rotor 103, which is also referred to as a turbine runner. Along the rotor 103 follow one another an intake housing 104, a compressor 105, for example, a toroidal combustion chamber 110, in particular annular combustion chamber 106, with a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust housing 109th

The annular combustion chamber 106 communicates with an annular annular hot gas channel 111, for example. There, for example, form four successive turbine stages 112, the turbine 108th

Each turbine stage 112 is formed, for example, from two blade rings. In the flow direction of a

Working medium 113 seen follows in the hot gas channel 111 of a row of vanes 115 a 120 formed from blades 120 series.

The guide vanes 130 are fastened to an inner housing 138 of a stator 143, whereas the moving blades 120 of a row 125 are attached to the rotor 103 by means of a turbine disk 133, for example.

Coupled to the rotor 103 is a generator or work machine (not shown).

During operation of the gas turbine 100, air 105 is sucked in and compressed by the compressor 105 through the intake housing 104. The compressed air provided at the turbine-side end of the compressor 105 is supplied to the burners 107 where it is mixed with a fuel. The mixture is then burned to form the working fluid 113 in the combustion chamber 110. From there, the working medium 113 flows along the hot gas channel 111 past the guide vanes 130 and the rotor blades 120. On the rotor blades 120, the working medium 113 expands in a pulse-transmitting manner, so that the rotor blades 120 drive the rotor 103 and drive the machine coupled to it.

The components exposed to the hot working medium 113 are subject to thermal loads during operation of the gas turbine 100. The guide vanes 130 and blades 120 of the first turbine stage 112 seen in the flow direction of the working medium 113 are in addition to the Ring combustion chamber 106 lining heat shield bricks most thermally stressed.

To withstand the prevailing temperatures, they can be cooled by means of a coolant.

Likewise, substrates of the components may have a directional structure, i. they are monocrystalline (SX structure) or have only longitudinal grains (DS structure).

As the material for the components, in particular for the turbine blade 120, 130 and components of the combustion chamber 110, for example, iron-, nickel- or cobalt-based superalloys are used. Such superalloys are known, for example, from EP 1204776 Bl, EP 1306454, EP 1319729 A1, WO 99/67435 or WO 00/44949; these writings are part of the revelation.

Likewise, blades 120, 130 may be anti-corrosion coatings (MCrAlX; M is at least one member of the group

Iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare earths or hafnium). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 Bl, EP 0 412 397 B1 or EP 1 306 454 A1, which are intended to be part of this disclosure.

On the MCrAlX may still be present a thermal barrier coating, and consists for example of ZrO ₂ , Y ₂ O ₄ -ZrO ₂ , that is, it is not, partially or completely stabilized by

Yttrium oxide and / or calcium oxide and / or magnesium oxide.

By suitable coating methods, e.g.

Electron beam evaporation (EB-PVD) becomes stalk-shaped

Grains produced in the thermal barrier coating.

The vane 130 has an inner housing 138 of the

Turbine 108 facing Leitschaufelfuß (not here shown) and a Leitschaufelkopf opposite the Leitschaufelfuß. The vane head faces the rotor 103 and fixed to a mounting ring 140 of the stator 143.

FIG. 4 shows a perspective view of a moving blade 120 or guide blade 130 of a turbomachine that extends along a longitudinal axis 121.

The turbomachine may be a gas turbine of an aircraft or a power plant for power generation, a steam turbine or a compressor.

The blade 120, 130 has along the longitudinal axis 121 consecutively a fastening region 400, a blade platform 403 adjoining thereto and an airfoil 406. As a guide blade 130, the blade 130 may have at its blade tip 415 another platform (not shown).

In the mounting region 400, a blade root 183 is formed, which serves for attachment of the blades 120, 130 to a shaft or a disc (not shown). The blade root 183 is designed, for example, as a hammer head. Other designs as Christmas tree or Schwalbenschwanzfuß are possible.

The blade 120, 130 has a leading edge 409 and a trailing edge 412 for a medium flowing past the airfoil 406.

In conventional blades 120, 130, for example, solid metallic materials, in particular superalloys, are used in all regions 400, 403, 406 of the blade 120, 130. Such superalloys are known, for example, from EP 1204776 Bl, EP 1306454, EP 1319729 A1, WO 99/67435 or WO 00/44949; These writings are part of Epiphany. The blade 120, 130 can be made by a casting process, also by directional solidification, by a forging process, by a milling process or combinations thereof.

Workpieces with a monocrystalline structure or structures are used as components for machines which are exposed to high mechanical, thermal and / or chemical stresses during operation. The production of such monocrystalline workpieces takes place e.g. by directed solidification from the melt. These are casting processes in which the liquid metallic alloy is transformed into a monocrystalline structure, i. to the single-crystal workpiece, or directionally solidified. Here, dendritic crystals are aligned along the heat flow and form either a columnar grain structure (columnar, i.e., grains that run the full length of the workpiece and here, in common usage, are referred to as directionally solidified) or a monocrystalline structure, i. the whole workpiece consists of a single crystal. In these processes, it is necessary to avoid the transition to globulitic (polycrystalline) solidification, since non-directional growth necessarily produces transverse and longitudinal grain boundaries which negate the good properties of the directionally solidified or monocrystalline component.

If the term generally refers to directionally solidified structures, it means both single crystals which have no grain boundaries or at most small-angle grain boundaries, as well as columnar crystal structures which have grain boundaries which probably run in the longitudinal direction, but have no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures. Such methods are known from US Pat. No. 6,024,792 and EP 0 892 090 A1; these writings are part of the revelation. Likewise, the blades 120, 130 may be coatings against corrosion or oxidation (MCrAlX; M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and is yttrium (Y) and / or silicon and / or at least one element of the rare earths, or

Hafnium (Hf)). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 Bl, EP 0 412 397 B1 or EP 1 306 454 A1, which are intended to be part of this disclosure.

On the MCrAlX still a thermal barrier coating may be present and consists for example of ZrO ₂ , Y ₂ O ₄ -ZrO ₂ , that is, it is not, partially or completely stabilized by yttria and / or calcium oxide and / or magnesium oxide. By means of suitable coating processes, such as electron beam evaporation (EB-PVD), stalk-shaped grains are produced in the thermal barrier coating.

Refurbishment means that components 120, 130 may need to be deprotected after use (e.g., through

Sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products. Optionally, even cracks in the component 120, 130 are repaired. This is followed by a re-coating of the component 120, 130 and a renewed use of the component 120, 130.

The blade 120, 130 may be hollow or solid. If the blade 120, 130 is to be cooled, it is hollow and may still film cooling holes 418 (indicated by dashed lines) on.

FIG. 5 shows a combustion chamber 110 of a gas turbine. The combustion chamber 110 is designed, for example, as a so-called annular combustion chamber, in which a multiplicity of burners 107 arranged around the rotation axis 102 in the circumferential direction open into a common combustion chamber space. For this purpose, the combustion chamber 110 in its entirety as configured annular structure which is positioned around the rotation axis 102 around.

To achieve a comparatively high efficiency, the combustion chamber 110 is designed for a comparatively high temperature of the working medium M of about 1000 ^° C. to 1600 ^° C. To union even under these unfavorable for the materials Betriebs¬ parameters a comparatively long operating time to be made ^¬, the combustion chamber wall 153 is provided on its side facing the medium M, Arbeitsme- facing side with a formed from heat shield elements 155. liner.

Each heat shield element 155 is equipped on the working medium side with a particularly heat-resistant protective layer or made of high-temperature-resistant material. These may be solid ceramic stones or alloys with MCrAlX and / or ceramic coatings. The materials of the combustion chamber wall and its coatings may be similar to the turbine blades.

Due to the high temperatures inside the combustion chamber 110 may also be provided for the heat shield elements 155 and for their holding elements, a cooling system.

The combustion chamber 110 is designed in particular for detecting losses of the heat shield elements 155. For this purpose, a number of temperature sensors 158 are positioned between the combustion chamber wall 153 and the heat shield elements 155.

Claims

claims

1. A method for producing a model for the investment casting of a at least one cavity having component, in particular a turbine component in the

the finished model has at least one core and the outer contour of the core at least partially surrounding it

Turbine component at least partially defining outer contour model (1),

- Producing the core of a hardenable core material (11), which cures in the course of Verfahrnes takes place, and

a production of the outer contour model (1) takes place from a burn-out or fusible material,

characterized in that

first, the outer contour model (1) with at least one of the at least one cavity of the component corresponding cavity (8a-8e) is prepared and then filled to produce the at least one core, the curable core material (11) in the at least one cavity (8a-8e) and is cured.

2. The method according to claim 1, characterized in that

as outer contour model (1) a resin model is used

3. The method according to claim 2, characterized in that

the resin model is produced by means of a rapid prototype process.

4. The method according to any one of the preceding claims, characterized in that the outer contour model (1) during filling and / or curing of the hardenable core material (11) by a stabilizing sheath (12, 13) is surrounded.

5. The method according to claim 4, characterized in that

the stabilizing sheath (12, 13) is produced by means of a rapid prototype process

6. The method according to claim 5, characterized in that

the stabilizing sheath (12, 13) by means of a

Stereo lithography process is made of resin.

7. The method according to claim 6, characterized in that

the resin used to make the sheath (12, 13) contains a mechanically stabilizing material.

8. The method according to claim 7, characterized in that

as a mechanically stabilizing material, a metal powder is used.

9. The method according to claim 5, characterized in that

the stabilizing sheath (12, 13) is made by rapid laser sintering of metal powder.

10. The method according to any one of the preceding claims, characterized in that

as the core material (11) is used a flowable material before curing, which in the at least one cavity (8a-8e) of the

Outside contour model (1) is poured, brushed or injected.

11. The method according to any one of the preceding claims, characterized in that

as the core material (11), a ceramic-based material is used.

12. A method for producing a casting mold for a component having at least one cavity, in particular a turbine component in which a model produced by a method according to one of claims 1 to 11 is used.