EP1920858B1 - Method for manufacturing a casting mould - Google Patents

Description

The invention relates to a method for producing a casting mold according to claim 1.

Formed as a hollow body components with complex shaped geometries and complex through-holes in the region of an outer wall of the component can be prepared in various ways.

Many components, in particular metallic components made of alloys, by casting method, eg. B. produced by the lost wax process.
In this case, in a first step, a casting mold is produced from a wax model of the component, which at least in part represents the negative of the component to be produced, in that the wax model is covered with ceramic or a sand mold.

Through holes in the walls of hollow components, such. B. film cooling holes of turbine components are always subsequently introduced by means of a laser and its laser beams, as shown in the U.S. Patent 6,329,015 B1 is shown. The laser beam guidance is very complicated.
Methods for producing a casting with subsequently introduced holes, in particular through-holes are therefore time-consuming. EP 0559251 A1 shows a method for producing a casting mold in which through holes in the casting are produced by separate pins.

It is therefore an object of the invention to provide a method for producing a casting mold with which the production of a component with holes, in particular with through holes, can be carried out more simply and more quickly.
The object is achieved by a method for producing a casting mold according to claim 1.

In this case, a mold is produced, which has corresponding projections, wherein in the intermediate step, at least one depression in the surface of the model is generated and wherein mold material is introduced into the recess to produce at least a part of a hole of the component to be produced during casting, and wherein at least one recess is completely filled with a material that gives a projection of the mold, wherein the recess when mounting the inner wall, the Kerns or the outer wall is filled with material and wherein the material is cured in the recess and is brought into connection with the inner wall or the outer wall.

In the subclaims further advantageous measures are listed.
The measures listed in the dependent claims can be combined with each other in an advantageous manner.

Figur 1

ein Bauteil mit einem Durchgangsloch,

Figur 2, 3, 4, 5

Gussformen mit verschiedenen Vorsprüngen zur Ausbildung eines Durchgangslochs,

Figur 6

eine Aufsicht auf eine innere Oberfläche einer Gussform,

Figur 7 - 10

Verfahrensteilschritte,

Figur 11

eine Gasturbine,

Figur 12

eine Brennkammer und

Figur 13

eine Turbinenschaufel.

Show it

FIG. 1

a component with a through hole,

FIGS. 2, 3, 4, 5

Molds with different protrusions to form a through-hole,

FIG. 6

a plan view of an inner surface of a mold,

FIGS. 7-10

Part of the process steps,

FIG. 11

a gas turbine,

FIG. 12

a combustion chamber and

FIG. 13

a turbine blade.

FIG. 1 1 shows a component 1 which, for example, has a cavity 31 at least in part of its volume and is connected to the mold 16 (FIG. Fig. 2, 3, 4 . 5 ) can be produced. In this case, the component 1 has at least one component wall 4, 4 ', in particular outer component walls 4, 4'.

By way of example, at least one hole 13, in this case a through hole 13, is formed in the wall 4. The hole 13 may also be a blind hole.

The component 1 may be metallic or ceramic, for example. For example, it is a turbine component 1 of a gas turbine 100 (FIG. Fig. 11 ) or steam turbine and, for example, a turbine blade 120, 130 (FIG. Fig. 11 . 13 ) or a heat shield element 155 (FIG. Fig. 12 ), which consists for example of an iron-, nickel- or cobalt-based superalloy.

In such components 1, through holes 13 are provided, for example, as cooling air holes 13 to cool the component 1 by film cooling.
The through hole 13 has, for example, a round or oval-shaped hole part 7, which widened from the cavity 31 to the outer surface 11 of the wall 4 to a diffuser 10, so that there the hole 13 deviates from the shape of the hole part 7.
The mold 16 for such components 1 with complex shapes of a through hole 13, 7 + 10 can be made easier and faster with the method according to the invention.

The wall of the component 1 is, for example, 2 to 6 mm, in particular 3 to 4 mm thick.
The hole part 7 has a diameter of 0.3 to 1.2 mm, in particular 0.6 to 0.8 mm.
The diffuser 10 is formed on the outer surface 11, for example, trapezoidal and has dimensions of 1.5 to 5mm x 1.5 to 5mm and goes to a depth of 1 to 1.5mm in the component wall 4, 4 'into it.

FIG. 2 As the prior art shows schematically a part of the mold 16, which consists of an inner wall 25, in particular a core 25 and an outer wall 28.
In the intermediate space 26 (cavity of the mold 16) between the inner wall 25 and outer wall 28, material 22, such as molten metal, poured and forms after cooling, for example, the wall 4 of the component. 1
The core 25 forms, for example, a part of the cavity 31 of the component 1.

In this intermediate space 26 at least one projection 19, 34, 37 is formed of molding material.
The projection 19, 34, 37 extends at least over part of the gap between an inner surface 20 of the inner wall 25 and an inner surface 21 of the outer wall 28.

Here, the continuous projection 19 extends continuously from the inner surface 20 of the inner wall to the inner surface 21 of the outer wall.

The continuous projection 19 has been formed by pouring ceramic of a through hole 13 in a wax model 43 of the component 1.

The continuous projection 19 in the gap 26 prevents filling with material 22 during casting, so that after removal of the mold 16 with its inner wall 25 and its outer wall 28 and the continuous projection 19, a through hole 13 results.

• Ein innerer Vorsprung 34 stellt das runde oder ovale (Fig. 6) Lochteil 7 des Durchgangslochs 13 dar.
• Ein äußerer Vorsprung 37 stellt den Diffusor 10 dar.
• Der durchgehende Vorsprung 19 kann aber auch über seinen gesamten Querschnitt rund oder oval ausgebildet sein und beispielsweise auch konstant in seiner Querschnittsfläche sein.

The continuous projection 19 is constructed, for example, as follows:

• An inner projection 34 represents the round or oval ( Fig. 6 ) Hole part 7 of the through hole 13.
• An outer projection 37 represents the diffuser 10.
• However, the continuous projection 19 can also be round or oval over its entire cross-section and, for example, also be constant in its cross-sectional area.

Optionally, after the casting of the component 1, a minimal, but compared to previous methods but significantly reduced post-processing of the through-hole 13 can take place.

FIG. 3 shows a first embodiment of a mold 16, which is produced by the method according to the invention. In contrast to the mold 16 after FIG. 2 The inner projection 34, 37 'does not extend continuously from an inner surface 20 of the inner wall 25 to an inner surface 21 of the outer wall 28.
The inner projection 34 is formed only on the inner surface 20 of the inner wall 25 and extends up to a certain distance d to the inner surface 21 of the outer wall 28th
During casting, when filling the cavity 26 with material 22, therefore, the passage opening 13 is not completely formed. In the area between the inner projection 34 and the inner surface 21 of the outer wall 28, material 22 is present after the casting of the component 1. However, the area is correspondingly thin, in particular membrane-like, so that it can be easily removed in a very short time. It can also be said that at the end of the casting process, the passage opening 13 of the component 1 to be produced is still somewhat closed.
This is useful, for example, if subsequently at least one coating is applied to the outer outer surface 11 of the component 1. Since the passage opening 13 is still closed, the passage opening 13 is also not contaminated or narrowed by the material of the coating. Only with a final processing step, the material of the thin compared to the thickness of the wall 4 coating and the little material 22, which still closes the passage opening 13, quickly and easily removed.
The coating is, for example, an MCrAlX alloy (M = Fe, Co, Ni and X = Y and / or a rare earth element) and optionally a ceramic coating as a thermal barrier coating (for example Y ₂ O ₃ - ZrO ₂ ) thereon.

The inner projection 34 can also have a support connection 40 (indicated by dashed lines) in order to support the inner projection 34, which projects freely into the intermediate space 26, against the outer wall 28.
The support connection 40 is formed smaller in cross section than the cross section of the inner projection 34, 37 ', which is opposite to the outer wall 28. The support connection 40 thus represents only a part of the through hole 13 to be produced.
The inner projection 34 may have at the end an advantageous portion 37 ', which in part the outer projection 37th ( Fig. 4 ) and does not touch the wall 21, but optionally has the support connection 40.

In particular, the complex shape of the diffuser 10 previously had to be elaborately incorporated into the molded component. This is omitted here for the most part, since only a relatively small upper portion of the diffuser 10 is to be reworked by removing material.
Since, in particular, the production of the areas lying deeper in the wall 4 means considerable expenditure, for example in laser guidance, this casting mold 16 has considerable advantages.

FIG. 4 shows a further embodiment of a trained mold 16, which was produced by the method according to the invention.
Here, the outer protrusion 37 is formed only on the inner surface 21 of the outer wall 28. The outer projection 37 represents the negative 37 of the diffuser 10 of the through-opening 13 to be produced. In particular, the diffuser 10 has a more complex geometry than a simple symmetrical hole and would therefore be very complicated to produce with subsequent incorporation. However, if the diffuser region 10 is already formed in the surface of the component 1 to be produced, it no longer has to be incorporated subsequently. It has only with comparatively little effort a simply formed hole part 7 ( Fig. 1 ) are incorporated from the diffuser region 10 in the component 1 in the wall 4. This can be done by laser processing or radio wire erosion as well as other methods.
Likewise, also here a corresponding support connection 40 between the projection 37 and the inner wall 25 may be present (indicated by dashed lines).

FIG. 5 shows a further embodiment of a trained mold 16, which was produced by the method according to the invention.

Starting from FIG. 4 Also, an inner projection 34 is formed on the inner surface 20 of the inner wall 25. The inner projection 34 forms a further part of this passage opening 13, namely the area of the hole part 7. The outer projection 37 represents the area of the diffuser 10 of the component 1 to be produced.
By the outer projection 37 and the inner projection 34, the processing time for the production of the hole 13 in the manufactured component 1 with respect to a component 1, which with a mold according to FIG. 4 was produced, shortened. In particular, such molds 16, in which there is no continuous connection between the inner wall 25 and outer wall 28, easy to produce, since the core 25 is produced separately from the wall 28 and is introduced into the mold 16 for casting.
The projections 34, 37 may directly abut each other or have a certain distance from each other.

FIG. 6 shows the top view of an outer wall 28 of a formed mold 16, which was prepared by the method according to the invention.

On the inner surface 21 of the outer wall 28 a plurality of projections 19 are formed. The reference numeral 34 indicates the area from which the hole part 7 will be formed.
The reference numeral 37 designates the region of the projection 19, which represents the diffuser region 10 of the through-hole 13 to be produced.

The FIGS. 7 to 10 show how a mold 16 according to FIGS. 3 to 6 is to produce according to the invention.

The FIG. 7 shows the inner wall 25 or the core 25 of the mold 16, on which a model 43, in particular made of wax, is present, which corresponds in its geometry and thickness to the component 1 to be produced. In this case, the inner wall 25 represents the core 25, for example. Thus, the model 43, for example, like the component 1 to be produced with the casting mold 16, is a hollow component.

According to the prior art, the wax model 43 is filled inside with a ceramic 25 ( Fig. 7 ) and externally covered with an outer wall 28 ( Fig. 8 ), in which case the model, in particular a wax model 43, is removed (eg by melting out), so that a casting mold 16 (FIG. Fig. 3, 4 ).
When material, for example, liquid metal is poured into the mold 16, the component 1 is formed.

According to the invention, at least one recess 46 in accordance with FIG FIG. 9 brought in.
This depression 46 is not the cavity of the model 43, but starts, for example, from the surface 58 of the model 43.

The recess 46 is formed as a blind hole ( FIG. 9 ), which does not extend to the inner wall 25, that extends over only a part of the wall thickness of the model 43.

The depression 46 can be introduced into the model 43 when the inner wall 25 or the core 25 has already been brought together with the model 43 ( Fig. 9 ).

The recess 46 can be made in various ways, for example by drilling, milling or laser machining.

In particular, this recess 46 may have a slanted hole or oblique "hole" 49 as shown in FIG FIG. 11 . 12 is shown.
Namely, an inner wall 25 or outer wall 28 having an oblique projection can not be produced by molding a ceramic into a corresponding mold and releasing the mold by peeling or loosening.

The recess 46 extends only partially in the model 43 (FIG. Fig. 9 ) and is completely filled with a ceramic material 52 ( Fig. 10 ) before the outer wall 28 is applied to the model 43 or with application of the outer wall 28, so that the mold 16 after removal of the model 43 according to FIG. 4 formed.

The FIG. 11 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 109. The annular combustion chamber 106 communicates with an annular annular hot gas channel 111, for example. There, for example, four turbine stages 112 connected in series form the turbine 108. Each turbine stage 112 is formed from two blade rings. As seen in the direction of flow of a working medium 113, in the hot gas channel 111 of a row of guide vanes 115, a series 125 formed of rotor blades 120 follows.

The vanes 130 are attached to the stator 143, whereas the blades 120 of a row 125 are mounted on the rotor 103 by means of a turbine disk 133. At the Ro Tor 103 coupled to a generator or a working 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 rotor blades 120 of the first turbine stage 112, viewed in the direction of flow of the working medium 113, are subjected to the greatest thermal stress in addition to the heat shield bricks lining the annular combustion chamber 106. In order to withstand the temperatures prevailing there, they are cooled by means of a coolant. Likewise, the blades 120, 130 can have coatings against corrosion (MCrAlX, M = Fe, Co, Ni, X = Y, rare earths) and heat (thermal barrier coating, for example ZrO ₂ , Y ₂ O ₄ -ZrO ₂ ).
Often the turbine blade 120, 130 is still air-cooled and has film cooling holes 13 which are connected to the casting mold 16 (FIG. Fig. 2-6 ) in the cast and / or directionally solidified turbine blade 120, 130.

The vane 130 has a guide vane foot (not shown here) facing the inner housing 138 of the turbine 108 and a vane head opposite the vane foot. The vane head faces the rotor 103 and fixed to a mounting ring 140 of the stator 143.

The FIG. 12 shows by way of example a combustion chamber 110 of a gas turbine 100.
The combustion chamber 110 is configured, for example, as a so-called annular combustion chamber, in which a plurality of burners 102 arranged around the turbine shaft 103 in the circumferential direction open into a common combustion chamber space. For this purpose, the combustion chamber 110 is configured in its entirety as an annular structure, which is positioned around the turbine shaft 103 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. In order to enable a comparatively long service life even with these, for the materials unfavorable operating parameters, the combustion chamber wall 153 is provided on its side facing the working medium M side with an inner lining formed from heat shield elements 155. 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. Due to the high temperatures in the interior of the combustion chamber 110, a cooling system is additionally provided for the heat shield elements 155 or for their holding elements.
Often the heat shield elements 155 have film cooling holes 13 or passages for fuel into the combustion chamber 110 created in the heat shield element 155 with the mold 16.

FIG. 13 shows a perspective view of a blade 120 or guide vane 130 of a turbomachine, which 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 are used in all regions 400, 403, 406 of the blade 120, 130.
The blade 120, 130 can in this case be produced by a casting process by means of the casting mold 16, also by means of directed 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, for example, by directed solidification from the melt. These are casting methods in which the liquid metallic alloy solidifies into a monocrystalline structure, ie a single-crystal workpiece, or directionally.

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.

The term generally refers to directionally solidified microstructures, which means both single crystals that have no grain boundaries or at most small angle grain boundaries, and stem crystal structures that have probably longitudinal grain boundaries but no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures.
Such methods are known from U.S. Patent 6,024,792 and the EP 0 892 090 A1 known.

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

As a protection against corrosion, the blade 120, 130, for example, corresponding mostly metallic coatings (MCrAlX) and as protection against heat mostly a ceramic coating.

LIST OF REFERENCE NUMBERS

1

component

4, 4 '

wall

7

hole part

10

diffuser

11

outer surface

13

Hole / through hole / blind hole

16

mold

19, 19 '

head Start

20

inner surface / inner wall

21

inner surface / outer wall

22

material

25

inner wall / core

26

gap

28

outer wall

31

cavity

34; 37 '

inner projection

37

Outer lead

40

support link

43

wax model

44

Wall of the model

46

deepening

49

oblique hole

52

Material / ceramics

55

whitespace

58

Surface of the model

100

gas turbine

102

axis of rotation

103

rotor

104

suction

105

compressor

106

annular combustion chamber

107

burner

108

turbine

109

exhaust housing

110

combustion chamber

111

Hot gas duct

112

turbine stages

113

working medium

115

vane row

120

blade

121

longitudinal axis

125

Blade row

130

vane

133

turbine disk

135

air

138

inner housing

140

fixing ring

143

stator

153

combustion chamber wall

155

Heat shield element

183

blade

300, 303

steam turbine

354, 357

turbine component

400

fastening area

403

blade platform

406

airfoil

409

leading edge

412

trailing edge

415

blade tip

418

Film cooling holes

Claims (6)

1. Method for the production of a casting mould (16), in which, in an intermediate step, a model (43) of a component (1) to be produced by means of the casting mould (16) is used, characterized in that, in the intermediate step, at least one depression (46) is generated in the surface (58) of the model (43), the depression extending only partially through a wall (44) of the model (43) and in that moulding material is introduced at least into the one depression (46), that the at least one depression (46) is filled up completely with a material (52), in order, during casting, to generate at least part of a hole (13) of the component (1) to be produced, and which results in the projection (19, 34, 37) of the casting mould (16), in that the depression (46) is filled with material (52) during the application of the inner wall (25), of the core (25) or of the outer wall (28), and in that the material (52) in the depression is cured and is connected to the inner wall (25) or the outer wall (28).
2. Method according to Claim 1, characterized in that the casting mould (16) at least consists of an inner wall (25) or of a core (25) and of an outer wall (28), and in that the inner wall (25) or the core (25) are already arranged in the model (43) when the depressions (46) are generated.
3. Method according to Claim 1, characterized in that the casting mould (16) at least consists of an inner wall (25) or of a core (25) and of an outer wall (28), and in that the depressions (46) are introduced into the model (43) before a wall (25, 28) is applied.
4. Method according to Claim 1, 2, or 3 characterized in that the at least one depression (46) is an oblique hole (49).
5. Method according to Claim 3 or 4, characterized in that an outer wall (28) is connected to the model (43), and in that the model (43) is removed so that the casting mould (16) is obtained.
6. Method according to Claim 1, characterized in that the casting mould (16) is used to produce a turbine component (120, 130, 155, 354, 357) of a gas turbine (100) or steam turbine (300, 303), in particular of a turbine blade (120, 130, 354, 357) or of a heat shield element (155).

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