EP1098725B1 - Method and device for producing a metallic hollow body - Google Patents

Description

The invention relates to a method and an apparatus for Production of a metallic hollow body with at least one Cavity, in particular a turbine blade with a Cooling air duct and several cooling air openings.

To manufacture metallic hollow bodies that have a cavity include, various methods are known, the Casting processes play a special role. casting process allow the production of precise, fully dimensioned components, the essential shape of the component in one Step, during casting, is carried out and possibly only processing steps for fine machining still required are. Such casting methods are therefore particularly suitable for Production of turbine blades, in particular gas turbine blades. To ensure permanently high temperatures during operation turbine blades, for example, are able to withstand metallic hollow body, the cavity of which as a cooling air duct is formed, which are acted upon by cooling air can. Turbine blades with a so-called film cooling have additional cooling air openings on their outer surface on, which open into the cooling air duct and a cooling air film Form on the outer surface of the turbine blade for cooling.

DE 38 23 287 A1 is a Medullary cavity sealing device specified, in which a Cavity-forming core surrounded by a wax coat becomes. The thickness of the wax jacket corresponds to the wall thickness of the Wall of the component to be cast. To make the Medullary sinus sealers are placed in the wax coat pins introduced, the inner ends of which touch the core, while the protrude the outer ends of the pins over the wax coat.

The wax coat with pins is then placed in a ceramic slurry submerged, enclosed by this and then heated so that the ceramic paste harden and can form a ceramic outer mold. While heating the wax coat melts, the from the pins held core remains fixed in its position. The hardened Ceramic porridge with the usually also ceramic core forms the mold, which is then made with molten metal is filled out. The material of the pens, for example, platinum can be melted or melted by the molten metal and diffuse into it. The material the pins are chosen so that it is essentially too no local, harmful alloy formation occurs. Around Errors occurring during the solidification of the metal component to avoid, e.g. due to heat loss in the ceramic outer mold protruding pins heat retention caps are attached to the pins, which help to avoid losing heat too quickly on the pins. For the production of a film-cooled turbine blade then cooling air openings through the outer wall drilled, which open into the cavity.

A disadvantage of this method is that the Pass the pins into the outer mold until the ends the pins over the surface of the finished component protrude what post-processing of the component is necessary makes. Furthermore, the pens could not be chosen as wide as desired to fix the core in place, otherwise locally unwanted alloys could arise. You can also not any number of platinum pencils for cost reasons can be used to fix the core.

To avoid reworking a finished component DE 33 12 867 A1 specifies a method in which the core forming the cavity is surrounded by a support is whose external dimensions do not exceed the surface of the protrude to the cast component. The core with support is then surrounded by a wax coat and in dipped a ceramic porridge. The core is supported Made of a material that is in the cast alloy dissolves and the properties of the component are not disadvantageous affected. Here too there is the disadvantage that in one additional processing step cooling air openings in the Wall of the turbine blade must be drilled.

Both methods also have the disadvantage that it already does when removing the wax coat, due to the different Thermal expansion behavior of the pins or the support and the core, with respect to a displacement of the core the later outer wall can come, which leads to a fluctuating Wall thickness leads.

The object of the invention is a method for the production to specify a metallic hollow body. It is another task the invention an apparatus for producing a metallic hollow body, in particular a turbine blade a gas turbine.

The object directed to a device is invented solved by a device for producing a metallic, at least one cavity and one the cavity surrounding wall having a hollow body, comprising a Outer casting mold, which has at least one inner core, which for Formation of the cavity is used, the outer mold in at least two outer parts are made divisible and the Inner core via at least one connecting element that the Training a passage opening in the wall in the Serves cavity, with an outer part of the outer mold connected is.

The invention is based on the knowledge that a mold, which was formed with the help of a wax-coated core, already deviations in the cavity released by the wax with regard to the desired wall thickness of the component to be cast having. The deviations in the location of the core with respect his desired position results in from the different Thermal expansion of the ceramic core, the metallic Pins or supports and the wax coat forming Wax. There may be further deviations when pouring of the cavity formed by the mold with molten Metal and subsequent solidification of the metal come. The different effects of heat towards the core and the pins or supports of the mold lead to a different thermal expansion, which under unfavorable Cause the core to twist and thus lead to an additional, local wall thickness deviation can.

The invention is based on the consideration of the casting mold without forming a lost wax coat and an improved one To achieve fixation of the core to the rest of the mold, so that no relative movements of the core with respect to the rest of the mold, which lead to an undesirable change in wall thickness can, are possible.

This is achieved according to the invention by a device which forms a divisible mold for a metallic hollow body. This divisible mold comprises one in several outer parts divisible outer mold and at least one inner core a connecting element. The outer mold essentially represents the negative of the outer surface of the hollow body to be cast represents, while the inner core to form the cavity serves. The inner core is via at least one connecting element with at least one outer part of the outer mold connected. The connecting elements fix the inner core with respect its position to the outer mold and form the passage openings through the wall of the component to be cast. Each connecting element is designed so that its Dimensions and its location the dimensions and the position a passage opening through the wall of the to be cast Component correspond in the cavity formed by the inner core. The number of connecting elements preferably corresponds the number of the components to be cast Passage openings. To the position of the inner core relative to To fix the external mold, the connecting elements range from the surface of the inner core to the outer mold and touch the outer parts such that no later when pouring Casting material between the connecting elements and the outer mold or can reach the inner core. This will make the Advantage achieved that the inner core and the outer mold have a defined distance from each other, which is the wall thickness of the component to be cast. The mold for the component to be cast consists of those joined together to form the outer mold External parts with the connecting elements connected inner cores and the connecting elements. Since the Mold can be made without a wax coat, it can not with regard to an undesirable change in position of the inner core the outer mold due to different thermal expansion of the inner core, the outer mold and / or the connecting elements come when the wax coat melts.

An inner core via at least one connecting element is advantageous firmly with an outer part of the outer mold connected. This has the advantage that the inner core even when pouring the mold with liquid metal Position with respect to the outer mold does not change.

An inner core with exactly one outer part is preferred connected. This ensures that the finished mold from at least two individual components can be assembled, wherein each component consists of exactly one outer part that if necessary with an inner core via assigned connecting elements is firmly connected. In addition to the fixed connection of the inner core and outer part used connecting elements further connecting elements can be assigned to the inner core, which serve to form further through openings.

To the high temperatures and the associated high thermal stress on the mold when pouring the component To be able to withstand, the outer mold preferably consists of a ceramic material. The inner core is also preferred made of a ceramic material.

For hollow bodies with a particularly complicated shape Cavity (e.g. a cavity with one or more constrictions) advantageously serve several inner cores for training of the cavity. This allows the geometry of each one Inner core can be made relatively simple, creating a inexpensive manufacture of the mold can be achieved.

Is the cavity, for example, as a supply channel for supply a turbine blade with cooling air provided, so extends the inner core forming the supply channel advantageously along a main direction of expansion and has a substantially trapezoidal or triangular cross-sectional area perpendicular to the main direction of expansion. This has the advantage that two inner cores that the Serve two different supply channels and which are attached to two different outer parts, in the Kind of interlocking and so the joining together the outer parts to the mold not hinder.

Is the cavity used to form a cool bag, e.g. one Cooling bag of a turbine blade, this is the cooling bag forming inner core preferably essentially plate-shaped. An inner core that forms a the cooler bag with the supply duct supplying cooling air serves, is then over the plate-shaped inner core with the External mold connected.

If a component to be cast has several cavities, then serve advantageously several inner cores to form the different cavities. To continue the stability of the mold to increase and prevent the inner cores that serve to form different cavities, relative to each other move, such inner cores are at least over a connecting element, in particular via spacer knobs, kept at a distance from each other.

The device described is preferably used for production a metallic, at least one cavity and a hollow body surrounding the cavity, used to manufacture a turbine blade of a gas turbine, the cavity being a cooling duct of the turbine blade is formed and several cooling air openings for the cooling channel are provided, each cooling air opening is formed by a passage opening. The usage the device has the advantage that the finished poured Turbine blade has a defined wall thickness and therefore the amount of cooling air required to cool the turbine blade to the maximum permissible surface temperature of the turbine blade can be coordinated. Overall, there is a extremely low cooling air requirement leading to high efficiency the gas turbine results. Another advantage results differs in that the turbine blade after removal of the Mold does not have to be reworked. Among other things, the Drilling the cooling air openings or removing the over the outer surface protruding pins when an inner core of the Casting mold according to the prior art with metallic pins was fixed in its position. They are also used to manufacture no precious metal pins (e.g. platinum) necessary for the mold, which on the one hand lowers the manufacturing costs and on the other hand the Reduced risk of local alloy formation.

The object directed to a method is achieved according to the invention solved by a process for producing a metallic Hollow body with at least one cavity and one the cavity surrounding wall, which has a passage opening, a mold is poured out with metal by an inner core that serves to form a cavity with at least one connecting element to an outer part of one in at least two outer parts connected to the outer mold is then joined together to form the outer mold be from the outer mold, the fasteners and cast the existing core with metal and the mold is finally removed.

The mold of a hollow body can be assembled piece by piece become. Each component of the mold consists of at least one outer part of the outer mold and, if appropriate one or more assigned inner cores, the with connecting elements on the outer parts of a component are attached. Each component in turn represents a component which can be composed of smaller units. In this way it is possible to have a mold for one complicated molded hollow body from a plurality of smaller Elements that have a relatively simple geometry, piece by piece. There is the advantage that a large number of pre-made or partially pre-made Elements (e.g. connecting elements, inner cores) for assembly the components of the mold can be used what the construction effort and thus the costs for production reduced. The outer parts of the prefabricated components are then assembled into a mold for the hollow body and firmly connected. Then the finished one Casting mold in a known manner with liquid metal and removed after the metal solidifies.

FIG. 1

Seitenansicht eines Hohlkörpers;

FIG. 2

Querschnitt des Hohlkörpers aus FIG.1 entlang der Linie I-I;

FIG. 3

geteilte Gußform für einen den Hohlkörper aus FIG.1;

FIG. 4

zusammengesetzte Gußform für einen Hohlkörper aus FIG.1;

FIG. 5

Schrägansicht auf einen Ausschnitt aus FIG. 3.

The device and the method for producing a hollow body are explained in more detail using the exemplary embodiments shown in the drawing. The figures show a schematic representation:

FIG. 1

Side view of a hollow body;

FIG. 2

Cross section of the hollow body of Figure 1 along the line II;

FIG. 3

split mold for a the hollow body from FIG.1;

FIG. 4

assembled casting mold for a hollow body from FIG. 1;

FIG. 5

Oblique view of a section from FIG. Third

Elements with the same effect each carry the same in the figures Reference numerals.

In FIG. 1 is a side view of a hollow body 1 Turbine blade with a blade area 2 for one Gas turbine shown. The turbine blade 1 has a number of cavities 3, 5, 7, 9, 11, 13, 15, 17, 19 and 21 on which are surrounded by a wall 23, as in cross section through the airfoil area 2 along the line I-I in FIG. 2 is shown. The cavities 3, 5, 7, 9, 11, 13, 15, 17, 19 and 21 form cooling channels 3, 5, 9, 15, 19 and 21 and cooling air pockets 7, 11, 13 and 17, which can be charged with cooling air are. The wall 23 of the turbine blade 1 has a plurality of passage openings 25, also as Cooling air openings 25 referred to, in the cooling air pockets 7, 11, 13 and 17 and in the cooling channel 3 open. By this cooling air openings 25 can cool air from the cooling channels inside the turbine blade 1 onto the outer surface 24 emerge from the wall 23 and form a cooling air film there.

FIG. 3 shows an apparatus for producing a turbine blade 1. The device consists of a ceramic Mold 27, the one divided into two outer parts 29A and 29B Outer mold 29 includes. Furthermore, the mold 27 comprises one Number of ceramic inner cores 33, 35, 37, 39, 41, 43, 45, 47, 49 and 51 which form the cavities 3, 5, 9, 15, 19 and 21 serve. The inner cores 33, 37, 41 are ceramic Connecting elements 53 connected to the outer part 29A and the inner cores 43, 47 and 51, respectively, with the outer part 29B. The inner cores 35 and 39 are also each via connecting elements 53 (spacer knobs) with the neighboring ones Inner cores 33 and 37 and 37 and 41 connected and spaced, while the remaining inner cores 45 and 49 each on only one further inner core 43 or 47 with connecting elements 53 are attached.

The different inner cores 33 to 51 are according to the The task of the cavities they form varies formed. The cooling air pockets 7, 11 13 and 17 are for example of plate-shaped inner cores 37, 41, 43 and 47 educated. The plate-shaped inner cores have holes 57 (see. 5) on the formation of webs not shown in the cooler bags 7, 11, 13 and 17 serve. Reinforce these bridges the mechanical stability of the turbine blade 1 in Area of the wall 23. On the plate-shaped inner cores 37, 41, 43 and 47, connecting elements 53 are glued, which in turn is glued to one of the outer parts 29A and 29B are. The ceramic connecting elements 53 correspond in FIG their dimensions and their location that they formed Cooling air openings 25 of the turbine blade 1 and therefore have preferably a cylindrical cross section.

In FIG. 4 is a cross section of the outer parts 29A and 29B and the inner cores 33, 35, 37, 39, 41, 43, 45, 47, 49 and 51 and the connecting elements 53 Mold 27 shown. The outer parts 29A and 29B are here firmly connected. In the area of the center of the mold 27 engage the inner cores 35, 39, 45 and 49 in the manner interlocking, making it easy Joining the outer parts 29A and 29B. Through the fixed Connection of each inner core to one of the two outer parts 29A or 29B is the position of each inner core with respect to FIG neighboring inner cores, and with respect to that of the outer parts 29A and 29B formed outer mold clearly determined.

FIG. 5 shows an oblique view of a detail from FIG. 3, the inner cores 37 and 35 for better illustration not yet with the outer part 29A or with the inner core 37 are connected. The plate-shaped inner core 37 is used Formation of the cooler bag 7 from the cooling air duct 5 with cooling air is supplied. The inner core 35 to form the Cooling air duct 5 serves extends along a main direction of expansion 55. The cross-sectional area 57 perpendicular to The main direction of expansion 55 of the inner core 35 has a essentially triangular shape. The connecting elements 53 on the one hand form cooling air openings 25 or connections from Cooling channel 35 to the cooler bag 37, on the other hand, they hold one fixed distance between the inner cores 37 and 35 and the Inner core 37 and the outer part 29A upright.

The mold 27 for the turbine blade 1 is in several Steps. Since the connecting elements 53 a have cylindrical cross section, they can be made of rod-shaped primary material cut to the required length and at the positions of the cooling air openings 25 on the inner cores 33, 37, 41, 43 and 49 e.g. be glued. Then the connecting elements 53, plate-shaped inner cores 37 and 41 or 43 and 47 and the Inner cores 33 and 51 fixed via the connecting elements 53 glued to the outer halves 29A and 29B. Then be the inner cores 35, 39, 45 and 49, which cooling air channels to supply the cooling air pockets 7, 11, 13 and 17 with cooling air form, with the inner cores 37, 41 assigned to them, 43 and 47 glued via connecting elements 53 (spacer knobs). The outer parts 29A and 29B then become the mold 27 put together and firmly connected. For education the turbine blade 1, the mold 27 with liquid Poured metal. After the metal solidifies, the mold becomes 27 e.g. removed by leaching, and then gives the finished molded turbine blade 1 free.

Claims (14)

1. Device for producing a metallic hollow body (1) having at least one cavity (3, 5, 17) and a wall surrounding the cavity, comprising an outer casting mould, which has at least one inner core (33, 35, 47), which serves to form the cavity, characterized in that the outer casting mould is designed so that it can be split into at least two outer parts (29A, 29B), and the inner core (33, 35, 47) is connected to an outer part (29A, 29B) of the outer casting mould via at least one connecting element (53), which serves to form a through-hole (25) in the wall (23) right into the cavity (3, 5, 7).
2. Device according to Claim 1, characterized in that the inner core (33) is firmly connected to an outer part (29A, 29B) of the outer casting mould via at least one connecting element (53).
3. Device according to Claim 1 or 2, characterized in that the outer casting mould is made of a ceramic material.
4. Device according to one of the preceding claims, characterized in that the inner core (33, 35, 47) is made of a ceramic material.
5. Device according to one of the preceding claims, characterized in that the inner core (33, 35, 47) is connected to just one outer part (29A, 29B).
6. Device according to one of the preceding claims, characterized in that a plurality of inner cores (33, 35, 47) serve to form the cavity.
7. Device according to one of the preceding claims, characterized in that the connecting element (53) is of cylindrical design.
8. Device according to one of the preceding claims, characterized in that a plurality of inner cores (33, 35, 47) are provided in order to form at least two cavities.
9. Device according to Claim 8, characterized in that at least two inner cores (33, 35, 47, 51), which serve to form different cavities, are connected to one another and kept at a distance from one another via a connecting element (53).
10. Device according to one of the preceding claims, characterized in that an inner core (33, 35, 45), which serves to form a supply passage (3, 5, 15) for cooling air, extends in a main extension direction (55) and has an essentially trapezoidal or triangular cross-sectional area (57) perpendicular to the main extension direction (55).
11. Device according to one of the preceding claims, characterized in that an essentially plate-shaped inner core (37, 41, 43, 47), which serves to form a cooling pocket (7, 11, 13, 17), is connected on the one hand to the outer casting mould and on the other hand to an inner core (35, 39, 45) serving to form a supply passage (5, 9 15) supplying the cooling pocket (7, 11, 13, 17) with cooling air.
12. Device according to one of the preceding claims, characterized in that the connecting element (53) is made of a material different from the inner core (33, 35, 47) and/or the outer casting mould.
13. Use of a device for producing a metallic hollow body (1) having at least one cavity (3, 5, 17) and a wall (23) surrounding the cavity, comprising an outer casting mould, which has at least one inner core (33, 35, 47), which serves to form the cavity (3, 5, 17), the outer casting mould being designed so that it can be split into at least two outer parts (29A, 29B), and the inner core (33, 35, 47) being connected to an outer part (29A, 29B) of the outer casting mould via at least one connecting element (53), which serves to form a through-hole (25) in the wall (23) right into the cavity (3, 5, 17), for producing a turbine blade (1) of a gas turbine, the cavity (3, 5, 17) being designed as a cooling passage, and a plurality of cooling-air holes being provided for the cooling passage, each cooling-air hole being formed by a through-hole (25) through the wall (24).
14. Method of producing a metallic hollow body (1) having at least one cavity (3, 5, 17) and a wall (23) which surrounds the cavity and has a through-hole (25), a casting mould (27) being filled with metal, characterized in that

    a) an inner core (33, 35, 47), which serves to form a cavity (3, 5, 17), is connected by at least one connecting element (53) to an outer part (29A, 29B) of an outer casting mould split into at least two outer parts (29A, 29B),

    b) the outer parts (29A, 29B) are joined to form the outer casting mould,

    c) the casting mould (27) consisting of the outer casting mould, the connecting elements (53) and the inner core (33, 35, 47) is filled with metal and

    d) the casting mould (27) is removed.

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