EP3225331B1 - Method for casting a contoured metal article, in particular made from tial - Google Patents

Description

The invention relates to a method of casting a contoured metal article using one or more molds.

Molds are typically used to cast a metal article from a melt. These define the contour of the finished, cast metal object via a cavity which is defined by the mold cavities of the detachably connectable mold parts. The melt is poured into the mold, after which it solidifies. Although a variety of different metals or metal alloys can be processed by a chill casting, but there are groups of materials that have poor casting properties, in particular problems arise when the contoured metal object has a varying over its longitudinal axis volume distribution with one or more undercuts.

An example of such a poorly castable material group is that of titanium aluminides. The material group of titanium aluminides, due to their low density of about 4 g / cm ³ and the good high temperature properties, offers the potential to replace superalloys in their field of use as a material for highly stressed components in reciprocating engines and gas turbines, especially blades, while achieving a weight advantage. Due to the poor casting properties of these materials, it is not possible to produce complex contoured components via a chill casting. For this reason, such components are usually produced via a combined casting / forging route. This includes the casting of a semi-finished product with rotationally symmetrical, usually cylindrical or conical geometry in a permanent metal form, ie the production of a geometrically very simply designed, no undercuts or the like having semi-finished product. The casting is followed by a multi-stage forming and a final heat treatment and finishing to show the final component. By The forgings can achieve good properties of the components, but this is associated with a relatively high material consumption and process complexity.

This could be reduced if it were possible to produce precontoured semi-finished products, which already have a volume distribution varying over the longitudinal axis with one or more undercuts, by means of a chill casting. The use of such a blank in the forging or machining process would allow over the previously known procedure, a reduction in the number of forming steps followed by heat treatment and finishing or even offer the possibility, as close as possible near-net shape cast directly by a combination of Heat treatment and finishing to make the prefabricated component.

Due to the poor casting properties of titanium aluminide alloys and their ductile-brittle transition during cooling and the extremely brittle behavior at room temperature, the casting of precontoured semi-finished profiles in permanent molds, in particular of profiles which have defined undercuts in the mold, not possible. This results in particular from the shrinkage behavior and the solid body contraction of the cooling TiAl alloy, ie the volume shrinkage. Because this results in particular in the area of the undercuts to a high load on the material, which can lead to damage to the casting up to the formation of cracks or breakage.

Out EP 0 992 305 A1 For example, a method and apparatus for making precision castings by centrifugal casting is known. To produce these castings serve casting molds with annular casting, which are divided by at least one plane and form a plurality of, at least substantially radially arranged to a spinning axis mold cavities. To produce a mold part is brought in each case a separate rotation guide for rotation, wherein two mold parts together with the associated rotation guides relative to each other in a closed position for the casting and solidification and be brought into an open position for the removal of precision castings.

EP 0 686 443 A1 discloses a method of making castings using a reusable casting mold which, at least at its melt-contacting surface, is comprised of at least one metal other than non-metallic impurities of tantalum, niobium, zirconium and / or their alloys. If, for example, the casting mold is a centrifugal casting mold, then it may also have a base body in which shells delimiting the mold cavity from the cited metals are arranged, while the base body itself consists of other metals or alloys. In the case of a centrifugal casting mold, preference is here given to titanium, titanium alloys or titanium aluminide as the base material.

Out DE 693 27 195 T2 For example, there is known a method for producing an aluminum-based alloy casting product by casting, wherein casting is performed under pressure using a die casting mold. Here, the casting material is introduced through an inlet into the mold, wherein the casting material in this case has certain property parameters and casting also takes place with a defined casting speed and a defined pressure.

US 2 367 727 A discloses a casting apparatus having a fixed mold part and a movable mold part which are fixedly connected to each other during the casting. The movable mold half is actively movable relative to the immovable mold half by means of a movement device. The movement device comprises a pressure-generating device and a corresponding valve device, via which a corresponding pressure can be applied to the mold halves, so that they are firmly joined together during casting. During cooling, the movable mold half is opened via the movement device.

DE 103 29 530 A1 discloses a casting and solidification process for components of intermetallic alloys. A special feature of this method is the introduction of a holding time at a temperature above the brittle-ductile transition temperature immediately after the casting process. This procedure enables the avoidance of hot cracks and stress cracks even in larger components made of intermetallic alloys.

The invention is therefore based on the problem to provide a method which allows the casting of poor casting properties having materials, in particular titanium aluminide alloys for the production of complex contoured metal objects.

To solve this problem, a method according to claim 1 is provided. Further expedient refinements can be found in the dependent claims.

The mold used in the invention is characterized in that means are provided which make it possible to open the mold during the cooling of the metal, so as to reduce cooling and shrinkage due to adjusting stresses in the blank so that they do not adversely affect the properties of the cast metal object. For this purpose, different opening mechanisms are provided, which may be provided individually or cumulatively.

According to a first alternative of the invention, the opening is obtained or induced by the cooling and thereby shrinking metal object itself. To make this possible, at least one mold cavity or mold cavity outside the actual cavity is provided with at least one surface against which the cooling metal shrinking article presses, either directly by being directly adjacent to it, or indirectly by overlying the metal cavity Metal object constructed pressure is transmitted by design to the surface. Upon cooling, the metal object changes size, in each spatial direction. The Formnestseitige surface is now arranged such that the shrinking metal object due to shrinkage directly presses against this surface or a built-up pressure against this surface acts, this pressure having a directional component or a proportion which is or more or less perpendicular to the parting plane between the two mold parts , About this pressure, the two mold parts, which are indeed for the actual casting on each other or to each other, but due to pressure apart are moved away from each other, so therefore opened. The greater the shrinkage-related volume shrinkage of the metal object, and therefore its size change, the further the mold parts are moved apart. On the shaping of the contoured metal object, this opening of the mold parts no longer has any influence, since the metal object is already solidified at least at the edge and with increasing cooling in the volume.

By this in a step or successively, obtained by the metal object itself opening the mold thus resulting between the metal object and the mold due to shrinkage stresses are reduced or degraded, so that the metal object can cool largely free of tension and solidify.

An alternative, but also cumulative on the mold predictable way to open the mold for stress relief provides as described the use of a controllable or actuatable actuator for quasi-active opening of the mold, this opening depending on the shrinkage behavior of the metal object or at least one directly takes place at the mold given physical parameters such as a given pressure or the mold temperature. According to this alternative of the invention, the mold parts are at least actively moved apart by means of at least one actuator element, respectively, so that they can move apart, so that stress relief is again possible by means of this mold part movement. It can be provided only one actuator, but also several distributed arranged actuator elements that can be controlled accordingly or work together. The Actuation of the actuator or the elements takes place in dependence on the active shrinkage behavior via a corresponding control device, which will be discussed below. Even a quasi-passive operation alone on the physical parameters, in particular the mold temperature is conceivable. Also, by opening or releasing the mold in this way, a release of stress in the metal object can consequently be achieved.

As described, the two different opening variants can be provided individually or cumulatively, that is complementary or supportive.

The first opening variant, ie the opening of the mold by the solidifying metal object itself, will be explained in more detail below. This is done as described by the fact that the solidifying metal object "works" against a defined surface during solidification and thus shrinkage, either directly or indirectly. This surface is designed according to an embodiment of the invention as an inclined surface which is at an angle> 0 ° and <90 ° to the parting plane, the angle should be preferably ≥15 °, in particular ≥30 ° and ≤75 °, in particular ≤60 ° , This oblique surface, which depending on the contour of the metal object or the cavity may just be slightly curved, so neither parallel nor perpendicular to the parting plane, but is at a corresponding angle, so that during solidification and the solid contraction of the metal object due to shrinkage a quasi vertical standing to the parting plane pressure component with which presses the metal object against the parting plane and thus against the mold part adjusts.

In this case, the surface can represent a boundary surface of a mold cavity and thus of the metal object itself. That is, the metal object is contoured to have a contoured surface that serves as a contact surface for the metal article. The mold parts are coupled together as described so that they can be moved apart by sufficient pressure that the metal object exerts on one or both parts of the mold, so they are not immovably clamped together. Alternatively or additionally, the Surface also be formed in the region of an additional mold cavity section. The cavity thus has an additional area which is delimited by at least one such area over which the opening possibility is realized. Such an additional mold cavity section can be formed, for example, by means of a so-called feeder, ie a volume region or mold cavity section which is filled with melt and which virtually provides a melt reservoir from which the melt can flow into the "main cavity" if required.

In the cases described above, the metal object presses directly against the surface. It is also conceivable, however, that in the additional mold cavity portion at least one insert is arranged, which has a complementary surface, and against which the metal object presses during cooling, such that the insert presses against the surface. Here the metal object works against the e.g. wedge-shaped insert and presses this against the kokillenteilseitige surface, so that the mold parts are pressed apart.

The parting plane between the at least two mold parts preferably runs essentially parallel to the longitudinal axis of the metal object. The surface or inclined surface is as described at an angle to this parting plane. Since the shrinkage or volume decrease in the longitudinal direction is usually greater than in one of the other spatial directions, thereby the required pressure can be realized and set a sufficient degree of opening.

In a simplest embodiment, only two mold parts are provided, each having a mold cavity, wherein at least one of the mold cavities has at least one surface or inclined surface, of course, may also be provided on a mold cavity a plurality of such surfaces, or at each mold cavity one or more such surfaces can be realized. However, it is also conceivable to provide more than two mold parts which each have a mold cavity and which complement each other to form the cavity, wherein the at least one surface is arranged such that at least two mold parts Move away from each other due to shrinkage, of course, a plurality of such surfaces can be provided. The specific position and number of surfaces, of which as described several can be provided on a mold cavity or on the complementary mold cavities, ultimately depends on the geometry and the undercut position or undercut number of the volume defined over the cavity and the location of the parting planes.

In the embodiments of the mold described above, the one or more surfaces are arranged virtually on the mold side or close to the mold. Alternatively, but also in addition, it is conceivable that the surface is an outer boundary surface of a mold part, wherein two mold parts with their surfaces abut each other in such a way that they are mutually displaceable due to pressure. The mold parts are thus positioned adjacent to each other with complementary inclined surfaces. If the metal object contracted as a result of shrinkage, a pressure acting on the mold parts builds up, causing the two mold parts coupled over the inclined surfaces to slide against one another, so that one movable mold part is moved away from the other stationary mold part. The metal object works here almost indirectly against the surfaces.

In this case, at least three mold parts may be provided, wherein a first mold part has two at an angle to each other extending surfaces on each of which a further mold part abuts with a corresponding surface, such that the two other mold parts are pressure apart and relative to the first mold part movable. The first mold part is here provided with two surfaces, which run quasi-pointed towards one another, on the edge side, on each of which a further mold part rests with its oblique surface. These two further Kokillenteile slide due to pressure on the first mold part, they move in opposite directions away from each other and also relative to the first mold part. The first mold part preferably consists of two individual parts, which are firmly connected to each other, for example via connecting screws, so that the metal object can be removed from the mold. It is expedient if the mold parts are guided guided by guide means to each other. The mold parts can be arranged and movable relative to one another such that the two further mold parts can be moved starting from an open position into a closed position during a rotation of the mold, from which they can be moved out again due to pressure. Thus, a centrifugal force-induced self-closing mechanism is provided. During a rotation, the movable mold parts move into the closed position and close the mold, so that the melt can be supplied. Against this self-closing mechanism works to relieve the metal object, the chill parts are pressed apart against the centrifugal force for stress reduction due to the contractions. In this case, the further mold parts clamping means may be assigned, which build up a restoring force in a rotational movement in the closed position. The clamping means, for example corresponding spring components comprising coil springs or plate spring assemblies, work together with the metal object against the centrifugal force and support the pressing of the mold.

As described, in the first alternative of the invention, the mold parts are virtually forced apart over the solidifying metal object itself. To make this possible, the mold parts are positively connected to each other via connecting sections or guides respectively engage form-fitting manner, wherein the mold parts are either held in the closed position, that the weight of the or the upper mold parts greater than the casting pressure and / or the buoyancy of the melt is, or via a restoring force generating clamping or clamping means, against which restoring force the Kokillenteile from the closed position to an open position are movable. The Kokillenteile are thus defined via the connecting portions or guides arranged relative to each other, so that there is a defined closed mold with a closed cavity. In the simplest embodiment, the mold parts can be kept in the closed position over their own weight. This is possible if the cavity does not have too complex geometry and does not rotate during casting or cooling. The cooling Casting therefore only has to work against the dead weight of the one part of the mold to be lifted. Usually, however, the mold parts are connected to each other via corresponding clamping or clamping means. These are now designed in the mold according to the invention in such a way that on the one hand they connect the mold parts sufficiently firmly together so that the mold can also rotate with a corresponding number of revolutions, usually several 100 rev / min, eg up to 400 rev / min. On the other hand, the clamping or clamping means are designed such that they generate a restoring force, against which one or both mold parts are movable from the closed position. The metal object thus "works" against this restoring force to separate the mold parts from each other. In order to produce this restoring force, the clamping or tensioning means comprise one or more spring elements, for example helical springs or disk springs or disc spring packets, etc., via which the chill parts are clamped together.

As described in the introduction, the second alternative of the invention provides for the use of at least one actuator element via which the mold parts can be actively moved apart. According to a development of the invention, such an actuator element can be a variable in its length actuator element which is supported on two wegzubewegenden Kokillenteilen or a mold part and a fixed support. Such an actuator element is, for example, an actuating cylinder which operates electrically, hydraulically or pneumatically. If the actuator element or the actuating cylinder is activated, it lengthens and pushes apart the mold parts. Of course, it is also possible to arrange a plurality of actuator elements or actuating cylinders at distributed positions, in particular when the mold is of greater dimensions, in order to realize a uniform mold partial movement or to expose different component areas.

The actuator element, which operates as described electrically, hydraulically or pneumatically, is preferably controllable via a control device for the preferably successive opening of the mold parts as a function of the shrinkage behavior. Alternatively to the successive opening exists the ability to control the actuator or the actuator during the solidification and shrinkage process only once to move the mold parts by a single, short movement of the closed position to the open position and to realize the voltage reduction. The opening time is chosen as a function of the solidification or shrinkage behavior, which is determined in advance in the course of a simulation, for example. If, after a certain time, the solidification process has progressed so far that a stable edge shell has formed, then this or that actuator elements can be controlled in order to open the mold and reduce possible stresses. Preferably, the mold is opened by a defined path in one step, so that the component can shrink free from stress. However, such an opening can also take place intermittently, that is to say that relatively short actuator movements take place, so that the mold is opened quasi stepwise at defined times. Preferably, however, the actuator element (s) are / is actuated via the control device for the successive opening of the mold as a function of the shrinkage behavior, that is to say that a controlled tracking takes place as a function of the shrinkage behavior or of the stress relief. The mold is thus slowly opened to make the discharge respectively the voltage reduction parallel to the volume change respectively to the shrinkage process, so that a regulated tracking with respect to developing tensions between casting and mold is established. Consequently, the control device associated with the mold or forming a part of the mold or the mold device controls the entire opening process in each case.

As an alternative to actively moving apart the mold parts via one or more actuator elements supported on both mold parts, it is conceivable for the actuator element, which can be controlled via a control device, to actuate a clamping device, via which two mold parts are firmly clamped together, to release the clamping of the mold parts. According to this alternative of the invention, therefore, the tension of the mold parts is suddenly released, so that there is an opening of the mold on the high internal pressure That is, in this case, the mold is in turn opened over the shrinking metal object itself. The initiation of this opening, however, takes place exclusively via the actuator element or elements which release or open the tensioning means, for example tensioned springs or tension levers. In this case, there is a quasi combination between the two different possibilities, in which case the actuator element does not serve to actively open the mold itself, but rather to actively release the clamping means and thus to initiate its own opening process itself. The opening time is chosen such that it despite shrinkage-induced tension between the metal object and the mold does not lead to a negative influence on the metal object.

If a plurality of clamping means are provided, then preferably each clamping means is associated with a separately controllable actuator element. These are preferably controlled simultaneously to release the clamping means simultaneously.

As described, the activation of the or each actuator element takes place as a function of the shrinkage behavior of the metal object. Thus, the volume contraction or the strength of the edge layer of the casting is included in the control. Since the mold parameters such as size of the cavity and thus the melt volume, the mold material and its thermal conductivity properties and the mold wall thickness, etc. are known, the solidification and shrinkage behavior can be estimated and the or each actuator element are controlled by the control device time-controlled. It is thus determined how the shrinkage process behaves with time in order to perform a time-based control based on the shrinkage curve. Alternatively, it is also conceivable that the control of the opening operation is realized pressure-based by corresponding sensors in the mold. Alternatively or additionally, a temperature-based control via a kokillenseitiges thermocouple is conceivable. According to a further alternative, it is also conceivable to carry out the control of the actuator elements as a function of a simulation of the shrinkage or solidification process. In the control device thus runs based on a number Boundary conditions and simulation parameters, a simulation of the shrinkage or solidification process of the molten metal from. This simulation is now the basis for the control of the or each actuator element, be it an actuator element, over which the mold parts are actively moved apart, be it an actuator element, via which a clamping means or the like is actuated.

The or each actuator element operates as described electrically, hydraulically or pneumatically. It is connected via one or more corresponding supply lines to a control device in the case of an electrically operating actuator element or a pump or conveyor in the case of a hydraulically or pneumatically operated actuator element. The supply lines are to lead to the actuator or to the mold, that a possible Kokillenrotation is possible. As described, casting is usually done under vacuum, with a correspondingly high temperature and a rotation at several 100 rpm, e.g. ≤ 400 rpm.

As described above, an actuator element which is variable in its length or a plurality of such actuator elements is preferably used. In addition to the use of such an element in the form of an actuating cylinder, it is alternatively conceivable to use as actuator element a metal element which changes its length as a function of the temperature of the mold. Again, the opening is done in dependence on a given kokilleitigig parameter, namely the temperature. Such a metal element consists of a material with the highest possible coefficient of thermal expansion, so that it changes its length correspondingly strongly with increasing temperature, and therefore lengthens, as a result of which the two mold parts on which the metal element is fixed are pressed apart. The temperature is entered directly via the mold which heats up during solidification and cooling, in which the metal element, of which of course several can be provided distributed, is arranged. The degree of heating of the mold is a measure of the degree of solidification of the metal object, so that opening of the mold for stress relief is also possible thereby. The metal element is eg at both relative to each other moving Kokillenteilen arranged in corresponding preferably form-compatible receptacles or depressions, so that a good heat transfer from the mold to the metal element is possible. The metal element has, for example, the shape of a pin or bolt.

In a further development of the invention, a coolant channel leading a coolant can be provided in one or more mold parts. About this coolant channel targeted cooling of the mold and thus a targeted heat dissipation is possible. This can consequently influence the solidification and cooling. Targeted preheating or tempering of the mold is also possible. The coolant used is usually a fluid, for example oil, water or compressed air. If a plurality of coolant channels are provided, they can be heated or operated at different temperatures in order to achieve different cooling conditions in different mold regions. The coolant channel, whereby, of course, a plurality of coolant channels can also be provided, can be guided in such a way that targeted specific die subregions are cooled in order, for example, to cool portions of the metal article with a high volume more than other regions or the like. If one or more such cooling channels are provided, the cooling effect is included in the determination of the control parameters for controlling the actuator element or elements, for example corresponding cooling parameters are taken into account in the simulation. For further control of the cooling and thus influencing the solidification and cooling, one or more of a higher or lower thermal conductivity than the mold material having metal insert, for example made of copper, and / or one or more mold parts to change the mold thickness outside on one or more Kokillenteilen locally thickened or worn away. The attachment or integration of one or more metal inserts means that heat can be better dissipated from the inside of the mold to the outside than would be the case by the mold material. If, alternatively or additionally, the mold thickness is locally reduced, there is likewise an improvement since the heat can be dissipated more quickly. The mold itself is preferably a metal permanent mold. It consists of one Metal material such as cast iron, steel, copper, niobium or molybdenum and any alloys formed therefrom. In principle, all metal materials can be used which can be used because of their physical properties and chemical resistance to the molten metal, preferably the TiAl melt.

The invention relates generally to a method for producing a high-strength component of α + γ - TiAl alloy for reciprocating engines and gas turbines, in particular aircraft engines, in which a melt of a TiAl alloy is provided, which in a centrifugal centrifugal casting process in one or more Mold is cast to one or more precontoured semi-finished products for a forging and / or processing technology further processing to the finished part, wherein the or each mold has a cavity with at least one undercut and one or more flat or free-form parting lines and by a by the contraction of the cooling member generated internal pressure itself and / or open via a dependent on a kokillenseitig given physical parameter controllable or actuatable actuator element during the solidification and cooling process.

The shrinking by cooling in particular over its longitudinal axis metal object presses according to the invention shrinkage or contraction condition directly or indirectly against a surface which is arranged such that the two mold parts are moved away from each other due to pressure.

The or each actuator element can be controlled by the control device time-controlled, pressure-controlled, temperature-controlled or depending on a simulation of the shrinking or solidification process.

The different opening mechanisms can be used either separately or cumulatively.

According to the invention, a metal article is cast from a titanium aluminide alloy, in particular (α + γ) titanium aluminide alloy, ie from poor casting properties and extremely brittle behavior at room temperature. As the mold, a permanent metal mold is used, made of a metal or a metal alloy, which has physical and chemical properties that permit or are sufficiently resistant to TiAl casting.

Preferably, but not necessarily, a mold of the type described above is used.

All statements concerning the mold apply in the same way for the inventive method, and vice versa.

Fig. 1

eine Prinzipdarstellung einer Kokille in einer Schnittansicht,

Fig. 2

eine Prinzipdarstellung eines Metallgegenstands einer ersten Ausführungsform, beispielsweise für die Herstellung einer Niederdruckturbinenschaufel ,

Fig. 3

eine Prinzipdarstellung einer Kokille einer zweiten Ausführungsform,

Fig. 4

eine Prinzipdarstellung eines Metallgegenstands einer zweiten Ausführungsform, beispielsweise für die Herstellung einer Niederdruckturbinenschaufel, in einer Seitenansicht a) und einer Draufsicht b), der in der Kokille nach Fig. 3 gegossen werden kann,

Fig. 5

eine erfindungsgemäß verwendbare Kokille einer ersten Ausführungsform in drei Ansichten zur Erläuterung des Öffnungsvorgangs der Kokille,

Fig. 6

eine erfindungsgemäß verwendbare Kokille einer zweiten Ausführungsform in drei Ansichten,

Fig. 7

eine erfindungsgemäß verwendbare Kokille einer dritten Ausführungsform in drei Ansichten,

Fig. 8

eine erfindungsgemäß verwendbare Kokille einer vierten Ausführungsform in drei Ansichten,

Fig. 9

eine erfindungsgemäß verwendbare Kokille einer fünften Ausführungsform in drei Ansichten,

Fig. 10

eine erfindungsgemäß verwendbare Kokille einer sechsten Ausführungsform mit randseitigen Ausnehmungen,

Fig. 11

eine erfindungsgemäß verwendbare Kokille einer siebten Ausführungsform in drei Ansichten,

Fig. 12

eine erfindungsgemäß verwendbare Kokille einer achten Ausführungsform in drei Ansichten,

Fig. 13

eine erfindungsgemäß verwendbare Kokille einer neunten Ausführungsform in drei Ansichten,

Fig. 14

eine erfindungsgemäß verwendbare Kokille einer zehnten Ausführungsform in zwei Ansichten,

Fig. 15

die Kokille aus Fig. 14 in drei weiteren Ansichten, und

Fig. 16

eine erfindungsgemäß verwendbare Kokille einer elften Ausführungsform in drei Ansichten.

Further advantages and details of the invention will become apparent from the embodiments described below and from the drawing. These show various embodiments of molds usable in the context of the method according to the invention. Showing:

Fig. 1

a schematic diagram of a mold in a sectional view,

Fig. 2

3 is a schematic diagram of a metal article of a first embodiment, for example for the production of a low-pressure turbine blade,

Fig. 3

a schematic diagram of a mold of a second embodiment,

Fig. 4

a schematic representation of a metal object of a second embodiment, for example for the production of a low-pressure turbine blade, in a side view a) and a plan view b), in the mold after Fig. 3 can be poured

Fig. 5

a mold used according to the invention of a first embodiment in three views for explaining the opening process of the mold,

Fig. 6

a mold used according to the invention of a second embodiment in three views,

Fig. 7

a mold used according to the invention of a third embodiment in three views,

Fig. 8

a mold used in the invention of a fourth embodiment in three views,

Fig. 9

a mold used according to the invention of a fifth embodiment in three views,

Fig. 10

an inventively usable mold of a sixth embodiment with edge-side recesses,

Fig. 11

a mold used in the invention of a seventh embodiment in three views,

Fig. 12

a mold usable according to the invention of an eighth embodiment in three views,

Fig. 13

a mold used in the invention of a ninth embodiment in three views,

Fig. 14

a mold used in the invention of a tenth embodiment in two views,

Fig. 15

the mold out Fig. 14 in three more views, and

Fig. 16

a mold used in the invention of an eleventh embodiment in three views.

Fig. 1 shows a mold 1 consisting of two Kokillenteilen 2a, 2b, each having a mold cavity 3a, 3b. In the assembled form, the two mold cavities 3a, 3b complement one another and define a cavity 4 to be filled with melt to cast a contoured metal article.

The two mold parts 2a, 2b are separable from one another along a plane of separation 5 which is flat in the example shown, in order to be able to remove the hardened metal object from the cavity 4.

In the example shown, the cavity 4 is designed to cast a metal object to make a low pressure turbine blade. The cavity 4 has a volume varying over its longitudinal axis with two larger volume regions 6a, 6b on the edge side and a medium, narrower volume region 6c. As can be seen, the volume regions 6a, 6b each have undercuts, resulting from the increase in diameter. They are delimited by inclined surfaces 7a, 7b and 8a, 8b, these surfaces running at an angle α or β to the parting plane 5. The volume sections 6a, 6b can be rotationally symmetrical, ie round, but they can also be triangular, quadrangular or polygonal or free-formed, depending on the desired shape.

Fig. 2 shows an example of a metal article 9, which is provided with a mold 1 according to Fig. 1 can be poured. As described, this metal object 9 serves as an example for producing a low-pressure turbine blade. It is characterized by a shroud 10, which is imaged in the volume region 6b, a blade root 11, which is imaged in the volume region 6a, and an airfoil 12, which is imaged in the volume region 6c. Its shape corresponds to that of the cavity 4, it is merely due to shrinkage slightly smaller in volume, compared with the volume of the cavity 4. This will be discussed below.

Fig. 4 shows in a side view a) and a plan view b) a second embodiment of a metal article 9, which is equally suitable for producing a low-pressure turbine blade and in a mold 1 according to Fig. 3 can be poured. This metal article 9 'also has a shroud 10', a blade root 11 'and an airfoil 12' on. On it, however, laterally projecting, a feeder 13 is formed, which allows a Materialnachfluss in the actual space of the cavity 4. This feeder 13 thus serves as a material reservoir. The cavity 4 has for this purpose, see Fig. 3 , a corresponding laterally expanded mold cavity portion 6d. As a result of the geometry of the feeder, this mold cavity section inevitably has corresponding oblique surfaces 15a, 15b so that the oblique surfaces 14a and 14b of the feeder 13 can be formed. These surfaces are in Fig. 3 shown. In Fig. 3 is in the upper part a by way of example a sectional view through the two mold parts 2a, 2b shown, while Fig. 3 in part b is a plan view of the mold part 2b, so the lower mold part shows.

Quasi starting from the basic form according to Fig. 1 is in the volume of the cavity 4, an additional volume region 6 d realized, which serves to form the feeder 13. This is defined by corresponding inclined surfaces 15a and 15b. The surfaces 15a, 15b are also visible at an angle γ to the parting plane 5 of the mold parts 2a, 2b. The angle of the surfaces 15a, 15b is here by way of example the same, but it can also be different.

When casting such metal articles 9, 9 ', as in FIGS Fig. 2 and 4 shown, for example, from a titanium aluminide alloy adjusts a considerable volume contraction of the casting during cooling, which would lead to high voltages of the metal object enclosed in the cavity 4, since the volume shrinkage obstructs the undercuts in the region of the volume sections 6a, 6b and 6d would. However, to realize a voltage reduction is, as in the following Fig. 5-9 is shown a way how the mold 1 can be opened defined to realize a voltage reduction.

Fig. 5 shows a first embodiment of a mold according to the invention consisting of the two mold parts 2a, 2b. These are guided on guides 17 successive. In the region of the guides 17 clamping means 18 are provided, for example in the form of spring elements 26, via which the two mold parts 2a, 2b are clamped against each other.

Starting from the image section a), the melt is first introduced into the cavity of the mold 1, which then slowly solidifies in the mold 1, so that the metal object 9 (likewise the metal object 9 'could be formed) forms.

With increasing solidification and cooling, the metal object 9 shrinks, as shown in the figure part b). The two arrows 19 indicate that the volume is reduced in particular axially, that is to say that the metal object is quasi shortened. After the metal object has solidified on the edge, possibly already in the entire volume, it comes to the fact that the metal object 9 presses against the surfaces 7a, 7b and 8a, 8b. Since these surfaces are at an angle α or β, which is> 0 ° and <90 ° and is preferably in the range between 20-70 °, in particular between 30-60 °, are the separation plane, results in a pressure component in the direction of arrow 20th , as shown in the figure part b). So it builds up an internal pressure. Due to the inclination of the corresponding surfaces 7a, 7b, 8a, 8b relative to the parting plane 5, the upper mold part 2a is now pushed away from the lower mold part 2b. This is done against the restoring force of the spring elements 26, which are compressed in this case. Obviously, the mold opens, according to sub-figure b) is the upper mold part 2 a already slightly spaced from the lower mold part 2 b. The angles of the surfaces can be the same, but they can also be different in different component areas.

If the cooling and thus the volume contraction continues to increase, as shown by the arrows 19 in subfigure c), then the metal object 9 presses or works more and more against the corresponding surfaces 7a, 7b, respectively 8a, 8b, so that the mold is always open.

The spring elements 26 are compressed further and further. The shrinkage and opening degree is exaggerated in the figures (this applies to all figures) in order to represent the principle of operation.

Because the mold in this case is successively opened by the successive shrinking metal object, the voltage between the metal object and mold parts 2a, 2b is inevitably reduced. These degraded stresses can no longer be detrimental to the metal object. The opening of the mold is done here solely by the shrinking metal object itself.

Fig. 6 shows an embodiment of a second embodiment of a mold 1 according to the invention, which consists in the example shown of four mold parts 2a, 2b, 2c and 2d, the respective mold cavities 3a, 3b, 3c and 3d have, which in turn form the cavity 4 in its entirety. The mold parts 2a and 2c are separated from the lower mold parts 2b, 2d by a horizontal parting plane 5 in the example shown. The mold parts 2a and 2b in turn are separated by a vertical parting plane 5 'from the mold parts 2c and 2d.

In the example shown, the chill parts 2a, 2b are again connected to one another via corresponding guides 17, wherein the guides 17 are again assigned corresponding clamping means 18 in the form of spring elements 26. The shape of the cavity is supposedly the same as Fig. 5 Similarly, the cavity 4 could also have the shape as shown by the metal object 9 '.

According to sub-figure 6a, melt is first introduced into the cavity 4 of the mold 1, which solidifies to form the metal object 9. Again, with increasing solidification and cooling, a volume contraction occurs, as indicated by the arrows 19, which is primarily in the longitudinal direction of the metal article 9. The metal object 9 also presses here against the surfaces 7a, 7b and 8a, 8b, which are realized here on the individual Kokillenteilen 2a - 2d. As a result of the pressure results in turn, a pressure component in the direction of the arrows 20. This results in that the chill parts 2 a, 2 b are moved apart, as part character b and in particular with progressive cooling, the sub-figure c shows. The mold 1 is opened in sections, it in turn comes to stress relief, even if only a section-wise opening of the mold.

If a metal object 9 'were cast, the cavity would have the in Fig. 3 shown shape. For opening, the metal object 9 'in this case would not only press against the inclined surfaces 7a, 7b, 8a and 8b, but additionally against the inclined surfaces 15a, 15b, that is to say that the solidifying feeder 13 also serves to counteract the mold opening to obtain the restoring force of the spring elements 26.

Fig. 7 shows an embodiment of a mold 1 according to the invention, in turn, for example, consisting of the two mold parts 2a, 2b, in which mold 1, an actuator element 21 is provided, via which the mold 1 can be actively opened.

In the example shown, the actuator element 21 is supported on the two mold parts 2 a, 2 b at corresponding bearing areas 23 a, 23 b. It is, for example, a positioning cylinder 22, which is electrically, hydraulically or pneumatically actuated, for which corresponding, not shown in detail supply or control lines are guided to the actuator 21.

Assuming again a metal object 9 is poured, that is, the cavity 4 has the respect Fig. 1 detailed geometry. Equally, a metal object 9 'with a corresponding cavity geometry could also be cast here.

After pouring the melt solidifies the metal object 9, as shown in part a. It comes as part figure b shows and indicated by the arrows 19, a volume shrinkage and thus a contraction in the longitudinal direction of the metal object 9, so that in turn tensions in the Build up metal object 9. In order to compensate for this, the actuator element 21 or the actuating cylinder 22 is actuated via a control device, not shown in more detail, so that it moves apart the chill parts 2a, 2b, as shown in the subfigures b, c by the arrows 20. Although works here, the metal object 9 against the corresponding inclined surfaces 7a, 7b, 8a, 8b, but this load entry in the mold is not respectively not alone responsible for opening the mold. The die opening can either be made exclusively by the actuator element 21, or by the actuator element 21, assisted by the "work" of the metal object.

Fig. 8 shows a further embodiment of a mold 1 according to the invention, which - comparable to Fig. 6 - Also consists of four Kokillenteilen 2a, 2b, 2c and 2d. Comparable to Fig. 7 Here, too, the two mold parts 2a, 2b are coupled via an actuator element 21, preferably an actuating cylinder 22, which is mounted on corresponding bearing sections 23a, 23b.

As Fig. 8 clearly shows, are here with increasing shrinkage of the metal article 9, which is exemplary cast here, the Kokillenteile 2a, 2b moved apart on the actuator 21 and the mold, see in particular part c, opened, so that it comes to stress reduction. Although press here, as shown by the arrows 19, the corresponding edges of the metal object 9 against the corresponding inclined surfaces 7a, 7b, 8a, 8b of the Kokillenteile 2a, 2d, but this pressure is not respectively not exclusively for the opening of the mold responsible. The opening of the mold or the moving apart of the mold parts 2a, 2b is initiated solely by the actuator element 21, the pressure of the metal object against the corresponding inclined surfaces acts possibly supportive.

Fig. 9 shows an embodiment of a mold 1 according to the invention, which in turn consists only of two mold parts 2a, 2b, which are clamped together by means of corresponding guides 17 with associated clamping elements 18 comprising the spring elements 26. Again it is assumed that a metal object 9 is poured with the appropriate geometry, that is, the cavity 4 has the respect Fig. 1 described form. Also provided here is an actuator element 21, for example, again an actuating cylinder 22, which is arranged on a support portion 23a of the mold part 2a, while it is arranged with its other end on a positionally fixed support 24.

After pouring the melt, it also comes to a solidification and cooling and thus a volume contraction by the metal object 9. This works, see part of Figure 2b, again against the inclined surfaces 7a, 7b, 8a, 8b. This pressure causes it to open the mold 1. The actuator element 21 supports this opening process, ie moves the mold part 2 a away from the mold part 2 b. In this case, therefore, the two opening mechanisms cooperate, that is, the opening is obtained both by the shrinking metal object 9 pressing on the mold parts 2 a, 2 b and the actuating cylinder 22 extending in length. In the open position shown in part c, the mold parts 2a, 2b have moved sufficiently far apart, there is a corresponding complete stress relief. As shown by the arrows 19 and 20, on the one hand, the metal object 9 has been shortened in the longitudinal direction, but at the same time, the mold part 2a has also been relatively moved away from the mold part 2b.

The actuation of the actuator 21, so for example of the actuating cylinder, takes place, as only in Fig. 9 The control can be time-controlled, that is, after a certain time after introduction of the melt, the actuator element 21 - regardless of which Kokillenausführungsform is now considered - is operated continuously to successively the mold part 2a from the mold part 2b to separate. In addition to time-based control, pressure-based or temperature-based control is also conceivable. Alternatively, it is conceivable to carry out the activation on the basis of a simulation which simulates the shrinkage and solidification process of the metal object 9. Exemplary is in Fig. 9 Furthermore, in each mold part 2a, 2b, a coolant channel 27 is shown, which is supplied via a coolant supply not shown in detail with coolant. Over this, the mold parts can be cooled accordingly. The coolant used is, for example, oil or water or air, or a combination of at least two of these coolants. If the control device 25 works via a simulation, this cooling is included in the simulation.

Additionally or alternatively, material deposits can also be provided on the mold parts, which influence the heat dissipation, which therefore have a higher or lower thermal conductivity than the mold material.

There is also the possibility of making changes in the local mold thickness on the outside of the mold, for example by removing material or applying material, in order to influence the local heat removal. A basic example is in Fig. 10 shown where the mold 1 has recesses 28 on the sides.

Fig. 11 shows an embodiment of a mold 1 according to the invention, in which the metal article itself has no corresponding oblique surfaces, but nevertheless undercuts in the cavity 4 are provided. Here, the inclined surfaces are provided on the adjoining abutting sides of the mold parts, such that in the case of a length contraction of the solidifying metal object, the two movable mold parts slide on the inclined surfaces of the stationary mold part and it comes to the mold opening.

Three mold parts 2a, 2b and 2c are provided. The stationary mold part 2a, which consists of two individual parts which are detachably screwed together (not shown in greater detail) to enable demoulding of the metal object 9, has two inclined surfaces 7a, 7b which converge towards one another in a wedge shape. Each of the movable mold parts 2b, 2c has an inclined surface 8a or 8b, wherein in the closed mold the mold parts 2b, 2c lie in a form-fitting manner against each other and over the inclined surfaces 8a, 8b on the surfaces 7a, 7b.

Shown is the already cast melt for forming the metal object 9, which is shown here quasi bone-shaped in the schematic diagram, cavitation and metal objects on the side no inclined surfaces are provided. To clamp the mold parts 2b and 2c, corresponding guides 17 with clamping means 18 comprising the spring elements 26 are again provided here.

The subfigure 11b shows the mold 1 during the casting process, for example during the rotation of the mold 1. As shown by the arrows 19 also shown here, the metal object 9 contracted due to shrinkage, in particular along its longitudinal axis. The widened region 29 of the metal article 9 presses contractually within its partial cavity against the corresponding undercut flanks on the mold parts 2b, 2c. As a result, the two mold parts 2b and 2c with their oblique surfaces 8a, 8b slide on the oblique surfaces 7a, 7b of the mold part 2a, and in this way successively forms a mold opening and thus a reduction in stress. The mold opening is represented by the arrows 20. The open mold is shown in part figure 2c, where it can be seen that the mold parts 2b and 2c, on the one hand, are displaced relative to the stationary mold part 2a, on the other hand, relative to one another.

If the mold no longer rotates after the partial solidification and the formation of a stable surface layer, the opening process can be realized substantially only by the tensioned spring elements 2b, which pull the mold parts 2b, 2c in the open position, virtually following the volume shrinkage.

Fig. 12 shows a comparable embodiment of such a mold 1, in which again three mold parts 2a, 2b and 2c are provided, wherein the mold parts 2b and 2c are movable relative to the stationary mold part 2a. They are guided relative to the mold part 2a via corresponding guides 30 movable.

The cavity 4 here also has no oblique surfaces as an example, again the cavity has a kind of bone shape.

Fig. 12a shows the initial state of the mold. In this initial state, the two mold parts 2b and 2c are virtually open. The mold 1 is therefore not closed.

The closing takes place only when in this embodiment, the mold 1 is set in rotation, wherein the centrifugal forces act cause the two mold parts 2b, 2c, guided over the guides 30, with their inclined surfaces 8a, 8b on the inclined surfaces 7a , 7b of the mold part 2a slide off and, as shown by the arrows 31, are moved to the closed position. In this position, the melt may be supplied to cast the metal article 9.

Again, the metal object solidifies and contracts over its longitudinal axis, as shown by the arrows 19. This length contraction and the force thus exerted on the mold parts 2b, 2c, acting in the direction of the longitudinal axis counteract the centrifugal force. Since the force due to contraction is significantly greater than the centrifugal force, with increasing solidification and thus shrinkage of the metal object 19, the mold parts 2b, 2c are moved apart as shown by the arrows 20, they slide with their inclined surfaces 8a, 8b on the inclined surfaces 7a, 7b of the stationary mold part. This also allows the voltage reduction to be achieved.

Fig. 13 shows a further embodiment of a mold 1 according to the invention, which the embodiment Fig. 12 comes close, as far as the basic structure of the mold 1 and the operating principle is concerned. In this regard, reference is made to the above statements.

Unlike the embodiment according to Fig. 12 Here, each movable mold element 2b, 2c is a restoring element 32 comprising a spring element 33 provided, which is respectively fixed to a support 34 and is coupled to the other end with the Kokillenteil 2b and 2c.

In the starting position according to part of Figure 13a, the mold parts 2b, 2c are also opened and moved relative to the mold part 2a here. The spring elements 33 are relaxed or contracted.

The closing of the mold 1 is also effected here by the centrifugal force during the rotation, as shown by the arrows 31. The centrifugal force causes the mold parts 2b, 2c with their sloping surfaces 8a, 8b on the inclined surfaces 7a, 7b of the stationary mold part 2a, guided over the guides 30, slide. This results in an elongation of the respective spring element 33, so that this builds up a restoring force. This restoring force thus counteracts the centrifugal force. It supports the over the solidifying metal object 9 induced opening process, as shown in part of Figure 13c. The shrinking along its longitudinal axis metal object, see the arrows 19, presses, as already to Fig. 12 described against the Kokillenteile 2b, 2c, so that they in turn slide on the Kokillenteil 2a. This sliding movement is supported by the spring elements 33, which in this case contract again.

If the mold no longer rotates after the partial solidification and the formation of a stable surface layer, the opening process can be realized substantially only by the tensioned spring elements 2b, which pull the mold parts 2b, 2c in the open position, virtually following the volume shrinkage.

Fig. 14 1 shows an embodiment of a mold 1, by way of example consisting of two mold parts 2a, 2b, specifically in part-figure 14a in a side view and in part-figure 14b in a plan view of the lower mold half 2b.

The opening process is obtained here via a plurality of thermally activated actuators 35 in the form of metal pins 36.

As an example, here again a cavity 4 is shown, the geometry of the cavity 4 from the Figures 1 - 9 corresponds, which therefore has corresponding inclined surfaces 7a, 7b and 8a, 8b, against which the metal object 9 presses. The opening process can be additionally supported by means of this mechanism already described above, but it can also be achieved by means of the adjusting elements 35 alone.

The adjusting elements 35 and the metal elements 36, which have the form of bolts or pins, are metal elements with the highest possible thermal expansion coefficient. Each metal element 36 is accommodated in corresponding receptacles 37 on the two mold parts 2a, 2b, wherein the geometry of the receptacles 37 preferably corresponds to the geometry of the metal element 36, so that a good heat transfer from mold to the metal element is given. Because the heating of the metal elements 36 takes place exclusively via the mold 1. After pouring the melt inevitably heats up during the cooling of the metal object 9, the mold 1. This also leads to a heating of the metal objects 36. These are designed such that they due to heating a Extension in the longitudinal direction, so they length themselves. Since they are supported on both sides of the mold parts 2a, 2b, an elongation inevitably causes the mold parts 2a, 2b are pressed apart, so that the mold 1 is opened. This is exemplary Fig. 15 shown.

Part Figure 15a shows the situation after the introduction of the melt to form the metal article 9. With increasing cooling and solidification it comes to the longitudinal contraction, as indicated by the arrows 19. At the same time, however, the metal elements 36, of which in Fig. 15 due to the fact that only one is shown. It comes to pushing apart the Kokillenteile 2 a, 2 b and thus to open the mold 1, as indicated by the arrow 20. This opening operation takes place in the example shown again against the restoring force of the clamping means 18, wherein also here the mold parts are defined via guides 17 are relatively movable. The opening process can essentially can be achieved solely by the metal elements 36, or in cooperation with the metal object. 9

Fig. 16 finally shows a mold 1, which is similar to the mold Fig. 3 is constructed. It consists of two mold parts 2a, 2b and has an additional lateral mold cavity section, which is delimited by inclined surfaces 15a, 15b. This mold cavity portion enables the formation of a feeder 13 on the metal object 9, as shown in part figure 16a. In addition, an insert 37 is accommodated in the mold cavity section which is wedge-shaped and has corresponding oblique surfaces 38a, 38b, with which it rests against the inclined surfaces 15a, 15b. The feeder 13 forms in direct connection to the insert 37. The feeder 13 has an example of a rounded geometry, but may also be shaped differently.

If the melt is poured in and solidifies the metal object 9, it contracts again over its longitudinal axis, as the arrows 19 show. The feeder 13 works against the insert 37, which, as shown by the arrow 39, is also displaced in the direction of the longitudinal axis. It pushes with its oblique surfaces 38a, 38b against the inclined surfaces 15a, 15b of the two Kokillenteile 2a, 2b, so that it comes to opening of the mold 1, as shown by the arrow 20. Partial figure 16c shows the opened mold 1. Here, therefore, the metal object 9 presses indirectly via the insert 37 against the surfaces of the mold parts 2a, 2b. The opening operation can either be done only via this applied via the insert 37 pressure, or in support of the also corresponding inclined surfaces having metal object 9, which presses against the corresponding inclined surfaces of the mold parts 2a, 2b.

The mold according to the invention, regardless of which embodiment, is used in particular for producing a metal object or a semifinished product with a volume distribution varying over the longitudinal axis for further processing of the finished product for forging and / or processing. The finished part may be used in particular, but not exclusively for use in a piston engine or a gas turbine, in particular in aircraft engines, be provided.

• 40 - 49% Al
• 1 - 10% Nb
• 0,01 - 10% wenigstens eines der Elemente Mo, Cr, Mn oder B

sowie ein Rest aus Ti und erschmelzungsbedingten Verunreinigungen.As described, a titanium aluminide alloy is preferably used to form the metal article 9 or 9 '. Such an alloy may have the following composition (in atomic%):

• 40 - 49% Al
• 1 - 10% Nb
• 0.01-10% of at least one of Mo, Cr, Mn or B

and a balance of Ti and impurities caused by melting.

• 42 - 48,5% Al
• 1,5 - 5,5% Nb
• 0,05 - 5% wenigstens eines der Elemente Mo, Cr, Mn oder B

sowie ein Rest aus Ti und erschmelzungsbedingten Verunreinigungen.An alloy of the following composition (in% by atom) is particularly preferred:

• 42 - 48.5% Al
• 1.5-5.5% Nb
• 0.05-5% of at least one of Mo, Cr, Mn or B

and a balance of Ti and impurities caused by melting.

• 43,3 - 48,2% Al
• 1,8 - 4,2% Nb
• 0,07 - 2,7% wenigstens eines der Elemente Mo, Cr, Mn oder B

sowie ein Rest aus Ti und erschmelzungsbedingten Verunreinigungen.In further concretization, an alloy of the following composition (in% by atom) is preferably used:

• 43.3 - 48.2% Al
• 1.8 - 4.2% Nb
• 0.07-2.7% of at least one of Mo, Cr, Mn or B

and a balance of Ti and impurities caused by melting.

As further alloying elements Ta, Si, V or C may be included. This applies to all the aforementioned compositions.

In the casting process, such an alloy is melted, for example, by VIM (Vacuum Induction Melting), VAR (Vacuum Arc Remelting) or PAM (Plasma Arc Melting) can be done and then poured into the mold, in which the melt solidifies in the manner described. The casting takes place either statically, pressure-assisted or in a combination of both, wherein preferably the centrifugal centrifugal casting process is used. The melt from the crucible / container is poured into a rotating casting system consisting of a melt distributor, running system and the mold or dies. The melting of the alloy and the casting is preferably carried out under vacuum, optionally also in a chemically inert atmosphere under inert gas.

Claims (17)

1. Method for producing a heavy-duty metal article (9, 9') from an α + γ - TiAl alloy for piston engines and gas turbines, in particular aircraft engines, in which a melt of a TiAl alloy is provided and is cast in a centrifugal casting process in one or more moulds (1) to form one or more pre-contoured semifinished products for further processing by forging and/or machining to form the finished part, wherein the or each mould (1) has a cavity (4) with at least one undercut and one or more planar or freely formed separating planes (5) and is opened during the solidifying and cooling-down process by an internal pressure itself that is produced by the contraction of the cooling-down metal article (9, 9') and/or by means of an actuator element (21) that can be activated or can be actuated in dependence on a physical parameter occurring on the mould side.
2. Method according to Claim 1, characterized in that, as a result of contraction, the metal article (9, 9') shrinking due to cooling down presses against an area (7a, 7b, 8a, 8b, 15a, 15b), wherein the area (7a, 7b, 8a, 8b, 15a, 15b) is arranged in such a way that, as a result of pressure, the two mould parts (2a, 2b, 2c, 2d) are moved away from one another.
3. Method according to Claim 1 or 2, characterized in that the or each actuator element (21) is activated by means of the control device (25) in a time-controlled, pressure-controlled or temperature-controlled manner or in dependence on a simulation of the shrinking or solidifying process.
4. Method according to one of the preceding claims, characterized in that a mould (1) is used, comprising at least two mould parts (2a, 2b, 2c, 2d) that can be releasably connected to one another and each comprise at least one impression (3a, 3b, 3c, 3d), wherein the impressions (3a, 3b, 3c, 3d) fit together when the mould (1) is closed to form a cavity (4) of a volume that varies along an axis and has one or more undercuts and can be released from one another along a planar or freely formed separating plane (5), wherein at least one area (7a, 7b, 8a, 8b, 15a, 15b) against which, as a result of contraction, pressure can be built up directly or indirectly by means of the metal article (9, 9') shrinking as it cools down is provided on at least one mould part, wherein the area (7a, 7b, 8a, 8b, 15a, 15b) is arranged in such a way that, as a result of pressure, the two mould parts (2a, 2b, 2c, 2d) can be moved away from one another, and/or wherein at least one actuator element (21) that can be actuated in dependence on the shrinkage behaviour or a physical parameter occurring on the mould side is provided for opening the mould (1) .
5. Method according to Claim 4, characterized in that it comprises using a mould in which

   - either clamping or tensioning means (18) that connect the mould parts (2a, 2b, 2c, 2d) in the closed position and are designed in such a way that they produce a restoring force against which the mould parts (2a, 2b, 2c, 2d) can be pressed out of the closed position by the shrinking metal article (9, 9') are provided,

   - or the mould parts (2a, 2b, 2c, 2d) can be moved into the closed position by rotation and tensioning means (26) that build up a restoring force when there is a movement into the closed position are provided, wherein the mould parts (2a, 2b, 2c, 2d) can be pressed out of the closed position both by the shrinking metal article (9, 9') and the restoring force,

   - or tensioning means that brace the mould parts (2a, 2b, 2c, 2d) firmly together in the closed position and can be released for opening the mould (1) by means of an actuator (21) that can be actuated in dependence on the shrinkage behaviour or a physical parameter occurring on the mould side and can be activated by means of a control device (25) are provided, and the mould parts (2a, 2b, 2c, 2d) can be pressed out of the closed position by the shrinking metal article (9, 9').
6. Method according to one of the preceding claims, characterized in that it comprises using a mould (1) in which the area (7a, 7b, 8a, 8b, 15a, 15b) is configured as a sloping area, which is at an angle (α, β, γ) of > 0° and < 90° to the separating plane (5), wherein preferably the angle (α, β, γ) is ≥ 15°, in particular ≥ 30° and ≤ 75°, in particular ≤ 60°.
7. Method according to one of the preceding claims, characterized in that it comprises using a mould (1) in which the area (7a, 7b, 8a, 8b) is provided on an impression (3a, 3b) and represents a delimiting area of the metal article (9), or in that the area (15a, 15b) is formed in the region of an additional impression portion (6d), wherein preferably at least one insert part (37), which has a complementary area (38a, 38b) and against which the metal article (9) presses when it cools down in such a way that the insert part (37) presses against the area (15a, 15b), is arranged in the additional impression portion (6d).
8. Method according to one of the preceding claims, characterized in that it comprises using a mould (1) which has more than two mould parts (2a, 2b, 2c, 2d) respectively having an impression (3a, 3b, 3c, 3d) that fit together to form the cavity (4), wherein the at least one area (7a, 7b, 8a, 8b, 15a, 15b) is arranged in such a way that, as a result of shrinkage, at least two mould parts (2a, 2b) move away from one another.
9. Method according to one of the preceding claims, characterized in that it comprises using a mould (1) in which the area (7a, 7b, 8a, 8b) is an outer delimiting area of a mould part (2a, 2b, 2c), wherein two mould parts (2a, 2b, 2c) lie with their areas (7a, 7b, 8a, 8b) against one another in such a way that, as a result of pressure, they can be displaced towards one another.
10. Method according to Claim 9, characterized in that it comprises using a mould (1) in which at least three mould parts (2a, 2b, 2c) are provided, wherein a first mould part (2a) has two areas (7a, 7b) running at an angle in relation to one another, against which a further mould part (2b, 2c) respectively lies with a corresponding area (8a, 8b) in such a way that, as a result of pressure, the two further mould parts (2b, 2c) can be moved apart from one another and in relation to the first mould part.
11. Method according to Claim 9 or 10, characterized in that it comprises using a mould (1) in which the mould parts (2a, 2b, 2c) are movable on one another in a guided manner by means of guiding means (30).
12. Method according to Claims 10 and 11, characterized in that it comprises using a mould (1) in which the mould parts (2a, 2b, 2c) are arranged and movable in relation to one another in such a way that, when there is a rotation of the mould (1), the two further mould parts (2b, 2c) can be moved from an open position into a closed position, from which they preferably can be moved out again as a result of pressure.
13. Method according to one of Claims 1 to 11, characterized in that it comprises using a mould (1) in which the mould parts (2a, 2b, 2c, 2d) engage in one another with a form fit by means of connecting portions or guides (17).
14. Method according to one of the preceding claims, characterized in that it comprises using a mould (1) in which the clamping or tensioning means (18) comprise one or more spring elements (26), by means of which the mould parts (2a, 2b, 2c, 2d) are braced together.
15. Method according to one of the preceding claims, characterized in that it comprises using a mould (1) in which a number of tensioning means are provided, to which a separately activatable actuator element (21) is respectively assigned.
16. Method according to one of the preceding claims, characterized in that the or each actuator element (21) can be activated by means of the control device (25) in a time-controlled, pressure-controlled or temperature-controlled manner or in dependence on a simulation of the shrinking or solidifying process.
17. Method according to one of the preceding claims, characterized in that the actuator element (21) operates electrically, hydraulically or pneumatically.

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