WO2003074210A2

WO2003074210A2 - Method and device for producing precision investment-cast ne metal alloy members and ne metal alloys for carrying out said method

Info

Publication number: WO2003074210A2
Application number: PCT/DE2003/000661
Authority: WO
Inventors: Manfred Renkel; Wilfried Smarsly
Original assignee: Mtu Aero Engines Gmbh
Priority date: 2002-03-07
Filing date: 2003-03-03
Publication date: 2003-09-12
Also published as: DE50301746D1; JP2005527375A; EP1480770A2; WO2003074210A3; DE10210001A1; US20050279481A1; EP1480770B1

Abstract

The invention relates to a method for producing precision investment-cast NE metal alloy members, especially for use in power unit technology. The inventive method is characterized by using a rotation casting method, whereby the outer shell of the casting molds (22) to be produced are fed via an inert pouring spout (14) which is fluidically optimized vis-à-vis the used alloys. These casting molds are likewise fluidically optimized at the sprue positions (19) and are arranged on a rotatably mounted casting device (11) in a manner as to be spatially adjustable. The casting molds can be inductively (30) heated during the casting process for the purpose of temperature adjustment. The components of the device are mounted in such a manner as to allow for a completely homogeneous filling of the casting molds by virtue of the Coriolis forces of the centrifugal forces to which the melt is subjected so that the cast metal is free from inclusions.

Description

Method and device for the precise investment casting of components made of non-ferrous metal alloys and non-ferrous metal alloys for carrying out the method

The investment casting of non-ferrous metal alloys, preferably of TiAl components, in particular for use in turbomachinery construction, is complex and difficult because alloy elements evaporate from the melt during the heating and the casting process, boundary layers which adversely affect the casting process are formed, and there is a risk of the formation of blowholes that lead to a destabilization of the alloy structure. It should also be taken into account here that the time for the actual casting process is negligible compared to the time for the heating process of the melt.

Such components manufactured by investment casting must therefore be reimbursed by a so-called HIP / experienced, i.e. A hot isostatic pressing process is used to compress the blowholes and the structure of the component produced by casting is to be stabilized by subsequent heat treatment.

Compliance with specified material specifications for such components to be manufactured in this way is therefore extremely cost-intensive and high reject rates are inevitable.

This is where the invention comes in, the task of which is to significantly improve the production of components from non-ferrous metal alloys, in particular for use in turbomachinery, by means of investment casting.

Starting from the known centrifugal casting, in which the centrifugal forces influence the shape, the mold filling and the crystallization of the melt by rotating a part of the casting device, this object is achieved according to the invention by a method for precision investment casting corresponding to the outer shape of the components to be manufactured, Casting molds consisting of heated mold shells, to which the melt is fed via a heated pouring device in such a way that a complete filling of the casting molds via the acceleration forces and the tion occurring Coriolis forces and the centrifugal forces applied to the melt.

According to a further feature of the invention, the melt for the casting process is deflected by means of the centrifugal forces against the flow direction determined by gravity by approximately 30 ° to 180 ° and forced into the casting molds by the Coriolis forces for homogeneous filling of the casting molds.

According to a further feature of the invention, the heated casting device and the heated casting molds are kept at predetermined process temperatures which correspond to the non-ferrous metal alloys used for the investment casting production and maintain their flowability, preferably 10 to 200 ° C. above the melting point of the non-ferrous metal alloy.

The method according to the invention has a number of advantages.

Surprisingly, it has been shown that the evaporation rate of the melt is reduced by the method according to the invention and the porosity of the cast parts with regard to the achievable reduction in the size of the pores in the melt is reduced and the structure is therefore finer than that by the flow-mechanically optimized design of the pouring device for utilizing the Coriolis forces are currently achievable. It is therefore no longer necessary to after-treat the cast parts removed from the mold for tempering by hot isostatic pressing and then adding heat to stabilize the alloy structure. This leads to a significant cost reduction in the production of such components and to savings in material costs for the non-ferrous metal alloys to be used in terms of quantity, composition and purity. In addition, the reject rate is reduced and post-treatment costs are greatly reduced, if not saved.

To carry out the method according to the invention, according to the invention, a vertically standing, rotatably mounted cup-shaped container with a streamlined bottom surface is used as a pouring device, with which the shell surface associated with its lateral surface and arranged at a predetermined distance from the bottom surface is used. communicate upright molds, the spatial angle of attack of which can be adjusted in relation to the respectively associated, also aerodynamically designed outlet openings of the container, all in such an arrangement that the mold is filled without flow breaks of the melt.

According to a preferred exemplary embodiment of the invention, containers and casting molds consist of ceramic which has little reaction to the melt and has embedded metal particles, so that containers and casting molds can be heated precisely, preferably inductively, by known inductors or by means of microwaves.

It is advantageous if, according to a further feature of the invention, the casting trough serving to supply the melt is also designed to be streamlined in relation to the melt and consists of ceramic which has little reaction to the melt and has embedded metal particles. According to a further exemplary embodiment of the invention, however, the melt can also be produced within the container of the pouring device during its rotation.

Finally, fillers and troughs can be made of coated steel, coated graphite, tantalum, titanium or niobium.

According to the invention, a TiAl alloy is used as the non-ferrous metal alloy with 30 to 33 wt.% Al, 4 to 6 wt.% Nb, 0.5 to 3 wt.% Mn and 0.1 to 0.5 wt. % B, balance Ti.

In the context of the invention, such a TiAl alloy with 0.5 to 3 wt.% Mn has an oxygen content of 0 to 2000 ppm, a carbon content of 0 to 2000 ppm, preferably 800 to 1200 ppm, and a nickel content of 100 to 2000 ppm and a nitrogen content of 0 to 2000 ppm. Of course, other non-ferrous metal alloys can also be used to carry out the precision casting production according to the invention.

Further features of the invention emerge from the subclaims. The invention is described below with reference to two exemplary embodiments shown schematically in the drawing.

Show it

Fig. 1 shows a first embodiment of an apparatus for performing the method according to the invention and

2 shows a modified embodiment of the device according to FIG. 1.

The device according to FIG. 1 shows a pouring device, which can be rotated about an axis 10 and is designated as a whole by the reference numeral 11, to which the melt is fed from a ladle 12 via a pouring trough 14 designed to be streamlined.

The pouring device 11 is mounted so that it can be rotated vertically - the drive device required for this is not shown for the sake of clarity - and comprises a cup-shaped container 15 with a rotationally symmetrical side wall 16 and a flow-optimized base 18 formed thereon at a distance a from the base 18 are located symmetrically on the circumference of the side wall 16, flow-mechanically optimized outlet openings 19, which communicate with molds 22 consisting of half-shells 20.

The molds are adjustably connected to the container 15 by spatial angles sr with respect to the associated outlet openings 19. The angle sr is set as a function of the specific weights of the non-ferrous metal alloy used, the casting temperature and the speed n of the container as well as the respective specific weight of the alloy, so that the entire feed is designed to be fluid-mechanically optimized.

The container 15 and the associated casting molds 22 are arranged in their predetermined position by means of a holder 23 made of suitable ceramic and serving as a matrix for this, which is clamped between a base plate 24 and a cover plate 26. The melt, heated to the casting temperature, can be removed from the casting ne 12 escaping melt and passed on via the trough 14 enter the container 15. Using suitable, precisely controllable heating devices 30 - such as, for example, inductors - both the pouring device 11 and casting trough 14 and the casting molds 22 are heated inductively in such a way that the melt remains at the casting temperature until the casting is complete. These temperatures, which maintain the flowability of the melt, correspond to the non-ferrous metal alloys used for investment casting. For this purpose, there are casting troughs 14, containers 15 and casting molds 22 made of low-reaction ceramic with embedded metal particles. Containers and casting molds can also consist of coated steel, tantalum, titanium or niobium.

As is known, the Coriolis force is the inertial force which, in addition to the guide force and the centrifugal force, acts on a body moving in a rotating system. The Coriolis force is perpendicular to the plane formed by the speed vector and the axis of rotation.

The non-ferrous metal alloy is a TiAl alloy with 30 to 33 parts by weight of aluminum, 4 to 6% by weight of niobium, 0.5 to 3% by weight of manganese and 0.1 to 0.5% by weight of boron, the rest Titanium for use. A TiAl metal alloy with an oxygen content of 0 to 2000 ppm, a carbon content of 0 to 2000 ppm, preferably 800 to 1200 ppm, a nickel content of 100 to 2000 ppm and a nitrogen content of 0 to 2000 ppm is preferred used.

For the casting process, the non-ferrous metal alloy located in the casting ladle 12 is converted into the desired melt by heating in the usual manner and, as already described, passes via the heated casting trough 14 into the rotating, likewise heated, pouring device 11, where it is gravitationally applied to the Bottom 18 of the container 15 arrives. As a result of the rotation of the container, centrifugal forces act on the melt, which bring about a reversal of the direction of flow of the melt from approximately 30 ° to 180 °, so that it rises against the inner wall of the side wall 16 up to the height of the outlet openings 19. Since the spatial angles of attack sr of the molds 22 are selected such that they coincide with the direction of the Coriolis force vectors, these act on the melt in addition to the centrifugal forces, with the result that the melt can not only enter the molds via the openings 19 but also <S3ss this fills the cavities of the casting molds adjoining the openings 19 quickly and safely as well as completely and homogeneously. After the melt has solidified, the molds are removed and the respective investment casting component is applied in the customary manner.

In the embodiment of the pouring device shown in FIG. 2, designated overall by reference numeral 40, the components of which correspond to the pouring device 1 1 are identified by the same reference numerals, the molds 22 which are adjustable in their angular position sr and held in the holder 23 are located at the upper edge of the in the pouring device 1 1 now rotatably mounted container 15. This has in this area a distributor 42 which acts as a nozzle for the melt. The outlet openings 19 leading to the inside of the casting mold 22 are - as in the exemplary embodiment according to FIG.

The non-ferrous metal alloy is here fed to the container 15 as a so-called ingot melting in the rotating container, so that the ladle 12 and pouring channel 14 of the exemplary embodiment according to FIG. 1 are omitted. For the insertion of the ingot into the container 15, the latter has a lid 44 which is openable for this purpose and to which the distributor 42 is fastened. For this purpose, the cover plate 26 is removably connected to the pouring device 40. Since the likewise inductively heatable container 15 is rotatably supported by itself in the pouring device 40, temperature-resistant seals 45 are provided between the inlet openings of the stationary molds 22 and the outlet openings 19 of the rotating container 15. The mode of operation of the pouring device described above corresponds to the mode of operation described in connection with FIG. 1, but the supply of the melt into the molds 22 and thus their filling is favorably influenced via the distributor 42 which develops the nozzle action.

For both embodiments, that is to say according to FIG. 1 and FIG. 2, it is provided that the cast components can still be heated in the casting molds to 600 to 700 ° C., which is also done inductively via the existing heating devices 30. In this way, the cooling rate of the cast components is kept low in a controlled manner in order to avoid cracks, breaks, etc. in the components. The cast components are only removed from the molds after the desired degree of cooling has been reached, which is to be selected depending on the composition of the non-ferrous metal alloy used With the invention described above, it is ensured for the first time that the Coriolis forces of the centrifugal forces applied to the melt can also act in a targeted manner and act on the melt in a similar way to a pressure ram and thus force the melt completely and homogeneously into the casting mold, that is to say fill it completely and without voids. without a damaging stall of the melt and a different solidification of the boundary layer. By heating the cast component in the mold, the cooling rate is kept low in a controlled manner, so that the residual stresses in the components that result from uncontrolled cooling and the resulting cracks, breaks, etc. are avoided.

Claims

claims

1.Procedure for the precision investment casting of components made of non-ferrous metal alloys, in particular for use in turbomachinery, with molds corresponding to the outer shape of the components to be produced and consisting of heated mold shells, to which the melt is fed via a heated rotatably mounted pouring device such that a complete The molds are filled via acceleration forces including the Coriolis forces of the centrifugal forces applied to the melt.

2. The method according to claim 1, characterized in that the melt for the casting process in the pouring device by means of the centrifugal forces against the flow direction determined by gravity by approximately 30 ° to 180 ° and when flowing into the molds by the acceleration forces including the Coriolis Forces to homogeneous filling of the molds is forced.

3. The method according to claims 1 and 2, characterized in that the heated rotatably mounted pouring device and the heated molds on predetermined, corresponding to the non-ferrous metal alloy used for the investment casting, their fluidity maintaining, preferably 10 ° to 200 ° C above the Melting point of the non-ferrous metal alloy process temperatures are kept.

4. The method according to claims 1 to 3, characterized in that the melt is generated outside or inside the pouring device.

5. The method according to claims 1 to 4, characterized in that for the controlled reduction of the cooling rate of the investment cast components still in the molds, these are heated to 100 ° to 900 ° C.

6. Device for performing the method according to claims 1 to 5, characterized in that a vertically standing rotatably mounted cup-shaped container (15) with a streamlined bottom surface is used as a pouring device (1 1) with which the on its lateral surface (side wall 16 ) arranged, at a predetermined distance (a) from the bottom surface (18) arranged from molded shells (22) communicate, whose spatial angle of attack (sr) can be adjusted in relation to the respectively assigned aerodynamically designed outlet opening (19) in the container (15), all in such an arrangement that a homogeneous mold filling takes place without stalling of the melt.

7. Device for performing the method according to claims 1 to 6, characterized in that the container (15) in the pouring device (40) rotatably mounted relative to the adjustable (solid angle sr) arranged molds (22) and for receiving one made of NE -Metal alloys existing ingots corresponding to the inside diameter of the container are provided with a closable cover (44).

8. The device according to claim 7, characterized in that the molds (22) are arranged near the upper edge of the container (15), the inlet openings of which are assigned to a container (15) arranged nozzle-unfolding distributor (42).

9. Device according to claims 6 to 8, characterized in that the container (15) and casting molds (22) consist of ceramic with little reaction to the melt with embedded metal particles.

10. The device according to claim 6, characterized in that a casting trough (14) serving to supply the melt is aerodynamically designed with respect to the melt and also consists of ceramic with low reaction to the melt with embedded metal particles.

1 1. Device according to claim 6, characterized in that containers and molds made of coated steel, coated graphite, tantalum, titanium or niobium.

12. The device according to claims 6 to 1 1, characterized in that the heating of the pouring device (10) and the molds (22) is carried out inductively or by microwaves.

13. non-ferrous metal alloy for carrying out the method according to claim 1, based on a TiAl metal alloy with 30 to 33 wt.% Al, 4 to 6 wt.% Nb, 0.5 to 3 wt.% Mn and 0, 1 to 0.5% by weight B, balance Ti.

14. non-ferrous metal alloy according to claim 13, based on a TiAl metal alloy with an oxygen content of 0 to 2000 ppm, a carbon content of 0 to 2000 ppm, preferably 800 to 1200 ppm, a Ni content of 100 to 2000 ppm and one N content from 0 to 2000 ppm.