CASTING APPARATUS AND CASTING METHOD FOR PRODUCTION OF METAL MATRIX COMPOSITE MATERIALS

Abstract

A casting apparatus for producing metal matrix composite materials includes a melt channel inclined in an apparatus flow direction, a flow pathway for a metal melt, and a particle feed device for adding solid particles to the metal melt. A casting method includes adding solid particles to a metal melt flowing in a continuous flow down a melt channel. The particle feed device is a shaft extending at least up to a base of the flow pathway and having a particle exit window in a casing of the shaft. The metal melt flowing down along the flow pathway is divided into two partial streams flowing around the channel projecting into and dividing the flow pathway. Where the partial streams combine again after flowing around the channel, the solid particles trickle into the confluence of the partial streams via a particle exit window in the channel located above the flow pathway.

Claims

1-10 (canceled)

11. A casting apparatus for producing metal matrix composite materials, the casting apparatus comprising: a melt channel being inclined in a flow direction of the casting apparatus and having a flow pathway for a metal melt, said flow pathway having a base; and a particle feed device for adding solid particles to the metal melt, said particle feed device forming a particle feed shaft extending at least to said base of said flow pathway, said particle feed shaft having a shaft casing and a particle exit window formed in said shaft casing.

12. The casting apparatus according to claim 11, wherein: said melt channel is configured as a melt channel tube having a tube casing; said particle feed shaft is guided through a casing feedthrough formed opposite said flow pathway in said tube casing of said melt channel tube to said flow pathway; and said particle exit window is disposed inside said melt channel tube.

13. The casting apparatus according to claim 12, wherein said particle feed shaft is configured as a particle feed tube.

14. The casting apparatus according to claim 13, wherein said particle feed tube has a smaller tube cross-section than said melt channel tube.

15. The casting apparatus according to claim 11, which further comprises a transverse base formed in said particle feed shaft and opening into said particle exit opening.

16. The casting apparatus according to claim 11, which further comprises an agitator projecting into said flow pathway, said agitator having a drive shaft disposed in said particle feed shaft.

17. The casting apparatus according to claim 11, wherein said melt channel is divided into two melt sub-channels upstream of a location at which the metal melt passes through said particle feed shaft, and said two melt sub-channels are combined again on said particle feed shaft.

18. A casting method for producing metal matrix composite materials, the casting method comprising: adding solid particles to a metal melt while the metal melt flows in a continuous flow down a melt channel; using a particle feed shaft projecting into a flow pathway of the melt channel to divide the flow pathway and to divide the metal melt flowing down along the flow pathway into two partial streams flowing around the particle feed shaft; and combining the partial streams again at a location after flowing around the particle feed shaft, and trickling the solid particles at the location into a confluence of the partial streams through a particle exit window in the particle feed shaft located above the flow pathway.

19. The casting method according to claim 18, which further comprises guiding the solid particles along a transverse base formed in the particle feed shaft to the particle exit window.

20. The casting method according to claim 18, which further comprises guiding the metal melt, before the metal melt passes the particle feed shaft, into two melt sub-channels of the melt channel being combined together again at the particle feed shaft.

Description

[0050] A preferred embodiment of the present invention is explained in more detail below with reference to figures. In the figures:

[0051] FIG. 1 shows schematically a side view of a particle feed portion of an embodiment of the casting apparatus according to the invention;

[0052] FIG. 2 shows schematically the particle feed portion from FIG. 1 in a perspective view; and

[0053] FIG. 3 shows schematically a particle feed portion of another embodiment of the casting apparatus according to the invention.

[0054] FIGS. 1, 2, and 3 illustrate the present invention by means of schematic views of a particle feed portion of two different embodiments of a casting apparatus according to the invention.

[0055] Upstream of the corresponding particle feed portion, the casting apparatus has at least one component not shown here, such as a metal melting and/or heat retention device for producing a metal melt and/or keeping metal melt hot.

[0056] Optionally, downstream of the corresponding particle feed portion, the casting apparatus may have at least one component not shown in the present figures, such as, for example, a mixing zone with at least one mechanical and/or electromagnetic stirrer for distributing solid particles introduced onto or into the metal melt in the particle feed portion.

[0057] The particle feed portion shown in each case has a melt channel 1 supplied with metal melt by the metal melting device and a particle feed shaft 2. In the embodiments shown, the melt channel 1 is tubular, i.e. in the form of a melt channel tube or in the form of two tubular melt sub-channels 14, 15 which initially diverge and then converge again. In the embodiments shown, the particle feed shaft 2 is also tubular, i.e. in the form of a particle feed tube.

[0058] The melt channel 1 is inclined in a corresponding flow direction A, A of the casting apparatus. Accordingly, a metal melt flows down a flow pathway 11 formed in the melt channel 1 in the flow direction A, A.

[0059] A through-opening is formed in a casing of the melt channel 1, which in the exemplary embodiments shown is a tube casing 12, through which through-opening the particle feed shaft 2 is guided into the interior of the melt channel 1.

[0060] The particle feed shaft 2 projects up to an inner wall of the melt channel 1 opposite the through-opening, i.e. through the flow path 11 in which the metal melt flows. The flow pathway 11 is divided into two partial streams by the particle feed shaft 2, which flow around the particle feed shaft 2 on both sides.

[0061] In the exemplary embodiments shown, the particle feed shaft 2 is in each case aligned at an angle of 90 or 45 to an axis of rotation of the melt channel 1, so that its inclination B is aligned at an angle of 90 or 45 to the inclination of the melt channel 1 corresponding to the flow direction A, A. However, in other embodiments of the present invention, the particle feed shaft 2 may also be perpendicular to the inclined melt channel 1, for example, so that an angle in a range of 30 to 60, for example 45, is formed between the center axis of the particle feed shaft 2 and the corresponding flow direction A, A in the melt channel 1.

[0062] The particle feed shaft 2 has an open particle exit window 22 in its shaft casing 21. Furthermore, a transverse base 23 opening into the particle exit window 22 is arranged in the particle feed shaft 2. The transverse base 23 is inclined in a particle exit direction C in the direction of the particle exit window 22.

[0063] The casting apparatus according to the invention works, for example, according to the following casting method:

[0064] A metal melt is first produced and/or kept hot in the metal melting and/or heat retention device of the casting apparatus. Optionally, the metal melt can be refined and/or modified in the metal melting and/or heat retention device. Like the preferably provided process chamber of the casting apparatus according to the invention, in which the particle feed portion is located, the metal melting and/or heat retention device is operated in a vacuum, i.e. at approx. 10.sup.4 to 1 mbar, or in a protective gas atmosphere.

[0065] In preferred embodiments of the casting apparatus according to the invention, there is a supply line, which can be locked by a vacuum-tight valve device, between the metal melting and/or heat retention device and the process chamber in which the particle feed portion is located. A vacuum melt container is coupled thereto.

[0066] Simple embodiments of the present invention can also be designed such that the particle feed portion is not located in a separate process chamber.

[0067] Once an identical pressure level has been reached throughout the casting apparatus, the valve device located between the metal melting and/or heat retention device and the process chamber in which the particle feed portion is located is opened and a valve device located between this process chamber and a casting chamber adjacent to the process chamber is closed.

[0068] The metal melt produced by the metal melting and/or heat retention device is guided into the vacuum melt container.

[0069] In one embodiment of the invention, the melt channel 1, which is introduced into the process chamber from the outside in a vacuum-tight manner, can project into the vacuum melt container from above, for example. In this embodiment, a first portion of the melt channel 1 forms a riser tube. The lower end of the riser tube is always located below a melt surface of the metal melt. An increase in pressure in the metal melting and/or heat retention device causes an increase in melt in the riser tube and thus in the melt channel 1.

[0070] When a critical fill level is reached between the melt surface and a lower riser tube edge, the melt channel 1 is filled from an additional melt container by means of gravity. It is also possible to operate the additional melt container under normal atmosphere and to fill the metal melt into the vacuum melt container with the riser tube due to the resulting pressure difference.

[0071] However, the present invention is independent of the way of adding the metal melt to the melt channel 1. In particular, the invention is not dependent on whether a riser tube as described above is used. The invention can also be used in gravity casting, for example.

[0072] The melt channel 1 is heated directly or indirectly with at least one heating element so that the metal melt cannot solidify in the melt channel 1 at any time.

[0073] Another portion of the melt channel 1 is inclined in the corresponding flow direction A, A, i.e. at an angle of about 30 to 60 downwards. As a result, the metal melt flows continuously, i.e. without tearing off, in the corresponding flow direction A, A within the melt channel 1, along the flow pathway 11 formed on a tube inner side of the melt channel 1.

[0074] Insofar as, as in the embodiment shown in FIG. 3, the melt channel 1 temporarily branches out into melt sub-channels 14, 15, the flow pathway 11 also branches out accordingly.

[0075] The metal melt, which initially flows as a total stream, is divided into two partial streams by the particle feed shaft 2 at the point where it projects into the flow pathway 11 and divides it. Preferably, the particle feed shaft 2 projects centrally into the flow pathway 11 so that the total stream of metal melt is divided evenly into the two partial streams. In the embodiments shown in FIGS. 1 and 2, the total stream is divided into the two partial streams in a Y-like manner.

[0076] In the embodiment of FIG. 3, the particle feed shaft 2 projects into the flow pathway 11 at the point where the two melt sub-channels 14, 15 are combined again.

[0077] The partial streams flow around the particle feed shaft 2 on both sides and combine again after passing the particle feed shaft 2.

[0078] When solid particles are introduced into the particle feed shaft 2, for example by means of a shaking unit connected to a storage silo or a vibration unit, they initially fall or slide onto the transverse base 23 located in the particle feed shaft 2, supported by the inclination B of the particle feed shaft 2. On the transverse base 23, the solid particles slide obliquely downwards, in accordance with the inclination of the transverse base 23 in the particle exit direction C, in the direction of the particle exit window 22.

[0079] The solid particles then trickle out of the particle exit window 22 downwards onto the partial streams of the metal melt flowing back together again. Preferably, the solid particles hit the metal melt exactly where the two partial streams flow together again, i.e. where there is initially a closing gap between the partial streams. This causes the solid particles to be trapped beneath the melt surface.

[0080] The inclination B or the angle of inclination of the particle feed shaft 2 determines the point at which the two partial streams combine again.

[0081] By adapting the cross-sections of the melt channel 1 and the particle feed shaft 2 in the region of its introduction into the flow pathway 11, almost any amount of melt can be provided with solid particles.

[0082] The guidance of the metal melt in the tube system described above means that there is no melt surface open to an oxygen-containing environment and, accordingly, unwanted oxide formation is largely prevented by the low oxygen content in or on the metal melt present in the process chamber.

[0083] After the solid particles have been injected into the metal melt, this MMC melt, which is now enriched with the solid particles, flows through a mixing zone of the casting apparatus to homogenize the solid particles and to wet them. To support mixing and wetting, an agitator, such as a two-to four-bladed agitator with a material-specific blade position, can be integrated in the melt channel 1 after the partial streams have been combined in order to reduce the viscosity of the MMC melt.

[0084] Finally, the MMC melt is filled into a casting mold to solidify there or is guided into a heatable collecting container in order to collect it there and to then add it to a further processing device, such as a printing or continuous casting line.

[0085] In the embodiment of the casting apparatus according to the invention described above, heating elements are preferably located on all components coming into contact with the metal melt or the MMC melt, with the exception of the casting mold, in order to avoid exposing the hot melt with the solid particles to the risk of premature solidification.