SUPPLY SYSTEM FOR SUPPLYING A MOULD WITH MOLTEN METAL, AND FACILITY AND MANUFACTURING METHOD IMPLEMENTING SAME

Abstract

A feed system for conveying a molten metal that is to make a casting, the system including a feed channel made of ceramic material that is configured to enable the molten metal to flow by gravity inside the feed channel, the feed channel having a first portion extending in a first direction, and at least one second portion extending in a second direction different from the first direction, the second portion being arranged downstream from the first portion and being connected to the first portion by a junction. The system further includes a damping channel having a first end opening out into the junction and a second end that is closed, the damping channel extending the first portion of the feed channel.

Claims

1. An installation made of ceramic material for fabricating a plurality of castings from a molten metal, the installation comprising: a vertical duct surmounted by a bush through which a liquid metal is to be introduced into the installation, the vertical duct including a distributor in the proximity of its bottom end; at least one feed system for conveying the molten metal for making the castings, each feed system comprising a feed channel configured to enable the molten metal to flow under gravity inside said feed channel, said feed channel having a first portion extending in a first direction from the distributor, and two second portions extending in a second direction different from the first direction, each second portion being arranged downstream from the first portion and being connected to the first portion by a junction; and at least two molds, each mold being connected to a second portion of the feed channel so that a molten metal can be conveyed from the feed system into each mold; wherein the feed system further comprises a damping channel having a first end opening out into the junction and a second end that is closed, said damping channel extending the first portion of the feed channel.

2. An installation according to claim 1, wherein the feed channel of the feed system presents a section that is circular, the length of the damping channel being greater than or equal to twice the diameter of the feed channel.

3. An installation according to claim 1, wherein the damping channel has a first portion extending between the first end and a second portion, said second portion extending between said first portion and said second end of the damping channel, said second portion being situated lower than said first portion.

4. An installation according to claim 3, wherein the second portion of the damping channel of the feed system extends in an inclined direction.

5. An installation according to claim 3, wherein the second portion of the damping channel of the feed system extends in a vertical direction.

6. An installation according to claim 1, wherein the damping channel of the feed system presents a section that is semicircular.

7. An installation according to claim 1, wherein the first and second directions are mutually orthogonal.

8. An installation according to claim 1, further comprising at least two grain selector ducts, each grain selector duct being connected both to a second portion of a feed channel and also to a mold.

9. An installation according to claim 1, wherein the molds are adapted to molding turbine blades of an aviation turbine engine.

10. A method of fabricating a plurality of castings from a molten metal, the method comprising: filling molds with a molten metal by introducing the molten metal into the bush of an installation according to claim 1; and implementing directed solidification of the metal present in each mold so as to obtain the casting.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other characteristics and advantages of the present invention appear from the following description made with reference to the accompanying drawings, which show embodiments having no limiting character. In the figures:

[0031] FIG. 1 shows an installation for fabricating a casting from a molten metal;

[0032] FIGS. 2A and 2B are views on a larger scale of the FIG. 1 installation showing a feed system;

[0033] FIGS. 3 and 4 show other examples of feed systems of the invention; and

[0034] FIG. 5 is a flow chart showing the main steps of a method of fabricating a casting by using an installation of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention is described below in its application to fabricating turbine blades for an aviation turbine engine by gravity lost wax casting. The present invention serves advantageously to reduce the inclusion of impurities in the casting due in particular to the metal penetrating into the mold feed system too suddenly, while also reducing the presence of oxides that can be transported by the first metal stream in the feed system.

[0036] FIG. 1 shows an installation 1 of the invention for fabricating a casting from a molten metal by a gravity bottom casting type casting method. For greater clarity, FIG. 1 shows only a portion of an installation of the invention, the portion that is not shown being identical.

[0037] In the present disclosure, the terms upstream and downstream are defined relative to the flow direction of molten metal within the installation.

[0038] The installation 1 comprises firstly a bush 2 through which a liquid metal can be introduced into the installation 1. The bush 2 lies above a vertical central duct 3 that includes a distributor 4 close to its bottom end, which is plugged. The distributor 4 is annular in shape around the central duct 3 and serves to distribute the metal that is introduced into the installation 1 among a plurality of feed systems 5. Each feed system 5 may be provided with a filter 6 that serves to eliminate a portion of any impurities that might be present in the liquid metal entering into the feed system 5. Each feed system 5 is connected, by channels that are described below, to molds 7 via grain selector ducts 8. In known manner, the grain selector ducts 8 serve to obtain parts that are monocrystalline after directed solidification. In this example, the molds 7 are adapted to fabricate turbine blades for an aviation turbine engine, i.e. they have the shape of such blades. It should be observed that in this example the installation stands on a horizontal base plate 10 that serves to support the entire installation 1 throughout the fabrication method that is described below. The base plate 10 may be designed to seed the first metal grains.

[0039] From upstream to downstream, a liquid metal can travel through the following portions under the effect of gravity: the bush 2; the central duct 3; the distributor 4; a feed system 5; a feed duct 8; and a mold 7. The mold 7 is thus filled from the bottom upwards, the grain selector duct 8 being connected to the mold 7 via a bottom portion of the mold 7.

[0040] FIGS. 2A and 2B show a feed system 5 of the invention in greater detail. The feed system 5 comprises a feed channel 51 arranged so that molten metal can be conveyed by gravity along the channel 51. The feed channel 51 has a first portion 51a that extends from the distributor 4 to the level of the base plate 10 in a first direction A (FIG. 2B), which direction is inclined relative to the horizontal in this example. The first portion 51a of the feed channel 51 is of circular section in this example. In the example shown, the first portion 51a of the feed channel 51 is not vertical, i.e. it is at an angle other than 90 relative to the top surface of the base plate 10.

[0041] The feed channel 51 also has two second portions 51b that are connected to the downstream end of the first portion 51a at a junction 52. The two portions 51b extend in directions that are different from the first direction A of the first portion 51a. In the example shown, the second portion 51b extends on either side of the junction 52 in a second direction B that is circumferential around the central duct 3. At the junction 52, the feed channel 51 is thus in the form of a T, the vertical bar of the T corresponding to the first portion 51a and the horizontal bar corresponding to the two second portions 51b of the feed channel 51. Each second portion 51b of the feed channel 51 is then connected by a channel 53 to a grain selector duct 8. In the installation shown in this figure, each second portion 51b of the feed channel 51 is connected to a second portion 51b of a neighboring feed system 5 so that together the second portions 51b of the installation 1 form a circular duct on the base plate 10 around the central duct 3. In this example, the second portions 51b of the feed channel 51 present a section that is semicircular. In a variant that is not shown, each second portion 51b of the feed channel need not be connected to a second portion 51b of a neighboring feed system 5.

[0042] In the invention, the feed system 5 also has a damping channel 54 that extends the first portion 51a of the feed channel 51 at the junction 52. The damping channel 54 opens out at a first end 54a (FIG. 2B) into the junction 52, and it is blind or obstructed at a second end 54b. In the example shown, the damping channel 54 presents a semicircular section of radius R having a flat portion that rests on the base plate 10. In order to conserve a constant section between the feed channel and the damping channel, the radius R may be such that R=(d/2)2.

[0043] The damping channel 54 extends in a direction C that is horizontal in this example. The directions A, B, and C of the portions 51a, 51b, and of the channel 54 are directions that extend in the immediate proximity of the junction 52. In this example, the projections of the directions A and C onto the base plate 10 coincide, and the directions B and C are mutually orthogonal at the junction 52.

[0044] It should be observed that the fact that the damping channel 54 extends the first portion 51a of the feed channel 51 does not necessarily mean that the directions A and C are identical. Extending the first portion 51a by means of the damping channel 54 enables the first stream of molten metal to go towards the damping channel 54 on penetrating into the feed system 5.

[0045] The path followed by a liquid metal inside the installation 1 is represented diagrammatically by continuous arrows in FIG. 2A.

[0046] FIG. 3 shows a feed system 5 in another embodiment of the invention. As above, the feed system 5 comprises a feed channel 151 provided with a first portion 151a extended downstream by a damping channel 154 and by two second portions 151b. The first portion 151a and the two second portions 151b meet at a junction 152. The damping channel 154 also opens out at its first end 154a into the junction 152 and it is blind or closed at its second end 154b. In this example, the feed channel 151 and the damping channel 154 are not supported by the base plate 10, and each of them presents a circular section of diameter d. The first portion 151a of the feed channel 151 extends in a first direction A that is horizontal, and the damping channel 154 extends in a direction C that coincides with the direction A. The two second portions 151b of the feed channel 151 extend on either side of the junction 152 in a second direction B that is horizontal and orthogonal to the direction A at the junction 152. In this example, the length L of the damping channel 154 may be equal to at least twice the diameter d of the damping channel 154, thus making it possible to conserve a constant section between the damping channel 154 and the feed channel 151.

[0047] FIG. 4 shows a feed system 5 in yet another embodiment of the invention. As above, the feed system 5 comprises a feed channel 251 provided with a first portion 251a extended downstream by a damping channel 254 and by two second portions 251b. The first portion 251a and the two second portions 251b meet at a junction 252. The damping channel 254 also opens out at its first end 254a into the junction 252 and it is blind at its second end 254b. The two second portions 251b of the feed channel 251 extend on either side of the junction 252 in a second direction B that is horizontal and orthogonal to the direction A at the junction 252.

[0048] In this example, the damping channel 254 has two portions 254c and 254d, whereas each of the above-described channels 54 and 154 has a single portion. The first portion 254c extends between the first end 254a and the second portion 254d; the second portion 254d extends between the first portion 254c and the second end 254d of the damping channel 254. The first portion 254c of the damping channel 254 extends in a first direction A that is horizontal, and the first portion 251a of the feed channel 251 extends in a direction C that coincides in this example with the direction A. The second portion 254d of the damping channel 254 extends in a direction D that is vertical in this example so that the second portion 254d is lower than the first portion 254c. This arrangement serves to further increase the effect of trapping the first metal stream by gravity. In this example, the second end 254b of the damping channel 254 is level with the base plate 10 so that the damping channel 254 rests on the base plate 10. It should be observed that the direction D need not be vertical and could merely be inclined, nevertheless, the effect of trapping the first metal stream is maximized when using a vertical direction. In this example, the feed and damping channels 251 and 254 are circular in section with the diameter d. The length L of the first portion 254c of the damping channel 254 may be greater than or equal to twice the diameter d.

[0049] It should be observed that in all of the above examples, the feed channel 51, 151, 251 has two second portions 51b, 151b, 251b, but it could have only one, or indeed it could have more than two.

[0050] The installation 1 as described above can be made entirely out of ceramic material, e.g. by a lost wax casting method. In known manner, a wax model of the installation 1 needs to be made initially. Thereafter, the wax model is covered in a ceramic shell by being dipped successively into an appropriate slurry (dipping/application of stucco). Thereafter, the ceramic is fired and the wax is removed in order to obtain the installation 1 made of ceramic material.

[0051] FIG. 5 shows the main steps of a method of fabricating a casting from a molten metal by using an installation 1 as described above. The first step E1 of the method consists in filling the mold 8 of the installation 1 by pouring a molten metal into the installation. To do this, it is possible to pour the metal directly into the bush 2 of the installation 1, and the metal can then be conveyed by gravity until it fills the mold 8.

[0052] The second step E2 consists in implementing directed solidification of the metal present in the mold so as to obtain the casting. Directed solidification is performed in an appropriate oven in which the installation is placed. The oven serves to control the growth of crystal grains e.g. so as to obtain parts that are monocrystalline. Once the part has solidified, it can be knocked out and subjected to finishing machining.