Apparatus for casting multiple components using a directional solidification process

Abstract

An apparatus for the simultaneous casting of multiple components using a directional solidification process includes; a pouring cup arranged on a centerline, an array of moulds encircling the pouring cup and centre line, an array of feed channels extending from the pouring cup to a top end of each mould, and a heat deflector. The heat deflector comprises a wall arranged between the array of moulds and the centerline extending along the length of the moulds and in thermal contact with the moulds.

Claims

1. An apparatus for the simultaneous casting of multiple components using a directional solidification process comprising: a support column; a pouring cup resting directly on the support column; an array of moulds including grain selector cavities at bottom ends of the moulds to assist in the initiation of single crystal formation within the moulds; a chill plate arranged at a bottom end of the array of moulds; a starter disposed on the chill plate; an array of feed channels extending from the pouring cup to each mould; and a heat deflector, wherein the apparatus is configured to be controllably cooled by withdrawal from a heat source surrounding the array of moulds in a direction opposite to a desired direction of solidification once the moulds have been filled, the heat deflector comprises a wall arranged to encircle the support column and on an opposite side of the array of moulds to the heat source, the wall extending lengthwise along the moulds and in thermal contact with the moulds, and a surface of the wall facing the moulds includes an array of local deflectors which are each shaped to follow the contour of a mould to which they are positioned adjacent and axially offset with respect to the mould based on a thermal behavior of a material in the mould, and the array of local deflectors are positioned such that the surface of the wall facing the moulds is axially offset at least at one point on one side of a radial inflection point on the surface of the wall and at another point on another side of the radial inflection point.

2. The apparatus as claimed in claim 1, wherein the array of moulds is circular and the wall is a circumferential wall.

3. The apparatus as claimed in claim 1, wherein the wall is multi-faceted.

4. The apparatus as claimed in claim 1, wherein the wall is modular.

5. The apparatus as claimed in claim 1, wherein the local deflectors are removably secured to the wall.

6. The apparatus as claimed in claim 1, wherein the local deflectors are integrally formed with the wall.

7. The apparatus as claimed in claim 1, wherein the wall and/or local deflectors are formed from a wax core surrounded by a high temperature capable material.

8. The apparatus as claimed in claim 7, wherein the high temperature capable material is selected from: a ceramic, carbon or graphite.

9. The apparatus as claimed in claim 1, wherein the wall and/or local deflectors are provided with a high emissive surface coating.

10. The apparatus as claimed in claim 9, wherein the surface coating is a magnesium oxide paint, an aluminium oxide paint or a titanium oxide paint.

11. The apparatus as claimed in claim 1, wherein the moulds define the shape of turbine blades.

12. The apparatus as claimed in claim 1, wherein the moulds define the shape of nozzle guide vanes, compressor blades or seal segments configured for use in a gas turbine engine.

13. The apparatus as claimed in claim 1, wherein the grain selector, the starter, and the controlled cooling together encourage growth of a single crystal structure in the material of the mould.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the invention is now described with reference to the accompanying Figures in which:

(2) FIG. 1 shows in schematic a known apparatus for the simultaneous manufacture of multiple cast components using a directional solidification process:

(3) FIG. 2 shows an apparatus in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF DRAWINGS AND SOME EMBODIMENTS

(4) FIG. 1 has been described in more detail above. In the arrangement of FIG. 1 it will be noted that a substantial void space exists between the moulds 3 and a central support column which supports the pouring cup 1. The void causes a heat sink between the support column and the moulds, which shadow some of the radiation from the heat source 6. As a consequence, the temperature profile from the heat source side to the pouring cup side of the mould is non-uniform. This can negatively affect the microstructure of the solidifying material and result in defects in the cast components.

(5) As can be seen in FIG. 2, an apparatus in accordance with an embodiment of the invention comprises a pouring cup 21 into which molten material M is poured. The pouring cup 21 sits on a cylindrical support column 27 having a centreline C-C. A plurality of feed channels 22 extend radially around the centrally arranged cup 21 to a top end of the moulds 23. Molten material M poured into the cup 21 flows along the feed channels 22 and into the moulds 23. Each mould 23 is provided with a grain selector 24a at a bottom end which terminates in a starter block 24b. The starter blocks 24b sit on a chill plate 25 which is maintained generally at a temperature below the melting point of the material M creating a temperature gradient from the bottom to the top of the moulds 23. During the pouring process, the moulds are enclosed by a heat source 26 which encircles the cup 21 and mould 23 assembly. The assembly is drawn in a controlled manner out of the heat source in the direction of arrow A to ensure directional solidification from the bottom of the moulds 23 to the top of the moulds 23. The combination of the grain selector and starter with controlled cooling encourages growth of a single crystal structure in the solidifying casting. As an alternative to the grain selector and starter block, a seed crystal might be included in the mould in the same manner as described for the apparatus of FIG. 1.

(6) A circumferential wall 28 is arranged to encircle the support column 27 and sits close to and in thermal contact with the moulds 23, the wall 28 includes three dimensional profiled local deflectors 29 which are profiled to follow a facing contour of the moulds 23. The local deflectors 23 are shown as integrally formed with the wall 28 but may comprise separate components which can be secured to the wall 28. The construction of the wall 28 and local deflectors 29 is such as to deflect heat emitted from the heat source 26 back towards a facing surface 23a of the moulds 23 which surfaces 23a would otherwise be shadowed from radiative heat travelling towards the central support column 27. This prevents a thermal gradient developing from the heat source side 23b to the support column side 23a of the moulds 23.

(7) Whilst the Figures illustrate a centrally arranged pouring cup, radially extending feed channels and a substantially circular array of moulds about the cup, the skilled addressee will understand that such an arrangement is not essential to the practising of the invention. The location of the source of molten fluid and the path taken from the source to the moulds does not impact on operation of the invention.

(8) It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.