GB2261394A

GB2261394A - Method of producing cast parts with channels

Info

Publication number: GB2261394A
Application number: GB9220746A
Authority: GB
Inventors: Gerhard Betz
Original assignee: Thyssen Guss AG
Current assignee: Thyssen Guss AG
Priority date: 1991-10-15
Filing date: 1992-10-02
Publication date: 1993-05-19
Also published as: FR2682312A1; DE4134066A1; GB9220746D0

Description

2L 31 - 1 - 1 METHOD OF PRODUCING CAST PARTS WITH CHANNELS The present

invention relates to a method of producing a cast part with at least one channel, especially a high-quality cast part of a metallic material, for example aluminium, iron, nickel, steel or copper, with fine or very fine channels.

It is known to produce fine channels, in the case of castings according to the lost-wax method, by producing a destructible and nonmetallic core, usually of ceramic, placing the core in a mould and removing the core after the casting. This method has two disadvantages.

On the one hand cores of ceramic are very sensitive to fracture and on the other hand, depending on length, the minimum diameter for the core is 3 to 6 millimetres, otherwise the internal support during casting is no longer given. Moreover, removal of the ceramic core after casting is connected with great difficulties, particularly if the channels represent a complicated tube system. It has therefore been sought, instead of producing channels, to place tubelets in the cast part and to use these as channels, so that the medium flowing through the tubelets generally does not come into contact with the cast part. In this case the tubelets are also led outside the cast part without joining to the material of the cast part.

There remains a need for a method of producing fine channels, and systems incorporating such channels, without having to use expensive ceramic cores which are susceptible to fracture. The possibility shall preferably also be given of achieving complicatedly constructed tube systems with fine channels.

According to the present invention there is provided a method of producing a cast part of metallic material with at least one channel therein, the method comprising the steps of placing a hollow body in a mould, the hollow body having a wall thickness of at most substantially 15 percent of the outer cross-sectional dimension of the body and being of a metallic material with a melting point higher than the intended metallic material of the cast part, and then casting the part in the mould so that the hollow body remains in the part after casting.

In a preferred example, the method serves for the production of small and smallest channels in a high-quality cast part, produced according to the lost-wax process, from a metallic material, such as aluminium-, iron, nickel, steel, copper, etc., wherein the hollow body, for example a tube, with a wall thickness of at most 15% of the tube outer diameter is placed in the mould and the hollow body consists of a metallic material, such as high-grade steel, titanium, etc., of which the melting point is higher than the melting point of the casting material, the hollow body remaining, without further function, in the cast part after the casting.

Advantageously, several hollow bodies or tubelets with branches and/or different diameters are used. Expediently, hollow bodies or tubelets for high temperature applications are provided with a protective coating, for example evaporated on according to a PH process, which preferably is as thin as possible.

The advantage of a method exemplifying the invention- is that such tubelets can be readily matched to the geometry of the.cast part and that the joining of the channel system can be effected outwardly. a]: the cast material and not at the part of a tubelet projecting beyond the contour of the cast part. This has the result that the tubelets only function as cores, which, however, do not need to be removed, but can remain in the cast part. Thus even tubelets with cracks can remain in the cast part and do not need to be removed.

In general, the diameterof the or each tubelet is at most to 20 millimetres and the wall thickness is 15%, i.e. 3 millimetres. In general, however, tubelets with an external diameter of about 3 millimetres, which then have a wall thickness of about 0.3 to 0.5 millimetres, are sufficient. These tubelets can be easily introduced into the casting mould so that they substantially follow the geometry of the cast part. There can also be incorporated, without further measures, a tube labyrinth or a system of tubelets of different diameter. Thus the tubelets can extend lengthwise externally of the contour of the cast part or lie in the cast part surface flush herewith.

Almost any metallic material can be used for the production of the hollow bodies or tubelets, as long as it has a higher melting point than the material of the cast part. It is thereby avoided that the tubelets melt during the casting.

The hollow bodies or tubelets can be of any desired cross-sectional shape, such as circular, rectangular, and polygonal with 6 or 8 sides.

Previously used tubelets, which as a rule were thick-walled, were employed in the sense of a material compound, wherein for example steel tubes must fulfill a quite specific specification predetermined by the manufacturer (bursting strength, maximum leakage rate, weldabilitY, corrosion resistance, etc.). Joining outwardly always took place directly at the tube ends, without going back to the cast material, which caused great difficulties in manufacture of cast parts. In particular, a greater or smaller gap formed between the tubelet and the wall of the cast part and the cooling effect in the mould could be so substantial that the molten metal hardened disadvantageously and caused cold run spots. Further, a considerable weight increase was often present, which is disadvantageous for aviation components. Due to the large wall thickness, the minimum external diameter was at most 6 to 8 millimetres, so that the wall thickness of the cast part was necessarily inconveniently high.

Claims

- 5 CLAIMS

1 A method of producing a cast part of metallic material with at least one channel therein, the method comprising the steps of placing a hollow body in a mould, the hollow body having a wall thickness of at most substantially 15 percent of the outer cross-sectional dimension of the body and being of a metallic material with a melting point higher than the intended metallic material of the cast part, and then casting the part in the mould so that the hollow body remains in the part after casting.

2. A method as claimed in claim 1, wherein the hollow body is tubular.

3. A method as claimed in claim 1 or claim 2, wherein the dimension i at most substantially 20 millimetres.

4. A method as claimed in any one of the preceding claims, wherein the hollow body is shaped to follow the geometry of the cast part.

5. A method as claimed in any one of the preceding claims, wherein the hollow body defines a plurality of channels.

6. A method as claimed in any one of the preceding claims, comprising the step of placing at least one further such hollow body in the mould prior to casting of the part.

7. A method as claimed in claim 6, wherein the hollow bodies define channels of different diameters.

8. A method as claimed in any one of the preceding claims, wherein the or each hollow body is provided with a protective coating.

9. A method as claimed in claim 8, wherein the protective coating is applied by evaporation in a PU process.

10. A method as claimed in claim 8 or claim 9, wherein the metallic material of the or each hollow body is steel.

11 A method as claimed in any one of the preceding claims, wherein the or each hollow body is so arranged in the mould as to extend outwardly of the exterior surface of the part after casting.

12. A method as c]aimed in any one of claims 1 to 10, wherein the or each hollow body is so arranged in the mould as to be flush with the exterior surface of the part after casting.

13. A method as claimed in claim 1 and substantially as hereinbefore described.

14. A cast part produced by a method of any one of the preceding claims.

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