GB2208389A

GB2208389A - A method of manufacturing components having portions of different wall thickness

Info

Publication number: GB2208389A
Application number: GB8818778A
Authority: GB
Inventors: Wolfgang Betz
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: MTU Aero Engines AG
Priority date: 1987-08-06
Filing date: 1988-08-08
Publication date: 1989-03-30
Anticipated expiration: 2008-08-08
Also published as: DE3726056C2; FR2619034B1; DE3726056A1; FR2619034A1; GB8818778D0; GB2208389B

Description

2208389 M&C FOLIO: 230P56736 WANGDOC: 0816k A method of manufacturing

components having portions of different wall thickness The invention relates to a method of manufacturing components having portions of very different wall thickness. by means of isostatic pressing in a mould shell.

In many cases in mechanical engineering. components are used having portions with very different wall thicknesses, e.g. in housings for drive mechanisms a relatively thin metal shell is supported by solid reinforcing ribs. Usually there are also connecting flanges and bearing bosses, which also require thicker wall thicknesses.

Nowadays three alternative methods are mainly used for manufacturing such components:

1. A solid forged blank is machined by cutting off waste chips until the desired structure is obtained.

2. Sheets, castings and machined piece parts are fixedly assembled in a suitable way. e.g. by welding.

2 3. The required component is produced entirely by casting.

The above-mentioned manufacturing methods are accompanied by problems. The first method listed requires high manufacturing costs alongside large losses of material due to the resulting waste. In addition. for reasons of production efficiency. the wall thickness cannot fall below certain dimensions.

The second method listed is very 'costly because of the required preparatory work and the welding. Problems particularly arise because of thermal distortion during welding, so that quality control requirements are high.

Finally, the third method of complete casting is accompanied by appreciable size and wall thickness restrictions.

An object of the invention is to avoid the disadvantages of the known manufacturing methods and to provide a method of manufacturing components, which consist of metallic powders pressed in a mould shell and which have areas of very different wall thickness, e.g. housings for drive mechanisms and drive mechanism parts, the steps of the method operating accurately, efficiently, and in particular economically with a relatively low If 3 input of production means.

Claims

The invention provides a method as claimed in Claim 1. The particular advantage of the method in accordance with the invention is that in relatively few production steps, the components to be manufactured can be finished true to size and with practically no wastage of material. Further preferred features of the invention are claimed in the subsidiary claims. Two preferred methods of manufacturing components in accordance with the invention are now described with reference to the accompanying drawings, wherein: Figs la and lb show in section the manufacture of a conical housing with annular flanges. reinforcing ribs and a pipe flange. and Figs 2a to 2g show in perspective and in section the manufacture of a turbine blade. As can be seen from Fig. la, to manufacture a conical housing. two frustoconical rings 1 and 2, which correspond to each other and are made of a highly workable material, e.g. a metal alloy with a titanium or 4 aluminium base. are placed one on top of the other and securely joined together at their upper and lower edges. e.g. welded, inflating tubes 4 being inserted in the weld seam 3. Wall surfaces a of the adjacent rings 1 and 2 which should not be connected to each other. i.e. the surfaces. a which lie inwardly of the future annular flanges 5. the reinforcing ribs 6 and the pipe flange 7. are coated with a separating compound. The wall surfaces b of the adjacent wall surfaces of the rings 1 and 2 are securely joined to each other e.g. by diffusion welding. After the diffusion welding. a compressed gas is blown in through the inflating tubes 4. whereby hollow spaces 8 are formed for the future ring flanges 5. the reinforcing ribs 6 and the pipe flange 7. In each case the size or the volume of the deformation of the outer ring 2 is defined by hollow moulds 9 outside the ring 2. these hollow moulds containing the rings and determining the outer configuration. The inner shape is ensured by appropriate inner mould dies (not shown). The hollow spaces 8 are now filled with powder. which may consist of the same material as the two rings 1 and 2. A desired atmosphere is then produced in the powder-filled hollow spaces 8; operation takes place with either a vacuum. a protective gas or a reaction gas. After the hollow spaces 8 are sealed gastight. the I 1 powder infills are compressed to the desired extent by means of hot isostatic pressing, a closing shape being achieved between the powder and the rings 1 and 2. To fix the inner configuration of the component, a supporting cone K is inserted. After pressing and if necessary a heat treatment. the component may. if required. be machined. As can be seen from Figs 2a to 2_q for manufacturing a turbine blade, a mould shell is formed essentially from four workable shell sheets 10. 11', 12 and 13 made of a nickel-based alloy which is very heat-resistant. the outer shell sheets 10 and 13 being provided with a layer 14 made of a corrosion-resistant material. The production steps are as follows: First the partial surfaces b of the adjacent six wall surfaces of the four shell sheets 10 to 13 are fixedly joined together. e.g. by diffusion welding (Figs. 2a, 2b). Then, by means of a tube 15 (Fig. 2c) extending outwards. compressed air L is blown in between the partial surfaces a (which are not to be joined together and which have previously been treated with a separating compound) of the facing wall surfaces of the two middle shell sheets 11 and 12. The partial surfaces a are expanded by the compressed air against a first twosided or two-part hollow mould 161. 1611 which defines a 6 central hollow mould space. As a result of the expansion a central hollow space 17 is formed. which forms the cooling medium channel of the turbine blade. This is then filled with an incompressible filler F (Fig. 2d). Afterwards. compressed air is blown in. by means of outwardly extending tubes 18 and 19. between the partial surfaces a. which are not to be joined. of the adjacent wall surfaces of the first shell sheet 10 and the second shell sheet 11. and of the third.shell sheet 12 and the fourth shell sheet 13. As a result, the partial surface a of the first shell sheet 10 and the partial surface a of the fourth shell sheet 13 are expanded against a second two-sided or two-part hollow mould 201. 2011. which defines the external shape of the component or turbine blade. The incompressible filler F is then removed from the central hollow space 17, whereupon the hollow spaces 21 and 22 between the first and second shell sheet 10 and 11. and between the third and fourth shell sheet 12 and 13. are filled with powder and sealed so as to be gastight. Finally the component is finished by means of isostatic pressing of the powder at a suitable temperature (Figs. 2e to 2g).

1-1 . 1 i T 1 7 Claims 1. A method of manufacturing a structural component having portions of different wall thickness. by means of hot isostatic pressing of a mould shell, characterized by the following method steps:

a) at least two three dimensional shaped shell walls are superimposed on each other in such a way. that the adjacent surfaces thereof contact each other over a first partial area and are space& from each other to form one or more hollow spaces in a second partial area.

b) the adjacent surfaces of the shell walls are joined together over the first partial area, and in the second partial area are fitted together along the edges of the hollow spaces so as to be undetachable, C) the hollow spaces are filled with powder, which can be compressed metallurgically, and are degassed and sealed, d) the filled shell is isostatically pressed to form the finished component.

2. A method of manufacturing a component with areas of varying wall thicknesses. by means of isostatic pressing 8 of a mould shell, characterized by the following method steps:

a) at least two shell walls with congruent cavities are superimposed so that adjacent surfaces lie against each other. and, at least along the edges of one partial area, are joined so as to be gastight and undetachable, b) a hollow space is produced within the gas tight. joined edges by means of inflating.

C) the hollow spaces are filled with metallurgically compressible powder and degassed and sealed, 1 d) the filled shell is isostatically pressed to form the finished component

3. A method as claimed in claim 2. wherein the shell walls are initially flat plates.

4. A method as claimed in any one of claims 1 to 3. wherein. before the shell walls are joined. they are coated with a separating agent adjacent the hollow spaces of the component which are to be filled with powder.

-7 1 9

5. A method as claimed in any one of claims 1 to 4. wherein the joining of the edges of the hollow spaces of the component which are to be filled with powder is carried out by means of weld seams. in particular roll weld seams.

6. A method as claimed in any one of claims 2 to 5, wherein the inflating of the shell walls takes place against hollow moulds or mould dies which are appropriately formed or form the finished component.

7. A method as claimed in any one of claims 2 to 6. wherein the inflating of the shell walls takes place in several stages.

8. A method as claimed in any one of claims 1 to 7, wherein the shell walls consist of heat-resistant sheets. preferably of a Ni-based alloy.

9. A method as claimed in any one of claims 1 to 8, wherein in addition to the shell walls. formed solid elements made of a metallic or non- metallic material are used as components of the mould shell.

10. A method as claimed in any one of claims 1 to 9. wherein the material of the mould shell is of the same nature as the material of the powder to be compressed.

11. A method as claimed in any one of claims 1 to lo, wherein nonmetallic powder, particularly ceramic powder is used.

12. A method as claimed in any one of claims 1 to 11, wherein theindividual shell walls consist of different materials.

13. A method as claimed in any one of claims 1 to 12, wherein the individual shell walls consist of layers of different materials.

14. A method as claimed in any one of claims 1 to 13. for manufacturing a turbine blade with a central cooling channel, characterized by the following method steps:

a) four flat shell sheets with essentially the same contour are joined together along their edges e.g. by diffusion welding. so as to be undetachable and to lie on top of each other; b) by means of a tube opening into a gap between the two middle shell sheets. the shell join is inflated against a first two-sided hollow mould defining a central hollow space.

c) the central hollow space thus produced, is 1 i i 1 Q filled with an incompressible filler; d) the gaps between the shell sheets, lying against each other are, by means of filling tubes, inflated against a second two-sided hollow mould defining the outer shape of the turbine blade:

e) the incompressible filler is removed from the central hollow space; f) the hollow spaces between the first and the second shell sheets and between the third and the fourth shell sheets inflating are filled with powder and the finished turbine blade is produced by isostatic pressing of the shell at a suitable temperature.

15. A method of manufacturing a structural component substantially as herein described with reference to Figs. la and lb. or 2a to 2_q of the accompanying drawings.

16. Structural components manufactured by a method as claimed in any one of the preceding claims.

Published 1988 at The Patent Office. State House. 66 71 High Ho'born. London WClR 4TP. Further copies may be obtained frorn The Patent Office, Sales Branch, St Mary Cray. Orpington, Kent BR5 3RD Printed by Multiplex techniques ltd. St. Mary Cray, Kent. Con 1'8"7 t)aies zrancn, bT, zaary uray. urpingTon, Yenz zro o tij rTinwa Dy jawupitm ui"iiqutb i. o -j - ay. -- -- - -