GB2269126A

GB2269126A - Method of producing a weld connection for structural parts of turbo engines

Info

Publication number: GB2269126A
Application number: GB9315182A
Authority: GB
Inventors: Reinhold Meier; Karl Kerger-Knilling
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: MTU Aero Engines GmbH
Priority date: 1992-07-31
Filing date: 1993-07-22
Publication date: 1994-02-02
Anticipated expiration: 2013-07-22
Also published as: GB9315182D0; GB2269126B; FR2694225B1; DE4225443C2; DE4225443A1; FR2694225A1; NL9301335A; NL192871C; NL192871B

Abstract

One of two structural parts 4 has a pocket-like recess 7 by means of which it is placed on the other structural part A along a corresponding joint edge. The space between the pocket-like recess and the other structural part is filled with a welding powder S and the two structural parts are then welded together by heating. The recess may be closed by bending in its sides 9 or it may be capped. The welding powder may be inserted through devices 10, 11 which are sealed prior to welding. <IMAGE>

Description

2269126_.

Method of producing a weld connection for structural parts of turbo machines The invention relates to a method according to the preamble of Claim 1.

Previous repair or weld connections have involved comparatively high expenditure on production and costs. In addition there is a risk of local weld defects.

In particular, when local blade renewal of fan or turbine blades is necessary, the new part is practically prefabricated before the welding process such that it is adapted to the profiling actually required; thus the separation edge of the old part is transferred extremely accurately to the new part, taking account of variable profile thickness and possible distortion of the blades. When the new part, prefabricated in this manner, has been welded edge-to-edge or butt welded to the old part, locally inadequate weld connections will have resulted over the entire length of the weld seam, the reasons for which lie in the thickness of the material which frequently varies to an extreme extent over the entire connection point. There are thus difficulties in adapting the 2 welding parameters to the different cross-sections as the weld seam progresses. Although an adaption of this type would be at least theoretically possible within the framework of electronicallynumerically controlled welding processes (mass production), the cost-intensive mechanical requirements necessary therefor are not justified within the context of the specific requirement of repairing a structural part of turbo engines.

The invention is based on the object of providing a method according to the initially mentioned type, by means of which an optimum connection between structural parts can be attained comparatively easily, in particular even when the geometry of the structural parts differs in the vicinity of the weld seam.

Claims

In accordance with the invention, the stated object is achieved by means

of the features given in the characterising part of Claim 1.

In this manner, an intimate melt-weld connection is attained over the entire lengths and widths of the structural parts. The welding powder, which is adapted in terms of material to the structural parts to be welded together (old part/new part), completely fills the spaces between the pocket and 3 the local section of the old part, such that, even when the wall thickness differs as a result of aerodynamic requirements, the welding material is distributed uniformly over the entire length and breadth of the mutual welding zone, this distribution of the welding material being supplemented for welding material parts which previously formed a pocket of the new part.

The invention avoids having to observe extremely precise manufacturing tolerances, namely with respect to the nature of the surface of the separation zone on the old part and also with respect to the nature of the new part, for example a pocket.

The new part, which can be manufactured such that it is over-dimensioned with respect to the structural dimensions actually required and is thus welded to the old part, enables deformations, possibly caused by stresses during welding, to dissipate, for which purpose suspension portions distributed accordingly and used to facilitate handling during welding can be employed on the new parts. Any structural distortion in the new part can be corrected to the actual dimensions required within the context of the existing over- 4 dimensioning by means of a subsequent machining operation performed after the welding process.

When the local portion of the old part has been inserted into a pocket of the new part - or vice versa - the remaining pocket volume can be formed as a function of the amounts of welding powder required and/or as a function of the selected dimensions of the powder particles and/or as a function of a chamber-like powder precompression. for adaptation to predetermined shape contours and dimensions.

With respect to the repairs of structural parts specific to engines in the case of turbo machine and aircraft engines, in accordance with the invention, the new parts can be prefabricated as standard structural parts, stored and fetched as required. This is possible, for example, when turbine blades are reconditioned which have recurrent blade damage, for example burning or hot gas corrosion on the leading or trailing edge which, in accordance with the invention, can also be repaired or renewed over the entire length of a vane blade.

The invention will now be explained in further detail, by way of example within the context of a repair process, with reference to the drawings, in which:

Figure 1 shows the side view of a fan rotor blade showing the separation zones on the blade side of damaged portions to be repaired; Figure
2 shows the rotor blade according to Figure 1 indicating new parts which are prefabricated in accordance with the invention, are mounted along the separation zones or welded to the old part along the latter; Figure
3 is a first embodiment of the new part for repairing the outer blade portion according to Figure 1 on the downstream side, with a pocket and powder filling, and placed on the relevant separation zone of the old part; Figure
4 shows a second embodiment of a new part for repairing the outer blade portion according to Figure 1 on the downstream side, with pocket and powder filling, and placed on the relevant separation zone of the old part; Figure
5 shows a third embodiment of a new part for repairing the blade portion according to Figure 1 and Figure 4, in this case illustrating
6 measures for sealing the power-filled pocket with respect to the local blade portion of the old part; Figure 6 shows another embodiment of the construction of the new part in perspective, indicating the complete local repair of the blade, including the blade tip, with reference to the blade portion end of the old part. shown brokenoff locally, in the pocket; and Figure
7 shows the plan view of a further new part combined with a locally damaged blade portion of which the material thickness varies.

In accordance with the repair procedure, locally damaged blade portions 2, 3 (Figure 1) of a fan rotor blade 1 of a gas turbine jet engine are separated along the separation zones T1. T2 with a preferably straight surface structure and are replaced by new parts 4, 5 (Figure 2) which are to be welded along the separation zones T1, T2 to the relevant old part A. In accordance with the invention - before the welding process - the new parts 4 and 5 are provided with a pocket-like recess 6 or 7 respectively; the old part A is introduced along the relevant separation zone T1, T2 into the new part 4 or 5 respectively. into 7 this recess 6 or 7 respectively; and the relevant new part 4 and 5 respectively can be mounted at the relevant separation zone T1, T2 on the old part A. Thus the new parts 4 and 5 respectively sit along the base of their pockets or grooves such that they are edge-to-edge or flush with the relevant separation zone T1, T2. Subsequently, the space remaining between the pocket-like recess 6 or 7 respectively and the old part A is to be filled with a metal powder
S suitable for welding the two parts together. Welding can then take place along the extension of the separation zones T1, T2. The welded new parts 4 and 5 respectively, initially welded with a rectangular or square cross-section, can be machined down to the blade contours actually required K (Figure 4) or K' (Figure 3) according to the blade portions 2, 3 in Figure 1.

As Figure 7 shows in particular at the top, the pocket-like recess 7 is further manufactured with a larger width than the locally largest thickness of the old part A; at all events, the relevant blade portion A is mounted with play in the pocket-like recess 6 (Figure 3) or 7 (Figures 47). Figure 7 shows clearly that, when the blade geometry is locally damaged and the wall thickness of the old part A varies in the longitudinal 8 direction of T2, the pocket 7 is adapted in such a manner that the powder filling S makes up the locally pre-determined material shrinkages in the old part A, over the entire length of the pocket, such that a uniform weld connection can be achieved comparatively easily.

As Figure 4 or 5 shows, the pocket-like recesses 7 can in principle be manufactured with a rectangular cross-section or optionally with a square cross-section. In accordance with Figure 6, the pocket-like recess 6 is provided with an approximately V-shaped cross-section which tapers from the open side to the base in order to achieve a powder filling S which is distributed on all sides and can be easily checked.

As can further be seen from all the Figures, the new parts 4 and 5 in each case are overdimensioned with respect to the blade portions actually required according to 2, 3 on the old part A (Figure 1). Depending on the given contour of the structural part to be repaired, the new parts can also be prefabricated such that they are substantially thinner than illustrated and welded to the old part A. In a further development, each new part 4 and 5 respectively can be 0.1 to 5 times wider than the locally maximum thickness of
9 the old part A in each case in the vicinity of the separation zones T1, T2.

As illustrated in accordance with Figure 6, for example, with respect to repairing the blade at the tip end, each relevant new part, for example 4, can be provided with an arc discharge marking M which extends at the level of the pocket or groove base and which simultaneously marks the structural part join along the relevant zone T1 in order to facilitate optimum welding.

As shown at the top righthand side of Figure 2 in dashed lines, each new part, for example 5, can be prefabricated with at least one additional retaining portion 8, for example with a bore 9, in order to facilitate handling of the new parts during welding or in order to achieve a required seat for a structural part, for further processing, after the welding process. However, the retaining portions can also be used to discharge heat from the welding process rapidly and uniformly such that the procedure is once again performed in such a way that stress and deformation are minimised, at least with respect to the new parts 4 and 5.

Figure 5 shows an embodiment in which the pocketlike recess 7 can be closed on its open side facing away from the base or bottom. As Figure 5 shows, it can be closed as a result of the wall portions 9. of the new part 4, forming the pocketlike recess being curved around locally towards the old part A. Alternatively, a lid-like closure device could also be provided for the pocket-like recess. It is thus possible to close the recess after - or before - it is filled with the welding powder S.

Figure 5 shows one example for closing the pocketlike recess 7, as mentioned, and subsequently providing the filling of welding powder S. For this purpose, inserts, which comprise passage openings for welding powder S supplied or discharged under pressure and which are formed as material supply devices
10 or as material discharge devices 11, are disposed in the portions of the wall parts 9 which are not curved and remain straight. The supply and discharge devices 10 and 11 respectively can be sealed before the structural parts are welded. Alternatively it would be conceivable to provide as supply and discharge devices in the wall parts 9 bores which are sealed in a stopper-like manner before the welding process.
11 The process according to the invention can be used to manufacture, repair or subsequently improve the quality of the following structural parts in the case of turbo machines and in particular gas turbine engines: turbine, compressor or fan blades - including stationary blades and rotor blades, flame tube wall parts or combustion chamber housings, compressor or turbine housings or rotors, or thrust nozzle flaps.

The invention can be employed in the local repair of areas subject to high temperatures, for example the leading or trailing edges or tips of turbine blades, according to which materials which are more highly alloyed and resistant to higher temperatures than those used for the original old part A can be used for the new parts. In this respect, in accordance with the invention, a structural part, for example a blade, can be prefabricated from the outset in a multi-part manner, for example piece by piece in accordance with different operating stresses (loads, temperatures, wear), and subsequently be connected by means of this welding process.

With respect to frequently occurring stress limits and expected damage. for example, the new parts can be based on so-called "unidirectionally
12 hardened" structural parts, that is single-crystal structural parts, in order to manage locally high tension stresses, for example on the vane blade, even better than is the case locally with the socalled old part, which would thus be easier and cheaper to manufacture from the point of view of material.

The invention is also suitable for so-called I'bliskslI, ie. mass produced integral rotor blade components, for example in an electrochemical treatment process, the preservation of the components by local blade repairs or renewal being justified precisely in this case, for example for disc or rotor sectors which have not been damaged.

The invention can advantageously be performed within the context of the following welding processes: EB (electron beam) welding, TIG welding (tungsten inert gas welding), plasma welding, plug welding or electrical resistance welding for example.

Provided they have not already been expressly claimed (claims), the above features form part of the subject matter of the invention per se and/or from the drawings.
13 CLAIMS 1. Method for producing a weld connection for structural parts of turbo machines, which are welded to one another along common end edges, characterised in that one of two parts comprises a pocket-like recess by means of which is it placed on the other part, the space between the pocketlike recess and the other part being filled with a welding powder, and the two parts being welded as a result of heating to the welding temperature.

2. Method according to Claim 1, characterised in that the pocket-like recess of the one part is manufactured with a larger width than the locally largest thickness of the other part.

3. Method according to Claim 1 or Claim 2, characterised in that the pocket-like recess is manufactured with a cross-section which tapers from the open side toward the base.

4. Method according to any one of Claims 1 to 3, characterised in that each part is prefabricated such that it is over-dimensioned with respect to the other part.
14. Application of the method according to any preceding claim to structural parts of turbine or compressor blades or of flame tube wall portions or housing structural parts of combustion chambers or of compressor or turbine housings or rotor portions or thrust nozzle flaps which are to be welded to one another.

16
15. Method for producing a weld connection substantially as described herein with reference to the accompanying drawings.

14 5. Method according to any one of Claims 1 to 4, characterised in that each part is manufactured such that it is 0.1 to 5 times thicker than the respective local maximum thickness of the other part.

6. Method according to one or more of Claims 1 to 5, characterised in that each part is provided with an impressed or stamped arc discharge marking on the outer wall thereof at the level of the base of the pocket.

7. Method according to Claim 4, characterised in that each part is prefabricated with at least one additional retaining portion.

8. Method according to one or more of Claims 1 to 7, characterised in that the pocket-like recess is sealed on the open side after being filled with the welding powder.

9. Method according to one or more of Claims 1 to 7, characterised in that the pocket-like recess is sealed on the open side before the welding process.

10. Method according to Claim 8 or 9, characterised in that the pocketlike recess is sealed on the open side as a result of wall portions of one part being bent towards the other structural part.

11. Method according to Claim 8 or Claim 9, characterised in that the pocket-like recess is sealed in a lid-like manner.

12. Method according to any one of Claims 9 to 11, characterised in that the pocket-like recess is firstly sealed or closed and is subsequently filled with the welding powder.

13. Method according to Claim 12, characterised in that the one structural part is provided with supply and discharge passages or insert parts respectively for the filling with or removal of the welding powder.