DE102009005173A1 - Turbine disk or compressor disk manufacturing method for use in aero gas turbine, involves repeatedly changing forger contour still internal characteristics to fulfill requirements at reduced damage characteristics - Google Patents

Abstract

The method involves adjusting a forger contour to distribution of residual tensile stress and internal compressive stress provided in an installation contour. Internal stress characteristics in the installation contour are determined, and the forger contour is accessed with respect to damage characteristics of a disk. The forger contour is changed in regions with the residual stress and the damage characteristics. The internal characteristics are determined, and the forger contour is changed again still the internal characteristics to fulfill requirements at reduced damage characteristics.

Description

The The invention relates to a process for the production of turbine or Compressor disks for gas turbines, in particular aircraft gas turbine, in which a forged blank with certain Forging contour of a heat treatment and a subsequent one cooling process subjected and then turned to the final contour.

turbine and compressor disks of gas turbines are due during operation subjected to high speeds and temperatures considerable stress. Independently from the external load are in the disk body In addition, generated by plastic deformation of the material residual stresses available. The with the external burden connected tensile stresses, which are independent of the external forces in Overlap the existing tensile residual stresses can lead to damage to the Disc material and - in particular in the highly stressed outer areas the discs - to Cracking and thus reducing the life. If the from the external load resulting tensile stresses in the highly loaded edge region of the disc but superimposed there existing residual compressive stresses be reduced, the tensile stress and thus the stress in these areas, so that the life of the discs is increased or the weight of the discs can be reduced.

The Production of the compressor or turbine disks is known to take place in one first process step by forging a cut blank to a forging with a certain forging contour. As a result of plastic deformation while forging becomes a residual stress state in the forging contour with in height and distribution of undefined residual stresses and compressive stresses generated. In the following process steps the forging contour becomes to reduce the residual stresses of a heat treatment and then one cooling process in an oil or water bath. While the cooling process go through the heat-treated Forging contour in the cooling medium three consecutive, as film boiling, as transition boiling, and as nucleate boiling of the cooling medium designated cooling phases. The last cooling phase, the so-called nucleate boiling, causes a high heat transfer from the forging contour to the cooling medium and leads to a correspondingly large, associated with the emergence of high voltages temperature gradients in the blacksmiths contour. Due to the tensions and resulting Strains due to plasticization occur in the fully cooled state on the outside the forging contour compressive stresses and in their interior tensile stresses, who are in balance with each other.

In the subsequent process step in which the forging contour on the final contour is turned off, which is used in the heat treatment and cooling in embossed the forging contour Residual stress state as a result of material removal changed again because the residual stresses to maintain the balance of power relocate inside the finished disc (final contour). As a result of this rearrangement of the impressed in the cooling process residual stress distribution can therefore in near-surface Areas of the disc tensile stresses arise, leading to the entrance mentioned Reduction of the service life of turbine and compressor disks to lead can.

By different cooling parameters although the residual stress state can be changed, but is one targeted influence on the residual stress distribution over the Cross section of the disc contour using the known cooling process parameters like flow velocity or flow guidance of the cooling medium on the workpiece surface and the type or initial temperature of the coolant is not possible, so that due to the tensile stresses occurring in edge areas material damage may occur or the actual Strength potential of the disc can not be used.

Of the Invention is based on the object, a method of the initially mentioned Type of production of turbine and Specify compressor discs that have a long life of the disc and the use of the strength potential of the disc in full guaranteed.

According to the invention Task with a method according to the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims.

Starting from a generic method for the production of turbine or compressor disks, the basic idea of the invention is that the forging contour is designed on the basis of an optimum residual stress profile in the installation contour. In other words, the forging contour is adapted to the distribution of tensile and compressive residual stresses present in the installation contour by determining the residual stress profile in the installation contour corresponding to a predetermined forging contour and evaluating it in terms of the damage behavior of the pane during operation and the forging contour in Areas with near-surface residual tensile stresses and corresponding unfavorable Schä di adjusted or changed. In the associated installation contour, the residual stress profile is again determined and evaluated. The change in the forging contour is repeated until the residual stress distribution determined in the respectively associated installation contour meets the requirements for a low damage behavior. The life of the compressor and turbine discs produced by this method as well as the safety can be increased. In addition, the strength potential of the discs is better utilized, so that a reduction in the weight of the disc is possible.

In Advantageous development of the invention, the method is through numerical simulation and based on "finite element method" calculations.

outgoing from a specified blacksmithing contour are based on a numerical simulation of the real heat treatment and cooling conditions with CFD methods the temperature fields of the forging contour determined.

On the basis of the previously determined time-dependent temperature distribution then the tensile stresses and compressive stresses that are impressed on the forging contour become calculated according to the "finite element method".

After that is in a numerical simulation by removing the corresponding Finished elements turned off the forging contour to the installation contour and which is calculated in this adjusting residual stress distribution according to the "finite element method".

Finally will the determined residual stress distribution on the basis of the wheel load evaluated in the operation with regard to the expected damage behavior and, where appropriate, an amended one, set to the previously determined residual stress distribution adapted forging contour. The adaptation or change the forging contour and the subsequent steps will take so long repeated until the residual stress profile in the installation contour a long life of the disc in question and a high level of safety shut down leaves.

One embodiment The invention will be explained in more detail in conjunction with the accompanying drawings. It demonstrate:

1 a flow chart for determining the forging contour with optimal residual stress distribution in the final contour of a compressor disk;

2 a typical first forging contour of a forging blank with the distribution of tensile residual stresses (light areas) and residual compressive stresses (dark areas) over the cross-sectional area;

3 the final contour of a compressor disk after turning off the forging blank according to 1 with residual stress distribution represented over its cross-sectional area;

4 the final contour of the compressor disk with a second residual stress distribution obtained from a second forging contour;

5 the final contour of the compressor disk with the third - optimal - residual stress distribution obtained from a third forging contour.

For the production of compressor or turbine disks with - starting from a inventively optimized Schmie dekontur a forging blank - optimal residual stress distribution in the final contour of the worm forged off the forging blank is in accordance with the in 1 reproduced flowchart in step A a first forging contour 1 ( 2 and 3 ).

For this blacksmith contour 1 in step B, using computational fluid dynamics (CFD) methods based on the respective real-world coolant and disk parameters, a numerical simulation of the forging contour heat treatment 1 of the forging blank. That is, after the heat treatment in an oven, in step B, the temperature fields of the first forging contour become 1 determined during the air cooling of the forging blank during its transfer in air from the furnace into a cooling bath and during cooling of the forging blank in the immersed in the cooling bath state.

In the following step C, on the basis of the time-dependent temperature distribution ascertained in step B, the residual stresses are calculated here - according to the "finite element method" (FEM) - due to plastic deformation during cooling due to the high temperature gradient Associated expansions and stresses are imprinted in the forging contour. The distribution of tensile and compressive stresses in the first forging contour 1 is in 2 , in the dark areas compressive stresses and light areas represent tensile stresses, reproduced by way of example. From this representation it can be seen that due to the local plasticization or permanent strains occurring on cooling at the edge of the forging contour, residual compressive stresses (dark) and inside the forge contour tensile stresses are impressed.

In the subsequent step D, the heat-treated forging contour is transformed into a first installation contour by numerical simulation 2 the compressor disk turned off by the not to the installation contour 2 belonging to finite elements of the blacksmith contour. The thereby changing residual stress distribution in the installation contour 2 , that is, the wrought forging contour or the final contour of the compressor disk, is also calculated according to the above-mentioned "finite element method".

In the next step E, taking into account the specific load on the compressor disk during operation, the height and the course of the - in 3 Tension stresses and compressive residual stresses are evaluated with regard to service life, safety or possible weight savings. In the present example (residual stress distribution according to 3 ) tensile residual stresses (bright areas) are partly at the edge of the first installation contour 2 , When the compressor disk is loaded during operation, the external tensile stresses and the residual tensile stresses present in the edge regions are superimposed. This can lead to damage to the disc, so that their life is limited and the required safety is not guaranteed or weight savings are not possible. The life analysis according to step E is answered in this case in step F with "no", so that a change of the first forging contour 1 is required.

The basis of the 1 described method steps are therefore with a in the - in 3 areas marked with residual tensile stresses at the edge of the installation contour changed forging contour 3 a forging blank repeated. That is, in step A is a modified, second blacksmithing contour 3 ( 4 ), then again the steps B to E of the flowchart according to 1 be performed. As 4 shows, the second installation contour having a different specific residual stress distribution is sufficient 4 still not the requirements of the life analysis according to step E, as well as in the changed from the second blacksmith contour 3 manufactured second installation contour 4 in a peripheral area still high tensile residual stresses occur, which would cause a damage to the compressor disk in operation and turned off their lifetime in an actually turned off from the second forging contour compressor disk.

It will therefore be another - third - Schmiedekontur 5 . 5 , determined from the result of the according to the flowchart 1 carried out steps a third installation contour with a third residual stress distribution arises. As 5 shows the tensile residual stresses (bright areas) in this case completely inside the third mounting contour 5 , that is, everywhere significantly away from their by residual compressive stresses (dark area embossed edge.) The residual compressive stresses in this form are superimposed on the operating forces acting on the disc outer tensile stresses and reduce this, so that the disc material is loaded to a lesser extent (Step E) is answered with "yes" in Step F. That is, the third forging contour found in the method 5 suffices as a result of shaping by forging as well as the heating and cooling conditions in the course of the heat treatment process in the wacky installation contour 6 with the inherent stress level and distribution impressed on it, the requirements placed on the damage behavior and thus the safety and service life of the relevant compressor disk.

1

first wrought contour

2

first Installation contour with first residual stress distribution

3

second wrought contour

4

second Installation contour with second residual stress distribution

5

third (final) wrought contour

6

third Installation contour with optimum residual stress distribution

Claims (2)

Process for the production of turbine or compressor disks for gas turbines, in particular aircraft gas turbines, in which a forging blank with a specific forging contour is subjected to a heat treatment and a subsequent cooling process and then turned to the installation contour, characterized in that the forging contour to the distribution present in the installation contour the compressive and compressive stresses is adjusted by the residual stress profile in the installation contour determined and evaluated in relation to the damage behavior of the disc during operation and changed the forging contour in areas with near-surface residual tensile stresses and corresponding unfavorable damage behavior and again determines the residual stress profile in the associated installation contour and is evaluated, wherein the change in the forging contour is repeated until the determined in the respective associated installation contour residual stress profile meets the requirements to a low damage behavior is sufficient. A method according to claim 1, characterized gekenn records that - starting from a specified forging contour step A); - the temperature fields of the forging contour are determined on the basis of a numerical simulation of the real heat treatment and cooling conditions with CFD methods (step B); On the basis of the time-dependent temperature distribution determined in step B, the tensile and compressive residual stresses impressed into the forging contour are calculated according to the "finite element method" (step C); - Then in a numerical simulation by removing the corresponding finite elements turned off the forging contour to the installation contour and is calculated in this adjusting residual stress distribution according to the "finite element method" (step D); and - the determined residual stress distribution on the basis of the wheel load during operation is evaluated with regard to the expected damage behavior (step E); and - if necessary, a changed forging contour is determined (step A) and steps B to E are repeated.