JP2015501878A - TA6Zr4DE titanium alloy part manufacturing method - Google Patents

Abstract

The present invention includes forging a blank in the α / β region to form a preform, hot stamping the preform to form a rough part in the β region of the titanium alloy, and heat treatment. Regarding the method. The present invention is characterized in that the rough part undergoes a local deformation ε of 1.2 or more during the punching step, and this punching step is terminated by rapid cooling at an initial cooling rate higher than 85 ° C./min. And The method of the present invention can be applied to manufacture rotating parts of turbomachines.

Description

  The present invention relates to a thermomechanical manufacturing method for manufacturing a TA6Zr4DE titanium alloy component and a component manufactured by the method.

  The present invention is particularly applicable to, but is not limited to, rotating parts of turbomachines such as discs, trunnions, and impellers. The present invention particularly relates to a disk of a high pressure compressor.

  Currently, in the technique used by the applicant, the high pressure compressor disk is manufactured by forging which includes forging a blank in the α / β region and hot stamping in the β region of the titanium alloy. The The punching is performed at about 1030 ° C.

  After this punching step with a press machine, a heat treatment cycle including a step of solution treatment in the α / β region of the alloy at a temperature of 970 ° C. (corresponding to β transus temperature −30 ° C.) is performed for 1 hour. Is called. This solution treatment step is followed by a quenching step in oil or water / polymer mixture.

  Next, an annealing treatment is performed at a temperature of 595 ° C. for 8 hours, and then cooled in air.

  If specific conditions are not taken into account when carrying out this production method, an alloy with a coarse microstructured zone is obtained. This coarse microstructured zone is particularly suitable for the range of −50 ° C. to + 200 ° C., especially when the oligocycle fatigue test is performed with stress applied for a certain dwell time. Compared to the same type of fatigue test, it is not preferable as a titanium alloy having excellent strength. By introducing a dwell time during which the maximum load is maintained, it is recognized that the life is shortened during this fatigue test, and this phenomenon is called a dwell effect. More specifically, the dwell effect includes creep at relatively low temperatures (below 200 ° C.), which, coupled with oligocycle fatigue, causes internal damage to the material that can cause the part to break prematurely.

  In particular, it is preferred to use an alloy known as “6242” containing about 6% aluminum, 2% tin, 4% zirconium, and 2% molybdenum. More specifically, this alloy is known in metallurgical terms as TA6Zr4DE alloy.

  A type of structure that results in a dwell effect phenomenon is shown in FIG. 1, with entangled needles all pointing in the same orientation located on either side of the particle limit 10. In this structure, called a “feathered” structure, the needles are arranged parallel to each other.

  On the other hand, when the α-phase needles are completely intertwined, that is, the α-phase needles are not bundled in a bundle of parallel needles but are arranged and distributed in completely different directions. 1 (see zone 20 in FIG. 1 and FIG. 2 as a whole), the dwell effect phenomenon is not produced, so that a preferable structure is obtained.

  Therefore, for applications in the aviation field, particularly for high pressure compressor disks, the engine is exposed to operating conditions in the temperature and stress range corresponding to the dwell effect phenomenon during takeoff and landing, so Very susceptible to effect phenomena. This phenomenon of dwell effect can cause fatigue cracks early and can even cause component failure.

  This dwell effect phenomenon has been well recognized by turbomachine manufacturers and has been the subject of numerous studies. The dwell effect phenomenon is also observed in all temperature-stabilized titanium alloys, that is, all β-class, α / β-class, near α-class, and α-class titanium alloys.

  The object of the present invention is a method for producing a thermomechanical part made of TA6Zr4DE titanium alloy, which can be carried out industrially, can overcome the drawbacks of the prior art, and in particular limits the scope of the dwell effect phenomenon. Is to provide the possibility to do.

  The object of the present invention is to improve the thermomechanical manufacturing method so that even if the component is subjected to cyclic stress at low temperatures, it is possible to obtain a component with an extended lifetime associated with the dwell effect phenomenon. It is.

  To achieve the above objectives, the present invention includes the steps of forging a blank in the α / β region to form a preform and hot forming the preform to form a rough part in the β region of the titanium alloy. A method of manufacturing a thermomechanical part made of TA6Zr4DE titanium alloy including a punching step and a heat treatment, wherein the rough part undergoes a local deformation ε of 1.2 or more during the punching step, and the punching step Relates to a process characterized in that it is terminated by quenching at an initial cooling rate of faster than 85 ° C./min, preferably faster than 100 ° C./min.

  The concept on which the present invention is based is consistent with the fact that it has been observed that parallel needles or “colony” regions that cause the dwell effect phenomenon are present in the material. This colony consists of relatively coarse and slender needles of primary alpha phase that are in contact with each other. The colony may have a length of a few mm and a thickness of 0.1 mm to 1.5 mm.

  When the material is stressed, the colony becomes a place where high dislocation density occurs, and when the colony is activated, slippage may occur between the needles without any specific thermal effect. This may cause destruction.

  The present invention, in particular, by forming an “entangled” type structure to minimize the dwell effect, thereby further minimizing the accumulation of dislocations and the risk of component destruction. In order to minimize the above, it is an object of the present invention to provide a production method capable of limiting the particle size and limiting the structure of the “colony” type by reducing the range in which dislocations can freely move.

  Therefore, the present invention utilizes not only that a certain minimum level of deformation is applied to the part to form a fine microstructure at the end of the punching step, but also the rough part obtained by the punching step, By cooling the rough part immediately and sufficiently quickly, this fine microstructure can be reliably maintained.

  For example, the cooling for completing the punching step is performed by quenching in water at a temperature of 60 ° C. or less.

  Advantageously, in the production method according to the invention, the heat treatment comprises a solution heat treatment in the α / β region of the alloy, immediately followed by cooling of the entire part at a cooling rate faster than 100 ° C./min.

  Preferably, the cooling to end the solution heat treatment is performed by quenching the part at a cooling rate higher than 150 ° C./min, in particular from 200 ° C./min to 450 ° C./min.

  Advantageously, the cooling to end the solution heat treatment is effected by quenching in oil or in a water / polymer mixture.

  Thus, due to this rapid cooling, the microstructure state is solidified at the end of the solution heat treatment step and further changes in this microstructure are avoided. This is because if the microstructure further changes, the needle-like portion of the α-phase colony that causes the dwell effect phenomenon may grow.

  In addition, by selecting rapid quenching, the β-phase martensitic transformation to α-phase (which results in a fairly fine microstructure) compared to seeding / growth-type phenomena (which results in a rather coarse microstructure) Is promoted.

More preferably, at the end of the production method of the present invention, the method of the present invention further comprises:
-After the quenching step to finish the solution heat treatment, an annealing step is carried out at a temperature of about 595 ° C for about 8 hours (h), followed by cooling in air.

  Advantageously, the production method according to the invention further comprises a machining step, in particular a pre-machining step, for reducing parts that are too large between the stamping step (and then cooling in water) and the solution heat treatment step. Including. Thereafter, other machining operations are performed to correct the dimensions of the part to a final shape.

  If pre-machining is added, the cooling rate is preferably faster than 350 ° C./min after the quenching step.

  In this way, the volume of the material that needs to be processed during the heat treatment can be reduced, so that the entire part can be cooled more quickly.

  The inventor has found that this manufacturing method, which allows for a finer structure, does not affect the thermomechanical properties of the material.

  The present invention further provides a thermomechanical component made of TA6Zr4DE titanium alloy using the manufacturing method described above.

  The thermomechanical parts made of titanium preferably form the rotating parts of turbomachines, in particular compressor disks, in particular high-pressure compressor disks.

  Finally, the invention further relates to a turbomachine fitted with a thermomechanical component meeting any of the above definitions.

  Other advantages and features of the invention will become apparent on reading the following description, given by way of example with reference to the accompanying drawings.

It is a diagram showing a microstructure formed using the conventional manufacturing method of the prior art described above. It is the figure which showed the microstructure of the type formed using the manufacturing method of this invention demonstrated above. It is the figure which showed the step of the manufacturing method of a prior art, and the manufacturing method of this invention. The figure which showed the lifetime result which performed the fatigue test ("trapezoidal shape cycle including dwell time) at the atmospheric temperature with respect to the part manufactured by the manufacturing method of the prior art, and the part manufactured by the manufacturing method of this invention. FIG. 6 is a diagram showing the results obtained in two zones (zone 3 and zone 5) of parts having different sizes.

  Referring to FIG. 3, there is shown, in particular, a prior art conventional heat treatment used by Applicant's company for high pressure compressor disks made of TA6Zr4DE or “6242” titanium alloy.

  First, a blank or billet of material is forged in the α / β region, for example, at 950 ° C., and then cooled in air to form a preform.

  The preform is then subjected to a hot stamping step in the β region of the titanium alloy at a temperature of 1030 ° C. (corresponding to β transus temperature + 30 ° C.), and after forging, is cooled in water to form a disk. A rough part (also known as a “forged blank”) is formed.

  After this punching step, heat treatment is performed including a solution heat treatment in the α / β region of the alloy at a temperature of 970 ° C. (corresponding to β transus temperature −30 ° C.) for 1 hour.

  This solution heat treatment step is followed by a quenching step in oil or water / polymer mixture (initially at a minimum cooling rate of 200 ° C. and then at a cooling rate of 200 ° C./min to 450 ° C./min. )

  Then, it cools in air at 595 degreeC for 8 hours, and annealing heat processing is performed.

  As shown in FIG. 1, a material having a microstructure having a colony composed of parallel α-phase needles located on both sides of the particle limit at a specific location is formed. These needle-like parts have an elongated cross section shown in the drawings, and their length often extends to several hundred micrometers.

In FIG. 2, the microstructure shown is that of the same titanium alloy as that of FIG. 1, except for the following different parts, after being processed by the manufacturing method described above:
-During the punching step, the blank undergoes a local deformation ε of 1.2 or more throughout. The minimum value ε of this local deformation is advantageously 1.5, preferably greater than 1.7, or even greater than 1.9, with a maximum exceeding 2.

  Under such circumstances, the number of parallel needle-like colonies decreases and the size decreases. Most of the needle-shaped parts are intertwined, and furthermore, the needle-shaped parts are different in size. As shown in FIG. 2, the size of all cross-sections of the needles is reduced and the length is maintained below 100 micrometers (μm), typically about 20 μm to 50 μm.

  Therefore, it can be expected that the dwell effect phenomenon is prevented by eliminating the accumulation of dislocations leading to the risk of destruction by eliminating the long needle-like portions of the parallel arrangement.

  By reducing the size of the needle-like part, the volume of the needle-like part is reduced and the contact area between the needle-like parts is reduced, so that defective parts such as dislocations or voids are difficult to move, resulting in defects. The moving distance of the part becomes shorter and the possibility of accumulation becomes smaller.

  In the present invention, the term “local deformation ε” is used to refer to an equivalent generalized deformation of the Mises meaning calculated by the Forge 2005 simulation software. The mathematical formula used for the calculation is as follows:

ここで、［ε］ｐｌは、塑性変形テンソルに相当する。

Here, [ε] pl corresponds to a plastic deformation tensor.

  In order to ensure that a minimum value of local deformation is obtained throughout at the end of the punching step, simulation is performed using computer aided design (CAD) means.

  In particular, the material obtained by the production method of the present invention as a whole has thermomechanical properties, in particular, the ability to withstand oligocycle fatigue under conditions subject to any deformation, and the material obtained by the prior art production method. There is nothing worse than the case.

  For high pressure compressor discs by applying stress using trapezoidal signals (no stress for 1 second, no stress for 40 seconds, no stress for 1 second) at ambient temperature with a maximum stress of 772 megapascals (MPa) The ability to withstand oligocycle fatigue was tested.

  Table 1 below summarizes the results for the number of cycles prior to failure for the test shown in FIG. 4 performed in zone 3 (corresponding to the hole) and zone 5 (corresponding to the web) of the disk. :

  In this way, it can be seen that the lifetime is increased, and the ability to withstand the dwell effect phenomenon is considerably increased from 1.5 times (zone 3) to 4 times (zone 5).

  As a comparison, a traction test (20 ° C. and 450 ° C. is performed as another mechanical inspection that proves that the strength of the part obtained by the manufacturing method of the present invention is at least comparable to that obtained from the standard range. ) And a creep elongation test at 500 ° C.

  Furthermore, for vibration fatigue testing by applying stress at a frequency of 80 hertz (Hz) and at ambient temperature, the lifetime is 3 parts compared to parts obtained from the standard range compared to parts obtained from the standard range. It turned out to be twice as long.

Claims (12)

  Made of TA6Zr4DE titanium alloy comprising forging a blank in the α / β region to form a preform, hot stamping the preform to form a rough part in the β region of the titanium alloy, and heat treatment A thermomechanical manufacturing method for manufacturing a part, wherein the rough part undergoes a local deformation ε of 1.2 or more during the hot punching step, which is faster than 85 ° C./min. The method is finished by rapid cooling at an initial cooling rate.   The manufacturing method according to claim 1, wherein the heat treatment includes a solution heat treatment in an α / β region of the alloy, and immediately after that, cooling is performed at a rate higher than 100 ° C./min.   The manufacturing method according to claim 1 or 2, wherein the cooling for ending the punching step is performed by quenching in water.   The method according to claim 2 or 3, wherein the cooling to finish the solution heat treatment is performed by quenching the part at an initial cooling rate higher than 150 ° C / min.   The process according to claim 4, characterized in that the cooling to end the solution heat treatment is carried out by quenching in oil or in a water / polymer mixture.   The manufacturing method according to claim 4, wherein a cooling rate at the quenching step for ending the solution heat treatment is 200 ° C / min to 450 ° C / min. 7. The method of claim 1, further comprising the step of annealing at a temperature of about 595 ° C. for about 8 hours after the quenching step for ending the solution heat treatment, and then cooling in air. The manufacturing method as described in any one.   The manufacturing method according to any one of claims 1 to 7, further comprising a machining step for reducing an excessively large part between the punching step and the solution heat treatment step.   A thermomechanical component made of a TA6Zr4DE titanium alloy manufactured using the manufacturing method according to any one of claims 1 to 8.   Thermomechanical component according to claim 9, characterized in that it forms a rotating component of a turbomachine.   Thermomechanical component according to claim 9 or 10, characterized in that it forms a high-pressure compressor disk.   A turbomachine comprising the thermomechanical component according to claim 9.

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