Size control method for large titanium alloy forgings

Abstract

A method for controlling the dimensions of large titanium alloy forgings includes: providing a titanium alloy forging blank and heat-treating it according to the manufacturing process; cutting multiple samples from the titanium alloy forging blank according to a depth gradient; performing mechanical property tests and microstructure analysis on the samples; fitting the mechanical property test results with the depth and the microstructure analysis results with the depth; and calculating the allowable machining allowance of the titanium alloy forging blank based on the fitting calculation results and the design requirements of the titanium alloy forging. This method can quantitatively establish the relationship between the dimensions and properties of large titanium alloy forgings, providing process guidance for the forging of titanium alloy forgings, improving processing efficiency, and optimizing production costs.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy forging, and specifically relates to a method for controlling the dimensions of large titanium alloy forgings. Background Technology

[0002] Large passenger bus engines are typical high-bypass turbofan engines. Compared to large transport engines, large passenger bus engines have higher requirements for lifespan, reliability, and economy. With the increase in the bypass ratio of commercial engines, the size of component configurations is increasing, and the structure is becoming increasingly complex. The engine fan disc is a key rotating component in the engine rotor; it is large in size, complex in structure, requires high mechanical properties, and is difficult to manufacture. Engine performance demands are placing increasingly higher performance requirements on compressor disc components; correspondingly, the performance requirements for forgings are also increasing. The large size and complex structure of the fan disc, when manufactured using titanium alloys, require comprehensive consideration of the hardenability of titanium alloys and the limitations imposed by heat treatment processes on structural dimensions. This leads to difficulties in controlling the microstructure and properties of forgings and the hardenability of heat treatment in existing large titanium alloy forging manufacturing processes. Therefore, this paper proposes a method for controlling the dimensions of large titanium alloy forgings. Improving the forging effect through dimensional control is of positive significance for improving the quality of large titanium alloy forgings. Summary of the Invention

[0003] The purpose of this invention is to provide a method for controlling the dimensions of large titanium alloy forgings, thereby improving the finished product quality of titanium alloy forgings.

[0004] According to an embodiment of the present invention, a method for controlling the dimensions of large titanium alloy forgings is provided, the method comprising the following steps:

[0005] Step a): Provide a titanium alloy forging blank, and perform heat treatment on the titanium alloy forging blank according to the manufacturing process of titanium alloy forging;

[0006] Step b): Cut multiple samples from the titanium alloy forging blank, wherein the cutting position of the samples is at a depth gradient from the surface of the titanium alloy forging blank;

[0007] Step c): Perform mechanical property tests and / or microstructure analysis on the samples respectively;

[0008] Step d): Based on the mechanical property test results, perform fitting calculations to determine the relationship between the strength and depth of the titanium alloy;

[0009] And / or,

[0010] The relationship between the microstructure parameters and depth of titanium alloy was calculated by fitting the microstructure analysis results.

[0011] Step e): Based on the calculation results of step d) and the mechanical properties and / or microstructure design requirements of the titanium alloy forging, calculate the allowable machining allowance for the titanium alloy forging blank.

[0012] This method can establish the correspondence between the size and performance of large titanium alloy forgings, guide the precise design and process formulation of forgings, optimize the performance of finished forgings, reduce production costs, and improve production efficiency.

[0013] Furthermore, in some embodiments, the method further includes step f): when the machining allowance calculated in step e) is less than the lower limit allowed by the forging process of the titanium alloy forging blank, the thickness of the titanium alloy forging blank is reduced by adding slots to optimize the configuration of the titanium alloy forging blank.

[0014] Furthermore, in some embodiments, the mechanical property test in step c) includes room temperature tensile testing and high temperature tensile testing.

[0015] Furthermore, in some embodiments, the titanium alloy is a TC4 alloy.

[0016] Furthermore, in some embodiments, the manufacturing method of the titanium alloy forging blank is as follows: providing a titanium alloy bar, heating the titanium alloy bar to 50°C below the phase transformation point, controlling the final forging temperature to be not lower than 750°C, the deformation amount to be 20%-45%, and air cooling to obtain a blank; heating the blank to 50°C below the phase transformation point, controlling the final forging temperature to be not lower than 750°C, the deformation amount to be 30%-70%, and air cooling to obtain the titanium alloy forging blank with the final shape.

[0017] Furthermore, in some embodiments, the microstructure analysis result in step d) is the content of primary α phase.

[0018] Furthermore, in some embodiments, the titanium alloy forging is configured as an aircraft engine fan disc.

[0019] Furthermore, in some embodiments, in step b), the sample has an orientation, the orientation including radial, axial and chordal directions along the aircraft engine fan disk.

[0020] Furthermore, in some embodiments, in step b), the sampling location of the sample includes the web, blade, mounting edge, and tenon groove area of ​​the aero-engine fan disk.

[0021] Furthermore, in some embodiments, the fitting calculation in step d) employs linear fitting. Attached Figure Description

[0022] Figure 1This is a schematic diagram of a half-section of an engine fan disc blank in one embodiment;

[0023] Figure 2 This is a schematic diagram of the sampling location in one embodiment;

[0024] Figure 3a This is a diagram showing the relationship between room temperature intensity and sampling depth in one embodiment;

[0025] Figure 3b This is a graph showing the relationship between high temperature intensity and sampling depth in one embodiment;

[0026] Figure 4 This is a diagram showing the relationship between the content of the primary α phase and the sampling depth in one embodiment;

[0027] Figure 5 This is a schematic diagram of the tensile strength-sampling depth fitting results in one embodiment;

[0028] Figure 6 This is a graph showing the relationship between high-temperature intensity and sampling depth in another embodiment;

[0029] Figure 7 This is a schematic diagram of the high-temperature intensity-sampling depth fitting results in another embodiment.

[0030] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and is not intended to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0032] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0033] In this article, terms such as "first" and "second" are used only to distinguish different objects and should not be interpreted as indicating relative importance or limiting the number, specific order, or primary and secondary relationship of the described technical features.

[0034] In this article, "multiple" means at least two.

[0035] With the development of the aviation industry, the bypass ratio of commercial passenger engines has gradually increased, and engine performance has also become increasingly higher. Correspondingly, the comprehensive requirements for engine performance, reliability, and economy have become increasingly stringent. As the size and complexity of engine parts increase, the performance of key components such as compressor discs has also been severely tested. The engine fan disc is a key component in aero engines, characterized by its large size, complex structure, high mechanical performance requirements, and significant manufacturing challenges. For example, the GE90 engine fan disc has a maximum outer diameter of approximately 760mm, a four-spoke structure, and is manufactured using powder forging and inertial friction welding processes; the GEnx-1B engine fan disc is a three-spoke powder forging, then welded together using inertial friction welding. However, welded structures often have weaker weld microstructure and residual stress, therefore, engine fan discs with integral forging structures are considered to have better overall performance.

[0036] However, typical alloys used for forging in aero-engines, such as TC4 alloy, have a theoretical hardenability of only 75mm. Forgings using solution and age hardening treatments must consider the limitations of structural cross-sectional dimensions. Large-size engine fan discs, due to their large thickness and poor hardenability, are prone to failing to meet high-temperature mechanical properties in the core. Wide-body passenger aircraft engine fan discs are even larger, with some designs using bar stock sizes reaching [missing information]. Controlling the microstructure and properties of fan disc forgings, as well as the hardenability of heat treatment, is difficult. The influence mechanism of the size effect on the static properties of aero-engine fan disc forgings is complex and influenced by various factors, such as forging deformation, heat treatment, and orientation relationships, making process and dimensional design very challenging.

[0037] To address the aforementioned issues, embodiments of the present invention provide a method for controlling the dimensions of large titanium alloy forgings. By establishing dimensional control rules for large aero-engine transmission components, this method provides support for precise forging design, forging process formulation, alloy selection, and strength analysis. When mass-producing forgings or adjusting process windows, the performance of the forgings can be predicted, and the forging machining allowance can be reasonably set, saving time and economic costs.

[0038] The method includes the following steps:

[0039] Step a): Provide a titanium alloy forging blank. The titanium alloy forging blank is forged from a cast titanium alloy bar through a process of blank forging and die forging. The titanium alloy forging blank is then subjected to appropriate heat treatment according to the forging process requirements of the titanium alloy part. In a preferred embodiment, the titanium alloy forging blank is a blank for an engine rotor component, such as an engine fan disc.

[0040] In one embodiment, the titanium alloy used is TC4 alloy, and its processing is as follows: heating the titanium alloy bar to 50°C below the phase transformation point, controlling the final forging temperature to be no less than 750°C, the deformation amount to be 20%-45%, and air cooling to obtain a blank; heating the blank to 50°C below the phase transformation point, controlling the final forging temperature to be no less than 750°C, the deformation amount to be 30%-70%, and air cooling to obtain a titanium alloy forging blank with the final shape.

[0041] Step b): Multiple test specimens are cut from the titanium alloy forging blank, with the specimens cut at a gradient depth from the surface of the titanium alloy forging blank. In a preferred embodiment, the specimens should be cut along the radial, axial, and tangential directions of the titanium alloy forging blank to reflect the anisotropy of the material in the forging. The specimen cutting locations should also cover typical areas of the titanium alloy forging blank. In a preferred embodiment, for an engine fan disc, the specimen cutting locations should include the web, blade, mounting plate, and tenon area of ​​the engine fan disc.

[0042] Step c): Perform mechanical property testing and microstructure analysis on the samples respectively. In a preferred embodiment, the mechanical property testing includes room temperature mechanical property testing and high-temperature mechanical property testing, with the temperature for high-temperature mechanical property testing depending on the service conditions of the titanium alloy forging. Microstructure analysis can include microstructure analysis under a metallographic microscope, scanning electron microscope, or transmission electron microscope. Depending on the design requirements, the objects of microstructure analysis can include the grain size of the titanium alloy structure, the volume fraction of different phases, and the texture characteristics of the titanium alloy structure.

[0043] Step d): Fit the mechanical property test structure and microstructure analysis results with the sample depth data to obtain the fitting functions for mechanical properties-depth and microstructure parameters-depth. In some embodiments, the fitting functions are linear functions.

[0044] Step e): Based on the mechanical property design requirements and microstructure design requirements of titanium alloy forgings, and combined with the fitting function obtained in step d), calculate the allowable machining allowance of the titanium alloy forging blank when the performance of the center of the titanium alloy forging blank meets the design requirements.

[0045] In a preferred embodiment, step f) is further included: when the calculation results show that the performance of the center of the titanium alloy forging blank meets the design requirements, and the machining allowance reserved for the titanium alloy forging blank is less than the minimum allowable value or even negative, a slot is added in the corresponding area according to the calculation results to reduce the thickness of the titanium alloy forging blank in that area, thereby achieving configuration optimization of the titanium alloy forging blank.

[0046] In a preferred embodiment, the dimensional control analysis of the engine fan disk of a wide-body passenger aircraft is performed as follows:

[0047] Ti-6Al-4V titanium alloy (TC4 alloy) bars were used as raw materials. The composition of the titanium alloy bars was Al 6.4%, V 4.2%, Fe 0.25%, C 0.01%, O 0.20%, H 40ppm, and Ti as the balance; the dimensions were as follows.

[0048] Billet preparation. Heat the bar stock to 50°C below the phase transformation point, control the final forging temperature to be not less than 750°C, air cool after forging, with a deformation of 20%-45%. The bar stock is forged into a blank of 750±5mm.

[0049] Die forging. The billet is heated to 50°C below its phase transformation point, and the final forging temperature is controlled to be no less than 750°C. After forging, it is air-cooled, with a deformation of 30%-70%, forging the billet into a structure such as... Figure 1 The engine fan disc blank shown.

[0050] The engine fan disc blank undergoes homogenization heat treatment at a temperature of (T). β -45)~(T β -35)±10℃, hold for 160±5min, water cooling; anneal at 700±6℃ for 220±5min, air cooling.

[0051] Next, sampling and testing will be conducted. Sampling locations are as follows: Figure 2 As shown, the sampling area for Sample 1 is a test ring, not part of the engine fan disk blank. The samples taken include microstructure metallographic samples and tensile property test samples. The tensile property test samples were taken from tangential, axial, and radial samples of the engine fan disk blank, and from representative areas of different thicknesses, including the web, blade, mounting edge, and tenon. The room temperature mechanical property test results for some samples are shown in Table 1.

[0052]

[0053]

[0054] Table 1. Results of room temperature mechanical properties test

[0055] The results of room temperature mechanical property tests and the results of high temperature mechanical property tests at 300℃ are as follows: Figure 3a and Figure 3b As shown.

[0056] Linear fitting was performed on the room temperature mechanical properties, such as Figure 5As shown, y = -2x + 1060, where y is the tensile strength (MPa) and x is the depth (mm). According to the fitting results, within a depth of 35mm from the surface of the blank, the strength decreases with increasing depth. Within a depth range of 35mm-100mm, the strength is essentially at its minimum. Therefore, for this blank sample, within a depth of 35mm, the strength is strongly correlated with depth, and is greatly affected by the heat treatment performance of the large component.

[0057] The titanium alloy fan disc exhibits strict control over the primary α-phase content. The statistical relationship between the proportion and depth of the primary α-phase in different samples is as follows: Figure 4 As shown in the figure, the fitting calculation shows that within a depth of 30 mm, the content of primary α phase is linearly positively correlated with the depth, and the content of primary α phase is higher at deeper depths.

[0058] Considering the complex shape and large thickness of the fan disc, as well as the coupled influence of forging and heat treatment processes on static strength performance, the upper limit of the cross-sectional thickness for manufacturing large-size forgings for TC4 aerospace applications is determined to be 70mm. When the cross-sectional thickness reaches 70mm-200mm, the mechanical properties of the forging are relatively low. When the thickness is too large, the blank configuration can be optimized by slotting the thicker structures such as the web.

[0059] Based on the above results, a thick TC4 forging is to be forged, with a maximum effective thickness of 100mm (50mm on one side). According to the fitting results, when the required center strength of the forging is not less than 944MPa, the allowable machining allowance on one side of the forging blank is 8mm; while if the required tensile strength of each region of the forging is not less than 950MPa, the allowable machining allowance on one side is 5mm.

[0060] In another embodiment, a narrow-body passenger aircraft fan disc is forged, and dimensional control analysis is performed.

[0061] The blanking for tray A uses Ti-6Al-4V titanium alloy (TC4 alloy) bars. The composition of the titanium alloy bars is Al 6.25%, V 4.0%, Fe 0.21%, C 0.007%, O 0.192%, H 20ppm, with Ti as the balance; the dimensions are as follows. The blanking for tray B uses Ti-6Al-4V titanium alloy (TC4 alloy) bars as raw materials. The composition of the titanium alloy bars is Al 6.42%, V 4.31%, Fe 0.19%, C 0.005%, O 0.20%, H 41ppm, with Ti as the balance; the dimensions are as follows.

[0062] The billet preparation process is as follows: the forging heating temperature is 50℃ below the phase transformation point, the final forging temperature is greater than 800℃, and air cooling is performed after forging. The deformation amount is ~40%. Bar stock forging

[0063] The rough forging process is as follows: rough forging with two heat treatments, the forging heating temperature is 50°C below the phase transformation point, the final forging temperature is greater than 800°C, and air cooling is performed after forging. Bar stock forging

[0064] The die forging process is as follows: two forging cycles, with the forging heating temperature being 40℃~50℃ below the phase transformation point, and the final forging temperature being greater than 800℃. After forging, the blank is air-cooled to forge the billet into a blank with the final shape.

[0065] The blank is subjected to homogenization heat treatment at a temperature of (T). β -40±10℃, hold for 60±6 min, then water cool; then hold at 700±6℃ for 120±12 min, then air cool to complete annealing.

[0066] Twelve tangential specimens, five radial specimens, and two axial specimens were cut from different locations on the fan disc forging blank for high-temperature mechanical property testing at room temperature and 300℃. The results of the high-temperature tensile test at 300℃ and their relationship with sampling depth are shown below. Figure 6 As shown. Fitting was performed on samples with a depth less than 40 mm, and the results are as follows. Figure 7 As shown, y1 = -1.74x + 736, y2 = -1.84x + 624; where y1 is the high-temperature tensile strength (MPa), y2 is the high-temperature yield strength (MPa), and x is the depth (mm). It can be seen that within a depth of less than 40mm, the mechanical properties are linearly negatively correlated with the depth; within a depth range of 40mm-100mm, the high-temperature strength remains relatively stable near the minimum strength. This indicates that within a blank depth of 40mm, the high-temperature strength is strongly correlated with the depth, and is significantly affected by the heat treatment performance of large parts.

[0067] Considering the complex shape and large size of the fan disc, and the coupled influence of forging and heat treatment processes on its high-temperature static strength, the optimal cross-sectional thickness was determined to be 80mm based on design performance requirements. When the cross-sectional thickness is in the range of 80mm-200mm, the strength is relatively low. This can be addressed by slotting in thicker structures such as the web to optimize the blank configuration and improve the forging performance.

[0068] The purpose of the above embodiments is to provide a more detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention, and not to limit the present invention. Within the scope of the present invention, optimization or equivalent substitution of the method steps involved, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. A method of dimensional control of large titanium alloy forgings, characterized by, Includes the following steps: Step a): Provide a titanium alloy forging blank, and perform heat treatment on the titanium alloy forging blank according to the manufacturing process of titanium alloy forging; Step b): Cut multiple samples from the titanium alloy forging blank, wherein the cutting position of the samples is at a depth gradient from the surface of the titanium alloy forging blank; Step c): Perform mechanical property tests and / or microstructure analysis on the samples respectively; Step d): Based on the mechanical property test results, perform fitting calculations to determine the relationship between the strength and depth of the titanium alloy; And / or, The relationship between the microstructure parameters and depth of titanium alloy was calculated by fitting the microstructure analysis results. Step e): Based on the calculation results of step d) and the mechanical properties and / or microstructure design requirements of the titanium alloy forging, calculate the allowable machining allowance for the titanium alloy forging blank.

2. The method of size control of large titanium alloy forgings according to claim 1, characterized by, It also includes step f): when the machining allowance calculated in step e) is less than the lower limit allowed by the forging process of the titanium alloy forging blank, the thickness of the titanium alloy forging blank is reduced by adding slots to optimize the configuration of the titanium alloy forging blank.

3. The method of claim 1, wherein The mechanical property tests in step c) include room temperature tensile tests and high temperature tensile tests.

4. The method of size control of heavy titanium alloy forgings according to claim 1 or 2 or 3, characterized by, The titanium alloy is TC4 alloy.

5. The method of size control of heavy titanium alloy forgings according to claim 4, characterized by, The manufacturing method of the titanium alloy forging blank is as follows: providing a titanium alloy bar, heating the titanium alloy bar to 50°C below the phase transformation point, controlling the final forging temperature to be not lower than 750°C, the deformation amount to be 20%-45%, and air cooling to obtain a blank; heating the blank to 50°C below the phase transformation point, controlling the final forging temperature to be not lower than 750°C, the deformation amount to be 30%-70%, and air cooling to obtain the titanium alloy forging blank with the final shape.

6. The method of size control of large titanium alloy forgings according to claim 4, characterized by, The microstructure analysis results in step d) are the content of primary α phase.

7. The method of size control of heavy titanium alloy forgings according to claim 1 or 2 or 3, characterized by, The titanium alloy forging is configured as an aircraft engine fan disc.

8. The size control method of large titanium alloy forgings according to claim 7, characterized by, In step b), the sample has an orientation, which includes radial, axial and chordal orientations along the aircraft engine fan disk.

9. The method of claim 7, wherein In step b), the sampling locations of the sample include the web, blade, mounting edge, and tenon groove area of ​​the aero-engine fan disk.

10. The method of size control of heavy titanium alloy forgings according to claim 1 or 2 or 3, characterized by, The fitting calculation in step d) uses linear fitting.

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