A rolling forming method for large-size large-torsion-angle titanium alloy rectifier blades

Abstract

The application discloses a rolling forming machining method for large-size and large-torsion-angle titanium alloy rectifier blades, and the part surface precision is ensured by means of controlling the rolling feed amount, adjusting the relative position of the part and the die during machining, adding an annealing procedure and optimizing the die profile; the part cracking risk is reduced by milling off part of the thickness on both sides of the blank and milling off two inclined angles on the end face as a crack stop; the rolling model surface is comprehensively optimized by supplementing the cross section data and adjusting the cross section data points according to the surface data during the trial rolling, the smooth connection of each cross section is ensured, the generation of the fold is effectively reduced, and the influence of the unqualified die on the rolling is avoided.

Description

Technical Field

[0001] This invention relates to the field of aero-engine processing technology, and more specifically, to a rolling forming method for large-size, large-torsion-angle titanium alloy rectifier blades. Background Technology

[0002] Aero-engine slewing blades are characterized by their thin profile, variable cross-section, and high forming precision requirements. There are currently three main processing technologies for aero-engine slewing blades:

[0003] 1. CNC Milling. This technology uses flat blanks as raw materials. The blades are modeled in 3D using UG (User-Generated Tooling). The parts are fixed to specific fixtures using specialized tools. When milling blades, two clamping operations are necessary to ensure that both the blade head and blade back are fully machined. Furthermore, the machining planes of the blades must be perfectly aligned during the two clamping operations. CNC milling can machine the blade profile in one operation, requiring only minor polishing of the milling cutter marks afterward. However, this method has a long processing cycle, involves a large number of milling operations from blank to blade shape, resulting in significant material waste and prolonged equipment downtime.

[0004] 2. Forging + CNC Milling. This forming process uses bar stock as a blank, which is then forged into a longer length using a pre-forging die. Simultaneously, the blade tenon size is widened. After shot peening, final die forging is performed. Excess dimensions are removed through trimming and grinding. Due to the poor precision of die forging, subsequent surface correction is required based on the part's profile. The final forging has a larger allowance than the final blade dimensions, therefore, CNC milling is still necessary to remove this allowance.

[0005] 3. Blade Rolling Forming Process. This process uses sheet metal as the initial blank and gradually shapes the blade through multiple rolling operations. To prevent defects such as cracks and creases caused by excessive deformation, the feed rate during each rolling pass must be strictly controlled. The final rolled blade profile allowance can be controlled within 0.5mm, or even zero. Subsequent milling processes are unnecessary; only surface polishing is required. However, rolled blades are generally used for small parts of 30-50mm. Larger blades are prone to surface defects such as bulging and arching, and larger twist angles can easily lead to crease defects.

[0006] The rectifier blade of a certain aero-engine is made of titanium alloy TC1. Titanium alloy has a large springback, making it difficult to control the surface accuracy. In addition, the blade size is greater than 180mm and the maximum twist angle of the cross section is 35°. Based on the above, if it is machined by CNC milling, the part size is large, the rigidity is poor during machining, and the surface accuracy of the part is difficult to guarantee. If it is machined by forging + CNC milling, the forging blank has a large allowance, and the subsequent CNC milling efficiency of the part is low. If the blade is machined by rolling, it is difficult to meet the surface requirements.

[0007] CN106001338A discloses a method for rolling high-temperature alloy blades without margin, including the following steps: a) a method for precision rolling and precision shaping of blades without margin, comprehensively considering the forming performance of the blade blank material, die design requirements, blank design requirements, and blade process rolling path, and formulating an improved die scheme and a blade process rolling path scheme; b) the rolled part of the blade process rolling path scheme is a blank without margin, adopting a half-cutting process that only removes the flash at the leading and trailing edges of the blade blank, and adding a process to ensure the blade's quality after the half-cutting process. The precision forming process ensures the surface conforms to the design requirements; c. Using an improved mold and following an optimized blade rolling process, the blade is processed to obtain a shaped blade; This application proposes a blade rolling method for high-temperature alloys. However, since the springback of titanium alloy TC1 is greater than that of high-temperature alloys, its surface accuracy is more difficult to control. Moreover, for the same amount of deformation, the rolling resistance of titanium alloy is greater than that of high-temperature alloys. If this method is used, the stress is difficult to eliminate. In addition, this blade rolling method is only suitable for rolling smaller blades and cannot guarantee the rolling processing of large blades. Summary of the Invention

[0008] To address the aforementioned processing problems of large-size, large-twist-angle titanium alloy rectifier blades, this invention provides a rolling forming method for large-size, large-twist-angle titanium alloy rectifier blades.

[0009] The technical solution of this invention is:

[0010] A method for rolling and forming large-size, large-twist-angle titanium alloy rectifier blades includes the following steps:

[0011] S1. Blank material treatment: Cut the blank material along the direction of the metal fiber of the titanium alloy plate, and mill inclined surfaces on both sides of the blank material in the direction of the fiber. The angle between the inclined surface and the upper surface of the workpiece is 30~45°. The thickness retained at the bottom of the inclined surface is 1 / 4~1 / 3 of the original total thickness of the workpiece. Two anti-crack openings are milled on the end face of the blank material.

[0012] S2. Pickling of raw materials;

[0013] S3. Annealing is performed after pickling;

[0014] S4. Adjust the blank to the center of the rolling die and perform multiple rolling processes. After each rolling process, annealing is required to eliminate the stress of the part. When the rolling process reaches a certain intermediate process, the part should be trial rolled. After the trial rolling, the part profile is measured to confirm the bulging and arching of the part profile. Adjust the relative position of the part and the die according to the measurement results to eliminate the bulging or arching.

[0015] S5. After the rolling process of the part is completed, the end material and excess flash are removed.

[0016] S6. Perform hot forming on the parts: First, put the parts into the mold and heat them. After heating, press them into shape. The hot forming parameters are: 680~700℃, hold for 50~60min, press them into shape after taking them out of the oven, and the pressure is 8-10MPa.

[0017] S7. Polish the parts;

[0018] S8. Inspect the parts.

[0019] Furthermore, the pickling process specifications in step S2 are as follows: HNO3 (ρ=1.42): 2L, HF (ρ=1.42): 1L, H2O: 7L, temperature: room temperature, time: 0.5~1min; followed by rinsing with running cold water for 1min~3min.

[0020] Furthermore, in step S4, there are 16 rolling processes, and the feed rates for each rolling process are 1, 1.2, 0.9, 0.9, 0.9, 0.9, 0.5, 0.5, 0.5, 0.5, 0.5, 0.3, 0.3, 0.3, 0.2, and 0 mm, respectively.

[0021] Furthermore, during the sixth rolling process, the parts are trial-rolled.

[0022] Furthermore, the annealing process parameters in steps S3 and S4 are as follows: heating rate 8~10℃ / min, holding temperature 780±10℃, holding time 2.5~3h, and annealing method is vacuum annealing.

[0023] Furthermore, in step S4, the die needs to be trial-rolled before use. Only after the trial rolling of the part passes can formal rolling proceed. The trial rolling step includes:

[0024] S401. Perform a trial molding of the mold and measure the surface data of the trial-rolled part. If the surface data is qualified, directly perform blue light scanning on the mold to obtain the three-dimensional model of the mold. If the surface data is not qualified, rework the mold and perform another trial molding until the surface data is qualified, and then perform blue light scanning to obtain the three-dimensional model of the mold.

[0025] S402. Use the 3D model obtained in step S401 to repair the remaining molds on site. After repair, perform trial molding. Then, fine-tune the surface of the rolling mold according to the surface data of the trial rolled part to finally obtain a qualified mold.

[0026] Further, in step S401, the surface data is adjusted using UG. For the problem of unevenness in a single cross section, the data of abrupt change points is adjusted to make the entire cross section smooth. For the problem of unevenness in the surface, a cross section is added between the two original uneven cross sections to make the two original cross sections smoothly connected. The mold is then repaired using the adjusted surface data model.

[0027] Furthermore, step S5 also includes machining holes on the part.

[0028] Furthermore, the inspection items in step S8 include the measurement of the surface dimensions of the part and visual inspection.

[0029] Furthermore, in step S6, the parts are naturally cooled to room temperature after the hot-forming operation is completed.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention ensures the surface accuracy of parts by controlling the rolling feed rate, adjusting the relative position of the parts and the die during processing, adding an annealing process, and optimizing the die surface. It reduces the risk of cracking by milling off a portion of the thickness on both sides of the blank and milling two bevels on the end face to prevent cracking. Furthermore, during trial rolling, it comprehensively optimizes the rolling die surface by supplementing cross-sectional data based on the surface data and adjusting the data points of each cross-section, ensuring smooth connection of all cross-sections, effectively reducing the generation of creases, and avoiding the impact of substandard dies on rolling.

[0032] The rolling process of this invention provides stable machining for forming large-size, large-twist-angle titanium alloy rectifier blades. Compared to CNC milling, this process achieves near-net-shape forming with less raw material waste. The rolling mill is also cheaper than a precision milling machine, and it can completely preserve the metal fibers of the part, resulting in significant advantages in part performance and machining costs. Compared to forging + CNC milling, the rolling process produces parts with high surface accuracy and small allowance, which can be controlled to 0.3mm, only 6% of the allowance of forging blanks. The rectifier blades produced by this process meet design requirements and have been successfully applied in the machining of large-size, large-twist-angle titanium alloy rectifier blades for aero-engines. Attached Figure Description

[0033] Figure 1 This is a flowchart of a rolling process for a large-size, large-torsion-angle titanium alloy rectifier blade according to the present invention.

[0034] Figure 2 This is a schematic diagram of the blade component of the present invention;

[0035] Figure 3 This is a schematic diagram of the blank shape in step S2 of Example 1;

[0036] Figure 4 This is a schematic diagram of the surface data model in Example 3. Detailed Implementation

[0037] To clearly illustrate the technical features of the present invention, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can also be implemented in other ways different from those described herein; therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below. Furthermore, in the description of the invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] Example 1

[0039] Please see Figures 1 to 3 This embodiment provides a method for rolling and forming a large-size, large-torsion-angle titanium alloy rectifier blade. The material of this part is TC1. A schematic diagram of the part is shown below. Figure 2 The blade is 181.89 mm long, while typical blades are 20-50 mm long. This part is 3-9 times the length of a typical blade, making it difficult to manufacture. The manufacturing method includes the following steps:

[0040] S1. Blank material processing: Cut the 1000×2000mm titanium alloy sheet along the metal fiber direction. The blank size is 123×78mm. Mill bevels on both sides of the blank in the fiber direction. The bevels are at an angle of 45° with the upper surface of the workpiece. The thickness at the bottom of the bevel is 1 / 3 of the original total thickness of the workpiece. Mill two anti-crack openings on the end face of the blank.

[0041] To preserve the metal fibers of the part completely, this step involves cutting the blank along the direction of the metal fibers during the blanking stage; simultaneously, to ensure the surface filling effect during rolling, such as... Figure 3 As shown, the blank shape is designed to be similar to the finished part. Tenons, 45° angles and crack-stopping openings are machined on the blank. Since the blade is thick in the middle and thin on both sides, part of the thickness is milled off on both sides of the blank, and two bevels are milled on the end face to stop cracking and reduce the risk of cracking of the part.

[0042] S2. Perform pickling on the raw material.

[0043] Since the blanks are sheet metal and the top and bottom surfaces are not machined, the surfaces are prone to oxidation and oil contamination, which can easily cause surface cracks during rolling. Therefore, the parts need to be pickled before rolling. The pickling process specifications are as follows: HNO3 (ρ=1.42): 2L, HF (ρ=1.42): 1L, H2O: 7L, temperature: room temperature, time: 0.5~1min; then rinse with running cold water for 1min~3min.

[0044] S3. After pickling, annealing is performed. Annealing can improve the internal structure of titanium alloy billets, eliminate internal stress, and prevent cracking during rolling.

[0045] S4. Adjust the blank to the center of the rolling die and perform 16 rolling processes. After each rolling process, annealing is required to relieve stress on the parts. The process is as follows: Rolling 1 → Annealing → Rolling 2 → Annealing → Rolling 3 → Annealing → Rolling 4 → Annealing → Rolling 5 → Annealing → Rolling 6 → Annealing → Rolling 7 → Annealing → Rolling 8 → Annealing → Rolling 9 → Annealing → Rolling 10 → Annealing → Rolling 11 → Annealing → Rolling 12 → Annealing → Rolling 13 → Annealing → Rolling 14 → Annealing → Rolling 15 → Annealing → Final Rolling. When the rolling process reaches the 6th process, the parts should be trial rolled. After the trial rolling, the part profile should be measured to confirm the bulging and arching of the part profile. Based on the measurement results, adjust the relative position of the parts and the die to eliminate bulging or arching, so as to avoid being unable to adjust after the subsequent rolling process. The feed rate for the rectifier blade rolling is shown in Table 1.

[0046] Table 1. Rolling feed rate of rectifier blades

[0047]

[0048] S5. After the rolling process of the part is completed, in addition to the forming of the shape, the part will produce flash. The end material and excess flash should be removed, and the holes on the part should be machined at the same time.

[0049] S6. Perform hot forming on the parts: First, put the parts into the mold and heat them. After heating, press them into shape. The hot forming parameters are: 680℃, hold for 50 minutes, press them into shape after taking them out of the oven, and the pressure is 8MPa. After the hot forming is completed, let them cool naturally to room temperature. This step can further ensure the surface accuracy of the parts.

[0050] S7. Polish the parts.

[0051] S8. Inspect the parts.

[0052] The rolling allowance of the blades produced in this embodiment can be controlled at 0.3mm, which is only 6% of the allowance of the forging blank; at the same time, the rectifier blades produced by this process can meet the design requirements and have been successfully applied to the processing of large-size, large-twist-angle titanium alloy rectifier blades for aero-engines.

[0053] Example 2

[0054] Please see Figures 1 to 3 This embodiment provides a method for rolling and forming a large-size, large-torsion-angle titanium alloy rectifier blade. The material of this part is TC1. A schematic diagram of the part is shown below. Figure 2 The blade is 181.89 mm long, while typical blades are 20-50 mm long. This part is 3-9 times the length of a typical blade, making it difficult to manufacture. The manufacturing method includes the following steps:

[0055] S1. Raw material processing: Cut the 1000×2000mm titanium alloy sheet along the metal fiber direction. The blank size is 123×78mm. Mill bevels on both sides of the raw material along the fiber direction. The bevels are at an angle of 30° with the upper surface of the workpiece. The thickness at the bottom of the bevel is 1 / 4 of the original total thickness of the workpiece. Mill two anti-crack openings on the end face of the raw material.

[0056] To preserve the metal fibers of the part completely, this step involves cutting the blank along the direction of the metal fibers during the blanking stage; simultaneously, to ensure proper surface filling during rolling, please refer to [the relevant documentation / reference]. Figure 3 The blank shape is designed to be similar to the finished part. Tenons, angles and crack-stopping openings are machined on the blank. Since the blade is thick in the middle and thin on both sides, part of the thickness is milled off on both sides of the blank, and two bevels are milled on the end face to stop cracking and reduce the risk of cracking of the part.

[0057] S2. Perform pickling on the raw material.

[0058] Since the blanks are sheet metal and the top and bottom surfaces are not machined, the surfaces are prone to oxidation and oil contamination, which can easily cause surface cracks during rolling. Therefore, the parts need to be pickled before rolling. The pickling process specifications are as follows: HNO3 (ρ=1.42): 2L, HF (ρ=1.42): 1L, H2O: 7L, temperature: room temperature, time: 0.5~1min; then rinse with running cold water for 1min~3min.

[0059] S3. After pickling, annealing is performed. Annealing can improve the internal structure of titanium alloy billets, eliminate internal stress, and prevent cracking during rolling.

[0060] S4. Adjust the blank to the center of the rolling die and perform 16 rolling processes. After each rolling process, annealing is required to relieve stress on the parts. The process is as follows: Rolling 1 → Annealing → Rolling 2 → Annealing → Rolling 3 → Annealing → Rolling 4 → Annealing → Rolling 5 → Annealing → Rolling 6 → Annealing → Rolling 7 → Annealing → Rolling 8 → Annealing → Rolling 9 → Annealing → Rolling 10 → Annealing → Rolling 11 → Annealing → Rolling 12 → Annealing → Rolling 13 → Annealing → Rolling 14 → Annealing → Rolling 15 → Annealing → Final Rolling. When the rolling process reaches the 6th process, the parts should be trial rolled. After the trial rolling, the part profile should be measured to confirm the bulging and arching of the part profile. Based on the measurement results, adjust the relative position of the parts and the die to eliminate bulging or arching, so as to avoid being unable to adjust after the subsequent rolling process. The feed rate for the rectifier blade rolling is shown in Table 1.

[0061] Table 1. Rolling feed rate of rectifier blades

[0062]

[0063] Furthermore, in step S4, the die needs to be trial-rolled before use. Only after the trial rolling of the part passes can formal rolling proceed. The trial rolling step includes:

[0064] S401. Perform a trial molding of the mold and measure the surface data of the trial-rolled part. If the surface data is qualified, directly perform blue light scanning on the mold to obtain the three-dimensional model of the mold. If the surface data is not qualified, rework the mold and perform another trial molding until the surface data is qualified, and then perform blue light scanning to obtain the three-dimensional model of the mold.

[0065] S402. Use the 3D model obtained in step S401 to repair the remaining molds on site. After repair, perform trial molding. Then, fine-tune the surface of the rolling mold according to the surface data of the trial rolled part to finally obtain a qualified mold.

[0066] Conventional trial molding methods adjust the trial molding data for a single mold. First, a trial rolling is performed on the mold. After the trial rolling is completed, the mold surface is measured on a profile measuring tool, and the unqualified data of each section is recorded. The model surface is adjusted and compensated using UG. After the model is adjusted, the mold is repaired based on this model. After the physical repair is completed, the trial rolling is performed again until the mold passes the trial rolling. When there are multiple sets of molds on site, multiple rolling and multiple measurements and adjustments are required, resulting in a long trial molding cycle. The trial molding method in this embodiment optimizes this method by establishing a three-dimensional model of the standard mold to repair the other molds, which greatly shortens the trial molding cycle.

[0067] S5. After the rolling process of the part is completed, in addition to the forming of the shape, the part will produce flash. The end material and excess flash should be removed, and the holes on the part should be machined at the same time.

[0068] S6. Perform hot forming on the parts: First, put the parts into the mold and heat them. After heating, press them into shape. The hot forming parameters are: 700℃, hold for 60 minutes, press them into shape after taking them out of the oven, and the pressure is 10MPa. After the hot forming is completed, let them cool naturally to room temperature. This step can further ensure the surface accuracy of the parts.

[0069] S7. Polish the parts.

[0070] S8. Inspect the parts.

[0071] Example 3

[0072] This embodiment differs from Embodiment 2 in that it provides a rework method for the mold in step S401 of Embodiment 2: The surface data is adjusted using UG; for issues with unevenness in a single cross-section, the data at abrupt change points is adjusted to make the entire cross-section smooth; for further issues with unevenness, a supplementary cross-section is added between the two original uneven cross-sections to ensure a smooth connection between them. The adjusted surface data model is as follows: Figure 4 As shown, the mold is repaired using the adjusted surface data model.

Claims

1. A large-size large-torque-angle titanium alloy rectifier blade rolling forming processing method, characterized in that, Includes the following steps: S1. Blank material treatment: Cut the blank material along the metal fiber direction of TC1 titanium alloy sheet, and mill inclined surfaces on both sides of the blank material in the fiber direction. The angle between the inclined surface and the upper surface of the workpiece is 30~45°. The thickness retained at the bottom of the inclined surface is 1 / 4~1 / 3 of the original total thickness of the workpiece. Two anti-crack openings are milled on the end face of the blank material. S2. Pickling of raw materials; S3. Annealing is performed after pickling; S4. Adjust the blank to the center of the rolling die and perform 16 rolling operations. The feed amount for each rolling operation is 1, 1.2, 0.9, 0.9, 0.9, 0.9, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.3, 0.3, 0.3, 0.2, and 0 mm, respectively. After each rolling operation, annealing is required to relieve the stress on the parts. When the rolling operation reaches a certain intermediate step, the parts should be trial rolled. After the trial rolling, the surface of the parts should be measured to confirm the bulging and arching of the parts. Based on the measurement results, the relative position of the parts and the die should be adjusted to eliminate bulging or arching. Before using the mold, a trial rolling test is required. Only after the trial rolling of the parts passes can formal rolling proceed. The trial rolling steps include: S401. Perform a trial molding of the mold and measure the surface data of the trial-rolled part. If the surface data is qualified, directly perform blue light scanning on the mold to obtain the 3D model of the mold. If the surface data is unqualified, rework the mold and perform another trial molding until the surface data is qualified, then perform blue light scanning to obtain the 3D model of the mold. During rework, adjust the mold surface data using UG. For the problem of unevenness of a single section, adjust the data of the abrupt change point to make the entire section smooth. For the problem of unevenness of the surface, add a section between the two original uneven sections to make the two original sections smoothly connected. Use the adjusted surface data model to rework the mold. S402. Use the 3D model obtained in step S401 to repair the remaining molds on site. After repair, perform a trial run. Then, fine-tune the surface of the rolling mold according to the surface data of the trial rolled part to finally obtain a qualified mold. S5. After the rolling process of the part is completed, the end material and excess flash are removed. S6. Perform hot forming on the parts: First, put the parts into the mold and heat them. After heating, press them into shape. The hot forming parameters are: 680~700℃, hold for 50~60min, press them into shape after taking them out of the oven, and the pressure is 8-10MPa. S7. Polish the parts; S8. Inspect the parts.

2. The rolling forming method for large-size, large-twist-angle titanium alloy rectifier blades according to claim 1, characterized in that: During the sixth rolling process, the part is test rolled.

3. The rolling forming method for large-size, large-twist-angle titanium alloy rectifier blades according to claim 1, characterized in that: The annealing process parameters in steps S3 and S4 are: heating rate 8~10℃ / min, holding temperature 780±10℃, holding time 2.5~3h, and annealing method is vacuum annealing.

4. The rolling forming method for large-size, large-twist-angle titanium alloy rectifier blades according to claim 1, characterized in that: Step S5 also includes machining holes on the part.

5. The rolling forming method for large-size, large-twist-angle titanium alloy rectifier blades according to claim 1, characterized in that: The inspection items in step S8 include the measurement of the surface dimensions of the part and the visual inspection.

6. The rolling forming method for large-size, large-twist-angle titanium alloy rectifier blades according to claim 1, characterized in that: In step S6, the parts are allowed to cool naturally to room temperature after the hot-forming process is completed.

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