Aerospace wear resistant transmission gear near net shape manufacturing method

Abstract

The application relates to the technical field of aerospace part manufacturing, in particular to a near-net forming manufacturing method for a wear-resistant transmission gear for aerospace, which comprises the following steps: S1, top forging: first, longitudinally placing a blank to perform top forging, and then turning over the blank to perform top forging again; S2, die forging; S3, correction; and S4, annealing. The near-net forming manufacturing method can effectively reduce raw material consumption and mechanical processing cost, and the size allowance of the transmission gear obtained through processing is less than or equal to 1 mm, and the mechanical performance is stable.

Description

Technical Field

[0001] This invention relates to the field of aerospace component manufacturing technology, specifically to a near-net-shape manufacturing method for wear-resistant transmission gears used in aerospace applications. Background Technology

[0002] Transmission gears are widely used in mechanical devices across various industries, such as automotive, aerospace, machinery manufacturing, metallurgy, and mining. In the automotive industry, transmission gears are used in components such as engines, transmissions, and differentials to match different speeds and torques, providing power output. In the aerospace field, transmission gears are used in critical parts of aircraft, such as landing gear and engine transmission systems, ensuring the safe and stable operation of aircraft.

[0003] Powder metallurgy high-speed steel is currently widely used in the field of aerospace transmission parts due to its excellent wear resistance. However, due to the limitations of its forming process, most parts are directly made from bar stock. The raw material consumption, production cost, and time and equipment consumption during the machining process are huge. Therefore, this near-net-shape forming manufacturing method can effectively reduce raw material consumption and reduce machining costs. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a near-net-shape manufacturing method for wear-resistant transmission gears used in aerospace applications.

[0005] A near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications includes the following steps:

[0006] S1, Upsetting:

[0007] The billet is heated to 1110-1130℃ as the initial forging temperature. After holding at this temperature for 20-80 minutes, the billet is upsetting: first, the billet is placed longitudinally and upset to form the shape, and then the billet is turned around and upset to form the shape again. The impact energy of the two upsettings is 40-60%, the deformation of the two upsettings is 25-35%, and the final forging temperature is 900-1000℃. After upsetting is completed, the billet is cooled.

[0008] S2, Die Forging:

[0009] The billet obtained in step S1 is heated to 1110-1130℃ as the initial forging temperature. After holding at this temperature for 30-90 minutes, the billet is die-forged with an impact energy of 40-60%, a deformation of 25-35%, and a final forging temperature of 900-1000℃. After die forging, the billet is then cooled.

[0010] S3, Correction:

[0011] The billet obtained in step S2 is heated to 890-910℃ and held for 8-20 minutes. The billet is then corrected with an impact energy of 10-30%, a deformation of 0-1.5%, and a final forging temperature of 850-910℃. After the correction is completed, the billet is cooled.

[0012] S4, Annealing:

[0013] The blank obtained in step S3 is annealed to achieve near-net-shape forming.

[0014] Furthermore, before starting step S1, the two ends of the blank are rounded to R3, and then rough machined until the surface roughness of the two ends is ≤Ra3.2.

[0015] Explanation: Rounding the corners to R3 can prevent stress concentration at both ends of the billet due to right angles during upsetting. During upsetting, the billet is subjected to greater pressure. If the ends are right angles, stress will accumulate at the corners, which can easily lead to cracking of the billet. The reduced roughness makes the two end faces smoother and flatter, which can better match the mold during upsetting. Accurate positioning can ensure the positional accuracy of the billet in the mold.

[0016] Furthermore, after step S1 is completed and before step S2 begins, the billet is shot blasted and polished.

[0017] Instructions: Shot blasting and grinding are used to remove oil stains, dirt, and residual coatings from the surface of forgings; grinding is used to remove defects such as cracks, pinholes, and folds from the surface of forgings. Note that after grinding, the area where defects are removed should be smoothly connected to the surrounding area.

[0018] Furthermore, after step S2 and before step S3, the billet is trimmed, sandblasted, polished and shot blasted, and the residual burrs and overcutting amount of the billet after trimming are ≤0.3mm.

[0019] Note: Remove grease, dirt, and other contaminants from the surface of the forging. If oxide scale is difficult to remove, shot blasting should be performed. Cracks, delamination, and folds on the machined surface of the forging should be completely removed by grinding, but at least 1 / 3 of the nominal machining allowance should be left on the forging. On the non-machined surface of the forging, pits, notches, scratches, and scratches with a depth not exceeding the negative deviation of one side are allowed to exist. Cracks, inclusions, wrinkles, oxide scale, and other defects should be completely removed, and the minimum limit dimension of one side of the forging must be guaranteed.

[0020] Furthermore, after step S3 is completed and before step S4 begins, the billet is subjected to sandblasting, grinding, and sandblasting.

[0021] Note: On the non-machined surface of the forging, pits, notches, scratches, and scratches with a depth not exceeding the negative deviation of one side are allowed to exist. Cracks, inclusions, wrinkles, oxide scale and other defects should be completely removed. All defects must ensure the minimum limit dimension of one side of the forging.

[0022] Furthermore, in step S4, the annealing temperature is 860–880°C, and the holding time is 175–185 min.

[0023] Explanation: Under these annealing conditions, the grain structure of the gear can be refined; high temperature accelerates the diffusion rate of metal atoms, making it easier for new crystal nuclei to form, while inhibiting grain growth; annealing treatment can promote more complete diffusion of alloying elements, making the chemical composition and structure inside the gear more uniform, thereby improving the consistency and stability of gear performance.

[0024] Furthermore, in steps S1, S2 and S3, the transfer time for transferring the billet obtained in each step to the next step after the gray cooling is ≤10s.

[0025] Note: Limiting the transfer time prevents the billet from cooling down and oxidizing in the air during the transfer process, which would make processing difficult.

[0026] Furthermore, the shot blasting uses steel shot with a diameter of 0.6 mm.

[0027] Note: The billet has high hardness. Using the above-mentioned steel shot can quickly remove impurities such as rust, scale, and old coatings from the surface of the billet, resulting in high processing efficiency.

[0028] Furthermore, it also includes immersing the blank after S3 correction in a chemical milling fluid in stages for rotary chemical milling treatment;

[0029] The blank includes a ring-shaped toothed groove machining section and a shaft section connecting the two ends of the toothed groove machining section, wherein the required toothed groove depth on the sidewall of the toothed groove machining section is 'a'.

[0030] The rotary milling process is as follows:

[0031] First stage: First, take 1 / 3 to 1 / 2a of the diameter of the tooth groove as the maximum immersion depth, immerse the blank in the first chemical milling fluid, rotate the blank around its own axis at a speed of 20 to 25 r / min, the temperature is 60 to 70℃, and the chemical milling rate is 0.05 to 0.06 mm / min. The first chemical milling fluid includes hydrochloric acid and hydrofluoric acid in a mass ratio of 1:1 to 1.2.

[0032] Second stage: Using 2 / 3 to 3 / 4 of the diameter of the tooth groove as the maximum immersion depth, immerse the blank in the second chemical milling fluid, rotate the blank around its own axis at a speed of 10 to 15 r / min, at a temperature of 25 to 35℃, and at a chemical milling rate of 0.03 to 0.04 mm / min. The second chemical milling fluid includes hydrochloric acid, hydrofluoric acid, and ammonium chloride in a mass ratio of 1:1.2:1.8 to 2.4.

[0033] The third stage: Finally, the billet is completely immersed in the third chemical milling fluid. The billet is rotated around its own axis at a speed of 15-20 r / min, the temperature is 60-70℃, and the chemical milling rate is 0.01-0.02 mm / min. The third chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1:2.5-3.

[0034] The hydrochloric acid has a mass concentration of 8-10%, the hydrofluoric acid has a mass concentration of 2.5-4%, and the ammonium chloride has a mass concentration of 2-5%.

[0035] Explanation: Staged chemical milling, with varying temperatures and rates at each stage, helps improve the surface quality of gear tooth grooves. In the first stage, at higher temperatures and rates, a certain degree of microscopic roughness forms on the material surface. As the second stage progresses, the temperature and rate decrease, which smooths the corrosion process on the material surface. The ammonium chloride in the second chemical milling fluid can also form a protective film on the material surface or alter the morphology of reaction products, thereby reducing surface defects. In the third stage, the temperature is increased again, but the rate is decreased, allowing for a final fine finishing process that makes the tooth groove surface smoother.

[0036] Compared with existing near-net-shape manufacturing methods for transmission gears, the advantages of this invention are:

[0037] The near-net-shape manufacturing method designed in this application can effectively reduce raw material consumption, lower machining costs, and produce transmission gears with a dimensional allowance of ≤1mm and stable mechanical properties. Attached Figure Description

[0038] Figure 1 This is a top view of the transmission gear processed by the present invention;

[0039] Figure 2 This is a side view of the transmission gear processed by the present invention. Detailed Implementation

[0040] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0041] Example 1: A near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications, comprising the following steps:

[0042] S1, Upsetting:

[0043] First, round the two ends of the HOP10V billet to R3, then rough machine it to Φ40×160mm with an end face roughness of Ra3.2. Then heat the billet to 1120℃ as the initial forging temperature, hold it at that temperature for 50 minutes, and then perform upsetting: first, place the billet longitudinally and upset it, then turn the billet around and upset it again. The impact energy of the two upsettings is 50%, and the deformation of the two upsettings is 30% each. The final forging temperature is 950℃, and the deformation of the upsetting is 30%. After upsetting, perform gray cooling. Then, use φ0.6mm steel shot to shot blast and grind the billet for 10 minutes.

[0044] S2, Die Forging:

[0045] The billet obtained in step S1 is heated to 1120℃ as the initial forging temperature. After holding at this temperature for 60 minutes, the billet is die-forged with an impact energy of 50%, a deformation of 30%, and a final forging temperature of 950℃. After die forging, the billet is then cooled.

[0046] The billet is subjected to edge trimming, sandblasting, grinding and shot blasting. The residual burrs and overcutting amount of the billet after edge trimming are 0.3mm. The shot blasting uses φ0.6mm steel shot and takes 10 minutes.

[0047] S3, Correction:

[0048] The billet obtained in step S2 is heated to 900℃ and held for 14 minutes. The billet is then corrected with an impact energy of 20%, a final forging temperature of 880℃, and a deformation of 1%. After correction, the billet is cooled with ash. Then, the billet is sandblasted and polished.

[0049] In steps S1, S2 and S3, the transfer time for transferring the billet obtained in each step to the next step after the gray cooling is 10 seconds.

[0050] S4, Annealing:

[0051] The blank obtained in step S3 is annealed at a temperature of 870°C for 180 minutes, and near-net-shape forming is completed.

[0052] Example 2: The difference between this example and Example 1 is that the billet is heated to 1110℃ as the initial forging temperature, held for 20 minutes, and the final forging temperature is 900℃.

[0053] Example 3: The difference between this example and Example 1 is that the billet is heated to 1130°C as the initial forging temperature, held for 80 minutes, and the final forging temperature is 1000°C.

[0054] Example 4: The difference between this example and Example 1 is that the impact energy of the two upsettings is 40%, the impact energy of the die forging is 40%, the deformation of the two upsettings and the one die forging is 25%, the correction impact energy is 10%, and the correction deformation is 0.2%.

[0055] Example 5: This example differs from Example 1 in that the impact energy of the two upsettings is 60%, the impact energy of the die forging is 60%, the deformation of the two upsettings and the one die forging is 35%, the correction impact energy is 30%, and the correction deformation is 1.5%.

[0056] Example 6: The difference between this example and Example 1 is that the billet obtained in step S1 is heated to 1110°C as the initial forging temperature, held for 30 minutes, and the final forging temperature is 900°C.

[0057] Example 7: The difference between this example and Example 1 is that the billet obtained in step S1 is heated to 1130°C as the initial forging temperature, held for 90 minutes, and the final forging temperature is 1000°C.

[0058] Example 8: The difference between this example and Example 1 is that the billet obtained in step S2 is heated to 890°C, held for 8 minutes, and the final forging temperature is 850°C.

[0059] Example 9: The difference between this example and Example 1 is that the billet obtained in step S2 is heated to 910°C and held for 20 minutes, and the final forging temperature is 910°C.

[0060] Example 10: The difference between this example and Example 1 is that the annealing temperature is 860℃ and the holding time is 175min.

[0061] Example 11: The difference between this example and Example 1 is that the annealing temperature is 880℃ and the holding time is 185min.

[0062] Example 12: This example differs from Example 1 in that, as Figure 1 and Figure 2 As shown, it also includes immersing the blank after S3 correction in a chemical milling fluid in stages for rotary chemical milling treatment;

[0063] The blank includes a ring-shaped toothed groove machining section and a shaft section connecting the two ends of the toothed groove machining section. The required toothed groove depth on the sidewall of the toothed groove machining section is 'a', where 'a' is 4 mm.

[0064] The rotary milling process is as follows:

[0065] First stage: First, take 5 / 12a, or 1.67mm, of the diameter of the tooth groove machining part as the maximum immersion depth, immerse the blank in the first chemical milling fluid, rotate the blank around its own axis at a speed of 22r / min, the temperature is 65℃, the chemical milling rate is 0.055mm / min, the first chemical milling fluid includes hydrochloric acid and hydrofluoric acid in a mass ratio of 1:1.1;

[0066] Second stage: Using 17 / 24a (2.83 mm) of the diameter of the tooth groove machining section as the maximum immersion depth, immerse the blank in the second chemical milling fluid, rotate the blank around its own axis at a speed of 12 r / min, the temperature is 30℃, and the chemical milling rate is 0.035 mm / min. The second chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1.2:2.1.

[0067] The third stage: Finally, the billet is completely immersed in the third chemical milling fluid. The billet is rotated around its own axis at a speed of 17 r / min, the temperature is 65℃, and the chemical milling rate is 0.015 mm / min. The third chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1:2.8.

[0068] The hydrochloric acid has a mass concentration of 9%, the hydrofluoric acid has a mass concentration of 3%, and the ammonium chloride has a mass concentration of 4%.

[0069] Example 13: This example differs from Example 12 in the following aspects: First stage: The maximum immersion depth is 1 / 3a of the diameter of the tooth groove machining part. The blank is immersed in the first chemical milling fluid and rotated around its own axis at a speed of 20 r / min. The temperature is 60℃ and the chemical milling rate is 0.05 mm / min. Second stage: The maximum immersion depth is 2 / 3a of the diameter of the tooth groove machining part. The blank is immersed in the second chemical milling fluid and rotated around its own axis at a speed of 15 r / min. The temperature is 25℃ and the chemical milling rate is 0.03 mm / min. Third stage: Finally, the blank is completely immersed in the third chemical milling fluid and rotated around its own axis at a speed of 20 r / min. The temperature is 60℃ and the chemical milling rate is 0.01 mm / min.

[0070] Example 14: This example differs from Example 12 in the following aspects: First stage: The maximum immersion depth is 1 / 2a of the diameter of the tooth groove machining part. The blank is immersed in the first chemical milling fluid and rotated around its own axis at a speed of 25 r / min. The temperature is 70℃ and the chemical milling rate is 0.06 mm / min. Second stage: The maximum immersion depth is 3 / 4a of the diameter of the tooth groove machining part. The blank is immersed in the second chemical milling fluid and rotated around its own axis at a speed of 10 r / min. The temperature is 35℃ and the chemical milling rate is 0.04 mm / min. Third stage: Finally, the blank is completely immersed in the third chemical milling fluid and rotated around its own axis at a speed of 15 r / min. The temperature is 70℃ and the chemical milling rate is 0.02 mm / min.

[0071] Example 15: This example differs from Example 12 in that the first chemical milling fluid includes hydrochloric acid and hydrofluoric acid in a mass ratio of 1:1, the second chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1.2:1.8, and the third chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1:2.5; the mass concentration of the hydrochloric acid is 8%, the mass concentration of the hydrofluoric acid is 2.5%, and the mass concentration of the ammonium chloride is 2%.

[0072] Example 16: This example differs from Example 12 in that the first chemical milling fluid includes hydrochloric acid and hydrofluoric acid in a mass ratio of 1:1.2, the second chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1.2:2.4, and the third chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1:3; the mass concentration of the hydrochloric acid is 10%, the mass concentration of the hydrofluoric acid is 4%, and the mass concentration of the ammonium chloride is 5%.

[0073] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and aims to illustrate the practical application effect of the present invention.

[0074] The tensile strength and hardness of the transmission gears obtained in each embodiment were tested, and the average value of three test results for each embodiment was taken as the final experimental result.

[0075] 1. Investigate the influence of parameters in each step on the tensile strength and hardness of the transmission gear.

[0076] Table 1 Tensile strength and hardness of Examples 1-11

[0077]

[0078] As shown in Table 1, excessively small or large parameters in upsetting, excessively small or large impact energy in each step, excessively small or large temperature in die forging, excessively small or large temperature in correction, and excessively small parameters in annealing will all reduce the tensile strength and hardness of the transmission gear. In Example 11, the annealing temperature is high and the time is long, which improves the tensile strength but reduces the hardness compared to Example 1. Therefore, from an economic point of view, the parameter effect of Example 1 is relatively better.

[0079] 2. Investigate the effect of corrected chemical milling treatment on the hardness of transmission gears.

[0080] Table 2 Hardness of Examples 12-16 and Comparative Examples 1-3

[0081]

[0082]

[0083] The difference between Comparative Example 1 and Example 12 is that the blank was completely immersed in the corresponding chemical milling fluid at each stage;

[0084] The difference between Comparative Example 2 and Example 12 is that the chemical milling fluid composition and mass concentration are the same in each stage;

[0085] The difference between Comparative Example 3 and Example 12 is that the milling rate is the same in each stage;

[0086] Comparing Examples 12-16 with Comparative Examples 1-3 and Example 1, it can be seen that the hardness of the gears subjected to chemical milling is further improved. However, Comparative Examples 1 and 2 may lead to excessive corrosion of the blanks, and the surface quality of Comparative Example 3 is reduced, thus affecting the hardness. Therefore, the chemical milling rules of Examples 12-16 are helpful in improving the hardness of transmission gears.

[0087] Comparing Examples 12-16, it can be seen that if the change in milling rate at each stage is too small or too large, and if the difference in the concentration of milling fluid at each stage is too small or too large, the improvement in the hardness of the transmission gear will be reduced. Therefore, in summary, the parameter effect of Example 12 is relatively better.

Claims

1. A near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications, characterized in that, Includes the following steps: S1, Upsetting: The billet is heated to 1110~1130℃ as the initial forging temperature. After holding at this temperature for 20~80 minutes, the billet is upsetting: first, the billet is placed longitudinally and upset to form the shape, and then the billet is turned around and upset to form the shape again. The impact energy of the two upsettings is 40~60%, the deformation of the two upsettings is 25~35%, and the final forging temperature is 900~1000℃. After upsetting is completed, the billet is cooled. S2, Die Forging: The billet obtained in step S1 is heated to 1110~1130℃ as the initial forging temperature. After holding at this temperature for 30~90 minutes, the billet is die forged with an impact energy of 40~60%, a deformation of 25~35%, and a final forging temperature of 900~1000℃. After die forging, the billet is cooled. S3, Correction: The billet obtained in step S2 is heated to 890~910℃ and held for 8~20 minutes. The billet is then corrected with an impact energy of 10~30%, a deformation of 0~1.5%, and a final forging temperature of 850~910℃. After the correction is completed, the billet is cooled. After S3 correction, the blank is immersed in the chemical milling fluid in stages for rotary chemical milling treatment; The blank includes a ring-shaped toothed groove machining section and a shaft section connecting the two ends of the toothed groove machining section, wherein the required toothed groove depth on the sidewall of the toothed groove machining section is 'a'. The rotary milling process is as follows: First stage: First, take 1 / 3 to 1 / 2a of the diameter of the tooth groove as the maximum immersion depth, immerse the blank in the first chemical milling fluid, rotate the blank around its own axis at a speed of 20 to 25 r / min, the temperature is 60 to 70℃, and the chemical milling rate is 0.05 to 0.06 mm / min. The first chemical milling fluid includes hydrochloric acid and hydrofluoric acid in a mass ratio of 1:1 to 1.

2. Second stage: Using 2 / 3 to 3 / 4a of the diameter of the tooth groove as the maximum immersion depth, immerse the blank in the second chemical milling fluid, rotate the blank around its own axis at a speed of 10 to 15 r / min, the temperature is 25 to 35℃, and the chemical milling rate is 0.03 to 0.04 mm / min. The second chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1.2:1.8 to 2.

4. The third stage: Finally, the billet is completely immersed in the third chemical milling fluid. The billet is rotated around its own axis at a speed of 15~20 r / min, the temperature is 60~70℃, and the chemical milling rate is 0.01~0.02 mm / min. The third chemical milling fluid includes hydrochloric acid, hydrofluoric acid and ammonium chloride in a mass ratio of 1:1:2.5~3. The hydrochloric acid has a mass concentration of 8-10%, the hydrofluoric acid has a mass concentration of 2.5-4%, and the ammonium chloride has a mass concentration of 2-5%. S4, Annealing: The blank obtained in step S3 is annealed at a temperature of 860~880℃ for a holding time of 175~185min, and near-net-shape forming is completed.

2. The near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications as described in claim 1, characterized in that, Before starting step S1, round the two ends of the blank to R3, and then rough machine until the surface roughness of the two ends is ≤Ra3.

2.

3. The near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications as described in claim 1, characterized in that, After step S1 is completed and before step S2 begins, the billet is shot blasted and polished.

4. The near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications as described in claim 3, characterized in that, After step S2 is completed and before step S3 begins, the billet is trimmed, sandblasted, polished and shot blasted. The residual burrs and overcutting amount of the billet after trimming are ≤0.3mm.

5. The near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications as described in claim 4, characterized in that, After step S3 is completed and before step S4 begins, the billet is sandblasted and polished.

6. The near-net-shape forming manufacturing method for wear-resistant transmission gears for aerospace applications as described in claim 1, characterized in that, In steps S1, S2 and S3, the transfer time from the billet obtained in each step to the next step after the gray cooling is ≤10s.

7. The near-net-shape manufacturing method for wear-resistant transmission gears for aerospace applications as described in claim 4, characterized in that, The shot blasting of the billet after step S1 and before step S2, as well as the shot blasting of the billet after step S2 and before step S3, all use φ0.6mm steel shot.

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