A method for reducing quenching residual stress of large 7050 aluminum alloy ring forgings

Abstract

The application provides a method for reducing quenching residual stress of large 7050 aluminum alloy ring forgings. The bulging method of the application changes the stress state in the bulging process of the ring forgings by the design and accurate control of the bulging die, so that the ring forgings are always in a compressed state in the bulging process, which is more conducive to the reduction and uniform distribution of the residual stress of the aluminum alloy ring forgings. Under the accurate control of the process parameters of the application, the bulging die has less influence on the structure and mechanical properties of the forgings, and the residual stress elimination effect is good, so that the deformation of the 7050 aluminum alloy ring forgings in the machining process can be effectively reduced, and the finished product rate of the parts is improved.

Description

Technical Field

[0001] This invention relates to a method for reducing residual stress during quenching of large 7050 aluminum alloy ring forgings, belonging to the field of heat treatment technology for aluminum alloy materials. Background Technology

[0002] Large-sized ring-shaped parts are widely used in aerospace, tank and shipbuilding, and petrochemical industries. Examples include load-bearing structures for aircraft engines, inner and outer rings of rocket engine bearings, large flanges for petrochemical applications, and gun mounts for naval guns. With the continuous advancement of my country's aerospace technology, the requirements for the size and performance of ring-shaped parts are becoming increasingly stringent, leading to a greater need for weight reduction. Aluminum alloys, due to their low density and high specific strength, are widely used in aerospace applications, resulting in significant weight reduction.

[0003] During the manufacturing process of large aluminum alloy ring forgings, uneven plastic deformation and temperature distribution can generate significant residual stress both inside and outside the forging. The closed-loop ring design of the forging also hinders the release of this residual stress, and increasing the size of the forging further exacerbates its generation. The presence of residual stress can lead to warping during subsequent processing, causing dimensional deviations and resulting in scrap. Even dimensionally acceptable parts will experience varying degrees of impact on their mechanical properties, fatigue performance, and corrosion resistance due to residual stress, shortening their service life and potentially causing safety accidents. Therefore, effectively reducing and controlling the residual stress in large aluminum alloy ring forgings is a key technology for producing qualified ring parts.

[0004] 7050 aluminum alloy is an age-hardening alloy. Its strength increase primarily stems from the formation of a supersaturated solid solution after deformation through solution treatment, which then precipitates uniformly during aging. However, during solution quenching, variations in the immersion sequence, thickness, and cooling rate of different parts of the forging result in macroscopic residual stresses in various areas. The non-uniformity of the temperature and stress fields in the forging leads to uneven precipitation of the precipitated phases, thus affecting the forging's performance. Therefore, the residual stress resulting from solution quenching is the main residual stress in the production process of large 7050 aluminum alloy ring forgings.

[0005] Currently, residual stress in ring forgings is typically reduced through two methods: heat treatment and bulging. Heat treatment often results in a loss of the forging's mechanical properties, so the heating temperature is usually low. However, insufficient heating makes it difficult to eliminate residual stress, thus limiting the effectiveness of heating methods in reducing residual stress. Traditional bulging methods only compress the inner surface of the forging, leaving the outer surface free and unrestricted. During bulging, the forging remains under tensile stress, making it difficult to uniformly control the deformation and resulting in uneven stress reduction. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for reducing the residual stress after quenching in large 7050 aluminum alloy ring forgings. This method can significantly reduce the residual stress after quenching in large 7050 aluminum alloy ring forgings, decrease the deformation of the forgings during subsequent machining, and improve the yield of finished parts.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A forming die includes N inner forming dies and N outer supporting dies, which are evenly distributed along the circumference of an annular forging. The inner forming dies are fitted to the inner surface of the annular forging, and the outer supporting dies are inverted L-shaped, each including a long side and a short side. The long side of the outer supporting die is fitted to the outer surface of the annular forging, and the short side of the outer supporting die is fitted to the top surface of the annular forging.

[0009] According to an embodiment of the present invention, the curvature of the inner bulging die is the same as the curvature of the inner surface of the annular forging; the curvature of the long side of the outer supporting die is the same as the curvature of the outer surface of the annular forging.

[0010] According to an embodiment of the present invention, N is 16, 18, 20 or 24.

[0011] According to an embodiment of the present invention, the perimeter of the N inner bulging dies combined is 75% or 80% of the perimeter of the inner surface (inner side) of the annular forging; the perimeter of the N outer supporting dies combined is 75% or 80% of the perimeter of the outer surface (outer side) of the annular forging.

[0012] According to an embodiment of the present invention, during the bulging process, the inner bulging die provides pressure to the inner surface of the annular forging, and the outer supporting die provides deformation resistance to the outer surface and top surface of the annular forging, ensuring that the top surface and outer surface of the annular forging are under compressive stress, thereby promoting uniform circumferential deformation of the inner and outer surfaces of the annular forging. Preferably, the long side of the outer supporting die provides deformation resistance to the outer surface of the annular forging, and the short side of the outer supporting die provides deformation resistance to the top surface of the annular forging.

[0013] According to an embodiment of the present invention, the bulging die can reduce the residual stress after quenching of large aluminum alloy ring forgings.

[0014] The present invention also provides a method for using the above-mentioned bulging mold, the method comprising the following steps:

[0015] Place the ring forging into the bulging mold, apply pressure to make the inner bulging mold fit against the inner surface of the ring forging, adjust the gap between the long side of the outer support mold and the outer surface of the ring forging, apply pressure again to bulge the ring forging, so that the inner bulging mold evenly squeezes the ring forging outward. When the outer surface of the ring forging fits against the long side of the outer support mold, hold the pressure for a period of time and then release the pressure.

[0016] The present invention also provides a method for reducing residual stress during quenching of large aluminum alloy ring forgings, the method being based on the above-mentioned bulging die, and the method comprising the following steps:

[0017] 1) Place the solution-quenched aluminum alloy ring forging into the bulging mold and apply pressure to make the inner bulging mold fit against the inner surface of the ring forging;

[0018] 2) Adjust the gap between the long side of the outer support mold and the outer surface of the ring forging to ensure that the deformation along the inner circumference of the ring forging in a single bulging is 0.5% to 1.5%;

[0019] 3) Apply pressure again to expand the ring forging, so that the inner bulging die evenly squeezes the ring forging outward. When the outer surface of the ring forging is in contact with the long side of the outer support die, hold the pressure for a period of time and then release the pressure.

[0020] 4) Rotating ring forgings;

[0021] 5) Repeat steps 2) to 4) to achieve uniform extrusion at each position of the large aluminum alloy ring forging.

[0022] According to an embodiment of the present invention, in step 1), the annular forging is a 7050 aluminum alloy annular forging. The annular forging is manufactured from an ingot through processes such as forging, punching, reaming, and ring rolling.

[0023] According to an embodiment of the present invention, in step 1), the wall thickness of the annular forging is less than the height of the annular forging. For example, the wall thickness of the annular forging is 50–150 mm; the height of the annular forging is 300–600 mm.

[0024] According to an embodiment of the present invention, in step 1), the inner diameter of the annular forging is greater than or equal to 2000 mm.

[0025] According to an embodiment of the present invention, in step 1), before solution quenching, the ring forging is further subjected to machining and shaping treatment, the purpose of which is to remove forging defects in the ring rolling process, ensure that the upper and lower ring surfaces are parallel, the inner and outer surfaces are smooth, and the roughness is less than Ra3.2.

[0026] According to an embodiment of the present invention, in step 1), the solution quenching includes solution treatment and quenching treatment. The temperature of the solution treatment is (477)℃ ± 5℃. The time of the solution treatment is determined according to the wall thickness of the ring forging, for example, more than 2 hours. The transfer time of the quenching treatment is less than or equal to 15s. The medium for the quenching treatment is water with a temperature not lower than 60℃.

[0027] For example, the solution quenching process is as follows: the furnace is loaded at a temperature of 477℃±5℃. When the material temperature reaches 477℃±5℃, the time is determined based on the wall thickness of the ring forging. After the heat treatment is completed, the ring forging is taken out and placed in water for quenching within 15 seconds. The quenching water temperature is not lower than 60℃.

[0028] According to an embodiment of the present invention, in step 1), in order to ensure the uniform distribution of residual stress during the quenching process, the ring forging is immersed in water as follows: the ring forging is immersed in water along its height direction, the water is stirred to maintain a uniform water temperature, and the quenching time is not less than 20 minutes.

[0029] According to an embodiment of the present invention, in step 1), the mold installation process is as follows: the annular forging is placed on the base, the bulging mold is adjusted so that the inner bulging mold and the outer support mold are evenly distributed along the circumference of the annular forging, and pressure is applied so that the inner bulging mold fits against the inner surface of the forging, and there is a gap between the long side of the outer support mold and the outer surface of the annular forging.

[0030] According to an embodiment of the present invention, in step 1), the gap between the long side of the outer support mold and the outer surface of the annular forging is calculated based on the diameter of the annular forging, ensuring that the deformation amount along the inner circumference of the annular forging in a single bulging is 0.5% to 1.5%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%.

[0031] According to an embodiment of the present invention, in step 3), a press (such as a hydraulic press) is used to perform pressure bulging, and the moving speed of the inner bulging mold is controlled at 0.1 mm / s to 0.5 mm / s, for example, 0.1 mm / s, 0.2 mm / s, 0.3 mm / s, 0.4 mm / s, or 0.5 mm / s.

[0032] According to an embodiment of the present invention, in step 3), the pressure is maintained for 120s to 160s, for example, 120s, 130s, 140s, 150s or 160s.

[0033] According to an embodiment of the present invention, in step 4), the annular forging is rotated by (360 / 4N×80%)° or (360 / 3N×75%)°, where N is the number of inner bulging dies.

[0034] According to an embodiment of the present invention, in step 5), the operation is repeated 4 times, during which the annular forging undergoes 4 bulging and 3 rotations; or, the operation is repeated 5 times, during which the annular forging undergoes 5 bulging and 4 rotations.

[0035] According to an embodiment of the present invention, in step 5), the bulging process needs to be completed within 4 hours after the annular forging is quenched and removed from the water.

[0036] According to an embodiment of the present invention, the annular forging is required to be laid flat after bulging and during aging, that is, the height direction of the annular forging is perpendicular to the ground.

[0037] According to an embodiment of the present invention, the method further includes manual aging processing.

[0038] According to an embodiment of the present invention, after bulging, the annular forging is placed in an aging furnace for artificial aging treatment. When the measured deformation of the annular forging is less than or equal to 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃ and the holding time is 6 to 8 hours. The second-stage aging temperature is 177±3℃ and the holding time is 6 to 8 hours.

[0039] According to an embodiment of the present invention, after bulging, the annular forging is placed in an aging furnace for artificial aging treatment. When the measured deformation of the annular forging is greater than 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃ and the holding time is 3 to 6 hours. The second-stage aging temperature is 177±3℃ and the holding time is 6 to 8 hours.

[0040] Studies have found that when the deformation of annular forgings is large, the deformation energy storage is high, the aging response is faster, and the heat preservation time can be appropriately shortened.

[0041] According to an embodiment of the present invention, the method includes the following steps:

[0042] 1) Place the solution-quenched aluminum alloy ring forging into a forming mold, and apply pressure to make the inner forming mold fit against the inner surface of the ring forging; the forming mold includes N inner forming molds and N outer supporting molds, the circumference of the N inner forming molds combined is 75% of the circumference of the inner surface (inner side) of the ring forging; the circumference of the N outer supporting molds combined is 75% of the circumference of the outer surface (outer side) of the ring forging;

[0043] 2) Adjust the gap between the long side of the outer support mold and the outer surface of the ring forging to ensure that the deformation along the inner circumference of the ring forging in a single bulging is 0.8% to 1.5%;

[0044] 3) Apply pressure again to expand the ring forging, so that the inner bulging die evenly squeezes the ring forging outward. When the outer surface of the ring forging is in contact with the long side of the outer support die, hold the pressure for a period of time and then release the pressure.

[0045] 4) Rotating ring forgings;

[0046] 5) Repeat steps 2) to 4) 4 times. During this time, the ring forging undergoes 4 expansions and 3 rotations, with each rotation being (360 / 3N×75%)°, achieving uniform extrusion at each position of the large aluminum alloy ring forging.

[0047] At this point, the bulging die includes N inner bulging dies and N outer support dies. The circumference of the combined N inner bulging dies is further controlled to be 75% of the circumference of the inner surface (inner side) of the annular forging. During use, a total of four bulging cycles are performed, with three rotations, each rotation being (360 / 3N × 75%)°, for a total rotation of (360 / N × 75%)°. This operation ensures that each position is uniformly compressed three times. By controlling the amount of deformation during each bulging cycle, the final deformation can be controlled.

[0048] According to an embodiment of the present invention, the method includes the following steps:

[0049] 1) Place the solution-quenched aluminum alloy ring forging into the bulging mold, and apply pressure to make the inner bulging mold fit against the inner surface of the ring forging; the bulging mold includes N inner bulging molds and N outer support molds, the perimeter of the N inner bulging molds combined is 80% of the perimeter of the inner surface (inner side) of the ring forging; the perimeter of the N outer support molds combined is 80% of the perimeter of the outer surface (outer side) of the ring forging;

[0050] 2) Adjust the gap between the long side of the outer support mold and the outer surface of the ring forging to ensure that the deformation along the inner circumference of the ring forging in a single bulging is 0.5% to 1.2%;

[0051] 3) Apply pressure again to expand the ring forging, so that the inner bulging die evenly squeezes the ring forging outward. When the outer surface of the ring forging is in contact with the long side of the outer support die, hold the pressure for a period of time and then release the pressure.

[0052] 4) Rotating ring forgings;

[0053] 5) Repeat steps 2) to 4) 5 times. During this time, the ring forging undergoes 5 expansions and 4 rotations, with each rotation being (360 / 4N×80%)°, achieving uniform extrusion at each position of the large aluminum alloy ring forging.

[0054] At this point, the bulging die includes N inner bulging dies and N outer support dies. Furthermore, the circumference of the combined N inner bulging dies is controlled to be 80% of the circumference of the inner surface (inner side) of the annular forging. During use, a total of 5 bulging cycles are performed, with 4 rotations, each rotation being (360 / 4N × 80%)°, for a total rotation of (360 / N × 80%)°. This operation ensures that each position is uniformly compressed 4 times. By controlling the amount of deformation during each bulging cycle, the final deformation amount can be controlled.

[0055] According to an embodiment of the present invention, the method includes the following steps:

[0056] Step 1: Select the bulging die. The bulging die consists of 18 inner bulging dies and 18 outer support dies. The curvature of the inner bulging dies and the outer support dies should be consistent with the curvature of the inner and outer surfaces of the forging, respectively. The circumference of the 18 inner bulging dies after combination is 75% of the inner circumference of the ring forging. The 18 outer support dies are inverted L-shaped, and their combined circumference is 75% of the outer circumference of the ring forging.

[0057] Step 2: Solution quenching. Place the 7050 aluminum alloy ring forging, which has a smooth surface and is free of forging defects, into an air-circulating furnace at a temperature of 477℃±5℃. Hold the forging at 477℃ for a specified time, determined by the thickness of the ring forging. After holding, remove the ring forging and quench it in water within 15 seconds. The quenching water temperature should not be lower than 60℃. The ring forging should be immersed in water along its height, with stirring to maintain a uniform temperature. The quenching time should be no less than 20 minutes.

[0058] Step 3: Mold installation. Place the 7050 aluminum alloy ring forging on the base of the bulging equipment. Adjust the bulging mold so that the inner bulging mold and the outer support mold are evenly distributed along the circumference of the forging. Apply pressure to make the inner bulging mold fit against the inner surface of the forging. Adjust the gap between the outer support mold and the outer surface of the ring forging. The gap value is calculated according to the diameter of the ring forging to ensure that the deformation of the forging along the inner circumference in a single bulging is 0.8% to 1.5%.

[0059] Step 4: Bulk shaping, which includes 7 steps;

[0060] Step 1. Press the press at a speed of 0.1 mm / s to 0.5 mm / s to make the inner bulging die evenly extrude the forging outward. When the outer surface of the ring forging is in contact with the outer support die, hold the pressure for 120 seconds.

[0061] Step 2. Depressurize, rotate the forging by 5°, and simultaneously adjust the gap between the outer support mold and the outer surface of the ring forging. The gap value is calculated based on the diameter of the ring forging to ensure that the deformation along the inner circumference of the forging in a single bulging is 0.8% to 1.5%.

[0062] Step 3. Repressurize and repeat Step 1;

[0063] Step 4. Depressurize, rotate, and repeat step 2;

[0064] Step 5. Repressurize and repeat step 1;

[0065] Step 6. Depressurize, rotate, and repeat step 2;

[0066] Step 7. Repressurize and repeat step 1;

[0067] The bulging process involves four bulging cycles and three rotations, each rotation being 5°, for a total rotation of 15°. The bulging process must be completed within four hours after the quenching process.

[0068] Step 5: Artificial aging. Place the 7050 aluminum alloy ring forging flat into the aging furnace for aging treatment. When the bulging deformation is less than 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃, and the holding time is 6-8 hours. The second-stage aging temperature is 177±3℃, and the holding time is 6-8 hours. When the bulging deformation is greater than 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃, and the holding time is 3-6 hours. The second-stage aging temperature is 177±3℃, and the holding time is 6-8 hours.

[0069] According to an embodiment of the present invention, the method includes the following steps:

[0070] Step 1: Select the bulging die. The bulging die consists of 18 inner bulging dies and 18 outer support dies. The curvature of the inner bulging dies and the outer support dies should be consistent with the curvature of the inner and outer surfaces of the forging, respectively. The circumference of the 18 inner bulging dies after combination is 80% of the inner circumference of the ring forging. The 18 outer support dies are inverted L-shaped, and their combined circumference is 80% of the outer circumference of the ring forging.

[0071] Step 2: Solution quenching. Place the 7050 aluminum alloy ring forging, which has a smooth surface and is free of forging defects, into an air-circulating furnace at a temperature of 477℃±5℃. Hold the forging at 477℃ for a specified time, determined by the thickness of the ring forging. After holding, remove the ring forging and quench it in water within 15 seconds. The quenching water temperature should not be lower than 60℃. The ring forging should be immersed in water along its height, with stirring to maintain a uniform temperature. The quenching time should be no less than 20 minutes.

[0072] Step 3: Mold installation. Place the 7050 aluminum alloy ring forging on the base of the bulging equipment. Adjust the bulging mold so that the inner bulging mold and the outer support mold are evenly distributed along the circumference of the forging. Apply pressure to make the inner bulging mold fit against the inner surface of the forging. Adjust the gap between the outer support mold and the outer surface of the ring forging. The gap value is calculated according to the diameter of the ring forging to ensure that the deformation of the forging along the inner circumference in a single bulging is 0.5% to 1.2%.

[0073] Step 4: Bulk shaping, which includes 9 steps;

[0074] Step 1. Press the press at a speed of 0.1 mm / s to 0.5 mm / s to make the inner bulging die evenly extrude the forging outward. When the outer surface of the ring forging is in contact with the outer support die, hold the pressure for 120 seconds.

[0075] Step 2. Depressurize and rotate the forging by 4°. At the same time, adjust the gap between the outer support mold and the outer surface of the ring forging. The gap value is calculated based on the diameter of the ring forging to ensure that the deformation of the forging along the inner circumference in a single bulging is 0.5% to 1.2%.

[0076] Step 3. Repressurize and repeat Step 1;

[0077] Step 4. Depressurize, rotate, and repeat step 2;

[0078] Step 5. Repressurize and repeat step 1;

[0079] Step 6. Depressurize, rotate, and repeat step 2;

[0080] Step 7. Repressurize and repeat step 1;

[0081] Step 8. Depressurize, rotate, and repeat step 2;

[0082] Step 9. Repressurize and repeat step 1;

[0083] The bulging process involves 5 bulging cycles and 4 rotations, each rotation being 4°, for a total rotation of 16°. The bulging process must be completed within 4 hours after quenching and removal from the water.

[0084] Step 5: Artificial aging. Place the 7050 aluminum alloy ring forging flat into the aging furnace for aging treatment. When the bulging deformation is less than 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃, and the holding time is 6-8 hours. The second-stage aging temperature is 177±3℃, and the holding time is 6-8 hours. When the bulging deformation is greater than 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃, and the holding time is 3-6 hours. The second-stage aging temperature is 177±3℃, and the holding time is 6-8 hours.

[0085] The beneficial effects of this invention are:

[0086] This invention provides a method for reducing residual stress during quenching of large 7050 aluminum alloy ring forgings.

[0087] The bulging method of this invention, through the design and precise control of the bulging die, alters the stress state of the ring forging during the bulging process, ensuring that the ring forging remains under pressure throughout the process. This is more conducive to reducing and uniformly distributing residual stress in the aluminum alloy ring forging. Under the precise control of the process parameters of this invention, the bulging die has minimal impact on the microstructure and mechanical properties of the forging, exhibits excellent residual stress elimination, and can effectively reduce deformation during the machining process of 7050 aluminum alloy ring forgings, thereby improving the yield of finished parts. Attached Figure Description

[0088] Figure 1This is a schematic diagram of the assembly of the bulging mold and the 7050 aluminum alloy ring forging during cold pressing.

[0089] The components include: 1. Inner bulging mold; 2. 7050 aluminum alloy ring forging; 3. Outer support mold. Detailed Implementation

[0090] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0091] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0092] Example 1

[0093] This embodiment provides a forming mold, which includes 18 inner forming molds 1 and 18 outer supporting molds 3. The inner forming molds 1 and outer supporting molds 3 are evenly distributed along the circumference of the annular forging 2. The inner forming molds are fitted to the inner surface of the annular forging, and the outer supporting molds are inverted L-shaped. Each outer supporting mold includes a long side and a short side. The long side of the outer supporting mold is fitted to the outer surface of the annular forging, and the short side of the outer supporting mold is fitted to the top surface of the annular forging. The curvature of the inner forming mold is the same as the curvature of the inner surface of the annular forging, and the curvature of the long side of the outer supporting mold is the same as the curvature of the outer surface of the annular forging.

[0094] Comparative Example 1

[0095] Comparative Example 1 provides a forming die, which includes 18 inner forming dies. The inner forming dies are evenly distributed along the circumference of the annular forging and fit against the inner surface of the annular forging. The curvature of the inner forming dies is the same as the curvature of the inner surface of the annular forging.

[0096] Example 2

[0097] A 7050 aluminum alloy ring forging was prepared using the same process. The ring forging had an inner diameter of 2250 mm, a thickness of 85 mm, and a height of 445 mm. The bulging die from Example 1 was selected, with an inner bulging die length of 295 mm and an outer support die length of 305 mm.

[0098] The forgings were solution treated at 477℃±5℃. After holding at this temperature, they were quenched in water at a height of 60℃, with a quenching transfer time of less than 15 seconds, and removed from the water after 20 minutes. After quenching, the forgings were placed on the base of the bulging equipment, and the positions of the forgings and molds were adjusted, with a 23mm gap between the outer surface of the forging and the mold. Bulging was performed at a speed of 0.3mm / s, and pressure was maintained for 120 seconds when the outer surface of the forging was in contact with the outer support mold. Pressure was then released, and the forging was rotated 5°, adjusting the gap between the forging and the outer support mold to 23mm. The pressure-expanding and pressure-relief rotation process was repeated, for a total of 4 bulging cycles and 3 rotations, each rotation being 5°, for a total rotation of 15°. The measured bulging amount after bulging was 3.4%. Artificial aging was performed using a two-stage aging process: the first stage aging temperature was 121±3℃, held for 5 hours, and the second stage aging temperature was 177±3℃, held for 7 hours, after which the forgings were air-cooled. The residual stress and mechanical properties of the forging at various locations were measured after heat treatment. The maximum residual stress was 44 MPa, and the minimum was 7 MPa. The tensile strength was 526 MPa, and the yield strength was 466 MPa. The maximum machining deformation of the forging was 0.4 mm.

[0099] Comparative Example 2

[0100] A 7050 aluminum alloy ring forging was prepared using the same process. The ring forging had an inner diameter of 2250 mm, a thickness of 85 mm, and a height of 445 mm. The bulging die from Comparative Example 1 was selected, with a die length of 295 mm.

[0101] The forgings were solution treated at 477℃±5℃. After holding at this temperature, they were quenched in water at a height of 60℃, with a quenching transfer time of less than 15 seconds, and removed from the water after 20 minutes. After quenching, the forgings were placed on the base of the bulging equipment, and the positions of the forgings and molds were adjusted. Bulging was then performed at a speed of 0.3 mm / s. When the bulging amount reached 1%, the pressure was released, and the forgings were rotated 5° to continue bulging. The pressure-pressurizing and depressurizing rotation process was repeated for a total of 4 bulging cycles and 3 rotations, each rotation being 5°, for a total rotation of 15°. The measured bulging amount after bulging was 2.8%. Artificial aging was performed using a two-stage aging process: the first-stage aging temperature was 121±3℃, held for 5 hours, and the second-stage aging temperature was 177±3℃, held for 7 hours, after which the forgings were air-cooled. The residual stress and mechanical properties of the forging at various locations were measured after heat treatment. The maximum residual stress was 191 MPa, and the minimum was 82 MPa. The tensile strength was 519 MPa, and the yield strength was 459 MPa. The maximum machining deformation of the forging was 2.2 mm.

[0102] Example 3

[0103] A 7050 aluminum alloy ring forging was prepared using the same process. The ring forging had an inner diameter of 2250 mm, a thickness of 85 mm, and a height of 445 mm. The bulging die from Example 1 was selected, with an inner bulging die length of 295 mm and an outer support die length of 305 mm. The forging was solution treated at a temperature of 477℃±5℃. After holding at this temperature, it was quenched in water along the height direction at a water temperature of 60℃. The quenching transfer time was less than 15 seconds, and the forging was removed from the water after 20 minutes. After quenching, the forging was placed on the base of the bulging equipment. The positions of the forging and the die were adjusted, with a 22 mm gap between the outer surface of the forging and the die. Bulging was performed at a speed of 0.3 mm / s. When the outer surface of the forging was in contact with the outer support die, the pressure was held for 120 seconds. Pressure was released, and the forging was rotated 5°, adjusting the gap between the forging and the outer support die to 22 mm. The pressure-applying bulging and depressurizing rotation process was repeated, for a total of 4 bulging cycles and 3 rotations, each rotation being 5°, for a total rotation of 15°. The measured bulging amount after bulging was 3.2%. Artificial aging was performed using a two-stage process: the first stage aging temperature was 121±3℃, held for 5 hours; the second stage aging temperature was 177±3℃, held for 7 hours, and then air-cooled after removal from the furnace. Residual stress and mechanical properties at various locations of the forging were measured after heat treatment. The maximum residual stress was 32 MPa, the minimum was 8 MPa, the tensile strength was 516 MPa, and the yield strength was 462 MPa. The maximum machining deformation of the forging was 0.3 mm.

[0104] Comparative Example 3

[0105] A 7050 aluminum alloy ring forging was prepared using the same process. The ring forging had an inner diameter of 2250 mm, a thickness of 85 mm, and a height of 445 mm. The bulging die from Example 1 was selected, with an inner bulging die length of 295 mm and an outer support die length of 305 mm. The forging was solution treated at a temperature of 477℃±5℃. After holding at this temperature, it was quenched in water along the height direction at a water temperature of 60℃. The quenching transfer time was less than 15 seconds, and the forging was removed from the water after 20 minutes. After quenching, the forging was placed on the base of the bulging equipment. The positions of the forging and the die were adjusted, with a gap of 18 mm between the outer surface of the forging and the die. Bulging was performed at a speed of 0.3 mm / s. When the outer surface of the forging was in contact with the outer support die, the pressure was held for 180 seconds. Pressure was released, and the forging was rotated 5°. The gap between the forging and the outer support die was adjusted to 18 mm. The pressure-applying bulging and depressurizing rotation process was repeated, for a total of 5 bulging cycles and 4 rotations, each rotation being 5°, for a total rotation of 20°. The measured bulging amount after bulging was 4.4%. Artificial aging was performed using a two-stage process: the first stage aging temperature was 121±3℃, held for 5 hours; the second stage aging temperature was 177±3℃, held for 7 hours, and then air-cooled after removal from the furnace. Residual stress and mechanical properties at various locations of the forging were measured after heat treatment. The maximum residual stress was 123 MPa, and the minimum was -65 MPa. The tensile strength was 509 MPa, and the yield strength was 468 MPa. The maximum machining deformation of the forging was 4.3 mm.

[0106] Example 4

[0107] A 7050 aluminum alloy ring forging was prepared using the same process. The ring forging had an inner diameter of 2250 mm, a thickness of 85 mm, and a height of 445 mm. The bulging die from Example 1 was selected, with an inner bulging die length of 295 mm and an outer support die length of 305 mm. The forging was solution treated at a temperature of 477℃±5℃. After holding at this temperature, it was quenched by immersing it in water along its height at a water temperature of 63℃. The quenching transfer time was less than 15 seconds, and the forging was removed from the water after 20 minutes. After quenching, the forging was placed on the base of the bulging equipment. The positions of the forging and the die were adjusted, with a gap of 18 mm between the outer surface of the forging and the die. Bulging was performed at a speed of 0.3 mm / s. When the outer surface of the forging was in contact with the outer support die, the pressure was held for 120 seconds. Pressure was released, and the forging was rotated 5°. The gap between the forging and the outer support die was adjusted to 15 mm. The pressure-applying bulging and depressurizing rotation process was repeated, for a total of 4 bulging cycles and 3 rotations, each rotation being 5°, for a total rotation of 15°. The measured bulging amount after bulging was 1.8%. Artificial aging was performed using a two-stage process: the first stage aging temperature was 121±3℃, held for 7 hours; the second stage aging temperature was 177±3℃, held for 7 hours, and then air-cooled after removal from the furnace. Residual stress and mechanical properties at various locations of the forging were measured after heat treatment. The maximum residual stress was 39 MPa, the minimum was -2 MPa, the tensile strength was 532 MPa, and the yield strength was 471 MPa. The maximum machining deformation of the forging was 0.3 mm.

[0108] Comparative Example 4

[0109] A 7050 aluminum alloy ring forging was prepared using the same process. The ring forging had an inner diameter of 2250 mm, a thickness of 85 mm, and a height of 445 mm. The bulging die from Example 1 was selected, with an inner bulging die length of 295 mm and an outer support die length of 305 mm. The forging was solution treated at a temperature of 477℃±5℃. After holding at this temperature, it was quenched by immersing it in water along its height at a water temperature of 63℃. The quenching transfer time was less than 15 seconds, and the forging was removed from the water after 20 minutes. After quenching, the forging was placed on the base of the bulging equipment. The positions of the forging and the die were adjusted, with a gap of 18 mm between the outer surface of the forging and the die. Bulging was performed at a speed of 0.3 mm / s. When the outer surface of the forging was in contact with the outer support die, the pressure was held for 90 seconds. Pressure was released, and the forging was rotated 10°. The gap between the forging and the outer support die was adjusted to 16 mm. The pressure-applying bulging and depressurizing rotation process was repeated, for a total of two bulging cycles and one rotation, each rotation being 10°, for a total rotation of 10°. The measured bulging amount after bulging was 1.2%. Artificial aging was performed using a two-stage process: the first stage aging temperature was 121±3℃, held for 7 hours; the second stage aging temperature was 177±3℃, held for 7 hours, and then air-cooled after removal from the furnace. Residual stress and mechanical properties at various locations of the forging were measured after heat treatment. The maximum residual stress was 183 MPa, the minimum was 82 MPa, the tensile strength was 510 MPa, and the yield strength was 461 MPa. The maximum machining deformation of the forging was 3.1 mm.

[0110] The bulging molds used in Examples 2-4 include 18 inner bulging molds and 18 outer support molds. The circumference of the combined 18 inner bulging molds is further controlled to be 75% of the circumference of the inner surface (inner side) of the annular forging. During use, a total of 4 bulging cycles and 3 rotations are performed, each rotation being 5°, for a total rotation of 15°. This operation ensures that each position is uniformly compressed 3 times. Combined with the control of the deformation amount during each bulging cycle, the final deformation amount is controlled. Comparative Examples 3 and 4 further compare the effects of different compression cycles and total compression amounts: Comparative Example 3 involves 5 bulging cycles and 4 rotations, each rotation being 5°, for a total rotation of 20°. This results in the position that rotates an extra 5° being compressed an extra time, leading to uneven overall deformation. Excessive deformation can also cause compressive stress (-65MPa) inside the forging, resulting in increased stress difference, uneven stress distribution, and processing deformation. Comparative Example 4 involves 2 bulging cycles and 1 rotation, each rotation being 10°, for a total rotation of 10°. The insufficient number of compression cycles results in poor residual stress reduction.

[0111] In summary, this application achieves uniform extrusion of large aluminum alloy ring forgings at each position by selecting a suitable bulging die and further combining it with the rotation angle for each rotation, controlling the amount of deformation per bulging, controlling the number of rotations, ensuring that all positions have the same number of bulging operations, and thus controlling the total amount of bulging deformation. This results in the reduction of residual stress in the quenching of large aluminum alloy ring forgings.

[0112] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reducing residual stress after quenching in large aluminum alloy annular forgings, the method being based on a forming die, the forming die comprising N inner forming dies and N outer supporting dies, the inner forming dies and outer supporting dies being evenly distributed along the circumference of the annular forging, the inner forming dies fitting against the inner surface of the annular forging, the outer supporting dies being inverted L-shaped, each outer supporting die comprising a long side and a short side, the long side of the outer supporting die fitting against the outer surface of the annular forging, and the short side of the outer supporting die fitting against the top surface of the annular forging; the method comprising the following steps: 1) The solution-quenched aluminum alloy ring forging is placed in an bulging mold, and pressure is applied to make the inner bulging mold fit against the inner surface of the ring forging; the bulging mold includes N inner bulging molds and N outer support molds, the circumference of the N inner bulging molds combined is 75% of the circumference of the inner surface of the ring forging; the circumference of the N outer support molds combined is 75% of the circumference of the outer surface of the ring forging; 2) Adjust the gap between the long side of the outer support mold and the outer surface of the ring forging to ensure that the deformation along the inner circumference of the ring forging in a single bulging process is 0.8%~1.5%; 3) Apply pressure again to expand the ring forging, so that the inner bulging die evenly squeezes the ring forging outward. When the outer surface of the ring forging is in contact with the long side of the outer support die, hold the pressure for a period of time and then release the pressure. 4) Rotating ring forgings; 5) Repeat steps 2) to 4) 4 times. During this time, the ring forging undergoes 4 expansions and 3 rotations, with each rotation being (360 / 3N×75%)°, achieving uniform extrusion at each position of the large aluminum alloy ring forging. In step 1), the wall thickness of the annular forging is 50~150mm; the height of the annular forging is 300~600mm; and the inner diameter of the annular forging is greater than or equal to 2000mm. In step 3), a press is used to apply pressure and bulge the material, and the moving speed of the inner bulging die is controlled at 0.1 mm / s to 0.5 mm / s. In step 3), maintain the pressure for 120s~160s; N is 16, 18, 20, or 24; The method also includes manual aging processing; After bulging, the ring forging is placed in an aging furnace for artificial aging treatment. When the measured deformation of the ring forging is less than or equal to 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃ and the holding time is 6~8 hours. The second-stage aging temperature is 177±3℃ and the holding time is 6~8 hours. When the measured deformation of the ring forging is greater than 2.0%, the artificial aging process adopts a two-stage aging process. The first-stage aging temperature is 121±3℃ and the holding time is 3~6 hours. The second-stage aging temperature is 177±3℃ and the holding time is 6~8 hours.

2. A method for reducing residual stress after quenching in large aluminum alloy annular forgings, the method being based on a forming die, the forming die comprising N inner forming dies and N outer supporting dies, the inner forming dies and outer supporting dies being evenly distributed along the circumference of the annular forging, the inner forming dies fitting against the inner surface of the annular forging, the outer supporting dies being inverted L-shaped, each outer supporting die comprising a long side and a short side, the long side of the outer supporting die fitting against the outer surface of the annular forging, and the short side of the outer supporting die fitting against the top surface of the annular forging; the method comprising the following steps: 1) The solution-quenched aluminum alloy ring forging is placed in an bulging mold, and pressure is applied to make the inner bulging mold fit against the inner surface of the ring forging; the bulging mold includes N inner bulging molds and N outer support molds, the circumference of the N inner bulging molds combined is 80% of the circumference of the inner surface of the ring forging; the circumference of the N outer support molds combined is 80% of the circumference of the outer surface of the ring forging; 2) Adjust the gap between the long side of the outer support mold and the outer surface of the ring forging to ensure that the deformation along the inner circumference of the ring forging in a single bulging process is 0.5%~1.2%; 3) Apply pressure again to expand the ring forging, so that the inner bulging die evenly squeezes the ring forging outward. When the outer surface of the ring forging is in contact with the long side of the outer support die, hold the pressure for a period of time and then release the pressure. 4) Rotating ring forgings; 5) Repeat steps 2) to 4) 5 times. During this time, the ring forging undergoes 5 expansions and 4 rotations, with each rotation being (360 / 4N×80%)°, achieving uniform extrusion at each position of the large aluminum alloy ring forging. In step 1), the wall thickness of the annular forging is 50~150mm; the height of the annular forging is 300~600mm; and the inner diameter of the annular forging is greater than or equal to 2000mm. In step 3), a press is used to apply pressure and bulge the material, and the moving speed of the inner bulging die is controlled at 0.1 mm / s to 0.5 mm / s. In step 3), maintain the pressure for 120s~160s; N is 16, 18, 20, or 24; The method also includes manual aging processing; After bulging, the ring forging is placed in an aging furnace for artificial aging treatment. When the measured deformation of the ring forging is less than or equal to 2.0%, the artificial aging adopts a two-stage aging process. The first-stage aging temperature is 121±3℃ and the holding time is 6~8 hours. The second-stage aging temperature is 177±3℃ and the holding time is 6~8 hours. When the measured deformation of the ring forging is greater than 2.0%, the artificial aging process adopts a two-stage aging process. The first-stage aging temperature is 121±3℃ and the holding time is 3~6 hours. The second-stage aging temperature is 177±3℃ and the holding time is 6~8 hours.

3. The method according to claim 1 or 2, characterized in that, The curvature of the inner bulging die is the same as the curvature of the inner surface of the annular forging; the curvature of the long side of the outer support die is the same as the curvature of the outer surface of the annular forging.

4. The method according to claim 1 or 2, characterized in that, In step 1), before solution quenching, the ring forging is machined and shaped to remove forging defects during the ring rolling process, ensure that the upper and lower ring surfaces are parallel, the inner and outer surfaces are smooth, and the roughness is less than Ra3.

2. And / or, in step 1), the solution quenching includes solution treatment and quenching treatment; the temperature of the solution treatment is 477℃±5℃; the transfer time of the quenching treatment is less than or equal to 15s; the medium of the quenching treatment is water with a temperature not lower than 60℃. And / or, in step 1), in order to ensure the uniform distribution of residual stress during the quenching process, the ring forging is immersed in water as follows: it is immersed in water along the height direction of the ring forging, and there should be stirring in the water to keep the water temperature uniform, and the quenching time is not less than 20 minutes.

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