A method for manufacturing a high-density aluminum alloy reverse extrusion formed aluminum pipe for a retainer

Abstract

The application provides a preparation method of high-density aluminum alloy counter-extrusion forming aluminum pipe for cage, and relates to the technical field of aluminum alloy forming processing of bearing cage. The method comprises the following steps: S1: selecting aluminum alloy bars of certain specifications; S2: heating the aluminum alloy bars at 460-480 DEG C; S3: counter-extrusion forming the heated aluminum alloy bars, the counter-extrusion forming temperature is 430-450 DEG C, and the pressure is 800-1600 tons; and S4: sequentially performing solid solution quenching treatment and artificial aging treatment on the counter-extrusion formed aluminum pipe to obtain a high-density aluminum alloy counter-extrusion forming aluminum pipe. The aluminum pipe is compact in structure, the grain size can reach grade 6-7, the grains are small and uniform, there are no defects such as pores and inclusions, the density is greater than or equal to 99.8%, and the aluminum pipe is significantly better than the aluminum pipe prepared by the existing ordinary extrusion and casting process, and is suitable for preparing bearing cages.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy forming and processing technology, and more specifically, to a method for preparing a high-density aluminum alloy reverse extrusion molded aluminum tube with a cage. Background Technology

[0002] 6082 aluminum alloy, as an Al-Mg-Si heat-treatable alloy, is widely used in the manufacture of high-performance structural components such as bearing cages due to its excellent mechanical and machinability. Currently, the main forming methods for 6082 aluminum alloy tubing include conventional forward extrusion and casting. However, aluminum tubing produced by conventional forward extrusion suffers from coarse grains (typically only grade 2-3), poor microstructure density, and a tendency to produce defects such as porosity and inclusions. Furthermore, it requires a large machining allowance and has low material utilization. Casting results in even lower density and higher porosity, making its mechanical properties insufficient to meet the requirements of high-performance bearing cages and unable to withstand loads under complex operating conditions.

[0003] Reverse extrusion, as an efficient plastic forming method, can achieve densification of billets through the directional flow of metal. However, the existing reverse extrusion process is not designed with reasonable parameters for 6082 aluminum alloy. It fails to optimize key parameters such as temperature and pressure based on its material properties, resulting in insufficient dimensional accuracy of the formed aluminum tube and failure to achieve the expected grain size. Furthermore, the heat treatment process is not properly integrated with the reverse extrusion process, which fails to fully realize the strengthening potential of 6082 aluminum alloy and makes it difficult to meet the requirements of bearing cages for billet density, strength, and dimensional accuracy.

[0004] For example, the core inventive concept of patent publication number CN121674755A lies in eliminating the traditional homogenization annealing process. By optimizing extrusion (temperature 420-500℃, extrusion ratio ≤30) and forging (450-560℃) parameters, and combining them with compositional design (such as adding Cr and Mn to form a dispersed phase), forgings with good mechanical properties can be directly prepared from cast billets. Its core is to eliminate homogenization; the total deformation amount in its deformation process (extrusion + forging) is enormous (forging deformation amount is about 70%), aiming to break down the coarse second phase in the cast structure through intense plastic deformation, thereby bypassing the homogenization process. However, it is well known in the art that the deformation amount in reverse extrusion forming is relatively limited, and its main purpose is to obtain tubes with precise dimensions. Therefore, directly transplanting the process parameters of CN121674755A for forgings with large deformation amounts to reverse extrusion tube forming cannot solve the core problem of how to obtain high-density, ultra-fine grain (target level 6-7) 6082 aluminum tubes with limited deformation.

[0005] Therefore, there is an urgent need for an optimized reverse extrusion forming method for 6082 aluminum alloy to overcome the defects of the existing process. Summary of the Invention

[0006] This invention aims to solve the following technical problems existing in the current 6082 aluminum alloy tubing forming technology, specifically when using reverse extrusion to prepare aluminum tubing for bearing cages: ① Existing technologies rely on large deformation amounts (such as 70% deformation in forging) to break down coarse phases and eliminate porosity. However, the deformation amount in reverse extrusion molding is limited by the pipe wall thickness and shape, making it impossible to simply replicate this technological approach. Therefore, it is necessary to solve the problem of how to achieve high density (≥99.8%) under small deformation conditions.

[0007] ②6082 aluminum alloy is prone to grain growth during hot working and solution treatment. This application needs to solve how to suppress grain coarsening during reverse extrusion and subsequent heat treatment to obtain ultrafine grains.

[0008] ③ The bearing cage requires extremely high dimensional accuracy and internal stress levels from the aluminum tube blank. Current technology does not consider the impact of the magnitude and distribution of residual stress after back extrusion on subsequent quenching, aging, and machining deformation. It is necessary to address how to establish a matching relationship between "back extrusion parameters - residual stress state - T6 heat treatment parameters" to effectively eliminate internal stress and ensure the dimensional stability of the final product.

[0009] To address the above problems, this invention provides a method for preparing high-density aluminum alloy reverse extrusion molded aluminum tubes, the method comprising the following steps: S1: Material cutting: Select 6082 aluminum alloy bars of a certain specification; further, select 6082 aluminum alloy bars and cut them with a saw according to the required aluminum tube specifications. After cutting, grind the end face to remove burrs and oxide scale to ensure that the end face is flat. The diameter of the bar is 5-8mm larger than the outer diameter of the final aluminum tube, and the length is 10-15mm larger than the length of the final aluminum tube, leaving room for subsequent processing.

[0010] S2: Heat the 6082 aluminum alloy bar at 460-480℃; after the core temperature of the bar reaches the set temperature, hold it for 30-60 minutes. The holding time is calculated at 1 minute / mm according to the thickness of the bar to ensure that the core and surface temperature of the bar are uniform, fully softened, and plasticity is improved, laying the foundation for subsequent reverse extrusion molding.

[0011] S3: The 6082 aluminum alloy bar after heat treatment is subjected to reverse extrusion forming. The reverse extrusion forming temperature is 430-450℃ and the pressure is 800-1600 tons. Due to the lateral constraint of the die, the metal cannot flow to the side and is forced to flow in the upward direction of the punch (opposite to the direction of the press force). The inner wall of the billet is close to the outer surface of the punch and the outer wall is close to the inner wall of the die cavity, gradually forming an aluminum tube that conforms to the die size. After extrusion, the pressure is slowly released and the aluminum tube is taken out of the die to avoid deformation of the aluminum tube due to excessive pressure release.

[0012] S4: The 6082 aluminum tube after reverse extrusion molding is subjected to solution quenching and artificial aging treatments to obtain a high-density aluminum alloy reverse extrusion molded aluminum tube. (See process flow diagram for reference.) Figure 1 As shown.

[0013] This application achieves a synergistic effect through the heating at 460-480℃ in step S2 and the reverse extrusion forming in step S3. The heating temperature in S2 is near the upper limit of the hot working window for 6082 aluminum alloy. At this temperature, the material undergoes sufficient dynamic recovery, significantly reducing deformation resistance and preventing abnormal grain growth. This creates the premise for the limited extrusion pressure in step S3 to be efficiently converted into a densification driving force. During the reverse extrusion process in S3, the metal is subjected to strong triaxial compressive stress within the closed die cavity, while the die temperature is controlled at 430-450℃, which has a certain cooling effect on the deformed material. Since step S2 has already softened the material to a critical state, the high pressure applied in S3 is almost entirely used to close and weld microscopic defects such as pores and porosity inside the cast bar, rather than being consumed in overcoming the matrix strength. Through the synergy of steps S2 and S3, this application achieves a density of ≥99.8%, solving the core contradiction of difficulty in eliminating porosity under small deformation.

[0014] Optionally, in step S2, the temperature of the heat treatment is 465-475℃.

[0015] For example, in step S2, the temperature of the heat treatment can be any point value or a range between any two points from 460℃, 461℃, 462℃, 463℃, 464℃, 465℃, 466℃, 467℃, 468℃, 469℃, 470℃, 471℃, 472℃, 473℃, 474℃, 475℃, 476℃, 477℃, 478℃, 479℃, or 480℃.

[0016] Optionally, in step S2, the heating rate is 5-8℃ / min. For example, in step S2, the heating rate can be any point value or a range between any two points from 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, or 8℃ / min.

[0017] Optionally, in step S3, the reverse extrusion molding temperature is 435-445℃. For example, in step S3, the reverse extrusion molding temperature can be any point value or a range between any two points from 430℃, 432℃, 434℃, 436℃, 438℃, 440℃, 442℃, 444℃, 446℃, 448℃, or 450℃.

[0018] Optionally, in step S3, the reverse extrusion molding pressure is 900-1300 tons. For example, in step S3, the reverse extrusion molding pressure can be 800 tons, 820 tons, 840 tons, 860 tons, 880 tons, 900 tons, 920 tons, 940 tons, 960 tons, 980 tons, 1000 tons, 1020 tons, 1040 tons, 1060 tons, 1080 tons, 1100 tons, 1120 tons, 1140 tons, 1160 tons, 1180 tons, or 1200 tons. The value at any point or between any two points of 1220 tons, 1240 tons, 1260 tons, 1280 tons, 1300 tons, 1320 tons, 1340 tons, 1360 tons, 1380 tons, 1400 tons, 1420 tons, 1440 tons, 1460 tons, 1480 tons, 1500 tons, 1520 tons, 1540 tons, 1560 tons, 1580 tons, or 1600 tons.

[0019] Optionally, in step S3, during the reverse extrusion molding process, the reduction rate is 5-10 mm / s. For example, the reduction rate can be any value or a range between any two points from 5 mm / s, 5.5 mm / s, 6 mm / s, 6.5 mm / s, 7 mm / s, 7.5 mm / s, 8 mm / s, 8.5 mm / s, 9 mm / s, 9.5 mm / s, or 10 mm / s.

[0020] Optionally, in step S3, during the reverse extrusion molding process, the heat-treated 6082 aluminum alloy bar is placed into a closed mold cavity preheated to 150-200℃. The mold is made of 4Cr5MoSiV1 material and is quenched and tempered to achieve a hardness of HRC58-62.

[0021] Optionally, the mold cavity size is matched with the final aluminum tube size, with a machining allowance of 1-2mm.

[0022] Optionally, in step S4, the solution quenching temperature is 530-550℃, held for 1-1.5 hours, and then cooled by water quenching at a rate controlled at 20-30℃ / s. For example, the solution quenching temperature can be any point value or a range between any two points from 530℃, 532℃, 534℃, 536℃, 538℃, 540℃, 542℃, 544℃, 546℃, 548℃, or 550℃.

[0023] Optionally, during artificial aging treatment, the temperature is controlled at 170-180℃ and held for 8-10 hours. For example, during artificial aging treatment, the temperature can be any point value or a range between any two points from 170℃, 172℃, 174℃, 176℃, 178℃, or 180℃.

[0024] Optionally, step S4 is also included: fixing the artificially aged aluminum tube onto a lathe fixture, using a diamond cutting tool to turn the inner and outer diameters of the aluminum tube, removing surface oxide scale, pits and other defects, controlling the turning allowance to be 0.8-1.2mm, the turning speed to be 800-1000r / min, and the feed rate to be 0.1-0.2mm / r. After turning, the end face of the aluminum tube is trimmed to ensure that the dimensional accuracy of the aluminum tube meets the design requirements, and finally obtaining a high-density, high-precision 6082 aluminum alloy tube blank.

[0025] Optionally, in the 6082 aluminum alloy bar stock, by mass fraction, the Mg content is 0.6-1.2%, the Si content is 0.7-1.3%, the Fe content is ≤0.5%, the Cu content is ≤0.1%, the Mn content is 0.4-1.0%, and the remainder is Al.

[0026] Compared with the prior art, the present invention achieves at least one of the following beneficial effects: (1) By optimizing the reverse extrusion process parameters and combining the material properties of 6082 aluminum alloy, the present invention controls the heating temperature, extrusion pressure and pressing rate to make the aluminum tube dense with a grain size of 6-7. The grains are fine and uniform, without defects such as pores and inclusions, and the density is ≥99.8%, which is significantly better than aluminum tubes prepared by existing ordinary extrusion and casting processes.

[0027] (2) After the reverse extrusion molding of the present invention, the size of the aluminum tube blank is close to the size of the product, and the subsequent machining allowance is only 1-2mm, which greatly reduces the amount of machining work, improves the material utilization rate, and reduces the production cost.

[0028] (3) The present invention adopts the T6 heat treatment process of "solution quenching + artificial aging" after reverse extrusion, and strictly controls the heat treatment parameters and process connection time, so that the tensile strength of the aluminum tube is increased to 290-330MPa, the yield strength reaches more than 240MPa, and the hardness reaches HB90-100. At the same time, the internal stress is effectively eliminated, and deformation is avoided in the subsequent machining process.

[0029] (4) The process steps of the present invention are simple, and mass production can be realized. It is suitable for the blank preparation needs of high-performance structural parts such as bearing cages, and has strong practicality and broad application prospects. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 An exemplary embodiment of the process flow diagram for high-density aluminum alloy reverse extrusion forming of aluminum tubes according to the present invention is shown. Detailed Implementation

[0031] To more clearly illustrate the overall concept of the present invention, a detailed description will be provided below with reference to the accompanying drawings and examples.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0033] Example 1 In an exemplary embodiment of the present invention, the method for preparing a high-density aluminum alloy reverse extrusion formed aluminum tube includes the following steps: S1: Select 6082 aluminum alloy bar stock, cut it with a saw according to the required aluminum tube specifications, and grind the end face after cutting to remove burrs and oxide scale to ensure that the end face is flat. The diameter of the bar stock is 6mm larger than the outer diameter of the final aluminum tube, and the length is 13mm larger than the length of the final aluminum tube, leaving room for subsequent processing.

[0034] S2: Place the cut 6082 aluminum alloy bar into a resistance furnace for heating. The heating temperature is controlled at 470℃ and the heating rate is 6℃ / min. When the core temperature of the bar reaches the set temperature, hold it for 40 minutes. The holding time is calculated at 1min / mm based on the bar thickness to ensure that the core and surface temperature of the bar are uniform, fully softened, and plasticity is improved, laying the foundation for subsequent reverse extrusion molding.

[0035] S3: Quickly remove the heated aluminum rod and place it into a closed mold cavity preheated to 440℃. The mold is made of 4Cr5MoSiV1 material, which has been quenched and tempered to achieve a hardness of HRC60. The mold cavity size matches the final aluminum tube size, with a 1.0mm machining allowance. Start the press and apply axial pressure, controlling the pressure at 900 tons and the pressing rate at 7mm / s. After extrusion, slowly release the pressure and remove the aluminum tube from the mold to avoid deformation of the aluminum tube due to excessive pressure release.

[0036] S4: Immediately after reverse extrusion (≤15s after pressure relief and removal), transfer the aluminum tube to a quenching device for solution quenching. The solution temperature is controlled at 540℃ and held for 1.2 hours. Then, water quenching is used for cooling at a rate of 25℃ / s to obtain a supersaturated solid solution. After solution quenching, the aluminum tube is placed in an aging furnace for artificial aging treatment at a temperature of 175℃ and held for 9 hours. Then, it is cooled to room temperature in the furnace to achieve the T6 state, which significantly improves the strength and hardness of the aluminum tube and eliminates the internal stress generated during reverse extrusion.

[0037] S5: Fix the heat-treated aluminum tube on the lathe fixture, and use a diamond turning tool to turn the inner and outer circles of the aluminum tube to remove the oxide scale, pits and other defects on the surface. The turning allowance is controlled at 1.0 mm, the turning speed is 900 r / min and the feed rate is 0.1 mm / r. After turning, the end face of the aluminum tube is trimmed to ensure that the dimensional accuracy of the aluminum tube meets the design requirements, and finally a high-density and high-precision 6082 aluminum alloy tube blank is obtained.

[0038] Example 2 In an exemplary embodiment of the present invention, the method for preparing a high-density aluminum alloy reverse extrusion formed aluminum tube includes the following steps: S1: Select 6082 aluminum alloy bar stock, cut it with a saw according to the required aluminum tube specifications, and grind the end face after cutting to remove burrs and oxide scale to ensure that the end face is flat. The diameter of the bar stock is 5mm larger than the outer diameter of the final aluminum tube, and the length is 10mm larger than the length of the final aluminum tube, leaving room for subsequent processing.

[0039] S2: Place the cut 6082 aluminum alloy bar into a resistance furnace for heating. The heating temperature is controlled at 460℃ and the heating rate is 5℃ / min. When the core temperature of the bar reaches the set temperature, hold it for 50 minutes. The holding time is calculated at 1min / mm based on the bar thickness to ensure that the core and surface temperature of the bar are uniform, fully softened, and plasticity is improved, laying the foundation for subsequent reverse extrusion molding.

[0040] S3: Quickly remove the heated aluminum rod and place it into a closed mold cavity preheated to 430℃. The mold is made of 4Cr5MoSiV1 material, which has been quenched and tempered to achieve a hardness of HRC58. The mold cavity size matches the final aluminum tube size, with a machining allowance of 0.8mm. Start the press and apply axial pressure, controlling the pressure at 800 tons and the pressing rate at 5mm / s. After extrusion, slowly release the pressure and remove the aluminum tube from the mold to avoid deformation of the aluminum tube due to excessive pressure release.

[0041] S4: Immediately after reverse extrusion (≤15s after pressure relief and removal), transfer the aluminum tube to a quenching device for solution quenching. The solution temperature is controlled at 530℃ and held for 1.2 hours. Then, water quenching is used for cooling at a rate of 20℃ / s to obtain a supersaturated solid solution. After solution quenching, the aluminum tube is placed in an aging furnace for artificial aging treatment at a temperature of 170℃ and held for 9 hours. Then, it is cooled to room temperature in the furnace to achieve the T6 state, which significantly improves the strength and hardness of the aluminum tube and eliminates the internal stress generated during reverse extrusion.

[0042] S5: Fix the heat-treated aluminum tube on the lathe fixture, and use a diamond turning tool to turn the inner and outer circles of the aluminum tube to remove the oxide scale, pits and other defects on the surface. The turning allowance is controlled within 1mm, the turning speed is 800r / min and the feed rate is 0.1mm / r. After turning, the end face of the aluminum tube is trimmed to ensure that the dimensional accuracy of the aluminum tube meets the design requirements, and finally a high-density and high-precision 6082 aluminum alloy tube blank is obtained.

[0043] Example 3 In an exemplary embodiment of the present invention, the method for preparing a high-density aluminum alloy reverse extrusion formed aluminum tube includes the following steps: S1: Select 6082 aluminum alloy bar stock, cut it with a saw according to the required aluminum tube specifications, grind the end face after cutting to remove burrs and oxide scale, and ensure that the end face is flat. The diameter of the bar stock is 8mm larger than the outer diameter of the final aluminum tube, and the length is 15mm larger than the length of the final aluminum tube, leaving room for subsequent processing.

[0044] S2: Place the cut 6082 aluminum alloy bar into a resistance furnace for heating. The heating temperature is controlled at 480℃ and the heating rate is 8℃ / min. When the core temperature of the bar reaches the set temperature, hold it for 50 minutes. The holding time is calculated at 1min / mm based on the bar thickness to ensure that the core and surface temperature of the bar are uniform, fully softened, and plasticity is improved, laying the foundation for subsequent reverse extrusion molding.

[0045] S3: Quickly remove the heated aluminum rod and place it into a closed mold cavity preheated to 450℃. The mold is made of 4Cr5MoSiV1 material, which has been quenched and tempered to achieve a hardness of HRC62. The mold cavity size matches the final aluminum tube size, with a machining allowance of 0.8mm. Start the press and apply axial pressure, controlling the pressure at 1200 tons and the pressing rate at 10mm / s. After extrusion, slowly release the pressure and remove the aluminum tube from the mold to avoid deformation of the aluminum tube due to excessive pressure release.

[0046] S4: Immediately after reverse extrusion (≤15s after pressure relief and removal), transfer the aluminum tube to a quenching device for solution quenching. The solution temperature is controlled at 550℃ and held for 1.2 hours. Then, water quenching is used for cooling at a rate of 30℃ / s to obtain a supersaturated solid solution. After solution quenching, the aluminum tube is placed in an aging furnace for artificial aging treatment. The aging temperature is controlled at 180℃ and held for 9 hours. Then, it is cooled to room temperature with the furnace to bring the aluminum tube to the T6 state, which significantly improves the strength and hardness of the aluminum tube and eliminates the internal stress generated during the reverse extrusion process.

[0047] S5: Fix the heat-treated aluminum tube on the lathe fixture, and use a diamond turning tool to turn the inner and outer circles of the aluminum tube to remove the oxide scale, pits and other defects on the surface. The turning allowance is controlled at 1mm, the turning speed is 1000r / min and the feed rate is 0.1mm / r. After turning, the end face of the aluminum tube is trimmed to ensure that the dimensional accuracy of the aluminum tube meets the design requirements, and finally a high-density and high-precision 6082 aluminum alloy tube blank is obtained.

[0048] Example 4 In an exemplary embodiment of the present invention, the method for preparing a high-density aluminum alloy reverse extrusion formed aluminum tube includes the following steps: S1: Select 6082 aluminum alloy bar stock, cut it with a saw according to the required aluminum tube specifications, and grind the end face after cutting to remove burrs and oxide scale to ensure that the end face is flat. The diameter of the bar stock is 6mm larger than the outer diameter of the final aluminum tube, and the length is 13mm larger than the length of the final aluminum tube, leaving room for subsequent processing.

[0049] S2: Place the cut 6082 aluminum alloy bar into a resistance furnace for heating. The heating temperature is controlled at 465℃ and the heating rate is 6℃ / min. When the core temperature of the bar reaches the set temperature, hold it for 40 minutes. The holding time is calculated at 1min / mm based on the bar thickness to ensure that the core and surface temperature of the bar are uniform, fully softened, and plasticity is improved, laying the foundation for subsequent reverse extrusion molding.

[0050] S3: Quickly remove the heated aluminum rod and place it into a closed mold cavity preheated to 440℃. The mold is made of 4Cr5MoSiV1 material, which has been quenched and tempered to achieve a hardness of HRC61. The mold cavity size matches the final aluminum tube size, with a 1.0mm machining allowance. Start the press and apply axial pressure, controlling the pressure at 850 tons and the pressing rate at 7mm / s. After extrusion, slowly release the pressure and remove the aluminum tube from the mold to avoid deformation of the aluminum tube due to excessive pressure release.

[0051] S4: Immediately after reverse extrusion (≤15s after pressure relief and removal), transfer the aluminum tube to a quenching device for solution quenching. The solution temperature is controlled at 535℃ and held for 1.2 hours. Then, water quenching is used for cooling at a rate of 25℃ / s to obtain a supersaturated solid solution. After solution quenching, the aluminum tube is placed in an aging furnace for artificial aging treatment at a temperature of 172℃ and held for 9 hours. Then, it is cooled to room temperature in the furnace to achieve the T6 state, which significantly improves the strength and hardness of the aluminum tube and eliminates the internal stress generated during the reverse extrusion process.

[0052] S5: Fix the heat-treated aluminum tube on the lathe fixture, and use a diamond turning tool to turn the inner and outer circles of the aluminum tube to remove the oxide scale, pits and other defects on the surface. The turning allowance is controlled at 1.0 mm, the turning speed is 900 r / min and the feed rate is 0.1 mm / r. After turning, the end face of the aluminum tube is trimmed to ensure that the dimensional accuracy of the aluminum tube meets the design requirements, and finally a high-density and high-precision 6082 aluminum alloy tube blank is obtained.

[0053] Example 5 In an exemplary embodiment of the present invention, the method for preparing a high-density aluminum alloy reverse extrusion formed aluminum tube includes the following steps: S1: Select 6082 aluminum alloy bar stock, cut it with a saw according to the required aluminum tube specifications, and grind the end face after cutting to remove burrs and oxide scale to ensure that the end face is flat. The diameter of the bar stock is 6mm larger than the outer diameter of the final aluminum tube, and the length is 13mm larger than the length of the final aluminum tube, leaving room for subsequent processing.

[0054] S2: Place the cut 6082 aluminum alloy bar into a resistance furnace for heating. The heating temperature is controlled at 475℃ and the heating rate is 6℃ / min. When the core temperature of the bar reaches the set temperature, hold it for 40 minutes. The holding time is calculated at 1min / mm based on the bar thickness to ensure that the core and surface temperature of the bar are uniform, fully softened, and plasticity is improved, laying the foundation for subsequent reverse extrusion molding.

[0055] S3: Quickly remove the heated aluminum rod and place it into a closed mold cavity preheated to 445℃. The mold is made of 4Cr5MoSiV1 material, which has been quenched and tempered to achieve a hardness of HRC62. The mold cavity size matches the final aluminum tube size, with a 1.0mm machining allowance. Start the press and apply axial pressure, controlling the pressure at 950 tons and the pressing rate at 7mm / s. After extrusion, slowly release the pressure and remove the aluminum tube from the mold to avoid deformation of the aluminum tube due to excessive pressure release.

[0056] S4: Immediately after the reverse extrusion, the aluminum tube (≤15s after depressurization and removal) is transferred to a quenching device for solution quenching. The solution temperature is controlled at 545℃ and held for 1.2h. Then, water quenching is used for cooling at a rate of 25℃ / s to obtain a supersaturated solid solution. After solution quenching, the aluminum tube is placed in an aging furnace for artificial aging treatment at a temperature of 178℃ and held for 9h. Then, it is cooled to room temperature with the furnace to bring the aluminum tube to the T6 state, which significantly improves the strength and hardness of the aluminum tube and eliminates the internal stress generated during the reverse extrusion process.

[0057] S5: Fix the heat-treated aluminum tube on the lathe fixture, and use a diamond turning tool to turn the inner and outer circles of the aluminum tube to remove the oxide scale, pits and other defects on the surface. The turning allowance is controlled at 1.0 mm, the turning speed is 900 r / min and the feed rate is 0.1 mm / r. After turning, the end face of the aluminum tube is trimmed to ensure that the dimensional accuracy of the aluminum tube meets the design requirements, and finally a high-density and high-precision 6082 aluminum alloy tube blank is obtained.

[0058] Comparative Example 1 The main difference from Example 1 is that in step S2, the heating temperature is 420°C. The other steps are the same as in Example 1.

[0059] Comparative Example 2 The main difference from Example 1 is that in step S2, the heating temperature is 520°C. The other steps are the same as in Example 1.

[0060] Comparative Example 3 The main difference from Example 1 is that, in step S3, the pressure of the reverse extrusion molding is 600 tons. The other steps are the same as in Example 1.

[0061] Comparative Example 4 The main difference from Example 1 is that, in step S3, the pressure of the reverse extrusion molding is 1800 tons. The other steps are the same as in Example 1.

[0062] Comparative Example 5 The main difference from Example 1 is that, in step S3, the mold temperature for reverse extrusion molding is 400°C. The other steps are the same as in Example 1.

[0063] Comparative Example 6 The main difference from Example 1 is that, in step S3, the mold temperature for reverse extrusion molding is 500°C. The other steps are the same as in Example 1.

[0064] Comparative Example 7 Based on Example 1, ordinary forward extrusion is used instead of S3 reverse extrusion.

[0065] Comparative Example 8 Based on Example 1, after heating in S2, S3 is not performed immediately. Instead, the sample is air-cooled to room temperature and then heated to 440°C for reverse extrusion treatment.

[0066] Test case The performance of the 6082 aluminum alloy tube blanks prepared in the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0067] Table 1

[0068] As shown in Table 1, the high-density aluminum alloy reverse extrusion formed aluminum tubes obtained by this application have fine and uniform grains, are free from defects such as pores and inclusions, have a density ≥99.8%, a grain size ≥6, a tensile strength ≥310MPa, a yield strength of ≥280MPa, and a hardness of HB90-100.

[0069] Furthermore, the residual stress of the aluminum tube prepared in this application is less than 30 MPa, which can effectively eliminate internal stress and avoid deformation during subsequent machining.

[0070] In Comparative Examples 1 and 2, in step S2, excessively high or low heating temperatures can lead to local grain coarsening and increased residual stress.

[0071] In Comparative Example 3, the density was insufficient when the pressure was below 800 tons. In Comparative Example 4, the pressure was too high, resulting in high density but also severe deformation, introducing excessive residual stress and potentially causing microcracks; the grains grew abnormally during solid solution treatment due to excessive deformation energy storage.

[0072] In Comparative Example 5, the excessively low mold temperature resulted in high residual stress and low density. In Comparative Example 6, the excessively high mold temperature led to grain coarsening.

[0073] In Comparative Example 7, the forward extrusion is dominated by tensile stress, which cannot effectively weld the pores, resulting in low density; uneven deformation and coarse grains (level 2-3); high residual stress and poor dimensional stability.

[0074] In Comparative Example 8, the delay led to the annihilation of high-temperature vacancies, with minimal impact on density and grain size, but a significant reduction in strength.

[0075] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage, characterized in that, The method for preparing the high-density aluminum alloy reverse-extruded aluminum tube with the cage includes the following steps: S1: Select 6082 aluminum alloy bars of a certain specification; S2: Heat-treat 6082 aluminum alloy bars at 460-480℃; S3: The 6082 aluminum alloy bar after heat treatment is subjected to reverse extrusion forming. The reverse extrusion forming temperature is 430-450℃ and the pressure is 800-1600 tons. S4: The 6082 aluminum tube after reverse extrusion molding is subjected to solution quenching and artificial aging treatment in sequence to obtain a high-density aluminum alloy reverse extrusion molded aluminum tube.

2. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S2, the heat treatment temperature is 465-475℃.

3. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S2, the heating rate is 5-8℃ / min.

4. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S3, the reverse extrusion molding temperature is 435-445℃.

5. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S3, the reverse extrusion molding process pressure is 900-1300 tons.

6. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S3, during the reverse extrusion molding process, the pressing rate is 5-10 mm / s.

7. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S3, during the reverse extrusion molding process, the heat-treated 6082 aluminum alloy bar is placed into a closed mold cavity that has been preheated to 150-200℃. The mold is made of 4Cr5MoSiV1 material and has been quenched and tempered to achieve a hardness of HRC58-62.

8. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 7, characterized in that, The mold cavity size matches the final aluminum tube size, with a machining allowance of 1-2mm.

9. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, In step S4, the solution quenching temperature is 530-550℃, and the temperature is held for 1-1.5h. Then, it is cooled by water quenching, and the cooling rate is controlled at 20-30℃ / s. When performing artificial aging treatment, the temperature should be controlled at 170-180℃ and kept at that temperature for 8-10 hours.

10. The method for preparing a high-density aluminum alloy reverse-extruded aluminum tube with a cage according to claim 1, characterized in that, High-density aluminum alloy reverse extrusion formed aluminum tubes have a density ≥99.8% and a grain size of 6-7.

Images