A multi-pass spinning method for improving the strength of high-strength aluminum alloy large-diameter thin-walled tubes

Abstract

The present invention relates to the field of metal material plastic processing technology and discloses a multi-pass spinning method for improving the strength of high-strength aluminum alloy large-diameter thin-walled tubes. The method comprises: thinning and spinning an aluminum alloy tube blank, then performing a recrystallization annealing at 400-450°C, water quenching the tube to room temperature after holding, and repeating the thinning and spinning and recrystallization annealing steps 1-5 times; solution treating the thinned tube blank by first holding it in a heat treatment furnace at 500-540°C, then water quenching the tube to room temperature; installing the solutionized tube blank on a cylindrical mandrel and spinning it to reduce it to the desired wall thickness; and finally artificial aging the tube blank at 160-200°C for 2-4 hours. The present invention adopts a multi-pass spinning method to effectively improve the strength of the aluminum alloy large-diameter thin-walled tube and is suitable for various types of aluminum alloy large-diameter thin-walled tubes for aerospace applications.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic processing of metal materials, and in particular to a multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube. Background Art

[0002] With the growing demand for lightweight, high-strength materials in the aerospace and high-end manufacturing sectors, large-diameter, thin-walled tubing made of high-strength aluminum alloys has become an ideal structural material due to its light weight, high mechanical strength, and excellent corrosion resistance. This thin-walled tubing can effectively reduce component weight while maintaining load-bearing capacity, improving overall structural performance. However, due to the thin-walled, large-diameter, and high-strength requirements of these tubing structures, their production and manufacturing process present significant challenges, particularly in balancing strength and formability.

[0003] Compared with traditional casting, extrusion, coil welding and machining methods, the spinning process has significant advantages in manufacturing large-diameter, thin-walled high-strength aluminum alloy pipes. The casting method is prone to coarse grains and defects, resulting in poor mechanical properties; although coil welding is flexible, it is easy to introduce thermal defects in welding, which in turn affects service reliability; the extrusion process is limited by the scale of equipment and it is difficult to achieve the forming of large-diameter and extremely thin-walled components; and the machining method has a large waste of material and a long processing cycle. In contrast, the spinning process achieves material densification and homogenization through multiple plastic forming passes, avoiding welding defects, and can obtain excellent dimensional accuracy and surface quality under seamless forming, which is especially suitable for products with high strength and lightweight requirements.

[0004] However, the existing single-pass spinning method for manufacturing large-diameter, thin-walled aluminum alloy tubes has obvious deficiencies in improving component performance. Since single-pass spinning cannot effectively refine the grain structure inside the material, the grains of the tubes are usually large after solid solution, which makes it difficult for the mechanical properties of the material to reach the ideal level. In addition, the deformation generated during the single-pass spinning process is large, which can easily lead to stress concentration inside the material, resulting in microcracks and surface defects, further affecting the fatigue life and service reliability of the components. Single-pass spinning is difficult to fully improve the performance of the material and cannot meet the strict requirements of high strength and high toughness in fields such as aerospace. Therefore, there is an urgent need to develop a spinning forming method that can improve the strength of high-strength aluminum alloy large-diameter, thin-walled tubes. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-pass spinning method for improving the strength of large-diameter, thin-walled tubes of high-strength aluminum alloys, so as to improve the bearing capacity of such components and solve the problem of poor material formability under single-pass spinning. Different from the traditional T8 heat treatment process, the present invention induces recrystallization heterogeneity through a pre-treatment of multi-pass small deformation spinning-annealing, and couples the solution treatment to obtain a heterogeneous grain structure. After the solution treatment, a certain amount of deformation is introduced again through thinning spinning, and artificial aging is performed to further improve the strength of the component. The present invention promotes theoretical research on the spinning forming and manufacturing of large-diameter, thin-walled tubes of high-strength aluminum alloys, and lays a good foundation for practical applications.

[0006] To achieve the above object, the present invention provides a multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube, which comprises the following steps:

[0007] S1, Thinning Spinning

[0008] The aluminum alloy tube blank is mounted on a cylindrical core mold and then thinned and spun.

[0009] S2, recrystallization annealing

[0010] The thinned tube blank is placed in a heat treatment furnace, heated to 400-450°C at a rate of 10-20°C per minute, and kept warm for at least 30 minutes. The tube blank is then removed from the heat treatment furnace and cooled to room temperature by water quenching. The preferred holding time is 1-2 hours.

[0011] Repeat steps S1 and S2 for a total of T times, 1≤T≤5;

[0012] S3, solution treatment

[0013] The recrystallized annealed tube is placed in a heat treatment furnace and heated to 500-540°C at a rate of 10-20°C per minute. The temperature is then maintained for at least 30 minutes. The tube is then removed from the heat treatment furnace and cooled to room temperature by water quenching. The preferred holding time is 1-2 hours.

[0014] S4, Spinning

[0015] The solution treated tube blank is mounted on a cylindrical core die and then thinned and spun to reduce the tube blank to the required wall thickness.

[0016] S5. Artificial aging

[0017] The solution treated pipe blank is placed in an aging furnace, heated to 160-200°C at a rate of 10-20°C per minute, kept warm for 2-4 hours, and then the pipe blank is taken out of the aging furnace and air-cooled to room temperature.

[0018] The spinning thinning rate R relative to the initial tube blank thickness in step S1 and its repeated steps i The relationship with the total spinning thinning rate R is as follows:

[0019] R i =(RR L ) / T

[0020] Among them, R L It is the spinning thinning rate of the tube blank after solution treatment in step S4 relative to the initial tube blank thickness.

[0021] As a further preferred technical solution of the present invention, the pipe blank in step S1 can be manufactured by casting, extrusion, or plate coil welding, and its inner diameter r satisfies:

[0022] 150mm≤r≤3000mm.

[0023] As a further preferred technical solution of the present invention, in step S2, the inner diameter of the cylindrical core mold is consistent with that of the initial tube blank.

[0024] As a further preferred technical solution of the present invention, in step S2, before the tube blank is installed on the cylindrical core mold, lubricating oil is applied to the surface of the cylindrical core mold; before the ironing spinning begins, lubricating oil is applied to the outer surface of the tube blank.

[0025] As a further preferred technical solution of the present invention, in step S1 and its repeated steps, and in step S4, multi-pass spinning is used in the corresponding steps to achieve thinning, and the reduction amount of each pass is one-quarter to one-fifth of the total reduction amount of the step.

[0026] As a further preferred technical solution of the present invention, in step S1 and its repeated steps, and in step S4, lubricating oil is applied to the surface of the cylindrical core mold before the tube blank is installed on the cylindrical core mold; lubricating oil is applied to the outer surface of the tube blank before spinning begins.

[0027] As a further preferred technical solution of the present invention, in step S4, the spinning thinning rate R of the tube blank after solutionizing relative to the initial tube blank thickness is L satisfy:

[0028] 5%≤R L ≤15%.

[0029] As a further preferred technical solution of the present invention, in step S1 and its repeated steps, as well as in step S4, the spinning process adopts a double-conical spinning wheel.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The method of the present invention first performs spinning thinning and recrystallization annealing on the initial tube blank, and then repeats these two steps in sequence for multiple times. Spinning thinning introduces a certain amount of deformation into the material, and the deformation tends to concentrate at the grain boundaries, so that the dislocation density near the grain boundaries is high, while the dislocation density within the grains is low. During recrystallization annealing, crystallization occurs in the area near the grain boundaries, and no recrystallization occurs within the grains. After repeating these two steps multiple times, the material is transformed into a heterogeneous structure, with large grains and small grains coexisting, and the material strength can be effectively improved through back stress strengthening. After the solid solution is completed, the coarse second phase distributed in the matrix dissolves back into the aluminum matrix lattice to form a supersaturated solid solution, achieving solid solution strengthening of the material; at the same time, the dissolution of the coarse second phase in the matrix can inhibit damage, fracture and failure caused by cracking of the second phase during the deformation of the material. Subsequently, the final spinning pass is performed to introduce an appropriate amount of deformation to work-harden the material. When the solutionized material is heated and held at a relatively low temperature, the solute atoms in the supersaturated solid solution tend to precipitate as intermetallic compounds, forming a dispersed nano-strengthening phase that effectively enhances the strength of the aluminum alloy. Furthermore, the introduction of deformation provides interfacial energy for precipitation during subsequent artificial aging, and the introduction of dislocations provides pathways for the diffusion of solute atoms. Therefore, a final short-term artificial aging treatment further enhances the strength of the large-diameter, thin-walled tube through dispersion precipitation strengthening, thereby increasing the component's load-bearing capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 This is a schematic diagram of the multi-pass spinning process for the high-strength aluminum alloy large-diameter thin-walled tube of the present invention.

[0034] Figure 2 The graphs are comparative diagrams of engineering stress-engineering strain curves of the final pipe sampled along the axial direction after performing steps S1 and S2 2, 4, 6, and 8 times in Examples 1-4, respectively.

[0035] Figure 3 The cross-sectional structure of the solid solution state pipe obtained after the solid solution treatment in step (6) after implementing steps S1 and S2 twice in Example 1 is the same as that of the pipe obtained by direct solid solution treatment in the existing process based on the same process parameters in Comparative Example 1, which is perpendicular to the circumferential direction.

[0036] Figure 4 The pipe obtained by performing steps S1 and S2 twice in Example 1 and the pipe obtained in Comparative Example 1 were sampled along the axial direction respectively, and tensile mechanical properties were tested, and the engineering stress-engineering strain curves of the two were compared.

[0037] Figure 5After implementing steps S1 and S2 twice in Example 1, samples were taken from the pipe that completed all process steps and the pipe obtained in Comparative Example 2 along the axial direction, and tensile mechanical properties were tested. The engineering stress-engineering strain curves of the two were compared.

[0038] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Terms such as "upper," "lower," "left," "right," "center," and "one" used in the preferred embodiments are for ease of description and are not intended to limit the scope of the present invention. Changes or adjustments to these relative terms, without substantially altering the technical content, are also considered within the scope of the present invention.

[0040] The present invention provides a multi-pass spinning method for improving the strength of large-diameter, thin-walled tubes made of high-strength aluminum alloys. First, the initial tube blank is thinned by spinning to introduce unevenly distributed dislocations into the material, with a high dislocation density near the grain boundaries and a low density within the grains. Recrystallization annealing is then performed to allow recrystallization to occur at the grain boundaries, while the deformation within the grains is small and insufficient to provide the energy required for recrystallization, so no recrystallization occurs. Since the overall deformation is small, the degree of recrystallization at the grain boundaries is relatively limited. Therefore, the spinning-recrystallization annealing steps need to be repeated multiple times to produce a certain number of small recrystallized grains at the grain boundaries, forming a heterogeneous structure and producing a back stress strengthening effect. The annealed tube blank is then solution-quenched to dissolve the large-particle second phase dispersed in the structure into the aluminum matrix for solid solution strengthening. A final spinning pass with a smaller deformation is then performed to allow the large-diameter, thin-walled tube to reach the desired wall thickness, while introducing a certain amount of deformation into the final component for work hardening. Cold working introduces distortion energy into the material, and dislocations provide pathways for the diffusion of solute atoms. These factors promote the precipitation of strengthening phases during artificial aging, so only a short artificial aging period is required to complete precipitation strengthening. This method effectively improves the strength of high-strength aluminum alloy large-diameter thin-walled tubes.

[0041] The specific method is as follows:

[0042] The present invention provides a multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube, comprising the following steps:

[0043] (1) Preparation of tube blank

[0044] a. The pipe blank is made of heat-treatable aluminum alloy by casting, plate coiling or multi-pass hot extrusion.

[0045] (2) Thinning and spinning

[0046] a. Install the pipe described in (1) onto the cylindrical core mold. Apply lubricating oil to the core mold surface before installing the pipe. Apply lubricating oil to the outer surface of the pipe before each spinning process.

[0047] b. After the spindle reaches the set speed, the roller first feeds in the radial direction of the tube, and then feeds in the radial direction of the tube. The thinning rate within the step is 15% to 30% of the initial tube thickness, which is completed in multiple passes, with each pass reducing 10% to 20% of the total reduction in the step.

[0048] (3) Recrystallization annealing

[0049] a. Anneal the tube obtained in step (2) to allow the cold-spun material to recrystallize. Place the tube in a heat treatment furnace in a vertical manner, heat it to 400-450°C at a rate of 10-20°C per minute, and keep it at that temperature for 1-2 hours.

[0050] b. Take the tube billet in (3-a) out of the furnace, transfer it to the quenching pool within 3 seconds, and cool it to room temperature by water cooling.

[0051] (4) Repeat the thinning spinning-recrystallization annealing steps 1 to 5 times

[0052] (5) Solution treatment

[0053] a. The tube blank obtained in (4) is subjected to a solid solution treatment to dissolve the second phase in the material structure into the matrix. The tube blank is placed in a heat treatment furnace using a vertical method, and the temperature is raised to 535°C at a rate of 10-20°C per minute and kept at this temperature for 1-2 hours.

[0054] b. Take the tube billet in (4-a) out of the furnace, transfer it to the quenching pool within 3 seconds, and cool it to room temperature by water cooling.

[0055] (6) Spinning

[0056] a. Install the solid solution tube obtained in (5) on the cylindrical core mold with rib grooves within 30 minutes. Apply lubricating oil on the surface of the core mold before installing the tube. Apply lubricating oil on the outer surface of the tube blank before spinning begins.

[0057] After the spindle reaches the set speed, the roller first feeds radially along the tube blank, and then feeds radially along the tube blank. The wall thickness is thinned to the required thickness of the component in multiple passes, with each pass reducing 10% to 20% of the total reduction in that step.

[0058] (7) Artificial aging

[0059] a. Artificially age the tube blank described in (6). Place the tube blank in an aging furnace in a vertical manner, heat it to 160-200°C at a rate of 10-20°C per minute, and keep it at that temperature for 2-4 hours.

[0060] b. Take the tube blank in (2-a) out of the furnace and cool it to room temperature by air cooling.

[0061] The following provides a specific embodiment of a multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to the present invention.

[0062] Example 1

[0063] The present embodiment provides a method for processing 2219 aluminum alloy pipes using a multi-pass spinning process (eg Figure 1 As shown in the figure, the target pipe to be prepared has an inner diameter of 300 mm, a wall thickness of 3 mm, and a height of 300 mm. The specific processing process is:

[0064] (1) Preparation of tube blank

[0065] aThe volume of the pipe blank is calculated using the structural diagram of the large-diameter thin-walled pipe. According to the principle of constant volume during plastic forming and the principle of nearly uniform plastic deformation, the 2219 aluminum alloy hot extrusion forming pipe is selected with a size of 300 mm and a wall thickness of 10 mm. It is cut into pipe blanks with a height of 90 mm using a sawing machine.

[0066] (2) Thinning and spinning

[0067] a. Install a cylindrical core mold with an outer diameter of 300mm and a height of 400mm onto the main shaft of the twin-wheel spinning machine. Apply lubricating oil to its surface. Then, install the tube blank onto the cylindrical core mold and secure it with bolts. Apply lubricating oil to the outer surface of the tube blank before spinning begins. Align the cutters so that the starting position of the two spinning wheels is at the end of the tube blank away from the main shaft, with a distance of 20mm between the starting position and the top of the tube.

[0068] b. Set the spinning program. Each spinning pass begins with radial reduction of the tube. After reaching the preset reduction, the spinning wheel advances axially toward the spindle. The total radial reduction per side is 3 mm, completed in multiple passes, with each pass reducing 20% ​​of the total. After each spinning cycle, the remaining wall thickness is measured on the spindle using a π ruler. The spindle speed is 60 rpm. A double-tapered spinning wheel is used, with a rake angle of 22.5°, a clearance angle of 27.5°, a fillet radius of 10 mm, and a thickness of 43 mm. The spinning feed ratio is 1.5 mm / r. After spinning, the tube is removed from the mandrel.

[0069] (3) Recrystallization annealing

[0070] a. Place the tube billet vertically in the heat treatment furnace, close the furnace door, set the heating program, and heat it up to 450℃ at a heating rate of 20℃ per minute, and keep it at that temperature for 1 hour.

[0071] b. After the insulation is completed, open the furnace door and use tongs to transfer the tube to the quenching pool within 3 seconds and cool it to room temperature with water.

[0072] (4) Repeat the thinning spinning-recrystallization annealing step once (i.e., the total number of thinning spinning-recrystallization annealing steps is 2), so that the tube blank is thinned to a wall thickness of 4 mm.

[0073] (5) Solution treatment

[0074] a. Place the recrystallized annealed tube in a vertical position in a heat treatment furnace, close the furnace door, set the heating program, and heat it to 535°C at a heating rate of 20°C per minute and keep it at that temperature for 1 hour.

[0075] b. After the insulation is completed, open the furnace door and use tongs to transfer the tube to the quenching pool within 3 seconds and cool it to room temperature with water.

[0076] (6) Spinning

[0077] a. Install a cylindrical core mold with an outer diameter of 300mm and a height of 400mm onto the main shaft of the twin-wheel spinning machine. Apply lubricating oil to its surface. Then, install the tube blank onto the cylindrical core mold and secure it with bolts. Apply lubricating oil to the outer surface of the tube blank before spinning begins. Align the cutters so that the starting position of the two spinning wheels is at the end of the tube blank away from the main shaft, with a distance of 20mm between the starting position and the top of the tube.

[0078] b. Set the spinning program. Each spinning wheel first presses down radially on the tube. After reaching the preset reduction, it feeds the tube axially toward the spindle. The total radial reduction per side is 1 mm, completed in five passes. Each pass increases the reduction by 0.2 mm while the starting position of the wheel remains unchanged, with an initial reduction of 0.2 mm. The spindle speed is 60 rpm, and the same double-tapered wheel as in step (2-b) is used. The spinning feed ratio is 1.5 mm / r. After spinning is complete, remove the fixing bolts and remove the tube from the core die.

[0079] (7) Artificial aging

[0080] a. Place the tube billet vertically in the aging furnace, close the furnace door, set the heating program, and heat it to 175℃ at a heating rate of 20℃ per minute, and keep it at this temperature for 2 hours.

[0081] b. After the insulation is completed, open the furnace door, use tongs to take out the tube blank, and air cool it to room temperature.

[0082] Examples 2-4

[0083] Examples 2-4 all prepare the same target tube as Example 1 and use the same tube blank. The difference from Example 1 is that in the "thinning and spinning" process in step (2), the total amount of single-side reduction in the radial pass of the tube is 3 mm, 1.5 mm, 1 mm, and 0.75 mm, respectively; and in step (4), the number of repeated thinning and spinning-recrystallization annealing is 3, 5, and 7 times, respectively (that is, the total number of thinning and spinning-recrystallization annealing is 4, 6, and 8).

[0084] For the above examples 1-4, after the aging period, tensile specimens were cut from the pipe along the axial direction to conduct tensile mechanical property tests and their strengths were compared (e.g. Figure 2 As shown in the figure, it can be seen that when the number of repetitions T ≤ 5, the tube strength increases with the number of repetitions. However, multiple repetitions of the thinning spinning-recrystallization annealing steps increase the process complexity, so the total number of times these two steps are performed is preferably between 2 and 6.

[0085] Comparative Example 1

[0086] As a comparative experiment of Example 1, the only difference is that: (2) thinning spinning, (3) recrystallization annealing and (4) repetition steps are omitted; the total amount of single-side reduction in the radial pass in step (6-b) is changed from 1 mm to 7 mm, and the rest of the process is consistent with Example 1.

[0087] The cross-sectional structure of the solid solution state pipe obtained after the solid solution treatment in step (6) of Example 1 is compared with the cross-sectional structure of the pipe obtained by direct solid solution treatment based on the existing process with the same process parameters in Comparative Example 1 (e.g. Figure 3 As shown in Figure 1, it can be seen that the solid solution pipe obtained in Comparative Example 1 has a very coarse structure, while the solid solution pipe obtained in Example 1 has a significant refinement effect and forms a heterogeneous structure. Samples were taken from the final pipes obtained in Example 1 and Comparative Example 1 along the axial direction, and tensile mechanical properties were tested to compare the tensile mechanical properties of the two (as shown in Figure 1). Figure 4 The above results show that the process of Example 1 successfully introduced heterogeneous structures into the high-strength aluminum alloy tube and significantly improved the strength of the final component.

[0088] Comparative Example 2

[0089] As a comparative experiment of Example 1, the only difference is that the artificial aging step (7) is omitted and the thinning spinning-recrystallization annealing step is repeated only once, and the rest of the process remains the same as Example 1.

[0090] Samples were taken from the final pipes obtained from Example 1 and Comparative Example 2 along the axial direction, and tensile mechanical properties were tested to compare the tensile mechanical properties of the two (e.g. Figure 5 The above results show that artificial aging can effectively improve the strength of the material.

[0091] In the present invention, excessively high or low temperatures during solution treatment are detrimental. For example, a solution temperature of 550°C can cause overheating, while temperatures below 490°C can affect the solution rate and final workpiece properties. Extensive experimental testing has shown that a solution temperature of 535°C is optimal. Artificial aging with temperatures that are too high or too low is also detrimental. For example, aging temperatures above 200°C can cause rapid coarsening of the precipitated phase in the material, resulting in a decrease in strength. However, aging temperatures below 160°C make it difficult for the strengthening phase to precipitate.

[0092] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube, characterized in that: The following steps are involved: S1, Thinning Spinning The aluminum alloy tube blank is mounted on a cylindrical core mold and then thinned and spun; S2, recrystallization annealing Place the thinned tube blank in a heat treatment furnace, heat it to 400-450°C at a rate of 10-20°C per minute, and keep it warm for at least 30 minutes. Then take the tube blank out of the heat treatment furnace and cool it to room temperature by water quenching. Repeat steps S1 and S2 for Second-rate, ; S3, solution treatment Repeat steps S1 and S2 for The finished pipe blank is placed in a heat treatment furnace and heated to 500-540°C at a rate of 10-20°C per minute. The temperature is kept at this temperature for at least 30 minutes. The pipe blank is then taken out of the heat treatment furnace and cooled to room temperature by water quenching. S4, Spinning The solution treated tube blank is mounted on a cylindrical core die and then thinned and spun to reduce the tube blank to the required thickness. S5. Artificial aging Place the solution treated pipe blank in an aging furnace, heat it to 160-200°C at a rate of 10-20°C per minute, and keep it at that temperature for 2-4 hours. Then take the pipe blank out of the aging furnace and air cool it to room temperature. In the above step S1 and its repeated steps, the spinning thinning rate relative to the initial tube blank thickness is Total thinning rate of spinning The following relationship is satisfied: ； in, It is the spinning thinning rate of the tube blank after solution treatment in step S4 relative to the initial tube blank thickness.

2. A multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to claim 1, characterized in that: The pipe blank in step S1 can be manufactured by casting, extrusion, or plate welding. satisfy: 。 3. The multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to claim 1, characterized in that: In step S2, the inner diameter of the cylindrical core mold is consistent with the inner diameter of the initial tube blank.

4. The multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to claim 1, characterized in that: In step S2, before the tube blank is mounted on the cylindrical core mold, lubricating oil is applied to the surface of the cylindrical core mold; before the ironing spinning begins, lubricating oil is applied to the outer surface of the tube blank.

5. The multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to claim 1, characterized in that: In step S1 and its repeated steps, and in step S4, multi-pass spinning is used in the corresponding steps to achieve thinning, and the reduction amount of each pass is one-quarter to one-fifth of the total reduction amount of the corresponding step.

6. The multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to claim 1, characterized in that: In step S1 and its repeated steps, and in step S4, before the tube blank is mounted on the cylindrical core mold, lubricating oil is applied to the surface of the cylindrical core mold; before spinning begins, lubricating oil is applied to the outer surface of the tube blank.

7. The multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to claim 1, characterized in that: In step S4, the spinning thinning rate of the tube blank after solutionizing relative to the initial tube blank thickness is satisfy: 。 8. A multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled tube according to any one of claims 1 to 7, characterized in that: In step S1 and its repeated steps, as well as in step S4, the spinning process adopts a double-conical spinning wheel.

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