Multi-pass spinning method for improving strength of high-strength aluminum alloy large-diameter thin-walled pipe

Abstract

The invention relates to the technical field of metal material plastic processing, and discloses a multi-pass spinning method for improving the strength of a high-strength aluminum alloy large-diameter thin-walled pipe, which comprises the following steps: carrying out thinning spinning on a pipe blank made of an aluminum alloy material, then carrying out recrystallization annealing at 400-450 DEG C, carrying out water quenching and cooling to the room temperature after heat preservation is finished, and carrying out heat preservation to obtain the high-strength aluminum alloy large-diameter thin-walled pipe. The thinning spinning step and the recrystallization annealing step are repeated for 1-5 times in total; carrying out solution treatment on the thinned pipe blank, firstly placing the pipe blank in a heat treatment furnace for heat preservation at 500-540 DEG C, and then carrying out water quenching and cooling to room temperature; the pipe blank obtained after solid solution is installed on a cylindrical core mold, then spinning is conducted, and the pipe blank is thinned to the needed wall thickness; and finally, carrying out artificial aging at 160-200 DEG C for 2-4 hours. The multi-pass spinning method is adopted, the strength of the aluminum alloy large-diameter thin-wall pipe is effectively improved, and the method is suitable for various aluminum alloy large-diameter thin-wall pipes in aerospace.

Description

Technical Field

[0001] The 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 fields, large-diameter thin-walled tubes made of high-strength aluminum alloys have become one of the ideal structural materials due to their light weight, high mechanical strength and excellent corrosion resistance. This thin-walled tube can effectively reduce the weight of components and improve the performance of the overall structure while ensuring the load-bearing capacity. However, since the tube structure requires the characteristics of thin walls, large diameters and high strength, its production and manufacturing process faces great challenges, especially in the balance between improving strength and ensuring formability.

[0003] Compared with traditional casting, extrusion, coil welding and machining methods, the spinning process has significant advantages in manufacturing high-strength aluminum alloy large-diameter thin-walled pipes. The casting method is prone to cause coarse grains and defects, resulting in poor mechanical properties; although coil welding is flexible, it is easy to introduce thermal defects during 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 materials and a long processing cycle. In contrast, the spinning process achieves material densification and homogenization through multiple plastic forming processes, avoids 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 manufacturing method for 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 tube are usually large after solid solution, which makes it difficult for the mechanical properties of the material to reach an 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 component. Single-pass spinning is difficult to fully improve the material performance and cannot meet the strict requirements of high strength and high toughness in fields such as aerospace. Therefore, it is urgent to develop a spinning forming method that can improve the strength of large-diameter, thin-walled high-strength aluminum alloy 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 and 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 taken out of 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 billet is placed in a heat treatment furnace, heated to 500-540°C at a rate of 10-20°C per minute, and kept warm for at least 30 minutes, then the tube billet is taken out of the heat treatment furnace and cooled to room temperature by water quenching, wherein 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 reduction ratio R in step S1 and its repeated steps relative to the initial tube blank thickness i The total thinning rate R of spinning satisfies the following relationship:

[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 tube blank in step S1 can be manufactured by casting, extrusion, or plate coiling, 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 the inner diameter 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 thinning 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, and 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 spin thinning and recrystallization annealing on the initial tube blank, and then repeats these two steps in sequence for multiple times. Spin thinning introduces a certain amount of deformation into the material, and the deformation is easily concentrated at the grain boundary, so that the dislocation density near the grain boundary is high, while the dislocation density within the grain is low. During recrystallization annealing, crystallization occurs in the area close to the grain boundary, and no recrystallization occurs within the grain. 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 the damage, fracture and failure caused by the 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 material after solid solution is heated and kept at a low temperature, the solute atoms in the supersaturated solid solution tend to precipitate in the form of intermetallic compounds, forming a dispersed nano-strengthening phase, which can effectively improve the strength of the aluminum alloy. In addition, the introduction of deformation provides the interface energy for precipitation for subsequent artificial aging, and the introduction of dislocations provides a channel for the diffusion of solute atoms. Therefore, finally through short-term artificial aging treatment, the strength of the large-diameter thin-walled tube is further improved through dispersion precipitation strengthening, thereby improving the bearing capacity of the component. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0034] Figure 2 The engineering stress-engineering strain curve comparison diagram of the final pipe sampled along the axial direction in Examples 1-4 in which steps S1 and S2 are respectively implemented 2, 4, 6, and 8 times.

[0035] Figure 3 The cross-sectional structure of the tube perpendicular to the circumferential direction is obtained by directly solutionizing the tube using the existing process with the same process parameters as in Comparative Example 1 after implementing steps S1 and S2 twice in total in Example 1 and then obtaining the solid solution tube after the solid solution treatment in step (6).

[0036] Figure 4 The final tube obtained by performing steps S1 and S2 twice in Example 1 and the tube 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 in Example 1 twice, the pipe that completed all the process steps and the pipe obtained in Comparative Example 2 were sampled along the axial direction, and tensile mechanical properties were tested, and 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 in conjunction with the embodiments. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The terms such as "upper", "lower", "left", "right", "middle" and "one" cited in the preferred embodiments are only for the convenience of description, and are not used to limit the scope of the present invention. The change or adjustment of the relative relationship shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0040] The present invention provides a multi-pass spinning method for improving the strength of a large-diameter, thin-walled tube of a high-strength aluminum alloy. 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 boundary and a low density inside the grain. Subsequently, recrystallization annealing is performed to allow recrystallization to occur at the grain boundary, while the deformation inside the grain is small and insufficient to provide the energy required for recrystallization, so that no recrystallization occurs. Since the overall deformation is small and the degree of recrystallization at the grain boundary is relatively limited, it is necessary to repeat the spinning-recrystallization annealing steps multiple times to produce a certain number of small recrystallized grains at the grain boundary to form a heterogeneous structure and produce a back stress strengthening effect. Subsequently, the annealed tube blank is solution-quenched to dissolve the large-particle second phase dispersed in the structure into the aluminum matrix for solution strengthening. Then, a final spinning with a smaller deformation is 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 dislocation energy provides a channel for the diffusion of solute atoms. These factors can promote the precipitation of strengthening phases during artificial aging. Therefore, 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 material is a tube blank of heat-treatable aluminum alloy prepared by casting or plate coil welding or multi-pass hot extrusion.

[0045] (2) Thinning Spinning

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

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

[0048] (3) Recrystallization annealing

[0049] a. Annealing the tube obtained in (2) to allow the cold-spun material to recrystallize. The tube is placed in a heat treatment furnace in a vertical manner, heated to 400-450°C at a rate of 10-20°C per minute, and kept at this temperature for 1-2 hours.

[0050] b. Take the tube 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. subjecting the tube blank obtained in (4) to a solid solution treatment so that the second phase in the material structure is dissolved into the matrix. The tube blank is placed in a heat treatment furnace in a vertical manner, 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) onto a cylindrical mandrel with rib grooves within 30 minutes. Apply lubricating oil to the surface of the mandrel before installing the tube. Apply lubricating oil to the outer surface of the tube blank before spinning.

[0057] b 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 reduced to the required thickness of the component, which is completed in multiple passes, with each pass reducing 10% to 20% of the total reduction in this step.

[0058] (7) Artificial aging

[0059] a. Perform artificial aging on the tube blank described in (6). The tube blank is placed in an aging furnace in a vertical manner, and the temperature is raised to 160-200°C at a rate of 10-20°C per minute, and kept at this 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 method for processing 2219 aluminum alloy tubes using a multi-pass spinning process provided in this embodiment (such as Figure 1 As shown), the target pipe is prepared with 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] a The 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 in 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 by a sawing machine.

[0066] (2) Thinning Spinning

[0067] a. Install the cylindrical core mold with an outer diameter of 300mm and a height of 400mm on the main shaft of the double-wheel spinning machine, then apply lubricating oil on its surface, and then install the tube blank on the cylindrical core mold, fix it with bolts, and apply lubricating oil on the outer surface of the tube blank before spinning. Set the tool so that the starting position of the spinning wheels on both sides is located at a section of the tube blank away from the main shaft, and the distance between the starting position and the top of the tube is 20mm.

[0068] b Set the spinning program. In each pass, the spinning wheel first presses down along the radial direction of the tube. After reaching the preset pressing amount, it feeds along the axial direction of the tube toward the spindle. The total amount of single-side pressing in the radial pass of the tube is 3mm, which is completed in multiple passes. The pressing amount in each pass is 20% of the total pressing amount in the pass. After each spinning is completed, the remaining wall thickness of the tube is measured on the spindle using a π ruler; the spindle speed is 60r / min, and a double-conical spinning wheel is used, with a front angle of 22.5°, a back angle of 27.5°, a fillet radius of R10 mm, and a thickness of 43mm; the spinning feed ratio is 1.5mm / r. After spinning, the tube is unloaded from the core mold.

[0069] (3) Recrystallization annealing

[0070] a. Place the tube blank in a heat treatment furnace vertically and close the furnace door. Set the heating program to increase the temperature to 450°C at a heating rate of 20°C per minute and keep it at this temperature for 1 hour.

[0071] b. After the insulation is completed, open the furnace door, 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 is 2), so that the tube blank is thinned to a wall thickness of 4 mm.

[0073] (5) Solution treatment

[0074] a. Place the recrystallization annealed tube in a heat treatment furnace in a vertical manner and close the furnace door. Set the heating program to heat the tube to 535°C at a heating rate of 20°C per minute and keep it at this temperature for 1 hour.

[0075] b. After the insulation is completed, open the furnace door, 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 the cylindrical core mold with an outer diameter of 300mm and a height of 400mm on the main shaft of the double-wheel spinning machine, then apply lubricating oil on its surface, and then install the tube blank on the cylindrical core mold, fix it with bolts, and apply lubricating oil on the outer surface of the tube blank before spinning. Set the tool so that the starting position of the spinning wheels on both sides is located at a section of the tube blank away from the main shaft, and the distance between the starting position and the top of the tube is 20mm.

[0078] b Set the spinning program. In each pass, the spinning wheel first presses down along the radial direction of the tube. After reaching the preset pressing amount, it feeds along the axial direction of the tube toward the spindle. The total single-sided pressing amount in the radial pass is 1mm, which is completed in five passes. The starting position of the spinning wheel remains unchanged and the pressing amount increases by 0.2mm in each pass. The initial pressing amount is 0.2mm. The spindle speed is 60r / min, and the same double-conical spinning wheel as in step (2-b) is used. The spinning feed ratio is 1.5mm / r. After spinning, remove the fixing bolts and remove the tube from the core mold.

[0079] (7) Artificial aging

[0080] a. Place the tube billet in the aging furnace vertically and close the furnace door. Set the heating program to increase the temperature to 175°C at a heating rate of 20°C 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, and air cool it to room temperature.

[0082] Embodiment 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 of 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; the number of repeated thinning and spinning-recrystallization annealing in step (4) 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-mentioned Examples 1-4, after the aging period, tensile specimens were cut from the tube along the axial direction to conduct tensile mechanical property tests, and their strengths were compared (e.g. Figure 2 As shown in FIG. 5 , it can be seen that when the number of repetitions T≤5, the strength of the tube increases with the number of repetitions. However, multiple repetitions of the thinning spinning-recrystallization annealing steps will increase the complexity of the process, so the total number of implementations of these two steps is preferably between 2 and 6 times.

[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-sided 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 microstructure of the solid solution tube obtained after the solid solution treatment in step (6) of Example 1 is compared with that of the tube 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 the figure, it can be seen that the solid solution tube obtained in comparative example 1 has a very coarse structure, while the solid solution tube obtained in example 1 has a significant refinement effect and forms a heterogeneous structure. Samples were taken from the tubes finally 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 the figure). Figure 4 The above results show that the process method of Example 1 successfully introduces heterogeneous structures into the high-strength aluminum alloy tube and significantly improves the strength of the final component.

[0088] Comparative Example 2

[0089] As a comparative experiment of Example 1, the only difference is that step (7) artificial aging is omitted and the thinning spinning-recrystallization annealing step is only repeated once, and the rest of the process is consistent with 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. The tensile mechanical properties of the two were compared (eg Figure 5 The above results show that artificial aging strengthening can effectively improve the strength of the material.

[0091] In the present invention, it is disadvantageous if the temperature in the solution treatment is too high or too low. For example, if the solution temperature reaches 550°C, overburning will occur, and if it is below 490°C, the solution rate and the final workpiece performance will be affected. After a large number of experimental tests, the solution temperature is best at 535°C. It is disadvantageous if the temperature in artificial aging is too high or too low. For example, when the aging temperature is higher than 200°C, the precipitated phase in the material will coarsen rapidly, causing a decrease in strength; and when the aging temperature is lower than 160°C, the strengthening phase is difficult 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 and spinning The aluminum alloy tube blank is mounted on a cylindrical core mold and then thinned and spun; S2, recrystallization annealing 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 taken out of the heat treatment furnace and cooled to room temperature by water quenching. Repeat steps S1 and S2 for a total of T times, 1≤T≤5; S3. Solution treatment The tube blank after repeating steps S1 and S2 for a total of T times is placed in a heat treatment furnace, and the temperature is raised to 500-540° C. at a rate of 10-20° C. per minute, and the temperature is kept at that temperature for at least 30 minutes, and then the tube blank is 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 mold, and then thinned and spun to reduce the tube blank to a desired thickness; S5. Artificial aging The solution treated tube blank is placed in an aging furnace, heated to 160-200°C at a rate of 10-20°C per minute, kept at this temperature for 2-4 hours, and then the tube blank is taken out of the aging furnace and air-cooled to room temperature; In the above step S1 and its repeated steps, the spinning thinning rate R relative to the initial tube blank thickness is i The total thinning rate R of spinning satisfies the following relationship: R i =(R-R L ) / T 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.

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 tube blank in step S1 can be manufactured by casting, extrusion, or plate coiling, and its inner diameter r satisfies: 150mm≤r≤3000mm.

3. 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: In step S2, the inner diameter of the cylindrical core mold is consistent with the inner diameter of the initial tube blank.

4. 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: 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 thinning spinning begins, lubricating oil is applied to the outer surface of the tube blank.

5. 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: In step S1 and its repeated steps, and in step S4, multiple passes of spinning are 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. 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: In step S1 and its repeated steps, and in step S4, before the tube blank is installed 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. 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: In step S4, the spinning thinning rate R of the tube blank after solutionizing relative to the initial tube blank thickness is L satisfy: 5％≤R L ≤15％。 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 8, characterized in that: In step S1 and its repeated steps, and in step S4, the spinning process adopts a double-conical spinning wheel.

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