A method for manufacturing an aluminum alloy thin-walled cylindrical member with a circumferential high internal rib

Abstract

The application discloses a manufacturing method of an aluminum alloy ring high-internal-rib thin-walled cylindrical part, and belongs to the technical field of metal plastic working. The manufacturing method mainly comprises the following steps: firstly, adopting near-zero thinning friction stir welding tools, an aluminum alloy plate is roll-welded into a thin-walled cylindrical part; secondly, the cylindrical part is installed in a upsetting die, and electric energy field assisted side wall constraint upsetting forming is carried out on the workpiece by adopting pulse current heating; finally, solid solution aging strengthening treatment is carried out, and finally, the high-performance aluminum alloy ring high-internal-rib thin-walled cylindrical part is obtained. The application has the advantages of high material utilization rate, wide application range, low cost, short manufacturing period and the like.

Description

Technical Field

[0001] This invention relates to the field of metal plastic processing technology, specifically to a method for manufacturing a thin-walled cylindrical part with high internal ribs in the circumferential direction of aluminum alloy. Background Technology

[0002] With the rapid development of high-tech industries such as spacecraft, satellites, and launch vehicles, high-end aerospace equipment, as a strategic high ground in international competition, is an important indicator of a nation's scientific and technological level and military strength. Currently, the next generation of spacecraft is developing towards greater payload capacity, longer range, higher speed, and lower carbon emissions, thus requiring its key load-bearing components to possess excellent characteristics such as high load-bearing capacity, high reliability, and lightweight design. Therefore, adopting lightweight, high-strength materials and large, thin-walled, integrated structures with significant weight-reduction benefits has become an inevitable choice for reducing flight mass, improving reliability, and increasing payload.

[0003] Large components of spacecraft, such as various modules and fuel tanks, mostly utilize aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical parts to meet the requirements of lightweight design and high-G flight stability. These components are characterized by high ribs and thin webs, with an internal rib height-to-width ratio ≥3. They impose stringent requirements on manufacturing precision, mechanical properties, and structural weight, making them very difficult to form. Currently, my country mostly uses traditional forming methods such as low-pressure casting and integral machining of forgings for these highly internally ribbed thin-walled cylindrical parts. This reliance on machining to ensure component dimensions results in the severing of the rib fiber structure (streamlines), leading to high defect sensitivity, low material utilization, and long processing cycles.

[0004] To address the aforementioned issues, several forming methods have been developed in recent years, including "equal material (spinning) + additive manufacturing" and welded modular manufacturing. Specific examples can be found in Chinese invention patent No. 201910320612.1 (Publication No. CN 109940079 B), entitled "A Method and Apparatus for Improving the Filling Height of Internal Ribs in Spinning Cylindrical Parts," and Chinese patent application No. 202210239847.X (Publication No. CN 114603027 A), entitled "A Multi-Stage Spinning Method for Internally Ribbed Cylindrical Parts with Follow-up Constraints." However, these methods all suffer from poor performance consistency, low component load-bearing capacity, high cost, and long processing times.

[0005] Therefore, there is an urgent need for a new method for integral plastic forming of high-performance aluminum alloy thin-walled cylindrical parts with high internal ribs, which aims to improve the manufacturing level of large thin-walled cylindrical parts with high internal ribs in my country. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to propose a low-cost, short-process, highly reliable, and versatile method for manufacturing thin-walled cylindrical parts with high internal ribs in the circumferential direction of aluminum alloy, in light of the above-mentioned technical status.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a method for manufacturing a thin-walled cylindrical part with high internal ribs in the circumferential direction of aluminum alloy, characterized by comprising the following steps:

[0008] Step 1: Design the core mold size according to the cylindrical part structure, and use near-zero thinning friction stir welding equipment to roll and weld the aluminum alloy sheet into a thin-walled cylindrical part that meets the design size requirements;

[0009] Step 2: Install the thin-walled cylindrical part obtained in Step 1 in the upsetting die, and use pulse current to heat the workpiece for electric energy field-assisted side wall constraint upsetting to obtain an aluminum alloy circumferential high internal rib thin-walled cylindrical part.

[0010] Step 3: The aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part obtained in Step 2 is subjected to heat treatment to strengthen it, and finally a high-performance aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part is obtained.

[0011] Preferably, the near-zero thinning friction stir welding fixture used in step 1 includes an external large shoulder and an internal small shoulder protruding relative to the external large shoulder. During welding, the internal small shoulder is pressed into the aluminum alloy sheet, providing pressure to ensure a dense weld formation. The end face of the external large shoulder is in contact with the surface of the aluminum alloy sheet, without being pressed in or pressed in to a small depth, thereby controlling the weld thinning amount and achieving near-zero thinning weld with equal strength to the base material, achieving the process effect of "one-time welding, two-time forming". In addition, the near-zero thinning friction stir welding fixture can be made simply and conveniently by machining two shoulders, the internal small shoulder and the external large shoulder, on the basis of a conventional welding fixture.

[0012] Preferably, the upsetting die in step 2 includes an outer upsetting die, an inner upsetting die, an upper die, and a mandrel. The upsetting die provides sidewall constraint for the thin-walled cylindrical part during the upsetting process: the outer upsetting die is located on and constrains the outer sidewall of the thin-walled cylindrical part; the inner upsetting die is connected to the mandrel via a spring, which causes the inner upsetting die to always have an outward tendency, thus positioning and constraining the lower inner sidewall of the thin-walled cylindrical part; the upper die has an inverted L-shaped cross-section, including a horizontal portion and a vertical portion. The horizontal portion is pressable down on and constrains the upper part of the thin-walled cylindrical part's sidewall, and the vertical portion is located on and constrains the inner sidewall of the thin-walled cylindrical part; a gap exists between the inner upsetting die and the upper die in the vertical direction.

[0013] To facilitate demolding of thin-walled cylindrical parts, preferably, the surface of the upsetting die in step 2 is coated with organic graphite lubricant.

[0014] Preferably, in step 2, the upper die is connected to a press, and the upper die can be pressed down by the slide of the press, so that the upper die and the forging inner die gradually close together, and a circumferential high inner rib of the thin-walled cylindrical part is formed in the gap between the forging inner die and the upper die.

[0015] Preferably, the electric field-assisted sidewall constraint upsetting process in step 2 mainly involves placing the thin-walled cylindrical part obtained in step 1 into the upsetting die, applying a high-density pulsed current, and using the resistance of the aluminum alloy itself to heat the cylindrical part, achieving rapid temperature rise. Since the grain refinement of aluminum alloy above the recrystallization temperature helps to improve the plasticity of the material, after reaching 20-50°C above the recrystallization temperature, the press is started, and the upper die is gradually closed under the drive of the press slide. The press slide speed is 0.3-1.8 mm / s, and the maximum upsetting pressure is 1000-1500 tons. After the press holds the pressure for 10-30 seconds, the press slide is raised, causing the upper die to disengage, cool down, and the annular high-ribbed thin-walled cylindrical part is taken out.

[0016] Preferably, in step 3, the circumferentially high-inner-ribbed cylindrical part is subjected to heat treatment with a solution temperature of 490-540℃, a solution time of 2-6h, and air cooling or water quenching; and an aging temperature of 165-195℃, an aging time of 8-36h, and air cooling.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] (1) This invention proposes a manufacturing method of “near-zero thinning friction stir welding coil into cylinder → electric field assisted upsetting and forming of reinforcement → heat treatment to strengthen component performance”. Compared with the existing “forging + machining”, “casting”, “welding and separate manufacturing” and “equal material + additive manufacturing” methods, this invention has the advantages of high material utilization, wide applicability, low cost, short manufacturing cycle and good component reliability.

[0019] (2) Conventional friction stir welding fixtures mainly consist of a shoulder and a stirring pin. The downward pressure of the shoulder can cause the plasticized material around the weld to overflow, thinning the weld and significantly reducing the load-bearing capacity of the joint. Therefore, in the "rolling into a cylinder" step, i.e., step 1, the near-zero thinning friction stir welding fixture used in this invention controls the zero downward pressure of the shoulder. It processes two shoulders, inner and outer, on the basis of a conventional welding fixture. The inner small shoulder has a certain protrusion relative to the large shoulder. During welding, the inner small shoulder presses in the material to provide pressure and ensure the dense formation of the weld. The end face of the outer large shoulder is in contact with the surface of the plate and is not pressed in or pressed in to a small depth, thereby controlling the amount of weld thinning and achieving near-zero thinning weld with equal strength to the base material, achieving the process effect of "one-time welding, two-time forming". Compared with conventional friction stir welding, the near-zero thinning friction stir welding fixture proposed in this invention has the advantages of simple fixture structure, high welding efficiency, effective reduction of weld flash and thickness reduction, increased weld load-bearing area, and improved joint load-bearing capacity.

[0020] (3) In the electric field-assisted upsetting process, i.e., step 2, the present invention applies a high-density pulsed current to the cylindrical part and uses the resistance of the aluminum alloy material itself to heat the cylindrical part, achieving rapid temperature rise. Compared with the traditional preheating and heat preservation method, it has the advantages of energy saving and environmental protection, low cost, fast heating speed, and precise control of workpiece temperature. Since the pulsed current has a significant electroplasticizing effect on the aluminum alloy material, under the constraint of the inner, outer and upper dies of the upsetting, it is possible to achieve integrated upsetting of aluminum alloy circumferential high inner rib cylindrical parts with electric field-assisted sidewall constraint. In this process, the annular inner rib is obtained by metal volume forming, so there is a continuous fibrous structure (streamline) between the inner rib and the web. In addition, the whole component has undergone the recrystallization of equiaxed grains, which makes the mechanical properties of the rib and the web have good consistency, low defect sensitivity and good component reliability. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the near-zero thinning friction stir welding fixture structure according to an embodiment of the present invention;

[0023] Figure 3 The diagram shows an electric field-assisted upsetting process according to an embodiment of the invention, (a) before upsetting and (b) after upsetting.

[0024] Figure 4 This is a schematic diagram of the structure of an aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical component manufactured using an embodiment of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and two embodiments.

[0026] Example 1

[0027] This embodiment describes the manufacturing method of a 2219 aluminum alloy thin-walled cylindrical part with circumferential high internal ribs (dimensions: outer diameter φ400mm, height 300mm, web wall thickness 12mm, circumferential internal rib width 10mm, internal rib height 30mm). The flowchart is as follows. Figure 1 As shown, the specific steps include the following:

[0028] Step 1: Design the core mold size according to the cylindrical part structure, and use near-zero thinning friction stir welding equipment to weld 10 rolls of 12mm thick 2219 aluminum alloy sheet into a thin-walled cylindrical part 3 with an outer diameter of φ400mm, a height of ≥300mm and a wall thickness of 12mm.

[0029] Step 2: Install the 2219 aluminum alloy thin-walled cylindrical part 3 into the upsetting die, such as... Figure 3As shown, the upsetting die mainly consists of an outer upsetting die 2, an inner upsetting die 5, an upper die 4, a mandrel 6, and a spring 7. It serves to constrain the thin-walled cylindrical part 3 by sidewalls. The die surface is uniformly coated with organic graphite lubricant, which facilitates subsequent demolding. The thin-walled cylindrical part 3 is placed in the upsetting die, and a pulsed current is applied to heat the thin-walled cylindrical part 3. After reaching 460±5℃, the press is started. The upper die 4 is driven by the press slide to gradually close the die. The press slide speed is 1.0mm / s, and the maximum upsetting pressure is 1200 tons. After the press holds the pressure for 20±2s, the press slide is raised, which drives the upper die 4 to disengage. After cooling, the 2219 aluminum alloy annular thin-walled cylindrical part 9 with high internal ribs is taken out. The web wall thickness is 12mm, the width of the circumferential internal rib is 10mm, and the height of the internal rib is 30mm.

[0030] Step 3: The 2219 aluminum alloy thin-walled cylindrical part with high circumferential internal ribs is heat-treated with a solution treatment temperature of 535±5℃ for 6 hours, followed by water quenching, an aging temperature of 180±5℃ for 32 hours, and air cooling. After machining and finishing the upper and lower ends of the cylindrical part, a high-performance thin-walled cylindrical part with high circumferential internal ribs of 2219 aluminum alloy with an outer diameter of φ400mm, a height of 300mm, a web wall thickness of 12mm, a circumferential internal rib width of 10mm, and an internal rib height of 30mm is obtained. The structural schematic diagram is shown below. Figure 4 As shown.

[0031] The mechanical properties of the 2219 aluminum alloy high-performance circumferentially highly internally ribbed thin-walled cylindrical parts were evaluated by sampling the internal rib section and the web section. The results showed that the tensile strength of the internal rib section was 450 MPa and the elongation after fracture was 12%, while the tensile strength of the web section was 440 MPa and the elongation after fracture was 10%.

[0032] Example 2

[0033] The manufacturing method of the 2A12 aluminum alloy thin-walled cylindrical part with circumferential high inner ribs (with dimensions of outer diameter φ400mm, height 300mm, web wall thickness 12mm, circumferential inner rib width 10mm, and inner rib height 30mm) of this embodiment includes the following steps:

[0034] Step 1: Design the core mold size according to the cylindrical part structure, and use near-zero thinning friction stir welding equipment to weld 10 rolls of 12mm thick 2A12 aluminum alloy sheet into a thin-walled cylindrical part 3 with an outer diameter of φ400mm, a height of ≥300mm and a wall thickness of 12mm.

[0035] Step 2: Install the 2A12 aluminum alloy thin-walled cylindrical part 3 into the upsetting die, such as... Figure 3As shown, a pulsed current is applied to heat the thin-walled cylindrical part 3 to 450±5℃. Then, the press is started. The upper mold 4 is driven by the press slide to gradually close. The press slide speed is 1.2mm / s, and the maximum upsetting pressure is 1100 tons. After the press holds the pressure for 15±2s, the press slide rises, causing the upper mold 4 to disengage and cool down. The 2A12 aluminum alloy annular thin-walled cylindrical part 9 with high internal ribs is then removed. The web wall thickness is 12mm, the circumferential internal rib width is 10mm, and the internal rib height is 30mm.

[0036] Step 3: The 2A12 aluminum alloy thin-walled cylindrical part 9 with high circumferential internal ribs is heat-treated. The solution treatment temperature is 495±5℃, the solution treatment time is 2h, followed by water quenching, aging temperature is 190±5℃, aging time is 8h, and air cooling is performed. This yields a high-performance 2A12 aluminum alloy thin-walled cylindrical part with high circumferential internal ribs, an outer diameter of φ400mm, a height of 300mm, a web wall thickness of 12mm, a circumferential internal rib width of 10mm, and an internal rib height of 30mm. A structural schematic diagram is shown below. Figure 4 As shown.

[0037] The mechanical properties of the 2A12 aluminum alloy high-performance circumferentially highly internally ribbed thin-walled cylindrical parts were evaluated by sampling the internal rib section and the web section. The results showed that the tensile strength of the internal rib section was 470 MPa and the elongation after fracture was 12%, while the tensile strength of the web section was 460 MPa and the elongation after fracture was 11%.

[0038] The method disclosed in this invention requires the use of near-zero thinning friction stir welding tools and upsetting dies. The preferred embodiments applicable to the above two embodiments are described below.

[0039] Conventional friction stir welding fixtures mainly consist of a shoulder and a stirring pin 11. Near-zero thinning friction stir welding fixtures, such as... Figure 2 As shown, two shoulders, an internal small shoulder 12 and an external large shoulder 13, are machined on the basis of conventional welding tools. The internal small shoulder 12 has a certain protrusion relative to the external large shoulder 13. During welding, the internal small shoulder 12 is pressed into the aluminum alloy plate 10 to provide pressure to ensure the weld formation. The end face of the external large shoulder 13 is in contact with the surface of the aluminum alloy plate 10 and is not pressed in or pressed in to a small depth, thereby controlling the amount of weld thinning.

[0040] Upsetting dies, such as Figure 3As shown, the assembly includes a base plate 1 and an outer forging die 2, an inner forging die 5, an upper die 4, and a mandrel 6, all mounted on the base plate 1. The outer forging die 2 is located on and constrains the outer side of the side wall of the thin-walled cylindrical part 3. The inner forging die 5 is connected to the mandrel 6 via a spring 7, which causes the inner forging die 5 to always have a tendency to move outward, thereby positioning and constraining the inner forging die 5 on the lower inner side of the side wall of the thin-walled cylindrical part 3. The upper die 4 has an inverted L-shaped cross-section, including a horizontal part and a vertical part. The horizontal part is pressable and located on and constrains the upper part of the side wall of the thin-walled cylindrical part 3, while the vertical part is located on and constrains the inner side of the side wall of the thin-walled cylindrical part 3. There is a gap between the inner forging die 5 and the upper die 4 in the vertical direction. The copper electrode 8 is connected to the thin-walled cylindrical part 3. After applying a pulse current to heat the thin-walled cylindrical part 3 to the specified temperature, the upper die 4 connected to the press is pressed down by the slide of the press, so that the upper die 4 and the upsetting inner die 5 gradually close. The circumferential high inner rib of the thin-walled cylindrical part 3 is formed in the gap between the upsetting inner die 5 and the upper die 4. After demolding, the whole part is taken out to obtain the annular high inner rib thin-walled cylindrical part 9.

[0041] The specification and claims of this invention use terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom," to describe various exemplary structural parts and elements of the invention. However, these terms are used herein merely for ease of explanation and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this invention can be arranged in different orientations, these terms indicating direction are for illustrative purposes only and should not be considered as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

Claims

1. A method for manufacturing a thin-walled cylindrical part with circumferential high internal ribs made of aluminum alloy, characterized in that, Includes the following steps: Step 1: Design the core mold size according to the cylindrical part structure, and use near-zero thinning friction stir welding equipment to roll and weld the aluminum alloy sheet into a thin-walled cylindrical part that meets the design size requirements; Step 2: Install the thin-walled cylindrical part obtained in Step 1 in the upsetting die, and use pulse current to heat the workpiece for electric energy field-assisted side wall constraint upsetting to obtain an aluminum alloy circumferential high internal rib thin-walled cylindrical part. Step 3: The aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part obtained in Step 2 is subjected to heat treatment to strengthen it, and finally a high-performance aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part is obtained. In step 2, the electric field-assisted sidewall constraint upsetting process mainly involves placing the thin-walled cylindrical part obtained in step 1 into the upsetting die, applying a pulsed current to heat the thin-walled cylindrical part until it reaches 20-50°C above the recrystallization temperature, then starting the press. The upper die gradually closes under the drive of the press slide, with the press slide speed being 0.3-1.8 mm / s and the maximum upsetting pressure being 1000-1500 tons. After the press holds the pressure for 10-30 seconds, the press slide rises, causing the upper die to disengage, allowing it to cool down, and then the annular, high-inner-rib thin-walled cylindrical part is removed.

2. The manufacturing method of the aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part according to claim 1, characterized in that: The near-zero thinning friction stir welding fixture used in step 1 includes an external large shoulder and an internal small shoulder that protrudes relative to the external large shoulder. During welding, the internal small shoulder is pressed into the aluminum alloy sheet to provide pressure and ensure the weld formation. The end face of the external large shoulder is in contact with the surface of the aluminum alloy sheet and is not pressed in or pressed in to a small depth.

3. The manufacturing method of the aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part according to claim 1, characterized in that: The upsetting die in step 2 includes an outer upsetting die, an inner upsetting die, an upper die, and a mandrel. The outer upsetting die is located on and constrains the outer side of the thin-walled cylindrical part's sidewall. The inner upsetting die is connected to the mandrel via a spring, which causes the inner upsetting die to always have an outward tendency, thereby positioning and constraining the inner upsetting die on the lower inner side of the thin-walled cylindrical part's sidewall. The upper die has an inverted L-shaped cross-section, including a horizontal part and a vertical part. The horizontal part is pressable down and constrains the upper part of the thin-walled cylindrical part's sidewall, while the vertical part is located on and constrains the inner side of the thin-walled cylindrical part's sidewall. There is a gap between the inner upsetting die and the upper die in the vertical direction.

4. The manufacturing method of the aluminum alloy circumferentially highly internally ribbed thin-walled cylindrical part according to claim 3, characterized in that: In step 2, the surface of the upsetting die is coated with organic graphite lubricant.

5. The method for manufacturing a thin-walled cylindrical aluminum alloy part with circumferential high internal ribs according to claim 3 or 4, characterized in that: In step 2, the upper die is connected to the press. The upper die can be pressed down by the slide of the press, so that the upper die and the forging inner die gradually close together, and the circumferential high inner rib of the thin-walled cylindrical part is formed in the gap between the forging inner die and the upper die.

6. The method for manufacturing a thin-walled cylindrical aluminum alloy component with circumferential high internal ribs according to claim 1, characterized in that: In step 3, the circumferentially high-inner-ribbed cylindrical part is subjected to heat treatment. The solution temperature is 490-540℃, the solution time is 2-6h, and it is air-cooled or water-quenched. The aging temperature is 165-195℃, the aging time is 8-36h, and it is air-cooled.

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