Hydraulic forming surface corrosion integrated forming device and process for special-shaped tube

Abstract

The application provides a special-shaped tube hydraulic forming surface corrosion prevention integrated forming device and process, which comprises a forming die and a hydraulic system, the forming die comprises an upper die, a lower die and a cavity, and the hydraulic system comprises: a first stopper which is sealingly and slidably installed at one end of the cavity, a conductive sheet and a wire being connected to the first stopper; a second stopper which is sealingly and slidably installed at the other end of the cavity, an electrode being arranged at the outer end of the second stopper, and a liquid channel being arranged on the second stopper and being communicated with the cavity; a micro-arc oxidation power source being connected with the wire and the electrode respectively; an electrolyte being injected into the cavity through the liquid channel; a first driving mechanism for driving the first stopper to slide; and a second driving mechanism for driving the second stopper to slide. The application adopts the conductive liquid to perform the hydraulic bulging to obtain the special-shaped tube, and directly performs the micro-arc oxidation surface corrosion prevention treatment on the inner wall of the formed tube under the action of the external power source, so that the forming process can be shortened and the production efficiency can be improved.

Description

Technical Field

[0001] This invention belongs to the field of pipe processing technology, specifically relating to an integrated forming device and process for hydraulic forming and surface anti-corrosion of irregularly shaped pipes. Background Technology

[0002] Irregularly shaped tubing is widely used in critical components of aircraft, rocket engines, missiles, and other fields, and has strict requirements for dimensional accuracy and mechanical properties. Traditional manufacturing processes for irregularly shaped tubing typically involve first forming the tubing using methods such as casting, cold drawing, and drilling, followed by surface anti-corrosion treatment in subsequent processes. However, these traditional processes suffer from problems such as high scrap rates, high production costs, low production efficiency, material waste, and difficulty in controlling precision.

[0003] To overcome the above-mentioned defects, some new processes use a filler method for forming, that is, the pipe is first filled and then the filler is removed.

[0004] For example, Chinese invention patent application CN108296332A discloses a method for forming irregularly shaped tubes, including a tube, a plug, gas to fill the tube, and a stamping die. In operation, the tube is first inflated until the pressure inside and outside the tube is balanced, and then the tube is placed in the stamping die for stamping. The advantage of this method is that it can make the wall thickness more uniform, but the air inside the tube is difficult to store, the operation is difficult, and after forming, a subsequent surface anti-corrosion treatment is required.

[0005] For example, Chinese invention patent application CN109795134A discloses a method for forming irregularly shaped tubes, including an inner support mold, an outer mold, silicone aerogel, a latex film, an inner support, and carbon fiber prepreg. In operation, a silicone aerogel insulation layer is sprayed onto the inner support, followed by a latex film coating. The inner support is then wrapped with carbon fiber prepreg and placed in the outer mold. Finally, the carbon fiber is cured and formed. The mold is opened, and hot air is used to melt and flow out the latex film, resulting in the irregularly shaped tube. The advantage of this device is that it produces irregularly shaped tubes with small shape deviations and smooth inner surfaces. However, it requires a wide variety of materials, resulting in low material utilization and poor controllability. Furthermore, surface anti-corrosion treatment is required after forming.

[0006] For example, Chinese invention patent application CN116197283A discloses a method for hot bending of titanium alloy tubes based on self-lubrication, including a bending die, a suspension, an electrolyte, an air plate, and a heating device. During operation, the bending die is first subjected to micro-arc oxidation to create a dense ceramic coating on its inner wall. Then, the heated tube is pushed into the bending die, where it deforms under the combined action of the tube and the die. This method can reduce the friction coefficient between the tube and the bending die. However, it does not perform micro-arc oxidation for corrosion protection after the tube is formed. Post-forming corrosion protection would lead to uneven corrosion protection, complex processes, and low production efficiency.

[0007] In summary, existing shaped tube forming processes all involve first forming the shaped tube, and then removing the formed shaped tube for surface anti-corrosion treatment such as electro-spark deposition or coating. This has the disadvantages of complex processes, high production costs, and low production efficiency. Moreover, traditional anti-corrosion treatment processes are difficult to treat the irregular areas of the shaped tube, resulting in inadequate surface treatment and affecting the performance of the shaped tube. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides an integrated forming device and process for hydraulic forming and surface anti-corrosion of irregular tubes. It uses a conductive liquid to perform hydraulic expansion to obtain irregular tubes, and at the same time, under the action of an external power source, the inner wall of the formed tube is directly subjected to micro-arc oxidation surface anti-corrosion treatment. This can shorten the forming process, improve production efficiency, reduce production costs, and improve the performance of irregular tubes, achieving a short-process forming that integrates plastic forming and surface modification.

[0009] The technical solution adopted by this invention to solve its technical problem is to provide an integrated forming device for surface corrosion protection of irregularly shaped tubes through hydraulic forming, including a forming mold and a hydraulic system. The forming mold includes an upper mold, a lower mold, and a cavity formed by the upper and lower molds after they are closed, which is configured with the irregularly shaped tube. The hydraulic system includes a first stop block, a second stop block, a micro-arc oxidation power supply, an electrolyte, a first driving mechanism, and a second driving mechanism.

[0010] The first stop block is sealed and slidably installed at one end of the cavity. A conductive sheet is provided on the end face of the first stop block inside the cavity. A wire is provided on the first stop block along the axial direction. One end of the wire is connected to the conductive sheet, and the other end extends out of the first stop block.

[0011] The second stop is sealed and slidably installed at the other end of the cavity. The second stop is made of conductive material, and an electrode is provided at the outer end of the second stop. A liquid channel communicating with the cavity is provided on the second stop.

[0012] The two poles of the micro-arc oxidation power supply are connected to a wire and an electrode, respectively.

[0013] The first driving mechanism is connected to the first stop and is used to drive the first stop to slide within one end of the cavity;

[0014] The second drive mechanism is connected to the second stop and is used to drive the second stop to slide inside the other end of the cavity;

[0015] The electrolyte is injected into the cavity through a liquid channel and can undergo a micro-arc oxidation reaction with the surface of the tube when connected to a micro-arc oxidation power source.

[0016] Optionally, the first stop is made of a conductive material.

[0017] Optionally, the first stop, the second stop, the conductive sheet, the wire, and the electrode are all made of conductive copper.

[0018] Optionally, the liquid channel is L-shaped, with its horizontal opening located at the inner end of the second stop and its vertical opening located at the top of the outer end of the second stop.

[0019] Optionally, the electrolyte is an aqueous solution containing Na2SiO3.

[0020] Optionally, the lower mold is provided with a liquid outlet communicating with the cavity.

[0021] Optionally, the liquid outlet is located below the first stop.

[0022] Accordingly, the present invention also provides an integrated forming process for surface corrosion protection of irregular tubes by hydroforming, which is based on the above-mentioned integrated forming device for surface corrosion protection of irregular tubes by hydroforming, and includes the following steps;

[0023] S1. First, prepare the upper and lower dies. Place the tube in the lower die cavity and move the upper die downward. The upper and lower dies together form a closed cavity to stamp the tube.

[0024] S2. Place the first stop block inside one end of the cavity and the second stop block inside the other end of the cavity. Drive the first stop block and the second stop block inward to the pipe port through the first drive mechanism and the second drive mechanism respectively.

[0025] S3. Electrolyte is injected into the pipe through the liquid channel of the second stop, and the pressure of the electrolyte is controlled to deform the pipe so as to gradually approach the cavity contour to complete the hydraulic expansion.

[0026] S4. Start the micro-arc oxidation power supply to cause the electrolyte in the cavity to react with the surface of the pipe in a micro-arc oxidation reaction, so as to form a dense coating on the inner surface of the pipe.

[0027] S5. Turn off the micro-arc oxidation power supply, remove the first and second blocks, move the upper mold upward, and take out the shaped tube.

[0028] Optionally, in step S2, the electrolyte pressure is greater than 31.6 MPa.

[0029] Optionally, in step S4, the conditions for the micro-arc oxidation reaction include: micro-arc oxidation is performed using a pulsed micro-arc oxidation power supply at a voltage of 300–600V, a power supply frequency of 50–500Hz, a duty cycle of 2%–5%, and a constant temperature for 5–20 minutes.

[0030] The beneficial effects of this invention are as follows: This invention uses a conductive electrolyte for hydraulic bulging of irregularly shaped tubing. Compared with existing technologies that use gas or iron sand as fillers, the electrolyte used in this invention is convenient to store, easy to operate, readily available, and highly controllable. Furthermore, after the irregularly shaped tubing is formed, the power supply can be immediately connected to perform micro-arc oxidation surface strengthening treatment on the inner wall of the tubing using the electrolyte, significantly shortening the process, reducing production costs, and improving production efficiency, achieving integrated short-process forming of plastic forming and surface modification. In addition, due to the good fluidity of the electrolyte, it can fill all areas of the inner wall of the irregularly shaped tubing, including irregular regions, to form a more uniform and dense coating inside the tubing, thereby improving the overall plasticity and surface strengthening performance of the irregularly shaped tubing. Attached Figure Description

[0031] The present invention will be described in detail below with reference to the accompanying drawings and examples. The advantages and implementation methods of the present invention will become more apparent from this description. The accompanying drawings are for illustrative purposes only and do not constitute any limitation on the present invention. In the accompanying drawings:

[0032] Figure 1 This is a schematic diagram of the structure of an integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming, provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the upper mold in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the lower mold structure in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the structure of the first stop block in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the structure of the second stop in an embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of the pipe structure before the irregular-shaped pipe is formed according to an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the irregular tube formed using an embodiment of the present invention.

[0039] In the diagram: 1-pipe, 2-cavity, 3-upper mold, 4-lower mold, 4.1-liquid outlet, 5-first stop, 5.1-conductive sheet, 5.2-wire, 6-second stop, 6.1-electrode, 6.2-liquid channel, 7-first cylinder, 8-second cylinder. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" or "several" means two or more.

[0043] like Figures 1-5 As shown, this invention provides an integrated forming device for surface corrosion protection of irregularly shaped tubes through hydraulic forming, comprising a forming mold and a hydraulic system. The forming mold includes an upper mold 3, a lower mold 4, and a cavity 2 formed by the closing of the upper and lower molds, which is configured with the irregularly shaped tube. The hydraulic system includes a first stop 5, a second stop 6, a micro-arc oxidation power source (not shown in the figure), an electrolyte (not shown in the figure), and a first drive mechanism (…). Figure 1 First cylinder 7) and second drive mechanism ( Figure 1The second cylinder 8). The first stop block 5 is sealed and slidably mounted on one end of the cavity 2 ( Figure 1 At the left end of the cavity, the first stop block 5 has a conductive sheet 5.1 on its end face inside the cavity. A wire 5.2 is axially mounted on the first stop block, with one end connected to the conductive sheet and the other end extending out of the first stop block. The second stop block 6 is sealed and slidably mounted at the other end of the cavity 2. Figure 1 The second stop (located at the right end) is made of conductive material, with an electrode 6.1 at its outer end and a liquid channel 6.2 communicating with the mold cavity. The two poles of the micro-arc oxidation power supply are connected to a wire and an electrode, respectively. A first driving mechanism is connected to the first stop and drives it to slide within one end of the mold cavity. A second driving mechanism is connected to the second stop and drives it to slide within the other end of the mold cavity. The electrolyte is injected into the mold cavity through the liquid channel and can undergo a micro-arc oxidation reaction with the tube surface when connected to the micro-arc oxidation power supply. In this embodiment, the first and second driving mechanisms can be either pneumatic cylinders or hydraulic cylinders.

[0044] In one embodiment, the first stop is made of a conductive material to increase conductivity. When the first stop is made of a conductive material, the conductive sheet can be integrally formed with it, and the wire can be directly installed on the outer end of the first stop. The first stop can also be made of a non-conductive material with enhanced sealing performance. In this case, a conductive sheet needs to be installed on the inner end of the first stop, and an axial groove is cut on the first stop to form a wire channel, through which the wire is connected to the conductive sheet.

[0045] In one embodiment, the first block, the second block, the conductive sheet, the wire, and the electrode are all made of conductive copper, which is readily available.

[0046] In one embodiment, such as Figure 1 , Figure 5 As shown, the liquid channel is L-shaped, with its horizontal opening located at the inner end of the second stop and its vertical opening located at the top of the outer end of the second stop, facilitating liquid injection into the cavity.

[0047] In one embodiment, a protruding electrode is provided at the inner end of the second stop to ensure that the stop is in contact with the electrolyte during hydraulic expansion.

[0048] In one embodiment, the electrolyte is an aqueous solution containing Na2SiO3, which is readily available and effective.

[0049] In one embodiment, such as Figure 1 , Figure 2As shown, the lower mold 4 is provided with a liquid outlet 4.1 that communicates with the cavity 2. When the power is off, the liquid outlet is opened, and the electrolyte in the cavity can flow out through the liquid outlet for collection. The liquid outlet can be opened at any position on the lower mold and can be sealed when not in use. More preferably, the liquid outlet is located below the first stop block, which allows the liquid outlet to be closed and opened through the first stop block, making operation more convenient.

[0050] Correspondingly, such as Figure 1 As shown, the present invention also provides an integrated forming process for surface corrosion protection of irregularly shaped tubes by hydraulic forming, which is based on the above-mentioned integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming, and includes the following steps;

[0051] S1. First, prepare the upper and lower molds, and then... Figure 6 The tube 1 shown is placed in the lower mold cavity, and the upper mold moves downward. The upper mold and the lower mold together form a closed cavity, and the tube is stamped and formed.

[0052] S2. Place the first stop block inside one end of the cavity and the second stop block inside the other end of the cavity. Drive the first stop block and the second stop block inward to the pipe port through the first drive mechanism and the second drive mechanism respectively. The first stop block and the second stop block can seal the cavity.

[0053] S3. Fill the pipe with electrolyte through the liquid channel of the second stop, and deform the pipe by controlling the pressure of the electrolyte to gradually approach the cavity contour to complete the hydraulic expansion. Specifically, the electrolyte pressure can be controlled by a high-pressure pump and valve.

[0054] S4. Start the micro-arc oxidation power supply, connect the wires and electrodes at both ends of the first and second blocks, so that the electrolyte in the cavity reacts with the surface of the pipe to form a dense coating on the inner surface of the pipe.

[0055] S5. Turn off the micro-arc oxidation power supply, remove the first and second blocks, move the upper mold upward, and take out the shaped tube.

[0056] In one embodiment, in step S2, the electrolyte pressure is greater than 31.6 MPa.

[0057] In one embodiment, in step S4, to ensure the effectiveness of the micro-arc oxidation reaction, the conditions for the micro-arc oxidation reaction include: using a pulsed micro-arc oxidation power supply for micro-arc oxidation, and performing micro-arc oxidation for 5 to 20 minutes under the conditions of a voltage of 300 to 600V, a power supply frequency of 50 to 500Hz, a duty cycle of 2% to 5%, and a constant temperature.

[0058] This invention is applicable to irregularly shaped tubes with complex spatial configurations, and can perform hydroforming and integrated surface anti-corrosion forming.

[0059] like Figure 1 As shown, the present invention is used to form... Figure 7 The present invention includes the following steps for the irregularly shaped tube shown:

[0060] 1) Stamping: The material of tube 1 is AlFeCoNiCrCu, where the total length of tube L = 380mm, the outer diameter of tube D = Φ40mm, and the wall thickness t = 2mm. Tube 1 is placed in mold cavity 2, and the upper mold 3 moves downward to form a closed mold cavity together with the lower mold 4 for stamping. The stamping process parameters include: pressure edge 180kN, mold clearance 1.65mm, stamping speed 3000mm / s, and friction coefficient 0.14.

[0061] 2) Sealing and liquid introduction: The first stop block 5 with a wire is pushed into the left side of the irregular tube for sealing. The wire is connected to the conductive plate and led out through the wire channel in the first stop block to facilitate the connection of the wire to the power supply in step 4). The second stop block 6 is inserted into the right side and sealed under hydraulic pressure. The electrode of the second stop block is designed with a small copper block at the outer end to facilitate the connection with the wire and the power supply in step 4) and the introduction of conductive electrolyte. The sealing of the irregular tube is achieved by applying pressure to the first and second stops with a hydraulic press to push them in, so that they are in close contact with both ends of the irregular tube without entering the tube material.

[0062] 3) Hydraulic bulging: After the first stop 5 feeds 50mm and the second stop 6 feeds 50mm, conductive electrolyte Na2SiO3 is injected into the pipe through the liquid channel 6.2 inside the stop 6. The injected electrolyte volume should be equal to that of the pipe. The concentrations of the components in the electrolyte are: Na2SiO3 18g / L, Na2WO4 3g / L, KF 3g / L, and KOH 4g / L. The electrolyte pressure is controlled by a high-pressure pump and valves, causing the pipe 1 to deform and gradually approach the outer contour of the cavity to complete the hydraulic bulging. The hydraulic press output... The pressure is set to 20-30MPa according to the pipe wall thickness and shape. During the expansion process, the second stop moves towards the center along the central axis of the pipe blank (only one advance of 14mm is given to the second stop during hydraulic expansion, which can reduce the thinning rate of the part), increasing the axial material supply, supplementing the axial material deformation, and gradually approaching the outer contour of the cavity to complete the hydraulic expansion. In actual expansion, the unit pressure p > 31.6MPa, the pressure control accuracy is 0.5MPa, and the displacement control accuracy can reach 0.1mm. After hydraulic expansion, the displacement of the first and second stops at both ends of the pipe is a total of 14mm.

[0063] 4) Micro-arc oxidation: Turn on the power and connect the wires 5.2 and electrodes 6.1 at both ends of the left and right blocks to cause a micro-arc oxidation reaction inside the pipe, forming a dense coating. The micro-arc oxidation surface treatment technology applies voltage to the irregularly shaped pipe through a dedicated micro-arc oxidation power supply, so that the AlFeCoNiCrCu high-entropy alloy on the inner surface of the irregularly shaped pipe interacts with the electrolyte Na2SiO3, forming a dense coating on the inner surface of the irregularly shaped pipe. The micro-arc oxidation uses the blocks as cathodes and AlFeCoNiCrCu high-entropy alloys as anodes, adopts a constant temperature mode, and performs micro-arc oxidation for 13 minutes under the conditions of 500V, 400Hz, and 3% duty cycle.

[0064] 5) Sampling: After hydraulic bulging and micro-arc oxidation are completed, turn off the power, remove the stops at both ends of the shaped tube from the tube opening, and the electrolyte inside the shaped tube will drain through the channel. Then, fully open the upper and lower molds to remove the sample. Figure 7 The image shows an irregularly shaped tube with a complex spatial configuration.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A hydraulic forming device for irregularly shaped tubes with integrated surface corrosion protection, comprising a forming mold, the forming mold including an upper mold, a lower mold, and a cavity formed by the upper mold and the lower mold after being closed, which is configured with the irregularly shaped tube, characterized in that, The device also includes a hydraulic system, which comprises a first stop, a second stop, a micro-arc oxidation power supply, an electrolyte, a first drive mechanism, and a second drive mechanism. The first stop block is sealed and slidably installed at one end of the cavity. A conductive sheet is provided on the end face of the first stop block inside the cavity. A wire is provided on the first stop block along the axial direction. One end of the wire is connected to the conductive sheet, and the other end extends out of the first stop block. The second stop is sealed and slidably installed at the other end of the cavity. The second stop is made of conductive material, and an electrode is provided at the outer end of the second stop. A liquid channel communicating with the cavity is provided on the second stop. The two poles of the micro-arc oxidation power supply are connected to a wire and an electrode, respectively. The first driving mechanism is connected to the first stop and is used to drive the first stop to slide within one end of the cavity; The second drive mechanism is connected to the second stop and is used to drive the second stop to slide inside the other end of the cavity; The electrolyte is injected into the cavity through a liquid channel and can undergo a micro-arc oxidation reaction with the surface of the tube when connected to the micro-arc oxidation power supply. The forming process of this device includes the following steps: S1. First, prepare the upper and lower dies. Place the tube in the lower die cavity and move the upper die downward. The upper and lower dies together form a closed cavity to stamp the tube. S2. Place the first stop block inside one end of the cavity and the second stop block inside the other end of the cavity. Drive the first stop block and the second stop block inward to the pipe port through the first drive mechanism and the second drive mechanism respectively. S3. Electrolyte is injected into the pipe through the liquid channel of the second stop, and the pressure of the electrolyte is controlled to deform the pipe so as to gradually approach the cavity contour to complete the hydraulic expansion. S4. Start the micro-arc oxidation power supply to cause the electrolyte in the cavity to react with the surface of the pipe in a micro-arc oxidation reaction, so as to form a dense coating on the inner surface of the pipe. S5. Turn off the micro-arc oxidation power supply, remove the first and second blocks, move the upper mold upward, and take out the shaped tube.

2. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1, characterized in that, The first stop is made of conductive material.

3. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1 or 2, characterized in that, The first block, the second block, the conductive sheet, the wire, and the electrode are all made of conductive copper.

4. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1, characterized in that, The liquid channel is L-shaped, with its horizontal opening located at the inner end of the second stop and its vertical opening located at the top of the outer end of the second stop.

5. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1, characterized in that, The electrolyte is an aqueous solution containing Na2SiO3.

6. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1, characterized in that, The lower mold is provided with a liquid outlet that communicates with the cavity.

7. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 6, characterized in that, The liquid outlet is located below the first stop.

8. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1, characterized in that, In step S3, the pressure of the electrolyte is greater than 31.6 MPa.

9. The integrated forming device for surface corrosion protection of irregularly shaped tubes by hydraulic forming according to claim 1, characterized in that, In step S4, the conditions for the micro-arc oxidation reaction include: micro-arc oxidation is performed using a pulsed micro-arc oxidation power supply, with a voltage of 300~600V, a power supply frequency of 50~500Hz, a duty cycle of 2%~5%, and a constant temperature for 5~20 minutes.

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