An ultrasonic-assisted stir-friction tunnel forming device and process

Abstract

The application provides an ultrasonic-assisted friction stir tunnel forming device and process, a static shaft shoulder is arranged outside a stirring needle assembly, the static shaft shoulder and a dynamic shaft shoulder are coaxially arranged, a discharge hole is arranged on a bottom wall of the static shaft shoulder, and a lower end surface of the dynamic shaft shoulder is lower than a lower end surface of the static shaft shoulder; the stirring needle assembly comprises an upper needle body, an annular boss and a lower needle body which are integrally formed and coaxial, a lower shaft shoulder is arranged on the bottom of the lower needle body, the lower end of the dynamic shaft shoulder, the upper needle body, the annular boss and the lower needle body can be simultaneously located in a workpiece, and the upper end of the lower shaft shoulder is tightly attached to the lower end surface of the workpiece. The steps comprise: surface treatment, fixing a metal plate by using a tool clamp, starting an ultrasonic device, starting a friction stir welding machine, driving the friction stir tunnel forming device to be transversely pressed into the metal plate from one side, so that the metal material of a machining area reaches a thermoplastic state, and moving along a preset path. The machining area surface forming quality is good, the sealing property around the tunnel is better, and the process flow is simple.

Description

Technical Field

[0001] This invention belongs to the field of friction stirring tunnel forming technology, specifically relating to an ultrasonic-assisted friction stirring tunnel forming device and process. Background Technology

[0002] Heat exchange devices and cooling systems are widely used in the automotive and aerospace industries. Among them, liquid cooling heat dissipation elements have high exchange efficiency. Currently, many liquid cooling heat dissipation elements use flexible hoses to transfer the cooling medium, which requires complex wiring and auxiliary fixing devices, making subsequent inspection and maintenance difficult.

[0003] Studies have shown that machining channels / tunnels inside workpieces can significantly optimize the performance of liquid cooling components. Currently, there are three main methods for fabricating / machining tunnels on metal sheets. The first is casting, but this method is limited by manufacturing processes, making it difficult to create complex tunnels and prone to defects such as porosity, inclusions, and hot cracks. The second method combines slotting with a cover plate to create tunnels, but this is complex, increasing structural weight and making the cover plate weld joints susceptible to corrosion and leakage. The third method is friction stir tunneling (FSC), a novel solid-state processing technology. This technology uses a high-speed rotating friction stir tunneling tool inserted into the workpiece surface. The thread and rotation direction work together to extract material from the workpiece while simultaneously welding the upper metal portion to seal it, forming a continuous, non-linear tunnel inside. This technology has broad application prospects in structural weight reduction, rapid prototyping of internal wiring channels and internal liquid cooling channels.

[0004] However, when traditional friction stir tools are applied to FSC technology, technical problems often arise, such as difficulty in material extraction, small tunnel volume, and unstable tunnel formation. These issues negatively impact the heat dissipation efficiency and corrosion resistance of the plate material, thus limiting its effectiveness. Furthermore, the material density from the top of the tunnel to the surface of the plate, produced using current FSC technology, is relatively low, affecting the tunnel's sealing performance and making it unable to withstand high fluid pressures.

[0005] Existing document CN113751858B discloses a method for forming tunnels using biaxial shoulder friction stir welding. This method utilizes the double-threaded structure of a biaxial shoulder friction stir welding tunnel processing device to allow the central material of a metal sheet to flow outwards, thereby forming a tunnel in the center of the sheet. However, it relies solely on the threads to drive material flow, resulting in a low material extraction rate and requiring the machining of grooves on the sheet surface, making the process complex. Document 2020100652176 discloses a stirring head for friction stir manufacturing and a method for preparing water-cooled channels using it. The stirring head has an integrally formed structure with a left-hand threaded frustum, a boss, and a right-hand threaded frustum arranged from top to bottom. This stirring head enables the integrated processing of water-cooled channels on water-cooled sheet blanks. However, the material density in the upper and lower regions of the water-cooled channel prepared using this method is also low, making it unable to withstand high fluid pressures. Summary of the Invention

[0006] At least in order to solve the technical problems mentioned in the background art, the present invention aims to provide an ultrasonic-assisted stirring friction tunnel forming device and process.

[0007] The present invention adopts the following technical solution.

[0008] An ultrasonic-assisted friction stir tunneling device includes a friction stir tool head and an ultrasonic generator disposed at the bottom of the friction stir tool head. The friction stir tool head includes a clamping part, a moving shoulder connected to the lower end of the clamping part, a stirring pin assembly connected to the lower end of the moving shoulder, a stationary shoulder disposed around the stirring pin assembly, the stationary shoulder and the moving shoulder being coaxially arranged, a discharge hole disposed on the bottom wall of the stationary shoulder, and the lower end face of the moving shoulder being lower than the lower end face of the stationary shoulder. The stirring pin assembly includes an integrally formed and coaxial upper pin body, an annular boss and a lower pin body, a lower shoulder disposed at the bottom of the lower pin body, the lower end of the moving shoulder, the upper pin body, the annular boss and the lower pin body being able to be located inside the workpiece simultaneously, and the upper end of the lower shoulder being in close contact with the lower end face of the workpiece.

[0009] As a preferred embodiment, the annular boss is triangular in shape, and the corners of the triangle are rounded and chamfered.

[0010] As a preferred embodiment, both the upper needle body and the lower needle body are provided with threads.

[0011] To further improve the material density of the area traversed by the upper needle body, the outer diameter of the moving shaft shoulder is larger than the diameter of the circle corresponding to the rotation trajectory of the annular boss.

[0012] To further improve the material density of the area traversed by the upper needle body, the lower end face of the moving shaft shoulder is 0.05 to 0.2 mm lower than the upper surface of the workpiece.

[0013] To improve the flatness of the workpiece surface processing area, the bottom surface of the stationary shoulder has an inward concave structure, and the space for temporary material storage is formed by the bottom surface of the stationary shoulder, the upper surface of the workpiece, and the outer wall of the moving shoulder.

[0014] To further improve the material density of the area traversed by the upper and lower needle bodies, an axial through hole is provided on the lower shoulder, and an axial blind hole is provided on the lower needle body. The axial blind hole extends from the bottom of the lower needle body to the center of the annular boss. The connecting rod is inserted into the axial through hole and the axial blind hole. The connecting rod does not contact the lower needle body and the lower shoulder, and the upper part of the connecting rod is fixedly connected to the annular boss. The lower end of the connecting rod is used to connect to the ultrasonic generator.

[0015] To improve the heat exchange performance of the prepared tunnel, the annular boss has multiple radially arranged needles on its sidewall. This design allows for the fabrication of tunnels with multiple grooves on their inner walls.

[0016] A tunnel forming method using the aforementioned friction stirring tunnel forming apparatus includes the following steps:

[0017] Step 1: Prepare the metal sheet (i.e., the workpiece), mechanically grind to remove oxides from the surface of the metal sheet, and wipe with chemical reagents to remove oil stains from the surface of the metal sheet;

[0018] Step 2: Fix the metal sheet with tooling fixtures and assemble the friction stir tunnel forming device on the friction stir welding machine so that the upper end of the lower shoulder can be close to the lower end face of the workpiece, and the lower end face of the moving shoulder is 0.05-0.2mm lower than the upper surface of the workpiece.

[0019] Step 3: Connect the ultrasonic generator and then start the ultrasonic device;

[0020] Step 4: Start the friction stir welding machine and drive the friction stir tunnel forming device to press the metal sheet laterally from one side, so that the metal material in the processing area reaches a thermoplastic state and moves along the preset path.

[0021] Step 5: After processing, drive the friction stir tunnel forming device away from the metal sheet, turn off the friction stir welding equipment and the ultrasonic generator, and place the metal sheet in the air to cool to room temperature.

[0022] As a preferred embodiment, during the movement of the friction stirring tunnel forming device, the lower end of the connecting rod slides along the surface of the strip-shaped ultrasonic terminal; or, the connecting rod is used as the ultrasonic terminal.

[0023] Beneficial effects: During the processing, the material in the area above the annular boss is subjected to the upsetting force applied by the moving shaft shoulder, causing it to be laterally squeezed and flow obliquely upward. With the addition of an ultrasonic generator to apply an upward force to the material, the oblique upward flow of the squeezed material is further promoted. At the same time, the vortex groove on the surface of the moving shaft shoulder applies a traction force to the material away from the axis, so that the material overflows from the edge of the moving shaft shoulder. As the stirring friction tunnel forming device moves along the predetermined path, a regular continuous channel / tunnel is formed in the area traversed by the annular boss.

[0024] During processing, the lower end of the moving shoulder is always driven into the surface of the metal sheet to a certain depth, providing forging force to the material below the moving shoulder. The annular boss provides support force to the material above it. The material between the moving shoulder and the annular boss is compacted and formed under the action of forging force and support force. Compared with the traditional friction stir tunnel forming technology, the tunnel sealing performance is better. At the same time, a stationary shoulder is provided around the moving shoulder. Its end face adopts an inward structure. The outermost part of the stationary shoulder is just in contact with the surface of the metal sheet. The material overflowing from the edge of the moving shoulder is stored in the space below the stationary shoulder. Under the action of forging and scraping at the edge of the stationary shoulder, part of the material in the space is refilled into the thinned part caused by the downward pressure of the moving shoulder, thereby eliminating the thinning of the processing area and forming a processing area with the same thickness as the base material. The remaining material is discharged from the discharge hole on the lower end face of the stationary shoulder. Compared with the traditional friction stir tunnel forming technology, the surface forming quality of the processing area of ​​the present invention is higher. Due to the upsetting effect of the stationary shoulder and the cooperation with other components, the material density between the annular boss and the surface of the metal sheet is improved, the tunnel has better sealing performance, and there is no need to pre-set grooves on the surface of the metal sheet, and no need to remove flash after processing, making the process simple.

[0025] As one of the key aspects of this invention, the ultrasonic waves are cleverly transmitted directly to the annular boss through the connecting rod. Combined with the limiting effect of the lower end face of the annular boss, the material in the area below the annular boss is prevented from flowing obliquely upward, thereby ensuring the density of the material between the annular boss and the lower shoulder.

[0026] This invention is highly adaptable (it can be used for tunnel forming of aluminum, magnesium, copper and titanium alloy plates), highly feasible, with a simple process flow and low cost, making it suitable for large-scale industrial production applications. Attached Figure Description

[0027] Figure 1 This is a three-dimensional schematic diagram of the stirring friction tunnel forming device in Example 1;

[0028] Figure 2 This is a three-dimensional schematic diagram of the stirring friction tool head of the stirring friction tunnel forming device in Example 1;

[0029] Figure 3This is a three-dimensional schematic diagram of the stirring pin assembly of the friction stirring tunnel forming device in Example 1;

[0030] Figure 4 This is a schematic diagram of the stirring friction tunnel forming device in use in Example 1;

[0031] Figure 5 This is a three-dimensional schematic diagram of the stirring friction tool head of the stirring friction tunnel forming device in Example 2;

[0032] Figure 6 This is a partial cross-sectional schematic diagram of the stirring needle assembly of the friction stirring tunnel forming device in Example 2;

[0033] Figure 7 This is a schematic diagram of the stirring friction tunnel forming device in use in Example 2;

[0034] Figure 8 This is a schematic diagram of the material flow path of the friction stirring tunnel forming device in the embodiment under operating conditions;

[0035] Figure 9 This is a three-dimensional schematic diagram of the stirring friction tool head of the stirring friction tunnel forming device in Example 3. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] Combination Figures 1 to 4 As shown, an ultrasonic-assisted friction stir tunneling device includes a friction stir tool head and an ultrasonic generator disposed at the bottom of the friction stir tool head. The friction stir tool head includes a clamping part 31, with a moving shoulder 32 connected to the lower end of the clamping part 31. A stirring needle assembly is connected to the lower end of the moving shoulder 32. A stationary shoulder 21 is disposed around the stirring needle assembly. The stationary shoulder 21 and the moving shoulder 32 are arranged coaxially. A discharge hole 22 is disposed on the bottom wall of the stationary shoulder 21. The lower end face of the moving shoulder 32 is lower than the lower end face of the stationary shoulder 21. The stirring needle assembly includes an integrally formed and coaxial upper needle body 10, an annular boss 11, and a lower needle body 12. A lower shoulder 13 is disposed at the bottom of the lower needle body 12. The lower end of the moving shoulder 32, the upper needle body 10, the annular boss 11, and the lower needle body 12 can be located inside the workpiece simultaneously. The upper end of the lower shoulder 13 is in close contact with the lower end face of the workpiece.

[0039] In this embodiment, the annular boss 11 is generally triangular, with rounded corners at the corners. Both the upper needle body 10 and the lower needle body 12 are threaded. The outer diameter of the moving shoulder 32 is larger than the diameter of the circle corresponding to the rotation trajectory of the annular boss 11. The lower end face of the moving shoulder 32 is lower than the upper surface of the workpiece by any value within the range of 0.05 to 0.2 mm. The bottom surface of the stationary shoulder 21 has a concave structure, with an angle of 15° between the concave surface and the horizontal plane. The space for temporary material storage is formed by the bottom surface of the stationary shoulder 21, the upper surface of the workpiece, and the outer wall of the moving shoulder 32.

[0040] In this embodiment, the lower end face of the moving shaft shoulder 32 has a vortex groove with a depth of 0.5 mm and a width of 1 mm; the thread pitch of the upper needle body 10 and the lower needle body 12 is 0.8 mm and the diameter is 7 mm; the diameter of the discharge hole 22 is 2 mm, and the side length of the annular boss 11 is 10 mm and the thickness is 4 mm.

[0041] Example 2

[0042] Combination Figures 5 to 7 As shown, an ultrasonic-assisted friction stir tunneling device includes a friction stir tool head and an ultrasonic generator disposed at the bottom of the friction stir tool head. The friction stir tool head includes a clamping part 31, with a moving shoulder 32 connected to the lower end of the clamping part 31. A stirring needle assembly is connected to the lower end of the moving shoulder 32. A stationary shoulder 21 is disposed around the stirring needle assembly. The stationary shoulder 21 and the moving shoulder 32 are arranged coaxially. A discharge hole 22 is disposed on the bottom wall of the stationary shoulder 21. The lower end face of the moving shoulder 32 is lower than the lower end face of the stationary shoulder 21. The stirring needle assembly includes an integrally formed and coaxial upper needle body 10, an annular boss 11, and a lower needle body 12. A lower shoulder 13 is disposed at the bottom of the lower needle body 12. The lower end of the moving shoulder 32, the upper needle body 10, the annular boss 11, and the lower needle body 12 can be located inside the workpiece simultaneously. The upper end of the lower shoulder 13 is in close contact with the lower end face of the workpiece.

[0043] In this embodiment, the annular boss 11 is generally triangular, with rounded corners at the corners. Both the upper needle body 10 and the lower needle body 12 are threaded. The outer diameter of the moving shoulder 32 is larger than the diameter of the circle corresponding to the rotation trajectory of the annular boss 11. The lower end face of the moving shoulder 32 is lower than the upper surface of the workpiece by any value within the range of 0.1 to 0.2 mm. The bottom surface of the stationary shoulder 21 has a concave structure, with an angle of 12° between the concave surface and the horizontal plane. The space for temporary material storage is formed by the bottom surface of the stationary shoulder 21, the upper surface of the workpiece, and the outer wall of the moving shoulder 32.

[0044] In this embodiment, the lower end face of the moving shaft shoulder 32 has a vortex groove with a depth of 0.5 mm and a width of 2 mm; the thread pitch of the upper needle body 10 and the lower needle body 12 is 1.2 mm and the diameter is 12 mm; the diameter of the discharge hole 22 is 2.5 mm; the side length of the annular boss 11 is 15 mm and the thickness is 5 mm.

[0045] In this embodiment, an axial through hole 41 is provided on the lower shoulder 13, and an axial blind hole 42 is provided on the lower needle body 12. The axial blind hole 42 extends from the bottom end of the lower needle body 12 to the center of the annular boss 11. The connecting rod 43 is inserted into the axial through hole 41 and the axial blind hole 42. The connecting rod 43 does not contact the lower needle body 12 and the lower shoulder 13. The upper part of the connecting rod 43 is fixedly connected to the annular boss 11, and the lower end of the connecting rod 43 is used to connect to the ultrasonic generator.

[0046] Example 3

[0047] An ultrasonic-assisted friction stirring tunnel forming device, referring to Embodiment 2 and in combination Figure 9 As shown, its main difference from Embodiment 3 is that the annular boss 11 has a plurality of radially arranged needles 14 on its sidewall.

[0048] Example 4

[0049] A tunnel forming method using the friction stirring tunnel forming apparatus of Example 1 includes the following steps:

[0050] Step 1: Prepare a metal sheet (i.e., workpiece 20, aluminum alloy sheet), with a thickness of 6-30mm. Remove oxides from the surface of the metal sheet by mechanical grinding, and wipe off oil stains from the surface of the metal sheet with chemical reagents (anhydrous ethanol or acetone solution).

[0051] Step 2: Fix the metal sheet with tooling fixtures and assemble the friction stir tunnel forming device on the friction stir welding machine so that the upper end of the lower shoulder 13 can be close to the lower end face of the workpiece, and the lower end face of the moving shoulder 32 is 0.1mm lower than the upper surface of the workpiece.

[0052] Step 3: Connect the ultrasonic generator and then start the ultrasonic device;

[0053] Step 4: Start the friction stir welding machine and drive the friction stir tunnel forming device to press the metal sheet laterally from one side, so that the metal material in the processing area reaches a thermoplastic state and moves along the preset path.

[0054] The rotating speed of the friction stir tool head is 300 rpm, the depth of the lower end face of the moving shaft shoulder 32 pressed into the metal plate 1 is 0.2 mm, and the traveling speed of the friction stir tunnel forming device is 200 mm / min.

[0055] During the movement of the friction stirring tunnel forming device, the lower end of the connecting rod 43 slides along the surface of the strip-shaped ultrasonic terminal (in this scheme, the connecting rod 43 mainly serves as a bridge to transmit ultrasonic waves to the annular boss 11); or, the connecting rod 43 can be used as an ultrasonic terminal.

[0056] Step 5: After processing, drive the friction stir tunnel forming device away from the metal sheet, turn off the friction stir welding equipment and the ultrasonic generator, and place the metal sheet in the air to cool to room temperature.

[0057] During processing, the material flow path in the processing area is combined Figure 8 As shown, the material in the area above the annular boss 11 is subjected to the upsetting force applied by the moving shoulder 32, causing it to be laterally squeezed and flow obliquely upward. With the ultrasonic generator applying an upward force to the material, the oblique upward flow of the squeezed material is further promoted. At the same time, the vortex groove on the lower surface of the moving shoulder 32 applies a traction force to the material away from the axis, so that the material overflows from the edge of the moving shoulder 32. As the stirring friction tunnel forming device moves along the predetermined path, a continuous channel / tunnel with a regular shape is formed in the area traversed by the annular boss 11.

[0058] During processing, the lower end of the moving shoulder 32 is always driven into the surface of the metal sheet to a certain depth, providing forging force to the material below the moving shoulder 32. The annular boss 11 provides support force to the material above it. The material between the moving shoulder 32 and the annular boss 11 is compacted and formed by the forging force and support force. Compared with the traditional friction stir tunnel forming technology, the tunnel sealing performance is better. At the same time, a stationary shoulder 21 is provided around the moving shoulder 32. Its end face adopts an inward structure, and the outermost side is just in contact with the surface of the metal sheet. The material overflowing from the edge of the moving shoulder 32 is stored in the space below the stationary shoulder 21. Under the forging and scraping action of the edge of the stationary shoulder 21, part of the material in the space is refilled into the thinned part caused by the downward pressure of the moving shoulder 32, thereby eliminating the thinning of the processing area and forming a processing area with the same thickness as the base material. The remaining material is discharged from the discharge hole on the lower end face of the stationary shoulder 21. Compared to traditional friction stir tunneling technology, the surface forming quality of the processed area in this invention is higher. Due to the upsetting effect of the stationary shoulder 21, the material density between the annular boss 11 and the surface of the metal sheet is improved, resulting in better tunnel sealing. Furthermore, it eliminates the need for pre-setting grooves on the metal sheet surface and for removing flash after processing, simplifying the process. A key feature of this invention is the ingenious transmission of ultrasonic waves directly to the annular boss 11 via the connecting rod 43. Combined with the limiting effect of the lower end face of the annular boss 11, this prevents the material below the annular boss 11 from flowing obliquely upwards, thus ensuring the material density between the annular boss 11 and the lower shoulder. Tunnels processed using this invention exhibit good load-bearing capacity. For example, a linear tunnel on an aluminum alloy sheet (25mm thick) with a cross-sectional size of 12mm*5mm and a length of 1200mm can withstand a fluid pressure of no less than 5MPa; a linear tunnel on an aluminum alloy sheet (25mm thick) with a cross-sectional size of 10mm*4mm and a length of 800mm can withstand a fluid pressure of no less than 8MPa.

Claims

1. An ultrasonic-assisted friction stir tunneling device, comprising a friction stir tool head and an ultrasonic generator disposed at the bottom of the friction stir tool head, characterized in that: The stirring friction tool head includes a clamping part (31), a moving shaft shoulder (32) is connected to the lower end of the clamping part (31), a stirring needle assembly is connected to the lower end of the moving shaft shoulder (32), a stationary shaft shoulder (21) is provided around the stirring needle assembly, the stationary shaft shoulder (21) and the moving shaft shoulder (32) are arranged coaxially, a discharge hole (22) is provided on the bottom wall of the stationary shaft shoulder (21), and the lower end face of the moving shaft shoulder (32) is lower than the lower end face of the stationary shaft shoulder (21); The stirring needle assembly includes an integrally formed and coaxial upper needle body (10), an annular boss (11), and a lower needle body (12). A lower shaft shoulder (13) is provided at the bottom of the lower needle body (12). The lower end of the moving shaft shoulder (32), the upper needle body (10), the annular boss (11), and the lower needle body (12) can be located in the workpiece at the same time. The upper end of the lower shaft shoulder (13) is closely attached to the lower end surface of the workpiece. The outer diameter of the moving shoulder (32) is greater than the diameter of the circle corresponding to the rotation trajectory of the annular boss (11); the lower end face of the moving shoulder (32) is 0.05~1mm lower than the upper surface of the workpiece; the bottom surface of the stationary shoulder (21) has an inward concave structure, and the space for temporary storage of material is formed by the bottom surface of the stationary shoulder (21), the upper surface of the workpiece, and the outer side wall of the moving shoulder (32); The material overflowing from the edge of the moving shoulder (32) is stored in the space below the stationary shoulder (21). Under the upsetting and scraping action of the stationary shoulder (21), part of the material in the space is refilled into the thinned part caused by the downward pressing of the moving shoulder (32), thereby eliminating the thinning of the processing area and forming a processing area with the same thickness as the base material. The remaining material is discharged from the discharge hole on the lower end face of the stationary shoulder (21). An axial through hole (41) is provided on the lower shoulder (13), and an axial blind hole (42) is provided on the lower needle body (12). The axial blind hole (42) extends from the bottom end of the lower needle body (12) to the center of the annular boss (11). The connecting rod (43) is inserted into the axial through hole (41) and the axial blind hole (42). The connecting rod (43) does not contact the lower needle body (12) and the lower shoulder (13). The upper part of the connecting rod (43) is fixedly connected to the annular boss (11), and the lower end of the connecting rod (43) is used to connect to the ultrasonic generator.

2. The friction stirring tunnel forming device according to claim 1, characterized in that: The annular boss (11) is triangular in shape, and the corner of the triangle is rounded and chamfered.

3. The friction stirring tunnel forming device according to claim 1, characterized in that: Both the upper needle body (10) and the lower needle body (12) are provided with threads.

4. The friction stirring tunnel forming apparatus according to any one of claims 1-3, characterized in that: The annular boss (11) has multiple radially arranged needles (14) on its sidewall.

5. A tunnel forming method using the stirring friction tunnel forming apparatus according to any one of claims 1-4, characterized in that the steps include... include: Step 1: Prepare the metal sheet, mechanically grind to remove oxides from the surface of the metal sheet, and wipe with chemical reagents to remove oil stains from the surface of the metal sheet; Step 2: Fix the metal plate with tooling fixtures and assemble the friction stir tunnel forming device on the friction stir welding machine so that the upper end of the lower shoulder (13) can be close to the lower end face of the workpiece and the lower end face of the moving shoulder (32) is 0.05~0.2mm lower than the upper surface of the workpiece. Step 3: Connect the ultrasonic generator and then start the ultrasonic device; Step 4: Start the friction stir welding machine and drive the friction stir tunnel forming device to press the metal sheet laterally from one side, so that the metal material in the processing area reaches a thermoplastic state and moves along the preset path; Step 5: After processing, drive the friction stir tunnel forming device away from the metal sheet, turn off the friction stir welding equipment and the ultrasonic generator, and place the metal sheet in the air to cool to room temperature.

6. The tunnel forming method according to claim 5, characterized in that: During the movement of the friction stirring tunnel forming device, the lower end of the connecting rod (43) slides along the surface of the strip-shaped ultrasonic terminal; or, the connecting rod (43) is used as the ultrasonic terminal.

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