Aluminum alloy plastic friction stir welding connection method and clamping fixture

Abstract

The present invention provides a method and a clamping fixture for friction stir welding of aluminum alloy and plastic. The method comprises the following steps: (1) grinding the surface of the aluminum alloy plate and pre-treating the overlapping interface with laser etching; (2) assembling an ultrasonic vibration head below the weld joint using a clamping fixture and performing friction stir welding on the upper surface of the weld joint; (3) performing laser post-processing on the welded sample. The method for friction stir welding of aluminum alloy and plastic adopts a method of combining ultrasonic vibration with friction stir welding and laser welding to break up or vibrate out the bubbles generated during the welding process into the molten pool, and the ultrasonic vibration evenly distributes the heat in the molten pool. The clamping fixture can not only tightly assemble the welding base material and the ultrasonic vibration head together, but also ensure close contact between the welding base materials.

Description

Technical Field

[0001] The invention relates to a method for connecting aluminum alloy and plastic by friction stir welding and a clamping fixture, belonging to the technical field of aluminum / plastic dissimilar material welding. Background Art

[0002] Aluminum alloys are widely used in automotive, aviation, and marine applications due to their lightweight, excellent ductility, and corrosion resistance. Thermoplastics, on the other hand, offer excellent machinability, fatigue resistance, corrosion resistance, and higher specific strength. Joining aluminum alloys and thermoplastics not only significantly reduces the weight of engineering components, achieving lightweight and green development goals, but also combines the advantages of both, offering promising prospects in automotive and engineering applications. In recent years, the main methods for joining aluminum alloys and plastics have been adhesive bonding, mechanical bonding, and welding. Adhesive bonding has drawbacks such as long curing times, sensitivity to ambient temperature, and environmental pollution from adhesives, while mechanical bonding, such as riveting, has drawbacks such as high stress concentration and additional weight. These limitations have limited the widespread application of both methods. Welding, a novel approach to joining two materials, not only ensures joint integrity and reliability but also allows for the formation of a chemical bond between the two materials at the interface through thermal interaction, effectively improving joint performance. In recent years, numerous researchers have proposed various welding methods for joining aluminum alloys and thermoplastics, such as laser welding and friction stir welding. The thermal effect on the interface during welding will also cause the plastic to decompose and produce bubbles. More and larger bubbles in the interface will lead to a serious decrease in the formability and mechanical properties of the joint. Therefore, it is necessary to inhibit the accumulation and growth of bubbles during welding.

[0003] In the invention patent with authorization announcement number CN107414291B and authorization announcement date 2020.05.22, a method of ultrasonic-assisted laser welding of dissimilar materials is disclosed. This method uses the energy of ultrasound to assist the laser welding process of dissimilar materials such as polymer materials and ceramics or metal materials. The vibration of the ultrasonic vibration head continuously acts on the entire joint area, but the laser welding process has a high heat input. A large number of pores are easily generated during the welding process, which are difficult to eliminate. In addition, the laser welding process does not have a tracking pressurization effect. The welding base material is constrained by the clamps on both sides, and the residual stress is large, which is not easy to release, thereby damaging the joint performance.

[0004] An invention patent application with application publication number CN106238901A and application publication date 2016.12.21 discloses an ultrasonic-assisted friction stir welding tool and welding method. This method uses ultrasonic energy to assist the friction stir welding process. An ultrasonic vibration head is assembled at a position where the stirring head does not rotate, and moves with the stirring head to achieve the function of real-time tracking vibration. However, this method is relatively unstable. The vibration head moves with the stirring head, resulting in uneven distribution of vibration energy in various parts of the joint, and the action time is short, which cannot achieve the purpose of eliminating bubbles.

[0005] In summary, the energy of ultrasonic vibration can effectively accelerate the decomposition and diffusion of bubbles in the molten pool. However, the high heat input of laser welding and its inability to track pressurization result in large bubbles that are difficult to eliminate. The design of ultrasonic-assisted devices for friction stir welding also presents problems such as energy instability. The uneven distribution of interfacial bonding forces caused by the curved interface in metal-plastic lap welding also urgently needs to be addressed. Therefore, existing processes and technologies still need to be improved and developed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology and provide a method and a clamping fixture for stir friction welding connection of aluminum alloy and plastic. The welding process in this method is complete. During the whole process, the parent material is always kept in close contact under the action of the clamping fixture, and the ultrasonic vibration is conducive to the overflow of bubbles, which promotes the formation of the weld, improves production efficiency, and effectively improves the performance of the weld joint.

[0007] This solution is achieved through the following technical measures: The aluminum alloy plastic friction stir welding connection method includes the following steps:

[0008] (1) The surface of the aluminum alloy plate is polished with sandpaper, and the lap joint interface is pre-treated by laser etching: the lap joint interface of the aluminum alloy plate after laser etching presents a regular groove-like morphology;

[0009] (2) Using a clamping fixture to assemble an ultrasonic vibrator under the weld joint and stir friction welding on the upper surface of the weld joint: the weld joint is in the form of an overlapped aluminum alloy plate on the upper side and a thermoplastic plastic plate on the lower side. The downward pressure of the stirring head used in the friction stir welding is equal to the length of its stirring needle and is less than the thickness of the aluminum alloy plate. The molten thermoplastic plastic plate will fill the groove due to the pressure of the stirring head, forming a mechanical interlock. After welding, the weld joint presents a curved interface, the groove in the center is widened, and the groove in the edge area is compressed;

[0010] (3) Perform laser post-processing on the welded samples: Use a laser beam to perform low-power laser welding on the edge area of ​​the curved interface, so that the thermoplastic plastic plate at the groove can be heated and melted again to fill the widened groove. During the laser post-processing process, the ultrasonic vibration head continues to work.

[0011] Preferably, the laser etching uses a laser power of 10-80 W, a frequency of 10-30 KHz, a scanning speed of 500-2000 mm / s, and a scanning interval of 50-400 μm.

[0012] Preferably, the welding speed of the friction stir welding is 100-1000 mm / min, the rotation speed of the stirring head is 1000-2000 rpm, the inclination angle of the stirring head relative to the vertical direction is 1-3°, and the insertion residence time of the stirring head is 2-10 s.

[0013] Preferably, the thickness of the aluminum alloy plate and the thermoplastic plastic plate are both 1.5-4 mm, the length of the aluminum alloy plate and the thermoplastic plastic plate are 75-200 mm, and the width is 50-100 mm.

[0014] Preferably, the laser post-processing uses a laser power of 100-300 W and a scanning speed of 100-300 mm / min.

[0015] Preferably, the scanning positions of the laser post-processing are located on both sides of the melt path of the friction stir welding.

[0016] Preferably, during the laser post-processing process, the ultrasonic vibration head is kept in close contact with the weld joint.

[0017] Preferably, the frequency of the ultrasonic vibration head is 10-20kHz and the power is 1000-3000W; the bottom of the ultrasonic vibration head is fixedly connected to a connecting rod, the bottom of the connecting rod is fixedly connected to a stepped disc-shaped joint, the bottom of the stepped disc-shaped joint is fixedly connected to an ultrasonic transducer, and the ultrasonic transducer provides energy for the ultrasonic vibration head.

[0018] The present invention also provides a clamping fixture, which includes a clamping shell and two pressing heads arranged on the front and rear sides of the clamping shell;

[0019] The bottom of the clamping shell is fixedly connected to a supporting column, and a mounting hole is provided at the bottom of the clamping shell to cooperate with the small end of the stepped disc-shaped joint. A through-hole adapted to the shape of the ultrasonic vibration head is provided on the right side of the clamping shell. An upper strip-shaped opening is provided on the top of the clamping shell to cooperate with the top of the ultrasonic vibration head. The right end of the upper strip-shaped opening is connected to the through-hole, and a gap is left between the left end and the left end of the clamping shell. A lower strip-shaped opening is provided at the bottom of the clamping shell to cooperate with the connecting rod, and the left and right ends of the lower strip-shaped opening are respectively connected to the mounting hole and the through-hole;

[0020] The pressure head includes a gantry pressure plate, the left and right ends of the gantry pressure plate are respectively fixed with pulling pins, the front and rear ends of the left and right sides of the clamping shell are respectively fixed with fixing pins, a tension spring is connected between the pulling pin and the corresponding fixing pin, and the left and right sides of the gantry pressure plate are respectively provided with strip-shaped sliding holes that slide with the corresponding fixing pins.

[0021] Preferably, the inner width of the gantry pressure plate is larger than the size of the aluminum alloy plate and the thermoplastic plastic plate along the welding direction; the center line of the strip sliding hole in the length direction passes through the center of the fixing pin and the pulling pin; rubber pads are respectively fixed on the top surface of the clamping shell, the inner side surface of the gantry pressure plate and the inner bottom surface of the clamping shell around the mounting hole.

[0022] The beneficial effects of the present invention can be known from the description of the above scheme. In the method of stir friction welding of aluminum alloy plastic, ultrasonic vibration is combined with stir friction welding and laser welding to break up or shake out the bubbles generated by the thermal decomposition of thermoplastic plastics during welding, effectively improving the forming performance of the weld joint. At the same time, the ultrasonic vibration makes the heat distribution in the molten pool more uniform, which is beneficial to improving the mechanical properties of the weld joint. The clamping fixture described in the present invention can tightly assemble the welding base material and the ultrasonic vibration head together, so that the ultrasonic vibration can track the welding molten pool, eliminating the instability of manually holding the ultrasonic vibration head. At the same time, it can ensure close contact between the welding base materials, prevent the large-scale generation of bubbles, and effectively improve the performance of the weld joint. It can be seen that compared with the prior art, the present invention has outstanding substantive characteristics and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of laser etching in the method for friction stir welding of aluminum alloy and plastic in the present invention.

[0024] Figure 2 Schematic diagram of the structure of the welded joint between aluminum alloy plate and thermoplastic plastic plate.

[0025] Figure 3It is a schematic diagram of the partial cross-section structure of the clamping fixture in the present invention.

[0026] Figure 4 This is a schematic diagram of the position of laser post-processing in the method for friction stir welding of aluminum alloy and plastic in the present invention.

[0027] In the figure, 1-rubber pad, 2-gantry pressure plate, 3-clamping shell, 4-support column, 5-aluminum alloy plate, 6-thermoplastic plastic plate, 7-ultrasonic vibration head, 8-ultrasonic transducer, 9-stirring head, 10-laser beam, 11-mounting hole, 12-bar sliding hole, 13-tension spring, 14-pull pin, 15-fixing pin, 16-lower bar opening, 17-through opening, 18-upper bar opening, 19-stepped disc joint, 20-connecting rod. DETAILED DESCRIPTION

[0028] In order to clearly illustrate the technical features of this solution, the solution is described below through specific implementation methods and in conjunction with the accompanying drawings.

[0029] A method for joining aluminum alloy and plastic by friction stir welding, comprising the following steps:

[0030] (1) Grind the surface of the aluminum alloy plate 5 with sandpaper, and perform laser etching pretreatment on the overlapping interface of the aluminum alloy plate 5, such as Figure 1 As shown, the lapped interface of the aluminum alloy plate 5 after laser etching presents a regular groove-like morphology; the laser power used in the laser etching is 10-80W, the frequency is 10-30KHz, the scanning speed is 500-2000mm / s, and the scanning spacing is 50-400μm;

[0031] (2) Using a clamping fixture, assemble the ultrasonic vibration head 7 below the weld joint and perform friction stir welding on the upper surface of the weld joint:

[0032] The frequency of the ultrasonic vibration head 7 is 10-20kHz, and the power is 1000-3000W. The bottom of the ultrasonic vibration head 7 is fixedly connected to a connecting rod 20, and the bottom of the connecting rod 20 is fixedly connected to a stepped disc-shaped joint 19. The bottom of the stepped disc-shaped joint 19 is fixedly connected to an ultrasonic transducer 8, and the ultrasonic transducer 8 provides energy for the ultrasonic vibration head 7.

[0033] The aluminum alloy plate 5 and the thermoplastic plastic plate 6 are both 1.5-4 mm thick, 75-200 mm long, and 50-100 mm wide. The welded joint is an overlapped joint with the aluminum alloy plate 5 on top and the thermoplastic plastic plate 6 on the bottom. The aluminum alloy plate 5, the thermoplastic plastic plate 6, and the ultrasonic vibration head 7 are assembled using the clamping fixture of the present invention to ensure a tight connection between the three.

[0034] The downward pressure of the stirring head 9 used in the friction stir welding is equal to the length of its stirring needle and less than the thickness of the aluminum alloy plate 5. The welding speed of the friction stir welding is 100-1000 mm / min, the rotation speed of the stirring head 9 is 1000-2000 rpm, the inclination angle of the stirring head 9 relative to the vertical direction is 1-3 degrees, and the insertion residence time of the stirring head 9 is 2-10 seconds. The molten thermoplastic plastic plate 6 is filled into the groove due to the pressure of the stirring head 9, forming a mechanical interlock. After welding, the weld joint presents a curved interface, the groove in the center is widened, and the groove in the edge area is compressed.

[0035] (3) Laser post-processing of welded samples:

[0036] The scanning position of the laser post-processing is located on both sides of the melt path of the stir friction welding, and the ultrasonic vibration head 7 is kept in close contact with the weld joint during the process. The laser power used in the laser post-processing is 100-300W, and the scanning speed is 100-300mm / min; the laser beam 10 is used to perform low-power laser welding on the edge area of ​​the curved interface, so that the thermoplastic plastic plate 6 at the groove can be heated and melted again to fill the widened groove. The ultrasonic vibration head 7 continues to work during the laser post-processing, and the ultrasonic vibration head 7 is kept in close contact with the weld joint during the laser post-processing.

[0037] The aluminum alloy plastic friction stir welding method of the present invention adopts a lap joint form with an aluminum alloy plate 5 on top and a thermoplastic plastic plate 6 on the bottom, and the lap joint is assembled with an ultrasonic vibrator 7 using a clamping fixture. During the friction stir welding process, the ultrasonic vibrator 7 continuously vibrates due to the energy provided by the ultrasonic transducer 8, which helps to disperse or overflow the bubbles generated by the decomposition of the thermoplastic plastic plate 6 due to the heat during the welding process, effectively improving the mechanical properties of the welded joint. Figure 1 As shown in FIG, the interface of the aluminum alloy plate 5 after laser etching presents a regular groove-like morphology. The molten thermoplastic plastic plate 6 will fill the groove due to the pressure of the stirring tip 9, forming a mechanical interlock. However, the length of the stirring needle is less than the thickness of the aluminum alloy plate 5, resulting in a curved interface of the weld joint after welding, as shown in FIG. Figure 3 As shown in the figure, the originally regular groove morphology is distorted to varying degrees. The groove in the center is widened, while the groove in the edge area is compressed, making it difficult to fill the plastic, resulting in a weak area in the weld joint. Figure 3 The edge area of ​​the curved interface shown is connected by low-power laser welding, so that the thermoplastic plastic plate 6 at the groove can be heated and melted again to fill the groove widened by the laser, thereby enhancing the performance of the weld joint. The ultrasonic vibration head 7 continues to work during the laser processing.

[0038] The present invention also provides a clamping fixture, such as Figure 2 As shown, it includes a clamping shell 3 and two pressing heads arranged on the front and rear sides of the clamping shell 3.

[0039] Among them, the bottom of the clamping shell 3 is fixedly connected with a supporting column 4, and the entire clamping fixture 3 is supported by the supporting column 4. The bottom of the clamping shell 3 is provided with a mounting hole 11 that cooperates with the small end of the stepped disc-shaped joint 19, and the right side of the clamping shell 3 is provided with a through-hole 17 that is adapted to the shape of the ultrasonic vibration head 7. The top of the clamping shell 3 is provided with an upper strip-shaped opening 18 that cooperates with the top of the ultrasonic vibration head 7. The right end of the upper strip-shaped opening 18 is connected to the through-hole 17, and a distance is left between the left end and the left end of the clamping shell 3. A lower strip opening 16 cooperating with the connecting rod 20 is provided at the bottom of the clamping shell 3, and the left and right ends of the lower strip opening 16 are respectively connected to the mounting hole 11 and the through opening 17; the ultrasonic vibration head 7 slides into the clamping shell 3 through the through opening 17, and the ultrasonic vibration head 7 is guided and limited by the upper strip opening 18 to ensure the stability of the movement of the ultrasonic vibration head 7. The lower strip opening 16 guides and limits the connecting rod 20, and the mounting hole 11 is used to accommodate the small end of the stepped disc-shaped joint 19, and the bottom of the large end of the stepped disc-shaped joint 19 contacts the inner bottom surface of the clamping shell 3.

[0040] The pressure head includes a gantry pressure plate 2, and the left and right ends of the gantry pressure plate 2 are respectively fixed with pulling pins 14, and the front and rear ends of the left and right sides of the clamping shell 3 are respectively fixed with fixing pins 15. A tension spring 13 is connected between the pulling pin 14 and the corresponding fixing pin 15, and the left and right sides of the gantry pressure plate 2 are respectively provided with strip sliding holes 12 that slide with the corresponding fixing pins 15.

[0041] The inner width of the gantry pressing plate 2 is larger than the size of the aluminum alloy plate 5 and the thermoplastic plastic plate 6 along the welding direction to ensure that the two gantry pressing plates 2 can go around to the top of the clamping shell 3 to press the aluminum alloy plate 5 and the thermoplastic plastic plate 6.

[0042] The center line of the strip sliding hole 12 in the length direction passes through the center of the fixing pin 15 and the pulling pin 14 to ensure that when the gantry pressure plate 2 is wound around the top of the clamping shell 3, the gantry pressure plate 2 can move vertically downward under the resetting action of the tension spring 13, so that the inner top surface of the gantry pressure plate 2 can fit tightly with the upper end surfaces of the aluminum alloy plate 5 and the thermoplastic plastic plate 6, avoiding the situation where the gantry pressure plate 2 is deflected and cannot fit tightly with the aluminum alloy plate 5 and the thermoplastic plastic plate 6, thereby ensuring the pressing effect of the gantry pressure plate 2 on the aluminum alloy plate 5 and the thermoplastic plastic plate 6.

[0043] Rubber pads 1 are fixed to the top surface of the clamping shell 3, the inner side surface of the gantry pressure plate 2, and the periphery of the mounting hole 11 in the inner bottom surface of the clamping shell 3. The rubber pads 1 can reduce the impact of ultrasonic vibration on the clamping fixture, and can also increase the friction between the contact surfaces of the gantry pressure plate 2 and the aluminum alloy plate 5 and the thermoplastic plastic plate 6, further ensuring the clamping effect of the gantry pressure plate 2 on the aluminum alloy plate 5 and the thermoplastic plastic plate 6.

[0044] When not in use, the two gantry pressure plates 2 are respectively placed on the front and rear sides of the clamping shell 3, and the ultrasonic vibration head 7 can slide into the interior of the clamping shell 3 along the through-hole 17 on the side of the clamping shell 3, so that the small end of the stepped disc-shaped joint 19 enters the mounting hole 11 and the large end is stuck at the edge of the mounting hole 11, so as to limit the horizontal displacement of the ultrasonic vibration head 7. At this time, the aluminum alloy plate 5 and the thermoplastic plastic plate 6 are assembled above the ultrasonic vibration head 7 along the lap joint form with the aluminum alloy plate 5 on top and the thermoplastic plastic plate 6 on the bottom, limiting the vertical displacement of the ultrasonic vibration head 7, so as to achieve the effect of vibrating the sample (aluminum alloy plate 5 and thermoplastic plastic plate 6). After that, the gantry pressing plate 2 is pulled outward by pulling the pin 14, so that the fixing pin 15 moves to the end of the strip sliding hole 12, and then the gantry pressing plate 2 is rotated to the top of the clamping shell 3, and the pulling pin 14 is released. The tension spring 13 is reset and tightened to fasten the gantry pressing plate 2 and the clamping shell 3 together, clamping the aluminum alloy plate (5) and the thermoplastic plastic plate (6). The magnitude of the clamping force is almost unaffected by the vibration of the fixture and the softening of the thermoplastic plastic plate 6 during the welding process. At the same time, the left and right sides of the gantry pressing plate 2 can resist the sides of the aluminum alloy plate 5 and the thermoplastic plastic plate 6 to prevent the two materials from moving with the stirring head 9 during the welding process. The ultrasonic transducer 8 provides energy for the ultrasonic vibration head 7. The clamping fixture is suitable for both stir friction welding and laser welding connection processes.

[0045] Technical features not described in the present invention can be implemented by existing technologies and will not be described in detail here. The present invention is not limited to the above-mentioned specific embodiments. Changes, modifications, additions or substitutions made by ordinary technicians in this field within the scope of the essence of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for joining aluminum alloy and plastic by friction stir welding, characterized by: It includes the following steps: (1) grinding the surface of the aluminum alloy plate (5) with sandpaper, and pre-treating the overlapping interface thereof by laser etching: the overlapping interface of the aluminum alloy plate (5) after laser etching presents a regular groove-like morphology; (2) Using a clamping fixture to assemble the ultrasonic vibration head (7) below the weld joint and stir friction welding is performed on the upper surface of the weld joint: the weld joint is in the form of an overlapped aluminum alloy plate (5) on the upper side and a thermoplastic plastic plate (6) on the lower side, the downward pressure of the stirring head (9) used in the stir friction welding is equal to the length of its stirring needle and is less than the thickness of the aluminum alloy plate (5), the molten thermoplastic plastic plate (6) is filled into the groove due to the pressure of the stirring head (9), forming a mechanical interlock, and after welding, the weld joint presents a curved interface, the groove in the center is widened, and the groove in the edge area is compressed; (3) Performing laser post-processing on the welded sample: The scanning position of the laser post-processing is located on both sides of the melt path of the stir friction weld, and a laser beam (10) is used to perform low-power laser welding on the edge area of ​​the curved interface, so that the thermoplastic plastic plate (6) at the groove can be heated and melted again to fill the widened groove. During the laser post-processing process, the ultrasonic vibration head (7) continues to work.

2. The method for friction stir welding of aluminum alloy and plastic according to claim 1, characterized in that: The laser etching adopts a laser power of 10-80W, a frequency of 10-30KHz, a scanning speed of 500-2000mm / s, and a scanning interval of 50-400μm.

3. The method for friction stir welding of aluminum alloy and plastic according to claim 2, characterized in that: The welding speed of the friction stir welding is 100-1000 mm / min, the rotation speed of the stirring head (9) is 1000-2000 rpm, the inclination angle of the stirring head (9) relative to the vertical direction is 1-3°, and the insertion residence time of the stirring head (9) is 2-10 s.

4. The method for friction stir welding of aluminum alloy and plastic according to claim 3, characterized in that: The thickness of the aluminum alloy plate (5) and the thermoplastic plastic plate (6) are both 1.5-4 mm, and the length of the aluminum alloy plate (5) and the thermoplastic plastic plate (6) are 75-200 mm and the width is 50-100 mm.

5. The method for friction stir welding of aluminum alloy and plastic according to claim 4, characterized in that: The laser post-processing adopts a laser power of 100-300W and a scanning speed of 100-300mm / min.

6. The method for friction stir welding of aluminum alloy and plastic according to claim 5, characterized in that: During the laser post-processing process, the ultrasonic vibration head (7) is kept in close contact with the welding joint.

7. The method for friction stir welding of aluminum alloy and plastic according to claim 6, characterized in that: The frequency of the ultrasonic vibration head (7) is 10-20kHz, and the power is 1000-3000W; The bottom of the ultrasonic vibration head (7) is fixedly connected to a connecting rod (20), the bottom of the connecting rod (20) is fixedly connected to a stepped disc-shaped joint (19), the bottom of the stepped disc-shaped joint (19) is fixedly connected to an ultrasonic transducer (8), and the ultrasonic transducer (8) provides energy for the ultrasonic vibration head (7).

8. A clamping fixture, characterized by: It comprises a clamping shell (3) and two pressing heads arranged on the front and rear sides of the clamping shell (3); The bottom of the clamping shell (3) is fixedly connected to a supporting column (4), the bottom of the clamping shell (3) is provided with a mounting hole (11) that matches the small end of the stepped disc-shaped joint (19), the right side of the clamping shell (3) is provided with a through-hole (17) that is adapted to the shape of the ultrasonic vibration head (7), the top of the clamping shell (3) is provided with an upper strip-shaped opening (18) that matches the top of the ultrasonic vibration head (7) according to any one of claims 1 to 7, the right end of the upper strip-shaped opening (18) is connected to the through-hole (17), and a distance is left between the left end and the left end of the clamping shell (3), the bottom of the clamping shell (3) is provided with a lower strip-shaped opening (16) that matches the connecting rod (20), and the left and right ends of the lower strip-shaped opening (16) are respectively connected to the mounting hole (11) and the through-hole (17); The pressure head includes a gantry pressure plate (2), the left and right ends of the gantry pressure plate (2) are respectively fixedly connected with a pulling pin (14), the front and rear ends of the left and right sides of the clamping shell (3) are respectively fixedly connected with a fixing pin (15), a tension spring (13) is connected between the pulling pin (14) and the corresponding fixing pin (15), and the left and right sides of the gantry pressure plate (2) are respectively provided with a strip sliding hole (12) that slides with the corresponding fixing pin (15).

9. The clamping fixture according to claim 8, characterized in that: The inner width of the gantry pressure plate (2) is greater than the dimensions of the aluminum alloy plate (5) and the thermoplastic plastic plate (6) along the welding direction; The center line of the strip-shaped sliding hole (12) in the longitudinal direction passes through the center of the fixing pin (15) and the pulling pin (14); Rubber pads (1) are respectively fixed to the top surface of the clamping shell (3), the inner side surface of the gantry pressure plate (2), and the periphery of the mounting hole (11) in the inner bottom surface of the clamping shell (3).

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