A friction stir welding method

Abstract

This invention discloses a friction stir welding method that addresses the poor adaptability of conventional friction stir welding for thick plate welding and filler alloying, as well as the problems of excessive heat input, alloy burn-off, joint softening, and numerous defects in traditional filler processes. It employs a synchronous filler welding scheme. The stirring pin rotation speed is pre-set to 800-1600 r / min, and the welding speed to 400-1000 mm / min. The hollow filler rod rotates in the same direction as the stirring pin, with a stationary shoulder pressure of -0.5 to 0 mm. During welding, the stirring pin plasticizes the base material to achieve metallurgical bonding, while the rod synchronously frictionally plasticizes and melts to fill the weld. After the welding pin is withdrawn to form a keyhole, the rod continues to press down to fill and close the weld. This invention eliminates the need for pre-grooving and pre-filling, simplifying the process and improving efficiency. It strictly controls heat input to avoid cumulative heat damage, alleviates alloy burn-off and joint softening, prevents weld thinning, and eliminates defects such as porosity and incomplete fusion. It optimizes weld formation, refines grain size, and improves the mechanical properties, corrosion resistance, and electrical conductivity of the joint. It is suitable for welding high-end equipment using aluminum alloys and dissimilar materials.

Description

Technical Field

[0001] This invention relates to the field of aluminum processing technology, and in particular to a friction stir welding method. Background Technology

[0002] Friction stir welding (FSW), as an advanced solid-state welding technology, is widely used for joining metals such as aluminum alloys and magnesium alloys, as well as dissimilar materials, due to its advantages such as no metal melting, no weld porosity or cracks, minimal weld deformation, and excellent mechanical properties. It is also widely applied in high-end equipment manufacturing fields such as aerospace and rail transportation. However, conventional FSW cannot meet the needs of special applications such as thick plate welding, weld metallization, large gap compensation, and surface shaping optimization. The industry often uses pre-weld pretreatment and post-weld repair and reinforcement filling processes, but existing technologies all have significant drawbacks. Specifically, the process of pre-filling with metal through slotting and then performing multiple FSWs can cause severe alloy element loss and significant weld thinning due to the cumulative heat input. Excessive heat input can also lead to joint softening and a significant decrease in mechanical properties. Using pre-placed welding wire or powder requires increased heat input to ensure fusion of the filler material, which can easily lead to defects such as porosity and lack of fusion, further exacerbating alloy loss and joint softening. Consumable friction heads often result in severe flash during the filling process, leading to uneven filling. Summary of the Invention

[0003] In view of this, the present invention discloses a friction stir welding method, comprising the following steps:

[0004] S1. Before welding, set the welding parameters of the friction stir welding device: the rotation speed of the stirring pin is 800~1600 r / min, the welding speed is 400~1000 mm / min, the rotation speed of the hollow filling rod is 800~1600 r / min, and the rotation direction of the hollow filling rod is the same as that of the stirring pin.

[0005] S2. During the welding process, the stirring pin rotates to complete the solid-phase plasticizing and stirring of the base material, realizing the metallurgical bonding between the base materials. At the same time, the hollow filling rod rotates independently, and the lower end face of the hollow filling rod contacts the surface of the base material, so that the hollow filling rod always fits the weld area. Under constant downward pressure, the lower end of the hollow filling rod generates heat through friction with the plasticized metal of the weld and gradually plasticizes and melts, filling into the interior of the weld, completing the synchronous filling and welding formation.

[0006] S3. When the stirring pin reaches the welding endpoint, the stirring pin rises and is pulled out of the weld. The hollow filling rod rotates and applies downward pressure to the weld surface to fill the keyhole formed after the stirring pin is pulled out. After the filling is completed, the hollow filling rod stops rotating and moves upward to separate from the weld.

[0007] The above design fundamentally solves the defects of existing friction stir welding filler and alloying. The hollow filler rod can be used as a welding wire, and welding and filler are completed simultaneously with the stirring pin. During the welding process, the high-speed rotating hollow filler rod comes into contact with the base material and generates frictional heat to soften it. Under axial pressure, the metal of the rod is clad onto the welding position. At the same time, driven by the stirring pin, the clad metal participates in the flow of the weld metal, transferring alloying elements into the weld for alloying. During welding, the hollow filler rod cooperates with the stationary shoulder, and the molten and plasticized metal moves in the concave surface, reducing the generation of flash.

[0008] The aforementioned technical methods eliminate the complex processes of traditional multiple welding operations, pre-placed welding wire powder, and separate post-weld filling. They eliminate the need for pre-grooving or additional filler, significantly simplifying the process and improving welding efficiency. Simultaneously, they avoid the cumulative heat input from multiple welding operations, effectively controlling the overall heat input and fundamentally alleviating the problems of alloy element burn-off and base material composition imbalance. This preserves the original strengthening properties of the alloy material and prevents excessive weld thinning, ensuring the effective thickness and load-bearing area of ​​the welded joint. Furthermore, the hollow filler rods can fill the keyhole formed by the stirring pin, simultaneously addressing defects such as porosity, cracks, and undercut that easily occur during fusion welding filling and repair. This improves weld formation quality, joint mechanical properties, corrosion resistance, and grain refinement, thereby enhancing the weld's electrical conductivity.

[0009] As a supplement to the technical solution of the present invention, in step S1, the formula for calculating the consumption length of the hollow filling rod is as follows:

[0010]

[0011] In the above formula, H is the length of the hollow filler rod consumed, in mm; D is the weld width, in mm; h is the shoulder pressing amount, in mm; L is the weld length, in mm; R is the outer diameter of the hollow filler rod, in mm; and r is the inner diameter of the hollow filler rod, in mm.

[0012] The shoulder of the friction stir welding device is a stationary shoulder. The downward pressure of the stationary shoulder during the welding process is -0.5~0mm, and the contact width between the stationary shoulder and the base material is 0.2mm~2mm.

[0013] By rationally controlling the amount of static shoulder compression and managing the consumption of hollow filler rods, it is possible to compact ductile metal, eliminate internal defects, optimize material flow, stabilize heat input, strictly control weld thinning and forming quality, stabilize alloy composition transition, balance heat input, improve the quality of metal plastic flow and solid-state bonding, and accurately compensate for material loss.

[0014] As a supplement to the technical solution of the present invention, the base material is 3mm thick 6061 aluminum alloy.

[0015] The hollow filled rod has the following composition: Si: 0.5%-0.8%, Mg: 0.8%-1.1%, Fe: 0.01%-0.2%, Cu: 0.15%-0.25%, Mn: 0.05%-0.15%, Cr: 0.08%-0.30%, Zn: 0.01%-0.1%, Ti: 0.02%-0.06%, Zr: 0.05%-0.25%.

[0016] The hollow filled bars can be prepared by aluminum alloy smelting, casting, and extrusion processes. The process route is as follows: raw material batching → high-temperature smelting in a smelting furnace → adjusting alloy composition → in-furnace melt purification → grain refinement → online melt purification (degassing and slag removal) → semi-continuous casting ingot → ingot homogenization treatment → billet sawing → billet rolling → heating of billet, mold, and extrusion cylinder → hollow bar extrusion (not limited to extrusion, such as forging) → drawing (not limited to drawing, such as hot rolling) → solution aging treatment → finishing → precision milling → surface cleaning → quality inspection.

[0017] As a supplement to the technical solution of the present invention, the base materials are 6061 aluminum alloy and 7003 aluminum alloy.

[0018] The hollow filled rod has the following composition: Si: 0.05%~0.2%, Mg: 0.6%~1.0%, Fe: 0.01%~0.20%, Cu: 0.06%~0.20%, Mn: 0.1%~0.30%, Cr: 0.01%~0.20%, Zn: 5.0%~6.5%, Ti: 0.03%~0.15%, Zr: 0.05%~0.25%, and Sc: 0.02%~0.1%.

[0019] Alloying in friction stir welding mainly occurs through stirring, recrystallization, and diffusion. During the welding thermal cycle, the reinforcing phase will re-dissolve and decompose. Adding Zr, Ti, Sc, and other components will form new reinforcing phases or solid solutions, refining the grain size. Additionally, adding Ti-B particles can form particle-reinforced aluminum matrix composite welds.

[0020] In friction stir welding of the same alloy, alloying can refine the grain size and reduce microstructure inhomogeneity and compositional segregation. In friction stir welding of dissimilar aluminum alloys, alloying can reduce the inhomogeneity of the two base materials, forming a multi-component solid solution. Furthermore, alloying components can be added according to the desired performance improvements.

[0021] As a supplement to the technical solution of the present invention, the friction stir welding device includes a rotating shaft, a stirring needle, a transmission shaft, a hollow filling rod, a first servo motor, and a rotation and lifting drive device.

[0022] The lower end of the rotating shaft is fixedly connected to the stirring needle, and the upper end of the rotating shaft is connected to the first servo motor. The first servo motor is used to drive the rotating shaft and the stirring needle to rotate.

[0023] Both the drive shaft and the hollow filling rod are hollow tubular structures. The drive shaft is sleeved on the outer circumference of the rotating shaft, and the hollow filling rod is sleeved on the outer circumference of the stirring needle. The lower end of the drive shaft is fixedly connected to the hollow filling rod.

[0024] The rotary lifting drive device includes a bracket, a spline nut, and a lead screw nut; the bracket is fixedly installed, and the outer peripheral wall of the drive shaft is provided with a first spirally extending raceway and a second raceway opened along the axis of the drive shaft.

[0025] The lead screw nut is rotatably mounted on the bracket via a bearing. The lead screw nut is sleeved outside the transmission shaft. The inner circumferential wall of the lead screw nut is provided with a spiral third raceway that matches the first raceway. The first raceway and the third raceway together form a first transmission channel for the rolling of the balls.

[0026] The spline nut is rotatably mounted on the bracket via a bearing. The spline nut is sleeved outside the transmission shaft and spaced apart from the lead screw nut. The inner circumferential wall of the spline nut is provided with a fourth raceway extending along its own axis. The second raceway and the fourth raceway enclose each other to form a second transmission channel for the rolling of the balls. Both the first transmission channel and the second transmission channel are provided with balls.

[0027] The first, second, third, and fourth raceways all have semi-circular cross-sections that fit the outer periphery of the corresponding balls.

[0028] As a supplement to the technical solution of the present invention, it also includes a second servo motor, a first lead screw, a first lead screw nut, and a first lead screw nut bracket; the second servo motor is fixedly installed and connected to the first lead screw via a coupling, and is used to drive the first lead screw to rotate; the first lead screw nut bracket is fixedly installed, the first lead screw nut is fixed on the first lead screw nut bracket and screwed to the first lead screw, and the first lead screw nut bracket is fixedly connected to the first servo motor.

[0029] As a supplement to the technical solution of the present invention, the rotary lifting drive device further includes a third servo motor, a fourth servo motor, a first belt, and a second belt; the third servo motor and the fourth servo motor are both mounted on the bracket, the output shaft of the third servo motor is connected to the lead screw nut via the first belt to drive the lead screw nut to rotate; the output shaft of the fourth servo motor is connected to the spline nut via the second belt to drive the spline nut to rotate.

[0030] As a supplement to the technical solution of the present invention, the rotary lifting drive device further includes a tensioning component, which includes a first tensioning wheel corresponding to the first belt and a second tensioning wheel corresponding to the second belt; the first tensioning wheel and the second tensioning wheel are rotatably connected to the bracket and respectively press against the outer surface of the corresponding belt.

[0031] As a supplement to the technical solution of the present invention, the bracket includes a bracket side plate, a bracket top plate, and a bracket bottom plate; the bracket side plate is arranged vertically, one end of the bracket top plate is fixedly connected to the top end of the bracket side plate, and one end of the bracket bottom plate is fixedly connected to the bottom end of the bracket side plate.

[0032] The lead screw nut is mounted on the top plate of the bracket via a deep groove ball bearing, and the third servo motor is mounted on the top plate of the bracket;

[0033] The spline nut is mounted on the base plate of the bracket via a deep groove ball bearing, and the fourth servo motor is mounted on the base plate of the bracket.

[0034] As a supplement to the technical solution of the present invention, it also includes a fixing sleeve, a first fastening bolt, and a second fastening bolt; the fixing sleeve is a hollow tubular structure with openings at the top and bottom, the upper end of the fixing sleeve is detachably connected to the drive shaft by bolts, the upper part of the hollow filling rod is inserted into the lower opening of the fixing sleeve, a threaded hole is provided on the side wall of the fixing sleeve, and the first fastening bolt is screwed into the threaded hole on the side wall of the fixing sleeve and presses against the hollow filling rod;

[0035] The lower end of the rotating shaft is provided with a circular groove for the upper part of the stirring needle to be inserted into the circular groove; the side wall of the rotating shaft is provided with a threaded hole, and the second fastening bolt is screwed into the threaded hole of the side wall of the rotating shaft and its end is pressed against the stirring needle.

[0036] As a supplement to the technical solution of the present invention, it also includes a bushing and a stationary shoulder; the bushing is fixedly installed, and the upper end of the stationary shoulder is fixedly connected to the lower end of the bushing by bolts.

[0037] The bushing is fitted around the outer periphery of the drive shaft and the fixed sleeve; the stationary shaft shoulder is fitted around the outer periphery of the hollow filling rod.

[0038] The bushing has a vertically extending strip-shaped through hole on its side wall; the first fastening bolt is positioned corresponding to the radial position of the strip-shaped through hole, and the radial width of the strip-shaped through hole is greater than the outer diameter of the head of the first fastening bolt.

[0039] As a supplement to the technical solution of the present invention, a through hole is provided on the side wall of the fixing sleeve; the setting position of the second fastening bolt corresponds to the radial position of the through hole on the side wall of the fixing sleeve, and the inner diameter of the through hole on the side wall of the fixing sleeve and the radial width of the strip-shaped through hole on the side wall of the bushing are both greater than the outer diameter of the head of the second fastening bolt.

[0040] As a supplement to the technical solution of the present invention, a lifting assembly is also included, which includes a structural cover, a fifth servo motor, a second lead screw, a slide plate, a support plate, a lifting seat, and a slide rail.

[0041] The structure cover is a shell structure with an internal cavity. The bottom plate of the structure cover is fixedly connected to the upper end of the bushing. A through hole is opened in the middle of the bottom plate of the structure cover for the transmission shaft to pass through. The rotary lifting drive device, the first servo motor, and the second servo motor are all located inside the structure cover. The bracket of the rotary lifting drive device and the first servo motor are both fixedly connected to the inner wall of the structure cover.

[0042] Both the slide and the second lead screw are vertically arranged. The second lead screw is located on one side of the slide and is a semi-threaded lead screw. A support plate is fixedly arranged on the side wall of the slide. A through hole is opened in the middle of the support plate for the second lead screw to pass through. The support plate and the optical axis section of the second lead screw are rotatably connected by a bearing.

[0043] The side wall of the slide is provided with a vertically arranged slide rail. One end of the lifting seat is fixedly connected to the side wall of the structural cover, and the other end is slidably guided by the slide rail. A nut is fixed in the middle of the lifting seat, and the nut and the middle threaded section of the second lead screw form a threaded transmission engagement.

[0044] The fifth servo motor is connected to the upper end of the second lead screw via a coupling.

[0045] Beneficial effects: The friction stir welding process disclosed in this invention can replace the pre-weld filler wire / powder process, realizing the simultaneous and integrated completion of friction stir welding, weld filling, and alloying. The entire process is a single-pass welding process. By generating heat through the rotational friction of hollow filler rods and coordinating with the stirring pin, the superimposed heat input caused by traditional multiple welding is avoided. The overall heat input is precisely controlled, which fundamentally alleviates the problems of alloy element burn-off and base material composition imbalance. The original strengthening properties of the alloy material are fully preserved, ensuring the effective thickness and load-bearing area of ​​the welded joint. This solves the technical problems of joint softening and sharp drop in mechanical properties in traditional processes. Attached Figure Description

[0046] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0047] Figure 2 This is a schematic diagram of the main structure of the present invention.

[0048] Figure 3 This is a three-dimensional structural diagram of the present invention.

[0049] Figure 4 for Figure 3 Schematic diagram of cross-section structure.

[0050] Figure 5This is a schematic diagram of the assembly structure of the bushing and the stationary shoulder.

[0051] Figure 6 This is a schematic diagram of the bushing and stationary shoulder structure.

[0052] Figure 7 This is a cross-sectional view of the bushing and the stationary shoulder.

[0053] Figure 8 This is a schematic diagram of the lifting assembly structure.

[0054] Figure 9 This is a schematic diagram of the lifting assembly structure.

[0055] Figure 10 This is a schematic diagram of the structural cover.

[0056] In the diagram: 1. Rotating shaft, 2. Stirring needle, 3. Drive shaft, 4. Hollow filling rod, 5. First servo motor, 6. Bracket, 7. Spline nut, 8. Lead screw nut, 9. Second servo motor, 10. First lead screw, 11. First lead screw nut, 12. First lead screw nut bracket, 13. Third servo motor, 14. Fourth servo motor, 15. First belt, 16. Second belt, 17. Bracket side plate, 18. Bracket top plate, 19. Bracket bottom plate, 20. Fixing sleeve, 21. First fastening bolt, 22. Second fastening bolt, 23. Bushing, 24. Stationary shaft shoulder, 25. Limiting nut, 26. Structural cover, 27. Fifth servo motor, 28. Second lead screw, 29. Slide plate, 30. Support plate, 31. Lifting seat, 32. Slide rail. Detailed Implementation

[0057] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0058] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0059] Example 1

[0060] This embodiment provides a friction stir welding process for 6061 aluminum alloy, including the following steps:

[0061] S1. The base material is a 3mm thick 6061 aluminum alloy plate, with a weld length of 100mm and a weld width of 10mm. The outer diameter of the hollow filler rod is 10mm, and the inner diameter is 5mm. The static shoulder is depressed by approximately -0.05mm via the fifth servo motor 27. The composition of the hollow filler rod is: Si: 0.6%, Mg: 0.9%, Fe: 0.19%, Cu: 0.20%, Mn: 0.08%, Cr: 0.09%, Zn: 0.01%, Zr: 0.05%, Ti: 0.02%.

[0062] Before welding, the welding parameters of the friction stir welding device are set as follows: the stirring pin rotation speed is 1000 r / min, and the welding speed is 400 mm / min; the consumption of hollow filler rods is calculated to be 50 mm. 3 Consuming 0.22mm of length:

[0063] The hollow filler rod rotates at a speed of 1000 r / min, and the rotation direction of the hollow filler rod is the same as that of the stirring needle. The shoulder of the friction stir welding device is a stationary shoulder, and the contact width between the stationary shoulder end plate and the base material is d = 0.8 mm.

[0064] S2. During welding, the stirring needle rotates to complete the solid-phase plasticizing and stirring of the base material, realizing the metallurgical bonding between the base materials. At the same time, the hollow filling rod rotates independently, and the lower end face of the hollow filling rod contacts the surface of the base material, so that the hollow filling rod always fits the weld area. Under constant downward pressure, the lower end of the hollow filling rod generates heat through friction with the plasticized metal of the weld and gradually plasticizes and melts, filling into the interior of the weld, completing the synchronous filling and welding formation.

[0065] S3. When the stirring pin reaches the welding endpoint, the stirring pin rises and is pulled out of the weld. The hollow filling rod rotates and applies downward pressure to the weld surface to fill the keyhole formed after the stirring pin is pulled out. After the filling is completed, the hollow filling rod stops rotating and moves upward to separate from the weld.

[0066] Example 2

[0067] The only difference between this embodiment and Embodiment 1 is step S1, which is as follows:

[0068] S1. The base material is a 3mm thick 6061 aluminum alloy plate, with a weld length of 100mm and a weld width of 10mm. The outer diameter of the hollow filler rod is 10mm, and the inner diameter is 5mm. The static shaft shoulder is depressed by approximately -0.15mm via the fifth servo motor 27. The composition of the hollow filler rod is: Si: 0.56%, Mg: 0.9%, Fe: 0.17%, Cu: 0.20%, Mn: 0.1%, Cr: 0.12%, Zn: 0.03%, Zr: 0.15%, Ti: 0.02%.

[0069] Before welding, the welding parameters of the friction stir welding device are set as follows: the stirring pin rotation speed is 1500 r / min, and the welding speed is 800 mm / min; the consumption of hollow filler rods is calculated to be 150 mm. 3 The hollow filler rod rotates at a speed of 1500 rpm, with a length consumption of 0.64 mm. The rotation direction of the hollow filler rod is the same as that of the stirring needle. The shoulder of the friction stir welding device is a stationary shoulder, with a contact width d = 1.0 mm between the stationary shoulder end plate and the base material.

[0070] Example 3

[0071] The only difference between this embodiment and Embodiment 1 is step S1, which is as follows:

[0072] S1. The base material is a 3mm thick 6061 aluminum alloy plate, the weld length is 100mm, the weld width is 10mm, the outer diameter of the hollow filler rod is 10mm, and the inner diameter of the hollow filler rod is 5mm. The composition of the hollow filler rod is: Si: 0.63%, Mg: 0.95%, Fe: 0.15%, Cu: 0.20%, Mn: 0.06%, Cr: 0.09%, Zn: 0.03%, Zr: 0.1%, Ti: 0.03%.

[0073] Before welding, the welding parameters of the friction stir welding device are set: the stirring pin rotation speed is 1200 r / min, the welding speed is 600 mm / min, and the stationary shoulder is pressed down by approximately -0.5 mm using the fifth servo motor 27. The consumption of hollow filler rod is calculated to be 500 mm. 3 The hollow filler rod rotates at a speed of 1200 r / min, with a length consumption of 2.13 mm. The rotation direction of the hollow filler rod is the same as that of the stirring needle. The shoulder of the friction stir welding device is a stationary shoulder, with a contact width d = 1.5 mm between the stationary shoulder end plate and the base material.

[0074] S2. During welding, the stirring needle rotates to complete the solid-phase plasticizing and stirring of the base material, realizing the metallurgical bonding between the base materials. At the same time, the hollow filling rod rotates independently, and the lower end face of the hollow filling rod contacts the surface of the base material, so that the hollow filling rod always fits the weld area. Under constant downward pressure, the lower end of the hollow filling rod generates heat through friction with the plasticized metal of the weld and gradually plasticizes and melts, filling into the interior of the weld, completing the synchronous filling and welding formation.

[0075] S3. When the stirring pin reaches the welding endpoint, the stirring pin rises and is pulled out of the weld. The hollow filling rod rotates and applies downward pressure to the weld surface to fill the keyhole formed after the stirring pin is pulled out. After the filling is completed, the hollow filling rod stops rotating and moves upward to separate from the weld.

[0076] Example 4

[0077] This embodiment provides a friction stir welding process for 6061 and 7003 aluminum alloys, including the following steps:

[0078] S1. The base materials are 3mm thick 6061 aluminum alloy plates and 7003 aluminum alloy plates. The weld length is 100mm, the weld width is 10mm, the outer diameter of the hollow filler rod is 10mm, and the inner diameter of the hollow filler rod is 5mm. The composition of the hollow filler rod is: Si: 0.05%, Mg: 0.85%, Fe: 0.15%, Cu: 0.06%, Mn: 0.18%, Cr: 0.01%, Zn: 5.7%, Ti: 0.03%, Zr: 0.1%, Sc: 0.1%.

[0079] Before welding, the welding parameters of the friction stir welding device are set: the stirring pin rotation speed is 1000 r / min, the welding speed is 450 mm / min, and the static shoulder pressure is controlled by the fifth servo motor 27 to be approximately -0.1 mm; the consumption of hollow filler rod is calculated to be 100 mm. 3 The hollow filler rod rotates at a speed of 1000 r / min, with a length consumption of 0.43 mm. The rotation direction of the hollow filler rod is the same as that of the stirring needle. The shoulder of the friction stir welding device is a stationary shoulder, with a contact width d = 1.0 mm between the stationary shoulder end plate and the base material.

[0080] S2. During welding, the stirring needle rotates to complete the solid-phase plasticizing and stirring of the base material, realizing the metallurgical bonding between the base materials. At the same time, the hollow filling rod rotates independently, and the lower end face of the hollow filling rod contacts the surface of the base material, so that the hollow filling rod always fits the weld area. Under constant downward pressure, the lower end of the hollow filling rod generates heat through friction with the plasticized metal of the weld and gradually plasticizes and melts, filling into the interior of the weld, completing the synchronous filling and welding formation.

[0081] S3. When the stirring pin reaches the welding endpoint, the stirring pin rises and is pulled out of the weld. The hollow filling rod rotates and applies downward pressure to the weld surface to fill the keyhole formed after the stirring pin is pulled out. After the filling is completed, the hollow filling rod stops rotating and moves upward to separate from the weld.

[0082] Example 5

[0083] The only difference between this embodiment and embodiment 4 is step S1, which is as follows:

[0084] S1. The base materials are 3mm thick 6061 aluminum alloy plate and 7003 aluminum alloy plate. The weld length is 100mm, the weld width is 10mm, the outer diameter of the hollow filler rod is 10mm, and the inner diameter of the hollow filler rod is 5mm. The composition of the hollow filler rod is: Si: 0.1%, Mg: 0.88%, Fe: 0.16%, Cu: 0.07%, Mn: 0.15%, Cr: 0.01%, Zn: 5.6%, Ti: 0.05%, Zr: 0.05%, Sc: 0.05%, balance Al.

[0085] Before welding, the welding parameters of the friction stir welding device were set: the stirring pin rotation speed was 1200 r / min, the welding speed was 600 mm / min, and the stationary shoulder was pressed down by approximately -0.25 mm using the fifth servo motor 27. The consumption of hollow filler rods was calculated to be 250 mm. 3 The consumption length is 1.07 mm; the rotation speed of the hollow filler rod is 1200 r / min. The shoulder of the friction stir welding device is a stationary shoulder, and the contact width between the stationary shoulder end plate and the base material is d = 1.5 mm.

[0086] Example 6

[0087] The only difference between this embodiment and embodiment 4 is step S1, which is as follows:

[0088] S1. The base materials are 3mm thick 6061 aluminum alloy plates and 7003 aluminum alloy plates. The weld length is 100mm and the weld width is 10mm. The outer diameter of the hollow filler rod is 10mm and the inner diameter is 5mm. The static shoulder is depressed by approximately -0.15mm by the fifth servo motor 27. The composition of the hollow filler rod is: Si: 0.16%, Mg: 0.9%, Fe: 0.15%, Cu: 0.08%, Mn: 0.16%, Cr: 0.02%, Zn: 5.7%, Ti: 0.03%, Zr: 0.15%, Sc: 0.05%, balance Al.

[0089] Before welding, the welding parameters of the friction stir welding device are set as follows: the stirring pin rotation speed is 1500 r / min, the welding speed is 750 mm / min, and the consumption of hollow filler rods is calculated to be 150 mm. 3 The consumption length is 0.64 mm; the rotation speed of the hollow filler rod is 1500 r / min. The shoulder of the friction stir welding device is a stationary shoulder, and the contact width between the stationary shoulder end plate and the base material is d = 0.8 mm.

[0090] Comparative Example 1

[0091] This comparative example provides the traditional friction stir welding process.

[0092] S1. The base material is a 3mm thick 6061 aluminum alloy plate. Before welding, the welding parameters of the friction stir welding device are set as follows: the stirring pin rotation speed is 1300r / min, and the welding speed is 700mm / min. The shoulder of the friction stir welding device is a moving shoulder.

[0093] S2. When the stirring pin reaches the welding endpoint, it rises and is withdrawn from the weld, completing the welding process.

[0094] Comparative Example 2

[0095] This comparative example provides a traditional pre-weld filler wire + friction stir welding process, including the following steps:

[0096] S1. The base material is a 3mm thick 6061 aluminum alloy plate. First, the base material is beveled, and then MIG welding is used for preliminary welding. During the welding process, the welding current is 90A and the welding speed is 900mm / min.

[0097] S2. Then, friction stir welding is used to weld the seam, keeping the distance between the stirring pin and the welding gun at 50mm. During the welding process, the stirring pin rotates at 1300r / min and the welding speed is 700mm / min.

[0098] The mechanical properties and corrosion depth of the welded joints in the examples and comparative examples were tested, and the test results are shown in the table below:

[0099] Table 1. Performance Testing Table for Welded Joints

[0100]

[0101] Because dissimilar aluminum alloy materials have different electrical conductivity and hardness, and the weld zone is a mechanical and diffusion mixture of the two alloys, the weld composition is uneven. Therefore, it is impossible to accurately represent the hardness and conductivity data of the welded joint of dissimilar metal 6061 and 7003 aluminum alloy plates.

[0102] This invention also discloses the friction stir welding apparatus used in the above-described self-filling friction stir welding method. For example... Figures 1 to 7 As shown, a self-filling friction stir welding device includes a rotating shaft 1, a stirring needle 2, a transmission shaft 3, a hollow filling rod 4, a first servo motor 5, and a rotation and lifting drive device.

[0103] The lower end of the rotating shaft 1 is fixedly connected to the stirring needle 2, and the upper end of the rotating shaft 1 is connected to the first servo motor 5 through a coupling. The rotation of the first servo motor 5 drives the rotation of the rotating shaft 1 and the stirring needle 2.

[0104] Both the drive shaft 3 and the hollow filler rod 4 are hollow tubular structures. The drive shaft 3 is sleeved on the outer circumference of the rotating shaft 1 and can rotate relative to the rotating shaft 1. The hollow filler rod 4 is sleeved on the outer circumference of the stirring needle 2. The lower end of the drive shaft 3 is fixedly connected to the hollow filler rod 4. The drive shaft 3 can drive the hollow filler rod 4 to rotate and move up and down relative to the rotating shaft 1. The hollow filler rod 4 is made of welding wire. During friction stir welding, the drive shaft 3 rotates and applies pressure to the hollow filler rod 4 in the direction of the workpiece, causing the lower end of the hollow filler rod 4 to contact the workpiece and generate frictional heat, causing the lower end to melt and fill the weld. The weld metallization effect can be achieved without the use of an external wire feeding system.

[0105] To realize the rotation and lifting functions of the drive shaft 3, the rotation and lifting drive device includes a bracket 6, a spline nut 7, and a lead screw nut 8, with the bracket 6 being fixedly installed.

[0106] The outer peripheral wall of the drive shaft 3 is provided with a first raceway extending in a spiral, and a second raceway opened along the axial direction of the drive shaft 3.

[0107] The lead screw nut 8 is rotatably mounted on the bracket 6 via a deep groove ball bearing. Specifically, the lead screw nut 8 is fixedly connected to the inner ring of the deep groove ball bearing, and the bracket 6 is fixedly connected to the outer ring of the deep groove ball bearing. The lead screw nut 8 is sleeved on the outside of the transmission shaft 3. The inner circumferential wall of the lead screw nut 8 is provided with a helical third raceway adapted to the first raceway. The first raceway and the third raceway together form a first transmission channel for the first ball to roll.

[0108] The spline nut 7 is rotatably mounted on the bracket 6 via a deep groove ball bearing. Specifically, the spline nut 7 is fixedly connected to the inner ring of the deep groove ball bearing, and the bracket 6 is fixedly connected to the outer ring of the deep groove ball bearing. The spline nut 7 is sleeved on the outside of the transmission shaft 3 and spaced apart from the lead screw nut 8. Its inner peripheral wall has a fourth raceway extending along its own axis. The second raceway and the fourth raceway together form a second transmission channel for the second ball to roll.

[0109] Both the first and second transmission channels are equipped with ball bearings, and the lifting and rotation functions of the lead screw are realized by the rotation of the lead screw nut 8 and the spline nut 7.

[0110] The above setup enables the hollow filler rod 4 to rotate via the drive shaft 3 during friction stir welding, providing static pressure towards the workpiece. This achieves the alloying effect of the weld seam, avoiding the problem of weld thinning. It replaces the traditional consumable friction head, avoiding issues such as severe flash and uneven filling.

[0111] As a supplement to the above technical solution, the first raceway, the second raceway, the third raceway, and the fourth raceway all have semi-circular cross sections, which enable them to fit the outer circumferential contour of the ball.

[0112] The outer peripheral wall of the drive shaft 3 is symmetrically provided with two second raceways, which are distributed with the axis of the drive shaft 3 as the center of symmetry.

[0113] As a preferred embodiment of the present invention, it further includes a second servo motor 9, a first lead screw 10, a first lead screw nut 11, and a first lead screw nut bracket 12, wherein the second servo motor 9 is fixedly mounted. The second servo motor 9 is connected to the first lead screw 10 via a coupling and is used to drive the first lead screw 10 to rotate. The first lead screw nut 11 is fixed to the first lead screw nut bracket 12 and is screwed to the first lead screw 10. The rotation of the first lead screw 10 drives the first lead screw nut bracket 12 to move up and down. The first lead screw nut bracket 12 is fixedly connected to the first servo motor 5.

[0114] With the above settings, the first servo motor 5 drives the rotation of the rotating shaft 1, and the rotation of the second servo motor 9 drives the lifting function of the rotating shaft 1. After welding is completed, the rotating shaft 1 can drive the stirring needle 2 to rise and detach from the weld. At this time, the transmission shaft 3 continues to work, so that the hollow filling rod 4 melts and fills the keyhole, so that there is no keyhole after friction stir welding.

[0115] As a supplement to the above technical solution, a limiting nut 25 is provided at the lower end of the first lead screw 10. The limiting nut 25 is screwed onto the first lead screw 10 and is used to limit the lifting stroke of the first lead screw 10.

[0116] As a preferred technical solution of the present invention, the rotary lifting drive device further includes a third servo motor 13, a fourth servo motor 14, a first belt 15, and a second belt 16. The third servo motor 13 and the fourth servo motor 14 are both mounted on the bracket 6. The output shaft of the third servo motor 13 is connected to the lead screw nut 8 via the first belt 15 to drive the lead screw nut 8 to rotate.

[0117] The output shaft of the fourth servo motor 14 is connected to the spline nut 7 via the second belt 16, and is used to drive the spline nut 7 to rotate.

[0118] The rotation speeds of the lead screw nut 8 and the spline nut 7 are precisely controlled by servo motors.

[0119] It also includes a servo motor control module, which is connected to the first servo motor 5, the second servo motor 9, the third servo motor 13, and the fourth servo motor 14 respectively, and is used to precisely adjust and control the speed and direction of each servo motor.

[0120] In the above technical solution, the welding time can be calculated by the weld length and welding speed. The consumed length of the hollow filling rod is equal to the vertical downward displacement length of the transmission shaft 3. Therefore, based on parameters such as the diameter of the lead screw nut 8, the diameter of the pulley on the third servo motor 13, and the lead of the transmission shaft 3, the vertical downward displacement length of the transmission shaft 3 and the number of rotations required by the third servo motor 13 during the welding time can be calculated.

[0121] As a supplement to the above technical solution, the bracket 6 includes a bracket side plate 17, a bracket top plate 18, and a bracket bottom plate 19. The bracket side plate 17 is vertically arranged, one end of the bracket top plate 18 is fixedly connected to the top end of the bracket side plate 17, and one end of the bracket bottom plate 19 is fixedly connected to the bottom end of the bracket side plate 17. Both the bracket top plate 18 and the bracket bottom plate 19 are provided with circular holes for installing deep groove ball bearings. The lead screw nut 8 is set at the circular hole position on the bracket top plate 18 through the deep groove ball bearing. Specifically, the outer ring of the deep groove ball bearing is fixedly connected to the side edge of the circular hole on the bracket top plate 18, and the lead screw nut 8 is fixedly connected to the inner ring of the deep groove ball bearing. The third servo motor 13 is set on the bracket top plate 18.

[0122] The spline nut 7 is mounted on the bracket base plate 19 at the position of the circular hole via a deep groove ball bearing. Specifically, the outer ring of the deep groove ball bearing is fixedly connected to the side edge of the circular hole in the bracket base plate 19, and the spline nut 7 is fixedly connected to the inner ring of the deep groove ball bearing. The fourth servo motor 14 is mounted on the bracket base plate 19.

[0123] As a supplement to the above technical solution, the rotary lifting drive device further includes a tensioning assembly (not shown in the figure). The tensioning assembly includes a first tensioning pulley corresponding to the first belt 15 and a second tensioning pulley corresponding to the second belt 16. Both the first and second tensioning pulleys are rotatably connected to the bracket 6 and respectively press against the outer surface of the corresponding belt. This is used to achieve the belt tensioning function and prevent belt slack from affecting control accuracy.

[0124] As a preferred technical solution of the present invention, such as Figures 4 to 7As shown, it also includes a fixing sleeve 20, which is a hollow tubular structure with openings at the top and bottom. The upper end of the fixing sleeve 20 is detachably connected to the drive shaft 3 by bolts. The upper part of the hollow filling rod 4 is inserted into the lower opening of the fixing sleeve 20. Threaded holes are provided on the side wall of the fixing sleeve 20. The hollow filling rod 4 is tightened by passing a first fastening bolt 21 through the threaded holes on the side wall of the fixing sleeve 20, thus fixing the hollow filling rod 4 to the fixing sleeve 20 and achieving a detachable connection between the hollow filling rod 4 and the fixing sleeve 20. When replacing the hollow filling rod 4, the hollow filling rod 4 can be detached from the fixing sleeve 20.

[0125] The lower end of the rotating shaft 1 is provided with a circular groove for the upper part of the stirring needle 2 to be inserted. The upper part of the stirring needle 2 is inserted into the circular groove at the lower end of the rotating shaft 1. The side wall of the rotating shaft 1 is provided with a threaded hole. The second fastening bolt 22 passes through the threaded hole on the rotating shaft 1 and tightens the stirring needle 2, so that the stirring needle 2 and the rotating shaft 1 are detachably connected.

[0126] As a preferred embodiment of the present invention, it also includes a bushing 23 and a stationary shoulder 24;

[0127] The bushing 23 is fixedly installed, specifically by means of a connecting piece and a stirring head that is friction-welded. The upper end of the stationary shoulder 24 is fixedly connected to the lower end of the bushing 23 by bolts. The bushing 23 serves to protect the device.

[0128] The bushing 23 has a vertical through hole at its axial center for the transmission shaft 3 and the fixed sleeve 20 to pass through. The bushing 23 is fitted onto the outer periphery of the transmission shaft 3 and the fixed sleeve 20 through the through hole.

[0129] The stationary shoulder 24 has a vertical through hole at its axial center for the stirring needle 2 and the hollow filling rod 4 to pass through. The stationary shoulder 24 is fitted onto the outer periphery of the hollow filling rod through the through hole.

[0130] The bushing 23 has a vertically extending strip-shaped through hole on its side wall, extending through to its central through hole. The position of the first fastening bolt 21 corresponds to the radial position of the strip-shaped through hole on the side wall of the bushing 23, and the radial width of the strip-shaped through hole is greater than the outer diameter of the head of the first fastening bolt 21. This structural design allows operating tools to be inserted through the strip-shaped through hole to directly tighten or loosen the first fastening bolt 21, thereby achieving rapid installation and removal of the hollow filling rod 4.

[0131] The static shoulder 24 has a concave structure, which constrains the flow of plasticized metal, prevents the plasticized metal from escaping, and applies axial upsetting force to the plasticized metal at the welding position to promote the formation of a dense weld. The concave design is conducive to the flow of plasticized metal and the transition of alloying elements. The contained metal fills the thinning at the welding position.

[0132] As a supplement to the above technical solution, a through hole is provided on the side wall of the fixing sleeve 20; the position of the second fastening bolt 22 corresponds to the radial position of the through hole in the side wall of the fixing sleeve 20, and the inner diameter of the through hole in the side wall of the fixing sleeve 20 and the radial width of the strip-shaped through hole in the side wall of the bushing 23 are both larger than the outer diameter of the head of the second fastening bolt 22. This structural design allows the operating tool to be inserted sequentially through the strip-shaped through hole in the side wall of the bushing 23 and the through hole in the side wall of the fixing sleeve 20 to directly tighten or loosen the second fastening bolt 22, thereby achieving rapid installation and disassembly of the stirring needle 2.

[0133] By setting the static shoulder 24 and the hollow filler rod 4, the heat generated during the welding process can be greatly reduced, effectively reducing the flash problem caused by excessive welding heat input, and achieving a more stable welding process.

[0134] As a supplement to the technical solution of this invention, a lifting assembly is also included, such as... Figures 8 to 10 As shown, the lifting assembly includes a structural cover 26, a fifth servo motor 27, a second lead screw 28, a slide plate 29, a support plate 30, a lifting seat 31, and a slide rail 32.

[0135] The structural cover 26 is a shell structure with an internal accommodating space. The upper end of the bushing 23 is fixedly connected to the bottom plate of the structural cover 26 by bolts. The bottom plate of the structural cover 26 has a through hole in the middle for the transmission shaft 3 to pass through. All components of the rotary lifting drive device, as well as the first servo motor 5 and the second servo motor 9, are located inside the structural cover 26. The bracket 6 of the rotary lifting drive device and the first servo motor 5 are fixedly connected to the inner wall of the structural cover 26 to achieve the fixing effect of the fixed end bracket 6 and the first servo motor 5.

[0136] The slide plate 29 and the second lead screw 28 are both vertically arranged, with the second lead screw 28 located on one side of the slide plate 29. The second lead screw 28 is a semi-threaded lead screw, with an external thread at the middle surface and smooth surfaces at the upper and lower parts. A support plate 30 is disposed on the side surface of the slide plate 29 to support the second lead screw 28. The support plate 30 has a through hole at its middle part through which the second lead screw 28 passes. The support plate 30 is connected to the upper part of the second lead screw 28 via a bearing. Specifically, the inner ring of the bearing is fixedly connected to the non-threaded section surface of the second lead screw 28, and the outer ring of the bearing is located in the through hole at the middle part of the support plate 30 and fixedly connected to the support plate 30, allowing the second lead screw 28 to rotate freely relative to the support plate 30. The support plate 30 has two sets, which are respectively connected to the outer surfaces of the first lead screw located above and below the middle threaded section.

[0137] A vertically arranged slide rail 32 is provided on the side surface of the slide plate 29. The first end of the lifting seat 31 is fixedly connected to the side wall of the structural cover 26 by bolts. The other end of the lifting seat 31 is slidably guided by the slide rail 32. A through hole is provided in the middle of the lifting seat 31. The nut is fixed in the through hole of the lifting seat 31 and forms a threaded engagement with the middle threaded section of the second lead screw 28, so that the second lead screw 28 can drive the lifting seat 31 to move up and down when it rotates. The fifth servo motor 27 is connected to the upper end of the second lead screw 28 through a coupling and is used to drive the second lead screw 28 to rotate.

[0138] Rotating the second lead screw 28 raises and lowers the structural cover 26, which in turn raises and lowers the stationary shoulder 24, thereby applying downward pressure to the weldment. The amount of downward pressure on the stationary shoulder is controlled by adjusting the vertical height of the structural cover 26 based on the rotation of the second lead screw 28, causing the structural cover 26 to move the stationary shoulder towards the weldment, thus adjusting the amount of downward pressure on the stationary shoulder. Before welding, the coordinate parameters and welding process parameters of the friction stir welding machine can be preset and input.

[0139] The side surface of the slide plate 29 away from the structural cover 26 is connected to the driving device for friction stir welding. The driving device includes a gantry frame, a transverse component, etc. The transverse component is set on the gantry frame and is used to drive the entire device to move along the length of the weld. The gantry frame and the transverse component are conventional technical means in the field of friction stir welding, and will not be described in detail here.

[0140] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A friction stir welding method, characterized in that, Includes the following steps: S1. Before welding, set the welding parameters of the friction stir welding device: the rotation speed of the stirring pin is 800~1600 r / min, the welding speed is 400~1000 mm / min, the rotation speed of the hollow filling rod is 800~1600 r / min, and the rotation direction of the hollow filling rod is the same as that of the stirring pin. S2. During the welding process, the stirring needle rotates to complete the solid-phase plasticizing and stirring of the base material. At the same time, the hollow filling rod rotates, and the lower end face of the hollow filling rod contacts the surface of the base material, so that the hollow filling rod always fits the weld area. The lower end of the hollow filling rod rubs against the plasticized metal of the weld to generate heat and gradually plasticize and melt, filling into the interior of the weld, thus completing the synchronous filling and welding formation. S3. When the stirring pin reaches the welding endpoint, the stirring pin rises and is pulled out of the weld. The hollow filling rod rotates to fill the keyhole formed after the stirring pin is pulled out. After the filling is completed, the hollow filling rod stops rotating and moves upward to separate from the weld.

2. The friction stir welding method according to claim 1, characterized in that, In step S1, the formula for calculating the consumed length of the hollow filling rod is: In the above formula, H is the length of the hollow filler rod consumed, in mm; D is the weld width, in mm; h is the shoulder pressing amount, in mm; L is the weld length, in mm; R is the outer diameter of the hollow filler rod, in mm; and r is the inner diameter of the hollow filler rod, in mm. The shoulder of the friction stir welding device is a stationary shoulder. The downward pressure of the stationary shoulder during the welding process is -0.5~0mm, and the contact width between the stationary shoulder and the base material is 0.2mm~2mm.

3. The friction stir welding method according to claim 1, characterized in that, In step S1, the base material is 6061 aluminum alloy, and the hollow filled rod has the following composition: Si: 0.5%-0.8%, Mg: 0.8%-1.1%, Fe: 0.01%-0.2%, Cu: 0.15%-0.25%, Mn: 0.05%-0.15%, Cr: 0.08%-0.30%, Zn: 0.01%-0.1%, Ti: 0.02%-0.06%, Zr: 0.05%-0.25%.

4. The friction stir welding method according to claim 1, characterized in that, In step S1, the base materials are 6061 aluminum alloy and 7003 aluminum alloy, respectively. The hollow filled rod has the following composition: Si: 0.05%~0.2%, Mg: 0.6%~1.0%, Fe: 0.01%~0.20%, Cu: 0.06%~0.20%, Mn: 0.1%~0.30%, Cr: 0.01%~0.20%, Zn: 5.0%~6.5%, Ti: 0.03%~0.15%, Zr: 0.05%~0.25%, and Sc: 0.02%~0.1%.

5. The friction stir welding method according to claim 1, characterized in that, The friction stir welding device includes a rotating shaft (1), a stirring needle (2), a transmission shaft (3), a hollow filling rod (4), a first servo motor (5), and a rotation lifting drive device; The lower end of the rotating shaft (1) is fixedly connected to the stirring needle (2), and the upper end of the rotating shaft (1) is connected to the first servo motor (5). The first servo motor (5) is used to drive the rotating shaft (1) to rotate. The drive shaft (3) and the hollow filling rod (4) are both hollow tubular structures. The drive shaft (3) is sleeved on the outer circumference of the rotating shaft (1), and the hollow filling rod (4) is sleeved on the outer circumference of the stirring needle (2). The lower end of the drive shaft (3) is fixedly connected to the hollow filling rod (4). The rotary lifting drive device includes a bracket (6), a spline nut (7), and a lead screw nut (8); the bracket (6) is fixedly installed, and the outer peripheral wall of the drive shaft (3) is provided with a first spirally extended raceway and a second raceway opened along the axis of the drive shaft (3); The lead screw nut (8) is rotatably mounted on the bracket (6) via a bearing. The lead screw nut (8) is sleeved on the outside of the transmission shaft (3). The inner circumferential wall of the lead screw nut (8) is provided with a spiral third raceway that is adapted to the first raceway. The first raceway and the third raceway enclose each other to form a first transmission channel for the rolling of the balls. The spline nut (7) is rotatably mounted on the bracket (6) via a bearing. The spline nut (7) is sleeved on the outside of the transmission shaft (3) and spaced apart from the lead screw nut (8). The inner circumferential wall of the spline nut (7) is provided with a fourth raceway extending along its own axis. The second raceway and the fourth raceway enclose each other to form a second transmission channel for the rolling of the balls. Both the first transmission channel and the second transmission channel are provided with balls.

6. The self-filling friction stir welding apparatus according to claim 5, characterized in that, It also includes a second servo motor (9), a first lead screw (10), a first lead screw nut (11), and a first lead screw nut bracket (12); the second servo motor (9) is fixedly installed and connected to the first lead screw (10) for driving the first lead screw (10) to rotate; the first lead screw nut (11) is fixed on the first lead screw nut bracket (12) and screwed to the first lead screw (10); the first lead screw nut bracket (12) is fixedly connected to the first servo motor (5); The rotary lifting drive device also includes a third servo motor (13), a fourth servo motor (14), a first belt (15), and a second belt (16); the third servo motor (13) and the fourth servo motor (14) are both mounted on the bracket (6). The output shaft of the third servo motor (13) is connected to the lead screw nut (8) via the first belt (15) to drive the lead screw nut (8) to rotate; the output shaft of the fourth servo motor (14) is connected to the spline nut (7) via the second belt (16) to drive the spline nut (7) to rotate.

7. The self-filling friction stir welding apparatus according to claim 6, characterized in that, The rotary lifting drive device also includes a tensioning component, which includes a first tensioning wheel corresponding to the first belt (15) and a second tensioning wheel corresponding to the second belt (16); the first tensioning wheel and the second tensioning wheel are rotatably connected to the bracket (6) and respectively press against the outer surface of the corresponding belt. The bracket (6) includes a bracket side plate (17), a bracket top plate (18), and a bracket bottom plate (19); the bracket side plate (17) is vertically arranged, one end of the bracket top plate (18) is fixedly connected to the top end of the bracket side plate (17), and one end of the bracket bottom plate (19) is fixedly connected to the bottom end of the bracket side plate (17). The lead screw nut (8) is mounted on the top plate (18) of the bracket via a deep groove ball bearing, and the third servo motor (13) is mounted on the top plate (18) of the bracket. The spline nut (7) is mounted on the bracket base plate (19) via a deep groove ball bearing, and the fourth servo motor (14) is mounted on the bracket base plate (19).

8. The self-filling friction stir welding apparatus according to claim 7, characterized in that, It also includes a fixing sleeve (20), a first fastening bolt (21), and a second fastening bolt (22); the fixing sleeve (20) is a hollow tubular structure with openings at the top and bottom. The upper end of the fixing sleeve (20) is detachably connected to the drive shaft (3) by bolts. The upper part of the hollow filling rod (4) is inserted into the lower opening of the fixing sleeve (20). The side wall of the fixing sleeve (20) is provided with threaded holes. The first fastening bolt (21) is screwed into the threaded hole on the side wall of the fixing sleeve (20) and it presses against the hollow filling rod (4). The lower end of the rotating shaft (1) is provided with a circular groove for the upper part of the stirring needle (2) to be inserted, and the upper part of the stirring needle (2) is inserted into the circular groove; a threaded hole is provided on the side wall of the rotating shaft (1), and the second fastening bolt (22) is screwed into the threaded hole on the side wall of the rotating shaft (1) and its end is pressed against the stirring needle (2).

9. The self-filling friction stir welding apparatus according to claim 7, characterized in that, It also includes a bushing (23) and a stationary shoulder (24); the bushing (23) is fixedly installed, and the upper end of the stationary shoulder (24) is fixedly connected to the lower end of the bushing (23) by bolts; The bushing (23) is fitted around the outer periphery of the transmission shaft (3) and the fixed sleeve (20); the stationary shoulder (24) is fitted around the outer periphery of the hollow filling rod (4); The bushing (23) has a vertically extending strip-shaped through hole on its side wall; the first fastening bolt (21) is positioned in a position corresponding to the radial position of the strip-shaped through hole, and the radial width of the strip-shaped through hole is greater than the outer diameter of the head of the first fastening bolt (21).

10. The self-filling friction stir welding apparatus according to claim 9, characterized in that, The side wall of the fixed sleeve (20) is provided with a through hole; the setting position of the second fastening bolt (22) corresponds to the radial position of the through hole on the side wall of the fixed sleeve (20), and the inner diameter of the through hole on the side wall of the fixed sleeve (20) and the radial width of the strip through hole on the side wall of the bushing (23) are both greater than the outer diameter of the head of the second fastening bolt (22); It also includes a lifting assembly, which includes a structural cover (26), a fifth servo motor (27), a second lead screw (28), a slide (29), a support plate (30), a lifting seat (31), and a slide rail (32). The structure cover (26) is a shell structure with an internal cavity. The bottom plate of the structure cover (26) is fixedly connected to the upper end of the bushing (23). A through hole for the transmission shaft (3) to pass through is opened in the middle of the bottom plate of the structure cover (26). The rotary lifting drive device, the first servo motor (5), and the second servo motor (9) are all located inside the structure cover (26). The bracket (6) of the rotary lifting drive device and the first servo motor (5) are both fixedly connected to the inner wall of the structure cover (26). The slide (29) and the second lead screw (28) are both vertically arranged. The second lead screw (28) is located on one side of the slide (29) and is a semi-threaded lead screw. A support plate (30) is fixedly arranged on the side wall of the slide (29). A through hole for the second lead screw (28) to pass through is opened in the middle of the support plate (30). The optical axis section of the support plate (30) and the second lead screw (28) are rotatably connected by bearings. The side wall of the slide (29) is provided with a vertically arranged slide rail (32). One end of the lifting seat (31) is fixedly connected to the side wall of the structural cover (26), and the other end is slidably guided by the slide rail (32). A nut is fixed in the middle of the lifting seat (31), and the nut and the middle threaded section of the second lead screw (28) form a threaded transmission engagement. The fifth servo motor (27) is connected to the upper end of the second lead screw (28) via a coupling.

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