Device and method for improving corrosion resistance of joint by friction stir welding synchronous multiple modification

Abstract

A device and method for improving the corrosion resistance of joints by friction stir welding with synchronous multiple modifications. The present invention relates to a device for friction stir welding and a method for welding using this device. To solve the problem that traditional friction stir welding joints are prone to corrosion and shorten the service life of workpieces, it includes a gyro-type welding tool, a modification device, and a fixing piece. The gyro-type welding tool includes a stirring pin, a shoulder, a mounting platform, and an upper cylinder. The upper cylinder, the shoulder, and the stirring pin are sequentially arranged and connected into one body from top to bottom. The mounting platform is sleeved on the shoulder, and multiple modification devices are installed and connected to the upper surface of the mounting platform along the circumferential direction. Each modification device is connected to a fixing piece. The present invention completes the work of welding and surface modification of the joint by a one-step method, with simple processes, no need for secondary machining, and low production costs. While improving the corrosion resistance of aluminum alloy joints, it does not lose their strength and plasticity. The present invention belongs to the technical field of aluminum alloy welding.

Description

Technical Field

[0001] The present invention relates to a friction stir welding device, and particularly to a device and method for synchronously and multiply modifying a friction stir welded joint to improve its corrosion resistance. The present invention belongs to the technical field of aluminum alloy welding. Background Art

[0002] High-strength aluminum alloys have characteristics such as high specific strength, low density, and light weight, and are widely used in fields such as aerospace and rail transit. Friction stir welding (FSW) involves temperature, force, and metallurgical interactions, and has advantages such as low temperature, green and pollution-free, low energy consumption, and small heat affected zone of the joint, which has a profound impact on aluminum alloy connection.

[0003] During the friction stir welding process, due to the stirring action and frictional heat generation, the grain morphology, grain size, and precipitation phases in each region of the joint are different. The nugget zone is affected by the stirring action, and the grains undergo sufficient severe plastic deformation and thermal cycle, the precipitation phases dissolve and precipitate again, and the grain structure is fine equiaxed; the thermo-mechanically affected zone experiences partial stirring action and thermal cycle, and the grains are curved and elongated; the heat affected zone only experiences the thermal cycle effect, the grain size is larger than that of the nugget zone and the thermo-mechanically affected zone, and the precipitation phases are severely coarsened, resulting in a relatively lower corrosion potential of this region compared to the nugget zone or the base material, and higher corrosion sensitivity. In a humid atmospheric environment or a marine environment, the joint corrosion phenomenon of high-strength aluminum alloys is more serious, restricting the further application of high-strength aluminum alloys.

[0004] The main factors affecting the corrosion resistance of the joint are: the surface roughness of the joint, residual stress, and precipitation phase. The rougher the joint surface, the larger its contact area with the corrosive medium, and the rougher the joint surface, the lower the electron work function, the easier it is to release electrons, and the higher the corrosion rate of the joint; the residual stress state of the joint is mainly tensile stress, and the residual tensile stress will promote the expansion of corrosion cracks during the corrosion process; the continuously distributed precipitation phases during the corrosion process are prone to acting as anodic corrosion channels, and the wide grain boundary precipitate-free zone and coarse precipitation phases will increase the corrosion potential difference between the precipitation phase and the surrounding matrix, reducing the corrosion resistance of the joint.

[0005] After retrieval, the invention patent with the publication number of CN116618817A and the publication date of August 22, 2023, discloses "A friction stir modification treatment tool and method for realizing the surface strengthening of a crystallizer copper plate", in which the rolling end is arranged in the same direction as the shoulder, and a plurality of connecting parts are connected to the upper surface of the rolling body along the circumferential direction. Since the positions of the rolling end and the shoulder are fixed, it is impossible to optimize the rolling diameter and rolling depth range of the repaired weld seam. Summary of the Invention

[0006] The present invention aims to solve the problem in the prior art that since the rolling end of the welding tool and the position of the shaft shoulder are fixed, it is impossible to optimize the rolling diameter and rolling depth range of the repaired weld seam. Furthermore, a device for improving the corrosion resistance of joints by friction stir welding with synchronous multiple modifications and a method for welding using this device are proposed. Through one-step process, while completing welding, the surface roughness, residual stress of the joint are synchronously reduced, and the precipitation phase on the surface layer is regulated to improve the corrosion resistance of the joint without loss of strength and plasticity.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows:

[0008] The present invention includes a gyro-type welding tool, a modification device and a fixing member. The gyro-type welding tool includes a stirring pin, a shaft shoulder, a mounting platform and an upper cylinder. The upper cylinder, the shaft shoulder and the stirring pin are sequentially arranged and connected into one body from top to bottom. The mounting platform is sleeved on the shaft shoulder. A plurality of modification devices are installed on the upper surface of the mounting platform along the circumferential direction, and each modification device is connected to a fixing member.

[0009] Furthermore, the modification devices are arranged along the circumferential direction and connected to the upper surface of the mounting platform. The modification device includes a bolt and a spherical bead, and the spherical bead is embedded at the lower end of the bolt.

[0010] Furthermore, the mounting platform is a disc body. A plurality of rectangular through holes are evenly arranged on the upper surface of the mounting platform along the circumferential direction. The bolts are inserted into the rectangular through holes, and a plurality of positioning holes for installing the fixing members are arranged on the outer end surface of the mounting platform.

[0011] Furthermore, the fixing member is threadedly connected to the positioning hole, and the end of the fixing member passes through the positioning hole and contacts the bolt.

[0012] Furthermore, the diameter of the shaft shoulder is 6 - 30 mm, the length of the stirring pin is 1 - 20 mm, and the diameter of the stirring pin is 1 - 20 mm.

[0013] A welding method using a device for improving the corrosion resistance of joints by friction stir welding with synchronous multiple modifications includes the following steps:

[0014] Step 1: Clean the butt joint surfaces of two plates to be welded, and then constrain them in a butt joint form on the workbench;

[0015] Step 2: Assemble the gyro-type welding tool, the modification device and the fixing member. By adjusting the corresponding positions of the fixing member and the modification device, set the rolling area and rolling depth of the modification device;

[0016] Step 3: Welding is carried out with corresponding process parameters. During the welding process, a weld seam is formed at the front end, and the spherical beads of the modification device roll and press the surface of the weld seam. The material overflowing from the workpiece when the shoulder penetrates into the workpiece during the front-end welding process is backfilled into the front-end weld seam through the spherical beads, and finally a joint with a smooth surface and no flash defects is formed.

[0017] Further, the rotational speed of the gyroscopic welding tool is 600 - 5000 r / min, the welding speed is 100 - 2000 mm / min, the inclination angle is 0 - 3°, and the downward pressure is 1.1 - 20.1 mm.

[0018] Further, the modification device maintains the same rotational speed and welding speed as the gyroscopic welding tool.

[0019] Further, the rolling depth is 0.05 - 0.3 mm, and the rolling area is 12 - 50 mm.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The present invention completes the work of welding and surface modification of the joint by a one-step method, reduces the processing procedures, greatly improves the actual production efficiency, and has the characteristics of simple process, low production cost, and high processing efficiency;

[0022] 2. The present invention can reduce the surface roughness of the joint, reduce the contact area between the joint and the corrosive medium, and improve the work function of the joint, thereby reducing the corrosion rate of the material;

[0023] 3. The present invention can promote the full flow of the surface layer material of the joint, refine the grain size of the surface layer, improve the compactness of the oxide film on the surface of the joint, and inhibit the occurrence of corrosion;

[0024] 4. During the process that the joint is not completely cooled, the present invention can, through the rolling and pressing treatment during welding, partially compensate the compressive strain generated by the cooling of the joint with the longitudinal tensile plastic strain generated, reduce the residual stress of the joint, and delay the crack propagation rate of corrosion. In addition, it can also play a role in reducing the instability deformation of the welded part;

[0025] 5. The present invention applies rolling and pressing treatment during welding. While improving the tensile performance of the joint, the elongation rate is hardly lost, realizing the decoupling of the strength-plasticity inversion relationship of aluminum alloy, and solving the technical problems that aluminum alloy urgently needs to solve;

[0026] 6. Without losing the mechanical properties of the aluminum alloy joint, the present invention can greatly improve the corrosion resistance of the joint;

[0027] 7. The present invention is not only applicable to improving the corrosion resistance of the same type of aluminum alloy, but also applicable to improving the corrosion resistance of dissimilar metals from several aspects such as improving the surface roughness of the joint, reducing the residual stress, and regulating the precipitation phase, with high universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 is the front view of the present invention;

[0030] Figure 3 is Figure 2 the sectional view of

[0031] Figure 4 is the surface roughness map of the joint before and after treatment.

[0032] Figure 5 is the corrosion morphology map of the joint before and after treatment.

[0033] Figure 6 is the engineering stress-strain curve of the joint before and after treatment in the stress corrosion environment.

[0034] Wherein:

[0035] 1 - Gyroscopic welding tool; 101 - Stirring pin; 102 - Shoulder; 103 - Mounting platform; 104 - Rectangular hole; 105 - Upper cylinder;

[0036] 2 - Modifying device; 201 - Bolt; 202 - Spherical bead;

[0037] 3 - Fixing part;

[0038] 4 - Workpiece. DETAILED DESCRIPTION OF THE INVENTION

[0039] Detailed Description of the Invention One: In combination with Figures 1 to 3 This embodiment is described. The device for improving the corrosion resistance of the joint by synchronous multiple modification in friction stir welding according to this embodiment includes a gyroscopic welding tool 1, a modifying device 2, and a fixing part 3. The gyroscopic welding tool 1 includes a stirring pin 101, a shoulder 102, a mounting platform 103, and an upper cylinder 105. The upper cylinder 105, the shoulder 102, and the stirring pin 101 are sequentially arranged and connected into one body from top to bottom. The mounting platform 103 is sleeved on the shoulder 102. A plurality of modifying devices 2 are installed on the upper surface of the mounting platform 103 along the circumferential direction and connected. Each modifying device 2 is connected to a fixing part 3.

[0040] During the welding process, the stirring pin 101 and the shoulder 102 of the gyroscopic welding tool 1 perform a stirring action and generate heat by friction on the workpiece 4, connecting the workpiece 4 and providing a platform for the modifying device 2.

[0041] Embodiment 2: Figures 1 to 3 Describe this embodiment. In this embodiment, the modification device 2 is arranged along the circumferential direction and connected to the upper surface of the mounting platform 103. The modification device 2 includes a bolt 201 and a spherical bead 202, and the spherical bead 202 is embedded at the lower end of the bolt 201. The bolt 201 is a stainless steel bolt.

[0042] The other components and connection relationships of this embodiment are the same as those of Embodiment 1.

[0043] Embodiment 3: Figures 1 to 3 Describe this embodiment. In this embodiment, the mounting platform 103 is a disc body, and a plurality of rectangular through holes 104 are evenly arranged along the circumferential direction on the upper surface of the mounting platform 103. The bolt 201 is inserted into the rectangular through hole 104, and a plurality of positioning holes for installing the fixing member 3 are provided on the outer end surface of the mounting platform 103.

[0044] The modification device 2 is composed of a modified stainless steel bolt 201 embedded with a spherical bead 202. The spherical bead 202 plays a role in rolling the weld during the welding process. During the rolling process, the spherical bead 202 keeps rotating, reducing the friction with the weld, lowering the height difference between the peaks and valleys of the weld arc pattern. Most importantly, it can modify the microstructure of the joint surface layer, causing the grain precipitation phase on the joint surface layer to dissolve back into the matrix, the coarsened precipitation phase continuously distributed at the grain boundaries to break and transform into a discontinuous distribution of fine precipitation phases, and the precipitate-free zone at the grain boundaries to become narrower.

[0045] The other components and connection relationships of this embodiment are the same as those of Embodiment 1 or 2.

[0046] Embodiment 4: Figures 1 to 3 Describe this embodiment. In this embodiment, the fixing member 3 is threadedly connected to the positioning hole, and the end of the fixing member 3 passes through the positioning hole and contacts the bolt 201.

[0047] The fixing member 3 limits and fixes the modification device 2 by means of the positioning hole of the gyroscopic welding tool 1.

[0048] The other components and connection relationships of this embodiment are the same as those of Embodiment 1, 2 or 3.

[0049] Embodiment 5: Figures 1 to 3 Describe this embodiment. In this embodiment, the diameter of the shaft shoulder 102 is 6 - 30 mm, the length of the stirring pin 101 is 1 - 20 mm, and the diameter of the stirring pin 101 is 1 - 20 mm.

[0050] The other components and connection relationships of this embodiment are the same as those of Embodiment 1, 2, 3 or 4.

[0051] Specific Embodiment Six: Combined with Figures 1 to 6 Describe this embodiment. This embodiment uses a welding method of a device for improving the corrosion resistance of joints by friction stir welding with synchronous multiple modifications, which specifically includes the following steps:

[0052] Step 1: Clean the butt joint surfaces of two plates to be welded, and then constrain them in a butt joint form on the workbench;

[0053] Step 2: Assemble the gyroscopic welding tool 1, the modification device 2, and the fixing member 3. By adjusting the corresponding positions of the fixing member 3 and the modification device 2, set the rolling area and rolling depth of the modification device 2;

[0054] Step 3: Perform welding through corresponding process parameters. During the welding process, a weld seam is formed at the front end. The spherical bead 202 of the modification device 2 rolls the surface of the weld seam. The material overflowing from the workpiece 4 when the shoulder 102 penetrates into the workpiece during the front-end welding process is backfilled to the front-end weld seam through the spherical bead 202, and finally a joint with a smooth surface and no flash defect is formed.

[0055] The other components and connection relationships of this embodiment are the same as those of Specific Embodiments One, Two, Three, Four, or Five.

[0056] Specific Embodiment Seven: Combined with Figures 1 to 6 Describe this embodiment. The rotation speed of the gyroscopic welding tool 1 in this embodiment is 600 - 5000 r / min, the welding speed is 100 - 2000 mm / min, the inclination angle is 0 - 3°, and the downward pressure is 1.1 - 20.1 mm.

[0057] The other components and connection relationships of this embodiment are the same as those of Specific Embodiments One, Two, Three, Four, Five, or Six.

[0058] Specific Embodiment Eight: Combined with Figures 1 to 6 Describe this embodiment. The modification device 2 in this embodiment maintains the same rotation speed and welding speed as the gyroscopic welding tool 1. The material of the spherical bead 202 is zirconia, stainless steel, etc.

[0059] The other components and connection relationships of this embodiment are the same as those of Specific Embodiments One, Two, Three, Four, Five, Six, or Seven.

[0060] Specific Embodiment Nine: Combined with Figures 1 to 6 Describe this embodiment. The rolling depth in this embodiment is 0.05 - 0.3 mm, and the rolling area is 12 - 50 mm.

[0061] The rolling depth and rolling area of the modification device 2 can be adjusted by the fixing device 3. The number of rolling times of the modification device 2 can be achieved by adjusting the distance from the spherical beads 202 to the stirring needle 101 (specifically, the distance from the center of the spherical bead to the center of the stirring needle), so that the distances from multiple spherical beads 202 to the stirring needle 101 are different.

[0062] The other components and connection relationships of this embodiment are the same as those of the first, second, third, fourth, fifth, sixth, seventh, or eighth specific embodiments.

[0063] Specific embodiment ten: Combined Figures 4 to 6 To illustrate this embodiment, the test for the corrosion resistance of the joint includes the following methods:

[0064] (1) Cyclic immersion corrosion: The test method and the evaluation of the corrosion grade refer to the cyclic immersion corrosion test standard of GB / T19746-2018. Compare the weight loss of the joint before and after treatment and observe the corrosion morphology of the joint surface by SEM. Evaluate the sensitivity of the two joints to corrosion through the weight loss results and SEM results.

[0065] (2) Intergranular corrosion test: The test method refers to the intergranular corrosion test standard of GB / T7998-2005. Compare the intergranular corrosion depth of the joint before and after treatment. Evaluate the sensitivity of the two joints to corrosion through the OM and SEM results.

[0066] (3) Constant load stress corrosion test: The constant load stress corrosion test is carried out in a salt spray corrosion test chamber with 3.5% NaCl. Place a constant load tensile device inside the test chamber, apply a constant load exceeding the yield strength to the joint tensile piece, and place it for 144h. Compare the tensile properties and the joint surface morphology of the joint before and after treatment under stress corrosion conditions to evaluate the sensitivity of the two joints to corrosion.

[0067] The principle of improving the corrosion resistance of friction stir welding joints of aluminum alloys in the present invention is as follows: The surface of traditional friction stir welding joints is relatively rough and accompanied by flash defects. The grains and precipitate phase sizes in the heat affected zone are severely coarsened. Compared with the base material or other welded areas, the corrosion potential is low, and it is relatively easy to dissolve as the anode. For the treated joints, the surface is smooth and the flash defects disappear. In a corrosive environment, the smooth surface of the joints can reduce the contact area with the corrosive solution, increase the work function of electrons, and increase the difficulty of electron release; the rolling treatment during welding can regulate the residual stress on the surface layer of the joints, reduce the residual tensile stress on the surface layer of the joints, and even convert the tensile stress of the joints into compressive stress; at the same time, the rolling treatment during welding can regulate the precipitated phases on the surface layer of the joints, dissolve part of the grain boundary precipitate phases back into the matrix, narrow the width of the grain boundary precipitate-free zone, and reduce the potential difference between the grain boundary precipitate phases and the grain boundary precipitate-free zone and the surrounding matrix. In addition, the severe plastic deformation generated by the spherical bead rolling breaks the precipitate phases on the surface layer of the joints, changes the continuous distribution into a discontinuous distribution, and reduces the size of the precipitate phases, blocking the channels for the precipitate phases to corrode as the anode. The above points work together to improve the corrosion resistance of the joints.

[0068] Example 1

[0069] The joint to be strengthened in this example is a 3-mm-thick 7075-T6 aluminum alloy thin plate. The butt surfaces of the two plates to be welded are cleaned, constrained on the workbench in a butt joint manner. The diameter of the shoulder 102 used is 10 mm, the length of the stirring pin 101 is 2.85 mm, the diameter of the stirring pin 101 is 5 mm, the welding speed is 300 mm / min, the rotational speed is 1000 rpm / min, the downward pressure of the shoulder 102 is 0.1 mm, and the rolling depth is 0.1 mm. During the welding process, the spherical bead 202 of the modification device 2 rolls the just-formed weld to obtain a joint with a smooth surface and no flash defects. Then, the surface roughness of the treated joint is tested, and the tests of immersion corrosion, intergranular corrosion, and stress corrosion are carried out. The results are as Figures 4 - 6 shown. The surface roughness of the joint after the rolling treatment during welding is 30.4 μm; for immersion corrosion, slight pitting corrosion pits appear in the heat affected zone; for the intergranular corrosion test, no intergranular corrosion phenomenon along the interface is observed on the cross-section of the joint; for the stress corrosion test, under the stress corrosion condition, almost no corrosion phenomenon occurs on the upper surface of the cross-section of the joint. The maximum tensile strength of the joint is 401 MPa, the elongation is 4.2%, and the yield strength is 269 MPa.

[0070] Comparative Example 1

[0071] The joint welded in this comparative example is a 3-mm-thick 7075 aluminum alloy thin plate. The butt surfaces of the two plates to be welded are cleaned, and they are constrained on the workbench in a butt joint manner. The diameter of the shoulder 102 used is 10 mm, the length of the stirring pin 101 is 2.85 mm, the diameter of the stirring pin 101 is 5 mm, the welding speed is 300 mm / min, the rotational speed is 1000 rpm / min, the downward pressure of the shoulder is 0.1 mm. The modification device 2 on the gyro-type welding tool 1 is removed to obtain a joint with a rough surface and flash defects. Then, surface roughness testing, immersion corrosion testing, intergranular corrosion testing, and stress corrosion testing are carried out on the joint. The results are as Figures 4 - 6 shown. The surface roughness of the joint of traditional FSW is 119.2 μm; for immersion corrosion testing, large corrosion holes (corrosion hole width is 94.6 μm) appear in the heat-affected zone; for intergranular corrosion testing, intergranular cracks with a depth of 82.1 μm along the interface are observed in the cross-section of the joint; for stress corrosion testing, under stress corrosion conditions, severe stress corrosion occurs at the shoulder positions on both sides of the upper surface of the cross-section of the joint. The maximum tensile strength of the joint is 322 MPa, the elongation is 1.5%, and the yield strength is 228 MPa.

[0072] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments by using the disclosed technical content. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments according to the technical essence of the present invention within the spirit and principle of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A device for improving the corrosion resistance of friction stir welding synchronous multiple modification joints, comprising a gyroscopic welding tool (1), a modification device (2) and a fixing member (3). The gyroscopic welding tool (1) includes a stirring pin (101), a shoulder (102), a mounting platform (103) and an upper cylinder (105). The upper cylinder (105), the shoulder (102) and the stirring pin (101) are sequentially arranged and connected integrally from top to bottom. The mounting platform (103) is sleeved on the shoulder (102). It is characterized in that: A plurality of modification devices (2) are connected to the upper surface of the mounting platform (103) along the circumferential direction, and each modification device (2) is connected to a fixing member (3). The modification device (2) is arranged along the circumferential direction and connected to the upper surface of the mounting platform (103). The modification device (2) includes a bolt (201) and a spherical bead (202), and the spherical bead (202) is embedded at the lower end of the bolt (201). The mounting platform (103) is a disc body. A plurality of rectangular through holes (104) are evenly distributed on the upper surface of the mounting platform (103) along the circumferential direction. The bolt (201) is inserted into the rectangular through hole (104), and a plurality of positioning holes for mounting the fixing member (3) are arranged on the outer end surface of the mounting platform (103). The fixing member (3) is threadedly connected with the positioning hole. The end of the fixing member (3) passes through the positioning hole and contacts the bolt (201). By adjusting the corresponding positions of the fixing member (3) and the modification device (2), the rolling area and rolling depth of the modification device (2) are set. The rolling area is 12 - 50 mm.

2. The device for improving the corrosion resistance of a joint by friction stir welding synchronous multi-modification according to claim 1, wherein: The diameter of the shoulder (102) is 6 - 30 mm, the length of the stirring pin (101) is 1 - 20 mm, and the diameter of the stirring pin (101) is 1 - 20 mm.

3. A welding method using a device for improving the corrosion resistance of joints by friction stir welding synchronous multiple modification, characterized in that: It includes the following steps: Step 1: Clean the butt joint surfaces of two plates to be welded, and then constrain them in a butt joint form on the workbench. Step 2: Assemble the gyroscopic welding tool (1), the modification device (2) and the fixing member (3). The modification device (2) is arranged along the circumferential direction and connected to the upper surface of the mounting platform (103). The modification device (2) includes a bolt (201) and a spherical bead (202), and the spherical bead (202) is embedded at the lower end of the bolt (201). A plurality of rectangular through holes (104) are evenly distributed on the upper surface of the mounting platform (103) along the circumferential direction. Insert the bolt (201) into the rectangular through hole (104). A plurality of positioning holes for mounting the fixing member (3) are arranged on the outer end surface of the mounting platform (103). The fixing member (3) is threadedly connected with the positioning hole. The end of the fixing member (3) passes through the positioning hole and contacts the bolt (201). By adjusting the corresponding positions of the fixing member (3) and the modification device (2), the rolling area and rolling depth of the modification device (2) are set. Step 3: Welding is carried out with corresponding process parameters. During the welding process, a weld seam is formed at the front end. The spherical bead (202) of the modification device (2) rolls and presses the surface of the weld seam. During the front-end welding process, the material overflowing from the workpiece (4) when the shoulder (102) penetrates into the workpiece is backfilled into the front-end weld seam through the spherical bead (202), and finally a joint with a smooth surface and no flash defect is formed.

4. The welding method of the device for improving the corrosion resistance of joints by friction stir welding synchronous multi-modification according to claim 3, characterized in that: The rotational speed of the gyroscopic welding tool (1) is 600 - 5000 r / min, the welding speed is 100 - 2000 mm / min, the inclination angle is 0 - 3°, and the downward pressure is 1.1 - 20.1 mm.

5. The welding method of the device for improving the corrosion resistance of joints by friction stir welding synchronous multiple modification according to claim 3, characterized in that: The modification device (2) maintains the same rotational speed and welding speed as the gyroscopic welding tool (1).

6. The welding method of the device for improving the corrosion resistance of joints by using friction stir welding synchronous multi-modification according to claim 3, characterized in that: The rolling depth is 0.05 - 0.3 mm.

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