A friction stir welding device and method for low-stress and high-strength aluminum-magnesium joints

Abstract

A stir friction welding device and method for low-stress and high-strength aluminum-magnesium joints. The present invention includes a control system, a cooling system and a welding device, wherein the welding device includes a split welding tool and a workbench, the welding workpiece is mounted on the workbench through a tool, the split welding tool is arranged above the welding workpiece, and the control system controls the cooling system to spray cooling water on the welding workpiece and recycle it. The purpose of the present invention is to solve the problem of low joint strength caused by high residual stress and large thickness of intermetallic compounds in traditional stir friction welding aluminum-magnesium heterogeneous joints. The present invention proposes a stir friction welding device and method for low-stress and high-strength aluminum-magnesium joints, wherein the joint is rolled during the welding process, and the rolled joint is simultaneously subjected to a quenching treatment, so as to achieve the connection of low residual stress and thin thickness of intermetallic compounds of aluminum-magnesium, and comprehensively improve the strength of the aluminum-magnesium joint.

Description

Technical Field

[0001] The invention relates to a friction stir welding device, in particular to a friction stir welding device and method for a low-stress and high-strength aluminum-magnesium joint. The invention belongs to the technical field of welding. Background Art

[0002] Magnesium alloys have the characteristics of high specific strength, low density, radiation resistance, electromagnetic shielding performance and good hot forming properties. Magnesium alloys have broad application prospects in the fields of electronic devices, automobile transportation, aerospace, etc. For aluminum-magnesium heterogeneous metal connections, the current welding difficulties are mainly concentrated in the following aspects:

[0003] First, aluminum alloy and magnesium alloy have higher thermal conductivity and thermal expansion coefficient, and the difference in thermal expansion coefficient of the two metals will produce welding residual stress during the fusion welding process.

[0004] Secondly, the differences in melting point, thermal conductivity and thermal expansion coefficient of the two materials will affect the welding thermal cycle and the crystallization process of the weld metal, leading to problems such as thermal cracks, pores, burnout of alloy elements and softening of the weld area.

[0005] Thirdly, a dense oxide film is easily formed on the surface of the aluminum-magnesium base material, which hinders the atomic diffusion and metallurgical bonding effect of the aluminum-magnesium heterogeneous materials during welding, and is not conducive to the improvement and use of the joint performance.

[0006] Finally, the eutectic reaction temperature of Al-Mg heterogeneous materials is low, and Al-Mg intermetallic compounds are easily generated at 437 °C.

[0007] In summary, the current aluminum-magnesium connection is mainly concentrated in fusion welding, brazing and stir friction. When welding by fusion welding, the above difficulties will be more prominent, and welding cracks and thick intermetallic compounds are prone to seriously affect the strength of the joint; aluminum-magnesium brazing joints have low strength and need to be carried out in a vacuum environment, which restricts its application field. Stir friction welding is a solid phase welding technology. No melting will occur during the welding process, and no defects such as pores and thermal cracks will be generated. Its low welding temperature can reduce the thickness of the intermetallic compound. The mechanical stirring of the welding tool can break the oxide film and reduce the impact of the oxide film on the joint. Compared with fusion welding and brazing, it is more suitable for the connection of aluminum-magnesium heterogeneous metals. However, conventional stir friction welding still has welding residual stress caused by the inherent difference in thermal expansion coefficients of aluminum and magnesium, as well as a large number of brittle aluminum-magnesium intermetallic compounds, which will still limit its further application and promotion.

[0008] Therefore, it is urgent to propose a stir friction welding device and method for low-stress and high-strength aluminum-magnesium joints, break through the traditional stir friction welding mode, and develop new welding technology to improve the strength of aluminum-magnesium heterogeneous joints to solve the above technical problems. Summary of the invention

[0009] The purpose of the present invention is to solve the problem of low joint strength caused by high residual stress and large thickness of intermetallic compounds in traditional stir friction welding aluminum-magnesium heterogeneous joints, and propose a stir friction welding device and method for low stress and high strength aluminum-magnesium joints. The joint is rolled during the welding process, and the rolled joint is simultaneously subjected to quenching treatment to achieve low residual stress and thin intermetallic compound thickness connection of aluminum-magnesium, and comprehensively improve the strength of aluminum-magnesium joints. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0010] The technical solution of the present invention:

[0011] Solution 1: A friction stir welding device for low-stress and high-strength aluminum-magnesium joints, comprising a control system, a cooling system and a welding device, wherein the welding device comprises a split welding tool and a workbench, the welding workpiece is mounted on the workbench through a tool, the split welding tool is arranged above the welding workpiece, and the control system controls the cooling system to spray cooling water on the welding workpiece and recycle it;

[0012] The split welding tool includes a rolling disc, a rolling ball, a limit nut, a rolling control part, a stirring needle, a stop part and a fastening part. The rolling control part is threadedly mounted with the limit nut, the rolling disc, the stop part and the fastening part from top to bottom, wherein the stop part and the fastening part clamp the rolling disc together with the limit nut. The rolling control part has a shoulder at the bottom, and a stirring needle is arranged at the center of the bottom of the shoulder. A plurality of rolling balls are arranged on the rolling disc, and the plurality of rolling balls are arranged in a circular array around the stirring needle.

[0013] Preferably, the number of the rolling balls is 1-9, and the rolling balls are arranged in a uniform circumferential array around the rolling balls.

[0014] Preferably, the rolling ball is fixedly mounted on the rolling disc via a mounting portion.

[0015] Preferably: the cooling system includes a circulating water pool, a compressed air machine, a water flow controller, a water spray pipe and a recovery pipe, and control valves are installed on the recovery pipe and the water spray pipe. The water spray pipe sprays the cooling water in the circulating water pool onto the welding workpiece through the compressed air machine and the water flow controller, and the recovery pipe recovers the cooling water sprayed on the welding workpiece into the circulating water pool through the compressed air machine.

[0016] Preferably, the control system controls the switch of the compressed air machine, and controls the adjustment and release of the water flow size of the water flow controller.

[0017] Scheme 2: A friction stir welding method for a low-stress and high-strength aluminum-magnesium joint is implemented based on a friction stir welding device for a low-stress and high-strength aluminum-magnesium joint described in Scheme 1, and comprises the following steps:

[0018] S1, after cleaning the welding workpiece, install it on the workbench through the tooling;

[0019] S2, then assemble the split welding tool and determine the welding seam processing depth of the rolling ball to the welding workpiece;

[0020] S3, stir friction welding is performed on the welding workpiece by using a split welding tool, and the rolling ball maintains the same rotation speed and welding speed as the stirring needle to act on the weld surface of the welding workpiece to perform rolling modification on the weld, and at the same time, the cooling system is started by the control system;

[0021] S4, the control system turns on the air compressor and controls the water flow controller to adjust the water flow size. At this time, the cooling water in the circulating water pool is sprayed on the weld surface of the welding workpiece through the water spray pipe to cool the weld. The remaining cooling water on the surface of the welding workpiece is re-sucked into the circulating water pool by the recovery pipe for recovery.

[0022] The present invention has the following beneficial effects:

[0023] 1. The friction stir welding method for low-stress and high-strength aluminum-magnesium joints of the present invention can achieve the regulation of the residual stress and the thickness of the intermetallic compound of the welding workpiece in one process, greatly improving the strength of the joint, so that it can be widely used in actual production;

[0024] 2. The welding rolling and cooling system of the welding device designed by the present invention can effectively refine the grain size of the joint surface and break up the intermetallic compounds continuously distributed on the joint surface, thereby improving the bearing capacity of the joint surface;

[0025] 3. The welding rolling and cooling system of the welding device of the present invention has a welding quenching design, which compensates for the compressive plastic strain generated in the thermal expansion process by the longitudinal plastic extension generated by rolling the incompletely cooled joint, and offsets the longitudinal plastic deformation generated by stretching the solidified joint by the temperature distortion field generated by welding quenching, thereby inhibiting the inherent compressive plastic deformation and the formation of intermetallic compounds in the welding process, greatly reducing the residual stress of the aluminum-magnesium heterogeneous joint, converting the surface residual tensile stress into compressive stress, improving the corrosion resistance of the aluminum-magnesium heterogeneous joint, reducing the microcracks inside the joint, and comprehensively improving the strength of the aluminum-magnesium joint.

[0026] 4. The rolling plate of the low-stress and high-strength aluminum-magnesium joint friction stir welding device of the present invention is detachable, so that one welding tool can be used for multiple purposes, saving resources, and the thickness range of the welding workpiece is wide, which can be better promoted in actual production;

[0027] 5. The present invention has a wide range of applications, and is not only applicable to the regulation of residual stress and intermetallic compounds of aluminum-magnesium heterogeneous metals, but also applicable to heterogeneous metals such as aluminum / copper, aluminum / steel, and aluminum / titanium.

[0028] 6. The present invention is also applicable to the regulation of thin plate metal welding deformation, reducing the residual stress of the joint and reducing welding deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of a friction stir welding device for low-stress and high-strength aluminum-magnesium joints;

[0030] Figure 2 It is a structural schematic diagram of the welding device of the present invention;

[0031] Figure 3 is an exploded view of the welding device of the present invention;

[0032] Figure 4 is a perspective view of a rolling disc of the present invention;

[0033] Figure 5 is a perspective view of a stopper of the present invention;

[0034] In the figure: 1-control system, 2-cooling system, 201-circulating water pool, 202-compressed air machine, 203-water flow controller, 204-control valve, 205-water spray pipe, 206-recovery pipe, 3-welding device, 301-rolling disc, 30101-installation part, 302-rolling ball, 303-limiting nut, 304-rolling control part, 305-stirring needle, 306-welding workpiece, 307-stop part, 308-fastening part, 309-clamping ring. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0036] The connection mentioned in the present invention is divided into fixed connection and detachable connection. The fixed connection is a non-detachable connection including but not limited to conventional fixed connection methods such as folding connection, rivet connection, bonding connection and welding connection. The detachable connection includes but not limited to conventional detachable methods such as threaded connection, snap connection, pin connection and hinge connection. When the specific connection method is not clearly defined, it is assumed that at least one connection method can always be found in the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example: a fixed connection is selected as a welding connection, and a detachable connection is selected as a hinge connection.

[0037] Specific implementation method 1: Combination Figure 1-Figure 5 The present embodiment is described. A friction stir welding device for a low-stress and high-strength aluminum-magnesium joint in the present embodiment comprises a control system 1, a cooling system 2 and a welding device 3. The welding device 3 comprises a split welding tool and a workbench. A welding workpiece 306 is mounted on the workbench through a tool. The split welding tool is arranged above the welding workpiece 306. The control system 1 controls the cooling system 2 to spray cooling water onto the welding workpiece 306 and recover the cooling water. The cooling system 2 is used to perform simultaneous cooling of the welding workpiece 306 during welding, thereby reducing the residual stress of the welding workpiece 306 and reducing welding deformation.

[0038] The split welding tool includes a rolling disc 301, a rolling ball 302, a limit nut 303, a rolling control part 304, a stirring needle 305, a stop part 307 and a fastening part 308. The rolling control part 304 is threadedly mounted with the limit nut 303, the rolling disc 301, the stop part 307 and the fastening part 308 from top to bottom, wherein the stop part 307 and the fastening part 308 clamp the rolling disc 301 together with the limit nut 303. The rolling control part 304 has a shoulder at the bottom, and a stirring needle 305 is arranged at the center of the bottom of the shoulder. A plurality of rolling balls 302 are arranged on the rolling disc 301, and the plurality of rolling balls 302 are arranged in a circular array around the stirring needle 305.

[0039] During the welding process, the stirring needle 305 and the shoulder provide friction heat and stirring action to achieve the connection of the welding workpiece 306. The rolling plate 301 is a detachable part. The center of the rolling plate 301 is processed with a threaded hole through which the rolling regulating part 304 is threadedly matched. The rolling regulating part 304 is a screw with an external thread. The upper and lower sides of the screw are processed with threads of two different rotation directions. The upper thread is threadedly matched with the limit nut 303, the rolling plate 301 and the stopper 307, and the lower thread is threadedly matched with the fastening part 308, and the top of the fastening part 308 is also embedded with a screw. A snap ring 309 is installed, the top of the snap ring 309 has a protrusion, and the bottom of the stop part 307 has a groove, the protrusion and the groove are clamped together, that is, the snap ring 309 is clamped between the stop part 307 and the fastening part 308. The snap ring 309 is designed in this way to increase the spacing, ensure that the fastening part 308 and the lower side thread of the rolling control part 304 are matched, and the stop part 307 can be tightened at the same time, so that the rolling depth of the weld can be adjusted. At the same time, by replacing rolling discs 301 of different specifications and adjusting the different installation positions of the rolling balls 302 on the rolling discs 301, the rolling range of the weld can be adjusted.

[0040] During the welding process, the rolling ball 302 simultaneously rolls the weld surface. At this time, the longitudinal plastic extension produced by rolling the weld in an incompletely cooled state compensates for the compressive plastic strain generated by the welding workpiece 306 during the thermal expansion process, thereby reducing the longitudinal residual tensile stress level of the weld and its adjacent areas, thereby achieving a reduction in the residual stress of the Al / Mg heterogeneous joint.

[0041] The number of the rolling balls 302 is 1-9, and the rolling balls 302 are evenly arranged in a circular array around the rolling balls 302 .

[0042] The rolling ball 302 is fixedly mounted on the rolling disc 301 via a mounting portion 30101 . The mounting portion 30101 has six through holes, and the rolling ball 302 is fixedly mounted via nuts.

[0043] The workbench is provided with an electric spindle that provides a welding driving source. The top of the rolling control part 304 is fixedly clamped on the electric spindle. The electric spindle drives the rolling ball 302, the rolling control part 304, and the stirring needle 305 on the rolling disk 301 to achieve synchronous rotation and advance in the welding direction.

[0044] The cooling system 2 includes a circulating water pool 201, a compressed air machine 202, a water flow controller 203, a water spray pipe 205 and a recovery pipe 206. Water cooling is used to assist welding during welding. Control valves 204 are installed on the recovery pipe 206 and the water spray pipe 205. The water spray pipe 205 sprays the cooling water in the circulating water pool 201 onto the welding workpiece 306 through the compressed air machine 202 and the water flow controller 203 to quench the welding workpiece 306. The recovery pipe 206 recovers the cooling water sprayed on the welding workpiece 306 to the circulating water pool 201 through the compressed air machine 202. The compressed air machine 202 releases and absorbs the cooling water by generating compressed gas, and the water flow controller 203 regulates the cooling water as needed.

[0045] The cooling system 2 also includes three control valves 204. The air compressor 202 is connected to the water flow controller 203 through the first control valve 204, the water flow controller 203 is connected to the water spray pipe 205 through the second control valve 204, and the air compressor 202 is connected to the recovery pipe 206 through the third control valve 204. The three control valves 204 respectively realize the switching control of the compressed gas and the cooling water.

[0046] The control system 1 controls the switch and operation status of the compressed air machine 202 , controls the switch of the three control valves 204 , and controls the adjustment and release of the water flow size of the water flow controller 203 .

[0047] The shoulder diameter of the rolling regulating part 304 is 6-50 mm, the length of the stirring needle 305 is 0-40 mm, and the diameter of the stirring needle 305 is 0-30 mm.

[0048] The rotation speed of the electric spindle is 200-6000rpm, the welding speed is 100-2000mm / min, the inclination angle is 0-4°, and the downward pressure is 0-1mm.

[0049] The material of the rolling ball 302 can be selected from high-speed tool steel, cemented carbide, tungsten-rhenium alloy and other materials, and the hardness of the selected material is not lower than the hardness of the material to be welded.

[0050] The materials to be welded of the welding workpiece 306 include but are not limited to aluminum / magnesium, aluminum / copper and aluminum / steel.

[0051] The principle of reducing the residual stress of the joint and the thickness of the intermetallic compound in this embodiment is as follows: the control system 1 performs in-situ rotational extrusion on the metal in the weld area that is not fully cooled by the rolling ball 302. The longitudinal tensile plastic strain generated by the rolling ball 302 can reduce the longitudinal residual tensile stress level of the weld and its adjacent areas. In addition, the welding quenching effect of the cooling system can eliminate the heat of the weld surface, reduce the degree of thermal expansion and contraction of the joint, and synergistically reduce the residual stress of the joint; at the same time, the welding quenching acts on the weld surface to quickly cool the joint, inhibit the formation of a large amount of brittle and hard intermetallic compounds, and reduce the thickness of the intermetallic compounds in the joint.

[0052] Specific implementation method 2: Combination Figure 1-Figure 5 The present embodiment is described. A friction stir welding method for a low stress and high strength aluminum-magnesium joint in the present embodiment is implemented by relying on a friction stir welding device for a low stress and high strength aluminum-magnesium joint described in the first embodiment, and specifically includes the following steps:

[0053] S1, after cleaning the welding workpiece 306, install it on the workbench through the tooling;

[0054] The welding workpiece 306 may be an aluminum alloy plate and a magnesium alloy plate to be welded. The aluminum alloy plate and the magnesium alloy plate are cleaned by acetone and alcohol ultrasonic cleaning in sequence, and then mounted on a workbench in a butt-jointed manner through a fixed clamping tooling constraint.

[0055] S2, then assemble the split welding tool, install the rolling ball 302 on the mounting part 30101 of the rolling disc 301, fix it with a nut, and then install the rolling disc 301 on the rolling control part 304, after determining the weld processing depth of the rolling ball 302 on the welding workpiece 306, lock and fix the rolling disc 301 with the limit nut 303, the stop part 307 and the fastening part 308.

[0056] S3, using a split welding tool to stir friction welding the welding workpiece 306 at a certain rotation speed and welding speed through a rotary drive mechanism, at this time, the rolling ball 302 maintains the same rotation speed and welding speed as the stirring needle 305 to act on the weld surface of the welding workpiece 306, and the weld is rolled and modified. At the same time, the cooling system 2 is controlled to start by the control system 1;

[0057] S4, the control system 1 turns on the air compressor 202, and at the same time controls the water flow controller 203 to adjust the water flow size. At this time, the cooling water in the circulating water pool 201 is sprayed on the weld surface of the welding workpiece 306 through the water spray pipe 205 to cool the weld. The remaining cooling water on the surface of the welding workpiece 306 will be re-sucked into the circulating water pool 201 for recovery by the recovery pipe 206 at the rear end. The synergistic effect of rolling and quenching during the welding process greatly reduces the residual stress of the joint and the thickness of the intermetallic compound.

[0058] The rolling depth is closely related to the thickness of the welding workpiece 306. When the welding workpiece 306 is a thin plate welding, if the rolling depth is too great, in addition to producing a rolling effect, a certain degree of joint thickness of the welding workpiece 306 will be milled, thereby reducing the joint thickness and thus reducing the bearing capacity of the joint; when the welding workpiece 306 is a medium and thick plate welding, the rolling depth is too low, the rolling effect along the depth of the plate cannot be effectively transmitted, and the residual stress regulation effect of the heterogeneous joint is not obvious.

[0059] For example, when the workpiece thickness is 1-5mm, the rolling depth range is 0.01-0.10mm, when the workpiece thickness is 5-10mm, the rolling depth range is 0.10-0.2mm, and when the workpiece thickness is 10-40mm, the rolling depth range is 0.2-1.0.

[0060] The residual stress of the joint is generally distributed in an M shape, and the residual stress is the largest in the heat-affected zone. Therefore, the rolling width obtained by the rotating rolling ball 302 is related to the residual distribution range of the heat-affected zone of the joint. The rolling width needs to completely cover the area of ​​the heat-affected zone of the joint. For example, the range of the heat-affected zone is generally 5mm beyond the edge of the weld. When the weld width is a, the rolling width is a+10, so the rolling width is 16-60mm.

[0061] The diameter of the rolling disc 301 is closely related to the rolling width. The rolling disc 301 provides a mounting platform for the rolling balls 302. The diameter of the rolling disc 301 should be larger than the rolling width. Therefore, when the rolling width is 16-60 mm, the rolling diameter is 20-80 mm.

[0062] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A friction stir welding device for low stress and high strength aluminum-magnesium joints, characterized in that: The invention comprises a control system (1), a cooling system (2) and a welding device (3), wherein the welding device (3) comprises a split welding tool and a workbench, a welding workpiece (306) is mounted on the workbench through a tool, the split welding tool is arranged above the welding workpiece (306), and the control system (1) controls the cooling system (2) to spray cooling water onto the welding workpiece (306) and recover the cooling water; The split welding tool comprises a rolling disc (301), a rolling ball (302), a limiting nut (303), a rolling control part (304), a stirring needle (305), a stopper (307) and a fastening part (308); the rolling control part (304) is threadedly mounted with the limiting nut (303), the rolling disc (301), the stopping part (307) and the fastening part (308) from top to bottom, wherein the stopping part (307) and the fastening part (308) clamp the rolling disc (301) together with the limiting nut (303); the rolling control part (304) has a shoulder at the bottom, and a stirring needle (305) is arranged at the center of the bottom of the shoulder; a plurality of rolling balls (302) are arranged on the rolling disc (301), and the plurality of rolling balls (302) are arranged in a circular array around the stirring needle (305); The rolling plate (301) is processed with a threaded hole through the center, and the rolling regulating part (304) is threadedly matched through the threaded hole. The rolling regulating part (304) is a screw with an external thread. The screw has threads with two different rotation directions on the upper and lower sides. The upper thread is threadedly matched with the limit nut (303), the rolling plate (301) and the stopper (307), and the lower thread is threadedly matched with the fastening part (308). A clamping ring (309) is also embedded at the top of (308), and the top of the clamping ring (309) has a protrusion, and the bottom of the stopper (307) has a groove. The protrusion and the groove are clamped together, that is, the clamping ring (309) is clamped between the stopper (307) and the fastening part (308). At the same time, by replacing a rolling disc (301) of different specifications and adjusting different installation positions of the rolling ball (302) on the rolling disc (301), the rolling range of the weld can be adjusted.

2. The friction stir welding device for low stress and high strength aluminum-magnesium joints according to claim 1, characterized in that: The number of the rolling balls (302) is 1-9, and they are arranged in a uniform circular array around the rolling balls (302).

3. The friction stir welding device for low stress and high strength aluminum-magnesium joints according to claim 1, characterized in that: The rolling ball (302) is fixedly mounted on the rolling disc (301) via a mounting portion (30101).

4. A friction stir welding device for low stress and high strength aluminum-magnesium joints according to any one of claims 1 to 3, characterized in that: The cooling system (2) comprises a circulating water pool (201), an air compressor (202), a water flow controller (203), a water spray pipe (205) and a recovery pipe (206). The recovery pipe (206) and the water spray pipe (205) are both provided with control valves (204). The water spray pipe (205) sprays cooling water in the circulating water pool (201) onto a welding workpiece (306) through the air compressor (202) and the water flow controller (203). The recovery pipe (206) recovers the cooling water sprayed onto the welding workpiece (306) into the circulating water pool (201) through the air compressor (202).

5. The friction stir welding device for low stress and high strength aluminum-magnesium joints according to claim 4, characterized in that: The control system (1) controls the switch of the compressed air machine (202), and controls the adjustment and release of the water flow size of the water flow controller (203).

6. A friction stir welding method for low stress and high strength aluminum-magnesium joints, which is realized by relying on the friction stir welding device for low stress and high strength aluminum-magnesium joints according to claim 5, characterized in that: The following steps are involved: S1, cleaning the welding workpiece (306) and installing it on a workbench through a tool; S2, then assembling the split welding tool and determining the welding seam processing depth of the rolling ball (302) on the welding workpiece (306); S3, performing friction stir welding on the welding workpiece (306) by using a split welding tool, the rolling ball (302) maintaining the same rotation speed and welding speed as the stirring needle (305) acts on the weld surface of the welding workpiece (306), performing rolling modification treatment on the weld, and at the same time, controlling the cooling system (2) to start through the control system (1); S4, the control system (1) turns on the compressed air machine (202), and at the same time controls the water flow controller (203) to adjust the water flow size. At this time, the cooling water in the circulating water pool (201) is sprayed on the weld surface of the welding workpiece (306) through the water spray pipe (205) to cool the weld. The cooling water remaining on the surface of the welding workpiece (306) is sucked back into the circulating water pool (201) by the recovery pipe (206) for recovery.

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