A friction stir welding apparatus and method

Abstract

The application discloses a kind of friction stir welding device and method, including being equipped with hollow cavity's stir rod, clamping body, welding machine spindle, support trolley, cooling device, water tank, guide rail and conduit;Cooling device is connected with the outer surface of welding machine spindle by sealing bearing;Clamping body is connected with welding machine spindle;Clamping body clamps stir rod one end;Stir rod other end passes through the workpiece to be welded and is adapted with support trolley;Guide rail is arranged below support trolley;Conduit includes first conduit and second conduit;First conduit one end is connected with the outlet of water tank, other end is connected with the inlet of cooling device;Second conduit one end is connected with the cooling liquid outlet of support trolley, other end is connected with the inlet of water tank.The application is by using the same or similar material quality stir rod with the workpiece to be welded, reduce the cost of stir head;By applying cooling to stir rod, improve the stability of welding;At the same time, stir rod penetrates workpiece, improve the welding quality and welding efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of friction stir welding, in particular to a new type of stirring tool and corresponding friction stir welding device and method. BACKGROUND

[0002] In 1991, the British Welding Institute invented friction stir welding, which is a outstanding welding technology invention that is contributing to the progress of world manufacturing technology. As a new solid-state joining process, compared with traditional fusion welding methods, it has the advantages of environmental protection, low residual stress, small workpiece deformation, etc., and is widely used in the connection of aluminum alloy, magnesium alloy, copper alloy, steel, titanium alloy and composite materials and other metal materials. For many years, friction stir welding has been highly valued by the manufacturing industry for its high quality, high efficiency, energy saving and pollution-free technical characteristics, and has been increasingly widely used in aerospace, aerospace, nuclear power, ocean development and other high-tech fields, as well as power, machinery manufacturing, oil drilling, automobile manufacturing and other industrial sectors.

[0003] Friction stir welding uses friction heat and plastic deformation heat as the welding heat source, a cylindrical or other shaped stir head is inserted into the joint of the workpiece, and through the high-speed rotation of the stir head, it is rubbed with the material to be welded workpiece, so that the temperature of the connecting part of the material is raised and softened, and at the same time, the material is stirred to form plastic flow to complete the welding.

[0004] However, since the stir head needs to be inserted into the workpiece to rotate and produce heat by friction, the stir head is therefore subjected to extremely harsh service environment, and is prone to wear and breakage and other problems. Moreover, as a non-consumable component, the strength and wear resistance of the stir head need to be much higher than that of the workpiece to be welded, resulting in a higher manufacturing cost of the stir head, especially when welding high melting point materials, a stir head made of refractory materials, including tungsten-based, cobalt-based, molybdenum-based, nickel-based alloys and polycrystalline cubic boron nitride (PCBN), etc., must be used, which has high cost and is difficult to process. In addition, sometimes due to the mismatch between the length of the stirring needle and the thickness of the material to be welded, the root of the weld is not fully stirred, resulting in incomplete penetration defects, and the mechanical properties of the joint are greatly reduced.

[0005] To this end, the patent CN213469953U invents a wind-cooled static shaft shoulder, a friction stir welding tool and a device, a plurality of gas passages are provided in the static shaft shoulder body, the passage outlet is located on the matching surface matched with the stir head, and the static shaft shoulder is cooled by air cooling. The device can enhance the rigidity of the stir head and reduce the bending degree of the stir head during welding, but the wear of the stir head is inevitable. The patent CN108044229B invents a water-cooled connecting device for high-melting-point material friction stir welding. The device uses a water-cooled connecting device to cool the tool holder, thereby cooling the spindle and the stir head, reducing the requirement for the stir head holding part-transition material, and prolonging the service life of the stir head. This scheme also cannot avoid the wear of the stir head, and the device indirectly cools the stir head through the heat conduction of the transition sleeve, and the cooling effect is weak. The patent CN110524105B invents a stirring tool capable of inducing plastic eddy current in a workpiece, and the welding is realized through the movement of the eddy current. Although the wear of the stir head is avoided, the depth of the induced eddy current is limited, which limits the thickness of the weldable workpiece. SUMMARY

[0006] Technical problem: The technical problem to be solved by the present application is to provide a friction stir welding device and method, which uses a stir rod made of low-value consumables to replace the conventional stir head, thereby reducing the manufacturing cost of the stirring tool. During welding, cooling medium is introduced into the center of the stir rod for forced cooling to prevent the stir rod from breaking and failing, thereby improving the welding reliability. At the same time, the stir rod made of low-value consumables can weld through any thickness at one time, thereby improving the welding quality and welding efficiency.

[0007] Technical solution: To solve the above technical problems, in a first aspect, the present application provides a friction stir welding device: comprising a stir rod provided with a hollow cavity, a clamping body, a welding machine spindle, a supporting trolley, a cooling device, a water tank, a guide rail and a conduit; the cooling device is connected with the outer surface of the welding machine spindle through a sealing bearing; the clamping body is connected with the welding machine spindle; the clamping body clamps one end of the stir rod; the other end of the stir rod passes through the workpiece to be welded and is adapted to the supporting trolley; the guide rail is arranged below the supporting trolley; the conduit comprises a first conduit and a second conduit; one end of the first conduit is connected with the outlet of the water tank, and the other end is connected with the inlet of the cooling device; one end of the second conduit is connected with the cooling liquid outlet of the supporting trolley, and the other end is connected with the inlet of the water tank; the cooling device, the welding machine spindle, the clamping body, the stir rod, the supporting trolley and the water tank are sequentially connected to form a cooling liquid circulation loop.

[0008] As a preferred example, the material of the stirring rod is completely same as the material of the welded workpiece or contains the same main metal element; the outer surface of the stirring rod is provided with a stepped structure, and the stirring rod is provided with a first through hole vertically penetrating through the stirring rod; the stepped structure is a circular truncated cone structure with the same diameter of the lower end surface and the stirring rod or a circular truncated cone structure with the diameter of the lower end surface larger than the diameter of the stirring rod; the diameter of the upper end surface of the stepped structure is larger than the diameter of the lower end surface; the upper end surface and the lower end surface of the stepped structure form a conical angle α, and 0°<α≤45°; the height of the stepped structure is equal to the thickness of the welded workpiece.

[0009] As a preferred example, the clamping body includes an upper and lower connected tool handle and a sleeve; the tool handle is provided with a second through hole in the center; the tool handle is connected with the main shaft of the welding machine; the inside of the sleeve is provided with a cavity, and the side wall is provided with a threaded through hole; the second through hole and the cavity are communicated; the cavity is used for sleeving the stirring rod; the threaded through hole is used for screwing in a fastener to fix the stirring rod; the hollow cavity of the stirring rod and the second through hole of the tool handle are communicated.

[0010] As a preferred example, the height of the cavity is equal to the distance from the upper end surface of the stepped structure to the top end of the stirring rod; the outer diameter of the lower end surface of the sleeve is greater than or equal to the upper surface diameter of the hole opened on the welded workpiece.

[0011] As a preferred example, the support trolley includes a frame body, and an upper layer rotating support structure and a lower layer rotating support structure on the frame body; the upper layer rotating support structure and the lower layer rotating support structure are coaxially arranged; the inner side of the upper layer rotating support structure is gap-fitted with the stirring rod; the upper surface of the lower layer rotating support structure is in contact with the bottom surface of the stirring rod; the support trolley is further provided with a third through hole longitudinally penetrating through the support trolley; the third through hole is arranged in the center of the support trolley; the third through hole is communicated with the hollow cavity of the stirring rod, and the bottom end of the third through hole forms an outlet of the support trolley; the support trolley moves synchronously with the stirring rod through a guide rail.

[0012] As a preferred example, the upper layer rotating support structure and the lower layer rotating support structure are both cylindrical roller bearing structures; the inner diameter of the upper layer rotating support structure is greater than or equal to the diameter of the stirring rod; the inner diameter of the lower layer rotating support structure is less than or equal to three fourths of the diameter of the stirring rod.

[0013] As a preferred example, the side wall of the main shaft of the welding machine is provided with a fourth through hole, and the center is provided with a hollow cavity, both of which are communicated; the cooling device is sleeved on the main shaft of the welding machine by the upper and lower two sealing bearings, and the cavity formed in the middle wraps the fourth through hole of the side wall of the main shaft of the welding machine; the fourth through hole of the main shaft of the welding machine and the second through hole of the clamping body are communicated through the hollow cavity in the inside of the main shaft of the welding machine. In the second aspect, the embodiment of the present application also provides a friction stir welding method, which includes the following steps:

[0014] Step 10) A circular hole with the same diameter as the stirring rod is arranged on the surface of the welded workpiece;

[0015] Step 20) the welding machine spindle drives the clamping body and the stirring rod to rotate and move downward at the same time, when the distance between the stepped structure and the welded workpiece is 5mm-10mm, the cooling liquid is inputted;

[0016] Step 30) when the upper surface of the stepped structure coincides with the upper surface of the welded workpiece, the stirring rod stops moving downward, at this time the stirring rod passes through the upper rotary support structure of the support trolley, and the lower end surface of the stirring rod is in contact with the upper surface of the lower rotary support structure;

[0017] Step 40) the welding machine spindle drives the clamping body and the stirring rod to rotate and move along the welding direction for welding; the support trolley moves synchronously with the stirring rod;

[0018] Step 50) when the welding is completed, the welding machine spindle is used to move upward while the clamping body and the stirring rod are rotating, so as to move out the welded workpiece, and then the input of the cooling liquid is stopped.

[0019] As a preferred example, the cooling liquid in step 20) is one of water, oil, liquid nitrogen and liquid carbon dioxide.

[0020] As a preferred example, in step 20), the cooling liquid circulates in the cooling device, the welding machine spindle, the clamping body, the stirring rod, the support trolley and the water tank.

[0021] Beneficial effects: compared with the prior art, the technical scheme of the present application has the following beneficial effects: the present application uses a stirring rod with the same or similar material as the welded workpiece to replace the conventional stirring head, and the stirring rod penetrates the workpiece, solving the problems of easy wear and tear and fracture of the conventional friction stir welding stirring head and the problem of incomplete penetration at the bottom of the workpiece, and at the same time, the thickness of the workpiece to be welded is not limited by the length of the stirring needle, and the mechanical properties of the welded joint and the welding efficiency are improved. At the same time, the method of inputting cooling liquid is adopted to improve the rigidity of the stirring rod, prevent the stirring rod from softening due to high temperature and cannot continue to weld, and maintain the stability of the welding. The upper rotary support structure of the support trolley prevents the material in the stirring zone of the workpiece from flowing downward, the guide rail guides the movement direction of the support trolley, ensures that the support point is always directly below the stirring tool, and reduces the friction force generated during movement, thereby improving the welding efficiency and welding quality. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the device structure diagram of the embodiment of the present application;

[0023] Figure 2 is the stirring rod structure schematic diagram of the circular truncated cone stepped structure with the same diameter as the stirring rod in the embodiment of the present application;

[0024] Figure 3is a cross-sectional view of a stirring rod structure with a circular-truncated step structure of the same diameter as the diameter of the lower end surface of the stirring rod in an embodiment of the present application;

[0025] Figure 4 is a schematic view of a clamping body structure in an embodiment of the present application;

[0026] Figure 5 is a cross-sectional view of a clamping body structure in an embodiment of the present application;

[0027] Figure 6 is a schematic view of a support trolley structure in an embodiment of the present application;

[0028] Figure 7 is a cross-sectional view of a support trolley structure in an embodiment of the present application;

[0029] Fig. 8(a) is a schematic view of the simultaneous rotation and downward movement of the clamping body and the stirring rod in step 20) of the method in an embodiment of the present application;

[0030] Fig. 8(b) is a schematic view of the introduction of cooling liquid in step 20) of the method in an embodiment of the present application;

[0031] Fig. 8(c) is a schematic view of step 30) of the method in an embodiment of the present application;

[0032] Fig. 8(d) is a schematic view of step 40) of the method in an embodiment of the present application;

[0033] Figure 9 is a schematic view of a stirring rod structure with a circular-truncated step structure of a larger diameter than the diameter of the stirring rod in an embodiment of the present application;

[0034] Figure 10 is a cross-sectional view of a stirring rod structure with a circular-truncated step structure of a larger diameter than the diameter of the stirring rod in an embodiment of the present application;

[0035] Figure 11 is a schematic view of a stirring rod structure with a step structure of a double-convex arc shape in an embodiment of the present application;

[0036] Figure 12 is a cross-sectional view of a stirring rod structure with a step structure of a double-convex arc shape in an embodiment of the present application;

[0037] Figure 13 is a schematic view of a stirring rod structure with a step structure of a double-concave arc shape in an embodiment of the present application;

[0038] Figure 14 is a cross-sectional view of a stirring rod structure with a step structure of a double-concave arc shape in an embodiment of the present application.

[0039] In the figure: stirring rod 1, clamping body 2, welding machine spindle 3, support trolley 4, cooling device 5, water tank 6, guide rail 7, conduit 8, stepped structure 1-1, first through hole 1-2, tool holder 2-1, second through hole 2-2, sleeve 2-3, cavity 2-4, threaded through hole 2-5, upper rotary support structure 4-1, lower rotary support structure 4-2, third through hole 4-3. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings.

[0041] As Figure 1 shown, the stirring friction welding device of the embodiment of the present application comprises a stirring rod 1 provided with a hollow cavity, a clamping body 2, a welding machine spindle 3, a support trolley 4, a cooling device 5, a water tank 6, a guide rail 7 and a conduit 8; the cooling device 5 is connected with the outer surface of the welding machine spindle 3 through a sealing bearing; the clamping body 2 is connected with the welding machine spindle 3; the clamping body 2 clamps one end of the stirring rod 1; the other end of the stirring rod 1 penetrates through the workpiece to be welded and is adapted to the support trolley 4; the guide rail 7 is arranged below the support trolley 4; the conduit 8 comprises a first conduit and a second conduit; one end of the first conduit is connected with the outlet of the water tank 6, and the other end is connected with the inlet of the cooling device 5; one end of the second conduit is connected with the cooling liquid outlet of the support trolley 4, and the other end is connected with the inlet of the water tank 6; the cooling device 5, the welding machine spindle 3, the clamping body 2, the stirring rod 1, the support trolley 4 and the water tank 6 are sequentially communicated to form a cooling liquid circulation loop.

[0042] In the stirring friction welding device with the above structure, the stirring tool made of low-value consumables has a simpler structure and very low cost; the stirring rod made of the same or similar material as the workpiece to be welded is used to perform penetrating welding on the workpiece, and the double-layer rotary support structure is arranged to cooperate with the stirring rod to perform welding, thereby reducing the cost while ensuring the welding quality and efficiency. For example, the material of the workpiece to be welded and the stirring rod is titanium alloy.

[0043] Before welding, a hole with the same diameter as the stir rod is set on the workpiece to be welded, then the stir tool is rotated and pressed down, when the step structure 1-1 is about to contact the surface of the workpiece to be welded, the cooling liquid is supplied, when the upper surface of the step structure 1-1 coincides with the upper surface of the workpiece to be welded, the pressing down is stopped, at this time, the bottom end of the stir rod 1 penetrates the workpiece to be welded and the upper rotary support structure 4-1, and contacts the upper surface of the lower rotary support structure 4-2, at this time, the stir rod 1 moves along the welding direction, and the support trolley 4 moves synchronously with the stir rod 1 to perform the welding work, during the welding process, the stir rod 1 rotates at high speed to rub and stir the workpiece material, thus generating friction heat and material plastic deformation heat, so that the material to be welded around the stir rod is softened by heat and forms plastic flow under the driving of the stir rod. At the same time, the cooling liquid flows through the center of the stir rod 1 to play a forced cooling role on the stir rod, greatly enhancing the rigidity of the stir rod 1, avoiding the softening of the stir rod due to excessive temperature, and maintaining the stability of the welding process. When the stir rod 1 moves along the direction of the weld seam to be welded, the plasticized material in front of the stir rod 1 is brought to the rear by the rotating stir rod, in this process, the original interface between the workpieces is broken, and permanent connection is formed between the exposed fresh metals through recrystallization, diffusion, chemical reaction and other metallurgical ways, ensuring the efficiency and quality of the welding.

[0044] Compared with the existing friction stir welding stir head, the stir rod made of the same or similar material as the workpiece material is adopted, the stir rod is a kind of low-value consumable, which is easier to obtain and has very low cost. After the stir rod is rotated and inserted into the workpiece, because the stir rod is the same or similar to the workpiece material, the stir rod is inevitably welded with the workpiece, and the stir rod also maintains a certain rotating speed. In this case, there is a speed gradient in the radial direction of the plasticized material between the stir rod and the workpiece when the plasticized material makes a circular motion. In order to form a stable plastic flow field, the stir rod needs to continuously transmit momentum to the workpiece. However, after the stir rod is subjected to friction heat, the stir rod will soften, and the momentum output capacity will inevitably decrease, causing system instability. Therefore, the cooling liquid is supplied to the center of the stir rod to forcibly cool the stir rod, so that the temperature distribution in the stir rod reaches a dynamic balance between "friction heating - forced cooling", which can reduce the temperature at the center of the stir rod to a certain extent, improve the rigidity of the stir rod, enhance the momentum output capacity of the stir rod, and make the plastic flow field between the stir rod and the workpiece maintain quasi-steady state during the welding process.

[0045] As Figure 2 , Figure 3 , Figures 9 to 14As shown, as a preferred example, the material of the stirring rod 1 is completely the same as or contains the same main metal element as the material of the workpiece to be welded; the stirring rod 1 is provided with a stepped structure 1-1 on the outer surface, and a first through hole 1-2 vertically penetrating the stirring rod 1; the stepped structure 1-1 is a circular truncated cone structure with the same diameter of the lower end surface as the diameter of the stirring rod 1 or a circular truncated cone structure with the diameter of the lower end surface larger than the diameter of the stirring rod 1; the diameter of the upper end surface of the stepped structure 1-1 is larger than the diameter of the lower end surface; the upper end surface and the lower end surface of the stepped structure 1-1 form a conical angle α, 0° < α ≤ 45°; and the height of the stepped structure 1-1 is equal to the thickness of the workpiece to be welded. The stirring rod 1 has the same material as or contains the same main metal element as the material of the workpiece to be welded, has a simple structure, and the material is easy to obtain, thereby reducing the cost; meanwhile, the stirring rod 1 penetrates the workpiece to be welded during welding, thereby solving the problems of easy wear and tear and fracture of the conventional friction stir welding stirring head and the problem of incomplete welding at the bottom of the workpiece. The side surface of the stepped structure 1-1 can also be a double-concave arc structure or a double-convex arc structure, and the double-concave or double-convex structure can be used to adjust the heat generation efficiency at different moments during the pressing stage, thereby optimizing the welding temperature field. For example, if the workpiece is pure aluminum, the stirring rod can also be an aluminum alloy in addition to being pure aluminum; if the workpiece is low-carbon steel, the stirring rod can also be alloy steel, that is, the stirring rod can be slightly harder than the workpiece, but the main metal element of the stirring rod is the same as that of the workpiece material, and in this case, the stirring rod still belongs to low-value consumables.

[0046] As shown in Figure 4 , Figure 5 As a preferred example, the clamping body 2 includes an upper and lower connected tool handle 2-1 and a sleeve 2-3; the center of the tool handle 2-1 is provided with a second through hole 2-2; the tool handle 2-1 is connected with the main shaft 3 of the welding machine; the inside of the sleeve 2-3 is provided with a cavity 2-4, and the side wall is provided with a threaded through hole 2-5; the second through hole 2-2 and the cavity 2-4 are communicated; the cavity 2-4 is used for sleeving the stirring rod 1; the threaded through hole 2-5 is used for screwing in a fastener to fix the stirring rod 1; the hollow cavity of the stirring rod 1 and the second through hole 2-2 of the tool handle 2-1 are communicated. The clamping body 2 fixes the stirring rod 1, so that the stirring rod 1 is more stable during welding, thereby ensuring the welding quality; meanwhile, the clamping body 2 is connected with the cooling device and provided with the second through hole 2-2, so that the cooling liquid enters the center of the stirring rod 1 through the second through hole 2-2 during welding, thereby reducing the temperature around the stirring rod 1 during work, and improving the continuity and efficiency of welding.

[0047] As a preferred example, the cavity 2-4 height is equal to the distance from the upper end surface of the step structure 1-1 to the top end of the stirring rod 1; the outer diameter of the lower end surface of the sleeve 2-3 is greater than or equal to the diameter of the upper surface of the hole opened on the welded workpiece, which is to prevent the material of the stirring zone from overflowing during welding. In addition, when the outer diameter of the lower end surface of the sleeve 2-3 is set to be larger, the outer diameter of the stirring rod 1 can also be increased, which ensures the stirring effect of the stirring rod 1 on the workpiece during the welding process, and the welding effect will be better.

[0048] As shown in Figure 6 、 Figure 7 As a preferred example, the support trolley 4 includes a frame body, and an upper rotary support structure 4-1 and a lower rotary support structure 4-2 located on the frame body; the upper rotary support structure 4-1 and the lower rotary support structure 4-2 are coaxially arranged; the inner side of the upper rotary support structure 4-1 is in clearance fit with the stirring rod 1; the upper surface of the lower rotary support structure 4-2 is in contact with the lower end surface of the stirring rod 1; the support trolley 4 is further provided with a third through hole 4-3 which longitudinally penetrates the support trolley 4; the third through hole 4-3 is arranged at the center of the support trolley 4; the third through hole 4-3 is in communication with the hollow cavity of the stirring rod 1, and the bottom end of the third through hole 4-3 forms a cooling liquid outlet of the support trolley 4; the support trolley 4 moves synchronously with the stirring rod 1 through the slide rail 7. The stirring rod 1 penetrates the welded workpiece and the upper rotary support structure 4-1, and is in contact with the upper surface of the lower rotary support structure 4-2. During welding, the upper rotary support structure 4-1 limits the stirring rod 1, so that the stirring rod 1 remains fixed in the up-down direction during the welding movement, and the welding effect is better. At the same time, the guide rail 7 guides the movement direction of the support trolley 4, ensures that the support point is always below the stirring tool, reduces the friction generated during the welding movement, and achieves a better welding effect.

[0049] As a preferred example, the upper rotary support structure 4-1 and the lower rotary support structure 4-2 are both cylindrical roller bearing structures; the inner diameter of the upper rotary support structure 4-1 is greater than or equal to the diameter of the stirring rod 1; the inner diameter of the lower rotary support structure 4-2 is less than or equal to three-fourths of the diameter of the stirring rod 1. The stirring rod 1 penetrates the upper rotary support structure 4-1 of the support trolley 4 and is placed on the upper surface of the lower rotary support structure 4-2. By setting the upper rotary support structure 4-1 to be larger, the stirring rod 1 can penetrate the upper rotary support structure 4-1 and be in contact with the surface of the lower rotary support structure 4-2. At the same time, by setting the inner diameter of the lower rotary support structure 4-2 to be smaller, the stirring rod 1 can be supported and move synchronously with the stirring rod 1. At the same time, the cooling liquid can also pass through the inner diameter and penetrate the third through hole 4-3 into the water tank 6, thereby stably realizing the circulation of the cooling liquid and the continuous welding.

[0050] As a preferred example, the fourth through hole is arranged on the side wall of the welding machine spindle 3, and a hollow cavity is arranged in the center and communicated with the fourth through hole; the cooling device 5 is sleeved on the welding machine spindle 3 by the upper and lower sealing bearing sleeves, a cavity is formed in the middle, and the fourth through hole of the welding machine spindle 3 is wrapped by the side wall of the welding machine spindle; the fourth through hole of the welding machine spindle 3 and the second through hole 2-2 of the clamping body 2 are communicated through the hollow cavity in the welding machine spindle 3. The components are communicated with each other, and during the welding process, the cooling liquid can be continuously and stably circulated, so that the stirring rod 1 can continuously maintain rigidity and will not be softened at high temperature, the welding process can be continuously carried out, and the safety and stability are better.

[0051] The embodiment of the present application also provides a friction stir welding method, comprising:

[0052] Step 10) arranging a circular hole with the same diameter as the stirring rod 1 on the surface of the workpiece to be welded;

[0053] Step 20) as shown in FIGS. 8(a) and 8(b), the welding machine spindle 3 drives the clamping body 2 to rotate and move downward at the same time as the stirring rod 1, and when the distance between the step structure 1-1 and the workpiece to be welded is 5mm-10mm, the cooling liquid is poured in;

[0054] Step 30) as shown in FIG. 8(c), when the upper surface of the step structure 1-1 coincides with the upper surface of the workpiece to be welded, the stirring rod 1 stops moving downward, at this time the stirring rod 1 passes through the upper layer rotating support structure 4-1 of the support trolley 4, and the lower end surface of the stirring rod 1 is in contact with the upper surface of the lower layer rotating support structure 4-2;

[0055] Step 40) as shown in FIG. 8(d), the welding machine spindle 3 drives the clamping body 2 to rotate and move along the welding direction to carry out welding as the stirring rod 1; the support trolley 4 moves synchronously with the stirring rod 1;

[0056] Step 50) when the welding is completed, the welding machine spindle 3 is used to move upward while the clamping body 2 and the stirring rod 1 are rotating, so as to move out of the workpiece to be welded, and then the pouring of the cooling liquid is stopped.

[0057] In the above-mentioned friction stir welding method, the stirring rod 1 made of the same or similar material as the workpiece to be welded is used, and during the welding, the stirring rod 1 penetrates the workpiece to be welded, thereby solving the problems of easy wear and tear and fracture of the conventional friction stir welding stirring head and the problem of incomplete welding at the bottom of the workpiece. Meanwhile, the stirring rod 1 can be set to different sizes according to the actual requirements of the workpiece to be welded, so that the welding is not limited by the size of the stirring rod 1, and the mechanical properties of the welded joint and the welding efficiency are improved. During the welding, the cooling liquid is poured into the welding device to cool it, so as to ensure the rigidity of the stirring rod 1, so that the stirring rod 1 will not soften and cannot continue to weld due to high temperature, and the cooling liquid continuously circulates during the welding process, thereby maintaining the continuity and stability of the welding process

[0058] As a preferred example, the cooling liquid in step 20) is one of water, oil, liquid nitrogen, and liquid carbon dioxide. Different cooling liquids are selected according to actual conditions and requirements, so that the overall device can adapt to more working conditions and have a wider application.

[0059] As a preferred example, in step 20), the cooling liquid circulates and flows in the cooling device 5, the welding machine spindle 3, the clamping body 2, the stirring rod 1, the support trolley 4, and the water tank 6. During the welding process, the cooling liquid circulates and flows, ensures that the welding device is continuously cooled, the stirring rod 1 is continuously maintained rigid, and the welding process is more safe and stable.

[0060] The above shows and describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above specific embodiments, and the above specific embodiments and descriptions in the specification are only to further illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. A friction stir welding device characterized by comprising: The utility model provides a kind of welding machine cooling device, including the stirring rod (1) with hollow cavity, clamping body (2), welding machine spindle (3), support trolley (4), cooling device (5), water tank (6), guide rail (7) and pipe (8);The cooling device (5) is connected with the outer surface of welding machine spindle (3) by sealing bearing;The clamping body (2) is connected with welding machine spindle (3);The clamping body (2) clamps one end of stirring rod (1);The other end of stirring rod (1) passes through the workpiece to be welded and is adapted with support trolley (4);The guide rail (7) is arranged below support trolley (4);The pipe (8) includes first pipe and second pipe;The first pipe one end is connected with the outlet of water tank (6), and the other end is connected with the inlet of cooling device (5);The second pipe one end is connected with the cooling liquid outlet of support trolley (4), and the other end is connected with the inlet of water tank (6);Cooling device (5), welding machine spindle (3), clamping body (2), stirring rod (1), support trolley (4), water tank (6) are sequentially communicated, and form cooling liquid circulation loop; The support trolley (4) includes a frame body, an upper rotary support structure (4-1) and a lower rotary support structure (4-2) located on the frame body. The upper rotary support structure (4-1) and the lower rotary support structure (4-2) are coaxially arranged; the inner side of the upper rotary support structure (4-1) is in clearance fit with the stirring rod (1); the upper surface of the lower rotary support structure (4-2) is in contact with the bottom surface of the stirring rod (1); the support trolley (4) is further provided with a third through hole (4-3) longitudinally penetrating through the support trolley (4); the third through hole (4-3) is arranged at the center of the support trolley (4); the third through hole (4-3) is in communication with the hollow cavity of the stirring rod (1), and the bottom end of the third through hole (4-3) forms a cooling liquid outlet of the support trolley (4); the support trolley (4) moves synchronously with the stirring rod (1) through the guide rail (7).

2. A friction stir welding apparatus as claimed in claim 1, wherein The material of the stirring rod (1) is completely the same as or contains the same main metal elements as the material of the workpiece to be welded; a stepped structure (1-1) is arranged on the outer surface of the stirring rod (1), and a first through hole (1-2) vertically penetrating through the stirring rod (1) is arranged; the stepped structure (1-1) is a circular truncated cone structure with the same diameter as the diameter of the stirring rod (1) at the lower end surface or a circular truncated cone structure with a larger diameter at the lower end surface than the diameter of the stirring rod (1); the diameter of the upper end surface of the stepped structure (1-1) is larger than the diameter of the lower end surface; the upper end surface and the lower end surface of the stepped structure (1-1) form a conical angle α, and 0° < α ≤ 45°; the height of the stepped structure (1-1) is equal to the thickness of the workpiece to be welded.

3. A friction stir welding device as claimed in claim 1, wherein The clamping body (2) comprises an upper and lower connected tool shank (2-1) and sleeve (2-3); the tool shank (2-1) is provided with a second through hole (2-2) in the center; the tool shank (2-1) is connected with the welding machine spindle (3); the sleeve (2-3) is internally provided with a cavity (2-4), and the side wall is provided with a threaded through hole (2-5); the second through hole (2-2) and the cavity (2-4) are communicated; the cavity (2-4) is used for nesting the stirring rod (1); the threaded through hole (2-5) is used for screwing in a fastener to fix the stirring rod (1); the hollow cavity of the stirring rod (1) and the second through hole (2-2) of the tool shank (2-1) are communicated.

4. A friction stir welding apparatus as claimed in claim 3, wherein The height of the cavity (2-4) is equal to the distance from the upper end surface of the step structure (1-1) to the top end of the stirring rod (1); the outer diameter of the lower end surface of the sleeve (2-3) is greater than or equal to the diameter of the upper surface of the hole opened on the welded workpiece.

5. A friction stir welding device as claimed in claim 1, wherein The upper layer rotary support structure (4-1) and the lower layer rotary support structure (4-2) are both cylindrical roller bearing structures; the inner diameter of the upper layer rotary support structure (4-1) is greater than or equal to the diameter of the stirring rod (1); the inner diameter of the lower layer rotary support structure (4-2) is less than or equal to three fourths of the diameter of the stirring rod (1).

6. A friction stir welding apparatus as claimed in claim 3, wherein The side wall of the welding machine spindle (3) is provided with a fourth through hole, and the center is provided with a hollow cavity, both of which are communicated; the cooling device (5) is sleeved on the welding machine spindle (3) by two upper and lower sealing bearings, and the cavity formed in the middle wraps the fourth through hole of the side wall of the welding machine spindle (3); the fourth through hole of the welding machine spindle (3) and the second through hole (2-2) of the clamping body (2) are communicated.

7. A friction stir welding method using the friction stir welding apparatus according to claim 1, characterized by The method comprises the following steps: Step 10) setting a circular hole with the same diameter as the stirring rod (1) on the surface of the welded workpiece; Step 20) rotating and moving downward the clamping body (2) and the stirring rod (1) driven by the welding machine spindle (3), and when the distance between the step structure (1-1) and the welded workpiece is 5mm-10mm, the cooling liquid is poured in; Step 30) when the upper surface of the step structure (1-1) coincides with the upper surface of the welded workpiece, the stirring rod (1) stops moving downward, at this time the stirring rod (1) passes through the upper layer rotary support structure (4-1) of the support trolley (4), and the lower end surface of the stirring rod (1) is in contact with the upper surface of the lower layer rotary support structure (4-2); Step 40) rotating the clamping body (2) and the stirring rod (1) driven by the welding machine spindle (3), and moving along the welding direction to weld; the support trolley (4) moves synchronously with the stirring rod (1); Step 50) when the welding is completed, the clamping body (2) and the stirring rod (1) are rotated upward by the welding machine spindle (3), and then the cooling liquid is stopped.

8. The friction stir welding method of claim 7, wherein The cooling liquid in step 20) is one of water, oil, liquid nitrogen and liquid carbon dioxide.

9. The friction stir welding method according to claim 7, wherein In step 20), the cooling liquid circulates and flows in the cooling device (5), the welding machine spindle (3), the clamping body (2), the stirring rod (1), the support trolley (4) and the water tank (6).

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