A free-rotation support device for assisting in vortex friction stir welding and its usage method

Abstract

The present invention relates to the technical field of friction stir welding, and particularly to a free-rotation support device for assisting vortex friction stir welding and a usage method thereof. The device includes a support body, a rotating body, and rolling elements. The rotating body is sleeved outside the support body, and the rolling elements are installed between the two, so as to achieve relative free-rotation movement. During welding, the upper surfaces of the support body and the rotating body are always in contact with the lower surface of the plate to be welded. The support body has no rotational movement and only makes a linear movement at the same speed as the welding speed; the rotating body makes a forced rotational movement driven by the flow of the upper material. The present invention first uses a computational simulation method to determine the geometric dimensions of the free-rotation support device, and then, by utilizing the free rotation of the rotating body, eliminates the boundary friction constraint on the material flow to a certain extent, and solves the problems such as insufficient material flow, insufficient weld depth, and low welding efficiency caused by the friction constraint of the traditional back-up pad.

Description

Technical Field

[0001] The present invention relates to the technical field of friction stir welding, and particularly to a free-rotation support device for assisting vortex friction stir welding and a usage method thereof. Background Art

[0002] The friction stir welding (FSW) technology invented by the Welding Institute of the United Kingdom in 1991 is a new type of solid-phase welding process. Since it can achieve the welding of high-strength metals such as aluminum alloys, magnesium alloys, and titanium alloys, it has now become a key technology for connecting lightweight alloy structural parts in defense fields such as aerospace and civil fields such as automobiles and high-speed rails.

[0003] During the process of friction stir welding, a cylindrical stirring pin extends into the joint of the workpiece. Through the high-speed rotation of the stirring head, it frictions with the material of the workpiece to be welded, so that the temperature of the material at the joint to be connected rises and softens, and at the same time, the material is stirred to complete the welding. However, during the welding process, the stirring head is subjected to complex thermal and mechanical actions such as high temperature, upsetting pressure, traveling resistance, and rotational friction torque, making the problems of wear and fracture of the stirring head become the key bottleneck of the friction stir welding technology.

[0004] Patent "CN110524105A" proposes a rotating welding tool and a welding method for vortex friction stir welding. Compared with the conventional friction stir welding method, the vortex friction stir welding process uses a stirring rod made of the same material as the base material instead of the stirring pin in the conventional friction stir welding method, which solves the problems of wear and fracture of the stirring head in the conventional friction stir welding method to a certain extent. However, due to the characteristics of the vortex friction stir welding process itself, during the self-adaptive formation process of the vortex, it is restricted by the lower temperature at the bottom of the workpiece and the friction force of the backing plate at the back, resulting in insufficient depth and intensity of the vortex, and then the root lack of fusion defect appears. Especially for medium and thick plate welding, like the traditional friction stir welding method, the root lack of fusion defect will seriously reduce the mechanical properties of the joint.

[0005] As a new type of friction stir welding process, there is no relevant research on how to increase the weldable thickness of eddy current friction stir welding, and welding auxiliary devices are yet to be developed. In the conventional friction stir welding method, in order to eliminate the defect of incomplete penetration at the root, the patent "CN101209511A" performed secondary shallow repair welding on the back of the weld during the friction stir welding process, and achieved significant results. However, the secondary repair welding will increase the cost of friction stir welding and reduce efficiency, and this method has great restrictions on the welding structure and welding environment. Patent "CN101733542A" discloses a device and method for using a homogeneous material pad and milling the pad after welding to eliminate the defect of unwelded root. However, this method not only increases the welding process and cost, but also may cause HOOK defects on the back of the weld, thereby reducing the performance of the joint. Patent "CN102513691A" proposes a stirring needle device and method for increasing the metal flow at the root of the weld, but because this method requires the stirring needle to be processed into a specific shape, the bearing capacity of the stirring needle is reduced, affecting its service life. Summary of the invention

[0006] The purpose of the present invention is to address the problems existing in the background technology and propose a free rotating support device and a method of use for assisting eddy current friction stir welding. The purpose is to improve the mechanical boundary conditions of eddy current motion, reduce the friction constraint between the bottom of the workpiece and the back pad, thereby increasing the depth and intensity of material flow, improving the welding efficiency, and avoiding root unwelded defects.

[0007] The technical solution of the present invention is a free-rotating support device for assisting eddy current friction stir welding, comprising a support body, a rotating body and a rolling body. The support body is located in the middle of the device and remains fixed to support the stirring rod, thereby preventing the welded plate from being deformed due to the downward pressure applied by the eddy current friction stir welding, thereby avoiding welding defects. The rotating body is sleeved on the outside of the support body, and the rolling body is assembled between the support body and the rotating body, and a plurality of rolling bodies are distributed in a ring array. The support body and the rotating body are truncated cone-shaped and cylindrical.

[0008] The rotating body freely rotates around the axis relative to the supporting body through the rolling body. The rolling body is assembled between the rotating body and the supporting body. The rolling body is a spherical roller, a tapered roller or a cylindrical roller, which realizes the free rotation of the rotating body around the axis relative to the supporting body. The existence of the rolling body converts the sliding friction of a large area into rolling friction, thereby reducing wear and increasing the service life.

[0009] The upper surfaces of the support body and the rotating body are in the same plane. The minimum length of the upper surface of the device in any direction is not less than 2 / 3 of the diameter of the stirring rod used. Its beneficial effect is that the device can achieve effective support, prevent the material from collapsing due to insufficient support area, and cause welding failure. The number of rotating bodies is single-layer or multi-layer, and the number and size of the rotating bodies are determined comprehensively according to the diameter of the stirring rod, processing requirements, actual working conditions, and numerical simulation calculations, but should meet: the diameter of the rotating body is not greater than the outer diameter of the end of the sleeve, not less than 2 / 3 of the diameter of the stirring rod, and the number of layers of the rotating body does not exceed 10 layers. The material flow area is completely included in the freely rotatable range of the auxiliary support device. By reasonably setting the size and number of the rotating bodies, the frictional constraint below the material flow area is eliminated to the greatest extent.

[0010] A method for using a freely rotatable support device for assisting in vortex friction stir welding includes the following specific steps:

[0011] S1. Use computer simulation software such as Ansys, Deform, or Abaqus to establish a numerical model of vortex friction stir welding and obtain a numerical simulation diagram of the material flow field distribution during vortex friction stir welding;

[0012] S2. Process the freely rotatable support device according to the simulation calculation results;

[0013] S3. Install the freely rotatable support device directly below the stirring rod and use the device for assisting welding.

[0014] S2 includes the following steps:

[0015] S21. Determine the number of rotating bodies, and the sizes of the support body and the rotating body according to the numerical simulation diagram of the flow field distribution obtained in S1, and carry out processing and manufacturing;

[0016] S22. Put the rotating body on the outside of the support body, with the rolling body located between the support body and the rotating body, and fit the rolling body with the grooves on the outer surface of the support body and the inner surface of the rotating body;

[0017] S23. If the rotating body is multi-layer, repeat step S22 until all layers of the rotating bodies are assembled.

[0018] S3 includes the following steps:

[0019] S31. Fix and install the assembled device in the working position;

[0020] S32. During the welding process, keep the upper surfaces of the support body and the rotating body in the device always in contact with the lower surface of the plate to be welded; the stirring rod and the support body are in the coaxial position;

[0021] S33. The support body has no rotational movement and moves linearly at the same traveling speed as the stirring rod in the working position.

[0022] During welding, the linear guide rail is fixed on the workbench. The two side brackets are installed parallel to both sides of the linear guide rail according to the width of the workpiece to be welded and fixed on the workbench. The slider slides into the linear guide rail. The assembled free-rotating support device is fixedly installed on the slider of the linear guide rail. The linear guide rail, the brackets, and the workbench are stationary.

[0023] The workpiece to be welded is fixed in the fixture, and the fixture is fixedly installed on the bracket. During the welding process, the upper surfaces of the support body and the rotating body are always in contact with the lower surface of the welded plate. The stirring rod and the support body are in a coaxial position. The support body has no rotational movement and moves linearly on the guide rail slider at the same traveling speed as the stirring rod to realize the welding process.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] 1. The present invention designs an auxiliary support device that can rotate freely. During the eddy current friction stir welding process, the rotating body can rotate freely following the flow of the material above, improving the frictional constraint of the back support on the material flow, reducing the frictional resistance of the traditional back pad to the material flow, increasing the material flow strength, thereby effectively improving the welding efficiency, improving the joint quality at the bottom of the weld, and eliminating the weak connection defects at the bottom of the weld.

[0026] 2. The present invention realizes the low-constraint free flow of the eddy current bottom material through the free-rotating support structure. Compared with the conventional eddy current friction stir welding, when the same weld depth requirement is met, the welding method of the present invention can achieve lower energy consumption, avoiding the joint softening or slipping phenomenon caused by excessive heat input, thereby improving the mechanical properties of the joint.

[0027] 3. The present invention can increase the weldable thickness of the workpiece to a certain extent by improving the frictional constraint of the back pad on the eddy current. Generally speaking, in the conventional eddy current friction stir welding, the quality of the weld is restricted by conditions such as the rotational speed of the stirring rod, the welding speed, and the diameter of the stirring rod. To ensure the qualified weld quality, within the optimal parameter range, the thickness of the welded plate will also be restricted. Using the auxiliary eddy current friction stir welding of the present invention can expand the applicable plate thickness range of this welding method and solve the problem of insufficient weldable thickness in eddy current friction stir welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a three-dimensional model schematic diagram of the free-rotating support device for the auxiliary eddy current friction stir welding of the present invention;

[0029] Figure 2It is a schematic cross-sectional view of the eddy current friction stir welding device according to Embodiment 1 of the present invention;

[0030] Figure 3 It is a schematic diagram of the relative positions of the components in the side view direction of the eddy current friction stir welding device according to Embodiment 1 of the present invention after removing the workbench 8, the bracket 7, and the fixture 6;

[0031] Figure 4 It is a schematic cross-sectional view of the free rotation support device according to Embodiment 2 of the present invention;

[0032] Figure 5 It is a numerical simulation diagram of the material flow field distribution during eddy current friction stir welding using a stirring rod with a diameter of 16 mm used in Embodiment 1 and Embodiment 2 of the present invention.

[0033] Reference numerals: 1, support body; 2, rotating body; 3, rolling body; 4, stirring rod; 5, sleeve; 6, fixture; 7, bracket; 8, workbench; 9, linear guide rail; 10, slider; 11, workpiece to be welded; 12, sealing ring; 13, cage; 14, connecting block. Detailed implementation manners

[0034] Embodiment 1

[0035] A free rotation support device for assisting eddy current friction stir welding and its usage method, in combination with Figure 1 , Figure 2 , Figure 3 and Figure 5 to illustrate this embodiment.

[0036] As Figure 1 , Figure 2 , Figure 3 and Figure 5 shown, the upper surface diameter dimension of a free rotation support device for assisting eddy current friction stir welding in this embodiment is 20 mm. When using a stirring rod 4 with a diameter of 16 mm and a sleeve with a front wall thickness of 2 mm for eddy current friction stir welding, a computer simulation software is used to establish a numerical model of eddy current friction stir welding based on physical laws, and a numerical simulation diagram of the material flow field distribution during eddy current friction stir welding is obtained. According to the numerical simulation results, the flow field is stratified (mainly according to the angular velocity gradient of the mass points in the flow field), and as Figure 5The 13 velocity zones of material flow shown. To ensure sufficient strength of each layer of the rotating body and the supporting body, when designing the free-rotating support device for assisting in vortex friction stir welding, the parts with a relatively small thickness of the material flow stratification are combined, and the rotating body is not designed and processed separately. In this embodiment, the number of rotating bodies 2 is preferably 3; the diameter of the upper surface of the supporting body is 3.2 mm, and the material flow velocity in this part is low, which is used as the supporting part; the inner diameter of the upper end surface of the inner rotating body is 4.8 mm, and the outer diameter is 7.2 mm. The material flow velocity in this part is relatively low, and it is a low-speed rotating rotating body; the inner diameter of the upper end surface of the middle rotating body is 8.8 mm, and the outer diameter is 15.2 mm. The material flow velocity in this part is relatively high, and it is a high-speed rotating rotating body; the inner diameter of the upper end surface of the outer rotating body is 16.8 mm, and the outer diameter is 20 mm. The parallel distance between the upper end surfaces of each layer of rotating bodies is 0.8 mm, and the taper is 2:1.

[0037] A free-rotating support device for assisting in vortex friction stir welding in this embodiment includes a supporting body 1, a rotating body 2, and a rolling body 3. The supporting body 1 has no rotational movement at the innermost side of the device and plays a supporting role. The rotating body 2 is sleeved outside the supporting body 1, and the rolling body 3 is assembled between the rotating body 2 and the supporting body 1 to realize the free rotational movement of the rotating body 2 around the axis with respect to the supporting body 1. The upper surfaces of the supporting body 1 and the rotating body 2 are in the same plane.

[0038] The bracket 7 is fixedly installed on the workbench 8 in parallel according to the width of the workpiece 11 to be welded. The linear guide rail 9 is fixedly installed in the middle of the two brackets 7. The slider 10 can slide on the linear guide rail 9. The supporting body 1 is directly fixed on the slider 10. The clamp 6 clamps the workpiece 11 to be welded and fixes it horizontally on the bracket 7. The lower surface of the workpiece 11 to be welded contacts the upper surface of the free-rotating support device for assisting in vortex friction stir welding. The stirring rod 4 is fixedly installed in the sleeve 5. The sleeve 5 and the stirring rod 4 in it contact the upper surface of the workpiece 11 to be welded. The stirring rod 4 is coaxially installed with the supporting body 1.

[0039] As Figure 2 and Figure 3 shown, in this embodiment, the type of the rolling body 3 is preferably a sphere, and the number of rolling bodies is preferably 20.

[0040] As Figure 2 and Figure 3 shown, the free-rotating support device for assisting in vortex friction stir welding of the above-mentioned Embodiment 1 is used for vortex friction stir welding. At the beginning of welding, the sleeve 5 drives the stirring rod 4 to rotate and press down. After the pressing amount reaches the requirement, it stays for a period of time. After the material flow of the workpiece 11 to be welded and the movement of the rotating body 2 in the free-rotating support device are stable, the stirring rod 4 starts to move along the welding direction to perform welding. During the welding process, the workpiece 11 to be welded, the linear guide rail 9, the clamp 6, the bracket 7, and the workbench 8 remain stationary. The free-rotating support device and the stirring rod 4 start from the same point and, at the same time, move linearly along the welding direction at the same speed until the welding is completed.

[0041] Compared with the friction stir welding process using a traditional back pad, in this embodiment, during the friction stir welding process, the rotating body 2 in the device of the present invention follows the material flow formed by the rotation of the stirring rod 4 and performs a free rotation movement, improving the frictional constraint of the back support, reducing the frictional resistance of the traditional back pad to the material flow, increasing the welding efficiency, avoiding the weak connection defect caused by insufficient material flow, thereby improving the weld performance and obtaining a good welded joint.

[0042] Embodiment 2

[0043] As an improvement of the free rotation support device for assisting friction stir welding in Embodiment 1, in combination with Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 to illustrate this embodiment, on the basis of the frustum structure in Embodiment 1 for the support body 1 and the rotating body 2, cylindrical structures are provided on the upper and lower end faces of the support body 1, and thin-walled cylindrical structures are provided on the upper and lower ends of the rotating body 2. The heights of the cylindrical and cylindrical structures are the same, and the upper surfaces of the support body 1 and the rotating body 2 are in the same plane. Sealing grooves are opened in the gaps between the cylindrical and cylindrical structures, that is, the gaps between the support body 1 and the rotating body 2, or between multiple rotating bodies 2, and the sealing ring 12 is installed. The connection and fixation between the support body 1 and the slider 10 selects the connection block 14. A blind hole is opened at the lower end of the support body 1 and is in interference fit with the convex platform provided on the upper end face of the connection block 14 to realize the fixation of the support body 1. The rolling elements 3 are installed in the cage 13 and cooperate with the grooves opened on the support body 1 or the rotating body 2. The positions of the rolling elements 3 and the cage 13 are evenly distributed throughout the device.

[0044] In this embodiment, the type of the rolling element 3 is preferably a cylindrical roller, and the number of the rolling elements is preferably 30.

[0045] The rest of the specific implementation schemes are the same as those in Embodiment 1.

[0046] The setting of the upper and lower cylindrical structures of the support body 1 and the rotating body 2 facilitates the transmission of the torque generated by the material flow during the welding process. The sealing ring 12 includes an upper sealing ring and a lower sealing ring. The upper sealing ring can prevent the softened material from entering the device and damaging the device. At the same time, the upper and lower sealing rings can play a dust-proof role. In this embodiment, the preferred lubrication method of the rolling element 3 is grease lubrication. The upper and lower sealing rings are provided to prevent the grease from flowing out and being lost, so that the rolling element 3 in the device can maintain the state of grease lubrication for a long time.

[0047] The rolling elements 3 are assembled in the cage 13 to limit the relative positional relationship of the rolling elements 3 and prevent the rolling elements 3 from colliding during the rotation of the rotating body 2, thereby extending the service life of the device.

[0048] The rolling elements are preferably cylindrical rollers, which improves the load-bearing capacity of the device for the welding pressure.

[0049] Through the improvement of Embodiment 1, this embodiment can improve the load-bearing capacity of the free-rotation support device for assisting eddy current friction stir welding, extend the service life of the device, improve the rolling environment of the rolling elements, ensure the smooth rotation of the rotating body 2 and the rolling of the rolling elements 3 in the device, and improve the reliability of the device in use.

[0050] It should be noted that the above are only several embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent substitution on some of them.

[0051] Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. Although the specific implementation manners of the present invention have been described in conjunction with the accompanying drawings above, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications or deformations that can be made without creative labor on the basis of the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A free-rotation support device for assisting in vortex friction stir welding, comprising a support body (1), a rotating body (2) and a rolling body (3), characterized in that: The support body (1) is located in the middle of the device and remains fixed to support the stirring rod (4); the rotating body (2) is sleeved outside the support body (1), and the rolling elements (3) are assembled between the support body (1) and the rotating body (2), and multiple rolling elements (3) are distributed in an annular array. Fix the assembled free-rotating support device to the working position. During the welding process, keep the upper surfaces of the support body (1) and the rotating body (2) in the device always in contact with the lower surface of the welded plate; the stirring rod (4) and the support body (1) are coaxial; the upper surfaces of the support body (1) and the rotating body (2) are in the same plane, and the minimum length of the upper surface of the device in any direction is not less than 2 / 3 of the diameter of the used stirring rod (4). The support body (1) has no rotational movement and moves linearly at the same traveling speed as the stirring rod (4) in the working position; the rotating body (2) rotates freely around the axis relative to the support body (1) through the rolling elements (3), and the rotating body (2) follows the material flow formed by the rotation of the stirring rod (4) and performs a free-rotating movement.

2. The free-rotation support device for assisting in vortex friction stir welding according to claim 1, wherein: The number of rotating bodies (2) is single-layer or multi-layer, and the number and size of the rotating bodies (2) are determined comprehensively according to the diameter of the stirring rod (4), processing requirements, actual working conditions, and numerical simulation calculations.

3. The free-rotation support device for assisting in vortex friction stir welding according to claim 2, wherein: The diameter of the rotating body (2) is not greater than the outer diameter of the end of the sleeve (5), and is not less than 2 / 3 of the diameter of the stirring rod (4), and the number of layers of the rotating body (2) does not exceed 10 layers.

4. The free-rotation support device for assisting vortex friction stir welding according to claim 1, wherein: The support body (1) and the rotating body (2) are frustum-shaped or cylindrical.

5. An auxiliary eddy current friction stir welding free rotation support device according to claim 1, characterized in that: The rolling elements (3) are spherical rollers, tapered rollers or cylindrical rollers.

6. A method for using a free-rotation support device for assisting friction stir welding with vortex, which is applied to the free-rotation support device according to any one of claims 1-5, characterized in that: It includes the following specific steps: S1. Use computer simulation software such as Ansys, Deform or Abaqus to establish a numerical model of the vortex friction stir welding, and obtain a numerical simulation diagram of the material flow field distribution during the vortex friction stir welding. S2. Process the free-rotating support device according to the simulation calculation results. S3. Install the free-rotating support device directly below the stirring rod (4) and use this device for auxiliary welding.

7. The method of using a free-rotation support device for assisting in vortex friction stir welding according to claim 6, characterized in that: S2 includes the following steps: S21. According to the numerical simulation diagram of the flow field distribution obtained in S1, determine the number of rotating bodies (2), and the sizes of the support body (1) and the rotating body (2), and perform processing and manufacturing. S22. Sleeve the rotating body (2) outside the support body (1), with the rolling elements (3) located between the support body (1) and the rotating body (2), and fit the rolling elements (3) with the grooves on the outer surface of the support body (1) and the grooves on the inner surface of the rotating body (2). S23. If the rotating body (2) is multi-layer, repeat step S22 until all layers of the rotating body (2) are fully assembled.

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