Multi-stage detachable stirring device for vortex friction stir welding and welding method

Abstract

The application relates to a multi-stage detachable stirring device for vortex friction welding, which comprises a tool shank, an upper sleeve, a lower sleeve and an outer sleeve; the upper end of the upper sleeve is connected with the lower end of the tool shank, and the lower end of the upper sleeve is connected with the upper end of the lower sleeve in a profile mode; after the upper sleeve and the lower sleeve are connected, an installation cavity for installing a stirring rod is formed in the interior, the upper section of the stirring rod is connected with the upper sleeve in a profile mode, the upper end surface of the stirring rod is bonded with the upper sleeve through volatile glue, and the lower section of the stirring rod is matched with the lower sleeve in a clearance mode; the outer sleeve is sleeved outside the upper sleeve and the lower sleeve, the upper section of the outer sleeve is left with a gap outside the upper sleeve and is connected through a locking screw, and the lower section is matched with the lower sleeve in a clearance mode. The problem that the stirring tool cannot be detached due to thermal expansion in conventional vortex friction welding is solved. The application also relates to a welding method based on the stirring device, after welding is completed, the stirring rod is automatically left at the end of the welding seam, the stirring rod is prevented from being difficult to detach, and spoon hole defects are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vortex friction stir welding, in particular to a multi-stage detachable stirring device for vortex friction stir welding and a welding method. BACKGROUND

[0002] Friction stir welding technology can effectively avoid defects such as cracks and pores, and has advantages such as high joint quality and small welding deformation.

[0003] In the process of friction stir welding, the stirring head is pressed into the joint of the welded material under the action of high-speed rotation and axial force. Due to the heat generated by high-speed rotation, the metal around the stirring head softens and heats to a plastic flow state. The stirring head moves along the joint direction, and the metal around the stirring head fills the cavity formed by the stirring rod walking under the action of stirring and extrusion, thereby realizing the connection of materials.

[0004] For high-strength and high-melting-point iron-based, titanium-based and nickel-based alloys, the traditional friction stir welding requires a large axial pressure and torque to generate enough heat to soften the welded material, which will cause serious wear and even breakage of the stirring head. To solve this problem, patent CN201910746986.X proposes a rotating welding tool and welding method for friction welding, which uses a rod with the same material as the base material and an additional sleeve as a stirring tool for friction stir welding. Since the stirring rod and the base material have the same material, the friction between the stirring rod and the workpiece can be regarded as internal friction. The homogeneous friction between them will generate enough viscous dissipation heat to soften the metal below the stirring rod to a plastic state. The stirring rod rotates at high speed to drive the softened material to form a stable plastic material vortex. During welding, the stirring tool moves forward, and under the action of the plastic material vortex, the surrounding material flows plastically to form a weld, realizing the connection of materials. The plastic material vortex actually plays the role of the stirring head in the conventional friction stir welding process, so this process is named vortex friction stir welding based on homogeneous friction, which is called vortex friction stir welding for short. Compared with the traditional friction stir welding process, the vortex friction stir welding has lower cost because the stirring rod is consumable and the structure is simple, and its low-cost advantage is more significant when applied to high-melting-point alloys such as titanium alloys.

[0005] In the prior art, for the vortex friction stir welding described above, in the use scenario where the working temperature is very high, such as titanium alloy vortex friction stir welding, due to the high working temperature, the pin and the outer sleeve are heated and expanded during the welding process, which makes it difficult to take out after welding. In addition, the pin is connected with each component by a locking screw, and the locking screw often cannot be taken out after use due to thermal expansion, which causes the components to be unable to be disassembled, the pin to be unable to be reused, and the process cost to be increased, thereby greatly limiting the application of the vortex friction stir welding process in the field of high-melting-point materials such as titanium alloy and high-strength steel. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a multi-stage separable stirring device for vortex friction stir welding and a welding method, aiming to solve the problem that the stirring tool in conventional vortex friction stir welding cannot be disassembled due to thermal expansion.

[0007] The technical scheme adopted by the present application is as follows:

[0008] The present application provides a multi-stage separable stirring device for vortex friction stir welding, comprising a tool holder, an upper sleeve, a lower sleeve and an outer sleeve, each component being coaxially installed;

[0009] The upper end of the upper sleeve is connected with the lower end of the tool holder, and the lower end of the upper sleeve is in surface connection and gap cooperation with the upper end of the lower sleeve;

[0010] After the upper sleeve and the lower sleeve are connected, an installation cavity for gap cooperation with the pin is formed inside, the upper segment of the pin is in surface connection with the upper sleeve, the upper end surface of the pin is bonded to the upper sleeve by volatile glue, and the lower segment of the pin is in gap cooperation with the lower sleeve;

[0011] The outer sleeve is sleeved outside the upper sleeve and the lower sleeve, the upper segment of the outer sleeve is spaced apart from the outer side of the upper sleeve and connected by a locking screw, and the lower segment is in gap cooperation with the lower sleeve.

[0012] Further technical scheme:

[0013] The upper sleeve is internally provided with an upper cavity 2-2 and a lower cavity 2-3 distributed in steps, both cavities are cylindrical, the diameter of the upper cavity 2-2 is smaller than that of the lower cavity 2-3, the side surface of the upper cavity 2-2 is provided with a first small plane 2-2-1, and the side surface of the lower cavity 2-3 is provided with a second small plane 2-3-1;

[0014] The upper segment of the pin is placed in the upper cavity 2-2 and in surface connection therewith, and the side surface of the pin is provided with a third small plane 5-1 matched with the first small plane 2-2-1;

[0015] The lower sleeve upper section is placed in the lower cavity 2-3 and is coupled with the profile surface thereof, and the lower sleeve side is provided with a fourth flat surface 3-3 matched with the second flat surface 2-3-1.

[0016] The first through hole 1-2 is provided in the inner part of the shank and the upper sleeve, the top end of which is located on the upper end surface of the shank, and the bottom end of which is communicated with the upper cavity 2-2.

[0017] The upper sleeve is cylindrical, and the outer side surface thereof is provided with a first fastening flat surface 2-1 connected with the outer sleeve through the fastening screw, and the first fastening flat surface 2-1 and the inner wall of the outer sleeve form a gap therebetween.

[0018] The outer sleeve is internally provided with an upper cavity 4-1 and a lower cavity 4-2 in a stepped distribution, the upper cavity 4-1 is cylindrical and is matched with the upper sleeve in a gap, and the side wall of the upper cavity 4-1 is provided with a threaded hole 4-3 for mounting the fastening screw;

[0019] The threaded hole 4-3 is away from the lower end of the lower sleeve.

[0020] The lower cavity 4-2 is used for being matched with the lower sleeve in a gap.

[0021] The upper section of the lower cavity 4-2 is cylindrical, and the lower section thereof is conical, the conical side wall is a second taper surface 4-4, and a transition platform 4-2-1 is formed between the upper section and the lower section.

[0022] The lower sleeve comprises an upper section and a lower section, the upper section is cylindrical, the lower section is conical, the conical side wall is a first taper surface 3-4, and a first shaft shoulder 3-1 matched with the transition platform 4-2-1 is formed between the upper section and the lower section.

[0023] The vertical height of the second taper surface 4-4 is not higher than that of the first taper surface 3-4, the taper angle of the first taper surface 3-4 is greater than that of the second taper surface 4-4, so that a gap is left between the first taper surface 3-4 and the second taper surface 4-4.

[0024] The taper angles of the first taper surface 3-4 and the second taper surface 4-4 are both 5-20°.

[0025] The lower cavity 4-2 is cylindrical as a whole, and is internally provided with a step 4-2-2.

[0026] The lower sleeve comprises an upper section, a middle section with a smaller diameter than the upper section, and a lower section, and a second shaft shoulder 3-5 matched with the step 4-2-2 is formed between the upper section and the middle section.

[0027] The lower sleeve is internally provided with a second through hole 3-2 for being matched with the stirring rod in a gap, and the diameter of the stirring rod is 10-100mm.

[0028] The shank is cylindrical, and the side surface thereof is provided with a second fastening flat surface 1-1 for being connected with the welding machine spindle through a screw.

[0029] The shank, the upper sleeve and the outer sleeve are made of tool steel; the lower sleeve is made of hard alloy, high-temperature alloy or ceramic material; the stirring rod is made of the same material as the workpiece to be welded.

[0030] The application also provides a welding method of the multi-stage separable stirring device for the vortex friction stir welding.

[0031] The upper sleeve and the lower sleeve connected with the shank are assembled into one, and then assembled with the outer sleeve into the stirring device;

[0032] The shank is installed on the spindle of the welding machine, and the lower end surface of the lower sleeve is aligned with the surface of the workpiece to ensure that the lower end surface of the lower sleeve is pressed into the upper surface of the workpiece by 0-2 mm during the welding process;

[0033] The height of the stirring device is lifted, a little volatile harmless glue is applied on the upper end surface of the stirring rod, the stirring rod is installed into the lower end surface of the lower sleeve, the upper end surface of the stirring rod is glued and fixed with the upper sleeve, and the lower end surface of the stirring rod extends out of the lower end surface of the lower sleeve;

[0034] The stirring device is rotated and pressed down, the lower sleeve is fully contacted with the workpiece, the stirring device is moved along the weld joint to be welded, and the welding is performed under a protective atmosphere;

[0035] When the welding reaches the end point, the welding speed of the spindle of the welding machine is reduced to zero, but the rotating speed is maintained, the upper sleeve is lifted, the spindle of the welding machine is stopped when the lower sleeve is lifted to a position 0-3 mm away from the surface of the workpiece, the stirring device is kept in this position and does not move until the stirring device is completely cooled;

[0036] The upper sleeve is continuously lifted to separate the lower sleeve from the stirring rod, so that the stirring rod is left at the end of the weld joint, and the welding is completed.

[0037] The application has the following beneficial effects:

[0038] The profile connection between the stirring device and the stirring rod realizes the circumferential positioning of the stirring rod, and the gap fit between the stirring device and the stirring rod facilitates the removal after the welding. The stirring device of the application is composed of multiple separable parts, the gaps or the gap fit are left between the parts, and the threaded holes are arranged at positions far away from the surface of the workpiece to be welded, which can effectively reduce the thermal influence of the welding process on the set screws, and not only facilitates the disassembly and assembly, but also avoids the problem that the stirring rod cannot be removed due to the thermal deformation.

[0039] The welding method of the application realizes the axial positioning of the stirring rod through gluing, the glue continuously volatilizes during the welding, and after the welding is completed, because the stirring rod and the sleeve are in the gap fit, when the stirring device is lifted, the stirring rod is immediately and automatically left at the end of the weld joint, which not only avoids the disassembly of the stirring rod, but also avoids the spoon hole defects at the end of the weld joint.

[0040] The knife handle, the upper sleeve, the lower sleeve and the outer sleeve of the present application are all non-consumables, which can be repeatedly used for a long time, improve the utilization rate of the stirring device and save the cost.

[0041] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a structure schematic view of the embodiment 1 of the present application.

[0043] Figure 2 It is a structure schematic view of the upper sleeve of the embodiment 1 of the present application.

[0044] Figure 3 It is a structure schematic view of the lower sleeve of the embodiment 1 of the present application.

[0045] Figure 4 It is a structure schematic view of the stirring rod of the embodiment 1 of the present application.

[0046] Figure 5 It is a structure schematic view of the outer sleeve of the embodiment 1 of the present application.

[0047] Figure 6 It is a sectional view of the embodiment 1 of the present application.

[0048] Figure 7 It is Figure 6 It is an enlarged view of the middle A part.

[0049] Figure 8 It is a sectional view of the embodiment 2 of the present application.

[0050] Figure 9 It is a structure schematic view of the outer sleeve of the embodiment 2 of the present application.

[0051] Figure 10 It is a structure schematic view of the lower sleeve of the embodiment 2 of the present application.

[0052] In the figure: 1, knife handle; 2, upper sleeve; 3, lower sleeve; 4, outer sleeve; 5, stirring rod;

[0053] 1-1, second fixing plane; 1-2, first through hole;

[0054] 2-1, first fixing plane; 2-2, upper cavity; 2-3, lower cavity; 2-2-1, first small plane; 2-3-1, second small plane;

[0055] 3-1, first shaft shoulder; 3-2, second through hole; 3-3, fourth small plane; 3-4, first taper surface; 3-5, second shaft shoulder;

[0056] 4-1, upper cavity; 4-2, lower cavity; 4-2-1, transition platform; 4-2-2, step; 4-3, threaded hole; 4-4, second conical surface; 5-1, third small plane. DETAILED DESCRIPTION

[0057] The specific embodiments of the present application are described below with reference to the accompanying drawings.

[0058] Example 1

[0059] Referring to Figures 1-7 , the multi-stage separable stirring device for vortex friction stir welding in this embodiment 1 comprises a tool holder 1, an upper sleeve 2, a lower sleeve 3 and an outer sleeve 4, and each part is coaxially installed;

[0060] As shown in Figure 1 , the upper end of the upper sleeve 2 is connected with the lower end of the tool holder 1, and the lower end of the upper sleeve 2 is connected with the upper end of the lower sleeve 3 in a form fit and clearance fit;

[0061] After the upper sleeve 2 is connected with the lower sleeve 3, an installation cavity for installing a stirring rod 5 is formed inside, and the stirring rod 5 is in clearance fit with the installation cavity: the upper section of the stirring rod 5 is connected with the upper sleeve 2 in a form fit, and the upper end surface of the stirring rod 5 is bonded with the upper sleeve 2 through volatile glue, and the lower section of the stirring rod 5 is in clearance fit with the inner wall of the lower sleeve 3;

[0062] The outer sleeve 4 is sleeved outside the upper sleeve 2 and the lower sleeve 3, and the upper section of the outer sleeve 4 is left with a gap on the outside of the upper sleeve 2 and is connected through a set screw, and the lower section is in clearance fit with the lower sleeve 3.

[0063] As shown in Figure 2 , the upper sleeve 2 is provided with an upper cavity 2-2 and a lower cavity 2-3 in a stepped distribution, both cavities are cylindrical, the diameter of the upper cavity 2-2 is smaller than that of the lower cavity 2-3, the side surface of the upper cavity 2-2 is provided with a first small plane 2-2-1, and the side surface of the lower cavity 2-3 is provided with a second small plane 2-3-1;

[0064] As shown in Figure 3 , the upper section of the lower sleeve 3 is placed in the lower cavity 2-3 and is connected with it in a form fit, and the side surface of the lower sleeve 3 is provided with a fourth small plane 3-3 matched with the second small plane 2-3-1; the inside of the lower sleeve 3 is provided with a second through hole 3-2 for clearance fit with the stirring rod 5;

[0065] As shown in Figure 4 , the upper section of the stirring rod 5 is placed in the upper cavity 2-2 and is connected with it in a form fit, and the side surface of the stirring rod 5 is provided with a third small plane 5-1 matched with the first small plane 2-2-1.

[0066] Referring to Figure 2The first through hole 1-2 is arranged in the inner part of the upper sleeve 2 and has its top end on the upper end face of the shank 1 and its bottom end communicated with the upper cavity 2-2.

[0067] The first through hole 1-2 is arranged in the inner part of the upper sleeve 2 and has its top end on the upper end face of the shank 1 and its bottom end communicated with the upper cavity 2-2.

[0068] As shown in Figure 5 , the outer sleeve 4 is provided with an upper cavity 4-1 and a lower cavity 4-2 in step distribution, the upper cavity 4-1 is cylindrical and used for clearance fit with the upper sleeve 2, the upper sleeve 2 is cylindrical and provided with a first fastening flat surface 2-1 (see Figure 2 ) on its outer side surface for connection with the outer sleeve 4 through a fastening screw, the first fastening flat surface 2-1 and the inner wall of the outer sleeve 4 form a gap therebetween, and the upper cavity 4-1 is provided with a threaded hole 4-3 on its side wall for installation of the fastening screw;

[0069] The threaded hole 4-3 is away from the lower end of the lower sleeve 3, i.e. far from the surface of the workpiece to be welded during operation;

[0070] The lower cavity 4-2 is used for clearance fit with the lower sleeve 3.

[0071] In the embodiment, the upper section of the lower cavity 4-2 is cylindrical and the lower section is conical, the conical side wall is a second taper surface 4-4, and a transition platform 4-2-1 is formed between the upper section and the lower section; Figure 3 correspondingly, the lower sleeve 3 comprises an upper section and a lower section, the upper section is cylindrical and the lower section is conical, the conical side wall is a first taper surface 3-4, and a first shaft shoulder 3-1 is formed between the upper section and the lower section for cooperation with the transition platform 4-2-1;

[0072] The vertical height of the second taper surface 4-4 is not higher than that of the first taper surface 3-4, the taper angle α of the first taper surface 3-4 is greater than the taper angle β of the second taper surface 4-4, so that a gap is left between the first taper surface 3-4 and the second taper surface 4-4, as shown in Figure 6 and Figure 7 .

[0073] Specifically, the taper angle of the first taper surface 3-4 and the taper angle of the second taper surface 4-4 are both 5-20°.

[0074] Specifically, the wall thickness of the upper section of the lower sleeve 3 is not less than 3 mm and the wall thickness of the lower section is not less than 1.5 mm.

[0075] Specifically, as shown in Figure 2 , the shank 1 is cylindrical and provided with a second fastening flat surface 1-1 on its side surface for connection with the main shaft of the welding machine through a screw.

[0076] The first to fourth small planes and the two fixing planes of the embodiment are specifically planes arranged on the circumferential outer wall and extending in the vertical direction. Through the corresponding cooperation between the small planes, circumferential limiting can be realized. The fixing planes can be circumferentially locked through the locking member (screw, etc.).

[0077] Embodiment 2

[0078] Referring to Figures 8-10 , the multi-stage separable stirring device for vortex friction stir welding in the embodiment 2 is the same as that in the embodiment 1 in other structures, and the difference is only that:

[0079] As shown in Figure 9 , the lower cavity 4-2 of the outer sleeve 4 in the embodiment is a cylinder as a whole, and a step 4-2-2 is arranged in the inner part; correspondingly, as shown in Figure 10 , the lower sleeve 3 includes an upper segment, a middle segment with a smaller diameter than the upper segment, and a lower segment, and a second shoulder 3-5 is formed between the upper segment and the middle segment and cooperates with the step 4-2-2.

[0080] Specifically, the width of the second shoulder 3-5 and the step 4-2-2 is 0.5-3mm.

[0081] The above two embodiments can realize the cooperation between the outer sleeve and the lower sleeve, so that the lower sleeve is limited in the outer sleeve.

[0082] In the above two embodiments, the components can be specifically set as follows during specific implementation according to actual conditions:

[0083] The height of the upper cavity 2-2 and the lower cavity 2-3 of the upper sleeve 2 is not less than 5mm, and the diameter of the upper cavity 2-2 is at least 6mm smaller than that of the lower cavity 2-3.

[0084] The diameter of the stirring rod 5 is 10-100mm.

[0085] The materials of the tool holder 1, the upper sleeve 2 and the outer sleeve 4 are tool steel;

[0086] The lower sleeve 3 is made of hard alloy or high-temperature alloy or ceramic material (such as polycrystalline cubic boron nitride);

[0087] The material of the stirring rod 5 is the same as that of the workpiece to be welded. The material of the workpiece to be welded can be titanium alloy.

[0088] The multi-stage separable stirring device for vortex friction stir welding in the above two embodiments can be assembled by a plurality of parts with different functions in sequence, and compared with the overall structure of the traditional stirring tool or the structure composed of the sleeve and the stirring rod, the disassembly and assembly are convenient, and the reusability of the stirring device is improved.

[0089] Embodiment 3

[0090] The embodiment 3 provides a welding method using the multi-stage separable stirring device for vortex friction welding in the embodiment 1 or 2, comprising the following steps:

[0091] The upper sleeve 2 and the lower sleeve 3 connected with the tool shank 1 are assembled into an integrated body, and then assembled with the outer sleeve 4 into the stirring device, wherein the components in the stirring device are coaxially arranged and have the same angular velocity during work;

[0092] The tool shank is installed on the spindle of a welding machine, and the lower end surface of the lower sleeve 3 is used to zero with the surface of a workpiece, so that the lower end surface of the lower sleeve 3 is pressed into the upper surface of the workpiece by 0-2 mm during the welding process;

[0093] The height of the stirring device is lifted, a little volatile harmless glue is applied on the upper end surface of the stirring rod 5, the stirring rod 5 is installed into the lower end surface of the lower sleeve 3, and the upper end surface of the stirring rod 5 is glued and fixed, and the lower end surface is stretched out of the lower end surface of the lower sleeve 3;

[0094] The stirring device is rotated and pressed downward, the lower sleeve 3 is fully contacted with the workpiece, the stirring device is moved along the weld seam to be welded, and the welding is performed under a protective atmosphere;

[0095] When the welding reaches the end point, the welding speed of the spindle of the welding machine is reduced to zero, but the rotating speed is kept, the upper sleeve 2 is pulled upward, when the lower sleeve 3 is lifted to be 0-3 mm away from the surface of the workpiece, the spindle of the welding machine is stopped, and the stirring device is kept in this position and does not move until the welding position is cooled (after the protective gas continues to work for 30 seconds, natural or air cooling is performed for 3-10 minutes);

[0096] The upper sleeve 2 is continuously pulled upward, the lower sleeve 3 is separated from the stirring rod 5, and the stirring rod 5 is left at the end of the weld, and the welding is completed.

[0097] In the embodiment, since the stirring rod 5 is gap-fitted between the upper sleeve and the lower sleeve, is only limited in the circumferential direction by the profile connection, and is prevented from rotating in the circumferential direction in the upper sleeve. Therefore, the stirring rod 5 is axially fixed by applying glue, during the welding process, the stirring device is pressed into the workpiece by a certain depth and moves along the weld seam at a certain speed, the stirring rod is subjected to axial downward pressure and is always limited between the workpiece and the stirring device, so that the axial direction cannot move. The glue is continuously volatilized by heat during the welding process, after the welding is completed, the axial limitation of the stirring rod is released, since the stirring rod is gap-fitted with the sleeve, when the stirring device is lifted, the stirring rod will not be lifted, so as to be left at the end of the weld, which can avoid the disassembly work of the stirring rod and the spoon hole defect at the end of the weld.

[0098] After the welding is completed, the disassembly can be realized according to the process opposite to the assembly, since the threaded hole 4-3 is far away from the lower end of the lower sleeve 3, that is, far away from the surface of the welded workpiece during work, and is not easy to be deformed by heat, so the disassembly is convenient. The shank, the upper sleeve, the lower sleeve and the outer sleeve are all non-consumable products, and can be repeatedly used.

[0099] Those skilled in the art can understand that the above only describes the preferred embodiments of the present application, and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, and for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced equivalently. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A welding method for a multi-stage separable stirring device used in eddy current friction stir welding, characterized in that, The stirring device includes a blade handle (1), an upper sleeve (2), a lower sleeve (3), and an outer sleeve (4), with each component installed coaxially. The upper end of the upper sleeve (2) is connected to the lower end of the knife handle (1), and the lower end of the upper sleeve (2) is connected to the upper end of the lower sleeve (3) with clearance fit. After the upper sleeve (2) is connected to the lower sleeve (3), an installation cavity is formed inside for clearance fit with the stirring rod (5). The upper section of the stirring rod (5) is connected to the profile of the upper sleeve (2), and the upper end face of the stirring rod (5) is bonded to the upper sleeve (2) by volatile adhesive. The lower section of the stirring rod (5) is clearance fit with the lower sleeve (3). The outer sleeve (4) is fitted over the outside of the upper sleeve (2) and the lower sleeve (3). The upper section of the outer sleeve (4) has a gap with the outer side of the upper sleeve (2) and is connected by a set screw. The lower section is fitted with the lower sleeve (3) with a clearance. The welding method includes: Assemble the upper sleeve (2) and lower sleeve (3) connected to the handle (1) into one piece, and then assemble them with the outer sleeve (4) to form a stirring device; Install the tool holder (1) on the welding machine spindle, and use the lower end face of the lower sleeve (3) to zero the workpiece surface to ensure that during the welding process, the lower end face of the lower sleeve (3) presses into the upper surface of the workpiece by 0-2 mm. Raise the height of the stirring device, apply a small amount of volatile harmless glue to the upper end face of the stirring rod (5), insert the stirring rod (5) into the lower end face of the lower sleeve (3), so that the upper end face of the stirring rod (5) is glued to the upper sleeve (2), and the lower end face extends out of the lower end face of the lower sleeve (3). Rotate and press down the stirring device until the lower sleeve (3) is in full contact with the workpiece. Move the stirring device along the seam to be welded and weld under a protective atmosphere. When the welding reaches the end point, the welding speed of the welding machine spindle drops to zero, but the rotation speed is maintained. The upper sleeve (2) is raised. When the lower sleeve (3) is raised to 0-3 mm from the workpiece surface, the welding machine spindle stops rotating. The stirring device stays in this position and remains stationary until the stirring device is completely cooled. Continue to lift the upper sleeve (2) to separate the lower sleeve (3) from the stirring rod (5), leaving the stirring rod (5) at the end of the weld to complete the welding.

2. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 1, characterized in that, The upper sleeve (2) has an upper cavity (2-2) and a lower cavity (2-3) arranged in a stepped manner. Both cavities are cylindrical. The diameter of the upper cavity (2-2) is smaller than that of the lower cavity (2-3). The upper cavity (2-2) has a first small plane (2-2-1) on its side, and the lower cavity (2-3) has a second small plane (2-3-1) on its side. The upper section of the stirring rod (5) is placed in the upper cavity (2-2) and connected to its surface, and the side of the stirring rod (5) is provided with a third small plane (5-1) that cooperates with the first small plane (2-2-1). The upper section of the lower sleeve (3) is placed in the lower cavity (2-3) and connected to its profile, and the side of the lower sleeve (3) is provided with a fourth small plane (3-3) that cooperates with the second small plane (2-3-1).

3. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 2, characterized in that, The handle (1) and the upper sleeve (2) are provided with a first through hole (1-2), the top of which is located on the upper end face of the handle (1), and the bottom end is connected to the upper cavity (2-2).

4. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 1, characterized in that, The upper sleeve (2) is cylindrical, and its outer side is provided with a first fixing plane (2-1) that is connected to the outer sleeve (4) by the set screw. A gap is formed between the first fixing plane (2-1) and the inner wall of the outer sleeve (4). The outer sleeve (4) has an upper cavity (4-1) and a lower cavity (4-2) arranged in a stepped manner. The upper cavity (4-1) is cylindrical and is clearance-fitted with the upper sleeve (2). The side wall of the upper cavity (4-1) is provided with a threaded hole (4-3) for installing the set screw. The threaded hole (4-3) is located away from the lower end of the lower sleeve (3); The lower cavity (4-2) is used to fit with the lower sleeve (3) with a clearance.

5. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 4, characterized in that, The lower cavity (4-2) has a cylindrical upper section and a conical lower section, with the conical sidewall being a second conical surface (4-4), and a transition platform (4-2-1) is formed between the upper and lower sections. The lower sleeve (3) includes an upper section and a lower section. The upper section is cylindrical and the lower section is conical. The conical sidewall is a first conical surface (3-4). A first shoulder (3-1) is formed between the upper and lower sections to cooperate with the transition platform (4-2-1). The vertical height of the second cone (4-4) is not higher than that of the first cone (3-4), and the cone angle of the first cone (3-4) is greater than that of the second cone (4-4), so that there is a gap between the first cone (3-4) and the second cone (4-4).

6. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 5, characterized in that, The cone angles of the first cone (3-4) and the second cone (4-4) are both 5-20°.

7. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 4, characterized in that, The lower cavity (4-2) is cylindrical in shape, and has a step (4-2-2) inside. The lower sleeve (3) includes an upper section, a middle section with a diameter smaller than that of the upper section, and a lower section. A second shoulder (3-5) is formed between the upper section and the middle section to cooperate with the step (4-2-2).

8. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 1, characterized in that, The lower sleeve (3) is provided with a second through hole (3-2) for clearance fitting with the stirring rod (5), and the diameter of the stirring rod (5) is 10-100 mm; The tool holder (1) is cylindrical and has a second fixing plane (1-1) on the side, which is used to connect to the welding machine spindle by screws.

9. The welding method for a multi-stage separable stirring device for eddy current friction welding according to claim 1, characterized in that, The tool holder (1), upper sleeve (2) and outer sleeve (4) are made of tool steel; the lower sleeve (3) is made of cemented carbide, high-temperature alloy or ceramic material; the stirring rod (5) is made of the same material as the workpiece to be welded.

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