A friction stir welding tool

Abstract

The present invention discloses a friction stir welding tool, which relates to the technical field of friction stir welding. The friction stir welding tool includes a stirring pin, a shoulder, a clamping part and a connecting component. The clamping part is fixed to the upper end of the shoulder, the stirring pin is slidably installed in the shoulder, the connecting component is installed on the side wall of the shoulder and is used to fixedly connect the stirring pin and the shoulder. The lower end of the stirring pin is a needle head part, and the needle head part includes a first inverted frustum, a second inverted frustum, a third inverted frustum and an inverted frustum-shaped needle tip part which are connected in sequence from top to bottom. The diameter of the upper end of the inverted frustum-shaped needle tip part is smaller than the diameter of the lower end of the third inverted frustum. A plurality of spiral stirring grooves are circumferentially arranged on the side wall of the second inverted frustum. A plurality of involute structures are circumferentially arranged on the bottom surface of the third inverted frustum. The winding direction of the involute structure is opposite to the spiral direction of the spiral stirring groove. Threads are arranged on the side wall of the inverted frustum-shaped needle tip part, so that the material can be fully broken at the interface, which is beneficial to increasing the effective lap width and the effective lap thickness.

Description

Technical Field

[0001] The present invention relates to the technical field of friction stir welding, and particularly to a friction stir welding tool head. Background Art

[0002] Friction stir welding is a solid-state welding technology that can avoid various metallurgical defects such as pores, hot cracks, and segregation generated during fusion welding. It can weld various types of aluminum alloys, including high-strength aluminum alloys such as series 2, series 5, and series 7 that are difficult to weld with traditional fusion welding. Friction stir welding lap joint is a type of friction stir welding. After stacking two plates together, the stirring pin penetrates into the upper plate, and heat is generated through the rotational shearing and extrusion deformation of the material by the welding tool. The forward movement of the welding tool enables metallurgical bonding between the upper and lower plates. Compared with friction stir welding butt joint, the lap joint has the advantages of simple pre-welding preparation and assembly, and can meet the welding requirements of various types of components, occupying an important position in industrial applications, and is widely used in the assembly of parts and products in the aviation industry, such as heat exchangers for aircraft sealed cabins, skins, stiffeners, wing frames, and floor decks.

[0003] During the experiment, a hook defect (Hook) and a cold lap defect (Cold lap) are often inevitably formed on the advancing side and the retreating side of the lap joint interface respectively. Currently, most of the conventional tool heads used are considered to solve the hook defect (Hook) and the cold lap defect (Cold lap) in terms of the thread direction, the diameter of the stirring pin, the shape of the stirring pin, etc. However, using the above methods still has problems such as insufficient interface stirring, too high Hook, and too long Cold lap extending into the weld nugget zone, thereby reducing the effective lap width and effective lap thickness of the joint. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a friction stir welding tool head that can fully break up the material at the interface, which is beneficial to increasing the effective lap width and effective lap thickness.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a friction stir welding tool, which includes a stirring pin, a shoulder, a clamping part and a connecting component. The clamping part is fixed to the upper end of the shoulder. The stirring pin is slidably installed in the shoulder. The connecting component is installed on the side wall of the shoulder and is used to fixedly connect the stirring pin and the shoulder. The lower end of the stirring pin is a needle head part, and the needle head part includes a first inverted frustum, a second inverted frustum, a third inverted frustum and an inverted frustum-shaped needle tip part that are connected in sequence from top to bottom. The diameter of the upper end of the inverted frustum-shaped needle tip part is smaller than the diameter of the lower end of the third inverted frustum. A plurality of spiral stirring grooves are circumferentially arranged on the side wall of the second inverted frustum. A plurality of involute structures are circumferentially arranged on the bottom surface of the third inverted frustum. The winding direction of the involute structure is opposite to the spiral direction of the spiral stirring groove. Threads are provided on the side wall of the inverted frustum-shaped needle tip part.

[0007] Preferably, the diameter of the upper end of the second inverted frustum is equal to the diameter of the lower end of the first inverted frustum, and the taper angle of the second inverted frustum is different from the taper angle of the first inverted frustum.

[0008] Preferably, the diameter of the upper end of the third inverted frustum is equal to the diameter of the lower end of the second inverted frustum, and the taper angle of the third inverted frustum is different from the taper angle of the second inverted frustum.

[0009] Preferably, the taper angle of the second inverted frustum is greater than the taper angle of the first inverted frustum, the taper angle of the third inverted frustum is less than the taper angle of the second inverted frustum, and the taper angle of the inverted frustum-shaped needle tip part is greater than the taper angle of the third inverted frustum.

[0010] Preferably, the taper angles of the first inverted frustum, the third inverted frustum and the inverted frustum-shaped needle tip part are all 40° - 90°, and the taper angle of the second inverted frustum is greater than 90°.

[0011] Preferably, a plane formed by milling is provided on one side of the upper part of the stirring pin. The connecting component includes a plurality of bolts. A plurality of threaded holes are provided on the side wall of the shoulder. Each bolt is used to be installed in one of the threaded holes and abuts against the plane.

[0012] Preferably, the plurality of spiral stirring grooves are evenly arranged at intervals of 45°, and the depth of the spiral stirring grooves is 0.2 - 0.6 mm.

[0013] Preferably, the plurality of involute structures are evenly arranged at intervals of 120°, and the height of the involute structures is 0.2 - 0.5 mm.

[0014] The present invention has achieved the following technical effects compared with the prior art:

[0015] The involute structure of the friction stir welding tool head of the present invention can fully stir at the lap joint interface, break the interface, which is beneficial to increasing the effective lap width. The third inverted frustum can depress the Hook to obtain the effective lap thickness. The spiral stirring groove can perform secondary stirring on the materials that the involute structure fails to break, which can maximize the promotion of the full stirring of the stirring pin and the workpiece weld material and provide sufficient heat input, and improve the problems of large temperature gradient and insufficient weld metal flow during lap joint. In the present invention, the spiral stirring groove on the second inverted frustum and the involute structure on the third inverted frustum are used for reverse stirring to promote the flow of materials towards the interface, which can promote the full stirring of the materials at the lap joint interface, is beneficial to breaking the Cold lap and making it disperse, and can stably perform friction stir lap welding. Compared with the existing tool head, the effective lap width and effective lap thickness obtained under the same process conditions are greatly improved, and problems such as unbroken interface and insufficient material flow are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 Structural schematic diagram of the friction stir welding tool head provided by the present invention;

[0018] Figure 2 Front view of the needle head of the stirring pin in the friction stir welding tool head provided by the present invention;

[0019] Figure 3 Three-dimensional structure diagram of the needle head of the stirring pin in the friction stir welding tool head provided by the present invention;

[0020] Figure 4 Bottom view of the friction stir welding tool head provided by the present invention;

[0021] Figure 5 Usage schematic diagram of the friction stir welding tool head provided by the present invention.

[0022] Explanation of reference numerals: 100, friction stir welding tool head; 1, stirring pin; 2, shoulder; 3, clamping part; 4, plane; 5, bolt; 6, first inverted frustum; 7, second inverted frustum; 8, third inverted frustum; 9, inverted frustum-shaped tip; 10, spiral stirring groove; 11, involute structure; 12, thread. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] The object of the present invention is to provide a friction stir welding tool head that can fully break the material at the interface, which is beneficial to increasing the effective overlap width and effective overlap thickness.

[0025] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0026] Embodiment 1:

[0027] As Figures 1-5 shown, this embodiment provides a friction stir welding tool head 100, which includes a stirring pin 1, a shoulder 2, a clamping part 3, and a connecting component. The clamping part 3 is fixed to the upper end of the shoulder 2. An axial hole for installing the stirring pin 1 is provided inside the shoulder 2. The stirring pin 1 is slidably installed in the shoulder 2, that is, the stirring pin 1 is installed in the axial hole. The connecting component is installed on the side wall of the shoulder 2 and is used to fixedly connect the stirring pin 1 and the shoulder 2. The lower end of the stirring pin 1 is a needle head part, and the needle head part includes a first inverted frustum 6, a second inverted frustum 7, a third inverted frustum 8, and an inverted frustum-shaped tip part 9 that are connected in sequence from top to bottom. The first inverted frustum 6, the second inverted frustum 7, the third inverted frustum 8, and the inverted frustum-shaped tip part 9 are coaxially arranged. The diameter of the upper end of the inverted frustum-shaped tip part 9 is smaller than the diameter of the lower end of the third inverted frustum 8. A plurality of spiral stirring grooves 10 are circumferentially arranged on the side wall of the second inverted frustum 7. A plurality of involute structures 11 are circumferentially arranged on the bottom surface of the third inverted frustum 8. The winding direction of the involute structure 11 is opposite to the spiral direction of the spiral stirring groove 10. In this embodiment, the spiral stirring groove 10 is closer to the shoulder 2, and the involute structure 11 is closer to the inverted frustum-shaped tip part 9. A thread 12 is provided on the side wall of the inverted frustum-shaped tip part 9. In this embodiment, the thread 12 provided on the side wall of the inverted frustum-shaped tip part 9 is a left-handed thread.

[0028] During operation, the rotation direction of the friction stir welding tool head 100 is opposite to the helix direction of the thread 12 on the inverted frustum-shaped tip 9. The thread 12 on the inverted frustum-shaped tip 9 causes the material to flow upward, enabling the material to gather at the interface. The involute structure 11 can fully stir at the lap interface, break the interface, which is beneficial for increasing the effective lap width. The third inverted frustum 8 can press down the Hook to obtain an effective lap thickness. The spiral stirring groove 10 can perform secondary stirring on the material that the involute structure 11 fails to break, which can maximize the promotion of full stirring between the stirring pin 1 and the workpiece weld material and provide sufficient heat input, improving the problems of large temperature gradient and insufficient flow of the weld metal during lapping.

[0029] According to the principle of friction stir welding, the interfaces in the friction stir welding lap joint mainly have three migration modes: upward migration, downward migration, and first upward and then downward migration. The reason for their formation is the vertical flow of the weld metal during welding. If the metal at the lap interface is not fully stirred, it will lead to excessive interface migration.

[0030] In this embodiment, the spiral stirring groove 10 on the second inverted frustum 7 and the involute structure 11 on the third inverted frustum 8 are used for reverse stirring, which can promote the full stirring of the material at the lap interface, is beneficial for breaking the interface, is beneficial for breaking the Cold lap and making it disperse, pressing down the Hook, and is conducive to controlling the lap interface migration, that is, avoiding excessive interface migration, enabling stable friction stir lap welding. Compared with the existing tool head, the effective lap width and effective lap thickness obtained under the same process conditions are greatly improved, avoiding problems such as unbroken interface and insufficient material flow. At the same time, the stress on the stirring pin 1 is small, improving the service life of the stirring pin 1. Under the action of heat generated by the friction between the shoulder 2 and the stirring pin 1 of the friction stir welding tool head 100 in this embodiment and the rotational stirring of the stirring pin 1, the surface of the welded joint is well formed, the tensile performance is improved, and the effective lap width and effective plate thickness are increased.

[0031] Specifically, the diameter of the upper end of the second inverted frustum 7 is equal to the diameter of the lower end of the first inverted frustum 6, and the taper angle of the second inverted frustum 7 is different from that of the first inverted frustum 6.

[0032] Specifically, the diameter of the upper end of the third inverted frustum 8 is equal to the diameter of the lower end of the second inverted frustum 7, and the taper angle of the third inverted frustum 8 is different from that of the second inverted frustum 7.

[0033] In this embodiment, the first inverted frustum 6, the second inverted frustum 7, the third inverted frustum 8, and the inverted frustum-shaped tip 9 arranged in sequence from top to bottom form a stepped structure.

[0034] In this embodiment, the taper angle of the second inverted frustum 7 is greater than that of the first inverted frustum 6, the taper angle of the third inverted frustum 8 is less than that of the second inverted frustum 7, the taper angle of the inverted frustum-shaped tip portion 9 is greater than that of the third inverted frustum 8, and the taper angle of the first inverted frustum 6 is less than that of the inverted frustum-shaped tip portion 9.

[0035] In this specific embodiment, the taper angles of the first inverted frustum 6, the third inverted frustum 8, and the inverted frustum-shaped tip portion 9 are all 40° to 90°, and the taper angle of the second inverted frustum 7 is greater than 90°.

[0036] Specifically, a plane 4 formed by milling is provided on one side of the upper part of the stirring needle 1. The connecting assembly includes a plurality of bolts 5. A plurality of threaded holes are provided on the side wall of the shoulder 2, and the threaded holes communicate with the axial holes. Each bolt 5 is used to be installed in a threaded hole and abut against the plane 4. The bolt 5 in this embodiment is an internal hexagonal bolt.

[0037] When the stirring needle 1 needs to be replaced, screw out the bolt 5 outward so that the bolt 5 no longer abuts against the plane 4, and then pull it out from the lower part of the shoulder 2. Install a new stirring needle 1, make the plane 4 of the stirring needle 1 opposite to the threaded hole, and screw in the bolt 5 inward so that it abuts against the plane 4.

[0038] In this specific embodiment, a plurality of spiral stirring grooves 10 are evenly arranged at intervals of 45°. The depth of the spiral stirring grooves 10 is 0.2 to 0.6 mm. In this embodiment, the upper end of the spiral stirring grooves 10 extends into the lower part of the side wall of the first inverted frustum 6.

[0039] In this specific embodiment, a plurality of involute structures 11 are evenly arranged at intervals of 120°. The height of the involute structures 11 is 0.2 to 0.5 mm.

[0040] In this specific embodiment, for a TiB2 / 2024 aluminum matrix composite material plate with a thickness of 2 mm, the stirring needle 1 has a structure of an inverted frustum with a left thread and a step at the tip. The diameter of the upper end of the first inverted frustum 6 is 6 mm, the diameter of the upper end of the second inverted frustum 7 is 5 mm, the diameter of the upper end of the third inverted frustum 8 is 3.5 mm, the diameter of the lower end of the third inverted frustum 8 is 3.2 mm, and the taper angle of the first inverted frustum 6 The taper angle of the second inverted frustum 7 The taper angle of the third inverted frustum 8 is 40°, and the taper angle of the inverted frustum-shaped tip portion 9 The length L of the stirring pin is 3 mm, and the end diameter d of the stirring pin is 1 mm. That is, in this embodiment, a relatively small stirring pin cone angle and a relatively large end diameter are adopted. According to the commonly used design principle in the industry, a single-ring structure with a shoulder diameter D of the stirring head of 10 mm and an inner concavity of 0.3 mm is adopted. Using the above stirring head, welding is carried out with a conventional process parameter combination of a rotational speed W of 600 r / min, a welding speed V of 118 mm / min, a downward pressure h of 0.2 mm, and an inclination angle β of 2.5°. A metallographic specimen is prepared by intercepting the cross-section of the joint weld. No defects such as holes and tunnels are observed, and the welding quality and joint performance meet the requirements, and the TiB2 / 2024 aluminum matrix composite material with a thickness of 2 mm can be stably penetrated. According to the above stirring head structure and welding inclination angle, Figure 5 A three-dimensional model of the stirring head and the workpiece to be welded during the welding process is established as shown. By intercepting and taking a macro photograph of the metallography, it can be seen that the lap width is significantly enlarged and the effective plate thickness is significantly increased.

[0041] Comparative Example 1:

[0042] Using an ordinary tapered-thread stirring head to weld a TiB2 / 2024 aluminum matrix composite material with a thickness of 2 mm under the same process parameters as in Example 1. A metallographic specimen is prepared by intercepting the cross-section of the joint weld. It is observed that there are obvious tunnel defects in the weld nugget zone and the interface is not completely broken.

[0043] Example 2:

[0044] The difference between the stirring pin in this embodiment and that in Example 1 is that there is no third inverted frustum 8 and involute structure 11. Welding is carried out with a conventional process parameter combination of a rotational speed W of 600 r / min, a welding speed V of 118 mm / min, a downward pressure h of 0.2 mm, and an inclination angle β of 2.5°. It is found that the interface is not broken and the Hook defect is still too high, resulting in a reduction in the effective lap thickness of the plate.

[0045] Example 3:

[0046] The difference between the stirring pin in this embodiment and that in Example 1 is that there is no involute structure 11. Welding is carried out with a conventional process parameter combination of a rotational speed W of 600 r / min, a welding speed V of 118 mm / min, a downward pressure h of 0.2 mm, and an inclination angle β of 2.5°. It is found that the interface is not completely broken, and the thread 12 on the conical tip 9 of the inverted frustum causes the material to flow upward, making the material gather at the interface. Although the Hook defect is reduced to some extent, the effective lap width is significantly reduced.

[0047] Example 4:

[0048] The difference between the stirring pin in this embodiment and that in the first embodiment is that the inverted frustum-shaped tip 9 has no thread 12. When welding is carried out using the conventional process parameter combination with a rotational speed W of 600 r / min, a welding speed V of 118 mm / min, a downward pressure h of 0.2 mm, and an inclination angle β of 2.5°, it is found that there are tunnel defects. Since there is no thread 12 on the inverted frustum-shaped tip 9, the material cannot flow sufficiently, and with the process parameters unchanged, the heat input is insufficient, resulting in tunnel defects at the interface.

[0049] Embodiment Five:

[0050] The difference between the stirring pin in this embodiment and that in the first embodiment is that there is no spiral stirring groove 10 on the second inverted frustum 7. When welding is carried out using the conventional process parameter combination with a rotational speed W of 600 r / min, a welding speed V of 118 mm / min, a downward pressure h of 0.2 mm, and an inclination angle β of 2.5°, it is found that the Hook is too high. Since the involute structure 11 on the third inverted frustum 8 breaks the interface and there is still a small amount of upward movement, with the process parameters unchanged, the effective plate thickness is reduced.

[0051] It can be seen from the data of the embodiments and the comparative examples that the friction stir welding tool head 100 of the present invention has a significantly better penetration effect than the friction stir welding tool heads of the prior art under the same process parameters.

[0052] In this specification, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A friction stir welding tool, characterized in that, It includes a stirring needle, a shoulder, a clamping part, and a connecting component. The clamping part is fixed to the upper end of the shoulder. The stirring needle is slidably installed in the shoulder. The connecting component is installed on the side wall of the shoulder and is used to fixedly connect the stirring needle and the shoulder. The lower end of the stirring needle is a needle head part, and the needle head part includes a first inverted frustum, a second inverted frustum, a third inverted frustum, and an inverted frustum-shaped needle tip part that are connected in sequence from top to bottom. The diameter of the upper end of the inverted frustum-shaped needle tip part is smaller than the diameter of the lower end of the third inverted frustum. A plurality of spiral stirring grooves are circumferentially arranged on the side wall of the second inverted frustum. A plurality of involute structures are circumferentially arranged on the bottom surface of the third inverted frustum. The winding direction of the involute structure is opposite to the spiral direction of the spiral stirring groove. Threads are provided on the side wall of the inverted frustum-shaped needle tip part.

2. The friction stir welding tool according to claim 1, characterized in that, The diameter of the upper end of the second inverted frustum is equal to the diameter of the lower end of the first inverted frustum, and the taper angle of the second inverted frustum is different from the taper angle of the first inverted frustum.

3. The friction stir welding tool according to claim 2, characterized in that, The diameter of the upper end of the third inverted frustum is equal to the diameter of the lower end of the second inverted frustum, and the taper angle of the third inverted frustum is different from the taper angle of the second inverted frustum.

4. The friction stir welding tool according to claim 3, characterized in that, The taper angle of the second inverted frustum is greater than the taper angle of the first inverted frustum. The taper angle of the third inverted frustum is less than the taper angle of the second inverted frustum. The taper angle of the inverted frustum-shaped needle tip part is greater than the taper angle of the third inverted frustum.

5. The friction stir welding tool according to claim 4, wherein The taper angles of the first inverted frustum, the third inverted frustum, and the inverted frustum-shaped needle tip part are all 40° - 90°, and the taper angle of the second inverted frustum is greater than 90°.

6. The friction stir welding tool according to claim 1, characterized in that, A plane formed by milling is provided on one side of the upper part of the stirring needle. The connecting component includes a plurality of bolts. A plurality of threaded holes are provided on the side wall of the shoulder. Each bolt is used to be installed in one of the threaded holes and abut against the plane.

7. The friction stir welding tool according to claim 1, characterized in that, The plurality of spiral stirring grooves are evenly arranged at intervals of 45°. The depth of the spiral stirring groove is 0.2 - 0.6 mm.

8. The friction stir welding tool according to claim 1, wherein The plurality of involute structures are evenly arranged at intervals of 120°. The height of the involute structure is 0.2 - 0.5 mm.

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