Stirring head based on aluminum alloy friction stir welding

Abstract

The invention provides a stirring head based on aluminum alloy friction stir welding, which comprises a connecting rod used for connecting a mounting assembly, the lower end face of the connecting rod is provided with a shaft shoulder, and the shaft shoulder is provided with an Archimedes spiral thread; the stirring needle is connected with the shaft shoulder, a conical thread is arranged at the lower end of the stirring needle, and the rotating direction of the conical thread is opposite to that of the Archimedes spiral thread. According to aluminum alloy friction stir welding, the right spiral conical thread is arranged at the head of the stirring needle, sufficient stirring can be conducted at the aluminum alloy metal interface overlapping edge, interface compounds are smashed, and the interface overlapping width is increased advantageously.

Description

Technical Field

[0001] This invention relates to the field of friction stir welding technology, and more specifically to a stirring head based on aluminum alloy friction stir welding. Background Technology

[0002] Friction stir welding (FSW) is a low-temperature solid-state welding technique. Unlike traditional welding methods (argon arc welding, vacuum brazing, and laser welding), FSW utilizes a high-speed rotating, specially shaped stirring pin inserted into the weld seam, moving along the weld seam trajectory while rotating. The friction between the stirring pin and the workpiece generates heat, softening the metal near the stirring pin and placing it in a plastic state. The connecting rod of the stirring head further rubs against the workpiece surface, and due to its angled design during welding, it generates further heat and prevents the plastic metal from being extruded. Under the mechanical stirring and forging action of the stirring head, the metals on both sides of the weld seam are thoroughly mixed and diffused, ultimately forming a dense solid-phase bond upon cooling.

[0003] With the development of friction stir welding, its application range is becoming wider and wider. Due to its low welding temperature, friction stir welding is often used for secondary welding in some fields. Its main purpose is to enhance the sealing performance and prevent the internal working fluid from flowing out. However, in some extreme and special cases (the weld is deep in the groove), conventional friction stir welding heads cannot use the angled welding method. In this case, when using a traditional welding head without an angle, the welding quality is seriously reduced, the weld interface is not dense enough, and even defects such as surface grooves and tunnels appear.

[0004] Furthermore, friction stir welding is a one-time forming process. Once a defect occurs, subsequent repair welding is very difficult, and the repair welding process is extremely prone to causing structural damage, which is difficult to salvage. Summary of the Invention

[0005] In view of this, the present invention provides a stirring head based on aluminum alloy friction stir welding, so as to effectively avoid the phenomenon of the stirring pin breaking due to heat during the welding process and reduce welding defects.

[0006] The present invention provides the following technical solution: a stirring head based on aluminum alloy friction stir welding, comprising: a connecting rod for connecting and mounting components, the lower end face of the connecting rod being provided with a shoulder, and the shoulder being provided with an Archimedean spiral thread; a stirring pin connected to the shoulder, the lower end of the stirring pin being provided with a tapered thread, and the direction of rotation of the tapered thread being opposite to the direction of rotation of the Archimedean spiral thread.

[0007] Furthermore, the Archimedes spiral thread is tangent to the outer wall of the stirring needle.

[0008] Furthermore, the upper sidewall of the connecting rod is provided with a radial through hole, and the upper end of the stirring needle is placed in the connecting rod and locked by a locking device passing through the radial through hole.

[0009] Furthermore, the stirring head based on aluminum alloy friction stir welding also includes a fastening clamping part located at the lower end of the mounting assembly. The fastening clamping part fixes the connecting rod to the axis of the mounting assembly by a locking spring.

[0010] Furthermore, the lower end of the stirring needle has a conical structure that is smaller at the bottom and larger at the top, with a conical thread on the outer wall of the conical structure.

[0011] Furthermore, the cone angle of the tapered structure is 10°~30°; the pitch of the tapered thread is 0.3mm~0.6mm; and the depth of the tapered thread is 0.2mm~0.5mm.

[0012] Furthermore, the pitch of the Archimedean spiral thread gradually increases from the center outwards, and the thread depth of the Archimedean spiral thread is 0.4mm to 0.9mm.

[0013] Furthermore, the lower end of the conical structure is a spherical structure.

[0014] Compared with the prior art, the beneficial effects that the at least one technical solution adopted by the present invention can achieve include at least the following: (1) The present invention provides a right-hand spiral conical thread on the head of the stirring needle for friction stir welding of aluminum alloy, which can fully stir at the overlap of the aluminum alloy metal interface, break up the interface compound, and help to strengthen the interface overlap width.

[0015] (2) This invention features a unique reverse Archimedean spiral thread at the shoulder of the stirring head for friction stir welding of aluminum alloys. During zero-angle friction stir welding, the thermoplastic metal at the stirring pin is fed into the weld joint through the reverse Archimedean spiral at the metal lap interface, reducing metal overflow and flash. Simultaneously, this thread allows for secondary stirring of any un-crushed material, maximizing the stirring between the stirring pin and the metal lap interface, providing sufficient heat input, and improving the uneven temperature gradient and poor fluidity of the metal material at the weld lap interface.

[0016] (3) The present invention separates the stirring needle and the connecting rod and connects them by a locking device. When an accident such as needle breakage occurs during the welding process, we only need to replace the stirring needle and do not need to replace the entire stirring head, which significantly saves manufacturing costs.

[0017] (4) This invention achieves zero-angle friction stir welding for aluminum alloys. Compared with the commonly available stirring heads on the market, it can obtain effective overlap width and welding strength at zero angle, resulting in a dense welding overlap area and avoiding problems such as unbroken interface and insufficient material flow. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the stirring head structure based on aluminum alloy friction stir welding provided by the present invention; Figure 2 A schematic diagram of the stirring pin head of the stirring head based on aluminum alloy friction stir welding provided by the present invention. Figure 3 Metallographic image of the interface section of the welded joint in Example 1; Figure 4 Metallographic image of the interface section of the welded joint in Example 2; Figure 5 Metallographic image of the interface section of the welded joint in Example 3; Figure 6 Metallographic image of the interface section of the welded joint in Example 4; Figure 7 For comparison, see the metallographic image of the welded joint interface section in Example 1; The reference numerals in the figure are as follows: 1. Stirring needle; 2. Shoulder; 3. Connecting rod; 4. Locking device; 5. Locking spring; 6. Fastening clamp; 7. Mounting assembly; 8. Tapered thread; 9. Archimedean spiral thread. Detailed Implementation

[0020] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] This invention provides a stirring head based on aluminum alloy friction stir welding, which is mainly used for solid-state welding of aluminum alloy plates, profiles and other components. Its core design lies in the cooperation of a special threaded shoulder and a stirring pin to optimize the plastic flow state of aluminum alloy materials during welding, reduce welding defects, and improve weld formation quality and mechanical properties.

[0023] like Figure 1 and Figure 2 As shown, the stirring head is composed of a stirring pin 1, a shoulder 2, a connecting rod 3, a locking device 4, a locking spring 5, a fastening clamping part 6, and an installation assembly 7. The conical thread 8 at the lower end of the stirring pin 1 and the Archimedean spiral thread 9 on the shoulder 2 rotate in opposite directions, forming a structural system that synergistically drives the material flow. This can effectively solve the defects such as weld voids and surface grooves that are prone to occur when welding aluminum alloys with traditional stirring heads.

[0024] The connecting rod 3 is a cylindrical metal rod. Its upper end is used to achieve coaxial connection with the installation component 7 of the welding equipment. The lower end face is integrally formed with a shoulder 2. The diameter of the shoulder 2 is smaller than the diameter of the connecting rod 3. Its function is to compact the plastic material on the surface of the workpiece during the welding process and prevent pits from appearing on the weld surface.

[0025] The lower end face of the shoulder 2 is machined with an Archimedean spiral thread 9. The special feature of this thread is that its pitch gradually increases from the center to the outside, and the specific thread depth is controlled within the range of 0.4mm to 0.9mm. Preferably, the starting point of the inner ring of the Archimedean spiral thread 9 is tangent to the outer wall of the stirring pin 1. The advantage of this design is that it allows the plastic material below the shoulder 2 to smoothly transition to the working area of ​​the stirring pin 1, avoiding the accumulation or stagnation of material at the junction of the shoulder and the stirring pin, and ensuring the continuity of material flow.

[0026] The upper end of the stirring needle 1 is connected to the shoulder 2, and its lower end is a tapered structure with a smaller bottom and a larger top. The cone angle of the tapered structure is 10°~30° (the optimal value is 15°). The outer wall of the tapered structure is machined with a conical thread 8. The pitch of the conical thread 8 is 0.3mm~0.6mm, the thread depth is 0.2mm~0.5mm, and the direction of rotation of the conical thread 8 is opposite to that of the Archimedean spiral thread 9 (for example, when the Archimedean spiral thread 9 is right-handed, the conical thread 8 is left-handed).

[0027] In addition, the lower end of the conical structure is a spherical structure. This design can reduce the resistance when the stirring pin 1 penetrates the aluminum alloy workpiece, reduce the local stress concentration of the workpiece during the welding start-up stage, and avoid the occurrence of welding start-up cracks in the workpiece.

[0028] To facilitate easy replacement of the stirring pin 1 (to accommodate aluminum alloy workpieces of different thicknesses), a radial through hole is provided on the upper side wall of the connecting rod 3. The upper end of the stirring pin 1 extends into the reserved cavity inside the connecting rod 3 and is locked in place by a locking device 4 passing through the radial through hole. The locking device 4 can be a pin or a fastening bolt, which is interference-fitted with the radial through hole. This ensures the coaxiality of the stirring pin 1 and the connecting rod 3 and transmits the torque during the welding process, preventing the stirring pin 1 from rotating and loosening.

[0029] To further ensure the overall coaxial stability of the stirring head, a fastening clamping part 6 is provided at the lower end of the mounting assembly 7. The fastening clamping part 6 is a ring clamping part, and its inner side is abutted against the side wall of the connecting rod 3 by 3 to 4 sets of evenly distributed locking springs 5. The locking springs 5 ​​are in a pre-compressed state, which can stably fix the connecting rod 3 at the axis of the mounting assembly 7, so as to avoid the stirring head being eccentric due to slight shaking of the main shaft of the equipment during the welding process, thereby preventing the defect of single-sided incomplete welding of the weld.

[0030] The limiting structure composed of the fastening clamping part 6 and the locking spring 5 can compensate for the slight radial displacement of the connecting rod 3 during the welding process. At the same time, the interference fit of the locking device 4 ensures the torque transmission efficiency of the stirring needle 1. The combination of the two enables the stirring head to maintain high coaxial accuracy under high-speed rotation and axial pressure conditions, ensuring the straightness and forming consistency of the weld.

[0031] During welding, when the stirring head rotates at high speed, the Archimedean spiral thread 9 of the shoulder 2 drives the plastic material below it to flow inward, while the conical thread 8 of the stirring pin 1 drives the surrounding plastic material to flow outward. The "inner and outer convection" effect formed by the opposite rotation directions not only re-stirs the metal material at the interface but also prevents material from flowing out, reduces flash, and helps to form a good overlap width and thickness. At the same time, it promotes sufficient stirring between the stirring pin 1 and the metal interface, increases heat input, and reduces the temperature gradient at the welding interface.

[0032] Example 1 In a specific implementation example, for a 4mm thick 6061 aluminum alloy plate, the stirring pin thread is a right-handed inverted conical thread. The main body diameter of the stirring pin is 2mm, the cone angle at the front end is 15°, the shoulder diameter is 8mm, and it has a left-facing Archimedean spiral thread with the pitch gradually increasing from the inside to the outside. Using the friction stir welding joint of the present invention, the welding speed is 2500r / min~5500r / min, the welding speed is 75mm / min~150mm / min, and the pressure is 0.2mm~0.4mm. It can be noted that the welding speed of this friction stir welding joint is much higher than that of ordinary conventional welding stirring heads. Therefore, a water-cooling plate is placed below the workpiece during welding to prevent the workpiece temperature from becoming too high. Metallographic samples are prepared by cutting the weld section of the joint, such as... Figure 3 The area within the black box shown is the welding area. No defects such as holes or tunnels were observed. The welded joints form a dense overlap with good overlap width.

[0033] Example 2 In specific implementation example two, for a 5mm thick 5A06 aluminum alloy plate, the stirring pin still has a right-hand helical inverted conical thread, the main body diameter of the stirring pin is 2.5mm, the cone angle at the front end is 30°, the diameter of the shoulder is 8mm, and it has an opposite Archimedean spiral thread. The stirring head of this invention is still used for friction stir welding. The zero-tilt angle welding speed is 2500r / min~5500r / min, the welding speed is 75mm / min~150mm / min, and the downward pressure is 0.2mm~0.5mm. Similar to example one, a water-cooled plate is provided under the welded workpiece. Metallographic samples are prepared by cutting the weld interface cross-section (e.g., ...). Figure 4 As shown in the figure, the weld interface is dense and has no obvious defects.

[0034] Example 3 In specific example three, for a 2mm thick 6061 aluminum alloy plate, the specifications of the stirring head used are the same as in example one, with no tilt angle. The welding speed is 2500r / min~5500r / min, the welding speed is 75mm / min~150mm / min, and the downward pressure is 0.2mm~0.5mm. Metallographic analysis is also performed on the weld interface section, as shown below. Figure 5 As shown, there are no obvious welding defects, and the weld interface is dense with no obvious defects.

[0035] Example 4 In specific example four, for a 4mm thick 6063 aluminum alloy plate, the specifications of the stirring head used are the same as in example one: no tilt angle, welding speed of 2500r / min~5500r / min, welding speed of 75mm / min~150mm / min, and downward pressure of 0.2mm~0.5mm. Similarly, metallographic images are prepared from the weld interface cross-section, such as... Figure 6 As shown, the overlap width of the welded interface section is good, there are no obvious welding defects, and there is no phenomenon of incomplete welding.

[0036] Comparison Example 1 In Comparative Example 1, a conventional friction stir welding joint was used, employing a single-ring structure with an inter-shaft diameter of 10 mm and an indentation of 0.3 mm, and a conventional process with a rotation speed of 600 r / min, a welding speed of 118 mm / min, and a downward pressure of 0.4 mm. However, unlike Example 1, this comparison focuses on the weld interface under zero tilt angle. Metallographic analysis of the weld interface section was performed using the same method, as shown... Figure 7 The weld section shown has obvious tunnel defects, indicating serious welding quality deficiencies.

[0037] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical solutions, and technical solutions in this invention can be freely combined and used.

Claims

1. A stirring head based on aluminum alloy friction stir welding, characterized in that, include: The connecting rod (3) is used to connect the mounting assembly (7). The lower end face of the connecting rod (3) is provided with a shoulder (2), and the shoulder (2) is provided with an Archimedean spiral thread (9). The stirring needle (1) is connected to the shoulder (2). The lower end of the stirring needle (1) is provided with a conical thread (8), and the direction of the conical thread (8) is opposite to the direction of the Archimedes spiral thread (9).

2. The stirring head based on aluminum alloy friction stir welding according to claim 1, characterized in that, The Archimedes spiral thread (9) is tangent to the outer wall of the stirring needle (1).

3. The stirring head based on aluminum alloy friction stir welding according to claim 1, characterized in that, The upper side wall of the connecting rod (3) is provided with a radial through hole, and the upper end of the stirring needle (1) is placed in the connecting rod (3) and locked by the locking device (4) passing through the radial through hole.

4. The stirring head based on aluminum alloy friction stir welding according to claim 1, characterized in that, The stirring head based on aluminum alloy friction stir welding also includes a fastening clamping part (6), located at the lower end of the mounting assembly (7). The fastening clamping part (6) fixes the connecting rod (3) to the axis of the mounting assembly (7) by a locking spring (5).

5. The stirring head based on aluminum alloy friction stir welding according to any one of claims 1 to 4, characterized in that, The lower end of the stirring needle (1) is a conical structure with a smaller bottom and a larger top, and a conical thread (8) is provided on the outer wall of the conical structure.

6. The stirring head based on aluminum alloy friction stir welding according to claim 5, characterized in that, The cone angle of the tapered structure is 10°~30°; the pitch of the tapered thread (8) is 0.3mm~0.6mm; and the depth of the tapered thread (8) is 0.2mm~0.5mm.

7. The stirring head based on aluminum alloy friction stir welding according to claim 5, characterized in that, The pitch of the Archimedes spiral thread (9) gradually increases from the center outwards, and the thread depth of the Archimedes spiral thread (9) is 0.4mm to 0.9mm.

8. The stirring head based on aluminum alloy friction stir welding according to claim 5, characterized in that, The lower end of the cone-shaped structure is a spherical structure.

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