Friction stir welding machine for aluminum alloys

Abstract

The application discloses a friction stir welding machine for aluminum alloy and relates to the technical field of metal welding.The friction stir welding machine comprises a base, a cross beam is arranged on the base in a sliding mode, a sliding seat is arranged on the cross beam in a sliding mode, a lifting plate is arranged in the sliding seat in a lifting mode, a fixing cylinder is fixed to the lifting plate, a shaft shoulder is arranged in the fixing cylinder in a rotating mode, the upper end of the shaft shoulder penetrates through the lifting plate and is connected to a rotating motor, a stirring needle is arranged in the shaft shoulder, the lower end of the stirring needle penetrates through the lower end of the shaft shoulder, a plurality of ridge blocks are circumferentially distributed on the side wall of the shaft shoulder, and the lower end surface of the ridge block is flush with the lower end surface of the shaft shoulder.The radial adjustment of the ridge block and the linkage mechanism between the ridge block and the depth of the stirring needle are used, so that the width and the depth of the welding molten pool are accurately, dynamically and coordinately controlled.

Description

Technical Field

[0001] This invention relates to the field of metal welding technology, specifically a friction stir welding machine for aluminum alloys. Background Technology

[0002] Aluminum alloys, with their excellent specific strength, corrosion resistance, and formability, have become key structural materials in high-end manufacturing industries such as aerospace, rail transportation, and new energy vehicles. However, traditional fusion welding processes for aluminum alloys (such as MIG and TIG) have significant limitations. Hot cracks easily occur during solidification of the molten pool, the high sensitivity of liquid metal to hydrogen leads to porosity defects, high heat input causes workpiece deformation, and softening often occurs in the heat-affected zone, seriously affecting the reliability of the joint. These challenges have spurred the birth and development of friction stir welding (FSW), a revolutionary solid-state joining technology.

[0003] Friction stir welding (FSW) achieves metallurgical bonding of materials through mechanical friction and plastic deformation. Its core process involves: a high-speed rotating stirring pin inserting into the welding interface while a shoulder presses against the workpiece surface; intense friction between the stirring pin and the material, and between the shoulder and the surface, generates heat, causing localized material to reach a plastic state; the rotating stirring pin powerfully agitates the plastic material, breaking up the oxide film and promoting thorough mixing; under the constraint of the shoulder, the softened material flows, fills, and re-solidifies upon cooling, forming a dense weld. Compared to fusion welding, FSW offers revolutionary advantages, completely avoiding porosity and hot cracking, achieving joint strength close to or even exceeding that of the base material, significantly reducing thermal deformation, and eliminating the need for welding materials and shielding gases. It is particularly adept at welding high-strength aluminum alloys, providing a high-quality, low-deformation solution for aluminum alloy structure manufacturing.

[0004] Current mainstream friction stir welding machines typically consist of a rigid frame, a three-axis motion system, a high-torque spindle, a downpressure control system, and a core welding fixture. The fixture comprises a fixed-diameter shoulder and a fixed-length stirring pin, often integrated as a single unit or requiring manual replacement. This design has several shortcomings in practical applications. First, it offers poor adaptability to weld pool size. The fixed shoulder diameter results in a constant heat-affected zone width, making it prone to burn-through due to excessive heat input when welding thin plates, while insufficient heat leads to incomplete root penetration when welding thick plates. For workpieces with varying thickness along their length, current technology struggles to achieve continuous high-quality welding, relying solely on time-consuming manual fixture replacement. Second, it lacks flexibility in heat input control. The fixed contact area limits the ability to directly control heat input through the heat source size, making it difficult to meet the demands of complex working conditions. Third, it suffers from a "keyhole" defect. The keyhole formed when the stirring pin retracts at the end of welding becomes a stress concentration source, severely weakening fatigue performance and requiring additional processing. Fourth, coordinating key parameters is difficult. The adjustment of the stirring pin length (which controls the depth of weld) and the shoulder diameter (which affects the width of weld) is independent and cumbersome, making it difficult to achieve dynamic matching between the two when welding workpieces of different thicknesses.

[0005] Therefore, it is necessary to provide a friction stir welding machine for aluminum alloys to solve the problems mentioned in the background art. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides the following technical solution: a friction stir welding machine for aluminum alloys, comprising a base, a crossbeam slidably mounted on the base, a slide block slidably mounted on the crossbeam, a lifting plate movably mounted in the slide block, a fixed cylinder fixed below the lifting plate, a shoulder rotatably mounted inside the fixed cylinder, the upper end of the shoulder penetrating through the lifting plate and connected to a rotary motor; a stirring needle is mounted inside the shoulder, the lower end of the stirring needle penetrating below the lower end of the shoulder; multiple ridge blocks are distributed circumferentially on the side wall of the shoulder, the lower end face of the ridge blocks being flush with the lower end face of the shoulder.

[0007] Furthermore, the sidewall of the shoulder has multiple slots, and each of the prism blocks can be radially slidably embedded in each slot.

[0008] Furthermore, a connecting ring is fixedly sleeved on the outer wall of the shoulder, and multiple sliding grooves are formed in the connecting ring, with each of the prism blocks slidably confined in each sliding groove.

[0009] Furthermore, each of the aforementioned grooves has side grooves on both sides of its side walls, and each of the aforementioned prism blocks is slidably disposed in the side grooves on both sides.

[0010] Furthermore, a first collar is slidably sleeved on the outer wall of the shoulder, and a push rod is hinged to the upper part of each of the prism blocks, with the upper end of each push rod hinged to the first collar.

[0011] Furthermore, a second collar is rotatably sleeved above the first collar, and connecting rods are hinged to both sides of the second collar; two symmetrical lead screws are rotatably arranged under the lifting plates on both sides of the fixed cylinder, and each lead screw is threadedly connected to a slider, the sliders are slidably connected to the lifting plates, and the two connecting rods are respectively hinged to the two sliders.

[0012] Furthermore, each of the two lead screws is connected to a side bevel gear near the fixed cylinder, and a central bevel gear is connected to the front of the lifting plate. The central bevel gear meshes with both of the side bevel gears, and a servo motor connected to the central bevel gear is also provided in the lifting plate.

[0013] Furthermore, the stirring needle can be axially slidably embedded in the lower end of the shoulder.

[0014] Furthermore, through grooves are provided on both sides of the shoulder sidewall above the prism block, and the first ring is fixed to the stirring needle through the through groove.

[0015] Furthermore, the lower end of the stirring needle is conical.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: The radially sliding rib design with circumferentially distributed ribs on the shoulder sidewalls of this invention, driven by a servo motor-driven bevel gear system, lead screw and slider mechanism, connecting rod, and push rod, allows for precise and synchronous adjustment of the outward or inward expansion or contraction of all ribs. When welding thick plates, the outward expansion of the ribs increases the contact area between the shoulder and the workpiece surface, significantly widening the molten pool and ensuring that the material on both sides of the weld is fully heated, stirred, and mixed within a larger heat-affected zone, achieving deep penetration and a strong connection, and avoiding incomplete penetration. When welding thin plates, the inward reduction of the ribs decreases the contact area and heat input, narrowing the molten pool and effectively preventing burn-through. When welding aluminum alloy workpieces with varying thickness along the length (such as stiffened plates or variable cross-section beams), the rib positions can be dynamically adjusted in real time during welding, synchronously changing the molten pool width to ensure uniform and sufficient connection quality throughout the weld. Furthermore, by adjusting the contact area, the total amount of frictional heat generated is indirectly controlled, which helps optimize heat input management and reduce excessive heat-affected zone and deformation. In addition, the prism block, as an extension of the lower surface of the shoulder, increases the frictional contact area and enhances the "ploughing" effect, which can improve thermal efficiency and expand the heat-affected zone. The angular structure of the prism block enhances the stirring and driving effect of the shoulder on the surface plastic material, promotes more uniform and sufficient flow and mixing of the material in the thickness and width directions, and reduces the risk of formation of internal defects such as tunnel defects and pores.

[0017] In this invention, the first ring is simultaneously hinged to the stirring pin and the push rods of all the edge blocks. Therefore, when the first ring is raised or lowered to adjust the extension length of the stirring pin, all the edge blocks will be driven to move radially in sync. When a thicker workpiece needs to be welded and the insertion depth of the stirring pin is increased, the edge blocks will automatically expand outward to increase the width of the molten pool. Conversely, when welding a thin plate and raising the stirring pin, the edge blocks will automatically reduce inward to decrease the width, thus matching the dual requirements of molten pool depth and width for welding different thicknesses. This makes the operation simpler and more efficient. The operator only needs to set a main target (such as plate thickness or target molten depth), and the equipment can automatically coordinate the pin depth and the effective diameter of the shoulder, reducing the complexity and error risk of manually adjusting multiple independent parameters. This ensures that the adjustment of depth and width is synchronous and linear, which is beneficial for maintaining the consistency of process parameters throughout the welding process or between different workpieces.

[0018] In the final stage of welding, this invention controls a servo motor to simultaneously retract the stirring pin completely into the shoulder and shrink the prism block to a minimum contact state. This allows the space left by the stirring pin during retraction to be rapidly filled and re-solidified by the material that is still in a plastic state and is continuously heated and stirred by the shrinking prism block. Ultimately, this effectively eliminates or significantly reduces exit holes, resulting in a complete weld end that is continuous on the surface and dense inside. This greatly improves the overall aesthetics and mechanical properties (especially fatigue strength) of the weld and reduces the need for subsequent grinding or repair. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a friction stir welding machine for aluminum alloys.

[0020] Figure 2 This is a three-dimensional structural diagram of the lifting plate in this invention;

[0021] Figure 3 This is a schematic cross-sectional view of the lifting plate in this invention;

[0022] Figure 4 This is an enlarged three-dimensional structural diagram of the lower end of the shoulder in this invention;

[0023] Figure 5 This is a schematic diagram of the cross-sectional structure of the edge block in this invention;

[0024] In the diagram: 1. Base; 2. Crossbeam; 3. Slide; 4. Lifting plate; 41. Rotary motor; 42. Lead screw; 43. Slider; 44. Connecting rod; 45. Side bevel gear; 46. Center bevel gear; 47. Servo motor; 5. Shoulder; 51. Edge block; 52. Slot; 53. Connecting ring; 54. Slide groove; 541. Side groove; 55. Push rod; 56. First ring; 57. Second ring; 58. Through groove; 6. Stirring needle; 7. Fixed cylinder. Detailed Implementation

[0025] Please see Figures 1-5 In this embodiment of the invention, a friction stir welding machine for aluminum alloys includes a base 1, a crossbeam 2 slidably mounted on the base 1, a slide block 3 slidably mounted on the crossbeam 2, a lifting plate 4 movably mounted in the slide block 3, a fixed cylinder 7 fixed below the lifting plate 4, a shoulder 5 rotatably mounted inside the fixed cylinder 7, the upper end of the shoulder 5 penetrating through the lifting plate 4 and connected to a rotary motor 41; a stirring needle 6 is mounted inside the shoulder 5, the lower end of the stirring needle 6 penetrating below the lower end of the shoulder 5; multiple ribs 51 are distributed circumferentially on the side wall of the shoulder 5, and the lower end face of the ribs 51 is flush with the lower end face of the shoulder 5.

[0026] The positions of the shoulder 5 and the stirring pin 6 can be changed by the crossbeam 2 and the slide block 3 to position them above the weld seam. The lifting plate 4 is driven to descend, allowing the stirring pin 6 to penetrate into the weld seam. At the same time, the lower end face of the shoulder 5 and the circumferentially distributed friction-enhancing and diameter-increasing ridge blocks 51 are tightly attached to the surface of the aluminum alloy weldment. The rotary motor 41 is started to drive the shoulder 5 to rotate at high speed and apply a predetermined downward pressure. The stirring pin 6 inside the shoulder 5 rotates accordingly. During this process, the shoulder 5 and the ridge blocks 51 generate intense friction and heat with the surface of the weldment and the stirring pin 6 with the weld seam material. This softens the material in the weld seam area to a plastic state. The softened material is fully mixed, flows, and re-solidifies, thereby firmly metallurgically bonding the aluminum alloy materials on both sides of the weld seam together to achieve high-quality friction stir welding.

[0027] In this embodiment, the sidewall of the shoulder 5 has multiple slots 52, and each of the prism blocks 51 can be radially slidably embedded in each slot 52.

[0028] By changing the radial position of the prism 51 in the slot 52, the diameter of the ring formed by each prism 51 can be adjusted, thereby adjusting the contact area between the shoulder 5 and the surface of the aluminum alloy weldment, and producing molten pools of different widths. The thicker the aluminum alloy weldment, the greater the width of the molten pool needs to be to ensure that the material can be fully mixed.

[0029] In this embodiment, a connecting ring 53 is fixedly sleeved on the outer wall of the shoulder 5. The connecting ring 53 has multiple sliding grooves 54, and each of the prism blocks 51 is slidably restricted in each sliding groove 54.

[0030] The connecting ring 53 can further restrict the circumferential position of the edge block 51, and better transmit the torque of the shoulder 5 to each edge block 51.

[0031] In this embodiment, side grooves 541 are provided in the two side walls of each of the sliding grooves 54, and the two sides of each of the prism blocks 51 are slidably disposed in the side grooves 541.

[0032] The side groove 541 can restrict the vertical position of the edge block 51, ensuring that the edge block 51 can only slide radially.

[0033] In this embodiment, a first collar 56 is slidably sleeved on the outer wall of the shoulder 5, and a push rod 55 is hinged to the upper part of each of the prism blocks 51, with the upper end of each push rod 55 hinged to the first collar 56.

[0034] In other words, by sliding the first ring 56 up and down, the push rod 55 can push the edge block 51 to slide radially, thereby synchronously adjusting the position of each edge block 51 and ensuring that the shape of the ring formed by each edge block 51 is uniform.

[0035] In this embodiment, a second collar 57 is rotatably sleeved above the first collar 56, and connecting rods 44 are hinged to both sides of the second collar 57; two symmetrical lead screws 42 are rotatably arranged under the lifting plates 4 on both sides of the fixed cylinder 7, and each lead screw 42 is threadedly connected to a slider 43. The sliders 43 are slidably connected to the lifting plates 4, and the two connecting rods 44 are respectively hinged to the two sliders 43.

[0036] In this embodiment, each of the two lead screws 42 is connected to a side bevel gear 45 near the fixed cylinder 7, and a central bevel gear 46 is connected to the front of the lifting plate 4. The central bevel gear 46 meshes with both side bevel gears 45, and a servo motor 47 connected to the central bevel gear 46 is also provided in the lifting plate 4.

[0037] In other words, by driving the center bevel gear 46 through the servo motor 47, the two lead screws 42 can rotate synchronously in opposite directions, thereby causing the two sliders 43 to rotate synchronously in opposite directions as well. This allows the two sliders 43 to move closer or further apart from each other, so that the connecting rod 44 can push the second ring 57 to slide up and down, thereby adjusting the radial position of each ridge block 51. This adjustment process can be carried out during the rotation of the shoulder 5, thus achieving the effect of real-time adjustment of the weld width.

[0038] In this embodiment, the stirring needle 6 is axially slidably embedded in the lower end of the shoulder 5.

[0039] By changing the length of the stirring pin 6 extending from the lower end of the shoulder 5, the depth of the stirring pin 6 inserted into the weld can be adjusted, which can produce molten pools of different thicknesses to adapt to aluminum alloy weldments of different thicknesses and avoid burning through the workpiece or insufficient welding.

[0040] In this embodiment, through grooves 58 are provided on both sides of the shoulder 5 sidewall above the prism block 51, and the first collar 56 passes through the through grooves 58 and is fixed to the stirring needle 6.

[0041] In other words, when the first ring 56 slides up and down, it will drive the stirring pin 6 to slide up and down, thereby changing the length of the stirring pin 6 extending from the lower end of the shoulder 5. The longer the stirring pin 6 extends from the lower end of the shoulder 5, the larger the diameter of the ring formed by each edge block 51 will be, in order to accommodate thicker aluminum alloy weldments, and vice versa.

[0042] In this embodiment, the lower end of the stirring pin 6 is conical. This results in a V-shaped weld seam during welding, preventing the loss of molten metal.

[0043] In practice, the aluminum alloy workpiece to be welded is fixed on the base 1 to ensure that the weld seam is aligned and the interface is tight without gaps; the operating beam 2 slides along the base 1, and the horizontal position of the slide block 3 on the beam 2 is adjusted so that the stirring needle 6 is precisely aligned with the weld seam starting point; the width of the molten pool is adjusted by starting the servo motor 47 to drive the central bevel gear 46 to drive the two bevel gears 45 to make the lead screw 42 rotate synchronously in opposite directions, and the slider 43 moves towards or away from each other, which pushes the second ring 57 up and down through the connecting rod 44, which drives the first ring 56 to rise and fall, and is synchronously adjusted by the push rod 55. The radial positions of all the edges 51 are such that when the edges 51 expand outward, the contact area increases and the molten pool widens, which is suitable for thick workpieces; when the edges 51 contract inward, the contact area decreases and the molten pool narrows, which is suitable for thin workpieces. While the first ring 56 is raised and lowered, the stirring pin 6 will slide along the axial direction of the shoulder 5 to adjust the extension length of the stirring pin 6: when the stirring pin 6 probes downward, the depth of the molten pool is deepened; when the stirring pin 6 is raised upward, the depth of the molten pool is shallowed. During the welding process, the lifting plate 4 is driven to descend, so that the stirring pin 6 penetrates into the weld, and the lower end face of the shoulder 5 and the edges 51 are tightly pressed against the surface of the workpiece. The rotary motor 41 drives the shoulder 5 to rotate at high speed, and the stirring needle 6 also rotates synchronously. The ridge block 51 enhances surface friction and expands the heat-affected zone. The stirring needle 6 stirs the material inside the weld, and the frictional heat brings the aluminum alloy to a plastic state. The slide block 3 moves at a constant speed along the weld direction, and the shoulder 5 and the stirring needle 6 move forward synchronously. During welding, the position of the ridge block 51 can be dynamically adjusted by the servo motor 47 to adapt to welds with varying thicknesses. The conical stirring needle 6 forms a V-shaped molten pool to prevent material overflow. When the weld end point is reached, the servo motor 47 is controlled to gradually raise the stirring needle 6 to fully retract into the shoulder 5. At the same time, the ridge block 51 retracts to the minimum contact area. During the process, the stirring needle 6 drills into the aluminum alloy weldment to create a hole (exit hole), which is gradually filled and closed by the flowing material, thus eliminating the exit hole.

[0044] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A friction stir welding machine for aluminum alloys, comprising a base (1), characterized in that, A crossbeam (2) is slidably mounted on the base (1), and a slide block (3) is slidably mounted on the crossbeam (2). A lifting plate (4) is slidably mounted in the slide block (3), and a fixed cylinder (7) is fixed under the lifting plate (4). A shoulder (5) is rotatably mounted inside the fixed cylinder (7). The upper end of the shoulder (5) passes through the lifting plate (4) and is connected to a rotary motor (41). A stirring needle (6) is provided inside the shoulder (5), and the lower end of the stirring needle (6) extends to the lower end of the shoulder (5); The shoulder (5) has multiple ridge blocks (51) distributed around its sidewall, and the lower end face of the ridge block (51) is flush with the lower end face of the shoulder (5). The shoulder (5) has multiple slots (52) on its sidewall, and each of the prism blocks (51) can be radially slidably embedded in each slot (52); The outer wall of the shoulder (5) is slidably fitted with a first collar (56), and each of the prism blocks (51) is hinged with a push rod (55) at the top, and the upper end of each push rod (55) is hinged to the first collar (56). The stirring needle (6) can be axially slidably embedded in the lower end of the shoulder (5); A second ring (57) is rotatably sleeved above the first ring (56), and connecting rods (44) are hinged on both sides of the second ring (57). Two symmetrical lead screws (42) are rotatably installed under the lifting plates (4) on both sides of the fixed cylinder (7). Each lead screw (42) is threaded with a slider (43). The slider (43) is slidably connected to the lifting plate (4), and the two connecting rods (44) are respectively hinged to the two sliders (43). Both of the lead screws (42) are connected to a side bevel gear (45) at one end near the fixed cylinder (7). A center bevel gear (46) is connected to the front of the lifting plate (4). The center bevel gear (46) meshes with both of the side bevel gears (45). A servo motor (47) connected to the center bevel gear (46) is also provided in the lifting plate (4). The shoulder (5) above the prism (51) has through grooves (58) on both sides of the side wall, and the first collar (56) passes through the through grooves (58) and is fixed to the stirring needle (6).

2. The friction stir welding machine for aluminum alloys according to claim 1, characterized in that, The outer wall of the shoulder (5) is fixedly fitted with a connecting ring (53), and multiple grooves (54) are opened in the connecting ring (53). Each of the prism blocks (51) is slidably restricted in each groove (54).

3. The friction stir welding machine for aluminum alloys according to claim 2, characterized in that, Each of the slide grooves (54) has a side groove (541) on both sides, and each of the prism blocks (51) is slidably disposed in the side groove (541) on both sides.

4. The friction stir welding machine for aluminum alloys according to claim 1, characterized in that, The lower end of the stirring needle (6) is conical.

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