Hollow welding tool for friction stir butt welding

Abstract

The utility model belongs to the technical field of welding, and particularly relates to a hollow welding tool for friction stir butt welding, which comprises a stirring head and a static shaft shoulder, the static shaft shoulder is fixedly connected with a conical frame fixed on a spindle box, the periphery of the stirring head is sleeved with the static shaft shoulder, and the stirring head and the static shaft shoulder are eccentrically arranged. The center of the bottom end face of a stirring needle of the stirring head is provided with a slow flow groove, the stirring needle of the stirring head is of a hollow design, the material fluidity of the area near the tip of the stirring needle in the welding process can be effectively enhanced, and the indirect action range of the stirring needle is enlarged. The defect of incomplete penetration of the root of the butt joint is effectively avoided; meanwhile, defect-free butt welding can be achieved under the condition that the length of the stirring needle is small, contact between the stirring needle and the base plate is avoided, the stirring needle is prevented from being broken, and the service life of the stirring needle is prolonged.

Description

Technical Field

[0001] This utility model belongs to the field of technical welding, specifically relating to a hollow welding tool for friction stir butt welding. Background Technology

[0002] Friction stir welding (FSW), as a solid-state joining technology, boasts advantages such as low welding temperature, high joint quality, and low material consumption. It not only enables high-quality connections of high-strength aluminum alloys but also aligns with the internationally recognized trend of energy conservation and emission reduction, earning it the reputation as a revolutionary green welding technology following laser welding. It is widely used in equipment manufacturing fields such as aerospace, shipbuilding, and vehicles. However, in conventional FSW welding, arc-shaped defects on the weld surface are determined by the movement characteristics of the stirring head. These defects are unavoidable and detrimental to surface quality and joint performance. Furthermore, in the final stage of welding, keyhole defects caused by the removal of the stirring head from the workpiece lead to severe stress concentration, worsening the joint's mechanical properties. Researchers have proposed improved methods and measures to address the keyhole problem after friction stir welding.

[0003] Chinese patent CN201820615823.9 discloses a stationary shoulder for friction stir welding of non-planar plates. The bottom end of the stationary shoulder is designed to mate with the surface of the non-planar plate being welded. Although this method can achieve welding of non-planar structures, the right-angle design of the leading edge of the stationary shoulder increases the thinning of the plate being welded during the welding process, and the coaxial assembly of the stirring head and the stationary shoulder increases the probability of interference during actual welding.

[0004] Chinese invention patent CN111906432B discloses a stirring friction lap method based on impingement flow, which designs a concave, opposing threaded stirring pin, causing the hook-shaped structure to bend downwards and significantly shortening the cold lap length within the weld nugget. While this method can achieve a downwardly bent hook-shaped structure or significantly shorten the cold lap length, the stirring head is highly sensitive to changes in process parameters. Furthermore, the special concave stirring pin profile causes damage to the keyhole morphology when the stirring pin is pulled out, resulting in an unstable joint interface morphology in practical engineering applications.

[0005] Chinese invention patent CN 111438433 A discloses a method and welding tool for measuring the peak temperature of the center region of an FSW weld. The tool includes a stirring tool, a shoulder, a stirring pin, and brazing filler metal with different melting points. The stirring tool contains a hollow stirring pin, with a ball of brazing filler metal placed inside the cavity. While this method employs a similar hollow stirring pin design, it only aims to prevent the brazing filler metal ball from accurately measuring the weld center temperature and does not consider the influence of stirring pin morphology changes on material flow behavior and weld formation during welding. Utility Model Content

[0006] This invention addresses the shortcomings of existing welding processes and tools, which cannot simultaneously and effectively alleviate arc marks and keyhole defects. Furthermore, existing welding tool systems suffer from high component manufacturing costs, complex coordination between components, and easy damage to structures such as stirring pins / sleeves. To address these issues, this invention proposes a hollow welding tool for friction stir butt welding.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A hollow welding tool for friction stir butt welding includes a stirring head and a stationary shoulder. The stationary shoulder is fixedly connected to a tapered frame fixed on a spindle box. The stationary shoulder is sleeved around the stirring head. The stirring head and the stationary shoulder are eccentrically arranged, and the gap between the stationary shoulder and the stirring head forms a centrifugal ring. A slow-flow groove is opened at the center of the bottom end face of the stirring needle of the stirring head.

[0009] The diameter D1 of the slow-flow channel is D2 / 2, where D2 is the outer diameter of the stirring needle, and 4mm≤D2≤20mm; the depth b of the slow-flow channel satisfies 2D1≤b≤5D1.

[0010] There is a longitudinal offset between the center of the inner ring of the bottom end face of the stationary shoulder and the center of the stirring head. The gaps between the left and right ends of the inner ring of the bottom end face of the stationary shoulder and the stirring head are the same. After the stirring needle is deformed, the center of the stirring head coincides with the center of the inner ring of the bottom end face of the stationary shoulder.

[0011] The longitudinal offset distance c between the center of the inner ring of the bottom end face of the stationary shoulder and the center of the stirring head satisfies c = 0.05~0.1mm; the diameter D3 of the inner ring of the bottom end face of the stationary shoulder satisfies D3 = D2 + 0.2mm.

[0012] With the end face of the stationary shoulder in the welding forward direction as the front side, the left and right outer edges of the bottom end face of the stationary shoulder are symmetrically provided with through grooves along the center line, so that the bottom end face of the stationary shoulder forms a boss structure, and the left and right side edges of the protruding end face of the boss structure are parallel to the center line of the stationary shoulder.

[0013] The distance between the left and right side edges of the protruding end face of the boss structure is e, which satisfies 1.2D3≤e≤0.9D4, and the protruding height of the boss structure is h, which satisfies 0.5mm≤h≤3mm.

[0014] A drag reduction angle is provided at the connection between the bottom end face edge of the stationary shoulder in the welding forward direction and the front end face edge, with a drag reduction angle radius R1 = 1mm to 3mm.

[0015] The outer ring diameter D4 of the bottom end face of the stationary shoulder satisfies D4=k×D3; k is any value between 1.5 and 4.

[0016] The beneficial effects of this utility model are:

[0017] 1. The bottom end face of the stationary shoulder adopts a boss structure in the direction parallel to the weld. The left and right side lines of the raised end face of the boss structure are parallel to the center line of the stationary shoulder, which can reduce the weld width and improve the welding quality. In addition, if the plate being welded is curved, the bottom end face of the stationary shoulder can be designed with the same radius of curvature as the plate being welded, which is also applicable to the entire mixing tool.

[0018] 2. The stationary shoulder and stirring head adopt an eccentric design of centrifugal ring (unequal initial assembly gap), which can effectively prevent the stirring head from shifting due to welding resistance during the welding process, thus avoiding friction or collision between the stirring head and the stationary shoulder, avoiding wear or even breakage of the stirring head, thereby increasing the service life of the stirring head and saving costs. At the same time, it can ensure that the stirring head and the stationary shoulder are in a small gap-equal spacing fit during the welding process, effectively reducing the leakage of material from the assembly gap during the welding process. In addition, the connection between the bottom end face and the front end face of the stationary shoulder is provided with a drag-reducing angle. This design helps to reduce the travel resistance during the welding process and prevents the stationary shoulder from pushing into the base material during the travel process, which would affect the forming quality.

[0019] 3. The stirring pin of the stirring head adopts a hollow design, which can effectively enhance the material flow in the area near the tip of the stirring pin during the welding process, increase the indirect action range of the stirring pin, and effectively avoid the generation of defects such as incomplete penetration at the root of the butt joint; at the same time, since defect-free butt welding can be achieved with a smaller stirring pin length, contact between the stirring pin and the backing plate is avoided, preventing the stirring pin from breaking and extending the service life of the stirring pin, which has great practical engineering significance. Attached Figure Description

[0020] Figure 1 This is a front sectional view of the hollow welding tool of this utility model;

[0021] Figure 2 for Figure 1 A bottom view of area A;

[0022] Figure 3A material flow diagram of the welding process using the welding tool of this utility model;

[0023] Figure 4 A comparison diagram showing the experimental results of welding using a welding tool with a circular bottom end face of a stationary shoulder and the welding tool of this utility model;

[0024] Among them, (a) is a diagram showing the experimental results of welding using a welding tool with a circular bottom end face of a stationary shoulder;

[0025] (b) A diagram showing the experimental results of welding using the welding tool of this utility model;

[0026] In the attached diagram: 1. Stationary shoulder; 2. Stirring head; 3. Flow retarder; 4. Centrifugal ring; 5. Groove; 6. Drag reduction angle. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0028] like Figures 1-2 As shown, a hollow welding tool for friction stir butt welding includes a stirring head 2 and a stationary shoulder 1. The stationary shoulder 1 is fixedly connected to a conical frame fixed on the spindle box. The stationary shoulder 1 is sleeved around the periphery of the stirring head 2. The stirring head 2 and the stationary shoulder 1 are eccentrically arranged, and the gap between the stationary shoulder and the stirring head forms a centrifugal ring 4. A flow-slowing groove 3 is formed at the center of the bottom end face of the stirring needle of the stirring head 2. The diameter D1 of the flow-slowing groove 3 is D2 / 2, where D2 is the outer diameter of the stirring needle, and 4mm≤D2≤20mm. The depth b of the flow-slowing groove 3 satisfies 2D1≤b≤5D1.

[0029] During welding, the stirring head 2 is coaxially connected to the main shaft, and the stirring head 2 is eccentrically positioned with the stationary shoulder 1 to form a centrifugal ring 4, preventing interference between the stirring pin and the stationary shoulder 1 during use. The stationary shoulder 1 is bolted to the tapered frame fixed on the main shaft box. During welding, the main shaft box moves along the welding direction at a certain welding speed, driving the stationary shoulder 1 to move at the same speed and providing sealing and upsetting for the welded joint. At the same time, the stirring pin of the stirring head 2 adopts a hollow design, which can effectively enhance the material flow in the area near the tip of the stirring pin during welding, increase the indirect action range of the stirring pin, and effectively avoid the generation of incomplete penetration defects at the root of the butt joint.

[0030] There is a longitudinal offset distance between the center of the inner ring of the bottom end face of the stationary shoulder 1 and the center of the stirring head 2. The gaps between the left and right ends of the inner ring of the bottom end face of the stationary shoulder 1 and the stirring head 2 are the same. After the stirring needle is deformed, the center of the stirring head 2 coincides with the center of the inner ring of the bottom end face of the stationary shoulder. The longitudinal offset distance c between the center of the inner ring of the bottom end face of the stationary shoulder and the center of the stirring head 2 satisfies c = 0.05mm to 0.1mm. The diameter D3 of the inner ring of the bottom end face of the stationary shoulder satisfies D3 = D2 + 0.2mm.

[0031] The design of the centrifugal ring 4 can effectively prevent the stirring pin of the stirring head 2 from being displaced due to welding resistance during the welding process, which would cause friction or collision between the stirring pin of the stirring head 2 and the stationary shoulder 1. This avoids wear or even breakage of the stirring pin of the stirring head 2, thereby increasing the service life of the stirring head 2 and saving costs.

[0032] With the end face of the stationary shoulder 1 in the welding forward direction as the front side, the left and right outer edges of the bottom end face of the stationary shoulder 1 are symmetrically provided with through grooves 5 along the center line, so that the bottom end face of the stationary shoulder 1 forms a boss structure. The left and right side edges of the protruding end face of the boss structure are parallel to the center line of the stationary shoulder 1. The distance between the left and right side edges of the protruding end face of the boss structure is e, which satisfies 1.2D3≤e≤0.9D4. The protrusion height of the boss structure is h, which satisfies 0.5mm≤h≤3mm.

[0033] The design of the boss structure of the stationary shoulder 1, with the left and right side lines of the protruding end face of the boss structure parallel to the center line of the stationary shoulder 1, can reduce the weld width and improve the welding quality.

[0034] A drag reduction angle 6 is provided at the connection between the bottom end face edge and the front end face edge of the stationary shoulder 1 in the welding forward direction. The radius of the drag reduction angle 6, R1, is 1mm to 3mm. The outer ring diameter D4 of the bottom end face of the stationary shoulder 1 satisfies D4 = k × D3; k is any value between 1.5 and 4.

[0035] The drag reduction angle 6 design helps to reduce the travel resistance during the welding process and prevents the stationary shoulder 1 from being pushed into the base material during travel, thus affecting the forming quality.

[0036] A hollow welding method for friction stir butt welding includes the following steps:

[0037] Step 1: Select a stirring head 2 with a suitable stirring needle length according to the thickness of the first plate and the second plate. The first plate and the second plate have the same thickness, ranging from 1.0mm to 5.0mm. The first plate and the second plate are made of the same type of aluminum alloy or dissimilar aluminum alloy materials. The first plate and the second plate are flat or curved plates.

[0038] Step 2: Clamp the first and second plates to be welded onto the fixture of the friction stir welding machine, wherein the first plate and the second plate are butted together;

[0039] Step 3: Install the stirring head 2 on the main shaft of the friction stir welding machine. The stirring head 2 rotates at a speed of 800rpm≤ω≤2100rpm and plunges into the first and second plates to be welded at a speed of 0.2mm / min≤ν≤2mm / min at the welding start position. When the stirring needle of the stirring head 2 reaches the predetermined plunging depth of 1.0mm~4.0mm and the stationary shoulder 1 penetrates into the thickness of the first plate by 0.2mm~0.5mm, the stirring head 2 stops plunging and continues to rotate for 2min~3min.

[0040] Step 4: The stirring head 2 advances at a welding ratio of 10 to 100 to promote material flow between the first and second plates and form a full metallurgical bond.

[0041] Step 5: After reaching the end of the weld, pull back the stirring head 2. The entire welding process is now complete.

[0042] pass Figure 3 It can be seen that, when the hollow welding tool of this utility model is used, it effectively enhances the material flow in the area near the tip of the stirring pin during the welding process, increases the indirect action range of the stirring pin, and effectively avoids the generation of defects such as incomplete penetration at the root of the butt joint.

[0043] Example 1

[0044] In this embodiment, the hollow welding tool has the following characteristics: the outer diameter of the stirring needle is D2 = 6 mm; the diameter of the flow-retarding groove 3 is D1 = 3 mm; the depth of the flow-retarding groove 3 is b = 12 mm; the diameter of the inner ring of the bottom end face of the stationary shoulder 1 is D3 = 6.2 mm; the longitudinal offset distance between the center of the inner ring of the bottom end face of the stationary shoulder 1 and the center of the stirring head 2 is c = 0.1 mm; the outer diameter of the bottom end face of the stationary shoulder 1 is D4 = 12.2 mm; the protrusion height of the boss structure on the bottom end face of the stationary shoulder 1 is h = 1.5 mm; the distance between the side lines of the protruding ends of the boss structure on the bottom end face of the stationary shoulder 1 is e = 10 mm; and the radius of the drag reduction angle 6 of the stationary shoulder 1 is R1 = 2 mm. The first and second plates are flat plates, both made of 2024 aluminum alloy, and both are 2 mm thick.

[0045] A hollow welding method for friction stir butt welding includes the following steps:

[0046] Step 1: Select a stirring head 2 with a suitable stirring needle length based on the thickness of the first and second plates;

[0047] Step 2: Clamp the first and second plates to be welded on the fixture of the friction stir welding machine, wherein the first plate and the second plate are butted together;

[0048] Step 3: Install the stirring head 2 on the main shaft of the friction stir welding machine. The stirring head 2 rotates at a speed of ω = 1200 rpm and plunges into the first and second plates to be welded at a speed of ν = 1.0 mm / min at the welding start position. When the stirring needle of the stirring head 2 reaches the predetermined plunging depth of 1.5 mm and the stationary shoulder 1 penetrates 0.2 mm into the thickness of the first plate, the stirring head 2 stops plunging and continues to rotate for 3 minutes.

[0049] Step 4: The stirring head 2 advances at a transfer ratio of 80 to promote material flow between the first and second plates and form a full metallurgical bond;

[0050] Step 5: After reaching the end of the weld, pull back the stirring head 2, and the entire welding process is complete.

[0051] Welding results are shown Figure 4 As shown, both existing welding tools with a circular bottom face of the stationary shoulder and the welding tool of this invention can achieve good surface morphology. The sealing effect of the stationary shoulder 1 prevents the formation of obvious burrs on the joint surface, and the "scraping" effect of the bushing avoids the formation of arc marks. Compared with welding with existing welding tools with a circular bottom face of the stationary shoulder, the welding tool of this invention results in a significantly reduced weld width on the joint surface due to the smaller scraping area.

[0052] Example 2

[0053] In this embodiment, the hollow welding tool has an outer diameter of 8mm for the stirring needle, a diameter of 4mm for the slow-flow groove 3, and a diameter of 8.2mm for the inner ring of the bottom end face of the stationary shoulder 1. The longitudinal offset distance between the center of the inner ring of the bottom end face of the stationary shoulder 1 and the center of the stirring head 2 is c = 0.1mm. The protrusion height h of the boss structure on the bottom end face of the stationary shoulder 1 is 1.5mm, and the distance e between the side lines of the protruding ends of the boss structure on the bottom end face of the stationary shoulder 1 is 10.5mm. The outer diameter D4 of the bottom end face of the stationary shoulder 1 is 12.5mm. The radius R1 of the drag reduction angle 6 of the stationary shoulder 1 is 2mm. The first plate and the second plate are flat plates. The material of the first plate is 2024 aluminum alloy, and the material of the second plate is 7050 aluminum alloy. The thickness of both plates is 3mm.

[0054] A hollow welding method for friction stir butt welding includes the following steps:

[0055] Step 1: Select a stirring head 2 with a suitable stirring needle length based on the thickness of the first and second plates;

[0056] Step 2: Clamp the first and second plates to be welded on the fixture of the friction stir welding machine, wherein the first plate and the second plate are butted together;

[0057] Step 3: Install the stirring head 2 on the main shaft of the friction stir welding machine. The stirring head 2 rotates at a speed of ω = 1500 rpm and plunges into the plate to be welded at a speed of ν = 1.5 mm / min at the welding start position. When the stirring needle of the stirring head 2 reaches the predetermined plunging depth of 4.0 mm and the stationary shoulder 1 penetrates 0.3 mm into the first plate thickness, the stirring head 2 stops plunging and continues to rotate for 2 minutes.

[0058] Step 4: The stirring head 2 advances at a transfer ratio of 100 to promote material flow between the first and second plates and form a full metallurgical bond;

[0059] Step 5: After reaching the end of the weld, pull back the stirring head 2, and the entire welding process is complete.

[0060] The use of a "hollow" stirring head 2 can avoid defects such as incomplete welding at the root of the joint, thereby achieving a good connection of dissimilar materials. At the same time, it can increase the distance between the tip of the stirring pin and the bottom of the plate, avoiding interference between the stirring pin and the backing plate, and effectively preventing the stirring pin from breaking.

[0061] Example 3

[0062] In this embodiment, the hollow welding tool has the following characteristics: the outer diameter of the stirring needle is D2 = 4 mm; the diameter of the slow-flow groove 3 is D1 = 2 mm; the depth of the slow-flow groove 3 is b = 4 mm; the inner ring diameter of the bottom end face of the stationary shoulder 1 is D3 = 4.2 mm; the longitudinal offset distance between the center of the inner ring of the bottom end face of the stationary shoulder 1 and the center of the stirring head 2 is c = 0.1 mm; the outer diameter of the bottom end face of the stationary shoulder 1 is D4 = 10 mm; the protrusion height of the boss structure on the bottom end face of the stationary shoulder 1 is h = 2 mm; the distance between the side lines of the protrusion end of the boss structure on the bottom end face of the stationary shoulder 1 is e = 7 mm; the radius of the drag reduction angle 6 of the stationary shoulder 1 is R1 = 3 mm; the first plate and the second plate are curved plates with a bending radius of 900 mm, made of 2024 aluminum alloy, and both are 2 mm thick.

[0063] A hollow welding method for friction stir butt welding includes the following steps:

[0064] Step 1: Select a stirring head 2 with a suitable stirring needle length based on the thickness of the first and second plates;

[0065] Step 2: Clamp the first and second plates to be welded on the fixture of the friction stir welding machine, wherein the first plate and the second plate are butted together;

[0066] Step 3: Install the stirring head 2 on the main shaft of the friction stir welding machine. The stirring head 2 rotates at a speed of ω = 1600 rpm and plunges into the plate to be welded at a speed of ν = 1.2 mm / min at the welding start position. When the stirring needle of the stirring head 2 reaches the predetermined plunging depth of 1.5 mm and the stationary shoulder 1 penetrates 0.2 mm into the first plate thickness, the stirring head 2 stops plunging and continues to rotate for 3 minutes.

[0067] Step 4: The stirring head 2 advances at a transfer ratio of 40 to promote material flow between the first and second plates and form a full metallurgical bond;

[0068] Step 5: After reaching the end of the weld, pull back the stirring head 2, and the entire welding process is complete.

[0069] The stationary shoulder 1 with drag-reducing angle can effectively avoid the scraping effect of the bushing without drag-reducing angle on the material at the weld tip during the welding of curved plates. At the same time, it reduces welding resistance to a certain extent and avoids interference between the stirring head and the stationary bushing, which could lead to needle breakage. The hollow design of the stirring head can effectively increase the indirect action range of the stirring needle, reducing the probability of stirring needle breakage and effectively avoiding root penetration defects.

Claims

1. A hollow welding tool for friction stir butt welding, characterized in that, It includes a stirring head and a stationary shoulder. The stationary shoulder is fixedly connected to a conical frame fixed on the main shaft box. The stationary shoulder is sleeved around the stirring head. The stirring head and the stationary shoulder are eccentrically arranged, and the gap between the stationary shoulder and the stirring head forms a centrifugal ring. A slow flow groove is opened at the center of the bottom end face of the stirring needle of the stirring head.

2. A hollow welding tool for friction stir butt welding according to claim 1, characterized in that, The diameter D1 of the slow-flow channel is D2 / 2, where D2 is the outer diameter of the stirring needle, and 4mm≤D2≤20mm; the depth b of the slow-flow channel satisfies 2D1≤b≤5D1.

3. A hollow welding tool for friction stir butt welding according to claim 1, characterized in that, There is a longitudinal offset between the center of the inner ring of the bottom end face of the stationary shoulder and the center of the stirring head. The gaps between the left and right ends of the inner ring of the bottom end face of the stationary shoulder and the stirring head are the same. After the stirring needle is deformed, the center of the stirring head coincides with the center of the inner ring of the bottom end face of the stationary shoulder.

4. A hollow welding tool for friction stir butt welding according to claim 3, characterized in that, The longitudinal offset distance c between the center of the inner ring of the bottom end face of the stationary shoulder and the center of the stirring head satisfies c = 0.05~0.1mm; the diameter D3 of the inner ring of the bottom end face of the stationary shoulder satisfies D3 = D2 + 0.2mm.

5. A hollow welding tool for friction stir butt welding according to claim 1, characterized in that, With the end face of the stationary shoulder in the welding forward direction as the front side, the left and right outer edges of the bottom end face of the stationary shoulder are symmetrically provided with through grooves along the center line, so that the bottom end face of the stationary shoulder forms a boss structure, and the left and right side edges of the protruding end face of the boss structure are parallel to the center line of the stationary shoulder.

6. A hollow welding tool for friction stir butt welding according to claim 5, characterized in that, The distance between the left and right side edges of the protruding end face of the boss structure is e, which satisfies 1.2D3≤e≤0.9D4, and the protruding height of the boss structure is h, which satisfies 0.5mm≤h≤3mm.

7. A hollow welding tool for friction stir butt welding according to claim 1, characterized in that, A drag reduction angle is provided at the connection between the bottom end face edge of the stationary shoulder in the welding forward direction and the front end face edge, with a drag reduction angle radius R1 = 1mm to 3mm.

8. A hollow welding tool for friction stir butt welding according to claim 1, characterized in that, The diameter D4 of the bottom end face of the stationary shoulder satisfies D4 = k × D3; k is any value between 1.5 and 4.

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