A friction stir riveting welding tool and method for dissimilar materials that combines large-area metallurgical bonding and mechanical interlocking riveting

Abstract

A friction stir riveting and welding tool and method for dissimilar materials that combines large-area metallurgical bonding and mechanical interlocking riveting. The present invention aims to solve the problems of reduced service performance of joints caused by complex structures, increased weight, weak single metallurgical bonding, and poor sealing in the connection of aluminum / steel dissimilar materials. It includes the design of a multi-needle tool and a riveting and welding structure. The multi-needle tool mainly includes a concave shoulder, a coaxial active stirring needle, and an eccentric driven stirring needle. The macro-micro mechanical interlocking structure of riveting and welding includes millimeter-level grooves pre-set on the surface of the steel plate and micron-level scratches prefabricated on the outer surface of the grooves. The micro-contact between the coaxial active stirring needle and the bottom surface of the groove ensures good metallurgical bonding and macro-mechanical interlocking riveting. The micro-contact between the eccentric driven stirring needle and the outer surface of the groove ensures a further increase in the metallurgical bonding area and micro-mechanical interlocking riveting, achieving high-strength connection and high-reliability sealing of aluminum / steel dissimilar materials. The present invention belongs to the field of solid-phase welding and manufacturing technology for aircraft.

Description

Technical Field

[0001] The present invention relates to a welding tool and a welding method, and particularly to a friction stir riveting welding tool and method for dissimilar materials that combines large-area metallurgical bonding and mechanical interlocking riveting. The present invention belongs to the technical field of solid-phase welding and manufacturing of aircraft. Background Art

[0002] The aluminum / steel dissimilar joints of fuel delivery pipes will withstand extreme working conditions such as cryogenic impact cycles, high-stress cyclic fatigue, and long-term stress corrosion during service. At present, the main connection methods for this structure include mechanical flange connection, brazing, and rotary friction welding. The use of bolts in mechanical flange connection results in a large redundant weight of the joint and poor sealing performance of the joint; the halide brazing flux in brazing easily reduces the corrosion resistance of the joint significantly; the fatigue performance of rotary friction welded joints is poor and problems such as low-stress or even stress-free cracking are prone to occur. Therefore, there is an urgent need to develop a high-quality connection method for aluminum / steel dissimilar materials to improve the service performance of the joints.

[0003] As a new type of solid-phase connection method, friction stir welding has the advantages of high weld quality, low heat input, and green and pollution-free. However, there are still several problems to be solved in conventional aluminum / steel friction stir welding: First, conventional welding tools can only ensure metallurgical bonding within the range of the action of the stirring pin, and it is difficult to achieve effective connection over a large area; Second, one of the welding requirements for conventional aluminum / steel lap joints is that the stirring pin is in interference contact with the steel plate, and sufficient stirring of the steel side by the welding tool is required to ensure effective metallurgical bonding, but this will cause severe wear of the welding tool; Third, after retrieval, the patents published with publication numbers such as CN116532781A, CN115922055A, and CN111805073A all use rivets as the connecting transition pieces, but the riveting forms are mainly point connections, and it is difficult to ensure the sealing performance of the circumferential joint structure.

[0004] Therefore, the existing connection methods for aluminum / steel dissimilar materials have problems such as complex structure, increased weight, weak single metallurgical bonding, and poor sealing performance, which reduce the service performance of the joints. Summary of the Invention

[0005] In view of the urgent need for high-strength connection and high-reliability sealing of aluminum / steel dissimilar materials, and to solve the problems of reduced service performance of joints caused by complex structure, increased weight, weak single metallurgical bonding, and poor sealing performance in the connection of aluminum / steel dissimilar materials, the present invention proposes a friction stir riveting welding tool and method that combines large-area metallurgical bonding and mechanical interlocking riveting.

[0006] The technical solutions adopted by the present invention to solve the above problems are as follows:

[0007] The present invention includes the design of a multi - needle welding tool and a riveting - welding structure. An aluminum plate and a steel plate are stacked from top to bottom. The multi - needle welding tool is placed directly above the aluminum plate and includes a clamping part, a transition part, a concave shoulder, a coaxial active stirring pin, and an eccentric driven stirring pin. The clamping part, the transition part, the concave shoulder, and the coaxial active stirring pin are connected integrally from top to bottom in sequence, and the eccentric driven stirring pin is located outside the coaxial active stirring pin. The riveting - welding structure is set as a macro - micro multi - scale mechanical interlocking structure. The macro - structure is millimeter - level grooves pre - set on the surface of the steel plate, and the micro - structure is micron - level indentations pre - fabricated on the outer surface of the steel - plate grooves.

[0008] A friction stir riveting - welding method that takes into account large - area metallurgical bonding and mechanical interlocking riveting, the method includes the following steps:

[0009] Step 1: According to the different sizes and performance requirements of the aluminum / steel dissimilar joints, design the dimensions of the concave shoulder, the coaxial active stirring pin, and the eccentric driven stirring pin of the multi - needle welding tool to ensure large - range thermo - mechanical coupling flow of the materials, so as to fill the macro - micro multi - scale mechanical interlocking structure and enhance the metallurgical bonding at the interface.

[0010] Step 2: Select aluminum plates and steel plates with appropriate sizes. Mechanically process millimeter - level grooves at the welding position of the steel plate, wipe the welding position with anhydrous ethanol or acetone to remove surface oil stains; sand the surface of the welding position to remove burrs.

[0011] Step 3: In a high - purity argon environment, use laser texturing to pre - set micron - level indentations on the bottom surface and the outer surface of the steel - plate grooves to avoid the hindrance of surface oxidation to the metallurgical reaction.

[0012] Step 4: Assemble the aluminum / steel lap - joint tooling. Place the aluminum plate on the upper part and the steel plate on the lower part of the aluminum plate. Use a pressing strip to fix the plates to ensure that there is no relative movement during the welding process; place the welding tool above the groove and prepare for welding.

[0013] Step 5: During welding, the welding tool rotates at high speed and penetrates into the plates until the coaxial active stirring pin slightly touches the bottom surface of the groove and the eccentric driven stirring pin slightly touches the outer surface of the groove; the thermoplasticized aluminum alloy flows into the groove and the indentations to form mechanical interlocking riveting, and the frictional heat and large plastic deformation induce atomic diffusion at the interface to form large - area metallurgical bonding, thereby achieving high - strength connection and high - reliable sealing of aluminum / steel dissimilar materials.

[0014] Step 6: After welding is completed, gradually withdraw the welding tool, and an aluminum / steel dissimilar joint that takes into account large - area metallurgical bonding and mechanical interlocking riveting can be obtained.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention takes into account both the dual action modes of large - area metallurgical bonding and mechanical interlocking riveting. The micro - contact between the co - axial active stirring pin and the bottom surface of the groove ensures good metallurgical bonding and macroscopic mechanical interlocking riveting. The micro - contact between the eccentric driven stirring pin and the outer surface of the groove ensures a further increase in the area of metallurgical bonding and microscopic mechanical interlocking riveting, achieving high - strength connection and high - reliable sealing of dissimilar aluminum / steel materials.

[0017] 2. The welding tool proposed by the present invention, which consists of a concave - shaped shoulder, a co - axial active stirring pin, and an eccentric driven stirring pin, can achieve large - area metallurgical bonding of aluminum / steel dissimilar joints and ensure their sealing performance.

[0018] 3. The present invention realizes a multi - pin welding tool that induces a macro - micro multi - scale mechanical interlocking structure filled with thermoplasticized aluminum alloy. Compared with the single metallurgical bonding of traditional welding, the bearing capacity of aluminum / steel dissimilar joints is significantly improved.

[0019] 4. The riveting head prepared by the present invention has no introduction of external materials, avoiding the problem of excessive weight of mechanical flange connection joints. In addition, the main phase of the riveting - welding interface is a thin - layer aluminum / steel intermetallic compound, avoiding the problem of poor corrosion resistance of joints caused by the introduction of other elements in brazing.

[0020] 5. The prepared riveting - welding joints of the present invention have good performance, and this method is applicable to the connection of most "soft / hard" - paired dissimilar materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the friction stir riveting process of the present invention;

[0022] Figure 2 is a schematic diagram of the multi - pin welding tool structure of the present invention;

[0023] Figure 3 is a steel plate with a macro - micro multi - scale mechanical interlocking structure for riveting - welding of the present invention;

[0024] Figure 4 is a riveting - welding joint that takes into account both large - area metallurgical bonding and mechanical interlocking riveting prepared by the present invention.

[0025] In the figure, 1 - multi - pin welding tool, 101 - clamping part, 102 - transition part, 103 - concave - shaped shoulder, 104 - co - axial active stirring pin, 105 - eccentric driven stirring pin, 2 - aluminum plate, 3 - steel plate, 301 - groove, 302 - micron - level indentation. DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE INVENTION I: Combination Figures 1 to 2The present embodiment is described. The friction stir riveting welding tool described in the present embodiment takes into account both large-area metallurgical bonding and mechanical interlocking riveting. Its basic structure includes a multi-needle welding tool 1, an aluminum plate 2 and a steel plate 3. The aluminum plate 2 and the steel plate 3 are stacked from top to bottom, and the multi-needle welding tool 1 is placed directly above the aluminum plate 2. The multi-needle welding tool 1 includes a clamping portion 101, a transition portion 102, an inner concave shoulder 103, a coaxial active stirring needle 104 and an eccentric driven stirring needle 105. The clamping portion 101, the transition portion 102, the inner concave shoulder 103 and the coaxial active stirring needle 104 are sequentially connected into one body from top to bottom, and the eccentric driven stirring needle 105 is located outside the coaxial active stirring needle 104. The number of eccentric driven stirring needles 105 is at least one. The upper surface of the steel plate 3 is provided with a groove 301, and the outer surface of the groove 301 is provided with a micron-level notch 302.

[0027] The present invention includes the design of a multi-needle welding tool and a riveted welding structure. Among them, the coaxial active stirring needle 104 and the eccentric driven stirring needle 105 are mainly characterized by a thread and a milled plane structure. The length of the former is larger than that of the latter. The end diameter and length difference between the two need to be determined according to the size of the steel plate groove 301, and the eccentricity needs to be designed according to the size and performance requirements. The riveted welding structure is set as a macro-micro multi-scale mechanical interlocking structure. The macro structure is a millimeter-level groove 301 pre-set on the surface of the steel plate 3, and the micro structure is a micron-level notch 302 pre-fabricated on the outer surface of the steel plate groove 301. The assembly method of the aluminum plate 2 on the top and the steel plate on the bottom is adopted. During the welding process, the welding tool 1 penetrates into the plate from the top of the groove 301 until the coaxial active stirring needle 104 micro-contacts the bottom surface of the groove 301 and the eccentric driven stirring needle 105 micro-contacts the outer surface of the groove 301. Under the action of friction heat and upsetting force, the thermoplasticized aluminum alloy flows into the groove 301 and the notch 302, achieving macro-micro mechanical interlocking riveting; at the same time, the welding tool, thermoplasticized aluminum alloy and steel are in close contact, and the friction heat and large plastic deformation induce atomic diffusion at the interface, achieving large-area metallurgical bonding. The micro-contact between the coaxial active stirring needle 104 and the bottom surface of the groove 301 ensures good metallurgical bonding and macro-mechanical interlocking riveting, and the micro-contact between the eccentric driven stirring needle 105 and the outer surface of the groove ensures a further increase in the metallurgical bonding area and micro-mechanical interlocking riveting, achieving high-strength connection and high-reliability sealing of aluminum / steel dissimilar materials.

[0028] Specific implementation method 2: Combination Figure 1 To illustrate this embodiment, in the friction stir riveting welding tool for dissimilar materials that takes into account both large-area metallurgical bonding and mechanical interlocking riveting, the thickness of the aluminum plate 2 is 2 to 50 mm, and the thickness of the steel plate 3 is 2 to 100 mm.

[0029] The other components and connection relationships of this embodiment are the same as those of the first embodiment.

[0030] Specific implementation method three: CombinationFigure 3 Regarding this embodiment, in a friction stir riveting welding tool for dissimilar materials that takes into account both large-area metallurgical bonding and mechanical interlocking riveting, the depth of the groove 301 is not greater than 0.9 times the thickness of the steel plate 3; the width of the groove 301 is 1 to 10 times the depth of the groove 301; the included angle between the bottom surface and the side surface of the groove 301 is 30° to 150°.

[0031] The other components and connection relationships of this embodiment are the same as those in the first or second specific embodiment.

[0032] Specific embodiment four: Combining Figure 1 and Figure 2 Regarding this embodiment, in a friction stir riveting welding tool for dissimilar materials that takes into account both large-area metallurgical bonding and mechanical interlocking riveting, the diameter of the concave shoulder 103 is 3 to 5 times the thickness of the aluminum plate 2.

[0033] The other components and connection relationships of this embodiment are the same as those in the first, second, or third specific embodiment.

[0034] Specific embodiment five: Combining Figures 1 to 3 Regarding this embodiment, in a friction stir riveting welding tool for dissimilar materials that takes into account both large-area metallurgical bonding and mechanical interlocking riveting, the end diameter of the coaxial active stirring pin 104 is 0 to 3 mm smaller than the width of the groove 301; the end diameter of the eccentric driven stirring pin 105 is 0.5 to 5 mm smaller than the end diameter of the coaxial active stirring pin 104; the eccentricity is 1 to 10 mm smaller than the radius of the shoulder 103 and 0 to 10 mm larger than the end diameter of the coaxial active stirring pin 104.

[0035] The other components and connection relationships of this embodiment are the same as those in the first, second, third, or fourth specific embodiment.

[0036] Specific embodiment six: Combining Figures 1 to 4 Regarding this embodiment, a friction stir riveting welding method for dissimilar materials that takes into account both large-area metallurgical bonding and mechanical interlocking riveting includes the following steps:

[0037] Step 1: According to the different sizes and performance requirements of the aluminum / steel dissimilar joint 4, design the dimensions of the concave shoulder 103, the coaxial active stirring pin 104, and the eccentric driven stirring pin 105 of the multi-needle welding tool 1 to ensure large-range thermo-mechanical coupling flow of the materials, so as to fill the macro-micro multi-scale mechanical interlocking structure and enhance the metallurgical bonding at the interface;

[0038] Step 2: Select aluminum plates 2 and steel plates 3 with appropriate sizes, mechanically process a millimeter-level groove 301 at the welding position of the steel plate 3, wipe the welding position with anhydrous ethanol or acetone to remove surface oil stains; polish the surface of the welding position with sandpaper to remove burrs;

[0039] Step 3: In an environment of high-purity argon, laser texturing is used to preset micron-scale indentations 302 on the bottom surface and the outer surface of the groove 301 of the steel plate 3 to avoid the hindrance of surface oxidation to the metallurgical reaction;

[0040] Step 4: Assemble the aluminum / steel lap joint tooling. Place the aluminum plate 2 on the upper part and the steel plate 3 on the lower part of the aluminum plate 2. Use a pressure bar to fix the plates to ensure no relative movement during welding. Place the welding tool 1 above the groove 301 and prepare for welding;

[0041] Step 5: During welding, the welding tool 1 rotates at high speed and penetrates into the plates until the coaxial active stirring pin 104 is in slight contact with the bottom surface of the groove 301 and the eccentric driven stirring pin 105 is in slight contact with the outer surface of the groove 301. The thermoplasticized aluminum alloy flows into the groove 301 and the indentations 302 to form a mechanical interlocking riveting. The frictional heat and large plastic deformation induce the diffusion of interface atoms to form a large-area metallurgical bond, thereby achieving high-strength connection and high-reliability sealing of dissimilar aluminum / steel materials;

[0042] Step 6: After welding is completed, the welding tool 1 is gradually withdrawn, and the aluminum / steel dissimilar joint 4 that combines large-area metallurgical bonding and mechanical interlocking riveting can be obtained.

[0043] The slight contact between the coaxial active stirring pin 104 and the bottom surface of the groove 301 ensures good metallurgical bonding and macroscopic mechanical interlocking riveting. The slight contact between the eccentric driven stirring pin 105 and the outer surface of the groove 301 ensures a further increase in the metallurgical bonding area and microscopic mechanical interlocking riveting, achieving high-strength connection and high-reliability sealing of dissimilar aluminum / steel materials.

[0044] Specific Embodiment 7: Combining Figures 1 to 4 To illustrate this embodiment, in a friction stir riveting welding method for dissimilar materials that combines large-area metallurgical bonding and mechanical interlocking riveting described in this embodiment, the spindle rotation speed is 200 - 5000 rpm, the welding speed is 50 - 5000 mm / min, the inclination angle range of the welding tool is 0° - 5°, and the penetration depth of the multi-pin welding tool 1 is 0.01 - 2 mm above the bottom surface of the groove 301.

[0045] The other components and connection relationships of this embodiment are the same as those in Specific Embodiments 1, 2, 3, 4, 5, or 6.

[0046] Specific Embodiment 8: Combining Figures 1 to 4 To illustrate this embodiment, in a friction stir riveting welding method for dissimilar materials that combines large-area metallurgical bonding and mechanical interlocking riveting described in this embodiment, the dissimilar materials can be other "soft / hard" combinations, such as aluminum / titanium, magnesium / steel, magnesium / titanium, polymer / metal, etc. During welding, the low-hardness material is placed on the upper part and the high-hardness material is placed on the lower part to ensure that the riveting welding structure is not damaged.

[0047] The other components and connection relationships of this embodiment are the same as those of the first, second, third, fourth, fifth, sixth, or seventh specific embodiments.

[0048] The above are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the relevant art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention and is based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims

1. A friction stir riveting welding tool for dissimilar materials that combines large-area metallurgical bonding and mechanical interlocking riveting, characterized by: The friction stir riveting welding tool that takes into account both large-area metallurgical bonding and mechanical interlocking riveting comprises a multi-needle welding tool (1), an aluminum plate (2) and a steel plate (3). The aluminum plate (2) and the steel plate (3) are stacked from top to bottom, and the multi-needle welding tool (1) is placed directly above the aluminum plate (2). The multi-needle welding tool (1) comprises a clamping portion (101), a transition portion (102), an inner concave shoulder (103), a coaxial active stirring needle (104) and an eccentric driven stirring needle (105). The clamping portion (101), the transition portion (102), the inner concave shoulder (103) and the coaxial active stirring needle (104) are sequentially connected into one body from top to bottom, and the eccentric driven stirring needle (105) is located outside the coaxial active stirring needle (104); a groove (301) is provided in the middle of the upper surface of the steel plate (3), and a micron-level notch (302) is provided on the outer surface of the groove (301).

2. The friction stir riveting welding tool for dissimilar materials that takes into account both large-area metallurgical bonding and mechanical interlocking riveting according to claim 1, characterized in that: The length of the coaxial active stirring needle (104) is greater than the length of the eccentric driven stirring needle (105).

3. A friction stir riveting welding tool that combines large-area metallurgical bonding and mechanical interlocking riveting according to claim 1, characterized in that: The number of the eccentric driven stirring needle (105) is at least one.

4. The friction stir riveting welding tool for achieving both large-area metallurgical bonding and mechanical interlocking riveting according to claim 1, characterized in that: The thickness of the aluminum plate (2) is 2 to 50 mm, and the thickness of the steel plate (3) is 2 to 100 mm.

5. The friction stir riveting welding tool for achieving both large-area metallurgical bonding and mechanical interlocking riveting according to claim 1, characterized in that: The depth of the groove (301) is not greater than 0.9 times the thickness of the steel plate (3); the width of the groove (301) is 1 to 10 times the depth of the groove (301); and the angle between the bottom surface and the side surface of the groove (301) is 30° to 150°.

6. The friction stir riveting welding tool for achieving both large-area metallurgical bonding and mechanical interlocking riveting according to claim 1, characterized in that: The diameter of the inner concave shaft shoulder (103) is 3 to 5 times the thickness of the aluminum plate (2).

7. The friction stir riveting welding tool for achieving both large-area metallurgical bonding and mechanical interlocking riveting according to claim 1, characterized in that: The diameter of the end of the coaxial active stirring needle (104) is 0-3 mm smaller than the width of the groove (301); the diameter of the end of the eccentric driven stirring needle (105) is 0.5-5 mm smaller than the diameter of the end of the coaxial active stirring needle (104); the eccentricity is 1-10 mm smaller than the radius of the shoulder (103), and 0-10 mm larger than the diameter of the end of the coaxial active stirring needle (104).

8. A method for welding a friction stir riveting welding tool that combines large-area metallurgical bonding and mechanical interlocking riveting according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: Step 1: designing the dimensions of the concave shaft shoulder 103, the coaxial active stirring needle (104) and the eccentric driven stirring needle (105) of the multi-needle welding tool (1) according to the different dimensions and performance requirements of the aluminum / steel heterogeneous joint (4); Step 2: Select an aluminum plate (2) and a steel plate (3) of suitable size, machine a prefabricated millimeter-level groove (301) at the position to be welded on the steel plate (3), wipe the position to be welded with anhydrous ethanol or acetone to remove surface oil stains; and grind the surface of the position to be welded with sandpaper to remove burrs; Step 3: In a high-purity argon environment, laser roughening is used to pre-set micron-level notches (302) on the bottom surface of the groove (301) and the outer surface of the groove (301) of the steel plate (3) to prevent surface oxidation from hindering the metallurgical reaction; Step 4: Assemble the aluminum / steel lap joint tooling, place the aluminum plate (2) on the upper part, and the steel plate (3) on the lower part of the aluminum plate (2), and use a pressure strip to fix the plates to ensure that there is no relative movement during the welding process; place the multi-needle welding tool (1) above the groove (301) and prepare for welding; Step 5: During welding, the multi-needle welding tool (1) rotates at high speed and penetrates into the plate until the coaxial active stirring needle (104) micro-contacts the bottom surface of the groove (301) and the eccentric driven stirring needle (105) micro-contacts the outer surface of the groove (301); the thermoplasticized aluminum alloy flows into the groove (301) and the notch (302) to form a mechanical interlocking riveting; Step 6: After welding is completed, the multi-needle welding tool (1) is gradually retracted to obtain an aluminum / steel heterogeneous joint (4) that combines large-area metallurgical bonding and mechanical interlocking riveting.

9. A method for welding a friction stir riveting welding tool that combines large-area metallurgical bonding and mechanical interlocking riveting according to claim 8, characterized in that: The main shaft rotation speed is 200-5000rpm, the welding speed is 50-5000mm / min, the welding tool inclination angle ranges from 0° to 5°, and the piercing depth of the multi-needle welding tool (1) is 0.01-2mm above the bottom surface of the groove (301).

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