Manufacturing method of aluminum-steel dissimilar material composite connection

Abstract

The application relates to the technical field of material connection, and discloses a composite connection manufacturing method for aluminum-steel dissimilar materials, which is used to solve the problem that aluminum-steel connection is difficult to consider mechanical performance, sealing performance and light weight at the same time. After the aluminum alloy plate and the steel plate are overlapped, friction rivet welding is carried out in the overlapping area to form point connection of mechanical interlocking; then laser fusion brazing is carried out along the overlapping edge of the aluminum alloy plate, aluminum alloy and welding wire are melted by controlling heat input, and the steel plate is not melted, thereby forming continuous metallurgical bonding line connection. The composite of the point connection and the line connection enables the load to be borne on the two connection forms, so that a high-strength connection joint is obtained; the continuous line connection weld closes the gap between the plates, so that the joint has sealing performance and the corrosion resistance is improved; meanwhile, the load is shared, the rivet amount is reduced, the connection weight is effectively reduced, and the structure is lightened.

Description

Technical Field

[0001] This invention relates to the field of material joining technology, specifically to a method for manufacturing composite joining of dissimilar aluminum and steel materials. Background Technology

[0002] In fields such as automotive manufacturing, the combined use of aluminum alloys and high-strength steel is becoming increasingly common to achieve lightweight structures. However, due to the significant differences in physical and chemical properties between aluminum and steel, achieving a reliable and durable connection between the two is a technical challenge in this application. When using traditional fusion welding for connection, the joint performance is easily severely degraded due to the formation of excessively thick and brittle intermetallic compounds at the interface.

[0003] To address this, the industry has developed several improved connection methods. For example, friction plug welding, a low-heat-input connection technology, uses the frictional heating generated by rotating rivets to press them in, creating high-strength joints with a thin intermetallic compound layer. However, friction plug welding is a point connection, and its strength depends on the number and density of rivets. To achieve high load-bearing capacity, a large number of rivets are required, significantly increasing the added weight of the structure and diminishing the lightweight effect of using lightweight materials. Furthermore, this discrete point connection cannot create an effective seal between the plates; the presence of lap joints provides channels for moisture and corrosive media to penetrate, reducing the structure's corrosion resistance.

[0004] Another method is laser brazing, which uses precise control of the laser heat source to melt the aluminum alloy side while leaving the steel plate unmelted, forming a continuous metallurgical weld. While this method achieves good sealing and simplifies the process compared to adhesive sealing by eliminating coating and curing steps, its overall load-bearing capacity is limited when used alone, and its mechanical properties are often insufficient when facing high load requirements.

[0005] Therefore, existing single connection technologies are insufficient to simultaneously meet the comprehensive performance requirements of aluminum-steel structures for high strength, high sealing, and lightweight. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for manufacturing composite connections of dissimilar aluminum and steel materials, which solves the deficiencies of existing aluminum-steel connection technologies in terms of mechanical properties, sealing performance, and lightweighting.

[0007] To address the above problems, the present invention provides the following technical solution:

[0008] A method for manufacturing a composite connection of dissimilar aluminum and steel materials includes the following steps:

[0009] S1. Place the aluminum alloy plate on the upper side of the steel plate and overlap it to form an overlapping part;

[0010] S2. Friction plug welding is performed on the overlapping area of ​​the lap joint to form a point connection consisting of friction plug welded rivets and friction plug welded fusion zone.

[0011] S3. For the lap joints processed in step S2, laser brazing is performed along the lap edge of the aluminum alloy plate of the lap joints to form a laser brazing weld as a line connection. The line connection and the point connection together constitute a composite connection of dissimilar aluminum and steel materials.

[0012] By adopting the above technical solution, this invention combines mechanical point connections with metallurgical line connections to form a structure in which points and lines work together to bear loads. Its technical principle lies in:

[0013] First, a point connection with stable mechanical properties is formed through friction plug welding. In this step, the friction plug welded rivet forms a mechanical interlock with the aluminum alloy plate and the steel plate, providing basic load-bearing capacity. At the same time, the heat generated by the rotational friction of the rivet promotes a local metallurgical reaction at the plate interface, forming a friction plug welded fusion zone, which further enhances the bonding strength of the point connection.

[0014] The subsequent laser brazing creates a continuous laser brazed weld at the lap edge. This weld acts as a physical barrier, sealing the gap between the plates and preventing the intrusion of corrosive media. Furthermore, as a line connection, it works synergistically with the discrete friction plug welds when the joint is under load, sharing some of the shear load and restraining the deformation of the plates around the rivets. This point-line composite load-bearing mechanism results in a joint with higher overall strength than a single connection method. Simultaneously, because the weld shares the load, the number of rivets required can be reduced, thus lowering the added weight of the structure while maintaining mechanical performance, achieving lightweighting.

[0015] Preferably, the surfaces of the aluminum alloy plate and the steel plate to be joined are pretreated before the overlap.

[0016] By adopting the above technical solution, grinding and cleaning the connecting surface can effectively remove the oxide layer and oil stains, providing a clean contact interface for subsequent friction plug welding and laser brazing, and ensuring the formation quality and consistency of the friction plug welding fusion zone and the laser brazing weld.

[0017] Preferably, in the friction plug riveting step, the spindle speed is 5500-6500 r / min, the axial pressure is 7-8 kN, and the spacing between adjacent friction plug riveting rivets is 60-70 mm; in the laser brazing step, the laser power is 2-3 kW, the wire feed speed is 3-4 m / min, and the welding speed is 4-5 mm / s.

[0018] By adopting the above technical solution, the optimal process parameter range for each step is defined. Within this parameter window, composite connection joints with better mechanical properties and connection quality can be obtained stably.

[0019] Preferably, the aluminum alloy plate is a 6000 series aluminum alloy, and the steel plate is hot-formed steel.

[0020] By adopting the above technical solution, this method is applicable to lightweight material systems commonly used in the automotive industry, and has a clear application background and practical value.

[0021] Preferably, in the laser brazing step, Al-Si based aluminum alloy welding wire is used as filler material.

[0022] By adopting the above technical solution, Al-Si welding wire has a low melting point and good fluidity, which is conducive to the wetting and spreading of molten metal on the steel plate surface. At the same time, it can reduce the sensitivity to hot cracking and ensure the forming quality of laser brazing weld.

[0023] Preferably, in the laser brazing step, the laser heat input is controlled by synergistic regulation of laser power, wire feed speed and welding speed, so that the aluminum alloy plate and aluminum alloy welding wire melt, while the steel plate does not melt, thus forming a brazed connection.

[0024] By adopting the above technical solution, precise control of heat input can be achieved to ensure the formation of a Fe-Al intermetallic compound transition layer of suitable thickness and dispersed structure at the interface between the aluminum alloy plate and the steel plate. This transition layer is the basis for achieving high-strength metallurgical bonding. At the same time, this control avoids the melting of the steel plate and the formation of a thick and continuous brittle intermetallic compound layer due to excessive heat input, thereby ensuring the mechanical properties of the joint.

[0025] Preferably, in the friction plug riveting step, the friction plug riveting is performed along the centerline of the lap area.

[0026] By adopting the above technical solution, the point connection, which serves as the main load-bearing unit, is arranged at the center of the lap area, which is conducive to the uniform transmission of load inside the joint and optimizes the stress distribution of the joint.

[0027] Preferably, the line connection is a sealing weld, i.e., a laser brazing weld, used to seal the lap joint between the aluminum alloy plate and the steel plate.

[0028] By adopting the above technical solution, the laser brazing weld not only provides a line connection but also serves as a seal, realizing the completion of structural connection and sealing in a single process. Compared with additional processes such as gluing, this simplifies the production process and improves manufacturing efficiency.

[0029] The above solution achieves the following beneficial technical effects:

[0030] This invention improves the overall mechanical properties of aluminum-steel dissimilar material joints. The combination of point connections formed by friction plug welding and line connections formed by laser brazing creates a point-line composite load-bearing structure. External loads are borne collaboratively by mechanically interlocked rivets and continuous metallurgically bonded welds. Compared to single connection methods, the overall tensile shear strength and connection stiffness of the joint are improved.

[0031] This invention provides a sealing performance for the joint and simplifies the manufacturing process. The continuous laser brazing weld formed at the lap edge acts as a physical barrier, sealing the lap gap between the aluminum and steel sheets, preventing the intrusion of corrosive media, and improving the joint's corrosion resistance. Furthermore, compared to processes using adhesive sealing, this invention eliminates the need for subsequent curing or drying steps, shortening the manufacturing cycle.

[0032] This invention achieves lightweighting of the connection structure. Because the laser brazing weld shares part of the load, the number of friction plug rivets used or the rivet spacing can be increased while meeting the same strength design requirements. Since rivets are the main source of added weight in the connection, this method reduces the additional weight generated to achieve the connection function, resulting in a lightweight structure. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the process for a composite joining method of dissimilar aluminum and steel materials according to the present invention.

[0034] Figure 2 This is a schematic diagram of the cross-sectional structure of the composite connector prepared according to the present invention.

[0035] Among them, 1. Aluminum alloy test plate; 2. Laser welding gun; 3. Aluminum alloy welding wire; 4. High-strength steel test plate; 5. Friction plug riveting rivet; 6. Laser brazing weld; 7. Friction plug riveting fusion zone. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Examples 1-3:

[0038] Example 1:

[0039] This embodiment provides a method for manufacturing a composite connection of dissimilar aluminum and steel materials, the process of which is as follows: Figure 1 As shown, the specific steps include:

[0040] S1: Pre-treatment of the workpiece to be welded.

[0041] Select 6061 aluminum alloy test plate 1 (120mm × 100mm × 1.5mm) and 22MnB5 high-strength steel test plate 4. Use 600-grit sandpaper to polish the surfaces of the aluminum alloy test plate 1 and the high-strength steel test plate 4 to be joined, removing impurities and oxide layers until the metal luster is exposed. Then, place the aluminum alloy test plate 1 and the high-strength steel test plate 4 in an acetone solution for ultrasonic cleaning. After cleaning, use a hair dryer to dry them for later use.

[0042] S2: Secure the panels according to the overlapping method.

[0043] The assembly is performed with aluminum alloy test plate 1 on the top and high-strength steel test plate 4 on the bottom, with the overlap length of the overlapping area set at 30mm. After clamping, the overlapping part consisting of aluminum alloy test plate 1 and high-strength steel test plate 4 is fixed on the workbench to ensure no relative displacement during subsequent welding.

[0044] S3: Friction plug welding is performed on the fixed lap joints at certain intervals.

[0045] Multi-point friction plug welding is performed along the centerline of the overlapping area. The selected welding parameters are: spindle speed of 4000 r / min, axial pressure of 6 kN, and spacing between adjacent rivets of 80 mm. The friction plug welding rivet 5 generates heat through rotational friction and is pressed into the plate. The dwell time is controlled at 0.2 s to complete the basic connection and form the friction plug welding fusion zone 7.

[0046] S4: Laser brazing is performed on the overlapping edge of the aluminum side.

[0047] Using laser welding torch 2, single-pass laser brazing was performed on the lap joint edge of aluminum alloy test plate 1. AlSi5 aluminum alloy welding wire 3 with a diameter of 1.0 mm was selected. The welding process parameters were set as follows: laser power 1 kW, wire feed speed 2 m / min, and welding speed 2 mm / s. During welding, the laser heat source melted the aluminum alloy test plate 1 and the aluminum alloy welding wire 3, while the high-strength steel test plate 4 remained unmelted. The molten metal wetted and spread on the surface of the high-strength steel test plate 4, and after cooling, formed a laser brazing weld 6, which was a sealing weld.

[0048] Finally, the point connection formed by the friction plug welded rivet 5 and the friction plug welded fusion zone 7, together with the line connection formed by the laser brazing weld 6, constitutes a composite connection structure, the cross-sectional morphology of which is shown in the figure below. Figure 2 As shown.

[0049] Example 2:

[0050] This embodiment provides a method for manufacturing a composite connection of dissimilar aluminum and steel materials, the process of which is as follows: Figure 1As shown, the specific steps include:

[0051] S1: Pre-treatment of the workpiece to be welded.

[0052] Select 6061 aluminum alloy test plate 1 (120mm × 100mm × 1.5mm) and 22MnB5 high-strength steel test plate 4. Use 600-grit sandpaper to polish the surfaces of the aluminum alloy test plate 1 and the high-strength steel test plate 4 to be joined, removing impurities and oxide layers until the metal luster is exposed. Then, place the aluminum alloy test plate 1 and the high-strength steel test plate 4 in an acetone solution for ultrasonic cleaning. After cleaning, use a hair dryer to dry them for later use.

[0053] S2: Secure the panels according to the overlapping method.

[0054] The assembly is performed with aluminum alloy test plate 1 on the top and high-strength steel test plate 4 on the bottom, with the overlap length of the overlapping area set at 40mm. After clamping, the overlapping part consisting of aluminum alloy test plate 1 and high-strength steel test plate 4 is fixed on the workbench to ensure no relative displacement during subsequent welding.

[0055] S3: Friction plug welding is performed on the fixed lap joints at certain intervals.

[0056] Multi-point friction plug welding is performed along the centerline of the overlapping area. The selected welding parameters are: spindle speed of 6000 r / min, axial pressure of 7.5 kN, and spacing between adjacent rivets of 65 mm. The friction plug welding rivet 5 generates heat through rotational friction and is pressed into the plate. The dwell time is controlled at 0.2 s to complete the basic connection and form the friction plug welding fusion zone 7.

[0057] S4: Laser brazing is performed on the overlapping edge of the aluminum side.

[0058] Using a laser welding torch 2, single-pass laser brazing was performed on the lap joint edge of the aluminum alloy test plate 1. A 1.0mm diameter AlSi5 aluminum alloy welding wire 3 was selected. The welding process parameters were set as follows: laser power 2.5kW, wire feed speed 3.5m / min, and welding speed 4.5mm / s. During welding, the laser heat source melted the aluminum alloy test plate 1 and the aluminum alloy welding wire 3, while the high-strength steel test plate 4 remained unmelted. The molten metal wetted and spread on the surface of the high-strength steel test plate 4, and after cooling, formed a laser brazing weld 6, which was a sealing weld.

[0059] Finally, the point connection formed by the friction plug welded rivet 5 and the friction plug welded fusion zone 7, together with the line connection formed by the laser brazing weld 6, constitutes a composite connection structure, the cross-sectional morphology of which is shown in the figure below. Figure 2 As shown.

[0060] Example 3:

[0061] This embodiment provides a method for manufacturing a composite connection of dissimilar aluminum and steel materials, the process of which is as follows: Figure 1 As shown, the specific steps include:

[0062] S1: Pre-treatment of the workpiece to be welded.

[0063] Select 6061 aluminum alloy test plate 1 (120mm × 100mm × 1.5mm) and 22MnB5 high-strength steel test plate 4. Use 600-grit sandpaper to polish the surfaces of the aluminum alloy test plate 1 and the high-strength steel test plate 4 to be joined, removing impurities and oxide layers until the metal luster is exposed. Then, place the aluminum alloy test plate 1 and the high-strength steel test plate 4 in an acetone solution for ultrasonic cleaning. After cleaning, use a hair dryer to dry them for later use.

[0064] S2: Secure the panels according to the overlapping method.

[0065] The assembly is performed with aluminum alloy test plate 1 on the top and high-strength steel test plate 4 on the bottom, with the overlap length of the overlapping area set at 50mm. After clamping, the overlapping part consisting of aluminum alloy test plate 1 and high-strength steel test plate 4 is fixed on the workbench to ensure no relative displacement during subsequent welding.

[0066] S3: Friction plug welding is performed on the fixed lap joints at certain intervals.

[0067] Multi-point friction plug welding is performed along the centerline of the overlapping area. The selected welding parameters are: spindle speed of 8000 r / min, axial pressure of 9 kN, and spacing between adjacent rivets of 50 mm. The friction plug welding rivet 5 generates heat through rotational friction and is pressed into the plate. The dwell time is controlled at 0.2 s to complete the basic connection and form the friction plug welding fusion zone 7.

[0068] S4: Laser brazing is performed on the overlapping edge of the aluminum side.

[0069] Using a laser welding torch 2, single-pass laser brazing was performed on the lap joint edge of the aluminum alloy test plate 1. A 1.0mm diameter AlSi5 aluminum alloy welding wire 3 was selected. The welding process parameters were set as follows: laser power 4kW, wire feed speed 5m / min, and welding speed 7mm / s. During welding, the laser heat source melted the aluminum alloy test plate 1 and the aluminum alloy welding wire 3, while the high-strength steel test plate 4 remained unmelted. The molten metal wetted and spread on the surface of the high-strength steel test plate 4, and after cooling, formed a laser brazing weld 6, which was a sealing weld.

[0070] Finally, the point connection formed by the friction plug welded rivet 5 and the friction plug welded fusion zone 7, together with the line connection formed by the laser brazing weld 6, constitutes a composite connection structure, the cross-sectional morphology of which is shown in the figure below. Figure 2 As shown.

[0071] Comparative Examples 1-5:

[0072] Comparative Example 1:

[0073] Compared with Example 2, the difference is that the laser brazing welding step in step S4 is omitted, that is, only friction plug riveting is performed, and no laser brazing weld 6 is formed. The spacing of the friction plug riveting rivets 5 remains unchanged at 65mm, and the remaining steps and parameters are the same.

[0074] Comparative Example 2:

[0075] Compared with Example 2, the difference is that the laser brazing welding step in step S4 is omitted, and the laser brazing weld 6 is not formed. The spacing between adjacent friction plug rivets 5 in step S3 is reduced from 65mm to 30mm, while the remaining steps and parameters are the same.

[0076] Comparative Example 3:

[0077] Compared with Example 2, the difference is that the friction plug riveting step in step S3 is omitted, that is, the friction plug riveting rivet 5 is not used. After the plate is fixed in step S2, the laser brazing connection in step S4 is directly performed to form the laser brazing weld 6. The remaining steps and parameters are the same.

[0078] Comparative Example 4:

[0079] Compared with Example 2, the difference is that the laser brazing welding in step S4 is replaced by an adhesive sealing process, that is, no laser brazing weld 6 is formed. Specifically, a one-component polyurethane structural adhesive is applied to the overlapping edge of the aluminum alloy test plate 1 and allowed to cure at room temperature for 24 hours. The remaining steps and parameters are the same.

[0080] Comparative Example 5:

[0081] Compared with Example 2, the difference is that the laser power in step S4 is increased from 2.5kW to 6kW, resulting in excessive heat input during welding, causing the lower high-strength steel test plate 4 to melt. The remaining steps and parameters are the same.

[0082] Test Examples 1-4:

[0083] Test Example 1: Process Feasibility Verification Test

[0084] Experimental steps:

[0085] The aluminum-steel composite joint samples prepared in Examples 1, 2, and 3 were selected for macroscopic forming quality testing. First, the samples were visually inspected and examined under low magnification to check the continuity and uniformity of the laser brazed weld 6 and the fit of the friction plug welded rivet 5 heads. Then, cross-sectional samples were cut using a wire cutting machine along a direction perpendicular to the centerline of the laser brazed weld 6 and the friction plug welded rivet 5. After the cut samples were progressively ground with sandpaper and mechanically polished, the aluminum side and the laser brazed weld 6 area were chemically etched using Keller's reagent. Finally, the wetting angle of the laser brazed area on the high-strength steel test plate 4 side was measured using a stereomicroscope and image measurement software. ), effective connection width ( ), the penetration depth on side 1 of the aluminum alloy test plate ( ), and observe whether there are macroscopic defects at the aluminum / steel interface and the interface between the friction plug welding rivet 5 and the plate.

[0086] Experimental data:

[0087] The weld formation dimensions and defect statistics of the samples in each embodiment obtained by measurement are shown in Table 1.

[0088] Table 1. Summary of Macroscopic Morphology and Dimensional Measurement Data of Aluminum-Steel Composite Connectors

[0089]

[0090] Note: In Example 3, a melting depth of 1.50 mm on the aluminum side indicates that the upper aluminum plate has been melted through, and the liquid metal directly contacts and spreads with the lower steel plate.

[0091] in conclusion:

[0092] Experimental data show that within a laser power range of 1.0kW to 4.0kW, this composite joining process can form continuous laser brazing welds without macroscopic defects.

[0093] The cross-sectional morphology of each embodiment shows that the upper aluminum alloy test plate 1 and the aluminum alloy welding wire 3 melt, while the interface of the lower high-strength steel test plate 4 remains flat and shows no signs of melting. This characteristic is consistent with the joining mechanism of fusion brazing. Through this mechanism, the molten aluminum alloy wets and spreads on the surface of the solid steel, increasing the effective bonding area, while avoiding the excessive entry of iron atoms into the molten pool due to the melting of the steel matrix, thereby inhibiting the excessive formation of brittle Fe-Al intermetallic compounds.

[0094] The mechanical locking structure, consisting of the friction plug welded rivet 5 and the friction plug welded fusion zone 7, provides pre-tightening and positioning for subsequent laser welding, effectively suppressing thermal deformation during the welding process. The resulting laser brazed weld 6 supplements the strength at the online connection level and metallurgically seals the gap between the plates. This structure not only increases the load-bearing area of ​​the joint but also blocks the intrusion channel of corrosive media.

[0095] Test Example 2: Tensile Shear Performance Test

[0096] Experimental steps:

[0097] The specimens prepared in Examples 1-3 and Comparative Examples 1-5 were selected and subjected to tensile shear tests using an electronic universal testing machine according to GB / T2651-2008. Three parallel specimens were prepared for each group. The testing machine clamped both ends of the specimen and applied a tensile load at a rate of 2 mm / min at room temperature until the specimen fractured, and the load displacement data were recorded. The maximum tensile shear force of each specimen was extracted from the data.

[0098] Experimental data:

[0099] The maximum failure load data of each group of specimens measured in the tensile shear test are summarized in Table 2.

[0100] Table 2. Tensile shear property test data of each group of specimens

[0101] in conclusion:

[0102] The average failure load of the joint in Example 2 was 13.4 kN, which was higher than that of Comparative Example 1 (5.8 kN) using only friction plug welding and Comparative Example 3 (7.9 kN) using only laser brazing. This indicates that there is a synergistic effect between the laser brazed weld 6 and the friction plug welded rivet 5 during the load-bearing process. The laser brazed weld 6 shares part of the shear load and constrains the deformation of the base material around the friction plug welded rivet 5.

[0103] Compared to Comparative Example 2 (12.1 kN) with closely spaced rivets, Example 2 exhibits approximately 10.7% higher strength, while reducing the number of friction plug rivets 5 by more than 50%. Compared to Comparative Example 4 (13.1 kN) which uses adhesive sealing, Example 2 achieves similar strength without requiring curing time and with a shorter process flow.

[0104] The joint strength of Comparative Example 5 (excessively high laser power) was the lowest (3.7 kN), and the fracture mode was brittle fracture of the laser-welded weld 6. Excessive heat input caused the high-strength steel test plate 4 to melt, forming a thick and continuous brittle Fe-Al intermetallic compound layer at the interface. This result indicates that controlling the heat input to achieve a fusion brazing mechanism where aluminum melts but steel does not, is a necessary process condition for obtaining high-strength aluminum-steel joints.

[0105] Test Example 3: Air tightness and corrosion resistance test

[0106] Experimental steps:

[0107] Air tightness and corrosion resistance tests were conducted on each group of samples. The air tightness test employed the bubble method: one end of the sample was sealed, and compressed air at 0.1 MPa was introduced. The sample was then immersed in water, and the presence of continuous bubbles within one minute was observed. The corrosion resistance test was conducted according to GB / T10125-2021, performing a 72-hour neutral salt spray test. After the test, the corrosion at the lap joint between aluminum alloy sample 1 and high-strength steel sample 4 was observed.

[0108] Table 3. Test results of sealing performance and corrosion resistance of each group of samples.

[0109] in conclusion:

[0110] Test results show that the samples of Examples 1-3, Comparative Examples 3 and 4 did not show air leakage or crevice corrosion, while the samples of Comparative Examples 1, 2 and 5 failed.

[0111] The continuous laser-welded seam 6 constitutes a physical barrier, which is the basis for achieving sealing performance. Comparative Examples 1 and 2, being purely mechanical connections, suffer from sealing failure due to interfacial gaps. Comparative Example 5 also fails to form an effective seal due to microscopic cracks caused by brittle phases within the laser-welded seam 6, indicating that the formation of a dense laser-welded seam 6 depends on the control of the brazing process window.

[0112] While Comparative Example 3 (pure laser welding) and Comparative Example 4 (adhesive sealing) also possess sealing properties, the former lacks sufficient mechanical properties, and the latter requires an additional adhesive curing process. The composite process of this invention achieves both structural connection and sealing in a single process, balancing joint strength and production efficiency.

[0113] Test Example 3: Evaluation of Lightweighting Effect

[0114] Experimental steps:

[0115] The joining weight gain of the samples in Examples 1-3 and Comparative Examples 1-3 was calculated. The joining weight gain includes the mass of the friction plug welded rivet 5 and the mass of the deposited aluminum alloy welding wire 3. The mass of the friction plug welded rivet 5 is the product of the standard mass of a single friction plug welded rivet 5 and the number of rivets. The mass of the deposited aluminum alloy welding wire 3 is calculated according to the formula... Calculation, where The density of aluminum alloy welding wire 3, The cross-sectional area of ​​aluminum alloy welding wire 3 is... For wire feeding speed, The length of laser brazing weld 6 is 100mm. This refers to the welding speed.

[0116] Experimental data:

[0117] The additional weight data generated by each group of specimens in achieving the connection function are summarized in Table 4. For ease of comparison, the average tensile shear force obtained in the preceding tests is also listed in the table.

[0118] Table 4. Weight gain and corresponding mechanical properties of each group of samples after connection.

[0119] Example 1 9.5 4.05 1.62 5.67 Example 2 13.4 4.05 2.51 6.56 Example 3 16.5 6.08 3.48 9.56 Comparative Example 1 5.8 4.05 0.00 4.05 Comparative Example 2 12.1 10.13 0.00 10.13 Comparative Example 3 7.9 0.00 2.51 2.51

[0120] in conclusion:

[0121] Data shows that the connection weight gain in Example 2 was 6.56g, and the strength was 13.4kN; to achieve a strength of 12.1kN, the connection weight gain in Comparative Example 2 was 10.13g. While achieving higher strength, the weight gain in Example 2 was 35% lower than that in Comparative Example 2.

[0122] In this composite connection process, the laser-brass weld 6 and the friction plug weld rivet 5 share the load. The presence of the laser-brass weld 6 distributes part of the shear load, thus reducing the number of friction plug weld rivets 5 and lowering the overall structural weight without affecting the overall load-bearing capacity of the joint. Comparative Example 2, as a purely mechanical connection, has strength dependent on the density of the friction plug weld rivets 5, leading to an increase in weight. Comparative Example 1 (sparse friction plug weld rivets 5) and Comparative Example 3 (pure laser-brass weld), although showing smaller weight increases, fail to meet structural requirements in terms of mechanical properties.

[0123] This composite process reduces the overall weight of the connection structure while meeting the same mechanical performance requirements by distributing the load between the mechanical connection points and the metallurgical connection lines.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a composite connection of dissimilar aluminum and steel materials, characterized in that, Includes the following steps: S1. Place the aluminum alloy plate (1) on the upper side of the steel plate (4) and overlap it to form an overlap piece. The overlap length of the overlap piece is 30-50mm. S2. Friction plug welding is performed on the overlapping area of ​​the overlapping parts to form a point connection consisting of friction plug welding rivets (5) and friction plug welding fusion area (7). The friction plug welding is performed along the center line of the overlapping area. The spindle speed of the friction plug welding is 4000-8000r / min, the axial pressure is 6-9kN, and the spacing between adjacent friction plug welding rivets (5) is 50-80mm. S3. For the lap joint after step S2, laser brazing is performed along the lap edge of the aluminum alloy plate (1) of the lap joint to form a laser brazing weld (6) as a line connection. The line connection is a sealing weld, that is, the laser brazing weld (6) is used to seal the lap gap between the aluminum alloy plate (1) and the steel plate (4). The line connection and the point connection together constitute a composite connection of aluminum and steel dissimilar materials. The laser brazing uses Al-Si aluminum alloy welding wire (3) as filler material. The laser power of the laser brazing is 1-4kW, the wire feeding speed is 2-5m / min, and the welding speed is 2-7mm / s. The laser heat input is controlled by the coordinated regulation of the laser power, wire feeding speed and welding speed, so that the aluminum alloy plate (1) and the aluminum alloy welding wire (3) melt, while the steel plate (4) does not melt, forming a brazing connection.

2. The method for manufacturing a composite connection of dissimilar aluminum and steel materials according to claim 1, characterized in that, Prior to step S1, a pretreatment step is included for the surfaces of the aluminum alloy plate (1) and the steel plate (4) to be joined. The pretreatment step includes: The surfaces to be joined are sanded with sandpaper and then ultrasonically cleaned with an organic solvent.

3. The method for manufacturing a composite connection of dissimilar aluminum and steel materials according to claim 1, characterized in that, In step S2, the spindle speed of the friction plug riveting is 5500-6500 r / min, the axial pressure is 7-8 kN, and the spacing between adjacent friction plug riveting rivets (5) is 60-70 mm.

4. The method for manufacturing a composite connection of dissimilar aluminum and steel materials according to claim 3, characterized in that, In step S3, the laser power of the laser brazing is 2-3kW, the wire feeding speed is 3-4m / min, and the welding speed is 4-5mm / s.

5. The method for manufacturing a composite connection of dissimilar aluminum and steel materials according to claim 1, characterized in that, The aluminum alloy plate (1) is a 6000 series aluminum alloy.

6. The method for manufacturing a composite connection of dissimilar aluminum and steel materials according to claim 1, characterized in that, The steel plate (4) is hot-formed steel.

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