A composite welding process for joining dissimilar aluminum and copper metals

Abstract

This application relates to the field of welding technology. Specifically, it relates to a composite welding process for connecting dissimilar aluminum and copper metals. An embodiment of this application provides a composite welding process for connecting dissimilar aluminum and copper metals, which includes: Step S1, cleaning the aluminum metal and copper metal to remove oxide scales; Step S2, splicing the aluminum metal and copper metal to form a welding area; Step S3, simultaneously performing laser welding and cold welding. On the premise of ensuring low heat input, it effectively increases the penetration depth of the welding, enhances the mechanical properties at the welded seam, and achieves high-quality and high-strength connection between dissimilar aluminum and copper metals.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and in particular to a composite welding process for connecting dissimilar metals of aluminum and copper. Background Art

[0002] With the rapid development of new energy vehicles, the battery technology that supports it has also developed rapidly. In order to reduce costs, the batteries of new energy vehicles use a large number of batteries for module connection. The connection between the modules uses copper connectors to connect the copper and aluminum positive and negative electrodes, which will inevitably cause reactions between dissimilar metals and increase the loss of power transmission. If dissimilar metal connectors can be used, the reaction between copper and aluminum can be effectively avoided.

[0003] Aluminum and copper have quite different physical and chemical properties, and there are many difficulties to overcome during welding. First, aluminum is prone to oxidation during welding, which affects the fusion of the filler metal and the base material. Second, aluminum and copper are sensitive to heat input during welding, and a variety of intermetallic compounds will be produced. These intermetallic compounds will greatly weaken the joint performance. Third, the residual stress is serious during the welding of aluminum and copper dissimilar metals, and cracks are prone to occur. Fourth, due to the good thermal conductivity of aluminum and copper, the welding pool cooling block, the gas generated during welding has no time to escape the gas, and pores are prone to occur.

[0004] Laser welding is a welding method that uses a focused laser beam as energy to generate heat to bombard the weldment. Due to the optical properties of lasers such as refraction and focusing, laser welding is very suitable for welding micro parts and parts with poor accessibility. Laser welding has high welding speed, accuracy, reliability and quality, but aluminum alloy has a low absorption rate for lasers, and a large amount of lasers will be reflected by aluminum alloys. Therefore, in actual production, high-energy-density laser beams or composite welding methods are often used to achieve aluminum alloy welding connections. As a result, low-boiling-point alloy elements are severely heated and welding strength is reduced.

[0005] Cold welding is a process that uses mechanical force, molecular force or electricity to diffuse the welding material to the surface of the equipment. Because the hardness, adhesion and strength of cold welding flux are particularly high, there is almost no shrinkage rate, and it can reliably prevent many chemical effects, physical stresses and mechanical stresses, etc., so people call it "liquid metal". The heat input of cold welding is small and the heat input is controllable, but its overall heat input is unstable compared to laser welding, and the molten pool depth is small. If the heat input is increased, the weld will also become wider.

[0006] Under certain process conditions, the process of effectively combining two or more materials with different physical and chemical properties is called dissimilar material composite welding. At present, scholars at home and abroad have carried out research on various welding methods such as hybrid welding for laser welding and achieved good welding results, which also provides a new direction for the welding of aluminum-copper dissimilar metals. Laser welding has a high welding speed, high precision and reliability quality, small cold welding heat input and controllable heat input. If the two are combined, the disadvantages of using laser welding or cold welding alone can be eliminated. However, at present, there are very few welding processes that use laser welding and cold welding in combination at home and abroad. Summary of the Invention

[0007] The purpose of this application is to provide a composite welding process for connecting aluminum-copper dissimilar metals, which effectively improves the welding penetration depth while ensuring low heat input, strengthens the mechanical properties of the welded joint, and realizes high-quality and high-strength connection between aluminum-copper dissimilar metals.

[0008] This application solves its technical problems by adopting the following technical solutions.

[0009] The embodiment of this application provides a composite welding process for connecting aluminum-copper dissimilar metals, which includes:

[0010] Step S1, clean the aluminum metal and copper metal to remove the oxide scale;

[0011] Step S2, splice the aluminum metal and copper metal to form a welding area;

[0012] Step S3, perform laser welding and cold welding simultaneously.

[0013] Compared with the prior art, the embodiment of this application has at least the following advantages or beneficial effects:

[0014] 1. This application proposes a composite welding process for connecting aluminum-copper dissimilar metals, which realizes the connection between aluminum-copper dissimilar metals, effectively avoids the reaction of dissimilar metals during the connection of battery modules, and effectively improves the power transmission efficiency.

[0015] 2. The composite welding process for connecting aluminum-copper dissimilar metals proposed in this application can achieve high-quality and high-strength connection between aluminum-copper dissimilar metals. Under low heat input, a large penetration depth is obtained, the tensile strength is high, and the wire performance at the joint is good, which can meet the industry standard (the tensile strength can reach 90 MPa, and the conductivity at the joint can reach more than 80% of that of pure copper connectors). Description of the Drawings

[0016] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic diagram of a composite welding process for connecting dissimilar aluminum and copper metals provided in Embodiment 1 of the present application.

[0018] Reference numerals: 1 - cold welding equipment, 2 - laser, 3 - copper metal, 4 - aluminum metal. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application. For those conditions not specified in the embodiments, they shall be carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchases.

[0020] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will refer to specific embodiments to detail the present application.

[0021] The embodiments of the present application provide a composite welding process for connecting dissimilar aluminum and copper metals, which includes:

[0022] Step S1, cleaning the aluminum metal and the copper metal to remove the oxide scale;

[0023] Step S2, splicing the aluminum metal and the copper metal to form a welding area;

[0024] Step S3, performing laser welding and cold welding simultaneously.

[0025] The atomic number of aluminum is relatively forward, and its chemical properties are active, making it extremely prone to oxidation. At room temperature, a dense oxide film will quickly form on the surface of aluminum, and its main component is aluminum oxide (Al 2 O 3 ), which hinders the continuous oxidation. Moreover, the melting point of Al 2 O 3 is much higher than the melting points of aluminum and copper, affecting the welding. The presence of Al 2 O 3 will also affect the fusion of the filler metal and the base metal. Therefore, certain measures need to be taken before and during welding to remove the oxide film and inhibit the generation of the oxide film.

[0026] The presence of scale will affect the strength and plasticity of the joint and also the smoothness of the welded area. Therefore, before splicing, the scale on the surfaces of aluminum and copper metals needs to be removed. Then, the aluminum and copper metals are spliced in the welding area, and subsequently, laser welding and cold welding are used for welding.

[0027] Laser welding has high welding speed, precision, and reliability quality. However, aluminum metal has a low absorption rate of laser, and a large amount of laser will be reflected. If a laser beam with a high energy density is used, the low-boiling-point aluminum metal will heat up severely, greatly reducing the welding strength and affecting the appearance of the welded area. Therefore, laser welding is not suitable for welding aluminum metal. Cold welding has a small heat input and the heat input can be controlled, but the overall heat input is unstable, the molten pool depth is small, and the joint strength is low. This application adopts a method of composite welding of laser welding and cold welding, attempting to further reduce the heat input and reduce the requirement for the precision of the welding position. The composite welding of laser welding and cold welding can effectively increase the penetration depth of welding and strengthen the mechanical properties of the welded seam while ensuring a low heat input, and it has a fast welding speed and high precision. The aluminum-copper dissimilar metal spliced part prepared by the composite welding process of this application can meet the requirements of industry standards in terms of the compressive strength of the joint and the electrical conductivity of the joint.

[0028] In some embodiments of this application, the above-mentioned aluminum metal includes aluminum or aluminum alloy, and the above-mentioned copper metal includes copper or copper alloy.

[0029] The composite welding process of this application can be applicable to the welding between aluminum and copper, aluminum and copper alloy, aluminum alloy and copper, and aluminum alloy and copper alloy.

[0030] In some embodiments of this application, in the above-mentioned step S1, the step of removing the scale includes: removing the scale on the surfaces of aluminum and copper metals, and then adding an organic solvent to an ultrasonic instrument, cleaning, and drying.

[0031] Methods for removing scale include mechanical methods, chemical methods, electro-chemical methods, etc. Mechanical methods include polishing, rolling, high-pressure water flushing, brushing, shot (peening) blasting, sandblasting, scale breaking, etc. Chemical methods use chemical substances such as acids and alkalis to react with the iron scale on the surface of steel materials to remove the scale. Chemical substances generally use strong acids and alkalis such as sulfuric acid, hydrochloric acid, nitric acid, and hydrofluoric acid. Electro-chemical pickling is to place the parts in an electrolyte and pass direct current to achieve the purpose of rust removal through chemical reactions.

[0032] Ultrasonic cleaning has high efficiency and good effect. Ultrasonic cleaning is based on the unique "cavitation effect" physical action when ultrasonic waves are transmitted in the cleaning liquid medium. The "cavitation effect" forms microscopic strong shock waves and high-speed jets acting on the surface of the object to be cleaned, so that the dirt is quickly crushed and peeled off, achieving the purpose of high-quality and high-efficiency cleaning. The ultrasonic wave expands negatively and compresses and explodes countless "cavities" strongly under positive pressure tens of thousands of times per second, generating countless microscopic shock waves at high frequencies. Therefore, the ultrasonic wave has strong cleaning ability and high cleaning efficiency for the complex inner and outer surface shapes, narrow slits, deep holes, corners, dead corners and other parts of the object to be cleaned immersed in the cleaning liquid, and the cleaning effect is good, which is beneficial to forming a smooth surface during welding.

[0033] The organic solvent cooperates with the ultrasonic cleaner to oscillate, causing a large number of small bubbles to be generated in the solvent. These small bubbles generate a strong mechanical force when forming, growing and precipitating, prompting the grease and dirt adhering to the surface of the workpiece to quickly separate, thus accelerating the cleaning process, shortening the cleaning time, and making the degreasing more rapid and thorough.

[0034] The organic solvent can be acetone, gasoline, petroleum solvent, turpentine, xylene, dichloroethane, trichloroethylene, tetrachloroethylene, etc. It has strong solubility, is not flammable, has low toxicity, is easy to operate, and has good effect on cleaning oil stains.

[0035] It should be noted that emulsification degreasing method, alkaline solution degreasing method, etc. can also be adopted to remove the oil stains on the metal surface.

[0036] In some embodiments of the present application, the welding speed of the above laser welding is 1.9 - 2.1 mm / s.

[0037] Under this parameter, the heat input generated by the coupling of the laser and the arc is stable, and a weld with stable welding quality can be obtained.

[0038] In some embodiments of the present application, the defocus amount of the above laser welding is 0 - 0.5 mm.

[0039] The defocus amount is the distance between the laser focus and the working substance. During the welding process, the defocus amount has a great influence on the welding quality. Laser welding usually requires a certain defocus amount because the power density at the center of the light spot at the laser focus is too high and it is easy to evaporate into holes. On each plane away from the laser focus, the power density distribution is relatively uniform. The defocus amount is directly related to the power density of the laser acting on the workpiece. During the laser heat treatment process, the defocus amount has a direct impact on the heat treatment effect. When the defocus amount is too large, the power density acting on the workpiece is too low to achieve the purpose of processing the workpiece; when the defocus amount is too small, the power density acting on the workpiece is too high, and it is easy to melt the laser irradiation point and damage the surface of the workpiece.

[0040] In this application, the defocus amount is set to 0 - 0.5 mm. In this way, the cold welding current can be effectively coupled with the laser, enabling the workpiece to be processed without damaging the surface of the workpiece.

[0041] In some embodiments of this application, the offset copper amount for the above laser welding is 0.2 - 0.4 mm.

[0042] When the melting points of two materials differ greatly, it will cause the metal on one side not to melt while the metal on the other side has already started to flow, affecting their combination. Since the melting point of copper is higher than that of aluminum, if the laser and the cold welding current directly hit the joint of aluminum and copper, the aluminum metal will melt first. After the aluminum metal melts, it will cause large cracks at the joint, and even the splicing may not be successful. In this application, the offset copper amount is set to 0.2 - 0.4 mm. In this way, this situation can be avoided and a good welding effect can be ensured.

[0043] In some embodiments of this application, the welding power of the above laser welding is 350 - 400 W.

[0044] Generally, a relatively high power is required for laser welding to achieve the connection of two workpieces. When welding dissimilar metals of aluminum and copper, due to the relatively high welding power, various intermetallic compounds are often generated at the joint. The existence of these hard and brittle intermetallic compounds will greatly weaken the joint performance. When laser welding is combined with cold welding, the power of laser welding is relatively low, which can effectively reduce the generation of intermetallic compounds at the joint. When the welding power is between 350 - 400 W, not only the generation of intermetallic compounds at the joint is reduced, but also the welding of dissimilar metals of aluminum and copper can be achieved, and the heat input generated by the coupling of the laser and the arc is stable, and a weld with stable welding quality can be obtained.

[0045] In some embodiments of this application, the above cold welding current is 75 - 85 A, the welding pulse interval of the above cold welding is 35 - 45 ms, and the welding action time of the above cold welding is 25 - 35 ms.

[0046] In this application, the parameters of the cold welding equipment are set as follows: the cold welding current is 75 - 85 A, the welding pulse interval of cold welding is 35 - 45 ms, and the welding action time of cold welding is 25 - 35 ms. Under the above parameters, the heat input generated by the coupling of the laser and the arc is stable, and a weld with stable welding quality can be obtained.

[0047] It should be noted that the welding action time can be adjusted according to the weld length or can also be set by automated integration.

[0048] In some embodiments of this application, in the above step S3, it further includes: protecting the above welding area with an inert medium.

[0049] Inert medium protection refers to the process of inerting media, places, operations, and areas with explosion and combustion risks using inert media. Commonly used inert media in industry are generally nitrogen, carbon dioxide, water vapor, flue gas, etc.

[0050] The melting points of aluminum and copper differ by nearly 400°C. During fusion welding, aluminum easily undergoes a violent oxidation reaction with air, generating impurities such as oxides and nitrides. The presence of impurities will affect the fusion between the filler metal and the base metal, and the strength and plasticity of the joint. Therefore, it is necessary to use inert medium protection for the operation area to inhibit the generation of impurities.

[0051] In some embodiments of the present application, the flow rate of the above-mentioned inert medium is 5 - 10 L / min.

[0052] If the flow rate of the inert medium is too small, it cannot effectively avoid the generation of impurities. If the flow rate is too large, it will cause waste. When the flow rate of the inert medium is 5 - 10 L / min, it can better inhibit the oxidation reaction between the metal and air.

[0053] The features and performance of the present application will be further described in detail below in conjunction with embodiments.

[0054] Example 1

[0055] As Figure 1 shown, composite welding is performed on aluminum metal 4 and copper metal 3.

[0056] Specifically, laser 2 welding and cold welding are used for composite welding of 6061 aluminum alloy and T2 copper with a specification of 60*60*1.5 (mm).

[0057] Step S1: Use a stiff brush at a 45° angle to the plate to remove the oxide scale on the surfaces of the aluminum alloy plate and the copper plate. Add acetone to the ultrasonic instrument to clean the oil stains on the surfaces of the aluminum alloy and copper, then perform a drying process, and keep the surface of the welding sample clean and dry.

[0058] Step S2: Assemble the aluminum alloy plate in the welding area through a mechanical device. The assembly method is splicing without gaps, and accurately align the aluminum alloy and copper plates through welding jigs.

[0059] Step S3: Program the welding operation trajectory and start welding. The laser 2 welding parameters are set as laser 2 leading, welding speed is 1.9 mm / s, defocus rate is 0 mm, welding power is 350 W, and the offset copper amount is 0.2 mm. The parameters of cold welding device 1 are set as: cold welding current is 75 A, cold welding pulse interval is 35 ms. The welding action time of cold welding is 25 ms. During the welding process, inert gas protection is used for the welding area, and the flow rate of the inert medium is 5 L / min.

[0060] Example 2

[0061] Laser 2 welding and cold welding are used for the composite welding of 6061 aluminum alloy and T2 copper with the specification of 60*60*1.5 (mm).

[0062] Step S1: Use a wire brush at an angle of 50° to the plate to remove the oxide scale on its surface. Add xylene to the ultrasonic instrument to clean the oil stain on the surface of the aluminum alloy, then perform a drying treatment, and keep the surface of the welding sample clean and dry.

[0063] Step S2: Assemble the aluminum alloy plate in the welding area through a mechanical device. The assembly method is splicing without gaps, and accurately butt-joint the aluminum alloy and copper plate through a welding fixture.

[0064] Step S3: Program the welding operation trajectory and start welding. The laser 2 welding parameters are set as laser 2 leading, the welding speed is 2.1 mm / s, the defocusing rate is 0.2 mm, the welding power is 390 W, the offset copper amount is 0.4 mm, and the parameters of cold welding equipment 1 are set as: the cold welding current is 85 A, and the cold welding pulse interval is 45 ms. The welding action time of cold welding is 30 ms. During the welding process, the welding area is protected by an inert gas, and the flow rate of the inert medium is 7 L / min.

[0065] Example 3

[0066] Laser 2 welding and cold welding are used for the composite welding of 6061 aluminum alloy and T2 copper with the specification of 60*60*1.5 (mm).

[0067] Step S1: Use a grinding machine to remove the oxide scale on the surfaces of the aluminum alloy plate and the copper plate. Add acetone to the ultrasonic instrument to clean the oil stain on the surface of the aluminum alloy, then perform a drying treatment, and keep the surface of the welding sample clean and dry.

[0068] Step S2: Assemble the aluminum alloy plate in the welding area through a mechanical device. The assembly method is splicing without gaps, and accurately butt-joint the aluminum alloy and copper plate through a welding fixture.

[0069] Step S3: Program the welding operation trajectory and start welding. The laser 2 welding parameters are set as laser 2 leading, the welding speed is 2.0 mm / s, the defocusing rate is 0.5 mm, the welding power is 400 W, the offset copper amount is 0.3 mm, and the parameters of cold welding equipment 1 are set as: the cold welding current is 80 A, and the cold welding pulse interval is 40 ms. The welding action time of cold welding is 35 ms. During the welding process, the welding area is protected by an inert gas, and the flow rate of the inert medium is 10 L / min.

[0070] Example 4

[0071] Laser 2 welding and cold welding are used for composite welding of aluminum plates and copper alloy plates with a specification of 60*60*1.5 (mm).

[0072] Step S1: Immerse the aluminum plates and copper alloy plates in sodium hydroxide to remove the oxide scale on their surfaces. Add gasoline to the ultrasonic instrument to clean the oil stains on the surfaces of the aluminum plates and copper plates, then perform a drying process and keep the surfaces of the welded samples clean and dry.

[0073] Step S2: Assemble the aluminum alloy plates in the welding area through a mechanical device. The assembly method is splicing without gaps, and accurately align the aluminum alloy and red copper plates through welding jigs.

[0074] Step S3: Program the welding operation trajectory and start welding. The laser 2 welding parameters are set as laser 2 leading, welding speed is 2.0 mm / s, defocus rate is 0 mm, welding power is 360 W, and the offset copper amount is 0.2 mm. The parameters of cold welding equipment 1 are set as: cold welding current is 78 A, cold welding pulse interval is 43 ms. The welding action time of cold welding is 31 ms. During the welding process, the welding area is protected by inert gas, and the flow rate of the inert medium is 6 L / min.

[0075] Example 5

[0076] Laser 2 welding and cold welding are used for composite welding of aluminum plates and copper plates with a specification of 60*60*1.5 (mm).

[0077] Step S1: Use a grinder to remove the oxide scale on the surfaces of the aluminum plates and copper plates. Add acetone to the ultrasonic instrument to clean the oil stains on the surfaces of the aluminum plates and copper plates, then perform a drying process and keep the surfaces of the welded samples clean and dry.

[0078] Step S2: Assemble the aluminum alloy plates in the welding area through a mechanical device. The assembly method is splicing without gaps, and accurately align the aluminum alloy and red copper plates through welding jigs.

[0079] Step S3: Program the welding operation trajectory and start welding. The laser 2 welding parameters are set as laser 2 leading, welding speed is 2.0 mm / s, defocus rate is 0.3 mm, welding power is 380 W, and the offset copper amount is 0.2 mm. The parameters of cold welding equipment 1 are set as: cold welding current is 83 A, cold welding pulse interval is 42 ms. The welding action time of cold welding is 32 ms. During the welding process, the welding area is protected by inert gas, and the flow rate of the inert medium is 7 L / min.

[0080] Comparative example

[0081] Laser 2 welding is performed on 6061 aluminum alloy and T2 red copper with a specification of 60*60*1.5 (mm).

[0082] Step S1: Use a steel brush at a 45° angle to the sheet metal to remove the oxide scale on the surfaces of the aluminum alloy sheet and the copper sheet. Add acetone to an ultrasonic instrument to clean the oil stains on the surfaces of the aluminum alloy and the copper, then perform a drying process and keep the surface of the welded sample clean and dry.

[0083] Step S2: Assemble the aluminum alloy sheet in the welding area through a mechanical device. The assembly method is splicing without gaps, and accurately butt-joint the aluminum alloy and the copper sheet through a welding fixture.

[0084] Step S3: Program the welding operation trajectory and start welding. Set the parameters of the laser 2 welding equipment as follows: welding time 35 ms, welding pulse interval 45 ms, welding current 160 A, and copper offset 0.2 mm.

[0085] Experimental Example

[0086] Use a universal material testing machine to detect the compressive strength of the aluminum-copper dissimilar metal spliced plates prepared in Examples 1-5 and the comparative example. Each group is repeated 3 times, and the results are shown in Table 1.

[0087] Table 1 Test results of compressive strength in Examples 1-5 and the comparative example

[0088]

[0089]

[0090] The tensile strength is the maximum nominal tensile stress that the specimen bears before being pulled apart. It is the critical value for the transition of the metal from uniform plastic deformation to local concentrated plastic deformation, and also the maximum load-bearing capacity of the metal under static tensile conditions. The experimental results show that the tensile strength at the joints of the aluminum-copper dissimilar metal spliced parts prepared in Examples 1-5 is greater than 90 Mpa, meeting the relevant requirements of the industry standard. The tensile strength at the joints of the aluminum-copper dissimilar metal spliced parts prepared in the comparative example is only 45.3 Mpa. As can be seen from Table 1, when using laser welding alone, the tensile strength at the joints is relatively small, unable to meet the requirements of the industry standard, and the weld seam is relatively large. In the case of using laser welding alone, the required welding current is relatively large, and the heat output is higher than that required for composite welding, affecting the welding effect.

[0091] In summary, the embodiment of the present application proposes a composite welding process for connecting aluminum-copper dissimilar metals, realizing the connection between aluminum-copper dissimilar metals, effectively avoiding the occurrence of dissimilar metal reactions during the connection of battery modules, and effectively improving the power transmission efficiency.

[0092] A composite welding process for connecting aluminum and copper dissimilar metals proposed in this application can achieve high-quality and high-strength connection between aluminum and copper dissimilar metals. At a low heat input, a large penetration depth is obtained, and the tensile strength is high. The wire performance at the joint is good and can meet the industry standards (the tensile strength can reach 90 MPa, and the electrical conductivity at the joint can reach more than 80% of that of pure copper connectors).

[0093] A composite welding process for connecting aluminum and copper dissimilar metals proposed in this application adopts a composite welding process combining laser welding and cold welding. The heat input is low, which can effectively reduce the generation of intermetallic compounds and ensure the penetration depth and strength at the splicing part.

[0094] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of this application claimed, but merely represents selected embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts fall within the scope of protection of this application.

Claims

1. A composite welding process for joining dissimilar aluminum and copper metals, characterized in that, it includes: Step S1, cleaning the aluminum metal and the copper metal to remove the oxide scale; Step S2, splicing the aluminum metal and the copper metal to form a welding area; Step S3, performing laser welding and cold welding simultaneously; The offset copper amount of the laser welding is 0.2 - 0.4 mm.

2. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, the aluminum metal includes aluminum or aluminum alloy, and the copper metal includes copper or copper alloy.

3. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, in the step S1, the step of removing the oxide scale includes: removing the oxide scale on the surfaces of the aluminum metal and the copper metal, and then adding an organic solvent into an ultrasonic instrument, cleaning, and drying.

4. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, the welding speed of the laser welding is 1.9 - 2.1 mm / s.

5. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, the defocus amount of the laser welding is 0 - 0.5 mm.

6. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, the welding power of the laser welding is 350 - 400 W.

7. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, the current of the cold welding is 75 - 85 A, the welding pulse interval is 35 - 45 ms, and the welding action time of the cold welding is 25 - 35 ms.

8. The composite welding process for joining dissimilar aluminum and copper metals according to claim 1, characterized in that, in the step S3, it further includes: protecting the welding area with an inert medium.

9. The composite welding process for joining dissimilar aluminum and copper metals according to claim 8, characterized in that, the flow rate of the inert medium is 5 - 10 L / min.

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