Resistance spot welding method for aluminum alloys

Abstract

This invention provides a resistance spot welding method for aluminum alloys. The method includes the following steps: Step S1, applying a first pressure to the area to be welded on the aluminum alloy using a welding electrode; Step S2, while maintaining the applied first pressure, rotating the welding electrode to break down the oxide film on the surface of the area to be welded; Step S3, adjusting the pressure of the welding electrode to a second pressure; Step S4, welding the aluminum alloy under the second pressure using the welding electrode to obtain a welded aluminum alloy. In Step S2, rotating the welding electrode causes it to slide against the surface of the aluminum alloy, which helps to break down the coating and oxide layer on the surface of the aluminum alloy, thereby reducing the contact resistance between the welding electrode and the aluminum alloy. The resistance spot welding method of this application is free from defects such as spatter, cracks, keyholes, and incomplete fusion, and the method is simple to operate and low in cost.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a resistance spot welding method for aluminum alloys. Background Technology

[0002] With the rapid development of the automotive industry, lightweighting has become a crucial trend in automotive design. Aluminum alloys, as a lightweight and high-strength material, are gradually replacing traditional steel and becoming one of the key materials in automobile manufacturing. The application of aluminum alloys not only reduces vehicle weight and improves fuel efficiency but also reduces emissions, meeting environmental protection requirements. Resistance spot welding, as a highly efficient welding process, is widely used in aluminum alloy body manufacturing due to its advantages of low cost, high speed, and high connection strength. However, during the application of resistance spot welding technology for aluminum alloys, a dense alumina film easily forms between the aluminum alloy and the air. This oxide film hinders the transmission of current, affecting the weld quality.

[0003] Currently, there are several ways to improve the quality of aluminum alloy resistance spot welding: (1) Before welding, the oxide film is removed by sanding the surface of the aluminum alloy plate with sandpaper, cleaning with alcohol or acetone, etc. However, the surface of the aluminum alloy plate is very easy to oxidize again after sanding and cleaning. This process solution cannot be effectively implemented and applied in industrial production; (2) For example, General Motors designed an electrode cap with a raised shape, which can puncture the oxide film during the welding process, thereby stabilizing the welding process. This method requires the design of a special electrode cap and a special grinding device, which brings additional costs. At the same time, due to the design of the raised electrode cap, there will be special marks on the surface of the weld after welding due to the raised design. Summary of the Invention

[0004] The main objective of this invention is to provide a resistance spot welding method for aluminum alloys, thereby solving the problem of difficulty in removing the oxide film from aluminum alloys in existing resistance spot welding methods.

[0005] To achieve the above objectives, according to one aspect of the present invention, a resistance spot welding method for aluminum alloy is provided, the resistance spot welding method comprising the following steps: step S1, applying a first pressure to the area to be welded of the aluminum alloy to be welded using a welding electrode; step S2, rotating the welding electrode while maintaining the applied first pressure to break the oxide film on the surface of the area to be welded; step S3, adjusting the pressure of the welding electrode to a second pressure; step S4, welding the aluminum alloy to be welded using the welding electrode under the second pressure to obtain a welded aluminum alloy.

[0006] Furthermore, the aforementioned first pressure is 1.0 to 3.0 kN.

[0007] Furthermore, the aforementioned rotation is performed along the circumference of the welding electrode; the rotation angle is ≥90°, preferably 90°~360°; or, the welding electrode is rotated back and forth with a rotation angle of 90°~180°.

[0008] Furthermore, the material of the welding electrode is copper or a copper alloy; preferably, the copper alloy is an alumina copper alloy or a chromium-zirconium copper alloy.

[0009] Furthermore, the above-mentioned welding electrode is a spherical welding electrode or a flat-head welding electrode; preferably, the arc radius of the arc-shaped welding end face of the spherical welding electrode is 20 to 100 mm; preferably, the diameter of the welding end face of the flat-head welding electrode is 4.0 to 8.0 mm.

[0010] Furthermore, the aforementioned second pressure is 2.5–5.0 kN.

[0011] Furthermore, the current for the above welding process is 20–35 kA; and / or the welding process time is 50–200 ms.

[0012] Furthermore, in step S1 above, after cleaning the aluminum alloy to be welded with an organic solvent, a first pressure is applied to the aluminum alloy to be welded; preferably, the organic solvent is alcohol and / or acetone.

[0013] Furthermore, the thickness of the aluminum alloy to be welded is 0.8 to 3.5 mm.

[0014] Furthermore, the aluminum alloy to be welded is either 5182 aluminum alloy or 6016 aluminum alloy.

[0015] Applying the technical solution of this invention, in step S1, a first pressure is applied to the area to be welded on the aluminum alloy using a welding electrode, which helps to achieve good contact between the welding electrode and the aluminum alloy. In step S2, rotating the welding electrode causes it to slide against the surface of the aluminum alloy, which helps to break down the coating and oxide layer on the surface of the aluminum alloy, thereby reducing the contact resistance between the welding electrode and the aluminum alloy. In step S3, the pressure of the welding electrode is adjusted to a second pressure suitable for welding, resulting in a weld nugget with a larger size at the weld point of the prepared aluminum alloy, which helps to improve the mechanical properties of the aluminum alloy. The resistance spot welding method of this application has no defects such as spatter, cracks, keyholes, and lack of fusion, and the method is simple to operate and has low cost. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A comparison diagram of the shear tensile load of welded aluminum alloy welds in Embodiment 1 and Comparative Example 1 of this application is shown. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] As analyzed in the background section of this application, there are several ways to improve the quality of aluminum alloy resistance spot welding: (1) Before welding, the oxide film is removed by sanding the surface of the aluminum alloy plate with sandpaper, cleaning with alcohol or acetone, etc. However, the surface of the aluminum alloy plate is very easy to re-oxidize after sanding and cleaning, and this process cannot be effectively implemented and applied in industrial production; (2) For example, General Motors designed an electrode cap with a raised shape, which can pierce the oxide film during the welding process, thereby stabilizing the welding process. This method requires the design of a special electrode cap and a special grinding device, which brings additional costs. At the same time, due to the design of the raised electrode cap, the surface of the weld point after welding will have special marks caused by the raised design. The existing aluminum alloy resistance spot welding method has the problem of difficulty in removing the oxide film of aluminum alloy. In order to solve the above problems, this application provides an aluminum alloy resistance spot welding method.

[0020] In a typical embodiment of this application, a resistance spot welding method for aluminum alloy is provided. The resistance spot welding method includes the following steps: Step S1, applying a first pressure to the area to be welded of the aluminum alloy using a welding electrode; Step S2, rotating the welding electrode while maintaining the applied first pressure to break the oxide film on the surface of the area to be welded; Step S3, adjusting the pressure of the welding electrode to a second pressure; Step S4, welding the aluminum alloy under the second pressure using the welding electrode to obtain a welded aluminum alloy.

[0021] In step S1, a first pressure is applied to the area of ​​the aluminum alloy to be welded using a welding electrode, which helps to ensure good contact between the welding electrode and the aluminum alloy. In step S2, rotating the welding electrode causes it to slide against the surface of the aluminum alloy, which helps to break down the coating and oxide layer on the surface of the aluminum alloy, thereby reducing the contact resistance between the welding electrode and the aluminum alloy. In step S3, the pressure of the welding electrode is adjusted to a second pressure suitable for welding, resulting in a weld nugget with a larger size at the weld point of the prepared aluminum alloy, which helps to improve the mechanical properties of the welded aluminum alloy. The resistance spot welding method of this application has no defects such as spatter, cracks, keyholes, and lack of fusion, and the method is simple to operate and has low cost.

[0022] In one embodiment of this application, the welding electrode is rotated by a welding robot.

[0023] In one embodiment of this application, the first pressure is 1.0 to 3.0 kN.

[0024] Excessive initial pressure can easily cause deformation of the aluminum alloy to be welded, while insufficient initial pressure is not conducive to the full destruction of the coating and oxide layer on the surface of the aluminum alloy. It is preferable to control the initial pressure within the above range, which helps to improve the mechanical properties of the aluminum alloy after welding while preventing deformation.

[0025] In one embodiment of this application, the rotation is performed along the circumference of the welding electrode; the rotation angle is ≥90°, preferably 90°~360°; or, the welding electrode is rotated back and forth at a rotation angle of 90°~180°.

[0026] Excessive rotation angle can easily lead to surface defects in aluminum alloys, while insufficient rotation angle is not conducive to the complete destruction of the coating and oxide layer on the aluminum alloy surface. It is preferable to control the rotation angle within the above-mentioned range, which helps to improve the mechanical properties of the welded aluminum alloy while maintaining the surface quality. The welding electrode can also be rotated back and forth at a small angle to destroy the coating and oxide layer on the surface of the aluminum alloy to be welded, preferably 2 to 4 times.

[0027] In order to further improve the mechanical properties of welded aluminum alloys, in one embodiment of this application, the material of the above-mentioned welding electrode is preferably copper or a copper alloy; the copper alloy is preferably an alumina copper alloy or a chromium zirconium copper alloy.

[0028] In one embodiment of this application, the welding electrode is a spherical welding electrode or a flat-head welding electrode; preferably, the arc radius of the arc-shaped welding end face of the spherical welding electrode is 20 to 100 mm; preferably, the diameter of the welding end face of the flat-head welding electrode is 4.0 to 8.0 mm.

[0029] Preferably controlling the arc radius of the arc welding end face of the spherical welding electrode and the diameter of the welding end face of the flat welding electrode within the above-mentioned range helps to ensure sufficient contact between the welding end face and the aluminum alloy to be welded, thereby helping to improve the efficiency of breaking the coating and oxide layer on the surface of the aluminum alloy to be welded.

[0030] In one embodiment of this application, the second pressure is 2.5 to 5.0 kN.

[0031] If the second pressure is too low, it will not be conducive to the formation of a larger weld nugget. If the second pressure is too high, it will easily cause deformation at the weld joint, which will not be conducive to improving the mechanical properties of the weld joint. It is preferable to control the second pressure within the above range, which will help improve the efficiency of resistance spot welding and increase the shear tensile load resistance at the weld joint.

[0032] In one embodiment of this application, the current for the welding process is 20-35 kA; and / or the welding process time is 50-200 ms.

[0033] Excessive welding current and prolonged welding time can easily lead to overmelting at the weld joint, while insufficient welding current and prolonged welding time can result in an undersized weld nugget. It is preferable to control the welding current and welding time within the above-mentioned ranges to help form a weld nugget of appropriate size, thereby helping to improve the mechanical properties of the welded aluminum alloy.

[0034] In one embodiment of this application, in step S1 above, after cleaning the aluminum alloy to be welded with an organic solvent, a first pressure is applied to the aluminum alloy to be welded; preferably, the organic solvent is alcohol and / or acetone.

[0035] Pretreatment of aluminum alloys to be welded with organic solvents helps remove grease and dirt from the surface, thereby improving the mechanical properties of the welded aluminum alloys.

[0036] In one embodiment of this application, the thickness of the aluminum alloy to be welded is 0.8 to 3.5 mm.

[0037] The resistance spot welding method of this application can handle aluminum alloys with a wide thickness range, especially for aluminum alloys with the above-mentioned thickness range, and can form a larger weld nugget.

[0038] In one embodiment of this application, the aluminum alloy to be welded is 5182 aluminum alloy or 6016 aluminum alloy.

[0039] The resistance spot welding method of this application can weld different types of aluminum alloys, and exhibits excellent welding performance, especially for the aforementioned types of aluminum alloys.

[0040] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0041] Examples 1-7, Comparative Examples 1-7

[0042] The surface of the aluminum alloy to be welded was cleaned with alcohol. A first pressure was applied to the area to be welded using a welding electrode. While maintaining the first pressure, the welding electrode was rotated circumferentially by a welding robot. After the electrode had rotated, the pressure was adjusted to a second pressure. Under the second pressure, a welding current was applied between the electrodes to weld the aluminum alloy. The second pressure was 2.5 kN, the welding current was 20 kA, and the welding time was 200 ms. The type of aluminum alloy, its thickness, the first pressure, the rotation angle, the welding electrode material, and the shape and dimensions of the welding electrode are shown in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] Example 8

[0047] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, thereby obtaining a welded aluminum alloy. The first pressure is 1.0 kN, and the welded aluminum alloy is finally obtained.

[0048] Example 9

[0049] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, thereby obtaining a welded aluminum alloy. The first pressure is 3.0 kN, and the final welded aluminum alloy is obtained.

[0050] Example 10

[0051] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, thereby obtaining a welded aluminum alloy. The first pressure is 0.5 kN, and the final welded aluminum alloy is obtained.

[0052] Example 11

[0053] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, thereby obtaining a welded aluminum alloy. The rotation angle is 360°, and the welded aluminum alloy is finally obtained.

[0054] Example 12

[0055] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, thereby obtaining a welded aluminum alloy. The rotation angle is 70°, and the welded aluminum alloy is finally obtained.

[0056] Example 13

[0057] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, resulting in a welded aluminum alloy with an arc radius of 20 mm.

[0058] Example 14

[0059] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated around the circumference of the welding electrode by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to perform welding, resulting in a welded aluminum alloy with an arc radius of 10 mm.

[0060] Example 15

[0061] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated circumferentially by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to weld the aluminum alloy, wherein the second pressure is 5.0 kN, the welding current is 35 kA, the welding time is 50 ms, and the final welded aluminum alloy is obtained.

[0062] Example 16

[0063] The difference from Example 1 is that alcohol is used to clean the surface of the aluminum alloy to be welded; a first pressure is applied to the welding area of ​​the aluminum alloy to be welded using a welding electrode; while maintaining the first pressure, the welding electrode is rotated circumferentially by a welding robot; after the welding electrode has rotated, the pressure of the rotated welding electrode is adjusted to a second pressure; under the second pressure, a welding current is applied between the welding electrodes to weld the aluminum alloy, wherein the second pressure is 2.3 kN, the welding current is 18 kA, the welding time is 250 ms, and the final welded aluminum alloy is obtained.

[0064] Comparative Example 8

[0065] The difference from Example 1 is that the surface of the aluminum alloy to be welded is cleaned with alcohol, and the welding position is polished with sandpaper; a second pressure is applied to the aluminum alloy to be welded using welding electrodes, and welding current is applied between the welding electrodes under the second pressure to weld the aluminum alloy. The second pressure is 2.5kN, the welding current is 20kA, and the welding time is 200ms.

[0066] Performance testing

[0067] The shear tensile load of the weld joint was measured using a static tensile testing device, and the tensile test was performed at a tensile rate of 10 mm / min.

[0068] The welded aluminum alloys prepared in the examples and comparative examples were subjected to measurements of the weld nugget diameter and the peak shear tensile load of the weld joint. The measurement results are shown in Table 2.

[0069] Table 2

[0070]

[0071]

[0072] In Table 1, the significant differences in the weld nugget diameter and peak shear tensile load of the weld joint between Examples 1-7 and Comparative Examples 1-7 are due to the substantial influence of the aluminum alloy type and thickness on these parameters. The difference between Examples 1, 8, 9, and 10 lies in the magnitude of the first pressure. The data shows that an excessively small first pressure is detrimental to increasing the weld nugget diameter and peak shear tensile load of the weld joint. The difference between Examples 1, 11, and 12 lies in the rotation angle. The data shows that an excessively small rotation angle is detrimental to increasing the weld nugget diameter and peak shear tensile load of the weld joint. The difference between Examples 1, 13, and 14 lies in the arc radius. The data shows that an excessively small arc radius is detrimental to increasing the weld nugget diameter and peak shear tensile load of the weld joint. The differences between Examples 1, 15, and 16 lie in the second pressure, welding current, and welding time. The data shows that insufficient second pressure, insufficient welding current, and excessive welding time are detrimental to increasing the weld nugget diameter and the peak shear tensile load of the weld joint. The difference between Example 1 and Comparative Example 1 lies in whether the welding electrode is rotated. The data shows that rotating the welding electrode at an appropriate angle helps to increase the weld nugget diameter and the peak shear tensile load of the weld joint.

[0073] Figure 1 This is a comparison diagram of the shear tensile load of welded aluminum alloy weld points in Embodiment 1 and Comparative Example 1 of this application. Figure 1 As can be seen from the data, the peak shear tensile load of the weld joint in Example 1 is 1373N, while the peak shear tensile load of the weld joint in Comparative Example 1 is 1132N.

[0074] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0075] In step S1, a first pressure is applied to the area of ​​the aluminum alloy to be welded using a welding electrode, which helps to ensure good contact between the welding electrode and the aluminum alloy. In step S2, rotating the welding electrode causes it to slide against the surface of the aluminum alloy, which helps to break down the coating and oxide layer on the surface of the aluminum alloy, thereby reducing the contact resistance between the welding electrode and the aluminum alloy. In step S3, the pressure of the welding electrode is adjusted to a second pressure suitable for welding, resulting in a weld nugget with a larger size at the weld point of the prepared aluminum alloy, which helps to improve the mechanical properties of the welded aluminum alloy. The resistance spot welding method of this application has no defects such as spatter, cracks, keyholes, and lack of fusion, and the method is simple to operate and has low cost.

[0076] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for resistance spot welding of aluminum alloys, characterized in that, The resistance spot welding method includes the following steps: Step S1: Apply a first pressure to the area of ​​the aluminum alloy to be welded using a welding electrode; Step S2: While maintaining the first pressure, rotate the welding electrode to break the oxide film on the surface of the area to be welded; Step S3: Adjust the pressure of the welding electrode to the second pressure; Step S4: Under the second pressure, the welding electrode is used to weld the aluminum alloy to be welded to obtain a welded aluminum alloy; the first pressure is 1.0~3.0kN; the rotation is performed along the circumference of the welding electrode; the rotation angle is 90°~360°; or, the welding electrode is rotated back and forth at a rotation angle of 90°~180°. The second pressure is 2.5~5.0kN; The welding electrode is a spherical welding electrode or a flat-head welding electrode; the arc radius of the arc-shaped welding end face of the spherical welding electrode is 20~100mm; the diameter of the welding end face of the flat-head welding electrode is 4.0~8.0mm. The welding current is 20~35kA, and the welding time is 50~200ms.

2. The resistance spot welding method according to claim 1, characterized in that, The welding electrode is made of copper or a copper alloy.

3. The resistance spot welding method according to claim 2, characterized in that, The copper alloy is an alumina copper alloy or a chromium-zirconium copper alloy.

4. The resistance spot welding method according to any one of claims 1 to 3, characterized in that, In step S1, the aluminum alloy to be welded is cleaned with an organic solvent, and then a first pressure is applied to the aluminum alloy to be welded.

5. The resistance spot welding method according to claim 4, characterized in that, The organic solvent is alcohol and / or acetone.

6. The resistance spot welding method according to any one of claims 1 to 3, characterized in that, The thickness of the aluminum alloy to be welded is 0.8~3.5mm.

7. The resistance spot welding method according to any one of claims 1 to 3, characterized in that, The aluminum alloy to be welded is 5182 aluminum alloy or 6016 aluminum alloy.

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