Copper-aluminum dissimilar metal laser lap welding method and system

Abstract

A copper-aluminum dissimilar metal laser overlap welding method and system, a copper-aluminum dissimilar metal laser overlap welding system, including a fixture, a high-frequency current system, and a laser welding system; a copper-aluminum dissimilar metal laser overlap welding method, including the following steps: step 1, providing an aluminum plate and a copper plate to be welded, and using a fixture to form an upper and lower overlap joint with the aluminum plate to be welded and the copper plate to be welded; step 2, providing a high-frequency current system; step 3, providing a laser welding system; step 4, starting the high-frequency current system, and the high-frequency current system feeds high-frequency current to the aluminum plate to be welded and the copper plate to be welded respectively; step 5, starting the laser welding system, the laser welding system outputs a focused laser beam to irradiate the aluminum plate to be welded, and the laser welding system blows welding shielding gas to the welding area to implement high-frequency current assisted laser welding; step 6, moving the laser welding head to the end point, closing the high-frequency current system and the laser welding system, and completing the welding process.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a copper-aluminum dissimilar metal laser lap welding method and system. Background Art

[0002] New energy vehicles are a strategic development industry in my country. The battery pack of new energy vehicles is made up of a large number of battery cells connected together, and the battery cell is composed of a shell, an electrolyte, a diaphragm, and two metals with different potential differences. For lithium batteries with a large energy density, the tabs are usually aluminum and copper, and the materials used to connect the electrodes include aluminum, copper, nickel-plated copper, etc. Therefore, in the battery manufacturing process, copper-aluminum dissimilar metals need to be connected.

[0003] The physical and chemical properties of aluminum and copper (such as thermal conductivity, thermal expansion coefficient and melting point) are quite different, and it is difficult to achieve effective welding of aluminum and copper using traditional welding methods. Due to the limited mutual solubility between aluminum and copper at room temperature, the aluminum-copper fusion welded joint forms an interface layer of brittle intermetallic compounds at the weld. Therefore, the strength and plasticity of the welded joint are reduced and cracks are easily generated, affecting the performance of the battery pack.

[0004] For copper-aluminum dissimilar metal lap joints, it is usually necessary to add metallurgical powder to improve the interface compound phase. The auxiliary process is relatively complicated, and residual powder particles are easy to affect the safety of use. In addition, due to the high thermal conductivity of copper and aluminum materials and the high reflectivity of conventional lasers, the welding method of directly irradiating the copper-aluminum dissimilar metal lap joints with a continuous high-power laser beam is prone to cause transitional melting of the material at the interface to generate a large amount of brittle intermetallic compounds, resulting in serious deterioration of the joint performance. Therefore, industry experts have placed their hopes on short-wavelength lasers such as blue and green lasers for copper-aluminum laser welding, but its brittle intermetallic compounds are still difficult to eliminate, and the laser is expensive. In addition, the current laser welding is mainly aimed at sheet thicknesses below 1 mm, and thicker copper-aluminum dissimilar metal lap joints are difficult to achieve reliable connection. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a copper-aluminum dissimilar metal laser lap welding method and system.

[0006] The technical solution adopted by one of the present invention to solve the technical problem is:

[0007] A copper-aluminum dissimilar metal laser lap welding method comprises the following steps;

[0008] Step 1, providing an aluminum plate and a copper plate to be welded, pre-bending the aluminum plate to be welded at a welding position to form a concave shape, pre-bending the copper plate to be welded at a welding position to form a convex shape, and using a clamp to form an upper and lower overlapping joint of the aluminum plate to be welded and the copper plate to be welded;

[0009] Step 2, providing a high-frequency current system, wherein the high-frequency current system includes a high-frequency power supply, a first contact electrode and a second contact electrode, wherein the first contact electrode and the second contact electrode are respectively connected to the aluminum plate to be welded and the copper plate to be welded;

[0010] Step 3, providing a laser welding system, wherein the laser welding system includes a laser, a transmission optical fiber, a laser welding head, and a welding shielding gas nozzle;

[0011] Step 4, starting the high-frequency current system, and the first contact electrode and the second contact electrode respectively feed high-frequency current to the aluminum plate to be welded and the copper plate to be welded;

[0012] Step 5, start the laser welding system, the laser welding head outputs a focused laser beam to irradiate the aluminum plate to be welded, and the welding shielding gas nozzle blows welding shielding gas to the welding area to implement high-frequency current assisted laser welding;

[0013] Step 6: The laser welding head moves to the end point, and the high-frequency current system and the laser welding system are turned off to complete the welding process.

[0014] Furthermore, the thickness of the aluminum plate to be welded and the copper plate to be welded are both 1 to 2 mm.

[0015] Furthermore, retractable pads are provided at both ends between the aluminum plate and the copper plate, and the retractable pads are used to adjust the gap δ between the welding area of ​​the aluminum plate to be welded and the welding area of ​​the copper plate to be welded, and are used to adjust the gap δ to 0.1-0.5 mm.

[0016] Furthermore, the laser is a high-brightness and high-reflection-resistant fiber laser.

[0017] Furthermore, the laser welding head is a beam swinging laser welding head.

[0018] Furthermore, in step 4, the frequency of the high-frequency current fed into the aluminum plate to be welded and the copper plate to be welded is 400-700kHz, the anode voltage is 1-3kV, and the anode current is 1-3A.

[0019] Furthermore, in step 5, the laser power of the laser is 3000-6000W, and the welding speed is 3-6m / min.

[0020] The technical solution adopted by one of the present invention to solve the technical problem is:

[0021] A copper-aluminum dissimilar metal laser lap welding system comprises a fixture, a high-frequency current system, and a laser welding system; the high-frequency current system comprises a high-frequency power supply, a first contact electrode, and a second contact electrode; the laser welding system comprises a laser, a transmission optical fiber, a laser welding head, and a welding shielding gas nozzle.

[0022] In one embodiment, the clamp further comprises a retractable spacer.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention designs the conventional copper-aluminum lap joint into an upper and lower copper-aluminum lap joint with concave and convex parts facing each other. Under the action of high-frequency current, due to the proximity effect and skin effect of the high-frequency current, strong resistance heat is generated in the raised lap area, which greatly reduces the heat input of copper-aluminum dissimilar metal lap welding, thereby reducing the thickness of the brittle compound layer of the joint and improving the joint performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the equipment layout structure of Example 1 of the present invention.

[0026] In the figure: 10, aluminum plate, 20, copper plate, 30, clamp, 35, retractable pad, 40, laser, 41, transmission optical fiber, 42, laser welding head, 43, laser beam, 44, welding shielding gas nozzle, 50, high-frequency power supply, 51, first contact electrode, 52, second contact electrode, 60, welding molten pool. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Example 1

[0029] like Figure 1 As shown, this embodiment includes providing a copper-aluminum dissimilar metal laser overlapping welding system, including a fixture 30, a high-frequency current system, and a laser welding system; the high-frequency current system includes a high-frequency power supply 50, a first contact electrode 51 and a second contact electrode 52, and the first contact electrode 51 and the second contact electrode 52 are respectively connected to the aluminum plate 10 to be welded and the copper plate 20 to be welded; the laser welding system includes a laser 40, a transmission optical fiber 41, a laser welding head 42, and a welding shielding gas nozzle 44, the laser welding head 42 is connected to the laser 40 through the transmission optical fiber 41, and the welding shielding gas nozzle 44 is connected to a shielding gas source; and the fixture 30 also includes a retractable pad 35.

[0030] Example 2

[0031] This embodiment provides a copper-aluminum dissimilar metal laser lap welding method, comprising the following steps:

[0032] Step 1, providing 1mm aluminum plate 10 and copper plate 20 to be welded, pre-bending the aluminum plate 10 to be welded at the welding position to be formed into a concave shape, pre-bending the copper plate 20 to be welded at the welding position to be formed into a convex shape, and using a clamp 35 to form an upper and lower overlapping joint of the aluminum plate 10 to be welded and the copper plate 20 to be welded; in this embodiment, retractable pads 35 are provided at both ends between the aluminum plate 10 to be welded and the copper plate 20 to be welded, and the retractable pads 35 adjust the gap δ between the welding area of ​​the aluminum plate 10 to be welded and the welding area of ​​the copper plate 20 to be welded, and the gap δ is 0.3mm;

[0033] Step 2, providing a high-frequency current system, wherein the high-frequency current system includes a high-frequency power supply 50, a first contact electrode 51 and a second contact electrode 52, wherein the first contact electrode 51 and the second contact electrode 52 are respectively connected to the aluminum plate 10 to be welded and the copper plate 20 to be welded;

[0034] Step 3, providing a laser welding system, the laser welding system comprising a laser 40, a transmission optical fiber 41, a laser welding head 42, and a welding shielding gas nozzle 44; in this embodiment, the laser 40 is a high-brightness anti-high-reflection optical fiber laser, and the laser welding head 42 is a beam swinging laser welding head;

[0035] Step 4, start the high-frequency current system, and the first contact electrode 51 and the second contact electrode 52 respectively feed high-frequency current to the aluminum plate 10 to be welded and the copper plate 20 to be welded; in this embodiment, the frequency of the high-frequency current fed to the aluminum plate 10 to be welded and the copper plate 20 to be welded is 550kHz, the anode voltage is 2kV, and the anode current is 2A;

[0036] Step 5, start the laser welding system, the laser welding head 42 outputs a focused laser beam 43 to irradiate the aluminum plate 10 to be welded, the welding shielding gas nozzle 44 blows welding shielding gas into the welding area, and implements high-frequency current-assisted laser welding; in this embodiment, the laser power of the laser 40 is 5000W and the welding speed is 4m / min.

[0037] Step 6: The laser welding head 42 moves to the end point, and the high-frequency current system and the laser welding system are turned off to complete the welding process.

[0038] Example 3

[0039] This embodiment provides a copper-aluminum dissimilar metal laser lap welding method, comprising the following steps:

[0040] Step 1, providing a 2mm aluminum plate 10 and a copper plate 20 to be welded, pre-bending the aluminum plate 10 to be welded at the welding position to be formed into a concave shape, pre-bending the copper plate 20 to be welded at the welding position to be formed into a convex shape, and using a clamp 30 to form an upper and lower overlapping joint of the aluminum plate 10 to be welded and the copper plate 20 to be welded; in this embodiment, retractable pads 35 are provided at both ends between the aluminum plate 10 to be welded and the copper plate 20 to be welded, and the retractable pads 35 adjust the gap δ between the welding area of ​​the aluminum plate 10 to be welded and the welding area of ​​the copper plate 20 to be welded, and the gap δ is 0.5mm;

[0041] Step 2, providing a high-frequency current system, the high-frequency current system comprising a high-frequency power supply 50, a first contact electrode 51 and a second contact electrode 52, the first contact electrode 51 and the second contact electrode 52 are respectively connected to the aluminum plate 10 to be welded and the copper plate 20 to be welded;

[0042] Step 3, providing a laser welding system, the laser welding system includes a laser 40, a transmission optical fiber 41, a laser welding head 42, and a welding shielding gas nozzle 44; in this embodiment, the laser 40 is a high-brightness anti-high-reflection optical fiber laser, and the laser welding head 42 is a beam swinging laser welding head;

[0043] Step 4, start the high-frequency current system, and the first contact electrode 51 and the second contact electrode 52 respectively feed high-frequency current to the aluminum plate 10 to be welded and the copper plate 20 to be welded; in this embodiment, the frequency of the high-frequency current fed to the aluminum plate 10 to be welded and the copper plate 20 to be welded is 550kHz, the anode voltage is 3kV, and the anode current is 3A;

[0044] Step 5, start the laser welding system, the laser welding head 42 outputs a focused laser beam 43 to irradiate the aluminum plate 10 to be welded, and the welding shielding gas nozzle 44 blows welding shielding gas into the welding area to implement high-frequency current-assisted laser welding; in this embodiment, the laser power of the laser 40 is 5500W and the welding speed is 6m / min.

[0045] Step 6: The laser welding head moves to the end point, and the high-frequency current system and the laser welding system are turned off to complete the welding process.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the technical solutions of the present invention have been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A copper-aluminum dissimilar metal laser lap welding method, characterized in that: The steps include: Step 1, providing an aluminum plate (10) and a copper plate (20) to be welded, pre-bending the aluminum plate (10) to be welded at a welding position to form a concave shape, pre-bending the copper plate (20) to be welded at a welding position to form a convex shape, and using a clamp (30) to form an upper and lower overlapping joint of the aluminum plate (10) to be welded and the copper plate (20) to be welded; The thickness of the aluminum plate (10) to be welded and the copper plate (20) to be welded are both 1 to 2 mm; Retractable pads (35) are provided at both ends between the aluminum plate (10) to be welded and the copper plate (20) to be welded, and the retractable pads (35) are used to adjust the gap δ between the welding area of ​​the aluminum plate (10) to be welded and the welding area of ​​the copper plate (20) to be welded, and are used to adjust the gap δ to 0.1-0.5 mm; Step 2, providing a high-frequency current system, the high-frequency current system comprising a high-frequency power supply (50), a first contact electrode (51) and a second contact electrode (52), the first contact electrode (51) and the second contact electrode (52) being connected to the aluminum plate (10) to be welded and the copper plate (20) to be welded, respectively; Step 3, providing a laser welding system, wherein the laser welding system comprises a laser (40), a transmission optical fiber (41), a laser welding head (42), and a welding shielding gas nozzle (44); Step 4, starting the high-frequency current system, wherein the first contact electrode (51) and the second contact electrode (52) respectively feed high-frequency current to the aluminum plate (10) to be welded and the copper plate (20) to be welded; the frequency of the high-frequency current fed to the aluminum plate (10) to be welded and the copper plate (20) to be welded is 400 to 700 kHz, the anode voltage is 1 to 3 kV, and the anode current is 1 to 3 A; Step 5, starting the laser welding system, the laser welding head (42) outputs a focused laser beam (43) to irradiate the aluminum plate (10) to be welded, and the welding shielding gas nozzle (44) blows welding shielding gas to the welding area to implement high-frequency current-assisted laser welding; the laser power of the laser (40) is 5000-6000W, and the welding speed is 3-6m / min; Step 6: The laser welding head moves to the end point, and the high-frequency current system and the laser welding system are turned off to complete the welding process.

2. The copper-aluminum dissimilar metal laser lap welding method according to claim 1, characterized in that: The laser (40) is a high-brightness, high-reflection-resistant optical fiber laser.

3. The copper-aluminum dissimilar metal laser lap welding method according to claim 2, characterized in that: The laser welding head (42) is a beam swinging laser welding head.

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