A laser welding method for performing stitch welding of a high-strength aluminum alloy plate

Abstract

The application discloses a laser welding method for stack welding processing of high-strength aluminum alloy plates, and comprises the following steps: step S1: two aluminum alloy plates are stacked on a processing tool to form a liquid cooling plate; step S2: welding track planning is performed, specifically comprising the following steps: firstly, a plurality of to-be-welded areas are planned for the liquid cooling plate, and each to-be-welded area has a plurality of areas to be formed with welds; welding is performed according to the following welding sequence: 1) taking the center of the liquid cooling plate as a reference, the to-be-welded area close to the center of the liquid cooling plate is welded first to form a center welding area; 2) the to-be-welded area adjacent to the center welding area is welded to form a second layer welding area, and the welding is sequentially performed layer by layer from the center to the outside to form n layer welding areas; 3) finally, the outer frame to-be-welded area of the liquid cooling plate is welded; and step S3: a laser is used to weld the liquid cooling plate according to the track planning, and an analog quantity is used to control the power of the laser to cooperate with the corresponding moving speed of the laser to perform welding. The welding method improves the strength of the liquid cooling plate and reduces the deformation amount.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology and relates to a laser welding method for lap welding of high-strength aluminum alloy plates. Background Technology

[0002] The rapid growth in new energy vehicle sales has driven the increase in the installed capacity of power batteries. New energy vehicle batteries rely heavily on liquid cooling plates, but the manufacturing of these plates still has much room for improvement. Currently, most liquid cooling plates for new energy power batteries are made of 3-series aluminum plates brazed together. Their structure consists of a 3-series stamped plate, aluminum-based brazing filler metal, and a 3-series base plate. This process is relatively thick, and the heating and bonding during brazing affects the mechanical strength of the 3-series aluminum plate, resulting in obvious drawbacks. Laser welding of high-strength aluminum alloy parts is a relatively mature technology that can reduce the weight of parts while maintaining structural strength. Therefore, it is conceivable that this new laser welding process could be used for welding high-strength aluminum alloy plates.

[0003] The liquid cooling plate structure includes a high-strength aluminum alloy upper plate and a high-strength aluminum alloy lower plate, which are laser-welded. The liquid cooling plate made by laser welding with a new process has greater strength, lighter weight, higher heat exchange efficiency and lower cost.

[0004] However, the new laser welding process also has certain technical problems:

[0005] 1. Due to the characteristics of lasers, aluminum alloy plates are easily melted through by lasers during laser welding, and cracks are easily formed at the weld.

[0006] 2. After welding, the inconsistent thermal deformation of the upper and lower aluminum alloy plates during laser welding results in uncontrollable deformation of the finished liquid-cooled plate.

[0007] 3. Laser welding has a small weld seam, so it cannot weld the entire mating surface of two high-strength aluminum alloy plates like brazing. Welding can only be done near the water channel. The spacing between the water channels and other factors need to be considered, and the trajectory needs to be planned to balance the welding difficulty and the strength of the finished liquid-cooled plate. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a laser welding method for lap welding high-strength aluminum alloy plates, thereby improving the weld quality of the liquid cooling plate after laser welding and reducing the deformation of the liquid cooling plate.

[0009] The present invention adopts the following technical solution:

[0010] A laser welding method for lap welding high-strength aluminum alloy plates, the method comprising the following steps:

[0011] Step S1: The high-strength aluminum alloy upper plate and the high-strength aluminum alloy lower plate are stacked on the processing fixture to form a liquid cooling plate; Step S2: The welding trajectory is planned according to the distribution of the liquid cooling plate water channel (the water channel is the flow channel of the liquid cooling plate). The welding trajectory planning specifically includes: firstly, several areas to be welded are planned on the liquid cooling plate, and each area to be welded has several areas to be formed by weld beads.

[0012] Then the laser is used for welding in the following welding sequence:

[0013] 1) Using the center of the liquid cooling plate as a reference, first weld the area to be welded that is close to the center of the liquid cooling plate to form a central welding area;

[0014] 2) Weld the adjacent areas to be welded in the central welding area to form the second welding area. Continue welding from the center outwards layer by layer to form n welding areas.

[0015] 3) Finally, the outer frame of the liquid cooling plate is welded to the welding area to improve the edge strength of the liquid cooling plate;

[0016] Step S3: The laser welds the liquid cooling plate according to the trajectory plan. The laser power is controlled by analog signal to match the laser moving speed. After welding, the liquid cooling plate is cleaned and the weld quality is checked.

[0017] Furthermore, in step S2, all areas to be welded within each welding zone are welded in a symmetrical welding sequence.

[0018] Furthermore, in the welding trajectory planning, a long weld segment welding strategy is adopted for areas where the width of the weld bead to be formed is greater than 10mm, i.e., wide weld beads, and a short weld segment combined with a long weld segment welding strategy is adopted for areas where the width of the weld bead to be formed is no more than 10mm, i.e., narrow weld beads.

[0019] Furthermore, the long weld segment welding strategy specifically includes: welding along the edge of the wide weld bead to form a linear long weld segment, which is used to improve the pressure resistance of the liquid cooling plate.

[0020] Furthermore, the short weld segment combined with the long weld segment welding strategy specifically includes: first forming a closed curved short weld segment by fitting the edge at the end of the narrow weld bead, and then extending it along the narrow weld bead to form a linear long weld segment, which is used to improve the pressure resistance of the liquid cooling plate.

[0021] Furthermore, the use of analog signals to control the laser power specifically includes: controlling the laser power in real time via an analog signal, where the analog signal is a continuously changing voltage or current signal representing the laser's output power level; and precisely controlling the laser's output power to increase or decrease linearly by adjusting the signal.

[0022] A liquid cooling plate, said liquid cooling plate being obtained by a laser welding method for lap welding high-strength aluminum alloy plates.

[0023] The beneficial effects of this invention are:

[0024] 1. By planning the welding trajectory of the liquid cooling plate, the deformation of the finished liquid cooling plate is reduced;

[0025] 2. By using a combination of short and long weld seams to weld the areas where weld beads are to be formed, the pressure resistance of the liquid cooling plate water channels is enhanced.

[0026] 3. Using analog signal control to control laser power output achieves gradual power increase and decrease, effectively improving the problem of excessive penetration at the beginning and end of the weld in laser welding, and enhancing weld strength. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the division of the area to be welded in the welding trajectory planning of one embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the distribution of the area to be formed and the weld morphology in an embodiment of the present invention.

[0029] Figure 3 is a schematic diagram of the main weld shapes designed according to the width of the area to be formed according to an embodiment of the present invention, wherein... Figure 3-1 This is a schematic diagram of a weld seam within a narrow weld bead. Figure 3-2 A schematic diagram of a weld seam within a wide weld bead; Detailed Implementation

[0030] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific examples. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.

[0031] A laser welding method for lap welding high-strength aluminum alloy plates, characterized in that the method includes the following steps:

[0032] Step S1: The high-strength aluminum alloy upper plate and the high-strength aluminum alloy lower plate are stacked on the processing fixture to form a liquid cooling plate;

[0033] Step S2: Based on the distribution of the liquid cooling plate channels, welding trajectory planning is performed. Specifically, the welding trajectory planning includes:

[0034] First, the liquid cooling plate is divided into several areas to be welded, and each area to be welded has several areas to be formed with weld beads.

[0035] Then the laser is used for welding in the following welding sequence:

[0036] 1) Using the center of the liquid cooling plate as a reference, first weld the area to be welded that is close to the center of the liquid cooling plate to form a central welding area;

[0037] 2) Weld the adjacent areas to be welded in the central welding area to form the second welding area. Continue welding from the center outwards layer by layer to form n welding areas.

[0038] 3) Finally, weld the outer frame of the liquid cooling plate to be welded.

[0039] Step S3: The laser welds the liquid cooling plate according to the trajectory plan. The laser power is controlled by analog signal to match the laser moving speed. After welding, the liquid cooling plate is cleaned and the weld quality is checked.

[0040] Example:

[0041] To demonstrate the invention more intuitively, specific projects will be used as examples to explain the specific implementation methods below.

[0042] 1) Pre-processing preparation. Ensure the processing environment is constant in temperature and humidity, with humidity below 50% and temperature above 10℃. Stack and fix the high-strength aluminum alloy upper plate (0.6mm thick water channel stamping plate) and high-strength aluminum alloy lower plate (1.0mm thick base plate) on the worktable. The edges and internal areas of both plates are reliably fixed by clamps, ensuring a tight fit. Install a 3KW laser at the end effector of a six-axis industrial robot, ensuring stable movement with the laser focus on the aluminum alloy plate surface during operation. Depending on the usage conditions, a three-axis module, collaborative robot, etc., can also be used to fix the laser. The laser parameters for this project include: using 99.999% nitrogen as the protective gas, with a working pressure of 0.1MPa, blowing gas 20mm away from the aluminum alloy plate surface, the laser entering at an 89° angle to the liquid cooling plate, a laser galvanometer amplitude of 1.1mm, a laser frequency of 250Hz, and a laser focal length of 200mm.

[0043] 2) Perform welding trajectory planning. For example... Figure 1 As shown, the areas to be welded are divided into five regions: A, B, C, D, and E. The welding sequence follows a symmetrical order: first the central region, then welding symmetrically layer by layer outwards, finally welding the outer frame to secure the entire edge of the liquid cooling plate. The specific order is: region B, region C, region A, region D, and region E. Figure 2 The upper right corner shows a schematic diagram of the weld seam within a narrow weld bead, while the lower right corner, marked by a red line, shows a schematic diagram of the area where the weld bead will be formed on the liquid cooling plate.

[0044] Figure 3 shows the weld shape designed based on the waterway distribution and the shape of the area where the weld bead is to be formed. When the width of the area where the weld bead is to be formed is less than or equal to 10 mm, it is called a narrow weld bead, and a specific weld bead shape is adopted. Figure 3-1 A standard weld bead consists of short weld segments at the ends, connected by longer weld segments. A weld bead with a width greater than 10mm is called a wide weld bead. Figure 3-2 The patterned weld, which is a long weld section welded at the edge of a wide weld bead, is used to ensure the pressure resistance of the liquid cooling plate water channel.

[0045] 3) Laser welding of the liquid-cooled plate is performed according to the planned trajectory. Analog signals are used to control the laser power and welding speed. This project uses an industrial robot to output a 0-10V DC voltage as the analog signal, corresponding to a 3KW laser power output. That is, an analog signal of 0V represents a laser power output of 0KW, an analog signal of 10V represents a laser power output of 3KW, and so on. Power ramp-up and ramp-down refer to the laser power output increasing or decreasing proportionally to time within a certain period. Specifically, the laser power gradually increases from 0KW to the target power output, and the laser power output gradually decreases from the current power output to 0KW. When using this method for laser welding, any changes in welding speed or power are addressed with gradual increases and decreases in speed and power. The welding parameters for short weld sections are: welding speed 2 m / min, welding power 26%, and power increase / decrease time 60 ms. The welding parameters for long weld sections are: welding speed 5 m / min, welding power 38%, and power increase / decrease time 25 ms. The welding parameters for the area of ​​the liquid-cooled plate where the weld bead is to be formed are: welding speed 4 m / min, welding power 35%, and power increase / decrease time 30 ms.

[0046] 4) After welding, wait 5 minutes for the liquid cooling plate to cool down, loosen the clamps, remove the liquid cooling plate, and clean it thoroughly. Inspect the weld quality of the finished liquid cooling plate.

[0047] To more intuitively demonstrate the advantages of this invention, a control group will be set up below for comparison with this invention.

[0048] Control group:

[0049] 1) Pre-processing preparation. Ensure the processing environment is constant in temperature and humidity, with humidity below 50% and temperature above 10℃. Stack and fix the high-strength aluminum alloy upper plate (0.6mm thick water channel stamping plate) and high-strength aluminum alloy lower plate (1.0mm thick base plate) on the worktable. The edges and internal areas of both plates are reliably fixed by clamps, ensuring a tight fit. Install a 3KW laser at the end effector of a six-axis industrial robot, ensuring stable movement with the laser focus on the aluminum alloy plate surface during operation. Depending on the usage conditions, a three-axis module, collaborative robot, etc., can also be used to fix the laser. The laser parameters for this project include: using 99.999% nitrogen as the protective gas, with a working pressure of 0.1MPa, blowing gas 20mm away from the aluminum alloy plate surface, the laser entering at an 89° angle to the liquid cooling plate, a laser galvanometer amplitude of 1.1mm, a laser frequency of 250Hz, and a laser focal length of 200mm.

[0050] 2) Plan the welding trajectory. Weld sequentially from left to right and from top to bottom according to the distribution of the area to be welded. Welding parameters are: welding speed 5m / min, welding power 38%.

[0051] 3) Perform laser welding of the liquid-cooled plate according to the planned trajectory. Use analog signals to control the laser power and coordinate with the corresponding welding speed for laser welding.

[0052] After welding, wait 5 minutes for the liquid cooling plate to cool down, then loosen the clamps, remove the liquid cooling plate, and clean it thoroughly. Inspect the weld quality of the finished liquid cooling plate.

[0053] Ten welding operations were performed using each of the two welding methods described above, and the resulting liquid-cooled plates underwent quality testing. The measured data are shown in Table 1.

[0054] The explosion test involves pressing water into a sealed water channel through a pre-installed water nozzle until the liquid cooling plate breaks.

[0055] The deformation test is as follows: using the height of the liquid cooling plate from the horizontal plane before welding as a reference, the deformation of the liquid cooling plate after welding is measured.

[0056]

[0057] Table 1

[0058] in conclusion:

[0059] A comparison in Table 1 shows that:

[0060] This method uses analog quantity control to achieve gradual power increase and decrease, employs a combination of zoned welding and long and short weld seams, and uses different welding parameters to effectively improve the problem of excessive penetration at the beginning and end of the weld seam in laser welding, enhance welding strength, reduce the deformation of the liquid cooling plate, enhance the strength of the finished liquid cooling plate, and reduce heat input.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A laser welding method for lap welding high-strength aluminum alloy plates, characterized in that, The method includes the following steps: Step S1: The high-strength aluminum alloy upper plate and the high-strength aluminum alloy lower plate are stacked on the processing fixture to form a liquid cooling plate; Step S2: Based on the distribution of the liquid cooling plate channels, welding trajectory planning is performed. Specifically, the welding trajectory planning includes: First, the liquid cooling plate is divided into several areas to be welded, and each area to be welded has several areas to be formed with weld beads. Then the laser is used for welding in the following welding sequence: 1) Using the center of the liquid cooling plate as a reference, first weld the area to be welded that is close to the center of the liquid cooling plate to form a central welding area; 2) Weld the areas to be welded adjacent to the central welding area to form the second welding area. Continue welding from the center outwards layer by layer to form n welding areas. 3) Finally, weld the outer frame of the liquid cooling plate to be welded. Step S3: The laser welds the liquid cooling plate according to the trajectory plan. The laser power is controlled by analog signal to match the corresponding laser movement speed for welding. After welding, the liquid cooling plate is cleaned and the weld quality is inspected. When planning the welding trajectory, a long weld segment welding strategy is adopted for areas with a width greater than 10mm, i.e., wide welds, and a short weld segment combined with a long weld segment welding strategy is adopted for areas with a width of no more than 10mm, i.e., narrow welds. The long weld segment welding strategy specifically includes: welding along the edge of the wide weld to form a linear long weld segment; the short weld segment combined with a long weld segment welding strategy specifically includes: first, fitting the edge at the end of the narrow weld to form a closed curved short weld segment, and then extending along the narrow weld to form a linear long weld segment.

2. The laser welding method for lap welding high-strength aluminum alloy plates according to claim 1, characterized in that, In step S2, all areas to be welded within each welding zone are welded in a symmetrical welding sequence.

3. The laser welding method for lap welding high-strength aluminum alloy plates according to claim 1, characterized in that, The method of controlling the laser power using analog signals specifically includes: controlling the laser power in real time through analog signals, where the analog signal is a continuously changing voltage or current signal representing the output power level of the laser; and precisely controlling the output power of the laser to increase or decrease linearly by adjusting the signal.

4. A liquid-cooled plate, characterized in that, The liquid cooling plate is obtained by the laser welding method for lap welding high-strength aluminum alloy plates according to any one of claims 1-3.

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