Equipment for liquid cooling plate laser welding and liquid cooling plate laser welding method

Abstract

The invention belongs to the technical field of laser welding, and particularly provides a liquid cooling plate laser welding method which comprises the following steps that a workpiece is placed on a welding tool clamp to be fixed; generating a welding path according to the liquid cooling plate three-dimensional model; and a multi-light-spot laser welding system is adopted for scanning the welding path, parameters of light spots projected to a welding seam are adjusted according to the position of the welding seam, and welding is conducted. According to the liquid cooling plate laser welding method, a plurality of light spots are adopted for combined action, an oxidation film on the surface of the aluminum alloy can be broken more effectively, small welding holes are stabilized, a molten pool is stirred, and therefore the generation tendency of air holes and hot cracks is remarkably reduced, and a welding seam with the compact interior and high strength is obtained. Multiple light spot parameters can be dynamically adjusted according to needs, a process window of aluminum alloy laser welding is expanded, the sensitivity of the welding process to laser power fluctuation and assembly clearance tiny changes is reduced, the process stability and repeatability are improved, and the differential requirements of complex welding seams are met.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, specifically relating to an equipment and method for laser welding of liquid-cooled plates. Background Technology

[0002] Liquid cooling plates are critical heat dissipation components in many high-power electronic devices, such as power batteries, servers, and power devices, requiring extremely high sealing performance of their flow channels. Traditional liquid cooling plate welding mainly employs brazing or friction stir welding. Brazing is energy-intensive, may produce harmful gases, and requires flux cleaning after welding. While friction stir welding offers better weld quality, it is slow, typically 0.3-1 m / min, and requires burr removal after welding, resulting in lower efficiency.

[0003] Laser welding, as a non-contact, high-speed, and easily automated processing technology, boasts advantages such as concentrated heat input, minimal deformation, and high speed, theoretically making it ideal for precision welding of liquid-cooled plates. However, when applying laser welding to aluminum alloy liquid-cooled plates, challenges arise. The aluminum alloy surface exhibits extremely high reflectivity to laser light, hindering energy absorption. Furthermore, the high thermal conductivity of aluminum alloys places extremely high demands on the stability of laser power. In addition, the "keyhole" effect during welding is unstable, easily leading to welding defects. The narrow process window in aluminum alloy laser welding makes it highly susceptible to defects such as porosity and hot cracking. To ensure complete sealing of the flow channel, extremely stringent requirements are placed on the workpiece assembly clearance, typically requiring <0.1mm. Moreover, traditional single-path side-blown shielding gas is insufficient to effectively isolate air and prevent weld oxidation under high-speed welding conditions.

[0004] Therefore, there is an urgent need for a laser welding method that can achieve high-quality and high-efficiency sealing welding of aluminum alloy liquid cooling plates. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of easy generation of pores and cracks, poor process stability, and excessively high requirements for assembly clearance in the laser welding of liquid-cooled plates in the prior art.

[0006] Therefore, the present invention provides a method for laser welding of liquid-cooled plates, comprising the following steps:

[0007] Fix the workpiece on the welding fixture;

[0008] Generate welding paths based on the 3D model of the liquid cooling plate;

[0009] A multi-spot laser welding system is used to scan the welding path, and the parameters of the laser spot projected onto the weld are adjusted according to the weld position to perform welding.

[0010] Specifically, the above-mentioned adjustment of the light spot parameters projected onto the weld is as follows: the light spots in the straight seam section are distributed in a matrix; the light spots in the corner section are distributed in a ring.

[0011] Specifically, the center-to-center distance between adjacent light spots in the straight slit section is 0.5~1mm, and the power of each light spot is evenly distributed; the annular diameter of the corner section is 2.0~3.0mm, and the power of the light spot located inside the corner section is lower than that of the outer side.

[0012] Specifically, the welding parameters of the above-mentioned multi-spot laser welding system are: total laser power 5-10 kW; welding speed not less than 15 m / min; defocusing amount -2 mm ~ +2 mm.

[0013] Specifically, the aforementioned liquid-cooled plate laser welding method also includes monitoring the molten pool morphology and weld temperature during welding.

[0014] Specifically, a gas protection device is used to deliver protective gas during the above welding process; the gas protection device has a gas flow channel that matches the shape of the weld.

[0015] Specifically, the nozzle of the aforementioned gas protection device is provided with multiple flow channels arranged in a circumferential manner; the lower end of the flow channels is arranged at an angle toward the center of the nozzle.

[0016] Specifically, the gas flow rate is 15-20 L / min.

[0017] Specifically, before fixing the workpiece, the welding contact surface of the workpiece is cleaned to remove oil and oxide layers.

[0018] Specifically, the aforementioned welding fixture is equipped with a vacuum adsorption chamber. After the workpiece is placed on the welding fixture and fixed, the vacuum system is activated to adsorb and fix the workpiece.

[0019] The present invention also provides an apparatus for laser welding of liquid-cooled plates, comprising:

[0020] Welding fixtures are used to hold workpieces to be welded.

[0021] A multi-spot laser welding system includes a control module and a welding module; the welding module is used to weld seams; the control module is used to adjust the spot parameters and control the welding module.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] The liquid-cooled plate laser welding method provided by this invention utilizes multiple laser spots working together to more effectively break the oxide film on the aluminum alloy surface, stabilize weld pinholes, and stir the molten pool, thereby significantly reducing the tendency for porosity and hot cracking, resulting in a dense, high-strength weld. The multi-spot parameters can be dynamically adjusted as needed, expanding the process window for aluminum alloy laser welding, reducing the sensitivity of the welding process to laser power fluctuations and minor changes in assembly gaps, improving process stability and repeatability. It breaks away from the traditional fixed spot distribution pattern, enabling real-time dynamic adjustment of the number, spacing, and power distribution of spots, adapting to the differentiated needs of complex welds (such as variable cross-sections and multi-angle welds). The welding speed is ≥15 m / min, far exceeding that of traditional friction stir welding, greatly improving production efficiency. Furthermore, the welding fixture combined with vacuum adsorption ensures a tight fit of the workpiece before welding, and in conjunction with the multi-spot welding process, achieves high-pressure sealing of the liquid-cooled plate flow channels, meeting stringent usage requirements.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the metallographic structure of the weld obtained in Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of the nozzle structure of a gas protection device in one embodiment.

[0027] Reference numerals: 1. Nozzle; 2. Flow channel. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0029] This invention provides a method for laser welding of liquid-cooled plates, comprising the following steps:

[0030] S1. Workpiece pretreatment

[0031] Clean the welding surface of the liquid-cooled plate workpiece to be welded, removing oil and oxide layers;

[0032] For oil stains, acetone or a specialized cleaning agent can be used for cleaning. For stubborn oil stains, a combination of ultrasonic cleaning and spray rinsing is recommended, with an ultrasonic frequency of 20-30kHz and a cleaning time of 3-5 minutes. For concealed areas such as inside flow channels, high-pressure spraying can be used to ensure no oil residue remains. After cleaning, use compressed air to dry the area to prevent secondary corrosion.

[0033] For the oxide layer of aluminum alloy workpieces, a combination of mechanical grinding and chemical polishing is used. Mechanical grinding uses alumina sandpaper to grind along the welding edge in one direction to remove the surface oxide film. Then, it is immersed in 5%-10% nitric acid solution for pickling for 10-15 seconds, rinsed immediately with deionized water, and finally dried at 60-80℃ for 15-20 minutes.

[0034] After cleaning, wipe the welding surface to ensure that the cloth is free of oil and stains, eliminate the impact of impurities on the weld pool stability, and ensure good metallurgical bonding at the welding interface.

[0035] S2. Clamping and Fixing

[0036] Select welding fixtures that match the workpiece, with a surface flatness of ≤0.03mm / 100mm. Preferably, the welding fixtures have built-in vacuum adsorption chambers, distributed in a 5-10mm area on both sides of the weld.

[0037] The pre-treated workpiece is placed into the welding fixture and clamped to ensure precise alignment of the upper and lower plates. For corner weld areas, adjustable pressure blocks are used for pre-fixation to prevent workpiece displacement during vacuum adsorption.

[0038] Start the vacuum system to tightly adhere the upper and lower plates to be welded using negative pressure. Use a feeler gauge to check the gap at the welding point and ensure that the gap is ≤0.1mm over the entire weld length. If the gap exceeds the standard, the workpiece position needs to be readjusted or the workpiece needs to be replaced.

[0039] A laser displacement sensor is used to scan along both sides of the weld at a distance of 10mm to detect that the deformation of the workpiece after clamping is ≤0.05mm. At the same time, the workpiece is gently pushed to ensure that it is not loose. The vacuum system can be equipped with a pressure alarm device, which will alarm and require maintenance when the pressure is lower than the threshold.

[0040] S3, Welding Path Planning

[0041] Welding paths are generated based on the 3D model of the liquid cooling plate. Rounded transitions with a radius of ≥5mm are used at corners to avoid instability of the molten pool caused by abrupt changes in the path. For multi-channel liquid cooling plates, the principle of welding short seams first and then long seams and symmetrical welding is adopted to reduce welding deformation.

[0042] S4, Laser Welding and Gas Protection

[0043] A multi-spot laser welding system is used to scan the welding path. Based on the scanning results, the molten pool is optimized by dynamically adjusting the synergistic effect of the multiple spots. The preferred welding parameters are: total laser power 5-10 kW; welding speed not less than 15 m / min; defocusing amount -2 mm to +2 mm; and the power of each sub-spot can be independently adjusted, typically 20%-30% of the total power. The welding system is equipped with a vision camera and an infrared thermometer to monitor the molten pool morphology and weld temperature in real time. A programmable spatial light modulator (SLM) is used to control the phase distribution of the spots via electrical signals, enabling switching between multiple distribution modes such as multi-spot matrix, ring, and linear. The power of each sub-spot is independently adjustable.

[0044] The shielding gas used during welding is selected according to the material of the workpiece. Pure argon is generally used for welding aluminum alloys. The gas flow rate is adjusted according to the welding speed, with an optimal gas flow rate of 15-20 L / min.

[0045] A gas protection device is used to deliver shielding gas. This device has nozzles that match the weld contour, forming a gas flow channel that conforms to the weld shape. This ensures that the shielding gas forms a laminar flow shielding curtain along the weld contour, eliminating dead zones and turbulence, effectively covering the weld pool and high-temperature zone throughout the entire process. The gas flow rate at corners is 10%-15% higher than in straight sections.

[0046] In one implementation, such as Figure 2 As shown, the nozzle 1 of the gas protection device is provided with multiple flow channels 2 arranged in a ring; the lower end of the flow channel 2 is inclined towards the central axis of the nozzle 1. The protective gas flows in the flow channel of the protective gas plate, and the flow channel outlet is directly opposite the welding focal point. Through the specially designed flow channel and outlet layout, the gas can accurately cover the specific weld seam, and the enhanced airflow is blown at a certain angle around the laser beam to suppress the plasma and stabilize the molten pool.

[0047] Before welding, the optical path and spot are calibrated, the laser is started, and the power of multiple spots is measured sequentially using a laser power meter. The power ratio of each spot is adjusted by a power distributor, with an error ≤1%. Shielding gas is supplied 5 seconds in advance, and the vision camera and infrared thermometer are started to track the weld seam.

[0048] The welding head moves along a preset trajectory, and the spot parameters are dynamically adjusted according to the weld position, specifically:

[0049] The multiple light spots in the straight seam section are arranged in a matrix shape; optionally, the center-to-center distance between adjacent light spots in the straight seam section is 0.5~1mm, which is adjusted according to the width of the weld. The power of each light spot is evenly distributed. Taking four light spots as an example, the power of each sub-spot is 25%.

[0050] The multi-spot distribution at the corner is switched to a ring distribution; optionally, the ring diameter at the corner is 2.0~3.0mm, and the power of the spot on the inner side of the corner is lower than that on the outer side. The power of the inner spot at the corner is reduced by 10%-15% to avoid burn-through, while the power of the outer spot is increased accordingly. Taking four spots as an example, the power of the two inner spots is reduced to 20%, while that of the outer spots is increased to 30%.

[0051] When welding variable cross-section sections, an additional auxiliary spot can be added to the thick plate side to supplement energy compared to straight or corner sections, expanding from four spots to five spots. The auxiliary spot power accounts for 10%, and the main spot power distribution is adjusted to 20%, 20%, 25%, and 25%.

[0052] During the welding process, a vision camera monitors the shape of the molten pool, and an infrared thermometer detects the temperature of the weld. If defects such as molten pool displacement or porosity occur, the system immediately adjusts the welding parameters until they return to normal.

[0053] Once the welding head reaches the preset endpoint, the laser is turned off, the scanning speed drops to 0, the shielding gas stops after a delay of 10-15 seconds, the welding head returns to the initial position, the vacuum system is depressurized, and the welding is completed.

[0054] In a more detailed implementation, the flow channel corners and the area connected to the nozzle can be preheated and segmented welded. The preheating power is 40%-50% of the welding power, and the preheating time is 2-3 seconds. When welding segments, each segment is 10-15 mm long and overlaps between segments by 2-3 mm to ensure uniform forming.

[0055] Furthermore, a high-frequency ultrasonic transducer (20-40kHz, 500-800W power) is integrated with the welding fixture. Ultrasonic vibration is transmitted to the workpiece welding area through the fixture, with the vibration direction parallel to the weld seam and the amplitude controlled between 5-15μm, adjusted according to the plate thickness, with a larger value for thicker plates. Introducing ultrasonic vibration simultaneously with laser welding utilizes the ultrasonic cavitation effect to refine grains, eliminate porosity, and improve the mechanical properties of the joint, making it particularly suitable for materials prone to porosity, such as aluminum alloys. For the bottom weld seam of the liquid-cooled plate flow channel, ultrasonic vibration extends the molten pool's existence time, ensuring full bonding between the molten pool and the base material, thus increasing the tensile strength of the joint.

[0056] S5, Quality Inspection

[0057] Allow the workpiece to cool naturally to room temperature using the welding fixture; forced air or water cooling is prohibited to avoid thermal stress cracking. Loosen the welding fixture and handle the workpiece gently, avoiding contact with the weld area.

[0058] Lightly sand the weld and surrounding area with sandpaper to remove weld slag and oxide stains. Sand along the length of the weld to avoid horizontal scratches. Wipe the weld surface with alcohol to remove dust and oil, ensuring the surface is clean and residue-free.

[0059] Aluminum alloy workpieces undergo vibration aging treatment at a frequency of 20-50Hz for 20-30 minutes. Stainless steel / titanium alloy workpieces do not require additional aging and will release stress naturally.

[0060] Observe the weld color. Aluminum alloy is silver-white / light yellow, and stainless steel is silver-gray. There should be no blackening or bluening (oxidation). Otherwise, it is determined that the shielding gas is insufficient and rework is required.

[0061] Take a section of the welded sample and perform a tensile test on a universal testing machine. The tensile strength of the joint is ≥ 85% of that of the base material. Perform a bending test (180°, bending mandrel diameter = 2 × plate thickness). The weld is free of cracks.

[0062] Metallographic microscopy revealed that the weld cross-section had uniform grains, no microcracks or porosity, clear fusion lines, and an oxide inclusion content of ≤0.5%.

[0063] The effects of the liquid-cooled plate laser welding method of the present invention will be studied through specific embodiments below.

[0064] Example 1:

[0065] This embodiment provides a laser welding method for liquid-cooled plates. The workpiece to be welded is an aluminum alloy liquid-cooled plate for power batteries, which is composed of an upper plate (1mm thick 5-series aluminum alloy with flow channels) and a lower plate (1.5mm thick 6-series aluminum alloy flat plate) stacked together. Sealing welding of the perimeter is required. The method includes the following steps:

[0066] S1. Workpiece pretreatment

[0067] Use acetone or a special cleaning agent to clean the welded contact surfaces of the upper and lower plates of the liquid cooling plate to thoroughly remove oil stains, then clean with anhydrous ethanol and let it air dry.

[0068] S2. Clamping and Fixing

[0069] Select a welding fixture that matches the workpiece, with a built-in vacuum adsorption chamber. Precisely align the cleaned upper and lower plates and place them on the welding fixture. Start the vacuum pump, and use negative pressure to tightly adsorb and adhere the upper and lower plates together. Use a feeler gauge to check the gap at the welding point, ensuring that the gap in the entire area to be welded is forcibly controlled within 0.1mm.

[0070] S3, Welding path planning and welding system setup

[0071] Welding paths are generated based on the 3D model of the liquid cooling plate.

[0072] The multi-spot laser welding system includes a fiber laser (wavelength 1070 nm) as the light source. The laser beam is fed into a four-spot welding head, which can split and focus a single laser beam into four independent and tunable energy spots. The welding head is mounted on a six-axis industrial robot.

[0073] A gas protection device is manufactured using 3D printing technology, with the shape of its gas outlet matching the weld seam trajectory of the liquid cooling plate to ensure that argon gas can uniformly cover the welding area.

[0074] S4, Laser Welding and Gas Protection

[0075] The preferred welding parameters are: total laser power 8 kW; welding speed 16 m / min; defocusing amount 0 mm; and the power of each sub-spot can be adjusted independently.

[0076] The laser and shielding gas (argon, 99.99% purity) are activated at a flow rate of 18 L / min. The welding head moves along the set welding path, with all four laser spots simultaneously emitting light for welding. The laser spot parameters are dynamically adjusted based on the weld position and width. The four laser spots work together on the weld to form a larger and more stable molten pool.

[0077] Once the welding head reaches the preset endpoint, the laser is turned off, the scanning speed drops to 0, the shielding gas is stopped after a 15-second delay, the welding head returns to its initial position, the vacuum system is depressurized, and the welding is completed.

[0078] S5, Quality Inspection

[0079] After the workpiece cools naturally to room temperature with the welding fixture, release the welding fixture, remove the workpiece gently, and avoid collision with the weld area.

[0080] Visual inspection revealed that the welds were continuous, smooth, and free of oxidation. Non-destructive testing showed no internal porosity, cracks, or other defects. A pressure test was performed on the liquid cooling plate flow channel; no leakage was observed after holding at 0.35 bar for 5 minutes, indicating good sealing. Metallographic analysis of the welds was performed as follows: Figure 1 As shown, the weld structure is uniform and fine, with good fusion and a narrow heat-affected zone.

[0081] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for laser welding of liquid-cooled plates, characterized in that, Includes the following steps: Fix the workpiece on the welding fixture; Generate welding paths based on the 3D model of the liquid cooling plate; A multi-spot laser welding system is used to scan the welding path, and the parameters of the laser spot projected onto the weld are adjusted according to the weld position to perform welding.

2. The liquid-cooled plate laser welding method as described in claim 1, characterized in that, The adjustment of the light spot parameters projected onto the weld seam is as follows: the light spots in the straight seam section are distributed in a matrix; the light spots in the corner section are distributed in a ring.

3. The liquid-cooled plate laser welding method as described in claim 2, characterized in that: The center-to-center distance between adjacent light spots in the straight slit section is 0.5~1mm, and the power of each light spot is evenly distributed; the annular diameter of the corner section is 2.0~3.0mm, and the power of the light spot located inside the corner section is lower than that of the outer side.

4. The liquid-cooled plate laser welding method as described in claim 1, characterized in that, The welding parameters for the multi-spot laser welding system are: total laser power 5-10 kW; welding speed not less than 15 m / min; defocusing amount -2 mm ~ +2 mm.

5. The laser welding method for liquid-cooled plates as described in claim 1, characterized in that: It also includes monitoring the molten pool morphology and weld temperature during welding.

6. The liquid-cooled plate laser welding method as described in claim 1, characterized in that: A gas protection device is used to deliver protective gas during welding; the gas protection device has a gas flow channel that matches the shape of the weld.

7. The liquid-cooled plate laser welding method as described in claim 6, characterized in that: The nozzle of the gas protection device is provided with multiple flow channels arranged in a circumferential manner; the lower end of the flow channels is inclined toward the central axis of the nozzle.

8. The liquid-cooled plate laser welding method as described in claim 1, characterized in that: Before fixing the workpiece, the welding contact surfaces of the workpiece are cleaned to remove oil and oxide layers.

9. The laser welding method for liquid-cooled plates as described in claim 1, characterized in that: The welder The fixture is equipped with a vacuum adsorption chamber. After the workpiece is placed on the welding fixture and fixed, the vacuum system is activated to adsorb and fix the workpiece.

10. An apparatus for laser welding of liquid-cooled plates, characterized in that, include: Welding fixtures are used to hold workpieces to be welded. A multi-spot laser welding system includes a control module and a welding module; the welding module is used to weld seams; the control module is used to adjust the spot parameters and control the welding module.

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