A composite annealing manufacturing method of an aluminum alloy water cooling plate

Abstract

This invention discloses a composite annealing manufacturing method for aluminum alloy water-cooled plates, relating to the field of aluminum alloy water-cooled plate manufacturing technology, including the following steps: S1. Composite slab preparation and pretreatment: 3003 aluminum alloy is selected as the core layer and 4343 aluminum alloy is selected as the double-sided brazing layer. After surface treatment and vacuum edge sealing, the composite slab is hot-rolled to obtain a 4343 / 3003 / 4343 three-layer composite aluminum slab; the composite aluminum slab is pre-annealed by heating to 320-360℃, holding for 2-4 hours, and then furnace-cooled to below 200℃ before being taken out of the furnace. This invention designs a three-stage composite annealing process—pre-annealing, intermediate graded composite annealing, and brazing stabilization annealing—to precisely address the stress generation points throughout the manufacturing process. This process sequentially eliminates residual internal stress generated during hot rolling, runner forming, and brazing, effectively solving the pain points of warping, deformation, and runner dimensional accuracy deviations in existing water-cooled plates. It ensures flatness ≤0.3mm / m and controls runner dimensional deviations within a reasonable range, thereby improving product assembly adaptability and operational stability.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy water-cooled plate manufacturing technology, and specifically to a composite annealing manufacturing method for aluminum alloy water-cooled plates. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage industries, the performance requirements of thermal management systems are increasing. Aluminum alloy water-cooled plates, as core heat dissipation components, are widely used in liquid cooling of equipment such as power battery packs, IGBT power modules, and server racks due to their advantages of lightweight, high thermal conductivity, and easy processing.

[0003] Existing manufacturing methods generally suffer from the following technical defects, which severely restrict the performance and application range of aluminum alloy water-cooled plates: Severe residual internal stress and poor dimensional stability: After the composite plate blank is formed by hot rolling, stamping / milling and other forming processes, a large amount of residual internal stress will be generated inside. If it is not effectively eliminated, it will easily lead to warping and deformation of the water-cooled plate after forming, deviation of the flow channel dimensional accuracy, affecting subsequent assembly and sealing performance, and even causing flow channel blockage or leakage. The composite interface has low bonding strength and is prone to leakage: the composite of the core layer and the brazing layer relies on physical bonding. The interface bonding is not strong. After welding or long-term use, delamination and cracking are likely to occur, leading to leakage of the cooling medium and affecting the safety and reliability of the heat dissipation system. In particular, it cannot meet the requirements of high-pressure liquid cooling system. It is difficult to achieve both mechanical properties and thermal conductivity: traditional single annealing process either leads to coarse grains, reducing the strength and fatigue resistance of water-cooled plates; or it leads to high hardness, reduced plasticity, and easy breakage during forming or use; at the same time, improper annealing process will affect the thermal conductivity of aluminum alloy and reduce heat dissipation efficiency. The process is lengthy, energy-intensive, and yields low quality: In the existing methods, the forming, annealing, and brazing processes are independent of each other and require multiple heating and cooling cycles. This not only makes the process cumbersome and the production efficiency low, but also leads to a significant increase in energy consumption. Furthermore, multiple heat treatments can easily cause oxidation and deformation of the slab, resulting in a yield rate that is generally below 90%.

[0004] Therefore, it is necessary to invent a composite annealing manufacturing method for aluminum alloy water-cooled plates to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a composite annealing manufacturing method for aluminum alloy water-cooled plates to solve the problems in the above-mentioned technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a composite annealing manufacturing method for aluminum alloy water-cooled plates, comprising the following steps: S1. Preparation and pretreatment of composite slab: 3003 aluminum alloy is selected as the core layer and 4343 aluminum alloy is selected as the double-sided brazing layer. After surface treatment and vacuum sealing, the composite slab is hot rolled to obtain a 4343 / 3003 / 4343 three-layer composite aluminum slab. The composite aluminum slab is pre-annealed by heating to 320-360℃, holding for 2-4 hours, and then cooling in the furnace to below 200℃ before being taken out of the furnace. S2. Cooling channel forming and straightening: The pre-annealed composite slab is precision stamped or milled to form cooling channel grooves. After forming, it is straightened to control the flatness to ≤0.3mm / m. S3. Intermediate composite annealing: The formed runner plate is subjected to graded intermediate composite annealing; S4. Assembly and Vacuum Brazing Co-annealing: Align and assemble the flow channel plate and cover plate, then place them in a vacuum brazing furnace, controlling the vacuum level to 5×10⁻⁶. - ³~1×10 - ²Pa, preheat to 280-320℃ and hold for 30 min, then raise the temperature to 580-595℃ and hold for 20-40 min, then cool with the furnace to 300℃ and hold for 60-90 min for stabilization annealing, and finally cool to below 100℃ and remove from the furnace; S5. Finishing and Inspection: The brazed water-cooled plate is finished for flatness and surface passivation, and then subjected to water pressure test. If there is no leakage after holding the pressure at 1.5-2.0MPa for 30 minutes, it is considered a finished product.

[0007] Preferably, the surface treatment in step 1 includes degreasing, pickling, and activation treatment performed sequentially. Degreasing is performed using an alkaline degreasing agent, pickling is performed using a 10%–15% nitric acid solution, and activation is performed using a 0.5%–1% hydrofluoric acid solution. After treatment, the surface is rinsed with deionized water and dried.

[0008] Preferably, in step 1, the hot rolling temperature is 420–450°C, the rolling pressure is 800–1200 MPa, the thickness of the slab after rolling is 2.5–5.0 mm, and the thickness ratio of the core layer to the brazing layer is 5:1–8:1.

[0009] Preferably, in step 2, the depth of the cooling channel groove is 2-6 mm, the width is 1-5 mm, the channel spacing is 5-10 mm, and the roughness Ra of the inner wall of the channel is ≤1.6 μm.

[0010] Preferably, in step 3, the first stage of the graded intermediate composite annealing is heated to 380-420°C at a heating rate of 8-12°C / min and held for 1.5-3 hours; the second stage continues to heat to 460-490°C and held for 1-2 hours; then the furnace is cooled in sections, first at 5°C / min to 300°C, and then air-cooled to room temperature.

[0011] Preferably, in step 3, the first stage of intermediate composite annealing is used to eliminate the internal stress generated during the flow channel forming process, and the second stage is used to promote the element diffusion between the core layer 3003 aluminum alloy and the brazing layer 4343 aluminum alloy to form a diffusion transition layer with a thickness of 5 to 10 μm.

[0012] Preferably, in step 4, the cover plate adopts the same 4343 / 3003 / 4343 three-layer composite structure as the composite slab blank, the cover plate thickness is 0.8-1.5mm, and the alignment error between the flow channel plate and the cover plate during assembly is ≤0.1mm.

[0013] Preferably, the heating rate of the vacuum brazing synergistic annealing in step 4 is 5-8℃ / min to avoid excessively rapid heating that could lead to slab deformation or uneven brazing filler flow.

[0014] Preferably, the surface passivation treatment in step 5 adopts a chromate passivation process, and the passivation film thickness is 0.5 to 1.0 μm, which improves the corrosion resistance of the water-cooled plate.

[0015] The technical effects and advantages provided by the present invention in the above technical solution are as follows: 1. This invention designs a three-stage composite annealing process of "pre-annealing - intermediate graded composite annealing - brazing stabilization annealing" to precisely correspond to the stress generation nodes in the entire manufacturing process, and eliminates the residual internal stress generated by hot rolling, flow channel forming and brazing processes in sequence. This effectively solves the pain points of warping, deformation and flow channel dimensional accuracy deviation in the existing technology of water-cooled plates, ensures flatness ≤0.3mm / m, controls flow channel dimensional deviation within a reasonable range, and improves product assembly adaptability and usage stability. 2. This invention, through the graded control of intermediate composite annealing, forms a 5-10 μm diffusion transition layer at the interface between the core layer (3003 aluminum alloy) and the brazing layer (4343 aluminum alloy), transforming the traditional physical bonding into diffusion bonding. This significantly improves the shear strength of the composite interface, completely solving the problems of weak bonding, easy delamination, and leakage between the core layer and the brazing layer. Combined with the sealing and strengthening effect of vacuum brazing synergistic annealing, the water-cooled plate can withstand high pressure of 1.5-2.0 MPa, meeting the requirements of high-pressure liquid cooling systems and extending the product's service life. 3. This invention achieves precise control of the grain size of the water-cooled plate by coordinating the temperature, holding time and cooling rate of the three-stage composite annealing process, so that the grain size is stabilized at 20-40μm. It effectively balances mechanical properties and thermal conductivity, ensuring high strength and good plasticity with tensile strength Rm≥180MPa and elongation A≥12%, and ensuring thermal conductivity ≥180W / (m·K). This avoids the problems of coarse grains or high hardness caused by traditional single annealing processes, and improves heat dissipation efficiency and structural reliability. 4. This invention integrates the processes of composite slab preparation, forming, graded annealing, vacuum brazing, stabilization annealing, finishing and testing into a unified whole, breaking the limitations of the independent separation of each process in the prior art. It reduces the repetitive operation of multiple heating and cooling, which not only simplifies the process flow and improves production efficiency, but also reduces energy consumption by 20% to 30%. At the same time, it avoids slab oxidation and deformation defects caused by multiple hot processing, increases the product yield to over 98%, reduces production costs, and is suitable for large-scale mass production. 5. This invention further optimizes the overall performance of the product by precisely controlling the surface treatment process, hot rolling composite parameters, flow channel forming accuracy, and passivation treatment requirements. The surface passivation film can improve the corrosion resistance of the water-cooled plate, the precision flow channel design ensures smooth flow of the cooling medium and improves heat dissipation efficiency, and the three-layer composite slab structure takes into account both lightweight and structural strength. It is suitable for high-requirement heat dissipation scenarios in many fields such as new energy vehicles, energy storage, and servers, and has extremely strong practicality and promotion value. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall manufacturing process of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] This invention provides, for example Figure 1 The method for manufacturing a composite annealing aluminum alloy water-cooled plate, as shown, includes the following steps: S1. Preparation and pretreatment of composite slab: 3003 aluminum alloy is selected as the core layer and 4343 aluminum alloy is selected as the double-sided brazing layer. After surface treatment and vacuum sealing, the composite slab is hot rolled to obtain a 4343 / 3003 / 4343 three-layer composite aluminum slab. The composite aluminum slab is pre-annealed by heating to 320-360℃, holding for 2-4 hours, and then cooling in the furnace to below 200℃ before being taken out of the furnace. S2. Cooling channel forming and straightening: The pre-annealed composite slab is precision stamped or milled to form cooling channel grooves. After forming, it is straightened to control the flatness to ≤0.3mm / m. S3. Intermediate composite annealing: The formed runner plate is subjected to graded intermediate composite annealing; S4. Assembly and Vacuum Brazing Co-annealing: Align and assemble the flow channel plate and cover plate, then place them in a vacuum brazing furnace, controlling the vacuum level to 5×10⁻⁶. - ³~1×10 -²Pa, preheat to 280-320℃ and hold for 30 min, then raise the temperature to 580-595℃ and hold for 20-40 min, then cool with the furnace to 300℃ and hold for 60-90 min for stabilization annealing, and finally cool to below 100℃ and remove from the furnace; S5. Finishing and Inspection: The brazed water-cooled plate is finished for flatness and surface passivation, and then subjected to water pressure test. If there is no leakage after holding the pressure at 1.5-2.0MPa for 30 minutes, it is considered a finished product.

[0019] The surface treatment in step 1 includes degreasing, pickling, and activation treatment in sequence. Degreasing is performed using an alkaline degreasing agent, pickling is performed using a 10%–15% nitric acid solution, and activation is performed using a 0.5%–1% hydrofluoric acid solution. After treatment, the surface is rinsed with deionized water and dried. The hot rolling temperature in step 1 is 420–450℃, the rolling pressure is 800–1200MPa, the thickness of the slab after rolling is 2.5–5.0mm, and the thickness ratio of the core layer to the brazing layer is 5:1–8:1.

[0020] In this embodiment, the three-step surface treatment process works synergistically to thoroughly remove oil and oxide scale from the plate surface, enhance surface activity, lay a good foundation for subsequent hot rolling composite, and avoid defects such as bubbles and delamination at the composite interface caused by impurities or oxide layers. Precise control of parameters for alkaline degreasing agent, nitric acid pickling, and hydrofluoric acid activation ensures cleaning effect while avoiding excessive corrosion of the plate surface and protecting plate performance. The control of temperature, pressure, and thickness parameters for hot rolling composite ensures tight adhesion between the core layer and the brazing layer, forming a preliminary physical bond. At the same time, controlling the thickness ratio of the core layer to the brazing layer balances the structural strength of the water-cooled plate and the subsequent brazing effect. The slab thickness of 2.5–5.0 mm can adapt to the design requirements of water-cooled plates in different scenarios. Vacuum sealing prevents air from entering during hot rolling, avoids interface oxidation, and further improves the quality of the composite slab.

[0021] In step 2, the depth of the cooling channel groove is 2-6 mm, the width is 1-5 mm, the channel spacing is 5-10 mm, and the roughness of the inner wall of the channel is Ra≤1.6 μm.

[0022] In this embodiment, the depth, width, and spacing parameters of the cooling channel grooves are precisely controlled to adapt to the heat dissipation requirements of different power devices. A depth of 2-6 mm and a width of 1-5 mm ensure the flow rate of the cooling medium while avoiding a decrease in the structural strength of the water-cooled plate due to excessive channel depth. A channel spacing of 5-10 mm allows for uniform distribution of the cooling medium, improving heat dissipation efficiency and ensuring uniform temperature across all areas of the water-cooled plate. The requirement of a channel inner wall roughness Ra≤1.6μm reduces resistance during the flow of the cooling medium, prevents burrs from scratching the sealing structure, and prevents impurities from accumulating and clogging the channel. The flatness requirement of ≤0.3 mm / m ensures the assembly accuracy of the channel plate and the cover plate, preventing assembly gaps from causing subsequent brazing leaks and guaranteeing the sealing performance of the water-cooled plate.

[0023] In step 3, the first stage of the graded intermediate composite annealing involves heating to 380–420°C at a heating rate of 8–12°C / min and holding for 1.5–3 hours. The second stage involves further heating to 460–490°C and holding for 1–2 hours. Subsequently, the material is furnace cooled in sections, first at 5°C / min to 300°C and then air-cooled to room temperature. The first stage of the intermediate composite annealing in step 3 is used to eliminate the internal stress generated during the flow channel forming process, and the second stage is used to promote element diffusion between the core layer 3003 aluminum alloy and the brazing layer 4343 aluminum alloy, forming a diffusion transition layer with a thickness of 5–10 μm.

[0024] In this embodiment, the two-stage design of graded intermediate composite annealing achieves the dual effects of "stress relief + interface strengthening," solving the pain points of residual internal stress and weak interface bonding in existing technologies. The temperature and holding time control in the first stage precisely eliminates the internal stress generated during the flow channel forming process, preventing warping and deformation of the flow channel plate and stabilizing the dimensional accuracy of the flow channel. The high-temperature diffusion design in the second stage promotes the mutual diffusion of elements such as aluminum, manganese, and silicon between the core layer and the brazing layer, forming a stable diffusion transition layer. This transforms traditional physical bonding into diffusion bonding, significantly improving the shear strength of the composite interface and fundamentally preventing delamination and cracking problems during subsequent use. The segmented cooling method avoids excessively rapid cooling that could generate new internal stress, while ensuring the stability of the diffusion transition layer structure, further improving the dimensional stability and mechanical properties of the flow channel plate.

[0025] In step 4, the cover plate adopts the same 4343 / 3003 / 4343 three-layer composite structure as the composite slab. The cover plate thickness is 0.8-1.5mm. During assembly, the alignment error between the flow channel plate and the cover plate is ≤0.1mm. In step 4, the heating rate of vacuum brazing synergistic annealing is 5-8℃ / min to avoid excessive heating that could cause slab deformation or uneven brazing filler flow.

[0026] In this embodiment, the cover plate adopts the same three-layer composite structure as the composite slab blank, which ensures that the thermal expansion coefficients of the cover plate and the flow channel plate are consistent, avoiding cracking and leakage caused by thermal expansion differences during brazing and use; the cover plate thickness of 0.8-1.5mm takes into account both sealing performance and lightweight requirements, and the alignment error requirement of ≤0.1mm ensures that the flow channel is tightly sealed without gaps during brazing; the vacuum degree control of vacuum brazing can avoid metal oxidation during brazing and improve the quality of brazed joints; the heating rate of 5-8℃ / min can prevent the slab blank from deforming and the brazing filler metal from flowing unevenly due to excessive heating, ensuring that the brazing filler metal fills the gaps evenly; preheating and heat preservation can eliminate assembly stress and make the temperature of the assembled parts uniform; the control of brazing temperature and heat preservation time can ensure that the brazed layer melts fully without damaging the core layer performance; the stabilization annealing at 300℃ can eliminate the residual internal stress generated during brazing, stabilize the structure and size of the water-cooled plate, and further improve the sealing performance and mechanical properties.

[0027] In step 5, the surface passivation treatment adopts chromate passivation process, and the passivation film thickness is 0.5~1.0μm, which improves the corrosion resistance of water-cooled plate.

[0028] In this embodiment, surface passivation treatment forms a dense passivation film on the surface of the water-cooled plate. This passivation film effectively isolates the water-cooled plate from the erosion of air, moisture, and cooling media, significantly improving its corrosion resistance and extending its service life. It is particularly suitable for applications in complex conditions such as new energy vehicles and energy storage. The passivation film thickness control of 0.5–1.0 μm ensures corrosion resistance without affecting the surface flatness of the water-cooled plate and subsequent assembly. The optional design of chromate passivation and chromium-free passivation processes adapts to different environmental requirements and application scenarios, balancing corrosion resistance and environmental friendliness. Simultaneously, the water pressure test after passivation further verifies the sealing performance of the water-cooled plate, ensuring no leakage and improving product qualification rate and reliability.

[0029] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite annealing manufacturing method for an aluminum alloy water-cooled plate, characterized in that, Includes the following steps: S1. Preparation and pretreatment of composite slab: 3003 aluminum alloy is selected as the core layer and 4343 aluminum alloy is selected as the double-sided brazing layer. After surface treatment and vacuum sealing, the composite slab is hot rolled to obtain a 4343 / 3003 / 4343 three-layer composite aluminum slab. The composite aluminum slab is pre-annealed by heating to 320-360℃, holding for 2-4 hours, and then cooling in the furnace to below 200℃ before being taken out of the furnace. S2. Cooling channel forming and straightening: The pre-annealed composite slab is precision stamped or milled to form cooling channel grooves. After forming, it is straightened to control the flatness to ≤0.3mm / m. S3. Intermediate composite annealing: The formed runner plate is subjected to graded intermediate composite annealing; S4. Assembly and Vacuum Brazing Co-annealing: Align and assemble the flow channel plate and cover plate, then place them in a vacuum brazing furnace, controlling the vacuum level to 5×10⁻⁶. - ³~1×10 - ²Pa, preheat to 280-320℃ and hold for 30 min, then raise the temperature to 580-595℃ and hold for 20-40 min, then cool with the furnace to 300℃ and hold for 60-90 min for stabilization annealing, and finally cool to below 100℃ and remove from the furnace; S5. Finishing and Inspection: The brazed water-cooled plate is finished for flatness and surface passivation, and then subjected to water pressure test. If there is no leakage after holding the pressure at 1.5-2.0MPa for 30 minutes, it is considered a finished product.

2. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 1, characterized in that: The surface treatment in step 1 includes degreasing, pickling, and activation treatments performed sequentially. Degreasing is performed using an alkaline degreasing agent, pickling is performed using a 10%–15% nitric acid solution, and activation is performed using a 0.5%–1% hydrofluoric acid solution. After treatment, the surface is rinsed with deionized water and dried.

3. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 1, characterized in that: In step 1, the hot rolling temperature is 420–450℃, the rolling pressure is 800–1200MPa, the thickness of the slab after rolling is 2.5–5.0mm, and the thickness ratio of the core layer to the brazing layer is 5:1–8:

1.

4. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 3, characterized in that: In step 2, the depth of the cooling channel groove is 2-6 mm, the width is 1-5 mm, the channel spacing is 5-10 mm, and the roughness of the inner wall of the channel is Ra≤1.6 μm.

5. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 1, characterized in that: In step 3, the first stage of the graded intermediate composite annealing is heated to 380-420°C at a heating rate of 8-12°C / min and held for 1.5-3 hours; the second stage continues to heat to 460-490°C and held for 1-2 hours; then it is furnace cooled in sections, first at 5°C / min to 300°C, and then air cooled to room temperature.

6. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 5, characterized in that: In step 3, the first stage of intermediate composite annealing is used to eliminate the internal stress generated during the flow channel forming process, and the second stage is used to promote the diffusion of elements between the core layer 3003 aluminum alloy and the brazing layer 4343 aluminum alloy, forming a diffusion transition layer with a thickness of 5-10 μm.

7. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 1, characterized in that: In step 4, the cover plate adopts the same 4343 / 3003 / 4343 three-layer composite structure as the composite slab blank, the cover plate thickness is 0.8~1.5mm, and the alignment error between the flow channel plate and the cover plate during assembly is ≤0.1mm.

8. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 1, characterized in that: In step 4, the heating rate of the vacuum brazing synergistic annealing is 5-8℃ / min to avoid excessively rapid heating that could lead to slab deformation or uneven brazing filler flow.

9. The composite annealing manufacturing method for an aluminum alloy water-cooled plate according to claim 1, characterized in that: In step 5, the surface passivation treatment adopts a chromate passivation process, and the passivation film thickness is 0.5-1.0 μm, which improves the corrosion resistance of the water-cooled plate.

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