Aluminum-based conducting bar surface functional layer and preparation system and process thereof

Abstract

The invention discloses an aluminum-based conducting bar surface functional layer and a preparation system and process thereof. The preparation process comprises the following steps: substrate pretreatment: removing surface pollutants through ethanol ultrasonic cleaning; preparing a transition layer: performing cold solid deposition on the copper-based composite powder to form the transition layer; functional layer cold spraying: constructing a functional conductive layer on the surface of the transition layer; preparing an anti-corrosion layer: constructing a composite protection system on the surface of the functional conductive layer; densification treatment is conducted, specifically, hole sealing densification treatment is conducted on the surface of the anti-corrosion layer; and detecting the quality of the coating. The functional layer comprises an aluminum-based layer, a copper metal transition layer, a nickel-based or tin-based conductive layer and an anticorrosive layer. By adopting the process, the equipment investment can be saved, the processing time can be saved, the metal lattice distortion can be effectively realized, the accurate control of the dislocation density of the material surface can be realized, the specific strength of the conducting bar material can be improved, and the light weight of the conducting bar can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles. Background Art

[0002] In the powertrain architecture of new energy vehicles, aluminum conductive bars serve as key components for high-voltage electrical connections, primarily responsible for transmitting high currents between the charging port and the battery pack. Electric vehicle charging systems must meet transmission requirements of 800-1000A and megawatt-level power handling. Aluminum-based conductive bars must meet three key performance criteria for electrical connection components: contact resistance stability, electrochemical compatibility, and mechanical vibration reliability. While traditional copper conductive bars offer excellent conductivity, they suffer from inherent drawbacks such as high weight density and high cost. In contrast, aluminum alloys can achieve a weight reduction of over 40% while maintaining sufficient conductivity and significantly reducing costs. However, replacing copper with aluminum requires overcoming significant hurdles such as interfacial contact stability, multi-material galvanic corrosion, and dynamic mechanical reliability. Currently, no method exists to construct a composite functional layer with both low contact resistance and high durability. Summary of the Invention

[0003] In order to solve the problems in the above background technology, the present invention provides an aluminum-based conductive bar surface functional layer and provides a process thereof to solve the above technical problems.

[0004] The technical solution for achieving the purpose of the present invention is: a process for preparing a functional layer on the surface of an aluminum-based conductive bar, comprising the following steps:

[0005] Substrate pretreatment: Surface contaminants were removed by ultrasonic cleaning with ethanol;

[0006] Preparation of transition layer: cold solid deposition of copper-based composite powder to form a transition layer;

[0007] Functional layer cold spraying: constructing a functional conductive layer on the surface of the transition layer;

[0008] Preparation of anti-corrosion layer: constructing a composite protection system on the surface of the functional conductive layer;

[0009] Densification treatment: sealing and densification treatment is carried out on the surface of the anti-corrosion layer;

[0010] Coating quality inspection.

[0011] The aluminum-based conductive bar surface treatment process described above involves surface treatment prior to cold spraying, layering during the transition layer treatment, and subsequent encapsulation. Compared to conventional preparation methods, the surface additive technology employed in this invention comprehensively considers coating performance indicators and process economic parameters in process selection. Compared to traditional surface treatment processes, it offers lower VOC emissions, significantly improved material utilization, and significantly reduced processing energy consumption. Furthermore, the process eliminates traditional manufacturing steps such as mold development and heat treatment. This significantly reduces equipment investment intensity and labor costs, significantly reduces the number of parts, and offers significant advantages in equipment maintenance costs.

[0012] In addition to saving equipment investment and processing time, the present invention completely adopts cold processing technology, which can effectively realize metal lattice distortion, achieve precise control of material surface dislocation density, improve the specific strength of the conductive bar material, and achieve lightweight conductive bar.

[0013] Further or optionally, the substrate pretreatment process is an ethanol ultrasonic cleaning process, specifically an ethanol ultrasonic cleaning process (40kHz) is adopted during the execution process, and the surface contaminant removal rate is required to be 99.98%, which meets the requirements of SSPC-SP1 standard.

[0014] In practice, it was found that after the SSPC-SP1 standard was implemented, the surface energy of the aluminum substrate was increased to 74mN·m -1 , reaching the matrix activation state.

[0015] Further or optionally, the process for preparing the transition layer uses compressed air or high-pressure nitrogen as the medium, the pressure range is 0.5-1.0 MPa, the gas temperature is 200-350°C, and the copper-based powder particle size is 5-90 μm. During the deposition process, the pressure, gas temperature and copper-based powder diameter can be adjusted to adjust the coating density and porosity. When the gas pressure is high, the copper-based powder particle size is small and the gas temperature is high, the coating tends to be denser and the porosity is lower.

[0016] Further or optionally, when the carrier gas temperature in the process of preparing the transition layer is 380°C, the spraying distance is 15 mm, and the spray gun movement speed is 300 mm / s, the density of the deposited layer can be increased to 99.2% and the porosity can be significantly reduced to below 0.8%.

[0017] Furthermore or optionally, the functional layer cold spraying process employs a pressure range of 0.5-1.0 MPa, a gas temperature of 300-450°C, and a copper-based powder particle size of 5-85 μm. During production, the electrical conductivity of the functional layer must be controlled to ≥40% IACS. In the above structure, the copper deposition layer of the transition layer effectively mitigates the stress gradient between the core layer and the surface layer of the guide rail, preventing the surface layer from shedding due to excessive stress differences.

[0018] Further or optionally, when the surface requirements are different, the anti-corrosion layer matrix used is also different. In the process of preparing the anti-corrosion layer, when the functional layer is tin-based, the anti-corrosion layer is a tin / aluminum alloy layer to achieve the anti-corrosion performance requirements; when the functional layer is nickel-based, the anti-corrosion layer is a nickel-aluminum alloy layer.

[0019] In the above structure, a copper metal transition layer is set between aluminum and nickel-tin. Its purpose is to reduce the potential gradient due to the small potential difference between copper and aluminum and nickel-tin, and slow down the galvanic corrosion between aluminum and nickel-tin. The above cold solid-state additive processing is beneficial to improving the bonding stability between the interfaces; the diffusion bonding between copper and aluminum is beneficial to reducing the interface resistance, improving the conductive efficiency, reducing the energy consumption in transmission, and thus reducing the heating of the aluminum row under high current conditions.

[0020] Furthermore or optionally, in order to reduce the dielectric corrosion caused by the nano-micrometer-scale voids that may remain on the surface of the aluminum busbar during use, a nano-silane sealant is sprayed during the densification process. The nano-silane particles can penetrate deep into the micropores and fill the voids by capillary action. The Si-O-Si network structure formed after the hydrolysis of silane can be bonded to the hydroxyl group on the surface of the material, further reducing the porosity of the aluminum busbar surface.

[0021] Furthermore, the present invention also provides an aluminum-based conductive bar surface functional layer processing system, which cooperates with the above-mentioned aluminum-based conductive bar surface functional layer preparation process, including a power supply unit, a powder supply unit, an air supply unit, a cold additive main control device, a spray gun and a posture control module. The cold additive main control device is connected to the air supply unit for preparing the transition layer and cold solid-state additive of the functional layer; the air supply unit is connected to compressed air and high-pressure nitrogen through a bus for air compression, and the cold additive main control device controls the air supply status of the air unit and the powder supply unit. The spray gun and the posture control module are connected to the operating console to control the spraying status.

[0022] During the operation, in order to reduce the cost of solid-state additive manufacturing, compressed air or high-pressure nitrogen is used for additive manufacturing. During the operation, the gas is accelerated after passing through the bus and then mixed with the powder after passing through the cold additive processing equipment. It is then sprayed out from the spray gun to form a copper-based metallurgical transition layer and a functional conductive layer on the surface of the aluminum busbar. Subsequently, a nickel / tin-based surface anti-corrosion layer continues to form on the surface. Finally, the aluminum busbar is removed from the operating table and enters the surface treatment process.

[0023] Furthermore, the present invention also provides a surface functional layer of an aluminum-based conductive bar, which is prepared by the above process and includes an aluminum base layer, a copper metal transition layer, a conductive layer, and a nickel-based or tin-based anti-corrosion layer, with a total thickness of less than 4 mm. The thickness of the copper metal transition layer is 0.2 mm, and the thickness of the nickel-based or tin-based conductive layer is 0.2 mm.

[0024] Using the above parameters, tests have shown that the electrical conductivity of the copper layer of the aluminum busbar produced using this process is 38.2% higher than that of the aluminum alloy substrate, and the contact potential difference can be stably controlled between 0.6 and 0.8 V. SEM scanning analysis shows that after 500 thermal cycles, no oxide is produced between the copper and aluminum interfaces, and the thickness of the metal diffusion layer is still less than 3μm, effectively inhibiting the formation of intermetallic compounds such as Cu9Al4.

[0025] Under the above conditions, the interface resistance between copper and aluminum can be maintained below 0.1mΩ, the Vickers hardness matching between the composite layer and the matrix material is as high as 93%, and the dislocation density ρ between the materials reaches 10 10 m -2 level, which is two orders of magnitude lower than traditional solid-state additive processes.

[0026] Further or optionally, the grain size of the copper metal transition layer is 2 to 8 μm, the surface roughness of the aluminum bar Ra is less than or equal to 6.3 μm, the bonding strength between the Cu layer and the Al layer is greater than 40 MPa, and the electrical conductivity reaches 58.5×10 6 S / m, its surface hardness can reach the standard of pure copper, the stress concentration coefficient between the nickel / tin layer and the aluminum layer is reduced to below 1.8, the interface shear strength is increased to 65MPa, and under the condition of random vibration of 10-200Hz, the contact resistance shear strength is only 32.7% of that of the thermal sprayed sample.

[0027] By adopting the above technical solution, the present invention has the following beneficial effects:

[0028] (1) The present invention provides a surface functional layer preparation process for an aluminum-based conductive bar. The surface treatment is performed before the cold solid-state additive process, and a layering process is performed during the transition layer treatment process, followed by encapsulation. Compared with conventional preparation methods, the surface additive technology used in the present invention comprehensively considers coating performance indicators and process economic parameters in process selection. Compared with traditional surface treatment processes, its VOC emissions are lower, material utilization is significantly improved, and processing energy consumption is significantly reduced. In addition, the process flow eliminates traditional manufacturing links such as mold development and heat treatment. The equipment investment intensity and labor costs are greatly reduced, the number of parts is significantly reduced, and the equipment maintenance cost advantage is very obvious.

[0029] (2) The present invention adopts ethanol ultrasonic cleaning as a substrate pretreatment process for the preparation process of the surface functional layer of an aluminum-based conductive bar, which can effectively improve the surface energy of the aluminum substrate and quickly reach the substrate activation state, which is beneficial to the interlayer bonding in the subsequent treatment process.

[0030] (3) The transition layer preparation process of the present invention's process for preparing a functional layer on the surface of an aluminum-based conductive bar uses a mixed gas of compressed air and high-pressure nitrogen as the medium, with a pressure range of 0.5 to 1.0 MPa, a gas temperature of 200 to 500°C, and a copper-based powder particle size of 5 to 75 μm. During the deposition process, the coating density and porosity can be adjusted by adjusting the pressure, gas temperature, and copper-based powder diameter. When the gas pressure is high, the copper-based powder particle size is small, and the gas temperature is high, the coating tends to be denser and have a lower porosity.

[0031] (4) The present invention provides a process for preparing the surface functional layer of an aluminum-based conductive bar by strictly controlling process parameters such as carrier gas temperature, deposition distance, and spray gun movement speed, which can effectively improve the density of the deposited layer and reduce the porosity of the deposited layer.

[0032] (5) The present invention adopts a process for preparing the surface functional layer of an aluminum-based conductive bar using two solid copper deposition layers as transition layers, which can effectively alleviate the stress gradient between the core layer and the surface layer of the conductive bar and prevent the surface layer from falling off due to excessive differences in interlayer stress gradients.

[0033] (6) In the process for preparing the surface functional layer of an aluminum-based conductive bar of the present invention, a nano-silane sealant is used for surface spraying after the transition layer is prepared. The high permeability of nano-silane and the Si-O-Si network structure generated on the surface of the material after the hydrolysis of silane are utilized to achieve surface sealing, thereby reducing the surface porosity of the aluminum bar.

[0034] (7) The present invention provides a process for preparing a surface functional layer of an aluminum-based conductive bar. During the production process, the carrier gas temperature, spraying distance and spray gun movement speed are controlled to effectively improve the density of the deposited layer and significantly reduce the porosity.

[0035] (8) The present invention also provides a surface functional layer processing system for aluminum-based conductive bars. The system uses compressed air and high-pressure nitrogen as a mixed gas for an aerodynamic device. It has good controllability and does not require a separate anti-corrosion layer preparation production line. Gas is used as a carrier during the preparation process, and its cost is relatively low. Compared with the existing cold additive preparation technology, it has great cost advantages.

[0036] (9) The present invention also provides a surface functional layer for an aluminum-based conductive bar, which adopts a multi-layer design of a copper base layer, a copper transition layer and an anti-corrosion layer, which can effectively improve the conductivity and contact potential stability of the aluminum bar substrate. The diffusion thickness between interfaces is small, which can effectively inhibit the formation of interlayer metal compounds.

[0037] (10) The surface functional layer of an aluminum-based conductive bar of the present invention selects the crystal size of the copper metal transition layer, effectively controls the bonding strength and interlayer conductivity between aluminum and copper, effectively reduces the stress concentration coefficient between interfaces, and reduces the shear strength of contact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments and in conjunction with the accompanying drawings, wherein

[0039] Figure 1 It is a structural schematic diagram of the present invention. Figure 2 It is a schematic diagram of the process of the present invention.

[0040] The reference numerals in the accompanying drawings are:

[0041] Aluminum base layer 1, copper metal transition layer 2, functional conductive layer 3, anti-corrosion layer 4. DETAILED DESCRIPTION

[0042] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0044] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances. The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0045] See Figure 1 A functional layer on the surface of an aluminum-based conductive bar is provided, comprising an aluminum base layer (1), a copper metal transition layer (2), a functional conductive layer (3) and an anti-corrosion layer (4).

[0046] like Figure 2 As shown, the preparation system includes a power supply unit, a powder supply unit, an air supply unit, a cold additive main control device, a spray gun and a posture control module. During the preparation process, compressed air and high-pressure nitrogen are used as the air supply unit. The compressed air and high-pressure nitrogen are mixed and then mixed through the cold additive main control device, and then connected to the powder supply unit for powder-gas mixing. The spray gun angle is adjusted by the posture control module. The powder accelerated by the compressed air is sprayed to form a copper metal transition layer on the surface of the pretreated aluminum bar. After the copper metal transition layer is prepared, the powder type of the powder supply unit is replaced with nickel powder or tin powder required for the functional conductive layer, and then spraying is carried out. After spraying is completed, an anti-corrosion layer is prepared on the surface. After the anti-corrosion layer is prepared, nano-silane sealant is sprayed on the surface of the anti-corrosion layer for sealing treatment.

[0047] During the above preparation process, the spray gun pressure range is controlled to be 0.5-1.0 MPa, the gas temperature is 200-500°C, and the copper-based powder particle size is 5-90 μm. The powder diameter and pressure are controlled according to the surface treatment requirements to achieve performance control of the transition layer and the functional layer.

[0048] During the spraying process, the total deposition layer thickness is controlled to be 0.2 to 4 mm, wherein the copper base layer thickness is controlled to be 0.2 mm, and the transition layer uses a nickel metal or tin metal layer, and the transition layer thickness is set to 0.2±0.05 mm.

[0049] Example 1

[0050]

[0051] Example 2

[0052]

[0053] X-ray diffraction (XRD) characterization results show that the coating grain size is controlled at 2 to 8 μm and the dislocation density ρ reaches 10 10 m -2 level, which is two orders of magnitude lower than the thermal spray process.

[0054] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for preparing a functional layer on the surface of an aluminum-based conductive bar, characterized in that The following steps are involved: Substrate pretreatment: Surface contaminants were removed by ultrasonic cleaning with ethanol; Preparation of transition layer: cold solid deposition of copper-based composite powder to form a transition layer; Functional layer cold spraying: constructing a functional conductive layer on the surface of the transition layer; Preparation of anti-corrosion layer: constructing a composite protection system on the surface of the functional conductive layer; Densification treatment: sealing and densification treatment is carried out on the surface of the anti-corrosion layer; Coating quality inspection.

2. The process for preparing a surface functional layer of an aluminum-based conductive bar according to claim 1, characterized in that: The substrate pretreatment process is an ethanol ultrasonic cleaning process.

3. The process for preparing a surface functional layer of an aluminum-based conductive bar according to claim 1, wherein: The process for preparing the transition layer uses compressed air or high-pressure nitrogen as a medium, the pressure range is 0.5-1.0 MPa, the gas temperature is 200-500° C., and the copper-based powder particle size is 5-90 μm.

4. The process for preparing a surface functional layer of an aluminum-based conductive bar according to claim 1, wherein: In the functional layer cold spraying process, nickel or tin is used as a transition layer, and the electrical conductivity of the functional layer is ≥40% IACS.

5. The process for preparing a surface functional layer of an aluminum-based conductive bar according to claim 1, wherein: In the process of preparing the anti-corrosion layer, When the functional layer is tin-based, the anti-corrosion layer is a tin-aluminum alloy coating; When the functional layer is nickel-based, the anti-corrosion layer is a nickel-aluminum alloy coating.

6. The process for preparing a surface functional layer of an aluminum-based conductive bar according to claim 1, characterized in that: During the densification process, nano-silane sealant is sprayed.

7. The process for preparing a surface functional layer of an aluminum-based conductive bar according to claim 3, wherein: In the process of preparing the transition layer, the carrier gas temperature is 380° C., the spraying distance is 15 mm, and the spray gun moving speed is 300 mm / s.

8. A system for treating the surface functional layer of an aluminum-based conductive bar, in conjunction with the process for preparing the surface functional layer of an aluminum-based conductive bar according to claims 1 to 7, characterized in that include: Power supply unit, powder supply unit, air supply unit, cold additive master control device, spray gun and posture control module. The cold additive master control device is connected to the air supply unit for preparing the transition layer and cold spraying the functional layer; the air supply unit is connected to compressed air and high-pressure nitrogen through a bus for air compression. The cold additive master control device controls the air supply status of the air unit and the powder supply unit. The spray gun and posture control module are connected to the operating console to control the spraying status.

9. A functional layer on the surface of an aluminum-based conductive bar, prepared by the process described in any one of claims 1 to 7, characterized in that The invention comprises an aluminum base layer (1), a copper metal transition layer (2), a functional conductive layer (3) and an anti-corrosion layer (4), with a total thickness of less than 4 mm, wherein the copper metal transition layer has a thickness of 0.2 mm, and the functional conductive layer (3) is a copper conductive layer with a thickness of 0.2 mm.

10. The aluminum-based conductive bar surface functional layer according to claim 9, characterized in that: The copper metal transition layer (2) has a grain size of 2 to 8 μm.

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