Method for preparing copper-aluminum composite plate with high bonding strength and conductivity by continuous casting and rolling

Abstract

The present application relates to the technical field of metal material preparation, and discloses a continuous casting and rolling preparation method of a copper-aluminum composite plate with high bonding strength and electrical conductivity, which comprises the following steps: copper strip substrate surface pretreatment: three-stage cleaning process of alkali cleaning, oil removal, acid cleaning, activation and deionized water cleaning to remove the oxide layer and oil stains on the surface of the copper strip substrate; aluminum liquid smelting and interface activity regulator addition: smelting of pure aluminum, and adding an interface activity regulator to the pure aluminum liquid during the smelting process, wherein the interface activity regulator is composed of rare earth element cerium and silicon element. Through the synergistic effect of the specific interface activity regulator, the bonding state of the copper-aluminum composite interface is effectively improved, the generation and growth of brittle intermetallic compounds are inhibited, the interface defects are reduced, the interface bonding stability of the copper-aluminum composite plate is significantly improved, the interface peeling risk is reduced, the technical problem of insufficient interface bonding strength in the traditional copper-aluminum composite plate casting and rolling process is solved, and the structural reliability of the product is enhanced.

Description

Technical Field

[0001] This invention relates to the field of metal material preparation technology, specifically a method for the continuous casting and rolling preparation of copper-aluminum composite plates with both high bonding strength and conductivity. Background Technology

[0002] Copper-aluminum composite plates combine the excellent electrical and thermal conductivity of copper with the lightweight, low-cost, and corrosion-resistant properties of aluminum. They can effectively alleviate the industry dilemma of copper resource shortage and aluminum overcapacity. They have a wide range of applications and broad market prospects in aerospace, transportation, electronics, power, decorative building materials, and other fields. Their preparation technology has always been one of the research hotspots and key directions in the field of metal composite materials.

[0003] Currently, the main methods for preparing copper-aluminum composite plates include explosive bonding, rolling bonding, extrusion-rolling bonding, casting-rolling bonding, and die casting bonding. Among these, explosive bonding and rolling bonding are two relatively mature methods used in current industrial production. Casting-rolling bonding, on the other hand, has become an important development direction for copper-aluminum composite plate preparation technology in recent years due to its advantages such as low energy consumption, simple process, high production efficiency, and ability to achieve continuous production. It is expected to realize the efficient and low-cost large-scale production of copper-aluminum composite plates.

[0004] Specifically, the explosive bonding method uses the impact force generated by the explosion of explosives to cause copper and aluminum materials to collide rapidly, achieving metallurgical bonding at the interface. This method can produce large-area copper-aluminum composite plates with high interface bonding strength. However, it has drawbacks such as poor production process safety, serious noise pollution, difficulty in precise control of the production process, low product dimensional accuracy, the need for complex subsequent leveling processes, and high production costs. It is not suitable for large-scale continuous production and is prone to local defects that lead to a decrease in conductivity. In fact, copper and aluminum may even detach during processing, seriously affecting product quality and production safety.

[0005] Rolling composite methods are divided into hot rolling composite and cold rolling composite. The core of this method is to use rolling pressure to cause plastic deformation at the interface between copper strip and aluminum strip, thereby destroying the surface oxide film and achieving diffusion bonding between atoms. This method has a mature production process and high product dimensional accuracy. However, it requires the separate preparation of copper strip and aluminum strip before composite rolling, which results in a long process flow, low production efficiency, and the need for high rolling pressure, which places high demands on the equipment. In addition, the interface is prone to problems such as oxidation and contamination, resulting in weak bonding and insufficient interfacial bonding strength, which limits the application range of the product.

[0006] Casting-rolling composite technology, as a short-process and efficient composite preparation technology, integrates casting, bonding, and forming of copper-aluminum composite plates, effectively shortening the production process and reducing production costs. Solid-liquid casting-rolling composite technology is currently the main research direction in this field. It achieves interface bonding and forming during the casting-rolling process by directly contacting molten aluminum with solid copper strip, further improving production efficiency and product continuity. However, existing casting-rolling composite methods still face significant technical bottlenecks in practical applications. The most critical issue is the tendency for brittle intermetallic compounds to form at the copper-aluminum interface, leading to insufficient interfacial bonding strength and a pronounced tendency for interface delamination. This severely affects the mechanical properties and service life of the product, limiting the widespread application of casting-rolling composite technology in the large-scale production of copper-aluminum composite plates.

[0007] Research has revealed significant differences in the atomic diffusion characteristics of copper and aluminum. During the casting and rolling process, when liquid aluminum comes into contact with solid copper strip, copper atoms rapidly dissolve and diffuse into the aluminum liquid, while aluminum atoms diffuse into the copper matrix. A chemical reaction occurs at the interface between the two, generating various brittle intermetallic compound phases such as CuAl2, CuAl, and Cu9Al4. These brittle intermetallic compounds have high strength, extremely poor plasticity, and a significantly different coefficient of thermal expansion compared to the copper and aluminum matrices. They are prone to cracking under stress and deformation, leading to interface cracking and peeling of the copper-aluminum composite plate. Meanwhile, in existing casting and rolling processes, if the oxide layer and oil stains on the surface of the copper strip are not completely removed, they will further hinder atomic diffusion and metallurgical bonding at the copper-aluminum interface, exacerbating the generation of interface defects. Furthermore, unreasonable control of process parameters such as casting and rolling temperature, casting and rolling speed, and cooling conditions will lead to excessively long interface reaction time, causing the brittle intermetallic compound layer to grow excessively and thicken, further reducing the interface bonding strength. In some existing casting and rolling processes, the thickness of the intermetallic compound layer at the interface of copper-aluminum composite plates can reach 5-10 μm or more, and the bonding strength is difficult to meet the requirements of practical applications. In some cases, the bonding strength of composite plates prepared by certain processes is only about 12 MPa, which cannot meet the mechanical performance requirements of industrial applications.

[0008] To address the aforementioned interfacial bonding issues, existing technologies have attempted improvements through surface pretreatment, adjusting casting and rolling process parameters, and adding single alloying elements. For example, some technologies employ a single acid or alkali washing process to treat the copper strip surface, but this is insufficient to completely remove the surface oxide layer and oil stains, and can easily cause excessive corrosion of the copper strip surface, affecting the interfacial bonding effect. Other technologies attempt to control the growth of interfacial intermetallic compounds by adjusting process parameters such as casting and rolling temperature, billet speed, and cooling flow rate. However, because the diffusion and chemical reactions of copper and aluminum atoms are not fundamentally suppressed, effective control of interfacial intermetallic compounds is difficult to achieve, and the adjustment range of process parameters is limited, easily leading to decreased production stability and lower product yield. Still other technologies attempt to add single rare earth elements or silicon elements to improve the interfacial bonding state, but the regulatory effect of a single element is limited, failing to achieve synergistic inhibition of the formation and growth of brittle intermetallic compounds, making it difficult to fundamentally solve the technical problem of insufficient interfacial bonding strength, and easily affecting the conductivity of the product. This fails to meet the mechanical and conductivity requirements of the composite plate, limiting the product's application scenarios.

[0009] In summary, existing methods for preparing copper-aluminum composite plates, especially the casting-rolling composite method, generally suffer from technical problems such as easy formation of brittle intermetallic compounds at the interface, insufficient interfacial bonding strength, obvious tendency of interfacial delamination, difficulty in balancing production efficiency and product qualification rate, and inability to simultaneously meet the requirements for mechanical and electrical properties. These problems make it difficult to adapt to industrial-scale production and the high-performance application requirements of copper-aluminum composite plates in various fields. Therefore, developing a continuous casting-rolling method for preparing copper-aluminum composite plates that can effectively control the copper-aluminum interface reaction, inhibit the formation of brittle intermetallic compounds, improve interfacial bonding strength, and achieve efficient and stable production has become a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a continuous casting and rolling method for preparing copper-aluminum composite plates that combines high bonding strength and electrical conductivity, thus solving the problems mentioned in the background section.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a continuous casting and rolling method for preparing copper-aluminum composite plates with both high bonding strength and conductivity, characterized by comprising the following steps:

[0012] (1) Surface pretreatment of copper strip substrate: A three-stage cleaning process of alkaline washing to remove oil, acid washing to activate, and deionized water cleaning is adopted to remove the oxide layer and oil stains on the surface of the copper strip substrate.

[0013] (2) Aluminum molten metal smelting and addition of interfacial activity regulator: pure aluminum is smelted, and an interfacial activity regulator is added to the pure aluminum molten metal during the smelting process. The interfacial activity regulator is composed of rare earth element cerium and silicon element.

[0014] (3) Continuous casting and rolling: A vertical continuous casting and rolling layout with aluminum liquid supplied from the top and copper strip drawn from the bottom is adopted. The pretreated copper strip is preheated and introduced into the casting and rolling zone. At the same time, aluminum liquid with added interfacial activity regulator is poured onto the surface of the copper strip and continuous casting and rolling is carried out through casting and rolling rolls. The casting and rolling rolls are water-cooled copper rolls.

[0015] (4) Online homogenization annealing: The cast and rolled copper-aluminum composite plate is fed into a homogenization annealing furnace online for annealing treatment to eliminate casting and rolling stress and promote short-range atomic diffusion at the interface, forming a stable metallurgical bond, and obtaining the finished copper-aluminum composite plate.

[0016] Preferably, the pickling solution in step (1) is a hydrochloric acid solution with a volume fraction of 10%-15%, and the pickling time is controlled to be 30-60 seconds.

[0017] Preferably, the amount of rare earth element cerium added in step (2) is 0.05%-0.3% of the mass fraction of pure aluminum liquid, and the amount of silicon added is 0.1%-0.5% of the mass fraction of pure aluminum liquid.

[0018] Preferably, the aluminum liquid pouring temperature in step (3) is controlled at 680-720℃, and the copper strip preheating temperature is controlled at 200-300℃.

[0019] Preferably, the length of the casting and rolling zone in step (3) is 40-60 mm, and the casting and rolling speed is controlled at 0.8-1.5 m / min.

[0020] Preferably, the surface temperature of the water-cooled copper roller in step (3) is controlled at 80-120°C, and rapid solidification is achieved through water cooling to suppress the reaction time at the copper-aluminum interface.

[0021] Preferably, the temperature of the homogenization annealing in step (4) is controlled at 300-350℃ and the holding time is controlled at 30-60 minutes.

[0022] Preferably, the rare earth element cerium described in step (2) is enriched at the copper-aluminum interface to suppress the diffusion rate of copper atoms into the aluminum matrix and slow down the growth kinetics of the intermetallic compound.

[0023] Preferably, in step (2), the silicon element preferentially forms a copper-silicon compound phase with copper to block direct contact between copper and aluminum and reduce the tendency to form brittle intermetallic compound phases.

[0024] Preferably, the prepared copper-aluminum composite plate has an intermetallic compound layer thickness of less than 3 μm, a shear bond strength greater than 60 MPa, and a conductivity of more than 65% of the international annealed copper standard.

[0025] This invention provides a continuous casting and rolling method for preparing copper-aluminum composite plates that combine high bonding strength and electrical conductivity. It offers the following advantages:

[0026] 1. This invention effectively improves the bonding state of copper-aluminum composite interfaces through the synergistic effect of specific interfacial activity regulators, inhibits the formation and growth of brittle intermetallic compounds, reduces interface defects, significantly improves the interfacial bonding stability of copper-aluminum composite plates, reduces the risk of interfacial delamination, solves the technical problem of insufficient interfacial bonding strength in the traditional copper-aluminum composite plate casting and rolling process, and enhances the structural reliability of the product.

[0027] 2. This invention adopts a combination of segmented copper strip surface pretreatment process and vertical continuous casting and rolling layout, which optimizes the process flow of copper-aluminum composite, realizes continuous and efficient preparation of copper-aluminum composite plates, simplifies the production process, and reduces the operation difficulty and cost in the production process. At the same time, by combining water-cooled casting and rolling with online homogenization annealing, the interface reaction process is effectively controlled, improving production efficiency and product qualification rate.

[0028] 3. This invention improves the interfacial bonding performance of copper-aluminum composite plates while taking into account the conductivity of the product through the synergistic optimization of interfacial active elements and process parameters. The resulting copper-aluminum composite plates have both excellent mechanical bonding properties and meet the conductivity requirements of practical applications, thus broadening the application scenarios of copper-aluminum composite plates and having good industrial application value and promotion prospects. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see the appendix Figure 1 The present invention provides a method for continuous casting and rolling of copper-aluminum composite plates that have both high bonding strength and conductivity, comprising the following steps.

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and several specific embodiments. Obviously, the described embodiments are only some preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The core equipment used in this invention is a vertical twin-roll continuous casting and rolling mill, equipped with a medium-frequency induction melting furnace, a continuous mesh belt annealing furnace, a copper strip surface pretreatment and cleaning line, an induction preheating device, and an online detection device. The copper strip substrate used is all industrial pure copper strip, and the pure aluminum used is all industrial pure aluminum ingot. The interfacial activity regulator is rare earth metal cerium powder (purity ≥99.90%, particle size 200 mesh) and industrial silicon particles (purity ≥99.80%, particle size 5-8mm). The pickling solution is prepared from industrial-grade concentrated hydrochloric acid (mass fraction 37%) and deionized water, with the deionized water used for cleaning having a conductivity ≤10μS / cm. The casting rolls are custom-made water-cooled copper rolls with a diameter of 650mm and a length of 1600mm, and the circulating water cooling system has a temperature control accuracy of ±2℃. The homogenization annealing furnace is a closed continuous mesh belt annealing furnace with a temperature control accuracy of ±5℃, enabling precise control of the heating and cooling rates.

[0034] The core process logic of this invention is as follows: a clean and activated interface is obtained through fine pretreatment of the copper strip surface; a cerium-silicon composite interface activity regulator is added to the aluminum melt to achieve precise control of the interface reaction; a vertical continuous casting and rolling process is used to achieve efficient copper-aluminum solid-liquid composite + rapid solidification to inhibit the growth of brittle phases; online homogenization annealing eliminates stress and promotes metallurgical bonding of the interface, and finally a high-performance copper-aluminum composite plate is prepared.

[0035] Example 1

[0036] This embodiment aims to prepare a copper-aluminum composite plate with a thickness of 1.5 mm (0.8 mm copper layer and 0.7 mm aluminum layer) and a width of 1200 mm. The specific preparation steps are as follows:

[0037] Copper strip substrate surface pretreatment

[0038] The T2 copper strip is treated with a three-stage automated cleaning process: alkaline washing for degreasing, acid washing for activation, and deionized water cleaning. The entire process is completed continuously on the cleaning line, and the seamless connection between each process avoids secondary oxidation of the copper strip.

[0039] Alkaline washing and degreasing: An 8% sodium hydroxide aqueous solution is used. The temperature of the cleaning tank is controlled at 60±2℃. The copper strip passes through at a speed of 2m / min. The alkaline washing time is 120s. The mineral oil, rolling oil and various organic contaminants on the surface of the copper strip are removed by high-pressure spray (pressure 0.3MPa) combined with ultrasonic vibration (frequency 28kHz). After alkaline washing, the residual liquid on the surface is removed by squeezing rollers.

[0040] Pickling and activation: A 12% hydrochloric acid solution is used. The pickling tank is at room temperature (25±3℃). The copper strip passes through at a speed of 2m / min and the pickling time is 45s. The hydrochloric acid reacts chemically with CuO and Cu2O on the surface of the copper strip to completely remove the oxide layer. At the same time, a micro-roughened activation surface is formed on the surface of the copper strip to improve the subsequent bonding effect with the aluminum liquid. The pickling time is strictly controlled to avoid excessive corrosion of the copper strip surface.

[0041] Deionized water cleaning: After pickling, the copper strip immediately enters a three-stage deionized water cleaning tank. The first stage involves high-pressure spraying (pressure 0.2MPa), the second stage involves immersion cleaning, and the third stage involves high-pressure rinsing. The total cleaning time is 30 seconds, ensuring that there is no acid or chloride ion residue on the surface of the copper strip. After cleaning, it is dried in a hot air drying section (drying temperature 80±5℃, hot air velocity 3m / s) for 60 seconds to obtain an activated copper strip with a clean, oxidation-free, and oil-free surface. After drying, it is sealed and temporarily stored for later use.

[0042] Aluminum molten metal smelting and addition of interfacial activity modifiers

[0043] Pure aluminum is smelted using a medium-frequency induction furnace, with nitrogen protection throughout the process (nitrogen flow rate 5L / min) to prevent high-temperature oxidation and impurity absorption by the molten aluminum.

[0044] Melting and heating: Add 1060 pure aluminum ingots in batches to the dried melting furnace and heat them to 740±5℃ at a heating rate of 10℃ / min. After the aluminum ingots are completely melted, turn off the heating power and use the residual heat of the furnace to keep them warm.

[0045] Aluminum liquid homogenization: The aluminum liquid was mechanically stirred using a graphite stirrer at a speed of 60 r / min for 15 min to ensure uniform temperature and composition. After stirring, the mixture was allowed to stand for 5 min.

[0046] Addition of regulator: A composite interfacial activity regulator is added to the homogenized pure aluminum liquid, wherein the amount of rare earth cerium powder added is 0.15% of the mass fraction of pure aluminum liquid, and the amount of industrial silicon particles added is 0.3% of the mass fraction of pure aluminum liquid; the addition is carried out in batches. First, the industrial silicon particles are added to the aluminum liquid and stirred for 10 minutes until the silicon particles are completely dissolved. Then, the cerium powder is mixed with a small amount of pure aluminum powder and added to the aluminum liquid. Stirring is continued for 12 minutes to ensure that the cerium powder is evenly dispersed in the aluminum liquid and to avoid local enrichment and segregation.

[0047] Degassing and settling: After the regulator is added, high-purity argon gas (purity ≥99.99%) is introduced into the aluminum liquid for degassing. The argon gas flow rate is 3L / min and the degassing time is 10min. Then, the temperature of the aluminum liquid is reduced to 720±5℃ and settling for 20min to allow the inclusions and bubbles in the aluminum liquid to float to the surface. The surface slag is removed by skimming spoon to obtain a qualified aluminum liquid with uniform composition, no impurities, and no bubbles, which is then ready for use.

[0048] Continuous casting and rolling

[0049] The vertical continuous casting and rolling layout adopts an upper-supply aluminum liquid and lower-draw copper strip layout. The temperature of aluminum liquid, copper strip, roll surface temperature and casting speed are monitored online throughout the casting and rolling process to ensure stable process parameters.

[0050] Equipment preheating and commissioning: Start the vertical twin-roll continuous casting and rolling mill, control the surface temperature of the water-cooled copper rolls to 100±2℃ through the circulating water cooling system, adjust the gap between the casting and rolling rolls to 1.5mm, start the traction device and adjust the speed; adjust the temperature of the induction preheating device to 250℃, and preheat the copper strip conveying channel.

[0051] Copper strip preheating and feeding: The pretreated activated copper strip is fed into the induction preheating zone through a traction device. The copper strip preheating temperature is precisely controlled at 250±5℃. After preheating, it is continuously and smoothly introduced into the casting and rolling zone to avoid copper strip deviation and wrinkling.

[0052] Aluminum liquid pouring: Qualified aluminum liquid is poured at a uniform speed onto the surface of the copper strip in the casting and rolling zone through an insulated top-supply chute. The chute temperature is controlled at 700±5℃, the aluminum liquid pouring temperature is 700±5℃, and the pouring speed is precisely matched with the copper strip traction speed to avoid aluminum liquid splashing and flow interruption.

[0053] Casting-rolling composite: The length of the casting-rolling zone is adjusted to 50mm, the casting-rolling speed is 1.2m / min, and the casting-rolling pressure is controlled at 12±1MPa. After the aluminum liquid spreads on the surface of the copper strip, it is rapidly cooled by water-cooled copper rollers (cooling rate 15℃ / s) to achieve rapid solidification. At the same time, under the action of casting-rolling pressure, atomic diffusion occurs at the copper-aluminum interface, achieving preliminary metallurgical bonding, and continuously producing copper-aluminum composite slabs with a thickness of 1.5mm. During the casting-rolling process, the online detection device monitors the slab thickness and surface flatness in real time and provides timely feedback to adjust the process parameters.

[0054] Online homogenization annealing

[0055] After casting and rolling, the copper-aluminum composite slab is directly fed into a continuous mesh belt annealing furnace via a conveyor device, realizing online connection between casting and rolling and annealing. This avoids energy consumption caused by secondary heating after the slab cools down, and also prevents interface oxidation.

[0056] Annealing process: The annealing furnace is filled with air atmosphere, and the annealing temperature is precisely controlled at 320±5℃ with a holding time of 45min. A stepped heating and cooling method is adopted, with a heating rate of 5℃ / min, from room temperature to 320℃. After holding, the cooling rate is 4℃ / min, and the temperature is slowly cooled to below 80℃.

[0057] Finished product cooling: After the annealed composite plate is sent out of the annealing furnace, it is naturally cooled to room temperature to obtain the finished copper-aluminum composite plate.

[0058] Performance testing: The finished copper-aluminum composite plate prepared in this embodiment was subjected to comprehensive performance testing, and the testing methods all followed national standards and industry specifications.

[0059] Interface microstructure: The interface was observed using a scanning electron microscope. The interface was smooth, free of oxide inclusions, unbonded areas, and microcracks. The intermetallic compound layer at the interface was of uniform thickness, with an average thickness of 2.2 μm.

[0060] Shear bond strength: The shear bond strength is 68 MPa. All interfacial fractures occurred on the aluminum matrix side, rather than at the copper-aluminum interface, proving that the interfacial bond strength is higher than that of the aluminum matrix itself.

[0061] Conductivity: The conductivity was measured at different locations on the composite board using an eddy current conductivity meter. The average conductivity was 68% IACS, indicating uniform conductivity.

[0062] Appearance and dimensions: The composite board has a flat surface, free from warping, cracks, and scratches, with a thickness tolerance of ±0.02mm and a width tolerance of ±1mm, exhibiting high dimensional accuracy;

[0063] Product qualification rate: After 500m of continuous production, the product qualification rate reached 99.2%.

[0064] Example 2

[0065] This embodiment aims to prepare a copper-aluminum composite plate with a thickness of 2.0 mm (1.0 mm copper layer and 1.0 mm aluminum layer) and a width of 1000 mm. The process parameters are selected from the lower limit of the scope defined in the claims. The specific preparation steps are as follows:

[0066] Surface pretreatment of copper strip substrate: T2 copper strip with a thickness of 1.0 mm and a width of 1000 mm was treated. The alkaline washing and degreasing process was the same as in Example 1. The pickling was carried out with a 10% hydrochloric acid solution at room temperature for 60 seconds. The deionized water cleaning and hot air drying processes were the same as in Example 1, resulting in a clean and activated copper strip.

[0067] Aluminum molten metal smelting and addition of interfacial activity regulators: The pure aluminum smelting, homogenization, and degassing processes are the same as in Example 1; rare earth cerium powder is added to the aluminum molten metal at a mass fraction of 0.05% of the pure aluminum molten metal, and industrial silicon particles are added at a mass fraction of 0.5% of the pure aluminum molten metal. The stirring, settling, and slag skimming processes are the same as in Example 1, and qualified aluminum molten metal is obtained.

[0068] Continuous casting and rolling: The surface temperature of the water-cooled copper roll is controlled at 80±2℃; the preheating temperature of the copper strip is controlled at 200±5℃; the pouring temperature of the aluminum liquid is 680±5℃; the length of the casting and rolling zone is adjusted to 40mm, the casting and rolling speed is 0.8m / min, and the casting and rolling pressure is controlled at 10±1MPa; the remaining casting and rolling processes and online monitoring are the same as in Example 1, and a copper-aluminum composite slab is obtained.

[0069] Online homogenization annealing: annealing temperature 300±5℃, holding time 60min; heating and cooling rates and cooling process are the same as in Example 1, to obtain the finished copper-aluminum composite plate.

[0070] Performance testing: The average thickness of the intermetallic compound layer at the interface is 2.5 μm; the shear bond strength is 65 MPa; the average conductivity is 67% IACS; the composite plate has a smooth surface, high dimensional accuracy, and no obvious defects; after continuous production of 500m, the product qualification rate is 98.8%.

[0071] Example 3

[0072] This embodiment aims to prepare a copper-aluminum composite plate with a thickness of 1.0 mm (0.6 mm copper layer and 0.4 mm aluminum layer) and a width of 1500 mm. The process parameters are selected from the upper limit of the range defined in the claims. The specific preparation steps are as follows:

[0073] Copper strip substrate surface pretreatment: T2 copper strip with a thickness of 0.6 mm and a width of 1500 mm was treated. The alkaline washing and degreasing process was the same as in Example 1. The pickling was carried out with a 15% hydrochloric acid solution at room temperature for 30 seconds. The deionized water cleaning and hot air drying processes were the same as in Example 1, resulting in a clean and activated copper strip.

[0074] Aluminum molten metal smelting and addition of interfacial activity regulators: The pure aluminum smelting, homogenization, and degassing processes are the same as in Example 1; rare earth cerium powder is added to the aluminum molten metal at a mass fraction of 0.3% of the pure aluminum molten metal, and industrial silicon particles are added at a mass fraction of 0.1% of the pure aluminum molten metal. The stirring, settling, and slag skimming processes are the same as in Example 1, and qualified aluminum molten metal is obtained.

[0075] Continuous casting and rolling: The surface temperature of the water-cooled copper roll is controlled at 120±2℃; the preheating temperature of the copper strip is controlled at 300±5℃; the pouring temperature of the aluminum liquid is 720±5℃; the length of the casting and rolling zone is adjusted to 60mm, the casting and rolling speed is 1.5m / min, and the casting and rolling pressure is controlled at 15±1MPa; the remaining casting and rolling processes and online monitoring are the same as in Example 1, and a copper-aluminum composite slab is obtained.

[0076] Online homogenization annealing: annealing temperature 350±5℃, holding time 30min; heating and cooling rates and cooling process are the same as in Example 1, to obtain the finished copper-aluminum composite plate.

[0077] Performance testing: The average thickness of the intermetallic compound layer at the interface is 2.8 μm; the shear bond strength is 62 MPa; the average conductivity is 65% IACS; the composite plate has a smooth surface, high dimensional accuracy, and no obvious defects; after continuous production of 500m, the product qualification rate is 98.5%.

[0078] Comparative verification

[0079] To fully verify the synergistic effect of the cerium-silicon composite interfacial activity regulator and the overall technical advantages of the process in this invention, three comparative examples were set up. The preparation equipment, copper-aluminum substrate, and most of the process steps of the comparative examples were completely consistent with those in Example 1, except that the method of adding the interfacial activity regulator was changed. Each group continuously produced 500m copper-aluminum composite plates and conducted performance tests.

[0080] Comparative Example 1

[0081] No interfacial activity modifiers were added, and the aluminum liquid was pure 1060 aluminum liquid. All other process steps and parameters were completely consistent with Example 1. Test results: The thickness of the intermetallic compound layer at the interface was 6.8 μm, with a large amount of brittle phase generated; the shear bond strength was only 32 MPa, and the interface was prone to peeling and cracking defects; the conductivity was 62% IACS, with uneven conductivity; the product qualification rate was only 82.5%, which cannot meet the requirements for industrial applications.

[0082] Comparative Example 2

[0083] Only rare earth cerium powder was added (at a concentration of 0.15% by mass of pure aluminum liquid), without the addition of silicon. All other process steps and parameters were identical to those in Example 1. Test results: The intermetallic compound layer thickness was 4.5 μm, and the growth of brittle phases was somewhat suppressed, but the effect was limited; the shear bond strength was 48 MPa, indicating improved interfacial bonding performance, but still not meeting the high strength requirements for industrial applications; the conductivity was 64% IACS; and the product qualification rate was 90.3%.

[0084] Comparative Example 3

[0085] Only industrial silicon particles were added (at a concentration of 0.3% by mass of pure aluminum liquid), without the addition of rare earth cerium powder. All other process steps and parameters were identical to those in Example 1. Test results: intermetallic compound layer thickness was 4.2 μm; shear bond strength was 45 MPa, with the improvement in intermetallic bonding performance being lower than that achieved with the addition of cerium powder alone; conductivity was 65% IACS; and the product qualification rate was 89.7%.

[0086] Results Analysis

[0087] A comparison of the performance test results of Examples 1-3 and Comparative Examples 1-3 clearly shows that:

[0088] Without the addition of a surface activity modifier, a large amount of brittle intermetallic compounds will be generated at the copper-aluminum interface, resulting in extremely low interfacial bonding strength, poor product qualification rate, and inability to meet the needs of industrial applications.

[0089] Adding rare earth elements such as cerium or silicon alone can only suppress the growth of brittle phases and improve the interfacial bonding strength to a certain extent, but the regulatory effect of a single element is limited and cannot achieve precise and efficient control of interfacial reactions.

[0090] This invention achieves a synergistic regulatory effect between rare earth elements cerium and silicon through the combined addition of these two elements: cerium enriches at the copper-aluminum interface, inhibiting the diffusion rate of copper atoms into the aluminum matrix and slowing down the growth of brittle intermetallic compounds from a kinetic perspective; silicon preferentially forms a copper-silicon compound phase with copper, blocking the direct contact between copper and aluminum atoms from a structural perspective and reducing the tendency for brittle phase formation. The two elements complement each other to achieve efficient regulation of the copper-aluminum interface reaction, significantly reducing the thickness of the brittle intermetallic compound layer, greatly improving the interfacial bonding strength, and simultaneously taking into account the conductivity of the composite plate.

[0091] Within the range of process parameters defined by this invention, regardless of whether the intermediate, lower, or upper limit values ​​are selected, high-performance copper-aluminum composite plates with an intermetallic compound layer thickness of less than 3 μm, a shear bond strength greater than 60 MPa, and a conductivity of more than 65% IACS can be prepared. This proves that the process parameter range of this invention is scientific and reasonable, and has good process stability and repeatability.

[0092] The scope of protection of this invention is not limited to the three specific embodiments described above. Any combination and adjustment within the range of process parameters defined in the claims of this invention shall fall within the scope of protection of this invention. The specific parameter adaptability is explained below:

[0093] Copper strip surface pretreatment: Any combination of hydrochloric acid solution volume fraction of 10%-15% and pickling time of 30-60s can thoroughly remove the oxide layer and oil stains on the copper strip surface while avoiding excessive corrosion; if the hydrochloric acid concentration is less than 10% or the pickling time is less than 30s, the oxide layer will not be completely removed; if the hydrochloric acid concentration is higher than 15% or the pickling time is longer than 60s, the copper strip surface will be excessively corroded, which will affect the bonding effect of the copper-aluminum interface.

[0094] Interfacial activity regulators: Any combination of rare earth cerium mass fraction of 0.05%-0.3% and silicon mass fraction of 0.1%-0.5% can achieve a synergistic regulatory effect between the two. If the cerium content is less than 0.05% or the silicon content is less than 0.1%, the regulator content is insufficient and cannot play an effective regulatory role. If the cerium content is greater than 0.3% or the silicon content is greater than 0.5%, too many impurity phases will be generated in the aluminum matrix, reducing the electrical conductivity and mechanical properties of the composite board.

[0095] Continuous casting and rolling process: Any combination of parameters, such as aluminum melt pouring temperature of 680-720℃, copper strip preheating temperature of 200-300℃, water-cooled copper roll surface temperature of 80-120℃, casting and rolling zone length of 40-60mm, and casting and rolling speed of 0.8-1.5m / min, can achieve efficient solid-liquid composite of aluminum melt and copper strip, while inhibiting the growth of brittle phases at the interface through rapid solidification. If the parameters exceed this range, problems such as aluminum melt solidification being too fast / too slow, insufficient / excessive diffusion at the copper-aluminum interface, and uncontrolled growth of brittle phases may occur, leading to a decrease in interfacial bonding performance.

[0096] Online homogenization annealing: Any combination of annealing temperature (300-350℃) and holding time (30-60 minutes) can effectively eliminate internal stress generated during casting and rolling, prevent deformation and cracking of composite plates, and promote short-range diffusion of atoms at the copper-aluminum interface to form a stable metallurgical bond. If the annealing temperature is below 300℃ or the holding time is less than 30 minutes, stress elimination is incomplete and interface diffusion is insufficient. If the annealing temperature is above 350℃ or the holding time is longer than 60 minutes, excessive diffusion will occur at the interface, generating more brittle phases, which will affect product performance.

[0097] The test results of the above embodiments and comparative examples are shown in Table 1 below:

[0098] Table 1 Comparison of Core Performance Testing between Examples and Comparative Examples

[0099]

[0100] The copper-aluminum composite plates prepared by the cerium-silicon composite interfacial activity regulator and the limited process in Examples 1-3 of this invention all meet the design requirements in terms of core performance: the thickness of the intermetallic compound layer at the interface is <3μm, the shear bond strength is >60MPa, the conductivity is ≥65%IACS, and the product qualification rate is ≥98.5%. Moreover, when the process parameters are adjusted within the limited range, the performance of the finished product is stable and there is no significant fluctuation. This proves that the process parameter range of this invention is scientific and reasonable, and has good repeatability and industrial adaptability.

[0101] In Comparative Example 1, without the addition of a regulator, a large amount of brittle phase was generated at the interface, with a layer thickness of 6.8 μm and a shear bond strength of only 32 MPa. This significantly reduced the product qualification rate, highlighting the necessity of interfacial activity regulators for improving the bonding performance of the copper-aluminum interface. In Comparative Examples 2 and 3, the addition of cerium or silicon alone could only suppress the growth of the brittle phase to a limited extent, and the shear bond strength was still below 50 MPa, far inferior to the effect of the examples. This fully verifies that the synergistic regulatory effect of cerium and silicon is the core key to improving interfacial performance, and neither can be omitted.

[0102] All embodiments achieved high interfacial bonding strength while maintaining excellent electrical conductivity, thus achieving a balance between mechanical and electrical properties. In contrast, the comparative examples had significant shortcomings in electrical conductivity or bonding performance due to numerous interfacial defects and limited control effects of single elements, demonstrating the precision of the process and control agent combination in this invention.

[0103] All the above-mentioned preparation methods with adjusted process parameters can stably produce copper-aluminum composite plates with an intermetallic compound layer thickness of less than 3μm, a shear bond strength of greater than 60MPa, and a conductivity of more than 65% of the international annealed copper standard. These methods can meet the high-performance application requirements of copper-aluminum composite plates in multiple fields such as aerospace, transportation, electronics and power, new energy, and decorative building materials.

Claims

1. A continuous casting and rolling method for preparing copper-aluminum composite plates with both high bonding strength and conductivity, characterized in that, Includes the following steps: (1) Surface pretreatment of copper strip substrate: A three-stage cleaning process of alkaline washing to remove oil, acid washing to activate, and deionized water cleaning is adopted to remove the oxide layer and oil stains on the surface of the copper strip substrate. (2) Aluminum molten metal smelting and addition of interfacial activity regulator: Pure aluminum is smelted, and an interfacial activity regulator is added to the pure aluminum molten metal during the smelting process. The interfacial activity regulator is composed of rare earth element cerium and silicon element. (3) Continuous casting and rolling: A vertical continuous casting and rolling layout with aluminum liquid supplied from the top and copper strip drawn from the bottom is adopted. The pretreated copper strip is preheated and introduced into the casting and rolling zone. At the same time, aluminum liquid with added interfacial activity regulator is poured onto the surface of the copper strip and continuous casting and rolling is carried out through casting and rolling rolls. The casting and rolling rolls are water-cooled copper rolls. (4) Online homogenization annealing: The cast and rolled copper-aluminum composite plate is fed into a homogenization annealing furnace online for annealing treatment to eliminate casting and rolling stress and promote short-range atomic diffusion at the interface, forming a stable metallurgical bond, and obtaining the finished copper-aluminum composite plate.

2. The method for continuous casting and rolling preparation of copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, The pickling solution in step (1) is a hydrochloric acid solution with a volume fraction of 10%-15%, and the pickling time is controlled to be 30-60 seconds.

3. The continuous casting and rolling method for preparing copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, In step (2), the amount of rare earth element cerium added is 0.05%-0.3% of the mass fraction of pure aluminum liquid, and the amount of silicon added is 0.1%-0.5% of the mass fraction of pure aluminum liquid.

4. The continuous casting and rolling method for preparing copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, The aluminum liquid pouring temperature in step (3) is controlled at 680-720℃, and the copper strip preheating temperature is controlled at 200-300℃.

5. The continuous casting and rolling method for preparing copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, The length of the casting and rolling zone in step (3) is 40-60mm, and the casting and rolling speed is controlled at 0.8-1.5m / min.

6. The method for continuous casting and rolling of copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, The surface temperature of the water-cooled copper roller in step (3) is controlled at 80-120℃. Rapid solidification is achieved through water cooling, which inhibits the reaction time at the copper-aluminum interface.

7. The method for continuous casting and rolling of copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, The temperature of the homogenization annealing in step (4) is controlled at 300-350℃, and the holding time is controlled at 30-60 minutes.

8. The method for continuous casting and rolling of copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, In step (2), the rare earth element cerium is enriched at the copper-aluminum interface to suppress the diffusion rate of copper atoms into the aluminum matrix and slow down the growth kinetics of intermetallic compounds.

9. The method for continuous casting and rolling of copper-aluminum composite plates with both high bonding strength and conductivity according to claim 1, characterized in that, In step (2), silicon preferentially forms a copper-silicon compound phase with copper to block direct contact between copper and aluminum and reduce the tendency to form brittle intermetallic compound phases.

10. The method for continuous casting and rolling of copper-aluminum composite plates with both high bonding strength and conductivity according to any one of claims 1-9, characterized in that, The prepared copper-aluminum composite plate has an intermetallic compound layer thickness of less than 3 μm, a shear bond strength greater than 60 MPa, and a conductivity exceeding 65% of the international annealed copper standard.

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