A copper-aluminum composite strip and its preparation method

Abstract

This invention relates to a copper-aluminum composite strip and its preparation method, belonging to the field of metal strip material preparation. The preparation method of the copper-aluminum composite strip of this invention includes the following steps: contacting molten aluminum at 680–700°C with an unpreheated copper strip and then casting and rolling it; during the casting and rolling process, controlling the temperature of the rolls to ≤100°C, and the running speed of the copper-aluminum composite strip to be 0.5–0.8 m / min. The copper-aluminum composite strip prepared by the method of this invention has a unique multi-level heterogeneous layered structure with a macroscopic copper / aluminum heterogeneous layered structure and a nanoscale double-layer copper-aluminum compound layer interface. This can significantly improve the conductivity and ultra-high ductility of the copper-aluminum composite strip while improving the preparation efficiency, allowing the copper-aluminum composite strip to be further processed by deep drawing, bending, or twisting to prepare high-end copper-aluminum composite conductive devices.

Description

Technical Field

[0001] This invention relates to a copper-aluminum composite plate and strip and its preparation method, belonging to the field of metal plate and strip preparation. Background Technology

[0002] Copper-aluminum layered composite plates combine the advantages of copper (low electrical resistance and high thermal conductivity) with aluminum (lightweight and inexpensive), achieving a synergistic effect in cost and performance between the two metals. They are widely used in power transmission, electronic communications, and new energy fields, achieving the goal of "saving copper with aluminum" and promoting optimal resource integration.

[0003] Mature preparation methods for copper-aluminum composite plates mainly include rolling composite method, casting-rolling composite method, hydrostatic extrusion + rolling, core-filled continuous casting + rolling, and explosive composite method. However, only rolling composite method and casting-rolling composite method can produce composite plates and strips. Industrial pure copper and pure aluminum both have good electrical conductivity and plasticity. During the composite process, under the influence of temperature or stress fields, the interface structure, copper layer, and aluminum layer microstructure of copper-aluminum composite plates prepared by different processes vary greatly, resulting in significant differences in their electrical and mechanical properties. When there is no diffusion and interfacial compound layer between copper and aluminum, the interface is mainly mechanically interlocked. Under relatively small stress and strain, copper and aluminum will crack and delaminate. When the interfacial layer formed by excessive diffusion between copper and aluminum is too thick, there are many types of brittle intermetallic compounds. Under relatively small stress, interphase cracking of different types of compounds and intergranular cracking of the same type of compound will occur, leading to interface failure. Both types of composite plates have poor plasticity and toughness, and poor deformation ability in subsequent deep processing.

[0004] For composite sheets and strips produced by the cold rolling + diffusion composite method, the copper and aluminum layers undergo significant plastic deformation during cold rolling, resulting in work hardening and a substantial reduction in plasticity. During diffusion annealing, as the annealing temperature increases and the holding time lengthens, diffusion occurs between the copper and aluminum interfaces, gradually forming multilayer compounds. Simultaneously, residual stress within the copper and aluminum layers gradually dissipates, and plasticity gradually recovers. When the interfacial compound layer is thin, the plasticity recovery of the copper and aluminum layers is minimal. When the plasticity of the copper and aluminum layers is fully recovered, the interfacial compound layer becomes too thick, and its elongation is lower than that of copper and aluminum under the condition that delamination and cracking do not occur at the composite sheet interface. Although the copper-aluminum composite sheets and strips produced by the cold rolling + diffusion composite method achieve metallurgical bonding at the interface, the copper-aluminum composite sheets have poor plasticity and toughness. During deep processing such as rolling, bending, twisting, and deep drawing, delamination, misalignment, and tearing of the copper layer surface are prone to occur, severely restricting their application in high-end advanced fields. When using the casting-rolling composite method to produce copper-aluminum composite plates and strips, in order to ensure the metallurgical bonding of the interface, the copper layer is preheated and the thickness of the cladding aluminum is increased to ensure the bonding strength of the composite plate. The resulting composite plate is relatively thick, with coarse grains, poor plasticity and toughness, weak deep processing capability, and complex process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing copper-aluminum composite plates and strips, which can significantly improve the plasticity and toughness of copper-aluminum composite plates and strips while achieving copper-aluminum metallurgical bonding.

[0006] The present invention also provides a copper-aluminum composite plate and strip prepared by the above preparation method.

[0007] To achieve the above objectives, the technical solution adopted in the preparation method of the copper-aluminum composite strip of the present invention is as follows:

[0008] A method for preparing a copper-aluminum composite strip includes the following steps: molten aluminum at 680–700°C is brought into contact with a copper strip that has not been preheated, and then cast and rolled; during the casting and rolling process, the temperature of the rolls is controlled to be ≤100°C, and the running speed of the copper-aluminum composite strip is 0.5–0.8 m / min.

[0009] The method for preparing copper-aluminum composite strips of this invention abandons the traditional preheating process of copper strip in the casting and rolling method. Instead, the aluminum melt is brought into contact with a room-temperature copper strip without preheating, and the high temperature of the liquid metal ensures the mutual diffusion of copper and aluminum atoms in the interface layer. At the same time, the temperature gradient from the copper-aluminum interface layer to the core of the aluminum layer is maintained by controlling the speed of the rolls and the belt feed, avoiding the situation of excessively thick copper-aluminum interface compound layer and coarse grains. A layered structure of double-layered nanocrystalline copper-aluminum compound is formed at the copper / aluminum interface. The aluminum melt spread on the copper strip is formed with a micron-level gradient crystal casting and rolling structure due to the cooling effect of the copper strip and the rolls. The copper-aluminum composite strip prepared by this invention has a unique multi-level heterogeneous layered structure with a macroscopic copper / aluminum heterogeneous layered structure and a nanoscale double-layered copper-aluminum compound layer interface. It can significantly improve the conductivity and ultra-high ductility of the copper-aluminum composite strip while improving the preparation efficiency. This allows the copper-aluminum composite strip to be further processed by deep drawing, bending or twisting to prepare high-end copper-aluminum composite conductive devices. Furthermore, the preparation method of the copper-aluminum composite strip of the present invention does not require preheating of the copper strip, and the process is simple, energy-saving, and economically effective.

[0010] Furthermore, the copper strip is subjected to degreasing and oil removal treatments in sequence, and then molten aluminum is brought into contact with the copper strip. The thickness of the copper strip is 0.9–2 mm, for example, 1 mm or 1.5 mm.

[0011] Furthermore, the copper layer thickness in the copper-aluminum composite strip accounts for 15-20%.

[0012] Furthermore, the thickness of the copper-aluminum composite strip is 6-10 mm.

[0013] Furthermore, the copper strip is a T2 copper rolled strip. T2 copper rolled strip has a rolled deformation structure and numerous twins, resulting in low resistivity and good plasticity. Using it as the copper strip can further improve the conductivity and plasticity of the copper-aluminum composite strip. Since pure aluminum has higher strength, toughness, and plasticity than aluminum alloys, the molten aluminum is preferably pure aluminum molten metal. When selecting T2 copper rolled strip and pure aluminum molten metal, the thickness of the interfacial nanocrystalline CuAl2 layer in the obtained copper-aluminum composite strip is 0.1–0.3 μm, and the thickness of the nanocrystalline Cu9Al4 layer is 0.2–0.4 μm.

[0014] Furthermore, the molten aluminum flows out through the distribution casting nozzle and then contacts an unpreheated copper strip. The height of the molten aluminum at the outlet of the distribution casting nozzle is 6–11 mm, for example, 7–11 mm.

[0015] Furthermore, the length of the casting and rolling zone is 60–80 mm. It can be understood that the length of the casting and rolling zone refers to the distance from the liquid outlet end of the casting nozzle to the center line of the two rolls.

[0016] Furthermore, the casting and rolling process is a horizontal continuous casting and rolling process. Furthermore, both the upper and lower rolls used in the horizontal continuous casting and rolling process are water-cooled rolls. During the rolling process, the copper strip is not preheated, and the water flow rate in the water-cooled rolls is adjusted to control the roll temperature to ≤100℃, preferably 40~90℃, for example, 60℃, 70℃, or 80℃. Typically, the gap between the upper and lower rolls is set to 90-98% of the total thickness of the copper-aluminum composite strip.

[0017] The technical solution adopted by the copper-aluminum composite strip of the present invention is as follows:

[0018] A copper-aluminum composite strip prepared by the above-mentioned method.

[0019] The copper-aluminum composite strip of this invention possesses a unique multi-level heterogeneous layered structure with a macroscopic copper / aluminum heterogeneous layered structure and a micro / nano-scale double-layer copper-aluminum compound layer interface, which can significantly improve the conductivity and ultra-high ductility and toughness of the copper-aluminum composite strip. When using T2 copper cast-rolled strip in the preparation process, the conductivity of the copper-aluminum composite strip reaches 85-90% IACS, the tensile strength can reach 90-100MPa, and the elongation can reach 45-47%, exceeding the elongation of T2 copper and industrial pure aluminum, exhibiting high conductivity and ultra-high strength and ductility. Attached Figure Description

[0020] Figure 1 The macroscopic and microscopic structures of the 10mm thick copper-aluminum composite strip prepared in Example 1 are shown.

[0021] Figure 2 This is a microscopic schematic diagram of the interface of the copper-aluminum composite plate and strip prepared in Example 1. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0023] Example 1

[0024] The preparation method of the copper-aluminum composite strip in this embodiment specifically includes the following steps:

[0025] Industrial pure aluminum ingots are melted into molten aluminum, and then the molten aluminum at a temperature of 680℃ is poured into the distribution casting nozzle through a filter screen.

[0026] T2 copper rolled strip with a thickness of 1.5mm is degreased and deoiled, and then enters the casting and rolling mill through rollers without preheating or heating.

[0027] After the pure aluminum molten liquid comes into contact with the room temperature T2 copper rolled strip at the outlet of the flow casting nozzle, it is continuously horizontally cast and rolled. Under the combined action of the temperature field and the casting and rolling pressure field, a copper-aluminum composite strip with a thickness of 10 mm is produced by casting and rolling.

[0028] During the horizontal continuous casting and rolling process, the height of the molten aluminum at the outlet of the casting nozzle is controlled at 11 mm, the length of the casting and rolling zone is 60 mm, the running speed of the copper-aluminum composite strip is 0.8 m / min, and the gap between the upper and lower rollers is 9.8 mm. By adjusting the water flow rate inside the rollers, the temperature of the upper and lower rollers is kept at 60℃ during the casting and rolling process, and a temperature gradient from low to high is formed between the upper and lower rollers and the center of the molten aluminum.

[0029] The copper-aluminum composite strip prepared in this embodiment has a total thickness of 10 mm, with a T2 copper layer thickness of 1.5 mm and the remaining thickness being aluminum; the copper-aluminum interface nanocrystalline CuAl2 layer has a thickness of 0.2 μm and the nanocrystalline Cu9Al4 layer has a thickness of 0.3 μm; the copper-aluminum composite strip has a conductivity of 87% IACS, a tensile strength of 98 MPa, and an elongation of 47% (surpassing T2 copper and industrial pure aluminum).

[0030] The macroscopic and microscopic structural diagrams of the copper-aluminum composite strip prepared in this embodiment are shown below. Figure 1 As shown, the microstructure at the copper-aluminum interface is as follows: Figure 2 As shown. By Figure 1 and Figure 2 It can be seen that the prepared copper-aluminum composite plate has a unique multi-level heterogeneous layered structure with a macroscopic millimeter-level copper / aluminum heterogeneous layered structure and a nano-level double-layer copper-aluminum compound layer interface.

[0031] Example 2

[0032] The preparation method of the copper-aluminum composite strip in this embodiment specifically includes the following steps:

[0033] Industrial pure aluminum ingots are melted into molten aluminum, and then the molten aluminum at a temperature of 690℃ is poured into the distribution casting nozzle through a filter screen.

[0034] T2 copper rolled strip with a thickness of 1.5mm is degreased and deoiled, and then enters the casting and rolling mill through rollers without preheating or heating.

[0035] After the pure aluminum melt comes into contact with the room temperature T2 copper rolled strip at the outlet of the flow casting nozzle, it is continuously horizontally cast and rolled. Under the combined action of the temperature field and the casting and rolling pressure field, an 8mm thick copper-aluminum composite strip is produced by casting and rolling.

[0036] During the horizontal continuous casting and rolling process, the height of the molten aluminum at the outlet of the casting nozzle is controlled at 9 mm, the length of the casting and rolling zone is 70 mm, the running speed of the copper-aluminum composite strip is 0.6 m / min, and the gap between the upper and lower rollers is 7.9 mm. By adjusting the water flow rate inside the rollers, the temperature of the upper and lower rollers is kept at 70℃ during the casting and rolling process, and a temperature gradient from low to high is formed between the upper and lower rollers and the center of the molten aluminum.

[0037] The copper-aluminum composite strip prepared in this embodiment has a total thickness of 8 mm, with a T2 copper layer thickness of 1.5 mm and the remaining thickness being aluminum; the copper-aluminum interface nanocrystalline CuAl2 layer has a thickness of 0.2 μm and the nanocrystalline Cu9Al4 layer has a thickness of 0.3 μm; the copper-aluminum composite strip has a conductivity of 88% IACS, a tensile strength of 100 MPa, and an elongation of 46% (surpassing T2 copper and industrial pure aluminum).

[0038] Example 3

[0039] The preparation method of the copper-aluminum composite strip in this embodiment specifically includes the following steps:

[0040] Industrial pure aluminum ingots are melted into molten aluminum, and then the molten aluminum at a temperature of 700°C is poured into the distribution casting nozzle through a filter screen.

[0041] The 1mm thick T2 copper rolled strip is degreased and deoiled, and then enters the casting and rolling mill through the upper roller. The upper and lower rollers are preheated and heated.

[0042] Pure aluminum molten liquid is continuously horizontally cast and rolled in contact with room temperature T2 copper rolled strip at the outlet of the flow casting nozzle. Under the combined action of temperature field and casting pressure field, a copper-aluminum composite strip with a thickness of 6mm is produced by casting and rolling.

[0043] During the horizontal continuous casting and rolling process, the height of the molten aluminum at the outlet of the casting nozzle is controlled at 7mm, the length of the casting and rolling zone is 80mm, the running speed of the copper-aluminum composite strip is 0.5m / min, and the gap between the upper and lower rollers is 5.9mm. By adjusting and controlling the water flow rate inside the rollers, the temperature of the upper and lower rollers is kept at 80℃ during the casting and rolling process, and a temperature gradient from low to high is formed between the upper and lower rollers and the center of the molten aluminum.

[0044] The copper-aluminum composite strip prepared in this embodiment has a total thickness of 6 mm, with a T2 copper layer thickness of 1.0 mm and the remaining thickness being aluminum; the copper-aluminum interface nanocrystalline CuAl2 layer has a thickness of 0.2 μm, and the nanocrystalline Cu9Al4 layer has a thickness of 0.2 μm; the copper-aluminum composite strip has a conductivity of 85% IACS, a tensile strength of 95 MPa, and an elongation of 45% (surpassing T2 copper and industrial pure aluminum).

[0045] Example 4

[0046] The copper-aluminum composite strip in this embodiment was prepared using the methods described in Examples 1 to 3 above, and will not be repeated here.

Claims

1. A method for preparing a copper-aluminum composite plate / strip, characterized in that: Includes the following steps: Molten aluminum at 680–700°C is brought into contact with unpreheated copper strip and then cast and rolled to form a double-layered nanocrystalline copper-aluminum compound structure at the copper / aluminum interface: the nanocrystalline CuAl2 layer has a thickness of 0.1–0.3 μm and the nanocrystalline Cu9Al4 layer has a thickness of 0.2–0.4 μm. During the casting and rolling process, the temperature of the rolls is controlled at 60–80°C, and the running speed of the copper-aluminum composite strip is 0.5–0.8 m / min. The copper layer accounts for 15–20% of the thickness of the copper-aluminum composite strip.

2. The method for preparing copper-aluminum composite strip according to claim 1, characterized in that: The thickness of the nanocrystalline CuAl2 layer is 0.2–0.3 μm, and the thickness of the nanocrystalline Cu9Al4 layer is 0.2–0.3 μm.

3. The method for preparing copper-aluminum composite strip according to claim 2, characterized in that: The thickness of the copper-aluminum composite strip is 6-10 mm.

4. The method for preparing copper-aluminum composite strip according to claim 1, 2, or 3, characterized in that: The copper strip is a T2 copper rolled strip, and the aluminum melt is a pure aluminum melt.

5. The method for preparing copper-aluminum composite strip according to claim 1, 2, or 3, characterized in that: The molten aluminum flows out through the distribution casting nozzle and then contacts the copper strip without preheating; the height of the molten aluminum at the outlet of the distribution casting nozzle is 6-11 mm.

6. The method for preparing copper-aluminum composite strip according to claim 1, 2, or 3, characterized in that: The length of the casting and rolling zone is 60-80 mm.

7. The method for preparing copper-aluminum composite strip according to claim 1, 2, or 3, characterized in that: The casting and rolling process is a horizontal continuous casting and rolling process.

8. A copper-aluminum composite strip prepared by the method of any one of claims 1 to 7.

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