Copper-aluminum alloy conducting bar and preparation method thereof

Abstract

The invention discloses a copper-aluminum alloy conducting bar and a preparation method. The method comprises the steps that electrolytic copper, an aluminum ingot, a manganese ingot and a copper-iron alloy are pretreated; casting the pretreated electrolytic copper, aluminum ingot, manganese ingot and copper-iron alloy to obtain a copper-aluminum alloy cast ingot; the copper-aluminum alloy cast ingot is subjected to high-temperature annealing treatment, and a homogenized copper-aluminum alloy cast ingot is obtained; carrying out hot working on the homogenized copper-aluminum alloy cast ingot to obtain a copper-aluminum alloy hot deformation blank; performing cold machining on the copper-aluminum alloy thermal deformation blank to obtain a copper-aluminum alloy semi-finished conducting bar; and performing low-temperature annealing treatment on the copper-aluminum alloy semi-finished conducting bar to obtain the copper-aluminum alloy conducting bar. By optimizing the components and the preparation process, various properties of the copper-aluminum alloy conducting bar can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal material processing, and particularly relates to a copper-aluminum alloy bar and a preparation method thereof. BACKGROUND

[0002] The copper-aluminum alloy is widely used in motor bars due to its excellent electrical conductivity, mechanical properties, corrosion resistance and wear resistance. However, the nuclear power motor needs to operate under extreme working conditions of high temperature, radiation and frequent start-stop. The traditional copper-aluminum alloy bar is prone to cracking due to the following reasons: 1. Limitation of low Fe content: the existing technology considers that Fe will form coarse brittle phases (such as FeAl3) with Al, which will aggravate the brittleness of the grain boundary, so Fe is limited to ≤0.1%; 2. Failure under high stress: the current can reach 600% of full load when the motor starts, and the bar generates thermal fatigue cracks due to resistance heat and mechanical vibration; 3. Defects of existing optimization schemes: although the addition of rare earth elements can refine the grains, it requires complex processes (such as vacuum melting) and high cost, which is difficult to be applied in industrialization.

[0003] In the prior art, the preparation of the copper-aluminum alloy bar mainly adopts the melting method, and the cracking is reduced by controlling the iron element content to be ≤0.1%. However, this low-iron-content alloy still has a risk of cracking under the complex working conditions of the nuclear power motor. If a high-iron-content alloy such as CuAl10Ni5Fe4 (Fe 3-5%) is used, the strength is improved through the Fe-Al phase, but the electrical conductivity is reduced and the brittleness is increased, which cannot meet the needs of the nuclear power motor; the control of the iron element content in the prior art is relatively conservative, and the potential of the iron element in improving the microstructure and anti-cracking performance is not fully utilized; although the addition of rare earth elements can refine the grains, it requires complex processes (such as vacuum melting) and high cost, which is difficult to be applied in industrialization. SUMMARY

[0004] In view of the defects in the prior art, the purpose of the present application is to provide a copper-aluminum alloy bar and a preparation method thereof, which aims to improve the performance of the copper-aluminum alloy bar.

[0005] To achieve the above purpose, the present application provides the following technical solutions: A copper-aluminum alloy bar, the components and mass percentages of each component of the copper-aluminum alloy bar are as follows: Al: 8.0% to 8.5%; Fe: 0.1% to 0.2%; Mn: 0.1% to 0.2%; Cu: the balance.

[0006] The application further provides a preparation method of the copper-aluminum alloy busbar, which comprises the following steps: pretreating electrolytic copper, aluminum ingots, manganese ingots and copper-iron alloy; melting and casting the pretreated electrolytic copper, aluminum ingots, manganese ingots and copper-iron alloy to obtain copper-aluminum alloy ingots; performing high-temperature annealing treatment on the copper-aluminum alloy ingots to obtain homogenized copper-aluminum alloy ingots; performing hot working on the homogenized copper-aluminum alloy ingots to obtain copper-aluminum alloy hot-deformed blanks; performing cold working on the copper-aluminum alloy hot-deformed blanks to obtain copper-aluminum alloy semi-finished busbars; and performing low-temperature annealing treatment on the copper-aluminum alloy semi-finished busbars to obtain copper-aluminum alloy busbars.

[0007] Optionally, the pretreatment of the electrolytic copper, aluminum ingots, manganese ingots and copper-iron alloy comprises the following steps: preheating the electrolytic copper, aluminum ingots and manganese ingots, and pre-melting the preheated manganese ingots and part of the preheated electrolytic copper to obtain Cu-20Mn intermediate alloy; and crushing the copper-iron alloy to obtain copper-iron alloy particles.

[0008] Optionally, the crushing of the copper-iron alloy comprises the following steps: crushing the copper-iron alloy by using liquid nitrogen cryogenic crushing combined with surface passivation process.

[0009] Optionally, the melting and casting of the pretreated electrolytic copper, aluminum ingots, manganese ingots and copper-iron alloy to obtain copper-aluminum alloy ingots comprises the following steps: melting another part of the preheated electrolytic copper to obtain copper liquid; and adding the crushed copper-iron alloy, the preheated aluminum ingots and performing refining to the copper liquid in sequence to obtain copper-aluminum alloy ingots.

[0010] Optionally, the melting of another part of the preheated electrolytic copper to obtain copper liquid comprises the following step: melting another part of the preheated electrolytic copper by using gradient temperature rising melting method.

[0011] Optionally, the high-temperature annealing treatment of the copper-aluminum alloy ingots to obtain homogenized copper-aluminum alloy ingots comprises the following steps: high-temperature melting of the copper-aluminum alloy ingots in a protective atmosphere to obtain solid-melted ingots; and performing multi-stage temperature control annealing on the solid-melted ingots to obtain homogenized copper-aluminum alloy ingots.

[0012] Optionally, the hot working of the homogenized copper-aluminum alloy ingots to obtain copper-aluminum alloy hot-deformed blanks comprises the following steps: heating and heat preservation of the homogenized copper-aluminum alloy ingots; deforming the heat-preserved homogenized copper-aluminum alloy ingots; quenching the deformed homogenized copper-aluminum alloy ingots; and tempering and air cooling of the quenched homogenized copper-aluminum alloy ingots to obtain copper-aluminum alloy hot-deformed blanks.

[0013] Optionally, the cold working of the copper-aluminum alloy hot-deformed blanks to obtain copper-aluminum alloy semi-finished busbars comprises the following steps: surface treatment of the hot-deformed blanks; and cold working of the surface-treated hot-deformed blanks to obtain copper-aluminum alloy semi-finished busbars.

[0014] Optionally, the low-temperature annealing treatment is performed on the copper-aluminum alloy semi-finished conductor bar to obtain a copper-aluminum alloy conductor bar, including: performing pulse current treatment on the copper-aluminum alloy semi-finished conductor bar. The copper-aluminum alloy semi-finished conductor bar after the pulse current treatment is subjected to a step-up temperature recrystallization annealing treatment, and the copper-aluminum alloy semi-finished conductor bar after the recrystallization annealing treatment is subjected to a stabilization treatment, and the copper-aluminum alloy conductor bar is obtained after cooling.

[0015] Compared with the prior art, the application has the following beneficial effects: By optimizing the design of the copper-aluminum alloy composition and controlling the Fe and Mn content to be 0.10% to 0.20%, the application can refine the grain, increase the recrystallization temperature, and inhibit the grain boundary sliding under high temperature or stress, thereby reducing crack initiation. The application innovatively adopts a complete set of precision preparation process including multi-physical field synergistic casting, multi-stage temperature control homogenization annealing, multi-directional alternating hot working, and pulse current assisted annealing, successfully forms a uniform ultra-fine grain structure containing a nano-scale Fe-Al dispersion strengthening phase in the alloy, significantly enhances the grain boundary strength, thereby simultaneously improving the strength, electrical conductivity, and thermal stability of the alloy, and finally enables the conductor bar product to have excellent anti-cracking performance, thereby providing key material support for high-reliability nuclear power equipment. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flowchart of a preparation method of a copper-aluminum alloy conductor bar according to an embodiment of the application; Figure 2 is a metallographic image of a copper-aluminum alloy conductor bar according to another embodiment of the application; Figure 3 is a metallographic image of a copper-aluminum alloy conductor bar with Fe content less than 0.1%; Figure 4 is a residual stress detection schematic diagram of a copper-aluminum alloy conductor bar with Fe content less than 0.1%; Figure 5 is a residual stress detection schematic diagram of a copper-aluminum alloy conductor bar according to another embodiment of the application. DETAILED DESCRIPTION

[0017] Specific embodiments of the application will be described in detail below with reference to the accompanying drawings. Although specific embodiments of the application are shown in the drawings, it should be understood that the application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the application and to fully convey the scope of the application to those skilled in the art.

[0018] It should be noted that some terms are used in the description and claims to refer to particular components. One of skill in the art will understand that one of skill in the art can use different nomenclature to refer to the same component. The description and claims do not differentiate components based on nomenclature, but rather on the functional differences between components. As used throughout the description and claims, "comprising" or "including" is to be interpreted as "including but not limited to." The description that follows is intended to provide a better understanding of the preferred embodiments of the present application, but is not intended to limit the scope of the application. The scope of the present application is defined by the appended claims.

[0019] In order to facilitate the understanding of the embodiments of the present application, further explanation and description will be made below with specific examples combined with the accompanying drawings, and each drawing does not constitute a limitation to the embodiments of the present application.

[0020] In one exemplary embodiment, the present application provides a copper-aluminum alloy conductor bar, the components and the mass percentage of each component are as follows: Al: 8.0% to 8.5%; Fe: 0.1% to 0.2%; Mn: 0.1% to 0.2%; Cu: the balance.

[0021] Further, the present application carries out multiple detections including metallographic analysis, mechanical properties and electrical conductivity on copper-aluminum alloy conductor bars with different proportions of components, and the detection results are shown in Table 1: Table 1

[0022] As can be seen from Table 1, compared with other alloys, alloy 3 performs best in tensile strength, elongation, electrical conductivity, thermal stability and ammonia fumigation test, and therefore, the component proportion of alloy 3 can be used as the best component proportion of the present application.

[0023] Figure 1 is a flowchart of a preparation method of a copper-aluminum alloy conductor bar provided by one exemplary embodiment of the present application, as shown in Figure 1 The method comprises the following steps: S100: pretreating electrolytic copper, aluminum ingot, manganese ingot and copper-iron alloy; S200: melting and casting the pretreated electrolytic copper, aluminum ingot, manganese ingot and copper-iron alloy to obtain a copper-aluminum alloy ingot; S300: high-temperature annealing treatment of the copper-aluminum alloy ingot to obtain a homogenized copper-aluminum alloy ingot; S400: hot working of the homogenized copper-aluminum alloy ingot to obtain a copper-aluminum alloy hot deformed blank; S500: cold working of the copper-aluminum alloy hot deformed blank to obtain a copper-aluminum alloy semi-finished conductor bar; S600: annealing the copper-aluminum alloy semi-finished conductor bar at low temperature to obtain a copper-aluminum alloy conductor bar.

[0024] In another example embodiment, in step S100, the pre-treatment of the electrolytic copper, aluminum ingot, manganese ingot and copper-iron alloy includes the following steps: S101: preheating the electrolytic copper, aluminum ingot and manganese ingot; In this step, for the electrolytic copper, the embodiment adopts a stepwise preheating process, which includes: first, heat preservation at 200°C for 1h to completely remove the adsorbed moisture, and then heating to 400°C to remove the surface oxides of the electrolytic copper, providing a low-oxygen and low-impurity high-purity raw material for subsequent high-temperature smelting. The aluminum ingot is preheated to 300°C under an inert gas (Ar) protective environment to actively peel off the Al2O3 film on its surface, which helps to improve the wettability and alloying efficiency during melting. The manganese ingot is preheated to 200°C to 250°C under an inert atmosphere (such as Ar gas) and heat preserved for 1h to 2h to remove the surface adsorbed moisture and slight oxides, avoiding the introduction of oxygen impurities in the subsequent smelting process. Then, the preheated manganese ingot and part of the preheated electrolytic copper are pre-smelted to prepare a Cu-20Mn intermediate alloy, which is crushed into uniform particles of 3mm to 5mm to improve the dispersibility of manganese and the uniformity of smelting, avoiding segregation and burning problems that easily occur when pure manganese is directly added.

[0025] In this embodiment, the electrolytic copper, aluminum ingot and manganese ingot are preheated to actively eliminate the moisture and oxides adsorbed on the surface of the raw materials, preventing the moisture and oxides from decomposing into hydrogen and oxygen gases and dissolving into the copper liquid during high-temperature smelting, thereby avoiding defects such as pores and slag in the ingot. At the same time, preheating can significantly reduce the temperature difference between the raw materials and the molten copper liquid, which is beneficial to reducing the thermal shock to the melt during addition, thereby improving the alloying efficiency.

[0026] S102: crushing the copper-iron alloy.

[0027] In this step, the embodiment adopts liquid nitrogen deep cooling crushing combined with a surface passivation process to crush the copper-iron alloy: first, the copper-iron alloy is deep-cooled in a liquid nitrogen environment at -50°C to fully embrittle the copper-iron alloy, and then mechanically crushed to obtain copper-iron alloy particles with uniform particle size; then, a phosphate passivation layer with a thickness of 1μm to 2μm is coated on the surface of the crushed copper-iron alloy particles to isolate oxygen and moisture and at the same time inhibit the oxidation tendency of Fe elements during subsequent smelting.

[0028] The above treatment process not only ensures the accurate control of the composition of the copper-iron alloy, but also helps to improve the purity of the melt and the mechanical properties of the conductor bar.

[0029] In another example embodiment, in step S200, the pre-processed electrolytic copper, aluminum ingots, manganese ingots, and copper-iron alloy are subjected to melting and casting to obtain copper-aluminum alloy ingots, including the following steps: S201: Melting another part of the preheated electrolytic copper to obtain a copper liquid; In this step, the present embodiment adopts a gradient temperature rising melting method. Under the protection of inert gas (Ar), another part of the electrolytic copper preheated to 400°C is melted in three stages: first, the temperature is raised to 800°C at a rate of 10°C / min to avoid the risk of material cracking caused by thermal stress; second, the temperature is raised to 1150°C at a rate of 20°C / min to 30°C / min to ensure that the preheated electrolytic copper is fully melted and has good fluidity; and finally, the temperature is kept constant at 1150°C for 20 minutes to promote the floating of impurities.

[0030] Compared with traditional direct high-temperature melting, the above stage melting process adopted in the present embodiment can reduce the gettering phenomenon of the copper liquid. Through inspection, it can control the oxygen content of the melt to be ≤8 ppm. At the same time, it can inhibit the generation of Cu2O brittle phase, thereby laying a foundation of high-purity and low-impurity melt for the addition of subsequent alloying elements.

[0031] S202: Adding the crushed copper-iron alloy, and the preheated aluminum ingots and manganese ingots to the copper liquid in sequence for refining to obtain copper-aluminum alloy ingots.

[0032] In this step, first, the copper-iron alloy (3mm to 5mm in diameter) crushed by deep cryogenic crushing is added to the copper liquid, and a 10Hz pulse magnetic field (peak strength 0.5T) is started at 1150°C to make the Fe element uniformly dispersed in the form of nanoclusters; then, the aluminum ingots preheated under Ar protection are added, and the aluminum liquid surface oxide film is broken by acoustic assistance (20kHz ultrasonic) to promote Al-Cu interdiffusion; finally, the Cu-20Mn intermediate alloy is added, and the micro-turbulence (Reynolds number Re>5000) generated by electromagnetic stirring is used to realize instantaneous homogenization of Mn.

[0033] In the refining stage, the present embodiment uses a composite refining agent composed of 60% borax, 30% cryolite, and 10% sodium chloride. At a high temperature of 1200°C, the above mixture rapidly reacts to generate a low-melting-point slag system with a melting point below 900°C. This slag system has good fluidity, adsorbability, and chemical activity, can efficiently capture and dissolve harmful impurity elements such as sulfur (S) and phosphorus (P) in the melt, and separate them from the copper-aluminum alloy liquid to the slag phase, thereby realizing deep purification and being beneficial to improving the purity and metallurgical quality of the final ingot.

[0034] The above melting process is controlled by multi-physical field synergy (electromagnetic-ultrasonic-thermodynamics), so that the composition deviation (Al / Fe / Mn) of the ingot can be controlled within ±0.05%, and the grain size reaches ASTM 4 level (only 6 level for traditional process), thereby providing non-segregation billets for subsequent hot working.

[0035] In another exemplary embodiment, in step S300, the high-temperature annealing treatment of the copper-aluminum alloy ingot to obtain a homogenized copper-aluminum alloy ingot includes the following steps: S301: Place the copper-aluminum alloy ingot in a protective atmosphere annealing furnace, and raise the furnace temperature to 850-880°C at a rate of ≤5°C / min, and after holding for 8-12h, melt to obtain a solid-melt ingot; This step can fully dissolve the brittle intermetallic compounds such as Fe-Al and Mn-Al formed in the copper-aluminum alloy ingot due to non-equilibrium solidification, to promote the solid solution of Al, Fe, Mn and other elements in the Cu matrix, thereby obtaining a single solid-melt ingot with composition supersaturation, and preparing for subsequent hot working treatment.

[0036] S302: Multi-stage temperature control annealing of the solid-melt ingot to obtain a homogenized copper-aluminum alloy ingot.

[0037] In this step, the present embodiment precisely controls the cooling program, slowly reduces the furnace temperature to the precipitation window of 750-780°C at a rate of 2°C / min, and holds for 4-6h, to realize fine regulation and control. By slowly cooling and holding, the Fe element can be uniformly precipitated in the form of nano-sized Fe-Al dispersed phase, to avoid the formation of coarse brittle phases (such as FeAl3), and at the same time, with the help of the thermal activation effect in this temperature range, the Mn element is further diffused to inhibit the grain boundary segregation, thereby improving the uniformity and stability of the homogenized copper-aluminum alloy ingot. After holding, the furnace temperature is further cooled to 500°C at a rate of ≤3°C / min, and the copper-aluminum alloy ingot is air-cooled to room temperature, to obtain a homogenized copper-aluminum alloy ingot.

[0038] This step controls the cooling rate to avoid thermal stress and non-uniform secondary phase precipitation caused by rapid cooling, thereby ensuring the organizational stability of the copper-aluminum alloy ingot.

[0039] In summary, compared with the traditional single high-temperature annealing treatment method, the present embodiment adopts multi-stage temperature control annealing and slow cooling process, on the basis of realizing composition homogenization, by precisely regulating the precipitation path of Fe element, it can induce the formation of high-density, nano-sized Fe-Al dispersed strengthening phase in the copper matrix. These nano-phases can effectively pin the grain boundaries, inhibit grain boundary sliding and crack initiation, thereby enhancing the grain boundary strength, and further improving the fatigue resistance and crack resistance of the copper-aluminum alloy ingot under the high temperature and high stress working conditions of nuclear power.

[0040] In another example embodiment, in step S400, the homogenized copper-aluminum alloy ingot is subjected to hot working to obtain a copper-aluminum alloy hot deformed blank, including the following steps: S401: heating the homogenized copper-aluminum alloy ingot to 780-800°C (within a precision range of ±5°C) and holding for 2-3 hours; In this step, the heating temperature of 780-800°C is below the solid solution line of the homogenized copper-aluminum alloy ingot, aiming to stabilize the nanoscale Fe-Al dispersed phase and at the same time to make the matrix in the best plastic state, preparing for subsequent deformation.

[0041] S402: deforming the homogenized copper-aluminum alloy ingot after holding; In this step, the homogenized copper-aluminum alloy ingot is first subjected to the first pass deformation in the temperature range of 800-780°C, with a deformation amount of 40-50%, at a high rate (strain rate ≥1 s -1 ) to break the original casting structure; Subsequently, the homogenized copper-aluminum alloy ingot after the first pass deformation is water mist cooled to 750-730°C, and subjected to the second pass deformation in the cross direction, with a deformation amount of 30-40%, at a medium rate (strain rate 0.3 s -1 -0.5 s -1 ) to promote dynamic recrystallization; Finally, the third pass finishing deformation is performed at a temperature of 720-700°C, with a deformation amount of 15-20%, at a low rate (strain rate ≤0.1 s -1 ) to refine the grains and eliminate internal stress.

[0042] In summary, the first pass is performed at a temperature of 800-780°C, with a large deformation amount of 40-50% and a high strain rate (≥1 s -1 ), aiming to completely break the as-cast dendritic structure to provide nucleation cores for dynamic recrystallization; the subsequent second pass is performed in the cross deformation direction, at a temperature of 750-730°C, with a moderate deformation amount of 30-40% and a medium strain rate (0.3 s -1 -0.5 s -1 ), which can effectively promote dislocation recombination and the completion of dynamic recrystallization, thereby refining the grains and improving the uniformity of the structure; finally, the third pass is performed at a temperature of 720-700°C, with a finishing deformation amount of 15-20% and a low strain rate (≤0.1 s -1 ), which not only can further eliminate the internal stress of the homogenized copper-aluminum alloy ingot, but also can obtain a fine equiaxed crystal structure with strong texture through controllable deformation, thereby improving the consistency of the transverse mechanical properties and high-temperature fatigue resistance of the blank.

[0043] S403: quenching the homogenized copper-aluminum alloy ingot after deformation; In this step, fine equiaxed crystals formed by dynamic recrystallization are locked by rapid cooling (water mist cooling rate ≥ 50℃ / s), and the brittle phase is inhibited from precipitating at the grain boundaries, obtaining a supersaturated solid solution.

[0044] S404: short (10min~15min) stress relief annealing of the homogenized copper-aluminum alloy ingot after quenching at 550℃~570℃, followed by air cooling, obtaining a copper-aluminum alloy hot deformation blank.

[0045] In this step, short stress relief annealing at 550℃~570℃ can eliminate internal stress and lattice distortion accumulated during hot working, while retaining the work hardening effect. Through annealing, dislocations can be rearranged and annihilated to reduce the residual stress inside the homogenized copper-aluminum alloy ingot, thereby avoiding cracks caused by stress concentration during subsequent cold working or direct service.

[0046] In summary, compared with traditional single-direction, single-pass hot working, the present embodiment uses multi-directional alternating deformation and multi-stage temperature control-rate coordinated control strategy, which not only completely breaks up the as-cast structure of the homogenized copper-aluminum alloy ingot, but also efficiently induces dynamic recrystallization process by precisely controlling the temperature interval and strain rate combination, thereby obtaining a uniform ultra-fine grain microstructure. The above process can effectively avoid the processing brittleness caused by Al2O3 film wrapping the grain boundaries and the local segregation of Fe element, which is beneficial to improving the uniformity of the material's transverse mechanical properties and its fatigue resistance under high temperature and high stress conditions, and ultimately can provide a high-quality copper-aluminum alloy hot deformation blank with fine structure, uniform composition and no internal defects for subsequent cold working process.

[0047] In another exemplary embodiment, in step S500, the cold working of the copper-aluminum alloy hot deformation blank to obtain a copper-aluminum alloy semi-finished product conductor bar includes the following steps: S501: surface treatment of the hot deformation blank; In this step, the oxide scale on the surface of the hot deformation blank is first removed by shot blasting (for example, using ceramic shots with a particle size of 0.2mm as impact medium), and beneficial compressive stress is introduced into the surface layer; then, the hot deformation blank is subjected to real-time precision milling, and the single-sided cutting amount is controlled to be 0.5mm~1.0mm to remove the surface defect layer, obtaining a clean surface blank, which provides a good foundation for subsequent uniform cold deformation.

[0048] S502: cold working of the surface-treated hot deformation blank using a "warm rolling-cold drawing" composite deformation process; In this step, the surface-treated hot deformed blank is first preheated to 280-320°C (under Ar protection), and then subjected to multi-pass warm rolling at this temperature range, with a total deformation of 50-60% and decreasing deformation per pass (about 30% for the first pass, and gradually decreasing for the subsequent passes).

[0049] Subsequently, the warm-rolled blank is immersed in liquid nitrogen (-196°C) for cryogenic treatment, and after 15 min of holding, is immediately subjected to drawing deformation in a special low-temperature drawing die, with a deformation of 30-40%, to obtain a copper-aluminum alloy semi-finished conductor with high strength, high dimensional accuracy, and good uniformity of the microstructure.

[0050] It should be noted that during the cold working process, when the cumulative cold deformation reaches 70% and 90%, respectively, an intermediate annealing treatment is inserted by applying a pulse current, i.e., a pulse current with a peak current density of 50 A / mm 2 and a pulse width of 100 ms is applied to the conductor under the protection of an atmosphere, and the treatment is performed in an intermittent manner for 5 cycles.

[0051] This non-thermal annealing treatment can efficiently eliminate local micro-stress, reduce dislocation pile-up, and induce non-classical recrystallization, forming sub-micron-sized grains with more uniform size, thereby avoiding the strength loss and grain growth caused by traditional low-temperature annealing.

[0052] In another exemplary embodiment, in step S600, the low-temperature annealing treatment of the copper-aluminum alloy semi-finished conductor to obtain a copper-aluminum alloy conductor includes the following steps: S601: Place the copper-aluminum alloy semi-finished conductor in a pulse current treatment device, and apply a high-density (80 A / mm 2 -100 A / mm 2 ), short pulse width (2-5 ms), and low duty cycle (5-10%) pulse current for 3-5 min under the protection of an inert atmosphere.

[0053] In this step, the pulse current treatment can efficiently eliminate micro-defects (such as vacancies and dislocation loops) generated in the subsequent processing of the copper-aluminum alloy semi-finished conductor, provide uniform nucleation sites for subsequent recrystallization, and avoid grain coarsening.

[0054] S602: Perform stepwise temperature rising recrystallization annealing treatment on the copper-aluminum alloy semi-finished conductor after pulse current treatment. In this step, the copper-aluminum alloy semi-finished conductor after pulse treatment is placed in a precision annealing furnace and subjected to the following treatment under a protective atmosphere: Firstly, the copper-aluminum alloy semi-finished product is heated slowly to 320-350°C at a rate of ≤3°C / min and kept for 30-45 min. This stage mainly realizes the recovery process to eliminate most of the macroscopic internal stress, and at the same time, a large number of fine subgrain structures are formed in the semi-finished product.

[0055] Subsequently, the temperature is continuously increased to 380-400°C (lower than the traditional recrystallization temperature of the alloy) at a rate of 5°C / min and kept for 60-90 min. In this stage, the subgrain structures formed in the previous stage are used as nucleation points to induce continuous recrystallization (or in-situ recrystallization), and finally, fine and uniform equiaxed recrystallized grains (grain size can reach ASTM 10 grade or finer) are formed.

[0056] S603: The copper-aluminum alloy semi-finished product after recrystallization annealing is subjected to stabilization treatment, and the copper-aluminum alloy conductor is obtained after cooling.

[0057] In this step, first, a mixed protective atmosphere containing a small amount of B2H6 (ethylborane, volume concentration 0.05%-0.1%) is introduced into the annealing furnace, and the treatment is carried out at 400°C for 15-20 min. In this process, boron atoms selectively segregate in the grain boundary region, which can effectively purify the grain boundary impurities and stabilize the grain boundary structure, thereby enhancing the softening resistance and grain boundary stability of the conductor at high temperature and under irradiation.

[0058] Then, the copper-aluminum alloy semi-finished product after stabilization treatment is subjected to cooling treatment, first cooled to 250°C at a rate of 10°C / min to promote the moderate precipitation of nanoscale strengthening phases (such as Fe-Al phase); then, the copper-aluminum alloy semi-finished product is taken out of the furnace and cooled to room temperature by inert gas (air speed adjustable), and the copper-aluminum alloy conductor is obtained.

[0059] Figure 2 is a metallographic image of the copper-aluminum alloy conductor prepared in the present application; Figure 3 is a metallographic image of a copper-aluminum alloy conductor with Fe content less than 0.1%; by comparison, Figure 2 and Figure 3 there are obvious differences in microstructure, in which, Figure 2 the copper-aluminum alloy conductor in has a relatively uniform grain structure, and the Fe-Al dispersion strengthening phase is uniformly distributed, indicating that the distribution of Fe element in the microstructure of the alloy is optimized, which helps to improve the grain boundary strength and thus enhance the crack resistance. While Figure 3 the alloy conductor with Fe content less than 0.1% in shows a relatively coarse grain structure, and there are many impurities enriched in the grain boundary, which may lead to a lower grain boundary strength, thus making it prone to cracking or failure under high temperature and mechanical stress. Through comparative analysis, Figure 2The copper-aluminum alloy conductor in the present application has obvious advantages in microstructure optimization and is more suitable for high-performance applications.

[0060] In addition, according to GB / T 10567.2-2007 Copper and Copper Alloy Wrought Products Residual Stress Test Method-Ammonia Fume Test Method, the residual stress of the copper-aluminum alloy conductor prepared in the present application and the existing copper-aluminum alloy conductor with Fe content less than 0.1% was detected, wherein, Figure 4 is a residual stress detection schematic diagram of the copper-aluminum alloy conductor with Fe content less than 0.1%; Figure 5 is a residual stress detection schematic diagram of the copper-aluminum alloy conductor prepared in the present application. Figure 5 As can be seen from the above, the copper-aluminum alloy conductor prepared in the present application presents a relatively uniform characteristic in residual stress distribution, indicating that the present application can successfully reduce the residual stress in the alloy by optimizing the alloy composition and processing technology, thereby improving the stability and crack resistance. In comparison, Figure 4 the residual stress distribution of the copper-aluminum alloy conductor with Fe content less than 0.1% shown in the above is relatively uneven, showing a higher residual stress concentration area, which may lead to more easily appearing cracks or other failure phenomena in high stress or high temperature working environment. Therefore, Figure 5 the conductor in the present application performs better in residual stress control and is suitable for high-performance applications.

[0061] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A copper-aluminum alloy conductor strip, characterized in that, The composition and mass percentage of the copper-aluminum alloy conductor strip are as follows: Al: 8.0% to 8.5%; Fe: 0.1% to 0.2%; Mn: 0.1% to 0.2%; Cu: Balance.

2. A method for preparing a copper-aluminum alloy conductor strip, characterized in that, The method includes: Pretreatment of electrolytic copper, aluminum ingots, manganese ingots, and copper-iron alloys; Pretreated electrolytic copper, aluminum, manganese ingots and copper-iron alloys are melted and cast to obtain copper-aluminum alloy ingots. High-temperature annealing is performed on copper-aluminum alloy ingots to obtain homogenized copper-aluminum alloy ingots. Hot working is performed on homogenized copper-aluminum alloy ingots to obtain hot-deformed copper-aluminum alloy billets. Cold working is performed on hot-deformed copper-aluminum alloy billets to obtain copper-aluminum alloy semi-finished guide bars. Low-temperature annealing is performed on copper-aluminum alloy semi-finished conductor bars to obtain copper-aluminum alloy conductor bars.

3. The method according to claim 2, characterized in that, The pretreatment of electrolytic copper, aluminum ingots, manganese ingots, and copper-iron alloys includes: Electrolytic copper, aluminum ingots, and manganese ingots are preheated, and the preheated manganese ingots and part of the preheated electrolytic copper are pre-melted to obtain Cu-20Mn master alloy. The copper-iron alloy is crushed to obtain copper-iron alloy particles.

4. The method according to claim 2, characterized in that, The crushing of the copper-iron alloy includes: The copper-iron alloy was crushed using liquid nitrogen cryogenic crushing combined with surface passivation.

5. The method according to claim 3, characterized in that, The process of melting and casting pretreated electrolytic copper, aluminum, manganese, and copper-iron alloys to obtain copper-aluminum alloy ingots includes: Another portion of the preheated electrolytic copper is melted to obtain molten copper; Crushed copper-iron alloy and preheated aluminum ingots are added sequentially to molten copper and then refined to obtain copper-aluminum alloy ingots.

6. The method according to claim 5, characterized in that, The process of melting another portion of the preheated electrolytic copper to obtain molten copper includes: Another portion of the preheated electrolytic copper was melted using a gradient heating melting method.

7. The method according to claim 2, characterized in that, The process of performing high-temperature annealing on copper-aluminum alloy ingots to obtain homogenized copper-aluminum alloy ingots includes: Copper-aluminum alloy ingots are placed in a protective atmosphere and melted at high temperature to obtain solid solution ingots; Multi-stage temperature-controlled annealing of solid solution ingots was performed to obtain homogenized copper-aluminum alloy ingots.

8. The method according to claim 2, characterized in that, The process of hot-working a homogenized copper-aluminum alloy ingot to obtain a hot-deformed copper-aluminum alloy billet includes: The homogenized copper-aluminum alloy ingot is heated and held at that temperature. Deformation is performed on the homogenized copper-aluminum alloy ingot after heat preservation. Rapidly cool the deformed homogenized copper-aluminum alloy ingot; The homogenized copper-aluminum alloy ingots after rapid cooling are tempered and air-cooled to obtain copper-aluminum alloy hot-deformation billets.

9. The method according to claim 2, characterized in that, The process of cold working a hot-deformed copper-aluminum alloy billet to obtain a semi-finished copper-aluminum alloy guide bar includes: Surface treatment of hot-deformed blanks; The hot-deformed blank after surface treatment is cold-worked to obtain copper-aluminum alloy semi-finished guide strips.

10. The method according to claim 2, characterized in that, The process of performing low-temperature annealing on the copper-aluminum alloy semi-finished conductor strip to obtain the copper-aluminum alloy conductor strip includes: The copper-aluminum alloy semi-finished conductor bar is subjected to pulse current treatment; The copper-aluminum alloy semi-finished conductor bar after pulse current treatment is subjected to step-heat recrystallization annealing. The copper-aluminum alloy semi-finished conductor strip after recrystallization annealing is stabilized and then cooled to obtain the copper-aluminum alloy conductor strip.

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