A copper alloy, a method for preparing the same, and an application thereof

Abstract

The present application relates to the technical field of copper alloy materials for cables, and particularly relates to a copper alloy, a preparation method and application thereof.The copper alloy comprises, in terms of mass content, In 0.15-0.45wt.%, Cr 0.10-0.30wt.%, Zr 0.05-0.18wt.%, Re 0.02-0.09wt.%, Ti 0.01-0.06wt.% and B 0.003-0.015wt.%;and the mass ratio of the In, Cr and Zr is (2.5-3):(1.67-2):1.The In-containing high-strength high-conductivity copper alloy of the present application realizes the softening resistance performance of multi-phase superposition and accumulation, and has the effects of high strength, high conductivity, low cost and easy industrialization, and solves the industry pain point of cable short-time overload softening.

Description

Technical Field

[0001] This invention relates to the field of copper alloy materials for cables, and in particular to a copper alloy, its preparation method, and its application. Background Technology

[0002] As the core carrier of power transmission, the operational stability of wires and cables directly determines the safety and reliability of the power system. During their service life, cables are frequently affected by factors such as power load fluctuations, extreme weather, and equipment failures, resulting in short-term overloads lasting ≤2 hours. Under these conditions, the conductor temperature can rapidly rise from the rated 90℃ to 120-200℃, and in extreme cases, exceed 200℃. The conductor softening caused by short-term overloads leads to a sharp drop in tensile strength and an abnormal increase in plasticity, which in turn causes problems such as conductor strand breakage, accelerated aging of the insulation layer, and irreversible increase in transmission loss, severely shortening the cable's lifespan and even causing safety accidents such as fires.

[0003] Currently, mainstream copper alloys used in cables have significant drawbacks: pure copper has excellent conductivity but extremely low strength, with a strength decrease of over 40% after a short-term overload at 150℃; Cu-Ag alloys offer improved softening resistance, but Ag is expensive, and excessive addition leads to a decrease in conductivity, hindering large-scale application; the reinforcing phases precipitated in conventional Cu-Cr-Zr alloys are prone to coarsening and dissolving under overload high temperatures, resulting in limited softening resistance and failing to meet the service requirements of frequent short-term overloads. Existing research on In-containing copper alloys mainly focuses on lead frames and contact wires, neglecting designs addressing the pain point of cable overload softening, lacking hierarchical multi-strength systems, and the inability of single / dual reinforcing phases to achieve comprehensive softening resistance, resulting in a lack of cumulative strengthening effects.

[0004] Invention patent application 202410817566.7 discloses an active brazing filler metal for brazing high thermal conductivity carbon materials to metals. It employs conventional brazing filler metal preparation processes, relying on a Cu-In-Sn ternary system to form the Cu2In phase, which is only an auxiliary strengthening phase for the weld seam, without any other nano-reinforcing phase design or optimized control of its size and distribution. It only addresses the short-term high temperature during brazing, without considering long-term repeated overload softening resistance, high conductivity, or wire processing performance. Existing copper alloys for cables suffer from insufficient resistance to short-term overload softening and an imbalance between cost and performance. To date, there is no In-containing copper alloy technology solution that addresses the pain point of short-term overload softening in cables by achieving a cumulative anti-softening effect through multi-phase nano-reinforcement synergy, indicating a significant technological gap in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a copper alloy, its preparation method, and its applications. The high-strength, high-conductivity copper alloy containing In for cables, designed to resist short-term overload softening, utilizes a Sn-free component window to construct a multi-nano reinforcement system, achieving multi-phase superposition and accumulation of softening resistance. This alloy balances high strength and high conductivity, low cost, and ease of industrialization, fundamentally solving the industry pain point of short-term overload softening in cables.

[0006] In a first aspect, the present invention provides a copper alloy, wherein the composition of the copper alloy, by mass content, is: In 0.15-0.45 wt.%, Cr 0.10-0.30 wt.%, Zr 0.05-0.18 wt.%, Re 0.02-0.09 wt.%, Ti 0.01-0.06 wt.%, B 0.003-0.015 wt.%; and the mass ratio of In, Cr and Zr is (2.5-3):(1.67-2):1.

[0007] Preferably, the copper alloy composition, by mass content, is: In 0.15-0.45 wt.%, Cr 0.10-0.30 wt.%, Zr 0.05-0.18 wt.%, Re 0.02-0.09 wt.%, Ti 0.01-0.06 wt.%, B 0.003-0.015 wt.%, with the balance being Cu and unavoidable impurities; the mass ratio of In, Cr, and Zr is (2.5-3):(1.67-2):1, and the mass ratio of In and Ti is (6.67-15):1.

[0008] Further preferably, the strengthening phases in the copper alloy include Cu2In nanophase, Cu3Ti2 nanophase, Cu5Zr nanophase and Cr nanophase.

[0009] More preferably, the size of the Cu2In nanophase is 20-80 nm, the size of the Cu3Ti2 nanophase is 15-60 nm, the size of the Cu5Zr nanophase is 10-50 nm, and the size of the Cr nanophase is 5-30 nm.

[0010] More preferably, in the copper alloy, the volume fraction of the Cu2In nanophase is 3.5%-8.2%.

[0011] Preferably, the volume fraction of the Cu3Ti2 nanophase is 2.0%-5.5%.

[0012] Preferably, the volume fraction of the Cu5Zr nanophase is 1.5%-4.0%.

[0013] Preferably, the volume fraction of the Cr nanophase is 1.0%-3.0%.

[0014] Preferably, the copper alloy has an electrical conductivity of ≥82% IACS.

[0015] Preferably, the tensile strength of the copper alloy is ≥480MPa.

[0016] Preferably, the tensile strength reduction rate of the copper alloy after being kept at 180°C for 2 hours is ≤8%.

[0017] Secondly, the present invention provides a method for preparing the copper alloy, comprising: obtaining a copper alloy billet, subjecting the copper alloy billet to DC pulse aging treatment, subjecting the DC pulse aging treated billet to continuous cold drawing, and then performing post-treatment.

[0018] Preferably, the DC pulse aging treatment includes: heating the copper alloy billet under a protective atmosphere, then aging it under a DC pulse current; followed by cooling and tempering; preferably, the heating temperature is 450-500℃; preferably, the current density of the DC pulse current is 15-30 A / mm. 2 The frequency is 100-200Hz, and the duty cycle is 30%-50%; preferably, the aging treatment temperature is 480-550℃; preferably, the tempering treatment temperature is 200-250℃.

[0019] Preferably, in the continuous cold drawing, the total deformation rate is 70%-90%; preferably, the drawing speed is 8-15m / min; preferably, the air-cooled temperature is controlled to below 50℃; preferably, the number of drawing passes is 8-12, the deformation rate of each pass is 6%-10%, and the intermediate annealing temperature between passes is 300-350℃.

[0020] Thirdly, the present invention provides the application of the copper alloy or the copper alloy obtained by the preparation method in cables, preferably in power transmission cables or special cable conductors.

[0021] The beneficial effects of this invention are at least as follows: The high-strength, high-conductivity copper alloy for cables that resists short-term overload softening provided by this invention can construct a four-phase hierarchical multi-nano reinforcement system with Cu2In as the core and combined with Cu3Ti2, Cu5Zr, and Cr inside the alloy. This achieves a multi-dimensional cumulative strengthening effect of matrix dispersion strengthening, dislocation movement hindrance, grain boundary pinning, and grain growth inhibition. The strength decay after short-term overload at 120-200℃ is ≤8%, while the conductivity is ≥82% IACS and the tensile strength is ≥480MPa. This fundamentally solves the industry pain point of short-term overload softening of cables and is suitable for the needs of large-scale cable production. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 An image of a quadruple nano-reinforcement system in a copper alloy provided in an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0026] Unless otherwise specified, the techniques or conditions described in the embodiments of this invention shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Devices, instruments, reagents, etc., without specified manufacturers, are all conventional products that can be purchased through legitimate channels. All experimental reagents and raw materials involved are commercially available products, and all reagents are analytical grade products.

[0027] This invention provides a copper alloy, the composition of which, by mass content, is: In 0.15-0.45 wt.%, Cr 0.10-0.30 wt.%, Zr 0.05-0.18 wt.%, Re 0.02-0.09 wt.%, Ti 0.01-0.06 wt.%, B 0.003-0.015 wt.%; the mass ratio of In, Cr and Zr is (2.5-3):(1.67-2):1.

[0028] In a preferred embodiment, the copper alloy comprises, by mass content: In 0.15-0.45 wt.%, Cr 0.10-0.30 wt.%, Zr 0.05-0.18 wt.%, Re 0.02-0.09 wt.%, Ti 0.01-0.06 wt.%, B 0.003-0.015 wt.%, with the balance being Cu and unavoidable impurities; the mass ratio of In, Cr and Zr is (2.5-3):(1.67-2):1, and the mass ratio of In and Ti is (6.67-15):1.

[0029] According to an embodiment of the present invention, the copper alloy is an In-containing high-strength and high-conductivity copper alloy for cables resistant to short-term overload softening (i.e., a high-strength and high-conductivity copper alloy for cables resistant to short-term overload softening). Its specific composition and dosage can ensure the synchronous and uniform precipitation of multiphase strengthening phases, and no Sn or other elements are added to the copper alloy to avoid interfering with the precipitation of strengthening phases and conductivity.

[0030] In this embodiment of the invention, the copper alloy composition does not contain Sn. Existing technologies generally believe that In requires synergy with Sn to stably precipitate Cu2In intermetallic compounds, and this phase can only achieve a single strength improvement in brazed welds, failing to meet the service requirements of cable conductors. This invention, through a Sn-free composition window design, combined with a multi-element synergistic ratio of In to Cr, Zr mass ratio (2.5-3):(1.67-2):1 and In to Ti mass ratio (6.67-15):1), achieves stable nucleation and precipitation of the Cu2In phase in a Sn-free system. Research has revealed that in the synergistic nucleation mechanism of this invention, because the atomic radius mismatch between Ti and Cu (approximately 14.1%) is much smaller than that of In (approximately 29.7%), and the diffusion coefficient of Ti in the Cu matrix is ​​much higher than that of In, coupled with the low solid solubility of Ti leading to supersaturation and a large nucleation driving force, Ti atoms can complete long-range diffusion earlier. Therefore, the Cu3Ti2 phase completes nucleation before the Cu2In phase. The preferentially formed Cu3Ti2 nanophase has a low lattice mismatch (approximately 6.2%) and low interfacial energy with Cu2In, providing a high-density heterogeneous nucleation core for the Cu2In phase. Through heterogeneous nucleation on the Cu3Ti2 surface, Cu2In achieves a significant reduction in the nucleation barrier, forming a core-shell precipitation structure, thus increasing the nucleation rate of the Cu2In phase by over 60%. This invention fundamentally solves the industry problem of easy coarsening and uneven distribution of the Cu2In phase in traditional processes, and resolves the challenge of balancing softening resistance with high strength and high conductivity. In a further preferred embodiment, the copper alloy composition, by mass content, is: In 0.23-0.36 wt.%, Cr 0.18-0.23 wt.%, Zr 0.09-0.13 wt.%, Re 0.04-0.06 wt.%, Ti 0.03-0.05 wt.%, B 0.006-0.011 wt.%, with the balance being Cu and unavoidable impurities. The mass ratio of In, Cr, and Zr is (2.56-2.77):(1.77-2):1, and the mass ratio of In and Ti is (7.20-7.67):1. The copper alloy within the preferred range exhibits the best overall performance.

[0031] According to embodiments of the present invention, the reinforcing phases in the copper alloy include Cu2In nanophase, Cu3Ti2 nanophase, Cu5Zr nanophase, and Cr nanophase. The size of the Cu2In nanophase is 20-80 nm, the size of the Cu3Ti2 nanophase is 15-60 nm, the size of the Cu5Zr nanophase is 10-50 nm, and the size of the Cr nanophase is 5-30 nm. Preferably, in the copper alloy, the volume fraction of the Cu2In nanophase is 3.5%-8.2%, the volume fraction of the Cu3Ti2 nanophase is 2.0%-5.5%, the volume fraction of the Cu5Zr nanophase is 1.5%-4.0%, and the volume fraction of the Cr nanophase is 1.0%-3.0%. The copper alloy is a high-strength, high-conductivity copper alloy for cables that resists short-term overload softening. The copper alloy contains a four-phase multi-nano reinforced system, which includes Cu2In nanophase, Cu3Ti2 nanophase, Cu5Zr nanophase and Cr nanophase. The copper alloy with the above-mentioned reinforced phases of specific size and volume fraction has better comprehensive performance and can be well used for short-time overload softening cables.

[0032] In this embodiment of the invention, a four-phase hierarchical multi-nano reinforcement system with Cu2In as the core is formed inside the copper alloy. The parameters and functions of each phase are as follows: there is no functional overlap, they complement each other, and a cumulative strengthening effect is achieved; Cu2In nanophase: size 20-80nm, volume fraction 3.5%-8.2%, melting point ≥660℃, excellent high-temperature stability, the core function is to inhibit the growth of Cu matrix grains under short-term overload high temperature, and prevent softening from the source; Cu3Ti2 nanophase: size 15-60nm, volume fraction 2.0%-5% Cu₂In phase: 0.5%, melting point ≥700℃, hardness higher than Cu₂In phase, its core function is to hinder dislocation slip and climb at high temperatures, suppressing softening caused by plastic deformation; Cu₅Zr nanophase: size 10-50nm, volume fraction 1.5%-4.0%, excellent high-temperature stability, its core function is to pin grain boundaries, suppressing high-temperature softening caused by grain boundary slip; Cr nanophase: size 5-30nm, volume fraction 1.0%-3.0%, its core function is matrix dispersion strengthening, improving the alloy's basic strength and high-temperature stability, filling the strengthening blind spots of the first three phases. The four phases synergistically form a full-level protection of matrix dispersion strengthening, dislocation movement inhibition, grain boundary pinning, and grain growth suppression, achieving a cumulative strengthening effect, and the anti-softening performance is far superior to single / dual strengthening systems.

[0033] In some embodiments of the present invention, the conductivity of the copper alloy is ≥82% IACS, the tensile strength of the copper alloy (25℃) is ≥480MPa, and the tensile strength attenuation rate of the copper alloy after being kept at 180℃ for 2 hours is ≤8%.

[0034] This invention eliminates the need for adding Sn or other elements. Instead, it utilizes a synergistic effect of certain amounts of In, Cr, Zr, and Ti to construct a four-phase hierarchical multi-nano-reinforced system. The size, volume fraction, and distribution of each reinforcing phase are optimized and controlled to achieve overload softening resistance. Based on synergistic nucleation and interface strengthening mechanisms, the four-phase nano-reinforced system achieves a synergistic softening resistance effect, breaking through the traditional bottleneck of copper alloys in cables where strength, conductivity, and softening resistance cannot be simultaneously achieved. Existing technologies generally believe that improving high-temperature softening resistance inevitably comes at the cost of conductivity. However, this invention achieves excellent softening resistance with a strength attenuation of ≤15% after short-term overload at 120-200℃, while maintaining high strength and high conductivity characteristics of ≥80% IACS and tensile strength ≥420MPa. According to Matthiessen's law, the influence of solid solution atom scattering in metal resistivity is far greater than that of nano-precipitated phases. The high conductivity mechanism of the alloy of this invention lies in the following: through a unique DC pulse aging treatment, elements such as In, Cr, Zr, and Ti fully precipitate as nano-reinforcing phases, significantly reducing the content of solid solution atoms in the matrix and achieving deep purification of the matrix, fundamentally and greatly reducing solid solution scattering. Simultaneously, the sizes of the four precipitated phases are all controlled at the nanoscale (5-80 nm), avoiding the formation of continuous electron-blocking paths. The negative impact of their weak scattering characteristics is far less than the positive gain brought by matrix purification, thus resolving the contradiction between high volume fraction precipitated phases and high conductivity. In some existing solutions, the Cu2In phase only plays a limited auxiliary strengthening role in the static environment of brazed welds. However, in the long-term service environment of the cable conductor under repeated overload and dynamic stress of this invention, it can synergistically achieve long-term anti-softening with the Cu3Ti2 phase, Cu5Zr phase, and Cr nano-phase, significantly improving the service stability and service life of the cable, filling a technological gap in this field.

[0035] This invention also provides a method for preparing the copper alloy, comprising: obtaining a copper alloy billet, subjecting the copper alloy billet to DC pulse aging treatment, continuously cold drawing the DC pulse aging treated billet, and then performing post-treatment. In a preferred embodiment, the DC pulse aging treatment is performed at 480-550℃ for 3-5 hours. The DC pulse aging treatment of this invention can simultaneously precipitate four-phase nano-strengthening phases and stabilize the strengthening phases by low-temperature tempering.

[0036] The high-strength, high-conductivity copper alloy containing In for cables that resists short-term overload softening provided by this invention uses a Sn-free component window design and a dedicated integrated process to construct a four-phase hierarchical multi-nano-reinforced system with Cu2In as the core. This achieves a multi-phase superposition and accumulation effect to resist softening, taking into account high strength and high conductivity, low cost and easy industrialization, fundamentally solving the industry pain point of short-term overload softening in cables.

[0037] In some embodiments of the present invention, the DC pulse aging treatment includes: heating the copper alloy billet under a protective atmosphere, then aging it under a DC pulse current; then cooling and tempering it; wherein the heating temperature is 450-500℃ and the time is 30-60 min; and the current density of the DC pulse current is 15-30 A / mm². 2 The frequency is 100-200Hz, and the duty cycle is 30%-50%; the aging treatment temperature is 480-550℃, and the time is 3-5 hours; the tempering treatment temperature is 200-250℃, and the time is 1-2 hours. This invention adopts a dedicated integrated DC pulse aging process, which effectively controls the synchronous precipitation of multiphase strengthening phases through parameter optimization, making it better suited for the industrial production of cable wires.

[0038] In some embodiments of the present invention, in the continuous cold drawing, the total deformation rate is 70%-90%; the drawing speed is 8-15m / min; the air-cooled temperature is controlled to below 50℃; the number of drawing passes is 8-12, the deformation rate of each pass is 6%-10%, the intermediate annealing temperature between passes is 300-350℃, and the holding time is 20-30min.

[0039] In a further preferred embodiment, the method for preparing the copper alloy includes: vacuum induction melting of the raw material of the copper alloy, segmented cooling casting to obtain a copper alloy ingot; homogenization annealing and hot forging of the copper alloy ingot to obtain a billet; DC pulse aging treatment of the billet to precipitate a strengthening phase in the matrix; continuous cold drawing of the DC pulse aging treated billet, followed by vacuum annealing.

[0040] In this embodiment of the invention, an integrated process of conventional casting, DC pulse aging, and continuous cold drawing is adopted, overcoming the limitations of traditional aging processes and existing brazing processes. This provides an interface strengthening mechanism under electro-thermal-mechanical multi-field coupling: Traditional understanding only considers DC pulses to improve aging efficiency, but cannot control the interface characteristics between the strengthening phase and the matrix. However, this invention, by optimizing the controlled pulse parameters, utilizes the electron wind effect of the pulse current and periodic Joule thermal fluctuations to form a gradient strain field at the interface between the Cu2In phase, Cu3Ti2 phase, Cu5Zr phase, Cr nanophase, and the matrix. Specifically, at 15-30 A / mm... 2Under the influence of high-density electron flow, the electron wind effect causes momentum transfer at the interface, driving the directional migration of atoms to form a compositional transition region and reducing the interface energy. Simultaneously, periodic Joule heating causes temperature fluctuations, and due to the difference in thermal expansion coefficients between the precipitated phase and the matrix, cyclic thermal strain occurs at the interface. These two factors synergistically promote atomic rearrangement and defect elimination (the aforementioned interface bonding strength was obtained by quantitatively determining the critical shear load using the FIB micropillar compression method with a nanoindenter after preparing micropillar samples with focused ion beam), increasing the interface bonding strength between the four phases and the matrix by more than 40%. Under short-term overload high temperatures of 120-200℃, the reinforcing phase does not experience interface debonding, coarsening, or dissolution, solving the problem of high-temperature instability of the reinforcing phase in traditional copper alloys. This interface regulation mechanism is unpredictable by existing technologies and cannot be achieved through conventional heat treatment processes. The process steps are indispensable and must be coordinated to optimize and regulate the size and distribution of the dual reinforcing phases, making it suitable for the industrial production of cable wires.

[0041] In some preferred embodiments of the present invention, the method for preparing the copper alloy includes: raw material pretreatment and batching, casting, ingot homogenization treatment, hot forging, DC pulse aging treatment, continuous cold drawing treatment, and finished product post-treatment. The high-strength, high-conductivity copper alloy for cables with resistance to short-term overload softening described in this invention uses high-purity Sn-free raw materials, which are batched according to the component dosage, and then ultrasonically cleaned and vacuum dried. Casting employs vacuum induction melting, with batches of materials added in a set sequence. Electromagnetic stirring throughout the process ensures uniform composition, and segmented temperature-controlled cooling prepares the ingots. During ingot homogenization, high-temperature holding under a protective atmosphere eliminates component segregation and internal stress, ensuring uniform solid solution of all elements. Then, hot forging is performed to shape the homogenized ingot into round billets of suitable dimensions, with heat treatment between passes to eliminate internal stress. DC pulse aging treatment is used, preheating under inert protection, followed by aging at 480-550℃ for 3-5 hours with controlled pulse parameters, simultaneously precipitating four-phase nano-strengthening phases, which are then stabilized by low-temperature tempering. Continuous cold drawing is then performed, with multiple passes and intermediate annealing between passes to produce cable wires of the target diameter. Finally, post-processing is performed, including vacuum annealing to eliminate internal stress, and the finished wire is obtained after testing.

[0042] In a further preferred embodiment, the DC pulse aging treatment includes: heating to 450-500℃ at a rate of 4-6℃ / min under high-purity Ar gas, and holding at that temperature for 30-60min; starting the DC pulse power supply and adjusting the parameters: current density of 15-30A / mm². 2 The process involves aging at 480-550℃ for 3-5 hours at a frequency of 100-200Hz and a duty cycle of 30%-50%, simultaneously precipitating Cu2In, Cu3Ti2, Cu5Zr, and Cr nanophases. Then, the temperature is lowered to 200-250℃ at a rate of 1-2℃ / min, held for 1-2 hours, and subjected to low-temperature tempering. Finally, the temperature is cooled to room temperature to stabilize and enhance the phase size and distribution.

[0043] In a further preferred embodiment, the continuous cold drawing process includes: polishing the round billet after DC pulse aging treatment, removing the oxide layer, immersing it in a graphite-based lubricant at 40-60℃ for 10-15 minutes; the continuous drawing speed is 8-15 m / min, the temperature is controlled by air cooling to 22-50℃, the total deformation rate is 70%-90%, it is completed in 8-12 passes, the deformation rate of each pass is 6%-10%, the intermediate annealing temperature between passes is 300-350℃, and the holding time is 20-30 minutes.

[0044] In a further preferred embodiment, the raw material pretreatment and batching process uses electrolytic copper with a purity ≥99.99wt.%, In ingots with a purity ≥99.95wt.%, and Cu-Cr, Cu-Zr, Cu-Re, Cu-Ti, and Cu-B master alloys as raw materials, with optimized batching and an error ≤±0.005wt.%. After cutting the raw materials into blocks, they are ultrasonically cleaned with anhydrous ethanol for 15-25 minutes at an ultrasonic power of 200-300W and an ultrasonic frequency of 40-60kHz. After ultrasonication, they are vacuum dried at 80-100℃ for 30-60 minutes and then cooled for later use.

[0045] In a further preferred embodiment, during the casting process: electrolytic copper is placed in a vacuum induction melting furnace, and a vacuum is drawn to ≤5×10⁻⁶. -3 High-purity Ar gas is introduced into the furnace at a pressure of 0.12-0.15 MPa; the temperature is increased to 1180-1250℃ at a rate of 8-12℃ / min, and held for 20-40 min until melted; the temperature is then increased to 1280-1350℃, and the materials are added in batches in the following order: Cu-Cr master alloy, Cu-Zr master alloy, Cu-Re master alloy, Cu-Ti master alloy, Cu-B master alloy, and In ingot, with an interval of 8-12 min between each batch. Electromagnetic stirring is performed for 5-8 min per batch during addition. Next, the electromagnetic stirring power is 150-250W and the electromagnetic stirring frequency is 50-80Hz; after all the materials are added, continue stirring for 15-25 minutes, let stand for 10-20 minutes to remove impurities; cool down to 1150-1200℃, and cast through a graphite mold at a speed of 0.5-1.2m / min. The mold adopts a three-stage temperature-controlled cooling system with cooling rates of 15-25℃ / min, 8-12℃ / min, and 3-5℃ / min, respectively, to prepare defect-free ingots with a diameter of 80-120mm.

[0046] In a further preferred embodiment, during the ingot homogenization treatment, the ingot is ground to remove the surface oxide scale, placed in an atmosphere-protected annealing furnace, and high-purity Ar gas is introduced. The temperature is raised to 900-950°C at 5-8°C / min and held for 4-6 hours, with nitrogen purging for at least 5 minutes every hour. After holding, the temperature is lowered to 500-550°C at 2-3°C / min and held for 2-3 hours, then cooled to room temperature with the furnace.

[0047] In a further preferred embodiment, in the hot forging process, the homogenized ingot is heated to 800-850℃ at a rate of 6-10℃ / min and held for 1.5-2.5h; then hot forging is performed at 750-820℃ with a forging rate of 5-8mm / s and a forging ratio of 3-5:1, completed in 3-5 passes, with a holding temperature of 780-800℃ for 20-30min between passes, to prepare a round billet with a diameter of 20-30mm.

[0048] In a further preferred embodiment, in the post-processing of the finished product, the vacuum degree of vacuum annealing is ≤5×10-3Pa, the temperature is increased to 350-400℃ at 3-5℃ / min, held for 1-2h, and then cooled to room temperature at 2-3℃ / min.

[0049] In a specific embodiment of the present invention, the method for preparing the copper alloy includes the following steps: Step 1: Raw material pretreatment and batching: Select electrolytic copper with a purity ≥99.99wt.%, In ingots with a purity ≥99.95wt.%, and Cu-Cr, Cu-Zr, Cu-Re, Cu-Ti, and Cu-B master alloys as raw materials (excluding Sn and other raw materials); accurately calculate the batching according to the above composition range, with an error ≤±0.005wt.%; after cutting the raw materials into blocks, ultrasonically clean them with anhydrous ethanol for 15-25 min (power 200-300W, frequency 40-60kHz), vacuum dry them at 80-100℃ for 30-60 min, and cool them for later use.

[0050] Step 2: Conventional Casting: Place the electrolytic copper into a vacuum induction melting furnace, evacuate to ≤5×10-3 Pa, and introduce high-purity Ar gas to 0.12-0.15 MPa inside the furnace; raise the temperature to 1180-1250℃ at 8-12℃ / min, and hold for 20-40 min until melted; raise the temperature to 1280-1350℃, and add the copper in batches in the following order: Cu-Cr master alloy, Cu-Zr master alloy, Cu-Re master alloy, Cu-Ti master alloy, Cu-B master alloy, and In ingot, with an interval of 8-12 minutes between each batch. During material addition, electromagnetic stirring is performed for 5-8 minutes per batch (power 150-250W, frequency 50-80Hz). After all materials are added, stirring continues for 15-25 minutes, followed by standing for 10-20 minutes to remove impurities. The temperature is then lowered to 1150-1200℃, and the material is cast through a graphite mold at a speed of 0.5-1.2 m / min. The mold employs a three-stage temperature-controlled cooling system with cooling rates of 15-25℃ / min, 8-12℃ / min, and 3-5℃ / min, respectively, to produce defect-free ingots with a diameter of 80-120 mm.

[0051] The mold employs a three-stage temperature control system: First stage cooling (mold inlet section: 0-500 mm): Cooling temperature range: 1150℃ to 850-900℃; Cooling rate: 15-25℃ / min; Cooling time: 10-20 min. Second stage cooling (mold middle section: 500-1000 mm): Cooling temperature range: 850-900℃ to 600-650℃; Cooling rate: 8-12℃ / min; Cooling time: 20-35 min. Third stage cooling (mold outlet section: 1000-1500 mm): Cooling temperature range: 600-650℃ to 350-450℃; Cooling rate: 3-5℃ / min; Cooling time: 50-90 min.

[0052] Step 3: Homogenization of ingots: Grind the ingots to remove the surface oxide scale, place them in an atmosphere-protected annealing furnace, introduce high-purity Ar gas, heat to 900-950℃ at 5-8℃ / min, hold for 4-6 hours, and purge with nitrogen for at least 5 minutes every hour; after holding, cool to 500-550℃ at 2-3℃ / min, hold for 2-3 hours, and cool to room temperature with the furnace to eliminate component segregation and internal stress, so that all elements are uniformly dissolved.

[0053] Step 4: Hot forging blanking: Heat the homogenized ingot to 800-850℃ at 6-10℃ / min and hold for 1.5-2.5h; hot forge at 750-820℃, forging rate of 5-8mm / s, forging ratio of 3-5:1, in 3-5 passes, with heat treatment between passes at 780-800℃ for 20-30min to prepare a round blank with a diameter of 20-30mm.

[0054] Step 5: DC pulse aging treatment: Place the round billet into a DC pulse aging furnace, introduce high-purity Ar gas, and heat to 450-500℃ at a rate of 4-6℃ / min, holding for 30-60 minutes for preheating; start the DC pulse power supply and adjust the parameters: current density 15-30A / mm 2 The frequency is 100-200Hz, the duty cycle is 30%-50%, and the temperature is aging at 480-550℃ for 3-5 hours to simultaneously precipitate four-phase nano-reinforcing phases. After aging, the temperature is reduced to 200-250℃ at 1-2℃ / min for low-temperature tempering treatment, and the holding time is 1-2 hours. The furnace is then cooled to room temperature to stabilize the size and distribution of the reinforcing phases.

[0055] Step 6: Continuous cold drawing treatment: Grind the round blank to remove the oxide layer, and immerse it in a graphite-based lubricant at 40-60℃ for 10-15 minutes. The graphite-based lubricant is an aqueous colloidal graphite emulsion, composed of the following components by mass fraction: 8.7-14.7 wt% natural flake graphite (particle size 1-5 μm), 82-88 wt% deionized water, 1.0-2.0 wt% sodium dodecylbenzenesulfonate, and 0.5-1.0 wt% polyvinyl alcohol. 0.1-0.3 wt% benzotriazole is fed into a continuous drawing machine at a speed of 8-15 m / min, and the temperature is controlled by air cooling to room temperature -50℃. The total deformation rate is 70%-90%, and the process is completed in 8-12 passes with a deformation rate of 6%-10% per pass. Intermediate annealing is performed between passes at a temperature of 300-350℃ for 20-30 min. After each drawing pass, the wire is ultrasonically cleaned to produce cable wires with a diameter of 1.0-5.0 mm.

[0056] Step 7: Post-processing of finished product: Place the wire into a vacuum annealing furnace, with a vacuum degree ≤5×10 -3 Pa, heated to 350-400℃ at 3-5℃ / min, held for 1-2 hours, and then cooled to room temperature at 2-3℃ / min to eliminate internal stress and stabilize the strengthening phase system. After dimensional and performance testing, the finished wire is obtained. The high-strength, high-conductivity copper alloy for cables resistant to short-term overload softening prepared in this embodiment of the invention has a four-phase multi-strength system, achieving a balance of high strength, high conductivity, and softening resistance. The strength attenuation rate after a short-term overload at 180℃ is ≤8%.

[0057] This invention also provides the application of the copper alloy in power transmission cables or special cable conductors. For long-term service scenarios of cable conductors, the core solution is to address the softening problem caused by repeated short-term overloads, while also considering high strength, high conductivity, corrosion resistance, and large-scale wire production.

[0058] Example 1 This embodiment provides an In-containing high-strength, high-conductivity copper alloy for cables resistant to short-term overload softening. The composition of this copper alloy, by mass fraction, is as follows: In: 0.20 wt.%, Cr: 0.15 wt.%, Zr: 0.08 wt.%, Re: 0.04 wt.%, Ti: 0.03 wt.%, B: 0.008 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.03 wt.%. No Sn element is added. The mass ratio of In to Cr and Zr is 2.5:1.875:1, and the mass ratio of In to Ti is 6.67:1.

[0059] In the alloy of this embodiment, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 4.1%; Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 2.5%; Cu5Zr phase with a size of 10-50 nm and a volume fraction of 2.0%; and Cr nanophase with a size of 5-30 nm and a volume fraction of 1.5%.

[0060] like Figure 1 The figure shows the four-fold nano-reinforcement system and its elemental analysis diagram in this embodiment. As can be seen from the figure, four different morphologies of reinforcing phases are distributed in the matrix, corresponding to the four colored plus signs. EDS analysis revealed its composition as follows: Figure 1 As shown in the right part, based on the atomic ratio, the strengthening phases are Cu2In nanophase, Cu3Ti2 nanophase, Cu5Zr nanophase, and Cr nanophase. According to the SEM and EDS test results, the Cu3Ti2 phase completes nucleation before the Cu2In phase, providing a high-density heterogeneous nucleation core for the Cu2In phase, thus increasing the nucleation rate of the Cu2In phase by more than 60%.

[0061] This embodiment also provides a method for preparing the above-mentioned copper alloy, which adopts the following steps: 1) Raw material pretreatment and batching: Electrolytic copper with a purity ≥99.99wt.%, In ingots with a purity ≥99.95wt.%, and Cu-Cr, Cu-Zr, Cu-Re, Cu-Ti, and Cu-B master alloys are selected as raw materials. No Sn-containing raw materials are selected. The batching is calculated according to the above composition range, with an error ≤±0.005wt.%. After the raw materials are cut into blocks, they are ultrasonically cleaned with anhydrous ethanol for 20 min (power 250W, frequency 50kHz), vacuum dried at 90℃ for 45 min, and then cooled for later use.

[0062] 2) Conventional casting: Electrolytic copper is placed in a vacuum induction melting furnace and evacuated to a vacuum level of 5×10⁻⁶. -3 Pa, high-purity Ar gas was introduced into the furnace at 0.13 MPa; the temperature was increased to 1200℃ at 10℃ / min and held for 30 min until melting; the temperature was increased to 1300℃, and materials were added in batches in the order of Cu-Cr master alloy, Cu-Zr master alloy, Cu-Re master alloy, Cu-Ti master alloy, Cu-B master alloy, and In ingot, with an interval of 10 min between each batch. During the addition, electromagnetic stirring was carried out for 6 min / batch (power 200W, frequency 65Hz); after all materials were added, stirring was continued for 20 min, and the mixture was allowed to stand for 15 min to remove impurities; the temperature was reduced to 1175℃, and the mixture was cast through a graphite mold at a speed of 0.8 m / min. The mold adopted a three-stage temperature-controlled cooling system with cooling rates of 20℃ / min, 10℃ / min, and 4℃ / min, respectively, to prepare a defect-free ingot with a diameter of 100 mm.

[0063] 3) Homogenization treatment of ingots: Grind the ingots to remove the surface oxide scale, place them in an atmosphere-protected annealing furnace, introduce high-purity Ar gas, heat to 925℃ at 7℃ / min, hold for 5h, and purge with nitrogen for 5min every 1h; after holding, cool to 525℃ at 2.5℃ / min, hold for 2.5h, and cool to room temperature with the furnace to eliminate component segregation and internal stress, so that all elements are uniformly dissolved.

[0064] 4) Hot forging: The homogenized ingot is heated to 825℃ at 8℃ / min and held for 2h; hot forging is carried out at 800℃ with a forging rate of 6mm / s and a forging ratio of 4:1, which is completed in 4 passes, with a holding temperature of 790℃ for 25min between passes, to prepare a round billet with a diameter of 25mm.

[0065] 5) DC pulse aging treatment: Place the round billet into a DC pulse aging furnace, introduce high-purity Ar gas, and heat to 480℃ at a rate of 5℃ / min, holding for 45min for preheating; start the DC pulse power supply and adjust the parameters: current density 20A / mm². 2 The frequency was 150 Hz and the duty cycle was 40%. The mixture was aged at 500 ℃ for 4 h, and four-phase nano-reinforcing phase was precipitated simultaneously. After aging, the temperature was reduced to 225 ℃ at 1.5 ℃ / min and held at that temperature for 1.5 h for low-temperature tempering. The mixture was then cooled to room temperature with the furnace to stabilize the size and distribution of the reinforcing phase.

[0066] 6) Continuous cold drawing treatment: Grind the round billet to remove the oxide layer, immerse it in graphite-based lubricant at 50℃ for 12 minutes; feed it into a continuous drawing machine, draw at 10 m / min, air cool and control the temperature to 40℃, the total deformation rate is 85%, complete in 10 passes, the deformation rate of each pass is 8.5%, hold at 320℃ for 25 minutes between passes for intermediate annealing, ultrasonic cleaning after each drawing, and prepare cable wire with a diameter of 3.0 mm.

[0067] The graphite-based lubricant is an aqueous colloidal graphite emulsion, which, by mass fraction, consists of the following components: 8.7 wt% natural flake graphite (particle size 1-5 μm), 88 wt% deionized water, 2.0 wt% dispersant (sodium dodecylbenzene sulfonate), 1.0 wt% binder (polyvinyl alcohol), and 0.3 wt% rust inhibitor (benzotriazole).

[0068] 7) Finished product post-processing: Place the wire in a vacuum annealing furnace with a vacuum degree of 5×10⁻⁶. -3 Pa is heated to 380℃ at 4℃ / min, held at that temperature for 1.5h, and then cooled to room temperature at 2.5℃ / min to eliminate internal stress and stabilize the strengthening phase system. After dimensional and performance testing, the finished wire is obtained.

[0069] The high-strength, high-conductivity copper alloy for cables that resists short-term overload softening provided in this embodiment is used in power transmission cables and special cable conductors.

[0070] Example 2 The only difference between this embodiment and Embodiment 1 is that the cable in this embodiment, which is resistant to short-term overload softening, uses an In-containing high-strength, high-conductivity copper alloy. The composition by mass fraction is as follows: In: 0.30 wt.%, Cr: 0.20 wt.%, Zr: 0.10 wt.%, Re: 0.06 wt.%, Ti: 0.04 wt.%, B: 0.010 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.02 wt.%, and no Sn element is added; the mass ratio of In to Cr and Zr is 3:2:1, and the mass ratio of In to Ti is 7.5:1.

[0071] In the alloy of this embodiment, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 5.0%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 3.5%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 2.8%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 2.1%.

[0072] The preparation method adopts the integrated process of this invention, and the core parameters are as follows: Step 5 DC pulse aging: current density is 25A / mm 2 The frequency is 180Hz, the duty cycle is 45%, the aging temperature is 520℃, and the aging time is 3.5h; Step 6: cold drawing: the total deformation rate is 80%, divided into 9 passes, the deformation rate of each pass is 9%, the intermediate annealing temperature between passes is 330℃, and the holding time is 20min; the parameters of the remaining steps are the same as in Example 1.

[0073] Example 3 The difference between this embodiment and Embodiment 1 is only that: the cable in this embodiment that resists short-term overload softening uses an In-containing high-strength, high-conductivity copper alloy, and its composition by mass fraction is as follows: In: 0.40 wt.%, Cr: 0.25 wt.%, Zr: 0.15 wt.%, Re: 0.08 wt.%, Ti: 0.05 wt.%, B: 0.012 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.04 wt.%, and no Sn element is added; the mass ratio of In to Cr and Zr is 2.67:1.67:1, and the mass ratio of In to Ti is 8:1.

[0074] In the alloy of this embodiment, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 6.8%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 4.6%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 3.4%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 2.5%.

[0075] The preparation method adopts the integrated process of this invention, and the core parameters are as follows: Step 5 DC pulse aging: current density is 28A / mm 2 The frequency is 120Hz, the duty cycle is 35%, the aging temperature is 540℃, and the aging time is 4.5h; Step 6: cold drawing: the total deformation rate is 88%, divided into 11 passes, the deformation rate of each pass is 8%, the intermediate annealing temperature between passes is 340℃, and the holding time is 30min; the parameters of the remaining steps are the same as in Example 1.

[0076] Example 4 The high-strength, high-conductivity copper alloy containing In used in this embodiment of the cable resistant to short-term overload softening has the following composition by mass fraction: In: 0.15 wt.%, Cr: 0.10 wt.%, Zr: 0.05 wt.%, Re: 0.02 wt.%, Ti: 0.01 wt.%, B: 0.003 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.048 wt.%, and no Sn element added; the mass ratio of In to Cr and Zr is 3:2:1, and the mass ratio of In to Ti is 15:1.

[0077] In the alloy of this embodiment, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 3.5%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 2.0%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 1.5%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 1.0%.

[0078] The specific steps for preparing the above-mentioned copper alloy are as follows: Step 1: Raw material pretreatment and batching: Select electrolytic copper with a purity ≥99.99wt.%, In ingots with a purity ≥99.95wt.%, and Cu-Cr, Cu-Zr, Cu-Re, Cu-Ti, and Cu-B master alloys as raw materials. Do not select any Sn-containing raw materials. Accurately calculate the batching according to the above composition range, with an error ≤±0.005wt.%. After cutting the raw materials into blocks, ultrasonically clean them with anhydrous ethanol for 15 min (power 200W, frequency 40kHz), vacuum dry them at 80℃ for 30 min, and cool them for later use.

[0079] Step 2: Conventional casting: Place the electrolytic copper into a vacuum induction melting furnace and evacuate it to a vacuum level of 4×10. -3Pa, high-purity Ar gas was introduced into the furnace at 0.12 MPa; the temperature was increased to 1180℃ at 8℃ / min and held for 20 min until melting; the temperature was increased to 1280℃, and materials were added in batches in the order of Cu-Cr master alloy, Cu-Zr master alloy, Cu-Re master alloy, Cu-Ti master alloy, Cu-B master alloy, and In ingot, with an interval of 8 min between each batch. During the addition, electromagnetic stirring was carried out for 5 min / batch (power of 150W, frequency of 50Hz); after all materials were added, stirring was continued for 15 min, and the mixture was allowed to stand for 10 min to remove impurities; the temperature was reduced to 1150℃, and the mixture was cast through a graphite mold at a speed of 0.5 m / min. The mold adopted a three-stage temperature-controlled cooling system with cooling rates of 15℃ / min, 8℃ / min, and 3℃ / min, respectively, to prepare a defect-free ingot with a diameter of 120 mm.

[0080] Step 3: Homogenization treatment of ingots: Grind the ingots to remove the surface oxide scale, place them in an atmosphere-protected annealing furnace, introduce high-purity Ar gas, heat to 900℃ at 5℃ / min, hold for 4 hours, and purge with nitrogen for 5 minutes every 1 hour; after holding, cool to 500℃ at 2℃ / min, hold for 2 hours, and cool to room temperature with the furnace to eliminate component segregation and internal stress, so that all elements are uniformly dissolved.

[0081] Step 4: Hot forging blanking: The homogenized ingot is heated to 800℃ at 6℃ / min and held for 1.5h; hot forging is carried out at 750℃ with a forging rate of 5mm / s and a forging ratio of 3:1, which is completed in 3 passes, with a holding temperature of 780℃ for 20min between passes, to prepare a round blank with a diameter of 30mm.

[0082] Step 5: DC pulse aging treatment: Place the round billet into a DC pulse aging furnace, introduce high-purity Ar gas, and heat to 450℃ at a rate of 4℃ / min, holding for 30 minutes for preheating; start the DC pulse power supply and adjust the parameters: current density 15A / mm². 2 The frequency was 100 Hz and the duty cycle was 30%. The mixture was aged at 480 ℃ for 3 hours, and four-phase nano-reinforcing phase was precipitated simultaneously. After aging, the temperature was reduced to 200 ℃ at 1 ℃ / min and held at that temperature for 1 hour for low-temperature tempering. The mixture was then cooled to room temperature with the furnace to stabilize the size and distribution of the reinforcing phase.

[0083] Step 6: Continuous cold drawing treatment: Grind the round billet to remove the oxide layer, immerse it in graphite-based lubricant at 40℃ for 10 minutes; send it into a continuous drawing machine, the drawing speed is 8m / min, air-cool and temperature controlled to room temperature, the total deformation rate is 70%, completed in 8 passes, the deformation rate of each pass is about 9%, the intermediate annealing is carried out at 300℃ for 20 minutes between passes, and ultrasonic cleaning is performed after each drawing to prepare cable wire with a diameter of 5.0mm.

[0084] The graphite-based lubricant is an aqueous colloidal graphite emulsion, which, by mass fraction, consists of the following components: 12wt% natural flake graphite (particle size 1-5μm), 86.4wt% deionized water, 1.0wt% sodium dodecylbenzenesulfonate, 0.5wt% polyvinyl alcohol, and 0.1wt% benzotriazole.

[0085] Step 7: Finished product post-processing: Place the wire into a vacuum annealing furnace with a vacuum degree of 3×10⁻⁶. -3 Pa is heated to 350℃ at 3℃ / min, held at that temperature for 1 hour, and then cooled to room temperature at 2℃ / min to eliminate internal stress and stabilize the strengthening phase system. After dimensional and performance testing, the finished wire is obtained.

[0086] This embodiment describes the application of a high-strength, high-conductivity copper alloy for cables that resists short-term overload softening in power transmission cables and special cable conductors.

[0087] Example 5 The high-strength, high-conductivity copper alloy containing In used in this embodiment of the cable resistant to short-term overload softening has the following composition by mass fraction: In: 0.45 wt.%, Cr: 0.30 wt.%, Zr: 0.18 wt.%, Re: 0.09 wt.%, Ti: 0.06 wt.%, B: 0.015 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.02 wt.%, and no Sn element added; the mass ratio of In to Cr and Zr is 2.5:1.67:1, and the mass ratio of In to Ti is 7.5:1.

[0088] In the alloy of this embodiment, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 8.2%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 5.5%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 4.0%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 3.0%.

[0089] The specific steps for preparing the above-mentioned copper alloy are as follows: Step 1: Raw material pretreatment and batching: Select electrolytic copper with a purity ≥99.99wt.%, In ingots with a purity ≥99.95wt.%, and Cu-Cr, Cu-Zr, Cu-Re, Cu-Ti, and Cu-B master alloys as raw materials. Do not select any Sn-containing raw materials. Accurately calculate the batching according to the above composition range, with an error ≤±0.005wt.%. After cutting the raw materials into blocks, ultrasonically clean them with anhydrous ethanol for 25 min (power 300W, frequency 60kHz), vacuum dry them at 100℃ for 60 min, and cool them for later use.

[0090] Step 2: Conventional casting: Place the electrolytic copper into a vacuum induction melting furnace and evacuate it to a vacuum level of 3×10.-3 Pa, high-purity Ar gas was introduced into the furnace at 0.15 MPa; the temperature was increased to 1250℃ at 12℃ / min and held for 40 min until melting; the temperature was increased to 1350℃, and materials were added in batches in the order of Cu-Cr master alloy, Cu-Zr master alloy, Cu-Re master alloy, Cu-Ti master alloy, Cu-B master alloy, and In ingot, with an interval of 12 min between each batch. During the addition, electromagnetic stirring was carried out for 8 min / batch (power 250W, frequency 80Hz); after all materials were added, stirring was continued for 25 min, and the mixture was allowed to stand for 20 min to remove impurities; the temperature was reduced to 1200℃, and the mixture was cast through a graphite mold at a speed of 1.2 m / min. The mold was cooled in three stages with controlled temperature, with cooling rates of 25℃ / min, 12℃ / min, and 5℃ / min, respectively, to prepare defect-free ingots with a diameter of 80 mm.

[0091] Step 3: Homogenization treatment of ingots: Grind the ingots to remove the surface oxide scale, place them in an atmosphere-protected annealing furnace, introduce high-purity Ar gas, heat to 950℃ at 8℃ / min, hold for 6 hours, and purge with nitrogen for 6 minutes every 1 hour; after holding, cool to 550℃ at 3℃ / min, hold for 3 hours, and cool to room temperature with the furnace to eliminate component segregation and internal stress, so that all elements are uniformly dissolved.

[0092] Step 4: Hot forging blanking: The homogenized ingot is heated to 850℃ at a rate of 10℃ / min and held for 2.5h; hot forging is carried out at 820℃ with a forging rate of 8mm / s and a forging ratio of 5:1, which is completed in 5 passes, with a holding temperature of 800℃ for 30min between passes, to prepare a round blank with a diameter of 20mm.

[0093] Step 5: DC Pulse Aging Treatment (Core Step): Place the round billet into a DC pulse aging furnace, introduce high-purity Ar gas, heat to 500℃ at 6℃ / min, and hold for 60min for preheating; start the DC pulse power supply and adjust the parameters: current density 30A / mm². 2 The frequency was 200 Hz and the duty cycle was 50%. The furnace was aged at 550 ℃ for 5 h to simultaneously precipitate four-phase nano-reinforcing phase. After aging, the temperature was reduced to 250 ℃ at 2 ℃ / min and held at that temperature for 2 h for low-temperature tempering. The furnace was then cooled to room temperature to stabilize the size and distribution of the reinforcing phase.

[0094] Step 6: Continuous cold drawing treatment: Grind the round billet to remove the oxide layer, immerse it in graphite-based lubricant at 60℃ for 15 minutes; feed it into a continuous drawing machine, the drawing speed is 15m / min, the temperature is controlled by air cooling to 50℃, the total deformation rate is 90%, it is completed in 12 passes, the deformation rate of each pass is 7.5%, the intermediate annealing is carried out at 350℃ for 30 minutes between passes, and ultrasonic cleaning is performed after each drawing to prepare cable wire with a diameter of 1.0mm.

[0095] The graphite-based lubricant is an aqueous colloidal graphite emulsion, which, by mass fraction, consists of the following components: 14.7 wt% natural flake graphite (particle size 1-5 μm), 82 wt% deionized water, 2.0 wt% sodium dodecylbenzenesulfonate, 1.0 wt% polyvinyl alcohol, and 0.3 wt% benzotriazole.

[0096] Step 7: Post-processing of finished product: Place the wire into a vacuum annealing furnace with a vacuum degree of 5×10⁻⁶. -3 Pa is heated to 400℃ at 5℃ / min, held for 2 hours, and then cooled to room temperature at 3℃ / min to eliminate internal stress and stabilize the strengthening phase system. After dimensional and performance testing, the finished wire is obtained.

[0097] The high-strength, high-conductivity copper alloy for cables that resists short-term overload softening provided in this embodiment is used in power transmission cables and special cable conductors.

[0098] Example 6 The same method as in Example 1 was used, with the main difference being that the composition of the copper alloy, by mass fraction, is as follows: In: 0.28 wt.%, Cr: 0.20 wt.%, Zr: 0.11 wt.%, Re: 0.05 wt.%, Ti: 0.038 wt.%, B: 0.009 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.025 wt.%, and no Sn element added; the mass ratio of In to Cr and Zr is 2.55:1.82:1, and the mass ratio of In to Ti is 7.37:1. In the alloy of this example, in the multi-nano strengthening system: the Cu2In phase has a size of 20-80 nm and a volume fraction of 4.5%, the Cu3Ti2 phase has a size of 15-60 nm and a volume fraction of 2.8%, the Cu5Zr phase has a size of 10-50 nm and a volume fraction of 2.2%, and the Cr nanophase has a size of 5-30 nm and a volume fraction of 1.7%.

[0099] Example 7 The same method as in Example 1 was used, with the main difference being that the composition of the copper alloy, by mass fraction, is as follows: In: 0.29 wt.%, Cr: 0.20 wt.%, Zr: 0.11 wt.%, Re: 0.05 wt.%, Ti: 0.038 wt.%, B: 0.009 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.025 wt.%, and no Sn element added; the mass ratio of In to Cr and Zr is 2.64:1.82:1, and the mass ratio of In to Ti is 7.37:1. In the alloy of this example, in the multi-nano strengthening system: the Cu2In phase has a size of 20-80 nm and a volume fraction of 5.6%, the Cu3Ti2 phase has a size of 15-60 nm and a volume fraction of 3.9%, the Cu5Zr phase has a size of 10-50 nm and a volume fraction of 3.0%, and the Cr nanophase has a size of 5-30 nm and a volume fraction of 2.3%.

[0100] Example 8 The same method as in Example 1 was used, with the main difference being that the composition of the copper alloy by mass fraction is as follows: In: 0.33 wt.%, Cr: 0.21 wt.%, Zr: 0.12 wt.%, Re: 0.06 wt.%, Ti: 0.044 wt.%, B: 0.010 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.020 wt.%, and no Sn element added; the mass ratio of In to Cr and Zr is 2.75:1.75:1, and the mass ratio of In to Ti is 7.50:1.

[0101] In the alloy of this embodiment, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 6.0%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 4.1%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 3.1%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 2.4%.

[0102] Comparative Example 1 The solder system is designed according to the invention patent application 202410817566.7. The specific components are as follows by mass fraction: Cu: 70wt.%, In: 15wt.%, Sn: 15wt.%, without adding Cr, Zr, Re, Ti and B elements. Conventional solder preparation process is adopted, without DC pulse aging and continuous cold drawing steps.

[0103] Comparative Example 2 (Dual-strengthened system, without Cu5Zr and nano-Cr phase) The only difference between this comparative example and Example 2 is that the components, by mass fraction, are: In 0.30 wt.%, Ti 0.04 wt.%, Re 0.06 wt.%, B 0.010 wt.%, with the balance being Cu. No Cr or Zr elements were added, and no Cu5Zr or nano-Cr phases were precipitated.

[0104] Comparative Example 3 (Pure Copper for Conventional Cables) Oxygen-free copper with a purity of ≥99.99wt.% is produced using conventional manufacturing processes in the cable industry.

[0105] Comparative Example 4 (the percentage content of the four-phase multi-strengthened system is relatively low) The only difference between this comparative example and Example 2 is that the high-strength, high-conductivity copper alloy containing In for cables resistant to short-term overload softening in this comparative example has the following composition by mass fraction: In: 0.10 wt.%, Cr: 0.08 wt.%, Zr: 0.05 wt.%, Re: 0.04 wt.%, Ti: 0.03 wt.%, B: 0.008 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.03 wt.%, and no Sn element is added; the mass ratio of In to Cr and Zr is 2:1.6:1, and the mass ratio of In to Ti is 3.33:1.

[0106] In the alloy of this comparative example, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 2.8%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 2.3%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 1.2%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 0.8%.

[0107] Comparative Example 5 (the percentage content of the four-phase multi-strengthened system is too high) The only difference between this comparative example and Example 2 is that the high-strength, high-conductivity copper alloy containing In for cables resistant to short-term overload softening in this comparative example has the following composition by mass fraction: In: 0.50 wt.%, Cr: 0.35 wt.%, Zr: 0.15 wt.%, Re: 0.04 wt.%, Ti: 0.10 wt.%, B: 0.008 wt.%, with the balance being Cu and unavoidable impurities, the total mass fraction of which is 0.03 wt.%, and no Sn element is added; the mass ratio of In to Cr and Zr is 3.33:2.33:1, and the mass ratio of In to Ti is 5:1.

[0108] In the alloy of this comparative example, the multi-nano strengthening system contains: Cu2In phase with a size of 20-80 nm and a volume fraction of 9.0%, Cu3Ti2 phase with a size of 15-60 nm and a volume fraction of 6.1%, Cu5Zr phase with a size of 10-50 nm and a volume fraction of 4.5%, and Cr nanophase with a size of 5-30 nm and a volume fraction of 3.3%.

[0109] Performance test comparison: The samples from each embodiment and the comparative example were subjected to performance tests under the same conditions. The test standards were: tensile strength according to GB / T 228.1-2021, conductivity according to GB / T 3048.2-2008, and the softening resistance test condition was 180℃ for 2 hours (simulating extreme short-term overload of the cable). The attenuation rate was calculated based on the strength change before and after the test. The test results are shown in Table 1 below. Table 1 Performance Test Results

[0110] The test results show that the four-phase multi-strengthened system of this invention achieves a balance between high strength, high conductivity, and softening resistance. The strength attenuation rate after a short-term overload at 180℃ is ≤8%, far superior to the comparative example, demonstrating a significant cumulative strengthening effect. Comparative example 1 exhibits extremely low conductivity and poor softening resistance, failing to meet the requirements of cable conductors and thus lacking technical comparability with this invention. The dual-strengthened system of comparative example 2 shows significantly lower softening resistance than the embodiments of this invention, fully demonstrating that the newly added Cu5Zr in this invention forms a significant cumulative strengthening effect with the nano-Cr phase, Cu2In, and Cu3Ti2 phases. Conventional pure copper in comparative example 3 exhibits extremely poor softening resistance, failing to meet the service requirements of cables under short-term overload.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A copper alloy, characterized in that, The copper alloy comprises, by mass content: In 0.15-0.45 wt.%, Cr 0.10-0.30 wt.%, Zr 0.05-0.18 wt.%, Re 0.02-0.09 wt.%, Ti 0.01-0.06 wt.%, B 0.003-0.015 wt.%; the mass ratio of In, Cr and Zr is (2.5-3):(1.67-2):1; the balance is Cu and unavoidable impurities; the mass ratio of In, Cr and Zr is (2.5-3):(1.67-2):1, and the mass ratio of In and Ti is (6.67-15):

1. The strengthening phases in the copper alloy include Cu2In nanophase, Cu3Ti2 nanophase, Cu5Zr nanophase and Cr nanophase; The Cu2In nanophase has a size of 20-80 nm, the Cu3Ti2 nanophase has a size of 15-60 nm, the Cu5Zr nanophase has a size of 10-50 nm, and the Cr nanophase has a size of 5-30 nm.

2. The copper alloy according to claim 1, characterized in that, In the copper alloy, the volume fraction of the Cu2In nanophase is 3.5%-8.2%, the volume fraction of the Cu3Ti2 nanophase is 2.0%-5.5%, the volume fraction of the Cu5Zr nanophase is 1.5%-4.0%, and the volume fraction of the Cr nanophase is 1.0%-3.0%.

3. The copper alloy according to claim 1, characterized in that, The conductivity of the copper alloy is ≥82% IACS; And / or, the tensile strength of the copper alloy is ≥480MPa; the tensile strength decay rate of the copper alloy after being kept at 180℃ for 2h is ≤8%.

4. The method for preparing the copper alloy according to any one of claims 1-3, characterized in that, include: Obtain a copper alloy billet, subject the copper alloy billet to DC pulse aging treatment, and then continuously cold draw the billet after DC pulse aging treatment.

5. The preparation method according to claim 4, characterized in that, The DC pulse aging treatment includes: heating the copper alloy billet under a protective atmosphere, then aging it under the action of a DC pulse current; then cooling it down and tempering it.

6. The preparation method according to claim 4 or 5, characterized in that, In the continuous cold drawing process, the total deformation rate is 70%-90%.

7. The use of the copper alloy according to any one of claims 1-3 or the copper alloy obtained by the preparation method according to any one of claims 4-6 in cables.

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