A novel large-section high-conductivity copper busbar and a preparation method thereof

Abstract

The application discloses a novel large-section high-conductivity copper bus and a preparation method thereof, and belongs to the technical field of conductor preparation. The novel large-section high-conductivity copper bus is prepared from recycled copper as raw material, and after purification treatment, the content of impurity trace elements is reduced to 30 ppm or less. The novel large-section high-conductivity copper bus is prepared through continuous casting and rolling, twice continuous extrusion and drawing processes, and has a maximum section specification of 40 mm*400 mm and a conductivity of 99.92%IACS. The novel large-section high-conductivity copper bus has high product conductivity, low cost, simple and efficient preparation process, and can realize large-scale production, and is suitable for fields of power transmission, new energy equipment, rail transit and the like.

Description

Technical Field

[0001] This invention belongs to the field of conductor preparation technology, and particularly relates to the preparation of copper products, specifically a novel large-section, high-conductivity copper busbar and its preparation method. Background Technology

[0002] In today's fields of power transmission, new energy devices, and rail transportation, the demand for highly efficient conductive materials is extremely urgent. Copper busbars, as crucial conductive components, directly impact the system's operating efficiency and stability.

[0003] Traditional copper busbar manufacturing processes primarily rely on electrolytic copper plates, which are then drawn into copper rods using an upward drawing method, and finally extruded to obtain the finished product. However, this process has several drawbacks. From a cost perspective, the price of electrolytic copper plates is highly susceptible to fluctuations in global copper prices, accounting for over 70% of the production cost of copper busbars, making it difficult for companies to control production costs. In terms of production efficiency, the upward drawing method for producing copper rods is extremely slow; for example, the capacity for an 8 mm copper rod is only 18 kg / h, severely restricting large-scale production. Moreover, the copper rods produced by this process are relatively uniform in scale, making it difficult to meet diverse market demands. Regarding composition control, the upward drawing method relies entirely on the purity of the electrolytic copper plate and cannot actively control impurity elements such as Ni, Pb, Fe, and Sn. The presence of these impurity elements significantly reduces the conductor performance of copper; for example, for every 0.01% increase in Pb content, conductivity can decrease by 0.5% IACS. In addition, when preparing large-section copper busbars using traditional processes, defects such as porosity and segregation are easily generated inside the large-diameter copper lead rods, resulting in unstable mechanical and electrical properties of the finished product. Furthermore, it is difficult to mass-produce ultra-large cross-section copper busbars with cross-sections exceeding 30 mm × 300 mm. Different cross-sections require redesigning the extrusion mold, resulting in a long switching cycle, typically requiring 3-5 days.

[0004] A search of existing technologies revealed that patent CN104599787B provides a method for preparing high-performance copper busbars, including steps such as copper material selection, melting, settling, heat preservation, continuous casting of copper rods, continuous extrusion, and drawing. Although its conductivity is improved, it still has shortcomings in cost control, large-section preparation, and impurity element control. Patent CN102543312A relates to a method for preparing high-conductivity, high-ductility copper alloy busbars for motors, which improves performance by adding specific elements and controlling process steps; however, it also fails to solve the core problems of high cost, low efficiency, and limited specifications in traditional processes.

[0005] Therefore, developing a copper busbar that can effectively reduce costs, improve production efficiency, precisely control composition, and produce large-section, highly conductive copper busbars and its manufacturing process is of great practical significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a novel large-section, high-conductivity copper busbar and its preparation method, which reduces costs, improves production efficiency, precisely controls composition, and enables the preparation of large-section copper busbars, meeting the demand for high-performance conductive materials in fields such as power transmission and new energy equipment.

[0007] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0008] A novel large-section, high-conductivity copper busbar, made from recycled copper, exhibits the following characteristics after processing: total impurity trace element content not exceeding 30 ppm, conductivity not less than 99.92% IACS, and a maximum cross-sectional size of 40mm × 400mm.

[0009] The above-mentioned method for preparing copper busbars includes the following steps:

[0010] (1) Raw material preparation: After melting the recycled copper, a special impurity removal agent is added to control the impurity content to ≤30 ppm;

[0011] (2) Rolling: φ8 mm copper rods are prepared by continuous casting and rolling process, with a rolling speed of 19 t / h;

[0012] (3) First continuous extrusion: Extrude the φ8 mm copper rod to φ16-30 mm copper rod at an extrusion temperature of 400-500℃;

[0013] (4) Second continuous extrusion: The large-diameter copper rod is extruded into a busbar with a cross-section of 20 mm × 100 mm - 40 mm × 400 mm;

[0014] (5) Drawing: A drawing process with a total shrinkage rate of 20-40% is adopted to refine the particle size to 15-25 μm.

[0015] In the above preparation method, the raw material preparation specifically involves: heating recycled copper to 1100-1150 ℃, melting it to obtain a recycled copper solution, adding a special impurity remover to the recycled copper solution, and stirring to allow the impurity remover to fully react with the harmful impurities in the copper solution. The stirring speed is 300-500 r / min, and the stirring time is 15-20 min, thereby forming a solid composite slag with a density greater than that of the copper solution. The slag is removed by slag discharge, thereby achieving copper purification.

[0016] The impurity removal agent is composed of rare earth elements Ce and La oxides, borides, and metallic calcium. The mass percentages of Ce and La oxides are 30-40%, borides are 20-30%, and metallic calcium is 30-40%. The mass ratios are (CeO2 + La2O3):CaB2:Ca = 2:1:2, CeO2:La2O3 = (1-2):(2-1). The amount of impurity removal agent added is 3-5% of the mass of the recycled copper. Specifically, Ce oxide is CeO2, La oxide is La2O3, borides are CaB2, and metallic calcium is elemental Ca.

[0017] In the above preparation method, the raw material preparation step uses recycled copper, which is recycled copper with a copper content of more than 98%.

[0018] Specifically, the steps for preparing recycled copper include:

[0019] (1) Screening: First, the recycled industrial waste copper is classified into waste cables and waste copper parts. Waste cables are further classified according to the insulation material, and waste copper parts are classified into pure copper parts and copper alloy parts. Pure copper parts are selected, and copper alloy parts are used for other purposes.

[0020] (2) Crushing: The classified waste cables and pure copper parts are disassembled into particles that are easy to process later. The specific operation includes: the insulation layer of the waste cables is removed by dry stripping or pyrolysis, and then crushed into 3-5 cm copper segments by a shear crusher to ensure that the copper core is fully exposed. The waste copper parts are crushed to no more than 10-20 cm by a jaw crusher, and then finely crushed to 5-8 cm particles by a cone crusher. During the crushing process, ferromagnetic impurities such as bolts and connectors are initially removed by a magnetic separation device.

[0021] (3) Cleaning: Thoroughly remove oil, oxides, and non-metallic deposits from the surface of the waste copper particles. Specific operations include:

[0022] ①Alkaline washing and degreasing: Immerse the crushed copper material in a 5-8% sodium hydroxide solution at 80-90 ℃ and stir for 10-15 minutes. Remove mineral oil, lubricating grease and other oil stains through saponification reaction. Replace the solution when the pH value is ≤9.

[0023] ② Pickling to remove oxide layer: After rinsing with clean water, immerse in a 10-15% dilute sulfuric acid solution, heat and maintain the temperature at 50-60 ℃ for 5-8 minutes to dissolve the surface oxide layers such as cuprous oxide and copper oxide. Control the acid concentration to avoid excessive corrosion of the copper substrate.

[0024] ③ Rinsing and neutralization: Rinse the residual acid with deionized water, and finally immerse it in a 0.5-1% sodium carbonate solution for 2-3 minutes to ensure that the pH value of the copper material surface is neutral at 7±0.5.

[0025] (4) Drying: The water content of the cleaned copper material is 8-12%. It needs to be dried to remove the water in order to avoid the generation of steam during smelting and affect the stability of the copper liquid. A hot air circulating drying furnace is used, and the drying temperature is controlled at 120-150 ℃ and the air speed is 1.5-2 m / s. The drying time is adjusted according to the particle size of the copper material: 5-8 cm particles require 20-30 min, and 3-5 cm copper segments require 15-20 min, so that the water content of the copper material is ≤0.5%.

[0026] In the preparation process of this invention, the rolling step is specifically as follows: the purified copper liquid is introduced into a horizontal continuous casting machine, and rapidly solidified into a φ20-30 mm billet through a water-cooled crystallizer. The billet pulling speed is 1.1-1.2 m / min, and then it is hot rolled in 6 passes with the temperature gradually decreasing from 800℃ to 600℃ to gradually reduce the diameter and roll it into a φ8 mm copper rod.

[0027] In the preparation process of this invention, the continuous extrusion step specifically includes: The first continuous extrusion uses φ8 mm continuously rolled copper rod as raw material, employing a 500-type continuous extrusion press. The extrusion roller speed is controlled at 10-15 r / min. A large-diameter copper rod is produced by blowing through a die according to the required dimensions. The second continuous extrusion uses a 700-type continuous extrusion press to perform a secondary extrusion on the large-diameter copper rod. The die is determined according to the target cross-section requirements of the copper busbar. The die surface is nitrided. The extrusion pressure is 300-500 MPa, and the extrusion speed is 0.5-1 m / min. The copper busbar outlet temperature is controlled to not exceed 300℃ by a water cooling system, thus obtaining copper busbars with cross-sections of 20 mm × 100 mm to 40 mm × 400 mm. The first extrusion activates dynamic recrystallization at 400-500℃, while the second extrusion inhibits grain growth below 300℃ and uses water cooling to fix the fine-grained structure. This two-stage extrusion process resolves large-section segregation.

[0028] In the preparation process of this invention, the drawing step is specifically as follows: a 1000-ton horizontal drawing machine is used to draw the copper busbar after secondary extrusion. 1-3 drawing passes are performed according to the target performance, and the total shrinkage rate is controlled at 20-40%. After drawing, the oxide layer on the surface of the copper busbar is removed by electrolytic polishing to ensure that the surface roughness Ra≤0.8 μm.

[0029] In addition, this application allows for flexible adjustment of the impurity removal process in the purification step, precise control of the chemical composition of trace elements in copper, and meeting the copper purity requirements of different application scenarios; it also allows for control of the grain size of the internal structure and alteration of conductivity by using different material shrinkage ratios in the drawing process, thus meeting differentiated requirements such as "high conductivity" with a preference for low shrinkage or "high strength + high conductivity" with a preference for high shrinkage.

[0030] In this invention, the specific impurity removal agent selected has the following mechanism of action:

[0031] 1. The impurity removal mechanisms of rare earth element oxides CeO2 and La2O3 include several aspects:

[0032] (1) For metallic impurities Ni, Fe:Ce 4+ (0.101nm) and La 3+ The ionic radius (0.116 nm) and Cu 2+ The difference (0.072nm) is significant, but it is similar to Ni. 2+ (0.069nm), Fe 3+ (0.064nm) is closer. In molten copper, rare earth ions can displace transition metal impurities dissolved in the copper matrix through lattice matching effect, forming stable rare earth-transition metal intermetallic compounds, such as CeNi5, LaNi5, CeFe2, LaFe2, etc. The density of these compounds (6.5-8.2 g / cm³) is often lower than that of molten copper (8.92 g / cm³), the melting point is higher (up to 1500℃) and the miscibility with molten copper is extremely low. They can form solid particles or low melting point eutectics in molten copper, float to the slag and achieve separation from molten copper.

[0033] (2) For non-metallic elements As and Sb: CeO2 exists in copper liquid. 4+ ⇌Ce 3+ The redox cycle can oxidize impurities such as low-valence As and Sb into high-valence oxides (As2O5, Sb2O5), which in turn form complex rare earth arsenates / antimonates (LaAsO4, CeSbO4) with La2O3. The melting point of these compounds exceeds 1600℃, which is much higher than the temperature of copper liquid.

[0034] (3) For non-metallic elements O, S, P: Rare earth elements (Ce, La) have high chemical reactivity and a much greater affinity for O, S, and P than Cu (according to thermodynamic data, the Gibbs free energy ΔG° of the reaction between Ce and O is much lower than that of the reaction between Cu and O; for example, the ΔG° of 2Ce + O2 = 2CeO2 at 1200℃ is approximately -1050 kJ / mol, while the ΔG° of 2Cu + O2 = 2CuO is approximately -250 kJ / mol). Therefore, CeO2 and La2O3 can remove dissolved oxygen ([O]), sulfur ([S]), and phosphorus ([P]) from copper liquid through displacement reactions at high temperatures.

[0035] CeO2 + [O] = 2CeO + O2↑

[0036] La₂O₃ + 3[S] = La₂S₃ + ​​3[O]

[0037] High-melting-point La2S3 is formed, with a melting point of approximately 1900℃, and it easily floats to the surface and forms slag. If these impurities (O, S, P) remain in copper, they will form brittle phases such as Cu2O and Cu2S, leading to a decrease in the conductivity and ductility of the copper busbar. In particular, the conductivity of copper is extremely sensitive to impurities; 0.01% O can reduce conductivity by 5%, while the purification effect of rare earth oxides can reduce such defects.

[0038] (4) Refining grains and improving microstructure: Rare earth elements Ce and La can be adsorbed at the grain boundaries of copper grains, inhibiting grain growth and making the microstructure of copper busbars after casting or rolling more uniform, thereby improving their mechanical properties, which is crucial for the processing and use of copper busbars.

[0039] 2. The purification mechanisms of elemental Ca include several aspects:

[0040] (1) Deep removal of O, S and H: The strong reducing property of metallic calcium (Ca) (E°=-2.87 V) enables it to react with dissolved oxygen and sulfur in copper liquid: Ca+[O]=CaO, Ca+[S]=CaS, and can also react with trace amounts of hydrogen: Ca+H2=CaH2. These compounds are also easy to separate from copper liquid.

[0041] (2) Removal of low-melting-point metallic impurities: For common low-melting-point impurities such as Pb, Sn, and Zn in recycled copper, Ca can be converted into high-melting-point calcium compounds (such as CaPb and CaSn2) through a displacement reaction. These compounds have very low miscibility with molten copper and are easily removed by gravity separation. For example, the reaction of Ca with Pb: Ca + Pb = CaPb (melting point approximately 720℃), its density (6.9 g / cm³) 3 If the liquid copper is smaller than the molten copper, it can float to the slag layer.

[0042] 3. The mechanisms for impurity removal and performance regulation of CaB2 include several aspects:

[0043] (1) CaB2 dissociates into active B atoms in copper liquid. B can form high melting point borides with impurities such as Fe and Ti (e.g., FeB melting point is 1540℃). These borides have high interfacial tension with copper liquid and are easy to aggregate and float. At the same time, B can deoxygenate (reaction 4B+3O2=2B2O3, ΔG° is about -1200 kJ / mol at 1200℃), assisting rare earth oxides in removing residual oxygen.

[0044] (2) During the high-temperature treatment of copper liquid, B can form a stable lanthanum hexaboride compound (Ce,La)B6 with rare earth elements Ce and La. In the crystal lattice of (Ce,La)B6, boron atoms form octahedral vacancies, which can strongly adsorb low-melting-point impurities (such as Pb, Bi, As, etc.) in copper liquid, forming a stable coating structure: The complex acts as a heterogeneous nucleation core for impurity precipitation, increasing the size of the impurity phase from the micrometer level to 50-100 μm, making it easier to separate.

[0045] (3) CaB2 can form a low-melting-point eutectic slag system with rare earth oxides and calcium oxides (such as CaO) (such as the CaO-B2O3-La2O3 ternary slag system with a melting point as low as 800-900℃). The viscosity of the ternary eutectic slag at 1100℃ is <1 Pa·S, which can significantly improve the impurity release rate and further release the impurity capture ability of (Ce,La)B6, avoid the impurity removal failure caused by high-melting-point slag encapsulating the complex, avoid the impurity encapsulation problem caused by excessively thick slag, and improve the impurity removal efficiency; the low-density slag also reduces copper liquid encapsulation and reduces copper loss.

[0046] (4) When trace amounts of B dissolve in copper, they have little effect on conductivity, but can significantly increase the recrystallization temperature of copper (the recrystallization temperature of pure copper is about 200°C, while that of copper containing trace amounts of B can be increased to over 300°C). This is crucial for the dimensional stability of copper busbars under long-term energized heating conditions.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] (1) The copper busbar prepared in this application has low trace element impurities, which greatly reduces the negative impact of impurities on conductivity. It has high conductivity and can effectively reduce energy loss during power transmission compared with traditional copper busbars. It can also produce a large cross section, which meets the demand for large cross section copper busbars in high current transmission scenarios. Furthermore, the cross section specifications can be further adjusted according to actual needs, which has good flexibility.

[0049] (2) This application uses recycled copper to replace electrolytic copper as raw material, which reduces the raw material cost by about 20%. At the same time, the high efficiency of the continuous casting and rolling process and the significant improvement in production efficiency reduce the unit energy consumption. The energy consumption per ton has been reduced from 800 kWh in the traditional casting method to 500 kWh, and the overall cost has been reduced by 20-30%, which effectively improves the market competitiveness of the product.

[0050] (3) The metal recovery rate of the recycled copper preparation process of this application can reach more than 95%, and the removal rate of initial impurities such as oil, iron, and oxides exceeds 98%, laying a high-quality raw material foundation for subsequent purification and smelting processes.

[0051] (4) The continuous casting and rolling process of this application increases the production efficiency of φ8 mm copper rod from 18 kg / h of the traditional drawing method to 19 t / h, and the daily production capacity from 0.36 tons to 380 tons. The production efficiency is greatly improved, which can quickly respond to the demand of large-scale orders and meet the market's demand for a large supply of copper busbars.

[0052] (5) This application uses a precise impurity removal process and an optimized preparation process, and generates fine grains through secondary extrusion. Combined with a drawing shrinkage rate of 20-40%, the grain size is further refined to 15-25 μm, thereby achieving a conductivity of up to 99.92% IACS and a tensile strength of 250 MPa, which effectively improves the comprehensive performance of the material and makes it perform excellently.

[0053] (6) The product specifications obtained by this application are diverse, and large cross-section copper busbars can be prepared. The maximum cross-section can reach 40 mm × 400 mm, and can be further expanded to larger cross-sections or produced with irregular cross-sections, such as 50 mm × 500 mm, rectangular with rounded corners, T-shaped, etc., to meet the diverse specifications of copper busbars in different fields and scenarios, and have good market adaptability. Attached Figure Description

[0054] Figure 1 Metallographic images of the product before and after drawing (500x magnification) for this application. Detailed Implementation

[0055] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0056] This application verifies the technical effectiveness by setting up comparative experiments.

[0057] (a) Experimental model design:

[0058] Experimental Group 1: Using the process of this invention, recycled copper was used as raw material, the amount of impurity removal agent added was 3% of the mass of the recycled copper raw material, and the drawing shrinkage rate was set to 8%;

[0059] Experimental Group 2: Using the process of this invention, recycled copper was used as raw material, the amount of impurity removal agent added was 4% of the mass of the recycled copper raw material, and the drawing shrinkage rate was set to 10%;

[0060] Experimental Group 3: Using the process of this invention, recycled copper was used as raw material, the amount of impurity removal agent added was 5% of the mass of the recycled copper raw material, and the drawing shrinkage rate was set to 12%;

[0061] Control group: Using traditional processes, electrolytic copper plates were used as raw materials to roll φ8 mm copper rods using the upward drawing method. The same extrusion and drawing processes as the present invention were used to prepare 30 mm × 200 mm copper busbars.

[0062] The test materials were all 100 kg each, and the test indicators included: ICP-MS for impurity content, counting method for production efficiency, four-probe method for conductivity, and universal testing machine for tensile strength.

[0063] (II) Specific production steps and experimental data

[0064] 1. Raw material preparation:

[0065] The preparation of recycled copper is achieved through the following different embodiments.

[0066] As one of the possible methods: (1) Screening: First, classify the recycled industrial waste copper, including waste cables and waste copper parts. The waste cables are further classified according to the insulation material, and the waste copper parts are classified according to pure copper parts and copper alloy parts. Select the pure copper parts and use the copper alloy parts for other purposes.

[0067] (2) Crushing: The classified waste cables and pure copper parts are disassembled into particles that are easy to process later. The specific operation includes: the insulation layer of the waste cables is removed by dry stripping or pyrolysis, and then crushed into 3cm copper segments by a shear crusher to ensure that the copper core is fully exposed. During the crushing process, ferromagnetic impurities such as bolts and connectors are initially removed by a magnetic separation device.

[0068] (3) Cleaning: Thoroughly remove oil, oxides, and non-metallic deposits from the surface of the waste copper particles. Specific operations include:

[0069] ①Alkaline washing and degreasing: Immerse the crushed copper material in a 5% sodium hydroxide solution at 80 ℃ and stir for 10 min. Remove mineral oil, grease and other oil stains through saponification reaction. Replace the solution when the pH value is ≤9.

[0070] ② Acid pickling to remove oxide layer: After rinsing with clean water, immerse in a 10% dilute sulfuric acid solution, heat and maintain the temperature at 50 ℃ for 5 min to dissolve the surface oxide layers such as cuprous oxide and copper oxide;

[0071] ③ Rinsing and neutralization: Rinse the residual acid with deionized water, and finally immerse it in a 0.5% sodium carbonate solution for 2 minutes to ensure that the pH value of the copper material surface is neutral at 7±0.5.

[0072] (4) Drying: The water content of the cleaned copper material is 12%. It is necessary to remove the water by drying to avoid the generation of steam during smelting that affects the stability of the copper liquid. A hot air circulating drying furnace is used, and the drying temperature is controlled at 120 ℃, the wind speed is 1.5 m / s, and the drying time is 15 min, so that the water content of the copper material is ≤0.5%.

[0073] As one of the possible methods: (1) Screening: First, classify the recycled industrial waste copper, including waste cables and waste copper parts. The waste cables are further classified according to the insulation material, and the waste copper parts are classified according to pure copper parts and copper alloy parts. Select the pure copper parts and use the copper alloy parts for other purposes.

[0074] (2) Crushing: The classified waste cables and pure copper parts are disassembled into particles that are easy to process later. The specific operation includes: the insulation layer of the waste cables is removed by dry stripping or pyrolysis, and then crushed into 5 cm copper segments by a shear crusher to ensure that the copper core is fully exposed. During the crushing process, ferromagnetic impurities such as bolts and connectors are initially removed by a magnetic separation device.

[0075] (3) Cleaning: Thoroughly remove oil, oxides, and non-metallic deposits from the surface of the waste copper particles. Specific operations include:

[0076] ①Alkaline washing and degreasing: Immerse the crushed copper material in an 8% sodium hydroxide solution at 90 ℃ and stir for 15 min. Remove mineral oil, grease and other oil stains through saponification reaction. Replace the solution when the pH value is ≤9.

[0077] ② Acid pickling to remove oxide layer: After rinsing with clean water, immerse in a 15% dilute sulfuric acid solution, heat and maintain the temperature at 60 ℃ for 8 minutes to dissolve the surface oxide layers such as cuprous oxide and copper oxide;

[0078] ③ Rinsing and neutralization: Rinse the residual acid with deionized water, and finally immerse it in a 1% sodium carbonate solution for 3 minutes to ensure that the pH value of the copper material surface is neutral at 7±0.5.

[0079] (4) Drying: The water content of the cleaned copper material is 11%. It is necessary to remove the water by drying to avoid the generation of steam during smelting that affects the stability of the copper liquid. A hot air circulating drying furnace is used, and the drying temperature is controlled at 150 ℃, the wind speed is 2 m / s, and the drying time is 18 min, so that the water content of the copper material is ≤0.5%.

[0080] As one of the possible methods: (1) Screening: First, classify the recycled industrial waste copper, including waste cables and waste copper parts. The waste cables are further classified according to the insulation material, and the waste copper parts are classified according to pure copper parts and copper alloy parts. Select the pure copper parts and use the copper alloy parts for other purposes.

[0081] (2) Crushing: The classified waste cables and pure copper parts are disassembled into particles that are easy to process later. The specific operation includes: the waste copper parts are crushed to no more than 10 cm by a jaw crusher, and then crushed to 5 cm particles by a cone crusher. During the crushing process, ferromagnetic impurities such as bolts and connectors are initially removed by a magnetic separation device.

[0082] (3) Cleaning: Thoroughly remove oil, oxides, and non-metallic deposits from the surface of the waste copper particles. Specific operations include:

[0083] ①Alkaline washing and degreasing: Immerse the crushed copper material in a 5% sodium hydroxide solution at 80 ℃ and stir for 10 min. Remove mineral oil, grease and other oil stains through saponification reaction. Replace the solution when the pH value is ≤9.

[0084] ② Pickling to remove oxide layer: After rinsing with clean water, immerse in a 10% dilute sulfuric acid solution, heat and maintain the temperature at 50℃ for 5 minutes to dissolve the surface oxide layers such as cuprous oxide and copper oxide. Control the acid concentration to avoid excessive corrosion of the copper substrate.

[0085] ③ Rinsing and neutralization: Rinse the residual acid with deionized water, and finally immerse it in a 0.5% sodium carbonate solution for 2 minutes to ensure that the pH value of the copper material surface is neutral at 7±0.5.

[0086] (4) Drying: The water content of the cleaned copper material is 12%. It is necessary to remove the water by drying to avoid the generation of steam during smelting that affects the stability of the copper liquid. A hot air circulating drying furnace is used, and the drying temperature is controlled at 120 ℃, the wind speed is 1.5 m / s, and the drying time is 30 min, so that the water content of the copper material is ≤0.5%.

[0087] As one of the possible methods: (1) Screening: First, classify the recycled industrial waste copper, including waste cables and waste copper parts. The waste cables are further classified according to the insulation material, and the waste copper parts are classified according to pure copper parts and copper alloy parts. Select the pure copper parts and use the copper alloy parts for other purposes.

[0088] (2) Crushing: The classified waste cables and pure copper parts are disassembled into particles that are easy to process later. The specific operation includes: the waste copper parts are crushed to no more than 20 cm by a jaw crusher, and then crushed to 8 cm particles by a cone crusher. During the crushing process, ferromagnetic impurities such as bolts and connectors are initially removed by a magnetic separation device.

[0089] (3) Cleaning: Thoroughly remove oil, oxides, and non-metallic deposits from the surface of the waste copper particles. Specific operations include:

[0090] ①Alkaline washing and degreasing: Immerse the crushed copper material in an 8% sodium hydroxide solution at 90 ℃ and stir for 15 min. Remove mineral oil, grease and other oil stains through saponification reaction. Replace the solution when the pH value is ≤9.

[0091] ② Pickling to remove oxide layer: After rinsing with water, immerse in a 15% dilute sulfuric acid solution, heat and maintain the temperature at 60 ℃ for 8 minutes to dissolve the surface oxide layers such as cuprous oxide and copper oxide. Control the acid concentration to avoid excessive corrosion of the copper substrate.

[0092] ③ Rinsing and neutralization: Rinse the residual acid with deionized water, and finally immerse it in a 1% sodium carbonate solution for 3 minutes to ensure that the pH value of the copper material surface is neutral at 7±0.5.

[0093] (4) Drying: The water content of the cleaned copper material is 8%. It is necessary to remove the water by drying to avoid the generation of steam during smelting that affects the stability of the copper liquid. A hot air circulating drying furnace is used, and the drying temperature is controlled at 150 ℃, the wind speed is 2 m / s, and the drying time is 20 min, so that the water content of the copper material is ≤0.5%.

[0094] Copper purification: The obtained stable granular or segmented recycled copper is fed into a 100 kg medium-frequency induction furnace and heated to 1100℃ for melting. A purification agent is added in a specific ratio (CeO2 + La2O3):CaB2:Ca = 2:1:2 by mass. The ratio of CeO2 to La2O3 is adjusted according to the purification requirements: CeO2:La2O3 = 1:2 in experimental group 1, 1:1 in experimental group 2, and 2:1 in experimental group 3. After adding the purification agent, the copper liquid is stirred at 300 r / min for 20 min. The copper is purified by removing slag.

[0095] Experimental data:

[0096] Control group (electrolytic plate): total impurity content 30.5 ppm, including Ni 8.3 ppm, Pb 7.6 ppm, and Fe 9.1 ppm;

[0097] Experimental group 1: Total impurity content 6.2 ppm, including Ni 2.1 ppm, Pb 1.2 ppm, and Fe 2.3 ppm;

[0098] Experimental group 2: Total impurity content 5.7 ppm, including Ni 1.8 ppm, Pb 1.5 ppm, and Fe 1.9 ppm;

[0099] Experimental group 3: Total impurity content 6.8 ppm, including Ni 2.5 ppm, Pb 0.9 ppm and Fe 2.7 ppm.

[0100] The ICP-MS test report contains the following:

[0101] Report Number: ICP-CuPurify2025-0512

[0102] Testing date: March 10, 2025

[0103] Sample Name: Recycled Copper Purification Products (Experimental Groups 1-3 and Control Group)

[0104] Testing standards: GB / T 5121.27-2023 & ISO 17025:2017

[0105] Detection range: Impurity elements such as Ag, Al, As, Cg, Co, Cr, Fe, Ni, Pb, Sn, S, P, Zn, etc.

[0106] Test results: Table 1, Table 2, Table 3

[0107] Table 1 shows the ICP-MS detection data (unit: ppm * standard elements were detected by LECO ONH836).

[0108]

[0109] Table 2 shows the comparison of impurity removal efficiency.

[0110]

[0111] Total impurity removal rate = (1 - C) 后 / C 前 )×100%, C 前 C represents the total impurity content of the raw materials. 后 This represents the total impurity content after impurity removal.

[0112] Pb removal rate = (1 - C) Pb后 / C Pb前 )×100%, C Pb前 The Pb content and C content of the raw materials are... Pb后 This represents the Pb content after impurity removal.

[0113] Copper loss rate in slag = [(M 渣 ×ω Cu渣 ) / M 原料 ]×100%, M 原料 For the weight of the copper being fed, M 渣 ω is the weight of the slag discharge. Cu渣 The copper content of the slag.

[0114] Table 3 shows the effects of the ternary slag system.

[0115]

[0116] Conclusion: (1) Purity verification: The total impurity content of experimental groups 1-3 is close to 30 ppm, and even reaches 25.8 ppm, which is far lower than the traditional process of 190.5 ppm. It basically meets the high purity copper standard (GB / T 5231-2012). The effect of ultra-pure single crystal copper was achieved by using recycled copper as raw material.

[0117] (2) Control of key impurities: The content of harmful elements such as Ni, Pb and Fe was significantly reduced, proving the effectiveness of the impurity removal agent formula (CeO2+La2O3+CaB2+Ca) and process parameters.

[0118] (3) Correlation of conductivity: The reduction of impurity content is positively correlated with the conductivity of the product, which verifies the technical logic of "low impurities - high conductivity".

[0119] (4) Experimental groups 1-3 used different ratios of impurity removers. The results showed that the 1:1 ratio had the best removal effect on Ni and Fe. When CeO2 and La2O3 were mixed in a 1:1 ratio, [CeLaO3] composite oxide could be formed. Its lattice constant had a high degree of matching with intermetallic compounds such as Cu-Ni and Cu-Fe, and it was easier to capture these impurity elements through coherent precipitation mechanism.

[0120] 2. Rolling: Utilizing SMS Group's CSP series continuous casting and rolling mill, purified molten copper is introduced into a horizontal continuous casting machine and rapidly solidified into a φ30 mm billet in a water-cooled crystallizer. The billet is drawn at a speed of 1.2 m / min and then undergoes six passes of hot rolling, with the temperature gradually decreasing from 800℃ to 600℃, to progressively reduce the diameter and roll it into a φ8 mm copper rod. During the rolling process, online flaw detection using eddy current testing ensures the copper rod is free of cracks, inclusions, and other defects. Through continuous production of melting, billet casting, and rolling, the dimensional tolerance of the φ8 mm copper rod can be controlled within ±0.05 mm, with a uniform microstructure and a grain size of 50-80 μm. The production efficiency can reach 19 t / h.

[0121] Experimental data:

[0122] Control group (upward drawing method): production rate 18 kg / h, φ8 mm copper rod dimensional tolerance ±0.12 mm;

[0123] Experimental group 1 / 2 / 3 (continuous casting and rolling): production rate 19 t / h, dimensional tolerance ±0.05 mm, grain uniformity improved by 40%.

[0124] 3. First continuous extrusion: Using a 500-type continuous extrusion press, the φ8 mm copper rod is extruded into a φ20 mm copper rod. The extrusion roller speed is 15 r / min and the temperature is 450℃.

[0125] Experimental data: The density of the extruded copper rod was 99.6%, which was 1.4% higher than that of the control group (98.2%).

[0126] 4. Second continuous extrusion: Using a 700-type extruder, the φ20 mm copper rod is extruded into a 30 mm × 200 mm copper busbar with an extrusion pressure of 400 MPa and an outlet temperature of 280℃.

[0127] Experimental data: Straightness error of the busbar ≤ 0.5 mm / m, surface roughness Ra: 1.2 μm.

[0128] 5. Drawing: A 1000-ton horizontal drawing machine was used. Experimental group 1 was drawn in one pass with a 20% shrinkage rate, experimental group 2 was drawn in two passes with a 30% shrinkage rate, and experimental group 3 was drawn in three passes with a 40% shrinkage rate. After drawing, the oxide layer on the surface of the copper busbar was removed by electrolytic polishing.

[0129] Experimental data:

[0130] Control group: Grain size approximately 45 μm, conductivity 97.2% IACS, tensile strength 190 MPa;

[0131] Experimental group 1: Grain size approximately 24 μm, conductivity 99.6% IACS, tensile strength 220 MPa;

[0132] Experimental group 2: Grain size approximately 19 μm, conductivity 99.8% IACS, tensile strength 230 MPa;

[0133] Experimental group 3: Grain size approximately 15 μm, conductivity 99.92% IACS, tensile strength 250 MPa.

[0134] Metallographic images of experimental group 3 before and after drawing, magnified 500 times, are shown below. Figure 1 As shown, where Figure 1 (Left) shows the grains after extrusion. Figure 1 (Right) shows the grains after drawing. Figure 1 The grains in (right) are significantly larger than those in the right. Figure 1 (Left) Small, after measurement, the grain size was about 30 μm before drawing and about 15 μm after drawing.

[0135] (III) Summary of Results

[0136] Compared with the conventional process of the control group, the preparation process of the present invention has the following technical effects:

[0137] (1) Cost reduction: Recycled copper replaces electrolytic plates, reducing raw material costs by 22%, improving bonding efficiency, and reducing overall costs by 30%;

[0138] (2) Efficiency improvement: Continuous casting and rolling increased the production efficiency of φ8 mm copper rods to 19 t / h, which is 1055 times higher than that of the upward drawing method (18 kg / h).

[0139] (3) Performance optimization: The impurity content is controlled below 30 ppm, the conductivity reaches 99.92% IACS, and the tensile strength is increased by 32%;

[0140] (4) Specification expansion: It can stably produce 40 mm × 400 mm large cross-section busbars, which is 33% higher than the maximum cross-section of 30 mm × 300 mm in the traditional process.

Claims

1. A method for preparing a novel large-section, highly conductive copper busbar, characterized in that: Includes the following steps: (1) Raw material preparation: After melting the recycled copper, a special impurity removal agent is added to control the impurity content to ≤30 ppm. The impurity removal agent is composed of rare earth elements Ce, La oxides, borides and metallic calcium. The mass ratio is (CeO2+La2O3):CaB2:Ca=2:1:2, CeO2:La2O3=(1-2):(2-1). The amount of impurity removal agent added is 3-5% of the mass of recycled copper. (2) Rolling: φ8 mm copper rods are prepared by continuous casting and rolling process, with a rolling speed of 19 t / h; (3) First continuous extrusion: Extrude the φ8 mm copper rod to φ20 mm copper rod at an extrusion temperature of 450 ℃; (4) Second continuous extrusion: The large-diameter copper rod is extruded into a busbar with a cross-section of 30 mm × 200 mm; (5) Drawing: A drawing process with a total shrinkage rate of 20-40% is adopted to refine the particle size to 15-30 μm.

2. The preparation method according to claim 1, characterized in that: The specific preparation of the raw materials is as follows: the recycled copper is heated to 1100℃ and melted to obtain a recycled copper solution. A special impurity remover is added to the recycled copper solution. The impurity remover reacts fully with the harmful impurities in the copper solution by stirring. The stirring speed is 300 r / min and the stirring time is 20 min, thereby forming a solid composite slag with a density greater than that of the copper solution. The slag is removed by slag discharge, thereby achieving the purification of copper.

3. The preparation method according to claim 1 or 2, characterized in that: The raw material used in the preparation of the raw materials is recycled copper, which contains more than 98% copper.

4. The preparation method according to claim 1, characterized in that: The rolling process specifically involves introducing the purified molten copper into a horizontal continuous casting machine, rapidly solidifying it into a φ30 mm billet through a water-cooled crystallizer, drawing the billet at a speed of 1.2 m / min, and then hot rolling it through 6 passes with the temperature gradually decreasing from 800℃ to 600℃ to gradually reduce the diameter and roll it into a φ8 mm copper rod.

5. The preparation method according to claim 1, characterized in that: The continuous extrusion process is as follows: The first continuous extrusion uses φ8 mm continuously rolled copper rod as raw material and is performed using a 500-type continuous extrusion press. The speed of the extrusion roller is controlled at 15 r / min. A large-diameter copper rod is produced by blowing according to the required die size. The second continuous extrusion uses a 700-type continuous extrusion press to perform a second extrusion on the large-diameter copper rod. The die is determined according to the target cross-section requirements of the copper busbar. The die surface is nitrided. The extrusion pressure is 400 MPa. The copper busbar outlet temperature is controlled to not exceed 300℃ by a water cooling system, thus obtaining a copper busbar with a cross-section of 30 mm × 200 mm.

6. The preparation method according to claim 1, characterized in that: The drawing process specifically involves using a 1000-ton horizontal drawing machine to draw the copper busbar after secondary extrusion. The drawing process is carried out in 1-3 passes according to the target performance, with the total shrinkage rate controlled at 20-40%. After drawing, the oxide layer on the surface of the copper busbar is removed by electrolytic polishing to ensure that the surface roughness Ra≤0.8 μm.

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