A continuous extrusion forming process method of high-conductivity copper bar

Abstract

This invention relates to the field of copper processing technology and discloses a continuous extrusion molding process for high-conductivity copper busbars. The method includes a composite coolant comprising poloxamer 407, a thixotropic modifier, triethanolamine borate, and benzotriazole. The extruded high-temperature copper busbar is immersed in a cooling tank, and the aforementioned coolant is first injected to form a co-current laminar flow. The polymer undergoes thermal cross-linking to form a thixotropic gel film on the copper busbar surface, achieving slow cooling at high temperature to promote dynamic recrystallization. Subsequently, the copper busbar passes through a V-shaped baffle into a high-pressure zone, where the aforementioned coolant is used for reverse high-pressure injection. Fluid shear force causes the gel film to disintegrate, resulting in a sudden change in heat transfer mode and rapid quenching, solidifying a fine-grained structure. Simultaneously, a passivation film is formed in situ on the copper busbar surface. Finally, the busbar is dried and wound up. This invention solves the problem of dynamically switching cooling rates in traditional processes by using a single coolant in conjunction with a step-flow field, producing copper busbar products with both high conductivity and good oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of copper processing technology, specifically to a continuous extrusion molding process for high conductivity copper busbars. Background Technology

[0002] High conductivity copper busbars are widely used in power transmission, electrical equipment and new energy fields. Continuous extrusion molding is the mainstream process for producing high-quality oxygen-free copper busbars. During continuous extrusion, the oxygen-free copper rod undergoes severe plastic deformation and generates a large amount of heat under the friction and pull of the extrusion roller. It is then extruded through the die hole. The high-temperature copper busbar after extrusion needs to be cooled to fix the crystal structure and reduce the temperature, so as to facilitate subsequent traction and winding operations.

[0003] Existing high-conductivity copper busbar extrusion molding processes mostly use a single cooling medium. This conventional cooling process makes it difficult to dynamically switch the cooling rate, resulting in a trade-off between the product's microstructure and macroscopic physical properties. In actual production, if conventional rapid water cooling is applied directly to the copper busbar immediately after extrusion, the metal surface temperature drops too quickly, causing thermal stress concentration on the copper busbar surface, which in turn leads to deformation defects or even microcracks, severely affecting surface quality. Conversely, if the extruded copper busbar is slowly cooled throughout the process to release thermal stress, the fine-grained structure that has just formed due to dynamic recrystallization at high temperatures cannot be fixed in time. Under the influence of residual heat over a long period of time, the grains will undergo secondary growth and coarsening. Grain coarsening not only reduces the mechanical strength of the copper busbar but also directly affects the electron transport efficiency between grain boundaries, making it difficult to meet the requirements for high conductivity.

[0004] Furthermore, when copper busbars at high temperatures are cooled out of the tank in a single coolant, their surfaces still exhibit high reactivity and react with dissolved oxygen or moisture in the surrounding environment, causing oxidation and discoloration of the copper busbar surface. This increases the cost of subsequent anti-oxidation treatment. Therefore, existing cooling processes make it difficult for the final copper busbar product to achieve both high conductivity and suppression of grain coarsening, while also possessing good surface physical properties and anti-oxidation effects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a continuous extrusion molding process for high conductivity copper busbars. This process solves the problem that using a single cooling medium in existing high conductivity copper busbar extrusion molding processes makes it difficult to achieve dynamic switching of cooling rates, which leads to grain coarsening, thermal stress defects, and surface oxidation in the copper busbars.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A continuous extrusion molding process for high conductivity copper busbars, the method comprising the following steps: A composite coolant was prepared by mixing deionized water, thixotropic modifier, poloxamer 407, triethanolamine borate, and benzotriazole. The oxygen-free copper rod is fed into a continuous extruder for plastic deformation and dynamic recrystallization, and then continuously extruded through a die to form a high-temperature solid copper busbar. After the copper busbar is extruded, it is immersed in a circulating cooling tank. The composite coolant is injected at the entry point along the direction of the copper busbar to form a co-current laminar flow, so that a vapor blanket is formed on the surface of the copper busbar and the polymer cross-links upon heating to form a thixotropic gel film. The copper busbar is then slowly cooled at high temperature under this wrapping. A baffle is provided along the direction of copper busbar travel in the cooling tank, and a high-pressure jet stream array is arranged downstream of the baffle. The copper busbar with thixotropic gel film passes through the baffle and enters the high-pressure jet zone. The composite coolant is used for reverse high-pressure jetting, which causes the thixotropic gel film to be disintegrated by strong hydrodynamic shearing, thereby achieving rapid quenching and passivation. The cooled copper busbar continues to move out of the tank, where the residual liquid film on the surface is dried and then pulled and wound up.

[0007] By adopting the above technical solution, due to the use of composite coolant and the special flow field of co-current and high-pressure counter-current in series, the cooling requirements of copper busbar at different stages are met, the grains are refined, and in-situ oxidation prevention is achieved.

[0008] The specific reaction and action process is as follows: after the freshly extruded high-temperature copper busbar is immersed in the cooling tank, its high surface temperature causes the coolant it comes into contact with to quickly vaporize and form a vapor film. At this time, due to its inverse temperature-sensitive properties, poloxamer 407 in the composite coolant undergoes a dehydration phase change in the area near the high-temperature copper busbar. With the synergistic effect of the thixotropic modifier, the dehydrated polymer chains rapidly crosslink around the vapor film to form a thixotropic gel film with a three-dimensional network structure.

[0009] This gel film adheres to the surface of the copper busbar in a laminar flow environment, increasing the radial heat transfer resistance and thus maintaining the heat transfer state at a low heat transfer coefficient. This allows the copper busbar to achieve high temperature slow cooling in the early stage. This slow cooling process not only releases the internal stress generated by extrusion, but also allows time for the dynamic recrystallization of the base metal, which helps to form equiaxed crystals.

[0010] As the copper busbar coated with gel film continues to move along the production line, passing through the baffle and entering the spray zone at the rear, the fluid environment changes. The high-pressure jet of liquid, arranged in the opposite direction, applies a strong hydrodynamic shear force to the surface of the copper busbar. Because the thixotropic gel film formed in the early stage has the rheological characteristics of shear thinning, once this external shear stress exceeds the yield strength, the cross-linked network inside the gel will break and disintegrate. Once the outer gel film breaks, the internal vapor film loses its physical constraint and collapses. The coolant then comes into direct contact with the high-temperature metal substrate, and the heat transfer mode changes from film boiling to nucleus boiling, increasing the heat transfer coefficient. This state change achieves a step change in the cooling rate, retaining the fine-grained structure formed in the early stage and inhibiting the secondary growth of grains.

[0011] As the cooling process progresses, when the vapor film and gel film rupture, the fresh copper substrate, which is at a higher temperature and has a certain surface activity, is exposed. The benzotriazole molecules contained in the cooling liquid system have lone pairs of electrons in their nitrogen atoms that coordinate with the empty orbitals of copper atoms. Combined with the effect of triethanolamine borate, a chelate passivation film is generated in situ on the metal surface. This film blocks the contact path between dissolved oxygen and the copper substrate in subsequent processes, preventing the copper busbar from oxidizing and discoloring when it leaves the tank with residual heat.

[0012] Preferably, the raw materials for preparing the composite coolant include: Deionized water: 89.0 to 94.0 parts; Thixotropic modifier: 0.2 to 0.5 parts; Polosham 407: 5.0 to 8.0 copies; Triethanolamine borate: 1.0 to 2.0 parts; Benzotriazole: 0.05 to 0.15 parts.

[0013] By adopting the above technical solution, the amount of poloxamer 407 and thixotropic modifier added is limited, so that the gel generated when the composite coolant undergoes a phase change upon heating can have a suitable shear yield stress. This prevents the gel film from falling off and being lost due to gravity in the early slow cooling zone, and also ensures that it can be smoothly disintegrated when subjected to shearing by the high-pressure fluid at the downstream end, thereby preventing uneven cooling caused by local residual film.

[0014] Preferably, the step of preparing the composite coolant by mixing deionized water, a thixotropic modifier, poloxamer 407, triethanolamine borate, and benzotriazole includes: mixing deionized water with the thixotropic modifier and subjecting the mixture to high-shear stirring at 20 to 30°C to obtain a basic thixotropic gel; cooling the basic thixotropic gel to 2 to 8°C, adding poloxamer 407 in batches and stirring continuously until dissolved; subsequently heating the system to 20 to 25°C, adding triethanolamine borate and benzotriazole sequentially, and stirring continuously.

[0015] By adopting the above technical solution, during the liquid preparation process, the solid thixotropic modifier is desorbed and dispersed in water by high-shear stirring at room temperature in the early stage; considering that the hydration degree of poloxamer molecules is high and the molecular chains are stretched at low temperature, it is dissolved in batches at a lower temperature. This variable temperature treatment method avoids the surface coating and agglomeration problems that occur when the polymer is directly added at room temperature, and makes the component distribution of the coolant more uniform.

[0016] Preferably, the thixotropic modifier is an organically intercalated modified synthetic lithium saponite, the raw materials for which include at least sodium magnesium lithium silicate and hexadecyltrimethylammonium bromide.

[0017] By adopting the above technical solution, the layered structure of sodium magnesium lithium silicate itself contains a lot of inorganic hydroxyl groups. After surface modification, quaternary ammonium salt cations are embedded into the mineral interlayer. The intervention of this long-chain alkyl group adjusts the hydrophilicity-hydrophobicity balance of the material, making it exhibit better compatibility when it is subsequently combined with poloxamer molecules. When the system is heated, this compatibility helps to increase the crosslinking point density, so that the formed gel film has sufficient structural strength.

[0018] Preferably, the organic intercalation modified synthetic lithium saponite is prepared by adding hexadecyltrimethylammonium bromide at a molar equivalent of 0.8 to 1.2 times the cation exchange capacity of sodium magnesium lithium silicate to a hydrated and exfoliated sodium magnesium lithium silicate suspension.

[0019] By adopting the above technical solution and matching the amount of modifier according to a specific ratio of lithium magnesium silicate cation exchange capacity, it is beneficial to control the degree of intercalation of ammonium bromide molecules between layers and the expansion state of interlayer spacing. Organic molecular chains are connected to the crystal lattice through cation exchange, and without destroying the heat resistance of inorganic materials, it can have thixotropic response characteristics suitable for the flow field changes in this process.

[0020] Preferably, the step of feeding the oxygen-free copper rod into a continuous extruder for plastic deformation and dynamic recrystallization, and continuously extruding it through a die to form a high-temperature solid copper busbar includes: controlling the surface temperature of the copper busbar at the extrusion die to be 640 to 680°C, and setting the extrusion line speed to be 10 to 25 m / min.

[0021] By adopting the above technical solution, the extrusion temperature and linear speed are controlled within this range. This mainly provides the necessary deformation energy storage and recrystallization driving force for the oxygen-free copper crystals during the forming stage. This allows the matrix to undergo dynamic recrystallization during the extrusion deformation process, generating a relatively uniform grain structure, which prepares the early structure for subsequent control of conductivity through segmented cooling.

[0022] Preferably, the step of immersing the copper busbar in a circulating cooling tank after extrusion and injecting composite coolant along the direction of copper busbar travel at the entry point to form a co-current laminar flow includes: controlling the copper busbar to remain in the air for 0.2 to 0.6 seconds after extrusion into the die before immersing it in the circulating cooling tank; and controlling the flow rate of the injected composite coolant to be between 0.5 and 1.2 m / s.

[0023] By adopting the above technical solution, the residence time of the copper busbar in the air is shortened in order to suppress the excessive oxidation of the high-temperature surface and the formation of a thick oxide layer, thereby preserving a certain surface activity for subsequent passivation treatment. At the same time, the injection flow rate of the coolant is limited to create a suitable speed difference between it and the extrusion speed, thereby forming a stable laminar flow boundary around the copper busbar. This reduces the physical scouring effect of the fluid on the vapor film generated in the early stage and maintains the heat transfer stability during the slow cooling stage.

[0024] Preferably, the step of setting a baffle along the copper busbar traveling in the cooling tank includes: setting a submerged V-shaped dynamic pressure baffle as a baffle, and setting the gap between the inner edge of the baffle and the running copper busbar to be 15 to 25 mm.

[0025] By adopting the above technical solution, the V-shaped baffle helps to straighten the fluid flowing from the front end and reduce disordered fluid disturbance. At the same time, the inner side of the baffle maintains a certain gap with the moving copper busbar. When the fluid flows through this narrow area, a throttling effect is generated. The change in fluid dynamic pressure and static pressure causes a local increase in turbulent kinetic energy, which makes the gel film attached to the surface of the copper busbar in an unstable state. This is equivalent to a certain degree of hydrodynamic disturbance in advance, which makes it easier to completely peel it off in the high-pressure area later.

[0026] Preferably, the step of using composite coolant for reverse high-pressure injection includes: setting the injection pressure of high-pressure injection to 1.5 to 2.5 MPa, and the injection direction to be at an angle of 45 to 60° opposite to the direction of copper busbar travel; controlling the sudden change in cooling rate during rapid quenching to greater than 150°C / s.

[0027] By adopting the above technical solution and limiting the angle of high-pressure injection, the impact force of the fluid can be better distributed in the peeling direction. The shear force of the fluid under high pressure acts on the gel film, causing its structure to disintegrate. The vapor layer inside dissipates accordingly. After losing the heat resistance of vapor, the increased heat transfer efficiency causes the copper busbar temperature to drop rapidly, quickly crossing the temperature range that would cause grain growth, and achieving the solidification of the crystal structure.

[0028] Preferably, the steps of continuing to move the cooled copper busbar out of the tank, drying the residual liquid film on the surface, and traction winding include: controlling the exit temperature of the copper busbar at 40 to 48°C; and using a high-pressure air knife with a spray pressure of 0.4 to 0.6 MPa to dry the residual liquid film on the surface.

[0029] By adopting the above technical solution and controlling the temperature range when the copper busbar leaves the tank, the main purpose is to retain a small amount of residual heat to assist in the evaporation of surface moisture, so as to avoid moisture retention due to excessively low temperature or subsequent surface discoloration due to excessively high temperature. With the help of air knives, the surface water film is blown away, which can keep the copper busbar in a relatively dry state when it is wound up, reducing the water vapor corrosion problem that will occur during subsequent storage.

[0030] This invention provides a continuous extrusion molding process for high conductivity copper busbars. It offers the following advantages: 1. This invention utilizes the temperature-sensitive and thixotropic properties of the composite coolant to create a stable high-temperature slow-cooling environment in the early stage of extrusion. After the extruded high-temperature copper busbar comes into contact with the coolant, poloxamer 407 undergoes a dehydration phase change upon heating and crosslinks with the thixotropic modifier. Under co-current laminar flow conditions, an encapsulating thixotropic gel film is formed on the surface of the copper busbar. This gel film increases the radial heat transfer resistance and stabilizes the underlying vapor layer, allowing the copper busbar to maintain a low heat transfer coefficient. This provides sufficient time for the dynamic recrystallization of the metal matrix, promotes the formation of equiaxed crystals, and releases the internal stress of extrusion.

[0031] 2. This invention achieves a step-like abrupt change in cooling rate through a specific flow field design, suppressing secondary grain growth. When the copper busbar with a gel film passes through the V-shaped dynamic pressure baffle and enters the high-pressure zone, the reverse high-pressure jet fluid at a specific angle and pressure applies a shear force exceeding its yield strength to the surface, causing the thixotropic gel film to disintegrate and the vapor film to collapse. At this time, the heat transfer mode rapidly changes from film boiling to nucleation boiling. The rapidly increasing heat transfer coefficient allows the copper busbar to be quenched instantly, solidifying the fine grain structure formed in the early stage in time, ensuring the high conductivity of the product.

[0032] 3. This invention simultaneously completes the in-situ anti-oxidation treatment of the copper busbar surface during the rapid quenching process. When the gel film is sheared and ruptured, the fresh pure copper substrate is exposed to the coolant. The benzotriazole molecules in the system coordinate with the empty orbitals of copper atoms through the lone pair electrons of nitrogen atoms, and under the synergistic effect of triethanolamine borate, a chelate film is generated in situ. This dense passivation film directly blocks the contact between dissolved oxygen and the copper substrate, preventing the copper busbar from undergoing surface oxidation and discoloration during the heated unloading and subsequent traction and winding processes. Attached Figure Description

[0033] Figure 1 This is a graph showing the variation of the system's energy storage modulus at different temperatures according to the present invention; Figure 2 This is a graph showing the continuous temperature-time variation during the operation of the simulated test piece of the present invention. Figure 3 This is a graph showing the transient cooling rate over time, generated by differentiating based on temperature changes according to the present invention. Figure 4 This is a diagram of the Tafel polarization curve of the present invention; Figure 5 This is the AC impedance spectrum of the present invention; Figure 6 This is a scatter plot showing the distribution of the comprehensive electrical and mechanical properties of the extruded copper busbar of the present invention. Figure 7 This is a graph showing the change in transmittance of sampling point A over time according to the present invention. Figure 8 This is a line graph comparing the absolute oxygen content of the extruded copper busbar samples of the present invention. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0036] Sodium magnesium lithium silicate, CAS number 53320-86-8; Polosham 407, CAS number 9003-11-6; Hexadecyltrimethylammonium bromide, CAS number 57-09-0; Triethanolamine borate, CAS number 15277-97-1; Benzotriazole, CAS number 95-14-7.

[0037] In this invention, the units of measurement for all materials and solvents are uniformly referred to as parts by weight.

[0038] Preparation Example 1: This preparation example provides a method for preparing organically intercalated modified synthetic lithium saponite, including the following steps: Add 3.0 parts of sodium magnesium lithium silicate to 97.0 parts of deionized water, and mechanically stir at 1200 rpm for 2.5 hours at 70°C to hydrate and strip the sodium magnesium lithium silicate. Prepare a 10 wt% hexadecyltrimethylammonium bromide aqueous solution. Take 1.0 molar equivalent of the hexadecyltrimethylammonium bromide aqueous solution according to the cation exchange capacity of sodium magnesium lithium silicate, and add the hexadecyltrimethylammonium bromide aqueous solution dropwise to the hydrated and stripped suspension. Continue the reaction at a constant temperature of 70°C for 3.5 hours.

[0039] After the reaction was completed, the suspension was centrifuged at 4000 rpm. The precipitate was washed four times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 90℃ for 18 hours. The precipitate was then pulverized by air jet to a particle size of less than 74 μm.

[0040] The resulting organically intercalated modified synthetic lithium saponite is then ready for use. Here, the organically intercalated modified synthetic lithium saponite is named thixotropic modifier A.

[0041] Preparation Example 2: This preparation example provides a method for preparing organically intercalated modified synthetic lithium saponite, including the following steps: Add 2.0 parts of sodium magnesium lithium silicate to 98.0 parts of deionized water, and mechanically stir at 1000 rpm for 2 hours at 60°C to hydrate and exfoliate the sodium magnesium lithium silicate. Prepare a 10 wt% hexadecyltrimethylammonium bromide aqueous solution. Take 0.8 molar equivalents of the hexadecyltrimethylammonium bromide aqueous solution according to the cation exchange capacity of sodium magnesium lithium silicate, and add the hexadecyltrimethylammonium bromide aqueous solution dropwise to the hydrated and exfoliated suspension. Continue the reaction at a constant temperature of 60°C for 2 hours.

[0042] After the reaction was completed, the suspension was centrifuged at 4000 rpm. The precipitate was washed three times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 80℃ for 12 hours. The precipitate was then pulverized by airflow to a particle size of less than 74 μm.

[0043] The resulting organically intercalated modified synthetic lithium saponite is then ready for use. Here, the organically intercalated modified synthetic lithium saponite is named thixotropic modifier B.

[0044] Preparation Example 3: This preparation example provides a method for preparing organically intercalated modified synthetic lithium saponite, including the following steps: Add 4.0 parts of sodium magnesium lithium silicate to 96.0 parts of deionized water, and mechanically stir at 1500 rpm for 3 hours at 80°C to hydrate and exfoliate the sodium magnesium lithium silicate. Prepare a 10 wt% hexadecyltrimethylammonium bromide aqueous solution. Take 1.2 molar equivalents of the hexadecyltrimethylammonium bromide aqueous solution according to the cation exchange capacity of sodium magnesium lithium silicate, and add the hexadecyltrimethylammonium bromide aqueous solution dropwise to the hydrated and exfoliated suspension. Continue the reaction at a constant temperature of 80°C for 4 hours.

[0045] After the reaction was completed, the suspension was centrifuged at 4000 rpm. The precipitate was washed five times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 100℃ for 24 hours. The precipitate was then pulverized by air jet to a particle size of less than 74 μm.

[0046] The resulting organically intercalated modified synthetic lithium saponite is then ready for use. Here, the organically intercalated modified synthetic lithium saponite is named thixotropic modifier C. Example

[0047] This embodiment provides a continuous extrusion molding process for high conductivity copper busbars, including the following steps: S1. Inject 91.55 parts of deionized water into a reactor equipped with a high-shear homogenizer, maintain the temperature at 25°C, slowly add 0.35 parts of thixotropic modifier A, and start high-shear stirring at 3000 rpm for 45 minutes to obtain a basic thixotropic gel; cool the basic thixotropic gel in the reactor to 5°C, add 6.5 parts of poloxamer 407 in batches, and stir continuously at 800 rpm for 3 hours using an anchor-type stirrer until the polymer is completely dissolved; raise the system temperature to 25°C, add 1.5 parts of triethanolamine borate and 0.1 parts of benzotriazole in sequence, and stir continuously for 30 minutes; pump the obtained composite coolant into the circulating cooling tank of the extrusion production line, and maintain the basic operating temperature at 38°C through an external heat exchanger.

[0048] S2. The oxygen-free copper rod is fed into a continuous extruder for plastic deformation and dynamic recrystallization, and a high-temperature solid copper busbar is formed by continuous extrusion through the die. The measured surface temperature of the copper busbar at the extrusion die is 660℃, and the extrusion line speed is set to 18m / min.

[0049] S3. After the copper busbar is extruded through the die, it stays in the air for 0.4s before being immersed in the first temperature zone of the circulating cooling tank. At the entry point, a homogeneous composite coolant is injected along the direction of copper busbar travel via a water distributor, with the flow rate controlled at 0.8m / s to form a co-current laminar flow. A vapor blanket is formed on the surface of the copper busbar, and the polymer cross-links upon heating to form a thixotropic gel film. The copper busbar is then slowly cooled at high temperature under the wrapping of this laminar vapor blanket.

[0050] S4. Based on the extrusion line speed and the set 18s cooling time requirement, a submerged V-shaped dynamic pressure baffle is fixedly installed 5.4m away from the inlet along the copper busbar's travel direction in the cooling tank. The gap between the inner edge of the baffle and the running copper busbar is set to 20mm. A ring-shaped high-pressure jet array is arranged close to the downstream of the baffle, using a homogeneous composite coolant. The jet pressure is set to 2.0MPa, and the jet direction is at a 50° angle to the copper busbar's travel direction. The copper busbar passes through the baffle and enters the high-pressure jet zone. The thixotropic gel film is subjected to strong hydrodynamic shearing and disintegration, and the cooling rate suddenly changes to more than 150℃ / s for rapid quenching and passivation.

[0051] S5. The copper busbar, after being cooled by step, continues to move forward, with the exit temperature controlled at 45℃; a high-pressure air knife of 0.5MPa is used to dry the residual liquid film on the surface and then pull and rewind it. Example

[0052] This embodiment provides a continuous extrusion molding process for high conductivity copper busbars, including the following steps: S1. Inject 93.75 parts of deionized water into a reactor equipped with a high-shear homogenizer, maintain the temperature at 20°C, slowly add 0.2 parts of thixotropic modifier B, and start high-shear stirring at 2500 rpm for 30 minutes to obtain a basic thixotropic gel; cool the basic thixotropic gel in the reactor to 2°C, add 5.0 parts of poloxamer 407 in batches, and stir continuously at 500 rpm for 2 hours using an anchor-type stirrer until the polymer is completely dissolved; raise the system temperature to 20°C, add 1.0 part of triethanolamine borate and 0.05 parts of benzotriazole in sequence, and stir continuously for 30 minutes; pump the obtained composite coolant into the circulating cooling tank of the extrusion production line, and maintain the basic operating temperature at 35°C through an external heat exchanger.

[0053] S2. The oxygen-free copper rod is fed into a continuous extruder for plastic deformation and dynamic recrystallization, and a high-temperature solid copper busbar is formed by continuous extrusion through the die. The measured surface temperature of the copper busbar at the extrusion die is 640℃, and the extrusion line speed is set to 10m / min.

[0054] S3. After the copper busbar is extruded through the die, it stays in the air for 0.2s before being immersed in the first temperature zone of the circulating cooling tank. At the entry point, a homogeneous composite coolant is injected along the direction of copper busbar travel through a water distributor, with the flow rate controlled at 0.5m / s to form a co-current laminar flow. A vapor blanket is formed on the surface of the copper busbar, and the polymer cross-links upon heating to form a thixotropic gel film. The copper busbar is then slowly cooled at high temperature under the wrapping of this laminar vapor blanket.

[0055] S4. Based on the extrusion line speed and the set 25s cooling time requirement, a submerged V-shaped dynamic pressure baffle is fixedly installed 4.17m away from the inlet along the copper busbar's travel direction in the cooling tank. The gap between the inner edge of the baffle and the running copper busbar is set to 15mm. A ring-shaped high-pressure jet array is arranged close to the downstream of the baffle, using a homogeneous composite coolant. The jet pressure is set to 1.5MPa, and the jet direction is at a 45° angle to the copper busbar's travel direction. The copper busbar passes through the baffle and enters the high-pressure jet zone. The thixotropic gel film is subjected to strong hydrodynamic shearing and disintegration, and the cooling rate suddenly changes to more than 150℃ / s for rapid quenching and passivation.

[0056] S5. The copper busbar, after being cooled by step cooling, continues to move forward, with the exit temperature controlled at 40℃; a high-pressure air knife of 0.4MPa is used to dry the residual liquid film on the surface and then pull and rewind it. Example

[0057] This embodiment provides a continuous extrusion molding process for high conductivity copper busbars, including the following steps: S1. Inject 89.35 parts of deionized water into a reactor equipped with a high-shear homogenizer, maintain the temperature at 30°C, slowly add 0.5 parts of thixotropic modifier C, and start high-shear stirring at 4000 rpm for 60 minutes to obtain a basic thixotropic gel; cool the basic thixotropic gel in the reactor to 8°C, add 8.0 parts of poloxamer 407 in batches, and stir continuously at 1000 rpm for 4 hours using an anchor-type stirrer until the polymer is completely dissolved; raise the system temperature to 25°C, add 2.0 parts of triethanolamine borate and 0.15 parts of benzotriazole in sequence, and stir continuously for 30 minutes; pump the obtained composite coolant into the circulating cooling tank of the extrusion production line, and maintain the basic operating temperature at 42°C through an external heat exchanger.

[0058] S2. The oxygen-free copper rod is fed into a continuous extruder for plastic deformation and dynamic recrystallization, and a high-temperature solid copper busbar is formed by continuous extrusion through the die. The measured surface temperature of the copper busbar at the extrusion die is 680℃, and the extrusion line speed is set to 25m / min.

[0059] S3. After the copper busbar is extruded through the die, it stays in the air for 0.6s before being immersed in the first temperature zone of the circulating cooling tank. At the entry point, a homogeneous composite coolant is injected along the direction of the copper busbar's movement through a water distributor, with the flow rate controlled at 1.2m / s to form a co-current laminar flow. A vapor blanket is formed on the surface of the copper busbar, and the polymer cross-links upon heating to form a thixotropic gel film. The copper busbar is then slowly cooled at high temperature under the wrapping of this laminar vapor blanket.

[0060] S4. Based on the extrusion line speed and the set 12s cooling time requirement, a submerged V-shaped dynamic pressure baffle is fixedly installed 5.0m away from the inlet along the copper busbar's travel direction in the cooling tank. The gap between the inner edge of the baffle and the running copper busbar is set to 25mm. A ring-shaped high-pressure jet array is arranged close to the downstream of the baffle, using a homogeneous composite coolant. The jet pressure is set to 2.5MPa, and the jet direction is at a 60° angle to the copper busbar's travel direction. The copper busbar passes through the baffle and enters the high-pressure jet zone. The thixotropic gel film is subjected to strong hydrodynamic shearing and disintegration, and the cooling rate suddenly changes to more than 150℃ / s for rapid quenching and passivation.

[0061] S5. The copper busbar, after being cooled by step cooling, continues to move forward, with the exit temperature controlled at 48℃; a high-pressure air knife of 0.6MPa is used to dry the residual liquid film on the surface and then pull and rewind it. Example

[0062] This embodiment provides a continuous extrusion molding process for high conductivity copper busbars, including the following steps: S1. Inject 91.55 parts of deionized water into a reactor equipped with a high-shear homogenizer, maintain the temperature at 25°C, slowly add 0.35 parts of thixotropic modifier A, and start high-shear stirring at 3000 rpm for 45 minutes to obtain a basic thixotropic gel; cool the basic thixotropic gel in the reactor to 5°C, add 6.5 parts of poloxamer 407 in batches, and stir continuously at 800 rpm for 3 hours using an anchor-type stirrer until the polymer is completely dissolved; raise the system temperature to 25°C, add 1.5 parts of triethanolamine borate and 0.1 parts of benzotriazole in sequence, and stir continuously for 30 minutes; pump the obtained composite coolant into the circulating cooling tank of the extrusion production line, and maintain the basic operating temperature at 38°C through an external heat exchanger.

[0063] S2. The oxygen-free copper rod is fed into a continuous extruder for plastic deformation and dynamic recrystallization, and a high-temperature solid copper busbar is formed by continuous extrusion through the die. The measured surface temperature of the copper busbar at the extrusion die is 660℃, and the extrusion line speed is set to 18m / min.

[0064] S3. After the copper busbar is extruded through the die, it stays in the air for 0.4s before being immersed in the first temperature zone of the circulating cooling tank. At the entry point, a homogeneous composite coolant is injected along the direction of copper busbar travel through a water distributor, and the flow rate is adjusted and controlled at 1.2m / s to form a co-current laminar flow. A vapor blanket is formed on the surface of the copper busbar, and the polymer cross-links upon heating to form a thixotropic gel film. The copper busbar is slowly cooled at high temperature under the wrapping of this laminar vapor blanket.

[0065] S4. A submerged V-shaped dynamic pressure baffle is fixedly installed 5.4m from the inlet along the direction of copper busbar travel in the cooling tank. The gap between the inner edge of the baffle and the running copper busbar is set to 20mm. A ring-shaped high-pressure jet array is arranged close to the downstream of the baffle. The same source composite coolant is used, and the jet pressure is set to 2.0MPa. The jet direction is adjusted to be 60° opposite to the direction of copper busbar travel. The copper busbar passes through the baffle and enters the high-pressure jet zone. The thixotropic gel film is disintegrated by strong hydrodynamic shearing, and the cooling rate suddenly changes to more than 150℃ / s for rapid quenching and passivation.

[0066] S5. The copper busbar, after being cooled by step, continues to move forward, with the exit temperature controlled at 45℃; a high-pressure air knife of 0.5MPa is used to dry the residual liquid film on the surface and then pull and rewind it.

[0067] Comparative Example 1: Compared with Example 1, the difference is that a commercially available conventional water-based coolant is used instead of the composite coolant of the present invention, and the submerged V-shaped dynamic pressure baffle and the annular high-pressure jet array are not installed in the cooling tank; all other aspects are the same.

[0068] Comparative Example 2: Compared with Example 1, the difference is that thixotropic modifier A is removed from the raw materials for preparing the composite coolant, and deionized water is used to make up the corresponding difference, while the rest are the same.

[0069] Comparative Example 3: Compared with Example 1, the difference is that the annular high-pressure jet array arranged close to the downstream of the baffle was not activated, and the film was broken by natural thermodynamic cooling only. All other aspects are the same.

[0070] Comparative Example 4: Compared with Example 1, the difference is that the distance L based on the cooling time conversion is not followed, and the distance L from the inlet of the submerged V-shaped dynamic pressure baffle and the high-pressure jet array is shortened from 5.4m to 2.0m. All other aspects are the same.

[0071] Comparative Example 5: Compared with Example 1, the difference is that: no submerged V-shaped dynamic pressure baffle is installed in the cooling tank, and the laminar flow in the direction of the inlet is closed; otherwise, they are the same.

[0072] Comparative Example 6: Compared with Example 1, the difference is that triethanolamine borate is removed from the raw materials for preparing the composite coolant, and deionized water is used to make up the corresponding difference, while the rest are the same.

[0073] Test Example 1: The composite coolant prepared in Example 1 and the comparative coolant prepared in Comparative Example 2 were measured separately as rheological test samples.

[0074] Temperature scanning tests were performed using a rotational rheometer with parallel plate clamps. A sample of a set volume was injected into the test platform, with the clamp gap set to 1.0 mm. Silicone oil was coated around the plate to prevent moisture evaporation at high temperatures. Within the linear viscoelastic region of a constant frequency of 1.0 Hz and a strain of 1.0%, the changes in storage modulus G' and loss modulus G'' of the system were tested at a heating rate of 2 °C / min in the range of 25 °C to 85 °C.

[0075] The sample was retained on the rotational rheometer platform for shear rate scanning. The platform temperature was kept constant at 75°C for 5 minutes to allow the sample to reach a fully gelled state. The shear rate was set to increase logarithmically, starting from 0.1 s⁻¹. -1 up to 1000s -1 The apparent viscosity of the system was tested and recorded as the shear rate increased.

[0076] Table 1: Test data of rheological modulus of coolant system at different temperatures 25 0.52 1.12 0.05 0.85 40 0.81 1.55 0.08 1.02 50 1.34 2.14 0.12 1.25 55 18.61 10.34 5.23 4.81 60 312.47 45.62 42.15 18.52 65 845.23 92.17 185.34 35.26 75 1250.71 134.55 240.67 42.19 85 1340.24 142.83 255.42 45.31 Table 2: Test data on the change of apparent viscosity of coolant system with shear rate at constant 75℃ 0.1 412.53 52.41 0.1 1.0 48.27 18.55 1.0 10.0 6.14 3.28 10.0 100.0 0.58 0.41 100.0 1000.0 0.07 0.06 1000.0 According to Tables 1 and 2, and Figure 1 It can be seen that the composite coolant used in Example 1 of the present invention exhibits fluid phase change and thixotropic characteristics. During the temperature scan in Table 1, the storage modulus G' of the system in Example 1 in the low-temperature range of 25°C to 50°C is less than the loss modulus G'', and the fluid exhibits conventional liquid characteristics. When the temperature rises to the critical region of 55°C, the hydrophobic blocks of polymer molecules dehydrate, leading to network rearrangement, and the storage modulus begins to exceed the loss modulus. As the temperature continues to rise, the storage modulus of Example 1 rises to 1250.71 Pa at 75°C. Compared with Comparative Example 2, which did not add inorganic thixotropic agents, its modulus is different. The formation of this physical cross-linked network supports the technical principle of constructing a high-viscosity hydrogel film on the surface of the high-temperature copper busbar, providing a material basis for maintaining stable heat exchange in laminar flow.

[0077] As can be seen from the isothermal shear scan data in Table 2, the system of Example 1, which has formed a gel structure, exhibits typical shear-thinning behavior at an extremely low shear rate of 0.1 s⁻¹. -1 At this point, the system viscosity remained at 412.53 Pa·s. This high and low shear condition corresponds to the co-current laminar flow environment in the initial stage of the copper busbar entering the circulation tank, allowing the gel membrane to stably encapsulate the steam blanket without being damaged by low-speed disturbances. When the shear rate increased to 1000 s⁻¹, the viscosity of the system decreased. -1 At that time, the apparent viscosity of Example 1 rapidly decreased to 0.07 Pa·s, a decrease of several orders of magnitude, and its high shear viscosity was basically the same as that of Comparative Example 2, close to the flow state of water-based fluid. This data change verifies that in the process steps, when the copper busbar runs to a specific spatial position and encounters high-pressure jet fluid shear, the gel network covering the metal surface can be mechanically disintegrated, the rupture of the gel film removes the isolation layer, and promotes the cooling medium to enter the nucleation boiling heat exchange zone, thereby realizing the abrupt change in cooling rate from the high-temperature slow cooling stage to the ultra-fast quenching stage, which meets the process conditions for suppressing impurity segregation and surface oxidation.

[0078] Test Example 2: The cooling process conditions provided in Example 1, the conventional water-based cooling process conditions provided in Comparative Example 1, and the cooling process conditions without high-pressure jet forced film rupture provided in Comparative Example 3 were selected as test objects.

[0079] Oxygen-free copper rods of the same specifications as those used in actual production were selected and processed into simulated test pieces. K-type high-temperature resistant armored thermocouple probes were pre-embedded at a depth of 1.5mm below the surface of the test piece and sealed and fixed with high-temperature resistant thermally conductive adhesive. The tail signal line of the thermocouple probe was connected to a high-speed data acquisition card arranged on the traction device, and the acquisition frequency was set to 100Hz.

[0080] The simulated test piece with embedded thermocouples was heated using an induction heating furnace to a surface temperature of 660°C to simulate the initial thermodynamic state of the copper busbar when it is extruded from the die.

[0081] The heated test piece is fed into the corresponding cooling tank at a constant linear velocity of 18 m / min. The data acquisition card synchronously records the continuous temperature change data of the test piece from the moment it comes into contact with the coolant, through the laminar flow zone, the dynamic pressure baffle, and the high-pressure jet flow zone, until it runs for 30 seconds.

[0082] The collected raw time and temperature data are imported into the analysis software, and the time is differentiated to calculate the transient cooling rate data under the corresponding process.

[0083] Table 3: Test data of time, temperature and cooling rate of simulated test specimens under different cooling processes 0.0 661.2 - 658.9 - 660.5 - 3.0 615.4 14.8 384.2 87.5 618.1 14.2 6.0 572.8 13.9 241.5 39.1 570.6 15.1 9.0 534.1 12.5 176.3 19.3 536.8 11.6 12.0 492.5 13.7 132.8 12.8 495.2 13.4 15.0 451.7 13.5 105.4 8.2 448.9 14.5 17.0 423.6 13.8 92.1 6.1 425.4 12.1 18.0 411.2 14.3 87.5 4.8 410.7 13.6 19.0 245.8 158.4 82.3 4.9 398.2 12.2 20.0 124.3 116.7 78.6 3.5 385.6 11.9 22.0 68.5 32.1 71.2 3.2 361.3 12.4 25.0 52.1 6.5 64.8 2.1 328.7 10.5 30.0 45.6 1.4 55.4 1.8 284.1 8.6 According to Table 3 and Figure 2 and Figure 3 It can be seen that the cooling process of Example 1 exhibits two distinct thermodynamic trajectories in the time dimension. In the high-temperature range of 0 to 18 seconds, the temperature decrease trend of Example 1 is gradual, and the average cooling rate is suppressed to about 13 to 15℃ / s. This indicates that the thixotropic gel film formed by the composite coolant on the surface of the high-temperature copper busbar plays a role in increasing the stability of the steam blanket and limiting the interface heat exchange efficiency. The cooling rate value corresponding to 0.0s is recorded as -, indicating that this moment is the initial thermodynamic state of the simulated test piece when it just comes into contact with the coolant. There is no prior temperature data to calculate the cooling rate, so it is not included in the cooling rate statistics.

[0084] Maintaining this high-temperature slow cooling range provides the necessary time window for the recovery of internal faults and the annihilation of vacancies in the copper matrix. In contrast, Comparative Example 1 uses a conventional water cooling process, which follows the heat transfer law of natural convection. The cooling rate is as high as 87.5℃ / s in the initial 0 to 3s of entering the tank, which causes the defects in the high-temperature metal to be rapidly dissolved and cannot be eliminated.

[0085] When the running time reached 18 seconds, the transient cooling rate of Example 1 underwent a step-like change. At 19 seconds, the cooling rate was measured to surge to 158.4℃ / s. This sudden change corresponds to the strong shearing action of the hydrodynamics in the high-pressure jet flow region of the process. The physically cross-linked network structure was disintegrated under force, the vapor coating was forcibly peeled off, and the heat exchange mode directly cut into the nucleus boiling region. Due to the lack of a high-pressure film breaking mechanism, Comparative Example 3 maintained a low-level slow cooling state of about 12℃ / s after 18 seconds. The slow cooling of metal below 400℃ will cause trace impurity elements to segregate and precipitate towards the grain boundaries.

[0086] The data from Example 1 show that by combining specific flow field control with a non-Newtonian fluid medium, nonlinear regulation of the heat transfer process can be achieved in continuously operating equipment, satisfying the rapid cooling conditions required to suppress impurity precipitation and prevent oxidation.

[0087] Test Example 3: Copper busbars prepared by the continuous extrusion cooling process of Example 1 and Comparative Example 1 were respectively taken as electrochemical test samples.

[0088] After cutting the sample into pieces, it was cold-mounted and encapsulated with epoxy resin, retaining an area of ​​1.0 cm². 2 The original copper busbar working surface was ultrasonically cleaned with deionized water and anhydrous ethanol for 5 minutes each, and then dried with cold air to serve as the working electrode.

[0089] A standard three-electrode electrochemical testing system was constructed, with a platinum sheet as the auxiliary electrode, a saturated calomel electrode as the reference electrode, and a 3.5% sodium chloride neutral aqueous solution as the test solution. The test temperature was kept constant at 25℃.

[0090] The working electrode was immersed in the solution and left to stand for 30 minutes to obtain a stable open circuit potential. Then, the polarization curve test was started. The scanning potential range was set to 250mV above and below the open circuit potential, and the scanning rate was set to 1mV / s. The response current density under different applied potentials was recorded to characterize the corrosion kinetics of the surface.

[0091] Electrochemical AC impedance spectroscopy was performed at open circuit potential. The amplitude of the applied sinusoidal AC signal was set to 10mV, and the test frequency range was set to 100kHz to 0.01Hz. The real and imaginary impedance data at each frequency point were recorded to analyze the resistance characteristics of the surface film.

[0092] Table 4: Test data of characteristic points of polarization curves of extruded copper busbar samples in 3.5% NaCl solution -0.352 <![CDATA[8.24×10 -6 ]]> <![CDATA[1.15×10 -3 ]]> -0.291 <![CDATA[3.12×10 -6 ]]> <![CDATA[3.68×10 -4 ]]> -0.246 <![CDATA[1.05×10 -6 ]]> <![CDATA[4.81×10 -6 ]]> -0.198 <![CDATA[2.14×10 -7 ]]> <![CDATA[1.94×10 -4 ]]> -0.153 <![CDATA[3.41×10 -8 ]]> <![CDATA[5.27×10 -4 ]]> -0.106 <![CDATA[1.63×10 -7 ]]> <![CDATA[1.83×10 -3 ]]> -0.054 <![CDATA[7.92×10 -7 ]]> <![CDATA[4.62×10 -3 ]]> 0.012 <![CDATA[2.58×10 -6 ]]> <![CDATA[8.15×10 -3 ]]> 0.089 <![CDATA[5.41×10 -6 ]]> <![CDATA[1.56×10 -2 ]]> 0.165 <![CDATA[9.87×10 -6 ]]> <![CDATA[2.84×10 -2 ]]> Table 5: AC impedance spectroscopy data of extruded copper busbar samples in 3.5% NaCl solution 45.6 182.4 15.2 31.6 312.8 1541.3 48.7 98.4 846.5 3215.7 105.4 162.8 1754.2 4532.1 185.3 195.2 3210.6 5118.4 246.8 212.5 4685.3 4963.8 321.4 198.7 6124.7 4021.5 385.6 154.3 7241.5 2845.2 432.1 96.5 8105.2 1624.8 475.8 45.2 8652.4 541.3 502.4 12.8 According to Table 4 and Figure 4 It can be seen that, in the Tafel polarization test, the self-corrosion potential of the sample in Example 1 is approximately -0.153V, corresponding to a corrosion current density of 10. -8 A / cm 2Compared to Comparative Example 1, its corrosion potential shifts positively, and the overall anodic and cathodic polarization current densities decrease by three to four orders of magnitude. This decrease in current density reflects the chemical reaction barrier present on the copper busbar surface. Under continuous extrusion cooling conditions, high-pressure jetting breaks the gel film and enters the rapid cooling stage. The benzotriazole molecules in the solution have the conditions to directly contact the metal interface. The nitrogen atoms in the molecules rely on lone pair electrons to coordinate with the empty orbitals of copper atoms, and then polymerize in situ on the oxygen-free or low-oxygen surface to form a Cu-BTA type network complex film.

[0093] According to Table 5 and Figure 5 It can be seen that the test results of the AC impedance spectrum and the polarization curve corroborate each other. In the Nyquist plot, the diameter of the semicircle corresponds to the charge transfer resistance of the electrode surface. The diameter of the semicircle on the surface of Comparative Example 1 is approximately 500 Ω·cm. 2 This conforms to the electrochemical characteristics of a typical slightly oxidized pure copper surface; while the semicircular diameter measured in Example 1 diffused to 8000 Ω·cm. 2 The exponential increase in the values ​​of real and imaginary impedance confirms that the in-situ formed complex film has high density and insulation properties. This film covers and cuts off the transmission path of electrons and corrosive ions at the metal solution interface. Comprehensive test data shows that, through the specific composition of the composite cooling medium, a quantifiable interface anti-oxidation shielding function can be provided during the extrusion stage without the need for an external protective gas chamber.

[0094] Test Example 4: The copper busbars with equal cross-sections produced after two hours of continuous and stable operation of the processes in Examples 1 to 4 and Comparative Examples 1 to 4 were respectively taken as macroscopic performance test samples.

[0095] Conductivity was tested using an eddy current conductivity meter. Five test areas 10 cm apart were selected along the length of each sample surface. Before testing, the test area surface was lightly sanded with fine sandpaper to eliminate external environmental interference. The instrument probe was pressed vertically against the test surface, and the international standard conductivity (%IACS) value at room temperature was recorded. The arithmetic mean of the five test points was taken as the final conductivity data of the sample.

[0096] Using CNC wire cutting equipment, each group of copper busbar samples was processed into standard dumbbell-shaped tensile specimens with a gauge length of 50 mm and a width of 12.5 mm along the extrusion direction.

[0097] The standard specimen is clamped in the upper and lower jaws of the universal testing machine, the extensometer is fixed in the gauge section, the crossbeam movement speed is set to 2 mm / min, and unidirectional axial tension is performed at room temperature of 25℃ until the specimen breaks. The maximum tensile load during the test is recorded and converted into tensile strength (MPa). Three parallel specimens are taken for testing under each set of process conditions and the average value is taken.

[0098] Table 6: Test Data of Macroscopic Electrical and Mechanical Properties of Examples and Comparative Samples Example 1 101.83 265.4 Example 2 101.58 262.7 Example 3 101.94 267.2 Example 4 101.76 265.9 Comparative Example 1 99.37 240.5 Comparative Example 2 100.21 251.8 Comparative Example 3 101.35 229.6 Comparative Example 4 99.78 259.4 According to Table 6 and Figure 6 It can be seen that the samples prepared in Examples 1 to 4 show consistent data characteristics in terms of conductivity and tensile strength, all distributed in the data range of conductivity greater than 101.5% IACS and tensile strength greater than 260 MPa. Compared with the conventional water-based coolant and flow field blocking process used in Comparative Example 1, the process of the Examples alleviates the technical contradictions caused by the traditional cooling method. In Comparative Example 1, the high initial cooling rate limits the repair of lattice defects in the metal after extrusion. A large number of dislocations and vacancies constitute dense electron scattering centers, so that the macroscopic conductivity remains at 99.37% IACS.

[0099] In Comparative Example 2, the tensile strength of the component without thixotropic modifier A was still acceptable, but the conductivity dropped to 100.21% IACS. This change in data confirms that without the physical cross-linking support provided by the inorganic thixotropic agent, the hydrogel film formed solely by polymer phase change lacks sufficient mechanical yield stress. Under the micro-perturbation of the flow field, this weakened gel film cannot stably wrap the steam blanket, causing the coolant to prematurely contact the surface and locally boil. This uncontrolled cooling rate accelerates the compression of the time window for slow cooling at high temperature, and the vacancies are not fully annihilated.

[0100] Comparative Example 3: When the high-pressure jet fluid array close to the downstream of the baffle is closed, the conductivity is high, but the tensile strength drops to 229.6 MPa. The removal of mechanical forced film breaking allows the copper busbar in the wrapped state to undergo a natural extension of slow cooling process in the medium and low temperature range below 400℃. In this temperature range, the metal has the thermodynamic conditions for the diffusion and migration of impurity elements. Trace impurities gradually segregate and precipitate towards the grain boundaries, which seriously weakens the bonding force between grain boundaries, causing the material to develop intergranular microcracks under tensile load.

[0101] Comparative Example 4 shortened the distance L between the baffle and the high-pressure jet to 2.0m, and the conductivity dropped to 99.78% IACS. The shortening of the distance prematurely introduced the fluid shear film breaking mechanism in physical space, cutting off the flat section of the temperature-time decay curve in advance. This premature ultra-rapid quenching interrupted the ongoing dynamic recovery and point defect dissipation processes inside the metal. The remaining defect grid re-limited the mean free path of electrons. The above cross-comparison data show that the non-Newtonian phase transition characteristics of polymers must be strictly matched with the spatial arrangement of the continuous flow field designed in order to construct a step cooling model that meets the dual metallurgical requirements of defect removal and impurity suppression.

[0102] Test Example 5: The process flow and equipment system provided in Example 1, and the process system of Comparative Example 5, which removes the co-current laminar flow injection and the V-shaped dynamic pressure baffle, were used as experimental objects for long-term testing.

[0103] Equal amounts of fresh composite coolant were injected into the two systems. The simulated extrusion line speed was set to 18 m / min. Simulated high-temperature copper busbars with a surface temperature of 660°C were continuously fed into the circulating cooling tank to maintain the normal operation of the heat exchanger outside the tank and keep the basic operating temperature between 36 and 40°C for 48 hours without interruption.

[0104] Three fixed sampling points were set in the cooling tank along the direction of copper busbar travel: sampling point A was located 0.5m after the entry point; sampling point B was located 4.9m from the entry point; and sampling point C was located 6.0m from the entry point.

[0105] At 0, 12, 24, 36 and 48 hours of system operation, 20 mL coolant samples were taken from each of the three sampling points.

[0106] After the extracted liquid sample was allowed to stand to eliminate microbubbles, it was injected into a 1cm quartz cuvette. The transmittance of the sample at a wavelength of 600nm was measured using a UV-Vis spectrophotometer. The transmittance at the initial 0 hours was used as 100% as the baseline. The relative transmittance data of the sample at each time point was recorded to characterize the thermal aging and carbonization turbidity of the cooling medium.

[0107] Table 7: Test data on the change of coolant transmittance in different areas over time under continuous operation conditions 0 100.0 100.0 100.0 100.0 100.0 100.0 12 98.4 97.9 98.1 82.5 81.2 84.7 24 96.2 96.5 95.8 65.4 68.3 71.9 36 94.7 93.8 94.2 51.2 56.4 58.6 48 92.5 91.6 92.3 38.7 42.1 47.3 According to Table 7 and Figure 7 Under continuous thermodynamic loading of 660℃ high-temperature metal for 48 hours, the fluid heat aging resistance of the two flow field structure designs differed. In Comparative Example 5, after the flow field isolation mechanism was removed, the transmittance of each sampling point decreased sharply. Among them, the transmittance of sampling point A, located in the slow cooling zone of the tank, dropped to 38.7% after 48 hours. The non-Newtonian polymer phase change gel film will adhere to the high-temperature metal surface for a long time in the static water area without laminar flow. The polymer molecular chain absorbs excessive heat energy, causing the C-C bonds and CO bonds to undergo thermal dissociation and carbonization. At the same time, due to the lack of physical blockage of the dynamic pressure baffle, the turbulent kinetic energy generated by the downstream high-pressure membrane breaking flow field is back-mixed and transferred to the upstream of the inlet, causing the generated carbonized impurities to diffuse and suspend in the entire cooling tank, making the macro fluid turbid.

[0108] In Example 1, the transmittance of the three sampling points remained above 91% throughout the same operating cycle. The laminar flow generated by the water distributor formed a parallel fluid drag force on the surface of the copper busbar. While maintaining the gel film encapsulation morphology, it pushed the outer polymer layer that had completed the endothermic phase change at the interface and showed signs of aging backward, avoiding local thermal retention of organic macromolecules. The V-shaped dynamic pressure baffle physically divided the circulation tank using a submerged narrow gap. When the turbulent vortex formed by the downstream high-pressure jet encountered the baffle, its reverse momentum was dissipated by the baffle surface. The system maintained the laminar flow stability of the upstream slow cooling zone and the turbulent intensity of the downstream rapid cooling zone. The above data reflects that the spatial isolation structure of the macroscopic flow field is the engineering basis for solving the thermal decomposition pollution of the polymer cooling medium and supporting the long-term stable operation of the continuous extrusion production line.

[0109] Test Example 6: Copper busbars prepared by continuous extrusion cooling process in Example 1 and Comparative Example 6 (with triethanolamine borate removed) were respectively taken as samples for quantitative testing of absolute oxygen content.

[0110] The sample was processed into standard test blocks with a mass of 1.0g to 1.5g using a slow wire EDM machine. Anhydrous ethanol was used as the working fluid during the processing to avoid secondary oxidation caused by moisture contact. The test blocks were ultrasonically cleaned in acetone solution for 10 minutes to remove surface impurities, and then dehydrated and dried in a vacuum drying oven.

[0111] The absolute oxygen content was determined using an oxygen, nitrogen, and hydrogen elemental analyzer. The treated test block was placed in a high-purity graphite crucible and sent into a pulse heating furnace in a helium carrier gas environment with a purity of 99.999% to heat to 2500℃ to completely melt the copper busbar sample.

[0112] The system records the spectral absorption signal of the carbon oxide gas generated by the reaction of oxygen-containing components in the molten sample with the graphite crucible and then enters the non-dispersive infrared detection cell with the carrier gas. The system integrates the absorption signal into the absolute oxygen content value of the sample according to the pre-calibrated reference curve. The samples under each process condition are tested in parallel 5 times.

[0113] Table 8: Data on Repeated Determination of Absolute Oxygen Content in Extruded Copper Busbar Samples 1 12.4 145.2 2 11.8 158.7 3 13.5 139.4 4 12.1 162.1 5 14.2 151.8 According to Table 8 and Figure 8It can be seen that in the quantitative analysis of oxygen in the copper busbar sample, the five measurements of Comparative Example 6 were all distributed in the range of 139ppm to 163ppm. This value reflects that when the high-temperature copper busbar at 600℃ or above comes into contact with the vaporized water vapor at the interface in the cooling tank without the addition of a specific deoxidizer, the trace oxygen dissolved in the aqueous phase is entrained with the gas-liquid boundary layer and undergoes an oxidation reaction with the metal matrix under thermodynamic drive, which causes the oxygen element to diffuse into the interstices of the copper lattice or form microscopic cuprous oxide inclusions.

[0114] In contrast, the five measurements in Example 1 were consistently within the extremely low range of 11 ppm to 15 ppm, meeting the oxygen content limit requirements of the high-purity oxygen-free copper standard. The magnitude of the above oxygen content values ​​confirms that the triethanolamine borate (TEAB) added to the composite coolant plays an in-situ chemical regulation role in the first temperature zone. When the copper is discharged into the tank and is enveloped by laminar flow and is in a high-temperature slow cooling state, the TEAB molecules undergo thermal dissociation in the water vapor mixing micro-gas chamber. The dissociation products, as oxygen scavengers, preferentially react with the free oxygen that has penetrated into the steam blanket to consume oxygen.

[0115] This competitive oxygen-consuming mechanism in the interface space reduces the oxygen partial pressure in the microenvironment of the metal surface, blocking the direct oxidation pathway of high-temperature metals. Test data shows that the formulation components, combined with the steam blanket wrapping effect, can replace the traditional inert gas protection furnace and achieve the construction of a pure interface in an open coolant tank.

[0116] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A continuous extrusion molding process for high conductivity copper busbars, characterized in that, The method includes the following steps: A composite coolant was prepared by mixing deionized water, thixotropic modifier, poloxamer 407, triethanolamine borate, and benzotriazole. The oxygen-free copper rod is fed into a continuous extruder for plastic deformation and dynamic recrystallization, and then continuously extruded through a die to form a high-temperature solid copper busbar. After the copper busbar is extruded, it is immersed in a circulating cooling tank. The composite coolant is injected at the entry point along the direction of the copper busbar to form a co-current laminar flow, so that a vapor blanket is formed on the surface of the copper busbar and the polymer cross-links upon heating to form a thixotropic gel film. The copper busbar is then slowly cooled at high temperature under this wrapping. A baffle is provided along the direction of copper busbar travel in the cooling tank, and a high-pressure jet stream array is arranged downstream of the baffle. The copper busbar with thixotropic gel film passes through the baffle and enters the high-pressure jet zone. The composite coolant is used for reverse high-pressure jetting, which causes the thixotropic gel film to be disintegrated by strong hydrodynamic shearing, thereby achieving rapid quenching and passivation. The cooled copper busbar continues to move out of the tank, where the residual liquid film on the surface is dried and then pulled and wound up.

2. The continuous extrusion molding process for high conductivity copper busbars according to claim 1, characterized in that, The raw materials for preparing the composite coolant include: Deionized water: 89.0 to 94.0 parts; Thixotropic modifier: 0.2 to 0.5 parts; Polosham 407: 5.0 to 8.0 copies; Triethanolamine borate: 1.0 to 2.0 parts; Benzotriazole: 0.05 to 0.15 parts.

3. The continuous extrusion molding process for high conductivity copper busbars according to claim 2, characterized in that, The steps for preparing the composite coolant by mixing the deionized water, thixotropic modifier, poloxamer 407, triethanolamine borate, and benzotriazole include: The deionized water and the thixotropic modifier are mixed and subjected to high-shear stirring at 20 to 30°C to obtain a basic thixotropic gel. The basic thixotropic gel is cooled to 2 to 8°C, and poloxamer 407 is added in batches while stirring continuously until dissolved. Subsequently, the system is heated to 20 to 25°C, and triethanolamine borate and benzotriazole are added sequentially while stirring continuously.

4. The continuous extrusion molding process for high conductivity copper busbars according to claim 1, characterized in that, The thixotropic modifier is an organically intercalated modified synthetic lithium saponite, and the raw materials for its preparation include at least sodium magnesium lithium silicate and hexadecyltrimethylammonium bromide.

5. The continuous extrusion molding process for high conductivity copper busbars according to claim 4, characterized in that, The organic intercalation modified synthetic lithium saponite is prepared by adding hexadecyltrimethylammonium bromide at a molar equivalent of 0.8 to 1.2 times the cation exchange capacity of sodium magnesium lithium silicate to a hydrated and exfoliated sodium magnesium lithium silicate suspension.

6. The continuous extrusion molding process for high conductivity copper busbars according to claim 1, characterized in that, The steps of feeding the oxygen-free copper rod into a continuous extrusion press for plastic deformation and dynamic recrystallization, and continuously extruding it through a die to form a high-temperature solid copper busbar include: The surface temperature of the copper busbar at the extrusion die is controlled at 640 to 680°C, and the extrusion line speed is set to 10 to 25 m / min.

7. The continuous extrusion molding process for high conductivity copper busbars according to claim 1, characterized in that, The step of injecting the composite coolant into the circulating cooling tank after the copper busbar is extruded, along the direction of copper busbar travel at the inlet point to form a co-current laminar flow, includes: After the copper busbar is extruded through the die, it is kept in the air for 0.2 to 0.6 seconds before being immersed in the circulating cooling tank; the flow rate of the injected composite coolant is controlled to be between 0.5 and 1.2 m / s.

8. The continuous extrusion molding process for high conductivity copper busbars according to claim 1, characterized in that, The step of installing baffles along the direction of copper busbar travel in the cooling tank includes: A submerged V-shaped dynamic pressure baffle is set as the baffle, and the gap between the inner edge of the baffle and the running copper busbar is set to 15 to 25 mm.

9. The continuous extrusion molding process for high conductivity copper busbars according to claim 8, characterized in that, The steps of using the composite coolant for reverse high-pressure injection include: The high-pressure injection pressure is set to 1.5 to 2.5 MPa, and the injection direction is at a 45 to 60° angle to the direction of copper busbar travel; the cooling rate during rapid quenching is controlled to change to more than 150°C / s.

10. The continuous extrusion molding process for high conductivity copper busbars according to claim 1, characterized in that, The steps of the cooled copper busbar continuing to move out of the tank, drying the residual liquid film on the surface, and being pulled and wound up include: The temperature of the copper busbar exiting the tank is controlled at 40 to 48°C; a high-pressure air knife with a spray pressure of 0.4 to 0.6 MPa is used to blow dry the residual liquid film on the surface.

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