Large-size copper-chromium-zirconium alloy contact wire and production process thereof

Abstract

The invention relates to a large-size copper-chromium-zirconium alloy contact wire and a production process thereof, and relates to the technical field of metal materials, the large-size copper-chromium-zirconium alloy contact wire comprises 0.3-1.2 wt% of chromium, 0.03-0.12 wt% of zirconium, less than or equal to 0.1 wt% of impurity elements, and the balance of copper; the cross section size of the large-size copper-chromium-zirconium alloy contact wire is 170-300 mm; the production process comprises the steps of up-drawing continuous casting, continuous extrusion, aging treatment and drawing forming. According to the large-size copper-chromium-zirconium alloy contact wire and the production process, through triple cooling, rapid cooling can be achieved, the solid solution effect of the copper-chromium-zirconium alloy is guaranteed, and the mechanical and conductive performance of the copper material is improved, so that the purposes that the hardness of the large-section-size copper-chromium-zirconium alloy contact wire is larger than or equal to 125 HV, the tensile strength is larger than or equal to 460 MPa, and the conductivity is larger than or equal to 75% IACS are achieved; finally, a double-bearing and double-guide structure is replaced, and the weight reduction requirement of a contact network system is met.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and in particular to a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process. Background Technology

[0002] With the continuous development of electrified railway and electric freight car technology in my country, the performance of the contact wire, a key component of the overhead contact system, directly affects whether electrified railways and urban rail transit can achieve high-speed and safe operation.

[0003] Among many high-strength, high-conductivity copper alloys, copper-chromium-zirconium alloy contact wires have become the preferred material for contact wires of high-speed railways with speeds of 380 km / h and above due to their advantages of high strength, high conductivity, resistance to high-temperature softening, wear resistance, and long service life.

[0004] Currently, the largest cross-sectional area of ​​copper and copper alloy contact wires in China is 150mm². In railway contact networks with heavy loads and high traffic density, a double-bearing, double-conductor mode is often used, consisting of two 120mm² cross-section catenary cables and two 150mm² cross-section contact wires, with a total cross-sectional area of ​​540mm², to meet the high current-carrying requirements of the contact network power supply. However, this size of contact wire has certain limitations in terms of current-carrying performance, energy consumption, and equipment lifespan, making it difficult to meet the development needs of electrified railways and emerging electrified highway markets.

[0005] The current mainstream production process for copper-chromium-zirconium alloy contact wires is "vacuum melting - hot rolling - cold rolling - heat treatment - drawing method", etc. Chinese invention patent application with publication number CN111519116A and publication date August 11, 2020 proposes a method for preparing long-length copper-chromium-zirconium alloy contact wires without solder joints, which includes the following process flow: casting, cold working, and annealing. This process flow ensures that the grains of the contact wire are small and uniform, and further produces long-length copper-chromium-zirconium alloy contact wires.

[0006] In response to the above technical solutions, the inventors discovered that cooling the wire blank in a water bath after solution treatment can achieve rapid cooling, suppress the premature precipitation of chromium and zirconium elements, and ensure the strengthening effect of subsequent aging treatment. However, in the process of preparing large-section wires, the above-mentioned water bath cooling method has the problem of long heat conduction path and slow cooling of the core, which leads to a small amount of premature precipitation of chromium and zirconium elements, affecting the final strength and conductivity of the contact wire.

[0007] Therefore, there is an urgent need to produce a large-section copper-chromium-zirconium alloy contact wire product that meets the strength requirements for contact wire use and has low conductor resistance. Summary of the Invention

[0008] To replace the double-bearing, double-conductor contact wire structure and achieve system weight reduction, this invention provides a large-section copper-chromium-zirconium alloy contact wire product with low conductor resistance, as well as a manufacturing process for producing large-section copper-chromium-zirconium alloy contact wires.

[0009] In a first aspect, the present invention provides a large-size copper-chromium-zirconium alloy contact wire, which adopts the following technical solution:

[0010] A large-size copper-chromium-zirconium alloy contact wire, the composition of which by mass percentage includes: 0.3-1.2 wt% chromium, 0.03-0.12 wt% zirconium, ≤0.1 wt% impurity elements, and the balance being copper; the cross-sectional dimensions of the large-size copper-chromium-zirconium alloy contact wire are 170-300 mm².

[0011] By employing the above technical solution, copper is used as the matrix, preserving its excellent electrical conductivity. Chromium and zirconium are used as trace alloying elements, aiming to maximize strength without significantly reducing conductivity. During heating, a small amount of chromium dissolves in copper, and upon cooling, it precipitates uniformly as fine chromium particles. These particles hinder dislocation movement, significantly increasing the alloy's strength. Simultaneously, due to the small amount of chromium dissolved, it has little obstacle to electronic conduction in the copper matrix, preventing a significant decrease in conductivity. If the chromium content is below 0.3 wt%, insufficient precipitated particles result in limited strength improvement; if it is above 1.2 wt%, coarse chromium phases will appear, which not only easily leads to material embrittlement but also significantly reduces conductivity.

[0012] The addition of zirconium can form a dispersed phase with chromium, refine the grains, and create a dual strengthening effect with chromium ions, thereby increasing strength. Zirconium can also reduce the impact of impurities on conductivity. The hard particles in the copper-chromium-zirconium alloy improve the wear resistance and corrosion resistance of large-size copper-chromium-zirconium alloy contact wires.

[0013] By using large-section copper-chromium-zirconium alloy contact wires, a single 150mm² cross-section catenary cable and a 170-300mm² cross-section contact wire can replace the double-bearing, double-conductor contact network structure. This reduces the amount of copper alloy used in the contact network, thereby reducing its weight and ultimately replacing the double-bearing, double-conductor structure, thus reducing energy consumption and system wear.

[0014] Optionally, a wear marking groove is provided along the length of the contact line, the depth of the wear marking groove is 0.3 to 0.5 mm, and the wear marking groove is either wavy or sawtooth.

[0015] By adopting the above technical solution, wear is one of the main failure modes of contact wires. However, the amount of wear cannot be directly judged by the naked eye. In the initial state, the marking groove is a clear recessed structure with a depth of 0.3 to 0.5 mm. Maintenance personnel can quickly judge the remaining depth of the groove by visual inspection or simple tools. When the overall diameter of the contact wire decreases due to long-term friction, the marking groove will gradually become shallower or even disappear. At this time, the wear of the contact wire can be directly inferred from the state of the groove, reducing manpower and equipment costs. In addition, although the wear marking groove on the side of the contact wire does not directly participate in conduction, it can indirectly reflect the operating status of the pantograph through its wear pattern. This allows for reverse investigation of potential faults in the contact network or pantograph, further ensuring system compatibility and safety.

[0016] Compared to traditional straight marking grooves, wavy, sawtooth, or intermittent marking grooves can more accurately reflect the wear and distribution of the contact wire, making it easier for maintenance personnel to make intuitive judgments.

[0017] Optionally, the wear marking groove is provided with a marking coating, which is made of one or a combination of epoxy resin coating or ceramic-based insulating coating.

[0018] By adopting the above technical solution, Joule heating will be generated due to resistance when current flows through the contact wire. If the current increases when the train starts, the temperature will rise sharply. The sliding friction between the pantograph and the contact wire will generate local high temperature. If the coating material is not heat-resistant enough, it will soften, carbonize or even burn. Not only will it lose its marking function, but it may also produce carbide particles, which will aggravate the wear of the pantograph and the contact wire. At the same time, the coating material needs to have strong wear resistance, friction resistance, hardness, insulation and corrosion resistance, and be suitable for contact wire drawing processing and long-term friction scenarios.

[0019] Secondly, the present invention provides a manufacturing process for a large-size copper-chromium-zirconium alloy contact wire, which adopts the following technical solution:

[0020] A manufacturing process for large-size copper-chromium-zirconium alloy contact wires includes the following steps:

[0021] Continuous casting: Copper-chromium-zirconium billet rods are prepared by continuous casting, and inert gas protection is used during casting;

[0022] Continuous extrusion: The copper-chromium-zirconium billet bar is extruded into a φ20~30mm copper-chromium-zirconium extrusion bar, and the temperature at the extrusion outlet is maintained at 650~750℃;

[0023] Multi-stage cooling: At the extrusion outlet, a nitrogen gas curtain layer and water mist cooling nozzles are used to force the extrusion rod to cool down. The maximum time interval between extrusion and cooling is ≤1 second, the overall cooling rate is not less than 80℃ / s, and the temperature is reduced to 250~300℃. Then, a cooling water tank is used to cool down the extrusion rod to below 80℃.

[0024] Aging treatment: Heat the copper-chromium-zirconium extrusion rod to 400-500℃, maintain for 3.5-5.5 hours, and then cool to below 180℃;

[0025] Drawing and forming: The conductor is drawn into a cross-section of 170-300 mm² through a four-stage linkage drawing process.

[0026] By adopting the above technical solution, the upward continuous casting can be carried out in a non-vacuum environment under an inert atmosphere of oxygen protective gas, such as argon. This prevents chromium and zirconium, two easily oxidized elements, from coming into contact with oxygen, thus ensuring the uniformity of the chemical composition of the cast copper-chromium-zirconium alloy wire rods and improving the purity of the product. This plays an important role in improving the conductivity and mechanical properties of large-size copper-chromium-zirconium alloy contact wires.

[0027] The copper-chromium-zirconium alloy is heated through continuous extrusion, with the extrusion outlet temperature maintained at 650–750°C. This allows the copper-chromium-zirconium alloy to remain in a solution state during continuous extrusion, dissolving the second phase within the alloy. This eliminates the need for specialized solution heating and heat preservation treatment, saving energy and reducing processing time, thus improving efficiency. After continuous extrusion, the extrusion bar is rapidly cooled within one second at a rate of ≥80°C / s. This reduces the time the extrusion bar is exposed to air, lowering the probability of surface oxidation. Simultaneously, it inhibits the precipitation of the second phase, preventing the aggregation and growth of chromium and zirconium during cooling, thereby ensuring the alloy's performance and maximizing the retention of the copper matrix's high conductivity. Rapid cooling also significantly reduces atomic diffusion rates, resulting in a nucleation rate exceeding the grain growth rate, leading to grain refinement and effectively improving the alloy's strength and hardness.

[0028] Nitrogen gas curtain cooling is used during cooling. As an inert gas, nitrogen can prevent oxidation and ensure the quality of large-size copper-chromium-zirconium alloy contact wires. In addition, nitrogen has good thermal conductivity and can transfer heat more evenly. When cooling large-section contact wires, it reduces the temperature gradient of different parts of the contact wire, achieves uniform cooling, promotes the precipitation of fine and uniform strengthening phases in the alloy, hinders dislocation movement, and improves the tensile strength and hardness of the alloy without reducing its electrical conductivity.

[0029] Water mist cooling improves cooling efficiency by atomizing water into tiny particles, which more effectively absorbs heat from the contact wire surface. Furthermore, the uniform spraying of water mist onto the contact wire surface ensures consistent cooling rates across all parts of the contact wire, reducing the probability of uneven cooling in certain areas. Finally, water mist cooling is relatively gentle, ensuring that the surface of the contact wire has a uniform rate of contraction and expansion, effectively reducing product deformation and improving product quality.

[0030] The rapid cooling methods, including nitrogen air curtain cooling, water mist cooling, and cooling water tank, reduce the temperature gradient in different parts after continuous extrusion of large cross-section contact lines, ensuring the uniformity of the material. Through continuous extrusion, chromium and zirconium elements can be uniformly dispersed, allowing the material to reach a state of fine crystals and supersaturated solid solution. At the same time, direct, rapid, and timely cooling in the supersaturated solid solution state saves the heating and heat preservation process, improves production efficiency, and saves energy.

[0031] Aging treatment at 400–500℃ can trigger the precipitation phase transformation of supersaturated solid solutions. Within this temperature range, chromium and zirconium atoms will uniformly precipitate from the copper matrix in the form of nanoscale metallic compounds, hindering dislocation movement in the copper matrix, causing plastic deformation, dispersion strengthening of the copper material, and improving its mechanical and electrical properties. After cooling to below 180℃, the atomic diffusion rate decreases sharply, and the size and distribution of the precipitated phases are locked. The hardness and corresponding strength, plasticity, and conductivity can remain stable for a long time, providing performance assurance for subsequent drawing and long-term service. Finally, the contact wire is drawn into finished product by a four-linkage drawing machine, so that the large cross-section copper-chromium-zirconium alloy contact wire achieves a hardness ≥125HV, tensile strength ≥460MPa, and conductivity ≥75%IACS.

[0032] Optionally, in the continuous extrusion process, a nitrogen gas curtain layer is first used to force-cool the extrusion rod, and then a water mist cooling nozzle is used to force-cool the extrusion rod.

[0033] By adopting the above technical solution, a nitrogen gas curtain is first used to cool the copper-chromium-zirconium alloy extrusion rod. The gas curtain can isolate water mist from the extrusion equipment, reducing the probability of water mist adhering in the extrusion equipment. In this way, the copper-chromium-zirconium billet rod is less likely to come into contact with condensed water during the extrusion process, resulting in localized cooling. This makes the temperature of the copper-chromium-zirconium billet rod more uniform during extrusion, reduces the generation of the second phase, and makes the copper-chromium-zirconium billet rod less prone to localized cooling deformation. After cooling with a nitrogen gas curtain, the surface temperature of the copper-chromium-zirconium billet rod is reduced, thereby reducing the surface oxidation and other activities of the copper-chromium-zirconium billet rod. When a water mist cooling nozzle is used to force-cool the extrusion rod, the surface of the copper-chromium-zirconium billet rod is less likely to be oxidized, improving the final quality of large-size copper-chromium-zirconium alloy contact wires.

[0034] Optionally, in the continuous extrusion process, the nitrogen in the nitrogen gas curtain layer is nitrogen at -40 to -60°C.

[0035] By adopting the above technical solution, based on the inertial isolation of nitrogen, the high density and strong cooling capacity of low-temperature nitrogen are utilized. Low-temperature nitrogen will significantly increase the density of nitrogen. At -100℃, the density of nitrogen is more than twice that of nitrogen at room temperature. High-density nitrogen is more likely to form a thick and stable gas curtain in the cooling area, which is not easily disturbed by external airflow, and the isolation effect is stronger. In addition, when low-temperature nitrogen comes into contact with the copper-chromium-zirconium extrusion rod at the high-temperature continuous extrusion outlet, it will absorb a large amount of heat through heat conduction and convection, causing the temperature of the copper-chromium-zirconium extrusion rod to drop rapidly.

[0036] Optionally, in the continuous extrusion process, the water mist in the high-pressure water mist cooling nozzle is water mist generated using cooling water at 5-8°C.

[0037] By adopting the above technical solution and using cooling water at 5-8℃, the temperature difference driving force between the cooling medium and the contact wire surface can be significantly improved, ensuring that the contact wire is rapidly cooled to room temperature. In this application, the cooling rate is at least 80℃ / s, which efficiently freezes the supersaturated solid solution, shortens the grain growth time, reduces grain boundary segregation and brittle phases, and ensures grain boundary cleanliness. The fine recrystallization nuclei formed at high temperature have not yet grown sufficiently before being rapidly cooled and fixed, ultimately obtaining a fine grain structure and improving the material strength.

[0038] Optionally, in the continuous extrusion process, the method for extruding the copper-chromium-zirconium billet rod into a φ20~30mm copper-chromium-zirconium extrusion rod is equal diameter extrusion.

[0039] By adopting the above technical solution and using the continuous extrusion method with equal diameter, the copper-chromium-zirconium alloy billet rod is in a state of strong triaxial compressive stress during the continuous extrusion process, which improves the plasticity of the metal; while reducing the extrusion resistance, recrystallization occurs, refining the alloy grains, crushing the cast dendrites into fine equiaxed crystals, and uniformly dispersing the chromium and zirconium strengthening phases, thereby improving the alloy strength.

[0040] Constant diameter extrusion accumulates strain through multiple shear deformations, refining the grains and reducing internal defects such as cracks and porosity that occur during the processing of large-section copper-chromium-zirconium alloy contact wires, thereby improving the mechanical and electrical properties of the product. In addition, during constant diameter extrusion, a large amount of deformation heat is generated inside the material due to plastic deformation. This deformation heat will raise the temperature of the extruded material, which is beneficial for subsequent direct cooling treatment.

[0041] Optionally, in the drawing forming process, the angles of the drawing die for the four-stage linkage drawing are: α angle: 4~6°, β angle: 20~25°.

[0042] By adopting the above technical solution, the α and β opening angles of the four forming dies are adjusted. If the α die angle is too small, it will increase the contact area between the extrusion rod and the die wall, increase the frictional resistance, and lead to an increase in drawing force. If the α die angle is too large, it will generate large deformation stress during the drawing process, which can easily cause damage and cracks to the material itself. The β angle helps to optimize the flow state of the material and reduce uneven deformation during the drawing process. If the β angle is not set properly, it may cause turbulent metal flow, resulting in defects such as drawing fracture and surface roughness, which will ultimately affect the dimensional accuracy and surface quality of the drawn product.

[0043] Optionally, in the drawing forming process, wear marking grooves are drawn on the side of the contact line.

[0044] In summary, the present invention has at least one of the following beneficial technical effects:

[0045] 1. By establishing multi-stage forced cooling, the copper-chromium-zirconium extrusion rod undergoes triple cooling after leaving the extruder outlet, achieving rapid cooling and ensuring the solid solution effect of the copper-chromium-zirconium alloy. After subsequent high-temperature aging treatment, the copper material is dispersion strengthened, improving its mechanical and electrical properties. Then, the contact wire is drawn into finished product by a four-linkage drawing machine, thereby achieving the goal of large-section copper-chromium-zirconium alloy contact wire with a hardness ≥125HV, tensile strength ≥460MPa, and conductivity ≥75%IACS. Ultimately, it replaces the double-bearing double-conductor structure, meeting the weight reduction requirements of the contact network system.

[0046] 2. Through continuous extrusion, chromium and zirconium elements can be uniformly dispersed, allowing the material to reach a state of fine crystals and supersaturated solid solution. At the same time, the supersaturated solid solution state allows for direct, rapid, and timely cooling, saving the heating and heat preservation process, improving production efficiency, and saving energy.

[0047] 3. By continuously extruding with equal diameter, the plasticity of the metal is improved, the alloy grains are refined, the dendrites are crushed into fine equiaxed grains, and the strength of the alloy is improved. During the extrusion process with equal diameter, a large amount of deformation heat will be generated inside the material due to plastic deformation. This deformation heat will raise the temperature of the extruded material, which is conducive to subsequent direct cooling treatment.

[0048] 4. By drawing and forming a visual wear marking groove with a depth of 0.3 to 0.5 mm on the side of the contact wire, the wear degree and distribution of the contact wire can be reflected more accurately, making it easier for maintenance personnel to make intuitive judgments, reducing labor and equipment costs, and further ensuring the safe operation of the contact network. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the cross-section of a large-size copper-chromium-zirconium alloy contact wire;

[0050] Figure 2 It is an air curtain cooling profile structure of a forced cooling device;

[0051] Figure 3 It is a water mist cooling profile structure of a forced cooling device;

[0052] Figure 4 It is a cross-sectional structure with dual-medium cooling of air curtain and water mist.

[0053] Reference numerals in the attached diagram: 1. Large-size copper-chromium-zirconium alloy contact wire; 2. Copper-chromium-zirconium extrusion rod; 3. Marking coating; 4. Wear marking groove; 5. Cooling zone; 6. Water mist nozzle; 601. Water mist nozzle; 602. Water mist pipeline; 7. Nitrogen curtain nozzle; 701. Air curtain nozzle; 702. Air curtain pipeline. Detailed Implementation

[0054] Due to limitations in material processing technology, the largest cross-sectional size of copper and copper alloy contact wires in China is currently 150mm². In railway contact networks with heavy loads and high traffic density, a double-bearing and double-conductor mode is often used, consisting of two 120mm² cross-section catenary cables and two 150mm² cross-section contact wires, to meet the high current carrying capacity requirements of the contact network power supply.

[0055] The dual-feeder cable + dual-contact wire design has revealed many shortcomings in practical applications.

[0056] From the perspective of system weight, the increased weight of the overhead contact system places higher demands on the strength and stability of the supporting structure, indirectly increasing the difficulty and cost of construction. In some lines with limited load-bearing capacity for infrastructure such as bridges and tunnels, an excessively heavy overhead contact system may even become a key factor restricting the construction and upgrading of the line.

[0057] From the perspective of current collection performance, during operation, the contact state between the two contact wires and the pantograph slide is difficult to be completely consistent. In addition, under the influence of external factors such as temperature changes and wind, the tension changes and sag adjustments of the two catenary wires are difficult to keep completely synchronized, which leads to differences in contact wire height and further deteriorates the current collection conditions.

[0058] From a construction and maintenance perspective, the double-bearing, double-conductor configuration significantly increases the complexity and difficulty of construction. During construction, it requires precise adjustment of parameters such as tension, height, and parallelism of the two load-bearing cables and two contact wires, placing extremely high demands on the technical skills of construction personnel and the precision of construction equipment, thus extending the construction period. In the subsequent operation and maintenance phase, the number of components requiring inspection and maintenance in the double-bearing, double-conductor structure doubles, resulting in a substantial increase in maintenance workload.

[0059] To effectively address the aforementioned shortcomings of the dual-bearer, dual-conductor design, it is necessary to adopt a single-bearer, single-conductor design. The single conductor in this design requires a contact wire with a cross-sectional area of ​​at least 150 mm². Existing processes include casting, cold working, and annealing. These processes ensure the fineness and uniformity of the contact wire grains, producing small-section copper-chromium-zirconium alloy contact wires with a cross-section of less than 150 mm². However, during the production of large-section contact wires using existing processes, it was found that the water-cooling method results in a long heat conduction path and slow core cooling, leading to the premature precipitation of small amounts of chromium and zirconium elements, which affects the final strength and conductivity of the contact wire.

[0060] Therefore, if you want to further improve the mechanical properties of large-section copper-chromium-zirconium alloy contact wires, water cooling alone cannot meet the mechanical properties of large-size copper-chromium-zirconium alloy contact wires. This is because water cooling will cause a large amount of water film to form on the surface of the copper-chromium-zirconium alloy rod, reducing cooling efficiency and copper solubility. In particular, it will cause slow cooling of the core, making the copper liquid solidification cavity longer, resulting in defects such as surface cracks and internal hollow cores, and causing the copper rod to break.

[0061] The present invention will be further described in detail below with reference to the embodiments.

[0062] Unless otherwise specified, the experimental methods used in the embodiments of this application are conventional methods, and the materials used are commercially available unless otherwise specified.

[0063] Example 1: This example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0064] A large-size copper-chromium-zirconium alloy contact wire, the composition of which by mass percentage includes: 0.75wt% chromium, 0.08wt% zirconium, ≤0.1wt% impurity elements, and the balance being copper; the cross-sectional dimension of the large-size copper-chromium-zirconium alloy contact wire 1 is 240mm².

[0065] Reference Figure 1 The wear marking groove 4 is provided along its length, and the depth of the wear marking groove 4 is 0.3-0.5 mm. In this embodiment, the depth of the wear marking groove 4 is 0.4 mm. The wear marking groove 4 can be either wavy or sawtooth-shaped; in this embodiment, a wavy shape is used. A marking coating 3 is provided inside the wear marking groove 4. The marking coating 3 is made of one or a combination of epoxy resin coating or ceramic-based insulating coating; in this embodiment, an epoxy resin coating is used.

[0066] A manufacturing process for large-size copper-chromium-zirconium alloy contact wires includes the following steps:

[0067] Continuous casting: φ30mm copper-chromium-zirconium billet rods are prepared by upward continuous casting, and inert gas protection is used during casting; the inert gas can be one or a combination of argon and helium, and argon is selected in this embodiment.

[0068] Continuous extrusion: The φ30mm copper-chromium-zirconium billet rod is extruded into a φ25mm copper-chromium-zirconium extrusion rod 2 through a continuous extrusion press, and the temperature at the extrusion outlet is maintained at 700℃.

[0069] Multi-stage cooling: See Figures 2 to 4 The copper-chromium-zirconium extrusion rod 2 is moved into the cooling zone 5, which is U-shaped with its opening facing upwards. A nitrogen gas curtain nozzle 7 and a water mist nozzle 6 are sequentially arranged at the opening of the cooling zone 5. The nitrogen gas curtain nozzle 7 includes a gas curtain head 701 and a gas curtain pipe 702. One end of the gas curtain pipe 702 is connected to a nitrogen gas source, and the other end is connected to the gas curtain head 701, which faces the copper-chromium-zirconium extrusion rod 2. The water mist nozzle 6 includes a water mist head 601 and a water mist pipe 602. One end of the water mist pipe 602 is connected to a water source, and the other end is connected to the water mist head 601, which also faces the copper-chromium-zirconium extrusion rod 2.

[0070] The copper-chromium-zirconium extrusion rod 2 moves gradually in the cooling zone 5. Nitrogen gas curtain nozzle 7 and water mist nozzle 6 spray nitrogen gas and water mist respectively, allowing the copper-chromium-zirconium extrusion rod 2 to be cooled first by the nitrogen gas curtain and then by the water mist. The room temperature nitrogen gas curtain layer and room temperature water mist cooling nozzles forcefully cool the extrusion rod. The interval between extrusion and cooling activation is 0.8s, with a comprehensive cooling rate ≥80℃ / s, reducing the extrusion rod temperature to 300℃. Then, a cooling water tank is used to further cool the extrusion rod to below 80℃ before it leaves the water tank.

[0071] Aging treatment: Heat the copper-chromium-zirconium extrusion rod 2 to 450℃, maintain for 4.5h, and then cool it with the furnace to below 180℃ before unloading.

[0072] Drawing process: The wire is drawn into a 240mm² cross-section through a four-stage linkage drawing process. The drawing die angles are: α angle: 3°, β angle: 26°.

[0073] The testing mainly examines the hardness, tensile strength, and conductivity of large-size copper-chromium-zirconium alloy contact wires.

[0074] Hardness: Hardness is an indicator of the wear resistance of the contact wire. When the hardness is high, the surface wear rate of the contact wire is reduced during long-term friction with the pantograph, which can effectively extend its service life. It is especially suitable for rail transit lines with high passenger volume and dense train traffic.

[0075] Tensile strength: Tensile strength is an indicator of the contact wire's resistance to tensile fracture. High tensile strength means that the contact wire can withstand greater tension during installation, ensuring the continuity and safety of the rail transit power supply system; insufficient tensile strength makes the contact wire prone to plastic deformation or even breakage under tension, directly leading to power outages and affecting the normal operation of the line.

[0076] Conductivity: Conductivity is an indicator of the power transmission efficiency and energy consumption of a contact wire. High conductivity results in less power loss during current transmission, ensuring a stable power supply to the receiving equipment. Low conductivity leads to increased power transmission loss, severe overheating of the line, shortened contact wire lifespan, and even safety hazards.

[0077] Example 2: This example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0078] Except for the use of a -50°C nitrogen gas curtain and a room-temperature water mist cooling nozzle to force cooling of the extrusion rod in the multi-stage cooling process, everything else is exactly the same as in Example 1.

[0079] Example 3: This example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0080] Except for the use of a -50°C nitrogen gas curtain and a 6°C water mist cooling nozzle to force cooling of the extrusion rod in the multi-stage cooling process, everything else is exactly the same as in Example 2.

[0081] Example 4: This example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0082] A manufacturing process for a large-size copper-chromium-zirconium alloy contact wire 1 includes the following steps:

[0083] Continuous casting: φ25mm copper-chromium-zirconium billet rods are prepared by upward continuous casting, and inert gas protection is used during casting.

[0084] Continuous extrusion: The φ25mm copper-chromium-zirconium billet rod is extruded into a φ25mm copper-chromium-zirconium extrusion rod 2 through a continuous extrusion press with the same diameter, and the temperature at the extrusion outlet is maintained at 700℃.

[0085] Everything else is exactly the same as in Example 3.

[0086] Example 5: This example discloses a large-size copper-chromium-zirconium alloy contact wire 1 and its manufacturing process.

[0087] Drawing process: The wire is drawn into a 240mm² cross-section through a four-stage linkage drawing process. The drawing die angles are: α angle: 5°, β angle: 22°.

[0088] Everything else is exactly the same as in Example 4.

[0089] Comparative Example 1: This comparative example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0090] Multi-stage cooling: Only a room temperature nitrogen gas curtain layer is used at the extrusion outlet to force the extrusion rod to cool down. The nitrogen gas curtain has a flow rate of 20 m / s and the time interval between extrusion and cooling is 0.8 s. The temperature of the extrusion rod is reduced to 300℃. Then, a cooling water tank is used to cool down the extrusion rod to below 80℃ before it leaves the water tank.

[0091] Everything else is the same as in Example 1.

[0092] Comparative Example 2: This comparative example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0093] Multi-stage cooling: At the extrusion outlet, only room temperature water mist cooling nozzles are used to force-cool the extrusion rod. The water mist flow rate is 120L / min, the water pressure is 0.6MPa, and the time interval between extrusion and cooling start is 0.8s. The temperature of the extrusion rod is reduced to 300℃. Then, a cooling water tank is used to further cool the extrusion rod to below 80℃ before it leaves the water tank.

[0094] Everything else is the same as in Example 1.

[0095] Comparative Example 3: This comparative example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0096] Multi-stage cooling: Cooling water tanks are used directly at the extrusion outlet to reduce the temperature of the extrusion rod to below 80°C before it leaves the water tank.

[0097] Everything else is the same as in Example 1.

[0098] Comparative Example 4: This comparative example discloses a large-size copper-chromium-zirconium alloy contact wire and its manufacturing process.

[0099] A manufacturing process for large-size copper-chromium-zirconium alloy contact wires includes the following steps:

[0100] Casting: Copper-chromium-zirconium alloy wire rods were prepared by the upward continuous casting method. The wire rod diameter was 30 mm. The weight of the wire rod was pulled up to 2.3 t. The mass fractions of each component of the wire rod are as described in Example 1.

[0101] Continuous extrusion: The annealed wire blank is subjected to continuous extrusion processing with an extrusion ratio of 0.4 and an extrusion speed of 5 m / min.

[0102] Solution treatment: The extruded wire blank is directly placed into an intermediate frequency furnace for online solution treatment. The solution temperature is controlled at 950℃ for 8 minutes. After solution treatment, the wire blank is cooled in a water tank.

[0103] Cold working: The solution-treated wire blank is cold-drawn to 18mm in 6 passes, with a total deformation of 64%.

[0104] Aging treatment: The cold-worked wire blank is aged at a temperature of 460℃ for 3 hours and then cooled in the furnace.

[0105] Finished product forming: The aged wire blank is cold-drawn into a 150mm² contact wire.

[0106] Stress-relief annealing: The finished product is subjected to stress-relief annealing treatment at a temperature of 300℃ for 2 hours.

[0107] The detection method is the same as in Example 1.

[0108] The large-size copper-chromium-zirconium alloy contact wires 1 prepared in Examples 1-5 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1:

[0109] Table 1:

[0110] Testing items Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Hardness (HV) 128 134 139 142 145 120 102 85 95 Tensile strength (MPa) 476 511 535 546 560 420 401 387 396 Electrical conductivity (IACS) 85% 91% 92% 90% 92% 87% 85% 63% 72%

[0111] By comparing Example 1 and Example 2, it can be seen that the nitrogen gas curtain layer at -50℃ used in Example 2 can better preserve the stability of the supersaturated solid solution. At low temperature, chromium and zirconium atoms are retained in excess in the copper matrix, which is reflected in the improved hardness, tensile strength and conductivity of the copper-chromium-zirconium alloy contact wire compared with Example 1.

[0112] By comparing Example 3 with Example 2, it can be seen that the 6°C water mist used in Example 3 removes heat faster than the room temperature water mist, allowing the extrusion rod to drop below the critical diffusion temperature of chromium and zirconium atoms in a shorter time, inhibiting the aggregation and precipitation of solute atoms, forming a more stable supersaturated solid solution, and resulting in a more significant work hardening effect, thus improving hardness and tensile strength.

[0113] By comparing Example 4 with Example 3, it can be seen that by using the equal diameter extrusion method, since there is no cross-sectional reduction, local overheating caused by excessive deformation is avoided, ensuring that the overall composition of the extrusion rod is uniform. At 700℃, the copper crystal lattice expands fully and chromium and zirconium atoms dissolve, providing a high-temperature matrix with uniform composition for subsequent multi-stage cooling. Therefore, the hardness and tensile strength are improved. However, the equal diameter extrusion may be unfavorable to electron movement, resulting in a slight decrease in conductivity.

[0114] By comparing Example 5 with Example 4, it can be seen that the α entrance angle of 5° reduces the resistance of metal flowing into the mold and avoids the desolvation of the supersaturated solid solution due to friction overheating; the β working zone angle of 2° ensures that the metal produces uniform plastic deformation during the drawing process, the dislocation density is moderately increased, and the hardness and tensile strength are further improved. The conductivity is mainly dominated by alloy composition, crystal defects, etc., and the conductivity is slightly higher than that of Example 4.

[0115] By comparing Comparative Example 1 and Example 1, it can be seen that the cooling rate is low when only nitrogen gas curtain is used for cooling at room temperature. The extrusion rod stays in the range above 300°C for too long, and chromium and zirconium atoms have enough time to diffuse and precipitate fine strengthening phases, which leads to the desolvation of supersaturated solid solution, alleviates lattice distortion, and reduces hardness and tensile strength compared to Example 1. Although the conductivity is slightly improved compared to Example 1 due to the precipitation of solute atoms.

[0116] By comparing Comparative Example 2 and Example 1, it can be seen that with only room temperature water mist cooling and no nitrogen gas curtain pretreatment, the water mist directly contacts the 700°C high-temperature extrusion rod, which easily forms a vapor layer on the high-temperature surface, hindering heat transfer and resulting in uneven cooling. The temperature difference between the surface and core of the extrusion rod can reach 50-80°C. The surface is fully supersaturated with solid solution, resulting in high hardness. The core, due to slow cooling, experiences local desolvation, resulting in low hardness. This leads to a brittle surface layer and a soft core on the contact line, reduced bending performance, and easy breakage during installation.

[0117] By comparing Comparative Example 3 and Example 1, it can be seen that directly immersing the 700℃ high-temperature extrusion rod in a water tank for cooling can easily lead to microcracks on the surface of the rod, which cause a sharp drop in tensile strength. At the same time, although the cooling rate of the water tank is fast, there is no nitrogen gas curtain to isolate the air, and the high-temperature rod is easily oxidized to form an oxide layer. The oxide layer increases the friction coefficient between the contact wire and the pantograph, and the wear rate increases, so the product cannot meet the requirements.

[0118] By comparing Comparative Example 4 and Example 1, it can be seen that because cooling is achieved directly using a cooling water bath, a large amount of continuous water film forms on the surface of the copper-chromium-zirconium alloy billet, hindering the outward transfer of heat from the core. The core cooling rate drops to 50-80°C / s, causing chromium and zirconium elements to precipitate prematurely in the core, forming coarse precipitates with sizes reaching 1-5 μm, far larger than the nanoscale precipitates after aging with small cross-sections. This results in higher conductivity, hardness, and tensile strength on the surface and lower values ​​in the core, leading to an overall decrease in average values. However, due to the 980°C high-temperature solution treatment time, the average hardness, average tensile strength, and average conductivity are slightly better than in Example 3. The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A large-size copper-chromium-zirconium alloy contact wire, characterized in that, The composition by mass percentage includes: 0.3-1.2 wt% chromium, 0.03-0.12 wt% zirconium, ≤0.1 wt% impurity elements, and the balance is copper; the cross-sectional dimensions of the large-size copper-chromium-zirconium alloy contact wire (1) are 170-300 mm².

2. The large-size copper-chromium-zirconium alloy contact wire according to claim 1, characterized in that, The contact line is provided with a wear marking groove (4) along its own length direction. The depth of the wear marking groove (4) is 0.3 to 0.5 mm. The wear marking groove (4) is either wavy or sawtooth.

3. A large-size copper-chromium-zirconium alloy contact wire according to claim 1 or 2, characterized in that, The wear marking groove (4) is provided with a marking coating (3), which is made of one or a combination of epoxy resin coating or ceramic-based insulating coating.

4. A manufacturing process for a large-size copper-chromium-zirconium alloy contact wire as described in any one of claims 1-3, characterized in that, The process includes the following steps: A manufacturing process for a large-size copper-chromium-zirconium alloy contact wire (1) includes the following steps: Continuous casting: Copper-chromium-zirconium billet rods are prepared by continuous casting, and inert gas protection is used during casting; Continuous extrusion: The copper-chromium-zirconium billet rod is extruded into a φ20~30mm copper-chromium-zirconium extrusion rod (2), and the temperature at the extrusion outlet is maintained at 650~750℃; Multi-stage cooling: At the extrusion outlet, a nitrogen gas curtain layer and water mist cooling nozzles are used to force the extrusion rod to cool down. The maximum time interval between extrusion and cooling is ≤1 second, the overall cooling rate is not less than 80℃ / s, and the temperature is reduced to 250~300℃. Then, a cooling water tank is used to cool down the extrusion rod to below 80℃. Aging treatment: Heat the copper-chromium-zirconium extrusion rod (2) to 400-500℃, maintain for 3.5-5.5h, and cool to below 180℃; Drawing and forming: The conductor is drawn into a cross-section of 170-300 mm² through a four-stage linkage drawing process.

5. The manufacturing process for a large-size copper-chromium-zirconium alloy contact wire according to claim 4, characterized in that, In the continuous extrusion process, a nitrogen gas curtain layer is first used to force the extrusion rod to cool down, and then a water mist cooling nozzle is used to force the extrusion rod to cool down.

6. The manufacturing process for a large-size copper-chromium-zirconium alloy contact wire according to claim 5, characterized in that, In the continuous extrusion process, the nitrogen in the nitrogen curtain layer is nitrogen at -40 to -60°C.

7. A manufacturing process for a large-size copper-chromium-zirconium alloy contact wire according to claim 6, characterized in that, In the continuous extrusion process, the water mist in the high-pressure water mist cooling nozzle is generated using cooling water at 5-8°C.

8. The manufacturing process for a large-size copper-chromium-zirconium alloy contact wire according to any one of claims 4-7, characterized in that, In the continuous extrusion process, the method for extruding the copper-chromium-zirconium billet rod into a φ20~30mm copper-chromium-zirconium extrusion rod (2) is equal diameter extrusion.

9. A manufacturing process for a large-size copper-chromium-zirconium alloy contact wire according to any one of claims 4-7, characterized in that, In the drawing forming process, the angles of the drawing die for the four-stage linkage drawing are: α angle: 4~6°, β angle: 20~25°.

10. The application of a large-size copper-chromium-zirconium alloy contact wire as described in any one of claims 1-3, or a contact wire prepared by any one of the manufacturing processes in claims 4-8, characterized in that, Contact wires are used in high-speed rail, urban rail transit, and other industrial fields.

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