Preparation method of high-speed rail catenary silicon bronze U-shaped wire clamp

Abstract

The application relates to the technical field of copper alloy wire rods, and discloses a preparation method of a high-iron catenary silicon bronze U-shaped wire rod, which comprises the following steps: heating and melting ingredients, and forcibly degassing the ingredients by using a composite refining covering agent to obtain a refined melt; adding copper phosphorus, copper cerium and copper boron intermediate alloys into the refined melt to obtain a micro-alloyed melt; adopting high-pressure water spraying to cool the alloy wire blank obtained after continuous casting and drawing out of a crystallizer; continuously cold drawing the alloy wire blank without intermediate annealing and controlling the die mouth surface temperature to obtain a drawn finished wire rod; and performing two-stage step heat treatment to obtain a high-strength high-conductivity silicon bronze wire rod and cold bending and stamping the high-strength high-conductivity silicon bronze wire rod into a U shape. The application is matched with the multi-element micro-alloying, continuous casting and rapid cooling, continuous cold drawing deformation and two-stage step aging heat treatment process, so that the strengthening phase is dispersedly precipitated and the matrix is purified, the crystal boundary binding force is improved, the tensile strength and the electrical conductivity are considered, and the room-temperature cold stamping forming performance is improved.

Description

Technical Field

[0001] This invention relates to the field of copper alloy wire technology, specifically a method for preparing silicon bronze U-shaped clip wire for high-speed railway contact networks. Background Technology

[0002] Components such as U-shaped clips in high-speed railway overhead contact systems are subjected to significant mechanical tension and current loads during actual use. Therefore, the materials used must possess high tensile strength, conductivity, and good room-temperature cold-forming properties. Silicon bronze is used in this field due to its precipitation-hardening properties. However, in existing technologies, conventional silicon bronze wires exhibit insufficient bonding strength at grain boundaries. When subjected to significant cold-forming processes such as room-temperature bending and stamping to create U-shaped structures, stress concentration can easily lead to intergranular cracking. Consequently, the room-temperature cold-bending and stamping performance of the material fails to meet actual processing requirements.

[0003] Existing continuous casting processes have limitations in controlling the cooling process of the billet. The cooling rate of the wire rod after leaving the crystallizer is usually insufficient to prevent premature precipitation of alloying elements. The premature precipitation of strengthening elements such as nickel and silicon during the cooling stage consumes the solute concentration inside the matrix, making it difficult for the material to maintain a supersaturated solid solution state. This reduces the driving force for subsequent heat treatment. Furthermore, existing processing methods lack the coordination of continuous cold deformation with large deformation, failing to introduce high-density dislocation defects into the wire rod, resulting in a lack of sufficient heterogeneous nucleation sites for the strengthening phase during subsequent precipitation.

[0004] Conventional aging heat treatment processes often employ a single-temperature holding period, making it difficult to control the nucleation and growth behavior of the strengthening phase in stages. Single-stage heat treatment is prone to causing discontinuous precipitation reactions and makes it difficult to fully desolvate and remove solute atoms dissolved in the copper matrix. Residual solute atoms in the matrix increase the electron scattering cross-section of the material, making effective matrix purification impossible. As a result, while the tensile strength of the wire is improved, its conductivity often decreases significantly. It is difficult to achieve both simultaneously, thus limiting the improvement of the overall performance of the finished product. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing silicon bronze U-shaped contact wire for high-speed railway contact networks. This method solves the problems of poor room temperature cold forming performance caused by intergranular cracking when silicon bronze wire is cold-deformed into a U-shaped structure, and the difficulty in balancing the tensile strength and conductivity of the wire in existing preparation processes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing silicon bronze U-shaped clips for high-speed railway contact wires, using the following technical solution: A method for preparing silicon bronze U-shaped clip wire for high-speed railway contact network includes the following steps: The ingredients are heated and melted, covered with a composite refining covering agent, and degassed by introducing inert gas to obtain a refined melt. Add copper-phosphorus master alloy, copper-cerium master alloy and copper-boron master alloy to the refined melt to obtain a micro-alloyed melt; The micro-alloyed melt is continuously cast and drawn out of the crystallizer, and then forced to cool down by high-pressure water spray to obtain alloy wire rod. The alloy wire blank is subjected to continuous cold drawing without intermediate annealing. A special cooling and lubricating liquid is used for spray cooling and the surface temperature of the wire is controlled at the instant it leaves the drawing die to obtain the drawn finished wire. The drawn finished wire is subjected to a two-stage stepped heat treatment and cooled to room temperature to obtain a high-strength, high-conductivity silicon bronze wire. The high-strength, high-conductivity silicon bronze wire is cold-bent and stamped into a U-shape to obtain the finished silicon bronze U-shaped card for high-speed railway contact network. Based on the mass percentage of the finished high-speed railway contact wire silicon bronze U-shaped clips, the composition includes: Ni 2.8wt%-3.2wt%, Si 0.7wt%-1.0wt%, P 0.01wt%-0.03wt%, Ce 0.02wt%-0.05wt%, B 0.005wt%-0.015wt%, balance Cu and unavoidable impurities, and the sum of the mass percentages of all components is 100%.

[0007] By adopting the above technical solution, and by combining a multi-element micro-alloying system with continuous casting rapid cooling, cold deformation, and stepped aging processes, the following effects are achieved: In terms of alloy composition design, Ni and Si elements in a specific ratio can precipitate nano-sized Ni2Si intermetallic compounds during subsequent heat treatment, resulting in precipitation strengthening. Trace amounts of P elements help reduce the surface tension of the copper melt and play a deoxidizing role. Ce and B elements form a composite microalloying, where Ce promotes the purification of grain boundaries and refines the cast grains, while B elements segregate at the grain boundaries, helping to improve the grain boundary bonding force, thereby suppressing intergranular cracking under large deformation conditions and improving the cold heading and stamping performance of the drawn finished wire.

[0008] During the solidification control stage, the continuous casting drawing is combined with high-pressure water spray forced cooling, enabling the alloy wire rod to achieve a large cooling rate during the crystallization stage. This rapid cooling condition inhibits the precipitation of Ni and Si elements during the cooling process, causing the strengthening phase elements to remain in the copper matrix in the form of supersaturated solid solutions, providing thermodynamic driving force for subsequent deformation and aging processes.

[0009] During the deformation and phase transformation process, the continuous cold drawing without intermediate annealing introduces a high density of dislocations inside the alloy wire blank, providing heterogeneous nucleation sites for the precipitated phase. The subsequent two-stage stepped heat treatment utilizes deformation energy storage to promote the dispersed precipitation of the Ni2Si phase within the crystal. The dislocations are pinned by the precipitated phase, maintaining the work hardening effect, while solute atoms inside the matrix undergo desolvation, reducing the electron scattering cross section, thus achieving a balance between strength and conductivity in the crystal structure.

[0010] Preferably, in the operation of heating and melting the ingredients, the ingredients include electrolytic copper, pure nickel plate and crystalline silicon, the heating temperature is 1180℃-1200℃, and the composite refining covering agent has a covering thickness of 20mm-30mm; in the operation of introducing inert gas, the flow rate of high-purity argon gas is 1.5L / min-2.0L / min, and the duration is 10min-15min.

[0011] By adopting the above technical solution, the heating temperature range helps the pure nickel plate and crystalline silicon dissolve in the copper matrix, reducing the generation of unfused high-melting-point inclusions; the corresponding thickness of the composite refining covering agent, combined with the introduction of high-purity argon gas, allows the argon gas bubbles to capture hydrogen and non-metallic inclusions inside the melt during their ascent, thereby facilitating physical adsorption and slagging reactions in the covering agent layer and reducing the gas content of the refined melt.

[0012] Preferably, the composite refining covering agent is obtained through a preparation process comprising the following operations: drying anhydrous borax at 120°C for 2 hours to remove surface adsorbed moisture; crushing calcined charcoal and passing it through an 80-mesh sieve to collect the sieve material for later use; and mixing the dried anhydrous borax with the prepared charcoal powder at a mass ratio of 2:1.

[0013] By adopting the above technical solution, the dried anhydrous borax melts at high temperature to form a slag layer, reducing the contact between the copper melt and oxygen in the air, and dissolving the floating metal oxides; the calcined charcoal provides a local reducing atmosphere inside the slag layer to reduce the oxidation loss of alloying elements and maintain the stability of the chemical composition of the smelting system.

[0014] Preferably, in the operation of adding copper-phosphorus master alloy, copper-cerium master alloy and copper-boron master alloy to the refined melt, the copper-phosphorus master alloy is added 15 minutes before continuous casting, and the copper-cerium master alloy and the copper-boron master alloy are added simultaneously 5-8 minutes before being drawn out of the furnace.

[0015] By adopting the above technical solution, the phased addition of different alloys helps to improve the yield of microalloying elements. First, the copper-phosphorus master alloy is added to consume the residual free oxygen in the melt. Then, the copper-cerium master alloy and the copper-boron master alloy, which have relatively high chemical activity, are added shortly before tapping, thereby reducing the loss of Ce and B elements due to their reaction with oxygen.

[0016] Preferably, in the continuous casting and drawing operation of the microalloyed melt, a horizontal continuous casting machine is used, and the temperature of the microalloyed melt is maintained at 1130℃-1160℃; the operating parameters of the horizontal continuous casting machine traction machine are: drawing time 0.8s-1.2s, stopping time 0.4s-0.6s, back-pushing time 0.1s-0.2s, and average drawing speed 200mm / min-300mm / min.

[0017] By adopting the above technical solution, the alternating operation of stretching, stopping and pushing causes the solidified shell of the inner wall of the crystallizer to detach and heal in time, compensates for liquid phase shrinkage, reduces the hot tearing defects on the surface of the continuous casting billet, and thus obtains the alloy billet with a relatively smooth surface and dense interior.

[0018] Preferably, in the operation of forced cooling by high-pressure water spray after exiting the crystallizer, the water pressure of the high-pressure water spray is set to 0.4MPa-0.6MPa, the water temperature is 15℃-25℃, and the forced control surface cooling rate reaches 120℃ / s-150℃ / s.

[0019] By adopting the above technical solution, the combination of water pressure and water temperature parameters helps to break the vapor film attached to the surface of the alloy wire rod, improve the heat transfer state to achieve the required cooling rate, thereby inhibiting the precipitation of coarse equilibrium phases at the grain boundaries and playing the role of solid solution quenching.

[0020] Preferably, in the continuous cold drawing operation of the alloy wire blank without intermediate annealing, the total processing deformation of the continuous cold drawing is controlled at 80%-85%, and the single-pass section shrinkage rate of the first two drawing passes is 20%-25%; in the operation of controlling the instantaneous surface temperature of the wire leaving the drawing die, the instantaneous surface temperature of the wire leaving the drawing die is controlled at 120℃-195℃.

[0021] By adopting the above technical solution, a larger total processing deformation can accumulate deformation structure inside the drawn finished wire. The higher section shrinkage rate in the first two passes is beneficial to the columnar crystal structure of the broken cast state. At the same time, limiting the upper limit of the surface temperature during drawing can reduce the dynamic recovery and reorganization of dislocations caused by heat generated by plastic deformation, and retain a better work hardening effect.

[0022] Preferably, the preparation process of the special cooling lubricant includes the following steps: weighing 95 parts by weight of basic water-based synthetic cutting fluid and injecting it into a room temperature mixing vessel, adding 5 parts by weight of sulfurized fatty oil extreme pressure additive, and continuously stirring and dispersing at room temperature for 40 minutes at a speed of 200 r / min; during the application stage, controlling the inlet temperature of the special cooling lubricant to be 10℃-20℃ and the single module spray flow rate to be 60L / min-90L / min.

[0023] By adopting the above technical solution, the extreme pressure additive of the sulfurized fatty oil can form an anti-shear film layer on the surface of the extrusion zone of the drawing die, reducing the coefficient of friction between the die and the wire; with the set spray parameters, the heat generated in the deformation zone can be quickly dissipated, which helps to maintain the dimensional accuracy of the drawn finished wire.

[0024] Preferably, the two-stage stepped heat treatment operation of the drawn finished wire is divided into a first stage and a second stage. The heat treatment parameters for the first stage are: heating to 300℃-320℃ at a heating rate of 5℃ / min-10℃ / min and holding for 1h-1.5h; the heat treatment parameters for the second stage are: heating to 450℃-480℃ at a heating rate of 15℃ / min-20℃ / min and holding for 3h-4h.

[0025] By employing the above technical solution, the first stage provides a relatively low thermal activation energy, promoting the aggregation of vacancies and solute atoms to form coherent precipitate precursors or GP regions to increase nucleation sites; the second stage provides the diffusion kinetic energy required for precipitate growth, promoting the growth of the Ni2Si strengthening phase and hindering dislocation slip. This stepwise heating method helps to mitigate discontinuous precipitation reactions, thereby improving the conductivity and yield strength of the material.

[0026] Preferably, in the operation of cold bending and stamping the high-strength, high-conductivity silicon bronze wire into a U-shape, a CNC automatic blanking and bending integrated machine is used to cut the wire to length and then stamp it at room temperature.

[0027] By adopting the above technical solution, the high-strength and high-conductivity silicon bronze wire is subjected to local plastic bending at room temperature without introducing a high-temperature heat-affected zone, thus maintaining the predetermined mechanical and electrical performance indicators, and finally obtaining a finished product of silicon bronze U-shaped card for high-speed rail contact network with stable structure and meeting dimensional requirements.

[0028] This invention provides a method for preparing silicon bronze U-shaped clip wires for high-speed railway contact wires, which has the following beneficial effects: 1. This invention employs a specific ratio of Ni to Si and a micro-alloying system containing multiple elements such as P, Ce, and B. The ratio of Ni to Si elements can precipitate intermetallic compounds during the heat treatment stage to generate precipitation strengthening. At the same time, Ce elements are used to purify grain boundaries and B elements are used to concentrate at grain boundaries to enhance grain boundary bonding force, thereby suppressing intergranular cracking under processing deformation conditions and improving the room temperature cold bending stamping forming performance of the prepared wire.

[0029] 2. This invention combines high-pressure water spraying for forced cooling after continuous casting with continuous cold drawing without intermediate annealing. The forced cooling with high-pressure water suppresses the precipitation of Ni and Si elements during the cooling stage, allowing the strengthening phase elements to remain in the matrix as a supersaturated solid solution. Subsequently, the continuous cold drawing with large deformation introduces high-density dislocations, providing heterogeneous nucleation sites for the precipitated phases and storing deformation driving force.

[0030] 3. This invention implements a two-stage stepped heat treatment on the drawn wire. In the first stage, at a relatively low temperature, vacancies and solute atoms are aggregated to form a coherent precipitate precursor. In the second stage, at a relatively high temperature, the strengthening phase is promoted to grow and dislocation slip is hindered. The stepped heating suppresses discontinuous precipitation reactions and promotes the desolvation of solute atoms in the matrix to reduce the electron scattering cross section. This achieves dislocation pinning and matrix purification within the material, thus balancing the tensile strength and conductivity of the wire. Attached Figure Description

[0031] Figure 1 Differential scanning calorimetry (DSC) charts of cold-drawn wires in Examples 1 to 3; Figure 2 The X-ray diffraction patterns are those of the finished wires from Embodiment 2 and Comparative Example 1 of the present invention. Detailed Implementation

[0032] 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.

[0033] Preparation Examples 1-2: Preparation Example 1: This preparation example provides a method for preparing a composite refining covering agent, including the following steps: (1) Place anhydrous borax in an oven and dry it at 120°C for 2 hours to remove surface adsorbed moisture; (2) Crush the calcined charcoal and pass it through an 80-mesh sieve. Take the sieve residue for later use. (3) The dried anhydrous borax and the prepared charcoal powder were put into a three-dimensional mixer at a mass ratio of 2:1 and mixed for 30 minutes to obtain a composite refining covering agent, which was then sealed and stored for later use.

[0034] Preparation Example 2: This preparation example provides a method for preparing a special cooling lubricant for high-strain cold drawing, including the following steps: (1) Weigh 95 parts by weight of the basic water-based synthetic cutting fluid and inject it into a room temperature mixing tank; (2) Add 5 parts by weight of sulfurized fatty oil extreme pressure additive to the mixing vessel; (3) Turn on the stirring device and stir and disperse at room temperature for 40 minutes at a speed of 200 r / min to make the extreme pressure additive evenly dispersed in the water-based cutting fluid, and obtain a special cooling and lubricating fluid for use.

[0035] Examples 1-3: Example 1:

[0036] This embodiment provides a method for preparing silicon bronze U-shaped clip wire for high-speed railway contact wire, including the following steps: (1) The final product was prepared with the following mass percentages: Ni 2.8wt%, Si 1.0wt%, P 0.01wt%, Ce 0.02wt%, B 0.005wt%, and the balance being Cu and unavoidable impurities. Calculated amounts of electrolytic copper, pure nickel plates, and crystalline silicon were added to a medium-frequency induction melting furnace and heated to 1180℃ until completely melted. After melting, the composite refining covering agent obtained in Preparation Example 1 was uniformly added to the surface of the melt, with a covering thickness of 20mm. Subsequently, inert gas was introduced for forced degassing. Specifically, high-purity argon gas with a purity ≥99.99wt% was used for forced stirring and degassing at a flow rate of 1.5L / min for 10min. After refining, the scum was mechanically removed to obtain the refined melt. (2) 15 minutes before the refined melt obtained in step (1) is exported for continuous casting, a certain amount of copper-phosphorus master alloy is added to the molten pool and stirred for 5 minutes; 5 minutes before the melt is discharged from the furnace, a certain amount of copper-cerium master alloy and copper-boron master alloy are added to the molten pool and stirred for 2 minutes to obtain micro-alloyed melt. (3) The microalloyed melt obtained in step (2) is introduced into the holding furnace of the horizontal continuous casting machine to maintain the melt temperature at 1130℃. The microalloyed melt is horizontally drawn through a graphite crystallizer. The traction machine operating parameters are set as follows: stretching time 0.8s, stopping time 0.4s, back-pushing time 0.1s, and average drawing speed 200mm / min. When the wire billet passes through the crystallizer and enters the secondary cooling zone, the annular high-pressure water spray system is immediately started. The spray water pressure is set to 0.4MPa and the water temperature is 25℃, so that the surface cooling rate of the wire billet reaches 120℃ / s and is forced to drop to room temperature. The wire billet is then coiled online to obtain an alloy wire billet with a single coil weight ≥500kg. (4) The alloy wire blank obtained in step (3) is directly introduced into the continuous wire drawing unit and continuously cold-drawn without intermediate annealing. The total processing deformation is controlled at 80%. The single-pass section shrinkage rate of the first two drawing passes is 20%. The drawing die and deformation zone are sprayed with the special cooling lubricant obtained in Preparation Example 2. The lubricant inlet temperature is controlled at 20°C and the single die spray flow rate is 60L / min. This forces the surface temperature of the wire to be controlled at 195°C at the instant it leaves the drawing die, thus obtaining the drawn finished wire. (5) The drawn finished wire obtained in step (4) is placed into an aging furnace for stepped heat treatment: in the first stage, the wire is heated to 300°C at a heating rate of 5°C / min and held for 1 hour; in the second stage, the wire is rapidly heated to 450°C at a heating rate of 15°C / min and held for 3 hours. After the holding period, the wire is removed from the furnace and water-cooled to room temperature to obtain the final high-strength and high-conductivity silicon bronze wire.

[0037] (6) The high-strength and high-conductivity silicon bronze wire obtained in step (5) is introduced into the CNC automatic feeding and bending machine, cut to length, and then cold-bent and stamped into U-shape at room temperature to obtain the finished product of silicon bronze U-shaped card for high-speed rail contact network.

[0038] Example 2:

[0039] This embodiment provides a method for preparing silicon bronze U-shaped clip wire for high-speed railway contact wire, including the following steps: (1) The final product was prepared with the following mass percentages: Ni 3.0wt%, Si 0.7wt%, P 0.02wt%, Ce 0.035wt%, B 0.01wt%, and the balance being Cu and unavoidable impurities. Calculated amounts of electrolytic copper, pure nickel plates, and crystalline silicon were added to a medium-frequency induction melting furnace and heated to 1190℃ until completely melted. After melting, the composite refining covering agent obtained in Preparation Example 1 was uniformly added to the surface of the melt, with a covering thickness of 25mm. Subsequently, inert gas was introduced for forced degassing. Specifically, high-purity argon gas with a purity ≥99.99wt% was used for forced stirring and degassing at a flow rate of 1.8L / min for 12min. After refining, the scum was mechanically removed to obtain the refined melt. (2) 15 minutes before the refined melt obtained in step (1) is exported for continuous casting, a certain amount of copper-phosphorus master alloy is added to the molten pool and stirred for 5 minutes; 6 minutes before the melt is discharged from the furnace, a certain amount of copper-cerium master alloy and copper-boron master alloy are added to the molten pool and stirred for 2 minutes to obtain micro-alloyed melt. (3) The microalloyed melt obtained in step (2) is introduced into the holding furnace of the horizontal continuous casting machine to maintain the melt temperature at 1145℃. The microalloyed melt is horizontally drawn through a graphite crystallizer. The operating parameters of the traction machine are set as follows: stretching time 1.0s, stop time 0.5s, back push time 0.15s, and average drawing speed 250mm / min. When the wire billet passes through the crystallizer and enters the secondary cooling zone, the annular high-pressure water spray system is immediately started. The spray water pressure is set to 0.5MPa and the water temperature is 20℃, so that the surface cooling rate of the wire billet reaches 135℃ / s and is forced to drop to room temperature. The wire billet is then wound online to obtain an alloy wire billet with a single coil weight ≥500kg. (4) The alloy wire blank obtained in step (3) is directly introduced into the continuous wire drawing unit and continuously cold drawn without intermediate annealing. The total processing deformation is controlled at 82.5%. The single-pass section shrinkage rate of the first two drawing passes is 22.5%. The drawing die and deformation zone are sprayed with the special cooling lubricant obtained in Preparation Example 2. The lubricant inlet temperature is controlled at 15°C and the single die spray flow rate is 75L / min. This forces the surface temperature of the wire to be controlled at 150°C at the instant it leaves the drawing die, thus obtaining the drawn finished wire. (5) The drawn finished wire obtained in step (4) is placed into an aging furnace for stepped heat treatment: in the first stage, it is heated to 310°C at a heating rate of 8°C / min and held for 1.2h; in the second stage, it is rapidly heated to 465°C at a heating rate of 18°C / min and held for 3.5h. After the holding period, the wire is removed from the furnace and water-cooled to room temperature to obtain the final high-strength and high-conductivity silicon bronze wire.

[0040] (6) The high-strength and high-conductivity silicon bronze wire obtained in step (5) is introduced into the CNC automatic feeding and bending machine, cut to length, and then cold-bent and stamped into U-shape at room temperature to obtain the finished product of silicon bronze U-shaped card for high-speed rail contact network.

[0041] Example 3:

[0042] This embodiment provides a method for preparing silicon bronze U-shaped clip wire for high-speed railway contact wire, including the following steps: (1) The final product was prepared with the following mass percentages: Ni 3.2wt%, Si 0.8wt%, P 0.03wt%, Ce 0.05wt%, B 0.015wt%, and the balance being Cu and unavoidable impurities. Calculated amounts of electrolytic copper, pure nickel plates, and crystalline silicon were added to a medium-frequency induction melting furnace and heated to 1200℃ until completely melted. After melting, the composite refining covering agent obtained in Preparation Example 1 was uniformly added to the surface of the melt, with a covering thickness of 30mm. Subsequently, inert gas was introduced for forced degassing. Specifically, high-purity argon gas with a purity ≥99.99wt% was used for forced stirring and degassing at a flow rate of 2.0L / min for 15min. After refining, the scum was mechanically removed to obtain the refined melt. (2) 15 minutes before the refined melt obtained in step (1) is exported for continuous casting, a certain amount of copper-phosphorus master alloy is added to the molten pool and stirred for 5 minutes; 8 minutes before the melt is discharged from the furnace, a certain amount of copper-cerium master alloy and copper-boron master alloy are added to the molten pool and stirred for 2 minutes to obtain micro-alloyed melt. (3) The microalloyed melt obtained in step (2) is introduced into the holding furnace of the horizontal continuous casting machine to maintain the melt temperature at 1160℃. The microalloyed melt is horizontally drawn through a graphite crystallizer. The traction machine operating parameters are set as follows: stretching time 1.2s, stopping time 0.6s, back-pushing time 0.2s, and average drawing speed 300mm / min. When the wire billet passes through the crystallizer and enters the secondary cooling zone, the annular high-pressure water spray system is immediately started. The spray water pressure is set to 0.6MPa and the water temperature is 15℃, so that the surface cooling rate of the wire billet reaches 150℃ / s and is forced to drop to room temperature. The wire billet is then wound online to obtain an alloy wire billet with a single coil weight ≥500kg. (4) The alloy wire blank obtained in step (3) is directly introduced into the continuous wire drawing unit and continuously cold-drawn without intermediate annealing. The total processing deformation is controlled at 85%. The single-pass section shrinkage rate of the first two drawing passes is 25%. The drawing die and deformation zone are sprayed with the special cooling lubricant obtained in Preparation Example 2. The lubricant inlet temperature is controlled at 10°C and the single-die spray flow rate is 90L / min. This forces the surface temperature of the wire to be controlled at 120°C at the instant it leaves the drawing die, thus obtaining the drawn finished wire. (5) The drawn finished wire obtained in step (4) is placed into an aging furnace for stepped heat treatment: in the first stage, it is heated to 320°C at a heating rate of 10°C / min and held for 1.5 hours; in the second stage, it is rapidly heated to 480°C at a heating rate of 20°C / min and held for 4 hours. After the holding period, the wire is removed from the furnace and water-cooled to room temperature to obtain the final high-strength and high-conductivity silicon bronze wire.

[0043] (6) The high-strength and high-conductivity silicon bronze wire obtained in step (5) is introduced into the CNC automatic feeding and bending machine, cut to length, and then cold-bent and stamped into U-shape at room temperature to obtain the finished product of silicon bronze U-shaped card for high-speed rail contact network.

[0044] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that the ingredients in step (1) do not contain Ce and B, and the corresponding balance is made up by Cu. In step (2), copper-cerium master alloy and copper-boron master alloy are not added. All other aspects are the same.

[0045] Comparative Example 2: Compared with Example 2, the difference is that the composite refining covering agent obtained in Preparation Example 1 was not added in step (1), but only conventional charcoal was used for surface covering, and the rest were the same.

[0046] Comparative Example 3: Compared with Example 2, the difference is that in step (3), when the wire rod passes through the crystallizer and enters the secondary cooling zone, the annular high-pressure water spray system is not started. The wire rod is naturally cooled to room temperature in the air, and the surface cooling rate is about 15℃ / s. The rest are the same.

[0047] Comparative Example 4: Compared with Example 2, the difference is that: in step (4), conventional water-based cutting fluid is used for cooling, the lubricant inlet temperature and spray flow rate are not strictly controlled, and the surface temperature of the wire reaches 250°C at the moment it leaves the drawing die. The rest are the same.

[0048] Comparative Example 5: Compared with Example 2, the difference is that step (5) does not use stepped heat treatment, but uses conventional single-stage aging heat treatment, heating the wire directly to 465°C at a heating rate of 18°C / min and holding it for 4.7h. The rest are the same.

[0049] Test Examples 1-5: Test Example 1: This test case aims to verify the feasibility of the phase transition dynamics basis and mechanism of the stepped aging treatment in this method.

[0050] Experimental steps: The cold-drawn finished wires obtained in step (4) of Examples 1 to 3 were cut as test samples. The surface oxide layer was removed by sanding and ultrasonic cleaning with anhydrous ethanol. After drying, 16.2 mg, 17.8 mg and 15.4 mg of the samples were weighed and placed in an alumina crucible and pressed.

[0051] Differential scanning calorimetry was used for testing. The alumina crucible containing the sample was placed on the sample tray of the instrument, while a blank alumina crucible of the same mass was placed on the reference tray.

[0052] High-purity argon gas with a purity of 99.999% was introduced into the test chamber at a flow rate of 45 mL / min to continuously purge the test chamber and maintain an inert atmosphere.

[0053] The program starts at room temperature and heats the sample to 600°C at a heating rate of 10°C / min. During the heating process, the heat flow rate difference signal between the sample and the reference is recorded.

[0054] After the test program is completed, the obtained heat flow change curve is baseline corrected using data processing software, and the starting temperature, peak temperature and exothermic value of each stage of heat release peak are calculated through integral processing.

[0055] Table 1. Differential scanning calorimetry characteristic test data of samples from Examples 1 to 3

[0056] in conclusion: Based on the data in Table 1 and Figure 1 The cold-drawn wire samples from Examples 1 to 3 all exhibited two exothermic peaks during the heating process. The first exothermic peak had an onset temperature between 285.3℃ and 294.1℃, and a peak temperature between 301.6℃ and 318.9℃. This exothermic phase corresponds to the segregation of solute atoms in the supersaturated copper-based solid solution and the early nucleation of the precipitated phase. The second exothermic peak had an onset temperature between 432.1℃ and 456.2℃, and a peak temperature between 451.8℃ and 478.4℃, with an exothermic enthalpy higher than the first stage. This exothermic phase corresponds to the growth of the precipitated phase and an increase in its volume fraction.

[0057] The above thermal analysis data indicates that the precipitation phase transformation of this silicon bronze system includes two main stages. Holding at a temperature within the range corresponding to the first exothermic peak is beneficial for the full nucleation of the precipitate and increases the nucleation density; holding at a temperature within the range corresponding to the second exothermic peak promotes further growth of the precipitate. The two exothermic peak temperature ranges obtained by testing are consistent with the stepped aging parameters of approximately 300°C in the first stage and approximately 450°C in the second stage in step (5) of the embodiment of the present invention. If conventional single-stage high-temperature aging is used, the nucleation stage will be skipped and the growth stage will be directly entered, which will easily lead to a reduction in the number of precipitates and uneven size distribution, thereby reducing the overall mechanical properties of the alloy.

[0058] Test Example 2: This test example is used to verify the phase existence form and precipitate structure of trace alloying elements in finished wire.

[0059] Experimental steps: Cut the finished wires obtained in Example 2 and Comparative Example 1, cut them longitudinally, and then use cold-mounting resin to mount the wire cross-section.

[0060] The test surfaces of the mounted samples were ground step by step using silicon carbide wet sandpaper, followed by mechanical polishing with diamond polishing fluid to remove the surface strain layer, ultrasonic cleaning with anhydrous ethanol, and drying with cold air.

[0061] The processed sample is fixed on the sample stage of the X-ray diffractometer, and the height is adjusted so that the sample surface is flush with the instrument's test reference plane.

[0062] Turn on the X-ray diffractometer, set the target material to Cu, use Kα radiation, set the working tube voltage to 40kV, and the tube current to 40mA. Set the scanning range of the diffraction angle 2θ to 20° to 90°, the scanning step size to 0.02°, and the scanning speed to 1° / min, and continuously scan the sample to record diffraction data.

[0063] The collected diffraction pattern data were processed by background subtraction and smoothing using analysis software. The peak positions and relative intensities of each diffraction peak were extracted and compared with standard powder diffraction cards (PDF cards) to calibrate the phase structure.

[0064] Table 2. X-ray diffraction characteristic peak parameters of samples from Example 2 and Comparative Example 1

[0065] in conclusion: Based on the data in Table 2 and Figure 2 In the diffraction patterns of the samples from Example 2 and Comparative Example 1, diffraction peaks of the matrix α-Cu were observed near diffraction angles of 43°, 50°, and 74°, while diffraction peaks of the Ni₂Si precipitate phase were observed near diffraction angles of 33°, 46°, and 52°. Additional diffraction peaks were measured near diffraction angles of 21.4° and 30.5° in the sample from Example 2, which were identified as the CeB₆ phase using a standard card. No diffraction signal corresponding to CeB₆ was detected in the test spectrum of the sample from Comparative Example 1.

[0066] The detection of the CeB6 phase in Example 2 indicates that the copper-cerium master alloy added during the preparation steps reacted with the copper-boron master alloy in the alloy melt to form the CeB6 phase. This phase remained within the alloy matrix during subsequent cooling and heat treatment processes. The above phase analysis data demonstrates that the trace elements added in the composition design can exist in the matrix in the form of compounds, verifying the microalloying design that forms stable particles in the alloy system.

[0067] Test Example 3: This test case is used to test the conventional room temperature mechanical and electrical properties of alloy wires and to examine the influence of preparation process parameters on the macroscopic properties of the material.

[0068] Experimental steps: Test samples were taken from the aged finished wires obtained in step (5) of Examples 1 to 3 and Comparative Examples 1 to 5. A wire segment with a length of 400 mm was taken as a tensile test specimen, and a gauge length was marked in the middle of the specimen; a wire segment with a length of 1000 mm was taken as a conductivity test specimen.

[0069] Room temperature tensile tests were performed using a universal testing machine. The tensile specimens were clamped at both ends in the upper and lower jaws of the testing machine, and the tensile rate was set to 2 mm / min. The machine was started, and the specimens were stretched until fracture. The load and displacement data during the tensile process were recorded. The tensile strength and yield strength of the specimens were calculated, and the gauge length after splicing the fracture surfaces was measured to calculate the elongation at fracture. Each group of samples was tested in triplicate, and the arithmetic mean was taken.

[0070] The oxide film on the surface of the conductivity test sample was removed by polishing, and the resistance value of the sample was measured at 20°C using a double-arm bridge.

[0071] The diameter of the conductivity sample at different locations was measured using a micrometer, and the average cross-sectional area was calculated. The resistivity of the sample was calculated by combining the measured resistance value with the sample length, and then converted to conductivity according to the annealed copper standard. Each group of samples was tested in triplicate, and the arithmetic mean was taken.

[0072] Table 3. Room temperature mechanical and electrical property test data of samples from Examples 1 to 3 and Comparative Examples 1 to 5

[0073] in conclusion: According to the data in Table 3, the tensile strength of the finished wires from Examples 1 to 3 ranged from 718.4 MPa to 784.3 MPa, the yield strength from 651.2 MPa to 721.8 MPa, the elongation after fracture from 9.1% to 11.6%, and the electrical conductivity from 46.5% IACS to 51.4% IACS. Comparing the data from Example 2 and Comparative Example 1, the strength and elongation of Example 2 were both higher than those of Comparative Example 1. Combined with the aforementioned phase analysis results, the compound particles generated by the addition of trace amounts of Ce and B elements can refine the grains, increase the number of grain boundaries, and thus improve the deformation resistance and plasticity of the material.

[0074] Comparing the data of Example 2 and Comparative Example 3, Comparative Example 3, which did not undergo high-pressure water spray quenching treatment, showed lower tensile strength, yield strength, and electrical conductivity compared to Example 2. At lower cooling rates, solute atoms in the supersaturated solid solution precipitate prematurely, forming coarse phases. The precipitation strengthening effect of these coarse phases is weak, and they consume solute within the matrix, leading to a reduction in the number of strengthening phases precipitated during subsequent aging treatment, thus causing a decrease in the strength and electrical conductivity of the alloy wire.

[0075] Comparing the data of Example 2 and Comparative Example 5, Comparative Example 5, which uses a single-stage aging treatment, has a conductivity similar to that of Example 2, but a lower yield strength. The single-stage rapid heating process lacks a low-temperature nucleation stage, resulting in a low nucleation rate of precipitates and a low density and large size of precipitates within the microstructure. In contrast, the stepped aging process of the Example 5 nucleates precipitates at a low temperature and controls their growth at a high temperature. The resulting precipitates are small in size and densely distributed, hindering dislocation movement and thus improving the yield strength of the wire.

[0076] Test Example 4: This test case is used to test the cold bending deformation capability of alloy wire under specific deformation conditions, and to examine the influence of the drawing temperature control parameters in the preparation process on the plastic forming capability and surface quality of the finished wire.

[0077] Experimental steps: Test samples were taken from the aged finished wires obtained in step (5) of Examples 1 to 3 and Comparative Example 4. A 250 mm long wire segment was cut as a test specimen for repeated bending, and 5 specimens were prepared in parallel for each group.

[0078] The test was conducted using a wire bending tester. A cylindrical stop with a radius of curvature of 5.0 mm was selected and installed on the tester based on the nominal diameter of the wire.

[0079] Insert one end of the specimen vertically into the clamping jaws of the testing machine and lock it in place. Suspend a weight at the free end of the specimen to apply axial tension, so that the specimen remains straight during the test.

[0080] Start the testing machine. The lever drives the sample to bend 90 degrees to the left at a frequency of 1 time / second and then return to the initial vertical position. Then bend 90 degrees to the right and return to the initial vertical position. This is recorded as completing one bending cycle.

[0081] Record the number of bends during the test machine operation until the specimen completely breaks. Record the test data for each group of 5 specimens and calculate the arithmetic mean.

[0082] Table 4. Test data on the number of repeated bending cycles of samples from Examples 1 to 3 and Comparative Example 4

[0083] in conclusion: According to the data in Table 4, the average number of bends for samples from Examples 1 to 3 ranged from 26.0 to 38.8, while the average number of bends for sample 4 was 7.8. The bend resistance of the Example samples was higher than that of Comparative Example 4.

[0084] The relatively low test data for Comparative Example 4 is related to the operating conditions during the drawing process. Comparative Example 4 did not use a dedicated cooling lubricant during the drawing process, nor did it control the lubricant inlet temperature, resulting in a higher instantaneous temperature at the drawing die. At higher temperatures, the wire surface is prone to dynamic recovery, leading to localized oxidation and microcracks, which affect the integrity of the wire surface structure.

[0085] In repeated cold bending tests, these surface defects easily cause stress concentration, which propagates into the material under bending stress, leading to sample fracture. The example employed temperature-controlled lubrication measures during the drawing process to control the surface temperature rise of the wire at the die exit, reducing surface microcracks caused by heat accumulation and preserving the uniform distribution of the work-hardened layer. This improved the wire's bending resistance and provided deformation allowance for the manufacture of products requiring deep drawing and cold bending, such as U-shaped clips.

[0086] Test Example 5: This test case is used to test the axial tensile and compressive fatigue life of alloy wire under alternating loads, and to investigate the influence of smelting and impurity removal processes and surface deformation control on the fatigue resistance of the material.

[0087] Experimental steps: Materials were cut from the aged finished wires obtained in step (5) of Example 2, Comparative Example 2 and Comparative Example 4, respectively, and processed into axial fatigue test specimens. The gauge length portion was then polished.

[0088] The test was conducted using a high-frequency electromagnetic fatigue testing machine. The two ends of the specimen were clamped in the upper and lower grips of the testing machine, and the specimen axis was adjusted to coincide with the loading axis.

[0089] The stress ratio was set to -1, and a symmetrical tensile-compressive alternating fatigue test was performed with the loading frequency set to 90Hz.

[0090] Four stress amplitudes were set at 350 MPa, 300 MPa, 250 MPa, and 200 MPa for testing. The testing machine was started and the number of cyclic loading cycles was recorded until the specimen completely fractured. If the number of cycles reached 1.0 × 10⁻⁶, the test was considered complete. 7 If the test still does not break, stop the test and record it as not broken.

[0091] For each stress amplitude, three specimens were tested in parallel for each group of samples. The number of failure cycles for each specimen was recorded, and the logarithmic mean life was calculated.

[0092] Table 5. Fatigue life test data of Example 2 and comparative sample under different stress amplitudes.

[0093] in conclusion: According to the data in Table 5, under stress amplitudes ranging from 350 MPa to 200 MPa, the logarithmic mean lifetime of the sample in Example 2 was higher than that of Comparative Example 2 and Comparative Example 4. At a stress amplitude of 200 MPa, the sample in Example 2 was cycled to 1.0 × 10⁻⁶ cycles. 7 No fracture occurred at this time, and the logarithmic mean lifetimes of the samples in Comparative Example 2 and Comparative Example 4 were 10. 5 With 10 6 Magnitude.

[0094] The test data for Comparative Example 2 were lower than those for Example 2. In Comparative Example 2, no composite refining covering agent was added during the smelting process, resulting in insufficient impurity removal from the melt and the presence of non-metallic inclusions within the alloy matrix. Under alternating stress, stress concentration occurred at the interface between the inclusions and the matrix, forming fatigue crack initiation sites. The initiation and propagation of internal cracks reduced the fatigue life of the material.

[0095] The fatigue life of Comparative Example 4 was also lower than that of Example 2. In Comparative Example 4, the die exit temperature was not controlled during the drawing process, resulting in microcracks on the wire surface. Fatigue testing is affected by the surface quality of the sample; these surface microcracks act as initial crack initiation sources under alternating loads, propagating into the matrix and accelerating fatigue failure. The Example 2, through melt refining and temperature-controlled drawing processes, reduced inclusions within the matrix and micro-defects on the surface, lowering the probability of crack initiation and improving the tensile and compressive fatigue resistance of the wire.

Claims

1. A method for preparing silicon bronze U-shaped clip wire for high-speed railway contact wire, characterized in that, Includes the following steps: The ingredients are heated and melted, covered with a composite refining covering agent, and degassed by introducing inert gas to obtain a refined melt. Add copper-phosphorus master alloy, copper-cerium master alloy and copper-boron master alloy to the refined melt to obtain a micro-alloyed melt; The micro-alloyed melt is continuously cast and drawn out of the crystallizer, and then forced to cool down by high-pressure water spray to obtain alloy wire rod. The alloy wire blank is subjected to continuous cold drawing without intermediate annealing. A special cooling and lubricating liquid is used for spray cooling and the surface temperature of the wire is controlled at the instant it leaves the drawing die to obtain the drawn finished wire. The drawn finished wire is subjected to a two-stage stepped heat treatment and cooled to room temperature to obtain a high-strength, high-conductivity silicon bronze wire. The high-strength, high-conductivity silicon bronze wire is cold-bent and stamped into a U-shape to obtain the finished silicon bronze U-shaped card for high-speed railway contact network. Based on the mass percentage of the finished high-speed railway contact wire silicon bronze U-shaped clips, the composition includes: Ni 2.8wt%-3.2wt%, Si 0.7wt%-1.0wt%, P 0.01wt%-0.03wt%, Ce 0.02wt%-0.05wt%, B 0.005wt%-0.015wt%, balance Cu and unavoidable impurities, and the sum of the mass percentages of all components is 100%. The composite refining covering agent is obtained through a preparation process comprising the following operations: Anhydrous borax was dried at 120℃ for 2 hours to remove surface adsorbed moisture. The calcined charcoal was crushed and passed through an 80-mesh sieve to collect the sieve material for later use. The dried anhydrous borax was mixed with the prepared charcoal powder at a mass ratio of 2:

1. In the operation of adding copper-phosphorus master alloy, copper-cerium master alloy and copper-boron master alloy to the refined melt, the copper-phosphorus master alloy is added 15 minutes before the continuous casting is carried out, and the copper-cerium master alloy and the copper-boron master alloy are added simultaneously 5-8 minutes before the melt is emptied from the furnace. In the operation of forced cooling by high-pressure water spray after exiting the crystallizer, the water pressure of the high-pressure water spray is set to 0.4MPa-0.6MPa, the water temperature is 15℃-25℃, and the surface cooling rate is forcibly controlled to reach 120℃ / s-150℃ / s. In the continuous cold drawing operation of the alloy wire blank without intermediate annealing, the total processing deformation of the continuous cold drawing is controlled at 80%-85%, and the single-pass section shrinkage rate of the first two drawing passes is 20%-25%; In the operation of controlling the instantaneous surface temperature of the wire as it leaves the drawing die, the instantaneous surface temperature of the wire as it leaves the drawing die is controlled between 120℃ and 195℃. The preparation process of the special coolant and lubricant includes the following steps: Weigh 95 parts by weight of basic water-based synthetic cutting fluid and inject it into a room temperature mixing tank. Add 5 parts by weight of sulfurized fatty oil extreme pressure additive and stir and disperse continuously at room temperature for 40 minutes at 200 r / min to obtain the product. During the application phase, the inlet temperature of the special cooling and lubricating fluid is controlled at 10℃-20℃, and the spray flow rate of a single module is 60L / min-90L / min. The two-stage stepped heat treatment process for the drawn finished wire is divided into a first stage and a second stage. The heat treatment parameters for the first stage are as follows: Heat to 300℃-320℃ at a heating rate of 5℃ / min-10℃ / min, and hold for 1h-1.5h; The parameters for the second stage of heat treatment are: Heat to 450℃-480℃ at a heating rate of 15℃ / min-20℃ / min, and hold for 3-4 hours.

2. The preparation method according to claim 1, characterized in that, In the operation of heating and melting the ingredients, the ingredients include electrolytic copper, pure nickel plate and crystalline silicon, the heating temperature is 1180℃-1200℃, and the composite refining covering agent has a covering thickness of 20mm-30mm. In the process of introducing inert gas, the flow rate of high-purity argon gas is 1.5L / min-2.0L / min, and the duration is 10min-15min.

3. The preparation method according to claim 1, characterized in that, In the continuous casting and drawing operation of the microalloyed melt, a horizontal continuous casting machine is used, and the temperature of the microalloyed melt is maintained at 1130℃-1160℃. The operating parameters of the horizontal continuous casting machine traction machine are as follows: The stretching time is 0.8s-1.2s, the stopping time is 0.4s-0.6s, the reverse pushing time is 0.1s-0.2s, and the average drawing speed is 200mm / min-300mm / min.

4. The preparation method according to claim 1, characterized in that, In the process of cold bending and stamping the high-strength, high-conductivity silicon bronze wire into a U-shape, a CNC automatic blanking and bending integrated machine is used to cut it to length and then stamp it at room temperature.

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