A high-strength copper-magnesium alloy contact wire and its manufacturing process

Abstract

This invention provides a high-strength copper-magnesium alloy contact wire and its preparation process, belonging to the field of contact wire technology. The process includes the following steps: Lanthanum nitrate, deionized water, and citric acid are stirred and slowly dripped into a magnesium powder suspension, while ammonia is added to adjust the pH. The mixture is stirred, centrifuged, washed, vacuum dried, placed in a tube furnace, purged with argon gas, heated, held at that temperature, and cooled to obtain Mg-La2O3 core-shell particles. Magnesium carbonate powder is mixed with diatomaceous earth, pressed into blocks, and baked to obtain a covering agent. A cathode copper plate is baked and melted at high temperature. Mg-La2O3 core-shell particles and boron-doped graphene-silicon material are added and stirred. The covering agent is gently placed on the surface of the melt, cooled, and drawn to obtain a copper-magnesium alloy cast rod. This rod is cut, preheated, extruded, and drawn to obtain a high-strength copper-magnesium alloy contact wire. This invention can achieve high conductivity while improving the tensile strength of the contact wire.

Description

Technical Field

[0001] This invention relates to the field of contact wire technology, specifically to a high-strength copper-magnesium alloy contact wire and its manufacturing process. Background Technology

[0002] Currently, the materials commonly used for contact wires in electrified railways include pure copper, copper-silver alloys, copper-tin alloys, and copper-magnesium alloys. Among these, the use of copper-tin alloys, copper-magnesium alloys, and multi-element copper alloys such as copper-chromium-zirconium is gradually increasing, primarily to improve the tensile strength of the contact wire and meet the increased suspension tension requirements of high-speed railways operating at speeds of 200 km / h and above. In railway electrification systems, the contact wire is responsible for transmitting electricity to electric locomotives and rolling stock, ensuring the normal operation of the railway. In this process, the tensile strength, conductivity, and softening resistance of the contact wire have become key indicators for evaluating its performance.

[0003] With the introduction of alloying elements such as copper-tin alloys and copper-magnesium alloys, the tensile strength of the contact wire has been significantly improved, but this has also led to a substantial decrease in conductivity. Taking copper-magnesium alloys as an example, their conductivity is only 62%~77% IACS (International Copper Association standard), far lower than the 97% IACS of pure copper. This decrease in conductivity means an increase in the impedance of the contact wire power supply line, resulting in increased power loss, especially under high current loads, where the power loss is significant and conductivity drops drastically.

[0004] In railway industry standards, copper-silver alloy contact wires have the same tensile strength as pure copper contact wires, but higher conductivity. The addition of silver to the copper-silver alloy primarily improves the material's resistance to softening, while ensuring that its tensile strength and conductivity are not lower than those of pure copper contact wires. The advantage of copper-silver alloys lies in their significantly improved resistance to softening, which is crucial for the long-term use of contact wires in high-temperature environments. Despite the improved softening resistance, the production cost of this alloy is significantly increased. Silver, as a precious metal, is expensive, making the application cost of copper-silver alloys much higher than that of pure copper, which is one of the reasons why its practical application is limited.

[0005] Therefore, there is a need to provide a high-strength copper-magnesium alloy contact wire and its manufacturing process to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides a high-strength copper-magnesium alloy contact wire and its preparation process, which can improve the tensile strength of the contact wire while meeting the requirements of high conductivity.

[0007] To achieve the above objectives, the present invention provides a process for preparing a high-strength copper-magnesium alloy contact wire, comprising the following steps:

[0008] S1. Lanthanum nitrate, deionized water, and citric acid are stirred to form a sol. The sol is then slowly dripped into a magnesium powder suspension while ammonia is added to adjust the pH to 9-10. The mixture is continuously stirred, centrifuged, washed, and vacuum dried. The mixture is then placed in a tube furnace, argon gas is introduced, the temperature is raised, held at the temperature, and cooled to obtain Mg-La2O3 core-shell particles.

[0009] S2. After mixing magnesium carbonate powder with diatomaceous earth evenly, press it into blocks and bake it to obtain a covering agent;

[0010] S3. The cathode copper plate is baked and melted at high temperature. Mg-La2O3 core-shell particles and boron-doped graphene-silicon material are added and stirred. A covering agent is lightly placed on the surface of the melt. After cooling, the copper-magnesium alloy rod is drawn and uniformly cut, preheated, extruded, and drawn to obtain a high-strength copper-magnesium alloy contact wire.

[0011] This invention prepares Mg-La2O3 core-shell particles via a sol-gel method, achieving gradient release of Mg in molten copper. During the smelting process, magnesium in the Mg-La2O3 core-shell particles does not immediately distribute uniformly throughout the alloy. Instead, its diffusion rate is controlled by the La2O3 shell, preferentially accumulating at copper grain boundaries. This effectively reduces the mechanical property degradation caused by lattice distortion. The aggregation of magnesium at grain boundaries forms a stronger interface, thereby enhancing the alloy's high-temperature stability and fatigue resistance. Furthermore, after the Mg-La2O3 core-shell particles are added during high-temperature melting, some magnesium reacts with La2O3 at high temperatures to form the LaMgO3 spinel phase, further enhancing grain boundary stability and preventing excessive grain growth. The LaMgO3 spinel phase can withstand higher temperatures and stress during tensile processes, further improving the tensile strength and long-term stability of the copper-magnesium alloy. In addition, the presence of La2O3 can refine grains, reduce inter-grain barriers, and decrease scattering effects during electron transport, further enhancing the alloy's conductivity.

[0012] This invention prepares a covering agent that optimizes the quality and efficiency of copper-magnesium alloy smelting through the synergistic effect of magnesium carbonate and diatomaceous earth. The addition of the covering agent isolates the melt from oxygen in the air, and the decomposition of magnesium carbonate at high temperatures to generate carbon dioxide gas further hinders oxygen contact with the melt, thereby further inhibiting the formation of an oxide film on the melt surface. This prevents the oxide film from obstructing current flow and reducing the alloy's conductivity. The diatomaceous earth ensures the stability and durability of the covering agent, avoiding the negative impacts of cracking or failure of the covering layer during smelting. Furthermore, it also avoids the problem of excessive oxides within the copper-magnesium alloy causing lattice defects and increased brittleness, which would lead to a decrease in the alloy's tensile strength.

[0013] This invention incorporates boron-doped graphene-silicon material into the melt to improve the conductivity of the contact wire. Boron replaces carbon atoms in the graphene lattice, introducing hole-type charge carriers and further enhancing electron mobility, resulting in higher overall conductivity. Simultaneously, B-Cu bonding reduces interfacial tension, enhancing the wettability of graphene to copper and preventing conductivity loss due to interfacial porosity. Silicon nanoparticles act as a carrier for graphene, binding to it via B-Si bonds and simultaneously forming a nanoscale Cu3Si phase with the copper matrix, creating a three-dimensional conductive network. This promotes uniform graphene dispersion while preventing conductivity loss due to metal lattice deformation.

[0014] Optionally, the magnesium powder suspension is obtained by dispersing pretreated magnesium powder in anhydrous ethanol and stirring at high speed for 30 minutes.

[0015] Optionally, the pretreated magnesium powder is obtained by soaking magnesium powder in dilute hydrochloric acid with a mass concentration of 5% for 10 minutes, washing with deionized water until neutral, then washing three times with anhydrous ethanol, and vacuum drying at 60°C for 12 hours.

[0016] This invention utilizes dilute hydrochloric acid to soak magnesium powder, dissolving magnesium oxide on the surface and adsorbing impurities, thereby improving the purity of the magnesium powder.

[0017] Optionally, in step S1, the stirring time is 6-10 hours, the washing agent is ethanol, the washing number is 3-5 times, the vacuum drying temperature is 60-80℃, the time is 5-7 hours, the heating rate is 10℃ / min, the temperature is raised to 400-600℃, and the holding time is 2 hours.

[0018] Optionally, in step S1, after cooling, the material is loaded into a fluidized bed CVD reactor, hydrogen is introduced, the temperature is raised to 800°C, held for 30 minutes, the temperature is adjusted to 950°C, methane is introduced, growth is carried out for 30 minutes, the methane is turned off, and the material is cooled to 200°C in a hydrogen atmosphere before switching to argon gas and cooling to room temperature to finally obtain Mg-La2O3 core-shell particles.

[0019] This invention utilizes methane as a carbon source. Through vapor-phase deposition, the carbon source in methane decomposes and is deposited in gaseous form on the surface of Mg-La2O3 core-shell particles to uniformly generate graphene, forming a dense layered structure that acts as a physical barrier to prevent oxygen penetration. The outer graphene layer ruptures at temperatures above 600°C, releasing magnesium and delaying magnesium release to further reduce magnesium burn-off rate. Furthermore, the ruptured graphene can be dispersed in the melt, further improving conductivity.

[0020] Optionally, in step S2, the baking temperature is 100℃~150℃ and the baking time is 3~5h.

[0021] Optionally, the boron-doped graphene-silicon material is obtained by mixing boric acid, graphene oxide and silicon, ball milling for 30-60 minutes, and sintering at 900°C for 3-5 hours in an argon and hydrogen atmosphere.

[0022] Optionally, in step S3, the cathode copper plate is baked for 10-20 minutes, placed in a crucible melting furnace, kept under a nitrogen atmosphere, and melted at 1200-1400℃. Mg-La2O3 core-shell particles and boron-doped graphene-silicon material are added and stirred for 2-4 hours. A covering agent is gently placed on the surface of the melt, and then cooled through a crystallizer. The melt is then drawn at a speed of 200-500 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 20-30 mm.

[0023] Optionally, after the copper-magnesium alloy cast rod is obtained by traction, it is uniformly cut into 5-10 pieces, preheated at 650-750℃, and then fed into a continuous extrusion press. The rod is then extruded at 500-600℃ and 1000-1500MPa to obtain a copper-magnesium alloy extrusion rod with a diameter of 25-30mm. After multiple drawing passes, a cross-section of 150mm is obtained. 2 High-strength copper-magnesium alloy contact wire.

[0024] The present invention preheats the copper-magnesium alloy cast rod, which can effectively reduce the internal stress of the copper-magnesium alloy cast rod, so that it has better ductility in the subsequent extrusion process and avoids cracks or excessive stress concentration.

[0025] Optionally, the high-strength copper-magnesium alloy contact wire comprises the following raw materials in parts by weight: 42-70 parts of cathode copper plate, 1.7-3.2 parts of Mg-La2O3 core-shell particles, 0.5-0.8 parts of boron-doped graphene-silicon material, and 1.9-2.3 parts of covering agent.

[0026] By employing the aforementioned mass ratio, this invention can improve the overall performance of copper-magnesium alloys in multiple aspects, optimizing their electrical conductivity, tensile strength, and thermal stability.

[0027] The above-described technical solution of the present invention has at least the following beneficial effects:

[0028] 1. This invention prepares Mg-La2O3 core-shell particles via a sol-gel method, achieving gradient release of magnesium in molten copper, controlling the diffusion rate of magnesium, and preferentially aggregating it at copper grain boundaries, thereby enhancing the alloy's high-temperature stability and fatigue resistance. Some magnesium reacts with La2O3 to form the LaMgO3 spinel phase, stabilizing grain boundaries, preventing excessive grain growth, and improving tensile strength and long-term stability. Furthermore, La2O3 refines the grains, reduces scattering effects, and improves the alloy's electrical conductivity.

[0029] 2. The covering agent of this invention improves the smelting quality and efficiency of copper-magnesium alloys through the synergistic effect of magnesium carbonate and diatomaceous earth. Magnesium carbonate decomposes at high temperatures to generate carbon dioxide gas, making it more difficult for oxygen to contact the melt, thus avoiding excessive surface and internal oxides that could negatively impact the alloy's conductivity and tensile strength. Diatomaceous earth ensures the stability and durability of the covering agent, preventing cracking or failure during the smelting process.

[0030] 3. This invention improves the conductivity of contact lines by adding boron-doped graphene-silicon material to the melt. Boron replaces carbon atoms in graphene, introducing hole-type charge carriers, enhancing electron mobility, and improving overall conductivity. B-Cu bonding reduces interfacial tension and enhances the wettability of graphene with copper. Silicon nanoparticles, acting as graphene carriers, bind to graphene through B-Si bonds to form a nanoscale Cu3Si phase, constructing a three-dimensional conductive network. This ensures uniform graphene dispersion and avoids conductivity degradation caused by metal lattice deformation. Attached Figure Description

[0031] Figure 1 This is a cross-sectional metallographic image of the product of Embodiment 1 of the present invention;

[0032] Figure 2 This is a cross-sectional metallographic image of the product in Embodiment 3 of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0034] Preparation: Soak 5 kg of magnesium powder in 5% dilute hydrochloric acid for 10 min, wash with deionized water until neutral, then wash three times with anhydrous ethanol, and vacuum dry at 60℃ for 12 h to obtain pretreated magnesium powder; disperse 4 kg of pretreated magnesium powder in 40 L of anhydrous ethanol and stir at high speed for 30 min to obtain magnesium powder suspension.

[0035] Example 1

[0036] 1 kg of lanthanum nitrate was dissolved in 23 L of deionized water and stirred until homogeneous. 0.8 kg of citric acid was added and stirred until completely dissolved to form a transparent sol. The sol was then slowly dripped into 30 L of magnesium powder suspension, while ammonia was added dropwise to adjust the pH to 9.6. The mixture was stirred continuously for 7 h, centrifuged, washed 5 times with ethanol, and vacuum dried at 80 °C for 6 h to obtain the Mg-La(OH)3 precursor. The precursor was placed in a tube furnace, argon was introduced, and the temperature was increased to 500 °C at 10 °C / min and held for 2 h. After natural cooling to room temperature, it was loaded into a fluidized bed CVD reactor, hydrogen was introduced, and the temperature was increased to 800 °C and held for 30 min. The temperature was then adjusted to 950 °C, and methane was introduced as a carbon source. The growth time was 30 min, the methane was turned off, and the mixture was cooled to 200 °C in a hydrogen atmosphere before switching to argon. After cooling to room temperature, Mg-La2O3 core-shell particles were obtained.

[0037] 15 kg of magnesium carbonate powder was mixed evenly with 5 kg of diatomaceous earth, pressed into blocks, and baked at 130 °C for 4 h to remove moisture, thus obtaining a covering agent. Boric acid, graphene oxide, and silicon were mixed, ball-milled for 60 min, and sintered at 900 °C for 5 h in a mixed atmosphere of argon and hydrogen to obtain boron-doped graphene-silicon material.

[0038] Ten cathode copper plates were suspended at the furnace opening and baked for 20 minutes before being placed in a crucible melting furnace and melted at 1400℃ under a nitrogen atmosphere. 2.6 kg of Mg-La2O3 core-shell particles and 0.8 kg of boron-doped graphene-silicon material were added and stirred for 4 hours. 2 kg of covering agent was gently placed on the surface of the melt, which was then cooled through a crystallizer and drawn at a speed of 300 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 25 mm. The covering agent thickness should not be less than 100 mm, and the covering agent should be cleaned every 12 hours.

[0039] A 2500mm copper-magnesium alloy cast rod was uniformly cut into 10 pieces. After preheating at 750℃ and preheating the surface of the extrusion roller, the copper-magnesium alloy cast rod was fed into a continuous extrusion press. Under the conditions of 600℃ and 1500MPa, a copper-magnesium alloy extruded rod with a diameter of 30mm was obtained. The extruded rod was then fed into a drawing device and drawn in multiple passes to obtain a cross-section of 150mm. 2 High-strength copper-magnesium alloy contact wire.

[0040] Example 2

[0041] 1 kg of lanthanum nitrate was dissolved in 23 L of deionized water and stirred until homogeneous. 0.8 kg of citric acid was added and stirred until completely dissolved to form a transparent sol. The sol was then slowly dripped into 30 L of magnesium powder suspension, while ammonia was added dropwise to adjust the pH to 9. The mixture was stirred continuously for 10 h, centrifuged, washed three times with ethanol, and vacuum dried at 60 °C for 7 h to obtain the Mg-La(OH)3 precursor. The precursor was placed in a tube furnace, argon was introduced, and the temperature was increased to 400 °C at 10 °C / min and held for 2 h. After natural cooling to room temperature, it was loaded into a fluidized bed CVD reactor, hydrogen was introduced, and the temperature was increased to 800 °C and held for 30 min. The temperature was then adjusted to 950 °C, and methane was introduced as a carbon source. The growth time was 30 min, the methane was turned off, and the mixture was cooled to 200 °C in a hydrogen atmosphere before switching to argon and cooling to room temperature to obtain Mg-La2O3 core-shell particles.

[0042] 15 kg of magnesium carbonate powder was mixed evenly with 5 kg of diatomaceous earth, pressed into blocks, and baked at 150 °C for 3 hours to remove moisture, thus obtaining a covering agent. Boric acid, graphene oxide, and silicon were mixed, ball-milled for 50 minutes, and sintered at 900 °C for 5 hours in a mixed atmosphere of argon and hydrogen to obtain boron-doped graphene-silicon material.

[0043] Six cathode copper plates were suspended at the furnace opening and baked for 10 minutes before being placed in a crucible melting furnace. They were then melted at 1400℃ under a nitrogen atmosphere. 2.1 kg of Mg-La2O3 core-shell particles and 0.8 kg of boron-doped graphene-silicon material were added and stirred for 3 hours. 1.9 kg of covering agent was gently placed on the surface of the melt. The melt was then cooled through a crystallizer and drawn at a speed of 500 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 20 mm. The covering agent thickness should not be less than 100 mm, and the covering agent should be cleaned every 12 hours.

[0044] A 2000mm copper-magnesium alloy cast rod was uniformly cut into 5 pieces. After preheating at 650℃ and preheating the surface of the extrusion roller, the copper-magnesium alloy cast rod was fed into a continuous extrusion press. Under the conditions of 600℃ and 1200MPa, a copper-magnesium alloy extruded rod with a diameter of 25mm was obtained. The extruded rod was then fed into a drawing device and drawn in multiple passes to obtain a cross-section of 150mm. 2 High-strength copper-magnesium alloy contact wire.

[0045] Example 3

[0046] 1 kg of lanthanum nitrate was dissolved in 23 L of deionized water and stirred until homogeneous. 0.8 kg of citric acid was added and stirred until completely dissolved to form a transparent sol. The sol was then slowly dripped into 30 L of magnesium powder suspension, while ammonia was added dropwise to adjust the pH to 10. The mixture was stirred continuously for 6 h, centrifuged, washed 5 times with ethanol, and vacuum dried at 80 °C for 5 h to obtain the Mg-La(OH)3 precursor. The precursor was placed in a tube furnace, argon was introduced, and the temperature was increased to 600 °C at 10 °C / min and held for 2 h. After natural cooling to room temperature, it was loaded into a fluidized bed CVD reactor, hydrogen was introduced, and the temperature was increased to 800 °C and held for 30 min. The temperature was then adjusted to 950 °C, and methane was introduced as a carbon source. The growth time was 30 min, the methane was turned off, and the mixture was cooled to 200 °C in a hydrogen atmosphere before switching to argon and cooling to room temperature to obtain Mg-La2O3 core-shell particles.

[0047] 15 kg of magnesium carbonate powder was mixed evenly with 5 kg of diatomaceous earth, pressed into blocks, and baked at 150 °C for 3 hours to remove moisture, thus obtaining a covering agent. Boric acid, graphene oxide, and silicon were mixed, ball-milled for 30 minutes, and sintered at 900 °C for 3 hours in a mixed atmosphere of argon and hydrogen to obtain boron-doped graphene-silicon material.

[0048] Seven cathode copper plates were suspended at the furnace opening and baked for 10 minutes before being placed in a crucible melting furnace. They were then melted at 1200℃ under a nitrogen atmosphere. 1.7 kg of Mg-La2O3 core-shell particles and 0.5 kg of boron-doped graphene-silicon material were added and stirred for 2 hours. 2 kg of covering agent was gently placed on the surface of the melt. The melt was then cooled through a crystallizer and drawn at a speed of 200 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 25 mm. The covering agent thickness should not be less than 100 mm, and the covering agent should be cleaned every 12 hours.

[0049] A 2400mm copper-magnesium alloy cast rod was uniformly cut into 8 pieces. After preheating at 700℃ and preheating the surface of the extrusion roller, the copper-magnesium alloy cast rod was fed into a continuous extrusion press. Under the conditions of 500℃ and 1000MPa, a copper-magnesium alloy extruded rod with a diameter of 28mm was obtained. The extruded rod was then fed into a drawing device and drawn in multiple passes to obtain a cross-section of 150mm. 2 High-strength copper-magnesium alloy contact wire.

[0050] Example 4

[0051] 1 kg of lanthanum nitrate was dissolved in 23 L of deionized water and stirred until homogeneous. 0.8 kg of citric acid was added and stirred until completely dissolved to form a transparent sol. The sol was then slowly dripped into 30 L of magnesium powder suspension, while ammonia was added dropwise to adjust the pH to 9.2. The mixture was stirred continuously for 7 h, centrifuged, washed four times with ethanol, and vacuum dried at 65 °C for 6.5 h to obtain the Mg-La(OH)3 precursor. The precursor was placed in a tube furnace, argon was introduced, and the temperature was increased to 500 °C at 10 °C / min and held for 2 h. After natural cooling to room temperature, it was loaded into a fluidized bed CVD reactor, hydrogen was introduced, and the temperature was increased to 800 °C and held for 30 min. The temperature was then adjusted to 950 °C, and methane was introduced as a carbon source. The growth time was 30 min, the methane was turned off, and the mixture was cooled to 200 °C in a hydrogen atmosphere before switching to argon and cooling to room temperature to obtain Mg-La2O3 core-shell particles.

[0052] 15 kg of magnesium carbonate powder was mixed evenly with 5 kg of diatomaceous earth, pressed into blocks, and baked at 120 °C for 3.5 h to remove moisture, thus obtaining a covering agent. Boric acid, graphene oxide, and silicon were mixed, ball-milled for 40 min, and sintered at 900 °C for 4 h in a mixed atmosphere of argon and hydrogen to obtain boron-doped graphene-silicon material.

[0053] Eight cathode copper plates were suspended at the furnace opening and baked for 15 minutes before being placed in a crucible melting furnace. They were then melted at 1300℃ under a nitrogen atmosphere. 3.2 kg of Mg-La2O3 core-shell particles and 0.7 kg of boron-doped graphene-silicon material were added and stirred for 3 hours. 3.2 kg of covering agent was gently placed on the surface of the melt. The melt was then cooled through a crystallizer and drawn at a speed of 400 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 30 mm. The covering agent thickness should not be less than 100 mm, and the covering agent should be cleaned every 12 hours.

[0054] A 2100mm copper-magnesium alloy cast rod was uniformly cut into 7 pieces. After preheating at 650℃ and preheating the surface of the extrusion roller, the copper-magnesium alloy cast rod was fed into a continuous extrusion press. Under the conditions of 550℃ and 1400MPa, a copper-magnesium alloy extruded rod with a diameter of 26mm was obtained. The extruded rod was then fed into a drawing device and drawn in multiple passes to obtain a cross-section of 150mm. 2 High-strength copper-magnesium alloy contact wire.

[0055] Example 5

[0056] 1 kg of lanthanum nitrate was dissolved in 23 L of deionized water and stirred until homogeneous. 0.8 kg of citric acid was added and stirred until completely dissolved to form a transparent sol. The sol was then slowly dripped into 30 L of magnesium powder suspension, while ammonia was added dropwise to adjust the pH to 9.7. The mixture was stirred continuously for 8 h, centrifuged, washed four times with ethanol, and vacuum dried at 70 °C for 5 h to obtain the Mg-La(OH)3 precursor. The precursor was placed in a tube furnace, argon was introduced, and the temperature was increased to 500 °C at 10 °C / min and held for 2 h. After natural cooling to room temperature, it was loaded into a fluidized bed CVD reactor, hydrogen was introduced, and the temperature was increased to 800 °C and held for 30 min. The temperature was then adjusted to 950 °C, and methane was introduced as a carbon source. The growth time was 30 min. The methane was turned off, and the mixture was cooled to 200 °C in a hydrogen atmosphere before switching to argon and cooling to room temperature to obtain Mg-La2O3 core-shell particles.

[0057] 15 kg of magnesium carbonate powder was mixed evenly with 5 kg of diatomaceous earth, pressed into blocks, and baked at 100°C for 3.5 h to remove moisture, thus obtaining a covering agent. Boric acid, graphene oxide, and silicon were mixed, ball-milled for 60 min, and sintered at 900°C for 3 h in a mixed atmosphere of argon and hydrogen to obtain boron-doped graphene-silicon material.

[0058] Nine cathode copper plates were suspended at the furnace opening and baked for 16 minutes before being placed in a crucible melting furnace. Under a nitrogen atmosphere, the plates were melted at 1300℃. 0.92 kg of Mg-La2O3 core-shell particles and 0.03 kg of boron-doped graphene-silicon material were added and stirred for 3 hours. 1.8 kg of covering agent was gently placed on the surface of the melt. The melt was then cooled through a crystallizer and drawn at a speed of 400 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 27 mm. The covering agent thickness should not be less than 100 mm, and the covering agent should be cleaned every 12 hours.

[0059] Ten 2500mm copper-magnesium alloy cast rods were uniformly cut into pieces. After preheating at 700℃ and preheating the surface of the extrusion rollers, the copper-magnesium alloy cast rods were fed into a continuous extrusion press. Under conditions of 550℃ and 1500MPa, copper-magnesium alloy extruded rods with a diameter of 30mm were obtained. The extruded rods were then fed into a drawing device and drawn in multiple passes to obtain a cross-section of 150mm. 2 High-strength copper-magnesium alloy contact wire.

[0060] Example 6

[0061] 1 kg of lanthanum nitrate was dissolved in 23 L of deionized water and stirred until homogeneous. 0.8 kg of citric acid was added and stirred until completely dissolved to form a transparent sol. The sol was then slowly dripped into 30 L of magnesium powder suspension, while ammonia was added dropwise to adjust the pH to 9. The mixture was stirred continuously for 9 h, centrifuged, washed three times with ethanol, and vacuum dried at 80 °C for 6 h to obtain the Mg-La(OH)3 precursor. The precursor was placed in a tube furnace, argon was introduced, and the temperature was increased to 400 °C at 10 °C / min and held for 2 h. After natural cooling to room temperature, it was loaded into a fluidized bed CVD reactor, hydrogen was introduced, and the temperature was increased to 800 °C and held for 30 min. The temperature was then adjusted to 950 °C, and methane was introduced as a carbon source. The growth time was 30 min, the methane was turned off, and the mixture was cooled to 200 °C in a hydrogen atmosphere before switching to argon and cooling to room temperature to obtain Mg-La2O3 core-shell particles.

[0062] 15 kg of magnesium carbonate powder was mixed evenly with 5 kg of diatomaceous earth, pressed into blocks, and baked at 110 °C for 5 h to remove moisture, thus obtaining a covering agent. Boric acid, graphene oxide, and silicon were mixed, ball-milled for 50 min, and sintered at 900 °C for 4.5 h in a mixed atmosphere of argon and hydrogen to obtain boron-doped graphene-silicon material.

[0063] Eight cathode copper plates were suspended at the furnace opening and baked for 20 minutes before being placed in a crucible melting furnace. Under a nitrogen atmosphere, the plates were melted at 1400℃. 1.9 kg of Mg-La2O3 core-shell particles and 0.6 kg of boron-doped graphene-silicon material were added and stirred for 4 hours. 3 kg of covering agent was gently placed on the surface of the melt. The melt was then cooled through a crystallizer and drawn at a speed of 400 mm / min to obtain a copper-magnesium alloy casting rod with a diameter of 27 mm. The covering agent thickness should not be less than 100 mm, and the covering agent should be cleaned every 12 hours.

[0064] A 2400mm copper-magnesium alloy cast rod was uniformly cut into 8 pieces. After preheating at 750℃ and preheating the surface of the extrusion roller, the copper-magnesium alloy cast rod was fed into a continuous extrusion press. Under the conditions of 600℃ and 1000MPa, a copper-magnesium alloy extruded rod with a diameter of 25mm was obtained. The extruded rod was then fed into a drawing device and drawn in multiple passes to obtain a cross-section of 150mm. 2 High-strength copper-magnesium alloy contact wire.

[0065] The present invention also includes comparative examples and related experiments.

[0066] Comparative Example 1

[0067] Compared with Example 1, the difference is that Mg-La2O3 core-shell particles were not prepared, and Mg powder was directly added. Other preparation steps and components remained unchanged, and a high-strength copper-magnesium alloy contact wire was finally obtained.

[0068] Comparative Example 2

[0069] Compared with Example 1, the difference is that no covering agent was prepared, and carbon black was used directly as the covering agent. Other preparation steps and components remained unchanged, and a high-strength copper-magnesium alloy contact wire was finally obtained.

[0070] Comparative Example 3

[0071] Compared with Example 1, the difference is that boron-doped graphene-silicon material was not prepared, and graphene was directly added. Other preparation steps and components remained unchanged, and a high-strength copper-magnesium alloy contact wire was finally obtained.

[0072] Performance testing

[0073] The high-strength copper-magnesium alloy contact wires prepared in Examples 1-6 and Comparative Examples 1-3 were tested for mechanical and electrical properties. The test conditions were: speed level: 400-450 km / h, test tension: 36-42 KN. The tests were conducted in accordance with the Chinese railway industry standard TB / T2809-2017 Copper and Copper Alloy Contact Wires for Electrified Railways. The mechanical property test results are shown in Table 1, and the electrical property test results are shown in Table 2.

[0074] Table 1

[0075]

[0076] As shown in Table 1, the high-strength copper-magnesium alloy contact wires prepared in Examples 1-6 have higher tensile strength, breaking force and fatigue resistance than comparative examples 1-3. They can all meet the requirements of CTMH in the Chinese railway industry standard TB / T2809-2017 and are suitable for high-strength, high-conductivity copper-magnesium alloy contact wires for 400km / h high-speed railway lines.

[0077] As shown in Table 1, Comparative Example 1, due to the direct addition of Mg powder, resulted in grain coarsening, leading to a significant decrease in mechanical properties. Furthermore, the addition of Mg-La2O3 core-shell particles in Example 1 played a crucial role in suppressing fatigue crack propagation. Comparative Example 2, using a traditional carbon black covering agent, exhibited the worst fatigue resistance, possibly due to the tendency of carbon black to sinter, leading to localized oxidation and stress concentration in the melt. The finished products obtained using the methods described in Examples 1-6 of this invention have finer grain sizes and more uniform internal dispersion of substances, making them less prone to agglomeration. Figures 1-2 The image shown is a metallographic diagram of the finished product, in which... Figure 1 This is a cross-sectional metallographic image of the product from Example 1. Figure 2 This is a cross-sectional metallographic image of the product in Example 3.

[0078] Table 2

[0079]

[0080] As shown in Table 2, the conductivity of all embodiments exceeded the standard requirements. Compared with Example 1, Comparative Example 1 had a significantly lower conductivity and a significantly higher resistivity due to the increased magnesium burn-off rate leading to more impurities in the copper matrix. Comparative Example 2 also had a significant impact on conductivity and resistivity due to residual carbon impurities from carbon black sintering, which reduced electron mobility. Compared with Comparative Example 3, Example 1's addition of boron-doped graphene-silicon material instead of the traditional direct addition of graphene significantly improved conductivity and resistivity.

[0081] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of high strength copper-magnesium alloy contact wire, characterized in that, Comprising the following steps: S1, stirring lanthanum nitrate, deionized water and citric acid to form a sol, then slowly dropping the sol into a magnesium powder suspension, while adding ammonia water to adjust the pH to 9-10, continuously stirring, centrifugal separation, washing, vacuum drying, then placing in a tube furnace, passing argon, heating to 500 DEG C, holding, cooling to obtain Mg-La2O3 core-shell particles; loading into a fluidized bed CVD reactor, passing hydrogen, heating to 800 DEG C, holding for 30min, adjusting the temperature to 950 DEG C, passing methane, growing for 30min, closing the methane, switching to argon after cooling to 200 DEG C in a hydrogen atmosphere, cooling to room temperature, finally obtaining Mg-La2O3 core-shell particles with graphene on the surface; S2, uniformly mixing magnesium carbonate powder and diatomite, then pressing into blocks, baking to obtain a covering agent; S3, baking 42~70 parts of cathode copper plate for 10~20 min, putting into crucible smelting furnace, keeping in nitrogen atmosphere, melting at 1200~1400℃, putting in 1.7~3.2 parts of Mg-La2O3 core-shell particles with graphene on the surface and 0.5~0.8 parts of boron-doped graphene-silicon material, stirring, and putting 1.9~2.3 parts of covering agent on the surface of the melt, then cooling through the crystallizer, and pulling at a speed of 200~500mm / min to get copper-magnesium alloy casting rod with a diameter of 20~30mm, then evenly cutting into 5~10 pieces, preheating at 650~750℃, then introducing into continuous extruder, extruding at 500~600℃, 1000~1500MPa to get copper-magnesium alloy extruded rod with a diameter of 25~30mm, then drawing through multiple passes to get copper-magnesium alloy wire rod with a cross section of 150mm 2 High-strength copper-magnesium alloy contact wire The boron-doped graphene-silicon material is obtained by mixing boric acid, graphene oxide and silicon, ball milling for 30-60min, sintering at 900 DEG C for 3-5h in an argon and hydrogen atmosphere.

2. The process for preparing high strength copper-magnesium alloy contact wire as claimed in claim 1 wherein, The magnesium powder suspension is obtained by dispersing pretreated magnesium powder in anhydrous ethanol, high-speed stirring for 30min.

3. The process for preparing high strength copper-magnesium alloy contact wire as claimed in claim 2 wherein, The pretreated magnesium powder is obtained by soaking magnesium powder in 5% dilute hydrochloric acid for 10min, washing with deionized water until neutral, then washing with anhydrous ethanol for 3 times, vacuum drying at 60 DEG C for 12h.

4. The process for preparing high strength copper-magnesium alloy contact wire as claimed in claim 1 wherein, In step S1, the time for continuous stirring is 6-10h, the washing agent used for washing is ethanol, the washing frequency is 3-5 times, the vacuum drying temperature is 60-80 DEG C, the time is 5-7h, the heating rate is 10 DEG C / min, and the holding time is 2h.

5. The process for preparing high strength copper-magnesium alloy contact wire as claimed in claim 1 wherein, In step S2, the baking temperature is 100 DEG C-150 DEG C, and the time is 3-5h.

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