A method for preparing a low temperature resistant cable

Abstract

The application relates to a preparation method of a low-temperature-resistant cable and relates to the technical field of cable preparation. The low-temperature-resistant cable is prepared by adopting copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder as a conductor prepared by depositing a nano-silver film on the surface of alloy micro wires, twisting the conductor according to requirements to obtain a core, mixing hydrogenated nitrile rubber, boron nitride nanosheets, refined paraffin, 4-hydroxycyclohexyl trimethoxysilane, ammonium polyphosphate, silicone oil and methyl methacrylate to prepare an insulation protective sleeve, and wrapping the core to obtain the low-temperature-resistant cable which can be applied to an intelligent power distribution system under extremely cold conditions. In the application, the initial resistance of the conductor under low temperature is reduced by optimizing the conductor, the NTC effect is effectively started, the heat conduction performance of the insulation protective sleeve is adjusted, the low-temperature brittle stop time of the cable under extremely cold conditions is reduced, the high-temperature stable temperature of the cable is reduced, the low-temperature brittleness and high-temperature aging of the cable insulation protective sleeve are effectively inhibited, and the working life of the cable in the intelligent power distribution system is prolonged.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, specifically to a method for manufacturing a low-temperature resistant cable and its application in an intelligent power distribution system under extremely cold conditions. Background Technology

[0002] Wires and cables are wire products used to transmit electrical (magnetic) energy, information, and realize the conversion of electromagnetic energy. In a broad sense, wires and cables are also simply called cables. In a narrow sense, cables refer to insulated cables, which can be defined as: an assembly consisting of one or more insulated cores, and their respective possible covering layers, a total protective layer, and an outer sheath. Depending on the application environment, the performance of the cable used in harsh or special scenarios needs to match the extreme requirements of the environment. Common types include high-temperature resistant cables (withstanding temperatures above 200℃, used in metallurgy and boiler equipment), low-temperature resistant cables (not brittle below -40℃, used in polar regions, cold storage, etc.), oil / acid and alkali resistant cables (resistant to chemical corrosion, used in chemical plants and oil fields), underwater cables (waterproof and water pressure resistant, used in submarine power transmission and underwater exploration equipment), and mining cables (impact resistant and crush resistant, used in underground coal mines), etc.

[0003] Low-temperature cables are special cables designed for extreme low-temperature environments and are widely used in polar scientific research, cold chain logistics, wind power, and other fields. Currently, mainstream low-temperature cables use modified thermoplastic polyester elastomer (RTPEF), polyurethane (TPU), silicone rubber, and other materials to prepare the insulating protective sheath, or optimize the conductor to improve the cable's low-temperature performance by balancing conductivity and resistance to cold brittleness.

[0004] When manufacturing insulation / protective sheaths for cryogenic cables, materials resistant to low temperatures, such as cross-linked polyethylene, silicone rubber, or fluoroplastics, are typically used. However, existing materials like traditional PVC become brittle below -25°C, polyethylene exhibits a significant decrease in elongation at break below -40°C, fluoroplastics are expensive and difficult to process, and materials like TPU are prone to molecular chain degradation at low temperatures, leading to a decrease in strength. Furthermore, the difference in shrinkage between the conductor and insulation materials at low temperatures can also cause interfacial stress concentration, leading to insulation layer cracking and peeling.

[0005] Hydrogenated nitrile butadiene rubber (HNBR) is a hydrogenated modified product of nitrile butadiene rubber (NBR). By reducing the number of double bonds in the molecular chain, its aging resistance is significantly improved while retaining the oil resistance of NBR. This makes it a performance-oriented material combining oil resistance, aging resistance, high and low temperature resistance, and high mechanical strength. Using it as the main material for cables results in a longer service life compared to conventional rubber and expands the application of cables in extreme or special environments, offering excellent cost-effectiveness. However, hydrogenated nitrile butadiene rubber still becomes embrittled below -30℃ due to impaired molecular chain movement, leading to long-term low-temperature embrittlement and failure of insulation sheaths made primarily from it. Furthermore, its poor thermal conductivity exacerbates the "icing and condensation" phenomenon on the cable surface at low temperatures due to temperature fluctuations, allowing moisture to penetrate and reducing the insulation resistance of the sheath, thus increasing the risk of leakage. Summary of the Invention

[0006] Based on the above problems, the purpose of this invention is to provide a cable that is resistant to low-temperature embrittlement and thermal aging.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned low-temperature resistant cable.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A cable resistant to low-temperature embrittlement and thermal aging includes a conductor and an insulating protective sheath. The conductor is characterized by being prepared by molten alloying copper, nickel, zinc, titanium, cobalt, tin, manganese, and graphite powder, cast and stretched to form alloy microwires, and then depositing a nano-silver film on the surface of the alloy microwires. The insulating protective sheath is prepared by smelting hydrogenated nitrile rubber, boron nitride nanosheets, refined paraffin wax, 4-hydroxycyclohexyltrimethoxysilane, ammonium polyphosphate, silicone oil, and methyl methacrylate.

[0010] Furthermore, the copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder are in a mass ratio of 84~86:1.2~1.5:2.5~3.5:2.5~4:1~1.5:0.5~0.8:1.0~1.2:5~6.

[0011] Furthermore, the preparation of the molten alloy involves mixing copper, manganese, nickel, cobalt, zinc, tin, titanium, and graphite powder under a vacuum of -0.08 to -0.09 MPa for 25 to 30 minutes, then introducing a mixture of oxygen and argon at a flow rate of 0.03 to 0.05 L / min and 0.1 to 0.2 L / min, heating to 450 to 550°C at a rate of 5 to 10°C / min, holding at this temperature for 1 to 2 hours, and then stopping the oxygen supply. Heat the mixture to 900-950℃ at a rate of 15-20℃ / min and hold for 30-60 minutes. After holding, heat the mixture to 1200-1250℃ at a rate of 5-8℃ / min and hold for 15-25 minutes. After holding, stir at 20-30 rpm for 30-40 minutes. Then cool the mixture to 580-620℃ at a rate of 80-100℃ / min, and then cool it to 400-450℃ at a rate of 20-25℃ / min. Set aside for later use.

[0012] Furthermore, the casting and stretching process involves casting the molten alloy into an 8-9 mm alloy rod at 400-450°C under argon protection, then cooling it to room temperature and stretching it multiple times to a diameter of 0.4-0.6 mm to obtain alloy microwires.

[0013] Furthermore, the stretching speed of the multi-pass stretching is 120~150mm / s, and the stretching rate of each pass is 15~20%.

[0014] Furthermore, the deposited silver nanofilm is deposited using magnetron sputtering, specifically under an argon atmosphere, with a working pressure of 0.3~0.5 Pa, a sputtering power of 3 kW, a deposition rate of 0.06~0.08 nm / s, and a film thickness of 180~200 nm.

[0015] Furthermore, the insulating protective sleeve contains, by weight, 80-100 parts hydrogenated nitrile rubber, 20-25 parts boron nitride nanosheets, 3-5 parts refined paraffin wax, 3-6 parts 4-hydroxycyclohexyltrimethoxysilane, 8-12 parts ammonium polyphosphate, 12-15 parts silicone oil, and 3-5 parts methyl methacrylate.

[0016] Furthermore, the melting temperature is 140~160℃, and the material is extruded using a twin-screw extruder.

[0017] A method for preparing a low-temperature resistant cable, characterized by comprising the following steps:

[0018] S1. A molten alloy is prepared using copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder as raw materials, and then cast and stretched to prepare alloy microwires. A conductor is then obtained by depositing a nano silver film on the surface of the alloy microwires.

[0019] S2. An insulating protective sleeve is prepared by mixing and melting hydrogenated nitrile rubber, boron nitride nanosheets, refined paraffin wax, 4-hydroxycyclohexyltrimethoxysilane, ammonium polyphosphate, silicone oil and methyl methacrylate;

[0020] S3. The conductor obtained in step S1 is stranded according to requirements to form a wire core. The sheath prepared in S2 is then wrapped around the wire core to obtain a low-temperature resistant cable.

[0021] Furthermore, in step S1, the molten alloy is prepared by mixing copper, manganese, nickel, cobalt, zinc, tin, titanium, and graphite powder, maintaining the mixture under a vacuum of -0.08 to -0.09 MPa for 25 to 30 minutes, introducing a mixture of oxygen and argon at a flow rate of 0.03 to 0.05 L / min and an argon flow rate of 0.1 to 0.2 L / min, and holding the mixture at 450 to 550°C. Then, the oxygen supply is stopped, and the mixture is held at 900 to 950°C and 1200 to 1250°C in stages to obtain the molten alloy.

[0022] Furthermore, the raw materials are stacked in sequence in the order of copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder, with the copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder in a mass ratio of 84~86:1.2~1.5:2.5~3.5:2.5~4:1~1.5:0.5~0.8:1.0~1.2:5~6.

[0023] In this conductor, the NTC effect mainly originates from the metal oxide formed by the Mn-Ni-Co ternary system, while copper is the main conductive component. Graphite is added as a carbon and oxygen source, which reacts with Ti and Mn to generate TiC-MnC composite carbide phase and Mn-Ni-Co metal oxide. The TiC-MnC composite carbide phase helps to enhance the NTC effect, thereby achieving temperature response regulation of the resistance.

[0024] The high interfacial barrier between carbides and the metal matrix leads to a high initial low-temperature resistance, posing a risk of excessive initial heat generation and thermal shock damage to the surface insulation sheath structure. Conversely, if the initial resistance is too low, the heat generation will be lower than the ambient heat dissipation, preventing the NTC effect from being activated. Zn and Sn, being low-melting-point components, form liquid phase channels first during the melting stage, accelerating the reaction of Ti, Mn, and graphite, as well as the uniform dispersion of carbides. Simultaneously, they lower the interfacial barrier between carbides and the metal matrix, significantly reducing the initial low-temperature resistance of the conductor while remaining within a suitable range. Under low-temperature conditions, the initial resistance can generate effective initial heat higher than the ambient heat dissipation, effectively activating the NTC effect and promoting temperature rise. The conductor resistance decreases as the temperature increases, forming a positive heat generation cycle. This facilitates stable heat generation during the temperature recovery process from extreme cold (-40℃), providing heating protection for the insulation sheath and inhibiting its low-temperature embrittlement.

[0025] In addition, Zn is a high CTE (coefficient of thermal expansion) component, Mn's CTE is close to that of Cu, and Sn's CTE is moderate. The three components work together to regulate the overall CTE of the conductor and shorten the CTE difference between the conductor and the insulating sheath. Furthermore, Sn forms a low-melting-point eutectic phase with Cu and Zn during the melting process, rather than a continuous solid solution, which can effectively suppress local segregation of Zn, avoid conductor cracking caused by uneven local thermal expansion, and prevent CTE mismatch between the conductor and the insulating sheath.

[0026] Furthermore, the segmented heat preservation involves first heating to 450-550°C at a rate of 5-10°C / min under an oxygen and argon atmosphere, holding for 1-2 hours, then stopping the oxygen supply, heating to 900-950°C at a rate of 15-20°C / min, holding for 30-60 minutes, then heating to 1200-1250°C at a rate of 5-8°C / min, holding for 15-25 minutes, then stirring at 20-30 rpm for 30-40 minutes, then cooling to 580-620°C at a rate of 80-100°C / min, and then cooling to 400-450°C at a rate of 20-25°C / min for later use.

[0027] Because there are many types of alloying elements and the melting temperatures of each element differ greatly, direct mixing and melting can cause component encapsulation and component segregation, leading to a decrease in conductor performance and the generation of cracks during subsequent stretching.

[0028] In this invention, copper, manganese, nickel, cobalt, zinc, tin, titanium, and graphite powder are layered sequentially (copper as the bottom layer and graphite powder as the top layer). The segmented heating and holding process employs a "progressive melting + gradient diffusion" design, with each stage precisely matching the characteristics of the raw materials. The first stage involves slow heating and long-term holding. At this temperature range, the low oxygen partial pressure promotes the selective oxidation of Mn, Ni, and Co, providing the material basis for the subsequent precipitation of the NTC phase. The second stage involves rapid heating and holding, reaching a temperature of 900-950℃. At this temperature, the precursor begins solid-phase diffusion, forming spinel nuclei. The third stage involves slow heating and short holding, reaching a temperature of 1200-1250℃. At this high temperature, the alloy completely melts, eliminating component segregation and precipitating a large number of fine NTC phase grains. These grains are uniformly dispersed in the copper matrix, forming the core conductive network of the NTC effect; ensuring the consistent distribution of the NTC phase throughout the conductor and avoiding localized areas lacking the NTC effect.

[0029] Furthermore, the casting and stretching process involves casting the molten alloy into an 8-9 mm alloy rod at 400-450°C under argon protection, then cooling it to room temperature and stretching it multiple times to a diameter of 0.4-0.6 mm to obtain alloy microwires.

[0030] Furthermore, the stretching speed of the multi-pass stretching is 120~150mm / s, and the stretching rate of each pass is 15~20%.

[0031] Furthermore, the deposited silver nanofilm is deposited using magnetron sputtering, specifically under an argon atmosphere, with a working pressure of 0.3~0.5 Pa, a sputtering power of 3 kW, a deposition rate of 0.06~0.08 nm / s, and a film thickness of 180~200 nm.

[0032] Furthermore, the insulating protective sleeve contains, by weight, 80-100 parts hydrogenated nitrile rubber, 20-25 parts boron nitride nanosheets, 3-5 parts refined paraffin wax, 3-6 parts 4-hydroxycyclohexyltrimethoxysilane, 8-12 parts ammonium polyphosphate, 12-15 parts silicone oil, and 3-5 parts methyl methacrylate.

[0033] Furthermore, the melting temperature is 140~160℃, and the material is extruded using a twin-screw extruder.

[0034] In the preparation of insulating sleeves using hydrogenated nitrile rubber as the main material, the addition of boron nitride nanosheets enhances the thermal conductivity of the insulating sleeve, facilitating the efficient transfer of heat generated by the conductor to the insulating sleeve. However, this also leads to rapid heat dissipation from the insulating sleeve to the environment. Furthermore, the polar hydroxyl groups on the surface of boron nitride make it prone to aggregation in the non-polar system dominated by rubber, resulting in poor heat transfer uniformity of the insulating sleeve. Therefore, 4-hydroxycyclohexyltrimethoxysilane is further added. Through hydrolysis and condensation reaction with boron nitride, the dispersion of boron nitride in the system is improved through steric hindrance and polarity adjustment. After the reaction between silane and boron nitride, the surface of boron nitride becomes hydrophobic. Liquid paraffin is added during the melting process. The hydrophobic interaction between the two and the fluidity of the paraffin itself allow the liquid paraffin to impregnate the boron nitride and fill the interlayer of boron nitride. After cooling and solidification, the paraffin solidifies and shrinks, forming gaps.

[0035] During cable use, under initial extremely cold conditions, the cable itself is at a low temperature. Paraffin is solid, and although boron nitride can improve the thermal conductivity of the insulation sheath, its thermal conductivity is relatively low due to the gaps between its layers. The insulation sheath dissipates heat slowly to the environment, increasing the rate of temperature rise of the cable. When the cable temperature rises to a higher temperature exceeding the threshold (>50℃), the paraffin in the insulation sheath transforms into a liquid phase. The flowing paraffin fills the gaps between the boron nitride layers, reducing the interfacial thermal resistance and connecting the heat conduction path of boron nitride, thereby improving the thermal conductivity of the insulation sheath. At high temperatures, the heat dissipation capacity is improved, thus dissipating the increased heat generated by NTC more quickly and reducing thermal aging. In other words, the addition of paraffin gives the insulation sheath a dynamic property of thermal conductivity that changes with temperature, exhibiting slow heat dissipation at low temperatures and fast heat dissipation at high temperatures.

[0036] Most specifically, a method for preparing a low-temperature resistant cable is characterized by comprising the following steps:

[0037] S1. Conductor preparation:

[0038] (1) The copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powders are stacked in layers according to the following order: mass ratio 84~86:1.2~1.5:2.5~3.5:2.5~4:1~1.5:0.5~0.8:1.0~1.2:5~6. The mixture is kept under a vacuum of -0.08~-0.09 MPa for 25~30 min. A mixture of oxygen and argon is introduced, with an oxygen flow rate of 0.03~0.05 L / min and an argon flow rate of 0.1~0.2 L / min, at a rate of 5~10 °C / min. The temperature is increased to 450-550℃ at a constant rate and held for 1-2 hours. Then, the oxygen supply is stopped, and the temperature is increased to 900-950℃ at a rate of 15-20℃ / min and held for 30-60 minutes. After holding, the temperature is increased to 1200-1250℃ at a rate of 5-8℃ / min and held for 15-25 minutes. After holding, the temperature is stirred at 20-30 rpm for 30-40 minutes. Then, the temperature is cooled to 580-620℃ at a rate of 80-100℃ / min, and then cooled to 400-450℃ at a rate of 20-25℃ / min. The mixture is then ready for use.

[0039] (2) At 400~450℃ and under argon protection, the molten alloy is cast into an alloy rod of 8~9mm, then cooled to room temperature, and stretched to a diameter of 0.4~0.6mm in multiple passes to obtain alloy microwires. The stretching speed of the multiple stretching passes is 120~150mm / s, and the stretching rate of each pass is 15~20%.

[0040] (3) Under an argon atmosphere, a nanosilver film was deposited by magnetron sputtering. The working pressure of magnetron sputtering was 0.3~0.5Pa, the sputtering power was 3kW, the deposition rate was 0.06~0.08nm / s, and the thickness of the deposited film was 180~200nm.

[0041] S2. Preparation of insulating protective sleeve:

[0042] According to the weight percentages, 80-100 parts of hydrogenated nitrile rubber, 20-25 parts of boron nitride nanosheets, 3-5 parts of refined paraffin wax, 3-6 parts of 4-hydroxycyclohexyltrimethoxysilane, 8-12 parts of ammonium polyphosphate, 12-15 parts of silicone oil, and 3-5 parts of methyl methacrylate are mixed in a mixer and extruded through a twin-screw extruder at a melting temperature of 140-160℃ to obtain a rubber sleeve.

[0043] S3. Cable preparation:

[0044] The conductor obtained in step S1 is stranded according to requirements to form a wire core. The wire core is then wrapped with the rubber sheath prepared in step S2 to obtain a low-temperature resistant cable.

[0045] In low-temperature environments, the aforementioned composite conductor effectively enhances the NTC effect while reducing the initial resistance of the conductor, regulating the initial heat generation of the conductor at low temperatures, effectively initiating the NTC effect, and generating a gradient cycle effect of temperature rise-resistance decrease-increase, thereby heating the insulating protective sleeve and improving the toughness of the insulating protective sleeve itself at low temperatures. This synergistic effect reduces the occurrence of low-temperature embrittlement of the insulating protective sleeve.

[0046] The present invention has the following technical effects:

[0047] This invention optimizes the conductor, reducing the initial resistance of the conductor at low temperatures, effectively activating the NTC effect, and adjusting the thermal conductivity of the insulation sheath to match the conductor. This reduces the low-temperature embrittlement dwell time of the cable under extremely cold conditions and lowers the high-temperature stable temperature of the cable, effectively inhibiting the low-temperature embrittlement and high-temperature aging of the cable insulation sheath. The intelligent features allow it to be applied to intelligent power distribution systems, extending the service life of the cable in intelligent power distribution systems under extremely cold conditions. Detailed Implementation

[0048] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0049] The graphite powder used in this invention has CAS number 7782-42-5 and was purchased from Zhongke Leiming (Beijing) Technology Co., Ltd.

[0050] Example 1

[0051] A method for preparing a low-temperature resistant cable includes the following steps:

[0052] S1. Conductor preparation:

[0053] (1) Take electrolytic copper (purity ≥99.9%, crushed into small pieces of 10×10mm, melting point 1080℃), electrolytic manganese (purity ≥99.7%, 3×3mm, melting point 1244℃), nickel particles (purity ≥99.9%, 3×3mm, melting point 1453℃), cobalt particles (purity ≥99.9%, 3×3mm, melting point 1495℃), zinc particles (purity ≥99.5%, melting point 419.5℃), tin particles (purity >99%, melting point 240℃), titanium particles (>99%, melting point 1668℃), and graphite powder (particle size 2~6μm, melting point above 3000℃) and vacuum dry them respectively to remove surface moisture and adsorbed gas, and set them aside for later use;

[0054] (2) Copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder were stacked in layers in the following order according to the mass ratio of 85:1.3:2.8:3:1.2:0.6:1.1:5.5. First, under a vacuum of -0.085 MPa, the mixture of oxygen and argon was introduced for 28 min. The oxygen flow rate was 0.04 L / min and the argon flow rate was 0.15 L / min. The temperature was increased to 500℃ at a rate of 6℃ / min and held for 1.5 h. Then, the oxygen was stopped and the temperature was increased to 920℃ at a rate of 16℃ / min and held for 50 min. After the holding period, the temperature was increased to 1220℃ at a rate of 6℃ / min and held for 20 min. After the holding period, the mixture was stirred at 25 rpm for 35 min. Then, the temperature was cooled to 600℃ at a rate of 90℃ / min and then cooled to 420℃ at a rate of 22℃ / min. The mixture was then set aside for later use.

[0055] (3) At 420℃ and under argon protection, the molten alloy was cast into an alloy rod of 8~9mm, then cooled to room temperature, and stretched to a diameter of 0.4~0.6 mm through multiple passes to obtain alloy microwires. The stretching speed of the multiple passes was 130mm / s, and the stretching rate of each pass was 16%.

[0056] (4) Under an argon atmosphere, a nanosilver film was deposited by magnetron sputtering. The working pressure of magnetron sputtering was 0.4 Pa, the sputtering power was 3 kW, the deposition rate was 0.07 nm / s, and the thickness of the deposited film was 190 nm.

[0057] S2. Preparation of Insulating Protective Sleeve

[0058] According to the weight percentages, 90 parts of hydrogenated nitrile rubber (Shore hardness 65A), 22 parts of boron nitride nanosheets, 4 parts of refined paraffin wax, 5 parts of 4-hydroxycyclohexyltrimethoxysilane, 10 parts of ammonium polyphosphate, 13 parts of silicone oil, and 4 parts of methyl methacrylate were mixed in a mixer and extruded through a twin-screw extruder at a melting temperature of 150°C to obtain the rubber sleeve.

[0059] S3. The conductor obtained in step S1 is twisted to form a wire core, and the wire core is wrapped with the rubber sheath prepared in step S2 to obtain a low-temperature resistant cable.

[0060] Comparative Example 1

[0061] Compared to Example 1, in the conductor preparation step, Zn was replaced with an equal amount of Mg, and Sn was not added; the rest of the steps were the same.

[0062] The conductor prepared in Example 1 has a conductivity of 29.4 MS / m, the conductor prepared in Comparative Example 1 has a conductivity of 18.3 MS / m, and the conductor prepared by adding only graphite powder to Cu has a conductivity of 33.7 MS / m.

[0063] The overall change of the cable with temperature:

[0064] (1) Take a conductor of the same length (1m) to be tested, polish it with sandpaper; remove the oxide layer at both ends, wipe it with anhydrous ethanol and let it dry for later use;

[0065] (2) Fix the conductor sample in the calibrated high and low temperature chamber with an insulating clamp to ensure that the sample is suspended (do not contact the chamber wall to avoid thermal conduction error); attach the PT100 temperature sensor to the middle surface of the conductor with high temperature tape (close contact with the conductor), and pass the sensor wire out from the lead hole of the high and low temperature chamber and connect it to the data logger;

[0066] (3) Connect the conductor to the DC resistance tester using the four-terminal method. Set the test temperature points as -40℃, -20℃, 0℃, 25℃, 50℃ and 80℃ respectively. After holding each temperature point for 30 minutes, record the corresponding resistance. Repeat the test 3 times for each temperature point. The relative standard deviation of the 3 repetitions ≤ ±1% is considered to be qualified for repeatability. Then take the average value as the resistance value corresponding to that temperature point.

[0067] The temperature coefficient of resistance (TCR) measures the sensitivity of resistance to temperature changes. The magnitude of the TCR determines whether a conductor can heat up rapidly at low temperatures and whether the temperature rise can be stabilized.

[0068] The change in the temperature coefficient of resistance (TCR) is calculated based on the tested resistance value. The calculation formula is as follows:

[0069]

[0070] Where T1 and T2 are two test temperature points, R T1 and R T2 These are the resistance values ​​corresponding to the temperature, and the test results are shown in Table 1.

[0071] Table 1:

[0072]

[0073] It can be seen that the conductor prepared in Example 1 exhibits a greater rate of resistance change with increasing temperature, while the heat generation gradually decreases with rising temperature. In Comparative Example 1, Mg readily deprives the oxygen source, leading to incomplete oxidation of Mn-Ni-Co. The unoxidized metal reacts with carbon to form high-resistivity carbides, resulting in a higher initial resistance. However, the rate of resistance change is significantly smaller with increasing temperature. This indicates that the NTC effect in Comparative Example 1 is excessively strong, generating too much initial heat. Furthermore, the temperature remains high for an extended period, which not only causes thermal shock to the insulating protective sleeve on the insulating surface, hindering the stability of the insulating protective sleeve structure on the conductor surface, but also accelerates the aging of the insulating protective sleeve due to prolonged exposure to high temperatures.

[0074] During the research and development process, we directly mixed and melted electrolytic copper, electrolytic manganese, nickel, zinc, tin and graphite powder, instead of stacking the components sequentially for smelting. The resulting conductor had extremely low heat generation at low temperatures and excessively high and uncontrollable heat generation at high temperatures, resulting in an uncontrolled NTC effect.

[0075] Comparative Example 2

[0076] Compared with Example 1, no refined paraffin was added in the step of preparing the insulating protective sleeve, and the remaining steps were the same as in Example 1.

[0077] Example 2

[0078] A method for preparing a low-temperature resistant cable includes the following steps:

[0079] S1. Conductor preparation:

[0080] (1) Take electrolytic copper (purity ≥99.9%, crushed into small pieces of 10×10mm, melting point 1080℃), electrolytic manganese (purity ≥99.7%, 3×3mm, melting point 1244℃), nickel particles (purity ≥99.9%, 3×3mm, melting point 1453℃), cobalt particles (purity ≥99.9%, 3×3mm, melting point 1495℃), zinc particles (purity ≥99.5%, melting point 419.5℃), tin particles (purity >99%, melting point 240℃), titanium particles (>99%, melting point 1668℃), and graphite powder (particle size 2~6μm, melting point above 3000℃) and vacuum dry them respectively to remove surface moisture and adsorbed gas, and set them aside for later use;

[0081] (2) Copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder were stacked in layers in the following order according to the mass ratio of 84:1.2:2.5:2.5:1:0.5:1.2:5. First, the mixture was kept at a vacuum of -0.08 MPa for 30 min. Then, a mixture of oxygen and argon was introduced at a flow rate of 0.03 L / min and 0.1 L / min. The temperature was increased to 450℃ at a rate of 5℃ / min and kept at that temperature for 2 h. Then, the oxygen was stopped and the temperature was increased to 900℃ at a rate of 15℃ / min and kept at that temperature for 60 min. After the temperature was kept at that temperature, the temperature was increased to 1250℃ at a rate of 5℃ / min and kept at that temperature for 15 min. After the temperature was kept at that temperature, the mixture was stirred at 20 rpm for 40 min. Then, the temperature was cooled to 580℃ at a rate of 80℃ / min and then cooled to 400℃ at a rate of 20℃ / min. The mixture was then set aside for later use.

[0082] (3) At 400℃ and under argon protection, the molten alloy is cast into an alloy rod of 8~9mm, then cooled to room temperature, and stretched to a diameter of 0.4~0.6mm in multiple passes to obtain alloy microwires. The stretching speed of the multiple passes is 120mm / s, and the stretching rate of each pass is 15%.

[0083] (4) Under an argon atmosphere, a nanosilver film was deposited by magnetron sputtering. The working pressure of magnetron sputtering was 0.3 Pa, the sputtering power was 3 kW, the deposition rate was 0.06 nm / s, and the thickness of the deposited film was 180 nm.

[0084] S2. Preparation of Insulating Protective Sleeve

[0085] According to the weight percentages, 80 parts of hydrogenated nitrile rubber (Shore hardness 65A), 20 parts of boron nitride nanosheets, 3 parts of refined paraffin wax, 3 parts of 4-hydroxycyclohexyltrimethoxysilane, 8 parts of ammonium polyphosphate, 12 parts of silicone oil, and 3 parts of methyl methacrylate were mixed in a mixer and extruded through a twin-screw extruder at a melting temperature of 140°C to obtain the rubber sleeve.

[0086] S3. The conductor obtained in step S1 is stranded according to requirements to form a wire core. The wire core is then wrapped with the sheath prepared in step S2 to obtain a low-temperature resistant cable.

[0087] Example 3

[0088] A method for preparing a low-temperature resistant cable includes the following steps:

[0089] S1. Conductor preparation:

[0090] (1) Take electrolytic copper (purity ≥99.9%, crushed into small pieces of 10×10mm, melting point 1080℃), electrolytic manganese (purity ≥99.7%, 3×3mm, melting point 1244℃), nickel particles (purity ≥99.9%, 3×3mm, melting point 1453℃), cobalt particles (purity ≥99.9%, 3×3mm, melting point 1495℃), zinc particles (purity ≥99.5%, melting point 419.5℃), tin particles (purity >99%, melting point 240℃), titanium particles (>99%, melting point 1668℃), and graphite powder (particle size 2~6μm, melting point above 3000℃) and vacuum dry them respectively to remove surface moisture and adsorbed gas, and set them aside for later use;

[0091] (2) Copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder were stacked in layers in the following order according to the mass ratio of 86:1.5:3.5:4:1.5:0.8:1.0:6. First, the mixture was kept at a vacuum of -0.09 MPa for 25 min. Then, a mixture of oxygen and argon was introduced at a flow rate of 0.05 L / min and 0.2 L / min. The temperature was increased to 550℃ at 10℃ / min and kept at that temperature for 1 h. Then, the oxygen was stopped and the temperature was increased to 950℃ at a rate of 20℃ / min and kept at that temperature for 30 min. After the temperature was kept at that temperature, the temperature was increased to 1200℃ at a rate of 8℃ / min and kept at that temperature for 25 min. After the temperature was kept at that temperature, the mixture was stirred at 30 rpm for 30 min. Then, the temperature was cooled to 620℃ at a rate of 100℃ / min and then cooled to 450℃ at a rate of 25℃ / min. The mixture was then set aside for later use.

[0092] (3) At 450℃ and under argon protection, the molten alloy is cast into an alloy rod of 8~9mm, then cooled to room temperature, and stretched to a diameter of 0.4~0.6mm in multiple passes to obtain alloy microwires. The stretching speed of the multiple stretching passes is 150mm / s, and the stretching rate of each pass is 20%.

[0093] (4) Under an argon atmosphere, a nanosilver film was deposited by magnetron sputtering. The working pressure of magnetron sputtering was 0.5 Pa, the sputtering power was 3 kW, the deposition rate was 0.08 nm / s, and the thickness of the deposited film was 200 nm.

[0094] S2. Preparation of Insulating Protective Sleeve

[0095] According to the weight percentages, 100 parts of hydrogenated nitrile rubber (Shore hardness 65A), 25 parts of boron nitride nanosheets, 5 parts of refined paraffin wax, 6 parts of 4-hydroxycyclohexyltrimethoxysilane, 12 parts of ammonium polyphosphate, 15 parts of silicone oil, and 5 parts of methyl methacrylate were mixed in a mixer and extruded through a twin-screw extruder at a melting temperature of 160°C to obtain a rubber sleeve.

[0096] S3. The conductor obtained in step S1 is stranded according to requirements to form a wire core. The wire core is then wrapped with the rubber sheath prepared in step S2 to obtain a low-temperature resistant cable.

[0097] Cable surface temperature change test under constant voltage:

[0098] Cables of equal length prepared for each embodiment and comparative example were placed in a high and low temperature test chamber and adjusted to a constant low temperature of -40℃±0.5℃. The wind speed was 0.5±0.1m / s to simulate a light outdoor breeze. A constant voltage of 24V was applied to the cable, and a PT100 sensor was fixed to the cable surface. The temperature change of the cable insulation sheath surface was tested and recorded (tested once every 1 minute). When the temperature reached -10℃, the total time was recorded (-40~-10℃ is the embrittlement dwell time). The temperature change was recorded every 1 minute. When the temperature reached 50℃, the total time was recorded again. The test was continued at the same frequency until the temperature fluctuation of the cable surface was ≤1℃ within 10 minutes. This was considered to have reached the high temperature stability temperature. After that, the surface temperature of the insulation sheath was recorded at a test frequency of 30 minutes / test for 24 hours. The long-term stability of the cable was tested by observing the temperature fluctuation of the cable surface throughout the entire test cycle.

[0099] Standardized cable parameters: cable test length: 1m; insulation sheath thickness: 1mm; conductor cross-sectional area: 1mm². The results are shown in Table 2.

[0100] Table 2:

[0101]

[0102] It can be seen that the cables in the various embodiments of the present invention have a shorter embrittlement time at -140~-10℃. After reaching the high temperature stability temperature, the temperature fluctuation within 24 hours is as low as ±1℃. In contrast, although the embrittlement time in Comparative Example 1 is shorter, the high temperature stability time is higher. The low temperature embrittlement time of the cable in Comparative Example 2 is longer. After reaching the high temperature stability temperature, the temperature fluctuation range of Comparative Example 1 and Comparative Example 2 is larger.

[0103] Insulation protective sleeve toughness change test:

[0104] (1) Low-temperature embrittlement toughness test: Take the insulating protective sleeves from each example and comparative example, cut them into standard impact strips (strip size: length 80mm × width 10mm × thickness 4mm), place the strips in a -40℃ low-temperature bath for 30min, and then take them out for rapid impact testing. Test according to GB / T1842-2020 "Thermoplastic Plastics Low-Temperature Impact Test Method", and record the impact toughness (KJ / m) of each strip. 2 Each group of tests consists of 3 splines, and the average value is taken.

[0105] (2) High-temperature aging toughness test: Take the insulating protective sleeves from each example and comparative example, cut them into dumbbell-shaped standard strips, place the strips in an 80℃ oven for 72h for aging, then take them out and test the tensile properties after high-temperature aging according to GB / T528-2009, and record the elongation at break and tensile strength. And calculate the retention rate of elongation at break and the retention rate of tensile strength (retention rate = performance after aging / performance before aging × 100%).

[0106] Bonding strength test after thermal cycling:

[0107] (1) Take a cable sample with a length of 50mm, with 5mm of conductor exposed at one end and an insulating protective sleeve at the other end. Use a tensile testing machine to hold the conductor at one end and the insulating protective sleeve at the other end, peel the insulating sleeve along the axial direction at 100mm / min, and record the initial peel strength (N / mm).

[0108] (2) Take another identical cable sample and perform a cycle of first heating at -40℃ for 2 hours, then heating to 80℃ and heating for 2 hours, for a total of 50 cycles. After the temperature transition time is ≤5 minutes, perform a peel test using the method in step (1), record the cyclic peel strength, and calculate the cyclic peel strength retention rate (retention rate = performance after cycle / performance before cycle × 100%). The results are shown in Table 3. The cross-sectional area of ​​the core in the above-tested cables is 1 mm². 2 .

[0109] Table 3:

[0110]

[0111] It can be seen that the insulating protective sleeves prepared in each embodiment exhibit relatively small temperature variations in toughness, elongation at break, and tensile strength, indicating that they possess excellent mechanical stability during temperature changes, resisting low-temperature embrittlement and thermal aging caused by temperature variations. After 50 cycles of thermal cycling from -40℃ to 80℃, their glass strength retention rate remains at approximately 85%. In Comparative Example 1, although the insulating protective sleeve is the same as in the embodiments, the use of Mg instead of Zn in the internal conductor, and the absence of Sn, leads to an increased difference in CTE between the conductor and the insulating protective sleeve. This results in reduced low-temperature shrinkage of the conductor, causing the insulating protective sleeve to develop microcracks under tension. Impact causes rapid crack propagation, leading to a decrease in mechanical properties such as toughness. Due to the increased difference in CTE between the conductor and the insulating protective sleeve, the accumulated stress at the interface exceeds the bonding strength threshold after multiple thermal cycles, resulting in damage to the interfacial bond and a decrease in peel strength. In Comparative Example 2, the insulating sleeve's heat dissipation mechanism cannot match temperature changes, causing its mechanical properties to degrade significantly with temperature changes. After 50 cycles of thermal cycling, its peel strength retention rate is as low as 65.0%.

Claims

1. A method for preparing a low-temperature resistant cable, characterized in that, Includes the following steps: S1. A molten alloy was prepared by using copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder in a mass ratio of 84~86:1.2~1.5:2.5~3.5:2.5~4:1~1.5:0.5~0.8:1.0~1.2:5~6. The alloy was then cast and stretched to form alloy microwires. A conductor was then obtained by depositing a nano-silver film on the surface of the alloy microwires. S2. An insulating protective sleeve is prepared by mixing and melting 80-100 parts of hydrogenated nitrile rubber, 20-25 parts of boron nitride nanosheets, 3-5 parts of refined paraffin wax, 3-6 parts of 4-hydroxycyclohexyltrimethoxysilane, 8-12 parts of ammonium polyphosphate, 12-15 parts of silicone oil, and 3-5 parts of methyl methacrylate, according to the weight percentage. S3. The conductor obtained in step S1 is stranded according to requirements to form a wire core. The sheath prepared in S2 is then wrapped around the wire core to obtain a low-temperature resistant cable.

2. The method for preparing a low-temperature resistant cable as described in claim 1, characterized in that: In step S1, the molten alloy is prepared by mixing copper, manganese, nickel, cobalt, zinc, tin, titanium, and graphite powder, maintaining the mixture under a vacuum of -0.08 to -0.09 MPa for 25 to 30 minutes, introducing a mixture of oxygen and argon, and holding the mixture at 450 to 550°C. After stopping the oxygen supply, the mixture is then held at 900 to 950°C and 1200 to 1250°C in stages to obtain the molten alloy. The oxygen flow rate is 0.03 to 0.05 L / min, and the argon flow rate is 0.1 to 0.2 L / min.

3. The method for preparing a low-temperature resistant cable as described in claim 2, characterized in that: The segmented heat preservation process involves heating the gas to 450-550°C at a rate of 5-10°C / min under a mixed atmosphere of oxygen and argon, holding it for 1-2 hours, then stopping the oxygen supply, heating the gas to 900-950°C at a rate of 15-20°C / min, holding it for 30-60 minutes, heating the gas to 1200-1250°C at a rate of 5-8°C / min, holding it for 15-25 minutes, stirring the gas at 20-30 rpm for 30-40 minutes, cooling the gas to 580-620°C at a rate of 80-100°C / min, and then cooling the gas to 400-450°C at a rate of 20-25°C / min for later use.

4. A method for preparing a low-temperature resistant cable as described in any one of claims 1-3, characterized in that: The casting and stretching process involves casting the molten alloy into an 8-9 mm alloy rod at 400-450°C under argon protection, then cooling it to room temperature and stretching it multiple times to a diameter of 0.4-0.6 mm to obtain alloy microwires.

5. The method for preparing a low-temperature resistant cable as described in claim 4, characterized in that: The stretching speed of the multi-pass stretching is 120~150mm / s, and the stretching rate of each pass is 15~20%.

6. The method for preparing a low-temperature resistant cable as described in claim 5, characterized in that: The deposited silver nanofilm was deposited using magnetron sputtering, specifically under an argon atmosphere, with a working pressure of 0.3~0.5 Pa, a sputtering power of 3 kW, a deposition rate of 0.06~0.08 nm / s, and a film thickness of 180~200 nm.

7. A method for preparing a low-temperature resistant cable, characterized in that, Includes the following steps: S1. Conductor preparation: (1) Copper, manganese, nickel, cobalt, zinc, tin, titanium and graphite powder are stacked in layers according to the following order and the mass ratio is 84~86:1.2~1.5:2.5~3.5:2.5~4:1~1.5:0.5~0.8:1.0~1.2:5~6. Under a vacuum of -0.08~-0.09 MPa, the mixture is kept for 25~30 min. A mixture of oxygen and argon is introduced, with the oxygen flow rate at 0.03~0.05 L / min and the argon flow rate at 0.1~0.2 L / min. The temperature is increased at a rate of 5~10℃ / min. The temperature is raised to 450-550℃ and held for 1-2 hours. Then, the oxygen supply is stopped, and the temperature is raised to 900-950℃ at a rate of 15-20℃ / min and held for 30-60 minutes. After holding, the temperature is raised to 1200-1250℃ at a rate of 5-8℃ / min and held for 15-25 minutes. After holding, the temperature is stirred at 20-30 rpm for 30-40 minutes. Then, the temperature is cooled to 580-620℃ at a rate of 80-100℃ / min, and then cooled to 400-450℃ at a rate of 20-25℃ / min. The mixture is then set aside for later use. (2) At 400~450℃ and under argon protection, the molten alloy is cast into an alloy rod of 8~9mm, then cooled to room temperature, and stretched to a diameter of 0.4~0.6mm in multiple passes to obtain alloy microwires. The stretching speed of the multiple stretching passes is 120~150mm / s, and the stretching rate of each pass is 15~20%. (3) Under an argon atmosphere, a nanosilver film was deposited by magnetron sputtering. The working pressure of magnetron sputtering was 0.3~0.5Pa, the sputtering power was 3kW, the deposition rate was 0.06~0.08nm / s, and the thickness of the deposited film was 180~200nm. S2. Preparation of insulating protective sleeve: According to the weight percentages, 80-100 parts of hydrogenated nitrile rubber, 20-25 parts of boron nitride nanosheets, 3-5 parts of refined paraffin wax, 3-6 parts of 4-hydroxycyclohexyltrimethoxysilane, 8-12 parts of ammonium polyphosphate, 12-15 parts of silicone oil, and 3-5 parts of methyl methacrylate are mixed in a mixer and extruded through a twin-screw extruder at a melting temperature of 140-160℃ to obtain a rubber sleeve. S3. Cable preparation: The conductor obtained in step S1 is stranded according to requirements to form a wire core. The wire core is then wrapped with the rubber sheath prepared in step S2 to obtain a low-temperature resistant cable.

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