Highly conductive insulated halogen-free fireproof special cable and preparation method and application thereof

Abstract

The application discloses a kind of high-conductivity insulation halogen-free fireproof special cable and its preparation method and application, belong to cable manufacturing technical field.Cable is from inside to outside by composite conductor layer, inner wrapping tape layer, inner insulation layer, outer insulation layer, shielding layer, outer wrapping tape layer and sheath layer composition;Composite conductor layer is formed by the stranding of multiple composite conductor filaments;Composite conductor filament is from inside to outside by three layers, respectively as: core copper, inner surface layer and outer surface layer;Inner surface layer is 18-32nm thick amorphous-nanocrystalline composite copper layer;Outer surface layer is 35-78nm thick graphene layer.The cable of the application has high conductivity, strong insulation and fire resistance, non-toxic fire resistance and other characteristics.The preparation method of the application significantly improves the conductivity, mechanical strength and high-temperature stability of the conductor through thermal-magnetic-optical multi-field coupling.

Description

Technical Field

[0001] This invention relates to a high-conductivity, insulated, halogen-free, fire-resistant special cable, its preparation method, and its application, belonging to the field of cable manufacturing technology. Background Technology

[0002] With increasingly stringent global requirements for environmental protection and safety, the application of special cables in these fields has shifted from "optional" to "essential." Against the backdrop of increasingly dense rail transit networks, ever-growing ship tonnage, and rapid advancements in aerospace technology, the performance improvement and widespread application of special cables have become crucial links in ensuring national and public safety.

[0003] Specialty cables, as a key transmission medium in modern high-tech fields, play an irreplaceable role in applications such as high-speed rail transit, large ships, and aerospace. In the high-speed rail transit sector, the fire safety requirements for cables in enclosed spaces such as subways and high-speed railways are extremely high. Traditional cables, once in fire, release large amounts of toxic fumes, seriously threatening passenger safety. Low-smoke halogen-free specialty cables, due to their low smoke density and lack of toxic gas production during combustion, have become the preferred choice for rail transit systems, effectively extending evacuation time and buying valuable time for emergency rescue.

[0004] Despite continuous improvements in high conductivity, insulation, halogen-free properties, and fire resistance, special cables still have many shortcomings in practical applications. Regarding high conductivity, traditional copper conductors are limited by their conductivity properties and are heavy and prone to oxidation, making it difficult to meet the lightweight and long-life requirements of the aerospace industry. In terms of insulation, the insulation layer of existing special cables is prone to degradation under high temperature, high humidity, and strong electromagnetic interference environments, leading to signal distortion or increased short-circuit risks. Insulation materials are prone to aging under extreme temperature changes, significantly shortening their service life and increasing maintenance costs and safety hazards. The inadequacy of halogen-free performance is mainly reflected in the fact that some low-smoke halogen-free cables still produce small amounts of harmful substances when burning, and although the smoke density is low, there is still clearly visible smoke, affecting visibility and breathing. Especially in enclosed spaces, even with reduced smoke density, long-term accumulation of smoke still poses a health threat to personnel. Regarding fire resistance, although existing flame-retardant cables can effectively suppress flame spread, under extreme high-temperature environments (such as above 750°C), the fire resistance of some cables is still insufficient, making it difficult to maintain line integrity for more than 90 minutes.

[0005] Therefore, those skilled in the art urgently need to develop a high-conductivity, insulated, halogen-free, fire-resistant special cable and its preparation method to solve the above problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-conductivity, insulated, halogen-free, fire-resistant special cable with high conductivity, strong insulation and fire resistance, and non-toxicity and fire resistance.

[0007] Meanwhile, this invention provides a method for preparing a high-conductivity, insulated, halogen-free, fire-resistant special cable. This method significantly improves the conductivity, mechanical strength, and high-temperature stability of the conductor through multi-field coupling of heat, force, magnetism, and light.

[0008] Meanwhile, this invention provides an application of a high-conductivity, insulated, halogen-free, fire-resistant special cable.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0010] A high-conductivity, insulated, halogen-free, fire-resistant special cable is composed of a composite conductor layer, an inner wrapping layer, an inner insulation layer, an outer insulation layer, a shielding layer, an outer wrapping layer, and a sheath layer from the inside out.

[0011] A method for manufacturing a high-conductivity, insulated, halogen-free, fire-resistant special cable mainly includes the following six steps:

[0012] S1. Single-wire preparation: Composite conductor single wires were prepared by continuous stretching-rapid quenching, multi-field coupling assisted stepwise plastic deformation, LT-CVD, and online annealing.

[0013] S2. Bundling: multiple composite conductor filaments are twisted together according to a set pattern to form a composite conductor.

[0014] S3. First wrapping: Wrap phlogopite tape around the stranded composite conductor to obtain an inner wrapping layer.

[0015] S4. Insulation Extrusion: The inner insulation layer, the outer insulation layer, and the shielding layer are simultaneously extruded using a double co-extrusion process.

[0016] S5. Secondary wrapping: A ceramicized silicone rubber tape is wrapped around the outside of the shielding layer to obtain an outer wrapping layer.

[0017] S6. Sheath extrusion: extrusion of halogen-free low-smoke polyolefin sheaths.

[0018] The halogen-free low-smoke polyolefin sheath is made by high-temperature hot extrusion of halogen-free low-smoke polyolefin particles.

[0019] Preferably, the preparation of monofilaments in S1 includes:

[0020] S11. Continuous casting of copper rods. Raw material: TU1 oxygen-free copper; rod diameter: φ3-25 mm; casting speed: 0.8–1.2 m / min. -1 Cooling water for the crystallizer: 18–22 °C.

[0021] S12. The copper rod prepared in S11 is drawn to the target diameter (0.033-2.76 mm) through a multi-stage wire drawing die. He-N2 (volume ratio 7:3) mixed spray cooling is applied at the die exit point. The spray pressure is 0.35-0.55 MPa, and the cooling rate is ≥1×10⁻⁶. 6 K / s.

[0022] S13. The monofilament obtained in S12 is subjected to multi-field coupled assisted stepwise plastic deformation under the positioning of guide rollers. This process comprehensively applies radial mechanical pressure, synchronous heating, pulsed magnetic field, and laser irradiation. The specific process parameters are as follows:

[0023] Radial pressure range: 1.5-2.1 GPa, 2.3-2.6 GPa, 2.8-3.2 GPa, applied in three steps, each holding pressure for 2–5 seconds;

[0024] Heating assistance: During the deformation process, 1-20 kHz medium-frequency induction heating is applied simultaneously, and the temperature is controlled at 200-350℃ to promote dynamic recrystallization and amorphization transformation.

[0025] Pulsed magnetic field assistance: A pulsed magnetic field with an intensity of 0.5–1.2 T and a frequency of 10–50 Hz is applied to the deformation zone to suppress grain growth and induce grain boundary pinning;

[0026] Laser irradiation assistance: The surface of the filament is synchronously scanned and irradiated with a 1064-1070 nm fiber laser at a power density of 0.5–2.0 kW / cm² and a scanning speed of 0.5–1.5 m / s to promote the formation of amorphization and nanocrystalline composite structures on the surface.

[0027] Deformation rate: 0.8–1.5 m / min, ensuring uniform strain and structural gradient evolution.

[0028] S14. Graphene was deposited on the surface of the conductor monofilament obtained in S13 using LT-CVD (low-temperature chemical vapor deposition) at a temperature of 400–600 °C, with a carbon source of ethylene and a flow rate of 10–30 sccm. The atmosphere was a mixture of argon and hydrogen (1:1 ratio), and the growth time was 15–90 min.

[0029] S15. Perform nitrogen annealing at 300-350℃ to passivate the graphene layer.

[0030] Preferably, in S1, the monofilament is prepared from the inside out and consists of three layers: a core copper layer, an inner surface layer (an amorphous-nanocrystalline composite copper layer with a thickness of 18-32 nm), and an outer surface layer (a graphene layer with a thickness of 35-78 nm).

[0031] Preferably, in S2, the stranding speed is set to 35-45 m / min, a right-hand stranding method is adopted, and the diameter tolerance of the stranded conductor is controlled within ±0.1 mm.

[0032] Preferably, in S3, the first wrapping adopts an overlapping wrapping method, with 2–3 layers, and the wrapping tension is controlled at 5–15 N.

[0033] Preferably, in S4, the insulating material is halogen-free cross-linked polyethylene (XLPE), the insulation thickness must meet the nominal value, and the extrusion temperature is controlled in stages: feeding stage 120–140℃, compression stage 150–170℃, homogenization stage 160–180℃.

[0034] Specifically, in S4, the process for insulating extrusion is as follows: Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material is dried at 150-170°C for 20-24 hours to remove moisture.

[0035] Plasticizing extrusion: Solid particles are gradually melted in the screw extruder through the feeding section, compression section and homogenization section (feeding section 120–140℃, compression section 150–170℃, homogenization section 160–180℃), and then coated with conductors through the die head, continuously coating the inner and outer insulation layers.

[0036] Cooling and setting: After extrusion, the insulation layer is cooled and cured in a water bath.

[0037] Then, a shielding layer is wrapped around the outer surface of the outer insulation layer.

[0038] The inner and outer insulation layers are both made of XLPE, and the shielding layer is made of aluminum foil / copper foil strip or wire.

[0039] The shielding materials include copper, aluminum, tin-plated copper wire, etc., and specific forms include metal braided mesh, aluminum foil / copper foil strip (usually with a layer of polyester or plastic substrate attached to enhance strength), and combined shielding (foil layer + braided mesh); the present invention uses a set of molds to continuously extrude two insulating layers, and then wraps the shielding layer.

[0040] Preferably, in S5, the secondary wrapping adopts 1-2 overlapping wrapping layers, with a wrapping angle of 30–45° and a tension of 10–20 N.

[0041] Preferably, the extrusion temperature of the S6 sheath is controlled at 160–170℃, the screw speed is 20–22 r / min, the traction speed is 50–100 m / min, and it is quickly shaped by water cooling tank (water temperature 20–30℃).

[0042] Preferably, in S13, the stepwise plastic deformation is multi-field coupled assisted stepwise plastic deformation (MF-SPD).

[0043] A high-conductivity, insulated, halogen-free, fire-resistant special cable is used in high-speed rail transportation, large ships, aerospace and other fields.

[0044] The present invention provides a high-conductivity, insulated, halogen-free, fire-resistant special cable with a conductor DC resistance of 0.0146-0.0199 MΩ / km at 20℃, a dielectric strength of 67-82 kV, an insulation resistance of 6970-8864 MΩ·km at 20℃, and a distance of 221-276 mm from the lower edge of the upper clamp when a single cable is vertically burned downwards. No hydrogen halide content was detected in the insulation layer or the sheath layer when the cable was burning.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] The cable of this invention features a multi-scale gradient heterostructure of "copper core-amorphous / nanocrystalline hybrid layer-graphene". Its synergistic effect is not a simple superposition of functions, but rather a fundamental optimization of core processes such as electron transport, phonon propagation, and atomic diffusion through precise control of the interfacial physicochemical state.

[0047] 1. Synergistic regulation of electron transport (high conductivity):

[0048] Band engineering and interface state passivation: Nanocrystalline copper, acting as an "electron highway," provides highly delocalized electron channels through its regular lattice, resulting in a high density of electronic states and high conductivity near the Fermi level. The key role of the amorphous copper phase is to fill and passivate the interface states between nanocrystals. These interface states are typically the centers and barriers to electron scattering. By forming coherent or semi-coherent interfaces, the amorphous phase significantly reduces the defect state density at the interface, decreasing diffuse electron scattering and enabling electrons to "tunnel" or "jump" more efficiently between grains.

[0049] Charge redistribution and ohmic contact in graphene: When graphene comes into contact with a hybrid layer, charge transfer occurs due to the difference in their work functions, forming a space charge region at the interface and inducing band bending, thus creating an ideal ohmic contact and greatly reducing contact resistance. Simultaneously, graphene's extremely high carrier mobility provides electrons on its surface with a nearly unobstructed lateral movement path, effectively increasing the effective surface area of ​​the conductor and further reducing overall impedance.

[0050] 2. Synergistic blocking of phonon and ion transport (strong insulation and fire resistance):

[0051] Multi-interface phonon scattering and thermal management: The key to improving insulation lies in suppressing the migration of charge carriers (such as copper ions and electrons). Numerous grain boundaries / phase boundaries within the hybrid layer, as well as the heterogeneous interface between the hybrid layer and graphene, constitute an extremely complex phonon scattering network. Phonons (quanta of lattice vibrations) are the primary carriers of heat energy transfer. These interfaces strongly scatter mid-to-high frequency phonons, significantly reducing the material's thermal conductivity (an advantage for insulation). This makes it difficult for sustained heat accumulation to form in localized hot spots, thermodynamically delaying the thermal breakdown process of the insulating medium.

[0052] The labyrinth effect and pinning effect of atomic diffusion: Under high temperature or electric field, copper ions / atoms tend to diffuse rapidly along grain boundaries (Kirkendall effect), leading to insulation degradation. Amorphous phases form continuous networks; their short-range ordered, long-range disordered structure itself acts as a high-energy barrier for atomic diffusion. Nanocrystals, like "islands" embedded in the amorphous matrix, effectively pinnify grain boundaries and block diffusion channels. Graphene, as the ultimate barrier, has a high sp... 2 The dense and chemically inert hybrid carbon ring structure physically prevents copper atoms from escaping and oxygen / water molecules from penetrating inward. These three factors together form a "maze," greatly extending the diffusion path and enhancing the intrinsic stability of the material.

[0053] 3. Interfacial reaction and self-protection at high temperatures (non-toxic and refractory):

[0054] Selective oxidation and densification: Refractoriness involves phase transformations and chemical reactions at high temperatures. Due to its uniform microstructure, amorphous copper tends to form a continuous, dense, and strongly adhered CuO protective layer (rather than porous Cu2O) during high-temperature oxidation. This oxide layer effectively prevents further oxidation of the internal copper and inhibits the generation of highly toxic Cu2O dust. The presence of nanocrystals refines this oxide film, making it less prone to cracking and peeling.

[0055] The solid-state carbon source effect of graphene: In a flame, the graphene layer is not simply ablated. It reacts with diffused oxygen or undergoes a structural transformation to form a sp2-rich layer. 3 A glassy carbon protective layer. This carbon layer is robust, isolating oxygen and heat, protecting the structure beneath. Simultaneously, graphene's high thermal conductivity quickly disperses hotspots, preventing the formation of lethal localized high temperatures and buying time for the aforementioned protective mechanism to take effect.

[0056] This invention achieves precise control over the microstructure of copper monofilaments through multi-field coupling of thermo-mechanical-magnetic-optical fields. Specifically:

[0057] Stepped high pressure promotes the accumulation of large strain, inducing grain refinement and the formation of amorphous phases;

[0058] Medium-frequency heating reduces deformation resistance and promotes dynamic recovery and the formation of amorphous-nanocrystalline composite structures;

[0059] Pulsed magnetic fields suppress grain boundary migration, enhance grain boundary pinning effect, and improve thermal stability;

[0060] Laser irradiation provides surface energy injection, promoting interfacial compatibility between surface amorphization and subsequent graphene layer growth.

[0061] This composite process is not a conventional method of intense plastic deformation. Its synergistic effect significantly improves the conductivity, mechanical strength and high-temperature stability of the conductor, and has outstanding non-obviousness and technical effect. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the cable structure of the present invention;

[0063] Figure 2 This is a microstructure diagram of the cable conductor of the present invention;

[0064] Figure 3 This is the microstructure of the hybrid layer of the cable conductor of the present invention. Detailed Implementation

[0065] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0066] A method for manufacturing a high-conductivity, insulated, halogen-free, fire-resistant special cable mainly includes the following six steps:

[0067] S1. Single-wire preparation: Composite conductor single wires were prepared by continuous stretching-rapid quenching, multi-field coupling assisted stepwise plastic deformation, LT-CVD, and online annealing.

[0068] Specifically, S11. The copper rod is prepared by continuous casting. Raw material: TU1 oxygen-free copper; rod diameter: φ8 mm; casting speed: 1.0 m / min. -1 The cooling water for the crystallizer is 20 °C.

[0069] S12. The copper rod prepared in S11 is drawn to the target diameter (1.00 mm) through a multi-stage wire drawing die. He-N2 (volume ratio 7:3) mixed spray cooling is applied at the die exit point. The spray pressure is 0.45 MPa, and the cooling rate is 1×10⁻⁶. 6 K / s.

[0070] S13. The monofilament obtained in S12 is subjected to multi-field coupled assisted stepwise plastic deformation under the positioning of guide rollers. This process comprehensively applies radial mechanical pressure, synchronous heating, pulsed magnetic field, and laser irradiation. The specific process parameters are as follows:

[0071] Radial pressure range: 1.8 GPa, 2.5 GPa, 3.0 GPa applied in three steps, each holding pressure for 3 seconds;

[0072] Heating assistance: During the deformation process, 10kHz medium-frequency induction heating is applied simultaneously, and the temperature is controlled at 250℃ to promote dynamic recrystallization and amorphization transformation.

[0073] Pulsed magnetic field assistance: A pulsed magnetic field with an intensity of 0.9 T and a frequency of 30 Hz is applied to the deformation zone to suppress grain growth and induce grain boundary pinning;

[0074] Laser irradiation assistance: The surface of the filament is synchronously scanned and irradiated with a 1064nm fiber laser at a power density of 1.0 kW / cm² and a scanning speed of 1.0 m / s to promote the formation of amorphization and nanocrystalline composite structures on the surface.

[0075] Deformation rate: 1.0 m / min, ensuring uniform strain and structural gradient evolution.

[0076] S14. Graphene was deposited on the surface of the conductor monofilament obtained in S13 using the LT-CVD (low-temperature chemical vapor deposition) method. Temperature: 500℃; carbon source: ethylene, flow rate: 20 sccm; atmosphere: argon / hydrogen mixture (ratio 1:1); growth time: 60 min.

[0077] S15. Perform nitrogen annealing at 325℃ to passivate the graphene layer.

[0078] Preferably, in S1, the monofilament is prepared from the inside out and consists of three layers: a core copper layer, an inner surface layer (an amorphous-nanocrystalline composite copper layer with a thickness of about 25 nm), and an outer surface layer (a graphene layer with a thickness of about 50 nm).

[0079] S2. Wire Stranding: Multiple composite conductor filaments are stranded into a composite conductor according to a set pattern. The stranding speed is set at 40 m / min, and a right-hand stranding method is used. The diameter tolerance of the stranded conductor is controlled within ±0.1 mm.

[0080] S3. Initial Wrapping: Wrap phlogopite tape around the stranded composite conductor to obtain an inner wrapping layer. The initial wrapping uses an overlapping wrapping method, with two layers, and the wrapping tension is controlled at 10N.

[0081] S4. Insulation Extrusion: The inner insulation layer, the outer insulation layer, and the shielding layer are simultaneously extruded using a double co-extrusion process.

[0082] Specifically, the insulation material is halogen-free cross-linked polyethylene (XLPE), the insulation thickness must meet the nominal value, and the extrusion temperature is controlled in stages: 130℃ in the feeding stage, 160℃ in the compression stage, and 170℃ in the homogenization stage.

[0083] Specifically, in S4, the process for insulating extrusion is as follows: Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material is dried at 160°C for 22 hours to remove moisture.

[0084] Plasticizing extrusion: Solid particles are gradually melted in the screw extruder through the feeding section, compression section and homogenization section (feeding section 130℃, compression section 160℃, homogenization section 170℃), and then coated with conductors through the die head, continuously coating the inner and outer insulation layers.

[0085] Cooling and setting: After extrusion, the insulation layer is cooled and cured in a water bath.

[0086] Then, a shielding layer is wrapped around the outer surface of the outer insulation layer.

[0087] Both the inner and outer insulation layers are made of XLPE, and the shielding layer is made of a metal woven mesh formed from aluminum foil strips.

[0088] S5. Secondary wrapping: A ceramicized silicone rubber tape is wrapped around the outside of the shielding layer to obtain an outer wrapping layer. The secondary wrapping uses two overlapping layers, with a wrapping angle of 30° and a tension of 15 N.

[0089] S6. Sheath Extrusion: Extrusion of halogen-free low-smoke polyolefin sheaths. The halogen-free low-smoke polyolefin sheaths are produced by high-temperature hot extrusion of halogen-free low-smoke polyolefin granules. The extrusion temperature of the S6 sheath is controlled at 165℃, the screw speed is 21r / min, the traction speed is 80m / min, and it is rapidly shaped through a water-cooling tank (water temperature 25℃).

[0090] A high-conductivity, insulated, halogen-free, fire-resistant special cable is used in high-speed rail transportation, large ships, aerospace and other fields.

[0091] like Figure 1 As shown in the figure, the high-conductivity insulated halogen-free fireproof special cable of this embodiment is composed of a composite conductor layer, an inner wrapping layer, an inner insulation layer, an outer insulation layer, a shielding layer, an outer wrapping layer, and a sheath layer from the inside out.

[0092] like Figure 2 As shown, the microstructure of a single filament of a cable conductor consists of three layers from the inside out: a copper core, an inner surface layer (amorphous / nanocrystalline hybrid layer), and an outer surface layer (graphene layer).

[0093] like Figure 3As shown in the figure, the surface of the copper conductor single wire has an "amorphous / nanocrystalline mixed layer," in which the islands are nanocrystalline. The selected area diffraction pattern of the area under transmission electron microscopy shows a clear two-dimensional lattice arrangement with obvious symmetry. After calibration, the crystal planes include (220), (202), etc., and their size is at the nanometer level, so it is a nanocrystalline structure. The selected area diffraction pattern of the structure around the islands under transmission electron microscopy shows diffuse concentric rings with a bright transmission spot in the center, surrounded by blurry, continuous diffraction rings without sharp structures, indicating that the structure is amorphous. Example 2

[0094] A method for manufacturing a high-conductivity, insulated, halogen-free, fire-resistant special cable mainly includes the following six steps:

[0095] S1. Single-wire preparation: Composite conductor single wires were prepared by continuous stretching-rapid quenching, multi-field coupling assisted stepwise plastic deformation, LT-CVD, and online annealing.

[0096] Specifically, S11. The copper rod is prepared by continuous casting. Raw material: TU1 oxygen-free copper; rod diameter: φ3 mm; casting speed: 0.8 m / min. -1 The cooling water for the crystallizer is 18 °C.

[0097] S12. The copper rod prepared in S11 is drawn to the target diameter (0.033 mm) through a multi-stage wire drawing die. He-N2 (volume ratio 7:3) mixed spray cooling is applied at the die exit point. The spray pressure is 0.35 MPa, and the cooling rate is 1.5 × 10⁻⁶. 6 K / s.

[0098] S13. The monofilament obtained in S12 is subjected to multi-field coupled assisted stepwise plastic deformation under the positioning of guide rollers. This process comprehensively applies radial mechanical pressure, synchronous heating, pulsed magnetic field, and laser irradiation. The specific process parameters are as follows:

[0099] Radial pressure range: 1.5GPa, 2.3GPa, 2.8GPa applied in three steps, each held for 2 seconds;

[0100] Heating assistance: During the deformation process, 1kHz mid-frequency induction heating is applied simultaneously, and the temperature is controlled at 200℃ to promote dynamic recrystallization and amorphization transformation.

[0101] Pulsed magnetic field assistance: A pulsed magnetic field with an intensity of 0.5 T and a frequency of 10 Hz is applied to the deformation zone to suppress grain growth and induce grain boundary pinning;

[0102] Laser irradiation assistance: A 1065nm fiber laser is used to synchronously scan and irradiate the surface of the wire material with a power density of 0.5 kW / cm² and a scanning speed of 0.5 m / s to promote the formation of amorphization and nanocrystalline composite structures on the surface.

[0103] Deformation rate: 0.8 m / min, ensuring uniform strain and structural gradient evolution.

[0104] S14. Graphene was deposited on the surface of the conductor monofilament obtained in S13 using the LT-CVD (low-temperature chemical vapor deposition) method. Temperature: 400℃; carbon source: ethylene, flow rate 10 sccm; atmosphere: argon / hydrogen mixture (ratio 1:1); growth time: 15 min.

[0105] S15. Perform nitrogen annealing at 300℃ to passivate the graphene layer.

[0106] Preferably, in S1, the monofilament is prepared from the inside out and consists of three layers: a core copper layer, an inner surface layer (an amorphous-nanocrystalline composite copper layer with a thickness of about 18 nm), and an outer surface layer (a graphene layer with a thickness of about 35 nm).

[0107] S2. Wire Stranding: Multiple composite conductor filaments are stranded into a composite conductor according to a set pattern. The stranding speed is set at 35 m / min, and a right-hand stranding method is used. The diameter tolerance of the stranded conductor is controlled within ±0.1 mm.

[0108] S3. Initial Wrapping: Phlogopite tape is wrapped around the stranded composite conductor to obtain an inner wrapping layer. The initial wrapping adopts an overlapping wrapping method, with 3 layers, and the wrapping tension is controlled at 5N.

[0109] S4. Insulation Extrusion: The inner insulation layer, the outer insulation layer, and the shielding layer are simultaneously extruded using a double co-extrusion process.

[0110] Specifically, the insulation material is halogen-free cross-linked polyethylene (XLPE), the insulation thickness must meet the nominal value, and the extrusion temperature is controlled in stages: 120℃ in the feeding stage, 150℃ in the compression stage, and 160℃ in the homogenization stage.

[0111] Specifically, in S4, the process for insulating extrusion is as follows: Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material is dried at 150°C for 20 hours to remove moisture.

[0112] Plasticizing extrusion: Solid particles are gradually melted in the screw extruder through the feeding section, compression section and homogenization section (feeding section 120℃, compression section 150℃, homogenization section 160℃), and then coated with conductors through the die head, continuously coating the inner and outer insulation layers.

[0113] Cooling and setting: After extrusion, the insulation layer is cooled and cured in a water bath.

[0114] Then, a shielding layer is wrapped around the outer surface of the outer insulation layer.

[0115] Both the inner and outer insulation layers are made of XLPE, and the shielding layer is made of a metal braided mesh formed by tin-plated copper wire and a copper foil layer.

[0116] S5. Secondary wrapping: A ceramicized silicone rubber tape is wrapped around the outside of the shielding layer to obtain an outer wrapping layer. The secondary wrapping uses one overlapping wrapping layer, with a wrapping angle of 45° and a tension of 10 N.

[0117] S6. Sheath Extrusion: Extrusion of halogen-free low-smoke polyolefin sheaths. The halogen-free low-smoke polyolefin sheaths are produced by high-temperature hot extrusion of halogen-free low-smoke polyolefin granules. The extrusion temperature of the S6 sheath is controlled at 160℃, the screw speed is 20r / min, the traction speed is 50m / min, and it is rapidly shaped through a water-cooling tank (water temperature 20℃).

[0118] The high-conductivity insulated halogen-free fireproof special cable of this embodiment is composed of a composite conductor layer, an inner wrapping layer, an inner insulation layer, an outer insulation layer, a shielding layer, an outer wrapping layer, and a sheath layer from the inside out.

[0119] The high-conductivity, insulated, halogen-free, fire-resistant special cable of this embodiment is used in high-speed rail transportation, large ships, aerospace and other fields. Example 3

[0120] A method for manufacturing a high-conductivity, insulated, halogen-free, fire-resistant special cable mainly includes the following six steps:

[0121] S1. Single-wire preparation: Composite conductor single wires were prepared by continuous stretching-rapid quenching, multi-field coupling assisted stepwise plastic deformation, LT-CVD, and online annealing.

[0122] Specifically, S11. The copper rod is prepared by continuous casting. Raw material: TU1 oxygen-free copper; rod diameter: φ10mm; casting speed: 1.1mm / min. -1 The cooling water for the crystallizer is 19°C.

[0123] S12. The copper rod prepared in S11 is drawn to the target diameter (1.20 mm) through a multi-stage wire drawing die. He-N2 (volume ratio 7:3) mixed spray cooling is applied at the die exit point. The spray pressure is 0.40 MPa, and the cooling rate is 1.0 × 10⁻⁶. 6 K / s.

[0124] S13. The monofilament obtained in S12 is subjected to multi-field coupled assisted stepwise plastic deformation under the positioning of guide rollers. This process comprehensively applies radial mechanical pressure, synchronous heating, pulsed magnetic field, and laser irradiation. The specific process parameters are as follows:

[0125] Radial pressure range: 1.6GPa, 2.4GPa, 2.9GPa applied in three steps, each held for 4 seconds;

[0126] Heating assistance: During the deformation process, 5kHz medium-frequency induction heating is applied simultaneously, and the temperature is controlled at 220℃ to promote dynamic recrystallization and amorphization transformation.

[0127] Pulsed magnetic field assistance: A pulsed magnetic field with an intensity of 0.6T and a frequency of 20Hz is applied to the deformation zone to suppress grain growth and induce grain boundary pinning;

[0128] Laser irradiation assistance: A 1064nm fiber laser is used to synchronously scan and irradiate the surface of the wire material with a power density of 0.8kW / cm² and a scanning speed of 1.2m / s to promote the formation of amorphization and nanocrystalline composite structures on the surface.

[0129] Deformation rate: 1.1 m / min, ensuring uniform strain and structural gradient evolution.

[0130] S14. Graphene was deposited on the surface of the conductor monofilament obtained in S13 using LT-CVD (low-temperature chemical vapor deposition). Temperature: 450℃; carbon source: ethylene, flow rate: 15 sccm; atmosphere: argon / hydrogen mixture (ratio 1:1); growth time: 40 min.

[0131] S15. Perform nitrogen annealing at 310℃ to passivate the graphene layer.

[0132] Preferably, in S1, the monofilament is prepared from the inside out and consists of three layers: a core copper layer, an inner surface layer (an amorphous-nanocrystalline composite copper layer with a thickness of about 20 nm), and an outer surface layer (a graphene layer with a thickness of about 45 nm).

[0133] S2. Wire Stranding: Multiple composite conductor filaments are stranded into a composite conductor according to a set pattern. The stranding speed is set at 40 m / min, and a right-hand stranding method is used. The diameter tolerance of the stranded conductor is controlled within ±0.1 mm.

[0134] S3. Initial Wrapping: Phlogopite tape is wrapped around the stranded composite conductor to obtain an inner wrapping layer. The initial wrapping uses an overlapping wrapping method, with two layers, and the wrapping tension is controlled at 8N.

[0135] S4. Insulation Extrusion: The inner insulation layer, the outer insulation layer, and the shielding layer are simultaneously extruded using a double co-extrusion process.

[0136] Specifically, the insulation material is halogen-free cross-linked polyethylene (XLPE), the insulation thickness must meet the nominal value, and the extrusion temperature is controlled in stages: 125℃ in the feeding stage, 155℃ in the compression stage, and 165℃ in the homogenization stage.

[0137] Specifically, in S4, the process for insulating extrusion is as follows: Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material is dried at 155°C for 24 hours to remove moisture.

[0138] Plasticizing extrusion: Solid particles are gradually melted in the screw extruder through the feeding section, compression section and homogenization section (feeding section 125℃, compression section 155℃, homogenization section 165℃), and then coated with conductors through the die head, continuously coating the inner and outer insulation layers.

[0139] Cooling and setting: After extrusion, the insulation layer is cooled and cured in a water bath.

[0140] Then, a shielding layer is wrapped around the outer surface of the outer insulation layer.

[0141] The inner and outer insulation layers are both made of XLPE, and the shielding layer is made of a metal woven mesh formed of copper foil wire.

[0142] S5. Secondary wrapping: A ceramicized silicone rubber tape is wrapped around the outside of the shielding layer to obtain an outer wrapping layer. The secondary wrapping uses two overlapping layers, with a wrapping angle of 30° and a tension of 10 N.

[0143] S6. Sheath Extrusion: Extrusion of halogen-free low-smoke polyolefin sheaths. The halogen-free low-smoke polyolefin sheaths are produced by high-temperature hot extrusion of halogen-free low-smoke polyolefin granules. The extrusion temperature of the S6 sheath is controlled at 160℃, the screw speed is 20r / min, the traction speed is 70m / min, and it is rapidly shaped through a water-cooling tank (water temperature 30℃).

[0144] The high-conductivity insulated halogen-free fireproof special cable of this embodiment is composed of a composite conductor layer, an inner wrapping layer, an inner insulation layer, an outer insulation layer, a shielding layer, an outer wrapping layer, and a sheath layer from the inside out.

[0145] The high-conductivity, insulated, halogen-free, fire-resistant special cable of this embodiment is used in high-speed rail transportation, large ships, aerospace and other fields. Example 4

[0146] A method for manufacturing a high-conductivity, insulated, halogen-free, fire-resistant special cable mainly includes the following six steps:

[0147] S1. Single-wire preparation: Composite conductor single wires were prepared by continuous stretching-rapid quenching, multi-field coupling assisted stepwise plastic deformation, LT-CVD, and online annealing.

[0148] Specifically, S11. The copper rod is prepared by continuous casting. Raw material: TU1 oxygen-free copper; rod diameter: φ25 mm; casting speed: 1.2 m / min. -1 The cooling water temperature for the crystallizer is 22°C.

[0149] S12. The copper rod prepared in S11 is drawn to the target diameter (2.76 mm) through a multi-stage wire drawing die. He-N2 (volume ratio 7:3) mixed spray cooling is applied at the die exit point. The spray pressure is 0.55 MPa, and the cooling rate is 1.0 × 10⁻⁶. 6 K / s.

[0150] S13. The monofilament obtained in S12 is subjected to multi-field coupled assisted stepwise plastic deformation under the positioning of guide rollers. This process comprehensively applies radial mechanical pressure, synchronous heating, pulsed magnetic field, and laser irradiation. The specific process parameters are as follows:

[0151] Radial pressure range: 2.1GPa, 2.6GPa, 3.2GPa applied in three steps, each holding pressure for 5 seconds;

[0152] Heating assistance: During the deformation process, 20kHz medium-frequency induction heating is applied simultaneously, and the temperature is controlled at 350℃ to promote dynamic recrystallization and amorphization transformation.

[0153] Pulsed magnetic field assistance: A pulsed magnetic field with an intensity of 1.2T and a frequency of 50Hz is applied to the deformation zone to suppress grain growth and induce grain boundary pinning;

[0154] Laser irradiation assistance: A 1070nm fiber laser is used to synchronously scan and irradiate the surface of the wire material with a power density of 2.0kW / cm² and a scanning speed of 1.5m / s to promote the formation of amorphization and nanocrystalline composite structures on the surface.

[0155] Deformation rate: 1.5 m / min, ensuring uniform strain and structural gradient evolution.

[0156] S14. Graphene was deposited on the surface of the conductor monofilament obtained in S13 using the LT-CVD (low-temperature chemical vapor deposition) method. Temperature: 600℃; carbon source: ethylene, flow rate: 30 sccm; atmosphere: argon / hydrogen mixture (ratio 1:1); growth time: 90 min.

[0157] S15. Perform nitrogen annealing at 350℃ to passivate the graphene layer.

[0158] Preferably, in S1, the monofilament is prepared from the inside out and consists of three layers: a core copper layer, an inner surface layer (an amorphous-nanocrystalline composite copper layer with a thickness of about 32 nm), and an outer surface layer (a graphene layer with a thickness of about 78 nm).

[0159] S2. Wire Stranding: Multiple composite conductor filaments are stranded into a composite conductor according to a set pattern. The stranding speed is set at 45 m / min, and a right-hand stranding method is used. The diameter tolerance of the stranded conductor is controlled within ±0.1 mm.

[0160] S3. Initial Wrapping: Wrap phlogopite tape around the stranded composite conductor to obtain an inner wrapping layer. The initial wrapping uses an overlapping wrapping method, with 3 layers, and the wrapping tension is controlled at 15N.

[0161] S4. Insulation Extrusion: The inner insulation layer, the outer insulation layer, and the shielding layer are simultaneously extruded using a double co-extrusion process.

[0162] Specifically, the insulation material is halogen-free cross-linked polyethylene (XLPE), the insulation thickness must meet the nominal value, and the extrusion temperature is controlled in stages: 140℃ in the feeding stage, 170℃ in the compression stage, and 180℃ in the homogenization stage.

[0163] Specifically, in S4, the process for insulating extrusion is as follows: Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material is dried at 170°C for 24 hours to remove moisture.

[0164] Plasticizing extrusion: Solid particles are gradually melted in the screw extruder through the feeding section, compression section and homogenization section (feeding section 140℃, compression section 170℃, homogenization section 180℃), and then coated with conductors through the die head, continuously coating the inner and outer insulation layers.

[0165] Cooling and setting: After extrusion, the insulation layer is cooled and cured in a water bath.

[0166] Then, a shielding layer is wrapped around the outer surface of the outer insulation layer.

[0167] The inner and outer insulation layers are both made of XLPE, and the shielding layer is made of a metal woven mesh formed of copper foil wire.

[0168] S5. Secondary wrapping: A ceramicized silicone rubber tape is wrapped around the outside of the shielding layer to obtain an outer wrapping layer. The secondary wrapping uses two overlapping layers, with a wrapping angle of 45° and a tension of 20 N.

[0169] S6. Sheath Extrusion: Extrusion of halogen-free low-smoke polyolefin sheaths. The halogen-free low-smoke polyolefin sheaths are produced by high-temperature hot extrusion of halogen-free low-smoke polyolefin granules. The extrusion temperature of the S6 sheath is controlled at 170℃, the screw speed is 22r / min, the traction speed is 100m / min, and it is rapidly shaped through a water-cooling tank (water temperature 30℃).

[0170] The high-conductivity insulated halogen-free fireproof special cable of this embodiment is composed of a composite conductor layer, an inner wrapping layer, an inner insulation layer, an outer insulation layer, a shielding layer, an outer wrapping layer, and a sheath layer from the inside out.

[0171] The high-conductivity, insulated, halogen-free, fire-resistant special cable of this embodiment is used in high-speed rail transportation, large ships, aerospace and other fields.

[0172] Comparative Example 1

[0173] Cable with grade EN 50264-3-1 600V 1.5M.

[0174] Comparative Example 2

[0175] The only difference between this comparative example and Example 1 is that the multi-field coupling assisted progressive plastic deformation process of S13 was not performed.

[0176] Comparative Example 3

[0177] The only difference between this comparative example and Example 1 is the single-layer insulation structure. That is, the inner insulation layer, outer insulation layer, and shielding layer are replaced with a single-layer insulation structure.

[0178] The method for preparing a single-layer insulation structure is as follows:

[0179] Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material was dried at 160°C for 22 hours to remove moisture.

[0180] Plasticizing extrusion: Solid particles are gradually melted in the screw extruder through the feeding section, compression section and homogenization section (feeding section 130℃, compression section 160℃, homogenization section 170℃), and then coated with conductors through the die head.

[0181] Cooling and shaping: After extrusion, the insulation layer is cooled and solidified in a water bath to form a continuous and uniform single-layer insulation structure.

[0182] Comparative Example 4

[0183] The only difference between this comparative example and Example 1 is that a two-stage radial pressure is applied in S13, instead of a three-stage radial pressure.

[0184] That is, the radial pressure range is 1.8GPa and 2.5GPa, applied in two steps, with each step held for 3 seconds.

[0185] Comparative Example 5

[0186] The only difference between this comparative example and Example 1 is that in S13, a four-stage radial pressure is applied, with radial pressure ranges of 1.8 GPa, 2.5 GPa, 3.0 GPa, and 3.6 GPa; each stage is held for 3 seconds.

[0187] Comparative Example 6

[0188] The only difference between this comparative example and Example 1 is that no heating-assisted process was used in S13.

[0189] Comparative Example 7

[0190] The only difference between this comparative example and Example 1 is that the pulsed magnetic field assisted process was not used in S13.

[0191] Comparative Example 8

[0192] The only difference between this comparative example and Example 1 is that laser irradiation-assisted process was not used in S13.

[0193] Comparative Example 9

[0194] The only difference between this comparative example and Example 1 is that:

[0195] Simultaneously apply medium-frequency induction heating, and control the temperature at 180℃;

[0196] A pulsed magnetic field with an intensity of 0.4 T and a frequency of 5 Hz is applied;

[0197] The surface of the filament was synchronously irradiated with a 1060 nm laser at a power density of 0.3 kW / cm² and a scanning speed of 0.2 m / s.

[0198] Comparative Example 10

[0199] The only difference between this comparative example and Example 1 is that:

[0200] Simultaneously apply medium-frequency induction heating, with the temperature controlled at 400℃;

[0201] A pulsed magnetic field with an intensity of 1.5 T and a frequency of 60 Hz is applied;

[0202] The surface of the filament was synchronously irradiated with a 1060 nm laser at a power density of 2.2 kW / cm² and a scanning speed of 2.0 m / s.

[0203] Inspection basis: TJ / CL313-2014 Provisional Technical Conditions for Electric Wires and Cables of High-Speed ​​Trains.

[0204] The test data is shown in Table 1 below.

[0205] Table 1 Comparison of Performance Parameters

[0206]

[0207] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0208] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0209] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made 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 high-conductivity, insulated, halogen-free, fire-resistant special cable, characterized in that, From the inside out, it consists of a composite conductor layer, an inner wrapping layer, an inner insulation layer, an outer insulation layer, a shielding layer, an outer wrapping layer, and a sheath layer. The composite conductor layer is formed by twisting together multiple composite conductor monofilaments. The composite conductor monofilament consists of three layers from the inside out: a copper core, an inner surface layer, and an outer surface layer. The inner surface layer is an amorphous-nanocrystalline composite copper layer with a thickness of 18-32 nm. The outer surface layer is a graphene layer with a thickness of 35-78 nm. The preparation of composite conductor monofilaments includes: S11. Continuous casting of copper rods using upward-drawing method. Raw material: TU1 oxygen-free copper. Rod diameter: φ3-25 mm. Casting speed: 0.8–1.2 mm / min. -1 Crystallizer cooling water: 18–22 °C; S12. The copper rod prepared in S11 is drawn through a multi-stage wire drawing die to a target diameter of 0.033-2.76 mm. He-N2 mixed jet cooling is applied at the die exit point, with a jet pressure of 0.35-0.55 MPa and a cooling rate ≥1×10⁻⁶. 6 K / s; S13. The single filament obtained in S12 is subjected to multi-field coupled assisted stepwise plastic deformation under the positioning of guide rollers; radial mechanical pressure, synchronous heating, pulsed magnetic field and laser irradiation are applied in combination: Radial pressure range: 1.5-2.1 GPa, 2.3-2.6 GPa, 2.8-3.2 GPa, applied in three steps, each holding pressure for 2–5 seconds; Heating assistance: During the deformation process, 1-20 kHz medium-frequency induction heating is applied simultaneously, and the temperature is controlled at 200-350℃; Pulsed magnetic field assistance: A pulsed magnetic field with an intensity of 0.5–1.2 T and a frequency of 10–50 Hz is applied to the deformation zone; Laser irradiation assistance: The surface of the filament is synchronously scanned and irradiated with a 1064-1070 nm fiber laser at a power density of 0.5–2.0 kW / cm² and a scanning speed of 0.5–1.5 m / s; Deformation rate: 0.8–1.5 m / min; S14. Graphene was deposited on the surface of the conductor monofilament obtained in S13 using the LT-CVD method. Temperature: 400–600℃; Carbon source: ethylene, flow rate 10–30 sccm; Atmosphere: argon / hydrogen mixture; Growth time 15–90 min. S15. Perform nitrogen annealing at 300-350℃ to passivate the graphene layer.

2. The high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, The inner wrapping layer is made of phlogopite mica tape.

3. The high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, The outer layer is made of ceramicized silicone rubber tape.

4. The high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, The sheath layer is made of halogen-free low-smoke polyolefin.

5. A high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, Both the inner and outer insulation layers are made of halogen-free cross-linked polyethylene (XLPE).

6. A high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, The shielding layer material includes metal braided mesh or combined shielding formed by copper foil strips or wires, aluminum foil strips or wires, or tin-plated copper wires; combined shielding includes foil layer + metal braided mesh.

7. A high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, In S12, the volume ratio of He to N2 is 7:

3.

8. A high-conductivity, insulated, halogen-free, fire-resistant special cable according to claim 1, characterized in that, In S14, the volume ratio of argon to hydrogen is 1:

1.

9. A method for preparing a high-conductivity, insulated, halogen-free, fire-resistant special cable according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Single-wire preparation: Composite conductor single wires were prepared by continuous stretching-rapid quenching, multi-field coupling assisted stepwise plastic deformation, LT-CVD, and online annealing; S2. Bundling: Bundling multiple composite conductor filaments together to form a composite conductor; S3. Initial wrapping: Wrapping an inner wrapping layer around the outside of the stranded composite conductor; S4. Insulation extrusion: The inner insulation layer, the outer insulation layer, and the shielding layer are simultaneously extruded using a double co-extrusion process; S5. Secondary wrapping: Wrap an outer wrapping layer around the shielding layer; S6. Sheath extrusion: Extruding the sheath layer.

10. The preparation method according to claim 9, characterized in that, In S2, the stranding speed is 35-45m / min, and the right-hand stranding method is adopted. The diameter tolerance of the stranded conductor is controlled within ±0.1mm.

11. The preparation method according to claim 9, characterized in that, In S3, the first wrapping adopts an overlapping wrapping method with 2–3 layers, and the wrapping tension is controlled at 5–15 N.

12. The preparation method according to claim 9, characterized in that, In S4, the process of insulating extrusion is as follows: Material pretreatment: Halogen-free cross-linked polyethylene (XLPE) raw material is dried at 150-170°C for 20-24 hours to remove moisture; Plasticizing extrusion: Halogen-free cross-linked polyethylene (XLPE) solid granules are gradually melted in a screw extruder through the feeding section, compression section, and homogenization section; the feeding section is 120–140℃, the compression section is 150–170℃, and the homogenization section is 160–180℃. The conductor is coated through the die head of the screw extruder, continuously coating the inner and outer insulation layers. Cooling and setting: After extrusion, the inner and outer insulation layers are cooled and solidified in a water bath; Then, a shielding layer is wrapped around the outer surface of the outer insulation layer.

13. The preparation method according to claim 9, characterized in that, In S5, the secondary wrapping adopts 1-2 layers of overlapping wrapping, with a wrapping angle of 30–45° and a tension of 10–20 N. In S6, the sheath extrusion temperature is 160–170℃, the screw speed is 20–22 r / min, the traction speed is 50–100 m / min, and it is quickly shaped by water cooling tank with a water temperature of 20–30℃.

14. The application of a high-conductivity insulated halogen-free fire-resistant special cable according to any one of claims 1 to 8 in high-speed rail transit, large ships, and aerospace fields.

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