High-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire and preparation method thereof

Abstract

The invention relates to the technical field of power transmission lines, in particular to a high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire and a preparation method thereof. The components of the core layer and the outer layer are improved, the outer surface of the stranded wire prefabricated body is coated with the nano-composite coating, and the core layer and the outer layer are respectively provided with the optical fiber sensing units, so that the strength, the elongation and the heat resistance of the aluminum-clad steel core aluminum alloy stranded wire are all improved, and the service life of the aluminum-clad steel core aluminum alloy stranded wire is prolonged. And meanwhile, the state of the aluminum-clad steel core aluminum alloy stranded wire in the using process can be monitored in real time.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of power transmission lines, in particular to a high-strength and high-elongation aluminum-clad steel core aluminum alloy strand and a preparation method thereof. BACKGROUND

[0002] The aluminum-clad steel core aluminum strand is a composite conductive wire material formed by twisting single wires made of high-strength steel cores with aluminum layers and pure aluminum or aluminum alloy, and is widely used in overhead power transmission lines. This composite conductive wire material effectively balances the weight and conductivity efficiency requirements by utilizing the mechanical strength provided by the steel core and the good electrical conductivity of the aluminum layer. The high-strength steel core improves the strength through cold drawing, but leads to a decrease in elongation and is prone to brittle fracture under extreme loads. The outer layer of pure aluminum or ordinary aluminum alloy softens at high temperatures and lacks heat resistance, resulting in a decrease in conductor load capacity. At the same time, the existing aluminum-clad steel core aluminum alloy conductor lacks state monitoring capabilities such as temperature, strain, and damage, and cannot meet the needs of smart grids.

[0003] In view of this, the application is proposed. SUMMARY

[0004] The purpose of the application is to provide a high-strength and high-elongation aluminum-clad steel core aluminum alloy strand and a preparation method thereof. By improving the composition of the core layer and the outer layer, coating a nano-composite coating on the outer surface of the strand preform after twisting, and arranging optical fiber sensing units in the core layer and the outer layer respectively, the strength, elongation and heat resistance of the aluminum-clad steel core aluminum alloy strand are all improved, and the state of the aluminum-clad steel core aluminum alloy strand during use can be monitored in real time.

[0005] To solve the above technical problems, the application adopts the following scheme: A high-strength and high-elongation aluminum-clad steel core aluminum alloy strand, the aluminum-clad steel core aluminum alloy strand comprising: A core layer composed of a plurality of high-carbon steel cores and a pure aluminum layer coated on the surface of the high-carbon steel cores to form an aluminum-clad steel core, and the pure aluminum layer and the high-carbon steel core form an iron-aluminum intermetallic compound diffusion layer through metallurgical bonding; An outer layer composed of a plurality of aluminum alloy single wires twisted together; An optical fiber sensing unit comprising at least one optical fiber encapsulated in a metal microtube, arranged at the center of the core layer and between the aluminum alloy single wires of the outer layer along the axial direction of the strand; The outer surface of the aluminum-clad steel core aluminum alloy strand is coated with a nano-composite coating.

[0006] Further, the tensile strength of the twisted aluminum-clad steel core is greater than or equal to 1820 MPa, the elongation is greater than or equal to 2.0%, and the direct current resistance at 20 DEG C is less than or equal to 123.15 ohm / km; the tensile strength of the aluminum alloy single wire is greater than or equal to 252 MPa, the elongation is greater than or equal to 2.0%, and the direct current resistance at 20 DEG C is less than or equal to 28.606 ohm / km.

[0007] Further, the high-carbon steel core has a carbon content of 0.6% to 0.8% by mass and contains vanadium and titanium in an amount of 0.05% to 0.15%; the pure aluminum layer is formed into a metallurgical bonding interface with the high-carbon steel core through a continuous extrusion coating process, the thickness of the metallurgical bonding interface is 15% to 20% of the diameter of the high-carbon steel core; and the thickness of the iron-aluminum intermetallic compound diffusion layer is 5 μm to 15 μm.

[0008] Further, the aluminum alloy single wire contains 0.5% to 0.8% of magnesium, 0.4% to 0.7% of silicon, 0.1% to 0.3% of zirconium, 0.02% to 0.1% of yttrium or lanthanum by mass, and the balance is aluminum and unavoidable impurities, and the content of the impurities is less than 0.3%.

[0009] Further, the nanocomposite coating contains 0.5% to 2% of graphene, 3% to 5% of silicon carbide nanoparticles, and 1% to 3% of aluminum oxide nanosheets by mass, and the balance is polyimide or silicone, and the thickness of the coating is 20 μm to 30 μm.

[0010] Further, in the core layer, the high-carbon steel core at the center of the core layer is laser drilled to form a hole for assembling the fiber sensing unit, and the hole is filled with epoxy resin; In the outer layer, the fiber sensing unit is co-twisted with the aluminum alloy single wire to form a shape.

[0011] Further, the fiber is a Bragg grating fiber or a distributed sensing fiber, the outer diameter of the metal microtube is 0.5 mm to 1.0 mm, and the inside of the metal microtube is filled with a silicone gel buffer layer; and the surface of the fiber is coated with a polyimide coating with a thickness of 15 μm to 20 μm.

[0012] A method for preparing a high-strength and high-elongation aluminum-clad steel core aluminum alloy strand, comprising the following steps: S1, high-carbon steel core pretreatment: the high-carbon steel core is subjected to pickling and electroplating of an aluminum transition layer, and then a pure aluminum layer is coated on the high-carbon steel core by a continuous extrusion process at 350°C to 450°C; after the encapsulated fiber sensing unit is inserted into the central hole of the high-carbon steel core, the aluminum-clad steel core is formed by drawing and sectional annealing; S2, preparation of heat-resistant aluminum alloy: aluminum, magnesium, silicon, zirconium, yttrium or lanthanum are vacuum melted, and an aluminum alloy single wire is prepared by electromagnetic stirring and continuous casting and rolling, and the final rolling temperature is ≤250°C; S3, co-twisting: the aluminum-clad steel core, the outer layer aluminum alloy single wire and the fiber sensing unit are co-twisted by using a constant tension stranding machine to obtain a strand preform, and the stranding pitch ratio is 10 to 14; and before the co-twisting, the aluminum alloy single wire is subjected to a pre-twist of 2° to 3°; S4, post-treatment: after the co-twisting, the strand preform is subjected to low-temperature annealing at 200°C for 30 min, and a nanocomposite coating is sprayed on the outer surface of the strand preform by using an electrostatic spraying process.

[0013] Further, the twisted wire preform formed by twisting in step S3 is sequentially subjected to low-temperature annealing, plasma cleaning and chemical bonding with a silane coupling agent after the plasma cleaning.

[0014] Further, the adhesion of the nanocomposite coating is greater than or equal to 15 MPa.

[0015] The present application has the following advantages: The present application improves the core layer and the outer layer, so that the core layer contains a high-carbon steel core containing V / Ti, the high strength and high plasticity of the steel core are coordinated, a pure aluminum layer and the high-carbon steel core form a metallurgical bonding interface through a continuous extrusion coating process, and the interface strength is improved. The outer aluminum alloy single wire contains yttrium or lanthanum, promotes the uniform distribution of Al3Zr nano phase, reduces the aggregation phenomenon of precipitated phase, improves the utilization rate of zirconium, and improves the heat resistance.

[0016] The optical fiber sensing unit is arranged in the high-carbon steel core at the center of the core layer and the aluminum alloy single wire, respectively, after the polyimide coating of the optical fiber is coated, the optical fiber is packaged in a metal micro tube through a high-temperature resistant epoxy resin, so that the aluminum-clad steel core aluminum alloy wire realizes monitoring of the temperature and stress distribution of the aluminum-clad steel core aluminum alloy wire in the use process, and prevents core breakage; at the same time, the polyimide coating, the silica gel buffer layer and the metal micro tube constitute a triple protection for the optical fiber, and ensure that the monitoring performance of the optical fiber sensing unit does not change in the subsequent twisting formation.

[0017] The nanocomposite coating is sprayed on the outer surface of the aluminum-clad steel core aluminum alloy by using an electrostatic spraying process, so as to improve the corrosion resistance of the aluminum-clad steel core aluminum alloy wire, and has no effect on the 20 DEG C direct current resistance. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a sectional structure schematic diagram of the aluminum-clad steel core aluminum alloy wire of the present application; Figure 2 Fig. 2 is a sectional structure schematic diagram of the aluminum-clad steel core at the center of the core layer of the present application.

[0019] Fig. 1 is a sectional structure schematic diagram of the aluminum-clad steel core aluminum alloy wire of the present application; DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0021] The relative arrangement, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application, unless otherwise specifically stated.

[0022] It should be understood that the sizes of the various parts shown in the drawings are not drawn in accordance with the actual proportional relationship for the convenience of description.

[0023] In addition, descriptions of well-known structures, functions, and configurations can be omitted for clarity and conciseness. Those of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made without departing from the spirit and scope of the disclosure.

[0024] Techniques, methods, and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the authorized description where appropriate.

[0025] In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary, and not as a limitation. Thus, other examples of the example embodiments can have different values.

[0026] Embodiment 1 A high-strength high-elongation aluminum-clad steel core aluminum alloy strand, referring to Figure 1 , comprising: (1) a core layer 1 composed of a plurality of high-carbon steel cores 10 and a pure aluminum layer 11 cladded on the surface of the high-carbon steel cores 10 to form an aluminum-clad steel core, and the pure aluminum layer 11 and the high-carbon steel core 10 form an iron-aluminum intermetallic compound diffusion layer 101 through metallurgical bonding.

[0027] The content of carbon in the high-carbon steel core 10 is 0.6% to 0.8%, and the high-carbon steel core 10 contains 0.05% to 0.15% of vanadium and titanium. The addition of vanadium (V) can make the precipitation strengthening of carbonitride, form a nanoscale VN / VC precipitate phase, thereby improving the yield strength; at the same time, it can inhibit the growth of austenite grains, and make VN not coarsen below 600°C, thereby maintaining the strengthening effect. Titanium (Ti) fixes nitrogen and oxygen to form TiN / TiO2, reduces the damage of free N to plasticity, improves the elongation performance, reacts with carbon to generate TiC to hinder grain boundary migration, improves the recrystallization temperature, and generates TiS with S in the steel, thereby reducing the porosity of the subsequent aluminum plating layer. The high-carbon steel core 10 contains C, V, and Ti, forms a (Ti, V) (C, N) composite phase, has a more uniform size, and realizes the synergy of high strength and high plasticity of the steel core.

[0028] The pure aluminum layer 11 forms a metallurgical bonding interface with the high-carbon steel core 10 through a continuous extrusion coating process, the thickness of the metallurgical bonding interface is 15% to 20% of the diameter of the high-carbon steel core 10; and the thickness of the iron-aluminum intermetallic compound diffusion layer 101 is 5 μm to 15 μm.

[0029] During the continuous extrusion coating, the pure aluminum layer 11 and the high-carbon steel core 10 undergo solid-state diffusion, the diffusion layer protrudes and is embedded in the pure aluminum layer 11, an anchoring effect is formed, and the iron-aluminum intermetallic compound diffusion layer 101 is generated between the steel and the aluminum to slow down the galvanic corrosion.

[0030] (2) The outer layer 2 is twisted by a plurality of aluminum alloy single wires 20. As shown in FIG. 2, the aluminum alloy single wires 20 in the outer layer 2 are twisted into two layers, and the outer layer 2 has a structure of 9+15. Figure 1

[0031] The aluminum alloy single wire 20 contains 0.5% to 0.8% of magnesium, 0.4% to 0.7% of silicon, 0.1% to 0.3% of zirconium, and 0.02% to 0.1% of yttrium or lanthanum, and the balance is aluminum and unavoidable impurities, and the content of the impurities is less than 0.3%. The magnesium and the silicon combine to generate a nanoscale Mg2Si precipitate phase, thereby improving the heat resistance of the aluminum alloy single wire 20 and reducing the melt viscosity; the zirconium reacts with the aluminum to generate an Al3Zr nanophase, thereby inhibiting recrystallization, and the Al3Zr nanophase is used as a heterogeneous core for grain refinement; the yttrium or lanthanum is used as a rare earth element, the rare earth element is segregated at the grain boundary, adsorbs impurities such as Fe / Si to form high-melting-point compounds (such as Y2O3 and LaAl3), thereby purifying the grain boundary; a dense oxide film (Y / Al2O3 composite oxide) is formed, thereby inhibiting pitting corrosion; and the yttrium or lanthanum can promote the uniform distribution of the Al3Zr nanophase, reduce the aggregation phenomenon of the precipitate phase, improve the utilization rate of the zirconium, and further improve the heat resistance.

[0032] ​(3) Fiber sensing unit 3, including at least one fiber 30 encapsulated in a metal microtube 32, arranged in the center of the core layer 1 and between the aluminum alloy single wires 20 of the outer layer 2. The fiber 30 is mainly located in the high carbon steel core 10 in the center of the core layer 1 and between any aluminum alloy single wire 20 of the outer layer 2. The fiber 30 is threaded through the center of the high carbon steel core 10 before the aluminum-clad steel core is drawn, and the fiber 30 is assembled between the outer layer 2 of the aluminum alloy single wire 20 mainly by co-twisting forming, that is, twisted forming with the aluminum-clad steel core and the aluminum alloy single wire 20.

[0033] In the core layer 1, referring to Figure 2 , the high carbon steel core 10 in the center of the core layer 1 is laser drilled to assemble the fiber sensing unit 3 hole 100, and the epoxy resin is filled in the hole 100. At this time, the length of the fiber 30 is slightly larger than the length of the high carbon steel core 10, so as to compensate for the axial compression strain in the subsequent co-twisting forming, and a fusion excess is reserved at both ends of the fiber 30. The specific length of the fiber 30 can be calculated according to the high carbon steel core 10, the thermal expansion coefficient of the steel core, the working temperature range and the process allowance, which will not be described here. Laser drilling is used to make the hole diameter of the hole 100 1.0±0.5mm, so that the fiber 30 encapsulated in the metal microtube 32 can be inserted into the hole 100 in the high carbon steel core 10 under the condition of nitrogen filling, preventing the metal microtube 32 from scratching the inner wall of the hole 100; and high-temperature resistant epoxy resin is filled between the hole 100 and the metal microtube 32 for fixation, while dispersing the interface stress and protecting the fiber 30 from damage during twisting. In addition, the metal microtube 32 is made of 316L stainless steel, which provides mechanical protection for the fiber 30 and also serves as electromagnetic shielding to block the conduction of high temperature to the fiber 30.

[0034] In the outer layer 2, the fiber sensing unit 3 is co-twisted with the aluminum alloy single wire 20. The fiber 30 here is encapsulated in the metal microtube 32 and then co-twisted with the aluminum alloy single wire 20 and the aluminum-clad steel core, wherein the length of the fiber 30 is slightly larger than the length of the aluminum alloy single wire 20.

[0035] The fiber 30 is a Bragg grating fiber 30 or a distributed sensing fiber 30, the outer diameter of the metal microtube 32 is 0.5mm~1.0mm, and the inside is filled with a silica gel buffer layer 33, and the surface of the fiber 30 is coated with a polyimide coating layer 31 with a thickness of 15μm ~20μm.

[0036] The fiber 30 at the center of the high-carbon steel core 10 of the core layer 1 is a Bragg grating fiber 30 (FBG), which is mainly used for monitoring the axial stress and fatigue damage of the core layer 1, and for early warning of overload of the high-carbon steel core 10 to prevent core breakage; and for preventing fatigue fracture. The fiber 30 between the aluminum alloy single wires 20 of the outer layer 2 is a distributed sensing fiber 30 (DTS), which is attached to the external environment to monitor the temperature and stress distribution of the stranded wire. The number of the fiber 30 in the metal microtube 32 can be set according to actual needs, which will not be described here.

[0037] On the other hand, the polyimide coating 31 on the surface of the fiber 30 is mainly resistant to chemical corrosion, and at the same time forms a triple protection for the fiber 30 together with the silica gel buffer layer 33 and the metal microtube 32, to ensure that the monitoring performance of the fiber sensing unit 3 does not change during subsequent stranding and forming.

[0038] (4) The outer surface of the aluminum-clad steel core aluminum alloy stranded wire is coated with a nano composite coating 4.

[0039] The nano composite coating includes 0.5% to 2% graphene, 3% to 5% silicon carbide nanoparticles, 1% to 3% aluminum oxide nanosheets, and the balance is polyimide or silicone resin, and the coating thickness is 20 μm to 30 μm.

[0040] It should be noted that the role of the nano composite coating in the stranded wire is that graphene improves thermal conductivity, mechanical strength and oxidation resistance; silicon carbide nanoparticles enhance wear resistance and high temperature stability; aluminum oxide nanosheets improve insulation and arc resistance; and polyimide or silicone resin improves high temperature resistance.

[0041] The tensile strength of the stranded aluminum-clad steel core is ≥1820 MPa, the elongation is ≥2.0%, and the 20℃ direct current resistance is ≤123.15 Ω / km; the tensile strength of the aluminum alloy single wire 20 is ≥252 MPa, the elongation is ≥2.0%, and the 20℃ direct current resistance is ≤28.606 Ω / km.

[0042] Example 2 A method for preparing a high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire, comprising the following steps: S1, high-carbon steel core 10 pretreatment: the diameter of 2.5mm high-carbon steel core 10 (carbon content of 0.6%, vanadium content of 0.05%, titanium content of 0.10%) is pickled with hydrochloric acid and corrosion inhibitor to remove the oxide layer on the surface of the high-carbon steel core 10; then electroplated with pure aluminum 30μm as a transition layer; then coated with a pure aluminum layer 11 using a continuous extrusion process at 350℃ to form a metallurgical bond interface with a thickness of 500μm; after the packaged optical fiber sensing unit 3 is inserted into the center channel 100 of the high-carbon steel core 10, it is drawn and annealed in sections to form an aluminum-clad steel core, with a cold drawing deformation of ≤15% and retained plasticity of the steel core; the section annealing is first high-temperature annealing at 400℃ for 1h to eliminate work hardening, and then low-temperature annealing at 250℃ for 2h to stabilize the aluminum layer grain.

[0043] S2, heat-resistant aluminum alloy preparation: aluminum (balance), magnesium (content of 0.5%), silicon (content of 0.6%), zirconium (content of 0.1%), yttrium (content of 0.06%) are vacuum melted, and an aluminum alloy single wire 20 (diameter of 3.5mm) is made by electromagnetic stirring and continuous casting and rolling with a final rolling temperature of ≤250℃. The oxygen content during vacuum melting is ≤50ppm to reduce impurities during the melting process.

[0044] S3, stranding: the aluminum-clad steel core, the outer layer 2 aluminum alloy single wire 20 and the optical fiber sensing unit 3 are stranded using a constant tension stranding machine to obtain a stranded wire preform, with a stranding pitch ratio of 10 and a 2° pre-twist applied to the aluminum alloy single wire 20 before stranding; S4, post-processing: after stranding, low-temperature annealing at 200℃ for 30min, plasma cleaning, and chemical bonding with a silane coupling agent, the roughness of the outer surface of the stranded wire preform is Ra=1.8μm; the outer surface of the stranded wire preform is sprayed with a nano-composite coating 4 (0.5% graphene, 3% silicon carbide nanoparticles, 3% aluminum oxide nanosheets, and the balance polyimide) using an electrostatic spraying process, with a thickness of 20μm and an adhesion of the nano-composite coating 4 of 15MPa.

[0045] Example 3, a method for preparing a high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire, comprising the following steps: S1, high-carbon steel core 10 pretreatment: the diameter of 2.5mm high-carbon steel core 10 (carbon content of 0.7%, vanadium content of 0.1%, titanium content of 0.05%) is pickled with hydrochloric acid and corrosion inhibitor to remove the oxide layer on the surface of the high-carbon steel core 10; then electroplated with pure aluminum 20μm as a transition layer; then coated with a pure aluminum layer 11 at 450℃ using a continuous extrusion process to form a metallurgical bonding interface with a thickness of 500μm; after the packaged optical fiber sensing unit 3 is inserted into the center channel 100 of the high-carbon steel core 10, it is drawn and annealed in sections to form an aluminum-clad steel core, with a cold drawing deformation of ≤15% and a retained steel core plasticity; the section annealing is first high-temperature annealing at 400℃ for 1h to eliminate work hardening, and then low-temperature annealing at 250℃ for 2h to stabilize the aluminum layer grain.

[0046] S2, heat-resistant aluminum alloy preparation: aluminum (balance), magnesium (content of 0.7%), silicon (content of 0.4%), zirconium (content of 0.3%), yttrium (content of 0.08%) are vacuum melted, and an aluminum alloy single wire 20 (diameter of 3.0mm) is made by electromagnetic stirring and continuous casting and rolling with a final rolling temperature of ≤250℃. The oxygen content during vacuum melting is ≤50ppm to reduce impurities during the melting process.

[0047] S3, stranding: the aluminum-clad steel core, the outer layer 2 aluminum alloy single wire 20 and the optical fiber sensing unit 3 are stranded using a constant tension stranding machine to obtain a stranded wire preform, with a stranding pitch ratio of 12 and a 3° pre-twist applied to the aluminum alloy single wire 20 before stranding; S4, post-processing: after stranding, low-temperature annealing at 200℃ for 30min, plasma cleaning, and chemical bonding with a silane coupling agent, the roughness of the outer surface of the stranded wire preform is Ra=2.0μm; the outer surface of the stranded wire preform is sprayed with a nano-composite coating 4 (1.0% graphene, 4% silicon carbide nanoparticles, 2% aluminum oxide nanosheets, and the balance polyimide) using an electrostatic spraying process, with a thickness of 25μm and an adhesion of the nano-composite coating 4 of 18MPa.

[0048] Example 4 A method for preparing a high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire, comprising the following steps: S1, Pretreatment of high-carbon steel core 10: The high-carbon steel core 10 (carbon content of 0.8%, vanadium content of 0.06%, titanium content of 0.1%) with a diameter of 3.0 mm is pickled with hydrochloric acid and corrosion inhibitor to remove the oxide layer on the surface of the high-carbon steel core 10; then electroplated with pure aluminum 25 μm as a transition layer; subsequently coated with a pure aluminum layer 11 using a continuous extrusion process at 400°C to form a metallurgical bonding interface with a thickness of 450 μm; after the encapsulated optical fiber sensing unit 3 is inserted into the central channel 100 of the high-carbon steel core 10, the aluminum-clad steel core is formed by drawing and sectional annealing, with a cold drawing deformation of ≤15% and the plasticity of the steel core being retained; the sectional annealing is first high-temperature annealing at 400°C for 1 h to eliminate work hardening, and then low-temperature annealing at 250°C for 2 h to stabilize the aluminum layer grains.

[0049] S2, Preparation of heat-resistant aluminum alloy: aluminum (balance), magnesium (content of 0.8%), silicon (content of 0.5%), zirconium (content of 0.2%), and lanthanum (content of 0.1%) are vacuum melted, subjected to electromagnetic stirring, and continuously cast and rolled to form an aluminum alloy single wire 20 (diameter of 3.2 mm) with a final rolling temperature of ≤250°C. The oxygen content during vacuum melting is ≤50 ppm to reduce impurities during the melting process.

[0050] S3, Stranding: the aluminum-clad steel core, the outer layer 2 aluminum alloy single wire 20, and the optical fiber sensing unit 3 are stranded using a constant tension stranding machine to obtain a stranded wire preform, with a stranding pitch ratio of 14 and a 3° pre-twist applied to the aluminum alloy single wire 20 before stranding; S4, Post-processing: after stranding, low-temperature annealing at 200°C for 30 min is performed, followed by plasma cleaning and chemical bonding using a silane coupling agent to make the roughness Ra of the outer surface of the stranded wire preform 2.1 μm; an electrostatic spraying process is used to spray a nano-composite coating 4 (2% graphene, 5% silicon carbide nanoparticles, 1% aluminum oxide nanosheets, and the balance of silicone) on the outer surface of the stranded wire preform, with a thickness of 30 μm and an adhesion of the nano-composite coating 4 of 19 MPa.

[0051] Comparative Example 1 Comparative Example 1 is basically the same as Examples 2-4, with the only difference being that the high-carbon steel core 10 does not contain vanadium and titanium.

[0052] Comparative Example 2 Comparative Example 2 is basically the same as Examples 2-4, with the only difference being that the high-carbon steel core 10 does not contain yttrium or lanthanum.

[0053] Comparative Example 3 Comparative Example 3 is basically the same as Examples 2-4, with the only difference being that a traditional epoxy coating is applied to the outer surface of the stranded wire preform after stranding.

[0054] Performance Test: The tensile strength and elongation of the high-carbon steel core 10 are tested according to GB / T 228.1-2010; the interfacial shear strength of the aluminum-clad steel core is determined according to GB / T 6396-2023; the direct current resistance of the high-carbon steel core 10 and the aluminum alloy single wire 20 is determined according to GB / T 3048.2-2007; the tensile strength and elongation of the aluminum alloy single wire 20 are determined according to GB / T 6892-2015; the salt spray life of the aluminum-clad steel core aluminum alloy strand is determined according to ASTM B117; and the adhesion of the coating is tested according to GB / T 30776-2014.

[0055] Table 1 Comparison table of performance data of aluminum-clad steel core aluminum alloy in examples 2-4 and comparative examples 1 and 2

[0056] Table 2 Comparison table of performance test of aluminum-clad steel core aluminum alloy in examples 2-4 and comparative example 3

[0057] According to Tables 1 and 2, the high-carbon steel core 10 and the aluminum alloy single wire 20 based on specific component contents, and the nano-composite coating 4 coated thereon, make the aluminum-clad steel core aluminum alloy strand have better performance data than comparative examples 1-3. Meanwhile, the optical fiber sensing unit 3 arranged in the high-carbon steel core 10 at the center of the core layer 1 and between the aluminum alloy single wires 20 makes the aluminum-clad steel core aluminum alloy strand realize intelligent monitoring in the use process, monitors the temperature and stress distribution of the aluminum-clad steel core aluminum alloy strand, and prevents core breakage.

[0058] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiments based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire, characterized in that: Aluminum clad steel core aluminum alloy stranded wire includes: The core layer (1) is composed of a plurality of high-carbon steel cores (10) and a pure aluminum layer (11) coated on the surface thereof to form an aluminum-clad steel core, and the pure aluminum layer (11) and the high-carbon steel core (10) are metallurgically bonded to form an iron-aluminum intermetallic compound diffusion layer (101); The outer layer (2) is formed by twisting a plurality of aluminum alloy single wires (20); The optical fiber sensing unit (3) comprises at least one optical fiber (30) encapsulated in a metal microtube (32), and arranged along the axial direction of the stranded wire at the center of the core layer (1) and between the aluminum alloy single wires (20) of the outer layer (2); The outer surface of the aluminum-clad steel core aluminum alloy stranded wire is coated with a nanocomposite coating (4).

2. The high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 1, characterized in that: The tensile strength of the stranded aluminum-clad steel core is ≥1820MPa, the elongation is ≥2.0%, and the DC resistance at 20℃ is ≤123.15Ω / km; the aluminum alloy single wire (20) is ≥252MPa, the elongation is ≥2.0%, and the DC resistance at 20℃ is ≤28.606Ω / km.

3. The high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 1, characterized in that: The high carbon steel core (10) has a carbon content of 0.6% to 0.8% by mass and contains 0.05% to 0.15% of vanadium and titanium; the pure aluminum layer (11) forms a metallurgical bonding interface with the high carbon steel core (10) through a continuous extrusion cladding process, and the thickness of the metallurgical bonding interface is 15% to 20% of the diameter of the high carbon steel core (10); and the thickness of the iron-aluminum intermetallic compound diffusion layer (101) is 5 μm to 15 μm.

4. The high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 1, characterized in that: Measured by mass percentage, the aluminum alloy single wire (20) includes 0.5% to 0.8% magnesium, 0.4% to 0.7% silicon, 0.1% to 0.3% zirconium, 0.02% to 0.1% yttrium or lanthanum, and the remainder is aluminum and unavoidable impurities, and the impurity content is less than 0.3%.

5. The high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 1, characterized in that: In terms of mass percentage, the nanocomposite coating (4) comprises 0.5% to 2% of graphene, 3% to 5% of silicon carbide nanoparticles, 1% to 3% of aluminum oxide nanosheets, and the remainder is polyimide or silicone resin, and the coating thickness is 20 μm to 30 μm.

6. The high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 1, characterized in that: In the core layer (1), a high carbon steel core (10) located at the center of the core layer (1) is laser-opened to form a channel (100) for assembling the optical fiber sensing unit (3), and epoxy resin is filled in the channel (100); In the outer layer (2), the optical fiber sensing unit (3) and the aluminum alloy single wire (20) are twisted together to form a structure.

7. The high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 1, characterized in that: The optical fiber (30) is a Bragg grating optical fiber (30) or a distributed sensing optical fiber (30), the outer diameter of the metal microtube (32) is 0.5 mm to 1.0 mm, and the interior thereof is filled with a silicone gel buffer layer (33), and the surface of the optical fiber (30) is coated with a polyimide coating (31) with a thickness of 15 to 20 μm.

8. A method for preparing high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire, characterized in that: The following steps are involved: S1, pretreatment of the high carbon steel core (10): pickling and electroplating the high carbon steel core (10) with an aluminum transition layer, followed by coating the high carbon steel core (10) with a pure aluminum layer (11) at 350°C to 450°C using a continuous extrusion process, inserting the encapsulated optical fiber sensing unit (3) into the central hole (100) of the high carbon steel core (10), and then drawing and segmented annealing to form an aluminum-clad steel core; S2, preparation of heat-resistant aluminum alloy: vacuum melting aluminum, magnesium, silicon, zirconium, yttrium or lanthanum, and then subjecting it to electromagnetic stirring, continuous casting and rolling to form an aluminum alloy single wire (20), with the final rolling temperature ≤250°C; S3, twisting and forming: using a constant tension stranding machine to twist the aluminum-clad steel core, the outer layer (2) aluminum alloy single wire (20) and the optical fiber sensing unit (3) to obtain a stranded wire preform, with a stranded pitch ratio of 10 to 14, and applying a 2° to 3° pre-twist to the aluminum alloy single wire (20) before twisting; S4, post-processing: after twisting, the strands are subjected to low-temperature annealing at 200°C for 30 min, and a nano-composite coating (4) is sprayed on the outer surface of the stranded wire preform using an electrostatic spraying process.

9. The method for preparing a high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 8, characterized in that: The stranded wire preform formed by stranding in step S3 is subjected to low temperature annealing and then plasma cleaning and chemical bonding using a silane coupling agent. The surface roughness Ra of the stranded wire preform after plasma cleaning is greater than or equal to 1.5 μm.

10. The method for preparing a high-strength and high-elongation aluminum-clad steel core aluminum alloy stranded wire according to claim 9, characterized in that: The adhesion of the nanocomposite coating (4) is ≥15 MPa.

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