Al-Mg-Si-RE-based aluminum alloy conductor for 10-35kV middle and low voltage cable and preparation method thereof

Abstract

The invention relates to the technical field of preparation of aluminum alloy conductor materials, and particularly discloses a preparation method of an Al-Mg-Si-RE-based aluminum alloy conductor for a 10-35kV middle and low voltage cable, which comprises the following steps: adding a microalloyed intermediate alloy into an aluminum melt by adopting an addition method, stirring, smelting, refining, and casting to form, thereby obtaining the Al-Mg-Si-RE-based aluminum alloy conductor for the 10-35kV middle and low voltage cable. And performing annealing, rolling, wire drawing and aging heat treatment to obtain a final product. Wherein in the smelting stage, raw materials are completely melted at 700-750 DEG C; hexachloroethane is used as a refining agent for refining; annealing at 330-350 DEG C and preserving heat for 4-8 hours; and aging at 300 DEG C for 10 hours after deformation. In the preparation of a wire of a 10-35kV medium and low voltage power cable, the aluminum alloy wire has high conductivity of 62.1-62.5% IACS (International Annealed Copper Standard) and tensile strength of 101-117MPa by simplifying the process steps and optimizing the element ratio on the premise of ensuring the controllable raw material cost, and the mechanical property and electrical property requirements of the medium and low voltage wire are balanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy conductor material preparation, and particularly relates to an Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cables and a preparation method thereof. BACKGROUND

[0002] Compared with copper conductors, aluminum alloy conductors have become the preferred material for copper replacement power transmission due to the advantages of low density (2.7g / cm3), low cost (only 30%-40% of copper), strong corrosion resistance, etc. The traditional 6-series aluminum alloy (such as 6061 and 6063) is often used in the current aluminum alloy conductor. However, there are still two major bottlenecks: 1. Insufficient electrical conductivity (usually the electrical conductivity of such cables is only 59-60% IACS, and an increase of 2% means a significant reduction in loss), resulting in high power transmission loss; 2. Low high-temperature strength (tensile strength decreases by more than 20% at >150℃), which easily causes thermal aging of the insulation layer and restricts its large-scale application in distribution networks. In the traditional 6-series aluminum alloy, the proportion of magnesium and silicon is usually controlled at Mg:Si≈1.73 to form the main strengthening phase Mg2Si, and the commonly used grades are 6061 alloy and 6063 alloy. Therefore, in recent years, the research focus of 6-series aluminum alloy has mainly concentrated on adding noble metals or optimizing performance through complex processes, but the effect is limited. A high-conductivity and heat-resistant aluminum alloy for cable conductors and an aluminum alloy conductor wire disclosed in CN110284017A emphasizes that Fe, Zr and Sc must be added and the hot extruded rod is subjected to online water cooling treatment to improve the heat resistance and mechanical properties of the alloy. CN104451288A discloses an aluminum alloy with high electrical conductivity and high tensile strength, which relies on the composite addition of Fe and Mn to make the tensile strength ≥170MPa but the electrical conductivity is only 56.5% IACS.

[0003] Based on the existing patents, the requirements of sacrificing a certain amount of mechanical strength to compensate for the electrical conductivity of 10-35kV medium and low voltage cables cannot be met. Therefore, the present application aims to provide a new preparation method of Al-Mg-Si-RE-based aluminum alloy conductor wire balancing electrical conductivity and mechanical strength, through "iron-free high-conductivity" alloy design (Fe≤0.05%) and short process design, to realize the lightweight laying and high-efficiency transmission of the power system and meet the needs of future power grid development. The electrical conductivity of the conductor wire is improved to 62.5% IACS (reaching the international leading level), and according to the data of the State Grid, 210 million degrees of electricity are saved per 10,000 kilometers of conductor wire per year, equivalent to economic benefits of 130 million yuan. The increase in electrical conductivity reduces power transmission loss by 1.5%-2%, and the whole life cycle of each ton of conductor wire reduces CO2 emission by 8.5 tons. SUMMARY

[0004] In view of the above, the present application provides a kind of 10~35kV middle-low voltage cable Al-Mg-Si-RE base aluminum alloy conductor preparation method, balance conductivity and mechanical strength, by optimizing short process process design and Mg-Si-RE synergistic strengthening (Mg0.6~1.0%, RE 0.1~0.3%), in no Fe condition realizes strength 101~117MPa, satisfies GB / T 30551-2014 standard (≥95MPa), realizes the lightweight and high efficiency transmission of power system, satisfies the demand of future power grid development.The specific technical scheme is as follows: A kind of 10~35kV middle-low voltage cable Al-Mg-Si-RE base aluminum alloy conductor preparation method, comprising the following steps: (1) melting: by adding method, micro-alloying inter-alloy and rare earth compound are placed in crucible, and temperature is raised to 750~800 ℃ and melted into melt;Pure aluminum particles are added to the melt, and the temperature is adjusted to 700~750 ℃ and stirred for 20~40 min to obtain the final melt; (2) refining: refining agent is added to the melt, and after stirring for 5 min, it is placed for 5~15 min, and the dross is removed, and then short-time solid solution is kept for 20~40 min to obtain refined melt; (3) pouring and cleaning: the refined melt is poured into preheated high-temperature mold and cooled and solidified, and washed with water to obtain ingot; (4) annealing and deformation: the ingot is annealed at 330~350 ℃ for 4~8 h, water quenching, and then cold rolling is made into Φ2.8 mm alloy square rod, and then cold drawing is made into Φ2 mm conductor forming to obtain Y-state Al-Mg-Si-RE base aluminum alloy conductor; (5) aging, to obtain the final R-state aluminum alloy conductor, i.e.10~35kV middle-low voltage cable Al-Mg-Si-RE base aluminum alloy conductor; The composition of the aluminum alloy conductor is as follows: silicon 0.4~0.6%, magnesium 0.6%~1%, boron 0.05%, copper 0.1%, rare earth elements 0.1%~0.3%, and the balance is aluminum and unavoidable impurities.

[0005] The technical scheme of the present application mainly improves the conductivity and mechanical strength of the aluminum conductor by adding alloy elements, simplifying the processing technology and controlling the heat treatment. The addition of boron can react with impurity elements in the aluminum alloy to form borides, thereby reducing the scattering effect of impurity elements on electrons and improving the conductivity of the alloy; copper can be solid-solved in the aluminum matrix to reduce lattice distortion and help form Al2Cu strengthening phase, thereby further improving the mechanical strength and heat resistance of the alloy during aging treatment; rare earth metal elements can significantly strengthen the aluminum alloy conductor material, refine the grains and purify the grain boundaries, and improve the strength and plasticity of the aluminum alloy by inhibiting impurity segregation and forming stable compounds. However, during the casting process, rapid cooling of the molten metal can cause thermal stress accumulation and increase the risk of cracks. Therefore, the cooling rate can be slowed down by preheating the mold to reduce thermal stress and thermal cracks, and a dense casting structure can be obtained by using different heat treatment methods. The short-time solid solution heat treatment at 700-750℃ for 30min makes the alloy elements uniformly dissolved in the aluminum matrix to form a supersaturated solid solution, which prepares for subsequent treatment (especially annealing and aging strengthening), while inhibiting Mg2Si coarsening, inhibiting abnormal grain growth and controlling oxidation loss. Annealing at 330-350℃ for 4-8h causes magnesium, silicon and other alloy elements in the supersaturated solid solution to precipitate in the form of dispersed second-phase small particles, while releasing part of the internal stress.

[0006] Impurity elements Fe (iron) and Zn (zinc) in the alloy are solid-solved in the aluminum matrix, which can cause significant lattice distortion, affecting not only the conductivity but also the plasticity and fatigue performance of the alloy. Therefore, we adopt the method of adding refining agents to optimize the melting system, and control the content of trace elements in the alloy by controlling the process parameters such as temperature and stirring, so as to remove or convert the impurity elements into harmless phases as much as possible.

[0007] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium-low voltage cables, the intermediate alloy is: aluminum-magnesium alloy, aluminum-silicon alloy, aluminum-silicon-boron alloy, and aluminum-copper alloy.

[0008] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium-low voltage cables, the method further comprises: pretreating the raw materials before melting: drying and weighing the aluminum-magnesium alloy, aluminum-silicon alloy, aluminum-silicon-boron alloy, aluminum-copper alloy, rare earth compound, pure aluminum particles and refining agent.

[0009] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium-low voltage cables, the refining agent is hexachloroethane (C2Cl6).

[0010] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cable, the amount of the refining agent is 1-5% of the total weight of the melt.

[0011] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cable, the aging process parameters are: 300℃ for 10h. After deformation, the aluminum alloy conductor wire is aged at 300℃ for 10h, so that the size and distribution of the second phase particles are adjusted, the size of the second phase particles is small and the distribution is uniform, the lattice distortion and dislocation density are reduced, the electron scattering and the influence on the electrical conductivity are reduced, and the mechanical properties of the aluminum alloy conductor material are optimized. The heat treatment scheme can balance the electrical conductivity and mechanical properties of the aluminum alloy conductor material.

[0012] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cable, the purity of the pure aluminum particles is ≥99.7%, the rare earth compound is cerium / lanthanum mixed nano-oxide, and the mass ratio of cerium to lanthanum in the rare earth compound is 7:3. The trace elements magnesium, silicon, boron, copper and rare earth metal elements added in the raw material formula can be added into the melt in the form of intermediate alloy or compound; wherein, the high-purity particles have low cost and can reduce the influence of impurities on the properties of the aluminum alloy, but the problems of slow dissolution speed and easy oxidation need to be overcome; the intermediate alloy has fast dissolution speed, uniform distribution, low oxidation tendency and high process safety.

[0013] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cable, the mold material is steel, cast iron, nickel, tungsten, molybdenum or graphite.

[0014] In another aspect, the application also provides an Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cable, which is prepared by the above preparation method.

[0015] Preferably, in the preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35kV medium and low voltage cable, the electrical conductivity of the aluminum alloy conductor wire is 62.1-62.5%IACS, the tensile strength is 101-117MPa, and the elongation is 14.3-14.8%.

[0016] Compared with the prior art, the application has the following beneficial effects: The preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor for 10-35 kV medium and low voltage cables has three innovations of "component design (without Fe+RE cooperation), process simplification (short-time solid solution by adding method smelting), and heat treatment optimization (medium temperature annealing+high temperature aging)", which balances the mechanical and electrical performance requirements of the medium and low voltage conductor under the premise of controllable raw material cost, meets the design requirements of the lightweight and high efficiency transmission of the power system, and provides key technical support for the lightweight and energy saving of the medium and low voltage cable. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating laborious work on the basis of these drawings.

[0018] Figure 1 The preparation process flow chart of the Al-Mg-Si-RE-based aluminum alloy conductor for 10-35 kV medium and low voltage cables is Y hard state and R soft state. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application will be described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments. Unless otherwise defined, all professional terms used below have the same meaning as understood by those skilled in the art. The professional terms used in this paper are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0020] Example 1 A preparation method of an Al-Mg-Si-RE-based aluminum alloy conductor for 10-35 kV medium and low voltage cables, the aluminum alloy conductor composition is 0.5% silicon, 0.65% magnesium, 0.05% boron, 0.1% copper, 0.2% rare earth compound with a mass ratio of Ce:La of 7:3, and the balance is aluminum and unavoidable impurities; the preparation process is as shown in Figure 1 The specific steps are as follows: (1) Melting: the micro-alloyed intermediate alloy and the rare earth compound are placed in the crucible by adding method, and the temperature is raised to 750℃ to melt into a melt; pure aluminum particles are added to the melt, and the temperature is adjusted to 700℃ and stirred for 20 min to obtain the final melt; (2) Refining: adding a refining agent to the melt, stirring for 5 min, then standing for 5 min, removing the dross, short-term solid solution heat preservation for 20 min, to obtain a refined melt; (3) Casting and cleaning: pouring the refined melt into a preheated high-temperature resistant mold, cooling and solidifying, and cleaning with water to obtain an ingot; (4) Annealing and deformation: annealing the ingot at 330℃ for 4h, water quenching, then cold rolling into a Φ2.8 mm alloy square rod, and then cold drawing into a Φ2 mm wire to form an Al-Mg-Si-RE-based aluminum alloy wire in Y state; (5) Aging at 300℃ for 10h to obtain the final aluminum alloy wire, which is an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium and low voltage cables; Example 2 A preparation method of an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium and low voltage cables, the composition of the aluminum alloy wire is as follows in terms of mass percentage: silicon 0.5%, magnesium 0.75%, boron 0.05%, copper 0.1%, Ce:La mass ratio of 7:3 rare earth compound 0.2%, and the balance being aluminum and unavoidable impurities; the preparation process is as shown in Figure 1 , and the specific steps are as follows: (1) Melting: placing the micro-alloyed intermediate alloy and rare earth compound in the crucible by adding method, heating to 750℃ to melt into a melt; adding pure aluminum particles to the melt, adjusting the temperature to 700℃, and stirring for 30 min to obtain a final melt; (2) Refining: adding a refining agent to the melt, stirring for 5 min, then standing for 10 min, removing the dross, short-term solid solution heat preservation for 30 min, to obtain a refined melt; (3) Casting and cleaning: pouring the refined melt into a preheated high-temperature resistant mold, cooling and solidifying, and cleaning with water to obtain an ingot; (4) Annealing and deformation: annealing the ingot at 340℃ for 6h, water quenching, then cold rolling into a Φ2.8 mm alloy square rod, and then cold drawing into a Φ2 mm wire to form an Al-Mg-Si-RE-based aluminum alloy wire in Y state; (5) Aging at 300℃ for 10h to obtain the final aluminum alloy wire, which is an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium and low voltage cables; Example 3 A preparation method of an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium and low voltage cables, the composition of the aluminum alloy wire is as follows in terms of mass percentage: silicon 0.5%, magnesium 0.85%, boron 0.05%, copper 0.1%, Ce:La mass ratio of 7:3 rare earth compound 0.2%, and the balance being aluminum and unavoidable impurities; the preparation process is as shown in Figure 1 , and the specific steps are as follows: (1) Melting: the micro-alloying intermediate alloy and rare earth compound were placed in the crucible by adding method, and melted into a melt by heating to 750℃; pure aluminum particles were added to the melt, and the temperature was adjusted to 700℃ for stirring for 30 min to obtain the final melt; (2) Refining: a refining agent was added to the melt, stirred for 5 min, and then placed for 10 min, and the dross was removed, and then short-term solid solution was preserved for 30 min to obtain a refined melt; (3) Casting and cleaning: the refined melt was poured into a preheated high-temperature mold to cool and solidify, and then washed with water to obtain an ingot; (4) Annealing and deformation: the ingot was annealed at 340℃ for 6h, water quenched, then cold rolled into a Φ2.8 mm alloy square rod, and then cold drawn into a Φ2 mm wire to form an Y-state Al-Mg-Si-RE-based aluminum alloy wire; (5) Aging at 300℃ for 10h to obtain the final aluminum alloy wire, which is an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium-low voltage cable.

[0021] Example 4 A preparation method of an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium-low voltage cable, the aluminum alloy wire composition is as follows in mass percentage: silicon 0.5%, magnesium 0.95%, boron 0.05%, copper 0.1%, Ce:La mass ratio of 7:3 rare earth compound 0.2%, and the balance is aluminum and unavoidable impurities; the preparation process is as shown in Figure 1 , and the specific steps are as follows: (1) Melting: the micro-alloying intermediate alloy and rare earth compound were placed in the crucible by adding method, and melted into a melt by heating to 750℃; pure aluminum particles were added to the melt, and the temperature was adjusted to 700℃ for stirring for 40 min to obtain the final melt; (2) Refining: a refining agent was added to the melt, stirred for 5 min, and then placed for 15 min, and the dross was removed, and then short-term solid solution was preserved for 40 min to obtain a refined melt; (3) Casting and cleaning: the refined melt was poured into a preheated high-temperature mold to cool and solidify, and then washed with water to obtain an ingot; (4) Annealing and deformation: the ingot was annealed at 350℃ for 8h, water quenched, then cold rolled into a Φ2.8 mm alloy square rod, and then cold drawn into a Φ2 mm wire to form an Y-state Al-Mg-Si-RE-based aluminum alloy wire; (5) Aging at 300℃ for 10h to obtain the final aluminum alloy wire, which is an Al-Mg-Si-RE-based aluminum alloy wire for 10-35kV medium-low voltage cable.

[0022] Comparative Example 1 The difference from Example 3 is that the magnesium content is about 0.5% (magnesium-silicon ratio is about 1), and the balance is aluminum.

[0023] Comparative Example 2 The difference from Example 3 is that the ingot is annealed at 300℃ for 6h, and the percentages of each element and other process parameters remain unchanged.

[0024] Comparative Example 3 The difference from Example 3 is that the ingot is annealed at 340℃ for 12h, and the percentages of each element and other process parameters remain unchanged.

[0025] Comparative Example 4 The difference from Example 3 is that the aging is at 210℃ for 10h, and the percentages of each element and other process parameters remain unchanged.

[0026] Comparative Example 5 The difference from Example is that the element ratio and preparation process of traditional 6 series aluminum alloy 6063 are used: silicon is about 0.5%, magnesium is about 0.75%, and the balance is aluminum.

[0027] Table 1 is the element ratio of the aluminum alloy wires of the examples and comparative examples.

[0028] Table 1 is the element ratio of the aluminum alloy wires of the examples and comparative examples. The electrical conductivity and mechanical properties of the Al-Mg-Si-RE-based aluminum alloy wires prepared in Examples 1-4 and Comparative Examples 1-5 are tested, and the results are shown in Table 2. As can be seen from Comparative Example 2 and Comparative Example 3, insufficient annealing temperature or excessive annealing time will result in a decrease in wire performance; compared with the comparative examples, the new Al-Mg-Si-RE-based aluminum alloy wires (Examples 1-4) prepared by the trace element ratio and process flow of the present application can all meet the electrical conductivity ≥62%IACS, among which Example 3 not only improves the electrical performance but also takes into account the mechanical performance (tensile strength ≥110MPa, elongation ≥14%), meeting the design requirements of lightweight laying and high-efficiency transmission of the power system.

[0029] Table 2 is the wire electrical conductivity and mechanical properties of Examples 1-4 and Comparative Examples. The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A method for preparing Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables, characterized in that, It comprises the following steps: (1) Melting: adopt the method of adding micro-alloying inter-alloy and rare earth compound in the crucible, heating to 750~800℃ to melt into the melt; adding pure aluminum particles to the melt, adjusting the temperature to 700~750℃, stirring and holding for 20~40min to obtain the final melt; (2) Refining: adding refining agent to the melt, stirring for 5min, then standing for 5~15min, removing the dross, and short-time solid solution holding for 20~40min to obtain the refined melt; (3) Casting and cleaning: pouring the refined melt into a preheated high-temperature mold, cooling and solidifying, and cleaning with water to obtain the ingot; (4) Annealing and deformation: annealing the ingot at 330~350℃ for 4~8h, water quenching, then rolling and drawing to form Y-state Al-Mg-Si-RE-based aluminum alloy wire; (5) Aging, obtaining the final aluminum alloy wire, which is the Al-Mg-Si-RE-based aluminum alloy wire for 10~35kV medium-low voltage cable; The aluminum alloy wire composition is as follows in mass percentage: silicon 0.4~0.6%, magnesium 0.6%~1%, boron 0.05%, copper 0.1%, rare earth elements 0.1%~0.3%, and the balance of aluminum and unavoidable impurities.

2. The method for preparing the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables according to claim 1, characterized in that, The inter-alloy is: aluminum-magnesium alloy, aluminum-silicon alloy, aluminum-boron alloy, and aluminum-copper alloy.

3. The preparation method of the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium-low voltage cables according to claim 1, characterized in that, It further comprises: Pretreatment of raw materials before melting: dry and weigh the aluminum-magnesium alloy, aluminum-silicon alloy, aluminum-boron alloy, aluminum-copper alloy, rare earth compound, pure aluminum particles, and refining agent respectively.

4. The method for preparing the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables according to claim 1, characterized in that, The refining agent is hexachloroethane.

5. The method for preparing the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables according to claim 1, characterized in that, The refining agent dosage is 1~5% of the total weight of the melt.

6. The method for preparing the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables according to claim 1, characterized in that, The aging process parameters are: 300℃ holding for 10h.

7. The method for preparing the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables according to claim 1, characterized in that, The purity of the pure aluminum particles is ≥99.7%, the rare earth compound is cerium / lanthanum mixed nano oxide, and the mass ratio of cerium to lanthanum is 7:

3.

8. The method for preparing the Al-Mg-Si-RE-based aluminum alloy conductor wire for 10-35 kV medium and low voltage cables according to claim 1, characterized in that, The mold material is steel, cast iron, nickel, tungsten, molybdenum, or graphite.

9. An Al-Mg-Si-RE based aluminum alloy conductor for 10-35 kV medium and low voltage cables, characterized in that, The aluminum alloy wire is prepared by the preparation method of any one of claims 1~8.

10. The Al-Mg-Si-RE based aluminum alloy conductor for 10-35 kV medium and low voltage cables according to claim 9, characterized in that, The aluminum alloy wire has a conductivity of 62.1~62.5%IACS, a tensile strength of 101~117MPa, and an elongation of 14.3~14.8%.

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