High-conductivity semi-hard aluminum alloy material and preparation method and application thereof

Abstract

The invention relates to a high-conductivity semi-hard aluminum alloy material as well as a preparation method and application thereof. The high-conductivity semi-hard aluminum alloy material comprises the following alloy elements in percentage by mass: 0.02-0.04% of B, 0.20-0.30% of Zr, 0.10-0.20% of La, 0.15-0.25% of Ce, less than or equal to 0.01% of (Ti + V + Cr + Mn) and the balance of aluminum and other inevitable trace impurity elements. Through the composite addition alloying design that the B element, the Zr element, the La element and the Ce element are added into the aluminum alloy, an Al3X strengthening phase is generated under a certain preparation technology, and the electric conductivity is improved on the basis that the strength and the heat resistance are guaranteed. The preparation method of the high-conductivity semi-hard aluminum alloy monofilament comprises two stages of aging treatment, in the first stage of aging treatment, heat preservation is carried out for 0.5-1 h at the temperature of 300-325 DEG C, in the second stage of aging treatment, heat preservation is carried out for 1-2 h within the range of 200-230 DEG C, and then room temperature cooling is carried out, due to the two stages of heat treatment, the precipitation speed is increased, the evolution process of a precipitated phase is changed, and finally the aluminum alloy monofilament with good comprehensive performance is obtained.

Description

Technical Field

[0001] The invention belongs to the field of power transmission conductor materials, and specifically relates to a high-conductivity semi-hard aluminum alloy material and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern society, the demand for electricity is growing. The demand for electricity in households, industries and commercial areas is increasing, especially during peak hours, when the power load often reaches its peak. The carrying capacity of traditional conductors is limited and it is difficult to meet the growing demand for electricity. Therefore, increasing the capacity of conductors has become a key measure to improve the power transmission capacity to ensure the stability and reliability of power supply. On the other hand, reducing the resistance of transmission conductors can improve the transmission efficiency of current. The loss of electric energy during transmission is reduced, which not only helps to save energy, but also reduces the cost of transmission and achieves economic benefits.

[0003] At present, the aluminum alloy conductors in the ordinary steel core aluminum stranded wire used in overhead transmission lines are mainly of two types: soft aluminum and hard aluminum. Soft aluminum conductors have higher conductivity, which can reach 63% IACS (International Annealed Copper Standard Conductivity), and can transmit electric energy more efficiently. However, the yield strength of soft aluminum conductors is relatively low, only 20-30 MPa, which may lead to creep relaxation at the joints and failure of joint connections during long-term use. Creep relaxation will increase the contact resistance, thereby affecting the transmission efficiency and safety of the line, and posing a safety hazard. Similarly, during the construction process, partial damage and scratches are prone to occur, affecting the construction efficiency. The tensile strength of high-conductivity hard aluminum conductors is 160-200 MPa, which is much higher than that of soft aluminum conductors, but its conductivity is lower than that of soft aluminum conductors, with a maximum of 61.5% IACS. Due to the low conductivity, it causes a large transmission loss during service, resulting in a waste of resources.

[0004] The above analysis shows that soft aluminum materials have low yield and tensile strength, and are prone to damage during construction, leaving safety hazards; although hard aluminum has excellent mechanical properties, it has low electrical conductivity and large transmission line losses. Therefore, it is necessary to develop an aluminum alloy conductor material with high electrical conductivity and good mechanical properties, and a certain degree of heat resistance, to achieve a synergistic improvement in mechanical and electrical properties. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the existing aluminum alloy has difficulty in achieving both strength and electrical conductivity and has poor heat resistance.

[0006] The purpose of the present invention is to adopt the following technical solutions to achieve:

[0007] The present invention provides a high-conductivity semi-hard aluminum alloy material, comprising the following alloy elements in percentage by mass: B:

[0008] 0.02~0.04%, Zr: 0.20~0.30%, La: 0.10~0.20%, Ce: 0.15~0.25%, (Ti+V+Cr+Mn)≤0.01%, the balance is aluminum and other inevitable trace impurity elements.

[0009] Preferably, the high-conductivity semi-hard aluminum alloy material is a high-conductivity semi-hard aluminum alloy monofilament.

[0010] Preferably, the electrical conductivity of the aluminum alloy monofilament at 20° C. is ≥ 63% IACS; and / or

[0011] The tensile strength of the aluminum alloy monofilament is 100-135 MPa; and / or

[0012] The elongation of the aluminum alloy monofilament is ≥3.0%; and / or

[0013] The room temperature strength residual rate of the aluminum alloy monofilament after being kept at 230° C. for 1 hour is ≥90%.

[0014] Based on the same inventive concept, the present invention also provides a method for preparing the high conductivity semi-hard aluminum alloy monofilament, comprising the following steps:

[0015] After the aluminum ingot is melted, Al-B, Al-Zr, Al-La, and Al-Ce master alloys are added to obtain aluminum alloy liquid;

[0016] Refining and casting the aluminum alloy liquid to obtain an aluminum alloy ingot;

[0017] Rolling the aluminum alloy ingot to obtain an aluminum alloy rod;

[0018] The aluminum alloy rod is drawn and aged to obtain the aluminum alloy monofilament.

[0019] Preferably, the aging includes first-level aging and second-level aging;

[0020] The first stage of aging is to keep the temperature at 300-325°C for the first time;

[0021] The second stage aging is to keep the temperature at 200-230°C for a second time and then cool to room temperature.

[0022] Preferably, the first time is 0.5 to 1 hour, and the second time is 1 to 2 hours.

[0023] Preferably, the step of melting the aluminum ingot and adding Al-B, Al-Zr, Al-La, Al-Ce master alloy to obtain aluminum alloy liquid comprises:

[0024] The aluminum ingot is completely melted at 730-750°C, and Al-B master alloy is added. After it is completely melted, Al-Zr, Al-La, and Al-Ce master alloys are added. After it is completely melted, electromagnetic stirring is performed for 20-30 minutes, and it is allowed to stand for 15-25 minutes to obtain aluminum alloy liquid.

[0025] Preferably, the refining step includes: controlling the temperature between 705 and 725° C., adding 0.25% to 0.6% of hexachloroethane by mass of the aluminum liquid, and then blowing in a chlorine-nitrogen mixed gas, wherein nitrogen accounts for 75 to 85%, for 10 to 15 minutes, and slagging after standing for 20 to 30 minutes.

[0026] Preferably, the casting step comprises: pouring the aluminum alloy liquid into a mold within a temperature range of 700 to 725° C. to obtain an aluminum alloy ingot.

[0027] Preferably, the rolling step comprises: keeping the aluminum alloy ingot at 500-520°C for 2-5 hours, and rolling it for 6-10 times to obtain Aluminum alloy rod, water cooling.

[0028] Preferably, the drawing step comprises: drawing the aluminum alloy rod through 10 to 15 passes to obtain Aluminum alloy monofilament;

[0029] The wire drawing speed is controlled within the range of 6 to 12 m / s, and the cross-sectional change rate of each drawing is controlled within the range of 15 to 25%.

[0030] Based on the same inventive concept, the present invention also provides an application of the high-conductivity semi-hard aluminum alloy monofilament or the high-conductivity semi-hard aluminum alloy monofilament prepared according to the preparation method in overhead power transmission lines.

[0031] The overhead transmission line can be formed by twisting the aluminum alloy monofilament with a core support material. There are multiple options for the core support material, mainly including galvanized Invar wire, extra-strong steel core wire or carbon fiber core wire.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The role and mechanism of each alloying element in the aluminum alloy material are as follows:

[0034] Boron: After adding B element to aluminum alloy, B can act as a modifier to effectively refine the grains of the alloy. The refined grains can reduce defects and stress concentration at the grain boundaries, thereby improving the mechanical and electrical properties of the alloy. The addition of B element also helps to purify the melt. In aluminum alloys, the presence of elements such as Cr, Mn, V, and Ti will affect the properties of the alloy. After adding B element, solid impurity compounds will be formed during the smelting process, and the effect of impurity removal will be achieved after filtration. After impurity removal, the grain boundaries of the aluminum alloy are purer after solidification, which improves the purity of the alloy. Due to the refinement of grains and the purification of grain boundaries, the electrical conductivity and tensile strength of aluminum alloys are improved. Especially after cold deformation, the improvement in tensile strength is more obvious. The addition amount of B element does not exceed 0.05wt.% (mass fraction).

[0035] Zirconium: When zirconium is added to aluminum alloy, it easily forms ZrAl3 compounds with aluminum, which can refine the casting grains of the alloy. Zirconium can inhibit the recrystallization behavior of aluminum alloy, increase the recrystallization temperature of the alloy, and reduce the recrystallized grain size of the alloy. This helps to improve the strength, hardness and heat resistance of the alloy. In addition, it can also improve fracture toughness and corrosion resistance. The appropriate addition does not affect the conductivity of the alloy. For semi-hard aluminum alloys, the addition of zirconium can maintain good mechanical properties without significantly reducing the conductivity, and significantly improves the heat resistance of the alloy, which plays an important role in improving the capacity of the conductor.

[0036] Lanthanum: The addition of La can purify the melt, reduce the hydrogen content in the aluminum liquid, reduce the pinhole rate and porosity, reduce inclusions and harmful elements, etc. In addition, it can promote the refinement of grains, because the La element can fill the surface defects of the alloy phase, reduce the surface tension on the interface between the new and old phases, and thus increase the growth rate of the crystal nucleus. At the same time, La can also form a surface active film between the grains and the molten liquid, prevent the grains from growing, and refine the alloy. The addition of La can improve the tensile strength, yield strength and elongation of aluminum alloys. When the amount of La added is small, the strength, elongation and conductivity increase at the same time, and when the amount added is too much, the elongation will decrease due to the formation of intermetallic phases. In terms of electrical properties, the addition of La reduces the solid solubility of impurity elements in the Al matrix, thereby enhancing the conductivity. La can promote the formation of a passivation film on the surface, reduce the corrosion resistance of the alloy, and improve the corrosion resistance of the alloy.

[0037] Cerium: La is usually used together with other rare earth elements in the casting process of aluminum alloys. This is because the addition of different rare earth elements can produce synergistic effects with different effects, thereby more effectively improving the performance of the alloy. For example, the combined use of La and rare earth elements such as Ce can further improve the strength and corrosion resistance of aluminum alloys. Rare earth Ce can play a role in melt purification and grain refinement. In the early stage of aging heat treatment, a dispersed phase with a small size and high density and an L12 structure is first precipitated, becoming the heterogeneous nucleation core of other precipitated phases, significantly shortening the nucleation incubation period of the precipitated phase, increasing the nucleation density of the precipitated phase, promoting the precipitation of the strengthening phase, and forming second phase particles with good thermal stability. The joint action of La and Ce regulates the distribution and number density of the precipitated phase, reduces the precipitation-free zone near the grain boundary in the alloy, and delays the coarsening process of the precipitated phase, which can significantly improve the mechanical properties of the alloy at high temperature and enhance the precipitation strengthening effect of the alloy. The microstructure can be regulated in both the solidification and phase precipitation stages to improve the comprehensive performance of the alloy.

[0038] Titanium, vanadium, chromium, manganese: trace amounts of transition elements such as titanium, vanadium, chromium, manganese, etc. in aluminum alloy conductors will have a great impact on electrical conductivity, especially when the transition elements exist in the aluminum alloy matrix in the form of solid solution. Because they absorb the free electrons in the conductor and then fill their own incomplete electron layer, the electrical conductivity of the alloy is reduced. The electrical conductivity of aluminum alloy is much more sensitive to these transition elements than silicon, that is, under the same conditions, the reduction in electrical conductivity caused by extremely trace amounts of transition elements is about five times that of the same amount of silicon. Therefore, the content of such elements must be strictly controlled in aluminum alloy conductor materials. The present invention strictly controls the content of transition elements, and the mass fraction of (Ti+V+Cr+Mn) is less than 0.01%.

[0039] The high conductivity semi-hard aluminum alloy material of the present invention comprises the following alloy elements in mass percentage: B: 0.02-0.04%, Zr: 0.20-0.30%, La: 0.10-0.20%, Ce: 0.15-0.25%, (Ti+V+Cr+Mn)≤0.01%, and the balance is aluminum and other inevitable trace impurity elements. By adding B element, Zr element, La element and Ce element to the aluminum alloy, an Al alloy is generated under a certain preparation process. 3 X-reinforced phase improves electrical conductivity while ensuring strength and heat resistance.

[0040] The high conductivity semi-hard aluminum alloy single wire of the present invention can generate fine dispersed Al by rolling or extrusion because trace rare earth elements La and Ce are added to the aluminum alloy. 3The X strengthening phase has a good match with the matrix, reduces lattice distortion, and thus improves the electrical conductivity of the alloy; and has good high-temperature stability, which can improve the strength and heat resistance of the heat-resistant aluminum alloy monofilament. Adding trace Zr elements can further improve the strength and heat resistance. Based on this alloy component formula, the content of impurity elements is controlled, and the preparation process parameters are optimized. The heat-resistant aluminum alloy monofilament prepared in this way can significantly improve the electrical conductivity while ensuring mechanical properties and heat resistance.

[0041] The preparation method of the high conductivity semi-hard aluminum alloy monofilament of the present invention comprises two-stage aging treatment, wherein the first stage aging treatment is carried out at 300-325°C for 0.5-1h, and the second stage aging treatment is carried out at 200-230°C for 1-2h and then cooled to room temperature. 3 The precipitation temperature of (Zr, La, Ce) strengthening phase is relatively high, so the first stage aging temperature is in the range of 300-325℃. The second stage aging temperature is relatively high to prevent Al 3 (Zr, La, Ce) grow too fast. The double-stage heat treatment speeds up the precipitation speed, changes the evolution process of the precipitation phase, and finally obtains aluminum alloy single wire with good comprehensive performance. The strengthening phase Al dispersed and precipitated during the aging process 3 (Zr, La, Ce), with a scale of nanometers, can further improve the mechanical properties of aluminum alloy monofilaments. The precipitation of the dispersed phase changes the existence of microalloying elements in the aluminum matrix from a solid solution state to a precipitation state, reducing the degree of lattice distortion of the aluminum matrix, thereby improving the conductivity of the aluminum alloy monofilament. The strengthening phase allows the wire to serve for a long time at a higher temperature (150°C) while ensuring tensile strength and conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a scanning electron microscope photograph of the high conductivity semi-hard aluminum alloy single wire of Example 1 of the present invention. DETAILED DESCRIPTION

[0043] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0044] The high conductivity semi-hard aluminum alloy material of the present invention comprises the following alloy elements in percentage by mass: B: 0.02-0.04%, Zr: 0.20-0.30%, La: 0.10-0.20%, Ce: 0.15-0.25%, (Ti+V+Cr+Mn)≤0.01%, and the remainder is aluminum and other inevitable trace impurity elements.

[0045] The high-conductivity semi-hard aluminum alloy material of the present invention is a high-conductivity semi-hard aluminum alloy monofilament, and the preparation method thereof comprises the following steps:

[0046] (1) Melting: Place a crucible containing an industrial pure aluminum ingot (purity not less than 99.7%) into a melting furnace, turn on the power to increase the temperature, and keep the temperature until the temperature reaches 730-750°C; after the industrial pure aluminum ingot is completely melted, add Al-B master alloy for boronization treatment, and after the Al-B master alloy is melted, add Al-Zr, Al-La, and Al-Ce master alloys respectively. After the master alloy is completely melted, use electromagnetic stirring for 20-30 minutes, and let it stand for 15-25 minutes to obtain aluminum alloy liquid.

[0047] (2) Refining: The temperature is controlled between 705 and 725°C, and 0.25% to 0.6% (i.e., 2.5 to 6 kg per ton of aluminum liquid) of hexachloroethane (C 2 Cl 6 ), then blow in a chlorine-nitrogen mixed gas, of which nitrogen accounts for 75-85%, for 10-15 minutes, and let it stand for 20-30 minutes before scraping.

[0048] (3) Casting: The aluminum alloy liquid is poured into a metal mold at a temperature range of 700 to 725° C. to form an aluminum ingot having a cross-sectional size of (16 to 25) × (16 to 25) mm. During the casting process, the aluminum liquid is filtered using a corundum filter tube, a foam ceramic filter plate or a glass mesh bag.

[0049] (4) Rolling: The aluminum alloy ingot is placed in a muffle furnace at a high temperature of 500-520° C. for 2-5 hours. After the insulation is completed, the ingot is rolled into an aluminum alloy round bar of φ8-10 mm through 6-10 passes. The ingot is immediately cooled by spraying water to obtain an aluminum alloy round bar with a tensile strength of 90-125 MPa and an elongation of not less than 10%.

[0050] (5) Drawing: The aluminum alloy round rod prepared above does not need to be heat treated and can be directly drawn. The drawing speed is controlled at 6-12 m / s, and the cross-sectional change rate of the aluminum alloy sample is controlled within the range of 15-25% each time. After 10-15 drawing passes, a φ3.0-4.5 mm aluminum alloy single wire is finally obtained.

[0051] (6) Aging: A short-time high temperature-low temperature aging method is used for heat treatment in a circulating forced air oven. The first stage aging temperature is kept at 300-325°C for 0.5-1h. The second stage aging temperature is kept at 200-230°C for 1-2h and then cooled to room temperature to obtain a high conductivity semi-hard aluminum alloy single wire.

[0052] The high-conductivity semi-hard aluminum alloy material of the present invention has the characteristics of high conductivity and good heat resistance, and is twisted with a steel core or a carbon fiber core to form an overhead conductor. The semi-hard aluminum conductor can take into account the technical advantages of the high strength of hard aluminum and the high conductivity of soft aluminum conductors. The high-conductivity conductor reduces line loss during power transmission. At the same time, the conductor has high strength, reduces the defects caused by scratches during construction, improves construction efficiency and quality, and ensures that the conductor is safe and reliable.

[0053] Examples 1 to 7, Comparative Examples 1 to 2

[0054] The compositions of the high conductivity semi-hard aluminum alloy monofilaments of Examples 1 to 7 and Comparative Examples 1 to 2 are shown in Table 1.

[0055] Table 1 Composition of high conductivity semi-hard aluminum alloy monofilaments of Examples 1 to 7 and Comparative Examples 1 to 2 (wt.%)

[0056]

[0057] The preparation method of the high conductivity semi-hard aluminum alloy monofilament of Example 1 is as follows:

[0058] (1) Melting: Place a crucible containing an industrial pure aluminum ingot (purity not less than 99.7%) into a melting furnace, turn on the power to increase the temperature, and keep the temperature after reaching the temperature range of 740°C; after the industrial pure aluminum ingot is completely melted, add Al-B master alloy for boronization treatment, and after the Al-B master alloy is melted, add Al-Zr, Al-La, and Al-Ce master alloys respectively. After the master alloy is completely melted, use electromagnetic stirring for 25 minutes, and let it stand for 20 minutes to obtain aluminum alloy liquid.

[0059] (2) Refining: The temperature is controlled between 715°C, and 0.5% (i.e. 5 kg per ton of aluminum liquid) of hexachloroethane (C 2 Cl 6 ), then blow in a chlorine-nitrogen mixed gas, of which nitrogen accounts for 75%, for 15 minutes, and let it stand for 30 minutes before scraping.

[0060] (3) Casting: The aluminum alloy liquid is poured into a metal mold at a temperature of 720° C. to form an aluminum ingot having a cross-sectional size of 20×20 mm. During the casting process, the aluminum liquid is filtered using a glass mesh bag.

[0061] (4) Rolling: The aluminum alloy ingot is placed in a muffle furnace at a high temperature of 500°C for 4 hours. After the insulation is completed, the ingot is rolled for 10 passes. The aluminum alloy round rod is immediately cooled by spraying water to obtain an aluminum alloy round rod.

[0062] (5) Drawing: The aluminum alloy round rod prepared above does not need to be heat treated and is directly drawn. The drawing speed is controlled at 10 m / s, and the cross-sectional change rate of the aluminum alloy sample is controlled within 20% each time. After 10 drawing passes, a φ3.84 mm aluminum alloy single wire is finally obtained.

[0063] (6) Aging: A short-time high temperature-low temperature aging method is used for heat treatment in a circulating forced air oven. The first stage aging temperature is kept at 315°C for 0.5 h. The second stage aging temperature is kept at 210°C for 2 h and then cooled to room temperature to obtain a high conductivity semi-hard aluminum alloy single wire.

[0064] The high conductivity semi-hard aluminum alloy single wire obtained in Example 1 was observed under a scanning electron microscope. The results are as follows: Figure 1 As shown, Figure 1 The energy spectrum analysis is performed at points A and B in the figure, and the results are shown in Table 2.

[0065] Table 2 Figure 1 Medium energy spectrum element analysis (wt.%)

[0066]

[0067] "Bal." stands for balance.

[0068] The process parameters of the high conductivity semi-hard aluminum alloy single wire preparation process of Examples 2 to 7 and Comparative Examples 1 to 2 are basically the same, wherein Comparative Examples 1 to 2 only undergo a single-stage aging treatment. The specific differences are shown in Table 3.

[0069] Table 3 Process parameters of high conductivity semi-hard aluminum alloy single wire preparation process of Examples 1 to 7 and Comparative Examples 1 to 2

[0070]

[0071] Continued

[0072]

[0073]

[0074] The mechanical properties of the aluminum alloy rods obtained in Examples 1 to 7 and Comparative Examples 1 to 2 were tested, and the test results are shown in Table 4.

[0075] Table 4 Mechanical properties test results of the aluminum alloy rods of Examples 1 to 7 and Comparative Examples 1 to 2

[0076]

[0077] The electrical and mechanical properties of the high conductivity semi-hard aluminum alloy monofilaments obtained in Examples 1 to 7 and Comparative Examples 1 to 2 were tested. The test results are shown in Table 5.

[0078] Table 5 Mechanical and electrical properties test results of high conductivity semi-hard aluminum alloy monofilaments of Examples 1 to 7 and Comparative Examples 1 to 2

[0079]

[0080] It can be seen from Table 4 that the Al-Zr-La-Ce system semi-hard aluminum alloy rod designed by the present invention has excellent mechanical properties. After double-stage aging, the high-conductivity semi-hard aluminum monofilament in the embodiment in Table 5 has good mechanical and electrical properties, conductivity ≥63% IACS (20°C), tensile strength of 100-135MPa, elongation ≥3.0%, and long-term heat resistance temperature of 150°C (room temperature strength residual rate ≥90% after 230°C insulation for 1h), which meets the service conditions. However, the comparative example only has single-stage aging in the heat treatment link, which cannot give full play to the comprehensive performance of the Al-Zr-La-Ce system, the conductivity does not exceed 61% IACS, the tensile strength does not reach 100MPa, and the heat resistance is also poor (room temperature strength residual rate ≤90% after 230°C insulation for 1h). Therefore, the Al-Zr-La-Ce system semi-hard aluminum alloy designed by the present invention is combined with the double-stage aging heat treatment process to finally obtain an aluminum alloy monofilament with excellent comprehensive performance.

[0081] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A high conductivity semi-hard aluminum alloy material, characterized in that: The alloy elements include the following mass percentages: B: 0.02-0.04%, Zr: 0.20-0.30%, La: 0.10-0.20%, Ce: 0.15-0.25%, (Ti+V+Cr+Mn)≤0.01%, and the balance is aluminum and other inevitable trace impurity elements.

2. The high conductivity semi-hard aluminum alloy material according to claim 1, characterized in that: The high-conductivity semi-hard aluminum alloy material is a high-conductivity semi-hard aluminum alloy monofilament.

3. The high conductivity semi-hard aluminum alloy material according to claim 2, characterized in that: The electrical conductivity of the aluminum alloy monofilament at 20° C. is ≥ 63% IACS; and / or The tensile strength of the aluminum alloy monofilament is 100-135 MPa; and / or The elongation of the aluminum alloy monofilament is ≥3.0%; and / or The room temperature strength residual rate of the aluminum alloy monofilament after being kept at 230° C. for 1 hour is ≥90%.

4. A method for preparing a high conductivity semi-hard aluminum alloy monofilament as claimed in claim 2, characterized in that: The following steps are involved: After the aluminum ingot is melted, Al-B, Al-Zr, Al-La, and Al-Ce master alloys are added to obtain aluminum alloy liquid; Refining and casting the aluminum alloy liquid to obtain an aluminum alloy ingot; Rolling the aluminum alloy ingot to obtain an aluminum alloy rod; The aluminum alloy rod is drawn and aged to obtain the aluminum alloy monofilament.

5. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 4, characterized in that: The statute of limitations includes the first-level statute of limitations and the second-level statute of limitations; The first stage of aging is to keep the temperature at 300-325°C for the first time; The second stage aging is to keep the temperature at 200-230°C for a second time and then cool to room temperature.

6. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 5, characterized in that: The first time is 0.5 to 1 hour, and the second time is 1 to 2 hours.

7. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 4, characterized in that: The step of melting the aluminum ingot and adding Al-B, Al-Zr, Al-La, and Al-Ce master alloys to obtain aluminum alloy liquid comprises: The aluminum ingot is completely melted at 730-750°C, and Al-B master alloy is added. After it is completely melted, Al-Zr, Al-La, and Al-Ce master alloys are added. After it is completely melted, electromagnetic stirring is performed for 20-30 minutes, and it is allowed to stand for 15-25 minutes to obtain aluminum alloy liquid.

8. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 4, characterized in that: The refining steps include: controlling the temperature between 705 and 725° C., adding hexachloroethane at 0.25% to 0.6% of the mass of the aluminum liquid, and then blowing in a chlorine-nitrogen mixed gas, in which nitrogen accounts for 75% to 85%, for 10 to 15 minutes, and standing for 20 to 30 minutes before slagging.

9. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 4, characterized in that: The casting step comprises: pouring the aluminum alloy liquid into a mold within a temperature range of 700 to 725° C. to obtain an aluminum alloy ingot.

10. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 4, characterized in that: The rolling step comprises: keeping the aluminum alloy ingot at 500-520° C. for 2-5 hours, rolling it through 6-10 passes to obtain an aluminum alloy rod with a diameter of 8-10 mm, and water cooling it.

11. The method for preparing a high conductivity semi-hard aluminum alloy monofilament according to claim 4, characterized in that: The drawing step comprises: drawing the aluminum alloy rod through 10 to 15 passes to obtain an aluminum alloy monofilament of φ3.0 to 4.5 mm; The wire drawing speed is controlled within the range of 6 to 12 m / s, and the cross-sectional change rate of each drawing is controlled within the range of 15 to 25%.

12. Use of the high-conductivity semi-hard aluminum alloy monofilament as claimed in claim 2 or 3 in an overhead power transmission line.

13. Use of a high-conductivity semi-hard aluminum alloy monofilament prepared by the preparation method according to any one of claims 4 to 11 in an overhead power transmission line.

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