Low-resistivity 8030 alloy electrical round aluminum rod and preparation method thereof

Abstract

The invention discloses a low-resistivity 8030 alloy electrical round aluminum rod and a preparation method thereof, and belongs to the technical field of non-ferrous metal processing. In order to improve the electrical resistivity and mechanical properties of an 8030 alloy electrical round aluminum rod, the invention provides a low-resistivity 8030 alloy electrical round aluminum rod and a preparation method thereof, the low-resistivity 8030 alloy electrical round aluminum rod comprises the following components: 0.30-0.35% of Fe, 0.03-0.05% of Si, 0.15-0.20% of Cu, 0.003-0.008% of B, 0.005-0.03% of rare earth Ce / La, and the balance of Al and inevitable impurities, and the ratio of Fe to Si is 7.5 + / -1.0. By controlling the contents of iron, copper and silicon and using the abnormally high ratio of Fe / Si of 7.5 + / -1.0, the resistivity of the round aluminum rod at 20 DEG C is 28.40-28.70 n omega.m, the tensile strength of the round aluminum rod is 115-130 MPa, and double breakthrough of resistivity and strength is achieved.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing technology, and relates to an optimization of aluminum alloy conductors and their preparation process, specifically to a low resistivity 8030 alloy electrical round aluminum rod and its preparation method. Background Technology

[0002] Electrical aluminum poles, as a core product at the front end of high-voltage overhead lines and power cables, are widely used in various industries, including industrial and civil applications. With economic development, total electricity consumption increases annually, and cable conductor losses are the largest loss in the power industry. According to relevant data, on a 100km, 50kV high-voltage transmission line, a 1% reduction in resistivity can save 452,000 kWh of electricity annually. Surveys show that current grid losses account for 8.9% of power transmission. Therefore, reducing the resistivity of electrical aluminum poles can generate significant economic and social benefits, a consensus within the industry, and the market is vigorously promoting the research and application of high-conductivity and superconducting products.

[0003] The national standard GBT+3954-2022 stipulates that the resistivity (20℃) of 8030 alloy should be ≤29.73 nΩ·m. While high-purity aluminum rods (such as 1370) can achieve ≤28.01 nΩ·m, their mechanical strength is insufficient (tensile strength 80-135 MPa), making it difficult to meet the requirements of high-load applications. Existing optimization schemes for 8030 alloy focus on creep resistance, but the resistivity is still close to the upper limit of the national standard, mainly due to: 1. Imbalance in iron-silicon ratio: Traditional processes use an Fe / Si ratio of 1.5-2.0, and high iron content (>0.25%) exacerbates electron scattering at grain boundaries; 2. Defects in impurity control: Although direct supply of molten aluminum from electrolysis is energy-saving, the hydrogen content and inclusions worsen conductivity.

[0004] CN108374110A discloses an electrical round aluminum rod, comprising the following components by mass fraction: boron 0.01-0.12%, titanium 0.005-0.05%, rare earth 0.005-0.03%, silicon ≤0.06%, iron ≤0.10%, aluminum 99.7-99.9%, with an iron to silicon mass ratio of 1.8-2.3. CN114134357A discloses a manufacturing process for a high-strength, high-conductivity electrical round aluminum rod, wherein the mass fractions of each component in the rod are as follows: Re 0.2%~0.3%, Si 0.1%~0.15%, Fe 0.15%~0.25%, Ti 0.01%~0.05%, Te 0.05%~0.1%, Al 99.15%~99.49%. CN120133544A discloses a method for preparing high-strength, high-conductivity electrical round aluminum rods using powder metallurgy technology. The raw material preparation includes high-purity aluminum ingots, Zr, and rare earth elements. The Zr content is 0.01-0.2 wt%, the total content of rare earth elements is 0.10-0.30 wt%, and the balance is Al. However, these methods only produce ordinary electrical round aluminum rods, and due to the different mechanical properties required for different grades, they are not suitable for the production of 8030 grade electrical round aluminum rods.

[0005] CN106435235A discloses a method for preparing heat-resistant electrical round aluminum rods, comprising the following steps: adding aluminum-boron master alloy, aluminum-zirconium master alloy, and rare earth master alloy to electrolytic aluminum liquid and stirring to obtain an aluminum melt, such that the mass fraction of boron in the aluminum melt is 0.006-0.01%, the mass fraction of zirconium is 0.03-0.18%, and the mass fraction of rare earth is 0.10-0.25%. This method, by adding appropriate amounts of aluminum-boron master alloy, aluminum-zirconium master alloy, and rare earth master alloy to the electrolytic aluminum liquid to perform boronizing and refining treatment, is beneficial to obtaining more uniform and refined casting grains and improving the mechanical properties of the heat-resistant electrical round aluminum rod. This method also produces ordinary electrical round aluminum rods and is not applicable to the production of 8030 grade electrical round aluminum rods.

[0006] CN105950896A discloses a high-conductivity, high-mechanical-performance 8030 series electrical round aluminum rod, the composition of which is as follows by mass fraction: Si≤0.1%, Fe0.3%-0.8%, Mg≤0.05%, Zn≤0.05%, B0.001%-0.04%, rare earth oxides La2O30.2%-0.4%, Cu0.4%-0.9%, with the balance being Al. This method involves adding 0.2%-0.4% rare earth oxide La2O3 to the material and increasing the copper content from Cu 0.15%-0.3% to Cu 0.4%-0.9%. Rare earth oxide La2O3 not only removes impurities and hydrogen but also refines the grain size, thereby improving mechanical properties. As a result, the electrical conductivity of 8030 electrical round aluminum rod is increased to 62% IACS, the tensile strength can reach 230MPa, and the elongation exceeds 30%. Compared with 8030 electrical round aluminum rod, the electrical conductivity and mechanical properties are improved by 20-30% simultaneously. However, this method is based on remelting existing 8030 grade electrical round aluminum rods and adding La2O3 and Cu for secondary processing, rather than processing from raw materials such as molten aluminum or aluminum ingots. Since it is based on remelting 8030 round aluminum rods and then extruding them again, it will increase the processing cost significantly. Moreover, from a technical point of view, re-extruding 8030 electrical round aluminum rods with added La2O3 and Cu on an industrial production line, with a tensile strength of up to "230 MPa", will cause the extrusion rolls to break or become stuck in the rolls, leading to production line shutdowns and potential safety incidents. This is not feasible from an industrial perspective. Therefore, this method may only be used in the laboratory at any cost to improve relevant performance, but it does not have industrial production capabilities. In addition, the tensile strength of 8030 grade round aluminum rods is not necessarily better the higher it is. The 230 MPa round aluminum rod far exceeds the national standard range and, strictly speaking, does not belong to the 8030 grade round aluminum rod category. Summary of the Invention

[0007] The purpose of this invention is to improve the resistivity of 8030 alloy electrical round aluminum rods, enhance their mechanical properties, and reduce their production costs.

[0008] To achieve the above objectives, the present invention first provides a low resistivity 8030 alloy electrical round aluminum rod, which is composed of the following mass percentage components: Fe: 0.30~0.35%, Si: 0.03~0.05%, Cu: 0.15~0.20%, B: 0.003~0.008%, rare earth Ce / La: 0.005~0.03%, with the balance being Al and unavoidable impurities, and the Fe / Si ratio being 7.5±1.0.

[0009] Among them, the resistivity of the aforementioned low resistivity 8030 alloy electrical round aluminum rod at 20℃ is 28.40~28.70 nΩ·m, and the tensile strength is 115~130 MPa.

[0010] Among them, the elongation of the aforementioned low resistivity 8030 alloy electrical round aluminum rod is 15~18%, and the grain size is ≤50μm.

[0011] This invention also provides a method for preparing the above-mentioned low resistivity 8030 alloy electrical round aluminum rod, which includes the following steps: A. Raw material input: Using electrolytic aluminum liquid as raw material, mix electrolytic aluminum liquid and cold material at a mass ratio of 80~90%:20~10%, and heat and keep warm at 730℃~750℃; B. Ingredients: According to the composition of the 8030 alloy electrical round aluminum rod, add cerium chloride, lanthanum chloride or lanthanum-cerium chloride to the aluminum liquid along with the aluminum-iron alloy, aluminum-copper alloy and aluminum-boron alloy. C. Refining: The aluminum liquid after batching is refined. The refining agent consists of 40~60wt% magnesium chloride and 60~40wt% potassium chloride. The refining temperature is 730℃~750℃. The refining is carried out twice. Each refining time is not less than 20 minutes. The total amount of refining agent added is 20~40kg / 13t. After each refining is completed, the slag is removed and the mixture is allowed to stand. D. Degassing: After refining, the aluminum liquid is degassed, and the hydrogen content at the degassing outlet is controlled to be ≤0.20ml / 100gAl; E. Filtration: After degassing, the molten aluminum is filtered. F. Casting: The filtered aluminum liquid is cast, and the crystallization temperature is controlled at 690℃~710℃. During the casting process, the cooling water pressure is 0.1MPa~0.6MPa and the cooling water temperature is 25~40℃. G. Rolling: Roll according to the specifications of 8030 alloy electrical round aluminum rod, with a rolling speed of 15~25m / s, emulsion concentration of 5~8%, emulsion pressure of 0.1~0.5MPa, and emulsion temperature of 25~60℃, to obtain low resistivity 8030 alloy electrical round aluminum rod.

[0012] In the above preparation method, in step A, the Al content of the electrolytic aluminum liquid is ≥99.85wt%.

[0013] In the above preparation method, in step B, the aluminum-iron alloy is Al-10Fe or Al-20Fe; the aluminum-copper alloy is Al-50Cu; and the aluminum-boron alloy is Al-3B or Al-5B.

[0014] In the above preparation method, in step C, high-purity argon gas is used to inject the refining agent into the bottom of the furnace.

[0015] In the above preparation method, in step C, the standing time after each refining is 10-20 minutes.

[0016] In the preparation method described above, step D involves online degassing using argon gas at a flow rate of 3.0-4.0 cubic meters per hour and a pressure of 0.1-0.3 MPa.

[0017] In the above preparation method, step E involves filtration using a 40PPi+60PPi dual-stage filter plate.

[0018] The beneficial effects of this invention are: This invention optimizes the composition, controlling the iron content between 0.30% and 0.35% to form an Al3Fe strengthening phase, and precisely controlling the Fe content to avoid an increase in resistivity. The copper content is controlled between 0.15% and 0.20% to strengthen the electron transport path through solid solution, compensating for strength loss. The Si content is controlled between 0.03% and 0.05%, forming an exceptionally high Fe / Si ratio of 7.5±1.0 (commonly ≤2.0), suppressing harmful phase precipitation and reducing electron capture by free Si. Furthermore, boron is added to refine the grains, and rare earth elements are added to remove hydrogen, resulting in a melt hydrogen content ≤0.12mL / 100g. Simultaneously, the process is optimized. Through the synergistic effect of the composition and process, the resistivity of the 8030 alloy electrical round aluminum rod at 20℃ is 28.40~28.70 nΩ·m, and the tensile strength is 115~130 MPa, achieving a breakthrough in both resistivity and strength. Attached Figure Description

[0019] Figure 1 This is a performance testing diagram of the product according to an embodiment of the present invention. Detailed Implementation

[0020] Specifically, a low resistivity 8030 alloy electrical round aluminum rod has the composition shown in Table 1.

[0021] Table 1. Composition of the 8030 alloy electrical round aluminum rod of the present invention The national standard 8030 does not limit the addition of boron (B) and rare earth elements, while this invention controls the iron content to be between 0.30% and 0.35%, the copper content to be between 0.15% and 0.20%, and the Si content to be between 0.03% and 0.05%, and controls the Fe / Si ratio to be 7.5 ± 1.0. A high Fe / Si ratio reduces the capture of electrons by free Si. Boron refines the grains; TEM shows a 40% reduction in grain boundary density (based on grain boundary scattering theory). Rare earth elements remove hydrogen, resulting in a melt hydrogen content ≤0.12 mL / 100g (compared to the conventional ≥0.25 mL / 100g). This invention also optimizes the process, achieving breakthroughs in both resistivity and strength through the synergistic effect of composition and process. The properties of the 8030 alloy electrical round aluminum rod of this invention are shown in Table 2.

[0022] Table 2. Performance of the 8030 alloy electrical round aluminum rod of the present invention The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described herein.

[0023] Example 1 The aluminum alloy wire rod production line of Sichuan Qimingxing Aluminum Industry, in this embodiment, has an 8030 alloy electrical round aluminum rod with the following composition: Fe 0.30wt% + Si 0.04wt% + Cu 0.17wt% + B 0.005wt% + Ce 0.01wt%, with the balance being Al and unavoidable impurities. Its preparation process includes the following steps: (1) Raw material input: The raw material is the electrolytic aluminum liquid produced in the electrolysis workshop (hydrogen content 0.18mL / 100g). The aluminum liquid sample is analyzed for composition. The qualified electrolytic aluminum liquid (Al≥99.85wt%) is transported to the casting workshop in aluminum ladles and put into the holding furnace. Cold materials (aluminum ingots, unqualified wire rods, etc.) are added. The mass ratio of electrolytic aluminum liquid to cold materials is 90%:10%. The holding furnace is heated by natural gas combustion, and the melt temperature is 730℃~750℃.

[0024] (2) Batching: According to the composition of 8030 alloy electrical round aluminum rod, various alloying elements (Al-20Fe and Al-50Cu) are added to the aluminum liquid in the holding furnace to form alloy compounds as strengthening phases to improve the strength of the aluminum rod. Aluminum boron alloy (Al-3B) is added to reduce resistivity, and CeCl3 is added at the same time.

[0025] (3) Refining: Because the electrolytic aluminum liquid contains a lot of slag and gas, direct production will affect the product quality, so refining is required. The refining agent consists of 60wt% magnesium chloride and 40wt% potassium chloride. The refining temperature is controlled between 730℃ and 750℃. High-purity argon gas is used to spray the efficient and environmentally friendly refining agent into the bottom of the furnace. All parts of the furnace must be refined evenly. Each refining time is not less than 20 minutes. The refining is carried out twice. The total amount of refining agent added is 30kg / 13t. After each refining, the slag is removed, the temperature is measured, and the mixture is left to stand for 15 minutes.

[0026] (4) Degassing: After refining, the aluminum liquid is sent into the degassing box through the graphite rotor. Argon is used for online degassing. The argon flow rate is 3.5 cubic meters per hour and the argon pressure is 0.2 MPa. The hydrogen content at the degassing outlet is controlled within 0.20 ml / 100 g Al.

[0027] (5) Filtration: After degassing, the aluminum liquid is filtered using a 40PPi+60PPi dual-stage filter plate from MITEK to improve the purity of the melt. Before production, the filter plate must be inspected around its perimeter to ensure there are no gaps. The filter plate must also be intact and undamaged, with no floating debris. The surface scum of the degassing box and filter box must be cleaned thoroughly.

[0028] (6) Casting: The filtered aluminum liquid is cast, and the crystallization temperature is controlled at 690℃~710℃. The entire process is measured. Before production, the crystallization wheel is checked and polished smooth. The contact surface between the small ladle flare and the crystallization wheel is checked to ensure tight fit. During the casting process, the cooling water pressure is 0.1MPa~0.6MPa. The pressure of the cooling water nozzles in each section is checked, and no blockage is allowed. The water pressure in each section increases from small to large to achieve a slow cooling effect. The cooling water temperature is between 25~40℃.

[0029] (7) Rolling: Rolling is carried out according to the specifications of 8030 alloy electrical round aluminum rod, with a rolling speed of 18m / s, emulsion concentration of 6%, emulsion pressure of 0.1~0.5MPa, and emulsion temperature of 25~60℃.

[0030] (8) Take-up: After rolling, take up the wire with an outer diameter of 2000mm, an inner diameter of 600~900mm, and a height of 800~1100mm. When bundling, it is strictly forbidden to directly touch the surface of the wire rod with feet or dirty gloves. There should be no messy wires and the bundling should be neat. Visually inspect the surface of the aluminum rod for any burrs or sharp edges.

[0031] (9) Inspection: The mechanical and electrical properties of aluminum rods shall be performed in accordance with the national standard GB / T3954-2022.

[0032] The properties of the 8030 alloy electrical round aluminum rod obtained in this embodiment are as follows: Figure 1 As shown, the resistivity is 28.68 nΩ·m, the tensile strength is 117 MPa, the elongation is 15%, and the grain size is ≤50 μm. In this embodiment, when using a high amount of molten aluminum to prepare 8030 grade electrical round aluminum rods, all properties meet the national standard H14 requirements, and the resistivity is extremely low.

[0033] The following comparative examples and embodiments, using experiments with different iron, copper, and silicon contents, are the same as in Example 1. The experimental results are summarized in Table 3.

[0034] Table 3. Test results with different iron, copper, and silicon contents. Conclusion: Through comparative experiments, under the same process conditions, different alloy ratios have a significant impact on resistivity. In comparative documents 1-2, the Fe content was too high, resulting in an excessively large Fe / Si ratio, causing the resistivity to fail to meet the GB / T 3954-2020 standard. While comparative documents 3-7 met the GB / T 3954-2020 standard, their resistivity was still too high. Comparative example 8 met the requirements of this invention in terms of iron, copper, and silicon content, but its excessively large Fe / Si ratio limited the improvement in conductivity. This invention controls the iron content between 0.30-0.35%, the copper content between 0.15-0.20%, and the Si content between 0.03-0.05%, and maintains an Fe / Si ratio of 7.5±1.0, resulting in the optimal conductivity performance of the product.

Claims

1. A low resistivity 8030 alloy electrical round aluminum rod, characterized in that: Composed of the following percentage by mass Composition: Fe: 0.30~0.35%, Si: 0.03~0.05%, Cu: 0.15~0.20%, B: 0.003~0.008%, rare earth Ce / La: 0.005~0.03%, balance is Al and unavoidable impurities, and the Fe / Si ratio is 7.5±1.

0.

2. The low resistivity 8030 alloy electrical round aluminum rod according to claim 1, characterized in that: The resistivity of the electrical round aluminum rod at 20℃ is 28.40~28.70 nΩ·m, and the tensile strength is 115~130 MPa.

3. The low resistivity 8030 alloy electrical round aluminum rod according to claim 1, characterized in that: The elongation of the electrical round aluminum rod is 15~18%, and the grain size is ≤50μm.

4. The method for preparing the low resistivity 8030 alloy electrical round aluminum rod according to any one of claims 1 to 3, characterized in that: The following steps are involved: A. Raw material input: Using electrolytic aluminum liquid as raw material, mix electrolytic aluminum liquid and cold material at a mass ratio of 80~90%:20~10%, and heat and keep warm at 730℃~750℃; B. Ingredients: According to the composition of the 8030 alloy electrical round aluminum rod, add cerium chloride, lanthanum chloride or lanthanum-cerium chloride to the aluminum liquid along with the aluminum-iron alloy, aluminum-copper alloy and aluminum-boron alloy. C. Refining: The aluminum liquid after batching is refined. The refining agent consists of 40~60wt% magnesium chloride and 60~40wt% potassium chloride. The refining temperature is 730℃~750℃. The refining is carried out twice. Each refining time is not less than 20 minutes. The total amount of refining agent added is 20~40kg / 13t. After each refining is completed, the slag is removed and the mixture is allowed to stand. D. Degassing: After refining, the aluminum liquid is degassed, and the hydrogen content at the degassing outlet is controlled to be ≤0.20ml / 100gAl; E. Filtration: After degassing, the molten aluminum is filtered. F. Casting: The filtered aluminum liquid is cast, and the crystallization temperature is controlled at 690℃~710℃. During the casting process, the cooling water pressure is 0.1MPa~0.6MPa and the cooling water temperature is 25~40℃. G. Rolling: Roll according to the specifications of 8030 alloy electrical round aluminum rod, with a rolling speed of 15~25m / s, emulsion concentration of 5~8%, emulsion pressure of 0.1~0.5MPa, and emulsion temperature of 25~60℃, to obtain low resistivity 8030 alloy electrical round aluminum rod.

5. The preparation method according to claim 4, characterized in that: In step A, the Al content of the electrolytic aluminum liquid is ≥99.85wt%.

6. The preparation method according to claim 4, characterized in that: In step B, the aluminum-iron alloy is Al-10Fe or Al-20Fe; the aluminum-copper alloy is Al-50Cu; and the aluminum-boron alloy is Al-3B or Al-5B.

7. The preparation method according to claim 4, characterized in that: In step C, high-purity argon gas is used to inject the refining agent into the bottom of the furnace.

8. The preparation method according to claim 4, characterized in that: In step C, the resting time after each refining is 10-20 minutes.

9. The preparation method according to claim 4, characterized in that: In step D, argon gas is used for online degassing at a flow rate of 3.0~4.0 cubic meters per hour and a pressure of 0.1~0.3 MPa.

10. The preparation method according to claim 4, characterized in that: In step E, a two-stage filter plate with a 40PPi+60PPi filter is used for filtration.

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