Aluminum-magnesium-silicon alloy monofilament and preparation method thereof

Abstract

The invention relates to an aluminum-magnesium-silicon alloy monofilament and a preparation method thereof. The aluminum-magnesium-silicon alloy monofilament provided by the invention comprises the following components in percentage by mass: 0.7-0.8% of Mg; 0.35 to 0.45 percent of Si; 0.20%-0.25% of mixed rare earth of La and Ce; 0.10% to 0.12% of B; and the balance of Al and inevitable impurity elements. After La-Ce rare earth is added into the aluminum-magnesium-silicon alloy, spheroidizing modification of a beta 'phase can be achieved, a large number of spherical precipitated phases can be precipitated in the aluminum-magnesium-silicon alloy, annihilation of dislocation can be relieved through the spherical precipitated phases in the work hardening process, and the ductility of the aluminum alloy is improved. According to the preparation method, the grain size of the aluminum-magnesium-silicon alloy monofilament is increased through annealing treatment, then drawing processing is carried out, a large number of dislocations are introduced to serve as nucleation particles for subsequent aging treatment, then aging heat treatment is carried out, high-density spherical precipitated phases which are evenly distributed are obtained, and therefore the better elongation rate is obtained.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy wires for long-distance overhead power transmission, specifically relating to an aluminum-magnesium-silicon alloy monofilament and its preparation method. Background Technology

[0002] With the advancement of new energy development and the continuous growth of social electricity consumption, the abundant power resources in western China and the high electricity demand in coastal areas have led to a surge in the demand for long-distance overhead transmission lines. Aluminum alloys, as metallic materials, possess advantages such as low density and ease of smelting, along with excellent mechanical properties and electrical conductivity. Therefore, since the 20th century, aluminum-magnesium-silicon alloy wires have gradually become the primary conductive material for overhead conductors. For aluminum-magnesium-silicon alloy wires, strength and conductivity are the most critical performance indicators. Higher strength ensures excellent mechanical properties of the transmission line, while higher conductivity significantly reduces energy loss during transmission. Therefore, researchers generally focus on optimizing the strength and conductivity of aluminum-magnesium-silicon alloy wires.

[0003] However, in recent years, with the rapid development of ultra-high voltage (UHV) transmission lines in my country, higher performance requirements have been placed on long-distance overhead transmission lines. This is mainly because UHV transmission lines face more severe operating conditions and complex and variable construction environments during their service. For example, in long-span construction, conductors need to cross mountains, rivers, or other natural obstacles, and the lines are subjected to greater mechanical stress. In addition, extreme weather conditions, such as high temperatures, icing, and strong winds, can also affect the stability and long-term durability of the conductors. Therefore, during the construction of long-span and complex terrain, the ductility and toughness of overhead transmission lines are directly related to the reliability and safety of the lines. Conductors with good ductility can not only operate stably for a long time in harsh environments, but also maintain a certain deformation capacity in the event of unexpected situations, reducing the risk of accidents.

[0004] In summary, the current performance requirements for aluminum alloy wires used in overhead transmission lines are: while ensuring high strength and conductivity, they must also possess good ductility to avoid safety hazards caused by brittle fracture. Therefore, improving the ductility of aluminum alloy wires, especially by optimizing the composition and processing of high-strength aluminum-magnesium-silicon alloys, has become one of the key directions for improving the performance of aluminum alloy wires used in overhead transmission lines. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of low plasticity in existing aluminum alloy wires.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] An aluminum-magnesium-silicon alloy monofilament comprising the following components by mass percentage: Mg: 0.70-0.80%; Si: 0.35-0.45%; La and Ce mixed rare earth elements: 0.20-0.25%; B: 0.10-0.12%; with the balance being Al and unavoidable impurity elements.

[0008] Preferably, among the unavoidable impurity elements, the content of Zn is less than 0.03%, the content of Fe is less than 0.1%, the content of Cr is less than 0.004%, the content of Mn is less than 0.005%, and the content of Cu is less than 0.004%.

[0009] This invention also provides a method for preparing the aforementioned aluminum-magnesium-silicon alloy monofilament, comprising the following steps:

[0010] Aluminum ingots with a purity greater than a preset purity threshold are melted in a furnace at 730–770°C to obtain molten liquid.

[0011] Mg, KBF4, Al-Si master alloy and La-Ce mixed rare earth were added sequentially to the molten liquid and stirred to obtain an alloy liquid;

[0012] The molten alloy is continuously cast and rolled to obtain an alloy rod with a diameter of 9.5 to 10.0 mm;

[0013] The alloy rod is drawn in the middle to obtain an alloy wire with a diameter of 4.5 to 5.5 mm;

[0014] The alloy wire was annealed at 480–530°C to obtain the annealed alloy wire.

[0015] The annealed alloy wire is then drawn a second time to obtain a single wire with a diameter of 3.0 to 3.5 mm;

[0016] The monofilament is subjected to aging heat treatment at 150–170°C to obtain the aluminum-magnesium-silicon alloy monofilament.

[0017] Preferably, the continuous casting and rolling process specifically includes: pouring the alloy liquid into a crystallizing wheel casting machine, with an initial casting temperature of 550-650°C, and then continuously rolling it in a three-roll mill, followed by water cooling to room temperature.

[0018] Preferably, during the continuous rolling process, the temperature entering the mill is 500–550°C, and the temperature after rolling is 450–500°C.

[0019] Preferably, during the intermediate drawing process, the temperature of the alloy rod does not exceed 70°C.

[0020] Preferably, during the secondary drawing process, the temperature of the alloy wire does not exceed 70°C.

[0021] Preferably, the annealing time is 3 to 5 minutes.

[0022] Preferably, the annealing treatment is followed by water cooling to room temperature.

[0023] Preferably, the aging time in the aging heat treatment is 4 to 12 hours.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The aluminum-magnesium-silicon alloy monofilament of the present invention comprises the following components by mass percentage: Mg: 0.7-0.8%; Si: 0.35-0.45%; La and Ce mixed rare earth: 0.20-0.25%; the balance being Al and unavoidable impurity elements. The addition of La-Ce rare earth elements to the aluminum-magnesium-silicon alloy enables spheroidization modification of the β′ phase, resulting in the precipitation of a large number of spherical precipitates within the alloy. These spherical precipitates can slow down dislocation annihilation during work hardening, thereby giving the aluminum alloy good work hardening ability and improving its elongation.

[0026] The method for preparing aluminum-magnesium-silicon alloy monofilament of the present invention increases the grain size of aluminum-magnesium-silicon alloy monofilament through annealing, followed by drawing to introduce a large number of dislocations as nucleation sites for subsequent aging treatment, and then performs aging heat treatment to obtain a uniformly distributed high-density spherical precipitate phase, thereby obtaining a better elongation. Attached Figure Description

[0027] Figure 1 This is a process flow diagram for preparing the aluminum-magnesium-silicon alloy monofilament of the present invention;

[0028] Figure 2 The image shows the microstructure of the aluminum-magnesium-silicon alloy monofilament prepared in Example 1 of this invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other instances that are improved or modified by those skilled in the art are within the scope of protection of the present invention. It should be understood that the embodiments of the present invention are only used to illustrate the technical effects of the present invention, and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the methods used in the embodiments are conventional methods.

[0030] This invention proposes an aluminum-magnesium-silicon alloy monofilament, wherein the monofilament comprises the following components by mass percentage:

[0031] Mg: 0.70–0.80%, Si: 0.35–0.45%, La and Ce mixed rare earth: 0.20–0.25%, B: 0.10–0.12%, Zn < 0.03%, Fe < 0.1%, Cr < 0.004%, Mn < 0.005%, Cu < 0.004%, balance Al.

[0032] The principle of spheroidization treatment for precipitates: Common precipitate shapes in aluminum alloys that provide strengthening effects include disc-shaped, needle-shaped, and spherical precipitates. Different shapes of precipitates have significantly different effects on the work hardening behavior of aluminum alloys. Relatively speaking, spherical precipitates can slow down dislocation annihilation during work hardening, thus giving the aluminum alloy good work hardening ability and improving its elongation. However, the main strengthening phase in traditional aluminum-magnesium-silicon alloys is the β′ phase, which is needle-shaped. Therefore, modifying the β′ phase to optimize its shape to spherical can give the aluminum-magnesium-silicon alloy better work hardening ability. Studies have shown that adding La-Ce rare earth elements to aluminum-magnesium-silicon alloys can achieve spheroidization modification of the β′ phase, resulting in a large number of spherical precipitates within the alloy, which is beneficial for improving the elongation of aluminum-magnesium-silicon alloy single filaments.

[0033] The method for preparing aluminum-magnesium-silicon alloy monofilaments proposed in this invention mainly includes the following steps: smelting, continuous casting and rolling, intermediate drawing, annealing, drawing, and aging; the preparation process flow is as follows: Figure 1 As shown.

[0034] Step 1: Melting. Add pure aluminum ingots with a purity of 99.6 wt.% to a vacuum induction melting furnace and heat to 730-770°C. After the aluminum ingots are completely melted, add Mg, KBF4, Al-Si master alloy and La-Ce mixed rare earth in sequence and stir for 60 minutes.

[0035] Step 2: Continuous casting and rolling. The molten aluminum-magnesium-silicon alloy liquid is poured into a crystallizing wheel casting machine. The initial casting temperature is 550-650℃. The cast billet enters a three-roll mill for continuous rolling. The temperature at the mill inlet is 500-550℃. The temperature after rolling is 450-500℃. It is then water-cooled to room temperature. The diameter of the aluminum-magnesium-silicon alloy rod obtained by rolling is 9.5-10.0mm.

[0036] Step 3: Intermediate drawing. The aluminum-magnesium-silicon alloy rod is drawn. Lubricating fluid is used during the drawing process to ensure the surface quality of the drawn wire and to cool it, so that the temperature of the aluminum-magnesium-silicon alloy wire does not exceed 70°C during the drawing process. The aluminum-magnesium-silicon alloy wire with a diameter of 4.5 to 5.5 mm is obtained.

[0037] Step 4: Annealing. The aluminum-magnesium-silicon alloy wire obtained in Step 3 is annealed at a temperature of 480-530℃ for 3-5 minutes, and then water-cooled to room temperature.

[0038] Step 5: Drawing. The aluminum-magnesium-silicon alloy wire obtained in Step 4 is drawn. Lubricating fluid is used during the drawing process to ensure the surface quality of the drawn wire and to cool it, so that the temperature of the aluminum-magnesium-silicon alloy wire does not exceed 70°C during the drawing process. Aluminum-magnesium-silicon alloy monofilaments with a diameter of 3.0 to 3.5 mm are obtained by drawing.

[0039] Step 6: Aging. The aluminum-magnesium-silicon alloy monofilament obtained in Step 5 is subjected to aging heat treatment at a temperature of 150-170℃ for 4-12 hours, followed by air cooling to room temperature.

[0040] The optimal principle for grain refinement and precipitation strengthening: Both grain refinement and nanoprecipitation can improve the strength of aluminum-magnesium-silicon alloy monofilaments. However, their influence on the elongation of aluminum-magnesium-silicon alloy monofilaments is different. After traditional drawing and plastic processing, the radial grains of aluminum-magnesium-silicon alloy monofilaments are mainly nanoscale, which seriously impairs the elongation of the monofilaments. Coherent precipitates that can be cut by dislocations have a relatively smaller impact on the elongation of aluminum-magnesium-silicon alloy monofilaments. Therefore, it is necessary to increase the grain size of the aluminum-magnesium-silicon alloy monofilaments. The strength loss caused by grain enlargement needs to be compensated by high-density nanoprecipitates. Dislocations can act as nucleation sites, promoting uniform precipitation of the precipitate phase. Therefore, this invention increases the grain size of the aluminum-magnesium-silicon alloy monofilaments through annealing, followed by drawing, with the aim of introducing a large number of dislocations as nucleation sites for subsequent aging treatment, followed by aging heat treatment to obtain a uniformly distributed, high-density spherical precipitate phase. By rationally selecting and designing fine-grain strengthening and precipitation strengthening, aluminum-magnesium-silicon alloy monofilaments can achieve better elongation.

[0041] Example 1

[0042] This embodiment provides an aluminum-magnesium-silicon alloy monofilament, the monofilament comprising the following components by mass percentage:

[0043] Mg: 0.75%, Si: 0.4%, La and Ce mixed rare earth: 0.25%, B: 0.12%; balance is Al and unavoidable impurity elements; among the unavoidable impurity elements, Zn < 0.03%, Fe < 0.1%, Cr < 0.004%, Mn < 0.005%, Cu < 0.004%.

[0044] The method for preparing the aluminum-magnesium-silicon alloy monofilament includes the following steps:

[0045] Step 1: Melting. Add pure aluminum ingots with a purity of 99.6 wt.% to a vacuum induction melting furnace and heat to 750°C. After the aluminum ingots are completely melted, add Mg, KBF4, Al-Si master alloy and La-Ce mixed rare earth in sequence and stir for 60 minutes.

[0046] Step 2: Continuous casting and rolling. The molten aluminum-magnesium-silicon alloy liquid is poured into the crystallizing wheel casting machine. The initial casting temperature is 600℃. The cast billet enters the three-roll mill for continuous rolling. The temperature at the mill inlet is 530℃. The temperature after rolling is 480℃. It is then water-cooled to room temperature. The diameter of the aluminum-magnesium-silicon alloy rod obtained by rolling is 9.5mm.

[0047] Step 3: Intermediate drawing. The aluminum-magnesium-silicon alloy rod is drawn using a water-soluble lubricant. The temperature of the aluminum-magnesium-silicon alloy wire does not exceed 50°C during the drawing process. An aluminum-magnesium-silicon alloy wire with a diameter of 5.0 mm is obtained by drawing.

[0048] Step 4: Annealing. The aluminum-magnesium-silicon alloy wire obtained in Step 3 is annealed at 480℃ for 5 minutes and then cooled to room temperature with water.

[0049] Step 5: Secondary drawing. The aluminum-magnesium-silicon alloy wire obtained in Step 4 is drawn. Water-soluble lubricant is used in the drawing process. The temperature of the aluminum-magnesium-silicon alloy wire does not exceed 50°C during the drawing process. An aluminum-magnesium-silicon alloy monofilament with a diameter of 3.0 mm is obtained by drawing.

[0050] Step 6: Aging. The aluminum-magnesium-silicon alloy monofilament obtained in Step 5 is subjected to aging heat treatment at a temperature of 170℃ for 8 hours, followed by air cooling to room temperature.

[0051] Examples 2-5

[0052] The composition of the aluminum-magnesium-silicon alloy monofilaments in Examples 2 to 5 is shown in Table 1.

[0053] Table 1 Different Compositions

[0054]

[0055] The preparation methods of aluminum-magnesium-silicon alloy monofilaments in Examples 2 to 5 are basically the same as those in Example 1, with the differences shown in Table 2.

[0056] Table 2 Differences in process parameters

[0057]

[0058] Comparative Example 1

[0059] The raw material composition of the aluminum-magnesium-silicon alloy wire in Comparative Example 1 is the same as that in Example 1, and the preparation process is as follows:

[0060] Step 1, smelting: Add pure aluminum ingots with a purity of 99.6 wt.% to a vacuum induction melting furnace, heat to 750°C, and after the aluminum ingots are completely melted, add Mg, KBF4 and Al-Si master alloy in sequence, and stir for 60 minutes.

[0061] The remaining steps are the same as those in Example 1.

[0062] Comparative Example 2

[0063] The raw material composition of the aluminum-magnesium-silicon alloy wire in Comparative Example 2 is the same as that in Example 1, and the preparation process is as follows:

[0064] Steps 1 and 2 of Example 1;

[0065] An aluminum-magnesium-silicon alloy rod is drawn using a water-soluble lubricant. The temperature of the aluminum-magnesium-silicon alloy wire does not exceed 50°C during the drawing process, and an aluminum-magnesium-silicon alloy wire with a diameter of 3.0 mm is obtained.

[0066] Step 6 of Example 1.

[0067] Test case

[0068] The performance of the aluminum-magnesium-silicon alloy monofilaments prepared in Examples 1-5, Comparative Example 1, and Comparative Example 2 was tested, and the results are shown in Table 1.

[0069] Table 3. Comparison of properties of aluminum-magnesium-silicon alloy monofilaments prepared in Examples 1 and 2.

[0070]

[0071] As shown in Table 1, compared with Comparative Example 1, the aluminum-magnesium-silicon alloy monofilament prepared in Example 1 has significant advantages in tensile strength, elongation, and conductivity. This indicates that the rare earth treatment, which spheroidizes the β′ phase within the aluminum-magnesium-silicon alloy monofilament, significantly optimizes its strength, toughness, and conductivity. A comparison of the performance of Example 1 and Comparative Example 2 reveals that while Comparative Example 2 has slightly higher strength, its elongation and conductivity are significantly lower, indicating that continuous drawing-induced grain refinement severely impairs the elongation and conductivity of the aluminum-magnesium-silicon alloy monofilament. In summary, the aluminum-magnesium-silicon alloy monofilament prepared using the process of this invention achieves a good balance of strength, elongation, and conductivity.

[0072] The microstructure of the aluminum-magnesium-silicon alloy monofilament prepared in Example 1 was observed, and the results are as follows: Figure 2 As shown, (a) represents the grain size characterization results, indicating that the radial grain size of the aluminum-magnesium-silicon alloy monofilament reaches the micrometer level; (b) represents the transmission results, showing that nanoscale spherical precipitates are observed within the aluminum-magnesium-silicon alloy monofilament. This demonstrates that the composition and process design of the aluminum-magnesium-silicon alloy monofilament of this invention can achieve the introduction of spherical nanophases and control a reasonable grain size.

[0073] 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 within the scope of the claims of the present invention pending approval.

Claims

1. An aluminum-magnesium-silicon alloy monofilament, characterized in that, The monofilament comprises the following components by mass percentage: Mg: 0.70–0.80%; Si: 0.35–0.45%; La and Ce mixed rare earth elements: 0.20-0.25%; B：0.10～0.12％； The balance consists of Al and unavoidable impurity elements.

2. The aluminum-magnesium-silicon alloy monofilament according to claim 1, characterized in that, Of the unavoidable impurity elements, the content of Zn is less than 0.03%, the content of Fe is less than 0.1%, the content of Cr is less than 0.004%, the content of Mn is less than 0.005%, and the content of Cu is less than 0.004%.

3. A method for preparing an aluminum-magnesium-silicon alloy monofilament as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Aluminum ingots with a purity greater than a preset purity threshold are melted in a furnace at 730–770°C to obtain molten liquid. Mg, KBF4, Al-Si master alloy and La-Ce mixed rare earth were added sequentially to the molten liquid and stirred to obtain an alloy liquid; The molten alloy is continuously cast and rolled to obtain an alloy rod with a diameter of 9.5 to 10.0 mm; The alloy rod is drawn in the middle to obtain an alloy wire with a diameter of 4.5 to 5.5 mm; The alloy wire was annealed at 480–530°C to obtain the annealed alloy wire. The annealed alloy wire is then drawn a second time to obtain a single wire with a diameter of 3.0 to 3.5 mm; The monofilament is subjected to aging heat treatment at 150–170°C to obtain the aluminum-magnesium-silicon alloy monofilament.

4. The preparation method according to claim 3, characterized in that, The continuous casting and rolling process specifically includes: pouring the alloy liquid into a crystallizing wheel casting machine, with an initial casting temperature of 550-650°C, and then continuously rolling it in a three-roll mill, followed by water cooling to room temperature.

5. The preparation method according to claim 3, characterized in that, During the continuous rolling process, the temperature entering the mill is 500-550℃, and the temperature after rolling is 450-500℃.

6. The preparation method according to claim 3, characterized in that, During the intermediate drawing process, the temperature of the alloy rod does not exceed 70°C.

7. The preparation method according to claim 3, characterized in that, During the secondary drawing process, the temperature of the alloy wire does not exceed 70°C.

8. The preparation method according to claim 3, characterized in that, In the annealing process, the annealing time is 3 to 5 minutes.

9. The preparation method according to claim 3, characterized in that, After annealing, the sample was cooled to room temperature with water.

10. The preparation method according to claim 3, characterized in that, In the aforementioned aging heat treatment, the aging time is 4 to 12 hours.

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