CN105609155B - A kind of high-conductivity hard aluminum wire monofilament and preparation method thereof - Google Patents

Abstract

The invention discloses a hard aluminum alloy wire monofilament for overhead wires with conductivity ≥ 63% IACS and tensile strength ≥ 163 MPa and a preparation method thereof. The composition of the aluminum alloy monofilament according to the mass percentage is: Zr: 0.01-0.05%, B: 0.01～0.05%, Sc: 0.05～0.2%, Fe: 0～0.14%, Si: 0～0.07%, (V+Ti+Cr+Mn): 0～0.012%, the rest is Al and unavoidable Trace impurities. The invention also discloses the preparation method of the wire monofilament, which adopts blowing _N2 to degas and remove slag, and does not need to add refining agent, thereby simplifying the preparation process of hard aluminum alloy, and the wire and cable conductor thus prepared can improve the conductivity rate (63%IACS, 20°C) and increased working strength (tensile strength ≥ 163MPa).

Description

A kind of high conductivity duralumin wire monofilament and its preparation method

【Technical field】

The invention relates to a method for manufacturing overhead wires of transmission lines in the electric power industry, in particular to a duralumin alloy monofilament for overhead wires and a preparation method thereof.

【Background technique】

Overhead transmission lines generally use steel-cored aluminum stranded wires as wires for power transmission and distribution. In order to solve the energy-saving transformation of transmission lines, reduce transmission line losses, and improve line life, steel-cored aluminum stranded wires made of high-conductivity hard aluminum alloys are generally used. Realize energy saving and consumption reduction of transmission lines. The use of high-conductivity duralumin wires on transmission lines has the following advantages: First, energy saving: Compared with the conductivity of conventional wires, the conductivity of high-conductivity duralumin wires has increased by about 3%, reducing resistance loss; second, reducing tower investment : Since the wind load of the conductor is reduced by about 10%, the tower weight can be reduced by about 0.5%; the third is to compress the width of the corridor: when the 500 kV double circuit of the same tower adopts the same section line, the corridor width can be reduced by 0.5 meters; the fourth is the operation reliability Strong: It can relatively reduce the noise and line loss caused by corona discharge. According to relevant statistics, in 2010, the power loss of transmission lines in some places was 171 billion kwh; by 2015, if 20% of the transmission lines use high-conductivity duralumin conductors, the total loss can be reduced by 1.026 billion kwh. Therefore, high-conductivity duralumin conductors play a vital role in upgrading and transforming some power grids, improving transmission efficiency, reducing line loss and operating costs. In the prior art, the preparation process of high-conductivity duralumin wire is relatively complicated, the product performance is unstable, the product conductivity is low, and a refining agent needs to be added during the refining process, and the common point of the existing refining agents is that the application range is narrow, The function is single, and several different refining agents need to be put in to achieve different purposes. And often the effect is not significant, or harmful to the cleanliness of the melt or the environment, and there are various problems in varying degrees.

Chinese patent CN103093855A discloses a high-conductivity rare-earth duralumin wire, its composition by weight percentage is: iron 0.0875%-0.145%, iron-silicon ratio controlled at 1.7-2.5, boron 0.01-0.12%, gadolinium 0.01-0.15% , and the rest is aluminum. The invention also discloses a preparation method of the high-conductivity rare earth duralumin wire, which mainly includes matching aluminum ingots, smelting, boriding, refining and other treatments to obtain duralumin with a conductivity of 63% IACS and a tensile strength of 160MPa wire. However, the refining agents such as potassium fluoroborate and sodium fluoroaluminate added in the preparation method have great environmental pollution.

【Content of invention】

In order to solve the above-mentioned deficiencies, in the technical solution provided by the present invention, trace alloying elements are added to control the impurity content in the alloy, and a heat treatment process is used to adjust the microstructure of the alloy to obtain a kind of electrical conductivity ≥ 63% IACS at 20 ° C, tensile strength Hard aluminum conductor monofilament with strength ≥163MPa.

Above-mentioned invention purpose is realized with following technical scheme:

A high-conductivity duralumin wire monofilament, the duralumin wire monofilament contains the following components by mass percentage: Zr: 0.01-0.05%, B: 0.01-0.05%, Sc: 0.05-0.2%, Fe: 0-0.14%, Si: 0-0.07%, the sum of the mass percentages of the four elements V, Ti, Cr and Mn is 0-0.012%, and the rest is Al and unavoidable trace impurities.

Preferably, the mass percentage of B is 0.03-0.05%.

A method for preparing a high-conductivity duralumin wire monofilament as described above, comprising the following steps:

(1) Smelting: After melting the aluminum ingot with a purity ≥ 99.7% at 720-750°C, add B, Zr, Sc, Fe, Si, V, Ti, Cr and Mn master alloys at 730-750°C. Stir the aluminum alloy liquid after the master alloy is completely melted;

(2) Refining: after 10-20 minutes of degassing and slag removal by introducing _N2 , the aluminum alloy liquid is refined at 730-750°C and left to stand for 30-60 minutes;

(3) Casting: casting the aluminum alloy solution obtained in step (2) at 700-720°C into a cylindrical mold preheated to 200-250°C for heat preservation, to obtain a duralumin round rod;

(4) Rod making: After the hard aluminum round rod is kept at 400-500°C for 0.5-2 hours, it is extruded into an aluminum alloy rod, and at the same time, cold water is sprayed on the extruded aluminum alloy rod;

(5) Wire drawing: use a wire drawing machine to cold draw the aluminum alloy rod at a speed of 15m/s, and use a steel mold to draw it through 10 to 20 passes, preferably 15 times, to obtain a duralumin monofilament;

(6) Annealing: anneal the duralumin monofilament, take it out and air cool to room temperature.

Preferably, the order of adding the master alloy in step (1) is to add the Al-B master alloy for boridation at 730-750° C., and then add the Al-Zr and Al-Sc master alloys at 750° C. after standing for 30 minutes.

More preferably, in step (4), water at room temperature is sprayed for 1 to 3 minutes.

Another preferred method is that in step (6), the duralumin monofilament is annealed at 140-180° C. for 3-6 hours.

The effect and mechanism of each alloy element in the technical scheme of the present invention are as follows:

Zr: The atomic radius of zirconium is slightly larger than that of aluminum. Zirconium diffuses in aluminum in the form of replacement, and its diffusion activation energy is high. The fine Al ₃ Zr phase precipitates to the subcrystalline grain boundary, which is not easy to aggregate and grow, and has high stability. , can prevent the occurrence of recrystallization, thereby effectively pinning dislocations and grain boundaries, hindering deformation and slippage in grains and grain boundaries, so that the strength can be improved. At the same time, the addition of zirconium can improve the creep resistance of the aluminum alloy, so that the aluminum alloy has only a small creep elongation at high temperature, so the distance between the overhead transmission lines and the transmission towers can be increased, and the Keep the overhang of the aluminum alloy wire small;

B: If the impurity elements exist in a solid solution state, they will have a great influence on the electrical conductivity, and the boronization treatment can effectively reduce the impurity content, that is, after adding a certain amount of B elements to the aluminum alloy, it can be combined with the transition group impurity elements Cr, Mn, V, Ti, etc. react to change from a solid solution state to a combined state and deposit at the bottom of the melt, thereby improving the conductivity of the aluminum alloy;

Sc: Scandium has a good dispersion strengthening effect on aluminum, and is an excellent grain refiner and good rejunction inhibitor for aluminum alloys. Adding trace scandium elements to aluminum alloys can form a large number of dispersed and coherent secondary Al ₃ Sc phase particles. On the one hand, these particles can strongly pin dislocations and subgrain boundaries, and have great influence on the substructure in the deformed structure. The strong stabilizing effect makes the cellular structure composed of entangled dislocations formed by the alloy during the deformation process recover to form sub-grain boundaries during the subsequent annealing process, and many sub-grain boundaries are composed of two-dimensional dislocation networks. It can exert a strong substructure strengthening effect on the alloy; on the other hand, these dispersed and coherent secondary A1 ₃ Sc phase fine particles can strongly pin dislocations, hinder the movement of dislocations, and greatly improve the dislocation slippage. Shear stress is required to cause alloy strengthening. At the same time, scandium element can react with some impurity elements in aluminum alloy to form a second phase, thereby improving the conductivity of aluminum alloy;

Fe: Aluminum contains a certain amount of iron, which is a major impurity in pure aluminum. Since the tools used for smelting and casting are all steel or cast iron, the iron will be carried into the aluminum by these tools, and when the scrap is remelted, iron and iron filings can be mixed in. Iron is detrimental to the mechanical properties of cast aluminum, because it usually appears in the form of coarse primary crystals, or in the form of Al-Fe-Si compounds, which increase the hardness of aluminum to a certain extent, but reduce the plasticity of aluminum. New research shows that iron can increase the strength of aluminum conductors without significantly reducing their electrical conductivity. However, there are also data showing that in actual production, the Fe/Si ratio in aluminum conductors should be 1.3 to 1.5. If it is too high, the resistivity will increase significantly, so attention should also be paid to controlling the iron content;

Si: Silicon element is a major impurity element in pure aluminum. As the Si content increases, the electrical conductivity of the alloy decreases. This is due to increasing the Si content in the alloy, the amount of free Si in the aluminum matrix increases, Si is a semiconductor, and the resistivity is much higher than that of the aluminum matrix, so the increase in the Si content reduces the effective conductive cross-sectional area of the aluminum matrix and reduces the conductivity of the alloy. . Therefore, the Si content should be minimized in hard aluminum alloys;

Cr, Mn, V and Ti are impurity elements in the alloy. These elements have the effects of refining grains, increasing the tensile strength of aluminum alloy at room temperature and improving heat resistance, but when they exist in a solid solution state in aluminum conductors, they can easily absorb free electrons in the conductor material and fill them Incomplete electron shell, this reduction in the number of conduction electrons leads to a reduction in the conductivity of aluminum conductors. Studies have shown that the harmful effect of every 1% (Cr+Mn+V+Ti) is 5 times that of every 1% Si on aluminum conductivity. Therefore, the content of these elements must be strictly controlled.

In the preparation method of the non-heat-treatable heat-resistant aluminum alloy monofilament provided by the present invention, it is smelted first, and after the pure aluminum ingot is completely melted, various alloying elements are sequentially put in, wherein B and Al have a eutectic reaction, and the alloying elements are easier to dissolve. It can be directly added into molten aluminum during the smelting process; Zr and Sc elements dissolve very slowly due to their high melting points, and require a large overheating to completely dissolve. Stir the molten aluminum with a mixer to fully homogenize the alloy elements; use nitrogen to remove hydrogen and slag from the molten aluminum. Heat the mold to prevent the shrinkage cavity caused by the large difference between the temperature of the mold and the molten aluminum temperature during the casting process of the molten aluminum. The mold is heated to 200-250°C and kept for 60-90 minutes, and then the molten aluminum is cast into a Ф45×100mm hard Aluminum round bar. It is extruded into a Ф9.5mm round aluminum rod by hot extrusion, and then drawn. The wire is cold drawn on a wire drawing machine at a speed of 15m/s, drawn through a steel mold for multiple passes, and finally a Ф3.05mm monofilament is obtained. The properties of the alloy are adjusted by annealing at 140-180°C for 3-6 hours.

Compared with the closest prior art, the beneficial effect of the present invention: the technical solution provided by the present invention, because trace elements of Sc are added to the hard aluminum alloy, can not only reduce the impurity content but also have the effect of grain refinement. While the aluminum alloy has high electrical conductivity, the aluminum alloy has good mechanical properties; the technical solution of the present invention avoids the appearance of precipitated phases due to the adoption of the method of quenching the duralumin round rod with cold water during hot extrusion; In the technical solution, only blowing _N2 to degas and remove slag is used, without adding refining agent, thus simplifying the preparation process of hard aluminum alloy, and the wire and cable conductors prepared thereby can improve the conductivity (63%IACS, 20°C) And increase working strength (tensile strength ≥ 163MPa).

【detailed description】

Unless otherwise specified, all implementation modes adopt existing smelting and extrusion equipment.

Example 1

Prepare the 63%IACS electrical conductivity duralumin wire monofilament of following composition and mass percentage thereof:

Melt the aluminum ingot with a purity of 99.7% in a medium frequency induction melting furnace at 720°C. Next, add Zr and Sc alloying elements to reach their final content respectively. The alloying elements are added in the form of master alloys. After the master alloys are completely melted, stir thoroughly; feed N ₂ for degassing and slag removal for 10 minutes. Put down the refined aluminum alloy liquid, let it stand for 40 minutes and cast it. Before casting, put the cylindrical low-carbon steel mold into the box furnace and heat it to 200°C, keep it warm for 20 minutes, and lower the temperature of the molten aluminum to 720°C, then pour the molten aluminum into the mold to prepare a mold with a size of Ф45×300mm long duralumin round rod. After the hard aluminum round rod is kept at 450°C for 1 hour, it is extruded into a Ф9.5mm aluminum alloy rod on an extruder, and at the same time, spray cold water at room temperature on the extruded aluminum alloy rod for 2 minutes. The aluminum alloy rod is cold-drawn on a high-speed wire drawing machine at a speed of 15m/s, and drawn through 15 passes using a steel die to finally obtain a Ф3.05mm duralumin monofilament. The aluminum alloy monofilament was annealed in a box furnace at 180°C for 3 hours, and then air-cooled to room temperature after taking it out. After testing, the electrical conductivity of the obtained duralumin monofilament was 63.01% IACS, the test strength was 163.15 MPa, and the elongation was 2.13%.

Example 2

Prepare the 63%IACS electrical conductivity duralumin wire monofilament of following composition and mass percent thereof:

In the smelting furnace, the aluminum ingot with a purity of 99.7% was melted at 720°C, and then heated to 740°C. In the form of an intermediate alloy, an aluminum-boron intermediate alloy was added for boridation. After standing for 30 minutes, at 750°C, Zr , Sc alloying elements, so as to reach their final content respectively, the alloying elements are added in the form of master alloy, and stir fully after the master alloy is completely melted; pass in _N2 for degassing and slag removal for 15 minutes, and refine the aluminum alloy at 750°C Liquid, cast after standing for 40min. Before casting, put the cylindrical low-carbon steel mold into the box furnace and heat it to 200°C, keep it warm for 20 minutes, and lower the temperature of the molten aluminum to 720°C, then pour the molten aluminum into the mold to prepare a mold with a size of Ф45×300mm long duralumin round rod. After the hard aluminum round rod is kept at 450°C for 1 hour, it is extruded into a Ф9.5mm aluminum alloy rod on an extruder, and at the same time, spray cold water at room temperature on the extruded aluminum alloy rod for 2 minutes. The aluminum alloy rod is cold-drawn on a high-speed wire drawing machine at a speed of 15m/s, and drawn through 15 passes using a steel die to finally obtain a Ф3.05mm duralumin monofilament. The aluminum alloy monofilament was annealed in a box furnace at 160°C for 4 hours, and then air-cooled to room temperature after taking it out. After testing, the electrical conductivity of the obtained duralumin monofilament was 63.07% IACS, the test strength was 163.52 MPa, and the elongation was 2.07%.

Example 3

Prepare the 63%IACS electrical conductivity duralumin wire monofilament of following composition and mass percent thereof:

In the melting furnace, the aluminum ingot with a purity of 99.7 is melted at 720°C, and when it rises to 730°C, an aluminum-boron intermediate alloy is added in the form of an intermediate alloy for boronization, and after standing for 30 minutes, at 750°C, add Zr, Sc alloying elements, so as to reach their final content respectively, the alloying elements are added in the form of master alloy, and fully stirred after the master alloy is completely melted; N ₂ is introduced to degas and remove slag for 20 minutes, and refine aluminum at 730°C Alloy liquid, cast after standing for 60 minutes. Before casting, put the low-carbon steel mold into the box furnace and heat it to 220°C, and cast the aluminum alloy liquid at 700°C into the cylindrical mold to prepare a duralumin round rod with a size of Ф45×300mm; After the rod is kept at 500°C for 40 minutes, it is extruded into a Ф9.5mm aluminum alloy rod on an extruder, and at the same time, cold water at room temperature is sprayed on the extruded aluminum alloy rod for 3 minutes to avoid the precipitation of precipitated phases. The aluminum alloy rod is cold-drawn on a wire drawing machine at a speed of 15m/s, and the steel mold is used for 15 passes to obtain a duralumin monofilament with a diameter of 3.05mm; Annealed in a type furnace for 6 hours, and then air-cooled to room temperature after taking it out. After testing, the electrical conductivity of the obtained duralumin monofilament is 63.05% IACS, the test strength is 163.36 MPa, and the elongation is 2.18%.

Example 4

Prepare the 63%IACS electrical conductivity duralumin wire monofilament of following composition and mass percent thereof:

Add an aluminum ingot with a purity of 99.7% to the medium-frequency induction melting furnace, and keep the temperature at 720°C to melt the pure aluminum. When the temperature rises to 730°C, start adding an aluminum-boron master alloy boron in the form of master alloy, statically After standing for 30 minutes, add Zr and Sc alloying elements at 750°C so that their final content is as shown above. The alloying elements are added in the form of an intermediate alloy, and the aluminum alloy liquid is fully stirred after the intermediate alloy is completely melted; Inject _N2 to degas and remove slag for 10 minutes, refine the aluminum alloy liquid at 750°C, and cast after standing for 40 minutes. Before casting, put the cylindrical low-carbon steel mold into the box furnace and heat it to 210°C, keep it warm for 20 minutes, and lower the temperature of the molten aluminum to 700°C, then pour the molten aluminum into the mold to prepare a mold with a size of Ф45×300mm long duralumin round rod. After the hard aluminum round rod is kept at 480°C for 1.5 hours, it is extruded into a Ф9.5mm aluminum alloy rod on an extruder, and at the same time, spray cold water at room temperature on the extruded aluminum alloy rod for 3 minutes. The aluminum alloy rod is cold-drawn on a high-speed wire drawing machine at a speed of 15m/s, and drawn through 15 passes using a steel die to finally obtain a Ф3.05mm duralumin monofilament. The aluminum alloy monofilament was annealed in a box furnace at 140°C for 6 hours, and then air-cooled to room temperature after taking it out. After testing, the electrical conductivity of the obtained duralumin monofilament was 63.02% IACS, the test strength was 163.05 MPa, and the elongation was 2.08%.

Example 5

Prepare the 63%IACS electrical conductivity duralumin wire monofilament of following composition and mass percent thereof:

Add an aluminum ingot with a purity of 99.7% to the medium-frequency induction melting furnace, and keep the temperature at 730°C to melt the pure aluminum. When the temperature rises to 740°C, start adding an aluminum-boron master alloy boron in the form of master alloy, statically After standing for 30 minutes, place Zr and Sc alloying elements at 750°C so that their final content is as shown above. The alloying elements are added in the form of an intermediate alloy. After the intermediate alloy is completely melted, the aluminum alloy liquid is fully stirred; Enter _N2 to degas and remove slag for 25 minutes, refine the aluminum alloy liquid at 750°C, and cast after standing for 40 minutes. Before casting, put the cylindrical low-carbon steel mold into the box furnace and heat it to 200°C, keep it warm for 20 minutes, and lower the temperature of the molten aluminum to 710°C, then pour the molten aluminum into the mold to prepare a mold with a size of Ф45×300mm long duralumin round rod. After the hard aluminum round rod is kept at 420°C for 1 hour, it is extruded into a Ф9.5mm aluminum alloy rod on an extruder, and at the same time, spray cold water at room temperature on the extruded aluminum alloy rod for 1 minute. The aluminum alloy rod is cold-drawn on a high-speed wire drawing machine at a speed of 15m/s, and drawn through 15 passes using a steel die to finally obtain a Ф3.05mm duralumin monofilament. The aluminum alloy monofilament was annealed in a box furnace at 150°C for 5 hours, and then air-cooled to room temperature after taking it out. After testing, the electrical conductivity of the obtained duralumin monofilament was 63.03% IACS, the test strength was 163.09 MPa, and the elongation was 2.12%.

In the table are the data of the examples.

Example Conductivity (%IACS) Tensile strength (MPa) Elongation (%) 1 63.01 163.15 2.13 2 63.07 163.52 2.07 3 63.05 163.36 2.18 4 63.02 163.05 2.08 5 63.03 163.09 2.12

The above is only a detailed description of the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. It should be understood that without departing from the spirit and scope of the claims of the present application, various modifications made by those skilled in the art still belong to the scope of the present invention.

Claims (4)

1. A high-conductivity duralumin wire monofilament is characterized in that the duralumin wire monofilament contains the following components by mass percentage: Zr: 0.01～0.05%, B: 0.01～0.05%, Sc: 0.05～ 0.2%, Fe: 0~0.14%, Si: 0~0.07%, V+Ti+Cr+Mn: 0~0.012%, the rest is Al and unavoidable trace impurities; The preparation method of the described high-conductivity duralumin wire monofilament comprises the following steps: (1) Smelting: After melting the aluminum ingot with a purity ≥ 99.7% at 720-750°C, add B, Zr, Sc master alloys at 730-750°C, and stir the aluminum alloy liquid after the master alloy is completely melted; (2) Refining: After blowing in _N2 to degas and remove slag for 10 to 20 minutes, refine the aluminum alloy liquid at 730 to 750°C and let it stand for 30 to 60 minutes; (3) Casting: reduce the temperature of the molten aluminum obtained in step (2) to 700-720°C, and cast it into a mold preheated to 200-250°C to keep warm, to obtain a duralumin round rod; (4) Rod making: After the hard aluminum round rod is kept at 400-500°C for 0.5-2 hours, it is extruded into an aluminum alloy rod, and water is sprayed on the extruded aluminum alloy rod at the same time; (5) Wire drawing: use a wire drawing machine to cold draw the aluminum alloy rod at a speed of 15m/s, and use a steel mold to draw it through 10 to 20 passes to obtain a duralumin monofilament; (6) Annealing: anneal the duralumin monofilament, take it out and air cool to room temperature; The order of adding the master alloy in step (1) is to add Al-B master alloy boride at 730-750°C, and after standing for 30min, add Al-Zr and Al-Sc master alloy at 750°C; In step (4), spray water for 1 to 3 minutes. 2. The duralumin wire monofilament according to claim 1, characterized in that the mass percentage of B is 0.03-0.05%. 3. The high-conductivity duralumin wire monofilament as claimed in claim 1, characterized in that the drawing times in the steel mold in step (5) are 15 times. 4. The high-conductivity duralumin wire monofilament according to claim 1, characterized in that in step (6), it is annealed at 140-180° C. for 3-6 hours.