CN103045915A - High conductivity moderately strong heat-resistant aluminum alloy monofilament and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of a power industry electric transmission line overhead conductor. The present invention provides a high conductivity moderately strong heat-resistant aluminum alloy monofilament and a preparation method thereof. The aluminum alloy conductor includes: 0.01-0.1% of Zr, 0.01-0.2% of B, 0.01-0.2% of Si, 0.05-0.3% of Fe, 0.2-0.5% of Mn, 0.01-0.15% of Er and/or 0.01-0.15% of Y, any two or three elements selected from the group consisting of V, Ti and Cr, and the balance being Al and inevitable trace impurities, wherein 0.1-0.15% of V, 0.01-0.05%of Ti, and 0.1-0.15% of Cr are included. The aluminum alloy monofilament prepared by the present invention is high in electrical conductivity, good in heat resistance, and high in tensile strength.

Description

A high-conductivity medium-strength heat-resistant aluminum alloy monofilament and its preparation method

【Technical field】

The invention belongs to the technical field of transmission line overhead conductors in the electric power industry, and specifically relates to a high-conductivity, medium-strong heat-resistant aluminum alloy monofilament and a preparation method thereof.

【Background technique】

Traditionally, the steel-cored aluminum stranded wires used in overhead transmission lines mostly use heat-resistant aluminum alloy wires due to the limitation of heat resistance. In order not to reduce the strength and increase the sag of the wire during long-term operation at normal operating temperature, trace alloy elements such as zirconium and titanium are usually added to electrical pure aluminum to increase the recrystallization temperature of aluminum to improve the heat resistance of aluminum. However, although the addition of zirconium and titanium alloy elements ensures heat resistance, it causes a decrease in the conductivity of the aluminum wire. The conductivity of the heat-resistant aluminum alloy wire developed in the early stage was low, and the conductivity of the heat-resistant aluminum alloy wire was increased to 60% IACS by adding rare earth elements and boron elements to control the existence of impurity elements. The application number is 201210189763.6, and the name is high-strength, high-conductivity and heat-resistant aluminum alloy wire and its preparation method. 0.30%, Fe: 0.05-0.20%, Si: 0.01-0.10%, other impurity element content ≤ 0.10%, the rest is aluminum high-strength, high-conductivity and heat-resistant aluminum alloy wire. The preparation method is: prepare raw materials and put them in a melting furnace , heating and degassing smelting, slag making, slag removal, continuous casting and rolling into heat-resistant aluminum alloy rods, heat treatment, and wire drawing machine to make heat-resistant aluminum alloy single wires. The tensile strength of the prepared hot aluminum alloy wire can reach 160MPa, the electrical conductivity can reach above 61% IACS, the long-term operating temperature can reach 180°C, and it can withstand the test operation of heating at 280°C for 1 hour, and the strength residual rate is greater than 90%. . However, in the preparation process of the above application, the prepared aluminum alloy wire or wire has low conductivity and low tensile strength, and the heating temperature required in the preparation process is high and heat treatment is required, resulting in high production costs.

Based on the above research and application background, my country urgently needs to develop high-conductivity and heat-resistant aluminum alloy wires to meet the development needs of my country's electric power industry. 61% IACS heat-resistant aluminum alloy monofilament, and cancel the heat treatment process to reduce costs, provide a raw material basis for the preparation of high-conductivity heat-resistant aluminum alloy wires, so that the heat-resistant aluminum alloy wires can achieve the purpose of increasing the transmission capacity and reducing the loss of transmission lines. In order to meet the construction needs of large-capacity transmission lines and urban expansion and transformation.

【Content of invention】

In order to overcome the above-mentioned problems, the present invention adopts microalloying, controls the content of various alloy elements, and uses rare earth modification to manufacture products with electrical conductivity ≥ 61% IACS, tensile strength greater than 180MPa, and heat-resistant temperature ≥ 120 ° C (180 ° C conditions) Heat-resistant aluminum alloy monofilament with residual strength > 90% under heat preservation for 1 hour), and cancel the heat treatment process to reduce costs, provide a raw material basis for the preparation of high-conductivity heat-resistant aluminum alloy wires, so that the heat-resistant aluminum alloy wires can increase the transmission capacity, The purpose of reducing the loss of transmission lines, so as to meet the construction needs of large-capacity transmission lines and urban expansion and transformation.

To achieve the above object, the present invention adopts the following technical solutions:

A high-conductivity, medium-strength, heat-resistant aluminum alloy monofilament is composed of the following elements in weight percent: Zr: 0.01-0.1%, B: 0.01-0.2%, Si: 0.01-0.2%, Fe: 0.05-0.3%, Mn: 0.2-0.5%, Er: 0.01-0.15% and/or Y: 0.01-0.15%, and any 2 or 3 elements among V, Ti, Cr, and the rest are Al and unavoidable trace impurities;

Said V: 0.1-0.15%, Ti: 0.01-0.05%, Cr: 0.1-0.15%.

A high-conductivity, medium-strength, and heat-resistant aluminum alloy monofilament of the present invention, wherein the sum of Er and Y contents is ≤0.25%.

A high-conductivity, medium-strength, and heat-resistant aluminum alloy monofilament of the present invention, wherein the sum of the contents of any two or three elements among V, Ti, and Cr is ≤0.3%.

A method for preparing an aluminum alloy monofilament of the present invention, comprising the steps of:

1) Smelting: After melting aluminum ingots with a purity ≥ 99.8%, add the alloying elements in sequence at 720-780°C to obtain molten aluminum;

2) Alloying: Stir the above aluminum liquid, remove hydrogen and slag, and alloy at 720-780°C for 25-50 minutes;

3) Casting rod: Preheat the mold to 200-220°C and keep it warm, cast the aluminum liquid obtained in step 2) into the mold to make an aluminum ingot, and after hot extrusion, the size is Φ10-60, 80-200mm Long aluminum rod;

4) Wire drawing: draw the aluminum alloy rod prepared in step 3) to obtain a monofilament of Φ2-3mm.

In the method provided by the present invention, the casting temperature of the molten aluminum in step 3) is 740°C.

In the method provided by the invention, the time for mold preheating and heat preservation is 10 to 30 minutes.

The method provided by the present invention is characterized in that the alloy elements added in the step 1) are simple substances or intermediate alloys.

In the method provided by the present invention, the order of adding alloy elements is: adding Zr, Er and/or Y last.

In the method provided by the present invention, the temperature of the Zr, Er and Y alloy elements added last is 740-780°C.

In the preparation method provided by the present invention, after the pure aluminum ingot is completely melted, the alloying elements are put in sequentially, among which Zr, Er, and Y elements are put in sequentially when the temperature of the molten aluminum rises above 740°C due to their high melting points. The temperature of the furnace was raised to 780°C, and the temperature was kept for 15-35 minutes. The aluminum liquid refining agent is used to remove hydrogen and slag for refining, and a mixer is used to stir the aluminum liquid to fully homogenize the alloying elements. The alloying temperature is 720-780 ° C, and the heat preservation is 25-50 minutes. 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. Heat the mold to 200-220°C and keep it warm for 10-30 minutes, and then cast the molten aluminum to a length of Ф60-150mm. 20 ~ 80mm aluminum ingot. It is extruded into a round aluminum rod of Ф10-60mm by hot extrusion, and then drawn. The wire is cold-drawn on the wire-drawing machine at a speed of 15m/s, and drawn through multiple sets of molds (diamond molds) for multiple passes, with a deformation of 10% to 15% each time, and finally obtains a monofilament with a diameter of Ф2 to 3mm.

Zr in the aluminum alloy monofilament used in the present invention: zirconium atomic radius is slightly larger than aluminum atomic radius, zirconium diffuses in aluminum in the form of replacement, its diffusion activation energy is high, and fine Al ₃ Zr phase is precipitated to the subcrystalline grain boundary , it is not easy to aggregate and grow, has high stability, can prevent recrystallization, and can effectively pin dislocations and grain boundaries at higher temperatures, hinder deformation and intragranular and grain boundary slippage, and make creep The resistance is improved, so that the heat resistance of the aluminum alloy has been 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;

Si: Silicon is an impurity element in aluminum that is second only to iron, which can improve the casting performance and welding fluidity of aluminum alloy, and can also make aluminum alloy have higher mechanical properties;

Fe: It is a dominant impurity in industrial pure aluminum, and it is also a major impurity in high-purity aluminum. Usually appear as coarse primary crystals, or exist in the form of aluminum-iron-silicon compounds, which increase the hardness of aluminum to a certain extent, but reduce the plasticity of aluminum. Although there are data showing that in actual production, the Fe/Si ratio in the aluminum conductor should be 1.3 to 1.5, but it does not significantly reduce its conductivity when it exceeds this range in the present invention;

V, Mn, Cr, Ti: These elements all have the effects of refining grains, increasing the tensile strength of aluminum alloy at room temperature and improving heat resistance, but each (1% Cr+Ti+Mn+V) has a harmful effect It is 5 times the detrimental effect of every 1% silicon on the conductivity of aluminum. It can be seen that strictly controlling the content of these elements has important practical significance for ensuring the quality of aluminum conductors;

Er, Y: Adding Er and Y can react with Fe and Si elements to form fine and dispersed compounds. On the one hand, because Fe and Si in Al are replaced, Fe and Si are precipitated, which reduces the resistivity; on the other hand, due to the precipitation The fine and uniform distribution of the phase can play a role in refining the grain, ensuring a high elongation of the aluminum rod and improving the strength of the aluminum alloy;

B: Adding an appropriate amount of Zr to the aluminum conductor can significantly improve the heat resistance of the alloy, but the addition of Zr will also have a negative impact on the conductivity of the alloy. Some studies have shown that adding an appropriate amount of B to the aluminum alloy containing Zr can Improve the electrical conductivity of the alloy while ensuring the heat resistance of the alloy. Existing data show that in the range of Zr:B=1:2, there will be no negative impact on the conductivity of the alloy. Excessive addition of B has a certain grain refinement effect on Zr-containing aluminum alloys, but it will reduce the high-temperature strength of the alloy and deteriorate the heat resistance of the alloy.

Compared with the prior art, the present invention has the following advantages:

1) The present invention cancels heat treatment by adjusting the addition sequence of alloying elements and holding time, thereby simplifying the preparation process and saving costs;

2) The aluminum alloy monofilament prepared by the present invention has high electrical conductivity (61%IACS, 20°C), good heat resistance (tensile strength greater than 180MPa, heat resistance temperature ≥ 120°C, remaining strength at 180°C for 1 hour >90%).

【Detailed ways】

Example 1

Add pure aluminum ingots with a purity of 99.8% to the medium frequency induction melting furnace, and melt the pure aluminum before keeping the temperature at 720°C. In the order of Mn, V, Ti, Cr, Zr, Er, Y, each alloy element is added in turn, so that their final content is: 0.05% Zr by mass fraction, 0.02% Er, 0.1% Y, 0.05% B , 0.03% of Si, 0.055% of Fe, 0.1% of V, 0.02% of Ti, 0.1% of Cr and 0.25% of Mn, the alloy elements are added in the form of master alloy, after stirring, refining, slag removal, in Cast at 760°C after holding for 40 minutes. Before casting, heat the low-carbon steel mold to 200°C, keep it warm for 10 minutes, and lower the temperature of the molten aluminum to 740°C, then pour the molten aluminum into the mold to form an aluminum alloy ingot, and heat-extrude the aluminum alloy rod through an extrusion machine Pressing, the extrusion temperature is 150°C. The extruded rods are molded sequentially, and then cold-drawn on a high-speed wire-drawing machine with a drawing speed of 15m/s and a section shrinkage rate of about 15% each time to obtain a Ф2.3mm heat-resistant aluminum alloy monofilament. After testing, the tensile strength of the heat-resistant aluminum alloy wire is 200MPa, and the electrical conductivity is 61.3% IACS. When kept at 180°C for 1 hour, the test strength is 185MPa, which is greater than 90% of the original strength.

Example 2

Add pure aluminum ingots with a purity of 99.8% to the medium-frequency induction melting furnace, and melt the pure aluminum before keeping the temperature at 720°C. When the temperature rises to 730°C, start to use B, Si, Fe, Mn , V, Ti, Cr, Zr, Er, Y in the order, add each alloy element in turn, so that their final content is: 0.09% of Zr, 0.03% of Er, 0.09% of Y, 0.08% of B, 0.05% of Si, 0.07% of Fe, 0.11% of V, 0.04% of Ti, 0.12% of Cr and 0.3% of Mn, the alloy elements are added in the form of simple substances, after stirring, refining, slag removal, at 750 ℃ Next, after 45 minutes of heat preservation, casting is carried out. Before casting, heat the low-carbon steel mold to 210°C and keep it warm for 20 minutes, then pour the aluminum liquid into the mold, lower the temperature of the aluminum liquid to 740°C, form an aluminum alloy ingot, and heat-extrude the aluminum alloy rod through an extrusion machine , The extrusion temperature is 150°C. The extruded rods are molded sequentially, and then cold-drawn on a high-speed wire-drawing machine with a drawing speed of 15m/s and a section shrinkage rate of about 15% each time to obtain a Ф2.5mm heat-resistant aluminum alloy monofilament. After testing, the tensile strength of the heat-resistant aluminum alloy wire is 205MPa, and the electrical conductivity is 61.5% IACS. When kept at 180°C for 1 hour, the test strength is 186MPa, which is greater than 90% of the original strength.

Example 3

Add pure aluminum ingots with a purity of 99.8% to the medium frequency induction melting furnace, and melt the pure aluminum before keeping the temperature at 720°C. In the order of Mn, V, Ti, Cr, Zr, Er, Y, each alloy element is added in turn, so that their final content is: 0.07% Zr by mass fraction, 0.10% Er, 0.12% Y, 0.15% B , 0.15% of Si, 0.21% of Fe, 0.12% of V, 0.05% of Ti, 0.14% of Cr and 0.5% of Mn, among which the rare earth elements are added in the form of master alloys, and the rest of the alloy elements are in the form of master alloys It is added in form, stirred, refined and slag-removed, and then cast at 755°C for 50 minutes. Before casting, heat the low-carbon steel mold to 200°C, keep it warm for 30 minutes, lower the temperature of the aluminum liquid to 740°C, then pour the aluminum liquid into the mold to form an aluminum alloy ingot, and heat-extrude the aluminum alloy rod through an extrusion machine , The extrusion temperature is 150°C. The extruded rods are molded sequentially, and then cold-drawn on a high-speed wire-drawing machine with a drawing speed of 15m/s and a section shrinkage rate of about 15% each time to obtain a Ф2.1mm heat-resistant aluminum alloy monofilament. After testing, the tensile strength of the heat-resistant aluminum alloy wire is 195MPa, the electrical conductivity is 61.8% IACS, and the residual strength is 178MPa after being kept at 180°C for 1 hour, which is greater than 90% of the original strength.

Example 4

Add pure aluminum ingots with a purity of 99.8% to the medium frequency induction melting furnace, and melt the pure aluminum before keeping the temperature at 720°C. In the order of Mn, V, Ti, Cr, Zr, Er, add each alloy element in turn, so that their final content is: 0.07% Zr, 0.10% Er, 0.12% Y, 0.15% B, 0.15% % Si, 0.21% Fe, 0.12% V, 0.05% Ti, 0.14% Cr and 0.5% Mn, among which the rare earth elements are added in the form of master alloys, and the rest of the alloy elements are added in the form of master alloys , after stirring, refining, slag removal, casting at 750°C after holding for 50 minutes. Before casting, heat the low-carbon steel mold to 200°C, keep it warm for 30 minutes, lower the temperature of the aluminum liquid to 740°C, then pour the aluminum liquid into the mold to form an aluminum alloy ingot, and heat-extrude the aluminum alloy rod through an extrusion machine , The extrusion temperature is 150°C. The extruded rods are molded sequentially, and then cold-drawn on a high-speed wire-drawing machine with a drawing speed of 15m/s and a section shrinkage rate of about 15% each time to obtain a Ф2.2mm heat-resistant aluminum alloy monofilament. After testing, the tensile strength of the heat-resistant aluminum alloy wire is 196MPa, the electrical conductivity is 61.5% IACS, and the residual strength is 179MPa after being kept at 180°C for 1 hour, which is greater than 90% of the original strength.

Example 5

Add pure aluminum ingots with a purity of 99.8% to the medium frequency induction melting furnace, and melt the pure aluminum before keeping the temperature at 720°C. In the order of Mn, V, Ti, Cr, Zr, Y, each alloy element is added in turn, so that their final content is: 0.07% Zr by mass fraction, 0.10% Er, 0.12% Y, 0.15% B, 0.15% % Si, 0.21% Fe, 0.12% V, 0.05% Ti, 0.14% Cr and 0.5% Mn, among which the rare earth elements are added in the form of master alloys, and the rest of the alloy elements are added in the form of master alloys , after stirring, refining, slag removal, casting at 755°C after holding for 50 minutes. Before casting, heat the low-carbon steel mold to 200°C, keep it warm for 30 minutes, lower the temperature of the aluminum liquid to 740°C, then pour the aluminum liquid into the mold to form an aluminum alloy ingot, and heat-extrude the aluminum alloy rod through an extrusion machine , The extrusion temperature is 150°C. The extruded rods are molded sequentially, and then cold-drawn on a high-speed wire-drawing machine with a drawing speed of 15m/s and a section shrinkage rate of about 15% each time to obtain a Ф2.3mm heat-resistant aluminum alloy monofilament. After testing, the tensile strength of the heat-resistant aluminum alloy wire is 193MPa, the electrical conductivity is 61.2% IACS, and the residual strength is 177MPa after being kept at 180°C for 1 hour, which is greater than 90% of the original strength.

Claims (9)

1. A high-conductivity, medium-strength, heat-resistant aluminum alloy monofilament, characterized in that the aluminum alloy wire is composed of the following elements by weight percentage: Zr: 0.01-0.1%, B: 0.01-0.2%, Si: 0.01- 0.2%, Fe: 0.05～0.3%, Mn: 0.2～0.5%, Er: 0.01～0.15% and/or Y: 0.01～0.15%, also contains any 2 or 3 elements of V, Ti, Cr, the rest Al and unavoidable trace impurities; Said V: 0.1-0.15%, Ti: 0.01-0.05%, Cr: 0.1-0.15%. 2. A high-conductivity, medium-strength, heat-resistant aluminum alloy monofilament as claimed in claim 1, characterized in that the sum of the contents of Er and Y is ≤0.25%. 3. A high-conductivity, medium-strength, heat-resistant aluminum alloy monofilament as claimed in claim 1, characterized in that the sum of the contents of any two or three of V, Ti, and Cr is ≤0.3%. 4. A method for preparing a high-conductivity, medium-strength, heat-resistant aluminum alloy monofilament as claimed in claim 1, comprising the steps of: 1) Smelting: Melt aluminum ingots with a purity ≥ 99.8% and add the alloying elements in sequence at 720-780°C to obtain molten aluminum; 2) Alloying: Stir the above aluminum liquid, remove hydrogen and slag, and alloy at 720-780°C for 25-50 minutes; 3) Casting rods: Preheat the mold to 200-220°C and keep it warm, lower the temperature of the molten aluminum obtained in step 2) to 740°C, cast it into the mold to make aluminum ingots, and make aluminum ingots with a size of Φ10 after hot extrusion ～60, 80～400mm long aluminum alloy rod; 4) Wire drawing: draw the aluminum alloy rod prepared in step 3) to obtain a monofilament of Φ2-3mm. 5. The method according to claim 4, characterized in that the order of adding the alloy elements is: B, Si, Fe, Mn, V, Ti, Cr elements are added when the temperature rises to 740 ° C, and kept for 10 minutes, Zr, Er, and Y elements are added in the range of 740-780°C, and kept warm for 15-35 minutes. 6. The method according to claim 4, characterized in that the casting temperature of the molten aluminum in step 3) is 740°C. 7. The method according to claim 4, characterized in that the time for the mold to be preheated and kept warm is 10 to 30 minutes. 8. The method according to claim 4, characterized in that the alloy elements added in the step 1) are simple substances or intermediate alloys. 9. The method according to claim 5, characterized in that the addition temperature of the last alloying element does not exceed 780°C.