A steel core heat-resistant aluminum alloy stranded wire for overhead conductor and a manufacturing method thereof

Abstract

The invention discloses a steel core heat-resistant aluminum alloy stranded wire for overhead conductors and a manufacturing method thereof. The steel core heat-resistant aluminum alloy stranded wire is sequentially provided with a central galvanized steel wire, a galvanized steel wire middle layer, a galvanized steel wire outer layer, a heat-resistant aluminum alloy wire inner layer, a heat-resistant aluminum alloy wire middle layer and a heat-resistant aluminum alloy wire outer layer in order from the center to the outside. Each layer is composed of multiple wires and is spirally wound on the inner layer in a direction opposite to the winding direction of the inner layer. The core wire of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors of the invention adopts a high-strength galvanized steel wire with a tensile strength of ≥1450MPa, and the outer wire adopts a heat-resistant aluminum alloy wire with an allowable continuous operating temperature of 180°C and a conductivity of ≥62%IACS. It has a higher heat-resistant temperature and lower resistance loss, can improve the transmission capacity of the line, reduce the power loss of the line, and meet the needs of ultra-high voltage, large-capacity transmission and substation and urban capacity expansion construction.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum stranded wire manufacturing, and in particular relates to a steel core heat-resistant aluminum alloy stranded wire for overhead conductors and a manufacturing method thereof. Background Art

[0002] Steel-core aluminum stranded wire is the carrier of long-distance overhead power transmission, and its performance directly determines the transmission capacity and power loss of the line. Traditional steel-core aluminum stranded wire has high resistivity and poor conductivity, resulting in small line transmission capacity and large power loss, causing huge waste of power resources. In addition, traditional steel-core aluminum stranded wire also has problems such as heavy weight, poor sag characteristics and corrosion resistance, short life cycle, and high maintenance cost, which can no longer adapt to the rapid development of the power industry.

[0003] In order to increase the transmission capacity of the transmission line and reduce the power loss of the transmission line, the heat resistance and conductivity of the steel core aluminum stranded wire must be further improved. However, there is a contradiction between the conductivity and heat resistance of aluminum alloys, which restrict each other and increase and decrease at the same time. The traditional method of improving the heat resistance of aluminum alloys by adjusting the alloy composition will lead to a decrease in conductivity, making it difficult to balance the improvement of conductivity and heat resistance. As a result, the existing steel core heat-resistant aluminum alloy stranded wire still generally has the problem of good heat resistance and poor conductivity or good conductivity and poor heat resistance. Therefore, the existing steel core heat-resistant aluminum alloy stranded wire for overhead conductors and its manufacturing method still need to be improved and developed. Summary of the invention

[0004] The purpose of the present invention is to provide a steel core heat-resistant aluminum alloy stranded wire for overhead conductors and a manufacturing method thereof in view of the above-mentioned problems and shortcomings, and to improve the heat resistance and conductivity of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors by optimizing the structure and manufacturing process of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors, thereby increasing the transmission capacity of the transmission line and reducing the power loss of the transmission line.

[0005] The technical solution of the present invention is achieved in this way:

[0006] The first aspect of the present invention provides a steel core heat-resistant aluminum alloy stranded wire for overhead conductors, which is characterized in that a central galvanized steel wire, a galvanized steel wire middle layer, a galvanized steel wire outer layer, a heat-resistant aluminum alloy wire inner layer, a heat-resistant aluminum alloy wire middle layer and a heat-resistant aluminum alloy wire outer layer are sequentially arranged from the center to the outside, the galvanized steel wire middle layer and the galvanized steel wire outer layer are respectively composed of a plurality of galvanized steel wires, the heat-resistant aluminum alloy wire inner layer, the heat-resistant aluminum alloy wire middle layer and the heat-resistant aluminum alloy wire outer layer are respectively composed of a plurality of heat-resistant aluminum alloy wires, the galvanized steel wire middle layer The galvanized steel wire is spirally wound around the center, the galvanized steel wire outer layer is spirally wound around the galvanized steel wire middle layer in the direction opposite to the winding direction of the galvanized steel wire middle layer, the heat-resistant aluminum alloy wire inner layer is spirally wound around the galvanized steel wire outer layer in the direction opposite to the winding direction of the galvanized steel wire outer layer, the heat-resistant aluminum alloy wire middle layer is spirally wound around the heat-resistant aluminum alloy wire inner layer in the direction opposite to the winding direction of the heat-resistant aluminum alloy wire inner layer, and the heat-resistant aluminum alloy wire outer layer is spirally wound around the heat-resistant aluminum alloy wire middle layer in the direction opposite to the winding direction of the heat-resistant aluminum alloy wire middle layer.

[0007] Preferably, the diameter of the galvanized steel wire is 1.5-2 mm, the tensile strength of the galvanized steel wire is ≥1450 MPa, the stress at 1% elongation is ≥1310 MPa, and the elongation after fracture is ≥2.5%. Since the high-strength galvanized steel wire with a tensile strength of ≥1450 MPa is a mature product and can be purchased on the market, the manufacturing method of the galvanized steel wire is not described here.

[0008] Preferably, the diameter of the heat-resistant aluminum alloy wire is 3-4 mm, the tensile strength of the heat-resistant aluminum alloy wire is ≥200 MPa, the strength retention rate after heating at 230°C for 1 hour is ≥94%, and the DC resistivity at 20°C is ≤0.0278Ω·mm 2 / m, electrical conductivity ≥62%IACS.

[0009] Preferably, the heat-resistant aluminum alloy wire is composed of the following components in mass percentage: Zr 0.25-0.3%, the balance being Al and unavoidable impurities, with a single impurity ≤0.05% and a total impurity content ≤0.1%.

[0010] A second aspect of the present invention provides a method for manufacturing a steel core heat-resistant aluminum alloy stranded wire for an overhead conductor, which is characterized by comprising the following steps in sequence:

[0011] Step 1: Melt and prepare aluminum alloy liquid at 700-720°C according to the composition and mass percentage of the heat-resistant aluminum alloy wire;

[0012] Step 2: using argon gas with a purity of 99.99% and a refining agent accounting for 0.1-0.2% of the weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid in the melting furnace for 10-20 minutes to remove slag, and then scrape off the slag on the surface of the aluminum alloy liquid;

[0013] Step 3: A mixed gas consisting of argon gas with a purity of 99.99% and chlorine gas with a purity of 99.99% is introduced through the air-permeable brick installed at the bottom of the smelting furnace to refine the aluminum alloy liquid for 10-20 minutes to remove hydrogen;

[0014] Step 4: introducing the aluminum alloy liquid in the smelting furnace into the launder, and allowing the aluminum alloy liquid to flow through the degassing box and the tubular filter box arranged on the launder in sequence for online dehydrogenation and slag removal;

[0015] Step 5: Continuously extruding the aluminum alloy liquid at 680-690° C. into an aluminum alloy round rod with a diameter of 9.5 mm under the conditions of a casting wheel speed of 26-28 rpm and a cooling water flow of 9-11 liters / minute;

[0016] Step 6: Drawing the aluminum alloy round rod into a heat-resistant aluminum alloy wire with a diameter of 3-4 mm;

[0017] Step seven: Twisting the heat-resistant aluminum alloy wire and the galvanized steel wire to obtain the steel-core heat-resistant aluminum alloy stranded wire for the overhead conductor.

[0018] Preferably, the refining agent in step 2 is composed of the following components in percentage by mass: ZnCl 2 44.6%, K 2 CO 3 25.8%, NaNO 3 7.9%, KF 10.5%, K 2 SO 4 7.4%, Li 2 SO 4 3.8%.

[0019] Preferably, the method for producing the refining agent in step 2 comprises the following steps in sequence:

[0020] (1) According to the composition and mass percentage of the refining agent, select ZnCl with a purity of ≥99.8% 2 , K 2 CO 3 、NaNO 3 , KF, K 2 SO 4 , Li 2 SO 4 To prepare ingredients for raw materials;

[0021] (2) heating and melting the raw materials at 1150°C under the protection of argon gas with a purity of 99.99%, and then cooling and solidifying them into a bulk refining agent;

[0022] (3) crushing the bulk refining agent into powder with a particle size of ≤2 mm to obtain the refining agent.

[0023] Hydrogen pores and inclusions are common defects inside the heat-resistant aluminum alloy wire. They will split the aluminum matrix in the heat-resistant aluminum alloy wire, hinder the movement of free electrons, and increase the scattering of free electrons, thereby causing the resistance of the heat-resistant aluminum alloy wire to increase and the conductivity to decrease. Hydrogen pores and inclusions will also cause local stress concentration inside the heat-resistant aluminum alloy wire, becoming the crack source and crack propagation direction of the heat-resistant aluminum alloy wire, thereby reducing the strength, plasticity and corrosion resistance of the heat-resistant aluminum alloy wire. Therefore, in order to solve the problem of mutual restriction between electrical conductivity and heat resistance, and to improve the electrical conductivity and heat resistance of the heat-resistant aluminum alloy wire at the same time, the purity of the heat-resistant aluminum alloy wire must be improved.

[0024] Traditional refining agents are mainly made of raw materials such as sodium salt, fluoride salt, chloride salt, hexachloroethane, etc., which are directly crushed and mixed. The interaction between the raw materials is not brought into play, resulting in a high melting point of the refining agent and low slag removal efficiency. In order to improve the slag removal efficiency of aluminum alloy liquid in the furnace, the inventor has developed an efficient and environmentally friendly refining agent through a large number of experimental studies. The refining agent is based on ZnCl 2 and K 2 CO 3 As the main ingredient, with a small amount of NaNO 3 , KF, K 2 SO 4 , Li 2 SO 4 , the raw materials are first heated to 1150℃ and melted under argon protection, then cooled, solidified and crushed into powdery refining agent, ZnCl 2 The melting point of NaNO is about 290℃. 3 The melting point is 306.8℃, K 2 CO 3 The melting point of K is 891℃, the melting point of KF is 858℃, and the melting point of K 2 SO 4 The melting point of Li is 1069℃. 2 SO 4 The melting point is 859℃, although K 2 CO 3 , KF, K 2 SO 4 , Li 2 SO 4 The melting point is higher, but through melting and solidification crystallization, K 2 CO 3 It forms KF·K with a melting point of only 688℃ 2 CO 3 Cocrystal, K 2 SO 4 With Li 2 SO 4 Forming K with a melting point of only 716°C 2 SO 4·Li 2 SO 4 Eutectic, which greatly reduces the melting point of the refining agent, making it easier to dissolve in the aluminum alloy liquid. 2 Decompose Cl 2 , K 2 CO 3 Decomposes CO 2 , NaNO 3 Decompose N 2 , CO 2 A large number of bubbles capture inclusions in the aluminum alloy liquid during the floating process, thus achieving a slag removal effect. 2 SO 4 ·Li 2 SO 4 The eutectic melts into liquid molten salt, which has a good wetting and spheroidizing effect on inclusions such as alumina, promotes the separation of inclusions from aluminum alloy liquid, and improves the efficiency of slag removal. In addition, the refining agent does not contain sodium salt and hexachloroethane, but only a small amount of fluoride salt, and is more environmentally friendly to use.

[0025] Preferably, the volume percentage of chlorine in the mixed gas in step three is 3-5%, and the flow rate of the mixed gas is 1-2 cubic meters per minute.

[0026] The main function of spraying refining agent on aluminum alloy liquid in the furnace is to remove slag. Although it also has a dehydrogenation effect, the dehydrogenation effect is poor because the refining agent inevitably contains moisture, which will cause the aluminum alloy liquid to absorb hydrogen during refining. In order to reduce the hydrogen content of the aluminum alloy liquid in the furnace, the present invention installs a plurality of porous air-permeable bricks in the smelting furnace, and then passes a mixed gas composed of argon and chlorine into the aluminum alloy liquid in the furnace through the air-permeable bricks. After the mixed gas passes through the porous air-permeable bricks, it is decomposed into small and uniform small bubbles. The small bubbles capture hydrogen in the aluminum alloy liquid during the floating process, and then float up and take out the aluminum alloy liquid, which plays a dehydrogenation role. Since a plurality of porous air-permeable bricks are evenly installed at the bottom of the smelting furnace, the bubbles are evenly distributed in the aluminum alloy liquid, and at the same time, the bubbles have a stirring effect on the aluminum alloy liquid when floating, avoiding the dead corner of degassing in the aluminum alloy liquid in the furnace, and improving the dehydrogenation efficiency of the aluminum alloy liquid. Chlorine is added to the mixed gas, because chlorine has a stronger binding force with hydrogen atoms, thereby further improving the dehydrogenation effect. After dehydrogenation through the air-permeable bricks at the bottom of the furnace, the hydrogen content of the aluminum alloy liquid in the smelting furnace can be reduced to below 0.2ml / 100gAl, thereby greatly improving the purity of the aluminum alloy liquid in the furnace.

[0027] Preferably, in the step 4, the rotation speed of the graphite rotor in the degassing box is 600-700 rpm, the gas flow on the graphite rotor is 1-2 cubic meters per hour, the gas pressure is 0.8-1MPa, and the gas is a mixed gas consisting of argon with a purity of 99.99% and chlorine with a purity of 99.99%, and the volume percentage of chlorine in the mixed gas is 3-5%.

[0028] The high-speed rotating graphite rotor in the degassing box breaks the mixed gas composed of argon and chlorine into tiny bubbles and enters the aluminum alloy liquid. The partial pressure difference of hydrogen between the aluminum alloy liquid and the bubbles is used to make the hydrogen atoms in the aluminum alloy liquid continuously diffuse into the bubbles, and then float up and escape from the aluminum alloy liquid with the bubbles, thereby removing hydrogen. After dehydrogenation in the degassing box, the hydrogen content of the aluminum alloy liquid can be reduced to below 0.08ml / 100gAl, thereby greatly improving the purity of the aluminum alloy liquid and ultimately improving the strength and conductivity of the heat-resistant aluminum alloy wire.

[0029] The filter medium of the tubular filter box in step four is a ceramic filter tube. The ceramic filter tube is made of silicon nitride ceramic particles with a particle size of 3-6 mm and a binder sintered at high temperature. There are a large number of tortuous pores inside. When the aluminum alloy liquid flows through the ceramic filter tube, inclusions are adsorbed or blocked on the surface of the ceramic filter tube and the inner wall of the pores, thereby achieving the effect of filtering and removing slag. The structure and use of the tubular filter box are available in public literature and will not be repeated here. Tubular filtration is a high-precision filtration. After tubular filtration, the removal rate of inclusions larger than 5μm in the aluminum alloy liquid can reach more than 98%, and the slag content of the aluminum alloy liquid can be reduced to 0.05mm 2 / kgAl or less, thereby greatly improving the purity of the aluminum alloy liquid and improving the strength and conductivity of the heat-resistant aluminum alloy wire.

[0030] The continuous casting and extrusion in step five is to pour the aluminum alloy liquid into a continuous casting and extruder, and extrude it through a mold after cooling through a casting and extrusion wheel to obtain an aluminum alloy round rod. Continuous casting and extrusion is a highly efficient short-process forming technology. Compared with conventional continuous casting and rolling, it has the advantages of small investment and small footprint. The specific structure and operation method of continuous casting and extrusion can be found in the literature, so they will not be repeated here. The twisting and forming described in step seven is to twist the heat-resistant aluminum alloy wire and the steel wire on a twisting machine according to the structure of the steel-core heat-resistant aluminum alloy twisted wire. Since the twisting machine is a conventional mechanical equipment, there is a large amount of literature available, so the structure and use of the twisting machine will not be repeated.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention optimizes the structure and manufacturing process of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors, adopts high-strength galvanized steel wire instead of ordinary steel wire as the core wire of the aluminum stranded wire, and adopts high-conductivity heat-resistant aluminum alloy wire to replace ordinary heat-resistant aluminum alloy wire on the outside. Therefore, compared with ordinary steel core heat-resistant aluminum alloy stranded wire, under the condition of equal cross-sectional area, the steel core heat-resistant aluminum alloy stranded wire for overhead conductors of the present invention has higher heat resistance and conductivity, which can improve the transmission capacity of the transmission line, improve the power loss of the transmission line, and meet the needs of ultra-high voltage, large capacity, long-distance transmission lines and urban capacity expansion and reconstruction project construction. In addition, compared with the traditional continuous casting and rolling process, the manufacturing process of the present invention is shorter, the equipment investment is small, the floor space is small, the production efficiency is high, and the production cost of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic structural diagram of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors described in Example 1 of the present invention.

[0034] Figure 2 This is a schematic structural diagram of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors described in Example 2 of the present invention.

[0035] Figure 3 This is a schematic structural diagram of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors described in Example 3 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with specific embodiments and the accompanying drawings.

[0037] Embodiment 1:

[0038] A steel core heat-resistant aluminum alloy stranded wire for overhead conductors, such as Figure 1As shown, in order from the center to the outside, a central galvanized steel wire 101, a galvanized steel wire middle layer 102, a galvanized steel wire outer layer 103, a heat-resistant aluminum alloy wire inner layer 201, a heat-resistant aluminum alloy wire middle layer 202 and a heat-resistant aluminum alloy wire outer layer 203 are sequentially arranged, the galvanized steel wire middle layer 102 is composed of 6 galvanized steel wires, the galvanized steel wire outer layer 103 is composed of 12 galvanized steel wires, the heat-resistant aluminum alloy wire inner layer 201 is composed of 11 heat-resistant aluminum alloy wires, the heat-resistant aluminum alloy wire middle layer 202 is composed of 17 heat-resistant aluminum alloy wires, the heat-resistant aluminum alloy wire outer layer 203 is composed of 23 heat-resistant aluminum alloy wires, the galvanized steel wire middle layer 1 02 is spirally wound around the central galvanized steel wire 101, the galvanized steel wire outer layer 103 is spirally wound around the galvanized steel wire middle layer 102 in a direction opposite to the winding direction of the galvanized steel wire middle layer 102, the heat-resistant aluminum alloy wire inner layer 201 is spirally wound around the galvanized steel wire outer layer 103 in a direction opposite to the winding direction of the galvanized steel wire outer layer 103, the heat-resistant aluminum alloy wire middle layer 202 is spirally wound around the heat-resistant aluminum alloy wire inner layer 201 in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire inner layer 201, and the heat-resistant aluminum alloy wire outer layer 203 is spirally wound around the heat-resistant aluminum alloy wire middle layer 202 in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire middle layer 202.

[0039] The diameter of the galvanized steel wire is 1.8 mm. After testing, the tensile strength of the galvanized steel wire is 1482 MPa, the stress at 1% elongation is 1327 MPa, and the elongation after fracture is 2.5%.

[0040] The heat-resistant aluminum alloy wire has a diameter of 3.5 mm and is composed of the following components in mass percentage: Zr 0.28%, the remainder being Al and unavoidable impurities, with a single impurity ≤0.05% and a total impurity content ≤0.1%.

[0041] The manufacturing method of steel core heat-resistant aluminum alloy stranded wire for overhead conductors comprises the following steps in sequence:

[0042] Step 1: Melting and preparing aluminum alloy liquid at 710°C according to the composition and mass percentage of the heat-resistant aluminum alloy wire;

[0043] Step 2: using argon gas with a purity of 99.99% and a refining agent accounting for 0.15% of the weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid in the melting furnace for 15 minutes to remove slag, and then scrape off the slag on the surface of the aluminum alloy liquid;

[0044] Step 3: A mixed gas consisting of argon with a purity of 99.99% and chlorine with a purity of 99.99% is introduced through the air-permeable brick installed at the bottom of the smelting furnace to refine the aluminum alloy liquid for 15 minutes to remove hydrogen. The volume percentage of chlorine in the mixed gas is 4%, and the flow rate of the mixed gas is 1.5 cubic meters / minute;

[0045] Step 4: introducing the aluminum alloy liquid in the smelting furnace into the launder, and making the aluminum alloy liquid flow through the degassing box and the tubular filter box arranged on the launder in sequence for online dehydrogenation and slag removal treatment, the rotation speed of the graphite rotor in the degassing box is 650 rpm, the gas flow rate on the graphite rotor is 1.5 cubic meters per hour, and the gas pressure is 0.9 MPa. The gas is a mixed gas composed of argon with a purity of 99.99% and chlorine with a purity of 99.99%, and the volume percentage of chlorine in the mixed gas is 4%;

[0046] Step 5: Continuously extruding the aluminum alloy liquid at 685° C. into an aluminum alloy round rod with a diameter of 9.5 mm under the conditions of a casting wheel speed of 27 rpm and a cooling water flow rate of 10 liters / minute;

[0047] Step 6: Drawing the aluminum alloy round rod into a heat-resistant aluminum alloy wire with a diameter of 3.5 mm;

[0048] Step seven: Twisting the heat-resistant aluminum alloy wire and the galvanized steel wire to obtain the steel-core heat-resistant aluminum alloy stranded wire for the overhead conductor.

[0049] Embodiment 2:

[0050] A steel core heat-resistant aluminum alloy stranded wire for overhead conductors, such as Figure 2 As shown, in order from the center to the outside, a central galvanized steel wire 101, a galvanized steel wire middle layer 102, a galvanized steel wire outer layer 103, a heat-resistant aluminum alloy wire inner layer 201, a heat-resistant aluminum alloy wire middle layer 202 and a heat-resistant aluminum alloy wire outer layer 203 are sequentially arranged, the galvanized steel wire middle layer 102 is composed of 6 galvanized steel wires, the galvanized steel wire outer layer 103 is composed of 12 galvanized steel wires, the heat-resistant aluminum alloy wire inner layer 201 is composed of 10 heat-resistant aluminum alloy wires, the heat-resistant aluminum alloy wire middle layer 202 is composed of 17 heat-resistant aluminum alloy wires, the heat-resistant aluminum alloy wire outer layer 203 is composed of 23 heat-resistant aluminum alloy wires, the galvanized steel wire middle layer 1 02 is spirally wound around the central galvanized steel wire 101, the galvanized steel wire outer layer 103 is spirally wound around the galvanized steel wire middle layer 102 in a direction opposite to the winding direction of the galvanized steel wire middle layer 102, the heat-resistant aluminum alloy wire inner layer 201 is spirally wound around the galvanized steel wire outer layer 103 in a direction opposite to the winding direction of the galvanized steel wire outer layer 103, the heat-resistant aluminum alloy wire middle layer 202 is spirally wound around the heat-resistant aluminum alloy wire inner layer 201 in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire inner layer 201, and the heat-resistant aluminum alloy wire outer layer 203 is spirally wound around the heat-resistant aluminum alloy wire middle layer 202 in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire middle layer 202.

[0051] The diameter of the galvanized steel wire is 2 mm. After testing, the tensile strength of the galvanized steel wire is 1450 MPa, the stress at 1% elongation is 1310 MPa, and the elongation after fracture is 2.9%.

[0052] The heat-resistant aluminum alloy wire has a diameter of 4 mm and is composed of the following components in mass percentage: Zr 0.3%, the remainder Al and unavoidable impurities, a single impurity ≤0.05%, and a total impurity ≤0.1%.

[0053] The manufacturing method of steel core heat-resistant aluminum alloy stranded wire for overhead conductors comprises the following steps in sequence:

[0054] Step 1: Melting and preparing aluminum alloy liquid at 700°C according to the composition and mass percentage of the heat-resistant aluminum alloy wire;

[0055] Step 2: using argon gas with a purity of 99.99% and a refining agent accounting for 0.2% of the weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid in the melting furnace for 20 minutes to remove slag, and then scrape off the slag on the surface of the aluminum alloy liquid;

[0056] Step 3: A mixed gas consisting of argon with a purity of 99.99% and chlorine with a purity of 99.99% is introduced through the air-permeable brick installed at the bottom of the smelting furnace to refine the aluminum alloy liquid for 10 minutes to remove hydrogen. The volume percentage of chlorine in the mixed gas is 5%, and the flow rate of the mixed gas is 2 cubic meters / minute;

[0057] Step 4: introducing the aluminum alloy liquid in the smelting furnace into the launder, and making the aluminum alloy liquid flow through the degassing box and the tubular filter box arranged on the launder in sequence for online dehydrogenation and slag removal treatment, the rotation speed of the graphite rotor in the degassing box is 600 rpm, the gas flow rate on the graphite rotor is 2 cubic meters / hour, the gas pressure is 1MPa, and the gas is a mixed gas composed of argon with a purity of 99.99% and chlorine with a purity of 99.99%, and the volume percentage of chlorine in the mixed gas is 5%;

[0058] Step 5: Continuously extruding the aluminum alloy liquid at 680° C. into an aluminum alloy round rod with a diameter of 9.5 mm under the conditions of a casting wheel speed of 28 rpm and a cooling water flow of 9 liters / minute;

[0059] Step 6: Drawing the aluminum alloy round rod into a heat-resistant aluminum alloy wire with a diameter of 4 mm;

[0060] Step seven: Twisting the heat-resistant aluminum alloy wire and the galvanized steel wire to obtain the steel-core heat-resistant aluminum alloy stranded wire for the overhead conductor.

[0061] Embodiment 3:

[0062] A steel core heat-resistant aluminum alloy stranded wire for overhead conductors, such as Figure 3As shown, in order from the center to the outside, a central galvanized steel wire 101, a galvanized steel wire middle layer 102, a galvanized steel wire outer layer 103, a heat-resistant aluminum alloy wire inner layer 201, a heat-resistant aluminum alloy wire middle layer 202 and a heat-resistant aluminum alloy wire outer layer 203 are sequentially arranged, the galvanized steel wire middle layer 102 is composed of 6 galvanized steel wires, the galvanized steel wire outer layer 103 is composed of 12 galvanized steel wires, the heat-resistant aluminum alloy wire inner layer 201 is composed of 10 heat-resistant aluminum alloy wires, the heat-resistant aluminum alloy wire middle layer 202 is composed of 17 heat-resistant aluminum alloy wires, the heat-resistant aluminum alloy wire outer layer 203 is composed of 23 heat-resistant aluminum alloy wires, the galvanized steel wire middle layer 1 02 is spirally wound around the central galvanized steel wire 101, the galvanized steel wire outer layer 103 is spirally wound around the galvanized steel wire middle layer 102 in a direction opposite to the winding direction of the galvanized steel wire middle layer 102, the heat-resistant aluminum alloy wire inner layer 201 is spirally wound around the galvanized steel wire outer layer 103 in a direction opposite to the winding direction of the galvanized steel wire outer layer 103, the heat-resistant aluminum alloy wire middle layer 202 is spirally wound around the heat-resistant aluminum alloy wire inner layer 201 in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire inner layer 201, and the heat-resistant aluminum alloy wire outer layer 203 is spirally wound around the heat-resistant aluminum alloy wire middle layer 202 in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire middle layer 202.

[0063] The diameter of the galvanized steel wire is 1.5 mm. After testing, the tensile strength of the galvanized steel wire is 1471 MPa, the stress at 1% elongation is 1318 MPa, and the elongation after fracture is 2.7%.

[0064] The heat-resistant aluminum alloy wire has a diameter of 3 mm and is composed of the following components in mass percentage: Zr 0.25%, the remainder being Al and unavoidable impurities, with a single impurity ≤0.05% and a total impurity content ≤0.1%.

[0065] The manufacturing method of steel core heat-resistant aluminum alloy stranded wire for overhead conductors comprises the following steps in sequence:

[0066] Step 1: Melting and preparing aluminum alloy liquid at 720°C according to the composition and mass percentage of the heat-resistant aluminum alloy wire;

[0067] Step 2: using argon gas with a purity of 99.99% and a refining agent accounting for 0.1% of the weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid in the melting furnace for 10 minutes to remove slag, and then scrape off the slag on the surface of the aluminum alloy liquid;

[0068] Step 3: A mixed gas consisting of argon with a purity of 99.99% and chlorine with a purity of 99.99% is introduced through the air-permeable brick installed at the bottom of the smelting furnace to refine the aluminum alloy liquid for 20 minutes to remove hydrogen. The volume percentage of chlorine in the mixed gas is 3%, and the flow rate of the mixed gas is 1 cubic meter / minute;

[0069] Step 4: introducing the aluminum alloy liquid in the smelting furnace into the launder, and making the aluminum alloy liquid flow through the degassing box and the tubular filter box arranged on the launder in sequence for online dehydrogenation and slag removal treatment, the rotation speed of the graphite rotor in the degassing box is 700 rpm, the gas flow rate on the graphite rotor is 1 cubic meter / hour, the gas pressure is 0.8MPa, and the gas is a mixed gas composed of argon with a purity of 99.99% and chlorine with a purity of 99.99%, and the volume percentage of chlorine in the mixed gas is 3%;

[0070] Step 5: Continuously extruding the aluminum alloy liquid at 690° C. into an aluminum alloy round rod with a diameter of 9.5 mm under the conditions of a casting wheel speed of 28 rpm and a cooling water flow rate of 11 liters / minute;

[0071] Step 6: Drawing the aluminum alloy round rod into a heat-resistant aluminum alloy wire with a diameter of 3 mm;

[0072] Step seven: Twisting the heat-resistant aluminum alloy wire and the galvanized steel wire to obtain the steel-core heat-resistant aluminum alloy stranded wire for the overhead conductor.

[0073] In Examples 1-3, the refining agent in step 2 is composed of the following components in percentage by mass: ZnCl 2 44.6%, K 2 CO 3 25.8%, NaNO 3 7.9%, KF 10.5%, K 2 SO 4 7.4%, Li 2 SO 4 3.8%, the production method of the refining agent comprises the following steps in sequence: (1) selecting ZnCl with a purity of ≥99.8% according to the composition and mass percentage of the refining agent; 2 , K 2 CO 3 、NaNO 3 , KF, K 2 SO 4 , Li 2 SO 4 (2) heating and melting the raw materials at 1150° C. under the protection of argon gas with a purity of 99.99%, and then cooling and solidifying them into a bulk refining agent; (3) crushing the bulk refining agent into powder with a particle size of ≤2 mm to obtain the refining agent.

[0074] Comparative Example 1:

[0075] The structure of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors, the composition of the heat-resistant aluminum alloy wire and the manufacturing method are the same as those in Example 1, except that the refining agent used in step 2 is a currently commonly used commercially available refining agent, and the refining agent is composed of the following components in mass percentage: 26.1% NaCl, 10.6% Na 2 SiF 6 , 17.1% Na 2 SO 4 , 6.9% CaF 2 , 9.3% C 6 Cl 6 , 14.3% Na 2 S 2 O 3 and 15.7% NaF. The production method of the refining agent is to directly crush the raw materials into powders with a particle size of ≤2 mm and then mix them.

[0076] Comparative Example 2:

[0077] The structure of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors, the component composition of the heat-resistant aluminum alloy wire and the manufacturing method are the same as those in Example 2, except that in step three, a mixed gas consisting of argon and chlorine is not introduced into the aluminum alloy liquid in the furnace through the furnace bottom air bricks for dehydrogenation treatment.

[0078] Comparative Example 3:

[0079] The structure of the steel core heat-resistant aluminum alloy stranded wire for overhead conductors, the composition of the heat-resistant aluminum alloy wire and the manufacturing method are the same as those in Example 3, except that in step 4, no tubular filter box is used to filter the aluminum alloy liquid.

[0080] Verification Example 1:

[0081] The melting points of the refining agents used in Example 1 and Comparative Example 1 were respectively detected by using an OXFORD-DSC500 differential scanning calorimeter, and the results are shown in Table 1. As can be seen from Table 1, the melting start temperature of the refining agent in Example 1 is 290°C, and the melting end temperature is only 716°C. The melting start temperature of the refining agent in Comparative Example 1 is 564°C, and the melting end temperature is 1249°C. By comparison, it can be seen that the refining agent developed by the present invention has a lower melting start temperature and melting end temperature, indicating that the refining agent developed by the present invention is easier to dissolve in the aluminum alloy liquid, which is beneficial to improving the slag removal effect.

[0082] Table 1 Melting point of refining agent in Example 1 and Comparative Example 1

[0083] Example 1 Comparative Example 1 Melting start temperature / ℃ 290 564 Melting end temperature / ℃ 716 1249

[0084] Verification Example 2:

[0085] The hydrogen content and slag content of the aluminum alloy liquid before casting and extrusion of Examples 1-3 and Comparative Examples 1-3 were tested on site using a HDA-V hydrogen meter and an Analyze PoDFA slag meter. The results are shown in Table 2. As can be seen from Table 2, the hydrogen content of the aluminum alloy liquid of Examples 1-3 is less than 0.08 ml / 100 gAl, and the slag content is less than 0.05 mm 2 / kgAl. Comparative Example 1 uses a traditional commercial refining agent for in-furnace spray refining, Comparative Example 2 does not use a ventilation brick at the bottom of the furnace for refining, and Comparative Example 3 does not use a tubular filter box for filtration, resulting in the gas-slag content of the aluminum alloy liquid being significantly higher than the gas-slag content of the aluminum alloy liquid in the embodiment. By comparison, it can be seen that the present invention can greatly improve the purity of the heat-resistant aluminum alloy wire.

[0086] Table 2 Hydrogen content and slag content of aluminum alloy liquid before casting

[0087]

[0088]

[0089] Verification Example 3:

[0090] Samples were taken from the heat-resistant aluminum alloy wires of Examples 1-3 and Comparative Examples 1-3, and then the room temperature tensile strength, DC resistivity and conductivity of the heat-resistant aluminum alloy wires were respectively tested, and the results are shown in Table 3. The heat-resistant aluminum alloy wires of Examples 1-3 and Comparative Examples 1-3 were respectively heated at 230°C for 1 hour, cooled to room temperature, and then the tensile strength of the heat-resistant aluminum alloy wires was respectively tested, and the tensile strength was divided by the room temperature tensile strength of the heat-resistant aluminum alloy wire before heating to obtain the strength retention rate, and the results are shown in Table 3. It can be seen from Table 3 that the room temperature tensile strength of the heat-resistant aluminum alloy wires of Examples 1-3 is ≥240MPa, the strength retention rate after heating at 230°C for 1 hour is ≥95%, the DC resistivity at 20°C is ≤0.0278Ω·mm2 / m, and the conductivity is ≥62%IACS. Since Comparative Example 1 uses traditional commercially available refining agents for in-furnace spray refining, Comparative Example 2 does not use ventilation refining through furnace bottom air bricks, and Comparative Example 3 does not use tubular filter boxes for filtration, the strength, conductivity and strength retention rate of the heat-resistant aluminum alloy wire are significantly lower than the strength, conductivity and strength retention rate of the heat-resistant aluminum alloy wire in the embodiment. Through comparison, it can be seen that the present invention can greatly improve the strength, heat resistance and conductivity of the heat-resistant aluminum alloy wire by improving the purity of the heat-resistant aluminum alloy wire.

[0091] Table 3 Tensile strength, resistivity, conductivity and strength retention of heat-resistant aluminum alloy wire

[0092]

[0093] The present invention is described by way of embodiments, but does not constitute a limitation to the present invention. With reference to the description of the present invention, other changes to the disclosed embodiments are easily conceivable to professionals in the field, and such changes should fall within the scope defined by the claims of the present invention.

Claims

1. A steel core heat-resistant aluminum alloy stranded wire for overhead conductors, characterized in that: A central galvanized steel wire, a galvanized steel wire middle layer, a galvanized steel wire outer layer, a heat-resistant aluminum alloy wire inner layer, a heat-resistant aluminum alloy wire middle layer and a heat-resistant aluminum alloy wire outer layer are sequentially arranged from the center to the outside, wherein the galvanized steel wire middle layer and the galvanized steel wire outer layer are respectively composed of a plurality of galvanized steel wires, the heat-resistant aluminum alloy wire inner layer, the heat-resistant aluminum alloy wire middle layer and the heat-resistant aluminum alloy wire outer layer are respectively composed of a plurality of heat-resistant aluminum alloy wires, the galvanized steel wire middle layer is spirally wound around the central galvanized steel wire, and the galvanized steel wire outer layer is spirally wound around the galvanized steel wire middle layer. The heat-resistant aluminum alloy wire inner layer is spirally wound on the galvanized steel wire middle layer in a direction opposite to the winding direction of the galvanized steel wire outer layer, the heat-resistant aluminum alloy wire middle layer is spirally wound on the heat-resistant aluminum alloy wire inner layer in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire inner layer, and the heat-resistant aluminum alloy wire outer layer is spirally wound on the heat-resistant aluminum alloy wire middle layer in a direction opposite to the winding direction of the heat-resistant aluminum alloy wire middle layer; the manufacturing method of steel core heat-resistant aluminum alloy stranded wire for overhead conductors comprises the following steps in sequence: Step 1: Melt and prepare aluminum alloy liquid at 700-720°C according to the composition and mass percentage of the heat-resistant aluminum alloy wire; Step 2: Use argon gas with a purity of 99.99% and a refining agent accounting for 0.1-0.2% of the weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid in the melting furnace for 10-20 minutes to remove slag, and then scrape off the slag on the surface of the aluminum alloy liquid; Step 3: A mixed gas consisting of argon with a purity of 99.99% and chlorine with a purity of 99.99% is introduced through the air-permeable brick installed at the bottom of the smelting furnace to refine the aluminum alloy liquid for 10-20 minutes to remove hydrogen; Step 4: introducing the aluminum alloy liquid in the smelting furnace into the launder, and allowing the aluminum alloy liquid to flow through the degassing box and the tubular filter box arranged on the launder in sequence for online dehydrogenation and slag removal; Step 5: Continuously extruding the aluminum alloy liquid at 680-690° C. into an aluminum alloy round rod with a diameter of 9.5 mm under the conditions of a casting wheel speed of 26-28 rpm and a cooling water flow of 9-11 liters / minute; Step 6: Drawing the aluminum alloy round rod into a heat-resistant aluminum alloy wire with a diameter of 3-4 mm; Step 7: Twisting the heat-resistant aluminum alloy wire and the galvanized steel wire to obtain the steel-core heat-resistant aluminum alloy stranded wire for the overhead conductor; The refining agent in step 2 is composed of the following components in mass percentage: ZnCl2 44.6%, K2CO3 25.8%, NaNO37.9%, KF 10.5%, K2SO4 7.4%, Li2SO4 3.8%; the production method of the refining agent comprises the following steps in sequence: (1) According to the composition and mass percentage of the refining agent, ZnCl2, K2CO3, NaNO3, KF, K2SO4 and Li2SO4 with a purity of ≥99.8% are selected as raw materials for batching; (2) The raw materials are heated and melted at 1150°C under the protection of argon gas with a purity of 99.99%, and then cooled and solidified into a bulk refining agent; (3) Crushing the bulk refining agent into powder with a particle size of ≤2 mm to obtain the refining agent.

2. The steel core heat-resistant aluminum alloy stranded wire for overhead conductor according to claim 1, characterized in that: The diameter of the galvanized steel wire is 1.5-2 mm, the tensile strength of the galvanized steel wire is ≥1450 MPa, the stress at 1% elongation is ≥1310 MPa, and the elongation after fracture is ≥2.5%.

3. The steel core heat-resistant aluminum alloy stranded wire for overhead conductor according to claim 1, characterized in that: The diameter of the heat-resistant aluminum alloy wire is 3-4 mm, the tensile strength of the heat-resistant aluminum alloy wire is ≥200 MPa, the strength retention rate after heating at 230°C for 1 hour is ≥94%, and the DC resistivity at 20°C is ≤0.0278 Ω•mm 2 / m, electrical conductivity ≥62%IACS.

4. The steel core heat-resistant aluminum alloy stranded wire for overhead conductor according to claim 1, characterized in that: The heat-resistant aluminum alloy wire is composed of the following components in mass percentage: Zr 0.25-0.3%, the balance being Al and inevitable impurities, with a single impurity ≤0.05% and a total impurity content ≤0.1%.

5. The steel core heat-resistant aluminum alloy stranded wire for overhead conductor according to claim 1, characterized in that: In the step 3, the volume percentage of chlorine in the mixed gas is 3-5%, and the flow rate of the mixed gas is 1-2 cubic meters per minute.

6. The steel core heat-resistant aluminum alloy stranded wire for overhead conductor according to claim 1, characterized in that: In the step 4, the rotation speed of the graphite rotor in the degassing box is 600-700 rpm, the gas flow on the graphite rotor is 1-2 cubic meters per hour, the gas pressure is 0.8-1 MPa, and the gas is a mixed gas consisting of argon with a purity of 99.99% and chlorine with a purity of 99.99%, and the volume percentage of chlorine in the mixed gas is 3-5%.

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