High strength aluminum clad steel wire and method of making same

Abstract

The application provides a high-strength aluminum-clad steel wire and a preparation method thereof, the aluminum-clad steel wire comprises a steel wire and an aluminum layer coated on the outer surface of the steel core, and the steel wire contains, by weight, C: 0.85%-0.90%, Si: 0.1%-0.5%, Mn 0.1%-0.5%, Al: 0.02%-0.05%, Cr: 0.10%-0.20%, Ca: 0.10%-0.15%, P≤0.020%, S≤0.025%, and the balance is iron and inevitable impurity elements; the preparation method comprises the following steps: preparing a billet, performing hot rolling on the billet, performing isothermal cooling on the steel wire, performing surface cleaning on the cooled steel wire, and then drawing the steel wire to a required wire diameter to obtain a steel wire, extruding the drawn steel wire to coat an aluminum layer to obtain a bus, and performing drawing treatment on the bus to obtain the aluminum-clad steel wire; the aluminum-clad steel wire preparation method provided by the application is simple in steps, convenient to operate, and the prepared aluminum-clad steel wire not only has high strength, but also has high conductivity.

Description

Technical Field

[0001] This invention relates to the field of aluminum-clad steel wire technology, and in particular to a high-strength aluminum-clad steel wire and its preparation method. Background Technology

[0002] Aluminum-clad steel wire is a bimetallic material formed by stretching steel after coating it with a layer of aluminum. Due to its combination of the high strength of steel and the excellent conductivity of aluminum, it is widely used in overhead transmission lines, primarily as a conductor reinforcing core, ground wire, and transmission line. In recent years, with the rapid development of power grid construction, especially in special environments such as salt spray and extreme cold, as well as in long-span transmission projects, higher requirements have been placed on the mechanical properties of aluminum-clad steel wire. Improving the tensile strength of aluminum-clad steel mainly relies on increasing the strength of the steel core. Chinese patent CN115449710A proposes an aluminum-clad steel wire made of high-silicon steel wire, with a maximum silicon content of 1.9% and a maximum manganese content of 1.1%. However, while high proportions of silicon and manganese can improve the strength of the steel core, they also lead to higher resistivity, affecting the conductivity of the finished aluminum-clad steel wire. Therefore, it is necessary to develop a method that can effectively improve the strength of aluminum-clad steel wire without reducing its conductivity. Summary of the Invention

[0003] The purpose of this invention is to provide a high-strength aluminum-clad steel wire and its preparation method, which can improve the strength of the steel wire without reducing the conductivity of the aluminum-clad steel wire, thereby solving the problems mentioned in the background art.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high-strength aluminum-clad steel wire, comprising a steel wire and an aluminum layer covering the outer surface of a steel core, wherein the steel wire contains, by weight, the following percentages: C: 0.85%~0.90%, Si: 0.1%~0.5%, Mn: 0.1%~0.5%, Al: 0.02%~0.05%, Cr: 0.10%~0.20%, Ca: 0.10%~0.15%, P≤0.020%, S≤0.025%, with the balance being iron and unavoidable impurity elements.

[0005] This invention provides a method for preparing high-strength aluminum-clad steel wire, the manufacturing method comprising:

[0006] Step 1, Steel wire heat treatment: The billet is heated at 1100℃~1200℃ for 80 minutes. By weight, the billet contains C: 0.85%~0.90%, Si: 0.1%~0.5%, Mn: 0.1%~0.5%, Al: 0.02%~0.05%, Cr: 0.10%~0.20%, Ca: 0.10%~0.15%, P≤0.020%, S≤0.025%, with the balance being iron and unavoidable impurities. The heated billet is rolled at a final rolling temperature of 900℃ to 1000℃ to form steel wire. The steel wire obtained after final rolling is then cooled.

[0007] Step 2, wire pretreatment: After cleaning the surface of the cooled steel wire, draw it to the required wire diameter;

[0008] Step 3, Aluminum rod pretreatment and coating: The drawn steel wire is extruded and coated with a layer of aluminum rod that has undergone surface treatment in a shot blasting machine to form a coated busbar;

[0009] Step 4, Synchronous Stretching: The clad busbar is simultaneously stretched multiple times to the required wire diameter to form aluminum-clad steel wire.

[0010] Preferably, the drawing speed in step 2 is controlled at 90-120 m / min, and the pass compression rate of the drawing process is 15%.

[0011] Preferably, in step 4, the synchronous stretching speed is 4-8 m / s, and the temperature of the aluminum-clad steel wire during stretching is 110℃.

[0012] Preferably, in step 4, the synchronous stretching uses lubricating powder or lubricating oil as the lubricating medium.

[0013] Preferably, the total compression rate of the multi-pass synchronous stretching in step 4 is less than 80%, and the number of stretching passes is 9.

[0014] Preferably, the mold used in step 4, multi-pass synchronous stretching, is a combination of a pressure mold and a tungsten steel mold.

[0015] Preferably, step 3, extrusion coating, is performed at a mold cavity temperature of 420~430℃, a pressure of 120~150MPa, and a coating speed of 50~150m / min.

[0016] Preferably, step 1 cooling involves cooling the steel wire obtained after final rolling to 750°C at a cooling rate of 45~50°C, then immediately immersing it in a lead bath for quenching to perform isothermal transformation, and then cooling it to room temperature.

[0017] Preferably, the lead bath is performed at a temperature of 580℃~600℃ and an immersion time of 80~100 seconds.

[0018] This invention, by employing specific chemical components, reducing the amount of Si and Mn, introducing appropriate proportions of Cr and Ca, and combining with an improved process route, helps to obtain a more uniform sorbitic structure. The resulting aluminum-clad steel wire not only possesses high strength but also high electrical conductivity. Furthermore, most existing aluminum-clad steel wire production processes involve smelting and hot-rolling the steel wire, then removing the oxide scale and performing rough drawing, requiring further heating to austenitize the wire. This heat treatment method is a secondary offline heat treatment, resulting in significant energy waste. This application only requires a single continuous heating of the steel wire to meet actual performance requirements, avoiding multiple heating processes, thereby reducing production costs and improving production efficiency, making it highly valuable in industrial applications. Attached Figure Description

[0019] Figure 1 This is a metallographic diagram of the steel wire provided in Embodiment 2 of the present invention. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention provides a high-strength aluminum-clad steel wire, comprising a steel wire and an aluminum layer covering the outer surface of a steel core. The chemical composition of the steel wire is shown in Table 1 by mass percentage. In addition to the chemical composition in Table 1, the balance is iron and unavoidable impurity elements.

[0022] Table 1

[0023]

[0024] Next, the method for manufacturing the high-strength aluminum-clad steel wire of the present invention will be described.

[0025] The billet is heated at 1100℃~1200℃ for 80 minutes. By weight, the billet contains C: 0.85%~0.90%, Si: 0.1%~0.5%, Mn: 0.1%~0.5%, Al: 0.02%~0.05%, Cr: 0.10%~0.20%, Ca: 0.10%~0.15%, P≤0.020%, S≤0.025%, with the balance being iron and unavoidable impurity elements. The heated billet is then rolled at a final rolling temperature of 900℃ to 1000℃ to form steel wire.

[0026] The steel wire rod obtained after the final rolling at a temperature above 900°C is cooled to 750°C by a combination of water cooling and air cooling at a cooling rate of 45~50°C / second. Then it is immediately immersed in a lead bath and isothermal transformation is performed at a temperature of 580°C~600°C for 80~100 seconds, and then cooled to room temperature.

[0027] The cooled steel wire is pickled online in industrial synthetic hydrochloric acid or sulfuric acid to remove the surface oxide scale, and then drawn in two passes to the required wire diameter. The drawing speed is controlled at 90-120 m / min, and the pass compression rate of the drawing process is 15%.

[0028] After the drawn steel wire is degreased and cleaned of surface impurities, it is sent to a medium-frequency induction heating furnace for preheating treatment. The steel wire is induction heated to 400°C, and then a layer of industrial pure aluminum rod that has been surface-treated by shot blasting is evenly covered around the outside of the steel wire by a continuous extrusion coating machine. Specifically, the coating busbar is formed with a die cavity temperature of 420~430°C, a pressure of 120~150MPa, and a coating speed of 50~150m / min.

[0029] The aluminum-clad steel wire is formed by combining a pressure die and a tungsten steel wire drawing die to create a composite mold. The busbar is then stretched to the required diameter in multiple passes using lubricating powder or lubricating oil as the lubricating medium. The temperature of the aluminum-clad steel wire is controlled at 110℃, and the total compression rate of the busbar is controlled to be less than 80%. The number of drawing passes is 9, thus forming the aluminum-clad steel wire.

[0030] The chemical composition shown in Table 1 above is heated at 1100℃~1200℃ for 80 minutes, and the heated billet is rolled to form steel wire. Then, it is heat-treated under the conditions shown in Table 2 below, and the steel wire is drawn and aluminum layer is extruded and coated under the conditions shown in Table 3 below. The busbar is drawn under the conditions shown in Table 4 below.

[0031] Table 2

[0032]

[0033] Table 3

[0034]

[0035] Table 4

[0036]

[0037] Performance testing

[0038] The tensile strength, electrical conductivity, and torsional properties of the aluminum-clad steel wires prepared in Examples 1-5 and Comparative Examples 1-4 were determined according to GB / T 17937-2024. The results are shown in Table 5.

[0039] Table 5 Performance Test Results

[0040]

[0041] This invention, by employing specific chemical components, reducing the amount of Si and Mn, introducing appropriate proportions of Cr and Ca, and combining with an improved process route, helps to obtain a more uniform sorbitic microstructure, ultimately resulting in high-strength, high-conductivity aluminum-clad steel wire. The optimal composition (0.90% C, 0.50% Si, 0.50% Mn, 0.05% Al, 0.02% Cr, 0.15% Ca, 0.01% P, 0.01% S, with the balance being Fe and unavoidable impurities) exhibits the best overall performance. Figure 1 The metallographic structure of the steel wire obtained from this composition.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength aluminum-clad steel wire, characterized in that, Includes the following steps: Step 1, Steel Wire Heat Treatment: The billet is heated at 1100℃~1200℃ for 80 minutes. The billet, by weight, contains C: 0.85%~0.90%, Si: 0.1%~0.5%, Mn: 0.1%~0.5%, Al: 0.02%~0.05%, Cr: 0.10%~0.20%, Ca: 0.10%~0.15%, P≤0.020%, S≤0.025%, with the balance being iron and unavoidable impurities. The heated billet is rolled at a final rolling temperature of 900℃ to 1000℃ to form steel wire. The steel wire obtained after final rolling is then cooled. The cooling process involves cooling the steel wire obtained after final rolling to 750°C at a cooling rate of 45-50°C / second, then immediately immersing it in a lead bath for quenching to achieve isothermal transformation, followed by cooling to room temperature; wherein the lead bath temperature is set to 580°C-600°C, and the immersion time is 80-100 seconds. Step 2, wire pretreatment: After cleaning the surface of the cooled steel wire, draw it to the required wire diameter; Step 3, Aluminum rod pretreatment and coating: The drawn steel wire is extruded and coated with a layer of aluminum rod that has undergone shot blasting surface treatment to form a coated busbar; Step 4, Synchronous Stretching: The clad busbar is simultaneously stretched multiple times to the required wire diameter to form aluminum-clad steel wire.

2. The method for preparing a high-strength aluminum-clad steel wire according to claim 1, characterized in that, In step 2, the drawing speed is controlled at 90-120 m / min, and the pass compression rate of the drawing process is 15%.

3. The method for preparing a high-strength aluminum-clad steel wire according to claim 1, characterized in that, In step 4, the synchronous stretching speed is 4-8 m / s, and the temperature of the aluminum-clad steel wire is 110℃ during stretching.

4. The method for preparing a high-strength aluminum-clad steel wire according to claim 1, characterized in that, Step 4, synchronous stretching, uses lubricating powder or lubricating oil as the lubricating medium.

5. The method for preparing a high-strength aluminum-clad steel wire according to claim 1, characterized in that, The total compression rate of the multi-pass synchronous stretching in step 4 is less than 80%, and the number of stretching passes is 9.

6. The method for preparing a high-strength aluminum-clad steel wire according to claim 1, characterized in that, The mold used in step 4, multi-pass synchronous stretching, is a combination of a pressure mold and a tungsten steel mold.

7. The method for preparing a high-strength aluminum-clad steel wire according to claim 1, characterized in that, Step 3, extrusion coating, is carried out at a mold cavity temperature of 420-430℃, a pressure of 120-150MPa, and a coating speed of 50-150m / min.

8. A high-strength aluminum-clad steel wire, prepared by the preparation method according to any one of claims 1-7, characterized in that, It includes steel wire and an aluminum layer covering the outer surface of the steel core. The steel wire contains, by weight, the following percentages: C: 0.85%~0.90%, Si: 0.1%~0.5%, Mn: 0.1%~0.5%, Al: 0.02%~0.05%, Cr: 0.10%~0.20%, Ca: 0.10%~0.15%, P≤0.020%, S≤0.025%, with the balance being iron and unavoidable impurity elements.

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