Production method of high-creep high-conductivity aluminum alloy wire

Abstract

The invention relates to a production method of a high-creep high-conductivity aluminum alloy wire. The high-creep high-conductivity aluminum alloy wire comprises alloy elements in percentage by weight as follows: 0.32%-0.4% of Si, 0.07%-0.12% of Fe, less than 0.01% of Mn, less than 0.1% of Cu, 0.4%-0.55% of Mg, less than 0.01% of Cr, less than or equal to 0.1% of Zn, 0.01%-0.02% of Ti and the balance of Al. The weight percentage of the alloy elements is as follows: Mg is 0.3 (Mn + Cr + Fe)-Si is less than 0.03. According to the high-conductivity aluminum alloy wire, various properties, including the mechanical property, the conductivity and the high-temperature creep resistance, of the 6-series aluminum alloy production wire can be improved without adding other rare earth elements, and the production cost of the high-conductivity aluminum alloy wire is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, specifically to a method for producing high-creep, high-conductivity aluminum alloy wire. Background Technology

[0002] Both aluminum and copper are commonly used materials for manufacturing electrical conductors, but they differ in several aspects, including price, conductivity, flexibility, stability, and load capacity. The advantages of copper wire are: 1. Copper wire has a lower resistivity than aluminum wire, resulting in better electrical and thermal conductivity and lower electrical losses; 2. Copper wire is more flexible, easier to bend, and has strong fatigue resistance; 3. Copper wire has good resistance to high-temperature creep, thereby reducing the possibility of loose cable joints and improving conductor connection. However, the disadvantages of copper wire are: 1. Copper wire is more expensive. Copper is a relatively scarce resource, and the costs of mining and refining are high, making copper wire generally more expensive than other metal materials; 2. Copper wire is heavier. Due to its higher density, it increases costs and difficulties during transportation and installation.

[0003] With the rapid development of the trend of replacing copper with aluminum in the manufacture of conductive materials, technicians have developed aluminum alloy conductive wires with different alloy compositions and using different processes, continuously improving various mechanical properties, conductivity properties, and high-temperature creep resistance of aluminum alloy wires. For example, in existing technologies, adding rare earth elements to aluminum-based materials can improve various properties of aluminum alloy wires. 1. Chinese Patent: Production Method of Heat-Resistant Aluminum Alloy Conductor Containing Zr; Application No.: 201610988764.5; 2. Chinese Patent: High Conductivity Creep-Resistant Aluminum Alloy Cable Conductor Containing Hf and Ce and its Preparation Method; Application No.: 201210249817.3; 3. A High Conductivity, Pressure-Resistant, Creep-Resistant Aluminum Alloy and its Manufacturing Method; Application No.: 201510600604.4; The above-mentioned production methods all improve the various properties of aluminum alloy wires by adding other elements, especially relying on the addition of rare earth elements. However, rare earth elements are globally scarce strategic resources and are expensive, so they do not significantly reduce the production cost of wires. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing high-creep, high-conductivity aluminum alloy wires. This method does not rely on the addition of other alloying elements. By strictly controlling the composition ratio of Mg, Mn, Cr, Fe, and Si in 6-series aluminum alloys, ensuring that their weight percentages conform to a specific mathematical relationship, and supplementing with a suitable aging process, the mechanical properties, conductivity, and high-temperature creep resistance of the aluminum alloy wires can be improved.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for producing high creep and high conductivity aluminum alloy wire, wherein the alloy composition is designed as follows: alloy element weight percentage Si: 0.32-0.4%, Fe: 0.07-0.12%, Mn: <0.01%, Cu: <0.1%, Mg: 0.4-0.55%, Cr <0.01%, Zn: ≤0.1%, Ti: 0.01-0.02%, with the balance being Al; The alloying elements mentioned above should meet the following alloy weight percentage: 0 < Si - 0.3 (Mn + Cr + Fe) - Mg / 1.73 < 0.03.

[0006] When various alloying elements are added to aluminum alloys, significant differences in microstructure appear in pure aluminum. When an alloying element with high solid solubility is added, no precipitates form. However, as the content of an alloying element increases further, exceeding its maximum solid solubility in aluminum, precipitates will appear. Because different alloying elements have varying solid solubility in aluminum, the effect of adding alloying elements on the alloy's electrical conductivity can be categorized into the following situations: 1. Alloying elements exist as solid solution atoms in aluminum, forming a solid solution, which causes lattice distortion in the aluminum matrix. During electron movement, they form scattering sources, hindering the normal movement of electrons, shortening the mean free path of electrons, and thus reducing the conductivity of the alloy.

[0007] 2. Alloying elements react with other alloying elements in aluminum to form precipitates. Coherent and semi-coherent precipitates are small in size and dispersed, which hinders the movement of electrons and reduces the conductivity of the alloy.

[0008] As the content of alloying elements increases, the overall electrical conductivity of the alloy tends to decrease, but the degree of decrease in electrical conductivity varies depending on the alloying element.

[0009] In summary, for Al-Mg-Si alloys requiring high electrical conductivity, besides controlling the raw materials and casting process, alloy composition design is the most crucial factor. Higher conductivity generally requires fewer dissolved solid atoms in the alloy, resulting in higher conductivity. For example, in Al-Mg-Si alloys, excess silicon dissolved in the aluminum matrix increases electron scattering and reduces the alloy's conductivity. The presence of excess Mg not only significantly reduces the solubility of Mg₂Si in aluminum, causing the strengthening phase to precipitate from the aluminum matrix, but also increases its own solid solubility in the aluminum matrix, leading to a significant decrease in the alloy's electrical conductivity.

[0010] The creep property of aluminum alloys is characterized by their ability to undergo plastic deformation under constant pressure below their yield strength. The main mechanisms are as follows: 1. Dislocation slip and climb mechanism: When a material undergoes creep deformation, the reinforcing phase in the matrix pins dislocations, thereby restricting their slip. Therefore, composite materials have a relatively higher dislocation density, which in turn increases the internal stress of the material, promoting the movement of high-density dislocations by climbing around obstacles.

[0011] 2. Grain boundary sliding mechanism: The interfacial bonding strength of polycrystalline metal materials is significantly lower at high temperatures than at room temperature. Under external stress, the grains in the material will deform along the stress direction, requiring grain boundary sliding to coordinate the deformation. This sliding mechanism mainly occurs under low-stress creep test conditions, because sufficiently high stress will excite more slip systems to coordinate material deformation.

[0012] 3. Atomic Diffusion Mechanism: When a material deforms primarily through atomic diffusion, two conditions generally need to be met: ① The externally applied stress is low enough that dislocation motion contributes little to creep deformation; ② The temperature is high enough that atoms have a high diffusion rate. Under tensile stress, the stress field within the material grains changes. Atoms and vacancies diffuse directionally from high-potential-energy locations to low-potential-energy locations. Vacancies diffuse directionally from grain boundaries perpendicular to the stress to grain boundaries parallel to the stress, while atoms diffuse in the opposite direction. This causes the grains parallel to the stress to elongate, ultimately leading to diffusion-induced creep deformation of the material.

[0013] For aluminum alloys and their composites, dislocation creep is the dominant deformation mechanism under high-temperature service conditions. Compared to materials operating at room temperature, high temperatures more readily activate dislocation slip within the matrix. During creep deformation, the reinforcing phase within the matrix pins dislocations, thus limiting their slip. However, the diffusion rates of vacancies and solute atoms such as Si and Mg in aluminum alloys are relatively fast. As service progresses, the precipitated second phase within the matrix significantly coarsens, severely diminishing its precipitation strengthening effect and ultimately leading to rapid failure through thermal fatigue or creep damage. Therefore, effectively controlling the thermal stability of the precipitated phase, thereby improving the high-temperature mechanical properties of the material, and obtaining a stable precipitated phase are beneficial for enhancing the creep resistance of the alloy.

[0014] The most important factors affecting the overall electrical conductivity and creep performance are the solid solution atoms, the size, type and quantity of precipitates in aluminum alloys. Reasonably controlling the proportion of alloying elements in Al-Mg-Si alloys can ensure that the matrix has stable precipitates and fewer solid solution atoms after aging.

[0015] The control principle for Mg, Mn, Cr, Fe, and Si is as follows: In Al-Mg-Si alloys, the main precipitates are Mg₂Si precipitates formed by the combination of Mg and Si. The formation of these precipitates mainly falls into three categories: β'', β', and β phases, corresponding to completely coherent, semi-coherent, and incoherent lattice types respectively. These precipitates all contribute to improving alloy properties, with their contribution to mechanical properties gradually decreasing while their high-temperature stability increases. Furthermore, Mn, Fe, and Cr in the alloy can combine with Si to form AlFeSi, AlMnSi, Al(FeMn)Si, and Al(FeCr)Si phases. The formation of these phases consumes some of the Si content. These phases are all high-temperature stable and beneficial to the alloy's creep resistance. Therefore, to obtain high creep resistance and high electrical conductivity, it is necessary to obtain more β phases and stable AlFeSi, AlMnSi, Al(FeMn)Si, and Al(FeCr)Si phases. Considering the atomic content of these phases and the difficulty of controlling them in actual production, the composition design is based on Si excess. Since the atomic radius of Si is smaller than that of Mg, the decrease in conductivity caused by Si excess is relatively small, which is beneficial to improving the conductivity of the product. Taking into account that the consumption of Si atoms mainly comes from the combination with Mg atoms to form the Mg2Si phase and the formation of stable intermediate alloys with Fe, Mn, and Cr elements, when all the above alloying elements have completed their combination and reaction, the content of Si in the solid solution remaining in aluminum reaches its minimum. This can not only ensure the mechanical properties of the wire and reduce defects in the metal lattice, thereby improving conductivity, but also generate stable precipitates. During creep, the precipitates will hinder dislocation slip and climb, resulting in good creep performance.

[0016] The process also includes the following steps: (1) Composition design and feeding: The feeding is carried out in batches. First, Si and aluminum ingots are fed, then Mn, Cr and Cu are added to the melted alloy, and finally Fe, Mg and Zn alloy is added in the settling furnace. (2) Addition of aluminum-titanium-boron wire: Aluminum-titanium-boron wire is added to the flow channel using a double wire feeder, and the feeding speed is controlled at 800-900 mm / min; (3) Degassing and slag removal: The ratio of chlorine and argon mixed gas is 5%~40%, the gas flow rate is 5~15m³ / h, and the four-stage degassing is: the first stage of degassing and slag removal is carried out in the static furnace, the second stage is carried out online in the flow channel using chlorine and argon gas for degassing and slag removal, the third stage is carried out online in the flow channel using argon gas for degassing and slag removal, and the fourth stage is carried out before casting to filter the gas and slag. (4) Casting: Hot-top semi-continuous casting is adopted; (5) Heat equalization: Heat equalize at 560±5℃ / 8h; after heat equalization, cool to 250℃ at 100℃-150℃ / h, and then cool to room temperature at 300-500℃ / h. (6) Sawing the car body: After homogenization, cut off the head and tail of the ingot with a thickness of more than 200 mm, and machine off the segregation layer of more than 10 mm. (7) Extrusion: Die temperature control: 450-480℃, ingot preheating temperature: 510-530℃, ingot gradient heating, extrusion cylinder temperature control: 430-450℃, extrusion speed control: <6m / min, extruded bar temperature at the front beam exit is controlled at 520-560℃, and online quenching is performed; (8) Pre-stretching: Tension stretching machine stretching rate 0.3%-0.5%; (9) After stretching, the bar is aged to finally obtain qualified aluminum alloy extruded bar samples.

[0017] In step (4), the casting temperature is 710-720℃ and the water flow rate is 4600-5000L / min.

[0018] In step (7), the temperature of the extruded profile at the outlet is >520℃ and the extrusion speed is <6m / min.

[0019] The aging process in step (9) is 260±5℃ / 11h.

[0020] The aging process in step (9) is 230±5℃ / 20h.

[0021] The aging process in step (9) is 240±5℃ / 12h-14h.

[0022] Since various aging regimes can achieve relatively acceptable material properties, in actual production, producers can choose different aging regimes based on cost or ultimate performance considerations. When it is necessary to improve the production efficiency of materials, a higher temperature and shorter time aging process is selected; when it is necessary to obtain materials with ultimate performance, a relatively lower temperature and longer time aging process is selected.

[0023] The produced aluminum alloy wire exhibits a creep deformation of <0.2 after a temperature of 200℃, a stress of 45 MPa, and a creep time of 24 h.

[0024] The produced aluminum alloy wire has an electrical conductivity >59% IACS.

[0025] The produced aluminum alloy wire has a yield strength ≥90 MPa and a tensile strength ≥120 MPa.

[0026] Advantages of this invention: 1. The aluminum alloy wire in this invention uses conventional 6-series alloy elements. By strictly controlling the content of key elements Mg, Mn, Cr, Fe, and Si, it achieves high creep resistance, high conductivity, and high mechanical properties. No rare earth elements need to be added during the entire manufacturing process, which significantly reduces manufacturing costs. The manufacturing process is easy to control, and the produced wire has considerable mechanical properties. The wire maintains its function as a conductive wire even when subjected to high temperatures and harsh environments.

[0027] 2. This invention offers a variety of aging processes to choose from, allowing for the selection of appropriate aging processes based on the actual application requirements of the wire, thus balancing the production efficiency and material performance of aluminum alloy wire. Attached Figure Description

[0029] Figure 1 This is a creep test curve diagram for Example 1; Figure 2 This is a creep test curve diagram for Example 2; Figure 3 This is a creep test curve diagram for Example 3; Figure 4 This is a creep test curve diagram for Example 4; Figure 5 Photos of the creep test site; Figure 6 These are photos of the specimens used in the creep test. Detailed Implementation

[0030] Comparative Examples 1-3; Examples 1-4 A method for producing high-creep, high-conductivity aluminum alloy wire with a diameter of 12.4 mm includes the following steps: (1) Composition design and feeding: The feeding is carried out in batches. First, Si and aluminum ingots are fed, then Mn, Cr and Cu are added to the melted alloy, and finally Fe, Mg and Zn alloy is added in the settling furnace. (2) Addition of aluminum-titanium-boron wire: Aluminum-titanium-boron wire is added to the flow channel using a double wire feeder, and the feeding speed is controlled at 800-900 mm / min; (3) Degassing and slag removal: The ratio of chlorine and argon mixed gas is 5%~40%, the gas flow rate is 5~15m³ / h, and the four-stage degassing is: the first stage of degassing and slag removal is carried out in the static furnace, the second stage is carried out online in the flow channel using chlorine and argon gas for degassing and slag removal, the third stage is carried out online in the flow channel using argon gas for degassing and slag removal, and the fourth stage is carried out before casting to filter the gas and slag. (4) Casting: Hot-top semi-continuous casting is adopted, with a casting temperature of 710-720℃ and a water flow rate of 4600-5000L / min; (5) Heat equalization: Heat equalize at 560±5℃ / 8h; after heat equalization, cool to 250℃ at 100℃-150℃ / h, and then cool to room temperature at 300-500℃ / h. (6) Sawing the car body: After homogenization, cut off the head and tail of the ingot with a thickness of more than 200 mm, and machine off the segregation layer of more than 10 mm. (7) Extrusion: Die temperature control: 450-480℃, ingot preheating temperature: 510-530℃, ingot gradient heating, extrusion cylinder temperature control: 430-450℃, extrusion speed control: <6m / min, extruded bar temperature at the front beam outlet is controlled at 520-560℃, and online quenching is performed; the online quenching controls the outlet temperature to be >520℃; the discharge speed to be <6m / min; (8) Pre-stretching: Tension stretching machine stretching rate 0.3%-0.5%; (9) After stretching, the bar is aged to finally obtain qualified aluminum alloy extruded bar samples.

[0031] The comparative and example samples were produced using different alloy compositions and aging processes; their mechanical properties, electrical conductivity, and high-temperature creep properties were tested. Alloy composition list:

[0032] List of calculation results for the mathematical relationship between the weight percentage of alloy components:

[0033] List of time limits:

[0034] Conductivity testing was conducted in accordance with GB / T 12966-2022 standard.

[0035] The high-temperature creep performance test was conducted in accordance with the GB / T 2039-2012 standard. The conditions were: creep temperature 200℃, creep stress 45MPa, continuous creep time 24h, and creep variation less than 0.5 was considered qualified.

[0036]

[0037] In summary, comparing Comparative Examples 1-3 with Example 1, it can be seen that the alloy composition conforming to the weight ratio of 0 < Si - 0.3 (Mn + Cr + Fe) - Mg / 1.73 < 0.03 has higher mechanical properties, electrical conductivity, and high-temperature creep performance.

[0038] The comparison of Examples 1-4 shows that the aging regime of 230±5℃ / 20h can maximize the improvement of the mechanical properties, electrical conductivity and high-temperature creep properties of the material; the aging regime of 260±5℃ / 11h can achieve the material meeting the basic performance requirements while minimizing the production time and maximizing production efficiency.

Claims

1. A method for producing a high-creep high-conductivity aluminum alloy wire, characterized by, The alloy component design is as follows: alloy element weight percentage Si: 0.32-0.4 %, Fe: 0.07-0.12, Mn: <0.01 %, Cu: <0.1 %, Mg: 0.4-0.55 %, Cr <0.01 %, Zn: <0.1 %, Ti: 0.01-0.02 %, and the balance is Al; The above alloy elements should satisfy the alloy weight percentage: 0 < Si-0.3 (Mn+Cr+Fe)-Mg / 1.73 < 0.

03.

2. The method of claim 1, wherein the high-creep, high-conductivity aluminum alloy wire is produced by the steps of: The process further comprises the following steps: ​ (1) component design and feeding: batch feeding is adopted, Si and aluminum ingot are first fed, then Mn, Cr and Cu are fed in the melted alloy, and finally Fe, Mg and Zn alloy are fed in the static furnace; (2) aluminum titanium boron wire adding: a double wire feeder is used to add aluminum titanium boron wire in the flow tank, and the feeding speed is controlled at 800-900 mm / min; (3) degassing and deslagging: the proportion of chlorine and argon mixed gas is 5%-40%, the gas flow is 5-15 m³ / h, four-stage degassing is adopted: the first stage is carried out in the static furnace, the second stage is carried out in the flow tank online, the third stage is carried out in the flow tank online, and the fourth stage is carried out before casting; (4) casting: hot top semi-continuous casting is adopted; (5) soaking: soaking at 560±5℃ / 8h, then cooling at 100-150℃ / h to 250℃, and then cooling at 300-500℃ / h to room temperature; (6) sawing and car bottoming: after soaking, the head and tail of the cast ingot with a length of more than 200 mm are cut off, and the skin segregation layer with a thickness of more than 10 mm is removed; (7) extrusion: mold temperature control: 450-480℃, cast ingot preheating temperature: 510-530℃, cast ingot gradient heating, extrusion cylinder temperature control: 430-450℃, extrusion speed control: <6 m / min, extruded rod temperature control at the front beam outlet: 520-560℃, online quenching is carried out; (8) pre-stretching: the stretching rate of the tension stretcher is 0.3%-0.5%; (9) the stretched rod is aged, and finally the qualified aluminum alloy extruded rod sample is obtained.

3. The method of claim 2, wherein the high-creep, high-conductivity aluminum alloy wire is produced by the steps of: The casting temperature in step (4) is 710-720℃, and the water flow is 4600-5000 L / min.

4. The method of claim 2, wherein the high-creep, high-conductivity aluminum alloy wire is produced by the steps of: In step (7), the extrusion outlet profile temperature is >520℃, and the material output speed is <6 m / min.

5. The method of claim 2, wherein the high-creep, high-conductivity aluminum alloy wire is produced by the steps of: In step (9), the aging process is 260±5℃ / 11h.

6. The method of claim 2, wherein the high-creep, high-conductivity aluminum alloy wire is produced by the steps of: In step (9), the aging process is 230±5℃ / 20h.

7. The method for producing high-creep, high-conductivity aluminum alloy wire according to claim 2, characterized in that, In step (9), the aging process is 240±5℃ / 12-14h.

8. The method for producing high-creep, high-conductivity aluminum alloy wire according to claim 1, characterized in that, The produced aluminum alloy wire has a creep deformation <0.2 after creep at a temperature of 200℃, a stress of 45 Mpa and a creep time of 24h.

9. The method for producing high-creep, high-conductivity aluminum alloy wire according to claim 1, characterized in that, The produced aluminum alloy wire has an electrical conductivity >59 %IACS.

10. The method for producing high-creep, high-conductivity aluminum alloy wire according to claim 1, characterized in that, The produced aluminum alloy wire has a yield strength ≥90 MPa and a tensile strength ≥120 MPa.

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