Casting process of casting rod for copper-magnesium alloy stranded wire, casting rod and stranded wire

Abstract

The invention relates to a casting process of a casting rod for a copper-magnesium alloy stranded wire, the casting rod and the stranded wire, and the casting process comprises the following steps: a, adding cathode copper into a power frequency induction furnace until the cathode copper is molten; b, sequentially adding a copper-magnesium alloy, metal silver and a copper-indium alloy, and melting into copper alloy liquid; c, a refining agent is added into the copper alloy liquid, and the surface of the copper liquid is covered with crystalline flake graphite; d, casting by adopting an up-drawing continuous casting method to obtain a casting rod for the copper-magnesium alloy stranded wire; the prepared casting rod for the copper-magnesium alloy stranded wire comprises the following components in percentage by mass: 0.11 to 0.17 percent of Mg, 0.05 to 0.20 percent of Ag, 0.08 to 0.30 percent of In, and the balance of copper except a small amount of impurities. According to the casting process of the casting rod for the copper-magnesium alloy stranded wire, the casting rod and the stranded wire, the casting process is stable, the prepared casting rod improves the fatigue resistance while ensuring the alloy strength and conductivity, and the stranded wire prepared from the casting rod is less affected by low temperature and reliable in performance.

Description

Technical Field

[0001] The invention relates to the technical field of alloy stranded wires, in particular to a casting process of a cast rod for copper-magnesium alloy stranded wires, a cast rod and a stranded wire. Background Art

[0002] The automotive wiring harness is the main network of the automotive circuit, which can be divided into two types: low-voltage wiring harness and high-voltage wiring harness. High-voltage wiring harness is mainly used in new energy vehicles. When in service, it is required to withstand high voltage, carry large current, and have good sealing, heat resistance and electromagnetic compatibility. In recent years, my country's new energy vehicle industry has flourished. In 2022, my country's production and sales of new energy vehicles will be about 7 million, driving the rapid growth of the market demand for automotive high-voltage wiring harnesses. As new energy vehicles continue to develop towards intelligence, networking, and electrification, the requirements for the service performance of high-voltage wiring harnesses are becoming more and more stringent.

[0003] In the prior art, automotive wiring harnesses have high requirements for conductivity and strength, and mainly use copper-magnesium binary alloy wires. However, cracks will appear on the surface of the copper-magnesium alloy wires during use and storage. This phenomenon will lead to an increase in the wire breakage rate during the stranding process. The presence of microcracks will also significantly reduce the low-temperature fatigue resistance of the stranded wire products and reduce reliability.

[0004] The existing copper-magnesium alloy wire has a certain resistance to high temperatures. However, when used in some cold areas or in winter, the bending fatigue performance of the copper-magnesium alloy stranded wire decreases significantly due to the decrease in temperature, and its reliability is further reduced.

[0005] Cast rod is the raw material for processing copper-magnesium alloy stranded wire, and plays a key role in the characteristics of copper-magnesium alloy stranded wire. Therefore, we improved and proposed a casting process, cast rod and stranded wire for cast rod for copper-magnesium alloy stranded wire. Summary of the invention

[0006] The purpose of the present invention is to provide a casting process, a cast rod and a stranded wire for a copper-magnesium alloy stranded wire. The casting process is stable, and the obtained cast rod improves the fatigue resistance while ensuring the alloy strength and conductivity. The stranded wire made of the cast rod is less affected by low temperature and has reliable performance.

[0007] The technical solution adopted by the present invention is: a casting process for a cast rod for a copper-magnesium alloy stranded wire, comprising the following steps: a. Add cathode copper into the industrial frequency induction furnace until it melts; b. Add copper-magnesium alloy, metallic silver and copper-indium alloy in sequence and melt them into copper alloy liquid; c. Adding a refining agent to the copper alloy liquid and covering the surface of the copper liquid with flake graphite; d. using an upward continuous casting method to cast the copper-magnesium alloy stranded wire cast rod; The obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg 0.11-0.17%, Ag 0.05-0.20%, In 0.08-0.30%, except for a small amount of impurities, the balance is copper.

[0008] As a preferred embodiment, the obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg 0.14%, Ag 0.10%, In 0.10%.

[0009] As a preferred solution, the mass percentage of magnesium in the copper-magnesium alloy is 10-25%, the total amount of impurities is less than 0.5%, and the balance is copper.

[0010] As a preferred embodiment, the casting temperature of the upward continuous casting method is 1240°C±10°C.

[0011] As a preferred solution, the copper-magnesium alloy is Cu-20Mg.

[0012] As a preferred solution, the mass percentage of indium in the copper-indium alloy is 8-15%, the total amount of impurities is less than 0.5%, and the balance is copper.

[0013] As a preferred solution, the copper-indium alloy is Cu-10In.

[0014] As a preferred embodiment, based on the total weight of the copper alloy liquid being 100%, the refining agent includes, by mass percentage, 0.05-0.18% cryolite, 0.05-0.10% potassium chloride, 0.30-0.50% borax, 0.10-0.20% fluorite and 0.01-0.05% lithium carbonate.

[0015] As a preferred embodiment, based on the total weight of the copper alloy liquid being 100%, the refining agent includes, by mass percentage, 0.16% cryolite, 0.08% potassium chloride, 0.40% borax, 0.15% fluorite and 0.03% lithium carbonate.

[0016] A cast rod for copper-magnesium alloy stranded wire comprises the following components by mass percentage: 0.11-0.17% Mg, 0.05-0.20% Ag, 0.08-0.30% In, and the balance is Cu except for a small amount of impurities.

[0017] The copper-magnesium alloy stranded wire is obtained by processing the cast rod for the copper-magnesium alloy stranded wire.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. In the composition of the cast rod for high-performance copper-magnesium alloy stranded wire of the present invention, silver element is added on the basis of binary copper-magnesium alloy. Silver has better electrical conductivity than copper. The silver element is solid-dissolved in the copper alloy, which can improve the strength of the alloy on the one hand; on the other hand, the addition of silver element can promote the formation of intracrystalline precipitation phase of copper-magnesium-silver, thereby increasing the fatigue performance of the alloy after being processed into a wire harness.

[0019] 2. In the composition of the high-performance copper-magnesium alloy stranded wire cast rod of the present invention, in addition to adding silver element, indium element is also added on the basis of the binary copper-magnesium alloy. When the indium content in copper exceeds 0.08wt%, Cu can be generated in the alloy phase after solidification. 11 The In9 phase is dispersed in the copper matrix. Its existence does not change with hot rolling or cold rolling. It not only improves the strength of the alloy, but also greatly improves the stability of the copper crystal structure, thereby improving the stability of the alloy processing wire harness performance and ensuring the bending fatigue performance of the wire harness product, especially the bending fatigue performance at low temperatures.

[0020] 3. The cracks on the surface of copper-magnesium binary alloy wire during storage may be caused by stress release during natural failure. The addition of indium, on the one hand, promotes the nucleation of recrystallization during processing and refines the alloy grains; on the other hand, the addition of indium forms Cu 11 The presence of In9 phase particles will reduce the interfacial energy of the grain boundaries, hinder the movement of the grain boundaries, reduce the probability of surface cracks caused by stress release during failure, reduce the wire breakage rate during twisting, and improve the fatigue performance of the product. DETAILED DESCRIPTION

[0021] The present invention is described in detail below by way of exemplary embodiments. However, it should be understood that, without further description, elements, structures and features in one embodiment may also be beneficially combined in other embodiments.

[0022] It should be noted that: unless otherwise defined, the technical terms or scientific terms used in this document shall have the usual meanings understood by people with ordinary skills in the field to which the invention belongs. The words "one", "an" or "the" and the like used in the patent application specification and claims of the present invention do not express quantity restrictions, but indicate the existence of at least one; the words "first", "second" and "third" used in this document shall not be regarded as restrictions on the order of components, but are only used to distinguish different components; words such as "include" or "comprise" and the like indicate that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalents, but do not exclude other elements or objects with the same function.

[0023] The present invention provides the following technical solution: a casting process for a cast rod for a copper-magnesium alloy stranded wire, comprising the following steps: a. Add cathode copper into the industrial frequency induction furnace until it melts; b. Add copper-magnesium alloy, metallic silver and copper-indium alloy in sequence and melt them into copper alloy liquid; c. Adding a refining agent to the copper alloy liquid and covering the surface of the copper liquid with flake graphite; d. Using the upward continuous casting method to cast copper-magnesium alloy stranded wire cast rods; The obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg 0.11-0.17%, Ag 0.05-0.20%, In 0.08-0.30%, except for a small amount of impurities, the balance is copper.

[0024] The fatigue of metal materials is closely related to the stability of their internal atomic structure. When the atomic structure can remain relatively stable and is not prone to structural changes when subjected to alternating stress, the fatigue life of the metal material will be improved accordingly. This stability stems from factors such as the interaction between atoms and the structural arrangement of the crystal. If there are structural defects or impurities between grains in the material, the structure of the entire crystal will change and affect the fatigue behavior of the entire material. Therefore, the fatigue performance of metal materials can be enhanced by improving the similarity and stability of the crystal structure and reducing structural defects and impurities. Adding an appropriate amount of silver can improve the hardness of copper alloys, thereby improving the wear resistance and fatigue resistance of copper alloys, which helps to avoid deformation and plastic deterioration of copper alloys. Silver can also effectively increase the fatigue limit of copper alloys, making them less prone to fatigue fracture during long-term use, thereby extending their service life. Indium can improve the ductility and conductivity of copper, thereby improving the quality of copper materials. This is because the difference in electronegativity between indium and copper elements, and the introduction of indium can change the crystal structure of copper, especially the precipitation of copper-indium phase, which can enhance the stability of the crystal structure of copper, thereby further improving the fatigue resistance of the material.

[0025] In the above embodiment, the copper content of the cathode copper is ≥99.99%.

[0026] In the above embodiment, the industrial frequency induction furnace used is an upward continuous casting furnace, which can be used to continuously produce copper rods of large lengths. The temperature during upward casting is 1240°C ± 10°C.

[0027] In the above embodiments, no specific requirements are made on the amount of flake graphite or the covering thickness in the casting process. Those skilled in the art can reasonably set the amount of flake graphite or the covering thickness according to the needs of on-site operations, as long as the purpose of the present invention can be achieved.

[0028] In certain embodiments of the present invention, the produced copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg 0.14%, Ag 0.10%, In 0.10%.

[0029] In certain embodiments of the present invention, the mass percentage of magnesium in the copper-magnesium alloy is 10-25%, the total amount of impurities is less than 0.5%, and the balance is copper.

[0030] In certain embodiments of the present invention, the casting temperature of the upward continuous casting method is 1240°C±10°C.

[0031] In certain embodiments of the present invention, the copper-magnesium alloy is Cu-20Mg.

[0032] In certain embodiments of the present invention, the mass percentage of indium in the copper-indium alloy is 8-15%, the total amount of impurities is less than 0.5%, and the balance is copper.

[0033] In certain embodiments of the present invention, the copper-indium alloy is Cu-10In.

[0034] In the present invention, based on the total weight of the copper alloy liquid as 100%, the refining agent includes, by mass percentage, 0.05-0.18% cryolite, 0.05-0.10% potassium chloride, 0.30-0.50% borax, 0.10-0.20% fluorite and 0.01-0.05% lithium carbonate.

[0035] In certain embodiments of the present invention, based on the total weight of the copper alloy liquid being 100%, the refining agent includes, by mass percentage, 0.16% cryolite, 0.08% potassium chloride, 0.40% borax, 0.15% fluorite and 0.03% lithium carbonate.

[0036] A cast rod for copper-magnesium alloy stranded wire comprises the following components by mass percentage: 0.11-0.17% Mg, 0.05-0.20% Ag, 0.08-0.30% In, and the balance is Cu except for a small amount of impurities.

[0037] The copper-magnesium alloy stranded wire is obtained by processing the cast rod for the copper-magnesium alloy stranded wire.

[0038] The copper-magnesium alloy stranded wire cast rod prepared above is subjected to an extrusion process and then a cold rolling process to obtain a copper-magnesium alloy single wire billet, which is then drawn by a wire drawing machine to form a copper-magnesium alloy single wire of a specified size, and finally a plurality of copper-magnesium alloy single wires are twisted into a copper-magnesium alloy stranded wire, which is mainly used for high-voltage wire harnesses of new energy vehicles.

[0039] The strength and conductivity of the copper-magnesium alloy stranded wire are related to the diameter of the single wire. The smaller the diameter of the single wire, the stronger the work hardening effect and the lower the conductivity.

[0040] Embodiment 1: A casting process for a cast rod for a copper-magnesium alloy stranded wire comprises the following steps: a. Add cathode copper with copper content ≥ 99.99% into the industrial frequency induction furnace until it melts; b. Add copper-magnesium alloy, metallic silver and copper-indium alloy in sequence and melt them into copper alloy liquid; The copper-magnesium alloy is Cu-20Mg, and the impurity content is less than 0.5wt%; The copper-indium alloy is Cu-10In, and the impurity content is less than 0.5wt%; c. Adding a refining agent to the copper alloy liquid and covering the surface of the copper liquid with flake graphite; Wherein, based on the total weight of the copper alloy liquid being 100%, the refining agent includes 0.17% cryolite, 0.08% potassium chloride, 0.40% borax, 0.15% fluorite and 0.03% lithium carbonate; d. When the temperature is 1245°C, the copper-magnesium alloy stranded wire casting rod is obtained by using the upward continuous casting method; The obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg0.14%, Ag0.10%, In0.10%, except for a small amount of impurities, the balance is copper.

[0041] The outer diameter of the cast rod for copper-magnesium alloy stranded wire obtained in this example was 20 mm.

[0042] The copper-magnesium alloy stranded wire prepared in this embodiment is made into copper-magnesium alloy monofilaments of specified sizes using a casting rod, and finally a plurality of copper-magnesium alloy monofilaments are twisted into a copper-magnesium alloy stranded wire.

[0043] The main technical indicators of the series of copper-magnesium alloy wire monofilaments prepared in this embodiment are shown in Table 1, and the main technical indicators of the series of copper-magnesium alloy strands prepared in this embodiment are shown in Table 2.

[0044] Table 1 Main technical indicators of copper-magnesium alloy wire monofilament Serial number Diameter of single wire (mm) Single filament tensile strength (MPa) Single fiber conductivity (%IACS) Monofilament winding (times) 1 2.1 680 79.8 15 2 1.0 691 78.1 11 3 0.18 735 76.4 7 Table 2 Main technical indicators of copper-magnesium alloy wire strands Serial number Stranded wire outer diameter (mm) Single filament tensile strength (MPa) Stranded wire breaking force (kN) The number of times the harness is bent when the load is 19.6N at room temperature 1 10.5 660 44.59 51000 2 10.5 665 46.8 50600 3 12.5 668 59.9 49000 Embodiment 2: A casting process for a cast rod for a copper-magnesium alloy stranded wire comprises the following steps: a. Add cathode copper with copper content ≥ 99.99% into the industrial frequency induction furnace until it melts; b. Add copper-magnesium alloy, metallic silver and copper-indium alloy in sequence and melt them into copper alloy liquid; The copper-magnesium alloy is Cu-15Mg, and the impurity content is less than 0.5wt%; The copper-indium alloy is Cu-15In, and the impurity content is less than 0.5wt%; c. Adding a refining agent to the copper alloy liquid and covering the surface of the copper liquid with flake graphite; Wherein, based on the total weight of the copper alloy liquid being 100%, the refining agent comprises 0.15% cryolite, 0.09% potassium chloride, 0.40% borax, 0.20% fluorite and 0.05% lithium carbonate; d. When the temperature is 1240°C, the copper-magnesium alloy stranded wire casting rod is obtained by using the upward continuous casting method; The obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg0.20%, Ag0.15%, In0.20%, except for a small amount of impurities, the balance is copper.

[0045] The outer diameter of the cast rod for copper-magnesium alloy stranded wire obtained in this example was 20 mm.

[0046] The copper-magnesium alloy stranded wire prepared in this embodiment is made into copper-magnesium alloy monofilaments of specified sizes using a casting rod, and finally a plurality of copper-magnesium alloy monofilaments are twisted into a copper-magnesium alloy stranded wire.

[0047] The main technical indicators of the series of copper-magnesium alloy wire monofilaments prepared in this embodiment are shown in Table 3, and the main technical indicators of the series of copper-magnesium alloy strands prepared in this embodiment are shown in Table 4.

[0048] Table 3 Main technical indicators of copper-magnesium alloy wire monofilament Serial number Diameter of single wire (mm) Single filament tensile strength (MPa) Single fiber conductivity (%IACS) Monofilament winding (times) 1 2.1 670 78.6 11 2 1.0 682 77.1 9 3 0.18 725 76.8 6 Table 4 Main technical indicators of copper-magnesium alloy wire strands Serial number Stranded wire outer diameter (mm) Single filament tensile strength (MPa) Stranded wire breaking force (kN) The number of times the harness is bent when the load is 19.6N at room temperature 1 10.5 650 43.59 49800 2 10.5 655 45.8 49000 3 12.5 656 57.9 48000 Comparative Example 1: The main technical performance indicators of the single wires used in the series of copper-magnesium alloy stranded wires prepared by using conventional binary copper-magnesium alloy casting rods currently used in the field (casting at 1250°C, the magnesium content in the copper-magnesium alloy rod is 0.25wt%, the copper liquid covers the flake graphite, and the outer diameter of the casting rod is 30mm) are shown in Table 5.

[0049] Table 5 Main technical indicators of copper-magnesium alloy wire monofilament Serial number Diameter of single wire (mm) Single filament tensile strength (MPa) Single fiber conductivity (%IACS) Monofilament winding (times) 1 2.1 626 78.1 8 2 1.0 618 76.4 7 3 0.18 693 75.1 4 By comparing Table 1 and Table 5, it can be seen that the strength of the 2.1 mm single wire in the stranded wire made of the copper-magnesium alloy cast rod provided in Example 1 is increased by 8.6%, the conductivity is increased by 2%, and the bending resistance (comparison of the number of single wire windings) is increased by 87.5%; the strength of the 0.18 mm single wire is increased by 6.1%, the conductivity is increased by 1.7%, and the bending resistance is increased by 75%, ensuring that the product is safe and reliable in use.

[0050] From the comparison between Table 3 and Table 5, it can be seen that the strength of the 2.1 mm single wire in the stranded wire made of the copper-magnesium alloy cast rod provided in Example 2 is increased by 7%, the conductivity is increased by 0.6%, and the bending resistance (comparison of the number of windings of the single wire) is increased by 37.5%; the strength of the 0.18 mm single wire is increased by 4.6%, the conductivity is increased by 2.3%, and the bending resistance is increased by 50%, ensuring that the product is safe and reliable in use. Combined with the above comparison, it can be seen that the performance of the stranded wire proposed by the present invention is improved at room temperature.

[0051] The alloy stranded wire prepared in Comparative Example 1 and the alloy stranded wire prepared in Example 1 were placed in a low temperature environment for testing, and the main technical indicators are shown in Table 6.

[0052] Table 6 Low temperature bending properties of copper-magnesium alloy stranded wire Serial number Stranded wire outer diameter (mm) The number of times the harness is bent when the load is 19.6N at room temperature The number of times the harness is bent at -35℃ and load 19.6N Alloy stranded wire prepared in Comparative Example 1 10.5 43500 21000 Alloy stranded wire prepared in Example 1 10.5 51000 27200 It can be seen from Table 6 that when the alloy stranded wire prepared in Comparative Example 1 is transferred from room temperature to low temperature, the bending resistance of the stranded wire bundle is reduced by 51.72%; while when the alloy stranded wire prepared in Example 1 is transferred from room temperature to low temperature, the bending resistance of the stranded wire bundle is reduced by 46.66%. In comparison, the copper-magnesium alloy stranded wire processed by the present invention is less affected by low temperature and has good adaptability.

[0053] The parts not described in detail in the above embodiments are prior art.

[0054] It should be noted that although the present invention is described by the above embodiments, the present invention may also have other various embodiments. Without departing from the spirit and scope of the present invention, it is obvious that those skilled in the art may make various corresponding changes and deformations to the present invention, but these changes and deformations should all fall within the scope of protection of the appended claims of the present invention and their equivalents.

Claims

1. A casting process for a cast rod for copper-magnesium alloy stranded wire, characterized in that: The following steps are involved: a. Add cathode copper into the industrial frequency induction furnace until it melts; b. Add copper-magnesium alloy, metallic silver and copper-indium alloy in sequence and melt them into copper alloy liquid; c. Adding a refining agent to the copper alloy liquid and covering the surface of the copper liquid with flake graphite; d. using an upward continuous casting method to cast the copper-magnesium alloy stranded wire cast rod; The obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg 0.11-0.17%, Ag 0.05-0.20%, In 0.08-0.30%, except for a small amount of impurities, the balance is Cu.

2. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: The obtained copper-magnesium alloy stranded wire cast rod comprises the following components by mass percentage: Mg 0.14%, Ag 0.10%, In 0.10%.

3. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: The mass percentage of magnesium in the copper-magnesium alloy is 10-25%, the total amount of impurities is less than 0.5%, and the balance is copper.

4. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: The copper-magnesium alloy is Cu-20Mg.

5. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: The mass percentage of indium in the copper-indium alloy is 8-15%, the total amount of impurities is less than 0.5%, and the balance is copper.

6. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: The copper-indium alloy is Cu-10In.

7. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: The casting temperature of the upward continuous casting method is 1240℃±10℃.

8. The casting process of a cast rod for copper-magnesium alloy stranded wire according to claim 1, characterized in that: Based on the total weight of the copper alloy liquid being 100%, the refining agent comprises, by mass percentage, 0.05-0.18% cryolite, 0.05-0.10% potassium chloride, 0.30-0.50% borax, 0.10-0.20% fluorite and 0.01-0.05% lithium carbonate.

9. A cast rod for copper-magnesium alloy stranded wire, characterized in that: The following components are included by mass percentage: Mg 0.11-0.17%, Ag 0.05-0.20%, In 0.08-0.30%, and the balance is Cu except for a small amount of impurities.

10. The copper-magnesium alloy stranded wire is obtained by processing the cast rod for the copper-magnesium alloy stranded wire according to claim 9.