Vacuum melting furnace and method for continuously producing high-purity oxygen-free copper using the same

Abstract

The application discloses a vacuum smelting furnace, which comprises a feeding system, a vacuum system, a smelting system, a heating and stirring system, a cooling system and a traction system; the feeding system is arranged on the top of the vacuum system and inlaid with the vacuum system; the smelting system and the heating and stirring system are arranged in the vacuum system; the cooling system is arranged at the bottom of the smelting system; and the traction system is sequentially connected with the vacuum system, the cooling system and the smelting system. The vacuum smelting furnace is used for continuously preparing high-purity oxygen-free copper, and the process is as follows: raw material pretreatment, vacuum smelting and down-drawing continuous casting. The prepared copper rod has a purity of more than 99.995%, an oxygen content of less than 1 ppm, an electric conductivity of 102% IACS, a tensile strength of more than 210 MPa and an elongation of more than 40%, and thus the performance indexes of the copper rod are excellent and the copper rod can meet the popularization demand.

Description

Technical Field

[0001] This invention belongs to the field of new non-ferrous metal material preparation technology, specifically relating to a vacuum melting furnace and its application in the continuous preparation of high-purity oxygen-free copper. Background Technology

[0002] The oxygen impurity content in copper and copper alloys has a significant impact on the material's properties. Higher oxygen content leads to a greater accumulation of cuprous oxide at grain boundaries, causing greater damage to electrical and mechanical properties. Oxygen-free copper possesses high purity and excellent electrical and thermal conductivity, as well as good processing and welding properties, making it widely used in high-fidelity communication cables, vacuum electronic components, and integrated circuit bonding wires, playing a vital role in national economic development. With industrial development and technological advancements, the oxygen content requirements for oxygen-free copper are increasingly stringent both domestically and internationally, gradually increasing from 100 ppm to 30 ppm, 10 ppm, and even below 5 ppm. The main production processes for oxygen-free copper include continuous casting and rolling, and the upward drawing method. Oxygen-free copper produced by continuous casting and rolling has an oxygen content of around 200 ppm, while oxygen-free copper produced by the upward drawing method has an oxygen content of 10–100 ppm. Copper is prone to oxidation and gas absorption at high temperatures; therefore, addressing the oxygen content issue in oxygen-free copper is crucial for the manufacturing technology of high-purity oxygen-free copper.

[0003] Chinese patent document CN107052290B (Patent 1) discloses a production process for high-purity, high-conductivity oxygen-free copper rods. Using Grade A electrolytic copper (copper content ≥ 99.9935%, oxygen content ≤ 65 ppm) as raw material, the smelting apparatus includes a smelting furnace and a holding furnace. A partition is provided between the smelting furnace and the holding furnace, consisting of a first partition, a second partition, and a third partition arranged sequentially. Charcoal and graphite flakes are used to cover the surface of the molten copper to ensure an oxygen-free state during melting. Nitrogen gas is introduced into the molten copper through an online degassing device and dispersed into tiny bubbles, ensuring uniform dispersion throughout the copper, thus achieving degassing and deoxidation. The produced oxygen-free copper rod has a copper content greater than 99.99% and an oxygen content less than 3 ppm. While the oxygen-free copper produced in the aforementioned document has a lower oxygen content, the addition of a deoxidizing medium introduces new impurities, and the production equipment is more complex and the production process is longer.

[0004] Chinese patent document CN104550789B (Patent 2) discloses a method for preparing high-purity oxygen-free copper rods through continuous directional solidification. Using cathode copper (copper content ≥ 99.99%, oxygen content ≤ 100 ppm) as raw material, a vacuum directional solidification furnace and a continuous directional solidification device are employed to produce high-purity oxygen-free copper rods with an oxygen content of less than 4 ppm and exhibiting a single-crystal structure or a continuous columnar crystal structure along its length. The process described in the aforementioned document requires a vacuum degree of 0.01–1 Pa, places high demands on the production equipment, and can only be produced in a single furnace, resulting in low production efficiency.

[0005] Vacuum melting, performed in a closed system, can almost completely eliminate the influence of oxygen without introducing new impurities. Oxygen impurity content can be controlled below 5 ppm, which helps improve the purity of the molten copper, reduce internal impurities and defects in the copper material, and enhance its performance. Currently, the application of vacuum melting technology for copper and copper alloys is still immature, mainly due to problems such as high oxygen content in products, unstable quality, low production efficiency, and poor electrical and mechanical properties, which limit the industrial application of vacuum melting technology. Summary of the Invention

[0006] This invention addresses the challenges of oxidation and gas absorption at high temperatures during copper smelting, as well as the difficulty in removing oxygen impurities. It provides a vacuum smelting furnace and its application in the continuous production of high-purity oxygen-free copper. Without adding other deoxidizing and impurity-removing media, a closed vacuum smelting method is employed. By designing and controlling several subsystems—including the feeding system, vacuum system, smelting system, heating and stirring system, cooling system, and traction system—oxidation and gas absorption during copper melting are reduced, preventing the introduction of new impurities. Vacuum conditions are used to remove other impurity elements, improving the purity of the molten metal and thus enhancing the electrical and mechanical properties of the product. The use of a chambered vacuum smelting system and periodic continuous feeding enables continuous, large-scale production of oxygen-free copper smelting and drawing.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] A vacuum melting furnace includes a feeding system, a vacuum system, a melting system, a heating and stirring system, a cooling system, and a traction system; the feeding system is located on top of and embedded in the vacuum system; the melting system and the heating and stirring system are located inside the vacuum system; the cooling system is located at the bottom of the melting system; and the traction system is connected in sequence to the vacuum system, the cooling system, and the melting system.

[0009] Furthermore, the feeding system includes a feeding tank, a feeding valve, and a feeding tank vacuum valve. The feeding valve is located near the bottom of the feeding tank, and the feeding tank vacuum valve is located near the top.

[0010] Furthermore, the vacuum system includes a smelting furnace and a smelting furnace vacuum valve, the smelting furnace vacuum valve being located near the top of the smelting furnace.

[0011] Furthermore, the smelting system includes a smelting crucible and a float plate, the float plate being disposed inside the smelting crucible.

[0012] Furthermore, the heating and stirring system includes an induction coil, which is disposed around the periphery of the melting system.

[0013] Furthermore, the cooling system includes a cooling device and a graphite crystallizer, wherein the cooling device encloses the graphite crystallizer.

[0014] Furthermore, the traction system includes a traction device and a traction rod, wherein the traction rod is connected to the traction device.

[0015] This invention also provides a method for continuously preparing high-purity oxygen-free copper using a vacuum melting furnace, comprising the following steps:

[0016] (1) Raw material pretreatment: Cut the cathode copper wire blank into copper granules with a length of 1-3 cm, wash with distilled water, and dry in a heat-preserving furnace at 90-150℃ for 1-3 hours.

[0017] (2) Vacuum melting: Load the raw materials processed in step 1 into the vacuum melting furnace, close the furnace door, turn on the cooling circulating water, the cooling water flow rate is 1000~8000L / h, and the cooling water temperature is 10~40℃; turn on the vacuum pump switch to draw a vacuum, the vacuum degree is 1~100Pa; turn on the heating power of the melting furnace, control the melting temperature at 1100℃~1280℃, and keep it at that temperature for 0.5~4 hours; at the same time, turn on the external electromagnetic field system, the electromagnetic field current intensity is 20A~150A;

[0018] (3) Downward continuous casting: Turn on the servo traction system switch to draw the copper rod out of the graphite crystallizer. The traction speed is 20-150 mm / min, the cooling water temperature is 15-35℃, and the vacuum degree of the melting furnace is maintained at 1-100 Pa to obtain high-purity oxygen-free copper rod.

[0019] Furthermore, after step (3), raw materials are added from the feeding tank every 1 to 2 hours, with each addition being 1 / 20 to 1 / 10 of the furnace capacity. By continuing the vacuum melting and continuous casting process, continuous production of high-purity oxygen-free copper can be achieved.

[0020] Furthermore, the high-purity oxygen-free copper rod has a diameter of 6-12 mm and an oxygen content of less than 1 ppm.

[0021] Compared with the prior art, the present invention has the following technical advantages:

[0022] (1) The present invention uses cathode copper with a purity of 99.95% and an oxygen content of 300ppm as raw material. The entire smelting and drawing process is carried out in a near-vacuum environment, realizing oxygen-free copper vacuum smelting and large-scale continuous production. The absence of impurities and the introduction of oxygen improve the purity and stability of the material.

[0023] (2) The present invention has the advantages of low raw material requirements, low oxygen content in products, short process flow, high production efficiency, and continuous large-scale production.

[0024] (3) The oxygen-free copper produced by this invention has a purity of over 99.995%, an oxygen content of less than 1 ppm, a conductivity of 102% IACS, a tensile strength of over 210 MPa, and an elongation of over 40%. Compared with the prior art, this invention reduces the oxygen content by over 66.7%, increases the tensile strength by over 15.8%, achieves a copper content of over 4N5, and maintains comparable conductivity and elongation. It is evident that this invention represents a significant advancement in technology. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the vacuum melting furnace used in this invention.

[0026] In the diagram: 1. Feeding tank; 2. Feeding valve; 3. Copper granules; 4. Feeding tank vacuum valve; 5. Smelting furnace; 6. Smelting furnace vacuum valve; 7. Smelting crucible; 8. Float; 9. Induction coil; 10. Molten copper; 11. Cooling device; 12. Graphite crystallizer; 13. Traction device; 14. Traction rod. Detailed Implementation

[0027] The present invention will now be described with reference to the accompanying drawings, so that those skilled in the art can fully understand the present invention.

[0028] like Figure 1 A vacuum melting furnace includes a feeding system, a vacuum system, a melting system, a heating and stirring system, a cooling system, and a traction system. The feeding system is located on top of and embedded in the vacuum system. The melting system and the heating and stirring system are located inside the vacuum system. The cooling system is located at the bottom of the melting system. The traction system is connected to the vacuum system, the cooling system, and the melting system in sequence.

[0029] The feeding system includes a feeding tank 1, a feeding valve 2, and a feeding tank vacuum valve 4. The feeding valve 2 is located near the bottom of the feeding tank 1, and the feeding tank vacuum valve 4 is located near the top. The copper granules 3 are placed in the feeding tank 1. The vacuum system includes a smelting furnace 5 and a smelting furnace vacuum valve 6. The smelting furnace vacuum valve 6 is located near the top of the smelting furnace 5. The smelting system includes a smelting crucible 7 and a float plate 8. The float plate 8 is located inside the smelting crucible 7, and the molten copper 10 is melted in the smelting crucible 7. The heating and stirring system includes an induction coil 9, which is located around the periphery of the smelting system. The cooling system includes a cooling device 11 and a graphite crystallizer 12. The cooling device 11 surrounds the graphite crystallizer 12. The traction system includes a traction device 13 and a traction rod 14, which is connected to the traction device 13.

[0030] Vacuum melting furnaces are used for the continuous production of high-purity oxygen-free copper.

[0031] Example 1: Preparation of oxygen-free copper rods with a diameter of 6 mm

[0032] Cathode copper wire blanks with a purity of 99.95%, an oxygen content of 300 ppm, and a diameter of φ3 mm were cut into copper granules with a length of 1-3 cm. After washing with distilled water, they were dried in a 100℃ holding furnace for 1.5 hours. The treated raw materials were then loaded into a vacuum melting furnace, the furnace door was closed, and the cooling circulating water was turned on at a flow rate of 2000 L / h and a temperature of 25℃. The vacuum pump was turned on to create a vacuum of 15 Pa. The furnace heating power was turned on, and the melting temperature was controlled at 1150℃ for 1 hour. Simultaneously, the external electromagnetic field system was turned on with a current intensity of 90 A. The servo traction system was turned on to pull the copper rod out of the graphite crystallizer at a traction speed of 60 mm / min. The cooling water temperature was 20℃, and the furnace vacuum was maintained at 15 Pa. This yielded a high-purity oxygen-free copper rod with a diameter of 6 mm and an oxygen content of 0.67 ppm. Raw materials are added from the feeding tank every hour, with each addition being 10 kg. By continuing the vacuum melting and continuous casting processes, continuous production of oxygen-free copper rods can be achieved.

[0033] Example 2: Preparation of oxygen-free copper rods with a diameter of 8 mm

[0034] Cathode copper wire blanks with a purity of 99.95%, an oxygen content of 300 ppm, and a diameter of φ3 mm were cut into copper granules with a length of 1-3 cm. After washing with distilled water, they were dried in a 120℃ holding furnace for 1 hour. The treated raw materials were then loaded into a vacuum melting furnace, the furnace door was closed, and the cooling circulating water was turned on at a flow rate of 3000 L / h and a temperature of 26℃. The vacuum pump was turned on to create a vacuum of 10 Pa. The furnace heating power was turned on, and the melting temperature was controlled at 1150℃ for 2 hours. Simultaneously, the external electromagnetic field system was activated with a current intensity of 100 A. The servo traction system was then activated to pull the copper rod out of the graphite crystallizer at a traction speed of 80 mm / min. The cooling water temperature was maintained at 20℃, and the furnace vacuum was kept at 10 Pa. This yielded a high-purity oxygen-free copper rod with a diameter of 8 mm and an oxygen content of 0.48 ppm. Raw materials are added from the feeding tank every hour, with each addition being 12 kg. By continuing the vacuum melting and continuous casting processes, continuous production of oxygen-free copper rods can be achieved.

[0035] Example 3: Preparation of oxygen-free copper rods with a diameter of 12 mm

[0036] Cathode copper wire blanks with a purity of 99.95%, an oxygen content of 300 ppm, and a diameter of φ3 mm were cut into copper granules with a length of 1-3 cm. After washing with distilled water, they were dried in a 100℃ holding furnace for 2 hours. The treated raw materials were then loaded into a vacuum melting furnace, the furnace door was closed, and the cooling circulating water was turned on at a flow rate of 5000 L / h and a temperature of 25℃. The vacuum pump was turned on to create a vacuum of 20 Pa. The furnace heating power was turned on, and the melting temperature was controlled at 1170℃ for 2 hours. Simultaneously, the external electromagnetic field system was activated with a current intensity of 110 A. The servo traction system was then activated to pull the copper rod out of the graphite crystallizer at a traction speed of 100 mm / min. The cooling water temperature was maintained at 20℃, and the furnace vacuum was kept at 20 Pa. This yielded a high-purity oxygen-free copper rod with a diameter of 12 mm and an oxygen content of 0.74 ppm. Raw materials are added from the feeding tank every hour, with each addition being 15 kg. By continuing the vacuum melting and continuous casting processes, continuous production of oxygen-free copper rods can be achieved.

[0037] Example 4: Preparation of oxygen-free copper rods with a diameter of 8 mm

[0038] Cathode copper wire blanks with a purity of 99.95%, an oxygen content of 300 ppm, and a diameter of φ3 mm were cut into copper granules with a length of 1-3 cm. After washing with distilled water, they were dried in a 120℃ holding furnace for 1 hour. The treated raw materials were then loaded into a vacuum melting furnace, the furnace door was closed, and the cooling circulating water was turned on at a flow rate of 5000 L / h and a temperature of 25℃. The vacuum pump was turned on to create a vacuum of 15 Pa. The furnace heating power was turned on, and the melting temperature was controlled at 1170℃ and held for 1.5 hours. At the same time, the external electromagnetic field system was turned on with a current intensity of 120 A. The servo traction system was turned on to pull the copper rod out of the graphite crystallizer at a traction speed of 90 mm / min. The cooling water temperature was 20℃, and the vacuum of the melting furnace was maintained at 15 Pa. This yielded a high-purity oxygen-free copper rod with a diameter of 8 mm and an oxygen content of 0.55 ppm. Raw materials are added from the feeding tank every hour, with each addition being 12 kg. By continuing the vacuum melting and continuous casting processes, continuous production of oxygen-free copper rods can be achieved.

[0039] Comparative Example 1

[0040] High-purity oxygen-free copper rods were prepared using the process described in the example of the Chinese patent document "A Production Process for High-Purity, High-Conductivity Oxygen-Free Copper Rods (Authorization Announcement No.: CN107052290B)".

[0041] Comparative Example 2

[0042] High-purity oxygen-free copper rods were prepared using the process described in Example 1 of the Chinese patent document "A method for continuous directional solidification preparation of high-purity oxygen-free copper rods (authorization announcement number: CN104550789B)".

[0043] The copper rods obtained in Examples 1-4 and Comparative Examples 1-2 were tested for oxygen content, copper content, conductivity, tensile strength, and elongation. The testing methods are as follows:

[0044] (1) The oxygen content shall be determined according to the method specified in YS / T 922.

[0045] (2) The copper content is obtained by the difference method, and the difference elements include Ag, As, Bi, Cd, Fe, Mn, Ni, Pb, Sb, Se, Sn, Te, Zn, P, S, Cl, and O.

[0046] (3) The conductivity shall be determined according to the method specified in GB / T 3048.2.

[0047] (4) The tensile strength shall be determined according to the method specified in GB / T 4909.3.

[0048] (5) The elongation shall be determined according to the method specified in GB / T 4909.3.

[0049] The test results of oxygen content, copper content, conductivity, tensile strength and elongation of the copper rod are shown in Table 1.

[0050] Table 1. Comparison of various indicators of copper rods in Examples 1-4 and Comparative Examples 1-2.

[0051]

[0052] As shown in Table 1, the oxygen-free copper produced by this invention has a purity of over 99.995%, an oxygen content of less than 1 ppm, a conductivity of 102% IACS, a tensile strength greater than 210 MPa, and an elongation greater than 40%. Compared with the comparative example (existing technology), this invention reduces the oxygen content by more than 66.7%, increases the tensile strength by more than 15.8%, achieves a copper content of 4N5 or higher, and maintains comparable conductivity and elongation. This demonstrates that the technology of this invention represents a significant advancement, and the resulting copper rod possesses advantages such as high purity, high conductivity, and high stability.

Claims

1. A method for continuously preparing high-purity oxygen-free copper using a vacuum melting furnace, characterized in that, Includes the following steps: (1) Raw material pretreatment: Cut the cathode copper wire blank into copper granules with a length of 1-3 cm, wash with distilled water, and dry in a heat-preserving furnace at 90-150℃ for 1-3 hours; (2) Vacuum melting: Load the raw materials processed in step (1) into the vacuum melting furnace, close the furnace door, turn on the cooling circulating water, the cooling water volume is 1000~8000L / h, and the cooling water temperature is 10~40℃; turn on the vacuum pump switch to draw a vacuum, the vacuum degree is 1~100Pa; turn on the heating power supply of the melting furnace, control the melting temperature at 1100℃~1280℃, and keep it at the temperature for 0.5~4 hours; at the same time, turn on the external electromagnetic field system, the electromagnetic field current intensity is 20A~150A; (3) Downward continuous casting: Turn on the servo traction system switch to draw the copper rod out of the graphite crystallizer. The traction speed is 20-150 mm / min, the cooling water temperature is 15-35℃, and the vacuum degree of the melting furnace is maintained at 1-100 Pa to obtain high-purity oxygen-free copper rod. After step (3), add raw materials from the feeding tank every 1 to 2 hours. Each time, the amount added is 1 / 20 to 1 / 10 of the furnace capacity. Continue to maintain vacuum melting and continuous casting processes to achieve continuous production of high-purity oxygen-free copper. The vacuum melting furnace includes a feeding system, a vacuum system, a melting system, a heating and stirring system, a cooling system, and a traction system; the feeding system is located on top of and embedded in the vacuum system; the melting system and the heating and stirring system are located inside the vacuum system; the cooling system is located at the bottom of the melting system; and the traction system is connected in sequence to the vacuum system, the cooling system, and the melting system. The feeding system includes a feeding tank, a feeding valve, and a feeding tank vacuum valve. The feeding valve is located near the bottom of the feeding tank, and the feeding tank vacuum valve is located near the top. The vacuum system includes a smelting furnace and a smelting furnace vacuum valve, wherein the smelting furnace vacuum valve is located near the top of the smelting furnace; The smelting system includes a smelting crucible and a float plate, wherein the float plate is disposed inside the smelting crucible. The heating and stirring system includes an induction coil, which is disposed around the periphery of the melting system. The cooling system includes a cooling device and a graphite crystallizer, wherein the cooling device encloses the graphite crystallizer; The traction system includes a traction device and a traction rod, with the traction rod connected to the traction device.

2. The method for continuously preparing high-purity oxygen-free copper using the vacuum melting furnace according to claim 1, characterized in that, The high-purity oxygen-free copper rod has a diameter of 6-12 mm and an oxygen content of less than 1 ppm.

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