Vacuum resistance furnace and melting method for ultra-high purity copper casting

Abstract

The present disclosure relates to a vacuum resistance furnace and a melting method for ultra-high purity copper. The vacuum resistance furnace comprises a furnace body (1), a vacuum mechanism, a heating mechanism (2) arranged in the furnace body (1), and a directional solidification mechanism (3) arranged below the furnace body (1). The heating mechanism (2) melts and refines the copper material by constructing a full-graphite thermal field; the directional solidification mechanism (3) is used to establish an axial temperature gradient after the copper material is melted, so that the copper liquid forms axial directional solidification; and the vacuum mechanism is used to maintain a vacuum environment inside the furnace body (1). By constructing a full-graphite thermal field and cooperating with the directional solidification mechanism to establish an axial temperature gradient, the present application can reduce secondary impurity pollution in the melting process, control the directional solidification of the copper liquid, and improve the purity and crystallization of the ultra-high purity copper ingot.

Description

Technical Field

[0001] This application relates to the field of metallurgical equipment technology, and more specifically to a vacuum resistance furnace and casting method for ultra-high purity copper melting and casting. Background Technology

[0002] High-purity metals (such as ultra-high-purity copper with a purity of 5N and above) are key basic materials for high-end fields such as semiconductor sputtering targets, high-fidelity audio cables, and high-strength, high-conductivity copper alloys.

[0003] Currently, high-purity metal casting mainly uses medium-frequency induction vacuum furnaces, but the following prominent problems generally exist in actual production: 1. Refractory material contamination: The crucibles of traditional medium-frequency induction furnaces are usually made of silicon-containing refractory materials (such as quartz sand, alumina, etc.) knotted or lined. Under high vacuum and high temperature conditions above 1300℃, these oxide refractory materials will decompose or evaporate, releasing impurities such as oxygen, silicon, and aluminum, which directly contaminate the molten metal, becoming the main bottleneck limiting further improvement in metal purity; 2. Skin effect leading to impurity enrichment: Medium-frequency induction heating has an inherent skin effect, that is, the current is mainly concentrated on the surface of the conductor. This uneven heating method will cause impurities on the surface of the graphite mold or metal ingot to accumulate towards the core, forming a severe impurity segregation layer with a depth of 30-50mm. This results in a large amount of skin removal during subsequent processing of the ingot, significantly reducing material utilization and making it difficult to fundamentally guarantee the purity of the ingot core. 3. Poor temperature uniformity: The skin effect of induction heating also leads to uneven temperature field distribution of the molten metal in the crucible, which is not conducive to stable directional solidification control and affects the crystallization quality and compositional uniformity of the ingot. Summary of the Invention

[0004] This application provides a vacuum resistance furnace and casting method for ultra-high purity copper casting. By constructing a full graphite thermal field and establishing an axial temperature gradient in conjunction with a directional solidification mechanism, the method aims to reduce secondary impurity contamination during the casting process, control the directional solidification of copper liquid, and improve the purity and crystallization quality of ultra-high purity copper ingots.

[0005] In a first aspect, this application provides a vacuum resistance furnace for ultra-high purity copper melting and casting, comprising: a furnace body; a heating mechanism disposed within the furnace body for melting and refining copper material by constructing a full graphite thermal field; a directional solidification mechanism disposed below the furnace body for establishing an axial temperature gradient after the copper material is melted, so that the copper liquid forms axial directional solidification; and a vacuum mechanism for maintaining a vacuum environment inside the furnace body.

[0006] In one alternative embodiment of the first aspect, the heating mechanism includes: a high-purity graphite container for containing copper material; and a graphite resistance heating component surrounding the high-purity graphite container and heating the high-purity graphite container by thermal radiation, wherein the high-purity graphite container and the graphite resistance heating component constitute a full graphite thermal field.

[0007] In one alternative embodiment of the first aspect, the graphite resistance heating assembly includes a plurality of graphite resistance rods, which are uniformly arranged circumferentially along the high-purity graphite container.

[0008] In one alternative embodiment of the first aspect, the graphite resistance rod has an arc-shaped segmented structure, and multiple arc-shaped segmented graphite resistance rods are spliced ​​around the graphite container to form a ring heating structure, so that the crucible is heated evenly in the circumference.

[0009] In one alternative embodiment of the first aspect, the purity of both the graphite resistance rod and the high-purity graphite container is not less than 99.999%, and the ash content of both the graphite resistance rod and the high-purity graphite container is less than 5 ppm.

[0010] In one alternative embodiment of the first aspect, the directional solidification mechanism includes: a cooling chamber disposed below the furnace body; an isolation valve disposed between the furnace body and the cooling chamber, configured to open after the high-purity graphite container has completed melting and refining, and to close after directional solidification is completed, so as to achieve selective communication between the furnace body and the cooling chamber; and a pull-down assembly for driving the high-purity graphite container vertically through the isolation valve into the cooling chamber, so that the high-purity graphite container enters the cooling area formed inside the cooling chamber.

[0011] In one alternative embodiment of the first aspect, a cooling ring is provided in the cooling chamber, the cooling ring is arranged circumferentially along the inner wall of the cooling chamber, the cooling ring is connected to an external cooling system, and the cooling ring is used to cool the high-purity graphite container entering the cooling chamber to form an axial temperature gradient.

[0012] In one alternative embodiment of the first aspect, the pull-down assembly includes: a tray for supporting the high-purity graphite container; a servo motor; and a ball screw transmission unit, one end of which is connected to the servo motor and the other end of which is connected to the tray, driving the tray to move vertically under the drive of the servo motor, thereby driving the high-purity graphite container to rise and fall within the furnace body and cooling chamber.

[0013] In one alternative of the first aspect, the tray is a water-cooled tray with a cooling channel inside, the cooling channel being connected to the external cooling system to cool the bottom of the high-purity graphite container.

[0014] Secondly, this application provides a casting method for preparing ultra-high purity copper ingots using a vacuum resistance furnace according to any one of the first aspects, comprising: loading copper material into a high-purity graphite container, sealing the furnace body, and using a vacuum mechanism to evacuate the furnace body to achieve a preset vacuum level; using a heating mechanism to heat the copper material until it is completely melted, and performing heat preservation refining treatment to remove gases and volatile impurities from the molten copper under a high vacuum environment; opening an isolation valve, using a pull-down assembly to drive the high-purity graphite container to move vertically at a preset speed, so that the high-purity graphite container gradually enters a cooling chamber, and forming a temperature gradient along the axial direction of the high-purity graphite container in the cooling chamber, causing the molten copper to solidify sequentially from bottom to top; after directional solidification is completed and sufficient cooling is achieved, removing the ingot from the cooling chamber, cutting off the top area of ​​the ingot, and obtaining a high-purity copper ingot.

[0015] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0016] The accompanying drawings, which are incorporated herein and form part of this specification, illustrate one or more embodiments of the present application and, together with the description, serve to explain the principles of the present application and to enable those skilled in the art to make and use the present application.

[0017] Figure 1 This is a schematic diagram of an exemplary vacuum resistance furnace for ultra-high purity copper melting and casting according to some embodiments of this application;

[0018] Figure 2 This is a schematic diagram of the structure of an exemplary furnace body according to some embodiments of this application;

[0019] Figure 3 This is a schematic diagram of an exemplary heating mechanism according to some embodiments of this application;

[0020] Figure 4 This is a schematic diagram of the structure of an exemplary graphite resistance heating assembly according to some embodiments of this application;

[0021] Figure 5 This is a schematic diagram of the structure of an exemplary graphite resistance rod according to some embodiments of this application;

[0022] Figure 6 This is a schematic diagram of an exemplary directional solidification mechanism according to some embodiments of this application;

[0023] Figure 7 This is a schematic diagram of the structure of an exemplary drop-down component according to some embodiments of this application;

[0024] Figure 8This is an exemplary diagram illustrating the use of a tray according to some embodiments of this application;

[0025] Figure 9 This is a schematic diagram of an exemplary cooling channel structure according to some embodiments of this application;

[0026] Figure 10 This is a schematic diagram of the structure of an exemplary tray according to some embodiments of this application;

[0027] Figure 11 This is a flowchart of an exemplary ultra-high purity copper melting and casting method according to some embodiments of this application. Detailed Implementation

[0028] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, the description of these embodiments is intended to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to provide a deeper understanding of embodiments of this application.

[0029] like Figure 1 As shown, this embodiment provides a vacuum resistance furnace for ultra-high purity copper melting and casting, including a furnace body 1, a heating mechanism 2 disposed in the furnace body 1, a directional solidification mechanism 3 disposed below the furnace body 1, and a vacuum mechanism.

[0030] The furnace body 1 serves as the main body of the vacuum resistance furnace for smelting. The furnace body 1 is used to form a sealed space required for copper smelting and refining. The heating mechanism 2 is located inside the furnace body 1, and the vacuum mechanism is connected to the furnace body 1 to maintain the vacuum environment inside the furnace body 1. The directional solidification mechanism 3 is located below the furnace body 1 and forms an independent cooling space with the furnace body 1. It is used to establish an axial temperature gradient after the copper material has been smelted to achieve directional solidification of the copper liquid.

[0031] In this embodiment, as Figure 2 As shown, the furnace body 1 includes a furnace cover 11, which is located on top of the furnace body 1 and is detachably connected to the furnace body 1 to form a sealing structure on the top of the furnace body 1. Preferably, a vacuum sealing structure is provided between the furnace cover 11 and the furnace body 1 to ensure that a high vacuum environment can be maintained inside the furnace body 1.

[0032] A top loading and unloading device 12 is integrated on the furnace cover 11. This device 12 is used for loading, replenishing, or removing material from the high-purity graphite container 21. During the loading stage, copper material is added to the high-purity graphite container 21 via the top loading and unloading device 12. After loading is complete, the furnace cover 11 is closed and sealed, and then the vacuum mechanism is activated for vacuuming. The loading and unloading device 12 is located at the top of the furnace body 1, allowing for copper loading without disassembling the heating mechanism 2 and the directional solidification mechanism 3, making operation more convenient.

[0033] Preferably, the top loading and unloading device 12 may include a loading port, a sealing cover, and an opening and closing mechanism. The loading port is connected to the inside of the furnace body 1. The sealing cover is used to close the loading port after loading is completed. The opening and closing mechanism is used to drive the sealing cover to open or close, so that the loading and unloading device 12 can meet the copper material filling requirements and ensure the sealing performance of the inside of the furnace body 1 during vacuuming and smelting.

[0034] Heating mechanism 2 is installed inside furnace body 1. Heating mechanism is used to melt and refine copper material by constructing a full graphite thermal field. During operation, heating mechanism 2 heats copper material to a molten state and maintains the temperature for a preset time under high temperature conditions, so that the gas and volatile impurities in the copper liquid are fully removed, providing pure copper liquid for subsequent directional solidification.

[0035] The directional solidification mechanism 3 is located below the furnace body 1. After the copper material has been melted and refined, the directional solidification mechanism 3 establishes an axial temperature gradient in the molten copper, causing the molten copper to solidify gradually in a preset direction, forming an axially oriented solidification structure. Specifically, the directional solidification mechanism 3 is arranged vertically opposite to the furnace body 1. After the copper material has been melted and refined, it drives the container carrying the molten copper to move towards the directional solidification area, causing the molten copper to gradually enter the cooling zone, forming an axial temperature gradient, and achieving sequential solidification of the molten copper along a preset direction.

[0036] The vacuum mechanism is connected to the furnace body 1. During the smelting process, the vacuum mechanism continuously extracts gas from the furnace body 1, maintaining a high vacuum environment inside the furnace body 1. This reduces contamination of the molten copper by air and external impurities, and promotes the precipitation of gases and volatile impurities from the molten copper, thereby improving the purity of the molten copper. Preferably, the vacuum mechanism can maintain a stable vacuum environment inside the furnace body 1 throughout the entire smelting and refining process, ensuring the stable operation of the ultra-high purity copper casting process.

[0037] Preferably, the vacuum mechanism includes a vacuum pump group, a vacuum pipeline and a vacuum detection component. The vacuum pump group is connected to the furnace body 1 and is used to evacuate the inside of the furnace body 1. The vacuum detection component is used to detect the vacuum level inside the furnace body 1 in real time and control the vacuum pump group to continue to run or stop running according to the detection results, so as to maintain a stable vacuum environment inside the furnace body 1.

[0038] Furthermore, in this embodiment, the vacuum mechanism preferably achieves a vacuum level of 6 × 10⁻⁶ within the furnace body 1. -1 The vacuum level is maintained at Pa or higher during the copper melting, heat treatment refining, and directional solidification processes. A higher vacuum environment reduces contamination of the molten copper by oxygen, water vapor, and other gases, promotes the escape of hydrogen and other volatile impurities from the molten copper, improves the purity of the molten copper, and reduces metal oxidation and impurity introduction during the smelting process, providing a stable vacuum environment for obtaining ultra-high purity copper ingots.

[0039] In this embodiment, by setting up a heating mechanism 2, a directional solidification mechanism 3, and a vacuum mechanism, the copper material sequentially completes the melting, refining, and directional solidification processes. The heating mechanism 2 provides uniform and stable heat to ensure the copper material is fully melted and refined. The vacuum mechanism provides a stable high-vacuum environment for the entire casting process, reducing impurity contamination and promoting impurity removal. The directional solidification mechanism 3 establishes an axial temperature gradient, causing the molten copper to solidify sequentially in a preset direction, enriching impurities in the final solidification area, improving the purity of the effective ingot area, and enhancing the uniformity of the ingot's microstructure to obtain ultra-high purity copper ingots.

[0040] Based on the above embodiments, such as Figure 3 As shown in the figure, this embodiment will further explain the heating mechanism 2.

[0041] The heating mechanism includes a high-purity graphite container 21 and a graphite resistance heating element 22. The high-purity graphite container 21 is disposed inside the furnace body and is used to hold the copper material to be melted. The graphite resistance heating element 22 is disposed around the periphery of the high-purity graphite container 21 and maintains a preset distance from the high-purity graphite container 21 to form a melting zone for holding the high-purity graphite container 21. Preferably, the high-purity graphite container 21 can be a high-purity graphite crucible, located at the center of the melting zone, so that it can receive heat radiation from all circumferential directions, making the copper material inside more uniformly heated.

[0042] Furthermore, after the graphite resistance heating component 22 is powered on, it generates heat and continuously supplies heat to the high-purity graphite container 21 by means of heat radiation as the main method and heat conduction as the auxiliary method. After absorbing the heat, the high-purity graphite container 21 transfers the heat to the copper material inside, causing the copper material to gradually heat up until it is completely melted, and completes the heat preservation and refining at the preset temperature.

[0043] In this embodiment, both the high-purity graphite container 21 and the graphite resistance heating component 22 are made of high-purity graphite material, and together they form a full graphite thermal field surrounding the melting zone. The use of the same material for both the high-purity graphite container 21 and the graphite resistance heating component 22 in forming the thermal field avoids the contamination caused by the decomposition or volatilization of dissimilar refractory materials such as quartz and alumina under high temperature and high vacuum conditions in traditional vacuum induction furnaces. Furthermore, the graphite resistance heating component 22 uses resistance radiation heating, which, compared to induction heating, eliminates the problem of localized overheating caused by the skin effect, resulting in a more uniform heat distribution within the thermal field and improving the temperature uniformity of the molten copper inside the high-purity graphite container 21.

[0044] Furthermore, the full graphite thermal field can undertake the function of melting copper material and can also form a stable heat preservation zone after the copper material is completely melted. Within the heat preservation zone, the copper liquid in the high-purity graphite container 21 maintains a uniform and stable temperature distribution, and continuously undergoes degassing and removal of volatile impurities in a vacuum environment, so that the copper liquid has high purity and a consistent thermal state before entering the directional solidification process.

[0045] In a preferred embodiment, the graphite resistance heating component 22 continuously supplies heat to the high-purity graphite container 21, gradually raising the temperature of the melting zone within the furnace body 1 to approximately 1300°C, so that the copper material inside the high-purity graphite container 21 is completely melted. After the copper material is completely melted, the high-purity graphite container 21 continues to be placed in the heat preservation zone for heat preservation refining, preferably for about 2.5 hours. During this heat preservation stage, the all-graphite thermal field maintains a relatively stable thermal environment, making the internal temperature of the copper liquid tend to be uniform, and continuously removing gases and volatile impurities from the copper liquid under high vacuum conditions, thereby improving the purity of the copper liquid.

[0046] Based on the above embodiments, this embodiment further describes the specific structure of the graphite resistance heating component 22.

[0047] The graphite resistance heating assembly 22 includes a plurality of graphite resistance rods 221, such as Figure 4 As shown, multiple graphite resistance rods 221 are evenly arranged around the high-purity graphite container 21 and are electrically connected to the power supply system. When the power supply system supplies power to each graphite resistance rod 221, each graphite resistance rod 221 generates heat through resistance heating, and together they radiate heat to the high-purity graphite container 21 located at the center.

[0048] Furthermore, multiple graphite resistance rods 221 are arranged in a ring around the high-purity graphite container 21, maintaining a preset distance between adjacent graphite resistance rods 221, and together forming a radiant heating zone. The radiant heating zone surrounds the high-purity graphite container 21, and the thermal radiation generated by each graphite resistance rod 221 is superimposed within the radiant heating zone, enabling the high-purity graphite container 21 to simultaneously receive radiant heat flow from multiple directions, thereby reducing the local temperature difference caused by unilateral heating and improving the uniformity of heating at all circumferential positions of the high-purity graphite container 21.

[0049] Preferably, multiple graphite resistance rods 221 extend along the axial direction of the high-purity graphite container 21, and their effective heating length covers the melting area of ​​the high-purity graphite container 21, so that all positions of the high-purity graphite container 21 can receive relatively uniform heat radiation, improving the overall temperature uniformity during the copper melting process. Furthermore, the multiple graphite resistance rods 221 are evenly distributed circumferentially, forming an approximately axisymmetric heat radiation environment around the outer periphery of the high-purity graphite container 21, which helps to reduce temperature fluctuations caused by local differences in heat flux density, keeping the molten copper in a stable thermal state throughout the melting process.

[0050] Furthermore, the number of graphite resistance rods 221 can be configured according to the size of the high-purity graphite container 21, the amount of material loaded, and the target melting temperature. For example, in different embodiments, the number of graphite resistance rods 221 can be set to four, six, eight, or more, as long as they can form a uniformly distributed radiant heat source around the high-purity graphite container 21. This embodiment does not limit this.

[0051] During operation, each graphite resistance rod 221 is simultaneously energized and heats up, forming a continuous, stable and uniformly distributed thermal radiation field in the radiation heating zone. After absorbing thermal radiation from all directions, the high-purity graphite container 21 transfers the heat to the internal copper material, causing the copper material to heat up synchronously as a whole. When the copper material gradually reaches its melting point, the temperature difference between different locations inside is relatively small, reducing phenomena such as insufficient melting and temperature stratification caused by local overheating or underheating.

[0052] This embodiment improves the heating uniformity of the high-purity graphite container 21 by uniformly arranging multiple graphite resistance rods 221 around the circumference of the high-purity graphite container 21, making the heat distribution of the entire graphite thermal field more stable.

[0053] Based on the above embodiments, such as Figure 5 As shown in the figure, this embodiment further explains the specific structure of the graphite resistance rod 221.

[0054] In this embodiment, each graphite resistance rod 221 adopts an arc-shaped segmented structure, which is arranged sequentially along the circumference of the high-purity graphite container 21 and together splices around the high-purity graphite container 21 to form a ring heating structure. Compared with the overall ring heating body, multiple arc-shaped segmented graphite resistance rods 221 can not only form a continuous ring heating area, but also maintain the relative independence between each graphite resistance rod 221, so as to facilitate installation, replacement and maintenance.

[0055] Furthermore, the curvature of each graphite resistance rod 221 is adapted to the outer periphery of the high-purity graphite container 21, ensuring a basically consistent radial distance between each graphite resistance rod 221 and the high-purity graphite container 21. When the graphite resistance rods 221 are energized and generate heat, the heat radiated by each graphite resistance rod 221 to the high-purity graphite container 21 can form a continuously distributed annular radiative heat field around its periphery, making the radiative heat flow received by each position on the outer periphery of the high-purity graphite container 21 more balanced, reducing the difference in heat flux density caused by local spacing changes, and improving the uniformity of circumferential heating of the high-purity graphite container 21.

[0056] Furthermore, the annular heating structure formed by multiple arc-shaped segmented graphite resistance rods 221 is continuously distributed around the circumference of the high-purity graphite container 21, so that the direction of heat radiation gradually changes from the traditional unilateral radiation to the surrounding radiation. The radiative heat flow generated in each direction is superimposed on each other on the outer periphery of the high-purity graphite container 21 and tends to be uniform, so that the heat can be transferred to the copper material inside the high-purity graphite container 21 more evenly, reducing the temperature fluctuations caused by local high or low temperatures.

[0057] Furthermore, the graphite resistance rods 221 adopt a segmented structure, and each graphite resistance rod 221 can be combined and configured according to the size and melting capacity of the high-purity graphite container 21. When it is necessary to adapt to high-purity graphite containers 21 of different specifications, the number, arc length, or splicing angle of the graphite resistance rods 221 can be adjusted to make the formed annular heating structure match the high-purity graphite container 21 without replacing the entire heating component, thereby improving the adaptability of the vacuum resistance furnace to different melting specifications.

[0058] During operation, each arc-shaped segmented graphite resistance rod 221 heats up synchronously and continuously releases heat into the annular radiant thermal field. The resulting annular heating structure keeps the high-purity graphite container 21 in a closed thermal radiation environment. As the copper gradually melts, the high-purity graphite container 21 maintains a small temperature difference around its circumference, creating a more uniform and stable temperature field inside the molten copper. This provides stable thermal field conditions for subsequent heat preservation refining and the establishment of an axial temperature gradient, while also reducing the impact of local temperature differences on directional solidification.

[0059] Based on the above embodiments, this embodiment further explains the material composition of the graphite resistance rod 221 and the high-purity graphite container 21.

[0060] In this embodiment, both the graphite resistance rod 221 and the high-purity graphite container 21 are made of high-purity graphite material, with a purity of not less than 99.999% and an ash content of less than 5 ppm. The high-purity graphite container 21, as the container for the copper material, remains in constant contact with the molten copper during the melting and refining process. The graphite resistance rod 221, as the heating element, operates at a high temperature throughout the entire melting process. Therefore, both are crucial components affecting the purity of the molten copper.

[0061] Furthermore, both the high-purity graphite container 21 and the graphite resistance rod 221 are made of the same grade of high-purity graphite material, enabling them to jointly form a clean melting environment. Under high vacuum and high temperature conditions, high-purity graphite material has low volatility and good chemical stability, which can reduce secondary pollution caused by impurities precipitated from the material itself. Moreover, since both the graphite resistance rod 221 and the high-purity graphite container 21 are made of the same type of material, the coexistence of dissimilar refractory materials such as quartz and alumina with graphite material in traditional vacuum melting equipment is avoided, thereby improving the purity of the material composition in the melting area.

[0062] Preferably, the ash content is below 5 ppm, meaning the total content of inorganic impurities in the graphite material is controlled at a low level to reduce the possibility of trace impurities such as silicon, aluminum, iron, and calcium being released and entering the molten copper under high-temperature conditions. When the graphite resistance rod 221 is continuously radiantly heated and the high-purity graphite container 21 is in a high-temperature working state for a long time, the low ash content can effectively reduce the migration of impurities into the molten copper, maintain the high purity of the molten copper, and achieve the directional enrichment of impurities during the subsequent directional solidification process.

[0063] Furthermore, the purity of the graphite resistance rod 221 and the high-purity graphite container 21 is preferably kept consistent, so that the entire graphite thermal field has relatively consistent physical properties and thermal stability. When the heating mechanism operates continuously for a long time, the graphite components have similar thermal conductivity, thermal expansion characteristics and high temperature resistance, which helps to maintain the stability of the thermal field structure, reduce local stress concentration or structural deformation caused by the difference in thermal expansion of different materials, and ensure that the thermal field maintains a stable heating state during multiple melting processes.

[0064] Furthermore, the purity and ash content described in this embodiment are preferred embodiments. Under the premise of meeting the requirements of high-purity smelting, the purity and ash content of graphite materials can also be adjusted according to the purity grade of the target copper material, the smelting capacity and the process requirements. As long as the material itself can reduce the contamination of the copper liquid and maintain the stable operation of the whole graphite thermal field, it should fall within the protection scope of this invention.

[0065] Based on the above embodiments, this embodiment further explains the overall structure and working process of the directional solidification mechanism 3.

[0066] like Figure 6 As shown, the directional solidification mechanism 3 includes a cooling chamber 31, an isolation valve 32, and a pull-down assembly 33. The cooling chamber 31 is located below the furnace body 1 and is arranged vertically in relation to the furnace body 1, forming independent working spaces. The interior of the furnace body 1 primarily creates a thermal environment for copper melting and heat preservation refining, while the cooling chamber 31 creates a cold environment for copper solidification, allowing the melting and solidification processes to occur at different temperature environments.

[0067] An isolation valve 32 is positioned between the furnace body 1 and the cooling chamber 31, at the connection point between them. The isolation valve 32 forms an isolation zone between the hot and cold zones. During the copper melting and holding refining stages, the isolation valve 32 remains closed, isolating the furnace body 1 and the cooling chamber 31 from each other to reduce the influence of the cooling chamber 31 on the internal hot zone of the furnace body 1, ensuring a stable temperature distribution in the melting and holding zones. After the copper melt has been melted and refined, the isolation valve 32 opens, creating a connecting channel between the furnace body 1 and the cooling chamber 31, allowing the high-purity graphite container 21 to enter the cooling chamber 31. After directional solidification is complete, the isolation valve 32 closes again, restoring the cooling chamber 31 and the furnace body 1 to their independent state.

[0068] The pull-down assembly 33 is used to drive the high-purity graphite container 21 to move vertically. When the isolation valve 32 is opened, the pull-down assembly 33 drives the high-purity graphite container 21 to gradually pass through the isolation zone from inside the furnace body 1 and enter the cooling chamber 31, so that the high-purity graphite container 21 gradually enters the cold zone from the hot zone. During this process, the high-purity graphite container 21 gradually enters the cooling zone formed in the cooling chamber 31, and establishes an axial temperature gradient from bottom to top in the cooling zone, forming a directional solidification zone.

[0069] Furthermore, the smelting zone and the cooling zone are located within the furnace body 1 and the cooling chamber 31, respectively. The smelting zone and the cooling zone are selectively connected through an isolation valve 32. During the smelting process when the isolation valve 32 is closed, a stable thermal field can be maintained. During the directional solidification process when the isolation valve 32 is open, an independent cold field environment can be established, avoiding the continuous impact of the heating process on the solidification process. As the high-purity graphite container 21 moves towards the cooling zone, the copper liquid inside it begins to solidify from the bottom. The solidification interface gradually advances upward along the axial direction, causing the copper liquid to solidify sequentially in a preset direction, promoting the migration of impurities to the final solidification area.

[0070] In this embodiment, the directional solidification mechanism adopts a cooperative working mode in which the furnace body 1 and the cooling chamber 31 are independent of each other, the isolation valve 32 is selectively connected, and the pull-down component 33 drives the high-purity graphite container 21 to move. This realizes the separation and sequential switching of the hot field and the cold field, so that the copper material can continuously complete the melting, refining and directional solidification process in the same set of equipment. This reduces the interference of the hot field on the cold field and is conducive to establishing a stable axial temperature gradient, thereby improving the compositional uniformity and purity of the ultra-high purity copper ingot.

[0071] Based on the above embodiments, this embodiment further describes the cooling structure within the cooling chamber 31.

[0072] like Figure 6 As shown, a cooling ring 34 is provided inside the cooling chamber 31. The cooling ring 34 is arranged circumferentially along the inner wall of the cooling chamber 31 and is connected to the external cooling system 4. Preferably, the cooling ring 34 forms a continuous annular cooling structure around the cooling chamber 31, so that a low-temperature region is formed uniformly distributed circumferentially on the inner wall of the cooling chamber 31.

[0073] Furthermore, the external cooling system continuously supplies cooling medium to the cooling ring 34, maintaining the cooling ring 34 at a low temperature and continuously absorbing the heat released by the high-purity graphite container 21 entering the cooling chamber 31 through heat exchange. The cooling ring 34 is continuously arranged circumferentially along the inner wall of the cooling chamber 31, forming an annular cooling zone surrounding the high-purity graphite container 21 inside the cooling chamber 31. When the high-purity graphite container 21 enters the annular cooling zone, its outer periphery can simultaneously receive cooling from multiple directions, making the heat dissipation of the high-purity graphite container 21 more balanced in all circumferential directions, reducing local cooling rate differences, and improving the overall cooling effect of the high-purity graphite container 21.

[0074] Furthermore, as the pull-down assembly 33 drives the high-purity graphite container 21 into the cooling chamber 31, the lower part of the high-purity graphite container 21 first enters the annular cooling zone, while the upper part remains in the thermal environment formed by the furnace body 1. The high-purity graphite container 21 forms a temperature distribution that gradually transitions from a low-temperature zone to a high-temperature zone along the vertical direction, and gradually establishes an axial temperature gradient. Under the action of this axial temperature gradient, the molten copper inside the high-purity graphite container 21 first begins to solidify at the end closest to the cooling chamber 31. Subsequently, the solidification interface gradually advances along the axial direction, forming a continuously moving gradient solidification zone inside the molten copper, thus achieving sequential solidification of the molten copper along a predetermined direction.

[0075] Preferably, a preset distance is maintained between the cooling ring 34 and the high-purity graphite container 21 to prevent contact between the two, ensuring the safety and stability of the high-purity graphite container 21 during lifting and lowering. This preset distance also creates a uniform annular heat dissipation space, allowing heat from the outer periphery of the high-purity graphite container 21 to be stably transferred to the cooling ring 34, further determining the axial temperature gradient.

[0076] In this embodiment, by setting a cooling ring 34 circumferentially on the inner wall of the cooling chamber 31, the cooling effect is evenly distributed around the high-purity graphite container 21. Combined with the process of the high-purity graphite container 21 gradually entering the cooling chamber 31 in the vertical direction, the cooling field is gradually established from local to overall, so that the copper liquid forms a stable axial temperature gradient and maintains the continuous advancement of the solidification interface. This provides uniform and controllable cooling conditions for the migration of impurities to the final solidification area and the stable growth of columnar crystal structure.

[0077] Preferably, the external cooling system can be a circulating cooling water system. The external cooling system provides circulating cooling water to the cooling ring 34, and the inlet pressure of the circulating cooling water is preferably 0.15–0.30 MPa. When the cooling water pressure is below 0.15 MPa, the flow rate of the cooling medium within the cooling ring 34 is low, reducing the heat carried away per unit time, which can easily lead to insufficient cooling capacity and a slower establishment of the axial temperature gradient. When the cooling water pressure is above 0.30 MPa, although the cooling capacity is further enhanced, excessively high cooling intensity can easily cause excessively large temperature gradients in the high-purity graphite container 21, leading to decreased stability of the solidification interface and hindering the continuous growth of columnar crystals. Therefore, controlling the cooling water inlet pressure within the range of 0.15–0.30 MPa can ensure cooling capacity while maintaining a relatively stable temperature distribution in the cooling zone, which is beneficial for forming a stable axial temperature gradient.

[0078] Based on the above embodiments, this embodiment further describes the specific structure of the drop-down component 33.

[0079] like Figure 7 As shown, the pull-down assembly 33 includes a tray 331, a servo motor 332, and a ball screw drive unit 333. The tray 331 is positioned below the high-purity graphite container 21 to support it and transmit its weight to the ball screw drive unit 333. One end of the ball screw drive unit 333 is connected to the servo motor 332, and the other end is connected to the tray 331. Driven by the servo motor 332, the rotational motion is converted into linear motion of the tray 331 in the vertical direction, driving the high-purity graphite container 21 to move up and down between the furnace body 1 and the cooling chamber 31.

[0080] Furthermore, the tray 331 is adapted to the high-purity graphite container 21, ensuring that the high-purity graphite container 21 maintains a stable support state during lifting and lowering, reducing tilting, swaying, or offset caused by uneven support, and ensuring the high-purity graphite container 21 maintains a stable posture during movement. The ball screw transmission unit 333 can drive the tray 331 to perform linear motion, causing the high-purity graphite container 21 to reciprocate between the furnace body 1 and the cooling chamber 31 along a preset motion trajectory.

[0081] Preferably, the servo motor 332 works in conjunction with the ball screw transmission unit 333 to give the tray 331 high position control accuracy and speed control accuracy. By adjusting the output speed of the servo motor 332, the pull-down speed of the high-purity graphite container 21 can be precisely controlled, so that the high-purity graphite container 21 gradually enters the cooling chamber 31 at a preset speed, without significant changes in cooling conditions due to fluctuations in movement speed, which is beneficial to the stability of the axial temperature gradient.

[0082] Furthermore, the ball screw transmission unit 333 adopts a rolling transmission method, which, compared with the ordinary sliding transmission structure, has the characteristics of low frictional resistance, high transmission efficiency, and high repeatability. This reduces speed fluctuations during the pull-down process, ensuring that the high-purity graphite container 21 maintains a uniform and stable motion. The tray 331, the high-purity graphite container 21, and the ball screw transmission unit 333 form a stable force transmission path, enabling the high-purity graphite container 21 to maintain stable movement while carrying molten copper, avoiding fluctuations in the molten copper surface due to vibration or impact, which would affect the solidification effect.

[0083] During operation, after the copper material is smelted and refined, the isolation valve 32 is opened, and the servo motor 332 drives the ball screw transmission unit 333 to rotate. The ball screw transmission unit 333 drives the tray 331 to slowly descend in the vertical direction. The high-purity graphite container 21 descends synchronously with the tray 331 and gradually enters the cooling chamber 31 from the furnace body 1.

[0084] Preferably, the servo motor 332 can adjust the rotational speed of the ball screw transmission unit 333 according to a preset control program, making the lifting speed of the tray 331 continuously adjustable, with an adjustment range preferably of 2–200 mm / min. Specifically, when the copper melt enters the directional solidification stage after melting, the pulling speed of the high-purity graphite container 21 can be set according to the ingot specifications, melt height, and target solidification structure. When the pulling speed is low, the high-purity graphite container 21 enters the cooling zone more slowly, resulting in a gentler axial temperature gradient, which is beneficial for forming a continuous columnar crystal structure. When the pulling speed is appropriately increased, the overall solidification time can be shortened, improving production efficiency. Therefore, a suitable pulling speed can be selected within the range of 2–200 mm / min according to the process requirements of different ingot specifications, balancing solidification quality and production efficiency.

[0085] In a preferred embodiment, the pull-down speed can be controlled at 3 to 5 mm / min. At this speed, the copper liquid solidification interface can continue to move upward steadily, allowing impurities to migrate more fully to the final solidification area and further improving the purity of the effective area of ​​the ingot.

[0086] Based on the above embodiments, such as Figure 8As shown in the figure, this embodiment further explains the specific structure of the tray 331.

[0087] In this embodiment, as Figure 9 As shown, the tray 331 adopts a water-cooled tray structure, and a cooling channel 3311 is provided inside, which is connected to an external cooling system. The external cooling system delivers a cooling medium to the cooling channel 3311, and the cooling medium circulates within the cooling channel 3311, continuously removing the heat absorbed by the tray 331, thus keeping the tray 331 at a low temperature.

[0088] Furthermore, the water-cooled tray 331 is positioned at the bottom support of the high-purity graphite container 21. When the high-purity graphite container 21 is placed on the tray 331, the bottom of the high-purity graphite container 21 can form a heat conduction path with the tray 331. As the cooling medium continues to circulate, the heat at the bottom of the high-purity graphite container 21 can be preferentially transferred to the tray 331 and carried out through the cooling channel 3311.

[0089] Furthermore, the cooling ring 34 installed in the cooling chamber 31 mainly provides circumferential cooling to the outer periphery of the high-purity graphite container 21, while the water-cooled tray 331 mainly provides axial cooling to the bottom of the high-purity graphite container 21. The two work together to form a composite cooling method that combines peripheral cooling and bottom cooling. Among them, the cooling ring 34 is responsible for establishing a uniform cooling environment, while the water-cooled tray 331 further enhances the heat dissipation capacity of the bottom of the high-purity graphite container 21, enabling the bottom of the high-purity graphite container 21 to reach the solidification temperature earlier than the upper part.

[0090] During operation, as the pull-down assembly 33 drives the high-purity graphite container 21 into the cooling chamber 31, the outer periphery of the high-purity graphite container 21 is continuously cooled by the cooling ring 34, while its bottom is further cooled by the water-cooled tray 331. Under the combined effect of peripheral and bottom cooling, a more stable axial temperature gradient is formed inside the high-purity graphite container 21, causing the molten copper to solidify preferentially at the bottom, forming a stable solidification interface. As the high-purity graphite container 21 continues to move downwards, the solidification interface gradually advances upwards along the axial direction, achieving directional solidification of the molten copper from bottom to top.

[0091] Furthermore, the cooling channel 3311 is arranged inside the tray 331, so that the cooling medium can complete the heat exchange without directly contacting the high-purity graphite container 21, which can avoid the impact of cooling medium leakage on the melting environment.

[0092] In this embodiment, the water-cooled tray 331 and the cooling ring 34 together constitute a multi-directional synergistic cooling system. By implementing differentiated cooling on the bottom and periphery of the high-purity graphite container 21, a cold field can be established along the axial direction of the high-purity graphite container 21, which is conducive to the formation of a directional solidification interface and can promote the migration of impurities to the final solidification area, thereby improving the purity of the effective area of ​​the ingot.

[0093] This embodiment further explains the internal cooling structure of tray 331.

[0094] like Figure 10 As shown, tray 331 is mounted on base plate 334, and a partition 335 is provided between tray 331 and base plate 334. The partition 335, tray 331, and base plate 334 together form a cooling cavity, and cooling channels 3311 are provided in the cooling cavity. In other embodiments, cooling channels 3311 may also be directly embedded in tray 331.

[0095] Furthermore, tray 331 also includes an inner tube 336 and an outer tube 337, both of which are connected to an external cooling system. The inner tube 336 is used to introduce the cooling medium supplied by the external cooling system into the cooling channel 3311, while the outer tube 337 is used to discharge the cooled medium, after absorbing heat, back to the external cooling system, forming a continuous cooling loop. There can be multiple inner tubes 336 and outer tubes 337.

[0096] Preferably, the outlet of the inner tube 336 is located on one side of the cooling channel 3311, the inlet of the outer tube 337 is located on the other side of the cooling channel 3311, and the outer tube 337 is located outside the inner tube 336, so that the cooling medium can fill the cooling channel 3311 along the preset flow path and cover most of the heat exchange area of ​​the tray 331, so as to reduce local insufficient flow rate and improve the heat dissipation performance of the bottom surface of the tray 331.

[0097] Furthermore, the partition 335 confines the cooling channel 3311 between the tray 331 and the base plate 334, ensuring that the cooling medium always circulates within the closed cooling chamber. On one hand, the partition 335 prevents the cooling medium from directly contacting the high-purity graphite container 21, improving the sealing performance of the entire cooling system; on the other hand, the partition 335 enhances the structural strength between the base plate 334 and the water-cooled tray 331, preventing the tray 331 from deforming when bearing the weight of the high-purity graphite container 21 and the molten copper, thus ensuring the high-purity graphite container 21 remains stable during the pull-down process.

[0098] During operation, the external cooling system continuously supplies cooling medium to the inner tube 336. The cooling medium enters the cooling channel 3311 through the inner tube 336, flows along the bottom of the tray 331 in the cooling chamber, exchanges heat with the tray 331, and then flows back to the external cooling system through the outer tube 337, forming a continuous circulating cooling. The cooling channel 3311 is distributed inside the tray 331. The heat generated at the bottom of the high-purity graphite container 21 can be quickly transferred to the circulating cooling medium through the tray 331 and continuously carried out of the system, keeping the tray 331 at a low temperature. An enhanced cooling zone is formed at the bottom of the high-purity graphite container 21, which, together with the cooling ring 34, establishes an axial temperature gradient, promoting the directional solidification of copper liquid from bottom to top. Based on the above embodiment, this embodiment provides a method for preparing ultra-high purity copper ingots using the aforementioned vacuum resistance furnace. This method relies on the aforementioned vacuum resistance furnace to complete the melting, refining, and directional solidification of copper material. Each step is carried out continuously, and the entire casting process can be completed without transferring the workpiece.

[0099] Specifically, such as Figure 11 As shown, the method includes the following steps S101-S104:

[0100] S101: Charging and Vacuuming. Specifically, firstly, the pretreated copper material is loaded into the high-purity graphite container 21, and the high-purity graphite container 21 is placed within the melting zone formed by the furnace body 1. Then, the furnace body 1 is closed and sealed. The vacuum mechanism is activated to perform vacuuming on the furnace body 1, so that the vacuum level inside the furnace body 1 reaches and is maintained at 6 × 10⁻⁶. -1 Pa or higher, the subsequent melting, heat preservation refining and directional solidification processes are completed in this vacuum environment to reduce the contamination of copper liquid by external gases and promote the removal of gases and volatile impurities in the copper liquid.

[0101] S102: Melting and Holding Refining. Specifically, the graphite resistance heating assembly 22 is activated, and each graphite resistance rod 221 is simultaneously energized and heats up, forming a uniform and stable radiative heat field within the entire graphite thermal field. This allows the high-purity graphite container 21 to continuously absorb heat and transfer it to the internal copper material. In a preferred embodiment, the temperature of the melting zone within the furnace body 1 rises to approximately 1300°C, completely melting the copper material to form molten copper. Subsequently, holding refining continues while maintaining the aforementioned melting temperature, preferably for approximately 2.5 hours. Under a high vacuum environment, hydrogen and other volatile impurities in the molten copper continuously escape, while the internal temperature of the molten copper tends to be uniform, improving the purity of the molten copper and providing a consistent thermal state for subsequent directional solidification.

[0102] S103: Hot and cold zone switching and directional solidification. Specifically, after the heat preservation refining is completed, the isolation valve 32 is opened to connect the furnace body 1 with the cooling chamber 31. Subsequently, the pull-down assembly 33 drives the high-purity graphite container 21 to slowly enter the cooling chamber 31 vertically, gradually moving the high-purity graphite container 21 away from the full graphite hot zone and into the cold zone environment. During the movement, the cooling ring 34 continuously and uniformly cools the periphery of the high-purity graphite container 21, while the water-cooled tray 331 simultaneously intensifies the cooling of the bottom of the high-purity graphite container 21. Together, they establish a stable axial temperature gradient, causing the copper liquid to solidify preferentially from the bottom and forming a solidification interface that gradually advances upward along the axial direction, thus achieving directional solidification of the copper liquid.

[0103] Preferably, the pull-down component 33 can adjust the moving speed of the high-purity graphite container 21 according to the solidification state of the copper liquid, so that the solidification interface can be kept stable and the axial temperature gradient can be avoided due to the moving speed being too fast or too slow, thereby improving the uniformity of the columnar crystal structure.

[0104] During the directional solidification process, the pull-down assembly 33 preferably drives the high-purity graphite container 21 into the cooling chamber 31 at a speed of 3 to 5 mm / min. The external cooling system continuously supplies circulating cooling water with a pressure of 0.15 to 0.30 MPa to the cooling ring 34, so that a stable cooling condition is formed around the periphery and bottom of the high-purity graphite container 21, and a stable axial temperature gradient is established.

[0105] S104: Cooling and Ingot Removal. Specifically, after the high-purity graphite container 21 has fully entered the cooling chamber 31 and the copper liquid has completed directional solidification, cooling continues to maintain the ingot, allowing it to cool fully to the preset temperature. The cooling system is then shut off, the furnace pressure is restored, and the high-purity graphite container 21 is removed from the cooling chamber 31, demolding to obtain a high-purity copper ingot. Preferably, the last solidified area at the top of the ingot is removed to eliminate impurity-rich portions, resulting in an ultra-high-purity copper ingot with high purity and a uniform columnar crystal structure.

[0106] Furthermore, in this embodiment, the melting, refining, and directional solidification processes are all continuously completed within the same vacuum resistance furnace. The high-purity graphite container 21 does not need to be transferred between different devices, reducing the risk of contamination from the copper molten metal being exposed to the external environment. It also avoids heat loss and process interruptions caused by repeated handling, making the melting process more stable. Moreover, the synergistic effect of the full graphite hot field and the directional solidification cold field allows the copper molten metal to form a stable axial temperature gradient while maintaining high purity, promoting the migration of impurities to the final solidification region and obtaining ultra-high purity copper ingots with uniform structure and high purity.

[0107] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and this application is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

[0108] List of reference numerals in the attached diagram:

[0109] Furnace body 1

[0110] Furnace lid 11

[0111] Loading and unloading device 12

[0112] Heating mechanism 2

[0113] High-purity graphite containers 21

[0114] Graphite resistance heating component 22

[0115] Graphite resistance rod 221

[0116] Directional solidification mechanism 3

[0117] Cooling chamber 31

[0118] Isolation valve 32

[0119] Drop-down component 33

[0120] Tray 331

[0121] Cooling channel 3311

[0122] Servo motor 332

[0123] Ball screw drive unit 333

[0124] Cooling ring 34

[0125] External cooling system 4

Claims

1. A vacuum resistance furnace for melting and casting ultra-high purity copper, characterized in that, include: Furnace body; A heating mechanism, located inside the furnace, is used to melt and refine copper materials by constructing a full graphite thermal field; A directional solidification mechanism is located below the furnace body and is used to establish an axial temperature gradient after the copper material is melted, so that the copper liquid forms axial directional solidification. A vacuum mechanism is used to maintain a vacuum environment inside the furnace body.

2. The vacuum resistance furnace according to claim 1, characterized in that, The heating mechanism includes: High-purity graphite containers for holding copper materials; A graphite resistance heating element is arranged around the periphery of the high-purity graphite container and heats the high-purity graphite container through thermal radiation. The high-purity graphite container and the graphite resistance heating element constitute a full graphite thermal field.

3. The vacuum resistance furnace according to claim 2, characterized in that, The graphite resistance heating assembly includes multiple graphite resistance rods, which are uniformly arranged circumferentially along the high-purity graphite container.

4. The vacuum resistance furnace according to claim 3, characterized in that, The graphite resistance rod has an arc-shaped segmented structure. Multiple arc-shaped segmented graphite resistance rods are spliced ​​around the graphite container to form a ring heating structure, so that the crucible is heated evenly in the circumference.

5. The vacuum resistance furnace according to claim 3, characterized in that, The purity of both the graphite resistance rod and the high-purity graphite container is not less than 99.999%, and the ash content of both is less than 5 ppm.

6. The vacuum resistance furnace according to claim 1 or 2, characterized in that, The directional solidification mechanism includes: A cooling chamber is located below the furnace body; An isolation valve, located between the furnace body and the cooling chamber, is configured to open after the high-purity graphite container has completed melting and refining, and to close after directional solidification, so as to achieve selective communication between the furnace body and the cooling chamber. A pull-down assembly is used to drive the high-purity graphite container vertically through the isolation valve into the cooling chamber, so that the high-purity graphite container enters the cooling area formed inside the cooling chamber.

7. The vacuum resistance furnace according to claim 6, characterized in that, A cooling ring is provided in the cooling chamber, which is arranged circumferentially along the inner wall of the cooling chamber. The cooling ring is connected to the external cooling system and is used to cool the high-purity graphite container entering the cooling chamber to form an axial temperature gradient.

8. The vacuum resistance furnace according to claim 7, characterized in that, The dropdown component includes: A tray for supporting the high-purity graphite container; Servo motor; The ball screw drive unit has one end connected to the servo motor and the other end connected to the tray. Driven by the servo motor, it drives the tray to move vertically, thereby driving the high-purity graphite container to rise and fall in the furnace body and cooling chamber.

9. The vacuum resistance furnace according to claim 8, characterized in that, The tray is a water-cooled tray with a cooling channel inside, which is connected to the external cooling system to cool the bottom of the high-purity graphite container.

10. A casting method for preparing ultra-high purity copper ingots using a vacuum resistance furnace according to any one of claims 1-9, characterized in that, include: The copper material is placed into a high-purity graphite container, the furnace body is sealed, and a vacuum mechanism is used to evacuate the furnace body to achieve a preset vacuum level inside the furnace body. The copper material is heated to complete melting using a heating mechanism and then subjected to heat preservation and refining treatment to remove gases and volatile impurities from the molten copper in a high vacuum environment. Open the isolation valve and use the pull-down assembly to drive the high-purity graphite container to move vertically at a preset speed, so that the high-purity graphite container gradually enters the cooling chamber. A temperature gradient is formed in the cooling chamber along the axial direction of the high-purity graphite container, so that the copper liquid solidifies from the bottom to the top. After directional solidification is complete and the ingot has cooled sufficiently, the ingot is removed from the cooling chamber, and the top area of ​​the ingot is cut off to obtain a high-purity copper ingot.

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