Method for preparing 5n high purity copper by electron beam reduction induced directional solidification

Abstract

The application belongs to the technical field of non-ferrous metal purification, and particularly discloses a method for preparing 5N high-purity copper by electron beam reduction and induced directional solidification, which comprises the following steps: loading pretreated 4N cathode copper into an electron beam smelting furnace feeding mechanism and independently vacuumizing each part of the furnace body; starting a high-voltage power supply and an electron gun preheating, and heating and melting the 4N cathode copper by No.1 electron gun at 150-200 kW and 0.5-1 kV and then flowing into a crystallizer; when the copper liquid fills 2 / 3 of the crystallizer, starting No.2 and No.3 electron guns and keeping the copper liquid in the crystallizer molten at 50-100 kW and 20-40 kV; after the copper liquid fills the crystallizer, reducing the power of No.3 electron gun to 5 kW; when the melt in the crystallizer starts to crystallize, slowly pulling the ingot into a cooling area; after the cast ingot enters the cooling area completely, cutting off the impurity enrichment area of the cast ingot to obtain 5N high-purity copper. The application has the characteristics of simple process, short production cycle, small impurity enrichment area and low oxygen and hydrogen content.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal purification technology, specifically to a method for preparing 5N high-purity copper by electron beam down-induced directional solidification, which is simple in process, has a short production cycle, a small impurity enrichment area, and low oxygen and hydrogen content. Background Technology

[0002] High-purity copper, with its low resistivity and high electromagnetic properties, is widely used in industries such as integrated circuits and sputtering targets. In integrated circuits, high-purity copper is primarily used in the metallization processes of front-end wafer fabrication and back-end packaging. In back-end packaging, with the development of advanced integrated circuit packaging technologies, copper targets are widely used in thin film fabrication processes such as under-bump metal layers, redistribution layers, and through-silicon vias (TSVs) to achieve high-density, reliable interconnections between chips and substrates. Therefore, thin films require stringent purity control of high-purity copper targets. For example, gaseous impurities (C, O), alkali metal impurities (Ca), and transition metal impurities (Fe) are strictly controlled, especially since high hydrogen and oxygen content can severely affect product performance. As technology nodes shrink, the impact of target purity on the performance and quality of thin film materials becomes even more pronounced.

[0003] Traditional refining techniques for high-purity copper mainly include electrolytic refining, anion exchange, and zone refining. Electrolytic refining requires a cycle of 7-10 days to purify 5N-6N high-purity copper, and the quality is unstable. Anion exchange suffers from complex processes, environmental concerns, and inconsistent quality. While zone refining has been used to prepare high-purity materials, its efficiency is low and its energy consumption is high. Therefore, some scholars and research institutions have begun to investigate other methods for preparing high-purity copper. For example, the Mianyang National Laboratory for Surface Physical Chemistry uses vacuum vertical zone melting and refining to achieve a copper purity of 99.997%; Jinchuan Group uses 4N electrolytic copper as raw material to prepare copper nitrate solution with a pH of 2.0-3.5, obtaining 6N electrolytic copper plates. Then, electron beam melting is used to significantly reduce the oxygen content, producing 6N high-purity copper ingots. Finally, electron beam melting is used to successfully produce ultra-pure copper ingots with a purity of 99.9999% and a weight of 25 kg. This technology represents the highest level of high-purity copper production in China. There are reports of research on producing 8N high-purity copper (free of C, N, H, P, and S gaseous elements) using electrolysis, with a production cycle of 20 days. However, the high oxygen content in the high-purity copper still cannot be removed. Furthermore, although British and Japanese scholars G. M. Lalev et al. used hydrogen plasma arc to refine 4N and 6N copper raw materials through 10 zone melting processes and found that the contents of Si, Ti and Fe decreased significantly at x / L = 0.03. However, there are few reports to date on the preparation of high-purity copper ingots using direct directional solidification technology of electron beam melting.

[0004] In existing technologies, electron beam melting is an important method for removing impurities from high-purity metals. It involves melting the metal in a melting crucible, causing impurities with vapor pressures greater than the metal to evaporate and be removed. Then, guided by an electron beam, the molten metal solidifies directionally from bottom to top in a solidification crucible. Some metallic impurities are removed by segregation and enrichment in the upward liquid phase. However, electron beam melting requires controlling the vertical irradiation area and power of the electron beam to achieve static, bottom-to-top directional solidification of the metal. Furthermore, for some metallic and non-metallic impurities with segregation coefficients close to 1, multiple directional purification processes are necessary, significantly increasing production costs and creating considerable environmental pressure. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing 5N high-purity copper by electron beam down-induced directional solidification, which is simple in process, has a short production cycle, a small impurity enrichment area, and low oxygen and hydrogen content.

[0006] This invention is implemented as follows: it includes the steps of material preparation, preliminary melting, full-capacity melting, and directional solidification, specifically as follows:

[0007] A. Feeding preparation: The pretreated 4N cathode copper is loaded into the feeding mechanism of the electron beam melting furnace, and then each part of the furnace is evacuated independently.

[0008] B. Preliminary melting: Turn on the high voltage power supply of the electron beam melting furnace and preheat the electron gun. Then, maintain the melting power of the No. 1 electron gun at 150-200kW and the voltage at 0.5-1kV to heat and melt the 4N cathode copper. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0009] C. Full power melting: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3 and keep the melting power at 50-100kW and voltage at 20-40kV to keep the 4N cathode copper liquid in the crystallizer in a molten state.

[0010] D. Directional solidification: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW; when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone; after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0011] Furthermore, the electron beam melting furnace is a three-gun electron beam furnace, and the melting power of a single gun in the three-gun electron beam furnace is not less than 200kW.

[0012] Furthermore, the radiation range of the No. 1 electron gun in the electron beam melting furnace is the feed inlet of the melting chamber, the crystallizer is strip-shaped and horizontally arranged, the radiation range of the No. 2 electron gun is the front 1 / 2 crystallizer, the radiation range of the No. 3 electron gun is the rear 1 / 2 crystallizer, and the direction of pulling the ingot in the directional solidification step is the direction from the No. 2 electron gun to the control area of ​​the No. 3 electron gun in the crystallizer.

[0013] Furthermore, in the feeding preparation step, the electron gun vacuum degree of the electron beam melting furnace is 0.8–1.2 × 10⁻⁶. - 3 Pa and the vacuum degree of the melting chamber is 4~6×10 -2 Pa.

[0014] Furthermore, the melting temperature of the 4N cathode copper in the preliminary melting step and / or full-power melting step is controlled at 1200-1250°C.

[0015] Furthermore, during the directional solidification step, when the 4N cathode copper liquid fills the crystallizer, the melting power of the No. 3 electron gun decreases from 50-100kW to 5kW within 30-60 minutes.

[0016] Furthermore, in the directional solidification step, the puller is horizontally pulled at a speed of 2.0 to 2.3 mm / min.

[0017] Furthermore, the impurity enrichment region of the ingot in the directional solidification step is the final solidification region of electron beam down-beam solidification and the final solidification region of directional solidification.

[0018] Furthermore, in the directional solidification step, the melting power of the No. 3 electron gun is gradually reduced from 50-100kW to 5kW at a rate gradient of 5-20kW every 5-10 minutes.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention utilizes the segregation effect, employing a stable No. 2 electron gun in conjunction with a variable No. 3 electron gun and horizontal dynamic ingot pulling. This creates electron beam descent to induce directional solidification in the vertical direction of the ingot and directional solidification in the horizontal direction, thereby forming two impurity enrichment regions at the rear and top of the ingot in the pulling direction. This facilitates the accumulation of impurities such as Na, Mg, P, V, S, Zn, Ga, Ag, Se, Sn, W, Au, Bi, and U in the direction of easy accumulation during solidification. Finally, by removing the impurity enrichment regions of the ingot, impurities in high-purity copper are eliminated, achieving the goal of purifying low-purity 4N electrolytic cathode copper to 5N.

[0021] 2. Compared with instantaneous beam reduction, the electron beam reduction-induced directional solidification of this invention, by controlling the reduction power and the ingot pulling speed and time, not only achieves slow beam reduction to facilitate the enrichment of impurities, but also allows impurity elements with insufficient segregation coefficients sufficient time to gradually accumulate in the liquid pool, effectively improving the purity of the final high-purity copper ingot, such as oxygen content below 2 ppm and hydrogen content below 1 ppm; moreover, the segregation effect is enhanced with prolonged solidification time, which can significantly reduce the final impurity enrichment area of ​​the ingot to improve material utilization; and by controlling the reduction speed and ingot pulling time, compared with electrolytic refining and multiple directional solidification methods, the production cycle can be significantly shortened and the production cost reduced.

[0022] 3. This invention directly uses 4N electrolytic cathode copper to achieve dynamic electron beam down-induced directional solidification and directional solidification by combining electron beam down-induced solidification with ingot pulling control, thereby removing impurities and preparing 5N high-purity copper. The process is not only relatively simple, but also the final high-purity copper has a high purity.

[0023] In summary, the present invention features simple process, short production cycle, small impurity enrichment area, and low oxygen and hydrogen content. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the electron gun distribution area and ingot pulling direction in the electron beam melting furnace of the present invention;

[0025] Figure 2 This is a schematic diagram of the impurity enrichment region of the 5N high-purity copper ingot prepared according to the present invention;

[0026] In the diagram: 1-4N cathode copper, 2-crystallizer, 3-pulling direction, 4-electron gun radiation range of No. 1, 5-electron gun radiation range of No. 2, 6-electron gun radiation range of No. 3, 7-5N copper ingot, 8-directional solidification impurity enrichment region, 9-electron beam down-induced directional solidification impurity enrichment region. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] like Figure 1 and 2 As shown, the present invention includes the steps of material preparation, preliminary melting, full-capacity melting, and directional solidification, the specific contents of which are as follows:

[0029] A. Feeding preparation: The pretreated 4N cathode copper is loaded into the feeding mechanism of the electron beam melting furnace, and then each part of the furnace is evacuated independently.

[0030] B. Preliminary melting: Turn on the high voltage power supply of the electron beam melting furnace and preheat the electron gun. Then, maintain the melting power of the No. 1 electron gun at 150-200kW and the voltage at 0.5-1kV to heat and melt the 4N cathode copper. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0031] C. Full power melting: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3 and keep the melting power at 50-100kW and voltage at 20-40kV to keep the 4N cathode copper liquid in the crystallizer in a molten state.

[0032] D. Directional solidification: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW; when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone; after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0033] The electron beam melting furnace is a three-gun electron beam furnace, and the melting power of a single gun in the three-gun electron beam furnace is not less than 200kW.

[0034] like Figure 1 As shown, the radiation range of electron gun No. 1 in the electron beam melting furnace is the feed inlet of the melting chamber. The crystallizer is strip-shaped and horizontally arranged. The radiation range of electron gun No. 2 is the front 1 / 2 of the crystallizer, and the radiation range of electron gun No. 3 is the rear 1 / 2 of the crystallizer. In the directional solidification step, the direction of ingot pulling is the direction from electron gun No. 2 to the control area of ​​electron gun No. 3 in the crystallizer.

[0035] In the feeding preparation step, the electron gun vacuum degree of the electron beam melting furnace is 0.8–1.2 × 10⁻⁶. -3 Pa and the vacuum degree of the melting chamber is 4~6×10 -2 Pa.

[0036] The melting temperature of 4N cathode copper in the preliminary melting step and / or full-capacity melting step is controlled at 1200–1250°C. Excessively high melting temperatures will cause a large amount of copper matrix to volatilize, resulting in a reduced yield of the final 5N high-purity copper.

[0037] During the directional solidification step, when the 4N cathode copper liquid fills the crystallizer, the melting power of electron gun No. 3 decreases from 50-100kW to 5kW within 30-60 minutes.

[0038] In the directional solidification step, the ingot is pulled horizontally at a speed of 2.0–2.3 mm / min. The ingot begins to solidify during the electron beam de-beaming process; therefore, the pulling rate for directional solidification needs to be higher than that for general directional solidification. This, combined with the solidification rate of the ingot during the electron beam de-beaming process, facilitates the enrichment of impurities, thereby improving the purity of the ingot.

[0039] like Figure 2 As shown, the impurity enrichment region of the ingot in the directional solidification step is the final solidification region of electron beam down-beam solidification and the final solidification region of directional solidification.

[0040] In the directional solidification step, the melting power of electron gun No. 3 is gradually reduced from 50-100kW to 5kW at a rate gradient of 5-20kW every 5-10 minutes.

[0041] In the feeding preparation step, the 4N cathode copper undergoes pretreatment by being cleaned and dried with deionized water before being loaded into the feeding mechanism of the electron beam melting furnace.

[0042] Example 1

[0043] S100: Pretreated 4N cathode copper is loaded into the feeding mechanism of the three-gun electron beam furnace, and then each part of the furnace is evacuated independently; the vacuum degree of the electron gun in the electron beam furnace is 1.0 × 10⁻⁶. -3 Pa, the vacuum degree of the melting chamber is 5×10 -2 Pa.

[0044] S200: Turn on the high voltage power supply of the three-gun electron beam furnace and preheat the electron gun. Then, adjust the melting power of the No. 1 electron gun to 200kW and the voltage to 0.9kV to heat the 4N cathode copper to 1200℃ and melt it. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0045] S300: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3, maintaining the melting power at 100kW and the voltage at 30kV, so that the 4N cathode copper liquid in the crystallizer remains in a molten state at 1200℃; wherein, the radiation range of electron gun No. 2 is the front 1 / 2 of the crystallizer, and the radiation range of electron gun No. 3 is the rear 1 / 2 of the crystallizer, and the direction of pulling the ingot is from the control area of ​​electron gun No. 2 to electron gun No. 3 within the crystallizer. Figure 1 As shown.

[0046] S400: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW (the power is gradually reduced from 100kW to 5kW at a rate gradient of 19kW every 8 minutes, for a total of 40 minutes); when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone (the pulling rate is controlled at 2.1mm / min); after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0047] Example 2

[0048] S100: Pretreated 4N cathode copper is loaded into the feeding mechanism of the three-gun electron beam furnace, and then each part of the furnace is evacuated independently; the vacuum degree of the electron gun in the electron beam furnace is 0.8 × 10⁻⁶. -3 Pa, the vacuum degree of the melting chamber is 6×10 -2 Pa.

[0049] S200: Turn on the high voltage power supply of the three-gun electron beam furnace and preheat the electron gun. Then, adjust the melting power of the No. 1 electron gun to 150kW and the voltage to 1kV to heat the 4N cathode copper to 1230℃ and melt it. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0050] S300: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3, maintaining the melting power at 100kW and the voltage at 40kV, so that the 4N cathode copper liquid in the crystallizer remains in a molten state at 1230℃; the radiation range of electron gun No. 2 is the front 1 / 2 of the crystallizer, and the radiation range of electron gun No. 3 is the rear 1 / 2 of the crystallizer. The direction of pulling the ingot is from electron gun No. 2 towards the control area of ​​electron gun No. 3 within the crystallizer. Figure 1 As shown.

[0051] S400: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW (the power is gradually reduced from 100kW to 5kW at a rate gradient of 15.8kW every 5 minutes, for a total of 30 minutes); when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone (the pulling rate is controlled at 2.3mm / min); after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0052] Example 3

[0053] S100: Pretreated 4N cathode copper is loaded into the feeding mechanism of the three-gun electron beam furnace, and then each part of the furnace is evacuated independently; the vacuum degree of the electron gun in the electron beam furnace is 1.2 × 10⁻⁶. -3 Pa, the vacuum degree of the melting chamber is 6×10-2 Pa.

[0054] S200: Turn on the high voltage power supply of the three-gun electron beam furnace and preheat the electron gun. Then, adjust the melting power of the No. 1 electron gun to 150kW and the voltage to 0.5kV to heat the 4N cathode copper to 1250℃ and melt it. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0055] S300: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3, maintaining the melting power at 50kW and the voltage at 20kV, so that the 4N cathode copper liquid in the crystallizer remains in a molten state at 1250℃; whereby electron gun No. 2 radiates over the front 1 / 2 of the crystallizer, and electron gun No. 3 radiates over the rear 1 / 2 of the crystallizer, with the pulling direction of the ingot being from electron gun No. 2 towards the control area of ​​electron gun No. 3 within the crystallizer. For example... Figure 1 As shown.

[0056] S400: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW (the power is gradually reduced from 50kW to 5kW at a rate gradient of 7.5kW every 10 minutes, for a total of 60 minutes); when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone (the pulling rate is controlled at 2.0mm / min); after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0057] Example 4

[0058] S100: Pretreated 4N cathode copper is loaded into the feeding mechanism of the three-gun electron beam furnace, and then each part of the furnace is evacuated independently; the vacuum degree of the electron gun in the electron beam furnace is 0.9 × 10⁻⁶. -3 Pa, the vacuum degree of the melting chamber is 4×10 -2 Pa.

[0059] S200: Turn on the high voltage power supply of the three-gun electron beam furnace and preheat the electron gun. Then, adjust the melting power of the No. 1 electron gun to 180kW and the voltage to 0.8kV to heat the 4N cathode copper to 1220℃ and melt it. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0060] S300: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3, maintaining the melting power at 100kW and the voltage at 36kV, so that the 4N cathode copper liquid in the crystallizer remains in a molten state at 1220℃; the radiation range of electron gun No. 2 is the front 1 / 2 of the crystallizer, and the radiation range of electron gun No. 3 is the rear 1 / 2 of the crystallizer. The direction of pulling the ingot is from electron gun No. 2 towards the control area of ​​electron gun No. 3 within the crystallizer. Figure 1 As shown.

[0061] S400: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW (the power is gradually reduced from 100kW to 5kW at a rate gradient of 9.5kW every 6 minutes, for a total of 60 minutes); when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone (the pulling rate is controlled at 2.0mm / min); after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0062] Example 5

[0063] S100: Pretreated 4N cathode copper is loaded into the feeding mechanism of the three-gun electron beam furnace, and then each part of the furnace is evacuated independently; the vacuum degree of the electron gun in the electron beam furnace is 1.1 × 10⁻⁶. -3 Pa, the vacuum degree of the melting chamber is 4×10 -2 Pa.

[0064] S200: Turn on the high voltage power supply of the three-gun electron beam furnace and preheat the electron gun. Then, adjust the melting power of the No. 1 electron gun to 150kW and the voltage to 1kV to heat the 4N cathode copper to 1220℃ and melt it. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0065] S300: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3, maintaining the melting power at 50kW and the voltage at 20kV, so that the 4N cathode copper liquid in the crystallizer remains in a molten state at 1220℃; where electron gun No. 2 radiates over the front 1 / 2 of the crystallizer, and electron gun No. 3 radiates over the rear 1 / 2 of the crystallizer, with the pulling direction being from electron gun No. 2 towards the control area of ​​electron gun No. 3 within the crystallizer. For example... Figure 1 As shown.

[0066] S400: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW (the power is gradually reduced from 50kW to 5kW at a rate gradient of 9kW every 6 minutes, for a total of 30 minutes); when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone (the pulling rate is controlled at 2.2mm / min); after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0067] Example 6

[0068] S100: Pretreated 4N cathode copper is loaded into the feeding mechanism of the three-gun electron beam furnace, and then each part of the furnace is evacuated independently; the vacuum degree of the electron gun in the electron beam furnace is 1.0 × 10⁻⁶. -3 Pa, the vacuum degree of the melting chamber is 5×10 -2 Pa.

[0069] S200: Turn on the high voltage power supply of the three-gun electron beam furnace and preheat the electron gun. Then, adjust the melting power of the No. 1 electron gun to 200kW and the voltage to 1kV to heat the 4N cathode copper to 1230℃ and melt it. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism.

[0070] S300: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron guns No. 2 and No. 3, maintaining the melting power at 100kW and the voltage at 40kV, so that the 4N cathode copper liquid in the crystallizer remains in a molten state at 1230℃; the radiation range of electron gun No. 2 is the front 1 / 2 of the crystallizer, and the radiation range of electron gun No. 3 is the rear 1 / 2 of the crystallizer. The direction of pulling the ingot is from electron gun No. 2 towards the control area of ​​electron gun No. 3 within the crystallizer. Figure 1 As shown.

[0071] S400: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW (the power is gradually reduced from 100kW to 5kW at a rate gradient of 7.9kW every 5 minutes, for a total of 60 minutes); when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone (the pulling rate is controlled at 2.3mm / min); after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper.

[0072] After the above embodiments were completed, the 5N high-purity copper samples were taken from the middle position. The metal impurity composition was analyzed by glow discharge mass spectrometry (GDMS), and the non-metallic impurities O, N, H and C were analyzed by O-NH analyzer and CS analyzer, respectively. The results are shown in Table 1 (unit is ppm).

[0073] Table 14 shows the main impurity element composition analysis of the 4N cathode copper and the 5N high-purity copper samples prepared in Examples 1-6.

[0074] .

[0075] The impurity elements listed in Table 1 are the main impurity elements in 4N cathode copper with a content greater than 0.1 ppm; those with a content less than 0.1 ppm are not listed.

[0076] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing 5N high-purity copper by electron beam down-induced directional solidification, characterized in that... The process includes feeding preparation, initial melting, full-capacity melting, and directional solidification, with the following specific steps: A. Feeding preparation: The pretreated 4N cathode copper is loaded into the feeding mechanism of the electron beam melting furnace, and then each part of the furnace is evacuated independently. B. Preliminary melting: Turn on the high voltage power supply of the electron beam melting furnace and preheat the electron gun. Then, maintain the melting power of the No. 1 electron gun at 150-200kW and the voltage at 0.5-1kV to heat and melt the 4N cathode copper. The molten 4N cathode copper flows into the crystallizer of the electron beam melting furnace from the feeding mechanism. C. Full power melting: When the 4N cathode copper liquid fills 2 / 3 of the crystallizer, turn on electron gun No. 2 and electron gun No. 3 and keep the melting power at 50-100kW and voltage at 20-40kV to keep the 4N cathode copper liquid in the crystallizer in a molten state. D. Directional solidification: When the 4N cathode copper liquid fills the crystallizer, reduce the melting power of electron gun No. 3 to 5kW; when the melt in the crystallizer begins to crystallize, slowly pull the ingot into the cooling zone; after all the ingots in the crystallizer have entered the cooling zone, cut off the impurity-rich area of ​​the ingot to obtain 5N high-purity copper. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification is characterized in that the radiation range of the No. 1 electron gun of the electron beam melting furnace is the feed inlet of the melting chamber, the crystallizer is strip-shaped and horizontally arranged, the radiation range of the No. 2 electron gun is the front 1 / 2 crystallizer, the radiation range of the No. 3 electron gun is the rear 1 / 2 crystallizer, and the direction of ingot pulling in the directional solidification step is the direction from the No. 2 electron gun to the control area of ​​the No. 3 electron gun in the crystallizer. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification is characterized in that, in the directional solidification step, when the 4N cathode copper liquid fills the crystallizer, the melting power of the No. 3 electron gun decreases from 50-100kW to 5kW within 30-60 minutes. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification is characterized in that the ingot is pulled horizontally at a speed of 2.0 to 2.3 mm / min during the directional solidification step. The method for preparing 5N high-purity copper by electron beam down-beam induced directional solidification is characterized in that the impurity enrichment region of the ingot in the directional solidification step is the final solidification region of electron beam down-beam solidification and the final solidification region of directional solidification. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification is characterized in that, in the directional solidification step, the melting power of electron gun No. 3 is gradually reduced from 50-100kW to 5kW at a rate gradient of 5-20kW every 5-10 minutes.

2. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification according to claim 1, characterized in that... The electron beam melting furnace is a three-gun electron beam furnace, and the melting power of a single gun in the three-gun electron beam furnace is not less than 200kW.

3. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification according to claim 1, characterized in that... In the feeding preparation step, the electron gun vacuum degree of the electron beam melting furnace is 0.8–1.2 × 10⁻⁶. -3 Pa and the vacuum degree of the melting chamber is 4~6×10 -2 Pa.

4. The method for preparing 5N high-purity copper by electron beam down-induced directional solidification according to claim 1, characterized in that... The temperature for melting the 4N cathode copper in the preliminary melting step and / or full-power melting step is controlled at 1200–1250°C.

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