A method for preparing 5N high-purity copper by zone melting

Abstract

This invention belongs to the field of non-ferrous metal purification technology, specifically disclosing a method for preparing 5N high-purity copper by zone melting. The method includes performing multi-pass zone melting on 4N cathode copper. The melting atmosphere during the multi-pass zone melting process is a mixture of argon and hydrogen, with hydrogen accounting for 5-30% of the volume in the mixture. By using a mixture of argon and hydrogen as the melting atmosphere for multi-pass zone melting, this invention fully utilizes the segregation effect to remove low-melting-point, volatile metallic impurities. Simultaneously, the hydrogen in the melting atmosphere, as a reducing gas, also removes both metallic and non-metallic impurities, particularly significantly reducing oxygen content. This allows for the preparation of 5N high-purity copper with low levels of non-metallic impurities and metallic impurities other than Fe. The method features simple process, low evaporation loss, low impurity content, and especially low oxygen 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 zone smelting, which is simple in process, has low evaporation loss, low impurity content, and especially low oxygen content. Background Technology

[0002] High-purity copper possesses excellent properties such as low resistivity and high electromagnetic activity, meeting the technical requirements of many cutting-edge technologies. It has been widely used in electronics, communications, superconductivity, aerospace, and other advanced fields, achieving excellent results. With technological advancements, the high-purity copper used in modern high-tech fields requires improved mechanical properties, corrosion resistance, and surface properties without sacrificing conductivity. However, various non-metallic and metallic impurities in high-purity copper have different effects on these properties, making the improvement of high-purity copper's purity particularly urgent.

[0003] Currently, the main technologies for high-purity copper include electrolytic refining, electron beam melting, directional solidification, anion exchange, and zone melting. Electrolytic refining is effective against almost all impurities except oxygen, but it has stringent requirements for the electrolyte, necessitating periodic removal of impurities. Furthermore, the sulfuric acid electrolysis method produces high-purity 5N copper with a high sulfur content, while the presence of nitrate ions in the nitric acid electrolysis method affects the stability of the electrolytic production. Electron beam melting is primarily effective against impurity elements with saturated vapor pressures higher than copper, such as Ag, Se, Te, S, Bi, and Pb. Its effectiveness against other elements is limited, and this melting method heavily relies on manual adjustment of equipment parameters, reducing the stability of the melting process. Directional solidification is mainly used for copper continuous casting and single-crystal preparation, and is typically combined with other purification methods to achieve high purity. For example, Fu Yabo et al. used electron beam vacuum melting and direct directional solidification technology to prepare 5N high-purity copper. The anion exchange method removes impurity ions from the copper solution through ion exchange, and then evaporates the solution to obtain high-purity CuCl2 and reduces it to obtain ultra-high-purity copper. However, the process is complex and it is difficult to mass-produce large copper ingots. Traditional zone melting is mainly effective for impurities with a segregation coefficient (i.e., K=CS / CL, where Cs is the concentration of impurities in the solid phase and CL is the concentration of impurities in the liquid phase) that is far from 1. However, it has limited effect on impurities with a segregation coefficient close to 1. Moreover, after multiple zone melting processes, the purification efficiency of zone melting is low.

[0004] Among the existing high-purity copper purification technologies, zone melting is the most widely used and easiest to industrialize method due to its simple and controllable process, lack of pollution, high product purity, and ability to produce homogeneous single crystals. It is suitable for the final stage of high-purity metal preparation. However, because the purification principle of zone melting relies on the segregation coefficient and saturated vapor pressure of the metal elements, it is only suitable for removing elements with significantly different segregation coefficients and vapor pressures from the bulk metal. Its removal effect on some metals is not ideal. Furthermore, although the national standard for 5N high-purity copper does not specifically limit the removal of non-metallic elements, high-purity copper, when used in applications such as copper sputtering targets, has higher requirements due to the adverse effects of non-metallic impurities, especially oxygen content. Traditional zone melting is not effective in removing non-metallic impurities; therefore, 5N high-purity copper obtained through traditional zone melting cannot be used for copper sputtering target preparation. In the existing technology, although there are technologies that use hydrogen plasma arc melting and a combination of hydrogen plasma arc melting and zone melting to remove metallic and non-metallic impurities, especially to reduce oxygen content, hydrogen plasma arc melting is an ultra-high temperature melting process. Its excessively high melting temperature will lead to increased metal evaporation loss, thereby reducing the metal yield. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing 5N high-purity copper by zone smelting, which is simple in process, has low evaporation loss, low impurity content, and especially low oxygen content.

[0006] The present invention is implemented as follows: 4N cathode copper is subjected to multi-pass zone melting, wherein the melting atmosphere in the multi-pass zone melting process is a mixture of argon and hydrogen, and the volume ratio of hydrogen in the mixture is 5-30%.

[0007] Furthermore, in the multi-pass regional melting process, the melting atmosphere of the subsequent passes, which account for 1 / 5 to 1 / 3 of the total melting passes, is a mixture of argon and hydrogen, while the melting atmosphere of the remaining melting passes is argon. The purity of the argon and hydrogen in the melting atmosphere is greater than 99.999%.

[0008] Furthermore, in the multi-pass zone melting process, a total of 10 to 15 melting passes are conducted, with the last 2 to 5 passes using a mixture of argon and hydrogen gas in the melting atmosphere, while the remaining melting passes use argon gas in the melting atmosphere.

[0009] Furthermore, the multi-pass zone melting process involves a total of 15 melting passes, with the 12th to 15th passes using a mixture of argon and hydrogen gas in the melting atmosphere, while the remaining melting passes use argon gas in the melting atmosphere.

[0010] Furthermore, the multi-pass zone melting process involves a total of 12 melting passes, with the final 9th ​​to 12th passes using a mixture of argon and hydrogen gas in the melting atmosphere, while the remaining melting passes use argon gas in the melting atmosphere.

[0011] Furthermore, the ventilation method in the multi-pass regional smelting process is as follows: each pass is ventilated separately, and each ventilation first removes the air from the refining chamber, then evacuates the vacuum, and then introduces the smelting atmosphere; or the ventilation method is as follows: when the smelting atmosphere of adjacent passes is consistent, the same gas is continuously introduced without interruption; when the smelting atmosphere is inconsistent, adjacent passes are ventilated separately, and the ventilation of the next pass first removes the air from the refining chamber, then evacuates the vacuum, and then introduces the corresponding smelting atmosphere.

[0012] Furthermore, in the multi-pass zone melting process, after the air in the refining chamber is purged, a vacuum is drawn until the pressure is 0.8–1.2 × 10⁻⁶. -4 Pa, and then the pressure of the smelting atmosphere introduced is 80-120 kPa.

[0013] Furthermore, in the multi-pass zone melting process, the heating tubes in the zone melting furnace are circumferentially distributed around the 4N cathode copper and arranged in a conical shape at an angle of 20 to 40 degrees to the 4N cathode copper. During the multi-pass zone melting process, the 4N cathode copper substrate moves toward the opening of the included angle of the heating tubes or the heating tubes move away from the opening of the included angle.

[0014] Furthermore, in the multi-pass zone melting, the melting temperature of 4N cathode copper is 1380–1430 K and the melting moving speed is 0.5–0.7 mm / min, and the pressure in the refining chamber of the zone melting furnace during the multi-pass zone melting is 8–12 Pa.

[0015] Furthermore, after the multi-pass zone melting is completed, the heating tubes are turned off and the melting atmosphere pressure is maintained at 8-12 Pa until the copper ingot cools to room temperature.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. This invention uses a mixture of argon and hydrogen as the melting atmosphere for multi-pass zone melting. While fully utilizing the segregation effect and saturated vapor pressure difference to remove low-melting-point volatile metallic impurities and gases, the hydrogen in the melting atmosphere, as a reducing gas, can further remove some high-melting-point metallic impurities and significantly reduce non-metallic impurities such as Si, S, O, N, and C, especially significantly reducing oxygen content. At the same time, through zone melting, impurities such as Na, Mg, P, V, Zn, Ga, Ag, Se, Sn, W, Au, Bi, and U in 4N cathode copper are driven to one end of the bar to form an impurity enrichment zone, thereby producing 5N high-purity copper with low content of non-metallic impurities and metallic impurities other than Fe.

[0018] 2. This invention controls the melting atmosphere in multi-pass zone melting, combined with the special arrangement of heating tubes and 4N cathode copper substrate in the zone melting furnace, as well as controlling the melting moving speed. This allows for a temperature gradient in the 4N cathode copper substrate during melting, which helps to agglomerate impurities in the copper substrate. Furthermore, by controlling the melting speed and melting power, the melting temperature can be effectively controlled. Combined with a reasonable vacuum degree during melting, this effectively removes metal impurities and gases, and keeps the volatilization loss of the copper substrate below 1%, thereby reducing the loss of the copper substrate and increasing the yield.

[0019] In summary, the present invention has the advantages of simple process, low evaporation loss, low impurity content, and especially low oxygen content. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the distribution and arrangement of heating tubes during the multi-pass zone melting process in an embodiment of the present invention;

[0021] In the diagram: 1-4N cathode copper rod, 2-heating tube, 3-melting movement direction (heating tube movement), α-the angle between the heating tube and one side of the 4N cathode copper. Detailed Implementation

[0022] 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.

[0023] like Figure 1 As shown, the present invention includes multi-pass zone melting of 4N cathode copper, wherein the melting atmosphere in the multi-pass zone melting process is a mixture of argon and hydrogen, wherein the volume ratio of hydrogen in the mixture is 5-30%.

[0024] In the multi-pass regional smelting process, the smelting atmosphere of the subsequent passes, which account for 1 / 5 to 1 / 3 of the total smelting passes, is a mixture of argon and hydrogen, while the smelting atmosphere of the remaining smelting passes is argon. The purity of the argon and hydrogen in the smelting atmosphere is greater than 99.999%.

[0025] The multi-pass zone melting process involves a total of 10 to 15 melting passes, with the last 2 to 5 passes using a mixture of argon and hydrogen gas, and the remaining passes using argon gas.

[0026] The multi-pass zone melting process involves a total of 15 melting passes, with the 12th to 15th passes using a mixture of argon and hydrogen gas in the melting atmosphere, while the remaining melting passes use argon gas in the melting atmosphere.

[0027] The multi-pass zone melting process consists of 12 passes, with the last 9th to 12th passes using a mixture of argon and hydrogen gas, while the remaining passes use argon gas.

[0028] The ventilation method in the multi-pass regional smelting process is as follows: each pass is ventilated separately, and each ventilation first removes the air from the refining chamber, then evacuates the vacuum, and then introduces the smelting atmosphere; or the ventilation method is as follows: when the smelting atmosphere of adjacent passes is consistent, the same gas is continuously introduced without interruption; when the smelting atmosphere is inconsistent, adjacent passes are ventilated separately, and the ventilation of the next pass first removes the air from the refining chamber, then evacuates the vacuum, and then introduces the corresponding smelting atmosphere.

[0029] In the multi-pass zone smelting process, after the air in the refining chamber is purged, a vacuum is created until the pressure reaches 0.8–1.2 × 10⁻⁶. - 4 Pa, and then the pressure of the smelting atmosphere introduced is 80-120 kPa.

[0030] In the multi-pass zone melting process, the heating tubes in the zone melting furnace are circumferentially distributed around the 4N cathode copper and arranged in a conical shape at an angle of 20° to 40° to the 4N cathode copper. During the multi-pass zone melting process, the 4N cathode copper substrate moves towards the opening of the included angle of the heating tubes, or the heating tubes move away from the opening of the included angle. The heating tubes arranged at an angle of 20° to 40° can generate gradually enhanced thermal radiation to the 4N cathode copper, thereby facilitating the segregation of impurities in the copper substrate.

[0031] In the multi-pass zone melting process, the melting temperature of 4N cathode copper is 1380–1430 K and the melting moving speed is 0.5–0.7 mm / min. The pressure in the refining chamber of the zone melting furnace during the multi-pass zone melting process is 8–12 Pa. By controlling the pressure and melting temperature in the refining chamber, the volatilization loss of the copper matrix can be ensured to be within 1%.

[0032] After the multi-pass zone melting is completed, the heating tubes are turned off and the melting atmosphere pressure is maintained at 8-12 Pa until the copper ingot cools to room temperature.

[0033] The 4N cathode copper undergoes pretreatment by being washed and dried with deionized water before being loaded into the zone smelting furnace.

[0034] Example 1

[0035] A 4N cathode copper rod (8mm in diameter and 80mm in length) is used as the smelting raw material and placed in a 5N high-purity graphite crucible. The graphite crucible is then placed in a quartz tube (i.e., the refining chamber, hereinafter the same) and fixed in place (to prevent it from moving during the smelting process). The heating tubes are arranged circumferentially around the 4N cathode copper and at a 30° angle to it. The two ends of the quartz tube are connected to ventilation facilities and sealed. Then, 15 passes of zone smelting can begin.

[0036] Melting operations 1-12: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 2 L / min to expel the air, and then a vacuum is drawn to 1.0 × 10⁻⁶. -4 Pa, then high-purity argon gas at 80 kPa is introduced, and the zone melting temperature is controlled at 1400 K, with the zone melting moving speed controlled at 0.7 mm / min (e.g., Pa). Figure 1 As shown in the figure, the vacuum level inside the quartz tube is adjusted and controlled at 10 Pa.

[0037] Melting operations 12-15: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 2 L / min to expel the air, and then a vacuum is drawn to 1.0 × 10⁻⁶. -4 Pa, then a mixture of argon and hydrogen (20% by volume) at 80 kPa is introduced, the zone melting temperature is controlled at 1400 K, the zone melting speed is 0.7 mm / min, and the vacuum degree in the quartz refining chamber is 10 Pa.

[0038] After the 15th melting is completed, the heating tube is turned off and the melting atmosphere and pressure of 10 Pa are maintained until the copper ingot cools to room temperature and is taken out of the furnace to obtain 5N high-purity copper.

[0039] Example 2

[0040] A 4N cathode copper rod (8mm in diameter and 80mm in length) is used as the smelting raw material and placed in a 5N high-purity graphite crucible. The graphite crucible is then placed inside a quartz tube and fixed in place (to prevent it from moving during the smelting process). The heating tubes are arranged circumferentially around the 4N cathode copper and at a 30° angle to it. The two ends of the quartz tube are connected to ventilation facilities and sealed. Then, 15 passes of zone smelting can begin.

[0041] Melting operations 1-12: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 1.5 L / min to expel the air, and then a vacuum is created to 1.2 × 10⁻⁶. -4 Pa, then high-purity argon gas at 120 kPa is introduced, and the temperature of the zone melting is controlled at 1380 K, the moving speed of the zone melting is controlled at 0.5 mm / min, and the vacuum degree in the quartz tube is adjusted and controlled at 8 Pa.

[0042] Melting operations 12-15: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 1.5 L / min to expel the air, and then a vacuum is created to 1.2 × 10⁻⁶. -4 Pa, then a mixture of argon and hydrogen (10% by volume) is introduced at 120 kPa. The zone melting temperature is controlled at 1380 K, the zone melting speed is 0.5 mm / min, and the vacuum degree in the quartz refining chamber is 8 Pa.

[0043] After the 15th melting is completed, the heating tube is turned off and the melting atmosphere and pressure of 8 Pa are maintained until the copper ingot cools to room temperature and is taken out of the furnace to obtain 5N high-purity copper.

[0044] Example 3

[0045] A 4N cathode copper rod (8mm in diameter and 80mm in length) is used as the smelting raw material and placed in a 5N high-purity graphite crucible. The graphite crucible is then placed inside a quartz tube and fixed in place (to prevent it from moving during the smelting process). The heating tubes are arranged circumferentially around the 4N cathode copper and at a 40° angle to it. The two ends of the quartz tube are connected to ventilation devices and sealed. Then, 15 passes of zone smelting can begin.

[0046] Melting operations 1-12: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 2.5 L / min to expel the air, and then a vacuum is created to 0.8 × 10⁻⁶. -4 Pa, then 100 kPa of high-purity argon gas is introduced, and the temperature of the zone melting is controlled at 1430 K, the moving speed of the zone melting is controlled at 0.7 mm / min, and the vacuum degree in the quartz tube is adjusted and controlled at 12 Pa.

[0047] Melting operations 12-15: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 2.5 L / min to expel the air, and then a vacuum is created to 0.8 × 10⁻⁶. -4 Pa, then a mixture of argon and hydrogen (15% by volume) is introduced at 100 kPa. The zone melting temperature is controlled at 1430 K, the zone melting speed is 0.7 mm / min, and the vacuum degree in the quartz refining chamber is 12 Pa.

[0048] After the 15th melting is completed, the heating tube is turned off and the melting atmosphere and pressure of 12 Pa are maintained until the copper ingot cools to room temperature and is taken out of the furnace to obtain 5N high-purity copper.

[0049] Example 4

[0050] A 4N cathode copper rod (8mm in diameter and 80mm in length) is used as the smelting raw material and placed in a 5N high-purity graphite crucible. The graphite crucible is then placed inside a quartz tube and fixed (to prevent it from moving during the smelting process). The heating tubes are arranged circumferentially around the 4N cathode copper and at a 40° angle to it. The two ends of the quartz tube are connected to ventilation devices and sealed. Then, 10 passes of zone smelting can begin.

[0051] Melting operations 1-8: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 1.8 L / min to expel the air, and then a vacuum is drawn to 1.1 × 10⁻⁶. -4Pa, then high-purity argon gas of 90 kPa is introduced, and the temperature of the zone melting is controlled at 1390 K, the moving speed of the zone melting is controlled at 0.6 mm / min, and the vacuum degree in the quartz tube is adjusted and controlled at 9 Pa.

[0052] 9th-10th melting: Before each melting, high-purity argon gas is introduced into the quartz tube at a rate of 1.8 L / min to expel the air, and then a vacuum is drawn to 1.1 × 10⁻⁶. -4 Pa, then a mixture of argon and hydrogen (15% by volume) at 90 kPa is introduced, the zone melting temperature is controlled at 1400 K, the zone melting speed is 0.6 mm / min, and the vacuum degree in the quartz refining chamber is 9 Pa.

[0053] After the 10th melting is completed, the heating tube is turned off and the melting atmosphere and pressure of 9 Pa are maintained until the copper ingot cools to room temperature and is taken out of the furnace to obtain 5N high-purity copper.

[0054] Example 5

[0055] A 4N cathode copper rod (8mm in diameter and 80mm in length) is used as the smelting raw material and placed in a 5N high-purity graphite crucible. The graphite crucible is then placed inside a quartz tube and fixed in place (to prevent it from moving during the smelting process). The heating tubes are arranged circumferentially around the 4N cathode copper and at a 20° angle to it. The two ends of the quartz tube are connected to ventilation facilities and sealed. Then, 12 passes of zone smelting can begin.

[0056] Melting operations 1-8: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 2 L / min to expel the air, and then a vacuum is drawn to 1.0 × 10⁻⁶. -4 Pa, then high-purity argon gas at 120 kPa is introduced, and the temperature of the zone melting is controlled at 1400 K, the moving speed of the zone melting is controlled at 0.5 mm / min, and the vacuum degree in the quartz tube is adjusted and controlled at 10 Pa.

[0057] Melting operations 9-12: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 2 L / min to expel the air, and then a vacuum is drawn to 1.0 × 10⁻⁶. -4 Pa, then a mixture of argon and hydrogen (30% by volume) is introduced at 120 kPa. The zone melting temperature is controlled at 1400 K, the zone melting speed is 0.5 mm / min, and the vacuum degree in the quartz refining chamber is 10 Pa.

[0058] After the 12th melting is completed, the heating tube is turned off and the melting atmosphere and pressure of 10 Pa are maintained until the copper ingot cools to room temperature and is taken out of the furnace to obtain 5N high-purity copper.

[0059] Example 6

[0060] A 4N cathode copper rod (8mm in diameter and 80mm in length) is used as the smelting raw material and placed in a 5N high-purity graphite crucible. The graphite crucible is then placed inside a quartz tube and fixed in place (to prevent it from moving during the smelting process). The heating tubes are arranged circumferentially around the 4N cathode copper and at a 20° angle to it. The two ends of the quartz tube are connected to ventilation facilities and sealed. Then, 12 passes of zone smelting can begin.

[0061] Melting operations 1-8: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 1.5 L / min to expel the air, and then a vacuum is drawn to 1.2 × 10⁻⁶. -4 Pa, then 100 kPa of high-purity argon gas is introduced, and the temperature of the zone melting is controlled at 1420 K, the moving speed of the zone melting is controlled at 0.7 mm / min, and the vacuum degree in the quartz tube is adjusted and controlled at 8 Pa.

[0062] Melting operations 9-12: Before each melting operation, high-purity argon gas is introduced into the quartz tube at a rate of 1.5 L / min to expel the air, and then a vacuum is created to 1.2 × 10⁻⁶. -4 Pa, then a mixture of argon and hydrogen (30% by volume) is introduced at 100 kPa. The zone melting temperature is controlled at 1420 K, the zone melting speed is 0.7 mm / min, and the vacuum degree in the quartz refining chamber is 8 Pa.

[0063] After the 12th melting is completed, the heating tube is turned off and the melting atmosphere and pressure of 8 Pa are maintained until the copper ingot cools to room temperature and is taken out of the furnace to obtain 5N high-purity copper.

[0064] 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).

[0065] Table 14 Comparison of main impurity element composition between 4N cathode copper and 5N high-purity copper prepared in Examples 1-6

[0066]

[0067] 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.

[0068] As shown in the table above, this invention uses a mixture of argon and hydrogen as the melting atmosphere for multi-pass zone melting. While fully utilizing the segregation effect and saturated vapor pressure difference to remove low-melting-point volatile metallic impurities and gases, the hydrogen in the melting atmosphere, as a reducing gas, can further remove some high-melting-point metallic impurities and significantly reduce non-metallic impurities such as Si, S, O, N, and C, especially significantly reducing oxygen content. At the same time, through zone melting, impurities such as Na, Mg, P, V, Zn, Ga, Ag, Se, Sn, W, Au, Bi, and U in 4N cathode copper are driven to one end of the bar to form an impurity enrichment zone, thereby producing 5N high-purity copper with low content of non-metallic impurities and metallic impurities other than Fe.

[0069] 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 zone melting, comprising performing multi-pass zone melting on 4N cathode copper, wherein the melting atmosphere during the multi-pass zone melting process is argon or a mixture of argon and hydrogen, characterized in that: The multi-pass zone melting process involves a total of 10-15 melting passes, with the last 2-5 passes using a mixture of argon and hydrogen gas, and the remaining passes using argon gas. The ventilation method involves separate ventilation for each pass, with each pass first purging the air from the refining chamber, then creating a vacuum, before introducing the melting atmosphere; alternatively, if the melting atmospheres of adjacent passes are consistent, the same gas is continuously and uninterruptedly introduced; if the melting atmospheres are inconsistent, adjacent passes are ventilated separately, with each subsequent pass first purging the air from the refining chamber, then creating a vacuum, before introducing the corresponding melting atmosphere. In the multi-pass zone melting process, after purging the air from the refining chamber, a vacuum is created to a pressure of 0.8-1.2 × 10⁻⁶. -4 The pressure of the smelting atmosphere introduced is 80-120 kPa; the volume percentage of hydrogen in the mixed gas is 5-30%, and the purity of argon and hydrogen in the smelting atmosphere is greater than 99.999%. In the multi-pass zone melting process, the heating tubes in the zone melting furnace are circumferentially distributed around the 4N cathode copper and arranged in a cone shape at an angle of 20 to 40° to the 4N cathode copper. During the multi-pass zone melting process, the 4N cathode copper substrate moves toward the direction of the opening of the included angle of the heating tubes or the heating tubes move away from the opening of the included angle. In the multi-pass zone melting process, the melting temperature of 4N cathode copper is 1380–1430 K and the melting moving speed is 0.5–0.7 mm / min. The pressure in the refining chamber of the zone melting furnace during the multi-pass zone melting process is 8–12 Pa.

2. The method for preparing 5N high-purity copper by zone melting according to claim 1, characterized in that... The multi-pass zone melting process involves a total of 15 melting passes, with the 12th to 15th passes using a mixture of argon and hydrogen gas in the melting atmosphere, while the remaining melting passes use argon gas in the melting atmosphere.

3. The method for preparing 5N high-purity copper by zone smelting according to claim 1, characterized in that... The multi-pass zone melting process consists of 12 passes, with the last 9th to 12th passes using a mixture of argon and hydrogen gas, while the remaining passes use argon gas.

4. The method for preparing 5N high-purity copper by zone melting according to claim 1, characterized in that... After the multi-pass zone melting is completed, the heating tubes are turned off and the melting atmosphere pressure is maintained at 8-12 Pa until the copper ingot cools to room temperature.

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