A method for purifying oxygen-free copper rod by using pulse current treatment

Abstract

The application discloses a method for purifying oxygen-free copper rod by using up-drawing continuous casting and pulse current treatment, and belongs to the technical field of oxygen-free copper rod manufacturing. The method comprises the following steps: heating copper in an up-drawing continuous casting furnace to a molten state; inserting at least two conductive bodies into the copper melt, wherein the conductive bodies are graphite electrodes or wiring copper rods capable of being pulled upward through the up-drawing continuous casting process; insulating and fixing the conductive bodies; applying pulse current to make impurities enriched in a certain area near the conductive bodies; removing the copper melt with enriched impurities, and normally up-drawing oxygen-free copper rods in the continuous casting bin. When the conductive bodies are the wiring copper rods, the impurities are continuously taken out by pulling the wiring copper rods; when the conductive bodies are the graphite electrodes, the copper melt around the graphite electrodes is periodically removed. The application realizes continuous purification of the copper melt, can stably produce TU1-grade oxygen-free copper rods with impurity content less than 0.008% and oxygen content less than 10 ppm, widens a process window, reduces production cost, and is suitable for large-scale industrial production of oxygen-free copper rods.

Description

Technical Field

[0001] This invention relates to the field of oxygen-free copper rod technology, and in particular to a method for purifying the melt in continuous casting of oxygen-free copper rods based on pulsed current processing. Background Technology

[0002] Copper busbars, copper wires, and other copper processed products possess excellent electrical and thermal conductivity, and are widely used in power, electronics, transportation, and other fields. Especially in recent years, the rapid development of my country's new energy vehicle industry has placed higher demands on the electrical conductivity and heat dissipation performance of copper busbars and copper wires, particularly in the areas of vehicle power batteries, drive motors, and high and low voltage wiring harnesses. The electrical and thermal conductivity of pure copper is closely related to its microstructure and internal defects; therefore, the raw material used in the production of copper busbars and copper wires—oxygen-free copper rods—must have a low oxygen content and fewer impurities and pores.

[0003] Currently, most manufacturers, both domestically and internationally, use the upward continuous casting method to produce oxygen-free copper rods. This method features low energy consumption and continuous production. The upward casting furnace is typically divided into three areas: the charging bin (melting zone), the transition bin, and the continuous casting bin. To ensure the copper molten metal is isolated from air, the charging bin and the transition bin are protected by a charcoal covering layer. However, in actual production, each time an electrolytic copper plate is added, the downward pressure of the copper plate causes localized damage to the charcoal layer, resulting in some copper molten metal being exposed to air. Furthermore, the periodic ash removal operation also exposes the copper molten metal to air. Oxygen and water from the air are thus absorbed into the copper molten metal, leading to increased oxygen content, impurities, and porosity in the copper rod. Existing research has shown that trace impurities such as sulfur, oxygen, and hydrogen have a significant impact on the process and product quality of oxygen-free copper rods produced by the upward continuous casting method. When the sulfur mass fraction exceeds 38 × 10⁻⁶, the oxygen content increases. -6 Oxygen levels exceeding 8×10 -5 Or hydrogen exceeds 0.8 × 10 -6 At that time, the process performance deteriorated significantly, and the breakage rate of rods and wires increased sharply during casting and stretching. Meanwhile, the quality and dryness of the charcoal, the quality of the electrolytic copper plate, and human factors in the feeding and ash removal operations all directly affected the purity of the copper melt.

[0004] To improve the cleanliness of molten copper, various copper molten purification methods have been developed in the prior art. For example, the method of adding deoxidizers and slag-forming agents involves adding rare earth elements, composite deoxidizers, and other components to the molten copper to react with impurities and form slag for removal. However, this method easily introduces new impurities, and the slag-forming process leads to metal loss and environmental pollution. Another method is bottom blowing to remove impurities, which involves introducing inert gas into the molten copper to remove gases and inclusions. However, this method requires large-scale modifications to the upper furnace, resulting in high equipment investment and energy consumption. Furthermore, the method of treating molten metal with pulsed current or pulsed electric fields has been reported in laboratory studies. CN113755892A discloses a method for removing multi-element impurities from scrap copper using pulsed current. This method involves inserting electrodes into the scrap copper molten metal and applying pulsed current to induce electromigration of impurity elements, thereby reducing the content of impurity elements inside the molten metal. However, this method only achieves the enrichment of impurities near the electrode, without addressing how to effectively remove the enriched impurities from the melt. It is a laboratory-based intermittent purification method and is difficult to directly apply to the continuous production scenario of upward casting. In addition, some studies have confirmed that pulsed current can cause oxide inclusions in Cu melt to migrate directionally and accumulate near the electrode under the action of electromagnetic and electromigration forces, but this also does not solve the problem of continuous removal of impurities after enrichment.

[0005] In summary, existing methods for producing oxygen-free copper rods using continuous casting generally suffer from the following shortcomings: 1. Under conventional charcoal covering protection, the feeding and ash removal operations inevitably introduce oxygen and impurities, placing stringent requirements on raw material quality and operational specifications, resulting in a narrow production process window and low tolerance for errors; 2. Existing copper melt purification methods (adding deoxidizers / slag-forming agents, bottom blowing, etc.) introduce new impurities, are difficult to modify equipment, and have high energy consumption; 3. While pulsed current purification technology has shown feasibility in laboratory studies, existing methods only achieve the migration and enrichment of impurities, lacking effective means to remove enriched impurities from the melt, thus failing to meet the needs of industrial production; 4. Copper rod quality fluctuates significantly due to melt contamination, making it difficult to stably produce high-grade TU1 oxygen-free copper rods. Therefore, there is an urgent need to develop a copper melt purification method that can broaden raw material selection and process window, improve production tolerance, and enable continuous industrial application. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention discloses a method for purifying the melt of oxygen-free copper rods in continuous casting based on pulse current processing.

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

[0008] A method for purifying the melt in continuous casting of oxygen-free copper rods based on pulsed current processing includes the following steps:

[0009] Step 1: Heat the copper in the upward continuous casting furnace to a molten state to obtain copper melt;

[0010] Step 2: Insert at least two conductors independently into the molten copper. The conductors are graphite electrodes or copper rods that can be pulled upwards by the upward continuous casting process.

[0011] Step 3: Insulate and fix the conductor so that it forms a current path only with the copper melt and the external pulse power supply;

[0012] Step 4: Apply a pulsed current to the conductor to enrich impurities in the copper melt in the vicinity of the conductor;

[0013] Step 5: Remove the copper melt rich in impurities around the conductor, and in the continuous casting chamber of the upward continuous casting furnace, draw the oxygen-free copper rod as the product upward through the upward continuous casting process.

[0014] Wherein, when the conductor is the copper rod, the removal method in step five is: by pulling the copper rod upward, the impurities accumulated nearby are continuously carried out of the copper melt along with the copper rod; when the conductor is the graphite electrode, the removal method in step five is: using an insulating tool to periodically remove the copper melt around the graphite electrode.

[0015] Furthermore, in step four, the process parameters of the pulse current are: voltage 1.2~36V, current 1~500A, pulse frequency 1~5000Hz, and the time for applying the pulse current is 5 minutes to 24 hours.

[0016] Furthermore, in step one, the temperature of the copper melt is 1140~1160℃.

[0017] Furthermore, the conductor is inserted into at least one region of the charging bin, transition bin, or continuous casting bin of the upper drawing continuous casting furnace.

[0018] Furthermore, the oxygen-free copper rod has a lead-in speed of 280-2800 mm / min, a cooling water inlet temperature of 20-35℃, an outlet temperature of 26-51℃, and a cooling water inlet-outlet temperature difference of 6-16℃.

[0019] Furthermore, when the conductor is the connecting copper rod, the lead-in speed of the connecting copper rod is 280~2800mm / min; and when the diameter of the connecting copper rod and the oxygen-free copper rod are the same, the lead-in speed of the connecting copper rod is not greater than the lead-in speed of the oxygen-free copper rod.

[0020] Furthermore, when the diameter of the connecting copper rod and the oxygen-free copper rod is 8mm, the rod speed is 2000~2800mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 26~45℃, and the cooling water inlet and outlet temperature difference is 6~10℃.

[0021] When the diameter of the connecting copper rod and the oxygen-free copper rod is 12.5mm, the rod speed is 680~720mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 26~45℃, and the cooling water inlet and outlet temperature difference is 6~10℃.

[0022] When the diameter of the connecting copper rod and the oxygen-free copper rod is 16mm, the rod pulling speed is 460~500mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 27~49℃, and the cooling water inlet and outlet temperature difference is 7~14℃.

[0023] When the diameter of the connecting copper rod and the oxygen-free copper rod is 20mm, the rod speed is 380~430mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 27~49℃, and the cooling water inlet and outlet temperature difference is 7~14℃.

[0024] When the diameter of the connecting copper rod and the oxygen-free copper rod is 25mm, the rod pulling speed is 280~340mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 30~51℃, and the cooling water inlet and outlet temperature difference is 10~16℃.

[0025] Furthermore, in step five, the method for removing the copper melt enriched with impurities is as follows: when the conductor is a graphite electrode, the copper melt enriched with impurities around the conductor is removed every 10 to 120 minutes using an insulating tool.

[0026] Furthermore, when the conductor is a connecting copper rod, the contact area between the connecting copper rod and the traction mechanism is insulated.

[0027] Furthermore, the copper rod obtained by the method is a TU1 grade oxygen-free copper rod with an impurity content of less than 0.008% and an oxygen content of less than 10ppm.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention overcomes the technical bottleneck of existing pulsed current impurity removal technologies, which can only achieve impurity migration and enrichment in the laboratory but cannot effectively remove them. For the first time, a connecting copper rod is introduced as a conductor into the pulsed current purification system. By pulling the connecting copper rod upwards as a conductor, impurities enriched near the electrode are continuously carried out of the melt along with the copper rod, realizing a complete closed-loop process of impurity migration from the melt interior → enrichment → continuous removal. Compared to existing technologies that only use graphite electrodes without actively removing enriched impurities (resulting in copper rods that only reach TU2 grade), this invention can stably produce TU1 grade oxygen-free copper rods, achieving an organic unity of continuous impurity removal process and industrial application, filling the gap in existing technologies for continuous purification using pulsed current in upward continuous casting.

[0030] 2. The oxygen-free copper rod produced using the method of this invention meets the quality standard of TU1 grade oxygen-free copper rod after testing. Compared with the oxygen-free copper rods conventionally produced by the existing upward continuous casting process, this invention achieves a substantial reduction in oxygen content control, effectively overcoming the technical defects of conventional processes caused by fluctuations in the oxygen content of the copper melt due to operations such as feeding and ash removal.

[0031] 3. This invention requires only the addition of a pulse power supply and a conductor, without the need for large-scale structural modifications to the upward-drawing furnace, resulting in minimal equipment investment. Due to the electrochemical purification principle of directly introducing the conductor into the melt, the increase in energy consumption is limited, far lower than that of existing impurity removal methods such as bottom blowing. Furthermore, the conductor used in this invention can be either a graphite electrode (low-cost solution) or a connecting copper rod (continuous impurity removal solution), allowing for flexible selection based on specific production needs and demonstrating excellent process adaptability.

[0032] 4. This invention removes high-impurity copper melt within a certain range of the positive and negative electrodes of the pulse current in a timely manner. In particular, by using a connecting copper rod to the positive and negative electrodes of the pulse current, the impurities enriched in the copper melt can be removed in a timely manner using the conventional method of producing oxygen-free copper rods. This solves the problem of the difficulty of continuous slag removal after slag formation in existing methods, and realizes the continuous impurity removal process. Attached Figure Description

[0033] Figure 1 This is an analysis diagram of the Fe element content in the copper rod after impurity removal by applying a pulsed current according to the present invention. Detailed Implementation

[0034] The following detailed description of the method for purifying molten copper in continuous casting using oxygen-free copper rods based on pulsed current processing, with reference to embodiments and comparative examples, illustrates the present invention in detail. Those skilled in the art should understand that the following embodiments are merely illustrative of the invention and do not constitute any limitation on the scope of protection of the invention. All equivalent substitutions or modifications made based on the concept of the present invention fall within the scope of protection of the present invention.

[0035] This invention provides a method for purifying the molten copper rod in continuous casting based on pulsed current treatment. The core of this method is to use pulsed current to cause impurity particles (such as oxides, sulfides and other intermetallic compounds) in the copper molten metal to undergo electromigration and enrichment in the vicinity of the conductor. The copper molten metal enriched with impurities is then removed from the molten pool by mechanical removal or continuous upward drawing, thereby achieving efficient purification of the copper molten metal.

[0036] The main equipment used in implementing the method of the present invention includes: an upward continuous casting furnace (usually divided into a charging bin, a transition bin, and a continuous casting bin), a pulse power supply (which can be a pulse welding machine power supply or a customized DC pulse power supply), a conductor (graphite electrode or a copper rod that can be pulled upward through the upward continuous casting process), wires, and an insulation fixing device.

[0037] In a basic embodiment of the present invention, the method includes the following steps:

[0038] Step 1: Heat the electrolytic copper plate or recycled material in the upward continuous casting furnace to a molten state to form copper melt. Maintain the temperature of the copper melt at 1130~1170℃, preferably 1140~1160℃, by precise temperature control (such as using thermocouples or laser thermometers).

[0039] Step Two: Insert at least two conductors independently into the molten copper. The conductors can be graphite electrodes or connecting copper rods that can be pulled upwards via the upward continuous casting process. During insertion, the conductors can be placed in any area of ​​the feeding chamber, transition chamber, or continuous casting chamber as needed. The insertion depth of the conductors should be determined based on the total depth of the molten copper: for graphite electrodes, the insertion depth should be less than the total depth of the molten copper, preferably 1 / 3 to 1 / 2 of the total depth; for connecting copper rods, the insertion depth is typically 15 to 17 mm (the same as for normal upward-drawing copper rods) to ensure stable upward drawing.

[0040] Step 3: Secure the conductor using insulating clamps, wooden frames, or other insulating components, ensuring it forms a current path only with the molten copper and the external pulse power supply. Pay particular attention to preventing the conductor from contacting conductors such as the furnace door or traction mechanism. When using a connecting copper rod as the conductor, the contact area between the copper rod and the traction mechanism must be insulated.

[0041] Step 4: Connect the positive and negative terminals of the pulse power supply to the two conductors respectively, and apply a pulse current. The process parameters for the pulse current are: voltage 1.2~36V, current 1~500A, pulse frequency 1~5000Hz, and current application time 5 minutes to 24 hours. Under these conditions, impurity ions in the copper melt (such as Fe) 2+ Pb 2+ Sn 2+ (etc.) and oxide inclusions will migrate and accumulate near the conductor under the action of an electric field.

[0042] Step 5: During or after the energizing process, remove the copper melt rich in impurities around the conductor, and independently pull the oxygen-free copper rod, which will be the product, upward in the continuous casting chamber.

[0043] When the conductor is a copper rod, the method for removing impurities is as follows: continuously pull the copper rod upwards. Because impurities accumulate near the rod, they are carried out of the molten copper as the rod is continuously pulled upwards. This copper rod, containing high levels of impurities, is not considered a final product. Its pulling speed should not exceed that of the oxygen-free copper rod used in normal production (when both have the same diameter).

[0044] When the conductor is a graphite electrode, the method for removing impurities is as follows: every 10 to 120 minutes, use an insulating tool to scoop out or scrape off the copper melt rich in impurities around the graphite electrode.

[0045] The lead-in speed of oxygen-free copper rods and connecting copper rods used in normal production is adjusted within the following range according to their diameter: when the diameter of the connecting copper rod is 8mm, its lead-in speed is 2000~2800mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 26~45℃, and the cooling water inlet and outlet temperature difference is 6~10℃.

[0046] When the diameter of the connecting copper rod is 12.5mm, its lead-in speed is 680~720mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 26~45℃, and the cooling water inlet and outlet temperature difference is 6~10℃.

[0047] When the diameter of the connecting copper rod is 16mm, its lead-in speed is 460~500mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 27~49℃, and the cooling water inlet and outlet temperature difference is 7~14℃.

[0048] When the diameter of the connecting copper rod is 20mm, its lead-in speed is 380~430mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 27~49℃, and the cooling water inlet and outlet temperature difference is 7~14℃.

[0049] When the diameter of the connecting copper rod is 25mm, its lead-in speed is 280~340mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 30~51℃, and the cooling water inlet and outlet temperature difference is 10~16℃.

[0050] Using the above method, TU1 grade oxygen-free copper rods with impurity content of less than 0.008% and oxygen content of less than 10ppm can be stably produced.

[0051] The technical effects of the present invention are further illustrated below through Examples 1-8 and Comparative Example 1. All embodiments employ an upward continuous casting furnace, the molten copper is formed by melting electrolytic copper plates, and the pulse power supply is a pulse welding machine power supply or a customized DC pulse power supply. Process parameters not specifically described in the embodiments are executed according to the above-described basic implementation method.

[0052] Example 1: This example provides a method for purifying the molten copper rod (20mm in diameter) used in upward continuous casting based on pulsed current treatment. The conductive material is a graphite electrode, and the copper molten metal enriched with impurities is removed by periodic scooping. The pulsed current is a DC pulse applied to the charging bin of the upward continuous casting furnace. The specific steps include:

[0053] Step 1: Power on and circulate water to the upper drawing continuous casting furnace. Adjust the voltage and current to bring the temperature of the molten copper in the charging bin, transition bin, and continuous casting bin to 1140℃. Machin the upper drawing head according to the diameter of the oxygen-free copper rod to be produced, install it on the upper drawing rod, and assemble it with the crystallizer for later use.

[0054] Step 2: Prepare the pulse DC welding machine power supply, two graphite electrodes, and wires. Insert the two graphite electrodes into the molten copper in the feeding bin, with the graphite electrodes submerged to a depth of 1 / 3 of the total depth of the molten copper.

[0055] Step 3: Secure the graphite electrodes with insulating clamps to prevent them from contacting conductors such as the furnace door or the upward-drawing mechanism. Connect the positive and negative terminals of the pulse power supply to the two graphite electrodes respectively.

[0056] Step 4: Activate the pulse power supply and apply a pulsed current to the molten copper in the feeding bin. Adjust the pulsed current parameters as follows: voltage 1.2V, current 1A, pulse frequency 1Hz, and pulse waveform as a rectangular wave. After 5 minutes of pulsed current application, impurities undergo electromigration under the influence of the current, gradually accumulating in the molten copper surrounding the positive and negative electrodes.

[0057] Step 5: Starting from the moment the power is turned on, every 10 minutes, use an insulated spoon to scoop out the copper melt rich in impurities around the positive and negative electrodes of the graphite electrode. Each time, the amount of copper melt removed is about 50mm around the electrode. The oxygen-free copper rod, which is the product, is then independently pulled upwards in the continuous casting chamber.

[0058] During the process, while the pulse current is applied, normal rod operation is carried out in the continuous casting chamber. The rod speed is 380 mm / min, the cooling water inlet temperature is 27℃, the outlet temperature is 35℃, and the inlet and outlet water temperature difference is 8℃.

[0059] Samples of continuously produced oxygen-free copper rods were taken, and the oxygen content was determined using an oxygen analyzer. The impurity element content was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The test results showed that the oxygen content of the oxygen-free copper rods was 8 ppm, and the conductivity was 101.3% IACS. The quality grade of the copper rods met the TU1 standard.

[0060] Example 2 provides a method for purifying the molten metal in the upward continuous casting of oxygen-free copper rods based on pulsed current treatment. The conductor is a graphite electrode, and the pulsed current is a DC pulse applied to the transition chamber of the upward continuous casting furnace. The specific steps are the same as in Example 1, and the specific parameters are shown in Table 1. The test results show that the oxygen content of the oxygen-free copper rod is 9 ppm, the conductivity is 101.1% IACS, and the quality grade of the copper rod meets the TU1 standard.

[0061] Example 3 provides a method for purifying the molten metal in the upward continuous casting of oxygen-free copper rods based on pulsed current treatment. The conductor is a graphite electrode, and the pulsed current is a DC pulse applied to the casting chamber of the upward continuous casting furnace. The specific steps are the same as in Example 1, and the specific parameters are shown in Table 1. The test results show that the oxygen content of the oxygen-free copper rod is 4 ppm, the conductivity is 101.2% IACS, and the quality grade of the copper rod meets the TU1 standard.

[0062] Example 4 provides a method for purifying molten copper melt in an upward continuous casting furnace using an oxygen-free copper rod (20mm in diameter) processed by pulsed current. The conductor is a 20mm diameter copper rod that can be pulled upwards during the upward continuous casting process. The copper melt, enriched with impurities, is removed by continuous upward pulling via an upward pulling mechanism. The pulsed current is a DC pulse applied to the casting chamber of the upward continuous casting furnace. The specific steps include:

[0063] Step 1: Preheat the upper drawing continuous casting furnace using the same method as in Example 1, so that the temperature of the copper melt reaches 1150°C.

[0064] Step 2: Prepare the DC pulse power supply and wires. Perform the connection operation using two copper rods in the continuous casting chamber. Immerse these two copper rods partially into the molten copper in the continuous casting chamber, serving as the positive and negative terminals of the pulse current. Connect the positive and negative terminals of the pulse power supply to the two copper rods respectively.

[0065] Step 3: The contact points between the wiring copper rod and the guide wheel of the traction mechanism are insulated to prevent current bypass.

[0066] Step 4: Start the pulse power supply and continuously apply a pulsed current to the molten copper in the continuous casting chamber. Adjust the pulsed current parameters as follows: voltage 36V, current 500A, pulse frequency 5000Hz, and pulse waveform as a square wave. Simultaneously with the application of the pulsed current (i.e., at the start of energization), impurities undergo electromigration under the influence of the current, gradually accumulating in the molten copper around the positive and negative electrodes (i.e., around the two upper copper rods).

[0067] Step 5: After applying the pulsed current for 24 hours, the connecting copper rod is continuously drawn upwards via the upward drawing mechanism to remove the copper molten metal enriched with impurities from the upward drawing continuous casting furnace. The drawing rod speed is 380 mm / min, which is no greater than the drawing rod speed for normal production of oxygen-free copper rods in the same upward drawing continuous casting furnace (the normal drawing rod speed in this embodiment is 390 mm / min). During the upward drawing process, the copper molten metal rich in impurities enriched around the connecting copper rod is removed along with the connecting copper rod. The cooling water inlet temperature is 30℃, the outlet temperature is 42℃, and the inlet and outlet temperature difference is 12℃.

[0068] Samples of continuously produced oxygen-free copper rods were taken, and the oxygen content was determined using an oxygen analyzer. The impurity element content was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The test results showed that the oxygen content of the oxygen-free copper rods was 3 ppm, and the conductivity was 101.3% IACS. The quality grade of the copper rods met the TU1 standard.

[0069] Example 5 provides a method for purifying the molten metal in the upward continuous casting of oxygen-free copper rods based on pulsed current processing. The conductor is an independently traction mechanism for the upward-drawn copper rod, and the pulse is a DC pulse applied to the transition chamber of the upward continuous casting furnace. The specific steps are the same as in Example 4, and the specific parameters are shown in Table 1. The test results show that the oxygen content of the oxygen-free copper rod is 4 ppm, the conductivity is 101.1% IACS, and the quality grade of the copper rod meets the TU1 standard.

[0070] Example 6 provides a method for purifying the molten metal in the upward continuous casting of oxygen-free copper rods based on pulsed current processing. The conductor is a wired copper rod capable of being pulled upwards via the upward continuous casting process. The pulse is a DC pulse applied to the charging hopper of the upward continuous casting furnace. The specific steps are the same as in Example 4, and the specific parameters are shown in Table 1. The test results show that the oxygen content of the oxygen-free copper rod is 3 ppm, the conductivity is 101.2% IACS, and the quality grade of the copper rod meets the TU1 standard.

[0071] Example 7 provides a method for purifying the molten metal in the upward continuous casting of oxygen-free copper rods based on pulsed current processing. The conductor is a wired copper rod capable of being pulled upwards via the upward continuous casting process. The pulse is a DC pulse applied to the casting chamber of the upward continuous casting furnace. The specific steps are the same as in Example 4, and the specific parameters are shown in Table 1. The test results show that the oxygen content of the oxygen-free copper rod is 7 ppm, the conductivity is 101.3% IACS, and the quality grade of the copper rod meets the TU1 standard.

[0072] Example 8 provides a method for purifying the molten metal of an oxygen-free copper rod (25mm in diameter) used in upward continuous casting based on pulsed current processing. The conductor is a 20mm diameter copper rod capable of being pulled upwards via the upward continuous casting process. The pulse is a DC pulse applied to the casting chamber of the upward continuous casting furnace. This example differs from Example 4 only in the diameter of the produced oxygen-free copper rod, demonstrating the versatility of the method for different product specifications. The specific steps are the same as in Example 4, and the specific parameters are shown in Table 1. The test results show that the oxygen content of the oxygen-free copper rod is 3ppm, the conductivity is 101.1% IACS, and the quality grade of the copper rod meets the TU1 standard.

[0073] Comparative Example 1 was performed according to the pulsed current method for removing impurities from copper melt disclosed in the prior art. A graphite electrode was used to apply a pulsed current to enrich the impurities, but step four (impurity removal) was omitted. Testing revealed that the oxygen and Fe content of the oxygen-free copper rod were both higher than the TU1 grade standard, only reaching the TU2 grade standard. This indicates that if the enriched impurities are not removed promptly, the impurity removal effect of the pulsed current will significantly decrease over time. The remaining steps were the same as in Example 3, and the specific parameters are shown in Table 1. The test results showed that the oxygen content of the oxygen-free copper rod was 12 ppm, the conductivity was 100.9% IACS, and the quality grade of the copper rod reached the TU2 grade standard.

[0074] Table 1 shows the main parameters in Examples 1-8 and Comparative Example 1.

[0075] Comparing Comparative Example 1 with Examples 1-8 reveals that simply applying a pulsed current to enrich impurities without removing the copper melt in the enriched region can lead to impurities forming an enriched layer around the electrode, potentially hindering further current action. Furthermore, impurities in the enriched layer may diffuse back into the copper melt, resulting in unsatisfactory impurity removal. In contrast, this invention removes the impurity-enriched copper melt simultaneously with or after applying the pulsed current, maintaining continuous impurity removal efficiency and ultimately obtaining oxygen-free copper rods with higher purity.

[0076] Examples 9-13 demonstrate the production parameter range of TU1 grade oxygen-free copper rods obtained by using the same pulse current parameters (voltage 36V, current 500A, frequency 5000Hz) and the same wiring method of the copper rod as in Example 4, only changing the diameter of the copper rod and the oxygen-free copper rod (both have the same diameter), the corresponding lead rod speed, the corresponding inlet and outlet water temperatures, and the inlet and outlet water temperature difference. The parameters are shown in Table 2 below.

[0077] Table 2 shows the parameters for producing oxygen-free copper rods of different diameters in Examples 9-13.

[0078]

[0079] Structures, components, and connection methods not described in detail in this invention are all prior art known to those skilled in the art unless otherwise specified. It is obvious to those skilled in the art that this invention is not limited to the details of the above exemplary embodiments, and that the invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the invention. Therefore, the above embodiments should be regarded as exemplary and non-limiting in all respects. The scope of this invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within this invention.

Claims

1. A method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing, characterized in that, Includes the following steps: Step 1: Heat the copper in the upward continuous casting furnace to a molten state to obtain copper melt; Step 2: Insert at least two conductors independently into the molten copper. The conductors are graphite electrodes or copper rods that can be pulled upwards by the upward continuous casting process. Step 3: Insulate and fix the conductor so that it forms a current path only with the copper melt and the external pulse power supply; Step 4: Apply a pulsed current to the conductor to enrich impurities in the copper melt in the vicinity of the conductor; Step 5: Remove the copper melt rich in impurities around the conductor, and in the continuous casting chamber of the upward continuous casting furnace, draw the oxygen-free copper rod as the product upward through the upward continuous casting process. Wherein, when the conductor is the copper rod, the removal method in step five is: by pulling the copper rod upward, the impurities accumulated nearby are continuously carried out of the copper melt along with the copper rod; when the conductor is the graphite electrode, the removal method in step five is: using an insulating tool to periodically remove the copper melt around the graphite electrode.

2. The method for purifying the molten metal in the continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 1, characterized in that, In step four, the process parameters of the pulse current are: voltage 1.2~36V, current 1~500A, pulse frequency 1~5000Hz, and the pulse current application time is 5 minutes to 24 hours.

3. The method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 1, characterized in that, In step one, the temperature of the copper melt is 1140~1160℃.

4. The method for purifying the molten metal in the continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 1, characterized in that, The conductor is inserted into at least one area of ​​the charging bin, transition bin, or continuous casting bin of the upper drawing continuous casting furnace.

5. The method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 1, characterized in that, The oxygen-free copper rod has a lead-in speed of 280-2800 mm / min, a cooling water inlet temperature of 20-35℃, an outlet temperature of 26-51℃, and a cooling water inlet-outlet temperature difference of 6-16℃.

6. The method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 5, characterized in that, When the conductor is the connecting copper rod, the lead-in speed of the connecting copper rod is 280~2800mm / min, and when the diameter of the connecting copper rod and the oxygen-free copper rod are the same, the lead-in speed of the connecting copper rod is not greater than that of the oxygen-free copper rod.

7. The method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 6, characterized in that, When the diameter of the connecting copper rod and the oxygen-free copper rod is 8mm, the rod speed is 2000~2800mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 26~45℃, and the cooling water inlet and outlet temperature difference is 6~10℃. When the diameter of the connecting copper rod and the oxygen-free copper rod is 12.5mm, the rod speed is 680~720mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 26~45℃, and the cooling water inlet and outlet temperature difference is 6~10℃. When the diameter of the connecting copper rod and the oxygen-free copper rod is 16mm, the rod pulling speed is 460~500mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 27~49℃, and the cooling water inlet and outlet temperature difference is 7~14℃. When the diameter of the connecting copper rod and the oxygen-free copper rod is 20mm, the rod speed is 380~430mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 27~49℃, and the cooling water inlet and outlet temperature difference is 7~14℃. When the diameter of the connecting copper rod and the oxygen-free copper rod is 25mm, the rod pulling speed is 280~340mm / min, the cooling water inlet temperature is 20~35℃, the outlet temperature is 30~51℃, and the cooling water inlet and outlet temperature difference is 10~16℃.

8. The method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 1, characterized in that, In step five, the method for removing the copper melt enriched with impurities is as follows: when the conductor is a graphite electrode, the copper melt enriched with impurities around the conductor is removed every 10 to 120 minutes using an insulating tool.

9. The method for purifying the molten metal in continuous casting of oxygen-free copper rods based on pulsed current processing according to claim 1, characterized in that, When the conductor is a copper connecting rod, the contact area between the copper connecting rod and the traction mechanism is insulated.

10. The method for purifying the molten metal in the continuous casting of oxygen-free copper rods based on pulsed current processing according to any one of claims 1-9, characterized in that, The copper rod obtained by the method is a TU1 grade oxygen-free copper rod with an impurity content of less than 0.008% and an oxygen content of less than 10ppm.

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