A method for preparing oxygen-free copper

Abstract

This invention discloses a method for preparing oxygen-free copper, relating to the field of metallurgical technology, comprising the following steps: Step S1, raw material pretreatment; Step S2, gradient melting and deoxidation; Step S3, gradient refining; Step S4, directional solidification casting; Step S5, heat treatment. The oxygen-free copper prepared by this method exhibits good mechanical properties, excellent electrical conductivity and heat resistance, and low oxygen content.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for preparing oxygen-free copper. Background Technology

[0002] In the fields of electronics and high-end electrical appliances, oxygen-free copper is widely used due to its excellent electrical and thermal conductivity, as well as good processing performance. With technological advancements, the requirements for the purity and performance of oxygen-free copper are becoming increasingly stringent. While traditional methods for preparing oxygen-free copper can achieve low oxygen content, they suffer from problems such as poor production continuity, high energy consumption, and high equipment costs, making it difficult to meet the requirements of high-end applications.

[0003] Existing methods for preparing oxygen-free copper mainly include electrolytic refining and vacuum melting. While electrolytic refining can improve copper purity to some extent, the composition control of the electrolyte is complex during the process, and it easily introduces other impurities, making it difficult to further reduce the oxygen content of the final product. Vacuum melting involves melting copper in a vacuum environment to reduce oxygen intrusion. However, this method requires extremely high-end equipment, is difficult to control the vacuum level, and the molten copper is prone to reacting with crucibles and other containers during melting, introducing other impurities. Furthermore, vacuum melting is time-consuming and costly, hindering large-scale production. Other publicly available oxygen-free copper preparation methods also suffer from limitations, such as insufficient precision in oxygen content control, difficulty in producing high-purity, high-performance oxygen-free copper, low production efficiency, and high costs.

[0004] To address the aforementioned issues, Chinese invention patent CN114150179B discloses an oxygen-free copper material, an oxygen-free copper material product, and a method for preparing the same, comprising the following steps: 1) refining copper liquid; wherein the composition of the copper liquid satisfies: O ≤ 0.0005 wt%; P ≤ 0.001 wt%; Fe ≤ 0.001 wt%; S ≤ 0.001 wt%; the total content of Pb, As, Bi, Sb, Zn, Sn, and Ni ≤ 0.0001 wt%; 2) transferring the copper liquid to a casting furnace and adding a copper-rare earth master alloy, followed by casting to obtain the oxygen-free copper material; wherein the amount of the copper-rare earth master alloy added satisfies: the mass of rare earth is 0.01-0.02 wt% of the mass of the copper liquid; wherein the mass fraction of rare earth in the copper-rare earth master alloy is 15-25 wt%. However, the oxygen content of the oxygen-free copper prepared by this method needs to be further reduced, and its electrical conductivity, heat resistance, and mechanical properties still need to be further improved.

[0005] It is evident that developing a method for preparing oxygen-free copper with good mechanical properties, excellent electrical conductivity and heat resistance, and low oxygen content meets market demand, has broad market value and application prospects, and is of great significance for promoting the development of the oxygen-free copper field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing oxygen-free copper with good mechanical properties, excellent electrical conductivity and heat resistance, and low oxygen content.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing oxygen-free copper, comprising the following steps:

[0008] Step S1, Raw material pretreatment: Place the electrolytic copper raw material in a vacuum baking oven and preheat for 1-2 hours to remove adsorbed water and volatile impurities; after cooling to room temperature, sandblast the surface oxide layer, ultrasonically clean with ethanol, and then blow dry with nitrogen to obtain copper material;

[0009] Step S2, Gradient Melting and Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1200-1220℃ at a rate of 5-8℃ / min until completely melted. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 30-40 minutes, with argon gas introduced at a flow rate of 4-6 L / min during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a flow rate of 15-20 L / min intensifies deoxidation for 15-20 minutes. Finally, the material is transferred to a holding furnace at 1150-1200℃, and argon gas is introduced at a flow rate of 1-5 L / min. Perform deoxygenation again for 20-30 minutes;

[0010] Step S3, Gradient Refining Process: After deoxidation, add a composite refining agent to the copper liquid and refine at 1100-1150℃ for 10-15 minutes. Then add red phosphorus and refine at 1140-1160℃ for 8-12 minutes. Finally, cool down to 1090-1110℃, add phosphorus copper master alloy, and apply a pulsed magnetic field. Continue refining for 5-8 minutes, then remove the slag and filter using a ceramic filter.

[0011] Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 100-120 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots.

[0012] Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace and heat it to 450-550℃ at a heating rate of 3-5℃ / min under nitrogen protection. Hold it at this temperature for 1-3 hours and then cool it to room temperature with the furnace.

[0013] Preferably, the purity of the electrolytic copper raw material in step S1 is ≥99.99%.

[0014] Preferably, the preheating temperature in step S1 is 240-255℃, and the vacuum degree is 1×10⁻⁶. -3 Pa.

[0015] Preferably, the reducing gas in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17.

[0016] Preferably, the ultrasonic vibration system in step S2 has an amplitude of 14-16 μm, a frequency of 19.5-20.5 kHz, and a power of 1-3 kW.

[0017] Preferably, the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer in step S2 is 3:1:0.5.

[0018] Preferably, the amount of titanium magnesium zirconium deoxidizer added in step S2 is 0.05-0.07% of the mass of the copper material.

[0019] Preferably, the coating thickness of the composite deoxidizer in step S2 is 180-200 mm.

[0020] Preferably, the composite deoxidizer in step S2 comprises the following components in parts by weight: 85-90 parts calcined charcoal, 5-8 parts calcium fluoride, 3-5 parts calcium oxide, 1-2 parts boron oxide, and 1-3 parts calcium boride.

[0021] Preferably, the mass ratio of the composite refining agent, red phosphorus, phosphorus copper master alloy, and copper liquid in step S3 is (0.01-0.02):0.03:0.02:100.

[0022] Preferably, the mass percentage concentration of phosphorus in the phosphorus copper master alloy in step S3 is 10-15%.

[0023] Preferably, the composite refining agent in step S3 comprises the following components in parts by weight: 2-4 parts of mixed rare earth, 0.3-0.6 parts of boron powder, 0.1-0.3 parts of magnesium, and 4-6 parts of calcium fluoride.

[0024] Preferably, the mixed rare earth is neodymium, yttrium, cerium and lanthanum mixed in a mass ratio of (5-8):(2-4):(1-3):(3-5).

[0025] Preferably, the magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%.

[0026] Preferably, in step S4, the upper temperature of the gradient cooling zone is 1180°C and the lower temperature is 1050°C; the cooling rate is maintained at 15-20°C / min.

[0027] Preferably, the crystallizer material of the downward continuous casting machine in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.28-0.35MPa, and the cooling water flow rate is 9-11m³ / h.

[0028] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0029] (1) The method for preparing oxygen-free copper disclosed in this invention has a short process flow, fast speed, low energy consumption, low dependence on equipment, high preparation efficiency and yield, and is suitable for continuous large-scale production. It has high promotion and application value.

[0030] (2) The method for preparing oxygen-free copper disclosed in this invention adopts a gradient-stage melting and deoxidation process, which can not only effectively remove dissolved oxygen, but also selectively remove interstitial oxygen, resulting in a significant reduction in the oxygen content of the oxygen-free copper product, thereby effectively improving the mechanical properties, electrical conductivity and heat resistance of the product; the ultrasonic cavitation effect and the gas flotation principle are introduced into the preparation of oxygen-free copper to form a "sound-gas-solid" three-phase synergistic deoxidation mechanism. The periodic pressure changes generated by ultrasound in the copper liquid will cause microcracks on the surface of nanoscale oxide inclusions, exposing active sites and promoting the adsorption reaction of deoxidizing elements. At the same time, the local high temperature generated when the cavitation bubble collapses will reduce the oxides on the inclusion surface, and the released oxygen atoms will form stable compounds with the deoxidizer; argon bubbles, as the carrier for capturing inclusions, will drive the movement of inclusions due to the wake effect generated during their ascent, while the acoustic flow effect of ultrasound can enhance the collision probability between inclusions and bubbles, thereby further reducing the oxygen content. The active components in the titanium magnesium zirconium deoxidizer have a strong affinity for oxygen and can react rapidly with oxygen in the copper liquid to generate Stable oxides such as MgO and ZrO are used. These oxides have low density and easily float to the surface of the molten copper, thus being removed. By precisely controlling the amount of deoxidizer added, as well as the deoxidation temperature and time, precise control of the oxygen content is achieved, resulting in a significant reduction in the oxygen content of oxygen-free copper. A reducing gas atmosphere is used to penetrate the interior of the melt at high temperatures, directly reducing dissolved oxygen and further lowering the oxygen content.

[0031] (3) The method for preparing oxygen-free copper disclosed in this invention comprises the following components by weight: 85-90 parts calcined charcoal, 5-8 parts calcium fluoride, 3-5 parts calcium oxide, 1-2 parts boron oxide, and 1-3 parts calcium boride. By rationally selecting the above components, the oxygen content of the product can be further reduced. Combined with other process parameters, this results in oxygen-free copper products with good mechanical properties, excellent electrical conductivity, and superior heat resistance.

[0032] (4) The method for preparing oxygen-free copper disclosed in this invention employs a gradient refining process. The composite refining agent comprises the following components by weight: 2-4 parts of mixed rare earth elements, 0.3-0.6 parts of boron powder, 0.1-0.3 parts of magnesium, and 4-6 parts of calcium fluoride. Through the synergistic effect of the components of the refining agent, further deoxidation and impurity removal can be achieved, improving the microstructure and properties, which is beneficial to improving product quality. The pulsed magnetic field synergistically enhances the efficiency of inclusion removal; through the reasonable selection of various parameters in the gradient refining process, both oxygen content and total impurity content can be reduced; and electrical conductivity and mechanical properties are synergistically optimized.

[0033] (5) The method for preparing oxygen-free copper disclosed in this invention adopts a directional solidification casting process, which can effectively improve the electrical conductivity, mechanical properties and high temperature stability of the product. Detailed Implementation

[0034] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. Example 1

[0035] A method for preparing oxygen-free copper includes the following steps:

[0036] Step S1, Raw material pretreatment: The electrolytic copper raw material is placed in a vacuum baking furnace and preheated for 1 hour to remove adsorbed water and volatile impurities; after being taken out and cooled to room temperature, the surface oxide layer is sandblasted, ultrasonically cleaned with ethanol, and then dried with nitrogen to obtain copper material;

[0037] Step S2, Gradient Melting Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1200℃ at a rate of 5℃ / min to melt. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 30 minutes, with argon gas at a flow rate of 4L / min being introduced during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a flow rate of 15L / min is used to enhance deoxidation for 15 minutes. Finally, the material is transferred to a holding furnace at 1150℃, and CO2 at a flow rate of 1L / min is introduced for further deoxidation for 20 minutes.

[0038] Step S3, Gradient refining treatment: After deoxidation, add composite refining agent to copper liquid and refine at 1100℃ for 10 minutes. Then add red phosphorus and refine at 1140℃ for 8 minutes. Finally, cool down to 1090℃, add phosphorus copper master alloy, and apply pulsed magnetic field at the same time. Continue refining for 5 minutes, then remove slag and filter with a ceramic filter.

[0039] Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 100 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots.

[0040] Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace, heat it to 450°C at a heating rate of 3°C / min under nitrogen protection, hold it at that temperature for 1 hour, and then cool it to room temperature with the furnace.

[0041] The purity of the electrolytic copper raw material mentioned in step S1 is ≥99.99%; the preheating temperature mentioned in step S1 is 240℃, and the vacuum degree is 1×10⁻⁶. -3 Pa; the reducing gas in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17; the amplitude of the ultrasonic vibration system in step S2 is 14 μm, the frequency is 19.5 kHz, and the power is 1 kW; the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer in step S2 is 3:1:0.5; the amount of titanium-magnesium-zirconium deoxidizer added in step S2 is 0.05% of the mass of copper material; the coverage thickness of the composite deoxidizer in step S2 is 180 mm.

[0042] The composite deoxidizer in step S2 comprises the following components by weight: 85 parts calcined charcoal, 5 parts calcium fluoride, 3 parts calcium oxide, 1 part boron oxide, and 1 part calcium boride; the mass ratio of the composite refining agent, red phosphorus, phosphorus-copper master alloy, and copper liquid in step S3 is 0.01:0.03:0.02:100; the phosphorus concentration in the phosphorus-copper master alloy in step S3 is 10% by weight; the composite refining agent in step S3 comprises the following components by weight... The following components are present in parts by weight: 2 parts mixed rare earth, 0.3 parts boron powder, 0.1 parts magnesium, and 4 parts calcium fluoride; the mixed rare earth is neodymium, yttrium, cerium, and lanthanum mixed in a mass ratio of 5:2:1:3; the magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%; the upper temperature of the gradient cooling zone in step S4 is 1180℃, and the lower temperature is 1050℃; the cooling rate is maintained at 15℃ / min.

[0043] The crystallizer material of the continuous casting machine described in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.28MPa, and the cooling water flow rate is 9m³ / h. Example 2

[0044] A method for preparing oxygen-free copper includes the following steps:

[0045] Step S1, Raw material pretreatment: The electrolytic copper raw material is placed in a vacuum baking furnace and preheated for 1.2 hours to remove adsorbed water and volatile impurities; after being taken out and cooled to room temperature, the surface oxide layer is sandblasted, ultrasonically cleaned with ethanol, and then dried with nitrogen to obtain copper material;

[0046] Step S2, Gradient Melting and Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1205℃ at a rate of 6℃ / min for melting. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 33 minutes, with argon gas flowing through at a rate of 4.5 L / min during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a rate of 16 L / min is used for enhanced deoxidation for 17 minutes. Finally, the material is transferred to a holding furnace at 1170℃, and argon gas is introduced at a rate of 2 L / min. Perform deoxygenation again for 23 minutes;

[0047] Step S3, Gradient refining treatment: After deoxidation, add composite refining agent to copper liquid and refine at 1120℃ for 12 minutes. Then add red phosphorus and refine at 1145℃ for 9 minutes. Finally, cool down to 1095℃, add phosphorus copper master alloy, and apply pulsed magnetic field at the same time. Continue refining for 6 minutes, then remove slag and filter with a ceramic filter.

[0048] Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 105 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots.

[0049] Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace, heat it to 480°C at a heating rate of 3.5°C / min under nitrogen protection, hold it at that temperature for 1.5 hours, and then cool it to room temperature with the furnace.

[0050] The purity of the electrolytic copper raw material mentioned in step S1 is ≥99.99%; the preheating temperature in step S1 is 245℃, and the vacuum degree is 1×10⁻⁶. -3 Pa; the reducing gas in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17; the amplitude of the ultrasonic vibration system in step S2 is 14.5 μm, the frequency is 20 kHz, and the power is 1.5 kW; the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer in step S2 is 3:1:0.5; the amount of titanium-magnesium-zirconium deoxidizer added in step S2 is 0.055% of the copper material mass; the coverage thickness of the composite deoxidizer in step S2 is 185 mm; the composite deoxidizer in step S2 includes the following components by weight: 87 parts calcined charcoal, 6 parts calcium fluoride, 3.5 parts calcium oxide, 1.2 parts boron oxide, and 1.5 parts calcium boride; the mass ratio of the composite refining agent, red phosphorus, phosphorus copper master alloy, and copper liquid in step S3 is 0.013:0.03:0.02:100.

[0051] In step S3, the phosphorus concentration in the phosphorus-copper master alloy is 12% by mass. The composite refining agent in step S3 comprises the following components by weight: 2.5 parts mixed rare earth, 0.4 parts boron powder, 0.15 parts magnesium, and 4.5 parts calcium fluoride. The mixed rare earth is a mixture of neodymium, yttrium, cerium, and lanthanum in a mass ratio of 6:2.5:1.5:3.5. The magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%. In step S4, the upper temperature of the gradient cooling zone is 1180℃, and the lower temperature is 1050℃; the cooling rate is maintained at 17℃ / min. The crystallizer material of the downward-drawing continuous casting machine in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.3MPa, and the cooling water flow rate is 9.5m³ / h. Example 3

[0052] A method for preparing oxygen-free copper includes the following steps:

[0053] Step S1, Raw material pretreatment: The electrolytic copper raw material is placed in a vacuum baking furnace and preheated for 1.5 hours to remove adsorbed water and volatile impurities; after being taken out and cooled to room temperature, the surface oxide layer is sandblasted, ultrasonically cleaned with ethanol, and then dried with nitrogen to obtain copper material;

[0054] Step S2, Gradient Melting and Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1210℃ at a rate of 6.5℃ / min for melting. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 35 minutes, with argon gas flowing through at a rate of 5 L / min during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a rate of 18 L / min is used for enhanced deoxidation for 18 minutes. Finally, the material is transferred to a holding furnace at 1180℃, and argon gas at a rate of 3 L / min is introduced. Perform deoxygenation again for 25 minutes;

[0055] Step S3, Gradient refining treatment: After deoxidation, add composite refining agent to copper liquid and refine at 1130℃ for 13 minutes. Then add red phosphorus and refine at 1150℃ for 10 minutes. Finally, cool down to 1100℃, add phosphorus copper master alloy, and apply pulsed magnetic field at the same time. Continue refining for 6.5 minutes, then remove slag and filter with a ceramic filter.

[0056] Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 110 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots.

[0057] Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace, heat it to 500°C at a heating rate of 4°C / min under nitrogen protection, hold it at that temperature for 2 hours, and then cool it to room temperature with the furnace.

[0058] The purity of the electrolytic copper raw material mentioned in step S1 is ≥99.99%; the preheating temperature mentioned in step S1 is 249℃, and the vacuum degree is 1×10⁻⁶. -3 Pa; the reducing gas in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17; the amplitude of the ultrasonic vibration system in step S2 is 15 μm, the frequency is 20 kHz, and the power is 2 kW; the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer in step S2 is 3:1:0.5; the amount of titanium-magnesium-zirconium deoxidizer added in step S2 is 0.06% of the copper material mass; the coverage thickness of the composite deoxidizer in step S2 is 190 mm; the composite deoxidizer in step S2 includes the following components by weight: 88 parts calcined charcoal, 6.5 parts calcium fluoride, 4 parts calcium oxide, 1.5 parts boron oxide, and 2 parts calcium boride.

[0059] In step S3, the mass ratio of the composite refining agent, red phosphorus, phosphorus-copper master alloy, and molten copper is 0.015:0.03:0.02:100; the phosphorus mass percentage concentration in the phosphorus-copper master alloy in step S3 is 13%; the composite refining agent in step S3 comprises the following components by weight: 3 parts mixed rare earth, 0.45 parts boron powder, 0.2 parts magnesium, and 5 parts calcium fluoride; the mixed rare earth is neodymium, yttrium, cerium, and lanthanum in a mass ratio of 6.5. The mixture is composed of 3:2:4; the magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%; the upper temperature of the gradient cooling zone in step S4 is 1180℃, and the lower temperature is 1050℃; the cooling rate is maintained at 18℃ / min; the crystallizer material of the downward continuous casting machine in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.32MPa, and the cooling water flow rate is 10m³ / h. Example 4

[0060] A method for preparing oxygen-free copper includes the following steps:

[0061] Step S1, Raw material pretreatment: The electrolytic copper raw material is placed in a vacuum baking furnace and preheated for 1.8 hours to remove adsorbed water and volatile impurities; after being taken out and cooled to room temperature, the surface oxide layer is sandblasted, ultrasonically cleaned with ethanol, and then dried with nitrogen to obtain copper material;

[0062] Step S2, Gradient Melting and Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1215℃ at a rate of 7.5℃ / min until completely melted. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 38 minutes, with argon gas flowing through at a rate of 5.5 L / min during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a rate of 19 L / min intensifies the deoxidation for 19 minutes. Finally, the material is transferred to a holding furnace at 1190℃, and argon gas at a rate of 4 L / min is introduced. Perform deoxygenation again for 28 minutes;

[0063] Step S3, Gradient refining treatment: After deoxidation, a composite refining agent is added to the copper liquid and refined at 1140℃ for 14 minutes. Then, red phosphorus is added and refined at 1155℃ for 11 minutes. Finally, the temperature is lowered to 1105℃, phosphorus copper master alloy is added, and a pulsed magnetic field is applied. The refining continues for 7.5 minutes, after which the slag is removed and filtered using a ceramic filter.

[0064] Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 115 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots.

[0065] Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace, heat it to 540°C at a heating rate of 4.5°C / min under nitrogen protection, hold it at that temperature for 2.5 hours, and then cool it to room temperature with the furnace.

[0066] The purity of the electrolytic copper raw material mentioned in step S1 is ≥99.99%; the preheating temperature mentioned in step S1 is 253℃, and the vacuum degree is 1×10⁻⁶. -3 Pa; the reducing gas in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17; the amplitude of the ultrasonic vibration system in step S2 is 15.5 μm, the frequency is 20.5 kHz, and the power is 2.5 kW; the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer in step S2 is 3:1:0.5; the amount of titanium-magnesium-zirconium deoxidizer added in step S2 is 0.065% of the copper material mass; the coverage thickness of the composite deoxidizer in step S2 is 195 mm; the composite deoxidizer in step S2 includes the following components in parts by weight: 89 parts calcined charcoal, 7.5 parts calcium fluoride, 4.5 parts calcium oxide, 1.8 parts boron oxide, and 2.5 parts calcium boride.

[0067] In step S3, the mass ratio of the composite refining agent, red phosphorus, phosphorus-copper master alloy, and molten copper is 0.018:0.03:0.02:100; the phosphorus mass percentage concentration in the phosphorus-copper master alloy in step S3 is 14%; the composite refining agent in step S3 comprises the following components by weight: 3.5 parts mixed rare earth, 0.55 parts boron powder, 0.25 parts magnesium, and 5.5 parts calcium fluoride; the mixed rare earth is neodymium, yttrium, cerium, and lanthanum in a mass ratio of 7.5: The mixture is composed of 3.5:2.5:4.5; the magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%; the upper temperature of the gradient cooling zone in step S4 is 1180℃, and the lower temperature is 1050℃; the cooling rate is maintained at 19℃ / min; the crystallizer material of the downward continuous casting machine in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.33MPa, and the cooling water flow rate is 10.5m³ / h. Example 5

[0068] A method for preparing oxygen-free copper includes the following steps:

[0069] Step S1, Raw material pretreatment: The electrolytic copper raw material is placed in a vacuum baking furnace and preheated for 2 hours to remove adsorbed water and volatile impurities; after being taken out and cooled to room temperature, the surface oxide layer is sandblasted, ultrasonically cleaned with ethanol, and then dried with nitrogen to obtain copper material;

[0070] Step S2, Gradient Melting Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1220℃ at a rate of 8℃ / min to melt. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 40 minutes, with argon gas at a flow rate of 6L / min being introduced during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a flow rate of 20L / min is used to enhance deoxidation for 20 minutes. Finally, the material is transferred to a holding furnace at 1200℃, and CO2 at a flow rate of 5L / min is introduced for further deoxidation for 30 minutes.

[0071] Step S3, Gradient refining treatment: After deoxidation, add composite refining agent to copper liquid and refine at 1150℃ for 15 minutes. Then add red phosphorus and refine at 1160℃ for 12 minutes. Finally, cool down to 1110℃, add phosphorus copper master alloy, and apply pulsed magnetic field at the same time. Continue refining for 8 minutes, then remove slag and filter with a ceramic filter.

[0072] Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 120 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots.

[0073] Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace, heat it to 550°C at a heating rate of 5°C / min under nitrogen protection, hold it at that temperature for 3 hours, and then cool it to room temperature with the furnace.

[0074] The purity of the electrolytic copper raw material mentioned in step S1 is ≥99.99%; the preheating temperature mentioned in step S1 is 255℃, and the vacuum degree is 1×10⁻⁶. -3 Pa; the reducing gas in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17; the amplitude of the ultrasonic vibration system in step S2 is 16 μm, the frequency is 20.5 kHz, and the power is 3 kW; the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer in step S2 is 3:1:0.5; the amount of titanium-magnesium-zirconium deoxidizer added in step S2 is 0.07% of the copper material mass; the coverage thickness of the composite deoxidizer in step S2 is 200 mm; the composite deoxidizer in step S2 includes the following components in parts by weight: 90 parts calcined charcoal, 8 parts calcium fluoride, 5 parts calcium oxide, 2 parts boron oxide, and 3 parts calcium boride.

[0075] In step S3, the mass ratio of the composite refining agent, red phosphorus, phosphorus copper master alloy, and copper liquid is 0.02:0.03:0.02:100; the mass percentage concentration of phosphorus in the phosphorus copper master alloy in step S3 is 15%; the composite refining agent in step S3 includes the following components by weight: 4 parts mixed rare earth, 0.6 parts boron powder, 0.3 parts magnesium, and 6 parts calcium fluoride; the mixed rare earth is neodymium, yttrium, cerium, and lanthanum mixed in a mass ratio of 8:4:3:5; the magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%; the upper temperature of the gradient cooling zone in step S4 is 1180℃, and the lower temperature is 1050℃; the cooling rate is maintained at 20℃ / min; the crystallizer material of the downward continuous casting machine in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.35MPa, and the cooling water flow rate is 11m³ / h.

[0076] Comparative Example 1

[0077] This example provides a method for preparing oxygen-free copper, which is basically the same as that in Example 1. The difference is that the ultrasonic vibration system is not started in step S2; boron oxide is replaced with an equal amount of calcined charcoal; and mixed rare earth elements are replaced with an equal amount of cerium.

[0078] Comparative Example 2

[0079] This example provides a method for preparing oxygen-free copper, which is basically the same as that in Example 1, except that a pulsed magnetic field is not applied in step S3; an equal amount of calcined charcoal is used instead of calcium boride; and an equal amount of lanthanum is used instead of mixed rare earth elements.

[0080] To further illustrate the beneficial technical effects of the oxygen-free copper preparation methods involved in the various embodiments of the present invention, the oxygen-free copper prepared by the methods involved in Examples 1-5 and Comparative Examples 1-2 was subjected to compositional analysis and related performance tests. The test results are shown in Table 1, and the test methods are as follows:

[0081] (1) Oxygen content detection: Oxygen was measured by infrared absorption method, referring to GB / T 5121.8-2008 Chemical analysis methods for copper and copper alloys, part 8: Determination of oxygen content;

[0082] (2) Conductivity: Refer to GB / T 351-2019 and use the four-probe method for testing at a test temperature of 20±0.5℃.

[0083] (3) Heat resistance: After each sample was subjected to continuous high temperature treatment at 900℃ for 60 minutes, the change in average grain size before and after the continuous high temperature treatment was calculated and compared. The heat resistance was measured by the growth rate of average grain size. The larger the value, the worse the heat resistance.

[0084] (4) Tensile strength: Tensile test shall be conducted in accordance with GB / T 228.1-2021.

[0085] Table 1

[0086]

[0087] As can be seen from Table 1, the oxygen-free copper prepared by the methods of the embodiments of the present invention has higher mechanical properties, heat resistance and electrical conductivity than the comparative product, and has a lower oxygen content. The combined use of ultrasonic vibration system, pulse magnetic field, boron oxide, mixed rare earth and calcium boride is beneficial to improving the above properties.

[0088] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing oxygen-free copper, characterized in that, Includes the following steps: Step S1, Raw material pretreatment: Place the electrolytic copper raw material in a vacuum baking oven and preheat for 1-2 hours to remove adsorbed water and volatile impurities; after cooling to room temperature, sandblast the surface oxide layer, ultrasonically clean with ethanol, and then blow dry with nitrogen to obtain copper material; Step S2, Gradient Melting Deoxidation: In a reducing gas atmosphere, copper material is added to a graphite crucible and heated to 1200-1220℃ at a rate of 5-8℃ / min to melt. After complete melting, the ultrasonic vibration system is started, and titanium-magnesium-zirconium deoxidizer is added simultaneously. Ultrasonic vibration deoxidation is performed for 30-40 minutes, with argon gas flowing through at a rate of 4-6 L / min during the vibration process. Then, a composite deoxidizer is applied, and bottom-blowing with argon gas at a rate of 15-20 L / min is used for enhanced deoxidation for 15-20 minutes. Finally, the material is transferred to a holding furnace at 1150-1200℃, and CO2 is introduced at a rate of 1-5 L / min for further deoxidation for 20-30 minutes. The composite deoxidizer comprises the following components by weight: 85-90 parts calcined charcoal, 5-8 parts calcium fluoride, 3-5 parts calcium oxide, 1-2 parts boron oxide, and 1-3 parts calcium boride. Step S3, Gradient Refining Process: After deoxidation, a composite refining agent is added to the copper liquid, and the mixture is refined at 1100-1150℃ for 10-15 minutes. Then, red phosphorus is added, and the mixture is refined at 1140-1160℃ for 8-12 minutes. Finally, the temperature is lowered to 1090-1110℃, a phosphorus copper intermediate alloy is added, and a pulsed magnetic field is applied. The mixture is then refined for another 5-8 minutes, after which the slag is removed and the mixture is filtered using a ceramic filter. The composite refining agent comprises the following components by weight: 2-4 parts of mixed rare earth, 0.3-0.6 parts of boron powder, 0.1-0.3 parts of magnesium, and 4-6 parts of calcium fluoride. The mixed rare earth is neodymium, yttrium, cerium, and lanthanum mixed in a mass ratio of (5-8):(2-4):(1-3):(3-5). Step S4, Directional solidification casting: Directional solidification casting is carried out using a bottom-feed continuous casting machine. The copper liquid passes through the water-cooled copper mold at a speed of 100-120 mm / min. A gradient cooling zone is set inside the mold to achieve directional growth of columnar crystals and obtain oxygen-free copper ingots. Step S5, Heat treatment: Place the oxygen-free copper ingot into an annealing furnace and heat it to 450-550℃ at a heating rate of 3-5℃ / min under nitrogen protection. Hold it at this temperature for 1-3 hours and then cool it to room temperature with the furnace.

2. The method for preparing oxygen-free copper according to claim 1, characterized in that, The purity of the electrolytic copper raw material mentioned in step S1 is ≥99.99%; the preheating temperature mentioned in step S1 is 240-255℃, and the vacuum degree is 1×10⁻⁶. -3 Pa.

3. The method for preparing oxygen-free copper according to claim 1, characterized in that, The reducing gas mentioned in step S2 is a mixture of carbon monoxide and argon in a volume ratio of 3:17; the amplitude of the ultrasonic vibration system mentioned in step S2 is 14-16 μm, the frequency is 19.5-20.5 kHz, and the power is 1-3 kW.

4. The method for preparing oxygen-free copper according to claim 1, characterized in that, In step S2, the mass ratio of Ti, Mg, and Zr in the titanium-magnesium-zirconium deoxidizer is 3:1:0.5; the amount of titanium-magnesium-zirconium deoxidizer added in step S2 is 0.05-0.07% of the mass of the copper material.

5. The method for preparing oxygen-free copper according to claim 1, characterized in that, The composite deoxidizer described in step S2 has a coverage thickness of 180-200 mm.

6. The method for preparing oxygen-free copper according to claim 1, characterized in that, The mass ratio of the composite refining agent, red phosphorus, phosphorus copper master alloy, and copper liquid in step S3 is (0.01-0.02):0.03:0.02:100; the mass percentage concentration of phosphorus in the phosphorus copper master alloy in step S3 is 10-15%.

7. The method for preparing oxygen-free copper according to claim 1, characterized in that, The magnetic field strength of the pulsed magnetic field in step S3 is 5T, the pulse frequency is 10Hz, and the duty cycle is 60%.

8. The method for preparing oxygen-free copper according to claim 1, characterized in that, In step S4, the upper temperature of the gradient cooling zone is 1180℃ and the lower temperature is 1050℃; the cooling rate is maintained at 15-20℃ / min; the crystallizer material of the downward continuous casting machine in step S4 is a water-cooled copper mold, the crystallizer water pressure is 0.28-0.35MPa, and the cooling water flow rate is 9-11m³ / h.

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