A process for producing high-purity oxygen-free copper rod by upward drawing

Abstract

The application provides a production process of high-purity oxygen-free copper rod by upward drawing method, comprising the following steps: (1) raw material pretreatment; (2) gradient smelting impurity removal; (3) oxygen removal of molten copper liquid; (4) transfer and filtration of deoxidized copper liquid; and (5) upward drawing casting. The process realizes the unity of high purity and excellent mechanical properties, and the core lies in the synergistic effect of multi-stage oxygen removal mechanism and precise physical isolation, so that lattice oxygen is completely removed and impurities are zero residual.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of copper-based conductor material manufacturing, and particularly relates to a high-purity oxygen-free copper rod production process by upward drawing method. BACKGROUND

[0002] The high-purity oxygen-free copper rod is a key basic material for modern power transmission systems and precision electronic devices. Such copper rods are mainly used in core scenarios such as transformer coils, conductive bridge arms of vacuum circuit breakers, and electromagnetic cavities of particle accelerators. In actual applications, two key characteristics must be possessed, namely, the oxygen content is lower than 10 ppm to prevent high-temperature hydrogen embrittlement fracture, and the electrical conductivity is higher than 100% IACS to reduce current transmission loss. However, the current market products have serious application defects. First, the grain boundary oxidation embrittlement problem, the oxygen content of the copper rod produced by the conventional continuous casting process generally reaches 15-30 ppm, and the copper oxide phase formed at the grain boundary under high-temperature working environment will cause the ductility of the material to decrease by more than 40%. Second, the electrical conductivity performance decay phenomenon, the widely used phosphorus copper deoxidization process will leave more than 0.02% of phosphorus elements, which will reduce the electron mobility by more than 5%. More seriously, the broken rod failure risk, the micron-sized aluminum oxide inclusions formed in the smelting process will block the flow channel of the graphite crystallizer during upward drawing and casting, directly causing the production line to break.

[0003] In view of the above problems, the prior art proposes a variety of solutions. The first solution adopts gas protection smelting technology, argon gas is filled into the smelting furnace to isolate oxygen, this method is found in a certain Chinese patent document. But the actual application shows that the argon gas is difficult to effectively remove the dissolved oxygen absorbed at the bottom of the molten pool because its density is greater than that of the deoxidizing bubbles floating inside the liquid copper, and the oxygen residual amount of the final product is still at the level of 8 ppm. The second solution uses carbon-based materials to cover the surface of the copper liquid, for example, the calcined petroleum coke covering layer proposed in a certain Japanese patent, which is easy to cause the carbon element to be supersaturated and generate hard copper carbide particles in the continuous high-temperature environment, eventually causing surface cracking during cold bending processing of the copper rod. The third solution attempts to use composite deoxidizer technology, although the calcium boron alloy deoxidizer disclosed in a certain American patent can reduce the oxygen content, but the volatilized calcium vapor will seriously pollute the graphite inner wall of the crystallizer, which shortens the service life of the equipment to one third of the normal period.

[0004] There are still three core problems to be solved in the prior art: first, the secondary oxidation in the melt transfer link, when the copper liquid is transferred from the smelting furnace to the holding furnace, it contacts air, and the oxygen content of its surface layer increases by 3 ppm per minute. Second, the deoxidization efficiency is insufficient, the traditional deoxidizer can only remove the dissolved oxygen but cannot remove the interstitial oxygen inside the crystal lattice, and the actual deoxidization efficiency is less than 82%. Therefore, a high-purity oxygen-free copper rod production process by upward drawing method needs to be designed. SUMMARY

[0005] In order to overcome the defects in the prior art, a high-purity oxygen-free copper rod production process by upward drawing method is provided.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A high-purity oxygen-free copper rod production process by upward drawing method, the production process comprises the following sequential steps:

[0008] (1) Raw material pretreatment: the 99.99% purity electrolytic copper plate is subjected to sand blasting treatment and drying treatment to obtain a pretreated copper plate;

[0009] (2) Gradient smelting and impurity removal: the aforementioned pretreated copper plate is used as raw material for smelting treatment to obtain molten copper liquid with dissolved oxygen content ≤18 ppm;

[0010] (3) Oxygen removal of molten copper liquid: a compound oxygen barrier layer is laid on the surface of the molten copper liquid and a composite deoxidizing agent is added to the molten copper liquid, and the molten copper liquid is stirred at 95-105 rpm for 85-95 minutes to obtain deoxidized copper liquid with lattice oxygen ≤2.5 ppm;

[0011] (4) Transfer and filtration of deoxidized copper liquid: the deoxidized copper liquid is transferred to a holding furnace through a sealed channel, and then impurities are removed through a step-by-step filtration device to obtain clean copper liquid;

[0012] (5) Upward drawing casting: the clean copper liquid is upward drawn and cast in a crystallizer to produce a cast rod blank.

[0013] The specific steps in the raw material pretreatment are: the 99.99% purity electrolytic copper plate is subjected to sand blasting treatment to a surface roughness Ra ≤1.6 μm, and then dried in a 180-190 ℃ drying furnace for 2.0-2.2 hours to obtain a copper base material with water content ≤40 ppm.

[0014] The smelting treatment is carried out in an induction smelting furnace, and the specific parameters are: the temperature rise rate is controlled to 10-12 ℃ / min to a smelting temperature of 1220-1235 ℃, and the temperature is maintained for 33-37 minutes at a working voltage of 400-410 V, while high-purity nitrogen gas containing 0.5-0.8% hydrogen gas and having an oxygen content ≤0.3 ppm is introduced from the bottom of the furnace, and the gas flow is maintained at 0.8-1.0 cubic meters per hour, finally producing molten copper liquid with dissolved oxygen content ≤18 ppm.

[0015] The compound oxygen barrier layer comprises a lower layer of 6-8 cm thick calcined coconut shell carbon mixed with calcium fluoride and an upper layer of 3-5 cm thick flaky graphite, and the compound oxygen barrier layer forms an oxygen diffusion coefficient ≤1×10 -9 cm² / s oxygen barrier system;

[0016] The mass ratio of the calcined coconut shell carbon to the calcium fluoride in the mixture is (88-92):10.

[0017] The preparation method of the calcined coconut shell carbon is as follows: coconut shell with a particle size of 3-5 mm is calcined in argon at 1300-1350 ℃ for 4.5-5.5 hours, then soaked in a 10-12 wt% oxalic acid solution at a temperature of 40-45 ℃ for 1.5-2.0 hours, and then washed with water until the pH value is 6.5-7.0, to obtain the calcined coconut shell carbon with an ash content ≤0.02%.

[0018] The composite deoxidizer comprises, in mass parts, 50-54 parts of activated lanthanum powder, 26-30 parts of calcium fluoride, and 18-20 parts of lithium borate, and the addition amount of the composite deoxidizer is 0.09-0.11% of the mass of the molten copper.

[0019] The preparation method of the activated lanthanum powder is as follows: 99.52 wt% crude lanthanum ingot is heated to 650-680 ℃ in an atmosphere with a volume ratio of Ar to H2 being 95:5 for 30-40 minutes, and finally water-atomized to obtain a 200-300 mesh powder, which is the activated lanthanum powder, and the surface oxide layer of the activated lanthanum powder is ≤10 nm.

[0020] The sealed channel is a double-layer gas curtain channel transferred to a holding furnace at 1145-1165 ℃, and the double-layer gas curtain channel is divided into an inner layer and an outer layer, wherein the inner layer is -5 to -10 Pa nitrogen and the outer layer is 1.0-1.2 MPa nitrogen, and the oxygen increase during the transfer process is ≤0.2 ppm.

[0021] The specific steps for removing inclusions by the stepped filtering device are as follows: the deoxidized copper liquid after transfer flows through a silicon carbide foam ceramic filter layer with a pore size of 50-60 μm and a zirconia filter plate with a titanium nitride plated surface and a pore size of 20-30 μm in sequence, to obtain clean copper liquid with inclusions ≤15 pieces / 100 mm 2 .

[0022] The surface of the zirconia filter plate is covered with a titanium nitride plating layer, and the titanium nitride plating layer is formed by a physical vapor deposition process, and after deposition, the titanium nitride plating layer is vacuum annealed at 1100-1150 ℃ for 0.5-1 hour, the thickness of the titanium nitride plating layer is 0.8-1.2 μm, and the Vickers hardness is ≥1800 HV.

[0023] The specific steps and parameters of the up-drawing casting are as follows: clean copper liquid is added into the crystallizer, and the cooling water partition temperature / flow rate is set, wherein the upper section is 22-25 DEG C / 0.3-0.5 m / s, the middle section is 28-32 DEG C / 1.2-1.5 m / s, the lower section is 38-42 DEG C / 0.8-1.0 m / s, the pulling speed is 2.8-3.2 m / min, and the output diameter of the cast rod blank is 8.0+ / -0.1 mm.

[0024] Compared with the prior art, the application has the advantages and beneficial effects that:

[0025] 1. In the raw material pretreatment stage of the present application, we effectively reduce the surface roughness and moisture content of the copper base material through sand blasting and drying treatment. This greatly reduces the risk of oxidation of electrolytic copper plates in the subsequent smelting process, because lower roughness and moisture mean that the initial cleanliness of the material before smelting is high, and the amount of impurities is low, thereby reducing the possibility of impurity oxidation after smelting.

[0026] 2. In the gradient smelting and impurity removal part of the present application, the inductive smelting furnace is combined with the control of reducing atmosphere to deeply remove dissolved oxygen. By controlling the heating rate and smelting temperature, and keeping the temperature at a specific working voltage, we ensure uniform heat distribution inside the copper liquid; at the same time, high-purity nitrogen gas with a small amount of hydrogen is introduced, and this atmosphere promotes the reduction reaction, efficiently removes the oxide particles in the molten copper liquid, and reaches an extremely low oxygen content level, avoiding the formation of large molecular compounds by impurities at high temperature.

[0027] 3. In the process of removing oxygen from the molten copper liquid, we design a combination mechanism of compound oxygen barrier layer and composite deoxidizer. The compound oxygen barrier layer adopts a multi-level structure, the lower layer mainly uses a mixture of calcined coconut shell carbon and calcium fluoride to provide a physical barrier to limit oxygen diffusion, and the upper layer uses flaky graphite to enhance the sealing property. This cooperates with the synergistic effect of composite deoxidizers such as activated lanthanum powder and lithium borate to chemically reduce the dissolved oxygen in the copper liquid. The special treatment of activated lanthanum powder enhances its reactivity, enabling it to rapidly combine with oxygen atoms, while calcium fluoride assists in the formation of slag, facilitating subsequent filtration and removal. This dual oxygen removal mechanism ensures that lattice oxygen is completely removed, greatly improving the chemical stability of the copper liquid.

[0028] 4. In the transfer and filtration steps, our double-layer gas curtain channel and stepped filtration device minimize the exposure process of the copper liquid. The inner negative pressure nitrogen gas and the outer high pressure nitrogen gas form a closed environment, cutting off the air contact path and preventing oxygen from re-entering; the stepped filtration adopts a multi-level pore size design of silicon carbide and zirconia filter plates, physically trapping small inclusions, and the surface plating layer is treated by a special process to enhance its high-temperature corrosion resistance, achieving efficient impurity interception. In this way, the cleanliness of the copper liquid is guaranteed, providing a foundation for the casting stage.

[0029] 5. In the upper casting stage, we optimized the cooling parameters of the crystallizer, set the temperature and flow rate of each zone to achieve precise thermal management. Different cooling rates in the upper, middle and lower sections ensure grain refinement and uniform distribution during solidification of the copper liquid; appropriate pulling speed controls the diameter and structure of the as-cast rod blank, avoiding the formation of dendritic crystal defects, thereby improving the overall density and mechanical strength of the as-cast rod blank, which helps subsequent deformation processing. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] In the present application, the sources of various raw materials are briefly described as follows:

[0032] Electrolytic copper plate: produced by Jiangxi Copper Group Co., Ltd., brand CU-CATH-1, meeting the GB / T 467-2010 standard, purity 99.99%.

[0033] Calcium fluoride: industrial grade product of Hubei Xingfa Chemical Group Co., Ltd., model XFC-01, purity ≥98%.

[0034] Coconut shell raw material (for preparing calcined coconut shell carbon): 3-5 mm particles provided by Hainan Libao Food Co., Ltd., natural and untreated.

[0035] Oxalic acid: analytical pure reagent of Sinopharm Chemical Reagent Co., Ltd., CAS 144-62-7, item number H1002.

[0036] Lithium borate: high-purity reagent of Changsha Tianjiu New Material Technology Co., Ltd., model LBO-4N, purity 99.99%.

[0037] Coarse lanthanum ingot (raw material for activated lanthanum powder): brand La-99.5 of Ganzhou Qiandong Rare Earth Group Co., Ltd., purity 99.52 wt%.

[0038] Argon: high-purity gas of Hangzhou Oxygen Machine Group Co., Ltd., model Ar-5N, purity 99.999%.

[0039] Hydrogen: high-purity gas of Linde Gas (China) Co., Ltd., model H2-5N, purity 99.999%.

[0040] Nitrogen: ultra-high-purity gas of Baosteel Gas Co., Ltd., Shanghai Baogang, model N2-6N, oxygen content ≤0.3 ppm.

[0041] Flaky graphite: Qingdao Heilong Graphite Co., Ltd. product, model FL-199, fixed carbon content ≥ 99%.

[0042] Silicon carbide foam ceramic filter layer: Shandong Industrial Ceramics Research and Design Institute Co., Ltd. custom filter material, pore size 50-60 μm, item number SiC-60P.

[0043] Zirconia filter plate base material: Guangdong Oriental Zirconium Technology Co., Ltd. product, model ZrO2-T500.

[0044] Titanium nitride target material: Xi'an Nobor PVD Special Target Material Co., Ltd. physical vapor deposition special target material, model TiN-01, purity 99.95%.

[0045] The technical solution of the present application is: a top drawing method for producing high-purity oxygen-free copper rods, which comprises the following sequential steps:

[0046] (1) Raw material pretreatment: sandblasting treatment and drying treatment are performed on an electrolytic copper plate with a purity of 99.99% to obtain a pretreated copper plate;

[0047] (2) Gradient melting and impurity removal: the aforementioned pretreated copper plate is used as a raw material for melting treatment to obtain molten copper liquid with a dissolved oxygen content of ≤18 ppm;

[0048] (3) Oxygen removal of molten copper liquid: a compound oxygen barrier layer is laid on the surface of the molten copper liquid, and a composite deoxidizing agent is added to the molten copper liquid, which is stirred at 95-105 rpm for 85-95 minutes to obtain deoxidized copper liquid with a lattice oxygen content of ≤2.5 ppm;

[0049] (4) Transfer and filtration of deoxidized copper liquid: the deoxidized copper liquid is transferred to a holding furnace through a sealed channel, and then impurities are removed through a stepped filtration device to obtain clean copper liquid;

[0050] (5) Top drawing casting: the clean copper liquid is top drawn and cast in a crystallizer to produce a cast rod blank.

[0051] The specific steps in the raw material pretreatment are: the 99.99% purity electrolytic copper plate is sandblasted to a surface roughness Ra ≤ 1.6 μm, then dried in a 180-190°C drying furnace for 2.0-2.2 hours to obtain a copper base material with a water content of ≤40 ppm.

[0052] The melting treatment is carried out in an induction melting furnace, and the specific parameters are: the temperature rise rate is controlled to 10-12°C / min to a melting temperature of 1220-1235°C, the holding time is 33-37 minutes at a working voltage of 400-410V, high-purity nitrogen gas containing 0.5-0.8% hydrogen gas with an oxygen content of ≤0.3 ppm is introduced from the bottom of the furnace, and the gas flow is maintained at 0.8-1.0 cubic meters per hour, finally producing molten copper liquid with a dissolved oxygen content of ≤18 ppm.

[0053] The compound oxygen barrier layer comprises a lower layer of 6-8 cm thick calcined coconut shell carbon and calcium fluoride mixture and an upper layer of 3-5 cm thick flake graphite, and forms an oxygen diffusion coefficient ≤1×10-9 cm² / s oxygen barrier system.

[0054] The mass ratio of the calcined coconut shell carbon and calcium fluoride mixture in the calcined coconut shell carbon and calcium fluoride mixture is 88-92:10.

[0055] The preparation method of the calcined coconut shell carbon is as follows: 3-5 mm particle size coconut shell is calcined in argon at 1300-1350 ℃ for 4.5-5.5 hours, then soaked in a 10-12 wt% oxalic acid solution at a temperature of 40-45 ℃ for 1.5-2.0 hours, and then washed with water until the pH value is 6.5-7.0 to obtain calcined coconut shell carbon with ash content ≤0.02%.

[0056] The composite deoxidizer comprises 50-54 parts of activated lanthanum powder, 26-30 parts of calcium fluoride, and 18-20 parts of lithium borate by mass, and the addition amount of the composite deoxidizer is 0.09-0.11% of the mass of the molten copper.

[0057] The preparation method of the activated lanthanum powder is as follows: 99.52 wt% crude lanthanum ingot is heated to 650-680 ℃ in an atmosphere with a volume ratio of Ar to H2 of 95:5 for 30-40 minutes, and finally water-atomized to obtain a 200-300 mesh powder, which is the activated lanthanum powder, and the surface oxide layer of the activated lanthanum powder is ≤10 nm.

[0058] The sealing channel is a double-layer gas curtain channel transferred to a 1145-1165 ℃ holding furnace, and the double-layer gas curtain channel is divided into an inner layer and an outer layer, wherein the inner layer is -5 to -10 Pa nitrogen and the outer layer is 1.0-1.2 MPa nitrogen, and the oxygen increase during the transfer process is ≤0.2 ppm.

[0059] The specific steps of the stepwise filtering device for removing inclusions are as follows: the deoxidized copper liquid after transfer flows through a silicon carbide foam ceramic filter layer with a pore size of 50-60 μm and a zirconia filter plate with a titanium nitride plated surface with a pore size of 20-30 μm in sequence to obtain clean copper liquid with inclusion ≤15 pieces / 100 mm².

[0060] The surface of the zirconia filter plate is covered with a titanium nitride plating layer, and the titanium nitride plating layer is formed by a physical vapor deposition process. The titanium nitride plating layer is vacuum annealed at 1100-1150 ℃ for 0.5-1 hour after deposition, and the thickness of the titanium nitride plating layer is 0.8-1.2 μm with a Vickers hardness ≥1800 HV.

[0061] The specific steps and parameters of the upward drawing casting are as follows: clean copper liquid is added into the crystallizer, and the temperature and flow rate of the cooling water are set, wherein the upper section is 22-25 DEG C / 0.3-0.5 m / s, the middle section is 28-32 DEG C / 1.2-1.5 m / s, the lower section is 38-42 DEG C / 0.8-1.0 m / s, the drawing speed is 2.8-3.2 m / min, and the cast rod blank with a diameter of 8.0+ / -0.1 mm is obtained.

[0062] The core advantage of the process is that the gradient melting and the physical isolation of the complex oxygen barrier are combined with the deep chemical reduction of the composite deoxidizer, so that the crystal lattice oxygen of the molten copper liquid is completely removed; combined with the double-layer air curtain sealing protection in the transfer process and the precise interception of the gradient filter device, the impurity particles are almost zero residue; finally, the upward casting relying on the partition cooling strategy maintains the oxygen-free characteristics, at the same time, the copper rod obtains uniform and dense grain structure and high ductility, and the stable combination of high electrical conductivity and excellent mechanical performance is achieved, avoiding the performance degradation risk common in traditional processes.

[0063] The technical solutions of the present application are further illustrated by the following examples and comparative examples, but the protection scope of the present application is not limited thereto.

[0064] Example 1

[0065] The application discloses a production process of high-purity oxygen-free copper rod by upward drawing method, which comprises the following sequential steps: (1) raw material pretreatment: electrolytic copper plates with a purity of 99.99% are treated by sand blasting to a surface roughness Ra of 1.6 microns, and then dried in a 190 DEG C drying furnace for 2.1 hours to obtain copper base materials with a water content of 40 ppm; (2) gradient smelting and impurity removal: the pretreated copper plates are smelted in an induction smelting furnace, the temperature rising rate is controlled to be 11 DEG C / min to 1228 DEG C, the temperature is kept for 35 minutes under a working voltage of 410 V, high-purity nitrogen gas containing 0.65% hydrogen (the oxygen content is less than or equal to 0.3 ppm) is introduced from the bottom of the furnace, the gas flow is maintained at 0.9 cubic meters per hour, and finally, the molten copper liquid with a dissolved oxygen content of not more than 18 ppm is obtained; (3) oxygen removal of the molten copper liquid: a compound oxygen barrier layer is laid on the surface of the molten copper liquid, the lower layer is a 7 cm-thick mixture of calcined coconut shell carbon and calcium fluoride (the mass ratio of the mixture of calcined coconut shell carbon and calcium fluoride is 90:10), and the upper layer is a 4 cm-thick flaky graphite, so that an oxygen diffusion coefficient of not more than 1*10-9 cm2 / s is formed; meanwhile, a composite deoxidizer (52 parts of activated lanthanum powder, 28 parts of calcium fluoride and 19 parts of lithium borate) is added, the adding amount is 0.10% of the mass of the molten copper, and the stirring speed is 100 rpm for 90 minutes, so that the deoxidized copper liquid with a crystal lattice oxygen content of not more than 2.5 ppm is obtained; the preparation method of the calcined coconut shell carbon is as follows: 4 mm particle size coconut shells are calcined in argon at 1325 DEG C for 5 hours, then soaked in an 11 wt% oxalic acid solution at a temperature of 42.5 DEG C for 1.75 hours, and then washed with water until the pH value is 6.75, so that the calcined coconut shell carbon with an ash content of not more than 0.02% is obtained; the preparation method of the activated lanthanum powder is as follows: 99.52 wt% crude lanthanum ingots are treated at 665 DEG C for 35 minutes in an atmosphere with an Ar and H2 volume ratio of 95:5, and finally, the water atomized powder with a particle size of 200-300 meshes is obtained, and the surface oxide layer of the activated lanthanum powder is not more than 10 nm; (4) transfer and filtration of the deoxidized copper liquid: the deoxidized copper liquid is transferred to a 1155 DEG C holding furnace through a double-layer gas curtain channel, the inner layer is -7.5 Pa nitrogen gas, the outer layer is 1.1 MPa nitrogen gas, and the oxygen increase during the transfer process is not more than 0.2 ppm; then, the deoxidized copper liquid is filtered through a step-by-step filtering device, sequentially flows through a 55 micron silicon carbide foam ceramic filter layer and a 25 micron zirconia filter plate coated with titanium nitride, so that the clean copper liquid with an inclusion content of not more than 15 pieces per 100 mm2 is obtained; the surface of the zirconia filter plate is covered with a titanium nitride coating layer formed by a physical vapor deposition process, the titanium nitride coating layer is annealed in vacuum at 1125 DEG C for 0.75 hours after deposition, the thickness of the titanium nitride coating layer is 1.0 micron, and the Vickers hardness is not less than 1800 HV; and (5) upward drawing casting: the clean copper liquid is added into a crystallizer, the cooling water partition temperature and flow rate are set as follows: the upper segment is 24 DEG C and 0.4 m / s, the middle segment is 30 DEG C and 1.35 m / s, and the lower segment is 40 DEG C and 0.9 m / s, the drawing speed is 3.0 m / min, and finally, the as-cast rod blank with a diameter of 8.0 mm is obtained.

[0066] Example 2

[0067] In this example, the same as in Example 1, the same is not described again, the difference is described as follows:

[0068] The production process of the upward drawing method high-purity oxygen-free copper rod comprises the following sequential steps: (1) raw material pretreatment: the 99.99% purity electrolytic copper plate is treated by sand blasting to a surface roughness Ra of 1.6 μm, and then dried in a 180℃ drying furnace for 2.2 hours to obtain a copper base material with a water content of 40 ppm; (2) gradient smelting and impurity removal: the pretreated copper plate is smelted in an induction smelting furnace, the temperature rising rate is controlled to be 10℃ / min to 1235℃, and the temperature is maintained for 37 minutes under a working voltage of 400V, while high-purity nitrogen gas containing 0.5% hydrogen gas (oxygen content ≤0.3 ppm) is introduced from the bottom of the furnace, the gas flow is maintained at 1.0 cubic meter per hour, and finally the molten copper liquid with a dissolved oxygen content of not more than 18 ppm is obtained; (3) oxygen removal of molten copper liquid: a compound oxygen barrier layer is laid on the surface of the molten copper liquid, wherein the lower layer is a 6cm thick mixture of calcined coconut shell carbon and calcium fluoride (the mass ratio of the mixture of calcined coconut shell carbon and calcium fluoride is 92:10), and the upper layer is a 5cm thick flaky graphite, forming an oxygen diffusion coefficient of not more than 1×10-9 cm² / s oxygen barrier system; at the same time, a composite deoxidizer (activated lanthanum powder 54 parts, calcium fluoride 26 parts, lithium borate 20 parts) is added, the amount of which is 0.09% of the mass of the molten copper, and the stirring speed is 105 rpm for 85 minutes to obtain a deoxidized copper liquid with a crystal lattice oxygen content of not more than 2.5 ppm. The preparation method of the calcined coconut shell carbon is as follows: 3mm particle size coconut shell is calcined in argon at 1350℃ for 4.5 hours, then soaked in 10wt% oxalic acid solution at 45℃ for 2.0 hours, and then washed with water until the pH value is 7.0 to obtain calcined coconut shell carbon with ash content of not more than 0.02%. The preparation method of the activated lanthanum powder is as follows: 99.52wt% crude lanthanum ingot is heated to 680℃ in an atmosphere of Ar and H2 with a volume ratio of 95:5 for 30 minutes, and finally water atomized to obtain 200-300 mesh powder, and the surface oxide layer of the activated lanthanum powder is not more than 10nm. (4) transfer and filtration of deoxidized copper liquid: the deoxidized copper liquid is transferred to a 1145℃ holding furnace through a double-layer gas curtain channel, wherein the inner layer is -10 Pa nitrogen and the outer layer is 1.2 MPa nitrogen, and the oxygen increase during the transfer process is not more than 0.2 ppm; then it passes through a gradient filtration device, sequentially flows through a silicon carbide foam ceramic filter layer with a pore size of 60 μm and a zirconia filter plate coated with titanium nitride with a pore size of 20 μm, to obtain a clean copper liquid with an inclusion content of not more than 15 pieces per 100 mm². The surface of the zirconia filter plate is covered with a titanium nitride coating layer formed by physical vapor deposition process, and the titanium nitride coating layer is annealed at 1150℃ in vacuum for 0.5 hours after deposition, the thickness of the titanium nitride coating layer is 1.2 μm, and the Vickers hardness is not less than 1800 HV. (5) upward drawing casting: the clean copper liquid is added into a crystallizer, the cooling water partition temperature and flow rate are set as follows: upper segment 25℃ and 0.3 m / s, middle segment 32℃ and 1.2 m / s, lower segment 42℃ and 0.8 m / s, and the drawing speed is 2.8 m / min, to produce a cast rod blank with a diameter of 8.0 mm.

[0069] Example 3

[0070] In this example, the same as in Example 1, the differences are described as follows:

[0071] The production process of the upward drawing method high-purity oxygen-free copper rod includes the following sequential steps: (1) raw material pretreatment: the 99.99% purity electrolytic copper plate is treated by sand blasting to a surface roughness Ra of 1.6 μm, and then dried in a 185℃ drying furnace for 2.0 hours to obtain a copper base material with a water content of 40 ppm. (2) Gradient smelting and impurity removal: the pretreated copper plate is smelted in an induction smelting furnace, the temperature rising rate is controlled to 12℃ / min to 1220℃, and the temperature is maintained for 33 minutes under a working voltage of 405V, while high-purity nitrogen gas containing 0.8% hydrogen gas (oxygen content ≤0.3 ppm) is introduced from the bottom of the furnace, the gas flow is maintained at 0.8 cubic meters per hour, and finally the molten copper liquid with a dissolved oxygen content of not more than 18 ppm is obtained. (3) Oxygen removal of molten copper liquid: a compound oxygen barrier layer is laid on the surface of the molten copper liquid, the lower layer is a mixture of 8 cm thick calcined coconut shell carbon and calcium fluoride (the mass ratio of the mixture of calcined coconut shell carbon and calcium fluoride is 88:10), and the upper layer is 3 cm thick flake graphite, forming an oxygen diffusion coefficient of not more than 1×10-9 cm² / s oxygen barrier system; at the same time, a composite deoxidizer (activated lanthanum powder 50 parts, calcium fluoride 30 parts, lithium borate 18 parts) is added, the amount is 0.11% of the mass of the molten copper, and the stirring speed is 95 rpm for 95 minutes to obtain a deoxidized copper liquid with a lattice oxygen content of not more than 2.5 ppm. The preparation method of the calcined coconut shell carbon is: the 5mm particle size coconut shell is calcined in argon at 1300℃ for 5.5 hours, then soaked in 12wt% oxalic acid solution at 40℃ for 1.5 hours, and then washed with water to pH 6.5 to obtain calcined coconut shell carbon with ash content of not more than 0.02%. The preparation method of the activated lanthanum powder is: the 99.52wt% crude lanthanum ingot is heated to 650℃ in an atmosphere of Ar and H2 with a volume ratio of 95:5 for 40 minutes, and finally the 200-300 mesh powder is obtained by water atomization, and the surface oxide layer of the activated lanthanum powder is not more than 10 nm. (4) Transfer and filtration of deoxidized copper liquid: the deoxidized copper liquid is transferred to a 1165℃ holding furnace through a double-layer gas curtain channel, the inner layer is -5 Pa nitrogen gas and the outer layer is 1.0 MPa nitrogen gas, and the oxygen increase during the transfer process is not more than 0.2 ppm; then it passes through a gradient filtration device, and then flows through a silicon carbide foam ceramic filter layer with a pore size of 50 μm and a zirconia filter plate coated with titanium nitride with a pore size of 30 μm, to obtain a clean copper liquid with an inclusion content of not more than 15 pieces per 100 mm². The surface of the zirconia filter plate is covered with a titanium nitride coating layer formed by physical vapor deposition process, and the titanium nitride coating layer is annealed at 1100℃ in vacuum for 1.0 hour after deposition, the thickness of the titanium nitride coating layer is 0.8 μm, and the Vickers hardness is not less than 1800 HV. (5) Upward drawing casting: the clean copper liquid is added into the crystallizer, the cooling water partition temperature and flow rate are set as follows: upper segment 22℃ and 0.5 m / s, middle segment 28℃ and 1.5 m / s, lower segment 38℃ and 1.0 m / s, and the drawing speed is 3.2 m / min, to produce a cast rod blank with a diameter of 8.0 mm.

[0072] Comparative Example 1

[0073] In this comparative example, the same as Example 1 is not repeated, and the differences are described as follows:

[0074] The proportion of activated lanthanum powder in the composite deoxidizer is 48 parts, lithium borate is 15 parts, and calcium fluoride is 25 parts. The amount of deoxidizer added is 0.07%.

[0075] Comparative Example 2

[0076] In this comparative example, the same as Example 2 is not repeated, and the differences are described as follows:

[0077] The mixture of the lower layer calcined coconut shell charcoal and calcium fluoride is replaced by a single material of flake graphite (thickness remains 4 cm), and the concentration of oxalic acid soaking is reduced to 8 wt%.

[0078] Comparative Example 3

[0079] In this comparative example, the same as Example 3 is not repeated, and the differences are described as follows:

[0080] In the gradient smelting process, no hydrogen is introduced, only high-purity nitrogen with oxygen content ≤0.3 ppm (no hydrogen content) is introduced, and the drying time is increased to 3.0 hours.

[0081] Comparative Example 4

[0082] In this comparative example, the same as Example 1 is not repeated, and the differences are described as follows:

[0083] The sealing channel only uses a single layer of nitrogen curtain (pressure remains -7.5 Pa), and no gradient filter device is used.

[0084] Comparative Example 5

[0085] In this comparative example, the same as Example 1 is not repeated, and the differences are described as follows:

[0086] The up-drawing casting cooling parameters are changed to uniform values (full section 28℃ / 1.0 m / s), and the drawing speed is increased to 4.0 m / min.

[0087] Performance Test Results and Analysis

[0088] The products of Examples 1-3 and Comparative Examples 1-5 were tested using general test methods. Each test index includes oxygen content (ASTM E112 method), electrical conductivity (ASTM E140 method), tensile strength (ASTM E8 method), elongation (ASTM E8 method), inclusion number (microscope counting method), and production interruption band rate (100 batches of continuous production statistics). The test results are shown in Table 1, and all numerical values are the average of three repeated tests.

[0089] Table 1 Analysis test results

[0090] Group Oxygen content (ppm) Electrical conductivity (%IACS) Tensile strength (MPa) Elongation (%) Inclusion count (number / 100 mm2) Breakage rate (%) Example 1 5.0 101.8 238 48 13 0.2 Example 2 5.3 101.5 241 46 14 0.3 Example 3 4.8 102.1 235 50 12 0.1 Comparative Example 1 12.7 98.2 225 32 28 5.8 Comparative Example 2 15.3 96.5 218 25 35 8.3 Comparative Example 3 14.8 97.1 220 29 30 7.2 Comparative Example 4 9.5 99.3 230 40 22 3.1 Comparative Example 5 8.1 100.0 228 42 20 4.5

[0091] As can be seen from Table 1, the oxygen content of all examples is stabilized at 4.8-5.3 ppm, far below the 10 ppm threshold, effectively avoiding the high-temperature hydrogen embrittlement fracture problem mentioned in the background art. This is due to the precise reduction atmosphere control in gradient smelting and the synergistic effect of the compound oxygen barrier layer and the composite deoxidizer in molten copper liquid oxygen removal. The oxygen residue of Comparative Example 1 increases significantly to 12.7 ppm due to insufficient deoxidizer, while the oxygen content of Comparative Example 2 increases to 15.3 ppm without a compound oxygen barrier layer, verifying the necessity of the combined mechanism. Looking at the examples, the reaction activity of activated lanthanum powder ensures the complete removal of lattice oxygen, and the slag formed by calcium fluoride is efficiently removed in gradient filtration, reducing the lattice oxygen content to not more than 2.5 ppm. In addition, the double nitrogen curtain design of the sealed channel controls the oxygen transfer to within 0.2 ppm, such as -7.5 Pa and 1.1 MPa nitrogen in Example 1, solving the key defect of secondary oxidation of the melt in the background art. The lithium borate in the deoxidizer removes impurities such as phosphorus, and the conductivity of the examples improves by more than 5% of the expected improvement.

[0092] The tensile strength and elongation show that the comprehensive mechanical properties of the examples are excellent, with a breakage rate of only 0.1-0.3%, far lower than that of the comparative examples (3.1-8.3%), proving that gradient filtration and cooling optimization solve the problem of inclusion blockage and breakage risk. The number of inclusions in Comparative Example 2 increases to 35 per 100 mm² due to a single oxygen barrier layer, with a breakage rate of 8.3%, highlighting the importance of a compound oxygen barrier layer. At the same time, the casting cooling partitioning of the examples ensures grain refinement and avoids dendritic crystal defects.

[0093] The examples all exhibit low inclusion numbers, which is the result of the compound oxygen barrier layer and gradient filtration, while the oxygen content, conductivity, and strength are matched, such as the 50% elongation of Example 3 far exceeding the 25% of Comparative Example 2 and the 29% of Comparative Example 3. This excellent performance echoes the solution to the energy and performance contradiction described in the beneficial effects - no annealing process reduces costs, while efficient deoxidization is achieved through precise process parameter settings.

[0094] The test results confirm the breakthrough of the present application over the defects in the background art, with the target of oxygen content below 10 ppm and conductivity above 100% IACS being fully achieved. The diversity of parameters in Examples 1-3 ensures the robustness of the scheme, and reasonable changes in process details avoid the carbon contamination problem in the prior art, providing a reliable scheme for the large-scale production of high-purity oxygen-free copper rods.

[0095] The above is the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles described in the present application, can also make several improvements and refinements, these improvements and refinements should also be considered as the scope of protection of the present application.

Claims

1. A process for producing high-purity oxygen-free copper rods using an upward drawing method, characterized in that, The production process includes the following sequential steps: (1) Raw material pretreatment: 99.99% pure electrolytic copper plate is sandblasted and dried to obtain pretreated copper plate; (2) Gradient melting and impurity removal: The pretreated copper plate was used as raw material to be melted to obtain molten copper liquid with dissolved oxygen content ≤18 ppm; (3) Deoxidation of molten copper liquid: A composite oxygen barrier layer is laid on the surface of molten copper liquid and a composite deoxidizer is added to the molten copper liquid. Stir at 95-105 rpm for 85-95 minutes to obtain a deoxidized copper liquid with lattice oxygen ≤2.5ppm. (4) Deoxidized copper liquid transfer and filtration: The deoxidized copper liquid is transferred to the holding furnace through a sealed channel, and then impurities are removed through a stepped filtration device to obtain clean copper liquid; (5) Upward casting: Clean copper liquid is upward cast in the crystallizer to produce cast rod billet; The smelting process is carried out in an induction melting furnace, with the following specific parameters: controlling the heating rate to 10-12℃ / min to a smelting temperature of 1220-1235℃, holding the temperature at 400-410V for 33-37 minutes, while simultaneously introducing high-purity nitrogen gas containing 0.5-0.8% hydrogen and with an oxygen content ≤0.3 ppm from the bottom of the furnace, maintaining the gas flow rate at 0.8-1.0 cubic meters per hour, and finally producing molten copper liquid with a dissolved oxygen content ≤18 ppm; The composite oxygen barrier layer comprises a lower 6-8 cm thick mixture of calcined coconut shell charcoal and calcium fluoride, and an upper 3-5 cm thick layer of flake graphite. The composite oxygen barrier layer has an oxygen diffusion coefficient ≤1×10⁻⁶. -9 An oxygen barrier system with a capacity of cm² / s; The mass ratio of calcined coconut shell char to calcium fluoride mixture in the calcined coconut shell char and calcium fluoride mixture is 88-92:10; The method for preparing the calcined coconut shell charcoal is as follows: calcining coconut shells with a particle size of 3-5 mm in argon at 1300-1350 ℃ for 4.5-5.5 hours, then soaking them in a 10-12 wt% oxalic acid solution at 40-45 ℃ for 1.5-2.0 hours, followed by washing with water until the pH value is 6.5-7.0, to obtain calcined coconut shell charcoal with an ash content of ≤0.02%; By weight, the composite deoxidizer comprises 50-54 parts activated lanthanum powder, 26-30 parts calcium fluoride, and 18-20 parts lithium borate, and the amount of the composite deoxidizer added is 0.09-0.11% of the mass of molten copper; The method for preparing the activated lanthanum powder is as follows: 99.52 wt% crude lanthanum ingots are heated to 650-680 ℃ for 30-40 minutes in an atmosphere with a volume ratio of Ar to H2 of 95:5, and finally water atomization is performed to obtain 200-300 mesh powder, which is the activated lanthanum powder. The surface oxide layer of the activated lanthanum powder is ≤10nm. The sealed channel is a double-layer gas curtain channel for transferring gas to a 1145-1165℃ holding furnace. The double-layer gas curtain channel is divided into an inner layer and an outer layer, wherein the inner layer is filled with nitrogen at -5 to -10 Pa and the outer layer is filled with nitrogen at 1.0-1.2 MPa. The oxygen increase during the transfer process is ≤0.2ppm.

2. The process for producing high-purity oxygen-free copper rods using the upward drawing method according to claim 1, characterized in that, The specific steps in the raw material pretreatment are as follows: 99.99% pure electrolytic copper plate is sandblasted until the surface roughness Ra≤1.6μm, and then dried in a drying oven at 180-190℃ for 2.0-2.2 hours to obtain copper substrate with a moisture content ≤40ppm.

3. The process for producing high-purity oxygen-free copper rods using the upward drawing method according to claim 1, characterized in that, The specific steps for removing inclusions using the cascade filtration device are as follows: the transferred deoxidized copper liquid flows sequentially through a silicon carbide foam ceramic filter layer with a pore size of 50-60 μm and a zirconium oxide filter plate with a pore size of 20-30 μm coated with titanium nitride, resulting in inclusions ≤15 per 100 mm. 2 Clean copper solution.

4. The process for producing high-purity oxygen-free copper rods by upward drawing according to claim 3, characterized in that, The surface of the zirconium oxide filter plate is covered with a titanium nitride coating, which is formed by physical vapor deposition. After deposition, the titanium nitride coating is vacuum annealed at 1100-1150℃ for 0.5-1 hour. The thickness of the titanium nitride coating is 0.8-1.2 μm, and the Vickers hardness is ≥1800 HV.

5. The process for producing high-purity oxygen-free copper rods by upward drawing according to claim 1, characterized in that, The specific steps and parameters for the upward casting are as follows: clean copper liquid is added into the crystallizer, and the cooling water zone temperature / flow rate is set, with the upper section at 22-25℃ / 0.3-0.5 m / s, the middle section at 28-32℃ / 1.2-1.5 m / s, and the lower section at 38-42℃ / 0.8-1.0 m / s. The traction speed is 2.8-3.2 m / min, producing a cast rod blank with a diameter of 8.0±0.1 mm.