Method for manufacturing corrosion-resistant copper pipes using recycled copper and corrosion-resistant copper pipes manufactured thereby

Abstract

This invention provides a method for manufacturing corrosion-resistant copper pipes using recycled copper, and the corrosion-resistant copper pipes manufactured thereby. [Solution] The manufacturing method includes step S1, which involves heating the copper solution in the shaft furnace to a set temperature and adjusting the concentration of the reducing gas in the shaft furnace so that the oxygen element content in the copper solution in the shaft furnace is greater than 30 ppm to remove primary impurities; step S2, which involves sequentially introducing the copper solution in the shaft furnace into a chute, a refining furnace, a standing furnace, and a casting furnace, sequentially lowering the temperature of the copper solution in the chute, refining furnace, standing furnace, and casting furnace, introducing an inert gas and a reducing gas into each of the chute, refining furnace, standing furnace, and casting furnace, and sequentially lowering the flow rate and pressure of the inert gas and reducing gas introduced into the chute, refining furnace, standing furnace, and casting furnace to remove secondary impurities; and step S3, which involves adding a phosphorus source to the copper solution in the casting furnace and performing casting, with the casting temperature set to 1165°C ± 5°C.

Description

Technical Field

[0001] This application claims the priority of Chinese Patent Application No. 202411806731.5, titled "Method and Apparatus for Manufacturing Oxygen-Free Copper Tubes Using Recycled Copper, Corrosion-Resistant Copper Tubes, and Casting Process", filed with the China National Intellectual Property Administration on December 10, 2024, and all of its contents are hereby incorporated by reference into this application.

[0002] This application relates to the field of copper processing, and particularly to a method for manufacturing corrosion-resistant copper tubes using recycled copper and the corrosion-resistant copper tubes manufactured thereby.

Background Art

[0003] Copper tubes are widely applied in the fields of marine equipment, aerospace, nuclear power generation, high-end equipment, and refrigeration. The copper used as the raw material for copper tubes is mainly mined from mines. Copper ore is mined from mines, and electrolytic copper is obtained through ore dressing and smelting. Copper tubes are manufactured using electrolytic copper, especially electrolytic copper with a purity higher than 99.9%, as the raw material. In order to reduce dependence on natural resources, alleviate environmental pressure, and provide a sustainable material source, oxygen-free copper tubes can be produced by recovering and recycling the copper in discarded electric wires and cables, automotive radiators and refrigerators, copper-containing castings, discarded bearings, discarded motors, discarded transformers, etc.

[0004] However, recycled copper has oxygen element, hydrogen element, and other elements such as arsenic element, antimony element, bismuth element, iron element, lead element, tin element, nickel element, zinc element, sulfur element, etc. compared with conventional copper derived from copper ore. Since oxygen element, hydrogen element, and other elements are all impurities in oxygen-free copper tubes, the same quality standard as the manufacturing of oxygen-free copper tubes using conventional copper can be achieved only by removing impurities in an additional purification step. Thus, it can be seen that when the raw materials of copper tubes are different, their manufacturing processes will inevitably be different. Compared with electrolytic copper, the impurities in recycled copper are more in variety and higher in content, and the performance deteriorates after copper is used, so it is more difficult to manufacture copper tubes using recycled copper.

[0005] Therefore, prior art, such as Chinese patent CN103725897A, discloses a method for directly producing high-purity oxygen-free copper by continuously dry smelting scrap copper, in which impurities are removed by oxidation-reduction, followed by the addition of borides and rare earth elements to remove hydrogen and deoxygenate the metal. However, this method may introduce other impurities such as borides and rare earth elements, and the residue of borides and rare earth elements affects the composition of oxygen-free copper tubes. Therefore, currently, oxygen-free copper tubes are often produced by reducing oxygen using reducing gas in the copper raw material production process. For example, Chinese utility model CN216780264U discloses a shaft furnace-copper ingot horizontal continuous casting apparatus in which raw tubes are produced using equipment such as a shaft furnace, refining furnace, mixing furnace, stationary furnace, and 7-strand continuous casting furnace. Gas-blowing bricks are provided in the bottom wall of the cavity of the refining furnace body, and reducing gas is blown in by a gas-blowing device to increase the amount of reducing gas, thereby removing oxygen from recycled copper tubes and adding phosphorus copper to remove impurities such as oxygen. However, the inventors of the present application have noted that in the above apparatus, gas is introduced only into the refining furnace, making it impossible to accurately control the oxygen content, which affects the quality of recycled copper tubes.

[0006] Furthermore, in order to improve the heat exchange efficiency of copper tubes and reduce energy consumption, copper tubes for heat exchangers in aerospace and other applications have evolved in the direction of thin walls and small diameters. However, thin walls make the copper tubes more susceptible to corrosion and perforation. The prior art, for example, Chinese patent CN105143478A, discloses a corrosion-resistant copper tube containing 0.05 to 1.0 weight percent of phosphorus, with the remainder being Cu and unavoidable impurities. However, the inventors of this application have recognized that, on the one hand, the high phosphorus content in such corrosion-resistant copper tubes can cause problems such as the copper tubes becoming brittle and hard, leading to cracking during bending or forming processes, and on the other hand, if hydrogen and oxygen elements are not removed from the copper tubes, the high content of hydrogen and oxygen elements results in a large amount of cuprous oxide in the copper tubes, a higher potential difference between grain boundaries and within the crystal, and the copper tubes still have low resistance to ant nest corrosion, making them susceptible to corrosion. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The objective of this invention is to provide a method for manufacturing corrosion-resistant copper pipes using recycled copper, thereby overcoming the shortcomings of the prior art and improving the corrosion resistance performance of the corrosion-resistant copper pipes. [Means for solving the problem]

[0008] To achieve the above objective, this invention employs the following technical means. A method for manufacturing corrosion-resistant copper pipes using recycled copper is: Step S1 involves heating the copper solution in the shaft furnace to a set temperature and adjusting the concentration of the reducing gas in the shaft furnace so that the oxygen element content in the copper solution in the shaft furnace is greater than 30 ppm, thereby removing primary impurities. Step S2 involves sequentially introducing the copper solution in the shaft furnace into the chute, smelting furnace, standing furnace, and casting furnace, sequentially lowering the temperature of the copper solution in the chute, smelting furnace, standing furnace, and casting furnace, introducing an inert gas and a reducing gas into each of the chute, smelting furnace, standing furnace, and casting furnace, and sequentially lowering the flow rate and pressure of the inert gas and reducing gas introduced into the chute, smelting furnace, standing furnace, and casting furnace to remove secondary impurities. The process includes step S3, which involves adding a phosphorus source to the copper solution in the casting furnace, setting the casting temperature of the copper solution to 1165°C ± 5°C, setting the flow rate of the primary cooling water in the crystallization apparatus to 45-55 L / min, setting the initial drawing speed to 100 mm / min, supplying secondary cooling water after the billet has been drawn, and gradually increasing the casting drawing speed within the range of 100-350 mm / min to produce a corrosion-resistant copper tube.

[0009] By using the above technical means, the present invention has the following advantages. First, the oxygen element has oxidizing properties and can react with hydrogen in impurities to produce water through oxidation-reduction reactions. The copper solution in the shaft furnace is heated to a set temperature, and the high temperature of the copper solution provides sufficient activation energy, promoting a faster reaction rate. The produced water is also heated and evaporates as steam, thereby reducing the hydrogen content in the copper solution. Furthermore, the oxygen element can react with other elements in the impurities other than hydrogen to produce oxides. These oxides generally do not dissolve in the copper solution, forming a slag phase. By removing the slag phase from the surface of the copper solution by scraping off the slag, the impurity content in the copper solution can be reduced. The oxygen element itself is an impurity that should be removed from the copper solution. If no other impurity removers are introduced and the types of impurities in the copper solution do not increase, then by performing a reverse operation, the oxygen element content in the copper solution in the shaft furnace is first increased to more than 30 ppm, so that a sufficient number of oxygen elements react with the impurities through oxidation, thereby performing primary impurity removal and ensuring the impurity removal effect. If the oxygen element content in the copper solution in the shaft furnace is less than 30 ppm, the impurity removal effect will be lower, and the impurity content in the copper solution will still be high, making impurity removal in subsequent processing steps more difficult. If the impurity removal capacity in subsequent processing steps is weak, the impurities in the ultimately produced oxygen-free copper tube will still be higher than the target value, which may affect the quality of the oxygen-free copper tube.

[0010] Next, because the reducing gas has reducing properties, it can react with the oxygen element in impurities to produce an oxygen-containing gas. This oxygen-containing gas is easily volatile, which can reduce the oxygen element content in the copper solution. Furthermore, the reducing gas can react with elements other than oxygen in the impurities to produce substances that can be separated from the copper solution, further reducing the impurity content. At high temperatures in the copper solution, impurities still react with oxygen to produce oxides, which are removed from the copper solution. Also, because high concentrations of reducing gas tend to form explosive mixtures when mixed with air, inert gas and reducing gas are introduced into the chute, smelting furnace, standing furnace, and casting furnace. Adding inert gas reduces the flammability range of such mixtures, thereby reducing safety risks. Adding inert gas increases the total amount of gas, which improves the rate at which the gas passes through the copper solution, contributing to improved reaction efficiency. As impurities in the copper solution pass through the chute, smelting furnace, standing furnace, and casting furnace in sequence, they are gradually reduced by the reducing gas, and the copper solution undergoes multi-stage impurity removal, resulting in refinement during the hydrogen removal and deoxygenation processes. This process achieves secondary impurity removal and better control of impurity content in the copper solution. Furthermore, as the temperature of the copper solution decreases sequentially in the chute, smelting furnace, standing furnace, and casting furnace, impurities tend to have lower solubility, precipitate from the copper solution, react with oxygen, and form an easily separable slag phase. In this way, impurities can be removed more thoroughly, improving the purity of oxygen-free copper tubes. The content of impurities decreases when they enter the next furnace after being removed in the previous furnace, and accordingly, the amount of reducing gas required can also be reduced. The flow rate and pressure of the inert gas and reducing gas introduced into the chute, smelting furnace, standing furnace, and casting furnace are sequentially reduced. This sequential reduction in the flow rate and pressure of the inert gas and reducing gas helps control the overflow of bubbles in the copper solution and reduces pore formation, ensuring that the hydrogen removal and deoxygenation effects are always within the set range. It also helps control the degree of stirring of the copper solution and ensure the effective progress of slag formation due to oxidation, improving the quality of oxygen-free copper tubes produced using recycled copper, reducing energy consumption, and improving process efficiency.

[0011] Furthermore, by setting the casting temperature to 1165°C ± 5°C, the high fluidity of the copper solution is ensured, which helps reduce casting defects. Additionally, by adding a phosphorus source to the copper solution, the phosphorus element can significantly improve the corrosion resistance of the corrosion-resistant copper pipe, especially when used in wet, acidic, alkaline, or seawater environments. It can also react with the oxygen element in the copper solution to form phosphorus oxides. Since these phosphorus oxides are volatile and escape at high temperatures, they reduce the oxygen element in the copper alloy. In addition to deoxygenation, phosphorus reacts with other elements in the impurities to form compounds that are easily separated from the copper solution, thus further achieving the objective of purifying the copper solution. By controlling the flow rate of the primary cooling water in the crystallization apparatus, the cooling rate of the copper solution can be effectively controlled, preventing internal stress and cracking due to excessive cooling. This also ensures rapid hardening of the corrosion-resistant copper tube, improving production efficiency. Furthermore, by gradually increasing the rate from an initial 100 mm / min to 350 mm / min, uniform heat dissipation is facilitated, reducing uneven deformation and internal stress accumulation, ensuring dimensional accuracy and surface quality of the corrosion-resistant copper tube, promoting uniform plastic deformation of the material, and improving the mechanical properties and pressure resistance of the corrosion-resistant copper tube. Additionally, by obtaining the copper solution using recycled copper in a method that produces oxygen-free copper tubes, the impurity content can be effectively reduced, thereby removing cuprous oxide, reducing the potential difference between grain boundaries and within the crystal, and providing the corrosion-resistant copper tube with excellent resistance to ant nest corrosion.

[0012] Another objective of this application is to provide a corrosion-resistant copper tube, wherein a corrosion-resistant copper tube is manufactured using the above-mentioned recycled copper method, and the oxygen content in the corrosion-resistant copper tube is less than 5 ppm, the hydrogen content is less than 0.3 ppm, the phosphorus content is 0.1% to 0.3%, and the remainder is copper.

[0013] According to the above technical means, by controlling the oxygen, hydrogen, and phosphorus content in corrosion-resistant copper pipes to less than 5 ppm for oxygen and less than 0.3 ppm for hydrogen, cuprous oxide can be effectively removed, and the potential difference between grain boundaries and within crystals can be reduced. This significantly reduces oxides and hydrogen embrittlement phenomena that can cause corrosion in corrosion-resistant copper pipes. Furthermore, by precisely controlling the phosphorus content, the corrosion resistance of the corrosion-resistant copper pipe can be significantly improved, especially when used in wet, acidic, alkaline, or seawater environments. An appropriate phosphorus content can also ensure the strength and hardness of the corrosion-resistant copper pipe. Phosphorus can also react with oxygen in the copper solution to form phosphorus oxides. Since phosphorus oxides are volatile and escape at high temperatures, the amount of oxygen in the copper alloy is reduced. In addition to deoxygenation, phosphorus reacts with other elements in impurities to form compounds that are easily separated from the copper solution, thereby further achieving the objective of purifying the copper. Next, the remainder is copper, which reduces the variety of elements and ensures a high copper content, thereby ensuring high electrical and thermal conductivity of the material, while also maintaining the high workability of copper itself. This makes it suitable for various processing processes such as molding, drawing, and welding, and facilitates the manufacture of pipes with complex shapes. [Brief explanation of the drawing]

[0014] The present invention will be further explained below with reference to the drawings. [Figure 1] This is a flowchart of the method for manufacturing oxygen-free copper tubes using recycled copper in Embodiment 2 of the present invention. [Figure 2] This is a schematic diagram of the apparatus for manufacturing oxygen-free copper tubes using recycled copper, according to Embodiment 3 of the present invention. [Modes for carrying out the invention]

[0015] To further clarify the purpose, technical means, and advantages of the embodiments of this application, the technical means of the embodiments of this application will be clearly and completely described below with reference to the drawings of the embodiments. It should be noted that the embodiments described are only a selection of embodiments of this application, not all embodiments.

[0016] The terms "first," "second," "third," "fourth," etc. (if any) in the specification, claims, and drawings of this application are for distinguishing similar subjects and are not intended to describe a specific order or sequence. It should be understood that the data used in this manner may be replaced in appropriate circumstances so that the embodiments of this application described herein may be carried out in an order other than that illustrated or described herein.

[0017] In the various embodiments of this application, for example, the magnitude of the sequence number of each process does not indicate the order of execution, and the execution order of each process should be determined by its function and internal logic. It should be understood that this does not limit the implementation process of the embodiments of this application.

[0018] In this application, “includes” and “have,” and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or equipment comprising a set of steps or units is not limited to those steps or units explicitly listed, and may include other steps or units not explicitly listed or specific to those processes, methods, products, or equipment.

[0019] In this application, please understand that "plural" refers to two or more. "And / or" is merely a relation that describes the related objects, and indicates that there may be three types of relationships. For example, with respect to X and / or Y, it may indicate three situations: X existing alone, X and Y existing simultaneously, and Y existing alone. The letter " / " generally indicates that the related objects before and after it are in an "or" relationship. "Including X, Y and Z" and "Including X, Y and Z" mean including all three of X, Y and Z; "Including X, Y or Z" means including one of the three of X, Y and Z; and "Including X, Y and / or Z" means including any one, any two or any three of the three of X, Y and Z.

[0020] The technical means of the present application will be described in detail below with specific examples. Some of the following specific examples can be combined or substituted for each other depending on the actual situation, and in some examples, the same or similar concepts or processes will be omitted from the explanation.

[0021] (Example 1) This invention provides a corrosion-resistant copper tube, and by controlling the oxygen, hydrogen, and phosphorus content in the corrosion-resistant copper tube to less than 5 ppm for oxygen and less than 0.3 ppm for hydrogen, it is possible to effectively remove cuprous oxide in corrosion-resistant copper tubes produced using recycled copper, reduce the potential difference between grain boundaries and within the crystal, and have a phosphorus content of 0.1% to 0.3%, with the remainder being copper, thereby reducing the potential difference between the grain boundaries and within the crystal. By significantly reducing oxide and hydrogen embrittlement phenomena and precisely controlling the phosphorus content, the phosphorus element can significantly improve the corrosion resistance of corrosion-resistant copper pipes, especially when used in wet, acidic, alkaline, or seawater environments. An appropriate phosphorus content ensures the strength and hardness of the corrosion-resistant copper pipes. Furthermore, by ensuring a low number of impurities and a high copper content in the corrosion-resistant copper pipes, high electrical and thermal conductivity of the material is ensured, while maintaining the high workability of copper itself. This makes it suitable for various processing processes such as forming, drawing, and welding, and facilitates the manufacture of pipes with complex shapes. Regarding the performance of corrosion-resistant copper tubing, its tensile strength is 250 MPa or higher, indicating a high ability to resist tensile fracture and making it suitable for applications involving large external forces. Furthermore, its yield strength is 60-80 MPa, contributing to improved forming performance. Its elongation is 45% or higher, meaning the copper tubing has high plastic deformation capacity and can withstand large deformations without breaking. Additionally, its solid residue is 0.1 mg / m or less, indicating low levels of solid impurities remaining inside the corrosion-resistant copper tubing, contributing to improved product purity and service life. Finally, its internal oil residue is 0.15 mg / m or less, meaning the corrosion-resistant copper tubing not only possesses high mechanical properties but also excellent corrosion resistance and processing performance, making it suitable for various demanding application environments.

[0022] If the phosphorus content in the corrosion-resistant copper tube is too low, the corrosion-resistant copper tube is likely to corrode. If the phosphorus content in the corrosion-resistant copper tube is too high, the corrosion-resistant copper tube becomes brittle and hard, affecting its ductility and toughness, and cracks may occur during the bending or forming process. Preferably, when the phosphorus content in the corrosion-resistant copper tube is 0.1% - 0.2%, the resistance of the copper tube to honeycomb corrosion can be ensured, and the phosphorus content in the corrosion-resistant copper tube can be reduced as much as possible.

[0023] The phosphorus content and copper content referred to in this specification refer to the mass ratio, which is determined by measuring and calculating the masses of phosphorus and copper elements in the corrosion-resistant copper tube.

[0024] The corrosion depth of the seamless female-threaded corrosion-resistant copper tube with φ6.35×0.23×0.12mm in 0.01% formic acid is less than 0.03mm. Of course, for corrosion-resistant copper tubes with other dimensions, the corrosion depth may be smaller.

[0025] (Example 2) As shown in Figure 1, the method for manufacturing oxygen-free copper tubes using recycled copper according to the present invention is mainly applied to the processing of recycled copper materials, which mainly contain oxygen, hydrogen, and other elemental impurities such as arsenic, antimony, bismuth, iron, lead, tin, nickel, zinc, and sulfur. First, oxygen has oxidizing properties and can react with hydrogen in the impurities to produce water through oxidation-reduction reactions. When the copper solution in the shaft furnace is heated to a set temperature, the high temperature of the copper solution provides sufficient activation energy, promoting a faster reaction rate. The produced water is also heated and evaporates as steam, thereby reducing the hydrogen content in the copper solution. Furthermore, oxygen can react with other elements in the impurities other than hydrogen to produce oxides. These oxides generally do not dissolve in the copper solution and form a slag phase. By removing the slag phase from the surface of the copper solution by scraping off the slag, the impurity content in the copper solution can be reduced. Since oxygen itself is an impurity to be removed from the copper solution, no other impurity removers are introduced, and the types of impurities in the copper solution do not increase. Next, because the reducing gas has reducing properties, it can react with the oxygen element in impurities to produce an oxygen-containing gas. This oxygen-containing gas is easily volatile, which can reduce the oxygen element content in the copper solution. The reducing gas can also react with other elements in the impurities besides oxygen to produce a substance that can be separated from the copper solution, further reducing the impurity content. At higher temperatures of the copper solution, the impurities still react with the oxygen element in an oxidation-reduction reaction, further reducing the impurity content. Furthermore, since high concentrations of reducing gas tend to form explosive mixtures when mixed with air, adding an inert gas can reduce the flammability range of such mixtures, thereby reducing safety risks. Additionally, as the temperature of the copper solution decreases, the solubility of impurities also decreases, and they tend to precipitate from the copper solution and react with the oxygen element to form an easily separable slag phase. In this way, impurities can be removed more thoroughly, further improving the purity of oxygen-free copper pipes.

[0026] Therefore, the method for manufacturing oxygen-free copper tubes using recycled copper in this embodiment is Step S1 involves heating the copper solution in the shaft furnace to a set temperature and adjusting the concentration of the reducing gas in the shaft furnace so that the oxygen element content in the copper solution in the shaft furnace is greater than 30 ppm, thereby removing primary impurities. Step S2 includes sequentially introducing the copper solution in the shaft furnace into a chute, a smelting furnace, a standing furnace, and a casting furnace, sequentially lowering the temperature of the copper solution in the chute, smelting furnace, standing furnace, and casting furnace, introducing an inert gas and a reducing gas into the chute, smelting furnace, standing furnace, and casting furnace, and sequentially lowering the flow rate and pressure of the inert gas and reducing gas introduced into the chute, smelting furnace, standing furnace, and casting furnace to remove secondary impurities and obtain an oxygen-free copper tube.

[0027] In step S1, by performing a reverse operation, the oxygen element content in the copper solution in the shaft furnace is first increased to more than 30 ppm, so that a sufficient amount of oxygen element reacts with the impurities through oxidation, thereby removing primary impurities and ensuring the effectiveness of impurity removal. If the oxygen element content in the copper solution in the shaft furnace is less than 30 ppm, the impurity removal effect will be lower, and the impurity content in the copper solution will still be high, making impurity removal in subsequent processing steps more difficult. If the impurity removal capacity in subsequent processing steps is weak, the impurities in the ultimately produced oxygen-free copper tube will still be higher than the target value, which may affect the quality of the oxygen-free copper tube.

[0028] In step S2, the copper solution in the shaft furnace is sequentially introduced into the chute, smelting furnace, standing furnace, and casting furnace. The temperature of the copper solution in the chute, smelting furnace, standing furnace, and casting furnace is sequentially lowered. Inert gas and reducing gas are introduced into the chute, smelting furnace, standing furnace, and casting furnace. The oxygen element in the copper solution is gradually reduced by the reducing gas as it passes through the chute, smelting furnace, standing furnace, and casting furnace in sequence, and impurities in the copper solution are gradually removed. Through multi-stage impurity removal, the copper solution achieves refinement control of the hydrogen element removal and deoxygenation process, achieving secondary impurity removal. The impurity content in the copper solution can be better controlled, and the impurities removed in the previous furnace are removed. The content decreases when the copper enters the next furnace, and accordingly, the amount of reducing gas required can also be reduced. The flow rate and pressure of the inert gas and reducing gas introduced into the chute, smelting furnace, standing furnace, and casting furnace are sequentially reduced. The sequentially reduced flow rate and pressure of the inert gas and reducing gas help control the overflow of bubbles in the copper solution and reduce pore formation, ensuring that the hydrogen removal and deoxygenation effects are always within the set range. It also helps control the degree of stirring of the copper solution and ensure the effective progress of slag formation by oxidation, improving the quality of oxygen-free copper tubes produced using recycled copper, reducing energy consumption, and improving process efficiency.

[0029] Furthermore, the reducing gas can react with oxides in the copper solution, and by adjusting the concentration of the reducing gas in the shaft furnace, the oxygen content in the copper solution can be adjusted. For example, by reducing the use of high-carbon fuels and switching coal or coke to low-carbon fuels or clean energy, the concentration of the reducing gas can be lowered, thereby allowing more oxygen to remain in the copper solution without being reduced by the reducing gas, and increasing the oxygen content in the copper solution in the shaft furnace to more than 30 ppm. Of course, the oxygen content in the copper solution can also be changed by directly introducing an oxygen-containing gas.

[0030] Specifically, the concentration of reducing gas in the shaft furnace, chute, smelting furnace, standing furnace, and casting furnace is gradually increased within a range of 2-5%. By gradually increasing the concentration of reducing gas, the impurity removal process can be controlled more precisely, and problems of over-oxidation or insufficient oxidation can be avoided. If the concentration of reducing gas is less than 2.0%, the efficiency of impurity reduction will decrease due to the low concentration of reducing gas, the production cycle will be longer, and it may not be possible to effectively remove impurities from the reduced copper, which may affect the quality of oxygen-free copper tubes. If the concentration of reducing gas is greater than 5%, the high concentration of reducing gas requires more energy for heating and mixing, increasing energy consumption. Using excessive reducing gas not only wastes resources but also increases raw material costs.

[0031] Preferably, by setting the reducing gas concentration in the shaft furnace to 2-3% and increasing the oxygen element content in the copper solution in the shaft furnace to more than 30 ppm, hydrogen elements in the copper solution are effectively removed, satisfying the requirement to keep the hydrogen element content in the copper solution below the set value. By setting the hydrogen element content to less than 0.5 ppm, the hydrogen element content can be more easily reduced to the target value in subsequent processing steps, with the target value of the hydrogen element content being less than 0.3 ppm. By maintaining the reducing gas concentration in the chute at 3-4% and gradually increasing the reducing gas concentration, the reducing atmosphere in the copper solution can be precisely controlled, optimizing the impurity removal process in the copper solution. Impurities in the copper solution are significantly reduced in the shaft furnace and chute, and tend to basically meet the quality requirements for oxygen-free copper tubes. Further impurity removal occurs in the subsequent smelting furnace, standing furnace, and casting furnace, but the effect is not significant, so it is sufficient to gradually increase the reducing gas concentration in the subsequent smelting furnace, standing furnace, and casting furnace within the range of 4-5%.

[0032] To uniformly introduce inert and reducing gases into the copper solution, ventilation bricks are installed in the chute, smelting furnace, standing furnace, and casting furnace. To ensure uniform distribution of inert and reducing gases in the copper solution and reduce localized supersaturation, an appropriate number of ventilation bricks can be selected according to the flow rate and pressure of the introduced inert and reducing gases. When the flow rate and pressure of the inert and reducing gases are high, more ventilation bricks are required to ensure uniform distribution of the gases, while when the flow rate and pressure are low, fewer ventilation bricks are required.

[0033] In this embodiment, seven ventilation bricks are installed at the bottom of the chute, six ventilation bricks at the bottom of the smelting furnace, five ventilation bricks at the bottom of the standing furnace, and four ventilation bricks at the bottom of the casting furnace. By adjusting the number of ventilation bricks according to actual production needs and product quality feedback, energy and costs are reduced while maintaining production efficiency.

[0034] Additionally, an appropriate number of ventilation bricks, such as two, three, four, five, six, seven, eight, or nine, may be installed at the bottom of the chute, smelting furnace, standing furnace, and casting furnace.

[0035] In other embodiments, it can be understood that different sizes of vent bricks may be selected to accommodate the introduction flow rates and pressures of the inert and reducing gases.

[0036] Furthermore, the flow rates of the inert gas and reducing gas introduced into the chute, smelting furnace, standing furnace, and casting furnace are sequentially reduced within the range of 10 to 30 L / min, and the pressures of the inert gas and reducing gas are sequentially reduced within the range of 0.1 to 0.5 MPa, ensuring that the hydrogen element removal and deoxygenation effects in the chute, smelting furnace, standing furnace, and casting furnace are always within the set range, while also reducing energy consumption. If the flow rates of the inert and reducing gases are greater than 30 L / min, the flow rate is too high, which can make the flow of the inert and reducing gases unstable and potentially destabilize the oxygen-free copper tube manufacturing process. This means that more energy sources will be needed to supply the inert and reducing gases, increasing production costs. If the flow rates of the inert and reducing gases are less than 10 L / min, the hydrogen removal and deoxygenation effects cannot reach the set range, resulting in lower quality oxygen-free copper tubes. If the pressure of the inert and reducing gases is greater than 0.5 MPa, the speed at which the inert and reducing gases pass through the copper solution is too fast, shortening the contact time between the inert and reducing gases and the copper solution, affecting the hydrogen removal and deoxygenation effects. If the pressure of the inert and reducing gases is less than 0.1 MPa, the inert and reducing gases cannot effectively enter the copper solution, reducing their hydrogen removal and deoxygenation effects.

[0037] Step S2 can be subdivided into the following steps. First, inert gas and reducing gas are blown into the chute from the bottom of the chute through each ventilation brick, and the flow rate of the inert gas and reducing gas blown through each ventilation brick is set to 25-30 L / min, and the pressure of the inert gas and reducing gas is set to 0.3-0.5 MPa, thereby reducing the oxygen element content in the copper solution inside the chute to less than 20 ppm and the hydrogen element content to less than 0.4 ppm, ensuring efficient removal of impurities.

[0038] Next, because the oxygen content in the copper solution entering the smelting furnace is lower than the oxygen content in the copper solution entering the chute, inert gas and reducing gas are blown into the smelting furnace from the bottom through each ventilation brick. By setting the flow rate of the inert gas and reducing gas blown in from each ventilation brick to 20-25 L / min and the pressure of the inert gas and reducing gas to 0.2-0.3 MPa, the oxygen content in the copper solution in the smelting furnace becomes less than 10 ppm and the hydrogen content becomes less than 0.4 ppm, satisfying the requirements for deoxygenation, effectively controlling the use of inert gas and reducing gas, and achieving both production efficiency and cost-effectiveness.

[0039] Furthermore, because the oxygen content in the copper solution placed in the standing furnace is lower than that in the copper solution placed in the refining furnace, inert gas and reducing gas are blown into the standing furnace from the bottom through each ventilation brick. By setting the flow rate of the inert gas and reducing gas blown in from each ventilation brick to 15-20 L / min and the pressure of the inert gas and reducing gas to 0.15-0.2 MPa, the oxygen content in the copper solution in the standing furnace becomes less than 5 ppm and the hydrogen content becomes less than 0.3 ppm, thus meeting the requirements for deoxygenation. This effectively controls the use of inert gas and reducing gas, avoids excessive processing and energy waste, and further improves both production efficiency and cost-effectiveness.

[0040] Finally, because the oxygen content in the copper solution placed in the casting furnace is lower than that in the copper solution placed in the standing furnace, inert gas and reducing gas are blown into the casting furnace from the bottom through each vent brick. By setting the flow rate of the inert gas and reducing gas blown in from each vent brick to 10-15 L / min and the pressure of the inert gas and reducing gas to 0.1-0.15 MPa, the oxygen content in the copper solution in the casting furnace becomes less than 5 ppm and the hydrogen content becomes less than 0.3 ppm, satisfying the requirements for oxygen removal. This effectively controls the use of inert gas and reducing gas, avoids excessive processing and energy waste, further balancing production efficiency and cost-effectiveness. By maintaining a low-oxygen and low-hydrogen environment in the final processing stage before casting, the purity of the copper solution is not reduced by external factors during the process of solidification and molding when the copper solution enters the mold, thereby improving the quality of the copper pipe.

[0041] Furthermore, the flow rates and pressures of the inert gas and reducing gas in the chute, smelting furnace, standing furnace, and casting furnace do not necessarily have to be as described above; other values ​​may be used, and the hydrogen and oxygen content in the final copper solution should be lower than the set values.

[0042] Furthermore, it is necessary to maintain the set temperature of the copper solution in the shaft furnace at 1200±20℃ in step S1, maintain the temperature of the copper solution in the chute at 1190±20℃ in step S2, and the temperature of the copper solution in the refining furnace at 1180±20℃, the temperature of the copper solution in the standing furnace at 1170±20℃, and the temperature of the copper solution in the casting furnace at 1160±10℃, while gradually decreasing the temperature of the copper solutions in the shaft furnace, chute, refining furnace, standing furnace, and casting furnace between 1220 and 1150℃. The high-temperature shaft furnace allows for rapid reaction, which helps remove most impurities from the copper solution. The copper solution then enters the chute as its temperature gradually decreases. As the temperature of the copper solution decreases, the impurities tend to have lower solubility, precipitate out of the copper solution, and react with oxygen to form easily separable oxides. This helps in the precipitation of oxides, thus allowing for more thorough removal of these impurities and improving the purity of the copper. The stepwise adjusted process flow helps in fine-tuning the chemical composition and physical state of the copper solution, reducing the impact of thermal stress on the microstructure of the copper solution. The resulting copper material has a more uniform composition, fewer inclusions, and better physical properties. If the temperature of the copper solution is above 1220°C, the temperature is too high, which can promote the dissolution of impurities and affect the purity of the oxygen-free copper tube. If the temperature of the copper solution is below 1150°C, the temperature is too low, which can slow down the oxidation process of impurities, reduce the slag efficiency, and potentially increase the impurity content in the oxygen-free copper tube.

[0043] Preferably, the reducing gas is CO, which is a powerful reducing agent that reacts with oxides in the copper solution to reduce the oxides to metallic copper, effectively removing oxides from the copper solution and improving the purity of recycled copper. The reduction process with CO is milder, does not abruptly change the properties of the copper solution, helps maintain the stability of the copper solution, facilitates subsequent processing steps such as refining and casting, improves the efficiency of the entire production chain and the quality of the product. Compared to other precious metal catalysts or complex chemical reagents, CO is a common industrial gas and has a relatively low cost, allowing for effective control of production costs by using CO as a reducing agent. Finally, the presence of CO reduces the solubility of hydrogen in the copper solution, promoting the precipitation of hydrogen as bubbles, which helps in the efficient removal of hydrogen, reduces the hydrogen embrittlement phenomenon of copper products, and improves their mechanical properties and service life.

[0044] Table 1 shows the composition of elements other than hydrogen and oxygen among the impurities in recycled copper.

[0045] [Table 1]

[0046] To remove elements other than hydrogen and oxygen from the impurities in recycled copper, it is preferable to set the temperature of the copper solution in the shaft furnace to 1200°C and the CO concentration in the shaft furnace to 2%. This allows for the removal of impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn by oxidation and slag formation, and the components of the resulting recycled copper are shown in Table 2.

[0047] [Table 2]

[0048] By controlling the CO concentration in the chute to 3.0%, it is preferable to raise the temperature of the copper solution to 1190°C. Impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn are further removed by oxidative slag formation, and the components of the obtained recycled copper are shown in Table 3.

[0049] [Table 3]

[0050] Using this process, after the copper solution is processed in the chute, the content of impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn meets the quality requirements for oxygen-free copper tubes. Subsequent processing of the copper solution in the refining furnace, standing furnace, and casting furnace results in small changes in the content of impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn, making detection difficult. This further optimizes the quality of oxygen-free copper tubes and is not recorded in a table.

[0051] Next, it is preferable to adjust the CO concentration in the smelting furnace to 3.5% to raise the temperature of the copper solution to 1180°C, and further remove impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn by oxidation and slag formation.

[0052] Next, it is preferable to adjust the concentration of CO in the standing furnace to 4% to raise the temperature of the copper solution to 1170°C, and further remove impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn by oxidation and slag formation.

[0053] Finally, it is preferable to adjust the CO concentration in the casting furnace to 4.5% to raise the temperature of the copper solution to 1160°C, and further remove impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn by oxidation and slag formation.

[0054] The above steps enable a gradual temperature reduction and gradual refining of the copper solution. The high-temperature stage, performed in a refining furnace, helps to rapidly react and remove most impurities; the gradual temperature reduction and subsequent entry into a standing furnace helps to precipitate impurities and further purify the solution; and finally, maintaining a relatively low temperature in a casting furnace helps to stabilize the components of the copper solution and reduce casting defects.

[0055] In this specification, the concentration of reducing gas refers to the volume ratio, which is obtained by measuring and calculating the volume occupied by the reducing gas in the shaft furnace, chute, smelting furnace, static furnace, and casting furnace. In this specification, the content of hydrogen, oxygen, and impurities refers to the mass ratio, which is determined by measuring and calculating the mass of hydrogen, oxygen, and impurities in the copper solution.

[0056] For other details not described in this embodiment, please refer to the above embodiment.

[0057] (Example 3) As shown in Figure 2, the apparatus for manufacturing oxygen-free copper tubes using recycled copper according to the present invention includes a shaft furnace 100, a chute 200, a smelting furnace 300, a standing furnace 400, and a casting furnace 500. The chute 200, smelting furnace 300, standing furnace 400, and casting furnace 500 are all fitted with ventilation bricks at the bottom for blowing in inert gas and reducing gas, thereby realizing the method for manufacturing oxygen-free copper tubes using recycled copper according to the above embodiment. An appropriate number of ventilation bricks can be selected according to the flow rate and pressure of the inert gas and reducing gas introduced into the chute 200, smelting furnace 300, standing furnace 400, and casting furnace 500.

[0058] For other details not described in this embodiment, please refer to the above embodiment.

[0059] (Example 4) In this embodiment, a method for manufacturing corrosion-resistant copper pipes using recycled copper is provided. By casting the copper solution obtained in the casting furnace in the method for manufacturing oxygen-free copper pipes using recycled copper, the content of impurities can be effectively reduced, cuprous oxide can be removed, and the potential difference between grain boundaries and within crystals can be reduced, resulting in corrosion-resistant copper pipes with excellent resistance to ant nest corrosion. By adding a phosphorus source to the copper solution, the phosphorus element can significantly improve the corrosion resistance of the copper pipes, especially when used in wet, acidic, alkaline, or seawater environments. It can also react with the oxygen element in the copper solution to form phosphorus oxides. Since the phosphorus oxides are volatile and escape at high temperatures, the oxygen content in the copper alloy is reduced. In addition to deoxygenation, the phosphorus element reacts with other elements in the impurities to form compounds that are easily separated from the copper solution, thereby further achieving the objective of purifying the copper solution. By setting the casting temperature of the copper solution to 1165℃±5℃, the high fluidity of the copper solution is ensured, which helps reduce casting defects and ensures a uniform distribution of alloys such as phosphorus. Furthermore, by setting the flow rate of the primary cooling water in the crystallization apparatus to 45~55L / min, the cooling rate of the copper solution is effectively controlled, which not only avoids internal stress and cracking due to excessive cooling but also ensures rapid hardening of the corrosion-resistant copper tube, thereby improving production efficiency. The drawing process involves setting the initial drawing speed to 100mm / min, supplying secondary cooling water after the billet is drawn, and gradually increasing the casting drawing speed within the range of 100mm / min to 350mm / min. This process allows for uniform heat dissipation, reduces uneven deformation and accumulation of internal stress, ensures dimensional accuracy and surface quality of the corrosion-resistant copper tube, facilitates uniform plastic deformation of the material, and improves the mechanical properties and pressure resistance of the corrosion-resistant copper tube.

[0060] Preferably, the casting and drawing speed is increased in stages from 100 mm / min, 170 mm / min, 200 mm / min, 250 mm / min, 300 mm / min, 330 mm / min, to 350 mm / min.

[0061] The drawing process consists of stretching, stopping, first retraction, stopping, second retraction, stopping, and then the next cycle of stretching. The periodic stretching and retraction reduces stress concentration inside the corrosion-resistant copper tube and prevents damage to the tube due to continuous stretching. The two retraction and stopping steps ensure a more uniform distribution of the copper solution, improving the structural strength and quality of the corrosion-resistant copper tube and ensuring its service life.

[0062] In other embodiments, the drawing process may be a general stretch, stop, retract, stop, and stretch for the next cycle, and it can be seen that the steps are simpler and production is more efficient.

[0063] Furthermore, to incorporate phosphorus into copper pipes, pre-alloyed phosphorus copper ingots or phosphorus copper wires may be directly added to the molten copper solution. Of course, phosphorus copper particles or powders may also be directly scattered into the copper solution. Alternatively, a copper alloy matrix with a high phosphorus content may be used and added to the copper solution after melting. Of course, the methods of adding phosphorus are not limited to these.

[0064] For other details not described in this embodiment, please refer to the above embodiment.

[0065] Apart from the preferred embodiments described above, the present application further includes other embodiments. All other embodiments derived from the embodiments of the present application without creative effort by those skilled in the art are all within the scope for which the present application seeks protection. [Explanation of symbols]

[0066] 100: Shaft furnace, 200: Chute furnace, 300: Smelting furnace, 400: Static furnace, 500: Casting furnace.

Claims

1. A method for manufacturing corrosion-resistant copper pipes using recycled copper, Step S1 involves heating the copper solution in the shaft furnace to a set temperature and adjusting the concentration of the reducing gas in the shaft furnace so that the oxygen element content in the copper solution in the shaft furnace is greater than 30 ppm, thereby removing primary impurities. Step S2 involves sequentially introducing the copper solution in the shaft furnace into the chute, smelting furnace, standing furnace, and casting furnace, sequentially lowering the temperature of the copper solution in the chute, smelting furnace, standing furnace, and casting furnace, introducing an inert gas and a reducing gas into each of the chute, smelting furnace, standing furnace, and casting furnace, and sequentially lowering the flow rate and pressure of the inert gas and reducing gas introduced into the chute, smelting furnace, standing furnace, and casting furnace to remove secondary impurities. A method for producing a corrosion-resistant copper tube using recycled copper, characterized by including step S3, which involves adding a phosphorus source to the copper solution in the casting furnace, setting the casting temperature of the copper solution to 1165°C ± 5°C, setting the flow rate of the primary cooling water in the crystallization apparatus to 45 to 55 L / min, setting the drawing speed at the start of casting to 100 mm / min, supplying secondary cooling water after the billet has been drawn, and gradually increasing the casting drawing speed within the range of 100 to 350 mm / min.

2. A method for producing corrosion-resistant copper pipes using recycled copper according to claim 1, characterized in that the concentration of reducing gas in the shaft furnace, the chute, the refining furnace, the standing furnace, and the casting furnace is sequentially increased within a range of 2 to 5%.

3. A method for producing corrosion-resistant copper pipes using recycled copper according to claim 2, characterized in that the concentration of reducing gas in the shaft furnace is set to 2-3%, the concentration of reducing gas in the chute is maintained at 3-4%, and the concentration of reducing gas in the refining furnace, the standing furnace, and the casting furnace is sequentially increased within the range of 4-5%.

4. A method for producing a corrosion-resistant copper tube using recycled copper according to claim 1, characterized in that the flow rates of the inert gas and reducing gas introduced into the chute, the refining furnace, the standing furnace, and the casting furnace are sequentially reduced within the range of 10 to 30 L / min, and the pressures of the inert gas and reducing gas are sequentially reduced within the range of 0.1 to 0.5 MPa.

5. The flow rate of the inert gas and reducing gas blown into the chute is set to 25 to 30 L / min, the pressure of the inert gas and reducing gas is set to 0.3 to 0.5 MPa, the oxygen element content in the copper solution in the chute is set to less than 20 ppm, and the hydrogen element content is set to less than 0.4 ppm. The flow rate of the inert gas and reducing gas injected into the refining furnace is set to 20 to 25 L / min, the pressure of the inert gas and reducing gas is set to 0.2 to 0.3 MPa, the oxygen content in the copper solution in the refining furnace is set to less than 10 ppm, and the hydrogen content is set to less than 0.4 ppm. The flow rate of the inert gas and reducing gas blown into the aforementioned standing furnace is set to 15 to 20 L / min, the pressure of the inert gas and reducing gas is set to 0.15 to 0.2 MPa, the oxygen element content in the copper solution in the aforementioned standing furnace is set to less than 5 ppm, and the hydrogen element content is set to less than 0.3 ppm. A method for producing a corrosion-resistant copper tube using recycled copper according to claim 4, characterized in that the flow rate of the inert gas and reducing gas blown into the casting furnace is 10 to 15 L / min, the pressure of the inert gas and reducing gas is 0.1 to 0.15 MPa, the oxygen element content in the copper solution in the casting furnace is less than 5 ppm, and the hydrogen element content is less than 0.3 ppm.

6. A method for producing corrosion-resistant copper pipes using recycled copper according to claim 1, characterized in that the temperature of the copper solution in the shaft furnace, the chute, the refining furnace, the standing furnace, and the casting furnace is sequentially reduced within a range of 1220 to 1150°C.

7. A method for manufacturing corrosion-resistant copper pipes using recycled copper according to claim 6, characterized in that the set temperature of the copper solution in the shaft furnace is maintained at 1200 ± 20°C, the temperature of the copper solution in the chute is maintained at 1190 ± 20°C, the temperature of the copper solution in the refining furnace is set to 1180 ± 20°C, the temperature of the copper solution in the standing furnace is set to 1170 ± 20°C, and the temperature of the copper solution in the casting furnace is set to 1160 ± 10°C.

8. After the removal of primary impurities in the shaft furnace, the impurities in the copper solution within the shaft furnace consist of arsenic ≤ 20 ppm, antimony ≤ 20 ppm, bismuth ≤ 20 ppm, iron ≤ 50 ppm, lead ≤ 50 ppm, tin ≤ 50 ppm, nickel ≤ 50 ppm, zinc ≤ 50 ppm, and sulfur ≤ 50 ppm. A method for manufacturing a corrosion-resistant copper tube using recycled copper according to claim 1, characterized in that, after processing in the chute, the impurities in the copper solution in the chute consist of arsenic ≤ 5 ppm, antimony ≤ 5 ppm, bismuth ≤ 5 ppm, iron ≤ 10 ppm, lead ≤ 10 ppm, tin ≤ 10 ppm, nickel ≤ 10 ppm, zinc ≤ 10 ppm, and sulfur ≤ 10 ppm.

9. A corrosion-resistant copper tube manufactured by a method for manufacturing a corrosion-resistant copper tube using recycled copper as described in any one of claims 1 to 8, characterized in that the content of oxygen in the corrosion-resistant copper tube is less than 5 ppm, the content of hydrogen is less than 0.3 ppm, the content of phosphorus is 0.1% to 0.3%, and the remainder is copper.

10. The corrosion-resistant copper tube according to claim 9, characterized in that it has a tensile strength of 250 MPa or more, a yield strength of 60 to 80 MPa, an elongation of 45% or more, a solid residue of 0.1 mg / m or less, and an internal oil residue of 0.15 mg / m or less.

11. The corrosion-resistant copper pipe according to claim 9, characterized in that the phosphorus element content is 0.1% to 0.2%.

12. The corrosion-resistant copper pipe according to claim 9, characterized in that the corrosion depth of a seamless female thread corrosion-resistant copper pipe measuring φ6.35 × 0.23 × 0.12 mm with 0.01% formic acid is less than 0.03 mm.

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