Method and device for preparing oxygen-free copper pipe from regenerated copper, corrosion-resistant copper pipe and casting process

Abstract

The invention discloses a method and a device for preparing an oxygen-free copper pipe from regenerated copper, a corrosion-resistant copper pipe and a casting process, and belongs to the field of copper treatment, and the corrosion-resistant copper pipe has the oxygen element content of less than 5 ppm, the hydrogen element content of less than 0.3 ppm, the phosphorus element content of 0.1-0.3% and the balance of copper element; the method for preparing the oxygen-free copper pipe through the regenerated copper comprises the steps that S1, molten copper in a shaft furnace is heated to the set temperature, the concentration of reducing gas in the shaft furnace is adjusted, the oxygen element content of the molten copper in the shaft furnace is increased to be larger than 30 ppm, and primary impurity removal is conducted; s2, the molten copper in the shaft furnace is sequentially introduced into a chute, a refining furnace, a standing furnace and a casting furnace, the temperature of the molten copper in the chute, the refining furnace, the standing furnace and the casting furnace is gradually decreased, inert gas and reducing gas are introduced into the chute, the refining furnace, the standing furnace and the casting furnace, and the flow and pressure of the inert gas and reducing gas introduced into the chute, the refining furnace, the standing furnace and the casting furnace are gradually decreased; and performing secondary impurity removal. The method is mainly used for preparing the oxygen-free copper pipe through the regenerated copper and preparing the corrosion-resistant copper pipe.

Description

Technical Field

[0001] The invention relates to the field of copper processing, in particular to a method and device for preparing an oxygen-free copper tube from recycled copper, and a corrosion-resistant copper tube and a casting process. Background Art

[0002] Copper tubes are widely used in marine equipment, aerospace, nuclear power, high-end equipment and refrigeration. In order to reduce dependence on natural resources, alleviate environmental pressure and provide a sustainable source of materials, copper from scrapped wires and cables, automobile radiators and refrigerators, copper-containing castings, scrap bearings, scrap motors, scrap transformers, etc. can be recycled and reused to produce oxygen-free copper tubes. However, compared with traditional copper derived from copper ore, recycled copper contains oxygen, hydrogen, and other elements such as arsenic, antimony, bismuth, iron, lead, tin, nickel, zinc, and sulfur. Oxygen, hydrogen and other elements are all impurities in oxygen-free copper tubes, and additional purification steps are required to remove impurities in order to achieve the same quality standards as traditional copper production of oxygen-free copper tubes. For this reason, existing technologies such as invention patent CN103725897A disclose a method for continuous refining of scrap copper by pyrometallurgy. The method for producing high-purity oxygen-free copper involves removing impurities through oxidation-reduction and then adding borides and rare earths for dehydrogenation and deoxidation. However, this method introduces other impurities such as borides and rare earths. The boride and rare earth residues affect the composition of the oxygen-free copper tube. Therefore, most current methods use reducing gases to reduce oxygen during the copper raw material production process to produce oxygen-free copper tubes. For example, utility model patent CN216780264U discloses a vertical furnace-horizontal continuous casting copper billet device. The billet is produced using equipment such as a vertical furnace, a refining furnace, a mixing furnace, a static furnace, and a seven-strand continuous casting furnace. The bottom wall of the refining furnace cavity is provided with air-blowing bricks. Reducing gas is blown in through the air-blowing device. By increasing the amount of reducing gas, the oxygen content in the regenerated copper tube is removed. Phosphor copper is also added to remove oxygen and other impurities. However, in the above-mentioned device, gas is only introduced into the refining furnace, and the oxygen content cannot be accurately controlled, which affects the quality of the regenerated copper tube.

[0003] At the same time, to improve the heat transfer efficiency of copper tubes and reduce energy consumption, copper tubes used in heat exchangers for aerospace and other applications are developing in the direction of thinner walls and smaller diameters. Thin walls make copper tubes more susceptible to corrosion and perforation. To this end, existing technologies, such as invention patent CN105143478A, disclose a corrosion-resistant copper tube containing phosphorus at a ratio of 0.05 to 1.0 weight percent, with the remainder consisting of Cu and unavoidable impurities. On the one hand, a high phosphorus content makes the copper tube brittle and hard, potentially causing cracks during bending or forming. On the other hand, if hydrogen and oxygen elements in the copper tube are not eliminated, the high hydrogen and oxygen contents will lead to a high content of cuprous oxide in the copper tube, resulting in a high potential difference between the grain boundaries and the intragranular space. The copper tube's resistance to anthill corrosion is still poor, and the copper tube is easily corroded. Summary of the Invention

[0004] The purpose of the present invention is to provide a corrosion-resistant copper tube, overcome the shortcomings of the existing technology, and improve the corrosion resistance of the corrosion-resistant copper tube.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a corrosion-resistant copper tube, wherein the oxygen content of the corrosion-resistant copper tube is less than 5ppm, the hydrogen content is less than 0.3ppm, the phosphorus content is 0.1% to 0.3%; and the balance is copper.

[0006] By adopting the above technical solution, by controlling the oxygen, hydrogen and phosphorus contents in the corrosion-resistant copper tube, strictly controlling the oxygen content to less than 5 ppm and the hydrogen content to less than 0.3 ppm, cuprous oxide can be effectively eliminated, and the potential difference between the grain boundaries and the intragranular space can be reduced, thereby significantly reducing the oxides and hydrogen embrittlement that may cause corrosion in the corrosion-resistant copper tube. In addition, the precise control of the phosphorus content can significantly improve the corrosion resistance of the corrosion-resistant copper tube, especially when used in humid, acidic or alkaline environments or seawater. The appropriate phosphorus content can also ensure the strength and hardness of the corrosion-resistant copper tube. Phosphorus can also react with oxygen in the copper liquid to form phosphorus oxides, which are volatile and will escape at high temperatures, thereby reducing the oxygen content in the copper alloy. In addition to deoxidation, phosphorus can also react with other elements in the impurities to form compounds that are easily separated from the copper liquid, thereby further achieving the purpose of purifying copper. Secondly, the remainder is copper element, which reduces the types of elements and ensures a higher copper content, ensuring the material's good electrical conductivity and thermal conductivity. At the same time, it also retains the good processability of copper itself, making it suitable for various forming, drawing, welding and other processing processes, and facilitating the manufacture of complex-shaped pipe fittings.

[0007] Furthermore, the corrosion-resistant copper tube has a tensile strength of not less than 250 MPa, a yield strength of 60-80 MPa, an elongation of not less than 45%, a solid residue of not more than 0.1 mg / m, and an inner wall residual oil of not more than 0.15 mg / m.

[0008] Using the above technical solution, the tensile strength is not less than 250MPa, indicating that the corrosion-resistant copper tube has a good ability to resist tensile failure and is suitable for application scenarios with large external forces. Secondly, the yield strength is 60-80MPa, which helps to improve the forming performance of the corrosion-resistant copper tube, and the elongation is not less than 45%, which means that the corrosion-resistant copper tube has good plastic deformation ability and can withstand large deformation without breaking. Then, the solid residue is not more than 0.1mg / m, which means that there are very few solid impurities remaining inside the corrosion-resistant copper tube, which helps to improve the purity and service life of the product. Next, the residual oil on the inner wall is not more than 0.15mg / m, which indicates that the inner surface of the corrosion-resistant copper tube is very clean, reducing the risk of corrosion caused by oil pollution, so that the corrosion-resistant copper tube not only has good mechanical properties, but also has excellent corrosion resistance and processing performance, suitable for a variety of harsh application environments.

[0009] Another object of the present invention is to provide a method for preparing an oxygen-free copper tube from recycled copper, comprising the following steps: S1: heating the copper liquid in the vertical furnace to a set temperature, adjusting the reducing gas concentration in the vertical furnace to increase the oxygen content of the copper liquid in the vertical furnace to greater than 30 ppm, and performing primary impurity removal; S2: The copper liquid in the vertical furnace is sequentially introduced into a chute, a refining furnace, a standing furnace, and a casting furnace. The temperature of the copper liquid in the chute, the refining furnace, the standing furnace, and the casting furnace gradually decreases. Inert gas + reducing gas are introduced into the chute, the refining furnace, the standing furnace, and the casting furnace. The flow rate and pressure of the inert gas + reducing gas introduced into the chute, the refining furnace, the standing furnace, and the casting furnace gradually decrease, and secondary impurity removal is performed to obtain an oxygen-free copper tube.

[0010] After adopting the above technical solution, the present invention has the following advantages: first, the oxygen element has oxidizing properties, and the oxygen element can react with the hydrogen element in the impurities to generate water through redox reaction, and the copper liquid in the vertical furnace is heated to the set temperature. The higher temperature of the copper liquid can provide sufficient activation energy, which promotes a faster reaction rate. The generated water will also be heated and evaporated in the form of water vapor, thereby reducing the hydrogen content in the copper liquid. At the same time, the oxygen element can also react with other elements in the impurities except hydrogen to generate oxides through oxidation reaction, and the oxides are usually insoluble in the copper liquid, but form a slag phase, which can be removed from the surface of the copper liquid by skimming, thereby reducing the impurity content in the copper liquid, and the oxygen element itself is It is an impurity that needs to be removed from the copper liquid. Without introducing other de-impurity agents, the types of impurities in the copper liquid will not increase. Therefore, the reverse operation can be performed to first increase the oxygen content of the copper liquid in the vertical furnace, and the oxygen content of the copper liquid is increased to greater than 30ppm. There can be enough oxygen to react with the impurities for oxidation, and a first-level impurity removal is performed to ensure the removal effect of the impurities. If the oxygen content of the copper liquid in the vertical furnace is lower than 30ppm, the impurity removal effect is poor, resulting in a still high impurity content in the copper liquid, which increases the difficulty of impurity removal in subsequent treatment steps. If the impurity removal ability in the subsequent treatment steps is weak, the impurities in the finally generated oxygen-free copper tube may still be higher than the target value, affecting the quality of the oxygen-free copper tube.

[0011] Secondly, since the reducing gas has reducing properties, the reducing gas can react with the oxygen element in the impurities to generate oxygen-containing gas through a reduction reaction. The oxygen-containing gas is volatile, thereby reducing the oxygen content in the copper liquid. At the same time, the reducing gas can also react with other elements in the impurities except oxygen to generate substances that can be separated from the copper liquid through a reduction reaction, further reducing the impurity content. However, the temperature of the copper liquid is relatively high, and the impurities will still react with the oxygen element to form an oxidation-reduction reaction to generate oxides that are removed from the copper liquid. Moreover, since high-concentration reducing gas is prone to form an explosive mixture when mixed with air, inert gas + reducing gas are introduced into the chute, refining furnace, standing furnace, and casting furnace. The addition of inert gas can reduce the flammability range of this mixture and reduce safety hazards. The addition of inert gas can also increase the total amount of gas, thereby increasing the speed at which the gas passes through the copper liquid, which helps to improve the reaction efficiency. In addition, the impurities in the copper liquid are gradually reduced by the reducing gas after passing through the chute, refining furnace, standing furnace, and casting furnace in sequence. The copper liquid has achieved dehydrogenation and deoxidation after multiple steps of impurity removal. Refined control of the process and secondary impurity removal can better control the content of impurities in the copper liquid, and the temperature of the copper liquid in the chute, refining furnace, standing furnace and casting furnace gradually decreases. As the temperature of the copper liquid decreases, the solubility of impurities will decrease, and they will be more likely to precipitate from the copper liquid and react with oxygen to form a slag phase that is easy to separate. This can more thoroughly remove impurities and improve the purity of the oxygen-free copper tube. The impurity content will decrease when entering the next furnace after being removed by the previous furnace. Accordingly, the required amount of reducing gas can also be reduced, so that the flow rate and pressure of the inert gas + reducing gas entering the chute, refining furnace, standing furnace and casting furnace gradually decrease. The gradually decreasing flow rate and pressure of the inert gas + reducing gas help control the overflow of bubbles in the copper liquid and reduce the formation of pores. It can also ensure that the effect of dehydrogenation and deoxidation is always within the set range. It also helps to control the stirring degree of the copper liquid, ensure the effective oxidation slagging, improve the quality of oxygen-free copper tubes produced by recycled copper, and reduce energy consumption and improve process efficiency.

[0012] Furthermore, the reducing gas concentration in the vertical furnace, chute, refining furnace, static furnace and casting furnace is gradually increased.

[0013] By adopting the above technical solution, as the reducing gas concentration gradually increases, the reduction reaction rate of the reducing gas and impurities becomes faster, thereby more effectively removing impurities. Gradually adjusting the reducing gas concentration makes the production process more flexible and can be adjusted according to different raw material or product requirements.

[0014] Furthermore, the reducing gas concentration in the vertical furnace, chute, refining furnace, static furnace and casting furnace is gradually increased from 2 to 5%.

[0015] By gradually increasing the reducing gas concentration using this technical solution, the impurity removal process can be more precisely controlled, avoiding over-oxidation or under-oxidation. If the reducing gas concentration is less than 2%, the lower reducing gas concentration may result in reduced impurity reduction efficiency, extending the production cycle and potentially failing to effectively remove impurities from the reduced copper, thus affecting the quality of the reduced copper. If the reducing gas concentration is greater than 5%, the high concentration of reducing gas may require more energy for heating and mixing, increasing energy consumption. Using excessive reducing gas not only wastes resources but also increases raw material costs.

[0016] Furthermore, the temperature of the molten copper in the vertical furnace, chute, refining furnace, static furnace and casting furnace is gradually reduced within the range of 1220-1150°C.

[0017] By adopting the above technical solution, at a higher temperature, the copper liquid maintains good fluidity, which is conducive to rapid reaction and effective removal of impurities. If the temperature of the copper liquid is higher than 1220°C, the excessively high temperature may promote the dissolution of impurities and affect the purity of the recycled copper. If the temperature of the copper liquid is lower than 1150°C, the temperature is too low and may slow down the oxidation process of impurities, reduce slag making efficiency, and result in a higher impurity content in the recycled copper.

[0018] Furthermore, the reducing gas is CO.

[0019] Using the above technical solution, CO is a powerful reducing agent that can react with oxides in the copper liquid to reduce them to metallic copper, thereby improving the purity of the recycled copper. The CO reduction process is relatively mild and will not drastically change the properties of the copper liquid, which is conducive to maintaining the stability of the copper liquid and facilitating subsequent processing steps such as refining and casting, thereby improving the efficiency of the entire production chain and product quality. Compared with other precious metal catalysts or complex chemical reagents, CO, as a common industrial gas, has a relatively low cost. Using CO as a reducing agent can effectively control production costs. Finally, the presence of CO can also reduce the solubility of hydrogen in the copper liquid, prompting the precipitation of hydrogen in the form of bubbles, which helps to efficiently remove hydrogen, reduce hydrogen embrittlement of copper products, and improve their mechanical properties and service life.

[0020] Another object of the present invention is to provide a device for preparing oxygen-free copper tubes from recycled copper, comprising a vertical furnace, a chute, a refining furnace, a static furnace and a casting furnace, wherein the chute, the refining furnace, the static furnace and the casting furnace are all equipped with breathable bricks at the bottom for blowing in inert gas + reducing gas, thereby realizing the method for preparing oxygen-free copper tubes from recycled copper as described in any of the above technical solutions.

[0021] By adopting the above technical solution, the breathable brick design ensures that the gas is evenly distributed at the bottom of the furnace, which increases the contact area and reaction efficiency between the gas and the copper liquid, helps to effectively reduce the impurity content in the copper liquid and improve the purity of the copper liquid.

[0022] Another object of the present invention is to provide a casting process for corrosion-resistant copper tubes, wherein a copper liquid is obtained from a casting furnace of the method for preparing oxygen-free copper tubes from recycled copper as described in any one of the above technical solutions, a phosphorus source is added to the copper liquid, and the casting temperature of the copper liquid is 1165°C. 5℃, the primary cooling water flow rate of the crystallizer is 45-55L / min, and a traction program is adopted. In the traction program, the casting pulling speed is 100mm / min. After the ingot is pulled out, the secondary cooling water is turned on, and the casting traction speed is gradually increased from 100 to 350mm / min to cast the corrosion-resistant copper tube described in the above technical solution.

[0023] Using the above technical solution, the casting temperature is set to 1165℃ 5℃, which ensures that the copper liquid has good fluidity and helps to reduce casting defects. At the same time, a phosphorus source is added to the copper liquid. The phosphorus element can significantly improve the corrosion resistance of the corrosion-resistant copper tube, especially when used in humid, acidic or alkaline environments or seawater. The phosphorus element can also react with the oxygen element in the copper liquid to form phosphorus oxides, which are volatile and will escape at high temperatures, thereby reducing the oxygen element in the copper alloy. In addition to deoxidation, phosphorus can also react with other elements in the impurities to form compounds that are easy to separate from the copper liquid, thereby further achieving the purpose of purifying the copper liquid. Controlling the primary cooling water flow rate of the crystallizer can not only effectively control the cooling rate of the copper liquid and avoid internal stress and cracks caused by too rapid cooling, but also ensure the rapid solidification of the corrosion-resistant copper tube and improve production efficiency. Secondly, gradually increasing the speed from the initial 100mm / min to 350mm / min helps to dissipate heat evenly, reduce uneven deformation and internal stress accumulation, ensure the dimensional accuracy and surface quality of the corrosion-resistant copper tube, and is conducive to uniform plastic deformation of the material, thereby improving the mechanical properties and pressure resistance of the corrosion-resistant copper tube. The method of preparing oxygen-free copper tubes from recycled copper to obtain copper liquid can effectively reduce the impurity content, thereby eliminating cuprous oxide and reducing the potential difference between the grain boundary and the grain. The corrosion-resistant copper tube has excellent resistance to anthill corrosion.

[0024] Furthermore, the traction procedure is: pull-stop-retreat-stop-retreat-stop-pull.

[0025] By adopting the above technical solution, through periodic stretching and retraction actions, the stress concentration inside the corrosion-resistant copper tube can be reduced, and damage to the corrosion-resistant copper tube caused by continuous stretching can be avoided. The two retraction steps can also ensure a more uniform distribution of the copper liquid, thereby improving the structural strength and quality of the corrosion-resistant copper tube, and also ensuring the service life of the corrosion-resistant copper tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 This is a flow chart of the method for preparing oxygen-free copper tubes from recycled copper in the present invention; Figure 2 This is a schematic structural diagram of the device for preparing oxygen-free copper tubes from recycled copper in the present invention; In the figure, 100 is a vertical furnace; 200 is a chute; 300 is a refining furnace; 400 is a static furnace; and 500 is a casting furnace. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0028] The terms "first," "second," "third," "fourth," and so forth (if any) in the description and claims of the present invention and in the accompanying drawings are used to distinguish similar items and are not necessarily used to describe a particular order or sequential sequence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present invention described herein can be practiced in sequences other than those illustrated or described herein.

[0029] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the processes does not mean the order of execution. The execution order of the processes should be determined by their functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0030] It should be understood that in the present invention, "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0031] It should be understood that in the present invention, "plurality" refers to two or more. "And / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, X and / or Y can represent three situations: X exists alone, X and Y exist at the same time, and Y exists alone. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "Including X, Y and Z" and "Including X, Y, Z" means that X, Y, and Z are all included. "Including X, Y or Z" means that one of X, Y, and Z is included. "Including X, Y and / or Z" means that any one, any two, or any three of X, Y, and Z are included.

[0032] The following specific embodiments are used to describe the technical solution of the present invention in detail. The following specific embodiments can be combined or replaced with each other according to actual conditions, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0033] Example 1:

[0034] The present invention provides a corrosion-resistant copper tube, which controls the oxygen, hydrogen and phosphorus contents in the corrosion-resistant copper tube. The oxygen content of the corrosion-resistant copper tube is less than 5 ppm and the hydrogen content is less than 0.3 ppm, thereby effectively eliminating cuprous oxide in the corrosion-resistant copper tube produced by recycled copper and reducing the potential difference between the grain boundary and the grain. The phosphorus content is 0.1% to 0.3%, and the balance is copper, so that the corrosion-resistant copper tube produced by recycled copper significantly reduces the oxides and hydrogen embrittlement that may cause corrosion in the corrosion-resistant copper tube. In addition, the precise control of the phosphorus content can significantly improve the corrosion resistance of the corrosion-resistant copper tube, especially when used in humid, acidic, alkaline or seawater conditions. The appropriate phosphorus content can also ensure the strength and hardness of the corrosion-resistant copper tube. Secondly, the corrosion-resistant copper tube has fewer types of impurities, ensures a higher copper content, ensures good electrical conductivity and thermal conductivity of the material, and also retains the good processability of the copper itself, is suitable for various forming, drawing and welding processes, and is convenient for manufacturing pipe fittings of complex shapes. To make the performance of corrosion-resistant copper tube: tensile strength is not less than 250MPa, corrosion-resistant copper tube has good resistance to tensile damage, suitable for application scenarios with large external forces, secondly, yield strength of 60~80MPa, which helps to improve the forming performance of corrosion-resistant copper tube, and elongation is not less than 45%, which means that the copper tube has good plastic deformation ability and can withstand large deformation without breaking, then, solid residue is not more than 0.1mg / m, which means that there are very few solid impurities remaining inside the corrosion-resistant copper tube, which helps to improve the purity and service life of the product, then, the residual oil on the inner wall is not more than 0.15mg / m, so that the corrosion-resistant copper tube not only has good mechanical properties, but also has excellent corrosion resistance and processing performance, suitable for a variety of harsh application environments.

[0035] If the phosphorus content in corrosion-resistant copper tubes is too low, they are susceptible to corrosion. If the phosphorus content is too high, the tubes become brittle and hard, affecting their ductility and toughness, and potentially causing cracks during bending or forming. Preferably, the phosphorus content in corrosion-resistant copper tubes is 0.1% to 0.2%, which minimizes the phosphorus content while ensuring the copper tubes' resistance to formicary pitting corrosion.

[0036] The phosphorus content and copper content mentioned in this article refer to the mass ratio, which is determined by measuring and calculating the mass of phosphorus and copper in the corrosion-resistant copper tube.

[0037] in, The corrosion depth of 6.35×0.23×0.12mm seamless internal thread corrosion-resistant copper tube in 0.01% formic acid can be less than 0.03mm. Of course, the corrosion depth can be even smaller in corrosion-resistant copper tubes of other sizes.

[0038] Example 2:

[0039] like Figure 1 As shown, the present invention provides a method for preparing oxygen-free copper tubes from recycled copper, which is mainly suitable for processing recycled copper materials. The recycled copper mainly contains oxygen and hydrogen, as well as 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 redox reactions. The copper liquid in the vertical furnace is heated to a set temperature. The high temperature of the copper liquid can provide sufficient activation energy, promoting a faster reaction rate. The generated water will also be heated and evaporated in the form of water vapor, thereby reducing the hydrogen content in the copper liquid. At the same time, oxygen can also react with other elements in the impurities other than hydrogen through oxidation reactions to produce oxides. The oxides are generally insoluble in the copper liquid and form a slag phase. The slag phase can be removed from the surface of the copper liquid by skimming, thereby reducing the impurity content in the copper liquid. Oxygen itself is an impurity that needs to be removed from the copper liquid. No other decontamination agent is introduced, and the types of impurities in the copper liquid will not increase. And, secondly, since the reducing gas is reducing, the reducing gas can react with the oxygen element in the impurities to generate oxygen-containing gas through a reduction reaction. The oxygen-containing gas is volatile, thereby reducing the oxygen content in the copper liquid. At the same time, the reducing gas can also react with other elements in the impurities except oxygen to generate substances separable from the copper liquid through a reduction reaction, further reducing the impurity content. However, the temperature of the copper liquid is relatively high, and the impurities will still react with the oxygen element to form an oxidation-reduction reaction, further reducing the impurity content. Moreover, since high-concentration reducing gas is prone to form an explosive mixture when mixed with air, adding an inert gas can reduce the flammability range of the mixture and reduce safety hazards. In addition, as the temperature of the copper liquid decreases, the solubility of the impurity content will also decrease, and it will be more inclined to precipitate from the copper liquid and react with the oxygen element to form a slag phase that is easy to separate. This can more thoroughly remove impurities and further improve the purity of the oxygen-free copper tube.

[0040] To this end, the method for preparing an oxygen-free copper tube from recycled copper in this embodiment includes the following steps: S1: The copper liquid in the vertical furnace is heated to the set temperature, and the reducing gas concentration in the vertical furnace is adjusted to increase the oxygen content of the copper liquid in the vertical furnace to more than 30ppm for primary impurity removal; S2: The copper liquid in the vertical furnace is sequentially introduced into the chute, refining furnace, standing furnace and casting furnace. The temperature of the copper liquid in the chute, refining furnace, standing furnace and casting furnace gradually decreases. Inert gas + reducing gas are introduced into the chute, refining furnace, standing furnace and casting furnace. The flow rate and pressure of the inert gas + reducing gas introduced into the chute, refining furnace, standing furnace and casting furnace gradually decrease, and secondary impurity removal is performed to obtain oxygen-free copper tubes.

[0041] S1 increases the oxygen content of the copper liquid in the vertical furnace through reverse operation, and increases the oxygen content of the copper liquid to greater than 30ppm, so that there is enough oxygen to react with impurities for oxidation, perform primary impurity removal, and ensure the removal effect of impurities. If the oxygen content of the copper liquid in the vertical furnace is lower than 30ppm, the impurity removal effect is poor, resulting in a still high impurity content in the copper liquid, which increases the difficulty of impurity removal in subsequent processing steps. If the impurity removal ability in the subsequent processing steps is weak, the impurities in the final generated oxygen-free copper tube may still be higher than the target value, affecting the quality of the oxygen-free copper tube.

[0042] In S2, the copper liquid in the vertical furnace is passed into the chute, refining furnace, standing furnace and casting furnace in turn. The temperature of the copper liquid in the chute, refining furnace, standing furnace and casting furnace gradually decreases. The chute, refining furnace, standing furnace and casting furnace are all introduced with inert gas + reducing gas. The oxygen element in the copper liquid is gradually reduced by the reducing gas in the chute, refining furnace, standing furnace and casting furnace in turn, and the impurities in the copper liquid are gradually removed. After multiple steps of impurity removal, the copper liquid can also achieve fine control of the process of removing hydrogen and deoxidizing elements, obtain secondary impurity removal, and better control the content of impurities in the copper liquid. The content of impurities is reduced after the previous furnace. After removal, the content will decrease when entering the next furnace. Correspondingly, the required amount of reducing gas can also be reduced, so that the flow rate and pressure of the inert gas + reducing gas entering the chute, refining furnace, static furnace, and casting furnace will gradually decrease. The gradually decreasing flow rate and pressure of the inert gas + reducing gas will help control the overflow of bubbles in the copper liquid and reduce the formation of pores. It can also ensure that the effect of dehydrogenation and deoxidation is always within the set range. It also helps to control the stirring degree of the copper liquid, ensure the effective oxidation slagging, improve the quality of oxygen-free copper tubes produced by recycled copper, and reduce energy consumption and improve process efficiency.

[0043] It should be noted that reducing gas reacts with oxides in the copper melt. Adjusting the reducing gas concentration in the shaft furnace can adjust the oxygen content in the copper melt. For example, by reducing the use of high-carbon fuels, such as coal or coke, and switching to low-carbon fuels or clean energy, the reducing gas concentration can be reduced. This allows more oxygen to remain in the copper melt rather than being reduced by the reducing gas, thereby increasing the oxygen content of the copper melt in the shaft furnace to greater than 30 ppm. Of course, the oxygen content of the copper melt can also be adjusted by directly introducing an oxygen-containing gas.

[0044] Specifically, the reducing gas concentration in the vertical furnace, chute, refining furnace, static furnace, and casting furnace is gradually increased from 2 to 5%. By gradually increasing the reducing gas concentration, the impurity removal process can be more accurately controlled to avoid problems of over-oxidation or under-oxidation. If the reducing gas concentration is less than 2.0%, the lower reducing gas concentration may lead to reduced impurity reduction efficiency, extend the production cycle, and may not be able to effectively remove impurities in the reduced copper, thereby affecting the quality of the oxygen-free copper tube. If the reducing gas concentration is greater than 5%, the high concentration of reducing gas may require more energy for heating and mixing, thereby increasing energy consumption. Using excessive reducing gas not only wastes resources, but also increases raw material costs.

[0045] Preferably, the reducing gas concentration of the vertical furnace is 2-3%, so that the oxygen content of the copper liquid in the vertical furnace is increased to greater than 30ppm, so as to effectively remove the hydrogen element in the copper liquid and make the hydrogen element content in the copper liquid lower than the set value, the set value hydrogen element content is less than 0.5ppm, so that the subsequent treatment steps can more easily reduce the hydrogen element content to the target value, the target value hydrogen element content is less than 0.3ppm. The reducing gas concentration of the chute is maintained at 3-4%. By gradually increasing the reducing gas concentration, the reducing atmosphere in the copper liquid can be accurately controlled and the impurity removal process in the copper liquid can be optimized. The impurities in the copper liquid can be significantly reduced in the vertical furnace and chute, basically tending to meet the quality requirements of oxygen-free copper tubes. The subsequent refining furnace, static furnace, and casting furnace further remove impurities, but the effect is not very obvious. Therefore, the reducing gas concentration of the subsequent refining furnace, static furnace, and casting furnace only needs to be gradually increased to 4-5%.

[0046] To ensure a more even flow of inert gas and reducing gas into the molten copper, air bricks are installed in the chute, refining furnace, static furnace, and casting furnace. The appropriate number of air bricks should be selected based on the flow rate and pressure of the inert gas and reducing gas, ensuring uniform distribution of the inert gas and reducing gas in the molten copper and reducing local oversaturation. When the flow rate and pressure of the inert gas and reducing gas are high, more air bricks are needed to ensure uniform gas distribution; when the flow rate and pressure of the inert gas and reducing gas are low, fewer air bricks are needed.

[0047] In this embodiment, 7 air bricks are installed at the bottom of the chute, 6 air bricks are installed at the bottom of the refining furnace, 5 air bricks are installed at the bottom of the static furnace, and 4 air bricks are installed at the bottom of the casting furnace. The number of air bricks is adjusted according to actual production needs and product quality feedback, saving energy and costs while maintaining production efficiency.

[0048] It should be noted that 2, 3, 4, 5, 6, 7, 8, 9 or other appropriate numbers of air bricks can also be installed on the bottom of the chute, refining furnace, static furnace and casting furnace.

[0049] It is understandable that in other embodiments, air-permeable bricks of different sizes may be selected to adapt to the flow rate and pressure of the inert gas+reducing gas.

[0050] Furthermore, the flow rate of inert gas + reducing gas introduced into the chute, refining furnace, standing furnace and casting furnace is gradually reduced within 10 to 30 L / min, and the pressure of inert gas + reducing gas is gradually reduced within 0.1 to 0.5 MPa, thereby ensuring that the effect of removing hydrogen and deoxidizing elements in the chute, refining furnace, standing furnace and casting furnace is always within the set range while reducing energy consumption. If the flow rate of the inert gas + reducing gas is greater than 30 L / min, the excessively high flow rate may cause the flow of the inert gas + reducing gas to be unstable, resulting in instability in the preparation process of the oxygen-free copper tube, and also means that more energy is required to provide the inert gas + reducing gas, which will increase production costs; if the flow rate of the inert gas + reducing gas is less than 10 L / min, the effect of dehydrogenation and deoxidation cannot reach the set range, resulting in poor quality of the produced oxygen-free copper tube; if the pressure of the inert gas + reducing gas is greater than 0.5 MPa, the speed at which the inert gas + reducing gas passes through the copper liquid is too fast, reducing the contact time between the inert gas + reducing gas and the copper liquid, affecting the effect of dehydrogenation and deoxidation; if the pressure of the inert gas + reducing gas is less than 0.1 MPa, the inert gas + reducing gas cannot effectively enter the copper liquid, thereby reducing its dehydrogenation and deoxidation effect.

[0051] S2 can be broken down into the following steps: first, inert gas + reducing gas is blown into the chute from the bottom of the chute through each breathable brick, wherein the flow rate of inert gas + reducing gas blown into each breathable brick is 25-30 L / min, and the pressure of inert gas + reducing gas is 0.3-0.5 MPa, so that the oxygen content of the copper liquid in the chute is less than 20 ppm, and the hydrogen content is less than 0.4 ppm, which can ensure efficient impurity removal.

[0052] Secondly, since the oxygen content in the copper liquid entering the refining furnace is lower than that in the copper liquid entering the chute, inert gas + reducing gas is blown into the refining furnace from the bottom of the refining furnace through each breathable brick, wherein the flow rate of inert gas + reducing gas blown into each breathable brick is 20~25L / min, and the pressure of inert gas + reducing gas is 0.2~0.3MPa, so that the oxygen content of the copper liquid in the refining furnace is less than 10ppm and the hydrogen content is less than 0.4ppm, which meets the requirements for deoxygenation, effectively controls the use of inert gas + reducing gas, and takes into account both production efficiency and cost-effectiveness.

[0053] Next, since the oxygen content in the copper liquid entering the static furnace is lower than that in the copper liquid entering the refining furnace, inert gas + reducing gas is blown into the static furnace from the bottom of the static furnace through each breathable brick, wherein the flow rate of the inert gas + reducing gas blown into each breathable brick is 15~20L / min, and the pressure of the inert gas + reducing gas is 0.15~0.2MPa, so that the oxygen content of the copper liquid in the static furnace is less than 5ppm and the hydrogen content is less than 0.3ppm, which meets the requirements for deoxygenation, effectively controls the use of inert gas + reducing gas, avoids excessive processing and waste of energy, and further takes into account production efficiency and cost-effectiveness.

[0054] Finally, since the oxygen content in the copper liquid entering the casting furnace is lower than that in the copper liquid entering the static furnace, inert gas + reducing gas is blown into the casting furnace from the bottom of the casting furnace through each breathable brick, wherein the flow rate of inert gas + reducing gas blown into each breathable brick is 10-15L / min, and the pressure of inert gas + reducing gas is 0.1-0.15MPa, so that the oxygen content of the copper liquid in the casting furnace is less than 5ppm and the hydrogen content is less than 0.3ppm, which meets the requirements for deoxidation, effectively controls the use of inert gas + reducing gas, avoids excessive processing and energy waste, and further takes into account production efficiency and cost-effectiveness. In the final processing stage before casting, a low oxygen and low hydrogen environment is maintained to ensure that the purity of the copper liquid will not be reduced due to external factors during the process of entering the mold and solidification, thereby improving the quality of the copper tube.

[0055] It should be noted that the flow rate and pressure of the inert gas + reducing gas in the chute, refining furnace, static furnace and casting furnace are not necessarily as described above, and other values ​​can also be used to ensure that the content of hydrogen and oxygen elements in the final copper liquid is lower than the set value.

[0056] Furthermore, the set temperature of the copper liquid in the vertical furnace in S1 is maintained at 1200±20℃, the temperature of the copper liquid in the chute in S2 is maintained at 1190±20℃, the temperature of the copper liquid in the refining furnace can also be 1180±20℃, the temperature of the copper liquid in the static furnace can also be 1170±20℃, and the temperature of the copper liquid in the casting furnace can be 1160±10℃. The copper liquid temperatures of the vertical furnace, chute, refining furnace, static furnace, and casting furnace must gradually decrease between 1220 and 1150℃. The higher temperature in the vertical furnace is conducive to rapid reaction and removal of most impurities in the copper liquid. The temperature of the copper liquid gradually decreases as it enters the chute. As the temperature of the copper liquid drops, the solubility of impurities decreases, and they are more likely to precipitate from the copper liquid and react with oxygen to form easily separable oxides, which helps the oxide precipitation. This can more thoroughly remove these and improve the purity of the copper. The step-by-step adjustment process is conducive to detailed control of the chemical composition and physical state of the copper liquid, reducing the impact of thermal stress on the microstructure of the copper liquid. The final copper material has a more uniform composition, fewer inclusions and better physical properties. If the copper liquid temperature is higher than 1220℃, the excessively high temperature may promote the dissolution of impurities and affect the purity of the oxygen-free copper tube. If the copper liquid temperature is lower than 1150℃, the temperature is too low and may slow down the oxidation process of impurities, reduce the slag-making efficiency, and result in a higher impurity content in the oxygen-free copper tube.

[0057] Preferably, the reducing gas is CO. CO is a powerful reducing agent that can react with oxides in the copper liquid to reduce them to metallic copper, effectively remove oxides in the copper liquid, and improve the purity of the recycled copper. The CO reduction process is relatively mild and will not drastically change the properties of the copper liquid, which is conducive to maintaining the stability of the copper liquid, facilitating subsequent refining, casting and other processing steps, and improving the efficiency and product quality of the entire production chain. Compared with other precious metal catalysts or complex chemical reagents, CO is a common industrial gas with a relatively low cost. Using CO as a reducing agent can effectively control production costs. Finally, the presence of CO can also reduce the solubility of hydrogen in the copper liquid, promote the precipitation of hydrogen in the form of bubbles, help to efficiently remove hydrogen, reduce hydrogen embrittlement of copper products, and improve their mechanical properties and service life.

[0058] It should be noted that the composition of impurities in recycled copper other than hydrogen and oxygen is shown in Table 1: Table 1 Content of other elements in the impurities of recycled copper except hydrogen and oxygen

[0059] In order to remove other elements except hydrogen and oxygen from the impurities of the recycled copper, the temperature of the copper liquid in the shaft furnace is preferably 1200°C, and the CO concentration in the shaft furnace is 2%. Impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn are removed by oxidation slagging. The composition of the recycled copper obtained is shown in Table 2: Table 2 Content of other elements except hydrogen and oxygen in the impurities of copper liquid in the shaft furnace

[0060] By controlling the CO concentration in the chute to 3.0%, the copper liquid temperature is preferably 1190°C, and impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn are further removed by oxidation slagging. The composition of the obtained recycled copper is shown in Table 3: Table 3 Content of other elements except hydrogen and oxygen in the impurities of copper liquid in the chute

[0061] With this process, after the copper liquid is treated in the chute, the impurity contents of Bi, Sb, As, Fe, Ni, Pb, Sn, S, Zn, etc. meet the quality requirements of oxygen-free copper tubes. The copper liquid is subsequently treated in the refining furnace, static furnace, and casting furnace. The content of impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, Zn, etc. changes little and is difficult to detect. In order to further optimize the quality of oxygen-free copper tubes, they are no longer recorded in a table.

[0062] Next, by adjusting the CO concentration in the refining furnace to 3.5%, the copper liquid temperature is preferably 1180°C, and impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn are further removed by oxidation slagging.

[0063] Then, by adjusting the CO concentration in the static furnace to 4%, the copper liquid temperature is preferably 1170°C, and impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn are further removed by oxidation slagging.

[0064] Finally, by adjusting the CO concentration in the casting furnace to 4.5%, the copper liquid temperature is preferably 1160°C, and impurities such as Bi, Sb, As, Fe, Ni, Pb, Sn, S, and Zn are further removed by oxidation slagging.

[0065] The above steps allow for gradual cooling and step-by-step refining of the copper melt. The high-temperature stage, carried out in the refining furnace, facilitates rapid reaction and removes most impurities. The temperature gradually decreases as it enters the resting furnace, aiding impurity precipitation and further purification. Finally, the lower temperature maintained in the casting furnace helps stabilize the copper melt's composition and reduce casting defects.

[0066] It should be noted that the reducing gas concentration mentioned herein refers to the volume ratio, determined by measuring and calculating the volume occupied by the reducing gas in the vertical furnace, chute, refining furnace, static furnace, and casting furnace. The hydrogen, oxygen, and impurity contents mentioned herein refer to the mass ratio, determined by measuring and calculating the mass of hydrogen, oxygen, and impurities in the copper liquid.

[0067] For other contents not described in this embodiment, please refer to the above embodiments.

[0068] Example 3:

[0069] like Figure 2 As shown, the present invention provides an apparatus for preparing oxygen-free copper tubes from recycled copper, comprising a vertical furnace 100, a chute 200, a refining furnace 300, a standing furnace 400, and a casting furnace 500. The chute 200, the refining furnace 300, the standing furnace 400, and the casting furnace 500 are all equipped with breathable bricks at the bottom for blowing in inert gas + reducing gas. To implement the method for preparing oxygen-free copper tubes from recycled copper in the above embodiment, the flow rate and pressure of the inert gas + reducing gas introduced into the chute 200, the refining furnace 300, the standing furnace 400, and the casting furnace 500 can be adjusted.

[0070] For other contents not described in this embodiment, please refer to the above embodiments.

[0071] Example 4:

[0072] This embodiment provides a casting process for a corrosion-resistant copper tube. The recycled copper raw material is cast using copper liquid obtained from a casting furnace of any of the above-mentioned methods for preparing oxygen-free copper tubes from recycled copper, which can effectively reduce the content of impurities, thereby eliminating cuprous oxide and reducing the potential difference between grain boundaries and within the grains. The corrosion-resistant copper tube has excellent resistance to anthill corrosion. Secondly, a phosphorus source is added to the copper liquid. The phosphorus element can significantly improve the corrosion resistance of the copper tube, especially when used in humid, acidic, alkaline or seawater environments. The phosphorus element can also react with the oxygen element in the copper liquid to form phosphorus oxides. The phosphorus oxides are volatile and will escape at high temperatures, thereby reducing the oxygen content in the copper alloy. In addition to deoxidation, the phosphorus element can also react with other elements in the impurities to form compounds that are easily separated from the copper liquid, thereby further achieving the purpose of purifying the copper liquid. The casting temperature of the copper liquid is 1165℃±5℃, which ensures that the copper liquid has good fluidity, helps to reduce casting defects, and ensures the uniform distribution of alloys such as phosphorus. Then the primary cooling water flow rate of the crystallizer is 45-55L / min, which can effectively control the cooling rate of the copper liquid and avoid internal stress and cracks caused by too rapid cooling, and ensure that the corrosion-resistant copper tube is quickly solidified, thereby improving production efficiency. A traction program is adopted, in which the casting pulling speed is 100mm / min. After the ingot is pulled out, the secondary cooling water is turned on, and the casting traction speed is gradually increased from 100mm / min to 350mm / min. The corrosion-resistant copper tube of Example 1 is cast to obtain uniform heat dissipation, reduce uneven deformation and internal stress accumulation, ensure the dimensional accuracy and surface quality of the corrosion-resistant copper tube, and is conducive to uniform plastic deformation of the material, thereby improving the mechanical properties and pressure resistance of the corrosion-resistant copper tube.

[0073] Preferably, the casting traction speed is increased step by step from 100 mm / min, 170 mm / min, 200 mm / min, 250 mm / min, 300 mm / min, 330 mm / min, and 350 mm / min.

[0074] The pulling process is: pull-stop-retract-stop-retract-stop-pull. This cyclical stretching and retraction reduces stress concentration within the corrosion-resistant copper tube, preventing damage to the tube caused by continuous stretching. The two retraction and stop steps also ensure a more even distribution of the copper liquid, improving the structural strength and quality of the corrosion-resistant copper tube and extending its service life.

[0075] It is understandable that in other embodiments, the pulling procedure may also be the common pull-stop-retract-stop-pull, which has simpler steps and more efficient production.

[0076] It should be noted that phosphorus can be added to the copper tube by directly adding pre-alloyed phosphorus copper ingots or wires to the molten copper. Alternatively, phosphorus copper particles or powders can be added directly to the molten copper. Alternatively, a copper master alloy containing a high phosphorus content can be melted and added to the molten copper. The method of adding phosphorus is not limited to this.

[0077] For other contents not described in this embodiment, please refer to the above embodiments.

[0078] In addition to the above-mentioned preferred embodiments, the present invention has other implementation modes. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection requested by the present invention.

Claims

1. Corrosion-resistant copper tube, characterized in that: The corrosion-resistant copper tube has an oxygen content of less than 5 ppm, a hydrogen content of less than 0.3 ppm, a phosphorus content of 0.1% to 0.3%, and the remainder is copper.

2. The corrosion-resistant copper tube according to claim 1, characterized in that: The corrosion-resistant copper tube has a tensile strength of not less than 250 MPa, a yield strength of 60-80 MPa, an elongation of not less than 45%, a solid residue of not more than 0.1 mg / m, and an inner wall residual oil of not more than 0.15 mg / m.

3. A method for preparing oxygen-free copper tubes from recycled copper, characterized in that: The following steps are involved: S1: heating the copper liquid in the vertical furnace to a set temperature, adjusting the reducing gas concentration in the vertical furnace, so that the oxygen content of the copper liquid in the vertical furnace is increased to greater than 30 ppm, and performing primary impurity removal; S2: The molten copper in the vertical furnace is sequentially introduced into a chute, a refining furnace, a standing furnace, and a casting furnace. The temperature of the molten copper in the chute, the refining furnace, the standing furnace, and the casting furnace gradually decreases. Inert gas + reducing gas are introduced into the chute, the refining furnace, the standing furnace, and the casting furnace. The flow rate and pressure of the inert gas + reducing gas introduced into the chute, the refining furnace, the standing furnace, and the casting furnace gradually decrease, and secondary impurity removal is performed to obtain an oxygen-free copper tube.

4. The method for preparing oxygen-free copper tube from recycled copper according to claim 3, characterized in that: The reducing gas concentration in the vertical furnace, chute, refining furnace, static furnace and casting furnace increases gradually.

5. The method for preparing oxygen-free copper tube from recycled copper according to claim 4, characterized in that: The reducing gas concentration in the vertical furnace, chute, refining furnace, static furnace and casting furnace is gradually increased from 2 to 5%.

6. The method for preparing oxygen-free copper tube from recycled copper according to claim 3, characterized in that: The temperature of the molten copper in the vertical furnace, chute, refining furnace, static furnace and casting furnace gradually decreases from 1220 to 1150°C.

7. The method for preparing oxygen-free copper tube from recycled copper according to claim 3, characterized in that: The reducing gas is CO.

8. A device for preparing oxygen-free copper tubes from recycled copper, characterized in that: The invention comprises a vertical furnace, a chute, a refining furnace, a static furnace and a casting furnace, wherein the chute, the refining furnace, the static furnace and the casting furnace are all provided with air-permeable bricks at the bottom for blowing in inert gas + reducing gas, so as to realize the method for preparing oxygen-free copper tubes from recycled copper as described in any one of claims 3 to 7.

9. A casting process for corrosion-resistant copper tubes, characterized in that: The copper liquid obtained from the casting furnace of the method for preparing oxygen-free copper tube from recycled copper as described in any one of claims 3 to 7 is cast, a phosphorus source is added to the copper liquid, the casting temperature of the copper liquid is 1165°C±5°C, the primary cooling water flow rate of the crystallizer is 45-55L / min, a traction program is adopted, in which the casting starting speed is 100mm / min, the secondary cooling water is turned on after the ingot is pulled out, and the casting traction speed is gradually increased within 100-350mm / min to obtain the corrosion-resistant copper tube as described in claim 1 or 2 by casting.

10. The casting process of the corrosion-resistant copper tube according to claim 9, characterized in that: The traction procedure is: pull-stop-retract-stop-retract-stop-pull.

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