A microalloyed copper alloy, a preparation method and applications thereof

Abstract

The application discloses a micro-alloyed copper alloy, a preparation method and application, and the micro-alloyed copper alloy comprises the following components in percentage by mass: trace elements: 0.05-2.0%, P: 0.015-0.04%, and the balance is Cu and inevitable impurities; wherein the trace elements comprise at least one of Ni or Zn. The copper alloy of the application can also add Mn. The application controls the type and proportion of trace elements to regulate the performance of the alloy, so that the prepared copper alloy has excellent corrosion resistance and stress fatigue resistance characteristics on the basis of maintaining good high strength and high pressure resistance and processing performance, and can overcome the problems of insufficient pressure resistance, poor corrosion resistance and fatigue resistance of the existing copper pipe, and has a wide application prospect in the fields of air conditioning, refrigeration, electronic communication, aerospace and the like. Meanwhile, the copper alloy of the application also has stable process performance and meets the requirements of large-scale production.

Description

Technical Field

[0001] This application relates to the field of alloys, and more particularly to a micro-alloyed copper alloy, its preparation method, and its application. Background Technology

[0002] Precision copper alloy materials play an irreplaceable role in many manufacturing fields such as aerospace, electronic communications, power transmission, energy equipment, heat exchange equipment, and medical devices due to their excellent thermal conductivity, electrical conductivity, and processability. The optimization and breakthrough of their performance are directly related to the reliability, energy efficiency, lightweight level and service life of key equipment, making them one of the important supporting materials for the development of modern industrial technology.

[0003] Taking heat exchange as an example, the core materials used in copper tubes are mainly phosphorus-deoxidized copper (TP1, TP2) and oxygen-free copper (TU2). These copper tubes not only have excellent thermal conductivity, enabling them to efficiently transfer heat from the refrigerant, but also possess good processing and welding properties, as well as certain pressure resistance and resistance to uniform corrosion. They are key tube materials used in heat exchangers of refrigeration systems.

[0004] Currently, the application and technological innovation of copper tubes in the heat exchange field are strongly influenced by two factors. On the one hand, the industry is accelerating the transformation to clean and low-carbon technologies and the conservation and utilization of copper resources to achieve synergistic development of environmental benefits and energy efficiency optimization. In recent years, new environmentally friendly refrigerants (such as CO2, R407c, and R410a) have been promoted for application due to their lower ozone layer depletion potential. These refrigerants are typical high-pressure refrigerants, and their refrigeration system operating pressure is 1.5 to 5 times higher than that of traditional medium- and low-pressure refrigerants (such as R22), which places higher demands on the pressure resistance of copper tubes. At the same time, in order to reduce manufacturing costs and conserve copper resources, copper tubes for refrigeration are gradually developing towards smaller weight and thinner walls, which further requires the material to maintain high pressure resistance and reliability even after thinning.

[0005] CN200910135785.2 discloses a high-pressure-resistant copper alloy containing at least 0.1–2.0% tin, 0.05–1.0% zinc, and 0.01–0.05% phosphorus, with the remainder being copper and impurities. This alloy exhibits higher pressure resistance compared to phosphorus-deoxidized copper, but the excessive tin content significantly deteriorates its cold-working and processing properties. Furthermore, tin has a low diffusion rate in copper, a large difference in melting point compared to copper, and severe dendrite segregation, which may lead to hot brittleness during high-temperature processing. Moreover, tin is significantly more expensive than copper, resulting in poor economic efficiency.

[0006] On the other hand, corrosive environments and complex operating conditions significantly affect the service life of copper pipes. Among these, carboxylic acid-induced anthill corrosion (named for the three-dimensional network corrosion morphology caused by the erosion of organic carboxylic acids) is a major cause of leakage failure in copper pipes of heating, ventilation, and air conditioning systems. This corrosion process occurs in humid environments with oxygen content >5 ppm, humidity >60%, and the presence of carboxylate ions (COOH-). Carboxylic acids erode the outer layer of copper oxide / copper hydroxide on the copper surface, generating unstable cuprous carboxylate complexes and cuprous oxide. The continuous accumulation of cuprous oxide leads to volume expansion, resulting in crack clusters, which in turn expose more copper surface to the corrosive environment, forming multi-directional corrosion pathways. Anthill corrosion can cause through-hole failure in thin-walled copper pipes within 90 days, leading to refrigerant leakage and system energy efficiency degradation.

[0007] CN202411806731.5 discloses a corrosion-resistant copper pipe with an oxygen content of <5ppm, a hydrogen content of <0.3ppm, a phosphorus content of 0.1-0.3%, and the balance being copper. However, at room temperature, the maximum solid solubility of phosphorus in copper is only 0.02%, which easily forms a brittle phase and covers the grain boundaries, increasing the brittleness of the alloy, making plastic processing more difficult, and reducing the service life of the copper pipe.

[0008] Furthermore, during the operation of heat exchange equipment (such as air conditioner outdoor units), continuous vibrations are transmitted to the connecting pipes. At structurally weak points, copper undergoes significant wavy slip due to cyclic loading, resulting in intense strain concentration and the formation of stationary slip bands (PSBs). Damage at the PSB interface accumulates continuously, eventually leading to microcrack nucleation and propagation, ultimately causing fatigue failure. This process is more pronounced during high-frequency compressor start-stop cycles. Simultaneously, the weakening of the pipe wall by anthole corrosion, the thermodynamic alternating loads caused by frequent refrigerant phase changes within the pipes, and the stress concentration caused by copper pipe bending during installation further exacerbate the risk of copper pipe fatigue failure.

[0009] CN202211649209.1 discloses a fatigue-resistant copper alloy containing 0.05–0.095% nickel, 0.05–0.095% tin, 0.005–0.1% iron, 0.001–0.1% aluminum, 0.015–0.04% phosphorus, and no more than 0.05% impurity elements, with the balance being copper. This invention primarily improves the overall strength of the alloy material and inhibits fatigue crack initiation through the use of iron. However, iron has extremely low maximum solid solubility in copper, easily forming a hard and brittle phase, reducing the processing performance of the copper alloy, and increasing the risks during bending and flaring of copper tubes. Meanwhile, iron oxidizes preferentially over copper, and its oxide (iron oxide Pilling-Bedworth ratio of approximately 2.15, hereinafter referred to as PB ratio) is not conducive to the formation of a dense oxide layer, weakening the protective film on the surface of copper alloys. The potential difference between +3 valent iron ions (+0.77V) and copper (+0.342V) also increases the risk of corrosion.

[0010] Furthermore, in harsh and complex environmental applications, such as marine engineering and aerospace, even more stringent requirements are placed on the safety and reliability of copper alloy materials. Therefore, given the shortcomings of existing technologies and the need for safety and reliability of materials used in harsh and complex environments, there is an urgent need to develop copper alloy materials with excellent stress fatigue resistance and corrosion resistance, as well as high strength, high pressure resistance, and good machinability. This would address the problems of insufficient pressure resistance and weak corrosion and fatigue resistance in existing copper alloy materials, making them suitable for various working conditions, especially improving their applicability under complex conditions. Summary of the Invention

[0011] The purpose of this invention is to provide a micro-alloyed copper alloy, its preparation method, and its applications. The copper alloy of this invention, while maintaining good high strength, high pressure resistance, and machinability, possesses excellent corrosion resistance and stress fatigue resistance, overcoming the problems of insufficient pressure resistance and poor corrosion and fatigue resistance in existing copper materials. Furthermore, the copper alloy of this invention also exhibits stable processing properties and can meet the needs of large-scale production.

[0012] The first aspect of the present invention provides a copper alloy comprising the following components in weight percentage: trace elements: 0.05-2.0%, P: 0.015-0.04%, and the balance being Cu and unavoidable impurities;

[0013] The trace elements include at least one of Ni or Zn.

[0014] Ni and Cu have infinite solid solution; their atomic radii differ by 3.2%. Ni can form a binary α solid solution with copper, causing copper lattice contraction and tensile stress distortion. Ni also plays a role in stabilizing the oxide film on the copper surface. NiO has a PB ratio of 1.65, enabling it to form a dense oxide film and stabilize the oxide layer on the copper surface. Ni in the oxide layer... 2+ It can enter Cu + The presence of vacancies in Cu increases the ionic resistance of the Cu2O film, raises the electron work function, and enhances the corrosion resistance of the alloy. Therefore, adding trace amounts of Ni to Cu can increase the corrosion potential, improve passivation ability, and reduce the corrosion rate of the alloy.

[0015] The maximum solid solubility of Zn in Cu is 39.9%, and the atomic radius difference is 4.2%. Zn can form a binary α solid solution with Cu, causing lattice expansion and compressive stress distortion. Simultaneously, Zn can reduce the stacking fault energy of Cu, promoting the transformation from wavy slip to planar slip and twinning activation, thereby improving the alloy's work hardening ability. It strengthens the alloy while maintaining high uniform elongation plasticity, achieving simultaneous strengthening and toughening. Under fatigue loading, planar slip and twinning make the local strain distribution of the copper alloy more uniform, hindering the formation of lodged slip bands. This changes the fatigue crack initiation mechanism of the copper alloy from interfacial cracking at the lodged slip band and matrix to more difficult-to-initiate grain boundary and twin boundary cracking, thus significantly improving the alloy's fatigue life. Furthermore, Zn's standard electrode potential is lower than Cu's, protecting the copper matrix and inhibiting grain boundary corrosion.

[0016] This invention modifies the properties of copper alloy materials by adding Ni and / or Zn. Both Ni and Zn have extremely high solid solubility in copper, with an atomic radius difference of no more than 5%, forming a substitutional solid solution with the copper matrix. Whether added alone or in combination, Ni and Zn do not precipitate a hard and brittle second phase that deteriorates plasticity and ductility, forming a single α-solid solution. This characteristic is unaffected by processing and heat treatment. The increase in lattice distortion of the copper matrix due to the addition of Ni and Zn is moderate, with a change in lattice constant not exceeding [a certain percentage]. While enhancing the critical shear stress for initiation of each slip system in face-centered cubic crystals and hindering dislocation movement, sufficient uniform elongation plasticity is maintained, and ample processing windows are reserved, thus achieving synergistic and controlled strong plasticity. Since there is no precipitation of a hard and brittle second phase or weakening of grain boundaries, it does not significantly affect the machinability and processing properties of the copper alloy. Furthermore, the addition of elements, individually or in combination, refines the matrix grains, increases the grain boundary area, accumulates a higher number density of geometrically necessary dislocations at the grain boundaries, alleviates localized stress concentration at grain boundaries, and effectively delays fatigue crack initiation.

[0017] Preferably, the trace element is Ni, and the content of Ni is 0.1% to 1.0%.

[0018] When the Ni content is less than 0.1%, the corrosion resistance and fatigue resistance are not significant; when the Ni content exceeds 1.0%, the processing performance of pipes such as bends fluctuates considerably. This invention controls the Ni content within the above range, ensuring that the copper alloy material has good corrosion resistance and fatigue resistance without affecting its processing performance.

[0019] Preferably, the trace element is Zn, and the Zn content is 0.1% to 1.0%.

[0020] When the Zn content is less than 0.1%, the strengthening and fatigue resistance effects are not significant, and there is no corrosion resistance in acidic atmospheres. When the Zn content exceeds 1.0%, the processing performance deteriorates rapidly. This invention controls the Zn content within the above range, ensuring that the copper alloy material has good strengthening and fatigue resistance effects, improves corrosion resistance, and does not affect its processing performance.

[0021] Preferably, the trace elements are Ni and Zn, and the total content of Ni and Zn is 0.2% to 1.0%.

[0022] The combined addition of Ni and Zn can produce a synergistic effect, simultaneously improving the corrosion resistance and fatigue resistance of the alloy. To more effectively leverage the synergistic effect of Ni and Zn, the addition amount of both should not be less than 0.2%, but to maintain the plasticity and processing properties of the material, the addition amount should not exceed 1.0%.

[0023] More preferably, the mass ratio of Ni to Zn satisfies: 1 ≤ Ni / Zn ≤ 3.

[0024] This invention controls the addition and ratio of Ni and Zn to prevent the local distortions of compressive and tensile stresses in the alloy from canceling each other out. Instead, the controlled addition and ratio of Ni and Zn achieve a superposition effect of distortions, resulting in bidirectional lattice distortion, increasing the material's configurational entropy, and enhancing the pinning effect on dislocations. This further strengthens the material and improves its compressive strength and fatigue resistance. The corrosion of Cu2O is mainly due to its large number of Cu vacancies. Ni ions can fill these vacancies, improving its stability. Zn ions have a larger radius than Cu ions, making it difficult to fill Cu vacancies, but the volume expansion of its oxide can fill oxide film defects, acting as a physical barrier. This invention, by controlling the addition and ratio of Ni and Zn, achieves a synergistic effect between the ZnO-dominated physical barrier and the NiO-dominated anti-permeability, delaying the diffusion of corrosive media and protecting the matrix. Simultaneously, the synergistic solid solution treatment of Ni and Zn regulates the local potential of the copper matrix, reducing the tendency for galvanic corrosion.

[0025] Ni, as the dominant element, should have a higher content than Zn, but not more than three times that of Zn; otherwise, it will not exert a synergistic effect. If the Ni / Zn ratio is unbalanced and the Ni content is insufficient, Ni's ability to suppress the high-temperature softening tendency of Zn will weaken. Simultaneously, the low-corrosion-driving-force micro-cells formed due to the smaller potential difference between Ni and Zn will be disrupted, reducing the beneficial effect. If Zn is excessive, its stronger strengthening effect or grain boundary segregation tendency can easily lead to poor processing performance.

[0026] Preferably, the trace element further includes Mn, and the content of Mn is 0.1-0.5%.

[0027] Mn can improve the passivation ability of copper alloys, especially in oxidizing environments (such as seawater and acidic media), where it forms a dense Mn oxide protective film, slowing down further corrosion. Simultaneously, Mn can enhance the strength and hardness of copper alloys through solid solution strengthening, delaying the initiation of fatigue cracks. When the Mn content is less than 0.1%, it does not synergistically improve the corrosion resistance and fatigue resistance of the material with Ni and Zn, and its pre-deoxidation and improved processing performance effects are also not significant. When its content exceeds 0.5%, it is more prone to segregation, affecting the processing and technological properties of the material.

[0028] It should be noted that the Fe content in the copper alloy of the present invention must be strictly controlled below 0.005%, because Fe phase precipitation will significantly deteriorate the material's processing performance, and the Fe phase will hinder the diffusion of Mn, affecting the formation of manganese oxide film during corrosion, thereby leading to a decrease in the material's corrosion resistance.

[0029] Preferably, the trace elements are Ni and Mn, and the total content of Ni and Mn is 0.1% to 1.0%.

[0030] Mn oxidation products can fill the Ni-reinforced Cu2O oxide film, further improving the corrosion resistance of copper alloy materials. Furthermore, the synergistic effect of Mn and Ni enhances the work hardening ability of the material, making it more fatigue-resistant under dynamic loads. This invention controls the total Ni and Mn content within the aforementioned range, fully leveraging the synergistic effect of Ni and Mn to effectively improve the corrosion resistance and fatigue resistance of the material, while maintaining good plasticity and avoiding adverse effects on processes such as pipe bending and flaring.

[0031] More preferably, the mass ratio of Ni to Mn satisfies Ni / Mn≥1.6.

[0032] The electrode potential of Mn is lower than that of Ni. Although the electrode potential difference between Mn and Ni is smaller than that between Mn and Cu, an excess of Mn will significantly increase the proportion of the anodic active region. Ni / Mn ≥ 1.6 can slow down galvanic-driven corrosion and optimize the properties of the oxide film.

[0033] Preferably, the trace elements are Zn and Mn, and the total content of Zn and Mn is 0.1% to 1.0%.

[0034] The oxidation products of Mn intertwine with those formed by zinc corrosion to compensate for defects in the Cu2O film, forming a denser and more stable mixed film, which can further improve the corrosion resistance of the material. Simultaneously, the grain-refining effect of Mn combined with the solid solution strengthening effect of Zn can reduce dislocation accumulation during fatigue and inhibit crack propagation. This invention controls the Zn and Mn contents within the aforementioned ranges, fully leveraging the synergistic effect of Zn and Mn to effectively improve the corrosion resistance and fatigue resistance of the material, preventing a decrease in material plasticity and avoiding deterioration of processing properties such as pipe bending and flaring.

[0035] More preferably, the mass ratio of Zn to Mn satisfies Zn / Mn≥1.5.

[0036] Mn has good corrosion resistance but weak strengthening effect. Maintaining the above Zn / Mn ratio can better synergistically improve the fatigue resistance and corrosion resistance of the material.

[0037] Preferably, the trace elements are Mn, Ni, and Zn, and the total content of Mn, Ni, and Zn is 0.2% to 1.0%. When the addition amount of Ni, Zn, and Mn is too low, its corrosion resistance and fatigue strengthening effect are insufficient. Therefore, it is preferred that their total content is not less than 0.2%. When their total addition amount is higher than 1%, the process performance deteriorates rapidly.

[0038] Preferably, the mass ratio of Mn, Ni and Zn satisfies 1≤(Ni+Mn) / Zn≤3, and Ni / Mn>1.

[0039] Both Ni and Mn possess corrosion-resistant properties, and their functions are complementary. Mn can work synergistically with Ni to stabilize the surface oxide film, and due to its lower corrosion potential, it corrodes and passivates before Ni during the corrosion process, providing continuous protection. Therefore, Ni and Mn should be added simultaneously, but their ratio to Zn should not be less than 1, and the Ni content should be greater than the Mn content to suppress the high-temperature softening characteristics of Zn and Mn. Excessive Zn, in addition to causing rapid deterioration of the material's processing performance, will also hinder the diffusion of Ni and Mn, impeding the formation of the passivation film during the corrosion process. Therefore, the mass ratio of Mn, Ni, and Zn (Ni+Mn) / Zn should not exceed 3.

[0040] More preferably, the total content of Mn, Ni, and Zn is 0.5% to 1.0%. When the addition amount of Ni, Zn, and Mn is higher than 0.5%, its corrosion resistance and fatigue strengthening effect are better.

[0041] More preferably, the mass ratio of Mn, Ni, and Zn satisfies 1 ≤ (Ni + Mn) / Zn ≤ 2, and Ni / Mn > 1. To balance the fluidity of the multi-element melt, reduce casting defects, further balance various properties, and increase the proportion of inexpensive elements, this invention further optimizes the mass ratio of Mn, Ni, and Zn ((Ni + Mn) / Zn not greater than 2).

[0042] Preferably, the content of the unavoidable impurities is no more than 0.06%. This invention controls the impurity content within the above range to prevent impurity element segregation at grain boundaries or the precipitation of brittle phases, which could lead to processing cracks and affect processing performance.

[0043] Preferably, the content of oxygen (O) in the unavoidable impurities is less than 17 ppm. This invention prevents the precipitation of the brittle Cu₂O phase and the occurrence of hydrogen embrittlement by controlling the O content within the above range.

[0044] Preferably, the copper alloy of the present invention is a single α phase. Mn, Ni, and Cu have infinite solid solubility, and Zn has a maximum solid solubility of 39.9% in Cu. All three have extremely high solid solubility and do not precipitate a second phase. Simultaneously, the atomic radius difference between the three atoms and the copper atom is less than 5%, forming a single solid solution according to the Hume-Rothery solid solution rule. In contrast, existing technologies such as high-phosphorus copper alloys have a matrix α phase and a second phase of phosphide precipitation. Although these have good corrosion resistance, the precipitated phosphides are located within the grains or at grain boundaries, leading to discontinuous matrix strain, increased brittleness, and decreased toughness. The α phase has a face-centered cubic crystal structure and abundant slip systems. The copper alloy of the present invention maintains its processability and machinability by ensuring a single α phase.

[0045] Preferably, the average grain size of the copper alloy of the present invention is 5–40 μm. According to the Hall-Page relation, grain refinement can improve material strength, and simultaneously increase crystal orientation diversity and deformation uniformity. Therefore, it is preferable that the average grain size of the copper alloy is within 40 μm. At the same time, grain refinement leads to an increase in grain boundary area, increasing the risk of Zn element grain boundary segregation and grain boundary corrosion. Therefore, the average grain size should not be less than 5 μm. More preferably, the average grain size of the copper alloy of the present invention is 5–20 μm. Compared with the prior art, the copper alloy of the present invention has a smaller grain size than conventional TP2 copper, resulting in stronger strengthening and more uniform deformation capabilities.

[0046] Preferably, the lattice constant of the copper alloy of the present invention is: To ensure the processing performance of copper alloys, alloying elements should be added with moderate strengthening. Excessive differences in atomic radii between added elements and the copper matrix, or excessive amounts of added elements, will significantly alter the lattice size and increase lattice distortion. The relationship between the lattice constant and the amount of solute atoms added is: a = k y c + a0, where a is the lattice constant after adding solute atoms of concentration c, and a0 is the lattice constant of phosphorus deoxidized copper. The k of the added element... y Value To prevent lattice mismatch and modulus mismatch from severely deteriorating processability and machinability, and to maintain a balance between strong and ductile properties, the lattice constant of the copper alloy of this invention is controlled within a certain range, taking into account the amount of added elements and the fluctuation of a0 itself.

[0047] Preferably, the configurational entropy of the copper alloy is 0.15–0.67 J / (mol·K). The configurational entropy of pure copper is 0 J / (mol·K), and it increases with the number of element types and their concentration. Adding nickel or zinc alone can provide a mild strengthening effect, effectively ensuring processing and technological performance, but the amount added is limited, making further improvement of material properties difficult. In this invention, the copper alloy, under the condition of limited element concentration, increases the configurational entropy of the copper alloy through multi-element composite addition. That is, the number of combinations in which alloy element atoms replace copper lattice atoms increases, achieving a quaternary solid solution configurational entropy of 0.67 J / (mol·K), approximately 54% higher than that of a binary solid solution. This allows the two-dimensional lattice distortion to develop into a multi-dimensional structure, significantly increasing tensile strength and fatigue failure period.

[0048] Preferably, the copper alloy has a yield strength ≤ 85 MPa, tensile strength ≥ 245 MPa, elongation after fracture ≥ 40%, and burst pressure that is more than 5% higher than that of phosphorus-deoxidized copper products of the same specification. The copper alloy of this invention possesses excellent compressive strength and other properties, meeting market demands for high-performance copper pipes.

[0049] Preferably, the copper alloy exhibits a corrosion leakage rate of ≤30% after 35 days of alternating hot and cold corrosion in a 0.8% formic acid aqueous solution atmosphere, and a fatigue failure period of ≥6.5×10 under a maximum stress of 60MPa. 5 .

[0050] The copper alloy of this invention, while possessing high strength and high pressure resistance, can significantly reduce corrosion leakage rate, greatly improve fatigue life, and ensure good machinability. Specifically, the corrosion leakage rate of the copper alloy of this invention can be reduced by more than 60% compared to copper alloys in the prior art, and the fatigue failure cycle can be increased by more than 10 times.

[0051] The present invention relates to a copper alloy that forms an oxide film containing trace elements during corrosion. The PB ratio of the oxide film containing trace elements is 1.5 to 1.8, and the thickness is 0.02 to 0.2 μm. The oxide film containing trace elements includes an oxide film containing Ni, an oxide film containing Zn, an oxide film containing Ni and Zn, or an oxide film containing Ni, Zn, and Mn.

[0052] When the alloying elements are Ni and / or Zn, the diffusion of corrosive media is mainly delayed through the physical barrier dominated by ZnO and / or the anti-permeation property dominated by NiO, protecting the matrix. In composite addition, it also plays a role in regulating the local potential of the copper matrix and reducing the tendency for galvanic corrosion. Under the same corrosion conditions, its oxide layer thickness is thinner than Cu2O, and the oxide layer composition is more uniform. When Ni, Zn, and Mn are added in combination, differences in elemental ion concentrations were observed at different depths of the oxide layer. At the surface, the oxide film mainly consists of Cu2O and trace amounts of NiO, Mn2O3, and ZnO, with ion ratios positively correlated with the alloy chemical composition. The subsurface layer, deeper than 10–20 nm, forms an oxide layer through diffusion control. Due to its low diffusion rate, Zn in the oxide layer... 2+ The content decreases. In the innermost low-oxygen region, a Cu2O and MnO oxide film mainly forms. Mn has a lower standard electrode potential than other elements, making it more affinityous for oxygen and easier to oxidize into a stable oxide film. Based on the measured elemental content of each layer, the PB ratio is calculated to be approximately 1.5–1.8, indicating a dense and defect-free local oxide film. The potential difference between different oxide layers in the multilayer film can induce a local micro-cell effect, preferentially oxidizing the highly active metal layer (Mn) and promoting the low-activity metal layer (Ni) to maintain a passivated state, achieving dynamic repair of the oxide film. Through the synergistic effect of chemical passivation, the migration of corrosive media to the substrate is inhibited. During the corrosion process, MnO can continuously form, inhibiting anodic dissolution in corrosion propagation. Especially when combined with Ni, it can make the open circuit potential more positive, and the resulting corrosion product film is more protective, thereby reducing the corrosion rate of the alloy.

[0053] The second aspect of the present invention provides a method for preparing the above-mentioned copper alloy, which is simple and suitable for large-scale production.

[0054] The method for preparing the copper alloy of the present invention includes the following steps: batching and smelting → continuous casting → rolling → diameter reduction → finished product annealing;

[0055] In the batching and smelting process, the raw materials that meet the proportions are smelted at 1150-1300℃, and after the raw materials are completely melted, they are kept at that temperature for more than 60 minutes.

[0056] In the finished product annealing process, the annealing temperature is 420-700℃ and the annealing time is 20-180min.

[0057] This invention improves the mechanical properties of the copper alloy by increasing the melting temperature and holding time of trace elements, thereby ensuring their full diffusion and homogenization. This stabilizes the mechanical properties of the billet and enhances subsequent processing performance. Simultaneously, the addition of microalloying elements alters the thermodynamic properties of the copper alloy, increasing the recrystallization temperature. Building upon this, the invention also dynamically adjusts the annealing temperature and time of the finished product, controlling the grain size and properties of the final product with lower energy consumption. This results in a copper alloy that maintains good high strength and high pressure resistance while exhibiting excellent resistance to anthill corrosion and stress fatigue, and whose processing performance meets application requirements. Preferably, the holding time in the batching and melting process is 60-240 minutes.

[0058] Preferably, in the batching and smelting process, Ni, Mn, and P are added in the form of master alloys, such as copper-nickel master alloys, copper-manganese master alloys, and phosphorus-copper master alloys. Zn is added in the form of zinc ingots.

[0059] According to the phase diagram, the melting points of copper-nickel and copper-manganese master alloys are approximately 1280℃ and 882℃, respectively, which are significantly lower than their pure metal melting points. Therefore, this invention chooses to add Ni and Mn in the form of master alloys, which is beneficial for promoting melting and reducing burn-off. The melting point of phosphorus copper master alloy is approximately 995℃, lower than that of pure copper, and there is no problem with it being difficult to melt.

[0060] Preferably, the mass percentage of Ni in the copper-nickel master alloy is 42-47%, the mass percentage of Mn in the copper-manganese master alloy is 28-32%, and the mass percentage of P in the phosphorus-copper master alloy is 13-15%. It should be noted that the Ni content in the copper-nickel master alloy, the Mn content in the copper-manganese master alloy, and the P content in the phosphorus-copper master alloy of the present invention may not fall within the above ranges, and commercially available master alloy products can be used.

[0061] Preferably, before smelting, the raw materials and auxiliary materials undergo a drying pretreatment. Specifically, the raw materials include copper, copper-nickel master alloy, copper-manganese master alloy, phosphor bronze master alloy, zinc ingots, etc. The auxiliary materials include charcoal / bamboo charcoal (particle size 20-60mm), graphite flakes (fixed carbon content ≥99%), etc. The charcoal / bamboo charcoal is used for protective covering of the molten copper in the melting furnace during settling, with a covering thickness of 100-150mm. The graphite flakes are used for protective covering of the molten copper in the holding furnace, with a covering thickness of 50-100mm.

[0062] After the batching and smelting process is completed, the molten copper is transferred to a holding furnace under nitrogen protection and held at a constant temperature before being continuously cast into a tube blank. The continuous casting can be horizontal or vertical. Horizontal continuous casting is preferred, wherein the holding temperature during horizontal continuous casting is 1180–1185℃, and the holding time is 8–10 min. The traction speed in the horizontal continuous casting process is 340–380 mm / min, the primary cooling water flow rate is 30–35 L / min, and the secondary cooling water flow rate is 65–75 L / min. This invention prepares tube blanks of the desired size through horizontal continuous casting. The outer diameter of the tube blank can be designed according to actual needs, for example, it can be 90–98 mm, specifically 92 mm.

[0063] Preferably, in the rolling process, the rolling speed is 1.2 to 2 m / min, and a rolled tube blank is obtained after rolling. The dimensions of the rolled tube blank can be designed according to actual needs, for example, the outer diameter of the rolled tube blank is 50 to 55 mm, and the wall thickness is 2.3 to 2.7 mm.

[0064] Preferably, the diameter reduction includes one or a combination of continuous drawing and coil drawing. For example, the diameter reduction of the present invention can employ continuous drawing or coil drawing alone, or a combination of continuous drawing-coil drawing, continuous drawing-continuous drawing, coil drawing-coil drawing, etc. The number of passes in coil drawing and continuous drawing can be adjusted according to actual needs.

[0065] Preferably, the diameter change can also be cold rolling, and the number of cold rolling passes can be adjusted according to actual needs.

[0066] Preferably, in the diameter-changing process, the cumulative deformation is ≥80%. By controlling the cumulative deformation within the above range, the present invention can ensure sufficient deformation energy is stored, promoting uniform recrystallization during subsequent annealing to obtain fine equiaxed crystals.

[0067] Preferably, the diameter change adopts a combined drawing and coil drawing process. The number of passes and specific process parameters of the drawing and coil drawing processes can be flexibly adjusted according to actual production needs to ensure that the final product meets the target model and size requirements.

[0068] Preferably, in the combined drawing process, the drawing speed is controlled at 70–90 m / min. After combined drawing, a precision tube blank with a significantly reduced outer diameter is obtained, providing a semi-finished product that meets dimensional requirements for subsequent processing steps. For example, after combined drawing, the outer diameter of a rolled tube blank with an outer diameter of 50–55 mm and a wall thickness of 2.3–2.7 mm is reduced to 30–35 mm, and the wall thickness is reduced to 1.4–1.7 mm.

[0069] After the continuous drawing process, the obtained precision tube blank is drawn in a coil to produce tubes of the required type and size, including but not limited to high-precision copper alloy tubes such as plain tubes, internally threaded tubes, special-shaped tubes, and capillary tubes.

[0070] Preferably, in the coiling process, the number of coiling passes is 5 to 9, with the first pass coiling speed at 400 to 450 m / min and subsequent passes at 450 to 800 m / min. For example, the number of coiling passes can be 7 to 9, with the first pass coiling speed at 400 to 450 m / min, the intermediate passes at 660 to 700 m / min, and the last three passes at 550 to 650 m / min. Alternatively, the number of coiling passes can be 5 to 7, with the first pass coiling speed at 400 to 450 m / min and subsequent passes at 700 to 800 m / min. After coiling, a rigid tube or smooth tube blank with the designed outer diameter and wall thickness is obtained.

[0071] Preferably, when preparing the optical tube, the annealing temperature of the finished product is 450–650°C, and the time is 20–120 min. Annealing promotes static recrystallization of the material, eliminates deformed structures, and results in fine and uniform grains in the prepared product, further improving its corrosion resistance and fatigue resistance. More preferably, the annealing temperature is 480–560°C, and the annealing time is 60–120 min.

[0072] Preferably, when preparing the internally threaded tube, the annealing temperature of the finished product is 420–600℃, and the time is 20–120 min. Annealing eliminates deformed structures, resulting in fine and uniform grains in the prepared product, further improving its corrosion resistance and fatigue resistance. More preferably, the annealing temperature is 420–560℃, and the annealing time is 30–90 min.

[0073] It should be noted that in the preparation of the internally threaded tube, after coil drawing, online annealing is performed to soften the tube blank. The preferred online annealing speed is 350–450 m / min, and the current is 4200–5000 A. Subsequently, the tube blank obtained from online annealing is subjected to internal thread spinning. The preferred spinning speed in the internal thread spinning process is 480–650 r / m, more preferably 550–600 r / m. Afterward, a final annealing treatment is performed to obtain the internally threaded tube.

[0074] It should be noted that the copper alloy composition provided by this invention is not only suitable for pipe production, but also for the preparation of various copper alloy products such as wire, bar, plate, strip, and profile. The production process can adopt existing mature processing technologies, such as extrusion, rolling, drawing, and forging, or optimize and adjust process parameters or develop new processing methods according to specific product performance requirements and application scenarios, such as continuous casting-hot rolling-cold rolling combined process, precision die forging, equal channel angle extrusion (ECAE) and other advanced forming technologies, to meet the diverse needs of different industries for copper alloy materials.

[0075] The third aspect of this invention provides applications of the aforementioned copper alloy or the copper alloy prepared by the aforementioned method in fields such as air conditioning and refrigeration, electronic communications, aerospace, marine engineering, and chemical and energy equipment. The copper alloy of this invention possesses high strength and high pressure resistance, resistance to anthill corrosion, and resistance to stress fatigue. It also exhibits good processing and technological properties, overcoming the problems of insufficient pressure resistance and poor corrosion and fatigue resistance found in existing copper tubes. It is suitable for operation in complex environments, and the preparation method is simple, adaptable to the requirements of large-scale production, and has broad application prospects in fields such as air conditioning and refrigeration, aerospace, and marine engineering.

[0076] Compared with the prior art, the present invention has at least the following technical effects:

[0077] This invention introduces a copper alloy by adding trace elements (Ni, Zn, Mn, etc.) that do not contain Fe or Sn to Cu. By controlling the type and ratio of these trace elements and improving the subsequent preparation process, the resulting copper alloy possesses excellent stress fatigue resistance and corrosion resistance, in addition to its good high strength, high pressure resistance, and machinability. This makes it suitable for various working conditions, especially complex ones, and has broad application prospects in fields such as air conditioning and refrigeration, and marine engineering. Furthermore, the preparation method of this copper alloy is simple and suitable for large-scale production. Attached Figure Description

[0078] Figure 1 (a) Figure 1 (b) Figure 1 (c) and Figure 1 (d) are metallographic images of the copper alloys of Comparative Example 24, Example 6, Example 13 and Example 16, respectively.

[0079] Figure 2 The XRD patterns are for Comparative Example 24, Example 6, Example 13 and Example 16.

[0080] Figure 3 The following are engineering stress-strain curves for Comparative Example 24, Example 6, Example 13, and Example 16.

[0081] Figure 4 The results of X-ray photoelectron spectroscopy (XPS) analysis of the surface, 10 nm and 20 nm depth of the sample after etching in a sealed box with 0.8% formic acid aqueous solution for 48 hours in Example 16 are shown.

[0082] Figure 5 The results of fine X-ray photoelectron spectroscopy (XPS) analysis of Mn and Zn at surface, 10 nm, and 20 nm depths after etching in a sealed chamber with 0.8% formic acid aqueous solution for 48 hours in Example 16 are shown. Figure 5(a) is the fine spectrum of Mn elements on the surface; Figure 5 (b) shows the fine elemental spectrum of the surface Zn; where Figure 5 (c) is the fine spectrum of Mn elements at an etching depth of 10 nm; Figure 5 (d) shows the fine spectrum of Zn elements at an etching depth of 10 nm; where Figure 5 (e) is the fine spectrum of Mn elements at an etching depth of 20 nm; Figure 5 (f) is the fine spectrum of Zn elements at an etching depth of 20 nm. Detailed Implementation

[0083] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0084] Existing copper materials suffer from insufficient adaptability to high-pressure environments, poor corrosion resistance, and susceptibility to fatigue failure during application. These problems severely restrict the reliability and service life of equipment manufactured using them. Furthermore, research indicates that improving the corrosion resistance and fatigue resistance of copper alloys often leads to a deterioration in their machinability and processing properties, failing to meet production and usage requirements.

[0085] To solve the above-mentioned technical problems, the design concept of this invention is as follows:

[0086] This invention modifies the properties of copper alloy materials by adding trace elements to copper. The preferred trace elements are nickel (Ni) and / or zinc (Zn), with atomic radii of 0.124 nm for Ni, 0.128 nm for Cu, and 0.134 nm for Zn. The number of valence electrons in Ni and Zn differs from that in copper by only one, allowing them to form substitutional solid solutions with the copper matrix. Ni and Zn have physical parameters similar to Cu, do not form interstitial solid solutions, and do not excessively increase lattice friction. They moderately strengthen the copper alloy without strongly increasing lattice distortion, which can lead to a narrow processing window, difficulty in controlling chemical composition, and significant impact on processing and manufacturing performance.

[0087] Ni and Cu have infinite solid solubility, and Zn also has extremely high maximum solid solubility in copper. Therefore, the trace addition of Ni and Zn will not precipitate hard and brittle second phases that deteriorate plasticity and ductility, and this characteristic is unaffected by processing and heat treatment. The increase in lattice distortion of the copper matrix due to the addition of Ni and Zn is moderate. While enhancing the critical shear stress for the initiation of each slip system in face-centered cubic crystals and hindering dislocation movement, it maintains sufficient uniform elongation plasticity, thus achieving a synergistic effect of strong plasticity. Since there is no precipitation of hard and brittle second phases or weakening of grain boundaries, it will not have a significant impact on the machinability and processing properties of copper alloys. In addition, the addition of trace elements refines the matrix grains, increases the grain boundary area, accumulates a higher number density of geometrically necessary dislocations at the grain boundaries, alleviates local stress concentration at grain boundaries, and effectively delays the initiation of fatigue cracks.

[0088] Ni also plays a role in stabilizing the oxide film on the copper surface. NiO has a PB ratio of 1.65, enabling it to form a dense oxide film, thus stabilizing the oxide layer on the copper surface. The Ni in this oxide layer... 2+ It can enter Cu + The presence of vacancies in Cu increases the ionic resistance of the Cu2O film, raises the electron work function, and enhances the corrosion resistance of the alloy. Therefore, adding trace amounts of Ni to Cu can increase the corrosion potential, improve passivation ability, and reduce the corrosion rate of the alloy.

[0089] Zn significantly reduces the stacking fault energy of Cu, promoting the transformation from wavy slip to planar slip and twinning activation, thereby improving work hardening capacity. It strengthens the copper alloy while maintaining high uniform elongation plasticity, achieving simultaneous strengthening and toughening. Under fatigue loads, planar slip and twinning make the local strain distribution of the copper alloy more uniform, hindering the formation of lodged slip bands. This transforms the fatigue crack initiation mechanism of the copper alloy from interfacial cracking at the lodged slip band and matrix to more difficult-to-initiate grain boundary and twin boundary cracking, thus significantly improving fatigue life.

[0090] Furthermore, to further enhance the corrosion resistance and fatigue resistance of copper alloys, a combination of Ni and Zn elements is preferred.

[0091] Furthermore, manganese (Mn) is added to the aforementioned copper-nickel, copper-zinc, and copper-nickel-zinc microalloyed copper alloys. Manganese is in the same period as copper in the periodic table, with atomic number 25 and an atomic radius of 0.127 nm. The number of valence electrons differs from copper by 4, and manganese has extremely high solid solubility in copper. Mn can further increase crystal distortion, improve strength, and enhance the compressive strength of copper alloys. Although Mn does not significantly affect the stacking fault energy of Cu, it readily improves the short-range order of copper alloys, promotes planar slip, and enhances deformation uniformity and slip reversibility, thereby increasing fatigue life. Simultaneously, the addition of trace amounts of Mn can slow down the anthill corrosion process, and its oxide film helps inhibit anodic dissolution. Especially in copper-nickel alloys, its addition can make the open-circuit potential more positive, and the resulting corrosion product film is more protective, thus reducing the corrosion rate of the alloy.

[0092] This invention, by controlling the types and proportions of the above-mentioned trace elements and combining them with subsequent preparation processes, enables the prepared copper alloy to have excellent stress fatigue resistance and corrosion resistance, in addition to its good high strength, high pressure resistance and processing performance. It is suitable for various working conditions, especially complex working conditions.

[0093] The present invention will be further described below with reference to specific embodiments. The performance parameters involved in the embodiments of the present invention are measured by the following methods.

[0094] The average grain size of the metallographic structure was tested according to GB / T 6394-2017 Method for Determination of Grain Size of Metals.

[0095] Yield strength, tensile strength, elongation after fracture, and other room temperature mechanical properties were tested in accordance with GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Test method at room temperature, on an electronic universal mechanical performance testing machine, using an extensometer, a gauge length of 50 mm, a tensile speed of 5 mm / min, and 3 parallel specimens.

[0096] The burst pressure was tested according to the pressure resistance test of "GB / T 241-2007 Hydraulic Test Method for Metal Pipes".

[0097] The bending test for process performance was conducted according to GB / T 244-2008, "Metallic Tubes - Bending Test Method". With the mandrel diameter 1.5 times the outer diameter of the copper tube, a 180° bend resulted in smooth inner and outer surfaces without wrinkles or cracks. The flaring test was conducted according to GB / T 17791-1999, "Seamless Copper Tubes for Air Conditioning and Refrigeration". A flaring taper of 60° and a flaring rate of 40%, or a flattened distance equal to the wall thickness, indicated excellent process performance if the sample did not exhibit any visible cracks or fissures.

[0098] For the anthill corrosion test, 50 parallel samples were taken for each copper alloy, each sample being 10 cm in length. First, the copper tube samples were pretreated by ultrasonically cleaning them for 3 minutes each with anhydrous ethanol, acetone, and deionized water to remove surface oil. The pretreated copper tubes were then suspended in a sealed chamber containing a 0.8% formic acid aqueous solution, with the solution volume to sample area ratio not less than 5 cm². 3 / cm 2 The samples were heated to 40°C in a water bath and kept at that temperature for 12 hours, then placed at room temperature for 12 hours. This hot and cold cycle was repeated for 35 days. The number of leaked samples was recorded. The leakage rate was calculated as: number of leaked samples / 50 × 100%.

[0099] High-cycle fatigue testing was conducted according to "GB / T 3075-2020 Method for Axial Force Control in Fatigue Testing of Metallic Materials" using a Shimadzu EHF-U series electro-hydraulic servo fatigue testing machine. The maximum applied stress was 60 MPa, the stress ratio was 0.1, the load waveform was a sine wave, and the fatigue failure cycle was recorded.

[0100] XRD pattern analysis was performed using a Rigaku Smartlab X-ray diffractometer from Japan, with a continuous scanning speed of 2° / min.

[0101] Examples 1-4

[0102] This embodiment provides a Ni microalloyed copper alloy material, and the specific preparation steps are as follows:

[0103] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0104] (2) After smelting electrolytic copper plates, Cu-14%P master alloy ingots were added to obtain phosphorus-deoxidized copper melt. The temperature of the prepared phosphorus-deoxidized copper melt was adjusted to 1290℃, and Cu-42%Ni master alloy ingots were added in proportion. The copper melt was stirred with a graphite rod, and the surface of the copper melt was covered with charcoal with a charcoal coverage thickness of 120mm. The temperature was maintained for about 3 hours to homogenize the trace elements. The composition of the copper melt, by mass percentage, was: 0.92% Ni, 0.0312% P, 11.42ppm O, with the balance being copper and unavoidable impurities.

[0105] (3) Under nitrogen protection, the copper liquid is transferred to the holding furnace and kept at a constant temperature. During the holding period, graphite phosphorus sheets are covered with a thickness of 50 mm. The holding temperature is 1185℃ and the time is 8 min. Then, it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0106] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0107] (5) The tube blank was rolled by a three-roll planetary rolling mill at a speed of 1.5 m / min, reducing the outer diameter to 51 mm. Then, it was continuously drawn at a speed of 70 m / min, reducing the outer diameter to 31 mm and the wall thickness to 1.4 mm. Afterward, it was coiled and drawn in 7 passes. The first pass was drawn at a speed of 400 m / min, the intermediate passes at 660 m / min, and the last three passes at 600 m / min. The resulting tube had an outer diameter of 9 mm and a wall thickness of 0.6 mm. Finally, it was vacuum annealed at 540 °C for 63 min, yielding Example 4.

[0108] (6) Electrolytic copper was added to the above-mentioned copper solution to dilute the Ni content. Simultaneously, a phosphorus copper alloy was added to maintain the phosphorus content in the copper solution between 0.015% and 0.04%. The above-described operation was then performed for heat preservation and homogenization, and pipe preparation was carried out to obtain Example 3. The above dilution steps were repeated to reduce the Ni content, and the above-described operation was performed for heat preservation and homogenization, and pipe preparation was carried out to obtain Examples 2 and 1. Then, sampling and testing were conducted.

[0109] The specific composition of the copper alloys in Examples 1 to 4 is shown in Table 1.

[0110] Examples 5-8

[0111] This embodiment provides a Zn microalloyed copper alloy material, and the specific preparation steps are as follows:

[0112] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0113] (2) After smelting electrolytic copper plates, Cu-14%P master alloy ingots are added to obtain phosphorus-deoxidized copper melt. The temperature of the prepared phosphorus-deoxidized copper melt is adjusted to 1180-1185℃, zinc ingots are added in proportion, and the burn-off ratio is calculated at 5%. The copper melt is stirred with a graphite rod, and the surface of the copper melt is covered with charcoal with a charcoal coverage thickness of 120mm. The temperature is maintained for about 2 hours to homogenize the trace elements. The composition of the copper melt, by mass percentage, is: 0.84% ​​Zn, 0.0302% P, 11.26 ppm O, with the balance being copper and unavoidable impurities.

[0114] (3) Under nitrogen protection, the copper liquid is transferred to the holding furnace and kept at a constant temperature. During the holding period, graphite phosphorus sheets are covered with a thickness of 50 mm. The holding temperature is 1180℃ and the time is 8 min. Then, it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0115] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0116] (5) The tube blank was rolled by a three-roll planetary rolling mill at a speed of 1.5 m / min, reducing the outer diameter to 51 mm. Then, it was continuously drawn at a speed of 70 m / min, reducing the outer diameter to 31 mm and the wall thickness to 1.4 mm. Afterward, it was coiled and drawn in 7 passes. The first pass was drawn at a speed of 400 m / min, the intermediate passes at 660 m / min, and the last three passes at 600 m / min. A smooth tube with an outer diameter of 9 mm and a wall thickness of 0.6 mm was produced through continuous drawing and coiling. Finally, it was vacuum annealed at 540 °C for 63 min, yielding Example 8.

[0117] (6) Electrolytic copper was added to the above-mentioned copper solution to dilute the Zn content, and phosphorus copper alloy was added simultaneously to maintain the phosphorus content between 0.015% and 0.04%. The above-mentioned operation was then performed for heat preservation and homogenization, and pipe preparation was carried out to obtain Example 7. The above dilution steps were repeated to reduce the Zn content, and the above-mentioned operation was performed for heat preservation and homogenization, and pipe preparation was carried out to obtain Examples 6 and 5. Sampling and testing were then conducted. The specific composition of the copper alloys in Examples 5-8 is shown in Table 1.

[0118] Examples 9, 10, and 19

[0119] This embodiment provides a Ni / Zn composite microalloyed copper alloy material, and the specific preparation steps are as follows:

[0120] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0121] (2) After smelting the electrolytic copper plate, Cu-14%P master alloy ingots are added to obtain phosphorus-deoxidized copper melt. The temperature of the prepared phosphorus-deoxidized copper melt is adjusted to 1290℃, and Cu-42%Ni master alloy ingots are added in a predetermined ratio. The copper melt is stirred with a graphite rod, and the surface of the copper melt is covered with charcoal with a thickness of 120mm. The temperature is maintained for about 2 hours to fully melt the raw materials. The temperature of the melt is then reduced to 1180-1190℃, and zinc ingots are added in a ratio. The copper melt is stirred with a graphite rod, and the temperature is maintained for about 2 hours to homogenize the trace elements.

[0122] (3) When the copper liquid is transferred to the holding furnace under nitrogen protection and kept at a constant temperature, it is covered with graphite phosphorus sheets with a thickness of 50 mm. The holding temperature is 1185℃ and the time is 8 min. Then it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0123] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0124] (5) The tube blank was rolled by a three-roll planetary rolling mill at a speed of 1.5 m / min, reducing the outer diameter to 51 mm. Then, it was continuously drawn at a speed of 70 m / min, reducing the outer diameter to 31 mm and the wall thickness to 1.4 mm. Afterward, it was coiled and drawn in 7 passes. The first pass was drawn at a speed of 400 m / min, the intermediate passes at 660 m / min, and the last three passes at 600 m / min. The tube, with an outer diameter of 9 mm and a wall thickness of 0.6 mm, was produced by continuous drawing and coiling. Finally, it was vacuum annealed at 540°C for 63 min, yielding Examples 9 and 10.

[0125] The rolled tube blank was coiled in 7 passes, with the first pass at a coiling speed of 400 m / min and subsequent passes at 700 m / min, resulting in a coiled internally threaded tube blank. The coiled internally threaded tube blank was then subjected to online annealing at a speed of 390 m / min and a current of 4800 A, followed by spinning at a speed of 480 r / m, and finally vacuum annealed at 470°C for 63 min, yielding Example 19. Samples were then taken for testing. The specific compositions of the copper alloys in Examples 9, 10, and 19 are shown in Table 1.

[0126] Examples 11, 12, and 18

[0127] This embodiment provides a Ni / Mn composite microalloyed copper alloy material, and the specific preparation steps are as follows:

[0128] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0129] (2) After smelting the electrolytic copper plate, Cu-14%P master alloy ingots are added to obtain phosphorus-deoxidized copper melt. The temperature of the prepared phosphorus-deoxidized copper melt is adjusted to 1290℃, and Cu-42%Ni master alloy ingots and Cu-30%Mn master alloy ingots are added in a preset ratio. The copper melt is stirred with a graphite rod, and the surface of the copper melt is covered with charcoal with a thickness of 120mm. The temperature is maintained for about 3 hours to homogenize the trace elements.

[0130] (3) When the copper liquid is transferred to the holding furnace under nitrogen protection and kept at a constant temperature, it is covered with graphite phosphorus sheets with a thickness of 50 mm. The holding temperature is 1185℃ and the time is 8 min. Then it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0131] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0132] (5) The tube blank was rolled by a three-roll planetary rolling mill at a speed of 1.5 m / min, reducing the outer diameter to 51 mm. Then, it was continuously drawn at a speed of 70 m / min, reducing the outer diameter to 31 mm and the wall thickness to 1.4 mm. Afterward, it was coiled and drawn in 7 passes. The first pass was drawn at a speed of 400 m / min, the intermediate passes at 660 m / min, and the last three passes at 600 m / min. The tube, with an outer diameter of 9 mm and a wall thickness of 0.6 mm, was produced by continuous drawing and coiling. Finally, it was vacuum annealed at 540 °C for 63 min, yielding Examples 11 and 12.

[0133] The rolled tube blank was coiled in 7 passes, with the first pass at a coiling speed of 400 m / min and subsequent passes at 700 m / min, resulting in a coiled internally threaded tube blank. The coiled internally threaded tube blank was then subjected to online annealing at a speed of 390 m / min and a current of 4800 A, followed by spinning at a speed of 480 r / m, and finally vacuum annealed at 470°C for 63 min, yielding Example 18. Samples were then taken for testing. The specific compositions of the copper alloys in Examples 11, 12, and 18 are shown in Table 1.

[0134] Examples 13 and 14

[0135] This embodiment provides a Zn / Mn composite microalloyed copper alloy material, and the specific preparation steps are as follows:

[0136] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0137] (2) After smelting the electrolytic copper plate, add Cu-14%P master alloy ingots to obtain phosphorus-deoxidized copper melt. Adjust the temperature of the prepared phosphorus-deoxidized copper melt to 1250℃, add Cu-30%Mn master alloy ingots according to the preset ratio, stir the copper liquid with a graphite rod, and cover the surface of the copper liquid with charcoal with a charcoal covering thickness of 120mm. Keep it at the temperature for about 2 hours to fully melt the raw materials. Reduce the temperature of the melt to 1180~1190℃, add zinc ingots according to the ratio, stir the copper liquid with a graphite rod, and keep it at the temperature for about 2 hours to homogenize the trace elements.

[0138] (3) When the copper liquid is transferred to the holding furnace under nitrogen protection and kept at a constant temperature, it is covered with graphite phosphorus sheets with a thickness of 50 mm. The holding temperature is 1185℃ and the time is 8 min. Then it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0139] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0140] (5) The tube blank was rolled by a three-roll planetary rolling mill at a speed of 1.5 m / min, reducing the outer diameter to 51 mm. Then, it was continuously drawn at a speed of 70 m / min, reducing the outer diameter to 31 mm and the wall thickness to 1.4 mm. Afterward, it was coiled and drawn in 7 passes. The first pass was drawn at a speed of 400 m / min, the intermediate passes at 660 m / min, and the last three passes at 600 m / min. The tube, with an outer diameter of 9 mm and a wall thickness of 0.6 mm, was produced by continuous drawing and coiling. Finally, it was vacuum annealed at 540 °C for 63 min, yielding Examples 13 and 14. The specific composition of the copper alloys in Examples 13 and 14 is shown in Table 1.

[0141] Examples 15-17

[0142] This embodiment provides a Ni, Zn, and Mn composite microalloyed copper alloy material, and the specific preparation steps are as follows:

[0143] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0144] (2) After smelting the electrolytic copper plate, Cu-14%P master alloy ingots are added to obtain phosphorus-deoxidized copper melt. The temperature of the prepared phosphorus-deoxidized copper melt is adjusted to 1290℃. Cu-42%Ni master alloy ingots and Cu-30%Mn master alloy ingots are added in a preset ratio. The copper melt is stirred with a graphite rod and the surface of the copper melt is covered with charcoal with a thickness of 120mm. The temperature is maintained for about 2 hours to fully melt the raw materials. The temperature of the melt is reduced to 1180-1190℃. Zinc ingots are added in a ratio. The copper melt is stirred with a graphite rod and then kept at the temperature for about 2 hours to homogenize the trace elements.

[0145] (3) When the copper liquid is transferred to the holding furnace under nitrogen protection and kept at a constant temperature, it is covered with graphite phosphorus sheets with a thickness of 50 mm. The holding temperature is 1185℃ and the time is 8 min. Then it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0146] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0147] (5) The tube blank was rolled by a three-roll planetary rolling mill at a speed of 1.5 m / min, reducing the outer diameter to 51 mm. Then, it was continuously drawn at a speed of 70 m / min, reducing the outer diameter to 31 mm and the wall thickness to 1.4 mm. Afterward, it was coiled and drawn in 7 passes. The first pass was drawn at a speed of 400 m / min, the intermediate passes at 660 m / min, and the last three passes at 600 m / min. The tubes were then continuously drawn and coiled to produce a 9 mm outer diameter and a 0.6 mm wall thickness. Finally, they were vacuum annealed at 540 °C for 63 min, yielding Examples 15-17.

[0148] Comparative Examples 20-23 provided CuNi, CuZn, CuNiZn, and CuZnMn alloy materials with higher levels of trace elements. The preparation method of Comparative Example 20 was the same as that of Example 4, the preparation method of Comparative Example 21 was the same as that of Example 8, the preparation method of Comparative Example 22 was the same as that of Example 9, and the preparation method of Comparative Example 23 was the same as that of Example 13, the difference being the different proportions of raw materials added due to changes in alloy composition. The specific compositions of the copper alloys in Comparative Examples 20-23 are shown in Table 2.

[0149] Comparative Examples 24 and 25 are existing copper tube samples from Zhejiang Hailiang Co., Ltd., made of TP2, with specifications of 9*0.6 and 7*0.24+0.15 respectively. Their specific composition is shown in Table 2.

[0150] The difference between Comparative Example 26 and Example 15 is that the annealing temperature of the finished product is 400°C and the annealing time is 63 min. The copper alloy composition is shown in Table 2.

[0151] Comparative Example 27

[0152] This comparative example provides a microalloyed copper alloy material containing Ni, Zn, Mn, and Fe. The specific preparation steps are as follows:

[0153] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0154] (2) After smelting electrolytic copper plates, Cu-14%P master alloy ingots are added to obtain phosphorus-deoxidized copper melt. The temperature of the prepared phosphorus-deoxidized copper melt is adjusted to 1290℃, and Cu-42%Ni master alloy ingots, Cu-30%Mn master alloy ingots, and Cu-10%Fe master alloy ingots are added in a predetermined ratio. The copper melt is stirred with a graphite rod, and the surface of the copper melt is covered with charcoal with a charcoal coverage thickness of 120mm. The temperature is maintained for about 2 hours to fully melt the raw materials. The melt temperature is then reduced to 1180-1190℃, and zinc ingots are added in a ratio. The copper melt is stirred with a graphite rod, and the temperature is maintained for about 2 hours to homogenize the trace elements. The composition of the copper melt, by mass percentage, is: 0.33%Ni, 0.39%Zn, 0.26%Mn, 0.0072%Fe, 0.0316%P, 10.39ppmO, with the balance being copper and unavoidable impurities.

[0155] The subsequent steps include horizontal continuous casting, rolling, continuous drawing, coil drawing, and finished product annealing processes, which are the same as in Example 17.

[0156] Comparative Example 28

[0157] This comparative example prepared a rolled tube blank with a nominal composition of Cu-0.5%Ni, characterized by a melting and holding time of 20 min.

[0158] (1) Prepare raw materials and auxiliary materials according to the nominal composition of the design, and dry them for later use.

[0159] (2) After melting the electrolytic copper plate, add Cu-14%P master alloy ingot to obtain phosphorus-deoxidized copper melt. Adjust the temperature of the prepared phosphorus-deoxidized copper melt to 1290℃, add Cu-42%Ni master alloy ingot in proportion, stir the copper liquid with a graphite rod, cover the surface of the copper liquid with charcoal with a thickness of 120mm, and keep it at the temperature for about 20min.

[0160] (3) Under nitrogen protection, the copper liquid is transferred to the holding furnace and kept at a constant temperature. During the holding period, it is covered with graphite phosphorus sheets with a thickness of 50 mm. The holding temperature is 1185℃ and the time is 8 min. Then, it is horizontally cast into a tube blank with a traction speed of 350 mm / min, a primary cooling water flow rate of 35 L / min, and a secondary cooling water flow rate of 70 L / min.

[0161] (4) The tube blank diameter is 92mm, the length is 16m, and then the surface is milled by 1mm.

[0162] (5) The tube blank is rolled by three-roll planetary rolling at a speed of 1.5m / min, and the outer diameter is reduced to 51mm.

[0163] Sampling tests were conducted, and the mechanical properties of the rolled tube blanks from Example 2 were compared.

[0164] The properties of the copper alloys in the embodiments and comparative examples of this invention are shown in Tables 3 and 4, respectively.

[0165] Examples 1-4 show that as the Ni content increases, the tensile strength, pressure resistance, corrosion resistance, and fatigue resistance of the copper alloy of the present invention improve simultaneously, and the bending and flaring process performance all meet the requirements. When the Ni content is 0.081%, compared with Comparative Example 24, its tensile strength increases by 2.1%, the burst pressure increases by 5.4%, the fatigue failure period increases by 0.45 times, the corrosion leakage rate is 22.0%, and the reduction rate is 69.4%. When the Ni content is 0.71%, compared with Comparative Example 24, its tensile strength increases by 7.9%, the burst pressure increases by 23.2%, the fatigue failure period increases by 6.3 times, and there is no corrosion leakage.

[0166] Comparative Example 20 shows that when the Ni content is increased to 1.48%, although its corrosion resistance and fatigue resistance are better than those of Examples 1-4, its elongation after fracture decreases to 17.2%, and the bending pipe has obvious wrinkles, which does not meet the requirements for use.

[0167] Examples 5-8 show that as the Zn content increases, the tensile strength, pressure resistance, corrosion resistance, and fatigue resistance of the copper alloy of the present invention improve simultaneously, and the bending and flaring process performance all meet the requirements. When the Zn content is 0.12%, compared with Comparative Example 24, its tensile strength increases by 3.8%, the burst pressure increases by 10.1%, the fatigue failure period increases by 0.93 times, and the corrosion leakage rate is 28.0%. As the Zn content increases to 0.84%, compared with Comparative Example 24, its tensile strength increases by 12.9%, the burst pressure increases by 36.3%, the fatigue failure period increases by 11.2 times, and the corrosion leakage rate decreases to 16.0%.

[0168] XRD pattern analysis (see Figure 2 Comparative Example 24 exhibits only a face-centered cubic phase with a lattice constant of . It is a single α phase, its metallographic diagram (see...) Figure 1 (a) shows that the average grain size is about 34 μm, the area of ​​grains with a size greater than 30 μm is greater than 25%, the configuration entropy is close to 0 J / (mol·K), the average thickness of the oxide film during corrosion is about 0.025 μm, the surface oxide film PB ratio is 1.68, and its ion concentration is obtained from the measured surface element concentration.

[0169] Example 6 added 0.52% Zn, its XRD pattern (see Figure 2 It remains a single face-centered cubic phase, i.e., the α phase, with a lattice constant expansion of... The configuration entropy increased to 0.26 J / (mol·K) due to the increased arrangement of Zn atoms with Cu matrix atoms after the addition of 0.52% Zn, which played a role in pinning dislocations. At the same time, its average grain size decreased to 13 μm due to the grain refinement effect of Ni (see...). Figure 1(b) The area ratio of grains with a size of 5-30 μm is not less than 90% to ensure sufficient grain boundary strengthening. In Example 6, the surface oxide film has a PB ratio of 1.67, and the average thickness of the oxide film during corrosion is about 0.064 μm, which is thicker than that of Comparative Example 24, and has a better effect on preventing media corrosion.

[0170] Comparative Example 21 shows that when the Zn content is increased to 1.54%, the elongation after fracture decreases to 13.9%, and the bending and flaring of the pipes do not meet the usage requirements.

[0171] The products prepared in Examples 9 to 17 are optical tubes.

[0172] The Ni / Zn content ratio of Example 9 was 1.45, and that of Example 10 was 2.69. The tensile strength, compressive strength, corrosion resistance, and fatigue resistance of Examples 9 and 10 were all better than those of Examples 1 to 8, demonstrating the synergistic effect of Ni and Zn and the characteristics of improving both corrosion resistance and fatigue resistance.

[0173] Comparative Example 22 shows that when the total amount of Ni and Zn added is high and the Ni and Zn ratio is mismatched, the tendency to become embrittled is severe, the elongation after fracture drops to 9.7%, and cracks occur in both bending and flaring, which does not meet the requirements for use.

[0174] Examples 11-14 demonstrate that Mn can further enhance the overall performance of copper-nickel and copper-zinc alloys. Compared to Example 2, Example 11, with the addition of 0.47% Ni and 0.28% Mn, shows a 14.2% increase in tensile strength, a 34.5% increase in burst pressure, a 12-fold increase in fatigue failure period, and no corrosion leakage. Example 12 also exhibits a Mn-strengthening effect compared to Example 3. Examples 13, compared to Example 6, and Examples 14, compared to Example 7, all demonstrate that Mn can further strengthen copper-zinc alloys and compensate for the poor resistance of copper and zinc to termite corrosion. Example 14, in particular, achieves a tensile strength of 280 MPa and a fatigue failure period of 7.3 × 10⁻⁶ MPa. 6 The corrosion leakage rate was only 10.0%, fully demonstrating the synergistic strengthening and corrosion resistance effects of Zn and Mn. Compared with Comparative Example 24, the overall performance of Examples 11-14 was significantly improved.

[0175] Examples 15-17 demonstrate that the composite addition of Ni, Zn, and Mn has the potential to further improve the overall performance of copper alloys, but the proportions of Ni, Zn, and Mn added should be strictly controlled. In Example 15, the (Ni+Mn) / Zn ratio was 2.65, which, compared to Comparative Example 24, increased tensile strength by 18.3%, burst pressure by 56.0%, and fatigue failure cycle by 17 times, while meeting the application requirements for process performance. With further control of the Ni, Zn, and Mn proportions, Examples 16 and 17, compared to Example 15, further improved tensile strength, compressive strength, corrosion resistance, and fatigue resistance.

[0176] In Example 16, after 48 hours of etching, Ni, Mn, and Zn were detected at the surface, at a depth of 10 nm from the surface, and at a depth of 20 nm from the surface. Figure 4 It can be seen that Ni / Ni at different depths on the same plane 2+ (Ni2p) distribution is relatively uniform, Zn / Zn 2+ The relative content of (Zn2p) gradually decreases, while the relative content of Mn and Mn ions (Mn2p) gradually increases. Ni / Ni2p is only found in the surface layer. 2+ The slightly higher (Ni2p) content indicates that the less reactive metal Ni oxidizes more slowly than the more reactive metal Mn on the subsurface, thus slowing down the oxidation process. Figure 5 XPS fine spectra of Mn and Zn elements show that the surface layer, due to its unique acidic environment, has Mn ions predominantly in the trivalent state, indicating the presence of trace amounts of Mn₂O₃. Figure 5 (a) and Figure 5 (b) It can be seen that Mn 3+ / Mn 2+ With Zn / Zn 2+ (Zn metal and Zn) 2+ The binding energies of the ions are 1021.7 eV and 1021.3 eV, respectively (the binding energies are so similar that they are indistinguishable). The relative ratio of the peak integral areas is approximately 0.53, indicating the presence of a relatively large amount of elemental Zn and ZnO on the surface. Figure 5 (c) and Figure 5 (d) It can be seen that after etching to a depth of 10 nm, Mn ions are converted into Mn... 2+ The main component is Mn, with a small amount of strong oxidizing Mn present. 4+ Mn 2+ / Mn 4+ With Zn / Zn 2+ The relative ratio of peak integral areas is approximately 2.18, indicating that the slow diffusion characteristics of Zn in Cu hinder Zn migration and Zn-participated oxidation, resulting in a significant decrease in the content of subsurface elemental Zn and ZnO. Figure 5 (e) and Figure 5 (f) It is known that with further etching to a depth of 20 nm, Mn ions are mainly Mn 2+ Form exists, Mn 4+ Further reduction, Mn 2+ / Mn 4+ With Zn / Zn 2+ The relative ratio of peak integral area is approximately 2.25, indicating that the oxidation rate decreases significantly at a depth of 20 nm, and the inner low-oxygen region mainly forms an oxide film composed of Cu2O and MnO. Therefore, in Example 16, the oxide film exhibits a relatively obvious multilayer structure during the ant hole corrosion process, meaning that the types and relative contents of oxides of each element differ along a plane perpendicular to the oxide film thickness direction.

[0177] The surface oxide film in Example 16 has a PB ratio of 1.65. Its ion concentration was obtained based on the measured surface element concentration. According to this element concentration, even with localized accumulation of Ni, Zn, and Mn oxides on the surface, the oxide film will not expand to the point of tearing the surface protective film or creating voids; instead, it will compensate for the deficiencies of the Cu2O oxide film. The average thickness of the oxide film during corrosion is approximately 0.057 μm, similar to that in Example 13, demonstrating its physical barrier and anti-permeation properties.

[0178] XRD pattern analysis (see Figure 2 In Example 16, after the addition of 0.35% Ni, 0.32% Zn, and 0.23% Mn, its XRD pattern still showed a single face-centered cubic structure phase, with the lattice constant expanding to [value missing]. The full width at half maximum (FWHM) of the (111) diffraction peak in Example 16 increased from 0.205 in Example 13 to 0.216, indicating a higher lattice distortion. Simultaneously, the main diffraction peak changed from (111) to (200), forming an orientation preference along the (200) crystal plane, which can hinder specific dislocation slip and improve tensile strength, compressive strength, and fatigue resistance. Furthermore, the average grain size of Example 16 was 10 μm (participating in…). Figure 1 (d) The area ratio of grains with a size of 5–30 μm is not less than 92%. The configuration entropy increases to 0.54 J / (mol·K) due to further increases in element concentration and element complexity, forming a complex multidimensional distortion field at the atomic level. This increases the critical shear stress for slip initiation, thus playing a stronger role in hindering dislocation movement. Overall, Ni, Zn, and Mn all have a grain-refining effect, but their refining effect mainly depends on the total amount of each element added, while the synergistic effect of composite element addition on grain refinement is not significant. However, the composite addition of elements obviously has a more significant impact on improving the corrosion resistance and fatigue resistance of copper alloys. The increase in configuration entropy of the quaternary solid solution and the continuous protection of the multi-layered oxide film and corrosion process give the copper alloy of this invention a significant performance improvement and very strong application value. See also Figure 3 It is evident that the tensile strength of copper alloys is significantly improved by doping with one or more of Ni, Zn, and Mn, and the effect of co-doping with Ni, Zn, and Mn is even better.

[0179] Examples 18 and 19 and Comparative Example 25 show that the internally threaded tubes prepared using the copper alloy of the present invention also exhibit a comprehensive improvement in tensile strength, pressure resistance, corrosion resistance and fatigue resistance.

[0180] The yield strength of the copper alloys in Comparative Examples 20 to 23 is generally between 100 and 130 MPa, and the tensile strength is greater than 330 MPa, but the elongation after fracture is less than 20%.

[0181] Comparative Example 26 was not fully annealed, and its metallographic structure was still dominated by large-area deformation structure. Compared with Example 15, its elongation after fracture was poor, the bent tube had severe wrinkles, and there were fine microcracks in both the bent tube and the flared end. Its process performance did not meet the requirements for use, and usually, excessively high annealing temperature will lead to excessive softening.

[0182] Comparative Example 27 was tested and found to have microcracks after bending and flaring, which did not meet the process performance requirements. Considering the yield in actual production, the Fe content of the copper alloy should be strictly controlled below 0.005%.

[0183] Comparative Example 28 illustrates that the Cu-0.5%Ni rolled tube blank prepared by melting and holding for only 20 minutes exhibits extremely high brittleness, fractures brittlely during tensile testing, has a fracture strength of 47 MPa, and shows obvious unmelted metal inclusions on the fracture surface, making further processing impossible. In contrast, the rolled tube blank of Example 2 has a tensile strength of 232 MPa and an elongation after fracture of 55.4%, demonstrating better processing performance. This indicates that the conventional melting and holding time for phosphorus-deoxidized copper is insufficient to completely melt and homogenize the high-melting-point metal, and the unmelted metal causes material brittleness, rendering it unprocessable.

[0184] Depend on Figure 1 As shown in Table 1-4, when the content of trace elements is 0.5-1.0%, the average grain size of the copper alloy is between 5 and 40 μm, and the area ratio of grains with a size of 5-30 μm is not less than 90%, the prepared copper alloy has better stress fatigue resistance and corrosion resistance on the basis of good high strength, high pressure resistance and processing performance.

[0185] It should be noted that, in addition to the embodiments disclosed in this invention, the applicant has tested the annealing temperature and time of other products of different specifications and found that pipes meeting the performance requirements of this invention can be obtained within the range of annealing temperature of 420 to 700°C and annealing time of 20 to 180 minutes.

[0186] Table 1 Chemical composition of the copper alloy in the examples

[0187]

[0188] Table 2 Chemical composition of comparative copper alloys

[0189]

[0190] Table 3. Properties of the copper alloys in the examples

[0191]

[0192] Note: "○" represents qualified; "×" represents unqualified; "-" represents no data for that item or the test has not expired.

[0193] Table 4. Properties of Comparative Copper Alloys

[0194]

[0195] Note: "○" represents qualified; "×" represents unqualified; "-" represents no data for that item or the test has not expired.

[0196] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A microalloyed copper alloy, characterized in that, It is composed of the following components by mass percentage: trace elements: 0.2-1.0%, P: 0.015-0.04%, with the balance being Cu and unavoidable impurities; The trace elements are Mn, Ni and Zn, and the mass ratio of Mn, Ni and Zn satisfies 1≤(Ni+Mn) / Zn≤3, and Ni / Mn>1.

2. The copper alloy according to claim 1, characterized in that, The total content of Mn, Ni and Zn is 0.5% to 1.0%.

3. The copper alloy according to claim 2, characterized in that, The mass ratio of Mn, Ni and Zn satisfies 1≤(Ni+Mn) / Zn≤2, and Ni / Mn>1.

4. The copper alloy according to any one of claims 1-3, characterized in that, The copper alloy is a single α phase.

5. The copper alloy according to any one of claims 1-3, characterized in that, The copper alloy has an average grain size of 5–40 μm and a lattice constant of .

6. The copper alloy according to any one of claims 1-3, characterized in that, The configurational entropy of the copper alloy is 0.15–0.67 J / (mol·K).

7. The copper alloy according to any one of claims 1-3, characterized in that, The copper alloy has a yield strength ≤85MPa, tensile strength ≥245MPa, elongation after fracture ≥40%, and burst pressure that is more than 5% higher than that of phosphorus deoxidized copper products of the same specification.

8. The copper alloy according to claim 7, characterized in that, The copper alloy exhibits a corrosion leakage rate of ≤30% after 35 days of alternating hot and cold corrosion in a 0.8% formic acid aqueous solution atmosphere, and a fatigue failure period of ≥6.5×10 under a maximum stress of 60MPa. 5 .

9. The copper alloy according to any one of claims 1-3, characterized in that, During the corrosion process, the copper alloy forms an oxide film containing trace elements. The PB ratio of the oxide film containing trace elements is 1.5 to 1.8, and the thickness is 0.02 to 0.2 μm.

10. The method for preparing the copper alloy according to any one of claims 1-9, characterized in that, The process includes the following steps: batching and smelting → continuous casting → rolling → diameter reduction → finished product annealing; In the batching and smelting process, the raw materials that meet the proportions are smelted at 1150-1300℃, and after the raw materials are completely melted, they are kept at that temperature for more than 60 minutes. In the finished product annealing process, the annealing temperature is 420-700℃ and the annealing time is 20-180min.

11. The method for preparing the copper alloy according to claim 10, characterized in that, In the batching and smelting process, Ni, Mn, and P are added in the form of copper-nickel master alloy, copper-manganese master alloy, and phosphorus-copper master alloy, respectively.

12. The preparation method according to claim 10 or 11, characterized in that, When the copper alloy is a bare tube, the annealing temperature of the finished product is 450-650℃ and the time is 20-120min.

13. The preparation method according to claim 10 or 11, characterized in that, When the copper alloy is an internally threaded tube, the annealing temperature of the finished product is 420-600℃ and the time is 20-120min.

14. The application of the copper alloy according to any one of claims 1-9 or the copper alloy prepared by the preparation method according to any one of claims 10-13 in the fields of air conditioning and refrigeration, electronic communication, aerospace, marine engineering or chemical and energy equipment.

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