High-performance copper alloy pipe and method for producing the same

Abstract

The application discloses a high-performance copper alloy pipe and a preparation method thereof. The copper alloy pipe is prepared by adding Sn, Ni and P elements into Cu, adjusting the content and ratio of the elements, and introducing high proportion of Σ3, Σ9 and Σ27 heavy site array grain boundaries by combining with recrystallization treatment process, so that the copper alloy pipe has high strength, high processing forming capacity, excellent pressure resistance, corrosion resistance and high-temperature softening resistance. Meanwhile, the application adds Zr, Co and B (optionally) elements on the basis of the alloy composition, so as to further improve the performance of the copper alloy pipe. The copper alloy pipe has higher tensile strength, processing forming property, pressure resistance, corrosion resistance and high-temperature softening resistance than the same specification TP2 copper pipe and the existing high-strength copper pipe, and meets the performance requirements of high-pressure-resistant and thin-wall seamless copper pipe, so that the application has wide application prospect in the heat exchange field.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of alloys, in particular to a high-performance copper alloy pipe and a preparation method thereof. BACKGROUND

[0002] Copper materials have become key materials in the fields of electronic communication and advanced thermal management, new energy and power transmission, high-end equipment manufacturing, etc. due to their excellent thermal conductivity, electrical conductivity, processing formability, and corrosion resistance. Their importance and application range continue to increase with technological progress. For example, in the field of heat exchange, as the core material of refrigeration and air conditioning heat exchangers and piping systems, copper materials not only need to have good bending, flaring, tube expanding, and welding processing performance, but also need to have higher strength to meet the increasingly fierce development requirements of high pressure resistance and thin walling.

[0003] Traditional phosphorus deoxidized copper pipes (TP2) have excellent bending, flaring, and tube expanding performance. A small amount of P element is added to the electrolytic copper to remove oxygen and improve its ductility, weldability, and corrosion resistance. However, the burst pressure of TP2 copper pipes is low and cannot meet the safety requirements under the background of the development of small weight thin-walled copper pipes.

[0004] To solve the problem of low burst pressure of TP2 copper pipes, various high-strength copper pipes have been developed in recent years. However, the high-strength copper pipes developed at present generally contain high Sn, Zn, and Ni content, which can meet the burst pressure requirements of copper pipes after wall reduction to some extent, but they generally have poor processing formability and insufficient plastic deformation capacity (specifically poor bending, flaring, and tube expanding performance).

[0005] Patent CN101469961B discloses a Sn and P containing copper alloy material containing 0.1% to 3.0% Sn and 0.005% to 0.1% P, having a tensile strength of 250 MPa or more, which enhances the circumferential tensile strength of the copper alloy by limiting the proportion of Goss texture and increasing the proportion of low-angle grain boundaries, thereby improving the burst pressure. However, low-angle grain boundaries are essentially accumulations of dislocations, and if their content is too high, they will exacerbate the brittleness tendency of the material, reduce the processing formability, and make the cold working performance of the material such as bending, flaring, and tube expanding worse.

[0006] Patent CN107739880A discloses a high-strength copper alloy material containing Ni, Sn and P. The material contains 0.3-0.7% Ni, 0.2-1.0% Sn and 0.01-0.07% P, has a tensile strength of 262-290 MPa, and can be processed into a seamed copper pipe by using a roll-bonding process. The copper material is prevented from wrinkling and cracking during pipe bending by controlling the elongation after fracture of the copper material to be 40-50%. However, the formability of the copper pipe under this condition cannot be effectively guaranteed, and the risk of flaring and expanding is extremely high. Moreover, the elongation after fracture of the copper pipe is lower than that of a TP2 copper pipe.

[0007] Therefore, in the current research and application of high-strength copper alloys, how to achieve a balance between strength and formability of the material has become a technical challenge for the development of copper alloy pipe materials for heat exchange. Among the many indicators for evaluating the performance of copper alloy pipes, the yield ratio is a key indicator for measuring the balance between the strength and formability of the material. Generally, a low yield ratio indicates that the material has a high tensile strength and a low yield strength, which enables the material to have excellent uniform deformation capability and low springback, facilitating processing deformation and enabling the material to withstand high failure stress, thereby resolving the problem of incompatibility between high strength and excellent formability.

[0008] The yield ratio of a TP2 copper pipe is usually between 0.30 and 0.35, while the yield ratio of a high-strength copper pipe is generally in the range of 0.4 to 0.6, which makes the high-strength copper pipe significantly inferior to the TP2 copper pipe in terms of bending, flaring and expansion performance. To solve the problem of balancing the strength and formability of high-strength copper alloy materials, it is necessary to develop new high-performance copper pipes with high strength and low yield ratio as the research goal to meet the development trend of lightweight and compact modern refrigeration equipment.

[0009] It should be noted that in the thin-walled application scenario, the copper pipe also faces two major technical challenges. First, thinning the wall thickness significantly reduces the resistance to pitting corrosion life, and the thinner the wall thickness, the more serious the damage. Moreover, in the presence of residual stress in the bent pipe part, the stress corrosion effect further accelerates the corrosion process. In addition, the high-temperature softening phenomenon during brazing is more prominent, and the burst pressure of the heat-affected zone of the thin-walled copper pipe can be reduced by 15-30%. The thinner the wall thickness, the higher the risk of overburning, and the more serious the deterioration of the pressure resistance performance.

[0010] Based on the above problems, it is necessary to develop a high-performance copper alloy pipe with high tensile strength, low yield ratio and excellent pitting corrosion resistance and high-temperature softening resistance to solve the poor formability problem of existing high-strength copper pipes, while meeting the high corrosion resistance and high-temperature softening resistance requirements of copper alloy materials under the background of thin-walled development, and promoting the development of heat exchange materials towards high efficiency, energy saving and green low carbon. SUMMARY

[0011] The application aims to provide a high-performance copper alloy pipe and a preparation method thereof. The application makes the copper alloy pipe have high strength, good processing formability, excellent corrosion resistance and high-temperature softening resistance by designing the composition of the copper alloy and improving the recrystallization process, so as to overcome many problems of the existing copper alloy pipe in the heat exchange field.

[0012] The design idea of the application is as follows:

[0013] The copper alloy pipe designed by the application has high tensile strength and low yield ratio to meet the requirements of high pressure resistance and excellent processing formability of copper materials in the heat exchange field. The application mainly reduces the yield ratio of the copper material by improving the tensile strength of the copper material and maintaining the yield strength basically unchanged, which requires the copper material to meet the following requirements: (1) having a single face-centered cubic (FCC) crystal structure phase without hard and brittle phase precipitation; (2) having a suitable grain size; and (3) having a high proportion of low-Σ heavy site lattice grain boundaries.

[0014] The low-Σ heavy site lattice grain boundary has low energy and coherent characteristics, and has lower hindering ability to dislocation in the early stage of deformation than random high-angle grain boundaries, which helps to limit the increase of yield strength. With the plastic deformation, dislocations gradually pile up at the interface, and the elastic strain field of the previous dislocations hinders the movement of subsequent dislocations, thereby strengthening the dislocation storage capacity, leading to the increase of flow stress and the increase of strain hardening rate, so that the copper alloy has higher tensile strength, thereby realizing low yield ratio.

[0015] The low-Σ heavy site lattice grain boundary has poor mobility, which can prevent abnormal grain growth of the copper alloy pipe during the pipe welding process, thereby improving the high-temperature softening resistance of the copper alloy pipe.

[0016] Compared with the random high-angle grain boundary, the low-Σ heavy site lattice grain boundary is purer, and its coherent property makes it difficult to accommodate solute atoms, so the intergranular corrosion sensitivity is weak. The increase of the proportion of (Σ9+Σ27) / Σ3 can effectively reduce the connectivity of the random high-angle grain boundary grid, hinder the expansion of intergranular corrosion along the grain boundary, and help to reduce the problem of intergranular corrosion and promote tunnel corrosion, thereby improving the corrosion life.

[0017] The application strengthens the copper alloy by the method of multi-element composite trace addition, controls the ratio and addition amount of each element to prevent the copper alloy from precipitating hard and brittle phases, so that the copper alloy has a single face-centered cubic crystal structure alpha phase; meanwhile, the application reduces the alloy system stacking fault energy, so that the copper alloy has the thermodynamic conditions for forming a high proportion of low-Σ heavy site lattice grain boundaries, and on this basis, the recrystallization treatment process is combined to introduce a high proportion of low-Σ heavy site lattice grain boundaries; the application also controls the grain size of the copper alloy by adjusting the annealing process, so as to obtain a copper alloy pipe with high strength, low yield ratio, corrosion resistance and high-temperature softening resistance.

[0018] The first aspect of the present application provides a high-performance copper alloy pipe, which is composed of the following components in mass percentage: 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, and the balance of Cu and inevitable impurities; and f1=[Sn]+10[P], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.5%≤f1≤1.05%, 1<f2≤5, wherein [Sn], [P] and [Ni] are the mass percentages of Sn, P and Ni respectively.

[0019] The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 μm, and the average grain size including twin boundaries is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 coincidence site lattice grain boundaries in the copper alloy pipe is ≥50%, and the ratio of the proportions of Σ9, Σ27 and Σ3 coincidence site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥3.5%.

[0020] In the present application, Sn element can be largely solid-solved in the Cu matrix, and a trace amount of addition will not precipitate a second phase.

[0021] In the present application, Sn element can improve the strength of the copper alloy pipe through solid solution strengthening. The solid solution strengthening effect of alloy elements on the copper alloy pipe mainly depends on the lattice mismatch coefficient and the shear modulus mismatch coefficient of solute atoms and matrix atoms, and the greater the two mismatch coefficients, the stronger the solid solution strengthening effect. The atomic radius difference between Sn and Cu is 23.4%, and the shear modulus increment of Sn to Cu matrix is about 1.35 GPa / at.%, which indicates that the two mismatch coefficients of Sn and Cu are large, and the solid solution strengthening effect of Sn on the Cu matrix is good, so Sn can effectively perform solid solution strengthening.

[0022] In the present application, Sn element can effectively reduce the stacking fault energy of the copper alloy system, so as to form a large number of stacking faults during the recrystallization process. These stacking faults act as nucleation points of annealing twins, and expand into complete annealing twins through atomic rearrangement. The annealing twin boundaries will also meet random high-angle grain boundaries during migration, and react to generate a large number of low-Σ coincidence site lattice grain boundaries (Σ3, Σ9, Σ27 coincidence site lattice grain boundaries, wherein Σ27 is divided into Σ27a and Σ27b), thereby consuming random high-angle grain boundaries and increasing the proportion of low-Σ coincidence site lattice grain boundaries.

[0023] It should be pointed out that when the addition amount of Sn element is too small, the reduction of alloy stacking fault energy and the improvement of solid solution strengthening effect are not obvious; but excessive addition will lead to hard and brittle δ phase (Cu 41 Sn 11The precipitation of Sn element, the microsegregation of Sn element and the grain boundary segregation make the intergranular binding force decrease and the hot working performance of the alloy deteriorate. Therefore, the content of Sn element is controlled to be 0.05%≤Sn≤0.6% in the present application, so that the high proportion of low-Sigma heavy site matrix grain boundary is introduced and the solid solution strengthening capacity of the alloy is improved, and the phenomena such as the precipitation of hard and brittle δ phase, the decrease of intergranular binding force and the deterioration of hot working performance are avoided.

[0024] Therefore, the copper alloy pipe has high strength and low yield ratio characteristics by adding Sn element to solid solution strengthen the copper alloy and reducing the alloy system stacking fault energy to introduce high proportion of low-Sigma heavy site matrix grain boundary, so that the high strength and excellent processing formability are highly coordinated, and the corrosion resistance and high temperature softening resistance are improved to some extent.

[0025] In the present application, the Ni element is added to improve the resistance of Cu matrix to pitting corrosion. The Ni ion can fill the defects of the cuprous oxide film layer on the surface of the copper alloy, so that the surface oxide layer of the copper alloy is more stable and dense, thereby reducing the pitting corrosion rate of the copper alloy, and as the content of Ni increases, the pitting corrosion resistance of the copper alloy is improved.

[0026] In the present application, Ni and Cu are isomorphous and have infinite solid solution characteristics, and do not precipitate a brittle second phase that has a deteriorating ductility effect.

[0027] In the present application, the Ni element also has a certain solid solution strengthening effect, but the atomic radius difference between Ni and Cu is only 3.2%, and the increase in shear modulus of the Cu matrix is only 0.19 GPa / at.%, and both of the two mismatch coefficients are much lower than that of Sn element, so the solid solution strengthening effect is limited, and therefore the Ni element only serves as a supplement to Sn element to strengthen the copper alloy.

[0028] It should be pointed out that the addition of Ni element will slightly increase the stacking fault energy of the alloy system, which is not conducive to the introduction of low-Sigma heavy site matrix grain boundary, i.e. not conducive to the reduction of the yield ratio of the copper alloy. Therefore, the addition amount of Ni should not be too high, and the ratio of Sn and Ni should be controlled to ensure a high proportion of low-Sigma heavy site matrix grain boundary.

[0029] Therefore, in order to significantly improve the pitting corrosion resistance of the copper alloy, and maintain the yield ratio, ductility and processing performance such as bending, flaring and expanding of the alloy, the content of Ni element is controlled to be 0.08%≤Ni<0.3% in the present application.

[0030] The present application improves the pitting corrosion resistance of the copper alloy by adding Ni element, and realizes the high coordination of mechanical properties and corrosion resistance by adding Sn and Ni elements. Among them, the Ni element makes up for the problem that Sn element cannot significantly improve the pitting corrosion resistance of the copper alloy thin-walled pipe, and the Sn element makes up for the negative problem of increasing the stacking fault energy of the alloy system.

[0031] In the present application, the trace addition of P element not only has the function of deoxidizing copper liquid, but also can further reduce the alloy system stacking fault energy with the help of P element. The P element has a stronger stacking fault energy reduction effect than Sn element, which can make up for the limited reduction of stacking fault energy caused by the limited content of Sn element. At the same time, P element can also improve the fluidity of copper liquid, making up for the problem of reducing the fluidity of copper liquid caused by Sn element.

[0032] It should be pointed out that the maximum solid solubility of P element is low, and excessive addition will form Cu3P phase, which will deteriorate the ductility of copper alloy by segregating at the grain boundary. Therefore, the present application limits the addition amount of P element to 0.015%≤P≤0.045%.

[0033] In the present application, the total addition amount of Sn and P elements and the ratio of Sn and Ni elements are controlled by weighting, so that f1≥0.5% and f2>1 to make the alloy have a certain low stacking fault energy, and at the same time cooperate with the subsequent recrystallization process to make the proportion of low Σ value heavy site lattice grain boundary≥50%, thereby realizing high strength and low yield ratio, and controlling the ratio of (Σ9+Σ27) / Σ3≥3.5% to provide certain corrosion resistance improvement. In addition, the present application controls f1≤1.05 and f2≤5 to prevent the solute atom concentration in the matrix from exceeding a certain limit when the addition amount of Sn element and the total element addition amount are too high, which will severely deteriorate the deformation ability of the matrix due to too small pinning distance, which is not conducive to maintaining low yield ratio. Controlling the upper limit of f1 and f2 values is also conducive to making the copper alloy of the present application have a single face-centered cubic crystal structure α phase.

[0034] The copper alloy pipe has a single face-centered cubic crystal structure α phase, which can avoid the initiation of micro-cracks caused by the deformation incoordination between the matrix and the second phase. At the same time, the face-centered cubic crystal structure phase has rich slip systems and strong plastic deformation ability, which is not easy to cause stress concentration, is conducive to promoting plastic deformation and maintaining low yield strength, and provides a microstructure basis for realizing low yield ratio.

[0035] According to the Hall-Petch relationship, grain refinement can increase the interface area and increase the resistance to dislocation movement, thereby increasing the yield strength and tensile strength to a certain extent. The present application controls the average grain size excluding twin boundaries to be 10-25 μm to maintain the yield strength from increasing too much. The twin boundaries divide the original grains, further reducing the grain size, but have low energy and coherent characteristics, which has a small increase in yield strength, but can avoid strain concentration and greatly improve the strain hardening ability. However, the average grain size including twin boundaries should not be too low, otherwise it will also cause the increase of yield strength. Therefore, the present application controls the average grain size including twin boundaries to be 5-20 μm to maintain a low yield strength, while providing a certain strain hardening ability to promote the improvement of tensile strength.

[0036] The application controls the proportion of the Sigma 3, Sigma 9 and Sigma 27 heavy site array grain boundaries to be more than 50%, so as to realize high strength and low yield ratio, improve the processing deformation ability of the alloy, and control the ratio of (Sigma 9+Sigma 27) / Sigma 3 to be greater than or equal to 3.5%, so as to improve the corrosion resistance of the alloy.

[0037] The copper alloy pipe prepared by the application has a yield strength of 60-90 MPa, a tensile strength of greater than or equal to 260 MPa, a yield ratio of 0.23-0.30, an elongation after fracture of greater than or equal to 50%, a burst pressure of the same specification TP2 copper pipe increased by greater than or equal to 7%, a wall thickness reduced by greater than or equal to 10% under the condition of maintaining the burst pressure, and a burst pressure attenuation rate of the welded pipe of less than or equal to 10%. After alternating cold and hot corrosion in a 0.4% formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of the single pipe is less than or equal to 170 mu m, the maximum corrosion depth at the elbow pipe is less than or equal to 190 mu m, the single pipe has an improved antihole corrosion resistance by more than 15% compared with the same specification TP2 copper pipe, and the attenuation rate of the corrosion resistance at the elbow pipe is less than or equal to 15%.

[0038] The second aspect of the application provides a high-performance copper alloy pipe, which is composed of the following components in mass percentage: 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, and the balance being Cu and inevitable impurities; and f1=[Sn]+10[P], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.5%≤f1≤1.05%, 1<f2≤5, wherein [Sn], [P] and [Ni] are the mass percentages of Sn, P and Ni respectively.

[0039] The copper alloy pipe has a single face-centered cubic crystal structure alpha phase, an average grain size of 10-25 mu m without considering the twin grain boundary, and an average grain size of 5-20 mu m considering the twin grain boundary; the total proportion of the Sigma 3, Sigma 9 and Sigma 27 heavy site array grain boundaries in the copper alloy pipe is greater than or equal to 68%, and the ratio of the proportions of the Sigma 9, Sigma 27 and Sigma 3 heavy site array grain boundaries satisfies (Sigma 9+Sigma 27) / Sigma 3≥10%.

[0040] The application adjusts the single recrystallization process to the repeated recrystallization process while keeping the chemical composition and content unchanged, further improves the total proportion of the Sigma 3, Sigma 9 and Sigma 27 heavy site array grain boundaries and the (Sigma 9+Sigma 27) / Sigma 3 value, and can further improve the strength, corrosion resistance and high-temperature softening resistance of the material, and reduce the yield ratio.

[0041] The present application controls the composition, ratio and microstructure parameters of elements in the above range, so that the yield strength of the prepared copper alloy is 65-90 MPa, the tensile strength is ≥ 285 MPa, the yield strength ratio is 0.21-0.28, the elongation after fracture is ≥ 50%, the burst pressure of the same specification TP2 copper pipe is increased by ≥ 20%, the wall thickness can be thinned by ≥ 18% under the condition of maintaining the burst pressure, and the burst pressure attenuation rate after welding is ≤ 5%. After alternating cold and hot corrosion in a 0.4% concentration formic acid aqueous solution for 21 days, the maximum corrosion depth of the single pipe is ≤ 155 μm, the maximum corrosion depth at the elbow is ≤ 165 μm, the single pipe has an improved antihole corrosion resistance by more than 20% compared with the same specification TP2 copper pipe, and the corrosion resistance attenuation rate at the elbow is ≤ 10%.

[0042] For the high-performance copper alloy pipe of the first and second aspects of the present application, preferably in the copper alloy pipe, f1 and f2 satisfy: 0.65% ≤ f1 ≤ 1.05%, and 3.4 ≤ f2 ≤ 5.

[0043] The present application further increases the values of f1 and f2, increases the content of solid solution elements, further improves the tensile strength, reduces the alloy system stacking fault energy, realizes the increase of the low Σ value heavy site lattice grain boundary proportion and the (Σ9+Σ27) / Σ3 value, and maintains the low yield strength ratio, thereby reducing the burst pressure attenuation rate and the corrosion resistance attenuation rate at the elbow to a certain extent.

[0044] Taking a single recrystallization process as an example, the present application controls the values of f1 and f2 in the above range, and the obtained copper alloy still has a single face-centered cubic crystal structure α phase, the average grain size without twin boundaries is 10-25 μm, and the average grain size with twin boundaries is 5-20 μm, which can provide a microstructure basis for realizing a low yield strength ratio. Meanwhile, the present application further increases the values of f1 and f2, increases the low Σ value heavy site lattice grain boundary proportion to ≥ 60%, increases the (Σ9+Σ27) / Σ3 ratio to ≥ 3.8%, so that the yield strength of the prepared copper alloy is between 65-90 MPa, the tensile strength is ≥ 270 MPa, the yield strength ratio is between 0.23-0.30, the elongation after fracture is ≥ 50%, the burst pressure of the same specification copper pipe is increased by ≥ 13%, the wall thickness can be thinned by ≥ 14% under the condition of maintaining the burst pressure, and the burst pressure attenuation rate after welding is ≤ 7%. After alternating cold and hot corrosion in a 0.4% concentration formic acid aqueous solution for 21 days, the maximum corrosion depth of the single pipe is ≤ 165 μm, the maximum corrosion depth at the elbow is ≤ 180 μm, the single pipe has an improved antihole corrosion resistance by more than 17% compared with the same specification TP2 copper pipe, and the corrosion resistance attenuation rate at the elbow is ≤ 12%.

[0045] The third aspect of the present application provides a high-performance copper alloy pipe, which is composed of the following components in mass percentage: 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, 0.001%≤Zr<0.03%, 0.001%≤Co<0.01%, 0≤B<0.01%, and the balance being Cu and inevitable impurities; and f1=[Sn]+10[P]+10[Zr], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.65%≤f1<1.15%, 1<f2≤5, wherein [Sn], [P], [Zr] and [Ni] are the mass percentages of Sn, P, Zr and Ni, respectively.

[0046] The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 μm, and the average grain size including twin boundaries is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 coincidence site lattice grain boundaries in the copper alloy pipe is ≥60%, and the ratio of Σ9, Σ27 and Σ3 coincidence site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥4.0%.

[0047] On the basis of Sn, Ni and P composite reinforced copper alloy, the present application further reduces the stacking fault energy of the alloy system by adding Zr element, greatly increases the proportion of low-Σ value coincidence site lattice grain boundaries, and realizes further improvement of strength and reduction of yield ratio; the high-temperature softening resistance of the copper alloy is improved by adding Co element, and the burst pressure decay rate of the copper pipe after pipe welding is significantly reduced. Meanwhile, B element can be optionally added to improve the quality of the cast blank, reduce the oxygen content, and further improve the corrosion resistance of the finished copper pipe.

[0048] Specifically, in the present application, the stacking fault energy of the copper alloy system is further reduced by adding a small amount of Zr element, so as to activate a higher proportion of stacking faults and form a higher proportion of low-Σ value coincidence site lattice grain boundaries, so as to further optimize the performance of the copper alloy. The effect of Zr element in reducing stacking fault energy is much stronger than that of Sn and P elements, which can not only work together with Sn and P elements to reduce the stacking fault energy to a lower level, but also can replace Sn element to some extent, reduce the amount of Sn element, and improve the economy of the alloy.

[0049] It should be pointed out that the solid solubility of Zr in Cu matrix is very limited. According to the Cu-Zr binary phase diagram, the maximum solid solubility of Zr in Cu at room temperature is less than 0.11%, and in actual use, the Zr content needs to be reduced to less than 0.03% to ensure that no brittle Zr-containing second phase is precipitated. Therefore, in order to ensure that Zr element can significantly reduce the stacking fault energy and at the same time ensure that no brittle Zr-containing second phase is precipitated, the present application strictly controls the addition amount of Zr element to be 0.001%≤Zr<0.03%.

[0050] In the present application, the Co element significantly improves the recrystallization temperature of the copper alloy due to its high melting point, and also has the function of pinning random high-angle grain boundaries, which can effectively limit the rapid migration of random high-angle grain boundaries during welding and inhibit the abnormal growth of grains, thereby improving the high-temperature softening resistance of the copper alloy. However, the solid solubility of Co element in Cu matrix is also very low. Therefore, in order to improve the high-temperature softening resistance and maintain a single face-centered cubic crystal structure, the present application controls the addition amount of Co element to be 0.001%≤Co<0.01%.

[0051] In the present application, the B element has the dual effects of oxygen removal and refinement of cast blank dendritic structure in copper liquid. B element reacts with cuprous oxide and free oxygen in copper liquid to form di boron trioxide, forming slag and floating up to achieve the effect of oxygen removal. However, the maximum solid solubility of B element in Cu matrix at room temperature is only 0.01%, therefore, in order to play the role of oxygen removal and grain refinement and maintain a single face-centered cubic crystal structure, the present application controls the addition amount of B element to be less than 0.01%.

[0052] In the present application, by controlling the total addition amount of Sn, P and Zr elements, the ratio of Sn and Ni elements, and the separate addition amount of Co and B elements, f1≥0.65% and f2>1, the strong layer dislocation energy reduction effect of Zr element is utilized to further reduce the layer dislocation energy or reduce the addition amount of Sn element, and the proportion of low Σ value heavy site lattice grain boundaries is increased to ≥60% by subsequent recrystallization process, so as to improve the strength while maintaining low yield ratio, and the ratio of (Σ9+Σ27) / Σ3 is increased to ≥4.0%, which is helpful to improve the corrosion resistance. At the same time, by controlling the separate addition amount of each element and making f1 value<1.15% and f2≤5, the copper alloy can maintain a single α phase.

[0053] By adjusting the composition and ratio of elements and controlling the microstructure parameters within the above range, the copper alloy prepared by the present application has a yield strength of 65-90 MPa, a tensile strength of ≥275 MPa, a yield ratio of 0.22-0.29, an elongation of ≥50%, a burst pressure of TP2 copper pipe of the same specification increased by ≥18%, a wall thickness reduced by ≥15% under the condition of maintaining the burst pressure, and a burst pressure attenuation rate of ≤6% after welding. After alternating cold and hot corrosion in a 0.4% formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of the single pipe is ≤165 μm, the maximum corrosion depth at the bend is ≤180 μm, the single pipe has an improved antihole corrosion resistance of more than 18% compared with the same specification TP2 copper pipe, and the corrosion resistance attenuation rate at the bend is ≤11%.

[0054] Preferably, in the copper alloy of the present application, 0.001%≤B<0.01% by mass percentage.

[0055] The application can reduce the oxygen content in the copper alloy to below 15 ppm while refining the cast blank dendritic structure, thereby improving the resistance to tunnel corrosion. After alternating cold and hot corrosion in a 0.4% concentration formic acid aqueous solution atmosphere for 21 days, the maximum depth of single tube corrosion is ≤155 μm, the maximum depth of corrosion at the elbow is ≤170 μm, the single tube tunnel corrosion resistance is increased by more than 21% compared with the same specification TP2 copper tube, and the corrosion resistance attenuation rate at the elbow is ≤10%.

[0056] The fourth aspect of the application provides a high-performance copper alloy pipe, which is composed of the following components with mass percentages: 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, 0.001%≤Zr<0.03%, 0.001%≤Co<0.01%, 0≤B<0.01%, and the balance being Cu and inevitable impurities; and f1=[Sn]+10[P]+10[Zr], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.65%≤f1<1.15%, 1<f2≤5, wherein [Sn], [P], [Zr] and [Ni] are the mass percentages of Sn, P, Zr and Ni, respectively.

[0057] The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size without considering the twin boundary is 10-25 μm, and the average grain size considering the twin boundary is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥72%, and the ratio of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥12%.

[0058] On the basis of the above-mentioned combination of alloying elements, the application combines a repeated recrystallization process to further improve the total proportion of Σ3, Σ9 and Σ27 grain boundaries of the alloy, (Σ9+Σ27) / Σ3≥12%, which can improve the strength while maintaining a low yield ratio, and effectively reduce the burst pressure decay rate after pipe welding and the corrosion resistance decay rate at the elbow.

[0059] The present application controls the composition, ratio and microstructure parameters of elements in the above range, so that the yield strength of the prepared copper alloy pipe is 65-90 MPa, the tensile strength is greater than or equal to 295 MPa, the yield strength ratio is 0.20-0.27, the elongation after fracture is greater than or equal to 50%, the burst pressure of the same specification TP2 copper pipe is increased by greater than or equal to 25%, the wall thickness can be thinned by greater than or equal to 20% under the condition of maintaining the burst pressure, and the burst pressure attenuation rate of the welded pipe is less than or equal to 2%. After alternating cold and hot corrosion in a 0.4% formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of the single pipe is less than or equal to 150 μm, the maximum corrosion depth at the elbow of the pipe is less than or equal to 160 μm, the single pipe has an improved antihole corrosion resistance by more than 23% compared with the same specification TP2 copper pipe, and the attenuation rate of the corrosion resistance at the elbow of the pipe is less than or equal to 7%.

[0060] Preferably, on the basis of the above repeated recrystallization process, by controlling the content of B element to be 0.001%≤B<0.01%, the oxygen content of the copper alloy can be reduced to less than or equal to 15 ppm, so that after alternating cold and hot corrosion in a 0.4% formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of the single pipe is less than or equal to 145 μm, the maximum corrosion depth at the elbow of the pipe is less than or equal to 155 μm, the single pipe has an improved antihole corrosion resistance by more than 25% compared with the same specification TP2 copper pipe, and the attenuation rate of the corrosion resistance at the elbow of the pipe is less than or equal to 5%.

[0061] The fifth aspect of the present application provides a preparation method of the above-mentioned high-performance copper alloy pipe, which can prepare a copper alloy seamless pipe, and the method can be realized by using the existing production line and has strong adaptability to the existing equipment.

[0062] Specifically, the preparation method of the high-performance copper alloy pipe of the present application comprises the following steps: batching and melting → continuous casting → rolling → drawing → recrystallization treatment; wherein,

[0063] Batching and melting: the raw materials meeting the ratio are melted;

[0064] Continuous casting: the molten liquid is continuously cast into a blank;

[0065] Rolling: the blank is rolled to obtain a rolled pipe blank;

[0066] Drawing: the rolled pipe blank is reduced in diameter;

[0067] Recrystallization treatment: by controlling the deformation amount and annealing parameters, a product with target performance is obtained.

[0068] On the basis of the alloying component and content design, the present application improves the proportion of low-Σ value heavy-site lattice grain boundaries by improving the recrystallization treatment process. The recrystallization treatment process can be divided into single recrystallization process and repeated recrystallization process, and the essence of the two recrystallization processes is to increase the formation proportion of low-Σ value heavy-site lattice grain boundaries by strain-induced grain boundary migration.

[0069] Preferably, the recrystallization treatment is a single recrystallization process, the single recrystallization is "disc drawing→product annealing", the total deformation of the disc drawing is not less than 80%, the product annealing temperature is 500-750℃, and the annealing time is 30-150 min.

[0070] In the present application, the single recrystallization has a large deformation and a high annealing temperature. A large number of strain-induced annealing twins are formed due to the low dislocation energy of the alloy system during annealing. The annealing twin boundaries (Σ3) formed in the migration process also meet random high-angle grain boundaries, and a large number of low-Σ-value high-index grain boundaries (Σ3, Σ9, Σ27a and Σ27b) are generated by reaction, thereby increasing the proportion of low-Σ-value high-index grain boundaries. Among them, the Σ9 and Σ27 high-index grain boundaries occupy the position of random high-angle grain boundaries, and break the random high-angle grain boundary network.

[0071] In the present application, by controlling the total deformation of the single recrystallization to be not less than 80% to accumulate sufficient strain energy, introducing high-density dislocations and destroying the original grain boundary structure, and based on the high-strain-energy structure, a large-scale recrystallization and grain boundary migration are driven by annealing at 500-750℃ for 30-150 min, thereby forming a low-Σ-value high-index grain boundary with a proportion of not less than 50%.

[0072] Preferably, the recrystallization treatment is a repeated recrystallization process, the repeated recrystallization is a cycle of "disc drawing→annealing" after 1-3 passes of disc drawing, the total deformation of the 1-3 passes of disc drawing before the cycle is ≤72%; in the multiple "disc drawing→annealing" cycles, the cycle number of "disc drawing→annealing" is 3-6 times, the disc drawing deformation in a single cycle is 25-35%, the annealing temperature is 500-600℃, and the annealing time is 10-70 min.

[0073] In the present application, the repeated recrystallization process has the characteristics of small deformation in a single pass and low annealing temperature. In the annealing at a lower temperature, selective recrystallization is preferentially induced at high defects, strain-induced annealing twins occur, and annealing twin boundaries also migrate and react with random high-angle grain boundaries to form low-Σ-value high-index grain boundaries without introducing strong crystal orientation, while the grain size is controlled not to grow too much. When the recrystallized structure is deformed again, the low-Σ-value high-index grain boundaries with low energy are not easily damaged, while the random high-angle grain boundaries can be continuously activated and migrated by deformation and annealing to form new annealing twins and low-Σ-value high-index grain boundaries. The low-Σ-value high-index grain boundaries are superimposed and accumulated to increase the proportion of low-Σ-value high-index grain boundaries.

[0074] The application is characterized in that the single-pass deformation amount of the control cycle is in the range of 25% to 35%, so that controllable strain energy is introduced, high-energy random high-angle grain boundaries are preferentially damaged, and existing low-energy boundaries are avoided from being damaged; and the annealing temperature and the annealing time of the control cycle are controlled, so that the strain energy is gradually released, high-strain-energy structures are selectively driven to preferentially recrystallize and form low-energy boundaries, and a higher proportion of low-Σ heavy site lattice grain boundaries can be accumulated through the cycle processing, and the control of the low-Σ heavy site lattice grain boundaries is more accurate.

[0075] Compared with the ordinary process and the single annealing process, the repeated recrystallization process of the application can significantly increase the number of low-Σ heavy site lattice grain boundaries after 3 to 6 cycles, the proportion of low-Σ heavy site lattice grain boundaries is higher than 65%, the proportions of Σ9, Σ27a and Σ27b are also significantly increased, and (Σ9+Σ27) / Σ3>10.3%, which effectively reduces the connectivity of the random high-angle grain boundary network. However, when the number of cycles exceeds 6, the proportion of low-Σ heavy site lattice grain boundaries will not increase significantly because the low-Σ heavy site lattice grain boundaries have reached a saturated state.

[0076] Preferably, in the ingredient smelting process, the ingredients are first dried and then smelted at 1170-1350℃. Among them, Ni, Co, B, Zr, P and Sn elements are added in the form of commercially available copper-nickel intermediate alloy, copper-cobalt intermediate alloy, copper-boron intermediate alloy, copper-zirconium intermediate alloy, phosphorus-copper intermediate alloy and copper-tin intermediate alloy. After the raw materials are completely melted, they are kept for 45-90 min to make the trace elements fully diffuse and homogenize. Adding trace elements in the form of intermediate alloy can promote melting, diffusion and reduce burning loss. Subsequently, the copper liquid is transferred to a casting furnace under nitrogen protection, the holding temperature of the casting furnace is 1180-1190℃, the holding time is 8-12 min, and then the pipe blank is continuously cast.

[0077] Preferably, the continuous casting process is horizontal continuous casting, the pulling speed is 330-380 mm / min, the primary cooling water flow is 30-35 L / min, and the secondary cooling water flow is 65-75 L / min. The outer diameter size of the horizontal continuous casting pipe blank can be designed according to actual needs, for example, it can be 88-98 mm, preferably 92 mm.

[0078] Preferably, in the rolling process, the rolling speed is 1.2-2.2 m / min, and the rolling pipe blank is obtained after rolling is completed. The size of the rolling pipe blank can be designed according to actual needs, for example, the outer diameter of the rolling pipe blank is 50-55 mm, and the wall thickness is 2.3-2.7 mm.

[0079] Preferably, the combined drawing process provides a semi-finished product meeting the dimensional requirements for subsequent processing, and the speed of the combined drawing is controlled at 70-92 m / min, and the precision tube blank obtained after the combined drawing has a significantly reduced outer diameter. For example, after the combined drawing, the outer diameter of the 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 thinned to 1.4-1.7 mm.

[0080] After the combined drawing process, the obtained precision tube blank is subjected to a single recrystallization process or a repeated recrystallization process to prepare a high-performance copper alloy tube material having a high proportion of low-Σ heavy-site lattice grain boundaries. The prepared tube material is not limited in size and includes, but is not limited to, a smooth tube and an internally threaded tube.

[0081] In the single recrystallization process, the passes of the disc drawing and the specific process parameters can be flexibly adjusted according to actual production needs to ensure that the final product meets the target specifications and size requirements, but it must be ensured that the total deformation of the disc drawing is ≥80% to store enough strain energy to effectively promote the formation of a recrystallized structure with uniform size in the finished product during annealing and significantly increase the proportion of low-Σ heavy-site lattice grain boundaries. For example, after 6-9 passes of disc drawing of the rolled tube blank with an outer diameter of 30-35 mm and a wall thickness of 1.4-1.7 mm, a smooth tube with an outer diameter of 5-12 mm and a wall thickness of 0.40-0.65 mm is prepared, and the total deformation is 81.5%-96.7%, wherein the disc drawing speed is 450-700 m / min.

[0082] In the repeated recrystallization process, the total deformation of the 1-3 passes of disc drawing before the cycle is ≤72%, and the specific pass deformation distribution and specific process parameters can be flexibly adjusted according to actual production needs. In the "disc drawing-annealing" cycle process, the passes of the disc drawing and the specific process parameters in a single cycle can also be flexibly adjusted according to actual production needs, but it is required to ensure that the total deformation of the disc drawing in a single cycle is 25%-35%, the annealing temperature in a single cycle is 500-600℃, the annealing time in a single cycle is 10-70 min, and the cycle number is 3-6 times to accumulate a high proportion of low-Σ heavy-site lattice grain boundaries and increase the (Σ9+Σ27) / Σ3 ratio. For example, after 1-2 passes of disc drawing of the rolled tube blank with an outer diameter of 30-35 mm and a wall thickness of 1.4-1.7 mm, an intermediate tube blank with an outer diameter of 20-26 mm and a wall thickness of 0.85-1.2 mm is prepared, and the "disc drawing-annealing" cycle process is performed to prepare a smooth tube with an outer diameter of 5-12 mm and a wall thickness of 0.40-0.65 mm, wherein the disc drawing speed is 450-700 m / min.

[0083] When the internal thread pipe is prepared by the single recrystallization process route, the pipe blank is required to be softened by the on-line annealing after the disc drawing process, and the on-line annealing process parameters are preferably: speed 300-450 m / min, current 3600-5000 A. Then the internal thread pipe blank obtained by the on-line annealing is subjected to internal thread spinning forming, and the spinning speed is preferably 480-650 r / m, and more preferably 550-600 r / m. Then the finished product annealing treatment is carried out, and the internal thread pipe is obtained, and the finished product annealing temperature is preferably 510-650 DEG C, and the annealing time is 30-120 min.

[0084] When the internal thread pipe is prepared by the repeated recrystallization process route, the last one pass 'disc drawing-annealing' cycle process is replaced by the 'internal thread forming-internal thread pipe annealing' process. The internal thread forming spinning speed is preferably 480-650 r / m, and more preferably 550-600 r / m. The internal thread pipe annealing temperature is preferably 500-580 DEG C, and the annealing time is 10-70 min.

[0085] It should be noted that the copper alloy composition provided by the present application is not only suitable for pipe production, but also can be applied to the preparation of various copper alloy products such as wire, bar, plate and strip. Its production process can not only use existing mature processing technologies such as extrusion, rolling, drawing and forging, but also can optimize and adjust the process parameters or develop new processing methods according to the specific product performance requirements and application scenarios to meet the diversified needs of different industries for copper alloy materials. The high-performance copper alloy pipe is not only suitable for the heat exchange field, but also can play an important role in the fields of ocean engineering and energy chemical industry, especially in the scenes with complex environment and high use requirements for material performance.

[0086] Compared with the prior art, the present application has at least the following technical effects:

[0087] (1) The present application adds Sn, Ni and P elements to Cu, controls the content and ratio of each element, and combines with the subsequent recrystallization treatment process, so that the copper alloy is strengthened in strength while having a high proportion of low Σ value heavy site array grain boundary, effectively reducing the yield ratio, maintaining high processing forming ability, and showing excellent application process performance such as bending, flaring and tube expanding, and having more excellent pressure resistance, corrosion resistance and high temperature softening resistance.

[0088] (2) The present application adds Zr, Co and B (optionally) elements on the basis of Cu, Sn, Ni and P elements, controls the content and ratio of each element, and combines with the subsequent improved recrystallization treatment process, so that the strength, plastic deformation ability, pressure resistance, corrosion resistance and high temperature softening resistance of the alloy are further improved compared with the copper alloy prepared by Cu, Sn, Ni and P elements.

[0089] (3) The recrystallization treatment process of the present application includes single recrystallization and repeated recrystallization, and can be implemented by using the existing production line, and has strong adaptability to the existing equipment. The copper alloy with excellent performance can be obtained by combining the designed alloy composition with the single recrystallization process. In combination with the repeated recrystallization process, the proportion of low-Σ value heavy-site lattice grain boundaries and the ratio of (Σ9+Σ27) / Σ3 are significantly improved, and the strength, plastic deformation capacity, pressure resistance, corrosion resistance and high-temperature softening resistance of the alloy are further improved compared with the copper alloy prepared by the single recrystallization process. BRIEF DESCRIPTION OF DRAWINGS

[0090] Figure 1 The process route map of the present application.

[0091] Figure 2 The X-ray diffraction (XRD) spectrum of Example 2, Example 5, Example 12, Example 15 and Comparative Example 1 of the present application.

[0092] Figure 3 The inverse pole figure (IPF) and grain boundary distribution map obtained by electron backscatter diffraction (EBSD) test of the sample of Example 2, the sample of Example 5 after 3 cycles of repeated recrystallization, the sample of Example 5 after 4 cycles of repeated recrystallization and the sample of Comparative Example 1, wherein (a) is the IPF of Comparative Example 1; (b) is the grain boundary distribution map of Comparative Example 1; (c) is the IPF of Example 2; (d) is the grain boundary distribution map of Example 2; (e) is the IPF of Example 5 after 3 cycles of repeated recrystallization; (f) is the grain boundary distribution map of Example 5 after 3 cycles of repeated recrystallization; (g) is the IPF of Example 5 after 4 cycles of repeated recrystallization; (h) is the grain boundary distribution map of Example 5 after 4 cycles of repeated recrystallization.

[0093] Figure 4 The engineering stress-strain curve of Example 2, Example 5, Example 12, Example 15 and Comparative Example 1 of the present application.

[0094] Figure 5 The typical corrosion morphology of the cross section of the sample after pitting corrosion of Example 2 and Comparative Example 1 is provided, and the corrosion depth is provided, wherein (a) is the cross section morphology of the sample after pitting corrosion test of Comparative Example 1; (b) is the cross section morphology of the elbow sample after pitting corrosion test of Comparative Example 1; (c) is the cross section morphology of the sample after pitting corrosion test of Example 2; (d) is the cross section morphology of the elbow sample after pitting corrosion test of Example 2.

[0095] Figure 6The pictures of the rupture after the water pressure burst test of the sample of the present application example 2 and the comparative example 1 and the pictures of the rupture after the water pressure burst test of the welded pipe sample, wherein (a) is the picture of the rupture after the water pressure burst test of the sample of the comparative example 1; (b) is the picture of the rupture after the water pressure burst test of the welded pipe sample of the comparative example 1; (c) is the picture of the rupture after the water pressure burst test of the sample of the example 2; (d) is the picture of the rupture after the water pressure burst test of the welded pipe sample of the example 2.

[0096] Figure 7 The Kernel average misorientation map (KAM map) measured after 5% tensile deformation of the present application example 2 and the comparative example 1, wherein (a) is the KAM map measured after 5% tensile deformation of the comparative example 1; (b) is the KAM map measured after 5% tensile deformation of the example 2. DETAILED DESCRIPTION

[0097] The technical solutions and advantages of the present application will be described more clearly and completely in combination with the drawings and specific embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0098] The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturers. The raw materials and reagents used are conventional products that can be purchased on the market.

[0099] The performance parameters involved in the embodiments of the present application are measured by the following methods.

[0100] The average grain size of the metallographic structure is tested according to GB / T 6394-2017 Metal Grain Size Determination Method.

[0101] The room temperature mechanical properties such as yield strength, ultimate tensile strength, elongation after fracture, etc. are tested on an electronic universal mechanical property testing machine according to GB / T 228.1-2010 Metal Materials Tensile Test Part 1: Room Temperature Test Method, using an extensometer with a gauge length of 50 mm and a tensile speed of 5 mm / min, and 3 parallel samples.

[0102] The burst pressure is tested for pressure resistance according to GB / T 241-2007 Metal Pipe Liquid Pressure Test Method to obtain the burst pressure of the copper alloy pipe; the same pressure resistance test is carried out after the copper pipe is welded to obtain the burst pressure of the welded pipe. The burst pressure decay rate of the welded pipe is defined as:

[0103] The burst pressure decay rate of the welded pipe = (burst pressure - burst pressure of the welded pipe) / burst pressure * 100%.

[0104] The process performance bending test was tested according to GB / T 244-2008 Metal Pipe Bending Test Method. Under the condition that the bending core diameter is 1.5 times the outer diameter of the copper pipe, the inner and outer surfaces are smooth after bending 180°, without wrinkles or cracks. The flaring test was tested according to GB / T 17791-1999 Seamless Copper Pipe for Air Conditioning and Refrigeration. The flaring cone is 60°, the flaring rate is 40% or the distance between the two walls after flattening is equal to the wall thickness, and the sample does not produce visible cracks and cracks, indicating that the process performance is excellent.

[0105] The termite hole corrosion test takes 13 parallel samples of each copper alloy, each sample length is 10 cm. First, the copper pipe sample is pretreated, ultrasonic cleaning with anhydrous ethanol, acetone, deionized water for 3 minutes respectively to remove oil stains on the surface of the copper pipe. Then seal the two ends of the copper pipe sample, only the outer surface of the copper pipe is exposed to the formic acid atmosphere. The pretreated copper pipe is hung in a sealed box containing 0.4% formic acid aqueous solution, the volume of the solution and the area of the sample are not less than 5 cm 3 / cm 2 , the water bath is heated to 40℃ and kept for 48 hours, then placed at room temperature for 48 hours, and the cold and hot alternation is repeated for 21 days. After the corrosion test, 7 equidistant cross sections are selected from each sample for corrosion depth test, the maximum corrosion depth of each sample is recorded, the average value of the maximum corrosion depth of the 13 parallel samples is taken as the maximum corrosion depth of the single pipe of the copper alloy under the above test conditions.

[0106] The bending pipe corrosion test is prepared according to the bending pipe test conditions, each sample length is 15 cm, the bending pipe center is located at the axial center of the sample, the sample is pretreated and sealed according to the above termite hole corrosion test steps, the outer side of the bending pipe is hung downward in the sealed box containing formic acid aqueous solution for corrosion, after the corrosion test, each sample is taken every 5 mm from both sides with the bending pipe center as the starting point, 3 cross sections are taken, a total of 7 cross sections including the bending pipe center cross section, corrosion depth test is carried out, the remaining test and data processing requirements are consistent with the termite hole corrosion test, and the maximum corrosion depth at the bending pipe is obtained.

[0107] The bending pipe corrosion resistance decay rate is defined as:

[0108] Bending pipe corrosion resistance decay rate = (maximum corrosion depth at bending pipe - maximum corrosion depth of single pipe) / maximum corrosion depth of single pipe * 100%.

[0109] XRD pattern test uses Japan Rigaku Smartlab X-ray diffractometer, continuous scanning speed is 1° / min, 2θ range is 35°-100°, copper target is used for testing.

[0110] EBSD testing was performed on a German Carl Zeiss Sigma 300 field emission scanning electron microscope equipped with an Oxford Symmetry S2 EBSD probe with a scan step size of 0.5 microns. Data analysis was performed using AZtec Crystal 2.1 software. Grain boundary types were determined according to Brandon’s criteria, where grain boundaries with 60° / <111> misorientation, angular deviation ≤ 8.7°, axial deviation ≤ 8.2° were defined as Σ3 grain boundaries, grain boundaries with 38.9° / <110> misorientation, angular deviation ≤ 5.0°, axial deviation ≤ 2.7° were defined as Σ9 grain boundaries, grain boundaries with 31.6° / <110> and 35.4° / <210> misorientation, angular deviation ≤ 2.9°, axial deviation ≤ 0.9° were defined as Σ27a grain boundaries and Σ27b grain boundaries.

[0111] Examples 1-4

[0112] Examples 1-4 provide a Sn, Ni, P-containing copper alloy material light pipe and a preparation method using a single recrystallization process route, wherein the specific preparation method of Example 1 includes the following steps:

[0113] S1. Proportioning and smelting

[0114] According to the designed chemical composition of the copper alloy, prepare electrolytic copper (purity ≥ 99.98%), copper-nickel intermediate alloy (Cu-42% Ni), phosphorus-copper intermediate alloy (Cu-14% P) and copper-tin intermediate alloy (Cu-50% Sn) raw materials and dry them for use. The intermediate alloy method of feeding is beneficial to reduce the melting temperature of high melting point elements, accelerate the dissolution, and reduce the element burning loss and oxidation.

[0115] After smelting the electrolytic copper plate, adjust the copper liquid temperature to 1200°C, add copper-nickel intermediate alloy, phosphorus-copper intermediate alloy and copper-tin intermediate alloy according to the proportion, use graphite rods to stir the copper liquid, and cover the surface of the copper liquid with charcoal to prevent oxidation and reduce burning loss, heat for 60 min to make the elements fully diffuse, promote the homogenization of the copper liquid, and provide time for the floating and escaping of gas and non-metallic inclusions, promote deoxidation and degassing. Pour the copper liquid into the casting furnace for casting preparation, use nitrogen protection during the pouring process to physically isolate air, reduce the risk of oxidation and inclusion absorption during the pouring process of the copper liquid, cover the surface of the copper liquid in the casting furnace with graphite scales to prevent oxidation, and the heat preservation temperature of the copper liquid in the casting furnace is 1185°C, and the heat preservation time is 10 min.

[0116] S2. Continuous casting

[0117] The cast copper liquid is continuously cast into a pipe blank in a casting furnace, the drawing speed is 350 mm / min, the primary cooling water flow rate is 35 L / min, and the secondary cooling water flow rate is 69 L / min. The pipe blank has an outer diameter of 92 mm, an inner diameter of 38.5 mm, and a fixed length of 8 m. Then, the pipe blank is subjected to face milling treatment to remove the surface oxide scale and avoid surface defects from entering the material in subsequent rolling processes. The face milling depth is 1 mm.

[0118] S3. Rolling

[0119] The continuous casting pipe blank is reduced in diameter by three-roll planetary rolling. In the rolling process, the pipe blank is heated by friction to assist deformation. The rolling speed is 1.4 m / min, the outer diameter is reduced to 51 mm, and the wall thickness is reduced to 2.4 mm.

[0120] S4. Drawing

[0121] The intermediate pipe blank after rolling is drawn to reduce the diameter. The drawing speed is 72 m / min, the outer diameter of the pipe blank is reduced to 31 mm, and the wall thickness is reduced to 1.4 mm.

[0122] S5. Single recrystallization process

[0123] The intermediate pipe blank after drawing is subjected to 7-pass disc drawing. The disc drawing speed of the 1st pass is 450 m / min, the disc drawing speed of the 2nd to 6th passes is 660 m / min, and the disc drawing speed of the 7th pass is 620 m / min. A bright pipe with an outer diameter of 9.52 mm and a wall thickness of 0.55 mm is produced. The total deformation of disc drawing is 88.1%. Then, the pipe blank is subjected to finished annealing in a vacuum atmosphere. The annealing temperature is 580°C, and the annealing time is 90 min. The copper alloy pipe of Example 1 is obtained. The specific chemical composition is shown in Table 1.

[0124] Example 2 is prepared by the same method as Example 1, except that in the step S1, the chemical composition of the copper alloy and the raw material ratio are different. The specific chemical composition is shown in Table 1.

[0125] Example 3 is different from Example 1 in that,

[0126] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different. The specific chemical composition is shown in Table 1.

[0127] In the step S5, the annealing temperature is 600°C, and the annealing time is 90 min. The purpose of changing the annealing temperature is to make the complete recrystallization degree of each example consistent after the chemical composition changes, i.e., the average grain size excluding twin boundaries is similar.

[0128] Example 4

[0129] This example is different from Example 1 in that,

[0130] In the step S1, the chemical composition of the copper alloy and the proportion of raw materials are different, and the specific chemical composition is shown in Table 1.

[0131] In the step S5, the annealing temperature is 600℃, and the annealing time is 90min.

[0132] Examples 5-6

[0133] Examples 5-6 provide a Sn, Ni, P-containing copper alloy material light tube and a preparation method thereof by using a repeated recrystallization process route.

[0134] Example 5 is different from example 1 in that,

[0135] In the step S1, the chemical composition of the copper alloy and the proportion of raw materials are different, and the specific chemical composition is shown in Table 1.

[0136] The step S5 is a repeated recrystallization process, and the specific process is as follows:

[0137] The intermediate pipe blank is subjected to 2 passes of disc drawing, the disc drawing speed of the 1st pass is 450m / min, the disc drawing speed of the 2nd pass is 660m / min, the outer diameter is reduced to 21mm, the wall thickness is reduced to 0.98mm, and the total deformation of disc drawing is 52.7%. Then, the "disc drawing-annealing" cycle process is implemented. In the first cycle, the disc drawing deformation is 30.3%, the disc drawing speed is 600m / min, the annealing temperature is 530℃, and the annealing time is 20min. In the second cycle, the disc drawing deformation is 29.4%, the disc drawing speed is 600m / min, the annealing temperature is 530℃, and the annealing time is 20min. In the third cycle, the disc drawing deformation is 29.2%, the disc drawing speed is 600m / min, the annealing temperature is 530℃, and the annealing time is 20min. In the fourth cycle, the disc drawing deformation is 27.9%, the disc drawing speed is 600m / min, the annealing temperature is 530℃, and the annealing time is 20min. The copper alloy pipe of example 5 is obtained, and the specific chemical composition is shown in Table 1.

[0138] Example 6 is different from example 5 in that,

[0139] In the step S1, the chemical composition of the copper alloy and the proportion of raw materials are different, and the specific chemical composition is shown in Table 1.

[0140] In the step S5, the annealing temperature is 540℃.

[0141] Examples 7-10

[0142] Examples 7-10 provide a Sn, Ni, P, Zr, Co-containing copper alloy light tube and a preparation method thereof by using a single recrystallization process route.

[0143] Example 7, 9 is different from example 1 in that,

[0144] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, in addition to the copper-nickel intermediate alloy, the copper-phosphorus intermediate alloy and the copper-tin intermediate alloy, the copper-cobalt intermediate alloy (Cu-10%Co) and the copper-zirconium intermediate alloy (Cu-10%Zr) are also needed to be added. The specific chemical composition is shown in Table 1.

[0145] Example 8, 10 is different from example 7 in that,

[0146] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, the specific chemical composition is shown in Table 1.

[0147] In the step S5, the annealing temperature is 620℃.

[0148] Example 11

[0149] The embodiment provides a copper alloy light pipe containing Sn, Ni, P, Zr, Co and B and a preparation method of the copper alloy light pipe by using a single recrystallization process.

[0150] The embodiment is different from example 7 in that,

[0151] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, in addition to the copper-nickel intermediate alloy, the copper-cobalt intermediate alloy, the copper-zirconium intermediate alloy, the copper-phosphorus intermediate alloy and the copper-tin intermediate alloy, the copper-boron intermediate alloy (Cu-5%B) is also needed to be added. The specific chemical composition is shown in Table 1.

[0152] Example 12-15

[0153] Examples 12-15 provide a copper alloy light pipe containing Sn, Ni, P, Zr, Co and optional B and a preparation method of the copper alloy light pipe by using a repeated recrystallization process.

[0154] Example 12 is the same as example 7 in chemical composition (the same batch of cast blanks), and is different from example 7 in that the step S5 is a repeated recrystallization process.

[0155] The repeated recrystallization process used in example 12 is the same as that in example 5.

[0156] Example 13 is different from example 12 in that,

[0157] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, the specific chemical composition is shown in Table 1.

[0158] In the repeated recrystallization process of the step S5, the annealing temperature of the "disk drawing-annealing" cycle process is 540℃, and the annealing time is 20min, so as to make the alloy completely recrystallize.

[0159] Embodiments 14 and 15 are different from embodiment 13 in that, in the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 1.

[0160] Embodiment 16

[0161] The embodiment provides a Sn, Ni, P, Zr, Co and B-containing copper alloy internal thread pipe and a preparation method thereof by using a repeated recrystallization process route.

[0162] The embodiment is different from embodiment 15 in that the chemical composition is the same (the same batch of cast blanks), and the difference is that,

[0163] In the step S5, the fourth cycle uses the "internal thread forming-internal thread pipe annealing" process to replace, the pipe blank after the third cycle is spin formed, the spinning speed is 550r / m, the internal thread pipe with a size of 7mm*0.23mm+0.1mm (outer diameter*bottom wall thickness+tooth height) is formed, and then annealing is performed, the annealing temperature is 570℃, and the annealing time is 30min.

[0164] Comparative example 1

[0165] The comparative example provides a copper pipe sample of Zhejiang Hailiang Co., Ltd., which is a TP2 light pipe, the size is 9.52mm*0.55mm (outer diameter*wall thickness), and the specific composition is shown in Table 2.

[0166] Comparative example 2

[0167] The comparative example provides a copper pipe sample of Zhejiang Hailiang Co., Ltd., which is a TP2 internal thread pipe, the size is 7mm*0.23mm+0.1mm, and the specific composition is shown in Table 2.

[0168] Comparative example 3

[0169] The comparative example provides a Cu-Sn-Ni-P copper alloy material with high Sn content and high f2 value and a specific step for preparing the Cu-Sn-Ni-P copper alloy material by using a single recrystallization process route.

[0170] The comparative example is different from embodiment 1 in that,

[0171] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 2.

[0172] In the step S5, the annealing temperature is 620℃, and the annealing time is 90min.

[0173] Comparative Example 4

[0174] The present comparative example provides a Cu-Sn-Ni-P copper alloy light pipe with low f1 and f2 values and the specific steps for preparing the same by using a single recrystallization process route.

[0175] The present comparative example differs from Example 1 in that,

[0176] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 2.

[0177] In the step S5, the annealing temperature is 620°C, and the annealing time is 90 min.

[0178] Comparative Example 5

[0179] The present comparative example provides a Cu-Sn-Ni-P copper alloy light pipe with high Ni content and low f2 value and the specific steps for preparing the same by using a single recrystallization process route.

[0180] The present comparative example differs from Example 1 in that,

[0181] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 2, and the melting temperature is increased to 1250°C.

[0182] In the step S5, the disc drawing speed of the 2nd to 6th passes is 600 m / min, the disc drawing speed of the 7th pass is 550 m / min, the annealing temperature of the finished product is 650°C, and the annealing time is 90 min.

[0183] Comparative Example 6

[0184] The present comparative example provides a Cu-Sn-Ni-P copper alloy light pipe with high Sn content and high f1 and f2 values and the specific steps for preparing the same by using a single recrystallization process route.

[0185] The present comparative example differs from Example 1 in that,

[0186] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 2, and the melting temperature is increased to 1250°C.

[0187] In the step S5, the disc drawing speed of the 2nd to 6th passes is 600 m / min, the disc drawing speed of the 7th pass is 550 m / min, the annealing temperature of the finished product is 650°C, and the annealing time is 90 min.

[0188] Comparative Example 7

[0189] The comparative example provides a Cu-Sn-Ni-P-Zr-Co copper alloy light pipe with high Co and Zr contents and specific steps for preparing the same by using a single recrystallization process route.

[0190] The comparative example differs from example 7 in that,

[0191] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 2.

[0192] In the step S5, the disc drawing speed of the 2nd to 6th passes is 600 m / min, the disc drawing speed of the 7th pass is 550 m / min, the annealing temperature of the finished product is 650℃, and the annealing time is 90 min.

[0193] Comparative example 8

[0194] The comparative example provides a Cu-Sn-Ni-P-Zr-Co-B copper alloy light pipe with high Zr, Co and B contents and specific steps for preparing the same by using a single recrystallization process route.

[0195] The comparative example differs from example 11 in that,

[0196] In the step S1, the chemical composition of the copper alloy and the raw material ratio are different, and the specific chemical composition is shown in Table 2, and the melting temperature is increased to 1250℃.

[0197] In the step S5, the disc drawing speed of the 2nd to 6th passes is 600 m / min, the disc drawing speed of the 7th pass is 550 m / min, the annealing temperature of the finished product is 650℃, and the annealing time is 90 min.

[0198] The chemical composition of the copper alloy of the examples and comparative examples of the present application and the values of f1 and f2 are shown in Tables 1 and 2. The proportion of low-Σ value coincident site lattice grain boundaries and the average grain size of the copper alloy of the examples and comparative examples of the present application are shown in Table 3. The subdivision table of the proportion of low-Σ value coincident site lattice grain boundaries and the influence of the number of cycles of the repeated recrystallization process on the proportion of coincident site lattice grain boundaries of the copper alloy of the examples and comparative examples of the present application are shown in Table 4. The mechanical properties, burst pressure and processing forming properties of the copper alloy of the examples and comparative examples of the present application are shown in Table 5. The ant termite hole corrosion resistance of the copper alloy of the examples and comparative examples of the present application is shown in Table 6.

[0199] Examples 1-3 and comparative example 1 show that, under the condition that the contents of Ni and P are basically unchanged, as the content of Sn increases, the values of f1 and f2 also increase, and the proportions of Σ3, Σ9 and Σ27 coincident site lattice grain boundaries increase to 57.36%, 61.12% and 62.97% respectively (see Tables 3 and 4). Figure 3 (a)、 Figure 3 (b)、 Figure 3 (c)、 Figure 3(d)), and the XRD test results show that it has a single alpha phase (see Figure 2 Meanwhile, from Examples 1-3, it can be seen that the yield strength and tensile strength of the copper alloy increase with the increase of Sn content (see Table 5), proving that Sn element has a significant solid solution strengthening effect, which can simultaneously increase the yield strength and tensile strength. Compared with Comparative Example 1, the tensile strength of Examples 1, 2 and 3 is increased by 12.1%, 17.7% and 21.1% respectively, but the yield strength of Example 1 does not exceed that of Comparative Example 1, indicating that a high proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries is conducive to providing a high proportion of low-energy, coherent low-Σ value heavy site lattice grain boundaries, and the restriction ability of this part of the grain boundary on the dislocation movement in the early stage of plastic deformation is lower than that of random high-angle grain boundaries, so it can maintain a low yield strength to a certain extent by reducing the resistance of the interface to dislocation movement in the early stage of deformation, so that the yield strength ratio is reduced to below 0.30.

[0200] According to Table 5, the burst pressure of the copper alloy pipe of the same specification increases with the increase of Sn content, and the burst pressure of Examples 1, 2 and 3 is increased by 7.3%, 14.2% and 20.7% respectively compared with Comparative Example 1. The burst pressure decay rate of the welded pipe of Examples 1, 2 and 3 is less than 10.0%, which is due to the introduction of a high proportion of low-Σ value heavy site lattice grain boundaries, which to a certain extent inhibits the grain boundary migration and abnormal grain growth at high temperature, thereby reducing the burst pressure decay rate after welding. The rupture position and morphology of the samples of Examples 2 after water pressure burst test and after water pressure burst test of the welded pipe are shown in Figure 6 .

[0201] According to Table 6, under the same formic acid atmosphere corrosion conditions, the maximum corrosion depth of Examples 1, 2 and 3 gradually decreases compared with Comparative Example 1, and the corrosion resistance is increased by 15.8%, 17.9% and 21.5% respectively. Compared with Comparative Example 1, Examples 1-3 have a certain amount of Ni, which helps to improve corrosion resistance. Although the Ni content of Examples 1-3 is similar, Example 3 has a higher total amount of Σ3, Σ9 and Σ27, and these low-Σ value heavy site lattice grain boundaries have better coherence, lower energy and less impurity element segregation, which are difficult to expand the corrosion channel, and do not have the effect of promoting the corrosion process of random high-angle grain boundaries. With the increase of (Σ9+Σ27) / Σ3 (see Table 4, data of Examples 1-3 and Comparative Example 1), the original random high-angle grain boundary grid is broken, and the original intergranular corrosion channel is broken, thereby slowing down the pitting corrosion process to a certain extent.

[0202] The corrosion resistance of Examples 1, 2 and 3 after bending is also improved compared with Comparative Example 1, and the corrosion resistance decay rate after bending is less than 17.0%, indicating that a high total amount of Σ3, Σ9 and Σ27 has a certain resistance to the conditions of stress corrosion and intergranular corrosion combined to promote pitting corrosion. From Figure 7It can be seen that compared with Comparative Example 1, the strain distribution of Example 2 is more uniform after 5% tensile deformation, and the average KAM value is lower, i.e. the strain concentration degree of Example 2 is far lower than that of TP2 copper, which indicates that the smaller grain size (twin boundary) and high proportion of low-Σ coincidence site lattice boundary are beneficial to promote uniform strain distribution, thereby reducing stress and intergranular corrosion effect.

[0203] Example 4 has higher Ni content than Example 2, and the f2 value is reduced, resulting in the total amount of Σ3, Σ9 and Σ27 being reduced to 57.42%, but it has better resistance to tunnel corrosion due to the higher Ni content, and the increase relative to Example 2 is 8.8%. However, due to the slightly lower total amount of Σ3, Σ9 and Σ27, the corrosion resistance decay rate at the elbow of Example 4 is higher than that of Example 2.

[0204] Examples 2 and 3 show that by controlling the f1 and f2 values in the preferred range of 0.65%≤f1≤1.05% and 3.4≤f2≤5, the tensile strength of the copper alloy can be further increased to 275 MPa or more, and the low yield ratio can be maintained, so that the copper alloy not only meets the requirements of bending, expanding and flaring processes, but also further improves the pressure resistance, corrosion resistance and heat softening resistance. Compared with Comparative Example 1, the burst pressure and single pipe corrosion resistance of Example 1 are only increased by 7.3% and 15.8%, respectively, while those of Example 3 are increased by 20.7% and 21.5%, respectively, which indicates that the pressure resistance and corrosion resistance of the copper alloy prepared by the preferred method are greatly improved. At the same time, the burst pressure decay rate and corrosion resistance decay rate of Example 3 are also lower than those of Example 1.

[0205] Comparative Example 3 shows that when the Sn atomic concentration reaches the limit of dilute solid solution solute atoms, the spacing between solute atoms will decrease, which greatly increases the ability of solute atoms to hinder dislocation movement, so that the beneficial effect of low-Σ coincidence site lattice boundary in Comparative Example 3 on reducing the yield ratio is almost offset by the hardening effect of solute atoms, which is manifested as good bending test but unqualified flaring test.

[0206] Comparative Example 4 shows that when the f1 and f2 values are too low, the total amount of Σ3, Σ9 and Σ27 cannot reach more than 50%, which makes it difficult to maintain good processing formability, so although the strength of Comparative Example 4 is improved and the bending test is qualified, the flaring performance is poor.

[0207] Comparative Example 5 shows that even if the copper alloy with high Ni content has a suitable f1 value, the elongation after fracture will be significantly deteriorated, the yield ratio is as high as 0.40, the flaring performance is extremely poor, and the bending performance also cannot meet the requirements.

[0208] Comparative Example 6 shows that the strong hardening effect brought by high Sn content makes Comparative Example 6 have a yield ratio as high as 0.39 and extremely poor flaring performance, and the bending performance also cannot meet the requirements.

[0209] Comparing Example 5 and 6 with Example 2 and 3 shows that for the copper alloy with similar chemical composition, the total amount of Σ3, Σ9 and Σ27 can be effectively accumulated by the repeated recrystallization process, and the total amount is increased from about 60% to 72-75% (see Table 3), and the average grain size (counting twin boundaries) is slightly reduced. Taking Example 2 and Example 5 as examples, the ratio of (Σ9+Σ27) / Σ3 is increased from 4.3% to 12.5% (see Table 4), which shows that the tensile strength, pressure resistance and the reduction of yield strength ratio of Example 5 are significantly improved under the condition of similar yield strength of Example 2. The burst pressure decay rate of the welded pipe of Example 5 is only 3.2%, and the corrosion resistance decay rate of the bent pipe is only 6.2%, which shows that high Σ3, Σ9 and Σ27 heavy site lattice grain boundary ratio and high (Σ9+Σ27) / Σ3 ratio are beneficial to improve the high temperature softening resistance of copper alloy and reduce the corrosion promoted by grain boundary and stress.

[0210] From the comparison of Example 7 and 9 with Example 2, and Example 8 and 10 with Example 3, it can be seen that the addition of trace Zr element on the basis of Sn, Ni and P composite addition can further improve the f1 value of the alloy, increase the Σ3, Σ9 and Σ27 heavy site lattice grain boundary ratio, further improve the tensile strength and burst pressure, and maintain a low yield strength ratio of about 0.22-0.29. The addition of trace Co element can generally reduce the decay rate of the welded pipe to within 6%. From the comparison of Example 10 and Example 8, it can be seen that further increasing the content of Zr and Co can further improve the pressure resistance, corrosion resistance and high temperature softening resistance of the alloy, and the burst pressure decay rate of the alloy is significantly reduced with the addition of Co and Zr elements.

[0211] Comparative Example 7 shows that when the content of Sn and Ni is appropriate, excessive addition of Zr and Co will reduce the elongation after fracture due to the introduction of hard and brittle second phase, increase the yield strength ratio, and at the same time, deteriorate the bending and flaring performance.

[0212] Comparing Example 11 with Example 7 shows that the addition of trace B element can effectively reduce the oxygen content of the alloy to below 15 ppm, and can greatly refine the size of the cast dendritic structure. Compared with Example 7, the improvement degree of the ant-termite corrosion resistance of Example 11 relative to TP2 alloy is increased from 18.7% to 23.5%.

[0213] Comparative Example 8 shows that the addition amount of Zr, Co and B elements cannot be too high, otherwise the hard and brittle inclusions formed by them will greatly increase the yield strength and yield strength ratio and reduce the ductility, thereby reducing the processing formability and seriously deteriorating the bending and flaring performance.

[0214] Examples 12-15 show that by comprehensively adjusting the contents of Sn, Ni, P, Zr, Co, B, and making the values of f1 and f2 both at a relatively optimal level, the comprehensive performance of the copper alloy pipe can be effectively improved by using the repeated recrystallization process. Compared with Comparative Example 1, the tensile strength of Example 12 is increased by about 27.6% (see Figure 4 ), and the copper alloy pipe has a yield ratio of not higher than 0.25 and excellent processing performance, the burst pressure is increased by more than 30%, but the burst pressure decay rate after pipe welding is less than 2%, the maximum corrosion depth of the single pipe under the same test conditions is less than 150 μm, and the maximum corrosion depth at the bent pipe is less than 160 μm. The XRD spectrum shows that reasonable control of the contents of Zr, Co and B can ensure the formation of a single α-phase solid solution of the copper alloy, and no hard and brittle second phase is precipitated (see Figure 2 ). The contents of Sn and Ni in Example 12 are basically the same as those in Example 2, but the contents of Zr, Co and B are significantly higher. The addition of Zr is beneficial to offset the hardening effect of Ni, Co and B elements, and makes the copper alloy have a high total amount of Σ3, Σ9 and Σ27, so that it maintains a low yield ratio of 0.25. Co is beneficial to improve the high-temperature softening resistance of the copper alloy. Due to the effect of Co, the burst pressure decay rate of Example 12 is only 1.8%. B mainly improves the ingot quality and reduces the oxygen content, so as to ensure the successful preparation of low-oxygen copper alloy material without casting defects by using the existing equipment.

[0215] Example 16 shows that the high-performance copper alloy pipe of the present application and the recrystallization process can be applied to the preparation of internal threaded pipes, and the performance indicators can achieve the expected effect.

[0216] Table 4 and Figure 3 show that the recrystallization cycle number of the repeated recrystallization process route has a significant effect on the proportion of Σ3, Σ9 and Σ27 heavy-site lattice grain boundaries. By analyzing the grain boundary distribution of the samples after 3 cycles of repeated recrystallization and 4 cycles of repeated recrystallization of Examples 5, 13 and 15, it can be seen that increasing the recrystallization cycle number can not only increase the proportion of Σ3 heavy-site lattice grain boundaries, but also significantly increase the proportions of Σ9, Σ27a and Σ27b heavy-site lattice grain boundaries, thereby increasing the (Σ9+Σ27) / Σ3 ratio and reducing the network connectivity of random high-angle grain boundaries. Obviously, if the cycle number is less than 3 recrystallization cycles, the comprehensive performance and cost balance brought by the repeated recrystallization process will be less than that of the single recrystallization process. Similarly, when the cycle number reaches 6 times, the proportion of low-Σ value heavy-site lattice grain boundaries tends to be saturated, and even if the recrystallization cycle is further increased, it is difficult to increase the total amount of Σ3, Σ9 and Σ27. Therefore, when the cycle number exceeds 6 times, the comprehensive performance and cost balance brought by the repeated recrystallization process will be less than that of the repeated recrystallization process with a cycle number between 3 and 6.

[0217] It should be finally pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the above embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0218] Table 1 Chemical composition of Examples 1-16

[0219]

[0220] Table 2 Chemical composition of Comparative Examples 1-8

[0221]

[0222]

[0223] Table 3 Low-Σ coincidence site lattice grain boundary proportion and average grain size of copper alloys of Examples and Comparative Examples

[0224]

[0225] Table 4 Subdivision table of low-Σ coincidence site lattice grain boundary proportion of copper alloys of Examples and Comparative Examples and effect of cycle number of repeated recrystallization process on coincidence site lattice grain boundary proportion

[0226]

[0227] Table 5 Mechanical properties, burst pressure and processing forming properties of copper alloys of Examples and Comparative Examples

[0228]

[0229]

[0230] Note: "O" represents qualified; "X" represents unqualified; "-" represents no data or test not failed for this item.

[0231] Table 6 Ant term tunnel corrosion resistance of copper alloys of Examples and Comparative Examples

[0232]

Claims

1. A high performance copper alloy tube characterized by, consisting of: 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, balance Cu and inevitable impurities; and f1=[Sn]+10[P], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.5%≤f1≤1.05%, 1 The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 mu m, and the average grain size including twin boundaries is 5-20 mu m; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥50%, and the ratio of the proportions of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥3.5%.

2. The high performance copper alloy tube of claim 1, wherein The tensile strength of the copper alloy pipe is ≥260 MPa, the yield strength ratio is 0.23-0.30, the burst pressure decay rate is ≤10%, after alternating cold and hot corrosion in a 0.4% concentration formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of a single pipe is ≤170 mu m, and the maximum corrosion depth at a bent pipe is ≤190 mu m.

3. A high performance copper alloy tube characterized by, consisting of: 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, balance Cu and inevitable impurities; and f1=[Sn]+10[P], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.5%≤f1≤1.05%, 1 The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 mu m, and the average grain size including twin boundaries is 5-20 mu m; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥68%, and the ratio of the proportions of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥10%.

4. The high performance copper alloy tube of claim 3, wherein The tensile strength of the copper alloy pipe is ≥285 MPa, the yield strength ratio is 0.21-0.28, the burst decay rate is ≤5%, after alternating cold and hot corrosion in a 0.4% concentration formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of a single pipe is ≤155 mu m, and the maximum corrosion depth at a bent pipe is ≤165 mu m.

5. A high performance copper alloy tube characterized by, consisting of, 0.05%≤Sn≤0.6%, 0.08%≤Ni<0.3%, 0.015%≤P≤0.045%, 0.001%≤Zr<0.03%, 0.001%≤Co<0.01%, 0≤B<0.01%, balance Cu and inevitable impurities; and f1=[Sn]+10[P]+10[Zr], f2=[Sn] / [Ni], f1 and f2 satisfy: 0.65%≤f1<1.15%, 1<f2≤5, wherein [Sn], [P], [Zr], [Ni] are mass percent of Sn, P, Zr, Ni respectively; The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 μm, and the average grain size including twin boundaries is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥60%, and the ratio of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥4.0%.

6. The high performance copper alloy tube of claim 5, wherein The tensile strength of the copper alloy pipe is ≥275 MPa, the yield strength ratio is 0.22-0.29, the burst attenuation rate is ≤6%, and after cold and hot alternating corrosion in a 0.4% concentration formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of a single pipe is ≤165 μm, and the maximum corrosion depth at a bent pipe is ≤180 μm.

7. The high-performance copper alloy tube according to claim 5 or 6, characterized in that, 0.001％≤B＜0.01％。 8. The high performance copper alloy tube of claim 7, wherein The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 μm, and the average grain size including twin boundaries is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥60%, and the ratio of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥4.0%.

9. A high performance copper alloy tube characterized by, The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 μm, and the average grain size including twin boundaries is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥60%, and the ratio of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥4.0%. The copper alloy pipe has a single face-centered cubic crystal structure alpha phase; the average grain size excluding twin boundaries is 10-25 μm, and the average grain size including twin boundaries is 5-20 μm; the total proportion of Σ3, Σ9 and Σ27 heavy site lattice grain boundaries in the copper alloy pipe is ≥60%, and the ratio of Σ9, Σ27 and Σ3 heavy site lattice grain boundaries satisfies: (Σ9+Σ27) / Σ3≥4.0%.

10. The high performance copper alloy tube of claim 9, wherein The tensile strength of the copper alloy pipe is ≥295 MPa, the yield strength ratio is 0.20-0.27, the burst attenuation rate is ≤2%, and after cold and hot alternating corrosion in a 0.4% concentration formic acid aqueous solution atmosphere for 21 days, the maximum corrosion depth of a single pipe is ≤150 μm, and the maximum corrosion depth at a bent pipe is ≤160 μm.

11. The high-performance copper alloy tube according to claim 9 or 10, characterized in that, 0.001％≤B＜0.01％。 12. The high performance copper alloy tube of claim 11, wherein, The maximum corrosion depth of the copper alloy pipe is less than or equal to 145 microns after alternating hot and cold corrosion in a 0.4% formic acid aqueous solution atmosphere for 21 days, and the maximum corrosion depth at a bent pipe is less than or equal to 155 microns.

13. The method of producing a high-performance copper alloy pipe according to any one of claims 1 to 12, characterized by, The method comprises the following steps: Batch smelting: smelting the raw materials according to the proportioning; Continuous casting: continuously casting the molten liquid into a blank; Rolling: rolling the blank to obtain a rolled pipe blank; Reducing: reducing the rolled pipe blank; Recrystallization treatment: obtaining a product with target performance by controlling the deformation amount and annealing parameters.

14. The method of producing a high-performance copper alloy pipe according to claim 13, characterized by, The recrystallization treatment is single recrystallization, the single recrystallization is "disk drawing→product annealing", the total deformation amount of the disk drawing is not less than 80%, the product annealing temperature is 500-750 DEG C, and the annealing time is 30-150 min.

15. The method of producing a high-performance copper alloy pipe according to claim 13, characterized by The recrystallization treatment is repeated recrystallization, the repeated recrystallization is a cycle of "disk drawing→annealing" after 1-3 passes of disk drawing, the total deformation amount of the 1-3 passes of disk drawing before the cycle is less than or equal to 72%; in the cycle of "disk drawing→annealing", the cycle number of "disk drawing→annealing" is 3-6 times, the disk drawing deformation amount in a single cycle is 25-35%, the annealing temperature is 500-600 DEG C, and the annealing time is 10-70 min.

Images