Copper alloy tube, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a copper alloy tube, and a preparation method therefor and the use thereof. The copper alloy tube comprises the following components in percentages by mass: 0.01%-0.80% of Sn, 0.005%-0.05% of P, 0.01%-0.10% of Zr, 0.001%-0.01% of B, 0.001%-0.01% of Mn, and the balance of Cu and inevitable impurities, wherein the copper alloy tube contains MnZr and BMn compound particles, the number of the MnZr compound particles on a cross section of the copper alloy tube is 0.005-0.15 / μm2, and the number of the BMn compound particles on the cross section is 0.005-0.2 / μm2. In the present invention, by adding Zr, B and Mn, controlling the content of Zr, B and Mn, the preparation process, etc., and regulating the numbers and uniformity of MnZr and MnB compounds, the tensile strength, ductility, corrosion resistance, and processing performance such as bending performance, flaring performance, welding performance and pressure resistance of the copper alloy tube are improved, and the prepared copper alloy tube fully meets the use requirements of heat transfer tubes for heat exchangers of air conditioners, connecting piping for indoor and outdoor units of air conditioners, etc.

Description

Copper alloy pipe and preparation method and application thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of copper alloy, and particularly relates to a copper alloy pipe and a preparation method and application thereof. BACKGROUND

[0002] With the development of new CO2 refrigerant for air conditioning, the copper alloy pipe for refrigeration and air conditioning, including the pipe for heat exchanger and the connecting pipe between indoor and outdoor, has higher requirements for the high-pressure resistance of the material. In order to meet this requirement, the scheme of replacing phosphorus deoxidized copper with Co-P or Sn-P copper alloy pipe with higher strength than phosphorus deoxidized copper has been proposed, which can fully meet the requirements of high strength and high-pressure resistance under the condition of thin wall of new CO2 refrigerant.

[0003] However, for the copper pipe for refrigeration and air conditioning, the traditional TP2 is prone to surface scratches and horn mouth deformation during connection, and the high-strength Co-P or Sn-P alloy pipe also has problems such as difficult bending, horn mouth cracking after pipe expansion, local softening after 800 DEG C brazing, and corrosion perforation in atmospheric environment, which may cause refrigerant leakage accident of the connected pipe. Therefore, even if the heat exchanger works well, the entire air conditioning system cannot work normally and effectively.

[0004] As a copper pipe for refrigeration and air conditioning, the characteristics of the pipe material itself and the processing characteristics directly affect the performance of the air conditioning system. Not only should the pipe material have good tensile strength, elongation, electrical conductivity, thermal conductivity and corrosion resistance, but also must have excellent bending, flaring, welding, pressure resistance and sealing properties and other processing and application characteristics.

[0005] Patent document CN101469961A discloses a heat exchanger copper alloy pipe with excellent breaking strength, which has a composition containing a specific amount of Sn and P, an average grain diameter of 30 μm or less, and a tensile strength of 250 MPa or more in the length direction of the pipe. The copper alloy pipe has a collective organization with an orientation distribution density of Goss orientation of 4% or less, so as to improve the breaking strength. The copper alloy pipe can be thin-walled even under high operating pressure of new refrigerants such as carbon dioxide and HFC fluorine freon, and has excellent breaking strength.

[0006] Patent document CN102051500A discloses a kind of copper alloy pipe for air conditioner and refrigeration, the copper alloy pipe contains Mn: 0.1~1.5wt%, P: 0.015~0.04wt%, mixed rare earth metal: 0.001~0.1wt%, the balance is Cu and inevitable impurities, and average grain size is 0.005~0.030mm.The current density of the copper alloy is more than 10% less than the current density of TP2 by corrosion electrochemical measurement.The copper alloy pipe can form a layer of dense structure, uniform thickness passivation film on the surface of copper alloy pipe in carboxylic acid or carboxylic acid atmosphere to hinder the diffusion of carboxylate in copper, and can meet the requirements of copper pipe for air conditioner and refrigeration.

[0007] Although the prior art has studied the copper alloy pipe for air conditioner, but the prior art usually only improves the performance of copper alloy pipe in one aspect, which leads to the comprehensive performance of copper alloy pipe cannot meet the processing application requirements of copper pipe for air conditioner, so that the copper alloy pipe is prone to cracking, poor thermal stability, easy corrosion and other problems during processing and use.Therefore, it is necessary to provide a copper alloy pipe and a preparation method thereof to improve the installation and use problems of copper pipe for refrigeration air conditioner. SUMMARY

[0008] The purpose of the present application is to provide a kind of copper alloy pipe and its preparation method and application.The copper alloy pipe of the present application has good tensile strength, elongation, electrical conductivity, thermal conductivity and corrosion resistance, and has excellent bending, flaring, welding and pressure resistance and other processing properties, and its preparation method is simple, which can be used for preparing heat conducting pipe of air conditioner heat exchanger, air conditioner indoor and outdoor machine connecting pipe and the like.

[0009] The first aspect of the present application provides a kind of copper alloy pipe, including the following mass percentage of components, Sn: 0.01~0.80%, P: 0.005~0.05%, Zr: 0.01~0.10%, B: 0.001~0.01%, Mn: 0.001~0.01%, the balance is Cu and inevitable impurities;The copper alloy pipe contains MnZr and BMn compound particles, the number of MnZr compound particles on the cross section of the copper alloy pipe is 0.005~0.15 / μm 2 , the number of BMn compound particles is 0.005~0.2 / μm 2 .

[0010] The present application adds Zr, B and Mn on the basis of Cu-Sn-P alloy composition, and controls the content and proportion, improves the strength, elongation, electrical conductivity, thermal conductivity and corrosion resistance of the copper alloy pipe by adjusting the number of MnZr and BMn compound in the alloy and the size and uniformity of the grain structure, and improves the bending, flaring, welding and pressure resistance and other processing properties.

[0011] The addition of Sn element can obviously improve the tensile strength and yield strength of the copper pipe, and inhibit the effect of grain coarsening. Sn, as a solute atom, has a size difference with the copper atoms in the matrix, and the strain field caused by the local crystal lattice distortion will change the interaction with dislocations, eventually increase the deformation resistance of the crystal, and produce the effect of solid solution strengthening. Meanwhile, it can improve the tensile strength and yield strength of the copper pipe, so as to meet the high pressure requirement under the condition of the same outer diameter and wall thickness of the copper pipe. In addition, the addition of Sn element has the effect of improving the heat resistance of the material, which is beneficial to the brazing process.

[0012] However, if the content of Sn is too high, it is not conducive to the electrical conductivity, thermal conductivity and elongation plasticity, and wrinkles or cracks are prone to occur in the bending part. When the content of Sn is less than 0.01%, the solid solution strengthening effect of Sn is not obvious, and the tensile strength and yield strength cannot be obviously improved. When the content of Sn is greater than 0.8%, the electrical conductivity, thermal conductivity and elongation plasticity are lost, which is not conducive to the refrigeration and processing of the copper pipe. In addition, too high content of Sn can cause segregation and obtain inhomogeneous as-cast structure, which leads to the obvious anisotropy of the mechanical properties of the copper pipe, and greatly reduces the uniformity of hardness and strength. Therefore, in the present application, the content of Sn is 0.01-0.80%.

[0013] P element can play the role of deoxidization and improving the fluidity of the melt, and at the same time, P can also improve the strength of the copper pipe, inhibit the grain growth, and improve the welding performance of the material. However, when the content of P increases, the grain boundary segregation is prone to occur, which seriously reduces the plasticity of the material and is not conducive to the pipe bending process of the copper pipe, and cracks are prone to occur. At the same time, the sensitivity of stress corrosion cracking will also be high.

[0014] When the content of P is less than 0.005%, the improvement effect of P on the copper pipe is not obvious. When the content of P is greater than 0.05%, the elongation plasticity is obviously lost. Therefore, in the present application, the content of P is controlled to be 0.005-0.05%.

[0015] The addition of Zr element can form a supersaturated solid solution in the copper matrix through solid solution treatment, and then the solid solution is decomposed into a dispersed distribution of precipitated phase during heat treatment, so as to improve the strength of the alloy. At the same time, the addition of Zr can greatly reduce the grain boundary energy, and produce solute drag and second phase pinning grain boundary, so as to improve the recrystallization temperature and heat resistance of the alloy, so that the alloy has high strength and high softening point. In addition, the solubility of Zr in Cu matrix is very low, and the low solubility of alloy element Zr has a very limited effect on the electrical conductivity and thermal conductivity of the alloy as a whole, which can ensure the good heat exchange effect of the alloy.

[0016] If the Zr content is less than 0.01%, the strength is not enough, and the effect of improving the recrystallization temperature is not obvious; if the Zr content is more than 0.1%, although the strength of the alloy is improved, the size of the precipitated phase increases and enrichment occurs, and the conductivity and plasticity decrease obviously. In order to obtain the best balance of strength, heat resistance, plasticity, conductivity and thermal conductivity, the content of Zr is controlled to be 0.01-0.10%.

[0017] B plays a role of deoxidization and grain refinement, and forms nanoscale boron metal compounds, which are fine and dispersedly distributed in the grain boundary, and strengthen the grain boundary, thereby inhibiting the alloy cracking caused by the penetration of oxygen from the surface of the alloy to the inside through the grain boundary, and promoting the formation of dynamic recrystallization, and improving the hardness and softening point of the alloy.

[0018] The addition of 0.001% or more of boron in the alloy can improve the strength, hardness, corrosion resistance and softening point of the alloy, and has little effect on the conductivity; but when the content of boron is more than 0.01%, the conductivity, thermal conductivity and plasticity of the alloy decrease. Therefore, the addition amount of B is controlled to be 0.001-0.01% in the present application.

[0019] Mn can be infinitely solid-solved in copper alloy, and plays a role of solid solution strengthening by being solid-solved in a large amount in the copper matrix. Mn element improves the strength and hardness of copper alloy, and the large amount of lattice distortion caused by solid solution also enhances the scattering effect of electrons, greatly reduces the conductivity and thermal conductivity of copper alloy, so the existing high-conductivity copper alloy often does not contain manganese element.

[0020] The content of Mn in the alloy of the present application is preferably 0.001-0.01%, if the content of Mn is less than 0.001%, the strengthening effect is not obvious, and the softening temperature cannot be improved, if the content of Mn is more than 0.01%, the MnZr and BMn intermetallic compounds exist in agglomeration, which affects the overall performance of the material, and has a great influence on the conductivity and thermal conductivity. Therefore, in the present application, the content of Mn is controlled to be 0.001-0.01%.

[0021] By adding an appropriate amount of Mn, the present application can make Mn and Zr, and Mn and B produce strong mutual interaction, produce high-melting-point MnZr and BMn hard intermetallic compound precipitates, which are uniformly distributed in the copper matrix, and play a role of dispersion strengthening, thereby ensuring the mechanical properties of the alloy. At the same time, because the softening point of the metal phase is >800℃, it can also improve the overall softening temperature of the alloy, improve the thermal stability of the alloy, and improve the local softening problem after brazing at 800℃.

[0022] However, if the MnZr and BMn intermetallic compound precipitated phase is unevenly distributed, it has a great influence on the alloy performance, is easy to cause cracking of the pipe during the later processing process such as pipe bending and pipe expansion, affects the normal use of the material, and also affects the electrical conductivity and thermal conductivity of the alloy, which is not conducive to the heat exchange efficiency of the pipe. Therefore, the uniform distribution of the MnZr and BMn intermetallic compound is of great significance to the improvement of the comprehensive performance of the material. The preparation method of the present application can realize the uniform dispersion of the MnZr and BMn intermetallic compound in the alloy by controlling the heat treatment and processing process.

[0023] Preferably, in the copper alloy pipe, the mass ratio of Zr to Mn satisfies: 0.1≤Mn / Zr≤1, and the mass ratio of B to Mn satisfies: 0.1≤Mn / B≤8.

[0024] The thermal stability of the alloy of the present application is greatly affected by the content of Zr, B and Mn. With the increase of the processing rate of the alloy, the dislocation density of the alloy gradually rises, and the stability at high temperature also deteriorates. In the case of dislocation density accumulation of the alloy, trace amounts of Zr and B are distributed on the grain boundary of the copper matrix, which can alleviate the excessive concentration of dislocation density of the matrix during the processing deformation, but excessive Zr and B are easy to segregate in the matrix.

[0025] A certain content of Mn can promote the formation of high-melting-point hard MnZr and BMn compounds, and avoid excessive Zr and B from gathering in the copper matrix in the form of single element; when Mn is excessive, the excessive solid solution of Mn will significantly reduce the electrical conductivity, thermal conductivity and processing performance of the alloy. Therefore, considering the thermal stability, electrical conductivity, thermal conductivity and processing performance of the alloy, the mass ratio of Zr, B and Mn is controlled to be 0.1≤Mn / Zr≤1 and 0.1≤Mn / B≤8.

[0026] By adding appropriate amounts of Zr, B and Mn, the present application utilizes the interaction of Zr, B and Mn in the high-temperature metal melt to form uniformly distributed MnZr and BMn compounds. The MnZr and BMn compounds have very high hardness, and the processing hardening of the Sn solid solution and the copper matrix and the dispersion strengthening effect of the hard MnZr and BMn compounds are superimposed, further improving the comprehensive mechanical properties of the alloy. On the other hand, since the B-Mn compound is a high-melting-point compound with a melting point exceeding 1800℃, the uniform distribution in the alloy matrix can effectively improve the thermal stability of the alloy.

[0027] Preferably, the average grain size of the copper alloy pipe is 15μm or less, and the standard deviation of the average grain size is 1.5μm or less.

[0028] To ensure the bending, expanding, flaring and other processing performance of the copper alloy pipe, the copper alloy structure grain is required to be refined and the deviation of each grain diameter is required to be inhibited. In the bending, expanding, flaring and other processing process, not only the average grain diameter has great influence on the bending processability, but also the deviation of the grain diameter has great influence on the bending processability. The fine and uniform structure grain can better cooperate with deformation and reduce stress concentration. Meanwhile, the more the grain boundaries, the better the corrosion resistance of the copper alloy. To obtain the copper alloy with high strength and excellent processability, the coarse grains in the copper alloy structure are reduced and each grain diameter is as fine as possible. Therefore, in the present application, the average grain diameter of the copper alloy pipe structure is controlled to be less than 15 μm, and the standard deviation of the average grain diameter is controlled to be less than 1.5 μm.

[0029] When the average grain diameter is more than 15 μm and the standard deviation of the average grain diameter is more than 1.5 μm, the coarse grains in the copper alloy structure increase, the deviation of each grain diameter becomes large, the bending, expanding, flaring and other processing performance deteriorate, and processing cracking is prone to occur, and serious accidents such as refrigerant leakage occur. More preferably, in the present application, the average grain diameter of the copper alloy pipe structure is less than 10 μm, and the standard deviation of the average grain diameter is less than 0.9 μm.

[0030] Preferably, the copper alloy pipe further comprises Fe and Si, and the total mass percentage content of the Fe and Si is less than 0.0030%.

[0031] One of the common corrosion failures of the copper alloy pipe in the atmospheric environment is intergranular corrosion. The grain boundary is the misfit area between the metal grains and is also a high-energy area with strong chemical activity, so in most cases the grain boundary corrodes faster than the grain itself. The phase formed by Fe and Si is prone to occur on the grain boundary, which is the key element to cause intergranular corrosion. Therefore, the content of Si and Fe is required to be less than 0.0030% in the present application, which reduces the probability of occurrence of intergranular corrosion. More preferably, the content of Si and Fe is less than 0.0015%.

[0032] As preferred, the copper alloy pipe of the present application further comprises X with a mass percentage content of 0.001-0.01%, and X is selected from at least one of Mg, Al, Cr, Ni or RE (rare earth element). Preferably, the RE includes La, Ce and Y.

[0033] The X element can play a certain degree of strengthening effect. In the melting and casting process, the X element can play a role of deoxidizer or as a nucleation center to improve the nucleation rate of the alloy, so as to achieve the purpose of purifying the melt and refining the grains. The reduction of the oxygen content of the alloy melt will reduce the tendency of the occurrence of oxidized inclusions; the small-grained ingot provides a good initial condition for the processing of the pipe product, which helps to improve the mechanical properties and processing properties of the pipe of the present application. When the content of the optional element X is less than 0.001%, the effect of purifying the melt and refining the grains is not obvious; when the content of the optional element X is higher than 0.01%, the excessive X element will have a greater negative impact on the electrical conductivity and thermal conductivity of the alloy, therefore, the content of the X element is controlled to be 0.001-0.01% in the present application.

[0034] As preferred, the tensile strength of the copper alloy pipe of the present application in the longitudinal direction is ≥250MPa, and the tensile strength in the circumferential direction is ≥235MPa.

[0035] The rupture problem of the copper pipe during the operation of the refrigerant is caused by the cracking at a certain point, and the root cause is that the pressure acting on the copper pipe in the circumferential direction is greater than that in the longitudinal direction under the operating pressure condition of the refrigerant, thereby causing the cracking. Therefore, to improve the pressure resistance of the copper pipe, the key is to improve the strength of the copper pipe in the circumferential direction and inhibit the occurrence of the cracking of the heat conduction pipe. When the tensile strength of the copper pipe in the circumferential direction is ≥235MPa, the copper pipe can withstand the simulation test of water pressure of 13MPa, which meets the operating pressure condition of the refrigerant, and the deformation resistance of the pipe is moderate, which is more suitable for bending installation; when the tensile strength of the copper pipe in the circumferential direction is <235MPa, there is a risk of pipe pressure rupture. Therefore, the tensile strength of the copper pipe in the circumferential direction of the present application is ≥235MPa.

[0036] As preferred, the yield strength YS of the copper alloy pipe of the present application in the circumferential direction is ≥ 200MPa. LD The ratio of the yield strength YS in the circumferential direction to the yield strength YS in the longitudinal direction is ≥0.95. TD LD TD

[0037] The deformation of the bending and expanding of the copper pipe directly depends on the anisotropy control of the copper alloy pipe, and the coordinated deformation in different directions is crucial for the bending and expanding processing. For example, the conventional tensile work hardening will inevitably greatly improve the strength of the copper pipe in a single longitudinal direction, which is not conducive to the bending and expanding processing of the copper pipe and is prone to cracking. Therefore, the smaller the anisotropy of the copper alloy pipe, the more conducive to the bending and expanding processing effect of the copper pipe.

[0038] ​​​The anisotropy of the copper alloy pipe in the present application mainly lies in the difference between the yield strength in the circumferential direction of the copper pipe and the yield strength in the longitudinal direction of the copper pipe. Under the condition of constant tensile strength, the increase of the yield strength in the circumferential direction of the copper pipe can enhance the burst pressure resistance of the pipe, and the increase of the yield strength in the longitudinal direction of the copper pipe can enhance the bending and expanding processing performance of the pipe, so that the pipe is not prone to crack when bent or flared. Therefore, the present application requires that the yield strength YS LD in the circumferential direction of the copper alloy pipe is greater than the yield strength YS TD in the longitudinal direction, i.e. YS LD / YS TD ≥ 0.95, which is beneficial to ensure higher bending and flaring processing performance. When YS LD / YS TD < 0.95, the yield strength in the longitudinal direction increases significantly under the condition of the increase of the yield strength of the copper alloy pipe, and the elongation decreases, which is not conducive to the bending and expanding processing of the pipe, and is prone to orange peel or crack.

[0039] Preferably, the average grain diameter of the copper alloy pipe in the present application is 15 μm or less, and the burst pressure resistance is 30 MPa or more.

[0040] Preferably, the average grain diameter of the copper alloy pipe in the present application is 20 μm or less after heating at 800 ℃ for 15 s, and the burst pressure resistance is 30 MPa or more.

[0041] Preferably, the average grain diameter of the copper alloy pipe in the present application is 25 μm or less after heating at 1000 ℃ for 15 s, and the burst pressure resistance is 29 MPa or more.

[0042] Preferably, the average grain diameter of the copper alloy pipe in the present application is 30 μm or less after heating at 1065 ℃ for 15 s, and the burst pressure resistance is 28 MPa or more.

[0043] The second aspect of the present application provides a preparation method of the copper alloy pipe, which comprises the following steps: melting, casting, homogenization annealing, extrusion, rolling, primary stretching, primary annealing, secondary stretching and secondary annealing.

[0044] The primary annealing temperature is 650-900 ℃, the annealing time is 0.1-2 h, and the cooling speed after the primary annealing is greater than 30 ℃ / s.

[0045] The elongation coefficient of the secondary stretching is 0.8-1.5.

[0046] The primary annealing aims to solid solution treatment of the pipe material after rolling and primary stretching cold working, which plays an important role in dispersion of Sn, Zr and Mn, and the dispersion of Sn, Zr and Mn can effectively control the grain size of the matrix. More importantly, the solid solution temperature can effectively control the subsequent precipitation and uniform distribution of MnZr and BMn compounds, and avoid the agglomeration of the compounds in the matrix. When the annealing temperature is higher than 900℃ and the time is more than 2h, the pipe material is prone to overheating, which leads to serious oxidation or melting of the grain boundary, and the subsequent processing has the risk of intergranular cracking; when the annealing temperature is lower than 650℃ and the time is less than 0.1h, the solid solution effect is poor, and it is difficult to achieve the subsequent precipitation and uniform distribution of MnZr and BMn compounds, which is not conducive to the comprehensive performance of the pipe material such as strength, pressure resistance and thermal stability. Therefore, in the present application, the primary annealing temperature is 650-900℃, and the annealing time is 0.1-2h.

[0047] The cooling speed in the solid solution treatment is very important, which directly affects the solid solution effect. When the rapid cooling speed is less than 30℃ / s, the solute atoms may precipitate on the surface of the copper matrix, which is not conducive to the aging strengthening effect in the subsequent process, and it is difficult to obtain a proper amount of MnZr and BMn compounds, which is not conducive to the improvement of the mechanical properties and thermal stability of the pipe material. Therefore, in the present application, the rapid cooling speed after the completion of the primary annealing heating is greater than 30℃ / s.

[0048] The purpose of the secondary stretching is to obtain the required outer diameter and wall thickness, and to determine the mother tube organization and performance of the pipe material, so the secondary stretching process is very important. In order to ensure the uniform deformation and uniform organization breakage of the mother tube, the extension coefficient of the secondary stretching process in the present application is controlled in the range of 0.8-1.5. When the extension coefficient of the secondary stretching process is less than 0.8, the recrystallized organization obtained by the primary annealing leads to insufficient organization breakage due to the too small extension coefficient, and it is difficult to obtain sufficient processing fiber organization, thereby affecting the good yield strength and pressure resistance performance of the final pipe material; when the extension coefficient of the secondary stretching process is greater than 1.5, the recrystallized organization obtained by the primary annealing has the problem of uneven organization due to the large deformation, which is not conducive to the thermal stability of the pipe material in bending, flaring and brazing processing. Therefore, in the present application, the extension coefficient of the secondary stretching is 0.8-1.5.

[0049] As a preferred embodiment, the secondary stretching passes are 5-8 passes, the extension coefficient of the first two passes is 1.2-1.5, and the extension coefficient of the last three passes is 0.8-1.3.

[0050] The pass design and the extension coefficient size of the secondary stretching process directly affect the texture formation of the "soft orientation" and "hard orientation" components of the pipe material, thereby affecting the hardness, strength and thermal stability of the pipe material. When the stretching pass is less than 5 passes, the large processing rate stretching of a single pass is determined in the case of less pass, at this time, the effect of strong stretching not only affects the pipe tolerance after disc drawing, but also increases the copper texture and Y orientation texture area ratio of hard orientation components, a large amount of dislocation pile-up and strain accumulation directly affect the grain size deviation and high-temperature thermal deformation performance of the final pipe material; when the stretching pass is more than 8 passes, the disc drawing processing efficiency is low, and the surface damage point is increased, which is not conducive to the bending and flaring performance of the pipe.

[0051] In the application, in order to obtain the copper alloy pipe with processing application performance, under the premise of ensuring the multi-pass stretching process, the extension coefficient of the first two passes is 1.2-1.5, and the extension coefficient of the last three passes is 0.8-1.3. In the extension process design process of more than 5 passes, the first two passes are called the pre-stretching stage, at this time, it is necessary to ensure that the grains are broken to the maximum extent and a large amount of deformation texture is formed to provide a suitable hard orientation component texture basis for subsequent annealing. When the extension coefficient of the first two passes in the pre-stretching stage is less than 1.2, the processing stress is small, the dislocation density generated is not enough, which not only cannot fully break the size angle grain boundary in the recrystallized structure, but also is not conducive to the formation of deformation texture, affecting the bending and flaring processing effect of the pipe material; when the extension coefficient of the first two passes in the pre-stretching stage is greater than 1.5, the stretching processing cannot guarantee the surface quality of the pipe material, and serious pipe breakage occurs. With the increase of the stretching processing pass, a large amount of recrystallized structure of the pipe material is converted into processing fiber structure, and a large amount of recrystallized texture is converted into deformation texture, at this time, the plasticity gradually decreases.

[0052] The extension coefficient design of the last three passes of stretching not only controls the stable surface quality of the disc-drawn pipe material, but also ensures that the copper texture, Gauss texture and Y orientation texture with a suitable area ratio distribution are obtained. When the extension coefficient of the last three passes of disc drawing is greater than 1.3, the Gauss texture with a certain area ratio cannot be guaranteed, the coordination deformation effect of the soft orientation component texture is reduced, and the size of the copper pipe high-temperature brazing structure is affected; when the extension coefficient of the last three passes of disc drawing is less than 0.8, the deformation texture with sufficient area ratio cannot be formed in the whole disc drawing process, which is insufficient to support the texture conversion required in the annealing process, and the thermal stability of the final pipe material is affected.

[0053] Preferably, the secondary annealing temperature is 400-650℃, and the annealing time is 0.5-8h.

[0054] The secondary annealing can obtain uniform and fine structure, so that the MnZr and BMn compounds are uniformly distributed, and meanwhile the pipe performance can be adjusted to be soft (O state). When the annealing temperature is higher than 650 DEG C and the time is more than 8h, the pipe structure is coarse and non-uniform, it is difficult to obtain ideal structure average grain diameter and structure average grain diameter deviation, meanwhile, the MnZr and BMn compounds are easy to appear agglomeration, which is not conducive to the pipe performance such as flaring, bending and the like; when the annealing temperature is lower than 400 DEG C and the time is less than 0.5h, the pipe residual processing structure is difficult to obtain proper amount of MnZr and BMn compounds, which is not conducive to the heat stability of pipe brazing processing. Therefore, the secondary annealing temperature in the application is controlled in 400-650 DEG C, and the annealing time is controlled in 0.5-8h.

[0055] The third aspect of the application provides the application of the copper alloy pipe in preparing the heat conducting pipe of air conditioner heat exchanger, air conditioner indoor and outdoor connecting pipe, indoor pipe or pipe assembly. The copper alloy pipe of the application has good tensile strength, elongation and corrosion resistance, and has excellent bending, flaring, welding and pressure resistance and other processing properties, and is particularly suitable for preparing the indoor and outdoor connecting pipe of air conditioner.

[0056] Compared with the prior art, the application has at least the following beneficial effects:

[0057] (1) The application adds Zr, B and Mn on the basis of Cu-Sn-P alloy composition, controls the content and proportion, adjusts the amount of MnZr and BMn compounds, the size and uniformity of the structure grain, improves the tensile strength, elongation, electrical conductivity, thermal conductivity and corrosion resistance of the copper alloy pipe, and improves the bending, flaring, welding and pressure resistance and other processing properties.

[0058] (2) The application adjusts the size of the structure average grain diameter of the copper alloy pipe, and strictly controls the standard deviation of the structure average grain diameter to be less than 1.5um, further improves the bending, flaring, welding and pressure resistance and other processing properties of the copper alloy pipe, and reduces the risk of cracking in the processing process.

[0059] (3) In the preparation process of the copper alloy pipe, the tensile and annealing processes are improved, the dispersion of Sn, Zr and Mn is realized, the size of the matrix grain, the subsequent precipitation and uniform distribution of MnZr and BMn compounds are effectively controlled, and the strength, pressure resistance and thermal stability of the material and its processing properties are improved.

[0060] (4) The longitudinal tensile strength of the copper alloy pipe of the application is greater than or equal to 250MPa, the circumferential tensile strength is greater than or equal to 235MPa, the circumferential yield strength YS LD The ratio of the longitudinal yield strength YS TD The ratio of the longitudinal yield strength YSLD / YS TD ≥0.95;in 800 ℃ condition, after heating for 15 s, the average grain diameter of the tissue is below 20 μm, the breaking pressure is above 30 MPa; in 1000 ℃ condition, after heating for 15 s, the average grain diameter of the tissue is below 25 μm, the breaking pressure is above 29 MPa; in 1065 ℃ condition, after heating for 15 s, the average grain diameter of the tissue is below 30 μm, the breaking pressure is above 28 MPa, and the alloy has excellent corrosion resistance, electrical conductivity and thermal conductivity, etc., fully meeting the application requirements of the heat conducting pipe of the air conditioner heat exchanger, the connecting pipe of the air conditioner indoor and outdoor units, etc., and is convenient to install and use. DETAILED DESCRIPTION

[0061] The application will be further described in detail below in combination with examples.

[0062] The specific components of the alloys of the examples and the comparative examples of the application are shown in Table 1.

[0063] The preparation process is: batching → smelting → casting → homogenization annealing → extrusion → rolling → primary stretching → primary annealing → secondary stretching → secondary annealing → cleaning. The specific preparation method is:

[0064] 1) Batching: the components in Table 1 are used for batching, electrolytic pure copper plate, pure Sn and phosphor copper CuP14 are used, and other elements are added in the form of intermediate alloy;

[0065] 2) Smelting: the smelting temperature is 1150-1200 ℃, and the charcoal covering thickness is 180-220 mm;

[0066] 3) Semi-continuous casting: the casting temperature is 1150-1180 ℃, the casting speed is 80-120 mm / min, and the specification

[0067] 4) Homogenization annealing: the annealing temperature is 650-900 ℃, and the annealing time is 0.5-2 h;

[0068] 5) Extrusion: the extrusion temperature is 750-950 ℃, the speed is 1-10 m / min, and the extrusion specification

[0069] 6) Rolling: the total processing rate is not more than 70%, the single pass processing rate is not more than 30%, and the specification

[0070] 7) Primary stretching: the single pass elongation coefficient is 1.2-1.6, and the specification

[0071] 8) Primary annealing: the annealing temperature is 650-900 ℃, the annealing time is 0.1-2 h, and the speed of rapid cooling is greater than 30 ℃ / s;

[0072] 9) Secondary stretching: single pass elongation coefficient is 0.8-1.5, specification

[0073] 10) Secondary annealing: annealing temperature is 400-650℃, annealing time is 0.5-8h;

[0074] 11) Cleaning: cleaning is performed by ultrasonic wave.

[0075] The key process parameter control of the embodiment and the comparative example of the application is shown in Table 2.

[0076] The comparative example 1 is C12200.

[0077] The comparative example 2 and the embodiment 1 are different in that the copper alloy pipe is prepared by a conventional method on the market. Specifically, compared with the embodiment 1, only one stretching and one annealing are used in the preparation process of the comparative example, and the condition of the one annealing is annealing at 460℃ for 4h.

[0078] The prepared embodiment and comparative example alloy are tested for microstructure grain size, compound particle number, tensile mechanical property, pressure resistance, flaring and salt spray corrosion at room temperature, and the microstructure grain size, tensile mechanical property and pressure resistance are tested after heating at a high temperature condition, such as 850℃, 1000℃ and 1065℃ for 15s in a simulated brazing processing environment, and the specific data is shown in Table 3.

[0079] The average grain size of the metallographic structure is tested according to the GB / T 6394-2017 Metal Grain Size Determination Method.

[0080] The room temperature tensile test is tested on an electronic universal mechanical property testing machine according to the GB / T 228.1-2010 Metal Material Tensile Test Part 1: Room Temperature Test Method, and the tensile speed is 5mm / min.

[0081] The pressure resistance test is tested according to the GB / T 241-2007 Metal Pipe Liquid Pressure Test Method.

[0082] The bending test is tested according to the 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.

[0083] The salt spray corrosion test is tested according to GB / T 10125-1997 "Artificial Atmosphere Corrosion Test-Salt Spray Test". The test pipe with a length of 50 mm is cut from the pipe, degreased and dried, and then placed in a salt spray test box with 5% NaCl+1% CH3COOH. Each different sample pipe is taken out every three days for observation and detection, and the longest time is 42 days. After sampling, the corrosion depth and perforation of the sample pipe section are observed, if the maximum corrosion depth of the sample is greater than the wall thickness of the sample pipe, it is determined that the sample pipe is perforated; if the maximum corrosion depth of the sample is less than the wall thickness of the sample pipe, the maximum corrosion depth in the section is recorded. The results are as follows: the average maximum corrosion depth of the sample pipe is the sum of the maximum corrosion depths of all test sample pipes divided by the number of all test sample pipes, and the perforation rate is the number of perforated sample pipes divided by the number of all test sample pipes.

[0084] The flaring test is tested according to GB / T 17791-1999 "Seamless Copper Tube for Air Conditioner and Refrigeration". When the flaring rate (punch 60°) of the copper alloy pipe is 40% or the distance between the two walls after flattening is equal to the wall thickness, the copper alloy pipe sample does not produce visible cracks and cracks, indicating that the copper alloy pipe has excellent process performance.

[0085] The horn mouth sealing test uses a helium detector to verify the leakage of the copper pipe horn mouth and the pipe joint after tightening (equipped with a stop valve and a copper nut). After tightening torque (24-28N), the electronic leak detector is used for detection, and no leakage represents good sealing. The number of test sample pipes is 10, and the leakage ratio is calculated. Evaluation method: 1. Test the leakage ratio under the conditions of normal 24N sealing torque and maximum 28N sealing torque; 2. After tightening according to the maximum sealing torque, disassemble, and test the leakage ratio after 3 rounds.

[0086] The microstructure and properties of the alloy of the inventive examples and comparative examples are shown in Table 3. The mechanical properties and processing application properties of the alloy of the inventive examples and comparative examples are shown in Tables 4 and 5, respectively.

[0087] Table 1 Alloy composition of the inventive examples and comparative examples

[0088] Table 2 Control of key process parameters of the inventive examples and comparative examples

[0089] Table 3 Microstructure and properties of the copper alloy pipe of the inventive examples and comparative examples

[0090] Table 4 Mechanical properties of the copper alloy pipe of the inventive examples and comparative examples

[0091] Table 5 Processing application properties of the copper alloy pipe of the inventive examples and comparative examples

Claims

1. A copper alloy pipe characterized by, A copper alloy pipe comprising, in mass percent, Sn: 0.01 to 0.80%, P: 0.005 to 0.05%, Zr: 0.01 to 0.10%, B: 0.001 to 0.01%, Mn: 0.001 to 0.01%, and the balance of Cu and unavoidable impurities, wherein the copper alloy pipe contains MnZr and BMn compound particles, and the number of MnZr compound particles on a cross section of the copper alloy pipe is 0.005 to 0.15 / μm 2 , and the number of BMn compound particles is 0.005 to 0.2 / μm 2 .

2. The copper alloy tube according to claim 1, characterized by The mass ratio of Zr to Mn satisfies 0.1≤Mn / Zr≤1, and the mass ratio of B to Mn satisfies 0.1≤Mn / B≤8.

3. The copper alloy tube according to claim 1, characterized by The copper alloy pipe has an average grain size of 15 μm or less, and a standard deviation of 1.5 μm or less.

4. The copper alloy tube according to any one of claims 1 to 3, characterized by, The copper alloy pipe contains Fe and Si, and the total mass percentage of Fe and Si is less than 0.0030%. The copper alloy pipe contains X in a mass percentage of 0.001-0.01%, and X is at least one of Mg, Al, Cr, Ni, and rare earth elements.

5. The copper alloy tube of claim 1, wherein The yield strength YS in the circumferential direction of the copper alloy pipe LD The ratio of the yield strength YS in the longitudinal direction TD to the yield strength YS in the circumferential direction satisfies: YS LD / YS TD ≥ 0.

95.

6. The copper alloy tube of claim 1, wherein The copper alloy pipe has an average grain size of 20 μm or less after being heated at 800℃ for 15 s, and a burst pressure of 30 MPa or more. The copper alloy pipe has an average grain size of 25 μm or less after being heated at 1000℃ for 15 s, and a burst pressure of 29 MPa or more. The copper alloy pipe has an average grain size of 30 μm or less after being heated at 1065℃ for 15 s, and a burst pressure of 28 MPa or more.

7. The method of producing a copper alloy pipe according to any one of claims 1 to 6, characterized by, The method comprises the following steps: melting, casting, homogenization annealing, extrusion, rolling, primary stretching, primary annealing, secondary stretching, and secondary annealing; the primary annealing temperature is 650-900℃, the annealing time is 0.1-2 h, and the cooling rate after primary annealing is greater than 30℃ / s; the elongation coefficient of the secondary stretching is 0.8-1.

5.

8. The preparation method according to claim 7, characterized in that, The secondary stretching is performed for 5-8 passes, the elongation coefficient of the first two passes is 1.2-1.5, and the elongation coefficient of the last three passes is 0.8-1.

3.

9. The production method according to claim 7 or 8, characterized by, The secondary annealing temperature is 400-650℃, and the annealing time is 0.5-8 h.

10. Application of the copper alloy pipe according to any one of claims 1-6 to the preparation of a heat conducting pipe of an air conditioner heat exchanger, an air conditioner indoor and outdoor machine connecting pipe, an indoor pipe, or a pipe assembly.

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