Microalloyed copper tube and method for its production and use

Abstract

This invention relates to the field of copper alloy tube manufacturing technology, providing a micro-alloyed copper tube, its manufacturing method, and its application. The micro-alloyed copper tube, by mass percentage, comprises the following components: P 0.015~0.025%, Sn 0.20~0.35%, Ni 0.05~0.10%, with the balance being Cu and unavoidable impurities. By introducing Sn and Ni elements and optimizing the content and proportion of each element in the micro-alloyed copper tube, this invention not only improves the tensile strength and compressive strength of the micro-alloyed copper tube but also maintains good ductility, combining high compressive strength with excellent processing performance. This solves the problem of synergistically improving the strength and processing plasticity of micro-alloyed copper tubes, meeting the mass application requirements of micro-alloyed copper tubes in air conditioning pipe assemblies.

Description

Technical Field

[0001] This invention relates to the field of copper alloy tube manufacturing technology, and particularly to micro-alloyed copper tubes, their manufacturing methods, and applications. Background Technology

[0002] Copper alloys are widely used in power, electronics, and air conditioning industries due to their excellent electrical and thermal conductivity and good processing performance. However, high copper prices have led to increasingly lower profit margins in the air conditioning industry. To reduce material costs, the wall thickness of copper tubing in air conditioning systems is commonly reduced. However, reducing the wall thickness leads to a decrease in the tensile strength of the copper tubing, resulting in a decrease in its pressure resistance and making it impossible to meet the requirements for high strength and high pressure resistance under thin-walled conditions.

[0003] Currently, the tensile strength of copper tubes is often enhanced by adding trace elements. For example, patent application number CN200910135785.2 discloses a copper alloy and a method for preparing the copper alloy. The copper alloy contains an α solid solution formed by trace elements and phosphorus-deoxidized copper. The trace elements include at least tin. The percentage of tin in the total weight of the copper alloy is 0.1% to 2.0%.

[0004] The aforementioned patents enhance the tensile strength of copper alloys and improve the pressure resistance of copper tubes by adding trace elements such as tin and zinc during the preparation of copper alloys. However, the increase in tensile strength leads to an increase in hardness and yield strength, and a decrease in elongation after fracture, which increases the processing difficulty of copper tubes and makes it difficult to achieve a comprehensive performance improvement, thus preventing the mass application of copper tubes in air conditioning pipe assemblies.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] This invention provides a microalloyed copper tube, its preparation method, and its application, in order to solve the defects of existing microalloyed copper tubes in that they are difficult to combine high pressure resistance and excellent processing performance, and to realize the mass application of microalloyed copper tubes in air conditioning pipe assemblies.

[0007] The present invention provides a microalloyed copper tube, which comprises the following components by mass percentage: P 0.015~0.025%, Sn 0.20~0.35%, Ni 0.05~0.1%, other elements ≤0.02%, and the balance being Cu and unavoidable impurities.

[0008] According to the microalloyed copper tube provided by the present invention, the mass ratio of Sn to Ni in the microalloyed copper tube is (2~7):1.

[0009] Preferably, the mass ratio of Sn to Ni in the microalloyed copper tube is (3~7):1. According to the microalloyed copper tube provided by the present invention, the unavoidable impurities include O (oxygen), and the mass percentage of O in the microalloyed copper tube is less than 0.003%.

[0010] According to the microalloyed copper tube provided by the present invention, the unavoidable impurities in the microalloyed copper tube have a mass percentage of ≤0.038%.

[0011] In some optional embodiments of the present invention, the unavoidable impurities account for less than 0.018% of the mass percentage in the microalloyed copper tube.

[0012] According to the microalloyed copper tube provided by the present invention, the mass percentage of Cu in the microalloyed copper tube is 99.5% or more.

[0013] According to the microalloyed copper tube provided by the present invention, the microalloyed copper tube satisfies one or more of the following characteristics: a. Tensile strength is 245~275 Newtons / mm²; b. Yield strength is 50~100 Newtons / mm²; c. Elongation after fracture ≥40%; d. Hardness ≤ 72HV.

[0014] The tensile strength, yield strength, and elongation after fracture were determined in accordance with the standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test method at room temperature".

[0015] The hardness was determined according to the standard JIS Z 2244 "Vickers Hardness Test - Part 1: Test Method".

[0016] Preferably, in feature a, the tensile strength is 245~268 Newtons per square millimeter; And / or, in feature b, the yield strength is 50~80 Newtons / mm²; And / or, in the feature d, the hardness is ≤60HV.

[0017] Preferably, the microalloyed copper tube further includes feature e, wherein the grain size of feature e is 0.010~0.035 mm.

[0018] The present invention also provides a method for preparing the microalloyed copper tube as described above, comprising the following steps: preparing materials according to the raw material composition of the microalloyed copper tube, and then sequentially performing smelting, continuous casting, rolling, diameter reduction and annealing treatment.

[0019] Preferably, the melting temperature is 1150~1200 degrees Celsius.

[0020] Preferably, the melting time is 60 to 90 minutes.

[0021] Preferably, the annealing temperature is 400-600 degrees Celsius and the annealing time is 50-120 minutes.

[0022] More preferably, the annealing step includes: first holding at 400±10 degrees Celsius for 25 to 35 minutes, then holding at 520±10 degrees Celsius for 30 to 40 minutes, and then holding at 580±10 degrees Celsius for 15 to 25 minutes.

[0023] The present invention also provides the application of the microalloyed copper tube as described above or the microalloyed copper tube prepared by the preparation method as described above in the preparation of air conditioning pipe assemblies.

[0024] Preferably, the air conditioning pipe assembly includes at least one of the following: heat-conducting pipe of an air conditioning heat exchanger, connecting pipe between the indoor and outdoor units of the air conditioner, and internal pipe.

[0025] This invention provides a microalloyed copper tube and its preparation method. By introducing Sn and Ni elements and optimizing the content and ratio of each element in the microalloyed copper tube, the tensile strength and pressure resistance of the microalloyed copper tube are not only improved, but also its good ductility is maintained at the same time. It has both high pressure resistance and excellent processing performance, which solves the problem of the difficulty in synergistically improving the strength and processing plasticity of microalloyed copper tubes, and meets the mass application requirements of microalloyed copper tubes in air conditioning pipe assemblies. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Unless otherwise stated, the term "multiple" means two or more. The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0029] When microalloyed copper tubes are applied to air conditioning pipe assemblies, there is a problem of incompatibility between their pressure resistance and processing performance. These problems seriously restrict the mass application of microalloyed copper tubes in air conditioning pipe assemblies. Furthermore, research shows that when the tensile strength of copper alloys is increased, it often leads to a significant increase in their yield strength and hardness, a decrease in elongation after fracture, and a decrease in weldability, making it impossible to meet production and usage requirements.

[0030] On one hand, embodiments of the present invention provide a microalloyed copper tube, which, by mass percentage, comprises the following components: P 0.015~0.025%, Sn 0.20~0.35%, Ni 0.05~0.1%, with the balance being Cu and unavoidable impurities.

[0031] This invention modifies the performance of microalloyed copper tubes by adding trace elements to copper. Tin (Sn) acts as the dominant element, providing solid solution strengthening, while nickel (Ni) acts as an auxiliary element, providing slight solid solution strengthening. The synergistic effect of the two not only improves the tensile strength and pressure resistance of the microalloyed copper tube but also maintains good corrosion resistance. After the addition of nickel, it functions as a dopant in the surface film of CuO2. CuO2 is a highly defective A-type semiconductor structure, and the cation holes are effectively occupied by Ni or doped into the defective CuO2 lattice, thereby improving the integrity of the copper alloy film. This ensures high pressure resistance, excellent processing performance, and good corrosion resistance.

[0032] Meanwhile, controlling the Sn content in the microalloyed copper tube to be within the range of 0.20~0.35% and the Ni content to be within the range of 0.05~0.10% can effectively improve tensile strength and maintain good corrosion resistance.

[0033] Adding phosphorus (P) to maintain a low oxygen content, controlling the P content between 0.015% and 0.025%, can significantly improve the weldability of microalloyed copper tubes, reduce potential cracks and bubbles during welding, and improve the strength and sealing of welded joints. However, when the phosphorus content exceeds 0.025%, coarse grains will form, reducing tensile strength and elongation after fracture, increasing processing difficulty, and raising the risk of processing defects.

[0034] To further improve the tensile strength of microalloyed copper tubes and maintain good corrosion resistance, the mass ratio of Sn to Ni is controlled at (2~7):1. When the mass ratio of Sn to Ni in the microalloyed copper tube is controlled within the above range, it can exert a better synergistic effect, which not only meets the requirements of strong corrosion resistance, but also effectively inhibits the significant decrease in elongation after fracture and the significant increase in yield strength and hardness while improving tensile strength. This also effectively improves its processing performance and meets the requirements of copper tube bending process.

[0035] The unavoidable impurities in the microalloyed copper tube have a mass percentage of ≤0.038%.

[0036] Based on the above-mentioned microalloyed copper tube, the content of O element is further controlled below 0.003%. When the content of O is controlled within the above range, the oxygen element exists in the form of (copper + cuprous oxide) eutectic at the grain boundaries of copper. Cuprous oxide can generate high-melting-point spherical particles. These particles are distributed inside the grains, which can eliminate grain boundary brittleness and effectively improve the ductility of the microalloyed copper tube, thereby improving the processing performance of the microalloyed copper tube.

[0037] On the other hand, embodiments of the present invention also provide a method for preparing a micro-alloyed copper tube, comprising the following steps: preparing materials according to the raw material composition of the micro-alloyed copper tube, and then sequentially performing smelting, continuous casting, rolling, diameter reduction and annealing treatment, wherein the smelting temperature is 1150~1200 degrees Celsius and the smelting time is 60~90 minutes; and / or, the annealing temperature is 400~600 degrees Celsius and the annealing time is 50~120 minutes.

[0038] This invention, by controlling the types and proportions of the above-mentioned added elements, enables microalloyed copper tubes to not only possess superior high-strength and pressure-resistant properties but also excellent processing performance. It also improves the weldability of the microalloyed copper tubes while maintaining strong corrosion resistance. Furthermore, in the reaction system composed of the above-mentioned elements, especially in the system where the mass ratio of Sn to Ni is (2~7):1, using specific melting and annealing temperatures within the above range effectively promotes the full dissolution of each element, reduces component segregation and inclusion formation, and suppresses grain coarsening. This achieves a synergistic improvement in pressure resistance and processing plasticity, enabling the prepared microalloyed copper tubes to simultaneously meet the following properties: tensile strength of 245~275 N / mm², yield strength of 50~100 N / mm², elongation after fracture ≥40%, hardness ≤72HV, and grain size of 0.010~0.035 mm. It not only improves the pressure resistance but also has excellent processing performance, which can meet the usage requirements of air conditioning pipe assemblies. While reducing the wall thickness of air conditioning pipe assemblies, it still has good pressure resistance and processing performance, making it suitable for mass application of air conditioning pipe assemblies and meeting the requirements of high strength, high pressure resistance, corrosion resistance and excellent processing performance under thin-wall conditions.

[0039] Furthermore, this invention has found that in a system composed of Sn and Ni in a mass ratio of (2~7):1, when the annealing adopts a gradient heating program of "first holding at 400±10 degrees Celsius for 25~35 minutes, then holding at 520±10 degrees Celsius for 30~40 minutes, and then holding at 580±10 degrees Celsius for 15~25 minutes", compared with the annealing method of a single heating program, the tensile strength can be increased by 5-10% and the elongation after fracture can be increased by 10-15%, thus significantly improving the pressure resistance and processing performance of the microalloyed copper tube.

[0040] The present invention will be further described below with reference to specific embodiments. The performance parameters involved in the embodiments of the present invention are measured by the following methods.

[0041] Tensile strength: Refer to standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature"; Yield strength: Refer to standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature"; Elongation after fracture: Refer to standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature"; Hardness: Refer to standard JIS Z 2244 "Vickers Hardness Test - Part 1: Test Method"; Grain size: Refer to standard JIS H 0501 "Method for evaluating the average grain size of forged copper and copper alloys"; Corrosion resistance: After 500 hours of neutral salt spray testing on the micro-alloyed copper tube, a basic pressure test (1.5 times the maximum working pressure) is conducted to observe for any cracking, bursting, or leakage.

[0042] Example 1 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.20%, Ni 0.05%, P 0.0245%, O 0.00065%, Cu 99.71%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 4:1.

[0043] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component of the microalloyed copper tube mentioned above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1170 degrees Celsius for 70 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 500 degrees Celsius for 80 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 1.

[0044] Example 2 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.25%, Ni 0.05%, P 0.0246%, O 0.00078%, Cu 99.66%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 5:1.

[0045] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1150 degrees Celsius for 60 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 400 degrees Celsius for 80 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 2.

[0046] Example 3 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.30%, Ni 0.05%, P 0.0239%, O 0.00118%, Cu 99.61%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 6:1.

[0047] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1200 degrees Celsius for 80 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Annealing at 600 degrees Celsius for 120 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 3.

[0048] Example 4 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.35%, Ni 0.05%, P 0.0237%, O 0.00095%, Cu 99.56%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 7:1.

[0049] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1170 degrees Celsius for 90 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 500 degrees Celsius for 50 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 4.

[0050] Example 5 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.2%, Ni 0.1%, P 0.0235%, O 0.00106%, Cu 99.66%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 2:1.

[0051] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1170 degrees Celsius for 70 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 500 degrees Celsius for 80 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 5.

[0052] Example 6 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.25%, Ni 0.1%, P 0.0245%, O 0.00112%, Cu 99.61%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 2.5:1.

[0053] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1170 degrees Celsius for 80 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 500 degrees Celsius for 80 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 6.

[0054] Example 7 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.30%, Ni 0.1%, P 0.0243%, O 0.00124%, Cu 99.56%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 3:1.

[0055] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1170 degrees Celsius for 80 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 500 degrees Celsius for 80 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 7.

[0056] Example 8 This embodiment provides a microalloyed copper tube, which is composed of the following components by mass percentage: Sn 0.35%, Ni 0.1%, P 0.0249%, O 0.00079%, Cu 99.51%, with the balance being other unavoidable impurities. The mass ratio of Sn to Ni in the microalloyed copper tube is 3.5:1.

[0057] This embodiment also provides a method for preparing micro-alloyed copper tubes, including the following steps: (1) Ingredient preparation: Prepare raw materials according to the mass percentage of each component in the microalloyed copper tube above; (2) Melting: Place the raw materials in a melting furnace and melt them at a temperature of 1170 degrees Celsius for 70 minutes; (3) Continuous casting: The molten liquid metal enters the casting furnace through the trough and enters the crystallizer. It solidifies into a billet shell under the cooling effect of primary and secondary water cooling. It is then horizontally drawn into a hollow tube billet, and then the surface oxide scale is removed through the milling process. (4) Rolling: The three-roll planetary mill rolls the milled billet with the rolls to make the billet surface bright and the structure fine and uniform; (5) Diameter reduction: The required pipe diameter and wall thickness are obtained through continuous drawing and multiple drawing passes; (6) Annealing: Anneal at 500 degrees Celsius for 80 minutes to obtain the microalloyed copper tube, named microalloyed copper tube 8.

[0058] Example 9 This embodiment is basically the same as embodiment 2, except that (6) annealing: first, it is kept at 400 degrees Celsius for 25 minutes, then at 520 degrees Celsius for 40 minutes, and then at 580 degrees Celsius for 15 minutes to obtain microalloyed copper tube 9.

[0059] Examples 1-9 provide a microalloyed copper tube, the raw material composition of which is shown in Table 1: Table 1 Chemical composition of the microalloyed copper tubes in the examples

[0060] The properties of the microalloyed copper tubes and TP2 copper tubes prepared in Examples 1-9 were measured in this invention, and the results are shown in Table 2: Table 2 Performance test results of microalloyed copper tubes 1-9 and TP2 copper tubes prepared in Examples 1-9

[0061] Note: "√" in the table indicates qualified, and "×" indicates unqualified.

[0062] As shown in the table above, compared with the performance of TP2 copper tubes, the micro-alloyed copper tubes 1-9 prepared by adding tin and nickel elements and optimizing the content of each element in this invention have higher tensile strength than TP2 copper tubes. Although the hardness and yield strength are increased, they are not significantly different from those of TP2 copper tubes, and the elongation after fracture is also not significantly different from that of TP2 copper tubes. This indicates that the micro-alloyed copper tubes of this invention can effectively suppress the significant increase in hardness and yield strength and the significant decrease in elongation after fracture while improving its tensile strength, controlling hardness, yield strength and elongation after fracture within a reasonable range, so that the micro-alloyed copper tubes have both high pressure resistance and excellent processing performance.

[0063] Meanwhile, the inventors used the micro-alloyed copper tubes prepared in Examples 1-9 to process air conditioning pipe assemblies (bent pipes, expansion and contraction openings) for verification experiments. They found that only minor adjustments to the processing equipment (such as the size of the mandrel and the front and rear positions of the mandrel) are needed to process air conditioning pipe assemblies that meet the process requirements.

[0064] The corrosion resistance of the microalloyed copper tubes prepared in Examples 1-9 was tested. It was found that none of the microalloyed copper tubes 1-9 showed any cracking, bursting or leakage after 500 hours of neutral salt spray treatment. This indicates that the microalloyed copper tubes of the present invention not only have high pressure resistance and excellent processing performance, but also strong corrosion resistance.

[0065] This invention, from testing the performance data of microalloyed copper tubes to verifying the processing technology, confirms that the performance indicators of the microalloyed copper tubes are controlled within the standard range of Table 3. This not only meets the requirements for improved pressure resistance but also demonstrates excellent processing performance, thus meeting the usage requirements of air conditioning pipe assemblies.

[0066] Table 3. Usage Standards for Microalloyed Copper Tubes in Air Conditioning Pipe Assemblies

[0067] To avoid difficulties in processing air conditioning pipe assemblies, the tensile strength of the micro-alloyed copper tube is controlled not only at its lower limit but also at its upper limit. The lower limit ensures the pressure resistance of the micro-alloyed copper tube, while the upper limit avoids processing difficulties for the pipe assembly. Simultaneously, the yield strength and hardness are specified to facilitate processing, reduce processing difficulty, and improve processing performance. The raw material composition and ratio of the micro-alloyed copper tube are controlled as follows: P 0.015~0.025%, Sn 0.20~0.35%, Ni 0.05~0.10%, other elements ≤0.02%, and the balance being Cu. This ensures that the prepared micro-alloyed copper tube meets the performance requirements of Table 3, facilitating its processing into air conditioning pipe assemblies and enabling its mass application in air conditioning pipe assemblies.

[0068] The welding performance of the microalloyed copper tubes prepared in Examples 1-9 and TP2 was measured in this invention, and the results are shown in Table 4: Table 4 Tensile strength of microalloyed copper tubes 1-9 and TP2 copper tubes after welding / Rm / (N / mm) 2 )

[0069] As shown in Table 4, the tensile strength of the microalloyed copper tube and TP2 copper tube of the present invention after welding is 213~225 N / mm. 2 Between these values, the tensile strength reached 80% of its pre-welding strength, indicating that the micro-alloyed copper tube still possesses good tensile strength after welding.

[0070] Comparative Examples 1-10 Comparative Examples 1-10 are basically the same as Example 1, except that the raw material composition is different. The raw material composition is shown in Table 5. The microalloyed copper tubes of Comparative Examples 1-10 are named microalloyed copper tubes 10-19 respectively.

[0071] Table 5 Chemical composition of the microalloyed copper tubes of Example 1 and Comparative Examples 1-10

[0072] The microalloyed copper tubes prepared in Example 1 and Comparative Examples 1-10 were tested according to the present invention, and the results are shown in Table 6: Note: "√" in the table indicates qualified, and "×" indicates unqualified.

[0073] The weldability of the microalloyed copper tubes prepared in Example 1 and Comparative Examples 1-10 after welding was determined in this invention, and the results are shown in Table 7: Based on the above performance analysis, the microalloyed copper tube of the present invention, by introducing Sn and Ni elements and optimizing the content and proportion of each element in the microalloyed copper tube, not only improves the tensile strength and pressure resistance of the microalloyed copper tube, but also ensures that its yield strength and hardness do not increase significantly and its elongation after fracture does not decrease significantly. This allows the microalloyed copper tube to improve its pressure resistance while maintaining good ductility, corrosion resistance and weldability, giving it both high pressure resistance and excellent processing performance. It can be used in batches in air conditioning pipe assemblies to meet production and usage requirements.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A micro-alloyed copper tube, characterized in that, The microalloyed copper tube comprises the following components by mass percentage: P 0.015~0.025%, Sn 0.20~0.35%, Ni 0.05~0.10%, with the balance being Cu and unavoidable impurities.

2. The microalloyed copper tube according to claim 1, characterized in that, The mass ratio of Sn to Ni in the microalloyed copper tube is (2~7):

1.

3. The microalloyed copper tube according to claim 2, characterized in that, The mass ratio of Sn to Ni in the microalloyed copper tube is (3~7):

1.

4. The microalloyed copper tube according to any one of claims 1-3, characterized in that, The unavoidable impurities include oxygen (O), which accounts for less than 0.003% of the mass percentage in the microalloyed copper tube.

5. The microalloyed copper tube according to any one of claims 1-3, characterized in that, The mass percentage of Cu in the microalloyed copper tube is above 99.5%.

6. The microalloyed copper tube according to any one of claims 1-3, characterized in that, The microalloyed copper tube satisfies one or more of the following characteristics: a. Tensile strength is 245~275 Newtons / mm²; b. Yield strength is 50~100 Newtons / mm²; c. Elongation after fracture ≥40%; d. Hardness ≤ 72HV.

7. The microalloyed copper tube according to claim 6, characterized in that, In characteristic a, the tensile strength is 245~268 Newtons / mm²; And / or, in feature b, the yield strength is 50~80 Newtons / mm²; And / or, in the feature d, the hardness is ≤60HV.

8. The microalloyed copper tube according to any one of claims 1-3, characterized in that, The microalloyed copper tube further includes feature e, wherein the grain size of feature e is 0.010~0.035 mm.

9. The method for preparing the microalloyed copper tube according to any one of claims 1-8, characterized in that, Includes the following steps: The raw materials for the microalloyed copper tube are prepared according to the specified composition, and then smelting, continuous casting, rolling, diameter reduction and annealing are carried out in sequence.

10. The method for preparing the microalloyed copper tube according to claim 9, characterized in that, The melting temperature is 1150~1200 degrees Celsius.

11. The method for preparing the microalloyed copper tube according to claim 10, characterized in that, The melting time is 60-90 minutes.

12. The method for preparing the microalloyed copper tube according to any one of claims 9-11, characterized in that, The annealing temperature is 400~600 degrees Celsius and the annealing time is 50~120 minutes.

13. The method for preparing the microalloyed copper tube according to claim 12, characterized in that, The annealing process includes: first holding at 400±10 degrees Celsius for 25 to 35 minutes, then holding at 520±10 degrees Celsius for 30 to 40 minutes, and then holding at 580±10 degrees Celsius for 15 to 25 minutes.

14. The application of the microalloyed copper tube according to any one of claims 1-8 or the microalloyed copper tube prepared by the preparation method according to any one of claims 9-13 in the preparation of air conditioning pipe assemblies.

15. The application of the microalloyed copper tube according to claim 14, characterized in that, The air conditioning pipe assembly includes at least one of the following: heat conduction pipe of the air conditioning heat exchanger, connecting pipe between the indoor and outdoor units of the air conditioner, and internal pipe.

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