Copper-based brazing filler metal, application of copper-based brazing filler metal and fluid pipeline comprising copper-based brazing filler metal

Abstract

The invention discloses copper-based brazing filler metal, application of the copper-based brazing filler metal and a fluid pipeline comprising the copper-based brazing filler metal. The copper-based brazing filler metal comprises, by weight, 3.5%-4.5% of P, 3.8%-4.8% of Ag, 8.5%-9.5% of Sn, 0.5%-1% of Ni and the balance Cu. According to the copper-based brazing filler metal, the copper-based brazing filler metal with the stable potential characteristic can be obtained through the synergistic effect of the five elements within the proper range. After the copper-based brazing filler metal is used for brazing the heat exchange tube made of metal copper, electrochemical corrosion is not prone to being generated, and the quality of a heat exchanger product comprising the heat exchange tube is stable.

Description

Technical Field

[0001] The present application relates to the field of brazing, and in particular to a copper-based brazing, its application and a fluid pipeline comprising the same. Background Art

[0002] Heat exchangers are used to transfer heat from hot fluid to cold fluid and have a wide range of uses. Heat exchangers usually include heat exchange tubes, and the fluid inside the heat exchange tubes and the fluid outside the heat exchange tubes exchange heat through the closing of the heat exchange tubes. Heat exchange tubes are generally made of metal copper, and the heat exchange tubes are usually brazed to form an integral fluid pipeline so that the fluid inside the heat exchange tubes can flow along the required path. The melting point of the brazing material is lower than that of the metal copper. After heating, the brazing material melts before the metal copper to fill the gap between the connected parts and join the connected heat exchange tubes together. Summary of the invention

[0003] In a first aspect, the present application provides a copper-based solder, which comprises, by weight percentage: P: 3.5%-4.5%, Ag: 3.8%-4.8%, Sn: 8.5%-9.5%, Ni: 0.5%-1%, and the balance Cu.

[0004] According to the first aspect above, the copper-based solder is used for welding between copper metals.

[0005] According to the above first aspect, the copper metal includes red copper metal.

[0006] According to the first aspect above, the solidus temperature of the copper-based solder is 560°C to 580°C.

[0007] According to the first aspect above, the liquidus temperature of the copper-based solder is 650°C to 670°C.

[0008] According to the first aspect above, the minimum brazing temperature of the copper-based brazing filler metal is 600°C to 620°C.

[0009] According to the above first aspect, the copper-based solder is a ring-shaped solder.

[0010] In a second aspect, the present application provides a use of the copper-based brazing filler metal according to any one of the first aspects for welding between heat exchange tubes of an air-conditioning unit.

[0011] According to the above second aspect, the heat exchange tube is made of copper metal.

[0012] In a third aspect, the present application provides a fluid pipeline, comprising: a first copper tube and a second copper tube, wherein the first copper tube and the second copper tube are connected by welding using the copper-based solder described in any one of the first aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of the structure of a copper-based solder according to an embodiment of the present application;

[0014] Figure 2 For use Figure 1 Schematic diagram of the structure of brazing two heat exchange tubes with copper-based brazing filler metal. DETAILED DESCRIPTION

[0015] Various specific embodiments of the present invention will be described below with reference to the accompanying drawings that form a part of this specification. It should be understood that although terms indicating directions, such as "front", "rear", "upper", "lower", "left", "right", "top", "bottom", etc., are used in this application to describe various example structural parts and elements of the present application, these terms are used here only for the purpose of convenience of description and are determined based on the example orientations shown in the accompanying drawings. Since the embodiments disclosed in this application can be arranged in different directions, these terms indicating directions are only for illustration and should not be regarded as limitations.

[0016] In the present application, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art.

[0017] Figure 1 A copper-based solder 100 according to an embodiment of the present application is shown. Figure 1 As shown, the copper-based solder 100 is an annular solder having a notch 101. The notch 101 can facilitate operators to sleeve the copper-based solder 100 around the periphery of the heat exchange tube.

[0018] Figure 2 Show use Figure 1 The structure diagram of the fluid pipeline formed by welding two heat exchange tubes with copper-based solder 100 is shown. Figure 2 As shown, the two heat exchange tubes include a first copper tube 211 and a second copper tube 212, and only the partial structural schematic diagram of the two heat exchange tubes at the welding position is shown in the figure. In this embodiment, the first copper tube 211 includes a cup section 214 formed by a conventional expansion process, and the second copper tube 212 is inserted into the cup section 214. The copper-based solder 100 is arranged between the first copper tube 211 and the second copper tube 212. The copper-based solder 100 in the shape of an annular solder is sleeved on the periphery of the second copper tube 212. By heating the copper-based solder 100 to a suitable brazing temperature, the copper-based solder 100 can be penetrated between the outer wall of the second copper tube 212 and the inner wall of the cup section 214 of the first copper tube 211. After the copper-based solder is cooled, the first copper tube 211 and the second copper tube 212 can be joined together to form a fluid pipeline 218.

[0019] In this embodiment, the top of the cup section 214 of the first copper tube 211 is further provided with an outer flange 213. The copper-based solder 100 is sleeved on the periphery of the second copper tube 212 and is contained in the outer flange 213. Therefore, when the copper-based solder 100 melts, it can better penetrate into the gap between the first copper tube 211 and the second copper tube 212, but will not penetrate into the outer wall of the first copper tube 211.

[0020] It can be understood by those skilled in the art that Figure 2 The first copper tube 211 and the second copper tube 212 shown in the figure are local structures. When actually brazing and connecting the fluid pipeline, the first copper tube 211 and the second copper tube 212 can be straight tubes or curved tubes or other required shapes to form a fluid pipeline of the required shape.

[0021] The copper-based solder 100 is generally a copper-phosphorus solder including phosphorus and copper elements. In the copper-phosphorus solder with phosphorus and copper as the main elements, copper and phosphorus can form a low melting point eutectic, making it suitable for the welding of copper metal. In order to ensure sufficient welding strength, the welding penetration needs to meet certain process standard requirements. The applicant found that when the first copper tube 211 and the second copper tube 212 are brazed using a general copper-phosphorus solder (GB / T6418-2008, solder model: BCu93P), during the penetration of the copper-phosphorus solder between the first copper tube 211 and the second copper tube 212, due to the insufficient wettability and fluidity of the copper-phosphorus solder, it is easy to cause uneven filling of the copper-phosphorus solder, so that an internal weld nodule is formed at the end face of the second copper tube 212 and the inner wall position of the first copper tube 211. Furthermore, after brazing is completed, due to the potential difference between the copper-phosphorus brazing filler metal and the metallic copper, when an electrolyte solution (such as air conditioning circulating water) is present, the metallic copper near the brazing filler metal is easily electrochemically corroded, making the first copper tube 211 and the second copper tube 212 easily corroded near the connection, affecting the structural stability of the fluid pipeline, and possibly causing leakage of the solution in the heat exchange tube or breakage of the heat exchange tube, etc.

[0022] The applicant also found that the potential characteristics of general copper-based solder are unstable. The electrolyte solution and temperature in the external environment will cause the actual potential of the copper-based solder to fluctuate, making the electrochemical corrosion of heat exchange tubes made of copper metal welded by the copper-based solder uncontrollable.

[0023] The present application provides a copper-based brazing filler metal. By selecting reasonable alloy elements and proportions, a copper-based brazing filler metal with stable potential characteristics can be obtained. After the copper-based brazing filler metal is used to braze a heat exchange tube made of metal copper, electrochemical corrosion is not easily generated, so that the quality of the heat exchanger product including the heat exchange tube is stable. In addition, the copper-based brazing filler metal has a low melting point, good wettability and fluidity, and can improve the welding quality and avoid welding quality defects such as internal weld nodules, pores, inclusions, and poor penetration.

[0024] In the present application, the copper-based solder 100 includes, by weight percentage: P (phosphorus): 3.5%-4.5%, Ag (silver): 3.8%-4.8%, Sn (tin): 8.5%-9.5%, Ni (nickel): 0.5%-1%, and the balance Cu (copper). The copper-based solder 100 can be made according to any conventional solder preparation method. In some embodiments, the copper-based solder 100 is obtained by mixing raw materials by weight percentage, and then smelting, casting, extrusion molding and surface treatment processes are performed.

[0025] In the present application, by adding appropriate contents of P and Ag elements, the copper-based solder 100 can have good wettability and fluidity. And by adding appropriate contents of Sn and Ni elements, the copper-based solder 100 can have a lower melting point. In some embodiments, the solidus temperature of the copper-based solder 100 is 560°C to 580°C. In some embodiments, the liquidus temperature of the copper-based solder 100 is 650°C to 670°C. In some embodiments, the minimum brazing temperature of the copper-based solder 100 is 600°C to 620°C. The melting temperature of the copper-based solder 100 is much lower than the melting temperature of copper metal (roughly about 1000°C), so the copper-based solder 100 of the present application is particularly suitable for brazing pipes made of copper metal.

[0026] The brazing effect of the copper-based solder of the present application is described below through some specific examples 1-3 and comparative examples 1-3. Examples 1-3 are examples of the copper-based solder of the present application. Comparative examples 1-3 are examples of several commercially available copper-based solders.

[0027] Table 1 shows the contents of various components of the copper-based solders of Examples 1 to 3 and the contents of various components of the copper-based solders of Comparative Examples 1 to 3. Table 2 shows the performance data of the copper-based solders of Examples 1 to 3 and the copper-based solders of Comparative Examples 1 to 3.

[0028] Table 1 Components and their weight percentages in Examples 1-3 and Comparative Examples 1-3

[0029]

[0030]

[0031] Table 2 Performance data of copper-based solders of Examples 1-3 and Comparative Examples 1-3

[0032] Solidus temperature / ℃ Liquidus temperature / ℃ Minimum brazing temperature / ℃ Example 1 580 670 620 Example 2 570 660 610 Example 3 560 650 600 Comparative Example 1 710 793 730 Comparative Example 2 660 745 690 Comparative Example 3 620 700 650

[0033] The copper-based brazing alloy of Example 2 and the copper-based brazing alloys of Comparative Examples 1-3 were used to braze ten short "U"-shaped heat exchange tubes and ten long "U"-shaped heat exchange tubes of the fan coil unit of the air conditioner to form a continuous fluid pipeline. After the welding was completed, the unit was continuously operated for 6 months, and circulating water flowed through the heat exchange tubes. Then the welding point of each heat exchange tube was dissected, and the results were as follows:

[0034] Among the 40 welds of 10 heat exchange tubes welded with the copper-based brazing filler metal of Comparative Example 1, 39 welds were electrochemically corroded, wherein the depth of the corrosion pits was 0.033-0.143 mm, and the length of the internal weld nodules was 1.331-6.713 mm.

[0035] Among the 40 welds of 10 heat exchange tubes welded with the copper-based brazing filler metal of Comparative Example 2, 28 welds were electrochemically corroded, wherein the depth of the corrosion pits was 0.018-0.148 mm, and the length of the internal weld nodules was 1.458-5.365 mm.

[0036] Among the 40 welds of 10 heat exchange tubes welded with the copper-based brazing filler metal of Comparative Example 3, 26 welds were electrochemically corroded, wherein the depth of the corrosion pits was 0.018-0.081 mm, and the length of the internal weld nodules was 0.862-4.382 mm.

[0037] Among the 40 welds of 10 heat exchange tubes welded with the copper-based brazing material of Example 2, electrochemical corrosion was found in 3 welds, wherein the depth of the corrosion pits was 0.018 to 0.042 mm, and no internal weld nodules were found.

[0038] The fan coil units of the air conditioners welded using the copper-based brazing filler metals of Example 1 and Example 3 had similar results to that of Example 2.

[0039] From the above welding results and the results shown in Table 1 and Table 2, it can be seen that the fluid pipeline welded using the copper-based solder of the present application not only has a greatly reduced degree of electrochemical corrosion, but also has a lower depth of corrosion pits. This shows that the copper-based solder of the present application has a strong ability to resist electrochemical corrosion and has good potential stability. In addition, no internal weld nodules are found at the weld of the fluid pipeline, indicating that the copper-based solder of the present application has good wettability and fluidity, and the penetration at the weld is more uniform. In addition, the melting point of the copper-based solder of the present application is low, and the minimum brazing temperature is also low, so the copper-based solder of the present application has good operability and can also improve welding performance.

[0040] The copper-based brazing filler metal of the present application can obtain a copper-based brazing filler metal with stable potential characteristics through the synergistic effect of five elements within a suitable range. After the copper-based brazing filler metal is used to braze a heat exchange tube made of metal copper, electrochemical corrosion is not easily generated, so that the quality of the heat exchanger product including the heat exchange tube is stable.

[0041] In addition, the copper-based solder of the present application has a low melting point, good wettability and fluidity, which can improve welding quality and avoid welding quality defects such as internal weld nodules, pores, inclusions, and poor penetration.

[0042] In addition, the content of precious metal silver in the copper-based solder of the present application is relatively low, which can save costs.

[0043] Although the present disclosure has been described in conjunction with the examples of the embodiments summarized above, it is obvious to those of ordinary skill in the art that various alternatives, modifications, variations, improvements and / or substantially equivalent solutions, whether known or now or foreseeable in the near future, may be apparent. Therefore, the examples of the embodiments of the present disclosure as stated above are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to include all known or earlier developed alternatives, modifications, variations, improvements and / or substantially equivalent solutions. The technical effects and technical problems in this specification are exemplary rather than restrictive. It should be noted that the embodiments described in this specification may have other technical effects and may solve other technical problems.

Claims

1. A copper-based solder, characterized in that: The copper-based solder comprises, by weight percentage: P: 3.5%-4.5%, Ag: 3.8%-4.8%, Sn: 8.5%-9.5%, Ni: 0.5%-1%, and the balance Cu.

2. The copper-based solder according to claim 1, characterized in that: The copper-based solder is used for welding between copper metals.

3. The copper-based solder according to claim 2, characterized in that: The copper metal includes red copper metal.

4. The copper-based solder according to claim 1, characterized in that: The solidus temperature of the copper-based solder is 560°C to 580°C.

5. The copper-based solder according to claim 1, characterized in that: The liquidus temperature of the copper-based solder is 650°C to 670°C.

6. The copper-based solder according to claim 1, characterized in that: The minimum brazing temperature of the copper-based brazing material is 600°C to 620°C.

7. The copper-based solder according to claim 1, characterized in that: The copper-based solder is a ring-shaped solder.

8. Use of the copper-based brazing filler metal according to any one of claims 1 to 7 for welding between heat exchange tubes of an air-conditioning unit.

9. The use according to claim 8, characterized in that: The heat exchange tube is made of copper metal.

10. A fluid pipeline, characterized in that include: A first copper tube and a second copper tube, wherein the first copper tube and the second copper tube are connected by welding using the copper-based solder according to any one of claims 1 to 7.

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