Aluminum pipe, heat exchanger and application of aluminum pipe

Abstract

The invention discloses an aluminum pipe, a heat exchanger and application thereof, and belongs to the technical field of heat exchange materials. The aluminum pipe comprises an aluminum pipe base material layer and a zinc impregnation layer arranged on the surface of the aluminum pipe base material layer. The zinc impregnation layer has a zinc concentration gradient which is gradually reduced from outside to inside; the maximum zinc concentration of the zinc impregnation layer is 0.01 to 10 weight percent; the thickness of the zinc impregnation layer is larger than 0 and smaller than or equal to 400 micrometers. The zinc impregnation layer is formed on the surface of the aluminum pipe base material layer, corrosion can be limited from expanding to the inner layer, longitudinal expansion of corrosion is avoided, pitting corrosion is inhibited, the zinc content distribution of the zinc impregnation layer at different zinc impregnation depths can be controlled by controlling the maximum zinc concentration and thickness of the zinc impregnation layer, and the corrosion resistance of the aluminum pipe is improved. The zinc impregnation layer has a good anodic protection effect on the aluminum pipe, pitting corrosion extension is effectively inhibited, the corrosion resistance of the aluminum pipe is improved, and the service life of the aluminum pipe is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat exchange materials, and particularly relates to an aluminum pipe, a heat exchanger and application thereof. BACKGROUND

[0002] In the field of heat exchange equipment, especially in the air conditioning industry, copper is often used as a metal material. However, with the rising price of copper, the use of copper requires huge costs. Therefore, it is an inevitable trend to seek new alternative materials. Aluminum alloy is an ideal metal material that can replace copper. However, compared with copper, aluminum is more prone to pitting corrosion in coastal and industrial atmospheric environments, which greatly shortens its service life and becomes a barrier to the replacement of copper with aluminum. Based on the corrosion reliability problem, surface corrosion protection treatment is performed on the aluminum heat exchanger to improve the corrosion resistance, which is an important research direction. Since the aluminum heat exchanger needs to be in contact with air, water and other media during operation, it is easy to be corroded, thereby affecting the service life and performance of the equipment. Therefore, how to improve the corrosion resistance of the aluminum heat exchanger is a problem to be solved in the field of heat exchange equipment manufacturing technology.

[0003] An important component of the aluminum heat exchanger is the aluminum pipe. For the corrosion protection of the aluminum pipe, the existing solutions mainly limit the alloy elements in the aluminum pipe to improve its corrosion resistance. For example, some solutions control the impurity metal elements (Cu, Fe, Ni, Co, etc.) in the aluminum pipe to reduce the content of harmful metals and improve the corrosion resistance of the alloy. In addition, some solutions coat an organic coating layer on the surface of the aluminum alloy to isolate the channel of the corrosion medium and form a physical corrosion protection purpose. However, the existing corrosion protection treatment technology still has some problems. First, the existing element impurity control technology depends on the improvement of metallurgical technology, which significantly increases the manufacturing cost and has limited effect on improving the corrosion resistance of the aluminum pipe. Second, the existing organic coating treatment technology seriously affects the heat transfer performance of the heat exchanger, which may cause the overall energy efficiency of the heat exchanger to decrease. If the organic coating layer has a leakage, aging damage area or the like, it cannot block the corrosion medium from contacting the surface of the aluminum pipe, and the aluminum pipe will still be pitted, and even the corrosion of the aluminum pipe will be accelerated (such as crevice corrosion). SUMMARY

[0004] The present application aims to solve one of the above technical problems in the prior art. To this end, one of the purposes of the present application is to provide an aluminum pipe with low cost, good pitting corrosion resistance and no effect on the heat transfer performance of the heat exchanger. The zinc infiltration layer in the aluminum pipe has a zinc concentration gradient gradually decreasing from outside to inside. The outer layer with high zinc concentration has a lower potential and is more prone to corrosion, so that the outer layer is preferentially corroded to the inner layer, effectively inhibiting the occurrence of pitting corrosion and improving the corrosion resistance and service life of the aluminum pipe.

[0005] The second purpose of the present application is to provide a preparation method of the above-mentioned aluminum pipe.

[0006] The third object of the present application is to provide a heat exchanger comprising the aluminum tube.

[0007] The fourth object of the present application is to provide a temperature regulating device.

[0008] To achieve the above objects, the technical solution adopted by the present application is:

[0009] The first aspect of the present application provides an aluminum tube comprising an aluminum tube substrate layer and a zinc diffusion layer formed on the surface of the aluminum tube substrate layer; the zinc diffusion layer has a zinc concentration gradient gradually decreasing from outside to inside; the maximum zinc concentration of the zinc diffusion layer is 0.01-10wt%; the thickness of the zinc diffusion layer is greater than 0 and less than or equal to 400μm.

[0010] The aluminum tube according to the first aspect of the present application has at least the following beneficial effects:

[0011] The present application forms a zinc diffusion layer on the surface of the aluminum tube substrate layer and controls the zinc diffusion layer to have a zinc concentration gradient gradually decreasing from outside to inside, i.e. the outer layer of the zinc diffusion layer has a higher zinc concentration and the inner layer has a lower zinc concentration, so as to improve the corrosion resistance of the aluminum tube. Since the self-corrosion potential of the aluminum tube with high zinc content is more negative during corrosion, the outer layer of the zinc diffusion layer acts as an anode and corrosion occurs preferentially, the self-corrosion potential of the aluminum tube with low zinc content is more positive, and the inner layer of the zinc diffusion layer is less prone to corrosion. By setting the corrosion rates of the inner and outer layers, the pitting corrosion that easily occurs in ordinary aluminum tubes is inhibited, and corrosion is more likely to initiate on the surface of the aluminum tube and expand in the transverse direction rather than in the longitudinal direction towards the interior of the aluminum tube. The corrosion of the aluminum tube of the present application is close to uniform corrosion, which can effectively inhibit the occurrence of pitting corrosion, greatly improve the service life of the aluminum tube, and the preparation cost of the aluminum tube is low, which is conducive to replacing copper tubes as the main material of heat exchangers. In addition, controlling the maximum zinc concentration of the zinc diffusion layer is conducive to controlling the zinc content and zinc distribution in the zinc diffusion layer, ensuring that the zinc diffusion layer has a suitable corrosion rate, thereby effectively protecting the aluminum tube. The specific thickness of the zinc diffusion layer is to ensure that the zinc diffusion layer has a good anodic protection effect on the aluminum tube.

[0012] In some embodiments of the present application, the material of the aluminum tube substrate layer is an aluminum alloy, and the aluminum alloy used for the aluminum tube substrate layer comprises the following alloying elements in mass percentage: Si: 0.01-0.6wt%, Fe: 0.01-0.6wt%, Mn: ≤1.5wt%, Ti: 0.005-0.3wt%, Cu: ≤0.1wt%, and unavoidable impurity elements.

[0013] The unavoidable impurities refer to the impurities that cannot be completely avoided in the production process of the material, which can be derived from raw materials, processing technology or environmental factors, etc. In some embodiments of the present application, the unavoidable impurities in the aluminum tube substrate layer are, for example, Zr, Cr, Ti, etc.

[0014] In some specific embodiments of the present application, the total content of impurity elements in the aluminum alloy used for the aluminum tube substrate layer is ≤0.15wt%.

[0015] In some specific embodiments of the present application, the content of a single impurity element in the aluminum alloy used for the aluminum tube substrate layer is ≤0.05wt%.

[0016] Controlling the content of impurity elements in the aluminum alloy can avoid the adverse effects of metal elements on the aluminum alloy, especially the effects on the potential of the aluminum alloy in the corrosion process.

[0017] In some specific embodiments of the present application, the alloying element in the aluminum alloy used for the aluminum tube substrate layer further includes zinc, and the content of zinc is ≤0.5wt%.

[0018] Controlling the content of zinc in the aluminum tube substrate layer to be low can ensure that the aluminum tube substrate layer has a high self-corrosion potential, and is not easy to be corroded in the use process, thereby prolonging the service life of the aluminum tube.

[0019] In some specific embodiments of the present application, the grain size in the aluminum tube substrate layer is ≤50μm.

[0020] In the present application, the grain in the aluminum tube substrate layer refers to the α phase (aluminum solid solution) in the microstructure thereof, which is the main phase in the aluminum alloy. The size of the grain is related to the mechanical properties and corrosion resistance of the material. Generally, the smaller the grain size, the higher the strength and the better the corrosion resistance. Controlling the grain size of the aluminum tube substrate layer in a specific range can improve the mechanical properties and corrosion resistance of the aluminum tube, and also can improve the appearance quality of the aluminum tube.

[0021] In some specific embodiments of the present application, the potential of the zinc diffusion layer gradually increases from the outside to the inside.

[0022] The zinc concentration in the aluminum tube is inversely proportional to the potential thereof. Since the zinc diffusion layer has a zinc concentration gradient that gradually decreases from the outside to the inside, the potential of the zinc diffusion layer gradually increases from the outside to the inside. By adjusting the zinc concentration of the zinc diffusion layer, the potential can be adjusted, so that the outer layer of the zinc diffusion layer is preferentially corroded to the inner layer, thereby achieving the effect of inhibiting pitting corrosion and improving corrosion resistance.

[0023] In some specific embodiments of the present application, the potential difference between the potential of the aluminum tube substrate layer and the lowest potential of the zinc diffusion layer is ≥30mV.

[0024] By adjusting the potential difference at different parts of the aluminum tube, the location and rate of corrosion can be controlled. Maintaining a certain potential difference between the outer layer of the aluminum tube and the substrate can prevent corrosion of the aluminum tube substrate. If the potential difference is too small, the zinc-impregnated outer layer cannot fully act as a sacrificial anode, and some of the substrate will still corrode, leading to leakage.

[0025] In some specific embodiments of the present invention, the zinc content of the aluminum tube is 0.01 to 1 wt%.

[0026] The zinc content of an aluminum tube refers to the ratio of the mass of zinc in the aluminum tube to the total mass of the aluminum tube. By controlling the zinc content of the aluminum tube within a specific range, the alloy composition of the aluminum tube and its overall performance can be controlled, giving it both good mechanical strength and corrosion resistance.

[0027] In some specific embodiments of the present invention, the cross-sectional shape of the aluminum tube includes at least one of a circle, a rectangle, or an ellipse.

[0028] The aluminum tube of this invention can have various cross-sectional shapes, including but not limited to circular, rectangular, and elliptical shapes. In some embodiments of this invention, the zinc-impregnated layer is particularly suitable for aluminum tubes with circular, rectangular, or elliptical cross-sectional shapes, effectively preventing pitting corrosion in the aluminum tube and achieving good corrosion resistance.

[0029] In some specific embodiments of the present invention, the inner wall of the aluminum tube is not threaded, or at least a portion of the inner wall is threaded.

[0030] The aluminum tube has threads on its inner wall, making it an internally threaded aluminum tube. This allows the fluid to rotate as it flows inside the tube, using centrifugal force to push water droplets in the vapor flow towards the tube wall, replenishing the water film, increasing fluid turbulence, improving the convective heat transfer coefficient, enhancing the heat transfer effect, and resulting in better cooling of the tube wall and excellent heat transfer performance. Alternatively, the aluminum tube of this invention can also be without threads, i.e., a plain aluminum tube can be used.

[0031] In some specific embodiments of the present invention, when at least a portion of the inner wall of the aluminum tube is provided with threads, the threads satisfy at least one of the following conditions: 1) the tooth height of the thread is 0.03 to 0.3 mm; 2) the tooth tip angle of the thread is 10 to 160°; 3) the helix angle of the thread is 1 to 65°; 4) the number of teeth of the thread is 18 to 72.

[0032] Adjusting the various parameters of the thread can achieve better convection and heat transfer effects.

[0033] In some specific embodiments of the present invention, the diameter of the aluminum tube is 1 to 20 mm;

[0034] In some specific embodiments of the present invention, the wall thickness of the aluminum tube is ≥0.1mm.

[0035] By comprehensively controlling parameters such as the diameter and wall thickness of the aluminum tube, the aluminum tube has good corrosion resistance as well as good mechanical strength, which prevents the aluminum tube from collapsing or leaking before reaching its expected lifespan during long-term service, thus ensuring that the aluminum tube has a long service life.

[0036] In some specific embodiments of the present invention, the single-tube ultimate pressure resistance value of the aluminum tube is ≥13MPa.

[0037] The aluminum tube provided by this invention has good pressure resistance, which provides more possibilities for the service scenarios of aluminum tubes.

[0038] In some specific embodiments of the present invention, the yield strength of the aluminum tube is 50-130 MPa;

[0039] In some specific embodiments of the present invention, the tensile strength of the aluminum tube is 80-250 MPa;

[0040] In some specific embodiments of the present invention, the elongation of the aluminum tube is ≥20%.

[0041] The aluminum tube provided by this invention has good mechanical properties, such as good yield strength, tensile strength or elongation, which is beneficial to improving the service life of the aluminum tube.

[0042] In some specific embodiments of the present invention, the aluminum tube, with a wall thickness of 0.4 to 0.5 mm, exhibits a leakage duration of ≥1000 h in seawater acidic salt spray testing.

[0043] In some specific embodiments of the present invention, the corrosion depth of the aluminum tube in a 500-hour seawater acidic salt spray test is ≤180μm.

[0044] The aluminum tube provided by this invention has a long leakage time and good leakage resistance in seawater acidic salt spray tests; and it has a small corrosion depth in long-term seawater acidic salt spray tests, with good corrosion resistance and long service life.

[0045] The second aspect of the present invention provides a method for preparing the aluminum tube described in the first aspect of the present invention, comprising the following steps: sequentially subjecting an aluminum tube substrate to zinc spraying and zinc diffusion treatment to obtain the aluminum tube.

[0046] The method for preparing the aluminum tube according to the second aspect of the present invention has at least the following beneficial effects:

[0047] The aluminum tube preparation method of this invention can produce aluminum tubes with good corrosion resistance and long service life, and the preparation process is simple and easy to implement.

[0048] In some specific embodiments of the present invention, the zinc spraying amount in the zinc spraying treatment is 4-14 g / m³. 2 .

[0049] By controlling the specific amount of zinc sprayed, the zinc content of the aluminum tube can be adjusted, as well as the distribution and concentration of zinc in the zinc-infiltrated layer, thereby giving the material a suitable potential and good corrosion resistance.

[0050] In some specific embodiments of the present invention, the zinc layer formed by the zinc spraying process covers an area of ​​≥50% of the surface of the aluminum tube substrate.

[0051] The percentage of zinc coverage area on the surface of the aluminum tube substrate also affects the penetration and distribution of zinc. Keeping the percentage of zinc coverage area within a specific range can improve the distribution of zinc in the zinc-infiltrated layer, thereby giving the material a suitable potential and good corrosion resistance.

[0052] In some specific embodiments of the present invention, the temperature of the zinc diffusion treatment is 300-600°C.

[0053] In some specific embodiments of the present invention, the zinc diffusion treatment time is 0.01 to 24 hours.

[0054] Zinc diffusion temperature and zinc diffusion time are important process parameters that affect the thickness of the zinc diffusion layer and have a significant impact on the distribution of zinc in the zinc diffusion layer. By using specific zinc diffusion temperature and zinc diffusion time, the zinc diffusion layer can meet the requirements of this invention, resulting in aluminum tubes and heat exchangers with good corrosion resistance and long service life.

[0055] In some specific embodiments of the present invention, the grain size in the aluminum tube substrate is ≤50μm.

[0056] In some specific embodiments of the present invention, the aluminum tube substrate contains a precipitated phase, and the grain size of the precipitated phase in the aluminum tube substrate is ≤10μm.

[0057] Controlling the grain size and precipitated phase grain size in the aluminum tube substrate ensures that the substrate has a suitable crystal structure and mechanical strength, as well as a good zinc diffusion effect.

[0058] A third aspect of the present invention provides a heat exchanger comprising the aluminum tube described in the first aspect of the present invention.

[0059] The heat exchanger according to the third aspect of the present invention has at least the following beneficial effects:

[0060] The heat exchanger made from the aluminum tube described in the first aspect of the present invention has good corrosion resistance, mechanical strength and service life.

[0061] In some specific embodiments of the present invention, the heat exchanger further includes fins, semi-circular tubes, or combinations thereof connected to the aluminum tube.

[0062] The aluminum tube provided by this invention can also be connected to fins to form a tube-fin heat exchanger, which can improve the heat transfer performance of the heat exchanger. Furthermore, it can be connected to a semi-circular tube; by connecting pipes of different shapes, heat exchange efficiency can be improved, and the functionality of the piping system can be expanded, such as by adding branches or circulation loops.

[0063] In some specific embodiments of the present invention, when the heat exchanger includes the fins, the fins are connected to the aluminum tube through a zinc-dipped layer.

[0064] In some specific embodiments of the present invention, the fin includes a fin substrate layer and a coating disposed on the surface of the fin substrate layer.

[0065] A coating is applied to the surface of the fin substrate layer to serve as a physical anti-corrosion layer and protect the fins.

[0066] In some specific embodiments of the present invention, the fin substrate layer is made of aluminum alloy.

[0067] In some specific embodiments of the present invention, the raw materials for preparing the coating include acrylic resin, alcohol ether, or a combination thereof. Acrylic resin is a hydrophilic material; its application to the surface of the fin substrate layer prevents the fins from being corroded by moisture, thus improving the corrosion resistance of the fins. Alcohol ether is mainly used as a solvent and film-forming aid, providing anti-fogging, anti-wrinkle, water-repellent properties, and improving the gloss of the coating.

[0068] In some specific embodiments of the present invention, the raw materials for preparing the coating also include water.

[0069] In some specific embodiments of the present invention, when the heat exchanger includes the semi-circular tube, the semi-circular tube is connected to the aluminum tube through a solder area.

[0070] The semi-circular tube and the aluminum tube are connected by a solder zone. The connection method is simple and easy to implement.

[0071] In some specific embodiments of the present invention, the raw materials for forming the solder zone include solder and flux.

[0072] In some specific embodiments of the present invention, the solder is selected from aluminum alloy solder.

[0073] In some specific embodiments of the present invention, the flux is selected from fluoride fluxes.

[0074] In some specific embodiments of the present invention, the welding temperature for forming the solder zone is 550–700°C.

[0075] Choosing the right solder, flux, and welding temperature can improve the welding effect of semi-circular tubes and aluminum tubes, and reduce the impact on the zinc concentration and potential distribution of the zinc-infiltrated layer on the aluminum tube surface, thus ensuring the corrosion resistance and service life of the aluminum tube.

[0076] A fourth aspect of the present invention provides a temperature regulating device, comprising the aluminum tube described in the first aspect of the present invention or the heat exchanger described in the third aspect of the present invention.

[0077] The temperature regulating device according to the fourth aspect of the present invention has at least the following beneficial effects:

[0078] By incorporating aluminum tubes or heat exchangers into temperature control devices, excellent temperature regulation can be achieved, and the corrosion resistance of the temperature control devices can be effectively improved, greatly extending their service life.

[0079] In some specific embodiments of the present invention, the temperature regulating device includes at least one of a refrigerator, an air conditioner, or a water heater. Attached Figure Description

[0080] Figure 1 This is a schematic diagram illustrating the corrosion process of the aluminum tube of this invention compared to that of a regular aluminum tube.

[0081] Figure 2 This is a schematic diagram of the arc zinc spraying process in this invention.

[0082] Figure 3 This is a cross-sectional view of the internally threaded aluminum tube of Example 1.

[0083] Figure 4 This is a graph showing the corrosion potential and zinc content of the aluminum tube in Example 3 of the present invention as a function of zinc penetration depth.

[0084] Figure 5 The results of SWAAT tests on aluminum tubes with different zinc spraying amounts in Examples 1 to 6 are shown.

[0085] Figure 6 This is a cross-sectional zinc concentration curve of the aluminum tube with a zinc penetration depth of 355 μm in Example 10.

[0086] Figure 7 The results of SWAAT tests on aluminum tubes with different zinc penetration depths in Examples 7-10 are shown. Detailed Implementation

[0087] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0088] A first aspect of the present invention provides an aluminum tube, comprising an aluminum tube substrate layer and a zinc-impregnated layer disposed on the surface of the aluminum tube substrate layer; the zinc-impregnated layer has a zinc concentration gradient that gradually decreases from the outside to the inside; the maximum zinc concentration of the zinc-impregnated layer is 0.01 to 10 wt%; and the thickness of the zinc-impregnated layer is greater than 0 and less than or equal to 400 μm.

[0089] This invention improves the corrosion resistance of aluminum tubes by forming a zinc-impregnated layer on the surface of the aluminum tube substrate and controlling the zinc concentration gradient of the zinc-impregnated layer to gradually decrease from the outside to the inside. This results in a higher zinc concentration in the outer layer and a lower zinc concentration in the inner layer. Because aluminum tubes with high zinc content have a more negative self-corrosion potential during corrosion, the outer layer of the zinc-impregnated layer acts as the anode and corrodes preferentially. Conversely, aluminum tubes with low zinc content have a more positive self-corrosion potential, making the inner layer less prone to corrosion. By setting the corrosion rates of the inner and outer layers, pitting corrosion, which is prone to occur in ordinary aluminum tubes, is suppressed. Corrosion is more likely to initiate on the surface of the aluminum tube and spread laterally rather than longitudinally into the interior. The corrosion of the aluminum tubes produced by this invention is close to uniform corrosion, effectively suppressing pitting corrosion and significantly extending the service life of the aluminum tubes. Furthermore, the low manufacturing cost of aluminum tubes makes them a suitable replacement for copper tubes as the main material for heat exchangers. In addition, controlling the maximum zinc concentration of the zinc-diffused layer helps to control the zinc content and distribution in the zinc-diffused layer, ensuring that the zinc-diffused layer has a suitable corrosion rate, thereby achieving effective protection for the aluminum tube. The specific thickness of the zinc-diffused layer is to ensure that the zinc-diffused layer has a good anodic protection effect on the aluminum tube.

[0090] Figure 1 This diagram illustrates the corrosion process of the aluminum tube of this invention and a conventional aluminum tube. (A) is a cross-sectional view of the conventional aluminum tube just beginning to corrode; (B) is a cross-sectional view of the aluminum tube of this invention just beginning to corrode; (C) is a cross-sectional view of the conventional aluminum tube after a period of corrosion; and (D) is a cross-sectional view of the aluminum tube of this invention after a period of corrosion. The gray area represents the corrosion location. It is evident that once corrosion occurs, the corrosion in a conventional aluminum tube extends longitudinally, leading to pitting corrosion, which easily causes leakage. In contrast, the aluminum tube of this invention, with its zinc-impregnated layer, controls the lateral expansion of corrosion, rather than its longitudinal expansion, thereby inhibiting pitting corrosion and preventing leakage. Specifically, the aluminum tube of this invention controls the surface potential of the aluminum tube through the zinc-impregnated layer, ensuring that at the zinc-impregnated layer location, the outer layer always corrodes preferentially over the inner layer. Therefore, corrosion of the outer layer only extends to the inner layer after the outer layer has corroded, achieving lateral corrosion expansion and preventing pitting corrosion.

[0091] In some embodiments of the present invention, the maximum zinc concentration of the zinc-impregnated layer is 0.1–8 wt%; in some specific embodiments of the present invention, the maximum zinc concentration of the zinc-impregnated layer is 0.3–6 wt%; in some examples of the present invention, the maximum zinc concentration of the zinc-impregnated layer is 0.5–5 wt%; non-limiting specific examples include 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, or 4.5 wt%.

[0092] In some embodiments of the present invention, the thickness of the zinc-infiltrated layer is 100–400 μm; in some specific embodiments of the present invention, the thickness of the zinc-infiltrated layer is 130–300 μm; in some examples of the present invention, the thickness of the zinc-infiltrated layer is 150–250 μm; non-limiting specific examples include 160 μm, 180 μm, 200 μm, 220 μm, or 240 μm.

[0093] In some embodiments of the present invention, the aluminum tube substrate layer is made of aluminum alloy, which comprises the following alloying elements by mass percentage: Si: 0.01–0.6 wt%, Fe: 0.01–0.6 wt%, Mn: ≤1.5 wt%, Ti: 0.005–0.3 wt%, Cu: ≤0.1 wt%, and unavoidable impurity elements. In some specific embodiments of the present invention, the aluminum alloy used in the aluminum tube substrate layer comprises the following alloying elements by mass percentage: Si: 0.03–0.53 wt%, Fe: 0.09–0.27 wt%, Mn: 0.38–1.13 wt%, Ti: 0.01–0.26 wt%, Cu: 0.0008–0.015 wt%, and unavoidable impurities.

[0094] Unavoidable impurities refer to impurities that cannot be completely avoided during the material production process. These impurities may originate from raw materials, processing techniques, or environmental factors. In some embodiments of this invention, unavoidable impurities in the aluminum tube substrate layer include Zr, Cr, and Ti.

[0095] In some embodiments of the present invention, the total impurity content of the aluminum alloy used in the aluminum tube substrate layer is ≤0.15wt%; in some specific embodiments of the present invention, the total impurity content of the aluminum alloy used in the aluminum tube substrate layer is 0.001-0.15wt%; in some examples of the present invention, the total impurity content of the aluminum alloy used in the aluminum tube substrate layer is 0.003-0.15wt%; non-limiting specific examples include 0.005wt%, 0.01wt%, 0.05wt%, 0.1wt%, or 0.12wt%.

[0096] In some embodiments of the present invention, the content of a single impurity element in the aluminum alloy used in the aluminum tube substrate layer is ≤0.05wt%; in some specific embodiments of the present invention, the content of a single impurity in the aluminum alloy used in the aluminum tube substrate layer is 0.001-0.05wt%; in some examples of the present invention, the content of a single impurity in the aluminum alloy used in the aluminum tube substrate layer is 0.003-0.045wt%; non-limiting specific examples include 0.005wt%, 0.01wt%, 0.02wt%, 0.03wt%, or 0.04wt%.

[0097] Controlling the content of impurity elements in aluminum alloys can avoid the adverse effects of metallic elements on aluminum alloys, especially their impact on the potential of aluminum alloys during corrosion.

[0098] In some embodiments of the present invention, the aluminum alloy used in the aluminum tube substrate layer further includes zinc as an alloying element, and the zinc content is ≤0.5wt%. In some specific embodiments of the present invention, the aluminum alloy used in the aluminum tube substrate layer further includes zinc as an alloying element, and the zinc content is ≤0.3wt%. In some examples of the present invention, the aluminum alloy used in the aluminum tube substrate layer further includes zinc as an alloying element, and the zinc content is ≤0.2wt%. Non-limiting specific examples include 0.006wt%, 0.008wt%, 0.01wt%, 0.04wt%, 0.07wt%, and 0.08wt%, with specific ranges such as 0.006~0.008wt%, 0.04~0.07wt%, etc.

[0099] By controlling the zinc content of the aluminum tube substrate layer to a low level, a high self-corrosion potential is ensured, making it less susceptible to corrosion during use and thus extending the service life of the aluminum tube.

[0100] In some non-limiting embodiments of the present invention, the aluminum alloy used for the aluminum tube substrate layer is such as 1050, 1060, 3003, 3103, 3026, etc.

[0101] In some embodiments of the present invention, the grain size in the aluminum tube substrate layer is ≤50μm; in some specific embodiments of the present invention, the grain size in the aluminum tube substrate layer is ≤30μm; in some examples of the present invention, the grain size in the aluminum tube substrate layer is 1 to 30μm; non-limiting specific examples include 5μm, 10μm, 15μm, 20μm or 25μm.

[0102] In this invention, the grains in the aluminum tube substrate layer refer to the α phase (aluminum solid solution) in its microstructure, which is the main phase in aluminum alloys. The grain size is related to the mechanical properties and corrosion resistance of the material. Generally, the smaller the grain size, the higher the strength and the better the corrosion resistance. Controlling the grain size of the aluminum tube substrate layer within a specific range can improve the mechanical properties and corrosion resistance of the aluminum tube, and also enhance the appearance quality of the aluminum tube.

[0103] In some embodiments of the present invention, the potential of the zinc-impregnated layer gradually increases from the outside to the inside; in some specific embodiments of the present invention, the surface potential of the zinc-impregnated layer is ≤-860mV, and the potential increases sequentially from the outside to the inside, with the highest potential being ≥-750mV.

[0104] The zinc concentration in an aluminum tube is inversely proportional to its potential. Since the zinc-diffused layer has a zinc concentration gradient that gradually decreases from the outside to the inside, the potential of the zinc-diffused layer gradually increases from the outside to the inside. By controlling the zinc concentration of the zinc-diffused layer, the potential can be adjusted, thereby making the outer layer of the zinc-diffused layer corrode preferentially over the inner layer, thus achieving the effect of inhibiting pitting corrosion and improving corrosion resistance.

[0105] In some embodiments of the present invention, the potential difference between the aluminum tube substrate layer and the lowest potential of the zinc-impregnated layer is ≥30mV; in some specific embodiments of the present invention, the potential difference between the aluminum tube substrate layer and the lowest potential of the zinc-impregnated layer is 30-300mV; in some examples of the present invention, the potential of the aluminum tube substrate layer is ≥-750mV, the lowest potential of the zinc-impregnated layer is ≤-860mV, and the potential difference between the two is ≥110mV.

[0106] By adjusting the potential difference at different parts of the aluminum tube, the location and rate of corrosion can be controlled. Maintaining a certain potential difference between the outer layer of the aluminum tube and the substrate can prevent corrosion of the aluminum tube substrate. If the potential difference is too small, the zinc-impregnated outer layer cannot fully act as a sacrificial anode, and some of the substrate will still corrode, leading to leakage.

[0107] In some embodiments of the present invention, the zinc content of the aluminum tube is 0.01 to 1 wt%; in some specific embodiments of the present invention, the zinc content of the tube is 0.05 to 0.9 wt%; in some examples of the present invention, the zinc content of the tube is 0.2 to 0.8 wt%; non-limiting specific examples include 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, or 0.7 wt%.

[0108] The zinc content of an aluminum tube refers to the ratio of the mass of zinc in the aluminum tube to the total mass of the aluminum tube. By controlling the zinc content of the aluminum tube within a specific range, the alloy composition of the aluminum tube and its overall performance can be controlled, giving it both good mechanical strength and corrosion resistance.

[0109] In some embodiments of the present invention, the cross-sectional shape of the aluminum tube includes at least one of a circle, a rectangle, or an ellipse.

[0110] The aluminum tube of this invention can have various cross-sectional shapes, including but not limited to circular, rectangular, and elliptical shapes. In some embodiments of this invention, the zinc-impregnated layer is particularly suitable for aluminum tubes with circular, rectangular, or elliptical cross-sectional shapes, effectively preventing pitting corrosion in the aluminum tube and achieving good corrosion resistance.

[0111] In some embodiments of the present invention, the inner wall of the aluminum tube is not threaded, or at least a portion of the inner wall is threaded.

[0112] The aluminum tube has threads on its inner wall, making it an internally threaded aluminum tube. This allows the fluid to rotate as it flows inside the tube, using centrifugal force to push water droplets in the vapor flow towards the tube wall, replenishing the water film, increasing fluid turbulence, improving the convective heat transfer coefficient, enhancing the heat transfer effect, and resulting in better cooling of the tube wall and excellent heat transfer performance. Alternatively, the aluminum tube of this invention can also be without threads, i.e., a plain aluminum tube can be used.

[0113] In some embodiments of the present invention, when at least a portion of the inner wall of the aluminum tube is provided with threads, the threads on the inner wall of the aluminum tube satisfy at least one of the following conditions: 1) the thread tooth height is 0.03 to 0.3 mm; 2) the thread tooth tip angle is 10 to 160°; 3) the thread helix angle is 1 to 65°; 4) the number of thread teeth is 18 to 72. In some specific embodiments of the present invention, when at least a portion of the inner wall of the aluminum tube is provided with threads, the threads on the inner wall of the aluminum tube simultaneously satisfy the following conditions: 1) the thread tooth height is 0.03 to 0.3 mm; 2) the thread tooth tip angle is 10 to 160°; 3) the thread helix angle is 1 to 65°; 4) the number of thread teeth is 18 to 72.

[0114] In some specific embodiments of the present invention, the tooth height of the thread is 0.04 to 0.28 mm; in some examples of the present invention, the tooth height of the thread is 0.05 to 0.25 mm; non-limiting specific examples include 0.1 mm, 0.15 mm, 0.2 mm or 0.22 mm.

[0115] In some specific embodiments of the present invention, the tooth tip angle of the thread is 15 to 145°; in some examples of the present invention, the tooth tip angle of the thread is 23 to 135°; non-limiting specific examples include 30°, 50°, 70°, 100° or 120°.

[0116] In some specific embodiments of the present invention, the helix angle of the thread is 3 to 60°; in some examples of the present invention, the helix angle of the thread is 5 to 50°; non-limiting specific examples include 6°, 10°, 12°, 14°, 20°, 30° or 40°.

[0117] In some specific embodiments of the present invention, the number of teeth on the thread is 20 to 70; in some examples of the present invention, the number of teeth on the thread is 25 to 60; non-limiting specific examples include 30, 35, 40, 45 or 50.

[0118] Adjusting the various parameters of the thread can achieve better convection and heat transfer effects.

[0119] In some embodiments of the present invention, the diameter of the aluminum tube is 1 to 20 mm; in some specific embodiments of the present invention, the diameter of the aluminum tube is 2 to 15 mm; non-limiting specific examples include 3 mm, 5 mm, 7 mm, 9.54 mm or 12.7 mm.

[0120] In some embodiments of the present invention, the wall thickness of the aluminum tube is ≥0.1mm; in some specific embodiments of the present invention, the wall thickness of the aluminum tube is 0.1~1mm; in some examples of the present invention, the wall thickness of the aluminum tube is 0.4~1mm; non-limiting specific examples include 0.5mm, 0.64mm, 0.7mm, 0.8mm or 0.9mm, and specific ranges include 0.4~0.5mm, 0.64~1mm, etc.

[0121] By comprehensively controlling parameters such as the diameter and wall thickness of the aluminum tube, the aluminum tube has good corrosion resistance as well as good mechanical strength, which prevents the aluminum tube from collapsing or leaking before reaching its expected lifespan during long-term service, thus ensuring that the aluminum tube has a long service life.

[0122] In some embodiments of the present invention, the single-tube ultimate pressure resistance value of the aluminum tube is ≥13MPa; in some specific embodiments of the present invention, the single-tube ultimate pressure resistance value of the aluminum tube is 13 to 30MPa; non-limiting specific examples include 15MPa, 20MPa, 22MPa, 25MPa or 28MPa.

[0123] The aluminum tube provided by this invention has good pressure resistance, which provides more possibilities for the service scenarios of aluminum tubes.

[0124] In some embodiments of the present invention, the yield strength of the aluminum tube is 50 to 130 MPa; non-limiting specific examples include 60 MPa, 70 MPa, 90 MPa, 100 MPa or 120 MPa.

[0125] In some embodiments of the present invention, the tensile strength of the aluminum tube is 80-250 MPa; in some specific embodiments of the present invention, the tensile strength of the aluminum tube is 95-170 MPa; non-limiting specific examples include 100 MPa, 120 MPa, 140 MPa, 150 MPa or 160 MPa.

[0126] In some embodiments of the present invention, the elongation of the aluminum tube is ≥20%; in some specific embodiments of the present invention, the elongation of the aluminum tube is ≥25%; in some examples of the present invention, the elongation of the aluminum tube is 25-50%; non-limiting specific examples include 30%, 35%, 40% or 45%.

[0127] The aluminum tube provided by this invention has good mechanical properties, such as good yield strength, tensile strength or elongation, which is beneficial to improving the service life of the aluminum tube.

[0128] In some embodiments of the present invention, the aluminum tube includes at least one of the following: internally threaded aluminum tube, plain aluminum tube, copper-aluminum connected aluminum tube, or air conditioning aluminum connecting tube.

[0129] Internally threaded aluminum tubes are aluminum tubes with threads on their inner walls. This allows the fluid to rotate as it flows inside the tube, thereby enhancing heat transfer and improving the cooling of the tube wall, resulting in excellent heat transfer performance.

[0130] In some specific examples of the present invention, the diameter of the internally threaded aluminum tube is 2 to 10 mm; non-limiting specific examples include 5 ± 0.05 mm, 7 ± 0.06 mm or 9.54 mm.

[0131] In some embodiments of the present invention, the wall thickness of the internally threaded aluminum tube is 0.1 to 1 mm; in some specific embodiments of the present invention, the wall thickness of the internally threaded aluminum tube is 0.4 to 0.5 mm; non-limiting specific examples include 0.40 ± 0.03 mm or 0.47 ± 0.03 mm.

[0132] In some embodiments of the present invention, under the condition of holding pressure for 1 minute, the single-tube ultimate pressure resistance value of the internally threaded aluminum tube is 13-15 MPa; more specifically, 13 MPa.

[0133] In some embodiments of the present invention, the yield strength of the internally threaded aluminum tube is 50-80 MPa.

[0134] In some embodiments of the present invention, the tensile strength of the internally threaded aluminum tube is 100-130 MPa.

[0135] In some embodiments of the present invention, the elongation of the internally threaded aluminum tube is ≥32%.

[0136] Plain aluminum tubes refer to aluminum tubes without threads on their inner wall, and have good weldability and machinability.

[0137] In some specific examples of the present invention, the diameter of the plain aluminum tube is 2 to 10 mm; non-limiting specific examples include 5 ± 0.05 mm or 7 ± 0.06 mm.

[0138] In some embodiments of the present invention, the wall thickness of the plain aluminum tube is 0.64 to 1.1 mm; non-limiting specific examples include 0.64 ± 0.05 mm, 1.00 ± 0.08 mm or 0.70 ± 0.08 mm.

[0139] In some embodiments of the present invention, under a pressure holding condition of 1 minute, the single tube ultimate pressure resistance value of the plain aluminum tube is 13 to 15 MPa; more specifically, 13 MPa.

[0140] In some embodiments of the present invention, the yield strength of the plain aluminum tube is 50-80 MPa.

[0141] In some embodiments of the present invention, the tensile strength of the plain aluminum tube is 100-130 MPa.

[0142] In some embodiments of the present invention, the elongation of the bare aluminum tube is ≥32%.

[0143] Copper-aluminum connecting pipes refer to a type of pipe material that connects copper pipes (copper-aluminum connecting copper pipes) and aluminum pipes (copper-aluminum connecting aluminum pipes). The connection can be achieved through processes such as cold drawing and welding. Copper pipes offer advantages such as good thermal conductivity and high corrosion resistance, while aluminum pipes offer advantages such as low density, light weight, and ease of processing.

[0144] In some specific examples of the present invention, the diameter of the copper-aluminum connecting aluminum tube is 2 to 10 mm; non-limiting specific examples include 5 ± 0.05 mm or 7 ± 0.06 mm.

[0145] In some embodiments of the present invention, the wall thickness of the aluminum tube connecting the copper and aluminum is 0.64 to 1.1 mm; non-limiting specific examples include 0.64 ± 0.05 mm, 1.00 ± 0.08 mm or 0.70 ± 0.08 mm.

[0146] In some embodiments of the present invention, under the condition of holding pressure for 1 minute, the single-tube ultimate pressure resistance value of the copper-aluminum connecting aluminum tube is 13-15 MPa; more specifically, it is 13 MPa.

[0147] In some embodiments of the present invention, the yield strength of the copper-aluminum connecting aluminum tube is 50-80 MPa.

[0148] In some embodiments of the present invention, the tensile strength of the copper-aluminum connecting aluminum tube is 95-130 MPa.

[0149] In some embodiments of the present invention, the elongation of the copper-aluminum connecting aluminum tube is ≥25%.

[0150] Air conditioner aluminum connecting pipes have advantages in welding technology, and because the refrigerant does not contain moisture, the inner wall of the air conditioner aluminum connecting pipe is less likely to corrode, resulting in a significant advantage in service life.

[0151] In some specific examples of the present invention, the diameter of the air conditioner aluminum connecting pipe is 2 to 13 mm; non-limiting specific examples include 6.35±0.12 mm, 9.52±0.12 mm or 12.7±0.15 mm.

[0152] In some embodiments of the present invention, the wall thickness of the air conditioning aluminum connecting pipe is 0.64 to 1.1 mm; non-limiting specific examples include 1 ± 0.19 mm.

[0153] In some embodiments of the present invention, under the condition of holding pressure for 1 minute, the single-pipe ultimate pressure resistance value of the air conditioning aluminum connecting pipe is 13-15 MPa; more specifically, it is 13 MPa.

[0154] In some embodiments of the present invention, the yield strength of the air conditioning aluminum connecting pipe is 50-80 MPa.

[0155] In some embodiments of the present invention, the tensile strength of the air conditioning aluminum connecting pipe is 95-130 MPa.

[0156] In some embodiments of the present invention, the elongation of the air conditioning aluminum connecting pipe is ≥30%.

[0157] In some embodiments of the present invention, the aluminum tube with a wall thickness of 0.4–0.5 mm exhibits a leakage duration of ≥1000 h in seawater acidic salt spray tests; in some specific embodiments of the present invention, the aluminum tube with a wall thickness of 0.4–0.5 mm exhibits a leakage duration of ≥1500 h in seawater acidic salt spray tests; in some examples of the present invention, the aluminum tube with a wall thickness of 0.4–0.5 mm exhibits a leakage duration of 1500–3000 h in seawater acidic salt spray tests; non-limiting specific examples include 1800 h, 2000 h, 2200 h, 2500 h, or 2800 h.

[0158] In some embodiments of the present invention, the corrosion depth of the aluminum tube in a 500-hour seawater acidic salt spray test is ≤180 μm; in some specific embodiments of the present invention, the corrosion depth of the aluminum tube in a 500-hour seawater acidic salt spray test is ≤150 μm; in some examples of the present invention, the corrosion depth of the aluminum tube in a 500-hour seawater acidic salt spray test is 50–150 μm; non-limiting specific examples include 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, or 140 μm.

[0159] The aluminum tube provided by this invention has a long leakage time and good leakage resistance in seawater acidic salt spray tests; and it has a small corrosion depth in long-term seawater acidic salt spray tests, with good corrosion resistance and long service life.

[0160] A second aspect of the present invention provides a method for preparing an aluminum tube according to the first aspect of the present invention, comprising the following steps: sequentially subjecting an aluminum tube substrate to zinc spraying and zinc diffusion treatment to obtain an aluminum tube.

[0161] The aluminum tube preparation method of this invention can produce aluminum tubes with good corrosion resistance and long service life, and the preparation process is simple and easy to implement.

[0162] In some embodiments of the present invention, the zinc spraying amount for zinc spraying treatment is 4–14 g / m³. 2 In some specific embodiments of the present invention, the zinc spraying amount for zinc spraying treatment is 6-13 g / m³. 2 In some examples of this invention, the zinc spraying amount for zinc spraying treatment is 8–12 g / m³. 2 Non-limiting specific examples include 9g / m³ 2 10g / m 2 Or 11g / m 2 .

[0163] By controlling the specific amount of zinc sprayed, the zinc content of the aluminum tube can be adjusted, as well as the distribution and concentration of zinc in the zinc-infiltrated layer, thereby giving the material a suitable potential and good corrosion resistance.

[0164] In some embodiments of the present invention, the zinc layer formed by zinc spraying has a coverage area of ​​≥50% on the surface of the aluminum tube substrate; the zinc layer formed by zinc spraying has a coverage area of ​​≥85% on the surface of the aluminum tube substrate; in some examples of the present invention, the zinc layer formed by zinc spraying has a coverage area of ​​85-100% on the surface of the aluminum tube substrate; non-limiting specific examples include 88%, 90%, 92%, 95% or 98%.

[0165] The percentage of zinc coverage area on the surface of the aluminum tube substrate also affects the penetration and distribution of zinc. Keeping the percentage of zinc coverage area within a specific range can improve the distribution of zinc in the zinc-infiltrated layer, thereby giving the material a suitable potential and good corrosion resistance.

[0166] In some embodiments of the present invention, the zinc spraying treatment includes arc zinc spraying, electroplating, or a combination thereof; in some specific embodiments of the present invention, the zinc spraying treatment is selected from arc zinc spraying.

[0167] Figure 2 This is a schematic diagram of the arc zinc spraying process in some specific embodiments of the present invention. The specific process is that, under the action of voltage and compressed air, the wire (specifically zinc wire) is pushed in the wire guide tube to form atomized metal particles, which are then sprayed onto the substrate through the nozzle to form a coating (zinc layer).

[0168] The specific parameters of the electric arc zinc spraying process can be adjusted according to the actual situation to meet the requirements of this invention for the amount of zinc sprayed or the zinc layer, thereby forming a structure such as a zinc-infiltrated layer with specific zinc distribution and specific potential characteristics, and improving the corrosion resistance of the aluminum tube.

[0169] In some embodiments of the present invention, the zinc diffusion treatment temperature is 300–600°C; in some specific embodiments of the present invention, the zinc diffusion treatment temperature is 350–550°C; in some examples of the present invention, the zinc diffusion treatment temperature is 400–500°C; non-limiting specific examples include 410°C, 430°C, 450°C, 470°C, or 490°C.

[0170] In some embodiments of the present invention, the zinc diffusion treatment time is 0.01 to 24 hours; in some specific embodiments of the present invention, the zinc diffusion treatment time is 0.1 to 18 hours; in some examples of the present invention, the zinc diffusion treatment time is 0.5 to 12 hours; non-limiting specific examples include 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, or 11 hours.

[0171] Zinc diffusion temperature and zinc diffusion time are important process parameters that affect the thickness of the zinc diffusion layer and have a significant impact on the distribution of zinc in the zinc diffusion layer. By using specific zinc diffusion temperature and zinc diffusion time, the zinc diffusion layer can meet the requirements of this invention, resulting in aluminum tubes and heat exchangers with good corrosion resistance and long service life.

[0172] In some embodiments of the present invention, the grain size in the aluminum tube substrate is ≤100μm; in some specific embodiments of the present invention, the grain size in the aluminum tube substrate is ≤30μm; in some examples of the present invention, the grain size in the aluminum tube substrate is 1 to 30μm; non-limiting specific examples include 5μm, 10μm, 15μm, 20μm or 25μm.

[0173] In some embodiments of the present invention, the aluminum tube substrate contains precipitated phases, and the grain size of the precipitated phases in the aluminum tube substrate is ≤10μm; in some specific embodiments of the present invention, the grain size of the precipitated phases in the aluminum tube substrate is ≤2.7μm; in some examples of the present invention, the grain size of the precipitated phases in the aluminum tube substrate is 0.1~2.7μm; non-limiting specific examples include 0.5μm, 1μm, 1.5μm, 2μm or 2.5μm.

[0174] Controlling the grain size and precipitated phase grain size in the aluminum tube substrate ensures that the substrate has a suitable crystal structure and mechanical strength, as well as a good zinc diffusion effect.

[0175] A third aspect of the present invention provides a heat exchanger comprising an aluminum tube according to the first aspect of the present invention.

[0176] The heat exchanger made from the aluminum tube of the first aspect of the present invention has good corrosion resistance, mechanical strength and service life.

[0177] In some embodiments of the present invention, the heat exchanger further includes fins, semi-circular tubes, or combinations thereof connected to aluminum tubes.

[0178] The aluminum tube provided by this invention can also be connected to fins to form a tube-fin heat exchanger, which can improve the heat transfer performance of the heat exchanger. Furthermore, it can be connected to a semi-circular tube; by connecting pipes of different shapes, heat exchange efficiency can be improved, and the functionality of the piping system can be expanded, such as by adding branches or circulation loops.

[0179] In some embodiments of the present invention, when the heat exchanger includes fins, the fins are connected to the aluminum tube through a zinc-dipped layer.

[0180] In some embodiments of the present invention, the method of connecting the fins to the aluminum tube is selected from expansion joint; in some specific embodiments of the present invention, the expansion joint steps include tube insertion and tube expansion.

[0181] In some embodiments of the present invention, the fin includes a fin substrate layer and a coating disposed on the surface of the fin substrate layer.

[0182] A coating is applied to the surface of the fin substrate layer to serve as a physical anti-corrosion layer and protect the fins.

[0183] In some embodiments of the present invention, the fin substrate layer is made of aluminum alloy.

[0184] In some embodiments of the present invention, the fin substrate layer is made of aluminum alloy; in some specific embodiments of the present invention, the aluminum alloy used in the fin substrate layer includes the following alloying elements by mass percentage: Si: ≤0.4wt%, Fe: ≤0.7wt%, Cu: ≤0.1wt%, Mn: 0.05~0.4wt%, Ti: ≤0.1wt%, Zn: ≤0.3wt%, and unavoidable impurity elements.

[0185] In some examples of the present invention, the aluminum alloy used for the fin substrate layer is 1030B, 3102 or 8011.

[0186] In some embodiments of the present invention, the raw materials for preparing the coating include acrylic resin, alcohol ether, or a combination thereof.

[0187] Acrylic resin, a hydrophilic material, is applied to the surface of the fin substrate layer to prevent moisture corrosion and improve corrosion resistance. Alcohol ethers are mainly used as solvents and film-forming aids, providing anti-fogging, anti-wrinkle, water-repellent properties, and enhancing coating gloss.

[0188] In some embodiments of the present invention, the raw materials for preparing the coating also include water.

[0189] In some embodiments of the present invention, when the heat exchanger includes a semi-circular tube, the semi-circular tube is connected to the aluminum tube through a solder zone.

[0190] The semi-circular tube and the aluminum tube are connected by a solder zone. The connection method is simple and easy to implement.

[0191] In some embodiments of the present invention, a solder zone is disposed at the cross-section of the aluminum tube. The solder zone connects the semi-circular tube and the aluminum tube. In some embodiments of the present invention, the raw materials for forming the solder zone include solder and flux.

[0192] In some embodiments of the present invention, the solder is selected from aluminum alloy solder; in some specific embodiments of the present invention, the aluminum alloy solder comprises the following alloying elements by mass percentage: Si: 11-13 wt%, Fe: 0.6-1 wt%, Cu: 0.1-0.5 wt%, Mn: 0.1-0.2 wt%, Mg: 0.05-0.2 wt%, Ti: 0.1-0.2 wt%, Zn: 0.1-0.3 wt%, and unavoidable impurity elements. In some examples of the present invention, the aluminum alloy solder is selected from aluminum alloy 4047.

[0193] In some embodiments of the present invention, the flux is selected from fluoride fluxes; in some specific embodiments of the present invention, the fluoride flux includes at least one of potassium fluoride (KF), aluminum fluoride (AlF3), potassium fluoroaluminate (KAlF4), cesium fluoroaluminate (CsAlF4) or potassium fluoroborate (KBF4); in some examples of the present invention, the fluoride flux is selected from potassium fluoroaluminate (KAlF4).

[0194] In some embodiments of the present invention, the mass ratio of solder to flux in the raw materials forming the solder zone is 1:(0.1 to 0.5); in some embodiments of the present invention, the mass ratio of solder to flux in the raw materials forming the solder zone is 1:(0.14 to 0.3); non-limiting specific examples include 1:0.15, 1:0.18, 1:0.2, 1:0.23 or 1:0.27.

[0195] In some embodiments of the present invention, the soldering temperature for forming the solder zone is 550–700°C; in some specific embodiments of the present invention, the soldering temperature for forming the solder zone is 580–680°C; in some examples of the present invention, the soldering temperature for forming the solder zone is 600–640°C; non-limiting specific examples include 610°C, 620°C, or 630°C.

[0196] Choosing the right solder, flux, and welding temperature can improve the welding effect of semi-circular tubes and aluminum tubes, and reduce the impact on the zinc concentration and potential distribution of the zinc-infiltrated layer on the aluminum tube surface, thus ensuring the corrosion resistance and service life of the aluminum tube.

[0197] In some embodiments of the present invention, after the semi-circular tube is connected to the aluminum tube through the solder area, the potential difference between the potential of the solder area and the potential of the aluminum tube surface is 0 to 100 mV.

[0198] Semicircular pipes refer to pipes with a semicircular cross-sectional shape. Due to their special shape, they can provide good load-bearing capacity and an aesthetically pleasing appearance. They can also improve heat exchange efficiency and expand the functionality of the piping system, such as adding branches or circulation loops.

[0199] In some specific examples of the present invention, the diameter of the semicircular tube is 2 to 10 mm; non-limiting specific examples include 5 ± 0.05 mm or 7 ± 0.06 mm.

[0200] In some embodiments of the present invention, the wall thickness of the semicircular tube is 0.64 to 1.1 mm; a non-limiting specific example is 1.00 ± 0.08 mm.

[0201] In some embodiments of the present invention, under the condition of holding pressure for 1 minute, the single-tube ultimate pressure resistance value of the semi-circular tube is 13-15 MPa; more specifically, 13 MPa.

[0202] In some embodiments of the present invention, the yield strength of the semicircular tube is 50-80 MPa.

[0203] In some embodiments of the present invention, the tensile strength of the semicircular tube is 95-130 MPa.

[0204] In some embodiments of the present invention, the elongation of the semi-circular tube is ≥30%.

[0205] A fourth aspect of the present invention provides a temperature regulating device, including an aluminum tube according to the first aspect of the present invention or a heat exchanger according to the third aspect of the present invention.

[0206] By incorporating aluminum tubes or heat exchangers into temperature control devices, excellent temperature regulation can be achieved, and the corrosion resistance of the temperature control devices can be effectively improved, greatly extending their service life.

[0207] In some embodiments of the present invention, the temperature regulating device includes at least one of a refrigerator, an air conditioner, or a water heater.

[0208] The following description, in conjunction with specific embodiments, provides further details.

[0209] Example 1

[0210] An aluminum tube is produced by the following steps:

[0211] Step 1: Select a suitable aluminum tube substrate. In this embodiment, an internally threaded aluminum tube was selected as the substrate material. The material is 3103 aluminum alloy, which has good thermal conductivity and corrosion resistance. The cross-sectional view of the internally threaded aluminum tube in this embodiment is shown below. Figure 3 As shown, the diameter of the internally threaded aluminum tube is 5±0.05mm or 7±0.06mm; the wall thickness is 0.40±0.03mm or 0.47±0.03mm; the thread tooth height is 0.05mm, 0.1mm or 0.25mm; the thread tooth tip angle is 28~130°±5°; the thread helix angle is 6±2°, 10±2° or 12±2°; the number of thread teeth is 40 or 50; the ultimate pressure of the internally threaded aluminum tube after holding pressure for 1 minute is 13.0MPa; the yield strength of the internally threaded aluminum tube is 50~80MPa, the tensile strength is 100~130MPa, and the elongation is ≥32%.

[0212] Step Two: Surface zinc spraying treatment of the aluminum tube. Using an electric arc zinc spraying method, zinc is evenly sprayed onto the surface of the aluminum tube, with the zinc spraying amount controlled at 2±2 g / m. 2 However, it is necessary to ensure that the amount of zinc sprayed is not zero.

[0213] Step 3: Perform zinc diffusion treatment. Place zinc-aluminum pipes with different zinc spraying amounts into the zinc diffusion furnace, adjust the zinc diffusion temperature to 500℃, and the zinc diffusion time to 6 hours, so that the zinc diffusion depth (i.e., the thickness of the zinc diffusion layer) ranges from 100 to 300 μm, and the maximum zinc concentration of the zinc diffusion layer is in the range of 0.5 to 5 wt%.

[0214] Step 4: Control the Zn content in the substrate, ensuring that the zinc content in the substrate is ≤0.2wt%.

[0215] Step 5: Control the grain size of the aluminum tube substrate. Control the grain size of the crystalline phase of the aluminum tube substrate to within 30μm and the grain size of the precipitated phase to within 2.7μm.

[0216] Step Six: Monitoring and Controlling Key Parameters. The zinc penetration depth is characterized using EPMA (electron probe microanalysis), and the overall zinc content of the aluminum tube is determined using ICP (inductively coupled plasma atomic emission spectrometry) results to ensure the effectiveness of the zinc spraying and zinc penetration treatments. The zinc content of the aluminum tube is controlled within the range of 0.01–0.8 wt%, and the surface potential of the zinc-treated aluminum tube is controlled to be ≤-860 mV. From the surface inwards, the potential increases sequentially, with the highest potential ≥-750 mV.

[0217] The final aluminum tube product is obtained through the above steps.

[0218] Example 2

[0219] An aluminum tube, differing from Example 1 in that the zinc spraying amount used in step two of this example is 4±2 g / m. 2 The remaining materials and steps are the same as in Example 1.

[0220] Example 3

[0221] An aluminum tube, differing from Example 1 in that the zinc spraying amount used in step two of this example is 6±2 g / m. 2 The remaining materials and steps are the same as in Example 1.

[0222] Example 4

[0223] An aluminum tube, differing from Example 1 in that the zinc spraying amount used in step two of this example is 8±2 g / m. 2 The remaining materials and steps are the same as in Example 1.

[0224] Example 5

[0225] An aluminum tube, differing from Example 1 in that the zinc spraying amount used in step two of this example is 10±2 g / m. 2 The remaining materials and steps are the same as in Example 1.

[0226] Example 6

[0227] An aluminum tube, differing from Example 1 in that the zinc spraying amount used in step two of this example is 12±2 g / m. 2 The remaining materials and steps are the same as in Example 1.

[0228] EPMA (electron probe microanalysis) was used to characterize the zinc penetration depth. Figure 4 This is a graph showing the corrosion potential and zinc content of the aluminum tube in Embodiment 3 of the present invention as a function of zinc penetration depth. Zinc penetration depth refers to the depth measured from the outer surface of the zinc penetration layer inwards. Figure 4 It is evident that aluminum tubes have a high-zinc surface region. In this high-zinc surface region, the zinc-infiltrated layer of the aluminum tube has the highest zinc concentration. As the zinc infiltration depth increases, the zinc content gradually decreases, while the corrosion potential gradually increases. The zinc concentration in the aluminum tube is inversely proportional to its potential. Adjusting the zinc concentration in the aluminum tube can regulate the potential.

[0229] The corrosion resistance of the aluminum tubes obtained in Examples 1-6 was tested: Referring to Appendix A3 of ASTM / G85-2019, the zinc-treated aluminum tubes underwent a seawater acid salt spray test (SWAAT). The initial leakage time of each aluminum tube was used to represent its indoor accelerated life. The test results are as follows: Figure 5 As shown. Figure 5 The results of SWAAT tests on aluminum tubes with different zinc spraying amounts in Examples 1-6 show that the zinc spraying amount is between 4 and 12 g / m. 2At that time, the initial leakage time of the aluminum pipes reached 1000 hours or more, and the zinc spraying amount was 4-8 g / m. 2 At that time, the initial leakage time of the aluminum pipes reached 1500 hours or more, and the zinc spraying amount was 6 g / m. 2 At that time, aluminum tubes exhibit the best corrosion resistance, reaching 2000 hours or more.

[0230] As can be seen, in Examples 1 to 6, the aluminum tube has a wall thickness of 0.4 to 0.5 mm and a zinc spraying amount of 4 to 12 g / m. 2 Under the conditions of acidic salt spray testing in seawater, the leakage time is ≥1000h; with a wall thickness of 0.4~0.5mm and a zinc spraying amount of 4~8g / m 2 Under these conditions, the leakage duration in the seawater acidic salt spray test is ≥1500h. Furthermore, with a wall thickness of 0.4~0.5mm, the corrosion depth of the aluminum tube in the 500h seawater acidic salt spray test is ≤150μm.

[0231] Example 7

[0232] An aluminum tube, differing from Example 1 in that the zinc spraying amount used in step two of this example is 6±2 g / m. 2 In step three, the zinc diffusion time is adjusted so that the zinc diffusion depth (i.e. the thickness of the zinc diffusion layer) of the aluminum tube is 60 μm. The other steps are the same as in Example 1.

[0233] Example 8

[0234] An aluminum tube differs from Example 7 in that the zinc diffusion time is adjusted in step three of this example so that the zinc diffusion depth (i.e., the thickness of the zinc diffusion layer) of the aluminum tube is 165 μm, while the other steps are the same as in Example 7.

[0235] Example 9

[0236] An aluminum tube differs from Example 7 in that the zinc diffusion time is adjusted in step three of this example so that the zinc diffusion depth (i.e., the thickness of the zinc diffusion layer) of the aluminum tube is 240 μm, while the other steps are the same as in Example 7.

[0237] Example 10

[0238] An aluminum tube differs from Example 7 in that the zinc diffusion time is adjusted in step three of this example so that the zinc diffusion depth (i.e., the thickness of the zinc diffusion layer) of the aluminum tube is 355 μm, while the other steps are the same as in Example 7.

[0239] EPMA (electron probe microanalysis) was used to characterize the zinc penetration depth. Figure 6 The graph shows the zinc concentration profile of the cross-section of the aluminum tube with a zinc penetration depth of 355 μm in Example 10. Additionally, referring to Appendix A3 of ASTM / G85-2019, the aluminum tubes obtained in Examples 7-10 were subjected to a seawater acidic salt spray test (SWAAT), and the initial leakage time of each aluminum tube was recorded. The results are shown below.Figure 7 As shown, Figure 7 The SWAAT test results for aluminum tubes with different zinc penetration depths in Examples 7-10 are shown. The results indicate that different zinc penetration depths affect the corrosion resistance of the aluminum tubes. In this example, when the zinc penetration depth is in the range of 165-355 μm, the initial leakage time of the aluminum tubes is over 1000 hours, and they all have good corrosion resistance. Furthermore, when the zinc penetration depth is in the range of 165-240 μm, the initial leakage time of the aluminum tubes is over 1400 hours, and the corrosion resistance is even better. It can be seen that the zinc penetration depth should be kept within a certain range. If the zinc penetration depth is too low or too high, the anodic protection effect of the zinc layer on the aluminum tube will be affected, and the corrosion resistance life of the aluminum tube will also be reduced.

[0240] The aluminum tubes in Examples 1-10 have good corrosion resistance and service life. When used as components of a heat exchanger, they can achieve good heat exchange and heat transfer effects, while also giving the heat exchanger good corrosion resistance and service life.

[0241] Example 3

[0242] A heat exchanger includes an aluminum tube, fins, and a semi-circular tube. The fins are connected to the aluminum tube via a zinc-dipped layer, and the semi-circular tube is connected to the aluminum tube via a solder zone. The aluminum tube is the same as the one prepared in Example 1. The fins consist of a fin substrate layer and a coating applied to the surface of the fin substrate layer. The fin substrate layer is made of 3102 aluminum alloy, and the coating is a hydrophilic acrylic resin coating. The aluminum tube and fins are connected using a tube-through and tube-expansion process. The raw materials forming the solder zone include solder and flux. The solder is an aluminum alloy solder, specifically 4047 aluminum alloy; the flux is a fluoride flux, specifically potassium fluoroaluminate (KAlF4), with a flux mass percentage of 13-17 wt%. Using the above-mentioned solder and flux, the aluminum tube and the semi-circular tube are welded at 600-640°C to obtain the heat exchanger in this example. In this example heat exchanger, the potential difference between the solder zone and the outer surface potential of the zinc-dipped aluminum tube is 0–100 mV.

[0243] The embodiments of the present invention form a zinc-impregnated layer of specific thickness and specific zinc concentration on the surface of the aluminum tube substrate, which has good corrosion resistance and leakage resistance, as well as good mechanical properties such as pressure resistance and tensile strength. After the aluminum tube is made into a heat exchanger, it can achieve good temperature regulation effect and effectively improve the corrosion resistance of the heat exchanger, greatly extending its service life. The aluminum tube and heat exchanger provided in the embodiments of the present invention have wide applications in the preparation of high-performance temperature regulation devices (such as refrigerators, air conditioners or water heaters).

[0244] In the aluminum tubes provided in this embodiment of the invention, because the self-corrosion potential of high-zinc-content aluminum tubes is more negative during the corrosion process, the outer layer of the zinc-diffused layer acts as the anode and corrodes preferentially. The self-corrosion potential of low-zinc-content aluminum tubes is more positive, and the inner layer of the zinc-diffused layer is less prone to corrosion. By setting the corrosion rates of the inner and outer layers, pitting corrosion, which is prone to occur in ordinary aluminum tubes, is suppressed. Corrosion is more likely to spread laterally to the surface of the aluminum tube rather than longitudinally to the interior. The corrosion occurring in the aluminum tubes of this embodiment of the invention is close to uniform corrosion, which can effectively suppress the occurrence of pitting corrosion, greatly improve the service life of the aluminum tubes, and the manufacturing cost of aluminum tubes is low, which is conducive to replacing copper tubes as the main material of heat exchangers.

[0245] In summary, this invention, by forming a zinc-infiltrating layer on the surface of the aluminum tube substrate, can limit the propagation of corrosion into the inner layer and prevent longitudinal corrosion, thereby inhibiting pitting corrosion. Furthermore, this invention can control the zinc content distribution at different zinc infiltration depths by controlling the maximum zinc concentration and thickness of the zinc-infiltrating layer, enabling the zinc-infiltrating layer to provide excellent anodic protection for the aluminum tube, effectively inhibiting pitting corrosion propagation, improving the corrosion resistance of the aluminum tube, and extending its service life.

Claims

1. An aluminum tube, characterized in that, It includes an aluminum tube substrate layer and a zinc-impregnated layer disposed on the surface of the aluminum tube substrate layer; the zinc-impregnated layer has a zinc concentration gradient that gradually decreases from the outside to the inside; the maximum zinc concentration of the zinc-impregnated layer is 0.01 to 10 wt%; the thickness of the zinc-impregnated layer is greater than 0 and less than or equal to 400 μm.

2. The aluminum tube according to claim 1, characterized in that, The aluminum tube substrate layer is made of aluminum alloy, and the aluminum alloy used in the aluminum tube substrate layer includes the following alloying elements by mass percentage: Si: 0.01~0.6wt%, Fe: 0.01~0.6wt%, Mn: ≤1.5wt%, Ti: 0.005~0.3wt%, Cu: ≤0.1wt%, and unavoidable impurity elements.

3. The aluminum tube according to claim 2, characterized in that, The total content of impurity elements in the aluminum alloy used in the aluminum tube substrate layer is ≤0.15wt%. And / or, in the aluminum alloy used for the aluminum tube substrate layer, the content of a single impurity element is ≤0.05wt%.

4. The aluminum tube according to claim 2, characterized in that, The aluminum alloy used in the aluminum tube substrate layer also includes zinc as an alloying element, and the zinc content is ≤0.5wt%.

5. The aluminum tube according to claim 1, characterized in that, The grain size in the aluminum tube substrate layer is ≤50μm.

6. The aluminum tube according to claim 1, characterized in that, The potential difference between the aluminum tube substrate layer and the lowest potential of the zinc-impregnated layer is ≥30mV.

7. The aluminum tube according to any one of claims 1 to 6, characterized in that, The zinc content of the aluminum tube is 0.01 to 1 wt%.

8. The aluminum tube according to any one of claims 1 to 6, characterized in that, The cross-sectional shape of the aluminum tube includes at least one of circular, rectangular, or elliptical shapes.

9. The aluminum tube according to claim 8, characterized in that, The inner wall of the aluminum tube is not threaded, or at least a portion of the inner wall is threaded.

10. The aluminum tube according to claim 9, characterized in that, When at least a portion of the inner wall of the aluminum tube is provided with threads, the threads on the inner wall of the aluminum tube satisfy at least one of the following conditions: 1) the tooth height of the threads is 0.03 to 0.3 mm; 2) The tooth tip angle of the thread is 10 to 160°; 3) The helix angle of the thread is 1 to 65°; 4) The number of teeth of the thread is 18 to 72.

11. The aluminum tube according to claim 8, characterized in that, The diameter of the aluminum tube is 1-20 mm; And / or, the wall thickness of the aluminum tube is ≥0.1mm.

12. The aluminum tube according to any one of claims 1 to 6, characterized in that, The single-tube ultimate pressure resistance value of the aluminum tube is ≥13MPa.

13. The aluminum tube according to any one of claims 1 to 6, characterized in that, The yield strength of the aluminum tube is 50–130 MPa; And / or, the tensile strength of the aluminum tube is 80–250 MPa; And / or, the elongation of the aluminum tube is ≥20%.

14. The aluminum tube according to any one of claims 1 to 6, characterized in that, The aluminum tube, with a wall thickness of 0.4–0.5 mm, exhibits a leakage duration of ≥1000 h in seawater acidic salt spray testing. And / or, the corrosion depth of the aluminum tube in a 500-hour seawater acidic salt spray test is ≤180μm.

15. A method for preparing an aluminum tube as described in any one of claims 1 to 14, characterized in that, Includes the following steps: The aluminum tube substrate is subjected to zinc spraying and zinc diffusion treatment in sequence to obtain the aluminum tube.

16. The preparation method according to claim 15, characterized in that, The zinc spraying amount for the zinc spraying treatment is 4–14 g / m³. 2 .

17. The preparation method according to claim 15, characterized in that, The zinc layer formed by the zinc spraying process covers an area of ​​≥50% of the surface of the aluminum tube substrate.

18. The preparation method according to claim 15, characterized in that, The zinc diffusion treatment temperature is 300–600°C; And / or, the zinc diffusion treatment time is 0.01 to 24 hours.

19. The preparation method according to claim 15, characterized in that, The grain size in the aluminum tube substrate is ≤50μm.

20. The preparation method according to claim 15, characterized in that, The aluminum tube substrate contains precipitated phases, and the grain size of the precipitated phases in the aluminum tube substrate is ≤10μm.

21. A heat exchanger, characterized in that, Includes the aluminum tube as described in any one of claims 1 to 14.

22. The heat exchanger according to claim 21, characterized in that, It also includes fins, semi-circular tubes, or combinations thereof connected to the aluminum tube.

23. The heat exchanger according to claim 22, characterized in that, When the heat exchanger includes the fins, the fins are connected to the aluminum tube through a zinc-diffused layer; the fins include a fin substrate layer and a coating disposed on the surface of the fin substrate layer; the material of the fin substrate layer is aluminum alloy; and / or, the raw materials for preparing the coating include acrylic resin, alcohol ether, or a combination thereof.

24. The heat exchanger according to claim 22, characterized in that, When the heat exchanger includes the semi-circular tube, the semi-circular tube is connected to the aluminum tube through a solder zone; the raw materials forming the solder zone include solder and flux; the solder is selected from aluminum alloy solder; and / or, the flux is selected from fluoride flux.

25. A temperature regulating device, characterized in that, It includes the aluminum tube as described in any one of claims 1 to 14 or the heat exchanger as described in any one of claims 21 to 24.

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