Aluminum alloy for air conditioners with high thermal conductivity and method for manufacturing the same

Abstract

The present invention discloses an aluminum alloy for air conditioners having high thermal conductivity, which contains as its components 0.08-0.5 wt.% Si, 0.15-1.0 wt.% Mg, 0.05-0.6 wt.% Fe (Mg / (Si+Fe)≦2.2), 0.005-0.2 wt.% Ti, and the balance Al, with a solute Mg content of ≦0.3%. The present invention also provides a method for producing an aluminum alloy for air conditioners having high thermal conductivity, and uses thereof. The aluminum alloy for air conditioners having high thermal conductivity of the present invention has excellent mechanical properties, satisfying strength and elongation characteristics, and thermal conductivity performance that is 10% or more higher than that of aluminum alloy foil for air conditioners of the prior art.

Description

Technical Field

[0001] The present invention relates to an aluminum alloy foil and a method for manufacturing the same, and particularly to an aluminum alloy for an air conditioner having high thermal conductivity and a method for manufacturing the same.

Background Art

[0002] With the development of China's economy and the continuous improvement of people's living standards, the penetration rate of air conditioners has been increasing year by year. Aluminum alloy has the advantages of low density, high specific strength, high thermal conductivity, easy processing, and high cost performance, so it is widely used in the manufacture of air conditioner heat exchange fins. In recent years, as air conditioners are becoming smaller, more efficient, and longer-lasting, the requirements for air conditioner heat exchange fins are gradually increasing, and aluminum foil for air conditioners is becoming thinner, having higher thermal conductivity, and higher formability.

[0003] Due to the special performance requirements of aluminum foil products for air conditioners, the requirements for thermal conductivity are high. The currently used aluminum foil for air conditioners is mainly Al-Mn-Fe-Si series aluminum alloys such as 3102 and 8011. Alloying elements such as Mn, Si, and Fe have a high content, so strengthening effects such as solid solution, grain refinement, and work hardening occur, but the thermal conductivity is impaired. Therefore, it is necessary to consider both the improvement of strength and elongation by alloying elements and the impairment to thermal conductivity. In addition, as the aluminum foil for air conditioners gradually becomes thinner, the requirements for its tensile strength, elongation rate, and surface hydrophilicity also increase accordingly, and the thickness accuracy is required to be 2% or less. Therefore, it is becoming increasingly difficult for existing Al-Mn-Fe-Si series aluminum alloys to meet the requirements.

[0004] Conventional aluminum foil for air conditioners is generally manufactured using either a hot rolling process or a cast rolling process. While the cast rolling process has a simple process flow and low energy consumption, the resulting product has unstable structure and performance. Coarse crystal grains tend to appear in the foil, resulting in extremely low deformation performance, a high susceptibility to cracking, and a significantly reduced yield. [Overview of the project] [Problems that the invention aims to solve]

[0005] In response to the shortcomings of the above-mentioned prior art, the present invention aims to provide an aluminum alloy for air conditioners that has high thermal conductivity, in order to solve the problem that conventional aluminum alloy foils have difficulty simultaneously meeting the requirements of high thermal conductivity, strength, and elongation. Another objective of the present invention is to provide a method for manufacturing an aluminum alloy for air conditioners that has high thermal conductivity. [Means for solving the problem]

[0006] The technical means of the present invention are as follows: The aluminum alloy for air conditioners having high thermal conductivity contains 0.08 to 0.5 wt.% Si, 0.15 to 1.0 wt.% Mg, 0.05 to 0.6 wt.% Fe (Mg / (Si+Fe) ≤ 2.2), 0.005 to 0.2 wt.% Ti, and the remainder Al, with a solid solution Mg amount ≤ 0.3%.

[0007] Furthermore, the aluminum alloy is in the H2x state, has an elongation of ≥14%, an Erichsen value of ≥5 mm, and a thermal conductivity of ≥210 W / (m·k).

[0008] Furthermore, the tensile strength of the aluminum alloy is 100 to 170 MPa.

[0009] Furthermore, the aluminum alloy further comprises at least one of ≤0.5 wt.% Cu and ≤0.4 wt.% Mn as its components.

[0010] Furthermore, the aluminum alloy further comprises at least one of ≤0.3 wt.% Zn, ≤0.3 wt.% Cr, and ≤0.3 wt.% Zr as components.

[0011] Furthermore, the aluminum alloy further contains ≤0.2 wt.% RE as a component.

[0012] Furthermore, the thickness of the aluminum alloy is 0.05 to 0.15 mm.

[0013] Furthermore, a hydrophilic coating layer is applied to the surface of the aluminum alloy. The hydrophilic coating layer can significantly improve the hydrophilicity and corrosion resistance of the surface. Preferably, graphene and silver ions may be added to further improve the thermal conductivity of the product and to obtain remarkable antibacterial and antifungal properties.

[0014] Furthermore, the above-mentioned aluminum alloy is used in the manufacture of air conditioner radiators.

[0015] A method for manufacturing an aluminum alloy for air conditioners having high thermal conductivity includes the steps of selecting raw materials, performing continuous casting and rolling to obtain a cast and rolled plate ingot, performing cold rough rolling, intermediate rolling, and finish rolling on the cast and rolled plate to obtain aluminum foil, and performing finished product annealing on the aluminum foil after rolling. When performing the continuous casting and rolling, the Ti content is controlled with aluminum titanium boron wire, the casting and rolling temperature is set to 670 to 715°C, the rolling speed is set to 0.3 to 1.2 m / min, the thickness of the cast and rolled plate ingot is controlled to 4.0 to 13.0 mm, and the grain size is controlled to Grade 1.

[0016] Furthermore, the annealing temperature of the finished product is set to 230-290°C, and the holding time is set to 9-15 hours.

[0017] The aluminum alloy of the present invention has Mg and Si as its main elements, where the Mg / (Si+Fe) value is less than 2.2 and the amount of solid-solution Mg is 0.3% or less.

[0018] The addition of Mg is primarily to form the Mg2Si precipitate phase. In the aluminum matrix, Fe and Si form α-AlFeSi and β-AlFeSi, with the added Fe consuming Si and reducing the amount of Mg2Si produced. Therefore, if Mg / (Si+Fe) > 2.2, there is a significant excess of Mg, the solid solution Mg content in the aluminum matrix is ​​> 0.3%, and lattice distortion is severe. The microscopic principle of metallic heat conduction is caused by the thermal motion of free electrons. Lattice distortion reduces the kinetic ability of heat conduction electrons, decreasing heat conduction performance. It also reduces the solubility of the Mg2Si precipitate phase, making the Mg2Si precipitate phase larger and coarser, thus reducing the strengthening effect. Therefore, by controlling the value of Mg / (Si+Fe) to less than 2.2 and controlling the solid solution amount of Mg to < 0.3%, Mg will not be in excess and will mainly form the alloy strengthening phase Mg2Si together with Si. The formation process of this phase is supersaturated solid solution (SS)-Mg,Si cluster-GP zone-metastable β'' phase-metastable β' phase-stable β(Mg2Si) phase. The β(Mg2Si) phase has no matching relationship with the matrix and completely detaches from it, eliminating matching strain. This reduces the degree of lattice strain within the lattice, decreasing the number and density of heat conduction electron scattering sources in the matrix lattice, increasing the free path of heat conduction electrons, and facilitating electron motion, thus guaranteeing high thermal conductivity.

[0019] When silicon (Si) is added to aluminum alloys, it can form various reinforcing particles together with other alloying elements, playing a positive role in improving mechanical properties. When the Mg / (Si+Fe) value is less than 2.2, Si mainly reacts with Mg to form the reinforcing phase Mg2Si, and is also in excess. However, the solubility of Si in aluminum alloys at room temperature is very low, and excess Si exists in the primary crystal form within α(Al), forming free Si particles. Excess Si can also promote the desolving of elements such as Mn, Fe, and Cr in the alloy, forming compounds and precipitation, thus reducing its impact on thermal conductivity. For example, Si reacts with Fe to form the AlFeSi phase, which enhances mechanical properties.

[0020] When the appropriate Fe content is within a certain range, it promotes the formation of crystal nuclei during the solidification process, resulting in grain refinement and improving the cast and rolled structure. The formed AlFeSi,FeAl3 strengthening phases help improve the mechanical properties of aluminum foil and can also reduce the degree of Mn segregation. However, as the Fe content increases, the primary phase in the matrix increases, which seriously affects the mechanical properties of the alloy.

[0021] Ti is added to aluminum alloys in the form of aluminum-titanium-boron wire, mainly together with Al to form Al2Ti and TiB2 phases. During crystallization, it acts as a non-spontaneous nucleation core, promoting heterogeneous nucleation, significantly refining the microstructure, and ensuring a first-grade grain size in the cast and rolled structure, thereby improving the formability of aluminum foil.

[0022] The first selected additive elements are Mn and Cu. Adding a small amount of Mn can create a uniformly dispersed Al6Mn phase, suppressing grain growth, significantly refining the microstructure, and improving the performance of aluminum foil. However, Mn is prone to segregation, causing microstructure inhomogeneity. Adding Cu can form an Al2Cu phase or CuAlGP zone, significantly improving the mechanical properties of the alloy. However, the AlCuGP zone is prone to maturation with the matrix and lattice distortion, reducing thermal conductivity. Furthermore, the AlCu phase is prone to precipitation at grain boundaries, leading to intergranular corrosion. Therefore, the amount of Mn and Cu added should be controlled.

[0023] The second selected additive elements are Zn, Cr, and Zr. The added Zn, together with Mg, forms a strengthening phase MgZn2, producing a significant strengthening effect. However, the Zn content significantly lowers the open-circuit potential of the aluminum alloy, reducing its corrosion resistance; therefore, the Zn content must be strictly controlled. Cr hardly dissolves in aluminum at room temperature, and the intermetallic compounds formed with Al can inhibit recrystallization nucleation and growth, improve the toughness of the aluminum alloy, and reduce its susceptibility to stress corrosion cracking. However, the added Cr degrades the surface quality of the aluminum foil, so its content must be strictly controlled. The main function of Zr is to refine the grain structure and inhibit recrystallization; however, the added Zr reduces the grain refinement effect of Ti, so its content should be controlled to 0.3% or less.

[0024] The third element selected is the rare earth element. Adding rare earth elements to aluminum alloys helps purify the molten material, lowers its surface tension, improves its fluidity, and is beneficial for casting, rolling, and forming. Furthermore, the Al3RE phase formed after adding rare earth elements to the aluminum alloy can act as a core for heterogeneous nucleation, significantly refining the grain structure and helping to control the uniformity of the structure. However, if too much rare earth element is added, large intercalated phases are likely to form, causing crack deformation during the rolling process and negatively affecting the forming of aluminum foil. Therefore, the total content of rare earth elements must be controlled to 0.2% or less.

[0025] The present invention adjusts the compatibility between the alloying components and the processing process to improve the process effect and material performance. Based on the selection of Al-Mg-Si alloy components, an accurate continuous casting and rolling control process is used. The casting and rolling temperature is controlled at a temperature of 670-715 °C, and the rolling speed is controlled at 0.3-1.2 m / min. In this case, the aluminum melt in the cavity of the casting nozzle has a smaller flow velocity difference at the edge part, rib plate and middle gap, and the flow rate is uniformly distributed, ensuring the fluidity and cooling uniformity of the melt during the casting and rolling process. If the rolling speed is too low, the flow rate of molten aluminum in the middle gap is the largest. If the rolling speed is too high, the aluminum melt is mostly distributed to the edge part and rib plate, and the molten aluminum is unevenly distributed, which has an adverse effect on the quality control of the cast and rolled plate. The thickness of the cast and rolled slab is controlled at 4.0-13.0 mm, giving full play to the advantages of the casting and rolling process and the compounding components of the present invention, realizing low energy consumption, process simplification, and low cost, and obtaining a cast and rolled slab of high-quality aluminum foil for air conditioners with a primary crystal grain size and a uniform structure. Thereby, a strong foundation is built to better adapt to the process parameters of rough rolling, intermediate rolling, finish rolling, and annealing.

[0026] The present invention uses a finished product annealing process at low temperature for a long time to reduce the anisotropy of the aluminum foil, which is beneficial to the plastic deformation ability and deep drawing performance of the aluminum foil, and obtains an aluminum foil for air conditioners with excellent balance in strength, elongation, Erichsen value, and excellent heat conduction performance.

Effects of the Invention

[0027] Compared with the prior art, the beneficial effects of the technical means according to the present invention are as follows.

[0028] Based on the innovative use of Al-Mg-Si alloys, by controlling the contents of Mg, Si, and Fe elements in the alloy and controlling the solid solution amount of Mg element to 0.3% or less, Mg and Si elements form fine Mg2Si particles, strengthen the grain boundaries, and improve the strength and thermal conductivity of the alloy. Furthermore, by controlling the contents of other alloy elements among the compounding components, the workability and plastic deformation ability of the product are improved, and it has higher thermal conductivity than 3-series aluminum alloys. The thermal conductivity of the alloy foil reaches 210 W / (m·k) or more, 10% higher than that of conventional products of the same type, with an elongation rate of ≧14% in the H2x state, an Erichsen value of ≧5 mm, and a tensile strength of 100 - 170 MPa.

[0029] Using the casting and rolling method to produce aluminum alloy foil for air conditioners, the compounding components of the alloy foil are reasonable, the process is scientific and the cost is low, which helps to improve the thermal conductivity and deformation performance of the aluminum foil, and also guarantees high surface quality and yield, meets the mechanical properties required for the forming of aluminum foil for air conditioners, and has high economic efficiency and use value.

Mode for Carrying Out the Invention

[0030] Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto.

[0031] (Examples) Raw materials were selected according to the alloy composition shown in Table 1, and continuous casting and rolling was performed to obtain cast and rolled sheet ingots. The raw materials were pure aluminum ingots, pure magnesium ingots, and intermediate alloys or alloying agents such as aluminum silicon, aluminum copper, and aluminum manganese, and recycled alloys may also be used. When continuous casting and rolling was performed, the Ti content was controlled with aluminum titanium boron wire, and RE elements were added in the form of mixed rare earth elements containing La or Ce. Cold rough rolling, intermediate rolling, and finish rolling were performed on the cast and rolled sheets to obtain aluminum foil, and the aluminum foil after rolling was annealed as a finished product. The casting and rolling temperature, rolling speed, thickness of the cast and rolled sheets, thickness of the finished product, and annealing temperature and time during finished product annealing were varied according to the method shown in Table 2. Finally, the mechanical properties and thermal conductivity of aluminum alloy foils obtained through various manufacturing routes were measured.

[0032] [Table 1]

[0033] [Table 2]

[0034] In the measurement of the above performance results, the alloys with example numbers 1-7, 14, 16, 18, 20, 22, and 24 all had a tensile strength of ≥120 MPa, a thermal conductivity of ≥210 W / (m·k), an Erichsen value of ≥5 mm, and an elongation of ≥14%.

[0035] In example number 8, Mg / (Si+Fe) was greater than 2.2, in example number 9, the Mg solid solution amount exceeded the range, resulting in a clear impact on thermal conductivity, Erichsen value, and elongation performance, and the thermal conductivity and Erichsen value performance could not meet the requirements, in example number 10, the Si content exceeded the range, in example number 11, the Fe content exceeded the range, mainly affecting the mechanical properties of the material, resulting in elongation ≤ 14% and Erichsen value ≤ 5 mm, in example number 12, the Mg content exceeded the range, in example number 13, the Ti content exceeded the range, resulting in a large impact on thermal conductivity performance, resulting in thermal conductivity ≤ 210 W / (m·k), in example number 15, In the example with example number 17, the added Cu element exceeds the limit, increasing the alloy strength, but the elongation is ≤14% and the Erichsen value is ≤5mm. In the example with example number 19, the added Zn exceeds the limit, resulting in a thermal conductivity of ≤210 W / (m·k) and an elongation of ≤14%. In the example with example number 21 and 23, the added Cr and Zr content exceeds the limit, resulting in a thermal conductivity of ≤210 W / (m·k), an elongation of ≤14%, and an Erichsen value of ≤5mm. In the example with example number 25, the added RE exceeds the limit, resulting in an elongation of ≤14% and an Erichsen value of ≤5mm.

[0036] Based on the results of other embodiments, the thermal conductivity is approximately 10% higher than that of conventional aluminum alloy foils commonly used for air conditioners (for example, commonly used 3102 aluminum alloy has a thermal conductivity of approximately 190 W / (m·k)). Furthermore, the elongation and Erichsen value are both superior to those of conventional technologies, satisfying the mechanical properties and performance requirements for forming aluminum foils for air conditioners. In addition, a hydrophilic coating layer can be selectively applied to the surface of the aluminum alloy foil obtained in the above embodiments. Graphene may be added to the hydrophilic coating layer to further improve the thermal conductivity of the product, and an antibacterial agent containing Ag ions may be added to the hydrophilic coating layer to improve the antifungal and antibacterial capabilities of the aluminum alloy foil, resulting in even better performance for the resulting air conditioner radiator product.

Claims

1. The composition consists of 0.08-0.5 wt.% Si, 0.15-1.0 wt.% Mg, 0.05-0.6 wt.% Fe (Mg / (Si+Fe) ≤ 2.2), 0.005-0.2 wt.% Ti, and the remainder Al, with a solid-solution Mg content of ≤ 0.3%. The thermal conductivity is ≥ 210 W / (m·K). Aluminum alloy foil for air conditioners, characterized by high thermal conductivity.

2. The state is H2x, the elongation rate is ≥ 14%, and the Erichsen value is ≥ 5 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 1.

3. The tensile strength is 100 to 170 MPa. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 2.

4. The composition further includes at least one of ≤0.5 wt.% Cu and ≤0.4 wt.% Mn. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 1.

5. The composition further includes at least one of ≤0.3 wt.% Zn, ≤0.3 wt.% Cr, and ≤0.3 wt.% Zr. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 1.

6. The composition further includes at least one of ≤0.3 wt.% Zn, ≤0.3 wt.% Cr, and ≤0.3 wt.% Zr. Aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 4.

7. The ingredients further include ≤0.2 wt.% RE. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 1.

8. The ingredients further include ≤0.2 wt.% RE. Aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 4.

9. The ingredients further include ≤0.2 wt.% RE. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 5.

10. The ingredients further include ≤0.2 wt.% RE. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 6.

11. The thickness is 0.05 to 0.15 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 1.

12. The thickness is 0.05 to 0.15 mm. Aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 4.

13. The thickness is 0.05 to 0.15 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 5.

14. The thickness is 0.05 to 0.15 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 6.

15. The thickness is 0.05 to 0.15 mm. Aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 7.

16. The thickness is 0.05 to 0.15 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 8.

17. The thickness is 0.05 to 0.15 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 9.

18. The thickness is 0.05 to 0.15 mm. The aluminum alloy foil for air conditioners having high thermal conductivity as described in claim 10.

19. A hydrophilic coating layer is applied to the surface. The aluminum alloy foil for air conditioners having high thermal conductivity as described in feature 11.

20. The aluminum alloy for air conditioners having high thermal conductivity according to any one of claims 1 to 19 is used in the manufacture of an air conditioner radiator. The use of aluminum alloy foil for air conditioners, characterized by high thermal conductivity.

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