High thermal conductivity aluminum alloy for air conditioners and its manufacturing method

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 manufacturing method thereof, and more particularly to an aluminum alloy for air conditioners having high thermal conductivity and a manufacturing method thereof. [Background technology]

[0002] As China's economy develops and people's living standards continue to improve, the prevalence of air conditioners is increasing year by year. Aluminum alloys are widely used to manufacture air conditioner heat exchanger fins due to their low density, high specific strength, high thermal conductivity, ease of processing, and cost performance. In recent years, air conditioners have become smaller, more efficient, and have longer lifespans, which has gradually increased the requirements for air conditioner heat exchanger fins. Aluminum foil for air conditioners is becoming thinner, more thermally conductive, and more deformable.

[0003] Due to their unique performance requirements, aluminum foil products for air conditioners require high thermal conductivity. Currently, aluminum foil for air conditioners is primarily made of Al-Mn-Fe-Si aluminum alloys such as 3102 and 8011. The high content of alloying elements such as Mn, Si, and Fe provides strengthening effects through solid solution, grain refinement, and work hardening, but at the expense of thermal conductivity. Therefore, while considering the strength and elongation benefits of alloying elements, it is also necessary to consider the impact on thermal conductivity. Furthermore, as aluminum foil for air conditioners continues to become thinner, the requirements for tensile strength, elongation, and surface hydrophilicity are correspondingly increasing, with thickness accuracy of 2% or less required. Therefore, it is becoming increasingly difficult for existing Al-Mn-Fe-Si aluminum alloys to meet these requirements.

[0004] Conventional aluminum foil for air conditioners is generally manufactured by a hot rolling process or a casting and rolling process. The casting and rolling process has a simple process flow and low energy consumption, but the structure and performance of the products manufactured by it are unstable, and coarse crystal grains are likely to appear in the foil, resulting in very poor deformability and prone to cracking, which significantly reduces yield. Summary of the Invention [Problem to be solved by the invention]

[0005] In response to the above-mentioned drawbacks of the prior art, an object of the present invention is to provide an aluminum alloy for air conditioners having high thermal conductivity, which overcomes the difficulty of conventional aluminum alloy foils in simultaneously satisfying the requirements for high thermal conductivity, strength, and elongation. Another object of the present invention is to provide a method for manufacturing an aluminum alloy for air conditioners having high thermal conductivity. [Means for solving the problem]

[0006] The technical means of the present invention are as follows: An aluminum alloy for air conditioners having high thermal conductivity contains, as its components, 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 balance Al, with a solute Mg content of ≦0.3%.

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

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

[0009] Furthermore, the aluminum alloy further contains at least one of the following components: ≦0.5 wt.% Cu and ≦0.4 wt.% Mn.

[0010] Furthermore, the aluminum alloy further contains at least one of the following components: ≦0.3 wt.% Zn, ≦0.3 wt.% Cr, and ≦0.3 wt.% Zr.

[0011] Furthermore, the aluminum alloy further comprises ≦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 can be added to further improve the heat conduction performance of the product and achieve significant antibacterial and antifungal properties.

[0014] Furthermore, the aluminum alloy is used to manufacture air conditioner radiators.

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

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

[0017] The aluminum alloy of the present invention is mainly composed of Mg and Si, in which the value of Mg / (Si+Fe) is less than 2.2 and the amount of dissolved Mg is 0.3% or less.

[0018] The addition of Mg is primarily due to the formation of the Mg2Si precipitate phase. In the aluminum matrix, Fe and Si form α-AlFeSi and β-AlFeSi, and the added Fe consumes Si, reducing the amount of Mg2Si. Therefore, when Mg / (Si + Fe) > 2.2, there is a significant excess of Mg, and the solute Mg content in the aluminum matrix is ​​greater than 0.3%, resulting in severe lattice distortion. The microscopic principle of metal thermal conductivity is caused by the thermal motion of free electrons. Lattice distortion reduces the mobility of thermally conductive electrons, reducing thermal conductivity. It also reduces the solubility of the Mg2Si precipitate phase, causing it to grow larger and coarser, reducing the strengthening effect. Therefore, by controlling the Mg / (Si + Fe) value below 2.2 and the solute Mg content < 0.3%, Mg is not excessive and primarily forms the alloy strengthening phase Mg2Si with Si. The formation process of this phase is as follows: supersaturated solid solution (SS) - Mg, Si cluster - GP zone - metastable β'' phase - metastable β' phase - stable β(Mg2Si) phase. The β(Mg2Si) phase is not coherent with the matrix and completely separates from it, eliminating the coherent distortion and reducing the degree of lattice distortion within the lattice. This reduces the number and density of thermal electron scattering sources in the matrix lattice, increases the free path of thermal electrons, and facilitates electron movement, ensuring high thermal conductivity.

[0019] When added to aluminum alloys, Si can form various strengthening particles with other alloying elements, significantly improving mechanical properties. When the Mg / (Si+Fe) ratio is less than 2.2, Si primarily reacts with Mg to form the strengthening phase Mg2Si, which is also in excess. However, the solubility of Si in aluminum alloys at room temperature is very low, so excess Si exists in the primary crystal form of α(Al) and forms free Si particles. Excess Si also promotes the desolvation of elements such as Mn, Fe, and Cr in the alloy, forming compounds and precipitating them, reducing their impact on thermal conductivity. For example, Si reacts with Fe to form the AlFeSi phase, improving mechanical properties.

[0020] When the Fe content is within a certain range, it can promote the formation of crystal nuclei during solidification, refine grains, and improve the cast and rolled structure. The formed AlFeSi and FeAl3 strengthening phases help improve the mechanical properties of aluminum foil and 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] Titanium is added to aluminum alloys in the form of aluminum titanium boron wire, and mainly forms Al2Ti and TiB2 phases together with Al. This acts as the core for non-spontaneous nucleation during crystallization, promoting heterogeneous nucleation and significantly refining the structure, ensuring first-class grain size in the cast and rolled structure, thereby improving the forming performance of aluminum foil.

[0022] The first selected additive elements are Mn and Cu. Adding a small amount of Mn produces a uniformly dispersed Al6Mn phase, inhibiting grain growth and significantly refining the structure, improving the performance of aluminum foil. However, Mn tends to segregate, causing structural inhomogeneity. Adding Cu forms an Al2Cu phase or CuAlGP zone, significantly improving the alloy's mechanical properties. However, the AlCuGP zone is easily matched with the matrix, causing lattice distortion, which reduces thermal conductivity. The AlCu phase is also easily precipitated at grain boundaries, causing intergranular corrosion. Therefore, the amounts of Mn and Cu added are controlled.

[0023] The second most commonly selected additive elements are Zn, Cr, and Zr. Zn, combined with Mg, forms the strengthening phase MgZn2, which significantly strengthens the alloy. However, the Zn content must be strictly controlled because it significantly reduces the open circuit potential and corrosion resistance of the aluminum alloy. Cr is practically insoluble in aluminum at room temperature, and the intermetallic compounds it forms with Al inhibit the nucleation and growth of recrystallization, improving the toughness of the aluminum alloy and reducing its susceptibility to stress corrosion cracking. However, the Cr content must be strictly controlled because it degrades the surface quality of aluminum foil. The primary function of Zr is to refine the grain structure and inhibit recrystallization. However, Zr content must be kept below 0.3% because it reduces the grain refinement effect of Ti.

[0024] The third element selected is rare earth elements. Adding rare earth elements to aluminum alloys helps purify the melt, lowering its surface tension and improving its fluidity, making it useful for casting, rolling, and forming. Furthermore, the Al3RE phase formed after adding rare earth elements to aluminum alloys can significantly refine the grain structure and control the uniformity of the structure by acting as a heterogeneous nucleation core. However, adding too many rare earth elements can easily result in the formation of large interstitial phases, which can cause cracking and deformation during the rolling process and adversely affect the forming of aluminum foil. Therefore, the total rare earth element content must be kept below 0.2%.

[0025] This invention improves process efficiency and material performance by adjusting the compatibility of alloy ingredients with the processing process. Based on the selection of Al-Mg-Si alloy ingredients, a precise continuous casting and rolling process is used. The casting and rolling temperature is controlled between 670 and 715°C, and the rolling speed is controlled between 0.3 and 1.2 m / min. In this case, the flow rate difference of the aluminum melt in the casting nozzle cavity between the edge, rib plate, and center gap is small, ensuring uniform flow distribution and ensuring uniformity of melt fluidity and cooling during the casting and rolling process. If the rolling speed is too low, the flow rate of the molten aluminum is greatest in the center gap. If the rolling speed is too high, the aluminum melt is distributed excessively to the edge and rib plate, resulting in uneven distribution of the molten aluminum, which adversely affects the quality control of the cast and rolled plate. The thickness of the cast-rolled slabs is controlled to 4.0-13.0 mm, and the advantages of the casting and rolling process and the compounded ingredients of the present invention are fully utilized, resulting in low energy consumption, a simplified process, and low cost, resulting in cast-rolled slabs of high-quality aluminum foil for air conditioners with first-class grain size and uniform structure, which lays a solid foundation for better adaptation to the process parameters of rough rolling, intermediate rolling, finish rolling, and annealing.

[0026] The present invention provides an aluminum foil for air conditioners that reduces the anisotropy of the aluminum foil by using a low-temperature, long-term finished product annealing process, which is useful for improving the plastic deformation ability and deep drawing performance of the aluminum foil, and has a balanced and excellent strength, elongation, and Erichsen value, as well as excellent thermal conductivity. [Effects of the Invention]

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

[0028] This innovative alloy is based on an Al-Mg-Si alloy. By controlling the Mg, Si, and Fe content and limiting the Mg solid solution content to 0.3% or less, the Mg and Si elements form fine Mg2Si particles, strengthening the grain boundaries and improving the alloy's strength and thermal conductivity. Furthermore, by controlling the content of other alloying elements in the alloy composition, the product's workability and plastic deformation capacity are improved, resulting in higher thermal conductivity than 3-type aluminum alloys. The alloy foil's thermal conductivity reaches 210 W / (m·k) or more, 10% higher than that of conventional products of the same type. It also has an elongation of 14% or more in the H2x state, an Erichsen value of 5 mm or more, and a tensile strength of 100-170 MPa.

[0029] The casting and rolling method is used to produce Al-Mg-Si aluminum alloy foil for air conditioners. The alloy foil has a reasonable composition, the process is scientific and low cost, and it helps improve the thermal conductivity and deformation performance of the aluminum foil. It also ensures high surface quality and yield, and meets the mechanical properties required for forming aluminum foil for air conditioners, making it highly economical and valuable in use. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will now be further described with reference to the following examples, which are not intended to limit the scope of the present invention.

[0031] (Example) Raw materials were selected according to the alloy composition in Table 1 and continuously cast and rolled to obtain cast-rolled plate 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. Recycled alloys may also be used. For continuous casting and rolling, the Ti content was controlled using aluminum-titanium-boron wire, and rare earth elements were added in the form of mixed rare earth elements containing La or Ce. The cast-rolled plate was subjected to cold rough rolling, intermediate rolling, and finish rolling to obtain aluminum foil. The rolled aluminum foil was then annealed. The casting and rolling temperature, rolling speed, thickness of the cast-rolled plate, thickness of the finished product, and annealing temperature and time during the annealing were varied as shown in Table 2. Finally, the mechanical properties and thermal conductivity performance of the aluminum alloy foils obtained by various manufacturing routes were measured.

[0032] [Table 1]

[0033] [Table 2]

[0034] In the above performance measurement, the alloys with Example Nos. 1 to 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 the example with Example No. 8, the Mg / (Si+Fe) ratio was greater than 2.2, and in the example with Example No. 9, the amount of Mg in solid solution exceeded the range, resulting in a clear impact on the thermal conductivity, Erichsen value, and elongation performance, and the thermal conductivity and Erichsen value performance did not meet the requirements. In the example with Example No. 10, the Si content exceeded the range, and in the example with Example No. 11, the Fe content exceeded the range, which mainly affected the mechanical properties of the material, resulting in an elongation of ≦14% and an Erichsen value of ≦5mm. In the example with Example No. 12, the Mg content exceeded the range, and in the example with Example No. 13, the Ti content exceeded the range, which significantly affected the thermal conductivity performance, resulting in a thermal conductivity of ≦210W / (m·k). In the example with Example No. 15, The added Cu element exceeds the range, increasing the alloy strength, but the elongation is ≦14% and the Erichsen value is ≦5mm. In the example with example number 17, the added Mn element exceeds the range, resulting in a thermal conductivity of ≦210W / (m·k) and an elongation of ≦14%. In the example with example number 19, the added Zn exceeds the range, resulting in a thermal conductivity of ≦210W / (m·k), an elongation of ≦14%, and an Erichsen value of ≦5mm. In the examples with example numbers 21 and 23, the added Cr and Zr contents exceed the ranges, respectively, resulting in a thermal conductivity of ≦210W / (m·k), an elongation of ≦14%, and an Erichsen value of ≦5mm. In the example with example number 25, the added RE exceeds the range, resulting in an elongation of ≦14%, and an Erichsen value of ≦5mm.

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

Claims

1. The alloy 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 balance Al, with a dissolved Mg content of ≦0.3%. An aluminum alloy for air conditioners having high thermal conductivity.

2. H2x state, elongation ≧ 14%, Erichsen value ≧ 5 mm, thermal conductivity ≧ 210 W / (m · k), 2. The aluminum alloy for air conditioners having high thermal conductivity according to claim 1.

3. The tensile strength is 100 to 170 MPa.

3. The aluminum alloy for air conditioners having high thermal conductivity according to claim 2.

4. Further containing at least one of Cu≦0.5 wt. % and Mn≦0.4 wt. % as components.

2. The aluminum alloy for air conditioners having high thermal conductivity according to claim 1.

5. Further containing at least one of ≦0.3 wt. % Zn, ≦0.3 wt. % Cr, and ≦0.3 wt. % Zr as a component; 2. The aluminum alloy for air conditioners having high thermal conductivity according to claim 1.

6. Further containing at least one of ≦0.3 wt. % Zn, ≦0.3 wt. % Cr, and ≦0.3 wt. % Zr as a component; 5. The aluminum alloy for air conditioners having high thermal conductivity according to claim 4.

7. Further comprising as a component ≦0.2 wt. % RE; 2. The aluminum alloy for air conditioners having high thermal conductivity according to claim 1.

8. Further comprising as a component ≦0.2 wt. % RE; 5. The aluminum alloy for air conditioners having high thermal conductivity according to claim 4.

9. Further comprising as a component ≦0.2 wt. % RE; 6. The aluminum alloy for air conditioners having high thermal conductivity according to claim 5.

10. Further comprising as a component ≦0.2 wt. % RE; 7. The aluminum alloy for air conditioners having high thermal conductivity according to claim 6.

11. The thickness is 0.05 to 0.15 mm.

2. The aluminum alloy for air conditioners having high thermal conductivity according to claim 1.

12. The thickness is 0.05 to 0.15 mm.

5. The aluminum alloy for air conditioners having high thermal conductivity according to claim 4.

13. The thickness is 0.05 to 0.15 mm.

6. The aluminum alloy for air conditioners having high thermal conductivity according to claim 5.

14. The thickness is 0.05 to 0.15 mm.

7. The aluminum alloy for air conditioners having high thermal conductivity according to claim 6.

15. The thickness is 0.05 to 0.15 mm.

8. The aluminum alloy for air conditioners having high thermal conductivity according to claim 7.

16. The thickness is 0.05 to 0.15 mm.

9. The aluminum alloy for air conditioners having high thermal conductivity according to claim 8.

17. The thickness is 0.05 to 0.15 mm.

10. The aluminum alloy for air conditioners having high thermal conductivity according to claim 9.

18. The thickness is 0.05 to 0.15 mm.

11. The aluminum alloy for air conditioners having high thermal conductivity according to claim 10.

19. A hydrophilic coating layer is applied to the surface; 12. The aluminum alloy for air conditioners having high thermal conductivity according to claim 11.

20. The aluminum alloy for air conditioners having high thermal conductivity according to any one of claims 1 to 19 is used for manufacturing air conditioner radiators.

1. Use of an aluminum alloy having high thermal conductivity for air conditioners.

21. A method for producing an aluminum alloy for air conditioners having high thermal conductivity according to any one of claims 1 to 18, The method includes the steps of selecting raw materials, performing continuous casting and rolling to obtain a cast-rolled plate ingot, performing rough cold rolling, intermediate rolling, and finish rolling on the cast-rolled plate ingot to obtain aluminum foil, and annealing the rolled aluminum foil as a finished product. When performing the continuous casting and rolling, the Ti content is controlled by an aluminum titanium boron wire, the casting and rolling temperature is 670 to 715°C, the rolling speed is 0.3 to 1.2 m / min, the thickness of the cast-rolled plate ingot is controlled to 4.0 to 13.0 mm, and the grain size is controlled to Grade 1. A method for producing an aluminum alloy for air conditioners, comprising:

22. The temperature during the annealing of the finished product is 230 to 290 ° C., and the heat retention time is 9 to 15 hours. The method for producing an aluminum alloy for air conditioners having high thermal conductivity according to claim 21.

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