A high-strength aluminum alloy fin material for air-cooled thermal management and a method of manufacturing the same

Abstract

This invention discloses a high-strength aluminum alloy fin material for air separation thermal management and its preparation method, relating to the field of aluminum alloy material technology. The chemical composition, by weight percentage, is: Fe: 0.15-0.65%, Si: 0.15-0.65%, Cu: 0.05-0.25%, Mn: 0.9-1.5%, Zr: 0.05-0.25%, with optional elements including Ti: 0-0.30%, Zn: 0-0.1%, La: 0-0.1%, Ca: 0-0.1%. The content of a single impurity is ≤0.05%, the total impurity content is ≤0.15%, and the remainder is Al and unavoidable impurities. The weight ratio of Fe to Si is 0.9-1.2:1. This invention, through basic strengthening with Mn and Zr, combined with composite microalloying of Ti / La / Ca / Zn, forms a stable and dispersed strengthening phase. After brazing, the tensile strength is ≥165MPa, and can reach up to 205MPa, which is significantly better than the traditional 3003 alloy (only 95MPa after brazing), effectively improving the burst pressure and structural stability of the equipment.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, specifically to a high-strength aluminum alloy fin material for air separation thermal management and its preparation method. Background Technology

[0002] In the thermal management equipment of the air separation industry, aluminum alloy fins serve as the core heat transfer element, and their performance directly determines the thermal efficiency, reliability, and service life of the equipment. Currently, 3003 aluminum alloy is widely used as the fin material in the industry. Although this alloy has good formability and a certain degree of corrosion resistance, it has significant drawbacks: The initial strength of 3003 aluminum alloy is limited. After vacuum brazing and high-temperature treatment, it will undergo annealing and softening, and the strength will decrease significantly. This results in insufficient burst pressure of the equipment, which limits the development of equipment towards higher working pressure and more compact structure. Some existing strengthening methods improve strength by increasing the Cu and Si content, but this significantly sacrifices corrosion resistance and poses safety hazards in oxidizing media such as liquid oxygen. Traditional hot and cold rolling processes are lengthy and energy-intensive, and it is difficult to precisely control the morphology and distribution of the second phase in the microstructure, resulting in insufficient uniformity and stability of material properties. Under vibration or high-pressure airflow impact, fins with insufficient strength are prone to deformation, affecting the smooth flow of air and heat transfer efficiency, and may even cause equipment failure. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a high-strength aluminum alloy fin material for air separation thermal management and its preparation method, thus solving the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a high-strength aluminum alloy fin material for air separation thermal management, comprising, by weight percentage: Fe: 0.15-0.65%, Si: 0.15-0.65%, Cu: 0.05-0.25%, Mn: 0.9-1.5%, Zr: 0.05-0.25%, with optional elements including Ti: 0-0.30%, Zn: 0-0.1%, La: 0-0.1%, Ca: 0-0.1%, with individual impurity content ≤0.05%, total impurity content ≤0.15%, and the remainder being Al and unavoidable impurities; wherein, the weight ratio of Fe to Si is 0.9-1.2:1, and '0%' in the optional elements indicates that the element content is below the detection limit (≤0.001%), i.e., the element is allowed not to be added. Furthermore, the chemical composition is as follows: Fe: 0.30-0.55%, Si: 0.45-0.55%, Cu: 0.10-0.20%, Mn: 1.2-1.4%, Zr: 0.10-0.20%, Ti: 0.15-0.25%, Zn: 0.02-0.08%, La: 0.03-0.08%, Ca: 0.03-0.08%.

[0005] Furthermore, the method for preparing the high-strength aluminum alloy fin material for air separation thermal management includes the following steps: Smelting: Prepare the ingredients according to the proportions and smelt at 740-760℃. During the smelting process, perform electromagnetic stirring at least twice, with each stirring lasting 20-30 minutes. After the composition is qualified, transfer it to a settling furnace. Settling and refining: Dehydrogenation is carried out in the settling furnace by suspension method, while powder refining is carried out simultaneously. Using Ar+1-5%Cl2 mixed gas as power, a pre-mixed refining agent and aluminum-calcium alloy powder are sprayed into the aluminum melt. The refining agent is a composite refining agent of Na3AlF6 and MgCl2 mixed in a weight ratio of 3:1. The amount of powder sprayed is 1.5-6 kg / ton of aluminum. After refining, the qualified composition is transferred to the external flow tank of the furnace. Modification treatment: In the external flow channel, when the temperature of the aluminum liquid drops to 690-710℃, add Al-Ti-C or Al-Ti-C-La composite modifier at a rate of 0.5-4 kg / ton of aluminum. External degassing and filtration: Online degassing is carried out using an SNIF device, which introduces a mixed gas of Ar / N2 + 1-5% Cl2. After degassing, the aluminum liquid is filtered through two stages of ceramic filter plates, 40 mesh and 60 mesh. Casting and rolling: The filtered molten aluminum is introduced into a casting and rolling mill and cast into a strip with a thickness of 5-8mm at 690-705℃. The exit temperature is not lower than 340℃. Homogeneous annealing: Hold the cast-rolled strip at 460-610℃ for 3-15 hours; First cold rolling: The homogeneously annealed strip is cold rolled to the intermediate thickness, with a final rolling reduction of 25-45% reserved; Intermediate annealing: Hold at 320-450℃ for 3-12 hours; Second cold rolling: Cold rolling to a finished thickness of 0.1-1.4 mm with a total reduction rate of 25-45%; Subsequent processing: Clean the finished aluminum strip with a 3-10% NaOH aqueous solution at 40-60℃, rinse with deionized water, squeeze dry, and then dry with hot air at 80-120℃. The surface dyne value should be ≥34. Then cut according to requirements. The surface dyne value test is carried out in accordance with GB / T14234-2008 standard at 23℃ and 50% relative humidity.

[0006] Furthermore, in the step of settling and refining, the refining agent and aluminum-calcium alloy powder are pre-mixed evenly by ball milling.

[0007] Furthermore, in the step-by-step deterioration treatment, a composite deteriorating agent is added through a wire feeder to achieve online uniform deterioration.

[0008] Furthermore, in the homogeneous annealing step, the homogeneous annealing temperature is 500-590℃, and the holding time is 6-10 hours to ensure that the non-equilibrium eutectic phase is fully dissolved. After the cast-rolled plate is taken out of the plate, it is naturally cooled to room temperature before undergoing homogeneous annealing treatment.

[0009] Furthermore, in the intermediate annealing step, the intermediate annealing temperature is 360-420℃, and the temperature is held for 4-8 hours to complete recrystallization and adjust the grain structure.

[0010] Furthermore, in the subsequent processing steps, the cleaning time is 5-15 minutes. After rinsing, there is no residual alkali on the surface of the aluminum strip. After rinsing with deionized water, the pH value of the aluminum strip surface is tested with pH test paper. If the pH value is in the range of 6.5-7.5, it means that there is no residual alkali.

[0011] This invention provides a high-strength aluminum alloy fin material for air separation thermal management and its preparation method, which has the following beneficial effects: This high-strength aluminum alloy fin material for air separation thermal management and its preparation method, through basic strengthening with Mn and Zr, combined with composite microalloying of Ti / La / Ca / Zn, forms a stable and dispersed strengthening phase. After brazing, the tensile strength is ≥165MPa, and can reach up to 205MPa, which is significantly better than the traditional 3003 alloy (only 95MPa after brazing), effectively improving the equipment's burst pressure and structural stability. The optimized Fe to Si ratio and precise control of impurities enable the alloy to maintain good formability, brazing performance and corrosion resistance on the basis of high strength, so as to meet the harsh requirements of air separation equipment in low temperature, high pressure and oxidizing media. The short-process technology of "casting and rolling instead of hot rolling" shortens the production cycle and reduces energy consumption; the amount of chlorine used in the refining and degassing process is small and the reaction is complete, avoiding environmental pollution; the entire process is continuous and controllable, with high production efficiency, and is suitable for large-scale industrial production. Attached Figure Description

[0012] Figure 1 The image shows the metallographic structure of the material obtained in Example 1 of this invention. Figure 2 The image shows a comparison of the room temperature tensile strength of the comparative example (3003 alloy) and the material of Example 1 of the present invention after vacuum brazing. Detailed Implementation

[0013] The embodiments of the present invention will be described in further detail below with reference to examples. These examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0014] Example 1 Selected composition (wt%): Fe: 0.25, Si: 0.30, Cu: 0.15, Mn: 1.2, Zr: 0.15, Ti: 0.20, Zn: 0.05, La: 0.06, Ca: 0.04, Al: balance.

[0015] The preparation process is as follows: Melting: 750℃, electromagnetic stirring twice, 25 minutes each time; Static refining: Injecting mixed gas (Ar + 3% Cl2), injecting refining agent and aluminum-calcium powder mixed in ball mill, dosage 4 kg / ton of aluminum; Modification treatment: Feeding Al-Ti-C-La wire at 700℃, dosage 2 kg / ton of aluminum; Degassing and filtration: SNIF degassing (Ar + 1.5% Cl2), 40 mesh + 60 mesh double-stage filtration; Casting and rolling: Casting and rolling temperature 695℃, plate thickness 6 mm; Homogenizing annealing: 590℃, holding for 8 h; First cold rolling: to a thickness of 2.0 mm; Intermediate annealing: 380℃, holding for 6 h; Second cold rolling: finished product thickness 1.4 mm (reduction rate 30%); Cleaning and drying: 5% NaOH, 50℃ cleaning; Rinsing with deionized water; Hot air drying at 100℃, the dyne value was measured to be 36; Slitting and packaging.

[0016] Comparative Example Using conventional 3003 aluminum alloy (composition: Mn: 1.0-1.5%, Fe: ≤0.7%, Si: ≤0.6%, Cu: 0.05-0.20%), fin materials of the same thickness are produced through a similar processing procedure.

[0017] Performance tests are as follows: The material from Example 1 of this invention was subjected to a vacuum brazing simulation test together with the comparative material (heated to 600°C and held for 10 minutes to simulate the brazing process), and then its room temperature mechanical properties were tested. The results are shown in the table below:

[0018] Test results show that the aluminum alloy material provided by this invention has significantly higher tensile strength than the traditional 3003 alloy, both before brazing and after undergoing a simulated high-temperature brazing process. This fully demonstrates the superior effect of this invention in improving the fin material's resistance to softening and the final component's load-bearing capacity.

[0019] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A high-strength aluminum alloy fin material for air separation thermal management, characterized in that: The chemical composition by weight percentage is as follows: Fe: 0.15-0.65%, Si: 0.15-0.65%, Cu: 0.05-0.25%, Mn: 0.9-1.5%, Zr: 0.05-0.25%, with optional elements including Ti: 0-0.30%, Zn: 0-0.1%, La: 0-0.1%, Ca: 0-0.1%. The content of a single impurity is ≤0.05%, the total impurity content is ≤0.15%, and the remainder is Al and unavoidable impurities. The weight ratio of Fe to Si is 0.9-1.2:

1. '0%' in the optional elements indicates that the element content is below the detection limit, meaning that the element is not allowed to be added.

2. The high-strength aluminum alloy fin material for air separation thermal management according to claim 1, characterized in that: The chemical composition is as follows: Fe: 0.30-0.55%, Si: 0.45-0.55%, Cu: 0.10-0.20%, Mn: 1.2-1.4%, Zr: 0.10-0.20%, Ti: 0.15-0.25%, Zn: 0.02-0.08%, La: 0.03-0.08%, Ca: 0.03-0.08%.

3. A method for preparing the high-strength aluminum alloy fin material for air separation thermal management as described in any one of claims 1-2, characterized in that: Includes the following steps: Smelting: Prepare the ingredients according to the proportions and smelt at 740-760℃. During the smelting process, perform electromagnetic stirring at least twice, with each stirring lasting 20-30 minutes. After the composition is qualified, transfer it to a settling furnace. Settling and refining: Dehydrogenation is carried out in the settling furnace by suspension method, while powder refining is carried out at the same time. Using Ar+1-5%Cl2 mixed gas as power, the pre-mixed refining agent and aluminum-calcium alloy powder are sprayed into the aluminum melt. The amount of powder sprayed is 1.5-6 kg / ton of aluminum. After refining, the qualified composition is transferred to the external flow channel of the furnace. Modification treatment: In the external flow channel, when the temperature of the aluminum liquid drops to 690-710℃, add Al-Ti-C or Al-Ti-C-La composite modifier at a rate of 0.5-4 kg / ton of aluminum. External degassing and filtration: Online degassing is carried out using an SNIF device, which introduces a mixed gas of Ar / N2 + 1-5% Cl2. After degassing, the aluminum liquid is filtered through two stages of ceramic filter plates, 40 mesh and 60 mesh. Casting and rolling: The filtered molten aluminum is introduced into a casting and rolling mill and cast into a strip with a thickness of 5-8mm at 690-705℃. The exit temperature is not lower than 340℃. Homogeneous annealing: Hold the cast-rolled strip at 460-610℃ for 3-15 hours; First cold rolling: The homogeneously annealed strip is cold rolled to the intermediate thickness, with a final rolling reduction of 25-45% reserved; Intermediate annealing: Hold at 320-450℃ for 3-12 hours; Second cold rolling: Cold rolling to a finished thickness of 0.1-1.4 mm with a total reduction rate of 25-45%; Subsequent processing: Clean the finished aluminum strip with a 3-10% NaOH aqueous solution at 40-60℃, rinse with deionized water, squeeze dry, dry with hot air at 80-120℃, and the surface dyne value is ≥34. Then cut according to requirements.

4. The method for preparing a high-strength aluminum alloy fin material for air separation thermal management according to claim 3, characterized in that: In the step of settling and refining, the refining agent and aluminum-calcium alloy powder are pre-mixed evenly by ball milling.

5. The method for preparing a high-strength aluminum alloy fin material for air separation thermal management according to claim 3, characterized in that: In the deterioration process, a composite deteriorating agent is added through a wire feeder to achieve uniform online deterioration.

6. The method for preparing a high-strength aluminum alloy fin material for air separation thermal management according to claim 3, characterized in that: In the homogeneous annealing step, the homogeneous annealing temperature is 500-590℃, and the holding time is 6-10 hours to ensure that the non-equilibrium eutectic phase is fully dissolved.

7. The method for preparing a high-strength aluminum alloy fin material for air separation thermal management according to claim 3, characterized in that, In the intermediate annealing step, the intermediate annealing temperature is 360-420℃, and the temperature is held for 4-8 hours to complete recrystallization and adjust the grain structure.

8. The method for preparing a high-strength aluminum alloy fin material for air separation thermal management according to claim 3, characterized in that: In the subsequent processing steps, the cleaning time is 5-15 minutes, and there is no residual alkali on the surface of the aluminum strip after rinsing.

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