5083 regenerated aluminum alloy for air separation equipment and preparation method thereof

Abstract

The invention belongs to the technical field of regenerated aluminum alloy, and discloses 5083 regenerated aluminum alloy for air separation equipment and a preparation method of the 5083 regenerated aluminum alloy. The method comprises the following steps: 1) placing a 5083 waste aluminum melt in a fractional crystallization device for fractional crystallization to obtain a secondary aluminum raw material; during step-by-step crystallization, cooling gas is introduced in a pulse manner for cooling; 2) measuring the components of the secondary aluminum raw material; and (3) remelting the secondary aluminum raw material, and adding pure metal based on the components of the secondary aluminum raw material to prepare the 5083 secondary aluminum alloy for the air separation equipment. The method disclosed by the invention is simple and relatively low in cost and energy consumption, does not need to add a fluorine / chlorine / boron-containing iron removal agent, does not generate fluorine / chlorine-containing wastes, and has no influence on the environment; impurities such as B are not introduced into the secondary aluminum, so that the component stability of the secondary aluminum is ensured. According to the method, impurity elements Fe / Si / Cu / Zn can be efficiently removed, meanwhile, Cr and Ti can be enriched, and carbon emission is low.

Description

Technical Field

[0001] This invention belongs to the technical field of recycled aluminum alloys, specifically relating to a 5083 recycled aluminum alloy for air separation equipment and its preparation method. Background Technology

[0002] 5083 aluminum alloy is an aluminum-magnesium alloy with aluminum as the base material. Solid solution strengthening is achieved by adding a high content of magnesium. Its typical composition is: Al≥94%; Mg: 4.0%-4.9%; Mn: 0.4%-1.0%; Cr: 0.05%-0.25%; Fe≤0.40%; Si≤0.40%; Cu≤0.10%; Zn≤0.25%; Ti≤0.15%. This alloy possesses excellent low-temperature toughness, superior corrosion resistance, medium-to-high strength, and good welding and forming properties, while retaining the lightweight advantages of aluminum alloys. It is a core material for liquid oxygen storage tanks, cryogenic pipelines, and heat exchangers in air separation equipment.

[0003] While meeting the typical composition requirements of 5083 aluminum alloy, the core components of air separation equipment require strict control of the Fe / Si / Cu / Zn content under extreme operating conditions involving cryogenic conditions and liquid oxygen. Taking liquid oxygen storage tanks as an example: excessive Fe will form coarse Al-Fe intermetallic compounds, which become brittle crack initiation sources in a -196℃ cryogenic environment, inducing cryogenic explosion of the liquid oxygen storage tank; excessive Si content promotes the precipitation of brittle Mg2Si phase at grain boundaries, significantly reducing the fatigue resistance of welded joints and leading to weld cracking and leakage; Cu reduces the corrosion resistance of the alloy; and Zn-containing phases have low potentials and are prone to intergranular corrosion. To ensure the normal operation of air separation equipment under extreme conditions, the Fe / Si / Cu / Zn content must be controlled at Fe ≤ 0.18%; Si ≤ 0.12%; Cu ≤ 0.05%; and Zn ≤ 0.15%.

[0004] Unlike Fe / Si / Cu / Zn, Cr and Ti are beneficial elements in 5083 aluminum alloy. Cr can react with the aluminum matrix to form CrMnAl. 13 and CrFeAl 17 Intermetallic compounds, such as Cr and Ti, can refine grains and inhibit recrystallization. Trace amounts of Ti can cause the Al melt to form numerous fine Al3Ti heterogeneous nucleation particles. The Al3Ti phase acts as a grain refiner, significantly refining the alloy microstructure and improving its strength, toughness, and corrosion resistance. Therefore, within the nominal range of 5083 (Cr: 0.05%-0.25%; Ti≤0.15%), increasing the Cr and Ti content can enhance the performance of 5083 aluminum alloy.

[0005] 5083 aluminum alloy is widely used in shipbuilding, vehicles, and other fields. With the scrapping of ships and vehicles, a large amount of waste 5083 aluminum alloy is generated, creating an urgent need for its recycling. Recycling this waste aluminum alloy, compared to producing primary aluminum, reduces energy consumption by approximately 95% and carbon emissions by over 90%, making it an essential step in achieving green and low-carbon development of electronic products and promoting resource recycling. However, the introduction of Fe / Si / Cu / Zn during the recycling process is unavoidable. To prepare 5083 recycled aluminum alloy suitable for air separation equipment, effective Fe / Si / Cu / Zn removal technologies must be developed.

[0006] Fe / Si / Cu / Zn can be removed using a three-layer liquid electrolysis method, but this method also removes a large amount of beneficial elements such as Mg / Mn / Cr / Ti and consumes a lot of energy.

[0007] Currently, the main technologies for removing Fe from aluminum alloys are the primary aluminum dilution method and the boride precipitation method. Chinese invention patent applications CN119571103 A and CN 116790947 A disclose a method for preparing recycled aluminum alloys by diluting waste aluminum with primary aluminum to reduce the content of impurities, including Fe. This method requires the addition of primary aluminum, increasing the company's costs and carbon emissions. Chinese invention patents CN104060118 A, CN 103740947 A, and CN 1940101 A disclose various boride flux methods for removing iron. The core principle is that boride reacts with iron to form high-melting-point, high-density boron-iron compounds, thereby achieving separation. However, due to the poor dispersibility of high-viscosity borides such as borax and boron oxide in aluminum melt, they are difficult to fully contact with iron, resulting in low removal rates. Chinese utility model CN ​​214655166 U discloses a vacuum distillation device suitable for removing Zn from waste aluminum alloys. This device uses vacuum distillation to separate Zn from Al, but it has high energy consumption and high carbon emissions. For Cu / Si, there is currently no publicly available mature removal method other than the three-layer liquid electrolysis method. Summary of the Invention

[0008] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a 5083 recycled aluminum alloy for air separation equipment and its preparation method. This invention removes Fe, Si, Cu, and Zn impurities from 5083 waste aluminum in a single step while simultaneously enriching Ti and Cr, thereby improving the strength, toughness, and corrosion resistance of the 5083 recycled aluminum alloy during impurity removal. The method of this invention is simple, has low cost and energy consumption, ensures stable composition of the recycled aluminum, and has low carbon emissions.

[0009] The objective of this invention is achieved through the following technical solution: A method for preparing 5083 recycled aluminum alloy for air separation equipment includes the following steps: 1) Melt 5083 scrap aluminum to obtain a melt; 2) The melt is placed in a stepwise crystallization apparatus, and the temperature of the melt is maintained at 665~670℃. Then, the melt placed in the apparatus is cooled by a cooling device set on the side wall of the apparatus. Aluminum primary crystals precipitate in the melt in contact with the cooled side wall. The aluminum primary crystals are scraped off and compacted by a scraping device that moves up and down. The scraping device has holes or gaps, and the aluminum melt passes through the holes or gaps while the aluminum primary crystals are scraped off and compacted. The aluminum primary crystals gather and grow by moving back and forth. After crystallization, the concentrated liquid is poured out, and the end of the aluminum ingot with more impurities is removed to obtain recycled aluminum raw material. The up and down speed of the scraping device is 5~10 times / min. After every 10 or more up and down movements, it rotates 80~100° along the horizontal plane. Specifically, after every 10~20 up and down movements, it rotates 90° clockwise or 90° counterclockwise in the horizontal plane. Stepwise crystallization ends when 30% of the concentrated liquid remains. 3) Determine the composition of recycled aluminum raw materials; 4) Remelt the recycled aluminum raw materials and add pure metals based on the composition of the recycled aluminum raw materials to formulate 5083 recycled aluminum alloy for air separation equipment.

[0010] The crystal scraping device is a tamping disc and tamping rod or an annular plunger. The tamping disc and tamping rod includes a tamping disc and a tamping rod disposed on the tamping disc. The tamping disc and tamping rod are provided with holes. The tamping disc and tamping rod move up and down and rotate periodically.

[0011] The cooling refers to cooling by pulsed introduction of cooling gas. The average velocity of the cooling gas introduction is 20-40 m / s. 3 / h. The pulsed method refers to passing the gas for 2-4 seconds, then pausing for 1 second, until stepwise crystallization is complete.

[0012] Cooling gas is introduced into the cooling device, causing primary aluminum crystals to precipitate from the melt in contact with the cooled sidewall. The cooling device is located on the upper sidewall of the step crystallization apparatus.

[0013] In step 2), the part of the aluminum ingot with more impurities can be removed by testing the composition of the aluminum ingot with an instrument, and the part with more impurities can be removed or 1 / 5 to 1 / 10 of the aluminum ingot that will crystallize later can be removed.

[0014] The composition of the 5083 waste aluminum, in mass percentage, is as follows: Mg: 4.17-4.27% Mn: 0.51-0.54% Fe: 0.57-0.60% Si: 0.44-0.46% Cu: 0.18-0.19% Zn: 0.27-0.30% Cr: 0.07-0.09% Ti: 0.04-0.06% Al: Balance.

[0015] The equilibrium distribution coefficients K for each element are: Mg - 0.3; Mn - 0.76; Fe - 0.023; Si - 0.1; Cu - 0.14; Zn - 0.43; Cr - 1.84; Ti - 9.4.

[0016] The 5083 waste aluminum is cleaned before melting; specifically, oil and impurities are removed from the surface of the 5083 waste aluminum.

[0017] The melting temperature is 720-760℃. Stirring is performed during the melting process, and the mixture is then left to stand at the desired temperature. The stirring time is 5-10 minutes; the standing and holding time is 30-60 minutes.

[0018] Step 3) Use an analyzer to detect the composition of recycled aluminum raw materials.

[0019] Step 4) The remelting temperature is 720-760℃. After adding pure metal, the aluminum melt needs to be stirred for 5-10 minutes.

[0020] During aluminum solidification, alloying elements exhibit differences in solubility between solid and liquid aluminum. Elements with an equilibrium partition coefficient K < 1 have higher solubility in liquid aluminum than in solid aluminum, causing them to migrate and accumulate in the remaining liquid phase during solidification. Conversely, elements with K > 1 migrate and accumulate in the solid phase during solidification. The K values ​​for Fe / Si / Cu / Zn are all less than 1, at 0.023, 0.1, 0.14, and 0.43, respectively; while the K values ​​for Cr and Ti are greater than 1, at 1.84 and 9.4, respectively. A stepwise crystallization method can be used to simultaneously remove Fe / Si / Cu / Zn while enriching Cr / Ti, achieving a synergistic improvement in multiple properties of recycled aluminum.

[0021] Compared with existing technologies, the present invention has the following advantages and beneficial effects: (1) The process of this invention is simple, with low cost and energy consumption. Using this invention to produce recycled aluminum does not require the addition of iron removal agents containing fluorine / chlorine / boron, and will not generate waste containing fluorine / chlorine, thus having no impact on the environment; it will also not introduce impurities such as B into the recycled aluminum, ensuring the stability of the recycled aluminum composition.

[0022] (2) The present invention adopts a pulse cooling method and a periodic rotating tamping plate and tamping rod. The periodic airflow impact destroys the thermal boundary layer on the surface of the cooling wall, thereby improving the heat exchange efficiency and cooling uniformity. The periodic rotation ensures that the side wall crystal layer is uniformly scraped off and compacted, avoiding local accumulation and local wear of the equipment.

[0023] (3) The present invention can efficiently remove impurity elements Fe / Si / Cu / Zn from 5083 waste aluminum, with removal rates of >90%, >80%, >70%, and >50%, respectively, and final contents of <0.06%, <0.09%, <0.05%, and <0.15%, ensuring that the air separation equipment can work under extreme conditions.

[0024] (4) The present invention uses a stepwise crystallization method to prepare recycled aluminum raw materials, and then adds pure metals to prepare 5083 recycled aluminum alloy for air separation equipment. The carbon emission is about 1.2t / t, which is about 90% less than that of primary aluminum and about 60% less than that of recycled aluminum prepared by the primary aluminum dilution method.

[0025] (5) While removing Fe / Si / Cu / Zn impurities from 5083 waste aluminum, the present invention can also enrich Cr and Ti, with an increase rate of >13% and >54% respectively, and a content of >0.09% and >0.07% respectively. While removing impurities, it can improve the strength, toughness and corrosion resistance of 5083 recycled aluminum alloy. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the main cross-sectional structure of the stepwise crystallization furnace used in this invention; 1-furnace cover; 2-tamping rod; 3-tamping plate; 4-insulation layer; 5-heating coil; 6-crucible; 7-aluminum melt; 8-cooling gas pipe; 9-cooling part; 10-aluminum primary crystal; 11-hole; 12-pure aluminum. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. A cross-sectional view of the apparatus (stepwise crystallization furnace) used in the stepwise crystallization process in the embodiments of the present invention is shown below. Figure 1 As shown, the furnace includes a hollow crucible 6, a tamping rod 2, a tamping pan 3, a furnace lid 1, and a furnace shell (not labeled in the figure). A heating coil 5 is located on the outer side of the crucible, and a cooling device is installed on one side wall of the crucible. One end of the tamping rod 2 is mounted on the tamping pan 3, and the other end passes through a hole in the furnace lid 1. The tamping pan 3 moves up and down with the tamping rod 2. The crucible 6 and the heating coil 5 are located inside the furnace shell. The crucible 6 has an opening at the top, which is covered by the furnace lid 1. The cooling device includes a cooling gas pipe 8 that passes through the furnace shell. Holes 11 are provided on the tamping pan and the tamping rod. An insulation layer 4 is provided between the furnace shell and the heating coil. The cooling pipe is located on the upper side wall of the crucible, encircling the side wall once.

[0028] The crucible 6 of this invention contains molten aluminum 7. Cooling gas is pulsed through a cooling gas pipe 8 and delivered to the side wall 9 (i.e., the cooling section) of the crucible to cool the melt. High-purity primary aluminum crystals 10 precipitate from the melt on the side wall. The fine primary aluminum crystals are then scraped and compacted to the bottom of the crucible by the up-and-down movement of a tamping rod and disc. This compaction action also squeezes out aluminum melt rich in impurities between the crystals. The holes 11 on the tamping rod and disc allow the molten aluminum to pass through. After 10 up-and-down movements of the tamping rod and disc, it is rotated 90° clockwise to ensure that the crystalline layer on the side wall is evenly scraped off and compacted, avoiding localized accumulation and wear on the equipment. This process is repeated, causing the primary aluminum crystals at the bottom to gradually aggregate and grow into larger and purer pure aluminum 12, achieving the purpose of aluminum purification.

[0029] Example 1 The composition of recycled aluminum base material 5083 waste aluminum in this embodiment is as follows: by mass percentage, Mg: 4.2532% Mn: 0.5211% Fe: 0.5866% Si: 0.4510% Cu: 0.1816% Zn: 0.2981% Cr: 0.0842% Ti: 0.0467% Al: Balance.

[0030] A method for preparing 5083 recycled aluminum alloy for air separation equipment includes the following steps: (1) Cleaning and batching: Use an alkaline degreasing agent to clean the surface of 5083 waste aluminum to remove oil and other impurities. After cleaning, weigh a certain amount of 5083 waste aluminum as recycled aluminum base material.

[0031] (2) Smelting: Place 5083 waste aluminum in a smelting furnace and melt it into a melt at 720℃. Stir it electromagnetically for 5 minutes to make the melt composition evenly distributed. After stirring, let it stand for 30 minutes.

[0032] (3) Stepwise crystallization treatment: The melt from step (2) is rapidly transferred to a stepwise crystallization furnace for stepwise crystallization treatment. During the treatment, the melt temperature is maintained at 665℃, and the melt is injected into the cooling pipes on the side wall of the stepwise crystallization furnace at an average rate of 20m. 3Cooling gas is pulsed at a rate of / h (3s per pulse, followed by a 1s pause) to induce the precipitation of primary pure aluminum crystals along the sidewall. A tamping disc and rod assembly moves up and down 5 times / min to scrape the fine primary aluminum crystals from the sidewall to the bottom of the crucible, mechanically compacting the bottom primary crystals. After each 10 up-and-down motions, the tamping disc and rod rotate 90° clockwise. During compaction, impurity-rich melt within the crystal interstices is squeezed out, while the melt can flow and exchange through the porous structure of the tamping disc and rod. Repeated scraping-compacting operations promote the aggregation and growth of the bottom primary crystals, ultimately forming large-sized pure aluminum crystals. After stepwise crystallization, the concentrated liquid rich in impurities above the pure aluminum is poured out, and the head of the aluminum ingot with more impurities is removed to obtain recycled aluminum raw material.

[0033] (4) Composition detection: The composition of the recycled aluminum raw material obtained in step (3) is detected using an analyzer.

[0034] (5) Preparation of 5083 aluminum alloy: Based on the composition of the recycled aluminum raw material in step (4), the raw material is remelted at 720°C. After remelting, necessary pure metals are added to make the raw material meet the composition of 5083 aluminum alloy for air separation equipment. After adding pure metals, the material is electromagnetically stirred for 5 minutes to make its composition uniform, and then cast into recycled aluminum ingots.

[0035] The composition and compositional changes of the recycled aluminum raw materials were detected as follows: Mg: 2.2742%, a decrease of 46.53% compared to 5083 scrap aluminum. Mn: 0.4731%, a decrease of 9.21% Fe: 0.0436%, a decrease of 92.57% Si: 0.0782%, a decrease of 82.66%. Cu: 0.0452%, a decrease of 75.11% Zn: 0.1466%, a decrease of 50.82% Cr: 0.0955%, up 13.42% Ti: 0.0741%, up 58.67% Al: Balance.

[0036] This embodiment achieves deep impurity removal: except for Mn (K=0.76, close to 1, which is difficult to remove by step crystallization), the removal rate of elements with K<1 reaches 45-93%, which meets the content requirements of Fe, Si, Cu and Zn for normal operation of air separation equipment under extreme conditions.

[0037] This embodiment also achieved the enrichment of beneficial elements: the increases in Cr and Ti were 13.42% and 58.67%, respectively, and the contents increased to 0.0955% and 0.0741%, respectively, thereby improving the toughness and corrosion resistance of recycled aluminum.

[0038] Due to the characteristic of stepwise crystallization in removing elements with K < 1, the Mg content in the finished recycled aluminum ingot is lower than the nominal value of 5083 aluminum alloy. When preparing 5083 aluminum alloy for air separation equipment, adding pure Mg is sufficient to meet the requirements.

[0039] Example 2 The composition of recycled aluminum base material 5083 waste aluminum in this embodiment is as follows: by mass percentage, Mg: 4.1743% Mn: 0.5198% Fe: 0.5903% Si: 0.4430% Cu: 0.1842% Zn: 0.2760% Cr: 0.0794% Ti: 0.0475% Al: Balance.

[0040] Compared with Example 1, the steps and conditions in the preparation method of 5083 recycled aluminum alloy for air separation equipment in this example are different: 1. Step (2) The melting temperature is 740℃, the electromagnetic stirring time is 7min, and the standing time is 45min.

[0041] 2. In step (3), the melt temperature is maintained at 667℃, and the average velocity of the cold gas introduced is 30m. 3 The frequency of tamping and tamping is 7 times / min.

[0042] 3. The remelting temperature in step (5) is 740℃ and the electromagnetic stirring time is 7min.

[0043] Other operating conditions are the same as in Example 1.

[0044] The composition and compositional changes of the recycled aluminum raw materials were detected as follows: Mg: 2.2829%, a decrease of 45.31% Mn: 0.4723%, a decrease of 9.14% Fe: 0.0524%, a decrease of 91.12% Si: 0.0798%, a decrease of 81.99% Cu: 0.0468%, a decrease of 74.59% Zn: 0.1379%, a decrease of 50.04% Cr: 0.0903%, up 13.73% Ti: 0.0735%, up 54.74% Al: Balance.

[0045] Similar to Example 1, this example also achieved the effects of deep impurity removal and enrichment of beneficial elements: except for Mn, the removal rate of elements with K < 1 reached 45-92%; the content of elements with K > 1 all increased, with Ti and Cr increasing by 54.74% and 13.73% respectively, and their contents increasing to 0.0775% and 0.0903% respectively.

[0046] Similar to Example 1, adding pure Mg is sufficient to meet the requirements when preparing 5083 aluminum alloy for air separation equipment.

[0047] Example 3 The composition of recycled aluminum base material 5083 waste aluminum in this embodiment is as follows: by mass percentage, Mg: 4.2613% Mn: 0.5301% Fe: 0.5793% Si: 0.4483% Cu: 0.1894% Zn: 0.2837% Cr: 0.0863% Ti: 0.0489% Al: Balance.

[0048] Compared with Example 1, the steps and conditions in the preparation method of 5083 recycled aluminum alloy for air separation equipment in this example are different: 1. Step (2) The melting temperature is 760℃, the electromagnetic stirring time is 10min, and the standing time is 60min.

[0049] 2. In step (3), the melt temperature is maintained at 670℃, and the average velocity of the cold air introduced is 40m. 3 / h, the frequency of tamping and tamping is 10 times / min.

[0050] 3. The remelting temperature in step (5) is 760℃ and the electromagnetic stirring time is 10min.

[0051] Other operating conditions are the same as in Example 1.

[0052] The composition and compositional changes of the recycled aluminum raw materials were detected as follows: Mg: 2.2815%, a decrease of 46.46%. Mn: 0.4826%, a decrease of 8.96% Fe: 0.0494%, a decrease of 91.47%. Si: 0.0827%, a decrease of 81.55% Cu: 0.0477%, a decrease of 74.82%. Zn: 0.1417%, a decrease of 50.05% Cr: 0.0978%, up 13.33% Ti: 0.0758%, up 55.01% Al: Balance.

[0053] Similar to Example 1, this example also achieved the effects of deep impurity removal and enrichment of beneficial elements: except for Mn, the removal rate of elements with K < 1 reached 45-92%; the content of elements with K > 1 all increased, with Ti and Cr increasing by 55.01% and 13.33% respectively, and their contents increasing to 0.0758% and 0.0978% respectively.

[0054] Similar to Example 1, adding pure Mg is sufficient to meet the requirements when preparing 5083 aluminum alloy for air separation equipment.

[0055] Comparative Example 1 This comparative example uses the same 5083 waste aluminum as in Example 1, and its composition is as follows: Mg: 4.2532% Mn: 0.5211% Fe: 0.5866% Si: 0.4510% Cu: 0.1816% Zn: 0.2981% Cr: 0.0842% Ti: 0.0467% Al: Balance.

[0056] Compared with Example 1, the process flow for this comparative example is as follows: 1. During step (3), the melt temperature is maintained at 665℃, and the melt is fed into the cooling pipes on the side wall of the stepwise crystallization furnace at an average rate of 20m. 3 Cooling gas is introduced at a rate of / h, but the tamping plate and rod are removed, causing the primary pure aluminum crystals precipitated at the cold source to be unable to be concentrated by the tamping plate and rod, thus preventing the stepwise crystallization process from being completed. The melt in the stepwise crystallization furnace will begin to solidify from the cold source, and the solid phase will diffuse in all directions until the entire melt is completely solidified, yielding recycled aluminum raw material.

[0057] 2. Step (5) requires the addition of primary aluminum.

[0058] The operating conditions for steps (1), (2), and (4) are the same as in Example 1.

[0059] Testing revealed that the composition of the finished recycled aluminum ingots remained unchanged compared to the raw materials, with Fe, Si, Cu, and Zn contents of 0.5866%, 0.4510%, 0.1816%, and 0.2981%, respectively. This does not meet the requirements for 5083 aluminum alloy used in air separation equipment (Fe≤0.18%; Si≤0.12%; Cu≤0.05%; Zn≤0.15%).

[0060] Unlike Example 1, this comparative example of recycled aluminum feedstock requires the addition of approximately 69% primary aluminum when preparing 5083 aluminum alloy for air separation equipment. In addition to primary aluminum, Mg also needs to be added to achieve the nominal value of 5083.

[0061] Comparative Example 2 This comparative example uses the same recycled aluminum base material, 5083 waste aluminum, as in Example 1, and its composition is as follows: Mg: 4.2532% Mn: 0.5211% Fe: 0.5866% Si: 0.4510% Cu: 0.1816% Zn: 0.2981% Cr: 0.0842% Ti: 0.0467% Al: Balance.

[0062] Compared with Example 1, the process flow for this comparative example is as follows: 1. In step (3), cooling gas is continuously introduced at a rate of 20 m / s. 3 / h; The tamping disc and tamping rod no longer rotate periodically as they move up and down.

[0063] The operating conditions for steps (1), (2), (4), and (5) are the same as in Example 1.

[0064] The composition and compositional changes of the recycled aluminum raw material detected in this comparative example are as follows: Mg: 2.5358%, a decrease of 40.38% Mn: 0.4887%, a decrease of 6.22% Fe: 0.0862%, a decrease of 85.30%. Si: 0.0998%, a decrease of 77.87%. Cu: 0.0477%, a decrease of 67.34%. Zn: 0.1631%, a decrease of 45.29% Cr: 0.0918%, up 9.90% Ti: 0.0718%, up 53.74% Al: Balance.

[0065] Compared to Example 1, the removal rates of all key impurity elements in Comparative Example 2 decreased across the board: Fe removal rate decreased from 92.57% to 85.30% (content 0.0862%), Si from 82.66% to 77.87%, Cu from 75.11% to 67.34%, and Zn from 50.82% to 45.29%. Although the content of impurities such as Fe and Si in the final recycled aluminum raw material was reduced, the decrease in removal efficiency resulted in a higher total amount of impurities, and the purification effect failed to reach the optimal level. At the same time, the enrichment rate of the beneficial element Cr also decreased from 13.42% to 9.90%, indicating a weakened performance optimization effect.

[0066] The results indicate that the specific process parameters for cooling and scraping have a decisive impact on the final purification efficiency of stepwise crystallization. The optimized process conditions of pulsed cooling and rotary scraping adopted in this invention can stably achieve higher impurity removal rates and enrichment rates of beneficial elements, thus providing a purer and higher-quality raw material basis for preparing high-performance 5083 recycled aluminum alloys for air separation equipment.

[0067] To better illustrate the present invention, the composition and composition changes of the recycled aluminum raw materials produced in the examples and comparative examples, as well as the formulation of 5083 aluminum alloy additives, are summarized in Table 1. In the table, "-" and "+" represent the decrease rate and increase rate of element composition, respectively.

[0068] Table 1. Composition of recycled aluminum raw materials in Examples 1-3 and Comparative Examples 1-2

[0069] The embodiments listed above are only used to better illustrate the core content of the technical solution of the present invention, and their specific parameters and operating conditions should not be construed as any limitation on the scope of protection of the present invention. Any equivalent transformations or reasonable improvements based on the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for producing 5083 recycled aluminum alloy for air separation equipment, characterized by: It comprises the following steps: 1) melt 5083 waste aluminum to obtain a melt; 2) place the melt in a fractional crystallization device, keep the temperature of the melt at 665-670 ℃, then cool the melt placed in the device by a cooling device arranged on the side wall of the device, the melt in contact with the cooled side wall precipitates aluminum primary crystals, the aluminum primary crystals are scraped off and compacted by the up-and-down movement of a scraping device, the scraping device is provided with holes or gaps, and the aluminum melt passes through the holes or gaps while the aluminum primary crystals are scraped off and compacted, so as to realize the up-and-down movement, and the aluminum primary crystals grow by gathering; After the crystallization is completed, pour out the concentrated liquid, remove the end with more impurities of the aluminum ingot, and obtain the regenerated aluminum raw material; the scraping device is rotated by 80-100° along the horizontal plane after completing more than 10 times of up-and-down movement; the cooling refers to cooling by pulse type cooling gas; 3) determine the composition of the regenerated aluminum raw material; 4) remelt the regenerated aluminum raw material, add pure metal based on the composition of the regenerated aluminum raw material to prepare 5083 regenerated aluminum alloy for air separation equipment.

2. The method for preparing 5083 recycled aluminum alloy for air separation equipment according to claim 1, characterized in that: The scraping device is rotated by 90° clockwise or 90° counterclockwise in the horizontal plane after completing 10-20 times of up-and-down movement; The pulse type refers to that the cooling gas is introduced for 2-4 s each time, and then paused for 1 s until the fractional crystallization is completed.

3. The method for preparing 5083 recycled aluminum alloy for air separation equipment according to claim 1, characterized in that: The speed of the up-and-down movement of the scraping device is 5-10 times / min; The cooling gas is introduced at an average velocity of 20 to 40 m 3 / h.

4. The method for preparing 5083 recycled aluminum alloy for air separation equipment according to claim 1, characterized in that: The scraping device is a tamping disc and tamping rod or a ring-shaped plunger; The tamping disc and tamping rod comprise a tamping disc and a tamping rod arranged on the tamping disc, and are provided with holes, and are rotated periodically in the up-and-down movement.

5. The method for preparing 5083 recycled aluminum alloy for air separation equipment according to claim 1, characterized in that: The fractional crystallization is ended when the crystallization is completed to 30% of the concentrated liquid; The cooling device is arranged on the side wall of the upper part of the fractional crystallization device, and the melt in contact with the cooled side wall precipitates aluminum primary crystals; The removal of the end with more impurities of the aluminum ingot in step 2) can be realized by detecting the composition of the aluminum ingot by an instrument, and removing the part with more impurities or 1 / 5-1 / 10 of the aluminum ingot crystallized in the later stage.

6. The method for preparing 5083 recycled aluminum alloy for air separation equipment according to claim 1, characterized in that: The composition of the 5083 waste aluminum is as follows: by mass percentage, Mg: 4.17-4.27% Mn: 0.51-0.54% Fe: 0.57-0.60% Si: 0.44-0.46% Cu: 0.18-0.19% Zn: 0.27-0.30% Cr：0.07-0.09% Ti: 0.04-0.06% Al: balance.

7. The method for preparing 5083 recycled aluminum alloy for air separation equipment according to claim 1, characterized in that: The 5083 waste aluminum is subjected to cleaning treatment before melting; specifically, the oil stains and impurities on the surface of the 5083 waste aluminum are removed. The temperature of the melting in step 1) is 720-760 ℃, and stirring is performed during the melting process, and the melt is statically kept after the melting; The remelting temperature in step 4) is 720-760 ℃, and the aluminum melt needs to be stirred after the addition of the pure metal, and the stirring time is 5-10 min.

8. The method for producing 5083 recycled aluminum alloy for air separation equipment according to claim 7, characterized in that: The stirring time during the melting process in step 1) is 5-10 min, and the static keeping time is 30-60 min.

9. A 5083 regenerated aluminum alloy prepared by the preparation method in any one of claims 1-8.

10. The 5083 regenerated aluminum alloy prepared by the preparation method in any one of claims 1-8 is used for air separation equipment.

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