Preparation process of pure aluminum powder for reducing sodium hydroxide in molten iron

Abstract

The application discloses a preparation process of pure aluminum powder for reducing melt iron-sodium-hydrogen, and specifically comprises the following steps: step 1, drying pure aluminum ingot and loading into a furnace, and continuously stirring after complete melting under inert atmosphere; step 2, adding dried iron-removing agent into the melt in step 1 under inert atmosphere, and continuously stirring; step 3, rotating and degassing and impurity-removing of the melt in step 2 by introducing dried inert gas; step 4, adding dried sodium-removing agent into the melt after step 3 treatment for sodium removal, and removing the dross on the surface of the melt after standing; and step 5, vacuumizing and atomizing the melt after step 4 treatment to obtain high-quality pure aluminum powder.

Description

Technical Field

[0001] This invention relates to the field of pure aluminum powder preparation technology, specifically to a preparation process for pure aluminum powder with reduced iron, sodium, and hydrogen content in the melt. Background Technology

[0002] Pure aluminum powder materials have shown broad application prospects in high-end electronics, composite materials, fine chemicals, and new energy fields. Therefore, higher requirements are being placed on the overall quality of pure aluminum powder materials. In addition to physicochemical properties such as particle size, shape, and activity, many application areas are paying more attention to the metallurgical quality and powder quality of pure aluminum powder materials, including the chemical composition, microstructure, and physical properties of the powder particles. Especially for high-end pure aluminum powders required in fields such as high-end electronics, the high purity requirements make it crucial to reduce elements such as iron, sodium, and hydrogen in the melt during the pure aluminum powder preparation process. Melt treatment is a vital step in the preparation of high-quality aluminum powder, determining the composition, microstructure, and properties of the pure aluminum powder material.

[0003] Existing melt treatment technologies mainly target the purification of aluminum alloy melts by removing Fe, Si, and oxide inclusions. These technologies primarily employ granular refining agents and rotary refining degassing devices to remove impurities and gas from the molten aluminum. The process mainly consists of two steps: First, the addition of the granular refining agent involves using a rotating graphite rod with an inert gas jet function at the bottom to stir the molten aluminum and create a vortex. The granular refining agent is then poured into the vortex through a conduit-like device, where it is drawn into the molten aluminum by the vortex. Second, refining and degassing: after the granular refining agent has been poured out, the baffle is lowered to a designated depth in the molten aluminum, the vortex disappears, and the rotating graphite rod continues to rotate and jet until the set time is completed, thus completing the refining and degassing of the molten aluminum. For high-purity aluminum used in the electronic-grade aluminum industry, the three-layer liquid electrolysis method is mainly used to achieve a purity of 4N~5N (99.99%~99.999%). Besides the disadvantages of energy consumption, environmental protection, and stringent operating procedures, trace alkali metals (Na, Ca) cannot be completely blocked, which is detrimental to ensuring its electrochemical and other physical properties. Therefore, it is necessary to develop a method to improve the purity of industrial pure aluminum ingots (99.85% purity) through a melt treatment process after melting, to achieve a purity of 4N to meet the needs of high-purity magnesium powder and other products required in the electronics industry. In particular, it is crucial to solve the problem of precise control over inclusions of elements such as Na, H, and Fe, as well as their oxides. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a preparation process for reducing the iron, sodium, and hydrogen content of the melt using pure aluminum powder, thereby solving the problem of ensuring the uniformity and cleanliness of the melt composition through precise control of elements such as Na, H, and Fe, as well as oxide inclusions.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A preparation process for reducing the iron, sodium, and hydrogen content of melted pure aluminum powder, the specific steps of which are as follows:

[0007] Step 1: After drying the pure aluminum material, load it into the furnace and stir continuously for 5 to 10 minutes under an inert atmosphere after it is completely melted;

[0008] Step 2: Under an inert atmosphere, add the dried iron removal agent to the melt from Step 1 and continue stirring for 30 to 60 minutes;

[0009] The amount of iron removal agent added is 2wt%~4wt% based on the mass percentage of the melt; the iron removal agent includes KCl, NaCl, Na2B4O7, NaF and MgCl2;

[0010] Step 3: Inert gas is introduced into the melt from Step 2 and rotated to remove gas and impurities from the melt; the inert gas is Ar gas, and the degassing and impurity removal operation time is 15 min to 45 min; the refining agent needs to be dried before use, and the drying temperature should be between 250-350℃, and the drying time should be no less than 2 hours.

[0011] Step 4: Add the dried sodium removal agent to the melt after step 3 to remove sodium, and remove the sodium-containing slag from the surface of the melt after standing.

[0012] Step 5: After placing the melt container processed in Step 4 into a sealed container, a vacuum is drawn, and the melt is injected into the inlet of the atomization production line to start atomization powder production and obtain pure aluminum powder products.

[0013] In steps 1 to 4, the temperature of the melt is maintained between 720°C and 770°C; the temperature at which atomization powdering begins in step 5 should also be between 720°C and 770°C.

[0014] Preferably, the iron removal agent comprises, by mass percentage, the following components: 5wt%~15wt% KCl, 5wt%~15wt% NaCl, 55wt%~65wt% Na2B4O7, 5wt%~15wt% NaF, and 5wt%~15wt% MgCl2.

[0015] Preferably, in step 2, a spraying device that works in conjunction with the rotary stirring degassing device is used to uniformly add the iron removal agent into the stirred melt and mix it evenly.

[0016] Preferably, in step 3, the spraying device adds the dried solid solvent while simultaneously rotating and stirring the melt to remove gas and impurities; the amount of refining agent added is 0.8wt%~2wt% based on the mass percentage of the melt.

[0017] Preferably, the refining agent comprises the following components, calculated by mass percentage: 20wt%~40wt% NaCl, 35wt%~55wt% KCl, and 15wt%~35wt% Na3AlF6.

[0018] Preferably, in step 4, the sodium removal agent is C2Cl6; the amount of sodium removal agent added is 2wt%-4wt% based on the mass percentage of the melt.

[0019] Preferably, the time between the complete melting of pure aluminum and the start of atomization powder spraying is ≤5h, of which the time spent at or above 750℃ is ≤2h.

[0020] Preferably, the stirring tool is a graphite rotor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention solves the problems of high impurity residue, high energy consumption, and unstable powder performance in traditional aluminum powder preparation by using a synergistic design of targeted impurity removal, deep melt purification, and low-temperature atomization. Specifically designed for high-quality pure aluminum powder or aluminum alloy powder, this invention optimizes and improves the composition of the iron removal agent, unexpectedly discovering an iron removal agent component with excellent iron removal effect. Combined with a rotary degassing device, and using rotary degassing and refining agents, it achieves homogenization and purification, realizing excellent effects in removing iron, sodium, and oxide inclusions, ensuring that the prepared pure aluminum powder and aluminum alloy powder meet high-quality production requirements.

[0023] 2. This invention optimizes the process flow and combines inert gas slag removal and refining flux-assisted blowing slag removal processes to develop iron removal agents and fluxes suitable for high-quality aluminum powder and aluminum alloy powder. It achieves precise control over Fe, Na and oxide inclusions and has achieved excellent results in practical applications, showing great potential for widespread application. Attached Figure Description

[0024] Figure 1 Pinhole observation diagram of oxide inclusions in aluminum ingots used as raw materials.

[0025] Figure 2 This is a pinhole observation image of the melt after the powdering pretreatment in Example 1. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0027] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0028] I. A preparation process for reducing the iron, sodium, and hydrogen content of molten pure aluminum powder

[0029] Step 1: Load pure aluminum or prepared aluminum alloy components into the furnace, and after complete melting, continue stirring for 10 to 20 minutes under an inert atmosphere;

[0030] Step 2: Under an inert atmosphere, add an iron removal agent to the melt from Step 1 and continue stirring for 30 to 60 minutes; wherein, the amount of iron removal agent added is 2 wt% to 4 wt% according to the mass percentage of the melt; the iron removal agent includes KCl, NaCl, Na2B4O7, NaF and MgCl2;

[0031] Step 3: Inert gas is introduced into the melt from Step 2 for rotary degassing and impurity removal; wherein, the inert gas is Ar, and the degassing and impurity removal time is 20 min to 30 min;

[0032] Step 4: Add the dried sodium removal agent to the melt treated in Step 3 to remove sodium, and then remove the slag on the surface of the melt;

[0033] Step 5: Vacuum atomize the melt processed in Step 4 to obtain high-quality aluminum powder or aluminum alloy powder.

[0034] In steps 1 to 4, the temperature of the melt is maintained at 720℃ to 770℃.

[0035] This invention, through in-depth research into the preparation process of pure aluminum powder, discovered that existing technologies for preparing pure aluminum from bauxite, limited by thermodynamics and cost, still result in aluminum ingots containing trace amounts of iron (typically 0.1wt%~0.3wt%). This necessitates iron removal treatment when using aluminum ingots as raw materials for subsequent processing. However, existing iron removal technologies primarily target the recycling of waste aluminum alloys. While these processes utilize dried iron-removing agents, the waste aluminum alloys themselves have high iron content (generally far exceeding 0.3wt%, typically above 0.5wt%). Even after iron removal treatment, the iron content can still reach above 0.1wt%, making it extremely difficult to further reduce the iron content in pure aluminum. Therefore, this invention addresses the technical problems in existing aluminum powder preparation processes, such as the difficulty in deeply removing impurities, incomplete melt purification leading to low powder purity, and high gas content. It proposes improvements from two aspects: the preparation process and the composition of the dried iron-removing agent. By constructing a synergistic treatment system of "step-by-step purification-directional impurity removal," it innovatively proposes a step-by-step impurity removal scheme. First, based on the differences in the physicochemical properties of different impurity elements in the aluminum melt, a five-element composite iron removal agent with borax as the matrix was designed after drying. The core idea of ​​this invention in designing the dried iron removal agent is to construct a composite molten salt system with highly efficient iron-capturing capabilities, achieving deep removal of iron impurities from the aluminum melt through the synergistic effect between flux components. Then, this invention, through the synergistic effect of Ar gas rotational degassing and a specific ratio of refining agent, breaks through the problem of simultaneously removing fine inclusions and gases inside the melt; finally, a sodium removal agent after drying C2Cl6 is precisely introduced, utilizing its high-temperature decomposition characteristics to achieve targeted removal of sodium. This invention also effectively suppresses oxidation and grain coarsening while ensuring melt fluidity by precisely controlling the melt treatment temperature window (720℃-770℃) and the total treatment time (≤5h). This multi-stage purification strategy not only significantly improves the removal efficiency of impurity elements, but also achieves a qualitative breakthrough in the purity, sphericity and physical properties of the aluminum powder produced through the synergistic effect of the treatment agents at each stage, providing an ideal raw material guarantee for high-performance aluminum-based composite materials.

[0036] In some embodiments of the present invention, the temperature of the melt is maintained at 720°C to 770°C in steps 1 to 4. In the preparation process described in the present invention, when preparing pure aluminum powder, the temperature of the melt is maintained between 720°C and 760°C. However, when entering the refining and degassing process (steps 2 to 4), the melt temperature is maintained at 740°C to 750°C. The melt temperature is set based on the fluidity of the molten aluminum before atomization and the balance between temperature and melt gas absorption; the higher the temperature, the greater the gas absorption. Furthermore, pure aluminum does not have an intermediate alloy melting process compared to other alloys, so its overall temperature range is slightly lower than that of other aluminum alloys. Therefore, the melt temperature can be 720°C, 730°C, 740°C, 750°C, 760°C, etc., as well as all ranges and sub-ranges between these values; it should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0037] In some embodiments of the present invention, the dried iron removal agent comprises, by mass percentage, the following components: 5 wt% to 15 wt% KCl, 5 wt% to 15 wt% NaCl, 55 wt% to 65 wt% Na₂B₄O₇, 5 wt% to 15 wt% NaF, and 5 wt% to 15 wt% MgCl₂. The present invention discovers that by using borax (Na₂B₄O₇) as the main component, the B₂O₃ produced by its decomposition at high temperature forms a stable ferroboron-boron compound (FeB₂O₄) with Fe, achieving chemical complexation and fixation of iron. By introducing KCl and NaCl to form a low-melting-point eutectic system, the overall viscosity of the flux is significantly reduced, promoting the separation efficiency of slag and molten aluminum. The addition of NaF further regulates the surface tension of the flux, enhancing its wetting and adsorption capacity for Fe-Al intermetallic compounds. The addition of MgCl₂ preferentially combines with free oxygen in the melt through a displacement reaction, inhibiting the formation of oxide inclusions. The components form a highly fluid molten salt film at high temperatures, effectively capturing dispersed Fe elements and their oxides, and enabling rapid slag flotation through density differences, ultimately forming a multi-dimensional synergistic iron impurity purification mechanism. If the proportions of the components in the dried iron remover deviate from the design range, it will disrupt the physicochemical balance of the molten salt system, leading to multi-dimensional failures. When the borax (Na2B4O7) content is below 55wt%, the amount of B2O3 generated in the flux is insufficient, failing to fully complex Fe elements, resulting in a sharp reduction in the formation of stable compounds such as FeB2O4, significantly reducing the Fe removal effect. Conversely, if it exceeds 65wt%, the high viscosity of the borate melt reduces the density difference between the slag and the molten aluminum, worsening the separation effect. Furthermore, when the total KCl / NaCl content is less than 10wt%, the eutectic point of the dried iron remover will increase, preventing it from fully melting at the 720℃ process temperature, forming solid inclusions that hinder interface renewal. If the total KCl / NaCl content exceeds 30wt%, excessive Cl...- This will exacerbate melt corrosion, leading to erosion of the equipment's inner walls and the introduction of Fe contamination, which in turn will increase the Fe content in the powder. When the NaF content is below 5 wt%, the flux surface tension increases, increasing the wetting angle of Fe-Al intermetallic compounds and significantly weakening the adsorption capacity for micron-sized FeAl3 particles; exceeding 15 wt% will cause toxic gases to be generated due to increased fluoride volatilization, and will also cause the loss of effective flux components. When the MgCl2 content is less than 5 wt%, it does not combine sufficiently with free oxygen in the melt, and the content of iron-oxygen inclusions will actually increase, resulting in a poorer iron removal effect; while an excess will trigger a magnesothermic reaction, and the generated MgO will form new inclusions with higher melting points. The imbalance of the proportions of each component ultimately leads to the synergistic failure of key parameters such as flux melting point, viscosity, and surface tension, resulting in a significant decrease in the removal rate of iron and the introduction of secondary pollutants, which will seriously affect the quality of the powder. Therefore, in step 2, the amount of the dried iron-removing agent added can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc., as well as all ranges and sub-ranges between these values; it should be understood that, in the implementation scheme, any of the above ranges can be combined with any other range. In the dried iron-removing agent, calculated according to the mass percentage of the dried iron-removing agent, the KCl content in the dried iron-removing agent can be 5wt%, 7wt%, 10wt%, 13wt%, 15wt%, etc., as well as all ranges and sub-ranges between these values; the NaCl content in the dried iron-removing agent can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 12wt%, 14wt%, 15wt%, etc., as well as all ranges and sub-ranges between these values; the Na2B4O7 content in the dried iron-removing agent can be 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 6 The content of NaF in the dried iron removal agent can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 12wt%, 14wt%, 15wt%, etc., and all ranges and sub-ranges between these values; the content of MgCl2 in the dried iron removal agent can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 12wt%, 14wt%, 15wt%, etc., and all ranges and sub-ranges between these values; it should be understood that, in the embodiments, any of the above ranges can be combined with any other ranges.

[0038] In some embodiments of the present invention, in step 2, a rotary degassing device is used to add the dried iron removal agent to the melt being stirred.

[0039] In some embodiments of the present invention, in step 3, while adding the refining agent using a rotary degassing device, rotary degassing and impurity removal are also performed simultaneously; the amount of refining agent added is 0.8wt%~2wt% based on the mass percentage of the melt. The refining agent comprises the following components based on the mass percentage: 20wt%~40wt% NaCl, 35wt%~55wt% KCl, and 15wt%~35wt% Na3AlF6. The present invention further removes oxygen and oxide inclusions from the melt by combining the addition of a refining agent with rotary degassing. The amount of refining agent added should not be too low, as this will prevent the formation of a continuous slag layer and result in poor inclusion removal; the amount added should also not be too high, as excessive flux will create eddy current damping during rotary degassing, affecting the removal effect and introducing flux impurities, which will instead lead to an increase in the oxygen content of the powder. Furthermore, the ratio of NaCl, KCl, and Na3AlF6 in the refining agent also needs to be controlled. If it is not within the specified range, the degassing and impurity removal effect will be significantly reduced. Therefore, in step 3, the amount of refining agent added can be 0.8wt%, 1.0wt%, 1.5wt%, 2.0wt%, etc., and all ranges and sub-ranges between these values; the content of NaCl in the refining agent can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, etc., and all ranges and sub-ranges between these values; the content of KCl in the refining agent can be 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, etc., and all ranges and sub-ranges between these values; the content of Na3AlF6 in the refining agent can be 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, etc., and all ranges and sub-ranges between these values; it should be understood that, in the implementation scheme, any of the above ranges can be combined with any other range.

[0040] In some embodiments of the present invention, in step 4, the dried sodium-removing agent is C2Cl6; the amount of the dried sodium-removing agent added is 2wt%-4wt% based on the mass percentage of the melt. Since the dried iron-removing agent and refining agent contain a certain amount of sodium, the dried sodium-removing agent is added in step 4 to remove sodium from the melt. The amount of the dried sodium-removing agent added can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, etc., as well as all ranges and sub-ranges between these values; it should be understood that, in embodiments, any of the above ranges can be combined with any other range.

[0041] In some embodiments of the present invention, the time between the complete melting of pure aluminum and atomization powder spraying is ≤5 hours. To avoid the melt absorbing air during processing, which could lead to an increase in impurity content, the melt processing time (from melting to atomization powder spraying) should be ≤5 hours.

[0042] In some embodiments of the present invention, the stirring tool is a graphite rotor. Using a graphite rotor for stirring prevents other elements in the equipment from entering the melt during the preparation process described in this invention, thus avoiding secondary contamination of the melt.

[0043] II. Examples and Comparative Examples

[0044] 1. Preparation of pure aluminum powder

[0045] Example 1

[0046] Step 1: Load the purchased pure aluminum ingot (100kg) into the furnace, and after melting, keep the melt temperature at 760℃ and stir continuously. The stirring tool is a graphite rotor. During stirring, the graphite rotor is pressurized with inert gas and stirred continuously for 10 minutes.

[0047] Step 2: Iron removal is achieved by adding a dried iron-removing agent to the melt while stirring using a rotary degassing device. The amount of dried iron-removing agent added is calculated to be 4 wt% based on the mass of the melt. This process lasts for 30 minutes, with the melt temperature at 750℃. The composition of the dried iron-removing agent is: 10% KCl + 10% NaCl + 60% Na₂B₄O₇ + 10% NaF + 10% MgCl₂.

[0048] Step 3: While adding the refining agent to the melt using a rotary degassing device, an inert gas is simultaneously introduced for rotary degassing and impurity removal. The gas is high-purity Ar (purity requirement: H₂O + O₂ < 5 ppm). This process lasts for 20 minutes, and the melt temperature is 750℃. The amount of refining agent added is 1 wt% based on the melt mass. The refining agent formula is 30% NaCl + 45% KCl + 25% Na₃AlF₆.

[0049] Step 4: Add the dried sodium removal agent to the melt treated in Step 3 to remove sodium. After standing for 5 minutes, remove the scum from the surface of the melt. The amount of dried sodium removal agent added is 3 wt% based on the mass of the melt.

[0050] Step 5: The melt after step 4 is protected by passing high-purity nitrogen gas (purity requirement: H2O+O2<5ppm), and then vacuum-atomized to obtain high-quality pure aluminum powder.

[0051] Example 2

[0052] The method is an adjustment based on Example 1, the difference being that the composition of the dried iron removal agent is 5% KCl + 5% NaCl + 65% Na2B4O7 + 10% NaF + 15% MgCl2. All other steps are exactly the same as in Example 1.

[0053] Example 3

[0054] The method is an adjustment based on Example 1, the difference being that the composition of the dried iron removal agent is 10% KCl + 10% NaCl + 55% Na2B4O7 + 15% NaF + 10% MgCl2. All other steps are exactly the same as in Example 1.

[0055] Example 4

[0056] The method is an adjustment based on Example 1, the difference being that the composition of the dried iron removal agent is 15% KCl + 15% NaCl + 60% Na2B4O7 + 5% NaF + 5% MgCl2. All other steps are exactly the same as in Example 1.

[0057] Example 5

[0058] The method is an adjustment based on Example 1, the difference being that the composition of the dried iron removal agent is 10% KCl + 15% NaCl + 60% Na2B4O7 + 10% NaF + 5% MgCl2. All other steps are exactly the same as in Example 1.

[0059] Comparative Example 1

[0060] This is an adjustment based on Example 1, the difference being that no dried iron removal agent was added, but the other steps are exactly the same as in Example 1.

[0061] Comparative Example 2

[0062] The method is based on Example 1, but with the following adjustment: the dried iron removal agent is added along with the pure aluminum raw material in step 1, while the other steps are exactly the same as in Example 1.

[0063] Comparative Example 3

[0064] The method is based on Example 1, but with the difference that step 4 is not performed. The other steps are exactly the same as in Example 6.

[0065] 2. Results Analysis

[0066] In the examples and comparative examples of pure aluminum powder, the contents of oxide inclusions, solid O / H, Fe, and Na in the aluminum ingots used as raw materials were detected. The oxide inclusion situation in the aluminum ingots used as raw materials is as follows: Figure 1As shown, the pinholes on the inspected surface were rated as level 3, with solid O content of 0.00060 wt%, solid H content of 0.00016 wt%, Fe content of 0.1 wt%, and Na content of 0.0056 wt%. Using this aluminum ingot as raw material, pure aluminum powder was prepared according to the methods of the above examples and comparative examples. The sample quality is shown in Table 1. In Example 1, samples were taken from the melt after pretreatment before powder preparation. The oxide inclusions in the melt are as follows... Figure 2 As shown in Table 1 and Figures 1-2 The removal effect of the preparation process described in this invention is compared.

[0067] Table 1

[0068]

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A preparation process for reducing the iron, sodium, and hydrogen content of melted pure aluminum powder, characterized in that, The specific steps are as follows: Step 1: After drying the pure aluminum material, load it into the furnace and stir continuously for 5 to 10 minutes under an inert atmosphere after it is completely melted; Step 2: Under an inert atmosphere, add the dried iron removal agent to the melt from Step 1 and continue stirring for 30 to 60 minutes; The amount of iron removal agent added is 2wt%~4wt% based on the mass percentage of the melt; the iron removal agent includes KCl, NaCl, Na2B4O7, NaF and MgCl2; Step 3: Inert gas is introduced into the melt from Step 2 for rotary blowing to remove gas and impurities from the melt; the inert gas is Ar gas, and the degassing and impurity removal operation time is 15 min to 45 min; the refining agent is dried before use at a temperature of 250-350℃ for a time of not less than 2 hours; the refining agent is added using a rotary degassing device. Step 4: Add the dried sodium removal agent to the melt after step 3 to remove sodium, and remove the sodium-containing slag from the surface of the melt after standing. Step 5: After placing the melt container processed in Step 4 into a sealed container, a vacuum is drawn, and the melt is injected into the inlet of the atomization production line to start atomization powder production and obtain pure aluminum powder products. In steps 1 to 4, the temperature of the melt is maintained at 720℃ to 770℃; in step 5, the temperature at which atomization powdering begins is 720℃ to 770℃. The iron removal agent contains the following components by mass percentage: 5wt%~15wt% KCl, 5wt%~15wt% NaCl, 55wt%~65wt% Na2B4O7, 5wt%~15wt% NaF, and 5wt%~15wt% MgCl2.

2. The preparation process according to claim 1, characterized in that, In step 2, a spraying device that works in conjunction with the rotary stirring degassing device is used to uniformly add the iron removal agent to the stirred melt and mix it evenly.

3. The preparation process according to claim 1, characterized in that, In step 3, the amount of refining agent added is calculated as 0.8wt%~2wt% based on the mass percentage of the melt.

4. The preparation process according to claim 3, characterized in that, The refining agent comprises the following components, calculated as a percentage by mass: 20wt% to 40wt% NaCl, 35wt% to 55wt% KCl, and 15wt% to 35wt% Na3AlF6.

5. The preparation process according to claim 1, characterized in that, In step 4, the sodium removal agent is C2Cl6; the amount of sodium removal agent added is 2wt%-4wt% based on the mass percentage of the melt.

6. The preparation process according to claim 1, characterized in that, The time between the complete melting of pure aluminum and the start of atomization powder spraying is ≤5h, of which the time spent at temperatures above 750℃ is ≤2h.

7. The preparation process according to claim 1, characterized in that, The stirring tool is a graphite rotor.

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