Equipment and method for refining aluminum by zone smelting

Abstract

This invention discloses an apparatus and method for purifying aluminum through zone melting, specifically relating to the field of aluminum purification. It includes: a moving assembly connected to a quartz tube, within which a graphite boat is placed. The graphite boat has different depths at its two ends, forming a pre-angled inclined surface inside. One end of the quartz tube has an exhaust opening; an induction coil sleeved on the outside of the quartz tube with a gap between them, and connected to a heating power source; the moving assembly capable of driving the quartz tube to move horizontally within the induction coil; an argon gas storage mechanism connected to the other end of the quartz tube via a pipeline; and an infrared thermometer located above the quartz tube, facing the central heating area of ​​the induction coil, used to monitor the temperature distribution on the sample surface within the graphite boat. Based on this apparatus, the compositional uniformity of aluminum can be improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum purification, and more particularly to an apparatus and method for purifying aluminum by zone smelting. Background Technology

[0002] Zone melting, especially horizontal zone melting, has become an important method for producing ultra-high purity aluminum of 6N (99.9999%) and above, as a highly efficient physical purification technology. The principle of this method is based on the difference in solubility of impurity elements in molten aluminum and solidified aluminum (i.e., the segregation effect). When a small melting zone slowly moves along the aluminum ingot, impurities with a distribution coefficient less than 1 accumulate towards the tail end of the melting zone, while impurities with a distribution coefficient greater than 1 accumulate at the head end. Through multiple cycles, ultra-high purity aluminum is finally obtained in the middle section of the ingot. Despite the advantages of zone melting in principle, existing technologies and equipment still have the following problems in practical applications: traditional heating methods are inefficient, and melting zone control is imprecise; imprecise melting zone control leads to low product purification rates; and product radial uniformity is poor. Summary of the Invention

[0003] The main objective of this application is to provide an apparatus and method for refining aluminum by zone melting, which aims to solve the problem of poor radial uniformity of products obtained by existing refining equipment.

[0004] To achieve the above objectives, this application provides a zone melting and refining device for aluminum, comprising: a moving assembly connected to a quartz tube, a graphite boat placed inside the quartz tube, the inner wall of the graphite boat being covered with a boron nitride layer, the two ends of the graphite boat having different depths, forming a slope at a preset angle inside, and an exhaust opening at one end of the quartz tube; an induction coil sleeved on the outside of the quartz tube with a gap between them, the induction coil being connected to a heating power source; the moving assembly capable of driving the quartz tube to move horizontally within the induction coil; an argon gas storage mechanism connected to the other end of the quartz tube via a pipeline; and an infrared thermometer located above the quartz tube, the infrared thermometer facing the central heating area of ​​the induction coil, used to monitor the temperature distribution on the sample surface inside the graphite boat; wherein, the preset angle is determined based on the height of the aluminum ingot to be refined, the length of the melting zone, and the solid density and liquid density of the aluminum ingot to be refined.

[0005] Optionally, the expression for the preset angle is:

[0006] In the formula, The height of the aluminum ingot to be refined. The length of the melting zone; This is the ratio of the solid density to the liquid density of the aluminum ingot to be purified.

[0007] Optionally, the moving component includes: a guide rail with a lead screw inside, a slider sleeved on the lead screw, a drive mechanism connected to one end of the lead screw, and a controller connected to the drive mechanism for controlling the moving speed of the slider; a connecting plate connected to the slider, and heat-insulating support frames connected to both ends of the connecting plate, with the quartz tube located on the heat-insulating support frames.

[0008] Optionally, a V-groove is provided at one end of the heat insulation support frame, and the quartz tube is located in the V-groove.

[0009] Optionally, the argon storage device includes an argon cylinder, the outlet pipeline of which is equipped with a pressure reducing valve and a flow control valve and is connected to a quartz tube.

[0010] To achieve the above objectives, this application also provides a method for refining aluminum through zone melting, using a zone melting apparatus, comprising: placing an aluminum ingot to be refined in a graphite boat, wherein the length of the aluminum ingot to be refined is 0.6-0.8 times the length of the graphite boat, and the placement position is such that the distance from the beginning and end of the graphite boat is equal; introducing argon gas into a quartz tube through an argon gas storage mechanism at a flow rate of 0.5-2.0 L / min; heating and melting through an induction coil, and moving the quartz tube horizontally within the induction coil by a moving component; monitoring the thermal field of the melting zone in real time using an infrared thermometer, and determining the width of the melting zone based on the temperature distribution of the thermal field, such that the width of the melting zone is 1.0-1.5 times the diameter of the aluminum ingot to be refined.

[0011] Optionally, argon gas is introduced into the quartz tube through an argon gas storage device at a flow rate of 0.5-2.0 L / min, including: purging and replacing the quartz tube for 10-30 minutes at a flow rate of 1.0-2.0 L / min during the initial stage of melting through the argon gas storage device, and using a flow rate of 0.5-1.0 L / min during the melting process.

[0012] Optionally, before placing the aluminum ingot to be purified in the graphite boat, the method further includes: immersing the aluminum ingot to be purified in a 20%-30% sodium hydroxide solution for 15-25 minutes for cleaning, immersing it in distilled water for 5-15 minutes for cleaning, and using anhydrous ethanol to dehydrate the cleaned aluminum ingot.

[0013] Compared with the prior art, the beneficial effects of this application are as follows: The zone melting and refining aluminum equipment of this invention employs an electromagnetic induction heating device composed of an induction coil and a heating power supply, replacing the traditional resistance heating method. Through its unique energy concentration and rapid thermal response characteristics, it achieves precise dynamic control of the temperature and shape of the molten zone, maintaining a reasonably wide and stable solid-liquid interface, creating ideal conditions for impurity separation. Real-time monitoring and feedback of the molten zone temperature field using an infrared thermometer, combined with the unique energy concentration and rapid thermal response characteristics of electromagnetic induction heating, enables precise dynamic adjustment of the molten zone length, position, and axial temperature gradient, maintaining a stable and flat solid-liquid interface. This effectively suppresses dendrite growth. The angle of the inclined plane inside the graphite boat is determined based on the height of the aluminum ingot to be purified, the length of the molten zone, and the solid and liquid phase densities of the ingot. This effectively utilizes the gravitational component to counteract the mass migration effect caused by the density difference between the solid and liquid phases, thereby suppressing the phenomenon of the material becoming "thicker at one end and thinner at the other." This inclined plane structure ensures the stability of the molten zone morphology, preventing aluminum melt from overflowing. Furthermore, by stabilizing the solid-liquid interface morphology, it significantly improves the axial and radial compositional uniformity of the product, effectively eliminating the problems of "high at the beginning and low at the end" and radial segregation, ultimately greatly improving the yield and quality consistency of high-purity aluminum. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a zone smelting and aluminum refining device according to this application; Figure 2 This is a purity test image of four positions on an aluminum ingot obtained from Example 1 of a method for refining aluminum by zone melting according to this application; Figure 3 This is a purity test image of four positions on an aluminum ingot obtained from Example 1 of a method for refining aluminum by zone melting according to this application; Figure 4 This is a purity test image of four positions on an aluminum ingot obtained from Example 1 of a method for refining aluminum by zone melting according to this application. Figure 5 This is a purity test image of four positions of an aluminum ingot obtained in Example 1 of the method for refining aluminum by zone melting according to this application. Figure 6 This is a purity test image of four positions on an aluminum ingot obtained from Comparative Example 1 of the method for refining aluminum by zone melting according to this application. Figure 7 This is a purity test image of four positions on an aluminum ingot obtained from Comparative Example 1 of the method for refining aluminum by zone melting according to this application. Figure 8 This is a purity test image of four positions on an aluminum ingot obtained from Comparative Example 1 of the method for refining aluminum by zone melting according to this application. Figure 9This is a purity test image of four positions of an aluminum ingot obtained from Comparative Example 1 of the method for refining aluminum by zone melting according to this application.

[0015] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] The first embodiment of the present invention provides a device for zone melting and purifying aluminum, including a moving component, an induction coil 1, an argon storage mechanism, and an infrared thermometer 2. A quartz tube 3 is connected to the moving component, and a graphite boat 4 is placed inside the quartz tube 3. The inner wall of the graphite boat is covered with a boron nitride layer, and the two ends of the graphite boat 4 have different depths, forming a bevel at a preset angle inside. One end of the quartz tube 3 is provided with an exhaust opening. The induction coil 1 is sleeved on the outside of the quartz tube 3, and there is a gap between the two. The induction coil 1 is connected to a heating power supply 14. The moving component can drive the quartz tube 3 to move horizontally inside the induction coil 1. The argon storage mechanism is connected to the other end of the quartz tube 3 through a pipeline. The infrared thermometer 2 is located above the quartz tube 3, and the infrared thermometer 2 faces the central heating area of ​​the induction coil 1 to monitor the temperature distribution on the sample surface inside the graphite boat 4. The preset angle is determined according to the height of the aluminum ingot to be purified, the length of the melting zone, and the solid density and liquid density of the aluminum ingot to be purified.

[0018] In this embodiment, an electromagnetic induction heating device composed of an induction coil 1 and a heating power supply 14 is used to replace the traditional resistance heating method. Through its unique energy concentration and rapid thermal response characteristics, it achieves precise dynamic control of the temperature and shape of the molten zone, maintaining a reasonably wide and stable solid-liquid interface, creating ideal conditions for impurity separation. Simultaneously, the alternating magnetic field induces a strong electromagnetic stirring force in the molten aluminum. This effect not only effectively breaks up the diffusion boundary layer in the melt but also significantly enhances the mass transfer process of impurities from the solidification front to the interior of the molten zone, improving the separation of various impurities, especially those with distribution coefficients close to... The high migration efficiency of the difficult-to-remove impurities in this invention, coupled with its non-contact heating characteristics that avoid introducing external contamination, ensures the high cleanliness requirements of the high-purity aluminum preparation process while improving purification efficiency and product purity. Furthermore, the electromagnetic induction heating device used in this invention generates an alternating magnetic field that has a unique synergistic purification effect on magnetic impurities such as iron (Fe) in the melt: on the one hand, the strong electromagnetic stirring effect enhances the macroscopic mass transfer process of all impurities; on the other hand, iron impurities, due to their inherent ferromagnetism, interact with the external strengthening magnetic field and are subjected to additional magnetization forces compared to other non-magnetic impurities. This magnetization force is transformed into a directional driving force in the magnetic field gradient and melt environment. This force, superimposed on the driving force based on the segregation effect, gives iron impurities a higher effective migration speed, allowing them to accumulate more efficiently towards the tail of the melt zone, thus achieving selective and enhanced removal of iron. The infrared thermometer 2 monitors and provides real-time feedback on the temperature field of the molten zone. Combined with the energy concentration and rapid thermal response characteristics unique to electromagnetic induction heating, precise dynamic adjustment of the length, position, and axial temperature gradient of the molten zone is achieved. This maintains a stable and flat solid-liquid interface, effectively suppressing dendrite growth. The preset tilt angle set inside the graphite boat 4 effectively utilizes the gravitational component to counteract the mass migration effect caused by the density difference between the solid and liquid phases, thereby suppressing the phenomenon of "thickening at one end and thinning at the other" in the material. This inclined structure ensures the stability of the molten zone morphology and prevents aluminum melt from overflowing. Furthermore, by stabilizing the solid-liquid interface morphology, it significantly improves the axial and radial compositional uniformity of the product, effectively eliminating the problems of "high at the beginning and low at the end" and radial segregation, ultimately greatly improving the yield and quality consistency of high-purity aluminum.

[0019] For example, the graphite boat 4 uses isostatically pressed high-purity graphite substrate with a purity ≥99.99% and a density ≥1.85 g / cm³. 3It has low porosity. The boron nitride purity is ≥99.99%, the boron nitride layer thickness is 10±5μm, the coating temperature resistance is ≥1000℃, and it does not wet the molten aluminum. The boron nitride layer can be prepared by vacuum impregnation combined with high-temperature sintering. Boron nitride has the characteristics of non-wetting with molten aluminum, chemical inertness, and high thermal stability, which can effectively avoid direct contact and adhesion between the molten aluminum and the graphite boat. The resulting benefits include: ① preventing impurities such as carbon and boron in the graphite boat from contaminating the high-purity aluminum ingot, ensuring product purity; ② the aluminum ingot can be easily demolded after the experiment without mechanical peeling, avoiding damage to the graphite boat surface and significantly extending the service life of the graphite boat; ③ the coating itself has high purity and will not introduce harmful impurities such as alkali metals, iron, and silicon, meeting the cleanliness requirements for the preparation of ultra-high purity aluminum.

[0020] Furthermore, preset angle The expression is:

[0021] In the formula, The height of the aluminum ingot to be refined. The length of the melting zone; This represents the ratio of the solid density to the liquid density of the aluminum ingot to be purified. Using the above formula, the graphite boat 4 with an inclination angle of less than 2° is calculated. This design strictly adheres to the compensation principle of mass transport during zone melting, and can solve the problem of poor radial uniformity of the product.

[0022] Specifically, the moving component includes a guide rail 5 with a lead screw inside. A slider 6 is sleeved on the lead screw, and one end of the lead screw is connected to a drive mechanism 7. The drive mechanism 7 is connected to a controller 8 for controlling the moving speed of the slider 6. A connecting plate 9 is connected to the slider 6, and heat-insulating support frames 10 are connected to both ends of the connecting plate 9. The quartz tube 3 is located on the heat-insulating support frame 10. Furthermore, a V-groove is formed at one end of the heat-insulating support frame 10, and the quartz tube 3 is located in the V-groove. The argon storage mechanism includes an argon cylinder 11. A pressure reducing valve and a flow control valve 12 are installed on the outlet pipe of the argon cylinder 11 and are connected to the quartz tube 3. The infrared thermometer 2 is connected to the connecting plate 9 via a support column 13, aligned with the central heating area of ​​the induction coil 1, and moves simultaneously with the quartz tube 3.

[0023] In this embodiment, the drive mechanism 7 can be a motor. The speed of the motor is controlled by the controller 8, so that the slider 6 moves at a constant speed along the lead screw and at a preset speed. Combined with the infrared thermometer 2, the temperature field of the melting zone is monitored and fed back in real time. Through real-time data interaction, the speed of the motor or the heating power of the induction coil 1 is adjusted, thereby realizing the adjustment of the moving speed and heating temperature of the quartz tube 3. This ensures that the movement of the heater is precisely synchronized with the formation of the melting zone, avoiding the destruction of the steady-state concentration field by mechanical vibration and thermal disturbance. This completely solves the "impurity back swallowing" phenomenon caused by interface instability, and significantly improves the impurity segregation efficiency and the purity of the final product.

[0024] A second embodiment of the present invention provides a method for refining aluminum by zone melting, using a zone melting aluminum refining device, specifically including the following steps: Step S1: Immerse the 4N aluminum ingot to be purified in a 20%-30% sodium hydroxide solution for 15-25 minutes, then immerse it in distilled water for 5-15 minutes, and finally dehydrate the cleaned aluminum ingot with anhydrous ethanol. Step S2: Place the dehydrated aluminum ingot to be purified into the graphite boat 4 and then into the quartz tube 3; wherein the length of the aluminum ingot to be purified is 0.6-0.8 times the length of the graphite boat, and the placement position is equal to the distance from the beginning and end of the graphite boat. For example, the graphite boat 4 is a rectangular trough with a length of 210 mm, a width of 26 mm, and a height of 26 mm; one end has a depth of 15 mm, and the other end has a depth of 22 mm; the quartz tube 3 has an outer diameter of 50 mm, a length of 440 mm, and a wall thickness of 2.5 mm.

[0025] Step S3: Argon gas is introduced into the quartz tube 3 through the argon gas storage mechanism at a flow rate of 0.5-2.0 L / min; Specifically, through the argon storage mechanism, the quartz tube 3 is purged and replaced for 10-30 minutes at a flow rate of 1.0-2.0 L / min at the initial stage of melting, and a flow rate of 0.5-1.0 L / min is used during the melting process.

[0026] Step S4: Start the power supply and motor, and adjust the motor speed through controller 8. Heat and melt the aluminum ingot to be purified through induction coil 1. To match the melting temperature of the aluminum ingot to ≥660℃, the heating power of the first melting pass is 18kW, and the heating power of the remaining passes is maintained at about 25kW to maintain the stability of the melting zone. The moving component drives the quartz tube 3 to move horizontally within the induction coil 1. The moving speed is preset to different values ​​according to the purification stage. The infrared thermometer 2 monitors the thermal field of the melting zone in real time. The width of the melting zone is determined according to the temperature distribution of the thermal field. The heating power of induction coil 1 is adjusted through controller 8 so that the width of the melting zone is 1.0-1.5 times the diameter of the aluminum ingot to be purified. The width of the melting zone is not less than 1.0 times the diameter to provide sufficient space for impurity diffusion and improve purification efficiency. The width of the melting zone is not more than 1.5 times the diameter to avoid melt instability and energy waste.

[0027] Example 1 Aluminum ingots with a purity of 99.99% (4N) and dimensions of Φ18 mm × 160 mm were used. The graphite boat had depths of 15 mm (shallow end) and 22 mm (deep end) at its two ends, forming an angle of approximately 1.9°. The aluminum ingot was placed in the graphite boat, equidistant from both ends. Fifteen zone melting passes were performed under argon protection. The first three melting passes had a melting rate of 3 mm / min, and the subsequent 12 passes had a melting rate of 1.8 mm / min. The induction heating power was automatically adjusted based on infrared temperature feedback to maintain the melting zone width at 1.0–1.5 times the diameter of the aluminum ingot.

[0028] The measured shape of the aluminum ingot after zone melting is approximately 16 cm in length, 15 mm in height at the first end, and 10 mm in height at the last end. There is a slight unevenness at one end, but no molten aluminum overflow, and the surface is smooth.

[0029] Comparative Example 1 (No tilt angle: flat-bottomed graphite boat) The difference from Example 1 is that the graphite boat has a flat bottom, a depth of 22 mm, and no tilt angle.

[0030] The measured shape of the aluminum ingot after zone melting is approximately 16 cm in length, 22 mm in height at the first end, and 6 mm in height at the second end. A severe unevenness (thicker at one end and thinner at the other) is observed, along with some molten aluminum overflow. Testing revealed that aluminum ingots with a purity greater than 99.9998% (5N8) are only about 3 cm long.

[0031] Comparative Analysis: Compared to flat-bottomed graphite boats without tilt angles, the tilted graphite boat designed based on the solid-liquid density difference of this invention can effectively offset some of the melt directional migration caused by the density difference between the aluminum solid and liquid phases, significantly reducing the shape distortion of the aluminum ingot (thicker at one end and thinner at the other), reducing radial component segregation, and improving the stability of the solid-liquid interface and the purity of the refined product. Because multiple dynamic factors such as electromagnetic stirring and axial temperature gradients affect the aluminum horizontal melting process, melt migration cannot be completely offset. Therefore, a slight shape difference still exists after using the tilted graphite boat, but the improvement effect is significant and the advantages are clear. In this embodiment, the length of the high-purity section (10 cm) obtained by this invention is 3.3 times that of the comparative example (3 cm), and aluminum melt overflow is avoided, resulting in a significant improvement in process stability.

[0032] The aluminum ingots obtained in Example 1 and the comparative example were divided into six equal segments along their length, numbered sequentially from the first end (starting end) to the last end as No. 6, No. 5, No. 4, No. 3, No. 2, and No. 1. Samples from positions 6, 5, 4, and 1 of both samples were taken, and their impurity content and purity were determined using glow discharge mass spectrometry (GDMS) (measured as the mass fraction of the main element after deducting all impurities, with results retained to four decimal places). The detection results for Example 1 are shown below. Figure 2-5 As shown, the purity of each segment was tested as follows: Segment 6: 99.9998% (5N8); Segment 5: 99.9998% (5N8); Segment 4: 99.9998% (5N8); Segment 1: 99.98% (3N8). The comparative test results are shown below. Figure 6-9 As shown, the purity of each segment was tested and found to be as follows: No. 6: 99.99986% (5N6); No. 5: 99.9998% (5N8); No. 4: 99.9993% (5N3); No. 1: 99.9899% (4N).

[0033] Therefore, among the aluminum ingots using the tilted graphite boat of this invention, three sections (No. 6, No. 5, and No. 4) had a purity ≥99.9998% (5N8), with the highest purity at the first end reaching 99.99988%. In contrast, among the samples without a tilted surface, only one section (No. 6) had a purity ≥99.9998% (5N8), with the purity of the remaining sections significantly decreasing. This indicates that the tilted graphite boat of this invention, designed based on the solid-liquid density difference, can significantly improve the purification effect of zone melting, resulting in higher purity and a longer high-purity section.

[0034] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A device for zone smelting and purifying aluminum, characterized in that, include: A movable component is connected to a quartz tube, a graphite boat is placed inside the quartz tube, the inner wall of the graphite boat is covered with a boron nitride layer, the two ends of the graphite boat have different depths, forming a slope at a preset angle inside, and one end of the quartz tube is provided with an exhaust opening. An induction coil is sleeved on the outside of the quartz tube with a gap between them, and the induction coil is connected to a heating power source; the moving component can drive the quartz tube to move horizontally inside the induction coil. An argon gas storage mechanism, wherein the argon gas storage mechanism is connected to the other end of a quartz tube via a pipeline; An infrared thermometer is located above the quartz tube, with the infrared thermometer facing the central heating area of ​​the induction coil, and is used to monitor the temperature distribution on the surface of the sample inside the graphite boat. The preset angle is determined based on the height of the aluminum ingot to be purified, the length of the melting zone, and the solid density and liquid density of the aluminum ingot to be purified.

2. The equipment for zone smelting and purifying aluminum according to claim 1, characterized in that, The expression for the preset angle is: In the formula, The height of the aluminum ingot to be refined. The length of the melting zone; This is the ratio of the solid density to the liquid density of the aluminum ingot to be purified.

3. The equipment for zone smelting and purifying aluminum according to claim 1, characterized in that, The moving component includes: The guide rail has a lead screw inside, a slider is sleeved on the lead screw, one end of the lead screw is connected to a drive mechanism, and the drive mechanism is connected to a controller for controlling the movement speed of the slider. A connecting plate is connected to the slider, and heat insulation support frames are connected to both ends of the connecting plate. The quartz tube is located on the heat insulation support frames.

4. The equipment for zone smelting and purifying aluminum according to claim 3, characterized in that, One end of the heat insulation support frame is provided with a V-shaped groove, and the quartz tube is located in the V-shaped groove.

5. The equipment for zone smelting and purifying aluminum according to claim 1, characterized in that, The argon storage mechanism includes an argon cylinder, and the outlet pipeline of the argon cylinder is equipped with a pressure reducing valve and a flow control valve, and is connected to a quartz tube.

6. A method for refining aluminum through zone melting, characterized in that, The apparatus for refining aluminum by zone smelting according to any one of claims 1-5 comprises: The aluminum ingot to be purified is placed in a graphite boat, wherein the length of the aluminum ingot to be purified is 0.6-0.8 times the length of the graphite boat; Argon gas is introduced into the quartz tube at a flow rate of 0.5-2.0 L / min through the argon gas storage mechanism; The ingot is heated and melted by an induction coil, and a quartz tube is moved horizontally within the induction coil by a moving component. The thermal field of the melting zone is monitored in real time by an infrared thermometer. The width of the melting zone is determined based on the temperature distribution of the thermal field, so that the width of the melting zone is 1.0-1.5 times the diameter of the aluminum ingot to be purified.

7. The method for refining aluminum by zone smelting according to claim 6, characterized in that, The process of introducing argon gas into the quartz tube through the argon gas storage mechanism at a flow rate of 0.5-2.0 L / min includes: Using an argon storage device, the quartz tube is purged and replaced for 10-30 minutes at a flow rate of 1.0-2.0 L / min during the initial stage of melting, and a flow rate of 0.5-1.0 L / min is used during the melting process.

8. The method for refining aluminum by zone smelting according to claim 6, characterized in that, Before placing the aluminum ingot to be purified into the graphite boat, the method further includes: The aluminum ingots to be purified are immersed in a 20%-30% sodium hydroxide solution for 15-25 minutes for cleaning, and then immersed in distilled water for 5-15 minutes for cleaning. The cleaned aluminum ingots are then dehydrated using anhydrous ethanol.

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