Method for reducing oxide inclusions in high-purity aluminum

Abstract

The invention relates to a method for reducing oxide inclusions in high-purity aluminum, which comprises the following steps: sequentially heating, electromagnetically stirring and rotatably blowing an aluminum raw material to obtain first molten aluminum; the first molten aluminum is sequentially subjected to first filtering and second filtering, second molten aluminum is obtained, and the second molten aluminum is cast to obtain high-purity aluminum; according to the method, all the working procedures are synergistic, oxide inclusions in the high-purity aluminum are efficiently removed, no extra refining agent needs to be added, introduction of other impurity elements is avoided, the high-purity aluminum with the purity reaching 5N5 or above and the oxide inclusions smaller than 1 ppm is obtained, and the high-purity requirement of the integrated circuit field for the aluminum target material is met.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity aluminum preparation, and in particular to a method for reducing oxide inclusions in high-purity aluminum. Background Art

[0002] High-purity aluminum thin films, the primary conductor material for integrated circuits, offer advantages such as low resistivity, ease of deposition and etching, and mature processing techniques. However, the purity of the high-purity aluminum target significantly impacts the performance of the sputtered film. Excessive inclusions in the target can easily form particles on the wafer during sputtering, leading to interconnects or short circuits. Inclusions in high-purity aluminum are primarily composed of Al2O3 and SiO2, ranging in size from 20μm to 200μm. SiO2 inclusions are primarily introduced from the ceramic fiber ropes of the flow channel baffles, while Al2O3 inclusions are primarily introduced as a reaction product of the oxidation reaction between the molten aluminum and furnace gases (O2, H2O), which form Al2O3. Therefore, technicians are dedicated to researching how to control the production process of high-purity aluminum to reduce tungsten oxide inclusions.

[0003] For example, CN111363940B discloses a method for reducing the formation of aluminum slag in the aluminum processing and smelting process. The method mainly uses a non-residue volatile liquid refining agent to refine and remove the slag from the aluminum liquid in the melting furnace and the holding furnace respectively, thereby reducing the slag content in the aluminum liquid. However, this method additionally introduces a refining agent, resulting in a lower purity of the aluminum ingots produced, which cannot meet the requirements of the oxide inclusion content of high-purity aluminum used in integrated circuits.

[0004] For example, CN115896476A discloses a purification process for aluminum and aluminum alloy melts, in which a combined refining process of de-alkali agent refining and adsorption and introduction of high-purity nitrogen through breathable bricks at the bottom of the furnace is used to carry out de-alkali element removal, slag removal and degassing in the smelting furnace, and a rotary spray degassing process with 30ppi and 50ppi double-stage filtration is used outside the furnace. However, de-alkali agents including KC1, NaCl, Na2AlF4, SiF2, NaCO3 and NaSO4 are added to the process, and many impurity elements are additionally introduced, which cannot meet the requirements of high-purity aluminum for the oxide inclusion content. Moreover, the double-stage filtration in the process uses a ceramic filter plate, and the removal of SiO2 inclusions is not considered.

[0005] In view of this, how to provide a method to reduce oxide inclusions in the production process of high-purity aluminum and prepare high-purity aluminum with a purity of 5N5 or above and a low oxide inclusion content to meet the current purity requirements in the field of integrated circuits is an urgent problem to be solved in this field. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for reducing oxide inclusions in high-purity aluminum, which significantly reduces inclusions such as Al2O3 and SiO2 in high-purity aluminum, solves the problem in the prior art that additional refining agents need to be added, resulting in the purity of aluminum products still unable to meet the high purity requirements of integrated circuits, and provides a reliable method for preparing high-purity aluminum targets.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for reducing oxide inclusions in high-purity aluminum, the method comprising the following steps:

[0009] (1) The aluminum raw material is heated, electromagnetically stirred, and rotary blown in sequence to obtain a first aluminum liquid;

[0010] (2) In step (1), the first aluminum liquid is filtered first and filtered second to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum.

[0011] The method of the present invention combines electromagnetic stirring with rotary blowing, and is combined with a two-stage filtration method including the first filtration and the second filtration, thereby significantly reducing oxide inclusions in high-purity aluminum. The electromagnetic stirring can avoid disturbing the surface of the aluminum liquid through non-contact stirring, thereby preventing Al2O3 slag on the surface of the aluminum liquid from being drawn into the interior of the aluminum liquid. The rotary blowing forms a large number of bubbles in the aluminum liquid and evenly disperses them. The process of the bubbles floating up brings the gas and inclusions inside the aluminum liquid to the surface of the aluminum liquid to form scum. Combined with the first filtration and the second filtration, oxide inclusions of different sizes in the aluminum liquid are effectively removed. The method can obtain high-purity aluminum with a purity of 5N5 or above without the need for additional refining agents, meeting the current development needs of the integrated circuit field.

[0012] It is worth noting that, in the method of the present invention, slag skimming is required to remove scum after the electromagnetic stirring process and the rotary blowing process are completed.

[0013] Preferably, the purity of the aluminum raw material in step (1) is ≥5N5, for example, it can be 5N5, 5N6, 5N7 or 5N8.

[0014] Preferably, the heating temperature in step (1) is 720-780°C, for example, it can be 720°C, 730°C, 740°C, 750°C, 760°C, 770°C or 780°C.

[0015] Preferably, the current of the electromagnetic stirring in step (1) is 100-200 A, for example, it can be 100 A, 120 A, 140 A, 160 A, 180 A or 200 A.

[0016] Preferably, the frequency of the electromagnetic stirring in step (1) is 4 to 5.5 Hz, for example, it can be 4 Hz, 4.2 Hz, 4.5 Hz, 4.8 Hz, 5.0 Hz, 5.2 Hz or 5.5 Hz.

[0017] The present invention further preferably has a current of 100 to 200 A for the electromagnetic stirring in step (1), and further preferably has a frequency of 4 to 5.5 Hz for the electromagnetic stirring in step (1). The combination of the two allows the inclusions inside the molten aluminum to separate from the molten aluminum and float to the surface to form scum, and inclusions of micron size and similar density to the molten aluminum can also be effectively removed under the action of electromagnetic force; if the current intensity or frequency of the electromagnetic stirring is too low, there will not be enough electromagnetic force to drive the inclusions to migrate to the surface of the molten aluminum, resulting in a decrease in the efficiency of inclusion removal; if the current intensity of the electromagnetic stirring is too high, the surface of the molten aluminum will be disturbed, resulting in more scum and inclusions entering the interior of the molten aluminum, which in turn increases the inclusion content; if the frequency of the electromagnetic stirring is too high, the electromagnetic force will only act on the surface of the molten aluminum, and the inclusions inside the molten aluminum will not be able to gather and float, resulting in a decrease in the efficiency of inclusion removal.

[0018] Preferably, the electromagnetic stirring time in step (1) is 10 to 20 minutes, for example, it can be 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes or 20 minutes.

[0019] Preferably, step (1) further includes pre-treating the aluminum raw material before heating.

[0020] Preferably, the pretreatment comprises washing and drying in sequence.

[0021] Preferably, the washing comprises sequentially performing acid washing, alkali washing and water washing.

[0022] The present invention further preferably includes sequentially performing acid washing, alkaline washing and water washing, the purpose of which is to treat the surface of the aluminum raw material to remove surface oxides and other impurities, avoid heating and melting into the aluminum liquid, reduce the burden of subsequent removal of inclusions in the aluminum liquid, and improve the efficiency of inclusion removal.

[0023] Preferably, the acid solution used for pickling comprises a nitric acid solution and / or a hydrochloric acid solution. Preferably, the concentration of the acid solution used for pickling is 5 to 15 wt%, for example, 5 wt%, 8 wt%, 10 wt%, 12 wt% or 15 wt%.

[0024] Preferably, the alkali solution used in the alkali washing includes sodium hydroxide solution and / or potassium hydroxide solution.

[0025] Preferably, the mass concentration of the alkali solution used in the alkali washing is 5-15wt%, for example, it can be 5wt%, 8wt%, 10wt%, 12wt% or 15wt%.

[0026] Preferably, the drying temperature is 50-100°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C.

[0027] Preferably, the heating in step (1) is carried out in a resistance furnace.

[0028] Preferably, the heating further includes preheating and keeping the resistance furnace warm.

[0029] The present invention further preferably includes preheating and keeping the resistance furnace warm before heating, so as to remove O2 and H2O in the resistance furnace, thereby reducing oxide inclusions formed by subsequent oxidation of the aluminum liquid.

[0030] Preferably, the preheating temperature is 220-280°C, for example, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C or 280°C.

[0031] Preferably, the insulation time is 0.5 to 2 hours, for example, it can be 0.5 hours, 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours or 2 hours.

[0032] Preferably, the rotary blowing in step (1) includes blowing protective gas into the aluminum liquid after electromagnetic stirring under the action of the rotor.

[0033] Preferably, the rotational speed of the rotor is 300-600 rpm, for example, it can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm.

[0034] Preferably, the protective gas includes argon and / or nitrogen. Preferably, the protective gas has a flow rate of 8 to 20 L / min, for example, 8 L / min, 10 L / min, 12 L / min, 15 L / min, 18 L / min, or 20 L / min.

[0035] The present invention further prefers that the gas flow rate of the protective gas is 8 to 20 L / min, which is conducive to forming more uniform and fine bubbles, thereby increasing the contact area between the bubbles and the aluminum liquid, and is also conducive to ensuring the residence time of the bubbles in the aluminum liquid. Both advantages improve the degassing and impurity removal effect; if the gas flow rate of the protective gas is too low, the bubble size will be too large and the floating speed will be too fast, resulting in the impurity gas and inclusions cannot be effectively removed; if the gas flow rate of the protective gas is too high, air entrainment will occur, causing water vapor and oxygen in the air to be entrained into the aluminum liquid, increasing the oxide content, and the formed bubbles will be aggregated and uneven, resulting in a poor degassing and impurity removal effect.

[0036] Preferably, the pore density of the first filter medium used in the first filtration in step (2) is ≤40 ppi, for example, it can be 40 ppi, 35 ppi, 30 ppi, 25 ppi or 20 ppi.

[0037] Preferably, the pore density of the second filter medium used in the second filtration in step (2) is ≥60 ppi, for example, it can be 60 ppi, 65 ppi, 70 ppi, 75 ppi or 80 ppi.

[0038] Preferably, the first filtration and the second filtration in step (2) are performed using a dual-stage filtration device, which includes a fluid channel and a first filter component and a second filter component sequentially arranged inside the fluid channel.

[0039] Preferably, the pore density of the first filter component is ≤40 ppi, for example, it can be 40 ppi, 35 ppi, 30 ppi, 25 ppi or 20 ppi.

[0040] Preferably, the pore density of the second filter component is ≥60 ppi, for example, it can be 60 ppi, 65 ppi, 70 ppi, 75 ppi or 80 ppi.

[0041] Preferably, a baffle is further provided inside the fluid channel.

[0042] Preferably, the baffle is provided at one end of the fluid passage close to the second filter component.

[0043] Preferably, the baffle is made of graphite fiber.

[0044] The present invention further prefers that the material of the baffle includes graphite fiber, avoiding the use of baffles made of ceramic material, thereby avoiding the introduction of SiO2 inclusions and further improving the removal efficiency of inclusions in high-purity aluminum.

[0045] Furthermore, the double-stage filtering device of the present invention has a simple structure, and the filtering components and baffles are easy to replace, thereby reducing filtering costs and facilitating operation.

[0046] As a further preferred technical solution of the present invention, the method comprises the following steps:

[0047] (1) Aluminum raw material with a purity of ≥5N5 is first pickled with an acid solution having a mass concentration of 5 to 15 wt%, then alkaline washed with an alkali solution having a mass concentration of 5 to 15 wt%, then washed with water and dried at 50 to 100° C., and then placed in a resistance furnace. The resistance furnace is preheated to 220 to 280° C. and kept warm for 0.5 to 2 h. The aluminum raw material is then heated to 720 to 780° C., and then electromagnetically stirred for 10 to 20 min at a current of 100 to 200 A and a frequency of 4 to 5.5 Hz. A protective gas is sprayed at a gas flow rate of 8 to 20 L / min under the action of a rotor with a rotation speed of 300 to 600 rpm to obtain a first aluminum liquid;

[0048] (2) In step (1), the first aluminum liquid is subjected to a first filtration and a second filtration using a two-stage filtration device to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum;

[0049] The two-stage filtration device includes a fluid channel and a first filter component, a second filter component and a baffle arranged in sequence inside the fluid channel; the pore density of the first filter component is ≤40ppi; the pore density of the second filter component is ≥60ppi; the material of the baffle includes graphite fiber.

[0050] Compared with the prior art, the present invention has at least the following beneficial effects:

[0051] (1) The method for reducing oxide inclusions in high-purity aluminum provided by the present invention adopts a method of combining electromagnetic stirring, rotary blowing, and first filtration and second filtration, which work together to gather fine inclusions inside the aluminum liquid and float them to the surface, and filter inclusions of different sizes inside the aluminum liquid in a graded manner, thereby significantly reducing the content of oxide inclusions in high-purity aluminum, and providing a reliable method for preparing high-quality aluminum targets in the field of integrated circuits.

[0052] (2) The method for reducing oxide inclusions in high-purity aluminum provided by the present invention further optimizes the magnetic field strength and frequency range of the electromagnetic stirring, and the two work synergistically to further improve the effect of fine inclusion aggregation and floating, and prevent surface slag from being drawn into the aluminum liquid. At the same time, the gas flow rate of the protective gas is further optimized to further improve the removal effect of oxide inclusions, so that the content of oxide inclusions is <1ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1Schematic diagram of the structure and connection relationship of the two-stage filtering device in Example 1 of the present invention;

[0054] In the figure: 1. resistance furnace; 2. fluid channel; 3. first filter component; 4. second filter component; 5. baffle; 6. casting platform. DETAILED DESCRIPTION

[0055] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0056] 1. Implementation

[0057] Example 1

[0058] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum, the method comprising the following steps:

[0059] (1) A 5N7 aluminum raw material was first acid-washed with a 10 wt % nitric acid solution for 50 min, then alkaline-washed with a 15 wt % potassium hydroxide solution for 30 min, then washed with water and dried at 80° C., and then placed in a resistance furnace 1. The resistance furnace 1 was preheated to 250° C. and kept warm for 1 h. The aluminum raw material was then heated to 750° C., and then electromagnetically stirred for 15 min at a current of 150 A and a frequency of 4.5 Hz, and then skimmed. Argon gas was blown at a gas flow rate of 15 L / min under the action of a rotor rotating at 500 rpm, and then the slag was skimmed to obtain a first aluminum liquid;

[0060] (2) In step (1), the first aluminum liquid is subjected to a first filtration and a second filtration using a two-stage filtration device to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum;

[0061] like Figure 1 As shown, the two-stage filtering device includes a fluid channel 2 and a first filter component 3, a second filter component 4 and a baffle 5 arranged in sequence inside the fluid channel 2; the pore density of the first filter component 3 is 30ppi; the pore density of the second filter component 4 is 70ppi; the material of the baffle 5 includes graphite fiber; and the casting is carried out in a casting platform 6.

[0062] Example 2

[0063] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum, the method comprising the following steps:

[0064] (1) A 5N8 aluminum raw material was first acid-washed with a 15 wt % nitric acid solution for 40 min, then alkaline-washed with a 15 wt % potassium hydroxide solution for 25 min, then washed with water and dried at 50° C., and then placed in a resistance furnace. The resistance furnace was preheated to 220° C. and kept warm for 2 h. The aluminum raw material was then heated to 720° C., and then electromagnetically stirred for 20 min at a current of 120 A and 4 Hz, and the slag was skimmed. Argon gas was injected at a gas flow rate of 8 L / min under the action of a rotor rotating at 300 rpm, and the slag was then skimmed to obtain a first aluminum liquid;

[0065] (2) In step (1), the first aluminum liquid is subjected to a first filtration and a second filtration using a two-stage filtration device to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum;

[0066] The two-stage filtration device includes a fluid channel and a first filter component, a second filter component and a baffle arranged in sequence inside the fluid channel; the pore density of the first filter component is 40ppi; the pore density of the second filter component is 60ppi; the material of the baffle includes graphite fiber.

[0067] Example 3

[0068] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum, the method comprising the following steps:

[0069] (1) A 5N6 aluminum raw material was first pickled with a 7 wt % hydrochloric acid solution for 60 min, then alkaline washed with a 10 wt % sodium hydroxide solution for 20 min and 25 min, then washed with water and dried at 100° C., and then placed in a resistance furnace. The resistance furnace was preheated to 280° C. and kept warm for 0.5 h. The aluminum raw material was then heated to 780° C., and then electromagnetically stirred at a current of 200 A and 5.5 Hz for 15 min and skimmed. Argon gas was injected at a gas flow rate of 20 L / min under the action of a rotor rotating at 600 rpm, and then the slag was skimmed to obtain a first aluminum liquid;

[0070] (2) In step (1), the first aluminum liquid is subjected to a first filtration and a second filtration using a two-stage filtration device to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum;

[0071] The two-stage filtration device includes a fluid channel and a first filter component, a second filter component and a baffle arranged in sequence inside the fluid channel; the pore density of the first filter component is 35ppi; the pore density of the second filter component is 65ppi; the material of the baffle includes graphite fiber.

[0072] Example 4

[0073] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the current of the electromagnetic stirring is 90A.

[0074] Example 5

[0075] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the current of the electromagnetic stirring is 210A.

[0076] Example 6

[0077] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the frequency of the electromagnetic stirring is 3 Hz.

[0078] Example 7

[0079] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the frequency of the electromagnetic stirring is 6.5 Hz.

[0080] Example 8

[0081] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the gas flow rate of the argon gas injection is 7 L / min.

[0082] Example 9

[0083] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the gas flow rate of the argon gas injection is 22 L / min.

[0084] Example 10

[0085] This embodiment provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as that of Example 1 except that the baffle is made of ceramic fiber.

[0086] 2. Comparative Example

[0087] Comparative Example 1

[0088] This comparative example provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as Example 1 except that the electromagnetic stirring is not performed in step (1).

[0089] Comparative Example 2

[0090] This comparative example provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as Example 1 except that step (2) only performs the first filtration.

[0091] Comparative Example 3

[0092] This comparative example provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as Example 1 except that step (2) only performs the second filtration.

[0093] In this comparative example, since the filtration speed of the first aluminum liquid was too slow, inclusions were easily accumulated, resulting in clogging of the filter component, which prevented the experiment from proceeding normally.

[0094] Comparative Example 4

[0095] This comparative example provides a method for reducing oxide inclusions in high-purity aluminum. The method is the same as Example 1 except that the electromagnetic stirring is not performed in step (1), and the de-alkali agent disclosed in Example 1 of CN115896476A is added for refining and adsorption before the rotary blowing.

[0096] In this comparative example, since a de-alkali agent was used for refining and adsorption, impurities such as K, Na and Si were additionally introduced, resulting in a purity of the obtained aluminum ingot of less than 5N.

[0097] 3. Test and its results

[0098] The high-purity aluminum obtained by the methods described in the above examples or comparative examples and the content of oxide inclusions therein were tested, and the results are shown in Table 1;

[0099] Table 1

[0100] project Oxide inclusion content Example 1 <1ppm Example 2 <1ppm Example 3 <1ppm Example 4 5ppm Example 5 8ppm Example 6 4ppm Example 7 6ppm Example 8 6ppm Example 9 7ppm Example 10 8ppm Comparative Example 1 10ppm Comparative Example 2 15ppm Comparative Example 3 - Comparative Example 4 -

[0101] In Table 1, “-” indicates that there are no relevant data;

[0102] From the data in Table 1 we can see that:

[0103] (1) It can be seen from Examples 1 to 3 that the method for reducing oxide inclusions in high-purity aluminum provided by the present invention effectively removes oxide inclusions in high-purity aluminum, and the oxide inclusion content is <1ppm, thereby significantly improving the purity of the aluminum target and meeting the purity requirements of the integrated circuit field for aluminum targets.

[0104] (2) Combining Example 1 with Examples 4 to 7, it can be seen that the current of the electromagnetic stirring described in Example 4 is too low or the frequency of the electromagnetic stirring described in Example 6 is too low, both of which lead to poor removal effect of oxide inclusions; the current of the electromagnetic stirring described in Example 5 is too high or the frequency of the electromagnetic stirring described in Example 7 is too high, both of which lead to deviation in the removal effect of oxide inclusions; this shows that the present invention further prefers that the current of the electromagnetic stirring is 100-200A, and further prefers that the frequency of the electromagnetic stirring is 4-5.5Hz. The two work together to make the electromagnetic stirring effect better, thereby further improving the removal effect of oxide inclusions in high-purity aluminum.

[0105] (3) From Example 1 and Examples 8 to 10, it can be seen that the gas flow rate of the argon gas sprayed in Example 8 or Example 9 is too low or too high, which leads to an increase in the content of the oxide inclusions; the baffle made of ceramic fiber material in Example 10 leads to the generation of silica inclusions; this shows that the present invention further prefers that the gas flow rate of the protective gas is 8 to 20 L / min, or further prefers that the material of the baffle includes graphite fiber, both of which further improve the removal effect of oxide inclusions in high-purity aluminum.

[0106] (4) From Example 1 and Comparative Examples 1 to 4, it can be seen that since electromagnetic stirring is not performed in Comparative Example 1, the fine inclusions inside the aluminum liquid are difficult to remove; in Comparative Example 2 or Comparative Example 3, only one-stage filtration is performed, resulting in the difficulty in removing smaller-sized inclusions, or the accumulation of inclusions of different sizes causes clogging of the filter components, reducing efficiency or making it impossible to conduct the experiment normally; in Comparative Example 4, a de-alkali agent is added, and impurities such as K, Na and Si are additionally introduced, resulting in the purity of the obtained aluminum ingot being less than 5N; this shows that the method of the present invention selects a method of combining electromagnetic stirring, rotary blowing, and the first filtration and the second filtration, which work together to efficiently remove oxide inclusions in high-purity aluminum.

[0107] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for reducing oxide inclusions in high-purity aluminum, characterized in that: The method comprises the following steps: (1) The aluminum raw material is heated, electromagnetically stirred, and rotary blown in sequence to obtain a first aluminum liquid; (2) In step (1), the first aluminum liquid is filtered first and filtered second to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum.

2. The method according to claim 1, characterized in that The purity of the aluminum raw material in step (1) is ≥5N5; Preferably, the heating temperature in step (1) is 720-780°C; Preferably, the current of the electromagnetic stirring in step (1) is 100 to 200 A; Preferably, the frequency of the electromagnetic stirring in step (1) is 4 to 5.5 Hz; Preferably, the electromagnetic stirring time in step (1) is 10 to 20 minutes.

3. The method according to claim 1 or 2, characterized in that Before the heating in step (1), the aluminum raw material is also pretreated; Preferably, the pretreatment comprises washing and drying in sequence; Preferably, the washing comprises sequentially performing acid washing, alkali washing and water washing.

4. The method according to claim 3, characterized in that The acid solution used in the pickling includes nitric acid solution and / or hydrochloric acid solution; Preferably, the mass concentration of the acid solution used in the pickling is 5 to 15 wt%; Preferably, the alkali solution used in the alkali washing includes sodium hydroxide solution and / or potassium hydroxide solution; Preferably, the mass concentration of the alkali solution used in the alkali washing is 5 to 15 wt%; Preferably, the drying temperature is 50-100°C.

5. The method according to any one of claims 1 to 4, characterized in that The heating in step (1) is carried out in a resistance furnace; Preferably, the heating further includes preheating and keeping the resistance furnace warm; Preferably, the preheating temperature is 220-280°C; Preferably, the insulation time is 0.5 to 2 hours.

6. The method according to any one of claims 1 to 5, characterized in that The rotary blowing in step (1) includes blowing protective gas into the aluminum liquid after electromagnetic stirring under the action of the rotor; Preferably, the rotation speed of the rotor is 300-600 rpm; Preferably, the protective gas comprises argon and / or nitrogen; Preferably, the protective gas has a flow rate of 8 to 20 L / min.

7. The method according to any one of claims 1 to 6, characterized in that In step (2), the pore density of the first filter medium used in the first filtration is ≤40 ppi; Preferably, the pore density of the second filter medium used in the second filtration in step (2) is ≥60 ppi.

8. The method according to any one of claims 1 to 7, characterized in that In step (2), the first filtration and the second filtration are performed using a dual-stage filtration device, which includes a fluid channel and a first filter component and a second filter component sequentially arranged inside the fluid channel.

9. The method according to claim 8, characterized in that The pore density of the first filter component is ≤40 ppi; Preferably, the pore density of the second filter component is ≥60ppi; Preferably, a baffle is further provided inside the fluid channel; Preferably, the baffle is provided at one end of the fluid passage close to the second filter component; Preferably, the baffle is made of graphite fiber.

10. The method according to any one of claims 1 to 9, characterized in that The method comprises the following steps: (1) Aluminum raw material with a purity of ≥5N5 is first pickled with an acid solution having a mass concentration of 5 to 15 wt%, then alkaline washed with an alkali solution having a mass concentration of 5 to 15 wt%, then washed with water and dried at 50 to 100° C., and then placed in a resistance furnace. The resistance furnace is preheated to 220 to 280° C. and kept warm for 0.5 to 2 h. The aluminum raw material is then heated to 720 to 780° C., and then electromagnetically stirred for 10 to 20 min at a current of 100 to 200 A and a frequency of 4 to 5.5 Hz. A protective gas is sprayed at a gas flow rate of 8 to 20 L / min under the action of a rotor with a rotation speed of 300 to 600 rpm to obtain a first aluminum liquid; (2) In step (1), the first aluminum liquid is subjected to a first filtration and a second filtration using a two-stage filtration device to obtain a second aluminum liquid, and the second aluminum liquid is cast to obtain high-purity aluminum; The two-stage filtration device includes a fluid channel and a first filter component, a second filter component and a baffle arranged in sequence inside the fluid channel; the pore density of the first filter component is ≤40ppi; the pore density of the second filter component is ≥60ppi; the material of the baffle includes graphite fiber.

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