Composite treatment method for reducing Fe / Si impurities in high-purity aluminum through rare earth alloying and segregation

Abstract

The invention belongs to the technical field of aluminum purification, and discloses a composite treatment method for reducing Fe / Si impurities in high-purity aluminum through rare earth alloying and segregation. The composite treatment method comprises the following steps: 1) preparing a pure aluminum raw material and an Al-RE rare earth intermediate alloy into a rare earth-pure aluminum mixed melt; 2) carrying out gradient cooling and heat preservation treatment on the mixed melt; (3) segregation treatment is conducted on the mixed melt; rE in the Al-RE rare earth intermediate alloy is Y and / or Yb. The rare earth elements Y and Yb are used for effectively removing Fe and Si in the high-purity aluminum raw material, and meanwhile, the melt viscosity can be effectively reduced to promote sedimentation of precipitates; y and Yb elements in the aluminum melt are more easily removed by using a segregation method. By means of the method, 2N8 industrial pure aluminum can be purified to the 3N5 level, and 4N6 high-purity aluminum can be purified to the 5N level. The method is simple and easy to implement and low in production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum purification, and particularly relates to a composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation. Background Art

[0002] High-purity aluminum (generally with a purity greater than 99.8%) has wide applications in industries such as semiconductors, electrical and electronics, and transportation due to its good electrical conductivity, thermal conductivity, processing and forming ability, and weak magnetic conductivity. High-purity aluminum with a purity of 3N8 - 4N8 (99.98% - 99.998%) is used in the production of electrolytic aluminum foil by more than 75%. For example, the aluminum used for the cathode foil of electrolytic capacitors has a purity of 99.998%, and the aluminum used for the anode foil has a purity of 99.95%. Aluminum with a purity of 5N+ (greater than 99.999%) is mainly used in the semiconductor industry, such as semiconductor sputtering targets, etc. The prices of aluminum with different purities vary greatly, and there is currently a broad demand in the market for high-purity aluminum, especially aluminum with a purity above 5N. Developing technologies for efficiently producing 5N high-purity aluminum has significant economic benefits and can meet the urgent needs of the market for the high-purity aluminum industry.

[0003] Currently, the main production methods of high-purity aluminum are the three-layer liquid method based on electrolysis and the segregation method based on solute redistribution during the solidification process. The three-layer liquid electrolytic refining of aluminum has high production efficiency and is conducive to batch production, but it has high energy consumption and serious environmental problems due to the use of fluoride electrolytes, and the current highest purity can reach the 4N level. The principle of the segregation method is to utilize the solubility difference of impurities in the aluminum melt to remove impurities with an equilibrium distribution coefficient k < 1. The smaller the k value, the easier it is to remove, but impurities with k > 1 cannot be removed. The segregation method is further divided into the fractional crystallization method, the directional solidification method, and the zone melting method.

[0004] The fractional crystallization method is the main production technology for producing high-purity aluminum at present. It has achieved mass production and has the advantages of low energy consumption and environmental protection. However, the production process is long and the efficiency is low. Chinese Patent Application CN118256736A discloses a purification device and a process for preparing 5N high-purity aluminum based on the fractional crystallization method. The basic implementation path of the disclosed device is that the aluminum liquid is cooled and crystallized by the sidewall cooling mechanism in a purification container that can move longitudinally at the bottom, and the solid aluminum is scraped off by a scraper to achieve purification. However, this patent only discloses a device based on the fractional crystallization method and does not involve the specific purification effect. The principle of the directional solidification method is to control the heat flow to form a temperature gradient to make the aluminum crystal grow directionally for purification. Chinese Patent CN102277505A discloses a method for purifying high-purity aluminum by directional solidification and its melting furnace. Its purification process includes four steps: material selection, melting, solidification purification, and finished product acquisition. The rate control in the directional solidification process is required to be strict. After each crystallization, it is necessary to cool down and sample, and then heat for re-purification, which is not conducive to mass production, and there are challenges in large-scale production. The above patents mainly disclose purification devices and do not involve how to efficiently reduce the content of key impurities Fe and Si in pure aluminum based on melt treatment.

[0005] The principle of the zone melting method is that the aluminum rod is locally melted, and the molten zone is moved sequentially. The solute is excluded into the melt by solute redistribution during the solidification process, thereby achieving purification. Chinese Patent Application CN110819823A discloses a preparation method of directionally zone-melted high-purity aluminum. This patent application optimizes the impurity removal efficiency by controlling the moving speed of the quartz tube, etc. The zone melting method can obtain high-purity samples, but the zone melting purification process requires repeated melting, the purification amount per furnace is small, and the energy consumption is high. To ensure solidification under equilibrium conditions, it is necessary to control the solidification process at a very low cooling rate. Therefore, the production efficiency of this method is low and it is not conducive to mass production.

[0006] In the purification production of aluminum alloys, the removal of Fe / Si impurities is the key. When preparing high-purity aluminum by the segregation method, it is difficult to efficiently remove Fe and Si impurity elements in the aluminum melt only by segregation, resulting in the impurity content of the product being difficult to meet the regulations. To solve this problem, the present invention performs rare earth alloying treatment on the pure aluminum melt, and then further uses the segregation method to reduce the content of Fe and Si impurities to achieve further purification. Summary of the Invention

[0007] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation. The present invention uses rare earth alloying and segregation to efficiently remove impurities such as Fe and Si in high-purity aluminum, and further improves the purity of high-purity aluminum.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare-earth alloying and segregation, comprising the following steps:

[0010] 1) Prepare a rare-earth-pure aluminum mixed melt from pure aluminum raw materials and Al-RE rare-earth master alloys;

[0011] 2) Perform gradient cooling and heat preservation treatment on the mixed melt;

[0012] 3) Perform segregation treatment on the mixed melt.

[0013] The Al content in the pure aluminum raw materials is ≥99.8%, specifically 2N8 industrial pure aluminum or 4N6 high-purity aluminum;

[0014] The RE in the Al-RE rare-earth master alloys is Y and / or Yb;

[0015] The Al-RE rare-earth master alloys are Al-Y rare-earth master alloys and / or Al-Yb rare-earth master alloys;

[0016] The Al-Y rare-earth master alloy is Al-10wt% Y, and the Al-Yb rare-earth master alloy is Al-10wt% Yb.

[0017] The addition amount of rare-earth RE satisfies the following conditions: the addition amount of Y is 1.5 to 50 times the Fe or Si content in the pure aluminum raw materials; when the Fe content in the pure aluminum raw materials ≥ the Si content, the addition amount of Y is 1.5 to 50 times the Fe content in the pure aluminum raw materials, when the Fe content in the pure aluminum raw materials < the Si content, the addition amount of Y is 1.5 to 50 times the Si content in the pure aluminum raw materials;

[0018] The addition amount of Yb is 1.5 to 50 times the Fe or Si content in the pure aluminum raw materials; when the Fe content in the pure aluminum raw materials ≥ the Si content, the addition amount of Yb is 1.5 to 50 times the Fe content in the pure aluminum raw materials, when the Fe content in the pure aluminum raw materials < the Si content, the addition amount of Yb is 1.5 to 50 times the Si content in the pure aluminum raw materials.

[0019] When the Al content in the pure aluminum raw materials is ≥99.8%, the Fe or Si content is ≥100ppm and Fe < 0.2%, Si < 0.1%, and the total impurity content < 0.2%, the addition amount of rare-earth RE is 1.5 to 8 times the Fe or Si content in the pure aluminum raw materials; when the Fe or Si content < 100ppm, the addition amount of rare-earth RE is 8 to 50 times the Fe or Si content in the pure aluminum raw materials.

[0020] Specifically, when the pure aluminum raw materials are 2N8 industrial pure aluminum, the addition amount of rare-earth RE is 1.5 to 8 times the Fe or Si content in the pure aluminum raw materials, preferably 1.5 to 5 times;

[0021] When the pure aluminum raw material is 4N6 high-purity aluminum, the addition amount of rare earth RE is 8 to 50 times, preferably 8 to 40 times, the content of Fe or Si in the pure aluminum raw material.

[0022] The specific steps of step 1): melt the pure aluminum raw material and the Al-RE rare earth master alloy, mix well, and keep it static and warm to obtain a rare earth-pure aluminum mixed melt. The melting temperature is 750 to 800 °C. The mixing is to stir and mix well after the high-purity aluminum is melted; the stirring time is 5 to 10 minutes; keep it static and warm for 3 to 60 minutes.

[0023] Before adding the Al-RE rare earth master alloy, a B-containing master alloy, such as an Al-B master alloy, can be added to the melted pure aluminum raw material.

[0024] In the gradient cooling and heat preservation treatment in step 2), first let the melt temperature drop to 710 to 730 °C at a rate of 1 to 2.5 °C / min and keep it warm for 60 to 120 minutes, then let the melt temperature drop to 675 to 685 °C at a rate of 1 to 2.5 °C / min and keep it warm for 60 to 120 minutes, and finally keep the melt temperature at 675 to 685 °C.

[0025] The segregation treatment in step 3) means that after stopping heating, cooling is carried out on one side or above the melt, and the melt crystallizes to form segregation.

[0026] The segregation treatment in step 3) specifically means closing the heating device of the segregation device. There is a lid above the melt placed in the cavity of the segregation device, and a cooling device is provided above the lid. After cooling by the cooling device, the melt in contact with the lid starts to crystallize from top to bottom to form segregation. The segregation time is 5 to 15 minutes.

[0027] After the segregation treatment is completed, cool it, take out the aluminum ingot, detect the components of different parts of the aluminum ingot, remove the part with more impurities, and obtain the required pure aluminum.

[0028] The 2N8 commercial pure aluminum contains the following components by mass:

[0029] Fe < 0.2%

[0030] Si < 0.1%

[0031] Al > 99.8%

[0032] The balance is other impurities, and the total impurity content < 0.2%.

[0033] The 4N6 high-purity aluminum contains the following components by mass:

[0034] Fe < 5 ppm

[0035] Si < 8 ppm

[0036] Al > 99.996%

[0037] The balance is other impurities, and the total sum of impurities < 40 ppm.

[0038] The 5N high-purity aluminum of the present invention contains the following components by mass:

[0039] Fe < 2.5 ppm

[0040] Si < 2.5 ppm

[0041] Al > 99.999%

[0042] The balance is other impurities, and the total sum of impurities < 10 ppm.

[0043] The principle of the present invention:

[0044] Precipitation reaction principle: Y and Yb have strong chemical activities and strong affinities with Fe and Si. In the Al melt, they are prone to react with Fe and Si impurity elements to form stable compounds of the AlFeSiRE phase. And within a certain range, as the addition amount of rare earth increases, more AlFeSiRE phases are formed. The excessive Y and Yb elements can fully react with Fe and Si impurity elements in the Al melt. The density of the AlFeSiRE phase is higher than that of the Al melt, so precipitation will occur and deposit at the bottom of the melt.

[0045] Principle of promoting precipitation settlement due to the reduction of melt viscosity: When Y and Yb enter the aluminum melt, they will cause changes in the atomic structure of the aluminum melt, making the stacking mode between atoms become loose. This will reduce the mutual force between atoms, resulting in a decrease in the internal friction during the flow of the melt, which macroscopically manifests as a reduction in the viscosity of the melt. In addition, rare earth elements can also form new chemical bonds with aluminum atoms. Different from the aluminum-aluminum bonds, these new chemical bonds will change the energy distribution inside the melt. This rare earth-aluminum bond energy makes the combination between atoms relatively weak, and atoms can move relatively more easily, resulting in a reduction in the melt viscosity. In addition, Y and Yb may adsorb at interfaces such as grain boundaries in the aluminum melt. This adsorption will reduce the interfacial energy, making the microstructure of the melt more stable and having better fluidity. The final result is also a reduction in the melt viscosity.

[0046] According to Stokes' law:

[0047]

[0048] Among them, ν is the sedimentation velocity of the particles, r is the particle radius, ρ is the particle density, ρ0 is the fluid density, g is the acceleration due to gravity, and η is the fluid viscosity. Under the condition that other conditions such as the size of the precipitated particles, the melt density, and the acceleration due to gravity are basically unchanged, the smaller the viscosity, the greater the sedimentation velocity, and the easier it is for the precipitate to deposit at the bottom of the melt. The melt with a small viscosity allows the precipitate to pass through the melt more smoothly and is not easily bound by the viscous force of the melt, which is conducive to separating the precipitate from the melt by a simple physical method (such as static sedimentation). In addition, the low-viscosity melt makes it easier for the precipitate particles to collide and agglomerate with each other. Once the particles agglomerate to form larger particle clusters, their sedimentation velocity will further increase.

[0049] Segregation principle: The segregation method is also known as the solidification purification method. Its principle is mainly to purify aluminum based on the different solubilities of impurity elements in the liquid phase and the solid phase. Through the segregation method, impurity elements with an equilibrium distribution coefficient less than 1 in aluminum can be effectively removed, and the smaller the equilibrium distribution coefficient of the impurity element, the easier it is to remove. The equilibrium distribution coefficients of rare earth elements Y and Yb in Al are both less than 0.003, and the equilibrium distribution coefficients of Fe and Si in Al are 0.023 and 0.1 respectively. The equilibrium distribution coefficients of Y and Yb in Al are approximately one-tenth of the distribution coefficients of Fe and Si. Therefore, the excess rare earth elements (Y and Yb) can be efficiently removed by the segregation method.

[0050] Process characteristics: In the process of preparing high-purity aluminum by the segregation method, the present invention additionally adds rare earth elements (Y and Yb) to remove the relatively difficult-to-remove Fe and Si impurity elements, ensuring that while no other impurity elements are introduced, the Fe and Si impurity elements are effectively removed. The excess Y and Yb in the aluminum melt can fully contact and react with the Fe and Si elements to form a stable compound, the AlFeSiRE phase, which precipitates at the bottom of the melt. After subsequent solidification, the impurities are removed by cutting off the bottom of the sample. The intermediate heat treatment processes such as heat preservation and cooling can allow the Y and Yb elements in the melt to have sufficient time to react with the Fe and Si impurity elements, and the formed AlFeSiRE phase precipitate can have sufficient time to deposit at the bottom, thereby improving the removal efficiency of the Fe and Si impurity elements. The addition of rare earth elements can also effectively reduce the viscosity of the melt, which can further promote the sedimentation effect of the precipitate phase.

[0051] In addition, excessive Y and Yb can be effectively removed by the segregation method in the subsequent process due to their small equilibrium distribution coefficients in the aluminum melt. Through cooling, primary crystals begin to crystallize at the positions in contact with the melt at low temperatures. As time increases, the small primary crystals at the contact positions gradually aggregate to form large crystals, and the crystals gradually grow from top to bottom along the direction of temperature transfer. At the same time, the impurity-containing liquid between the lattices is squeezed into the mother liquor below, separating the solid layer with higher purity from the liquid layer containing impurities. This method of removing Fe and Si impurity elements is applicable to the purification of aluminum by the segregation method. Compared with the traditional single segregation method process, the addition of rare earth elements can more effectively remove Fe and Si impurity elements, and the amount of rare earth elements to be added is less, the required cost is lower, the addition process is simple and no other impurity elements are introduced additionally.

[0052] Compared with the existing separate segregation method process, the present invention has the following outstanding advantages and beneficial effects:

[0053] (1) The present invention proposes a method for preparing high-purity aluminum that can both remove key impurity elements (Fe and Si) and reduce the melt viscosity, and can effectively remove the added elements by the segregation method.

[0054] (2) After microalloying the rare earths (Y / Yb) and then performing segregation solidification, the present invention can efficiently remove Fe / Si impurities in the pure aluminum melt and ensure that the content of other impurity elements meets the regulations. It can purify 2N8 industrial pure aluminum to the 3N5 level, and 4N6 high-purity aluminum can be purified to the 5N level.

[0055] (3) The present invention effectively removes impurity elements with an equilibrium distribution coefficient less than 1 in the high-purity aluminum raw materials by the segregation method, effectively removes the key impurities Fe and Si by adding rare earth aluminum alloys, and makes the rare earth master alloy fully react with Fe and Si and settle through gradient heat preservation treatment, realizing the efficient removal of impurity elements in the raw materials.

[0056] (4) The preparation process of the present invention is relatively simple, without applying other rough purification materials, without using complex equipment, with low cost and energy consumption, and can be used for large-scale batch production of 5N ultra-high-purity aluminum for the semiconductor industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic main sectional view structure diagram of the segregation furnace used in the present invention; 1 - water inlet, 2 - water outlet, 3 - cooling copper tube, 4 - graphite lid, 5 - graphite crucible, 6 - heating coil, 7 - 316 stainless steel sleeve, 8 - heat insulating asbestos, 9 - support frame, 10 - quartz tube, 11 - lifting platform, 12 - aluminum melt;

[0058] Figure 2Schematic diagram of sample cutting; 10 represents height 1, 30 represents height 3, 50 represents height 5, and 90 represents height 9;

[0059] Figure 3 Removal rates of Fe impurities in samples of Comparative Examples 2-3 and Examples 1-2 at different heights;

[0060] Figure 4 Removal rates of Si impurities in samples of Comparative Examples 2-3 and Examples 1-2 at different heights;

[0061] Figure 5 Removal rates of Fe impurities in samples of Comparative Examples 5-7 and Examples 3-6 at different heights;

[0062] Figure 6 Removal rates of Si impurities in samples of Comparative Examples 5-7 and Examples 3-6 at different heights. Specific embodiments

[0063] The present invention will be described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. Taking 2N8 commercially pure aluminum and 4N6 high-purity aluminum raw materials as examples, the process flow and implementation effects are described based on comparative examples and examples.

[0064] The structural schematic diagram of the segregation device (segregation furnace) adopted in the embodiment of the present invention is as Figure 1 shown, including a furnace body 5 with a cavity (such as a graphite crucible), a lid 4 arranged above the opening of the furnace body, a cooling pipe 3 (cooling copper pipe) arranged above the lid. The furnace body 5 is placed in a stainless steel sleeve 7, and there is a heat-insulating asbestos 8 between the stainless steel sleeve 7 and the furnace body 5. The stainless steel sleeve 7, the furnace body 5 and the lid 4 are arranged in a quartz tube 10, and a heating coil 6 is arranged outside the quartz tube 10; the stainless steel sleeve 7 and the furnace body 5 are arranged on a lifting table 11 through a support frame 9. The cavity of the furnace body is filled with molten aluminum 12.

[0065] The cooling pipe 3 includes a water inlet 1 and a water outlet 2. The cooling pipe 3 is in close contact with the lid 4.

[0066] Sample preparation and component detection: First, use wire cutting to cut at 1 cm, 3 cm, and 5 cm from the sample surface (the contact position between the graphite lid and the sample), and then use a lathe to level the sample surface from top to bottom (denoted as height 0.1), the composition at 1 cm from the surface (denoted as height 1), the composition at 3 cm from the surface (denoted as height 3), the composition at 5 cm from the surface (denoted as height 5), and the bottom of the sample is 9 cm from the surface (denoted as height 9), and use a direct-reading spectrometer to detect the components at different heights of the sample.

[0067] Figure 2 Schematic diagram of sample cutting; 10 represents height 1, 30 represents height 3, 50 represents height 5, and 90 represents height 9.

[0068] Comparative Example 1: 2N8 commercial pure aluminum

[0069] This comparative example uses 2N8 commercial pure aluminum (mass fraction, Fe 1000 ppm, Si 400 ppm, Al 99.8%, with the balance being other impurity elements, the same throughout the text) as the raw material. The specific steps and process parameters are as follows:

[0070] (1) Preparation of pure aluminum: Weigh a portion of the required weight of 2N8 commercial pure aluminum.

[0071] (2) Melting of the sample: Place the weighed 2N8 commercial pure aluminum in a graphite crucible in a melting furnace for melting. The melting temperature is 800 °C. After melting completely in 90 min, stir for 5 min to make the composition uniform, and then keep it standing and insulated for 5 min.

[0072] (3) Gradient cooling and heat preservation treatment: Use computer-aided cooling and solidification thermal analysis (CA-CCTA) to monitor the change of the melt temperature. Cool the melt in step (2) at a rate of 2 °C / min, keep it at 720 °C for 60 - 120 min and at 680 °C for 60 - 120 min. When the melt temperature drops to 400 - 500 °C, take out the graphite crucible and graphite lid and place them at room temperature.

[0073] (4) Preparation of the sample: Separate the graphite crucible and graphite lid to take out the sample. The shape of the sample is the same as the inner shape of the graphite crucible. Next, mark the surface of the sample, i.e., the place where the sample is in contact with the graphite lid, as height 0.1 (subsequently, about 0.1 cm of the height will be turned off), 1 cm away from the sample surface as height 1, 3 cm away from the sample surface as height 3, 5 cm away from the sample surface as height 5, and 9 cm away from the sample surface, i.e., the bottom of the sample in contact with the bottom of the graphite crucible, as height 9.

[0074] (5) Detection of composition: Use wire cutting to cut at sample heights 1, 3, and 5 respectively to obtain four samples. Then, use a lathe to plane the surfaces of the sample at heights 0.1, 1, 3, 5, and 9, and detect the composition at these 5 places. Figure 2 It is a schematic diagram of the cutting of the sample in Comparative Example 1 (the same for all comparative examples and examples).

[0075] Through composition detection, the contents of Fe and Si impurity elements in the 2N8 samples in Comparative Example 1 are basically the same at different heights. Therefore, it can be considered that without adding rare earth elements and segregation treatment, it is impossible to effectively change the distribution of Fe and Si impurity elements at different heights in the samples of Comparative Example 1.

[0076] Comparative Example 2: 2N8 commercial pure aluminum + Y (mass fraction is 2000 ppm)

[0077] This comparative example uses 2N8 commercial pure aluminum and rare earth master alloy (Al-10Y) as raw materials for batching, and controls the mass contents of final Y, Fe, and Si elements in high-purity aluminum (the mixed system of 2N8 commercial pure aluminum and rare earth master alloy) to be 2000 ppm, 1000 ppm, and 400 ppm respectively through calculation. The specific steps and process parameters are as follows:

[0078] (1) Preparation of pure aluminum: According to the mass contents of Y, Fe, and Si elements in pure aluminum being 2000 ppm, 1000 ppm, and 400 ppm respectively, calculate and weigh the required 2N8 commercial pure aluminum and Al-10Y rare earth master alloy for pure aluminum, and prepare the sample according to the requirements.

[0079] (2) Melting of the sample: Place the weighed 2N8 commercial pure aluminum and rare earth master alloy in a graphite crucible in a melting furnace for melting. The melting temperature is 800 °C. After complete melting, stir for 5 min to make the composition uniform, and then keep it standing and insulated for 5 min.

[0080] The subsequent steps are exactly the same as those in Comparative Example 1.

[0081] Through component detection, the contents of Fe and Si impurity elements in the sample of Comparative Example 2 gradually increase from top to bottom. Compared with the components in the 2N8 commercial pure aluminum raw material, the mass contents of Fe impurity elements at heights of 0.1, 1, 3, and 5 are reduced by 32.5%, 30.0%, 27.7%, and 21.0% respectively, and increase by 30.4% at a height of 9; the mass contents of Si impurity elements at heights of 0.1, 1, 3, and 5 are reduced by 30.3%, 29.5%, 28.0%, and 20.3% respectively, and increase by 34.8% at a height of 9. Through comprehensive data analysis, compared with Comparative Example 1, adding an excessive amount of Y element in Comparative Example 2 is beneficial to removing Fe and Si impurity elements.

[0082] Comparative Example 3: 2N8 commercial pure aluminum + Yb (mass content is 2000 ppm)

[0083] This comparative example uses 2N8 commercial pure aluminum and rare earth master alloy (Al-10Yb) as raw materials for batching, and controls the mass contents of final Yb, Fe, and Si elements in high-purity aluminum to be 2000 ppm, 1000 ppm, and 400 ppm respectively through calculation. Except that the added master alloy is different from that in Comparative Example 2, the rest of the specific steps and process parameters are the same as those in Comparative Example 2.

[0084] Through component detection, the contents of Fe and Si impurity elements in the sample of Comparative Example 3 gradually increase from top to bottom. Compared with the components in the 2N8 industrial pure aluminum raw material, the mass contents of Fe impurity element at heights of 0.1, 1, 3, and 5 are reduced by 38.5%, 33.2%, 28.4%, and 23.5% respectively, and increase by 46.0% at a height of 9; the mass contents of Si impurity element at heights of 0.1, 1, 3, and 5 are reduced by 36.3%, 31.0%, 30.0%, and 21.3% respectively, and increase by 43.8% at a height of 9. Through comprehensive data analysis, compared with Comparative Example 1, adding an excessive amount of Yb element in Comparative Example 3 is beneficial to removing Fe and Si impurity elements, and the effect of Comparative Example 3 is better than that of Comparative Example 2.

[0085] Comparative Example 4: 4N6 high-purity aluminum

[0086] This comparative example uses 4N6 high-purity aluminum (mass content, Fe 3.6 ppm, Si 3.4 ppm, Al 99.996%, and the balance is other impurity elements, the same throughout the text) as the raw material for batching. The specific steps and process parameters are as follows:

[0087] (1) Preparation of high-purity aluminum: Weigh two portions of the required weight of 4N6 high-purity aluminum raw material, one for melt viscosity detection and the other for subsequent experiments.

[0088] (2) Melt viscosity detection: Put the 4N6 high-purity aluminum used for melt viscosity detection into the graphite crucible inside the ultra-high temperature rheometer, set the temperature to above the melting point of the Al melt (800 °C) and heat for one hour, introduce argon protective gas at a flow rate of 300 - 400 mL / min, and then measure the melt viscosity at 680 °C and 670 °C.

[0089] (3) Melting of high-purity aluminum: Melt the weighed raw materials in the graphite crucible in the melting furnace at a melting temperature of 800 °C. After complete melting, stir for 5 min to make the composition uniform, and then keep it standing and heat-insulated for 5 min.

[0090] (4) Gradient cooling and heat-insulation treatment: The specific steps are the same as those in Comparative Example 1.

[0091] (5) Preparation of samples: The specific steps are the same as those in Comparative Example 1.

[0092] (6) Detection of components: The specific steps are the same as those in Comparative Example 1.

[0093] Through viscosity detection, in Comparative Example 4, for 4N6 high-purity aluminum, as the temperature decreases, the melt viscosity increases. Through composition detection, in Comparative Example 4, without any treatment, the contents of Fe and Si impurity elements in the 4N6 sample at different heights are basically the same. Therefore, it can be considered that without rare earth elements and segregation method treatment, the distribution of Fe and Si impurity elements at different heights in the sample of Comparative Example 4 cannot be effectively changed.

[0094] Comparative Example 5: 4N6 high-purity aluminum + Y (mass content is 40 ppm)

[0095] In this comparative example, 4N6 high-purity aluminum and rare earth master alloy (Al-10Y) are used as raw materials for batching, and the mass contents of Y, Fe, and Si elements in high-purity aluminum are controlled to be 40 ppm, 3.6 ppm, and 3.4 ppm respectively through calculation. The specific steps and process parameters are as follows:

[0096] (1) Preparation of high-purity aluminum: According to the mass contents of Y, Fe, and Si elements in high-purity aluminum being 40 ppm, 3.6 ppm, and 3.4 ppm respectively, calculate and weigh the required 4N6 high-purity aluminum and Al-10Y rare earth master alloy for high-purity aluminum, and prepare two samples according to the requirements, one for melt viscosity detection and the other for subsequent experiments.

[0097] (2) The same as Comparative Example 4.

[0098] (3) Melting of high-purity aluminum: The weighed raw materials 4N6 high-purity aluminum and Al-10Y rare earth master alloy are melted in a graphite crucible in a melting furnace. The melting temperature is 800 °C. After melting completely for 90 min, stir for 5 min to make the composition uniform, and then keep it standing and insulated for 5 min.

[0099] The subsequent steps are exactly the same as those in Comparative Example 4.

[0100] Compared with the melt viscosity of 4N6 high-purity aluminum in Comparative Example 4, in Comparative Example 5, after adding 40 ppm of Y element, the melt viscosity is reduced. Through composition detection, the contents of Fe and Si impurity elements in the sample of Comparative Example 5 gradually increase from top to bottom. Compared with the composition in the 4N6 high-purity aluminum raw material, the mass contents of Fe impurity elements at heights of 0.1, 1, 3, and 5 are reduced by 25.0%, 25.0%, 19.4%, and 19.4% respectively, and increase by 44.4% at height 9; the mass contents of Si impurity elements at heights of 0.1, 1, 3, and 5 are reduced by 26.5%, 23.5%, 20.6%, and 17.6% respectively, and increase by 47.1% at height 9. Through comprehensive data analysis, compared with Comparative Example 4, after adding an excessive amount of Y element in Comparative Example 5, the melt viscosity is reduced, making the precipitate phase easier to settle, which is beneficial to the removal of Fe and Si impurity elements.

[0101] Comparative Example 6: 4N6 high-purity aluminum + Yb (mass content is 40 ppm)

[0102] In this comparative example, 4N6 high-purity aluminum and rare earth master alloy (Al-10Yb) were used as raw materials for batching, and the mass contents of Yb, Fe, and Si elements in the high-purity aluminum were controlled to be 40 ppm, 3.6 ppm, and 3.4 ppm respectively through calculation. Except that the added master alloy was different from that in Comparative Example 5, the other specific steps and process parameters were the same as those in Comparative Example 5.

[0103] Compared with the melt viscosity of 4N6 high-purity aluminum in Comparative Example 4, the melt viscosity decreased after adding 40 ppm Yb element in Comparative Example 6. Through composition detection, the contents of Fe and Si impurity elements in the sample of Comparative Example 6 gradually increased from top to bottom. Compared with the composition in the 4N6 high-purity aluminum raw material, the mass contents of Fe impurity element decreased by 27.8%, 25.0%, 22.2%, and 19.4% at heights of 0.1, 1, 3, and 5 respectively, and increased by 44.4% at height 9; the mass contents of Si impurity element decreased by 26.5%, 26.5%, 23.5%, and 20.6% at heights of 0.1, 1, 3, and 5 respectively, and increased by 50.0% at height 9. Through comprehensive data analysis, compared with Comparative Example 4, adding an excessive amount of Yb element in Comparative Example 6 decreased the melt viscosity, making the precipitate phase easier to settle, which was beneficial to removing Fe and Si impurity elements.

[0104] Comparative Example 7: 4N6 high-purity aluminum + segregation treatment

[0105] In this comparative example, 4N6 high-purity aluminum was used as the raw material for batching, and the specific steps and process parameters were as follows:

[0106] (1) Preparation of high-purity aluminum: Select 4N6 high-purity aluminum raw material and weigh the required weight as the target sample, and one portion is used for the next segregation purification experiment according to the requirements.

[0107] (2) Detection of melt viscosity: The melt viscosity was the same as that of the 4N6 high-purity aluminum melt in Comparative Example 4.

[0108] (3) Melting of high-purity aluminum: The weighed raw materials for the segregation purification experiment were melted in a graphite crucible in a segregation furnace (see Figure 1 ). The graphite crucible was placed in a protective sleeve, and the side wall and bottom of the protective sleeve contained heat-insulating asbestos, which could ensure that heat was only transferred through the top of the graphite crucible. Next, high-purity aluminum was melted at a temperature of 800 °C. After melting completely in 90 min, it was stirred for 5 min to make its composition uniform, and then kept warm for 5 min.

[0109] (4) Gradient cooling and heat preservation treatment: Use computer-aided cooling solidification thermal analysis (CA-CCTA) to monitor the change of the melt temperature. Cool the melt in step (3) at a rate of 2 °C / min, keep it warm at 720 °C and 680 °C for 60 - 120 min respectively, and finally keep the melt temperature in the crucible at 680 °C.

[0110] (5) Segregation: Next, turn off the heating coil of the furnace and use computer-aided cooling solidification thermal analysis (CA-CCTA) to monitor the change of the melt temperature. Next, place the copper tube with circulating cooling water above the graphite lid and fit it tightly, so that the heat in the graphite crucible and the graphite crucible lid is transferred from bottom to top through the copper tube. Since the copper tube is closely attached to the graphite crucible lid, the temperature at the lid is relatively low, which can ensure that the melt inside the graphite crucible starts to crystallize from top to bottom, forming a segregation process (generally segregate for 5 - 10 min).

[0111] (6) Sample preparation: The steps for sample preparation are the same as those in Comparative Example 4.

[0112] (7) Composition detection: The steps for composition detection are the same as those in Comparative Example 4.

[0113] Through composition detection, the contents of Fe and Si impurity elements in the sample of Comparative Example 7 gradually increase from top to bottom. Compared with the composition in the 4N6 high-purity aluminum raw material, the mass contents of Fe impurity elements at heights of 0.1, 1, 3, and 5 are reduced by 22.2%, 19.4%, 13.9%, and 13.9% respectively, and increase by 38.9% at height 9; the mass contents of Si impurity elements at heights of 0.1, 1, 3, and 5 are reduced by 23.5%, 20.6%, 20.6%, and 11.8% respectively, and increase by 44.1% at height 9. Through comprehensive data analysis, compared with Comparative Example 4, the segregation method in Comparative Example 7 is beneficial to removing Fe and Si impurity elements.

[0114] To further illustrate the implementation effect of the present invention, the present invention will be described below in conjunction with embodiments.

[0115] Example 1: 2N8 industrial pure aluminum + Y (2000 ppm) + segregation treatment

[0116] In this example, 2N8 industrial pure aluminum and rare earth master alloy (Al-10Y) are used as raw materials for batching, and the mass contents of Y, Fe, and Si elements in high-purity aluminum are controlled at 2000 ppm, 1000 ppm, and 400 ppm respectively through calculation. The specific steps and process parameters are as follows:

[0117] (1) Pure aluminum preparation: According to the mass contents of Y, Fe, and Si elements in high-purity aluminum being 2000 ppm, 1000 ppm, and 400 ppm respectively, weigh the required 2N8 industrial pure aluminum and Al-10Y rare earth master alloy, and prepare the sample according to the requirements.

[0118] (2) Pure aluminum melting: Place the weighed raw materials in a graphite crucible in a segregation furnace (such as Figure 1 ) for melting. The graphite crucible is placed in a protective sleeve, and the side wall and bottom of the protective sleeve contain heat-insulating asbestos, which can ensure that heat is only transferred through the top of the graphite crucible. The melting temperature is 800 °C; after melting completely for 90 min, stir for 5 min to make its composition uniform, and then keep it static and heat-insulated for 5 min.

[0119] (3) Gradient cooling and heat-insulating treatment: Use computer-aided cooling and solidification thermal analysis (CA-CCTA) to monitor the change of the melt temperature. Cool the melt in step (2) at a rate of 2 °C / min, keep it heat-insulated at 720 °C and 680 °C for 60 - 120 min respectively, and finally keep the melt temperature in the crucible at 680 °C.

[0120] (4) Segregation: Next, turn off the heating coil of the furnace, and use computer-aided cooling and solidification thermal analysis (CA-CCTA) to monitor the change of the melt temperature. Next, place a copper tube with circulating cooling water above the graphite lid and fit it tightly, so that the heat in the graphite crucible and the graphite crucible lid is transferred from bottom to top through the copper tube. Since the copper tube is closely attached to the graphite crucible lid, the temperature at the lid is relatively low, which can ensure that the melt inside the graphite crucible starts to crystallize from top to bottom, forming a segregation process.

[0121] (5) Sample preparation: The specific steps are the same as those in Comparative Example 1.

[0122] (6) Component detection: The specific steps are the same as those in Comparative Example 1.

[0123] Through component detection, the contents of Fe and Si impurity elements in the sample of Example 1 gradually increase from top to bottom. Compared with the components in the 2N8 commercially pure aluminum raw material, the mass contents of the Fe impurity element at heights of 0.1, 1, 3, and 5 are reduced by 81.5%, 81.0%, 80.8%, and 80.0% respectively, and increase by 88.2% at a height of 9; the mass contents of the Si impurity element at heights of 0.1, 1, 3, and 5 are reduced by 78.3%, 77.5%, 77.3%, and 75.5% respectively, and increase by 85.8% at a height of 9. The element contents of the sample in Example 1 at heights of 0.1 - 5 meet the industry standard of 3N5 high-purity aluminum, and 3N5 high-purity aluminum is successfully prepared. Through comprehensive data analysis, adding an excessive amount of Y element in Example 1 and then performing segregation treatment is beneficial to removing Fe and Si impurity elements, and the effect is better than that of Comparative Examples 1 - 3.

[0124] Example 2: 2N8 commercially pure aluminum + Yb (2000 ppm) + segregation treatment

[0125] In this example, 2N8 commercially pure aluminum and rare earth master alloy (Al-10Yb) are used as raw materials for batching, and the mass contents of Yb, Fe, and Si elements in high-purity aluminum are controlled to be 2000 ppm, 1000 ppm, and 400 ppm respectively through calculation. Except that the added master alloy is different from that in Example 1, the remaining specific steps and process parameters are the same as those in Example 1.

[0126] Through component detection, the contents of Fe and Si impurity elements in the sample of Example 2 gradually increase from top to bottom. Compared with the components in the 2N8 commercially pure aluminum raw material, the mass contents of the Fe impurity element at heights of 0.1, 1, 3, and 5 are reduced by 82.0%, 81.5%, 81.2%, and 80.5% respectively, and increase by 90.1% at a height of 9; the mass contents of the Si impurity element at heights of 0.1, 1, 3, and 5 are reduced by 80.0%, 78.5%, 78.3%, and 76.5% respectively, and increase by 90.3% at a height of 9. The element contents of the sample in Example 2 at heights of 0.1 - 5 meet the industry standard of 3N5 high-purity aluminum, and 3N5 high-purity aluminum is successfully prepared. Through comprehensive data analysis, adding an excessive amount of Yb element in Example 2 and then performing segregation treatment is beneficial to removing Fe and Si impurity elements, and the effect is better than that of Comparative Examples 1 - 3 and Example 1.

[0127] Example 3: 4N6 high-purity aluminum + Y (mass content is 40 ppm) + segregation treatment

[0128] In this embodiment, 4N6 high-purity aluminum and rare-earth master alloy (Al-10Y) are used as raw materials for batching, and through calculation, the mass contents of the final rare earth Y, Fe, and Si elements in the high-purity aluminum are controlled to be 40 ppm, 3.6 ppm, and 3.4 ppm respectively. Except that the contents of the raw high-purity aluminum and the added master alloy are different from those in Embodiment 1, the remaining specific steps and process parameters are the same as those in Embodiment 1.

[0129] Through composition detection, the contents of Fe and Si impurity elements in the sample of Embodiment 3 gradually increase from top to bottom. Compared with the composition in the 4N6 high-purity aluminum raw material, the mass contents of the Fe impurity element at heights of 0.1, 1, 3, and 5 are reduced by 44.4%, 44.4%, 38.9%, and 38.9% respectively, and increase by 88.9% at a height of 9; the mass contents of the Si impurity element at heights of 0.1, 1, 3, and 5 are reduced by 47.1%, 44.1%, 41.2%, and 38.2% respectively, and increase by 76.5% at a height of 9. The average content of the Y element at heights of 0.1, 1, 3, and 5 is 0.4 ppm, and the removal rate is 99.0%. The element contents of the sample in Embodiment 3 at heights of 0.1 to 5 meet the industry standard of 5N high-purity aluminum, and 5N high-purity aluminum is successfully prepared. Through comprehensive data analysis, after adding an excessive amount of Y element in Embodiment 3 and then performing segregation treatment, it is beneficial to remove Fe and Si impurity elements and will not introduce more impurities additionally, and the effect is better than that of Comparative Examples 4 to 7.

[0130] Embodiment 4: 4N6 high-purity aluminum + Y (mass content is 100 ppm) + segregation treatment

[0131] In this embodiment, 4N6 high-purity aluminum and rare-earth master alloy (Al-10Y) are used as raw materials for batching, and through calculation, the mass contents of the final rare earth Y, Fe, and Si elements in the high-purity aluminum are controlled to be 100 ppm, 3.6 ppm, and 3.4 ppm respectively. In this embodiment, the contents of the raw high-purity aluminum and the added master alloy are different from those in Embodiment 1, and the melt viscosity needs to be detected. The steps for detecting the melt viscosity are the same as those in step (2) of Comparative Example 4. The remaining specific steps and process parameters are the same as those in Embodiment 1.

[0132] Through melt viscosity detection, it can be found that compared with the melt viscosity of 4N6 high-purity aluminum in Comparative Example 4, the melt viscosity decreased after adding 100 ppm of Y element in Example 4. Through composition detection, the contents of Fe and Si impurity elements in the sample of Example 4 gradually increased from top to bottom. Compared with the composition in the 4N6 high-purity aluminum raw material, the mass contents of Fe impurity element at heights of 0.1, 1, 3, and 5 decreased by 63.9%, 61.1%, 61.1%, and 55.6% respectively, and increased by 177.8% at height 9; the mass contents of Si impurity element at heights of 0.1, 1, 3, and 5 decreased by 70.6%, 64.7%, 61.8%, and 58.8% respectively, and increased by 97.1% at height 9. The average content of Y element at heights of 0.1, 1, 3, and 5 was 0.5 ppm, and the removal rate was 99.5%. The element contents of the sample in Example 4 at heights of 0.1 - 5 met the industry standard of 5N high-purity aluminum, and 5N high-purity aluminum was successfully prepared. Through comprehensive data analysis, adding an excessive amount of Y element in Example 4 and then performing segregation treatment was beneficial to removing Fe and Si impurity elements and would not introduce many additional impurities, and the effect was better than that of Comparative Examples 4 - 7 and Example 3.

[0133] Example 5: 4N6 high-purity aluminum + Yb (mass content is 40 ppm) + segregation treatment

[0134] In this example, 4N6 high-purity aluminum and rare earth master alloy (Al-10Yb) were used as raw materials for batching, and the mass contents of the final rare earth Yb, Fe, and Si elements in high-purity aluminum were controlled to be 40 ppm, 3.6 ppm, and 3.4 ppm respectively through calculation. Except that the contents of the raw material high-purity aluminum and the added master alloy were different from those in Example 1, the rest of the specific steps and process parameters were the same as those in Example 1.

[0135] Through component detection, the contents of Fe and Si impurity elements in the sample of Example 5 gradually increase from top to bottom. Compared with the components in the 4N6 high-purity aluminum raw material, the mass contents of Fe impurity element at heights of 0.1, 1, 3, and 5 are reduced by 50.0%, 47.2%, 47.2%, and 41.7% respectively, and increase by 97.2% at height 9; the mass contents of Si impurity element at heights of 0.1, 1, 3, and 5 are reduced by 50.0%, 50.0%, 44.1%, and 41.2% respectively, and increase by 79.4% at height 9. The average content of Yb element at heights of 0.1, 1, 3, and 5 is 0.4 ppm, and the removal rate is 99.0%. The element contents of the sample in Example 5 at heights of 0.1 to 5 meet the industrial standard of 5N high-purity aluminum, and 5N high-purity aluminum is successfully prepared. Through comprehensive data analysis, adding an excessive amount of Yb element in Example 5 and then performing segregation treatment is beneficial to removing Fe and Si impurity elements, and does not introduce more impurities additionally, and the effect is better than that of Comparative Examples 4 to 7 and Example 3.

[0136] Example 6: 4N6 high-purity aluminum + Yb (mass content is 100 ppm) + segregation treatment

[0137] In this example, 4N6 high-purity aluminum and rare earth master alloy (Al-10Yb) are used as raw materials for batching, and the mass contents of the final rare earth Yb, Fe, and Si elements in high-purity aluminum are controlled to be 100 ppm, 3.6 ppm, and 3.4 ppm respectively through calculation. The contents of the raw high-purity aluminum and the added master alloy in this example are different from those in Example 1, and the melt viscosity needs to be detected. The steps for detecting the melt viscosity are the same as those in step (2) of Comparative Example 1, and the rest of the specific steps and process parameters are the same as those in Example 1.

[0138] Through component detection, the contents of Fe and Si impurity elements in the sample of Example 6 gradually increase from top to bottom. Compared with the components in the 4N6 high-purity aluminum raw material, the mass contents of Fe impurity element at heights of 0.1, 1, 3, and 5 are reduced by 66.7%, 66.7%, 63.9%, and 61.1% respectively, and increase by 200.0% at height 9; the mass contents of Si impurity element at heights of 0.1, 1, 3, and 5 are reduced by 70.6%, 67.6%, 67.6%, and 61.8% respectively, and increase by 114.7% at height 9. The average content of Yb element at heights of 0.1, 1, 3, and 5 is 0.5 ppm, and the removal rate is 99.5%. The element contents of the sample in Example 6 at heights of 0.1 to 5 meet the industrial standard of 5N high-purity aluminum, and 5N high-purity aluminum is successfully prepared. Through comprehensive data analysis, adding an excessive amount of Yb element in Example 6 and then performing segregation treatment is beneficial to removing Fe and Si impurity elements, and does not introduce more impurities additionally, and the effect is the best among all comparative examples and examples.

[0139] To better compare and illustrate the differences in the processes and effects of each comparative example and example, the melt viscosity data are respectively summarized in Table 1, the content data of Fe and Si impurity elements at different heights (2N8 raw materials) are summarized in Table 2, and the content data of Fe and Si impurity elements at different heights (4N6 raw materials) are summarized in Table 3. All examples of the present invention remove Fe and Si impurity elements in high-purity aluminum through rare earth alloying, and remove excessive rare earth elements and remaining Fe and Si impurity elements through segregation method. This process can effectively purify high-purity aluminum without introducing other impurity elements additionally. In particular, for the high-purity aluminum samples finally prepared in Examples 1-2, the Al purity is greater than 3N5 at a height of 0.1-5, and for the high-purity aluminum samples finally prepared in Examples 4-6, the Al purity is greater than 5N at a height of 0.1-5. In 2N8 high-purity aluminum, the comprehensive performance of Example 2 based on adding 2000 ppm Yb and synergistic treatment with segregation is relatively excellent; in 4N6 high-purity aluminum, the comprehensive performance of Example 6 based on adding 100 ppm Yb and synergistic treatment with segregation is relatively excellent.

[0140] Table 1 Melt Viscosity of 4N6 High-Purity Aluminum in Comparative Examples and Examples at 680 °C and 670 °C

[0141]

[0142] Table 2 Content of Fe and Si Impurity Elements at Different Heights in Comparative Examples and Examples (2N8 Raw Materials)

[0143]

[0144] Table 3 Content of Fe and Si Impurity Elements at Different Heights of Samples in Comparative Examples and Examples (4N6 Raw Materials)

[0145]

[0146]

[0147] Figure 3 is the removal rate of Fe impurities at different heights for the samples of Comparative Examples 2-3 and Examples 1-2;

[0148] Figure 4 is the removal rate of Si impurities at different heights for the samples of Comparative Examples 2-3 and Examples 1-2;

[0149] Figure 5 is the removal rate of Fe impurities at different heights for the samples of Comparative Examples 5-7 and Examples 3-6;

[0150] Figure 6 is the removal rate of Si impurities at different heights for the samples of Comparative Examples 5-7 and Examples 3-6.

[0151] The embodiments of the present invention are not limited by the above-described embodiments. Any other changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation, characterized in that: It includes the following steps: 1) Prepare a rare earth-pure aluminum mixed melt from pure aluminum raw materials and an Al-RE rare earth master alloy; 2) Perform gradient cooling and heat preservation treatment on the mixed melt; 3) Perform segregation treatment on the mixed melt; In the Al-RE rare earth master alloy, RE is Y and / or Yb; The Al-RE rare earth master alloy is an Al-Y rare earth master alloy and / or an Al-Yb rare earth master alloy; The addition amount of rare earth RE satisfies the following conditions: the addition amount of Y is 1.5 to 50 times the content of Fe or Si in the pure aluminum raw materials; when the Fe content in the pure aluminum raw materials ≥ the Si content, the addition amount of Y is 1.5 to 50 times the Fe content in the pure aluminum raw materials, and when the Fe content in the pure aluminum raw materials < the Si content, the addition amount of Y is 1.5 to 50 times the Si content in the pure aluminum raw materials; The addition amount of Yb is 1.5 to 50 times the content of Fe or Si in the pure aluminum raw materials; when the Fe content in the pure aluminum raw materials ≥ the Si content, the addition amount of Yb is 1.5 to 50 times the Fe content in the pure aluminum raw materials, and when the Fe content in the pure aluminum raw materials < the Si content, the addition amount of Yb is 1.5 to 50 times the Si content in the pure aluminum raw materials.

2. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation according to claim 1, wherein: When the Al content in the pure aluminum raw materials ≥ 99.8%, the Fe or Si content ≥ 100 ppm and Fe < 0.2%, Si < 0.1%, and the total impurity < 0.2%, the addition amount of rare earth RE is 1.5 to 8 times the content of Fe or Si in the pure aluminum raw materials; when the Fe or Si content < 100 ppm, the addition amount of rare earth RE is 8 to 50 times the content of Fe or Si in the pure aluminum raw materials.

3. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation according to claim 2, characterized in that: The Al content in the pure aluminum raw materials ≥ 99.8%; the Al-Y rare earth master alloy is Al-10wt%Y, and the Al-Yb rare earth master alloy is Al-10wt%Yb.

4. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by rare earth alloying and segregation according to claim 2, characterized in that: The pure aluminum raw materials are 2N8 industrial pure aluminum or 4N6 high-purity aluminum; When the pure aluminum raw materials are 2N8 industrial pure aluminum, the addition amount of rare earth RE is 1.5 to 8 times the content of Fe or Si in the pure aluminum raw materials; When the pure aluminum raw materials are 4N6 high-purity aluminum, the addition amount of rare earth RE is 8 to 50 times the content of Fe or Si in the pure aluminum raw materials.

5. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by rare earth alloying and segregation according to claim 4, characterized in that: When the pure aluminum raw materials are 2N8 industrial pure aluminum, the addition amount of rare earth RE is 1.5 to 5 times the content of Fe or Si in the pure aluminum raw materials; When the pure aluminum raw materials are 4N6 high-purity aluminum, the addition amount of rare earth RE is 8 to 40 times the content of Fe or Si in the pure aluminum raw materials.

6. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation according to claim 1, characterized in that: In step 2), the gradient cooling and heat preservation treatment is to first reduce the melt temperature to 710 - 730 °C at a rate of 1 - 2.5 °C / min and keep it for 60 - 120 min, then reduce the melt temperature to 675 - 685 °C at a rate of 1 - 2.5 °C / min and keep it for 60 - 120 min, and finally keep the melt temperature at 675 - 685 °C; In step 3), the segregation treatment refers to cooling on one side or above the melt after stopping heating, and the melt crystallizes to form segregation.

7. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation according to claim 6, characterized in that: The segregation treatment described in step 3) specifically refers to turning off the heating device of the segregation device. There is a lid above the melt placed in the cavity of the segregation device, and a cooling device is provided above the lid. After being cooled by the cooling device, the melt in contact with the lid starts to crystallize from top to bottom, forming segregation.

8. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation according to claim 1, characterized in that: After the segregation treatment is completed, it is cooled, the aluminum ingot is taken out, the compositions of different parts of the aluminum ingot are detected, and the parts with more impurities are removed to obtain the required pure aluminum.

9. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by rare earth alloying and segregation according to claim 1, characterized in that: The specific steps of step 1): Melting the pure aluminum raw material and the Al-RE rare earth master alloy, mixing them evenly, and keeping them static and warm to obtain a rare earth-pure aluminum mixed melt.

10. The composite treatment method for reducing Fe / Si impurities in high-purity aluminum by using rare earth alloying and segregation according to claim 9, characterized in that: The temperature of the melting is 750-800 °C; the mixing evenly is to stir and mix evenly after the high-purity aluminum is melted; the stirring time is 5-10 min; Keep it static and warm for 3-60 min.

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