A method for producing 5n high purity aluminum

Abstract

The application belongs to the technical field of aluminum purification, and discloses a method for preparing 5N high-purity aluminum. The method comprises the following steps: 1) melting 4N5 high-purity aluminum raw material to remove impurity elements with a distribution coefficient greater than 1, and obtaining a high-purity aluminum melt; 2) adding Fe and Si elements to the high-purity aluminum melt to prepare a segregation liquid; 3) performing step-by-step crystallization treatment on the segregation liquid; and 4) taking out the aluminum ingot, removing the end with more impurities, and remelting the ingot to obtain 5N high-purity aluminum. The method can effectively remove the added Fe and Si impurity elements, and does not introduce impurity elements which are difficult to remove by the segregation method. The segregation rate of Fe and Si impurity elements is more than 90% by the method, the removal rate of Fe and Si impurity elements is between 70% and 90%, and 5N high-purity aluminum is obtained. The method is simple and easy to implement, and has low production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum purification, and particularly relates to a method for preparing 5N high-purity aluminum. BACKGROUND

[0002] High-purity aluminum generally refers to pure aluminum material with a purity of greater than 99.95%, which is mainly used in the fields of wire manufacturing, capacitor electrode foil, sputtering target material, semiconductor devices, optoelectronic storage media, computer storage hard disks, etc. The application field is closely related to the purity. In the industry, high-purity aluminum alloy with a purity of greater than 99.95% is simply referred to as 3N5, and high-purity aluminum with an aluminum content of greater than or equal to 99.999% is simply referred to as 5N high-purity aluminum, which is mainly used in advanced manufacturing fields represented by semiconductor devices. The manufacturing process of 5N high-purity aluminum is complex, and the production cost is high.

[0003] According to the basic principle, the main methods for producing high-purity aluminum at present include three-layer liquid and segregation method. The three-layer liquid production has high efficiency, but has high energy consumption and generates a large amount of hazardous waste containing fluorine, and can only produce 4N high-purity aluminum. The segregation method has the advantages of relatively low energy consumption, no pollutant emission, etc., and can obtain higher purity. The main principle of the segregation method is that the equilibrium composition of the solid phase and the liquid phase will change with the decrease of the temperature in the solidification of the melt, and the redistribution of solute elements will produce enrichment or depletion in the interface front, which will show uneven distribution of solute elements on the macroscopic level. The main processes of the segregation method at present include step crystallization, directional solidification and zone melting. Among them, the step crystallization method can be continuously produced and has high efficiency, and is the main method for producing high-purity aluminum, especially 5N high-purity aluminum or above.

[0004] The step crystallization method in the segregation method is a common method for purifying high-purity aluminum, and the basic principle is as follows: the aluminum melt is placed in a crucible, and a cooling device is placed on the side wall of the crucible to cool the local area. The aluminum liquid will solidify and crystallize in the place with lower temperature, and then the aluminum primary crystal is scraped off from the side wall to the bottom by a stirring disc device. The aluminum crystals in the bottom gather to form large crystals, and then high-purity aluminum is obtained by solid-liquid separation. The step crystallization method can effectively remove impurity elements with a balance distribution coefficient K < 1 in aluminum, and the smaller the K value of the impurity element, the easier it is to remove. However, impurity elements with K > 1 in aluminum cannot be removed by the step crystallization method.

[0005] Chinese invention patent application CN 118256736A discloses a purification device and a process for preparing 5N high-purity aluminum based on the step crystallization method. The process cools the aluminum liquid in the longitudinally movable purification container, so that the aluminum liquid crystallizes on the inner wall. When the solid aluminum is scraped off, the bottom of the purification container gradually moves downward with the increase of the aluminum content, until it completely separates from the container. However, the process has high operation difficulty, complex technology, and requires high-precision equipment and mechanical structure, and the purification efficiency is relatively low, which is not conducive to large-scale batch production of 5N high-purity aluminum.

[0006] In the process of preparing high-purity aluminum by fractional crystallization based on segregation, the outer cooling zone of the furnace wall of the segregation furnace is cooled based on air blowing to crystallize the furnace wall, and then the high-purity aluminum crystals are scraped off to the bottom of the segregation furnace by a tamping disc, and the tamping disc is finally moved up and down repeatedly by the support of a tamping rod to realize the production of high-purity aluminum. The tamping disc movement process needs to overcome the resistance brought by the viscosity of the melt, and can induce torque generation. The higher the viscosity of the melt, the greater the movement speed, and the greater the resistance and torque generated. When the resistance and torque are too large, the tamping disc is prone to breakage, and even the tamping rod and the tamping disc support are broken, which seriously affects the production efficiency and manufacturing cost.

[0007] How to reduce the viscosity of high-purity aluminum melt and ensure efficient segregation is very important for producing higher purity (5N and above). Moreover, in the production of higher purity high-purity aluminum, efficient removal of Fe / Si impurities is very important. Although the segregation coefficients of Fe and Si in the solidification process of Al melt are 0.023 and 0.1 respectively, both of which belong to elements that can be efficiently removed based on segregation; however, how to efficiently remove impurities while reducing the viscosity of aluminum melt for efficient segregation is one of the problems that people need to solve. SUMMARY

[0008] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a method for preparing 5N high-purity aluminum. The method of the present application is simple, has high purification efficiency, realizes the preparation of 5N high-purity aluminum, and the method of the present application can effectively mass-produce 5N high-purity aluminum.

[0009] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0010] A method for preparing 5N high-purity aluminum, comprising the following steps:

[0011] 1) Melting 4N5 high-purity aluminum raw material, removing impurity elements with a balance distribution coefficient greater than 1, and obtaining a high-purity aluminum melt;

[0012] 2) Adding Fe and Si elements to the high-purity aluminum melt to prepare a segregation liquid;

[0013] 3) Step crystallization treatment is performed on the segregation liquid;

[0014] 4) Taking out the aluminum ingot, removing the end with more impurities, and remelting the ingot to obtain 5N high-purity aluminum.

[0015] The removal of impurity elements with a balance distribution coefficient greater than 1 in step 1) means adding Al-B intermediate alloy to the melt and mixing uniformly, and then standing and heat preservation.

[0016] The amount of B is calculated according to the content of impurity elements with equilibrium distribution coefficient greater than 1 in the high-purity aluminum raw material; B and the impurity elements (such as Cr, V, Ti) with equilibrium distribution coefficient greater than 1 in the high-purity aluminum raw material completely react to form precipitates (such as CrB2, TiB2, VB2, ZrB2 precipitates), which are deposited at the bottom of the melt, and the amount of B is determined by calculation.

[0017] The mixing is stirring mixing, and the stirring time is 5-10 min; and the standing time is 2-60 min.

[0018] After removing the impurity elements with equilibrium distribution coefficient greater than 1 in step 1), refining and slag removal are performed. The refining and slag removal are performed by adding a refining agent and a slag removal agent, mixing uniformly, and then standing and removing the surface dross and the bottom precipitates. The commercial trade names of the refining agent and the slag removal agent are YT-J-1 and YT-D-4 respectively, and the two are mixed according to a mass ratio of 1:1, and the total amount of addition is 1% of the weight of the melt. The refining and slag removal are conventional operations.

[0019] The melting temperature in step 1) is 720-800℃.

[0020] In step 2), the addition of Fe and Si elements means adding Al-Fe intermediate alloy and Al-Si intermediate alloy, mixing uniformly, and standing and keeping warm.

[0021] The Al-Fe intermediate alloy is Al-20wt%Fe, and the Al-Si intermediate alloy is Al-20wt%Si.

[0022] The mixing is stirring mixing, and the stirring time is 5-10 min; and the standing time is 2-60 min.

[0023] The prepared segregation solution is used to detect the viscosity of the melt by using a high-temperature melt viscosity detection device.

[0024] In step 2), the amount of Fe and Si elements satisfies the following conditions: after Fe and Si elements are added to 4N5 high-purity aluminum raw material, the total content of Fe is 20-200ppm, preferably 30-120ppm; the total content of Si is 20-200ppm, preferably 30-120ppm; and the mass content ratio of Fe / Si is (0.2-6):1, preferably (0.4-4):1, more preferably (0.5-4):1, more preferably (1.5-3.5):1.

[0025] The fractional crystallization treatment in step 3) refers to keeping the temperature of the segregation liquid at 665-670℃, and then cooling the segregation liquid placed in the device through the cooling device arranged on the side wall of the device, and the segregation liquid in contact with the side wall precipitates aluminum primary crystals, and the segregation liquid is stirred while the aluminum primary crystals are scraped off, and the operation is repeated, and the aluminum primary crystals are gathered and grown to complete the fractional crystallization.

[0026] The aluminum primary crystals are scraped off and compressed, specifically, the aluminum primary crystals are scraped off and compressed to the bottom of the cavity of the device filled with the segregation liquid.

[0027] The segregation liquid is stirred while the aluminum primary crystals are scraped off, and the aluminum primary crystals are gathered and grown, which refers to scraping off and compacting the aluminum primary crystals through the up-and-down movement of the crystal scraping device, and the crystal scraping device is provided with holes or gaps, and the aluminum melt passes through the holes or gaps while the aluminum primary crystals are scraped off and compacted, and the aluminum primary crystals are gathered and grown through such up-and-down movement.

[0028] The crystal scraping device is a tamping disc and tamping rod or a ring-shaped plunger. The tamping disc and tamping rod comprise a tamping disc and a tamping rod arranged on the tamping disc, and the tamping disc and tamping rod are provided with holes, and the tamping disc and tamping rod move up and down.

[0029] The speed of the up-and-down movement of the crystal scraping device is 5-10 times / min.

[0030] The cooling refers to cooling by introducing cooling gas. The speed of introducing the cooling gas is 10-50 m 3 / h.

[0031] In step 4), the end of the aluminum ingot with more impurities can be detected by an instrument to detect the composition of the aluminum ingot, and the part with more impurities can be removed or 1 / 5-1 / 10 of the aluminum ingot crystallized later can be removed.

[0032] The melting temperature of the remelted ingot is 700-780℃.

[0033] The 5N high-purity aluminum of the present application, key impurities and their contents (by mass):

[0034] Fe <2.5 ppm

[0035] Si <2.5 ppm

[0036] Al >99.999%

[0037] The balance is other impurities, including Cu <1.0 ppm, Zn <0.9 ppm, Ti <1.0 ppm, V <1.0 ppm, B <1.0 ppm; among the remaining other impurities, Mn, Mg, Cr, Ni, Ga, Zr, Pb, etc. are included, and the content of a single impurity is <0.5 ppm;

[0038] The total of other impurities is <10 ppm.

[0039] Principles of the present application:

[0040] Melt viscosity reduction principle: The influence of iron atoms and silicon atoms on the viscosity of aluminum melt is relatively complex. When the addition amount of Fe and Si is small, the addition of iron and silicon elements will reduce the viscosity of the aluminum melt. The atomic radius of iron (about 126 ppm) and the atomic radius of silicon (about 118 pm) are smaller than that of aluminum. The addition of Fe and Si elements will cause changes in the atomic structure of the melt, which can play a certain "lubricating" role in the aluminum melt, making the relative sliding between aluminum atoms easier, which is manifested in the macroscopic as a decrease in melt viscosity. From the perspective of interatomic interaction energy, there is a certain interaction energy between aluminum atoms in the aluminum melt. When iron and silicon elements are added, new chemical bonds can be formed between aluminum atoms. The new Fe-Al bond and Si-Al bond are different from the Al-Al bond, which changes the energy state of the entire melt system. This new chemical bond makes the combination between atoms relatively weak, making the relative movement between atoms easier, thereby reducing the viscosity of the melt. At the same time, the presence of Fe and Si atoms disrupts the ordered arrangement of aluminum atoms, making the structure of the melt relatively loose. During the flow of the liquid, this change in structure reduces the internal friction of the melt, thus reducing the viscosity of the melt.

[0041] Segregation principle: The essence of the segregation method is the phenomenon of solute atoms in the solid phase and liquid phase during solidification. Through the segregation method, impurity elements with a balance distribution coefficient less than 1 in aluminum, such as Fe and Si, can be effectively removed. The balance distribution coefficients of Fe and Si in aluminum are 0.023 and 0.10, respectively, and the smaller the balance distribution coefficient of impurity elements in aluminum, the easier they are to remove.

[0042] Process characteristics: the 5N high purity aluminum in the application is based on the further reduction of Fe / Si impurities in 4N5 high purity aluminum to achieve 5N purity requirements. The application proposes a "reverse" path, which increases Fe / Si impurities in 4N5 to reduce viscosity, and then realizes efficient removal based on segregation. Under the premise of not introducing other impurities, Fe / Si impurities are introduced into the aluminum melt. During fractional crystallization, the temperature at the bottom of the device is slightly higher than the melting point of aluminum, and the side wall cooling pipe is passed through the cooling gas. The side wall is used to precipitate high-purity aluminum primary crystals by using the segregation effect. Through the up and down movement of the tamping rod on the tamping disc, the aluminum primary crystals are scraped off to the bottom of the device and compacted, and the aluminum melt rich in impurities is squeezed out between the crystals. The holes on the tamping disc and tamping rod facilitate the passage of aluminum melt. In the early stage of fractional crystallization, the tamping disc and tamping rod can effectively scrape off the primary crystals. As the aluminum primary crystals accumulate, although the viscosity of the melt increases, the stroke of the tamping disc and tamping rod decreases and the resistance decreases, ensuring that the segregation proceeds smoothly. Through repeated operation, the aluminum primary crystals are aggregated into larger and purer aluminum crystals, realizing the purification of aluminum. Continuous fractional crystallization can continuously remove Fe and Si impurities, so that the content of Fe / Si impurities in the final aluminum ingot is reduced to below 2.5ppm. The method is suitable for purifying aluminum by fractional crystallization method. Compared with the traditional segregation method, the cost is low, the addition is simple, no new impurities are introduced, and it is conducive to large-scale production of 5N high purity aluminum.

[0043] Compared with the existing method, the application has the following outstanding advantages and beneficial effects:

[0044] (1) The application is based on a reverse research idea, which reduces the melt viscosity by pre-adding Fe / Si in high-purity aluminum, which is more conducive to the smooth progress of fractional crystallization method, and the process is relatively simple and the cost is relatively low.

[0045] (2) The application can realize efficient removal of key impurity elements (Fe and Si) in high-purity aluminum, and the removal rate of Fe and Si impurity elements is close to 90%.

[0046] (3) The melt viscosity reduction rate of Fe / Si addition is between 30% and 50%, the segregation rate of Fe / Si elements can reach more than 90%, and the content of key impurity elements in the product meets the specified requirements.

[0047] (4) The preparation process of the application is relatively simple, without the need to apply other rough purification materials, without the need to use complex equipment, with low cost and energy consumption, and suitable for batch production and large-scale manufacturing of 5N ultra-high purity aluminum for semiconductor industry. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is a schematic diagram of the main view of the fractional crystallization furnace used in the application; 1- furnace cover, 2- tamping rod, 3- tamping disc, 4- hole, 5- aluminum melt, 6- cooling gas pipe, 7- solid aluminum, 8- cooling part, 9- aluminum primary crystal, 10- heating coil, 11- furnace shell;

[0049] Figure 2 Figure for fracture of connection between tamping disc and tamping rod caused by too large melt viscosity in process of adopting fractional crystallization method;

[0050] Figure 3 Melt viscosity change of high-purity aluminum in Examples 1-5 at 680℃ and 670℃;

[0051] Figure 4 Fe and Si impurity segregation rate of high-purity aluminum samples prepared in Comparative Examples 3 and 5 and Examples 1-5;

[0052] Figure 5 Fe and Si impurity element removal rate of high-purity aluminum samples prepared in Comparative Examples 3 and 5 and Examples 1-5. DETAILED DESCRIPTION

[0053] The present application will be described in detail below with specific examples, but the embodiments of the present application are not limited thereto. Taking 4N5 high-purity aluminum raw material as an example, the process flow and implementation effect are explained based on comparative examples and examples. The segregation rate is the removal degree of Fe / Si impurity elements before and after fractional crystallization, and the removal rate is the removal degree of Fe / Si impurity element content compared with the Fe / Si content in 4N5 raw material after fractional crystallization.

[0054] The device (fractional crystallization furnace) used in the fractional crystallization in the embodiments of the present application is shown in the sectional view as Figure 1 shown, including a furnace body with a cavity, a tamping rod 2, a tamping disc 3, a furnace cover 1 and a furnace shell 11, a heating coil 10 is provided on the outside of the furnace body, and a cooling device is provided on one side wall of the furnace body, one end of the tamping rod 2 is arranged on the tamping disc 3, the other end of the tamping rod 2 passes through the aperture on the furnace cover 1, and the tamping disc 3 moves up and down with the tamping rod 2; the furnace body and the heating coil 10 are arranged in the furnace shell 11, the furnace body is open at the top and is covered by the furnace cover 1; the cooling device includes a cooling gas pipe 6, and the cooling gas pipe passes through the furnace shell. Holes 4 are provided on the tamping disc and the tamping rod.

[0055] The furnace body of the present application is filled with aluminum melt 5, and the cooling gas is delivered to the side wall 8 (i.e. the cooling part) of the furnace body through the cooling gas pipe 6 to cool the melt in the furnace body. The melt at the side wall precipitates high-purity aluminum primary crystals 9, and then the fine aluminum primary crystals are scraped off to the bottom of the furnace body (such as a crucible) and compacted by the up-and-down movement of the tamping disc and the tamping rod, and the compacting action can also squeeze out the aluminum melt between the crystals which is rich in impurity elements, and the holes 4 on the tamping disc and the tamping rod can allow the aluminum melt to pass through. Such repeated operations make the aluminum primary crystals at the bottom gradually gather and grow into larger and purer aluminum crystals 7, which can achieve the purpose of aluminum purification.

[0056] Figure 2 Figure for fracture of connection between tamping disc and tamping rod caused by too large melt viscosity in process of adopting fractional crystallization method;

[0057] Comparative Example 1: 4N5 high purity aluminum

[0058] The raw material of this comparative example is 4N5 high purity aluminum (mass content, Fe 10 ppm, Si 8 ppm, Cu 12 ppm, Mn 0.5 ppm, Mg 2.0 ppm, Cr 0.3 ppm, Ni 1.0 ppm, Zn 2.0 ppm, Ga 3.0 ppm, V 0.1 ppm, B 1.7 ppm, Ti 0.3 ppm, Zr 0.1 ppm, Pb 1.4 ppm, Al 99.9957%, same throughout). The specific steps and process parameters are as follows:

[0059] (1) High purity aluminum preparation: select 4N5 high purity aluminum raw material and weigh the required weight, prepare two portions of high purity aluminum, one for high purity aluminum melt viscosity detection, the other for subsequent fractional crystallization treatment.

[0060] (2) Melt pretreatment: melt the high purity aluminum raw material in the pretreatment furnace, the melting temperature is 720°C, after melting, according to the impurity content in the raw material, add Al-B master alloy for impurity removal (the amount of B added is determined by calculating to completely react with Cr, V, Ti in high purity aluminum raw material to generate CrB2, TiB2, VB2, ZrB2 precipitates), after uniform electromagnetic stirring, stand and keep warm, and obtain the segregation liquid.

[0061] (3) Viscosity detection: place the high purity aluminum for melt viscosity detection into the crucible inside the ultrahigh temperature rheometer, set the temperature to be above the Al melt melting point and heat for one hour, after melting, pass in argon gas, the gas flow rate is 260 mL / min, then measure the rotational speed of 0.1 revolutions per second, and detect the melt viscosity at temperatures of 680°C and 670°C, respectively.

[0062] (4) Fractional crystallization treatment: move the segregation liquid obtained in step (2) into the segregation furnace for fractional crystallization treatment, keep the aluminum melt at a temperature of 670°C, pass in cooling gas (the temperature of the cooling gas is room temperature) into the cooling pipe on the side wall of the segregation furnace, the gas flow rate is 20 m 3 / h, high purity aluminum primary crystals are precipitated on the side wall of the segregation furnace, then the fine aluminum primary crystals are scraped off to the bottom of the crucible and compacted by the up and down movement of the tamping disc and tamping rod (the movement speed is 5 times / min), the compaction action can also squeeze out the aluminum melt rich in impurity elements between the crystals, the holes on the tamping disc and tamping rod can allow the aluminum melt to pass through. Repeat this process to gradually accumulate the aluminum primary crystals at the bottom into larger and purer aluminum crystals, which can achieve the purpose of aluminum purification (the aluminum crystals gradually crystallize from the bottom up, the time is about 12 h).

[0063] (5) Remelting into ingot: After the completion of fractional crystallization, the concentrated liquid inside the crucible is poured out, and after the completion of pouring out of the concentrated liquid, the head of the aluminum ingot is cut off (the crystallization process is gradually crystallized from the bottom of the fractional crystallization furnace upwards, the bottom crystallizes first, and the last crystallization place is the top, that is, the head, and 1 / 5 to 1 / 10 of the aluminum ingot needs to be cut off, or the composition of each part of the aluminum ingot is detected by an instrument, and the part with more impurities is cut off), then the remaining aluminum ingot is remelted and then uniformly distributed by electromagnetic stirring, and then cast into an ingot to obtain high-purity aluminum.

[0064] The melt viscosity of the 4N5 high-purity aluminum melt detected in step (3) at 680°C and 670°C was 20.2 [Pa·s], 22.3 [Pa·s], respectively. By performing the steps in Comparative Example 1, it was found that in the early stage of step (4) fractional crystallization treatment, due to the too large melt viscosity, the resistance of the moving process of the tamping disc and tamping rod was large, which caused the tamping disc and tamping rod to break, and the fractional crystallization process failed. The fracture occurred at the connection between the tamping disc and the tamping rod, as shown in FIG. 1. Figure 2

[0065] Composition detection: The composition of the high-purity aluminum obtained in step (5) was detected.

[0066] The Al content in the composition of the high-purity aluminum obtained in the detection furnace was 99.9957%, the Fe impurity element content was 10.0 ppm, and the Si impurity element content was 8.0 ppm. Without removing the Fe and Si impurity elements, the prepared high-purity aluminum cannot meet the composition requirements of 5N high-purity aluminum.

[0067] Comparative Example 2: 4N5 high-purity aluminum + Fe (mass content of 40 ppm)

[0068] This comparative example uses 4N5 high-purity aluminum and Al-20Fe intermediate alloy as raw materials for batching, wherein the composition of the 4N5 high-purity aluminum is the same as that of Comparative Example 1. The mass content of Fe element in the high-purity aluminum (i.e. the mixed system of 4N5 high-purity aluminum and Al-20Fe intermediate alloy) is controlled to be 40 ppm by calculation. The specific steps and process parameters are as follows:

[0069] (1) High-purity aluminum preparation: According to the mass content of Fe and Si elements in high-purity aluminum being 40 ppm and 8.0 ppm respectively, 4N5 high-purity aluminum and Al-20Fe intermediate alloy required for high-purity aluminum are calculated and weighed respectively, and two samples are prepared according to the requirements, one for melt viscosity detection and the other for subsequent fractional crystallization treatment.

[0070] ​(2) Melt pretreatment: Put the high-purity aluminum raw material into the pretreatment furnace to melt, and the melting temperature is 740°C. After melting, according to the impurity content in the raw material, calculate and add Al-B intermediate alloy to remove impurities (the amount of B added is determined by calculating the amount of B added to completely react with Cr, V, Ti in the high-purity aluminum raw material to generate CrB2, TiB2, VB2, ZrB2 precipitates). Refine and remove slag. Next, add Al-20Fe intermediate alloy to the high-purity aluminum melt, and after uniform electromagnetic stirring, stand and keep warm to make the mass content of Fe element in the melt 40 ppm, and obtain the segregation liquid.

[0071] (3) Viscosity detection: The melt prepared in step (2) is subjected to viscosity test.

[0072] (4) Step-by-step crystallization treatment: The segregation liquid obtained in step (2) is moved into the segregation furnace for step-by-step crystallization treatment. The aluminum melt is kept at a temperature of 669°C, and cooling gas is introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 30 m 3 / h. High-purity aluminum primary crystals are precipitated on the side wall of the segregation furnace. Next, the fine aluminum primary crystals are scraped off to the bottom of the crucible and compacted by the up-and-down movement of the stirring disc and stirring rod (movement speed is 6 times / min). The compaction action can also squeeze out the aluminum melt between the crystals which is rich in impurity elements. The holes on the stirring disc and stirring rod allow the aluminum melt to pass through. Repeat the process until the aluminum primary crystals at the bottom gradually grow into larger and purer aluminum crystals, achieving the purpose of aluminum purification.

[0073] (5) Remelting into ingot: After completing the step-by-step crystallization, the concentrated liquid inside the crucible is poured out. After the concentrated liquid is poured out, the head of the aluminum ingot is cut off (1 / 5 to 1 / 10 of the aluminum ingot needs to be cut off, or the composition of each part of the aluminum ingot is detected by an instrument, and the part with more impurities is cut off). Next, the remaining aluminum ingot is remelted, and then electromagnetic stirring is used to make the composition uniform, and then the aluminum ingot is cast to obtain high-purity aluminum.

[0074] Composition detection: The composition of the high-purity aluminum obtained in step (5) is detected by an instrument.

[0075] The melt viscosity of the high-purity aluminum melt detected in step (3) at 680°C and 670°C is 15.1 [Pa·s] and 18.1 [Pa·s], respectively, which is lower than that of the 4N5 high-purity aluminum in Comparative Example 1. By performing the steps in Comparative Example 2, it is found that in the early stage of step (4) step-by-step crystallization treatment, due to the too high melt viscosity, the resistance during the up-and-down movement of the stirring disc and stirring rod is large, which causes the stirring disc and stirring rod to break, and the step-by-step crystallization process fails.

[0076] The high-purity aluminum obtained in the testing furnace had an Al content of 99.9931%, an Fe impurity element content of 38 ppm, and a Si impurity element content of 7.8 ppm. The segregation rates of Fe and Si impurity elements were 5.0% and 2.5%, respectively. The prepared high-purity aluminum could not meet the composition requirements of 5N high-purity aluminum.

[0077] Comparative Example 3: 4N5 high-purity aluminum + Fe (mass content 80 ppm)

[0078] This comparative example uses 4N5 high-purity aluminum and Al-20Fe master alloy as raw materials, with the composition of the 4N5 high-purity aluminum being the same as in Comparative Example 1. The final Fe element content in the high-purity aluminum (i.e., the mixed system of 4N5 high-purity aluminum and Al-20Fe master alloy) is controlled to be 80 ppm through calculation. Specific steps and processes are as follows:

[0079] (1) Preparation of high-purity aluminum: Based on the mass contents of Fe and Si elements in high-purity aluminum being 80ppm and 8.0ppm respectively, calculate and weigh the required amount of 4N5 high-purity aluminum and Al-20Fe master alloy. Prepare two samples according to the requirements, one for melt viscosity testing and the other for subsequent stepwise crystallization treatment.

[0080] (2) Melt pretreatment: High-purity aluminum raw material is melted in a pretreatment furnace at a melting temperature of 760℃. After melting, the impurity content in the raw material is calculated, and Al-B master alloy is added to remove impurities. Refining and slag removal are then performed. Next, Al-20Fe master alloy is added to the high-purity aluminum melt, and after electromagnetic stirring to ensure uniformity, the melt is kept at a constant temperature until the Fe element mass content in the melt is 80ppm, thus obtaining a segregation solution.

[0081] (3) Viscosity test: The viscosity of the melt prepared in step (2) is tested using the same method as in Comparative Example 1.

[0082] (4) Stepwise crystallization treatment: The segregated liquid obtained in step (2) is transferred into a segregation furnace for stepwise crystallization treatment. The aluminum melt is maintained at a temperature of 667°C. Cooling gas is introduced into the cooling pipes on the side wall of the segregation furnace at a gas introduction rate of 35 m / s. 3 At a rate of 7 times per minute, high-purity primary aluminum crystals precipitate on the sidewall of the segregation furnace. Next, the fine primary aluminum crystals are scraped down to the bottom of the crucible and compacted by the up-and-down movement of the tamping disc and rod (7 times / min). This compaction also squeezes out aluminum melt rich in impurities from between the crystals. The holes in the tamping disc and rod allow the aluminum melt to pass through. This process is repeated, causing the primary aluminum crystals at the bottom to gradually aggregate and grow into larger, purer aluminum crystals, thus achieving the purpose of aluminum purification.

[0083] (5) Remelting into ingots: The specific operation process is exactly the same as that of Comparative Example 1.

[0084] The melt viscosity of the high-purity aluminum melt detected in Comparative Example 3 at 680°C and 670°C was 13.2 [Pa-s], 15.6 [Pa-s], respectively, which was lower than the melt viscosity of the 4N5 high-purity aluminum in Comparative Example 1 and Comparative Example 2. By performing the steps in Comparative Example 3, it was found that the step (4) fractional crystallization process could be successfully completed, and the composition of the high-purity aluminum obtained finally had an Al content of 99.9980%, an Fe impurity element content of 3.0 ppm, and a Si impurity element content of 3.5 ppm, and the segregation rates of the Fe and Si impurity elements were 96.3% and 56.3%, respectively. Compared with Comparative Example 1, the removal rates of the Fe and Si impurity elements were 70.0% and 56.3%, respectively, and the high-purity aluminum prepared could not meet the composition requirements of 5N high-purity aluminum.

[0085] Comparative Example 4: 4N5 high-purity aluminum + Si (mass content of 40 ppm)

[0086] This comparative example used 4N5 high-purity aluminum and Al-20Si intermediate alloy as raw materials for batching, and the composition of the 4N5 high-purity aluminum was the same as that in Comparative Example 1. The mass content of the final Si element in the high-purity aluminum (i.e., the mixed system of the 4N5 high-purity aluminum and the Al-20Si intermediate alloy) was controlled to be 40 ppm by calculation, and the specific steps and processes were as follows:

[0087] (1) High-purity aluminum preparation: according to the mass contents of the Fe and Si elements in the high-purity aluminum being 10 ppm and 40 ppm, respectively, the required 4N5 high-purity aluminum and Al-20Si intermediate alloy were calculated and weighed, and two samples were prepared according to the requirements, one for melt viscosity detection and the other for subsequent fractional crystallization treatment.

[0088] (2) Melt pretreatment: the high-purity aluminum raw material was melted in a pretreatment furnace, and the melting temperature was 740°C. After melting, Al-B intermediate alloy was added according to the impurity content in the raw material for impurity removal. Refining and deslagging were performed. Next, the Al-20Si intermediate alloy was added to the high-purity aluminum melt, and after electromagnetic stirring, the melt was allowed to stand and be kept at a temperature, so that the mass content of Si element in the melt was 40 ppm, and the segregation liquid was obtained.

[0089] (3) Viscosity detection: the melt prepared in step (2) was subjected to viscosity test, and the test method was the same as that in Comparative Example 1.

[0090] (4) Fractional crystallization treatment: the segregation liquid obtained in step (2) was moved into a segregation furnace for fractional crystallization treatment, and the aluminum melt was kept at a temperature of 669°C. Cooling gas was introduced into the cooling pipe on the side wall of the segregation furnace, and the gas introduction speed was 30 m 3The high-purity aluminum primary crystals are precipitated on the side wall of the segregation furnace, and then the fine aluminum primary crystals are scraped off to the bottom of the crucible by the up-and-down movement of the tamping plate and tamping rod (movement speed of 6 times / min) and compacted, and the compacting action can also squeeze out the aluminum melt rich in impurity elements between the crystals, and the holes on the tamping plate and tamping rod can allow the aluminum melt to pass through. Such repeated operations can gradually gather the aluminum primary crystals at the bottom into larger and purer aluminum crystals, so as to achieve the purpose of aluminum purification.

[0091] (5) Remelting into ingot: the specific operation process is completely the same as that of Comparative Example 1.

[0092] The melt viscosities of the high-purity aluminum melt detected in Comparative Example 4 at 680℃ and 670℃ are 14.4 [Pa·s], 16.3 [Pa·s] respectively, which are lower than the melt viscosity of the 4N5 high-purity aluminum in Comparative Example 1. By performing the steps in Comparative Example 4, it is found that in the early stage of the step (4) fractional crystallization treatment, the tamping plate and tamping rod are broken due to the large resistance during the up-and-down movement, and the fractional crystallization process fails. The composition of the high-purity aluminum obtained by step (5) is detected by an instrument, and the Al content in the composition of the high-purity aluminum obtained in the furnace is 99.9931%, the Fe impurity element content is 9.6ppm, the Si impurity element content is 37ppm, and the segregation rates of Fe and Si impurity elements are 4.0% and 7.5% respectively, so the prepared high-purity aluminum cannot meet the composition requirements of 5N high-purity aluminum.

[0093] Comparative Example 5: 4N5 high-purity aluminum + Si (mass content of 80ppm)

[0094] This comparative example uses 4N5 high-purity aluminum and Al-20Si intermediate alloy as raw materials for batching, and the composition of the 4N5 high-purity aluminum is the same as that of Comparative Example 1. The mass content of the final Si element in the high-purity aluminum (i.e. the mixed system of 4N5 high-purity aluminum and Al-20Si intermediate alloy) is controlled to be 80ppm by calculation, and the specific steps and processes are as follows:

[0095] (1) High-purity aluminum preparation: according to the mass content of Fe and Si elements in high-purity aluminum being 10ppm and 80ppm respectively, 4N5 high-purity aluminum and Al-20Si intermediate alloy required for high-purity aluminum are calculated and weighed respectively, and two samples are prepared according to the requirements, one for melt viscosity detection and the other for subsequent fractional crystallization treatment.

[0096] (2) Melt pretreatment: the high-purity aluminum raw material is put into the pretreatment furnace for melting, and the melting temperature is 750℃. After melting, Al-B intermediate alloy is added for impurity removal according to the impurity content in the raw material. Refining and deslagging. Then Al-20Si intermediate alloy is added to the high-purity aluminum melt, and after electromagnetic stirring, it is placed and kept warm to make the mass content of Si element in the melt be 80ppm, and the segregation liquid is obtained.

[0097] (3) Viscosity detection: The melt prepared in step (2) was subjected to viscosity test, and the test method was the same as that in Comparative Example 1.

[0098] (4) Fractional crystallization treatment: The segregation liquid obtained in step (2) was moved into a segregation furnace for fractional crystallization treatment, the aluminum melt was kept at a temperature of 668℃, cooling gas was introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 35m 3 / h, high-purity aluminum primary crystals were precipitated from the side wall of the segregation furnace, and then the fine aluminum primary crystals were scraped off to the bottom of the crucible by the up-and-down movement of the tamping disc and tamping rod (movement speed was 7 times / min) and compacted, and the compacting action could also squeeze out the aluminum melt rich in impurity elements between the crystals, and the holes on the tamping disc and tamping rod could allow the aluminum melt to pass through. Such repeated operations allowed the aluminum primary crystals at the bottom to gradually gather and grow into larger and purer aluminum crystals, achieving the purpose of aluminum purification.

[0099] (5) Remelting into ingot: The specific operation process was completely the same as that in Comparative Example 1.

[0100] The melt viscosity of the high-purity aluminum melt detected in Comparative Example 5 at 680℃ and 670℃ was 12.1 [Pa·s], 14.3 [Pa·s] respectively, which was lower than that of the 4N5 high-purity aluminum in Comparative Example 1. By performing the steps in Comparative Example 5, it was found that the fractional crystallization process in step (4) could be successfully completed, and the composition of the finally obtained high-purity aluminum was that the content of Al was 99.9982%, the content of Fe impurity element was 2.7ppm, the content of Si impurity element was 3.0ppm, the segregation rates of Fe and Si impurity elements were 73.0%, 96.3% respectively, compared with Comparative Example 1, the removal rates of Fe and Si impurity elements were 73.0%, 62.5% respectively, and the prepared high-purity aluminum could not meet the composition requirements of 5N high-purity aluminum.

[0101] To further illustrate the implementation effect of the present application, the present application will be described below in conjunction with examples.

[0102] It should be noted that the raw materials used in the examples were all 4N5 high-purity aluminum, and the composition was the same as that in the comparative examples. The significant difference between all the examples and the comparative examples was that Fe and Si were added at the same time, and the addition amount of Fe and Si and the Fe / Si mass ratio were different in different examples.

[0103] Example 1: 4N5 high-purity aluminum + Fe (mass content was 40ppm) + Si (mass content was 40ppm)

[0104] The present example is prepared with 4N5 high purity aluminum, Al-20Fe intermediate alloy, Al-20Si intermediate alloy as raw materials, wherein the composition of 4N5 high purity aluminum is the same as that of Comparative Example 1. The mass content of Fe and Si elements in the final high purity aluminum (i.e. the mixed system of 4N5 high purity aluminum, Al-20Fe intermediate alloy and Al-20Si intermediate alloy) is controlled to be 40 ppm by calculation. The specific steps and process parameters are as follows:

[0105] (1) High purity aluminum preparation: according to the mass content of Fe and Si elements in high purity aluminum being 40 ppm, the required 4N5 high purity aluminum, Al-20Fe intermediate alloy and Al-20Si intermediate alloy for the target high purity aluminum are calculated and weighed respectively, and two samples are prepared according to the requirements, one for melt viscosity detection and the other for the next step of segregation purification experiment.

[0106] (2) Melt pretreatment: the high purity aluminum raw material is melted in the pretreatment furnace, and the melting temperature is 760℃. After melting, Al-B intermediate alloy is added for impurity removal according to the impurity content in the raw material (the amount of B added is determined by calculating to completely react with Cr, V, Ti in the high purity aluminum raw material to generate CrB2, TiB2, VB2, ZrB2 precipitates). Refining and deslagging are carried out. Then a certain amount of Al-20Fe intermediate alloy and Al-20Si intermediate alloy is added to the high purity aluminum melt, and after electromagnetic stirring, it is placed and kept warm, so that the mass content of Fe and Si elements in the melt is 40 ppm, and the segregation liquid is obtained.

[0107] (3) Viscosity detection: the melt prepared in step (2) is subjected to viscosity test, and the test method is the same as that of Comparative Example 1.

[0108] (4) Step-by-step crystallization treatment: the segregation liquid obtained in step (2) is moved into the segregation furnace for step-by-step crystallization treatment. The aluminum melt is kept at a temperature of 668℃, and cooling gas is introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 30 m 3 / h. High purity aluminum primary crystals are precipitated on the side wall of the segregation furnace. Next, the fine aluminum primary crystals are scraped off to the bottom of the crucible and compacted by the up-and-down movement of the stirring disc and rod (movement speed is 6 times / min). The compaction action can also squeeze out the aluminum melt between the crystals which is rich in impurity elements. The holes on the stirring disc and rod allow the aluminum melt to pass through. This process is repeated until the aluminum primary crystals on the bottom gradually grow into larger and purer aluminum crystals, achieving the purpose of aluminum purification.

[0109] (5) Remelting into ingot: the specific operation process is exactly the same as that of Comparative Example 1.

[0110] The melt viscosity of the high-purity aluminum melt detected in step (3) at 680°C and 670°C was 13.3 [Pa·s], 15.2 [Pa·s], respectively, which was lower than the melt viscosity of the 4N5 high-purity aluminum in Comparative Example 1. By performing the steps in Example 1, it was found that the step (4) fractional crystallization process could be successfully completed, and the final composition of the high-purity aluminum had an Al content of 99.9990%, an Fe impurity element content of 2.4 ppm, and a Si impurity element content of 2.4 ppm, and the segregation rates of the Fe and Si impurity elements were 94.0% and 94.0%, respectively. Compared with Comparative Example 1, the removal rates of the Fe and Si impurity elements were 76.0% and 70.0%, respectively. Other impurity elements met the composition requirements of 5N high-purity aluminum, and thus 5N high-purity aluminum was successfully prepared.

[0111] Example 2: 4N5 high-purity aluminum + Fe (mass content of 40 ppm) + Si (mass content of 80 ppm)

[0112] In this example, 4N5 high-purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy were used as raw materials for batching, and the composition of the 4N5 high-purity aluminum was the same as that in Comparative Example 1. The mass contents of Fe and Si elements in the final high-purity aluminum were controlled to be 40 ppm and 80 ppm, respectively, by calculation. The specific steps and process parameters are as follows:

[0113] (1) High-purity aluminum preparation: according to the mass contents of Fe and Si elements in the high-purity aluminum being 40 ppm and 80 ppm, respectively, the required 4N5 high-purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy were calculated and weighed, and two samples were prepared according to the requirements, one for melt viscosity detection and the other for the next step of segregation and purification experiment.

[0114] (2) Melt pretreatment: the high-purity aluminum raw material was melted in a pretreatment furnace at a melting temperature of 770°C, and after melting, Al-B intermediate alloy was added for impurity removal according to the impurity content in the raw material. Refining and deslagging were performed. Next, Al-20Fe intermediate alloy and Al-20Si intermediate alloy were added to the high-purity aluminum melt, and after electromagnetic stirring, the melt was allowed to stand and heat, so that the mass contents of Fe and Si elements in the melt were 40 ppm and 80 ppm, respectively, to obtain a segregation liquid.

[0115] (3) Viscosity detection: the melt prepared in step (2) was subjected to viscosity test, and the test method was the same as that in Comparative Example 1.

[0116] (4) Fractional crystallization treatment: the segregation liquid obtained in step (2) was moved into a segregation furnace for fractional crystallization treatment, and the aluminum melt was kept at a temperature of 667°C. Cooling gas was introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 30 m 3The high-purity aluminum primary crystals are precipitated on the side wall of the segregation furnace, and then the fine aluminum primary crystals are scraped off to the bottom of the crucible by the up-and-down movement of the tamping plate and tamping rod (movement speed of 6 times / min) and compacted, and the compacting action can also squeeze out the aluminum melt rich in impurity elements between the crystals, and the holes on the tamping plate and tamping rod can allow the aluminum melt to pass through. Such repeated operations make the aluminum primary crystals at the bottom gradually gather and grow into larger and purer aluminum crystals, so that the purpose of aluminum purification can be achieved.

[0117] (5) Remelting into ingot: the specific operation process is completely the same as that of Comparative Example 1.

[0118] The melt viscosities of the high-purity aluminum melt detected in Example 2 at 680℃ and 670℃ are 11.5 [Pa·s] and 13.2 [Pa·s] respectively, which are lower than the melt viscosity of the 4N5 high-purity aluminum in Comparative Example 1. By performing the steps of Example 2, it is found that the step (4) fractional crystallization process can be successfully completed, and finally the composition of the high-purity aluminum obtained has an Al content of 99.9990%, an Fe impurity element content of 2.3 ppm, and a Si impurity element content of 2.4 ppm, and the segregation rates of Fe and Si impurity elements are 94.3% and 97.0% respectively. Compared with Comparative Example 1, the removal rates of Fe and Si impurity elements are 77.0% and 70.0% respectively. Other impurity elements meet the composition requirements of 5N high-purity aluminum, so 5N high-purity aluminum is successfully prepared.

[0119] Example 3: 4N5 high-purity aluminum + Fe (mass content of 80 ppm) + Si (mass content of 40 ppm)

[0120] In this example, 4N5 high-purity aluminum, Al-20Fe intermediate alloy and Al-20Si intermediate alloy are used as raw materials for batching, and the composition of the 4N5 high-purity aluminum is the same as that of Comparative Example 1. The mass contents of Fe and Si elements in the high-purity aluminum (i.e. the mixed system of 4N5 high-purity aluminum, Al-20Fe intermediate alloy and Al-20Si intermediate alloy) are controlled to be 80 ppm and 40 ppm respectively by calculation. The specific steps and process parameters are as follows:

[0121] (1) High-purity aluminum preparation: according to the mass contents of Fe and Si elements in the high-purity aluminum being 80 ppm and 40 ppm respectively, the required 4N5 high-purity aluminum, Al-20Fe intermediate alloy and Al-20Si intermediate alloy for the target high-purity aluminum are calculated and weighed respectively, and two samples are prepared according to the requirements, one for melt viscosity detection and the other for the next step of segregation and purification experiment.

[0122] (2) Melt pretreatment: Put the high-purity aluminum raw material into the pretreatment furnace for melting, and the melting temperature is 780°C. After melting, according to the impurity content in the raw material, a certain amount of Al-B intermediate alloy is added to remove impurities. Refining and deslagging. Next, a certain amount of Al-20Fe intermediate alloy and Al-20Si intermediate alloy is added to the high-purity aluminum melt, and after electromagnetic stirring, it is placed and kept warm (30 min), so that the mass content of Fe and Si elements in the melt is 80 ppm and 40 ppm respectively, and the segregation liquid is obtained.

[0123] (3) Viscosity detection: The melt prepared in step (2) is subjected to viscosity test, and the test method is the same as that of Comparative Example 1.

[0124] (4) Step crystallization treatment: The segregation liquid obtained in step (2) is moved into the segregation furnace for step crystallization treatment. The aluminum melt is kept at a temperature of 666°C, and cooling gas is introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 40 m 3 / h. High-purity aluminum primary crystals are precipitated on the side wall of the segregation furnace. Next, the fine aluminum primary crystals are scraped off to the bottom of the crucible by the up-and-down movement of the stirring disc and stirring rod (movement speed is 8 times / min), and the fine aluminum primary crystals are scraped off to the bottom of the crucible by the up-and-down movement of the stirring disc and stirring rod (movement speed is 8 times / min). The compaction action can also squeeze out the aluminum melt between the crystals which is rich in impurity elements, and the holes on the stirring disc and stirring rod can allow the aluminum melt to pass through. Repeat the above steps until the aluminum primary crystals at the bottom gradually grow into larger and purer aluminum crystals, achieving the purpose of aluminum purification.

[0125] (5) Remelting into ingot: The specific operation process is exactly the same as that of Comparative Example 1.

[0126] The melt viscosity of the high-purity aluminum melt detected in Example 3 at 680°C and 670°C is 11.9 [Pa·s] and 14.0 [Pa·s] respectively, which is lower than that of 4N5 high-purity aluminum in Comparative Example 1. By the steps in Example 3, it is found that the step (4) crystallization process can be successfully completed, and the composition of the finally obtained high-purity aluminum contains 99.9993% of Al, 1.0 ppm of Fe impurity element, and 1.2 ppm of Si impurity element. The segregation rates of Fe and Si impurity elements are 98.8% and 97.0% respectively, and the removal rates of Fe and Si impurity elements are 90.0% and 85.0% respectively compared with Comparative Example 1. Other impurity elements meet the composition requirements of 5N high-purity aluminum, so 5N high-purity aluminum is successfully prepared.

[0127] Example 4: 4N5 high-purity aluminum + Fe (mass content is 80 ppm) + Si (mass content is 80 ppm)

[0128] The present example uses 4N5 high purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy as raw materials for batching, wherein the composition of 4N5 high purity aluminum is the same as that of Comparative Example 1. The mass content of Fe and Si elements in the target high purity aluminum (i.e., the mixed system of 4N5 high purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy) is controlled to be 80 ppm through calculation, and the specific steps and process parameters are as follows:

[0129] (1) High purity aluminum preparation: according to the mass content of Fe and Si elements in the target high purity aluminum being 80 ppm, the required 4N5 high purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy for the target high purity aluminum are calculated and weighed, and two samples are prepared according to the demand, one for melt viscosity detection and the other for the next step of segregation purification experiment.

[0130] (2) Melt pretreatment: the high purity aluminum raw material is melted in the pretreatment furnace, and the melting temperature is 790℃. After melting, Al-B intermediate alloy is added according to the impurity content in the raw material to remove impurities. Refining and deslagging are carried out. Next, a certain amount of Al-20Fe intermediate alloy and Al-20Si intermediate alloy are added to the high purity aluminum melt, and after electromagnetic stirring, the melt is placed and kept (the time for standing and keeping is 30 min) to make the mass content of Fe and Si elements in the melt be 80 ppm, and the segregation liquid is obtained.

[0131] (3) Viscosity detection: the melt prepared in step (2) is tested for viscosity, and the test method is the same as that of Comparative Example 1.

[0132] (4) Stepwise crystallization treatment: the segregation liquid obtained in step (2) is moved into the segregation furnace for stepwise crystallization treatment. The aluminum melt is kept at a temperature of 665℃, and cooling gas is introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 30 m 3 / h. High purity aluminum primary crystals are precipitated on the side wall of the segregation furnace. Next, the fine aluminum primary crystals are scraped off to the bottom of the crucible and compacted by the up-and-down movement of the stirring disc and rod (the movement speed is 7 times / min). The compaction action can also squeeze out the aluminum melt between the crystals which is rich in impurity elements. The holes on the stirring disc and rod allow the aluminum melt to pass through. This process is repeated until the aluminum primary crystals at the bottom are gradually gathered and grown into larger and purer aluminum crystals, achieving the purpose of aluminum purification.

[0133] (5) Remelting into ingot: the specific operation process is exactly the same as that of Comparative Example 1.

[0134] The melt viscosity of the high-purity aluminum melt detected in Example 4 at 680℃ and 670℃ was 9.8 [Pa-s], 12.1 [Pa-s] respectively, which was lower than that of the 4N5 high-purity aluminum in Comparative Example 1. By performing the steps in Example 4, it was found that the step (4) fractional crystallization process could be successfully completed, and the final composition of the high-purity aluminum had an Al content of 99.9990%, an Fe impurity element content of 2.0 ppm, and a Si impurity element content of 2.3 ppm, and the segregation rates of Fe and Si impurity elements were 97.5% and 97.1% respectively. Compared with Comparative Example 1, the removal rates of Fe and Si impurity elements were 80.0% and 71.3% respectively. Other impurity elements met the composition requirements of 5N high-purity aluminum, and thus 5N high-purity aluminum was successfully prepared.

[0135] Example 5: 4N5 high-purity aluminum + Fe (mass content of 90 ppm) + Si (mass content of 30 ppm)

[0136] In this example, 4N5 high-purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy were used as raw materials for batching, and the composition of the 4N5 high-purity aluminum was the same as that in Comparative Example 1. The mass content of Fe and Si elements in the target high-purity aluminum was controlled to be 90 ppm and 30 ppm respectively by calculation, and the specific steps and process parameters were as follows:

[0137] (1) High-purity aluminum preparation: according to the mass content of Fe and Si elements in the target high-purity aluminum being 90 ppm and 30 ppm respectively, the required 4N5 high-purity aluminum, Al-20Fe intermediate alloy, and Al-20Si intermediate alloy were calculated and weighed respectively, and two samples were prepared according to the requirements, one for melt viscosity detection and the other for the next step of segregation and purification experiment.

[0138] (2) Melt pretreatment: the high-purity aluminum raw material was melted in the pretreatment furnace at a melting temperature of 800℃, and after melting, Al-B intermediate alloy was added for impurity removal according to the impurity content in the raw material. Refining and deslagging were performed. Next, Al-20Fe intermediate alloy and Al-20Si intermediate alloy were added to the high-purity aluminum melt, and after electromagnetic stirring, the melt was allowed to stand and keep for 30 min, so that the mass content of Fe and Si elements in the melt was 90 ppm and 30 ppm respectively, and the segregation liquid was obtained.

[0139] (3) Viscosity detection: the melt prepared in step (2) was tested for viscosity, and the test method was the same as that in Comparative Example 1.

[0140] (4) Fractional crystallization treatment: the segregation liquid obtained in step (2) was moved into the segregation furnace for fractional crystallization treatment, and the aluminum melt was kept at a temperature of 665℃, and cooling gas was introduced into the cooling pipe on the side wall of the segregation furnace at a speed of 50 m 3The high-purity aluminum primary crystals are precipitated on the side wall of the segregation furnace, and then the fine aluminum primary crystals are scraped off to the bottom of the crucible by the up-and-down movement of the tamping plate and tamping rod (the movement speed is 10 times / min) and compacted, and the compacting action can also squeeze out the aluminum melt rich in impurity elements between the crystals, and the holes on the tamping plate and tamping rod can allow the aluminum melt to pass through. Through such repeated operations, the aluminum primary crystals at the bottom are gradually gathered and grown into larger and purer aluminum crystals, and the purpose of aluminum purification can be achieved.

[0141] (5) Remelting into ingot: the specific operation process is completely the same as that of Comparative Example 1.

[0142] The melt viscosities of the high-purity aluminum melt detected in Example 5 at 680℃ and 670℃ are 12.0 [Pa·s], 14.2 [Pa·s] respectively, which are lower than those of the 4N5 high-purity aluminum in Comparative Example 1. Through the steps in Example 5, it is found that the step (4) fractional crystallization process can be successfully completed, and the composition of the high-purity aluminum finally obtained is that the content of Al is 99.9993%, the content of Fe impurity element is 0.9 ppm, and the content of Si impurity element is 1.0 ppm, and the removal rates of Fe and Si impurity elements are 99.0%, 96.7% respectively, which are 91.0%, 87.5% respectively compared with Comparative Example 1. Other impurity elements all meet the composition requirements of 5N high-purity aluminum, and thus 5N high-purity aluminum is successfully prepared.

[0143] In order to better compare and illustrate the process and effect differences of the comparative examples and examples, the melt viscosity data are summarized in Table 1, and the element content data are summarized in Table 2.

[0144] The reasons for the experimental failure of Comparative Example 1, Comparative Example 2 and Comparative Example 4 are that the melt viscosity is not reduced to a level that can smoothly proceed the fractional crystallization process, and the resistance encountered by the tamping plate and tamping rod in the up-and-down movement process is too large, so the experiment cannot be successfully completed; Comparative Example 3 and Comparative Example 5 prove that the addition of a large amount of Fe element alone and the addition of a large amount of Si element alone can reduce the melt viscosity to a level that can smoothly proceed the fractional crystallization process, but the high-purity aluminum prepared cannot meet the composition requirements of 5N high-purity aluminum. All the examples of the present application reduce the melt viscosity by adding Fe and Si elements before the fractional crystallization method, and remove the excessive Fe and Si impurity elements by the fractional crystallization method, which can effectively purify the high-purity aluminum, promote the smooth progress of the fractional crystallization process and will not introduce other impurity elements, and all successfully prepare 5N high-purity aluminum. In particular, the effects of Example 3 and Example 5 are the best, and the optimal Fe / Si ratio before the fractional crystallization process is 2-3.

[0145] Table 1 Melt viscosities of high-purity aluminum at 680℃ and 670℃ in comparative examples and examples

[0146]

[0147] Table 2: High purity aluminum element content (unit: ppm) prepared in the comparative examples and examples

[0148]

[0149] Figure 3 Variation of melt viscosity of high purity aluminum in Comparative Examples 1-5 and Examples 1-5 at 680°C and 670°C;

[0150] Figure 4 Fe and Si impurity segregation rate of high purity aluminum samples prepared in Comparative Example 3, Comparative Example 5, and Examples 1-5;

[0151] Figure 5 Fe and Si impurity element removal rate of high purity aluminum samples prepared in Comparative Example 3, Comparative Example 5, and Examples 1-5.

[0152] The embodiments of the present application are not limited to the described examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacements, and are included in the protection scope of the present application.

Claims

1. A method for preparing 5N high-purity aluminum, characterized in that: Includes the following steps: 1) Melt 4N5 high-purity aluminum raw material, remove impurity elements with a balance distribution coefficient greater than 1, and obtain high-purity aluminum melt; 2) Fe and Si elements are added to high-purity aluminum melt to prepare a segregation solution; 3) Perform stepwise crystallization on the segregation solution; 4) Remove the aluminum ingot, remove the end with more impurities, and remelt it into an ingot to obtain 5N high-purity aluminum; In step 2), the amount of Fe and Si added must meet the following conditions: after adding Fe and Si to 4N5 high-purity aluminum raw material, the total Fe content is 30~120ppm, the total Si content is 30~120ppm, and the Fe / Si mass content ratio is (1.5~3.5):1; The stepwise crystallization process described in step 3) refers to maintaining the temperature of the segregation solution at 665~670℃, and then cooling the segregation solution placed in the device through a cooling device set on the side wall of the device. The segregation solution in contact with the side wall precipitates aluminum primary crystals. While scraping off the aluminum primary crystals, the segregation solution is stirred. This process is repeated until the aluminum primary crystals aggregate and grow, thus completing the stepwise crystallization. The process of scraping off the primary aluminum crystals while stirring the segregation liquid, and the agglomeration and growth of the primary aluminum crystals, refers to the scraping and compaction of the primary aluminum crystals by moving up and down the scraping device. The scraping device is equipped with holes or gaps, and the aluminum melt passes through the holes or gaps while the primary aluminum crystals are scraped off and compressed. This back-and-forth movement allows the primary aluminum crystals to agglomerate and grow. The cooling refers to the process of introducing cooling gas for cooling; The up-and-down movement speed of the scraping device is 5-10 times / min; The cooling gas flow rate is 10~50m. 3 / h.

2. The method for preparing 5N high-purity aluminum according to claim 1, characterized in that: In step 1), removing impurity elements with a balance distribution coefficient greater than 1 means adding an Al-B master alloy to the melt, mixing it thoroughly, and then allowing it to stand at a constant temperature. The amount of B added is calculated based on the content of impurity elements with a balance distribution coefficient greater than 1 in the high-purity aluminum raw material.

3. The method for preparing 5N high-purity aluminum according to claim 1, characterized in that: After removing impurity elements with a balance distribution coefficient greater than 1 in step 1), the refining process is carried out to remove slag. The melting temperature described in step 1) is 720~800℃.

4. The method for preparing 5N high-purity aluminum according to claim 1, characterized in that: The addition of Fe and Si elements mentioned in step 2) refers to the addition of Al-Fe master alloy and Al-Si master alloy, mixing them evenly, and keeping them at a constant temperature.

5. The method for preparing 5N high-purity aluminum according to claim 4, characterized in that: The Al-Fe master alloy is Al-20wt%Fe, and the Al-Si master alloy is Al-20wt%Si; The static heat preservation time is 2~60 minutes.

6. The method for preparing 5N high-purity aluminum according to claim 1, characterized in that: In step 4), the part of the aluminum ingot with more impurities is removed by testing the composition of the aluminum ingot with an instrument, and 1 / 5 to 1 / 10 of the aluminum ingot with more impurities is removed or the later crystallized aluminum ingot is removed. The melting temperature of the remelted ingot is 700~780℃.

Images