Preparation method of aluminum-scandium intermediate alloy

Abstract

The invention provides a preparation method of an aluminum-scandium intermediate alloy, which comprises the following steps: mixing an aluminum source, mixed molten salt and a scandium source to obtain a first mixture, and smelting to obtain a first melt; when the smelting treatment reaches the specified temperature, stirring treatment is carried out on the interface of the metal melt and the mixed molten salt melt in the surface layer of the first melt; when the smelting treatment lasts for a specified time, a deoxidant is added into the first melt for continuous smelting treatment, and a second melt is obtained; slag charge in the second melt is separated, and molten metal is obtained; and cooling and molding the molten metal to obtain the aluminum-scandium intermediate alloy. The aluminum source, the mixed molten salt and the scandium source are fully stirred through the induced electromagnetic force, the contact area and the mass transfer efficiency among the liquid-phase aluminum source, the liquid-phase molten salt and the solid-phase scandium source are increased, and the element segregation phenomenon is improved. The mixed molten salt can form a low-melting-point molten salt system, a liquid phase environment is provided, reduction and diffusion of a scandium source are promoted, and meanwhile the molten salt is used for dissolving and adsorbing impurities and purifying melt.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and in particular to a method for preparing aluminum-scandium master alloys. Background Technology

[0002] Aluminum-scandium master alloys are widely used in aerospace, marine, high-speed trains, and sporting goods. Traditional methods for preparing aluminum-scandium master alloys fail to ensure sufficient contact between scandium salts and molten aluminum or molten salts, resulting in low scandium reduction efficiency, unstable scandium yield, incomplete reaction, and unsatisfactory impurity removal by molten salts, leading to high levels of inclusion elements. Furthermore, traditional methods involve aluminum-scandium master alloy preparation in static or weakly convective environments, which make it difficult to guarantee sufficient reaction between scandium salts and molten aluminum. This results in uneven scandium distribution in the molten aluminum, causing scandium segregation and leading to the agglomeration and coarsening of Al3Sc particles in the aluminum-scandium master alloy. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for preparing an aluminum-scandium master alloy, which aims to improve scandium yield and segregation of the aluminum-scandium master alloy, and obtain an aluminum-scandium master alloy with low impurity content and fine and dispersed Al3Sc particles.

[0004] This application provides a method for preparing an aluminum-scandium master alloy, comprising the following steps:

[0005] S1. An aluminum source, a scandium source, and a mixed molten salt are mixed to obtain a first mixture. The first mixture is then smelted to obtain a first melt. The first melt includes a molten metal and a mixed molten salt melt located on the surface of the molten metal. The molten metal includes a melt originating from an aluminum source and / or a scandium source.

[0006] S2. When the smelting process reaches 900℃-1300℃, the surface of the first melt is stirred and smelted to obtain a second melt; wherein, the surface of the first melt includes the interface between the molten metal and the mixed molten salt melt.

[0007] S3. Separate the slag from the second melt to obtain molten metal;

[0008] S4. Cool the molten metal to form an aluminum-scandium intermediate alloy.

[0009] In this process, both the heating and stirring processes in the smelting treatment are carried out using electromagnetic induction, and the mixed molten salt includes alkali metal halides and aluminum metal halides.

[0010] The above-described method for preparing aluminum-scandium master alloy utilizes induced electromagnetic force to thoroughly stir the aluminum source, mixed molten salt, and scandium source. This increases the contact area and mass transfer efficiency between the liquid-phase aluminum source, liquid-phase molten salt, and unmelted solid-phase scandium source, reduces unreacted scandium source, steadily improves scandium yield, accelerates the aluminothermic reduction reaction rate, enhances scandium reduction efficiency, and mitigates scandium segregation in the final product. The mixed molten salt forms a low-melting-point molten salt system, providing a liquid-phase environment for the formation of the aluminum-scandium master alloy, promoting the reduction and diffusion of the scandium source. Simultaneously, the molten salt dissolves and adsorbs impurities in the raw materials, purifying the melt and effectively removing impurities. Furthermore, by utilizing specific smelting and electromagnetic stirring processes, the smelting process achieves rapid melting of the aluminum source, mixed molten salt, and scandium source. The stirring process, employing relatively low electromagnetic induction power, ensures continuous renewal of the interface between the liquid-phase aluminum source, liquid-phase molten salt, and solid-phase scandium source, promoting the continuous aluminothermic reduction and impurity removal reactions, improving reduction efficiency, and reducing scandium segregation. The process is simple, the equipment is inexpensive, and it is suitable for large-scale production. Simultaneously, the electromagnetic induction stirring during smelting ensures a relatively uniform distribution of scandium atoms in the melt, laying the foundation for subsequent uniform nucleation. The fluid shear force generated by electromagnetic stirring can, to some extent, disperse agglomerated Al3Sc particles, making it difficult for them to cluster and grow. Electromagnetic stirring promotes uniformity of temperature and scandium concentration within the melt, eliminating localized overheating and high scandium concentration areas, thus ensuring the production of an aluminum-scandium master alloy with finely dispersed Al3Sc particles.

[0011] In some embodiments, the stirring process in step S2 satisfies one or more of the following conditions:

[0012] (1) The stirring time is 25 min to 110 min;

[0013] (2) The electromagnetic induction frequency of the stirring process is 500Hz-1300Hz;

[0014] (3) The electromagnetic induction power of the stirring process is 20kW-60kW;

[0015] (4) The area where the electromagnetic induction magnetic field is applied during the stirring process is 5 mm to 100 mm below the surface of the first melt to the interface between the metal melt and the mixed molten salt melt.

[0016] In some embodiments, the smelting process in step S2 and / or step S3 satisfies one or more of the following conditions:

[0017] (1) The total time for the smelting process in step S2 is 30 min to 150 min;

[0018] (2) The electromagnetic induction power of the smelting process is 30kW-70kW;

[0019] (3) The electromagnetic induction frequency of the smelting process is 800Hz-1300Hz.

[0020] In some embodiments, the mixed molten salt further includes the slag obtained in step S3; optionally, in step S1, the mass ratio of the slag obtained in step S3 in the mixed molten salt to the aluminum source is (0-10):1000.

[0021] And / or, the total mass ratio of the alkali metal halide and the aluminum metal halide to the mass ratio of the aluminum source is (5-15):100.

[0022] In some embodiments, the alkali metal halide and the aluminum metal halide satisfy at least one of the following conditions (1)-(3):

[0023] (1) The alkali metal halide accounts for 75%-85% of the total mass of the alkali metal halide and the aluminum metal halide;

[0024] (2) The alkali metal halide includes at least one of sodium fluoride, sodium chloride, potassium fluoride and potassium chloride;

[0025] (3) The aluminum metal halide includes aluminum fluoride.

[0026] In some embodiments, the mass ratio of the sodium fluoride, the sodium chloride, the potassium fluoride, the potassium chloride, and the aluminum fluoride is (5-25):(0-15):(30-55):(0-20):(5-35).

[0027] In some embodiments, the mass ratio of the scandium source to the aluminum source is (14-30):1000;

[0028] And / or, the scandium source includes at least one of scandium oxide, scandium fluoride, and scandium carbonate.

[0029] In some embodiments, the mass ratio of scandium oxide, scandium fluoride and scandium carbonate is (8-16):(18-28):(0-10).

[0030] In some embodiments, the following steps are included before obtaining the second melt:

[0031] After the melting process reaches 900℃-1300℃ and continues for 20min-110min, an oxygen scavenger is added to the first melt and the melting process continues.

[0032] In some embodiments, the scavenger includes at least one of metallic aluminum, metallic magnesium, and aluminum-magnesium alloys, and the mass ratio of the scavenger to the aluminum source is (0.1-6):1000. Attached Figure Description

[0033] Figure 1 This is a schematic flowchart of a method for preparing an aluminum-scandium master alloy according to an embodiment of this application.

[0034] Figure 2 This is a scanning electron microscope image of an edge sample taken from the aluminum-scandium intermediate alloy in Example 1 of this application;

[0035] Figure 3 This is a scanning electron microscope image of a sample taken from the center of the aluminum-scandium master alloy in Example 1 of this application;

[0036] Figure 4 This is a particle size distribution diagram of the aluminum-scandium master alloy in Example 1 of this application. Detailed Implementation

[0037] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments. Preferred embodiments of the invention are shown below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of the invention will be achieved.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] Scandium is one of the most effective strengthening elements for aluminum alloys. Even trace amounts of scandium added to aluminum alloys can effectively improve their mechanical properties, heat resistance, corrosion resistance, and weldability. High-performance aluminum alloys are key lightweight materials for high-end equipment in aerospace, additive manufacturing, and transportation. Metallic scandium has a melting point of 1541℃ and is chemically reactive. When preparing aluminum-scandium alloys, scandium must be added as a master alloy; therefore, aluminum-scandium master alloys are a crucial raw material for preparing scandium-containing aluminum alloys. The application of aluminum-scandium master alloys is limited by price factors. In recent years, the price of aluminum-scandium master alloys has decreased, and the application of scandium in aluminum alloys has increased year by year.

[0040] The main methods for preparing aluminum-scandium master alloys are the scandium-aluminum metal doping method, the aluminothermic reduction method, and the molten salt electrolysis method. The scandium-aluminum metal doping method has high production costs, and the product is difficult to use as an additive in aluminum alloys, thus limiting the application of scandium in aluminum alloys. The molten salt electrolysis method has high equipment requirements, high investment for large-scale production, and generates corrosive fumes and gases during the electrolysis process, resulting in significant pollution and high energy consumption.

[0041] The aluminothermic reduction reaction is a two-phase reaction between molten aluminum and a molten salt system, either liquid or solid-liquid. The reaction rate depends to some extent on the contact area and mass transfer efficiency between the two phases. The scandium yield in the production of aluminum-scandium master alloys via the aluminothermic reduction method is typically less than 90%. During the aluminothermic reduction process, severe molten salt volatilization occurs, causing significant environmental pollution, and the product exhibits substantial scandium segregation. The production scale of aluminum-scandium master alloys is small, the process and product stability are poor, and large-scale production is difficult.

[0042] Existing technologies provide a method for preparing fine intermetallic compound particle aluminum-scandium master alloys. However, this method uses a high proportion of molten salt, resulting in products with severe molten salt inclusions. Another existing technology provides a method for preparing aluminum-scandium master alloys using molten salt electrolysis of a chloride-oxide system. This method, through molten salt electrolysis, has a production time of 4-10 hours, a relatively long production cycle, and the presence of calcium salts in the molten salt easily leads to residual calcium impurities, which significantly detrimental to the heat resistance of aluminum alloys. A further existing technology provides a method for preparing aluminum-scandium master alloys, but this technology focuses on improving the production efficiency of aluminum-scandium master alloys and does not address the segregation problem.

[0043] Meanwhile, traditional methods for preparing aluminum-scandium master alloys using the aluminothermic reduction reaction suffer from insufficient contact between the molten salt, aluminum melt, and scandium source interface, resulting in incomplete reduction reactions. This leads to low scandium reduction rates and unstable yields. The incomplete reaction also results in ineffective impurity removal by the molten salt, leading to high levels of inclusion elements. In actual production of aluminum-scandium master alloys, it is difficult to ensure sufficient reaction between the scandium salt and the aluminum melt. Consequently, the prepared aluminum-scandium master alloy exhibits scandium segregation, and its Al3Sc particles tend to agglomerate and coarsen, affecting product quality and reliability.

[0044] In summary, there is a need to develop a method for preparing aluminum-scandium master alloys using low-cost scandium raw materials, thereby reducing the production cost of aluminum-scandium master alloys and achieving high scandium yield, low product impurity content, low molten salt inclusions, uniform scandium distribution, and fine and dispersed Al3Sc particles.

[0045] Please see Figure 1 This application provides a method for preparing an aluminum-scandium master alloy, comprising the following steps:

[0046] An aluminum source, a scandium source, and a mixed molten salt are mixed to obtain a first mixture. The first mixture is then smelted to obtain a first melt. The first melt includes a molten metal and a mixed molten salt melt located on the surface of the molten metal. The molten metal includes melts originating from an aluminum source and / or a scandium source.

[0047] S2. When the smelting process reaches 900℃-1300℃, the surface of the first melt is stirred and smelted to obtain a second melt; wherein, the surface of the first melt includes the interface between the molten metal and the mixed molten salt melt.

[0048] S3. Separate the slag from the second melt to obtain molten metal;

[0049] S4. Cool the molten metal to form an aluminum-scandium intermediate alloy.

[0050] In this process, both the heating and stirring processes in the smelting treatment are carried out using electromagnetic induction, and the mixed molten salt includes alkali metal halides and aluminum metal halides.

[0051] As an example, the melting temperature can be 900℃, 1000℃, 1050℃, 1100℃, 1200℃, 1300℃, or within the range of 1000℃-1200℃ formed by any two of the above values.

[0052] As an example, the duration of the smelting process can be 30 min, 45 min, 60 min, 70 min, 75 min, 90 min, 120 min, 150 min, or within the range of 45 min to 120 min formed by any two of the above values.

[0053] The above-described method for preparing aluminum-scandium master alloy utilizes induced electromagnetic force to thoroughly stir the aluminum source, mixed molten salt, and scandium source. This increases the contact area and mass transfer efficiency between the liquid-phase aluminum source, liquid-phase molten salt, and unmelted solid-phase scandium source, reduces unreacted scandium source, steadily improves scandium yield, accelerates the aluminothermic reduction reaction rate, enhances scandium reduction efficiency, and mitigates component segregation in the final product. The mixed molten salt forms a low-melting-point eutectic system, providing a liquid environment for the formation of the aluminum-scandium master alloy, promoting the reduction and diffusion of the scandium source. Simultaneously, the molten salt dissolves and adsorbs impurities in the raw materials, purifying the melt and effectively removing impurities. Furthermore, by utilizing specific smelting and electromagnetic stirring processes, the smelting process achieves rapid melting of the aluminum source, mixed molten salt, and scandium source. The stirring process, employing relatively low electromagnetic induction power, ensures continuous renewal of the interface between the liquid-phase aluminum source, liquid-phase molten salt, and solid-phase scandium source, promoting the continuous aluminothermic reduction and impurity removal reactions, improving reduction efficiency, and reducing scandium segregation. The process is simple, the equipment is inexpensive, and it is suitable for large-scale production. Simultaneously, the electromagnetic induction stirring during smelting ensures a relatively uniform distribution of scandium atoms in the melt, laying the foundation for subsequent uniform nucleation. The fluid shear force generated by electromagnetic stirring can, to some extent, disperse agglomerated Al3Sc particles, making it difficult for them to cluster and grow. Electromagnetic stirring promotes uniformity of temperature and scandium concentration within the melt, eliminating localized overheating and high scandium concentration areas, thus ensuring the production of an aluminum-scandium master alloy with finely dispersed Al3Sc particles.

[0054] Understandably, since the melting points of the mixed molten salt and aluminum source are both lower than those of the scandium source, during the heating process of smelting, the mixed molten salt and aluminum source turn into the liquid phase before the scandium source.

[0055] Understandably, the density of the liquid-phase mixed molten salt melt is less than the density of the metal melt formed by the aluminum source and the scandium source. After adding interfacial stirring, the first melt consists of the mixed molten salt melt, the undissolved solid scandium source, and the metal melt from top to bottom. The undissolved solid scandium source is suspended in the two-phase interface between the mixed molten salt melt and the metal melt.

[0056] In some embodiments, the stirring process lasts for 25 min to 110 min.

[0057] As an example, the stirring time can be 25 min, 30 min, 45 min, 50 min, 75 min, 90 min, 100 min, 110 min, or 30 min to 100 min within the range of any two of the above values.

[0058] In some embodiments, the electromagnetic induction frequency of the stirring process is 500Hz-1300Hz.

[0059] As an example, the electromagnetic induction frequency of the stirring process can be 500Hz, 550Hz, 700Hz, 850Hz, 1000Hz, 1200Hz, 1300Hz, or any two of the above values ​​within the range of 550Hz-1200Hz.

[0060] In some embodiments, the electromagnetic induction power of the stirring process is 20kW-60kW.

[0061] As an example, the electromagnetic induction power of the stirring process can be 20kW, 30kW, 35kW, 40kW, 50kW, 60kW, or 30kW-50kW within the range of any two of the above values.

[0062] In some embodiments, the region where the electromagnetic induction of the stirring process applies the magnetic field is a region 5 mm to 100 mm below the surface of the first melt to the interface between the molten metal and the mixed molten salt melt.

[0063] In some embodiments, the total melting time in step S2 is 30 min to 150 min.

[0064] As an example, the total melting time in step S2 can be 30 min, 45 min, 60 min, 70 min, 90 min, 105 min, 120 min, 150 min, or within the range of 45 min to 120 min formed by any two of the above values.

[0065] In some embodiments, the electromagnetic induction power of the smelting process is 30kW-70kW.

[0066] As an example, the electromagnetic induction power of the smelting process can be 30kW, 40kW, 50kW, 60kW, 70kW, or 40kW-60kW within the range of any two of the above values.

[0067] In some embodiments, the electromagnetic induction frequency of the smelting process is 800Hz-1300Hz.

[0068] As an example, the electromagnetic induction frequency of the smelting process can be 800Hz, 900Hz, 1000Hz, 1050Hz, 1100Hz, 1200Hz, 1300Hz, or any two of the above values ​​within the range of 900Hz-1200Hz.

[0069] In some embodiments, the mixed molten salt also includes the slag obtained in step S3.

[0070] Optionally, in step S1, the mass ratio of the slag obtained in step S3 in the mixed molten salt to the aluminum source is (0-10):1000.

[0071] As an example, the mass ratio of the slag obtained in step S3 of the mixed molten salt to the aluminum source can be 0.25:1000, 0.5:1000, 5:1000, 10:1000, or any two of the above values ​​within the range of (0.25-5):1000.

[0072] Optionally, taking 30Kg of aluminum source as an example, the mass of the slag obtained in step S3 can be 0g-300g; as an example, the mass of the mixed molten salt can be 0g, 7.5g, 15g, 150g, 300g or 7.5g-150g within the range of any two of the above values.

[0073] Optionally, taking 50Kg of aluminum source as an example, the mass of the slag obtained in step S3 can be 0g-300g; as an example, the mass of the mixed molten salt can be 0g, 12.5g, 25g, 250g, 500g or 12.5g-250g within the range of any two of the above values.

[0074] In some embodiments, the total mass ratio of alkali metal halide and aluminum metal halide to the mass of aluminum source is (5-15):100.

[0075] As an example, the total mass ratio of alkali metal halides and aluminum metal halides to the mass of the aluminum source can be 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 15:100, or any two of the above values ​​within the range of (6-10):100.

[0076] Optionally, taking a 30kg aluminum source as an example, the total mass of the alkali metal halide and the aluminum metal halide can be 1500g-4500g; as an example, the mass of the mixed molten salt can be 1500g, 1800g, 2100g, 2400g, 2700g, 3000g, 4500g, or within the range of 1800g-3000g formed by any two of the above values.

[0077] Optionally, taking 50 kg of aluminum source as an example, the mass of the slag obtained in step S3 can be 3000 g to 7500 g; as an example, the mass of the mixed molten salt can be 2500 g, 3000 g, 3500 g, 4000 g, 4500 g, 5000 g, 7500 g, or 3000 g to 5000 g within the range of any two of the above values.

[0078] In some embodiments, an oxygen scavenger is added to the first melt for further melting, wherein the melting process is continued for 10 min to 25 min.

[0079] As an example, the smelting process can continue for 10 min, 15 min, 20 min, 25 min, or within the range of 15 min to 20 min formed by any two of the above values.

[0080] In some embodiments, the alkali metal halide accounts for 75%-85% of the total mass of the alkali metal halide and aluminum metal halide.

[0081] In some embodiments, the alkali metal halide includes at least one of lithium fluoride, lithium chloride, lithium bromide, lithium iodide, sodium fluoride, sodium chloride, sodium bromide, sodium iodide, potassium fluoride, potassium chloride, potassium bromide, and potassium iodide.

[0082] In some embodiments, the alkali metal halide includes at least one of sodium fluoride, sodium chloride, potassium fluoride, and potassium chloride.

[0083] In some of these embodiments, the alkali metal halide includes sodium fluoride and / or potassium chloride.

[0084] In some embodiments, the aluminum metal halide includes at least one of aluminum fluoride, aluminum chloride, aluminum bromide, and aluminum iodide.

[0085] In some of these embodiments, the aluminum metal halide includes aluminum fluoride.

[0086] In the above-mentioned method for preparing aluminum-scandium master alloy, aluminum fluoride can react with scandium oxide in the scandium source to generate highly active scandium fluoride. Scandium fluoride will then generate aluminum fluoride through an aluminothermic reduction reaction. Therefore, aluminum fluoride plays a role in the cyclic transformation and increases the driving force of the reduction reaction during the scandium source reduction process, thereby increasing the reduction reaction rate.

[0087] In some embodiments, the mass ratio of sodium fluoride, sodium chloride, potassium fluoride, potassium chloride and aluminum fluoride is (5-25):(0-15):(30-55):(0-20):(5-35).

[0088] Optionally, the mass ratio of sodium fluoride, sodium chloride, potassium fluoride, potassium chloride and aluminum fluoride is (10-20):(0-10):(35-50):(0-15):(10-30).

[0089] Optionally, the mass ratio of sodium fluoride, sodium chloride, potassium fluoride, potassium chloride and aluminum fluoride is (10-20):(5-10):(35-50):(5-15):(10-30).

[0090] The above-mentioned method for preparing aluminum-scandium master alloys uses a multi-element eutectic system composed of various metal halides to reduce the operating temperature of the aluminothermic reduction reaction. At the same time, the system formed by various molten salts can transfer impurity components in the aluminum source and / or scandium source to the molten salt slag layer through chemical reaction, thereby significantly reducing the content of impurity components in the final product and achieving refining and impurity removal.

[0091] In some embodiments, the mass ratio of scandium source to aluminum source is (14-30):1000.

[0092] In some embodiments, the scandium source includes at least one of scandium oxide, scandium fluoride, and scandium carbonate.

[0093] In some of these embodiments, the mass ratio of scandium oxide, scandium fluoride, and scandium carbonate is (8-16):(18-28):(0-10).

[0094] Optionally, the mass ratio of scandium oxide, scandium fluoride and scandium carbonate is (10-15):(20-26):(0-8).

[0095] In some of these embodiments, the purity of the aluminum source is 99.7%-99.999%.

[0096] In some of these embodiments, the aluminum source includes aluminum ingots.

[0097] In some of these embodiments, the purity of the scandium source is 85%-99.9%.

[0098] The above-mentioned method for preparing aluminum-scandium master alloys uses low-cost scandium raw materials to prepare aluminum-scandium master alloys, thereby reducing the cost of aluminum-scandium master alloys.

[0099] In some embodiments, the following steps are included before obtaining the second melt:

[0100] After the melting process reaches 900℃-1300℃ and continues for 20min-110min, an oxygen scavenger is added to the first melt and the melting process continues.

[0101] Optionally, the oxygen scavenger includes at least one of metallic aluminum, metallic magnesium, and aluminum-magnesium alloys.

[0102] In some embodiments, the mass ratio of scavenger to aluminum source is (0.1-6):1000.

[0103] As an example, the mass ratio of scavenger to aluminum source can be 0.1:1000, 0.25:1000, 0.5:1000, 1:1000, 1.5:1000, 2:1000, 2.5:1000, 3:1000, 5:1000, 6:1000, or any two of the above values ​​within the range of (0.25-5):1000.

[0104] Optionally, taking 30Kg of aluminum source as an example, the mass of the deoxidizer can be 3g-180g; as an example, the mass of the deoxidizer can be 3g, 7.5g, 15g, 30g, 45g, 60g, 75g, 90g, 150g, 180g or any two of the above values, ranging from 7.5g to 150g.

[0105] Optionally, taking 50Kg of aluminum source as an example, the mass of the deoxidizer can be 5g-300g; as an example, the mass of the deoxidizer can be 5g, 12.5g, 25g, 50g, 75g, 100g, 125g, 150g, 250g, 300g, or within the range of any two of the above values, which is 12.5g-300g.

[0106] In the above-mentioned method for preparing aluminum-scandium master alloy, an aluminum-magnesium alloy containing magnesium is added as an oxygen scavenger. Magnesium is more chemically active than aluminum, which can further reduce the residual unreacted scandium source at high temperature, improve scandium yield, and reduce the impurity oxygen content in the system.

[0107] In some embodiments, the aluminum source and / or scandium source contains impurity components, including at least one element selected from iron, silicon, oxygen, sodium, potassium, and calcium.

[0108] In some embodiments, step S1, mixing the aluminum source, the mixed molten salt, and the scandium source, further includes the following steps: the mixing method includes manual stirring and / or ball milling.

[0109] In some embodiments, the manual stirring time is 5-15 minutes.

[0110] In some embodiments, the ball milling speed is 80 r / min-300 r / min and the ball milling time is 15 min-60 min.

[0111] In some embodiments, step S4, cooling and shaping the molten metal further includes the following steps: casting the molten metal into a water-cooled mold, and demolding it after cooling to obtain an aluminum-scandium master alloy.

[0112] In some embodiments, the temperature of the cooling water in the water-cooled mold is 5°C-30°C.

[0113] In some embodiments, the water-cooled mold is made of at least one of cast iron, stainless steel, and copper.

[0114] The above-mentioned method for preparing aluminum-scandium master alloy employs electromagnetic stirring, which effectively promotes the reaction efficiency between molten salt and aluminum and scandium sources, allowing for large-scale production. Simultaneously, specific electromagnetic induction parameters for the first and second melting processes ensure uniform composition of the first and second melts, reducing segregation and promoting uniform nucleation of aluminum-scandium master alloy particles. Furthermore, specific water-cooling operations achieve high-speed cooling, reducing elemental segregation time during cooling and promoting particle growth in the aluminum-scandium master alloy.

[0115] The following are specific examples.

[0116] Example 1

[0117] Please see Figures 2-4 A method for preparing an aluminum-scandium master alloy includes the following steps:

[0118] S10. Weigh 30 kg of aluminum ingot with a purity of 99.85%, 3000 g of mixed molten salt, and 1473 g of scandium ingot with a purity of 99.9%. Mix them evenly by ball milling at 300 r / min for 60 min to obtain a mixture.

[0119] The mixed molten salt includes 480g sodium fluoride, 240g sodium chloride, 1200g potassium chloride, 360g potassium fluoride, 720g aluminum fluoride, and 150g slag, which is derived from the slag recovered from the aluminothermic reaction.

[0120] The scandium source includes 388g scandium oxide, 891g scandium fluoride, and 194g scandium carbonate.

[0121] S20. Place the mixture into a graphite crucible, weigh the graphite crucible containing the mixture, and place it into an electromagnetic induction melting furnace for heating and melting. The electromagnetic induction power is 60kW and the frequency is 1100Hz to obtain the first melt. When the temperature of the first melt reaches 1200℃, apply an electromagnetic field to 10mm-50mm below the surface of the first melt for electromagnetic stirring. The electromagnetic induction power of the applied electromagnetic field is 50kW and the frequency is 1200Hz.

[0122] S30. When the temperature of the first melt reaches 1200℃ and the melting process continues for 100 minutes, 100g of aluminum-magnesium alloy is added to the first melt, and the melting process continues for 20 minutes to obtain the second melt.

[0123] S40. Separate the second melt to obtain molten metal and slag, and recover the slag.

[0124] S50, cold molten metal is poured into a 30°C stainless steel water-cooled mold to obtain an aluminum-scandium master alloy.

[0125] Example 2

[0126] The preparation method of Example 2 is basically the same as that of Example 1, except for the following: aluminum ingot mass, mixed molten salt mass and proportion of each component, scandium source mass and proportion of each component, ball mill speed and time, slag mass, smelting parameters, deoxidizer mass and water-cooled mold temperature and material.

[0127] Right now:

[0128] S10. Weigh 50 kg of aluminum ingot with a purity of 99.70%, 4000 g of mixed molten salt, and 3252 g of scandium source with a purity of 90%, and mix them evenly by ball milling at 150 r / min for 45 min to obtain a mixture.

[0129] The mixed molten salt includes 706g sodium fluoride, 235g sodium chloride, 1882g potassium chloride, 471g potassium fluoride, 706g aluminum fluoride, and 150g slag, which is derived from the slag recovered from the aluminothermic reaction.

[0130] The scandium source includes 952g scandium oxide, 1983g scandium fluoride, and 317g scandium carbonate.

[0131] S20. Place the mixture into a graphite crucible, weigh the graphite crucible containing the mixture, and place it into an electromagnetic induction melting furnace for heating and melting. The electromagnetic induction power is 50kW and the frequency is 1000Hz to obtain the first melt. When the temperature of the first melt reaches 1100℃, apply an electromagnetic field to 50mm-100mm below the surface of the first melt for electromagnetic stirring. The electromagnetic induction power is 40kW and the frequency is 1000Hz.

[0132] S30. When the temperature of the first melt reaches 1200℃ and the melting process continues for 45 minutes, 100g of aluminum-magnesium alloy is added to the first melt, and the melting process continues for 15 minutes to obtain the second melt.

[0133] S40. Separate the second melt to obtain molten metal and slag, and recover the slag.

[0134] S50, pour cold molten metal into a 15℃ copper water-cooled mold to obtain an aluminum-scandium master alloy.

[0135] Example 3

[0136] The preparation method of Example 3 is basically the same as that of Example 1, except for the following: aluminum ingot mass, mixed molten salt mass and proportion of each component, scandium source mass and proportion of each component, ball mill speed and time, slag mass, smelting parameters, deoxidizer mass and water-cooled mold temperature and material.

[0137] Right now:

[0138] S10. Weigh 50 kg of aluminum ingot with a purity of 99.70%, 3500 g of mixed molten salt, and 2976 g of scandium source with a purity of 90%, and mix them evenly by ball milling at 150 r / min for 45 min to obtain a mixture.

[0139] The mixed molten salt includes 667g sodium fluoride, 333g sodium chloride, 1667g potassium chloride, 167g potassium fluoride, 666g aluminum fluoride, and 150g slag, which is derived from the slag recovered from the aluminothermic reaction.

[0140] The scandium source includes 921g scandium oxide, 1842g scandium fluoride, and 213g scandium carbonate.

[0141] S20. Place the mixture into a graphite crucible, weigh the graphite crucible containing the mixture, and place it into an electromagnetic induction melting furnace for heating and melting. The electromagnetic induction power is 45kW and the frequency is 1050Hz to obtain the first melt. When the temperature of the first melt reaches 1050℃, apply an electromagnetic field to 20mm-60mm below the surface of the first melt for electromagnetic stirring. The electromagnetic induction power of the applied electromagnetic field is 35kW and the frequency is 850Hz.

[0142] S30. When the temperature of the first melt reaches 1200℃ and the melting process continues for 50 minutes, 125g of aluminum-magnesium alloy is added to the first melt, and the melting process continues for 20 minutes to obtain the second melt.

[0143] S40. Separate the second melt to obtain molten metal and slag, and recover the slag.

[0144] S50, pour cold molten metal into a 10℃ copper water-cooled mold to obtain an aluminum-scandium master alloy.

[0145] Example 4

[0146] The preparation method of Example 4 is basically the same as that of Example 1, except for the following: aluminum ingot mass, mixed molten salt mass and proportion of each component, scandium source mass and proportion of each component, ball mill speed and time, slag mass, smelting parameters, deoxidizer mass and water-cooled mold temperature and material.

[0147] Right now:

[0148] S10. Weigh 50 kg of aluminum ingot with a purity of 99.99%, 4000 g of mixed molten salt, and 1911 g of scandium source with a purity of 99%, and mix them evenly by manual stirring for 10 minutes to obtain a mixture.

[0149] The mixed molten salt includes 706g sodium fluoride, 235g sodium chloride, 1882g potassium chloride, 471g potassium fluoride, 706g aluminum fluoride, and 250g slag, which is derived from the slag recovered from the aluminothermic reaction.

[0150] The scandium source includes 541g scandium oxide, 1082g scandium fluoride, and 288g scandium carbonate.

[0151] S20. Place the mixture into a graphite crucible, weigh the graphite crucible containing the mixture, and place it into an electromagnetic induction melting furnace for heating and melting. The electromagnetic induction power is 60kW and the frequency is 1200Hz to obtain the first melt. When the temperature of the first melt reaches 1200℃, apply an electromagnetic field to 20mm-40mm below the surface of the first melt for electromagnetic stirring. The electromagnetic induction power of the applied electromagnetic field is 50kW and the frequency is 1200Hz.

[0152] S30. When the temperature of the first melt reaches 1200℃ and the melting process continues for 70 minutes, 50g of aluminum-magnesium alloy is added to the first melt, and the melting process continues for 20 minutes to obtain the second melt.

[0153] S40. Separate the second melt to obtain molten metal and slag, and recover the slag.

[0154] S50, pouring cold molten metal into a 30°C cast iron water-cooled mold, yields an aluminum-scandium master alloy.

[0155] Example 5

[0156] The preparation method of Example 5 is basically the same as that of Example 1, except for the following: aluminum ingot quality, mixed molten salt quality and proportion of each component, scandium source quality and proportion of each component, ball mill speed and time, slag quality, smelting parameters, deoxidizer quality, and water-cooled mold temperature and material.

[0157] Right now:

[0158] S10. Weigh 50 kg of aluminum ingot with a purity of 99.85%, 2500 g of mixed molten salt, and 1871 g of scandium source with a purity of 85%. Mix them manually for 5 minutes to obtain a uniform mixture.

[0159] The mixed molten salt includes 455g sodium fluoride, 1591g potassium chloride, 454g aluminum fluoride and 100g slag, which is derived from the slag recovered from the aluminothermic reaction.

[0160] The scandium source includes 624g of scandium oxide and 1247g of scandium fluoride.

[0161] S20. Place the mixture into a graphite crucible, weigh the graphite crucible containing the mixture, and place it into an electromagnetic induction melting furnace for heating and melting. The electromagnetic induction power is 40kW and the frequency is 900Hz to obtain the first melt. When the temperature of the first melt reaches 1000℃, apply an electromagnetic field to 40mm-80mm below the surface of the first melt for electromagnetic stirring. The electromagnetic induction power of the applied electromagnetic field is 30kW and the frequency is 550Hz.

[0162] S30. When the temperature of the first melt reaches 1200℃ and the melting process continues for 30 minutes, 25g of aluminum-magnesium alloy is added to the first melt, and the melting process continues for 15 minutes to obtain the second melt.

[0163] S40. Separate the second melt to obtain molten metal and slag, and recover the slag.

[0164] S50, pour cold molten metal into a 5℃ cast iron water-cooled mold to obtain an aluminum-scandium master alloy.

[0165] Comparative Example 1

[0166] The preparation method of Comparative Example 1 is basically the same as that of Example 5, except that the step of stirring the mixture and / or deoxidizer by electromagnetic induction in the first and second melting processes is omitted.

[0167] Comparative Example 2

[0168] The preparation method of Comparative Example 2 is basically the same as that of Example 5, except that the mixed molten salt contains only potassium chloride and does not contain sodium fluoride or aluminum fluoride.

[0169] Comparative Example 3

[0170] The preparation method of Comparative Example 3 is basically the same as that of Example 5, except that ordinary cast iron molds are used for casting, and water cooling is not used.

[0171] The aluminum-scandium master alloys prepared in each embodiment and comparative example were tested in the following ways:

[0172] (1) Inductively coupled plasma (ICP) testing: ICP testing was performed on samples taken at the center and diagonal positions of the prepared aluminum-scandium master alloy ingots to determine the Sc content, impurity content and segregation degree. Table 1 shows the element content and average particle size of the aluminum-scandium master alloys prepared in each example and comparative example. Table 2 shows the Sc segregation results of the aluminum-scandium master alloys prepared in each example and comparative example.

[0173] (2) Scanning electron microscope: Samples were taken from the central position and diagonal positions of the prepared aluminum scandium master alloy ingots respectively for scanning electron microscope tests to observe the particle size of the aluminum scandium master alloy.

[0174]

[0175] Table 1

[0176] Table 2

[0177]

[0178] From Table 1 - Table 2 and Figures 2-4 It can be seen that through Examples 1 - 5 and Comparative Examples 1 - 3, Comparative Example 1 proves that the stirring provided by the electromagnetic field plays a key role, which can enhance the contact between the aluminum source, scandium source and molten salt, make the reaction more sufficient, significantly improve the reduction yield of scandium, and can effectively promote the homogenization of the melt composition and reduce the segregation of the aluminum scandium master alloy; Comparative Example 2 proves that fluorides, especially aluminum fluoride, have an important effect on the removal of impurities such as iron and silicon; Comparative Example 3 proves that rapid water cooling plays an important role in achieving low segregation and small particle size. The rapid solidification of water cooling can effectively inhibit the particle growth and Sc element segregation of the aluminum scandium master alloy. The Al3Sc particles are fine, dispersed and evenly distributed, with an average size of 5 - 20 μm.

[0179] It can be seen from Examples 1 - 5 that the Sc in the product of the present application is uniform, the Sc content is stable, and the fluctuation of the Sc content is less than ±0.3 wt%; the primary Sc yield is greater than 90%, and the comprehensive Sc yield is greater than 93%. The product has low impurity content. The contents of impurity elements such as Fe, Si, O, Na, K, Ca are low. The contents of impurity elements are as follows: Fe < 0.01 wt.%, Si < 0.01 wt.%, O < 0.01 wt.%, Na < K < 0.001 wt.%, Ca < 0.001 wt.%. Fe and O are conventional impurities in aluminum alloys, and Na, K, Ca are elements that affect the heat resistance of aluminum alloys and have a greater negative impact on the heat resistance of aluminum alloys. The O content has an impact on additive manufacturing applications. The aluminum scandium master alloy prepared in the present application avoids the influence of impurity elements on the performance of the aluminum scandium master alloy.

[0180] The technical features of the above - described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above - described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0181] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an aluminum-scandium master alloy, characterized in that, Includes the following steps: S1. An aluminum source, a scandium source, and a mixed molten salt are mixed to obtain a first mixture. The first mixture is then smelted to obtain a first melt. The first melt includes a molten metal and a mixed molten salt melt located on the surface of the molten metal. The molten metal includes a melt originating from an aluminum source and / or a scandium source. S2. When the smelting process reaches 900℃-1300℃, the surface of the first melt is stirred and smelted to obtain a second melt; wherein, the surface of the first melt includes the interface between the molten metal and the mixed molten salt melt. S3. Separate the slag from the second melt to obtain molten metal; S4. Cool the molten metal to form an aluminum-scandium intermediate alloy. In this process, both the heating and stirring processes in the smelting treatment are carried out using electromagnetic induction, and the mixed molten salt includes alkali metal halides and aluminum metal halides.

2. The method for preparing the aluminum-scandium master alloy as described in claim 1, characterized in that, The stirring process described in step S2 satisfies one or more of the following conditions: (1) The duration of the stirring treatment is 25 min to 110 min; (2) The electromagnetic induction frequency of the stirring process is 500Hz-1300Hz; (3) The electromagnetic induction power of the stirring process is 20kW-60kW; (4) The area where the electromagnetic induction magnetic field is applied during the stirring process is 5 mm to 100 mm below the surface of the first melt to the interface between the metal melt and the mixed molten salt melt.

3. The method for preparing the aluminum-scandium master alloy as described in claim 1, characterized in that, The smelting process described in step S2 and / or step S3 satisfies one or more of the following conditions: (1) The total time for the smelting process in step S2 is 30 min to 150 min; (2) The electromagnetic induction power of the smelting process is 30kW-70kW; (3) The electromagnetic induction frequency of the smelting process is 800Hz-1300Hz.

4. The method for preparing the aluminum-scandium master alloy as described in claim 1, characterized in that, The mixed molten salt also includes the slag obtained in step S3; optionally, in step S1, the mass ratio of the slag obtained in step S3 in the mixed molten salt to the aluminum source is (0-10):1000. And / or, the total mass ratio of the alkali metal halide and the aluminum metal halide to the mass ratio of the aluminum source is (5-15):

100.

5. The method for preparing the aluminum-scandium master alloy as described in claim 1, characterized in that, The alkali metal halide and the aluminum metal halide satisfy at least one of the following conditions (1)-(3): (1) The mass of the alkali metal halide accounts for 75%-85% of the total mass of the alkali metal halide and the aluminum metal halide; (2) The alkali metal halide includes at least one of sodium fluoride, sodium chloride, potassium fluoride and potassium chloride; (3) The aluminum metal halide includes aluminum fluoride.

6. The method for preparing the aluminum-scandium master alloy as described in claim 5, characterized in that, The mass ratio of the sodium fluoride, sodium chloride, potassium fluoride, potassium chloride and aluminum fluoride is (5-25):(0-15):(30-55):(0-20):(5-35).

7. The method for preparing the aluminum-scandium master alloy according to any one of claims 1 to 6, characterized in that, The mass ratio of the scandium source to the aluminum source is (14-30):1000; And / or, the scandium source includes at least one of scandium oxide, scandium fluoride, and scandium carbonate.

8. The method for preparing the aluminum-scandium master alloy as described in claim 7, characterized in that, The mass ratio of scandium oxide, scandium fluoride and scandium carbonate is (8-16):(18-32):(0-10).

9. The method for preparing the aluminum-scandium master alloy as described in claim 1, characterized in that, Before obtaining the second melt, the following steps are also included: After the melting process reaches 900℃-1300℃ and continues for 20min-110min, an oxygen scavenger is added to the first melt and the melting process continues.

10. The method for preparing the aluminum-scandium master alloy as described in claim 9, characterized in that, The deoxidizer comprises metallic magnesium and / or an aluminum-magnesium alloy, and the mass ratio of the deoxidizer to the aluminum source is (0.1-6):1000.

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