Rare earth aluminum intermediate alloy and preparation method thereof

Abstract

The invention provides a rare earth aluminum intermediate alloy and a preparation method thereof. The preparation method comprises the following steps: S1, removing waste residues on the surface of a first melt after melting to obtain a first melt; the first melt comprises metal aluminum and rare earth aluminum raw materials; the melting temperature ranges from 800 DEG C to 1200 DEG C; s2, the second mixture is subjected to heat preservation treatment, and a second melt is obtained; the second mixture comprises the first melt, rare earth fluoride and alkali metal halide; s3, the second melt is separated, and molten metal and rare earth aluminum slag are obtained; and S4, the molten metal is poured and cooled, and the rare earth aluminum intermediate alloy is obtained. The method is simple in process, short in operation process, environmentally friendly, safe, low in cost and high in rare earth metal yield, and the prepared rare earth aluminum intermediate alloy is small in segregation, fine in intermediate phase grain, uniform in distribution and free of agglomeration.

Description

Technical Field

[0001] The invention relates to a rare earth aluminum master alloy and a preparation method thereof. Background Art

[0002] In recent years, the application of lightweight alloys has received more and more attention. Aluminum and aluminum alloys are widely used in aerospace, automobile, shipbuilding, cable and wire, house construction and other fields due to their advantages of low density, good electrical and thermal conductivity, good corrosion resistance, good plasticity and easy processing. However, with the improvement of usage conditions, new high-performance aluminum alloy materials need to be developed. Changing the alloy composition is one of the important means to develop new aluminum alloys. Among them, rare earth elements, as one of the key and effective micro-alloying elements, are widely used in the preparation of high-performance aluminum and its alloy materials due to their special chemical properties.

[0003] Rare earth aluminum intermediate alloys can be prepared by the doping method. Since rare earth metals are relatively active and their melting points are quite different from those of metallic aluminum, the aluminum liquid must be in a relatively large overheated state during the smelting process, resulting in large burnout. In addition, the intermediate phase of the rare earth aluminum intermediate alloy obtained is unevenly distributed, the grain size is large, and there is agglomeration problem, which is not conducive to subsequent utilization. In addition, the cost of the rare earth pure metal preparation process is high, the yield is low, and impurities such as tungsten and calcium will be introduced. If vacuum thermal reduction and molten salt electrolysis are used, the equipment required is relatively complex. The latter has a low conversion rate and requires long-term continuous production. At present, the mechanism of the electrolysis process is not clear, and the actual operation is difficult.

[0004] Therefore, there is an urgent need for a method for preparing a rare earth aluminum master alloy, which has a simple process, low operation difficulty, and can prepare a rare earth aluminum master alloy with a good microstructure. Summary of the invention

[0005] The invention provides a rare earth aluminum master alloy and a preparation method thereof to overcome the problems of the prior art, such as complicated process, great operation difficulty, high cost and difficulty in preparing a rare earth aluminum master alloy with uniform intermediate phase distribution, small grain size and no agglomeration. The method has the advantages of simple process, short operation flow, environmental protection and safety, low cost and high yield of rare earth metals. The prepared rare earth aluminum master alloy has small segregation, fine and uniform intermediate phase grains and no agglomeration; and the rare earth content of the master alloy between batches is relatively stable.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a method for preparing a rare earth aluminum master alloy, which comprises the following steps:

[0008] S1, removing the waste slag on the surface of the first melt after melting to obtain a first melt; the first melt comprises metallic aluminum and rare earth aluminum raw materials; the melting temperature is 800-1200° C.; the rare earth aluminum raw materials are: rare earth aluminum slag obtained by aluminothermic reaction, and / or the rare earth aluminum slag in the following step S3;

[0009] S2, subjecting the second mixture to heat preservation treatment to obtain a second melt; the second mixture includes the first melt, rare earth fluoride and alkali metal halide; the temperature of the heat preservation treatment is 800-1100° C.;

[0010] S3, separating the second melt to obtain molten metal and rare earth aluminum slag;

[0011] S4, pouring the molten metal and cooling it to obtain a rare earth aluminum master alloy.

[0012] In the present invention, the rare earth aluminum master alloy is prepared by aluminothermic reduction reaction.

[0013] In step S1 of the present invention, the waste residue will affect the subsequent slagging effect of adding rare earth fluoride and alkali metal halide; by removing the waste residue, not only the fluidity of the rare earth aluminum slag material produced subsequently can be improved, but also the yield of rare earth elements can be improved.

[0014] In some embodiments, in step S1, the rare earth aluminum raw material includes aluminum and rare earth elements; preferably, the rare earth elements include yttrium, scandium, lanthanum, neodymium, samarium, terbium, erbium or thulium; preferably, the content of the rare earth elements is above 0.5%, where % is the percentage of the mass of the rare earth elements to the total mass of the rare earth aluminum raw material.

[0015] In the present invention, those skilled in the art should know that the rare earth element in the rare earth aluminum raw material should be the same as the rare earth element in the rare earth fluoride in step S2.

[0016] In a specific embodiment, the content of the rare earth element is greater than 1%, where % is the percentage of the mass of the rare earth element to the total mass of the rare earth aluminum raw material, preferably 1%-5%, such as 1.41% or 1.93%.

[0017] In a specific embodiment, the content of the aluminum element is 3%-15%, where % is the percentage of the mass of the aluminum element to the total mass of the rare earth aluminum raw material, preferably 5%-10%, such as 5.61% or 6.26%.

[0018] In a specific embodiment, the rare earth aluminum raw material further includes alkali metal elements, fluorine elements and oxygen elements.

[0019] Preferably, the content of the alkali metal element is 10%-20%, where % is the percentage of the mass of the alkali metal element to the total mass of the rare earth aluminum raw material, and more preferably 12%-15%, such as 12.32% or 14.10%.

[0020] Preferably, the content of fluorine element is 50%-80%, where % is the percentage of the mass of fluorine element to the total mass of rare earth aluminum raw material, more preferably 65%-70%, such as 68.00% or 69.30%.

[0021] Preferably, the content of oxygen element is 5%-15%, where % is the percentage of the mass of oxygen element to the total mass of rare earth aluminum raw material, more preferably 10%-12%, for example 10.36% or 10.71%.

[0022] In one embodiment, in step S1, the rare earth aluminum raw material includes 68.00% of F element, 14.10% of Na element, 5.61% of Al element, 1.93% of Sc element and 10.36% of O element.

[0023] In one embodiment, in step S1 , the waste slag includes 67.00% of F element, 13.43% of Na element, 7.81% of Al element, 0.63% of Sc element and 11.13% of O element.

[0024] In the present invention, the amount ratio of metallic aluminum and rare earth aluminum slag, as well as the appropriate melting temperature and time are set to have a positive impact on the uniform distribution of the intermediate phase of the rare earth aluminum master alloy.

[0025] In the art, the rare earth element content in the rare earth aluminum raw material is low, and it is generally collected and processed separately. In addition, the detection of the rare earth element content in the rare earth aluminum raw material or rare earth aluminum slag material fluctuates greatly, and there is no specific content value; if introduced into the raw material, it will affect the stability of the rare earth content in the master alloy.

[0026] In some embodiments, in step S1, the mass ratio of the metal aluminum to the rare earth aluminum raw material is 1:(0.03-0.1), preferably 1:(0.04-0.08), preferably 1:(0.04-0.06), such as 1:0.04, 1:0.041, 1:0.045, 1:0.049, 1:0.051, 1:0.054, 1:0.057 or 1:0.06. By controlling the ratio of the metal aluminum to the rare earth aluminum raw material, a master alloy with a stable rare earth content can be further obtained.

[0027] In some embodiments, in step S1, the melting temperature is 850-1100°C, preferably 880-1050°C, such as 880°C, 900°C, 920°C, 950°C or 1050°C.

[0028] In some embodiments, in step S1, the aluminothermic reaction is: reacting metallic aluminum with rare earth fluoride.

[0029] In some embodiments, in step S1, the aluminothermic reaction is: reacting metallic aluminum with rare earth oxides.

[0030] In some embodiments, in step S1, the temperature of the thermite reaction is 800-1200°C.

[0031] In some embodiments, in step S1, the metallic aluminum includes an aluminum ingot.

[0032] In some embodiments, in step S1, the melting time is 10-30 min, preferably 10-20 min, more preferably 10-15 min, such as 10 min or 15 min.

[0033] In some embodiments, in step S1, the melting process is performed in a crucible of a medium frequency induction melting furnace.

[0034] In the present invention, during the melting process, if continuous stirring is performed, that is, the first stirring time interval is low or 0, the aluminum liquid will be exposed and the rare earth elements will be burned; during the melting process, if the stirring interval is long, for example, 15 minutes, it will lead to incomplete reaction.

[0035] In some embodiments, in step S1, the melting process is carried out under first stirring, and the interval time of the first stirring is 5-10 minutes, preferably 5-8 minutes, for example 5 minutes; the first stirring method includes induction cooker stirring and / or mechanical stirring; preferably, the mechanical stirring includes graphite rod stirring.

[0036] In some embodiments, in step S2, the mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.03-0.18), preferably 1:(0.05-0.15), and more preferably 1:(0.05-0.13), for example 1:0.05, 1:0.059, 1:0.06, 1:0.07 or 1:0.13.

[0037] In some embodiments, in step S2, the mass ratio of the metallic aluminum to the alkali metal halide is 1:(0.03-0.08), preferably 1:(0.03-0.07), more preferably 1:(0.035-0.07), for example 1:0.035, 1:0.04, 1:0.05, 1:0.06 or 1:0.07.

[0038] In some embodiments, in step S2, the temperature of the heat preservation treatment is 900-1100°C, more preferably 920-1070°C, for example 920°C, 950°C, 970°C, 980°C, 1000°C or 1070°C.

[0039] In some embodiments, in step S2, the heat preservation treatment time is 30-60 min, preferably 40-60 min, such as 40 min, 50 min or 60 min.

[0040] In some embodiments, in step S2, the heat preservation process is carried out under second stirring, and the interval time of the second stirring is 5-10 minutes, preferably 5 minutes; the second stirring method includes induction cooker stirring and / or mechanical stirring; preferably, the mechanical stirring is graphite rod stirring.

[0041] Among them, the simultaneous use of induction furnace stirring and mechanical stirring can reduce the intermediate phase grain size of the rare earth aluminum alloy, make the composition more uniform, kinetically promote the reaction between the metal liquid and the slag, further improve the yield and reduce the reaction time.

[0042] In some embodiments, in step S2, the rare earth fluoride is yttrium fluoride, scandium fluoride, lanthanum fluoride, neodymium fluoride, samarium fluoride, terbium fluoride, erbium fluoride or thulium fluoride; the rare earth elements in the rare earth fluoride are consistent with the rare earth elements in the rare earth aluminum alloy material.

[0043] In the present invention, the rare earth element in the rare earth aluminum raw material of step S1 and the rare earth element in the rare earth fluoride of step S2 can be the same or different; when the above two rare earth elements are the same, the final product is a binary master alloy; when the above two rare earth elements are different, the final product is a ternary master alloy.

[0044] In the present invention, the alkali metal halide does not participate in the aluminothermic reaction, but can reduce the melting point of the slag system, dissolve the oxide preferably added, have a wetting effect between the aluminum liquid and the slag system, and promote the aluminothermic reaction. Here, the slag system can be a rare earth aluminum slag material.

[0045] In some embodiments, in step S2, the alkali metal halide is potassium fluoride, lithium fluoride, sodium fluoride, sodium fluoroaluminate, potassium chlorofluoroate or calcium fluoride.

[0046] In some embodiments, in step S2, the second mixture further comprises rare earth oxides; the rare earth oxides are consistent with the rare earth elements in the rare earth fluorides. By adding the rare earth oxides, a portion of the rare earth fluorides can be replaced to obtain a rare earth aluminum master alloy without affecting the yield, thereby reducing a portion of the fluorination cost.

[0047] In a specific embodiment, the rare earth oxide includes yttrium oxide, scandium oxide, lanthanum oxide, neodymium oxide, samarium oxide, terbium oxide, erbium oxide or thulium oxide.

[0048] In a specific embodiment, the mass ratio of the metallic aluminum to the rare earth oxide is 1:(0.002-0.02), preferably 1:(0.002-0.01), for example 1:0.002, 1:0.006, 1:0.007, 1:0.008, 1:0.009 or 1:0.01.

[0049] In some embodiments, in step S2, the second mixture does not contain potassium cryolite and sodium cryolite.

[0050] In some embodiments, in step S3, the separation temperature is 750-900°C, preferably 780-900°C, for example 780°C, 800°C, 810°C, 820°C or 900°C.

[0051] In the present invention, the second melt obtained in step S2 is a molten metal having rare earth aluminum slag on its surface.

[0052] In some embodiments, in step S3, the separation method includes removing rare earth aluminum slag from the surface of the second melt.

[0053] In one embodiment, in step S3, the rare earth aluminum slag material includes 69.30% of F element, 12.32% of Na element, 6.26% of Al element, 1.41% of Sc element and 10.71% of O element.

[0054] In the present invention, the pouring temperature is higher than the liquidus temperature, which refers to the highest temperature at which the melt changes from liquid to solid, also known as the "initial crystallization temperature".

[0055] In the present invention, the cooling process ensures that the rare earth aluminum master alloy solidifies rapidly to suppress the growth and agglomeration of the intermediate phase.

[0056] In some embodiments, in step S4, the cooling method includes water cooling, air cooling or cooling using a cooler.

[0057] In some embodiments, the pouring temperature is 750-900°C, preferably 780-900°C, such as 780°C, 800°C, 810°C, 820°C or 900°C.

[0058] In some embodiments, the pouring speed is 0.25-0.3 L / s.

[0059] In some embodiments, the time for the molten metal to be cooled to a completely solidified state is less than 20 seconds.

[0060] In some embodiments, the time for cooling the molten metal to room temperature is 10-15 minutes to facilitate demolding.

[0061] The present invention also provides a rare earth aluminum master alloy, which is prepared by the preparation method of the rare earth aluminum master alloy as described above.

[0062] In some embodiments, the rare earth element content of the rare earth aluminum master alloy is less than 10%, where % is the ratio of the mass of the rare earth element to the total mass of the rare earth aluminum master alloy; preferably, it is greater than 1.5% and less than 8.5%.

[0063] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0064] The reagents and raw materials used in the present invention are commercially available.

[0065] The positive and progressive effects of the present invention are:

[0066] 1. In the preparation process of the present invention, rare earth aluminum slag produced by thermite reaction is used, and the rare earth aluminum slag is recycled, thereby reducing the use of fluoride salts, being more environmentally friendly and economical, and having a higher yield of rare earth elements in the raw materials.

[0067] 2. The preparation method of the present invention can achieve a higher yield of rare earth metals, and the preferred solution can reach at least 79%.

[0068] 3. The molten salt system in the present invention adopts a fluoride salt system, which is more stable than a chloride salt system and less prone to moisture absorption, making production safer and more stable.

[0069] 4. The intermediate phase of the rare earth aluminum master alloy prepared by the present invention is evenly distributed and the grain size is relatively small; and the rare earth content of the master alloy is relatively stable between batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 This is a process flow chart for preparing a rare earth aluminum master alloy according to Example 1 of the present invention;

[0071] Figure 2This is an electron microscope image of the aluminum-scandium master alloy prepared in Example 2 of the present invention;

[0072] Figure 3 This is an electron microscope image of the aluminum-scandium master alloy prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0073] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0074] Example 1

[0075] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy. Figure 1 This is a process flow chart for preparing rare earth aluminum master alloy in this embodiment.

[0076] The aluminum yttrium slag used in this embodiment is a slag previously obtained by a thermite reaction, wherein the thermite reaction is as follows: an aluminum ingot is placed in a medium frequency induction furnace and melted at 900°C for 10 minutes, yttrium oxide, yttrium fluoride and potassium fluoride are added thereto, and the mixture is kept warm for 40 minutes, and then the aluminum yttrium slag is fished out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum yttrium slag; the mass ratio of the aluminum ingot, yttrium oxide, yttrium fluoride and potassium fluoride is 1:0.008:0.09:0.04.

[0077] The preparation steps are as follows:

[0078] The materials in the preparation method are: 16.5 kg aluminum ingot, 0.743 kg aluminum yttrium slag, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, and the mass ratio thereof is 1:0.045:0.008:0.09:0.04.

[0079] S1. Add aluminum ingots and aluminum yttrium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt them at 900° C. for 10 min, stirring the materials evenly with a graphite rod every 5 min to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0080] S2, adding the above-mentioned mass of yttrium oxide, yttrium fluoride and potassium fluoride to the first melt, and heating to 900° C. to completely melt the materials, and heat-treating for 40 minutes, stirring the materials evenly with a graphite rod every 5 minutes to obtain a second melt;

[0081] S3, after the heat preservation is completed, the temperature drops to 800°C, and the aluminum yttrium slag material on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum yttrium slag material in step S1;

[0082] S4. Pour the molten metal into a cooler and cool it to obtain an aluminum-yttrium master alloy; the pouring temperature is 750-900°C, and the pouring speed is 0.25-0.3L / s; the time for the molten metal to cool to a completely solidified state is less than 20s; the time for the molten metal to cool to room temperature is 10-15min.

[0083] Example 2

[0084] This embodiment discloses a method for preparing an aluminum-scandium intermediate alloy.

[0085] The aluminum-scandium slag used in this embodiment is a slag previously obtained by a thermite reaction, wherein the thermite reaction is as follows: an aluminum ingot is placed in a medium frequency induction furnace and melted at 900°C for 15 minutes, scandium oxide, scandium fluoride and sodium fluoride are added thereto, and the mixture is kept warm for 40 minutes, and then the aluminum-scandium slag is fished out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum-scandium slag; the mass ratio of the aluminum ingot, scandium oxide, scandium fluoride and sodium fluoride is 1:0.002:0.059:0.06.

[0086] The preparation steps are as follows:

[0087] The materials in the preparation method are: 20kg aluminum ingot, 0.8kg aluminum scandium slag, 0.04kg scandium oxide, 1.18kg scandium fluoride, 1.2kg sodium fluoride, and the mass ratio is 1:0.04:0.002:0.059:0.06;

[0088] S1, adding aluminum ingot and aluminum-scandium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heating and melting at 900° C. for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scraping off the waste slag on the surface of the first melt to obtain a first melt;

[0089] S2, adding the above-mentioned mass of scandium oxide, scandium fluoride and sodium fluoride to the first melt, and heating to 1000° C. to completely melt the materials, and heat-treating for 60 minutes, stirring the materials evenly with a graphite rod every 5 minutes to obtain a second melt;

[0090] S3, after the heat preservation is completed, the temperature drops to 900° C., the aluminum-scandium slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-scandium slag in step S1;

[0091] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-scandium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0092] The aluminum-scandium slag in step S1 includes 68.00% of F element, 14.10% of Na element, 5.61% of Al element, 1.93% of Sc element and 10.36% of O element;

[0093] The waste slag in step S1 includes 67.00% of F element, 13.43% of Na element, 7.81% of Al element, 0.63% of Sc element and 11.13% of O element;

[0094] The aluminum-scandium slag in step S3 includes 69.30% of F element, 12.32% of Na element, 6.26% of Al element, 1.41% of Sc element and 10.71% of O element. The element contents of the above slag and waste slag are obtained by XRF scanning analysis.

[0095] Example 3

[0096] This embodiment discloses a method for preparing an aluminum-lanthanum intermediate alloy.

[0097] The aluminum-lanthanum slag used in this embodiment is a slag previously obtained by an aluminothermic reaction, wherein the aluminothermic reaction is as follows: an aluminum ingot is placed in a medium frequency induction furnace and melted at 950°C for 15 minutes, lanthanum oxide, lanthanum fluoride and sodium fluoride are added thereto, and the mixture is kept warm for 50 minutes, and then the aluminum-lanthanum slag is fished out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum-lanthanum slag; the mass ratio of the aluminum ingot, lanthanum oxide, lanthanum fluoride and sodium fluoride is 1:0.006:0.07:0.04.

[0098] The preparation steps are as follows:

[0099] The materials in the preparation method are: 14.5 kg aluminum ingot, 0.827 kg aluminum lanthanum slag, 0.087 kg lanthanum oxide, 1.015 kg lanthanum fluoride, 0.58 kg sodium fluoride, and the mass ratio is 1:0.057:0.006:0.07:0.04;

[0100] S1. Add aluminum ingots and aluminum lanthanum slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt at 950° C. for 15 min, stirring the materials evenly with a graphite rod every 5 min to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0101] S2, adding the above-mentioned mass of lanthanum oxide, lanthanum fluoride and sodium fluoride to the first melt; and heating to 970°C, the materials are completely melted, and the heat treatment is carried out for 50 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0102] S3, after the insulation is completed, the temperature drops to 780°C, and the aluminum lanthanum slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum lanthanum slag in step S1;

[0103] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-lanthanum intermediate alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0104] Example 4

[0105] This embodiment discloses a method for preparing an aluminum-neodymium intermediate alloy.

[0106] The aluminum-neodymium slag used in this embodiment is a slag previously obtained by a thermite reaction, and the thermite reaction is: placing an aluminum ingot in a medium frequency induction furnace and melting it at 900°C for 15 minutes, then adding neodymium oxide, neodymium fluoride and lithium fluoride thereto, keeping warm for 40 minutes, and then fishing it out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum-neodymium slag; the mass ratio of the aluminum ingot, neodymium oxide, neodymium fluoride and lithium fluoride is 1:0.007:0.05:0.06.

[0107] The preparation steps are as follows:

[0108] The materials in the preparation method are: 13.8 kg aluminum ingot, 0.566 kg aluminum-neodymium slag, 0.097 kg neodymium oxide, 0.69 kg neodymium fluoride, and 0.828 kg lithium fluoride, and the mass ratio thereof is 1:0.041:0.007:0.05:0.06;

[0109] S1. Add aluminum ingots and aluminum-neodymium slag into a graphite crucible of a medium-frequency induction furnace; heat and melt at 920° C. for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0110] S2, adding the above-mentioned mass of neodymium oxide, neodymium fluoride and lithium fluoride to the first melt; and heating to 950°C, the materials are completely melted, and the heat treatment is carried out for 40 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0111] S3, after the heat preservation is completed, the temperature is lowered to 820°C, and the aluminum-neodymium slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-neodymium slag in step S1;

[0112] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-neodymium intermediate alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0113] Example 5

[0114] This embodiment discloses a method for preparing an aluminum-samarium intermediate alloy.

[0115] The samarium aluminum slag used in this embodiment is a slag previously obtained by a thermite reaction, wherein the thermite reaction is as follows: an aluminum ingot is placed in a medium frequency induction furnace and melted at 950°C for 15 minutes, samarium oxide, samarium fluoride and sodium fluoride are added thereto, the mixture is kept warm for 60 minutes, and then the aluminum slag is fished out from the surface of the high-temperature liquid phase with a tool to obtain the samarium aluminum slag; the mass ratio of the aluminum ingot, samarium oxide, samarium fluoride and sodium fluoride is 1:0.009:0.06:0.035.

[0116] The preparation steps are as follows:

[0117] The materials in the preparation method are: 14.8 kg aluminum ingot, 0.725 kg aluminum samarium slag, 0.133 kg samarium oxide, 0.888 kg samarium fluoride, 0.518 kg sodium fluoride, and the mass ratio is 1:0.049:0.009:0.06:0.035;

[0118] S1. Add aluminum ingots and aluminum samarium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt them at 900° C. for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0119] S2, adding the above-mentioned mass of samarium oxide, samarium fluoride and sodium fluoride to the first melt; and heating to 950°C, the materials are completely melted, and the heat treatment is carried out for 60 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0120] S3, after the heat preservation is completed, the temperature is lowered to 810°C, and the aluminum-samarium slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-samarium slag in step S1;

[0121] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-samarium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0122] Example 6

[0123] This embodiment discloses a method for preparing an aluminum-terbium intermediate alloy.

[0124] The aluminum-terbium slag used in this embodiment is a slag previously obtained by a thermite reaction, wherein the thermite reaction is as follows: an aluminum ingot is placed in a medium frequency induction furnace and melted at 880°C for 15 minutes, terbium oxide, terbium fluoride and lithium fluoride are added thereto, and the mixture is kept warm for 50 minutes, and then the aluminum-terbium slag is fished out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum-terbium slag; the mass ratio of the aluminum ingot, terbium oxide, terbium fluoride and lithium fluoride is 1:0.01:0.05:0.05.

[0125] The preparation steps are as follows:

[0126] The materials in the preparation method are: 15.1 kg aluminum ingot, 0.906 kg aluminum terbium slag, 0.151 kg terbium oxide, 0.755 kg terbium fluoride, and 0.755 kg lithium fluoride, and the mass ratio thereof is 1:0.06:0.01:0.05:0.05;

[0127] S1. Add aluminum ingots and aluminum-terbium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt at 880° C. for 15 min, stirring the materials evenly with a graphite rod every 5 min to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0128] S2, adding the above-mentioned mass of terbium oxide, terbium fluoride and lithium fluoride to the first melt; and heating to 920°C, the materials are completely melted, and the temperature is kept for 50 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0129] S3, after the heat preservation is completed, the temperature is lowered to 800° C., the aluminum-terbium slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-terbium slag in step S1;

[0130] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-terbium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0131] Example 7

[0132] This embodiment discloses a method for preparing an aluminum-erbium intermediate alloy.

[0133] The aluminum-erbium slag used in this embodiment is the slag previously obtained by thermite reaction, and the aluminothermic reaction is: placing an aluminum ingot in a medium frequency induction furnace and melting it at 1050°C for 15 minutes, then adding erbium oxide, erbium fluoride and sodium fluoride thereto, keeping warm for 40 minutes, and then fishing it out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum-erbium slag; the mass ratio of the aluminum ingot, erbium oxide, erbium fluoride and sodium fluoride is 1:0.008:0.13:0.07.

[0134] The preparation steps are as follows:

[0135] The materials in the preparation method are: 13.6 kg aluminum ingot, 0.694 kg aluminum erbium slag, 0.109 kg erbium oxide, 1.768 kg erbium fluoride, and 0.952 kg sodium fluoride, and the mass ratio thereof is 1:0.051:0.008:0.13:0.07.

[0136] S1. Add aluminum ingots and aluminum erbium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt them at 1050° C. for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0137] S2, adding the above-mentioned mass of erbium oxide, erbium fluoride and sodium fluoride to the first melt; and heating to 1070°C, the materials are completely melted, and the temperature is kept for 40 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0138] S3, after the heat preservation is completed, the temperature is lowered to 810°C, and the aluminum-erbium slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-erbium slag in step S1;

[0139] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-erbium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0140] Example 8

[0141] This embodiment discloses a method for preparing an aluminum-thulium intermediate alloy.

[0142] The aluminum thulium slag used in this embodiment is a slag previously obtained by a thermite reaction, wherein the thermite reaction is as follows: an aluminum ingot is placed in a medium frequency induction furnace and melted at 1050°C for 15 minutes, thulium oxide, thulium fluoride and sodium fluoride are added thereto, and the mixture is kept warm for 40 minutes, and then the aluminum thulium slag is fished out from the surface of the high-temperature liquid phase with a tool to obtain the aluminum thulium slag; the mass ratio of the aluminum ingot, thulium oxide, thulium fluoride and sodium fluoride is 1:0.009:0.06:0.05.

[0143] The preparation steps are as follows:

[0144] The materials in the preparation method are: 16.0 kg aluminum ingot, 0.864 kg aluminum thulium slag, 0.144 kg thulium oxide, 0.96 kg thulium fluoride, and 0.8 kg sodium fluoride, and the mass ratio thereof is 1:0.054:0.009:0.06:0.05;

[0145] S1. Add aluminum ingots and aluminum thulium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt at 950° C. for 15 min, stirring the materials evenly with a graphite rod every 5 min to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0146] S2, adding the above-mentioned mass of thulium oxide, thulium fluoride and sodium fluoride to the first melt; and heating to 980°C, the materials are completely melted, and kept warm for 50 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0147] S3, after the insulation is completed, the temperature is lowered to 900° C., the aluminum-thulium slag material on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-thulium slag material of step S1;

[0148] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-thulium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0149] Example 9

[0150] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy; compared with Example 1, this embodiment does not perform stirring during the heat preservation treatment in step S2.

[0151] Specifically, the preparation steps are as follows:

[0152] The materials in the preparation method are: 16.5 kg aluminum ingot, 0.743 kg aluminum yttrium slag obtained in step S3 of Example 1, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, and the mass ratio thereof is 1:0.045:0.008:0.09:0.04;

[0153] S1. Add aluminum ingots and aluminum yttrium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt them at 900° C. for 10 min, stir the materials evenly with a graphite rod every 5 min to form a first melt, and then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0154] S2, adding the above-mentioned mass of yttrium oxide, yttrium fluoride and potassium fluoride to the first melt; and heating to 900° C., the materials are completely melted, and the temperature is kept for 40 minutes (without stirring);

[0155] S3, after the insulation is completed, the temperature drops to 800°C, and the aluminum yttrium slag on the surface of the second melt is fished out with tools and preserved;

[0156] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-yttrium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0157] Example 10

[0158] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy; compared with Example 1, the melting temperature in step S1 and the insulation treatment temperature in step S2 of this embodiment are higher, which are 1200°C.

[0159] Specifically, the preparation steps are as follows:

[0160] The materials in the preparation method are: 16.5 kg aluminum ingot, 0.743 kg aluminum yttrium slag obtained in step S3 of Example 1, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, and the mass ratio thereof is 1:0.045:0.008:0.09:0.04.

[0161] S1. Add aluminum ingots and aluminum yttrium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt them at 1200° C. for 10 min, stirring the materials evenly with a graphite rod every 5 min to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0162] S2, adding the above-mentioned mass of yttrium oxide, yttrium fluoride and potassium fluoride to the first melt; and heating to 1200° C. to completely melt the materials, and heat preservation treatment for 40 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0163] S3, after the heat preservation is completed, the temperature drops to 800° C., the aluminum yttrium slag material on the surface of the second melt is fished out with a tool and preserved as the aluminum yttrium slag material in step S1;

[0164] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-yttrium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0165] Embodiment 11

[0166] This embodiment is a method for preparing an aluminum-erbium intermediate alloy. Compared with Embodiment 7, the holding time in step S2 of this embodiment is shorter, that is, 20 minutes.

[0167] Specifically, the preparation steps are as follows:

[0168] The materials in the preparation method are: 18.6 kg aluminum ingot, 0.949 kg aluminum erbium slag obtained in step S3 of Example 7, 0.149 kg erbium oxide, 2.418 kg erbium fluoride, and 1.302 kg sodium fluoride, and the mass ratio thereof is 1:0.051:0.008:0.13:0.07.

[0169] S1. Add aluminum ingots and aluminum erbium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heat and melt at 1050° C. for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0170] S2, adding the above-mentioned mass of erbium oxide, erbium fluoride and sodium fluoride to the first melt; and heating to 1070°C, the materials are completely melted, and the temperature is kept for 20 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0171] S3, after the heat preservation is completed, when the temperature drops to 810°C, the aluminum-erbium slag of the second melt is fished out with tools and stored;

[0172] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-erbium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0173] Example 12

[0174] This embodiment is a method for preparing an aluminum-scandium intermediate alloy. Compared with embodiment 2, the amount of sodium fluoride added in step S2 of this embodiment is lower, which is 0.4 kg; and the mass ratio of the aluminum ingot to the sodium fluoride is 1:0.02.

[0175] Specifically, the preparation steps are as follows:

[0176] The materials in the preparation method are: 20kg aluminum ingot, 0.8kg aluminum scandium slag, 0.04kg scandium oxide, 1.18kg scandium fluoride, 0.4kg sodium fluoride, and the mass ratio is 1:0.04:0.002:0.059:0.02;

[0177] S1, adding aluminum ingot and aluminum-scandium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heating and melting at 900°C for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scraping off the waste slag on the surface of the first melt to obtain a first melt;

[0178] S2, adding the above-mentioned mass of scandium oxide, scandium fluoride and sodium fluoride to the first melt; and heating to 1000° C. to completely melt the materials, and heat preservation treatment for 60 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0179] S3, after the insulation is completed, the temperature drops to 900°C, and the aluminum-scandium slag on the surface of the second melt is fished out with tools and preserved;

[0180] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-scandium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0181] Embodiment 13

[0182] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy; compared with Example 2, the amount of sodium fluoride added in step S2 of this embodiment is higher, which is 1.6 kg; the mass ratio of the aluminum ingot to the sodium fluoride is 1:0.08.

[0183] Specifically, the preparation steps are as follows:

[0184] The materials in the preparation method are: 20 kg aluminum ingot, 0.8 kg aluminum scandium slag obtained in step S3 of Example 2, 0.04 kg scandium oxide, 1.18 kg scandium fluoride, and 1.6 kg sodium fluoride, and the mass ratio thereof is 1:0.04:0.002:0.059:0.08;

[0185] S1, adding aluminum ingot and aluminum-scandium slag materials according to the above amounts into a graphite crucible of a medium frequency induction furnace; heating and melting at 900° C. for 15 minutes, stirring the materials evenly with a graphite rod every 5 minutes to form a first melt; then scraping off the waste slag on the surface of the first melt to obtain a first melt;

[0186] S2, adding the above-mentioned mass of scandium oxide, scandium fluoride and sodium fluoride to the first melt; and heating to 1000° C. to completely melt the materials, and heat preservation treatment for 60 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0187] S3, after the heat preservation is completed, the temperature drops to 900° C., the aluminum-scandium slag on the surface of the second melt is fished out with a tool and preserved to serve as the aluminum-scandium slag in step S1;

[0188] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-scandium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0189] Embodiment 14

[0190] This embodiment is a method for preparing an aluminum-neodymium intermediate alloy. Compared with embodiment 4, this embodiment does not add aluminum-neodymium slag in step S1.

[0191] Specifically, the preparation steps are as follows:

[0192] The materials in the preparation method are: 13.8 kg aluminum ingot, 0.097 kg neodymium oxide, 0.69 kg neodymium fluoride, 0.828 kg lithium fluoride, and the mass ratio is 1:0.007:0.05:0.06;

[0193] S1. Add aluminum ingot, neodymium oxide, neodymium fluoride and lithium fluoride into a graphite crucible of a medium frequency induction furnace; heat to 950°C and melt for 40 minutes, stirring the materials evenly with a graphite rod every 5 minutes to obtain a melt;

[0194] S2. After the heat preservation is completed, when the temperature drops to 820°C, the aluminum-neodymium slag on the surface of the melt is fished out with tools and preserved;

[0195] S3, pouring the molten metal into a cooler and cooling it to obtain an aluminum-neodymium intermediate alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0196] Embodiment 15

[0197] This embodiment is a method for preparing an aluminum-scandium intermediate alloy. Compared with embodiment 2, in this embodiment, aluminum ingots, aluminum-scandium slag, scandium oxide, scandium fluoride, and sodium fluoride are mixed and melted together.

[0198] Specifically, the preparation steps are as follows:

[0199] The materials in the preparation method are: 20 kg aluminum ingot, 0.8 kg aluminum-scandium slag obtained in step S3 of Example 2, 0.04 kg scandium oxide, 1.18 kg scandium fluoride, and 1.2 kg sodium fluoride, and the mass ratio thereof is 1:0.04:0.002:0.059:0.06;

[0200] S1. Add aluminum ingot, aluminum-scandium slag, scandium oxide, scandium fluoride and sodium fluoride into a graphite crucible of a medium frequency induction furnace according to the above amounts; heat to 1000° C., heat and melt for 60 minutes to completely melt the materials, and stir the materials evenly with a graphite rod every 5 minutes to obtain a molten material;

[0201] S2. After the insulation is completed, when the temperature drops to 900°C, the aluminum-scandium slag on the surface of the melt is fished out with tools and preserved;

[0202] S3, pouring the molten metal into a cooler and cooling it to obtain an aluminum-scandium master alloy; the casting conditions of this embodiment are the same as those of embodiment 1.

[0203] In the above embodiments and comparative examples, the purity of the aluminum ingots used is 99.99% or more, the purity of the rare earth oxides and fluorides is 99.9% or more, and the purity of the alkali metal halide is 99.7% or more.

[0204] Comparative Example 1

[0205] This comparative example is a method for preparing an aluminum-scandium master alloy, which comprises the following steps:

[0206] (1) Production of aluminum-scandium master alloy by doping method: weigh 20 kg aluminum ingot and 0.04 kg metal scandium, with a mass ratio of 1:0.002, wherein the metal scandium is a crude scandium obtained by calcium thermal reduction of scandium fluoride;

[0207] (2) Opening a high vacuum medium frequency induction melting furnace, placing an aluminum ingot and metal scandium into a graphite crucible;

[0208] (3) Close the furnace cover and vent valve, turn on the vacuum system, and draw the vacuum degree to below 0.1Pa;

[0209] (4) Turn on the medium frequency power supply, adjust the power to 15kw, bake the furnace for 20 minutes, then adjust to 45kw, observe the situation in the furnace, wait until the material is completely melted, and measure the temperature through infrared. When it reaches 1000℃, reduce the power to 20kw and keep it at 1000℃ for 30 minutes;

[0210] (5) After the heat preservation is completed, the power is turned off and the molten metal is poured into the mold to obtain the aluminum-scandium master alloy.

[0211] Comparative Example 2

[0212] This comparative example is a method for preparing an aluminum-yttrium intermediate alloy; compared with Example 1, the melting temperature in step S1 and the insulation treatment temperature in step S2 of this comparative example are lower, which are 750°C, and there is no cooling process after the insulation treatment is completed.

[0213] Specifically, the preparation steps are as follows:

[0214] The materials in the preparation method are: 16.5 kg aluminum ingot, 0.743 kg aluminum yttrium slag obtained in step S3 of Example 1, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, and the mass ratio thereof is 1:0.045:0.008:0.09:0.04.

[0215] S1. Add aluminum ingot and aluminum yttrium slag into a graphite crucible of a medium frequency induction furnace according to the above amount; heat and melt at 750° C. for 10 min, stirring the material evenly with a graphite rod every 5 min to form a first melt; then scrape off the waste slag on the surface of the first melt to obtain a first melt;

[0216] S2, adding the above-mentioned mass of yttrium oxide, yttrium fluoride and potassium fluoride to the first melt; and heating to 750°C, the materials are completely melted, and the temperature is kept for 40 minutes, during which the materials are stirred evenly with a graphite rod every 5 minutes to obtain a second melt;

[0217] S3. After the heat preservation is completed, the aluminum yttrium slag on the surface of the second melt is fished out with tools and stored;

[0218] S4, pouring the molten metal into a cooler and cooling it to obtain an aluminum-yttrium master alloy; the casting conditions of this comparative example are the same as those of Example 1.

[0219] Effect Example 1

[0220] The rare earth aluminum intermediate alloys of Examples 1-15 and Comparative Examples 1-2 were sampled at four different locations to detect their rare earth main components; the rare earth main component analysis method adopted a conventional chemical titration method in the art; the sample was dissolved with acid, and titrated with EDTA standard solution using xylenol orange as an indicator; the rare earth content was determined by EDTA titration, with a determination range of 1%-20%wt, and the process was: dissolution→concentration→fractionation→titration→result calculation.

[0221] Table 1 is the main component detection data of samples of Examples 1-8, and Table 2 is the main component detection data of samples of Comparative Examples 1-2 and Examples 9-15. The average value is taken to obtain the rare earth content of the alloy ingot, and the yield is calculated, yield = mass of rare earth elements in the alloy ingot / (mass of rare earth elements in rare earth oxides + mass of rare earth elements in rare earth fluorides). The results show that the yield of the rare earth aluminum intermediate alloy prepared by the present method embodiment is above 60%.

[0222] Table 1

[0223] project Sample name Test items Position 1 Position 2 Location 3 Position 4 Mean Yield Example 1 Aluminum Yttrium Alloy Y%(wt) 4.52％ 5.12％ 5.05％ 4.93％ 4.91％ 85.30％ Example 2 Aluminum Scandium Alloy Sc%(wt) 2.35％ 2.45％ 2.29％ 2.38％ 2.37％ 89.00％ Example 3 Aluminum-Lanthanum Alloy La%(wt) 4.51％ 4.56％ 4.72％ 4.32％ 4.53％ 92.00％ Example 4 Aluminum Neodymium Alloy Nd%(wt) 3.22％ 3.33％ 3.17％ 3.30％ 3.26％ 81.20％ Example 5 Aluminum Samarium Alloy Sm%(wt) 4.26％ 4.30％ 4.52％ 4.70％ 4.45％ 91.20％ Example 6 Aluminum Terbium Alloy Tb%(wt) 4.08％ 3.78％ 3.95％ 3.75％ 3.89％ 89.50％ Example 7 Aluminum Erbium Alloy Er%(wt) 8.19％ 7.44％ 8.03％ 8.24％ 7.98％ 84.70％ Example 8 Aluminum Thulium Alloy Tm%(wt) 4.56％ 4.63％ 4.52％ 4.60％ 4.58％ 91.50％

[0224] Table 2

[0225]

[0226]

[0227] Compared with Example 1, Example 9 lacks the graphite rod stirring during the insulation process, and the yield is reduced by 21.3%. During the insulation process, the slag floats on the surface of the molten metal. The electromagnetic stirring of the medium frequency induction furnace coil itself is not enough. Mechanical stirring is also required to promote the contact area between the metal and the slag reaction, and kinetically promote the reaction, thereby improving the yield.

[0228] Compared with Example 1, the holding temperature of Example 10 is 300° C. higher and the yield is reduced by 6.3%. High temperature promotes the forward reaction, but high temperature also causes the rare earth elements in the alloy to burn out, thereby reducing the yield.

[0229] Compared with Example 1, the insulation temperature of Comparative Example 2 is 150°C lower, and the yield is reduced by 59%. During the insulation process, the slag formation effect on the surface of the molten metal is poor, and the slag fluidity is poor, which hinders the reaction between the slag and the molten metal, and the yield is reduced.

[0230] Compared with Example 7, the holding time of Example 11 is 20 minutes shorter, and the yield is reduced by 14.5%. Insufficient holding time leads to insufficient reaction between the metal and the slag, and the yield will be reduced.

[0231] In Example 12, compared with Example 2, the addition ratio of sodium fluoride is 0.04 less, and the yield is reduced by 23.5%. The addition of less sodium fluoride is not conducive to lowering the melting point of the slag, resulting in poor slagging effect, hindering the reaction between the slag and the molten metal, and reducing the yield.

[0232] In Example 13, compared with Example 2, the addition ratio of sodium fluoride is increased by 0.02, and the yield is reduced by 1.3%. The addition of more sodium fluoride has a smaller effect on the yield, so the excess alkali metal halide has little effect on the reaction and will cause a waste of raw materials.

[0233] In Example 14, compared with Example 4, no rare earth aluminum slag was added, and the yield was reduced by 8.9%. The process step did not recycle the rare earth aluminum slag, and the yield was reduced.

[0234] In Example 15, compared with Example 2, the scandium oxide, scandium fluoride and sodium fluoride in step (4) are added together with the aluminum-scandium slag in step (2), and the yield is reduced by 17.95%. The aluminum-scandium slag itself is a slag generated by thermite reaction. Melting in one step of synthesis will reduce the concentration of rare earth elements in the feed, reduce the fluidity of the slag, and inhibit the reaction.

[0235] Effect Example 2

[0236] This effect example analyzes the impurity content and purity of the products of Example 2 and Comparative Example 1. The samples of the aluminum-scandium alloy of Example 2 and Comparative Example 1 are simultaneously tested for other impurity elements, and the test method is a conventional ICP test in the art. Table 3 shows the impurity test data of the samples of Comparative Example 1 and Example 2.

[0237] Table 3

[0238]

[0239] It can be seen that the aluminum-scandium alloy prepared by the cross-doping method of Comparative Example 1 obviously has more tungsten and calcium impurities. The main reason for this result is that in the process of using calcium thermal reduction to prepare metal scandium, excessive calcium and metal scandium are alloyed with tungsten crucibles, thereby introducing impurities from the raw materials into the aluminum-scandium alloy in Comparative Example 1; if the introduction of impurities from the raw materials is to be avoided, the metal scandium needs to be purified by secondary distillation, but at the same time it will lead to complicated processes and increased costs.

[0240] The preparation method of the present application directly reduces and alloys the rare earth elements in oxides and fluorides, which reduces the process steps of intermediate metal purification compared to the doping method, has a short operation process and low cost; and, based on the effect of the existing technology, the present method can further improve the purity of the aluminum-scandium alloy product and reduce the impurity content therein.

[0241] Effect Example 3

[0242] This effect example analyzes the mesophase distribution and grain size of the products of Example 2 and Comparative Example 1.

[0243] Specifically, the alloy ingots obtained in Example 2 and Comparative Example 1 were wire cut to obtain metallographic samples with a side length of less than 1 cm, and electron microscope metallographic analysis was performed on the samples to obtain Figure 2 and Figure 3 The analysis results. Figure 2 This is an electron microscope image of the aluminum-scandium master alloy of Example 2; Figure 3 This is the electron microscope image of the aluminum-scandium master alloy of comparative example 1.

[0244] contrast Figure 2 and Figure 3 It can be seen from the displayed results that the intermediate phase grains of the alloy samples prepared by the doping method are agglomerated, and the grain size is 16-143μm, which is large and unevenly distributed; while the intermediate phase of the alloy samples prepared by this method is evenly distributed and the grain size is relatively small, at 10-34μm.

Claims

1. A method for preparing a rare earth aluminum master alloy, characterized in that: It includes the following steps: S1, removing the waste slag on the surface of the first melt after melting to obtain a first melt; the first melt comprises metallic aluminum and rare earth aluminum raw materials; the melting temperature is 800-1200° C.; the rare earth aluminum raw materials are: rare earth aluminum slag obtained by aluminothermic reaction, and / or the rare earth aluminum slag in the following step S3; S2, subjecting the second mixture to heat preservation treatment to obtain a second melt; the second mixture includes the first melt, rare earth fluoride and alkali metal halide; the temperature of the heat preservation treatment is 800-1100° C.; S3, separating the second melt to obtain molten metal and rare earth aluminum slag; S4, pouring the molten metal and cooling it to obtain a rare earth aluminum master alloy.

2. The method for preparing the rare earth aluminum master alloy according to claim 1, characterized in that: Step S1 satisfies one or more of the following conditions: ① The rare earth aluminum raw material includes aluminum and rare earth elements; preferably, the rare earth elements include yttrium, scandium, lanthanum, neodymium, samarium, terbium, erbium or thulium; preferably, the content of the rare earth elements is above 0.5%, where % is the percentage of the mass of the rare earth elements to the total mass of the rare earth aluminum raw material; ② The mass ratio of the metallic aluminum to the rare earth aluminum raw material is 1:(0.03-0.1), preferably 1:(0.04-0.08); ③ The melting temperature is 850-1100°C; ④ The aluminothermic reaction is: reacting metallic aluminum with rare earth fluoride, and / or reacting metallic aluminum with rare earth oxide.

3. The method for preparing the rare earth aluminum master alloy according to claim 2, characterized in that: Step S1 satisfies one or more of the following conditions: ① The content of the rare earth element is above 1%, where % is the percentage of the mass of the rare earth element to the total mass of the rare earth aluminum raw material, preferably 1%-5%; ② The content of aluminum is 3%-15%, where % is the percentage of the mass of aluminum to the total mass of the rare earth aluminum raw material, preferably 5%-10%; ③ The rare earth aluminum raw material further comprises alkali metal elements, fluorine elements and oxygen elements; preferably, the content of the alkali metal elements is 10%-20%, % is the percentage of the mass of the alkali metal elements to the total mass of the rare earth aluminum raw material, more preferably 12%-15%; preferably, the content of the fluorine element is 50%-80%, % is the percentage of the mass of the fluorine element to the total mass of the rare earth aluminum raw material, more preferably 65%-70%; preferably, the content of the oxygen element is 5%-15%, % is the percentage of the mass of the oxygen element to the total mass of the rare earth aluminum raw material, more preferably 10%-12%; ④ The mass ratio of the metallic aluminum to the rare earth aluminum raw material is 1:(0.04-0.06), for example, 1:0.04, 1:0.041, 1:0.045, 1:0.049, 1:0.051, 1:0.054, 1:0.057 or 1:0.06; ⑤ The melting temperature is 880-1050°C, for example 880°C, 900°C, 920°C, 950°C or 1050°C; ⑥The temperature of the aluminothermic reaction is 800-1200°C.

4. The method for preparing the rare earth aluminum master alloy according to claim 1, characterized in that: Step S1 satisfies one or more of the following conditions: ① The metal aluminum includes aluminum ingots; ② The melting time is 10-30 min, preferably 10-20 min; ③ The melting process is carried out in a crucible of a medium frequency induction melting furnace; ④ The melting process is carried out under the first stirring, and the interval time of the first stirring is 5-10 minutes, preferably 5-8 minutes, for example 5 minutes; the first stirring method includes electromagnetic stirring and / or mechanical stirring.

5. The method for preparing the rare earth aluminum master alloy according to claim 4, characterized in that: The melting time is 10-15 min, for example 10 min or 15 min; And / or, the mechanical stirring includes graphite rod stirring.

6. The method for preparing the rare earth aluminum master alloy according to claim 1, characterized in that: Step S2 satisfies one or more of the following conditions: ① The mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.03-0.18); ② The mass ratio of the metallic aluminum to the alkali metal halide is 1:(0.03-0.08), preferably 1:(0.03-0.07); ③ The temperature of the heat preservation treatment is 800-1100°C; ④ The heat preservation treatment time is 30-60min, preferably 40-60min; ⑤ The heat preservation process is carried out under the second stirring, the interval time of the second stirring is 5-10 minutes, preferably 5 minutes; the second stirring method includes electromagnetic stirring and / or mechanical stirring; ⑥ The rare earth fluoride is yttrium fluoride, scandium fluoride, lanthanum fluoride, neodymium fluoride, samarium fluoride, terbium fluoride, erbium fluoride or thulium fluoride; the rare earth element in the rare earth fluoride is consistent with the rare earth element in the rare earth aluminum alloy material; ⑦ The alkali metal halide is potassium fluoride, lithium fluoride, sodium fluoride, sodium fluoroaluminate, potassium chlorofluoroate or calcium fluoride; ⑧The second mixture also includes rare earth oxides; the rare earth oxides are consistent with the rare earth elements in the rare earth fluorides.

7. The method for preparing the rare earth aluminum master alloy according to claim 6, characterized in that: Step S2 satisfies one or more of the following conditions: ① The mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.05-0.15), preferably 1:(0.05-0.13); ② The mass ratio of the metallic aluminum to the alkali metal halide is 1:(0.035-0.07); ③ The temperature of the heat preservation treatment is 900-1100°C, preferably 920-1070°C; ④ The heat preservation time is 40min, 50min or 60min; ⑤ The mechanical stirring includes graphite rod stirring; ⑥ The rare earth oxide is yttrium oxide, scandium oxide, lanthanum oxide, neodymium oxide, samarium oxide, terbium oxide, erbium oxide or thulium oxide; ⑦ The mass ratio of the metallic aluminum to the rare earth oxide is 1:(0.002-0.02), preferably 1:(0.002-0.01).

8. The method for preparing the rare earth aluminum master alloy according to claim 1, characterized in that: In step S3, the separation temperature is 750-900°C, preferably 780-900°C, such as 780°C, 800°C, 810°C, 820°C or 900°C; And / or, the separation method includes removing rare earth aluminum slag from the surface of the second melt.

9. The method for preparing the rare earth aluminum master alloy according to claim 1, characterized in that: Step S4 satisfies one or more of the following conditions: ① The cooling method includes water cooling, air cooling or cooling by a cooler; ② The pouring temperature is 750-900°C, preferably 780-900°C, such as 780°C, 800°C, 810°C, 820°C or 900°C; ③ The pouring speed is 0.25-0.3L / s; ④ The time for the molten metal to cool to a completely solidified state is less than 20 seconds; ⑤ The time for the metal liquid to cool to room temperature is 10-15 minutes.

10. A rare earth aluminum master alloy, characterized in that: It is prepared by the preparation method of the rare earth aluminum intermediate alloy as described in any one of claims 1 to 9; Preferably, the rare earth element content of the rare earth aluminum master alloy is less than 10%, where % is the ratio of the mass of the rare earth element to the total mass of the rare earth aluminum master alloy; more preferably, it is greater than 1.5% and less than 8.5%.

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