CN113881973B - Method for preparing aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as supplementary electrolyte - Google Patents
Method for preparing aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as supplementary electrolyte Download PDFInfo
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Abstract
The invention provides a method for preparing an aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as a supplementary electrolyte. The method comprises the following steps: step 1, adding Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 F, mixing to obtain a mixture; heating the mixture, preserving heat and cooling to obtain scandium-containing fluoride molten salt, and marking as molten salt I; step 2, heating and melting the aluminum ingot, and then adding molten salt electrolyte powder in batches, wherein the molten salt electrolyte powder comprises m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 Marked as molten salt II; after the fused salt II is melted, adding the fused salt I into the fused salt II to serve as a supplementary electrolyte to form fused salt III; electrolysis is then commenced and molten salt I is replenished to molten salt III during electrolysis and the composition of the electrolyzed molten salt during electrolysis is maintained within the composition range of molten salt III. The invention solves the problems of low utilization rate of scandium fluoride, high cost and the like in the prior art.
Description
Technical Field
The invention relates to the field of alloy manufacturing, in particular to a method for preparing an aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as a supplementary electrolyte.
Background
After the aluminum alloy is added with trace scandium (the mass fraction is 0.07-0.35%), the strength, the plastic toughness, the high temperature resistance, the corrosion resistance, the welding performance and the like can be obviously improved, the aluminum alloy becomes a fourth generation aerospace material following the aluminum-lithium alloy, and has wide application prospects in the fields of aerospace, aviation, rail traffic, ship welding load structural members, aluminum alloy pipes for alkaline corrosive medium environments, railway oil tanks and the like. Because of the large difference between the melting points of scandium and aluminum, the aluminum-scandium master alloy is generally used as the raw material in the industrial production of the aluminum-scandium alloy.
The intermediate alloy produced by the molten salt electrolysis method has the characteristics of continuous production, high space-time yield, easy process control, convenient introduction of automation, uniform element distribution, high alloy quality, small waste residue and the like, and is widely applied to producing products such as aluminum, magnesium, rare metals and the like. The molten salt system adopted by the aluminum scandium intermediate alloy prepared by the current electrolytic method mainly comprises three major categories of fluoride, chloride and fluorochloride. The chloride system mainly takes scandium chloride and pure aluminum as raw materials, and scandium is electrolytically precipitated in a composite molten salt system formed by the scandium chloride and alkali metal chloride to prepare the aluminum-scandium alloy. By adopting the method, the aluminum-scandium master alloy with scandium content of 8.0% can be prepared. However, the scandium chloride adopted by the method is easy to absorb water, so that the preparation process is complex, the storage is difficult, the volatilization loss of the scandium chloride is large at high temperature, and the scandium chloride is not suitable for production and application. The fluochloride system takes scandium oxide and pure aluminum as raw materials, and scandium is electrolytically precipitated in an electrolyte system consisting of scandium fluoride, scandium chloride and lithium fluoride to prepare the aluminum-scandium master alloy. The method can prepare the aluminum-scandium master alloy with scandium content of 2.0-6.0%. However, the method also adopts scandium chloride, which also causes problems of harsh preparation process and storage conditions, and is not suitable for production and application. Therefore, compared with chloride and fluorochloride electrolytes, the fluoride electrolyte has better use effect and is more suitable for industrial large-scale application.
The fluoride system mainly takes alumina and scandium oxide as raw materials at present, and scandium and aluminum are co-precipitated in an sodium cryolite electrolyte system through electrolysis to prepare the aluminum-scandium alloy. Such as: chinese patent CN1184356C discloses an electrolytic production method of aluminum-scandium alloy, which takes scandium and aluminum oxide as raw materials, and n NaF. AlF 3 (n is between 2.0 and 3.0) -LiF-CaF 2 -MgF 2 Is an electrolyte system, the electrolysis temperature is 900.0-990.0 ℃, and the aluminum-scandium alloy with the scandium content of 0.1-3.0% is prepared by the electrolytic precipitation of scandium and aluminum. However, the method adopts sodium cryolite as a main electrolyte, and has the advantages of low oxide solubility, high electrolysis temperature, low scandium precipitation ratio (less than 5.0 percent) and low productivity in unit time. Chinese patent CN107502923A uses n NaF. AlF 3 -ScF 3 -LiF-MF 2 (n is 2-3, M is Mg andor Ca) is a molten salt electrolyte system, and the aluminum-scandium intermediate alloy with the scandium weight content of 0.1-20.0 percent can be prepared. However, the electrolyte system described in this patent is prepared by direct addition of ScF 3 And (4) preparation. On one hand, scandium fluoride is slow in dissolution and easy to generate precipitates, so that the utilization rate of scandium fluoride is reduced; scandium fluoride, on the other hand, is more expensive than scandium fluorideHigh scandium, high production cost of aluminum scandium alloy. Comprehensively, the method is not beneficial to reducing the product cost.
Therefore, the existing aluminum-scandium alloy production process needs to be further improved.
Disclosure of Invention
The invention mainly aims to provide a method for preparing an aluminum-scandium alloy by electrolysis by using scandium-containing fluoride molten salt as a supplementary electrolyte, so as to solve the problem that ScF is directly added in the prior art 3 The problems of low utilization rate of scandium fluoride, high cost and the like in the electrolytic preparation of the aluminum-scandium alloy.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for producing an aluminum-scandium alloy by electrolysis of a scandium-containing fluoride molten salt as a replenishing electrolyte, including the steps of:
step 1, adding Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 F is mixed to give a mixture, and m 1 Is 2.1 to 3.0 1 1.1 to 1.6 of Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is (1.5-30.6), (20.0-95.0), (3.0-35.0) and (2.0-55.0); heating the mixture, preserving heat and cooling to obtain scandium-containing fluoride molten salt, and marking as molten salt I; according to the weight percentage, in the molten salt I, the content of potassium is 1-10%, the content of scandium is 1-20%, and the weight ratio of scandium to oxygen is more than or equal to 45;
step 2, heating and melting the aluminum ingot, and adding molten salt electrolyte powder in batches, wherein the molten salt electrolyte powder comprises m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 Is denoted as molten salt II, and m 2 Is 2.8 to 3.0,m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 The weight ratio of (70.0-90.0), (1.0-10.0), (4.0-9.9), (0.1-6.0); after the fused salt II is melted, adding the fused salt I into the fused salt II as a supplementary electrolyte to form fused salt III, wherein the potassium content in the fused salt III is 0.1-5% and the scandium content is 3-15% in parts by weight, and the weight ratio of scandium to oxygen is more than or equal to 45;electrolysis is then commenced and molten salt I is replenished to molten salt III during electrolysis and the composition of the electrolyzed molten salt during electrolysis is maintained within the composition range of molten salt III.
Further, sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is (24.5-30.6), (20.2-43.2), (20.5-34.5) and (14.5-49.3).
Further, m 1 Is 2.8,n 1 Is 1.1; sc (Sc) 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F to F is 30.6.
Further, in the step 1, the mixture is heated to be molten, and then heat preservation and cooling are carried out to obtain the scandium-containing fluoride molten salt.
Further, heating the mixture to be molten, and then preserving heat under the condition of mechanical stirring, wherein the heat preservation time is more than or equal to 0.5h; after cooling, the scandium-containing fluoride fused salt is ground and sieved by a 100-mesh sieve.
Further, in step 2, in the electrolysis process, sc is treated by taking aluminum as a cathode and molten salt III as a molten salt electrolyte 2 O 3 And Al 2 O 3 Carrying out fused salt electrolysis to obtain an aluminum-scandium alloy; and supplementing the molten salt I into the molten salt III in the electrolysis process, and maintaining the components of the electrolyzed molten salt in the component range of the molten salt III in the electrolysis process.
Further, sc 2 O 3 And Al 2 O 3 The weight ratio of the components is 40.0-99.0.
The invention provides a method for preparing an aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as a supplementary electrolyte. The feed stock for the preparation of the supplemental electrolyte of the present invention comprises Sc 2 O 3 、m 1 NaF·AlF 3 (molecular ratio m is 2.1-3.0) and n 1 KF·AlF 3 (the molecular ratio n is 1.1 to 1.6) and NH 4 F. Scandium-containing fluoride fused salt powder is prepared through the processes of mixing, heating, heat preservation, cooling and the like. M in the raw material 1 NaF·AlF 3 And n KF AlF 3 Mainly Sc to dissolve 2 O 3 Promoting Sc 2 O 3 Fluorination reaction, etc. NH (NH) 4 F reacts with scandium oxide dissolved in the molten salt to produce scandium-containing fluoride. The scandium fluoride is uniformly distributed in the molten salt prepared in the mode. When the molten salt is used as a supplementary electrolyte and added into an electrolytic cell, compared with the direct addition of scandium fluoride, the molten salt has the characteristics of rapid dissolution, difficult generation of precipitate, high utilization rate of scandium fluoride, low cost and the like.
Secondly, the scandium-containing fluoride fused salt is used as a supplementary electrolyte for electrolysis to prepare the aluminum-scandium alloy, and a certain amount of elpasolite is added into the electrolyte, so that the dissolution of oxides can be improved when a higher scandium precipitation ratio is ensured, the current efficiency is improved, the oxide precipitation is reduced, the service life of an electrolytic cell is prolonged, and the like.
In a word, the method for preparing the aluminum-scandium alloy by the electrolyte electrolysis after the improvement of using the scandium-containing fluoride as the supplementary electrolyte can avoid the problems of low dissolving speed, easy generation of precipitate and the like caused by directly adding scandium fluoride under the condition of ensuring higher scandium precipitation ratio, improve the utilization rate of the scandium fluoride and reduce the production cost. Meanwhile, the scandium-containing fluoride molten salt contains a certain amount of potassium cryolite, so that the dissolution of oxides can be improved, the current efficiency can be improved, the precipitation of the oxides can be reduced, the service life of the electrolytic cell can be prolonged, and the like.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the problems of slow dissolving speed of scandium fluoride, easy generation of precipitate, high price of scandium fluoride, increase in the cost of aluminum-scandium alloy and the like exist when the aluminum-scandium alloy is prepared by directly adding scandium fluoride through molten salt electrolysis in the prior art.
In order to solve the above problems, the present invention provides a method for preparing an aluminum-scandium alloy by electrolysis using a scandium-containing fluoride molten salt as a replenishing electrolyte, comprising the steps of: step 1, adding Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 F is mixed to give a mixture, and m 1 Is 2.1 to 3.0 1 1.1 to 1.6 of Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is (1.5-30.6), (20.0-95.0), (3.0-35.0) and (2.0-55.0); heating the mixture, preserving heat and cooling to obtain scandium-containing fluoride molten salt, and marking as molten salt I; according to the weight percentage, in the molten salt I, the content of potassium is 1-10%, the content of scandium is 1-20%, and the weight ratio of scandium to oxygen is more than or equal to 45; step 2, heating and melting the aluminum ingot, and adding molten salt electrolyte powder in batches, wherein the molten salt electrolyte powder comprises m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 Is denoted as molten salt II, and m 2 Is 2.8 to 3.0,m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 The weight ratio of (70.0-90.0), (1.0-10.0), (4.0-9.9), (0.1-6.0); after the fused salt II is melted, adding the fused salt I into the fused salt II as a supplementary electrolyte to form fused salt III, wherein the potassium content in the fused salt III is 0.1-5% and the scandium content is 3-15% in parts by weight, and the weight ratio of scandium to oxygen is more than or equal to 45; electrolysis is then commenced and molten salt I is replenished to molten salt III during electrolysis and the composition of the electrolyzed molten salt during electrolysis is maintained within the composition range of molten salt III.
The feed stock for the preparation of the supplemental electrolyte of the present invention comprises Sc 2 O 3 、m 1 NaF·AlF 3 (molecular ratio m is 2.1-3.0) and n 1 KF·AlF 3 (the molecular ratio n is 1.1 to 1.6) and NH 4 F. Scandium-containing fluoride fused salt powder is prepared through the processes of mixing, heating, heat preservation, cooling and the like. M in the raw material 1 NaF·AlF 3 And n 1 KF·AlF 3 Mainly Sc to dissolve 2 O 3 Promote Sc 2 O 3 Fluorination reaction, etc. NH (NH) 4 F reacts with scandium oxide dissolved in the molten salt to generate scandium-containing fluoride. The scandium fluoride is uniformly distributed in the molten salt prepared in the mode. When the molten salt is added to the electrolytic cell as a supplemental electrolyte, the addition of scandium fluoride is more favorable than the addition of scandium fluoride directlyThe scandium fluoride rapid dissolving and precipitating agent has the characteristics of rapid dissolving, difficult generation of precipitate, high utilization rate of scandium fluoride, low cost and the like. It should be noted that the molten salt I added at high temperature is easily dissolved in the molten salt II to form the molten salt III. The solubility of the aluminum liquid in the molten salt is low, so that the influence on the temperature rise analysis result of the molten salt III can be ignored.
Secondly, the scandium-containing fluoride fused salt is used as a supplementary electrolyte for electrolysis to prepare the aluminum-scandium alloy, and a certain amount of elpasolite is added into the electrolyte, so that the dissolution of oxides can be improved when a higher scandium precipitation proportion is ensured, the current efficiency is improved, the oxide precipitation is reduced, the service life of an electrolytic cell is prolonged, and the like.
In a word, the method for preparing the aluminum-scandium alloy by the electrolyte electrolysis after the improvement of using the scandium-containing fluoride as the supplementary electrolyte can avoid the problems of low dissolving speed, easy generation of precipitate and the like caused by directly adding scandium fluoride under the condition of ensuring higher scandium precipitation ratio, improve the utilization rate of the scandium fluoride and reduce the production cost. Meanwhile, the scandium-containing fluoride fused salt contains a certain amount of potassium cryolite, so that the dissolution of oxides can be improved, the current efficiency can be improved, the oxide precipitation can be reduced, the service life of the electrolytic cell can be prolonged, and the like.
In order to ensure the addition effect of the replenishing electrolyte, the content of the element of the scandium-containing fluoride molten salt (denoted as molten salt I) serving as the replenishing electrolyte needs to be controlled, wherein the content of potassium is 1.0-10.0%, the content of scandium is 1.0-20.0%, and the mass ratio of scandium to oxygen is more than or equal to 45.0.
In order to ensure a higher scandium precipitation ratio in the process of preparing the aluminum-scandium alloy through electrolysis, the content of elements in the molten salt for electrolysis needs to be controlled, and the content of potassium is 0.1-5.0%, the content of scandium is 3.0-15.0%, and the mass ratio of scandium to oxygen is more than or equal to 45.0.
In a preferred embodiment, sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is (24.5-30.6), (20.2-43.2), (20.5-34.5) and (14.5-49.3). This is more advantageous for improving the solubility of scandium oxide and promoting oxygenThe scandium fluorination reaction has a better promotion effect on further improving the utilization rate of scandium. Most preferably, m 1 Is 2.8,n 1 Is 1.1; sc (Sc) 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is 30.6.
The above heating process is favorable for the reaction of scandium oxide and ammonium fluoride, and in a more preferred embodiment, in step 1, the mixture is heated to be molten, and then is subjected to heat preservation and cooling to obtain the scandium-containing fluoride molten salt.
In a preferred embodiment, after the mixture is heated to be molten, the mixture is kept warm under the condition of mechanical stirring, and the temperature keeping time is more than or equal to 0.5h; after cooling, the scandium-containing fluoride fused salt is ground and sieved by a 100-mesh sieve. This can further improve the dispersibility and solubility of scandium fluoride formed by the fluorination reaction in the supplemental electrolyte, and is more advantageous for improving the utilization rate of scandium fluoride when used as the supplemental electrolyte.
In the above electrolysis, it is preferable to use aluminum as a cathode and molten salt III as a molten salt electrolyte for Sc 2 O 3 And Al 2 O 3 Carrying out fused salt electrolysis to obtain an aluminum-scandium alloy; and supplementing the molten salt I into the molten salt III in the electrolysis process, and maintaining the components of the electrolyzed molten salt in the component range of the molten salt III in the electrolysis process. In the electrolysis process, the supplement of the molten salt I can be irregular and continuous, and specifically, the molten salt can be sampled at any time in the electrolysis process and the components can be analyzed so as to maintain the molten salt system in the required range of the molten salt III.
During the specific operation, sc 2 O 3 And Al 2 O 3 Adding into an electrolytic bath in small amount for multiple times or uniformly and continuously, and performing molten salt electrolysis by direct current. In a preferred embodiment, sc 2 O 3 And Al 2 O 3 The weight ratio of the components is 40.0-99.0. The proportion of the scandium and the scandium is controlled in the range, so that the higher scandium precipitation ratio is ensured.
In a specific operation, the cathode is a liquid cathode. The aluminum is added as an aluminum block or liquid aluminum.
In the specific operation process, the graphite rod is used as an anode in the molten salt electrolysis process.
Preferably, the molten salt electrolysis process is a continuous process, and the aluminum-scandium alloy extraction amount accounts for 1.0-50.0 wt% of the total alloy amount.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
(1) Subjecting Sc to 2 O 3 、m NaF·AlF 3 (molecular ratio m is 2.8), n KF AlF 3 (molecular ratio n is 1.1) NH 4 F drying and mixing, the mixture Sc 2 O 3 、m NaF·AlF 3 、n KF·AlF 3 、AlF 3 、NH 4 F mass ratio 30.6, 20.2, 34.5, heating to melt, keeping temperature, cooling, grinding and sieving with a 100-mesh sieve to obtain scandium-containing fluoride molten salt (molten salt I) powder for use as a replenishing electrolyte, wherein the molten salt I has a potassium content of 10.0% by weight, a scandium content of 20.0% by weight, and a scandium-to-oxygen mass ratio of about 45.0.
(2) Heating and melting an aluminum ingot, adding molten salt electrolyte powder (recorded as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is 1.0 3 (molecular ratio m is 2.8), liF, sc 2 O 3 、Al 2 O 3 The molten salt component m NaF AlF 3 、LiF、Sc 2 O 3 、Al 2 O 3 The mass ratio of (1) to (9) is 89.0. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form molten salt for electrolysis (the molten salt is marked as molten salt III), wherein the molten salt III comprises 5.0% of potassium, 13.2% of scandium and 45.0 of scandium to oxygen in mass ratio by weight percent. Thereafter, electrolysis is started, and molten salt I is replenished in an irregular mode and scandium oxide is added in a regular mode in the electrolysis process so as to maintain the composition of the molten salt III to be stable. An aluminum-scandium alloy product with the weight percentage of metal scandium of 5.2 percent and the total weight percentage of aluminum and scandium of more than or equal to 99.0 percent can be obtained at the cathode, and the electrolysis processThe operation is stable. Wherein the utilization rate of scandium-containing fluoride added by the supplement molten salt is 95.0%, and the utilization rate of the oxide is 97.0%.
Example 2
(1) Preparation of scandium-containing fluoride fused salt
(2) Heating and melting an aluminum ingot, and then adding molten salt electrolyte powder (recorded as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is (1.0). Molten salt II composition was the same as in example 1. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form molten salt for electrolysis (the molten salt is marked as molten salt III), wherein the molten salt III comprises 3.0% of potassium, 10.5% of scandium and 45.0 of scandium to oxygen in mass ratio by weight percent. Thereafter, electrolysis is started, and molten salt I is replenished in an irregular mode and scandium oxide is added in a regular mode in the electrolysis process so as to maintain the composition of the molten salt III to be stable. An aluminum-scandium alloy product with the metal scandium content of 4.1 percent by weight and the total weight percent of aluminum and scandium content of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added in the supplement molten salt is 95.0%, and the utilization rate of the oxide is 95.0%.
Example 3
(1) The preparation method of the scandium-containing fluoride molten salt is the same as that of example 1.
(2) Heating and melting an aluminum ingot, and then adding molten salt electrolyte powder (marked as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is 1.0. Molten salt II composition was the same as in example 1. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form molten salt for electrolysis (the molten salt is denoted as molten salt III), wherein the molten salt III comprises 1.0% of potassium, 7.8% of scandium and 22.2% of scandium and oxygen by weight percent. Thereafter, electrolysis is started, and molten salt I is replenished in an irregular mode and scandium oxide is added in a regular mode in the electrolysis process so as to maintain the composition of the molten salt III to be stable. An aluminum-scandium alloy product with the metal scandium weight percentage of 1.9 percent and the total weight percentage of aluminum and scandium of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added in the supplement molten salt is 95.0%, and the utilization rate of oxides is 93.0%.
Example 4
(1) Subjecting Sc to 2 O 3 、m NaF·AlF 3 (molecular ratio m is 2.8), n KF. AlF 3 (molecular ratio n is 1.1) NH 4 F drying and mixing, the mixture Sc 2 O 3 、m NaF·AlF 3 、n KF·AlF 3 、AlF 3 、NH 4 The mass ratio of F is 30.6.
(2) Heating and melting an aluminum ingot, and then adding molten salt electrolyte powder (marked as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is 1.0 3 (molecular ratio m is 2.8), liF, sc 2 O 3 、Al 2 O 3 The molten salt component m NaF AlF 3 、LiF、Sc 2 O 3 、Al 2 O 3 The mass ratio of (1) to (9) is 89.0. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form molten salt for electrolysis (the molten salt is marked as molten salt III), wherein the molten salt III comprises 3.0% of potassium, 10.5% of scandium and 45.0 of scandium to oxygen in mass ratio by weight percent. After that, the electrolysis is started, and the molten salt I is replenished in an irregular way and scandium oxide is added in a regular way in the electrolysis process to maintain the stable composition of the molten salt III. An aluminum-scandium alloy product with the metal scandium weight percentage of 4.2 percent and the total weight percentage of aluminum and scandium of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added by the supplement molten salt is 98.0%, and the utilization rate of the oxide is 96.0%.
Example 5
(1) Subjecting Sc to 2 O 3 、m NaF·AlF 3 (molecular ratio m is 2.8), n KF AlF 3 (molecular ratio n is 1.1) NH 4 F drying and mixing, the mixture Sc 2 O 3 、m NaF·AlF 3 、n KF·AlF 3 、AlF 3 、NH 4 Of FThe mass ratio of the molten salt I to the electrolyte is 24.5.
(2) Heating and melting an aluminum ingot, and then adding molten salt electrolyte powder (marked as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is 1.0 3 (molecular ratio m is 2.8), liF, sc 2 O 3 、Al 2 O 3 The molten salt component m NaF. AlF 3 、LiF、Sc 2 O 3 、Al 2 O 3 89.0. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form molten salt for electrolysis (the molten salt is marked as molten salt III), wherein the molten salt III comprises 1.8% of potassium, 9.3% of scandium and 45.0 of scandium to oxygen in mass ratio by weight percent. Thereafter, electrolysis is started, and molten salt I is replenished in an irregular mode and scandium oxide is added in a regular mode in the electrolysis process so as to maintain the composition of the molten salt III to be stable. An aluminum-scandium alloy product with the metal scandium content of 3.5 percent by weight and the total weight percent of aluminum and scandium content of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added by the supplement molten salt is 94.0%, and the utilization rate of the oxide is 94.0%.
Example 6
(1) Subjecting Sc to 2 O 3 、m NaF·AlF 3 (molecular ratio m is 2.8), n KF AlF 3 (molecular ratio n is 1.1), NH 4 F drying and mixing, the mixture Sc 2 O 3 、m NaF·AlF 3 、n KF·AlF 3 、AlF 3 、NH 4 The mass ratio of F to F is 13.8.
(2) Heating an aluminum ingotAdding molten salt electrolyte powder (marked as molten salt II) in batches after melting, wherein the mass ratio of the aluminum ingot to the molten salt is 1.0 3 (molecular ratio m is 2.8), liF, sc 2 O 3 、Al 2 O 3 The molten salt component m NaF AlF 3 、LiF、Sc 2 O 3 、Al 2 O 3 The mass ratio of (1) to (9) is 89.0. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form the molten salt for electrolysis (the molten salt is denoted as the molten salt III), wherein the molten salt III comprises 1.2% of potassium, 7.2% of scandium and 45.0 of scandium to oxygen in mass ratio by weight percent. After that, the electrolysis is started, and the molten salt I is replenished in an irregular way and scandium oxide is added in a regular way in the electrolysis process to maintain the stable composition of the molten salt III. An aluminum-scandium alloy product with the metal scandium content of 2.3 percent by weight and the total weight percent of aluminum and scandium of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added by the supplement molten salt is 93.0%, and the utilization rate of the oxide is 92.0%.
Comparative example 1
(1) Compared with the example 1, NH is not added in the preparation process of the scandium-containing fluoride molten salt 4 F, preparing the molten salt I, wherein the molten salt I comprises 10.0% of potassium, 20.0% of scandium and a mass ratio of scandium to oxygen of about 45.0.
(2) Heating and melting an aluminum ingot, and then adding molten salt electrolyte powder (marked as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is 1.0. The molten salt electrolyte powder composition was the same as in example 1. After the molten salt II is completely melted, adding the molten salt I to the molten salt II in batches to form molten salt for electrolysis (the molten salt is marked as molten salt III), wherein the molten salt III comprises 3.0% of potassium, 10.5% of scandium and 45.0 of scandium to oxygen in mass ratio by weight percent. After that, the electrolysis is started, and the molten salt I is replenished in an irregular way and scandium oxide is added in a regular way in the electrolysis process to maintain the stable composition of the molten salt III. An aluminum-scandium alloy product with the metal scandium weight percentage of 4.2 percent and the total weight percentage of aluminum and scandium of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added in the supplement molten salt is 91.0%, and the utilization rate of oxides is 95.0%.
Comparative example 2
This example directly uses scandium fluoride as the supplemental electrolyte.
Heating and melting an aluminum ingot, and then adding molten salt electrolyte powder (recorded as molten salt II) in batches, wherein the mass ratio of the aluminum ingot to the molten salt is (1.0). The molten salt electrolyte powder components were the same as in example 1. After the molten salt II is completely melted, adding scandium fluoride to the molten salt II in batches to form molten salt for electrolysis (the molten salt is marked as molten salt III), wherein the content of scandium is 12.5% in the molten salt III in percentage by weight, and the mass ratio of scandium to oxygen is 45.0. Thereafter, electrolysis is started, and molten salt I is replenished in an irregular mode and scandium oxide is added in a regular mode in the electrolysis process so as to maintain the composition of the molten salt III to be stable. An aluminum-scandium alloy product with the metal scandium weight percentage content of 4.0 percent and the total weight percentage content of aluminum and scandium of more than or equal to 99.0 percent can be obtained at the cathode, and the operation of the electrolysis process is stable. Wherein the utilization rate of scandium-containing fluoride added by the supplement molten salt is 88.0%, and the utilization rate of the oxide is 90.0%.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the aluminum-scandium alloy prepared by adopting scandium-containing fluoride molten salt as electrolyte after improvement of supplementary electrolyte shows higher scandium fluoride utilization rate and oxide utilization rate. Comparing examples 2 and 4 with comparative example 1, it is found that when the content of potassium and scandium in the molten salt is the same and the scandium-containing fluoride molten salt is used as a supplementary electrolyte, the larger the scandium-to-oxygen mass ratio is, the higher the scandium fluoride utilization ratio is. Compared with the comparative example 2, the comparison of the example 2 shows that when the scandium fluoride content in the molten salt is equivalent, the scandium content in the prepared aluminum-scandium alloy is similar, but the fluoride utilization rate and the oxide utilization rate are higher than those of the aluminum-scandium alloy prepared by directly adding scandium fluoride. This is because scandium fluoride has a slow dissolution rate, and a part of scandium fluoride forms refractory precipitates with the oxide in the process, which results in a decrease in the utilization rate of the oxide. Comparative example 1 in comparison with comparative example 2, it was found that the utilization of the scandium-containing compound was higher than that of the direct addition of scandium fluoride, even if only the oxide was added to the fluoride molten salt and then the molten salt was added to the electrolyte in the form of a supplemental electrolyte. Comparative examples 1 to 3 found that the oxide utilization rate was gradually increased as the potassium content in the molten salt for electrolysis was increased.
In a word, the method for preparing the aluminum-scandium alloy by the electrolyte electrolysis after the improvement of using the scandium-containing fluoride as the supplementary electrolyte can avoid the problems of low dissolving speed, easy generation of precipitate and the like caused by directly adding scandium fluoride under the condition of ensuring higher scandium precipitation ratio, improve the utilization rate of the scandium fluoride and the utilization rate of the oxide, and reduce the production cost. Meanwhile, the scandium-containing fluoride molten salt contains a certain amount of elpasolite, and when the scandium-containing fluoride molten salt is used as a supplementary electrolyte, the scandium-containing fluoride molten salt can improve the dissolution of oxides, is beneficial to improving the utilization rate of the oxides, further reduces the precipitation amount, prolongs the service life of an electrolytic cell, and the like.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A method for preparing an aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as a supplementary electrolyte is characterized by comprising the following steps:
step 1, adding Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 F is mixed to give a mixture, and m 1 Is 2.1 to 3.0 1 1.1 to 1.6 of Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is (1.5-30.6), (20.0-95.0), (3.0-35.0) and (2.0-55.0); heating the mixture, preserving heat and cooling to obtain scandium-containing fluoride molten salt, and marking as molten salt I; according to the weight percentage, in the molten salt I, the content of potassium is 1-10%, the content of scandium is 1-20%, and the weight ratio of scandium to oxygen is more than or equal to 45;
step 2, heating and melting the aluminum ingot, and adding the aluminum ingot in batchesFeeding a molten salt electrolyte powder comprising m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 Is denoted as molten salt II, and m 2 Is 2.8 to 3.0,m 2 NaF·AlF 3 、LiF、Sc 2 O 3 And Al 2 O 3 The weight ratio of (70.0-90.0), (1.0-10.0), (4.0-9.9) and (0.1-6.0); after the fused salt II is melted, adding the fused salt I into the fused salt II to serve as a supplementary electrolyte to form fused salt III, wherein the fused salt III comprises 0.1-5% of potassium, 3-15% of scandium and more than or equal to 45% of scandium and oxygen by weight; electrolysis is then commenced and the molten salt III is replenished with molten salt I during electrolysis and the composition of the electrolyzed molten salt during electrolysis is maintained within the composition range of the molten salt III.
2. The method of claim 1, wherein Sc 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is (24.5-30.6), (20.2-43.2), (20.5-34.5) and (14.5-49.3).
3. Method according to claim 1 or 2, characterized in that m 1 Is 2.8,n 1 Is 1.1; sc (Sc) 2 O 3 、m 1 NaF·AlF 3 、n 1 KF·AlF 3 And NH 4 The weight ratio of F is 30.6.
4. The method according to claim 1 or 2, wherein in the step 1, the mixture is heated to be molten, and then is subjected to heat preservation and cooling to obtain the scandium-containing fluoride molten salt.
5. The method as claimed in claim 4, wherein the mixture is heated to be molten and then is kept warm under the condition of mechanical stirring for more than or equal to 0.5h; after cooling, the scandium-containing fluoride fused salt is ground and sieved by a 100-mesh sieve.
6. The method according to claim 1 or 2, wherein in step 2, the electrolysis process uses aluminum as a cathode, the molten salt III as a molten salt electrolyte, and Sc 2 O 3 And Al 2 O 3 Carrying out fused salt electrolysis to obtain the aluminum-scandium alloy; and supplementing the molten salt I to the molten salt III during the electrolysis and maintaining the composition of the electrolyzed molten salt in the composition range of the molten salt III during the electrolysis.
7. The method of claim 6, wherein Sc 2 O 3 And Al 2 O 3 The weight ratio of the components is 40.0-99.0.
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