Method for producing aluminum alloys

Abstract

The invention relates to production of alloys based on aluminum. A method is proposed for producing aluminum-based alloys by electrolysis, according to which low-consumable anode of aluminum pot is used as a source of alloying elements. At the same time, in order to optimize master alloy consumption, one of the following options is chosen: dissolution of alloying elements from slightly soluble anodes; adding oxides and/or fluorides and/or carbonates of alloying elements to electrolyte melt of aluminum pot; simultaneous dissolution of alloying elements from slightly soluble anodes with addition of oxides and/or fluorides and/or carbonates of alloying elements to electrolyte melt of aluminum pot. The method comprises the following stages: introducing alloying elements into molten cathode aluminum by dissolving them in electrolyte melt of aluminum pot from low-consumable anode and/or by adding oxides/and fluorides and/or carbonates of alloying elements into electrolyte melt of aluminum pot; reduction of alloying elements introduced into electrolyte melt of aluminum pot on molten cathode aluminum to form the base for aluminum alloys; determining percentage of elements in the base for aluminum alloys; and bringing alloys to a given composition by adding alloying elements to the base for aluminum alloys in the required amount. The result is multicomponent aluminum alloys of a given composition with introduction of alloying admixtures in the process of aluminum production by electrolysis, and then the alloy is brought to a predetermined composition, providing simplification of technology and control, reducing master alloy consumption which leads to lower cost of aluminum alloy production.

Claims

1. A method of aluminum-based alloys production by electrolysis, according to which a low-consumable anode of an aluminum pot is used as a source of alloying elements characterized in that the method includes the following stages: introducing the alloying elements into an electrolyte melt of the aluminum pot by dissolving the alloying elements simultaneously from the low-consumable anode and from at least one of oxides, fluorides, and carbonates of the alloying elements added to the electrolyte melt of the aluminum pot, reducing the alloying elements introduced to the electrolyte melt of the aluminum pot on a molten cathode aluminum, obtaining a base for the aluminum-based alloys, determining a percentage of the alloying elements in the base for the aluminum-based alloys, and bringing the aluminum-based alloys to a given composition by adding the alloying elements in a form of master alloys to the base for the aluminum-based alloys in the required amount, wherein introducing the alloying elements into the electrolyte melt is carried out periodically at a feed rate that ensures constant concentration of each of the alloying elements in the electrolyte melt and in the aluminum-based alloy.

2. The method according to claim 1, wherein an oxide-fluoride melt is used as an electrolyte for the electrolyte melt.

3. The method according to claim 1, wherein a metal alloy is used as the low-consumable anode.

4. The method according to claim 1, wherein determining the percentage of the alloying elements in the base for the aluminum-based alloy is carried out by analytical methods.

5. The method according to claim 1, wherein the feed rate is adjusted according to an analysis of concentrations of the alloying elements in at least one of the electrolyte melt and the aluminum-based alloy, wherein: with a decrease in concentration of at least one of the electrolyte melt and the aluminum based alloy, the feed rate is increased, and with an increase in concentration of at least one of the electrolyte melt and the aluminum-based alloy, the feed rate is reduced.

Description

SHORT DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a diagram of the most well-known and widely used process for producing aluminum alloys from electrolytic aluminum.

(2) A5, A7 or A85 aluminum grades are obtained in pot with carbon anodes. The resulting aluminum is pumped out of the pot, poured into alloying furnace, where aluminum is mixed with master alloys, which contain alloying admixtures with X1, X2, X3, . . . concentrations. Type and amount of master alloy is determined depending on target composition of aluminum alloy.

(3) FIG. 2 shows a diagram of the first option of the proposed method for production of aluminum alloys.

(4) We are talking about the option of introducing alloying elements into molten cathode aluminum by dissolving them in molten electrolyte of aluminum pot from low-consumable anode. The diagram differs from the diagram in FIG. 1 by the fact that during electrolysis, instead of carbon anodes, low-consumable anodes are used, from which in the course of electrolysis alloying admixtures contained in the anode enter the aluminum. The diagram of the method in FIG. 2 differs from the method in the prototype by presence of the stage for measuring Y1, Y2, Y3, . . . concentrations of alloying admixtures in the resulting aluminum (base for aluminum alloys) and the stage of bringing the base to a predetermined alloy composition. At the last stage, the base for aluminum alloys is poured into alloying furnace and then mixed with master alloys containing alloying admixtures with X1, X2, X3, . . . concentrations. Type and amount of master alloy are determined depending on the target composition of aluminum alloy, taking into account difference between the target concentration of each alloying element in aluminum alloy and its concentration in the base for aluminum alloy.

(5) FIG. 3 shows a diagram of another option of the proposed method for producing aluminum alloys.

(6) We are talking about the option of introducing alloying elements into molten cathode aluminum by dissolving them in electrolyte melt of aluminum pot from low-consumable anode and by adding oxides and/or fluorides and/or carbonates of alloying elements into electrolyte melt of aluminum pot. The diagram differs from the diagram in FIG. 2 by the fact that during electrolysis, oxides/fluorides or carbonates of alloying elements are introduced into electrolyte of aluminum pot, which are then transferred to the base for aluminum alloys together with alloying elements from a low-consumable anode. In this case, additional operations are the measurement of concentration of alloying elements in electrolyte and the adjustment of feed rate of oxides and/or fluorides and/or carbonates of alloying elements to maintain their stable concentration in electrolyte and the base for aluminum alloys. The rest of the scheme is similar to the scheme in FIG. 2

DETAILED DESCRIPTION OF THE ESSENCE OF THE INVENTION

(7) In contrast to the known method for producing alloys, the diagram of which is shown in FIG. 1, the proposed method involves obtaining alloys in several stages. Options of the proposed method shown in FIG. 2 and FIG. 3 allow to obtain the desired concentration of alloying elements as follows: at the first stage, in the pot the alloying elements are transferred from slightly soluble anode to aluminum cathode with Y1, Y2, Y3, . . . concentrations in aluminum; at the second stage, Y1, Y2, Y3, . . . concentrations are measured, required weights of alloying elements are calculated to adjust to the target concentration, and the calculated weights of alloying elements (both introduced into the aluminum during electrolysis and others needed to obtain alloys of a given composition) are added to the resulting aluminum in alloying furnace.

(8) Compared with the existing method of aluminum alloys production by alloying primary aluminum with master alloys, the proposed method makes it possible to reduce involvement of master alloy containing alloying elements. Reduction of master alloy consumption for production of aluminum alloy by partially alloying aluminum by dissolving anode material and/or adding alloying element compounds to aluminum pot will reduce the cost of production of aluminum alloy, since the cost per weight unit of alloying element included in anode or added compounds of alloying elements is significantly lower than the cost per weight unit of alloying element in master alloy. For example, the cost per weight unit of silicon in quartz sand is 2.5-3 times less than the cost of silicon in AlSi50 master alloy (as of 2015).

(9) In contrast to the analogs and the prototype, any of alternative options of the proposed method for producing aluminum alloys provides for determination of percentage of elements in the base for aluminum alloys and further bringing of alloys to a given composition by adding alloying elements to the base. This ensures production of aluminum alloys of stable and desired composition. In addition, the choice of anode composition is simplified, since there is no need to achieve a compromise between anode wear rate and the need to add to anode composition the alloying elements that increase anode corrosion rate.

(10) This allows to use the most resistant anodes and, consequently, reduce their consumption. Also, due to inclusion in the aluminum alloys production method of the stage of bringing alloys to a given composition, the need for strict control over parameters of electrolysis process is eliminated, since in the event of a change in the composition of the base of aluminum alloy due to possible technological deviations, the amount of alloying elements added to the alloy base will be adjusted accordingly when the alloy is brought to a given composition. This simplifies electrolysis process.

(11) Thus, the task of reduction of the cost of aluminum alloy production is solved by reducing consumption of master alloy containing alloying elements and reducing the cost of production of base for aluminum alloy.

(12) Comparison of the proposed solution with the closest analogue revealed the following differences.

(13) In one option of implementation of the proposed method, the feed oxides/fluorides/carbonates of alloying elements into aluminum pot is used as a source of alloying elements. Aluminum alloy is received in several stages: introduction into molten cathode aluminum of alloying elements by dissolving them in electrolyte melt of aluminum pot from low-consumable anode and/or adding oxides/fluorides/carbonates of alloying elements to electrolyte melt of aluminum pot, reduction of alloying elements, introduced into electrolyte melt of aluminum pot on molten cathode aluminum, obtaining the base for aluminum alloys, determination of percentage of elements in the base for aluminum alloys, and bringing alloys to a given composition by adding alloying elements to the base for aluminum alloys in the required amount.

(14) In one option of the method of aluminum alloys production, i.e. when oxides and/or fluorides and/or carbonates of alloying elements are added to electrolyte melt of aluminum pot, chemical compounds of several different elements are added to electrolyte melt, which ensures production of multicomponent alloys, in contrast to the known methods for producing aluminum alloys by adding oxides of only one of alloying elements into electrolyte melt. In addition, unlike the analogs and the prototype, by controlling concentration of admixtures in electrolyte and aluminum, a more stable concentration of added alloying elements in the base for aluminum alloys is provided for a long time.

(15) In another option of the method of aluminum alloys production, i.e. while simultaneously adding oxides and/or fluorides and/or carbonates of alloying elements to electrolyte melt of aluminum pot, anode consumption decreases as compared to the prototype, since concentration gradient of elements in the electrolyte volume and anodic layer of the electrolyte is decreased.

(16) Combination of features that characterize the proposed method allows to obtain multicomponent alloys of a given and stable composition, reduce consumption of master alloy containing alloying elements, and also to reduce consumption of slightly soluble anodes and simplify the electrolysis technology and, due to this technical effect obtained with the help of the claimed method, to produce aluminum alloys at lower cost as compared to the known technology.

(17) Implementation of the Invention

(18) The proposed method is implemented as follows.

Example 1

Dissolution of Alloying Elements from Slightly Soluble Anodes

(19) For testing the proposed method of aluminum alloys production, at the first and the second stages alloys were prepared using aluminum electrolysis in the pot, current 3 kA. A low-consumable anode of the following composition (wt. %) was used: Fe—65, Cu—35, and the electrolyte used was of the following composition (wt. %): NaF—43, CaF.sub.2—5, Al.sub.2O.sub.3—5, AlF.sub.3—47. At the next stage, periodically taken cathode aluminum samples were sent to optical emission analysis, the results of which were used to calculate master alloy weight to bring the alloy base to the required chemical composition of 8011 aluminum alloy containing the following elements (in wt. %): Silicon: 0.5-0.9 Iron: 0.6-1.0 Copper: up to 0.1 Manganese: ≤0.2 Magnesium: ≤0.05 Chrome: ≤0.05 Zinc: ≤0.1 Titanium: ≤0.08 Other admixtures in total: ≤0.15%
Calculation of master alloy consumption for the proposed method of aluminum alloy production is given in Table 1. Pouring was carried out once every three days. After measuring iron and silicon concentration in the aluminum on ARL optical emission spectrometer, we calculated AlFe80 and AlSi50 master alloy weight and brought the alloy to the composition of 8011 aluminum alloy by adding the calculated amount of master alloys to the base.

(20) TABLE-US-00001 TABLE 1 8011 alloy production stage Time after start Alloy bays production AlFe80 AlSi50 of the stage master alloy master alloy experiment, Weight consumption, consumption, days Al, kg Fe, % Si, % kg kg 50 68.1 0.617 0.05 0.165 0.890 53 68.5 0.611 0.05 0.172 0.895 56 68.2 0.604 0.05 0.177 0.891 59 69.5 0.682 0.05 0.112 0.908 62 65.4 0.638 0.05 0.142 0.855 65 69.2 0.611 0.05 0.173 0.904 68 67.3 0.601 0.05 0.177 0.879 71 66.8 0.598 0.05 0.178 0.873 74 68.7 0.596 0.05 0.185 0.898

(21) Average consumption of AlFe80 master alloy according to the proposed method was 2.4 kg per ton of aluminum.

(22) In the production of 8011 alloy using the known method (alloying of graded aluminum in alloying furnace), when using A7 aluminum as a raw material, consumption of AlFe80 master alloy is 9.4 kg per ton of aluminum.

(23) Thus, as a result of use of the proposed method, aluminum alloy with lower consumption of AlFe80 master alloy was obtained as compared to the known method for producing alloy by adding AlFe80 master alloy to graded electrolytic aluminum, namely, saving of AlFe80 master alloy in production of 8011 aluminum alloy was 7 kg/t.

(24) Consumption of AlSi50master alloy in the proposed and known method is the same. In addition, it can be seen that it is impossible to produce 8011 alloy at the first and the second stages, i.e. the method of the prototype does not allow to solve the technical problem.

Example 2

Simultaneous Dissolution of Alloying Elements From Slightly Soluble Anodes and Adding Oxides and/or Fluorides and/or Carbonates of Alloying Elements to Electrolyte Melt of Aluminum Pot

(25) To test the proposed method of aluminum alloys production, at the first and the second stages the base for alloys was obtained by aluminum electrolysis in the pot, current 3 kA. In this case, a slightly soluble anode of the following composition (wt. %) was used: Fe—65, Cu—35, and the electrolyte used was of the following composition (wt. %): NaF—43, CaF.sub.2—5, Al.sub.2O.sub.3—5, AlF.sub.3—47. Silicon oxide was fed into the pot, flow rate 340 grams per day.

(26) Electrolyte and aluminum samples were analyzed daily for silicon content with the help of PANalytical MagiX X-ray fluorescence spectrometer and ARL optical emission spectrometer, which was maintained at 800 ppm and 8000 ppm, respectively. Since these values were stable during the electrolysis, and silicon concentration in the base for aluminum alloy corresponded to its target concentration in 8011 alloy, consumption of silicon oxide in the electrolysis process was not adjusted.

(27) At the next stage, samples of periodically extracted cathode aluminum were sent for optical emission analysis. Pouring was done once every three days. After measuring iron and silicon concentration in aluminum, we calculated AlFe80 master alloy weight and brought the alloy to the composition of 8011 aluminum alloy by adding the calculated amount of master alloy to the base. Calculation of master alloy consumption in this option of the proposed method of producing aluminum alloy is shown in Table 2.

(28) TABLE-US-00002 TABLE 2 8011 alloy production Time after start stage of the Alloy base production stage AlFe80 master alloy experiment, days Al weight, kg Fe, wt. % consumption, kg 80 67.4 0.589 0.187 83 68.5 0.594 0.186 86 68.2 0.583 0.195 89 69.1 0.571 0.208 92 66.4 0.579 0.193 95 68.3 0.567 0.209 98 68.6 0.551 0.224 101 69.7 0.548 0.230 104 66.4 0.549 0.218

(29) As a result of application of the proposed method, aluminum alloy was obtained with Fe content in the range of 0.62%-0.72%, and Si, in the range of 0.78%-0.84%. Average consumption of AlFe80 master alloy in the proposed method was 3 kg per ton of aluminum.

(30) As a result of application of the proposed method, aluminum alloy was obtained with lower master alloys consumption as compared to the known method of alloy production by adding master alloys to grade electrolytic aluminum, namely, saving of AlFe80 master alloy in production of 8011 aluminum alloy was 7.2 kg/t, and saving of master alloy AlSi50 was 13 kg/t. In addition, it can be seen that it is impossible to produce 8011 alloy at the first and the second stages, i.e. the method of the prototype does not allow to solve the technical problem.

(31) Example 2 can also be an example of implementation of the second option of the proposed method of aluminum alloys production, since when using a carbon anode instead of a low-consumable anode in the electrolysis process (at the first and the second stages of the process), silicon from silicon oxide added to electrolyte will be added to the base for aluminum alloy and iron concentration in the base will correspond to graded aluminum. Therefore, in this option of the proposed method of 8011 aluminum alloy production, only saving of AlSi50 master alloy in the amount of 13 kg/t will be achieved. To save AlFe80 master alloy, it is necessary to add iron oxides/fluorides or carbonates to electrolyte at the stage of production of the base for aluminum alloy.

(32) The above individual implementation options of the invention are not the only possible. Various modifications and improvements are allowed, without departing from the scope of the invention as defined by the claims.