RU2652905C1 - Method of obtaining aluminium-silicon alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to non-ferrous metallurgy, in particular to electrolytic production of aluminium, and can be used in the preparation of aluminum alloys with a high content of silicon (silumins) of the grades AK5M2, AK7, AK7pch, AK8M3, AK9, AK12 and others. Method of obtaining aluminium-silicon alloys comprises loading a charge mixture into an electrolysis cell and electrolysis in a molten electrolyte, wherein the charge mixture used is microsilica, which is loaded into aluminium containers in an amount corresponding to silicon content in the aluminium alloy of 2 to 10 wt%, the containers are preheated to a temperature of 300 to 400 °C, and then introduced into the electrolysis cell under the electrolyte layer, the electrolysis being carried out by continuously circulating the melt in the electrolyte at a temperature of 940 to 950 °C and voltage on the electrolysis cell from 4.25 to 4.30 V.

EFFECT: method makes it possible to obtain aluminium-silicon alloys directly in an electrolysis cell, efficiently use wastes of silicon production without dusting during loading, reduce power consumption due to the direct addition of microsilica into the melt, and also makes it possible to control the loading of charge materials depending on the specified silicon content in the alloy.

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Description

The invention relates to the field of metallurgy of non-ferrous metals, in particular to the electrolytic production of aluminum, and can be used in the preparation of aluminum alloys with a high content of silicon (silumin) grades AK5M2, AK7, AK7pch, AK8M3, AK9, AK12 and others.

A known method for producing cast aluminum-silicon alloys (RF patent No. 2322522, publ. 04/20/2008). The essence of the method consists in the fact that primary silumin is used as a charge, sand-clay casting return, chill casting return with a ratio of components, wt.%, Respectively (1 ÷ 1.6) :( 2.3 ÷ 3.6) :( 2 ÷ 2.6). Smelting is carried out according to the following technology: melting the mixture containing primary silumin and returning the sand-clay casting, overheating the melt at a temperature of 1000 ° C to 1050 ° C, cooling the melt by introducing from 60 to 70% of the mass return of the chill casting, subsequent loading at temperature from 825 ° C to 875 ° C of the remainder of the return of the chill casting, refining and casting.

The disadvantages of the method are the high energy costs of heating the mixture and significant losses of raw materials during loading operations, as well as low yield.

A known method of producing cast aluminum alloys from recycled materials (RF patent No. 2351670, publ. 10.04.2009), including the melting of the main charge, overheating of the melt at a temperature of from 990 ° C to 1000 ° C, holding the melt at the temperature of overheating, cooling the melt loading into it a solid metal charge: the first portion is introduced at an overheating temperature and ranges from 8 to 10% by weight of the main charge; the second portion is introduced at a temperature of from 860 ° C to 870 ° C and makes up from 4 to 6% of the mass of the main charge, the third portion is introduced at a temperature of from 750 ° C to 760 ° C and makes up from 4 to 6% of the mass of the main charge, refining and melt casting.

The disadvantages of the method are the multi-stage process and high energy costs, since the method involves high temperatures of overheating, and the resulting alloy has a low level of mechanical properties.

A known method of producing silumins (RF patent No. 2094515, publ. 10/27/1997), including the melting of aluminum, the introduction into the melt of slag production of aluminum-based alloys or sintering, resulting from the casting of aluminum-silicon alloys, as well as the introduction of quartz sand and hydrogen melt.

The disadvantages of the method are the complexity and low efficiency of the process, as well as a high level of impurities in the resulting alloys.

A known method of remelting silicon dusty waste in solid-liquid aluminum (RF patent No. 2180013, publ. 02.27.2002), comprising melting an aluminum melt, introducing crystalline lumpy silicon at a temperature of 1350 ° C to 1650 ° C with simultaneous bubbling and cooling of the melt inert gas, introducing pulverized crystalline silicon mixed with wet aluminum chips, a stream of inert gas in an amount of from 5 to 16% of the total weight of the silicon introduced into the melt.

The disadvantages of the method are low efficiency due to incomplete dissolution of pulverized silicon, as well as a high level of danger when introducing silicon wastes into the melt with wet aluminum chips.

A known method of producing aluminum-silicon alloys in aluminum electrolysis cells (RF patent No. 2556188, publ. 07/10/2015), adopted as a prototype, including preparation by mechanical activation of a charge mixture containing aluminosilicate raw materials, including spent hearth, and a reverse electrolyte of an aluminum electrolyzer and alumina, loading the charge mixture into the cell, followed by electrolysis in the molten electrolyte.

The disadvantages of the method are the high energy costs necessary to implement the processes of interaction of all charge components with the melt, the need for overheating of the melt, as well as the high yield of coal foam, which when heated is accompanied by carburization of the aluminum electrolyte electrolyte and the formation of cryolite-alumina deposits on the bottom.

The technical result of the invention is to reduce energy costs in obtaining aluminum-silicon alloys, simplifying the process, as well as involving in the production of aluminum alloys waste from silicon production (microsilicon).

The technical result is achieved by using microsilica as a charge mixture, which is loaded into aluminum containers in an amount corresponding to the silicon content in the aluminum alloy from 2 to 10 wt. %, the containers are preheated to a temperature of 300 ° C to 400 ° C, and then introduced into the electrolyzer under the electrolyte layer, while the electrolysis is carried out with continuous circulation of the melt in the electrolyte at a temperature of from 940 ° C to 950 ° C and a voltage of 4.25 to 4.30 V.

The method is as follows. Microsilica is loaded into aluminum tube containers with such an estimated amount to reach a predetermined level of silicon in aluminum (from 2% to 10%), taking into account the absorption of silicon from 91% to 92%. Then the containers, compressed at the ends on both sides, are placed in a dispenser of a standard tuyere and heated over a completed window in a cryolite-alumina crust to a temperature of 300 to 400 ° C. After heating, the containers are introduced into the melt using a standard tuyere into specially prepared “windows” in the crust of the electrolysis bath. Input takes place at a temperature of 940 to 950 ° C and a voltage of 4.25 to 4.30 V. Aluminum containers are melted in a metal layer in 5-8 seconds, while particles of microsilicon under the action of metal moving in the bath at a speed of 15 to 20 cm / sec, float and fall into the aluminum-electrolyte interface, where electrochemical reduction takes place.

The use of an electrolyzer to obtain aluminum-silicon alloys ensures a stable metal temperature, while liquid sodium fluoroaluminates have a modifying and refining effect on the alloy, and the continuous circulation of the metal in the electrolyzer due to the dynamic melt flow under the influence of electromagnetic forces creates the conditions for complete dissolution of microsilica without its ascent on the surface of the electrolyte.

The calculated values between the silicon and aluminum contents and their limiting amount are determined in each specific case, depending on the given brand of silumin. If the content of impurities is exceeded under conditions of electrolytic production of aluminum, various options for adjusting the chemical composition are possible.

To prepare the aluminum alloy, a group of 2 electrolyzers is selected. A7E grade primary aluminum melt obtained in electrolysis cells for aluminum production is used as a base. The amount of metal in the electrolyzer is from 6 to 6.5 tons.

The method is illustrated by the following examples.

Example 1. In the electrolytic cell brand S8BM in the presence of 6500 kg of cathode aluminum, 780 kg of microsilica was introduced by the proposed method. The input took place at a temperature of 940 ° C and a voltage of 4.25 V. After measuring the metal level, metal samples were taken to determine the chemical composition. It takes 60 minutes to prepare the aluminum alloy. After dissolution of the silicon raw material during the electrolytic process, an aluminum-silicon alloy with a Si content of 5.02 wt. % corresponding to the brand AK7.

The percentage of absorption of silicon was 93.2%.

Example 2. The method is carried out identically to example 1. In the electrolytic cell with cathodic aluminum weighing 6000 kg, 1500 kg of microsilica were introduced by the proposed method. Input takes place at a temperature of 950 ° C and a voltage of 4.25 V. After dissolving the silicon raw materials during the electrolytic process, an aluminum-silicon alloy with a Si content of 10.1 wt. %

The percentage of absorption of silicon was 92.5%.

Example 3. The method is carried out identically to example 1. In the electrolytic cell with cathodic aluminum weighing 6000 kg, 1500 kg of microsilica were introduced by the proposed method. Input takes place at a temperature of 940 ° C and a voltage of 4.30 V. After dissolving the silicon raw materials during the electrolytic process, an aluminum-silicon alloy with a Si content of 10.06 wt. %

The percentage of absorption of silicon was 93.6%.

Example 4. The method is carried out identically to example 1. In the electrolytic cell with cathode aluminum weighing 6000 kg, 1500 kg of microsilica were introduced by the proposed method. The input takes place at a temperature of 950 ° C and a voltage of 4.30 V. After dissolving the silicon raw materials during the electrolytic process, an aluminum-silicon alloy with a Si content of 9.9 wt. %

The percentage of absorption of silicon was 92.4%.

Example 5. The method is carried out identically to example 1. In the electrolyzer brand S8BM in the presence of 6500 kg of cathode aluminum, 780 kg of microsilica were introduced by the proposed method. The input took place at a temperature of 880 ° C and a voltage of 4.1 V. After dissolving the silicon raw materials during the electrolytic process, an aluminum-silicon alloy with a Si content of 4.1 wt. %

The percentage of absorption of silicon was 73.4%.

Example 6. The method is carried out identically to example 1. In the electrolytic cell with cathodic aluminum weighing 6000 kg, 1500 kg of microsilica were introduced by the proposed method. Input takes place at a temperature of 1030 ° C and a voltage of 4.4 V. After dissolving the silicon raw materials during the electrolytic process, an aluminum-silicon alloy with a Si content of 8.0 wt. %

The percent absorption of silicon was 70.1%.

The advantages of the method are the production of aluminum-silicon alloys directly in the cell, the reduction of energy consumption in the production of alloys in foundries, the efficient use of silicon waste, the absence of dusting during loading, and the ability to control the charge of charge materials depending on the specified silicon content in the alloy. The use of direct input microsilica technology provides an increased service life by reducing the number of cracks and pores in the cathode lining during the reaction of microsilicon with carbon on the bottom of the electrolysis bath.

Claims (1)

A method of producing aluminum-silicon alloys, including loading the charge mixture into the electrolyzer and electrolysis in the molten electrolyte, characterized in that microsilica is used as the charge mixture, which is loaded into aluminum containers in an amount corresponding to the silicon content in the aluminum alloy from 2 to 10 wt. %, the containers are preheated to a temperature of 300 to 400 ° C, and then introduced into the electrolyzer under the electrolyte layer, while the electrolysis is carried out with continuous melt circulation in the electrolyte at temperature from 940 to 950 ° C and voltage across the cell from 4.25 to 4.30 V.