RU2016110C1 - Method of reprocessing of silicon waste - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: silicon of fraction (0.1-20 mm) is added on the surface of aluminium melt at 670-680 C following by heating of melt up to 720-750 C at the rate 2.5-4 degree/min. Method is used at silicon waste reprocessing. EFFECT: improved method of enzyme preparing. 1 tbl

Description

 The invention relates to ferrous metallurgy, in particular to a technology for processing silicon waste in the production of aluminum-silicon alloys.

 It is known that to obtain aluminum-silicon alloys, crystalline silicon fractions of 20-50 mm are used, and the pulverized and fine fractions after crushing and screening are sent to the dump, which leads to a decrease in the degree of use of silicon in the production of the above alloys (M. B. Altman and others. Melting and casting of light alloys. M., Metallurgy, 1969, p. 270).

The closest to the proposed invention in terms of technical nature and the achieved result is a method of processing silicon dust fraction (0.3-1.0 mm), formed from crushing and transportation of crystalline silicon, including the introduction of the specified silicon fraction into molten and heated to a temperature of 850-900 ^C (above the melting temperature 190-240 ° ^C) in aluminum alloys as an additive alyuminievokremnievyh by injecting it under the level of the melt with inert gas or immersing in compressed form with the weighting agent and fluxes (Auth. Binding. N 1,124,599, cl. C 22 C, 1983).

 The disadvantage of this method is the low digestibility of pulverized silicon, which is only 60%. A silicon fraction of less than 0.3 mm is not absorbed, and more than 1 mm is partially absorbed (less than 60%). Low digestibility significantly increases the preparation time of the alloy, since in order to achieve the required concentration of silicon in the resulting alloy, it is necessary to introduce a larger amount of pulverized silicon (1.6 times more). An increase in the duration of smelting leads to increased losses of metal (aluminum and silicon, additionally) from the oxidation of the melt.

 The aim of the invention is to increase the digestibility of silicon and reduce metal loss from oxidation of the melt by reducing the duration of the smelting.

The goal is achieved in that the silicon recycling method comprising administering to silicon dust and the fine fraction (0-20 mm) in the molten aluminum, with stirring, silicon these fractions are administered to the surface of the melt, heated to a temperature of 10-20 ° C above ^the temperature melting, and after introducing the silicon melt Temperature was raised to 720-750 ^{° C} at a rate ^of 2.5-4 C / min. Upon receipt of hypereutectic aluminum-silicon alloys, silicon wastes are introduced into the silumin melt.

Introduction silicon waste dust and small fractions (0-20 mm) on the surface of the melt, heated to a temperature of 10-20 ° C above ^the melting temperature, followed by raising the melt temperature to 720-750 ^C at a certain speed provides increased digestibility and reduced silicon metal losses from oxidation of the melt by reducing the duration of the smelting.

Assimilation of silicon dust and small fractions (0-20 mm) increases due to the intensive mixing these fractions in the silicon melt is heated to a temperature of 10-20 ° C above ^the melting temperature, which creates favorable conditions for its effective assimilation during rising to the melt temperature 720-750 ^about With a certain speed. With an increase in the assimilation of silicon, its losses are reduced, which means that the amount of pulverized and fine fractions introduced into the silicon melt decreases, which is necessary to achieve the required silicon concentration in the alloy, which leads to a decrease in the preparation time of the alloy and, as a result, to a reduction in the loss of metal (aluminum and silicon -optional) from oxidation of the melt.

 The selected limits of the method parameters are limited by the following factors.

1. Introduction silicon dust and small fractions (0-20 mm) melt heated to a temperature above the melting temperature of more than 20 ^{° C,} leads to a rapid deterioration in the silicon melt kneading, which reduces its absorption and increases loss of metal oxidation of the melt by increasing the melting duration, and administering these fractions in the silicon melt is heated to a temperature above the melting point less than 10 ^{° C} is not possible due to the convergence of the melt temperature and its melting temperature eniya.

2. Increasing the temperature of the melt after administration silicon above 750 ^{° C} leads to an increase of metal loss and reduction below 720 ^{° C} - does not provide a high digestibility (which below digestibility silicon fraction 20-50 mm alloy by the known method of preparation, equal to 96.5% )

3. Increase in melt rate of temperature rise of more than 4 ^{° C} / min, leads to a significant reduction in the digestibility (well below 96.5%), while lower than 2.5 ° ^C / min - in increased loss of metal melt from oxidation.

 As a result of a search in the patent and scientific and technical literature, no technical solutions were found with features distinguishing the proposed method from the prototype, namely: allowing intensive mixing of silicon dust and fine fractions (0-20 mm), thereby creating favorable conditions for efficient its assimilation, which, in turn, creates wide opportunities for the use of silicon waste as an additive in the production of aluminum-silicon alloys, and at a lower cost.

 The implementation of the method is carried out upon receipt of aluminum-silicon alloys of the type AL2 and AK18. Silicon wastes of pulverized and fine fractions (0-20 mm) obtained by crushing and transporting crystalline silicon and sent after screening to the dump are used as additives. Primary aluminum of grades A5, A6 and A0 is used as the basis - a melt for introducing silicon wastes, and pig iron silumin is used to produce AK18 alloy.

EXAMPLE EXAMPLE 1 The preheated crucible furnace IAT-6M (capacity 6 tons) the aluminum ingots were charged in an amount of 4500 kg, it is melted and the melt is brought to a temperature of 10 ° C above ^the melting temperature, t. E. Up to ^about 670 C, in which 556 kg of silicon dust and fine fractions (0-20 mm) are loaded onto the melt surface based on the production of AL2 alloy with a silicon content of 11% (excluding losses). Overheating liquidus above 10 ^{° C} is maintained throughout the period of administration of said fractions of silicon, and after the completion of its introduction, the melt temperature was raised to 720 ^C at a rate of 2.5 ° ^C / min. Samples are taken to determine the chemical composition. After cooling the slag, samples are taken from it to determine the amount of metal and oxides in it. Slag is weighed. The absorption of silicon and the loss of metal are determined. An AL2 alloy is obtained with a silicon content of 10.87%. The absorption of silicon is 98.8%.

In examples 2 and 3, silicon wastes are processed analogously to example 1 with the following parameters. EXAMPLE 2. EXAMPLE superheat temperature above 15 ^{° C} liquidus temperature of the melt after its increase ^to 730 C temperature rise speed stages 3 ° ^C / min
EXAMPLE 3. EXAMPLE superheat temperature above 20 ° ^C liquidus temperature of the melt after its increase to 750 ^{° C} tem- perature rise rate 4 ° ^C / min.

 In example 4, silicon wastes are processed similarly to examples 1-3 with the introduction of silicon pulverized and fine fractions (0-20 mm) in the silumin melt.

EXAMPLE EXAMPLE 4. The furnace is charged with 4800 kg pig with silumin the silicon content of 10.8%, the contents are melted and the melt is brought to a temperature of 10 ° C above ^the melting temperature, t. E. To 605 ° ^C at which on the melt surface is loaded with silicon dust and fine fractions (0-20 mm) in an amount of 422 kg based on the production of AK18 alloy with a silicon content of 18% (excluding losses). After introducing the silicon waste melt temperature was raised to 720 ^C at a rate of 2.5 ° ^C / min. An alloy with a silicon content of 17.68 is obtained. Digestibility is 98.2%.

 In examples 5 and 6, silicon wastes are processed analogously to example 4 within the declared intervals.

 In examples 7-11, silicon wastes are processed similarly to examples (1-6) outside the declared intervals.

 Silicon waste is processed by a known method.

 The test results are shown in the table.

 From the table it is seen that the use of the proposed method for processing waste silicon dust and fine fractions (examples 1-6) provides an increase in the assimilation of silicon by 37.4-38.5% and a reduction in metal loss from oxidation of the melt by 3.2-3.8 kg / t (including aluminum - by 2.8-3.6 kg / t) by reducing the melting time by 19% upon receipt of the AL2 alloy and by 38% - the AK18 alloy. The specific consumption of silicon dust and fine fractions is reduced by an average of 70.8 kg / t of the resulting alloy.

Claims (1)

WASTE PROCESSING OF SILICON WASTE, including the introduction of silicon into the aluminum melt with stirring, characterized in that, in order to increase the degree of absorption of silicon, reduce the duration of the melting process and the loss of aluminum and silicon, the introduction of silicon fractions of 0.1 - 20.0 mm is carried out on the surface the melt at 670 - 680 ^o With the subsequent heating of the melt to 720 - 750 ^o With a speed of 2.5 - 4.0 deg./min

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