RU2429305C2 - Procedure for production of silicon containing reagent for production of aluminium-silicon alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure consists in preparation of crushed crystal silicon and halogen containing flux. Also, crushed crystal silicon is preliminary dampened, further, halogen containing flux in a solid powder-like state is applied on dampened silicon, and silicon covered with flux is dried. In particular cases of implementation of the invention crystal silicon is preliminary dampened with organic substance, for example, water solution of carboxy-methyl-cellulose or non organic substance, for example, water or water solution of sodium silicate. Mixture of halogenide containing flux with starch and/or flour is applied on dampened silicon. As halogenide containing flux there is used one-component flux or multi-component flux, of complex halogenide of alloying and/or alloy modifying element.

EFFECT: efficient processing crystal silicon practically of any fraction at foundry; reduced energy expenditures and time for alloy production; reduced gas contents and contents of non-metallic inclusions in aluminium-silicon alloys; fine disperse homogenous structure of foundry products.

10 cl, 1 tbl, 3 ex

Description

The present invention relates to the production of silicon and to a technology for producing alloys using crystalline silicon, for example aluminum-silicon alloys.

For the preparation of aluminum-silicon alloys, crystalline silicon of fractions of 5-50 mm is used, obtained after crushing and sieving of crystalline silicon produced by the electrothermal method. Fractions of less than 5 mm, constituting 3-6% of the volume of crystalline silicon produced, form “waste” and, as a rule, are not used in foundry production, since with the existing technology for the preparation of alloys, to a large extent (up to 85%) are transferred to slag. Significant losses of silicon in the slag and when using fractions of 5-50 mm - up to 5-10%.

One of the known ways to increase the extraction of silicon in the alloy and reduce its losses is the use of flux in the process of preparing the alloy. In this case, the simultaneous supply of silicon and flux to the melt is preferable.

A known method of producing a silicon-containing aluminum alloy (RF patent No. 2258757, C22C 1/02, 2005, [1]), comprising introducing a stream of inert gas into the aluminum melt or its alloy of dust and fines of crystalline silicon while processing the melt with a halide-containing flux, in which the minimum amount of flux used in the processing of metal is determined from the equation:

M _f = 0.09 M _Si / d _Si ,

where M _f - the mass of halide-containing flux, kg,

M _Si is the mass of crystalline silicon, kg,

d _Si is the average diameter of silicon particles, mm, calculated by the equation: d _Si = ∑C _i · d _i ,

where C _i is the content of fractions of crystalline silicon, fractions of a unit;

d _i - particle diameter of fractions, mm

In this case, crystalline silicon with a grain size of 0.2-5.0 mm is used, the halide-containing flux can be loaded onto the surface of the metal melt, pre-mixed with crystalline silicon, introduced by blowing into the metal melt simultaneously with dust and fines of crystalline silicon.

The supply of a halogen-containing flux to the surface of the molten metal and blowing it through the lance simultaneously with dust and fines of crystalline silicon will lead to its losses and worsen the environmental situation in the foundry, as well as the additional consumption of inert gas and the presence of a special installation for purging metal with powders.

A known method of producing aluminum-silicon alloy with a silicon content of 2-22 wt.%, Including in one embodiment, the implementation of the supply to the aluminum melt of fractions of crystalline silicon 0.3-1.0 mm, pre-compressed with barium chloride and flux based on sodium chloride and potassium at a mass ratio of crystalline silicon of a fraction of 0.3-1.0 mm, barium chloride and flux equal to 7: 1 ÷ 2: 1-3, respectively. The process temperature is maintained at 780–820 ° С, the melt is intensively mixed (WO 88/02409, С22С 1/02, 1988 [2]).

According to the purpose, technical essence and the presence of significant similar features - the use of crushed crystalline silicon and halogen-containing flux for the preparation of silicon-containing aluminum reagent for the preparation of aluminum-silicon alloys, the known solution was chosen as the closest analogue.

In the known solution, the supply of reagents to the melt level is achieved due to the higher density of the loaded arranged solid reagent, but additional costs are required for mixing the reagents and their pressing, which requires special equipment. Compressed briquettes should be non-hygroscopic - for a safe process, have sufficient strength for their transportation and when loaded into the melt (the briquette should not be destroyed by thermal shock, but dissolve gradually, which guarantees the dissolution of small fractions of silicon). It is quite difficult to provide all the above requirements for a pressed briquette. The destruction in the volume of the metal of the assembled solid reagent obtained by pressing to the dissolution of silicon leads to the transition of a significant part of it to slag. Significantly cooking time of the alloy. High temperatures of the alloy preparation process lead to unproductive losses of flux components, to losses of metals with slag.

The objectives of the proposed technical solution are to increase the technical and economic indicators for the production of crystalline silicon through the use of almost all fractions of crushed crystalline silicon, increase the production efficiency of aluminum-silicon alloys and improve the quality of foundry products.

Technical results are:

- efficient processing of crystalline silicon of virtually any fraction in the foundry;

- reduction of specific (per 1 ton of production) flux consumption, reduction of aluminum and silicon losses;

- reduction of energy costs and time in the preparation of the alloy;

- reduction of gas content and the content of non-metallic inclusions in the alloy;

- obtaining a finely divided homogeneous structure of foundry products.

Technical results are achieved by the fact that in the method for producing a silicon-containing reagent for the preparation of aluminum-silicon alloys, including the preparation of crushed crystalline silicon and a halide-containing flux, crushed crystalline silicon is pre-moistened, then a halogen-containing flux is applied to the wetted silicon, which is in a solid and powdery state, and is carried out in a solid and powder state flux-coated silicon.

In this case, crystalline silicon can be pre-moistened with an inorganic or organic substance, for example, water, an aqueous solution of sodium silicate, an aqueous solution of carboxymethyl cellulose, as a halogen-containing flux, a single-component flux, a multi-component flux, including a complex halide of an alloying and / or alloy alloy element, can be used. , a mixture of halide-containing flux with starch and / or flour.

The technical essence of the proposed solution is as follows.

Known methods of processing crushed crystalline silicon in the production of aluminum-silicon alloys using fluxes increase the extraction of silicon into the alloy, but do not solve the problem completely, require additional material and energy costs for preparing a silicon-containing reagent and introducing it into the melt, leading to unproductive consumption flux and the release of harmful gaseous compounds into the working area.

In the proposed technology, the above problems are solved by the fact that crushed crystalline silicon is pre-wetted with an inorganic or organic substance, and then coated with a halide-containing flux in a powder state.

The process of applying a solid powder halide-containing flux to wetted areas of the surface of crushed silicon does not require special equipment and significant costs.

It is not a prerequisite that the entire surface of silicon pieces and particles of any size is completely wetted, since the smaller the silicon fraction, the larger the surface area has the same volume of material and the greater the amount of liquid moisten the larger surface area, and the larger the wetted surface will fix dry powder flux. Thus, a kind of self-regulation of the amount of flux in the resulting silicon-containing reagent occurs, depending on the size of crystalline silicon: the smaller the silicon fraction, the greater the amount of flux will stick to silicon particles (pieces) and the greater the amount of flux will contain the same volume of material. The amount of halogen-containing flux necessary and sufficient to ensure high technical and economic indicators of the alloy preparation process is controlled by the amount of flux supplied to a certain wetted volume of silicon and the crystalline silicon fineness used to obtain a compacted silicon-containing reagent.

After wetted crystalline silicon is treated with a dry powder flux and the flux adheres to wetted surfaces, it is dried until the wetting agent solidifies (before moisture is removed) and the resulting silicon-containing reagent is ready for transportation and use.

In the proposed solution, preliminary preparation of crystalline silicon for subsequent dissolution in the melt is practically carried out. The essence of such preparation is as follows. One of the reasons that impede the dissolution of crystalline silicon in a melt, for example aluminum or its alloy, is the presence of an SiO ₂ oxide film on the surface of solid silicon of any size. The oxide film degrades the wettability of silicon by liquid aluminum and prevents the dissolution of silicon. When crystalline silicon pretreated with a halogen-containing flux is loaded into the aluminum melt, the oxide film is removed as a result of its dissolution in the flux. The consequence of this is the rapid and effective dissolution of silicon in aluminum.

Pretreatment of crystalline silicon with a halide-containing flux in a solid state makes it possible to obtain a solid reagent containing both silicon and a halide-containing flux, with the possible necessary content of an alloying and / or modifying element. It becomes possible to simultaneously load all the necessary components of the prepared silicon-containing alloy. In addition, an intensification of the alloy preparation process is achieved due to the processing of the melt by refining agents, alloying and / or alloy-modifying elements.

Upon receipt of the above results, flux consumption, energy costs for preparing the alloy are significantly reduced, losses of crystalline silicon with slag are reduced, the quality of the alloy obtained is improved by reducing the content of non-metallic and gas inclusions in it, as well as by obtaining a finely dispersed, uniform structure of A1 eutectic (α ) - Si. The proposed method is more technologically advanced, since no special equipment is required for implementation; during processing, the reagents are preliminarily prepared for effective dissolution and for flux study of the entire melt volume. This will also reduce the energy costs of the process as a whole and increase its efficiency, to obtain high technical and economic results in the preparation of the alloy due to a more complete processing of crystalline silicon and increase its extraction into the alloy, shortening the preparation time. The implementation of the proposed technical solution improves the quality of the alloy by reducing the content of non-metallic and gas inclusions in it, as well as by obtaining a finely dispersed homogeneous metal structure.

A comparative analysis of the proposed technical solution with the solution for the closest analogue shows the following.

The known solution and the proposed are characterized by common similar features: obtaining a silicon-containing reagent for the preparation of aluminum-silicon alloys using crushed crystalline silicon and a halide-containing flux.

In the solution for the closest analogue, compaction is carried out by pressing crystalline silicon with a halide-containing flux in the form of barium chloride and flux based on sodium and potassium chlorides at certain ratios of components. The obtained compressed material is fed into a metallurgical vessel for preparing the alloy.

The proposed technical solution differs from the solution according to the closest analogue in that the preparation of a silicon-containing reagent is carried out in three stages: pre-wetted crushed crystalline silicon, then a halide-containing flux in a solid powder state is applied to wetted silicon, and the resulting reagent is dried.

Moreover, crushed crystalline silicon can be pre-moistened with an inorganic or organic substance, for example, water, an aqueous solution of sodium silicate, an aqueous solution of carboxymethyl cellulose, as a halide-containing flux, a single-component flux, a multi-component flux, including a complex dopant and / or complex halide, can be used; alloy of the element, a mixture of halide-containing flux with starch and / or flour.

The presence in the proposed solution of signs that are distinct from the signs characterizing the known technical solution for the closest analogue allows us to conclude that the proposed solution meets the condition of patentability of the invention of "novelty."

A comparative analysis of the proposed technical solutions with other known solutions in this field shows the following.

A known method of melting waste aluminum alloys (USSR AS No. 1242532, C22B 7/00, C22C 1/06, 1986 [3]), including heating and melting the mixture in the presence of flux, downloading slag and draining the liquid metal, wherein the surface of the mixture at 350-450 ° C is coated with a flux with a melting point above the temperature of the mixture, but below its melting temperature, the mixture is heated until the flux softens, after which a metal melt is introduced under the flux, and the resulting mass is heated until completely melted. As a flux, a mixture of sodium and potassium chlorides in a ratio of 1: 1 by weight is used.

In a known solution, the mixture is impregnated with a halogen-containing flux, bringing it to softness, and the resulting mass is heated until it is completely melted. This technology requires significant energy costs for the implementation, possible unproductive consumption of flux.

A known method of producing an aluminum alloy, comprising treating the charge with a halide-containing flux and introducing the charge into the aluminum melt or its alloy, in which the processing of the charge with a halide-containing flux is carried out until a density of 1.2-1.3 is obtained for the density of the liquid metal (RF patent No. 2072178, 22C 1/06, 1997 [4]), while a composition of a fused mixture of cryolite with aluminum fluoride, metal chloride — an alloy component, barium, potassium and sodium chlorides is used as a halide-containing flux.

In a known solution, the processing of the mixture for the preparation of the alloy is carried out by a molten halide-containing flux, and the final goal of the treatment is to achieve a density of the resulting reagent equal to 1.2-1.3 of the density of the liquid metal into which this reagent is loaded. Significant energy costs for the preparation of the reagent, since it is necessary to melt the halide-containing flux.

The proposed solution does not require significant energy costs for the preliminary preparation of charge materials. In contrast to the known solutions, in the preparation of a silicon-containing reagent using crushed crystalline silicon and a halide-containing flux, the aggregate state of the flux component does not change. The wetting of crystalline silicon and the application of a halide-containing flux in a solid powder state onto a wetted surface does not require energy-intensive equipment. The heat treatment of the obtained material includes only drying the reagent until the wetting agent hardens (until moisture is removed).

A known method of producing silicon, in which as a silicon-containing reagent in the composition of the mixture for reducing melting of silicon in an ore-thermal furnace, silicon gas cleaning dust is used pre-briquetted with a binder, for example sulfite-alcohol liquor (AS USSR No. 1344735, С01В 33/02, 1987 [5]). The dust is mixed with a binder - sulphite-alcohol liquor, taken in an amount of 4-6% by dry weight and 20% water and briquetted on a roller press. The resulting briquettes are dried at 220 ° C for 20-25 minutes, and then served on mixing with the main charge.

The proposed solution differs from the known one in the following:

1) as directed: obtaining a silicon-containing reagent for the preparation of aluminum-silicon alloys, and not receiving a silicon-containing reagent for smelting silicon;

2) to obtain a silicon-containing reagent, a halide-containing flux is additionally used;

3) on the technical nature: the preparation of the reagent is carried out by applying to the wetted silicon-containing material a halide-containing flux in a solid powder state, and not by briquetting a silicon-containing material with a binder.

A known method of producing silicon, in which as a silicon-containing reagent in the composition of the mixture for reductive silicon melting in an ore-thermal furnace, molded silicon gas treatment dust is used, which has been pretreated at the stage of its capture with an organic binder (RF patent No. 2094372, С01В 33/025, 1997 [ 6]). A molded silicon-containing reagent is obtained by pulsing atomization of a liquid organic binder in the form of, for example, coal tar pitch, coal tar or petroleum bitumen, followed by condensation of the resulting material and its water cooling, through a nozzle into the dust gas treatment strip of silicon. The obtained granules are mixed with the main charge.

The proposed solution differs from the known one in the following:

1) as directed: obtaining a silicon-containing reagent for the preparation of aluminum-silicon alloys, and not obtaining a silicon-containing reagent for smelting silicon;

2) to obtain a silicon-containing reagent, a halide-containing flux is additionally used;

3) on the technical nature: the preparation of the reagent is carried out by applying to the wetted silicon-containing material a halide-containing flux in a solid powder state, followed by drying, and not trapping and condensation of the silicon-containing material with a binder followed by cooling of the reagent with water.

As a result of the comparative analysis, no technical solutions have been identified, characterized by a combination of features similar to the combination of features of the proposed solution, which allows us to conclude that the proposed technical solution meets the patentability condition of the invention “inventive step”.

The proposed technology for obtaining a silicon-containing reagent for the preparation of aluminum-silicon alloys is implemented, in the General case, as follows. The crushed crystalline silicon is wetted, and then a halogen-containing flux in a powder state is applied to the wetted surface and the resulting reagent is dried until the wetting agent solidifies or evaporates. In this case, a flux crust forms on the surface of crystalline crushed silicon. Thus obtained silicon-containing reagent is ready for use.

To obtain comparative results, pilot tests were conducted on the preparation of aluminum-silicon alloys according to traditional technology, according to technology according to the technical solution - the closest analogue and according to the proposed technology. The readiness of the alloy was determined by the results of rapid analyzes for the content of the main components.

Example 1. Traditional technology.

A batch of crushed crystalline silicon of various fractions (from 50 mm to 20 mm) weighing 8.00 ± 0.05 kg was prepared. Silicon was loaded into a heated ladle, and molten aluminum of technical purity (200 ± 3 kg) having a temperature of 750 ± 5 ° C was poured on top. The melt was periodically mixed until the silicon was completely dissolved. After that, samples of the obtained alloy were taken for analysis and slag was weighed.

Example 2. By the closest analogue.

A batch of crushed crystalline silicon of various fractions (from 50 mm to 20 mm) weighing 7.20 ± 0.05 kg and crystalline silicon fraction 0.3 ÷ 1.0 mm weighing 0.8 ± 0.003 kg were prepared. Crystalline silicon fractions of 0.3 ÷ 1.0 mm weight of 0.8 kg were pressed with 0.230 ± 0.003 kg of barium chloride and 0.343 ± 0.003 kg of flux, which is a mixture containing 52 wt.% NaCl, 36 wt.% KCl, 12 wt.% Na ₃ AlF ₆ . Crystalline silicon and a silicon-containing reagent were placed in a heated ladle and poured with a melt of aluminum of technical purity (200 ± 3 kg), having a temperature of 800 ± 5 ° С, with periodic mixing of the melt until silicon was completely dissolved. After that, samples of the obtained alloy were taken for analysis and slag was weighed.

Example 3. By the proposed method.

A batch of crushed crystalline silicon of various fractions (from 50 mm or less, including fines and dust fractions after sieving) with a weight of 8.00 ± 0.05 kg was prepared. A portion of silicon was placed on a tray installed at an angle of ≈30 ° to the horizon and the layer was irrigated with an aqueous solution of liquid glass and mixed periodically. Then, the wetted silicon was sprinkled with powdery flux of the following composition: 52 wt.% NaCl, 36 wt.% KCl, 12 wt.% Na ₃ AlF ₆ with periodic stirring. The flux-coated silicon was dried in an oven at a temperature of 250 ± 5 ° C for 20 minutes. Weighed heat-treated silicon-containing reagent. The silicon-containing reagent was placed in a heated ladle and poured with molten aluminum of technical purity (200 ± 3 kg), having a temperature of 800 ± 5 ° C, with periodic stirring of the melt until the silicon was completely dissolved. After that, samples of the obtained alloy were taken for analysis and slag was weighed.

The initial data and experimental results are shown in the table.

No. Parameter Dimension Technology Traditional According to the prototype Proposed one Aluminum weight kg 200 ± 3 200 ± 3 200 ± 3 2 Silicon weight kg 8.00 ± 0.05 8 (7.2 + 0.8) ± 0.05 8 ± 0.05 3 Aluminum temperature ° C 750 ± 5 800 ± 5 800 ± 5 four The amount of flux kg - 0.573 ± 0.03 0.915 ± 0.03 5 Additive Duration min 2.0 2.0 2.0 6 Duration
alloy preparation min 37.0 25.0 21.0 7 Extraction of silicon into alloy % the weight. 94.75 97.4 98.7 8 Amount of slag kg 29.1 25.6 21.1 9 Alumina Alloy Content % the weight. 0,021 0.018 0.016 10 The content in the alloy of hydrogen cm ^3/100 g alloy 0.23 0.19 0.18

The experimental results show the following.

The use of the proposed silicon-containing reagent for the preparation of aluminum-silicon alloys provides high extraction of silicon into the alloy with lower flux consumption, minimum process time and minimal loss of aluminum and silicon to the slag, in comparison with known technologies.

In addition, the proposed technical solution is acceptable for using fluxes with the widest range of melting points, as well as for alloying aluminum-silicon alloys.

In general, the use of the proposed solution will ensure the effective use in the production of crystalline silicon alloys of any fractions, including less than 5 mm, increasing technical and economic efficiency of both the production of crystalline silicon and foundry processing, by increasing the consumer properties of the products.

Information sources

1. RF patent No. 2258757, C22C 1/02, 2005

2. WO 88/02409, C22C 1/02, 1988.

3. A.S. USSR No. 1242532, C22B 7/00, C22C 1/06, 1986

4. RF patent No. 2072178, 22C 1/06, 1997

5. A.S. USSR No. 1344735, СВВ 33/02, 1987

6. RF patent No. 2094372, С01В 33/025, 1997.

Claims (10)

1. A method of obtaining a silicon-containing reagent for the preparation of aluminum-silicon alloys, including the preparation of crushed crystalline silicon and a halide-containing flux, characterized in that the crushed crystalline silicon is pre-wetted, then a halide-containing flux in a solid powder state is applied to the wetted silicon, and drying is performed silicon flux. 2. The method according to claim 1, characterized in that the crystalline silicon is pre-wetted with an inorganic substance. 3. The method according to claim 1, characterized in that the crystalline silicon is pre-wetted with an organic substance. 4. The method according to claim 1, characterized in that the crystalline silicon is pre-wetted with water. 5. The method according to claim 1, characterized in that a mixture of a halide-containing flux with starch and / or flour is applied to the wetted silicon. 6. The method according to claim 1, characterized in that the crystalline silicon is pre-wetted with an aqueous solution of sodium silicate. 7. The method according to claim 1, characterized in that the crystalline silicon is pre-wetted with an aqueous solution of carboxymethyl cellulose. 8. The method according to claim 1, characterized in that as a halide-containing flux using a single component flux. 9. The method according to claim 1, characterized in that a multicomponent flux is used as the halide-containing flux. 10. The method according to claim 1, characterized in that as a halogen-containing flux, a complex halide of an alloying and / or alloy-modifying element is used.