EP0283517B1 - Method of obtaining aluminosilicon alloy containing 2-22 per cent by weight of silicon - Google Patents

Abstract

The method consists, in its first variant in dissolving a 20-50 mm fraction of crystalline silicon in liquid aluminium at a temperature of 780-820°C while continually mixing the ingredients in a reverberatory furnace until obtaining an alumino-silicon melt and while simultaneously introducing, under the level of the melt, a 0,3-1.0 mm fraction of crystalline silicon with a jet of an inert gas. The second variant of the method consists in the joint dissolving of the mentioned fractions of silicon in the liquid aluminium at a temperature of 780-820°C while continually mixing the ingredients in the reverberatory furnace, the 0.3-1.0 mm fraction of silicon being pressed together with barium chloride and a flux before dissolving. The alloy may be used in the automobile and tractor industry, as well as for production of consumer goods.

Description

field of use

The invention relates to the field of metallurgy of non-ferrous metals and alloys, and in particular to processes for the production of aluminum-silicon alloy with a silicon content of 2 to 22 mass%.

Previous state of the art

A method is known for producing an aluminum-silicon alloy with a silicon content of 2 to 22% by mass, which consists in exposing alumina and silicon to separate comminution. A feed material is prepared from the carbon-containing material and the comminuted alumina and the comminuted silicon, the components mentioned being used in calculated amounts. Then briquettes are made from the feed, which are placed in an ore reduction electro furnace. By reducing the load, primary aluminum-silicon alloy is obtained. In addition, the alloy produced from non-metallic inclusions is refined and processed into aluminum-silicon construction alloys (I.A. Troitsky, V.A. Zheleznov "Metallurgia aluminiya", published I977, Verlag "Metallurgiya", Moscow, pp. 368-375).

Disadvantages of the process mentioned include the low degree of utilization of silicon and the low quality of the alloy produced as a result of an increased content of non-metallic inclusions therein. The process control according to the above-mentioned process is associated with a high degree of slag formation and with substantial heat losses for the slag formation (up to 10%). The process consists of several stages and requires a large amount of electricity.

A method for producing aluminum-silicon alloy containing silicon is known from 2 to 22% by mass, which is that the separation of the crushed crystalline sicilium into fractions with the decrease of a fraction of 20 to 50 mm and a fraction of 0.3 to 1.0 mm (the last fraction is thrown away) and the crystalline silicon of the fraction of 20 to 50 mm is dissolved in the liquid aluminum at a temperature of 780 to 820 ° C. in a radiation furnace with mixing with the accumulation of aluminum-silicon melt. (MBAltman, AALebedev, MVChukhov "Plavka i litje legkikh splavov" / melting and casting of light alloys), published I969, Verlag "Metallurgiya", Moscow, pp. 270-27I).

The described method ensures that an increased degree of utilization of silicon is achieved and that an alloy of good quality is produced as a result of a reduced content of non-metallic inclusions in it (aluminum oxide and hydrogen). In addition, this process enables the degree of slag formation to be reduced. The process is technologically easy to carry out and does not require a large amount of electricity.

It is known that when the crystalline silicon is comminuted, the fraction from 20 to 50 mm has an average yield of 95% and the fraction from 0.3 to 1.0 mm has an average yield of 4.5%. According to this method, the crystalline silicon of the fraction from 0.3 to 1.0 mm is not used for the production of the aluminum-silicon alloy, which causes a loss of deficient raw material.

Disclosure of the invention

The invention has for its object to change the conditions of the process control of the dissolution of the crystalline silicon in the process for the production of aluminum-silicon alloy with a silicon content of 2 to 22 mass% so that the possibility is created of crystalline silicon Fraction of 0.3 to 1.0 mm to use and thereby to avoid the loss of deficient raw material and to improve the quality of the alloy produced.

This object is achieved in that the method according to the invention (its first variant) for the production of aluminum-silicon alloy with a silicon content of 2 to 22 mass%, which separates the crushed crystalline silicon into fractions with the removal of a fraction of 20 to 50 mm and a fraction of 0.3 to 1.0 mm, the dissolution of the crystalline silicon of the fraction of 20 to 50 mm in liquid aluminum at a temperature of 780 to 820 ° C with mixing in a radiation furnace with the accumulation of aluminum Silicon melt provides, according to the invention, simultaneously with the dissolution of the crystalline silicon of the fraction from 20 to 50 mm, the crystalline silicon of the fraction from 0.3 to 1.0 mm in an amount of 3 to 10%, based on introduces the total mass of the crystalline silicon feed under the melt plane with an inert gas jet.

The stated object is also achieved in that in the process according to the invention (its second variant) for producing an aluminum-silicon alloy with a silicon content of 2 to 22% by mass, the separation of the comminuted crystalline silicon into fractions with the decrease a fraction of 20 to 50 mm and a fraction of 0.3 to I, 0 mm, the dissolution of the crystalline silicon of the fraction of 20 to 50 mm in liquid aluminum at a temperature of 780 to 820 ° C with mixing in a blast furnace with The occurrence of an aluminum-silicon melt provides, according to the invention, the dissolution of the crystalline silicon of the fraction from 20 to 50 mm together with the crystalline silicon of the fraction from 0.3 to 1.0 mm with a mass ratio of the fractions of 80-85: 20- I5 is carried out, taking the crystalline silicon fraction from 0.3 to 1.0 mm before dissolving with barium chloride and a flux based on sodium - and Potassium chlorides at a mass ratio of the crystalline silicon of the fraction of 0.3 to 1.0 mm to the barium chloride and to the flux are compressed (7: I) to (2: I-3).

The method according to the invention (its two variants) makes it possible to use the crystalline silicon of the fraction from 0.3 to 1.0 mm, thereby avoiding the loss of deficient raw material. The method according to the invention also makes it possible to produce an alloy with a better quality due to a lower content of non-metallic inclusions therein (aluminum oxide and hydrogen).

By introducing the crystalline silicon of the fraction from 0.3 to 1.0 mm with the inert gas jet below the melt level with the simultaneous dissolution of the crystalline silicon of the fraction from 20 to 50 mm (first variant of the process) the increase in the residence time of the fine Silicon fraction in the melt volume reached, which means that the time for the fine fraction to dissolve in the melt is sufficient before it manages to float to the surface.

The inert gas also promotes the removal of non-metallic inclusions (hydrogen and aluminum oxide) from the melt when it reaches the melt.

By pressing the crystalline silicon of the fraction from 0.3 to 1.0 mm together with barium chloride and flux (second variant of the process), compressed material is obtained, the density of which lies above the density of the melt, which means that the fraction of Excludes 0.3 to 1.0 mm to the surface of the melt. This makes it possible to carry out the joint dissolution of the crystalline silicon of the fraction from 20 to 50 mm and the fraction from 0.3 to 1.0 mm. The presence of a flux in the composition of the compressed material enables the content of hydrogen and alumina decrease in the aluminum-silicon melt.

In the practice of producing aluminum-silicon alloys with a silicon content of 2 to 22% by mass, it was found that the fraction of crystalline silicon with a particle size of 20 to 50 mm appears to be particularly optimal for the process control, since the minimal loss of silicon is observed in its dissolution.

As mentioned above, the crystalline silicon fraction of 20 to 50 mm when crushed has an average yield of 95% and the fraction of 0.3 to 1.0 mm has an average yield of 4.5%. In the past, the fraction from 0.3 to 1.0 mm was not used for the production of an aluminum-silicon alloy, which caused the loss of deficient raw material. The present invention proposes a method for producing an aluminum-silicon alloy using the fraction from 0.3 to 1.0 mm.

In the method according to the invention, the dissolution of the crystalline silicon in the liquid aluminum is provided at a temperature of 780 to 820 ° C. The temperature of the dissolution mentioned is due to the specific mode of operation of the radiation furnace and to the conditions of the process control of the production of the alloy in the furnace.

According to the first variant of the process, the introduction of the crystalline silicon of the fraction from 0.3 to 1.0 mm in an amount below 3%, based on the total mass of the silicon feed, with the inert gas jet leads to a low degree of utilization of equipment , and the introduction of the said fraction in an amount over 10%, based on the total mass of the silicon feed, leads to a large consumption of inert carrier gas.

According to the second variant of the method according to the invention, the fraction of crystalline silicon is from 20 to 50 mm and the fraction from 0.3 to 1.0 mm with their mass ratio equal to 80 to 85:20 to I5 used. The use of the crystalline silicon of the fraction from 0.3 to 1.0 mm in an amount above the upper limit in the above ratio is not appropriate because it leads to the need for the amount of barium chloride which is pressed together with the fraction of 0.3 to 1.0 mm and used with the flux to enlarge, which in turn leads to an undesirable increase in the viscosity of the melt. The use of the crystalline silicon fraction from 0.3 to 1.0 mm in an amount below the lower limits in the stated ratio is not recommended, since the effectiveness of the process control is noticeably impaired.

, $\text{γ₂ = 2,48 g/cm³}$

, worin γ_I - die Dichte des flüssigen Aluminiums ist und γ₂ - die Dichte des zusammengepressten Materials ist.According to the second variant of the proposed invention, the crystalline silicon of the fraction from 0.3 to 1.0 mm is pressed together with barium chloride and a flux in a mass ratio equal to (7: I) to (2: I to 3). The choice of the lower limit for the barium chloride and for the flux is due to the fact that a minimum density of the compressed material is achieved which exceeds the density of the liquid aluminum ${\text{(γ}}_{\text{I.}}\text{= 2.4 g / cm³}$

, $\text{γ₂ = 2.48 g / cm³}$

, where γ _I - is the density of the liquid aluminum and γ₂ - is the density of the compressed material.

The upper limit for the barium chloride and flux in the ratio mentioned is determined by the fact that a further increase in the content of barium chloride and flux leads to an undesirable increase in the viscosity of the melt and to an unproductive consumption of flux.

Best execution variants of the invention

According to the first variant, the method according to the invention for producing aluminum-silicon alloy with a silicon content of 2 to 22% by mass is carried out as follows.

The crushed crystalline silicon is fractionated in fractions from 20 to 50 mm and from 0.3 to 1.0 mm, after which the fraction from 20 to 50 mm is placed in a radiation oven. Then the required amount of liquid aluminum is poured into the furnace at a temperature of 780 to 820 ° C. The crystalline silicon of the fraction of 20 to 50 mm is dissolved in the liquid aluminum at the temperature mentioned and with mixing with the formation of an aluminum-silicon melt. Mixing can be carried out, for example, using centrifugal pumps from "Carborundum" (USA), gas dynamopumps and electromagnetic mixing devices (ADAndreev, VBGogin, GSMakarov "High-performance melting of aluminum alloys", published I980, "Metallurgia", Moscow, S. 89-95).

Simultaneously with the dissolution of the crystalline silicon of the fraction from 20 to 50 mm, the crystalline silicon of the fraction from 0.3 to 1.0 mm in an amount of 3 to 10%, based on the total mass of the silicon, with one jet of inert gas, for example nitrogen, argon, introduced under the melt plane. The formation of the jet of the inert gas in a mixture with the crystalline silicon of the fraction from 0.3 to 1.0 mm takes place in a fluidized bed apparatus. When the crystalline silicon of the fraction from 0.3 to 1.0 mm is introduced with the inert gas jet below the melt level, the silicon of the said fraction is completely dissolved as a result of the increase in its residence time in the melt volume.

The degree of skill of the alloy to be produced is determined by the results of a rapid analysis according to the content of basic components of the alloy and the admixtures, after which the finished alloy is cast in molds.

The second variant is the method according to the invention for the production of aluminum-silicon alloy with a silicon content of 2 to 22 mass% as follows.

The crushed crystalline silicon is fractionated in fractions from 20 to 50 mm and from 0.3 to 1.0 mm. Thereafter, the crystalline silicon of the fraction from 0.3 to 1.0 mm with barium chloride (weighting agent) and with a flux based on sodium and potassium chloride with a mass ratio of crystalline silicon to barium chloride and flux equal to 7: I to 2 : I-3 pressed together. As a flux, for example, a mixture can be used which is composed of 52 to 57 mass% NaCl, 30 to 35 mass% KCl and 10 to 15 mass% Na₂SiF₆. Then the crystalline silicon of the fraction from 20 to 50 mm and the produced compressed material containing the silicon fraction from 0.3 to 1.0 mm are placed in the radiation furnace. These are given in such an amount that the mass ratio of the silicon fraction from 20 to 50 mm to the silicon fraction from 0.3 to 1.0 mm is 80-85: 20: I5. Thereafter, the required amount of liquid aluminum is poured into the furnace at a temperature of 780 to 820 ° C. and the crystalline silicon of the two fractions is dissolved together in the liquid aluminum at the temperature mentioned and mixed with the formation of an aluminum-silicon Melt through. Under such process control conditions, the crystalline silicon of the fraction from 0.3 to 1.0 mm manages to dissolve in the melt volume due to the increase in its residence time.

The mixing mentioned is carried out in a similar manner to that described in the first variant of the process.

The level of skill of the alloy to be produced is determined by the results of a rapid analysis according to the content of basic components of the alloy and the admixtures, after which the finished alloy is cast in molds.

In order to better explain the present invention, the following examples are given for their specific implementation.

Example I (first variant of the method according to the invention.

The crushed crystalline silicon is fractionated in fractions from 20 to 50 mm and from 0.3 to 1.0 mm, after which the fraction from 20 to 50 mm in an amount of 2650 kg is drawn into a blasting furnace with a capacity of 25000 kg on the liquid metal. Then 22,250 kg of the liquid aluminum are poured into the furnace at a temperature of 800.degree. The crystalline silicon of the fraction of 20 to 50 mm is dissolved in the liquid aluminum at the temperature mentioned and with mixing with the formation of an aluminum-silicon melt. Mixing takes place using an electromagnetic mixing device.

Simultaneously with the dissolution of the crystalline silicon of the fraction from 20 to 50 mm, the crystalline silicon of the fraction from 0.3 to 1.0 mm in an amount of 270 kg (10%, based on the total mass of the silicon feed) with a Nitrogen jet introduced below the melt level. The calculated amount of silicon in the melt is II.7% by mass. When the crystalline silicon of the fraction from 0.3 to 1.0 mm is introduced with a nitrogen jet below the melt level, the silicon of the said fraction is completely dissolved.

The skill level of the alloy is determined by the results of a rapid analysis of the content of basic components of the alloy and the admixtures, after which the finished alloy with a silicon content of II.4% by mass is poured into molds.

Below are examples of the implementation of the inventive method according to the first variant in the above-mentioned radiation furnace in Table I.

Example I (second variant of the method according to the invention)

The crushed crystalline silicon is fractionated in fractions from 20 to 50 mm and from 0.3 to 1.0 mm. Then the crystalline silicon of the fraction from 0.3 to 1.0 mm in an amount of 584 kg is pressed together with I66.8 kg barium chloride and 250.2 kg flux (the mass ratio of the silicon fraction with the barium chloride and the flux is 7: 2 or 3). The flux is a mixture composed of 52% by mass NaCl, 34% by mass KCl and 14% by mass Na₂SiF₆. Then in the blasting furnace with a capacity of 25000 kg, based on the liquid metal, crystalline silicon of the fraction of 20 to 50 mm in an amount of 2336 kg and the produced compressed material, which contains the silicon fraction from 0.3 to 1.0 mm. The mass ratio of the silicon fraction from 20 to 50 mm to the silicon fraction from 0.3 to 1.0 mm is 80:20. The calculated amount of silicon in the alloy is II.7 mass%. Then poured 22,250 kg of liquid aluminum into the furnace at a temperature of 800 ° C. and the crystalline silicon of the two fractions was dissolved together in liquid aluminum at the temperature mentioned and mixed with the formation of an aluminum-silicon melt. Under such conditions of process control, the silicon of the fraction from 0.3 to 1.0 mm manages to dissolve due to the increase in its residence time in the melting volume.

The aforementioned mixing is carried out using an electromagnetic mixing device.

The degree of skill of the alloy is determined by the results of a rapid analysis of the content of basic components of the alloy and the admixtures, after which the finished alloy with a silicon content of II.4% by mass is poured into molds.

The following examples for the implementation of the method according to the invention in accordance with the second variant in the above-mentioned radiation furnace are listed in Table 2. The flux described in Example I of the second variant of the method is used in the examples.

The effectiveness of the method according to the invention (of its two variants) was assessed on the basis of the results of the analysis of the alloy for the content of hydrogen and aluminum oxide and for the degree of utilization of the crystalline silicon of the fraction from 0.3 to 1.0 mm.

The content of hydrogen and aluminum oxide in the alloy was determined according to the methodology described in the book by MBAltman, AALebedev and MVChukhrov "Melting and Casting Light Alloy", published in 1969, Verlag "Metallurgia", Moscow, pp. 663-674 has been described.

The degree of utilization of the crystalline silicon of the fraction from 0.3 to 1.0 mm was determined as follows for both variants of the method according to the invention.

Initially, the process was carried out using only the 20 to 50 mm silicon fraction. This resulted in an aluminum-silicon alloy with a certain silicon (C _I ) content. Then it happened the process control using the silicon fraction from 20 to 50 mm and the silicon fraction from 0.3 to 1.0 mm with their mass ratio, which corresponds to the first or second variant of the method. This gave an aluminum-silicon alloy with a certain content of silicon (C₂). In the two cases of process control, the calculated content of silicon in the alloy was the same.

worin
C_I - Gehalt an Silizium in der Legierung ist, die unter Verwendung des kristallinen Siliziums der Fraktion von 20 bis 50 mm hergestellt wurde, Masse%.
C₂ - Gehalt an Silizium in der Legierung, die unter Verwendung des kristallinen Siliziums der Fraktion von 20 bis 50 mm und von 0,3 bis I,0 mm hergestellt wurde, Masse%.The degree of utilization of the crystalline silicon of the fraction from 0.3 to 1.0 mm (y%) was calculated using the following formula:

wherein
C _I content of silicon in the alloy made using the crystalline silicon fraction from 20 to 50 mm, mass%.
C₂ - silicon content in the alloy, which was produced using the crystalline silicon fraction from 20 to 50 mm and from 0.3 to I, 0 mm, mass%.

Characteristic data of the effectiveness of the method according to the invention according to its two variants and according to the known method, which were determined according to the above-mentioned methodologies, are listed in Table 3.

A comparative analysis of the information given in Table 3 shows that the use of the method according to the invention (of its variants) enables the hydrogen content in the finished alloy to be reduced on average by 30% and the aluminum oxide content by 37% on average.

The method according to the invention makes it possible to use the crystalline silicon of the fraction from 0.3 to 1.0 mm, which excludes the loss of deficient raw material. As can be seen from the information in Table 3, the high degree of utilization of the silicon of the fine fraction mentioned is guaranteed, this degree is practically the same as the degree of utilization of the silicon of the fraction from 20 to 50 mm according to the known method.

Industrial applicability

The proposed invention can be used in the field of metallurgy of non-ferrous metals and alloys for producing an aluminum-silicon alloy with a silicon content of 2 to 22% by mass. The alloy mentioned can be used for the production of molded castings for the needs of the motor vehicle, auto and tractor industries and for the production of consumer goods.

Claims (2)

1. A process for the production of an aluminium-silicon alloy with a silicon content of 2 to 22 % by mass, which comprises the separation of the crushed, crystalline silicon into fractions, of which the 20 to 50 mm fraction and the 0.3 to 1.0 mm fraction are selected, and comprising the dissolution of the 20 to 50 mm crystalline silicon fraction in liquid aluminium at a temperature of 780 to 820°C, with mixing, in a radiation furnace, whereby an aluminium-silicon melt is formed, characterised in that simultaneously to the dissolution of the 20 to 50 mm crystalline silicon fraction, the 0.3 to 1.0 mm crystalline silicon fraction is introduced below the plane of the melt, in a quantity of 3 to 10% relative to the total mass of the batch of crystalline silicon, with an inert gas jet.
2. A process for the production of an aluminium-silicon alloy with a silicon content of 2 to 22 % by mass, which comprises the separation of the crushed crystalline silicon into fractions, of which the 20 to 50 mm fraction and the 0.3 to 1.0 mm fraction are selected, and comprising the dissolution of the 20 to 50 mm crystalline silicon fraction in liquid aluminium at a temperature of 780 to 820°C, with mixing, in a radiation furnace, whereby an aluminium-silicon melt is formed, characterised in that the dissolution of the 20 to 50 mm crystalline silicon fraction is carried out together with that of the 0.3 to 1.0 mm crystalline silicon fraction with a mass ratio of the fractions of (80 to 85) : (20 to 15), where the 0.3 to 1.0 crystalline silicon fraction is compressed, prior to the dissolution, with barium chloride and with a fluxing agent based on sodium chloride and potassium chloride, with a mass ratio of the 0.3 to 1.0 mm crystalline silicon fraction to the barium chloride and the fluxing agent of (7:1) to (2:1 to 3).