RU2034927C1 - Method to produce hypereutetic aluminum-silicon alloys - Google Patents

Abstract

FIELD: aluminum-silicon manufacturing. SUBSTANCE: melt alloying by silicon is performed in two stages: first silicon at 1350 - 1650 C is introduced in molten aluminum or its alloy with concurrent melt bubbling and cooling with inert gas down to a temperature of 40 to 100 C above liquidus temperature of the produced alloy, then dust-like crystalline silicon in the amount of 5 to 16 per cent of total weight of silicon being introduced, is introduced by a jet of inert gas. Alloy strength increases by 17 per cent, ductility increases by 22 per cent at the expense of modifying its structure in the second stage. Uniformity of chemical composition of the alloy is increased, gas content is decreased by a factor of 1.2. Time to prepare the alloy decreases by 24 per cent, that allows one to perform productivity of melting/delivering plant, and increase alloy cost price at the expense of it. That is why dust-like silicon is used to alloy and modify the alloy. The dust-like silicon is a waste of aluminum/silicon alloy manufacturing. EFFECT: increased quality of the alloy at the expense of producing unified chemical composition, and comminuting primary silicon crystals, melt duration reducing of melting process and reducing cost price of the alloy. 2 cl, 1 tbl

Description

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

 A known method of producing aluminum-silicon alloys, including loading a solid charge into a molten metal, melting it, introducing alloying elements, reloading a solid charge, refining and modification (see ed. St. N 1196405, class C 22 C, 1/06, published. 1985).

 The disadvantage of this method is that the improvement of the alloy structure is achieved by conducting an independent operation to modify the melt, which leads to an increase in the duration of melting and the cost of the alloy.

The closest in technical essence and the achieved result to the invention is a method for producing aluminum-silicon alloys, including the introduction of silicon into molten and heated to 850-900 ^о С aluminum in the form of pieces of 20-50 mm in diameter, mixing, cooling and casting.

 The disadvantage of this method is the low productivity of the process due to the slow dissolution of the silicon introduced into the melt having a low temperature. In addition, the quality of the alloy obtained is low due to the significant heterogeneity of the chemical composition and the large size of the primary silicon crystals, which require the introduction of an additional melt processing operation, which also increases the melting time, reduces the productivity of the process, resulting in an increase in the cost of the alloy. Dusty silicon is not used, which further increases the cost of the resulting alloy.

 The aim of the invention is to improve the quality of the alloy by obtaining a homogeneous chemical composition and grinding crystals of primary silicon, reducing the duration of smelting and reducing the cost of the alloy.

The goal is achieved in that the process for the preparation of hypereutectic aluminum-silicon alloys, comprising doping the silicon melt with stirring, cooling and casting, alloying is carried out in two stages: first in the molten aluminum or its alloy is introduced with the temperature 1350-1650 ^{° C} silicon with simultaneous and cooling the melt by sparging with inert gas to a temperature of 40-100 ° C above ^the liquidus temperature of the alloy and then introduced into the pulverized crystalline silicon inert gas stream in an amount from about 5-16% total weight of silicon introduced into the melt.

Doping of the silicon melt in two steps: first the administration of a molten aluminum or a silicon alloy at a temperature ^of 1350-1650 C and with simultaneous cooling of the melt by bubbling an inert gas to a temperature of 40-100 ° C above ^the liquidus temperature of the alloy obtained, and then administering the pulverized crystalline silicon with an inert gas jet in an amount of 5-16% of the total weight of silicon introduced into the melt, allows to improve the quality of the alloy by obtaining a uniform chemical composition and grinding of crystals of primary silicon, with Kratom duration of melting and reducing the cost of the alloy.

 The alloying of the melt with silicon in two stages allows simultaneous high-temperature alloying, which ensures high productivity of the process, and alloying of the melt, combining modification at low temperatures. As a result of the two-stage process of alloying, a reduction in the duration of melting as a whole is achieved.

The introduction of silicon into the melt in a first doping step with a temperature of 1350-1650 ^{° C} dramatically reduces the duration of melting at this stage by accelerating the diffusion of silicon into the melt as a result of the high temperature silicon melt boundary. In this case, the process of transferring silicon from this boundary deep into the melt is facilitated by bubbling the melt with an inert gas, at which not only a high uniformity of the chemical composition of the molten alloy is achieved, but also its cooling to the temperature necessary for the second stage of alloying the melt with silicon. The use of an inert gas as a mixer and cooler in the first stage of alloying allows you to simultaneously refine the melt from the gas.

The introduction of pulverized crystalline silicon with an inert gas jet in the second stage of alloying after cooling the melt provides (along with additional alloying) the modification of the resulting alloy and further cooling of the melt to the casting temperature. When this cooling of the melt in the first stage to a temperature of 40-100 ° C above ^the liquidus temperature of the alloy and the amount of pulverized crystalline silica (5-16% by weight of silicon introduced into the melt) injected in the second stage are interconnected and this relationship is due to the inhomogeneity particle size distribution of silicon dusty waste. The effect is achieved due to the fact that part of the dust fraction will inevitably melt, while the other part, being melted, creates stable crystallization centers.

 Thus, as a result of two stages of alloying the melt with silicon, an improvement in the quality of the alloy is achieved both by increasing the uniformity of its chemical composition and reducing gas content, and by grinding the crystals of primary silicon, which contributes to an increase in mechanical properties (strength and ductility).

 A significant reduction in the duration of smelting in the first stage of alloying provides its second stage with simultaneous modification with a total reduction in the duration of preparation of the alloy, which helps to increase the productivity of the melting-distributing unit and thereby reduce the cost of the alloy. This is also facilitated by the use of pulverized silicon in the second stage of alloying, which is a waste product of the production of aluminum-silicon alloys.

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

Reduction of silicon introduced into the melt temperature of less than 1350 ^{° C} leads to a sharp braking process of silicon diffusion into the melt, which increases the duration of melting, and increase of more than 1650 ^{° C} is inappropriate because of increased loss of aluminum.

Cooling the melt to a temperature above the liquidus of overheating by more than 100 ^{° C} reduces the effect of modification and less than 40 ^C, it is impractical due to increased duration of melting.

 A decrease in the amount of powdered crystalline silicon introduced is less than 5% of the total weight of silicon introduced into the melt leads to the disappearance of the modifying effect, and an increase of more than 16% increases the melting time without an additional modifying effect.

 As a result of the search in the patent and scientific and technical literature, no technical solutions with features distinguishing the proposed invention from the prototype were found, namely: allowing the two-stage alloying of the melt to be combined with the modification of the alloy.

The implementation of the method is carried out in the preparation of hypereutectic aluminum-silicon alloy (aluminum + + 17% silicon). Melting lead in a melting-distributing furnace. For use silicon alloy at a temperature ^of 1350-1650 C, produced in a furnace-type rudovosstanovitelnoy RKO-25KrI and pulverized crystalline silicon with grain size up to 5 mm, which is a waste of production.

PRI me R 1. In the furnace pour 4180 kg of molten raw aluminum (calculated). The aluminum melt at a temperature of 750 ^{° C} is introduced silicon with temperature ¹³⁵⁰ C in an amount of 841 kg. The melt was bubbled with nitrogen and cooled to a temperature of 700 ° ^C or 40 ° C above ^the liquidus temperature of the resulting alloy (containing 17% silicon). Then, pulverized crystalline silicon is introduced into the melt by a stream of nitrogen in an amount of 44 kg or 5% of the total weight of silicon (885 kg) introduced into the melt. Get 5,000 kg of aluminum alloy with 17% silicon (taking into account the loss of aluminum 30 kg and silicon 35 kg). Before casting, samples are taken from the alloy to determine the uniformity of the chemical composition and gas content in the alloy. On thin sections determine the degree of grinding of crystals of primary silicon. Samples are tested for mechanical properties (tensile strength and elongation).

 In examples 2 and 3, an aluminum alloy with 17% silicon is obtained analogously to example 1 with the following parameters.

PRI me R 2. 1. The temperature introduced into the melt of silicon 1500 ^about C.

2. Melt temperature after cooling of 730 ° ^C or 70 ° C above ^the liquidus temperature of the resulting alloy.

 3. The amount of powdered crystalline silicon introduced is 95 kg or 10.5% of the total weight of silicon introduced into the melt (905).

PRI me R 3. 1. The temperature introduced into the melt of silicon 1650 ^about C.

2. Melt temperature after cooling of 760 ° ^C or 100 ° C above ^the liquidus temperature of the resulting alloy.

 3. The amount of powdered crystalline silicon introduced is 148 kg or 16% of the total weight of silicon (925 kg) introduced into the melt.

 In examples 4-9, an aluminum alloy with 17% silicon is obtained analogously to examples 1-3 outside the proposed ranges.

 Get an alloy of aluminum with 17% silicon by a known method.

 The test results are shown in the table.

 The table shows that the use of the proposed method for the production of hypereutectic aluminum-silicon alloys (examples 1-3) provides an increase in the quality of the alloy: the tensile strength increases by 17% on average, the elongation increases by 22% (the size of primary silicon crystals decreases by 1.3 times). The gas content is reduced by 1.2 times. The uniformity of the chemical composition of the alloy increases. The preparation time of the alloy is reduced by 24%, which allows to increase the productivity of the melting-distributing unit and thereby reduce the cost of the alloy. The use of pulverized silicon, which is a waste of the production of aluminum-silicon alloys, also contributes to this.

Claims (2)

1. METHOD FOR PRODUCING ZAEUTEKTIC ALUMINUM-SILICON ALLOYS, including alloying a melt with silicon with stirring, cooling and casting, characterized in that the alloying is carried out in two stages: first, silicon with a temperature of 1350-1650 ^o С is introduced into the melt with simultaneous bubbling and cooling the melt with an inert gas to a temperature of 40-100 ^{° C.} above the liquidus temperature of the resulting alloy, and then pulverized crystalline silicon is injected with an inert gas stream.  2. The method according to p. 1, characterized in that the pulverized crystalline silicon is introduced in an amount of 5 to 16% of the total mass of silicon introduced into the melt.

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