SU1125277A1 - Charge for smelting silicocalcium - Google Patents

Abstract

CHARGE FOR MELTING SILICO CALCIUM, including lime, silicon, and fluorspar, distinguishing a so that, in order to intensify the recovery process. Calcium during melting of the charge and increasing its content in the alloy, it additionally contains metallic barium or its silicides in the following ratio of components, May. %: 28-33 Fluoride silicon 6-10 spar Barium metal or its silicon 0, 5-3.0 cides Lime Else

Description

The invention relates to the field of ferrous metallurgy, specifically to the production of ferroalloys, in particular, to the charge for smelting high calcium silicocalcium (Ca over 25%) having a density lower than the density of slag.

The known mixture for melting silicocalcium, consisting of lime, ferrosilicon, fluorspar and additives of calcium carbide in an amount of 5-20% by weight of lime ffj.

A disadvantage of the known charge is a reduced calcium content in the alloy. In the process of melting the charge, the rate of saturation of the alloy with calcium is lowered. As the duration increases, silicon flint occurs, which, in turn, leads to a decrease in the calcium content in the alloy.

Closest to the proposed composition and the effect achieved is a mixture for smelting high calcium silicium containing lime, silicon (siliceous reducing agent, such as ferrosilicon FS90, technical crystalline silicon) and fluorspar 2j

The disadvantages of the known charge are the low rate of calcium saturation of the alloy and at the same time its low content in the alloy, not exceeding 32%.

The process of calcium saturation (interaction of silicon with calcium oxide of lime) takes place during the melting of the charge. Due to the high melting point of lime, as well as the high strength of the CaO compound, the reaction process by reaction

4CaO + 5Siggjjg -ZCaSi iZCaO-SiO (1)

passes slowly. At the end of the melting of the mixture, the alloy is not completely saturated with calcium. The calcium content in the alloy is not more than 32%.

In saturated (saturation degree 100%), free silicon alloy is absent, and calcium is bound to calcium disilicides (CaSigi).

The prolonged holding of the alloy under the arcs after the charge has been melted, although it leads to an approximation to the absorption of calcium by the alloy, but this significantly increases the loss of silicon and calcium, which ultimately leads to a decrease in the calcium content.

Along with this, the inhibition of smelting reduces the productivity of the furnace and impairs the technical and economic indicators of production. The melting of the melted charge under the electrodes leads to cooling of the lower horizons of the melt, increasing the hearth and to the intake of the tape with chilled slag, which makes it difficult for the melt to flow out of the furnace, requires additional burning of the tap with a rod, which ultimately also leads to a decrease in calcium content. by reducing its solubility when released into the iron alloy rods.

The aim of the invention is to intensify the process of calcium reduction during the melting of the charge and increase its content in the alloy.

The goal is achieved by the fact that the charge for the silico-smelting sinter, including silica and fluorspar, additionally contains metallic barium or its silicides in the following ratio, wt.%:

Silicon 28-33 Fluoride

spar6-10

Barium metal or its silicides О, 5-3 Lime Else Components of the charge: silicon (crystalline silicon, ferrosilicon

FS90 grades according to GOST 1415-78 or I

tall metal with a content of more than 87% silicon with Fe, Mn, Cr, etc. impurities) granulated or crushed to a fraction of less than 50 mm, barium according to TU 48-05-44-71 with a barium content of more than 90% or barium silicides , fluorspar (CaFj more than 50%) according to GOST 7618-70 lime from shaft furnaces according to TU 14-139-7-72 fractions less than 60 mm with a calcium oxide content of at least 90 were weighed and loaded into an electric furnace bath as a homogeneous mixture. llfcjXTy has been melted.

When barium is introduced into the charge during the melting process, the following interactions take place: Ba-nSijj g-BaSi (2)

2BaSin + 6CaO 2BaO + 4CaSi2 + 2CaOSi02 + t (2n - :)) SicBo6- (3)

2BaO + 2CaO- - (2p + 1) 81, „„ 2BaSi “+ 2CaO.SiO, (4)

where Sig is free silicon, i.e. to silicon, not related to silicides-.

Barium combines with silicon to form barium silicides.

Barium silicides react with calcium oxide to form calcium silicoids, barium oxide, dicalcium silicate and free silicon.

Barium oxide, when interacting with free silicon in the presence of calcium oxide, again transforms into barium silicide, which was in the initial period of melting of this material. This process proceeds continuously with the participation of barium until the calcium alloy is completely saturated.

The course of the reaction (3) and (4) is ensured by the high strength of the compound in the right side of the reaction of dicalcium silicate (lN - 538 kcal / mol).

The total interaction over reactions (3) and (A) is expressed by the equation

8CaO + 10Si (.g 4CaSi2-2 -2 (2CaOSi02)

those. The saturation of the alloy with hydrogen is due to the formation of calcium disilicide with the participation of barium. Barium is involved in the reaction as a catalyst in the reduction process.

calcium.

 /

The barium in the charge significantly speeds up the process of calcium alloying of the alloy and at the time of completion of the charge melting the alloy is completely saturated with calcium (there is no free silicon in the alloy), the calcium content in the alloy is 34-37%.

After the end of melting, half of the barium injected from the charge remains in the obtained silicicopy, which is in full accordance with reactions (3) and (4).

Barium, like calcium, is a deoxidizing and desulfurizing agent, in which silicocalcium is used.

When using its alloy with silicon instead of barium, the alloy is first produced by fusion. While the silicon obtained silicide ()

taken into account along with the silicon specified in. The mixtures are separately (the amount of silicon specified in the process separately, and the silicon of the barium sili- gade in the mixture amounts to 28-33 wt.% of the mass of the charge).

After the charge is melted, the melt is poured into the ladle without additional holding in the furnace and then the silicocalcium is poured, and then the slag, which is under the alloy.

The ratio of the amounts of silicon and lime is determined from the condition of providing silicocalcium with a high calcium content. When the amount in the charge: 5 silicon less than 28%, there is an unnecessary cost of electricity for remelting lime (it becomes unnecessary), over-consumption of lime and the formation of a hot melt oxide melt in the lower horizons of the furnace, which causes the growth of the furnace bottom and the opening of the furnace.

If the silicon in the charge is more than 33%, then the alloy is obtained with free 5 (not bound to silicides) silicon, not saturated with calcium.

If in the charge of fluorspar less than 6%, the slag is obtained refractory, which leads to a significant loss of alloy in it, as well as to an increase in the bottom due to the deposition of the refractory slag and slagging of the tap.

An increase in the amount of fluorspar in the charge is more than 10% too much and leads to an increase in the cost of the smelting process of silicocalcium.

When introduced into the mixture of barium metal or in the form of silicides less than 0.5% of its total mass Q, the saturation of the alloy with calcium, and no increase in its content in the alloy is observed.

The introduction of more than 3% of the total mass of the charge into the charge of barium reduces the calcium content in the alloy by increasing the content of barium in it, which binds a part of silicon to silicides.

Example. The test charge conducted on industrial furnace, closed vault, with a transformer capacity of 3.5 MB-A. The working step voltage was 5 (150V).

The composition of the mixture and indicators of melting silicocalcium (average ps variaitam) are presented in the table.

The ratio of components in the proposed mixture for smelting silicocalcium according to the boundary values of the components (option 1 and 3), the average value (option 2) and the known mixture (option 4). In each variant, three melts were performed. In the first version, the charge included 78A, 74 kg (28%) silicon, 280 to (10%) fluorspar, 84 kg (3%) bari, 1654 kg (59%) lime, and according to the second (average) variant - 783.0 kg (30.5%) of silicon, 205 kg (8%) of fluorspar, 45 kg (1.75%) of bari, 1534 kg (89,) of lime, according to the third variant - 785.61 kg (33%) of , 143 kg (6%) of fluorspar, 12 kg of bari (0.5%), 1440 kg (60.5%) of lime. By physical properties, lime was a solid lumpy material with pieces of 20-60 mm in size,. silicon metal in the form of hard fractions of 5-50 mm, fluorspar in the form of a natural mineral with a size of 5-80 mm, barium in the form of metal ingots, molded with a diameter of 50 mm and a length of about 100 mm. The mixture was a homogeneous mixture of solid components, which during the tests were melted in an electric arc furnace. The melting point of the mixture was 1650–1700 ° C. After the mixture was melted, the resulting products (slag and metal) were poured from the furnace into a ladle. The metal-silicocalcium was poured into molds and used further to deoxidize the steel. In the fourth embodiment, the same charge components were used as in options 1-3, but without bari. The number of heats in option three. A comparison was made of a series of heats (option 5, three heats) at the proposed charge, but barium was specified as barium silicate, preliminarily smelted in an electric furnace, which in its composition corresponds to barium disilicide shaft (the composition of the charge is similar to the second melting variant) in barium silicide 75.2%, silicon 21.67%, the rest is an impurity of iron and other elements. In the fifth version of the sample of silicon. . corrected for barium silicon injected with silicide. A comparison of the results of the melting shows that the calcium content in silicocalcium in the melts given on the proposed charge is 2.4-4.8% higher than in the melts with the known charge, and in the melts carried out using barium silicide in the mixture, the excess of calcium content in relation to the alloy obtained from the known mixture reaches 5.5%. An increase in the calcium content in the alloy increased the furnace productivity in the base alloy (30% Ca) on the proposed charge by 9.4-19.6%, and in the smelting using the barium silicide charge by 21.2% compared to the known charge. The intensity of the calcium reduction process, expressed as the rate of calcium saturation of the alloy (this is an increase in calcium content per unit time) in the melts of options 1-3 increased by 8.5–15.25%, and in melts using barium silicide by 18.6% compared with the melting of the known charge. The degree of saturation of the alloy with calcium in swimming trunks on the proposed charge increased by 11.523%, and in swimming trunks using barium silicide to 26.7% compared with the melting of the known charge. The degree of saturation (Cu) is determined by the formula,% Ca fact. 100 Sleep Sa Nash. The calcium content corresponding to saturated (% Ca sat.) Is determined from the conditions of the composition of the alloy consisting of CaSi and FeSi. Iron in the alloy is an impurity. In the fifth variant (using barium silicide) the degree of saturation of the alloy is calcium over 100%. This is due to the fact that the calcium reduction process in this case is so complete that in the final alloy the iron (as shown by X-ray diffraction analysis) is partially due to silicon in monosilicide, which led to an even higher calcium content when using barium silicide compared to metal barium (0.7%) and shows the advantage of using barium syicide. The effectiveness of the proposed silicate melting smelting is achieved by intensifying the calcium reduction process during the melting process. At the same time, the calcium content in the resulting alloy increases, which is the main target element of the final product.

The economic effect in the smelting of silica clamps on the proposed

The charge was achieved by increasing the calcium content in the alloy, reducing the constant production costs due to an increase in the alloy yield (30% Ca). The expected economic effect from the introduction of the charge for sprinkling the chemical scale is 150 thousand rubles. in year.

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Claims (1)

MIXTURE FOR Smelting SILICOCALCY, including lime, silicon and fluorspar, distinguishing me clearly in order to intensify the recovery process. calcium during the melting of the charge and increasing its content in the alloy, it additionally contains metallic barium or its silicides in the following ratio of components, May »% · Silicon Fluorspar Barium metal or its silicides Lime 28-33 6-10 0.5-3.0 Else SU „„ 1125277>