SU1521780A1 - Method of melting chromium-containing charge preparation - Google Patents

Abstract

The invention relates to ferrous metallurgy and can be used in the smelting of chromium-containing charge blanks in arc steelmaking furnaces. The purpose of the invention is to increase the yield of metal, increase the degree of extraction of alloying elements and reduce the cost of finished products. Screenings of graphitization in the amount of 10-15 kg / t, together with screenings of magnetic separation, dump slags from the production of low-carbon ferrochrome at a ratio of 1: (5-10) are given to the decay zone of the electrodes after filling and each basement. 5-10 minutes before the release, the temperature of the metal is adjusted to 1530-1580 ° C and slag is deactivated by graphitization screenings in an amount of 3-5 kg / ton. The use of the invention allows to increase the extraction of chromium by 8% and the yield of 5%. 2 tab.

Description

The invention relates to ferrous metallurgy and can be used in the smelting of chromium-containing strip billet in arc steelmaking furnaces.

The purpose of the invention is to increase the yield of a suitable metal, increase the degree of extraction of alloying elements and reduce the cost of production.

Ferrochrome screenings are obtained by magnetic separation of waste slags from the production of low-carbon ferrochrome by the silicothermic method.

Composition of magnetic screenings of ferrochrome production: CaO 50-52; Sio

25-28; MgO 8-12; Сг ,, 0з 3-7; Or 2-7; rest. In the screenings for the production of ferrochrome, residual chromium forms part of the sparingly hard MgO Cr Os spinel, whose solubility increases with the addition of SiOi. The reduction of chromium oxides by carbon is increased with the addition of S10g. Therefore, to reduce the melting temperature of the slag, to obtain a consistently high rate of reduction of chromium oxides, screenings of the heat insulating charge of graphitization furnaces were introduced into the system (carbon content 77%, ash 23%, which contributes SiOi30%, Sic 5%), Additive in

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A furnace of 10–15 kg / t of carbon-containing materials, together with magnetic screenings of ferrochrome production, provides the most complete reduction of chromium, promotes the formation of carbon monoxide, which reduces the oxidizing potential of the furnace atmosphere, reduces carbon alloying elements. The reduction of chromium oxide with carbon is proceeding according to the reaction + 2С 2Сг + ЗСО. The initial temperature of the beginning of the reaction is IZAO G.

In the decay zone of the electrodes at a temperature above 1240 ° C, chromium oxide is completely reduced by solid carbon.

In addition, the introduction of a mixture of magnetic screenings for the production of graphite-containing ferrochrome and-screenings containing silicon carbide, which is in the form of inclusions in relics of coke, in the decay zone of the electrodes, gives better slag foaming, which reduces the loss of metal by evaporation, more stable arc burning, more e fast metal heating, reduces overheating of the furnace lining.

When carbon-containing materials are introduced into the furnace less than 10 kg per 1 ton of filling, the reduction of chromium oxides proceeds more slowly, the formation of carbon monoxide decreases, the oxidizing potential of the furnace atmosphere increases, which leads to an increase in the loss of alloying elements, reduces the efficiency of using magnetic screenings of ferrochrome production. ,

The increase in the consumption of carbon-containing materials above 15 kg / t does not lead to a significant change in the rate of reduction, a further increase in the amount of reduced chromium.

The screenings of graphitization, containing silicon carbides in the form of inclusions in the relics of coke, break up the chrome-spinelidy, foamed slag, accelerate the heating of the metal, provide earlier slagging, create a reducing atmosphere in the furnace, which ultimately leads to an increase in the degree of extraction of alloying elements.

The content of screenings for the production of ferrochrome is 5-10 times higher than that of carbon-containing materials.

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em more efficient use. chromium waste. The number of screenings for the production of ferrochrome on smelting is determined by the required basicity of the slag and the initial silicon content in the charge metal. Additive in the furnace, after the melting of the filling, magnetic screenings of ferrochrome production in the amount of 50-150 kg per 1 ton of the charge contributes to the formation of slag with a basicity of 1-1.5, reduces the loss of alloying elements. Magnetic screenings of ferrochrome production, containing 50-52% CaO, have a melting point well below the melting point of lime. The price of 1 ton of screenings for the production of ferrochrome is lower than the price of 1 ton of lime by 20 rubles. In addition, screenings containing small ferrochrome beads, chromium oxides, are an additional source of chromium supply to metal-bearing metals. Magnetic screenings produced by ferrochrome, which are squeezed in a mixture with graphitization waste, are quickly dispersed in the high-temperature zone. by reacting with carbon, they are restored. Early slagging and reducing atmosphere in the furnace protect the alloying elements from oxidation.

Thus, the following properties appear:

earlier than 1-1 pack of frothy slag having a lower melting point;

the use of inexpensive materials to replace scarce fluorspar and lime with a mixture of chromium-containing fluxes;

the mixture is electrically conductive, low-melting, cheaper than lime, additionally introduces chromium and chromium oxides, and waste slags are used, t, e, a low-waste technology of smelting charge billet is created.

Before the metal is released from the furnace, the oxides of the alloying elements are restored from the slag by the introduction of graphitization screenings powder, which have silicon carbide in their composition, but not in a free form, but in the form of inclusions in the relics of coke, which ensures a higher degree of restoration of the alloying elements. Used for deoxidation graphitization screenings have greater recovery

they have a greater bulk density than coke, coal which also positively reflects the degree of extraction of alloying, provides a more complete recovery.

Introduction to a furnace at a metal temperature of 1530–1580 ° C with 3.0 kg of graphitization screenings allows an average recovery of 3.5 kg of chromium. When added to pshak less than 3 kg / ton of screenings of graphitization, the kinetic conditions for the reduction of oxides from the slag deteriorate, which leads to an increase in the loss of alloying elements. Increasing the flow rate of graphitization above 5 kg / t does not lead to a further increase in the chromium recovery rate.

The deacidification of slag by graphitization screenings, which both carbon and silicon carbide are introduced into the furnace, contributes to the destruction of chrome-spinels and the dilution of slag; reduces the content of CrijO from slag to 3%; reduces slag mass by 2-3 times, which provides an increase in the extraction of alloying elements,

When the temperature of the metal is below 1530 ° C, the viscosity of the slag increases, its physicochemical properties deteriorate, which leads to a decrease in the degree of chromium extraction.

Increasing the temperature more leads to the fact that the duration of smelting increases, the content of slag increases

When slag deoxidation lasts less than 5 minutes, it does not have time to react; all the seated carbon containing the material, - reduces chromium extraction.

When slag is deoxidized for more than 10 minutes, the duration of smelting increases unnecessarily.

The proposed method of resource-saving smelting of chrome-containing charge billet allows: to engage in production of previously unused screenings of ferrochrome production and screenings of heat insulating charge of graphitization furnaces, which increases the degree of chromium extraction, increase the yield of the finished metal.

This is confirmed by pilot-scale industrial melts, which were carried out in an electric arc furnace at

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Smelting charge blanks B26; 1.5 tons of chips were loaded into the furnace. After | A mixture of 20 kg of graphitization screenings and 180 kg of magnetic screenings of ferrochrome production was introduced into the decay zone of the electrodes by melting the charge. Having loaded 1.4 tons of chips with the first basement and smelted them, another 30 kg of graphitization screenings and 180 kg of magnetic screenings of ferrochrome production were introduced into the furnace.

After melting all the chips piled up in the furnace with five basements, 5 tons) and heating the molten metal to 1540 ° C, 30 kg of graphitization screenings powder were applied to the slag. After 7 min, the metal was released into the ladle.

The chemical composition of the slag before the release from the furnace of the metal charge blank B26 according to the known and proposed technology is given in table 1,

The results obtained by the proposed and well-known method of smelting charge blanks B26, are shown in Table 2.

Analysis of the data given in Tables 1 and 2 shows that using the proposed method for smelting charge billets provides the following advantages compared with the known: the amount of chromium oxides in slag decreases from 2A to: 10.3%, manganese oxides from 9.2 to 4.2%, chromium recovery increased by 8 ,. nickel by 3%, the yield of the suitable (liquid) metal is increased by 5%,

Claims (1)

Invention Formula The method of melting the chromium-containing charge billet, inclusive chunks batch loading of chips, the introduction of a mixture of carbon-containing and slag-forming materials in a crushed form at a ratio of 1: (5-10} after melting the filling and each after the bottom of the basement, deacidification of carbon-containing materials, o characterized in that, in order to increase the yield of the metal, increase the degree of extraction of alloying elements and reduce the cost, graphitization screenings in the amount of carbonaceous materials are used as carbon-containing materials. e 10–15 kg per 1 ton of filling; as slag-forming materials, screening of magnetic separation of waste slags from the production of green carbon ferrochrome, while the entire mixture of these materials is given into the decay zone of the electrodes, and 5–10 minutes before the release of the metal temperature, t up to 1530- and slag is cleared by graphitization screenings in the amount of 3-5 kg per 1 ton of the entire metal fill, Table 1  Unnecessarily increased consumption by excluding gr. 4 taiin Uyepppnvvtsts loss of chrome, nickel The yield is reduced, l Reduced extraction of chrome, the yield of non-galle. Table