RU2354735C2 - Method of receiving of chrome-bearing alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used for processing of chrome ore, concentrates and aluminium-bearing wastes of non-ferrous metallurgy. In the method in the capacity of aluminium-bearing material it is used preprepared aluminium-bearing wastes from manufacturing of secondary aluminium in amount 0.6-1.1 wt % per 1 wt % of content Cr₂O₃ in chrome-ore concentrate. Isolation of received in furnace melt is implemented with blending during 10-15 minutes, after which it is preliminary pumped out in slag pan 70-90% of dross major part from the total dross mass, then it is pumped out part of the rest slag into metallic reservoir, isolated during 3-5 minutes and discharged the rest part and metal to the same metallic reservoir.

EFFECT: invention provides developing of the new technology of chrome-bearing alloy, providing substitution of expensive reductant by significantly cheaper aluminium-bearing wastes from the aluminium production and increasing of extraction ratio of chrome into the metal.

1 ex, 1 tbl

Description

The invention relates to the field of ferrous and non-ferrous metallurgy, in particular to the processing of chromium-containing materials by reduction smelting in electric furnaces, can be used for the processing of chromite ores, concentrates and aluminum-containing waste from non-ferrous metallurgy.

A known method for producing chromium-containing alloys, which is most widely used in Russia for the production of medium- and low-carbon ferrochrome varieties, which includes crushing and drying of chromite ores, reducing silicothermic smelting using ferrosilicon chromium processing and subsequent casting of the obtained metal. Silicon contained in ferrosilicochrome [Karnoukhov V.N. is used as a reducing element]. Low-carbon ferrochrome technology. / V.N.Karnoukhov, Yu.I. Voronov, V.P. Zaiko, V.I. Zhuchkov. - Yekaterinburg: Ural Branch of the Russian Academy of Sciences, 2001. - 482 p.].

The main disadvantage of this method is its two-stage, justified by the need for smelting in the first stage carbothermal conversion ferrosilicochrome in ore-reducing electric furnaces, which requires the involvement of additional melting capacities in the production cycle.

As a prototype adopted the closest in technological essence to the claimed method for producing chromium-containing alloys, which includes the preparation of chromium-ore material to obtain chromium-ore concentrate and its mixing with aluminum-containing and fluxing materials, melting and aluminothermic reduction in a furnace, aging the obtained melt, consisting of slag and metal , and the release of metal and slag into the metal receiver. As the reducing element is used aluminum contained in aluminum powder [Lyakishev NP Aluminothermy. / N.P. Lyakishev, Yu.L. Pliner, G.F. Ignatenko, S.I. Lappo. - M.: Metallurgy, 1978.- 424 p. (prototype)].

The advantage of this method is the possibility of obtaining low-carbon ferrochrome in a one-stage method due to the exclusion of redistributed ferrosilicochrome from the charge. The main disadvantage of this method is the use of an expensive reducing agent - aluminum powder, the high cost of which served as one of the main reasons for the low utilization of the aluminothermic method for the production of ferrochrome at domestic metallurgical enterprises.

The objective of the present invention is to develop a new aluminothermic method for producing a chromium-containing alloy, which allows to replace the expensive aluminum powder with a much cheaper aluminum-containing reducing agent.

The technical result of the present invention is to increase the extraction of chromium in the final metal melt due to a more complete dispersal throughout the volume of the reducing element, which favorably affects the kinetics and mechanism of the chromium reduction process.

The specified technical result is achieved by the fact that in the method for producing a chromium-containing alloy, which includes preparing a chromium-ore material to obtain a chromium-ore concentrate and mixing it with aluminum-containing and fluxing materials, melting and aluminothermic reduction in a furnace, holding the melt consisting of slag and metal, and releasing the metal and slag into a metal receiver, according to the invention, pre-prepared aluminum-containing materials are used as an aluminum-containing material secondary aluminum production moves in an amount 0.6-1.1 wt.% to 1 wt.% content of Cr ₂ O ₃ in hromorudnom concentrate obtained extract is carried out with stirring for 10-15 minutes in the melt furnace, after which a pre-download slag 70-90% of the main part of the slag of the total mass of slag, then download part of the remaining slag into the metal receiver, incubated for 3-5 minutes and release the rest of the slag and metal into the same metal receiver.

The essence of the invention lies in the fact that the inventive method for producing a chromium-containing alloy allows you to create the conditions necessary for smelting medium- and low-carbon ferrochrome varieties with an content of 60 to 80 wt.% Chromium in an electric furnace without the use of expensive aluminum powder. The proposed method for producing a chromium alloy allows you to use a cheap type of reducing agent - aluminum-containing waste from aluminum production. The inventive method also allows you to involve in the processing of waste production of non-ferrous metallurgy.

Before melting, the chromium-ore material must be crushed to achieve a fraction of less than 3 mm, dried and fired to remove residual moisture and reduce carbon content.

Aluminum-containing wastes from aluminum production must also be subjected to preliminary preparation: crushing, enrichment by separation to obtain a metal concentrate containing 40-70% aluminum metal, and averaging.

Before melting, it is necessary to thoroughly mix the charge materials, which is justified by the large difference in the densities of the chromium-ore and aluminum-containing materials. The degree of mixing of chromium alloys with the proposed method depends on the degree of extraction of chromium into metal and the aluminum content in the final product, which is limited by the requirements of GOST 4757-91 - not more than 0.2% aluminum in low-carbon ferrochrome grades (ФХ001-ФХ010).

The amount of aluminum-containing waste equal to 0.6-1.1 wt.% Per 1 wt.% Cr ₂ O ₃ in the chromium ore concentrate is sufficient not only for the complete reduction of chromium, but also iron from the oxide melt. Moreover, the lower limit of the amount of aluminum-containing waste belongs to the richer in aluminum metal concentrate, and the upper limit to the poorer.

A decrease in the amount of aluminum-containing waste in the charge of less than 0.6 wt.% Per 1 wt.% Cr ₂ O ₃ in the chromium ore concentrate will reduce the degree of extraction of chromium in the metal due to the lack of aluminum for the occurrence of reduction reactions in full.

An increase in the amount of aluminum-containing waste in the charge of more than 1.1 wt.% By 1 wt.% Cr ₂ O ₃ in the chromium ore concentrate will lead to unreasonable overspending of the reducing agent, deterioration of the technical and economic indicators of smelting and the formation of ferrochrome with a high aluminum content.

After the occurrence of the reduction reactions, the melt is held in the furnace for 10-15 minutes with stirring, which allows deeper refining of the metal melt and more complete extraction of chromium into the metal due to the precipitation of small metal beads from the slag phase. After exposure, the bulk of the slag is downloaded (70-90% of the total mass of slag) into a special slag. Then, part of the remaining slag (30-50%) is released into the metal receiver, soaked for 3-5 minutes and the rest of the slag and metal are released into the same metal receiver. Additional refining of the metal passing through the slag melt, helps to increase chromium extraction and lower carbon content in the final product.

The invention is illustrated by the following examples.

The inventive method for producing a chromium-containing alloy was tested in laboratory conditions at the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences.

The following materials and equipment were used:

1. Raw materials.

A chromite ore concentrate containing, wt.%: 58.1 Cr ₂ O ₃ , 11.0 Fe _total , 16.5 MgO, 1.1 Al ₂ O ₃ , 3.4 SiO ₂ .

2. The reducing agent.

Aluminum powder containing 98 wt.% Al.

Aluminum-containing metal concentrates prepared by separating waste from the production of secondary aluminum: aluminum slag (20.9 wt.% Al) and nastilya (waste collected from the surface of the furnace and auxiliary equipment after a series of smelts for the production of secondary aluminum with an average content of 35.2 wt .% Al). To conduct experimental swimming trunks, two types of metal concentrate were made:

- poor with 40 wt.% Al;

- rich with 70 wt.% Al.

3. The flux.

Freshly calcined lime with a CaO content of 88 wt.%.

3. Muffle furnace.

4. Electric Tamman.

The order of the swimming trunks was as follows. All charge materials were supplied with a fraction of less than 3 mm. The chromite ore concentrate was preliminarily calcined in a muffle furnace for 2 hours at 700 ° C. The calcined ore was thoroughly mixed with aluminum-containing metal concentrate and lime (the amount of lime was taken as 60% by weight of the metal concentrate) and loaded into corundum crucibles, which were placed in the working space of the furnace. After that, the temperature in the furnace was increased, the mixture was melted and the aluminothermic reduction of chromium and iron was carried out. Upon completion of the reduction reactions, the melt was kept in an oven for 14 minutes with stirring. The bulk (75 wt.%) Of the slag was downloaded. Then, part of the remaining slag (40%) was drained into a preheated metal detector, and after 3 minutes, the rest of the slag and metal were released into the same metal detector.

The main indicators of experimental swimming trunks are presented in the table. In all melts, the carbon content in the final metal did not exceed 0.1 wt.%.

Tests showed that the proposed method for producing a chromium-containing alloy allows low-carbon grades of ferrochrome from chromium-containing materials and aluminum-containing waste from aluminum production to be smelted in an electric furnace without using aluminum powder in the charge. Comparing the technological indicators of smelting by the proposed method and prototype, it should be noted that with approximately equal chromium content in the final ferroalloy (table - melting No. 1, 3, 4) in the proposed method, an increase in the extraction of chromium in metal (from 88 to 90%) is observed due to more complete dispersal of the reducing element in volume. The economic effect of using the proposed invention is achieved mainly through the use of a cheap type of reducing agent - aluminum-containing non-ferrous metallurgy waste instead of expensive aluminum powder.

The results of experimental smelting of a chromium alloy according to the claimed method of obtaining No. p / p Type of reducing agent The amount of reducing agent, wt.% For 1 wt.% Cr ₂ O ₃ in chromium concentrate The estimated amount of aluminum-containing material for melting, g * The content in ferrochrome, wt.% Extraction of Cr in the metal,% Note Cr Al Prototype one Aluminum powder 0.44 25.56 74.1 0.11 88 The proposed method 2 Metal Concentrate (70 wt.% Al) 0.50 29.05 72.5 0.08 79 outside the proposed method 3 Metal Concentrate (70 wt.% Al) 0.62 36.02 74.0 0.15 90 four Metal Concentrate (40 wt.% Al) 1.10 63.91 73.3 0.20 90 5 Metal Concentrate (40 wt.% Al) 1.30 75.53 71.5 3.82 91 beyond the limits
claimed
way * The amount of all charge materials was calculated per 100 g of chromium ore concentrate with a content of 58.1 wt.% Cr ₂ O ₃ .

Claims (1)

A method for producing a chromium-containing alloy, including preparing chromium-ore material to obtain chromium-ore concentrate and mixing it with aluminum-containing and fluxing materials, melting and aluminothermic reduction in a furnace, holding the obtained melt consisting of slag and metal, and discharging the metal and slag into a metal receiver, characterized in that as the aluminum-containing material using pre-prepared aluminum-containing waste production of secondary aluminum in the amount of 0.6-1.1 wt.% for 1 wt.% the content of Cr ₂ O ₃ in the chromium ore concentrate, the melt obtained in the furnace is kept under stirring for 10-15 minutes, after which 70-90% of the main part of the slag of the total mass of slag is preliminarily downloaded to the slag, then download part of the remaining slag into the metal receiver, stand for 3-5 minutes and release the rest of the slag and metal into the same metal receiver.