RU2403305C2 - Charge for obtaining high-carbon ferrochrome - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: charge contains utilisable waste of in-house manufacture, poor lump chromite ore as chrome ore materials with Cr/Fe ratio 1.8-2.2 or its concentrate of 4-100 mm fraction, mixture of coke breeze of 10-25 mm fraction as carbon reducing agent, at the following component content, wt %: coke breeze 6-8, coal 4-5, silicone containing flux 2-4, utilisable waste of in-house manufacture 4-8, poor lump chromite ore its concentrate - the rest.

EFFECT: invention allows obtaining high-carbon ferrochrome as per simplified technique, without costs for preliminary agglomeration of small rich chromite ores, partially using cheaper carbon reducing agent and reducing specific consumption of electrodes.

Description

The invention relates to the field of ferrous metallurgy, in particular to blends for producing high-carbon ferrochrome, can be used for processing poor chromite ores with a Cr ₂ O ₃ content _of 35-40%.

A charge is known for producing high-carbon ferrochrome (with a Cr content of over 65%) in ore-reducing electric furnaces, which is most widely used in the CIS countries, which includes rich lump chromite ore of the Kempirsai deposit, coke, semi-coke, silicon-containing flux and recycled waste from the production of ferrochrome. The composition of the charge was as follows, kg:

Chrome ore: - lumpy 300-400 - ordinary 300-200 Coke 75 Semi-coke 60 Ferrosilicochrome slag 0-30 Recycled waste 0-100

[Gasik M.I., Lyakishev N.P., Emlin B.I. Theory and technology for the production of ferroalloys / M.: Metallurgy 1988. S.329-337].

The main disadvantage of this charge is the impossibility of using poor chromite ores with a Cr ₂ O ₃ content _of 36-40% (to which the majority of chromite ores of domestic deposits belong).

The prototype is a mixture for producing high-carbon ferrochrome in ore reduction furnaces, used at the Serov Ferroalloy Plant, containing, wt.%: Chromium materials (in the form of briquettes from fines rich in chromite ore (45-50% Cr ₂ O ₃ ) - 30-55, carbon reducing agent (coke) - 11-15, silicon-containing fluxing materials - 2-6, poor chromite ore - the rest.

[Zhuchkov V.I., Zayakin O.V., Halperin L.L., Ostrovsky Y.I. and others. The mixture for producing high-carbon ferrochrome // RF Patent No. 2241057 (prototype)].

The advantage of this method is the possibility of partial involvement in the processing of poor chromite ores. The main disadvantages are the need to introduce an additional stage of preparation of ores for smelting, preliminary sintering of fines of rich chromite ores.

The technical result of this invention is the development of a new composition of the mixture, which allows to scale up poor domestic chromite ores in the process of producing high-carbon ferrochrome and partially replace expensive coke with cheaper carbonaceous reducing agents.

The specified technical result is achieved by the fact that the mixture for producing high-carbon ferrochrome in ore-reducing electric furnaces with a Cr content of 50-60 wt.% Alloy, containing chromium materials, a carbon reducing agent, a silicon-containing flux, according to the invention, it additionally contains recycled waste of its own production, as chrome ore materials contains poor lumpy chromite ore with a ratio of Cr / Fe of 1.8-2.2 or its concentrate fraction 4-100 mm, as a carbon reducing agent using comfort mixture of coke fraction of 10-25 mm and coal fraction of 10-50 mm, with the following components, wt.%:

Coke 6-8 Coal 4-5 Silicon-containing flux 2-4 Recycled waste own production 4-8 Poor chromite ore or her concentrate Rest

The essence of the invention lies in the fact that the inventive charge for producing high-carbon ferrochrome allows the production of high-carbon ferrochrome with a content, wt.%: 50-60 Cr, 0.9-2.9 Si, 0.02-0.04 P and 7.5 -8.2% C from poor ores with a Cr / Fe ratio of 2.2-1.8 without the use of rich chromite ore and recycle domestic waste. Unlike the prototype, this mixture allows to obtain high-carbon ferrochrome using a simplified technology, without the cost of preliminary agglomeration of fine rich chromite ores, partially use a cheaper carbon reducing agent and reduce the specific consumption of electrodes.

The range of contents of the components given in the composition of the mixture is explained as follows:

With the introduction of Coxic in an amount of less than 6 wt.%, The degree of reduction of chromium and iron decreases due to the lack of carbon in the course of the corresponding reduction reactions.

When the amount of coke is increased by more than 8 wt.%, An unreasonable overconsumption of the reducing agent occurs, thermodynamic conditions arise that contribute to a better reduction of silicon, which leads to a decrease in the carbon content in the alloy. The aggressive effect of metal and slag on the magnesite lining of the furnace increases.

An increase in the P / Cr ratio (a decrease in the content of Cr ₂ O ₃ in the ore to 35-40 wt.% While maintaining the phosphorus content at the level of 0.003-0.004 wt.%) In poor chromite ores requires the use of phosphorus-friendly reducing agents and does not allow the use of ordinary coke . The use of expensive coke with a low phosphorus content (less than 0.03 wt.%) Significantly increases the cost of high-carbon ferrochrome. To reduce the cost of reducing agents, it is proposed to use a mixture of coal (4-5 wt.%) And coke (6-8 wt.%), Which is sufficient to restore iron, chromium, carbonization of ferrochrome and allows to obtain high-carbon ferrochrome with a phosphorus content of less than 0.04 wt.%. An increase in coal content of more than 5 wt.% Leads to an excessive increase in the temperature of the top, which complicates the maintenance of the electric furnace and can lead to emergency situations.

To adjust the chemical composition of the slag from the production of high-carbon ferrochrome, silicon-containing fluxing materials are introduced into the charge: crushed slag from the production of ferrosilicochrome of the ФХС48 grade (50% SiO ₂ , 15% Al ₂ O ₃ , 15% Si _met. , 10% Cr _met. ), Ferrosilicon of the ФС45 grade and FS65 (25-40% SiO ₂ , 30% Al ₂ O ₃ , 20-30% Si _met. ) or quartzite (97% SiO ₂ ). The content of fluxing materials in the charge (2-4 wt.%) Is determined by the requirements for the production of slags, ensuring the normal course of the melting process. So, with an excess of fluxes (more than 4%), the slag turns out to be fusible, the furnace course is cold, so the chromium from the ore part is not completely restored, the metal can solidify on the bottom of the furnace. If the flux mixture is less than 2%, the slag is refractory and viscous, which causes difficulties in the discharge of slag from the furnace. In this case, the loss of chromium increases due to entanglement of the metal kings in viscous slag.

The number of fluxing additives, compared with the prototype, is reduced due to the use of waste from our own production (metallized slag, bursts, etc.). With a decrease in the content of own production waste in the charge of less than 4 wt.%, It is necessary to increase the amount of fluxing additives to adjust the composition of the slag. With an increase in domestic production waste of more than 6 wt.%, A violation of the melting course can occur.

The invention is illustrated by the following examples.

The claimed charge for producing high-carbon ferrochrome was tested in the smelting shop No. 1 of the Serov Ferroalloys Plant OJSC.

The following materials and equipment were used:

1. The concentrate of the Saranovsky field, containing, wt.%: 39,0 Cr ₂ O ₃ ; 18.8 FeO; 4.6 SiO ₂ ; 14.7 MgO; 15.9 Al ₂ O ₃ ; 0.3 CaO; 0.0029 P.

2. Coke Severstal OJSC (84.6% C, 0.026% P).

3. Coal of the Krasnogorsk open pit (85.5% C, 0.029% P).

4. Silicon-containing flux of two types:

- ferrosilicochrome slag containing, wt.%: 50 SiO ₂ ; 15 Al ₂ O ₃ ; 10 MgO; 15 Si _met. ; 10 Cr _met. ; 5 Fe _met. .

- screenings of quartzite containing, wt.%: 97.0 SiO ₂ ; 0.5 Al ₂ O ₃ ; 0.3 MgO; 0.5 FeO.

5. Circulating waste of own production, containing, wt.%: 35 SiO ₂ ; 8 MgO; 10 Al ₂ O ₃ ; 10 Fe _total ; 20 Cr _total

6. Electric arc furnace type RKO-23.

The mixture to obtain high-carbon ferrochrome contained, wt.%:

Saranovsky concentrate (fraction 4-100 mm) 77,2 Coxic (fraction 10-25 mm) 7.8 Coal (fraction 10-50 mm) 4.8 Silicon-containing flux 3.9 Recycled waste of own production 6.3

Melting was carried out in a continuous way, with a constant top level maintained by periodically loading the charge into the furnace as it was melted. Release was made every 2 hours of operation of the furnace.

Tests showed that the proposed mixture for producing high-carbon ferrochrome allows smelting ferrochrome from poor chromite ores of domestic deposits with a Cr / Fe ratio of 2.2-1.8, corresponding to the FeCr50 grade GOST 4757-91. The economic effect of using the proposed invention is achieved mainly through the use of cheap low-grade chrome ore raw materials from domestic deposits instead of expensive imported rich chromite ore, the possibility of eliminating one stage of the redistribution of ore materials (sintering process) from the technological cycle of production of high-carbon ferrochrome, and the partial use of a cheap type of carbonaceous reducing agent instead expensive low-phosphorous coke.

Claims (1)

The mixture for producing high-carbon ferrochrome in ore-reducing electric furnaces with a Cr content of 50-60 wt.% Alloy, containing chromium-containing materials, a carbon reducing agent, a silicon-containing flux, characterized in that it additionally contains recycled waste of its own production, contains chromium-poor lumpy chromite as materials ore with a ratio of Cr / Fe of 1.8-2.2 or its concentrate of a fraction of 4-100 mm, a mixture of coke fraction of 10-25 mm and coal of a fraction of 10-50 mm p is used as a carbon reducing agent When the following content of components, wt.%:
Coke 6-8 Coal 4-5 Silicon-containing flux 2-4 Recycled waste of own production 4-8 Poor chromite ore or its concentrate Rest.