RU2802459C1 - Method for production of steel in electric arc furnace - Google Patents

Abstract

FIELD: ferrous metallurgy.

SUBSTANCE: production of steel in an electric arc furnace. Metal charge is supplied to the furnace, including scrap metal and liquid iron, while the amount of liquid iron is 70-90% of the mass of the metal charge, scrap metal is melted, oxygen is blown, and melt is discharged. First, scrap metal is loaded into the furnace, then liquid cast iron is poured with simultaneous purging of the bath with oxygen with a gradual increase in its consumption from 8000 m³/h to 14000 m³/h as the cast iron is poured, while the scrap metal is melted due to the heat of the exothermic reaction as a result of the oxidation of cast iron impurities.

EFFECT: invention makes it possible to produce steel without consuming electricity and electrodes while providing conditions for effective slag formation and dephosphorization.

1 cl, 1 tbl

Description

The present invention relates to the field of ferrous metallurgy, in particular to the production of steel in an electric arc furnace.

There is a known method for smelting steel in an electric arc furnace (invention patent RU 2543658, published on March 10, 2015), which includes feeding scrap metal and liquid cast iron into the furnace as a metal charge, melting the scrap metal, adding slag-forming materials, purging the bath with oxygen and releasing the melt. According to the known method, liquid cast iron is poured into the furnace in an amount of 40-70% by weight of the metal charge, after which the bath is purged with oxygen at a flow rate of 1800-2200 nm3/hour for 12-25% of the purge time, then the oxygen consumption is increased to 5000-7000 nm3/hour and the bath is purged in a given mode for 28-40% of the purging time, then the oxygen consumption is reduced to 3000-5000 nm3/hour and the purging is carried out in a given mode until it ends.

There is a known method for smelting steel in an electric arc furnace (invention patent RU 2778340, published on May 26, 2022), which includes feeding scrap metal and liquid cast iron into the furnace as a metal charge, melting scrap metal using an electric arc, adding slag-forming materials, and blowing with oxygen. According to a known solution, liquid cast iron is poured into the furnace in an amount of 70-90% of the mass of the metal charge, after which the bath is purged with oxygen at a flow rate of 2000-8000 nm3/hour for 12-25% of the purge time, then the oxygen flow is increased to 5000- 10,000 nm3/hour and purging is carried out in a given mode for 12-25% of the purging time, then the oxygen consumption is increased to 10,000-15,000 nm3/hour and purging is carried out in a given mode until it ends. This method was chosen by the applicant as the closest analogue.

The disadvantages of the known methods are the need to melt the solid part of the metal charge using electric arcs, which increases the cost of steel due to the consumption of electricity and electrodes, as well as the increased duration of melting.

The technical problem solved by the claimed invention is to reduce the consumption of electricity and electrodes.

The technical result is the creation of a steel production method that allows steel smelting without the consumption of electricity and electrodes while simultaneously providing conditions for effective slag formation and dephosphorization. At the same time, the claimed method provides a reduction in the duration of smelting and a reduction in the cost of steel smelting.

This technical result is achieved by the fact that in the known method of producing steel in an electric arc furnace, which includes feeding metal charge into the furnace, including scrap metal and liquid cast iron, with the amount of liquid cast iron being 70-90% of the mass of the metal charge, melting scrap metal, blowing with oxygen and release of melt, according to the invention, first, scrap metal is poured into the furnace, then liquid cast iron is poured with simultaneous purging of the bath with oxygen with a gradual increase in its flow rate to 14,000 m ³ /hour as cast iron is poured, while the scrap metal is melted due to the heat of an exothermic reaction as a result of the oxidation of cast iron impurities without the use electric arcs

The need to increase oxygen consumption is due to the following factors:

- the need to oxidize a large amount of impurities (carbon, silicon, phosphorus) entering the bath as cast iron is poured;

- oxygen consumption is increased gradually to 14,000 m ³ /hour as cast iron is poured to prevent the destructive effect of the oxygen stream on the furnace lining and to prevent the decarburization process from being too intense to prevent boiling of slag residues from the previous melting.

Reducing the share of liquid cast iron to less than 70% leads to the need to increase the share of scrap metal, which does not allow the melt to be heated to the temperature required before release without current. And, as a consequence, it leads to the need to heat the melt with the energy of electric arcs and increase the duration of melting. When the proportion of liquid cast iron increases to more than 90%, the proportion of metal scrap decreases, which leads to overheating of the melt, increased wear of the furnace lining and an increase in the period of its refilling.

Consumption of liquid cast iron from 70 to 90% with simultaneous high-intensity blowing of the melt with oxygen allows, due to exothermic reactions that occur during the oxidation of cast iron impurities (carbon, phosphorus and silicon), to increase the temperature of cast iron during its pouring into the furnace and thereby ensure the temperature necessary for melting solid metal charge, carrying out slag formation and dephosphorization without supplying electric arc energy.

An increase in oxygen consumption above 14,000 m ³ /hour will lead to an overly intense decarburization process, which may result in overoxidation of the melt and a decrease in the durability of the lining.

This technology makes it possible to reduce the duration of melting by 4-6 minutes compared to the prototype.

The declared limits were selected experimentally. The parameters and indicators of the experimental heats are given in the table:

Smelting option Share of liquid cast iron in the charge, % Electricity consumption,
kW*h/t Electrode consumption, kg/t Phosphorus content before release, % Temperature
metal
before
release,
degree Refilling duration, min Prototype 55 272 1.6 0.005 1655 3 Proposed 65 90 0.3 0.005 1655 3 70 0 0 0.006 1655 3 80 0 0 0.005 1660 3 90 0 0 0.005 1660 5 95 0 0 0.009 1690 10

The inventive method of steel smelting was implemented when steel was smelted in a 120-ton electric arc furnace.

Smelting was carried out using liquid pig iron in an amount of 75% (94 tons) by weight of the metal charge. Before pouring cast iron into the furnace, 15 tons of metal scrap were filled. After filling the scrap, cast iron was poured into the furnace through a special chute using two 60-ton cast-iron ladles in succession. During the filling process, gaseous oxygen was introduced into the furnace through 4 injectors with a flow rate varying during the blowing process from 8000 to 14000 m ³ /hour, as well as lime and dolomite. The melt was not heated by electric arcs. After reaching a carbon content of 0.06%, the melt was released with a melt temperature of 1640 degrees.

Claims (1)

A method for producing steel in an electric arc furnace, including feeding a metal charge into the furnace, including scrap metal and liquid cast iron, with the amount of liquid cast iron being 70-90% of the mass of the metal charge, melting the scrap metal, blowing with oxygen and releasing the melt, characterized in that first, scrap metal is poured into the furnace, then liquid cast iron is poured with simultaneous purging of the bath with oxygen with a gradual increase in its flow rate from 8000 m ³ / h to 14000 m ³ / h as the cast iron is poured, while the scrap metal is melted due to the heat of the exothermic reaction in as a result of oxidation of cast iron impurities.