RU2787133C1 - Method for the production of steel in an electric arc furnace - Google Patents

Abstract

FIELD: ferrous metallurgy.

SUBSTANCE: invention relates to the field of ferrous metallurgy, in particular to the production of steel in an electric arc furnace. Metal charge is supplied to the furnace, including solid metal charge and liquid iron, oxygen is blown and melt is discharged. First, liquid iron is poured into the furnace, at the same time, the bath is purged with oxygen with a gradual increase in its flow rate from 8000 to 14000 m³/h as the iron is poured, in the second half of the oxidation process, solid metal charge in the form of hot briquetted iron is introduced, while the amount of liquid iron is 85 -95% of the weight of the metal charge.

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.

A known method of steel smelting in an electric arc furnace (patent for invention RU 2092574, publ. 10.10.1997), including the loading of solid oxidizers, slag-forming materials, solid metal charge from an iron-steel house, their heating, pouring liquid iron, purging the bath with a gaseous oxidizer, melting, oxidizing and recovery refining of the melt and its release, according to the invention, solid oxidizers and solid cast iron are introduced in the form of ingots from a solid oxidizer filled with liquid iron, and solid and liquid cast iron are used as a metal charge, while the total amount of cast iron is kept in the range of 51-95% from the total mass of the metal charge, maintaining the ratio of solid to liquid iron, respectively, equal to 1: (0.1-10).

A known method of steelmaking in an electric arc furnace (patent for invention RU 2543658, publ. 03/10/2015), including the supply of scrap metal and liquid iron to the furnace as a metal charge, melting of scrap metal, addition of slag-forming materials, purging of the bath with oxygen and release of the melt, according to the invention, pouring liquid iron into the furnace is carried out 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 purging time, then the oxygen consumption is increased to 5000-7000 nm3/hour and the bath is purged in the specified 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 the specified mode until it ends. This method is chosen by the applicant as the closest analogue.

The disadvantage of the known methods is the need to melt the solid part with electric arcs, which increases the cost of steel due to the consumption of electricity and electrodes.

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 providing conditions for effective slag formation and dephosphorization.

Due to the fact that the costs of electricity and electrodes are excluded, the cost of steel smelting by the inventive method is reduced.

The specified technical result is achieved by the fact that in the known method of steel production in an electric arc furnace, including the supply of metal charge into the furnace, including solid metal charge and liquid iron, oxygen purge and melt discharge, according to the invention, liquid iron is first poured into the furnace, at the same time purging the bath with oxygen with a gradual increase in its consumption, in the second half of the oxidation process, a solid metal charge is introduced in the form of hot briquetted iron, while the amount of liquid iron is 85-95% by weight of the metal charge. At the same time, in the process of blowing, the oxygen consumption is increased from 8000 to 14000 m3/h as the cast iron is poured.

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

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

- at the beginning of the melt, the oxygen consumption is reduced to prevent the destructive effect of the oxygen jet on the furnace lining and to prevent the decarburization process from being too intense to prevent the boiling of slag residues from the previous melt.

A decrease in oxygen consumption below 8000 m3/h will lead to an increase in the duration of oxidation of carbon and other impurities, and an increase in oxygen consumption above 14000 m3/h will lead to an overly intensive decarburization process, which may result in overoxidation of the melt and a decrease in lining durability.

Hot briquetted iron is introduced in the second half of the oxidation process as a coolant.

The increased consumption of liquid iron from 85 to 95% makes it possible, due to the exothermic reaction that occurs during the oxidation of the carbon of the cast iron, to provide the melt temperature necessary for slag formation and dephosphorization without supplying electric arc energy. Thus, the method allows to exclude the consumption of electricity and electrodes.

The claimed limits are selected empirically. The parameters and indicators of experimental swimming trunks are given in the table:

Smelting option The share of liquid iron in the charge, % Electricity consumption,
kWh/t Electrode consumption, kg/t Phosphorus content before release, % Temperature
metal
front
release,
degree Filling time, min Prototype 55 272 1.6 0.005 1655 3 Proposed option 80 0 0 0.007 1655 3 85 0 0 0.006 1660 3 90 0 0 0.004 1655 3 95 0 0 0.004 1660 four one hundred 0 0 0.008 1680 nine

Reducing the proportion of liquid iron less than 85% leads to the need to increase the proportion of hot briquetted iron, which worsens the conditions for dephosphorization of the melt. With an increase in the proportion of liquid iron over 95%, the proportion of hot briquetted iron decreases, which leads to overheating of the melt, increased wear of the furnace lining and an increase in the period of its filling.

The inventive method of steelmaking was implemented when steelmaking in an arc 120 t electric furnace.

Smelting was carried out using liquid iron in the amount of 91% (120 tons) by weight of the metal charge. Pig iron was poured into the furnace through a special chute with two 60-ton cast-iron ladles in succession. During pouring, gaseous oxygen was introduced into the furnace through 4 injectors with a flow rate varying in the course of blowing from 8000 to 14000 m3/hour. In the process of pouring the second ladle, 12 tons of hot briquetted iron were added to the furnace. The release of the melt was made with a melt temperature of 1655 degrees.

Claims (1)

A method for producing steel in an electric arc furnace, which includes feeding a metal charge into the furnace, including a solid metal charge and liquid iron, purging with oxygen and discharging the melt, characterized in that liquid iron is first poured into the furnace, and the bath is simultaneously purged with oxygen with a gradual increase in its consumption from 8000 to 14000 m ³ /h as the iron is poured, in the second half of the oxidation process solid metal charge is introduced in the form of hot briquetted iron, while the amount of liquid iron is 85-95% by weight of the metal charge.