RU2451091C1 - Method of steel making in arc-type furnaces - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves supply of charge, melting, oxygen blowing, addition of lime with content of active lime of not less than 85% and coke during melting process and oxygen blowing. Lime with content of active lime of 40-70% together with metal junk is added to the furnace to the charge. Coke with particles with size of 5-40 mm is added during melting process and blowing process. Coke with particles with size of 0-3 mm is added after melting process is finished.

EFFECT: reduction of duration of melting process and electric power consumption.

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Description

The invention relates to ferrous metallurgy, in particular to methods of steel smelting in 120-ton arc furnaces.

The prior art there are many methods to accelerate slag formation during steelmaking. Known, for example, is a method for inducing slag during steelmaking, including supplying slag to the surface of the slag during the melting and finishing of thinning additives, while staurolite concentrate in the amount of 2-8 kg / t of steel mixed with solid oxidizing agent is introduced in the ratio 1 : (0.2-1.0), respectively (USSR AS No. 783344, IPC 3 C21C 5/04, publ. 11/30/1980, bull. No. 44).

The disadvantage of this method is to reduce the basicity of the slag due to the content in the staurolite concentrate of silicon dioxide and aluminum, which does not significantly increase the degree of metal desulfurization.

There is also known a method of producing steel in a converter, which allows to intensify the process of slag formation, including scrap filling, cast iron casting, the addition of slag-forming materials (lime), through which nepheline cake is introduced into the converter in the amount of 5-30 kg / ton of steel (USSR AS No. 929710, IPC 3 C21C 5/28, publ. 05.23.1982, bull. No. 19).

The disadvantage of this method is to reduce the basicity of the slag due to the content in nepheline 22.5-24.0% of silicon dioxide, which does not allow to increase the degree of metal desulfurization.

The closest in terms of the set of features and the technical result achieved is a method of steel smelting in arc furnaces, including charging the mixture, melting, blowing with oxygen, lapping, in which foamy slag is induced with additives of fluorspar, coke and lime in an amount of 15-30 kg / ton in portions 5-10 receptions with a ratio of components, respectively (0.01-0.08) :( 0.05-0.10) :( 0.86-0.90), and the first portion of slag-forming plants is planted at a consumption of 300-400 kW h / t of electricity with a simultaneous increase in oxygen consumption from 500-1000 to 1200-1800 ³ / h, and the last portion added after oxygen blowing a coke fraction 2-10 mm (AS USSR №1370150, IPC 3 S21S 5/52, publ. 30.01.1988, Bul. №4).

The disadvantage of this method is the insufficient foaming of slag, which increases the duration of the smelting, energy consumption.

The objective of the proposed method is to accelerate slag formation in the furnace due to the effective foaming of slag.

The technical result obtained in this case is to reduce the duration of the smelting and power consumption.

The problem is achieved by achieving a technical result is solved by the method of steel smelting in arc furnaces, including filling the charge, melting, purging with oxygen, an additive during melting and purging with oxygen, lime with an active lime content of at least 85% and coke, finishing according to which, according to the invention , lime with a content of active lime of 40-70% is introduced into the furnace charge together with scrap, in the furnace, coke with a fraction of 5-40 mm is added during melting and purging, and coke with a fraction of 0-3 mm is introduced at the end of melting.

The essence of the invention is as follows. Putting together a lime scrap with an active lime content of 40-70% allows you to accelerate early slag formation in the furnace, since such lime intensely releases carbon dioxide, which leads to the bubbling of slag melt, which contributes to the dissolution of pieces of lime and the formation of liquid slag. The lime additive in the furnace during the process of melting and blowing with oxygen with an active lime content of at least 85% is due to the fact that by this moment the content of iron oxides in the slag is 10-15%, which significantly accelerates the dissolution of this lime in the slag.

When the content of active lime is less than 40%, the temperature loss of the melt increases, which leads to an excessive consumption of electricity and an increase in the duration of smelting, when the content of active lime is more than 70%, the consumption of electricity and the duration of smelting also increase, since the rate of carbon dioxide emission decreases, which leads to a later slag formation and shielding of the electric arc by slag. The content of active lime introduced in the process of melting and purging with oxygen, less than 85% leads to supercooling of the metal melt and, as a consequence, to an increase in the duration of smelting and increased energy consumption. The introduction of coke in the process of melting with a fraction of 5-40 mm is due to the fact that it is such a fraction that allows coke to reach (when added from above through the arch) a slag melt and to efficiently foame under conditions of charge melting. When the coke fraction is less than 5 mm, part of this material is removed by the exhaust gases from the furnace working space, which reduces the foaming efficiency (the melting time and energy consumption increase), when the coke fraction is more than 40 mm, the coke does not manage to completely react with iron oxides in the slag and is removed from the working the space of the furnace together with downloadable slag, which also reduces the efficiency of foaming. The coke additive with a fraction of 0-3 mm (coke dust) after the charge is melted (by blowing through wall injectors) is due to the fact that this material foams the slag in the best way, which is important in the absence of an unmelted charge that shields the thermal radiation of the electric arc. The addition of coke with a fraction of 0-3 mm (coke dust) until the mixture is completely melted reduces the foaming efficiency, since a significant part of this material settles on unmelted pieces of the mixture and does not reach the slag melt.

The proposed method of steelmaking is implemented in the electric steelmaking shop of Ural Steel OJSC. 78 tons of scrap and 2 tons of lime with an active lime content of 50% are poured into a 120-ton furnace, then 50 tons of molten iron are poured, the transformer is turned on, and oxygen is purged. During the melting process, 581 kg of coke with a fraction of 10-30 mm (coke breeze) are introduced into the furnace. 10 min after turning on the furnace, 2-3 tons of lime with an active lime content of 86% are planted, and after the charge is melted - 362 kg of coke with a fraction of 1-3 mm (coke dust), then the melt is heated to 1625 ° C and melting is released into the steel pouring ladle . The duration of the smelting is 49 min, the energy consumption of 233 kW · h / t. The indicators of the experimental heats are shown in the table, it follows from them that, compared with the prototype, the duration and time of the heats are significantly reduced. The economic effect of the steel production method used in the ESPC is 4780 rubles / t.

Claims (1)

The method of steel smelting in arc furnaces, including filling the charge, melting, blowing with oxygen, an additive during melting and oxygen blowing of lime with an active lime content of at least 85% and coke, lapping, characterized in that the charge is introduced into the furnace together with scrap in the furnace lime with an active lime content of 40-70%, while during melting and blowing, coke is planted with a fraction of 5-40 mm, and at the end of melting, coke is introduced with a fraction of 0-3 mm.