RU2294382C1 - Charge for smelting the steel in the arc-furnaces - Google Patents

Abstract

FIELD: ferrous metallurgy; compositions of the charges for smelting the steel in the arc-furnaces.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy, in particular, to the composition of the charge for smelting the steel in the arc-furnaces. The charge contains the iron-carbon alloy at the following ratio of the components (in mass %): carbon - 2.0-4.0, manganese - 0.05-0.30, silicon - less than 0.01, chromium - less than 0.15, copper - less than 0.10, nickel - less than 0.10, sulfur - less than 0.030, phosphor - less than 0.030, arsenic - less than 0.008, titanium - less than 0.15, aluminum - less than 0.04, iron - the rest. The invention allows to reduce duration of the smelt and to improve the quality of the smelted steel due to reduction of the concentration of impurities of the non-ferrous metals.

EFFECT: the invention ensures reduction of the smelt duration, improvement of the quality of the smelted steel, reduction of the concentration of the non-ferrous metals admixture.

Description

The invention relates to ferrous metallurgy, and specifically to the composition of the charge for steelmaking in electric arc furnaces.

Known iron-carbon alloy - pig iron used in steelmaking [1], containing 0.5-0.9% Si, not more than 1.5% Mn, not more than 0.05% S, not more than 0.30% R.

Significant disadvantages of this material are:

- a high concentration of silicon, leading to an increase in the multiplicity of slag, an increase in the consumption of lime and electricity for the formation of furnace slag;

- a high concentration of manganese, which increases the duration of smelting due to the removal of a significant excess, for a certain steel grade, of manganese content and contributes to the erosion of the furnace lining, as well as steel contamination by non-metallic slag inclusions of an exogenous nature;

- a high concentration of sulfur and phosphorus makes it difficult to smelting high-quality steel grades, increases the duration of smelting, the consumption of charge materials and energy costs for redistribution.

A known method of producing steel in an electric arc furnace, including filling in a scrap metal furnace, feeding cast iron, melting a metal charge, oxidizing carbon with gaseous oxygen, dephosphorizing steel by adding portions of iron ore or sinter in a mixture with lime, downloading slag through a threshold of the working window, deoxidizing steel and slag in the furnace, the release of steel into the ladle under the furnace slag, an additive in the ladle of a desulfurizing mixture consisting of lime, fluorspar and aluminum powder, characterized in that the composition of the filling lead sinter or iron ore in an amount of 30-60 kg / t of steel, after melting a metal charge at an electric power consumption of 220-320 kWh / t of scrap metal, molten iron is poured into the furnace at a temperature of at least 1200 ° C with a pouring speed of 6-12 t / min, carry out oxidation with gaseous oxygen with a flow rate of 1500-3000 nm ³ / h, the ratio of the adherent iron ore or sinter in a mixture with lime is supported respectively (1-2) :( 2.5-3.5) at a flow rate of 70-110 kg / t of steel, after which slag is lowered through the threshold of the working window, and the ratio of lime, fluorspar and powder aluminum in the desulfurization mixture introduced into the bucket is supported respectively (1.1-1.5) :( 0.3-0.5) :( 0.05-0.1) with a mixture flow rate of 14-18 kg / t of steel [2 ].

Significant disadvantages of this method of steelmaking are:

- significant melting time associated with the need for oxidation of impurities in cast iron (carbon, silicon, phosphorus);

- increased consumption of electrodes due to elongation of the melting caused by the oxidation of impurities;

- high energy consumption associated with the formation of a large amount of slag obtained by binding oxides of oxidized silicon cast iron with calcium oxides, as well as the need to melt the required additives of slag-forming;

- increased content of "residual" ("non-ferrous") impurities (chromium, nickel, copper, etc.) found in recycled scrap, not oxidized during the oxidation period and not diluted when using the claimed amounts of molten iron, which ultimately complicates, in some cases, it does not allow smelting steel of a given chemical composition.

There is also known a method of steelmaking in an electric arc furnace, including the filling of scrap metal and lime, the melting of scrap metal, pouring molten iron, oxidizing carbon with gaseous oxygen, dephosphorization, the subsequent release of steel into the ladle, the additive in the ladle during the production of slag-forming mixture, characterized in that instead of liquid cast iron is used in an amount of 30-60% of the weight of the filling intermediate product containing 2.0-3.5% C, less than 0.01% Si, less than 0.015% P, less than 0.025% S, which is poured at a temperature of 1280-1400 ° C from above to the furnace after scrap metal penetration at an energy consumption of 180-300 kWh / t of scrap metal, the temperature in the furnace during carbon oxidation is maintained no more than 1700 ° C, the steel and slag in the furnace are not deoxidized, the discharge is carried out with cut-off furnace slag leaving 10-15% of the total liquid mass metal in the furnace, a slag-forming mixture consisting of lime and fluorspar in a ratio of (0.8-1.2) :( 0.2-0.5) with a flow rate of 10-17 kg / t of steel and necessary ferroalloys [3].

Significant disadvantages of this method of steelmaking are:

- the inability to transport molten iron over long distances;

- the need to regulate the pouring conditions of liquid iron in connection with possible emissions from the furnace.

Also known is ingots for metallurgical processing, containing an iron-carbon alloy and an oxide-containing material, and it contains components in the following ratio, wt.%:

iron-carbon alloy 50.0-99.5

oxide-containing material 0.5-50.0

while it is made with pores and voids, the volume of which is 0.1-0.7 of the total volume of ingots [4] - prototype.

A significant drawback of this material when used is a large amount of slag formed from an oxide-containing material, and therefore the melting time and production costs associated with an increase in the slag ratio in the furnace are increased.

The desired technical results of the invention are: reducing the duration of the smelting, improving the quality of the smelted steel by reducing the concentration of impurities of non-ferrous metals.

For this purpose, a charge for steelmaking in electric arc furnaces is proposed, containing iron-carbon alloy, the alloy containing, wt.%:

Carbon 2.0-4.0 Manganese 0.05-0.30 Silicon less than 0.01 Chromium less than 0.15 Copper less than 0.10 Nickel less than 0.10 Sulfur less than 0,030 Phosphorus less than 0,030 Arsenic less than 0,008 Titanium less than 0.15 Aluminum less than 0.04 Iron rest

The claimed limits are selected experimentally.

The carbon concentration in the inventive material was selected on the basis that it is impossible to conduct an active oxidation period in an electric arc furnace when the carbon content is less than 2.0%, and with an increase in carbon content of more than 4.0%, the melting time increases due to the oxidation of the "excess" concentration carbon.

With an increase in silicon content of more than 0.01%, a significant amount of lime is necessary to neutralize the SiO ₂ formed during oxidation, and therefore significant heat losses are observed and the consumption of electricity and electrodes increases.

The manganese content is selected on the basis of the following prerequisites: when the manganese content is less than 0.05%, a significant amount of manganese-containing ferroalloys must be introduced to bring the steel to the levels required by State standards, on the contrary, with an increase in the manganese concentration in the claimed material, more than oxidation excess manganese, which increases the duration of the heat.

Exceeding the declared concentrations of phosphorus and sulfur in the claimed material leads to more intense dephosphorization and desulfurization of steel, which in turn is associated with an increase in the duration of smelting, the consumption of electricity and electrodes.

The concentration of chromium, nickel, copper and arsenic was selected on the basis of obtaining the required concentrations of these elements (taking into account the use of scrap metal) in high-grade steel grades with a regulated concentration of impurities.

The content of titanium and aluminum is selected on the basis of the exclusion of non-metallic inclusions of titanium and aluminum oxides in the finished steel, which sharply reduces the mechanical properties of high-quality steels.

The inventive charge for electric arc furnaces was obtained in open-hearth 420-ton furnaces from liquid pig iron. Decarburization, desiliconization, dephosphorization, and desulfurization were made with additives of lime and agglomerate. After release, the inventive charge was poured into ingots on a filling machine. Further, the ingots obtained were used in steelmaking in 100-ton electric arc furnaces with a transformer with a capacity of 95 MVA.

The inventive material was used both as the sole component of the charge, and as a binder material in a mixture with scrap metal. When smelting according to the claimed method at 26 heats, steel grades ШХ15, ШХ15СГ, ШХ 4, НЭ76Ф, Э76Ф, ст 80-90 reduced the melting time compared to using pig unprepared cast iron by 7 minutes. In the production of steel intended for the production of NE76F and E76F railroad rails, the content of chromium and nickel is reduced to 0.03%, copper to 0.05%, steel contamination with non-metallic inclusions is reduced (the average line length of aluminum and titanium-containing oxides does not exceed 0.5 mm).

Information sources

1. GOST 805-95 "Converted cast iron. Technical conditions."

2. RF patent No. 2197535, cl. C 21 C 5/52, 7/06.

3. Application No. 2003136330/02 (038952) of the Russian Federation, IPC ⁷ C 21 C 5/52, 7/06.

4. RF patent No. 2087546, cl. C 21 C 5/52, 5/04, C 22 V 1/00.

Claims (1)

The mixture for steelmaking in electric arc furnaces containing iron-carbon alloy, characterized in that the alloy contains the following components, wt.%: Carbon 2.0-4.0 Manganese 0.05-0.30 Silicon Less than 0.01 Chromium Less than 0.15 Copper Less than 0.10 Nickel Less than 0.10 Sulfur Less than 0,030 Phosphorus Less than 0,030 Arsenic Less than 0,008 Titanium Less than 0.15 Aluminum Less than 0.04 Iron Rest