RU1792980C - Method of deoxidizing low-carbon steel - Google Patents

Abstract

Usage: ferrous metallurgy, namely the deoxidation of steel melted in a steelmaking unit, for example, a twin furnace, an oxygen converter, winding units and out-of-furnace steel processing. Oxidation of the metal at the outlet from the furnace with a carbon content of 0.01 - 0.02% according to the calculation formula on a computer depending on the technical parameters of the sinter, the excessive peroxidation of the metal is reduced by blowing powdered coke into the metal, the amount of which is also determined by the formula Ok 750. /% C UK (Of - 0,050) kg, where Q is the charge of the furnace, kg; % C - carbon content in coke,%; uk - fumes of coke,%; Of - the actual oxygen content in the metal at the outlet,%. 1 s p. f-ly, 2 tab.

Description

The invention relates to ferrous metallurgy, in particular to methods for the deoxidation of steel; and smelted, for example, in twin-chamber furnaces, oxygen converters, direct steelmaking units, a. also during out-of-furnace steel processing.

Known for steel production,. which includes the continuous determination of the oxygen content in the liquid metal by the magnitude of the electromotive force arising in the electrochemical cell, and the introduction of reagents acting on the oxidation into metigl (- the steel axis until a predetermined oxygen concentration in the steel is obtained.

The closest to the proposed technical essence is the method of dissolution steel, which includes a continuous determination of the activity of oxygen in liquid metal by the magnitude of electromotive

the force arising in the electrochemical cell immersed in the metal using the standard, and the introduction of reagents into the metal that affect the oxidation of the stllis to obtain a given oxygen activity.

In the known method, due to the introduction of a standard in the electrochemical cell that corresponds to the specified oxidation limit for a given steel grade and premature injection of reagents, the desired steel oxidation is obtained:

However, these methods have the disadvantage that when using these electrochemical cells under industrial conditions, their partial destruction due to temperature and chemical effects is observed. So during operation it was found that reliability

Xi

yu yu

00

about

measurement did not exceed 80%. That is, in the most favorable embodiment, only 80% of the surfactants can be obtained with a given oxidation using the measurement scheme under consideration.

The purpose of the invention is to increase the reliability of determining the oxidation of steel and to obtain optimal oxidation of the metal. This is achieved by the fact that the level of oxidation of the metal is determined by calculating the oxygen content in the metal according to the formula obtained by statistical processing of experimental data of 200 industrial melts:

Of -0.140 + 0.00077 + 0.000295 (FeO) +

+ 0.114 t 0.53 0.000847 V + + 0.0016 Nf + 0.0009 I -P 0.000646 Vt -.

-0.302 Vc - 0.183 C,

where C is the carbon content at the time of release,%;

. (FeO) - the content of iron oxide in the slag at the time of release,%;

t is the temperature of the metal at the time of release, ° C;

MP - the manganese content in the metal at the time of release,%: CaO

B - slag basicity at the moment

Si02 release, dimensionless quantity;

Nf is the distance from the tuyere head to the arch at the moment of completion of the purge, m;

I is the intensity of the purge of the metal with oxygen at the time of completion of the purge, thousand m / h;

Vt is the heating rate at the outlet, ° C / min;

Vc is the decarburization rate at the outlet,% C / min.

The oxidation of the metal at the outlet of the steelmaking unit varies widely. So for boiling steels, the oxidation fluctuation can be in the range of 0.020 ... 0.120% O. This leads to a significant spread in the oxidation values of the metal in the ladle, and therefore to destabilization of quality indicators. An analysis of the array of pilot melts shows that the average value of the metal cracking at the outlet from the furnace for low carbon steels (C 0.10%) is 0.050% and corresponds to optimal quality indicators (maximum yield, minimum scrap of the first limit).

To ensure a stable value of the oxidation of the metal at the outlet from the furnace, if information on the oxidation of the metal is available, the amount of

the oxidant that must be added to the furnace or to the ladle to remove excess metal over-oxidation according to the equation:

Q 75 o / g V (° F - ° 05 °) - KG JO YK

where QK is the amount of coke mill added to remove peroxidation, kg;

Q - furnace charge, kg;

% C - carbon content in coke,

5

0

5

0

%;

UK-yrap coke,%;

Of - the actual oxygen content in the metal at the outlet,%.

If the level of oxidation of the metal before release is below optimal, it can be increased by intensifying the purging of the metal with oxygen.

The proposed method is carried out as follows. In the course of melting refinement, starting with carbon 0.20 and lower, the actual oxygen content in the metal is calculated on a computer depending on the technological parameters of the melting according to equation (1). Let the actual oxygen content, calculated according to equation (1), be 0.080% at the metal outlet from the furnace. In order to remove excessive over-oxidation in this case, the amount of coke, calculated according to equation (2), should be added to the furnace:

5

0

5

0

5

Ok 75

300 10J

(0,080-0,050) 12.9 kg

87-60 where Q 300 103 kg - furnace charge

% C 87% - carbon content in coke ;. UK 60% - waste of coke in the furnace.

After adding this amount of deoxidant to the furnace, ladle deoxidation is carried out on the basis of the calculation of the required Mn content in the finished product (if deoxidized with ferromanganese), without any adjustment for the metal's oxidized state. .

Technological testing of the deoxidation method gives the following results

Analysis of the data in the table shows that the discrepancy between the compared oxidized ™ determination results in each case does not exceed 0.005%. The reliability of the oxidation determinations of the sample served was 100% for calculation and 75% for measurement.

An analysis of the data on the stability of metal oxidation (Table 2) shows that on melts with regulation of oxidation, its fluctuation in the ladle was within 0.029 ... 0.036, and on ordinary melts 0.023 ... 0.042 and, accordingly, yield (boiling grades steel) averaged 84.1% (experimental melts) and 82.2% (ordinary melts).

Claims (2)

SUMMARY OF THE INVENTION 1. A method for the oxidation of low-carbon steel, including the continuous determination of the activity of oxygen in a liquid metal and the introduction of a reagent into the metal when the oxidation value deviates from the predetermined value, with the exception of In order to increase the reliability of determination of steel oxide and steel and to obtain a metal with an oxidation of 0.50%, coke is used as a reagent, which is blown from the furnace or ladle in the amount calculated according to equation O gd sn %; Ok 75 % WITH (Of - 0.050), kg QK is the amount of coke blown for peroxidation, kg; О - furnace charge, kg; % C is the carbon content in krksik, j yk - fumes of coke,%; Of - the actual oxygen content in the metal at the outlet,%. by t 2. The method according to claim 1, wherein the oxidative potential of the metal from a furnace with carbon content yes 0.01 - 0.020% is determined by the equation Of 0.140 + 0.00077 j + 0.000295 (FeO) + + 0.114t 103- 0.53 0.0008478 + + 0.0016 NF + 0.0009 I + 0.000646 Vt -0, 302 Vc- 0.183 С. where C is the carbon content at the outlet,%; (FeO) is the content of iron oxide in the slag at the outlet. %; t is the temperature of the metal at the outlet, ° C; MP - the manganese content in the metal at the output,%; n CaO ° о; l is the basicity of slag on the production of SiOa ske, dimensionless quantity; Nf is the distance from the tuyere head to the arch of the furnace at the time of completion of the oxygen purge, m; I is the intensity of the metal purge with oxygen at the time the purge is completed, thousand m3 / h; Vt is the metal heating rate at the outlet. ° C / min; s Vc - current decarburization rate Comparison of the method for controlling metal oxidation Table 1 TABLE 2 Comparison of oxidized ™ metal in conventional and pilot melts