RU1812212C - Method of steel deoxydation in tilting open-hearth furnace - Google Patents

Abstract

Usage: black metallurgists, steelmaking in open-hearth furnaces. SUMMARY OF THE INVENTION: Deoxidizing materials are introduced into the furnace by means of troughs, then the furnace is tilted, melting is carried out in series into two ladles, and finally, steel in the ladle is oxidized with manganese-containing ferroalloys. Preliminary deoxidation of steel is carried out by co-introduction of low-silica ferrosilicon with lime in a trough at a ratio of (3-4) :( 1-2), which are layered in layers with the placement of lime in the lower layer. The consumption of ferrosilicon is 3.3-5.3 kg / ton of steel. The materials are introduced into the bath by lowering the trough into the slag layer and turning it, after which the furnace is shaken at an angle of 3-7 °. two or three times. 1 tab.

Description

The invention relates to ferrous metallurgy and can be used in the smelting of steel in swing open-hearth furnaces.

The purpose of the invention is to save manganese-containing ferroalloys and increase the degree of metal dephosphorization.

To achieve this goal, the preliminary deoxidation of steel is carried out by co-introducing low silica ferrosilicon with lime at ratios 3-4 ... 1-2 in the tin, located in layers with the placement of lime in the lower layer, and the consumption of ferrosilicon is 3.3. .5.3 kg / t of steel, while the materials are introduced into the bath by lowering the trough into the slag layer and turning it, after which the furnace is shaken at an angle of 3 ... 70 two or three times.

The combined introduction of low-silica ferrosilicon with lime into the bath from the trough allows eliminating a decrease in wasps, - slag news during the deoxidation of steel 3 with silicon, and a decrease in the slag basicity is prevented when the ratio of ferrosilicon and lime is 3.0 ... 4.0: 1.0 .. .2.0. If the ratio is greater than 4: 1, then after the introduction of ferrosilicon with lime, the basicity of the slag decreases and phosphorus is reduced. This is due to the fact that the added amount of lime is not sufficient to neutralize the silicon oxides formed during steel deoxidation.

With a small ratio of ferrosilicon to lime (less than 3: 2), metal re-phosphorization is also observed. This is due to the fact that the adhering lime does not completely dissolve in a short time.

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a short period of time and swims in the bath in the form of a slagged block.

Layer-by-layer arrangement of ferrosilicon and lime in the trough with placement of the latter in the lower layer allows them to be introduced into the desired layers of the bath (ferrosilicon in metal, and lime in slag). With this arrangement of additives, the duration of contact of ferrosilicon with slag decreases and the deoxidation of the metal increases, and the fumes of silicon decrease. The efficiency of metal deoxidation even more increases when, before the introduction of additives (ferrosilicon together with lime), a minimum thickness of the furnace slag layer in the tipping zone of the trough is created. This is achieved by lowering the bottom of the mold into the slag and turning it by raking it to the side. In order to increase the mass transfer of silicon over the volume of the bath and reduce its fume, it is proposed to carry out two-three-time swaying of the furnace at an angle of 3 ... 70. It has been experimentally established that if the bath is shaken less than two times with an inclination angle of less than 3 °, then the metal will be oxidized after 3 ... 5 minutes (the boiling process stops) on about 1/3 of the surface of the bath. With a three-time sway and an angle of inclination of the furnace by 7 °, the boiling process over the entire surface ceases after about 5 minutes. Therefore, swinging the bath more than three times and tilting the oven at an angle of more than 7 ° is not practical.

The proposed method makes it possible to efficiently deoxidize a metal upon introduction of ferrosilicon containing 17 ... 25% silicon in the amount of 3.3 ... 5.3 kg / t of steel, which is at least 0.09% silicon.

In order to evaluate the effectiveness of the proposed method under the conditions of an open-hearth workshop in 450 tons of swing open-hearth furnaces, experimental melts of rail steel were melted (C 0.71 ... 0.82%, Mn 0.75 ... 1.05%, Si 0.18. ..0.4%, S 0.040%, P 0.035%).

The results of the experimental swimming trunks are shown in the table,

As can be seen from the table, when conducting experimental melts according to the proposed method (var. 2 ... 4), the highest efficiency of the deoxidation process was obtained. At a low flow rate of ferrosilicon (3.2 kg / t, var. 1), effective soothing of the bath is not achieved; after 5 minutes, decarburization of the metal is observed.

With an increased consumption of ferrosilicon (more than 5.3 kg / t of steel, var. 5), metal refosphorization occurs, even in that case.

if you introduce more lime. This is because the lime does not have time to dissolve in a short time.

Increased metal rephosphorization

occurs both at high and low ratio of ferrosilicon and lime (options 5, 6). This is due to the fact that, at a low consumption of lime, the addition of ferrosilicon reduces the basicity of slag, and at high

- it does not completely dissolve, the slag becomes heterogeneous with low refining ability.

To increase the mass transfer and intensify the process of dissolution of ferrosilicon and lime, two or three single swaying of the furnace is provided. With a one-time rocking of the furnace (var. 8), boiling of the bath is not eliminated.

Mass transfer efficiency also

decreases with slight tilt of the furnace (less than 3 °, var. 9).

According to tests conducted in an industrial environment, the invention, in comparison with the prototype, has

the following advantages: reduced consumption of ferroalloys (manganese by 1.1 and silicon by 0.73 ... 0.9 kg / t of steel); increased degree of steel dephosphorization by 35%.

The application of the proposed method

steel smelting and will allow due to the saving of ferroalloys to get a good economic effect.

Example. Steel (rail) smelting was carried out in 450 tons of a swing open-hearth furnace. Used cast iron of the following composition; 4.1% C, 0.86% Mp, 0.57% SI; 0.041% S and 0.47% R. Melting charge: 310 tons of pig iron, 137 tons of scrap, 48 tons of iron ore and 20 tons of limestone. In the course of the smelting, intermediate slag was downloaded and brought in with new lime and scale. The smelting process was completed at a carbon content of 0.73%, manganese 0.07%, silicon 0.03%, sulfur 0.031%, phosphorus 3 ra 0.02%. The temperature of the steel is 1580 ° C. Preliminary deoxidation of the steel was carried out by ferrosilicon (22% Si), by introducing it into the furnace with a trough using a multi-filling machine. 1760 kg of ferrosilicon (4.0 kg / t of steel) were loaded into the lower cavity of the trough, and 440 kg of lime (the ratio of ferrosilicon to lime is 4: 1) was loaded into the upper cavity. The mold with ferrosilicon and lime was introduced through the central filling window of the furnace and lowered into the slag to a depth of approximately

50 ... 100 mm and by rotating the trunk of the filling machine, materials were poured into the melt. Then, the open-hearth furnace was tilted twice at an angle of 5 °. Twelve minutes after the preliminary deoxidation, pll.ku steel was released consecutively into two 220 tons of cosh.

The final deoxidation of rail steel was carried out in the ladle with ferromanganese (1100 kg), silicomanganese (1630 kg) and a silicon-magnesium-titanium alloy (550 kg - var. Z).

The chemical composition of the finished steel: 0.72% carbon, 0.94% manganese, 0.25% silicon, 0.022% sulfur and 0.0194% phosphorus.

Manganese consumption was 8.7 kg / t of steel, and the degree of dephosphorization of steel during the period of deoxidation and production was 8.3%.

According to option 2 of the table, 1450 kg of ferrosilicon (3.3 to g / t of steel) and 960 kg of lime were loaded into the mold. The open-hearth furnace was tilted twice at an angle of 3 °. The final deoxidation of steel in the ladle with ferromanganese 1100 kg and silicomanganese 1650 kg and a silicon-magnesium-titanium alloy 550 kg. Manganese consumption is 8.71 kg / t of steel. Dephosphorate became 7.7%.

In Embodiment 4, 2330 kg of ferrosilicon 5.3 kg / t and 1660 kg of lime were loaded into the mold. The open-hearth furnace was tilted three times at an angle of 7 °. Final deoxidation with ferromanganese (1100 kg), silicomanganese

(1660 kg) and silicon-magnesium-titanium alloy (550 kg). Manganese consumption 8.72 kg / t steel, dephosphorization 10%.

Formula A Invented

The method of steel deoxidation in a swinging open-hearth furnace, which includes introducing deoxidizing materials into the furnace by means of troughs followed by tilting the furnace, releasing the smelting in two ladles in series, and final steel deoxidation in the ladle with manganese-containing ferroalloys, which is without tearing in order to save

manganese-containing ferroalloys and an increase in the degree of metal dephosphorization, preliminary deoxidation of steel is carried out by co-introduction of low-silica ferrosilicon with lime at a ratio of (3-4) :( 1-2) located in layers in a layer, and the consumption of ferrosilicon is 3 , 3-5.3 kg / t of steel, while the materials are introduced into the bath by lowering the trough into the layer

slag and its rotation, after which the furnace is shaken at an angle of 3-7 ° two or three times.