SU1759886A1 - Method of stalemating in basic oxygen furnace - Google Patents

Abstract

Use: ferrous metallurgy, steel production in converters. Summary of the Invention: In steelmaking, the carbon content in the metal is measured at the end of the purge, the metal is released, the final slag is left for subsequent smelting, carbon-containing material is placed on it for 1-2 minutes after the metal is released in amounts of 3.5-4; 2.5-3 and 1.8-2.5 kg / t of the set with a carbon content of 0.03-0.07, 0.08-0.11 and 0.12-0.17%, respectively. Then they overwhelm the scrap, pour the cast iron. slag-forming materials are set down, the melt is blown in two periods with the intermediate slag being charged at a consumption of 25-30 m3 of oxygen per 1 ton of blown iron. Coals with a carbon content of 70-90% are used as carbon-containing materials. 1 hp f-ly. 1 tab. (L

Description

This invention relates to the steel industry.

There is a known method of steelmaking in a converter, leaving the final slag and transferring it to an inert state by adding fluxes, which are products of the reduction of iron ores (French patent Ns 1336627, cl. C 21 C 5/32, 1963).

The disadvantage of this method is the scarcity of the materials used, their high cost, as well as relatively low deacidability.

The closest in technical essence and the achieved result to the proposed is a method of steel smelting in an oxygen converter, including leaving the previous slag melting, carbonaceous slag additive

materials, filling scrap, pouring iron, blowing a liquid bath, downloading the intermediate slag (ed.St. USSR № 1167205. cl. C 21 C 5/28, 1985).

This method has several disadvantages: ad hoc input of a deoxidizing carbon-containing material, which leads to its overspending or to the input of an insufficient amount to achieve the desired effect based on the conditions of smelting; late download of the intermediate slag due to the specificity of the process, which does not allow to achieve maximum savings of the process iron; the loss of part of the carbon-containing material due to the part falling directly into the metal and combustion in the bulk of the metal, and not slag.

The purpose of the invention is to reduce the specific consumption of slag-forming materials and

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an increase in the yield of liquid steel due to the regulation of the input of carbon-containing materials and slag melting mode.

To do this, in the steelmaking method in the converter, including measuring the carbon content in the metal at the end of the purge, discharging the metal, leaving the final slag for subsequent smelting, adding carbonaceous materials to the slag, filling the scrap, pouring iron, adding the slag-forming materials, blowing the melt in two periods with downloading the intermediate slag, carbonaceous materials are added during 1-2 minutes after the metal is released from the converter, while the carbon content in the metal of the previous melting is 0.03-0.07 % prisit 3.5-4 kg / t set-top converters of carbon-containing materials, with a carbon content of 0.08-0.11% - 2.5-3 kg / t charge with a carbon content of 0.12-0.177% -1, 8-2.5 kg / ton of sludge, the intermediate slag is bled when 25-30 m of oxygen is consumed per ton of blown iron. At the same time, carbon with a carbon content of 70-90% is used as carbon-containing materials.

The essence of the proposed method is to conduct slag deoxidation in order to reduce iron oxides and remove intermediate slag prior to the addition of slag-forming materials at the moment the minimum content of iron oxides in the slag is possible, which allows the steelmaking process to occur with minor losses. The reduction of iron oxides from the final slag is necessary to avoid emissions during the casting of iron into the converter (loss of charge), as well as to reduce the loss of iron with downloadable intermediate slag. Iron oxides are in the final slag mainly in the form of eutectics with other components of the slag and are better removed during direct deoxidation than when exposed to carbon of the melt. As the slag does not coagulate when optimally deoxidized, but only slightly thickens, a smaller amount of iron oxides is required to achieve sufficient fluidity during the purging process. In addition, the slag fluid flow is also enhanced by reducing its basicity, since oxidizable silicon iron goes into slag in the form of SlOa. Since the download, the generated (renewed) slag before the expiration of 50% of the duration of the purge is not a complicated process. With the downloadable slag, the iron is lost no more than the amount recovered from the final slag. Iron, which is used for dissolving lime and the formation of highly basic slag after downloading the intermediate slag, is not lost with the slag, but passes to the next melt, since the entire final slag is left. Irretrievable iron loss occurs only with slag, which covers the metal mirror in the casting ladle. Thus, the proposed process has minimal metal loss with slag, which is fundamental to the metal balance.

5 It is important that the timing of the intermediate slag be collected. First, the download must be performed at the time of the lowest possible according to the conditions of the process of the content of iron oxides in the slag. Secondly, this moment should be determined by the end of the process of oxidation of silicon of cast iron in order to avoid downloading to the complete oxidation of silicon, which will require the addition of a greater amount of 5 slag-forming materials to achieve high basicity of the final slag, as well as the need to minimize the time spent for the updated low-base (1.5-2 units) of slag due to its negative effect on the lining of the converter.

The selected time limit for the addition of carbon-containing materials after the metal has been removed from the converter for 2 minutes is due to the fact that the highly basic (3.5-4 units) final slag, as heat is lost (its temperature decreases), can be rolled up or covered with a solid crust after 2 minutes . After this, the carbon-containing material acts on the slag as a deoxidizing agent slightly, and mostly burns on its surface. Carrying out carbon-containing additive earlier than 1 min after metal release 5 is not possible for organizational and technical reasons related to the time spent on installing the converter in a vertical position and the inertia of the bulk materials additive system along the 0 supply path.

Full slag deoxidation (up to iron oxides content of 1-2%) is difficult to achieve and not required. To safely cast iron to slag, it is sufficient to have 5-6% of iron oxides in slag 5. It is possible to determine the initial content of iron oxides in the slag with a high degree of accuracy by the metal baffle, i.e. carbon content. In the case of a carbon content in the metal of 0.03-0.07%, the slag significantly

it is oxidized and the content of iron oxides in it is in the range of 18-25%. When the carbon content in the metal is in the range of 0.08-0.11%, the slag is less oxidized and contains iron oxides 15-17%, and when the carbon content in the metal is 0.12-0.17%, the slag practically does not over-oxidize and contains iron oxides less than 15%. On this basis, as well as taking into account fluctuations in the carbon content of carbon-containing materials (coal), the costs of carbon-containing material are determined.

The determination of the carbon-containing material consumption by carbon content in the metal is reliable enough and does not require a long wait for slag analysis. Consequently, there is practically no performance loss.

The selected parameters for downloading the intermediate slag in the period of consumption of 25–30 m of oxygen per 1 ton of blown pig iron allows to achieve the best results on the yield of liquid steel, without leading to increased wear of the lining.

Downloading the intermediate slag to the consumption of 25 m3 of oxygen per 1 ton of blown iron is inefficient, since At this point, the oxidation rate of carbon is still far from the highest values and in the melt there are many iron oxides that are lost with the slag being charged. In addition, at a low purge intensity, by this time silicon will not have time to oxidize completely. Downloading the intermediate slag after the consumption of 30 m3 of oxygen per 1 ton of blown iron is impractical, since slag active in relation to the lining is formed. In the process of working out the proposed technology, pig iron with a silicon content of up to 1; 2% was recycled, and a refining analysis showed that removing silicon with a cast iron consumption of 800 kg / t of steel ends up consuming 18-20 m3 of oxygen 1 ton of processed iron. Therefore, if 25-30 m3 of oxygen are consumed per 1 ton of pig iron, silicon can be removed into slag with its content in the iron up to 1.8%.

For the slag deoxidation, coal of the grades AU, ASh and AK with carbon content from 70 to 90% was tested. When using them, reliable results were obtained, which indicates the possibility of their use as carbon-containing materials for deacidification of slag.

PRI me R. After the purging of the liquid bath in the 160-ton converter is completed, the temperature of the melt is measured and metal and slag samples are taken for chemical analysis. After determining the chemical analysis of the metal, taking into account the temperature measurement, incl. carbon content, in the case of obtaining satisfactory results, the metal is released from the converter. Otherwise, additional blowing or other corrective operations are performed with subsequent re-measurement of temperature and sampling to obtain satisfactory results with subsequent release of the metal.

After the metal is discharged, the converter is moved to a vertical position and a certain amount of carbon-containing material (coal) is seated on the final slag, depending on the carbon content of the previously released metal. Moreover, its additive is produced 1-2 minutes after the release of the metal. In the event of a time reserve before scrap filling, the converter swings. The converter then tilts toward the loading side. 45 tons of scrap metal and 115 tons of liquid iron are poured into it. When casting iron, there is no intense flame outflow or emissions from the converter.

After the cast iron is cast, the converter is placed in a vertical position and the flushing of the liquid bath begins. Blowing is stopped after the consumption of 3100 m3 of oxygen (28 m3 per 1 ton of blown iron) and the intermediate slag is downloaded. With the resumption of blowdown, 6 tons of lime are set in the converter. At the end of the purge, the temperature of the melt is measured and metal and slag are sampled.

The data on the industrial melts performed are given in the table. When conducting the heats noted in the table, pig iron with a carbon content of 4.2% and silicon of 0.7-0.9% is processed. manganese 0.4-0.6%, sulfur 0.025-0.030%. For the deoxidation of the final slag, coal AU was used with a carbon content of 80-85%.

In addition to the conventional control of melts, slag was sampled — the final coal before and after the addition, as well as the intermediate for downloading, the sampling of metal during slag downloading, the time of coal addition to the slag relative to the end of the metal release from the converter and the moment of stopping blowing for intermediate slag on oxygen consumption.

A comparative analysis of the data in the table shows that the best performance is achieved in swimming trunks, carried out according to the parameters of the formula of the invention. The proposed technology makes it possible to increase the yield of liquid steel by 45 kg / t of charge metal and reduce the specific consumption of slag-forming materials by 30 kg / t of steel.

Claims (2)

Claim 1. Method for smelting steel in a converter, including measuring carbon content in metal at the end of a purge, discharging metal, leaving final slag for subsequent smelting, adding carbon-containing materials to slag, filling up scrap, pouring iron, adding slag-forming materials, blowing melt into two period with the download of intermediate sludge, characterized in that, in order to reduce the expenditure of slag-forming materials and increase the yield of suitable steel, carbon-containing materials are added within 1-2 minutes after the metal is released from the converter, while at a carbon content of 0.33-0.7%, 3.5 to 4.0 kg / ton of carbon-containing materials are set, carbon 0.08-0.11% sit down 2, kg / t cages, and when the content carbon 0.12-0.17% is applied down 1.8-2.5 kg / ton of the charge, respectively; the intermediate slag is downloaded from spending 25-30 m blown iron. .3. oxygen per 1 ton 2. The method according to claim 1, wherein that as carbon-containing materials use coals with a carbon content of 70-90%.