SU1346679A1 - Method of producing high-carbon steel - Google Patents

Abstract

The proposal relates to ferrous metallurgy and can be used in smelting high carbon steel in converters. In order to improve the refining of the metal from sulfur and phosphorus, it has been proposed, before and after the intermediate slurry download, to cyclically change the position of the tuyere while simultaneously reducing the oxygen consumption. Oscillation of the tuyere within 1-2 minutes with an amplitude of 25-30 calibers from the working position of the tuyere with a simultaneous decrease in oxygen consumption of 1.5-2 times leads to foaming of the slag before its downloading and the rapid formation of reactive slag at the moment of its introduction after downloading . 1 tab. cl with 4 05 05 CO

Description

113

The invention relates to ferrous metallurgy, specifically to the production of carbon steel in oxygen converters,

The purpose of the invention is to improve the desulphurization and dephosphorization of the metal, improving the quality of steel.

Entering scrap with a significant amount of lime allows for the first minutes of the blowdown, when slag is filled with iron oxides as a result of the elevated position of the tuyere and intensive oxidation of the pig iron occurs, it is faster to achieve high slag basicity. This contributes to the earlier dephosphorization of the metal. However, during this period, there is an eh, e many pieces of undissolved lime, which increase the slag heterogeneity. Subsequently, when the lance is brought to the working level of blowdown, the deterioration of shpoobrazovanie contributes to an increase in the intensity of carbon burn-up. Therefore, at this moment to eliminate the fluorspar additive before downloading the intermediate slag, a brief cyclical raising and lowering of the blowing lance with a simultaneous decrease in the intensity of blowing is performed. This technique allows to increase the mixing of the slag with the added lime and dramatically increase the content of iron oxides in it. As a result, both undigested chunks of lime and lime introduced during this period are quickly dissolved in the slag. Shpak becomes highly basic, homogeneous and reactive with respect to phosphorus and sulfur, which makes it possible to increase the transfer of a significant amount of phosphorus and partly sulfur from metal to slag.

After the slag is removed from the converter, the operation again is performed to cyclically change the position of the tuyere while simultaneously introducing lime. The slag quickly becomes fluid-mobile and until the end of the purge, when the temperature of the metal and slag is high enough, favorable conditions are created for conducting deep metal desulphurization. Thus, taking a cyclic change in the position of the tuyere with a simultaneous decrease in the intensity of blowing and introducing lime into the converter allows the dephosphorization to be carried out successfully before downloading.

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15

20

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and after downloading the desulfurization of the metal.

The duration of the cyclic change in the position of the tuyere within the above limits is determined by the amount of iron oxides formed at this moment in the slag. If the duration of this procedure is more than 2 minutes, the slag is saturated with a significant amount of iron oxides, which is undesirable, since the slag foams and downloading it will be difficult. In addition, a high content of iron oxides will adversely affect the durability of the converter lining. When the cyclic position of the tuyere is less than 1 minute in the slag, an insufficient amount of iron oxides is required to completely dissolve the lime introduced at that moment, which leads to incomplete removal of phosphorus and sulfur from the metal.

In order to eliminate slag over-oxidation during the cyclical change of the position of the tuyere, the intensity of blowing is reduced. If the intensity of the blow is reduced by less than 1, 5 times, as compared with the operating mode of the purge, then slag will be over-oxidized. In the case of a decrease in the intensity of blown more than 2 times, an insufficient amount of iron oxides for rapid dissolution of lime is formed in the slag. In addition, the rate of carbon burnout from metal decreases, which will negatively affect the duration

40 swimming trunks.

By a cycle is understood a change in the position of the tuyere from the moment it is lifted from the working level of the purge to the extreme upper position, equal to

45 to 25-30 caliber (amplitude) and lowering of the tuyere to the working level. The proposed amplitude parameters and the number of cycles are determined by the intensity of mixing the slag melt with the lime introduced into the converter, as well as the speed of raising and lowering the tuyere. If the amplitude of changing the position of the tuyere is more than 30 calibrations given, the intensity of the mixing of slag and lime will decrease . In addition, with such an amplitude, there is a danger of a jet falling on the converter lining. If amplitude

thirty

3

If the position of the tuyere is equal to less than 25 calibres, then the amount of iron that is necessary for the rapid dissolution of lime will not form in the slag. The intensity of the slag mixing with lime will be reduced when using less than five cycles of displacing the tuyere. Increasing the cycles more than 15 times is not advisable since the intensity of mixing remains constant. The table shows the data obtained in the implementation of the proposed method, depending on the proposed parameters of the steel smelting in the basic oxygen furnace. Example 1. The known method. In the 350-ton converter load 70 tons of scrap metal and pour 292 tons of liquid iron containing,%: Si 0.47; Mp 0.57; P 0.18; S - 0.028 with a temperature of 1350 ° C. Lime in the amount of 49.8 kg / t, steel (56% of the total weight) was injected into the scrap before the iron was cast. A portion of lime (28.1 kg / t steel) is injected from 1 to 2 minutes of purging. Fluorspar in the amount of 3.2 kg / t is placed in the converter for 8 and 15 minutes of purging. The purge starts at the position of the 3 m tuyere and at the 4th minute of the purge it is lowered to the working level (1.3 m) which is kept until the intermediate slag starts to download and then until the end of the purge. Oxygen consumption during the entire purge period is 900 min / min. At the 15th minute of the purge, an intermediate slag was downloaded, having a basicity of 2.3 and containing 21.3% of the total amount of iron oxides. The content of phosphorus and sulfur in the metal, respectively, is 0.021% and O, 027%. After the slag is loaded, 1.2 kg / ton of fluorite steel and 11.2 kg / ton of lime steel are placed in the converter. Blowing is completed when the carbon content in the metal is 0.66% and the temperature is 1570 C. The finished steel contains,%: С 0.71; Mp 0.62; S 0.021; P 0,017.

PRI mme R 2. The proposed method. 350-ton converter download

five

72 tons of scrap are poured and 290 tons of pig iron having the composition,%: Si 0.49; Mp 0.53; P 0.19; S 0,030 with a temperature of 1355 C. Scrap before pouring

55.3 kg / ton of usable steel (68% of the total weight) was injected into the pig iron. At the 8th minute of the blowdown, 1.2 kg / ton of steel spiked spar was set down. The purge starts at the position of the lance 3.1 m and at the 4th minute it is lowered to the working level (1.2 m), which is maintained until the start of the cyclic change.

5 polo-wife tuyere.

The purge rate is 900 nm / min. 1.5 minutes before the intermediate slag is used, 0 operations are performed to cycle the position of the tuyere. To do this, reduce the oxygen consumption to 500 nm / min (1.5 times less than the operating mode) and lift and lower the tuyere 5 to a height of 2.5 m (28 given calibers) in the number of nine cycles. After two cycles, lime was introduced into the converter in the amount of 10 kg / ton of steel. After the end of the operation, cyclically changing the position of the tuyere (on the 15th minute of the blowdown), an intermediate schlak is downloaded, which has a basicity of 3.7 and contains 26.3% of the total amount of iron. The phosphorus and sulfur contents in the metal are 0.016 and 0.021%, respectively. After the slag is downloaded, the cyclic position of the tuyere is again performed for 0 Ij3 minutes. The amplitude of oscillation of the tuyere is 2.5 m (28 given caliber) / in an amount of 13 cycles and an oxygen consumption of 500 nm / min. The amount of precipitated lime in process 5 of this operation is 13 kg / ton of steel. After completion of the cyclic positioning operation, the tuyere is lowered to a level of 1.3 m and the oxygen consumption is increased to 900 nm / Q / min. The purge is completed when the carbon content is 0.68% and the temperature of the metal is 1575 C. The finished steel contains,%: С 0.72; Mp 0.58; S 0.014; P 0,01I.

Claims (1)

From the examples and data in the table it can be seen that the proposed method allows to obtain a lower content of phosphorus and sulfur in the finished steel by 0.006% and 0.007%, respectively, while reducing the consumption of lime by 10.8 kg / ton and fluorspar by 3.6 kg / t fit steel. A decrease in phosphorus and sulfur in steel makes it possible to improve the quality of cable steel and increase the percentage of steel production for steel cord. Invention Formula Method for the production of high carbon steel in the converter, including Editor G. Volkova Order 5097/26 Compiled by M.Pribavkin Tehred I.Popovich Corrector Circulation 549Subscribe VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab ,, d.4 / 5 .Production and printing enterprise, Uzhgorod, Projecto st., 4 stepwise blowing mode, intermediate slag loading in the smelting process, characterized in that, in order to improve metal desulfurization and dephosphorization, to improve the quality of steel, cyclic changes in the tuyere position in the amount of 1–2 minutes before and after slag downloading 5–15 cycles with an oscillation amplitude of 25–30 given calibers from the operating level of the purge with a simultaneous decrease of 1.5–2.0 times the flow rate of the gas relative to the operating mode to blow. Proof-reader I.Erdeyi