SU1049551A1 - Method for smelting steel in converter - Google Patents

Abstract

A METHOD FOR MELTING STEEL IN AN OXYGEN CONVERTER, including metal purging with oxygen, preliminary deoxidation with an aluminum bath and final deoxidation and doping during melt production, characterized in that, in order to increase the degree of absorption of deoxidants and alloying elements, improve the quality of the metal and increase the yield of the melt. Deoxidation is carried out after 98-99% of the time of purging by addition to a ferroaluminium bath, with an aluminum content of 55-65% in an amount of 2.5-3.5 kg / ton of steel.

Description

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WITH

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The invention of the OTIIOCHTCH is to the ferrous metallurgy and can be used in the smelting of steel in oxygen converters.

There is a method of smelting oxygen-converter steel, in which at the end of the metal blowing into the bath, thermoanthracite and ground ferrosilicon are seated in an amount of 1 kg / ton of steel. After bleaching for 3-5 minutes, silico-manganese and ferrosilicon are introduced into the bath. Aluminum is given under the metal stream during l.

The disadvantage of this method is the late addition of aluminum and the introduction of silicon into the metal with a high content of oxygen in it, which leads to an increased contamination of the steel with large silicate THS inclusions that do not have time to ascend and remain in the ingot, reducing the quality.

The closest in technical essence and the achieved result of the invention is a method of smelting steel in a converter, including metal purging with oxygen, preliminary bath deoxidation with aluminum and final deoxidation and doping during the production of smelting, in which aluminum, precoating with carbonaceous composition, is introduced through slag, after being purged with oxygen, into the converter bath 2.

The disadvantage of this method is the low degree of absorption of deoxidizing agents and alloying elements, leading to a deterioration in the quality of the metal due to an increase in the content of non-metallic inclusions and a decrease in yield.

This deficiency is a consequence of the slight absorption of the aluminum converter introduced into the bath due to its considerable combustion during the passage through the slag J1, also due to the fact that it is introduced into the metal, which is in a quiescent state. This worsens the mixing of aluminum with metal, limits its contact with oxygen dissolved in the metal, as a result of which part of the aluminum floats to the bottom without providing the necessary oxidizing effect.

The purpose of the invention is to increase the degree of absorption of deoxidizing agents and alloying elements, improving the quality of the metal and increasing the yield of useful material.

The goal is achieved by the fact that according to the method of smelting steel in oxygen converters, including the blowing of metal with oxygen, preliminary deoxidation

aluminum bath and the final deoxidation and alloying during the release of smelting, preliminary deoxidation is carried out after 98-99% of the time of purging by addition to the ferroaluminium bath with an aluminum content of 55-65% in the amount of 2.53, 5 kg / ton S . .

The essence of the invention lies in the fact that the introduction of aluminum into the metal in the form of its alloy with iron improves its degree of assimilation, since ferroaluminium is more than twice as heavy as pure aluminum. The process of aluminum addition is simplified, since ferroaluminium, like most ferroalloys, has a lumpy shape and is introduced into the bath through the bulk material supply system existing in each converter, t, e, the process is completely mechanized.

The proposed method was tested on a 350 tonne converter with a flow rate of liquid iron of 72% and scrap metal of 28%. First, the effect of melt mixing on absorption was investigated; aJ umini metal. The consumption of ferroaluminium in experimental swimming trunks was 1 t. The ferroaluminium injection time was changed from the 96% time point from the start of the purge to 30 seconds after the end. purge. The purge duration varied from 15 to 25 minutes. For each mode of operation, three experimental melts were carried out, the averaged data on the absorption of aluminum are shown in Table. one.

A ferroaluminium additive in a mogent less than 98% of the purge time results in an almost complete burnout of aluminum, which is due to the long contact time of oxygen to blow from the bath. The addition of ferroaluminium at the time of the end of the purging of the bath with oxygen or some time after the end of the purging also results in a pronounced carbon loss of aluminum. This is due to the lack of mixing of the bath and the large loss of miminumin in the slag.

The best results were obtained with an additive of ferroaluminium after 98-99% of the purge time. Purging the bath after the ferroaluminium additive for 9-30 seconds, depending on the intensity of the purge, contributes to the effective mixing of ferroaluminium with the metal and provides a high degree of aluminum absorption.

The aluminum content in ferroa: tyumine varied from 45 to 75%. Experimental melting was carried out in a 350-ton oxygen converter with a flow rate of liquid iron, 72% and scrap metal 28%. The consumption of ferroaluminium for smelting was 1 ton. The duration of the purge was equal to 20 minutes at a flow rate of 1100 m3 / min of oxygen. Ferroaluminium was seated after 98.5% of the production time. For each mode held on three experimental melting. Indicators of experimental heats are given in Table. 2. When using ferroaluminium with an aluminum content of less than 55%, the absorption of aluminum is very low. This is due to the fact that such ferroaluminium is unstable during storage and spontaneously disintegrates into a powder, which during the additive is taken out in large quantities from the converter. Ferroaluminium, which has more than 65% aluminum, is poorly absorbed by the metal, since its specific gravity approaches the specific gravity of the slag. The best indicators are obtained using ferroaluminium with an aluminum content. Such aluminum is resistant to spontaneous dissipation or during storage and technological manufacturing and use. When it is added to the bath, due to its good density and high specific weight, good contact with the metal is achieved and a high degree of absorption of aluminum is ensured. In order to determine the optimal consumption of ferroaluminium, melting was carried out in a 350-ton converter with a liquid iron casting of 72% and scrap metal of 28%. The duration of the purge was 20 minutes at an oxygen consumption of 1100 m / min. Ferroaluminium with an aluminum content of 61% was crouched after 98.6% of the purge time. The consumption of ferroaluminium varied from 525 to 1575 kg per smelting, which corresponded to 1.5-4.5 kg / t of steel. For each mode of operation held on three experimental melting. The obtained characteristics of the converter are given in table. 3, When the consumption of ferroaluminium is less than 2.5 kg / t, the necessary (0.02-0.03) level of its content is not provided either in the metal before deoxidation. With a consumption of more than 3.5 kg / t, the content of aluminum in the metal exceeds a specified level, which is not desirable. The best results were obtained with a consumption of ferroaluminium of 2.5-3.5 kg / t of steel. Stabilization of the aluminum content in the metal (0.02–0.03%) ensures a constant oxidation of the steel guarantees obtaining the necessary steel composition for the main registering elements (manganese, silicon vanadium, titanium). The specified aluminum content in steel also provides an increase in the fluidity and Texology of the metal during casting on continuous casting machines. Entering ferroaluminium prior to the addition of silicon-containing deoxidizing agents significantly reduces the amount of large silicate inclusions in the steel. Short-term purging with oxygen promotes the formation of good contact between ferroaluminium and iron-carbon melt and the rapid process of its clearing of harmful impurities, especially from sulfur. Ferroaluminium, due to its higher specific weight compared with aluminum, is better absorbed by metal. Iron in ferroaluminum increases the yield of the metal. The pre-deoxidation of the bath with aluminum contributes to an increase in the yield, as a result of which a part of iron and manganese is transferred from slag to metal hours and is significantly reduced, the waste of scavengers and alloying materials. Example. 290 tons of pig iron and 110 tons of scrap metal were loaded into the oxygen converter. Oxygen purge was carried out at an intensity of 700. Lime in the amount of 10 tons sat down on scrap metal before pouring the iron, and then another 3.6 tons of lime were introduced at 3.6 and 12 minutes. 0.8 t fluorspar was applied in portions for 6, 15 and 20 minutes. Over 20 hours, the end of the purge, which lasted 25 minutes, 1 t of ferroaluminium with an aluminum content of 61% was placed in the bath. During production, manganese, silicon, vanadium and titanium were introduced into the metal. In order to study the quality of the metal, samples were taken from the converter before release and from the ladle. For comparison, melting was carried out with an additive in an aluminum bath after the metal was purged with oxygen. The results are given in Table. 4. As can be seen from the table. 4, the content of non-metallic inclusions and oxygen decreases by 2.7 times, sulfur, by 1.7 times. The nitrogen content remains at the same level. The proposed method provides stable results on the assimilation of alloying elements. At this m, the increase in the absorption is, abs,%: silicon 22 manganese 13, vanadium 7, titanium 20. The yield of the suitable metal increased by 1.2%. Rolled from experimental metal, has improved physical and mechanical properties. The economic effect due to the increase in steel output by 1.2% will amount to the production of 0.3 million tons of steel 288 thousand rubles. in year.

510495514

Indicators

Operation mode

Table 1

Ferroaluminium additive time,% from the start of blowing 9697 98 Duration of blowing 15 minutes, consumption

Purge time after the ferroaluminium additive, s3627189O Alumi-ini content in the metal at the outlet,% O 0.005 0.021 Duration of purge 20 min, consumption

Purge time after ferroaluminium additive, s4836 24 12O Aluminum content in the metal on release,% O 0.003 0.025

The duration of the blow 25 minutes, oxygen consumption 700 MVMHH

Purge time after ferroaluminium additive, s604530 15O

Gshuminium content

in metal on the run,% About 0.003 0.027 0.032 0.018 0.011

Indicators Aluminum content in ferroaluminium,% 45 50 55 Aluminum content in metal at the outlet,% 0.010 0.011 0.020

Table of faces Mode of operation 30 s after 99 100 oxygen purging 1500 MVMHH 0.028 0.016 0.008 oxygen 1100 0.028 0.015 0.009 $ 60 b 70 75 0.026 0.025 0.015 0.012 Specific consumption of ferroaluminium, kg / t Aluminum content of metal per exhaust 01111 0.016 ke,%

Table 3 0.021 0.026 0.030 0.033 0.038

Claims (1)

METHOD OF STEEL MELTING IN OXYGEN CONVERTER, including metal purging with oxygen, preliminary deoxidation of the bath with aluminum and final deoxidation and alloying during the smelting process, characterized in that, in order to increase the degree of assimilation of deoxidizers and alloying elements, improve the quality of the metal and increase the yield, preliminary deoxidation is carried out after 98-99% of the purge time by adding ferroaluminum to the bath, with an aluminum content of 55-65% in the amount of 2.5-3.5 kg / t of steel. >