RU2140993C1 - Method of steel melting - Google Patents

Abstract

FIELD: ferrous metallurgy, particularly, methods of steel melting in oxygen converters by monoprocess. SUBSTANCE: method includes introduction into converter during processing of vanadium iron, of knocked out lining of electrolysis baths of aluminium production in amount of 10-40 kg/t of steel by portions. The first portion is introduced into bottom of converter, on remained slag form previous heat in amount of 60-90% of its weighed portion. The remaining amount is introduced upon lapse of 10-95% of blowing time. Additional amount of said knocked out lining may be introduced in case metal temperature prior to steel discharge is below the required value. After this, metal is blown with oxygen as required. EFFECT: reduced harmful effluents to shop atmosphere, increased fraction of scrap in iron charge and higher stability of converter lining. 2 cl, 1 tbl

Description

 The invention relates to ferrous metallurgy, and more particularly to methods of steelmaking in oxygen converters.

 A known method of steelmaking in an oxygen converter using, together with scrap metal waste anodes or cathodes of electric furnaces of aluminum production [1].

 The production of aluminum is carried out by electrolysis of alumina in fluoride and alkaline melts. The hearth for producing aluminum, which serves as the cathode of the furnace, is laid out from carbon plates. The furnace vault is the anode. Coal stoves are made of pressed fine coke or thermoanthracite and coal tar. During the operation of aluminum bathtubs, the carbon lining is impregnated with fluoride and alkaline compounds and fails. The lining (cathode-furnace), which has expired, is broken down and dumped. The lining sample contains: 50-70% carbon, 10-12% fluoride compounds, 4-6% aluminum oxides, 10-11% sodium oxides. The content of sulfur and phosphorus in them is 0.1-0.2%.

 Introduction to the converter together with scrap cathodes and anodes according to the method [1] negatively affects the ecology of the atmosphere of the workshop. At the moment the converter for casting iron is pulled, a significant amount of white gas is released under the influence of high temperature from the evaporation of sodium oxides and partially fluoride compounds.

 The closest to the proposed technical essence and the achieved result is a method of steelmaking in a converter using a lining of the lining of electrolysis baths for aluminum production in the amount of 1-5 kg / t of finished steel [2].

 The use of lining breakouts in converter smelting within 1-5 kg / t of steel allows to reduce the slag oxidation while increasing its reactivity.

 However, despite the presence of carbon in the punch, the amount of punch introduced into the converter up to 5 kg / t does not allow changing the ratio of pig iron plus scrap to decrease the share of pig iron and increase the share of scrap, since the amount of heat generated from the interaction of a small amount of carbon with oxygen in the blast is not significant .

 So, for example, 500 kg of a cut-out or in terms of the carbon component of 350 kg of carbon are introduced into a 100 t cage converter. In this case, the amount of carbon in the metal charge increases by only 0.35%. This amount of carbon, taking into account the costs of heating the breakdown, the exothermic reaction between carbon and iron oxides of slag and heat loss in the converter, is not enough to obtain the amount of thermal energy spent by the increased additive for scrap metal.

 Also, there is not enough thermal energy from the addition of a break-out in an amount of up to 5 kg / t of steel and in the smelting of high- and medium-carbon steel grades. In this case, it is necessary to increase the proportion of cast iron in the metal charge or to purge the metal to very low carbon contents, which negatively affects the resistance of the converter lining due to an increase in iron oxide in the sludge.

 The objective of the invention is to reduce harmful emissions into the atmosphere, the price, increasing the share of scrap in the metal mill and increasing the durability of the lining of the Converter.

 The problem is solved in that according to the method of steel smelting in a converter by a monoprocess, including filling scrap metal, pouring molten iron, blowing metal with oxygen, adding portions in the course of blowing out the lining of the electrolysis bathtubs of aluminum production, metal production, according to the invention, the lining of the electrolysis bathtubs of aluminum production 10-40 kg / t of suitable steel are introduced into the converter as follows: the first portion is introduced to the bottom of the converter to the remaining slag from the previous smelting in the amount of 60-9 0% of its weight, and the rest after 10-95% of the purge time.

 When the temperature of the metal is obtained before steel production is lower than necessary, a lining of the aluminum electrolysis bathtubs is additionally introduced and the metal is added with oxygen before production.

 Putting a hole in the bottom of the converter to the remaining slag from the previous smelting allows it to reduce the content of iron oxides in it while increasing its liquid mobility. The slag aggressiveness with respect to refractories decreases sharply, and due to its fluidity it easily enters the pores and recesses of the lining, thereby better “slagging” the bottom of the converter, which entails an increase in the lining resistance.

 In addition, the introduction of a cut to the bottom of the converter allows reducing the amount of emissions from the evaporation of sodium and fluorine compounds directly into the atmosphere of the workshop as a result of the fact that, firstly, these compounds will dissolve in the slag, and secondly, when loading scrap metal, the latter will be a kind of screen and delay harmful fumes.

 The amount of sagging in the range of 10-40 kg / t of suitable steel is determined by the amount of heat generated from the oxidation of the carbon of the sinking, which is sufficient to compensate for the heat from oxidation of impurities of molten iron, the proportion of which is proportionally reduced as a whole in the metal filling.

 If the amount of knockout seated on the remaining slag is less than 60% of 10 kg / t of suitable steel, i.e. 6.0 kg / t of suitable steel, the amount of heat released, taking into account its losses due to heating of a break-out, entrainment with exhaust gases, losses due to heating of the converter lining, etc. will not be enough to compensate for the heat from oxidation of a reduced proportion of cast iron in the metal plant.

 In the case of an increase in the consumption of the cut-out, seated on the remaining slag, more than 90% of 40 kg / t, i.e. 36 kg / t of suitable steel, carbon of the breakout can quickly react with iron oxides of slag and blast oxygen with the release of a significant amount of carbon monoxide and, therefore, taking into account the low basicity in the initial purge period, lead to foaming of slag. In this case, it is necessary to stop the purge and download the slag, which will lead to an increase in the duration of the smelting and heat loss from the converter.

 The remaining break in the amount of 1.0-16.0 kg / t of suitable steel is introduced into the converter along the purge process to improve slag formation of the smelting. Given that the punch contains fluorosodium compounds, it contributes, firstly, to a faster dissolution of lime, and, secondly, reduces the viscosity of the slag melt.

 In the process of purging the metal, a knockout should be introduced into the converter no earlier than after 10% of the purge time, because during this period, intense phosphorus oxidation from metal to slag occurs. The presence of carbon in the sump reduces the oxidation of phosphorus due to a decrease in the content of iron oxides in the slag, since in subsequent periods of purging the conditions for the removal of phosphorus into the slag are not created, the finished steel will have an increased phosphorus content.

 After more than 95% of the purge time has elapsed, a knockout should not be introduced, since its mass does not have time to dissolve in the metal and slag before the metal is released from the converter.

 Typically, the metal is purged before it is released from the converter to increase the temperature when the carbon content in the metal is less than 0.1%. In this case, the increase in metal temperature occurs due to the intense oxidation of iron, as a result of which the yield of suitable steel decreases and the content of iron oxides in the slag increases, which negatively affects the resistance of refractories. The introduction of a knockout during the metal purge period allows the introduction of an additional amount of carbon into the metal, thereby preventing the oxidation of iron. Therefore, the waste of metal and the content of iron oxides in the slag is significantly reduced.

 Analyzing the foregoing, we can conclude that in the present invention there are signs that are new and essential, allowing to achieve the task, compared with the known method, and the claimed method meets the criterion of "novelty."

 From known sources of information, it was not revealed the use of new features of the claimed method according to their functional purpose and the achieved result, which meets the criterion of "inventive step".

 An example implementation of the method. In the 160-t converter, after the metal was drained and the slag of the previous melting was left in it, a weighed portion of the lining of the aluminum production electrolysis baths was introduced. Then, the required amount of scrap was dumped into the converter. On the part of the heats, scrap of the lining was introduced into the scrap (prototype). After filling the scrap, the required amount of cast iron was poured, the mold was lowered and the metal was purged. In the process of purging, as the slag formation of the melting worsens (the phenomenon of “slag folding”), the required amount of lining breakdown was introduced into the converter. In the event that insufficient metal temperature was obtained at the end of the purge necessary for casting on the UNRS, metal was blown “at a temperature” with the introduction of a knockout before the start of blowing.

 The consumption of the lining breakdown, the time of its additives in the converter and the results of the melting are presented in the table.

 From the presented table it can be seen that, in comparison with the prototype, when using slag on the slag remaining in the converter in the amount of 6-36 kg / t suitable steel, the consumption of cast iron is reduced and the amount of gas emission is reduced.

 Thus, the claimed method can be implemented in the industrial production of converter steel on existing metallurgical equipment using available raw materials.

Sources of information
1. Copyright certificate of the USSR N 988877, cl. C 21 C 5/28, 1981

 2. Copyright certificate of the USSR N 840130, cl. C 21 C, 5/28, 1979

Claims (2)

 1. A method of steelmaking in a converter by a monoprocess, including filling scrap metal, pouring molten iron, purging metal with oxygen, an additive in the course of purging in portions of the lining of aluminum electrolysis bathtubs, metal production, characterized in that the lining of aluminum electrolysis bathtubs is introduced into the converter in the amount of 10 - 40 kg / t of suitable steel, while the first portion of the breakdown in the amount of 60 - 90% of its weight is introduced into the slag left in the converter from the previous heat, and the rest of the breakdown administered after 10 to 95% of the oxygen purge time.  2. The method according to claim 1, characterized in that when obtaining the metal temperature before steel is lower than necessary, a lining of the aluminum electrolysis bathtubs is additionally introduced and the metal is blown with oxygen.

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