SU1604165A3 - Method of producing steel in converter - Google Patents

Abstract

PURPOSE:To obtain steel of low H2 content with high refining efficiency, by blowing prescribed quantity of O2 of all supplied oxygen into the bottom of a furnace through a bottom blowing nozzle and blowing the remaining oxygen down to the surface of molten steel through a lance pipe for all the duration of oxygen blowing. CONSTITUTION:For all the duration of blowing of oxygen into molten steel 4 in a furnace 1, gas 6 which is 2-20% by volume or less, preferably 2-13% of O2 or a mixture of O2 and neutral gas of all supplied oxygen is blown into the bottom of the molten steel through a bottom blowing double pipe nozzle consisting of an inner pipe 7 and an outer pipe 8 and the remaining oxygen is blown onto the surface of the molten steel through a top blowing lance pipe 2. The oxygen top blowing conditions are altered depending on the quantity of the gas introduced into the bottom of the molten steel. To be concrete, the more the quantity of the bottom blown gas is, the more weakly the top oxygen is blown by adjusting its quantity and the height of the lance pipe. As a result, the iron oxide content of slag 5 is controlled and strong stirring and mixing are caused by the bottom blown gas to accelerate metal slag reaction.

Description

This invention relates to a method of using oxygen for refining limiting cast iron in a converter or other similar vessel used for refining, in particular to a method for refining limiting cast iron by supplying oxygen from above the surface of the melt together with a gas, such as oxygen or a mixture of oxygen and low-reactive gas from the bottom of the melt .

According to the method, the refining process is carried out by changing the ratio of the oxygen consumption of the upper blowing to the consumption of oxygen in the bottom blast supplied during the refining, and the result is determined that if the ratio of oxygen is; the bottom blow to the total supply of quicks) .g- .a exceeds about 17 vol.%, the manganese holding during the blow does not increase significantly and the iron content in pshak also does not decrease significantly. When the ratio of oxygen at the bottom blast to the total oxygen supply exceeds 17 vol.%, Emissions and splashing occur, while the yield of iron decreases. When the ratio of oxygen at the bottom of the blast to the total oxygen supply increased and exceeded 30 vol .-%, the refining operation was far from

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It was satisfactory because more metal adhered to the walls of the converter throat, and water was often leaked for cooling due to erosion of the tuyere head. Based on this, the upper limit of the oxygen ratio for the lower one is blown to the total oxygen supply, i.e. 17 vol.%, The lower limit was - 2 vol%, for the following reasons. When using a single tuyere, it is necessary to produce low carbon and high carbon steel, the minimum ratio of oxygen content for the bottom blow to the total oxygen supply that is required to move the molten metal and efficiently refine more profitable low carbon steel is 4-5% by volume and Consequently, the minimum oxygen ratio for the bottom blowing to the total oxygen supply that is required for refining high carbon steel using the same tuyere may be reduced to about 2% by volume. Accordingly, the proposed method requires that from 2 to 17 vol.% Of oxygen be supplied through a single converter, which is an exact limit that provides improved refining due to the strong mixing effect of oxygen injected from the bottom, and this method eliminates the undesirable phenomena that occur when the supply is excessive. bottom-blown oxygen without the introduction of lime powder during the top or bottom blowing.

To prevent slag emissions, it is important to control the composition of the slag, especially by its iron content and its characteristics. As a result of repeated experiments, it was found that the release can be predicted as follows. At the initial stage of refining, most of the required lime is supplied, preferably in separate proportions, to the end of desilication, i.e., lime is preferably introduced in portions after consumption of 15-20 Nm of oxygen per ton of steel and simultaneously oxygen is introduced through the top blast, which was compared strong at the initial stage than at the last stage, and at the initial stage no iron ore was used, as a result, at the initial stage

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the stages received dry slag, since the increase in the iron content in the slag was stopped, or the viscosity of the spike was reduced, while the output of gas bubbles was simplified, and as a result, the slag formation from .СаО in the place of overheating was accelerated. In order to achieve this effect, most of the required oxygen is supplied during the upper blowing, or the slag formed is cooled and does not interact with a large amount of loaded lime.

According to the proposed method, the oxygen blown from the bottom of the converter can be mixed with a slow-reacting gas, such as argon, nitrogen and carbon dioxide, which can even be independently used for a certain length of time. Thanks to this modification, the method for producing low carbon steel is simplified. The addition of nitrogen allows the production of steel containing nitrogen or the consumption of hydrocarbon gas as a coolant is reduced, resulting in a further decrease in the hydrogen content of the steel.

This method also provides a reduction in metal emissions and a reduction in the nodular metal on the tuyere due to a softer blow of oxygen from the tuyere to the surface of the molten metal during the raffin process: blowing or changing the force to blow between the initial and the last stages of refining and / or iron ore and lime.

When the gas supplied from the bottom of the furnace passes through the melt layer and the slag layer, a significant amount of carbon monoxide and other gas that passes through the slag layer is formed in comparison with the usual process of sepxt to blow it, and depending on the properties of the formed slag, an excessive ejection of metal is observed, as a result, the refining process is difficult at the initial and intermediate stages. x when a significant amount of carbon monoxide is formed. This effect occurs because at the initial stage of refining the desilication reaction dominates over other reactions, resulting in a molten slag with a high content of SiOj, Since.

This type of slag has a high viscosity and it reduces the rate of penetration of a large amount of gas containing mainly carbon monoxide into the slag, then carbon monoxide is formed at a higher rate than the groove is released from the slag. As a result, a large number of bubbles accumulate in the slag. the amount increases in volume and overflows through the throat of the converter.

If the initial stage of refining is carried out in such a way that the total iron content in the molten slag is high, then a strong release is noted. But effective refining, free from overshoot, can be achieved, firstly, as a result of this, that at the initial stage of refining, at the level of the position of the tuyere, a relatively solid oxygen jet is blown into the bottom than at the last stage of refining, for example, the ratios L / Lp, t, e, the ratio of the depth of the cavity L formed by the upper oxygen blast to the depth of the molten metal Lp, and it is more than a certain value, in order to ensure the optimum level of total iron. in the slag and at the same time ensure the formation of slag from CaO. As a result, the refining process proceeds in such a way that a viscous molten slag consisting mainly of FeO - SiOg. is not formed until the formation of carbon monoxide in the molten steel is active the initial refining stage, secondly, at the last stage of refining, for example, when approximately or more than 40 Nm of oxygen is introduced per ton of steel, the lance for the upper one is raised high to increase the total iron content in the slag neither

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strong mixing of metal and slag. Therefore, it is undesirable to use iron ores at the initial stage of refining, but to use it in separate parts during and after the intermediate period. At the same time, lime and iron ores are fed into

the form of pieces through the throat of the converter, as it is ocyD ec otcl ets in a conventional converter with a top-blowing system. In addition, low carbon and high carbon steels can be obtained at low cost without significant loss in the iron or manganese content and without increasing the oxygen content in the melt. Accordingly, the losses of additional alloying elements, for example, aluminum, manganese and silicon due to oxidation, are minimized. At the same time, high manganese extraction can be achieved.

from manganese ores. Due to the reduced supply of oxygen in the lower blast, steel is obtained, in the usual way LD, an additional decrease in the hydrogen content in the steel can

to be achieved by supplying a mixture of lower oxygen blowing with a low-reactive gas, such as argon, nitrogen or carbon dioxide, for a certain period of time, moreover.

the mixture contains 80 vol.% or less of oxygen and 20 vol%, or more than a low-reactive gas for a corresponding period of time, or apply such gas independently for

short length of time. Mixing nitrogen gas with underblow oxygen leads to the additional formation of a3ova, which is necessary to produce a nitrogen-containing

steel and, for example, when using a bottom blowing gas that does not contain essentially nitrogen, the final nitrogen content in steel can be reduced to 15 p, p, tp, or less. Besides

slag formation and the achievement of the corresponding, you can use scrap of dephosphation. Thus, according to the invention, molten slag of high basicity is formed in the final stage of refining, when not too much carbon monoxide is to be formed in the molten metal, and rapid de-phosphation and other refining reactions are achieved due to

The size of the gas when applying the bottom blowing. When the blast of a given amount of oxygen was stopped, the supply of oxygen at the upper lance terminated and simultaneously through the inner tube and through the gap between the inner and outer tubes, argon or nitrogen was supplied. The furnace was tilted and then the temperature was measured and

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The size of the gas when applying the bottom blowing. When the blast of a given amount of oxygen was stopped, the supply of oxygen at the upper lance terminated and simultaneously through the inner tube and through the gap between the inner and outer tubes, argon or nitrogen was supplied. The furnace was tilted and then the temperature was measured and

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chemical composition of steel by t-sampling,

The table shows the percentage of oxygen for the bottom blowing and the total gas content in percent for the bottom blowing, as well as the composition of the metal and slag.

The use of this technology allows to reduce the total iron content of JQ in the slag and thereby increase the yield of the liquid metal, as well as to reduce or increase the nitrogen content in the steel.

The drawing shows schematically a furnace for refining.

An example, the method is carried out in a 75-toHHOM converter (drawing) with an upper blowing system, where the end of the converter 1 (oven) contains lance 2 for the upper oxygen inlet, bottom

3 of the furnace, on which the molten steel 4 and slag 5 are located, the converter is equipped with pipes 6 for bottom gas blowing 7. During the refining operation, pure oxygen was supplied through these pipes, and during charging. Molten metal before refining and at the end of refining was supplied with a slowly reacting 30 ha. to prevent clogging of the nozzles. At position 8, the pipe of the nozzle of the casing is marked. During the refining process 35, at least a gas, oil-like kerosene or an oil mist containing oil sprayed with neutral gas, as a cooler to prevent erosion of 40 pipes, passed through the gap between the inner 6 and outer 8 pipes, but in the example of the inner tube 6, the slow-reacting gas passed through the said gap during the loading of the molten metal and at the end of refining. 45 A pipe was connected to a container containing a gas (not shown) through a device (not shown) to regulate the flow rate of oxygen or the slow reacting (inert) gas 50 that must pass through the inner pipe. The pipe 10 was connected to another tank containing a gas (not shown) through a device (not shown) to regulate the speed of the oxygen flow and the cooling

gas, for example, C1 „H, reacting

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for the lower one, oxygen, or a mixture of oxygen and a slowly reacting gas, was supplied. During the refining operation, the gas flow rate or type of gas flowing through the inner tube was changed to prevent emissions, decrease the hydrogen content in the steel, and increase the nitrogen content in the steel. Propane was fed through the gap between the inner tube and the outer tube, except that only a slow-reacting gas was supplied when a mixture of oxygen and a slow-reacting gas was injected into the morning tube. The flow rate of the gas passing through the inner tube was changed by changing the diameter of the casing nozzle.

Before the start of the refining operation, the furnace loaded approximately JO tons of scrap and 65 tons of molten pig iron, while the inner tube 6 was supplied with the minimum amount of argon gas or nitrogen, which is required to prevent clogging of the nozzle, as well as through the gap between the inner tube and outer tube 8. Then the furnace was installed in a vertical position, the lance 2 for the upper one was lowered to a predetermined height and refining started. After that, oxygen was supplied through the inner tube 6, and propane was passed through the gap between the inner tube 6 and the outer tube 8. During the refining operation, the height of the tuyeres: | g 2 for the upper blow was adjusted accordingly, depending on the type of steel to be produced, and the flow rate of the bottom gas to blow,

In the refining process, fluxing materials, such as lime, iron ores and fluorspar, were loaded through the kiln neck. When the silicon content in the molten iron is high, the emission at the initial as well as the intermediate refining stages was prevented by feeding most of the lime and fluorspar into the first half of the refining process and feeding most of the iron ore at the intermediate stage and after completion of active decarburization. When the blast. A given amount of oxygen is stopped, the supply of oxygen from the upper Fursh is terminated and simultaneously along the inner tube and argon or nitrogen is fed through the gap between the inner and outer tubes. The furnace was tilted and the temperature and chemical composition of the steel were measured by sampling. samples.

The table shows the percentage of oxygen for the top blowing, the percentage of oxygen for the bottom blowing and the total gas percentage for the bottom blowing, as well as the composition of the metal and slag.

The application of the proposed technology allows reducing the iron content in the slag and increasing the yield of the suitable one and reducing or increasing the nitrogen content in the steel.

Claims (2)

1. A method of steel production in a converter that includes supplying oxygen to a bath with molten metal through nozzles located below the melt surface, and simultaneously supplying oxygen through the upper lance to blow with a force at which the penetration depth of the upper oxygen jet melt less deep; S ten 15 20 25 thirty molten bins, input of lime, iron ore, and fluorspar. and the replacement of oxygen supplied through the bottom slopes with a gas with low reactivity or a mixture of oxygen and gas with low reactivity during refining periods, which differ from a chain of increase in the efficiency of the process, oxygen or a mixture of oxygen and gas with low reactivity is fed under the surface of the molten metal through the nozzles of the lower one to blow during all refining periods in the amount of 2-17% by volume of the total consumption of sour ode with more than half of lime consumption for melting is introduced in the initial period, and the iron ore in the intermediate and final periods refining, wherein the iron and lime. The ore is introduced in pieces through the throat of the converter. 2. The method of pop. 1, which is distinguished by the fact that the oxygen supplied through the lower blowing nozzles is inflated with a gas with a low reactivity or a mixture of oxygen and a gas with a low reactivity during the final refining period. one I.JL | YL1 s Iliiiti ) 0) S OO ABOUT about sh tM t about 00 about about " N 1L "H to about about about S  m ABOUT g ABOUT . to to x ag4 g-.s yo3 H t about - from p2 I in f I Ш "L " t-t about 1Л1 S. ““ I G4 SP Yu 00 yy and well with pn one T "L 00 / 7 J e-V "L V V l l Editor M. Nedoluzhenko Compiled by V. Samsonov Tehred M. Didyk Order 3395 Circulation 500 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101   V l t Proofreader A. Osaulenko Subscription