KR840002047B1 - Converter steel making process - Google Patents

Abstract

In a converter steel-making process, oxygen is supplied from an upper lance and gas is simulataneously supplied from a bottom nozzle. During the refining operation, oxygen and mixed gas, which reacts slowly with oxygen, are supplied from the bottom nozzle at 2 vol. % - 17 vol.% of computed amount. This converter steel-making process is characterized by the refining process, which involves blowing the remaining oxygen from the upper lance on to the surface of the molten steel.

Description

Steelmaking method

1 shows an example of a refining furnace for carrying out the present invention, and is a schematic diagram of the refining furnace.

FIG. 2 is a graph showing the relationship between iron content (% by weight) of slugs, which are indicative of intake conditions and refining efficiency, for each low odor gas flow rate vo1% (C: 0.03 0.10% by weight when stopping pouring at 75 ton converter) In the case of).

In each case of the present invention (low odor gas flow rate of 3 Vol%, 5 Vo1%, 7 Vo1%, and 13 Vo1%), the iron content in the slug is displayed to be lower than the iron content in the slug by the LD method. have.

The present invention relates to a method for refining pig iron using oxygen (industrial pure oxygen, such as) in a converter or such refining vessel, and when refining, oxygen is removed from the lower portion in the upper part of the molten iron bath. Oxygen black using a double-pipe nozzle relates to a refining method for reconnaissance that simultaneously supplies a slow reactive gas and a mixed gas of oxygen. Prior to the detailed description of the invention will be described the difference between the present invention and the prior art as follows.

The pure oxygen uptake converter steelmaking method which attaches oxygen to the molten iron bath surface in a converter is widely performed as what is called an LD method. When oxygen is added to the bath surface of the molten iron, in the range where the carbon content in the bath is high, the refining reaction is actively progressed due to the stirring effect of the collision energy of oxygen to be installed and the carbon monoxide gas generated in the bath, so that the carbon content in the bath is 0.8. When the carbon dioxide is decarburized to less than 0.1% by weight, in particular, the generation of carbon monoxide gas becomes less active, and the agitation of the bath is weakened rapidly so that the decarburization rate decreases and the oxygen level in the strong bath rapidly increases, Becomes peroxide, and the iron oxide content in the slurry also increases. For this reason, iron loss and manganese loss at the time of finishing blow increase, and are added to molten steel. The recovery rate of alloy addition of manganese, silicon, aluminum, etc. was low, and the economic loss was also a big problem.

On the other hand, the method of West German Patent No. 1909779 itself corresponds to a double tube which is known by French Patent No. 1450719, and melts together with powder lime through the inner tube from the bottom of the oxygen converter, that is, from the bottom. It is characterized by supplying and refining in (iv). Hydrocarbon is supplied between the inner tube and the outer tube as the gas for cooling through the annular cavity. This proposal makes it possible to change the low odor air of Thomas converter, which is a conventional low odor converter, to oxygen, and protects the bottom of the converter and the double pipe nozzle by cooling gas, and maintains its proper life as a converter. It is called OBM / Q-BOP and it is put to practical use.

However, this method also has the following drawbacks. In other words, if the carbon content of the bath decreases, the production of carbon monoxide decreases, and the hydrogen content of the bath increases, reaching 4 to 6 ppm. Therefore, this increased hydrogen causes various problems in the next step after scouring. Depending on the type of steel, dehydrogenation will be required.

When blown into a strong bath, there is a characteristic that the stirring of the strong bath is excessive in order to reduce a large amount of highly active oxygen, which is explosive and rapidly reacting, in a large double-pipe nozzle. As a result of this, the ashes of quicklime added as refining materials are difficult to produce, and there are disadvantages such as sloping (slug of slugs and molten steel) and high adhesion to furnace holes.

Sloping can only be reduced by introducing lime powder into the oxygen stream and suppressing the explosive reaction of oxygen.However, the number of nozzles increases when the lime powder is blown from the bottom of the furnace. In addition, the hydrogen content of the low carbon content is not only high, but also the melting loss of the bottom refractory of the furnace is increased, the production and conveyance of blown lime powder, the equal distribution technology for blowing through a plurality of nozzles, the oxygen from the lime powder In terms of facility and maintenance costs such as countermeasures for sending pipes, there is a big burden and problems.

In the case of high carbon steel having a carbon content of 0.25% by weight or more, the dephosphorization reaction does not proceed sufficiently. Therefore, once carbon in molten steel is removed to 0.10% by weight or less, dephosphorization is carried out. There is a drawback that the solvent is difficult unless it is based on the so-called column-based method of adding a chelating agent.

The cold method of US Pat. No. 3,953,199, which is proposed as a method for resolving the drawbacks of the LD method and the OBM / Q-BOP method, is a method of refining pig iron using pure oxygen, and when oxygen is attached to the bath surface from above by a lance, At the same time, in the deodorizing low odor combination method in which oxygen is distributed even as the bottom of the furnace using a double pipe nozzle, at the beginning of the refining process, the oxygen is refined substantially from the upper side. It is characterized by increasing the oxygen supply of and refine | purifying by oxygen from a double tube nozzle substantially.

According to the example of this proposal, since lime can be added with oxygen from the upper side, the slug temperature rises and the production | generation of slug is promoted. This method reduces the carbon content in the bath, produces less carbon monoxide, and decreases the agitation of the bath. Therefore, the flow rate of oxygen sent from the double tube nozzle at the bottom of the furnace needs to be increased to about 50%. In the early and middle stages, even if the oxygen flow rate of low odor is reduced to the minimum flow rate for preventing molten steel from intervening in the double tube nozzle, considerable oxygen is reduced. That is, in the method according to this proposal, since a large amount of oxygen is blown into the bath by the double-pipe nozzle, as in the case of the above-described OBM / Q-BOP, the problem of quicklime ashing or the entrance to the furnace There are problems such as adhesion, and in order to solve this problem, as described in the embodiment of this proposal, quick lime is oxygen-installed in a strong bath to solve the above-mentioned problems by effects such as low odor lime of OBM / Q-BOP. There is a need. Again, in this proposal, the effect of effect is described very qualitatively, so the extent of the effect cannot be judged.

In addition, Belgian Patent No. 780,910, which uses a combination of lower odor and lower odor, aims to burn carbon monoxide gas generated by reaction with oxygen introduced from the bottom with upper oxygen to improve thermal efficiency. The technical idea is completely different from the present invention, which will be described later, which mainly aims at a significant improvement in the yield.

In addition, the method of Belgian Patent No. 872,620 improves the thermal efficiency of the converter by increasing the amount of charge in the furnace by blowing the steel on the steel surface and under the bath surface as refining oxygen when refining the steel in the converter. 20 ~ 80% of the total amount of oxygen from the nozzle installed on the upper side wall of the converter is installed on the bath surface, and the remaining oxygen and lime powder are blown from the bottom nozzle of the furnace, and the amount of oxygen and lime powder blown from the bottom nozzle of the furnace is transferred to the bottom of the furnace. It differs from this invention in that refining operation is difficult unless it blows in from a heavy pipe nozzle.

In other words, the present invention limits the low odor oxygen flow rate to 2 Vol% or more and less than 17V1%, preferably 2 V1% or more and 13 V1% or less, so that the lime powder is blown together with the fresh air or the low odor oxygen, without using the conventional high odor converter. As a result of the addition of bulky lime from the inlet of the furnace, it ensures high refining efficiency and maintains the stability of the upper lance and, in addition, the low steel of hydrogen which does not have a great difference with the hydrogen level of the ordinary upper sequencing converter. It can be manufactured as a simpler facility. Therefore, in the above-mentioned conventional invention, the same effect as the present invention cannot be expected.

Accordingly, an object of the present invention is to solve the technical problems of both the oxygen squeezing steelmaking method and the low smelting steelmaking method. The purpose is to provide.

This invention is the converter steelmaking method which aimed at the significant improvement of the refinement | purification ability by a refreshing oxygen. The present invention is a steelmaking method aimed at improving operational problems such as sloping (slug and ejection of molten steel and spitting (spraying of fine grains of steel)).

In the present invention, the amount of total Fe in the slug (that is, the iron content in terms of iron oxide in slug) is about 9 to 13% by weight, particularly in the case of a so-called low carbon steel solvent having an oxygen content of 0.10% by weight or less. By controlling it, while achieving sufficient dephosphorization reaction, the manganese level at the time of finishing termination can be raised significantly, and the drawback of high hydrogen content which is one of the drawbacks of the OBM / Q-BOP method is high. You can improve by making less absolute. Again, the OBM / Q-BOP method aims to use the slug control function of the promotion effect of the slug-metal reaction of the present invention. As the dephosphorization reaction can be achieved, a significant improvement in the refining function, such as being able to be solvented by the catch carbon method without taking the carbon concentration down, can be realized. That is, even if it does not follow the method of blowing lime together with low odor oxygen as in the OBM / Q-BOP method, it is possible to achieve by intensifying the mixing efficiency by the low odor gas and the optimization of the top lance leaching condition according to the amount of low odor gas. By combining organically with the control function of the slug formation, the sludge is formed using the same mass of lime as used in the LD method, and the amount of iron oxide in the slug is controlled to the most suitable level to efficiently control the refining process. It can be realized.

In addition, the oxygen flow conditions from above are changed according to the level of gas introduced from the bottom of the furnace. Specifically, as the amount of gas introduced from the bottom of the furnace increases, the bleeding jet from the top adjusts the flow rate of the oxygen to be sent and the Higgs height. It is possible to control the amount of iron oxide in the slug by weakly attaching it. At the same time, the metal slug reaction is actively activated by the vigorous stirring mixing effect of the low odor gas, and the refining reaction is carried out efficiently. Can promote.

The dephosphorization reaction, which is a major problem in steelmaking, is described as follows. The conditions such as the charter rate, the level of the charter, the capacity of the stonework, etc. are generally the same, and the phosphorus at the time of mounting stop is less than 0.10% by weight or less and the temperature at the time of mounting stop is 1600 to 1630 ° C. In order to achieve 0.020%, in the conventional LD converter, since the stirring is weak and the refining reaction does not proceed sufficiently, 20 to 25% by weight of total Fe in the slug is required. According to the present invention, the total Fe in the slug is 9 to 13% by weight. Since only% is required, iron loss and manganese loss are greatly reduced, and the amount of refractory loss due to slug is also reduced, and the refining can be performed very efficiently.

Even in the conventional upsetting furnace, it is not impossible to lower the iron in the slug while being blown under the strong upsetting condition that the oxygen jet can reach the bottom of the furnace, but in addition to the intense spitting, the bottom of the oxygen jet fire point As there was the risk of loss of furnace bottom of converter, it was not practical.

According to the present invention, the OBM / Q-BOP method does not require the injection of lime powder from the bottom of the furnace, which is indispensable because the flow rate of low odor is excessive, so that the low odor gas flow rate and the odor picking conditions are selected, and thus, very smooth cleaning operation is possible. It was confirmed that refining from low carbon steels to high carbon steels was possible in a practically highly desirable condition with little iron loss in the slug, high manganese level at the time of mounting stop, and no hydrogen level as well as the conventional LD method. In addition, when a gas having a low nitrogen content is used as the low odor gas, the nitrogen level at the time of stopping installation can be set to a low level of 15 ppm or less despite the carbon content. In this field name, since the refinement is possible under the condition of low total Fe content in the slug, when manganese ore is used instead of iron ore, manganese powder can be reduced and recovered much more advantageously than the conventional LD converter.

As described above, the present invention solves the drawbacks of the LD method and at the same time provides a refining effect superior to that of the OBM / Q-BOP method. It can be carried out as a simple facility that does not require a transport facility, and therefore, it is easy to convert from an LD converter. In the upper blast furnace, there was a limit to high speed scavenging due to the increase of spitting and the increase of the amount of iron oxide in the slug, but by injecting oxygen from the bottom to enhance the stirring of the bath, the upper lance was raised to increase the amount of oxygen to the bath surface. It is mounted in a state where the impact of the oxygen jet is alleviated. Therefore, it is also easy to increase the sum of the rate of sending oxygen without increasing the speeding than that of the LD converter of the same size, and the refining efficiency can be high.

MEANS TO SOLVE THE PROBLEM The present inventors carried out the drilling by changing the ratio of the upper oxygen flow rate and the low oxygen consumption flow rate in the pre-treatment period, on the basis of the development of the steelmaking method which eliminated the fault in the uptake method and the low odor method, and adopting both advantages. It was confirmed that the effect of the increase in the mounting stop manganese by the oxygen absorption rate and the reduction of the steel ball 2 in the slug did not increase significantly even when the low oxygen absorption rate was approximately 17Vo1% or more.

In addition, when the low oxygen content exceeds 17Vo1%, the present invention does not deodorize lime, resulting in an operation problem such as slipping and spitting, resulting in a large decrease in iron recovery. When the low oxygen content ratio is 30Vo1% or more again, leakage accidents due to the attachment of the upper lance and damage to the lance tip frequently occur, and practical operation is very difficult. Therefore, the upper limit of the low oxygen absorption rate of this invention was set to less than 17 Vol%.

In addition, the lower limit is effectively reduced to low carbon steel, which is economically effective when the low carbon steel and the high carbon steel are ingested in the same tuyere. The ratio of is 4-5Vo1%, and therefore, the ratio of low odorable oxygen which can be taken up when blowing high carbon steel in the same tuyeres is determined by lowering to about 2Vo1%.

In this way, the number of ventilation holes for injecting low-oxygen is minimal, and the effect of reducing the cost of equipment and the maintenance cost of cargo or equipment in the bottom of the furnace is also brought about.

Therefore, it is possible to secure the improvement of the blowing efficiency by strengthening the stirring by low oxygen, and at the same time, the proper low oxygen flow rate, which does not cause the problem caused by excessively low oxygen content without reducing the blowing of lime powder by any method of high smell. It can be seen that is more than 2Vo1% and less than 17Vo1%.

In addition, the upper limit of the low odor gas flow rate is 17 Vo1% in the dedicated solvent furnace for low carbon steel, but the low odor gas flow rate ratio of 2 to 13 is preferably used for efficiently drilling the steel from the low carbon steel to the used carbon steel using the same converter. It becomes%.

As described above, the lower limit of the flow rate of the blown oxygen from the bottom of the furnace of the present invention is determined as the minimum necessary amount to exhibit the stirring mixing effect of the practical bath, and if the upper limit is increased above the amount, the gas flow rate from the bottom is increased. In the present invention in which the control width of the slug properties is substantially eliminated even by changing the pick-up picking condition, the dropping or spitting of the lime powder is not carried out. Was determined by disappearing.

In addition, in the present invention, a slow reactive gas such as Ar, N ₂ and Co ₂ can be mixed with low odor, and can be used alone within a specific period. Accordingly, it is possible to make the solvent of the ultra low carbon steel more easily, to carry out by adding nitrogen in the case of N-containing steel, or to further reduce the amount of hydrocarbon for cooling, and to further reduce the hydrogen content in the steel.

In addition, the present invention has a small amount of slipping by optimizing the introduction of and / or iron ore or lime by relatively soft blowing the oxygen from the lance to the bath surface over the entire period or by varying its strength in the early and late stages. Provide a refining method to prevent this. In other words, when the gas blown from the bottom of the furnace is dissipated through the molten steel and the slug layer, the amount of gas, such as CD, penetrates the slug layer significantly increases as compared to the conventional wiping method. Therefore, depending on the characteristics of the slug, Significantly higher occurrences lead to severe sloping and difficult operation during the early stages of the blow. It is thought that this is due to the formation of molten slug having a high SiO ₂ content by the de-silicon reaction proceeding preferentially at the beginning of converter conversion. That is, since this type of slug has a high viscosity, the velocity of a large amount of CD gas as a main component floats through the slug and passes through the slug, which causes the generation rate of CO gas to be greater than that of the gas. It is thought that the volume of the slug increases and overflows from the furnace inlet due to the residual accumulation of many bubbles in the slug.

This phenomenon is the same in the OBM / Q-BOP method, and as a solution thereof, a method of preventing slipping by injecting powder containing lime as a main component at the bottom of the furnace according to the amount of de-silicon at the beginning of blowing is proposed. In the meantime, the present invention is characterized in that the lime powder is not odorized, and since the low odor gas flow rate is essentially small, it is practically difficult to reduce a sufficient amount of powder lime.

The present invention is based on the finding that the control of the slag composition, in particular the Fe _m D _n component content and the slug property control, are important to prevent the slipping. That is, the lime of the placenta is preferably divided at the beginning of the blowing, and is added to the pickling passage of 15 Nm ³ to 20 Nm ³ O ² / Ton Steel as the amount of oxygen to be delivered to the point of depolarization at the end of the desilicon reaction. It is relatively strong (hard) compared to the end of the blow, and it waits for the use of iron ore in the end, thereby suppressing the increase of the total amount of Fe in the initial slug, drying the slug or injecting the placenta oxygen. The slugs are cooled by lowering the viscosity of the slugs and facilitating the scattering of bubbles due to the characteristics of the present invention or by promoting the oxidation of CaO in a wide flash point area, or by adding a large amount of lime. It was found in the course of several experiments that the inactivation can suppress the slipping.

As described in the above description or the embodiment, it is characterized in that the operation is performed by raising the lance height as compared with the normal top converter, but the lance operation during the drilling has the following effects. In other words, if the molten slug is formed by increasing the total Fe content in the slug at the beginning of the blow, severe sloping may occur, but for example, the same amount of acid may be relatively strong (hard) compared to the end of the pickling condition. If it is, it is operated by lowering the lance height, increasing the ratio of the depth of the bath (L ₀ ) to the cavity depth (L) resulting from the squeezing (L / L ₀ ) above a certain value, and the total Fe content among the slugs is most suitable. In addition, by promoting CaO goods in the flash point area, during the active generation of CO gas in the initial bath of the blowing operation, the operation that does not form viscous molten slug mainly composed of FeaSiO ₂ is performed. with, near the point at which the amount of the end chwisan for example more than 40Nm ³ / TS of blow, for example increasing the sangchwi lance height, increasing the level of total Fe and the slag, promote good when Hameuroseo enough to conduct dephosphorization without generation of the slope scouring shopping can be a great blow to conduct efficiency. At the time when the generation of CO in the bath is less at the end of the extreme blow, the molten slug of high base degree is formed, and refining such as descaling is performed by vigorous stirring mixing of the bath slug by low blowing gas blowing. It's a quick shutdown. Therefore, in view of these technical ideas, in the use of iron ore, the use of the initial stage of blowing is not preferable, and it is preferable to use it after the middle stage.

In view of the trend of the slug composition at the time of blowing, it is preferable to suppress the formation of the molten slug by controlling the total Fe in the initial slug to be lower than 10% by weight, for example. In other words, when iron ore is added to the initial stage of smelting or the odor pickling conditions are extremely relaxed (soft), when the total Fe content in the slug is increased to form viscous molten slug mainly composed of FeO-SiO ₂ , severe sloping phenomenon occurs. This was observed. This is a common molten iron ratio. In the initial stage, the movement of the bath is weakened due to the presence of infiltrated debris, and the total Fe is increased in the slug. It is thought that this is because the total Fe rises in the slug and the molten slug easily forms at the same time as it becomes active.

If in the practice of the present invention Weigh the total Fe amount in the slag is very important factor is the oxygen supply rate as described above, constant, sangchwi condition according to jeochwi gas flow rate as described above, for example, the L / L ₀ In addition to being possible by changing, it is also possible by changing the oxygen supply rate.

In other words, if the oxygen feed rate is increased while maintaining the low odor gas flow rate and the L / L ₀ of the fresh smell, it is possible to increase the total Fe amount in the slug while increasing the FeO production rate. And the depth of the bath cavitation by the upper lance in this specification shall be evaluated by following Formula.

n: Distance between lance tip and stop bath surface, lance height (mm)

A: Corresponds to L when h = 0 and is obtained by the formula (2) (mm)

FO ₂ : delivery speed Nm ³ / Hr

n: number of nozzle holes of upper chuck

d: nozzle diameter (mm)

K: Constant determined by nozzle angle θ (table below)

Therefore, it is possible to change the L / L ₀ by considering factors such as the lance height (h), the uptake nozzle hole diameter (d), the jet flow rate or the delivery speed. In this case, it is desirable to change the lance height factor in actual operation.

In other words, the present invention limits the low oxygen content to 2Vo1% or more but less than I7 Vol%, preferably 2 to 13% by volume, so that lime powder is blown together with the low odor and black odor. It is a method of adding bulky lime from the inlet of a furnace like the furnace, and according to the present invention, steel from low carbon steel to high carbon steel can be stably dissolved with low loss of iron and manganese, and also have low oxygen content in molten steel. . Therefore, it is possible to efficiently recover manganese from manganese ore while reducing oxygen loss when adding alloy elements such as Al, Mn, and Si. Moreover, since the low odor oxygen flow rate is small, the low amount of hydrogen in steel is obtained without the balance with the conventional LD method. In addition, a slow reaction gas such as Ar, N ₂ CO ₂ or the like is mixed with low odor in a timely manner (the mixed gas is composed of 80 Vo 1% or less of oxygen and 20 Vol% or more of slow reactive gas) or by using alone for a short time. In addition, it is possible to reduce the hydrogen content in the steel or to make the ultra-low carbon solvent more easily, and to select nitrogen gas in the nitrogen-containing steel solvent and to have it from the blown gas at the same time. In the case of using a gas containing no nitrogen, it is possible to bring the salsoleven to 15 ppm or less. In addition, by agitation with low odor gas, it is possible to use a large piece of scrap or the like which has been limited in the conventional upsetting converter.

As described above, the present invention has the characteristics of being metallurgically and economically desirable, and since it does not require a small number of blow openings, it does not require the injection of lime powder, and thus the installation is simple. It is also easy to retrofit, and it is an invention to supply a steelmaking technology of high technical value that can increase the cost of maintenance of the refractory and the bottom refractory of the furnace, and at the same time can increase the efficient production capacity as clear in the present specification.

On the basis of the practice of the present invention, a structure as shown schematically in FIG. 1 in which three nozzles of a double pipe structure are also known in the bottom of a furnace of a top converter having a self-known oxygen lance for installation. 75 tons of converters were used.

In the drawing, reference numeral 1 denotes the main body of the furnace, 2 denotes the odor picking lance 3, the bottom of the furnace, 4 denotes a bath, 5 a slug, 6 a low odor gas, and 7 a low odor. During the refining of the double tube, pure oxygen is introduced, and a slow reactive gas for preventing closure is introduced at the time of chartering before the start of refining and at the end of the refining. (8) shows the appearance of the double pipe, and in the gap between (7) and (8), any of the oil mists obtained by atomizing oil or oil such as hydrocarbon gas or kerosene as neutral gas during refining, It flows as a coolant for prevention, and slow reactivity value flows at the time of charter loading and the termination of blow like the inner pipe. The pipe 10 is connected to the gas tank through a flow adjusting device such as oxygen, a slow reactive gas, and the like that flows into the inner pipe. The tube 9 is connected to the gas dunk via a cold working gas such as hydrocarbon gas and a slow reactive gas blade flow adjusting device.

Low odor nozzles supply oxygen, a mixture of oxygen and a slow reactive gas or a slow reaction gas to the inner tube, but for the purpose of suppressing slipping, reducing hydrogen content in the steel, and adding acid to the heavy nitrogen content. The gas flow rate of the inner pipe and the kind of gas were also changed according to the blowing process. As a general rule, propane gas was blown as a general rule, but when the mixed visibility with a slow reactive gas was used in the inner tube, a slow reactive gas was also replaced.

TABLE 1

The gas flow rate which selects the double pipe nozzle diameter and makes it flow into an inner pipe was changed in various ways.

When the molten iron is charged, it is about 10 tons of argon or nitrogen gas while flowing the minimum flow rate of argon or nitrogen gas necessary to prevent the nozzle from closing in the inner pipe (7) and the outer pipe (8) of the double pipe nozzle set at the bottom of the furnace. After 65 tons of molten iron was taken, the furnace was lowered to start picking up. Subsequently, the inner tube 7 of the low odor double-pipe nozzle was replaced with oxygen and the outer 8 with propane gas, and blown while controlling the height of the upper lance 2 in accordance with the low odor gas flow rate by the steel grade.

In the meantime, refining members, such as quicklime, iron ore, fluorescent ore, were added from the inlet of a furnace. If molten iron is high, the quicklime and fluorite are added to the first half of the blow to suppress the slipping in the middle of the blow mill, and the iron ore is the placenta after the decarburizing peak after the middle stage. It was preferable to add the amount. When the pick-up from the upper lance (2) is stopped at the end of the predetermined amount of pick-up, the inner and outer tubes of the low-odor double tube nozzle are replaced with argon or nitrogen gas, the furnace is tilted, and the temperature is measured by temperature sampling. The effect was confirmed.

In the first table,

In case of uptake lances from case defense 1 to lawsuit 12,

hard is L / L ₀ = 0.6 or more

midium is more than L / L ₀ = 0.4 or less than 0.6

soft L / L ₀ = 0.4 or less

Means.

Moreover, in the upsetting lance condition up to case number 13,

hard is L / L ₀ = 0.8

Means.

An application claiming priority will be described below, which is incorporated by reference herein in its entirety.

1) Japan Patent Application Lawyer 46162/79 (Application Date April 16, 1979)

2) // 100009/79 (filed August 6, 1979)

Claims (1)

In the converter steelmaking method, by supplying oxygen from the upper lance and gas at the lower odor nozzle simultaneously, the mixed gas of oxygen or oxygen and the georeactive gas is lowered at 2 Vo1. To 17 Vo1%, and the remaining oxygen is attached to the molten steel from the upper lance and refined.

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