KR101458202B1 - Method of providing tundish flux for steel making operation using electric furnace - Google Patents

Abstract

The present invention relates to a method for introducing a tundish flux during an electric furnace steelmaking operation which can increase the effect of removing inclusions in steel. In the method of feeding a tundish flux during an electric furnace steelmaking operation according to an embodiment of the present invention, a first step of introducing a tundish flux into a molten steel of a tundish in a first performance in which a performance process is started; And a step of adding a tundish flux to the molten steel of the tundish at the n-th performance during the performance process.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing a tundish flux,

The present invention relates to a method for introducing a tundish flux during an electric furnace steelmaking operation, and more particularly, to a tundish flux input method during an electric furnace steelmaking operation which can increase the effect of removing inclusions in a steel.

The steelmaking process employs a continuous casting process to continuously make semi-finished products using molten steel. In the continuous casting process, when the molten steel in the ladle is injected into the tundish, the productivity is improved through the continuous casting method in which the new ladle is moved to the injection position to continuously inject the ladle.

In general, aluminum deoxidized steel or silicon deoxidized steel, which is produced using a blast furnace and requires high cleanliness, should strictly control not only the components of molten steel but also nonmetallic inclusions in the steel during the steelmaking process. Since the role of the tundish in the continuous casting process, which is a subsequent step of the steelmaking process, is important in order to control the cleanliness of the produced steel, the tundish flux is supplied to secure the refining ability of the molten steel in the tundish have.

The tundish fluxes are classified into CaO-Al ₂ O ₃ fluxes and CaO-SiO ₂ fluxes depending on the type of inclusions. The CaO-Al ₂ O ₃ fluxes control the alumina inclusions And CaO-SiO ₂ fluxes are mainly used to control silica inclusions, which is a problem in the operation of silicon deoxidization steel.

On the other hand, in consideration of the tundish flow, a small amount of tundish flux was injected into the hot water portion at the beginning of the continuous casting process. However, since the amount of slag flowing into the tundish increases as the number of tandem performances increases, there is a problem that the increased slag is mixed with the introduced tundish flux to reduce the effect of removing inclusions.

In recent years, low-carbon steels used as shaped steel have also been required to have a high degree of cleanliness due to the increasingly complicated and diverse demands of customers. Accordingly, tundish flux has been used for cleanliness control only in high-clean steel produced by using blast furnace. In recent years, however, cleanliness control is required also in normal steel (low carbon steel) production using electric furnace. For this purpose, CaO-Al ₂ O ₃ -based fluxes for controlling alumina inclusions are mainly used, but since silica inclusions are also a problem in recent years, it is also necessary to use CaO-SiO ₂ fluxes for controlling them.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a method for adding a tundish flux during operation of an electric furnace to increase the effect of removing inclusions in steel.

According to an aspect of the present invention, there is provided a tundish according to an embodiment of the present invention includes: a first step of inputting a tundish flux into molten steel of a tundish in a first performance in which a performance process is started; And adding the tundish flux to the molten steel of the tundish at the n-th performance during the performance process, thereby providing a tundish flux input method during the electric furnace steelmaking operation.

In an embodiment of the present invention, the amount of the tundish flux injected in the first step of introducing the tundish flux may be 0.25 to 0.5% of the amount of the tundish in the tundish.

In one embodiment of the present invention, the tundish flux may be introduced at a time when 10 to 20% of the molten steel is filled in the tundish.

In one embodiment of the present invention, the tundish flux may be introduced into the entire tundish in the tundish in the first step of introducing the tundish flux.

In one embodiment of the present invention, the n-th performance may be when the thickness of the slag generated in the tundish is 15 to 25 mm.

In one embodiment of the present invention, in the n-th performance, the tundish flux may be injected into the molten steel in the tundish.

In one embodiment of the present invention, the amount of the tundish flux injected in the step of adding the tundish flux may be the same as the amount of the tundish flux injected in the step of firstly introducing the tundish flux.

In one embodiment of the present invention, the tundish flux comprises 48.5 to 50.5% of SiO ₂ , 43.7 to 45.7% of CaO, 0.4 to 2.4% of MgO, and 1.8 to 3.8% of Al ₂ O ₃ , . ≪ / RTI >

According to an embodiment of the present invention, a silica-based inclusion can be controlled by injecting a CaO-SiO ₂ flux in an electric furnace low-carbon steel production.

According to an embodiment of the present invention, a tundish flux is firstly input to a first performance, which is an initial stage of a performance process, and an n-th performance is performed when the effect of the tundish flux is drastically reduced due to a large slag layer generated in the tundish The effect can be improved and sustained by adding tundish flux to the tundish.

In addition, according to an embodiment of the present invention, the tundish flux is further added at the time of n-th performance, so that even if the number of performances is increased, the slag basicity can be increased to increase the SiO ₂ absorption rate in the slag. Further, the MnO and FeO concentrations in the slag can be kept low, so that the effect of preventing the molten steel from being reoxidized can be enhanced, and the total oxygen concentration in the molten steel can be reduced, thereby improving the cleanliness of the molten steel. As a result, the manufacturing cost of the product can be reduced by eliminating the cause of the intervening material defects, which is a problem in the subsequent rolling process.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a flowchart illustrating a method of introducing a tundish flux during an electric furnace steelmaking operation according to an embodiment of the present invention.
2 is a process diagram showing a process according to a method of applying a tundish flux during an electric furnace steelmaking operation according to an embodiment of the present invention.
3 is a graph showing changes in slag basicity in a method of introducing a tundish flux during an electric furnace steelmaking operation and a comparative example according to an embodiment of the present invention.
FIG. 4 is a graph showing changes in the absorption capacity of oxidative inclusions in slag in the tundish flux injection method and the comparative example during the electric furnace steelmaking operation according to the embodiment of the present invention.
5 and 6 are graphs showing changes in oxidation degree of the tundish flux injection method and the comparative example during the electric furnace steelmaking operation according to the embodiment of the present invention.
FIG. 7 is a graph showing changes in the total oxygen amount in the molten steel of the tundish flux injection method and the comparative example during the electric furnace steelmaking operation according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flowchart illustrating a method for inputting a tundish flux during an electric furnace steelmaking operation according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating a method for inputting a tundish flux during an electric furnace steelmaking operation according to an embodiment of the present invention. Fig.

As shown in FIG. 1 and FIG. 2 (a), the method of feeding a tundish flux during the electric furnace steelmaking operation according to an embodiment of the present invention includes turning the tundish into molten steel in the first performance, And a step S10 of charging the dish flux first.

Here, the steelmaking operation of the present invention may be an electric furnace ordinary steel (low carbon steel) operation.

The tundish flux may be introduced at a time when 10 to 20% of molten steel in the first performance is filled in the tundish 200.

In the first performance, the tundish flux may be introduced into the entire surface of the molten bath in the tundish 200, and the amount of the tundish flux may be 0.25 to 0.5% of the amount of molten steel in the tundish 200.

Tundish flux input may be in the CaO-SiO ₂ based flux for the silica-based inclusions control, in _{weight%, SiO 2: 48.5 ~ 50.5} %, CaO: 43.7 ~ 45.7%, MgO: 0.4 ~ 2.4% , and Al ₂ O ₃ : 1.8 to 3.8%.

As shown in Figs. 1 and 2 (b), in the n-th performance during the performance process, a step S20 of adding a tundish flux to the molten steel of the tundish 200 may be performed. Here, the n-th performance may be a process of supplying n-th ladle's molten steel to the tundish 200.

The n-th performance may be when the thickness of the slag produced in the tundish 200 during continuous casting is 15-25 mm. That is, the tundish flux can be further added to the n-th performance in which the thickness of the slag generated in the tundish 200 during continuous casting is 15 to 25 mm.

The n-th performance may be present more than once during the continuous casting. That is, when the thickness of the slag produced in the tundish 200 during continuous casting is 15 to 25 mm, it may be n-th performance. Therefore, the n-th performance may occur several times as the number of annual performances increases.

In the n-th performance, the tundish flux may be introduced into the molten steel in the tundish, and the tundish flux input in the n-th performance may be the same as the tundish flux input in the first performance. In other words, the tundish flux injected in the n-th performance may be a CaO-SiO ₂ flux for controlling silica-based inclusions, and contains 48.5 to 50.5% of SiO ₂ , 43.7 to 45.7% of CaO, 0.4 to 45.7% of MgO To 2.4% and Al ₂ O ₃ : 1.8 to 3.8%. Also, the amount of tundish flux input in the n-th performance may be equal to the amount of tundish flux input in the first performance.

In the present invention, the effect of removing inclusions in the steel can be increased by first introducing the tundish flux in the first performance and further adding the tundish flux to the molten steel of the tundish in the n-th performance.

[Example]

Hereinafter, an embodiment of the present invention will be described in order to verify the effect of removing the inclusions in the steel according to the tundish flux input method during the electric furnace steelmaking operation.

FIG. 3 is a graph showing changes in slag basicity in a method of introducing a tundish flux into a furnace during an electric furnace making operation according to an embodiment of the present invention, and FIG. 4 is a graph showing changes in slag basicity of a tundish during a steel making operation in accordance with an embodiment of the present invention. FIG. 5 and FIG. 6 are graphs showing changes in oxidation degree of the tundish flux during the electric furnace steelmaking operation according to one embodiment of the present invention and the graphs showing changes in oxidation degree in the comparative example. And FIG. 7 is a graph showing changes in the total oxygen amount in the molten steel in the method of introducing the tundish flux during the electric furnace steelmaking operation according to an embodiment of the present invention and the comparative example.

First, in order to verify the effect of removing the inclusions in the steel according to the method of introducing the tundish flux, the tundish flux was not used (Comparative Example 1), and the tundish flux was applied only once for the first time without addition of the tundish flux (Comparative Example 2).

division Tundish flux input (times) When to put tundish flux Location of Tundish Flux Comparative Example 1 0 - - Comparative Example 2 One 1st performance Main hot water center Example 2 1st performance, 1st performance 1st performance: All of the melting pot
N-th performance: natamu center

Table 1 shows the operating conditions of Comparative Example 1, Comparative Example 2 and this embodiment.

Comparative Example 2 was carried out under conditions as close as possible to the conventional running method. That is, the tundish flux was applied to the tundish at the first performance, which is the starting point of the performance process. Generally, the first performance is a time when there is little slag in the tundish, and the tundish flux applied to the tundish is put into the main tumb section considering the flow of the tundish. When the tundish is replaced .

In the comparative examples 1 and 2 and the present embodiment, tundishes under the same conditions were used and were performed at the same performance intervals. In addition, the tundish fluxes used in Comparative Example 2 and the present Example were the same CaO-SiO ₂ flux, and the tundish flux amounts charged per cycle were the same.

The components of the tundish flux injected into the tundish in the comparative example 2 and the present embodiment are shown in Table 2.

ingredient SiO ₂ CaO MgO Al ₂ O ₃ weight% 48.5 to 50.5 43.7 to 45.7 0.4 to 2.4 1.8 to 3.8

In this embodiment, the tundish flux is introduced at the time when the tundish is filled with about 15% of the molten steel in the first performance, that is, the first performance, which is the starting point of the performance process. Here, the amount of water contained in the ladle was 140 tons, and 15% of the amount of ladle water was 21 tons.

At this time, 70kg of tundish flux was injected, which corresponds to 0.33% of 21ton of tundish. In addition, the tundish flux was evenly distributed throughout the bath surface.

That is, unlike the ordinary operation method (Comparative Example 2), in this embodiment, at the time when the molten steel of about 15% of the amount of molten steel stored in the tundish is filled in the first performance, the tundish flux is supplied to the molten- And evenly throughout.

Meanwhile, in the embodiment of the present invention, when the thickness of the slag generated in the tundish was 15 to 25 mm, the tundish was added during the fourth performance. Generally, as the number of annual performances increases, the amount of slag introduced during the process of injecting molten steel into the tundish from the ladle of the previous process increases, and this mixes with the tundish flux to form a new slag composition. Will continue to decrease. Therefore, the slag basicity is reduced and the inclusion absorption ability is lowered. This phenomenon occurred at the time of the fourth performance in the embodiment of the present invention, at which point the slag of 15 to 25 mm thickness was formed in the tundish. In this embodiment, at this time, that is, at the time of the fourth performance, the same flux as that at the time of the first input is added secondarily in the same amount as that at the first input, centering on the molten steel portion.

As a result, as shown in FIG. 3, in the embodiment of the present invention, a high slag basicity was shown from the beginning of the performance, and the slag basicity was maintained almost constant even after the fourth performance. On the other hand, in Comparative Example 1 in which no tundish flux is applied, the lowest basicity is shown in the first performance, and the basicity is gradually increased as the number of years of performance is increased. However, the basicity is lower than the basicity according to the embodiment of the present invention. In Comparative Example 2 in which the tundish flux was applied only during the first performance, the slag basicity increased to 3, but decreased significantly after 3.

If the basicity of the slag is high, the fluidity of the slag can be increased, and the absorption ability of the SiO ₂ -based oxidative inclusions in the slag can be improved. Thus, as shown in Figure 3, when through the operating process according to the present embodiment can increase than the slag basicity in the conventional operation process, in particular a SiO ₂ based absorption capacity of the oxidation-resistant inclusions because it can continue to increase during open play It is possible to increase the refining effect.

These effects are well shown in FIG. That is, as shown in FIG. 4, the change of the SiO ₂ -based oxidative inclusions in the slag was observed. In Comparative Example 1, the concentration of SiO _{2 in} the slag continuously decreased after the first performance. That is, in the case of Comparative Example 1, the absorption ability of the SiO ₂ -based oxidative inclusions after the first performance is continuously decreased. Also in Comparative Example 2, the concentration of SiO _{2 in} the slag decreased after the first performance, indicating that the absorption ability of the SiO ₂ -based oxidative inclusion was decreased.

On the other hand, in this example, the change in the concentration of SiO ₂ in the slag was small throughout the entire performance after the first performance. That is, it can be seen that the absorbing ability of the SiO ₂ -based oxidative inclusions is stably and continuously maintained after the first performance, especially after the fourth performance in this embodiment. As a result, in the embodiment of the present invention, it is understood that the slag basicity is increased from the beginning of the performance and maintained during the continuous performance, thereby increasing the fluidity of the slag and increasing the SiO ₂ absorption rate in the slag. In the case of the comparative example 2, the tundish flux input effect continues only from the beginning of the performance until the fourth performance (that is, the time when the slag having a thickness of 15 to 25 mm is generated in the tundish). On the other hand, The effect can continue to be continued.

As described above, according to the present embodiment, the initial slag can be stabilized and the effect can be continued throughout the performance.

As shown in FIG. 5, when the MnO concentration in the slag was changed, in Comparative Example 1, the MnO concentration was high during the performance from the beginning of the performance. In the case of Comparative Example 2, the MnO concentration was increased as the number of performances increased. In particular, MnO concentration was continuously increased during the fifth performance after the fourth performance. On the other hand, in the case of this embodiment, the low MnO concentration in the initial performances is maintained despite the increase in the number of performances.

Further, as shown in FIG. 6, even in the case of the FeO concentration change in the slag, in the case of Comparative Example 1, a high FeO concentration is exhibited throughout the year from the beginning of the performance. In the case of Comparative Example 2, a high FeO concentration is exhibited in the fourth performance. On the other hand, in the case of the present embodiment, the FeO concentration is kept low despite the increase in the number of performances.

In addition, as shown in FIG. 7, the concentration of total oxygen (T. [O]) in the molten steel was the lowest in the examples of the present invention, and the total oxygen concentration in such low molten steel was maintained constant .

As described above, according to the present embodiment, the MnO and FeO concentrations in the slag can be kept low even when the number of performances is increased, so that the effect of preventing the reoxidation of the molten steel can be enhanced and the total oxygen concentration in the molten steel can be reduced, have. Therefore, it is possible to reduce the manufacturing cost of the product by eliminating the cause of the intervening material defects which are a problem in the subsequent rolling process.

Meanwhile, in the present invention, the number of performances was set to 9, and the tundish flux was further added in the fourth performance where the thickness of the slag generated in the tundish was 15 to 25 mm. However, in the case of a process in which the number of performances is further increased, the n-th performance in which the thickness of the slag generated in the tundish is 15 to 25 mm may occur more than once, and at this time additionally of the tundish flux, .

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

101: Ladle
200: Tundish

Claims (8)

In a first performance in which a performance process is started, the ladle molten steel is filled in the tundish, and the tundish flux is firstly introduced into the molten steel in the tundish; And
Further comprising the step of adding the tundish flux to the molten steel of the tundish during performance when the thickness of the slag generated in the tundish is 15 to 25 mm during the performance process after the first performance How to put tundish flux during operation. The method according to claim 1,
Wherein the amount of the tundish flux injected in the first step of introducing the tundish flux is 0.25 to 0.5% of the amount of the tundish in the tundish. The method according to claim 1,
Wherein the tundish flux is introduced into the tundish at a time when 10 to 20% of the molten steel is filled in the tundish during the first feeding of the tundish flux, How to put tundish flux. The method according to claim 1,
Wherein the tundish flux is introduced into the entire tundish in the tundish during the first tundish flux injection step. delete The method according to claim 1,
Wherein the tundish flux is introduced into the molten steel in the tundish in the step of additionally adding the tundish flux to the tundish. The method according to claim 1,
Wherein the amount of the tundish flux injected in the step of adding the tundish flux is the same as the amount of the tundish flux injected in the step of firstly inputting the tundish flux. The method according to claim 1,
Wherein the tundish flux is composed of 48.5 to 50.5% of SiO ₂ , 43.7 to 45.7% of CaO, 0.4 to 2.4% of MgO, and 1.8 to 3.8% of Al ₂ O ₃ , How to put tundish flux during operation.

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