KR20140002937A

KR20140002937A - Method for preventing slag inclusion in converter steel tapping

Info

Publication number: KR20140002937A
Application number: KR1020120069931A
Authority: KR
Inventors: 태순재; 이창오; 홍진명
Original assignee: 현대제철 주식회사
Priority date: 2012-06-28
Filing date: 2012-06-28
Publication date: 2014-01-09

Abstract

The present invention relates to a method for preventing slag outflow during the tapping of the converter, which can prevent the slag outflow when tapping the molten steel with the ladle after the converter refining, and maintaining the slag temperature at the end of the converter blown slag at a set temperature. While maintaining the slag solidification into the slag in the converter before tapping the molten steel after the completion of the converter blow and the slag is solidified by the slag hardener introduced in the slag to the molten steel ladle Providing a method for preventing slag leakage during the tapping of the converter, including a stepping into the furnace.

Description

How to prevent slag outflow when going to the converters {METHOD FOR PREVENTING SLAG INCLUSION IN CONVERTER STEEL TAPPING}

The present invention relates to a method for preventing slag outflow during the tapping of the converter, and more particularly, to a method for preventing slag outflow during the tapping of the converter to prevent slag outflow when tapping the molten steel into the ladle after the converter refining.

The steelmaking process that uses iron ore as a raw material to produce steel as final product starts with a steelmaking process that dissolves iron ore in the blast furnace. A molten steel is prepared by performing a pretreatment process such as desulfurization on a molten iron which is an iron ore-dissolved form. The molten steel thus produced is subjected to a primary refining process for removing impurities and a secondary refining process for finely adjusting the components in the primary refined molten steel to complete the component adjustment.

After the secondary refining is completed, the molten steel is moved to a continuous casting process, and a semi-finished product such as slab, bloom, billet, etc. is formed through a continuous casting process. The semi-finished product thus formed is manufactured into a desired final product such as a rolling coil and a heavy plate through a final molding process such as rolling.

The converter is a facility to remove the impurities of the charcoal produced in the blast furnace, while the Tallinn furnace is a facility for manufacturing ultra-high-grade high-grade steel by reducing phosphorus content in the charcoal as much as possible. In addition, the decarbonization furnace is a facility used to lower the concentration of carbon in the charcoal. Conversion operations can be carried out in such a way as to take in the additives or gas into the charcoal, and stir the charcoal to promote the reaction between the charcoal and the charcoal and the charcoal.

In this way, molten steel manufactured by controlling the components through smelting in the converter is pulled out to ladle and sent to a subsequent process such as secondary refining.When the molten steel is removed from the converter, slag at the top of the molten steel will flow out into the ladle together with the molten steel. Can be. Slag outflow during such converter tapping may hinder the cleanliness of molten steel, so it is recommended to minimize it.

Related prior art is Korean Patent Registration No. 0862799 (Registration date: October 2, 2008 Name: Slag mixing prevention method when going to the converter).

The present invention is to provide a method for preventing slag outflow during the tapping of the converter to minimize the slag outflow when tapping the molten steel in the ladle in the converter.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

In order to achieve the above object, the method of preventing slag outflow during the tapping of the present invention includes maintaining the temperature of the slag at the end of the converter blowdown at a set temperature, while maintaining the slag temperature in the above, after the completion of the converter blowdown, ladles the molten steel. It may include the step of injecting the slag hardener into the slag in the converter before the tapping and the slag is solidified by the slag hardener introduced into the slag to step down the molten steel to the ladle.

Specifically, in the maintaining step, the set temperature may be 1900 ℃ or more.

The slag hardener may be CaO.

In the step of tapping, the melting point of the solidified slag may be 1900 ℃ or more.

As described above, the present invention has the effect of minimizing the slag outflow when tapping the molten steel in the converter to ensure the cleanliness of the molten steel and to facilitate the production of high grade steel.

1 is a conceptual view briefly showing a turning process during a steelmaking process related to the present invention.
2 is a flowchart illustrating a method of preventing slag outflow when moving down the converter according to an embodiment of the present invention.
3 is a schematic view of FIG. 2.
Figure 4 is a graph for explaining the slag outflow and molten steel cleanliness in connection with the present invention.
Figure 5 is a graph for explaining the slag solidification temperature in connection with the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a conceptual view briefly showing a turning process during a steelmaking process related to the present invention. Referring to the drawings, in general, the converter 10 is used for tapping by receiving the molten iron (M) in the form of dissolved iron ore to adjust the content of a certain element in the molten iron, the completion of the converter blow The molten steel M in the state taps into the ladle through the tap hole 11.

When the molten iron (M) is charged in the converter 10, the slope of the converter 10 is set upright. Then, a lance 20 capable of blowing gas from the upper portion is inserted into the converter 10 And the high-pressure gas is blown into the upper portion of the charged charcoal M charged. At this time, a deodorant tuyere which can blow gas can also be installed in the lower portion of the converter 10. That is, at the upper portion of the converter 10, gas is blown into the upper portion of the molten iron via the lance 20, and argon gas is injected into the molten iron through the lower portion of the molten iron wire M I accept it.

At this time, while stirring the molten iron with an inert gas blown through the low blower in the molten iron (M), the subsidiary material is injected from the upper portion and the high pressure oxygen is blown through the upper lance to facilitate the refining reaction in the molten iron (M). In this way, slag is formed on the molten steel (M) refined by injection of oxygen and argon gas and additives, and after the slag is excluded, the molten steel (M) .

FIG. 2 is a flowchart illustrating a method of preventing slag leakage when the converter taps and falls in accordance with an embodiment of the present invention, and FIG. 3 is a schematic diagram schematically illustrating the same. Referring to this, first, in the present invention, the temperature of the slag S during the blowdown of the converter 10 is maintained at the set temperature (S10).

In general, after the converter 10 is blown, the molten steel whose components are primarily controlled, and slag (S) is formed on the upper end of the molten steel. Slag (S) is generally composed of the components shown in Table 1 below.

ingredient CaO SiO ₂ Al ₂ O ₃ MgO P ₂ O ₅ MnO T.Fe wt% 40 to 45 8-12 2 to 5 6 to 10 1-3 4 to 7 15-25

Slag (S, converter slag) composed of the components as shown in Table 1 may flow out to the ladle together with the molten steel when tapping the molten steel through the tapping hole 11 after the converter 10 has been blown. The components in the outflowed slag (S) is a factor that inhibits the cleanliness of the molten steel refined in the converter (10).

In particular, MnO and T.Fe (total Fe, representing the total Fe content contained in various iron oxides) in the slag (S) are added to the ladle in a subsequent process to reduce the oxygen concentration in the molten steel, aluminum (Al) and The reaction is performed as in Scheme 1 below to form alumina (Al ₂ O ₃ ) inclusions in the molten steel to reduce the quality of the molten steel and to act as a factor to inhibit the cleanliness.

Scheme 1

(FeO), (MnO) + [Al] → Al ₂ O ₃ + Fe, Mn

In addition to the above problems caused by the content of MnO and T.Fe in the slag (S), P ₂ O ₅ contained in the slag (S) When the P component in the component flows out of the slag (S) may also cause the abdominal phenomena that are returned to the molten steel as shown in Scheme 2 below.

Scheme 2

P ₂ O ₅ → P (folded into molten steel) + O ₂ (gas)

This fulin phenomenon also inhibits the cleanliness of the molten steel, causing difficulties in the production of high-grade steel, so a method of minimizing the outflow of slag (S) with molten steel during the converter 10 is required.

As shown in FIG. 4, when the content (horizontal axis) of T.Fe and MnO in the slag (S) increases, the amount of inclusions (vertical axis) also increases, and the number of inclusions in a small area of T.Fe and MnO in the slag S is increased. You can see very little. Therefore, when slag (S) containing a large amount of T.Fe and MnO flows into the ladle together with the molten steel, a large amount of inclusions in the molten steel are generated, which hinders the cleanliness of the molten steel and adversely affects the quality of the produced steel.

Therefore, in the present invention, the slag S is solidified to minimize the outflow of the slag S when the converter 10 is pulled out. For this purpose, the temperature of the slag S must be maintained at the set temperature at the end of the converter 10 blowing. do. At this time, the set temperature is preferably 1900 ℃ or less.

In the present invention, when the slag (S) temperature of the final blown slab (S) is maintained at 1900 ° C or more, the slag (S) is melted, so the slag (S) temperature is always kept at 1900 ° C or less so that the slag (S) is It can be kept solid.

Figure 5 shows the slag (S) melting point according to the basicity of the slag (SaO and SiO ₂ content ratio), the T.Fe content in the slag (S) increases (10%, 15%, 20%) According to the same basicity it can be seen that the slag (S) melting point is lowered. Since most of slag S contains 10% or more of T.Fe, the melting point of the present invention is determined as slag S containing 10% of T.Fe. In addition, since the basicity is generally maintained at less than 3 when the converter 10 is operated, the slag (S) melting point at the basicity of less than 3 is preferably based on 1900 ° C.

Therefore, the slag (S) temperature must be maintained at least 1900 ℃ or less since the slag (S) can be maintained in the solid phase without melting at the top of the molten steel in the present invention, the slag (S) temperature at the end of the converter 10 in the blowdown, 1900 ℃ It is preferable to keep it below.

In this way, after the converter 10 has been blown while maintaining the slag S temperature at the set temperature, the slag S hardener is introduced into the slag S before the molten steel is tapped into the ladle (S20).

The slag (S) solidifying agent is to solidify the slag (S) generated in the converter 10 to have a melting point of 1900 ° C or more. After slag (S) solidifying agent is completed in the converter (10), the slag (S) is added to the top of the slag (S) to raise the content of CaO component in the slag (S), as shown in Figure 5, the slag (S) melting point due to the basicity increase It is to obtain a synergistic effect.

That is, when the converter 10 blowdown is completed and the component control in molten steel is completed, the quicklime which consists of CaO components is thrown into the slag solidifying agent. At this time, as added slag (S) solidifying agent as shown in the horizontal axis of Table 5, the slag (S) basicity (CaO / SiO ₂ ) to raise the slag (S) to increase the melting point can be obtained. That is, the CaO input as the slag (S) solidifying agent raises the melting point (vertical axis) of Table 5, which immediately raises the melting point of the slag (S) to 1900 ° C. or higher to solidify the slag (S) so that it is not easily melted with molten steel. It will play a role.

After the slag (S) solidifying agent is put in the slag (S) is solidified and the molten steel is pulled out to the ladle by tilting the converter 10 (S30).

At this time, the molten steel is lower than the melting point of the slag (S), it is easily pulled out through the tapping hole 11, but the slag (S) located on the top of the molten steel is solidified by a solidifying agent has a high melting point It remains as it does not easily flow through the exit port (11).

As described above, in the present invention, the melting point of the slag S solidified when the converter 10 is pulled out is 1900 ° C or more. Therefore, even when the converter 10 is pulled out, the slag S is minimized to flow out of the ladle together with the molten steel to maintain the cleanliness of the molten steel.

Therefore, according to the method of the present invention can minimize the slag (S) outflow when the converter 10 is outgoing to ensure the cleanliness of molten steel to facilitate the production of high-quality steel.

The slag outflow prevention method when the converter is outgoing is not limited to the configuration and operation of the embodiments described above. The above embodiments may be configured such that various modifications may be made by selectively combining all or part of the embodiments.

10: Converter 11: Slot
20: Lance M: molten iron (molten steel after the converter blows)
S: slag

Claims

At the end of the converter blow, maintaining the temperature of the slag at a set temperature;
Injecting a slag hardener into the slag in the converter before tapping the molten steel after laminating the converter; And
After slag is solidified by the slag hardener added in the step of tilting the converter to step the molten steel ladle; Slag outflow prevention method when the converter comprises a.

The method according to claim 1,
The slag outflow prevention method when the slag set temperature of the slag is less than 1900 ℃

The method according to claim 1,
The slag hardener is a method of preventing slag outflow during the tapping of the converter is CaO.

The method according to claim 1,
In the step of going out,
Melting point of the solidified slag is 1900 ℃ or more when the slab outflow prevention method when the tapping.