KR20050005622A - Refining method for reducing silicon in a ladle furnace process of electric furnace - Google Patents

Abstract

PURPOSE: To provide a refining method for reducing silicon in the ladle furnace process of an electric furnace, wherein refining operation is performed in the state that concentration of SiO2 in slag is reduced to improve quality of steel, and utilization rate of calcium oxide is increased to contribute to cost reduction. CONSTITUTION: The refining method is characterized in that refining operation is performed by discharging slag from molten steel with excessive slag mixing amount and molten steel with high silicon£Si|pick-up during refining treatment in order to prevent disqualification of components due to silicon£Si|pick-up in a mini mill refining operation, thereby controlling thickness of slag in a ladle to less than 80 mm and controlling an amount of SiO2 in slag to 9 to 12%, wherein the refining method comprises the steps of injecting calcium oxide into the slag discharged molten steel in an injection quantity of 500 to 800 kg, and controlling a molten steel stirring flow rate to 10 to 30 Nm¬3/hr during refining treatment operation for stabilization of silicon£Si|component, thereby lowering activity of SiO2 in slag.

Description

Refining method for reducing silicon in a ladle furnace process of electric furnace}

The present invention relates to an operation method for reducing double silicon [Si] during the molten steel component refining process of a ladle furnace (LF) facility, and more particularly, to manufacturing molten steel in an electric furnace of a mini mill steel mill. In order to prevent component separation caused by silicon [Si] pick-up during the refining work to make clean steel in LF facility, silicon dioxide in slag is excluded by excluding slag during LF treatment. The present invention relates to an electric furnace refining method that can reduce the amount of composite silicon [Si] by controlling the gas flow rate during LF treatment after adding quicklime (CaO) to reduce the amount of SiO ₂ ) and to reduce the concentration of SiO _{2 in} the slag. .

In general, the conventional silicon ablation operation uses a method of reducing SiO ₂ concentration in slag in molten steel withdrawn from an electric furnace and a method of lowering SiO ₂ activity in slag, that is, a large amount of quicklime is added during refining. Is done.

Among them, the method used in the refining operation is to inject a large amount of quicklime. This method increases the amount of quicklime input according to the amount of SiO ₂ present in the slag contained in the molten steel when the molten irons left in the electric furnace arrive at the LF. In the molten steel with excessive slag incorporation, it is difficult to reduce abdominal silicon [Si] due to quick lime injection alone, resulting in a silicon [Si] component separation, and hardening of excessively added quick lime in the ladle 1 as shown in FIG. Due to the phenomenon (solidification), the molten steel can harden and calcium wire, which is introduced to separate and injure alumina inclusions and other oxide inclusions, cannot be added. Therefore, as shown in FIG. 1, nitrogen or argon is injected into the porus plug 3 located at the bottom of the ladle, and strong bubbling is performed to fracture the solid hot water surface and to arc the three-phase electrode rod 2 on the upper ladle. By generating the arc and re-heating by the arc heat, the amount of power is increased and the product is produced out of order due to the deterioration in quality due to the silicon [Si] component separation.

Therefore, the present invention has been made to solve the above problems, the present invention is to reduce the concentration of SiO _{2 in} the slag during the refining operation to perform the refining operation to maintain the stable components of the steel to improve the quality of the steel In addition, the purpose of the present invention is to provide an electric furnace refining method for reducing silicon during ladle refining, which can contribute to cost reduction by increasing the utilization rate of quicklime.

1 is a pattern of operation during ladle refining according to the prior art

2 is an electric furnace refining pattern diagram for silicon reduction during ladle refining according to an embodiment of the present invention

3 is a graph showing the performance of the transition silicon according to the SiO ₂ composition ratio in the refining slag in the embodiment according to the present invention

Figure 4 is a graph showing the performance of the silicon change in accordance with the stirring flow rate in the embodiment of the present invention

<Explanation of symbols for the main parts of the drawings>

1: Ladle 2: 3 phase electrode

3: forrus plug 4: slag port

In order to achieve the above object, the present invention provides molten steel with excessive slag mixing and silicon [Si] rising molten steel to remove the slag during LF treatment in order to prevent component separation caused by the rise of silicon [Si] during refining operation. Is controlled to within 80mm and the amount of SiO _{2 in} slag is reduced to less than 9 ~ 12% of SiO _{2 in} slag, the amount of quicklime is set to 500 ~ 800kg, and the stirring flow rate of molten steel during the refining process is stabilized to stabilize silicon [Si]. It provides an electric furnace refining method for reducing the silicon during ladle refining, characterized by reducing the concentration of SiO ₂ in the slag to 10 ~ 30Nm 3 / hr to perform the refining operation.

Hereinafter, the present invention will be described in detail.

FIG. 2 is a reference diagram illustrating a silicon reduction operation pattern in molten steel manufacturing using an electric furnace according to the present invention, in which deoxidizer and a solvent are added to molten steel ladles 1 pulled out of the electric furnace to perform SiO in slag. _{When 2} is excessively contained and a silicon component gap is expected due to the increase in silicon [Si], slag is removed from the slag pot 4 during the refining process to prevent the silicon component gap. The amount of SiO ₂ inside is reduced to within 9-12%. At this time, by excluding SiO ₂ amount reduced by the molten steel within the silicon dioxide, a small amount, that is, _{SiO 2 (%) = (W} SiO 2 (SiO 2) / CaO + LF input arrives the slag amount present in the slag) is reduced. As the slag in the ladle is managed within 80 mm, the amount of SiO ₂ in the slag is reduced, and in order to prevent double silicon ([Si] synergism) during the refining process, the lime is added to reduce the SiO ₂ concentration in the slag and the gas flow rate during the treatment. It is possible to significantly reduce the SiO ₂ activity by controlling the effect of preventing silicon component separation.

On the other hand, and by tapping the molten steel from the electric furnace, the slag amount in the molten steel reached the LF equipment is about 1.5 ton (Ton) in a typical operating method, SiO ₂ content of 8 to 14%, so the slag thickness that is managed by the minimil refining operation is about 80 It is about mm. If the slag amount is 1.5 tons, the amount of SiO ₂ present in the slag is estimated to be about 10%. The amount of SiO ₂ is 150 kg. When 500 kg of quicklime is added, the SiO ₂ (%) in 1.5 tons of slag is 150 kg / 2.0 ton = about 7.5%. According to the above-mentioned formula, i.e., the amount of slag is increased according to the amount of slag according to SiO ₂ (%) {= amount of SiO ₂ / CaO present in slag + amount of slag of LF deposited steel} to maintain the stability of silicon [Si] component. Can be.

As described, the synergy reaction of silicon according to the amount of SiO ₂ present in the slag is based on the following reaction.

[Al] +3/4 (SiO ₂ ) → 1/2 (Al ₂ O ₃ ) +3/4 [Si] 4 [Al] +3 (SiO ₂ ) → 2 (Al ₂ O ₃ ) +3 [Si ]

EXAMPLE

Referring to the embodiment of the present invention configured as described above are as follows.

The operation was carried out by applying the present invention in an electric furnace LF process. If the slag contains an excessively high SiO ₂ ratio of 15% or more, the amount of SiO ₂ in the slag is 9 to 9 in order to perform the step of reducing silicon [Si] and to perform the step of preventing silicon according to the present invention. The slag composition in Table 1 and the slag composition in Table 1 and the SiO _{2 in} the refined slag in FIG. 3 were compared by comparing the composition of CaO, Al ₂ O ₃ , and SiO ₂ in the slag at the initial stage of the refining process. The performance [Si] transition (unit:%) graph according to the composition ratio and the performance [Si] transition graph according to the stirring flow rate of FIG. 4 are shown, and each data is the average performance of three times.

division (CaO) (Al ₂ O ₃ ) (SiO ₂ ) The present invention Conventional method The present invention Conventional method The present invention Conventional method Case 1 32.93 19.66 4.78 6.08 11.01 18.67 Case 2 31.27 22.37 2.5 5.76 8.43 16.58 Case 3 30.13 20.05 2.81 6.1 9.32 17.28

According to the above present invention, SiO ₂ activity in reducing the SiO ₂ content of the slag 8 to 11% and after the polishing process during work calcium oxide added to keep the molten steel flow stirred 10 ~ 30N㎥ / hr and subjected to operation result slag (Slag) It is possible to significantly lower the degree to maintain the stability of the silicon [Si] component, and to obtain the effect of preventing the double silicon ([Si] synergism).

Claims (2)

In order to prevent component dislocation due to the rise of silicon [Si] in mini mill refining operation, molten steel with excessive amount of slag and silicon [Si] rising molten steel eliminates slag during refining process, and manages slag within ladle within 80mm and SiO within slag _An electric furnace refining method for reducing silicon during ladle refining, characterized in that the amount of refining is less than 9 to 12%. The method of claim 1, In the slag-excluded molten steel, the amount of quicklime is set to 500 to 800 kg, and the stirring rate of molten steel is 10 to 30 Nm3 / hr during the refining treatment to stabilize the silicon [Si] component, thereby lowering SiO ₂ activity in the slag. Furnace refining method for reducing the silicon during ladle refining.