WO2020096308A1 - Refining agent and method for refining molten steel using same - Google Patents

Abstract

An embodiment of the present invention relates to a refining agent which removes at least phosphorus (P) in impurities contained in molten steel and includes slag powder from which Ca2SiO4 is precipitated, wherein the slag powder is generated during the steel making process. Therefore, the refining agent according to an embodiment of the present invention can reduce the cost for preparation thereof and thus enables a refining operation at a low cost. In addition, the present invention can reduce the cost required for landfill of slag powder as the slag powder is recycled as a refining agent. Further, the refining agent according to embodiments enables the formation of slag having improved solubility of P and thus can enhance the dephosphorization efficiency thereof.

Description

Refining agent and method for refining molten iron using the same

The present invention relates to a refining agent and a molten iron refining method using the same, and more particularly, to a refining agent capable of removing P (phosphorus) from the molten iron and a refining method using the same.

Among the various slags generated during the steelmaking process, some of them are differentiated into a fine particle form or a powder state in the cooling process.

As a more specific example, after performing deoxidation and desulfurization to remove oxygen and S (sulfur) from molten iron using Si and CaO in an AOD (Argon Oxygen Decarburization) refining furnace, cooling the resulting slag to room temperature, cooling In the process, the slag is differentiated as a fine particle form or powder, not a lump form.

Since the eruption slag exists in a powder state, when handling, it causes environmental problems such as being blown around the work area or workshop. Accordingly, the granulated slag is entirely buried or used as a raw material for cement.

However, in order to embed the differentiated slag, the cost for landfill is not only additionally incurred, but as environmental regulations are strengthened, it is necessary to separate and treat the eruption slag to suppress environmental pollution. There is an additional problem.

(Advanced technical literature)

Japanese registered patent JP4546661

The present invention relates to a refining agent prepared by recycling slag generated during the steelmaking process and a method for refining molten iron using the same.

The present invention relates to a refining agent capable of forming slag having high solubility of P (phosphorus), a low melting point, and a method of refining molten iron using the same.

The present invention is a refining agent that removes at least P (phosphorus) among impurities contained in the molten iron, is a differentiated slag generated in a steelmaking process, and includes a differentiated slag in which Ca ₂ SiO ₄ is precipitated.

The differentiation slag includes CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ .

Among the differentiation slag, CaO is 49 wt% to 62 wt%, SiO ₂ is 22 wt% to 38 wt%, MgO is 20 wt% or less, Al ₂ O ₃ is 10 wt% or less, CaF ₂ is 3 wt% to 10 wt%, S is 0.3 wt % Or more, 1 wt% or less, FeO 5 wt% or less, and Cr ₂ O ₃ 5 wt% or less.

In addition to the differentiation slag, additional CaO is further included.

It is preferable that the mass ratio (additional CaO mass / differentiated slag mass) of the said additional CaO and differentiation slag is 1.0 or more and 2.6 or less.

The mass ratio of the additional CaO and the differentiated slag (additional CaO mass / differentiated slag mass) is adjusted to more than 2.1 and 2.6 or less, and among impurities contained in the molten iron, S (sulfur) is removed together with P (phosphorus).

The differentiation slag includes slag generated and cooled in the process of refining molten iron using Si and CaO.

Method for refining a molten iron according to an embodiment of the present invention includes a process of supplying oxygen to the molten iron; It includes; a dephosphorization process to remove P (phosphorus) in the molten iron by introducing a differentiation slag precipitated Ca ₂ SiO ₄ as the molten iron.

The differentiation slag includes CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ .

When the P content in the molten iron is 300 ppm or more, a process of adding additional CaO to the molten iron includes.

When the P content in the molten iron is 300 ppm or more and less than 600 ppm, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiating slag injected into the molten iron is added to be 1.0 or more and less than 1.5, and the P content in the molten iron When it is 600 ppm or more and less than 1000 ppm, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiating slag injected into the molten iron is added to be 1.5 or more and less than 2.2, and the P content in the molten iron is 1000 ppm or more and 1500 ppm In the case below, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiating slag inputted to the molten iron is 2.2 or more and 2.6 or less.

Comprising the step of put the CaF ₂ into the molten iron, and CaF ₂ input is input to the hot metal is added to 15% of the added CaO amount is added to the molten iron.

In the dephosphorization process, the desulfurization to remove S (sulfur) in the molten iron is performed together, and in the dephosphorization and desulfurization together, the mass ratio of the additional CaO and differentiation slag (additional CaO mass / differentiated slag mass) is Do not exceed 2.1.

And calculating the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and differentiation slag for the defluxing, and calculating the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and differentiation slag for the defluxing. In doing so, it is calculated by applying the amount (wt%) of S (sulfur) to be removed to the amount of dehydration of the following formula.

[Equation]

In the dephosphorization process, in carrying out desulfurization to remove S (sulfur) in the molten iron, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and differentiation slag according to the content of P in the molten iron, and the desulfurization Of the additional CaO and the differentiation slag mass ratio (additional CaO mass / differentiation slag mass), the additional CaO and the differentiation slag are introduced so as to have a relatively large mass ratio.

The refining agent according to the embodiments of the present invention can reduce the cost for providing the refining agent by recycling the eruption slag generated during the steelmaking process, thereby enabling low-cost refining operation. And, by recycling the eruption slag as a refining agent, it is possible to reduce the cost of landfilling the eruption slag.

Further, according to the refining agent according to the embodiments, it is possible to form a slag with improved solubility of P, and there is an effect of improving the dephosphorization efficiency.

1 is a conceptual view showing a refiner according to embodiments of the present invention and molten iron to which they are applied

Figure 2 is a graph showing the amount of dephosphorization (ppm) according to the mass ratio of CaO and differentiation slag (CaO / differentiated slag mass ratio)

3 is a graph comparing the input amount of CaF ₂ when using the refiner according to the embodiment and the refiner according to the comparative example

Figure 4 is a graph showing the amount of deflux (wt%) according to the CaO / differentiation slag mass ratio

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the scope of the invention to those skilled in the art. It is provided to inform you completely.

The present invention relates to a refining agent containing slag generated during the steelmaking process and a method for refining molten iron using the same. More specifically, the present invention is a slag generated during the steelmaking process, and provides a refining agent comprising a differentiated slag in which Ca ₂ SiO ₄ is precipitated, and a molten iron refining method for removing P (phosphorus) from molten iron using the same.

During the steelmaking process, slag is generated during the refining operation to remove impurities in the molten iron. That is, slag is produced by the reaction of oxygen and a refining agent blown or injected into the slag with molten iron. The resulting slag is at a high temperature, for example, 1600 ° C. or higher, and is excreted after refining is finished and naturally cooled to room temperature.

On the other hand, among the slag generated during the steelmaking process, when cooled to room temperature, there is a slag that is not clogged and solidified, but differentiates in the form of fine particles or dust.

Then, when analyzing the differentiated slag (hereinafter, the differentiated slag), a Ca ₂ SiO ₄ solid phase precipitated.

In this way, the differentiated slag is mainly generated when the slag produced in the process of refining the molten iron using Si and CaO is cooled. More specifically, after introducing Si and CaO into an AOD (Argon Oxygen Decarburization) refining furnace, after deoxidation and desulfurization, the excreted slag is differentiated into fine particle form in the cooling process.

Thus, the reason why the slag is differentiated is due to the Ca ₂ SiO ₄ phase in the slag.

Upon cooling of the slag, as the temperature decreases, the Ca ₂ SiO ₄ phase in the slag undergoes phase transformation from α-type to α-type to γ-type. At this time, α-type of 3.07 g / cm ^3, α 'type, γ-type of 3.31g / cm ³ has a density of 2.97 g / cm ^3.

On the other hand, since the phase transformation from the α type to the α 'type occurs in the liquid state, there is no problem of expansion and contraction due to the phase transformation. However, when the phase transformation from α 'type to room temperature stable phase γ type is accompanied by a large volume expansion of about 14%, the slag is cooled to form a dust and becomes a very fine powder form.

This eruption slag not only causes environmental problems such as being blown around the work area or the work area, but can also adversely affect the health of workers.

In order to solve such a problem, the eruption slag is usually buried, and it is not only costly for this, but also requires additional treatment for the eruption slag so as to suppress environmental pollution. There is.

On the other hand, in the embodiment of the present invention, the eruption slag generated in the steelmaking process is recycled to prepare or use a refining agent. More specifically, a refining agent capable of removing P (phosphorus) in molten iron is prepared by recycling the eruption slag in which Ca ₂ SiO ₄ solid phase is precipitated.

On the other hand, for the dephosphorization, if oxygen is blown into a container (for example, a ladle or a converter), and a general dephosphorization refining agent, that is, CaO (for example, quicklime) is added, FeO such as CaO, SiO ₂ , FeO or Fe ₂ O _3, etc. A slag comprising is formed. Then, P (phosphorus) in the molten iron moves to the slag and reacts with Fe oxide to become the solid phase P ₂ O ₅ (see Scheme 1), and P ₂ O ₅ is absorbed into the slag.

[Scheme 1]

2P + 5FeO-> P ₂ O ₅ + 5Fe

At this time, CaO in the slag lowers the activity of the absorbed P ₂ O ₅ , thereby preventing P in the slag from being picked up again by molten iron. That is, the solid phase P ₂ O ₅ absorbed by the slag is dissolved in the slag by the liquid CaO in the slag, whereby P remains in the slag.

On the other hand, when the solubility of P is low in the slag, the absorbed P ₂ O ₅ is not dissolved in the slag, and there is a problem of picking up again with molten steel.

Thus, the higher the solubility of the slag to dissolve P, the higher the dephosphorization rate.

Further, when the slag on the molten iron is in a liquid phase compared to the solid phase, the surface area is large, so that the solubility to melt P is improved.

In addition, the first slag formed on the molten iron bath surface is a solid phase, and is liquefied according to the temperature. The lower the melting point of the refining agent to be introduced, the more liquefaction is promoted.

In an embodiment of the present invention, a Ca ₂ SiO ₄ solid phase is prepared by recycling the differentiated slag, the solubility in P is improved, and a refiner having a low melting point is provided.

In addition, the molten iron for refining with the refining agent according to the embodiment may have, for example, a P content of 1500 ppm or less, more specifically 200 ppm or more and 1500 ppm or less.

Hereinafter, a refiner according to an embodiment of the present invention will be described in detail with reference to FIG. 1.

1 is a conceptual view showing a refining agent according to embodiments of the present invention and molten iron to which they are applied.

Another refining agent in the embodiment is a refining agent that removes P (phosphorus) from molten iron, as shown in FIG. 1, and includes a differentiating slag generated in a steelmaking process, more specifically, a differentiating slag in which Ca ₂ SiO ₄ is precipitated. . In addition, the refining agent may further include CaO (hereinafter, additional CaO) in addition to the differentiated slag.

In other words, the refining agent contains the differentiated slag on which Ca ₂ SiO ₄ is precipitated alone, or contains the differentiated slag and additional CaO.

Hereinafter, a refiner comprising only the differentiated slag (hereinafter, differentiated slag) on which Ca ₂ SiO ₄ is precipitated is referred to as a refiner according to the first embodiment, and a refiner according to the second embodiment of the slag containing the differentiated slag and additional CaO. Name it.

Then, according to the content of P in the molten iron to be removed, the refiner according to the first embodiment is added, or the refiner according to the second embodiment is introduced. That is, the first refining agent is added to the molten iron having a P content of less than 300 ppm, and the refining agent according to the second embodiment is refined to the molten iron having a P content of 300 ppm or more.

And, in the dephosphorization of the molten iron having a P content of 300 ppm or more using the refining agent according to the second embodiment, the weight ratio of the additional CaO and the differentiated slag (additional CaO mass / differentiated slag mass) is adjusted and input. It will be described below.

Differentiated slag is a slag in which Ca ₂ SiO ₄ is precipitated, and can be prepared by recovering from slag generated in a refining process using Si and CaO.

More specifically, after introducing Si and CaO into an AOD (Argon Oxygen Decarburization) refining furnace, after deoxidation and desulfurization, the excreted slag may be cooled.

The slag contains CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ , and a Ca ₂ SiO ₄ phase is deposited. More specifically, CaO is 49 wt% to 62 wt%, SiO ₂ is 22 wt% to 38 wt%, MgO is 20 wt% or less (over 0 wt%, 20 wt% or less), and Al ₂ O ₃ is 10 wt% or less for the entire slag ( 0 wt% or more, 10 wt% or less), CaF ₂ 3 wt% to 10 wt%, S 0.3 wt% or more, 1 wt% or less, FeO 5 wt% or less (0 wt% or more, 5 wt% or less), Cr ₂ O ₃ It contains less than 5wt% (more than 0 wt%, less than 5wt%).

And, the particle size of the differentiation slag may be 0.5 mm or less.

As described above, the refining agent according to the embodiment includes Ca ₂ SiO ₄ precipitates, and the slag produced by introducing the refining agent has high solubility to dissolve P.

This is because the slag produced by the refiner according to the embodiment may include Ca ₂ SiO ₄ comprises a precipitate, slag of Ca ₂ SiO ₄ and P ₂ O ₅ by a Ca ₂ SiO ₄ -Ca ₃ P ₂ O ₈ form a stable solid solution of Because it forms. That is, the atoms of P ₂ O ₅ are substituted and mixed into the crystals of Ca ₂ SiO _{4 as} a solid phase to form a solid solution in the form of Ca ₂ SiO ₄ -Ca ₃ P ₂ O ₈ .

In this way, the P ₂ O ₅ being a solid solution of _{Ca 2 SiO 4 -Ca 3 P 2} O 8 form by the reaction of Ca ₂ SiO ₄ of the slag, and the P is stably present in the slag, which due to the hot metal P Picking up is suppressed or prevented.

In addition, since the refining agent contains slag generated during the refining process using Si and CaO, the refining agent contains CaO (CaO in the differentiated slag). Accordingly, when the slag is formed by introducing the refining agent according to the embodiment, the slag has a solubility to dissolve P by CaO and Ca ₂ SiO ₄ . In other words, the slag produced by the refining agent according to the embodiment further has a solubility by Ca ₂ SiO ₄ as well as a solubility of P by CaO.

Therefore, according to the slag produced by the refining agent according to the embodiment, the solubility of dissolving P has an effect that is improved compared to the formed slag using the conventional refining agent (CaO), thereby improving the dephosphorization rate.

In the embodiment, as described above, in the molten iron having a P content of less than 300 ppm, the first refining agent containing only the differentiated slag is added, and in the molten iron having a P content of 300 ppm or more, in the second embodiment containing the differentiated slag and additional CaO The refining agent is added to refine it.

Thus, the use of the refining agent according to the first embodiment or the refining agent according to the second embodiment according to the content of P is based on the basicity (CaO / SiO ₂ ) of the slag.

In molten iron having a P content of less than 300 ppm, even if the slag has a low basicity (CaO / SiO ₂ ) of less than 2.0, P can be sufficiently removed at a target concentration. Therefore, it can be dephosphorized using the refiner according to the first embodiment, which does not further contain additional CaO.

However, in the case of molten iron having a P content of 300 ppm or more, the basicity (CaO / SiO ₂ ) of the slag is preferably 2.0 or more and 4.0 or less.

In the case of molten iron having a P content of 300 ppm or more, the amount of oxygen blown or injected into the molten iron is relatively larger than that of the molten iron. At this time, if the basicity of the slag is less than 2.0, while the content of Fe oxide in the slag increases, the Ca ₂ SiO ₄ phase in the slag dissociates, solubility in P decreases. Therefore, P cannot be sufficiently removed from the molten iron.

Conversely, when the basicity (CaO / SiO ₂ ) of the slag exceeds 4.0, there is a problem that the desalination rate is reduced because the slag is difficult to liquefy.

Therefore, in the case of molten iron having a P content of 300 ppm or more, the basicity of the slag is adjusted to 2.0 or more and 4.0 or less. To this end, in the case of molten iron having a P content of 300 ppm or more, a second refiner in which additional CaO is further added or mixed into the eruption slag is introduced as molten iron, and the basicity of the resulting slag is 2.0 or more and 4.0 or less.

2 is a graph showing the amount of dephosphorization (ppm) according to the mass ratio (additional CaO / differentiated slag mass ratio) of additional CaO and differentiation slag.

For the experiment, a refiner according to a second example containing an eruption slag and additional CaO was prepared, and dephosphorization was performed by introducing the refiner into a molten iron having a P of 1500 ppm.

The differentiation slag used in the experiment is shown in Table 1 below.

ingredient CaO SiO ₂ Al ₂ O ₃ MgO CaF ₂ S FeO Cr ₂ O ₃ Content (wt%) 50.49 26.80 3.12 9.88 6.23 0.32 1.47 2.01

To compare the amount of dephosphorization according to the additional CaO / differentiated slag mass ratio, a plurality of refining agents having different CaO / differentiated slag mass ratios were prepared, and the amount of dephosphorization (ppm) was detected by introducing them into different operations. The dephosphorization amount (ppm) is the difference between the P content in the molten iron before the dephosphorization and the P content in the molten iron after the dephosphorization. At this time, the desalination was performed using the same molten iron and refining agent in each of the ladle and the converter.

Referring to FIG. 2, as the additional CaO / differentiated slag mass ratio increases, the content of P removed from the molten iron, that is, the amount of desorption increases, and then tends to decrease again based on the mass ratio 2.3.

In the embodiment, through the change in the amount of dephosphorization according to the additional CaO / differentiated slag mass ratio, an additional CaO / differentiated slag mass ratio to be introduced into the molten iron is derived or selected.

For example, an additional CaO / differentiated slag mass ratio can be derived or selected to be the maximum amount of dephosphorization.

Referring to FIG. 2 as an example, the maximum amount of dephosphorization is when the additional CaO / differentiated slag mass ratio is about 2.3, and thus, in desalting the molten iron with P of 1500ppm, the additional CaO / differentiated slag mass ratio can be introduced to be 2.3. have.

However, the present invention is not limited thereto, and an additional CaO / differentiated slag mass ratio may be selected to ensure an appropriate amount of dephosphorization lower than the maximum amount of dephosphorization. That is, it can be added so that a predetermined value is a small value or a large value from the additional CaO / differentiated slag mass ratio showing the maximum amount of dephosphorization.

For example, the maximum amount of dephosphorization in FIG. 2 is when the additional CaO / differentiated slag mass ratio is 2.3, and thus, in desalting the molten iron having P of 1500 ppm, the additional CaO / differentiated slag mass ratio may be added to be 2.2 to 2.4.

In the embodiment, the additional CaO / differentiated slag mass ratio is adjusted according to the content of P in the molten iron, and in the same manner as the above-described method, appropriate or additional CaO / according to the content of P is ensured so that an appropriate or targeted amount of dephosphorization is secured. Differentiation slag mass ratio can be derived, and an example is shown in Table 2.

P content in molten iron (ppm) Additional CaO: differentiation slag mass ratio (additional CaO mass / differentiation slag mass) 300≤P <600 1.0≤additional CaO / differentiation slag <1.5 600≤P <1000 1.5≤additional CaO / differentiation slag <2.2 1000≤P≤1500 2.2≤additional CaO / differentiated slag≤2.6

As shown in Table 2, in the case of molten iron having a P content of 300 ppm or more and less than 600 ppm, it can be refined using an additional CaO / differentiated slag mass ratio of 1.0 or more and a 1.5 or less refining agent, and in the case of a molten iron having a P content of 600 ppm or more and less than 1000 ppm , Additional CaO / differentiated slag mass ratio can be refined using a refining agent having a mass ratio of 1.5 or more and less than 2.2, and in the case of molten iron having a P content of 1000 ppm or more and 1500 ppm or less, a refining agent having a mass ratio of CaO / differentiated slag of 2.2 or more and 2.6 or less Can be refined using a refining agent.

In this way, as the content of P in the molten iron to be refined increases, an additional CaO / differentiated slag mass ratio is increased. Accordingly, the solubility of the slag to dissolve P is increased, and P can be removed to a target level. This is because, as the additional CaO / differential slag mass ratio increases, solid solution formation of Ca ₂ SiO ₄ -Ca ₃ P ₂ O ₈ is promoted.

On the other hand, when the mass ratio of the additional CaO / differentiated slag exceeds 2.6, the melting point of the slag becomes high and the amount of dephosphorization cannot be secured, so the mass ratio of the additional CaO / differentiated slag is preferably adjusted to 2.6 or less.

In the refining agent according to the second embodiment as described above, a mixture in which additional CaO and differentiation slag is mixed may be added, or additional CaO and differentiation slag may be separately added.

At the time of refining of the molten iron, CaF ₂ is added together with a refining agent for liquefaction of slag. In the embodiment, the amount of addition is determined according to the mass of additional CaO contained in the refining agent to be added (see Equation 1).

[Equation 1]

According to Equation 1, CaF ₂ is added in an amount of 15% of the mass (kg) of additional CaO contained in the refining agent.

For example, when the content of P in the molten iron is less than 300 ppm, since the refiner according to the first embodiment that does not contain additional CaO is used, according to Equation 1, the CaF ₂ input amount is 0. That is, when the content of P in the molten iron is less than 300ppm, CaF ₂ is not added and it is possible to liquefy the slag without inputting CaF ₂ .

As another example, in the case of molten iron having a P content of 300 ppm or more in the molten iron, the refining agent according to the second embodiment including eruption slag and additional CaO is used. Accordingly, according to Equation 1, in the case of molten iron having a P content of 300 ppm or more in the molten iron, the amount of CaF ₂ is calculated in a predetermined amount, and the slag can be liquefied when CaF ₂ is added to the calculated amount.

Here, the mass of the additional CaO contained in the refining agent is smaller than the mass of CaO conventionally added as a refining agent. Thus, even when the content of P in the molten iron is 300ppm or more, the amount of CaF ₂ can be reduced compared to the prior art.

As described above, by using the refining agent according to the embodiment, CaF ₂ may not be added or may be added in a smaller amount than in the prior art. Accordingly, the cost associated with CaF ₂ input can be reduced.

And, failure to input the CaF _2, CaF _2, even if the input to a small amount compared to the prior art, it is possible to liquefaction of the slag. This is because the melting point (1600 ° C to 1700 ° C) of the refining agent containing the differentiated slag on which Ca ₂ SiO ₄ is precipitated is lower than that of the conventional refining agent CaO (about 2572 ° C).

3 is a graph comparing the input amount of CaF ₂ when using the refiner according to the embodiment and the refiner according to the comparative example.

Here, another refining agent in the examples is a refining agent containing additional CaO and differentiation slag, and the refining agent according to the comparative example is a refining agent containing only CaO. Differentiation slag was used for the differentiation slag of the composition of Table 1 described above.

And, in the experiment, it was set as the condition for removing the same amount of P of 1000 ppm in the molten iron.

As shown in FIG. 3, in removing 1000 ppm of P, 250 kg of CaF ₂ was added in the case of the comparative example, but 160 kg in the case of the example, and the amount of CaF ₂ was less than that of the comparative example.

From this, it can be seen that according to the refining agent according to the embodiment, even if a small amount of CaF ₂ is added compared to when using the refining agent according to the comparative example, it is easy to liquefy the slag. This is because the melting point of the refining agent included in the examples is lower than that of the conventional refining agent CaO.

In the above, refining for removing P (phosphorus) from molten iron using the refining agent according to the embodiments has been described.

However, by using the refining agent according to the embodiments, desulfurization to remove S (sulfur) from the molten iron along with Tallinn may be simultaneously performed. At this time, desulfurization can be performed according to the additional CaO / differentiated slag mass ratio.

4 is a graph showing the amount of desulfurization (wt%) according to the mass ratio of CaO / differentiated slag.

For the experiment, a refining agent according to a second embodiment containing an eruption slag and additional CaO was prepared, and the refining agent was added to the molten iron.

The charter used in the experiment is the same as the charter used in the experiment of FIG. 2, and the differentiation slag is shown in Table 1 described above.

In the refining agent according to the second embodiment, a plurality of refining agents having different CaO / differentiated slag mass ratios were prepared, and the amount of desulfurization (wt%) according to each of these refining agents was detected. Here, the desorption amount (wt%) is a difference value between the S content in the molten iron before refining and the S content in the molten iron after finishing refining.

Referring to FIG. 4, it can be confirmed that desorption is possible when the additional CaO / differentiated slag mass ratio exceeds 2.1. That is, when the additional CaO / differentiated slag mass ratio exceeds 2.1, the amount of desulfurization (wt%) exceeds 0 wt%.

This is because the S content of the eruption slag used as a refining agent is higher than 0.3 wt%. In other words, the refining agent already contains 0.3 wt% or more of S. Therefore, if the additional CaO / differentiated slag mass ratio is 2.1 or less, defluxing is not possible, and when it exceeds 2.1, defluxing is possible.

Thus, when desulfurization is carried out with Tallinn, the additional CaO / differentiated slag mass ratio must be adjusted to exceed 2.1.

At this time, the additional CaO / differentiated slag mass ratio for achieving the target desulfurization amount (wt%) can be calculated using Equation 2 below.

[Equation 2]

In Equation 2, it is calculated that if the desulfurization value exceeds 0, the additional CaO / differentiated slag mass ratio must exceed 2.1.

In calculating an additional CaO / differentiated slag mass ratio to achieve a target deflux amount (wt%), the value of the deflux amount to be removed is applied to the 'deflux amount (wt%)' of Equation 2. The predetermined additional CaO / differentiated slag mass ratio is calculated by Equation 2, which is a value exceeding 2.1.

When the additional CaO / differentiated slag mass ratio is calculated by Equation 2, it is compared with the additional CaO / differentiated slag mass ratio according to the content of P in the molten iron.

In addition, among the additional CaO / differentiated slag mass ratio calculated by Equation 2 and the additional CaO / differentiated slag mass ratio according to the content of P in the molten iron, the final mass ratio (additional CaO / differentiated slag mass ratio) to be introduced as a molten iron Select and input.

Hereinafter, the molten iron refining method using the refining agent according to the embodiment will be described. At this time, the contents overlapping with the above-mentioned contents are omitted or briefly described.

First, the molten iron to remove P (phosphorus) is loaded into a container. Here, the container may be a ladle or a converter.

Thereafter, gas oxygen is blown into the container using a lance, and a refining agent is added. At this time, in addition to gaseous oxygen, a material containing Fe ₂ O ₃ may be further added as solid oxygen.

The refining agent introduced into the molten iron contains an eruption slag in which Ca ₂ SiO ₄ is precipitated. At this time, according to the content of P in the molten iron to be refined, the refining agent according to the first embodiment is added, or the refining agent according to the second embodiment is introduced.

That is, when the P content in the molten iron is less than 300ppm, the refiner according to the first embodiment containing only the differentiated slag is introduced. As another example, when the P content in the molten iron is 300ppm or more, the refiner according to the second embodiment containing the differentiation slag and additional CaO is added. At this time, an additional CaO / differentiated slag mass ratio is adjusted according to the P content in the molten iron to be treated.

Then, the amount of CaF ₂ is determined according to the mass of the additional CaO among the refiners injected into the molten iron (see Equation 1).

At this time, since the refining agent according to the embodiment has a lower melting point than that of the conventional refining agent, CaF ₂ may not be added or the amount of CaF ₂ may be reduced compared to the prior art.

In this way, when oxygen is blown into the molten iron and a refining agent is added, slag is generated by reaction between the blown or charged oxygen, the refining agent and the molten iron. Then, the produced slag is liquefied.

P of molten iron moves to the generated slag and becomes P ₂ O ₅ as it reacts with Fe oxide. And P ₂ O ₅ is dissolved in the slag. That is, P is not picked up again as molten iron, but is dissolved in the slag so as to remain in the slag, and thus becomes dephosphorized by removing P from the molten iron.

In this way, P ₂ O ₅ absorbed by the slag is dissolved in the slag, and according to the slag produced by the refiner according to the embodiment, it has solubility due to CaO and Ca ₂ SiO ₄ . That is, some of the generated P ₂ O ₅ is dissolved in the slag by liquid CaO in the slag, stably remains in the slag, and other P ₂ O ₅ is in the crystal of Ca ₂ SiO _{4 as} a solid phase. By substitution and mixing, the solid solution in the form of Ca ₂ SiO ₄ -Ca ₃ P ₂ O ₈ remains stably in the slag.

Therefore, according to the slag produced by the refining agent according to the embodiment, there is an effect of improving the solubility of dissolving P. Therefore, the dephosphorization ability to remove P (phosphorus) among molten iron is improved.

In addition, by recycling the eruption slag generated during the steelmaking process to prepare a refining agent, the cost for preparing the refining agent can be reduced, and low-cost refining operation is possible.

And, by recycling the eruption slag as a refining agent, it is possible to reduce the cost of landfilling the eruption slag.

The refining agent according to the embodiments of the present invention can reduce the cost for providing the refining agent by recycling the eruption slag generated during the steelmaking process, thereby enabling low-cost refining operation. And, by recycling the eruption slag as a refining agent, it is possible to reduce the cost of landfilling the eruption slag.

Claims (15)

As a refiner for removing at least P (phosphorus) among impurities contained in the molten iron, A refining slag generated in the steelmaking process and comprising a refining slag in which Ca ₂ SiO ₄ is precipitated. The method according to claim 1, The differentiation slag is a refiner comprising CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ . The method according to claim 2, Among the differentiation slag, CaO is 49 wt% to 62 wt%, SiO ₂ is 22 wt% to 38 wt%, MgO is 20 wt% or less, Al ₂ O ₃ is 10 wt% or less, CaF ₂ is 3 wt% to 10 wt%, S is 0.3 wt % Or more, 1wt% or less, FeO of 5wt% or less, Cr ₂ O ₃ of 5wt% or less. The method according to any one of claims 1 to 3, A refiner further containing additional CaO in addition to the differentiation slag. The method according to claim 4, A refining agent having a mass ratio (additional CaO mass / differentiated slag mass) of 1.0 or more and 2.6 or less of the additional CaO and the differentiated slag. The method according to claim 5, A refining agent that removes S (sulfur) together with P (phosphorus) among impurities contained in the molten iron, wherein the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiated slag is adjusted to be greater than 2.1 and 2.6 or less. The method according to any one of claims 1 to 3, The eruption slag, using Si and CaO, a refining agent containing slag generated and cooled in the process of refining molten iron. The process of supplying oxygen with molten iron; A dephosphorization process in which P 2 (phosphorus) is removed from the molten iron by introducing an eruption slag in which Ca ₂ SiO ₄ is precipitated as the molten iron; Method for refining the molten iron containing. The method according to claim 8, The differentiation slag is a molten iron refining method comprising CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ . The method according to claim 8, When the P content in the molten iron is 300ppm or more, the molten iron refining method comprising the step of introducing additional CaO into the molten iron. The method according to claim 10, When the P content in the molten iron is 300 ppm or more and less than 600 ppm, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiating slag inputted to the molten iron is added to be 1.0 or more and less than 1.5, When the P content of the molten iron is 600ppm or more and less than 1000ppm, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiation slag introduced into the molten iron is added to be 1.5 or more and less than 2.2, When the P content of the molten iron is 1000ppm or more and 1500ppm or less, the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and the differentiation slag injected into the molten iron is 2.2 or more and 2.6 or less. The method according to claim 10, Including the process of introducing CaF ₂ into the molten iron, The CaF ₂ input to the molten iron is a molten iron refining method to input 15% of the additional CaO input to the molten iron. The method according to claim 11, In the dephosphorization process, desulfurization to remove S (sulfur) in the molten iron is carried out together, In performing the dephosphorization and desulfurization together, the molten iron refining method in which the mass ratio of the additional CaO and the differentiated slag (additional CaO mass / differentiated slag mass) is greater than 2.1. The method according to claim 13, Comprising the process of calculating the mass ratio (additional CaO mass / differentiation slag mass) of the additional CaO and differentiation slag for the desulfurization, In calculating the mass ratio (additional CaO mass / differentiated slag mass) of the additional CaO and differentiation slag for the desulfurization, the molten iron is calculated by applying the amount of S (sulfur) to be removed to the desulfurization amount of the following formula Refining method. [Equation]

The method according to claim 14, In the dephosphorization process, in the desulfurization to remove S (sulfur) in the molten iron together, Among the mass ratio of the additional CaO and the differentiating slag according to the content of P in the molten iron (additional CaO mass / differential slag mass), and the mass ratio of the additional CaO and differentiating slag for defluxing (additional CaO mass / differential slag mass), relatively The molten iron refining method in which the additional CaO and the differentiation slag are introduced so as to have a large mass ratio.

Images