KR102156718B1 - Refining agent and method for refining molten iron - Google Patents

Abstract

An embodiment of the present invention is a scouring agent that removes at least P (phosphorus) among impurities contained in molten iron, and is a differentiated slag generated in a steelmaking process, and includes a differentiated slag in which Ca ₂ SiO ₄ is precipitated.
Therefore, according to the refining agent according to an embodiment of the present invention, it is possible to reduce the cost for preparing the refining agent, thereby enabling a low-cost refining operation. And, as the differentiated slag is recycled as a refining agent, it is possible to reduce the cost required for the burial of the differentiated slag.
Further, according to the scouring agent according to the embodiments, slag with improved solubility of P can be formed, thereby improving dephosphorization efficiency.

Description

Refining agent and method of refining molten iron using the same{REFINING AGENT AND METHOD FOR REFINING MOLTEN IRON}

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

Among the various slags generated during the steel making process, some of them are differentiated into fine particles or powders during the cooling process.

As a more specific example, after performing deoxidation and degassing to remove oxygen and S (sulfur) from molten iron using Si and CaO in an AOD (Argon Oxygen Decarburization) refining furnace, the resulting slag is cooled to room temperature, cooling In the process, the slag is differentiated into a fine particle form or powder rather than a lump form.

Since the differentiated slag exists in a powder state, it causes environmental problems such as being blown around the work area or the work area when handled. Accordingly, the entire amount of the differentiated slag is buried or used as a raw material for cement.

However, in order to landfill the differentiated slag, not only does it incur additional cost for landfilling, but as environmental regulations are strengthened, it is necessary to separately process and landfill the differentiated slag to suppress environmental pollution. There is a problem that requires more.

Japanese registered patent JP4546661

The present invention relates to a refining agent prepared by recycling slag generated during a steelmaking process, and a hot-metal refining method using the same.

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

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

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

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

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

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

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 not more than 2.6, to remove S (sulfur) along with P (phosphorus) among the impurities contained in the molten iron.

The differentiated slag includes slag that has been cooled by being generated in the process of refining molten iron using Si and CaO.

The molten iron refining method according to an embodiment of the present invention includes the process of supplying oxygen to molten iron; And a dephosphorization process of removing P (phosphorus) from the molten iron by introducing the differentiated slag in which Ca ₂ SiO ₄ is precipitated into the molten iron.

The differentiated 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, the process of adding additional CaO to the molten iron is included.

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

Including the process of introducing CaF ₂ into the molten iron, the amount of CaF ₂ inputted into the molten iron is 15% of the amount of the additional CaO added into the molten iron.

In the dephosphorization process, degassing to remove S (sulfur) in the molten iron is performed together, and in performing dephosphorization and degassing together, the mass ratio of the additional CaO and differentiated slag (additional CaO mass/differentiated slag mass) is Put it in excess of 2.1.

Including the process of calculating the mass ratio (additional CaO mass/differentiated slag mass) for the degassing, and calculating the mass ratio (additional CaO mass/differentiated slag mass) of the additional CaO and differentiated slag for the degassing. In doing so, it is calculated by applying the amount (wt%) of S (sulfur) to be removed to the deflow amount in the following equation.

[Equation]

In the dephosphorization process, in performing degassing to remove S (sulfur) in the molten iron, the mass ratio of additional CaO and differentiated slag according to the content of P in the molten iron (additional CaO mass/differentiated slag mass), and the degassing Of the mass ratio (additional CaO mass/differentiated slag mass) for the additional CaO and differentiated slag, the additional CaO and the differentiated slag are added so that the mass ratio is relatively large.

The refining agent according to the embodiments of the present invention can reduce the cost for preparing the refining agent by recycling the differentiated slag generated during the steelmaking process to prepare a refining agent, thereby enabling a low-cost refining operation. And, as the differentiated slag is recycled as a refining agent, it is possible to reduce the cost required for the burial of the differentiated slag.

Further, according to the scouring agent according to the embodiments, slag with improved solubility of P can be formed, thereby improving dephosphorization efficiency.

1 is a conceptual diagram showing a refining agent according to embodiments of the present invention and a molten iron to which they are applied
Figure 2 is a graph showing the amount of dephosphorylation (ppm) according to the mass ratio of CaO and differentiated slag (CaO/differentiated slag mass ratio)
3 is a graph comparing the input amount of CaF ₂ when using the scouring agent according to the embodiment and the scouring agent according to the comparative example
4 is a graph showing the amount of deflow (wt%) according to the mass ratio of CaO/differentiated slag

Hereinafter, an embodiment 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 a variety of different forms, and only the present embodiments make the disclosure of the present invention complete, and the scope of the invention to those of ordinary skill in the art. It is provided to be fully informed.

The present invention relates to a refining agent containing slag generated during a steelmaking process and a hot-metal refining method using the same. More specifically, the present invention is a slag generated during the steelmaking process, and provides a refining agent including the 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, during the refining operation to remove impurities in molten iron, slag is generated. That is, the slag is produced by the reaction of the oxygen and the refining agent blown or introduced into the slag and the molten iron. The resulting slag is high temperature, for example, 1600°C or higher, and is discharged after refining 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 differentiated into a form such as fine particles or dust, rather than agglomerated and solidified.

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

In this way, the differentiated slag is mainly generated when the slag generated in the process of refining molten iron using Si and CaO is cooled. More specifically, after Si and CaO are added to an Argon Oxygen Decarburization (AOD) refining furnace, deoxidation and degassing are performed, the slag that is excluded is differentiated into fine particles during the cooling process.

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

When the slag is cooled, as the temperature decreases, the Ca ₂ SiO ₄ phase in the slag is phase transformed into α type -->α'type--> 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 a liquid state, there is no problem of expansion and contraction due to the phase transformation. However, as the phase transformation from α'type to γ type, which is a stable phase at room temperature, accompanied by a large volume expansion of about 14%, as the slag is cooled, it is formed into dust and becomes a very fine powder form.

Such differentiated slag not only causes environmental problems such as being blown around the work site or the work site, but also may adversely affect the health of workers.

In order to solve such a problem, since the differentiated slag is usually buried in landfill, not only does it require a cost, but since the differentiated slag has to be separately treated and buried to suppress environmental pollution, additional cost is required for this. There is.

On the other hand, in the embodiment of the present invention, a refining agent is prepared or used as a refining agent by recycling the differentiated slag generated in the steel making process. More specifically, a scouring agent capable of removing P (phosphorus) in molten iron is prepared by recycling the differentiated slag in which the Ca ₂ SiO ₄ solid phase is deposited.

On the other hand, for dephosphorization, when oxygen is blown into a container (e.g., a ladle or converter), and a general dephosphorization refining agent, that is, CaO (such as quicklime) is introduced, Fe oxides such as CaO, SiO ₂ and FeO or Fe ₂ O ₃ A slag containing is formed. In addition, in the molten iron, P (phosphorus) moves to the slag and reacts with the Fe oxide to become solid P ₂ O ₅ (see Reaction Formula 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 to prevent P in the slag from being picked up again as molten iron. That is, the solid P ₂ O ₅ absorbed into the slag is dissolved into the slag by the liquid CaO in the slag, and thus P remains in the slag.

On the other hand, when the slag has a low solubility of P, the absorbed P ₂ O ₅ is not dissolved in the slag, and a problem occurs in that the slag is picked up again into molten steel.

Accordingly, the higher the solubility at which the slag dissolves P, the better the dephosphorization rate is.

Further, when the molten iron slag is in a liquid state compared to that in a solid state, the solubility of melting P is improved because the surface area thereof is large.

In addition, the initial slag formed on the molten metal surface is solid and liquefied according to the temperature, and the lower the melting point of the added refining agent, the faster the liquefaction.

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

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

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

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

The refining agent according to the embodiment is a refining agent that removes P (phosphorus) in molten iron, and, as shown in FIG. 1, includes the differentiated slag generated in the steel making process, more specifically, the differentiated slag in which Ca ₂ SiO ₄ is precipitated. . In addition, the scouring agent may further contain CaO (hereinafter, additional CaO) in addition to the differentiated slag.

In other words, the scouring agent alone contains the differentiated slag in which Ca ₂ SiO ₄ was precipitated, or contains the differentiated slag and additional CaO.

Hereinafter, the scouring agent containing only the differentiated slag in which Ca ₂ SiO ₄ is precipitated (hereinafter, the differentiated slag) is referred to as the scouring agent according to the first embodiment, and the slag containing the differentiated slag and additional CaO is referred to as the scouring agent according to the second embodiment. Name it.

Then, the refining agent according to the first embodiment or the refining agent according to the second embodiment is added according to the content of P in the molten iron to be removed from P. 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 added to the molten iron having a P content of 300 ppm or more.

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

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

More specifically, it may be a slag obtained by injecting Si and CaO into an Argon Oxygen Decarburization (AOD) refining furnace, performing deoxidation and degassing, and cooling the exhausted slag.

Such 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, with respect to the entire slag, CaO is 49wt% to 62wt%, SiO ₂ is 22wt% to 38wt%, MgO is 20wt% or less (more than 0 wt%, 20wt% or less), Al ₂ O ₃ is 10wt% or less ( More than 0 wt%, 10 wt% or less), CaF ₂ is 3 wt% to 10 wt%, S is 0.3 wt% or more, 1 wt% or less, FeO is 5 wt% or less (more than 0 wt%, 5 wt% or less), Cr ₂ O ₃ 5wt% or less (more than 0wt%, 5wt% or less) is contained.

In addition, the particle diameter of the differentiated slag may be 0.5 mm or less.

As described above, the scouring agent according to the embodiment contains Ca ₂ SiO ₄ precipitates, and the slag produced by adding the scouring agent has a 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 solid phase is determined in the Ca ₂ SiO ₄ incorporated atom is substituted for P ₂ O _5, is because _{Ca 2 SiO 4 -Ca 3 P 2} O 8 form a solid solution in the form of.

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 It is inhibited or prevented from being picked up.

In addition, since the refining agent contains slag generated in the refining process using Si and CaO, the refining agent contains CaO (CaO in powdered slag). Accordingly, when slag is formed by adding the refining agent according to the embodiment, the slag has a solubility of dissolving P by CaO and Ca ₂ SiO ₄ . In other words, the slag prepared by the scouring agent according to the embodiment has not only the solubility of P by CaO but also the solubility by Ca ₂ SiO ₄ .

Therefore, according to the slag produced by the refining agent according to the embodiment, the solubility for dissolving P is improved compared to the slag formed by 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, a first refining agent containing only differentiated slag alone was added, and in the molten iron having a P content of 300 ppm or more, a second embodiment including differentiated slag and additional CaO The scouring agent is added and refined.

In this way, 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 due to 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 dephosphorylated by using the scouring agent according to the first embodiment in which additional CaO is not further included.

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

In the case of the molten iron having a P content of 300 ppm or more, the amount of oxygen injected or inputted into the molten iron is relatively larger than that of the other case. At this time, when the basicity of the slag is less than 2.0, the content of the Fe oxide in the slag increases, the Ca ₂ SiO ₄ phase in the slag is dissociated, and the solubility in P decreases. Thus, P cannot be sufficiently removed during molten iron.

On the contrary, when the slag has a basicity (CaO/SiO ₂ ) exceeding 4.0, there is a problem that the slag is difficult to liquefy and the dephosphorization rate decreases.

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 refining agent obtained by adding or mixing additional CaO to the differentiated slag is added to the molten iron. At this time, the basicity of the resulting slag is 2.0 or more and 4.0 or less.

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

For the experiment, a refining agent according to the second embodiment was prepared containing differentiated slag and additional CaO, and dephosphorization was performed by adding the refining agent to a molten iron having a P of 1500 ppm.

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

In order to compare the amount of dephosphorylation according to the mass ratio of additional CaO/differentiated slag, a plurality of refining agents having different mass ratios of additional CaO/differentiated slag were prepared, and these were added to different operations to detect the amount of dephosphorylation (ppm). The amount of dephosphorylation (ppm) is the difference between the P content in the molten iron before dephosphorization and the P content in the molten iron after completion of dephosphorization.

At this time, dephosphorization was performed in each of the ladle and the converter using the same molten iron and refining agent.

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

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

For example, an additional CaO/differentiated slag mass ratio can be derived or selected so that the maximum amount of dephosphorylation is achieved.

Referring to FIG. 2 as an example, the maximum amount of dephosphorylation is when the mass ratio of additional CaO/differentiated slag is about 2.3, and thus, in dephosphorization of molten iron having a P of 1500 ppm, the additional CaO/differentiated slag mass ratio can be added 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 dephosphorylation lower than the maximum amount of dephosphorylation. That is, it can be added so that it may become a predetermined numerical value small value or a large value from the mass ratio of additional CaO/differentiated slag showing the maximum amount of dephosphorylation.

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

In the embodiment, the mass ratio of additional CaO/differentiated slag is adjusted according to the content of P in the molten iron, in this case, in the same manner as described above, in order to ensure an appropriate or target range of dephosphorylation amount, appropriate additional CaO/ Differentiated slag mass ratio can be derived, and examples are shown in Table 2.

P content in molten iron (ppm) Additional CaO: differentiation slag mass ratio
(Additional CaO mass/differentiated slag mass) 300≤P<600 1.0≤additional CaO/differentiated slag<1.5 600≤P<1000 1.5≤additional CaO/differentiated 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 a scouring agent having an additional CaO/differentiated slag mass ratio of 1.0 or more and less than 1.5, 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 of 1.5 or more and less than 2.2 can be used for refining.

Further, in the case of molten iron having a P content of 1000 ppm or more and 1500 ppm or less, the additional CaO/differentiated slag mass ratio can be refined using a scouring agent using a scouring agent of 2.2 or more and 2.6 or less.

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

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

In the addition of the refining agent according to the second embodiment as described above, a mixture of additional CaO and differentiated slag may be added, or additional CaO and differentiated slag may be separately added.

During the refining of molten iron, CaF ₂ is added together with a scouring agent to liquefy the slag, and in Examples, the amount of added CaO is determined according to the mass of additional CaO contained in the added scouring agent (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 scouring agent.

For example, when the content of P in the molten iron is less than 300 ppm, since the refining agent according to the first embodiment that does not contain additional CaO is used, according to Equation 1, the input amount of CaF ₂ is zero. That is, when the P content in molten iron is less than 300 ppm, no CaF _{2 is} added, and even without the addition of CaF ₂ , the slag can be liquefied.

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 containing differentiating 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 as a predetermined amount, and the slag can be liquefied when CaF ₂ is added with the calculated amount.

Here, the mass of additional CaO contained in the scouring agent is smaller than the mass of CaO that is conventionally introduced as a scouring agent. Accordingly, even when the content of P in the molten iron is 300 ppm or more, the amount of CaF _{2 added} can be reduced compared to the conventional one.

In this way, according to the use of the scouring agent according to the embodiment, CaF ₂ may not be added or may be added in a small amount compared to the conventional one. Accordingly, it is possible to reduce the cost of CaF ₂ input.

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 scouring agent containing the differentiated slag in 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 scouring agent according to the example and the scouring agent according to the comparative example.

Here, the refining agent according to the embodiment is a refining agent containing additional CaO and differentiated slag, and the refining agent according to the comparative example is a refining agent containing only CaO. As the differentiated slag, the differentiated slag of the composition of Table 1 described above was used.

And, at the time of the experiment, it was set as the condition of removing the same amount of P in the molten iron|metal.

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

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

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

However, using the scouring agent according to the embodiments may be performed simultaneously with dephosphorization to remove S (sulfur) in molten iron. At this time, it is possible to perform desulfurization according to the mass ratio of additional CaO/differentiated slag.

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

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

The molten iron used in the experiment was the same as the molten iron used in the experiment of FIG. 2 above, and the differentiated slag is shown in Table 1 described above.

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

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

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

Therefore, in the case of degassing with dephosphorization, the mass ratio of additional CaO/differentiated slag should be adjusted to exceed 2.1.

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

[Equation 2]

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

In calculating the additional CaO/differentiated slag mass ratio to achieve the target deflux (wt%), the value of the deflux to be removed is applied to the'deflux (wt%)' of Equation 2. A predetermined additional CaO/differentiated slag mass ratio is calculated by Equation 2, and this value exceeds 2.1.

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

And, of 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, a relatively large mass ratio is used as the final mass ratio (additional CaO/differentiated slag mass ratio). Select and put in.

Hereinafter, a method for refining molten iron using a scouring agent according to an embodiment will be described. In this case, the content overlapping with the above description will be omitted or briefly described.

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

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

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

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

In addition, the amount of CaF ₂ added is determined according to the mass of additional CaO among the scouring agents added to the molten iron (see Equation 1).

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

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

Among molten iron, P moves to the generated slag and becomes P ₂ O ₅ as it reacts with the 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 that it remains in the slag, and thus P is removed from the molten iron.

In this way, when P ₂ O ₅ absorbed into the slag is dissolved in the slag, the slag produced by the refining agent according to the embodiment 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 the liquid CaO in the slag, and remains stably in the slag, and the other part of P ₂ O ₅ is in the solid crystal of Ca ₂ SiO ₄ It is substituted and mixed and becomes a solid solution in the form of Ca ₂ SiO ₄ -Ca ₃ P ₂ O ₈ , so that it stably remains in the slag.

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

In addition, by recycling the differentiated slag generated during the steelmaking process to prepare a refining agent, it is possible to reduce the cost for preparing the refining agent, thereby enabling a low-cost refining operation.

And, as the differentiated slag is recycled as a refining agent, it is possible to reduce the cost required for the burial of the differentiated slag.

Claims (15)

As a scouring agent that removes at least P (phosphorus) among impurities contained in molten iron,
It is the differentiated slag generated in the steelmaking process, and contains additional CaO in addition to the differentiated slag in which Ca ₂ SiO ₄ is precipitated and the above differentiated slag,
A scouring agent having a mass ratio (additional CaO mass/differentiated slag mass) of 1.0 or more and 2.6 or less, and a melting point of 1600°C to 1700°C. The method according to claim 1,
The differentiated slag is a scouring agent containing CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ . The method according to claim 2,
Of the differentiated slag, CaO is 49wt% to 62wt%, SiO ₂ is 22wt% to 38wt%, MgO is 20wt% or less, Al ₂ O ₃ is 10wt% or less, CaF ₂ is 3wt% to 10wt%, S is 0.3wt % Or more, 1wt% or less, FeO is 5wt% or less, Cr ₂ O ₃ A scouring agent containing 5wt% or less. delete delete The method according to any one of claims 1 to 3,
A scouring agent for removing S (sulfur) along with P (phosphorus) among impurities contained in the molten iron by adjusting the mass ratio of the additional CaO and the differentiated slag (additional CaO mass/differentiated slag mass) to more than 2.1 and not more than 2.6. The method according to any one of claims 1 to 3,
The differentiated slag, using Si and CaO, a refining agent comprising the cooled slag generated in the process of refining molten iron. The process of supplying oxygen by molten iron;
A dephosphorization process of removing P (phosphorus) from the molten iron by adding a scouring agent having a melting point of 1600°C to 1700°C, including the differentiated slag in which Ca ₂ SiO ₄ is precipitated and additional CaO;
Including,
The refining agent is a molten iron refining method in which a mass ratio (additional CaO mass/differentiated slag mass) of the additional CaO and differentiated slag is 1.0 or more and 2.6 or less. The method of claim 8,
The differentiated slag is a molten iron refining method comprising CaO, SiO ₂ , MgO, Al ₂ O ₃ , CaF ₂ , S, FeO, Cr ₂ O ₃ . delete The method of claim 8,
When the P content of the molten iron is 300 ppm or more and less than 600 ppm, the mass ratio (additional CaO mass/differentiated slag mass) of additional CaO and differentiated slag added to the molten iron is 1.0 or more and less than 1.5,
When the P content of the molten iron is 600 ppm or more and less than 1000 ppm, the mass ratio (additional CaO mass/differentiated slag mass) of additional CaO and differentiated slag added to the molten iron is 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 of the additional CaO and the differentiated slag (additional CaO mass/differentiated slag mass) to be added to the molten iron is 2.2 or more and 2.6 or less. The method of claim 8,
Including the process of adding CaF ₂ to the molten iron,
The amount of CaF ₂ input into the molten iron is a method of refining a hot metal in which 15% of the amount of the additional CaO input into the molten iron is added. The method of claim 11,
In the dephosphorization process, degassing to remove S (sulfur) in the molten iron is performed together,
In performing the dephosphorization and degassing together, a hot metal refining method in which the mass ratio of the additional CaO and the differentiated slag (additional CaO mass/differentiated slag mass) exceeds 2.1. The method of claim 13,
Including the process of calculating the mass ratio (additional CaO mass/differentiated slag mass) of the additional CaO and differentiated slag for the degassing,
In calculating the mass ratio (additional CaO mass/differentiated slag mass) for the degassing, the amount of S (sulfur) to be removed (wt%) is applied to the degassing amount of the following equation. Refining method.
[Equation]

The method of claim 14,
In the dephosphorization process, in carrying out degassing to remove S (sulfur) in the molten iron,
Among the mass ratios of additional CaO and differentiated slag according to the content of P in the molten iron (additional CaO mass/differentiated slag mass), and the mass ratio of additional CaO and differentiated slag for degassing (additional CaO mass/differentiated slag mass), relatively A hot metal refining method in which the additional CaO and differentiated slag are added so as to have a large mass ratio.

Images