KR102173170B1 - Mold flux and casting method using the same - Google Patents

Abstract

The present invention relates to a mold flux and a casting method using the same, and more particularly, to a mold flux capable of improving the quality and productivity of cast steel and a casting method using the same.
The mold flux according to the embodiment of the present invention is a mold flux used for casting of steel, based on the total weight %, 15 to 20% by weight of calcium oxide (CaO), 18 to 50% by weight of silicon oxide (SiO ₂ ), 5 to 15% by weight of fluorine (F), and 3 to 10% by weight of at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O).

Description

Mold flux and casting method using the same {MOLD FLUX AND CASTING METHOD USING THE SAME}

The present invention relates to a mold flux and a casting method using the same, and more particularly, to a mold flux capable of improving the quality and productivity of cast steel and a casting method using the same.

The casting process is a process of injecting molten steel into a mold having a certain internal shape, and continuously drawing the cast slab solidified in the mold to the lower side of the mold to manufacture semi-finished products of various shapes such as slabs, blooms, billets, and beam blanks.

In the casting process, mold flux is injected into the molten steel in the mold, and the mold flux injected onto the molten steel flows into the gap between the mold and the solidification shell, and comes into contact with the water-cooled mold, thereby providing a lubricating action that prevents the fracture of the solidified cast piece. do.

In addition to the lubricating action, the mold flux also serves to keep the molten steel warm by absorbing and dissolving non-metallic inclusions separated from the molten steel, preventing reoxidation of the molten steel, and suppressing the release of heat to the atmosphere.

On the other hand, the electrical steel sheet is a soft magnetic material made of superior electromagnetic properties compared to other steel materials, as a result of reducing iron loss, which represents the amount of energy lost as heat during energy exchange between electricity and magnetism by adding silicon. At this time, in order to increase electromagnetic properties such as reduction of iron loss of the material and improvement of magnetic flux density, a method of increasing the content of silicon (Si) and aluminum (Al) in the steel material is mainly used.

However, in the case of casting steel containing a large amount of silicon (Si) and aluminum (Al), the main component of the mold flux, silicon oxide (SiO ₂ ), and the aluminum (Al) component in the molten steel react, and the mold flux The content of silicon oxide (SiO ₂ ) decreases, and the content of aluminum oxide (Al ₂ O ₃ ) increases, and its composition changes.

As described above, when a change occurs in the components in the mold flux, the melting point of the mold flux rapidly increases to form a solid slag having a high melting point crystalline phase. In addition, the viscosity of the mold flux increases, so that the mold flux does not flow smoothly between the molten steel and the mold. Therefore, the mold flux loses the lubricating function, and as a result, there is a problem that stable casting is difficult.

KR 10-2002-0044233 A

The present invention provides a mold flux capable of minimizing a change in components of the mold flux during a casting process and a casting method using the same.

In addition, the present invention provides a mold flux capable of improving casting efficiency and a casting method using the same.

The mold flux according to the embodiment of the present invention is a mold flux used for casting of steel, and based on the total weight %, calcium oxide (CaO) is 15 to 20% by weight, silicon oxide (SiO ₂ ) is 18 to 50% by weight. , 5 to 15% by weight of fluorine (F) and 3 to 10% by weight of at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O).

The mold flux may have a basicity (CaO/SiO ₂ ) of 0.4 to 0.8.

Based on the total weight %, the lithium oxide (Li ₂ O) may be included in an amount of 4 to 6 wt %, and the potassium oxide (K ₂ O) may not be included.

Based on the total weight %, the potassium oxide (K ₂ O) may be included in an amount of 5 to 7 wt %, and the lithium oxide (Li ₂ O) may not be included.

With respect to the total weight %, sodium oxide (Na ₂ O) may be further included in an amount of 10% by weight or less.

The lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are all included, and the lithium oxide (Li ₂ O) and the potassium oxide (K ₂ O) are 8 to 10% by weight based on the total weight %. Can include.

With respect to the total weight %, the lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) may be included in an amount calculated from Equation 1 below.

[Equation 1]

K = a×L + b

(Where a is -0.7 to -0.8, b has a value of 7 to 9, L is the weight% of the lithium oxide (Li ₂ O) relative to the total weight%, K is the potassium oxide relative to the total weight% It represents the weight% of (K ₂ O).)

Based on the total weight %, 5% by weight or less of boron oxide (B ₂ O ₃ ) may be further included.

The mold flux may not contain aluminum oxide (Al ₂ O ₃ ).

In addition, the casting method according to an embodiment of the present invention, the process of preparing the mold flux described in any one of the above; Injecting molten steel into the mold; And a process of casting a cast steel by supplying a mold flux to the upper part of the molten steel.

The cast steel may contain 1 to 3.5% by weight of silicon (Si) and 0.5 to 2.5% by weight of aluminum (Al) based on the total weight %.

In the process of casting the cast, the mold flux flows between the solidified shell formed from the molten steel and the mold, and the mold flux introduced between the solidified shell and the mold is 50% by weight or less of solid slag based on the total weight%. Can be formed.

The process of casting the cast steel may be performed continuously with respect to a ladle filled with the molten steel a plurality of times.

The cast slab may include an electrical steel sheet used in an electric device.

According to a mold flux according to an embodiment of the present invention and a casting method using the same, in order to control the melting point of the mold flux, at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) is used to form a mold during the casting process. It is possible to minimize changes in the components of the flux.

In addition, it is possible to prevent the formation of solid slag having a composition of CaO-Na ₂ O-Al ₂ O ₃ that impairs the lubrication performance by minimizing the sodium oxide (Na ₂ O) component in the mold flux. Can improve quality.

1 is a diagram showing a state in which mold flux is introduced during a casting process.
2 is a view showing a state in which the mold flux flowing between the solidified shell and the mold forms solid slag.
3 is a view showing a casting result according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only the embodiments of the present invention 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 fully inform you. In the drawings, the same reference numerals refer to the same elements.

1 is a diagram showing a state in which mold flux is introduced during a casting process.

Referring to FIG. 1, in the casting process, when molten steel entrained in a tundish (not shown) flows into the mold 20 through the immersion nozzle 10, solidification of the molten steel starts in the water-cooled mold 20 And the intermediate product, cast iron, is obtained. At this time, mold flux is injected onto the molten steel in the mold 20 to form a powder layer P in a non-melted state and a slag layer S in a molten state, and the liquid slag layer S is a mold ( It flows into the gap between 20) and the solidification shell (I). In this way, the slag layer (S) introduced into the gap between the mold 20 and the solidification shell (I) is washed down by the cooling water sprayed to cool the cast steel while descending along with the cast steel drawn in the downward direction of the casting facility. Is consumed.

The mold flux is an artificial synthetic slag in the form of powder or granules that is injected onto the molten steel M, and acts as a lubricating function to prevent fracture of the solidified cast piece by contact with the water-cooled mold 20. In addition to the lubricating action, the mold flux serves to keep the molten steel (M) warm by absorbing and dissolving non-metallic inclusions separated from the molten steel (M), preventing reoxidation of the molten steel, and suppressing the release of heat to the atmosphere. Hereinafter, it will be described in detail with respect to the component of the mold flux according to an embodiment of the present invention.

The mold flux according to the embodiment of the present invention is a mold flux used for casting of steel, based on the total weight %, 15 to 20% by weight of calcium oxide (CaO), 18 to 50% by weight of silicon oxide (SiO ₂ ), 5 to 15% by weight of fluorine (F), and 3 to 10% by weight of at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O). In addition, the mold flux may contain inevitable impurities in addition to calcium oxide (CaO), silicon oxide (SiO ₂ ), and alkali metal oxides, due to the characteristics of being manufactured from ore raw materials.

Calcium oxide (CaO) and silicon oxide (SiO ₂ ) are components for controlling the basicity (CaO/SiO ₂ ) of the mold flux.

Calcium oxide (CaO) may be included in an amount of 15% by weight or more and 20% by weight or less based on the total weight% of the mold flux. If the content of calcium oxide (CaO) is less than 15% by weight, the basicity (CaO/SiO ₂ ) is extremely low and the viscosity of the mold flux increases, making it difficult to obtain a required viscosity value for lubrication. In addition, if the content of calcium oxide (CaO) exceeds 20% by weight, silicon oxide (SiO ₂ ) is consumed by the reaction with molten steel, so that the basicity (CaO/SiO ₂ ) increases, and a high melting point crystal phase can be formed. Therefore, calcium oxide (CaO) may be included in an amount of 15 to 20% by weight based on the total weight%.

Silicon oxide (SiO ₂ ) may be included in an amount of 18% by weight or more and 50% by weight or less based on the total weight% of the mold flux. If the content of silicon oxide (SiO ₂ ) is less than 18% by weight, the basicity (CaO/SiO ₂ ) increases and a high melting point crystal phase may be formed, and if the content of silicon oxide (SiO ₂ ) exceeds 50% by weight, Since the viscosity increases due to low basicity, the lubricating ability of the mold flux may be lowered, and silicon oxide (SiO ₂ ) may be included in an amount of 18 to 50% by weight based on the total weight%.

Here, the content of calcium oxide (CaO) and silicon oxide (SiO ₂ ) may be controlled so that the mold flux has a basicity (CaO/SiO ₂ ) of 0.4 or more and 0.8 or less. That is, if the basicity (CaO/SiO ₂ ) of the mold flux is less than 0.4, the viscosity of the mold flux increases and the inflow of the mold flux between the solidified shell and the mold 20 decreases. It is easy to cause an accident called out). In addition, if the basicity (CaO/SiO ₂ ) of the mold flux exceeds 0.8, the melting point of the mold flux increases, which impairs the lubrication performance, and it is not possible to stably maintain the mold flux layer on the molten steel. Due to the re-oxidation, the amount of inclusions is locally increased, which is liable to lead to surface defects.

Fluorine (F) is a component for suppressing heat transfer by crystallizing cuspidine (Cuspidine, 3CaO-2SiO ₂ -CaF ₂ ) as the main crystal phase, and is 5% by weight or more and 15% by weight or less based on the total weight% of the mold flux. Can be included as Here, if the content of fluorine (F) is less than 5% by weight, the solidification temperature decreases, resulting in an increase in the amount of heat and the initial slow cooling. If it exceeds 15% by weight, there is no change in the melting point of the slag, but the viscosity is too low. The consumption of flux increases rapidly and may cause surface defects of the cast steel.

The mold flux may further include boron oxide (B ₂ O ₃ ). Boron oxide (B ₂ O ₃ ) has the effect of inhibiting the formation of a high melting point crystal phase, but when it is contained in excess of 5% by weight, it rather promotes the formation of the crystal phase, including boron oxide (B ₂ O ₃ ). In this case, it may be included in an amount greater than 0% by weight and less than 5% by weight based on the total weight% of the mold flux.

Meanwhile, the mold flux may not contain aluminum oxide (Al ₂ O ₃ ). When casting a steel containing a large amount of silicon (Si) and aluminum (Al) as described later, the mold flux is denatured in its components, and aluminum oxide (Al ₂ O ₃ ) is continuously generated. The flux may be prepared and introduced in a state that does not contain aluminum oxide (Al ₂ O ₃ ). Here, since the mold flux may contain inevitable impurities, it goes without saying that a trace amount of aluminum oxide (Al ₂ O ₃ ) may be included.

Lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are components for controlling the melting point of the mold flux, and at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) is the total weight of the mold flux. It may be included in an amount of 3% by weight or more and 10% by weight or less based on %.

In the case of manufacturing an electrical steel sheet used in electric devices by increasing the content of silicon (Si) and aluminum (Al) among the steel components, silicon (Si) is 1% by weight or more, 3.5% by weight based on the total weight of the molten steel. % Or less, and aluminum (Al) is contained in an amount of 0.5% by weight or more and 2.5% by weight or less based on the total weight% of molten steel. Such an electrical steel sheet contains a large amount of silicon (Si) and aluminum (Al) and is mainly used for high-efficiency motors for electric vehicles. However, in the case of casting a steel containing a large amount of silicon (Si) and aluminum (Al) as described above, the mold flux is the main components of silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) as follows: As a result, degeneration occurs.

[Reaction Scheme]

SiO ₂ (Mold Flux) + Al (Molten Steel) → Si (Molten Steel) + Al ₂ O ₃ (Mold Flux)

As a result of the reaction according to the above reaction equation, the content of silicon oxide (SiO ₂ ) in the mold flux decreases, and the content of aluminum oxide (Al ₂ O ₃ ) increases. At this time, if a large amount of sodium oxide (Na ₂ O) is contained in the mold flux, sodium oxide (Na ₂ O) reacts with calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ) components in the mold flux, resulting in CaO- A solid slag made of a high melting point compound having a composition of Na ₂ O-Al ₂ O ₃ is formed. Thus, in order to suppress the reaction of sodium oxide (Na ₂ O) with calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ) components in the mold flux, the sodium oxide (Na ₂ O) component in the mold flux is minimized. Needs to be.

Accordingly, in an embodiment of the present invention, in order to minimize the content of sodium oxide (Na ₂ O), the mold flux is included in a predetermined amount of at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O). It can be prepared to minimize the formation of solid-state slag of CaO-Na ₂ O-Al ₂ O ₃ from the mold flux.

In the first embodiment of the present invention, an embodiment in which only lithium oxide (Li ₂ O) is used among lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) will be described.

That is, the mold flux may contain lithium oxide (Li ₂ O) in an amount of 3% by weight or more and 10% by weight or less, and may not contain potassium oxide (K ₂ O). If the content of lithium oxide (Li ₂ O) is less than 3% by weight, if sodium oxide (Na ₂ O) is not separately used, the melting point of the mold flux cannot be sufficiently controlled, and the melting point of the mold flux increases, When used together with sodium oxide (Na ₂ O), there is still a problem in that solid slag made of a compound having a high melting point having a composition of CaO-Na ₂ O-Al ₂ O ₃ is formed. In addition, when the content of lithium oxide (Li ₂ O) exceeds 10% by weight, a high melting point compound having a composition of Li ₂ O-Al ₂ O ₃ is formed.When only lithium oxide (Li ₂ O) is used Lithium oxide (Li ₂ O) may be included in an amount of 3 to 10% by weight, and lithium oxide (Li ₂ O) is 4% by weight in order to further lower the formation rate of solid slag to about 45% by weight as shown in Table 1 below. % Or more and 6% by weight or less.

In addition, in the second embodiment of the present invention, an embodiment in which only potassium oxide (K ₂ O) among lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) is used will be described.

The mold flux may contain 3% by weight or more and 10% by weight or less of potassium oxide (K ₂ O) based on the total weight %, and may not contain lithium oxide (Li ₂ O). If the content of potassium oxide (K ₂ O) is less than 3% by weight, if sodium oxide (Na ₂ O) is not separately used, the melting point control of the mold flux becomes insufficient, and it is used with sodium oxide (Na ₂ O). In this case, there is a problem in that solid slag formed of a compound having a high melting point having a composition of CaO-Na ₂ O-Al ₂ O ₃ as in the first embodiment is formed. In addition, when the content of potassium oxide (K ₂ O) exceeds 10% by weight, a high melting point compound having a composition of K ₂ O-Al ₂ O ₃ and K ₂ O-SiO ₂ -Al ₂ O ₃ is formed. , the case of using only the potassium (K ₂ O) potassium oxide (K ₂ O) may be included from 3 to 10% by weight oxide, the more the formation rate of the solid slag, as shown in Table 2 below to about 45% by weight To lower the potassium oxide (K ₂ O) may be included in an amount of 5% by weight or more and 7% by weight or less.

In addition, in the third embodiment of the present invention, an embodiment in which both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are used among lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) will be described. .

Here, even when both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are used, the sum of the content of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) is the total weight of the mold flux. It may be included in an amount of 3 to 10% by weight based on %. However, when both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are used, the melting point control of the mold flux is less than 8% by weight of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O). Not enough, or solid slag consisting of a high melting point compound having a composition of CaO-Na ₂ O-Al ₂ O ₃ is formed, and lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) exceed 10% by weight In this case, a high melting point compound having a composition of Li ₂ O-Al ₂ O ₃ , K ₂ O-Al ₂ O ₃ or K ₂ O-SiO ₂ -Al ₂ O ₃ may be generated. Therefore, when both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are included, the lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are 8% by weight or more, 10% by weight based on the total weight%. % Or less, and lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are 8.5% by weight or more, in order to further lower the formation rate of solid slag to about 45% by weight, as shown in Table 3 below, It may be contained in 9.5% by weight or less.

Here, when the mold flux contains both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O), the lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are based on the total weight% of the mold flux. , The lithium oxide (Li ₂ O) and the potassium oxide (K ₂ O) may be included in a content relationship calculated from Equation 1 below.

[Equation 1]

K = a×L + b

(Where a is -0.7 to -0.8, b has a value of 7 to 9, L is the weight% of the lithium oxide (Li ₂ O) relative to the total weight%, K is the potassium oxide relative to the total weight% It represents the weight% of (K ₂ O).)

In the case where the mold flux contains both lithium oxide (Li ₂ O) and the potassium oxide (K ₂ O), the above equation 1 is an appropriate ratio of solid slag formed from the mold flux, for example, 50% by weight or less The relationship between the content of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) that satisfies is regressively derived, and a description thereof will be described later with reference to Table 3.

In the case of each embodiment of the present invention described above, the alkali metal oxide may further include 10% by weight or less of sodium oxide (Na ₂ O). Here, sodium oxide (Na ₂ O) may not be included in the alkali metal oxide, and even when included, the content thereof is controlled to be greater than 0% by weight and less than 10% by weight based on the total weight% of the mold flux. As described above, sodium oxide (Na ₂ O) has the effect of lowering the viscosity of the mold flux as the content of sodium oxide (Na ₂ O) is added. However, when casting molten steel with a high content of silicon (Si) and aluminum (Al), CaO- To form a solid slag made of a high melting point compound having a composition of Na ₂ O-Al ₂ O ₃ , sodium oxide (Na ₂ O) may be contained in an amount of 10% by weight or less, and the content of sodium oxide (Na ₂ O) Sodium oxide (Na ₂ O) may be included in an amount of 7% by weight or less in order to minimize and effectively reduce the proportion of solid slag formed from the mold flux.

Hereinafter, a casting method according to an embodiment of the present invention will be described in detail. Here, a description that overlaps with the above-described contents in relation to the mold flux according to the embodiment of the present invention will be omitted.

The casting method according to an embodiment of the present invention includes the process of preparing the above-described mold flux, the process of injecting molten steel into the mold 20, and the process of casting a cast iron by supplying the mold flux to the upper portion of the molten steel.

First, in the process of preparing the mold flux, based on the total weight% of the mold flux, calcium oxide (CaO) is 15 to 20% by weight, silicon oxide (SiO ₂ ) is 18 to 50% by weight, and fluorine (F) is 5 to 20% by weight. A mold flux containing 15% by weight and 3 to 10% by weight of at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) is prepared. In this case, the mold flux may further include 5% by weight or less of boron oxide (B ₂ O ₃ ), and may not include aluminum oxide (Al ₂ O ₃ ). Furthermore, the mold flux is lithium oxide (Li ₂ O) is 4 to 6% potassium oxide by weight when containing only lithium (Li ₂ O) oxidation of the lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) (K ₂ O) potassium oxide (K ₂ O) is 5 to 7% by weight, potassium oxide (K ₂ O) and lithium oxide (Li ₂ O) in the case of containing both potassium oxide (K ₂ O) and oxidation Lithium (Li ₂ O) may be included in 8 to 10% by weight as described above.

In the process of preparing molten steel, silicon (Si) is contained in an amount of 1% by weight or more and 3.5% by weight or less, and aluminum (Al) is contained in an amount of 0.5% by weight or more and 2.5% by weight with respect to the total weight% of molten steel through a refining process such as refining. Molten steel containing a large amount of less than% can be prepared. Here, the process of preparing the mold flux and the process of preparing the molten steel do not have a time-series relationship, and it goes without saying that either one of the mold flux and the molten steel may be prepared first, or the mold flux and the molten steel may be prepared simultaneously.

When the mold flux and molten steel are provided, molten steel M is injected into the mold 20 using the immersion nozzle 10 through a ladle and a tundish. Then, when the molten steel M is injected into the mold 20, a mold flux is supplied to the upper portion of the molten steel M to cast a cast iron.

The mold flux supplied to the upper part of the molten steel (M) is at least partially dissolved by the sensible heat of the molten steel (M), thereby forming a liquid slag layer (S). In this case, a powder layer P may be formed on the slag layer S. The liquid slag layer (S) flows into the gap between the mold 20 and the solidification shell (I), and performs a lubricating action between the solidified (solidified shell) cast steel and the mold 20, and the cast steel is cast. .

Here, when casting a cast steel using molten steel containing 1% by weight or more and 3.5% by weight or less of silicon (Si) and 0.5% by weight or more and 2.5% by weight or less of aluminum (Al), the mold flux Silicon oxide (SiO ₂ ), a main component of, reacts with aluminum (Al) in molten steel to produce aluminum oxide (Al ₂ O ₃ ). At this time, in the casting method according to an embodiment of the present invention it is sodium (Na ₂ O) the reaction of aluminum oxide produced by the same and the by sodium (Na ₂ O) oxidation to minimize the components oxide contained in the mold flux (Al ₂ O It can prevent the combination with ₃ ). That is, in order to control the melting point of the mold flux, at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) can be used to effectively suppress the change in the components of the mold flux caused by sodium oxide (Na ₂ O). have. In addition, the formation of solid slag having a composition of CaO-Na ₂ O-Al ₂ O ₃ is prevented by minimizing the sodium oxide (Na ₂ O) component, and the total weight% of the mold flux flowing between the solidified shell and the mold 20 It can be controlled to form a solid slag of 50% by weight or less.

Hereinafter, an experimental example of casting a cast steel by a casting method according to an embodiment of the present invention will be described.

First, the content of calcium oxide (CaO) and silicon oxide (SiO ₂ ) is controlled so that the basicity (CaO/SiO ₂ ) of the mold flux has 0.4 to 0.8, and fluorine (F) is 6.7 with respect to the total weight% of the mold flux. A mold flux containing 3.5 wt% of boron oxide (B ₂ O ₃ ) and at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) was prepared. The prepared mold flux was heated to about 1500° C. to sufficiently melt it into a liquid state, and then maintained at about 1000° C. to measure the proportion of solid slag consisting of a high melting point crystal phase formed from the mold flux.

Here, Table 1 below shows the results of experiments using only lithium oxide (Li ₂ O) among lithium oxide (Li ₂ O) and potassium oxide (K ₂ O). Here, the solid slag ratio refers to the weight% ratio of the solid slag formed between the solidified shell (I) and the mold 20 to the entire mold flux introduced between the solidified shell (I) and the mold 20.

[Table 1]

As shown in Table 1, when lithium oxide (Li ₂ O) is included in an amount of 3 to 10% by weight based on the total weight% of the mold flux, it is found that the solid slag ratio at about 1000°C is maintained at 50% by weight or less. I can. That is, when the content is reduced so that sodium oxide (Na ₂ O) is included in 6.5% by weight, and lithium oxide (Li ₂ O) is included in 3% by weight (Example 1-1), the solid slag is about 50 It was found that it was formed in a proportion of weight percent. In addition, lithium oxide (Li ₂ O) is 4% by weight (Example 1-2), 5.5% by weight (Example 1-3), 7% by weight (Example 1-4), 8% by weight (Example 1 Even when included as -5), it was found that the solid slag was formed in a ratio of about 45% by weight or 50% by weight. Here, it can be seen that when lithium oxide (Li ₂ O) is included in an amount of 4 to 6% by weight, the formation rate of solid slag can be minimized to about 45% by weight.

On the other hand, when lithium oxide (Li ₂ O) is contained in an amount of less than 3% by weight with respect to the total weight% of the mold flux, that is, when lithium oxide (Li ₂ O) is contained in 2.1% by weight (Comparative Example 1-1), the solid state The slag will increase at a rate of 60% by weight. In addition, when lithium oxide (Li ₂ O) is contained in excess of 10% by weight relative to the total weight% of the mold flux, that is, when lithium oxide (Li ₂ O) is included in 11% by weight (Comparative Example 1-2) It can be seen that the proportion of solid slag increases rapidly to 75% by weight.

In addition, Table 2 below shows the experimental results using only potassium oxide (K ₂ O) among lithium oxide (Li ₂ O) and potassium oxide (K ₂ O).

[Table 2]

As shown in Table 2, when potassium oxide (K ₂ O) is included in an amount of 3 to 10% by weight based on the total weight% of the mold flux, it is found that the solid slag ratio at about 1000°C is maintained at 50% by weight or less. I can. That is, when the content is reduced so that sodium oxide (Na ₂ O) is included in 6.5% by weight, and potassium oxide (K ₂ O) is included in 4% by weight (Example 2-1), the solid slag is about 50 It was found that it was formed in a proportion of weight percent. In addition, potassium oxide (K ₂ O) was 5.5 wt% (Example 2-2), 7 wt% (Example 2-3), 8 wt% (Example 2-4), 10 wt% (Example 2 Even when included as -5), it was found that the solid slag was formed in a ratio of about 45% by weight or 50% by weight. Here, it can be seen that when the potassium oxide (K ₂ O) is included in an amount of 5 to 7% by weight, the formation rate of solid slag can be minimized to about 45% by weight.

On the other hand, when potassium oxide (K ₂ O) is contained in less than 3% by weight relative to the total weight% of the mold flux, that is, when potassium oxide (K ₂ O) is included in 2% by weight (Comparative Example 2-1), the solid state The slag will increase at a rate of 55% by weight. In addition, when potassium oxide (K ₂ O) is contained in excess of 10% by weight relative to the total weight% of the mold flux, that is, when lithium oxide (Li ₂ O) is included in 12% by weight (Comparative Example 2-2) It can be seen that the proportion of solid slag increases rapidly to 65% by weight.

In addition, Table 3 below shows the experimental results using both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O).

[Table 3]

As shown in Table 3, when lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are included in an amount of 3 to 10% by weight based on the total weight% of the mold flux, the solid slag ratio at about 1000°C is 50 It can be seen that there is a change from wt% to 60 wt%. That is, lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) were 6% by weight (Example 3-1), 7.5% by weight (Example 3-2), and 8% by weight (Example 3-3). , 9.1 wt% (Example 3-4), 10 wt% (Example 3-5) When included in the solid slag ratio is changed in the range of 45% by weight to 60% by weight. At this time, in order to maintain the proportion of solid slag below 50% by weight, lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) may be included in an amount of 8 to 10% by weight based on the total weight%, and lithium oxide ( Li ₂ O) and potassium oxide (K ₂ O) in the case of including 8.5 to 9.5% by weight, it can be seen that the formation rate of solid slag can be minimized to about 45% by weight.

On the other hand, when lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are contained in excess of 10% by weight with respect to the total weight% of the mold flux, that is, lithium oxide (Li ₂ O) and potassium oxide (K ₂ O ) Is included in 11% by weight (Comparative Example 3-1) and 12% by weight (Comparative Example 3-2), it can be seen that the ratio of solid slag increases rapidly to 55% by weight or 65% by weight.

Here, when lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are included in 8% by weight (Example 3-3), lithium oxide (Li ₂ O) is included in about 2% by weight, and oxidation Potassium (K ₂ O) is included in about 6% by weight. In addition, when lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are included in an amount of 9.1% by weight (Example 3-4), lithium oxide (Li ₂ O) is included in an amount of about 3.5% by weight, and oxidation Potassium (K ₂ O) is included in about 5.6% by weight. In addition, in addition, when lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are included in an amount of 10% by weight (Example 3-5), lithium oxide (Li ₂ O) is included in an amount of about 6% by weight. And potassium oxide (K ₂ O) is included in about 4% by weight. Thus, when both lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) are included as alkali metal oxides, the content of potassium oxide (K ₂ O) decreases as the content of lithium oxide (Li ₂ O) increases. The content relationship can be controlled so that the above-described equation 1 is satisfied when regressively deriving the content relationship of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) in which the ratio of solid slag is 50% by weight or less. I can see what it says.

Here, the reason for controlling the solid slag to be formed at 50% by weight or less with respect to the total weight% of the mold flux flowing between the solidified shell (I) and the mold 20 can be seen from FIG. 2. That is, as shown in Figure 2 (a), when the mold flux flowing between the solidified shell (I) and the mold (20) forms a solid slag exceeding 50% by weight based on the total weight%, the solid slag is cast It can be seen that it breaks during the process and loses its lubrication function. On the other hand, as shown in Fig.2(b), when the mold flux flowing between the solidification shell (I) and the mold 20 is formed in 50% by weight or less based on the total weight%, the cast steel is liquid slag of 50% by weight or more. As a result, the lubrication proceeds smoothly and can be cast.

In addition, when the mold flux flowing between the solidified shell (I) and the mold 20 is 50% by weight or less based on the total weight%, the process of casting the cast steel may be continuously performed for the ladle filled with the molten steel multiple times. .

In Figure 3, the casting result of a comparative example using a mold flux containing only sodium oxide (Na ₂ O) without lithium oxide (Li ₂ O) and potassium oxide (K ₂ O), and oxidation in an amount of 8.5 to 9.5% by weight Casting results of the examples using a mold flux containing both lithium (Li ₂ O) and potassium oxide (K ₂ O) were compared.

As shown in a comparative example in FIG. 3(a), when the mold flux introduced between the solidification shell (I) and the mold 20 contains only sodium oxide (Na ₂ O), continuous casting is difficult, so that it is accommodated in one ladle. Casting proceeded only for molten steel and casting was completed. At this time, the solid slag exhibited a formation rate of 99% by weight after one casting was performed as shown in the comparative example in FIG. 3(b).

On the other hand, when the mold flux introduced between the solidification shell (I) and the mold 20 contains lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) as shown in the example in FIG. 3 (a) 3 It was possible to continuously cast the molten steel accommodated in the two ladles. At this time, it was found that the solid slag exhibited a formation rate of 48% by weight even after three castings were performed, as shown in the example of FIG. 3(b), so that the lubricating performance was maintained.

As described above, according to the mold flux and the casting method using the same according to the embodiment of the present invention, casting using at least one of lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) to control the melting point of the mold flux It is possible to minimize the change in the components of the mold flux during the process.

In addition, it is possible to prevent the formation of solid slag having a composition of CaO-Na ₂ O-Al ₂ O ₃ that impairs the lubrication performance by minimizing the sodium oxide (Na ₂ O) component in the mold flux. Can improve quality.

In the above, preferred embodiments of the present invention have been described and illustrated using specific terms, but such terms are only for clearly describing the present invention, and embodiments of the present invention and the described terms are the technical spirit of the following claims. And it is obvious that various changes and changes can be made without departing from the scope. Such modified embodiments should not be individually understood from the spirit and scope of the present invention, and should be said to fall within the scope of the claims of the present invention.

10: immersion nozzle 20: mold

Claims (14)

As a mold flux used in the casting of steel,
Based on the total weight %, calcium oxide (CaO) is 15 to 20% by weight, silicon oxide (SiO ₂ ) is 18 to 50% by weight, fluorine (F) is 5 to 15% by weight, and lithium oxide (Li ₂ O) Potassium oxide (K ₂ O) is included in an amount of 8 to 10% by weight,
A mold flux containing lithium oxide (Li ₂ O) and potassium oxide (K ₂ O) in an amount calculated from Equation 1 below with respect to the total weight %.
[Equation 1]
K = a×L + b
(Where a is -0.7 to -0.8, b has a value of 7 to 9, L is the weight% of the lithium oxide (Li ₂ O) relative to the total weight%, K is the potassium oxide relative to the total weight% It represents the weight% of (K ₂ O).) The method according to claim 1,
The mold flux is a mold flux having a basicity (CaO/SiO ₂ ) of 0.4 to 0.8. delete delete The method according to claim 1,
Mold flux further comprising 10% by weight or less of sodium oxide (Na ₂ O) based on the total weight %. delete delete The method according to claim 1,
Mold flux further comprising 5% by weight or less of boron oxide (B ₂ O ₃ ) based on the total weight %. The method according to claim 1,
The mold flux is a mold flux that does not contain aluminum oxide (Al ₂ O ₃ ). The process of preparing the mold flux according to any one of claims 1, 2, 5, and 8 to 9;
Injecting molten steel into the mold; And
Casting method comprising; the process of casting a cast steel by supplying a mold flux to the upper part of the molten steel. The method of claim 10,
The casting method contains 1 to 3.5% by weight of silicon (Si) and 0.5 to 2.5% by weight of aluminum (Al) based on the total weight %. The method of claim 10,
In the process of casting the cast steel,
The mold flux is introduced between the solidification shell formed from the molten steel and the mold,
The casting method in which the mold flux introduced between the solidified shell and the mold forms a solid slag of 50% by weight or less based on the total weight%. The method of claim 10,
The process of casting the cast steel,
A casting method made continuously for a ladle filled with the molten steel in a plurality of circuits. The method of claim 10,
The casting method, wherein the cast steel sheet is used in an electric device.

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