KR100944407B1 - Mold flux for continuous casting of high al steel grade - Google Patents

Abstract

PURPOSE: A mold flux for continuous casting of high Al steel is provided to prevent an accident during operating, and to prevent a high fusion point compound from being created. CONSTITUTION: A mold flux for continuous casting of high Al steel comprises CaO 10.7~18.2%, SiO2 35.6~38.9%, MgO 2.5~3.1%, Al2O3 2.7~3.2%, Na2O 15.6~17.7%, F 12.9~13.8%, B2O3 0%, Li2O 2.6~3.2%, and C 5.1~7.1%. The basicity of the mold flux for continuous casting of high Al steel is 0.28 to 0.51. A melting point of the mold flux is 730 to 810°C, and a viscosity is 1.2 to 1.8 poise.

Description

Mold flux for continuous casting of high aluminum steel

The present invention relates to a mold flux suitably used in a continuous casting process of high aluminum steel having a dissolved Al content of 0.1% by weight or more.

Mold flux is an important consumable subsidiary material used as an additive in the continuous casting process of steel, and is injected onto the molten steel surface in the mold to produce a steel shell of good surface quality. The mold flux receives the heat of molten steel to form a molten slag layer, a sintered layer, and an unmelted layer from the bottom, and the slag layer is introduced into the mold and the slab and consumed.

Hereinafter, a product composed of raw materials for achieving required properties is referred to as a mold flux, and a molten state in which the mold flux is dissolved to function is called slag.

The manufacturing composition of the mold flux is based on the weight percent (wt%) of the natural raw material containing the unique chemical component or the melted raw material which is artificially mixed and melted to obtain the required chemical component. Prepare by mixing. All contents of the mold flux and slag configurations below represent weight percent (wt%).

 The produced mold fluxes are classified into granular and powdery forms according to their shape. Granules are prepared by mixing the appropriate amount of raw materials with water together with additives to maintain the granules in a proportion, making them into a suspension solution and then spraying them into the dryer. Are manufactured.

The mold flux applied to the casting process is the same as in FIG. 1, and it is to be noted that the portion is enlarged than it is to explain the mold flux and the molten slag which are the background of the present invention. 1, (5) shows the unmelted powder layer, (6) shows the sintered layer, and (7) shows the molten slag layer. (1) is a mold (Mold), (2) is a path (SEN) through which molten steel is transferred to the mold, (3) represents molten steel, and (4) represents the discharge port of the molten steel, respectively.

 The molten slag introduced between the mold and the solidified slab 12 has a thickness of about 1 mm, which forms two kinds of layers in the horizontal cross section. The high temperature solidification slab performs the lubrication function in the liquid state (8), and the copper plate side in which the coolant flows forms a solid state (9) made of crystalline phase, and then the temperature of the solidification slab decreases. At the bottom of the mold, the entire slag layer is in a solid state. Denoted at 10 is an air gap that occurs when the slab and slag layers contract. Then, the solidified slag attached to the slab through the mold is consumed while being removed by the cooling water sprayed on the slab.

The main function of the mold flux is to improve the initial solidification of the molten steel in the mold. The most important functions of the mold flux are the heat insulation function of the molten steel by the mold flux layer applied on the molten steel, the lubrication function by the slag film introduced between the mold and the slab, and the control of the heat transfer rate. In order to perform these functions well, the properties in the mold flux must be controlled. It controls the melting characteristics of the mold flux for the thermal insulation function, the viscosity and solidification temperature of the slag for the lubrication function, and the crystallization temperature and the degree of crystallization for the heat transfer rate control function. As the casting speed is recently increased, the viscosity is adjusted to secure the inflow of slag for lubrication, and the thermal conductivity control function by the crystallization and solidification temperature of the slag to cool it properly as the hot molten steel injection rate is increased is important. It is becoming. Adjusting the physical properties of such mold flux can be achieved by controlling the constituent chemical components.

Chemical properties that control the above properties and also constitute the mold flux include CaO, SiO ₂ , MgO, Al ₂ O ₃ , Fe ₂ O ₃ , F, Na ₂ O, Li ₂ O, B ₂ O ₃ , fixed carbon Etc. When the components are classified according to the properties controlling the physical properties, fixed carbon (Free C) to control the melt rate, Al ₂ O ₃ , MgO, Na ₂ O, F, Li ₂ O to control the viscosity or solidification temperature And so on.

In particular, the ratio (CaO wt% / SiO ₂ wt%), which is the ratio of the weight% of CaO to the weight% of SiO ₂ , is referred to as basicity. Such basicity controls viscosity, solidification temperature and crystallization degree. That is, as the basicity increases, the solidification temperature, the degree of crystallization and the crystallization temperature increase, and when the basicity decreases, the viscosity increases, and the crystallization behavior shows the opposite trend.

As the content of Al ₂ O ₃ increases, the viscosity and melting point increase, and the solidification temperature decreases. In addition, as the content of fixed carbon increases, the melting rate becomes slow, and as the content of Na ₂ O, F, Li ₂ O, B ₂ O _3, etc. belonging to the melting agent increases, the viscosity and melting temperature (Melting point) Will be lowered.

Based on the above mold flux properties, the content of the components should be appropriately adjusted according to the change in casting conditions such as casting speed and the diversification of molten steel components to show proper physical properties. These mold fluxes are, of course, also known to be affected by changes in casting conditions, which can change the properties of the molten slag.

 The viscosity and crystallization which are important properties related to the present invention among the above-described mold flux properties will be described in more detail.

Viscosity, the physical property of the mold flux, which is important for lubrication of cast steel, is a function of temperature and slag composition, as is known. Viscosity in the composition of components is based on the fact that SiO ₂ molecules are connected in the form of chains and act as a limiting element of slag flow, and the components that modify or modify the chains as mentioned above to flow or strengthen By controlling the viscosity. Therefore, the higher the content of SiO ₂ , that is, the lower the basicity, the higher the viscosity. In addition, the viscosity increases as the content of Al ₂ O ₃ , which is a component that strengthens the bond of the chain, increases. Based on the properties of these components, in order to obtain the required viscosity, it is necessary to add and adjust the fluxes described above. The viscosity of the mold flux thus designed is lower as the molten steel is higher, and becomes higher as the temperature is lowered and eventually solidifies.

 As the slag cools, some of the components combine to form crystals, which act as a barrier to heat transfer from the cast to the mold, a fact well known in mold flux studies to date. The formation of the crystal is made by the thermal energy supplied from the molten steel and the composition of the slag, and the degree of crystal phase created on the surface of the mold side with respect to the transverse thickness of the inflow slag layer is called crystallinity ratio. As the crystal is formed by the chemical composition and the thermal energy, unexpected crystal phases are formed by the components flowing into the slag from the molten steel or generated by the reaction between the molten steel and the slag.

A typical crystal formed from the mold flux is a crystal phase called Cuspidine (3CaO 2 SiO ₂ CaF ₂ ), and when looking at the composition of the crystal phase, CaO and SiO ₂ in the composition participate in crystallization in a large proportion. It can be seen that the composition content of CaO is the most. From this, it can be seen that the formation of the crystal phase is affected by the basicity as described above. More specifically, when the basicity is 1.0 or more, the creation of the cuspine crystal phase increases, and as the crystallinity is large, the heat extraction to the template Since the slab may be soft cooled due to the small size, the liquid slag layer may also be relatively small, which may cause a problem in that lubrication is disadvantageous. On the contrary, when the basicity is 1.0 or less, the viscosity becomes high, so that the flow of components to form crystals becomes difficult, and the content of CaO becomes relatively small, making formation of couspines difficult. The viscosity can be lowered by the addition of flux, but due to the low content of CaO, the formation of cousidine is hardly achieved at a basicity of 1.0 or less. As a result, although it is excellent in performing a lubrication function, it becomes impossible to perform the control function of heat extraction suitably.

For example, in the case of peritectic steel grade, which is a type of molten steel according to the content of C in the molten steel, cracks are frequently generated due to a higher stress generated inside the molten steel than other steel grades. do. The reason for the occurrence of such stress is that the variation of the stress that shrinks due to the thickness of the non-uniform solidified cast piece, and cracks occur in the place where the thickness is thin to solve the variation of the stress. The requirement of the mold flux to control this is to cool the cast slab to make the thickness of the cast slag uniform. In order to achieve a complete cooling of the cast steel as well as various casting conditions, it is necessary to sufficiently control the heat release of the cast steel by sufficient crystallinity of the mold flux.

The present invention is to solve the problem of lubrication of the cast slab, which is a problem of the conventional mold flux generated in the casting of high aluminum steel, to produce a mold flux of a new configuration for this purpose, to suppress the production of high melting point compounds, to prevent the occurrence of operational accidents In addition, it aims to improve the quality of the produced cast steel and to avoid the inconvenience of the production and use of mold flux by avoiding the use of expensive raw materials.

A feature of the present invention resides in constituting a mold flux with a component composition of a region capable of preventing formation of a high melting point binder, which is a problem with conventional mold fluxes. The steel to be applied to the present invention is a high aluminum steel with a dissolved Al content of 0.1% by weight or more, and during continuous casting, the reaction between molten steel and the mold flux is excessively activated according to the following reaction formula, thereby failing to achieve lubrication and complete cooling. It causes problems.

4Al (molten steel) + 3SiO ₂ (slag) → 2Al ₂ O ₃ + 3Si

This reaction shows that Al in molten steel and SiO ₂ in slag react, Al is oxidized and flows into slag in Al ₂ O ₃ state, and SiO ₂ is reduced to Si (metal) and absorbed into molten steel.

When the general mold flux is applied, since the SiO ₂ in the mold flux is consumed by the above reaction, the basicity is increased, the solidification temperature is significantly increased, and the Al ₂ O ₃ component is increased so that the viscosity is rapidly increased. The lack of the SiO ₂ component and the excessive amount of Al ₂ O ₃ make it difficult to form spidine.

Therefore, in order to suppress the above reaction, the SiO ₂ component in the powder is designed to be extremely low, and since the crystallization degree due to couspine is not formed as required, it is not possible to achieve the purpose of complete cooling, thus forming another crystal phase. It is intended to be composed of the composition of the ingredients.

  In addition to the components and physical properties of the slag as described above, in the case of conventional mold fluxes, a high temperature crystal compound is formed, thereby causing a slag bear to grow excessively on the mold wall, which is an operational problem, and thus inflow of the molten slag. This is inhibited. Thus, the overgrowth of the slag bears leads to a lack of lubrication, which causes break out, which is an accident in which the solidified cast steel and the mold copper plate are stuck.

 In general, the slag bear (11 in FIG. 1) is formed by melting molten slag, unmelted mold powder, hot melt formed by reaction, and the like on the molten slag in contact with the mold copper plate and cooling to solidify. If the slag bear is small, it is not a problem, but if the slag bear is large, it is not found or if it is not removed in a timely manner, breakout occurs. In the case of the conventional mold flux, the slag bear is overgrown because the high temperature crystal compounds formed during the reaction with molten steel do not dissolve and adhere to the slag bear.

In the known technique for the mold flux used for continuous casting of high aluminum steel, the content of SiO ₂ is designed to be low, and the content of Li ₂ O is adjusted to 7 to 13% by weight to form a crystal phase of LiAlO ₂ , which results in slow cooling. Achieving the purpose. At present, however, globally, the demand for lithium increases, the price rises, supply and demand is difficult, and efforts to lower the content and development of raw materials containing fluxes that can replace the function of Li ₂ O in the manufacture of mold fluxes have been made. It is going on. In the case of the other type of high-fluid steel mold flux, the content of SiO ₂ is low, and sodium fluoride dicalcium silicate (Na F Ca ₂ SiO ₄ ) is controlled by controlling the content of Na ₂ O and F. We use crystal phase of). As a result of applying the SiO ₂ ultra low mold fluxes, Al ₂ O ₃ which is rapidly increasing in slag and CaO which was not involved in the formation of the crystal phase are combined to form high temperature crystal phase Gelenite (Ca ₂ Al ₂ SiO ₇ ). Or Mayenite (Ca ₁₂ Al ₁₄ O ₃₃ ) was formed. As such, when the casting conditions are changed, such as when the reaction time is prolonged due to the change in the content of Al ₂ O ₃ generated by the reaction and introduced into the slag and the change in the circumferential speed, the conventional mold fluxes are subjected to such high temperature compounds. And the compounds are those with melting points in the region of 1500 ° C. or higher.

Since the extremely low type of SiO ₂ , which is a design direction of a conventional mold flux, exhibits the above problems, the present invention is not intended to limit the SiO ₂ content to an extremely low level in order to suppress reaction of Al in slag and molten steel. By measuring the decrease amount of SiO _{2 and} the increase amount of Al ₂ O ₃ by the reaction, by measuring the change in the physical properties of the slag according to the amount of change of the component to predict the physical properties after the reaction, taking into account the changes in the physical properties to the required physical properties after the reaction It designed in the direction which comprises a mold flux with respect to. The present invention will be described in more detail as to why the design background is different. In the prior art, the SiO ₂ contained in the mold flux is extremely limited in order to suppress the reaction, but the SiO ₂ component is completely removed due to physical properties such as viscosity. It cannot be removed, and therefore it is inevitable that Al ₂ O ₃ generated by the substitution reaction between the contained SiO ₂ component and Al in molten steel flows into the slag. Relatively large CaO content is a problem. Since the crystal is formed by receiving the thermal energy of molten steel during the cooling of the slag, the crystal phase is formed first from the crystal phase that requires high temperature thermal energy, and these high temperature crystal phases are melted at a high temperature even during melting. In the case of conventional mold fluxes, most of them are trying to achieve heat transfer control by creating new crystal phases, but before the target crystal phase is formed, relatively high content of CaO is introduced due to the low content of SiO ₂ . It combines with Al ₂ O ₃ to form the high temperature crystal phase mentioned above. In addition, this causes a large amount of expensive raw materials containing the Li ₂ O component to be added. Thus, a new crystal phase was created using Li ₂ O belonging to the flux, and the melting point and viscosity were lowered to consume the high temperature crystal phase before it was formed, thereby reducing the risk. However, since the conventional products of high basicity have the above-mentioned risks due to the composition of the components, the formation of high melting point compounds occurs when the reaction time is long due to the change in casting conditions such as slow casting speed. The occurrence of breakout was inevitable.

The configuration of the present invention for solving the problems of the prior art is as follows.

[1] A mold flux used for continuous casting of high aluminum steel having an Al content of at least 0.1 wt% in molten steel,

By weight% CaO: 10.7 ~ 18.2%, SiO ₂ : 35.6 ~ 38.9%, MgO: 2.5 ~ 3.1%, Al ₂ O ₃ : 2.7 ~ 3.2%, Na ₂ O: 15.6 ~ 17.7%, F: 12.9 ~ 13.8% , B ₂ O ₃ : 0%, Li ₂ O: 2.6-3.2%, C: 5.1-7.1%, and basic casting for continuous casting of high aluminum steel, characterized in that it satisfies the range of 0.28 ~ 0.51 Mold flux.

[2] The mold flux for continuous casting of high aluminum steel according to [1], wherein the mold flux has a melting point of 730 to 810 ° C and a viscosity of 1.2 to 1.8 poise.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described in detail. However, this invention is not limited to these embodiment.

For the practice of the present invention, first, the application of the conventional mold flux was tested to determine the amount of Al ₂ O ₃ content change to increase in the slag. The components of the molten steel to which the experiment was applied are 0.2 to 0.3% by weight of C and 0.6% by weight of Al. In the present experiment, the conventional mold flux refers to a product that has been classified and applied according to the C content (%) in molten steel. Hereinafter, all content% indicated in the present Example means weight% (wt%).

division basicity SiO ₂ (%) CaO (%) MgO (%) Al ₂ O ₃ (%) Na2O (%) F (%) Li ₂ O (%) C (%) Reference Example 1 (Mold Flux A) 1.0 35.5 35.9 0.8 2.9 7.9 9.6 0.6 5.1 Reference Example 2 (Mold Flux B) 0.8 31.4 26.0 0.6 5.8 14.4 11.7 1.7 6.2

  division Reference example 1 A slag (40 minutes) Reference Example 2-1 B slag (10 minutes) Reference Example 2-2 B Slag (25 Minutes) Reference Example 2-3 B slag (40 minutes) basicity 2.1 1.45 1.72 1.85 SiO ₂ (%) 18.5 21.3 17.1 15.3 CaO (%) 38.2 30.8 29.5 28.2 MgO (%) 2.4 1.0 0.9 0.6 Al ₂ O ₃ (%) 23.1 21.1 25.7 28.8 Na ₂ O (%) 7.7 12.8 13.4 14.0 F (%) 9.3 12.3 12.1 12.0 Li ₂ O (%) 0.6 1.7 1.6 1.6

By applying the two kinds of products shown in Table 1, the slag was collected according to the change of time during casting and the components were analyzed. As a result, the results shown in Table 2 were obtained.

The quality of the cast slab was poor due to the rapid change of the component, but after repeating the test several times, it was possible to obtain the tendency of the component change as shown in FIG.

As shown in the result of FIG. 2, it can be seen that the amount of decrease of SiO _{2 and} the amount of increase of Al ₂ O ₃ by the reaction are 20% or more. In addition, it was found that the Al ₂ O ₃ content in the slag increased by 30-35% even when the Al content of the molten steel was 0.8% to 1.5%. As the Al content of molten steel increased, the increase of Al ₂ O _{3 in the} slag increased, but the time to reach its peak was almost the same.

The change in the physical properties according to the sudden change of components is as follows. The change of viscosity was measured by collecting slag when the reaction between molten slag and molten steel reached its peak and then reached a steady state and the casting operation was stabilized. In the case of the viscosity of the mold flux, which is a measure of lubrication, the increase and decrease amounts of SiO ₂ and Al ₂ O ₃ , which are components that increase viscosity, cancel each other, so the increase in viscosity does not change rapidly, but the effect on viscosity Since Al ₂ O ₃ is larger than SiO ₂ , the viscosity increased by 2 poise when the content of Al ₂ O ₃ introduced into the slag was 20%, and increased by 3.5 poise by 30%. This is also the reason why the present invention is designed with low basicity. In the embodiment of the present invention, high basicity mold fluxes were simultaneously applied as a comparative example for effect comparison. Table 3 shows the components of the high basic mold flux as an example of the present invention and a comparative example.

When applying the mold fluxes of Table 3, the important points to be checked are whether or not the generation of high melting point compound and the ability to control the heat transfer rate control function by the new crystal phase when applying the present invention, and the change of composition The amount of change in viscosity with respect to the lubrication was. As a result, Comparative Examples A to C formed the above-mentioned high melting point compounds (geleneite was formed in all of Comparative Examples A to C, and Mayenite was further formed in Comparative Example A having a high content of CaO). When the casting speed was lower, these high melting point binders were formed more violently and floated in the form of lumps on the molten steel. As these combinations were attached to the slag bears, the slag bears were enlarged and the inflow of molten slag became disadvantageous. As a result, breakouts, which were operation accidents, occurred, and it was impossible to measure the heat transfer rate control function in Comparative Examples A to C.

division Example A Example B Example C Example D Comparative Example A Comparative Example B Comparative Example C basicity 0.28 0.51 0.34 0.60 3.9 2.9 2.4 SiO ₂ (%) 38.2 35.6 38.9 32.0 9.3 10.2 10.2 CaO (%) 10.7 18.2 13.1 19.1 36.8 29.1 25.0 MgO (%) 2.5 3.0 3.1 3.0 1.8 0.3 0.4 Al ₂ O ₃ (%) 3.1 2.7 3.2 3.2 15.6 28.1 31.1 Na ₂ O (%) 16.5 15.6 17.7 16.0 9.3 9.8 10.4 F (%) 13.8 12.9 13.2 12.2 9.0 9.5 9.5 Li ₂ O (%) 2.6 3.0 3.2 2.5 4.2 4.4 4.4 C (%) 7.1 6.5 5.1 6.5 6.0 2.2 2.2 Melting point (℃)  770 810 730 850 1050 1100 1110 Viscosity 1.2  1.5 1.8 0.5 0.2 1.4 2.1

3 shows the crystal phases formed by diffraction analysis by collecting slag of Examples A to D. The X-axis of the phase shows the measured diffraction angle and the Y-axis shows the intensity of peak. As can be seen from Figure 3, in the present invention, a high melting point binder was not formed, and it can be seen that Na ₂ Si ₂ O ₅ and Na ₂ Si ₃ O ₇ , which are Na Si O-based crystal phases, were formed. Some unidentified crystals in FIG. 3 were the crystals of Fluorite (CaF ₂ ), which may occur in small amounts during the cooling of the slag. The crystal phases shown in FIG. 3 were all formed in Examples A to D, and there was a difference in the intensity of the peaks. Since the intensity of the peak varies with the amount of crystalline phase, this indicates that the same crystalline phase was formed in all the examples, and there was only a difference in the content of the formed crystalline phase.

To obtain the results of the functions performed by these crystal phases, heat flux, which is a measure of the slow cooling and heat transfer control results of slag, and a consumption amount, which is a measure of lubricating function, were measured. This is commonly used in the casting process or the industry, the heat transfer can be measured by calculating the temperature difference between the inlet and outlet of the mold cooling water, the consumption is the mold flux consumed for the cast molten steel (ton) Measured by the amount (kg). Table 4 records the heat transfer amount in the casting process to which the mold flux of the present example was applied and the consumption after 40 minutes, at which point the reaction between the mold flux and the molten steel reached its peak.

  division Heat transfer amount (MW / ㎡) Consumption (ton / kg) 10 minutes 20 minutes 30 minutes 40 mins  Example A 1.44 1.34 1.30 1.30 0.26  Example B 1.60 1.45 1.35 1.34 0.25  Example C 1.60 1.41 1.33 1.30 0.23

In Comparative Examples A to C, breakout, which is an operation accident, occurred as described above, and measurement of the above items was not possible.

The measurement position of heat transfer amount was the wide face of slab which is the casting object of the said steel grade. As shown in Table 4, the reaction reached its peak as time passed, and it was found that the heat transfer amount was stabilized by the crystal phase applied to the present invention. In addition, since the consumption of the products according to the present invention described in Table 4 is similar to that of casting a general steel, it can be seen that the lubrication function was properly performed.

Another concern that was concerned in the application of the present invention was the possibility of a component difference from the surface of the cast steel with respect to the entire cast steel by the Si component introduced into the molten steel by the reaction of the molten steel and the molten slag. However, as a result of confirming the quality of the cast steel, it was found that the reaction amount of the molten slag to the molten steel corresponds to a very small amount, which was not a cause for concern.

Based on the above experiment, the scope of the composition of the present invention and the range of specific physical properties were defined, and the definition thereof is as follows.

The mold flux of the present invention is a mold flux used in continuous casting, in particular, it is applied to steel grades in which the Al content in molten steel is 0.1% or more and 1.5% or less, and the composition is CaO: 10.7 ~ by weight. 18.2%, SiO ₂ : 35.6-38.9%, MgO: 2.5-3.1%, Al ₂ O ₃ : 2.7-3.2%, Na ₂ O: 15.6-17.7%, F: 12.9-13.8%, B ₂ O ₃ : 0 %, Li ₂ O: 2.6 to 3.2%, C: 5.1 to 7.1%, the basicity is in the range of 0.28 to 0.51, in addition to inevitable impurities. Moreover, it is preferable that the viscosity which is the specific required physical property of the mold flux comprised in this way is 1.2-1.8 poise, and melting point is 730-810 degreeC.

Hereinafter, the above definition of the present invention will be described in detail.

First, the content of SiO ₂ is preferably 38.9% or less in order to obtain the required viscosity value for securing the consumption amount, and when the content is less than 35.6%, SiO ₂ is consumed by the reaction, so that the required crystal phase was not generated.

When the CaO content is less than 10.7%, the basicity is extremely low and the viscosity is too high. Therefore, it is difficult to obtain the required viscosity value for lubrication. When the CaO content is higher than 18.2%, the basicity is increased by the consumption of SiO ₂ by the reaction with molten steel. Since the formation of water began, the titration amount was limited to 18.2% or less.

MgO is added to adjust the viscosity and melting point, but when the content of MgO in the composition of the present invention is more than 3.1%, an irregular crystal phase MgSiO ₄ is formed, which is disadvantageous in performing the function of adjusting the thermal conductivity, so the upper limit thereof is 3.1. Limited to% or less.

When the content of Al ₂ O ₃ is greater than 3.2%, the viscosity value of the composition of the present invention increases rapidly, resulting in breakout, which is an operation accident due to lack of lubrication.

The content of Na ₂ O was found to be 15.6% or more for the formation of crystal phases required by the present invention and the adjustment of the crystallinity according to the steel grade. The lower limit of the Na ₂ O component was composed of light elements and reduced by volatilization at a high temperature. Therefore, it was limited to 15.6% or more to secure a crystalline phase. In use, the viscosity value and the melting point were drastically lowered, so the upper limit of the content was limited to 17.7% or less.

Since the content of F is extremely low basicity of this invention, in order to ensure the viscosity value for lubrication, the lower limit was limited to 12.9% or more. In addition, when the content of F is more than 13.8%, the viscosity of the mold flux becomes so low that the consumption increases sharply and causes surface defects of the cast steel. Therefore, it is preferable to adjust the upper limit of the content to 13.8% or less.

In the case of B ₂ O ₃ and Li ₂ O belonging to the flux, since the raw materials including these components are expensive, the content is limited to a small amount, and thus B ₂ O ₃ is not contained, and the upper limit of Li ₂ O is 3.2%. Limited to. In addition, the lower limit of Li ₂ O was limited to 2.6% or more for the required viscosity value.

In addition, in the case of C is used to control the melting rate, since the melting point of the present invention is lower than the general mold flux, the melt rate is too fast when less than 5.1% did not properly perform the warming function. In addition, in the case of more than 7.1%, the melt rate was slow to form an amount of molten slag suitable for the casting rate.

Basicity is the effect of numerically limiting SiO ₂ and CaO components. When the basicity is less than 0.28, the viscosity is so high that the viscosity is further increased by the reaction with molten steel. Since the high melting point compound is formed by the content of CaO, the upper limit of basicity is limited to 0.51 or less.

Intended to limit the scope of the viscosity of the material properties of the present invention with 1.2 ~ 1.8poise high basicity, but has a secure configuration than the mold flux, to as short as possible a response time of the molten steel, Further, the introduction of Al ₂ O ₃ The lower limit is limited to 1.2 poise in consideration of the viscosity increase of 2 to 3.5 poise, and the upper limit is limited to 1.8 poise or less because the increase in viscosity is not added when the upper limit is more than 1.8 poise. .

The melting point was also designed to be lower than that of a conventional mold flux. The lower limit of the range was 730 ° C. because the melting point was excessively melted and the molten slag layer was excessive. In addition, when melting exceeded 810 degreeC, since melting became slow, appropriate lubrication could not be achieved with respect to casting speed, and the upper limit was limited to 810 degreeC or less.

As can be seen in the embodiment of the present invention, by applying the present invention it was possible to solve the operation of the conventional casting process, it was possible to produce a cast product of good quality. In addition, in the production of mold flux, supply and demand is smooth, and by using low-cost raw materials, it is possible to achieve a cost reduction effect on demand and suppliers.

1 is a schematic configuration diagram of a general continuous casting device.

Fig. 2 is a graph showing the change of components due to the reaction between steel grades having high Al content in molten steel and molten slag.

Figure 3 is a diffraction analysis data showing the crystal phase generated by the present invention solidification.

Explanation of the sign

One … Mold 2. Path to which molten steel is transferred to the mold (SEN)

3…. Molten steel 4. Outlet of molten steel

5…. Undissolved powder layer 6. Sintered Layer

7. Molten slag layer 8. Liquid slag

9... Solid state slag 10.. Air gap

11. Slag bear 12... Cast

Claims (2)

A mold flux used for continuous casting of high aluminum steel having an Al content of at least 0.1% by weight in molten steel, By weight% CaO: 10.7 ~ 18.2%, SiO ₂ : 35.6 ~ 38.9%, MgO: 2.5 ~ 3.1%, Al ₂ O ₃ : 2.7 ~ 3.2%, Na ₂ O: 15.6 ~ 17.7%, F: 12.9 ~ 13.8% , B ₂ O ₃ : 0%, Li ₂ O: 2.6-3.2%, C: 5.1-7.1%, and basic casting for continuous casting of high aluminum steel, characterized in that it satisfies the range of 0.28 ~ 0.51 Mold flux. The mold flux for continuous casting of high aluminum steel according to claim 1, wherein the mold flux has a melting point of 730 to 810 ° C and a viscosity of 1.2 to 1.8 poise.

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