KR101356928B1 - Method of manufacturing high purity molten steel and the refining device thereof - Google Patents

Abstract

The present invention relates to a method and a refining apparatus for manufacturing molten steel with excellent cleanliness, and in particular, to provide a method and apparatus for refining inclusions by dropping molten steel over the entire process of the playing process in the steelmaking process and dropping it onto slag. .
In particular, the present invention includes a molten steel supply device for supplying molten steel and a molten steel refiner for receiving and refining molten steel injected from the molten steel supply device, the molten steel as a molten steel refiner in the molten steel supply device Molten steel injection step of injecting; A droplet forming step of forming the injected molten steel into droplets in a molten steel refining apparatus; A slag passing step of passing the slag by dropping the dropped molten steel; And an inclusion removal step in which residual inclusions of the dropleted molten steel are removed while passing through the slag.

Description

Method of manufacturing high purity molten steel and the refining device

TECHNICAL FIELD The present invention relates to a method and a refining apparatus for manufacturing high clean molten steel, and more particularly, to a method for manufacturing high clean molten steel by forming molten steel into droplets and a refining apparatus for the same.

In general, when non-metallic inclusions present in steel remain on cast steels without being removed between the steelmaking process and the casting process, steel sheet causes large inclusion defects (scab) or sliver defects. In addition, in the case of the wire steel sheet, it may cause a break. On the other hand, in the case of the stainless steel sheet, when the non-metallic inclusions remain in the steel sheet, problems occur in corrosion resistance, which eventually adversely affects the quality of the final product.

In general, oxygen gas is blown into steel in various facilities (electric converter, RH, AOD, VOD) for the purpose of decarburization of molten steel. After decarburization at the target concentration is reached, the molten steel has a high oxygen concentration. Therefore, a deoxidizing agent is added for the purpose of reducing the oxygen concentration, and an alloy or a pure substance mainly composed of Al, Si, Mn or the like is used. However, when alumina (Al ₂ O ₃ ), silica (SiO ₂ ) or a deoxidizer is added as a deoxidation product, a composite oxide is present in the steel. On the other hand, the slag inclusions in the steel due to the slag and simultaneous tapping when present in the AOD refining furnace exist in the river, and these slag inclusions may precipitate high melting spinel inclusions as the temperature drops.

As a result, it is necessary to minimize or reduce the adverse effects of quality on the final product by suppressing or eliminating inclusions from the steelmaking process to the performance process before the solidification of molten steel is completed.

The present invention is to provide a method for producing a high clean molten steel by suppressing or removing the inclusions from the steelmaking process to the reproducing process.

In addition, the present invention is to provide a refining apparatus for producing the high clean molten steel.

According to one embodiment of the present invention, a molten steel supply device for supplying molten steel and a molten steel refiner for receiving and refining molten steel injected from the molten steel supply method for producing a high clean molten steel, the molten steel in the molten steel supply device A molten steel injection step of injecting molten steel into a refining apparatus; A droplet forming step of forming the injected molten steel into droplets in a molten steel refining apparatus; A slag passing step of passing the slag by dropping the dropped molten steel; And an inclusion removal step in which residual inclusions of the dropleted molten steel are removed while passing through the slag.

In the present invention, the molten steel injection step injects molten steel in the form of a long nozzle or molten steel stream.

In the present invention, the molten steel supply device and the molten steel refining device is a steel ladle, or the molten steel supply device is a casting ladle and the molten steel refining device is a tundish.

In addition, the present invention may further comprise the step of temporarily storing the molten steel for droplets after the molten steel injection step before the molten steel droplets formed and flowing the stored molten steel to the droplet forming step.

In the present invention, the molten steel droplet forming step is to drop the injected molten steel through the droplet forming portion having a plurality of droplet holes.

In the present invention, the droplet hole is preferably 1mm or more and 6.5mm or less in diameter.

Further, in the present invention, the slag is a refined slag having a thickness of 20 mm or more and 200 mm or less, wherein (% CaO) + (% SiO ₂ ) + (% Al ₂ O ₃ ) + (% MgO) <95%, and (% CaO ): 30-45%, (% SiO ₂ ): 15-35%, (% Al ₂ O ₃ ): 15-30%, (% MgO): 10-20%.

In still another embodiment of the present invention, a molten steel refining apparatus is provided, wherein the molten steel refining apparatus includes a droplet forming apparatus for forming droplets of molten steel to be injected.

In the present invention, the molten steel refining device is a tundish, the tundish is provided with the droplet forming apparatus inside the tundish body, the droplet forming apparatus is located adjacent to the lower region in which the molten steel is injected.

In addition, in the present invention, the droplet forming apparatus includes a droplet forming unit formed with a plurality of droplet holes for droplet-forming molten steel in the center of the container, the circumference of the container is formed of a side wall extending upward.

Further, in the present invention, the droplet forming apparatus forms a molten steel receiving portion under the molten steel injection region inside the tundish body in order to accommodate the molten steel injected from the molten steel supply device, and the molten steel injected into the droplet forming portion through the molten steel receiving portion. To flow.

In addition, in the present invention, the molten steel receiving portion has a molten steel storage space therein and is formed adjacent to the inner side and the lower side of the tundish body below the molten steel injection region.

In addition, in the present invention, the droplet forming unit forms an opening on the opposite side of the region in which the plurality of droplet holes are formed so that the upper end portion of the molten steel accommodating portion is passed through the opening or coupled to the upper portion of the outer peripheral surface of the molten steel storage space of the molten steel accommodating portion. Can be.

In addition, in the present invention, the droplet forming unit may be supported by a weir mounted inside the tundish body, or one side wall of the droplet forming unit may be supported by the weir and the other side wall may be supported by the molten steel receiving unit.

In addition, in the present invention, one side wall of the droplet forming unit may be supported by the weir and the other side wall may be supported by being coupled to the inner surface of the tundish body.

In the present invention, the side wall of the droplet forming portion adjacent to the molten steel receiving portion is formed lower than the other side wall.

In another embodiment of the present invention, the molten steel refining apparatus is a steel ladle, and the ladle further includes a droplet forming apparatus for forming droplets of molten steel injected from the molten steel supply apparatus, the droplet forming apparatus is a central portion of the container And a droplet forming unit in which a plurality of droplet holes are formed to droplet molten steel.

Further, in the present invention, the container circumference of the droplet forming portion is formed of a side wall extending upward and is supported on the inner wall of the ladle.

Further, in the present invention, the droplet forming apparatus forms a molten steel receiving portion on any area inside or outside the ladle to accommodate molten steel injected from the molten steel supplying device, and the molten steel injected into the droplet forming portion through the molten steel receiving portion. To flow.

According to the present invention, it is possible to manufacture molten steel with excellent cleanliness by minimizing inclusions from the steelmaking process to the playing process.

In addition, the present invention can provide a refining apparatus for producing molten steel with excellent cleanliness to economically manufacture high clean steel with excellent quality in the final product.

1 is a process schematic diagram illustrating a method for manufacturing high clean molten steel according to an embodiment of the present invention.
2A and 2B are graphs showing a relationship between slag thickness and total oxygen content in molten steel in one embodiment of the present invention.
3 is a photograph showing continuously the phenomenon that the molten steel droplets reacted on the slag surface in one embodiment of the present invention.
Figures 4a, 4b, 4c is a graph showing the relationship between the slag thickness and the number density of inclusions in the solidified specimen in one embodiment of the present invention.
FIG. 5 is a graph showing the relationship between total oxygen content in molten steel according to the size of droplet holes in the droplet forming apparatus according to an embodiment of the present invention.
6A, 6B, and 6C are cross-sectional views schematically showing a molten steel refining apparatus according to another embodiment of the present invention.
7A is a plan view particularly showing a droplet forming unit in the molten steel refining apparatus according to another embodiment of the present invention.
7B and 7C are a plan view and a cross-sectional view, in particular, showing a droplet forming portion in the molten steel refining apparatus according to another embodiment of the present invention.
8A is a schematic cross-sectional view of a molten steel refining apparatus according to another embodiment of the present invention.
8B is a plan view of the droplet forming apparatus in particular in the molten steel refining apparatus according to another embodiment of the present invention.
8C is a plan view illustrating a droplet forming unit of the droplet forming apparatus according to still another embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, the present invention will be described in more detail with reference to the drawings, and the advantages and features of the present invention, and a method for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms. In the following description, when a part is connected to another part, it is only directly connected. It also includes a case in which another device is electrically connected in the middle. In the drawings, parts not relating to the present invention are omitted for clarity of description, and like parts are denoted by the same reference numerals throughout the specification.

Various techniques have been known as a method for manufacturing high clean molten steel by suppressing or removing inclusions from the steelmaking process to the reproducing process, before the solidification of molten steel is completed.

First, in the steelmaking process, a method for controlling separation of inclusions by controlling molten steel stirring time and stirring strength during ladle refining is known. (JP-A-2007-231410, JP-A-2008-240126).

In addition, there has been disclosed a method for improving flotation resolution by agglomeration of inclusions caused by electromagnetic vibrations. (Korean Patent Publication No. 2003-52424).

However, the method of removing the inclusions by floating separation of the inclusions in the steel by the slag present in the upper part of the molten steel by using the above-described stirring, microbubble, electromagnetic vibration, etc. There is a limit to moving.

On the other hand, in the playing process, a method of removing inclusions through inert gas blowing into a nozzle, which is a molten steel passage supplied from a ladle to a tundish, is known. (Japanese Patent 2001-3216384).

In addition, there has been disclosed a method of maximizing inclusion injury by controlling the molten steel by installing a shock pad in the tundish. (US Patent US5551672, Republic of Korea Patent Publication 2004-55392)

However, the method of blowing the inert gas into the nozzle during the regeneration process can cause pin-hole sliver defects on the surface of the steel sheet when the micro bubbles remain, and the method of controlling the molten steel through the installation of a shock pad also raises all the molten steel. There is a problem that the removal efficiency of the inclusions is not high because it can not be made.

The present invention is completely different from the above known techniques and approaches in the manufacture of high clean steel, and the present invention can be applied particularly in the whole process from the steelmaking process to the playing process.

One embodiment of the present invention is centered on a method of manufacturing molten steel supplied from a ladle to a tundish and a refining apparatus thereof, and another embodiment is a method and a refining apparatus for manufacturing high clean steel in a steelmaking process. Is made of. Hereinafter, the present invention will be described based on a high clean molten steel manufacturing process as a basic technical idea that can be applied to all processes of the steelmaking process and the playing process, and then the refining apparatus that can be applied to each process will be described.

1. High clean Molten steel  Manufacturing Process

First, a process of manufacturing high clean molten steel as an embodiment of the present invention will be described. The present invention can be started in the step of injecting molten steel into the molten steel refining apparatus for receiving and refining molten steel injected from the molten steel supply device for supplying molten steel for steel production. Thereafter, a droplet forming step of forming the injected molten steel into droplets in a molten steel refining apparatus is performed. Thereafter, the slag passing step of passing the slag by dropping the dropletized molten steel and the inclusions removing step of removing the inclusions of the dropleted molten steel through the slag while passing the slag can produce high clean molten steel. have.

The molten steel supply device and the molten steel refining device may each use a ladle used in a steelmaking process, or the molten steel refining device may use a tundish of a casting step.

In the present invention, when the molten steel is injected into the molten steel refining device from the molten steel supply device, molten steel may be injected in the form of a molten steel stream or may be injected using a long nozzle. At this time, the molten steel injected into the molten steel refining device from the molten steel supply device may directly pass through the droplet forming unit provided in the molten steel refining device to perform a droplet forming process, and then drop the molten steel to pass the slag.

However, in such a case, problems of impact or scattering may occur during the fall of the molten steel, and in consideration of this, an additional molten steel receiving part may be provided in the molten steel refining apparatus. Therefore, it is preferable to add the step of temporarily storing the molten steel for droplets after the molten steel injection step before the molten steel droplets are formed.

In the molten steel droplet forming step, the injected molten steel is formed into fine droplets of a predetermined size to pass through the slag, because the molten steel falls through the droplet forming portion in the form of a container having a plurality of droplet holes.

In addition, the droplets of molten steel can be passed through the slag to remove the inclusions, the slag may be used to refine the slag of a predetermined thickness or more. The slag may be provided below the droplet forming unit in advance.

As an embodiment of the present invention, the molten steel supply apparatus is a casting ladle and the molten steel refining apparatus is a tundish. That is, when the present invention is applied in the casting step, it may be a process of supplying molten steel from the ladle to the tundish. At this time, when the molten steel supplied from the ladle, the molten steel supply device, is supplied to the tundish, the molten steel refining device, molten steel droplets are formed through a droplet forming unit, which is a refractory container having a hole having a diameter of 1 mm or more and 6.5 mm or less mounted inside the tundish. The formed molten steel can be dropped into a slag layer having an appropriate composition of 20 mm or more in thickness to remove inclusions in the molten steel droplets into the slag layer.

1 schematically shows a process in which molten steel is pulverized by a droplet forming apparatus provided in a molten steel refining apparatus according to an embodiment of the present invention, which is applicable to all processes including a steelmaking process and a playing process. To illustrate the technical idea of the.

As can be seen in Figure 1, the molten steel droplet forming apparatus provided in the molten steel refining apparatus forms the molten steel supplied from the molten steel supply apparatus into fine droplets (a) of a constant size. Then, the molten steel droplet (a) having a certain size falls and collides with the surface of the slag (b) consisting of the composition according to the embodiment of the present invention. In the collision process, the molten steel droplets are absorbed into the slag while the molten steel droplets pass through the slag b, and the molten steel droplets dropped by the specific gravity difference are absorbed into the lower molten steel layer c. In this case, the molten steel that has passed through the slag (b) is formed of molten steel having excellent cleanliness at the bottom because the inclusions are removed by the slag (b). In the present invention, the molten steel is dropleted through the droplet forming apparatus in the molten steel refining apparatus and the slag having a predetermined thickness passes through the slag so that the inclusions such as the molten steel droplet interface are absorbed into the slag in the process of refining so that the refining process can be performed. Characterized in that.

2A and 2B are graphs showing the relationship between total oxygen content in molten steel according to the thickness of slag when molten steel droplets pass through the slag. In particular, in Figs. 2a and 2b, the relationship between the total oxygen content is shown by using the slag each having a different composition. In one embodiment of the present invention, the total oxygen content in the molten steel was analyzed for the specimen obtained by sampling the molten steel passed through the slag. The iron content and inclusion oxygen content in the steel can be obtained through the following equation (1).

[Formula 1]

Total oxygen = soluble oxygen + insoluble oxygen

In general, the dissolved oxygen is determined by the temperature and the molten steel component, so that the dissolved oxygen has a constant value when the temperature and the molten component are constant. Therefore, when the temperature and the molten steel component is constant, the relative difference between the total oxygen represents the difference in the content of the inclusions, it is possible to confirm the removal efficiency of the inclusions through the entire oxygen content trend.

2A and 2B, when the slag is used, the removal efficiency of the inclusion increases gradually as the slag thickness is increased, compared to the total oxygen content when the slag thickness is 0 mm, that is, when no slag is used. However, it can be seen that the inclusion removal efficiency is almost constant above a certain critical thickness of the slag. 2A and 2B also show that the removal efficiency of the inclusions is constant at or above a threshold value of a certain thickness, even when different types of slag are used. As a result, in one embodiment of the present invention, when the inclusions are removed through the dropletization of molten steel, the slag having a predetermined thickness passes through the slag, but the slag thickness exceeds the predetermined threshold value. 2a and 2b it can be seen that the slag thickness according to an embodiment of the present invention should be at least 20mm.

3 is a photograph showing continuously the phenomenon that the molten steel droplets reacted on the slag surface in one embodiment of the present invention. As can be seen in the figure, the molten steel formed as droplets can remove inclusions when they pass through the slag surface. First, when the molten steel drops fall on the slag surface, the shape change of the droplets (t ₀ to t ₈ ) with time will be described. In the continuous photograph, the molten steel droplet first comes into contact with the surface of the slag. After (t ₀ ), the molten steel droplets collided with the slag surface appear to be thinly spread (Spreading, t ₁ to t ₈ ) by contacting the slag over 50% on the surface of the slag over time. The moving distance decreases and the moving speed also increases, so that the removal of the inclusions occurs easily. On the other hand, as can be seen in Figures 2a and 2b it can be seen that the removal of most inclusions occurs mostly when the molten steel droplets impinge on the slag surface from the result of the small difference in inclusion removal efficiency above the critical slag thickness. On the other hand, when the slag thickness is below the critical thickness, the removal efficiency may decrease or increase, which may occur. When the slag thickness is below the critical thickness, when the molten steel collides with the slag, the slag may be removed together with the inclusions. This is because it is suspended and incorporated into the lower molten steel to increase the oxygen content in the steel. Therefore, in the present invention, it is important to secure the slag thickness at least 20 mm or more. On the other hand, in the slag of the present invention, the upper limit is 200 mm in consideration of the equipment aspect.

4A, 4B, and 4C are graphs showing the inclusions remaining on the solidification specimens after slag refinement of molten steel according to the slag thickness. As can be seen from the figure, when the classification according to the inclusion size (2.5 ㎛ or more, 5 ㎛ or more, 10 ㎛ or more) category is shown, as the slag thickness increases the residual inclusion density decreases. However, it can be seen that the effect of removing the inclusions is insufficient in the droplet refining passing through the slag layer below the critical thickness. Then, from the results of FIGS. 2A and 2B and 4A, 4B and 4C, the slag thickness at which the droplets collide during the refining of molten steel has a critical thickness for maximizing inclusion removal effect and minimizing side effects such as slag inflow. It can be seen that. In particular, in the embodiment of the present invention, it is preferable to secure the thickness of the slag layer at least 20 mm or more.

On the other hand, when the molten steel droplets fall to the slag, the effect of the slag composition on the inclusion removal efficiency is shown in Table 1. As can be seen from Table 1, the composition of A1 and A2 showed 30 ~ 33ppm total oxygen reduction after droplet refining, which showed excellent removal efficiency, but the Al ₂ O ₃ content of remaining inclusions was 15 ~ 23%, respectively. Increased to a high degree. Therefore, as a result of this, A1 and A2 composition is not suitable because the high melting point in the inclusions due to the increase in Al ₂ O ₃ content of the inclusions, even if the inclusion refining efficiency is high, the possibility of adversely affecting the quality. On the other hand, the composition of B1 ~ B3 can be lowered as the Al ₂ O ₃ content of the residual inclusions decreases after droplet refining, but the total oxygen reduction amount is 12 ~ 24ppm, which is not suitable because the removal efficiency of the inclusions is low. However, the amount of total oxygen reduction after the droplet refining with C1 ~ C3 composition is 32 ~ 39ppm, and the removal efficiency of the inclusions is very good, and it is good at -3% ~ + 2% level in terms of the change of Al ₂ O ₃ content in the residual inclusions. It can be confirmed that the effect is high by the droplet refining slag composition. Therefore, in one embodiment of the present invention, the slag composition of the lower portion of the molten steel drops falling during the refining of the droplets is CaO: 30-45%, SiO ₂ : 15-35%, Al ₂ O ₃ : 15-30%, MgO: 10- It can be seen that it is preferable to have a composition of 20%.

Furtherance Slag Composition (wt.%) Droplet refining
order
Oxygen change (ppm) Al2O3 content in residual inclusions
change(%) CaO SiO ₂ Al ₂ O ₃ MgO A1 52.4 - 40.2 7.4 -30 + 23% A2 36.5 - 52.4 11.1 -33 + 15% B1 32.7 40.7 - 26.6 -23 -3% B2 24.8 47.1 - 28.1 -24 -8% B3 7.7 59.5 - 32.8 -12 -10% C1 30 35 15 20 -32 -3% C2 44 26 20 10 -39 -2% C3 44 16 30 10 -34 + 2%

FIG. 5 illustrates the size of the droplet hole in a molten steel refiner, particularly in a refractory having a fine droplet hole between a ladle and a tundish in order to determine the relationship between the droplet size formed by the droplet forming unit in the molten steel refiner and the total oxygen content. It is a graph showing the effect of refining inclusions (total oxygen content change).

That is, since the molten steel dropletized in the present invention is formed through the droplet forming hole of the droplet forming apparatus, the size of the droplet hole allows to estimate the desirable size of the molten steel droplet of the present invention. In one embodiment of the present invention, a fine droplet hole is formed on the lower region of the molten steel refining apparatus, in which molten steel is injected in order to droplet molten steel during the supply of molten steel from the ladle to the tundish or the supply of the molten steel from the ladle to the ladle. When the refractory container provided is located and molten steel is supplied to the container, the molten steel forms molten steel droplets through the fine droplet holes of the refractory. As can be seen in Figure 5 in one embodiment of the present invention it can be seen that the total oxygen content decreases as the size of the droplet hole of the refractory container is reduced. In addition, it can be seen that as the droplet hole size of the refractory container increases, the average value and the deviation of the total oxygen content also increase. Therefore, this is due to the increase in the size of the molten steel droplets according to the increase in the size of the droplet hole of the droplet forming portion, which is a refractory container, and thus the reduction of inclusion removal efficiency due to the decrease in the area ratio per unit volume. On the other hand, when the size of the droplet hole is 6.5 mm or more, there is no significant difference from the case where the droplet refining is not performed, and it is understood that the droplet refining effect is hardly exhibited. On the other hand, when the diameter of the droplet hole is 1 mm or less, it is difficult to form droplets by surface tension, so the lower limit is preferably 1 mm. Therefore, from the result of FIG. 5, it is desirable to ensure the refractory hole size of 1 mm or more and 6.5 mm or less in order to ensure inclusion refining efficiency when the molten steel is formed by installing a droplet forming apparatus having fine droplet holes in the molten steel refining apparatus. Able to know.

2. Refining device in the playing process

Next, a case where the molten steel refining apparatus of the present invention is applied to a playing process will be described. The molten steel refining apparatus of the present invention can be applied to all kinds of molten steel storage tanks, such as ladle that is supplied with molten steel in the steelmaking process, but the following first describes an embodiment for applying the method of refining molten steel to tundish first. do.

Figure 6a is a schematic cross-sectional view showing the structure of the ladle and tundish for droplet formation according to an embodiment of the present invention, in particular a tundish including the droplet forming apparatus of the present invention and a ladle for supplying molten steel to the tundish do. Hereinafter, the tundish is made of a tundish body and a tundish cover. Therefore, the tundish body mentioned below may be understood as a tundish.

As shown in FIG. 6A, in the refining process through molten steel droplets according to the present invention, molten steel 6 is first supplied from the ladle 5 to the tundish body 14. At this time, the molten steel 6 stored in the ladle 5 is a tundish body in the form of a molten steel stream 11 through a pouring box 8 by an opening and closing portion 7 or a collector nozzle below the ladle 5. It is supplied to the open area of 14. The molten steel 6 supplied to the tundish body 14 in the form of the molten steel stream 11 is first subjected to a dropletization process by a droplet forming apparatus formed at one side of the tundish body 14, and then to molten steel. Is dropped and passes through the slag 15 to be refined. Reference numeral 1 denotes that the molten steel that has been dropped falls. Then, the molten steel from which the inclusions are removed through the slag 15 flows to the lower portion of the weir 16 and is stored in the tundish body 14.

This will be described in more detail with reference to the droplet forming apparatus. The droplet forming apparatus according to an embodiment of the present invention receives the molten steel receiving portion 13 for temporarily storing the molten steel 6 supplied from the ladle 5 and the molten steel stored in the molten steel receiving portion 13. And a droplet forming unit 12 for accumulating. Preferably, the droplet forming apparatus is mounted adjacent to the opening of the tundish body 14 receiving the molten steel 6 from the ladle 5. In particular, the molten steel receiving portion 13 is mounted adjacent to the lower portion of the region where the molten steel is supplied to the tundish body 14 through the injection box 8 below the ladle 5 to accommodate the molten steel therein. It has a space and acts as a kind of temporary storage of molten steel made of refractory material. And the molten steel receiving portion 13 is mounted separately on the inner side of the tundish body (14).

And the molten steel supplied from the ladle (5) by the molten steel receiving portion 13 absorbs a portion of the impact drop is supplied to the molten steel to the adjacent droplet forming portion (12). Meanwhile, the droplet forming unit 12 for dropleting the molten steel introduced through the molten steel container 13 is preferably in the form of a refractory container in which the size and number of holes are set so as to correspond to a normal casting speed. The refractory container forms a plurality of droplet holes 25 in a central portion thereof. And the side wall extending around the droplet forming portion 12 to be supported in the tundish (14). Looking at this in more detail, the droplet forming portion 12 is formed to be supported over the outer peripheral surface of the upper end of the molten steel receiving portion 13 so as not to cover the opening region receiving the molten steel of the upper end of the molten steel receiving portion (13). . In addition, one side wall of the droplet forming unit 12 is mounted to be supported on the inner surface of the tundish body 14 and the other side wall is provided with at least one weir 16 inside the tundish body 14. To be supported by the weir (16). In this case, the droplet forming unit 12 is designed to be inclined to the outer shape of the droplet forming unit 12 when the tundish side is inclined so as to be supported by the inner surface of the tundish body 14, Of course, the tundish body 14 may be provided with a protrusion and the like so that the side wall of the droplet forming unit 12 may be supported. That is, the method of mounting the droplet forming unit 12 inside the tundish body 14 may be applied in various ways, and this does not depart from the scope of the present invention. On the other hand, the tundish body 14 is covered by the tundish cover 10 and the molten steel refined through the dropletization process is located under the tundish flux 17 inside the tundish body 14 and playing process Is discharged through.

In the present invention, the refining slag 15 located below the droplet forming unit 12 is a slag in a molten state for performing refining by dropletizing molten steel, and is distinguished from the flux indicated by reference numeral 17.

Meanwhile, FIG. 6B illustrates another structure of the ladle and the tundish according to the present invention. In FIG. 6B, the molten steel 6 is directly injected into the molten steel container 13 by providing the long nozzle 9 in the opening / closing portion 7 below the ladle 5 without the injection box 8 as illustrated in FIG. 6A. To be possible. When the molten steel 6 is injected from the ladle 5 through the long nozzle 9 as described above, the drop impact decreases when the molten steel 6 falls into the molten steel accommodating part 13, thereby preventing scattering of molten steel. .

Figure 6c also shows another structure of the tundish according to the present invention. In FIG. 6C, the refining process is performed by allowing molten steel to directly pass through the droplet forming unit 12 without a separate molten steel receiving unit temporarily storing molten steel injected from a molten steel storage unit such as a ladle. That is, FIG. 6C shows that the droplet forming apparatus of the present invention may be constituted only by the droplet forming unit without a separate molten steel container.

7A, 7B and 7C show the detailed structure of the droplet forming unit 12 disclosed in Figs. 6A, 6B and 6C. First, referring to FIG. 7A, the droplet forming unit 12 according to the present invention has a container shape having a shape corresponding to an inner surface of the tundish so as to be easily mounted in the tundish. The droplet forming unit 12 has an open opening 26 having a shape corresponding to the opened area of the molten steel receiving unit 13 so that the droplet forming unit 12 may be seated on the molten steel receiving unit 13. It is provided. Thus, a plurality of droplet holes 25 are formed in the side surface of the opening 26. The droplet hole 25 is formed to form molten steel injected through the molten steel receiving portion 13 in the form of droplets so that the slag can pass through the slag in the lower portion, taking into account the casting speed and the efficiency of the refining process. It can be formed as. Although not shown in the drawing, the molten steel accommodating part 13 is formed of a refractory in the form of a column, and an upper end thereof is connected in an extended state through the opening 26, or a separate member is extended through the opening 26. It is also conceivable to communicate with the opening / closing portion 7 of the field or the injection box 8. The outer wall 12 ′ of the droplet forming unit 12 may be supported by the inner surface of the tundish body 14 and the weir 16 formed in the tundish body 14. In addition, the outer circumferential surface 26 ′ of the opening 26 may be seated at an upper end of the molten steel accommodating part 13 or may be mounted to each other through the molten steel accommodating part 13 having a columnar shape through the opening 26. .

FIG. 7B is a plan view showing still another embodiment of the droplet forming unit of the present invention particularly with respect to FIG. 6C, and FIG. 7C is a front sectional view of FIG. 7B. The droplet forming portion 12a as shown in the figure is formed in a substantially rectangular container shape so as to approximately correspond to the shape of one side of the tundish body 14. The outer wall 12a ′ of the droplet forming unit 12 may be mounted on the inner side of the tundish body 14 and the weir 16, and may be injected with molten steel from a molten steel reservoir such as a ladle to form droplets. A plurality of droplet holes 25 are formed.

As such, the molten steel supplied from the molten steel supply device storing the molten steel, such as ladle, is filled with the molten steel accommodating part, and then the molten steel flows into the droplet forming part, thereby forming a droplet process. Droplet molten steel passes through the slag to refine the inclusions to produce high clean steel. However, the molten steel accommodating part is not necessarily required, and as shown in FIG. 6C, molten steel may be directly introduced into the droplet forming part in the storage tank for storing the molten steel to perform the dropletization process. The molten slag is injected into the lower portion of the droplet forming unit or the solid slag is added to form a refined slag of a predetermined thickness or more so that the molten steel passed through the droplet can be refined.

6A, 6B, 6C, and 7A and 7B illustrate an apparatus for dropping molten steel in a tundish body when molten steel is introduced into the tundish from the ladle. However, it is a matter of course that the droplet forming apparatus of the present invention can be applied to all processes of the steelmaking process in addition to the silk playing process. Hereinafter, an example of the molten steel refining apparatus applicable to such a steelmaking process is demonstrated.

3. Refining device in steelmaking process

FIG. 8A illustrates that molten steel is supplied from the ladle to the ladle in order to carry out droplet refining of the molten steel component and the deoxidation completed molten steel in the steelmaking process to perform refining by droplet formation. 8b shows a plan sectional view of the ladle receiving molten steel from the bottom.

In an embodiment of the present invention, a supply ladle for supplying molten steel in a molten steel supply device and an accommodating ladle for receiving molten steel as a receiving portion are shown. In this case, in order to offset the impact amount of the molten steel 6 injected through the nozzle 29 in the upper ladle 5 for supplying the molten steel 6, the lower ladle 20 is separately provided on one side of the outer circumferential surface of the lower ladle 20. The molten steel receiving portion 23 is formed. The upper ladle 5 supplies molten steel to the molten steel accommodating portion 23 using an opening or closing portion of the ladle or a long nozzle 29. The molten steel 6 stored in the molten steel receiving portion 23 then flows into the droplet forming portion 22 beyond the adjacent sidewall 21 of the lower ladle 20. The molten steel 6 introduced from the droplet forming unit 22 performs a droplet forming process through a plurality of droplet holes 25 '. The molten steel that has been dropleted then falls and passes through a slag 24 of a predetermined thickness mounted inside the lower ladle 20. The droplet forming unit 22 may be mounted to be coupled to the inner side of the lower ladle 20 or seated on the side wall. The molten steel dropleted through the plurality of droplet holes 25 ′ passes through the lower slag 24 while falling, and droplet refining is performed. At this time, the lower ladle 20 is filled with an inert gas such as argon gas to prevent reoxidation of molten steel. An inert gas such as argon gas may be introduced through the upper cover 27 or supplied through the lower odor plug. The lower ladle 20 may be covered by the ladle cover 27.

8C shows a plan view of the droplet forming portion itself in this embodiment.

As shown in the figure, the droplet forming portion 22 in this embodiment is formed of a refractory container of a type corresponding to one side of the inner circumferential surface of the ladle. A plurality of droplet holes 25 'are formed at the center of the container, and the circumference of the container is formed of sidewalls 22' extending upwardly, and the sidewalls are configured to be supported by the inner circumferential surface of the lower ladle 5.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalents thereof are included in the scope of the present invention Should be interpreted.

5: ladle 6: molten steel
7: opening and closing section 8: injection box
9: long nozzle 10: tundish cover
11: molten steel stream 12, 22: droplet forming portion
13, 23: molten steel receiving portion 14: tundish body
15: slag 16. Weir
25, 25 'Droplet Hole

Claims (31)

In the method for manufacturing high clean molten steel, including a molten steel supply device for supplying molten steel and a molten steel refiner for receiving and refining molten steel injected from the molten steel supply device,
A molten steel injection step of injecting molten steel into the molten steel refining apparatus from the molten steel supply apparatus;
A temporary storage step of temporarily storing the injected molten steel in a molten steel accommodating portion formed under the molten steel injection region;
A droplet forming step of flowing the stored molten steel into a molten steel refining apparatus and then forming droplets;
A slag passing step of passing the slag by dropping the dropped molten steel; And
And an inclusion removal step in which residual inclusions of the dropleted molten steel are removed while passing through the slag. The method of claim 1,
High molten steel manufacturing method, characterized in that the injection using the long nozzle in the molten steel injection step. The method of claim 1,
And injecting molten steel in the form of a molten steel stream in the molten steel injecting step. The method of claim 1,
The molten steel supply apparatus is a ladle or tundish manufacturing method. The method of claim 1,
And said refining device is a ladle or tundish. delete The method of claim 1,
The molten steel droplet forming step is a high clean molten steel manufacturing method characterized in that the injected molten steel falls through the droplet forming portion having a plurality of droplet holes. The method of claim 7, wherein
The droplet hole is a high clean molten steel, characterized in that 1mm or more and 6.5mm or less. The method of claim 1,
The slag is a high clean molten steel, characterized in that the liquid refined slag. 10. The method of claim 9,
The slag is a high clean molten steel manufacturing method, characterized in that the thickness of 20mm or more and 200mm or less. The method of claim 1,
The slag is (% CaO) + (% SiO ₂ ) + (% Al ₂ O ₃ ) + (% MgO) <95%, (% CaO): 30-45%, (% SiO ₂ ): 15- 35%, (% Al ₂ O ₃ ): 15 to 30%, (% MgO): 10 to 20%. In the molten steel refining apparatus for refining using molten steel injected from the molten steel supply device,
The molten steel refining apparatus includes a droplet forming apparatus for forming droplets of molten steel to be injected,
The droplet forming apparatus is a high clean molten steel refining device, characterized in that for forming a molten steel receiving portion in the lower portion of the molten steel injection zone inside the molten steel refiner body to receive the molten steel injected from the molten steel supply device. The method of claim 12,
The molten steel refining device is a high purity molten steel refining device, characterized in that the tundish. The method of claim 13,
The tundish is provided with the droplet forming apparatus inside the tundish body, the droplet forming apparatus is a high purity molten steel refining device, characterized in that located adjacent to the lower region injecting molten steel. 15. The method of claim 14,
The droplet forming apparatus includes a droplet forming unit in which a plurality of droplet holes are formed in the central portion of the container to form droplets of molten steel. 16. The method of claim 15,
High purity molten steel refining device, characterized in that the circumference of the vessel formed of the droplet forming portion is formed of a side wall extending upward. 16. The method of claim 15,
The droplet forming apparatus is a high purity molten steel refining device, characterized in that for flowing the molten steel injected from the molten steel supply unit through the molten steel receiving portion to the droplet forming portion. 18. The method of claim 17,
The molten steel receiving portion is provided with a molten steel storage space therein, and the high clean molten steel refining apparatus, characterized in that formed adjacent to the inner surface and the lower surface of the tundish body below the molten steel injection region. 18. The method of claim 17,
The droplet forming unit may form an opening on an opposite side of the region where the plurality of droplet holes are formed so that the upper end of the molten steel accommodating part is coupled through the opening or coupled to the upper end of the outer circumferential surface of the molten steel storage space of the molten steel accommodating part. Clean molten steel refining device. 19. The method of claim 18,
The droplet forming unit is a high clean molten steel refining device, characterized in that supported by the weir mounted inside the tundish body. 20. The method of claim 19,
One side wall of the droplet forming unit is supported by a weir and the other side wall is a high clean molten steel refining apparatus, characterized in that supported by. 20. The method of claim 19,
One side wall of the droplet forming unit is supported by the weir and the other side wall is a high clean molten steel refining apparatus, characterized in that coupled to the inner surface of the tundish body. 20. The method of claim 19,
The sidewall of the droplet forming portion adjacent to the molten steel receiving portion is formed lower than the other sidewall. 16. The method of claim 15,
The droplet hole is a high clean molten steel refining device, characterized in that the diameter of 1mm or more and 6.5mm or less. 16. The method of claim 15,
Refining slag having a thickness of 20 mm or more and 200 mm or less is formed in a lower region falling through the droplet hole of the droplet forming part, and the slag is% CaO) + (% SiO ₂ ) + (% Al ₂ O ₃ ) + (% MgO ) <95%, (% CaO): 30-45%, (% SiO ₂ ): 15-35%, (% Al ₂ O ₃ ): 15-30%, (% MgO): 10-20% High clean molten steel refining device comprising a. The method of claim 12,
The molten steel refining device is a high clean molten steel refining device, characterized in that the steel ladle. The method of claim 26,
The ladle further includes a droplet forming apparatus for forming droplets of molten steel injected from the molten steel supply apparatus, wherein the droplet forming apparatus includes a droplet forming unit in which a plurality of droplet holes are formed in the central portion of the container to droplet the molten steel. Highly clean molten steel refining device, characterized in that. 28. The method of claim 27,
The vessel circumference of the droplet forming portion is formed of a side wall extending upwardly and the high clean molten steel refining apparatus, characterized in that supported on the inner wall of the ladle. 28. The method of claim 27,
The droplet forming apparatus is characterized in that for forming a molten steel receiving portion in any area inside or outside the ladle to accommodate the molten steel injected from the molten steel supply device and flowing the injected molten steel to the droplet forming portion through the molten steel receiving portion. High clean molten steel refining device. 28. The method of claim 27,
The droplet hole is a high clean molten steel refining device, characterized in that the diameter of 1mm or more and 6.5mm or less. 28. The method of claim 27,
Refining slag having a thickness of 20 mm or more and 200 mm or less is formed in a lower region falling through the droplet hole of the droplet forming part, and the slag is% CaO) + (% SiO ₂ ) + (% Al ₂ O ₃ ) + (% MgO ) <95%, (% CaO): 30-45%, (% SiO ₂ ): 15-35%, (% Al ₂ O ₃ ): 15-30%, (% MgO): 10-20% High clean molten steel refining device comprising a.

Images