Specification
Name of the invention: melt treatment device
Technical field
[One]
The present invention relates to a melt treatment apparatus, and more particularly, to a melt treatment apparatus capable of improving inclusion removal ability by reducing a stagnation area.
Background
[2]
Conventional continuous casting facilities include a ladle that carries molten steel, a Tundish that temporarily stores molten steel from the ladle, and a slab while continuously receiving molten steel from the ladle. It consists of a mold that first solidifies and a cooling bed that performs a series of molding operations by secondary cooling the cast steel continuously drawn from the mold.
[3]
When performing the continuous casting process of casting cast steel using the continuous casting facility, it is important to keep the molten steel in the tundish for a sufficient time. For example, the molten steel must remain inside the tundish for a sufficient time, so that inclusions can be smoothly floated and separated from the molten steel. In order to keep the molten steel in the tundish for a sufficient time, it is necessary to actively induce an upward flow of the molten steel in the tundish.
[4]
In Patent Document 1 below, by breaking away from the flow control method of molten steel using dams and weirs, after constructing a number of refractory dams in tundish such as dams, auxiliary dams, and guide dams, argon gas is injected into molten steel through auxiliary dams. As a result, a method of inducing the upward flow of molten steel is suggested. In addition, in Patent Document 2, after installing the impact pad and the separation wall on the lower side of the shroud nozzle, the molten steel collides with the impact pad and passes through the space between the separation wall and the impact pad to actively induce an upward flow of molten steel. The way is presented.
[5]
However, the methods presented in Patent Documents 1 and 2 add manufacturing cost to build a number of dams in the Tundish, complicate the installation work, and the rear surface of a number of refractory dams and separation walls (the side facing the exit of Tundish). ) And near the area far from the impact pad, there is a problem of increasing the stagnation area where the flow rate of molten steel is very low.
[6]
In particular, when the stagnation area of ​​molten steel increases in the tundish, the degree to which the molten steel stays in the stagnation area increases, and the retention time of the molten steel becomes excessively long. That is, if the stagnation area of ​​molten steel increases in the tundish, the molten steel cannot secure an adequate residence time in the tundish. In addition, when the inclusions enter the stagnant area, the inclusions stay in the center of the stagnant area due to the low flow rate of the molten steel, but cannot be separated from the molten steel, and flow into the mold, resulting in poor quality of inclusion properties in the cast steel.
[7]
Therefore, it is important to secure an appropriate residence time of molten steel as well as securing a sufficient residence time of molten steel for floating separation of inclusions existing in molten steel. It is also important to reduce the size of the congestion area. In other words, it is of utmost importance to reduce the size of the stagnation area while keeping the molten steel in the tundish for a sufficient and appropriate time. To this end, it is necessary to minimize the occurrence of a stagnation area while actively inducing an upward flow of molten steel in the tundish.
[8]
The technology that serves as the background of the present invention is published in the following patent documents.
[9]
(Patent Document 1) KR10-2014-0085127 A
[10]
(Patent Document 2) KR10-1602301 B1
Detailed description of the invention
Technical challenge
[11]
The present invention provides a melt treatment apparatus capable of securing a sufficient and adequate residence time of the melt accommodated in a container.
[12]
The present invention provides a melt treatment apparatus capable of improving inclusion removal ability by reducing a stagnant area of ​​a melt.
[13]
The present invention provides a melt treatment apparatus capable of widely distributing an upward flow reaching the upper surface of the melt.
Means of solving the task
[14]
A melt processing apparatus according to an embodiment of the present invention includes: a container in which a space for receiving a melt is formed, a melt injection unit is disposed on one side, and a melt outlet is formed on the other side; And a dam positioned between the injection unit and the discharge port so that one side faces the injection unit directly, and installed at the bottom of the container to be connected to both sidewalls in the longitudinal direction, wherein the dam includes a melt formed below the injection unit. It is installed in the falling area, and the upper surface is located above the melt.
[15]
The dam may be installed at an edge of the fall area.
[16]
The other surface of the dam may directly face sidewalls in the width direction of the outlet side.
[17]
The size of the fall area may be proportional to the size of the inner diameter of the injection unit, and a distance between one surface of the dam and the injection unit may be proportional to the size of the fall area.
[18]
The distance between one surface of the dam and the injection part may be formed in a range of 2.5 to 5 times the inner diameter of the injection part.
[19]
The dam may have an upper surface height of 0.5 to 0.75 times the height of the molten material.
[20]
It may further include a through hole formed in the dam.
[21]
The through hole is formed under the dam, is formed in a direction from one side to the other side, and an inner wall may be directly connected to the floor.
Effects of the Invention
[22]
According to an embodiment of the present invention, a dam is installed at the bottom of the container so as to be located at the edge of the hot water part of the melt, and the height of the upper surface of the dam is optimized to optimize the flow field of the melt. Accordingly, a sufficient and appropriate residence time of the melt accommodated in the container can be ensured, and the stagnant area of ​​the melt can be reduced, thereby improving the ability to remove inclusions. In addition, by inducing a strong flow of molten steel in the hot water portion to the upper surface of the melt, forming an upward flow, the upward flow reaching the upper surface of the melt can be widely distributed, and the inclusion removal ability can be further improved.
[23]
Accordingly, it is possible to smoothly float and separate the inclusions in the melt, thereby improving the cleanliness of the melt and improving the quality of the product produced from the melt.
[24]
In addition, it is not necessary to install an additional structure for reducing the flow rate of the melt in the container, and the size and number of refractory structures installed in the container can be minimized and optimized, and since the structure can be simplified, manufacturing cost can be reduced. .
Brief description of the drawing
[25]
1 is a view for explaining a modeling structure for evaluating the flow of a melt treatment apparatus according to an embodiment and comparative examples of the present invention.
[26]
2 is a view showing a flow evaluation result of a melt treatment apparatus according to an embodiment and comparative examples of the present invention.
[27]
3 is a diagram showing quantitative values ​​of flow characteristics of a melt derived from flow evaluation results according to examples and comparative examples of the present invention.
[28]
4 is a view for explaining a modeling structure for evaluating the flow of the melt treatment apparatus according to the embodiment and comparative examples of the present invention.
[29]
5 is a diagram showing quantitative values ​​of flow characteristics of a melt derived from flow evaluation results according to Examples and Comparative Examples of the present invention.
[30]
6 is a view showing a flow evaluation result according to embodiments of the present invention.
[31]
7 and 8 are schematic diagrams of a melt treatment apparatus according to an embodiment of the present invention.
Mode for carrying out the invention
[32]
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, and will be implemented in various different forms. Only the embodiments of the present invention are provided to complete the disclosure of the present invention and to completely inform the scope of the invention to those of ordinary skill in the relevant field. In order to describe an embodiment of the present invention, the drawings may be exaggerated, and the same reference numerals in the drawings refer to the same elements.
[33]
A melt treatment apparatus according to an embodiment of the present invention provides a technical feature capable of improving an inclusion removal ability by reducing a stagnation area of ​​a melt while increasing an area reaching an upward flow of an upper surface of the melt. The melt treatment apparatus according to an embodiment of the present invention is applied to a continuous casting process of a steel mill, but may be applied to various casting processes using various melts. An embodiment of the present invention will be described based on the continuous casting process.
[34]
7 and 8 are schematic diagrams showing a melt treatment apparatus according to an embodiment of the present invention. At this time, FIG. 7 is a cross-sectional view of a melt treatment device, and FIG. 8 is a perspective view of a melt treatment device. Here, the direction in which one side wall 1a in the width direction and the other side wall 1b in the width direction are spaced apart from each other is one direction, and the direction in which the injection part 2 extends is the vertical direction. And the other direction is the direction that intersects both one direction and the height direction. For example, the direction in which the dam 3 of FIG. 8 extends is the other direction. One direction may be referred to as a length direction, the other direction may be referred to as a width direction, and the vertical direction may be referred to as a height direction.
[35]
A melt treatment apparatus according to an embodiment of the present invention will be described with reference to FIGS. 7 and 8. The melt processing apparatus includes a container 1 in which a space for receiving a melt is formed inside, a melt injection part 2 is disposed on one side, and a melt outlet 1c is formed on the other side, and an injection part 2 on one side. It is located between the injection part 2 and the outlet 1c so as to face directly, and includes a dam 3 installed at the bottom of the container 1 and connected to both side walls 1d in the longitudinal direction.
[36]
At this time, the dam 3 is installed in the falling area of ​​the melt formed under the injection part 2, and the upper surface is located above the melt.
[37]
The melt (not shown) may include molten steel. The melt is immersed in a transport container, such as a ladle (not shown), is transported to the melt processing device, and may be disposed on the upper side of the container 1 and connected to the injection unit 2. The melt may be injected into the container 1 through the injection unit 2. Of course, the melt can be varied in addition to molten steel.
[38]
On the other hand, the lower part of the melt is a section from the bottom of the container 1 to less than 0.5 times the height of the hot water surface of the melt. In addition, the upper part of the melt is a section from a height of 0.5 times the height of the metal surface of the melt to the height of the metal surface of the melt. For example, if the height of the bottom of the container 1 is 0 and the height of the hot water surface of the melt is 1, the height from 0 to less than 0.5 is the lower part of the melt, and the height from 0.5 to 1 is the upper part of the melt.
[39]
Here, the height of the hot water surface of the molten material means the height of the molten material formed at a constant height in the container 1 in a steady state during the continuous casting process. For example, the height of the metal surface of the melt may be referred to as the level of the molten steel or the level of the metal surface. On the other hand, the steady state means a steady state with respect to the flow of the melt in the container 1.
[40]
The injection unit 2 is a refractory nozzle through which the melt can pass, and may be a shroud nozzle. The injection part 2 is mounted on a manipulator (not shown), and by raising the manipulator, an opening at the top can be coupled to a collector nozzle (not shown) of the transport container. The injection part 2 is disposed on one side of the container 1, is spaced apart from the bottom of the container 1, the opening at the lower end is located inside the container 1, and at least a portion may be immersed in the melt.
[41]
A falling area (hereinafter, referred to as a falling area) of the melt is formed under the injection part 2. The falling area is the area through which the melt injected into the container 1 passes first through the injection part 2. In the falling region, the melt supplied from the injection unit 2 collides with the bottom of the container 1 and then flows along the bottom with relatively high energy at a predetermined speed. Thereafter, as it moves away from the fall zone, the velocity of the melt gradually decreases, and the melt can flow at a normal flow rate with relatively low energy.
[42]
The falling area is formed on the bottom of the container 1, and its center c is aligned in the vertical direction with a central axis (not shown) in the vertical direction passing through the center of the injection unit 2. The size of the fall area, for example, the width in one direction is proportional to the size of the inner diameter of the injection part 2. When the inner diameter of the injection part 2 increases, the size of the drop area increases in proportion to the inner diameter of the injection part 2. Here, the inner diameter of the injection part 2 is the inner diameter based on the opening of the lower end of the injection part 2, and one direction is the extension direction of the container 1, from the injection part 2 toward the discharge port 1c. It can be a direction.
[43]
The distance between the edge end and the center c of the falling region in one direction may be 2.5 to 5 times the inner diameter d of the injection part 2. In the falling zone, the melt may actively flow at a speed within a predetermined range. The melt in the fall zone has a meaningful velocity.
[44]
At this time, the fact that the melt has a meaningful velocity means that the melt has a speed sufficient to form an upward flow instead of falling after it collides with the dam 3 and overflows. The flow of the melt in the drop zone can affect the formation of the total flow of the melt in the vessel 1, and in this respect, the fall zone is a significant area. On the other hand, the fall area is also called a hot water bath.
[45]
The container 1 has a melt receiving space formed therein, a melt injection part 2 is disposed on one side, and a melt outlet 1c is formed on the other side. The container 1 may for example comprise a tundish. In this case, the tundish may be a rectangular tundish that is elongated in one direction.
[46]
The container 1 has a rectangular bottom extending in one direction and the other direction crossing one direction, and both longitudinal sidewalls 1d extending in one direction along both long sides of the edge of the bottom and protruding in the vertical direction, And one sidewall 1a in the width direction and the other sidewall 1b in the width direction extending in the other direction along both short sides of the edge of the floor and protruding in the vertical direction. The injection part 2 is disposed relatively close to one side wall 1a in the width direction, and the outlet 1c is formed relatively close to the other side wall 1b. The bottom of the container 1 may have a step shape with a height of the other side lower than that of one side.
[47]
A melt accommodation space is formed by the bottom, both sidewalls 1d in the length direction, one sidewall 1a in the width direction, and the other sidewall 1b in the width direction. Both sidewalls 1d in the longitudinal direction face each other in the other direction, and one sidewall 1a in the width direction and the other sidewall 1b in the width direction face each other in one direction.
[48]
The injection unit 2 may be disposed on one side of the bottom, and the injection unit 2 may be disposed above the container 1 by being spaced apart from one side of the bottom in the vertical direction. In addition, the outlet 1c may be formed by passing through the other side of the floor in the vertical direction. A discharge nozzle (not shown), for example, an immersion nozzle is installed from the lower side of the container 1 through the discharge port 1c, and a mold (not shown) is disposed surrounding the lower portion of the immersion nozzle. The discharge port 1c is opened by a slide gate (not shown), and the melt may be discharged into a mold. The mold can solidify the melt into a cast iron.
[49]
A cooling table (not shown) is installed under the mold. The cooling zone can perform a series of forming operations by cooling and lowering the cast pieces continuously drawn from the mold. The cast piece that has passed through the cooling zone may be cut at a cutting part (not shown) and transferred to a rolling facility, or transferred to various post-treatment facilities depending on the purpose.
[50]
The container 1 has a function of controlling and distributing the supply amount of the melt to a mold (not shown), a function of reducing the pressure caused by the load of the melt, such as iron static pressure, and a function of removing inclusions through the flow control of the melt to improve cleanliness. Functions. At this time, a dam 4 is installed at the bottom of the container 1 to remove inclusions. The dam 4 serves to increase the residence time of the melt by controlling the flow of the melt so that the slag and inclusions contained in the melt float to the upper surface of the melt, such as a hot water surface. As the slag and inclusions floating on the upper surface of the melt are separated from the melt, mixing of the inclusions and slag into the mold can be minimized.
[51]
The dam 3 is located between the injection unit 2 and the discharge port 1c so that one side faces the injection unit 2 directly, is installed at the bottom of the container 1, extends in the other direction, and extends to both side walls in the longitudinal direction. It is connected to the opposite side of (1d). The dam 3 is supplied from the injection part 2 to the container 1 to raise the flow of the melt flowing along the bottom to the top of the container 1.
[52]
One side of the dam 3 is a side facing the side 1a and the injection part 2 in the width direction of both sides of the dam 3 extending in the width direction and the vertical direction. The other surface of the dam 3 is a surface facing the other side wall 1b and the outlet 1c in the width direction of both sides of the dam 3 described above. At this time, one surface of the dam 3 may be referred to as a front surface, and the other surface of the dam 3 may be referred to as a rear surface.
[53]
The fact that the dam 3 is located between the injection part 2 and the discharge port 1c so that one side of the dam 3 faces the injection part 2 directly means that no separate structure is installed between the dam 3 and the injection part 1. Means that. Here, the separate structures include various walls including weirs and auxiliary dams, containers such as impact pads, and other various structures having various shapes. That is, since a separate structure is not installed between the dam 3 and the injection unit 2, one surface of the dam 3 can directly face the injection unit 2. As the dam 3 is installed facing the injection part 2 directly, the melt supplied to the falling area is directly affected by the dam 3 without interference, and the flow can be controlled. That is, after the melt falls on the floor, it first collides with the dam 3 to form an upward flow.
[54]
At this time, since the momentum of the molten material decreases as the distance from the falling area decreases, the dam 3 may be installed in the falling area to effectively induce an upward flow of the molten material. At this time, in order to avoid direct collision with the falling melt, the dam 3 is installed at the edge of the falling region in the other direction so as to face the melt within the falling region. The dam 3 may first contact the melt flowing along the bottom of the container 1 in a direction from one side of the container 1 to the other side at this installation position. That is, the dam 3 is directly exposed to the melt in the falling area at the edge of the falling area and can directly contact it. In this case, direct contact means that the melt and the dam 3 come into contact with priority before the melt first comes into contact with a separate structure and the flow is controlled. Of course, since only the dam 3 is formed in the falling area, the melt in the falling area can only contact the dam 3 except for the bottom and side walls of the container 1.
[55]
Meanwhile, the other surface of the dam 3 may directly face the sidewall 1b in the width direction of the outlet 1c side. That is, a separate structure is not installed between the dam 3 and the outlet 1c. In this way, only one dam 3 is installed inside the container 1, and the flow of the melt can be controlled by one dam 3.
[56]
The distance between one surface of the dam 3 and the injection part 2 may be proportional to the size of the fall area. As the size of the fall area increases, the distance L between one surface of the dam 3 and the injection unit 2 may increase. In this case, the distance between the one surface of the dam 3 and the injection unit 2 may be formed in a range of 2.5 to 5 times the inner diameter d of the injection unit. Accordingly, at least one surface of the dam 3 may be located at the edge of the fall area. The dam 3 may have an upper surface located above the melt. Based on the bottom near one side of the container 1, the height H of the upper surface of the dam 3 may be formed in a range of 0.5 to 0.75 times the height of the hot water surface of the melt. If the height of the upper surface of the dam 3 is less than 0.5 times the height of the hot water surface of the molten material, a smooth upward flow cannot be formed, and it is difficult for the molten material to rise to the hot surface in a large area. If it exceeds 0.75 times the height of the hot water surface of the melt, the dam 3 not only interferes with the wide spread of the rising current on the hot water surface of the melt, but in particular, the height of the upper surface of the dam 3 exceeds 0.75 times the height of the hot water surface of the melt. When the molten material rises above the current level of hot water, it overflows and may overflow to the outside of the container 1.
[57]
The melt treatment device described above is referred to as a melt treatment device according to the first embodiment. Hereinafter, a melt treatment apparatus according to a second embodiment of the present invention will be described. The melt treatment apparatus according to the second embodiment of the present invention includes the above-described configurations of the melt treatment apparatus according to the first embodiment, and further includes a through hole (not shown) formed in the dam 3.
[58]
The through hole is formed under the dam 3, is formed in a direction from one side of the container 1 to the other side, and the inner wall may be directly connected to the bottom of the container 1.
[59]
According to embodiments of the present invention, only the dam 3 is installed in the container 1, the installation position is the edge of the falling area, and the upper surface is located above the melt. In this way, by designing the inner profile of the container 1 and controlling the flow of the melt, it is possible to create an upward flow from the falling area, and induce the flow of the melt so that the stagnation area in the container 1 is less than 10%. In this way, it is possible to improve the efficiency of removing inclusions by 50% or more compared to the prior art. In addition, it is possible to reduce the manufacturing cost of refractory materials and the manufacturing cost of molten steel due to the non-use of weirs. The dam structure of the melt treatment apparatus according to the embodiments of the present invention described above may be referred to as a tundish dam structure having a stagnation area of ​​less than 10% for manufacturing ultra-clean steel.
[60]
Hereinafter, it will be described in detail in comparison with the comparative examples that the melt treatment apparatus according to the above-described embodiments of the present invention can broadly distribute the upward flow reaching the upper surface of the melt while improving the inclusion removal ability by reducing the stagnant area of ​​the melt. do.
[61]
1 is a view for explaining a modeling structure for evaluating the flow of a melt treatment apparatus according to an embodiment and comparative examples of the present invention. 2 is a view showing a flow evaluation result of a melt treatment apparatus according to an embodiment and comparative examples of the present invention. 3 is a diagram showing quantitative values ​​of flow characteristics of a melt derived from flow evaluation results according to examples and comparative examples of the present invention.
[62]
The melt treatment apparatus according to the embodiments of the present invention is a device for reducing inclusions in the melt as much as possible according to the shape and design value of the dam in the continuous casting process. By analyzing the characteristics, the inner shape of the container 1, such as the shape and design value of the dam 3, was designed with an optimal profile.
[63]
1A is a modeling structure of a melt treatment apparatus according to a first embodiment of the present invention, and in this case, the height of the upper surface of the dam 3 may be 2/3 of the height of the melt water surface, for example 600mm. 1B is a modeling structure of a melt treatment apparatus according to a first comparative example, and no structure is installed in the container 1. (C) of FIG. 1 is a modeling structure of the melt treatment apparatus according to the second comparative example in which the impact pad 4 is installed directly under the injection part 2, and (d) is a subsidiary with a height of 40 mm in the falling area. This is a modeling structure of a melt treatment apparatus according to a third comparative example in which a dam 5 is installed and a dam having a through hole is installed at the rear thereof. In this case, in the third comparative example, the dam having the through hole is not installed to face the injection part 2 directly. At this time, the height of the upper surface of the dam having the through hole is 450 mm, which is 1/2 of the height of the molten water surface, and the installation position is outside the fall area. Meanwhile, in order to be distinguished from the dam 3 of the first embodiment, a dam provided with a through hole is hereinafter referred to as 3'.
[64]
1E is a modeling structure of a melt treatment apparatus according to a fourth comparative example of the present invention, in which only the auxiliary dam 5 is installed in the falling area. 1F is a modeling structure of a melt treatment apparatus according to a fifth comparative example of the present invention. The auxiliary dam 5 is installed at a distance of 1500 mm. Meanwhile, in the modeling structures of FIG. 1, the inner diameter of the injection port was 160 mm.
[65]
2A to 2F are the results of numerical analysis of the internal flow of the container 1 with the modeling structure of FIGS. 1A to 1F in order. In the case of (c) showing the second comparative example, it can be seen that the upward flow toward the hot water surface of the molten material is strongly formed, but the upward flow reaching area (A) is smaller than that of Example 1. In the case of (a) showing the first embodiment, it can be seen that the upstream reaching area (A) is most widely distributed. Accordingly, it can be seen that the contact opportunity between the slag of the molten surface and the inclusions of the melt in the embodiment is greater than that of the comparative examples.
[66]
In contrast to Example 1 of Figure 2 (a) and Comparative Example 3 of (d), only the dam 3 is installed in the fall zone, so that the dam 3 must contact the melt before the auxiliary dam 5, and rise. It can be seen that the increase of the flow reach area (A) is effective. Comparing Example 1 of FIG. 2A and Comparative Example 4 of (e), it can be seen that the design value of the height of the dam 3 of the example for increasing the upstream reaching area A is quite effective. In contrast to Example 1 of FIG. 2A and Comparative Example 3 of FIG. 2 and Comparative Example 5 of (f), it can be seen that it is important to install the dam 3 in the fall area.
[67]
The structure of the dam 3 of the melt treatment apparatus according to the embodiments of the present invention is an optimized profile for the purpose of increasing the plug volume in the melt and reducing the dead volume, and the residence time distribution curve The ability to remove inclusions in the melt can be evaluated through the graph.
[68]
3 shows quantitative values ​​for analyzing the flow characteristics of a melt through a residence time distribution curve graph for the modeling shape of the Example and Comparative Examples shown in FIG. 1.
[69]
First, the residence time distribution curve is, after configuring the continuous casting equipment for the water model experiment, while performing the water model experiment of the continuous casting process, a predetermined amount of the test solution (dye) is injected into the injection part for 2 to 3 seconds, and the outlet The concentration of the solution is detected over time and the result is expressed as a graph on the dimensionless time axis.
[70]
That is, the residence time distribution curve can be said to be a standard concentration graph according to dimensionless time measured at the outlet when dye is added to the inlet side of the flow. Of course, this curve can also be derived using numerical analysis instead of numerical model experiments. Using the residence time distribution curve, it is possible to determine, for example, the mixing degree of molten steel and the effect of inclusion separation and flotation according to the change in the capacity and internal shape of the tundish.
[71]
In the figure, the minimum time (Min. Time) is the time when the concentration of the experimental solution is first detected. Peak Time is the time when the concentration of the test solution is highest. The mean time is a value obtained by dividing the inner volume of the container 1 by the flow rate of the melt injection in the injection unit 2. The melt injection flow rate is the same for both the Examples and Comparative Examples, but the inner volume of the container 1 is different depending on the inner profile of the container 1.
[72]
The active mean residence time is a value obtained by dividing the area of ​​the curve when the measured average time has a dimensionless value of 2 or more by the average residence time. The active region fraction or the active volume fraction is a fraction of the region in which molten steel is mixed, and includes a plug volume fraction and a mixed volume fraction. The stagnation area fraction or stagnation volume fraction is the fraction of the area in which the melt flows very slowly with twice the average residence time of the melt in the vessel.
[73]
For example, the molten steel volume in the tundish is divided into an active volume and a dead volume. The active volume is an area where molten steel is mixed, and the dead volume is an area where no mixing occurs. The active volume is divided into a plug volume and a mixed volume. In the plug volume, molten steel flows through a pipe at the same velocity, and interlayer mixing does not occur, and mixing in the flow direction, that is, in the transverse direction, occurs in all areas. The mixed volume is the area where mixing is maximized and the area where mechanical stirring occurs. The dead volume, also known as the stagnation area, is the area of ​​fluid that moves very slowly within the container and stays for twice the average residence time. Meanwhile, Vp in the drawing refers to the plug volume fraction, Vd refers to the stagnation area fraction, and Vm refers to the mixed volume fraction.
[74]
In the figure, the smaller the congestion volume fraction is, the more advantageous for the inclusion separation flotation, and the larger the Vp/Vd and Vp/Vm values, the more advantageous for the inclusion flotation separation. Since the residence time distribution curve and the quantitative values ​​of the flow characteristics derived therefrom are widely known in the field of flow analysis, detailed descriptions thereof will be omitted.
[75]
The peak time is related to the plug volume, and it can be seen that it shows the largest value in the embodiment. The case of Example 1 is the best result. Looking at the proportion of the congestion area, it can be seen that Example 1 and Comparative Example 2 were less than 10%. It can be seen that all other comparative examples exceed 10%. Comparing Example 1 and Comparative Example 1, it can be seen that the reduction in the congestion area is effective at 4.7% to 5.8%. This is a 41% to 50% inclusion removal effect in terms of inclusion removal ability. In addition, in order to effectively remove inclusions, the fraction of the plug volume should be high and the fraction of the stagnant area should be low, and Example 1 and Comparative Example 2 show the best results.
[76]
However, when referring to FIG. 2 above, considering the reaching area of ​​the ascending flow as well, it can be seen that the example is more effective than the comparative example 2. In addition, since Comparative Example 2 is complicated to manufacture, has a high cost, and has a weakness in durability, it is understood that the case of the embodiment meets the purpose of reducing the congestion area, but the structure is simple and the upward flow can be widely distributed on the water surface. Proved.
[77]
4 is a view for explaining a modeling structure for evaluating the flow of the melt treatment apparatus according to the embodiment and comparative examples of the present invention. 5 is a diagram showing quantitative values ​​of flow characteristics of a melt derived from flow evaluation results according to Examples and Comparative Examples of the present invention. 6 is a view showing a flow evaluation result according to embodiments of the present invention.
[78]
Hereinafter, the flow evaluation was further performed by changing the installation location, the number and the presence or absence of through holes with the design value of the upper surface height of the dam 3 according to an embodiment of the present invention.
[79]
In the drawing, P1 is the installation position of the dam 3 according to the first embodiment, P2 is a position separated by a distance L from P1 to the rear, and P3 is a position separated by a distance of 2L from P1 to the rear. At this time, L was set to 500 mm and flow was evaluated.
[80]
The location of FIG. 5 is the installation location of the dam 3, for example, P1 + P2 in Comparative Examples 10 and 11 means that the dam 3 is installed at both the P1 and P2 locations. The rest also indicate the installation location as well. Whether or not a hole is formed means whether or not a through hole is formed.
[81]
6A is a numerical analysis result of the internal flow of the container 1 for Example 1 of FIG. 5, and (b) is a numerical analysis result of the internal flow of the container 1 for Example 2.
[82]
Looking at the value of the congestion area, it can be seen that the first and second embodiments have very small values. That is, it can be seen that the dam is constructed as in Example 1, but if the through hole is installed, the ability to remove inclusions is further improved. On the other hand, in Comparative Examples 6 to 17, it can be confirmed that installing a dam far away or installing several more in addition to the fall zone adversely affects the ability to remove inclusions. Thus, as in the embodiment of the present invention, if one dam is installed at the edge of the falling area in the container 1 and the height of the upper surface is the upper part of the melt, the size of the stagnant area can be significantly reduced to around 5%, As shown in (a) and (b) of Fig. 6, it can be seen that the upward flow can reach a wide area of ​​the hot water surface, and thus it can be seen that the inclusions can be reduced as much as possible.
[83]
On the other hand, if the design factor of the dam 3 designed as described above is further explained in a different way, the distance between the center (c) of the fall area and one side wall (1a) in the width direction is the center (c) of the fall area and the dam (3) It should be greater than the distance between one side of the drop area and less than the distance between the center (c) of the fall area and the other side of the dam 3, and the width, for example, thickness in one direction of the dam 3 should be in the range of 50mm to 200mm. Of course, the height of the upper surface of the dam 3 must be larger than 1/2 of the height of the molten water surface and smaller than 3/4. When the dam 3 is designed to have such a design value, since the size of the congestion area is small and the distribution area of ​​the upstream flow is wide, effective inclusion reduction is possible as in the flow evaluation result described above.
[84]
As described above, according to the embodiment of the present invention, the distance between one surface of the dam 3 and the injection unit 2 is in the range of 2.5 to 5 times the inner diameter of the injection unit 2, and The height of the upper surface can be in the range of 0.5 to 0.7 times the height of the hot water surface of the melt. Thereby, before the turbulent energy of the melt flowing into the hot water is dissipated, the turbulence of the melt in the hot water is controlled using the dam 3 to cause the melt to overflow to the top of the dam 3, and sufficient Upstream flow can be stably formed. Accordingly, it is possible to reduce the size of the stagnant region of the melt to the level of half of the conventional, and to improve the inclusion removal ability in the continuous casting process using the melt treatment apparatus.
[85]
For example, a melt treatment device was applied to a continuous casting process, a plurality of charge continuous casting processes were performed, and a cast steel was cast, and the cast steel was sampled to inspect inclusions. As a result, on average, the total number of inclusions decreased by about 40% compared to the prior art, and large inclusions with a size exceeding 20 μm decreased by about 51% compared to the prior art. In addition, inclusions having a size of 10 to 15 μm were reduced by 35% compared to the prior art, and inclusions having a size of 15 to 20 μm were reduced by 40% compared to the prior art.
[86]
The above embodiments of the present invention are for explanation of the present invention and are not intended to limit the present invention. It should be noted that the configurations and methods disclosed in the above embodiments of the present invention will be modified in various forms by combining or intersecting with each other, and such modified examples can be seen as the scope of the present invention. That is, the present invention will be implemented in a variety of different forms within the scope of the claims and the technical idea equivalent thereto, and a person in the technical field to which the present invention corresponds can various embodiments within the scope of the technical idea of ​​the present invention. You will be able to understand.
Claims
[Claim 1]
A container in which a melt receiving space is formed therein, a melt injection part is disposed on one side, and a melt discharge port is formed on the other side; And a dam positioned between the injection unit and the discharge port so that one side faces the injection unit directly, and installed at the bottom of the container and connected to both sidewalls in the longitudinal direction, wherein the dam includes a melt formed under the injection unit. A melt treatment device installed in a falling area and having an upper surface positioned above the melt.
[Claim 2]
The apparatus of claim 1, wherein the dam is installed at an edge of the falling area.
[Claim 3]
The apparatus of claim 1, wherein the other surface of the dam directly faces sidewalls in the width direction of the outlet side.
[Claim 4]
The apparatus of claim 1, wherein a size of the fall area is proportional to a size of an inner diameter of the injection unit, and a distance between one surface of the dam and the injection unit is proportional to a size of the fall area.
[Claim 5]
The apparatus of claim 1, wherein a distance between one surface of the dam and the injection unit is formed in a range of 2.5 to 5 times the inner diameter of the injection unit.
[Claim 6]
The apparatus of claim 1, wherein the dam has an upper surface height in a range of 0.5 to 0.75 times the height of the hot water surface of the melt.
[Claim 7]
The melt treatment apparatus according to any one of claims 1 to 6, further comprising a through hole formed in the dam.
[Claim 8]
The apparatus of claim 7, wherein the through hole is formed under the dam, is formed in a direction from one side to the other, and an inner wall is directly connected to the bottom.