CN111448012A

CN111448012A - Molten material processing apparatus

Info

Publication number: CN111448012A
Application number: CN201880079794.1A
Authority: CN
Inventors: 金星茁; 徐正道; 安钟泰
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2017-12-11
Filing date: 2018-12-07
Publication date: 2020-07-24
Also published as: KR20190069093A; JP2021505397A; WO2019117553A1; EP3725430A4; KR102033642B1; EP3725430A1

Abstract

The present invention provides a molten material processing apparatus including: a container having a molten material accommodating space formed therein, and having a molten material inlet portion disposed at one side of the container and a molten material outlet formed at the other side of the container; and a dam positioned between the inlet portion and the outlet such that one surface of the dam directly faces the inlet, the dam being provided on a bottom of the vessel to be connected to both side walls in a length direction, the dam being provided in a molten material falling region on a lower side of the inlet portion, and the dam having an upper surface on an upper portion of the molten material. The molten material processing apparatus increases the arrival area of the upward flow and reduces the congested area of the molten material, thereby enabling the inclusion removal capability to be improved.

Description

Molten material processing apparatus

Technical Field

The present invention relates to a molten material processing apparatus, and more particularly, to a molten material processing apparatus that reduces dead volume to improve inclusion removal capability.

Background

The continuous casting apparatus generally includes: a ladle for transporting molten steel; a tundish for receiving molten steel from the ladle and temporarily storing the molten steel; a mold for preliminarily solidifying the molten steel into a slab while continuously receiving the molten steel from the tundish; and a cooling zone for secondary cooling of the slab continuously drawn out of the crystallizer and performing a series of forming operations.

When a continuous casting process for casting a slab is performed using such a continuous casting apparatus, it is important to maintain molten steel in a tundish for a sufficiently long time. For example, when molten steel is maintained in a tundish for a sufficient period of time, inclusions may be smoothly floated and separated from the molten steel. In order to maintain the molten steel in the tundish for a sufficiently long time, it is necessary to actively induce the upward flow of the molten steel in the tundish.

The following patent document 1 proposes the following method: the method is used to construct a plurality of refractory dams such as a dam, an auxiliary dam, and an induction dam within a tundish, and then inject argon gas into molten steel through the auxiliary dam, thereby actively inducing an upward flow, rather than using a method of controlling the flow of molten steel using the dam and the dam. Further, patent document 2 proposes the following method: the method is for installing an impact pad and a partition wall at a lower side of a long nozzle and allowing molten steel to collide with the impact pad and pass through a space between the partition wall and the impact pad, thereby actively inducing an upward flow of the molten steel.

However, in the methods proposed in patent document 1 and patent document 2, constructing a plurality of dams inside a tundish requires additional manufacturing cost, and installation becomes complicated. In addition, a dead volume in which a flow rate of molten steel is extremely low in bottom surfaces (surfaces toward the steel outlet hole of the tundish) of the plurality of refractory dams and the partition walls and in a region away from the impact pad is increased.

In particular, when the dead volume of the molten steel in the tundish increases, the degree to which the molten steel is held in the dead volume becomes inappropriate, and the residence time of the molten steel may become excessively long. That is, when the dead volume of the molten steel in the tundish increases, an appropriate residence time of the molten steel in the tundish cannot be secured. Also, when the inclusions enter the dead volume, they are retained in the center of the dead volume due to the low flow rate of the molten steel, which prevents the inclusions from floating and separating from the molten steel. The inclusions flow into the mold and cause quality defects in the slab related to the inclusions.

Therefore, in addition to ensuring a sufficient residence time of the molten steel to float and separate inclusions present in the molten steel, it is also important to ensure an appropriate residence time of the molten steel. Furthermore, it is important to reduce the size of the dead volume. That is, it is critical to reduce the size of the dead volume while maintaining the molten steel in the tundish for a sufficient but appropriate period of time. For this reason, it is necessary to minimize the generation of dead volume while actively inducing the upward flow of molten steel in the tundish.

The background art of the present invention is disclosed in the following patent documents.

(patent document 1) KR10-2014-0085127A

(patent document 2) KR10-1602301B1

Disclosure of Invention

Technical problem

The present invention provides a molten material processing apparatus capable of ensuring a sufficient and appropriate residence time of a molten material contained in a container.

The invention provides a molten material processing apparatus capable of reducing the dead volume of a molten material to improve the inclusion removal capability.

The present invention provides a molten material processing apparatus capable of widely distributing an upward flow reaching a top surface of a molten material.

Technical scheme

A molten material processing apparatus according to an embodiment of the present invention includes: a container including a molten material accommodating space formed therein, a molten material inlet portion disposed at one side of the container, and a molten material outlet formed at the other side of the container; and a dam located between the molten material inlet portion and the molten material outlet such that one surface of the dam directly faces the molten material inlet portion, and the dam is installed on the bottom of the container and connected to both longitudinal direction side walls, wherein the dam is installed on a falling region of the molten material formed below the molten material inlet portion, and the dam has a top surface located in an upper portion of the molten material.

The dam may be mounted on an edge portion of the falling area.

The other surface of the dam may directly face the width-direction side wall on the molten material outlet side.

The size of the falling area may be proportional to the inner diameter of the molten material inlet portion, and the distance between one surface of the dam and the molten material inlet portion may be proportional to the size of the falling area.

The distance between one surface of the dam and the molten material inlet portion may be in the range of 2.5 to 5 times the inner diameter of the molten material inlet portion.

The height of the top surface of the dam may be in the range of 0.5 to 0.75 times the melt height of the molten material.

The molten material processing apparatus may further include a through hole formed in the dam.

A through hole may be formed in the lower portion of the dam, the through hole being defined in a direction from one side toward the other side and having an inner wall directly connected to the bottom.

Advantageous effects

According to an embodiment, the dam is installed on the bottom of the vessel to be located on the edge of the pouring zone of the molten material, and the height of the top surface of the dam can be optimized, thereby optimizing the flow field of the molten material. By so doing, a sufficient and appropriate residence time of the molten material contained in the container can be ensured and the dead volume of the molten material can be reduced to improve the inclusion removal capability. Further, a strong flow of molten steel in the pouring zone is directed to the top surface of the molten material to form an upward flow, thereby widely distributing the upward flow reaching the top surface of the molten material and further improving the inclusion removal ability.

Therefore, inclusions in the molten material can be smoothly floated and separated to improve the cleanliness of the molten material, thereby improving the quality of a product made of the molten material.

Further, it may not be necessary to install an additional structure for reducing the flow rate of the molten material within the vessel, and the size and number of refractory structures installed within the vessel may be minimized and optimized to simplify the structure. Therefore, the manufacturing cost can be reduced.

Drawings

Fig. 1 is a diagram illustrating a model structure for flow evaluation of a molten material processing apparatus according to an embodiment of the present invention and a comparative example.

Fig. 2 is a graph showing the flow evaluation results of the molten material processing apparatuses according to the embodiment of the present invention and the comparative example.

Fig. 3 is a graph showing quantified values of flow characteristics of molten materials derived from flow evaluation results according to the embodiment of the present invention and comparative examples.

Fig. 4 is a diagram illustrating a model structure for flow evaluation of a molten material processing apparatus according to an embodiment of the present invention and a comparative example.

Fig. 5 is a graph showing quantified values of flow characteristics of molten materials derived from flow evaluation results according to the embodiment of the present invention and comparative examples.

Fig. 6 is a diagram illustrating a flow evaluation result according to an embodiment of the present invention.

Fig. 7 and 8 are schematic views of a molten material processing apparatus according to an embodiment of the present invention.

Detailed description of the preferred embodiments

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments of the invention are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size is exaggerated for clarity of illustration, and like reference numerals refer to like elements throughout.

The molten material processing apparatus according to the embodiment of the present invention provides the following technical features: this technical feature allows the dead volume of the molten material to be reduced while increasing the area reached by the upward flow in the top surface of the molten material, thereby improving the inclusion removal ability. The molten material processing apparatus according to the embodiment of the present invention is used in a continuous casting process of a steel mill, and may also be used in various casting processes using various molten materials. Embodiments of the present invention will be described with reference to a continuous casting process.

Fig. 7 and 8 are schematic views illustrating a molten material processing apparatus according to an embodiment of the present invention. Here, fig. 7 is a sectional view of the molten material processing apparatus, and fig. 8 is a perspective view of the molten material processing apparatus. Here, as shown in fig. 7, one direction refers to a direction in which one width-direction side wall 1a is spaced apart from the other width-direction side wall 1b, and the vertical direction refers to a direction in which the molten material inlet portion 2 extends. Further, the other direction refers to a direction perpendicular to both the one direction and the height direction. For example, the other direction is a direction in which the dam 3 of fig. 8 extends. The one direction may be referred to as a longitudinal direction, the other direction may be referred to as a width direction, and the vertical direction may be referred to as a height direction.

A molten material processing apparatus according to an embodiment of the present invention will be described with reference to fig. 7 and 8. The molten material processing apparatus includes a container 1, the container 1 including a molten material accommodating space formed therein, a molten material inlet portion 2 disposed at one side of the container 1, and a molten material outlet 1c formed at the other side of the container 1. The molten material processing apparatus includes a dam 3, the dam 3 being located between the molten material inlet portion 2 and the molten material outlet 1c such that one surface of the dam 3 directly faces the molten material inlet portion 2, and the dam 3 being mounted on the bottom of the container 1 and connected to the two longitudinal direction side walls 1 d.

Here, the dam 3 is installed on a falling region of the molten material formed below the molten material inlet portion 2, and the dam 3 has a top surface in an upper portion of the molten material.

The molten material (not shown) may include molten steel. The molten material is stored in a delivery vessel, such as a ladle (not shown), and delivered to a molten material processing apparatus. The molten material may be located above the container 1 and connected to the molten material inlet portion 2. The molten material may be injected into the container 1 through the molten material inlet part 2. Further, the molten material may include various materials in addition to the molten steel.

Here, the lower portion of the molten material is a section ranging from the bottom of the vessel 1 to a height less than 0.5 times the height of the melt of the molten material. Further, the upper portion of the molten material is a section ranging from a height of 0.5 times the melt height of the molten material to the melt height of the molten material. For example, when the height of the bottom of the container 1 is zero and the melt height of the molten material is 1, a height from 0 to less than 0.5 corresponds to a lower portion of the molten material, and a height from 0.5 to 1 corresponds to an upper portion of the molten material.

Here, the melt height of the molten material refers to a height of the molten material having a constant height within the vessel 1 in a steady state during the continuous casting process. For example, the melt height of the molten material may be referred to as the level of molten steel or the melt level. Here, the steady state means that the flow of the molten material in the vessel 1 is in a steady state.

The molten material inlet portion 2 is a refractory nozzle through which the molten material can pass, and may be a long nozzle. The molten material inlet port 2 is mounted on a manipulator (not shown), and when the manipulator is lifted, an opening of an upper end of the molten material inlet port 2 may be coupled to a drain port (not shown) of a conveying container. The molten material inlet part 2 may be disposed at one side of the container 1 and spaced apart from the bottom of the container 1. Further, an opening of a lower end of the molten material inlet portion 2 may be located inside the container 1, and at least a portion of the molten material inlet portion 2 may be immersed in the molten material.

A molten material falling region (hereinafter referred to as a falling region) is defined below the molten material inlet portion 2. The falling region is a region through which the molten material having passed through the molten material inlet part 2 and then having been injected into the container 1 first passes. In the falling region, the molten material having relatively high energy after falling from the molten material inlet part 2 and colliding with the bottom of the container 1 may flow along the bottom at a predetermined flow rate. Subsequently, as moving away from the falling region, the flow rate of the molten material gradually decreases, and the molten material having relatively low energy may flow at a normal flow rate.

A falling area is formed on the bottom of the container 1, and the center c of the falling area is vertically aligned with a vertical central axis (not shown) passing through the center of the molten material inlet portion 2. The size of the falling area, for example, the width in one direction is proportional to the inner diameter of the molten material inlet portion 2. As the inner diameter of the molten material inlet portion 2 increases, the size of the falling area also increases in proportion to the inner diameter of the molten material inlet portion 2. Here, the inner diameter of the molten material inlet portion 2 may be an inner diameter with respect to an opening of a lower end of the molten material inlet portion 2, and one direction may be a direction from the molten material inlet portion 2 toward the molten material outlet 1c, such as a direction in which the container 1 extends.

The distance between the edge end of the falling region in one direction and the center c may be 2.5 to 5 times the inner diameter d of the molten material inlet portion 2. In the drop zone, the molten material may actively flow at a predetermined range of flow rates. The molten material in the drop zone has a meaningful flow rate.

Here, the molten material has a meaningful flow rate means that the molten material has a flow rate sufficient to form an upward flow rather than a downward flow after colliding with the dam 3 and overflowing. The flow of molten material in the drop zone affects the overall flow of molten material within the vessel 1 and, therefore, the drop zone may be a very meaningful area. The drop zone may be referred to herein as a pour zone.

The container 1 includes an accommodating space formed in the container 1, a molten material inlet portion 2 disposed at one side of the container 1, and a molten material outlet 1c formed at the other side of the container 1. The container 1 may comprise, for example, a tundish. Here, the tundish may be a rectangular tundish elongated in one direction.

The container 1 may comprise: a rectangular bottom portion extending in one direction and another direction perpendicular to the one direction; two longitudinal-direction side walls 1d extending along two long sides of an edge of the bottom in the one direction and protruding vertically, respectively; and one width-direction side wall 1a and the other width-direction side wall 1b, the one width-direction side wall 1a and the other width-direction side wall 1b extending along two short sides of the edge of the bottom in the other direction and protruding vertically, respectively. The molten material inlet portion 2 may be disposed relatively close to one width-direction side wall 1a, and the molten material outlet 1c may be disposed relatively close to the other side wall 1 b. The bottom of the container 1 may have a stepped portion in which the height of the other side is lower than the height of the one side.

The molten material accommodating space may be formed by a bottom, two longitudinal direction side walls 1d, one width direction side wall 1a, and the other width direction side wall 1 b. The two longitudinal-direction side walls 1d face each other in the other direction, and the one width-direction side wall 1a and the other width-direction side wall 1b face each other in the one direction.

The molten material inlet port 2 is disposed at one side of the bottom, and the molten material inlet port 2 may be vertically spaced apart from one side of the bottom and disposed in an upper portion of the container 1. Further, the molten material outlet 1c may be formed by vertically passing through the other side of the bottom. An outlet nozzle (not shown), for example, a submerged nozzle, is installed to pass through the molten material outlet 1c from below the vessel 1, and a mold (not shown) is arranged to surround a lower portion of the submerged nozzle. The opening degree of the molten material outlet 1c is adjusted by a slide gate (not shown) and the molten material can be discharged into the mold. In the mold, the molten material may be solidified into a slab.

A cooling zone (not shown) may be provided below the crystallizer. In the cooling zone, a series of forming operations are carried out by cooling and pushing downwards the slab continuously drawn from the crystallizer. The slab having passed through the cooling zone is cut by the cutting means and then may be conveyed to a rolling facility or various post-processing facilities according to the purpose.

The container 1 has the following functions: regulating and distributing the supply of molten material to a crystallizer (not shown); reducing pressure due to the weight of the molten material, such as ferrostatic pressure; and removing inclusions by flow control of the molten material to improve cleanliness. Here, a dam 4 is installed on the bottom of the container 1 to remove foreign substances. The dam 4 has the following functions: the flow of the molten material is controlled to increase the residence time of the molten material, thereby floating slag and inclusions contained in the molten material to a top surface of the molten material, for example, a melt surface. Since slag and inclusions floating to the top surface are separated from the molten material, the mixture of inclusions and slag entering the mold can be minimized.

The dam 3 is positioned between the molten material inlet portion 2 and the molten material outlet 1c such that one surface of the dam 3 directly faces the molten material inlet portion 2, and the dam 3 is mounted on the bottom of the vessel 1, the dam 3 extending in the other direction and being connected to the facing surfaces of the two longitudinal-direction side walls 1 d. The dam 3 may ascend the flow of the molten material, which is supplied from the molten material inlet portion 2 to the container 1 and flows along the bottom, toward the upper portion of the container 1.

One surface of the dam 3 is a surface facing the molten material inlet portion 2 and one width-direction side wall 1a of two side surfaces 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 molten material outlet 1c and the other width direction side wall 1b, of the above-mentioned two side surfaces of the dam 3. Here, 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.

The feature that the dam 3 is located between the molten material inlet portion 2 and the molten material outlet 1c such that one surface of the dam 3 directly faces the molten material inlet portion 2 means that there is no partition structure between the dam 3 and the molten material inlet portion 1. Here, the partition structure may include various walls such as a weir and an auxiliary dam, a container such as an impact pad, and other various structures having different shapes. That is, since a partition structure is not installed between the dam 3 and the molten material inlet portion 2, one surface of the dam 3 may directly face the molten material inlet portion 2. The dam 3 is installed to directly face the molten material inlet portion 2, and the flow of the molten material supplied to the falling area can be controlled by being directly influenced by the dam 3 without interference. That is, the molten material first collides with the dam 3 after falling to the bottom, and thus an upward flow can be formed.

Here, since the momentum of the molten material decreases as it moves away from the falling region, the dam 3 may be installed on the falling region so as to effectively induce the upward flow of the molten material. Here, in order to avoid direct collision of the dam 3 with the falling molten material, the dam 3 is installed on an edge portion in the other direction of the falling area, facing the molten material in the falling area. At this mounting position, the dam 3 may first come into contact with the molten material flowing along the bottom of the vessel 1 in a direction from one side of the vessel 1 toward the other. That is, at the edge portion of the falling area, the dam 3 may be directly exposed to the molten material within the falling area and may be in direct contact with the molten material within the falling area. Here, the direct contact means that the molten material is first in contact with the dam 3, for example, before the flow of the molten material is controlled due to collision with the partition structure. Of course, since only the dam 3 is provided in the falling area, the molten material in the falling area may be in contact with only the dam 3, except for the bottom and the side wall of the container 1.

Here, the other surface of the dam 3 may directly face the width-direction side wall 1b at the molten material outlet 1 c. That is, there is also no separation structure between the dam 3 and the molten material outlet 1 c. As described above, only one dam 3 is installed in the vessel 1, and the flow of the molten material can be controlled by one dam 3.

The distance between one surface of the dam 3 and the molten material inlet portion 2 may be proportional to the size of the falling region, as the size of the falling region increases, the distance L between one surface of the dam 3 and the molten material inlet portion 2 may increase, here, the distance between one surface of the dam 3 and the molten material inlet portion 2 may be in the range of 2.5 to 5 times the inner diameter d of the molten material inlet portion, accordingly, at least one surface of the dam 3 may be located on an edge portion of the falling region, the top surface of the dam 3 may be located in an upper portion of the molten material, the height H of the top surface of the dam 3 may be in the range of 0.5 to 0.75 times the melt height of the molten material with respect to the bottom near one side of the container 1, when the height of the top surface of the dam 3 is less than 0.5 times the melt height of the molten material, a smooth upward flow may not be formed, and the molten material widely rises to the melt surface, when the height of the top surface of the dam 3 exceeds 0.75 times the melt height of the molten material, the melt may be prevented from spreading widely, and thus, the molten material may flow beyond the melt surface of the melt may be difficult to overflow, and the melt material may overflow to the outside the melt of the container, the melt may exceed the melt level of the melt 75.

The above molten material processing apparatus is referred to as a molten material processing apparatus according to the first embodiment. Hereinafter, a molten material processing apparatus according to a second embodiment of the present invention will be described. The molten material processing apparatus according to the second embodiment of the present invention includes the components described in the molten material processing apparatus according to the first embodiment, and further includes a through hole (not shown) to be formed in the dam 3.

A through hole may be formed in the lower portion of the dam 3, the through hole being limited in a direction from one side of the container 1 toward the other side, and the through hole having an inner wall directly connected to the bottom of the container 1.

According to an embodiment of the invention, only a dam 3 is installed in the vessel 1. Further, the mounting position of the dam 3 is set to be at the edge portion of the falling area, and the top surface of the dam 3 is located in the upper portion of the molten material. The inner contour of the vessel 1 is designed as described above and the flow of the molten material is controlled. Therefore, an upward flow can be generated from the falling region, and the flow of the molten material can be induced so that the dead volume inside the container 1 is less than 10%. By doing so, the inclusion removal efficiency can be improved by 50% or more when compared with the related art. In addition, since the weir is not used, the manufacturing cost for the refractory can be reduced, and the manufacturing cost of the molten steel can be reduced. The dam structure of the molten material processing apparatus according to the embodiment of the present invention described above may be referred to as a tundish dam structure having a dead volume of 10% or less, for example, for manufacturing ultra-pure steel.

Hereinafter, it will be described in detail that the above-described molten material processing apparatus according to the embodiment of the present invention can widely distribute the upward flow reaching the top surface of the molten material while reducing the dead volume of the molten material to improve the inclusion removal capability when compared to the comparative example.

Fig. 1 is a diagram illustrating a model structure for flow evaluation of a molten material processing apparatus according to an embodiment of the present invention and a comparative example. Fig. 2 is a graph showing the flow evaluation results of the molten material processing apparatuses according to the embodiment of the present invention and the comparative example. Fig. 3 is a graph showing quantified values of flow characteristics of molten materials derived from flow evaluation results according to the embodiment of the present invention and comparative examples.

The molten material processing apparatus according to an embodiment of the present invention is an apparatus for finally reducing inclusions in a molten material according to the shape and design parameters of a dam in a continuous casting process. In this device, various types of structures are constructed in the container 1, and then the flow characteristics are analyzed. Thus, the internal shape within the vessel 1, such as the shape and design parameters of the dam 3, is designed to have an optimal profile.

In fig. 1 (a), a model structure of a molten material processing apparatus according to embodiment 1 of the present invention is provided. Here, the height of the top surface of the dam 3 is 2/3, for example, 600mm, which is the melt height of the molten material. In fig. 1 (b), a model structure of a molten material processing apparatus according to comparative example 1 is provided. There is no integral structure within the container 1. In (c) of fig. 1, there is provided a model structure of the molten material processing apparatus according to comparative example 2 in which an impact pad 4 is installed directly below the molten material inlet portion 2, and in (d), there is provided a model structure of the molten material processing apparatus according to comparative example 3 in which an auxiliary dam 5 having a height of a top surface as low as 40mm is installed in a falling region and a dam including a through hole is installed behind the auxiliary dam. Here, in comparative example 3, the dam including the through-hole was not installed to directly face the molten material inlet portion 2. Here, the top surface of the dam including the through-hole is 1/2, for example, 450mm in melt height of the molten material, and the mounting position is outside the falling region. Further, the dam including the through-hole is indicated by reference numeral 3' to distinguish from the dam 3 of embodiment 1.

In fig. 1 (e), a model structure of a molten material processing apparatus according to comparative example 4 of the present invention is provided. Only the auxiliary dam 5 is installed in the falling area. In fig. 1 (f), a model structure of a molten material processing apparatus according to comparative example 5 of the present invention is provided. The auxiliary weir 5 is installed away from the falling area and closer to the molten material outlet 1c than the molten material inlet portion 2, for example, at a position spaced from the center of the falling area by 1500 mm. Here, the inner diameter of the molten material inlet in the model structure of fig. 1 was set to 160 mm.

In fig. 2 (a) to (f), respective numerical analysis results for the internal flow of the container 1 in the model structures in fig. 1 (a) to (f) are provided. In the case of (c) illustrating comparative example 2, it can be confirmed that the upward flow facing the melt surface of the molten material is strongly formed, but the area a reached by the upward flow is smaller than that of embodiment 1. In the case of embodiment 1 (a), it was confirmed that the area a reached by the upward flow was most widely distributed. Therefore, it was confirmed that the chance of contact between slag on the melt surface and inclusions of molten material was higher in this embodiment when compared with the comparative example.

When comparing embodiment 1 in (a) of fig. 2 with comparative example 3 in (d), it can be confirmed that the area a to which the upward flow reaches is effectively increased when only the dam 3 is installed in the falling area and the dam 3 comes into contact with the molten material earlier than the auxiliary dam 5. When comparing embodiment 1 in (a) of fig. 2 with comparative example 4 in (e), it can be confirmed that the design parameter of the height of the dam 3 in this embodiment is significantly effective for increasing the area a reached by the upward flow. When comparing embodiment 1 in (a) of fig. 2 with comparative example 3 in (d) and comparative example 5 in (f), it can be found that it is important to install the dam 3 in the drop zone.

The structure of the dam 3 of the molten material processing apparatus according to the embodiment of the present invention has an optimized profile to increase the plug-like volume within the molten material and reduce the dead volume. The inclusion removal capacity in the molten material can be evaluated by the residence time profile.

FIG. 3 shows quantified values that can analyze the flow characteristics of the molten material by means of residence time distribution plots for the modeled shapes of the embodiment and comparative example shown in FIG. 1.

First, a continuous casting apparatus for a numerical model experiment is constructed, the numerical model experiment for a continuous casting process is performed, a certain amount of an experimental solution (dye) is injected within 2 to 3 seconds, and the concentration of the solution is detected at an outlet for a certain period of time. The results are plotted on a dimensionless time axis and thus the residence time distribution curve is plotted.

That is, the residence time distribution curve may be a standard concentration curve over a dimensionless time measured at the outlet when the dye is input to the inlet of the stream. Of course, the curve may be derived using numerical analysis rather than numerical model experimentation. Using the residence time distribution curve, the degree of mixing of molten steel and the inclusion floating/separating effect can be determined, for example, from the change in the capacity and the internal shape of the tundish.

In the figure, the minimum time is the time at which the concentration of the test solution is first detected. The peak time is the time at which the concentration of the test solution is highest. The average time is a value obtained by dividing the internal volume of the vessel 1 by the input flow rate of the molten material into the molten material inlet portion 2. In this embodiment and the comparative example, the input flow rates of the molten materials were equal to each other, but the inner volumes of the containers 1 were different from each other according to the inner contour of the containers 1.

The effective average residence time is a value obtained by dividing the area of the curve by the average residence time when the dimensionless value of the measured average time is 2 or more. The effective area fraction or effective volume fraction is the fraction of the area in which the molten steel is mixed and includes the plug volume fraction and the mixing volume fraction. The dead zone fraction or dead volume fraction is the fraction of the following region: in this zone, the molten material flows very slowly for a time twice as long as the mean residence time of the molten material in the container.

For example, the volume of molten steel in the tundish is divided into an effective volume and a dead volume. The effective volume is the area where the molten steel is mixed, while the dead volume is the area where no mixing occurs. The effective volume is divided into a plug volume and a mixing volume. In the plug-like volume, the molten steel flows at a constant flow rate by means of a tube flow, and mixing in the flow direction, i.e., in the horizontal direction, occurs over the entire area without interlayer mixing. The mixing volume is the region where mixing is highest and mechanical stirring occurs. The dead volume is called the stagnation zone and is the zone where the fluid moves very slowly within the vessel and the residence time is twice as long as the average residence time. Here, in the drawing, Vp is referred to as a plug volume fraction, Vd is referred to as a dead volume fraction, and Vm is referred to as a mixed volume fraction.

In the drawing, since the dead volume fraction is small, it is advantageous to float and separate the inclusions. The values of Vp/Vd and Vp/Vm are large, so that the inclusion can be floated and separated. Since residence time distribution curves and quantified values of flow characteristics derived from the residence time distribution curves are well known in the field of flow analysis, detailed descriptions thereof will be omitted.

The peak time is related to the plug volume and it can be confirmed that the highest value is shown in this embodiment. That is, embodiment 1 shows the best results. As for the ratio of dead volume, it can be confirmed that embodiment 1 and comparative example 2 show a value of less than 10%. It was confirmed that the other comparative examples were all greater than 10%. When embodiment 1 is compared with comparative example 1, it can be confirmed that there is an effect of reducing the dead volume by 4.7% to 5.8%. In terms of inclusion removal ability, there is an inclusion removal effect of 41% to 50%. Furthermore, in order to remove inclusions efficiently, the fraction of the plug volume must be high and the fraction of the dead volume must be low. Embodiment 1 and comparative example 2 show the best results.

However, referring to fig. 2 and considering the area where the upward flow reaches, it can be confirmed that this embodiment is more effective than comparative example 2. Further, comparative example 2 is complicated to manufacture, its cost is increased, and durability is poor. Thus, it was confirmed that this embodiment reduces the dead volume, has a simple structure, and can make the upward flow widely distributed on the melt surface.

Fig. 4 is a diagram illustrating a model structure for flow evaluation of a molten material processing apparatus according to an embodiment of the present invention and a comparative example. Fig. 5 is a graph showing quantified values of flow characteristics of molten materials derived from flow evaluation results according to the embodiment of the present invention and comparative examples. Fig. 6 is a diagram illustrating a flow evaluation result according to an embodiment of the present invention.

Hereinafter, by the design parameters of the top surface height of the dam 3 according to the embodiment of the present invention, the flow evaluation is further performed while changing the installation position, the number of dams, and the presence of the through portion.

In the drawings, P1 is the installation position of the dam 3 according to embodiment 1, P2 is a position spaced L apart from P1 in the rearward direction, and P3 is a position spaced 2L apart from P1 in the rearward direction, here, L is set to 500mm, and flow evaluation is performed.

The position in fig. 5 is the mounting position of the dam 3. For example, P1+ P2 in comparative example 10 and comparative example 11 means that the dam 3 is installed at both the P1 position and the P2 position. Likewise, others also represent mounting locations. The presence of holes refers to the presence or absence of through holes.

In fig. 6 (a), the results of numerical analysis of the internal flow of the container 1 of embodiment 1 of fig. 5 are shown. In (b), the results of numerical analysis of the internal flow of the container 1 of embodiment 2 are shown.

Examining the values of the dead zone, it can be confirmed that embodiment 1 and embodiment 2 have very small values. That is, when the dam is constructed as in embodiment 1 and is provided with the through-hole, it is confirmed that the inclusion removing ability is further improved. On the other hand, referring to comparative examples 6 to 17, it was confirmed that the inclusion removing ability was adversely affected when the dam was installed farther or several dams were installed in positions other than the falling region. Therefore, when one dam is installed on the edge portion of the falling region within the vessel 1 and the height of the top surface of the dam is in the upper portion of the molten material as in the embodiment of the present invention, it can be confirmed that the size of the dead volume is significantly reduced to about 5%, the upward flow reaches a large area of the melt surface as shown in (a) and (b) of fig. 6, and the inclusions are finally reduced.

Here, further explaining the design factor of the dam 3 as designed above in a different manner, the distance between the center c of the falling area and one width direction side wall 1a must be greater than the distance between the center c of the falling area and one surface of the dam 3 and smaller than the distance between the center c of the falling area and the other surface of the dam 3. The width, for example, the thickness of the dam 3 in one direction must be 50mm to 200 mm. Of course, the height of the top surface of dam 3 must be greater than 1/2 and less than 3/4 the melt height of the molten material. When the dam 3 is designed to have these design parameters, the size of the dead volume is reduced and the distribution area of the upward flow is widened. Therefore, as described previously in the flow evaluation results, inclusions can be effectively reduced.

As described above, according to the embodiment of the present invention, the distance between one surface of the dam 3 and the molten material inlet portion 2 may be in the range of 2.5 times to 5 times the inner diameter of the molten material inlet portion 2, and the height of the top surface of the dam 3 is in the range of 0.5 times to 0.7 times the melt height of the molten material. Thus, the dam 3 is used to control the turbulence of the molten material within the pouring zone before the turbulent energy of the molten material flowing in the pouring zone is dissipated. Therefore, the molten material may overflow the upper portion of the dam 3, and a sufficient upward flow can be stably formed. Therefore, the size of the dead volume of the molten material can be reduced to a half level when compared with the related art, and the inclusion removing ability can be improved when compared with the related art in the continuous casting process using the molten material processing apparatus.

For example, a molten material processing apparatus is used in a continuous casting process, and a multi-feed continuous casting process is performed to cast a slab. The cast slab was sampled and inspected for inclusions. As a result, the total number of inclusions was reduced by about 40% on average as compared with the related art, and large-sized inclusions having a size exceeding 20 μm were reduced by about 51% as compared with the related art. Further, inclusions having a size of 10 to 15 μm are reduced by about 35% compared to the related art, and inclusions having a size of 15 to 20 μm are reduced by about 40% compared to the related art. That is, it also has an effect of reducing fine inclusions.

The above embodiments of the present invention have been made for the purpose of describing the present invention, but the above embodiments 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 may be modified into various forms by combination or crossover, and these modified embodiments may also be considered to be within the scope of the present invention. That is, the present invention can be embodied in various forms within the scope of the claims and their equivalents, and it will be understood by those skilled in the art that various embodiments may be made within the technical idea of the present invention.

Claims

1. A molten material handling apparatus comprising:

a container including a molten material accommodating space formed therein, a molten material inlet portion disposed at one side of the container, and a molten material outlet formed at the other side of the container; and

a dam located between the molten material inlet portion and the molten material outlet such that one surface of the dam directly faces the molten material inlet portion, and the dam is installed on the bottom of the vessel and connected to two longitudinal-direction side walls,

wherein the dam is installed on a falling region of the molten material formed below the molten material inlet part, and the dam has a top surface in an upper portion of the molten material.

2. The molten material handling apparatus according to claim 1, wherein the dam is mounted on an edge portion of the drop zone.

3. The molten material handling apparatus according to claim 1, wherein the other surface of the dam directly faces a width-direction side wall on a molten material outlet side.

4. The molten material processing apparatus according to claim 1, wherein the size of the drop zone is proportional to an inner diameter of the molten material inlet portion, and

a distance between the one surface of the dam and the molten material inlet portion is proportional to the size of the falling region.

5. The molten material handling apparatus according to claim 1, wherein a distance between the one surface of the dam and the molten material inlet portion is in a range of 2.5 to 5 times an inner diameter of the molten material inlet portion.

6. The molten material handling apparatus of claim 1, wherein the top surface of the dam has a height in a range of 0.5 to 0.75 times a melt height of the molten material.

7. The molten material handling apparatus according to any one of claims 1 to 6, further comprising a through hole formed in the dam.

8. The molten material handling apparatus according to claim 7, wherein the through hole is formed in a lower portion of the dam, the through hole being defined in a direction from the one side toward the other side, and having an inner wall directly connected to the bottom.