JP5888165B2 - Steel continuous casting method and equipment - Google Patents

Description

  The present invention relates to a steel continuous casting method and equipment therefor, and more particularly, when molten steel is poured from a tundish into a mold through an immersion nozzle, in order to suppress nozzle clogging with the immersion nozzle due to non-metallic inclusions in the molten steel. TECHNICAL FIELD The present invention relates to a steel continuous casting method and equipment for casting a slab having few bubble defects caused by an inert gas blown into the steel.

  In continuous casting of steel, molten steel staying in a tundish is poured into a mold through an immersion nozzle disposed below the tundish. At this time, when the molten steel in the tundish contains non-metallic inclusions such as alumina, the non-metallic inclusions adhere to and accumulate on the inner wall surface of the immersion nozzle, and the immersion nozzle is clogged. When the immersion nozzle is blocked, various problems occur in the casting operation and the slab quality. For example, the flow pattern of the molten steel in the mold is changed, the cleaning effect of the solidified shell by the molten steel flow is lowered, non-metallic inclusions and bubbles are trapped under the slab surface layer, and the quality of the slab is lowered. This problem is particularly serious in a continuous casting machine not equipped with an electromagnetic stirring facility for molten steel in a mold, and causes a fatal defect.

  Therefore, in order to prevent non-metallic inclusions from adhering or accumulating on the inner wall of the immersion nozzle, an inert gas such as Ar gas or nitrogen gas is blown into the molten steel flowing down in the molten steel flow path in the immersion nozzle, and the A method for preventing the adhesion / deposition of non-metallic inclusions by cleaning the inner wall of the immersion nozzle with an active gas has been implemented. For example, Patent Document 1 proposes a method of blowing a mixed gas of Ar gas and nitrogen gas limited to 4 NL or less per ton of molten steel, and Patent Document 2 discloses gas blowing individually into the upper nozzles of the tundish. The upper and lower gas blowing parts are provided with a gas blowing part that can be dissolved in molten steel or a mixed gas of molten gas and Ar gas, and Ar gas from the lower gas blowing part. A method of blowing in is proposed. In Patent Document 3, when a mixed gas of Ar gas and gas soluble in molten steel is blown, the Ar gas flow rate is determined by the cross-sectional area of the mold, and the entire gas flow rate is determined by the molten steel injection amount (throughput). A method is proposed, and in Patent Document 4, an upper nozzle is provided with two upper and lower gas blowing portions, Ar gas is mixed from the upper gas blowing portion, and nitrogen gas and Ar gas are mixed from the lower gas blowing portion. A method of blowing gas has been proposed. Patent Document 5 proposes a method of increasing the nitrogen gas blowing flow rate from the casting time when no nozzle clogging occurs while keeping the Ar gas blowing flow rate constant when the tendency of nozzle clogging has occurred. Non-metallic inclusions adhering to the inner wall of the immersion nozzle are removed to eliminate nozzle clogging.

  Among the inert gases, nitrogen gas is soluble in molten steel, so that it does not remain as a bubble defect in the surface layer portion of the slab. On the other hand, when molten steel into which Ar gas has been blown is injected into the mold, the Ar gas may be trapped by the solidified shell, and the trapped Ar gas causes slabs of cellular defects such as heges. There is a risk of bringing in. Even if it is any method of patent documents 1-5, since Ar gas is blown in into molten steel, this Ar gas may be trapped by the solidification shell.

  Further, in Patent Document 6, a bubble recovery unit having a predetermined size is formed inside an immersion nozzle, and Ar gas is supplied into the bubble recovery unit. A method has been proposed in which bubbles are recovered from molten steel that is pressurized and directed into the mold. Patent Document 7 discloses a box in which a discharge port of an immersion nozzle faces upward, a suction pipe is provided and a lower part is opened so as to surround the discharge port, and a molten steel flow flowing out from the discharge port is provided in the box. When the flow is lowered and then lowered, a vacuum pump is connected to the suction pipe, and the trapped Ar bubbles are sucked into the space formed by the molten steel surface and the box lid, and the molten steel A method for promoting the floating separation of Ar bubbles from the air has been proposed.

Japanese Patent Laid-Open No. 62-038747 JP-A-11-057958 JP-A-2005-30489 JP 2009-066603 A JP 2011-110561 A JP 2011-240395 A JP 2003-266155 A

  The methods of Patent Document 1 to Patent Document 5 are effective in suppressing nozzle clogging due to non-metallic inclusions, but cannot prevent the inert gas flowing into the mold from being trapped in the solidified shell. The generated inert gas leads to bubble defects such as lashes after rolling.

  Patent Document 6 relates to a technique for collecting bubbles by suppressing the outflow of bubbles into the mold, but even if the technique of Patent Document 6 cannot completely suppress the outflow of bubbles in the mold, Bubbles flowing out into the mold are trapped by the solidified shell. Patent Document 7 is a technique in which a discharge port of an immersion nozzle faces upward, a box surrounding the discharge port is provided, and Ar bubbles in the molten steel in the box are separated. However, since the flow of the molten steel tends to stay, the nozzle is clogged. In addition, if the recovery of bubbles from the molten steel before flowing out into the mold is not complete, the bubbles flowing out into the mold are trapped by the solidified shell.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce bubbles trapped in the solidified shell by more reliably reducing the amount of gas components contained in the molten steel in the mold. It is to provide a continuous casting method and equipment for steel.

  As a result of earnestly examining the method for recovering the inert gas flowing out into the mold, the present inventor is a secondary refining method used for the RH (Ruhrstahl-Heraeus) method and the final refining of stainless steel in steel refining. As seen in the VOD (Vacuum Oxygen Decarburization) method, etc., a method to reduce the amount of gas components contained in molten steel by depressurizing the atmosphere facing the molten steel (the upper space where the molten steel surface contacts) is put into practical use. The present inventors have studied the application of the technical idea of decompressing the atmosphere to the atmosphere facing the molten steel in the mold of the continuous casting equipment, and have completed the present invention.

That is, the gist of the present invention for solving the above problems is as follows.
(1) A steel continuous casting method in which molten steel into which an inert gas has been blown is injected into a mold through an immersion nozzle disposed below the tundish, the entire molten steel surface in the mold being A continuous casting method of steel, wherein a mold cover that covers an upper space is placed on the mold, and the upper space is decompressed.
(2) The steel continuous casting method according to (1), wherein the pressure in the upper space is maintained at 0.5 atm or less.
(3) Steel continuous casting equipment, an immersion nozzle disposed below the tundish, a mold disposed below the immersion nozzle, and a mold for cooling molten steel, and placed on the mold A mold cover that covers the entire upper surface of the molten steel surface in the mold and through which the immersion nozzle passes, and a pressure reducing device that is connected to the mold cover and depressurizes the upper space. Steel continuous casting equipment.

  According to the present invention, by depressurizing the upper space of the entire molten steel surface in the mold, the separation of gas components in the molten steel can be promoted, and the gas components remaining in the molten steel are reduced. Thereby, the quantity of the gas component supplemented by the solidification shell is reduced more reliably. By reducing the gas component remaining in the molten steel, defects near the surface of the slab are reduced, and thereby surface defects after hot rolling of the slab are reduced.

It is a schematic sectional drawing of the site | part of the tundish and casting_mold | template of the continuous casting installation of this invention. It is a schematic sectional drawing of the upper nozzle which blows inactive gas in molten steel.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of a tundish and mold part of the continuous casting equipment of the present invention. As shown in FIG. 1, a continuous casting facility 1 includes a tundish 3 that accommodates molten steel 2, a nozzle 4 that is connected to the tundish 3, and a mold 5 that is disposed below the nozzle 4, A mold cover 6 placed on the mold 5 and a pressure reducing device 7 connected to the mold cover 6 are provided. FIG. 1 shows a bottom surface portion of the tundish 3, and the tundish 3 has an iron shell 31 that is an outer shell and a refractory 32 that is constructed inside the iron shell 31. Yes. The molten steel 2 accommodated in the tundish 3 flows into the nozzle 4 and is then injected into the mold 5 from the nozzle 4.

  At the bottom of the tundish 3, an upper nozzle 41 that fits the refractory 32 is installed, a sliding nozzle 42 is disposed in contact with the lower surface of the upper nozzle 41, and further, in contact with the lower surface of the sliding nozzle 42, An immersion nozzle 43 is arranged. The nozzle 4 includes an upper nozzle 41, a sliding nozzle 42, and an immersion nozzle 43, and forms a molten steel passage 21 through which the molten steel 2 flows. A molten steel discharge hole 22 through which the molten steel 2 passes when the molten steel 2 is injected from the tundish 3 into the mold 5 through the immersion nozzle 43 is formed on the side surface of the immersion nozzle 43. In the upper nozzle 41, an inert gas such as Ar gas or nitrogen gas is allowed to flow into the molten steel 2 flowing down in the molten steel flow path 21 in order to prevent adhesion and accumulation of non-metallic inclusions on the inner wall of the immersion nozzle 43. It is blowing.

  FIG. 2 is a schematic cross-sectional view of the upper nozzle 41 that blows an inert gas into the molten steel. The upper nozzle 41 is composed of three parts, an upper gas blowing part 41a, a lower gas blowing part 41b, and a main body part 41e surrounding the upper gas blowing part 41a and the lower gas blowing part 41b. 41f is arranged. The upper gas blowing portion 41a and the lower gas blowing portion 41b are made of alumina porous brick, and the main body portion 41e is made of relatively dense alumina.

  Two gas introduction pipes 41c and 41d are disposed through the iron skin 41f, the gas introduction pipe 41c opens to the upper gas blowing section 41a, and the gas introduction pipe 41d opens to the lower gas blowing section 41b. Yes. That is, the gas supplied from the gas introduction pipe 41c is blown into the molten steel in the molten steel flow path 21 via the upper stage gas blowing part 41a, while the gas supplied from the gas introduction pipe 41d is passed through the lower stage gas blowing part 41b. Thus, it is configured to be blown into the molten steel channel 21. Ar gas, nitrogen gas, or a mixed gas of Ar gas and nitrogen gas is blown from the upper gas blowing portion 41a and / or the lower gas blowing portion 41b.

  The sliding nozzle 42 has an upper fixing plate 45, a sliding plate 46, and a lower fixing plate 47, and each plate is provided with a through-hole penetrating the plate. In the sliding nozzle 42, the upper fixing plate 45, the lower fixing plate 47, and the sliding plate 46 overlap each other so that the through holes of the respective plates communicate with each other, and the communicated through holes become a part of the molten steel channel 21. It is configured. The sliding plate 46 is connected to a reciprocating actuator 48. When the sliding plate 46 is moved in the horizontal direction by the operation of the reciprocating actuator 48, the sliding plate 46 is fixed to the upper fixed plate 45 and the lower fixed plate 45. It moves between the plates 47 while being in contact with them. As a result, the through hole of the sliding plate 46 is displaced from the through hole of the upper fixing plate 45 and the lower fixing plate 47, so that the horizontal cross-sectional area of the molten steel passage 21 in the sliding nozzle 42 (the opening degree of the sliding nozzle 42). The amount of molten steel passing through the molten steel passage 21 can be controlled.

  The immersion nozzle 43 is used with its tip immersed in the molten steel 2 so that the molten steel discharge hole 22 formed in the lower part is buried in the molten steel 2 in the mold 5. The mold 5 is composed of an opposing mold long side 51 and an opposing mold short side 52 that is housed inside the mold long side 51, and is formed by the mold long side 51 and the mold short side 52. The molten steel 2 is injected from the molten steel discharge hole 22 of the immersion nozzle 43 into the mold 5 to be formed, and a molten steel surface 23 is formed in the mold 5.

  As shown in FIG. 1, the mold cover 6 is placed on the mold 5, and a through-hole 64 that penetrates in the vertical direction is formed in the mold cover 6. The immersion nozzle 43 is inserted into the through hole 64 so as to be slidable with respect to the mold cover 6. Further, an upper space 26 is formed below the mold cover 6 and above the molten steel surface 23 over the entire molten steel surface 23. In order to prevent outside air from flowing into the upper space 26 through the gap between the through hole 64 and the immersion nozzle 43, the upper surface of the mold cover 6 near the through hole 64 and the side surface of the immersion nozzle 43 are in close contact with each other. A seal member 63 having flexibility is attached. Furthermore, a groove is formed on the upper surface of the mold long side 51 and the mold short side 52 constituting the mold 5, and a flexible member having flexibility, for example, an O-ring 53 is fitted over the groove. The mold cover 6 is in contact with the O-ring 53. Due to the weight of the mold cover 6, the mold cover 6 comes into close contact with the O-ring 53, and the mold long side 51 and the mold short side 52 come into close contact with the O-ring 53. Thereby, it is possible to prevent outside air from flowing into the upper space 26 through the gap between the mold 5 and the mold cover 6. The mold cover 6 is placed on the mold 5 so as to cover the upper space 26, so that the outside air in the upper space 26 flows from between the through hole 64 and the immersion nozzle 43 and between the mold 5 and the mold cover 6. Inflow can be prevented, and the upper space 26 of the entire molten steel surface 23 can be a closed space.

  FIG. 1 shows a form in which the mold powder 24 is poured into the molten steel 2 in the mold 5 and a layer of the mold powder 24 is formed on the molten steel surface 23. In this embodiment, the mold cover 6 covers the entire molten steel surface 23 and the upper space 26 of the layer of mold powder 24. On the other hand, when the mold powder 24 is not put into the molten steel 2 in the mold 5, the mold cover 6 covers the upper space 26 of the entire molten steel surface 23. In the present invention, that the mold cover 6 covers the upper space 26 of the entire molten steel surface 23 means that the mold cover 6 covers the upper space 26 formed above the entire molten steel surface 23, The mold cover 6 includes a form that covers the upper space 26 of the entire molten steel surface 23 and covers the upper space 26 of the entire molten steel surface 23 and the layer of the mold powder 24.

  The mold cover 6 is provided with a discharge passage 61. The decompression device 7 is connected to the mold cover 6 through the discharge passage 61, and the decompression device 7 decompresses the upper space 26 that has become a closed space through the discharge passage 61 and remains in the molten steel 2. The gas component is separated from the molten steel 2 through the entire molten steel surface 23 in the mold 5. The decompression device 7 may employ a known device that can be used in the technical field, such as a vacuum pump. Note that the pressure in the upper space 26 is preferably set to 0.5 [atm] or less by the decompression device 7. If the pressure is 0.5 [atm] or less, the gas component remaining in the molten steel 2 of the mold 5 can be more reliably separated from the molten steel 2.

  An aluminum killed steel 2 melted in a primary refining furnace such as a converter or electric furnace or a secondary refining furnace such as an RH vacuum degassing apparatus is poured into a tundish 3 from a ladle (not shown). When the amount of molten steel staying in the dish 3 reaches a predetermined amount, the sliding plate 46 is moved in the horizontal direction to increase the opening of the sliding nozzle 42, and the molten steel 2 is injected into the mold 5 through the molten steel passage 21. . The molten steel 2 is injected into the mold 5 from the molten steel discharge hole 22 as a discharge flow toward the mold short side 52. The molten steel 2 injected into the mold 5 is cooled by the mold 5 to form a solidified shell 25.

  After confirming that a predetermined amount of molten steel 2 has been injected into the mold 5, the mold cover 6 is placed on the mold 5, and the decompression device 7 starts depressurization of the upper space 26 of the entire molten steel surface 23. . A pinch roll (not shown) installed below the mold 5 after the molten steel discharge hole 22 is immersed in the molten steel 2 in the mold and the outer shell becomes the solidified shell 25 while maintaining the reduced pressure state of the upper space 26. To start drawing a slab having unsolidified molten steel 2 inside. Even after the start of drawing, the slab drawing speed is increased while controlling the position of the molten steel surface 23 to a substantially constant position in the mold 5 while maintaining the aforementioned reduced pressure state, and the casting is continued while maintaining the speed. . In this way, the upper space 26 is depressurized during continuous casting of steel.

  The mold cover 6 is provided with a charging port 62 from which the mold powder 24 is charged onto the molten steel surface 23 in the mold 5. The mold powder 24 melts and flows into the gap between the solidified shell 25 and the mold 5 to prevent the molten steel 2 from being oxidized, and exhibits an effect as a lubricant. In addition, after pouring the molten steel 2 into the mold 5, the mold 5 is periodically vibrated up and down, so-called oscillation is performed to prevent seizure between the solidified shell 25 and the mold 5, and when the slab is pulled out. The friction between the side wall surface of the mold 5 and the solidified shell 25 is reduced. Since the seal member 63 bends in response to the vibration of the mold 5, it prevents inflow of outside air into the upper space 26 through a gap between the through hole 64 of the mold cover 6 and the side surface of the immersion nozzle 43. .

  Since the inert gas is blown into the molten steel 2 injected into the mold 5 from the upper nozzle 41, the inert gas is taken in, and the decompression device 7 depressurizes the upper space 26, whereby the molten steel 2. The inert gas taken in is directed to the decompressed upper space 26 and further discharged from the upper space 26 toward the discharge passage 61. By reducing the gas component remaining in the molten steel 2, it is possible to reduce bubbles trapped by the solidified shell, thereby reducing defects near the surface of the slab, and thus after hot rolling of the slab. Reduces surface defects.

  It is preferable that the continuous casting facility 1 further includes a lifting device 8 that is connected to the mold cover 6 and moves the mold cover 6 up and down. The lifting device 8 also functions as an urging device that urges the mold cover 6 toward the mold 5 in order to increase the degree of decompression of the upper space 26 by the decompression device 7. In order to effectively depressurize the upper space 26, it is desirable that the degree of adhesion of the O-ring 53 to the mold cover 6 and the degree of adhesion of the O-ring 53 to the mold long side 51 and the mold short side 52 be higher. . The lifting device 8 urges the mold cover 6 toward the mold 5, so that the degree of adhesion is increased and the gap between the mold cover 6 and the mold 5 can be reliably eliminated. Further, the mold cover 6 can be moved upward by the lifting device 8 to remove the mold cover 6 from the mold 5, and maintenance inside the mold 5 and replacement of the O-ring 53 can be performed.

  In addition, although illustration is abbreviate | omitted, the casting_mold | template 5 and the casting_mold | template cover 6 may be provided inside the casting_mold | template 5 or the casting_mold | template cover 6 by providing the water supply flow path and drainage flow path through which cooling water passes, A mechanism for cooling the seal member 63 may be provided in the mold cover 6.

  In the above embodiment, the inert gas is blown into the molten steel 2 from the upper nozzle 41. However, the present invention is not limited to this configuration, and the sliding nozzle 42 and the immersion nozzle 43, which are constituent elements of the nozzle 4, are as shown in FIG. It is also possible to provide a mechanism similar to the configuration to blow an inert gas into the molten steel 2 from the sliding nozzle 42 and the immersion nozzle 43.

  As described above, by depressurizing the upper space 26 of the entire molten steel surface 23 in the mold 5, the gas component remaining in the molten steel 2 is reduced, and defects near the surface of the slab obtained from the molten steel 2 are observed. This reduces surface defects after hot rolling of the slab.

  Steel was continuously cast using the continuous casting equipment 1 shown in FIG. A tundish 3 having a size capable of accommodating up to 30 tons of molten steel was prepared. The mold long side 51 and the mold short side 52 were prepared so that the long side inside the mold was 1300 mm and the short side inside the mold was 220 mm, and the size of the mold 5 was set. A mold cover 6 suitable for the size of the mold 5 was prepared, and the mold cover 6 was placed on the mold 5.

  Using a converter and VOD method, 180 tons of molten stainless steel equivalent to SUS430 was melted. As the molten steel 2, this molten stainless steel was poured from the ladle into the tundish 3, and then poured into the mold 5 through the nozzle 4. The casting speed was 1.0 m / min, a pinch roll (not shown) was driven, the slab was started to be drawn from the mold 5, and steel was continuously cast.

  During continuous casting of steel, the upper nozzle 41 shown in FIG. 2 was used to blow Ar gas at 5 NL / min and nitrogen gas at 4 NL / min into the molten steel 2 passing through the upper nozzle 41. After starting the drawing of the slab, the pressure in the upper space 26 was set to 0.8 atm by the decompression device 7 (Invention Example 1). Except that the pressure reducing device 7 is set so that the pressure in the upper space 26 of the molten steel surface 23 in the mold 5 is 0.5, 0.1, 0.01, 0.001 atm, the same as Example 1 of the present invention. The steel was continuously cast (Invention Examples 2 to 5). Further, in order to compare with Examples 1 to 5 of the present invention, the molten steel surface 23 in the mold 5 was opened to the atmosphere without placing the mold cover 6 on the mold 5 (Comparative Example). Since the mold cover 6 is not placed on the mold 5, the molten steel surface 23 is under atmospheric pressure (1 atm) from above.

<Evaluation of Invention Examples 1 to 5 and Comparative Example>
In the continuous casting process of steels of Examples 1 to 5 of the present invention and the comparative example, a sample (full width size) having a length of 200 mm was taken from the slab slab in the steady region after the end of continuous casting. The surface of the collected sample was ground by 0.5 mm, and the number of holes (hereinafter referred to as “bubbles”) due to bubbles having a diameter of 0.1 mm or more appearing on the ground surface was counted. Further, the ground surface was ground again by 0.5 mm, and the number of bubbles on the surface was counted repeatedly until the sample surface for 10 mm from the surface in the initial state of the sample was ground. Table 1 shows the number of bubbles counted in the inventive examples 1 to 5 relative to the number of bubbles in the comparative example when the number of bubbles counted in the comparative example is 100. It is shown as an index. For convenience, the item of the pressure [atm] in the upper space in the comparative example is described as 1.0.

  A surface inspection was performed on the steel sheet obtained after hot-rolling the slab into a steel sheet having a thickness of 5 mm × 1270 mm and annealing and pickling. Linear defects having a width of 0.1 mm or more on the surface of the steel plate were counted. In Table 2, when the number of linear defects in the comparative example is 100, the number of linear defects counted in Examples 1 to 5 of the present invention is relatively relative to the number of linear defects in the comparative example. The represented value is shown as a defect number index. In Table 2, as in Table 1, the item of the pressure [atm] in the upper space in the comparative example is described as 1.0.

  By reducing the pressure in the upper space 26 of the entire molten steel surface 23 inside the mold 5, the gas component remaining in the molten steel 2 is reduced as shown in Table 1, and the vicinity of the surface of the slab obtained from the molten steel 2 is reduced. It was found that it was possible to reduce the defects, and as shown in Table 2, it was found that the surface defects of the steel sheet obtained after hot rolling of the slab could be reduced.

1 Continuous Casting Equipment 2 Molten Steel 3 Tundish 4 Nozzle 5 Mold 6 Mold Cover 7 Depressurizer 8 Elevator 21 Molten Steel Flow Channel 22 Molten Steel Discharge Hole 23 Molten Steel Surface 24 Mold Powder 25 Solidified Shell 26 Upper Space 31 Iron Skin 32 Refractory 41 Upper nozzle 41a Upper gas blowing portion 41b Lower gas blowing portion 41c Gas introduction tube 41d Gas introduction tube 41e Main body portion 41f Iron skin 42 Sliding nozzle 43 Immersion nozzle 45 Upper fixed plate 46 Sliding plate 47 Lower fixed plate 48 Reciprocating actuator 51 Mold Long side 52 Mold short side 53 O-ring 61 Discharge passage 62 Input port 63 Seal member 64 Through hole

Claims (3)

A continuous steel is obtained by injecting molten steel into which a mixed gas of Ar gas and nitrogen gas is blown from an upper nozzle installed above the immersion nozzle through an immersion nozzle disposed below the tundish. A casting method,
A mold cover covering the upper space of the entire molten steel surface in the mold is placed on the mold in contact with an O-ring fitted in a groove formed on the upper surface of the mold long side and the upper surface of the mold short side. In addition, in order to prevent inflow of outside air through the through hole for passing the immersion nozzle of the mold cover, a flexible sealing member is closely attached to the upper surface of the mold cover and the side surface of the immersion nozzle. A continuous casting method for steel , wherein the upper space is decompressed.   2. The steel continuous casting method according to claim 1, wherein the pressure in the upper space is maintained at 0.5 atm or less. Steel continuous casting equipment,
An immersion nozzle located below the tundish;
An upper nozzle for injecting a mixed gas of Ar gas and nitrogen gas into the molten steel flowing above the immersion nozzle, which is installed above the immersion nozzle ;
Is disposed below the immersion nozzle, and the mold to cool the molten steel,
The upper part of the entire molten steel surface in the mold is placed on the mold in contact with an O-ring fitted in a groove formed on the upper surface of the mold long side and the upper surface of the mold short side constituting the mold. A mold cover that covers the space and through which the immersion nozzle passes,
A flexible sealing member for tightly attaching to the upper surface of the mold cover and the side surface of the immersion nozzle and preventing inflow of outside air through the through hole for passing the immersion nozzle of the mold cover. When,
Are connected to the mold cover, a pressure reducing device for reducing the pressure of the upper space,
A continuous casting facility for steel, comprising:

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