JP6844367B2 - Hot water supply method for sliding nozzle, lower plate, lower nozzle and molten steel - Google Patents

Description

The present invention relates to a sliding nozzle for controlling the flow rate of molten steel by sliding a plurality of plates having openings, a lower plate for the sliding nozzle, a lower nozzle, and a method for supplying molten steel to hot water from a ladle using them. It is a thing.

In the continuous steel casting process, the molten steel whose composition and temperature have been adjusted in the refractory process is transported to a continuous casting machine in which the continuous casting process is performed while being stored in a ladle which is a refractory container. The transported molten steel is injected into a mold of a continuous casting machine via a tundish. A sliding nozzle is mainly used as a molten steel flow rate adjusting mechanism at the bottom of the ladle to adjust the flow rate of molten steel injected into the tundish and shut off the hot water supply. The molten steel flow rate adjusting mechanism at the bottom of the ladle adjusts the flow rate of molten steel so as to keep the amount of molten steel in the tundish constant, and shuts off the injection when the supply of molten steel in the ladle is completed. Further, a immersion nozzle is arranged at the bottom of the tundish together with a molten steel flow rate adjusting function, and molten steel is supplied from the immersion nozzle into the mold while adjusting the molten steel flow rate. The molten steel flow rate adjustment function at the bottom of the tundish adjusts the molten steel flow rate so as to keep the molten metal level in the mold constant. A sliding nozzle or stopper is used as the molten steel flow rate adjusting mechanism at the bottom of the tundish.

In continuous casting, it is necessary to continuously supply molten steel to the mold while exchanging the ladle to perform continuous casting. Since the supply of molten steel from the ladle to the tundish is interrupted when the ladle is replaced, the continuity of casting is maintained by supplying the stored molten steel in the ladle.

On the other hand, the airtightness between the tundish body and the tundish lid is not sufficient, and the atmosphere is mixed in the molten steel upper space in the tundish. In addition, since the molten steel injection flow from the ladle to the tundish is blocked from the atmosphere, an injection pipe and a long nozzle are arranged, but it is difficult to make it completely airtight. Therefore, in the tundish, the formation of non-metal inclusions due to the reoxidation of the molten steel is constantly occurring, which may cause the quality of the molten steel to deteriorate. In a simple injection method, reoxidation due to oxygen in the gas is likely to occur by involving the gas around the hot water drop portion.

Therefore, the tundish has a function of supplying molten steel to the mold while maintaining a predetermined flow rate as described above, and also has a function of floating and separating impurities in the molten steel in the tundish. Formed by slag inevitably mixed during steel refining, non-metal inclusions such as alumina produced from aluminum added for deoxidation, and molten steel reoxidation in tundish as described above. It has a function of floating and separating the non-metal inclusions formed in the tundish by utilizing the fact that the specific gravity is smaller than the specific gravity of steel. This prevents non-metal inclusions present in the molten steel from being supplied into the mold as they are, prevents them from being mixed into the slab, and causes defects during rolling caused by non-metal inclusions. Cracks and harmful internal defects can be suppressed.

When inert gas bubbles are mixed in the molten steel in the tundish, the non-metal inclusions in the molten steel are taken in and float when the bubbles float and separate in the tundish, which promotes the removal of the non-metal inclusions in the molten steel. It is effective in doing so.

Patent Document 1 discloses a method of injecting an inert gas from an injection nozzle into the molten steel being injected when injecting from a ladle into a tundish through an injection nozzle. If the distance from the hot water surface of the tundish to the position where the porous brick is installed is within 1.4 m, even if the inside of the nozzle becomes negative pressure, the inside of the nozzle is completely filled with the falling molten steel, so gas can be easily supplied. It is said that it can be mixed in molten steel.

In Patent Document 2, when the molten metal is injected into the tundish by the injection nozzle provided at the bottom of the pan, an inert gas is blown into the vicinity of the molten metal outlet at the bottom of the pan to suspend the gas in the injection flow. After dropping this injection flow through an injection nozzle filled with inert gas while maintaining a non-contact state with the inner surface of the nozzle, it collides with the molten metal surface at the lower part of the nozzle to make the gas bubbles in the molten metal finer. A method has been proposed in which the particles are divided and impurities are taken into the bubbles and removed. The gas blowing is disclosed in a form in which the gas is blown from a nozzle above the sliding nozzle or from the upper plate of the sliding nozzle.

Japanese Patent No. 3216384 Japanese Patent No. 3241523

It is difficult to maintain sufficient airtightness between the sliding nozzle at the bottom of the ladle and the injection tube provided below the sliding nozzle, and therefore it is difficult to evacuate the inside of the injection tube. Therefore, in the method described in Patent Document 1, even if gas is blown from the side surface of the injection pipe with a porous brick, the gas cannot be mixed into the injected molten steel. Further, there is a demand for a method in which gas is mixed into the injected molten steel by the method described in Patent Document 2 to exhibit the effect of removing inclusions from the molten steel, but the effect of removing inclusions is further increased. For that purpose, it is necessary to blow fine bubbles into the injected molten steel without loss.

The present invention provides a sliding nozzle, a lower plate for a sliding nozzle, a lower nozzle, and a hot water supply of molten steel for supplying molten steel from a ladle using them, which enables fine air bubbles to be blown into the injected molten steel without loss. The purpose is to provide a method.

That is, the gist of the present invention is as follows.
(1) A lower plate used for a sliding nozzle that controls the flow rate of molten steel by sliding a plurality of plates having openings. The plate directly above the lower plate in contact with the lower plate is called a direct upper plate, and the sliding nozzle is viewed from the lower plate. The direction in which the plate directly above moves when the flow rate of the molten steel passing through is reduced is called the "closing direction", and a gas blowing portion is provided on the side surface of the opening of the lower plate, and the gas blowing portion in the circumferential direction of the opening position, the said of opening the circumferential surface of the lower plate is provided biased in the closing direction, the閉方both sides within a range of 90 ° each direction of opening circumferential portion of the lower plate, on both sides total 180 A lower plate for a sliding nozzle, which is only in the range within ° and can blow gas from the outside of the lower plate via the gas blowing portion.
(2) A sliding nozzle for controlling the flow rate of molten steel by sliding a plurality of plates having openings, characterized in that the lower plate for the sliding nozzle described in (1) above is used as the lower plate. Sliding nozzle to do.
(3) A lower nozzle arranged in contact with the lower part of a sliding nozzle for controlling the flow rate of molten steel by sliding a plurality of plates having openings, and a plate directly above the sliding nozzle in contact with the lower plate is called a direct upper plate. The direction in which the plate directly above moves when the flow rate of molten steel passing through the sliding nozzle is reduced when viewed from the lower plate is called the "closing direction". position of the gas blow-off portion in the circumferential direction, wherein of the opening circumferential surface of the lower nozzle is provided biased in the closing direction, on both sides of the閉方direction of the opening circumferential portion of the lower nozzle 90 The lower nozzle is characterized in that the range is within ° and the total of both sides is within 180 °, and gas can be blown from the outside of the lower nozzle via the gas blowing portion.
(4) A method of supplying hot water of molten steel via a sliding nozzle arranged at the bottom of a pan, using the sliding nozzle described in (2) above as the sliding nozzle and arranging it at the opening of the lower plate of the sliding nozzle. A hot water supply method for molten steel, which is characterized in that molten steel is supplied while blowing inert gas from the gas blowing portion.
(5) A method of supplying hot water of molten steel via a sliding nozzle arranged at the bottom of a water heater, using the lower nozzle described in (3) above as a lower nozzle arranged in contact with the lower side of the sliding nozzle. A hot water supply method for molten steel, which comprises supplying molten steel while blowing inert gas from a gas blowing portion arranged at the opening of a lower nozzle.

According to the present invention, when injecting molten steel from one molten steel container into another molten steel container using a sliding nozzle, an inert gas bubble is effectively mixed in the injection flow, and a non-metal from the molten steel in another molten steel container is mixed. It becomes possible to effectively remove inclusions.

It is a figure which shows the sliding nozzle of this invention, (A1) (A2) (A3) is a side sectional view, (B1) (B2) (B3) are B1-B1, B2-B2, B3-B3 arrow sectional views, respectively. It is a figure. It is a figure which shows the sliding nozzle, (A1) (A2) is a side sectional view, (B1) (B2) are B1-B1 and B2-B2 arrow sectional views, respectively. It is a figure explaining the opening degree of a sliding nozzle. It is a figure which shows the relationship between the opening degree of a sliding nozzle and an opening angle. Ar gas blowing part of sliding nozzle and T.D. in molten steel in tundish. It is a figure which shows the relationship of O concentration.

A sliding nozzle for controlling the flow rate of molten steel will be described with reference to FIGS. 1 to 3. The sliding nozzle 1 has two or three plates, and each plate has an opening through which molten steel passes. When having two plates, it is composed of an upper plate 2 and a lower plate 4 (see FIGS. 1 (A1) and B1), and when the upper plate 2 is fixed and the lower plate 4 is slid by the sliding device 28, By increasing or decreasing the area of the overlapping portion between the opening 30U of the upper plate 2 and the opening 30L of the lower plate 4, the amount of molten steel passing through is increased or decreased to control the molten steel flow rate. When having three plates, it is composed of an upper plate 2, a sliding plate 3, and a lower plate 4 (see FIGS. 1 (A2) and (B2)), and the upper plate 2 and the lower plate 4 are fixed and the sliding plate 3 is slid. By sliding on the moving device 28, the area of the overlapping portion between the openings (30U, 30L) of the upper plate 2 and the lower plate 4 and the opening 30S of the sliding plate 3 is increased or decreased, so that the amount of molten steel passing through is increased or decreased. Control the molten steel flow rate.

In the case of two plates and the case of three plates, the plate directly above the lower plate 4 in contact with the lower plate 4 is referred to as "directly above plate 5" here. In the case of two plates as shown in FIG. 1 (A1), the upper plate 2 is the plate 5 directly above, and in the case of three plates as shown in FIG. 1 (A2), the sliding plate 3 is the plate 5 directly above. The direction in which the plate 5 directly above moves when the flow rate of the molten steel passing through the sliding nozzle 1 is reduced when viewed from the lower plate 4 is referred to as a "closing direction 44". In the case where the lower plate 4 slides on the two plates, the lower plate 4 moves to the left (sliding direction 45) in FIG. 1 (A1) when the flow rate of the molten steel is reduced. When viewed from the lower plate 4, the directly above plate 5 (upper plate 2) moves relatively to the right. Therefore, the right direction in FIG. 1 (A1) is the "closing direction 44". On the other hand, in the case of the method in which the sliding plate 3 slides with three prerates, the sliding plate 3 moves in the left direction (sliding direction 45) in FIG. 1 (A2) when the flow rate of the molten steel is reduced. Seen from the lower plate 4, the plate 5 directly above (sliding plate 3) moves to the left. Therefore, the left direction in FIG. 1 (A2) is the "closing direction 44".

As shown in FIG. 3, the opening diameter of each plate of the sliding nozzle 1 is d, and the distance between the opening center OL of the opening 30L of the lower plate and the opening center OU of the plate 5 directly above is set as x. When x = 0, it is fully open, and when x ≧ d, it is fully closed. Here, the opening degree r (%) is r = (d−x) / d × 100 (1)
far. Further, the opening angle θ at the opening degree r is defined. At the opening degree r, the intersections of the circumference of the opening 30L of the lower plate 4 and the circumference of the opening 30U of the plate 5 directly above are generated at two points. The angle between the first intersection and the second intersection when viewed from the opening center OL of the lower plate 4 is defined as the opening angle θ. In FIG. 3, when the opening of the plate directly above is located at 30U 2 , the opening angle θ ₂ is 120 ° _{because x 2} = d / 2 and the opening r _{2 is 50%.} Further, in FIG. 3, when the opening of the plate directly above is located at 30U 1 _{, x 1} = 0.7 × d is substituted into the above equation (1), and since the opening r ₁ is 30%, the opening angle θ ₁ is about 91 °. The relationship between the opening r and the opening angle θ is shown in FIG.

When a sliding nozzle is used to flow molten steel from the ladle to the tundish or from the tundish into the mold, 100%> r without opening the sliding nozzle fully (r = 100%) under normal steady state. By narrowing the opening degree, the desired molten steel flow rate is realized. The value obtained by dividing the overlapping area of the opening 30L of the lower plate 4 and the opening 30U of the directly above plate 5 by the cross-sectional area of the opening 30L of the lower plate 4 and multiplying by 100 is defined as the opening area ratio (%).

A case where a sliding nozzle 1 is provided at the bottom of a molten steel container such as a ladle or a tundish to control the flow rate of molten steel will be described with respect to the flow of molten steel in the vicinity of the sliding nozzle 1. Taking a three-plate sliding nozzle (see FIG. 1 (A2)) as an example, the same applies to the case of two plates (see FIG. 1 (A1)). The upper nozzle 6 is embedded in the bottom of the molten steel container 20, and the sliding nozzle 1 is arranged below the upper nozzle 6. A lower nozzle 7 is arranged below the sliding nozzle 1. Hereinafter, a case where the molten steel container 20 is a ladle 21 and the lower molten steel container 22 is a tundish 23 will be described as an example. When the molten steel container 20 is a tundish 23, the immersion nozzle may be directly arranged below the sliding nozzle 1. In this case, the immersion nozzle is included and is referred to as the lower nozzle 7.

When the opening degree of the sliding nozzle 1 is set to about half-open, the opening in the upper nozzle 6 and the opening in the upper plate 2 and the sliding plate 3 are filled with molten steel to form a filled molten steel flow 41. On the other hand, with respect to the openings of the lower plate 4 and the lower nozzle 7, the molten steel does not fill the openings, and the molten steel flow flowing down through the molten steel passage formed at the overlapping portion of the lower plate opening and the plate opening directly above is generated. It will flow down as an unfilled molten steel flow 42 (see FIGS. 1 (A2) and 1 (B2)). Using the above-defined opening area ratio, the initial velocity of the unfilled molten steel stream 42 flowing down from the lower plate 4 is "100 /" by comparing the flow velocities of the filled molten steel stream 41 descending in the upper nozzle 6 or the upper plate 2. The flow velocity increases by the "opening area ratio". Conversely, the flow velocity of the filled molten steel flow 41 in the upper nozzle 6 and the upper plate 2 becomes slower.

In the invention described in Patent Document 2, an example is disclosed in which a two-plate sliding nozzle is used and an inert gas is blown from the opening side surface of the upper nozzle or the opening side surface of the upper plate. As described above, since the openings of both the upper nozzle and the upper plate are filled with molten steel, the injected inert gas is taken into the molten steel. The gas bubbles taken in try to rise at a relative velocity that rises in the molten steel. As described above, the molten steel descent velocity in the opening of the upper nozzle and the upper plate is slower than the initial velocity of the molten steel flow below it, so that some or all of the blown air bubbles 43 are lower than the molten steel flow velocity. There is a concern that the bubbles 43 rise at a high speed and are not taken into the molten steel flow that rises and flows down into the molten steel container 20 (see FIG. 2 (see A1)). On the other hand, if the inert gas is blown from the opening side surface of the lower plate 4 of the sliding nozzle 1, the flow velocity of the molten steel passing through the lower plate 4 is high, so that the molten steel flowing down stays at a good yield and the molten steel below is blown. It is expected that the proportion of non-metal inclusions contributing to the floating separation in the container 22 (tandish 23 or continuous casting mold) will be high (see FIG. 2 (A2)).

Therefore, based on the above idea, an experiment was conducted in which the inert gas was blown from the lower plate 4 of the sliding nozzle 1 or the opening side surface of the lower nozzle 7. 5 tons of aluminum killed steel with a C concentration of 0.2% by mass melted in an atmospheric melting furnace are housed in a pan 21 (molten steel container 20) and passed through a three-plate sliding nozzle 1 provided at the bottom of the pan 21. Hot water was supplied into a tundish 23 (molten steel container 22) having a capacity of 1.5 tons. A molten steel outlet is provided at the bottom of the tundish, and the flow rate is adjusted so that the amount of molten steel in the tundish is constant. The opening diameter d of the sliding nozzle 1 of the ladle 21 is 50 mm. The sliding plate 3 was slid and fixed at an opening degree r = 50%. About the method of blowing from the opening side surface of the upper plate 2 (FIGS. 2 (A1) (B1)) and the method of blowing from the opening side surface of the lower plate 4 (FIGS. 2 (A2) (B2)) using Ar gas as the inert gas. I experimented. Both the upper plate 2 and the lower plate 4 are provided with through ports 11 in the entire circumferential direction of the opening 30 to serve as a gas blowing portion 8. That is, Ar gas was blown from the through holes 11 using a plate (upper plate 2, lower plate 4) provided with 16 through ports 11 having a diameter of 0.3 mm on the upper and lower sides, for a total of 32 pieces.

A sampler was immersed in the molten metal near the molten steel outlet of the tundish 23 to collect a molten steel sample. The obtained sample was subjected to the measurement of the total oxygen concentration in order to evaluate the concentration of oxide-based inclusions such as _{Al 2} O _3. The total oxygen concentration (TO) is determined by melting the collected sample in a graphite crucible and reacting oxygen in the steel with carbon in the crucible to obtain carbon monoxide gas, which is then carbon monoxide gas by an infrared absorption detector. Was detected and obtained.

FIG. 5 shows the flow rate of Ar gas blown from the sliding nozzle 1 on the horizontal axis and the total oxygen concentration (TO) (ppm) of the molten steel on the vertical axis. The level at which Ar gas is blown from the upper plate 2 is a black triangle (the entire circumference of the upper plate), and the level at which Ar gas is blown from the lower plate 4 is a white square (the entire circumference of the lower plate). As is clear from the figure, it is better to blow Ar gas from the lower plate 4 than to blow Ar gas from the upper plate 2. It became clear that O was reduced. Further, when Ar gas is blown from the lower plate 4, T.I. As a result, the amount of decrease in O increased. From the above experimental results, it is clear that when the inert gas is blown into the molten steel from the plate of the sliding nozzle 1, the effect of reducing non-metal inclusions in the molten steel in the tundish 23 is increased by blowing from the lower plate 4. became.

By the way, as described above, in a normal use state where the sliding nozzle 1 is not fully opened, the molten steel flow passing through the opening 30 of the lower plate 4 does not fill the entire opening of the lower plate 4, but the lower plate opening 30. It flows down in the "closed direction 44" of the above. Therefore, there is a concern that the inert gas blown from the opposite side of the “closing direction 44” of the opening circumference of the lower plate 4 will not be taken into the molten steel. Therefore, next, as shown in FIGS. 1 (A2) and 1 (B2), the inert gas blowing portion 8 is provided on the opening circumferential surface of the lower plate 4 and is biased toward the “closing direction 44” to blow the inert gas. An experiment was conducted. That is, the through holes 11 having a diameter of 0.3 mm are set in two steps, 22.5 ° each, in a range of 45 ° on each side of the opening circumference 44 of the lower plate 4 in the closing direction 44, and a range of 90 ° in total on both sides. It was provided and used as a gas blowing unit 8. A total of 10 pieces are provided, 5 pieces each on the top and bottom. Since the opening r of the sliding nozzle is fixed at 50% and the opening angle θ = 120 ° (see FIG. 1 (B2) and FIG. 3), among the unfilled molten steel flows 42 flowing down in the lower plate 4. The side in contact with the opening side surface of the lower plate 4 is in the range of the opening angle θ = 120 ° on the closing direction 44 side. All the through ports 11 are provided within the range of 90 °, and the inert gas blown out from the through ports 11 immediately contacts the unfilled molten steel stream 42 and is taken into the unfilled molten steel stream 42. Can be expected.

In FIG. 5, which is the same as the above experiment, the result (example of the present invention) in which gas is blown only into the range of 90 ° in total in the closing direction 44 of the opening 30 of the lower plate 4 is shown in a black rhombus (lower plate closing direction). As is clear from the figure, if the Ar gas flow rates are the same, the examples of the present invention include T.I. It was clarified that the amount of O reduction was the largest and the effect of reducing non-metal inclusions in the molten steel in the tundish 23 was the best. Further, in the same example of the present invention, as the Ar gas flow rate is increased, T.I. The amount of O reduction also increases.

When adjusting the opening degree of the sliding nozzle 1, when the opening degree is slightly lower than 100% (fully open), the molten steel flow flowing down comes into contact with the side surface of the lower plate opening within an opening angle of 180 °. .. Therefore, when be localized position of the gas blowout portion 8 provided on side surfaces of the opening 30 of the lower plate 4, the closing direction 4 4 sides within a range of 90 ° each of the opening circumferential portion of the lower plate 4, on both sides total If the range is within 180 ° , the inert gas can be blown into the molten steel at the entire position where the flowing unfilled molten steel flow 42 contacts the opening 30 of the lower plate 4 regardless of the opening degree of the sliding nozzle 1. .. When the sliding nozzle 1 is directed so as to maximize the yield of Ar gas when the opening degree is about half open, the range in which the gas blowing portion 8 is provided can be narrowed from 90 ° on both sides. For example, the arrangement position of the gas blowout unit 8 in the circumferential direction of the opening may be in the range within 60 ° to each of the opposite sides of the closing direction 4 4 of the opening circumferential portion of the lower plate 4. Alternatively, the range may be within 45 ° on each side.

That is, in the present invention, the lower plate 4 used for the sliding nozzle 1 that controls the flow rate of molten steel by sliding a plurality of plates having openings, and the plate directly above the lower plate 4 in contact with the lower plate 4 is called the upper plate 5, and the lower portion. Seen from the plate 4, the direction in which the plate 5 directly above moves when the flow rate of the molten steel passing through the sliding nozzle 1 is reduced is called the "closing direction 44", and the gas blowing portion 8 is provided on the side surface of the opening 30 of the lower plate 4. and, positions of the gas blowout unit 8 in the circumferential direction of the opening 30, a range within 90 ° on both sides of the closing direction 4 4 of the opening circumferential portion of the lower plate 4, only a range within 180 ° at both sides total This is a lower plate for a sliding nozzle, which is characterized in that gas can be blown from the outside of the lower plate 4 via the gas blowing portion 8. A sliding nozzle 1 for controlling the flow rate of molten steel by sliding a plurality of plates having openings, wherein the lower plate 4 of the present invention is used as the lower plate 4. ..

The present invention can be effectively implemented with any of a two-plate sliding nozzle and a three-plate sliding nozzle. When the lower plate 4 slides on the two plates, as shown in FIGS. 1 (A1) and 1 (B1), the direction opposite to the sliding direction 45 when the lower plate is closed is the "closing direction 44". Yes, a gas blowing portion 8 is provided on the closing direction 44 side of the circumference of the opening 30 of the lower plate 4. When the central sliding plate 3 slides on the three plates, the sliding direction 45 during the closing operation of the sliding plate 3 is the "closing direction 44" as shown in FIGS. 1 (A2) and 1 (B2). The gas blowing portion 8 is provided on the closing direction 44 side of the circumference of the opening 30 of the lower plate 4.

Further, in the present invention, as shown in FIGS. 1 (A3) and 1 (B3), the gas blowing portion 8 may be provided in the lower nozzle 7 arranged in contact with the lower side of the sliding nozzle 1. That is, the lower nozzle 7 is arranged so as to be in contact with the lower side of the sliding nozzle 1 that controls the flow rate of molten steel by sliding a plurality of plates having openings, and the plate directly above the sliding nozzle 1 in contact with the lower plate 4 is directly above the plate. It is called 5, and the direction in which the plate 5 directly above moves when the flow rate of molten steel passing through the sliding nozzle 1 is reduced when viewed from the lower plate 4 is called the "closing direction 44", and the side surface of the opening 30 of the lower nozzle 7 is gas. has a balloon portion 8, position of the gas blowout unit 8 in the circumferential direction of the opening 30, a range within 90 ° on both sides of the closing direction 4 4 of the opening circumferential portion of the bottom nozzle 7, on both sides total 180 The lower nozzle is only in the range within ° , and is characterized in that gas can be blown from the outside of the lower nozzle 7 via the gas blowing portion 8. By arranging the lower nozzle 7 in contact with the lower side of the sliding nozzle 1, the inert gas can be effectively blown into the unfilled molten steel flow 42 flowing down the opening 30 of the lower nozzle 7 at a high flow velocity.

The gas blowing portion 8 provided on the lower plate 4 or the lower nozzle 7 may be a single or a plurality of through holes 11 or a porous plug. Inside the lower plate 4 (lower nozzle 7), a through port 11 or a gas flow path 9 continuous from the porous plug to the outside is provided, and at the gas flow path inlet opened to the outside, an external inert gas supply source is provided. The inert gas can be supplied to the gas blowout unit 8 by connecting the pipes from the above.

Next, a hot water supply method for molten steel using the sliding nozzle 1 and the lower nozzle 7 of the present invention will be described. In the method of the present invention in which molten steel is supplied via a sliding nozzle 1 arranged at the bottom of a pan 21, the sliding nozzle of the present invention is used as the sliding nozzle and is arranged in the opening 30 of the lower plate 4 of the sliding nozzle 1. Hot water is supplied to the molten steel while blowing inert gas from the gas blowing portion 8 (FIGS. 1 (A1), (B1), (A2), and (B2)). Alternatively, in the method of the present invention in which the molten steel is supplied via the sliding nozzle arranged at the bottom of the pan 21, the lower nozzle 7 of the present invention is used as the lower nozzle arranged in contact with the lower side of the sliding nozzle 1. Hot water is supplied to the molten steel while blowing an inert gas from the gas blowing portion 8 arranged in the opening 30 of the nozzle 7 (FIGS. 1 (A3) and (B3)). As a result, the inert gas bubbles 43 are effectively mixed in the molten steel housed in the molten steel container 22 (for example, the tundish 23) that has received hot water, so that the inert gas bubbles float in the molten steel in the molten steel container 22. At this time, the non-metal inclusions in the molten steel are captured and floated and separated on the surface of the molten steel, so that the non-metal inclusions in the molten steel can be effectively removed.

1 Sliding nozzle 2 Upper plate 3 Sliding plate 4 Lower plate 5 Directly above plate 6 Upper nozzle 7 Lower nozzle 8 Gas outlet 9 Gas flow path 10 Piping 11 Through port 20 Ladle 20 Ladle 22 Ladle 22 Tundish 28 Sliding device 30 Opening 41 Filled molten steel flow 42 Non-filled molten steel flow 43 Bubbles 44 Closing direction 45 Sliding direction

Claims (5)

A lower plate used for a sliding nozzle that controls the flow rate of molten steel by sliding a plurality of plates having openings. The plate directly above the plate in contact with the lower plate is called a direct upper plate, and the molten steel that passes through the sliding nozzle when viewed from the lower plate. The direction in which the plate directly above moves when the flow rate is reduced is called the "closing direction", and the gas blowing portion is provided on the side surface of the opening of the lower plate, and the position of the gas blowing portion in the circumferential direction of the opening is provided biased to the closing direction of the opening circumferential surface of the lower plate, the閉方both sides within a range of 90 ° each direction of opening circumferential portion of the bottom plate, within 180 ° at both sides total A lower plate for a sliding nozzle, which has only a range and can blow gas from the outside of the lower plate via the gas blowing portion. A sliding nozzle for controlling a molten steel flow rate by sliding a plurality of plates having openings, wherein the lower plate for the sliding nozzle according to claim 1 is used as the lower plate. A lower nozzle that is arranged in contact with the lower part of a sliding nozzle that controls the flow rate of molten steel by sliding a plurality of plates having openings, and a plate directly above the sliding nozzle that is in contact with the lower plate is called a direct upper plate, and is called a lower plate. From the viewpoint, the direction in which the plate directly above moves when the flow rate of molten steel passing through the sliding nozzle is reduced is called the "closing direction", and the side surface of the opening of the lower nozzle has a gas blowing portion, and the circumferential direction of the opening. position of the gas blow-off portion in the said of opening the circumferential surface of the lower nozzle is provided biased in the closing direction, of the opening circumferential portion of the lower nozzle the閉方both sides within 90 ° each direction The lower nozzle is characterized in that the range and the total of both sides are within 180 °, and gas can be blown from the outside of the lower nozzle via the gas blowing portion. A method of supplying hot water of molten steel via a sliding nozzle arranged at the bottom of a pan, wherein the sliding nozzle according to claim 2 is used as the sliding nozzle, and a gas blowing portion arranged at the opening of the lower plate of the sliding nozzle. A hot water supply method for molten steel, which is characterized in that molten steel is supplied while blowing an inert gas from the water. A method of supplying hot water of molten steel via a sliding nozzle arranged at the bottom of a water heater, wherein the lower nozzle according to claim 3 is used as the lower nozzle arranged in contact with the lower side of the sliding nozzle, and the opening of the lower nozzle is used. A hot water supply method for molten steel, which is characterized in that molten steel is supplied while blowing inert gas from a gas outlet arranged in.

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