JPS62279059A - Submerged nozzle - Google Patents

Abstract

PURPOSE:To prevent nozzle clogging without any disturbance to molten flow and molten surface in a mold by exhausting gas, supplied to a molten passage from a gas supplying means, by gas exhausting means. CONSTITUTION:At the time of starting flow of molten steel into the mold 3 from a tundish 1 through the molten steel passage of a nozzle body 42, argon gas is supplied from a gas passage 22 toward the arrow 24 direction and gas flow is formed in the nozzle body 42. Then, argon gas is supplied to a gas supplying pipe 44 and injected to the molten steel passage through porous brick 50 and also gas in the molten steel passage is exhausted by driving a suction pump 60 through a penetrating hole brick 54 toward the arrow 58 direction. The gas supplied through the brick 50 becomes to bubbles and the gas flow injected from the gas passage 22 encloses the bubbles and descended to the molten steel passage, and its partial is made to gas film covering the inner wall of the nozzle to restrict sticking of the inclusions. On the other hand, by controlling exhausting pressure in the pressure range from 1 atmosphere pressure to the inner pressure of the nozzle by the pump 60, the gas in the molten steel passage is exhausted.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] This invention has a molten metal flow path through which a molten metal flows and a discharge hole through which a molten layer is discharged. The present invention relates to an immersion nozzle that injects molten metal by immersing its discharge hole into self-molten metal in a mold while supplying gas to a molten metal passage. [Prior art] In continuous steel casting, a nozzle attached to the bottom of a tundish is immersed in molten steel, and the opening of this nozzle is adjusted by vertical movement of a stopper, while molten steel is injected from the tundish into the mold. are doing. In this case, if injection continues for a long time, non-metallic inclusions such as alumina will adhere to the inner wall of the nozzle, causing nozzle clogging. Argon gas is also ejected from the nozzle to prevent inclusions from adhering to the inner wall of the nozzle.

A conventional gas blow nozzle (immersion nozzle) 2 will be explained with reference to FIG. The upper end of the cylindrical gas plow nozzle 2 is connected to the injection hole 25 at the bottom of the tundish 1, and the lower end of the nozzle 2 is immersed in molten steel 30 in the mold 3. This nozzle wall 5 is equipped with argon gas supply pipes 4 and 6. A supply port of the gas supply pipe 4 is introduced into the nozzle wall 5 and connected to a porous brick 12 at the end of the nozzle wall through a slit 8 formed around the entire circumference of the nozzle wall 5. Similarly, the supply port of the gas supply pipe 6 is also introduced into the nozzle 15 and connected to the porous brick 14 below through a 1° slit formed over the entire circumference of the nozzle wall 5. Note that a plurality of discharge holes 26 for discharging molten steel are opened laterally at the lower end of the nozzle 2.

On the other hand, a stopper 20 is disposed at a position aligned with the injection hole 25, and its vertical movement opens and closes the injection hole 25 and adjusts the amount of molten steel injected. A gas passage 22 is formed at the axial center of this stopper 20.

In such a gas blow nozzle 2, argon gas is supplied from the gas passage 22 of the stopper 20 in the direction of the arrow 24 and is ejected into the molten steel flow path of the nozzle 2, and is ejected from the gas supply pipe 4.6 in the direction of the arrow 16. Argon gas is supplied in 18 directions to open the slits 8 and 10 and the porous bricks 12.
．． 14 into the molten steel flow path. gas passage 22
The argon gas jetted out becomes a gas flow descending in the center area of the molten steel passage, while the gas supplied through the porous bricks 12 and 14 becomes bubbles near the inner surface of the nozzle 2. For this reason, the descending gas flow and air bubbles coexist in the molten steel flow path, suppressing the adhesion of inclusions to the nozzle inner wall, and preventing the occurrence of nozzle clogging.

[Problems to be Solved by the Invention] By the way, in the conventional gas blow nozzle 2, in order to increase the effect of preventing nonmetallic inclusions from adhering to the inner wall of the nozzle, the gas passage 22 and the gas supply pipe 4.6 are It is necessary to increase the amount of argon gas supplied. However, if the gas supply rate is increased to 82/min or more, a large amount of gas 28 will be ejected from the discharge hole 26 at the lower end of the nozzle, and this gas 28 will disturb the molten steel flow and the molten metal surface (meniscus) in the mold 3.
I-side scratches occur. When this hot water surface crack occurs,
The thickness of the solidified shell 31 formed on the inner wall of the mold 3 becomes uneven, the molten steel surface is exposed, the molten steel 30 is oxidized, and the slag 32 that covers the molten steel surface is mixed into the molten steel 30, causing the solidified shell 31 to become uneven. There is a disadvantage that the quality of the slab is deteriorated due to the problem that it is trapped in the cast iron. For this reason, there are restrictions on the amount of gas supplied to the molten steel flow path, and conventionally it has not been possible to effectively prevent the occurrence of nozzle clogging. There is a problem in that it is not possible to increase the number of continuous casting operations.

This invention was made in view of such circumstances, and
An object of the present invention is to provide an immersion nozzle that can effectively prevent nozzle stickiness without disturbing the flow of molten metal and the surface of the molten metal in a mold.

[Means for Solving the Problems] The immersion nozzle according to the present invention has a molten metal flow path through which the molten metal flows and a discharge hole through which the molten metal is discharged, and a gas is supplied to the molten metal flow path. In an immersion nozzle that injects the molten metal by immersing the discharge hole in the mold self-molten metal, the immersion nozzle includes a gas supply means for supplying gas to the molten metal passage through a supply passage formed in the nozzle wall, and a gas supply means formed in the nozzle wall. and a gas discharge means for discharging gas from the molten metal passage through the discharge passage.

[Function] In the immersion nozzle according to the present invention, the gas supply means supplies gas to the molten metal flow passage through the supply passage formed in the nozzle wall, and the gas discharge means supplies gas through the discharge passage formed in the nozzle wall. Since the gas is discharged from the molten metal passage through the molten metal passage, even if the amount of gas supplied to the molten metal passage is increased, the gas in the molten metal passage is discharged by the gas discharge means, and a large amount of gas is discharged from the discharge hole at the lower end of the nozzle. This avoids the situation where the water spouts out. Thereby, nozzle stickiness can be effectively prevented without disturbing the molten metal flow and the molten metal level in the mold. Note that it is preferable to allow a certain amount of gas to flow out from the discharge hole into the mold by adjusting the gas supply amount and gas discharge amount in the molten metal passage.

[Example] If the amount of argon gas supplied to the molten steel flow path is reduced to prevent the above-mentioned molten metal surface from flaring, and the gas is prevented from flowing out from the discharge hole, inclusions tend to adhere to the discharge hole. . Therefore, it is considered necessary to flow an appropriate amount of gas into the mold from the discharge hole in order to suppress the adhesion of inclusions over the entire surface of the inner wall of the nozzle. Therefore, in order to suppress the amount of gas flowing out from the discharge hole into the mold while maintaining a predetermined amount of argon gas supply l, a pore is formed below the inner surface of the nozzle, and a molten steel flow path is formed through the pore. The argon gas supplied to the molten steel was discharged, and the discharge pressure was further adjusted to control the internal pressure of the molten steel passage to a predetermined pressure, and good results were obtained. It has been found that porous bricks have a low porosity and are therefore not suitable as a member for discharging gas from molten steel channels.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

1 and 2 are schematic diagrams showing a first embodiment of the present invention. A tundish 1 containing molten steel is disposed above a mold 3 for continuous casting. A stopper 20 is disposed at a position aligned with the injection hole 64 at the bottom of the tundish 1, and the stopper 20 is supported so as to be movable up and down, and is provided with appropriate up-and-down driving means (not shown).

By moving the stopper 20 up and down, the nozzle opening 64 is opened and closed, and the amount of molten steel injected is adjusted. A gas passage 22 opening at the lower end is formed at the axial center of the stopper 20, and the gas passage 22 is connected to an argon gas supply source (not shown). A cylindrical refractory nozzle body 42 is provided between the tundish 1 and the mold 3, and its upper end is connected to the injection hole 64 at the bottom of the tundish 1, and its lower end is connected to the molten steel 30 in the mold 3. is immersed in. The surface of this molten steel 301 is covered with slag 32. Further, a solidified shell 31 is formed in contact with the water-cooled mold of the mold 3. A stainless steel gas supply pipe 44 is attached to the nozzle body 42,
A stainless steel gas exhaust pipe 46 is attached below it. Both the gas supply pipe 44 and the gas discharge pipe 46 are substantially perpendicular to the axis of the nozzle body 42 . A supply port of the gas supply pipe 44 is introduced into the nozzle body 42 and connected to the porous brick 50 via a slit 48 . Further, an outlet of the gas exhaust pipe 46 is also introduced into the nozzle body 42,
It is connected to a through-hole brick 54 via a slit 52. The slit 48° 52 is formed around the entire circumference of the wall of the nozzle body 42 at a position approximately half the thickness thereof, for example,
The gap is 0.41. Moreover, the porous brick 50 is provided over the entire circumference of the upper end of the nozzle body 42.

On the other hand, the through-hole brick 54 has the nozzle body 42I! The nozzle body 42M is fitted into the lower nozzle body 42M. The plurality of through holes formed in the through hole brick 54 open approximately perpendicularly to the inner wall of the nozzle, and have an inner diameter of, for example, 0.4+-. On the other hand, the gas supply pipe 44
The gas supply side of is connected to an argon gas supply II (not shown).

Further, the gas exhaust pipe 46 is connected to the inlet side of a suction pump 60 equipped with a pressure control mechanism (not shown), and the outlet side of the pump 60 is connected to an argon gas recovery container (
(not shown).

Further, a plurality of discharge holes 66 for discharging molten steel are branched at the lower end of the nozzle body 42, and are each opened laterally.

In the immersion nozzle 40 configured in this way, when the stopper 20 is pulled up to open the injection hole 64 and molten steel begins to flow from the tundish 1 into the mold 3 via the molten steel flow path of the nozzle body 42, the gas passage 22 Argon gas from
For example, it is supplied in the direction of arrow 24 at a supply rate of 12β/min. Then, the argon gas descends through the molten steel passage, and a gas flow reaching the lower part is formed in the nozzle body 42.

On the other hand, at this time, argon gas is supplied to the gas supply pipe 44 in the direction of the arrow 56, and the gas is ejected into the molten steel passage through the porous brick 50, and the suction pump 60 is driven to supply the gas through the through-hole brick 54. The gas in the molten steel flow path is discharged in the direction of arrow 58.

The gas supplied through the porous brick 50 becomes bubbles, and the gas flow ejected from the gas passage 22 of the stopper 20 entrains these bubbles. Then, the gas flow containing the bubbles descends along with the molten steel through the molten steel flow path, and a portion thereof becomes a gas film that covers the inner wall of the nozzle, thereby suppressing the adhesion of inclusions to the inner wall of the nozzle. When the gas is ejected into the molten steel flow path of the nozzle body 42, the internal pressure of the nozzle body 42 becomes higher than 1 atmosphere. On the other hand, the discharge pressure (suction force) of the pump 60 is controlled to a pressure level of 1 atm or higher and lower than the nozzle internal pressure to discharge the gas from the molten steel passage. Since the gas discharge pressure is controlled in this way, the gas in the molten steel passage can be discharged while preventing the molten steel from entering the slits 52.

FIG. 3 shows a second embodiment of the invention. In this second embodiment, a slit 74 is used as a gas exhaust means in the nozzle body 72 instead of the through-hole brick 54 of the first embodiment.
The slit 74 is formed substantially parallel to the inner wall and extends around the entire circumference of the nozzle, and is connected to the gas discharge pipe 46 and opens downward to the molten steel flow path. Even in this case, the argon gas in the molten steel passage can be effectively discharged through the slit 74. In addition, the slit 74
Since the molten steel flow path is opened toward the bottom, it is possible to effectively prevent molten steel from entering into the slit 74.

FIG. 4 is a graph showing the effect of the submerged nozzle according to the embodiment of the present invention, with the nozzle clogging index of the conventional gas blow nozzle plotted on the horizontal axis and the nozzle clogging index of the submerged nozzle of the present invention plotted on the vertical axis. It is a diagram.

Continuous casting conditions were to perform the same slow casting at the same time, and with the conventional gas blow nozzle, the argon gas supply rate was 812/min, and with the submerged nozzle of this example, the argon gas supply rate was 1/min.
2λ/min. The gas supply amount of the gas blow nozzle is 8ρ.
The reason for setting the value to 1/min is that if the amount of gas is less than 8, the surface of the molten metal inside the mold 3 is quiet, and if the amount of gas supplied exceeds this amount, a large amount of gas will be ejected from the discharge hole 66, causing the flow of molten steel and the surface of the molten steel. This is because it becomes disordered. As is clear from FIG. 4, the nozzle clogging index of this embodiment is lower than that of the prior art, and nozzle clogging is less likely to occur.

FIG. 5 shows a comparison between the conventional gas blow nozzle and the submerged nozzle according to the embodiment of the present invention, with the horizontal axis representing the argon gas supply amount and the vertical axis representing the nozzle clogging index and the surface roughness index. It is a graph diagram.

In the figure, the mouth represents the results obtained using the immersion nozzle of this invention, Δ represents the results obtained using the conventional gas blow nozzle, and O represents the results obtained using the conventional gas blow nozzle.
indicates the nozzle clogging index at each gas flow rate. This fifth
As is clear from the figure, the immersion nozzle of this example can increase the amount of argon gas supplied by more than 70% compared to the conventional gas blow nozzle, and can dramatically reduce the occurrence of nozzle stickiness. At the same time, it is possible to prevent the molten steel flow and the molten metal level from being disturbed, and to prevent the slag 32 from being caught in the ms shell 31. Therefore, the number of times of casting can be increased without degrading the quality of the slab.

In addition, although the above-mentioned embodiment relates to a tundish immersion nozzle in which the flow rate is adjusted by a stopper, the present invention is not limited to this, and the present invention can be applied to a tundish immersion nozzle in which the flow rate is adjusted by a sliding nozzle.

[Effects of the Invention] According to the immersion nozzle of the present invention, the gas supplied to the molten metal passage by the gas supply means is discharged by the gas exhaust means, so when the amount of gas supplied to the molten metal passage is increased. However, a situation in which a large amount of gas is blown out from the discharge hole immersed in the mold self-molten metal can be avoided. Therefore, nozzle clogging can be effectively prevented without disturbing the melt flow and the molten metal level in the mold.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a first embodiment of the present invention, Fig. 2 is a partially enlarged view of Fig. 1, Fig. 3 is a schematic diagram showing a second embodiment, and Fig. 4 is an embodiment. A graph diagram showing a comparison between nozzle clogging of the immersion nozzle and nozzle clogging of a conventional nozzle,
FIG. 5 shows the submerged nozzle according to the embodiment and the conventional gas blow nozzle 20; stopper, 22: gas passage, 4
0; Immersion nozzle, 42; Nozzle body, 44: Gas supply pipe, 46; Gas discharge pipe, 48.52, 74; Slit, 5
0: Bolus brick, 54: Through hole brick, 60; Pump, 66; Discharge hole Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 4

Claims (1)

[Claims] An immersed nozzle that has a molten metal channel through which molten metal flows and a discharge hole from which the molten metal is discharged, and injects the molten metal by immersing the discharge hole into the molten metal in a mold while supplying gas to the molten metal channel. , a gas supply means for supplying gas to the molten metal passage through a supply passage formed in the nozzle wall, and a gas exhaust means for discharging gas from the molten metal passage through a discharge passage formed in the nozzle wall. An immersion nozzle comprising: