KR20010059585A - Refractory tube for using in the continuously casting machine - Google Patents

Abstract

PURPOSE: A refractory pipe for a continuous caster is provided which is used when controlling the amount of molten steel flowing into a mold from a tundish using a slide gate during continuous casting. CONSTITUTION: In a refractory pipe for a continuous caster comprising an upper nozzle installed at the lower part of a tundish so as to heat molten steel supplied into a mold, a slide gate installed at the lower part of the upper nozzle so as to control the supply amount of molten steel supplied into the mold, and a submerged entry nozzle guiding the supplied molten steel into the mold, the refractory pipe further comprises a cylindrical eccentricity nozzle (20) equipped with a penetrating hole having the same diameter as the inner diameter of the slide gate, and projectingly mounted on the position as high as a certain height from the bottom surface of the tundish, wherein the eccentricity nozzle is equipped with a plurality of slots (22), and the slots are eccentrically formed from the center of the inner diameter of the nozzle at the side surface of the eccentricity nozzle.

Description

Refractory tube for using in the continuously casting machine}

The present invention relates to a refractory pipe for a continuous casting machine for use when adjusting the amount of molten steel flowing from a tundish to a mold during a continuous casting operation using a slide gate.

In general, in continuous casting, the apparatus for controlling the amount of molten steel when injecting molten steel from the tundish into the mold is composed of an upper nozzle, an upper plate, a lower plate, and an immersion nozzle, as shown in FIG. do. Non-metallic inclusions exist in the molten steel temporarily stored in the tundish, so when the molten steel is transferred to the mold, nonmetallic inclusions are attached to the refractory inner wall between the upper nozzle and the immersion nozzle to prevent the molten steel from entering the mold.

One of the conventional techniques for preventing such clogging is to form a porous material of a part of the upper nozzle or the immersion nozzle as shown in (a) of FIG. 2, and argon gas, which is an inert gas. Gas) is continuously blown at about 5-10Nl per minute (Figure 2.a).

The blown argon gas forms a bubble or bubble film to prevent such clogging by flowing along the inner wall of the upper nozzle to the immersion nozzle or by allowing the bubble to collect and move non-metallic inclusions.

However, the blown argon gas has a low temperature, so the molten steel is cooled and the cooled molten steel is attached to the inner wall surface of the porous upper nozzle or the immersion nozzle as it is, blocking the porous hole and causing a bubble or bubble membrane to be poorly formed. There is a limit in preventing clogging between the upper nozzle and the immersion nozzle.

Alternatively, the amount of argon gas introduced is about 5-10Nl per minute, so that fine argon bubbles mixed into the mold through the immersion nozzle move together with the molten steel. Some are floated and removed, but some remain in the molten steel and remain in the produced slabs or in the slab slabs produced by being collected in the solidification layer. do.

Another conventional technique introduced to solve the problem of clogging of refractory material and foaming defects caused by argon gas blowing during the movement of molten steel from the upper nozzle to the immersion nozzle is to apply an additional device on the upper nozzle or to adjust a new molten steel by a stopper method. The device is configured to generate a vortex rotational flow, which causes non-metallic inclusions to flow along the center of the molten steel flow due to the difference in specific gravity of molten steel and non-metallic inclusions when moving the molten steel from the upper nozzle to the immersion nozzle. It is to minimize the occurrence of bubble defects in cast steel that is not blown or canceled.

One technique for suppressing the plugging of the immersion nozzle by using the vortex rotational flow is to have the vortex rotational flow effect of the molten steel passing through the immersion nozzle forming a spiral groove in the inner wall of the immersion nozzle as in Application No. 95-26284.

However, this method adds a processing cost because the helical groove must be machined on the inner wall of the zigzag nozzle.

In addition, as the performance increases, the groove is filled by attachment, etc., and the occurrence of the vortex rotational flow is drastically reduced, and the success or failure of the technology depends on the size of the groove, making it difficult to realize the technology. Clogging may occur in the upper plate, the lower plate and the immersion nozzle portion immediately below the lower plate at which the swirling flow starts.

The grooves induce a vortex rotational flow, but because the rotational flow is weak and must be accompanied by blowing argon gas, it is impossible to suppress the occurrence of bubble defects in the solidified crucible cast from the mold.

The proposed utility model 97-35387 introduced an eccentric slot nozzle with one slot on the upper nozzle to induce vortex rotational flow without blowing argon gas, thereby preventing the plugging of the immersion nozzle and completely preventing bubble defects. I have suggested.

However, as shown in Fig. 2 (b), when only one single slot is installed, the slot size must have a cross-sectional area corresponding to the maximum opening ratio of the slide gate.

In this case, the size of the eccentric slot occupies most of the diameter of the upper nozzle, so that the vortex rotational flow driven into the upper nozzle is weak, and thus the nozzle clogging cannot be completely prevented.

As shown in Fig. 3, in the case of controlling the amount of molten steel using a stopper, a method of using a vortex rotational flow by a PCV (Precision Control Valve) method was proposed in Arba, Wolftechnology, Switzerland, and RTV (Revolving Tuve) at Didier, Switzerland. Value).

This method uses the vortex rotational flow to solve the problem of air mixing, which is a problem in the slide gate method. However, the refractory structure is complicated and the refractory price is high, and the flow control is limited to the stopper method. Device.

On the other hand, when the molten steel is completed in the end ladle and the molten steel is lowered in the tundish, a vortex is generated on the molten steel surface and settles in a funnel shape, thereby generating a vortex in which slag and air are mixed.

Therefore, the mixed slag remains as a non-metallic inclusion in the slab, resulting in defects in the final product, and the error rate of molten steel also decreases because the amount of residual water in the tundish must be left to complete the casting before the vortex is generated.

If a refractory vortex prevention dam is installed near the tundish exit under one of the methods designed to prevent end-cast vortex registration numbers 161799 or 95762, the flow stagnation zone of the molten steel will occur in the tundish. There is an inconvenience in construction that has to take measures to injure the inclusions badly and prevent the refractory from falling out during casting, there is a disadvantage that the price of the refractory is additionally required.

Accordingly, an object of the present invention is to introduce an eccentric slot nozzle on the upper nozzle to induce swirl flow without blowing argon gas to prevent clogging of the immersion nozzle and to completely prevent the occurrence of bubble defects. The current must be strengthened, and the vortex is prevented in order to increase the error rate by minimizing the end-of-cast tundish residue and to suppress the occurrence of nonmetallic inclusions in the cast steel.

Another object of the present invention is to use a slide gate type molten steel control device in a continuous casting machine, by using a stepped eccentric slot nozzle to induce vortex rotation flow strongly. To prevent refractory blockage caused by the accumulation of non-metallic inclusions on the inner wall of the upper nozzle, upper plate, lower plate, and immersion nozzle, and to minimize the occurrence of bubble defects in cast steel produced by injecting or minimizing argon gas. have.

Further, another object of the present invention is to attach a circular protrusion to the top of the designed stepped eccentric slot nozzle to suppress the formation of vortex generated when lowering the amount of residual tundish, thereby improving the error rate of the residual tang and at the same time mixing the tundish slag. Its purpose is to minimize the nonmetallic inclusions in the cast.

Therefore, according to the present invention, in order to achieve the above object, an upper nozzle for supplying hot water to the molten steel is provided in the bottom of the tundish and a slide for adjusting the supply amount of the molten steel is provided in the mold below the upper nozzle The refractory pipe of the continuous casting machine including a gate and an immersion nozzle for guiding the supplied molten steel into the mold has a through hole having the same diameter as the inner diameter of the slide gate, and protrudes by a predetermined height from the bottom surface of the tundish. It further comprises a cylindrical eccentric nozzle which is mounted, characterized in that the eccentric nozzle has a plurality of slots formed eccentrically from the center of the nozzle inner diameter at its side.

1 is a view showing a refractory pipe for a typical continuous casting machine.

2 is a view showing that the porous brick is installed inside the upper nozzle according to a conventional embodiment.

Figure 3 (a) and (b) is a view showing that the stopper is mounted on the upper nozzle according to the prior embodiment.

Figure 4 is a view showing that the stepped eccentric slot nozzle is mounted on the upper nozzle according to an embodiment of the present invention.

Figure 5 is a side view showing a stepped eccentric nozzle according to an embodiment of the present invention.

6 is a cross-sectional view of a stepped eccentric nozzle according to an embodiment of the present invention.

Figure 7 (a) and (b) is a photograph showing the water model experiment of the inclusion behavior when applying the conventional nozzle and the eccentric nozzle of the present invention.

8 (a) and (b) are photographs showing the water model experiment of the vortex behavior when applying the conventional nozzle and the eccentric nozzle of the present invention.

<Description of Symbols for Major Parts of Drawings>

1: tundish

2, 12: upper nozzle

3: slide gate

4, 14: immersion nozzle

20: stepped eccentric nozzle

22: slot

24: cover

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

According to an embodiment of the present invention, the stepped eccentric slot nozzle for preventing nozzle clogging and vortex is installed at a lower portion of the tundish and an upper nozzle for hot water supply of molten steel supplied into the mold, and a slide gate for adjusting the amount of molten steel supplied into the mold. It consists of an immersion nozzle which induces molten steel into the mold.

In the continuous casting machine refractory pipe of such a nozzle, the stepped eccentric slot nozzle is formed cylindrical nozzle having a through hole of the same diameter as the slide gate inner diameter and can be drawn by a predetermined height from the bottom surface of the tundish, the cylindrical The top of the nozzle hole is blocked by a cover wider than the outer diameter, and a rectangular slot is installed on the upper side, which is eccentrically formed from the center of the nozzle inner diameter, and two or more slots are formed by stepped slots having a step height difference. .

Therefore, the rotational force is strongly generated in the molten steel drawn through the eccentric slot to strengthen the centripetal force of the inclusions in the molten steel while the molten steel descends along the nozzle inner wall, thereby moving the inclusions to the center of the nozzle, and the residual amount of the tundish is below a certain height. This prevents the formation of a vortex on the top of the eccentric slot nozzle when lowered.

That is, as shown in FIG. 4, the cylindrical shape designed of the refractory material is inserted into the upper nozzle and the surroundings are fixed by castable fire.

Fig. 5 is a schematic view showing a plan view and a front view of a stepped eccentric slot, in which three rectangular slots having an eccentricity are formed stepwise in the circumferential direction.

The number of eccentric slots is two or more, and the total area is formed to be similar to the maximum opening area of the slide gate.

If each slot area is small, there is an advantage of strong vortex rotational force, but there is a concern that the slot is clogged. If the slot is too large, there is no risk of being clogged, but the weakness of the rotational force is weakened.

In addition, the stepped eccentric slot nozzle cylindrical upper portion is formed to be closed to cover a predetermined width wider than the outer diameter.

6 shows a cross-sectional view of the stepped eccentric slot, the slot is formed to be inclined into the through hole and each corner of the inlet is rounded so that no reverse flow occurs in the flow path.

The stepped eccentric slot of the present invention serves as an inlet portion of the tundish molten steel and the drawn molten steel is lowered by generating a vortex rotational force from the upper part of the tundish, and on the contrary, when the vortex rotational flow is generated by the density difference as an inclusion in the molten steel. This moves to the center of the through hole of the tundish nozzle.

At this time, since the eccentric slots are formed in a stepped manner, the rotational force is stronger than that of forming multiple slots in the same position. Because if multiple slots are formed in the same position, the molten steel coming into each slot will meet and the lightning force will be weakened due to the collision force, but the stepped eccentric slots that form stepped slots will have molten steel in different positions. As it is drawn, the vortex rotational flow is maintained as it is, and the vortex rotational force is accelerated by the molten steel drawn in the lower slot.

In addition, since the stepped eccentric slot according to the present invention has a circular protrusion attached to the upper portion, vortex formation generated when the residual amount of the tundish is lowered is suppressed.

<Example>

7 is a photograph that simulates the behavior of inclusions under the slide gate in a male model experiment.

In the picture, the white part shows bubbles. The bubbles have a density difference with water, and they move along the center due to centripetal force when the vortex rotation occurs. Fig. 7 (a) shows the case where the stepped eccentric slot nozzle is not mounted, and Fig. 7 (b) shows the case where the stepped eccentric slot nozzle is mounted.

As shown in the figure, bubbles are uniformly distributed inside the refractory when the stepped eccentric slot nozzle is not mounted, but when the eccentric slot nozzle is applied, the bubbles do not move along the refractory inner wall but along the center of the molten steel flow. Nonmetallic inclusions that move along the nozzle inner wall will cause refractory blockages.

However, it can be seen that the inclusions in the molten steel move along the center of the molten steel flow without being distributed on the front of the refractory due to the swirl flow induced by the stepped eccentric slot, which is the nonmetal in the molten steel flowing along the immersion nozzle from the upper nozzle. It shows that clogging caused by inclusions can be prevented.

Since the stepped eccentric slot nozzle is a protruding door at the bottom of the tundish, the vortex can be formed quickly in case of using only the existing upper nozzle.

In addition, since molten steel is introduced through the eccentrically positioned slots, it is possible to promote the formation of vortex by causing rotational flow in the tundish molten steel. FIG. 9 shows the vortex formation while stopping the water supply while maintaining the water level at a certain height in the water model experiment for the case of using only the existing upper nozzle and the case of using the stepped 3-hole eccentric slot nozzle.

As shown in the figure, the vortex was formed quickly when the upper nozzle was used, but the vortex was not formed at the same height when the stepped eccentric slot was used.

This is because the vortex prevention circular protrusion is formed on the top of the stepped eccentric slot nozzle, and the influence on the vortex generated at the hot water surface in the tundish by the flow into the stepped eccentric slot is considered to be small.

The above is summarized as follows.

That is, the stepped eccentric slot nozzle for preventing nozzle clogging and vortex is installed at the lower part of the tundish, the upper nozzle for hot water supply of molten steel supplied to the mold, the slide gate for adjusting the amount of molten steel supplied to the mold, and the molten steel to induce the molten steel into the mold. A continuous casting machine refractory pipe composed of immersion nozzles, comprising: a cylindrical nozzle having a through hole having the same diameter as the slide gate inner diameter and protruding a predetermined height from the bottom surface of the tundish, wherein the top of the through hole of the cylindrical nozzle has an outer diameter; It is blocked by a wider cover, and a rectangular slot is installed on the upper side, and is formed eccentrically from the center of the nozzle inner diameter, and formed into stepped slots having two to four slots with a step difference. Rotation force is strongly generated in the incoming molten steel while the molten steel descends along the nozzle inner wall. A strong centrifugal force of the steel inclusions to result in shifts in the inclusions in the center portion of the nozzle, thereby preventing the vortex formation in the slot nozzle against the eccentric top is lowered below a predetermined height jantang amount of the tundish.

Therefore, according to the present invention, by strongly inducing swirl flow to the molten steel flowing in the submerged enty nozzle (SEN) from the upper nozzle of the lower tundish, the non-metallic inclusions contained in the molten steel Minimize clogging due to accumulation of non-metallic inclusions on the inner wall of upper nozzle, upper plate, lower plate, upper and lower slide gates, and immersion nozzle by moving along the center of molten steel flow. You can.

In addition, it is possible to minimize or not blow the argon gas blown in order to prevent clogging of the upper nozzle and the immersion nozzle, thereby minimizing the blow hole defects that occur in the slabs produced in the front-end machine. .

In addition, since the slag is prevented from being mixed into the mold together with the molten steel by the generated vortex when the molten steel level of the end-dish tundish is lowered, the mixing of the tundish slag can be suppressed. By minimizing the occurrence of slag inclusions and minimizing the amount of tundish residues, the molten steel error rate can be improved.

The foregoing is merely illustrative of the preferred embodiments of the present invention and those skilled in the art to which the present invention pertains may make modifications and changes to the present invention without departing from the spirit and gist of the invention as set forth in the appended claims. It should be recognized.

Claims (4)

An upper nozzle installed at a lower portion of the tundish to supply molten steel supplied into the mold, a slide gate installed at the lower portion of the upper nozzle to adjust the supply amount of the molten steel supplied into the mold, and an immersion nozzle to guide the supplied molten steel into the mold. In the refractory pipe of the continuous casting machine comprising: Further comprising a cylindrical eccentric nozzle having a through hole having the same diameter as the inner diameter of the slide gate protruding from the bottom surface of the tundish by a predetermined height, And the eccentric nozzle has a plurality of slots formed eccentrically from the center of the nozzle inner diameter at the side thereof. The refractory pipe for continuous casting machine according to claim 1, wherein the side of the eccentric nozzle has a plurality of stepped slots having a step difference in height. An upper nozzle installed at a lower portion of the tundish to supply molten steel supplied into the mold, a slide gate installed at the lower portion of the upper nozzle to adjust the supply amount of the molten steel supplied into the mold, and an immersion nozzle to guide the supplied molten steel into the mold. In the refractory pipe of the continuous casting machine comprising: Further comprising a cylindrical nozzle having a through hole of the same diameter as the inner diameter of the slide gate, Refractory pipe for continuous casting machine, characterized in that a cover having a diameter larger than the outer diameter is provided on the upper portion of the cylindrical nozzle. The refractory pipe for continuous casting machine according to claim 3, further comprising a plurality of stepped slots formed eccentrically from the center of the nozzle inner diameter at the side of the cylindrical nozzle and having a step difference in height.