JPH01133653A - Tundish for continuous casting - Google Patents

Abstract

PURPOSE:To reduce remaining molten metal and to improve the product quality by arranging first and second weirs composing of refractory in inner part of a tundish and setting a metal plate having the same quality as the molten metal to cutout part of the second weir. CONSTITUTION:The first weir 10 is arranged at the bottom part of the tundish 2 and also the second weir 15 (20) is arranged near discharging hole 6 of the molten metal. Further, the cutout part is arranged at a part of the weir 20 and the metal plate 21 having the same kind of component composition as the molten metal is set. Then, height of the weir 20 is made to the prescribed height, such as about 120mm, and depth of the cutout part is set to about 60mm. Mixture of inclusion into the discharged molten metal at the time of starting the casting is prevented with the height of the weir 20 having the metal plate 21. At the end period of the casting, by melting the metal plate 21, the height of the weir 20 is made to low, and the remained molten metal is reduced while preventing mixture of slag. Therefore, the remaining molten metal is reduced and also the product quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a tundish for continuous casting that temporarily stores molten metal from a ladle and supplies it to a mold.

[Conventional technology and its problems]

A conventional technique will be described with reference to the accompanying drawings.

Fig. 3 shows a ladle 1, a tundish 2, and a mold 3 for continuous casting according to the prior art.As is well known, molten steel in the ladle is injected into the tundish 2, and then passed through an immersion nozzle 4. It enters the mold 3 and is cooled in the mold and the cooling zone below to become a slab.

The role of the tundish is to maintain a constant level of molten metal in the tamp 4-/sh in order to stabilize the flow rate of the molten metal rising from the immersion nozzle 4, and to float and separate slag, slag and non-metallic inclusions.

Figures 4 (a) and (b) are tanditsh 2 of Figure 3.
This is an enlarged view of the vicinity of the molten metal outlet, where (a) is a longitudinal sectional view and (b) is a plan view. The tundish 2 illustrated here is for two strands, with one area surrounded by the first weir lO and the tundish side wall, the outflow zone 11.
and two areas with outflow ports 6 on both sides, outflow zone 12
It is divided into three areas. In FIGS. 2a and 2b, a part of the right side is omitted for clarity.

A second weir 15 is provided near the outlet 6 connected to the dip tube. During casting, the molten metal from the ladle first enters the central zone 11, where slag etc. are floated and separated, and then transferred to the first zone.
It flows into the outflow zone 12 from the communication lower provided at the lower part of the weir, and is injected into the mold 3 through the outflow port 6 and the dip pipe 4. The second weir 15 prevents the refractory material and other impurities in the ladle nozzle and tundish from entering the mold through the molten metal outlet 6 while being mixed into the molten metal at the beginning of casting.

This is because the second #115 is installed, and the molten metal mixed with foreign substances injected at the beginning of casting is temporarily stopped at the second weir 15, which gives time for the foreign substances to float and separate. By being given.

The molten metal that overflowed the second weir 15 heads toward the molten metal outlet 6 with impurities floating on the surface, but only the molten metal flows out from the molten metal outlet 6. Since the molten metal mixed with contaminants flowing into the outflow zone 12 is limited to the initial stage of casting, the contaminants mixed in at the beginning are pushed up by the molten metal flowing in later and do not enter the mold from the molten metal outlet 6. Therefore, the second weir 15 has no particular role during regular casting.

Just before the end of casting, the level of the molten metal in the tundish decreases and when it reaches the vicinity of the communicating lower, the slag floating in the central zone 11 or the slag injected from the ladle passes through the communicating lower while being mixed in the molten metal. There is a risk that it may enter the mold.

The flow of the molten metal into the mold is completed by closing the sliding nozzle 8 provided at the top of the immersion tube, but the timing for closing is when most of the molten metal in the central zone 11 of the tundish has flowed out, and at this time the molten metal at the end of casting is The above-mentioned through-liquid slug is mixed in, but this is dammed by the second dam 15. However, if the second weir is high, a large amount of molten steel remains in the tundish, which becomes a major factor in reducing yield.

The present invention has been made in view of the above circumstances, and aims to provide a tundish that prevents impurities at the beginning of casting and slag at the end of casting from flowing into the mold, and further reduces residual molten metal as much as possible. .

[Means for solving problems]

The continuous casting tundish of the present invention includes a container for temporarily storing molten metal, a first weir and a second weir made of a refractory material inside the container, and an outlet for the molten metal at the bottom of the container. It is characterized in that the upper part of the two weirs is cut out, and a metal plate of the same type as the molten metal is provided in the cutout part.

[For production]

At the beginning of casting, the molten metal that flows into the tundish contains refractory materials and other impurities, but it is once stopped by the second weir of the present invention, and after floating and separating the impurities, it heads toward the exit of the tundish, so that the impurities enter the mold. There is no risk.

In addition, at the end of casting, the molten metal level in the tundish decreases and before the slag flows out, the sliding nozzle at the molten metal outlet is closed without checking the molten metal level, but the metal plate installed at the second weir is melted during casting. Since the height of a part of the second weir is low, it is possible to reduce the residual molten metal in the tundish when the nozzle is closed.

Rainbow in the Pig r1 [Invention #≠Wandering Hand] This invention will be specifically described below with reference to the accompanying drawings. FIG. 1 relates to an embodiment of the present invention, and shows a sketch of the second weir of Tanditsh. The parts other than the second weir are the same as those in FIGS. 3 and 4 of the prior art, so the explanation will be made with reference to these figures.

It was noted that the process of mixing contaminants at the beginning of casting and slag at the end of casting into the molten metal is different. That is, since the contaminants in the ladle l or tundish 2 at the time of casting enter the molten metal outlet 6 of the tundish, time is required for the contaminants to float and separate, and for this reason, it is better to have a higher second weir. Conceivable.

On the other hand, slag in the final stage of casting is already in the central zone 11.
If the time change in the drop in the molten steel level at the end of casting in the central zone 11 is accurately grasped, and the timing of closing the nozzle at the molten metal outlet 6 is not mistaken, the second
It was considered that the weir could be considerably lower than the original height mentioned above.

It has been known from past experience that approximately 120mm is sufficient for the height of the second weir required at the beginning of casting, regardless of operating conditions. In the final stage of PI manufacturing, it is actually unavoidable that slabs are mixed in due to the flow of molten metal, so we investigated the necessary and sufficient height of the second weir to prevent slag from entering the mold. This is the second
As shown in the figure.

At this time, the inner diameter of the molten metal outlet 6 is 75 to 80+u+, the drawing speed at the final stage of casting is 0.5 cm/min, and the degree of opening of the molten metal outlet 6 is 12 to 14% of the fully opened state.

The horizontal axis is the casting height, and the vertical axis is the frequency index of slag mixed into the mold. As a result, it was found that the required height of the second weir at the final stage of casting was 60 layers.

Based on the above results, a second weir 20 shown in FIG. 2 was invented. A metal plate 21 having substantially similar composition to the molten metal is used as a part of the weir plate in the notch part of the second weir 20 provided with the notch. The height of the second weir 20 is 120m as mentioned above.
(2) The height of the notch was 60 mm.

The second #120 configured as described above is provided at the same position as the second weir 15 shown in FIG. In this way, contaminants can be prevented from entering the bottle at the beginning of casting, and at the end of casting, the metal plate 21 has already melted and the second
The notch portion of the weir 20 has a height of 6011II to prevent slag from getting mixed in, and at the same time, it is possible to minimize residual steel.

The residual steel was approximately 6T in the prior art, but this could be reduced to 3T with the present invention.

〔Effect of the invention〕

According to this invention, since the second weir installed near the outlet of the tundish is sufficiently high, there is no possibility that foreign matter such as refractory material mixed into the molten metal at the beginning of casting will float and separate and flow into the mold. Further, since the metal plate provided in the second weir is melted during casting and the height of the second weir is reduced, the amount of residual molten metal in the tundish can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a sketch showing the second bottle according to the present invention, Fig. 2 is a graph showing the relationship between the height of the second weir and the frequency index of slag injection into the mold, and Fig. 3 is a longitudinal section of the continuous casting device. Top view, Figure 4(a) is a vertical cross-sectional view of Tanditshu, Figure 4(b)
is a plan view of FIG. 4<a). 1... Ladle, 2... Tundish, 3... Mold, 4... Immersion pipe, 5... Slab, 6... Outlet, 7
...Communication port, 8...Sliding nozzle, lO・
...First weir, 11... Central zone, 12... Outflow zone, 15.20... Second weir, 21... Metal plate.

Claims (1)

[Claims] A tundish comprising a container for temporarily storing molten metal, a first weir and a second weir made of refractory material inside the container, and an outlet for the molten metal at the bottom of the container, in which the upper part of the second weir is cut out. A tundish for continuous casting, characterized in that a metal plate having the same composition as the molten metal is provided in the notch portion.