JP2003245757A - Tundish - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tundish which suppresses a flow itself to try to flow into a molten steel flow passage from the upstream of a lower weir and can accelerate the float-up and separation of inclusions by leading the whole amount of the molten steel poured into the tundish to an upper part inside the tundish, in the tundish having the lower weir at an inner bottom and in which the molten steel flow passage is formed at the lower part of the lower weir. <P>SOLUTION: The tundish 1 in which a colliding member 6 to deviate the direction of the molten steel flowing from the molten steel flow passage 5 by colliding with the molten steel flow poured from a molten steel pan 1 is arranged on the upstream of the lower weir 4, or the tundish 2 in which the upstream is raised from the lower weir 4 and an upstream opening of the molten steel flow passage 13 is formed in the bottom face of the raised part 14. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tundish, and more specifically, to obtain a slab with high cleanliness and to reduce the residual amount of molten steel in the tundish at the end of casting to improve the product yield. Regarding a suitable tundish.

[0002]

2. Description of the Related Art In continuous casting of steel, a tundish having a lower weir at its inner bottom has been generally used in order to obtain a slab having a high cleanliness. This lower weir guides the molten steel poured from the molten steel pan into the tundish to the upper part of the tundish, and promotes the floating separation of non-metallic inclusions in the molten steel from the molten metal surface. Molten steel remains on the upstream side of the lower weir, which also reduces the product yield. In order to eliminate this cause, a tunnel-shaped molten steel flow path has been provided at the bottom of the lower weir to discharge the residual molten steel at the end of casting to the downstream side.

However, in the tundish in which the molten steel flow path is provided at the bottom of the lower weir, a short-circuited flow in which the injection flow from the molten steel pan flows through the molten steel flow path into the mold is inevitably generated and inclusions are present. However, there is a problem in that it cannot be applied to casting for products requiring high cleanliness because the floating effect is reduced. In order to solve this problem, in Japanese Patent Laid-Open No. 1-224152, for example, as shown in FIG. 3 as a conventional example 1, a molten steel flow passage 5 provided at a lower portion of a lower weir 4 has a molten steel flow passage substantially downstream thereof. A tundish has been proposed in which a short-circuit flow prevention collision member 11 having the same size is installed. In this tundish 2, the molten steel flowing out from the molten steel flow path 5 to the downstream side hits the collision member 11 and changes its direction.
Although it does not flow out to the non-metallic inclusions, a flow 12 is generated along the bottom portion that passes by the side of the collision member 11, and the height of the collision member 11 is low and the molten steel is insufficiently guided upward. The floating effect of was insufficient.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides a tundish having a lower weir at the inner bottom and a molten steel flow path below the lower weir, from the upstream side of the lower weir. The purpose of the present invention is to provide a tundish that suppresses the flow itself that is about to flow into the molten steel flow path and guides the total amount of molten steel injected into the tundish to the upper part of the inside of the tundish to promote the floating separation of inclusions. To do.

[0005]

The present invention, which has achieved the above object, provides a tundish in which a lower weir is provided at the inner bottom of a tundish and a molten steel flow path is provided at the lower part of the lower weir. The tundish is characterized in that a collision member for colliding the molten steel flow injected from the molten steel ladle and deflecting the direction of the molten steel flow from the molten steel flow path is provided (invention 1).
Is.

The present invention also provides a tundish comprising a lower weir at the bottom of the tundish and a molten steel flow path connecting the upstream side and the downstream side of the lower weir below the lower weir.
A tundish (invention 2), characterized in that an upstream portion is raised from the lower weir, and an upstream side opening portion of the molten steel flow passage is provided on a bottom surface of the raised portion.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings. FIG. 1 shows an example of the present invention 1 (present invention example 1).
As shown, the present invention 1 is a tundish 2 in which a lower weir 4 is provided at the inner bottom of a tundish and a tunnel-shaped molten steel flow path 5 is provided below the lower weir.
On the upstream side of the lower weir 4, a collision member 6 is provided which collides the molten steel flow injected from the molten steel ladle 1 and deflects the direction of the molten steel flow from the molten steel flow path 5.

The molten steel flow injected from the molten steel ladle 1 collides with the molten metal falling portion on the bottom surface of the tundish, and then changes into a flow along the bottom portion. This flow is guided to the upper part in the tundish by colliding with the lower weir 4. In the above-mentioned conventional example 1 shown in FIG. 3, since a part of the flow along the bottom portion directly flows into the molten steel flow path 5 provided at the bottom portion of the lower weir, some of the inclusions in the molten steel that have flowed directly into the bottom portion. Almost never floated and separated, and flowed out into the mold as it is, often causing product defects due to inclusions.

On the other hand, in the present invention 1 shown in FIG.
On the inlet side (upstream side) of the molten steel flow passage, a collision member 6 that changes the direction of the injection flow from the molten steel ladle so as to divert the molten steel flow passage 5 from the molten steel flow passage 5 is provided. Changes in a direction away from the molten steel flow path 5. That is, the molten steel flow that flows along the bottom after injection is converted into the flow 10 toward the molten metal surface 7. The flow 10 toward the molten metal surface 7 proceeds almost straight by the inertial force of the molten steel, collides with the lower weir 4, and then proceeds further away from the molten steel flow path 5. At this time, a negative pressure is generated between the collision member 6 and the lower weir 4 due to the ejector effect of the molten steel flow flowing around the collision member 6. This negative pressure acts to cause the molten steel in the molten steel flow path 5 to flow backward from the downstream side to the upstream side, so that part of the injection flow does not flow into the molten steel flow path 5.

As described above, according to the first aspect of the present invention, the outflow of the injection flow from the molten steel flow channel is effectively prevented, and the total amount of the molten steel injected from the molten steel ladle rises near the molten metal surface 7 in the tundish. It is possible to further reduce defects due to inclusions. Here, it is preferable that the gap between the collision member 6 and the lower weir 5 be narrow, but if it is too narrow, the gap is clogged due to adhesion of non-metallic inclusions, etc., and the residual molten steel on the upstream side of the lower weir at the end of casting is discharged. Can interfere with
If it is too wide, the flow of molten steel once diverted may flow back to the molten steel flow path direction, and the effect of the collision member may be reduced, so the interval is preferably about 30 to 300 mm.

Further, in order to suppress the generation of the wraparound flow toward the molten steel flow passage, it is desirable that the height of the collision member 6 be larger than the opening height of the molten steel flow passage 5. Further, for the same reason as above, it is desirable that the width of the collision member 6 is larger than the opening width of the molten steel flow path 5, and the difference in width on one side is equal to or more than the distance between the collision member and the lower weir. Is desirable. When the width of the collision member is the full width of the tundish, the flow velocity is uniform in the entire width direction, and the floating effect of inclusions after the rise is greater, but some molten steel remains on the upstream side of the collision member. Therefore, the width of the collision member should be appropriately set according to the level of cleanliness required for the product.

Further, the shape of the collision member is such that the molten steel flow after the collision with the lower weir is easily guided in the direction away from the molten steel flow path direction, and the flow direction is smoothly changed to the collision member. A shape that does not disturb the flow on the downstream side is suitable, and, for example, a shape in which the collision surface is an inclined surface can be preferably used. Next, FIG. 2 shows an example of the present invention 2 (present invention example 2).
As shown, the present invention 2 is a tunnel-shaped molten steel flow having a lower weir 4 at the bottom of the tundish and connecting the upstream side and the downstream side of the lower weir below the lower weir. In the tundish 2 having the passage 13, the bottom portion upstream from the lower weir 4 is entirely raised, and the upstream side opening of the molten steel flow passage 13 is provided on the bottom surface of the raised portion 14. In the present invention 2, since the direction of the injection flow from the molten steel ladle 1 forms an angle close to a right angle with respect to the opening surface of the molten steel flow path 13, the molten steel flow path of the injection flow is also formed by this as in the present invention 1. The flow into 13 is effectively prevented, and the same effect as in the first aspect of the invention can be obtained.

[0013]

EXAMPLE Using Examples 1 and 2 of the present invention shown in FIGS. 1 and 2,
A continuously cast slab was produced under the following conditions. <Basic conditions> ・ Tundish capacity 50ton ・ Number of strands 2 strands ・ Molded steel injection speed 8ton / min (4ton / strand) ・ Tundish shape Bottom width 0.8 m, Molten steel depth 1.4 m, Distance from injection position to lower weir 0.6 m ・ Bottom weir shape / size Rectangular plate shape Width 1.2 m × height 0.3 m × thickness 0.1 m ・ Bottom weir position Bottom, center of width <Conditions of Inventive Example 1> m × 0.12 m ・ Collision member shape / size Collision surface is formed with slope, height: 0.15 m, width: 0.5 m ・ Gap between collision member and weir 0.1 m <Conditions of Inventive Example 2> · Raised height 0.2 m ・ Distance between the molten steel flow path upstream side opening and the lower weir 0.2 m ・ Molten steel flow path cross sectional size Width 0.3 m × 0.1 m Also, using the conventional example 1 shown in Fig. 3, continuous casting slab under the same basic conditions as above. Was manufactured. The collision surface size of the collision member on the downstream side of the lower weir was set to be approximately the same as the molten steel flow path cross section.

As the conventional example 2, the one in which the collision member 11 and the molten steel flow path 5 were eliminated from the conventional example 1 of FIG. 3 was used, and casting was carried out under the same basic conditions. This conventional example 2
Has a large floating separation effect of non-metallic inclusions, but has a drawback that a large amount of molten steel remains. FIG. 4 shows the results of investigating the occurrence rate of defects by comparing the slabs cast using the above-mentioned invention examples 1 and 2 and conventional examples 1 and 2. It can be seen that the product defect occurrence rates due to inclusions are significantly reduced in the present invention examples 1 and 2 as compared with the conventional example 1 and are reduced to the same level as in the case of using the conventional example 2 without the molten steel flow path.

[0015]

As described above, according to the present invention, even if a molten steel flow path is provided under the lower weir provided in the inner bottom of the continuous casting tundish, the floating separation of inclusions is equivalent to the case where the molten steel flow path is not provided. Therefore, it is possible to reduce product defects caused by inclusions without increasing the amount of molten steel remaining in the tundish at the end of casting.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of the present invention 1 (a: side sectional view,
b: plane sectional view).

FIG. 2 is a schematic view showing an example of the present invention 2 (a: side sectional view,
b: plane sectional view).

FIG. 3 is a schematic view (a: side sectional view, b: plane sectional view) showing Conventional Example 1.

FIG. 4 is a graph showing a comparison of defect occurrence rates due to inclusions in products cast using the present invention and a conventional tundish.

[Explanation of symbols]

1 molten steel pot 2 tundish 3 Molten steel 4 lower weir 5 Molten steel flow path 6 Collision member (present invention) 7 Hot water surface 8 molds 9 Injection flow from molten steel pan 10 Flow toward the surface 11 Collision member (conventional) 12 Flow along the bottom 13 Molten steel flow path 14 Raised part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuji Takeuchi             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd.

Claims (2)

[Claims] 1. A tundish having a lower weir at the inner bottom of the tundish and a molten steel flow path provided at the lower part of the lower weir, wherein the molten steel flow injected from a molten steel ladle is collided with the upstream side of the lower weir. And a collision member for diverting the direction of the molten steel flow from the molten steel flow path. 2. A tundish comprising a lower weir at the bottom of the tundish and a molten steel flow path connecting the upstream side and the downstream side of the lower weir below the lower weir. A tundish, which is raised, and an upstream side opening of the molten steel flow path is provided on a bottom surface of the raised portion.