JPH08197207A - Tundish provided with openable/closable weir - Google Patents

Abstract

PURPOSE: To obtain a tundrsh which can be reused in hot condition and pours molten steel having high cleanliness by floating up and separating inclusions into a mold for continuous casting. CONSTITUTION: The tundish is provided with a tundish body 10 having an opening space, in which a weir projected into the inner part is not fixed to the inner wall and a tundish weir 20 stood as freely ascendable and descendable to the bottom wall 14 of the tundish body 10, and the tundish weir 20 is separated from the tundish body 10 in the unstationary state. As the tundish weir 20, the one provided with an opening/closing weir 21 dividing the inner part of the tundish into an upstream zone and a downstream zone or further, the weir for adjusting the depth from the molten steel surface, is used. By this constitution, since the inner part of the tundish is largely opened, the maintenance management is executed in extremely simple and the inclusions are floated up and separated with the opening/closing weir 21 and the molten steel having high cleanliness is poured into the mold for continuous casting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to non-metallic inclusions (hereinafter referred to as
The present invention relates to a tundish that has excellent floating separation properties of inclusions), can be reused hot, and is excellent in refractory workability.

[0002]

2. Description of the Related Art Molten steel melted in a smelting furnace such as a converter or an electric furnace is received in a ladle, passed through a secondary refining process such as RH vacuum degassing, and then continuously cast through a tundish. It is sent to a casting mold and manufactured into a continuous cast slab. In order to improve the cleanliness of the slab, various improvements have been made regarding the operating conditions in the smelting furnace and the refining conditions in the ladle. In the ladle, various refining agents are added as needed to remove the impurity elements contained in the molten steel. Further, the molten steel may be degassed by the vacuum treatment. The molten steel whose cleanliness has been improved in this way is poured into a continuous casting mold through a tundish. However, the molten steel contacts the atmospheric gas and the refractory lining while passing through the tundish, and is easily contaminated by gas absorption, elution of the lining material, and the like. Further, in the molten steel supplied from the ladle to the tundish, inclusions such as Al ₂ O ₃ refined by the refining reaction remain without being removed from the molten steel.

Inclusions contained in molten steel cause blockage of long nozzles and immersion nozzles during continuous casting, making the casting conditions unstable. If inclusions are brought into the continuous casting slab, they will cause defects in the subsequent rolling stage and reduce productivity. Therefore, in order to remove inclusions contained in the molten steel in the tundish, various proposals have been conventionally made. For example, in Japanese Laid-Open Patent Publication No. 1-224152, a plurality of molten steels are forcibly changed in the tundish to form an upward flow to promote floating separation of inclusions contained in the molten steel. Tundish with a weir is introduced. Also, JP-A-63-7245
Japanese Patent Publication No. 2 discloses a tundish weir having a hole inclined upward with respect to the molten metal flow direction.

[0004]

When the weir is provided in the tundish, the cleanliness of molten steel is certainly improved by the floating separation effect. However, if the internal space of the tundish is partitioned intricately by the upper weir and the lower weir, maintenance will be troublesome, and a great deal of labor will be required to replace the weir. In addition, there is a possibility that the molten steel will be contaminated by the weir, and the amount of molten steel that flows into the continuous casting mold as an unsteady flow at the beginning and end of pouring will increase,
The production yield of steel products with the required cleanliness decreases. In addition, in a tundish with a weir, in order to discharge molten steel from the tundish at the end of pouring, an opening commonly called "mouse passage" is provided between the bottom of the tundish and the lower part of the weir. However, a large amount of inclusions are exhausted in a short time after passing through the mouse, which causes a significant decrease in the floating separation effect of the weir.

Recently, in order to improve productivity and reduce refractory cost, it has been considered to use the tundish for the next charge while still hot. In this case, if there are a plurality of weirs in the tundish, it takes a lot of man-hours and time to restore the inside of the tundish, and the tundish cannot be put into a state ready for the next use without changing the heat. In this respect, the tundish weir is required to have a structure as simple as possible. However, the molten steel poured from the ladle contains a large amount of various inclusions at the initial stage of pouring, and is particularly contaminated due to the influence of slag floating in the ladle at the end of pouring. When these contaminated molten steels are supplied to the continuous casting mold, the quality of the obtained continuous casting slab is deteriorated. The tundish weir is extremely effective as a means for reducing the amount of contaminated molten steel flowing from the tundish into the continuous casting mold as much as possible, and there is a demand for a tundish having a simplified structure after securing its action. The present invention has been devised in order to meet such a requirement, and simplifies the internal structure of the tundish while ensuring the action of the tundish weir, thereby facilitating maintenance and maintenance. The purpose is to enable hot reuse of.

[0006]

In order to achieve the object, a tundish of the present invention has a tundish body having an open space in which a weir protruding inward is not fixed to the inner wall, and a bottom wall of the tundish body. In the unsteady state, the tundish weir is separated from the tundish main body. As a tundish weir, a single open / close weir that divides the inside of the tundish into upstream and downstream areas, and in addition to the open / close weir, a depth adjustment weir that maintains the depth from the molten steel level to the top surface within a certain range Is used.

[0007]

EXAMPLE As shown in FIG. 1, in the tundish of this example, a tundish weir 20 is provided so as to be able to move up and down on a tundish main body 10 which is widened upward. The tundish body 10 has a refractory lining 12 on a furnace wall 11 constructed of refractory bricks, and has a trapezoidal cross section that widens upward. A support wall 13 is formed in the middle of the furnace wall 11 with its side surface standing up substantially vertically. The inner space of the tundish main body 10 is basically an open space, except for the supporting wall 13 which projects. The support wall 13 is
In the vicinity of the bottom wall 14 of the tundish body 10, it hardly projects from the side wall 15. Inner surface 17 of support wall 13
Rises almost vertically from the bottom wall 14, so that the upper part of the support wall 13 projects inward from the outwardly sloping side wall 15, as shown in FIG. The tundish of this embodiment has a structure in which the tundish weir 20 disposed inside is supported by the support wall 13.
In place of the tundish weir 20 in the groove provided in the side wall 15.
It is also possible to adopt a structure for supporting the.

The tundish weir 20 is provided with an opening / closing weir 21 that moves up and down along the support wall 13 in order to prevent molten steel from remaining inside the tundish. A combination of the depth adjusting weir 22 (see FIG. 4) and the opening / closing weir 21 is also used so that the height from the top surface of the weir to the molten steel surface can be adjusted as needed. As shown in FIG. 3, the tundish body 10 is mounted on the tundish car 30 and reciprocates between the casting position and the retracted position. A drive motor 31 is loaded on the tundish car 30, and power from the drive motor 31 is transmitted to the tundish weir 20 via the elevating mechanism 32 and the support arm 33. The tundish car 30 is provided with a work deck 34 in which an operation panel and the like are arranged in order to move the tundish car 30 and move the tundish weir 20 up and down.

The lifting position of the opening / closing weir 21, and further the depth adjusting weir 22, is adjusted by the amount of movement of the lifting mechanism 32. In a steady state in which the molten steel 2 supplied from a ladle (not shown) through the long nozzle 1 is fed into the continuous casting mold (not shown) through the immersion nozzle 3, the opening / closing weir 21 is shown in FIG. As described above, the tundish body 10 is erected while being in contact with the bottom wall 14. On the other hand, the height of the depth adjusting weir 22 is adjusted according to the level of the molten steel 2 so that the depth from the level of the molten steel 2 to the top surface is optimized. The depth from the molten metal surface to the top surface of the depth adjusting weir 22 is preferably set to 1/3 or more of the depth from the molten metal surface to the bottom wall 14 of the tundish. If the depth of the top surface of the depth adjusting weir 22 is less than 1/3 of the depth of the bottom wall 14 of the tundish, the original damming effect of the weir is weakened and a sufficient upward flow is formed for floating inclusions. Not done.

When supplying the molten steel 2 to the tundish, the lower end surfaces of the opening / closing weir 21 and the depth adjusting weir 22 are attached to the bottom wall 1.
4 and the immersion nozzle 3 is closed by a stopper 4. When the fed molten steel 2 accumulates in the tundish and the molten metal 2 has a high molten metal surface to some extent, the opening / closing weir 21 and the depth adjusting weir 22 are lowered and brought into contact with the surface of the bottom wall 14.

In this state, the inside of the tundish is divided into an upstream region and a downstream region by the tundish weir 20. The molten steel 2 supplied from the long nozzle 1 becomes an upflow 5 along the tundish weir 20 in the upstream region and flows to the vicinity of the molten metal surface, as shown by the arrow in FIG. In this process, the inclusions contained in the molten steel 2 float and separate from the molten steel 2 due to the difference in specific gravity. At this time, when the flux layer 6 is suspended on the molten metal surface, the floating inclusions are efficiently captured by the flux layer 6. The molten steel 2 from which the inclusions have been floated and separated becomes a descending flow 7 having high cleanliness, flows into the downstream region, and is supplied to the continuous casting mold through the immersion nozzle 3. In order to efficiently carry out the floating separation, the upward flow 5 needs to pass as close to the molten metal 2 molten metal surface as possible. However, when the amount of hot water supplied from the long nozzle 1 is larger than the amount of pouring molten metal into the continuous casting mold, the molten metal level in the tundish rises. Also,
When the molten steel 2 supplied from the ladle is low or when the ladle is replaced, the molten steel in the tundish decreases as continuous casting continues, and the molten metal level decreases. In this embodiment, the height position of the depth adjusting weir 22 is adjusted by the elevating operation of the elevating mechanism 32 according to the fluctuation of the molten steel 2 level.

For example, in a tundish containing molten steel 2 at a depth of 1200 mm in a steady state,
The depth from the surface of the molten steel 2 to the top surface of the depth adjusting weir 22 is 6
The height position of the depth adjusting weir 22 is adjusted so that it is maintained at about 00 mm. This makes the tundish weir 2
The molten steel 2 rising along 0 flows into the downstream region from the upstream region under constant conditions suitable for floating separation of inclusions. When the continuous casting work for one cast is completed and the next cast is prepared, the opening / closing weir 21 and the depth adjusting weir 22 are both moved up and down.
Withdraw from the tundish body 10 by. The tundish main body 10 in which the opening / closing weir 21 and the depth adjusting weir 22 are pulled up is an open space in which only the support wall 13 projects, so that repair work and the like becomes extremely simple. Therefore, it is possible to prepare for the next charge without changing the heat.
Although the case where the tundish weir 20 including the depth adjusting weir 22 is used has been described in the above example, the depth adjusting weir 22 may be omitted. In this case, the bottom wall 14
It is preferable to use the opening / closing weir 21 having a height of ⅓ to ⅕ of the depth from to the surface of the molten metal in the steady state. As a result, an appropriate upward flow is formed, the inclusions are efficiently floated and separated, and the adverse effects such as the intrusion of the floating inclusions and the slag due to the extremely disturbed surface of the molten metal are prevented.

[0013]

As described above, in the tundish of the present invention, the tundish weir that divides the inside into the upstream region and the downstream region is provided so as to be opened and closed. Therefore, in the state where the tundish weir is removed, the internal space of the tundish is largely opened, repair work and the like are extremely simple, and it is possible to prepare for the next charge while being hot.
Also, when the distance from the molten metal surface to the weir top surface is maintained within a certain range, inclusions are efficiently floated and separated from the molten steel rising along the weir in the upstream region, and molten steel with high cleanliness continues from the downstream region. It is sent to the casting mold. Further, it is possible to sufficiently follow fluctuations in the molten steel level when the ladle is replaced, and prevent deterioration of cleanliness.

[Brief description of drawings]

[Figure 1] Tundish equipped with an openable and closable tundish weir

FIG. 2 is a perspective view of the tundish body.

[Figure 3] Tundish car equipped with a tundish

FIG. 4 is a diagram for explaining molten steel flow in a tundish.

[Explanation of symbols]

1: Long nozzle 2: Molten steel 3: Immersion nozzle
4: Stopper 5 :: Upflow 6: Flux layer 7: Downflow 10: Tundish body 11: Furnace wall 12: Refractory lining 13: Support wall 14: Bottom wall 15: Side wall 17: Inner surface of support wall 20: Tundish weir 21: Opening and closing weir 22: Depth adjusting weir
30: Tundish car 31: Drive motor 32: Lifting mechanism 33: Support arm 34: Work deck

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadahiro Go, 11-1 Showa-cho, Kure-shi, Hiroshima Nisshin Steel Co., Ltd.

Claims (2)

[Claims] 1. A tundish main body having an open space in which a weir projecting inward is not fixed to an inner wall, and a tundish weir vertically erected on a bottom wall of the tundish main body, A tundish in which the tundish weir is separated from the tundish body in a steady state. 2. The tundish weir according to claim 1 comprises an opening and closing weir and a depth adjusting weir, and the depth of the molten steel from the molten metal surface to the top surface is maintained within a certain range depending on the molten metal surface. A tundish in which the depth adjusting weir is linked to an elevating mechanism for adjusting the height position of the depth adjusting weir.