JPH07102432B2 - Cover protection for continuous casting equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt level protection cover in a continuous casting facility having a moving mold wall.

[0002]

2. Description of the Related Art One of continuous casting of thin plates has a twin roll mold which is an example of a moving mold wall. As shown in FIG. 4, this twin roll type continuous casting equipment includes a pair of mold rolls (hereinafter referred to as rolls) 21A and 21B arranged in parallel with each other, and these rolls 21.
Both rolls 21A and 21 are arranged in contact with the end faces of A and 21B.
A weir body 23 (only one of which is not shown) for forming a molten steel receiver 22 between B and a tundish 25 having a pouring nozzle 24 for injecting molten steel into the molten steel reservoir 22 were provided. When continuously casting thin plates with this configuration,
In the state where molten steel is contained in 22, both rolls 21A, 21
When B is rotated in the direction of arrow A, the slab shells formed on the surfaces of the rolls 21A and 21B are merged and pressed at the central portions of both rolls 21A and 21B to form a single slab, and the thin plate slab 26 Is continuously withdrawn.

By the way, conventionally, when the surface of the molten steel injected into the molten steel receiver 22 is oxidized or the temperature thereof is lowered, oxides, shells formed on the surface, or tundish or nozzle refractory material floating on the molten metal surface are eluted. And the like are entrained in the flow of molten metal and cause defects on the inner or outer surface of the thin plate slab 26. For this reason, conventionally, the upper surface of the molten steel was covered with a cover, and an inert gas was injected into the cover to prevent oxidation. However, with the use of an inert gas, since the space in the cover has a large capacity and a large surface area, a large amount of heat due to radiation causes a problem that molten steel cools from the molten metal surface to form a molten metal shell. In order to solve the problem, the present inventor proposed the bath cover shown in FIG. 5 by Japanese Patent Application No. 1-441439 (filed on February 21, 1991). This proposes a bath surface protection cover 36 in which the heat insulating material 34 is floated in the molten steel thickness receiver 33 and the immersion wall 35 is provided on the roll 31A, 31B side of the heat insulating material 34.

[0004]

[PROBLEMS TO BE SOLVED BY THE INVENTION] However, the roll 31
Since the surfaces of A and 31B and the facing surface of the immersion wall 35 are formed substantially parallel to each other, as shown in FIG. 6, in the space 37 between the surfaces of the rolls 31A and 31B and the immersion wall 35, the roll 31A is formed. ，
When 31B is rotated in the direction of arrow A, due to the viscosity of molten steel,
A flow E that moves downward along with the movement of the slab shell 32 generated on the surfaces of the rolls 31A and 31B and a flow F that flows upward along the immersion wall portion 35 to replenish the molten steel in the space 37 are formed. To be done. Then, a flow G detouring from the flow E to the flow F is generated where these flows E and F come into contact with each other, and as a result, a circulating flow (stagnation) H of molten steel is formed in the space 37.
Then, this circulating flow H is cooled and solidified floating crystals are generated. This solidified floating crystal is roll 31A, 31B
When the slab is taken into the slab shell 32 on the surface and cast, the slab becomes an internal defect, resulting in a defect in the product.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide a molten metal surface protection cover in a continuous casting facility in which product casts are less likely to have defects.

[0006]

In order to solve the above-mentioned problems, the molten metal surface protection cover in the continuous casting equipment of the present invention is poured into a molten steel receiver formed between a pair of moving mold walls arranged in parallel with each other. A cover that covers the entire surface of the molten steel is placed on the surface of the molten steel, and both sides of the cover that face the moving mold wall are immersed in the molten steel surface with a predetermined gap on the surface of the moving mold wall. The immersing dipping walls are hung so that the gap between the surface of the moving mold wall and the immersing wall becomes narrower toward the upper upstream side of the moving mold wall.

[0007]

With the above construction, the surface of the molten steel surface of the molten steel receiver is covered by the cover body, and the molten shell of the molten steel surface and floating impurities move to the moving mold wall side and are generated on the moving mold wall. Since the immersion wall portions are provided on both sides of the cover body so as not to be taken into the cast slab shell, and the space between the immersion wall portion and the moving mold wall is formed to be narrower toward the upper part. When the molten steel in the space moves downward as the slab shell moves, new molten steel flows upward along the dipping wall portion to supplement the molten steel that has flown out. This time,
Since the space portion gradually becomes narrower, it flows downward from the side closer to the moving mold wall as the slab shell moves, so that no circulating flow or stagnation occurs in the space between the dipping wall portion and the moving mold wall. Therefore, solidified floating crystals are not generated in this space, and the molten shell of the molten steel and the floating impurities are not introduced, so that a homogeneous product can be manufactured.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 1A and 1B are mold rolls (hereinafter, simply referred to as rolls), which are examples of moving mold walls arranged in parallel with each other, and both of these rolls 1
At the position between A and 1B, a pair of rolls 1A and 1B and a pair of weir bodies (also called short side weirs, only one of which is shown) 2 arranged in contact with both end faces of both rolls 1A and 1B. The molten steel receiver 3 is formed by cooperation. Reference numeral 4 denotes a pouring nozzle main body for guiding molten steel into the molten steel receiver 3 from this tundish (not shown), and is provided so as to hang down from the tundish.

A plan view rectangular shape that covers the entire molten steel molten metal surface 3a (hereinafter, simply referred to as molten metal surface), more precisely, the molten metal molten metal surface 3a and the rolls 1A and 1B except their contact portions (tangential portions). A shaped cover body 5 is supported at a predetermined position above the molten metal surface via a supporting member 6 such as a molten steel receiver 3. On the lower surfaces of both sides of the cover body 5, immersion walls 7 parallel to the axes of the rolls 1A and 1B and having a predetermined gap with the surfaces of the rolls 1A and 1B and having an inverted triangular cross-section are hung down. It is immersed in the bath surface 3a. As shown in FIG. 2, the inclined surface 7a of the immersion wall portion 7 facing the rolls 1A and 1B is
The roll 1A is set so that the gap between the roll 1A and the surface of 1B becomes smaller from the lower downstream gap a of the rolls 1A and 1B to the upper upstream gap b, and the roll 1A is formed in a flat shape or a curved convex shape indicated by an imaginary line. , 1B and the dip wall 7 form a space 8 that becomes narrower toward the top.

Further, the cover body 5 is provided with an inert gas supply pipe 9A for injecting an inert gas such as N ₂ gas or Ar gas into the space between the molten metal surface 3a and the rolls 1A, 1B. In order to prevent air from being caught in the molten steel through the gap b between the cover body 5 and the cover body 5, N ₂ gas is introduced into the gap b.
An inert gas supply pipe 9B for blowing an inert gas such as Ar gas is arranged.

In the above structure, when casting is started,
The cover body 5 cuts off the contact with the outside by the cover body 5 and prevents the temperature of the molten steel from decreasing. When the rolls 1A and 1B are rotated in the direction of the arrow A, the slab shell 10 generated on the surface moves downward together with the rolls 1A and 1B as shown in FIG. Viscous molten steel is
It becomes a flow B that moves downward according to the slab 10 and flows downward from the space 8. In order to make up for the moved molten steel, new molten steel flows in C upward along the inclined surface 7a of the immersion wall portion 7. However, since the space 8 becomes narrower in the upper part, the flow C contacts the flow B in the approaching part.
The detour flow D is formed in order from 11 to be accompanied by the flow B and detoured, and flows out from the space 8. Therefore, the molten steel flowing into the space 8 by the flow C is sequentially discharged from the space 8 by the flow B, and no circulating flow or stagnation occurs and solidified floating crystals are not generated.

Further, even if a molten metal shell is formed on the surface of the molten metal surface 8 or if there are floating impurities contained in the powder or molten steel when powder is used, the slab shell is blocked by the immersion wall portion 7. Since it is not taken into the slab 10, no foreign matter is mixed into the slab shell 10 and no defect occurs in the thin plate slab 12 drawn from between the rolls 1A and 1B. In addition,
From the inert gas supply pipe 10B to the cover body 5 and the rolls 1A and 1
The inert gas is supplied to the gap b between the molten steel and B, and the oxidation of the molten steel is reliably prevented.

In the above embodiment, the cover body 5 is fixed above the surface of the molten steel, but as shown in FIG. 3, it may be constituted by the heat insulating material 15 which floats up and down on the surface of the molten steel. In this case, since the heat insulating material 15 and the molten steel surface directly contact,
It can reliably keep molten steel warm and prevent oxidation without using powder. In FIG. 3, 16 is a stopper that regulates the lower limit of the heat insulating material 15, and 18 is an indicator needle 17a of the molten metal level detection rod 17.
It is a level detector that detects the position of the molten metal surface. In addition,
The same members as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted.

Further, in each of the above-mentioned embodiments, the weir body 2 is set to the roll 1.
Although the sliding contact is made from the side surfaces of both end surfaces of A and 1B, for example, the weir body 2 may be placed in sliding contact from above the end portions of the rolls 1A and 1B. Further, although the twin roll type is described in each of the embodiments, it is obvious that the present invention can be applied to a belt type or caterpillar type continuous casting facility instead of the roll.

[0015]

According to the above-mentioned structure of the present invention, the surface of the molten steel surface of the molten steel receiver is covered with the cover body, and the molten shell of the molten steel surface and floating impurities move to the moving mold wall side and move. Immersion wall portions are provided on both sides of the cover body so as not to be taken into the slab shell generated on the mold wall, and the space between the immersion wall portion and the moving mold wall is narrower toward the top. Since it is formed, when the molten steel in the space moves downward as the slab shell moves, new molten steel flows upward along the dipping wall portion to supplement the molten steel. At this time, in the contact portion of the flow, since it flows out sequentially downward with the movement of the slab shell from the side close to the moving mold wall in the space portion that gradually narrows toward the upper reason side, the immersion wall portion and the moving mold wall There is no flow or stagnation that circulates in the space.
Therefore, solidified floating crystals are not generated in this space, and the molten shell of the molten steel and the floating impurities are not introduced, so that a homogeneous product can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a molten metal surface protection cover showing an embodiment of a thin plate continuous casting facility according to the present invention.

FIG. 2 is an enlarged cross-sectional view explaining the operation of the same molten metal surface protection cover.

FIG. 3 is a sectional view of a molten metal surface protection cover showing another embodiment.

FIG. 4 is a cross-sectional view of a molten metal surface protection cover showing a conventional example.

FIG. 5 is a sectional view of a molten metal surface protection cover showing another conventional example.

FIG. 6 is an enlarged cross-sectional view explaining the operation of the conventional example.

[Explanation of symbols]

 1A, 1B Mold roll 2 Weir body 3 Molten steel receiver 4 Cover body 7 Immersion wall portion 7a Inclined surface 10 Cast slab 12 Thin plate cast slab 15 Heat insulating material a Downstream side gap b Upstream side gap

Claims (1)

[Claims] 1. A cover body for covering the entire surface of a molten steel poured into a molten steel receiver formed between a pair of moving mold walls arranged in parallel with each other is provided.
From both sides of the cover body facing the moving mold wall, a predetermined gap is hung on the moving mold wall surface to hang the respective immersion wall portions that are immersed in the molten steel surface, and a gap between the moving mold wall surface and the immersion wall portion. Is formed so that it becomes narrower toward the upper upstream side of the wall of the moving mold, and the molten metal surface protection cover in the continuous casting equipment is characterized.