JP2003181603A - Pouring nozzle for casting thin strip-like slab - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pouring nozzle which, in a method for continuously casting a thin strip-like slab, can uniformize the temperature of the whole of molten steel within a pouring basin to prevent the occurrence of a solidified product on the surface of the molten steel and, at the same time, can realize stable and uniformized solidification. <P>SOLUTION: A pouring nozzle 13 includes a cylindrical part 2 provided in the upper part and a flat part 1 provided in the lower part. The flat part 1 includes narrow wall surfaces 6, 6 and wide wall surfaces 7, 7. A flat nozzle hole having a shape along the narrow wall surfaces 6, 6 and the wide wall surfaces 7, 7 is provided within the flat part 1. A lateral opening 4 is provided in the narrow wall surface 6, and a lateral opening 5 is provided in the wide wall surface 7. A slit-shaped downward extended opening, which is in communication with the lateral opening 4, is provided at the lower end of the flat nozzle hole. The center part of the lower end of the flat nozzle hole is connected by a connecting part. <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 pouring nozzle used for casting a strip cast in a twin-drum type continuous casting method.

[0002]

2. Description of the Related Art A pool of water formed by a pair of cooling drums having rotating shafts horizontally approaching each other and rotating in opposite directions, and a pair of side dams crimped to both end surfaces of the cooling drum,
A twin-drum type continuous casting method in which molten strip is poured through a pouring nozzle to produce thin strip cast pieces (hereinafter sometimes simply referred to as "cast pieces"), which has a uniform quality due to stable manufacturing technology. Various techniques have been used to produce cast slabs.

For example, in Japanese Patent Laid-Open No. 64-5650,
A method and an apparatus for preventing the formation of a solidified product on the surface of the molten metal in the molten metal pool while preventing the surface of the molten metal from waviness are disclosed. This conventional technique is a method of immersing a pouring nozzle in a basin and discharging the molten metal in a substantially horizontal direction. By using this technology, it is possible to prevent the formation of solidified matter on the surface of the molten metal, and to prevent the surface of the molten metal from waviness, thus stabilizing the formation of the solidified shell on the peripheral surface of the cooling drum. Can be made.

However, according to this prior art in which the molten metal is discharged in the horizontal direction, inhomogeneity of the molten metal temperature in the lower part of the pool is unavoidable, and the formation of the slab at the closest contact point of the cooling drum becomes unstable. Occurs. That is, the molten metal discharged horizontally from the pouring nozzle approaches the cooling drum and then descends, and the flow velocity is accelerated by viscous flow and thermal convection accompanying the rotation of the cooling drum, but in any case it goes vertically downward. The vector is small, and the pouring discharge flow descends while spreading in the width direction of the slab. As a result, it is inevitable that the temperature of the molten metal becomes uneven in the width direction in the lower part of the pool. Even if the deviation of this temperature nonuniformity is slight, it has a great influence when the solidified shells are stuck together at the closest contact point of the cooling drum to form a slab, so that the uniformity of product quality is significantly impaired. .

In order to discharge the molten metal from the pouring nozzle in the horizontal direction and to make the temperature distribution in the width direction uniform, the pouring nozzle width must be substantially the same as the cooling drum width. In this case, for example, a pouring nozzle for manufacturing a strip cast product having a plate width of 1000 mm or more is large and has a complicated structure, which is technically very difficult and expensive to manufacture.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 2-258145 discloses an apparatus for making the downward flow velocity of the molten metal substantially uniform in the width direction of the slab. In this device, a core is attached to the molten metal outlet of the tundish, and two manifolds are provided above and below between the slits of the core. By having such a structure, the molten metal is retained in each manifold due to the passage resistance of the molten metal at the slits, and the molten metal flow velocity in the width direction of the slab is averaged, so that the downward flow velocity of the molten metal It can be made almost uniform in the plate width direction.

However, in this method, since the molten metal mainly goes vertically downward, the stirring and renewal of the molten metal on the surface of the molten metal neglects and stays, and it is not possible to sufficiently prevent the formation of a solidified product. Especially near the contact points between the side weir and both ends of the cooling drum, the molten metal is particularly likely to stay. In addition to hindering the casting, there is a problem that it can also stop casting. Furthermore, this technique also requires a pouring nozzle having a width substantially equal to the width of the cast piece in order to prevent uneven flow of the molten metal, which makes the structure of the apparatus complicated and expensive.

[0008]

In all of the above conventional techniques, it was difficult to make the temperature of the molten metal in the molten metal pool uniform in the width direction of the slab and in the vertical direction. If the horizontal flow of the molten metal is delayed, a solidified product is generated on the surface of the molten metal, and if the molten metal flow below the vertical direction is delayed, the solidified shells at the closest contact point of the cooling drum become non-uniform. In manufacturing a strip cast having a plate width of 1000 mm or more, in order to avoid these problems by the conventional technique, it was necessary to make the structure of the device large and complicated.

According to the present invention, the temperature of the molten metal in the molten metal pool is made uniform to prevent the solidified matter on the surface of the molten metal and to stabilize and uniformize the solidified shell bonding, which is small and simple. It is an object to provide a pouring nozzle that is available at a low cost.

[0010]

The main points of the present invention are as follows. (1) A pouring nozzle having a flat nozzle hole in a lower portion of which a horizontal cross-sectional shape of a space through which the molten metal passes is flat, wherein a lateral opening is formed in a narrow wall surface of the flat nozzle hole, and the flat pouring nozzle. A pouring nozzle for casting a thin strip cast product, which has a slit-shaped downward opening at the lower end of the hole. (2) The thin wall surface according to (1), wherein each of the narrow wall surfaces facing each other of the flat nozzle hole has a shape narrowing downward, and each of the wide wall surfaces facing each other has a shape spreading downward. Pouring nozzle for strip casting. (3) The pouring nozzle for casting thin strip slabs according to (1) or (2), wherein the lateral opening of the narrow wall surface is vertically long. (4) The pouring nozzle for casting thin strip cast slabs according to (3), wherein the lateral opening of the narrow wall surface is narrowed downward. (5) The slab casting pouring nozzle according to any one of (1) to (4), wherein the flat nozzle hole has a lateral opening on a wide wall surface. (6) The casting nozzle for casting thin strip slabs according to (5), characterized in that the lateral opening of the wide wall surface is horizontally long. (7) The above-mentioned (1), which has a connecting portion that connects wide wall surfaces facing each other at the lower end of the flat nozzle hole.
A pouring nozzle for casting a strip cast product according to any one of (6) to (6). (8) The casting nozzle for casting thin strip slabs according to (7), wherein the upper surface of the connecting portion has a mountain shape formed by a pair of inclined surfaces when viewed from the side of the wide wall surface.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The principle and function of the present invention will be described below. Generally, most of the molten metal has its specific gravity increased due to the temperature decrease, so that it is lowered by thermal convection. Therefore, the upper part of the molten metal in the pool is hot and the lower part is cold,
It tends to be uneven. In the twin drum type continuous casting method, there are two additional factors that make the temperature distribution of the molten metal in the molten metal pool uneven.
There is one. One is (1) the molten metal descends by viscous flow while being cooled by the cooling drum rotating downward, and the other is (2) the low temperature immediately before solidification accompanying the solidification shell when the solidification shell is pressed by the pair of cooling drums. That is, molten steel is squeezed and moved into the pool.

These phenomena are peculiar phenomena inevitably occurring in the twin drum type continuous casting method. Therefore, it is extremely important to sufficiently stir the molten metal in the molten metal pool portion so as to make the molten metal temperature uniform.

Among the factors for making the temperature distribution in the basin part non-uniform as described above, (2) the low temperature molten steel is drawn up by the cooling drum in the vicinity of the closest contact point of the cooling drum. Since the layout is such that the cylindrical cooling drums are brought close to each other and the solidified shells are bonded to each other, the molten metal pool is extremely narrow near the nearest contact point of the cooling drum.
Therefore, the molten metal in the narrow portion cannot be sufficiently agitated by the molten metal supply method in which the molten metal is indirectly sent from the upper part of the pool portion to the narrow portion. Therefore, it is necessary to direct the pouring discharge flow downward and supply the molten metal directly toward the narrow portion.

In order to uniformly supply the molten metal to the narrow portion in the width direction, as shown in FIGS. 1 to 3, the pouring nozzle 13 is used.
An elongated slit-shaped opening 9 is formed in the lower end of the slab in the width direction of the slab. As an alternative to the slit-shaped openings 9, small-diameter openings may be densely arranged in the width direction of the slab, but this is not preferable because there is a risk of clogging of the pouring nozzle.

By the way, if the direction of the pouring discharge flow is only downward, the flow of the molten metal on the surface of the molten metal pool is delayed, so that the formation of a solidified product cannot be avoided. Further, considering that the solidified matter is easily generated on the wall surface of the side dam, not only the slit-shaped downward opening 9 is provided at the lower end of the flat nozzle hole 1a, but also the lateral opening 4 is provided on the narrow wall surface 6. It is necessary to stir the molten metal in the upper part of the pool.

Further, in order to agitate the molten metal in the vertical direction in the pool 11, it is desirable that the lateral opening 4 of the narrow wall surface 6 is set to be vertically long. Further, if necessary, it is preferable to add the opening 5 to the wide wall surface 7 because the stirring and renewal of the molten metal is further promoted.

In order to prevent uneven flow of the molten metal in the flat nozzle hole 1a having the slit-shaped downward opening 9 at the lower end,
It is desirable that the narrow wall surface 6 of the flat nozzle hole 1a is narrowed downward and the wide wall surface 7 is widened downward so that the flatness in a horizontal section changes smoothly in the vertical direction.

As a method of preventing uneven flow in the flat nozzle hole 1a, a connecting portion 8 is installed at the lower end of the flat nozzle hole 1a so as to connect the wide surfaces, and the upper surface of the connecting portion 8 is viewed from the wide wall surface 7 side. When a mountain shape is formed by a pair of inclined surfaces 8a and 8a, the connecting portion 8 serves as a watershed and the molten metal flow is symmetrically distributed to the left and right ends of the drum. The connecting portion 8 also functions as a strength reinforcing member.

Based on the above consideration, the inventors of the present invention have invented a pouring nozzle with a simple structure and a low cost, which can effectively equalize the temperature of the molten metal in the molten metal pool in the twin-drum type continuous casting method. Embodiments of the present invention will be specifically described below with reference to FIGS. 1 to 4.

The pouring nozzle 13 according to the present invention is formed by a cylindrical portion 2 at the upper portion of the nozzle and a flat portion 1 at the lower portion of the nozzle. Molten metal passes through the cylindrical nozzle hole 3 and the flat nozzle hole 1
Enter a. By changing the cross section of the nozzle hole from a cylindrical shape to a flat shape, the flow resistance of the molten metal is added at the cylindrical nozzle hole 3 so that the molten metal fills the inside of the pouring nozzle hole, and the lateral opening 4 of the narrow wall surface is widened. The liquid is discharged into the hot water pool 11 through the lateral opening 5 on the wall surface and the slit-shaped downward opening 9.

The dimensional relationship between the widths b and c of the lateral opening 4 of the narrow wall surface is b> c. That is, the lateral opening 4 of the narrow wall surface is formed in a downward narrowed shape. The lateral opening 5 of the wide wall is a rectangular shape having a long width.

FIG. 2 shows the pouring nozzle 13 shown in FIG.
The longitudinal sectional view of the A direction is shown. In FIG. 2, the narrow wall surfaces 6 and 6 are symmetrically formed at an angle β, and as shown in FIG. 1, the narrow wall surfaces 6 and 6 are narrowed downward.

A connecting portion 8 is provided between the wide wall surfaces 7 and the lower end portion of the wall 7 to connect the wide wall surfaces to each other. The connecting portion 8 is a mountain shape having an upper pointed height h.

FIG. 3 shows a vertical cross-sectional view of the pouring nozzle shown in FIG. 1 in the BB direction. In FIG. 3, the cooling drums 10, 10, the molten metal pool portion 11, and the cast piece 12 are also shown together, and the positional relationship between each of them during casting is shown. The wide wall surfaces 7 and 7 are formed symmetrically at an angle α, as shown in FIG.
As described above, the wide wall surfaces 7 and 7 are spread downward.

FIG. 4 is a plan view in which the bottom surface of the pouring nozzle 13 is looked up from the CC direction in FIG. The space through which the molten metal passes was circular in the cylindrical portion 2 above the pouring nozzle, but at the lower end of the flat portion 1 it was flattened into an elongated rectangle. The slit-shaped downward opening 9 at the lower end of the flat nozzle hole is connected to the lateral opening 4 of the narrow wall surface. The reason is that the part where the molten metal discharge flow is the most difficult to reach is
This is to reduce the flow resistance by forming notches so that the molten metal is discharged toward the drum closest contact points at both end portions of the drum so that the molten metal is discharged there.

It should be noted that the narrow wall surface 6 is formed to be narrowed downward and the wide wall surface 7 is formed to be spread downward, so that the flat nozzle hole 1a continuously extends downward. Because of the flattening, the pressure loss is applied to the molten metal in the flattened nozzle hole 1a, the molten metal flow becomes a uniform turbulent flow, and the flow direction toward the both ends of the molten metal pool portion 11 is automatically formed. . As a result, for example, when the drum width is 1000 mm, the conventional nozzle width of 800 mm can be downsized to 600 mm.

Further, the slit-shaped downward opening 9 is
Since the slab 12 has a slit shape elongated in the width direction, the molten metal is directly and evenly supplied to the vicinity of the closest contact point kp of the cooling drum 10. Therefore, the low temperature molten steel in this portion is not stirred and eliminated. It becomes possible to heat. Due to this effect, it is possible to eliminate the uneven bonding of the solidified shells at the cooling drum nearest point kp, which could not be achieved stably by the pouring nozzle according to the conventional invention.

Furthermore, the molten metal is discharged from the lateral opening 4 of the narrow wall and the lateral opening 5 of the wide wall,
Since the molten metal flow is not delayed on the surface of the molten metal pool 11, it is possible to prevent the formation of a solidified product on the surface of the molten metal.

By the way, a to h of each opening of the pouring nozzle
Regarding the numerical value of, it is necessary to be practically optimized by the molten metal throughput amount based on the dimensions of the cooling drum 10 and the plate thickness of the slab 12 or the casting speed. However, the flow pattern of the molten metal in the pool 11 is For example, it can be appropriately calculated by numerical analysis or a flow simulation experiment using a water model. Regarding the values of α and β, α is 15 ° to 35 ° and β is 9 when casting a general strip casting.
It is desirable to set in the range of 0 ° to 140 °, but it is not limited to this depending on the melting throughput amount. However, no matter how these are set, the manufacturing cost can be significantly reduced as compared with the pouring nozzle according to the conventional invention.

[0030]

As described above, with the pouring nozzle of the present invention, the temperature of the molten metal in the molten metal pool is made uniform throughout and the formation of solidified shells is prevented while preventing the formation of solidified matter on the surface of the molten metal. It is possible to provide a compact, simple, and inexpensive pouring nozzle that can be stabilized and made uniform.

[Brief description of drawings]

FIG. 1 is an external perspective view of a pouring nozzle showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view taken along the line AA of FIG.

3 is a vertical cross-sectional view taken along the line BB of FIG.

FIG. 4 is a plan view in the CC direction of FIG.

[Explanation of symbols]

1 ... Flat part 1a ... Flat nozzle hole 2 ... Cylindrical part 3 ... Cylindrical nozzle hole 4 ... Sideways opening of narrow wall 5 ... Lateral opening of wide wall 6 ... narrow wall 7 ... Wide wall 8 ... Wide wall connection 9 ... Slit-shaped downward opening 10 ... Cooling drum 11 ... Hot water pool 12 ... Slab 13 ... Pouring nozzle of the present invention α: the angle between the wide walls β: Angle between narrow walls a: Height of sideways opening of narrow wall b: Width of the upper side of the sideways opening of the narrow wall c: width of the lower side of the sideways opening of the narrow wall d: Height of sideways opening on wide wall e ... Width of the lateral opening on the wide wall f: Length parallel to the wide wall of the lower slit-shaped opening g: Length parallel to the wide wall of the connecting part h ... Height of connecting part kp ... Cooling drum closest point

Continued front page    (72) Inventor Tomohide Takeuchi             3434 Shimada, Hikari-shi, Nippon Steel Works             Inside the Shoko Ironworks (72) Inventor Hideaki Kobayashi             3434 Shimada, Hikari-shi, Nippon Steel Works             Inside the Shoko Ironworks (72) Inventor Keiji Tsusunari             20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd.             Inside the surgical development headquarters (72) Inventor Hideaki Yamamura             20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd.             Inside the surgical development headquarters (72) Inventor Takehiko Fuji             20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd.             Inside the surgical development headquarters F-term (reference) 4E004 DA13 FA01 FB02 FB04 FB06                       NA05 NB07 SA02

Claims (8)

[Claims] 1. A pouring nozzle having a flat nozzle hole in a lower portion of which a horizontal cross-sectional shape of a space through which the molten metal passes is flat, wherein a lateral opening portion is formed on a narrow wall surface of the flat nozzle hole and the flat pouring nozzle. A pouring nozzle for casting thin strip slabs, which has a slit-shaped downward opening at the lower end of the hot water nozzle hole. 2. The shape of each of the facing narrow wall surfaces of the flat nozzle hole is downwardly narrowed, and the shape of each of the facing wide wall surfaces is downwardly widened.
A pouring nozzle for casting a thin strip slab as described in. 3. The pouring nozzle for casting a thin strip cast product according to claim 1, wherein the lateral opening of the narrow wall has a vertically long shape. 4. The pouring nozzle for casting a thin strip cast product according to claim 3, wherein the lateral opening portion of the narrow wall surface is narrowed downward. 5. The casting nozzle for casting slab according to claim 1, wherein the flat nozzle hole has a lateral opening on a wide wall surface. 6. The pouring nozzle for casting thin strip cast slabs according to claim 5, wherein the lateral opening of the wide wall has a horizontally long shape. 7. The pouring nozzle for casting strip cast slabs according to claim 1, further comprising a connecting portion that connects wide wall surfaces facing each other at a lower end of the flat nozzle hole. 8. The pouring nozzle for casting thin strip slabs according to claim 7, wherein the upper surface of the connecting portion has a mountain shape formed by a pair of inclined surfaces when viewed from the side of the wide wall surface. .