JP2968155B2 - Flat nozzle for continuous casting of wide thin cast slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting apparatus for wide and thin cast slabs, such as a twin-drum continuous casting apparatus, which is used when a molten metal is supplied from a tundish into a moving mold. The present invention relates to a lower structure of a flat nozzle having a slit-shaped nozzle hole on a side wall.

[0002]

2. Description of the Related Art Conventionally, for example, in continuous casting using a twin-drum type continuous casting apparatus, FIG.
, A pair of rotating cooling drums Ra, R
b and side weirs Sa, Sb abutting on both ends of the drum
The molten metal e is supplied from the inside of the tundish through the inner nozzle a and the outer nozzle b into the moving mold formed by the above method, and while the molten metal e is formed at a predetermined level in the moving mold, the molten metal is cooled by the cooling drum. A solidified shell is formed, and the solidified shell is pressed and integrated at a gap formed at the closest part of the pair of cooling drums to obtain a wide thin cast slab c.

[0003] At this time, in order to obtain a homogeneous thin cast slab,
It is necessary to minimize the fluctuation of the position of the meniscus formed in the moving mold, and therefore, it is required that the control accuracy of the supply amount of the molten metal into the moving mold be further improved.

In order to meet such a demand, for example, in the invention of Japanese Patent Application Laid-Open No. 63-203254, a flat nozzle incorporating a filter f made of a porous refractory and a fusible metal member d has been proposed.

In the nozzle shown here, as shown in FIG. 4, the lower part of the inner nozzle a is provided inside the upper opening of the flat outer nozzle b, and the outer nozzle b is flat and has a lower closed end ( Since there is a slit-shaped nozzle hole o in the side wall near the (bottom) portion, there is a great concern that the bottom portion of the outer nozzle may be broken depending on the magnitude of pressure loss of the molten metal at the start of continuous casting.

In order to eliminate this concern, here, a porous refractory f and a fusible metal member d having a melting point lower than that of the cast metal and having a mesh shape or a plate shape are incorporated in the outer nozzle b so as to be used at the start of casting. A high pressure loss is applied inside the outer nozzle b, and the outer nozzle b
The inside of the tundish, the inner nozzle a, the outer nozzle b, and the molten metal in the moving mold are made densely continuous, and the pressure loss in the outer nozzle b is set to a low pressure loss state such that the nozzle does not break. To perform continuous casting.

The outer nozzle b used here has a flat shape as shown in FIG. 4 in order to uniformly supply the molten metal e in the width direction of the cooling drums Ra and Rb in the sump portion p. A slit-shaped nozzle hole o for discharging the molten metal laterally to the cooling drum side on the side wall near the lower closed end (bottom).
Are formed.

A filter f made of a fusible metal d and a porous refractory is provided on the bottom side of the flat nozzle to apply a pressure loss to the molten metal from the inner nozzle a to keep the molten metal flow dense.
However, after continuous casting is started and the flat nozzle is filled with the molten metal, the flat nozzle rises together with the fusible metal and its function is reduced.

Further, since these are supported at the bottom of the flat nozzle, particularly when the continuous casting is started, when the molten metal is supplied from the tundish to the flat nozzle via the inner nozzle, a relatively large portion is formed on the bottom of the flat nozzle. Melt impact force is applied.

The molten metal impact force P applied to the bottom of the flat nozzle per unit area is P = (r / g) · (2 gH)
[However, r: weight per unit area of molten metal, g: gravitational acceleration, H: head difference], and when there is no support in the slit-shaped nozzle hole, assuming that the bottom is a simple support beam, The maximum shear force F at the support portions at both ends is F = PI / 2, where I is the length of the bottom.

In a flat nozzle having a slit-shaped nozzle hole in which a support does not exist between the support portions at both ends, the tensile strength of the support portions at both ends must be not less than the maximum shearing force F in order to prevent the bottom portion from being broken. For this reason, in the conventional case, the thickness of the refractory at both ends is increased, and the cost is increased due to an increase in the weight of the refractory, or in some cases, the stagnation flow of the molten metal on the surface of the molten metal in the moving mold near the both ends support. The metal is attached and grows at the support portions at both ends, and the molten metal cannot be stably supplied into the moving mold.
There is a concern that the controllability of the meniscus position is reduced, a stable continuous casting operation cannot be performed, and it is difficult to cast a homogeneous slab. .

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a continuous casting of a wide and thin cast slab having slit-shaped nozzle holes on both sides of a cooling drum near a lower closed end and a filter and a fusible metal disposed at a bottom. In the flat nozzle, after the start of continuous casting, the filter and the meltable metal are prevented from being lifted, and at the same time, the both ends of the slit-shaped nozzle hole formed on the side wall near the lower closed end (bottom) are made as thin as possible.
An object of the present invention is to provide a flat nozzle lower structure in which a bottom portion is not easily broken by molten metal impact.

[0013]

SUMMARY OF THE INVENTION The present invention is directed to a continuous casting of a wide and thin cast slab having slit-shaped nozzle holes on both sides of a cooling drum near a lower closed end and a filter and a fusible metal disposed at a bottom. In the flat nozzle, a filter locking shelf is provided on the inner wall above the slit-shaped nozzle hole, where the upper part of the filter is locked, the fusible metal is placed on the filter, and the fusible metal is placed on the inner wall. It is a flat nozzle for continuous casting of a wide and thin cast slab characterized by being fixed.

[0014]

In the present invention, a filter retaining shelf is provided on the inner wall above the slit-shaped nozzle hole to support the filter and the fusible metal and receive the impact of the molten metal during the continuous casting start. The load applied to both ends of the slit-shaped nozzle hole can be significantly reduced.
Further, the filter and the fusible metal are fixed to the lower inner wall surface, so that they can be prevented from rising after the continuous casting start, and the function thereof can be prevented from lowering.

Accordingly, the lower (including bottom) wall immersed in the molten metal in the moving mold during the continuous operation of continuous casting is made thinner to suppress the generation of stagnation flow of the molten metal on the surface of the molten metal in the moving mold. It prevents the adhesion and growth of ingots, secures the functions of the filter and the fusible metal, enables the stable supply of molten metal, and stably maintains the continuous casting operation for a long time. Also, the effect of reducing the cost of refractory can be expected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS. 1 (a) to 1 (c). The main body 2 of the flat nozzle 1 of the present invention is divided into an upper part 2a and a lower part 2b.
A wire mesh-shaped fusible metal 4 for imparting pressure loss to the molten metal from the intermediate nozzle 3 and a filter 5 made of a porous refractory are built in, and slit-shaped nozzle holes 6a are provided in both side walls near the lower closed end. 6b is provided. A lower portion 2b of the flat nozzle which is in contact with the molten metal, and an electrode 7 for energizing and heating for reducing the thermal shock to the filter 5 or adjusting the temperature of the molten metal are attached to the sides.

In the flat nozzle 1 of the present invention, the inner wall surface at the bottom of the cooling drum has an inclined surface having a narrower downward portion, and the inclined surface above the slit-shaped nozzle holes 6a and 6b is used for locking a filter. A locking shelf 8 is provided, and a filter 5 is disposed on the lower surface including the inclined surface and the locking shelf. This retaining shelf supports the filter 5 and the fusible metal 4 placed on the upper surface thereof, and receives a molten metal impact force at the start of continuous casting. This is for preventing a load from being applied, and has sufficient strength.

The outer surface (excluding the upper surface) of the filter 4 is formed in a shape substantially conforming to the lower inner wall surface of the flat nozzle, and is arranged so as not to form a gap between the shelf and the inclined surface in a locked state. The fusible metal 3 is placed on the upper surface of the filter 4.

Although this fusible metal is not as strict as the filter 4, the outer surface of the fusible metal is formed so as to substantially match the lower inner wall surface of the flat nozzle in a state where it is placed here. It is fixed by a fixing piece 9 provided on the lower inner wall surface. This is to prevent the filter from floating together with the fusible metal when the flat nozzle is filled with molten metal after the start of continuous casting.
Instead of the fixing piece 9, a fusible metal or a filter may be bonded and fixed to the lower inner wall surface with an adhesive containing ceramics, for example.

[0020] In the present invention constructed as described above, for example, in nozzle width H680mm, if the bottom area of 135 cm ² of the flat nozzle 1, the hot bending strength of 60 kg / cm ² Class Al ₂ O ₃ -C If a refractory of the system is used, the load applied to the support portions 2c and 2d at both ends of the slit-shaped nozzle hole 5 can be reduced to about そ の of that in the conventional example. More specifically, even when the thickness of the supporting portions at both ends is reduced to 15 mm, the bottom is not broken at the time of the continuous casting start, and no stagnant flow is generated on the surface of the molten metal near the bottom, so that the long-term operation is possible. , The continuous casting operation can be performed stably, and a homogeneous slab can be cast.

FIG. 2 shows a state in which the upper end of the flat nozzle 1 of the present invention configured as described above is in contact with and fixed to a tundish 10. A refractory 12 is lined inside the outer skin 11 at the bottom of the tundish 10, and an intermediate nozzle insertion hole 14 formed by a refractory block 13.
Is provided. The insertion hole 14 is an inclined hole whose diameter decreases downward and becomes smaller.
1 through.

The intermediate nozzle 3 having a tapered surface whose upper outer peripheral surface is locked to the inner surface of the insertion hole is inserted into the insertion hole 14 from the inside of the tundish 10. The lower end of the intermediate nozzle is a closed end, and nozzle holes 3a and 3b are provided in a side wall near the lower end.

Above the intermediate nozzle 3, a stopper 15 for controlling the amount of molten metal supplied from the tundish 10 is disposed so as to be vertically adjustable. That is, the intermediate nozzle 3
By adjusting the gap between the upper end surface of the mold and the lower end surface of the stopper 15, the amount of molten metal supplied into the moving mold can be controlled.

An intermediate nozzle 3 is inserted into the upper opening 1a of the flat nozzle 1 of the present invention, and the upper end surface of the upper opening 1a of the flat nozzle is
The flat nozzle 1 is integrated with the outer skin 11 of the tundish 10 by a support 16, a movable support 17 fixed to the support, and a bolt / nut 18 for fixing the flat nozzle 1. Abuts and is fixed to

After the flat nozzle 1 of the present invention has been brought into contact with and fixed to the tundish 10 in this manner,
After the filter 4 is preheated by the heating electrode 7 and positioned with respect to the moving mold, the stopper 1
5, a predetermined gap is formed between the lower end surface of the stopper and the upper end surface of the intermediate nozzle 3, and the molten metal is supplied from the tundish 10 to the flat nozzle 1 via the intermediate nozzle 3.
The molten metal is filled in the flat nozzle 1 by the pressure loss effect of the fusible metal 4 and the filter 5, and the molten metal is filled in the tundish 1.
0, the intermediate nozzle 3 and the flat nozzle 1
It is supplied into the moving mold from the slit-shaped nozzle holes 6a and 6b at the lower part of the flat nozzle, and a continuous casting is performed while forming a pool at a predetermined level. After the shift to the steady operation, the position of the stopper 15 is adjusted and the molten metal supply amount is controlled so that the position of the meniscus in the moving mold does not fluctuate as much as possible.

In the flat nozzle according to the present invention, the filter 5 and the fusible metal 4 are supported by the retaining shelf 8 for supporting the filter having sufficient strength on the lower inner wall thereof, and the molten metal at the time of continuous casting is started. Since it is configured to receive an impact force, both ends of the slit-shaped nozzle hole 5 are supported.
Since 2d is formed to be thin, there is little adhesion and growth of metal due to the generation of stagnant flow on the surface of the molten metal in the vicinity of 2d.

Further, the fixing piece 9 can prevent the filter 5 and the fusible metal 4 from floating, prevent their functions from being lowered, and have good controllability of the molten metal supply amount, and can suppress fluctuation of meniscus. Therefore, the continuous casting operation can be stabilized for a long time, and a uniform thin cast piece can be stably cast.

The present invention is not limited to this embodiment, but can be modified as appropriate within a range that satisfies the structure of the first aspect. For example, this flat nozzle 1
The slit-shaped nozzle hole 6 may be continuous or divided into a plurality of sections in the horizontal direction, and may also be provided on the side weir side.

Further, the mounting structure of the flat nozzle of the present invention is not the main part of the present invention.
Nut 18 and outer skin 11 of tundish 10
Although the support 16 is separately provided and supported by an appropriate means, the support 16 is provided separately. Further, the flat nozzle 1 is divided into an upper part and a lower part, but may be formed integrally.

[0030]

According to the present invention, a filter retaining shelf is provided on the inner wall above the slit-shaped nozzle hole to support the filter and the fusible metal and receive the molten metal impact force at the start of continuous casting. The load applied to both ends of the slit-shaped nozzle hole can be significantly reduced. Further, the filter and the fusible metal are fixed to the lower inner wall surface, and after the continuous casting is started, these are prevented from rising, and the function thereof can be prevented from being lowered.

Accordingly, the lower (including bottom) wall immersed in the molten metal in the moving mold during the continuous operation of continuous casting is made thinner to suppress the generation of stagnation flow of the molten metal on the surface of the molten metal in the moving mold. It prevents the adhesion and growth of ingots, secures the functions of the filter and the fusible metal, enables the stable supply of molten metal, and stably maintains the continuous casting operation for a long time. Also, the effect of reducing the cost of refractory can be expected.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory views showing an embodiment of the present invention, in which FIG. 1A is a partially cutaway front view, FIG. 1B is a partially cutaway side view in FIG. FIG. 1 is an enlarged partial cross-sectional plan view showing a main part in an embodiment of the present invention.

FIG. 2 is an explanatory sectional view showing an example of a flat nozzle mounting structure according to the present invention.

FIG. 3 is an elevational view showing an example of a conventional twin-drum continuous casting apparatus.

FIG. 4 is an explanatory sectional view showing an example of a conventional flat nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat nozzle 1a Upper opening part 2a Upper part 2b Lower part 2c, 2d Both ends support part 3 Intermediate chisel 4 Meltable metal 5 Filter 6a, 6b Slit-shaped nozzle hole 7 Electric heating electrode 8 Locking shelf 9 Fixed piece 10 Tundish 11 Skin iron Leather 12 Refractory 13 Refractory block 14 Insertion hole 15 Stopper 16 Support 17 Movable support 18 Bolt / nut a Inner nozzle b Outer nozzle c Cast piece d Meltable metal member e Molten metal f Porous refractory (filter) p Pool Part Ra, Rb Cooling drum Sa, Sb Side weir

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshimori Fukuda 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nippon Steel Corporation Hikari Works (72) Inventor Hideo Tsukiji 1-1-1, Higashihama-machi, Yawatanishi-ku, Kitakyushu-shi, Fukuoka No. Kurosaki Ceramics Co., Ltd. (72) Inventor Hiroyuki Miyamoto 1-1, Higashihama-cho, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Prefecture (72) Inventor Yukio Inoue 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation (56) References JP-A-63-203254 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/06 B22D 11/10 B22D 41/50

Claims (1)

(57) [Claims] 1. A flat nozzle for continuous casting of a wide and thin cast slab having a slit-shaped nozzle hole on both side walls at the bottom and a filter and a fusible metal having a lower melting point than the cast metal at a lower portion. A filter locking shelf is provided on the inner wall above the filter, where the upper part of the filter is locked, the fusible metal is placed on the filter, and the fusible metal is fixed to the inner wall. Flat nozzle for continuous casting of thin cast slabs.